Patent ID: 12262402

DESCRIPTION OF EMBODIMENTS

<Overview>

FIG.1schematically illustrates a mobile (cellular) telecommunication system1including a mobile telephone3(or other compatible communication device/user equipment) served via base stations5-1and5-2. As those skilled in the art will appreciate, whilst one mobile telephone3and two base stations5are shown inFIG.1for illustration purposes, the system, when implemented, will typically include other base stations and mobile telephones.

A user of the mobile telephone3can communicate with other users and/or remote servers via the base stations5and a core network7. The core network7comprises, 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.

The MME11manages general mobility aspects of the mobile telephone3and ensures that connectivity is maintained with the mobile telephone3as it is moving within the geographical area covered by the communication system (and/or as the mobile telephone3is handed over between base stations of the communication system). The MME11also handles control-plane signaling for the mobile telephone3and manages the various bearers associated with the mobile telephone3(e.g. such as an Evolved Packet System (EPS) bearer and/or a radio bearer) e.g by controlling the S-GW13and the P-GW15(and/or possibly other network nodes) via which such bearers are provided.

The S-GW13provides a connection between the mobile telephone3and the core network7(via the base station5-1) 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-GW15, although it is often complemented by an external bearer as well (for example, another EPS bearer and/or the like) between the P-GW15and a communication end-point outside the core network7(e.g. in an external network20). It will be appreciated that, whilst shown as separate entities, the functionalities of the S-GW13and the P-GW15could be implemented in a single gateway element.

As will he understood by those skilled in the art, each base station5operates one or more base station cells (not shown) in which communications can be made between the base station5and the mobile telephone3using one or more suitable communication links (e.g. radio links) provided between the mobile telephone3and the respective serving base station5. Each of the communication links may be carried over one or more associated component carriers (F1, F2).

In this system, a dual connectivity service is provided to compatible user equipment (such as the mobile telephone3) using split bearer configuration (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)5-1and the other base station is configured as a secondary base station (SeNB)5-2. The base stations5are connected to each other via an appropriate base station to base station communication interface (e.g. an ‘X2’ interface). In this example, the base stations5are connected to each other using a non-ideal backhaul.

The MeNB5-1is configured to provide a primary component carrier F1in the licensed spectrum and the SeNB5-2is configured to provide a secondary component carrier F2that is in the unlicensed spectrum and is therefore subject to the so called listen-before-talk (LBT) requirements, in order to provide fair and efficient co-existence.

The MeNB5-1is connected to the core network7via an S1 interface in order to provide both user-plane (‘S1-U’) communication via the S-GW13(for MeNB-split bearers) and control-plane (‘S1-MME’) communication with the MME11(for all bearers). Although inFIG.1the SeNB5-2is shown not to be connected to the core network7directly, it may also be connected indirectly, e.g. via the external network20. Although not shown inFIG.1, the SeNB5-2has user-plane (‘S1-U’) connectivity via the MeNB5-1over the non-ideal backhaul.

The mobile telephone3may 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 appropriate 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 MeNB5-1, the SeNB5-2, or both. Data associated with one of the mobile telephone's3communication bearers may be transmitted on the same radio link/carrier (although data for different bearers may be transmitted over different radio links/carriers).

In this system, the base stations5-1,5-2(and the mobile telephone3) are configured for dual connectivity using a split bearer, that is data packets are transmitted to the mobile telephone3over a communication bearer via a first communication bearer path provided by MeNB5-1and/or via a second communication bearer path provided by the SeNB5-2. In this particular example, the splitting of the communication bearer is in the PDCP entity of the MeNB5-1. Thus, PDCP, RLC, MAC and PHY functionalities for the split bearer are provided in the MeNB5-1, while RLC, MAC and PHY functionalities for the communication bearer are provided in the SeNB5-2, for example. When a downlink data packet is received by the MeNB5-1it performs appropriate processing of the data packet. For example, the MeNB5-1may route the data packet from the PDCP layer of the MeNB5-1to the SeNB5-2for transmission towards the mobile telephone3, or pass the data packet from the PDCP layer to the lower layers for transmission towards the mobile telephone3.

Advantageously, the MeNB5-1is configured to determine which of the base stations5-1,5-2is to transmit data packets towards the mobile telephone based on information indicating availability of a communications channel on component carrier F2. Beneficially, in order to facilitate this action by the MeNB5-1, information identifying the availability of the channel is provided by the SeNB5-2.

For example, the SeNB5-2may detect the availability of a communications channel on the carrier F2and provide feedback to the MeNB5-1in the form of a value of an available buffer size. Specifically, the SeNB5-2reports the available buffer size corresponding to the UE3as ‘0’ if the communications channel on carrier F2is unavailable, and reports the available buffer size corresponding to the UE3as a non-zero value if the channel is available. In this particular example, the base station5-2uses the DL DATA DELIVERY STATUS frame as described in TS 36.425 (see Table 1 below) for this purpose and more specifically one, or both, of the two parts (‘information elements (IEs)’) of that frame reserved for a “desired buffer size” (e.g. the “Desired buffer size for the E-RAB” and/or the “Minimum desired buffer size for the UE”). Where the Desired buffer size for the E-RAB IE is used this effectively informs the MeNB5-1of the availability of a communication channel for a specific E-RAB and UE (i.e. on a per UE and per E-RAB basis) and where the Minimum desired buffer size for the UE IE is used this effectively informs the MeNB5-1of the availability of a communication channel for a specific UE (i.e. on a per UE and per E-RAB basis). Effectively, therefore, use of the Desired buffer size for the E-RAB IE provides a finer granularity because it can individually provide channel status information for each respective E-RAB provided via the UE whereas use of the Minimum desired buffer size for the UE IE provides a coarser granularity for a whole UE.

TABLE 1DL DATA DELIVERY STATUS (PDU Type 1) FormatBitsNumber76543210of OctetsPDU Type (=1)SpareFinalLost1FramePacketInd.ReportHighest successfully delivered PDCP2Sequence NumberDesired buffer size for the E-RAB4Minimum desired buffer size for the UE4Number of lost X2-U Sequence Number1ranges reportedStart of lost X2-U Sequence Number range4* (Number ofEnd of lost X2-U Sequence Number rangereported lostX2-u SNranges)Spare extension0-4

The MeNB5-1is also configured to start a timer upon receiving the availability information. The timer has a predetermined time period. Before expiry of the predetermined time period, the availability information is considered to be valid. After expiry of the predetermined time period, the availability information is considered to be invalid. Thus, when the information provided by the SeNB5-2indicates that the communications channel on carrier F2is unavailable, the MeNB5-1can perform flow control procedures during the predetermined time period. In one advantageous example, the flow control procedure performed by the MeNB5-1when the carrier F2is unavailable includes stopping the transmission of further data to the base station5-2. Furthermore, the MeNB5-1can beneficially instruct the SeNB5-2to not transmit packets which have already been sent to the SeNB5-2and which are buffered in a transmission queue for transmission to the UE3. Moreover, the MeNB5-1can itself transmit these packets to the UE3.

In summary, it is possible to ensure that the flow of data via the MeNB or SeNB can be suitably controlled based on the availability of a communications channel on the carrier F2in the unlicensed spectrum for transmission of data by the SeNB5-2to the UE3. Accordingly, the user experience can be enhanced by a reduction or elimination of delays associated with channel allocation and/or scheduling on the secondary carrier F2in the unlicensed spectrum.

<Mobile Telephone>

FIG.2is a block diagram illustrating the main components of the mobile telephone3shown inFIG.1. As shown, the mobile telephone3has a transceiver circuit31that is operable to transmit signals to and to receive signals from a base station5via one or more antenna33. The mobile telephone3has a controller37to control the operation of the mobile telephone3. The controller37is associated with a memory39and is coupled to the transceiver circuit31. Although not necessarily shown inFIG.2, the mobile telephone3may of course have all the usual functionality of a conventional mobile telephone3(such as a user interface35) 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 memory39and/or may be downloaded via the telecommunications network or from a removable data storage device (RMD), for example.

The controller37is configured to control overall operation of the mobile telephone3by, in this example, program instructions or software instructions stored within the memory39. As shown, these software instructions include, among other things, an operating system41, a communications control module43, a dual connectivity module45, and a measurement module47.

The communications control module43controls communications between the mobile telephone3and the base station(s)5. The communications control module43also controls the separate flows of uplink data and downlink data and control data to be transmitted to the base station5(and other nodes, e.g. the MME11, via the base station5).

The dual connectivity module45coordinates (with assistance by the communications control module43) communications over the split communication bearer forming part of a dual connectivity service. The dual connectivity module45also controls communications with the MeNB5-1over the associated carrier F1and communications with the SeNB5-2over the associated carrier F2.

The measurement module47measures noise level and/or an interference level on physical resources. In one example described below this is used, by the measurement module47, to determine a status of the communication channel for example whether or not the channel is busy. This status can then be reported either to the SeNB5-2or the MeNB5-1. The UE3may, for example, report that the channel is busy (unavailable) to the SeNB5-2by sending a channel quality indicator (CQI) with an Out-Of-Range (OOR) value, or any other suitable means. The SeNB5-2can use this as assistance information and provide channel availability information to the MeNB5-1based on any of other methods described herein. Alternatively, or in addition, the UE3may report a channel status directly to the MeNB5-1. For example, if the UE3is aware of resource allocation of the SeNB5-2and determines that noise or interference received on physical resources originates from neighbouring devices, the UE3can report to the MeNB5-1that the channel is busy (and hence unavailable). Alternatively, the UE3can report interference or noise levels from multiple sources (including SeNB5-2transmissions) to the MeNB5-1so that the MeNB5-1can determine that the UE3is not scheduled on the carrier F2and control the flow of data via the MeNB5-1.

<Master Base Station>

FIG.3is a block diagram illustrating the main components of a master base station5-1shown inFIG.1. The master base station5-1is a communications node providing services to user equipment3within its coverage area. In the exemplary embodiments according to the invention, communications between the various base stations5and the mobile telephone3are coordinated. As shown, the master base station5-1includes a transceiver circuit51which transmits signals to, and receives signals from, the mobile telephone3via at least one antenna53. The master base station5-1also transmits signals to and receives signals from the core network7and other neighbouring base stations (e.g. the SeNB5-2) via a network interface55(X2/non-ideal backhaul interface for communicating with neighbouring base stations and S1 interface for communicating with the core network7). The operation of the transceiver circuit51is controlled by a controller57in accordance with software stored in memory59. The software includes, among other things, an operating system61, a communications control module63, a dual connectivity module65, an S1 module67, an X2 module68, a flow control module69and a timing module71.

The communications control module63controls communications between the master base station5-1and the SeNB5-2, the mobile telephone3, and the core network devices.

The dual connectivity module65coordinates communications over the communication bearer (or bearers) forming part of a dual connectivity service for the mobile telephone3served by this base station.

The dual connectivity module65includes the PDCP, RLC, MAC, and PHY entities (layers) responsible for communicating data packets (that belong to MeNB-specific bearers) via the base station5-1when it is configured as an MeNB. The dual connectivity module65is also responsible for communicating data packets of the split bearer to the SeNB5-2.

The S1 module67handles S1 signalling (e.g. generates, sends, and receives messages/PDUs formatted in accordance with the S1 protocol) between the base station5and the core network7entities (such as the MME11and the S-GW13). For example, the S1 module67is responsible for receiving downlink data packets from the core network7and passing the received data packets to the dual connectivity module65(via the PDCP entity), when the base station5-1is configured to operate as an MeNB.

The X2 module68handles X2 signalling (e.g. generates, sends, and receives messages/PDUs formatted in accordance with the X2 application protocol) between the master base station5and other base stations, such as the secondary base station5-2. For example, the X2 module68is responsible for exchanging, with the corresponding X2 module of the secondary base station5-2, signalling (e.g. control signaling and/or data packets) relating to the SeNB-specific bearer.

The flow control module69receives information indicating availability of a communications channel on the carrier F2for the split communication bearer from the SeNB5-2, i.e., for the communication bearer path between the SeNB5-2and the mobile telephone3. For example, the base station5-2may detect the availability of the channel and provide feedback to the base station5-1in the form of a value of an available buffer size. Specifically, in one example, the base station5-2reports the available buffer size corresponding to the UE3as ‘0’ if the channel on carrier F2is unavailable, and reports the available buffer size corresponding to the UE3as a non-zero value if the channel on carrier F2is available. In this particular case, the base station5-2uses the DL DATA DELIVERY STATUS frame (e.g. as illustrated in Table 1) for this purpose.

The flow control module69is responsible for ensuring that an appropriate communication bearer path is used for the data packets transmitted for each items of user equipment (such as the mobile telephone3) served by this base station and the other base station. Specifically, the flow control module69uses the information received by the flow control module69to perform flow control. In particular, when the information received from the base station5-2indicates that the communications channel on carrier F2is unavailable the flow control module69prevents the transmission of further packets to the base station5-2. The flow control module69also generates an instruction, which is transmitted to the base station5-1, to not transmit packets which have already been sent to the base station5-2and which are buffered in a transmission queue for transmission to the UE3. Moreover, the flow control module69controls the base station5-1to transmit these packets to the UE3.

The timer module71commences timing when the information from the base station5-2is received. The timing is performed for a predetermined time period during which the information provided by the base station5-2is considered to be valid. The flow control module69performs flow control as described above during the predetermined time period when the information provided by the base station5-2indicates that the channel on carrier F2is unavailable.

<Secondary Base Station>

FIG.4is a block diagram illustrating the main components of the secondary base station5-2shown inFIG.1. The secondary base station5-2is a communications node providing services to user equipment3within its coverage area. As shown, the secondary base station5-2includes a transceiver circuit51which transmits signals to, and receives signals from, the mobile telephone3via at least one antenna53. The secondary base station5-2also transmits signals to and receives signals from the core network7and other neighbouring base stations (e.g. the MeNB5-1) via a network interface55(X2/non-ideal backhaul interface for communicating with neighbouring base stations and an optional S1 interface for communicating with the core network7). The operation of the transceiver circuit51is controlled by a controller57in accordance with software stored in memory59. The software includes, among other things, an operating system61, a communications control module63, a dual connectivity module65, an S1 module67, an X2 module68, and a channel status module70.

The communications control module63controls communications between the secondary base station5-2and the MeNB5-1, the mobile telephone3, and the core network devices.

The dual connectivity module65coordinates communications over the communication bearer (or bearers) forming part of a dual connectivity service for the mobile telephone3served by this base station.

The dual connectivity module65includes the RLC, MAC, and PHY entities (layers) responsible for communicating data packets via the base station5-2when it is configured as an SeNB for dual connectivity split bearer. In this particular split bearer SeNB configuration, the dual connectivity module65does not include a PDCP entity.

The S1 module67handles S1 signalling (e.g. generates, sends, and receives messages/PDUs formatted in accordance with the S1 protocol) between the base station5and the core network7entities (such as the MME11and the S-GW13).

The X2 module68handles X2 signalling (e.g. generates, sends, and receives messages/PDUs formatted in accordance with the X2 application protocol) between the secondary base station5-2and other base stations, such as the master base station5-1. For example, the X2 module68is responsible for exchanging, with the corresponding X2 module of the master base station5-1, signalling (e.g. control signalling) relating to the SeNB-specific bearer.

The channel status module70detects availability of the communications channel on carrier F2. The communications control module63then provides feedback to the base station5-1as described earlier for example.

In the above description, the mobile telephone3and the base stations5are described for ease of understanding as having a number of discrete modules (such as the communications 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.

<Operation>

A number of different examples will now be described that illustrate how the invention can be put into effect using the mobile telephone3and the base stations5(as exemplary dual connectivity network points) ofFIG.1. As discussed above, dual connectivity service can be provided by configuring the mobile telephone3to communicate with both the MeNB5-1and at least one SeNB5-2, using a split communication bearer.

FIG.5illustrates (using continuous lines) an exemplary bearer configuration for the provision of one particular split bearer configuration (namely Alternative 3C. Other alternatives are also contemplated of course). For comparison,FIG.5also illustrates (using dashed lines) an MeNB-specific bearer, the description of which is omitted herein for the sake of simplicity. InFIG.5, some of the protocol layers and functions (e.g. control-plane) implemented by the base stations5are also omitted. WhilstFIG.5illustrates 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.

In the split bearer configuration depicted inFIG.5, the S1 control-plane (e.g. ‘S1-MME’) for the mobile telephone3is provided by the MeNB5-1. User-plane communication (e.g. a communication hearer that is associated with carrier F2ofFIG.1) is provided for the mobile telephone3via the SeNB5-2with involvement of the MeNB5-1. In particular, downlink data packets can be sent from a remote endpoint over an associated communication bearer through the core network7(e.g. via the S-GW13) and received at the PDCP layer of the MeNB5-1. The communication bearer is split at the PDCP, with data packets either forwarded to the lower layers (i.e. the RLC, MAC, and PHY layers) of the MeNB5-1for transmission to the mobile telephone3(using carrier F1), or routed to the RLC layer of the SeNB5-2before they are transmitted to the mobile telephone3over the PHY layer of the SeNB5-2(using carrier F2).

EXAMPLE 1

First Example

FIG.6is an exemplary timing diagram illustrating a procedure performed by elements of the mobile telecommunication system1in which the SeNB5-2determines channel availability for a particular the mobile communication device3and reports it to the MeNB5-1which then performs appropriate flow control.

The procedure occurs when the MeNB5-1is transmitting downlink data to the SeNB5-2for onward transmission to a mobile communication device (shown as user equipment ‘UE’)3, as illustrated at step S603. At step S605, the SeNB5-1determines the availability of the communications channel for that mobile communication device3on carrier F2for transmission of data packets. Then, at step S607, the SeNB5-1transmits a status report to the MeNB5-1. For example, if the channel on carrier F2is busy or unavailable, the SeNB5-2transmits a DL DATA DELIVERY STATUS frame to the MeNB5-1with the value of the available buffer size set to ‘0’. On the other hand, if the channel on carrier F2is available, the SeNB5-2transmits a DL DATA DELIVERY STATUS frame to the MeNB5-1with the value of available buffer size as non-zero. The MeNB5-1performs flow control for that mobile communication device3based on the received information. For example, if the channel for that mobile communication device3on carrier F2is available the MeNB5-1may continue to send data to that mobile communication device3via the SeNB5-2(not shown). However, if the carrier F2is unavailable the MeNB5-1stops sending further packets to SeNB5-2(step S611). At step S613, the MeNB5-1instructs the SeNB5-2not to transmit data to the mobile communication device3which has already been sent to the SeNB5-2but not transmitted to the mobile communication device3. In response to receiving the instruction, the SeNB5-2deletes the data from its transmission queue at step S615. At step S617, the MeNB5-1itself sends the data to the mobile communication device3. It will be appreciated that order of steps S611, S613and S617can be rearranged.

Steps S611, S613and S617can be performed at the expiry of a predetermined time period that commences upon receipt of the channel status report. Thus, a timer can be set at step S609.

EXAMPLE 2

Second Example

FIG.7illustrates a modification of the procedure shown inFIG.6in which the SeNB5-2determines channel availability for a particular the mobile communication device3and reports it to the core network7(e.g. the MME11or S-GW13), rather than the MeNB5-1, and it is an entity in the core network7which initiates the performance of appropriate flow control. In this case, steps S703, S705, S709, S711, S713, S715and S717correspond to S603, S605, S609, S611, S613, S615and S617, respectively, thus their description is omitted herein.

However, in this example, the SeNB5-2reports the availability of the channel on carrier F2to the S-GW or MME (EPC) or S1-GW at step S706instead of to the MeNB5-1as in the first embodiment (albeit possibly using different signalling). Then, at step S708, the MME11instructs the MeNB5-1to perform flow control, for example to increase or decrease DL packet transmission via the SeNB. In particular, the when the channel report status indicates that the carrier F2is unavailable, the S-GW or MME (EPC) or S1-GW can instruct the MeNB5-1to reduce the throughput to the SeNB5-2.

EXAMPLE 3

Third Example

FIG.8illustrates another exemplary modification of the procedure shown inFIG.6in which the mobile communication device3provides information to the SeNB5-2to assist the SeNB5-2to determine channel availability for that mobile telephone3for reporting to the MeNB5-1which then performs appropriate flow control.

In this case, steps S807, S809, S811, S813, S815and S817correspond to S607, S609, S611, S613, S615and S617, respectively, thus their description is omitted herein.

In this example, the mobile communication device3receives downlink data via the MeNB5-1and SeNB5-2(steps803-1and803-2). Then at step S801, the mobile communication device3determines the status of the downlink communication channel on the carrier F2and reports a channel status to the SeNB5-2at step S802for use as assistance information. For example, the determination can be based on a measurement of a noise level or interference level on physical resources and the mobile communication device3may report the carrier busy status by sending a carrier quality indication (CQI) with the value set appropriately (e.g. to ‘OOR’) (or using any other suitable mechanism). At step S804, the SeNB5-2uses this as assistance information to assist a determination of channel availability and provides the resulting channel availability to the MeNB5-1as described with reference toFIG.6.

EXAMPLE 4

Fourth Example

FIG.9illustrates another exemplary modification of the procedure shown inFIG.6which is similar to the example ofFIG.8but in this case the mobile communication device3provides channel status information directly to the MeNB5-1rather than SeNB5-2.

In this case, S909, S911, S913, S915and S917correspond to S609, S611, S613, S615and S617, respectively, thus their description is omitted. herein for brevity and clarity.

In this example, the mobile communication device3receives downlink data via the MeNB5-1and SeNB5-2(steps903-1and903-2). Then at step S901, the mobile communication device3determines the status of the downlink communication channel on the carrier F2and reports a channel status to the MeNB5-1at step S904. For example, if the mobile communication device3is aware of resource allocation made by the SeNB5-2and determines that noise or interference received on physical resources originates from neighbouring devices, the mobile communication device3reports the channel as being busy (and hence unavailable) to the MeNB5-1. Alternatively, the mobile communication device3can report interference or noise levels from multiple sources (including SeNB5-2transmissions) to the MeNB5-1so that the MeNB5-1can determine that the mobile communication device3should not be scheduled on the unlicensed channel on carrier F2. The MeNB5-1can then perform flow control as described with reference toFIG.6.

<Modifications and Alternatives>

Detailed exemplary embodiments have been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above embodiments whilst still benefiting from the inventions embodied therein.

In the above examples, the base station5-2is configured as an eNB. However, it may alternatively be an access point of a wireless local area network.

In the above exemplary embodiments, the communication bearer is split in the PDCP entity of the MeNB. However, the communication bearer may be split above the PDCP layer (IP packet), or in or above the MAC layer (CA architecture).

In the above examples the channel availability is determined and reported for each item of user equipment (i.e. on a per UE basis). It will be appreciated that the availability of the unlicensed carrier may be reported per node (i.e. for all UEs served by the base station) as opposed to per UE. In this case per UE fairness is maintained by the secondary base station. In this variation, the secondary base station detects/listens to the channel status on the unlicensed carrier(s), and reports the status to master base station. If the unlicensed channel becomes busy/unavailable then the secondary base station reports that the availability of this carrier is ‘false’ to the master base station. If the channel becomes not busy/available then the secondary base station reports that the availability of this carrier is ‘true’. In this case the report of carrier availability may be in a form similar to the reporting of eNB resource status measurements.

Examples of resource reporting initiation procedures used by an eNB to request measurements from another eNB are described, for example, in section 20.2.2.10 of TS 36.300 and Section 8.3.6 of TS 36.423, the contents of which are incorporated herein by reference. The reporting of channel availability by the secondary base station to the master base station can be implemented using such kind of resource reporting procedures. For example, the master base station can request unlicensed spectrum availability from the secondary base station, and the secondary base stations replies with an unlicensed spectrum availability status response. However, instead of a request by the master base station, the reporting could be periodic or event triggered (e.g., when one or other of the buffers has been filled up). Furthermore, the reporting could be a combination of periodic and event triggered (e.g., when the buffer is filled up then report periodically until the time buffer is below the threshold). In this approach, the reporting is per node rather than per UE or per E-RAB.

In a variation of this, the secondary base station may report the availability of the channel to the master base station on a per UE basis (e.g. by using a buffer status of zero to report channel unavailability as described with reference toFIG.6and elsewhere above) and carrier availability on a per node basis. This combination is advantageous because it allows the master base station to determine whether a buffer status of zero has arisen as a result of a genuine full buffer or because the channel has become available. If the master base station determines that the buffer status of zero has arisen as a result of the channel becoming available it can apply flow control as described previously.

In at least some of the above examples, availability of a channel on the unlicensed carrier is detected by the secondary base station and this information is passed on to a master base station which then performs associated flow control. However, the secondary base station may alternatively or additionally estimate a time at which the channel is next available and provide this information to the master base station instead of information identifying whether or not the channel is available. The master base station may then perform associated flow control by planning the next scheduling cycle for the secondary base station based on the received timing information for example by ensuring that downlink data is not routed via the secondary base station until the estimated time at which the channel becomes available.

Similarly, the secondary base station may alternatively or additionally estimate a probability of channel availability (e.g. an average fraction or proportion of the time that the channel is available at the secondary base station regardless of whether it is actually used by the secondary base station). The master base station may then perform associated flow control by basing a decision on routing data via the secondary base station on the probability that the channel is available (e.g. by routing via the secondary base station only if the probability is above a predetermined threshold).

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 appreciated that either of the carriers F1and/or F2may be provided via a relay, a remote radio head, and/or the like instead of a base station.

In the above examples, each base station is described as comprising an eNB. However, it will be appreciated that the master base station can be a macro or pico LTE base station and the secondary base station can be a WLAN AP. The LTE base station and WLAN AP may be involved in carrier aggregation whereby the LTE base station provides packets to the WLAN AP. The UE can use both the LTE base station and the WLAN RF for communication.

In the above examples, each base station is described to provide a single carrier (F1or 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).

In the above examples, the information is received directly from the other base station. However, the information can be received from the other base station indirectly for example via the core network3, and/or from the UE3, either directly or indirectly for example via the other base station.

In the above description, there is only instance of split bearer shown. However, it will be appreciated that any number of split bearers may be provided for a particular UE. For example, multiple split bearers may be provided.

In the above description, the dual connectivity architecture described in TR 36.842 as Alternative 3C is referred to. However, this is for convenience only to aid understanding of the systems and methods described herein. It will be appreciated that the systems and methods described herein can be implemented as other architectures including, for example, inter eNB or inter RAT carrier aggregation architectures.

In the above description, the SeNB is described to generate and send a DL DATA DELIVERY STATUS frame for reporting the information. However, it will be appreciated that a different message and/or a different application protocol may also be used.

The base station may be configured to operate as a master base station of said dual connectivity configuration and the other base station may be configured to operate as a secondary base station of the dual connectivity configuration.

In the above exemplary embodiments, a mobile telephone based telecommunications system was described. As those skilled in the art will appreciate, the signaling 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.

In the exemplary embodiments described above, the mobile telephone and the base stations will each include transceiver circuit. Typically this circuit will be formed by dedicated hardware circuits. However, in some exemplary embodiments, part of the transceiver circuit may be implemented as software run by the corresponding controller.

In the above exemplary 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.

Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

This application is based upon and claims the benefit of priority from UK patent application No. 1501617.3, filed on Jan. 30, 2015, the disclosure of which is incorporated herein in its entirety by reference.