Patent Description:
The concept of proximity based services (ProSe) within a cellular communications network environment has been identified as a mechanism for improving communication capacity and quality for service for UEs operating within such an environment while improving network capability by UEs off-loading. D2D communication is intended to allow for appropriate quality of service communication, between UEs operating within a cellular network environment and employing some network resources but not requiring communication through the network.

Recent developments and discussions within the <NUM>rd Generation Partnership Product (3GPP) community have identified requirements for D2D functionality and which include in particular the support of unicast communications between UEs, for example UE pairs, in D2D communication or the support of broadcast or groupcast communications between UEs, for example from some UE towards other UEs.

However, current proposals remain limited and, while some potential features have been identified and discussed, proposals for various aspects such as the configuration of physical channel resources remain limited and as yet undeveloped.

Such known discussions have centered on potential core system assumptions. That is, while potential agreement has been reached that a cell's uplink spectrum should be used for D2D communication, there are currently only proposals that the allocation of radio resources for D2D communication be centralised within the cell base station (eNB) or Cluster Head of the cluster of terminal devices. Also a further proposal is that the assignment of resources for D2D communication be performed with reference to the legacy Physical Downlink Control Channel (PDCCH) of the cellular network. Yet further it has also been discussed that multiplexing between cellular uplink and D2D transmissions, that is either data and/or control-related information, within a common subframe can be employed and that a specific Physical Control Channel be introduced for D2D communication (P2CCH) to carry control information directly between the UEs engaged in D2D communication, i.e. the so-called peer UEs of a D2D pair. Such a proposed P2CCH D2D channel can support functionality such as a Hybrid Automatic Repeat Request (HARQ) mechanism for the exchange of Ack/Nack feedback between the peer UEs, or for the estimate of radio conditions between the peer UEs, such as the exchange of Channel Quality Indicator (CQI) information.

Further, in addition to the newly proposed control channel, a new Physical Shared Channel is illustrated for D2D communication (P2SCH) for the transport of data, such as user data or user signalling, directly between the peer UEs.

In relation to such proposals, there are different suggestions for resource allocation/configuration in relation to D2D communication scenarios within cellular communication networks. However current suggestions exhibit inefficiencies and tend to have an undesired impact on the cellular environment and in particular in relation to the legacy Physical Uplink Control Channel (PUCCH) and base station (eNB) functionality of a cell.

One such known system is disclosed in <CIT> and which comprises a mechanism for allocating communication resources of a cellular communication network to D2D communication but which is disadvantageously limited and simply focuses on legacy radio resources, such as the frequency-band and resource-pool to be employed for D2D communication.

<CIT> discloses a method and apparatus for enabling scheduling and control of direct link communication in a cellular communication system. A method for use in a first wireless transmit/receive (WTRU) may include transmitting a request for device-to-device (D2D) communication resources to an enhanced Node B (eNB). The first WTRU may receive an allocation of resources for multiple transmission time intervals (TTI) to be used for D2D communications from the eNB. The first WTRU may schedule D2D communications with a second WTRU to be performed during the allocated resources.

<CIT> discloses a method comprising obtaining at a network node a scheduling reference point with a fluctuation range based at least in part on at least one metric for a plurality of cellular user equipments (UEs) and at least a pair of device-to-device (D2D) UEs; signaling the scheduling reference point and the fluctuation range to the art least pair of D2D UEs; allocating radio resources to the pair of D2D UEs according to one of more allocation criteria; receiving metrics updates from the pair of D2D UEs and the plurality of cellular users; and adjusting the scheduling reference point and the fluctuation range according to the received metric updates.

<CIT> discloses a method for performing device-to-device communication in an LTE-TDD cellular wireless communication system, comprising: allocating frequency resource for a user equipment in need of the device-to-device communication, wherein a format of the frequency resource is identical with a format used by a cellular link in the cellular wireless communication system; and the user equipment performs the device-to-device communication on the frequency resource, wherein the user equipment uses the same wireless access mode at a transmitter and a receiver.

<CIT> discloses, for a case in which there is an active connection established between a cellular network and a user equipment UE and the UE has simultaneously an active connection within a local network distinct from the cellular network, providing an indication within a resource allocation message communicated between the cellular network and the UE which is used to identify whether a radio resource allocated by the resource allocation message is for the cellular network or for the local network. The local network may be a D2D network and the message may be directed to a C-RNTI associated with the D2D network.

The present invention seeks to provide a mobile communication terminal device and a related method.

The invention is set out in the independent claims appended hereto.

The invention is now described further, by way of example only, with reference to the accompanying drawings in which:.

Referring now to <FIG> there is provided a schematic representation of terminal devices within a cellular communication network environment <NUM> and comprising a base station device in the form of an eNB <NUM>, a first mobile radio communications terminal device such as a first UE <NUM> and a second such mobile radio communications device such as a second UE <NUM>.

As illustrated by the signalling to be discussed further below, the first and second UEs <NUM>, <NUM> are arranged to exchange cellular uplink and downlink signalling with the eNB <NUM> by way of uplink and downlink control and shared channels in accordance with cellular communication functionality. In addition, and in accordance with the field of the present invention, the UEs <NUM>, <NUM>, are also arranged for D2D communication with advantageously reduced/limited impact on the cellular network resources. Schematically illustrate therefore are uplink control/data channels PUCCH/PUSCH <NUM> for uplink control/data traffic from the first <NUM> and second <NUM> UEs to the eNB <NUM>. There are also schematic illustrated downlink control/data channels PDCCH/PDSCH <NUM> for receipt at each of the UEs <NUM>, <NUM> of data from the network, i.e. eNB <NUM>.

As noted, the UEs <NUM>, <NUM> are also arranged to form a UE pair for mutual D2D communication and, in this context, and on the basis of the concept of the present invention, D2D control information <NUM>, such as HARQ feedback signalling, can be exchanged between the two UEs <NUM>, <NUM> by way of a physical control channel, and D2D data can be exchanged <NUM> between the two UEs <NUM>, <NUM> by way of a physical shared data channel. Such control and data channels are specific to the D2D communications and within the present application are identified as P2CCH and P2SCH respectively.

While a single cell common Radio Access Network (RAN) is illustrated with reference to <FIG>, it should be appreciated that the present invention can be employed by a D2D UE pair according to various network configuration scenarios. That is, in addition to adoption in relation to a UE pair such as operating under Frequency Division Duplex (FDD) or Time Division Duplex (TDD) RAN coverage in an intra-cell scenario such as that in <FIG>, where both UEs <NUM>, <NUM> are served by a single cell, the invention also finds use in relation to an inter-cell coverage scenario in which the UEs are served by different cells/eNBs.

Yet further, the invention can also be adopted in relation to UEs operating outside RAN coverage as discussed further herein but still allowing for the exchange of D2D data between a UE pair by way of unicast communication.

It should also be appreciated from the above summary of the present invention and the following discussions, that the invention is advantageous in providing for management of the coexistence of legacy uplink channels PUCCH, PUSCH, and D2D channels P2CCH, P2SCH within the uplink band spectrum consisting of PUCCH and PUSCH. As a particular advantage, the invention allows for both UE devices within a D2D UEs pair to identify the location of radio resources in time and/or frequency, at which transmission/reception should be attempted in the uplink band so as to access the D2D control information related to that D2D UEs pair link. Also, the invention allows for the cellular network node device, such as the eNB, to discriminate between transmissions on the legacy uplink channels from those on the D2D channels and, in general terms, allows for the reduction in potential interference between the channels and impact of one on the other.

With regard to <FIG>, there are illustrated schematic representations of the structure of adjacent subframes and related Resource Blocks providing for adoption of the P2CCH and P2SCH channels within the context of the present invention for D2D communication and particularly for coexistence with the legacy uplink control and shared data channels, PUCCH, PUSCH.

Turning first to <FIG>, the Resource Blocks considered in the frequency domain and within the adjacent subframes <NUM>, <NUM>, within their frequency spectrum, are divided between PUCCH channel element <NUM>, D2D P2CCH channel element <NUM> for D2D control information exchanges between the D2D UEs pair, a PUSCH channel <NUM> for cellular network data uplink exchanges, and a D2D P2SCH channel <NUM> for D2D data exchanges between that pair.

<FIG> illustrates the coexistence between the uplink and D2D channels on a Frequency Division Multiplex basis such that Resource Blocks of the adjacent subsequent subframe <NUM> exhibit the same characteristics as the preceding subframe <NUM>.

Turning now to <FIG>, there is provided similar structural diagram of adjacent subframes <NUM>, <NUM> within a series and again, by reference to the frequency spectrum, being divided between uplink control channel PUCCH portions <NUM>, D2D control channel P2CCH portions <NUM> and <NUM>, in this particular example, Uplink and/or D2D shared channels PUSCH/P2SCH for data exchanges. Again, the structure of the subsequent subframe <NUM> mirrors that of the initial subframe <NUM> so as to represent a full FDM scenario within the uplink channel spectrum between the uplink and D2D control PUCCH/P2CCH and data PUSCH/P2SCH channels.

While it would be possible to employ time division multiplexing for the coexistence of the uplink and D2D control and data channels, such an arrangement may exhibit a more restricted operation as regards legacy PUCCH bandwidth availability, and increased latency, for the respective control channels, or can further inhibit the flexibility of the eNB in dividing the uplink spectrum bandwidth between the D2D uplink transmissions and thus adapting to network load.

One particular example of an arrangement for arriving at an FDM subframe structure such as illustrated in particular with reference to <FIG>, is now described with reference to <FIG>.

<FIG> illustrates in particular the adoption of new system parameters serving to define the location of the P2CCH channel for the D2D communication.

The location of this D2D control channel P2CCH is advantageously defined by way of two parameters, referenced to the frequency spectrum employed by uplink Resource Blocks and first comprising a frequency offset parameter by means of which the D2D control channel P2CCH is offset relative to the legacy uplink control channel PUCCH, and also the actual D2D control channel P2CCH bandwidth. Such parameters are shown in <FIG> which illustrates in the context of one subframe, a Resource Block <NUM> encompassing a frequency spectrum (not shown) in a vertical direction as illustrated in <FIG> and, as previously noted, employing uplink control channel portions <NUM>, D2D control channel portions <NUM> and shared general portion <NUM> for uplink and/or D2D data.

As illustrated by the arrows P2CCH_Off associated with each of the uplink control channel regions <NUM>, the D2D control channel <NUM> is offset, in accordance with the frequency division multiplexing requirements, relative to the uplink control channel <NUM>. The second parameter comprises the bandwidth of the D2D control channel <NUM> which, in <FIG> is illustrated by double-headed arrow P2CCH_BW.

Thus, the D2D parameters P2CCH_Off and P2CCH_BW serve to define the location, through frequency offset, and bandwidth, of each of the D2D control channels <NUM>. The remainder of the Resource Block spectrum then not employed by the UE respective uplink and D2D control channels <NUM>, <NUM> is available for the shared communication channel <NUM>. Of course the alternative of <FIG> with respective FDM D2D and uplink shared data channels can be similarly employed.

As noted previously, the parameters exhibited by the present invention can also be employed in accordance with different network radio coverage scenarios.

In particular, for the radio coverage scenario in which the D2D UEs pair are within network coverage, the parameters tend to be unique to each cell and the values are provided to camped-on UEs through the radio resource control SIB signalling. That is, for intra-cell coverage where both of the D2D UEs pair are within the same cell, both UEs can compute the location of the Resource Blocks, and the number of allocated Resource Blocks to be used, by running an algorithm which can be such as that employed for identification of the Resource Blocks in the PUCCH channel, and adding the aforementioned P2CCH_Off value to the outcome.

For a radio coverage scenario in which the D2D UEs pair are in inter-cell coverage, the D2D UEs pair are likely to have different values for the offset and bandwidth parameters duplet and so a common duplet should be identified. As outlined further below, such common duplet can be defined by reference to the intersection of the two P2CCH zones, and the P2CCH_BW parameters can be advantageously employed for computing such a common duplet.

Further details of determining the parameters employed within the invention and the common duplet are outlined further below. However, with regard to an out-of-coverage network scenario, the D2D UEs pair may also exhibit different values for the duplet, which can arise from pre-set values, or previously received values when under network coverage, and a similar procedure to that adopted in relation to the inter-cell coverage to determine a common duplet as discussed further below can be employed.

A further feature of the invention relates to a procedure for a recipient UE in a D2D UEs pair to position/assign an appropriate P2CHH channel for the transfer of control information such as D2D HARQ feedback signalling.

Various forms of algorithm are possible for such location/assignment although one particularly advantageous embodiment is based upon algorithms employed for the assignment of, for example, control channel radio resources of the legacy PUCCH channel based upon information concerning the location of assigned information in the legacy downlink control channel PDCCH.

Such legacy algorithm and the associated assignment/location is known from legacy LTE systems such as disclosed in 3GPP Technical Specification TS <NUM> in section <NUM>, and but for completeness, the principal sections are outlined below as follows:.

The block of complex-valued symbols z(i) shall be multiplied with the amplitude scaling factor βPUCCH in order to conform to the transmit power PPUCCH specified in Section <NUM>. <NUM> in [<NUM>], and mapped in sequence starting with z(<NUM>) to resource elements. PUCCH uses one resource block in each of the two slots in a subframe. Within the physical resource block used for transmission, the mapping of z(i) to resource elements (k,l) not used for transmission of reference signals shall be in increasing order of first k, then l and finally the slot number, starting with the first slot in the subframe.

The physical resource blocks to be used for transmission of PUCCH in slot ns are given by <MAT>.

Mapping of modulation symbols for the physical uplink control channel is illustrated in <FIG>. <NUM>-<NUM>.

In case of simultaneous transmission of sounding reference signal and PUCCH format <NUM>, 1a or 1b, one SC-FDMA symbol on PUCCH shall punctured.

For the D2D communication arising in relation to the present invention, the assigned/location of the required P2CCH is derived from the use of such known algorithm wherein both UEs in a D2D pair receive the assignment for the D2D transmission for data, and the UE receiving the data is arranged to run the aforementioned legacy algorithm which provides a "virtual" Resource Blocks location in the physical uplink control channel. The receiving UE can then add the aforementioned offset P2CCH_Off value to the outcome of the algorithm within the frequency spectrum as disclosed in relation to <FIG> so as to move to the "effective" computed Resources Blocks in the P2CCH zone.

An example of the transmission sequence arising between an eNB and a D2D UE pair, for both the legacy signalling, and for D2D control channel configuration according to an embodiment of the present invention is now discussed further with reference to <FIG>.

<FIG> represents a timing diagram within a frequency spectrum (vertical access but not specifically illustrated) encompassing both a downlink carrier and uplink carrier and also illustrating the UE Resource Blocks appearing within a series of subframes <NUM>, <NUM>, <NUM> relating, as noted, to both the legacy signalling and the D2D control and data channel P2CCH, P2SCH signalling within the legacy uplink spectrum.

Within subframe <NUM>, and within the downlink carrier spectrum, there is provided a physical downlink channel <NUM> within which a eNB (not shown) assigns a Resource Block <NUM> for downlink traffic and within which the eNB also assigns a Resource Block <NUM> for D2D communication between first and second UEs of a D2D pair. The subframe. <NUM>, also includes a Resource Block <NUM> representing a downlink shared channel by means of which the eNB sends data <NUM> related to the RB assignment <NUM> to the UE.

With regard to the legacy elements of the signalling, a downlink HARQ resource location algorithm is applied so as to identify a portion within PUCCH channel <NUM> employed by a first UE while sending HARQ feedback <NUM> on downlink reception at the first UE. Within the next subframe <NUM> illustrated, a physical control channel <NUM> is calculated on the basis of the legacy algorithm as discussed above. However, with regard to the Resource Block <NUM> assigned by the eNB for D2D communication, the first UE sends D2D data <NUM> to the second UE within the D2D pair. Referring to the Resource Block structure within the subframe <NUM>, there is again provided a physical uplink control channel <NUM>, and a physical control channel <NUM>, for D2D communication and associated shared data channel <NUM>. Referring again to the assignment by the eNB of the Resource Block <NUM> D2D communication, the adapted D2D HARQ resource location algorithm is applied to provide for the required HARQ signalling <NUM> on D2D reception.

Although, within the context of the control channel signalling, reference is made above to the HARQ mechanism, it should be appreciated that the subject matter of the present invention could equally be implemented in relation to any other required control information, such as for example CQI information.

As also discussed above, the present invention is not limited solely to D2D UE pairs operating D2D communication within the same cell, and inter-cell, or indeed out-of-coverage, adoption of the concept of the present invention can also be achieved.

An appropriate interworking rule is proposed to cover embodiments relating to inter-cell, or out-of-coverage, D2D communication for a UE pair. In both instances, the two UEs in the D2D pair do not exhibit the same duplet, i.e. offset value and/or control channel bandwidth, since they are camping on different cells. However, to allow for the D2D communication, both UEs can be arranged to compute the intersection/overlap of their respective P2CCH zones to identify a common duplet and such feature is described further with reference to <FIG>.

<FIG> illustrates Resource Block structures for first <NUM>, and second <NUM> UEs within a D2D UE pair, and both of which include functionality according to a feature of the present invention so as to provide for a virtual common Resource Block configuration <NUM> as illustrated.

The basic structure illustrated within the sub-frames for each of the two UEs <NUM>, <NUM> is based upon a feature of an embodiment of the present invention illustrated with reference to <FIG>. As such, they provide for a FDM scheme within the frequency spectrum of the legacy uplink channel, and wherein the Resource Block structure includes uplink control channel zones, offset derived D2D control channel zones, and shared data channels for uplink and/or D2D communication as required.

However, as illustrated, in view of the differences arising from the two UEs <NUM>, <NUM> camping on different cells, there is quite likely to be a lack of coincidence between the respective boundaries of the respective D2D control channels P2CCH. That is, UE <NUM> exhibits an upper boundary for its D2D control channel equivalent to "offset <NUM> + bandwidth <NUM>"; and UE <NUM> exhibits an upper boundary for its D2D control channel P2CCH of "offset <NUM> + bandwidth <NUM>" where respective "offset <NUM>", <NUM> and "offset <NUM>", <NUM> are determined relative to the legacy uplink control channels PUCCH as discussed above.

In order to arrive at the common configuration structure <NUM>, the upper boundary is determined as the minimum of the two values <NUM>, <NUM>, whereas the lower boundary is determined as the maximum of the two offset values <NUM>, <NUM> and as illustrated by the dotted lines in <FIG>.

Applying such combined limits leads to a common P2CCH control channel <NUM> as illustrated and so allows for adoption of the mechanism of the present invention for inter-cell and out-of-coverage scenarios.

Turning now to <FIG>, there is provided a schematic illustration of a mobile terminal device offering communication over cellular network and comprising for example, a UE <NUM> of a D2D UE pair.

The UE <NUM> includes standard functionality such as a transmission/reception interface comprising an antenna <NUM> and transmission/reception circuitry <NUM> in addition to memory functionality <NUM>, processor functionality <NUM> and a user interface <NUM>.

In accordance with the present invention, the processor functionality <NUM> includes means for achieving the required channel configuration according to the present invention so as to enable the D2D communication exchanges exhibiting the advantages presented by the invention. That is, the processor functionality <NUM> can be arranged to determine and/or apply parameter values arising in accordance with the present invention and serving to identify the frequency offset values and bandwidth values as discussed.

In particular, the processor functionality <NUM> can be arranged to determine the aforementioned frequency offset value by reference to legacy algorithms determining initial physical Resource Blocks for control information transportation and applying the required frequency offset to the results obtained therefrom. In this manner, such D2D UE <NUM> can determine the location of the required physical Resource Blocks for the transport of D2D control information, although it should be appreciated here that other mathematical operation, i.e. sum, subtraction etc. can be employed.

As will also be appreciated, various mechanisms exist for supporting the signalling exchange for the D2D control channel system parameters according to the present invention, and which can relate to the particular network terminal and/or node devices involved in the signalling exchange.

For example, while for exchanges between a terminal node such as eNB and a mobile terminal such as a UE, RRC System Information Broadcast (SIB) messages/parameters can be employed, an eNB can broadcast its own cell parameter set. Also the eNB can broadcast a parameter set of neighbouring cells if required and which can prove useful for out-of-coverage embodiments as discussed above.

For communication between the UEs, it can of course prove necessary to supply data for computing the common configuration features such as discussed in relation to <FIG>. Here, transport options include use of a discovery beacon to convey P2CCH parameters and/or the use of initial access signalling in legacy random access procedures such as the D2D UE pair exchanging initial access messaging including their specific P2CCH parameters. Other alternative option is that specific P2CCH parameter set data can be employed and also, if required, a camped-on cell identity can prove advantageous in allowing retrieval of a parameter set in the neighbouring cell P2CCH parameters within the SIB.

For network terminal node, e.g. eNB to eNB, signalling, use can be made of X2 interface messages/parameters which can also prove useful for building neighbouring cell P2CCH messages/parameters as required.

As will therefore be appreciated from the above, the present invention provides for an advantageous scheme that can be readily embodied within a channel configuration procedure, terminal device operation procedure, and related computer program product, to advantageously allow for D2D capable UEs to determine which part of the legacy uplink band can be advantageously dynamically used for D2D, and P2CCH purposes in particular.

It should be appreciated that in particular there can be provided system parameters to define the location of a proposed P2CCH channel, such parameters comprising:
P2CCH Frequency Offset employed to compute the frequency shifting from legacy
PUCCH and hence get the P2CCH lower boundary if the offset is added to the PUCCH lower boundary; and
P2CCH bandwidth employed to get the P2CCH upper boundary.

A particular algorithm function can be employed for location of physical resource blocks for D2D physical control channel, and such proposed algorithm can be based on legacy LTE algorithm found in Technical Specification <NUM> as noted above. After running the legacy algorithm to find initial physical resource blocks to transport control information, P2CCH Frequency Offset can be used to allow the D2D UEs to find physical resource blocks to transport D2D control information. Of course it should be appreciated that other mathematical operation could be used such as sum, subtraction, etc..

Further exemplary detail of the manner and transfer of physical control information can be as suggested by 3GPP Technical Specification <NUM>.

Suggested signalling options for P2CCH system parameters can comprise the use of RRC signalling to provide the proposed system parameters: SIB or dedicated RRC messages, and such parameters could also be pre-configured in the UEs: pre-set by the network operator in USIM or predefined by the 3GPP specifications.

The advantageous adoption of the above-mentioned interworking computation rule for non matching cell-derived parameter can focus upon the intersection of the P2CCH zones Computed from the P2CCh Frequency Offset and P2CCH bandwidth parameters could be chosen to find the common duplet used by UEs which have been provided different P2CCH configuration. Of course, any other rule using the P2CCH Frequency Offset and P2CCH bandwidth parameters could also be used such as union rule, sum rule etc..

The signalling for such interworking can allow for the exchange of the proposed system parameters between eNB using X2 interface. Further, the proposed system parameters could also be exchanged between UEs using discovery beacons or legacy radio access signalling between D2D UEs.

The efficient dynamic operation and assignment of D2D channel resources according to the present invention is achieved in a particular advantageous manner. In particular, there is little if any limiting impact on legacy PUCCH, and hence it remains possible to maintain downlink cellular capacity.

Further, radio interference between legacy PUCCH and P2CCH can readily be avoided by setting P2CCH_Off to create the right separation/distance between the two channels. There is also an advantageously limited impact on eNB scheduler through the persistent availability of cellular control signalling whose scheduling can be separated from D2D scheduling.

There is also only limited added complexity from the UE point of view, particularly when considering reuse of the legacy algorithm.

Finally it remains possible to maintain Single Carrier characteristics for SC-FDMA transmission in all channels and thus minimizing as much as possible PUSCH fractioning.

Claim 1:
A mobile terminal device (<NUM>) configured to support device-to-device communication with a further mobile terminal device (<NUM>), the mobile terminal device (<NUM>) comprising:
means for determining a location of a device-to-device, D2D, control channel by:
a first parameter comprising a frequency offset parameter indicating that the D2D control channel is offset relative to a physical uplink control channel, PUCCH, and
a second parameter indicating a number of resource blocks forming a bandwidth available for the D2D control channel.