Communications System, Infrastructure Equipment, Communications Devices and Method
Field of the Disclosure
The present invention relates to communications systems, infrastructure equipment, and
communications devices for communicating data, and methods of communicating data.
Background of the Disclosure
Third and fourth generation mobile telecommunication systems, such as those based on the
3GPP defined UMTS and Long Term Evolution (LTE) architecture are able to support more
sophisticated services than simple voice and messaging services offered by previous generations of
mobile telecommunication systems.
For example, with the improved radio interface and enhanced data rates provided by LTE
systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile
video conferencing that would previously only have been available via a fixed line data connection.
The demand to deploy third and fourth generation networks is therefore strong and the coverage area
of these networks, i.e. geographic locations where access to the networks is possible, is expected to
increase rapidly.
The anticipated widespread deployment of third and fourth generation networks has led to the
parallel development of a class of devices and applications which, rather than taking advantage of the
high data rates available, instead take advantage of the robust radio interface and increasing ubiquity
of the coverage area. Examples include so-called machine type communication (MTC) applications,
which are typified by semi-autonomous or autonomous wireless communication devices (i.e. MTC
devices) communicating small amounts of data on a relatively infrequent basis. Examples include socalled
smart meters which, for example, are located in a customer's house and periodically transmit
information back to a central MTC server data relating to the customers consumption of a utility such
as gas, water, electricity and so on.
Whilst it can be convenient for a terminal such as an MTC type terminal to take advantage of
the wide coverage area provided by a third or fourth generation mobile telecommunication network
there are at present disadvantages. Unlike a conventional third or fourth generation mobile terminal
such as a smartphone, an MTC-type terminal is preferably relatively simple and inexpensive. The type
of functions performed by the MTC-type terminal (e.g. collecting and reporting back data) do not
require particularly complex processing to perform. As such, certain classes of telecommunications
device, such as MTC devices, support "low capability" communication applications that are
characterised, for instance, by the transmission of small amounts of data at relatively infrequent
intervals. MTC devices are constructed so that individually they represent little burden on
telecommunications networks and thus can be deployed in greater numbers than equivalent "full
capability" terminals in the same networks.
In many scenarios, it is preferable to provide terminals dedicated to such "low capability"
communication applications with a simple receiver unit (or transceiver unit) having capabilities more
commensurate with the amount of data likely to be transmitted to (or from) the terminal.
To support MTC terminals, it has been proposed to introduce a "virtual carrier" operating
within a bandwidth of one or more "host carriers": the proposed virtual carrier concept preferably
integrates within the communications resources of conventional OFDM based radio access
technologies and subdivides frequency spectrum in a similar manner to OFDM. Unlike data
transmitted on a conventional OFDM type downlink carrier, data transmitted on the virtual carrier can
be received and decoded without needing to process the full bandwidth of the downlink OFDM host
carrier. Accordingly, data transmitted on the virtual carrier can be received and decoded using a
reduced complexity receiver unit: with concomitant benefits such as increased simplicity, increased
reliability, reduced form-factor and lower manufacturing cost.
However, when operating alongside each other the differing capabilities of conventional LTE
devices and MTC devices may lead to increased complexity resource allocation and scheduling.
Consequently, efficient operation of a wireless telecommunications system for MTC devices and
conventional and legacy LTE devices is therefore desirable.
Other examples of "low capability" devices include those devices with a smaller number of
receiving antennas than devices of "full capability" terminals and those devices with an ability to
process a smaller number of information bits in a given time span than "full capability terminals".
Typically, "full capability" and "low capability" may be determined by reference to the
specifications of a telecommunications network, and the specifications may make relative capability
explicitly or implicitly stated.
Summary of the Disclosure
According to an example embodiment of the present disclosure, there is provided a method of
transmitting data from a communications device to a mobile communications network or receiving
data from the mobile communications network at the mobile communications device includes
providing, by the mobile communications network, a wireless access interface, for transmitting and
receiving data to and from communications devices. The wireless access interface provides
communications resources within a system bandwidth and in time divided units providing
communications resources within the system bandwidth for allocating to communications devices of a
first type and a second type. The first type of the communications devices have a different capability
to the second type of communications devices. The method comprises generating, at the
communications device, a random access message, by selecting a sequence from a predetermined set
of sequences, which have been allocated to the communications devices of the second type and
transmitting the random access message from the communications device to the wireless
communications network. The predetermined sequences may be for example preamble signatures (a
bit sequence) and may include the same bits transmitted at a different frequency or time resource, so
that a sequence may be a resource region arrangement. The sequence is therefore arranged to identify
the communications device. The method further comprises in response to the random access
message, receiving a random access response at the communications device transmitted according to
the capability of the communications device of the second type, the random access message being
recognised as being from a communications device of the second type from the selected one of the
predetermined sequences allocated to the communications devices of the second type. According to
this method a mobile communications network can be arranged to differentiate between
communications devices of different types by allocating different sequences for use in forming the
random access messages between the different types of communications devices and therefore
respond to the random access message differently according to the capability of the communications
devices of the different types.
According to a conventional arrangement for transmitting data on an up-link of a wireless
access interface formed by a mobile communications network, a communications device is arranged
to request communications resources on the up-link by transmitting a random access request. In
response the mobile communications network transmits a random access response message in the
shared resource of the down link of the wireless access interface.
As indicated above, embodiments according to the present disclosure have been devise in
order to provide a mobile communications network to respond differently to communications devices
of different types by allocating different sets of sequences for forming random access messages to
devices of different types, so that in response to the random access message, the communications
network can recognise the devices of the different types and transmit a random access response
message in accordance with the type of the device. The type of the communications device may
represent a different capability of the device. For example, as indicated above the devices may have
a different maximum bandwidth of a communications channel in which signals are received, a
different minimum number of antennas available to the communications devices of the first type
compared with the communications devices of the second type or a different maximum rate of
processing information bits.
More generally by arranging for the different sets of sequences to be allocated to different
types of communications devices, the mobile communications network can partition the
communications resources of the system bandwidth between the communications devices of the
different types. Accordingly some of the communications resources of the system bandwidth may be
'hidden' from one of the types of the communications devices.
In one example the communications device of the second type may be a reduced capability
device, which is arranged to communicate via a virtual carrier. If the wireless access interface is
arranged to include a virtual carrier then any response to a random access message must be
transmitted within the shared resources of the virtual carrier. However if the mobile communications
network is not able to distinguish between conventional communications devices (legacy UEs) and
reduced capability devices (MTC UEs), then any and all responses to random access messages for all
communications devices must be transmitted within the resources of the virtual carrier. This would
then restrict the capacity of the mobile communications network to allocate the communications
resources of the wireless access interface for all communications devices (legacy and MTC type).
According to the present technique reduced capability devices (MTC UEs) are provided with
a predetermined subset of sequences, which form the preambles of random access messages. As such
the mobile communications network can respond to such random access messages from reduced
capability devices within the resources of the virtual carrier and respond to random access messages
to conventional/legacy devices within any of resources of the shared channel, thereby avoiding or at
least reducing any restriction of the network's ability to allocate communications resources.
In other examples the mobile communications network is arranged to configured the wireless
access interface so that communications resources for the communications device to transmit the
random access messages are adapted to the capability of the different types of communications
devices.
Various further aspects and embodiments of the disclosure are provided in the appended
claims, including, but not limited to, a communications device, infrastructure equipment and methods
of communicating data between a communications device and in infrastructure equipment.
Brief Description of the Drawings
Embodiments of the present disclosure will now be described by way of example only with
reference to the accompanying drawings wherein like parts are provided with corresponding reference
numerals and in which:
Figure 1 provides a schematic diagram illustrating an example of a conventional mobile
telecommunications network;
Figure 2 provides a schematic diagram illustrating a conventional 3GPP long term evolution
radio frame;
Figure 3 provides a schematic diagram illustrating an example of a conventional LTE
downlink radio sub-frame;
Figure 4 provides a schematic diagram illustrating a conventional LTE "camp-on" procedure;
Figure 5 provides a schematic diagram illustrating an LTE downlink radio sub-frame in which
includes a virtual carrier;
Figure 6 provides a diagram of an example RCC connection procedure in an LTE network;
Figure 7a provides an illustration of an LTE contention based access request procedure;
Figure 7b provides an illustration of an LTE non-contention based access request procedure;
Figure 8 is a simplified representation of a sub-frame of a down-link wireless access interface
corresponding to the example shown in Figure 3, showing a "T-shaped" virtual carrier;
Figure 9a is a schematic block diagram of a communications device according to the present
technique; and Figure 9b is a schematic block diagram of an adapted base station (eNodeB) according
to the present technique;
Figure 10 is an illustrative flow diagram providing an example operation of the
communications device and the base station of Figures 9a and 9b according to the present technique;
and
Figure 11 is a pictorial representation of sequences of resources which are used to form a
predetermined set of sequences for forming the random access message by a reduced capability
device according to an example of the present technique,
Figure 1 provides an example of resource reservation according to an example of the present
technique; and
Figure 13 provides an example of resource reservation accordingly to an example of the
present technique.
Detailed Description of Example Embodiments
Network Architecture
Figure 1 provides a schematic diagram illustrating a conventional mobile communications
system. The system includes a plurality of base stations 101 connected to a core network 102 where
the base stations and core network are arranged to provide a wireless radio interface. Each of the
plurality of base station provides a service area 103 and serves a plurality of communications devices
104 which are located within the service area 103. Each of the communications devices 104 within a
service area transmits and receives data to and from the base station 101 over a radio uplink and a
radio downlink respectively of the wireless interface. Correspondingly, each base station transmits
and receives data to and from the communications devices that are within its service area over the
radio downlink and radio uplink respectively. Data transmitted to the base stations 101 may be routed
to the core network 102 so that services such as for example voice calling, internet access,
authentication, mobility management and charging and so on may be provided. In some examples
Figure 1 may represent an LTE network and the base stations may be referred to as enhanced Node B
(eNodeB or eNB) and in other examples the base station and core network may be referred to
infrastructure equipment. In an LTE network the communications devices may also be referred to as
user equipment (UE), which may for example be mobile telephones, tablets, machine type
communications devices etc. However, in other examples the communications devices may be
referred to as mobile terminals and communications devices etc.
Mobile telecommunications networks or systems utilise a wide variety of different radio
interfaces, for example, 3GPP LTE utilises an Orthogonal Frequency Division Multiplexing (OFDM)
radio interface. OFDM operates by dividing the available bandwidth into a plurality of orthogonal sub
carriers and then dividing up this resource to form a predetermined structure which can convey data to
the communications devices in a system. In the downlink of an LTE system the available resources
are divided temporally into radio frames which last 10ms, with each frame comprising 10 subframes
which each last 1ms. The subframes of an LTE signal are then further divided into OFDM symbols
and resource blocks that comprise 1 subcarriers over a period of 0.5ms or 6 or 7 symbols. These
resource blocks form the physical channels of a LTE subframe which are used to carry data on the
downlink and the uplink.
Figure 2 shows a schematic diagram illustrating an OFDM based LTE downlink radio frame
201. The LTE downlink radio frame is transmitted from an LTE base station (known as an enhanced
Node B) and lasts 10 ms. The downlink radio frame comprises ten sub-frames, each sub-frame lasting
1 ms. A primary synchronisation signal (PSS) and a secondary synchronisation signal (SSS) are
transmitted in the first and sixth sub-frames of the LTE frame. A primary broadcast channel (PBCH)
is transmitted in the first sub-frame of the LTE frame. The PSS, SSS and PBCH are discussed in more
detail below.
Figure 3 provides a schematic diagram providing a grid which illustrates the structure of an
example of a conventional downlink LTE sub-frame. The sub-frame comprises a predetermined
number of symbols which are transmitted over a 1ms period. Each symbol comprises a predetermined
number of orthogonal sub-carriers distributed across the bandwidth of the downlink radio carrier.
The example sub-frame shown in Figure 3 comprises 14 symbols and 1200 sub-carriers
spaced across a 20MHz bandwidth. The smallest unit on which data can be transmitted in LTE is
twelve sub-carriers transmitted over one sub-frame. For clarity, in Figure 3, each individual resource
element is not shown, instead each individual box in the sub-frame grid corresponds to twelve subcarriers
transmitted on one symbol.
Figure 3 shows resource allocations for four LTE terminals 340, 341, 342, 343. For example,
the resource allocation 342 for a first LTE terminal (UE 1) extends over five blocks of twelve subcarriers,
the resource allocation 343 for a second LTE terminal (UE2) extends over six blocks of
twelve sub-carriers and so on.
Control channel data is transmitted in a control region 300 of the sub-frame comprising the
first n symbols of the sub-frame where n can vary between one and three symbols for channel
bandwidths of 3MHz or greater and where n can vary between two and four symbols for channel
bandwidths of 1.4MHz. For clarity, the following description relates to host carriers with channel
bandwidth of 3MHz or greater where the maximum value of n will be 3. The data transmitted in the
control region 300 includes data transmitted on the physical downlink control channel (PDCCH), the
physical control format indicator channel (PCFICH) and the physical HARQ indicator channel
(PHICH).
The PDCCH contains control data indicating which sub-carriers on which symbols of the subframe
have been allocated to specific LTE terminals. Thus, the PDCCH data transmitted in the control
region 300 of the sub-frame shown in Figure 3 would indicate that UE1 has been allocated the first
block of resources 342, that UE2 has been allocated the second block of resources 343, and so on. The
PCFICH contains control data indicating the size of the control region (i.e. between one and three
symbols) and the PHICH contains HARQ (Hybrid Automatic Request) data indicating whether or not
previously transmitted uplink data has been successfully received by the network.
In certain sub-frames, symbols in a central band 310 of the sub-frame are used for the
transmission of information including the primary synchronisation signal (PSS), the secondary
synchronisation signal (SSS) and the physical broadcast channel (PBCH). This central band 310 is
typically 72 sub-carriers wide (corresponding to a transmission bandwidth of 1.08 MHz). The PSS
and SSS are synchronisation signals that once detected allow the LTE terminal 104 to achieve frame
synchronisation and determine the cell identity of the enhanced Node B transmitting the downlink
signal. The PBCH carries information about the cell, comprising a master information block (MIB)
that includes parameters that the LTE terminals require to access the cell. Data transmitted to
individual LTE terminals on the physical downlink shared channel (PDSCH) can be transmitted in the
remaining blocks of resource elements of the sub-frame. Further explanation of these channels is
provided in the following sections.
Figure 3 also shows a region of PDSCH containing system information transmitted on a
broadcast channel and extending over a bandwidth of R344.
The number of sub-carriers in an LTE channel can vary depending on the configuration of the
transmission network. Typically this variation is from 72 sub carriers contained within a 1.4MHz
channel bandwidth to 1200 sub-carriers contained within a 20MHz channel bandwidth as shown in
Figure 3. As is known in the art, data transmitted on the PDCCH, PCFICH and PHICH is typically
distributed on the sub-carriers across the entire bandwidth of the sub-frame. Therefore a conventional
LTE terminal must be able to receive the entire bandwidth of the sub-frame in order to receive and
decode the control region.
Conventional Camp on Procedure
Figure 4 illustrates a conventional LTE "camp-on" process, which is the process followed by
a terminal so that it can decode downlink transmissions that are sent by a base station via a downlink
channel on a carrier band. Using this process, the terminal can identify the parts of the transmissions
that include system information for the cell and thus decode configuration information for the cell.
As can be seen in Figure 4, in a conventional LTE camp-on procedure, the terminal first
synchronizes with the base station (step 400) using the PSS and SSS in the centre band 310 of the
carrier as mentioned above. As can be seen with reference to Figure 3 the centre band 310 has a
bandwidth range R310, where the band is at the centre of the carrier (i.e. occupying the central subcarriers).
The terminal detects this centre band and detects the PSS and SSS which indicate the cyclic
prefix duration and the Cell ID. In LTE the PSS and SSS are only transmitted in the first and sixth
sub-frames of each radio frame. Of course, in a different system, for example a non-LTE system, the
band 310 may not be at the centre of the carrier band and may be wider or narrower than 72 subcarriers
or 1.08 MHz. Likewise, the sub-frames may be of a different size or sizes.
The terminal then decodes the PBCH (step 401), also carried on the centre band 310, where
the PBCH includes in particular the Master Information Block (MIB). The MIB indicates in
particular the bandwidth R32oof the downlink carrier, the System Frame Number (SFN), and the
PHICH configuration. Using the MIB carried on the PBCH, the terminal can then be made aware of
the bandwidth R32oof the carrier. Because the terminal also knows where the central band 310 is, it
knows the exact range R320 of the downlink carrier.
For each sub-frame, the terminal then decodes the PCFICH which is distributed across the
entire width of carrier 320 (step 402). As discussed above, an LTE downlink carrier can be up to 20
MHz wide (1200 sub-carriers) and an LTE terminal therefore has to have the capability to receive and
decode transmissions on a 20 MHz bandwidth in order to decode the PCFICH. At that stage, with a
20MHz carrier band, the terminal operates at a much larger bandwidth (bandwidth of R320) than
during steps 400 and 401 (bandwidth of R310) relating to synchronization and PBCH decoding.
The terminal then ascertains the PHICH locations (step 403) and decodes the PDCCH (step
404), in particular for identifying system information transmissions and for identifying its personal
allocation grants. The allocation grants are used by the terminal to locate system information and to
locate its data in the PDSCH. Both system information and personal allocations are transmitted on
PDSCH and scheduled within the carrier band 320. Steps 403 and 404 also require the terminal to
operate on the entire bandwidth R320 of the carrier band.
At steps 402 to 404, the terminal decodes information contained in the control region 300 of a
sub-frame. As explained above, in LTE, the three control channels mentioned above (PCFICH,
PHICH and PDCCH) can be found across the control region 300 of the carrier where the control
regions extends over the range R320 and occupies the first one, two or three OFDM symbols of each
sub-frame as discussed above. In a sub-frame, typically the control channels do not use all the
resource elements within the control region 300, but they are scattered across the entire region, such
that a LTE terminal has to be able to simultaneously receive the entire control region 300 for decoding
each of the three control channels.
The terminal can then decode the PDSCH (step 405) which contains system information or
data transmitted for this terminal.
As explained above, in an LTE sub-frame the PDSCH generally occupies groups of resource
elements which are neither in the control region nor in the resource elements occupied by PSS, SSS or
PBCH. The data in the blocks of resource elements 340, 341, 342, 343 shown in Figure 3 have a
smaller bandwidth than the bandwidth of the entire carrier although to decode these blocks, a terminal
first receives the PDCCH across the frequency range R320 and if the PDCCH indicates that a PDSCH
resource should be decoded, once it has received the entire sub-frame, it then decodes only the
PDSCH in only the relevant frequency range indicated by the PDCCH. So for example, UE 1
discussed above decodes the whole control region 300 and then the data in the resource block 342.
Virtual Downlink Carrier
Certain classes of devices, such as MTC devices (e.g. semi-autonomous or autonomous
wireless communication devices such as smart meters as discussed above), support communication
applications that are characterised by the transmission of small amounts of data at relatively
infrequent intervals and can thus be considerably less complex than conventional LTE terminals. In
many scenarios, providing low capability terminals such as those with a conventional highperformance
LTE receiver unit capable of receiving and processing data from an LTE downlink frame
across the full carrier bandwidth can be overly complex for a device which only needs to
communicate small amounts of data. This may therefore limit the practicality of a widespread
deployment of low capability MTC type devices in an LTE network. It is preferable instead to provide
low capability terminals such as MTC devices with a simpler receiver unit which is more
proportionate with the amount of data likely to be transmitted to the terminal. As set out below, in
accordance with examples of the present disclosure a "virtual carrier" is inserted in a conventional
OFDM type downlink carrier (i.e. a "host carrier"). Unlike data transmitted on a conventional OFDM
type downlink carrier, data transmitted on the virtual carrier can be received and decoded without
needing to process the full bandwidth of the downlink host OFDM carrier. Accordingly, data
transmitted on the virtual carrier can be received and decoded using a reduced complexity receiver
unit.
Figure 5 provides a schematic diagram illustrating an LTE downlink sub-frame which
includes a virtual carrier inserted in a host carrier in accordance with an example of the present
disclosure.
In keeping with a conventional LTE downlink sub-frame, the first n symbols (n is three in
Figure 5) form the control region 300 which is reserved for the transmission of downlink control data
such as data transmitted on the PDCCH. However, as can be seen from Figure 5, outside of the
control region 300 the LTE downlink sub-frame includes a group of resource elements below the
central band 310 which form a virtual carrier 501. As will become clear, the virtual carrier 501 is
adapted so that data transmitted on the virtual carrier 501 can be treated as logically distinct from the
data transmitted in the remaining parts of the host carrier and can be decoded without first decoding
all the control data from the control region 300. Although Figure 5 shows the virtual carrier occupying
frequency resources below the centre band, in general the virtual carrier can alternatively either
occupy frequency resources above the centre band or frequency resources including the centre band.
If the virtual carrier is configured to overlap any resources used by the PSS, SSS or PBCH of the host
carrier, or any other signal transmitted by the host carrier that a communications device operating on
the host carrier would require for correct operation and expect to find in a known pre-determined
location, the signals on the virtual carrier can be arranged such that these aspects of the host carrier
signal are maintained.
As can be seen from Figure 5, data transmitted on the virtual carrier 501 is transmitted across
a limited bandwidth. This could be any suitable bandwidth providing it is smaller than that of the host
carrier. In the example shown in Figure 5 the virtual carrier is transmitted across a bandwidth
comprising 12 blocks of 12 sub-carriers (i.e. 144 sub-carriers) which is equivalent to a 2.16MHz
transmission bandwidth. Accordingly, a terminal receiving data transmitted on the virtual carrier need
only be equipped with a receiver capable of receiving and processing data transmitted over a
bandwidth of 2.16MHz. This enables low capability terminals (for example MTC type terminals) to
be provided with simplified receiver units yet still be able to operate within an OFDM type
communication network which, as explained above, conventionally requires terminals to be equipped
with receivers capable of receiving and processing an OFDM signal across the entire bandwidth of the
signal.
As explained above, in OFDM based mobile communication systems such as LTE, downlink
data is dynamically assigned to be transmitted on different sub-carriers on a sub-frame by sub-frame
basis. Accordingly, in every sub-frame the network must signal which sub-carriers on which symbols
contain data relevant to which terminals (i.e. downlink grant signalling).
Accordingly, as can be seen in Figure 5, the final symbols of the virtual carrier can be
reserved as a virtual carrier control region 502 which is allocated for the transmission of control data.
In some examples the number of symbols comprising the virtual carrier control region 502 is fixed for
example three symbols. In other examples the virtual carrier control region 502 can vary in size, for
example between one and three symbols.
The virtual carrier control region can be located at any suitable position within the virtual
carrier for example in the first few symbols of the virtual carrier. In the example of Figure 5 this could
mean positioning the virtual carrier control region on the fourth, fifth and sixth symbols. However,
fixing the position of the virtual carrier control region in the final symbols of the sub-frame can
provide an advantage because the position of the virtual carrier control region need not vary even if
the number of symbols of the host carrier control region varies. This simplifies the processing
undertaken by communication devices receiving data on the virtual carrier because there is no need
for them to determine the position of the virtual carrier control region every sub-frame as it is known
that it will always be positioned in the final symbols of the sub-frame.
In a further embodiment, the virtual carrier control symbols may reference virtual carrier
PDSCH transmissions in a separate sub-frame.
In some examples the virtual carrier may be located within the centre band 310 of the
downlink sub-frame. This would minimise the reduction in host carrier PDSCH resources caused by
the insertion of a virtual carrier since the resources occupied by the PSS/SSS and PBCH would be
contained within the virtual carrier region and not the host carrier PDSCGH region. Therefore,
depending on for example the expected virtual carrier throughput, the location of a virtual carrier can
be appropriately chosen to either exist inside or outside the centre band according to whether the host
or virtual carrier is chosen to bear the overhead of the PSS, SSS and PBCH.
The virtual carrier concept is also described in a number of co-pending patent applications
(including GB 1101970.0, GB 1101981.7, GB 1101966.8, GB 1101983.3, GB 1101853.8, GB
1101982.5, GB 1101980.9 and GB 1101972.6), the contents of which are incorporated herein by
reference.
LTE Random Access Procedure
LTE system information comprises a configuration of a number of identifiers or identifying
sequences. These identifiers/sequences are then included in preambles which are used for random
access for communications devices. The uplink subframes may comprise a corresponding physical
random access channel (PRACH) over which preambles or other identifying numbers or sequences
may be sent where the possible locations of PRACH channels are indicated in the system information
according to sets of possibilities defined in system specifications. According to one aspect of the
present technique the PRACH and the identifiers/sequences which are used by the different types of
communications devices are dynamically configured in order to allocate different communications
resources of the wireless access interface. This will be explained shortly. However, first the random
access procedure will be explained in more detail below.
Figure 6 provides a diagram illustrating the process by which a communications device may
connect to a base station in an LTE network and therefore transition between RRC Idle to
RRC Connected. Initially the communications device is not synchronised with the OFDM frames and
therefore the communications device is required to perform the previously described camp-on
procedure. Once synchronised with the downlink frames the communications device is able to receive
the control information on the PDCCH and PBCH and subsequently receive the system information
which conveys the identifiers for the preambles, the number of preambles available for use in the cell
e.g. 64 and PRACH location which is used for an uplink random access procedure. Once an identifier
has been received and or selected the associated preamble is transmitted over the PRACH channel to
the base station as a random access request message illustrated by the communication 601 in Figure 6.
The transmission of the random access request message to the base station indicates that the
communications device requires resources in the up-link and possibly the downlink to be allocated. In
response to receiving the random access request message the base station allocates resources to the
communications device and transmits a random access request response message 602 to the
communications device. The random access response 602 indicates to the communications device the
resources which have been allocated to it and allows the communications device to synchronise with
the uplink frames of the base station so that a further random access procedure is not required and
timing advance can be implemented.
In response to receiving the random access response 602 and being synchronised with the
uplink frames of the base station, the communications device may transmit a radio resource control
(RRC) connection request 603 to the base station over the up-link resources allocated to the
communications device in the random access response 602. This RRC connection request represents a
request to the communications network to establish a radio communications bearer for transmitting
data to and/or from the communications device and the communications network or base station,
however, it may also be a request for other types of service from the base station. When the RRC
connection request message 603 has been received by the base station the base station acknowledges
the correct receipt of the request by transmitting an acknowledgment 604 to the communications
device. The acknowledgment 604 does not represent a successful connection but simply the correct
reception of the data within the RRC connection request. The correct reception of the request may be
assessed via the use of a cyclic redundancy check (CRC) or similar error detection methods. A further
request confirming an RRC connection setup 606 is required to be transmitted and received by the
base station and communications device respectively. In a mobile communication system such as that
depicted in Figure 1, when a connection or other request is made by a communications device this
request may be required to be passed onto a subsequent entity in the core network, for example an
base station may pass a request onto an MME or SGW. Consequently, the processing time associated
with an RRC connection request may be variable and a response to a RRC connection request may not
be transmitted by the base station to a communications device immediately. In order take account of
this situation, in an LTE system the communications device attempts to receive a response to the RRC
connection request in a window of a predetermined duration. In response to the sending of the RRC
connection request the communications device commences a wait timer 605 during which the
communications device attempts to receive a response to the RRC connection request. For example,
in an LTE system the device sets a wait timer to a one of a plurality of predetermined values specified
by a timer T300 that is broadcast by the base station in the system information block, where the timer
may have a value of up to 2000ms. Once the RRC connection request has been processed and the
connection is confirmed, a RRC connection setup message 606 is transmitted to the communications
device and received by the communications device if it is transmitted before expiry of the wait timer
at the communications device. Once the communications device has received the RRC connection
setup the communications device transmits an acknowledgement 607 to the base station in order to
acknowledge the safe receipt of the RRC connection setup message. If an acknowledgment is not
received by the base station, the base station may retransmit the RRC connection setup message.
Contention and Non-Contention Based LTE Random Access Procedures
Whilst Figure 6 provides a general overview of the random access procedure the exact
content of the messages may vary depending upon the exact variety of random access procedure being
performed. For instance, a random access procedure in an LTE system may be contention or noncontention
based procedure depending on the base station the communications device and a nature
purpose of the data which is to be sent once the a connection is established.
Figure 7a illustrates an LTE contention based random access procedure that a user device
may perform in order to request access to an LTE network. Firstly, the user device selects a random
access preamble from a set of contention based random access preambles that has been broadcast in a
system information block (SIB) such as SIB2 in a downlink frame by the base station. The user device
then transmits the selected random access preamble 701 to the base station where this transmission
acts as an access request message for requesting access to the network, the preamble acts as a user
device identifier and the preamble 701 is equivalent to 601 of Figure 6. The random access preamble
may be transmitted on a physical channel within the wireless access interface such as a physical
random access channel (PRACH) of an uplink frame. Once the random access preamble has been
received by the base station, at step 702 the base station transmits a response message, such as for
example, a random access response (RAR which equivalent to 602 of Figure 6). The resources in time
and frequency of a downlink channel, such as a physical downlink shared channel (PDSCH), in which
the user device can find the RAR are indicated in a message on a control channel such as physical
downlink control channel (PDCCH) addressed to a random access radio network temporary identifier
(RA-RNTI) and which is transmitted in the same subframe as the response message. This message is
therefore required to be received prior to receiving the response message. In particular, a downlink
control information (DCI) message informing the user device of the resources where the response
message can be found in the current subframe is sent on the PDCCH, where the RA-RNTI is formed
from a time and, in some examples, a frequency identifier of transmission of the associated access
request message. The response message contains at least the identity of the received preamble, a
timing alignment command, an allocated uplink resource grant and a temporary Cell RNTI (C-RNTI).
Upon receiving the response message, the user device transmits a scheduled transmission containing
its intended message, such as a radio resource controller (RRC) connection request, in the allocated
uplink resources as shown by step 703 where the message may be an RRC connection request as
shown by 603 in Figure 6. Finally at step 704, upon receiving the intended message the base station
transmits a contention resolution message which may be equivalent to the acknowledgment 604 of
Figure 6. The contention resolution message is then acknowledged by the user device to which the
contention resolution message is addressed, for example with a HARQ ACK/NACK. This procedure
thus overcomes the possibility of multiple user devices utilising the same preamble and or
transmitting a random access request over the same channel at the same time.
Figure 7b illustrates an example of a non-contention based random access procedure for
requesting resources or for preforming handover in an LTE network where the preamble is allocated
to the communications device by the base station from a predefined set of non-contention based
preambles. At step 751, prior to the transmission of a random access preamble from the user device in
the access request message, the base station allocates a preamble from a non-contention based set of
preambles to the user device. This allocation may be performed via a format 1A downlink control
information (DCI) message on the PDCCH or in a handover command if the user device has recently
entered a cell served by the base station. At step 752 the user device transmits its allocated preamble
to the base station. Once the preamble has been received at the base station, the base station transmits
a response message, such as for example a random access response, at step 753 where the response
message contains similar information to the response message sent at step 702 of Figure 7a. Once the
response message has been received at the user device, the user device then transmits its intended
message in the allocated uplink resources indicated in the response message.
Although the contention and non-contention based random access procedures have been
described separately, the two approaches may co-exist in a cell or system where a set of preambles is
divided into contention based and non-contention based groups. This division and size of the groups
may be indicated by the base station in the SIB2 using the fields numberofRaPreambles and
sizeOfRaPreamblesGroup for example so that the communications device can select a preamble from
the appropriate group when it is required to perform a random access procedure.
When performing random access procedures for conventional LRE device such as non-MTC
devices and other legacy devices, the random access response may be transmitted in any of the
available resources in the PDSCH, where the location is indicated in the PDCCH. Accordingly, to be
able to receive the random access response the conventional devices are required to be operable to
receive data from across substantially the entire bandwidth of the system. Whilst this does not present
a problem for conventional LTE devices, this approach does not take account of the reduced
bandwidth capability of low cost and complexity devices such as MTC devices which may be
configured to operate with across a reduced bandwidth and or in accordance the virtual carrier concept
described above. For instance, if a random access response intended for an MTC is transmitted in the
PDSCH outside of the virtual carrier the intended MTC device will be unable to receive the random
access response.
In order to overcome this problem, base stations may be configured to transmit random access
responses in a restricted set of PDSCH resources across which the virtual carrier may operate.
Consequently, MTC device will be able to receive their intended random access responses without
being required to increase their reception bandwidth. However, although this addresses the MTC
reception issue, this approach may result in congestion in the restricted set of PDSCH recourse
because substantially all random access response will be required to be transmitted in the restricted set
of resources as the base station may not able to differentiate between random access requests from
MTC and random access requests from conventional LTE devices. Thus the base station may not be
capable of scheduling only MTC random access responses for the restricted set of resources. The
effect of the congestion may manifest itself in a number of forms, for instance cell capacity as a whole
may be reduced because fewer random access responses can be scheduled overall, and fewer
communications devices may be served at initially RRC connection thus leading to call setup delays.
Both of these effects may adversely impact on end user service.
The problem of resource allocation in systems where MTC or other reduced bandwidth
devices and conventional LTE devices coexist has been addressed in documents that have been
submitted for discussion to the 3GPP standardisation process, including "Analysis of RAN2 Impacts
of Low Cost UE" ZTE (R2- 133908) [9], "Capabilities of Low Cost/Complexity MTC UEs" Ericsson
(R2-134299) [10], and "Impacts of Narrow Bandwidth Characteristic of Low Cost MTC UE" LG
Electronics Inc. (R2-134371). For instance, in "Capabilities of Low Cost/Complexity MTC UEs"
Ericsson (R2-134299) [11], in order to overcome the problem described above, it is proposed that
base stations may be configured to transmit random access responses in a restricted set of PDSCH
resources across which the virtual carrier may operate. Consequently, MTC device will be able to
receive their intended random access responses without being required to increase their reception
bandwidth. However, although this addresses the MTC reception issue, this approach may result in
congestion in the restricted set of PDSCH recourse because substantially all random access response
will be required to be transmitted in the restricted set of resources as the base station may not able to
differentiate between random access requests from MTC and random access requests from
conventional LTE devices. Thus the base station may not be capable of scheduling only MTC random
access responses for the restricted set of resources. The effect of the congestion may manifest itself in
a number of forms, for instance cell capacity as a whole may be reduced because fewer random access
responses can be scheduled overall, and fewer communications devices may be served at initially
RRC connection thus leading to call setup delays. Both of these effects may adversely impact on end
user service.
Adapted Random Access Procedure
A wireless access interface which is adapted to include a virtual carrier resource may be
thought of as providing a "T-shape" because the control channel, which corresponds to the LTE
PDCCH forms a first part of a sub-frame and stretches across the system bandwidth, whereas the
virtual carrier resources are formed substantially within the centre of the shared channel resources,
corresponding to the PDSCH of LTE, thus forming a T-shape. In a T-Shaped allocation, MTC UEs
will receive full bandwidth PDCCH, but is configured to receive PDSCH allocation only within a
restricted narrow bandwidth. This would reduce the baseband processing required at the MTC UE,
hence would lower the implementation cost of such UE. In order to maintain backward compatibility,
it will be desired that the PDCCH structure is kept unchanged.
A simplified representation of a T-shaped arrangement of a wireless access interface
including a virtual carrier is shown in Figure 8. As can be seen in Figure 8, control channel 70 which
for the example of LTE is the PDCCH is shown at the start of a sub-frame which also includes a
shared channel which corresponds to the PDSCH for LTE. Substantially in the centre of the PUSCH
is a region of resources forming a virtual carrier 74 which includes data resource allocation for
reduced capability devices also known as MTC UEs.
As explained above sequences which are used to identify a communications device which has
transmitted a random access signal are formed from a set of sequences. The sequences form
preambles of the random access messages. The sequences may be spreading sequences but in other
examples the "sequence" may refer not only to the possible preamble signature (i.e. the actual bits)
but may also include the same bits transmitted in a different frequency or time resource. The sequence
may also mean "resource region arrangements" so that "sequence" may be used interchangeably with
"resource region arrangement".
According to the present technique the network reserves a subset of sequences or random
access preambles which the reduced capability UEs use when transmitting a random access message.
According to this arrangement the communications network can avoid having to schedule the random
access response messages in the restricted subset of resources of the virtual carrier for all UEs.
In a first embodiment, this is achieved by arranging for the MTC UEs to select only among a
subset of random access preambles which are indicated to be for use with low cost devices.
Furthermore conventional UEs (LTE Release 1 UEs) which are not reduced capability devices can
avoid selecting one of these number N reserved random access preambles. UEs not operable in
accordance with this disclosure are unaware of this arrangement, and hence the probability of a legacy
UE being impacted is N/64 (if there are 64 random access preambles). In one example other legacy or
conventional UEs selecting a preamble which is not in the reserved range can be scheduled outside of
the reduced bandwidth region.
A communications device (MTC UE) 104 and an adapted eNodeB 101 are shown in Figures
9a and 9b. As shown in Figure 9a, the MTC UE includes a transmitter 220 and a receiver coupled to
an antenna 223 and a controller 224. The controller 224 also has access to a data store which includes
the predetermined sequences for forming the random access messages. Similarly, the adapted
eNodeB 101 includes a transmitter 230 and a receiver 232 coupled to an antenna 234 and a controller
236. The controller 236 has access to a data stored 238 which has stored therein the set of sequences
or preambles for forming the random access messages.
Figure 10 provides a schematic signalling flow diagram representing an example operation of
the MTC UE 104 and the base station 101 according to the present technique:
Ml : Optionally, the adapted eNodeB 101 is arranged to select the predetermined set of
sequences from a set of sequences for use by MTC UEs which are accessing the communications
resources of the virtual carrier. In one example, the adapted eNodeB 101 then transmits an indication
of the predetermined set of sequences, which are allocated to the MTC UEs within a cell using a
broadcast channel. For the example of LTE this can be done using the system information (SI), which
includes the indication of the allocation of the predetermined set of preambles (sequences) for
generating the random access messages. As explained below, in one example a total set of sequences
comprises non-contention based sequences and contention based sequences, and the predetermined set
of sequences which are allocated to the MTC UEs are selected from the non-contention based
sequences
S2: The communications device 104 generates a random access message, by selecting a
sequence from the predetermined set of sequences, which have been allocated to MTC UEs which are
transmitting or receiving signals via the virtual carrier bandwidth.
M4: The communications device 104 transmits the random access message from the
communications device via the wireless access interface provided by the wireless communications
network.
M6: In response to the random access message, the communications device 104 receives a
random access response message at the communications device transmitted from communications
resources allocated to the communications device within the virtual carrier bandwidth, the random
access message being recognised as being from a reduced capability terminal from the selected one of
the predetermined sequences allocated to reduced capability terminals.
In a second embodiment, in which the mobile communications network configures the
allocation of preamble sequences, the mobile communications network reduces the number of
preambles signalled to legacy UEs using the parameter numberOfRA-Preambles. The parameter
indicates the number of contention based (i.e. non-dedicated) preambles available, which are those
available for use in initial access. The remaining available preambles are non-contention based, i.e.
dedicated preambles. These can be explicitly signalled to the UE in a PDCCH order for use e.g. at
handover.
As indicated above, the mobile communications network would then signal to MTC UEs the
number of preambles reserved for MTC, taken from among the non-contention based, i.e. dedicated,
preambles. The mobile communications network can avoid scheduling those preambles, which have
been allocated to MTC UEs to legacy UEs, which legacy UEs believe are non-contention based, i.e.
dedicated preambles, when the legacy UE needs a non-contention based preamble. This means that
the mobile communications network can now unambiguously distinguish MTC UE from legacy and
other UEs.
For this example, the probability of contention is increased for legacy UEs, which are now
contending in for example 40 contention-based preambles instead of 64. Or, if the non-contention set
is not increased, latency of handover for example, may be increased because of a longer waiting for a
non-contention based preamble to become available as the set of such preambles has become smaller.
Therefore, in another example another resource domain may be used to give an adapted eNB 101
enough flexibility to minimize the effect of a reduced preamble space on conventional/legacy UEs.
One or more of the other domains can therefore allow fully unambiguous differentiation, and not
affect legacy UEs as long as the time and frequency resources do not overlap.
The additional configuration of random access preambles may also be used by the MTC UE
to determine whether or not access to a cell is allowed. For example, in case of high load, the network
may want to assign all of the possible preambles to non-MTC UEs in order to increase the PRACH
capacity for those UEs. By disabling or removing the configuration of additional set of
communications resources, which may be effectively "hidden" from a class of communications
devices, such as MTC-UEs by controlling the sequences allocated to different types of
communications devices, a mobile communications network can control access to the available
communications resources. For example, this arrangement can be effectively used to bar a cell or
prevents access to the cell by MTC UEs.
An example allocation of the predetermined sequences (preambles) from a total set of
sequences is illustrated in Figure 11. The total set of sequences referred to as random access
preambles is represented pictorially in Figure 11. As can be seen in Figure 1 1 each of the random
access preambles sequences 1 to N can be allocated to either contention based access 90 or noncontention
based access 92. Non-contention based access is allocated to UEs for example when
performing handover. Contention based preambles are allocated to UEs which are requesting the grant
of resources in the shared channel 72 of the system bandwidth. As shown in Figure 9 in one example,
a set of preambles from the non-contention based preambles are allocated to MTC UEs for performing
uplink contention access for requesting resources within the virtual carrier.
Example Technical Implementation
In one implementation example, the information element RACH-ConfigCommon is
transmitted by an adapted eNodeB to the communications devices in the mobile communications
network in an information block type 2 and is used to provide configuration information for random
access. "numberOfRA-Preambles" indicates the number of non-dedicated random access preambles in
TS 36.321. The following example changes are needed:
RACH-ConfigCommon ::= SEQUENCE {
An example
The mobile communications network signals the values:
• numberOfRA-Preambles = n40
• numberOfRA-Preambles-MTC = n8
The preambles in the range 0 -39 are used by legacy and other UE when transmitting a
contention-based random access preamble.
The preambles in the range 40-47 may be used by MTC UEs for transmitting contention
based preambles. For this example the legacy UEs believe these are for dedicated preambles and do
not use them at all because UE MAC cannot select for contention based random access, and the
mobile communications network does not assign these for non-contention based. The preambles in
the range 48-63 are for use when performing procedures requiring non-contention based preamble
(e.g. handover). This configuration allows the mobile communications network to schedule the
random access response within a restricted subset of resources to reduced bandwidth UEs without
affecting the overall system performance for legacy UEs.
As explained above, an aspect of the present technique as described for example for the
second embodiment, the communications network can be arranged to 'hid resources'. Conventional
UEs which are not configured in accordance with the present technique can receive and interpret the
preamble (sequence) configurations as normal and are unaware that they are being prevented from
using some subset of the possible preambles (sequences), which is to say that some preamble
resources are hidden from such UEs. On the other hand, UEs operable in accordance with the present
disclosure may be provided with a configuration of the random access resources including the
predetermined set of sequences and therefore that their access to preambles is specifically restricted.
The restricted access can therefore be used to match their reduced capability. According to the present
technique the UE type is unambiguously indicated to the eNodeB because the contention-based
preamble reservation is hidden from legacy UEs, but the network and MTC UEs are aware of this
arrangement.
An example of using another resource domain is in a TDD LTE system. In such a system,
there can be more than one resource region arrangement in a subframe in which a random access
channel (PRACH) can be transmitted by UEs, whereas in FDD there is always exactly one resource
region arrangement per subframe for PRACH. According to LTE Release 1 1 specifications, it is
possible to define up tosixty four (64) resource region arrangements for forming preambles of random
access messages for TDD, but only fifty seven (57) are defined and available for the network to
configure. In the example of the LTE Release 11 specifications, up to six (6) of these fifty seven
resource region arrangements can be available in a TDD uplink subframe. Therefore, in this
example, the specifications can be updated to use some or all o f the remaining seven
configurations of TDD PRACH to differentiate the allocation of communications resources for
different types of communications devices such as for MTC UEs. The seven new configurations can
be defined to be non- overlapping in time/-frequency resource with the fifty seven existing
configurations. An MTC UE therefore receives both the legacy TDD random access configuration
including the predetermined set of sequences for generating random access messages, and so has
access to those random access resources, as well receiving an additional configuration of one (or
more) among the seven new configurations. A low complexity UE is then required to use only the
new configuration it has, whereas other UEs operable in accordance with this disclosure can use either
the existing or the new random access configuration. Thus, the eNB knows whether the UE has a
reduced capability by virtue of whether it transmits a random access message with one of the
allocated and predetermined sequences for the preamble of the random access message in the new or
existing configuration. UEs not configured in accordance with the present disclosure have the new
PRACH resources hidden from them.
Further example implementation of the present technique is provided in Figures 12 and 13.
Figure 1 provides an example of resource or preamble reservation in accordance with the present
technique. The set of 64 preambles has been divided into three sets. A first set 1201 of 32 preambles
(i.e. preambles 0 to 31) is for use by legacy or conventional LTE devices in contention-based random
access requests. When used by such devices the base station may respond to random access request
anywhere in the entire bandwidth of the system. A second set 1202 of eight preambles is primarily
reserved for use by MTC or other reduced bandwidth devices for contention based random access
requests but legacy devices also view this set as contention based random access preambles and so
may also select preambles from this set. When a base station receives a random access request which
utilises a preamble from the second set the base station transmits the random access response in a
reduced set of resources, such as within the virtual carrier bandwidth for example so that MTC
devices are capable of receiving the response. The preambles of the third set 1203, which has a size of
24, are utilised as dedicated non-contention based random access preambles where the preambles may
be used by all devices but are allocated by the base station for procedures such as handover for
example. An indication of the preamble reservations and set sizes may be provided to
communications devices in broadcast resources such as one of the system information blocks. For
example a field such as numberOfRA-Preambles-MTC may be used to indicate that the numbed of
MTC preambles is eight and therefore that the MTC devices should select from these preambles, and
a field such as numberOfRA-Preambles may be used to indicate the number preambles intended for
use by legacy devices is 40.
Figure 13 provides a further example of preamble reservation or allocation in accordance with
an example of the present technique. As in Figure 12, the set of 64 preambles divided into three sets.
A first set 1301 of 40 preambles is equivalent to the first set of Figure 12 and is intended for use as
non-dedicated preambles for contention based random access procedures by legacy communications
devices. The remaining 24 preambles, although divided into two sets i.e. a second set 1302 and a third
set 1303, in contrast to Figure 12 both these sets are viewed as non-contention based preambles by
legacy devices so that they are not selected by such devices. The preambles of the second set 1302 are
used as contention based random access preambles by MTC devices and the base station avoids
allocating the preambles of the second set to legacy devices. The preambles of the third set 1303 are
used as a set of non-contention based random access preambles and the base station is free to allocate
these to any communications device. As described with reference to Figure 12, indications of the
preamble sets may be provided to the communications devices such that MTC devices and legacy
devices select contention based preambles from the correct sets(s).
The following numbered paragraphs defined further example aspects and features of the
present technique:
1. A method of transmitting data from a communications device to a mobile
communications network or receiving data from the mobile communications network at the mobile
communications device, the method comprising
providing, by the mobile communications network, a wireless access interface, for
transmitting and receiving data to and from communications devices, the wireless access interface
providing communications resources within a system bandwidth and in time divided units providing
communications resources within the system bandwidth for allocation to communications devices of a
first type and a second type, the first type of the communications devices having a different capability
to the second type of communications devices,
generating, at the communications device, a random access message, by selecting a sequence
from a predetermined set of sequences, which have been allocated to the communications devices of
the second type,
transmitting the random access message from the communications device to the wireless
communications network, and
in response to the random access message, receiving a random access response at the
communications device transmitted according to the capability of the communications device of the
second type, the random access message being recognised as being from a communications device of
the second type from the selected one of the predetermined sequences allocated to the
communications devices of the second type.
2. A method according to paragraph 1, wherein the wireless access interface includes a
virtual carrier defining a set of communications resources of the system bandwidth for preferable
allocation to communications devices of the second type for transmitting or receiving signals within
the communications resources of the virtual carrier bandwidth, and the receiving the random access
response at the communications device transmitted according to the capability of the communications
device of the second type, includes
receiving the random access response at the communications device from communications
resources allocated to the communications device within the virtual carrier bandwidth, the
communications device of the second type having a reduced capability compared to communications
devices of the first type.
3. A method according to paragraphs 1 or 2, wherein the transmitting the random access
message from the communications device to the wireless communications network, includes
configuring, by the mobile communications network, the communications resources of the
wireless access interface for the communications device of the second type to transmit the random
access message, and
transmitting the random access message from the communications device to the wireless
communications network in communications resources configured by the mobile communications
network.
4. A method according to paragraph 3, wherein the configuring, by the mobile
communications network, the communications resources of the wireless access interface for the
communications device of the second type to transmit the random access message includes
configuring communications resources for transmitting the random access message in
dependence on the capability of the communications device of the second type.
5. A method according to paragraph 4, wherein the configuring, by the mobile
communications network, the communications resources of the wireless access interface for the
communications device of the second type to transmit the random access message includes
configuring the communications resources of the wireless access interface to include one or
more random access channels for the communications device of the second type to transmit the
random access message.
6. A method according to paragraph 1, comprising
transmitting to the communications device from the mobile communications network an
indication of the predetermined set of sequences, which are allocated to the reduced capability devices
for generating the random access messages.
7. A method according to paragraph 6, comprising
selecting the predetermined set of sequences from a set of sequences comprising sequences
for generating non-contention based random access messages and sequences for generating
contention based random access messages , wherein the predetermined set of sequences which are
allocated to the reduced capability devices for contention based random access are selected from the
sequences for generating non-contention based random access messages.
8 A method according to any of paragraphs 1 to 7, wherein the different capability of
the first type of the communications devices compared to the second type of communications devices,
includes a maximum bandwidth of a communications channel in which signals are received, which
the communications device of the second type can decode compared with the communications devices
of the first type.
9 . A method according to any of paragraphs 1 to 7, wherein the different capability of
the first type of the communications devices compared to the second type of communications devices,
includes a minimum number of antennas available to the communications devices of the first type
compared with the communications devices of the second type.
10. A method according to any of paragraphs 1 to 7, wherein the different capability of
the first type of the communications devices compared to the second type of communications devices,
includes a maximum rate of processing information bits by the communications device of the second
type compared with the communications devices of the first type.
11. A communications device for transmitting data to a mobile communications network
or receiving data from the mobile communications network, the communications device comprising
a transmitter unit configured to transmit signals representing data via a wireless access
interface to an infrastructure equipment of the mobile communications network, the wireless access
interface providing communications resources within a system bandwidth and in time divided units
providing communications resources in the system bandwidth for allocation to communications
devices of a first and a second type, the first type of the communications devices having a different
capability to the second type of communications devices,
a receiver configured to receive signals from the infrastructure equipment via the wireless
access interface, and
a controller configured in combination with the transmitter and the receiver
to generate a random access message, by selecting a sequence from a predetermined set of
sequences, which have been allocated to the communications devices of the second type,
to transmit the random access message from the communications device to the mobile
communications network, and
in response to the random access message, to receive a random access response transmitted
according to the capability of the communications device of the second type, the random access
message being recognised as being from a reduced capability terminal from the selected one of the
predetermined sequences allocated to reduced capability terminals.
1 . A communications device according to paragraph 11, wherein the wireless access
interface includes a virtual carrier defining a set of communications resources of the system
bandwidth for preferable allocation to communications devices of the second type for transmitting or
receiving signals within the communications resources of the virtual carrier bandwidth, and the
controller is configured in combination with the receiver to receive the random access response in
accordance with the capability of the communications device of the second type by receiving the
random access response at the communications device from communications resources allocated to
the communications device within the virtual carrier bandwidth, the communications device of the
second type having a reduced capability compared to communications devices of the first type.
13. A communications device according to paragraphs 1 1 or 12, wherein the controller is
configured in combination with the transmitter to transmit the random access message from the
communications device to the wireless communications network the communications resources of the
wireless access interface, which have been configured by the mobile communications network by the
communications device of the second type to transmit the random access message.
14. A communications device according to paragraph 13, wherein the communications
resources of the wireless access interface are configured by the mobile communications network for
transmitting the random access message in dependence on the capability of the communications
device of the second type.
15. A communications device according to paragraph 14, wherein the communications
resources of the wireless access interface configured by the mobile communications network for
transmitting the random access message includes providing one or more a random access channels for
the communications device of the second type to transmit the random access message.
16. A communications device according to paragraph 11, wherein the controller is
configured in combination with the receiver
to receive from the mobile communications network an indication of the predetermined set of
sequences, which are allocated to the reduced capability devices for generating the random access
messages.
17. A communications device according to paragraph 16, wherein the predetermined set
of sequences are selected from a set of sequences comprising sequences for generating non-contention
based random access messages and sequences for generating contention based random access
messages , wherein the predetermined set of sequences which are allocated to the reduced capability
devices for contention based random access are selected from the sequences for generating noncontention
based random access messages.
18. A communications device according to any of paragraphs 11 to 17, wherein the
different capability of the first type of the communications devices compared to the second type of
communications devices, includes a maximum bandwidth of a communications channel in which
signals are received, which the communications device of the second type can decode compared with
the communications devices of the first type.
19. A communications device according to any of paragraphs 11 to 17, wherein the
different capability of the first type of the communications devices compared to the second type of
communications devices, includes is a minimum number of antennas available to the
communications devices of the first type compared with the communications devices of the second
type.
20. A communications device according to any of paragraphs 1 to 7, wherein the
different capability of the first type of the communications devices compared to the second type of
communications devices, includes a maximum rate of processing information bits by the
communications device of the second type compared with the communications devices of the first
type.
2 1. An infrastructure equipment for forming part of a mobile communications network,
the infrastructure equipment comprising
a transmitter unit configured to transmit signals via a wireless access interface to
communications devices, and
a receiver configured to receive signals from the communications devices via the wireless
access interface, and
a controller configured in combination with the transmitter and the receiver to form the
wireless access interface, the wireless access interface providing communications resources within a
system bandwidth and, in time divided units providing communications resources in the system
bandwidth for allocation to the communications devices of a first type and a second type, the first type
of the communications devices having a different capability to the second type of communications
devices, wherein the controller is configured in combination with the transmitter and the receiver
to receive a random access message from one of the communications device via the wireless
access interface, the communications device being a communications device of the second type and
the random access message having been generated by the communications device of the second type
by selecting a sequence from one of a predetermined set of sequences, which have been allocated to
communications devices of the second type,
to identify from the received random access message that the communications device which
transmitted the random access message is a communications device of the second type, and
in response to the random access message, to transmit a random access response according to
the capability of the communications device of the second type, the random access message being
recognised as being from a reduced capability terminal from the selected one of the predetermined
sequences allocated to communications devices of the second type.
22. An infrastructure equipment according to paragraph 21, wherein the wireless access
interface includes a virtual carrier defining a set of communications resources of the system
bandwidth for preferable allocation to communications devices of the second type for transmitting or
receiving signals within the communications resources of the virtual carrier bandwidth, and the
receiving the random access response at the communications device transmitted according to the
capability of the communications device of the second type, the controller is configured in
combination with the transmitter and the receiver
to transmit the random access response at the communications device from communications
resources allocated to the communications device within the virtual carrier bandwidth, the
communications device of the second type having a reduced capability compared to communications
devices of the first type.
23. An infrastructure equipment according to paragraphs 2 1 or 22, wherein the controller
is configured in combination with the transmitter and the receiver
to configure the communications resources of the wireless access interface for the
communications device of the second type to transmit the random access message, and
to transmit the random access message from the communications device to the wireless
communications network in communications resources configured by the mobile communications
network.
24. An infrastructure equipment according to paragraph 23, wherein the controller is
configured in combination with the transmitter and the receiver
to configure the communications resources of the wireless access interface for receiving the
random access message in dependence on the capability of the communications device of the second
type.
25. An infrastructure equipment according to paragraph 24, wherein the controller is
configured in combination with the transmitter and the receiver to configure the communications
resources of the wireless access interface to include one or more a random access channels for the
communications device of the second type to transmit the random access message.
26. An infrastructure equipment according to paragraph 21, wherein the controller is
configured in combination with the transmitter
to transmit to the communications devices from the mobile communications network an
indication of the predetermined set of sequences, which are allocated to the reduced capability devices
for generating the random access messages.
27. An infrastructure equipment according to paragraph 26, wherein the controller is
configured
to select the predetermined set of sequences from a set of sequences comprising sequences for
generating non-contention based random access messages and sequences for generating contention
based random access messages , wherein the predetermined set of sequences which are allocated to
the reduced capability devices for contention based random access are selected from the sequences
for generating non-contention based random access messages.
28. An infrastructure equipment according to any of paragraphs 2 1 to 27, wherein the
different capability of the first type of the communications devices compared to the second type of
communications devices, includes a maximum bandwidth of a communications channel in which
signals are received, which the communications device of the second type can decode compared with
the communications devices of the first type.
29. An infrastructure equipment according to any of paragraphs 2 1 to 27, wherein the
different capability of the first type of the communications devices compared to the second type of
communications devices, includes is a minimum number of antennas available to the
communications devices of the first type compared with the communications devices of the second
type.
30. An infrastructure equipment according to any of paragraphs 2 1 to 27, wherein the
different capability of the first type of the communications devices compared to the second type of
communications devices, includes a maximum rate of processing information bits by the
communications device of the second type compared with the communications devices of the first
type.
31. A mobile communications network including an infrastructure equipment according
to any of paragraphs 2 1 to 30.
32. A communications system comprising a communications device according to any of
paragraphs 11 to 20 and an infrastructure equipment according to any of paragraphs 2 1 to 30.
33. A computer readable medium having stored thereon a computer program, which
when loaded onto a processor performs the method of any of paragraphs 1 to 10.
Various further aspects and features of the present invention are defined in the appended
claims. It will appreciated that the example of LTE and terminology in respect of LTE has been
provided for one example only and other access networks which are 3GPP or non-3GPP may be used.
REFERENCES
[1] UK patent application GB 1101970.0
[2] UK patent application GB 1101981.7
[3] UK patent application GB 1101966.8
[4] UK patent application GB 1101983.3
[5] UK patent application GB 1101853.8
[6] UK patent application GB 1101982.5
[7] UK patent application GB 1101980.9
[8] UK patent application GB 1101972.6
[9] Document submitted for discussion at 3GPP TSG-RAN WG2 #84 "Analysis of RAN2
Impacts of Low Cost UE" ZTE (R2-133908)
[10] Document submitted for discussion at 3GPP TSG-RAN WG2 #84 "Capabilities of Low
Cost/Complexity MTC UEs" Ericsson (R2- 134299)
[11] Document submitted for discussion at 3GPP TSG-RAN WG2 #84 "Impacts of Narrow
Bandwidth Characteristic of Low Cost MTC UE" LG Electronics Inc. (R2-134371)
Claims
1. A method of transmitting data from a communications device to a mobile
communications network or receiving data from the mobile communications network at the mobile
communications device, the method comprising
providing, by the mobile communications network, a wireless access interface, for
transmitting and receiving data to and from communications devices, the wireless access interface
providing communications resources within a system bandwidth and in time divided units providing
communications resources within the system bandwidth for allocation to communications devices of a
first type and a second type, the first type of the communications devices having a different capability
to the second type of communications devices,
generating, at the communications device, a random access message, by selecting a sequence
from a predetermined set of sequences, which have been allocated to the communications devices of
the second type,
transmitting the random access message from the communications device to the wireless
communications network, and
in response to the random access message, receiving a random access response at the
communications device transmitted according to the capability of the communications device of the
second type, the random access message being recognised as being from a communications device of
the second type from the selected one of the predetermined sequences allocated to the
communications devices of the second type.
2. A method as claimed in Claim 1, wherein the wireless access interface includes a
virtual carrier defining a set of communications resources of the system bandwidth for preferable
allocation to communications devices of the second type for transmitting or receiving signals within
the communications resources of the virtual carrier bandwidth, and the receiving the random access
response at the communications device transmitted according to the capability of the communications
device of the second type, includes
receiving the random access response at the communications device from communications
resources allocated to the communications device within the virtual carrier bandwidth, the
communications device of the second type having a reduced capability compared to communications
devices of the first type.
3. A method as claimed in Claim 1, wherein the transmitting the random access message
from the communications device to the wireless communications network, includes
configuring, by the mobile communications network, the communications resources of the
wireless access interface for the communications device of the second type to transmit the random
access message, and
transmitting the random access message from the communications device to the wireless
communications network in communications resources configured by the mobile communications
network.
4. A method as claimed in Claim 3, wherein the configuring, by the mobile
communications network, the communications resources of the wireless access interface for the
communications device of the second type to transmit the random access message includes
configuring communications resources for transmitting the random access message in
dependence on the capability of the communications device of the second type.
5. A method as claimed in Claim 4, wherein the configuring, by the mobile
communications network, the communications resources of the wireless access interface for the
communications device of the second type to transmit the random access message includes
configuring the communications resources of the wireless access interface to include one or
more random access channels for the communications device of the second type to transmit the
random access message.
6. A method as claimed in Claim 1, comprising
transmitting to the communications device from the mobile communications network an
indication of the predetermined set of sequences, which are allocated to the reduced capability devices
for generating the random access messages.
7 . A method as claimed in Claim 6, comprising
selecting the predetermined set of sequences from a set of sequences comprising sequences
for generating non-contention based random access messages and sequences for generating
contention based random access messages , wherein the predetermined set of sequences which are
allocated to the reduced capability devices for contention based random access are selected from the
sequences for generating non-contention based random access messages.
8. A method as claimed in Claim 1, wherein the different capability of the first type of
the communications devices compared to the second type of communications devices, includes a
maximum bandwidth of a communications channel in which signals are received, which the
communications device of the second type can decode compared with the communications devices of
the first type.
9. A method as claimed in Claim 1, wherein the different capability of the first type of
the communications devices compared to the second type of communications devices, includes a
minimum number of antennas available to the communications devices of the first type compared
with the communications devices of the second type.
10. A method as claimed in Claim 1, wherein the different capability of the first type of
the communications devices compared to the second type of communications devices, includes a
maximum rate of processing information bits by the communications device of the second type
compared with the communications devices of the first type.
11. A communications device for transmitting data to a mobile communications network
or receiving data from the mobile communications network, the communications device comprising
a transmitter unit configured to transmit signals representing data via a wireless access
interface to an infrastructure equipment of the mobile communications network, the wireless access
interface providing communications resources within a system bandwidth and in time divided units
providing communications resources in the system bandwidth for allocation to communications
devices of a first and a second type, the first type of the communications devices having a different
capability to the second type of communications devices,
a receiver configured to receive signals from the infrastructure equipment via the wireless
access interface, and
a controller configured in combination with the transmitter and the receiver
to generate a random access message, by selecting a sequence from a predetermined set of
sequences, which have been allocated to the communications devices of the second type,
to transmit the random access message from the communications device to the mobile
communications network, and
in response to the random access message, to receive a random access response transmitted
according to the capability of the communications device of the second type, the random access
message being recognised as being from a reduced capability terminal from the selected one of the
predetermined sequences allocated to reduced capability terminals.
1 . A communications device as claimed in Claim 11, wherein the wireless access
interface includes a virtual carrier defining a set of communications resources of the system
bandwidth for preferable allocation to communications devices of the second type for transmitting or
receiving signals within the communications resources of the virtual carrier bandwidth, and the
controller is configured in combination with the receiver to receive the random access response in
accordance with the capability of the communications device of the second type by receiving the
random access response at the communications device from communications resources allocated to
the communications device within the virtual carrier bandwidth, the communications device of the
second type having a reduced capability compared to communications devices of the first type.
13. A communications device as claimed in Claim 11, wherein the controller is
configured in combination with the transmitter to transmit the random access message from the
communications device to the wireless communications network the communications resources of the
wireless access interface, which have been configured by the mobile communications network by the
communications device of the second type to transmit the random access message.
14. A communications device as claimed in Claim 13, wherein the communications
resources of the wireless access interface are configured by the mobile communications network for
transmitting the random access message in dependence on the capability of the communications
device of the second type.
15. A communications device as claimed in Claim 14, wherein the communications
resources of the wireless access interface configured by the mobile communications network for
transmitting the random access message includes providing one or more a random access channels for
the communications device of the second type to transmit the random access message.
16. A communications device as claimed in Claim 11, wherein the controller is
configured in combination with the receiver
to receive from the mobile communications network an indication of the predetermined set of
sequences, which are allocated to the reduced capability devices for generating the random access
messages.
17. A communications device as claimed in Claim 16, wherein the predetermined set of
sequences are selected from a set of sequences comprising sequences for generating non-contention
based random access messages and sequences for generating contention based random access
messages , wherein the predetermined set of sequences which are allocated to the reduced capability
devices for contention based random access are selected from the sequences for generating noncontention
based random access messages.
18. A communications device as claimed in Claim 11, wherein the different capability of
the first type of the communications devices compared to the second type of communications devices,
includes a maximum bandwidth of a communications channel in which signals are received, which
the communications device of the second type can decode compared with the communications devices
of the first type.
19. A communications device as claimed in Claim 11, wherein the different capability of
the first type of the communications devices compared to the second type of communications devices,
includes is a minimum number of antennas available to the communications devices of the first type
compared with the communications devices of the second type.
20. A communications device as claimed in Claim 1, wherein the different capability of
the first type of the communications devices compared to the second type of communications devices,
includes a maximum rate of processing information bits by the communications device of the second
type compared with the communications devices of the first type.
2 1. An infrastructure equipment for forming part of a mobile communications network,
the infrastructure equipment comprising
a transmitter unit configured to transmit signals via a wireless access interface to
communications devices, and
a receiver configured to receive signals from the communications devices via the wireless
access interface, and
a controller configured in combination with the transmitter and the receiver to form the
wireless access interface, the wireless access interface providing communications resources within a
system bandwidth and, in time divided units providing communications resources in the system
bandwidth for allocation to the communications devices of a first type and a second type, the first type
of the communications devices having a different capability to the second type of communications
devices, wherein the controller is configured in combination with the transmitter and the receiver
to receive a random access message from one of the communications device via the wireless
access interface, the communications device being a communications device of the second type and
the random access message having been generated by the communications device of the second type
by selecting a sequence from one of a predetermined set of sequences, which have been allocated to
communications devices of the second type,
to identify from the received random access message that the communications device which
transmitted the random access message is a communications device of the second type, and
in response to the random access message, to transmit a random access response according to
the capability of the communications device of the second type, the random access message being
recognised as being from a reduced capability terminal from the selected one of the predetermined
sequences allocated to communications devices of the second type.
22. An infrastructure equipment as claimed in Claim 21, wherein the wireless access
interface includes a virtual carrier defining a set of communications resources of the system
bandwidth for preferable allocation to communications devices of the second type for transmitting or
receiving signals within the communications resources of the virtual carrier bandwidth, and the
receiving the random access response at the communications device transmitted according to the
capability of the communications device of the second type, the controller is configured in
combination with the transmitter and the receiver
to transmit the random access response at the communications device from communications
resources allocated to the communications device within the virtual carrier bandwidth, the
communications device of the second type having a reduced capability compared to communications
devices of the first type.
23. An infrastructure equipment as claimed in Claim 21, wherein the controller is
configured in combination with the transmitter and the receiver
to configure the communications resources of the wireless access interface for the
communications device of the second type to transmit the random access message, and
to transmit the random access message from the communications device to the wireless
communications network in communications resources configured by the mobile communications
network.
24. An infrastructure equipment as claimed in Claim 23, wherein the controller is
configured in combination with the transmitter and the receiver
to configure the communications resources of the wireless access interface for receiving the
random access message in dependence on the capability of the communications device of the second
type.
25. An infrastructure equipment as claimed in Claim 24, wherein the controller is
configured in combination with the transmitter and the receiver to configure the communications
resources of the wireless access interface to include one or more a random access channels for the
communications device of the second type to transmit the random access message.
26. An infrastructure equipment as claimed in Claim 21, wherein the controller is
configured in combination with the transmitter
to transmit to the communications devices from the mobile communications network an
indication of the predetermined set of sequences, which are allocated to the reduced capability devices
for generating the random access messages.
27. An infrastructure equipment as claimed in Claim 26, wherein the controller is
configured
to select the predetermined set of sequences from a set of sequences comprising sequences for
generating non-contention based random access messages and sequences for generating contention
based random access messages , wherein the predetermined set of sequences which are allocated to
the reduced capability devices for contention based random access are selected from the sequences
for generating non-contention based random access messages.
28. An infrastructure equipment as claimed in Claim 21, wherein the different capability
of the first type of the communications devices compared to the second type of communications
devices, includes a maximum bandwidth of a communications channel in which signals are received,
which the communications device of the second type can decode compared with the communications
devices of the first type.
29. An infrastructure equipment as claimed in Claim 21, wherein the different capability
of the first type of the communications devices compared to the second type of communications
devices, includes is a minimum number of antennas available to the communications devices of the
first type compared with the communications devices of the second type.
30. An infrastructure equipment as claimed in Claim 21, wherein the different capability
of the first type of the communications devices compared to the second type of communications
devices, includes a maximum rate of processing information bits by the communications device of the
second type compared with the communications devices of the first type.
31. A mobile communications network including an infrastructure equipment as claimed
in Claim 21.
32. A communications system comprising a communications device as claimed in Claim
11 and an infrastructure equipment as claimed in Claim 2 1.
33. A computer readable medium having stored thereon a computer program, which
when loaded onto a processor performs the method of Claim 1.