Patent Description:
Within the Long Term Evolution-Advance (LTE-A) aspects of the <NUM>rd Generation Partnership Project (3GPP) enhancements to the Universal Mode Telecommunications System (UMTS) there is included the provision of D2D communication between two appropriately proximate mobile radio communication devices. D2D represents an example of such Proximity Services (ProSe) and the terms can be considered as equivalent and interchangeable when used herein.

Examples of such ProSe devices comprise cellular network User Equipment (UE) devices in which the UEs transmit data signals to each other by way of direct signalling using cellular resources but without the signalling passing through a network base station such as an eNB. The facilitation of D2D communication within a cellular network environment offers a wide variety of advantages such as those arising from the offloading of communication between two UEs from the wireless network, and improvements to local area coverage and resource efficiency, whilst also decreasing the required transmitter power of the UEs.

<CIT> discloses a mobile communication system allowing user data to be communicated directly between a plurality of radio terminals with no radio base station intervening therebetween. The communication of the user data performed directly between the plurality of radio terminals is performed by use of some of radio resources allocated to the mobile communication system. The plurality of radio terminals include a transmission side terminal that transmits the user data and a reception side terminal that receives the user data. The mobile communication system switches between a first allocation mode in which the transmission side terminal or the reception side terminal allocates radio resources to be used for communicating the user data and a second allocation mode in which the radio base station allocates the radio resources to be used for communicating the user data.

However, the integration of D2D functionality within a wireless communications network environment requires appropriate management of D2D communication, for example so as to limit its impact on network communications Current proposals exhibit disadvantages particularly as regards the level of efficiency of operation and, in particular, the deployment of radio resources for mobile radio communication devices seeking D2D communication.

The present invention provides a UE, an eNB and associated methods of facilitating D2D communication within a wireless communication network environment and having advantages over known such methods and systems and for example as regards efficiencies of operation and the deployment of radio resources.

Further particular disadvantages are found in current proposed D2D methods and systems and relate in particular to the selection of a radio resource allocation-mode for both D2D discovery and communication signalling and, in particular, the employment of so-called Autonomous Mode radio resource allocation. Potential problems and limitations can arise with regard to the Quality of Service (QoS) provided for D2D radio communications devices and/or potential inefficient use of D2D radio resources particularly as regards the size of an Autonomous Mode pool offering a selection of potential radio resources for use.

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

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

An example, which does not fall within the scope of the claims, relates to an arrangement comprising a method and related system by which a mobile terminal device of a wireless communication network, such as for example a UE operating in a cellular network, can be authorized to employ an appropriate radio resource allocation mode so as to arrive at particular advantages with regard to Quality of Service levels and radio resource employment.

In the illustrated example, reference is made to two particular radio resource allocation modes proposed for D2D communication and comprising so-called Autonomous Mode allocation and Scheduled Mode allocation.

Such two modes of resource allocation have been defined within 3GPP discussions for proximity services such as D2D and relating to both discovery and communication signalling.

Autonomous Mode, which is generally identified as "Type <NUM>" for discovery signalling and "Mode <NUM>" for communication signalling, allows a UE to perform D2D transmission autonomously and so thereby autonomously determine which radio resource to employ. Such determination can be based upon a multi-access protocol which, for example, can be similar to known CSMA-CA or WiFi multi-access protocols. The radio resources are then chosen by the UE in an autonomous manner from a pool of radio resources, which pool can be explicitly configured by the network. Such configuration can be provided by network terminal device, such as an eNB, and so that the resources are then made available for D2D transmission, and thus not permitted for use in legacy cellular uplink allocation.

For Scheduled Mode allocation, generally identified within the context of 3GPP as "Type 2B" for discovery signalling and "Mode <NUM>" for communication signalling, the eNB is arranged to allocate a particular radio resource to the UE for D2D signalling in a scheduled manner which can, for example, be similar to the manner employed for legacy cellular uplink allocation, and as in response to a request from the UE.

The 3GPP discussions further define that the choice of radio resources to be allocated for any UE can be under the control of the network operator. However there has been no discussion or appreciation of how a particular UE might identify which radio resource allocation mode to employ and, as such, various disadvantages as discussed above, and relating in particular to quality of service and resource-employment efficiency are envisaged.

Such disadvantages are considered more relevant insofar as the 3GPP discussions have allowed for a network environment, such as the cells of a cellular network, to support both the Autonomous and Scheduled Radio Resource allocation-modes simultaneously. In particular, it is envisaged that a strategy might be employed where Autonomous Mode resource allocation can be employed for UEs located near the cell edge, primarily since scheduled mode is difficult to apply in inter-cell environments, and that Scheduled Mode tends to be employed for UEs located more centrally within the cell. It will therefore be apparent that some proximity service users such as UE devices seeking D2D communication and operating within the same cell, will be served by way of Autonomous Mode resource location, where others in the cell will be served through Scheduled Mode resource allocation.

Reference is now made to <FIG> which provides a schematic illustration of such potential common deployment of resource allocation modes within a common network environment.

Within <FIG>, the common network environment comprises a cell <NUM> of a cellular network and illustrated with its network terminal device, eNB <NUM>.

Within the cell <NUM> are a plurality of UEs <NUM>-<NUM> seeking D2D communication to assist with, for example, offloading from the cellular network comprising the cell <NUM> and eNB <NUM>.

Primarily due to their location within the cell, UEs <NUM>, <NUM> and <NUM> are arranged to seek radio resources by way of D2D Scheduled Mode resource allocation.

In this manner the eNB transmits signalling A to the UEs <NUM>, <NUM>, <NUM> providing a D2D scheduled resource pool configuration. A particular one UE <NUM> of the UEs wishing to initiate D2D communication signalling then returns a D2D resource request B to the eNB <NUM> which, in turn, replies with a D2D resource response C assigning the particular radio resources to be employed by the UE <NUM> which can then commence its D2D transmission D as required.

With regard to the UEs <NUM>, <NUM>, <NUM> which, generally due to their more outer cell-location are arranged to seek radio resource allocation in accordance with D2D Autonomous Mode allocation, the eNB <NUM> provides signalling E to the UEs <NUM>, <NUM>, <NUM> providing a D2D autonomous resource pool configuration. This resource-pool configuration provides a list of radio resources that can be selected for use by the UE seeking to initiate D2D transmission.

In the illustrative example, the UE <NUM> is arranged to select at least one radio resource from the resource pool received in signalling E from the eNB <NUM>, and then to commence its D2D transmissions F in accordance with such radio resource(s).

Thus in summary, D2D Scheduled Mode dictates that UEs willing to transmit D2D information according to that mode should request radio resource scheduling whereas, for D2D Autonomous Mode, UEs willing to transmit D2D information should employ, and make a selection from, a configured autonomous mode resource pool.

As appreciated from the description of the inventive concept outlined above, and the following discussions, a particular aspect of the present invention proposes new radio configuration parameters from the network to allow control of D2D Autonomous Mode in terms of radio resource usage and transmission behaviour. Further, novel indications can also be sent by the D2D UEs to the network to adapt the radio resource used for D2D autonomous mode according to the network need.

In particular, the present invention can prove particularly advantageous in addressing issues related to autonomous mode resource allocation and specifically to those relating to the radio resource pool employed for Autonomous Mode allocation. As one particular example, it is identified that if the Autonomous Mode pool is small having regard to the number of UEs seeking autonomous operation, this can lead to insufficient QoS for the proximity service users. Alternatively, if the Autonomous Mode pool is too large having regard to the number of potential users, this can lead to inefficient use of the D2D radio resources particularly insofar as any such unused resources could be employed for legacy cellular communication which of course has an impact on network capacity.

The present invention proves advantageous in addressing such issues.

As will be appreciated the invention can adapt operational characteristics for terminal devices, such as a UE and eNB, and also the signalling for support these characteristics. In further detail of a particular embodiment, a default Radio Resource allocation mode for D2D communication is introduced for each cell, and which can determine the behaviour of the UEs in the cell. For example, in a "Default Scheduled Mode (SM)", the UEs are required to send resource requests to the eNB prior to any transmission according to resources in the Autonomous Mode (AM) pool. The eNB can decide, on an individual request basis, if the requesting UE should be served via SM or be allowed to use AM under certain conditions, such as for example related to time, observed quality of D2D service or transmitted data volume, and which can be prescribed by the eNB. Thus, an "authorized" UE can then use AM as long as the configured conditions are met. Subsequently it can send a new request to eNB (provided it still has data to transmit). However in a "Default AM Mode", the UEs are allowed to use AM, and thus have access to, and select from, the AM pool without prior authorization from the eNB. Thus depending on eNB configuration, such UEs may either remain in AM indefinitely, or only as long as some condition on observed D2D QoS is met. It should be noted that even in the "indefinite use" configuration, the eNB may request optionally the reporting of observed QoS (either periodically or based on triggers). As an example, the "QoS" criteria can be based on various metrics associated with the protocol used in the AM pool.

The functionality allows the eNB to control the use of AM in different ways, and advantageously making various policies/strategies available for network operators. Possible examples of the use of such functionality are outlined as follows.

The first example, which does not fall within the scope of the claims, comprises a so-called pro-active tight-control approach and in which, starting from a default mode setting "Default SM", the eNB is aware of all UEs willing to use D2D and the eNB can dynamically predict the load of the AM pool. If it identifies some upcoming bottleneck, it can change the size of AM pool through a SIB change procedure. However, since this is likely only to have a "mid-term" effect, it can instantaneously move the requesting UEs to SM and therefore a different pool of resources. In the same way, eNB can predict under-use of AM pool and change its size if appropriate.

A second example, which does not fall within the scope of the claims, comprises a so-called reactive loose-control approach. Here an insufficient AM pool will be detected by the eNB through QoS-triggered reporting. Although the eNB will not individually control UEs, it will however extend AM pool via a SIB procedure. In this configuration, the under-use of the AM pool can be detected via the observed-QoS reporting if activated by eNB.

As will therefore be appreciated, the setting of conditions and associated values is particularly advantageous in allowing the eNB/operator to make trade-offs between control efficiency and signalling cost.

Reference is now made to <FIG> which comprises an illustration of signalling between an eNB <NUM> and a UE <NUM> and related to the exemplary parameters, and wherein the network behaviour involves "Scheduled Mode" resource allocation.

At <NUM>, the "DefaultProSeRRAMode" information is set to "SM" and is broadcast to all UEs camping on the cell or the " SM " is default UE implementation mode. Then at steps <NUM>, <NUM>, and for a UE <NUM> willing to transmit for D2D service, a random access or scheduled request procedure <NUM> is initiated and the UE <NUM> sends a MAC D2D Buffer Status Report <NUM> as a Radio Resource request to the eNB <NUM> according to the default behaviour.

The eNB responds <NUM> to the request either by an individual allocation of Resource Blocks so that the SM is used to serve the UE, or by an explicit "AMAuthorization" message <NUM> sent to the requesting UE <NUM>. This authorization includes a configuration defining the behavior expected of the UE <NUM> and a "AMAuthorizationCondition" parameter which describes the condition under which the authorization is given to the UE <NUM>. A "AMReportingOptions" parameter is also included and which describes how the UE <NUM> is expected to report its use of AM.

Then at <NUM>-<NUM> the authorization procedure continues such that at <NUM> the UE starts all internal processes related to the received authorized message <NUM>, at <NUM> the UE can operate in AM for ProSe/D2D transmissions, and at <NUM> it is determined whether a "NbrOfTransmissionFailure" threshold has been reached. When the "Authorization Condition" as defined in the received configuration is no longer met, the UE stops using AM, and reports <NUM> to the eNB according to the "ReportingOption", using an "AMReport" message, possibly along with a new request for radio resources if more are needed. At <NUM>, the eNB <NUM> may take further action based upon the UE "AMReport" message. Such further action can comprise control to move the UE <NUM> in SM mode if the amount of radio resources requested by the UE can be served in such mode, otherwise the UE is left in AM mode and the procedure can return to the step initiated by signalling <NUM>.

A second exemplary scenario, which does not fall within the scope of the claims, is now described wherein the network behaviour radio resource by default comprises "Autonomous Mode" and is illustrated with reference to <FIG> again with an eNB <NUM> and UE <NUM> pair exchanging signalling.

The "DefaultProSeRRAMode" information is set to "AM" <NUM> and is broadcast to all UEs camping on the cell or the " AM " is default UE implementation mode.

Such by-default authorization includes a configuration <NUM> defining the behavior expected from all UEs in the cell when using AM for D2D, and which includes an "AMAuthorizationCondition" parameter which describes the condition under which the authorization is given to the UE <NUM>, and a "AMReportingOptions" parameter which describes how the UE <NUM> is expected to report its use of AM to the network.

A UE <NUM> willing to transmit as part of a D2D service is, by default, allowed to use the AM pool and internal processes <NUM>, <NUM> and <NUM> start in the UE <NUM> to employ AM resource allocation. That is at <NUM> the UE <NUM> starts all internal processes related to received AMAuthorizationConditins, and can start computing AverageDataRate vaues. At <NUM> the UE operates in AM for ProSe/D2D transmissions and at <NUM> it is determined if the AvergaeDataRate threshold reached.

As and when the "AuthorizationCondition" defined in the received configuration is no longer met, a random access or scheduling request procedure <NUM> is initiated and the UE <NUM> can request/report <NUM> to the eNB <NUM> according to the "ReportingOption", using an "AMReport" message. A new request for radio resources can be made if more are needed.

Finally, at <NUM>, the eNB <NUM> can take further action upon receipt of the UE "AMReport" message. This further control action can comprise a move the UE in SM mode if the amount of radio resources requested can be served in such mode, otherwise the UE can be left functioning in AM mode and with a return to the procedure initiated by step.

A further exemplary scenario is wherein the network behaviour by default is again "Autonomous Mode" and is illustrated with reference to <FIG> again with reference to eNB <NUM> and UE <NUM>. Here, the AM mode is to be applied as default but without conditions, i.e. only reporting requirements.

As before, this by-default authorization includes a configuration <NUM> defining the behavior expected from all UEs in the cell when using AM for D2D services and which includes, an "AMReporting" parameter which describes the condition under which the authorization is given to the UE.

A UE <NUM> willing to transmit as part of a D2D service is allowed, by default, to use the AM pool and internal processes <NUM>, <NUM><NUM> start in the UE <NUM> to employ AM resource allocation. That is at <NUM> the UE <NUM> starts all internal processes related to received AMAuthorizationConditions, and can start computing AverageDataRate values. At <NUM> the UE operates in AM for ProSe/D2D transmissions and at <NUM> it is determined if the AverageDataRate threshold reached.

As and when the "Authorization Condition" defined in the received configuration is no longer met, a random access or scheduling request procedure <NUM> is initiated and the UE <NUM> can request/report <NUM> to the eNB <NUM> according to the "ReportingOption", using an "AMReport" message. A new request for radio resources can be made if more are needed.

At <NUM>, the eNB can as before take further action upon receipt of the UE "AMReport" message. Such controlling action can comprise an increase in AM pool size and if the pool sizes increased at <NUM>, the UE can continue at <NUM> to operate in AM for D2D transmissions.

Turning now to <FIG>, there is provided a schematic illustration of a network terminal device, such as an eNB <NUM> arranged to operate according to appropriate signalling steps of either of <FIG>, <FIG> and <FIG> as discussed above.

The network terminal device <NUM> contains the functionality of an interface <NUM> connected to transmission/reception circuitry <NUM> which, in turn, is operatively connected to a controller <NUM> operatively connected to memory functionality <NUM>.

As will be appreciated, the controller <NUM> with the transmission/reception circuitry <NUM> and the memory functionality <NUM> for controlling both cellular signalling for the cellular communication between UE devices within its cell, and also D2D communication between such UE devices and as outlined in relation to the system and methods discussed above. The controller <NUM> when providing for D2D communication between UE devices, is first arranged to confirm a default radio resource allocation mode for the cell, so that UEs seeking D2D communication can identify the default mode. The controller <NUM> can determine whether or not the UE should change from the default mode and so whether or not to seek radio resource allocation via Autonomous Mode or Scheduled Mode. If autonomous mode is to be employed, the controller <NUM> is arranged to forward authorisation signalling containing authorisation conditions/reporting parameters which the UE should meet if it is to continue to operate in Autonomous Mode. The controller <NUM>, by way of the transmitter/receiver circuitry <NUM> is arranged to receive signalling reports from the UE indicating whether or not the operational requirements are still met, and so as to determine whether control signalling is to be subsequently issued to the UE to re-assert, or switch, the resource allocation mode.

As noted above, <FIG> comprises a schematic diagram of a mobile radio communications device such as a UE <NUM> including standard mobile radio communications device functionality such as an antenna <NUM> operatively connected to transmission/reception circuitry <NUM> operatively connected to control circuitry <NUM> which is in turn, connected to memory functionality <NUM> and a user interface <NUM>. As again illustrated schematically, the control circuitry <NUM> includes first <NUM> and second <NUM> elements arranged to control the radio resource allocation mode adopted by the device <NUM>. That is, a first element <NUM> of the control circuitry <NUM> is arranged via, the transmission/reception circuitry <NUM>, to receive Autonomous Mode authorisation signalling from a network device, such as for example the eNB of <FIG>. In accordance with the functionality discussed above, the authorisation signalling includes one or more conditions relating to operational characteristics and/or reporting requirements to be met by the UE in order to continue to operate in accordance with the assigned Autonomous Mode. The first element <NUM> of the control circuitry is therefore arranged to identify such conditions and monitor on and ongoing basis whether such conditions continue to be met.

If such conditions are no longer met, then the second element <NUM> of the control circuitry <NUM> is arranged to establish appropriate reporting signalling and transmit the same by way of the transmission/reception circuitry <NUM> to two the network device. The control circuitry <NUM> can then be arranged to receive further control signalling from the network device which can determine whether or not Autonomous Mode operation is retained, or whether the radio resource allocation mode is switched to, for example, Schedule Mode as discussed above.

Further detail of various examples of configuration options and parameters of the present invention are outlined below.

The "AMAuthorizationConditions" parameter can take any one or more of the following values.

"AuthorizedDuration" requires that the UE should only use AM during a certain time (value provided within the parameter).

"AuthorizedRBNb" requires that the UE should only use AM for a certain number of Resource Blocks.

"AuthorizedDataTransfer" requires that the UE should only use AM for a certain amount of data.

"MinimalOQoS" requires that the UE should only use AM as long as a minimal observed QoS is met. The parameter includes a sub-parameter "AMOQoSMetrics" to be used for QoS observation. An example of such a metric is the actual rate of successful transmission of data transferred over a sliding window of time or a "MAxN-bofTransmissionFailure". A further sub-parameter "AMOQoSThreshold" can also be included and to be used for QoS checking.

Any one or more of the above conditions can form part of the configuration and in which case the UE should take into account a logical "AND" of all conditions present in the received configuration.

In the absence of "AMAuthorizationConditions" information, as an option, it can be determined at the UEs that there is no limit to the use of the AM and the AM pool.

Sub-parameters can also be proved for the"AMReportingOptions" parameter. That is "AMReportRequestedIndication" can be used for the UE to identify if it is expected to report to eNB.

"AMReportPeriod" can be used for the UE to determine if it is expected to report to eNB on a periodical basis and, if so, at which level of periodicity.

"AMReportOQoSMetricsType" can be used for the UE to identify which metrics it must use -for reporting. This can be similar to the "AMOQoSMetrics" sub-parameters introduced above.

Signalling options for both scenarios can be as follows:
"DefaultProSeRRAMode" information can be added to SIB messaging as a new IE. That is "SM" or "AM" can be defined as the default Radio Resource Allocator mode-setting if no information is present in the SIB.

"AMAuthorization" can be implemented using a new MAC Control Element. Further AMAuthorization configuration parameters, such as "AMAuthorizationConditions" and "AMReportingOptions", can be carried either as a new IE by SIB (for cell-wide values) or AMAuthorization MAC CE (for UE-specific values) or by a new RRC dedicated message (for UE-specific values).

The "AMReport" signalling can carry information such as "AMReportType" to indicate to an eNB whether this is a periodic report or one triggered by threshold-passing, or
"AMReportOQoSMetricsType", which can have the same structure as in AMReportingOptions above. "AMReportOQOSMetricsValue", can serve to carry the actual value of the metric and can be implemented either as a new MAC Control Element, or as a new dedicated RRC message.

As will be appreciated from the above, particular advantages arise in relation to the present invention which enables real time autonomous pool management for ensuring appropriate QoS for UEs in autonomous mode resource allocation. In such scenarios, typically the eNB could immediately serve a UE by way of Scheduled Mode allocation if problems are likely to be experienced in autonomous mode. Further the invention can enable a trade-off between signalling load and efficiency of autonomous pool management, typically by adjusting the duration of authorization. Still further, an eNB can determine which UEs are involved in D2D signalling at any particular time. This can prove further advantageous in providing greater accuracy than can be achieved by reference to the mere number of D2D capable UEs and can thereby allow for much more accurate, detailed, i.e. fine-grained, management of radio resources within a cell.

It should of course be appreciated that the invention is not restricted to the details of the foregoing and can be provided in relation to any appropriate wireless network communication environment employing appropriate network terminal and mobile devices as required.

The program can be stored and provided to the computer device using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM (Compact Disc-Read Only Memory), CD-R (CD-Recordable), CD-R/W(CD-ReWritable), and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory), etc.). The program may be provided to the computer device using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to the computer device via a wired communication line, such as electric wires and optical fibers, or a wireless communication line.

Claim 1:
A user equipment, UE, (<NUM>), comprising:
a memory (<NUM>) storing instructions; and
a controller (<NUM>) configured to process the instructions to:
support device to device communication;
operate in two modes for resource allocation for the device to device communication, wherein the two modes include:
scheduled resource allocation in which a network device (<NUM>) schedules radio resources for device to device communication, wherein the UE (<NUM>) sends a scheduling request to the network device (<NUM>) and the network device (<NUM>) schedules the radio resources for device to device communication; and
autonomous resource selection in which the UE (<NUM>) selects radio resources from a resource pool for device to device communication;
receive, from the network device (<NUM>), a signalling including information for configuring a pool of radio resources, wherein the information indicates radio resources that the UE (<NUM>) is allowed to use for device to device transmission, when at least one condition is met, in the autonomous resource selection;
wherein, in a case where the UE (<NUM>) is configured to use scheduled resource allocation and the at least one condition is met, the controller (<NUM>) is configured to process the instructions to use autonomous resource selection temporarily, even though the UE (<NUM>) is configured to use scheduled resource allocation, using the radio resources identified by the information for configuring the pool of radio resources, and
characterized in that the controller (<NUM>) is configured to use the radio resources identified by the information for configuring the pool of radio resources for a time period signalled by the network device (<NUM>) in a Radio Resource Control, RRC, message.