Resource allocation for the relaying of device-to-device discovery messages

A method, an apparatus, and a computer-readable medium for wireless communication are provided. The apparatus receives a discovery message through a device-to-device communication channel using a first resource element corresponding to a first time slot and a first frequency resource. The device-to-device communication channel may be a wireless communication channel. Upon reception of the discovery message, the apparatus determines a second resource element corresponding to a second time slot and a second frequency resource based on the first time slot and the first frequency resource in a deterministic resource allocation manner. The apparatus may alter the discovery message for rebroadcast in a deterministic message alteration manner. The apparatus rebroadcasts the discovery message using the second resource element. The discovery message may be rebroadcast through the same device-to-device communication channel in which the discovery message is received.

BACKGROUND

Field

The present disclosure relates generally to communication systems, and more particularly, to the relaying of device-to-device discovery messages.

Background

SUMMARY

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus for wireless communication are provided. The apparatus receives a discovery message through a device-to-device communication channel using a first resource element corresponding to a first time slot and on a first frequency resource. Upon reception of the discovery message, the apparatus determines a second resource element corresponding to a second time slot and a second frequency resource based on the first time slot and the first frequency resource in a deterministic resource allocation manner. The apparatus may alter the discovery message for rebroadcast in a deterministic message alteration manner. The apparatus rebroadcasts the discovery message using the second resource element.

DETAILED DESCRIPTION

The E-UTRAN includes the evolved Node B (eNB)106and other eNBs108, and may include a Multicast Coordination Entity (MCE)128. The eNB106provides user and control planes protocol terminations toward the UE102. The eNB106may be connected to the other eNBs108via a backhaul (e.g., an X2 interface). The MCE128allocates time/frequency radio resources for evolved Multimedia Broadcast Multicast Service (MBMS) (eMBMS), and determines the radio configuration (e.g., a modulation and coding scheme (MCS)) for the eMBMS. The MCE128may be a separate entity or part of the eNB106. The eNB106may also be referred to as a base station, a Node B, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The eNB106provides an access point to the EPC110for a UE102. Examples of UEs102include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a wearable device, a smart watch, or any other similar functioning device. The UE102may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

The eNB106is connected to the EPC110. The EPC110may include a Mobility Management Entity (MME)112, a Home Subscriber Server (HSS)120, other MMEs114, a Serving Gateway116, a Multimedia Broadcast Multicast Service (MBMS) Gateway124, a Broadcast Multicast Service Center (BM-SC)126, and a Packet Data Network (PDN) Gateway118. The MME112is the control node that processes the signaling between the UE102and the EPC110. Generally, the MME112provides bearer and connection management. All user IP packets are transferred through the Serving Gateway116, which itself is connected to the PDN Gateway118. The PDN Gateway118provides UE IP address allocation as well as other functions. The PDN Gateway118and the BM-SC126are connected to the IP Services122. The IP Services122may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service (PSS), and/or other IP services. The BM-SC126may provide functions for MBMS user service provisioning and delivery. The BM-SC126may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN), and may be used to schedule and deliver MBMS transmissions. The MBMS Gateway124may be used to distribute MBMS traffic to the eNBs (e.g.,106,108) belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

FIG. 2is a diagram illustrating an example of an access network200in an LTE network architecture. In this example, the access network200is divided into a number of cellular regions (cells)202. One or more lower power class eNBs208may have cellular regions210that overlap with one or more of the cells202. The lower power class eNB208may be a femto cell (e.g., home eNB (HeNB)), pico cell, micro cell, or remote radio head (RRH). The macro eNBs204are each assigned to a respective cell202and are configured to provide an access point to the EPC110for all the UEs206in the cells202. There is no centralized controller in this example of an access network200, but a centralized controller may be used in alternative configurations. The eNBs204are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway116. An eNB may support one or multiple (e.g., three) cells (also referred to as a sectors). The term “cell” can refer to the smallest coverage area of an eNB and/or an eNB subsystem serving a particular coverage area. Further, the terms “eNB,” “base station,” and “cell” may be used interchangeably herein.

Channel estimates derived by a channel estimator658from a reference signal or feedback transmitted by the eNB610may be used by the TX processor668to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor668may be provided to different antenna652via separate transmitters654TX. Each transmitter654TX may modulate an RF carrier with a respective spatial stream for transmission.

FIG. 7is a diagram of a device-to-device (D2D) communications system700. The device-to-device communications system700includes a plurality of wireless devices704,706,708,710. The device-to-device communications system700may overlap with a cellular communications system, such as for example, a wireless wide area network (WWAN). Some of the wireless devices704,706,708,710may communicate together in device-to-device communication using the DL/UL WWAN spectrum, some may communicate with the base station702, and some may do both. For example, as shown inFIG. 7, the wireless devices708,710are in device-to-device communication and the wireless devices704,706are in device-to-device communication. The wireless devices704,706are also communicating with the base station702.

The exemplary methods and apparatuses discussed infra are applicable to any of a variety of wireless device-to-device communications systems, such as for example, a wireless device-to-device communication system based on FlashLinQ, WiMedia, Bluetooth, ZigBee, or Wi-Fi based on the IEEE 802.11 standard. To simplify the discussion, the exemplary methods and apparatus are discussed within the context of LTE. However, one of ordinary skill in the art would understand that the exemplary methods and apparatuses are applicable more generally to a variety of other wireless device-to-device communication systems.

Proximity services (ProSe) render information with proximity relevance to subscribers of mobile devices. Proximity services, for instance, may be used by advertising points to deliver coupons to subscribers who pass a store where these coupons can be redeemed. In another use case, proximity services are exploited by friend-finder applications that alert subscribers upon (unknowingly) approaching the location of one of their friends or family members.

Proximity services can be realized via device-to-device discovery mechanisms as supported by a device-to-device communication system, for example, based on LTE-Direct (LTE-D). Such mechanisms provide wireless resources which are used by mobile devices to receive discovery messages transmitted by peer devices. Due to the finite propagation of the wireless signals, such D2D discovery messages are inherently range-limited hence conveying the experience of proximity upon detection.

While the discovery range is inherently determined by the wireless signal propagation environment and the power levels of the participating devices, the desired proximity range is defined by the superseding application, which may be significantly different from the discovery range. Especially in urban environments, where wireless signal propagation is limited due to the dense infrastructure, the discovery range may be too small for many proximity services.

One way to address this mismatch between the discovery range and the desired proximity range is to allow discovery messages to be rebroadcast (relayed) by discovering devices (i.e., the device receiving the discovery message) and therefore propagate along two or more hops. For such rebroadcasts, additional MAC layer resources may be allocated. Since multiple devices may receive and rebroadcast the same message, in one configuration, resource allocation may occur in a manner that minimizes the interference due to rebroadcasts while maximizing the benefit of multiple rebroadcasts. In such configuration, a resource allocation scheme is proposed for a time-slotted MAC layer.

In one configuration, rebroadcast of the same message by multiple devices may be coordinated by having each rebroadcasting device allocate a time slot and frequency resource that is derived in a deterministic resource allocation manner from the time slot and frequency resource where the original message is received. Further, all message alterations prior to rebroadcast (bit stream and waveform changes) may be executed in a deterministic message alteration manner. In such configuration, the utilization of resources used for rebroadcast of the same message by multiple devices may be minimized. Moreover, over the air (OTA) combining of multiple rebroadcast signals at the antenna of a rebroadcast receiver may be performed, leading to a statistically higher signal strength.

FIG. 8is a diagram illustrating an example of resource allocation for the relaying of device-to-device discovery messages in a device-to-device communications system800. The D2D communications system800includes several wireless devices802,804,806, and808. Some of the wireless devices802,804,806, and808may communicate together in device-to-device communication using the DL/UL WWAN spectrum. For example, as shown inFIG. 8, the wireless device802is in device-to-device communication with wireless devices804and806. The wireless devices804and806are also in device-to-device communication with wireless device808. In one configuration, each of the wireless devices802,804,806, and808may be a UE (e.g., the UE102or206).

In one configuration, the wireless device802broadcasts a discovery message810through a D2D communication channel using a MAC layer resource (e.g., a first resource element corresponding to a first time slot and a first frequency). The discovery message810may be received by the wireless devices804and806. Upon reception of the discovery message810on the D2D channel from the wireless device802, the wireless device804determines (at812) a MAC layer resource for rebroadcast (e.g., a second resource element corresponding to a second time slot and a second frequency) based on the MAC layer resource for receiving the discovery message810(e.g., the first resource element corresponding to the first time slot and the first frequency) in a deterministic resource allocation manner. In one configuration, the deterministic resource allocation manner refers to a manner that can be equally applied by all re-broadcasters (e.g.,804and806) of the same discovery message (e.g.,810). In one configuration, the deterministic resource allocation manner ensures that all re-broadcasters (e.g.,804and806) of the same discovery message determine the same MAC layer resource for rebroadcast of the discovery message.

In one configuration, the first resource element may be within a first frame. In such configuration, the deterministic resource allocation manner may refer to determining the second resource element that is the same resource element within a second frame that is a fixed number of frames after the first frame.

In one configuration, the deterministic resource allocation manner may refer to the addition of an offset to the first time slot and/or the addition of an offset to the first frequency. In one configuration, the offset to the time slot or to the frequency may be a fixed number. For example, the second time slot may be determined by applying a delay of a fixed number of time slots to the first time slot. Similarly, the second frequency may be determined by applying a fixed frequency shift to the first frequency. In one configuration, the offset to the time slot or frequency may be derived based on a set of parameters that is known to all rebroadcasting devices (e.g.,804and806). In such configuration, the set of parameters may include one or more of: an index of the first time slot, an index of the first frequency, time of reception of the discovery message810, or at least a portion of the content of the discovery message810. Similarly, upon reception of the discovery message810on the D2D channel from the wireless device802, the wireless device806determines (at814) the MAC layer resource for rebroadcast (e.g., the second resource element corresponding to the second time slot and the second frequency) based on the MAC layer resource for receiving the discovery message810(e.g., the first resource element corresponding to the first time slot and the first frequency) in the same deterministic resource allocation manner as wireless device804.

In one configuration, the wireless device804alters (at816) the discovery message810for rebroadcast/relay in a deterministic message alteration manner. In one configuration, the deterministic message alteration manner may refer to the same processing/modification of the discovery message (e.g.,810) that may be performed by all re-broadcasters (e.g.,804and806) of the discovery message. In such configuration, all re-broadcasters of a discovery message alter/modify the discovery message in the same way, and generates identical altered discovery message for rebroadcast. In one configuration, the deterministic message alteration manner may refer to the deterministic change of a flag of the discovery message, such as the insertion of a rebroadcast flag in the discovery message. In one configuration, the deterministic message alteration manner may refer to one or more of: the increment of a hop counter, the update of a cyclic redundancy check (CRC) or message authenticator, or the encryption of the message. For message authentication and encryption, the same key may be used among all rebroadcasting devices of the same discovery message. Similarly, the wireless device806alters (at818) the discovery message810for rebroadcast/relay in the same deterministic message alteration manner as wireless device804.

Once the MAC layer resource for rebroadcast is determined in the deterministic resource allocation manner and the discovery message810is altered in the deterministic message alteration manner, the wireless device804may rebroadcast the discovery message810as an altered discovery message820through a D2D communication channel using the determined MAC layer resource (e.g., the second resource element) for rebroadcast. Similarly, once the MAC layer resource for rebroadcast is determined in the same deterministic resource allocation manner as wireless device804and the discovery message810is altered in the same deterministic message alteration manner as wireless device804, the wireless device806may rebroadcast the discovery message810as the altered discovery message820through a D2D communication channel using the determined MAC layer resource (e.g., the second resource element) for rebroadcast.

The wireless device808may receive the rebroadcast/relayed discovery message820using the second resource element from both the wireless device804and the wireless device806. The wireless device808may perform an OTA combining of the discovery message820signals received from the wireless devices804and806, thus leading to a statistically higher signal strength for the discovery message820.

In one configuration, a D2D channel may refer to a wireless protocol that permits exchange of discovery messages between wireless devices. Such a D2D channel may be provided by technologies such as LTE-D, near-me area network (NAN), Social WiFi, iBeacon, 802.11 ad-hoc mode, for instance. In one configuration, the D2D channel may share wireless resources such as spectrum with other wireless services. For example, a D2D channel based on LTE-Direct or WiFi-Direct may share wireless resources with other wireless services. In one configuration, D2D discovery may use dedicated wireless resources.

In one configuration, the rebroadcast/relay of the discovery message820occurs on a D2D channel used for proximity services. The D2D channel for rebroadcast/relay of discovery message820may be the same D2D channel as where the discovery message810is received.

In one configuration, synchronization of the wireless devices802,804,806, and808may occur via a beacon signal supported by a wireless network infrastructure such as wireless access points or base stations in a cellular system. In one configuration, devices participating in D2D discovery (e.g.,802,804,806, and808) may use GPS or other satellite-based timing systems for time synchronization. In one configuration, the devices participating in D2D discovery (e.g.,802,804,806, and808) may mutually synchronize each others' clocks via periodic beacons transmitted and received.

In one configuration, the method of resource allocation for the relaying of D2D discovery messages may be applied to a time-unsynchronized system. In such configuration, devices may receive D2D discovery messages at any point in time, and the rebroadcast time may be set to a deterministic time frame after the time where the message is received. In such a case, the internal clock of all devices may be different. The resource allocation method may still be applicable as long as the drift among the internal clocks of the rebroadcast devices is small over the time frame between reception and rebroadcast of the discovery message.

FIG. 9is a diagram900illustrating an example of resource allocation for relaying or rebroadcasting of discovery messages. Specifically, this example shows that rebroadcast devices (e.g., UEs904and906) use the same time slot and the same frequency resource within a frame that is a fixed number k of frames after the frame in which the original discovery message is received. In one configuration, this example of resource allocation for relaying or rebroadcasting of discovery messages may be used in the D2D communications system800described above with reference toFIG. 8.

In this example, UE902originally broadcast a discovery message912through a D2D communication channel using resource element910awithin a frame i. In one configuration, the UE902may be the wireless device802described above with reference toFIG. 8, and the original discovery message912may be the discovery message810described above with reference toFIG. 8. In one configuration, each frame may have 6 time slots and 6 frequency resources. In such configuration, the resource element910amay be the time-frequency resource element corresponding to the third time slot and the third frequency resource. The discovery message912may be received by UE904using the same resource element910b(e.g., corresponding to the third time slot and the third frequency resource) within the frame i. Similarly, the discovery message912may be received by UE906using the same resource element910cwithin the frame i. The reception of original broadcast from the UE902by UEs904and906is a single hop discovery.

Upon reception of the discovery message912on the D2D channel from the UE902, the UE904determines (at914) to rebroadcast/relay the original discovery message using the same resource element920b(e.g., corresponding to the third time slot and the third frequency resource) within frame i+k, which is a frame that is a fixed number k of frames after the frame i. Similarly, upon reception of the discovery message912on the D2D channel from the UE902, the UE906determines (at916) to rebroadcast/relay the original discovery message using the same resource element920c(e.g., corresponding to the third time slot and the third frequency resource) within the frame i+k. In one configuration, the UEs904and906may be the wireless devices804and806described above with reference to FIG.8, and the rebroadcast/relayed discovery message922may be the discovery message820described above with reference toFIG. 8.

UE908may receive signals of the rebroadcast/relayed discovery message922at the same resource element920d(e.g., corresponding to the third time slot and the third frequency resource) within the frame i+k from both the UE904and the UE906. In one configuration, the UE908may be the wireless device808described above with reference toFIG. 8. The reception of the rebroadcast/relayed discovery message922at the UE908is a multi-hop discovery. In one configuration, the UE908may perform an OTA combining of the discovery message signals received from the UEs904and906, thus leading to a statistically higher signal strength for the rebroadcast/relayed discovery message.

In one configuration, rebroadcast of the same discovery message by multiple devices (e.g., UEs904and906) may be coordinated by having each rebroadcasting device allocate (e.g., at914or916) a time slot and frequency resource (e.g., the resource element920) that is derived in a deterministic resource allocation manner from the time slot and frequency resource in which the original message is received (e.g., the resource element910). In one configuration, the deterministic resource allocation manner may be the deterministic resource allocation manner described above with reference toFIG. 8. Further, all message alterations done prior to rebroadcast (e.g. such as changes to bit stream and waveform) may be executed in a deterministic message alteration manner. In one configuration, the deterministic message alteration manner may be the deterministic message alteration manner described above with reference toFIG. 8.

In one configuration, all rebroadcasts of the same discovery message may be superimposed on the same time-frequency resource (e.g., the resource element920) and use the same waveform. This minimizes the resource utilization for message rebroadcast. It further avoids interference between the rebroadcasts of the same message. It further allows over-the-air combining of the waveform signals from multiple rebroadcasts at the antenna of a rebroadcast receiver, leading to a statistically higher signal strength.

In one configuration, the D2D communication channel used for discovery uses a time-synchronized frame structure, where each frame is subdivided into multiple time slots (e.g., six time slots within frame i). One example for such D2D communication channel is LTE. In one configuration, the rebroadcasting device (e.g., UE904or906) determines the time slot (e.g., third time slot) within the frame where a discovery message is received (e.g., frame i). The rebroadcasting device then schedules the message for rebroadcast at the same time slot of the kthframe (e.g., frame i+k) after the frame where the message is received. The number k may advantageously be the same for all re-broadcasters (e.g., UEs904and906) of the same discovery message. In one configuration, the number k may have been configured for all devices. In another configuration, the number k may be derived in a deterministic random resource allocation process based on information that is available to all re-broadcasters of the same discovery messages, such as content of the discovery message or the time when the reception of the discovery message occurs.

If the frequency band used for D2D discovery is divided into several frequency resources, such as in LTE Direct, the rebroadcasting device (e.g., UE904or906) may determine the frequency resource where the discovery message is received (e.g., the third frequency resource), and select the same frequency resource when rebroadcasting the discovery message. The rebroadcasting device may select a different frequency resource in a deterministic resource allocation manner, i.e. in a manner that can be equally applied by all re-broadcasters of the same discovery message. For instance, in one configuration, the frequency resource for rebroadcast may be shifted by a fixed amount with respect to the frequency resource in which the discovery message is received. The amount of shift may depend on parameters such as the index of the initial frequency resource, the time of reception of the discovery message, at least a portion of the content of the discovery message, or other parameters that are known to all re-broadcasters of the same discovery message.

In one configuration, the resource allocation for relaying or rebroadcasting of discovery messages illustrated inFIG. 9may be applied to LTE-Direct, which supports a time-synchronized frame structure and a division of the frequency band into several frequency resources. In other configurations, instead of frames, the resource allocation for relaying or rebroadcasting of discovery messages illustrated inFIG. 9may be applied to other temporal structures, such as subframes, superframes, or Transmit Time Intervals (TTI), etc.

In one configuration, the rebroadcasting device (e.g., UE904or906) may use the same frequency resource (e.g., the third frequency resource) in the frequency spectrum as where the original discovery message is received. In another configuration, the frequency resource used for rebroadcast may be shifted by a certain fixed or deterministic amount in the frequency spectrum from the frequency resource in which the original discovery message is received. In yet another configuration, the original broadcast and the relay/rebroadcast of the discovery message may operate without subdivision of the frequency band, i.e. where the entire frequency band is used for a discovery code transmission.

FIG. 10is a diagram1000illustrating another example of resource allocation for relaying or rebroadcasting of discovery messages. Specifically, this example shows that rebroadcast devices (e.g., UEs1004and1006) use a delay of a fixed number of k time slots and a constant shift in frequency resource with respect to the time slot and frequency resource where the original discovery message is received. In one configuration, this example of resource allocation for relaying or rebroadcasting of discovery messages may be used in the D2D communications system800described above with reference toFIG. 8.

In this example, UE1002originally broadcast a discovery message1012through a D2D communication channel using resource element1010a. In one configuration, the UE1002may be the wireless device802described above with reference toFIG. 8, and the original discovery message1012may be the discovery message810described above with reference toFIG. 8. In one configuration, the resource element1010amay be the time-frequency resource element corresponding to the third time slot and the third frequency resource. The discovery message1012may be received by UE1004using the same resource element1010b(e.g., corresponding to the third time slot and the third frequency resource). Similarly, the discovery message1012may be received by UE1006using the same resource element1010c. The reception of original broadcast from the UE1002by UEs1004and1006is a single hop discovery.

Upon reception of the discovery message1012on the D2D channel from the UE1002, the UE1004determines (at1014) to rebroadcast/relay the original discovery message using the resource element1020b(e.g., corresponding to the 24th time slot and the fifth frequency resource), which is a fixed delay of 21 time slots and a constant shift of two frequency resources with respect to the resource element1010b. Similarly, upon reception of the discovery message1012on the D2D channel from the UE1002, the UE1006determines (at1016) to rebroadcast/relay the original discovery message using the resource element1020c(e.g., corresponding to the 24th time slot and the fifth frequency resource), which is a fixed delay of 21 time slots and a constant shift of two frequency resources with respect to the resource element1010c. In one configuration, the UEs1004and1006may be the wireless devices804and806described above with reference toFIG. 8, and the rebroadcast/relayed discovery message1022may be the discovery message820described above with reference toFIG. 8.

UE1008may receive signals of the rebroadcast/relayed discovery message1022at the same resource element1020d(e.g., corresponding to the 24th time slot and the fifth frequency resource) from both the UE1004and the UE1006. In one configuration, the UE1008may be the wireless device808described above with reference toFIG. 8. The reception of the rebroadcast/relayed discovery message1022at the UE1008is a multi-hop discovery. In one configuration, the UE1008may perform an OTA combining of the discovery message signals received from the UEs1004and1006, thus leading to a statistically higher signal strength for the rebroadcast/relayed discovery message.

In one configuration, rebroadcast of the same discovery message by multiple devices (e.g., UEs1004and1006) may be coordinated by having each rebroadcasting device allocate a time slot and frequency resource (e.g., the resource element1020) that is derived in a deterministic resource allocation manner from the time slot and frequency resource where the original message is received (e.g., the resource element1010). In one configuration, the deterministic resource allocation manner may be the deterministic resource allocation manner described above with reference toFIG. 8. Further, all message alterations done prior to rebroadcast (e.g. such as changes to bit stream and waveform) may be executed in a deterministic message alteration manner. In one configuration, the deterministic message alteration manner may be the deterministic message alteration manner described above with reference toFIG. 8.

In one configuration, all rebroadcasts of the same discovery message may be superimposed on the same time-frequency resource (e.g., the resource element1020) and use the same waveform. This minimizes the resource utilization for message rebroadcast. It further avoids interference between the rebroadcasts of the same message. It further allows over-the-air combining of the waveform signals from multiple rebroadcasts at the antenna of a rebroadcast receiver, leading to a statistically higher signal strength.

In one configuration, devices (e.g., UEs1002,1004,1006, and1008) are time-synchronized while a stringent frame structure is not supported. In such configuration, the delay between the reception of the original broadcast and the rebroadcast can be based on a time constant (e.g., 21 time slots), which may be fixed or may be derived in a deterministic resource allocation manner based on other information that is known to all re-broadcasters (e.g., UEs1004and1006).

FIG. 11is a flowchart1100of a method of wireless communication. Specifically, this figure illustrates a method of resource allocation for relaying or rebroadcasting of discovery messages. The method may be performed by a UE (e.g. the UE102,206, the device804,806, the UE904,906,1004,1006, or the apparatus1202/1202′). At1102, the UE receives a discovery message through a device-to-device communication channel using a first resource element corresponding to a first time slot and a first frequency resource. In one configuration, the received discovery message may be the discovery message810,912, or1012described above with reference toFIG. 8, 9, or10, respectively. In one configuration, the first resource element may be the resource element910or1010described above with reference toFIG. 9 or 10. In one configuration, the D2D communication channel may be a wireless communication channel.

At1104, the UE determines a second resource element corresponding to a second time slot and a second frequency resource based on the first time slot and the first frequency resource in a deterministic resource allocation manner. In one configuration, the second resource element may be the resource element920or1020described above with reference toFIG. 9 or 10. In one configuration, operations performed at1104may correspond to operations described above with reference to812or814ofFIG. 8, or914or916ofFIG. 9, or1014or1016ofFIG. 10. In one configuration, the deterministic resource allocation manner may be the deterministic resource allocation manner described above with reference toFIG. 8.

In one configuration, the device-to-device communication channel may use a synchronized time slotted structure. The synchronized time slotted structure may be a frame, subframe, superframe, or TTI. For example, the synchronized time slotted structure may be the frame i or i+k described above with reference toFIG. 9. In such configuration, the first resource element may be a resource element (e.g.,910ofFIG. 9) within a first synchronized time slotted structure (e.g., the frame i ofFIG. 9), and the second resource element may be the same resource element (e.g.,920ofFIG. 9) within a second synchronized time slotted structure (e.g., the frame i+k ofFIG. 9) that is a fixed number of synchronized time slotted structures after the first synchronized time slotted structure.

In one configuration, the second time slot (e.g., the time slot of the resource element1020inFIG. 10) may be determined by applying a delay of a fixed number of time slots to the first time slot (e.g., the time slot of the resource element1010inFIG. 10). In one configuration, the second frequency resource (e.g., the frequency resource of the resource element1020inFIG. 10) may be determined by applying a shift to the first frequency resource (e.g., the frequency resource of the resource element1010inFIG. 10). In one configuration, the shift applied to the first frequency resource may be a fixed shift (e.g., a shift of two frequency resources). In another configuration, the shift applied to the first frequency resource may be derived based on a set of parameters that is known to all re-broadcasters. In such configuration, the set of parameters may include one or more of: an index of the first frequency resource, a time of reception of the discovery message, or at least a portion of the content of the discovery message.

At1106, the UE may alter the discovery message for rebroadcast in a deterministic message alteration manner. In one configuration, operations performed at1106may correspond to operations described above with reference to816or818ofFIG. 8. In one configuration, the deterministic message alteration manner may be the deterministic message alteration manner described above with reference toFIG. 8.

At1108, the UE rebroadcasts the altered discovery message using the second resource element. In one configuration, the altered discovery message may be the discovery message820,922, or1022described above with reference toFIG. 8, 9, or10, respectively. In one configuration, the altered discovery message may be rebroadcast through the same device-to-device communication channel through which the original discovery message is received.

FIG. 12is a conceptual data flow diagram1200illustrating the data flow between different means/components in an exemplary apparatus1202. The apparatus1202may be a UE (e.g.,804,806,904,906,1004, or1006). The apparatus1202includes a reception component1204that may receive discovery message from a peer UE1250. In one configuration, the reception component1204may perform operations described above with reference to1102ofFIG. 11.

The apparatus1202includes a transmission component1210that transmits/rebroadcast discovery message to a peer UE1252. In one configuration, the transmission component1210may perform operations described above with reference to1108ofFIG. 11. In one configuration, the reception component1204and the transmission component1210communicate with each other to coordinate communications for the apparatus1202.

The apparatus1202may include a rebroadcast resource allocation component1208that determines the MAC layer resource for rebroadcast of the discovery message in a deterministic resource allocation manner. In one configuration, the rebroadcast resource allocation component1208may optionally receive discovery message information from the reception component1204, and determines the MAC layer resource for rebroadcast based on the discovery message information. In such configuration, the discovery message information may include one or more of: an index of the time slot for receiving the discovery message, an index of the frequency resource for receiving the discovery message, time of reception of the discovery message, or at least a portion of the content of the discovery message. In one configuration, the rebroadcast resource allocation component1208may determine the MAC layer resource for rebroadcast using a fixed delay in time and/or a constant shift on frequency. In one configuration, the deterministic resource allocation manner may be the deterministic resource allocation manner described above with reference toFIG. 8. In one configuration, the rebroadcast resource allocation component1208may perform operations described above with reference to812or814ofFIG. 8, 914 or 916ofFIG. 9, 1014 or 1016ofFIG. 10, or1104ofFIG. 11.

The apparatus1202may include a message alteration component1206that may alter the discovery message in a deterministic message alteration manner. The message alteration component1206may receive the discovery message from the reception component1204. In one configuration, the deterministic message alteration manner may be the deterministic message alteration manner described above with reference toFIG. 8. In one configuration, the message alteration component1206may perform operations described above with reference to816or818ofFIG. 8, or1106ofFIG. 11.

FIG. 13is a diagram1300illustrating an example of a hardware implementation for an apparatus1202′ employing a processing system1314. The processing system1314may be implemented with a bus architecture, represented generally by the bus1324. The bus1324may include any number of interconnecting buses and bridges depending on the specific application of the processing system1314and the overall design constraints. The bus1324links together various circuits including one or more processors and/or hardware components, represented by the processor1304, the components1204,1206,1208,1210and the computer-readable medium/memory1306. The bus1324may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system1314may be coupled to a transceiver1310. The transceiver1310is coupled to one or more antennas1320. The transceiver1310provides a means for communicating with various other apparatus over a transmission medium. The transceiver1310receives a signal from the one or more antennas1320, extracts information from the received signal, and provides the extracted information to the processing system1314, specifically the reception component1204. In addition, the transceiver1310receives information from the processing system1314, specifically the transmission component1210, and based on the received information, generates a signal to be applied to the one or more antennas1320. The processing system1314includes a processor1304coupled to a computer-readable medium/memory1306. The processor1304is responsible for general processing, including the execution of software stored on the computer-readable medium/memory1306. The software, when executed by the processor1304, causes the processing system1314to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory1306may also be used for storing data that is manipulated by the processor1304when executing software. The processing system1314further includes at least one of the components1204,1206,1208, and1210. The components may be software components running in the processor1304, resident/stored in the computer readable medium/memory1306, one or more hardware components coupled to the processor1304, or some combination thereof. The processing system1314may be a component of the UE650and may include the memory660and/or at least one of the TX processor668, the RX processor656, and the controller/processor659.

In one configuration, the apparatus1202/1202′ may include means for receiving a discovery message through a device-to-device communication channel using a first resource element corresponding to a first time slot and a first frequency resource. In one configuration, the means for receiving may be the transceiver1310, the one or more antennas1320, the reception component1204, or the processor1304. In one configuration, the means for receiving may perform operations described above with reference to1102ofFIG. 11.

In one configuration, the apparatus1202/1202′ may include means for determining a second resource element corresponding to a second time slot and a second frequency resource based on the first time slot and the first frequency resource in a deterministic resource allocation manner. In one configuration, the means for determining may be the rebroadcast resource allocation component1208or the processor1304. In one configuration, the means for determining may perform operations described above with reference to812or814ofFIG. 8, 914 or 916ofFIG. 9, 1014 or 1016ofFIG. 10, or1104ofFIG. 11.

In one configuration, the apparatus1202/1202′ may include means for altering the discovery message for rebroadcast in a deterministic message alteration manner. In one configuration, the means for altering the discovery message may be the message alteration component1206or the processor1304. In one configuration, the means for altering the discovery message may perform operations described above with reference to816or818ofFIG. 8, or1106ofFIG. 11.

In one configuration, the apparatus1202/1202′ may include means for rebroadcasting the altered discovery message using the second resource element. In one configuration, the means for rebroadcasting the altered discovery message may be the transceiver1310, the one or more antennas1320, the transmission component1210, or the processor1304. In one configuration, the means for rebroadcasting the altered discovery message may perform operations described above with reference to1108ofFIG. 11.

The aforementioned means may be one or more of the aforementioned components of the apparatus1202and/or the processing system1314of the apparatus1202′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system1314may include the TX Processor668, the RX Processor656, and the controller/processor659. As such, in one configuration, the aforementioned means may be the TX Processor668, the RX Processor656, and the controller/processor659configured to perform the functions recited by the aforementioned means.