BR112016016836B1 - METHOD AND APPARATUS FOR RESOURCE ALLOCATION FOR DISTRIBUTED DEVICE-TO-DEVICE SYNCHRONIZATION - Google Patents

Abstract

METHOD AND APPARATUS FOR RESOURCE ALLOCATION FOR DISTRIBUTED DEVICE-TO-DEVICE SYNCHRONIZATION. The present invention relates to a method, an apparatus and a computer program product for wireless communication in connection with improving resource allocation for D2D distributed synchronization in densely populated communications systems. In one example, a communication device is equipped to transmit a synchronization signal during a beacon period of a synchronization channel. In one aspect, the synchronization channel may include the beacon period, a paging period, and a TIB period. The communication device may further be equipped to monitor at least one of the beacon period, paging period or TIB period of the synchronization channel for one or more signals from one or more UEs in a D2D network, and determine as to whether transmission of information during at least one of the beacon period, paging period or TIB period based, at least in part, on monitoring.

Description

CROSS REFERENCE TO RELATED ORDER

[0001] This application claims the benefit of US Patent Application No. 14/160,381, entitled “METHOD AND APPARATUS FOR RESOURCE ALLOCATION FOR DISTRIBUTED DEVICE TO DEVICE SYNCHRONIZATION” and filed on January 21, 2014, which is expressly incorporated herein by reference in its entirety.

BASICS OF THE INVENTION FIELD OF INVENTION

[0002] The present invention relates generally to communications systems and, more particularly, to the allocation of resources for distributed device-to-device (D2D) synchronization in densely populated communications systems.

BACKGROUND OF THE INVENTION

[0003] Wireless communication systems are widely used to provide various telecommunications services, such as telephony, video, data, messages and broadcasts. Typical wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple access technologies include Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Access Single Carrier Frequency Division Multiple Access (SC-FDMA) and Time Division Synchronous Code Division Multiple Access (TD-SCDMA).

[0004] These multiple access technologies have been adopted in various telecommunications standards that provide a common protocol that allows different wireless devices to communicate at a city, national, regional and even global level. An example of a telecommunications standard is LTE. LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP). LTE is designed to better support mobile broadband Internet access, with better spectral efficiency, lower costs, better services, use of new spectrum and better integration with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL) and multi-input, multi-output (MIMO) antenna technology. LTE can also support direct device-to-device (peer-to-peer) communication.

[0005] In a D2D communication system, where user equipments (UEs) may not have access to any synchronization source (e.g., wireless access network (WAN)-based), positioning system receiver-based global (GPS), etc.), UEs can achieve synchronizations through the use of a distributed protocol. In this protocol, resources for synchronization (e.g., sync channel resources) can be allocated on a slow time scale (e.g., once every second) to reduce battery overhead as well as the amount of resources used. for synchronization. Furthermore, multiple UEs may transmit on various transmission resources available on the synchronization channel, and may receive transmissions on these resources to obtain timing structure information, frame structure information, timing and frequency corrections, information related to allocations from other channels, etc.

[0006] In a densely populated D2D communication system, these synchronization channel resources can be heavily reused, as all UEs attempt to transmit on each occurrence of the synchronization channel. Such transmission may interfere with each other and cause failures and/or reduce the ability of the UEs to decode the information in the broadcast message. This interference can also make erroneous time and frequency measurements.

[0007] As such, a system and method for improving synchronization channel design for densely populated D2D communication systems may be desired.

SUMMARY OF THE INVENTION

[0008] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of those aspects. This summary is not a broad overview of all aspects covered, and is not intended to identify key or critical elements of all aspects, nor to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0009] According to one or more aspects and their corresponding description, various aspects are described in connection with improving resource allocation for distributed D2D synchronization in densely populated communications systems. In one example, a communication device is equipped to transmit a synchronization signal during a beacon period of a synchronization channel. In one aspect, the synchronization channel may include the beacon period, a paging period, and a timing information block (TIB) period. The communication device may further be equipped to monitor at least one of the beacon period, the paging period or the TIB period of the synchronization channel for one or more signals from one or more UEs in a D2D network, and determine regarding the transmission of information during at least one of the beacon period, the paging period or the TIB period based, at least in part, on control.

[0010] According to related aspects, a method for improving resource allocation for distributed D2D synchronization in densely populated communications systems is provided. The method may include transmitting, by a UE, a synchronization signal during a beacon period of a synchronization channel. In one aspect, the synchronization channel may include the beacon period, a paging period, and a TIB period. Furthermore, the method may include monitoring at least one of the beacon period, the paging period, or the TIB period of the synchronization channel for one or more signals from one or more UEs in a D2D network. Furthermore, the method may include determining whether to transmit information during at least one of the beacon period, the paging period, or the TIB period based, at least in part, on the control.

[0011] Another aspect relates to a communications apparatus enabled to improve resource allocation for distributed D2D synchronization in densely populated communications systems. The communication apparatus may include means for transmitting a synchronization signal during a beacon period of a synchronization channel. In one aspect, the synchronization channel may include the beacon period, a paging period, and a TIB period. Furthermore, the communications apparatus may include means for monitoring at least one of the beacon period, the paging period, or the TIB period of the synchronization channel for one or more signals from one or more UEs in a D2D network. Furthermore, the communications apparatus may include means for determining whether to transmit information during at least one of the paging period or the TIB period based, at least in part, on control.

[0012] Another aspect refers to a communications device. The apparatus may include a processing system configured to transmit a synchronization signal during a beacon period of a synchronization channel. In one aspect, the synchronization channel may include the beacon period, a paging period, and a TIB period. Furthermore, the processing system may be configured to monitor at least one of the beacon period, the paging period, or the TIB period of the synchronization channel for one or more signals from one or more UEs in a D2D network. Furthermore, the processing system may be further configured to determine whether to transmit information during at least one of the paging period or the TIB period based, at least in part, on the control.

[0013] Yet another aspect relates to a computer program product of a UE, which may have a computer-readable medium, including code for transmitting, by the UE, a synchronization signal during a beacon period of a channel. synchronization. In one aspect, the synchronization channel may include the beacon period, a paging period, and a TIB period. Additionally, the computer-readable medium may include code for monitoring at least one of the beacon period, the paging period, or the TIB period of the synchronization channel for one or more signals from one or more UEs in the D2D network. . Furthermore, the computer-readable means may include a code for determining whether to transmit information during at least one of the paging period or the TIB period based, at least in part, on the control.

[0014] To achieve the above and related purposes, the one or more aspects comprise the following characteristics described in detail and particularly highlighted in the claims. The following description and accompanying drawings set forth in detail certain illustrative features of one or more aspects. These characteristics are indicative, however, of only some of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating an example of a network architecture. FIG. 2 is a diagram illustrating an example of an access network. FIG. 3 is a diagram illustrating an example of a DL frame structure in LTE. FIG. 4 is a diagram illustrating an example of a UL frame structure in LTE. FIG. 5 is a diagram illustrating an example of an evolved Node B and user equipment in an access network. FIG. 6 is a diagram illustrating a device-to-device communications network. FIG. 7 is a block diagram illustrating timing structures of the device-to-device communications network as time progresses, in accordance with one aspect. FIG. 8 is a diagram illustrating a device-to-device communications network that is configured to improve resource allocation for distributed D2D synchronization, in accordance with one aspect. FIG. 9A is a flowchart of a first wireless communication method. FIG. 9B is a flowchart of another wireless communication method. FIG. 9C is a flowchart that continues the method of FIG. 9B. FIG. 10 is a conceptual data flowchart illustrating the flow of data between different modules/means/components in an exemplary apparatus. FIG. 11 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The detailed description presented below in connection with the attached drawings is intended to be a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be practiced. The detailed description includes specific details for the purpose of providing a complete understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some cases, well-known structures and components are shown in block diagram form to avoid obscuring such concepts.

[0016] Various aspects of telecommunications systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the detailed description below and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the particular application and design limitations imposed on the overall system.

[0017] By way of example, an element, or any part of an element, or any combination of the elements can be implemented with a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionalities described throughout this invention. One or more processors in the processing system may execute the software. Software should be interpreted broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects , executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0018] Consequently, in one or more exemplary embodiments, the described functions can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, functions may be stored in or encoded as one or more instructions or code in a computer-readable medium. Computer-readable media includes computer storage media. Storage media can be any available media that can be accessed by a computer. By way of example, and not as a limitation, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to transport or store desired program code in the form of instructions or data structures, and which can be accessed by a computer. Disk and disc as used herein include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where discs generally reproduce data magnetically, whereas discs reproduce data optically with lasers. Combinations of the foregoing should also be included within the scope of computer-readable media.

[0019] FIG. 1 is a diagram illustrating a network architecture in LTE 100. The network architecture in LTE 100 may be referred to as an Evolved Packet System (EPS) 100. The EPS 100 may include one or more user equipment (UE) 102 , an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS) 120, and carrier IP Services 122. The EPS may interconnect. if with other access networks, but for simplicity these entities/interfaces are not shown. As shown, EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this description can be extended to networks that provide circuit-switched services.

[0020] The E-UTRAN includes the Evolved Node B (eNB) 106 and other eNBs 108. The eNB 106 provides user and control plane protocol terminations for the UE 102. The eNB 106 may be linked to the other eNBs 108 via backhaul (e.g. an X2 interface). The eNB 106 may also be referred to as a base station, 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 eNB 106 provides an access point to the EPC 110 for a UE 102. Examples of UEs 102 include a cell phone, a smartphone, a session initiation protocol (SIP) phone, a portable computer, 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, or any other operating device similar. The UE 102 may 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 portable device, a user agent, a mobile client, a client, or some other appropriate terminology.

[0021] The UEs 102 may form a D2D link 103. In one aspect, the D2D link 103 may be configured to allow the UEs 102 to communicate with each other. In another aspect, a UE 102 may act as a leader of a group of UEs that are capable of communicating with each other using the D2D link 103. Examples of the D2D link 103 are provided with reference to IEEE 802.11p based communications . Dedicated short-range communications (DSRC) wave systems based on IEEE 802.11p provide a basic safety message format where devices (e.g., vehicles) can periodically announce their position, speed, and other attributes to other devices ( e.g. other vehicles), allowing neighboring traffic to track their positions and avoid collisions, improve traffic flow, etc. Furthermore, the communication protocols in these systems do not prevent pedestrians (with their user equipment (UEs)) from using this spectrum and periodically transmitting basic safety messages that can indicate information such as their presence to the vehicles around them.

[0022] The eNB 106 is connected via an S1 interface to the EPC 110. The EPC 110 includes a Mobility Management Entity (MME) 112, other MMEs 114, a Server Gateway 116 and a Packet Data Network Gateway (PDN ) 118. The MME 112 is the control node that processes signaling between the UE 102 and the EPC 110. Generally, the MME 112 provides carrier and connection management. All user IP packets are transferred through the Server Gateway 116, which in turn is connected to the PDN Gateway 118. The PDN Gateway 18 provides UE IP address allocation as well as other functions. The PDN Gateway 118 is connected to the Operator's IP Services 122. Operator's IP Services 122 may include the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a PS Transmission Service (PSS).

[0023] FIG. 2 is a diagram illustrating an example of an access network 200 in an LTE network architecture. In this example, the access network 200 is divided into a series of cellular regions (cells) 202. One or more lower power class eNBs 208 may have cellular regions 210 that overlap with one or more of the cells 202. The eNB of Lower power class 208 may be a femto cell (e.g., household eNB (HeNB)), pico cells, micro cells, or the remote radio head (RRH). The macro eNBs 204 are each assigned to a respective cell 202 and are configured to provide an access point for the EPC 110 for all UEs 206, 212 in cells 202. Some of the UEs 212 may be in device-to-device communication. -device. There is no centralized controller in this example of an access network 200, but a centralized controller may be used in alternative configurations. The eNBs 204 are responsible for all radio-related functions, including radio carrier control, admission control, mobility control, scheduling, security, and connectivity to the server gateway 116.

[0024] The modulation and multiple access scheme employed by access network 200 may vary depending on the particular telecommunications standard to be deployed. In LTE applications, OFDM is used in DL and SC-FDMA is used in UL to support both frequency division duplexing (FDD) and time division duplexing (TDD). As those skilled in the art will readily appreciate from the detailed description below, the various concepts presented here are well suited for LTE applications. However, these concepts can be easily extended to other telecommunications standards using other modulation and multiple access techniques. By way of example, these concepts can be extended to Data Optimized Evolution (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by the Third Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employ CDMA to provide broadband Internet access to mobile stations. These concepts can also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband CDMA (W-CDMA) and other CDMA variants such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM using OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP2 organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and multiple access technology employed will depend on the specific application and the general design limitations imposed on the system.

[0025] FIG. 3 is a diagram 300 illustrating an example of a DL frame structure in LTE. One frame (10 ms) can be divided into 10 subframes of equal size. Each subframe can include two consecutive time slots. A resource grid can be used to represent two time slots, each time slot including a resource block. The resource grid is divided into several resource elements. In LTE, a resource block contains 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements. For an extended cyclic prefix, a resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. A physical DL control channel (PDCCH), a physical shared DL channel (PDSCH), and other channels can be mapped to resource elements.

[0026] FIG. 4 is a diagram 400 illustrating an example of a UL frame structure in LTE. The resource blocks available to the UL can be divided into a data section and a control section. The control section can be formed at both ends of the system bandwidth and can have a configurable size. Resource blocks in the control section can be assigned to UEs for transmitting control information. The data section can include all resource blocks not included in the control section. The UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all contiguous subcarriers in the data section.

[0027] A UE may be assigned resource blocks 410a, 410b in the control section to transmit control information to an eNB. The UE may also be assigned resource blocks 420a, 420b in the data section to transmit data to the eNB. The UE may transmit control information on a UL physical control channel (PUCCH) regarding resource blocks assigned in the control section. The UE may transmit only data or both data and control information on a UL shared physical channel (PUSCH) for resource blocks assigned in the data section. A UL transmission can span both slots of a subframe and can hop across frequency.

[0028] A set of resource blocks may be used to perform initial system access and achieve UL synchronization on a physical random access channel (PRACH) 430. The PRACH 430 carries a random sequence and cannot carry any data/ UL signage. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for PRACH. The PRACH attempt is performed in a single subframe (1 ms) or in a sequence of a few contiguous subframes and a UE can only make a single PRACH attempt per frame (10 ms).

[0029] FIG. 5 is a block diagram of an eNB 510 communicating with a UE 550 in an access network. In DL, packets from the upper layer of the core network are provided to a controller/processor 575. The controller/processor 575 implements the L2 layer functionality. In DL, the controller/processor 575 provides header compression, encryption, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE 550 based on various priority indicators. The controller/processor 575 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 550.

[0030] The transmission processor (TX) 516 implements various signal processing functions for the L1 layer (i.e., the physical layer). Signal processing functions include coding and interleaving to facilitate forward error correction (FEC) in the UE 550 and mapping to signal constellations based on various modulation schemes (e.g., binary phase keying (BPSK), phase keying quadrature (QPSK), M-ary phase keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM)). The encoded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g. pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel that carries a stream of time-domain OFDM symbols. The OFDM symbol stream is spatially pre-coded to produce multiple spatial streams. Channel estimates from a channel estimator 574 can be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 550. Each spatial stream is then provided to a different antenna 520 via a separate transmitter 518TX. Each 518TX transmitter modulates an RF carrier with a respective spatial stream for transmission.

[0031] In the UE 550, each receiver 554RX receives a signal through its respective antenna 552. In another aspect, the UE 550 may communicate with other UEs in a manner similar to how the UE 550 communicates with the eNB 510. Each receiver 554RX retrieves information modulated on an RF carrier and provides the information to the receive processor (RX) 556. The RX processor 556 implements various L1 layer signal processing functions. The RX processor 556 performs spatial processing on the information to recover any spatial streams destined for the UE 550. If multiple spatial streams are destined for the UE 550, they can be combined by the RX processor 556 into a single OFDM symbol stream. The RX 556 processor then converts the stream of OFDM symbols from the time domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the signal constellation points most likely transmitted by the eNB 510. These indicative decisions may be based on channel estimates calculated by the channel estimator 558. The indicative decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 510 on the physical channel. Data and control signals are then supplied to the 559 controller/processor.

[0032] Controller/processor 559 implements the L2 layer. The controller/processor may be associated with a memory 560 that stores program codes and data. Memory 560 may be referred to as a computer-readable medium. In UL, the 559 controller/processor provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover packets from the upper layer of the core network. The upper layer packets are then provided to a data collector 562, which represents all protocol layers above the L2 layer. Various control signals may also be provided to the data collector 562 for L3 processing. The 559 controller/processor is also responsible for error detection using an acknowledge (ACK) and/or negative acknowledge (NACK) protocol to support HARQ operations.

[0033] In UL, a data source 567 is used to provide upper layer packets to the controller/processor 559. The data source 567 represents all protocol layers above the L2 layer. Similar to the functionality described in connection with DL transmission by eNB 510, controller/processor 559 implements the L2 layer for the user plane and control plane, providing header compression, encryption, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB 510. The controller/processor 559 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 510.

[0034] Channel estimates obtained by a channel estimator 558 from a reference or feedback signal transmitted by the eNB 510 may be used by the TX processor 568 to select appropriate modulation and coding schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 568 are provided to the different antenna 552 through separate transmitters 554TX. Each 554TX transmitter modulates an RF carrier with a respective spatial stream for transmission.

[0035] The UL transmission is processed in the eNB 510 in a manner similar to that described in connection with the receiver function in the UE 550. Each receiver 518RX receives a signal through its respective antenna 520. Each receiver 518RX recovers modulated information about a RF carrier and provides the information to an RX 570 processor. The RX 570 processor can implement the L1 layer.

[0036] Controller/processor 575 implements the L2 layer. The controller/processor 575 may be associated with a memory 576 that stores program codes and data. Memory 576 may be referred to as a computer-readable medium. In the UL, the controller/processor 575 provides demultiplexing between the logical and transport channels, packet reassembly, decryption, header decompression, control signal processing to recover upper layer packets from the UE 550. Upper layer packets from the 575 controller/processor may be provided for the core network. The 575 controller/processor is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

[0037] FIG. 6 is a diagram of a device-to-device communications system 600. The device-to-device communications system 600 includes a plurality of wireless devices 604, 606, 608, 610. The device-to-device communications system 600 may overlay a cellular communications system, such as, for example, a wireless wide area network (WWAN). Some of the wireless devices 604, 606, 608, 610 can communicate together in device-to-device communication using the WWAN DL/UL spectrum, some can communicate with the base station 602, and some can do both. For example, as shown in FIG. 6, the wireless devices 608, 610 are in device-to-device communication and the wireless devices 604, 606 are in device-to-device communication. The wireless devices 604, 606 are also communicating with the base station 602.

[0038] The wireless device may alternatively be referred to by those skilled in the art as a user equipment (UE), a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a wireless node , a remote unit, a mobile device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a portable device, an agent user interface, a mobile client, a client, or some other suitable terminology. The base station may alternatively be referred to by those skilled in the art as an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), a set of extended services (ESS), a B-Node, an evolved B-Node, or some other appropriate terminology.

[0039] The exemplary methods and apparatus discussed above are applicable to any of a variety of wireless device-to-device communication 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, exemplary methods and devices are discussed within the context of LTE. However, one of ordinary skill in the art will understand that the exemplary methods and apparatus are applicable more generally to a variety of other wireless device-to-device communication systems.

[0040] FIG. 7 is a block diagram representing a communication structure 700 for a D2D communication system as time 702 progresses. The structure can be used by any UEs in the D2D communication system.

[0041] As represented in FIG. 7, the communication structure 700 may include a synchronization period 704 and a communication period 706. As described herein, the synchronization period 704 may also be referred to as a synchronization channel.

[0042] In one aspect, the synchronization period 704 can be divided into three periods (e.g., sub-channels), including a beacon period 708, a paging period 710, and a block information transmission period. timing (TIB) 712.

[0043] In one aspect, during the beacon period 708, all UEs following the same timing structure may transmit on the resources in the beacon period. Since there may be a few (e.g., 1-2) resources in the beacon period 708, multiple UEs may transmit on the same resources. In such an aspect, information transmitted during beacon period 708 may be specific to the timing structure rather than a transmitting UE. In other words, multiple UEs transmitting on a resource in beacon period 708 may transmit the same synchronization signal.

[0044] In one aspect, paging period 710 may be allocated to a random access subchannel. As such, transmissions during paging period 710 may be event-triggered. In other words, a UE may not transmit paging resources on a periodic basis. In one aspect, an event that may trigger a transmission during paging period 710 may include detecting a synchronization signal transmission in beacon period 708 without being able to decode any TIB broadcast messages. This case may arise when only a subset of UEs can transmit TIB broadcast messages and there may not be a TIB broadcast in the vicinity of the UE. The UE may then request a broadcast transmission of detailed timing information in the broadcast period of TIB 712. In another aspect, an event that may trigger a transmission during the paging period 710 may include a determination by the UE that the paging period diffusion of TIB 712 is excessively accumulated. The UE may transmit information on a random access resource in the paging period 710 to indicate resource accumulation in the TIB period 712. For example, when a GPS-enabled UE cannot find a locally unused TIB resource, the UE may indicate the accumulation of resources by transmitting information about a random access resource in the paging period 710. In yet another aspect, an event that may trigger a transmission during the paging period 710 may include a UE indicating some information, such as , but not limited to, the availability of an improved timing structure within the local proximities, transmitting information in a random access resource in the paging period 710.

[0045] In one aspect, the diffusion period of TIB 712 may include multiple features (e.g., 10-20 features) that may be designed to be orthogonal to each other. Furthermore, resources in the broadcast period of TIB 712 can be reused by UEs that are not in local proximity. In one aspect, only a subset of UEs may transmit on one of the resources available in the TIB period 712. In one such aspect, a UE may determine whether to transmit during the TIB period based on information received over a WAN, information received during the paging period 710, etc. In one aspect, information transmitted about resources during the TIB 712 period may include, but is not limited to: frame structure information used in the timing structure, the age of the timing structure (e.g., a time elapsed since that the timing structure was created), a resource ID on which information is being transmitted, other timing-related information that the UE may decide to transmit (such as the presence of another timing structure in the neighborhood, etc.), etc. . In another aspect, information transmitted during the TIB period may span multiple occurrences of synchronization period 704. In yet another aspect, information transmitted about resources during the TIB period may be specific to the transmitting UE (e.g., a MAC ID of the transmitter, a duration that the UE intends to continue transmitting on the resource, a preference as to whether the UE prefers to transmit resources during the TIB period, etc.).

[0046] FIG. 8 is a diagram of a communications system 800 that is configured to support D2D communications.

[0047] In one aspect, multiple UEs (e.g., 802-810) may synchronize to a common timing structure within a D2D communication group 820. The UEs 802-810 may synchronize using a distributed D2D synchronization protocol, such as as described above with reference to FIG. 7. As described above, each UE (e.g., 802-810) may transmit to the D2D communication group 820 information 822 during a beacon period of a synchronization period. In such an aspect, information 822 transmitted during the beacon period may be specific to the timing structure of the D2D communication group 820 rather than a transmitting UE (e.g., 802-810). In other words, multiple UEs (e.g., 802-810) transmitting on a resource in the beacon period may transmit the same 822 synchronization signal.

[0048] In an operational aspect, one or more UEs (e.g., UE 808) may transmit a signal 824 during a paging period based on the occurrence of one or more events. For example, an event that may trigger a transmission 824 during the paging period may include detecting a beacon transmission without being able to decode any TIB broadcast messages. In another aspect, an event that may trigger a transmission 824 during the paging period may include the UE determining that the TIB transmission period is excessively accumulated. The UE may transmit information 824 on a random access resource in the paging period to indicate resource accumulation in the TIB broadcast period. For example, when a GPS-enabled UE cannot find a locally unused TIB resource, the UE may indicate resource accumulation by transmitting information 824 on a random access resource in the paging period. In yet another aspect, an event that may trigger a transmission 824 during the paging period may include a UE indicating some information, such as, but not limited to, the availability of an improved timing structure within the local vicinity via the transmission of information 824 in a random access resource in the paging period.

[0049] Furthermore, in an operational aspect, one or more UEs (e.g., the UE 804) may transmit a signal 826 during a TIB broadcast period. In one aspect, only a subset of UEs can transmit a signal 826 from one of the resources available in the TIB period. In such an aspect, a UE may determine whether to transmit during the TIB period based on information received over a WAN 818, information 824 received during the paging period, etc. In one aspect, information 826 transmitted on resources during the TIB period may be specific to the transmitting UE (e.g., a MAC ID of the transmitter, a duration that the UE intends to continue transmitting on the resource, a preference as to whether the UE prefers to transmit resources during the TIB period, etc).

[0050] FIGS. 9A, 9B and 9C illustrate various methodologies according to various aspects of the subject matter. Although, for the sake of simplicity of explanation, the methodologies are shown and described as a series of acts or sequence steps, it must be understood and appreciated that the subject matter claimed is not limited by the order of the acts, as some acts may occur in orders different from and/or concomitantly with other acts from those shown and described here. For example, those skilled in the art will understand and appreciate that a methodology could be carried out as a series of interrelated states or events, and/or substantially in parallel. Furthermore, the various methodologies described in the blocks below can be performed individually or in any combination.

[0051] FIG. 9A is a flowchart of a first wireless communication method 900. The method can be performed by a UE in a D2D network that is configured with distributed synchronization.

[0052] In block 902, the UE may transmit a synchronization signal during a beacon period of a synchronization channel. For example, the internal timing information module 1008 of the apparatus 1002 may provide the synchronization signal 1020 for transmission by the transmission module 1012. In one aspect, the synchronization channel may include the beacon period, a paging period, and a TIB period. In one such aspect, the synchronization signal may include information associated with the timing structure used in the D2D network. Furthermore, in such an aspect, the TIB period may include 10 or more orthogonal features. In another aspect, the ITO may include a frame structure used in a timing structure for the D2D network, an age of the timing structure, a resource ID on which information is being transmitted, timing-related information associated with at least one of a currently timing structure or a proposed timing structure, etc., or any combination thereof.

[0053] In block 904, the UE monitoring at least the paging period and/or the TIB period of the synchronization channel for one or more signals from one or more UEs in the D2D network. For example, the receiving module 1004 may monitor signals 1022 received from one or more UEs 804-810 in the D2D network 800. In another aspect, the UE may monitor a beacon transmission during the beacon period. In another aspect, the UE may monitor and receive a request for timing-related information for the D2D network during the paging period. If, in block 904, the UE does not detect any signals during the paging period and/or the synchronization channel TIB period, then the UE may resume transmitting during a subsequent instance of the synchronization channel beacon period in the block 902.

[0054] If, in block 904, the UE monitors any at least one signal received from the one or more UEs in the D2D network, then, in block 906, the UE determining whether to transmit information during at least one of the period of paging or the TIB period. If the UE determines that no information is being transmitted, then the UE may resume transmitting during a subsequent instance of the synchronization channel beacon period in block 902. If the UE determines that there is information to be transmitted, then in block 908 the UE can transmit the information. For example, the receiving module 1004 may provide any received signals 1022 to the timing information processing module 1006 that may provide an indication 1024 to the timing information transmission determination module 1010 as to whether any timing information has been requested. . In another exemplary aspect, the receiving module 1004 may receive superior timing information from, for example, a network entity 818, and may provide an indication 1024 to the timing information transmission determination module 1010 to know whether any timing information should be broadcast. The timing information transmission module 1010 may process the indication(s) 1024 and determine which information 1026 to transmit and during which period (e.g., paging period, TIB period, etc.) the information 1026 should be transmitted by transmission module 1012. In one aspect, the determination may be based on information received over a WAN, information received during the paging period, etc. In one aspect, the UE may determine that it is unable to decode information received during a TIB period, and in response may transmit paging information during the paging period. In one aspect, where the UE can determine that it has information to transmit during the TIB period and also that more than a threshold number of resources are being used during the TIB period, then the UE can transmit a backlog indication of resources during the paging period. In another aspect, where the UE is aware of the presence of an upper timing structure, then the UE may transmit an indication of availability of the upper timing structure during the paging period. In one aspect, the UE may receive a request for timing information during the paging period, and may transmit the timing information during the TIB period. In another aspect, where the UE does not detect any signal during the paging or TIB periods, the UE may transmit a synchronization signal during the beacon period and/or timing-related information during the TIB period.

[0055] FIG. 9B is a flowchart of another method 930 of wireless communication. The method can be performed by a UE in a D2D network that is configured with distributed synchronization. FIG. 9C is a flowchart 970 that continues the method 930 of FIG. 9B.

[0056] In block 932, the UE is in a listening mode, where the UE can monitor at least one of a beacon period, a paging period, or a Timing Information Block (TIB) period for signals from one or more UEs in the D2D network. The beacon period, paging period, and TIB period can be part of a synchronization channel. In block 934, the UE determines whether a beacon transmission is detected. When no beacon transmission is detected, the UE determines, in block 942, whether the listening mode has ended. If the listen mode has not ended, the UE returns to block 932 and continues to monitor at least one of the beacon period, the paging period, or the timing information block (TIB) period. If the listen mode has ended, the UE proceeds to block 944 to generate a synchronization signal. In block 946, the UE generates timing information and the TIB and then transmits, in block 950, the synchronization signal during a following beacon period.

[0057] When beacon transmission is detected in block 934, the UE proceeds to block 936 to listen for a TIB period. Next, in block 938, the UE determines whether a TIB transmission is decoded. If no TIB transmission is decoded, the UE in block 940 generates a paging information packet requesting timing information. The UE then proceeds to block 948 to generate a synchronization signal. If TIB transmission is detected in block 938, the UE proceeds directly to block 948 to generate the synchronization signal. The UE then proceeds to block 950 to transmit the synchronization signal during a following beacon period.

[0058] In block 952, the UE determines whether a paging information packet is generated. If the paging information packet is generated, the UE in block 954 transmits the paging information packet. The UE then proceeds to block 972.

[0059] If the paging information packet is not generated, the UE in block 956 listens for the paging transmissions. In block 958, the UE determines whether a paging transmission requesting timing information is received. If no paging transmission is received, the UE proceeds to block 972. However, if the paging transmission is received, the UE in block 960 determines to transmit the TIB during a following TIB period. The UE then proceeds to block 962 to determine whether to transmit the TIB. If the UE determines to transmit the TIB, the UE proceeds to block 944 to generate a synchronization signal and continue operation accordingly. However, if the UE determines not to transmit the TIB, the UE proceeds to block 948 to generate a synchronization signal and continue operation accordingly.

[0060] In block 972, the UE determines whether the TIB is generated. If the TIB is generated, the UE in block 974 transmits the TIB during a following TIB period. Thereafter, in block 976, the UE listens for TIB transmissions. If the TIB is not generated in block 972, the UE proceeds directly to block 976 to listen for TIB transmissions.

[0061] In block 978, the UE determines whether any TIB transmission is decoded. If no TIB transmission is decoded, the UE reverts to listen mode in block 932. If a TIB transmission is decoded, the UE in block 980 determines whether backlog exists in the TIB period. If there is backlog, the UE in block 982 generates a paging information packet indicating backlog. Thereafter, the UE in block 984 determines whether better timing is available. If the backlog does not exist in block 980, the UE proceeds directly to block 984.

[0062] If the best timing is available in block 984, the UE in block 986 generates a paging information packet that indicates the best timing. Thereafter, the UE proceeds to block 960 and continues operation accordingly. If the best timing is not available in block 984, the UE proceeds directly to block 960 to continue the operation.

[0063] FIG. 10 is a conceptual data flowchart 1000 illustrating the flow of data between different modules/means/components in an example apparatus 1002. The apparatus may be a UE (e.g., UE 802-810). As described with reference to FIG. 9, apparatus 1002 includes a receiving module 1004, timing information processing module 1006, internal timing information module 1008, timing information transmission determination module 1010, and transmission module 1012.

[0064] The apparatus may include additional modules that perform each of the steps of the algorithm in the aforementioned flowcharts of FIGs. 9A, 9B and 9C. As such, each block in the aforementioned flowcharts of FIGs. 9A, 9B, and 9C may be realized by a module and the apparatus may include one or more such modules. Modules may be one or more hardware components specifically configured to perform the indicated process/algorithm, implemented by a processor configured to perform the indicated process/algorithm, stored within a computer-readable medium for execution by a processor, or some combination of the same.

[0065] FIG. 11 is a diagram 1100 illustrating an example of a hardware implementation for an apparatus 1002' that employs a processing system 1114. The processing system 1114 may be implemented with a bus architecture, generally represented by the bus 1124. The bus 1124 may include any number of communicating buses and bridges, depending on the specific application of the processing system 1114 and overall design constraints. The buses 1124 connect various circuits, including one or more processors and/or hardware modules, represented by the processor 1104, the modules 1004, 1006, 1008, 1010, 1012, and the computer-readable medium 1106. The bus 1124 may also connect several 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 further.

[0066] The processing system 1114 may be coupled to a transceiver 1110. The transceiver 1110 is coupled to one or more antennas 120. The transceiver 1110 provides a means for communicating with various other devices via a transmission medium. The processing system 1114 includes a processor 1104 coupled to a computer-readable medium, a processor 1106. The processor 1104 is responsible for general processing, including executing software stored on the computer-readable medium 1106. The software, when executed by the processor 1104, causes the processing system 1114 to perform the various functions described above for any particular apparatus. The computer-readable medium 1106 may also be used for storing data that is manipulated by the processor 1104 during the execution of the software. The processing system further includes at least one of modules 1004, 1006, 1008, 1010 and 1012. The modules may be software modules running on processor 1104, resident/stored on computer readable medium 1106, one or more modules of hardware coupled to the processor 1104, or some combination thereof. The processing system 1114 may be a component of the UE 550 and may include memory 560 and/or at least one of the TX processor 568, the RX processor 556, and the controller/processor 559.

[0067] In one embodiment, the apparatus 1002/1002' for wireless communication in a distributed synchronization D2D network includes means for transmitting a synchronization signal during a beacon period of a synchronization channel, means for monitoring at least one of the beacon period, the paging period or the TIB period of the synchronization channel for one or more signals from one or more UEs in the D2D network, and means for determining whether to transmit information during at least one of the period of paging or TIB period based, at least in part, on control. In one aspect, the synchronization channel may include the beacon period, the paging period, and the TIB period. In one aspect, the apparatus 1002/1002' means for monitoring may be further configured to monitor a beacon transmission during the beacon period, and the means for determining may be further configured to determine that the information is not capable of being decoded during the TIB period. In such an aspect, the apparatus 1002/1002' may further include means for transmitting paging information during the paging period. In one aspect, the apparatus 1002/1002' means for determining may be further configured to determine that the apparatus has information to be transmitted during the TIB period, and determine that more than a threshold number of resources are being used during the period. of TIB. In such an aspect, the apparatus 1002/1002' may further include means for transmitting an indication of resource accumulation during the paging period. In one aspect, the determining apparatus 1002/1002' means for determining may be further configured to determine that a superior timing structure is available. In such an aspect, the apparatus 1002/1002' may further include means for transmitting an indication of availability of the upper timing structure during the paging period. In one aspect, the apparatus 1002/1002' means for determining may be further configured to determine the transmission of information during the TIB period based on information received over a WAN, information received during the paging period, etc. In one aspect, the apparatus 1002/1002' means for monitoring may be further configured to receive a request during the paging period, and the means for determining may be further configured to determine that the request is for information related to the timing for the paging period. D2D network. In such an aspect, the apparatus 1002/1002' may further include means for transmitting timing-related information during the TIB period. In one aspect, the apparatus 1002/1002' means for monitoring can be further configured not to detect signals during the paging period or TIB period. In such an aspect, the apparatus 1002/1002' may further include means for transmitting the synchronization signal during the beacon period of the synchronization channel, or transmitting timing-related information during the TIB period of the synchronization channel.

[0068] The aforementioned means may be one or more of the aforementioned modules of the apparatus 1002 and/or the processing system 1114 of the apparatus 1002' configured to perform the functions enumerated by the aforementioned means. As described above, the processing system 1114 may include the TX processor 568, the RX processor 556, and the controller/processor 559. As such, in one configuration, the aforementioned means may be the TX processor 568, the RX processor 556, and the controller/processor 559 configured to perform the enumerated functions by the aforementioned means.

[0069] It is understood that the specific order or hierarchy of steps in the described processes is an illustration of exemplary approaches. Based on design preferences, it is understood that the specific order or hierarchy of steps in processes can be rearranged. Additionally, some steps can be combined or omitted. The attached method claims present elements of the various steps in a sample order, and are not to be limited to the specific order or hierarchy presented.

[0070] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Accordingly, the claims should not be limited to the aspects shown herein, but should be granted the broadest scope in accordance with the language of the claims, in which reference to an element in the singular is not intended to mean “one and only one”, unless specifically so stated, but rather “one or more”. Unless specifically indicated otherwise, the term “one” refers to one or more. All structural and functional equivalents to elements of the various aspects described throughout this invention, which are known or which later become known to those of ordinary skill in the art are expressly incorporated herein by reference and are to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be dedicated to the public, regardless of whether such disclosure is expressly enumerated in the claims. No element of the claim should be construed as a means plus function unless the element is expressly enumerated using the expression “means for.”

Claims (9)

1. Method (900) of wireless communications to a user equipment, UE, in a device-to-device, D2D, distributed synchronization network, comprising: monitoring (932) at least one of a beacon period, a period paging period or a timing information block period, TIB, for one or more signals from one or more UEs in the D2D network, characterized by the fact that the beacon period, the paging period and the TIB period are included in a synchronization channel; detecting (934) a beacon transmission during the beacon period and decoding (938) timing information from at least one transmission in the TIB period; and transmitting (950) a synchronization signal that includes information associated with a timing structure to the D2D network from the UE during a subsequent beacon period of the synchronization channel. 2. Method (900) of wireless communications to a user equipment, UE, in a device-to-device, D2D, distributed synchronization network, comprising: monitoring (932) at least one of a beacon period, a period paging period, or a timing information block period, TIB, for one or more signals from one or more UEs in the D2D network, characterized by the fact that the beacon period, the paging period and the TIB period are included in a synchronization channel; detecting (934) a beacon transmission during the beacon period and determining (938) that timing information is not decoded during the TIB period; and transmitting (940) paging information comprising a request to transmit information related to the timing of the D2D network during a subsequent paging period and transmitting a synchronization signal (950) during a subsequent beacon period based on the determination that the information timings are not decoded during the TIB period. 3. Method (900) of wireless communications to a user equipment, UE, in a device-to-device, D2D, distributed synchronization network, comprising: monitoring (932) at least one of a beacon period, a period paging period or a timing information block period, TIB, for one or more signals from one or more UEs in the D2D network, characterized by the fact that the beacon period, the paging period and the TIB period are included in a synchronization channel; determine that the UE has information to be transmitted during the TIB period; determine that a number of resources being used during the TIB period are greater than a threshold; and transmitting (982) a resource accumulation indication during a subsequent paging period and transmitting a synchronization signal (950) during a subsequent beacon period based on the determination that the series of resources being utilized during the TIB period is greater than the threshold. 4. The method of claim 1, wherein the TIB period includes 10 or more orthogonal features. 5. Method according to claim 1, characterized by the fact that the information to be transmitted during the TIB period comprises at least one of: a frame structure used in a timing structure for the D2D network; an age of the timing structure; a resource ID on which information is being transmitted; or timing-related information associated with at least one of a current timing structure or a proposed timing structure. 6. Method (900) of wireless communications to a user equipment, UE, in a device-to-device, D2D, distributed synchronization network, comprising: monitoring (932) at least one of a beacon period, a period paging period or a timing information block period, TIB, for one or more signals from one or more UEs in the D2D network, characterized by the fact that the beacon period, the paging period and the TIB period are included in a synchronization channel; receive (956) a request during the paging period; determining (958) that the request is for timing-related information for the D2D network; and transmitting (960) the timing-related information during a subsequent TIB period. 7. Method (900) of wireless communications to a user equipment, UE, in a device-to-device, D2D, distributed synchronization network, comprising: monitoring (932) at least one of a beacon period, a period paging period or a timing information block period, TIB, for one or more signals from one or more UEs in the D2D network, characterized by the fact that the beacon period, the paging period and the TIB period are included in a synchronization channel; not detect signals during the paging period or the TIB period; and transmitting, in response to the detection, at least one of: a synchronization signal during a subsequent beacon period of the synchronization channel; or timing-related information for the D2D network during a subsequent TIB period of the synchronization channel. 8. Apparatus (1000) for wireless communications in a device-to-device, D2D, distributed synchronization network, characterized in that it comprises: means for carrying out the method as defined in any one of claims 1 to 7. 9. Computer-readable memory (1106) characterized by the fact that it comprises instructions stored therein which, when executed, perform the method as defined in any one of claims 1 to 7.