WO2012052911A1

WO2012052911A1 - Method and apparatus for co-operative reception for network controlled device to device

Info

Publication number: WO2012052911A1
Application number: PCT/IB2011/054607
Authority: WO
Inventors: Sami-Jukka Hakola; Timo Kalevi Koskela; Vinh Van Phan
Original assignee: Nokia Corporation
Priority date: 2010-10-22
Filing date: 2011-10-17
Publication date: 2012-04-26

Abstract

An apparatus for mapping uplink control signals from devices operating in a communication system comprising heterogenous networks. In one embodiment, the apparatus associates an uplink radio resource on a random access channel with a downlink radio resource on a control channel and maps between a downlink common control message sent on the downlink radio resource and a group-wise reply from a plurality of devices which form a device-to- device cluster sent on the uplink radio resource using the association. In another embodiment, an apparatus switches a transmission order in response to receiving a downlink control message, determines a group-wise reply to the downlink control message from a plurality of devices which form a device-to-device cluster, maps the downlink subframe in which the downlink control message was received to an uplink subframe and sends the group- wise reply in the mapped uplink subframe.

Description

METHOD AND APPARATUS FOR CO-OPERATIVE RECEPTION FOR NETWORK

CONTROLLED DEVICE TO DEVICE

TECHNICAL FIELD:

The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs and, more specifically, relate to mapping uplink control signals from devices operating in heterogeneous networks (e.g., cellular and D2D).

BACKGROUND:

This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.

The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:

3GPP third generation partnership project

ACK acknowledgement

CQI channel quality indicator

D2D device to device (sometimes termed machine to machine M2M or peer-to-peer P2P)

DL downlink (eNB towards UE)

eNB E-UTRAN Node B (evolved Node B)

E-UTRAN evolved UTRAN

HARQ hybrid automatic repeat request

LTE/LTE-A long term evolution/ long term evolution-advanced

MME mobility management entity

NAS non access stratum

NAK negative acknowledgement

PDCCH physical downlink control channel

PDSCHphysical downlink shared channel

PUCCH physical uplink control channel

RACH random access channel

RRC radio resource control

SI system information

SR scheduling request

TDD time division duplex

UE user equipment

UL uplink (UE towards eNB)

UTRAN universal terrestrial radio access network

Wireless access regimens are being developed to integrate new network topologies into a cellular network, and both industry and university researchers are working toward how to best implement such telecommunication integrations. One example of this integration is heterogeneous networks, which in the 3GPP LTE LTE-A terminology is to be a deployment of macro, micro, pico, and femto cells, and relay nodes, in the same spectrum being used by the LTE/LTE-A cellular signaling system. One aspect of such a heterogeneous system is to enable heterogeneous local communication directly among devices and machines (e.g., within the macro, micro, pico, and femto cells) under supervision of the LTE/LTE-A network.

Consider some non-limiting examples of such local domain communications under supervision of the cellular network. The network may control device-to-device (D2D) communications including communication within the various clusters of devices. The network may allow autonomous or semi-autonomous D2D communication within the overall radio architecture of the cellular network. There may be a grid or group of local machines communicating with each other locally while performing certain tasks in a co-operative way. There may be an advanced cellular device (mobile) acting as a gateway for several low-capability devices or machines to access the cellular network. And there may be co-operative downloading or multicasting within a cluster of devices/machines.

One reason D2D communications is attractive for further research is that D2D communications find and use spectrum 'holes', portions of the licensed spectrum which are not in use at the moment by the LTE/LTE-A network which holds the license. Scheduled radio resources are still used for at least some control signaling for the D2D devices, such as for example control signaling between the D2D devices and the cellular network. In order that the use of D2D cells remains practical, this control signaling over scheduled radio resources on the air interface is kept to reasonable volume.

In this vein it is appears advantageous that the cellular network make a single transmission of a control message directed to each device in a D2D cluster. But conventional cellular ACK NAK HARQ timing protocols would then have each D2D device responding in the same UL frame, leading to two problems: a) transmission collisions which render the replies un-decodable by the cellular network; and/or b) the cellular network not knowing which properly received reply is from which D2D device. The latter arises because ACK/NAK/HARQ replies do not identify the sending party specifically but rather the UL subframe in which they are sent maps unambiguously to a DL subframe which the network uses to identify the sending party. The UEs similarly map but in the forward direction, from the DL they received to the UL on which they send their reply. By example, 3GPP TS 36.300 v 10.0.0 (2010-06) details the signaling process for the UE to multiplex its HARQ feedback into its PUSCH transmission. In this case the cellular network recognizes the sender of the HARQ from mapping the PUSCH on which the HARQ was received to the PDCCH which assigned that PUSCH to a specific UE. CQI reports and scheduling requests also map similarly.

Therefore the timing arrangement in many conventional cellular protocols which avoids having to signal a UE identifier in many UL transmissions does not work if multiple D2D devices in a cluster are replying to a single DL message from the cellular network. If instead the cellular network signaled each D2D device separately then of course the volume of DL control messages is increased since there would then be as many DL messages as there are devices in the D2D cluster.

SUMMARY OF THE INVENTION:

These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by embodiments of the present invention, which include an apparatus, method and system for control signaling between the network and a D2D cluster which is operative in both DL and UL while using less signaling overhead than if the network signaled each D2D device in the cluster separately. In one embodiment, an apparatus for mapping uplink control signals from devices operating in a communication system comprising heterogenous networks. In one embodiment, the apparatus associates an uplink radio resource on a random access channel with a downlink radio resource on a control channel and maps between a downlink common control message sent on the downlink radio resource and a group-wise reply from a plurality of devices which form a device-to-device cluster sent on the uplink radio resource using the association. In another embodiment, an apparatus switches a transmission order in response to receiving a downlink control message, determines a group- wise reply to the downlink control message from a plurality of devices which form a device-to-device cluster, maps the downlink subframe in which the downlink control message was received to an uplink subframe and sends the group- wise reply in the mapped uplink subframe.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS :

Figure 1 illustrates various devices of a heterogeneous network showing division of control planes between cellular and D2D networks and also showing data path within the D2D network.

Figure 2 is a schematic timing diagram showing a highly asymmetric transmission order among devices within the D2D cluster which does not support the timing arrangement set forth at Figure 4.

Figure 3 is a schematic timing diagram showing a symmetric transmission order among devices within the D2D cluster which is implicitly changed from that of Figure 3 in order to support the timing arrangement set forth at Figure 4, according to an exemplary embodiment of the invention.

Figure 4 is a schematic timing diagram showing a timing pattern between a DL control message sent by the eNB to all devices of a D2D cluster and one UL reply from the whole D2D cluster, according to an embodiment of the invention.

Figure 5 is a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention.

Figures 6 and 7 are logic flow diagrams that each illustrates the operation of a method, and a result of execution of computer program instructions tangibly embodied on a computer readable memory showing procedures for mapping between UL and DL subframes (Figure 6) and for the inter-cluster operations (Figure 7) in accordance with exemplary embodiments of the invention.

DETAILED DESCRIPTION :

For heterogeneous networks it may be considered that there are two control planes; one between the network and the D2D cluster as a whole, and the other between the UEs within the D2D cluster itself. Figure 1 illustrates this concept. The cellular network is embodied as a MME 14 and an eNB 12 serving a D2D cluster of UEs 10-1 and 10-2. Control signaling in the cellular network is along cellular control links 13 between the MME 14 and the eNB 12 which may or may not be wireline links, and also along cellular control links 15-1 and 15-2 across the air interface between the eNB 12 and the various UEs 10-1 and 10-2. The two UEs are grouped as a D2D cluster, and so the D2D communications utilize D2D control link 18 for control messages while data within the D2D cluster is on the user data link 19.

By example, the cellular control links 15-1 , 15-2 may be used for resource allocation(s) optionally with buffer status reporting, CQI reporting, and SRs from the devices 10-1 , 10-2. The D2D control link 18 may be used for pair-wise resource allocation (i.e. how the D2D devices share assigned resources among themselves), exchanging measurement information locally (which identify the spectrum 'holes'), and buffer status information of specific D2D devices 10-1 , 10-2.

In the description below, for the described common control messages the signaling on links 15-1 and 15-1 is a single control message transmitted once in the DL by the eNB 12 to the D2D cluster. As will be described there is also a single reply message UL from the D2D cluster to the eNB 12. While each D2D device 10-1, 10-2 will independently receive the once-transmitted DL control message, it is convenient to express the single UL reply message as being sent by a cluster head, designated 10-1 herein but which may be any device within the D2D cluster. The single reply sent UL is representative for the whole D2D cluster and is therefore termed a group-wise reply. This convention does not preclude other control messages being directed to an individual device of the cluster, whose individual reply is not representative of the D2D cluster as a whole.

Figure 1 illustrates two UEs or D2D devices 10-1 (alternatively device 1 or Dl) and 10-2 (alternatively device 2 or D2) in the D2D cluster though the principles detailed below are readily extended to D2D clusters with more than two devices. Additionally, it is merely exemplary that the detailed examples below are in the context of the LTE system as the principles detailed below may be extended to other types of radio access technologies and cellular networks in which the D2D cluster may operate, such as but not limited to WCDMA, GERAN, WiFi, and other hierarchical type wireless systems.

Consider conventional timing processes in LTE. Regardless of DL asynchronous scheme or UL synchronous scheme, for the HARQ process there is a strict round -trip time between the transmitting DL subframe of a transport block and the UL receiving subframe of the expected ACK/NACK. As noted above, as a general proposition this approach will not work if all of the D2D devices in a cluster are to respond to the same DL message.

The above collisions problems and confusion as to which UE sent which reply message are resolved by exemplary embodiments of the invention which do not use the conventional implicit mapping of PUCCH resources for sending the group-wise ACK/NACK to the eNB, as is specified in current LTE Release 8-9 for individual replies to the PUCCH. In exemplary embodiments a contention-free RACH resource or resources are assigned for the D2D cluster (or local transmission) for sending their group-wise reply within a certain time period. In exemplary embodiments the DL common control message and the UL RACH on which the group-wise reply is sent are spaced in time a sufficient amount in order to allow for a certain number of local signaling exchanges among the D2D devices, possibly even re-transmission of the DL control message within the D2D cluster.

Note that this exemplary embodiment of using an allocated contention-free RACH resource within a configured time limit for sending a response or an ACK to a DL reception from an eNB by a local node/UE under control of the eNB represents a simple and effective way to enable a flexible HARQ round trip time, as opposed to the strict HARQ timing in current E-UTRAN implicit mapping of DL subframe to UL subframe. Such implicit mapping and strict timing can in many instances limit how much cellular relays and/or further local D2D communications can be supported. Note also that this exemplary embodiment can be implemented within an LTE system (or other radio access technologies) without any notable structural changes, and without additional signaling overhead to the E-UTRAN (or other) system itself.

Stated somewhat generally, in an exemplary embodiment there is an association made between an UL radio resource on a random access channel and a DL radio resource on a control channel. As is detailed below, this association may arise from explicit signaling of an indication of the UL radio resource, such as for example in the PDCCH itself (i.e., in the PDCCH fields), or multiplexed with DL data sent in a PDSCH which is allocated to the cluster by the PDCCH. The association is then used to map between a DL common control message sent on the DL radio resource and a group-wise reply from the D2D cluster sent by the cluster head device 10-1 on the UL radio resource. As above, the UL radio resource may be a contention free RACH allocated for the group- wise reply, and the DL radio resource may be the PDCCH or the PDSCH which the PDCCH allocates. The explicit indication may be an offset that is signaled DL in RRC signaling, in which the offset is from the DL radio resource to a preamble for the RACH. By example such an offset may be a specific RACH preamble joined with timing information which offsets from the DL common control message.

The above generally stated embodiment may be realized from the perspective of the cellular network access node eNB 12 which sends the DL common control message and which receives the group-wise reply from the cluster head. Similarly it may be realized from the perspective of the cluster head device 0-1 , which receives the DL common control message from the network access node/e B 2 and which sends the group-wise reply to it. Figures 2-3 illustrate further detail of the above exemplary embodiment in which the D2D transmission order is automatically changed due to reception of the common control message from the cellular network. At Figure 2 the DL control message is received within some reception window 204 which is prior to a time threshold 201 detailed further with respect to Figure 4. The reception window 204 may depend on a common discontinuous reception period DRX assigned for the D2D cluster. The current transmission order 230 among the D2D devices 10-1 , 10-2 at Figure 2 is highly asymmetric, which may be in place for example if one device 10-2 is downloading/receiving a large media file from the other transmitting device 10-1. The notations ' 1 ' and '2' in the various blocks of the D2D transmission order 230 indicate which device is allowed to transmit in the block. When such a highly asymmetric D2D transmission order 230 is current for the time between when the common control message is received DL (DL window 204) and the time the group-wise reply is to be sent (UL window 206), there is no opportunity for the cluster head device 10-1 to collect the ACK NAK replies from the other devices 10-2 within the cluster. Despite that the time span between DL window 204 and UL window 206 may be sufficient, the current D2D transmission order configuration 230 may not support local D2D exchange of the reception information, nor of local re-transmission opportunities of the common control packet as will be detailed below with respect to Figure 4.

According to an exemplary embodiment from the perspective of any of the clustered devices 10-1 , 10-2, detection on the PDCCH of the PDSCH resource allocation for the cluster (which by example is indicated by a cluster-specific RNTI for the PDSCH allocation) automatically triggers, implicitly, each D2D device 10-1 , 10-2 to switch from the current D2D transmission order 230 to a new D2D transmission order 330 as illustrated by example at Figure 3 which provides transmit opportunities for each of at least two different devices 10-1 , 10-2 in the D2D cluster. This new transmission order 330 is pre-stored in the local memories of the D2D devices 10-1 , 10-2, and may in an exemplary embodiment be a default transmission order that allows two D2D devices to each have a transmit opportunity prior to the mapped UL subframe (in the UL window 206), or three D2D devices, or more. In an embodiment there is a different default D2D transmission order for each different cluster size: a first transmission order is used if the cluster has 2 devices, a second transmission order is used if the cluster has 3 devices, etc. No additional signaling is needed to inform the devices which of the various default orders to use so long as they each know how many total devices are in the cluster in which they lie.

In the exemplary embodiment shown at Figure 3, reception of the downlink common message 302 targeted to both clustered devices 10-1 , 10-2 triggers at least one transmit opportunity for both devices within a certain D2D exchange window 340, starting from the reception of the common message 302, so they can send their ACK or NAK of the common eNB DL message 302 to each other (the cluster head device need not send its own ACK on a D2D link). In certain exemplary embodiments such as is detailed at Figure 4 below, this new D2D transmission order allows the D2D devices 10-1 , 10-2 to carry out one or more re -transmissions if such are necessary. Regardless, the new transmission order 330 enables the cluster head device 10-1 to prepare a combined feedback response 320 in time to send it in the mapped UL subframe 420 in the UL transmission window.

The exemplary embodiment of Figure 4 illustrates one implementation of the D2D signaling as well as operation with respect to the time threshold 401 noted briefly above. This time threshold 401 is defined for the continuous downlink allocation in a frame, and indicates that if the common control message 402 message arrives on a continuous downlink before the time threshold 401 (e.g., the threshold may be a subframe index number which repeats in each frame), then the ACK/NACK response slot (subframe #8 in Figure 4) detailed above applies for the D2D cluster's group-wise reply 420. Otherwise there is a later ACK/NACK response slot (not specifically shown at Figure 4) in which the group-wise reply 420 should be sent. In an exemplary embodiment the later slot is mapped implicitly from the last subframe in which any part of the common control message 402 was received.

It is desirable that in a serving cellular TDD system, configured with a high ratio of DL subframes to UL subframes in a radio frame or superframe, the eNB could send a common control plane message to the D2D cluster during early subframes of a long downlink period. This is to allow enough time for the D2D devices to exchange at least local ACK NACK information after which the cluster head device sends a single ACK/NAK that represents the whole cluster. This additional time may be also used to carry out internal or local re-transmission within the D2D cluster over the D2D connection 18, 19 as described for Figure 3. In this regard, these early subframes are set off by the time threshold 401, which by example may be signaled to the D2D devices 10-1, 10-2 in broadcast SI or dedicated RRC signaling. The value of this time threshold (subframe index number) may by example be determined by the eNB 12 based on local cell configurations such as TDD downlink/uplink ratio, cell load or available resources, and/or states and conditions of D2D users and connections.

In an exemplary embodiment, the time threshold 401 is specific for a desirable local transmission or operation of D2D or relays under control of the eNB or serving cellular system, such as the cooperative reception scheme of D2D set forth at Figure 4. As noted above, the general teachings of Figure 4 can be readily applied to the case in which there are more than two devices in the D2D cluster.

At Figure 4 there is assumed two D2D devices 10-1 , 10-2 in the whole cluster. For convenience the subframes on the eNB system are indexed #0 through #8 at the top of Figure 4. Assume for Figure 4 that the time threshold 401 indicates subframe #2. At Figure 4 the eNB sends in subframe #1 its DL control message 402 to the D2D cluster. Assume that the cluster head device 10-1 properly receives this DL control message 402 but the other D2D device 10-2 does not. There is sufficient time between the UL subframe #8 which is to carry the group-wise ACK or NAK 420 and the DL subframe #1 which carried the DL control message 402 so that the devices 10-1 , 10-2 in the cluster can communicate on the D2D links 18, 19 their individual ACK/NAK replies for the DL control message using the new D2D transmission order 330. The cluster head thereby collects ACK/NAK indications from each other device in the cluster and reports a single group- wise ACK NAK 420 for the D2D cluster as a whole.

So long as the DL control message 402 is received not later than the time threshold 401 , there is sufficient time for this D2D exchange and so mapping between the DL subframe #1 on which the DL control message 402 was sent DL and the UL subframe #8 on which the group-wise ACK NAK is sent UL proceeds normally, by example using the mapped RACH as detailed above.

The D2D exchange window 340 may be tailored for D2D purposes to allow a retransmission 4 2 opportunity as seen at Figure 4. The eNB 12 may do this by semi-dynamically configuring the time threshold 401 forward or backward according to the number of devices in the D2D cluster (assuming the eNB is aware of this number). And/or the eNB 12 can do this by how far spaced in time is the RACH UL subframe from the DL subframe in which the eNB sends its common control message indicating that RACH. By non-limiting example the inter-cluster signaling 410, 412, 414 may occur on predefined resources on unlicensed spectrum, or on certain allocated downlink resources if D2D is allowed on cellular downlink subframes. These communications are among the D2D clustered devices and so UL and DL are not particularly informative terms as to message direction.

In the specific example of Figure 4 the second device 10-2 did not correctly receive the DL control message 402 from the eNB 12, and so signals its individual NAK 410 for the DL message 402. The eNB 12 is not necessarily listening on this D2D link 18, 19 and so the eNB 12 at this point is unaware of the second device's NAK 410. The cluster head 10-1 receives the individual NAK 410 and re-transmits 412 the DL common control message 402 originally sent by the eNB 12 in subframe #1. The second device 10-2 properly receives and decodes the re -transmitted message 412 and sends its individual ACK 214 to the cluster head 10-1. All this inter-cluster signaling 410, 412, 414 occurs prior to the mapped UL subframe #8, and so the cluster head 10-1 has compiled all the ACKs and/or NAKs from all devices in the cluster and sends a group-wise ACK 420 in the RACH UL subframe #8 which mapped normally from the PDCCH DL subframe #1 which carried the DL control message 402.

If instead at Figure 4 the re-transmission 412 was unsuccessful and the second UE 10-2 sent a NAK at message 414, the cluster head 10- 1 would in one embodiment send a NAK as its group-wise reply 420 to the eNB 12 since not every other device in the cluster reported an ACK to the cluster head 10-1. Similarly, if all other devices reported an individual ACK but the cluster head itself 10-1 did not properly receive the DL control message 402 (and could not get it re-transmitted in time from another device in the cluster), then the cluster head 10-1 would also report a NAK in the mapped UL subframe #8 for the group-wise reply 420. In some implementations there will be sufficient time for a re-transmission opportunity between the DL subframe #2 and its mapped UL subframe #8 as shown at Figure 4, but other implementations may have more devices in the cluster leaving no additional time for any inter-cluster re-transmissions 412.

From the perspective of the cluster head device, it receives a DL control message 402 and also receives from each other device in a local cluster of communicating devices an individual reply 410, 412 to the DL control message. The cluster head device 10-1 then determines a group-wise reply 420 from all of the received individual replies 410, 414 and from the cluster head device's own reply to the DL control message, maps a DL subframe #2 in which the DL control message 402 was received to an UL subframe #S, and sends the group-wise reply 420 in the mapped UL subframe #8. In this case the cluster head maps the sub frames to one another using the first timing. In one exemplary embodiment the first timing is conventional LTE/LTE-A HARQ timing. In another embodiment this first timing is different from normal cellular operation in order to allow the local D2D retransmission 412 detailed above before the group-wise ACK NAK 420 needs to be sent.

Figure 4 is premised on the DL control message 402 being sent no later than the threshold 401 which is indicated by the eNB 12 via signaling (e.g., SI or RRC). If the DL control message 402 is in fact sent later than that time 401, by example in subframe #5 of Figure 4, then in this exemplary embodiment the eNB 12 and cluster head 10-1 concludes there is insufficient time to accomplish the inter-cluster signaling 410, 412, 414 prior to arrival of the UL subframe #8 that maps from the DL subframe #1 according to the signaled indication, and instead the eNB 12 and cluster head 10-1 use an alternate mapping to a later UL subframe as noted above (e.g., normal cellular system timing such as implicit mapping with a fixed round robin time).

Any of the various embodiments above may be adopted for all DL control messages from the eNB 12 to the D2D cluster, or they may be to certain types of common control messages,. And/or to certain channels. Such limitations may be incorporated into a wireless specification so that all communicating parties are aware of them without explicit signaling over the air interface. Additionally, there may be different timing patterns for different types of DL control messages, also within a published specification, so as to tailor the allowed time for the inter-cluster signaling detailed above to typical inter-cluster signaling which occurs for different types of DL common control messages.

One technical effect of these teachings is that these various exemplary embodiments allow for saving air-interface resources and increasing efficiency and performance of D2D integration into a cellular system by facilitating cooperative reception of D2D with possible local retransmissions. Another technical effect is that implementation does not require any major changes to the serving cellular systems.

Now are detailed at Figure 5 a simplified block diagram of various electronic devices and apparatus that are suitable for use in practicing the exemplary embodiments of this invention. In Figure 5 a wireless network 1 is adapted for communication over a bi-directional wireless link 15DL/UL with various user mobile apparatus via a network access node such as a Node B (base station), and more specifically an eNB 12. The network 1 may include a network control element (NCE) 14 which provides connectivity with a further network such as a publicly switched telephone network and/ or a data communications network (e.g., the internet). The NCE 14 may also be referred to as a mobility management entity MME and/or a gateway GW. The UE 10-1 of Figure 5 is in the position of the local D2D cluster head device 10-1, and the D2D links 18, 19 are with a second UE 10-2 which may be constructed similar as the first UE 10- 1 and which represents the other clustered D2D device 10-2.

The UE 10-1 includes a controller, such as a computer or a data processor (DP) 10A, a computer-readable memory medium embodied as a non-transient memory (MEM) 10B that stores a program of computer instructions (PROG) IOC, and a suitable radio frequency RF) transmitter and receiver 10D for bidirectional wireless communications with the eNB 12 via one or more antennas. The eNB 12 also includes a controller, such as a computer or a data processor (DP) 12A, a computer-readable memory medium embodied as a non-transient memory (MEM) 12B that stores a program of computer instructions (PROG) 12C, and a suitable RF transmitter and receiver 12D for communication with the UE 10-1 via one or more antennas. The eNB 12 is coupled via a data / control path 13 such as an SI interface to the NCE 14. The eNB 12 may also be coupled to another eNB via data / control path 16, which may be implemented as an X2 interface.

At least one of the PROGs I OC and 12C is assumed to include program instructions that, when executed by the associated DP, enable the device 10-1 , 10-2, 12 to operate in accordance with the exemplary embodiments of this invention, as detailed above. That is, the exemplary embodiments of this invention may be implemented at least in part by computer software executable by the DP 10A of the UE 10-1 (and/or the DP or the 10-2) and/or by the DP 12A of the eNB 12, or by hardware, or by a combination of software and hardware (and firmware).

For the purposes of describing the exemplary embodiments of this invention the UE 10-1 may be assumed to also include a D2D transmission order controller 10F which operates to switch from a current D2D transmission order 230 to a new D2D transmission order upon receipt of a common control message from the eNB 12. At the eNB 12 there is a subframe timing mapper 12E which operates to associate and map a RACH UL subframe to a PDCCH DL subframe in which the eNB 12 sends a common control message to a D2D cluster in order to identify the devices 10-1 , 10-2 to which a group-wise reply, received on the RACH UL subframe, pertains. The UE 10 has a similar subframe timing mapper 10E which maps in the time-forward direction, from DL to UL subframes.

In general, the various embodiments of the UEs 10-1 , 10-2 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.

The computer readable MEMs 10B and 12B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DPs 10A and 12A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multicore processor architecture, as non-limiting examples.

Figure 6 is a logic flow diagram that illustrates, in accordance with various exemplary embodiments of the invention, the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, and an apparatus controlled by a processor running computer instructions stored on a memory. Figure 6 illustrates variously from the perspective of the eNB 12 or the cluster head device 10- 1.

[0001 ] At block 602 there is an association made between an uplink radio resource on a random access channel and a downlink radio resource on a control channel. At block 604 the association is used to map between a downlink common control message sent on the downlink radio resource and a group-wise reply from a plurality of devices which form a device-to-device cluster sent on the uplink radio resource.

Further portions of Figure 6 are optional. Block 606 stipulates that the UL radio resource on the RACH is a contention free RACH allocated for the group-wise reply, and the DL radio resource on the control channel is one of a PDCCH and a PDSCH. In various examples as noted above, the associating at block 602 may be via an explicit indication sent downlink such as included with the common control message or multiplexed to data sent downlink on a shared channel allocated by the common control message; and/ or the explicit indication may be an offset that is signaled downlink in RRC signaling, in which the offset is from the DL radio resource to a preamble for the RACH.

Block 608 has the further element of using the received DL common control message as an implicit indication to switch a current transmission order among the D2D cluster to a new transmission order in which at least the cluster head device and a second device of the D2D cluster each have a transmit opportunity before the UL radio resource. By example the new transmission order may be a default transmission order which the cluster head device switches to without explicit signaling among the device-to-device cluster.

Block 610 has the additional element of comparing a frame time of the DL common control message to a previously stored time threshold. Based on the comparing, the group-wise reply is sent on the UL radio resource for the case in which the frame time is not later than the time threshold; else the group-wise reply (or an individual reply) is sent on a different UL radio resource for the case in which the frame time is later than the time threshold. By example the different UL radio resource maps implicitly to the DL radio resource according to a HARQ process having a fixed round trip time for any given frame time of the DL common control message. The time threshold may be signaled downlink in at least one of system information and dedicated radio resource control signaling.

Figure 7 is a logic flow diagram that illustrates, in accordance with various exemplary embodiments of the invention, the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, and an apparatus controlled by a processor running computer instructions stored on a memory. Figure 7 illustrates from the perspective of the cluster head device 10-1.

At block 702 the cluster head device receives a downlink control message; and at block 704 in response to receiving the downlink control message, the cluster head device switches a current transmission order for a local cluster of communicating devices to a new transmission order. At block 706 and in accordance with the new transmission order, the cluster head device receives, from each other device in a local cluster of communicating devices, an individual reply to the downlink control message. Block 70S shows that the cluster head device determines, from all of the received individual replies and from a reply of the cluster head device itself, a group-wise reply to the downlink control message. At block 710 a downlink subframe in which the downlink control message was received is mapped to an uplink subframe; and at block 712 the cluster head device sends the group-wise reply in the mapped uplink subframe.

Further portions of Figure 7 are optional. At block 714 the cluster head device uses the received downlink control message as an implicit indication to switch the current transmission order among the local D2D cluster to the new transmission order of block 704. The new transmission order is characterized in that at least the cluster head device and a second device of the D2D cluster each have a transmit opportunity before the mapped uplink subframe.

At block 716 the receiving set forth at block 706 is expanded so that, in response to the cluster head device receiving from a second device a negative acknowledgement, the cluster head device sends to the second device a re-transmission of the downlink control message and receives a positive acknowledgement from the second device to the re-transmission. In this case of successful re-transmission, the group-wise reply of block 70S is determined using the positive acknowledgement and not the negative acknowledgement.

At block 718 which may include further any of the other optional blocks of Figure 7, the mapped downlink sub frame is within a RACH and the mapping uses an explicit indication within the control message for the case in which the DL control message is received no later than a time threshold indicated on a downlink; and the mapped DL subframe is within a PUCCH and the mapping is implicit from the DL subframe for the case in which the DL control message is received later than the time threshold.

The process elements set forth at Figures 6 or 7 may be embodied as a memory storing a program of computer readable instructions that when executed by at least one processor result in the actions set forth at Figures 6 and/or 7. In another embodiment an apparatus comprises at least one processor and at least one memory storing computer program code; in which the at least one memory and the computer program code are configured with the at least one processor to cause the apparatus at least to perform the elements set forth at Figures 6 and/or 7. In a still further embodiment there is an apparatus comprising determining means for determining as set forth at block 602, and mapping means for mapping a reply as set forth at block 604. The determining and mapping means may be a processor operating in conjunction with a program stored on a computer readable memory.

In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as nonlimiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The various blocks shown in Figures 6 or 7 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). At least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention. Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this invention.

It should be noted that the terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples.

Claims

WHAT IS CLAIMED:

1. A method comprising:

associating an uplink radio resource on a random access channel with a downlink radio resource on a control channel; and

mapping between a downlink common control message sent on the downlink radio resource and a group-wise reply from a plurality of devices which form a device-to-device cluster sent on the uplink radio resource using the association.

2. The method according to claim 1 , in which the uplink radio resource on the random access channel is a contention free random access channel (RACH) allocated for the group- wise reply, and the downlink radio resource on the control channel is one of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

3. The method according to claim 1 , in which the associating is via an explicit indication sent downlink.

4. The method according to claim 3, in which the explicit indication is included with the common control message or is multiplexed to downlink data.

5. The method according to claim 3, in which the explicit indication is multiplexed to data which is sent downlink on a shared channel allocated by the common control message.

6. The method according to claim 3, in which the explicit indication comprises an offset that is signaled downlink in radio resource control signaling, in which the offset is from the downlink radio resource to a preamble for the random access channel.

7. The method according to any one of claims 1 through 6, executed by a network access node which sends the downlink common control message and which receives the group-wise reply from a cluster head of the device-to-device cluster.

8. The method according to any one of claims 1 through 6, executed by a cluster head device of the device-to-device cluster, which receives the downlink common control message from a network access node and which sends the group-wise reply to the network access node.

9. The method according to claim 8, further comprising:

the cluster head device using the received downlink common control message as an implicit indication to switch a current transmission order among the device-to-device cluster to a new transmission order in which at least the cluster head device and a second device of the device-to-device cluster each have a transmit opportunity before the uplink radio resource.

10. The method according to claim 9, in which the new transmission order is a default transmission order which the cluster head device switches to without explicit signaling among the device-to-device cluster.

1 1. The method according to any one of claims 1 through 6, further comparing a frame time of the downlink common control message to a previously stored time threshold; in which:

the group- wise reply is sent on the uplink radio resource for the case in which the frame time is not later than the time threshold; else

the group-wise reply is sent on a different uplink radio resource for the case in which the frame time is later than the time threshold.

12. The method according to claim 1 1 , in which the different uplink radio resource maps implicitly to the downlink radio resource according to a hybrid automatic repeat request process having a fixed round trip time for any given frame time of the downlink common control message.

13. The method according to claim 1 1 , in which the time threshold is signaled downlink in at least one of system information and dedicated radio resource control signaling.

14. A memory storing a program of computer readable instructions that when executed by at least one processor result in actions comprising:

mapping between a downlink common control message sent on the downlink radio resource to a group-wise reply from a plurality of devices which form a device-to-device cluster sent on the uplink radio resource using the association.

15. An apparatus, comprising:

at least one processor; and

at least one memory storing computer program code; the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus at least to:

associate an uplink radio resource on a random access channel with a downlink radio resource on a control channel; and

map between a downlink common control message sent on the downlink radio resource and a group-wise reply from a plurality of devices which form a device-to-device cluster sent on the uplink radio resource using the association.

16. An apparatus, comprising:

storing means for storing an association of an uplink radio resource on a random access channel with a downlink radio resource on a control channel; and

mapping means for mapping between a downlink common control message sent on the downlink radio resource and a group- wise reply from a plurality of devices which form a device-to- device cluster sent on the uplink radio resource using the stored association.

17. A method comprising:

receiving at a cluster head device a downlink control message;

in response to receiving the downlink control message, switching a current transmission order for a local cluster of communicating devices to a new transmission order;

in accordance with the new transmission order, receiving at the cluster head device from each other device in the local cluster of communicating devices an individual reply to the downlink control message;

determining at the cluster head device, from all of the received individual replies and from a reply of the cluster head device, a group-wise reply to the downlink control message;

mapping a downlink subframe in which the downlink control message was received to an uplink subframe; and

sending the group-wise reply from the cluster head device in the mapped uplink subframe.

18. The method according to claim 17, in which receiving from each other device the individual reply comprises:

in response to receiving at the cluster head device from a second device a negative acknowledgement, the cluster head device sending to the second device a re-transmission of the downlink control message and receiving a positive acknowledgement from the second device to the re-transmission; in which group-wise reply is determined using the positive acknowledgement and not the negative acknowledgement.

19. The method according to any one of claims 17 through 18, in which:

the mapped downlink subframe is within a random access channel and the mapping uses an explicit indication in the control message for the case in which the downlink control message is received no later than a time threshold indicated on a downlink; and

the mapped downlink subframe is within a physical uplink control channel and the mapping is implicit from the downlink subframe for the case in which the downlink control message is received later than the time threshold.