Description
Title of Invention: COMMUNICATION SYSTEM
Technical Field
[0001] The present invention relates to a communication system and to components thereof
for providing communication services to mobile or fixed communication devices. The
invention has particular, but not exclusive, relevance to connectivity via multiple base
stations in Long Term Evolution (LTE) Advanced systems as currently defined in a s
sociated 3rd Generation Partnership Project (3GPP) standards documentation.
Background Art
[0002] In a cellular communications network, user equipment (UE) (such as mobile
telephones, mobile devices, mobile terminals, etc.) can communicate with other user
equipment and/or remote servers via base stations. LTE systems include an Evolved
Universal Terrestrial Radio Access Network (E-UTRAN) and an Evolved Packet Core
(EPC) network (or simply 'core network'). The E-UTRAN includes a number of base
stations ('eNBs') for providing both user-plane (e.g. Packet Data Convergence
Protocol (PDCP), Radio Link Control (RLC), Medium Access Control (MAC) and
PHYsical (PHY) layers) and control-plane (e.g. Radio Resource Control (RRC))
protocol terminations towards the UE.
[0003] Recent developments in communication networks have seen increased deployment of
so called 'small' cells operated by Low Power Nodes (LPNs), such as pico eNBs,
femto eNBs, home eNBs (HeNBs) or the like, which cells have a smaller coverage area
than existing macro cells operated by a higher power (regular) macro base station.
Networks comprising a number of different cell types, for example a network
comprising a macro cell and a femto cell, are referred to as Heterogeneous Networks,
or HetNets. In the following description the term base station is used to refer to any
such macro base station or LPN.
[0004] Conventionally, a mobile telephone is configured to communicate via one base
station (using an associated radio link). However, in a study on small cell en
hancements for E-UTRA and E-UTRAN (3GPP technical report (TR) no. 36.842, the
contents of which are incorporated herein by reference), a so-called 'dual connectivity'
functionality was introduced to improve, for example, the coverage of high data rates
for user equipment, temporary network deployment, cell edge throughput and/or to
increase system throughput. The dual connectivity feature established techniques for
compatible mobile telephones (and other user equipment) to communicate with
multiple network points, substantially simultaneously. Specifically, this 'dual con
nectivity' functionality refers to an operation mode where a given mobile telephone
(operating in RRC_CONNECTED mode) consumes radio resources provided by at
least two different network points (e.g. two or more base stations). Typically, one of
the network points involved in the dual connectivity functionality is a macro base
station and the other network point (or a plurality of network points) comprises a low
power node (or plurality of low power nodes).
[0005] Each network point (also referred to as 'access point') involved in the provision of
dual connectivity for a mobile telephone may assume a different role. One of the
network points may be referred to as a master base station (MeNB) and each one of the
other network points may be referred to as a secondary base station (SeNB). Typically,
the various secondary base stations involved in the provision of dual connectivity are
coupled (to the MeNB and hence the core network) via a so-called non-ideal backhaul.
Further, in a dual connectivity scenario, one of the base stations (the MeNB) routes
control plane signalling to the core network via an associated interface (e.g. the SI
interface), regardless of whether or not the other base station is also connected to the
core network for user plane communication (e.g. to a serving gateway).
[0006] The MeNB/SeNB roles do not necessarily depend on each base station's capabilities/
type (e.g. power class) and may be different for different mobile telephones (even
when using the same base stations).
[0007] In accordance with the dual connectivity functionality, a mapping between the
mobile telephone's radio (communication) bearer(s) and the base stations may be
realised as follows:
- a so-called Master Cell Group (MCG) bearer in which a radio bearer is served by
the MeNB only (or 'MeNB-specific bearer');
- a so-called Secondary Cell Group (SCG) bearer in which a radio bearer is served
by the SeNB only (or 'SeNB-specific bearer'); and
- a split bearer in which a radio bearer is served by the MeNB and the SeNB.
[0008] In order to ensure that an appropriate level of service (e.g. a desired data rate) can be
provided for each user in the communication network, the network operator assigns
various parameters that determine an aggregate maximum bit rate (AMBR) that can be
provided to the users (subscribers) in the network per subscriber and per access point.
Specifically, for each subscriber, the Home Subscriber Server (HSS) holds an a s
sociated 'HSS_APN-AMBR' parameter (per APN) and an 'HSS_UE-AMBR'
parameter, forming part of the user's subscription data.
[0009] The HSS_APN-AMBR (APN Aggregate Maximum Bit Rate) parameter for a
particular (subscriber's) user communication device limits the non-guaranteed
aggregate bit rate across all PDN connections by that user communication device via a
particular APN. The actual 'APN-AMBR' parameter to be used (enforced) by the
given access point (e.g. P-GW) is provided by the MME based on subscription data
obtained from the HSS.
[0010] The HSS_UE-AMBR (UE Aggregate Maximum Bit Rate) parameter for a particular
(subscriber's) user communication device limits the total traffic of that user commu
nication device on uplink and downlink (via the serving base station). The actual
'UE-AMBR' parameter to be used (enforced) by the serving base station is provided
by the MME based on subscription data obtained from the HSS. Specifically, the
MME computes the UE-AMBR parameter such that it equals the smaller of the sum of
all HSS_APN-AMBR parameters of active APNs and the HSS-UE-AMBR parameter.
This is further illustrated in the 3GPP TS 23.401 standard, the contents of which are in
corporated herein by reference. The MME transmits the calculated UE-AMBR
parameter to the serving base station, which base station is thus able to allow/discard
data traffic for the user communication device in accordance with the UE-AMBR
parameter. This is further illustrated in the 3GPP TS 36.413 and TS 36.300 standards,
the contents of which are incorporated herein by reference.
[001 1] Thus traffic sent/received by a particular user communication device in excess of the
bit rate indicated by the UE-AMBR parameter may get discarded by a rate shaping
function of the base station serving that user communication device, and traffic
exceeding the bit rate indicated by the applicable APN-AMBR parameter may get
discarded by a rate shaping function of the corresponding APN. The UE-AMBR
parameter and the APN-AMBR parameter are applicable across all non-Guaranteed Bit
Rate (non-GBR) bearers of a particular subscriber (i.e. a user communication device
associated with that subscriber).
[0012] Each base station guarantees a downlink guaranteed bit rate associated with a socalled
guaranteed bit rate (GBR) bearer, enforces a downlink maximum bit rate (MBR)
associated with a particular GBR bearer and enforces a downlink Aggregate Maximum
Bit Rate (AMBR) associated with a group of non-GBR bearers. Further, in the uplink,
by limiting the total grant of communication resources to an item of user equipment,
the base station can ensure that a UE-AMBR for a respective group of non-GBR
bearers associated with each item of user equipment, plus the sum of MBRs is not
exceeded.
[0013] There is a general consensus that, during dual connectivity, the MeNB should
manage the UE-AMBR and provide, to the SeNB, information which assists the SeNB
to provide both downlink and uplink AMBR enforcement when the SCG bearer option
is applied.
[0014] The overall UE-AMBR enforced for a particular dual connectivity UE may be split
between an MeNB-specific UE-AMBR (M E AMBR) for that UE and an SeNB-specific
UE-AMBR (SUE AMBR) for that UE. The SUE-AMBR is sent to the SeNB by the MeNB
managing the overall UE-AMBR, and the SeNB enforces the SUE AMBR accordingly.
[0015] However, the inventors have realised that, as a result of non-GBR bearers of a UE
potentially being distributed between the MeNB and SeNB during dual connectivity,
and contrary to the current consensus, the generally accepted route forward can result
in a sub-optimal solution in which, for example, the UE-AMBR is not always split
between the master and secondary base stations in the most efficient manner.
[0016] For example, when there is a lot of data in SeNB's buffer which is not sent due to en
forcement of the S E AMB and the data rate of data arriving in MeNB is significantly
lower than M AMBR, then the actual data rate available to the UE may be significantly
lower than the overall UE-AMBR that the UE is entitled to by contract. Similarly,
when there is a lot of data in MeNB's buffer which is not sent due to enforcement of
the M AMBR, and the data rate of data arriving in SeNB is significantly lower than S UE
AMBR, then the actual data rate available to the UE may be significantly lower than the
overall UE-AMBR that the UE is entitled to by contract. Thus, the UE may suffer data
loss due to UE-AMBR enforcement unnecessarily.
[0017] To help illustrate this issue, a number of examples of unnecessary data loss are
summarises below:
[0018] Downlink - Unnecessary packet dropping in SeNB:
For a particular UE, the value of UE-AMBR may be e.g. 10Mbps for distribution
between the two radio bearers used by the UE (e.g. E-RAB#1 provided via the MeNB
and E-RAB#2 provided via the SeNB). In this case, for example, the following p a
rameters may be configured (for the UE's non-GBR bearers):
-AMBR = 5Mbps (for communication bearers over E-RAB#1 via the MeNB)
SUE AMBR =5Mbps (for communication bearers over E-RAB#2 via the SeNB)
However, when E-RAB#1 has almost no activity but the communication bearers over
E-RAB#2 carry a large amount of data, it is possible that the aggregated data rate for
E-RAB#2 may exceed the allowed 5Mbps. In this case, therefore, the SeNB enforces
the S E AMBR by dropping data packets for the UE that are determined to be above the
user's allowance (S E AMBR) - This may result, from a user point of view, in the UE only
receiving an effective 5Mbps (assuming that E-RAB#1 has no activity and S E AMBR for
E-RAB#2 is set to 5Mbps) while the contracted UE-AMBR is 10Mbps.
[0019] Downlink - Unnecessary packet dropping in MeNB:
Similarly, using the parameters of the previous example (M E AMBR = 5Mbps and S UE
AMBR =5Mbps), there may be scenarios in which the MeNB may drop data packets for a
particular UE unnecessarily.
[0020] For example, when E-RAB#2 via the SeNB has almost no activity but the commu
nication bearers provided over E-RAB#1 carry a large amount of data, it is possible
that the aggregated data rate for E-RAB#1 may exceed the allowed 5Mbps via that
base station (MeNB). The MeNB may thus start dropping data packets resulting, from
a user point of view, in the UE only receiving an effective 5Mbps while its contracted
UE-AMBR is 10Mbps.
[0021] It will be appreciated that similar scenarios are also possible for the enforcement of
uplink UE-AMBRs.
[0022] In summary, when the communication bearers for a particular UE in dual con
nectivity exhibit an imbalance (at least temporarily) between the base stations serving
the UE, it may be difficult or impossible to ensure that the aggregated data rate for a
particular UE meets the data rate (UE-AMBR) associated with the user's subscription.
Summary of Invention
[0023] Accordingly, preferred embodiments of the present invention aim to provide methods
and apparatus which overcome or at least partially alleviate at least one of the above
issues.
[0024] In one aspect, the invention provides a base station configured to operate as part of a
dual connectivity configuration in which a control-plane connection for a user commu
nication device is provided via the base station and at least one communication bearer
between a core network and the user communication device is provided via at least a
further base station, said base station comprising: means for obtaining an aggregate
maximum bit rate specific to said user communication device and for obtaining in
formation relating to a data rate required for said user communication device via said
further base station; means for generating information identifying a bit rate specific to
said further base station, for use in enforcement of an aggregate maximum data
throughput for said user communication device via said further base station, wherein
said bit rate specific to said further base station is generated based on: i) said aggregate
maximum bit rate specific to said user communication device; and ii) said obtained in
formation relating to a data rate required for said user communication device via said
further base station; and means for providing, to said further base station, said in
formation identifying said bit rate specific to said further base station.
[0025] In one aspect, the invention provides a secondary base station configured to operate
as part of a dual connectivity configuration in which a control-plane connection for a
user communication device is provided via a master base station, different to said
secondary base station, and at least one communication bearer between a core network
and the user communication device is provided via said secondary base station, said
secondary base station comprising: means for determining a data rate required for said
user communication device via said secondary base station; means for providing, to
said master base station, information relating to said determined data rate required for
said user communication device via said secondary base station; and means for
receiving, from said master base station, information identifying a bit rate specific to
said secondary base station, wherein said bit rate specific to said secondary base station
is based on: i) an aggregate maximum bit rate specific to said user communication
device; and ii) said data rate required for said user communication device via said
secondary base station.
[0026] In one aspect, the invention provides a system comprising the above described base
station, the above described secondary base station, and a user communication device.
[0027] In one aspect, the invention provides a method performed by a base station
configured to operate as part of a dual connectivity configuration in which a controlplane
connection for a user communication device is provided via the base station and
at least one communication bearer between a core network and the user commu
nication device is provided via at least a further base station, the method comprising:
obtaining an aggregate maximum bit rate specific to said user communication device,
and information relating to a data rate required for said user communication device via
said further base station; generating information identifying a bit rate specific to said
further base station, for use in enforcement of a maximum data throughput for said
user communication device via said further base station, wherein said bit rate specific
to said further base station is generated based on: i) said aggregate maximum bit rate
specific to said user communication device; and ii) said obtained information relating
to a data rate required for said user communication device via said further base station;
and providing, to said further base station, said information identifying said bit rate
specific to said further base station.
[0028] In one aspect, the invention provides a method performed by a secondary base station
configured to operate as part of a dual connectivity configuration in which a controlplane
connection for a user communication device is provided via a master base
station, different to said secondary base station, and at least one communication bearer
between a core network and the user communication device is provided via said
secondary base station, the method comprising: determining a data rate required for
said user communication device via said secondary base station; providing, to said
master base station, information relating to said determined data rate required for said
user communication device via said secondary base station; and receiving, from said
master base station, information identifying a bit rate specific to said secondary base
station, wherein said bit rate specific to said secondary base station is based on: i) an
aggregate maximum bit rate specific to said user communication device; and ii) said
data rate required for said user communication device via said secondary base station.
[0029] The invention provides, for all methods disclosed, corresponding computer programs
or computer program products for execution on corresponding equipment, the
equipment itself (user equipment, nodes or components thereof) and methods of
updating the equipment.
[0030] Each feature disclosed in this specification (which term includes the claims) and/or
shown in the drawings may be incorporated in the invention independently (or in com
bination with) any other disclosed and/or illustrated features. In particular but without
limitation the features of any of the claims dependent from a particular independent
claim may be introduced into that independent claim in any combination or indi
vidually.
Brief Description of Drawings
[0031] Embodiments of the invention will now be described, by way of example only, with
reference to the attached figures in which:
[fig.l]Figure 1 schematically illustrates a mobile telecommunication system of a type
to which the invention is applicable;
[fig.2]Figure 2 is a block diagram illustrating the main components of the mobile
telephone forming part of the system shown in Figure 1;
[fig.3]Figure 3 is a block diagram illustrating the main components of the master base
station forming part of the system shown in Figure 1;
[fig.4]Figure 4 is a block diagram illustrating the main components of the secondary
base station forming part of the system shown in Figure 1;
[fig.5]Figure 5 illustrates an exemplary way in which dual connectivity can be
provided in the system shown in Figure 1 using an SeNB-specific bearer;
[fig.6]Figure 6 is an exemplary timing diagram illustrating a procedure performed by
elements of the mobile telecommunication system; and
[fig.7]Figure 7 illustrates a modification of the procedure shown in Figure 6.
[fig.8]Figure 8 illustrates another modification of the procedure shown in Figure 6.
Description of Embodiments
[0032]
Figure 1 schematically illustrates a mobile (cellular) telecommunication system 1
including a mobile telephone 3 (or other compatible communication device / user
equipment) served via the base stations 5-1 and 5-2. As those skilled in the art will ap
preciate, whilst one mobile telephone 3 and two base stations 5 are shown in Figure 1
for illustration purposes, the system, when implemented, will typically include other
base stations and mobile telephones.
[0033] A user of the mobile telephone 3 can communicate with other users and/or remote
servers via the base stations 5 and the core network 7. The core network 7 comprises,
amongst other things, a mobility management entity (MME) 11, a serving gateway
(S-GW) 13, and a Packet Data Network (PDN) Gateway (P-GW) 15.
[0034] The MME 11 manages general mobility aspects of the mobile telephone 3 and
ensures that connectivity is maintained with the mobile telephone 3 as it is moving
within the geographical area covered by the communication system (and/or as the
mobile telephone 3 is handed over between base stations of the communication
system). The MME 11 also handles control-plane signalling for the mobile telephone 3
and manages the various bearers associated with the mobile telephone 3 (e.g. such as
an Evolved Packet System (EPS) bearer and/or a radio bearer) e.g. by controlling the
S-GW 13 and the P-GW 15 (and/or possibly other network nodes) via which such
bearers are provided.
[0035] The S-GW 13 provides a connection between the mobile telephone 3 and the core
network 7 (via the base station 5-1) for sending and receiving user plane data over an
associated communication bearer (e.g. an EPS bearer). The communication bearer
normally terminates at the P-GW 15, although it is often complemented by an external
bearer as well (for example, another EPS bearer and/or the like) between the P-GW 15
and a communication end-point outside the core network 7 (e.g. in an external network
20). It will be appreciated that, whilst shown as separate entities, the functionalities of
the S-GW 13 and the P-GW 15 could be implemented in a single gateway element.
[0036] As will be understood by those skilled in the art, each base station 5 operates one or
more base station cells (not shown) in which communications can be made between
the base station 5 and the mobile telephone 3 using one or more suitable commu
nication links (e.g. radio links) provided between the mobile telephone 3 and the r e
spective serving base station 5. Each of the communication links may be carried over
one or more associated component carriers (Fl, F2).
[0037] In this system, a dual connectivity service can be provided to compatible user
equipment (such as the mobile telephone 3) using an appropriately configured commu
nication bearer or bearers (e.g. as specified in 3GPP TR 36.842). In the case of dual
connectivity, one of the base stations is configured as a master base station (MeNB)
5-1 and the other base station is configured as a secondary base station (SeNB) 5-2.
The base stations 5 are connected to each other via an appropriate base station to base
station communication interface (e.g. an 'X2' interface). In this example, the base
stations 5 are connected to each other using a non-ideal backhaul.
[0038] The MeNB 5-1 is connected to the core network 7 via an SI interface in order to
provide both user-plane ('Sl-U') communication via the S-GW 13 (for MeNB-specific
bearers and any split bearers) and control-plane ('SI -MME') communication with the
MME 11 (for all bearers). The SeNB 5-2 is also connected to the core network 7 via an
appropriate SI interface in order to provide user-plane ('Sl-U') communication over at
least some of its communication bearers (e.g. SeNB-specific bearers). Although in
Figure 1 the SeNB 5-2 is shown to be connected to the core network 7 directly, it may
also be connected indirectly, e.g. via the external network 20. Although not shown in
Figure 1, the SeNB 5-2 may also have user-plane ('Sl-U') connectivity via the MeNB
5-1 over the non-ideal backhaul (e.g. when using a split bearer configuration).
[0039] The mobile telephone 3 may be configured with multiple communication bearers (for
example, a first communication bearer for voice, a second communication bearer for
video, a third communication bearer for internet data, etc.), e.g. in order to provide
different transmission priorities for different services. Each communication bearer (and
each data packet sent over the communication bearers) is associated with an ap
propriate quality of service (QoS) identifier, such as a QoS class indicator (QCI) value,
in order ensure that the appropriate transmission priorities can be met regardless
whether such communication bearers are provided via the MeNB 5-1, the SeNB 5-2, or
both. Data associated with one of the mobile telephone's 3 communication bearers
may be transmitted on the same radio link/carrier (although data for different bearers
may be transmitted over different radio links/carriers).
[0040] In this system, the base stations 5-1, 5-2 (and the mobile telephone 3) are configured
to provide dual connectivity using at least an SeNB-specific bearer, i.e. a commu
nication bearer served via the SeNB 5-2 for communicating user-plane data for the
mobile telephone 3. The setting up of such a bearer may be initiated b y the MeNB 5-1,
when appropriate. A s part of this dual connectivity service, in this example, PDCP,
RLC, MAC, and PHY functionalities for the communication bearer are provided b y the
SeNB 5-2. Thus, when a downlink data packet is received b y the SeNB 5-1 (from the
core network 7 over the S I interface), the SeNB 5-1 performs appropriate processing
of the data packet (and passes the data packet from the PDCP layer to the lower layers)
for transmission towards the mobile telephone 3.
[0041] Advantageously, the base stations 5-1, 5-2 are also configured to enforce an a s
sociated aggregate maximum bit rate (i.e. UE-AMBR) parameter for the non-GBR
communications of the mobile telephone 3. Specifically, the MeNB 5-1 obtains the
value of the UE-AMBR from the MME 11 when it is setting up an initial context for
the mobile telephone 3, e.g. a s part of a connection establishment procedure between
the mobile telephone 3 and the base station 5-1. The MeNB 5-1 is also configured to
derive, from the obtained UE-AMBR, the applicable aggregate maximum bit rates M
-AMBR and S E AMB for the MeNB 5-1 and the SeNB 5-2, respectively. In this case, the
UE_AMBR and the S UE AMBR may be chosen such that their sum is equal to the UEAMBR,
which ensures that the mobile telephone 3 does not exceed its associated
aggregate maximum bit rate even when it is using a dual connectivity service.
[0042] For example, the MeNB 5-1 may be configured to derive, from the overall UEAMBR
to be enforced for a particular dual connectivity UE, an MeNB-specific UEAMBR
(MUE AMBR) for that UE and an SeNB-specific UE-AMBR (S E-AMBR) for that UE
based on the following equation:
UE-AMBR = MuE-AMBR + SUE-AMBR
[0043] Each base station 5- 1 and 5-2 is responsible for ensuring that an appropriate (base
station specific) aggregate maximum bit rate is enforced for the mobile telephone 3
connected to that base station. Thus, the MeNB 5- 1 enforces the M E-AMBR for the
mobile telephone's 3 communications via the MeNB's 5- 1, and the SeNB 5-2 enforces
the S E AMB for the mobile telephone's 3 communications via the SeNB's 5-2.
[0044] Advantageously, in this example, the MeNB 5- 1 is operable to obtain, from the
SeNB 5-2, information relating to a current data rate for the mobile telephone 3 via the
SeNB 5-2. The obtained information may comprise, for example, a data rate value
measured at the SeNB 5-2, an indication that the data rate (via the SeNB 5-2) is above
a predetermined threshold, an indication that a transmission buffer at the SeNB 5-2 is
above a predetermined threshold, an indication that a predetermined number of data
packets (e.g. at least one data packet) has been dropped at the SeNB 5-2, and/or the
like. The information (data rate/indication) provided by the SeNB 5-2 may relate to the
non-GBR bearers associated with the mobile telephone 3 at the SeNB 5-2, although it
may relate to other bearers as well.
[0045] When appropriate, the MeNB 5- 1 is beneficially able to update the applicable M UE
AMBR and/or SUE AMBR based on the information obtained from the SeNB 5-2 and provide
an updated SUE AMBR to the SeNB 5-2.
[0046] For example, when the obtained information indicates that the mobile telephone's 3
data rate via the SeNB 5-2 is likely to exceed (or has exceeded) the associated data rate
allowance (S E AMBR), and the MeNB 5- 1 determines that its own data rate is (at least
momentarily) below the associated data rate allowance (M E AMBR), the MeNB 5- 1 is
able to update the applicable M E AMBR and/or S E AMBR parameters to alleviate the risk
of a potential drop of data packets at the SeNB 5-2. For example, the MeNB 5- 1 may
decrease the value of the M E AMBR parameter and increase the value of the S E AMBR
parameter (but ensuring that UE-AMBR = M E AMBR + S E AMBR) - Once an updated S UE
AMBR parameter is derived by the MeNB 5- 1, it is forwarded to the SeNB 5-2 (over the
X2 interface) so that the SeNB 5-2 can apply the updated S E AMBR parameter to the
mobile telephone's 3 subsequent communications via the SeNB 5-2.
[0047] Similarly, when the obtained information indicates that the mobile telephone's 3 data
rate via the SeNB 5-2 is below the associated data rate allowance (S E AMBR), and the
MeNB 5- 1 determines that its own data rate is (at least momentarily) is about to exceed
the associated data rate allowance (M E AMBR), the MeNB 5- 1 is able to update the ap
plicable M E AMBR and/or SUE AMBR parameters to alleviate the risk of a potential drop of
data packets at the MeNB 5- 1. For example, the MeNB 5- 1 may increase the value of
the M E AMBR parameter and decrease the value of the SUE AMBR parameter (but ensuring
that UE-AMBR = M E AMBR + S UE AMBR) - Once an updated S UE AMBR parameter is derived
by the MeNB 5- 1, it is forwarded to the SeNB 5-2 (over the X2 interface) so that the
SeNB 5-2 can apply the updated SUE-AMBR parameter to the mobile telephone's 3
subsequent communications via the SeNB 5-2.
[0048] In summary, when the communication bearers for a particular UE in dual con
nectivity exhibit an imbalance (at least temporarily) between the base stations serving
the UE, it is possible to ensure, based on the information exchanged between the base
stations 5-1 and 5-2, that the aggregated data rate for a particular UE (via all base
stations involved in the dual connectivity service) meets the data rate (UE-AMBR) a s
sociated with the user's subscription.
[0049]
Figure 2 is a block diagram illustrating the main components of the mobile telephone
3 shown in Figure 1. As shown, the mobile telephone 3 has a transceiver circuit 3 1 that
is operable to transmit signals to and to receive signals from a base station 5 via one or
more antenna 33. The mobile telephone 3 has a controller 37 to control the operation of
the mobile telephone 3. The controller 37 is associated with a memory 39 and is
coupled to the transceiver circuit 31. Although not necessarily shown in Figure 2, the
mobile telephone 3 may of course have all the usual functionality of a conventional
mobile telephone 3 (such as a user interface 35) and this may be provided by any one
or any combination of hardware, software and firmware, as appropriate. Software may
be pre-installed in the memory 39 and/or may be downloaded via the telecommu
nications network or from a removable data storage device (RMD), for example.
[0050] The controller 37 is configured to control overall operation of the mobile telephone 3
by, in this example, program instructions or software instructions stored within
memory 39. As shown, these software instructions include, among other things, an
operating system 41, a communications control module 43, and a dual connectivity
module 45.
[0051] The communications control module 43 controls communications between the
mobile telephone 3 and the base station(s) 5. The communications control module 43
also controls the separate flows of uplink data and downlink data and control data to be
transmitted to the base station 5 (and other nodes, e.g. the MME 11, via the base
station 5).
[0052] The dual connectivity module 45 coordinates (with assistance by the communications
control module 43) communications over the respective communication bearer(s)
forming part of a dual connectivity service. The dual connectivity module 45 also
controls communications with the MeNB 5-1 over the associated carrier Fl and com
munications with the SeNB 5-2 over the associated carrier F2.
[0053]
Figure 3 is a block diagram illustrating the main components of the master base
station 5-1 shown in Figure 1. The master base station 5-1 is a communications node
providing services to user equipment 3 within its coverage area. In the embodiments
according to the invention, communications between the various base stations 5 and
the mobile telephone 3 are coordinated. As shown, the master base station 5-1 includes
a transceiver circuit 5 1 which transmits signals to, and receives signals from, the
mobile telephone 3 via at least one antenna 53. The master base station 5-1 also
transmits signals to and receives signals from the core network 7 and other
neighbouring base stations (e.g. the SeNB 5-2) via a network interface 55
(X2/non-ideal backhaul interface for communicating with neighbouring base stations
and SI interface for communicating with the core network 7). The operation of the
transceiver circuit 5 1 is controlled by a controller 57 in accordance with software
stored in memory 59. The software includes, among other things, an operating system
61, a communications control module 63, a dual connectivity module 65, an SI
module 67, an X2 module 68, and an AMBR module 69.
[0054] The communications control module 63 controls communications between the
master base station 5-1 and the SeNB 5-2, the mobile telephone 3, and the core
network devices.
[0055] The dual connectivity module 65 coordinates communications over the commu
nication bearer (or bearers) forming part of a dual connectivity service for the mobile
telephone 3 served by this base station.
[0056] The dual connectivity module 65 includes the PDCP, RLC, MAC, and PHY entities
(layers) responsible for communicating data packets (that belong to MeNB-specific
bearers) via the base station 5-1 when it is configured as an MeNB.
[0057] The SI module 67 handles SI signalling (e.g. generates, sends, and receives
messages/PDUs formatted in accordance with the SI protocol) between the base
station 5 and the core network 7 entities (such as the MME 11 and the S-GW 13). For
example, the SI module 67 is responsible for receiving downlink data packets from the
core network 7 and passing the received data packets to the dual connectivity module
65 (via the PDCP entity), when the base station 5-1 is configured to operate as an
MeNB.
[0058] The X2 module 68 handles X2 signalling (e.g. generates, sends, and receives
messages/PDUs formatted in accordance with the X2 application protocol) between the
master base station 5 and other base stations, such as the secondary base station 5-2.
For example, the X2 module 68 is responsible for exchanging, with the corresponding
X2 module of the secondary base station 5-2, signalling (e.g. control signalling and/or
data packets) relating to the SeNB-specific bearer.
[0059] The AMBR module 69 is responsible for ensuring that an appropriate aggregate
maximum bit rate is enforced for the data packets transmitted for each items of user
equipment (such as the mobile telephone 3) served by this base station (either directly,
or indirectly, via another base station as part of a dual connectivity service). In order to
do so, the AMBR module 69 obtains, from the MME 11 and for each mobile telephone
3 served by this base station 5-1, information identifying the aggregate maximum bit
rate allowed (e.g. subscribed) for the user associated with that mobile telephone 3.
When dual connectivity is configured for a particular mobile telephone 3, the AMBR
module 69 determines the applicable aggregate maximum bit rates M E-AMBR and S UE
AMBR for use in enforcement of a maximum throughput for the mobile telephone's 3
non-GBR communication bearers at the MeNB 5-1 and the SeNB 5-2, respectively.
The AMBR module 69 enforces the M E-AMBR for the MeNB's 5-1 communications
with the mobile telephone 3 (e.g. for MeNB-specific bearers), and provides (via the X2
module 68) the applicable S E AMBR to the SeNB 5-2 (for SeNB-specific bearers, and
optionally split bearers).
[0060] In some embodiments, the AMBR module 69 is configured to obtain (e.g. via the X2
module 68) information relating to a current data rate for the mobile telephone 3 via
the SeNB 5-2. The obtained information may comprise, for example, a data rate value
measured at the SeNB 5-2, an indication that the data rate (via the SeNB 5-2) is above
a predetermined threshold, an indication that a transmission buffer at the SeNB 5-2 is
above a predetermined threshold, an indication that a predetermined number of data
packets (e.g. at least one data packet) has been dropped at the SeNB 5-2, and/or the
like. When appropriate, the AMBR module 69 updates the applicable M E AMBR and/or
SUE AMBR based on the information obtained from the SeNB 5-2 and provides the
updated S E AMBR to the SeNB 5-2.
[0061]
Figure 4 is a block diagram illustrating the main components of the secondary base
station 5-2 shown in Figure 1. The secondary base station 5-2 is a communications
node providing services to user equipment 3 within its coverage area. As shown, the
secondary base station 5-2 includes a transceiver circuit 5 1 which transmits signals to,
and receives signals from, the mobile telephone 3 via at least one antenna 53. The
secondary base station 5-2 also transmits signals to and receives signals from the core
network 7 and other neighbouring base stations (e.g. the MeNB 5-1) via a network
interface 55 (X2/non-ideal backhaul interface for communicating with neighbouring
base stations and an optional SI interface for communicating with the core network 7).
The operation of the transceiver circuit 51 is controlled by a controller 57 in ac
cordance with software stored in memory 59. The software includes, among other
things, an operating system 61, a communications control module 63, a dual con
nectivity module 65, an SI module 67, an X2 module 68, and an AMBR module 69.
[0062] The communications control module 63 controls communications between the
secondary base station 5-2 and the MeNB 5-1, the mobile telephone 3, and the core
network devices.
[0063] The dual connectivity module 65 coordinates communications over the commu
nication bearer (or bearers) forming part of a dual connectivity service for the mobile
telephone 3 served by this base station.
[0064] The dual connectivity module 65 includes the PDCP, RLC, MAC, and PHY entities
(layers) responsible for communicating data packets via the base station 5-2 when it is
configured as an SeNB.
[0065] The SI module 67 handles SI signalling (e.g. generates, sends, and receives
messages/PDUs formatted in accordance with the SI protocol) between the base
station 5 and the core network 7 entities (such as the MME 11 and the S-GW 13).
[0066] The X2 module 68 handles X2 signalling (e.g. generates, sends, and receives
messages/PDUs formatted in accordance with the X2 application protocol) between the
secondary base station 5-2 and other base stations, such as the master base station 5-1.
For example, the X2 module 68 is responsible for exchanging, with the corresponding
X2 module of the master base station 5-1, signalling (e.g. control signalling) relating to
the SeNB-specific bearer.
[0067] The AMBR module 69 is responsible for ensuring that an appropriate aggregate
maximum bit rate is enforced for the data packets transmitted for each items of user
equipment (such as the mobile telephone 3) connected to this base station 5-2 whilst
configured as an SeNB. In order to do so, the AMBR module 69 obtains, from the
MeNB 5-1 and for each mobile telephone 3 served by this base station 5-2, information
identifying the aggregate maximum bit rate allowed (SUE AMBR) for that mobile
telephone 3 via the base station 5-2 (for the mobile telephone's 3 SeNB-specific
bearers). The AMBR module 69 enforces the S E AMBR for the SeNB's 5-2 commu
nications with the mobile telephone 3.
[0068] In some embodiments, the AMBR module 69 is configured to obtain (e.g. from the
dual connectivity module 65) information relating to a current data rate for the mobile
telephone 3 via the SeNB 5-2. The obtained information may comprise, for example, a
data rate value measured at the SeNB 5-2, an indication that the data rate (via the
SeNB 5-2) is above a predetermined threshold, an indication that a transmission buffer
at the SeNB 5-2 is above a predetermined threshold, an indication that a predetermined
number of data packets (e.g. at least one data packet) has been dropped at the SeNB
5-2, and/or the like. When appropriate, the AMBR module 69 provides (via the X2
module 68) the information obtained from dual connectivity module 65 to the MeNB
5-1.
[0069] In the above description, the mobile telephone 3 and the base stations 5 are described
for ease of understanding as having a number of discrete modules (such as the commu
nications control modules and the dual connectivity modules). Whilst these modules
may be provided in this way for certain applications, for example where an existing
system has been modified to implement the invention, in other applications, for
example in systems designed with the inventive features in mind from the outset, these
modules may be built into the overall operating system or code and so these modules
may not be discernible as discrete entities. These modules may also be implemented in
software, hardware, firmware or a mix of these.
[0070]
A number of different examples will now be described that illustrate how the
invention can be put into effect using the mobile telephone 3 and the base stations 5 (as
exemplary dual connectivity network points) of Figure 1. As discussed above, dual
connectivity service can be provided by configuring the mobile telephone 3 to com
municate with both the MeNB 5-1 and at least one SeNB 5-2, using respective commu
nication bearers.
[0071] Figure 5 illustrates (using continuous lines) an exemplary bearer configuration for the
provision of an SeNB-specific communication bearer. For comparison, Figure 5 also
illustrates (using dashed lines) an MeNB-specific bearer and a split bearer, the de
scriptions of which are omitted herein for the sake of simplicity. In Figure 5, some of
the protocol layers and functions (e.g. control-plane) implemented by the base stations
5 are also omitted. Whilst Figure 5 illustrates the downlink direction only (as indicated
by the arrows), a similar bearer configuration may be realised for the uplink direction
as well, e.g. by reversing the direction of data transmissions, where appropriate.
[0072] In the case of an SeNB-specific bearer, the SI control-plane (e.g. 'Sl-MME') for the
mobile telephone 3 is provided by the MeNB 5-1. Control-plane signalling for the
mobile telephone 3 can be exchanged with the SeNB 5-2 via the base station to base
station interface (e.g. X2), when required, or it can be communicated directly between
the MeNB 5-1 and the mobile telephone 3.
[0073] In a conventional or 'regular' communication bearer configuration that may be used
in a both single and dual connectivity scenarios, the MeNB 5-1 handles the SI userplane
for a communication bearer (e.g. a communication bearer that is associated with
carrier Fl of Figure 1) associated with the mobile telephone 3. Downlink data packets
for the mobile telephone 3 are received by the MeNB 5-1 at the PDCP layer, and
forwarded to the lower layers (i.e. the RLC, MAC, and PHY layers) for transmission to
the mobile telephone 3.
[0074] In this case, as indicated by the dashed arrows between the PDCP, RLC, MAC, and
PHY layers of the MeNB 5-1, (downlink) user data from the core network 7 is
processed within the base station 5-1, and transmitted over the air interface (using
carrier Fl) between the base station 5-1 and the mobile telephone 3 (not shown in
Figure 5) using the services of the PHY layer.
[0075] According to the communication bearer configuration of the SCG type that may be
used in a dual connectivity scenario (shown in continuous lines in Figure 5), user-plane
communication (e.g. a communication bearer that is associated with carrier F2 of
Figure 1) may be provided for the mobile telephone 3 via the SeNB 5-2, without
involving the MeNB 5-1. In this case, downlink data packets can be sent from a remote
endpoint over an associated communication bearer through the core network 7 (e.g. via
the S-GW 13) and received at the PDCP layer of the SeNB 5-2. After PDCP
processing, the data packets are passed to the RLC layer, then to the MAC layer,
before they are transmitted to the mobile telephone 3 (not shown in Figure 5) over the
PHY layer of the SeNB 5-2 (using carrier F2).
Example 1
[0076] First embodiment
Figure 6 is an exemplary timing diagram illustrating a procedure performed by
elements of the mobile telecommunication system 1.
[0077] The procedure begins in step S601, in which the MME 11 provides the value of the
UE-AMBR parameter to the MeNB 5-1. In this case, the UE-AMBR is provided as
part of an initial context setup procedure for the mobile telephone 3. Although not
shown in Figure 6, it will be appreciated that the MME 11 may be configured to derive
the value of the UE-AMBR from subscription data for a user associated with the
mobile telephone 3. Such subscription data may be obtained from another entity, e.g. a
Home Subscriber Server (HSS), as appropriate.
[0078] Next, the MeNB 5-1 derives the (UE-specific) M E-AMBR and SUE AMBR parameters
from the UE-AMBR, e.g. such that the sum of the M E-AMBR and the S E AMBR does not
exceed the value of the UE-AMBR. For example, the MeNB 5-1 may be configured to
distribute, at least initially, the aggregated maximum data rate (UE-AMBR) equally
between the base stations 5-1 and 5-2, i.e. both the M E AMBR and the SUE AMBR may be
set to 50% of the UE-AMBR associated with the mobile telephone 3. However, the
MeNB 5-1 may also be configured to allocate a larger part (percentage) of the ag
gregated maximum data rate to one base station than the part of the aggregated
maximum data rate it allocates to the other base station. As generally shown in step
S603, the MeNB 5-1 and SeNB 5-2 are thus able to apply their respective M E AMBR and
SUE AMBR parameters for the mobile telephone's 3 communications via that base station
5-1 and 5-2.
[0079] In step S605, which may be performed e.g. in response to a request (shown at S604)
and/or periodically, the SeNB 5-2 (using its AMBR module 69) determines a data rate
for the (SeNB-specific) communication bearers (e.g. non-GBR bearers) associated
with the mobile telephone 3 (via the SeNB 5-2). Once the data rate associated with the
mobile telephone 3 has been determined, the SeNB 5-2 (using its X2 module 68)
generates and sends, in step S607, an appropriately formatted signalling message (e.g.
an Έ -RAB Status Report' X2 message) to the MeNB 5-1, and includes in this message
(e.g. in a suitable information element thereof) information identifying the mobile
telephone's 3 data rate.
[0080] In step S609, the MeNB 5-1 (using its AMBR module 69), derives updated
(UE-specific) M E-AMBR and SUE AMBR parameters (e.g. such that UE-AMBR = M E-AMBR
+ S E AMBR) by taking into account the received information identifying the mobile
telephone's 3 data rate at the SeNB 5-2.
[0081] For example, the MeNB 5-1 (using its AMBR module 69) may increase the value of
the S E AMBR parameter (and simultaneously decrease the value of the M E AMBR
parameter such that UE-AMBR = M E AMBR + S E AMBR) when the information received
from the SeNB 5-2 indicates that the mobile telephone's 3 data rate at the SeNB 5-2 is
likely to exceed the currently enforced SUE AMBR (configured at S603), and the AMBR
module 69 of the MeNB 5-1 determines that the MeNB's 5-1 data rate does not exceed
the data rate allowance (M E AMBR) associated with the mobile telephone 3. Similarly,
the MeNB 5-1 (using its AMBR module 69) may increase the value of the M E AMBR
parameter and simultaneously decrease the value of the SUE AMBR parameter (such that
UE-AMBR = M E AMBR + S UE AMBR) when the information received from the SeNB 5-2
indicates that the mobile telephone's 3 data rate at the SeNB 5-2 does not exceed the
currently enforced S E AMBR (configured at S603), and the AMBR module 69 of the
MeNB 5-1 determines that the MeNB's 5-1 data rate is likely to exceed the data rate
allowance (M E AMBR) associated with the mobile telephone 3.
[0082] Once an updated S E AMBR parameter is derived by the MeNB 5-1, the MeNB 5-1
(using its AMBR module 69) generates and sends, at step S611, an appropriately
formatted signalling message to the SeNB 5-2 (over the X2 interface), and includes in
this message the updated S E AMBR-
[0083] In step S613, the SeNB 5-2 (using its AMBR module 69) starts to apply the updated
SUE AMBR parameter to the mobile telephone's 3 subsequent communications via the
SeNB 5-2. Similarly, as shown in step S615, the MeNB 5-1 (using its AMBR module
69) also starts to apply the updated M E AMBR parameter to the mobile telephone's 3
subsequent communications via the MeNB 5-1.
Example 2
[0084] Second embodiment
Figure 7 illustrates a modification of the procedure shown in Figure 6. In this case,
steps S701 and S703 correspond to S601 and S603, respectively, thus their description
is omitted herein.
[0085] However, in this example, as generally shown at step S705, the SeNB 5-2 (using its
dual connectivity module 65) determines that a predetermined number of data packets
(e.g. at least one data packet) has been dropped (i.e. failed to be sent) for the mobile
telephone 3, due to the enforcement of the associated S UE-AMBR parameter.
[0086] Therefore, the SeNB 5-2 2 (using its X2 module 68) generates and sends, in step
S707, an appropriately formatted signalling message (e.g. an Έ -RAB Status Report'
X2 message) to the MeNB 5-1, and includes in this message (e.g. in a suitable in
formation element thereof) an indication that one or more data packets for the mobile
telephone 3 have been dropped (could not be delivered) due to data rate enforcement.
[0087] In step S709, by taking into account the received indication, the MeNB 5-1 (using its
AMBR module 69), derives updated (UE- specific) M E-AMBR and S UE AMB parameters
(e.g. such that UE-AMBR = M E-AMBR + S E-AMBR) -
[0088] For example, the MeNB 5-1 (using its AMBR module 69) may increase the value of
the SUE AMBR parameter (and simultaneously decrease the value of the M E AMBR
parameter such that UE-AMBR = M E AMBR + S UE AMBR) when the SeNB's 5-2 message
indicates that a predetermined amount of data packets have been dropped (assuming
that the MeNB's 5-1 data rate does not exceed the data rate allowance (M E AMBR) a s
sociated with the mobile telephone 3). Similarly, the MeNB 5-1 may decrease the
value of the SUE AMBR parameter (and simultaneously increase the value of the M E AMBR
parameter such that UE-AMBR = M E AMBR + S UE AMBR) when the SeNB's 5-2 message
indicates that no data packets have been dropped (e.g. since applying the current S UE
AMBR parameter and/or since a preceding notification was sent by the SeNB). Advan
tageously, the MeNB 5-1 may be able to increase (e.g. gradually) its own data rate al
location (M E AMBR) for the mobile telephone 3 as long the mobile telephone's 3 com
munications via the SeNB 5-2 remain unaffected (e.g. no packets are dropped at the
SeNB 5-2).
Example 3
[0089] Third embodiment
Figure 8 illustrates another exemplary modification of the procedure shown in Figure
6. In this case, steps S801 and S803 correspond to S601 and S603, respectively, thus
their description is omitted herein.
[0090] However, in this example, as generally shown at step S805, the SeNB 5-2 (using its
dual connectivity module 65) determines that the status of its transmission buffer meets
a predetermined trigger (e.g. the transmission buffer and/or processing time is above a
predetermined threshold). It will be appreciated that such predetermined trigger may
result from the enforcement of the S E AMBR parameter associated with the mobile
telephone 3.
[0091] Therefore, the SeNB 5-2 2 (using its X2 module 68) generates and sends, in step
S807, an appropriately formatted signalling message (e.g. an Έ -RAB Status Report'
X2 message) to the MeNB 5-1, and includes in this message (e.g. in a suitable in
formation element thereof) information relating to the status of its transmission buffer
(for the mobile telephone 3). It will be appreciated that the information relating to the
status of the SeNB's 5-2 transmission buffer may also be sent periodically, i.e. re
gardless whether or not a trigger has been detected at step S805.
[0092] In step S809, by taking into account the received information relating to the status of
the SeNB's 5-2 transmission buffer, the MeNB 5-1 (using its AMBR module 69),
derives updated (UE-specific) M E-AMBR and S UE AMBR parameters (e.g. such that UEAMBR
= MuE-AMBR + SUE AMBR)-
[0093] For example, the MeNB 5-1 (using its AMBR module 69) may increase the value of
the S E AMBR parameter (and simultaneously decrease the value of the M E AMBR
parameter such that UE-AMBR = M E AMBR + S UE AMBR) when the SeNB's 5-2 message
indicates that SeNB's 5-2 transmission buffer is over a predetermined threshold
(assuming that the MeNB's 5-1 data rate does not exceed the data rate allowance (M UE
AMBR) associated with the mobile telephone 3). Similarly, the MeNB 5-1 may decrease
the value of the S UE AMBR parameter (and simultaneously increase the value of the M UE
AMBR parameter such that UE-AMBR = M E AMBR + S UE AMBR) when the SeNB's 5-2
message indicates that the SeNB's 5-2 transmission buffer is not over (e.g. it is below)
a predetermined threshold. Advantageously, the MeNB 5-1 may be able to increase
(e.g. gradually) its own data rate allocation (M E AMBR) for the mobile telephone 3 as
long the mobile telephone's 3 communications via the SeNB 5-2 remain unaffected
(e.g. the transmission buffer at the SeNB 5-2 stays below the predetermined threshold).
[0094] Modifications and Alternatives>
Detailed embodiments have been described above. As those skilled in the art will ap
preciate, a number of modifications and alternatives can be made to the above em
bodiments whilst still benefiting from the inventions embodied therein.
[0095] In the above examples, the MeNB is described to comprise a macro base station.
However, it will be appreciated that the MeNB may comprises any type of base station,
e.g. a pico base station, a femto base station, a home base station. Further, it will be ap
preciated that either of the carriers F l and/or F2 may be provided via a relay, a remote
radio head, and/or the like instead of a base station.
[0096] In the above examples, each base station is described to provide a single carrier (Fl
or F2). However, it will be appreciated that each base station may provide a plurality
of carriers (e.g. the same and/or different set of carriers).
[0097] It will be appreciated that whilst the above examples are described with reference to
a communication bearer of the SCG type, the description is equally applicable to any
other types of communication bearers, including MeNB- specific and/or 'split' commu
nication bearers (e.g. as specified in 3GPP TR 36.842).
[0098] In the above description of Figure 5, there is only one instance of MCG bearer, one
instance of SCG bearer, and one instance of split bearer shown. However, it will be ap
preciated that any number and/or any types of bearers, in any combination may be
provided for a particular UE. For example, multiple bearers of each type and/or any
combination of bearers of different types may be provided. In any case, the actual
bearer configuration is based on the associated QCI value. For example, if there are
two SCG bearers (both bearers being non-GBR) for a particular UE, then the aggregate
data rate on these two SCG bearers should not exceed the S UE-AMBR associated with the
UE. In another example, if there is one split bearer and one SCG bearer for a particular
UE (both bearers being non-GBR), then the aggregate data rate on the SCG bearer and
on the SeNB part of the split bearer should not exceed the S UE-AMBR associated with the
UE.
[0099] In the above embodiments, the MeNB is described to derive (and provide to the
SeNB) an updated S UE-AMBR parameter by taking into account the information (data rate,
packet drop indication, and/or the like) received from the SeNB. However, it will be
appreciated that the MeNB may also be configured to send an indication to the SeNB
to discard or ignore, at least temporarily, any previously sent S UE-AMBR parameter
(instead of deriving an updated S UE-AMBR parameter). This may beneficially allow the
SeNB to avoid unnecessarily dropping data packets for the mobile telephone. In this
case, the SeNB may be configured to suspend enforcement of the S UE-AMBR parameter at
least until a predetermined time period, until receipt of a new S UE-AMBR parameter from
the MeNB, and/or until the SeNB has emptied or reduced below a threshold the
amount of data held in its transmit buffer for the mobile telephone.
[0100] In the above description of Figure 6, the SeNB is described to generate and send an
Έ -RAB Status Report' signalling message formatted in accordance with the X2 ap
plication protocol. However, it will be appreciated that a different message and/or a
different application protocol may also be used. For example, the SeNB may be
configured to include information relating to its data rate in a suitable field (e.g. an
'enforcement result' field, 'AMBR information' field, 'data rate' field and/or the like)
in a Frame Protocol message.
[0101] It will be appreciated that the SeNB may generate and send the data rate information
(at step S607) either periodically and/or when a predetermined trigger is met. Such a
predetermined trigger may include any of the following:
- the data rate for the mobile telephone is higher than (or equal to) the associated S
UE AMBR;
- the data rate for the mobile telephone is higher than (or equal to) the associated S
-AMBR minus an offset (e.g. 10% below the S E-AMBR) ;
- expiry of an associated timer;
- transmission buffer being over a predetermined threshold (which may be indicative
of an insufficient for SUE-AMBR being configured for the mobile telephone);
- a sudden change (e.g. increase/decrease) in the data rate required for the mobile
telephone;
- the SeNB has additional capacity that can be allocated to communication bearers
associated with the mobile telephone;
- receipt of a data rate error indication from the mobile telephone (or from lower
layers of the SeNB); and
- receipt of a request from the MeNB (e.g. as shown at step S604).
[0102] It will be appreciated that when the SeNB sends the packet drop indication to the
MeNB (at step S707), it may also send information identifying the data rate for the
mobile telephone. In other words, steps S607 and S707 may be combined.
[0103] It will also be appreciated that the SeNB may be configured to provide, to the MeNB
over the X2 interface, information identifying the number of data packets discarded
during a given time period (e.g. at the RLC and/or MAC layers). Based on this in
formation, the MeNB may be able to determine a measure of an associated "Packet
Discard Rate" at the SeNB (for the mobile telephone), and update the MUE-AMBR and/or
S -AMBR accordingly. For example, the MeNB may increase the value of the SUE-AMBR
by at least the determined "Packet Discard Rate" for the mobile telephone (up to the
associated UE-AMBR).
[0104] It will be appreciated that the base stations (MeNB and SeNB) may be configured to
provide each other information relating to their own data rates for the mobile telephone
served by both base stations. Further, it will be appreciated that the MeNB may be
configured to determine under-utilisation of its communication resources allocated for
the mobile telephone (e.g. the MeNB may be configured to determine that the mobile
telephone's data rate via the MeNB is below a threshold value/percentage and/or it is
below the associated M E AMBR minus an offset). In this case, the MeNB may be
configured to provide an appropriate indication to the SeNB, which in turn may cause
the SeNB to exceed/ignore, at least temporarily, the associated S E AMBR for the mobile
telephone (whilst still enforcing the UE-AMBR value, i.e. M E AMBR + SUE-AMBR) -
[0105] Alternatively, the MeNB may be configured to inform the MME about the current
values of the MUE-AMBR and/or the SUE AMBR to be enforced at the MeNB and the SeNB,
respectively. In this case, the MME may be configured to forward the values of the M
uE-AMBR and/or the S UE AMBR to the S-GW and the S-GW may be configured to forward
the values of the M UE-AMBR and/or the S UE AMBR to the P-GW. Advantageously, the PGW
may be able to perform the enforcement of the M UE-AMBR and/or the S UE AMBR parameters
(e.g. by performing data rate enforcement with the value of M AMBR for com
munication bearers provided via the MeNB and performing data rate enforcement with
the value of SUE-AMBR f r communication bearers provided via the SeNB). This al
ternative may require a new (or modified) signalling message to be sent between the
MeNB and the MME over the S I interface (i.e. for the provision of the M AMBR and/or
the S UE-AMBR to the MME).
[0106] The base station (e.g. MeNB) may comprise means for deriving a bit rate specific to
the base station, wherein the sum of the bit rate specific to the base station and the bit
rate specific to the further base station (e.g. SeNB) does not exceed the aggregate
maximum bit rate specific to the user communication device.
[0107] The information relating to a data rate required for the user communication device
via said further base station may comprise at least one of: information relating to a data
rate (e.g. non-GBR data rate) arriving at said further base station for the user commu
nication device, an indication of a data loss associated with the user communication
device at said further base station, and information identifying a buffer status for said
user communication device.
[0108] The information relating to a data rate required for said user communication device
via said further base station may comprise information relating to data packets
transmitted over one or more non-guaranteed bit rate communication bearers a s
sociated with said user communication device.
[0109] The base station may be configured to operate as a master base station of said dual
connectivity configuration and the further base station may be configured to operate as
a secondary base station of said dual connectivity configuration.
[0110] The generating means (of the base station) may be operable to, when said in
formation relating to a required data rate (via the further base station) is not available,
generate an initial bit rate specific to the further base station, to be used in enforcement
of a maximum data throughput over said at least one communication bearer via said
further base station, based on the aggregate maximum bit rate specific to the user com
munication device. In this case, the providing means may be operable to provide the
initial bit rate specific to said further base station to said further base station (e.g. prior
to said obtaining means obtaining said information relating to a data rate required for
the user communication device via said further base station).
[0111] The base station may further comprise means for controlling the establishment of
said at least one communication bearer between the core network and the user commu
nication device via said further base station; wherein said establishment of said at least
one communication bearer may comprise providing, to said further base station, said
initial bit rate specific to said further base station.
[01 12] The providing means may be configured to provide, to said further base station, said
information identifying said bit rate specific to said further base station over a base
station to base station interface (e.g. an X2 interface).
[0113] The providing means (of the secondary base station) may be operable to provide said
information to said master base station periodically and/or upon request by the master
base station and/or upon detecting a predetermined trigger. The providing means may
be operable to provide said information by sending at least one message to said master
base station over a base station to base station interface.
[01 14] In the above embodiments, a mobile telephone based telecommunications system
was described. As those skilled in the art will appreciate, the signalling techniques
described in the present application can be employed in other communications system.
Other communications nodes or devices may include user devices such as, for
example, personal digital assistants, laptop/tablet computers, web browsers, etc.
[0115] In the embodiments described above, the mobile telephone and the base stations will
each include transceiver circuitry. Typically this circuitry will be formed by dedicated
hardware circuits. However, in some embodiments, part of the transceiver circuitry
may be implemented as software run by the corresponding controller.
[0116] In the above embodiments, a number of software modules were described. As those
skilled in the art will appreciate, the software modules may be provided in compiled or
un-compiled form and may be supplied to the base stations as a signal over a computer
network, or on a recording medium. Further, the functionality performed by part or all
of this software may be performed using one or more dedicated hardware circuits.
[01 17] This invention has been described above by way of the embodiment, but this
invention is not limited to the embodiment described above. Various changes that can
be understood by a person skilled in the art can be made to the configuration and
details of this invention within the scope of this invention. Various other modifications
will be apparent to those skilled in the art and will not be described in further detail
here.
[0118] This application is based upon and claims the benefit of priority from United
Kingdom patent application No. 1414139.4, filed on August 8, 2014, the disclosure of
which is incorporated herein in its entirety by reference.

Claims
A base station configured to operate as part of a dual connectivity con
figuration in which a control-plane connection for a user commu
nication device is provided via the base station and at least one commu
nication bearer between a core network and the user communication
device is provided via at least a further base station, said base station
comprising:
means for obtaining an aggregate maximum bit rate specific to said
user communication device and for obtaining information relating to a
data rate required for said user communication device via said further
base station;
means for generating information identifying a bit rate specific to said
further base station, for use in enforcement of an aggregate maximum
data throughput for said user communication device via said further
base station, wherein said bit rate specific to said further base station is
generated based on: i) said aggregate maximum bit rate specific to said
user communication device; and ii) said obtained information relating
to a data rate required for said user communication device via said
further base station; and
means for providing, to said further base station, said information
identifying said bit rate specific to said further base station.
The base station according to claim 1, further comprising means for
deriving a bit rate specific to said base station; and wherein the sum of
said bit rate specific to said base station and said bit rate specific to said
further base station does not exceed said aggregate maximum bit rate
specific to said user communication device.
The base station according to claim 1 or 2, wherein said information
relating to a data rate required for said user communication device via
said further base station comprises at least one of: information relating
to a data rate arriving at said further base station for said user commu
nication device, an indication of a data loss associated with said user
communication device at said further base station, and information
identifying a buffer status for said user communication device.
The base station according to any of claims 1 to 3, wherein said in
formation relating to a data rate required for said user communication
device via said further base station comprises information relating to
data packets transmitted over one or more non-guaranteed bit rate comWO
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munication bearers associated with said user communication device.
[Claim 5] The base station according to any of claims 1 to 4, wherein said base
station is configured to operate as a master base station of said dual
connectivity configuration and said further base station is configured to
operate as a secondary base station of said dual connectivity con
figuration.
[Claim 6] The base station according to any of claims 1 to 5, wherein said
generating means is operable to, when said information relating to a
required data rate is not available, generate an initial bit rate specific to
said further base station, to be used in enforcement of a maximum data
throughput over said at least one communication bearer via said further
base station, based on said aggregate maximum bit rate specific to said
user communication device, and said providing means is operable to
provide said initial bit rate specific to said further base station to said
further base station (e.g. prior to said obtaining means obtaining said
information relating to a data rate required for said user communication
device via said further base station).
[Claim 7] The base station according to claim 6, further comprising means for
controlling the establishment of said at least one communication bearer
between the core network and the user communication device via said
further base station; wherein said establishment of said at least one
communication bearer comprises providing, to said further base station,
said initial bit rate specific to said further base station.
[Claim 8] The base station according to any of claims 1 to 7, wherein said
providing means is configured to provide, to said further base station,
said information identifying said bit rate specific to said further base
station over a base station to base station interface.
[Claim 9] A secondary base station configured to operate as part of a dual con
nectivity configuration in which a control-plane connection for a user
communication device is provided via a master base station, different to
said secondary base station, and at least one communication bearer
between a core network and the user communication device is provided
via said secondary base station, said secondary base station comprising:
means for determining a data rate required for said user communication
device via said secondary base station;
means for providing, to said master base station, information relating to
said determined data rate required for said user communication device
via said secondary base station; and
WO 2016/021125 PCT/JP2015/003641
means for receiving, from said master base station, information
identifying a bit rate specific to said secondary base station, wherein
said bit rate specific to said secondary base station is based on: i) an
aggregate maximum bit rate specific to said user communication
device; and ii) said data rate required for said user communication
device via said secondary base station.
[Claim 10] The secondary base station according to claim 9, wherein said
providing means is operable to provide said information to said master
base station periodically and/or upon request by the master base station
and/or upon detecting a predetermined trigger.
[Claim 11] The secondary base station according to claim 9 or 10, wherein said
providing means is operable to provide said information by sending at
least one message to said master base station over a base station to base
station interface.
[Claim 12] A system comprising a base station according to any of claims 1 to 8, a
secondary base station according to any of claims 9 to 11, and a user
communication device.
[Claim 13] A method performed by a base station configured to operate as part of a
dual connectivity configuration in which a control-plane connection for
a user communication device is provided via the base station and at
least one communication bearer between a core network and the user
communication device is provided via at least a further base station, the
method comprising:
obtaining an aggregate maximum bit rate specific to said user commu
nication device, and information relating to a data rate required for said
user communication device via said further base station;
generating information identifying a bit rate specific to said further
base station, for use in enforcement of an aggregate maximum data
throughput for said user communication device via said further base
station, wherein said bit rate specific to said further base station is
generated based on: i) said aggregate maximum bit rate specific to said
user communication device; and ii) said obtained information relating
to a data rate required for said user communication device via said
further base station; and
providing, to said further base station, said information identifying said
bit rate specific to said further base station.
[Claim 14] A method performed by a secondary base station configured to operate
as part of a dual connectivity configuration in which a control-plane
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connection for a user communication device is provided via a master
base station, different to said secondary base station, and at least one
communication bearer between a core network and the user commu
nication device is provided via said secondary base station, the method
comprising:
determining a data rate required for said user communication device via
said secondary base station;
providing, to said master base station, information relating to said de
termined data rate required for said user communication device via said
secondary base station; and
receiving, from said master base station, information identifying a bit
rate specific to said secondary base station, wherein said bit rate
specific to said secondary base station is based on: i) an aggregate
maximum bit rate specific to said user communication device; and ii)
said data rate required for said user communication device via said
secondary base station.
[Claim 15] A computer implementable instructions product comprising computer
implementable instructions for causing a programmable commu
nications device to perform the method of claim 13 or 14.