Semi-Persistent Scheduled Resource Release Procedure
in a Mobile Communication Network
FIELD OF THE INVENTION
The invention relates to a method for deactivating a semi-persistent resource allocation
of a user equipment in an LTE-based mobile communication system. Furthermore, the
invention also related to a user equipment and a eNode B implementing this method.
TECHNICAL BACKGROUND
Long Term Evolution (LTE)
Third-generation mobile systems (3G) based on WCDMA (Wideband Code Division
Multiple Access) radio-access technology are being deployed on a broad scale all
around the world. A first step in enhancing or evolving this technology entails introducing
High-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, also referred to
as High Speed Uplink Packet Access (HSUPA), giving a radio-access technology that is
highly competitive.
In a longer time perspective it is, however, necessary to be prepared for further
increasing user demands and an even tougher competition from new radio access
technologies. To meet this challenge, 3GPP has initiated the study item Evolved UTRA
and UTRAN (see 3GPP Tdoc. RP-040461, "Proposed Study Item on Evolved UTRA and
UTRAN", and 3GPP TR 25.912: "Feasibility study for evolved Universal Terrestrial Radio
Access (UTRA) and Universal Terrestrial Radio Access Network (UTRAN)", version
7.2.0, June 2007, available at http://www.3gpp.org and both being incorporated herein by
reference), aiming at studying means to achieve additional substantial leaps in terms of
service provisioning and cost reduction. As a basis for this work, 3GPP has concluded on
a set of targets and requirements for this long-term evolution (LTE) (see 3GPP TR
25.913, "Requirements for Evolved UTRA and Evolved UTRAN", version 7.3.0, March
2006, available at http://www.3gpp.org, incorporated herein by reference) including for
example:
- Peak data rates exceeding 100 Mbps for the downlink direction and 50 Mbps for the
uplink direction.
- Mean user throughput improved by factors 2 and 3 for uplink and downlink
respectively
- Cell-edge user throughput improved by a factor 2 for uplink and downlink
- Uplink and downlink spectrum efficiency improved by factors 2 and 3 respectively.
- Significantly reduced control-plane latency.
- Reduced cost for operator and end user.
- Spectrum flexibility, enabling deployment in many different spectrum allocations.
The ability to provide high bit rates is a key measure for LTE. Multiple parallel data
stream transmission to a single terminal, using multiple-input-multiple-output (MIMO)
techniques, is one important component to reach this. Larger transmission bandwidth
and at the same time flexible spectrum allocation are other pieces to consider when
deciding what radio access technique to use. The choice of adaptive multi-layer OFDM,
AML-OFDM, in downlink will not only facilitate to operate at different bandwidths in
general but also large bandwidths for high data rates in particular. Varying spectrum
allocations, ranging from 1.25 MHz to 20 MHz, are supported by allocating
corresponding numbers of AML-OFDM subcarriers. Operation in both paired and
unpaired spectrum is possible as both time-division and frequency-division duplex is
supported by AML-OFDM.
LTE architecture
The overall architecture is shown in Fig. 1 and a more detailed representation of the E-
UTRAN architecture is given in Fig. 2. The E-UTRAN consists of base stations (referred
to as Node Bs or eNode Bs in the 3GPP terminology), providing the E-UTRA user plane
(PDCP/RLC/MAC/PHY) and control plane (Radio Resource Control - RRC) protocol
terminations towards the mobile terminal (referred to as UE in the 3GPP terminology).
The eNodeB hosts the Physical (PHY), Medium Access Control (MAC), Radio Link
Control (RLC), and Packet Data Control Protocol (PDCP) layers that include the
functionality of user-plane header-compression and encryption. It also offers Radio
Resource Control (RRC) functionality corresponding to the control plane. It performs
many functions including radio resource management, admission control, scheduling,
enforcement of negotiated UL QoS, cell information broadcast, ciphering/deciphering of
user and control plane data, and compression/decompression of DL/UL user plane
packet headers.
The eNode Bs are interconnected with each other by means of the X2 interface. The
eNode Bs are also connected by means of the S1 interface to the EPC (Evolved Packet
Core), more specifically to the MME (Mobility Management Entity) by means of the S1-
MME and to the Serving Gateway (SGW) by means of the S1-U. The S1 interface
supports a many-to-many relation between MMEs / Serving Gateways and eNode Bs.
The SGW routes and forwards user data packets, while also acting as the mobility
anchor for the user plane during inter-eNodeB handovers and as the anchor for mobility
between LTE and other 3GPP technologies (terminating S4 interface and relaying the
traffic between 2G/3G systems and PDN GW). For idle state UEs, the SGW terminates
the downlink data path and triggers paging when downlink data arrives for the UE. it
manages and stores UE contexts, e.g. parameters of the IP bearer service, network
internal routing information. It also performs replication of the user traffic in case of lawful
interception.
The MME is the key control-node for the LTE access-network. It is responsible for idle
mode UE tracking and paging procedure including retransmissions. It is involved in the
bearer activation/deactivation process and is also responsible for choosing the SGW for
a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN)
node relocation. It is responsible for authenticating the user (by interacting with the HSS).
The Non-Access Stratum (NAS) signaling terminates at the MME and it is also
responsible for generation and allocation of temporary identities to UEs. It checks the
authorization of the UE to camp on the service provider's Public Land Mobile Network
(PLMN) and enforces UE roaming restrictions. The MME is the termination point in the
network for ciphering/integrity protection for NAS signaling and handles the security key
management. Lawful interception of signaling is also supported by the MME. The MME
also provides the control plane function for mobility between LTE and 2G/3G access
networks with the S3 interface terminating at the MME from the SGSN. The MME also
terminates the S6a interface towards the home HSS for roaming UEs.
OFDM with Frequency-Domain Adaptation
The AML-OFDM-based (AML-OFDM = Adaptive MultiLayer-Orthorgonal Frequency
Division Multiplex) downlink has a frequency structure based on a large number of
individual sub-carriers with a spacing of 15 kHz. This frequency granularity facilitates to
implement dual-mode UTRA/E-UTRA terminals. The ability to reach high bit rates is
highly dependent on short delays in the system and a prerequisite for this is short sub-
frame duration. Consequently, the LTE sub-frame duration is set as short as 1 ms in
order to minimize the radio-interface latency. In order to handle different delay spreads
and corresponding cell sizes with a modest overhead the OFDM cyclic prefix length can
assume two different values. The shorter 4.7 ms cyclic prefix is enough to handle the
delay spread for most unicast scenarios. With the longer cyclic prefix of 16.7 ms very
large cells, up to and exceeding 120 km cell radius, with large amounts of time
dispersion can be handled. In this case the length is extended by reducing the number of
OFDM symbols in a sub-frame.
The basic principle of Orthogonal Frequency Division Multiplexing (OFDM) is to split the
frequency band into a number of narrowband channels. Therefore, OFDM allows
transmitting data on relatively flat parallel channels (subcarriers) even if the channel of
the whole frequency band is frequency selective due to a multipath environment. Since
the subcarriers experience different channel states, the capacities of the subcarriers vary
and permit a transmission on each subcarrier with a distinct data-rate. Hence, subcarrier-
wise (frequency domain) Link Adaptation (LA) by means of Adaptive Modulation and
Coding (AMC) increases the radio efficiency by transmitting different data-rates over the
subcarriers. OFDMA allows multiple users to transmit simultaneously on the different
subcarriers per OFDM symbol. Since the probability that all users experience a deep
fade in a particular subcarrier is very low, it can be assured that subcarriers are assigned
to the users who see good channel gains on the corresponding sub-carriers. When
allocating resources in the downlink to different users in a cell, the scheduler takes
information on the channel status experienced by the users for the subcarriers into
account. The control information signaled by the users, i.e. CQI, allows the scheduler to
exploit the multi-user diversity, thereby increasing the spectral efficiency.
Localized vs. Distributed mode
Two different resource allocation methods can be distinguished upon when considering a
radio access scheme that distribute available frequency spectrum among different users
as in OFDMA. The first allocation mode or "localized mode" tries to benefit fully from
frequency scheduling gain by allocating the subcarriers on which a specific UE
experiences the best radio channel conditions. Since this scheduling mode requires
associated signaling (resource allocation signaling, CQI in uplink), this mode would be
best suited for non-real time, high data rate oriented services. In the localized resource
allocation mode a user is allocated continuous blocks of subcarriers.
The second resource allocation mode or "distributed mode" relies on the frequency
diversity effect to achieve transmission robustness by allocating resources that are
scattered over time and frequency grid. The fundamental difference with localized mode
is that the resource allocation algorithm does not try to allocate the physical resources
based on some knowledge on the reception quality at the receiver but select more or
less randomly the resource it allocates to a particular UE. This distributed resource
allocation method seems to be best suited for real-time services as less associated
signaling (no fast CQI, no fast allocation signaling) relative to "localized mode" is required.
The two different resource allocation methods are shown in Fig. 3 and Fig. 4 for an
OFDMA based radio access scheme. As can be seen from Fig. 3, which depicts the
localized transmission mode, the localized mode is characterized by the transmitted
signal having a continuous spectrum that occupies a part of the total available spectrum.
Different symbol rates (corresponding to different data rates) of the transmitted signal
imply different bandwidths (time/frequency bins) of a localized signal. On the other hand,
as can be seen from Fig. 4, the distributed mode is characterized by the transmitted
signal having a non-continuous spectrum that is distributed over more or less the entire
system bandwidth (time/frequency bins).
Hybrid ARQ Schemes
A common technique for error detection and correction in packet transmission systems
over unreliable channels is called hybrid Automatic Repeat request (HARQ). Hybrid ARQ
is a combination of Forward Error Correction (FEC) and ARQ.
If a FEC encoded packet is transmitted and the receiver fails to decode the packet
correctly (errors are usually checked by a CRC (Cyclic Redundancy Check)), the
receiver requests a retransmission of the packet. Generally (and throughout this
document) the transmission of additional information is called "retransmission (of a
packet)", although this retransmission does not necessarily mean a transmission of the
same encoded information, but could also mean the transmission of any information
belonging to the packet (e.g. additional redundancy information).
Depending on the information (generally code-bits/symbols), of which the transmission is
composed, and depending on how the receiver processes the information, the following
Hybrid ARQ schemes are defined:
In Type I HARQ schemes, the information of the encoded packet is discarded and a
retransmission is requested, if the receiver fails to decode a packet correctly. This
implies that all transmissions are decoded separately. Generally, retransmissions contain
identical information (code-bits/symbols) to the initial transmission.
In Type II HARQ schemes, a retransmission is requested, if the receiver fails to decode a
packet correctly, where the receiver stores the information of the (erroneous received)
encoded packet as soft information (soft-bits/symbols). This implies that a soft-buffer is
required at the receiver. Retransmissions can be composed out of identical, partly
identical or non-identical information (code-bits/symbols) according to the same packet
as earlier transmissions. When receiving a retransmission the receiver combines the
stored information from the soft-buffer and the currently received information and tries to
decode the packet based on the combined information. (The receiver can also try to
decode the transmission individually, however generally performance increases when
combining transmissions.) The combining of transmissions refers to so-called soft-
combining, where multiple received code-bits/symbols are likelihood combined and
solely received code-bits/symbols are code combined. Common methods for soft-
combining are Maximum Ratio Combining (MRC) of received modulation symbols and
log-likelihood-ratio (LLR) combining (LLR combing only works for code-bits).
Type II schemes are more sophisticated than Type I schemes, since the probability for
correct reception of a packet increases with receive retransmissions. This increase
comes at the cost of a required hybrid ARQ soft-buffer at the receiver. This scheme can
be used to perform dynamic link adaptation by controlling the amount of information to be
retransmitted. E.g. if the receiver detects that decoding has been "almost" successful, it
can request only a small piece of information for the next retransmission (smaller number
of code-bits/symbols than in previous transmission) to be transmitted. In this case it
might happen that it is even theoretically not possible to decode the packet correctly by
only considering this retransmission by itself (non-self-decodable retransmissions).
Type III HARQ schemes may be considered a subset of Type II schemes: In addition to
the requirements of a Type II scheme each transmission in a Type III scheme must be
self-decodable.
HARQ Protocol operation for unicast data transmissions
A common technique for error detection and correction in packet transmission systems
over unreliable channels is called hybrid Automatic Repeat request (HARQ). Hybrid ARQ
is a combination of Forward Error Correction (FEC) and ARQ.
If a FEC encoded packet is transmitted and the receiver fails to decode the packet
correctly (errors are usually checked by a CRC (Cyclic Redundancy Check)), the
receiver requests a retransmission of the packet
In LTE there are two levels of re-transmissions for providing reliability, namely, HARQ at
the MAC layer and outer ARQ at the RLC layer. The outer ARQ is required to handle
residual errors that are not corrected by HARQ that is kept simple by the use of a single
bit error-feedback mechanism, i.e. ACK/NACK. An N-process stop-and-wait HARQ is
employed that has asynchronous re-transmissions in the downlink and synchronous re-
transmissions in the uplink.
Synchronous HARQ means that the re-transmissions of HARQ blocks occur at pre-
defined periodic intervals. Hence, no explicit signaling is required to indicate to the
receiver the retransmission schedule.
Asynchronous HARQ offers the flexibility of scheduling re-transmissions based on air
interface conditions. In this case some identification of the HARQ process needs to be
signaled in order to allow for a correct combing and protocol operation. In 3GPP LTE
systems, HARQ operations with eight processes is used. The HARQ protocol operation
for downlink data transmission will be similar or even identical to HSDPA.
In uplink HARQ protocol operation there are two different options on how to schedule a
retransmission. Retransmissions are either "scheduled" by a NACK (also referred to as a
synchronous non-adaptive retransmission) or are explicitly scheduled by the network by
transmitting a PDCCH (also referred to as synchronous adaptive retransmissions). In
case of a synchronous non-adaptive retransmission the retransmission will use the same
parameters as the previous uplink transmission, i.e. the retransmission will be signaled
on the same physical channel resources, respectively uses the same modulation
scheme/transport format.
Since synchronous adaptive retransmission are explicitly scheduled via PDCCH, the
eNodeB has the possibility to change certain parameters for the retransmission. A
retransmission could be for example scheduled on a different frequency resource in
order to avoid fragmentation in the uplink, or eNodeB could change the modulation
scheme or alternatively indicate to the user equipment what redundancy version to use
for the retransmission. It should be noted that the HARQ feedback (ACK/NACK) and
PDCCH signaling occurs at the same timing. Therefore the user equipment only needs to
check once whether a synchronous non-adaptive retransmission is triggered (i.e. only a
NACK is received) or whether eNode B requests a synchronous adaptive retransmission
(i.e. PDCCH is signaled).
L1/L2 Control Signaling
In order to inform the scheduled users about their allocation status, transport format and
other data related information (e.g. HARQ) L1/L2 control signaling is transmitted on the
downlink along with the data. This control signaling is multiplexed with the downlink data
in a sub-frame (assuming that the user allocation can change from sub-frame to sub-
frame). Here, it should be noted, that user allocation might also be performed on a TTI
(Transmission Time Interval) basis, where the TTI length is a multiple of the sub-frames.
The TTI length may be fixed in a service area for all users, may be different for different
users, or may even by dynamic for each user. Generally, then the L1/2 control signaling
needs only be transmitted once per TTI.
The L1/L2 control signaling is transmitted on the Physical Downlink Control Channel
(PDCCH). It should be noted that assignments for uplink data transmissions, uplink
(scheduling) grants, are also transmitted on the PDCCH.
Generally, the information sent on the L1/L2 control signaling may be separated into the
two categories, Shared Control Information and Dedicated Control Information:
Shared Control Information (SCI) carrying Cat 1 information
The SCI part of the L1/L2 control signaling contains information related to the resource
allocation (indication). The SCI typically contains the following information:
- User identity, indicating the user which is allocated
- RB allocation information, indicating the resources (Resource Blocks, RBs) on which a
user is allocated. Note, that the number of RBs on which a user is allocated can be
dynamic.
- Duration of assignment (optional), if an assignment over multiple sub-frames (or TTIs)
is possible
Depending on the setup of other channels and the setup of the Dedicated Control
Information (DCI), the SCI may additionally contain information such as ACK/NACK for
uplink transmission, uplink scheduling information, information on the DCI (resource,
MCS, etc.).
Dedicated Control Information (DCI) carrying Cat 2/3 information
The DCI part of the L1/L2 control signaling contains information related to the
transmission format (Cat 2) of the data transmitted to a scheduled user indicated by Cat
1. Moreover, in case of application of (hybrid) ARQ it carries HARQ (Cat 3) information.
The DCI needs only to be decoded by the user scheduled according to Cat 1.
The DCI typically contains information on:
- Cat 2: Modulation scheme, transport-block (payload) size (or coding rate), MIMO
related information, etc. (Note, either the transport-block (or payload size) or the code
rate can be signaled. In any case these parameters can be calculated from each other
by using the modulation scheme information and the resource information (number of
allocated RBs)).
- Cat 3: HARQ related information, e.g. hybrid ARQ process number, redundancy
version, retransmission sequence number.
Details on L1/L2 control signaling information
For downlink data transmissions L1/L2 control signaling is transmitted on a separate
physical channel (PDCCH). This L1/L2 control signaling typically contains information on:
- The physical resource(s) on which the data is transmitted (e.g. subcarriers or
subcarrier blocks in case of OFDM, codes in case of CDMA). This information allows
the UE (receiver) to identify the resources on which the data is transmitted.
- The transport format, which is used for the transmission. This can be the transport
block size of the data (payload size, information bits size), the MCS (Modulation and
Coding Scheme) level, the Spectral Efficiency/the code rate, etc. This information
(usually together with the resource allocation) allows the user equipment (receiver) to
identify the information bit size, the modulation scheme and the code rate in order to
start the demodulation, the de-rate-matching and the decoding process. In some
cases the modulation scheme maybe signaled explicitly.
- Hybrid ARQ (HARQ) information:
- Process number Allows the user equipment to identify the Hybrid ARQ process on
which the data is mapped
- Sequence number or new data indicator: Allows the user equipment to identify if
the transmission is a new packet or a retransmitted packet
- Redundancy and/or constellation version: Tells the user equipment, which hybrid
ARQ redundancy version is used (required for de-rate-matching) and/or which
modulation constellation version is used (required for demodulation)
- UE Identity (UE ID): Tells for which user equipment the L1/L2 control signaling is
intended for. In typical implementations this information is used to mask the CRC of
the L1/L2 control signaling in order to prevent other user equipments to read this
information.
To enable an uplink packet data transmission, L1/L2 control signaling is transmitted on
the downlink (PDCCH) to tell the user equipment about the transmission details. This
L1/L2 control signaling typically contains information on:
- The physical resource(s) on which the user equipment should transmit the data (e.g.
subcarriers or subcarrier blocks in case of OFDM, codes in case of CDMA).
- The transport Format, the UE should use for the transmission. This can be the
transport block size of the data (payload size, information bits size), the MCS
(Modulation and Coding Scheme) level, the Spectral Efficiency, the code rate, etc.
This information (usually together with the resource allocation) allows the user
equipment (transmitter) to pick the information bit size, the modulation scheme and
the code rate in order to start the modulation, the rate-matching and the encoding
process. In some cases the modulation scheme maybe signaled explicitly.
- Hybrid ARQ information:
- Process number: Tells the user equipment from which Hybrid ARQ process it
should pick the data
- Sequence number or new data indicator: Tells the user equipment to transmit a
new packet or to retransmit a packet
- Redundancy and/or constellation version: Tells the user equipment, which hybrid
ARQ redundancy version to use (required for rate-matching) and/or which
modulation constellation version to use (required for modulation)
- UE Identity (UE ID): Tells which user equipment should transmit data. In typical
implementations this information is used to mask the CRC of the L1/L2 control
signaling in order to prevent other user equipments to read this information.
There are several different flavors how to exactly transmit the information pieces
mentioned above. Moreover, the L1/L2 control information may also contain additional
information or may omit some of the information. E.g.:
- HARQ process number may not be needed in case of a synchronous HARQ protocol
- A redundancy and/or constellation version may not be needed if Chase Combining is
used (always the same redundancy and/or constellation version) or if the sequence of
redundancy and/or constellation versions is pre defined.
- Power control information may be additionally included in the control signaling
- MlMO related control information, such as e.g. precoding, may be additionally
included in the control signaling.
- In case of multi-codeword MIMO transmission transport format and/or HARQ
information for multiple code words may be included
For uplink resource assignments (for the Physical Uplink Shared Channel - PUSCH)
signaled on the PDCCH in LTE, the L1/L2 control information does not contain a HARQ
process number, since a synchronous HARQ protocol is employed for LTE uplink. The
HARQ process to be used for an uplink transmission is given by the timing. Furthermore
it should be noted that the redundancy version (RV) information is jointly encoded with
the transport format information, i.e. the redundancy version information is embedded in
the transport format (TF) field. The TF field respectively MCS field (Modulation and
Coding Scheme field) has for example a size of 5 bits, which corresponds to 32 indices.
Three TF/MCS table indices are reserved for indicating RVs 1, 2 or 3. The remaining
MCS table indices are used to signal the MCS level (transport block size - TBS) implicitly
indicating RVO. The TBS/RV signaling for uplink assignments on PDCCH is shown in
Table 1 below. An exemplary PDCCH for uplink resource assignments is shown in Fig.
5. The fields FH (Frequency Hopping), Cyclic shift and CQI (Channel Quality Index) are
physical layer parameters and of no specific importance for understanding the invention
described herein, so that their description is omitted. The size of the CRC field of the
PDCCH is 16 bits. For further, more detailed information on the information fields
contained in a PDCCH for uplink resource assignments, e.g. DCI format 0, it is referred
to section 5.3.3.1 of 3GPP TS 36.212 "Evolved Universal Terrestrial Radio Access (E-
UTRA); Multiplexing and channel coding (Release 8)", version 8.3.0, June 2008,
available at http://www.3gpp.org and the entire document being incorporated herein by
reference. Even though the field providing transport format respectively modulation and
coding scheme and redundancy version information is referred to as "modulation and
coding scheme and redundancy version" it will be for the further description of the
invention only referred to as modulation and coding scheme (MCS) field.
For downlink resource assignments (for the Physical Downlink Shared Channel -
PDSCH) signaled on PDCCH in LTE the redundancy version is signaled separately in a
two-bit field. Furthermore the modulation order information is jointly encoded with the
transport format information, similar to the uplink case there is 5 bit MCS field signaled
on PDCCH. Three of the indices are reserved for the signaling of an explicit modulation
order, i.e. those indices do not provide any transport format (transport block size)
information. The remaining 29 indices signal modulation order and transport block size
information as shown in Table 3 below. For further, more detailed information on the
PDCCH formats for downlink resource assignment it is again referred to section 5.3.3.1
of 3GPP TS 36.212. For example, section 5.3.3.1.3 describes the DCI format 1A, which
is one of the DCI formats for scheduling PDSCH. For downlink assignments the field
providing transport block size and modulation order information is referred to as
"modulation and coding scheme" field the term that will also be used in the description of
this invention.
UL/DL grant reception behavior
Generally the grant reception procedure (i.e. the procedure of receiving a resource
assignment) is split between Physical layer and MAC layer. The Physical layer detects
an uplink/downlink resource assignment on the PDCCH, extracts and determines certain
information from the PDCCH fields and reports this to MAC layer. The MAC layer is
responsible for the protocol procedures, i.e. HARQ protocol operation for uplink/downlink
transmissions. Also the scheduling procedures for dynamic as well as semi-persistent
scheduling are handled within the MAC layer.
When receiving a resource assignment on the PDCCH for uplink respectively downlink,
the physical layer needs to determine certain information from received PDCCH fields
which are required for the further processing of the assignments in MAC layer. As
described in 3GPP TS 36.213, the Physical layer needs to determine the modulation
order and transport block size in the PDSCH for a downlink resource assignment. The
calculation of modulation order and transport block size is described in section 7.1.7 of
3GPP TS 36.213. Transport block size together with the HARQ process ID and the NDI
bit is delivered to the MAC layer, which requires this information for performing the
downlink HARQ protocol operation. The information delivered from Physical layer (Layer
1) to MAC (Layer 2) is also referred to as HARQ information.
Similar to the downlink, the Physical layer calculates modulation order and transport
block size from received PDCCH containing the uplink resource assignment as
described in section 8.6 of 3GPP TS 36.213. the Physical layer reports the calculated
transport block size, redundancy version (RV) as well as NDI information of the PDCCH
within the HARQ information to the MAC layer.
Semi-Persistent Scheduling (SPS)
In the downlink and uplink, the scheduling eNodeB dynamically allocates resources to
user equipments at each transmission time interval via the L1/L2 control channel(s)
(PDCCH) where the user equipments are addressed via their specific C-RNTIs. As
already mentioned before the CRC of an PDCCH is masked with the addressed user
equipment's C-RNTI (so-called dynamic PDCCH). Only a user equipment with a
matching C-RNTI can decode the PDCCH content correctly, i.e. the CRC check is
positive. This kind of PDCCH signaling is also referred to as dynamic (scheduling) grant.
A user equipment monitors at each transmission time interval the L1/L2 control
channel(s) for a dynamic grant in order to find a possible allocation (downlink and uplink)
it is assigned to.
In addition, E-UTRAN can allocate uplink/downlink resources for initial HARQ
transmissions persistently. When required, retransmissions are explicitly signaled via the
L1/L2 control channel(s). Since retransmissions are scheduled, this kind of operation is
referred to as semi-persistent scheduling (SPS), i.e. resources are allocated to the user
equipment on a semi-persistent basis (semi-persistent resource allocation). The benefit
is that PDCCH resources for initial HARQ transmissions are saved. For details on semi-
persistent scheduling, see 3GPP TS 36.300, "Evolved Universal Terrestrial Radio
Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN);
Overall description; Stage 2 (Release 8)", version 8.5.0, June 2008 or 3GPP TS 36.321
"Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC)
protocol specification (Release 8)", version 8.2.0, June 2008, both available at
http://www.3gpp.org and incorporated herein by reference.
One example for a service, which might be scheduled using semi-persistent scheduling
is Voice over IP (VoiP). Every 20 ms a VoIP packet is generated at the codec during a
talk-spurt. Therefore eNodeB could allocated uplink or respectively downlink resource
persistently every 20 ms, which could be then used for the transmission of Voice over IP
packets. In general, semi-persistent scheduling is beneficial for services with a
predictable traffic behavior, i.e. constant bit rate, packet arrival time is periodic.
The user equipment also monitors the PDCCHs in a sub-frame where it has been
allocated resources for an initial transmission persistently. A dynamic (scheduling) grant,
i.e. PDCCH with a C-RNTI-masked CRC, can override a semi-persistent resource
allocation. In case the user equipment finds its C-RNTI on the L1/L2 control channel(s) in
the sub-frames where the sub-frame has a semi-persistent resource assigned, this L1/L2
control channel allocation overrides the semi-persistent resource allocation for that
transmission time interval and the user equipment does follow the dynamic grant. When
sub-frame doesn't find a dynamic grant it will transmit/receive according to the semi-
persistent resource allocation.
The configuration of semi-persistent scheduling is done by RRC signaling. For example
the periodicity, i.e. PS_PERIOD, of the persistent allocation is signaled within Radio
resource Control (RRC) signaling. The activation of a persistent allocation and also the
exact timing as well as the physical resources and transport format parameters are sent
via PDCCH signaling. Once semi-persistent scheduling is activated, the user equipment
follows the semi-persistent resource allocation according to the activation SPS PDCCH
every PS_PERIOD. Essentially the user equipment stores the SPS activation PDCCH
content and follows the PDCCH with the signaled periodicity.
In order to distinguish a dynamic PDCCH from a PDCCH, which activates semi-
persistent scheduling, i.e. also referred to as SPS activation PDCCH, a separate identity
persistent allocation critical, the main focus lies on falsely activated uplink semi-
persistent resource allocations.
In case the UE falsely detects a SPS UL PDCCH (i.e. an uplink resource assignment for
a semi-persistent resource allocation), the content of the PDCCH is some random value.
Consequently UE transmits on PUSCH using some random RB location and bandwidth
found in the false positive grant, which subjects the eNode B to UL interferences. With
50% probability UE jams more than half the bandwidth of the system since the Resource
Allocation field is random. The user equipment is looking for ACK/NACK in the location
corresponding to the (false positive) semi-persistent uplink resource allocation. The
eNode B is not transmitting any data to the user equipment and the user equipment will
decode the "acknowledgment" for its transmission (ACK/NACK) pretty random. When a
NACK is received user equipment performs a synchronous non-adaptive retransmission.
When ACK is received user equipment is suspended until the next SPS occasion, and
the MAC may assume the transport block has been successfully received and decoded
at the eNode B.
Essentially as a consequence of a false activation of a semi-persistent resource
allocation for the uplink, a talk spurt can be lost completely or partially several times
during a normal voice call. In addition, a false activation of a semi-persistent resource
allocation for the uplink causes unnecessary interference to the system.
Given the severe consequences it is desirable to significantly increase the average time
of false semi-persistent scheduling activations. One means to lower the false alarm rate
to an acceptable level is to use a "Virtual CRC in order to expand the 16-bit CRC: The
length of the CRC field can be virtually extended by setting fixed and known values to
some of the PDCCH fields that are not useful for semi-persistent scheduling activation.
The user equipment shall ignore the PDCCH for semi-persistent resource activation if the
values in these fields are not correct. Since MIMO operation with semi-persistent
scheduling does not seem to be that useful, the corresponding PDCCH fields could be
used in order to the increase the virtual CRC length. One further example is the NDI
field. As already mentioned the NDI bit should be set to 0 on a PDCCH for semi-
persistent scheduling activation. The false alarm rate could be further reduced by
restricting the set of transport block sizes, which are valid for a semi-persistent
scheduling activation.
As mentioned above, a semi-persistent scheduling resource release is signaled by
means of an PDCCH similar to an SPS activation. In order to use the resource for SPS
efficiently, it's desirable that resources can be re-allocated quickly, for example in VoIP
by means of explicit release of a persistent allocation during silence periods in speech,
followed by a re-activation when the silence periods ends. Therefore it should be noted
that at a semi-persistent scheduling resource release an SPS RRC configuration, e.g.
PS_PERIOD, remains in place until changed by RRC signaling. Therefore PDCCH is
used for an efficient explicit release (de-activation) of semi-persistent scheduling.
One possibility would be sending a semi-persistent scheduling activation with a zero-size
resource allocation. A zero-size allocation would correspond to a resource allocation of 0
physical resource blocks (RB) which would effectively deactivate the semi-persistent
resource allocation. This solution requires that a PDCCH message, i.e. uplink/downlink
resource assignment, is able to indicate "ORBs" as one possible resource block
allocation. Since this is not possible with the PDCCH formats agreed on in the 3GPP, a
new „0RB" entry would need to be introduced in resource block assignment field for
PDSCH and PUSCH. This would however also have impact on the Physical layer-to-
MAC Layer interaction in the user equipments, as the Physical layer would further need
to be adapted to inform the MAC layer on the deactivation of the semi-persistent
resource allocation.
SUMMARY OF THE INVENTION
One object of the invention is to provide a mechanism for deactivating a semi-persistent
resource allocation in a LTE system that is not requiring any changes to the Physical
layer-to-MAC layer interface and/or preferably no changes to the PDCCH formats agreed
by the 3GPP.
The object is solved by the subject matter of the independent claims. Advantageous
embodiments of the invention are subject matters of the dependent claims.
One aspect of the invention is to use (existing) physical control channel signaling related
to a semi-persistent resource allocation for deactivating the semi-persistent resource
allocation to a user equipment (or in other words releasing the grant for the semi-
persistent resource allocation) by defining a special control channel signaling content as
a deactivation command for the semi-persistent resource allocation. More specifically,
the control channel signaling contains a New Data Indicator (NDI) and a modulation and
coding scheme field, and a specific combination of the New Data Indicator value and a
modulation and coding scheme index signalled within the modulation and coding scheme
field is defined to indicate the deactivation of the semi-persistent resource allocation.
According to a second alternative aspect of the invention, the semi-persistent resource
allocation is configured by RRC signaling. The RRC signaling is indicating a special
transport block size to the user equipment that, when indicated in a resource assignment
for the semi-persistent resource allocation on a physical control channel, is commanding
the user equipment to deactivate the semi-persistent resource allocation.
Both aspects of the invention do not impact the user equipments operation concerning
the handling of resource assignments (grants) and do therefore also not impact the
interface between Physical layer and MAC layer as presently defined by the 3GPP.
The invention according to one embodiment is related to a method for deactivating a
semi-persistent resource allocation in an LTE-based mobile communication system. The
user equipment (a mobile terminal in the 3GPP terminology) is receiving control
signalling that is including a New Data Indicator and a modulation and coding scheme
field. The control signalling is received via a control channel (such as the PDCCH) from
an eNode B (a base station in an LTE system). If the New Data Indicator and the
modulation and coding scheme field of the control signalling indicate a predetermined
combination of a New Data Indicator value and a modulation and coding scheme index,
the user equipment is deactivating the semi-persistent resource allocation.
Another embodiment of the invention is directed to the operation of the eNode B. The
eNode B generates for the user equipment control signalling comprising a New Data
Indicator and a modulation and coding scheme field. The New Data Indicator and the
modulation and coding scheme field include a predetermined combination of a New Data
Indicator value and a modulation and coding scheme index that is to cause the user
equipment to deactivate the semi-persistent resource allocation. The eNode B transmits
the control signalling via a control channel to the user equipment to thereby cause the
user equipment to deactivate the semi-persistent resource allocation.
According to a further embodiment of the invention, the predetermined combination of
the New Data Indicator value and the modulation and coding scheme index is the New
Data Indicator value being 0 (indicating an activation of semi-persistent scheduling) and
the modulation and coding scheme index indicating no transport block size Information.
Hence, in this exemplary embodiment of the invention, indices of the modulation and
coding scheme field are reused that are commonly not used for a resource assignment
to activate or reactivate the semi-persistent resource allocation.
In an alternative embodiment of the invention, the predetermined combination of the New
Data Indicator value and the modulation and coding scheme index is the New Data
Indicator value being 1 (indicating a retransmission of a data packet) and the modulation
and coding scheme index indicating a transport block size to the user equipment that is
different to the transport block size of the initial transmission of the data. In this
exemplary embodiment, the different transport block size for the retransmission is
considered a release command for the grant of the semi-persistent resource allocation
so that the semi-persistent resource allocation is deactivated.
In a further embodiment, the control signalling is protected by a CRC field that is masked
with an RNTI assigned to the user equipment for identification in signalling procedures
related to the semi-persistent resource allocation. This feature is not only protecting the
content of the control signalling but also allows addressing the control signalling to the
desired user equipment and its relation to semi-persistent scheduling, as described
previously herein.
According to another embodiment of the invention, at least one field of the control
signalling from the eNode B is set to a predetermined value, for validating said control
signalling as a semi-persistent resource deactivation indication. This allows to lower the
false alarm rate as will be explained below in further detail.
In another embodiment, the concept of the invention is employed to handle semi-
persistent resource allocations for uplink and downlink. The modulation and coding
scheme field indicates one of plural modulation and coding scheme indices. Further it is
assumed that there is a subset of at least three indices that indicate no transport block
size information. The user equipment is deactivating
- a semi-persistent resource allocation for the uplink, in case a first predetermined
modulation and coding scheme index of said subset is indicated in the modulation
and coding scheme field,
- a semi-persistent resource allocation for the downlink, in case a second
predetermined modulation and coding scheme index of said subset is indicated in the
modulation and coding scheme field, and
- a semi-persistent resource allocation for the downlink and a semi-persistent resource
allocation for the uplink, in case a third predetermined modulation and coding scheme
index of said subset is indicated in the modulation and coding scheme field.
In a different embodiment of the invention said control signalling is downlink control
signalling from the eNode B used for scheduling of downlink transmissions. Said control
signalling includes the first predetermined modulation and coding scheme index for
deactivating the semi-persistent resource allocation for the uplink. By using the downlink
scheduling related control signalling for indicating the uplink semi-persistent resource
release, it is possible to reuse mechanisms applied to only the downlink scheduling
related control signalling for uplink purposes.
According to a further embodiment of the invention, the reception of the control signalling
is acknowledged by the user equipment by transmitting an ACK message to the eNode
B. It is possible to acknowledge the reception of control signalling, whereas the prior art
only foresees the acknowledgment of transport blocks. This increases the reliability of
the semi-persistent resource release indication. Furthermore, the acknowledgment is
applicable to the downlink scheduling related control signalling, thus allowing the
acknowledgment for downlink scheduling related control signalling as well for the uplink
indication of semi-persistent resource release.
The method according to another embodiment of the invention further comprises
signalling from the eNode B to the user equipment an RRC message that indicates a
periodicity of the semi-persistent resource allocation and a range of allowable transport
block sizes that can be configured by a control channel signalled from the eNode B to the
user equipment. In a variation of this embodiment, the RRC message further indicates
HARQ information on the HARQ process used for downlink transmissions to the user
equipment according to the semi-persistent resource allocation.
Another embodiment of the invention is related to an alternative method for deactivating
a semi-persistent resource allocation of a user equipment in an LTE-based mobile
communication system according to the second aspect of the invention. In this method
the user equipment receives a RRC message configuring the semi-persistent resource
allocation and indicating a transport block size that when indicated in control signalling
related to the semi-persistent resource allocation is causing the user equipment to
deactivate the semi-persistent resource allocation. Moreover, the user equipment is
receiving control signalling related to the semi-persistent resource allocation from an
eNode B. The control signalling is yielding a transport block size for the semi-persistent
resource allocation. The user equipment deactivates the semi-persistent resource
allocation, if the transport block size indicated in the control signalling matches the
transport block size indicated in the RRC message.
In a variation of this embodiment the control signalling is comprising a resource
allocation field value that is indicating the number of resource blocks allocated to the
user equipment and a modulation and coding scheme index that is indicating a
modulation and coding scheme, the user equipment is further determining the transport
block size yielded by the control signalling based on the resource allocation field value
and the modulation and coding scheme index.
In another embodiment of the invention, the operation of an eNode B in accordance with
the above-mentioned alternative method for deactivating a semi-persistent resource
allocation of a user equipment in an LTE-based mobile communication system is
considered. The eNode B transmits a RRC message to the user equipment for
configuring the semi-persistent resource allocation. This RRC message is indicating a
transport block size that when yielded by control signalling related to the semi-persistent
resource allocation is causing the user equipment to deactivate the semi-persistent
resource allocation. Furthermore, the eNode B generates control signalling related to the
semi-persistent resource allocation and yielding the transport block size indicated by said
RRC message, and transmits the control signalling to the user equipment to thereby
cause the user equipment to deactivate the semi-persistent resource allocation.
In a further embodiment of the invention, the RRC message indicates the periodicity of
the semi-persistent resource allocation and a range of allowable transport block sizes
that can be used for the activation of semi-persistent scheduling. In a variation, the RRC
message could additionally indicate HARQ information on the HARQ process used for
downlink transmissions according to the semi-persistent resource allocation to the user
equipment.
According to another embodiment of the invention, for uplink semi-persistent scheduling,
the modulation and coding scheme field is indicating one of plural predetermined indices.
Thereby, a non-empty subset of the predetermined indices is used to jointly encode
modulation scheme, transport block size and redundancy version for an uplink data
transmission, while the remaining indices are used to encode only a redundancy version
for an uplink data transmission.
Alternatively, for downlink semi-persistent scheduling, the modulation and coding
scheme field is indicating one of plural predetermined indices, wherein a non-empty
subset of the predetermined indices is used to jointly encode modulation scheme and
transport block size for a downlink transmission to be received by the user equipment,
while the remaining indices are used to encode only a modulation scheme for a downlink
transmission.
In an exemplary embodiment of the invention, the control channel is a PDCCH and/or the
control signalling is comprised is a resource assignment to the user equipment.
Furthermore, the invention is also related to the apparatuses and computer readable
media for performing the method for deactivating a semi-persistent resource allocation
according to the various embodiments and aspects of the invention described herein.
In this connection, another embodiment of the invention is providing a user equipment
for use in an LTE-based mobile communication system that is comprising a receiver for
receiving via a control channel from an eNode B control signalling that is including a New
Data Indicator and a modulation and coding scheme field, and a processing unit for
deactivating the semi-persistent resource allocation, if the New Data Indicator and the
modulation and coding scheme field of the control signalling signal a predetermined
combination of a New Data Indicator value and a modulation and coding scheme index.
The invention according to a further embodiment is related to an eNode B for use in an
LTE-based mobile communication system that is comprising a scheduler for generating
for the user equipment control signalling comprising a New Data Indicator and a
modulation and coding scheme field including a predetermined combination of a New
Data Indicator value and a modulation and coding scheme index that is causing the user
equipment to deactivate the semi-persistent resource allocation, and a transmitter for
transmitting said control signalling via a control channel to the user equipment to thereby
cause the user equipment to deactivate the semi-persistent resource allocation.
Likewise, the invention according to another embodiment is also related to a computer
readable medium storing instructions that when executed by a processor of a user
equipment cause the user equipment to deactivate a semi-persistent resource allocation
in an LTE-based mobile communication system, by receiving via a control channel from
an eNode B control signalling that is including a New Data Indicator and a modulation
and coding scheme field, and deactivating the semi-persistent resource allocation, if the
New Data Indicator and the modulation and coding scheme field of the control signalling
signal a predetermined combination of a New Data Indicator value and a modulation and
coding scheme index.
Another embodiment of the invention is providing a computer readable medium storing
instructions that when executed by a processor of an eNode B, cause the eNode B to
deactivate a semi-persistent resource allocation of a user equipment by generating for
the user equipment control signalling comprising a New Data Indicator and a modulation
and coding scheme field including a predetermined combination of a New Data Indicator
value and a modulation and coding scheme index that is causing the user equipment to
deactivate the semi-persistent resource allocation, and transmitting said control
signalling via a control channel to the user equipment to thereby cause the user
equipment to deactivate the semi-persistent resource allocation.
A further embodiment of the invention is related to the second aspect of the invention
and a user equipment for use in an LTE-based mobile communication system,
comprising a receiver for receiving a RRC message configuring a semi-persistent
resource allocation and indicating a transport block size that when indicated in control
signalling related to the semi-persistent resource allocation is causing the user
equipment to deactivate the semi-persistent resource allocation. The receiver of the user
equipment is adapted to receive control signalling related to the semi-persistent resource
allocation from an eNode B, wherein the control signalling is yielding a transport block
size for the semi-persistent resource allocation. Furthermore, the user equipment
comprises a processing unit for deactivating the semi-persistent resource allocation, if
the transport block size indicated in the control signalling matches the transport block
size indicated in the RRC message.
In a variation, the control signalling is comprising a resource allocation field value that is
indicating the number of resource blocks allocated to the user equipment and a
modulation and coding scheme index that is indicating a modulation and coding scheme,
and the user equipment's processing unit is further adapted to determine said transport
block size yielded by the control signalling based on the resource allocation field value
and the modulation and coding scheme index.
Another embodiment of the invention is related to an eNode B for use in an LTE-based
mobile communication system, comprising a transmitter for transmitting a RRC message
to a user equipment for configuring a semi-persistent resource allocation, wherein the
RRC message is indicating a transport block size that when yielded by control signalling
related to the semi-persistent resource allocation is causing the user equipment to
deactivate the semi-persistent resource allocation, a scheduler for generating control
signalling related to the semi-persistent resource allocation and yielding the transport
block size indicated by said RRC message, and a transmitter for transmitting the control
signalling to the user equipment to thereby cause the user equipment to deactivate the
semi-persistent resource allocation.
In a further embodiment, the invention is providing a computer readable medium storing
instructions that when executed by a processor of a user equipment cause the user
equipment to deactivate a semi-persistent resource allocation in an LTE-based mobile
communication system, by receiving a RRC message configuring the semi-persistent
resource allocation and indicating a transport block size that when indicated in control
signalling related to the semi-persistent resource allocation is causing the user
equipment to deactivate the semi-persistent resource allocation, receiving control
signalling related to the semi-persistent resource allocation from an eNode B, wherein
the control signalling is yielding a transport block size for the semi-persistent resource
allocation, and deactivating the semi-persistent resource allocation, if the transport block
size indicated in the control signalling matches the transport block size indicated in the
RRC message.
In a variation of this embodiment, the control signalling is comprising a resource
allocation field value that is indicating the number of resource blocks allocated to the
user equipment and a modulation and coding scheme index that is indicating a
modulation and coding scheme, and the computer readable medium is further storing
instructions that when executed by the processor of the user equipment cause same to
determine the transport block size yielded by the control signalling based on the resource
allocation field value and the modulation and coding scheme index.
Another embodiment is related to a computer readable medium storing instructions that
when executed by a processor of an eNode B, cause the eNode B to deactivate a semi-
persistent resource allocation of a user equipment by transmitting a RRC message to the
user equipment for configuring the semi-persistent resource allocation, wherein the RRC
message is indicating a transport block size that when yielded by control signalling
related to the semi-persistent resource allocation is causing the user equipment to
deactivate the semi-persistent resource allocation, generating control signalling related to
the semi-persistent resource allocation and yielding the transport block size indicated by
said RRC message, and transmitting the control signalling to the user equipment to
thereby cause the user equipment to deactivate the semi-persistent resource allocation.
BRIEF DESCRIPTION OF THE FIGURES
In the following, the invention is described in more detail in reference to the attached
figures and drawings. Similar or corresponding details in the figures are marked with the
same reference numerals.
Fig. 1 shows an exemplary high level architecture of a 3GPP LTE system,
Fig. 2 shows an exemplary overview of the E-UTRAN of the high level
architecture of a 3GPP LTE system in Fig. 1,
Fig. 3 shows an exemplary allocation of radio resources of an OFDM channel in
localized transmission mode,
Fig. 4 shows an exemplary allocation of radio resources of an OFDM channel in
distributed transmission mode,
Fig. 5 shows an exemplary format of a resource assignment message (PDCCH)
for allocating uplink resources to a mobile terminal,
Fig. 6 shows an exemplary signaling procedure for activating an uplink semi-
persistent resource allocation between a user equipment (UE) and an
eNode B according to an exemplary embodiment of the invention,
Fig. 7 and 8 show different exemplary signaling procedure for deactivating an uplink
semi-persistent resource allocation between a user equipment (UE) and
an eNode B according to exemplary embodiments of the invention,
Fig. 9 and 10 show flow charts of the basic operation of the Physical layer entity and
the MAC-iayer entity of a user equipment according to exemplary
embodiments of the invention to realize a deactivation of semi-persistent
scheduling,
Fig. 11 shows a flow chart of the basic operation of the Physical layer entity, the
MAC-layer entity and the RRC entity in a user equipment according to
exemplary embodiments of the invention to realize a deactivation of semi-
persistent scheduling, and
Fig. 12 and 13 show exemplary RRC message formats for configuring a semi-persistent
scheduling according to exemplary embodiments of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The following paragraphs will describe various embodiments of the invention. For
exemplary purposes only, most of the embodiments are outlined in relation to an
(evolved) communication system according to LTE discussed in the Technical
Background section above.
One aspect of the invention is to use (existing) physical control channel signaling related
to a semi-persistent scheduling for deactivating the semi-persistent resource allocation to
a user equipment (or in other words releasing the grant for the semi-persistent resource
allocation) by defining a special combination of control channel signaling values as a
deactivation command for the semi-persistent resource allocation. More specifically, the
physical control channel signaling may be a resource assignment related to the semi-
persistent resource allocation that is commonly used to allocate or reallocate radio
resources to the user equipment for the semi-persistent resource allocation. The control
signaling, respectively the resource assignment information is assumed to contain a New
Data Indicator and a modulation and coding scheme field. A special combination of the
New Data Indicator value and a modulation and coding scheme index, which is signalled
within the modulation and coding scheme field, is defined to indicate the deactivation of
the semi-persistent resource allocation (or in other words releases a previous resource
assignment (grant) for the semi-persistent resource allocation).
According to one embodiment of the invention, a semi-persistent resource allocation in
an LTE-based mobile communication system is deactivated by the eNode B generating
special control signalling information (e.g. a resource assignment) for the user equipment
that is containing a predetermined combination of a New Data Indicator value and a
modulation and coding scheme index that is to cause the user equipment to deactivate
the semi-persistent resource allocation. The eNode B signals this control signalling
information to the user equipment, which is receiving the control signalling information
and processes it. If the user equipment detects the control signalling information to
contain a predetermined combination of a New Data Indicator value and a modulation
and coding scheme index, the user equipment is deactivating the semi-persistent
resource allocation.
There are different possibilities how to define the predetermined combination (or
combinations) of a New Data Indicator value and a modulation and coding scheme index
that are to release the grant for a semi-persistent resource allocation - which can be also
referred to as a resource release command. In one example, the modulation and coding
scheme index in the resource assignment is indicating no transport block size while the
New Data Indicator is indicating an activation of semi-persistent scheduling i.e. is set to
0. As no initial data transmission can be sent/received properly without having
knowledge of the transport block size, a modulation and coding scheme index indicating
no transport block size is typically unused for a resource assignment or reassignment in
connection with semi-persistent scheduling and can therefore be used as a resource
release command.
Another possibility to communicate a resource release command for a semi-persistent
resource allocation is to indicate a change in the transport block size for a retransmission
of a semi-persistently scheduled data packet, which is especially applicable to scenarios
where HARQ in combination with soft-combining is used. In order to allow soft combining
of different transmissions of a data packet, their transport block size needs to be
constant throughout the transmission of the data packet (i.e. for the initial transmission
and all retransmissions). If a change in the transport block size is signalled for a
retransmission (i.e. the resource allocation in terms of the number of resource blocks
allocated for the transmission and the modulation and coding scheme index is resulting
in another transport block size), the user equipment could interpret this combination of
the New Data Indicator value being 1 and the changing transport block size to instruct a
deactivation of the semi-persistent resource allocation.
The two alternative implementations described above may however have one drawback:
The resource release command is not allocating any resources to the user equipment so
that it can only be used to release the grant for the semi-persistent resource allocation.
An alternative solution and aspect of the invention which would overcome such potential
drawback is to adapt the RRC signaling procedure for configuring the semi-persistent
resource allocation. In this alternative solution, the RRC signaling is indicating a special
transport block size to the user equipment that, when indicated in a resource assignment
for the semi-persistent resource allocation is commanding the user equipment to
deactivate the semi-persistent resource allocation.
Hence, when signaling a resource assignment indicating this specifically designated
transport block size (i.e. the number of resource blocks allocated for the transmission
according to the resource allocation field of the resource assignment and the modulation
and coding scheme index thereof is resulting in the specially designated transport block
size), the user equipment may still use the resource assignment for
transmission/reception and will further deactivate the semi-persistent resource allocation
for future transmissions/receptions. However, a potential drawback of this solution in
comparison to using a special combination of the New Data Indicator value and
modulation and coding scheme index may be that this solution would require changes to
the RRC control signalling specification.
Nevertheless, both solutions discussed above do not impact the user equipment's
operation concerning the handling of resource assignments (grants) and do therefore
also not impact the interface between Physical layer and MAC layer as presently defined
by the 3GPP.
Next the different aspects of the invention will be outlined in further detail below under
reference to a LTE-based mobile communication system using semi-persistent
scheduling as outlined in the Technical Background section. Fig. 6 shows an exemplary
signaling procedure for activating an uplink semi-persistent resource allocation between
a user equipment (UE) and an eNode B according to an exemplary embodiment of the
invention. As indicated above, semi-persistent scheduling is configured using RRC
signalling between a user equipment and an eNodeB (not shown in Fig. 6). More
specifically, the configuration of the semi-persistent resource allocation via RRC
signalling configures the periodicity (SPS interval in Fig. 6) of the semi-persistent
resource allocation, i.e. the periodic time instances the user equipment is to receive data
on the physical downlink shared channel (PDSCH) or transmit data on the physical
uplink shared channel (PUSCH). By convention, the transmission occurring to/from the
user equipment at the indicated periodic time instances are initial transmissions of data.
Retransmission for semi-persistently scheduled initial transmissions are either indicated
by a PDCCH, i.e. explicitly scheduled or - for the uplink case - could be also triggered
by a NACK in order to request a non-adaptive retransmission.
Furthermore it should be noted that a PDCCH scheduling a SPS retransmission, the
CRC of the PDCCH is also masked with the SPS C-RNTI. The distinction between
(re)activation of semi-persistent scheduling and SPS retransmissions is done based on
the NDI. For example a NDI bit value set to 0 indicates an activation of semi-persistent
allocation, whereas a NDI bit value set to 1 indicates a retransmission.
The actual activation of semi-persistent scheduling is realized by sending a PDCCH
including a resource allocation to the user equipment in which the NDI value is set to 0
(SPS PDCCH). The NDI bit value set to 0 in connection with the resource allocation
related to semi-persistent scheduling activates (or reactivates, i.e. overwrites the grant of
a previous activation) the semi-persistent scheduling - given that a valid transport block
size is signalled by the SPS PDCCH. The resource allocation is protected by a CRC field
masked with an RNTI specifically assigned to the user equipment for control signalling
procedures related to the semi-persistent scheduling of uplink or downlink resources,
such as the SPS C-RNTI of the user equipment. In case the CRC field of a PDCCH
(respectively, the content of the PDCCH) is being masked with the SPS C-RNTI of the
user equipment this means that the PDCCH control information is for semi-persistent
scheduling of this user equipment.
The PDCCH including the resource allocation is granting physical channel resources to
the user equipment, same will periodically use for transmissions/reception of data via
PUSCH/PDSCH that is scheduled on a semi-persistent basis. Accordingly, the user
equipment stores the content of the resource allocation on the PDCCH (and updates
thereof). As mentioned above, the eNode B may or may not send a dynamic grant for
retransmission of a semi-persistently scheduled initial transmission of data. If a dynamic
grant for the SPS retransmission is sent 601, the user equipment obeys same,
otherwise, if no dynamic grant is sent 602 the user equipment uses the already granted
physical resources used for the previous transmission of the packet for the
retransmission, i.e. non-adaptive retransmission.
Fig. 7 shows an exemplary signaling procedure for deactivating an uplink semi-persistent
resource allocation between a user equipment and an eNode B according to an
exemplary embodiment of the invention. For exemplary purposes it is assumed that a
uplink semi-persistent resource allocation has been configured before, for example as
shown in Fig. 6. In this exemplary embodiment of the invention, it is assumed that the
eNode B sends a PDCCH for the semi-persistent resource allocation of the user
equipment, here a SPS UL PDCCH (deactivation), that is containing a special
combination of NDI bit value and the modulation and coding scheme index comprised
therein - see Fig. 5. In this exemplary embodiment, in order to signal an explicit release
of uplink SPS resources, the eNode B sends a PDCCH for semi-persistent scheduling
(re)activation (SPS UL PDCCH (deactivation)) which does not provide any transport
block size information. This will be interpreted by the user equipment as a command to
release the semi-persistent scheduling resources, i.e. to deactivate the semi-persistent
scheduling (e.g. until the next activation is received). Furthermore, it should be noted that
the PDCCH for deactivating the semi-persistent resource allocation can be sent at any
time instant, e.g. in response to the eNode B detecting a no-speech period in VoIP
communication transmitted using semi-persistent scheduling.
In a more specific exemplary embodiment of the invention, it is assumed that the
modulation and coding scheme field (MCS index) is defined as in 3GPP TS 36.213,
section 8.61 (see Table 8.6.1-1) for the uplink, shown in Table 1 below:

For the uplink, a PDCCH indicating a modulation and coding scheme index (lMcs)
between 29 and 31 is indicating no transport block size information (TBS Index) and is
commonly not used for (re)activation of semi-persistent scheduling. According to this
exemplary embodiment, for signaling an explicit SPS resource release command, the
eNode B signals an uplink resource assignment the CRC of which is masked with SPS
C-RNTI (SPS UL PDCCH) with the NDI bit set to 0, in order to indicate activation of
semi-persistent scheduling, and a modulation and coding scheme index equal to 29, 30
or 31. According to this embodiment, one (or more) of modulation and coding scheme
indices 29 to 31 is interpreted by the user equipment to deactivate the uplink semi-
persistent resource allocation (i.e. to release the currently valid SPS grant) in case of an
uplink PDCCH addressed with SPS C-RNTI and NDI bit set to 0 is received. This is
exemplarily illustrated in the modified excerpt of Table 1 below:

In case semi-persistent scheduling has not been activated before, the user equipment
ignores the received SPS UL PDCCH.
The user equipment can distinguish between an SPS deactivation for a downlink semi-
persistent resource allocation and an uplink semi-persistent resource allocation based on
the DCI format of the PDCCH. For example, the DCI format 0 as specified in 3GPP TS
36.213 is used in order to signal an uplink SPS resource release, whereas DCI format 1
or 1A as specified in 3GPP TS 36.213 is used for a downlink SPS resource release.
In this connection it should be also noted that the definition of the modulation and coding
scheme field for downlink transmissions is slightly differing from the definition for the
uplink as shown in Table 1 above. For downlink transmissions, the indices of the
modulation and coding scheme field are defined as shown in section 7.1.7.1 of 3GPP TS
36.213 (see Table 7.1.7.1-1) which is shown below:

Similar to the example for UL PDCCHs, the user equipment is interpreting one (or more)
of the modulation and coding scheme indices 29 to 31 as a deactivation command for
the downlink semi-persistent resource allocation (i.e. to release the currently valid SPS
grant) in case of a DL PDCCH addressed with SPS C-RNTI and NDI bit set to 0 is
received. Accordingly, in a further exemplary embodiment the definitions of Table 3
above are redefined as follows:

In a further embodiment of the invention, the three MCS indices 29, 30 and 31 shown in
Tables 1 and 3 above are reused to identify whether the uplink, downlink, or uplink and
downlink resources of the semi-persistent resource allocation should be released.
Accordingly, one possible definition of the meaning of the modulation and coding scheme
indices 29 to 31 in an uplink and/or downlink SPS PDCCH with the NDI bit set to 0 could
be defined as follows:

One benefit of this exemplar/ embodiment may be seen in that only one DCI format of
the PDCCH needs to be used for the SPS deactivation signaling for the downlink as well
as for the uplink direction, in comparison to the embodiments discussed with respect to
Tables 1 to 4 above, where the user equipment distinguished uplink and downlink SPS
deactivation based on the PDCCH's DCI format.
For example, the smallest DCI format, i.e. smallest PDCCH payload size, could be used
for the SPS release indication, which would improve the radio efficiency. Alternatively the
DCI format allowing the most possible "virtual CRC" bits can be used in order to reduce
the false release probability.
Generally, since the CRC field of a PDCCH indicating a release of SPS resource is
masked with the SPS C-RNTI of the addressed user equipment and the NDI bit of the
PDCCH is set to zero, a PDCCH indicating a SPS release can be seen as a special SPS
activation PDCCH. As already mentioned, the activation of SPS is indicated by a PDCCH
addressed to the UE's SPS C-RNTI with the NDI bit set to zero. Basically, an "SPS
release" PDCCH can be understood as an "SPS activation" PDCCH with the MCS field
set to some reserved predetermined MCS indice(s), e.g. MCS indices 29 to 31.
Expressed in another way, a SPS release indication can be seen as an SPS activation
indication providing no Transport bbck size information.
Therefore, the embodiments of the invention may be advantageously combined with
several techniques aiming at reducing the false SPS activation rate that are currently
under discussion within 3GPP for the SPS activation (see the Technical Background
section above). One means to lower the false alarm rate to an acceptable level is to
extend to CRC length virtually by setting fixed and known values/indices to some of the
PDCCH fields that are not useful for semi-persistent scheduling.
Generally, the virtual CRC extension that can be applied to an SPS activation PDCCH is
also applicable to the SPS resource release PDCCH so as to lower the false alarm rate
of a UE falsely considering a PDCCH to be destined to itself. In more detail, the length of
the 16-bit CRC field of the PDCCH indicating a release of SPS resources can be virtually
extended by setting fixed and known values to some of the PDCCH fields that are not
useful for semi-persistent scheduling activation respectively release. For instance, for a
UL PDCCH indicating the release of DL SPS resource the TPC field can be set to "00"
and/or the cyclic shift DM RS field can be set to "000", for a DL PDCCH indicating the
release of DL SPS resources the HARQ process ID field can be set to "000" and the RV
field can be set to "00". Similarily the Resource allocation field within a PDCCH indicating
a release of SPS resources can be set to a fixed predetermined value.
The UE can verify a received PDCCH with the CRC masked by the Semi-Persistent C-
RNTI, and when the new data indicator field is set to zero, as a valid SPS release
indication by checking that these fields which are used for the virtual CRC extension are
set to the correct values. Only if the UE verified the received downlink control information
on the PDCCH as a valid semi-persistent release indication, the UE releases the
configured SPS resources. Thereby, the probability of a falsely received PDDCH
indicating SPS release can be lowered in the same way as for the SPS activation. Hence
the average time of false semi-persistent scheduling releases can be significantly
increased.
It should be noted that the term DL PDCCH is used here to indicate a PDCCH with a DCI
format used for PDSCH scheduling like for example DCI format 1 or 1A or 2. In the same
way, the term UL PDCCH should be understood as a PDCCH with a DCI format used for
scheduling PUSCH, like for example DCI format 0.
Next, the operation of Physical Layer and MAC Layer upon reception of a SPS PDCCH
according to different embodiments of the invention will be described in further detail.
Please note that in the following a distinction between an uplink SPS resource release
and a downlink SPS resource release is made only where appropriate. Generally, the
explanations are equally applicable to the processing of SPS UL PDCCH and SPS DL
PDCCH, unless indicated otherwise. Furthermore, the description of Fig. 9 and Fig. 10
below assume for exemplary purposes only that the PDCCH comprises a resource
assignment as shown in Fig. 5.
Fig. 9 shows an exemplary handling of a received PDCCH at the Physical Layer and the
MAC Layer of a user equipment. In this context, it should be noted that the flow chart of
Fig. 9 is only illustrating the most important steps in view of the concept of the invention.
Obviously, as will be partly explained in more detail below, further steps may be
performed as required to properly process a PDCCH at the user equipment.
The user equipment first receives 901 a PDCCH and checks 902 whether or not the
PDCCH is comprising a CRC field masked with an SPS C-RNTI of the user equipment. If
not, i.e. the PDCCH's CRC is masked with a C-RNTI, the user equipment processes 903
the PDCCH as a dynamic grant for scheduled transmissions/receptions. In case the
PDCCH is addressed to the user equipment with its SPS C-RNTI, the Physical layer
entity of the user equipment is checking 904 the NDI bit value. If the NDI bit value is
equal to 1, the SPS PDCCH is for a retransmission of semi-persistently scheduled data
and is processed 905 accordingly.
If the NDI bit is equal to 0, i.e. the PDCCH is an SPS (re)activation, the Physical layer
entity of the user equipment further processes other PDCCH fields like the modulation
and coding scheme field (MCS field).
In this exemplary embodiment, if a modulation and coding scheme index of 29 or higher
is signaled and the SPS PDCCH is for uplink semi-persistent scheduling, the redundancy
version (RV) is for example set to 1 for modulation and coding scheme index 29 (see
Tables 1 and 2 above) and the transport block size is set to "undefined", i.e. no indication
of transport block size.
Consequently the Physical layer entity of the user equipment reports 909 an received UL
PDCCH addressed to the SPS C-RNTI with NDI bit equals 0, RV=1 and transport block
size= "undefined" to the MAC layer entity of the user equipment. The MAC layer entity is
generally responsible for the scheduling and thus also handles SPS related operations.
In case the reception of an UL PDCCH addressed with SPS C-RNTI, NDI = 0, RV=1 and
TB size = "undefined" is reported from the Physical layer entity, the MAC layer entity
detects 910 the uplink SPS resource release based on the missing transport size
information for an SPS activation PDCCH. Accordingly, the user equipment deletes the
stored grant for the semi-persistent resource allocation and stops transmitting
(respectively receiving) data according to the semi-persistent resource allocation.
In case the Physical layer entity is detecting a modulation and coding scheme index
smaller than 29 being signaled in the SPS PDCCH, the Physical layer determines the
is introduced. Basically, the CRC of a SPS activation PDCCH is masked with this
additional identity which is in the following referred to as SPS C-RNTI. The size of the
SPS C-RNTI is also 16 bits, same as the normal C-RNTI. Furthermore the SPS C-RNTI
is also user equipment-specific, i.e. each user equipment configured for semi-persistent
scheduling is allocated a unique SPS C-RNTI.
*
In case a user equipment detects a semi-persistent resource allocation is activated by a
corresponding SPS PDCCH, the user equipment will store the PDCCH content (i.e. the
semi-persistent resource assignment) and apply it every semi-persistent scheduling
interval, i.e. periodicity signaled via RRC. As already mentioned, a dynamic allocation,
i.e. signaled on dynamic PDCCH, is only a "one-time allocation".
Similar to the activation of semi-persistent scheduling, the eNodeB also can deactivate
semi-persistent scheduling. There are several options how a semi-persistent scheduling
de-allocation can be signaled. One option would be to use PDCCH signaling, i.e. SPS
PDCCH indicating a zero size resource allocation, another option would be to use MAC
control signaling.
Reduction of SPS false activation
When the user equipment monitors the PDCCH for assignments, there is always a
certain probability (false alarm rate), that the user equipment falsely considers a PDCCH
destined to itself. Essentially, situations may occur where the CRC check of the PDCCH
is correct even though the PDCCH was not intended for this user equipment, i.e. CRC
passes even though there is a UE identifier (UE ID) mismatch (unintended user). These
so-called "false alarm" might occur, if the two effects of transmission errors caused by
the radio channel and UE ID mismatch cancel each other. The probability of a falsely
positive decoded PDCCH depends on the CRC length. The longer the CRC length, the
lower the probability that a CRC-protected message is erroneously decoded correctly.
With the CRC size of 16 bit the false alarm probability would be 1.5e-05. It should be
noted that due to the introduction of a separate identity for the discrimination of dynamic
PDCCHs (dynamic C-RNTI) and SPS PDCCHs (SPS C-RNTI), false alarms are even
more frequent.
On the first glance the probability might appear to be sufficiently low, however the
impacts of a falsely positive decoded semi-persistent scheduling PDCCH are quite
severe as will be outlined in the following. Since the effects are in particular for uplink
signaled transport block size from the modulation and coding scheme index and the
number of allocated resource blocks in the resource assignment (RA) field, and provides
907 an indication on the reception of an SPS PDCCH together with the determined
transport block size, NDI=0, and the signaled redundancy version to the MAC layer entity
of the user equipment, which stores the information provided by the Physical layer entity
and (re)actives the semi-persistent resource allocation.
The procedure for a downlink SPS resource release can be implemented in a similar
manner. However in this case a SPS DL PDCCH with modulation and coding scheme
index of 29 would indicate an explicit modulation order (see Tables 3 and 4 above)
instead of an RV like for the uplink. Also for the downlink case, the transport block size
would be "undefined" for a modulation and coding scheme index of 29 or higher, which
would be reported to MAC layer entity in a similar fashion as explained above. The MAC
layer entity detects an SPS resource release for a downlink semi-persistent resource
allocation based on the missing transport block size information delivered from Physical
layer entity for the received SPS DL PDCCH.
It should be noted that the exemplary embodiments discussed with respect to Fig. 9
above assume that a modulation and coding scheme index of 29 being sent in a SPS
UL/DL PDCCH with a NDI bit value set to 0 is triggering the deactivation of the semi-
persistent resource allocation. It is to be noted that also the modulation and coding
scheme index of 30 or 31 could be used instead, or as shown in Table 5, each of the with
modulation and coding scheme indices 29, 30 and 31 could trigger a respective
deactivation of an uplink, downlink or uplink & downlink semi-persistent resource
allocation.
Another alternative exemplary handling of a received PDCCH at the Physical Layer and
the MAC Layer of a user equipment is shown in the flow chart of Fig. 10. In the
embodiments discussed so far SPS release signaling has assumed that a SPS activation
PDCCH is used where the NDI bit value is set 0. In this exemplary embodiment a
PDCCH assigning a SPS retransmission, i.e. the NDI bit value is set to 1, indicates a
explicit release of SPS resources. For retransmissions the transport block size needs to
be constant for the all transmissions of a data packet, i.e. its initial transmission and all
retransmissions, if a HARQ protocol using soft combining is used - otherwise no soft
combining would be possible. The case where the transport block size signaled within a
PDCCH for a SPS retransmission differs from the transport block size used for the initial
transmission could be interpreted as an SPS resource release. In the dynamic
the related SPS grant for the semi-persistent resource allocation and is deactivating the
transmission of semi-persistently scheduled data.
Generally, it should be noted that upon uplink SPS deactivation, the user equipment is
not transmitting any data (This is commonly referred to a user equipment making a
Discontinued Transmission (DTX)). Upon receiving a downlink SPS deactivation, there
are several alternatives how the user equipment could react. For example, the user
equipment could not decode the PDSCH in response to a received PDCCH indicating a
DL SPS resource release (downlink data is sent on the PDSCH within the same TTI as
the corresponding PDCCH) and would consequently transmit no ACK or NACK in the
uplink, i.e. DTX of HARQ feedback, or could alternatively acknowledge the reception of
the PDCCH by sending an acknowledgement (ACK) for the PDCCH to the eNode B.
In particular, in prior art systems like the current specified LTE-based mobile
communication system the transmission of HARQ ACKs and NACKs on the uplink is only
foreseen for transport blocks of the shared channel PDSCH corresponding to the
PDCCH. The PDCCH itself cannot be acknowledged with an ACK or NACK message.
Therefore, the DL SPS release message encoded into the DL PDCCH cannot be
acknowledged in the prior art. It should be noted that the term DL PDCCH is used here,
to indicate a PDCCH with a DCI format used for PDSCH scheduling like for example DCI
format 1 or 1A or 2. In the same way, the term UL PDCCH should be understood as a
PDCCH with a DCI format used for scheduling PUSCH, like for example DCI format 0.
However, according to an embodiment of the invention, a DL PDCCH indicating a
release of DL SPS resources is acknowledged by the UE by means of sending an HARQ
ACK in response thereto to the eNB. The possibility of acknowledging a DL PDCCH
increases the reliability of the SPS release mechanism, since it is possible for the eNB to
determine whether the UE has correctly received the SPS release instruction. In case
that the eNB detects no HARQ ACK in response to having sent a SPS release indication,
the eNB could repeat the DL PDCCH indicating the release of DL SPS resources.
As already mentioned, in prior art systems the HARQ receiver which resides in the UE
for the downlink direction acknowledges or doesn't acknowledge the correct reception,
respectively correct decoding, of a transport block received on the DL-SCH by sending
an HARQ ACK/NACK to the HARQ transmitting entity for the uplink direction which
resides in the eNB. The HARQ ACK/NACK is for example transmitted on an uplink
physical control channel (PUCCH) or could be also multiplexed with higher layer data on
the UL shared channel (UL-SCH).
Further details on the determination of the uplink resource for HARQ ACK/NACK can be
found in section 10.1 of 3GPP TS36.213 version 8.4.0.
The uplink resources for the HARQ ACK/NACK transmission are generally implicitly
assigned by the DL PDCCH indicating the corresponding scheduled downlink shared
channel transmission. As already outlined, when receiving a DL PDCCH indicating the
release of DL SPS resources there is no corresponding DL-SCH transmission, i.e. no
transport block is transmitted together with a DL PDCCH indicating a release of DL SPS
resources. The DL PDCCH is only commanding the release of the semi-persistent
scheduling resources but doesn't grant a physical channel resource for receiving a
transport block on the DL-SCH. Nonetheless, the UE could use the uplink resources
assigned for the HARQ ACK/NACK for a received transport block on the DL-SCH in
order to confirm/acknowledge the reception of a DL PDCCH indicating a release by
means of an HARQ ACK. Also the timing of the HARQ ACK confirming the reception of
the DL PDCCH indicating a release of SPS resources could be the same as for a
received transport block on DL-SCH.
The above embodiment applies for the downlink SPS release via the DL PDCCH. For the
uplink, in case the UL SPS release is transmitted via a UL PDCCH, it is not possible to
confirm the reception of the UL PDCCH indicating a release of uplink SPS resources by
an HARQ ACK in the same way as for the downlink case in order to achieve the same
reliability for the SPS release procedure. More specifically, for the case of UL
assignments there are no resources available for an HARQ ACK/NACK sent by the UE
on the uplink , since for the uplink direction the HARQ ACK/NACK is sent by the eNB in
the downlink. In detail, when the UE receives an UL assignment indicated by a PDCCH,
a transport block is transmitted in response thereto on the UL-SCH to the corresponding
eNB, that in turn acknowledges the reception/decoding of the transport block from the
UE by an HARQ ACK/NACK. Thus, the acknowledgment of the UL PDCCH would
require a completely new and complex UE behavior, which would hinder the
acknowledgment of any UL SPS release mechanism.
Another embodiment of the invention allows the use of a DL PDCCH for releasing also
UL SPS resources, thus enabling the acknowledgment of the reception of the PDCCH
indicating a release of UL SPS resources by acknowledging the DL PDCCH. In more
detail, the embodiment explained with reference to Table 5 introduced the possibility to
use the multiple MCS indices, e.g. 29, 30 and 31 in order to identify whether the uplink,
downlink or uplink & downlink SPS resources should be released. One benefit is that
only one DCI format for the PDCCH needs to be used to indicate the release of SPS
resources for downlink as well as for uplink direction, compared to other embodiments
(referring to description for Tables 1 to 4), where the UE distinguishes uplink and
downlink SPS deactivation/release based on the PDCCH's DCI format.
In one exemplary embodiment the release of DL SPS resources is indicated by a
PDCCH scheduling a PDSCH transmission having the CRC masked with the SPS C-
RNTI, the NDI bit set to zero and the modulation and coding scheme index equal to 31 or
respectively '11111' in binary notation. The release of uplink SPS resources is similarly
indicated by a PDCCH scheduling a PDSCH transmission having the CRC masked with
the SPS C-RNTI, the NDI bit set to zero and the modulation and coding scheme index
equal to 30 or respectively '11110' in binary notation.
Consequently, the DCI format could be for example 1, 1A or 2 when using the DL
PDCCH for releasing the DL SPS resources. In addition, when using DCI format 1 or 1A,
the DL PDCCH may further contain another MCS Index for indicating the UL SPS
resource release, e.g. MCS Index 29 in Table 5. As a result, the UL SPS resource
release indication can also be acknowledged by the UE through an HARQ ACK sent in
response to the received DL PDCCH indicating release of UL SPS resources, and thus
the same high reliability can be achieved for UL as for DL SPS deactivation.
Using the DCI format 1A in order to indicate UL as well as DL SPS resource release
would have the advantages, that a DCI format 1A can be decoded by each UE which is
configured by higher layers to decode PDCCHs with the CRC masked by the SPS C-
RNTI. Furthermore, the DCI format 1A is monitored by the mobile in the common search
space as well as in the UE-specific search irrespective of the downlink transmission
mode. Another advantage would be that the DCI format 1A denotes the DCI format with
the smallest payload which is used for semi-persistent scheduling related control
signalling. Details on the UE procedure related to monitoring of PDCCH for control
information can be found in section 9.1.1 of TS36.213 version 8.4.0.
One potential advantage of the embodiments discussed above, in particular with respect
to Figs. 7, 9 and 10, is that no changes to existing PDCCH fields as specified for LTE are
required and further, no adaption of the Physical layer-to-MAC layer interface in the user
equipments is required. Another potential advantage is that no changes to the grant
reception procedure in the user equipment are necessary. The Physical layer entity of
the user equipment can receive an UL/DL PDCCH and reports the received resource
assignment on the PDCCH together with the corresponding HARQ information to the
MAC layer entity. The user equipment's MAC layer entity can perform the necessary
operations for dynamically scheduled respectively semi-persistently scheduled
transmissions, i.e. HARQ operations, based on the received information from the
Physical layer entity.
In contrast, the solution discussed in the Technical Background section of introducing a
SPS resource allocation size of zero ("ORBs") to deactivate a semi-persistent resource
allocation would for example require that the Physical layer entity detects an SPS
resource release based on the "ORBs" indication within the resource allocation field and
reports this to MAC layer entity. This in turn requires a new inter-layer signaling between
Physical layer entity and MAC layer entity in the user equipment, since in the current LTE
standards, the MAC layer entity performs the scheduling operation, i.e. detecting of SPS
activation / retransmission / resource release and performing the corresponding actions,
as described above.
In the embodiments discussed above with respect to Figs. 7, 9 and 10, it has been
assumed that the modulation and coding scheme index that - in combination with the
value of the NDI - is indicating the deactivation of the semi-persistent resource allocation
is an index that is indicating no transport block size, i.e. which is not suitable for the
activation or reactivation of semi-persistent scheduling. However it should be noted that it
is not necessarily required to use only one of the modulation and coding scheme indices
for deactivating the semi-persistent scheduling, that does not provide an transport block
size information, such as indices 29, 30 and 31 shown in Tables 1 to 5 above. It's
generally possible to reserve any arbitrary modulation and coding scheme index out of
the modulation and coding scheme indices representabie according to the given
modulation and coding scheme field size (e.g. 5 bits resulting in 32 indices), in order to
indicate a SPS resource release. Obviously the selected modulation and coding scheme
index may thus not be used for an SPS activation or reactivation.
The selection of a modulation and coding scheme index indicating a valid transport block
size may be nevertheless advantageous in connection with trying to reduce the
probability of a false SPS activation by setting fixed and known values to some of the
PDCCH fields. According to one exemplary embodiment of the invention only a limited
number of modulation and coding scheme indices out of the set of available indices
could be allowed for use in a PDCCH that is activating or reactivating semi-persistent
scheduling. For example, those "allowed indices" might be those modulation and coding
scheme indices the most significant bit of which is 0, so that allowed range of modulation
and coding scheme indices that can be used to activate or reactivate a semi-persistent
resource allocation is restricted to indices 0 to 15 when exemplarily considering a 5 bit
modulation and coding scheme field as exemplified in Tables 1 to 4 above. Any PDCCH
that is indicating SPS (re)activation (CRC is masked with SPS C-RNTI and the NDI bit
value is set to 0) and further indicating a modulation and coding scheme index outside
the allowed range - i.e. the indicated modulation and coding scheme index in the
PDCCH is > 15 - would be ignored by the user equipment's Physical layer entity, i.e. the
PDCCH is not reported to the MAC layer entity and is thus not activating semi-persistent
scheduling. According to this embodiment, one of the 16 modulation and coding scheme
indices allowed for the activation of semi-persistent scheduling would thus have to be
selected to indicate a deactivation of the semi-persistent scheduling. For example it
could be defined that the highest modulation and coding scheme index within the allowed
range of modulation and coding scheme indices used for a SPS (re)activation, indicates
an SPS resource release, e.g. modulation and coding scheme index 15. This would
however reduce the number of modulation and coding scheme indices which could be
effectively used for an SPS (re)activation.
Another option may be to allow only a subset of possible modulation and coding scheme
indices for the activation or reactivation of semi-persistent scheduling as discussed
above, but to use one or all other modulation and coding scheme indices invalid for the
activation of the semi-persistent scheduling as an explicit SPS resource release
indication. For example, if modulation and coding scheme indices 0 to 15 are defined
allowable for activating semi-persistent scheduling, the modulation and coding scheme
index of 16 could be used to command to the user equipment to release to
corresponding SPS resource. When comparing this option to the solution of defining one
of the modulation and coding scheme indices valid for SPS activation as a SPS resource
release indication, the advantage of this option is that the eNode B has more freedom in
choosing among indices can be used for SPS activation.
However, this embodiment and option may require a change to the Physical layer
operation of the user equipment and may also require further inter-layer communication
between the Physical layer entity and the MAC layer entity in the user equipment
depending on the implementation. As the MAC layer entity is only informed on the
transport block size signaled in the PDCCH, the MAC layer entity is not informed and
may not conclude on the actually signaled modulation and coding scheme index, as
different modulation and coding scheme indices may result in the same transport block
size depending on the number of resource blocks assigned to the user equipment.
Hence, the processing of the PDCCH in the Physical layer entity needs to be adapted to
detect that the PDCCH is signaling a SPS deactivation by checking the NDI bit value and
the modulation and coding scheme index in the SPS PDCCH.
Accordingly, the Physical layer entity could inform the MAC layer entity on a SPS
resource release by indicating an "undefined" transport block size to the MAC layer entity
in response to the NDI bit value in the PDCCH being set to 0 and a modulation and
coding scheme field includes a (predetermined) index which is for example an invalid
modulation and coding scheme index for SPS activation. This possibility would require
only a change to the processing of the PDCCH in the Physical layer entity, however no
new inter-layer communication between Physical layer and MAC layer is needed.
Alternatively, the Physical layer entity could explicitly inform the MAC layer entity on a
SPS resource release by introducing a respective inter-layer communication between
Physical layer entity and MAC layer entity in the user equipment.
Next, further embodiments of the invention according to the second aspect of the
invention will be discussed with respect to Figs. 8, 11, 12 and 13. In contrast to using a
predetermined combination (or combinations) of the NDI bit value and modulation and
coding scheme index (indices) to signal a SPS resource release, the following
embodiments discussed with respect Figs. 8, 11, 12 and 13 use a specially designated
transport block size that is indicating an SPS resource release to the user equipment.
The embodiments according to this alternative aspect of the invention may be
advantageously combined with several techniques aiming at reducing the false SPS
activation rate that are currently under discussion within 3GPP (see the Technical
Background section above). One means to lower the false alarm rate to an acceptable
level is to extend to CRC length virtually by setting fixed and known values/indices to
some of the PDCCH fields that are not useful for semi-persistent scheduling. Further,
another possibility used in one embodiment of the invention is to restrict the set of
transport block sizes, which is allowed for an SPS activation.
In the current LTE specification, semi-persistent scheduling is configured by RRC
signaling using a message, which includes semi-persistent scheduling related
parameters. This message includes the SPS periodicity (SPS Interval in Fig. 6) and - for
downlink semi-persistent scheduling operation - HARQ process information.
According to this exemplary embodiment, the RRC signaling message for configuring the
semi-persistent scheduling further includes information on allowed transport block sizes,
i.e. transport block sizes that may be used in connection with an SPS activation or
reactivation. Every time a PDCCH for SPS activation is received at the MAC layer entity,
the MAC layer entity checks whether the indicated transport block size in the PDCCH is
within the set of allowed transport block sizes, i.e. is a valid transport block size for SPS
activation. Since the transport block size signaled in a PDCCH depends on the number
of allocated resource blocks and the modulation and coding scheme, one alternative
would be to signal a minimum and maximum allowed transport block size within the SPS
configuration message to indicate a range of transport block sizes that can be used for
SPS activation or reactivation. All transport block sizes between this minimum and
maximum value would thus be valid transport block sizes for an SPS activation or
reactivation. It should be noted that there are also further alternative how to restrict the
allowed transport block sizes for a semi-persistent scheduling (re)activation, for example
by signaling via RRC the corresponding modulation and/or coding scheme indices and
resource allocation sizes resulting in valid transport sizes.
For the indication of an SPS resource release, the RRC protocol could be further
modified to include to the SPS configuration related parameters a predetermined
transport block size, which when signaled in a PDCCH is indicating a SPS resource
release. This transport block size is referred to as "release TBS" in the following. Fig. 12
exemplarily illustrates a SPS configuration message according to an exemplary
embodiment of the invention including a "release TBS" field that is indicating the
specified release TBS value.
Fig. 8 shows an exemplary signaling procedure for deactivating an uplink semi-persistent
resource allocation between a user equipment and an eNode B according to an
exemplary embodiment of the invention, where a RRC configured release TBS is used to
deactivate a semi-persistent resource allocation to the user equipment. In comparison to
the signaling in Fig. 7, it should be noted that the deactivation of semi-persistent
scheduling according to the exemplary embodiment in Fig 8 has the advantage that the
PDCCH is not only commanding the deactivation of the semi-persistent scheduling but
also grants a physical channel resource for receiving/transmitting a final data packet.
The signaling in Fig. 8 is essentially similar to that shown in Fig. 7. However, the SPS UL
PDCCH for deactivating the semi-persistent resource allocation (SPS UL PDCCH
(deactivation)) is yielding the release TBS by signaling a corresponding number of
allocated resource blocks and modulation and coding scheme index resulting in this
transport block size. As indicated above, a further difference to the signaling in Fig. 7 is
that the SPS UL PDCCH (deactivation) is not only triggering the deactivation of the semi-
persistent resource allocation at the user equipment but is so-to-say also providing at the
same time a dynamic grant for one further transmission using the resource allocation and
transport format signaled within the SPS UL PDCCH (deactivation) i.e. in this example
the uplink semi-persistent scheduling is deactivated upon having received the SPS UL
PDCCH (deactivation) and the UE is making one initial data uplink transmission
according to the uplink assignment signaled within the SPS UL PDCCH (deactivation)
(initial transmission with dynamic grant from SPS UL PDCCH (deactivation)) and
corresponding retransmissions, if any).
Although the example in Fig. 8 is related to uplink semi-persistent scheduling, it should
be noted that this concept may be equally applied to downlink semi-persistent
scheduling. In the latter case the SPS DL PDCCH (deactivation) will indicate a
downlink transmission on the resources and with the transport format as indicated in the
SPS DL PDCCH (deactivation) and furthermore the deactivation of the downlink semi-
persistent scheduling at the user equipment. For example the eNode B could signal a
release of semi-persistent scheduling and , at the same time, a RRC message for
releasing the bearer using the semi-persistently scheduled resources, i.e. a VoIP bearer.
Fig. 11 is showing a flow chart of the operation of Physical layer entity, MAC layer entity
and RRC entity within a user equipment according to another embodiment of the
invention in case a release TBS is used to indicate a SPS resource release to the user
equipment. Fig. 11 is not distinguishing between uplink semi-persistent scheduling and
downlink semi-persistent scheduling but the basic steps shown in the flow chart equally
apply to both scenarios.
As indicated above, semi-persistent scheduling of the user equipment is configured 1101
by means of a corresponding RRC configuration message as for example exemplarily
depicted in Fig. 12 or Fig. 13 that is sent by the serving eNode B. The RRC entity of the
user equipment is thus aware of the release TBS (TBSrelease) upon having received such
configuration message. The RRC entity provides 1102 the release TBS to the MAC layer
entity, which is storing 1103 the release TBS.
Upon reception 1104 of a POCCH at the Physical layer entity of the user equipment, the
Physical layer entity is checking 1105, whether the CRC field of the PDCCH has been
masked by the eNode B with a SPS C-RNTI of the user equipment, i.e. whether it is
destined to the user equipment and whether it is related to semi-persistent scheduling. In
case the PDCCH's CRC field is not masked with the SPS C-RNTI of the user equipment,
the Physical layer entity processes 1106 the PDCCH as a dynamic grant. Otherwise, the
Physical layer entity is checking 1107 next, whether the NDI bit value is set to 0 thereby
detecting whether the SPS PDCCH is relating to an activation respectively deactivation
of the semi-persistent scheduling or a retransmission of a semi-persistently scheduled
initial transmission. In case the SPS PDCCH is for a retransmission of a semi-
persistently scheduled initial transmission, the SPS PDCCH is further processed 1108
accordingly.
If the SPS PDCCH indicates an activation respectively deactivation of the semi-
persistent scheduling, the Physical layer entity is calculating 1109 the transport block
size (TBS) signaled in the SPS PDCCH and is reporting 1110 the transport block size,
the NDI and the redundancy version (RV) signaled in the SPS PDCCH to the MAC layer
entity. The MAC layer entity checks 1111, whether the SPS PDCCH indicates a transport
block size (TBS) that is equal to the release TBS (TBSrelease) in order to conclude,
whether the SPS PDCCH is signaling an activation or a deactivation of the semi-
persistent scheduling.
In case the MAC layer entity of the user equipment determines the transport block size
(TBS) signaled within the SPS PDCCH equals the release TBS, the MAC layer entity of
the UE will release 1113 the corresponding SPS resource and will deactivate the semi-
persistent scheduling. Furthermore, the user equipment processes the received SPS
PDCCH in a similar fashion as a dynamic assignment and transmits/receives a data
packet accordingly. Otherwise, the MAC layer entity is concluding that the SPS PDCCH
is signaling an activation of the semi-persistent scheduling. Accordingly, the MAC layer
entity will store/update 1112 the grant of the SPS PDCCH and (re)activate the semi-
persistent resource allocation.
The "release TBS" could be a transport block size outside the range of valid transport
block sizes for SPS activation (outside the range defined by min TBS and max TBS) or
could alternatively be a transport block size within the signaled transport block size range
allowed for SPS activation.
The release TBS approach described above in connection with Fig. 8, 11 and 12 has
one potential advantage over the above described solutions where a combination of NDI
bit value and modulation and coding scheme index has been used to signal a SPS
resource release. With the latter solution an entire PDCCH is required in order to
release SPS resources. There is no PDSCH respectively PUSCH allocation possible with
this type of release PDCCH, i.e. a release PDCCH that is signaling a predetermined
combination of NDI bit value and modulation and coding scheme index cannot be used in
order to allocate resource for an uplink transmission or downlink reception, since no
transport block size information can be provided by the PDCCH given that a modulation
and coding scheme index yielding no transport block size information is used in the
combination of NDI bit value and modulation and coding scheme index indicating the
SPS resource release.
In contrast thereto when defining a release TBS as described above, it is possible to
allocate PDSCH respectively PUSCH with the release PDCCH. As described above in
connection with Fig. 8, the user equipment when receiving a SPS PDCCH indicating the
release TBS UE will release the corresponding SPS resources and obey the assignment
signaled by the SPS PDCCH as in case a normal dynamic grant has been received. It
should be noted that even though the PDCCH is addressed with the SPS C-RNTI, the
user equipment acts as having received a dynamic resource assignment in parallel to the
SPS resource release indication. With respect to the PDCCH resource usage the
definition of a release TBS may be thus more efficient compared to the definition of a
"release combination" of NDI bit value and modulation and coding scheme index.
On the other hand, the definition of a release TBS will introduce changes to the RRC
message configuring the semi-persistent scheduling as the user equipment needs to be
informed on the release TBS. To avoid the overhead of the signaling overhead for
configuring the release TBS via the RRC message, the release TBS could be a
predefined value. Considering the exemplary RRC message format of Fig. 12, one option
could be that the "release TBS" field is removed and the release TBS for deactivating
semi-persistent scheduling is implicitly given, i.e. the "min TBS" field or the "max TBS"
field do not only indicate the valid range of transport block sized that is allowed for SPS
(re)activation but one of the two transport block sizes could also indicate the release
TBS.
Alternatively, considering that the available resource allocation sizes in terms of resource
blocks and available modulation and coding schemes for semi-persistent scheduling
yield a minimum or maximum transport block size that can be signaled in a PDCCH, the
smallest possible transport block size or the highest possible transport block size that
can be signaled in the PDCCH could implicitly indicate, i.e. define the release TBS. In
this alternative, the transport block size indicating the SPS resource release does not
necessarily lie within the range of the valid transport block sizes for an SPS activation.
Furthermore, similar to the example discussed with Table 5 above, also when defining a
release TBS for semi-persistent scheduling, individual release TBSs for uplink, downlink
and uplink&downlink semi-persistent scheduling could be defined. This is exemplarily
shown in Fig. 13, where the fields UL release TBS, DL release TBS and UL&DL release
TBS individually indicate the transport block size indicating a release of uplink, downlink
and uplink&downlink SPS resources, respectively. In this example, it is optionally further
possible to define that the SPS resources are only released in case same are indicated
in an SPS DL PDCCH or SPS UL PDCCH.
As a further variant of the second aspect of the invention where a release TBS is used
for indicated deactivation of semi-persistent scheduling, the RRC entity of the eNode B
could also signal one combination of modulation and coding scheme index and resource
allocation size instead of signaling a release TBS. The difference is that there are
potentially multiple combinations of modulation and coding scheme indices and resource
allocation size values which correspond to the same TB size. In this case the Physical
layer would be required to check for an SPS resource release, i.e. check whether the
RRC signaled combination of modulation and coding scheme index and resource
allocation size was received by a SPS PDCCH and inform MAC layer correspondingly.
In the flow charts of Figs. 9 to 11, it has been indicated that the Physical layer entity first
checks, whether the CRC field of the PDCCH is masked with the user equipment's SPS
C-RNTl or not. Of course, the Physical layer entity could also first check, whether the
CRC field of the PDCCH is masked with the user equipment's C-RNTI or not to
determine whether it is a dynamic grant and, if not, could subsequently check whether
the CRC field of the PDCCH is masked with the user equipment's SPS C-RNTI or not.
Another embodiment of the invention relates to the implementation of the above
described various embodiments using hardware and software. It is recognized that the
various embodiments of the invention may be implemented or performed using
computing devices (processors). A computing device or processor may for example be
general purpose processors, digital signal processors (DSP), application specific
integrated circuits (ASIC), field programmable gate arrays (FPGA) or other
programmable logic devices, etc. The various embodiments of the invention may also be
performed or embodied by a combination of these devices.
Further, the various embodiments of the invention may also be implemented by means of
software modules, which are executed by a processor or directly in hardware. Also a
combination of software modules and a hardware implementation may be possible. The
software modules may be stored on any kind of computer readable storage media, for
example RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD,
etc.
Furthermore, it should be noted that the terms mobile terminal and mobile station are
used as synonyms herein. A user equipment may be considered one example for a
mobile station and refers to a mobile terminal for use in 3GPP-based networks, such as
LTE.
In the previous paragraphs various embodiments of the invention and variations thereof
have been described. It would be appreciated by a person skilled in the art that
numerous variations and/or modifications may be made to the present invention as
shown in the specific embodiments without departing from the spirit or scope of the
invention as broadly described.
It should be further noted that most of the embodiments have been outlined in relation to
a 3GPP-based communication system and the terminology used in the previous sections
mainly relates to the 3GPP terminology. However, the terminology and the description of
the various embodiments with respect to 3GPP-based architectures are not intended to
limit the principles and ideas of the inventions to such systems.
Also the detailed explanations given in the Technical Background section above are
intended to better understand the mostly 3GPP specific exemplary embodiments
described herein and should not be understood as limiting the invention to the described
specific implementations of processes and functions in the mobile communication
network. Nevertheless, the improvements proposed herein may be readily applied in the
architectures described in the Technical Background section. Furthermore, the concept
of the invention may be also readily used in the LTE RAN currently discussed by the
3GPP.
WE CLAIM :
1. A method for deactivating a semi-persistent resource allocation in an LTE-based
mobile communication system, wherein a user equipment performs the steps of:
receiving via a control channel from a Node B control signalling that is including a
New Data Indicator and a modulation and coding scheme field, and
deactivating the semi-persistent resource allocation, if the New Data Indicator and
the modulation and coding scheme field of the control signalling signal a
predetermined combination of a New Data Indicator value and a modulation and
coding scheme index.
2. A method for deactivating a semi-persistent resource allocation to a user equipment
in an LTE-based mobile communication system, wherein a Node B performs the
steps of:
generating for the user equipment control signalling comprising a New Data Indicator
and a modulation and coding scheme field including a predetermined combination of
a New Data Indicator value and a modulation and coding scheme index that is
causing the user equipment to deactivate the semi-persistent resource allocation,
and
transmitting said control signalling via a control channel to the user equipment to
thereby cause the user equipment to deactivate the semi-persistent resource
allocation.
3. The method according to claim 1 or 2, wherein the predetermined combination of the
New Data Indicator value and the modulation and coding scheme index is the New
Data Indicator value being 0 and the modulation and coding scheme index indicating
no transport block size Information.
4. The method according to claim 1 or 2, wherein the predetermined combination of the
New Data Indicator value and the modulation and coding scheme index is the New
Data Indicator value indicating a retransmission of a data packet and the modulation
and coding scheme index indicating a transport block size to the user equipment that
is different to the transport block size of the initial transmission of the data packet.
5. The method according to one of claims 1 to 4, wherein the control signalling is
protected by a CRC field that is masked with an RNTI assigned to the user
equipment for identification in signalling procedures related to the semi-persistent
resource allocation.
6. The method according to claim 5, wherein at least one field of the control signalling
from the eNode B is set to a predetermined value, for validating said control
signalling as a semi-persistent resource deactivation indication.
7. The method according to claim one of claims 1 to 6, wherein the modulation and
coding scheme field indicates one of plural modulation and coding scheme indices,
and there is a subset of at least three indices that indicate no transport block size
information, and
wherein the user equipment is deactivating:
- a semi-persistent resource allocation for the uplink, in case a first predetermined
modulation and coding scheme index of said subset is indicated in the modulation
and coding scheme field,
- a semi-persistent resource allocation for the downlink, in case a second
predetermined modulation and coding scheme index of said subset is indicated in
the modulation and coding scheme field, and
- a semi-persistent resource allocation for the downlink and a semi-persistent
resource allocation for the uplink, in case a third predetermined modulation and
coding scheme index of said subset is indicated in the modulation and coding
scheme field.
8. The method according to claim 7, wherein said control signalling is downlink control
signalling from the eNode B used for scheduling of downlink transmissions and
includes the first predetermined modulation and coding scheme index for
deactivating the semi-persistent resource allocation for the uplink.
9. The method according to one of claims 1 to 8, wherein the reception of the control
signalling is acknowledged by the user equipment by transmitting an ACK message
to the eNode B.
10. The method according to one of claims 1 to 9, further comprising signalling from the
Node B to the user equipment an RRC message that indicates a periodicity of the
semi-persistent resource allocation and a range of allowable transport block sizes
that can be configured by a control channel signalled from the Node B to the user
equipment.
11. The method according to claim 10, wherein the RRC message further indicates
HARQ information on the HARQ process used for downlink transmissions to the user
equipment according to the semi-persistent resource allocation.
12. The method according to one of claims 1 to 11, wherein the modulation and coding
scheme field is indicating one of plural predetermined indices, wherein a non-empty
subset of the predetermined indices is used to jointly encode modulation scheme,
transport block size and redundancy version for an uplink data transmission, while
the remaining indices are used to encode only a redundancy version for an uplink
data transmission.
13. The method according to one of claims 1 to 11, wherein the modulation and coding
scheme field is indicating one of plural predetermined indices, wherein a non-empty
subset of the predetermined indices is used to jointly encode modulation scheme
and transport block size for a downlink transmission to be received by the user
equipment, while the remaining indices are used to encode only a modulation
scheme for a downlink transmission.
14. The method according to one of claims 1 to 13, wherein control channel is a PDCCH
and/or the control signalling is comprised is a resource assignment to the user
equipment.
15. A user equipment for use in an LTE-based mobile communication system
comprising:
a receiver for receiving via a control channel from a Node B control signalling that is
including a New Data Indicator and a modulation and coding scheme field, and
a processing unit for deactivating the semi-persistent resource allocation, if the New
Data Indicator and the modulation and coding scheme field of the control signalling
signal a predetermined combination of a New Data Indicator value and a modulation
and coding scheme index.
16. A Node B for use in an LTE-based mobile communication system comprising:
a scheduler for generating for the user equipment control signalling comprising a
New Data Indicator and a modulation and coding scheme field including a
predetermined combination of a New Data Indicator value and a modulation and
coding scheme index that is causing the user equipment to deactivate the semi-
persistent resource allocation, and
a transmitter for transmitting said control signalling via a control channel to the user
equipment to thereby cause the user equipment to deactivate the semi-persistent
resource allocation.
17. A computer readable medium storing instructions that when executed by a processor
of a user equipment cause the user equipment to deactivate a semi-persistent
resource allocation in an LTE-based mobile communication system, by:
receiving via a control channel from a Node B control signalling that is including a
New Data Indicator and a modulation and coding scheme field, and
deactivating the semi-persistent resource allocation, if the New Data Indicator and
the modulation and coding scheme field of the control signalling signal a
predetermined combination of a New Data Indicator value and a modulation and
coding scheme index.
18. A computer readable medium storing instructions that when executed by a processor
of a Node B, cause the Node B to deactivate a semi-persistent resource allocation of
a user equipment by:
generating for the user equipment control signalling comprising a New Data Indicator
and a modulation and coding scheme field including a predetermined combination of
a New Data Indicator value and a modulation and coding scheme index that is
causing the user equipment to deactivate the semi-persistent resource allocation,
and
transmitting said control signalling via a control channel to the user equipment to
thereby cause the user equipment to deactivate the semi-persistent resource
allocation.

The invention relates to a method for deactivating a semi-persistent resource allocation of a user equipment in an LTE-based mobile communication system. Furthermore, the invention also related to a user equipment and a eNode B implement ing this method. To provide a mechanism for deactivating a semi-persistent resource allocation in a LTE system which is not requiring any changes to the Physical layer-to-MAC layer interface and/or preferably no changes to the PDCCH formats agreed by the 3GPP a combination of NDI value and MCS index is defined that is commanding the release of SPS resources. Alternatively, another solution proposed to define a special transport block size that when signaled in a PDCCH is commanding the release of SPS resources.