CN104812058A

CN104812058A - Method for implementing synchronization between D2D terminals and D2D terminal device

Info

Publication number: CN104812058A
Application number: CN201410601153.1A
Authority: CN
Inventors: 张世昌; 李迎阳; 孙程君; 付景兴; 杨云川
Original assignee: Beijing Samsung Telecommunications Technology Research Co Ltd; Samsung Electronics Co Ltd
Current assignee: Beijing Samsung Telecommunications Technology Research Co Ltd; Samsung Electronics Co Ltd
Priority date: 2014-01-24
Filing date: 2014-10-30
Publication date: 2015-07-29
Also published as: WO2015111851A1

Abstract

The inventions provide a method for implementing synchronization between D2D terminals. For a D2D terminal which is able to detect the synchronization source of the cellular network and is located at the edge of the cellular cell, if the D2D synchronization signal of the same level D2D terminal cannot be detected within a certain area, D2D signal is continuously transmitted with a particular period. According to a detection result of the synchronization signal of the next level terminal, the transmission density of the D2D synchronization signal is adjusted. For a D2D synchronization terminal which is able to detect the synchronization source of the cellular cell, D2D synchronization signal is transmitted in response to a trigger synchronization signal triggered by a D2D terminal outside the coverage of the synchronization source of the cellular network. For a D2D terminal which is beyond the coverage of the synchronization source of the cellular cell, synchronization signal is transmitted/detected or trigger synchronization signal is transmitted according to actions of the D2D terminal in the coverage of the synchronization source of the cellular cell. According to the technical solution provided by the present disclosure, synchronization between D2D terminals may be implemented effectively.

Description

Method for realizing synchronization between D2D terminals and D2D terminal equipment

Technical Field

The present application relates to the field of mobile communication technologies, and in particular, to a method and an apparatus for implementing synchronization between D2D terminals in a D2D communication system.

Background

Currently, the D2D (Device to Device) communication technology has been accepted by the 3GPP standard by its great potential value in the public safety field and the general civil communication field, and becomes a candidate evolution direction of the LTE-a (LTE advanced) system.

According to the current 3GPP conclusion, the D2D terminal will perform D2D communication in a half-duplex manner, and when the D2D terminal is under the wireless network coverage condition, the D2D communication will only occupy the uplink carrier frequency (FDD system) or uplink subframe (TDD system). Also, the working assumption of the current 3GPP is that the structure of PUSCH in the current LTE system will be followed for communication between D2D, i.e. the information bits communicated between D2D terminals will be carried on a wireless signal generated based on SC-FDMA multiple access technique.

However, the correct reception of SC-FDMA radio signals requires strict time and frequency synchronization of the transmitting end and the receiving end, which means that a plurality of D2D terminals performing D2D communication must be in a state of time and frequency synchronization. However, in an actual D2D communication environment, a plurality of D2D terminals that may perform D2D communication form a D2D group, and there may not be a common synchronization source among a plurality of D2D terminals in the D2D group, for example, some or all D2D terminals in the D2D group are out of coverage of a radio cell, or D2D terminals in the D2D group are under coverage of different radio cells, and the radio cells are in an asynchronous state. Therefore, in the D2D communication environment, some D2D terminals need to transmit synchronization signals, which are used as synchronization sources to achieve time-frequency synchronization between D2D terminals in a certain D2D group.

In a cellular wireless communication environment, an eNB transmits a synchronization signal at a fixed time period, and a terminal in a cell realizes initial time-frequency synchronization with the eNB by detecting the synchronization signal transmitted by the eNB. Unlike eNB, however, the D2D terminal is typically battery powered and has limited power and ability to continuously transmit synchronization signals. In addition, in what environment within the D2D group, the D2D terminal should transmit the synchronization signal, in what case should stop transmitting the synchronization signal, how the D2D terminal should detect the synchronization signal to achieve synchronization with other D2D terminals within the D2D group, and so on, these problems will affect the synchronization between the D2D terminals and ultimately the communication between the D2D, and there is no solution to the above problems at present.

Disclosure of Invention

The present application aims to solve at least one of the above technical drawbacks, and in particular provides a method for achieving mutual synchronization of D2D terminals within a D2D cluster, including:

a method for supporting a D2D terminal to realize synchronization comprises the following steps:

the D2D terminal detects the synchronization source of the cellular network and determines the transmission/detection configuration of the D2D synchronization signal; the sending/detecting configuration comprises a sending/detecting period, and a sending window and a detecting window corresponding to each stage of synchronous terminal;

and the IC terminal which detects the synchronization source of the cellular network and the OOC terminal which does not detect the synchronization source of the cellular network transmit/detect D2D synchronization signals according to the transmission/detection configuration.

Preferably, the sending/detecting D2D sync signals by the IC terminal includes:

a1, when the IC terminal is at the edge of the cellular network cell or receives the D2D synchronous signal detection indication of the base station, the IC terminal selects a window w in the sending window of each long period of the same synchronous terminal according to the sending/detection configuration of the D2D synchronous signal_l,iIn the window w_l,iDetecting a D2D synchronization signal of a peer synchronization terminal; when the IC terminal determines that the D2D synchronization signal of the peer synchronization terminal is not detected, or when the IC terminal reports the D2D synchronization signal detection result of the peer synchronization terminal to the base station and receives a D2D synchronization signal transmission instruction of the base station, execute step a 2; the period of the sending/detecting configuration is divided into a long period and a basic period, the long period comprises M basic periods, M is a positive integer, i is a long period P_lIs the index of the basic period in (1), l is the transmission/detectionConfiguring the identification of the middle and long periods;

a2 in the window w_l,iD2D synchronization signal is sent for the next-stage synchronization terminal to synchronize.

Preferably, the sending/detecting D2D sync signals by the IC terminal includes:

a1, when the IC terminal is located at the edge of the cellular network cell or receives the D2D synchronous signal detection indication of the base station, the IC terminal detects the D2D synchronous signal of the same synchronous terminal at each sub-frame n of the long period according to the transmission/detection configuration of the D2D synchronous signal; when the IC terminal determines that the D2D synchronization signal of the peer synchronization terminal is not detected, or when the IC terminal reports the D2D synchronization signal detection result of the peer synchronization terminal to the base station and receives a D2D synchronization signal transmission instruction of the base station, execute step a 2; wherein mod (n- Δ, P)_u) The period of the transmission/detection configuration is divided into long periods P, 0_lAnd a basic period P_uLong period P_lComprising N fundamental periods P_uL is the identification of the long period in the sending/detecting configuration, and delta is the deviation of a preset long period detecting window;

a2, one transmission window w per long period_lSending a D2D synchronization signal for the synchronization of the secondary synchronization terminal; wherein, w_lThe sub-frame number n corresponding to the sub-frame in which it is located_lSatisfies the following conditions: mod (n)_l-Δ，P_l) 0, or mod (n)_l-Δ-N_ID×P_u，P_l) 0, wherein N_IDMod (RNTI, N), which is the ID of the IC terminal in the cell.

Preferably, after the step a2 is executed, the method further includes: the IC terminal is in the sending/detecting windowDetecting a synchronous signal of a peer synchronous terminal, and stopping the sending of the D2D synchronous signal after detecting the synchronous signal of the peer synchronous terminal; in the absence of detection ofWhen the synchronization signal of the peer terminal is synchronized, the process returns to step a 2;

wherein,sub-frame number ń corresponding to the sub-frame in which it is located_lSatisfies the following conditions: mod (ń)_l-Δ，P_u) 0 and ń_l≠n_l。

Preferably, the determining that the IC terminal is located at the cell edge of the cellular network includes:

when the reference signal receiving power of the cellular network cell detected by the IC terminal is less than a set threshold TH_ccThen, it is determined that the IC terminal is located at the cell edge of the cellular network.

Preferably, after the step a2, the method further comprises:

the IC terminal transmits/detects the synchronous signal according to D2D in the window w_l,iDetecting the D2D synchronous signal of the next-stage synchronous terminal in the sending window of the second-stage synchronous terminal in the basic period, and dividing the window w_l,iThe sending windows of other peer synchronizing terminals detect the D2D synchronizing signal of the peer synchronizing terminal; when the D2D synchronous signal of the next-stage synchronous terminal is detected, the transmission density of the D2D synchronous signal is increased.

Preferably, the increasing the transmission density of the D2D synchronization signal includes: the IC terminal is arranged in the window w_l,iAnd the sending window w of the D2D synchronous signal of the other peer synchronous terminal is not detected_l,jSending the D2D synchronization signal; wherein j is an index of the transmission window of the D2D synchronization signal of the other peer synchronization terminal in the long period l.

Preferably, after increasing the transmission density of the D2D sync signals, the IC terminal detects the D2D sync signal of the next-stage sync terminal in the transmission window of the second-stage sync terminal in the basic period of the window where the D2D sync signal is transmitted, and returns to step a2 when the D2D sync signal of the next-stage sync terminal is not detected in the transmission windows of all the corresponding second-stage sync terminals.

Preferably, the sending D2D synchronization signal by the IC terminal includes: the IC terminal detects the trigger synchronous signal sent by the secondary synchronous terminal, and then the IC terminal sends the trigger synchronous signal with the period P indicated in the sending/detecting configuration_ICFor the period, the D2D synchronization signal is transmitted in the transmission window of the primary synchronization terminal.

Preferably, the IC terminal detects the trigger synchronization signal in each detection window of the primary synchronization terminal according to the transmission/detection configuration.

Preferably, after the D2D synchronization signal is transmitted in the transmission window of the primary synchronization terminal, the method further includes: and the IC terminal detects the D2D synchronous signal of the next-level synchronous terminal in a detection window corresponding to the sending window of the first-level synchronous terminal, and stops sending the D2D synchronous signal after the D2D synchronous signal of the next-level synchronous terminal cannot be detected.

Preferably, the sending/detecting D2D synchronization signals by the OOC terminal includes:

and the OOC terminal sequentially executes the operation of sending/detecting the D2D synchronization signal on each carrier supported by the OOC terminal according to the pre-stored priority of the carrier corresponding to the cellular network cell.

Preferably, for any carrier, when the OOC terminal is at the set time T_OOCAnd after the D2D synchronous signals are detected on any carrier, the OOC terminals are synchronized according to the D2D synchronous signal with the highest level in the detected D2D synchronous signals.

Preferably, after detecting the D2D synchronization signal on any one of the carriers, the method further comprises:

b1, the OOC terminal selects the window w of the highest level synchronizing signal in the detected D2D synchronizing signals_k,iAccording to the window w_k,iThe level information k in the detected D2D synchronization signal determines that the synchronization level is k +1 and the window w is_k,iThe OOC terminal in the basic period has the same level of sending window w_t,iDetecting a D2D synchronization signal of a terminal of the same level as the OOC terminal; the period of the sending/detecting configuration is divided into a long period and a basic period, the long period comprises M basic periods, M is a positive integer, and i is an index of the basic period in which the window of the highest-level synchronization signal is detected;

b2, if the OOC terminal is the last-stage synchronous terminal and the OOC terminal is in the window w_t,iThe D2D synchronization signal of the terminal of the same class is not detected, or if the OOC terminal is located in an edge area covered by the synchronization signal of the upper-level synchronization terminal and is a non-final-stage terminal, and the OOC terminal is located in the window w_t,iThe detected D2D synchronous signal receiving power of the synchronous terminal at the same level is less than the set threshold TH_bOr, if the OOC terminal is far from the edge area covered by the upper synchronous terminal and is a non-final-stage terminal, and the OOC terminal is in the window w_t,iIf the D2D synchronization signal of the peer terminal is not detected, performing step b 3;

b3, the OOC terminal is in the window w_t,iA D2D synchronization signal is sent.

Preferably, after the step b3, the method further comprises:

when the OOC terminal is located in an edge area covered by an upper synchronous terminal and is a non-final terminal, the OOC terminal configures in the window w according to the sending/detecting of the D2D synchronous signal_t,iDetecting the D2D synchronous signal of the next synchronous terminal in the transmitting window of the next synchronous terminal in the basic period, and dividing the window w_t,iThe sending windows of other peer synchronizing terminals detect the D2D synchronizing signal of the peer synchronizing terminal; when the D2D synchronous signal of the next-stage synchronous terminal is detected, the transmission density of the D2D synchronous signal is increased.

Preferably, the increasing the transmission density of the D2D synchronization signal includes: the OOC terminal is at the window w_t,iAnd the sending window w of the D2D synchronous signal of the other peer synchronous terminal is not detected_t,jSending the D2D synchronization signal; wherein j is an index of the transmission window of the D2D synchronization signal of the other peer synchronization terminal in the long period l.

Preferably, after increasing the transmission density of the D2D synchronization signals, the OOC terminal detects the D2D synchronization signal of the next synchronization terminal in the transmission window of the next synchronization terminal in the basic period of the window for transmitting the D2D synchronization signals, and returns to step b3 when the D2D synchronization signal of the next synchronization terminal is not detected in the transmission windows of all the corresponding next synchronization terminals.

c1, the OOC terminal selects the window w of the highest level synchronizing signal in the detected D2D synchronizing signals_k,iAccording to the window w_k,iThe detected level information k in the D2D synchronous signal determines that the synchronization level thereof is k +1, and when the OOC terminal is positioned in the edge area covered by the synchronous signal of the upper synchronous terminal and is a non-final synchronous terminal, the OOC terminal selects a sending window w from the sending windows of the same level of the OOC terminal in each long period l according to the sending/detecting configuration of the D2D synchronous signal_l,iiIn the window w_l,iiDetecting a D2D synchronization signal of a terminal of the same class as the OOC terminal; the period of the sending/detecting configuration is divided into a long period and a basic period, the long period includes M basic periods, M is a positive integer, i is an index of the basic period where the window of the highest-level synchronization signal is detected, and ii is an index of the basic period where the selected sending window is located in the long period l;

c2 if in the window w_l,iiThe OOC terminal does not detect the D2D synchronous signal of the terminal at the same level as the OOC terminal, and the OOC terminal is arranged at each long cycleThe window w of period l_l,iiA D2D synchronization signal is sent.

Preferably, for any carrier, when the OOC terminal does not detect any D2D synchronization signal on the any carrier within a set time, the OOC terminal selects a window w in the transmission window of each long-period l primary or secondary synchronization terminal according to the transmission/detection configuration of the D2D synchronization signal_l,iIn the window w with a period of l_l,iSending an independent D2D synchronization signal for the next-stage synchronization terminal to synchronize; the period of the sending/detecting configuration is divided into a long period and a basic period, wherein the long period comprises M basic periods, M is a positive integer, and i is an index of the basic period in the long period.

Preferably, for any carrier, when the OOC terminal is at the set time T_OOCWhen no D2D synchronous signal is detected on any carrier, the OOC terminal sends a trigger synchronous signal and a detection D2D synchronous signal on any carrier in a time division mode, and if the set time T is after the trigger synchronous signal is sent_trD2D synchronous signals are not detected, and the step D is executed;

d. the OOC terminal transmits/detects the synchronous signals according to the D2D and in each long period P_lSelecting a window w from the sending windows of the primary or secondary synchronous terminals_l,iWith P_lFor a period in the window w_l,iSending an independent D2D synchronization signal for the next-stage synchronization terminal to synchronize; the period of the sending/detecting configuration is divided into a long period and a basic period, wherein the long period comprises M basic periods, M is a positive integer, and i is an index of the basic period in the long period.

Preferably, after the step d, the method further comprises:

the OOC terminal transmits/detects the configuration according to the D2D synchronous signal in the window w_l,iDetecting the D2D synchronous signal of the next-stage synchronous terminal in the sending window of the second-stage or third-stage synchronous terminal in the basic period, and dividing the windoww_l,iThe sending windows of other peer synchronizing terminals detect the D2D synchronizing signal of the peer synchronizing terminal; when the D2D synchronous signal of the next-stage synchronous terminal is detected, the transmission density of the D2D synchronous signal is increased.

Preferably, the increasing the transmission density of the D2D synchronization signal includes: the OOC terminal is at the window w_l,iAnd the sending window w of the D2D synchronous signal of the other peer synchronous terminal is not detected_l,jSending the D2D synchronization signal; wherein j is the long period P of the sending window of the D2D synchronization signal of the other peer synchronization terminal not detected_lThe index in (1).

Preferably, after increasing the transmission density of the D2D synchronization signals, the OOC terminal detects the D2D synchronization signal of the next-stage synchronization terminal in the transmission window of the secondary or tertiary synchronization terminal in the basic period of the window for transmitting the D2D synchronization signals, and returns to step D when the D2D synchronization signal of the next-stage synchronization terminal is not detected in the transmission windows of all corresponding secondary or tertiary synchronization terminals.

Preferably, for any carrier, when the OOC terminal is at the set time T_OOCWhen no D2D synchronous signal is detected on any carrier, the OOC terminal sends a trigger synchronous signal and a detection D2D synchronous signal on any carrier in a time division mode, and if the set time T is after the trigger synchronous signal is sent_trAnd D2D synchronous signals are detected, the OOC terminal stops sending the trigger synchronous signals and the detection D2D synchronous signals on any carrier in a time division mode, and steps b 1-b 3 are executed.

A D2D terminal device, comprising: the system comprises a cellular network synchronization source detection unit, a configuration receiving unit, an IC terminal synchronization unit and an OOC terminal synchronization unit;

the cellular network synchronization source detection unit is configured to detect a synchronization source of a cellular network, instruct the IC terminal synchronization unit to perform synchronization processing when the synchronization source is detected, and instruct the OOC terminal synchronization unit to perform synchronization processing when the synchronization source is not detected;

the configuration receiving unit is used for receiving the sending/detecting configuration of the D2D synchronous signal; the sending/detecting configuration comprises a sending/detecting period, and a sending window and a detecting window corresponding to each stage of synchronous terminal;

the IC terminal synchronization unit is configured to send/detect a D2D synchronization signal according to the sending/detecting configuration after receiving the notification from the cellular network synchronization source detection unit;

and the OOC terminal synchronization unit is configured to send/detect a D2D synchronization signal according to the sending/detecting configuration after receiving the notification of the cellular network synchronization source detection unit.

According to the technical scheme, for the D2D terminal which can detect the synchronization source of the cellular network cell and is positioned at the edge of the cellular network cell, when the synchronization signals of other D2D terminals of the same level can not be detected in a certain range, the D2D signal is continuously transmitted according to a certain period and time offset, and the transmission density of the D2D synchronization signal is adjusted according to the detection result of the synchronization signal of the next level of terminal; or for a D2D terminal capable of detecting a cell synchronization source of a cellular network, sending a D2D synchronization signal according to a trigger synchronization signal from a D2D terminal outside the cell synchronization source of the same cellular network. For D2D terminals outside the coverage of the cellular network cell synchronization source, the synchronization signal is detected/sent or triggered according to the behavior of the D2D terminals within the coverage of the cellular network cell synchronization source. Through the scheme provided by the application, the synchronization between the D2D terminals can be simply and efficiently realized.

Drawings

FIG. 1 is a flow chart of an implementation of the scheme of the present application;

FIG. 2 is a schematic diagram of one possible transmit/detect configuration;

FIG. 3 is a flowchart of an implementation of the present application;

FIG. 4 is a flowchart of a second implementation of the present application;

FIG. 5 is a flowchart of a third implementation of the present application;

FIG. 6 is a flowchart of a fourth implementation of the present application;

FIG. 7 is a flow chart of a fifth implementation of the present application;

FIG. 8 is a flowchart of a sixth implementation of an embodiment of the present application;

FIG. 9 is a flowchart of a seventh implementation manner of the present application;

fig. 10 is a schematic diagram of a basic structure of a D2D terminal device in the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below by referring to the accompanying drawings and examples.

In the D2D communication environment, there may not be a common synchronization source between D2D terminals in the D2D group, so in the D2D communication environment, the D2D terminals with potential communication requirements may not be synchronized by the same synchronization source (such as eNB in cellular communication) in some cases, however, as proposed in the background art, synchronization is a prerequisite for any communication by the D2D terminals. In order to solve the above problem, the present application proposes a method for implementing synchronization between D2D terminals in a D2D group, as shown in fig. 1, including the following steps:

step 110: the D2D terminal detects the synchronization source R of the cellular network and determines the D2D synchronization signal transmission/detection configuration.

The D2D terminal may detect signals transmitted by a cell of the cellular network (including synchronization signals, cell downlink reference signals (CRS), etc.), and determine whether the synchronization source R of the cellular network can be successfully detected according to the detected signal strength or other criteria. If a certain D2D terminal can successfully detect the synchronization source R of the cellular network, the D2D terminal is called an IC terminal, whereas if a certain D2D terminal cannot successfully detect the synchronization source R of the cellular network, the D2D terminal is called an OOC terminal.

It should be noted that the IC terminal and the OOC terminal are referred to a specific cellular network synchronization source R, for example, if the D2D terminal a is under the coverage of the cellular network synchronization source R and the D2D terminal B is under another coverage of the cellular network synchronization source different from R, the D2D terminal B is referred to as the OOC terminal.

If the IC terminal is called a primary synchronization terminal, the OOC terminal which directly depends on the D2D synchronization signal forwarded by the IC terminal to realize synchronization is called a secondary synchronization terminal, the OOC terminal which directly depends on the D2D synchronization signal forwarded by the secondary synchronization terminal to realize synchronization is called a tertiary synchronization terminal, and the like until the final synchronization terminal.

The sending/detecting configuration may be defined directly by the standard or configured by the cellular network or some D2D central control node, including sending/detecting period, sending window and detecting window corresponding to each level of synchronous terminal.

Specifically, the transmission/detection period may include a basic period transmission/detection configuration and a long period transmission/detection configuration. The basic periodic transmission/detection configuration includes one or more of the following information: basic period P_u、P_uInner transmit/detect window time offset Δ, P_uThe corresponding relation between the inner sending window and the detecting window, and the sending/detecting carrier frequency CF; if P is included in the transmission/detection configuration_uThe information of the corresponding relation between the inner sending window and the detection window is in P_uEach transmit/detect time offset corresponds to a D2D sync signal transmit/detect window. Each P_uOne or more transmit/detect windows may be included.

The long period transmission/detection configuration includes a transmission/detection window period P_l. SendingDetection Window period P_lBy M basic transmission/detection periods P_uWhere M may be equal to 1, or some random value, or some standard definition or cellular network cell or some D2D central control node configured value. When M is equal to 1, the long period and the basic period are the same, which means that there is only one transmission detection configuration period at this time.

One possible long period transmission/detection configuration (example one) is shown in fig. 2, where in fig. 2, the period P is_lTwo basic periods are included, each basic period has 4 transmitting/receiving windows corresponding to each stage of synchronous terminals, delta_wi(wi is more than or equal to 0 and less than or equal to 2) is a sending window of the w + 1-level synchronous terminal, the next window adjacent to the window is a detection window corresponding to the window, and delta is₃The corresponding window is the transmission window of the final terminal. In the figure, the sending window of the lower synchronization terminal is the detection window of the upper synchronization terminal. In practical applications, such a relationship will generally be followed. However, the transmission window of a terminal of a certain class is not necessarily followed by the detection window of the same class.

Another possible long period transmit/detect configuration (example two) is shown in FIG. 2, where in FIG. 2, the period P is_lTwo basic periods are included, each basic period has 4 transmitting/receiving windows corresponding to each stage of synchronous terminals, delta_wi(wi is more than or equal to 0 and less than or equal to 2) is the sending window of the w + 1-th level synchronous terminal, and delta₃The corresponding window is the transmission window of the final terminal. The definition of the correspondence between the transmission window and the detection window is not included in the transmission/detection configuration.

Step 120: and the IC terminal and the OOC terminal transmit/detect the synchronous signals with the corresponding formats according to the corresponding transmitting/detecting configurations.

The D2D synchronization signal transmitted by each level D2D terminal carries the level information of the D2D terminal, and the last-level synchronization terminal can forward the synchronization signal but is not used by other D2D terminals for synchronizing with the synchronization source R. Whether a certain window is a sending window or a detection window is relative to a certain level of synchronous terminals, and the sending window of a certain level of synchronous terminals can be the receiving window of other levels of synchronous terminals, and vice versa.

In order to facilitate understanding of the present application, the following further explains the above technical solution of the present application in an inter-device interaction mode by combining specific application cases as follows:

the first embodiment is as follows:

in this embodiment, the target terminal may successfully detect the synchronization source of the cellular network cell, that is, the IC terminal. The terminal firstly judges whether the terminal is positioned at the edge of the cellular network cell according to the detected strength of the downlink reference signal of the cellular network cell, further detects the power of the D2D synchronous signal of the same-level synchronous terminal for the IC terminal positioned at the edge of the cellular network cell, and starts to send the D2D reference signal with a long period in the sending/detecting configuration if the detected power of the synchronous signal is less than a certain set threshold. Or, the IC terminal may start to detect the D2D synchronization signal of the peer synchronization terminal by receiving the indication of the base station, report the detection result to the base station, and determine whether to send the D2D synchronization signal according to the indication of the base station.

An IC terminal which transmits D2D synchronization signals in a long period detects D2D synchronization signals from a next synchronization terminal in a transmission window of the next synchronization terminal, detects D2D reference signals from other peer synchronization terminals in the transmission windows of other peer synchronization terminals, and after detecting the D2D synchronization signals from the next synchronization terminal, the IC terminal increases the density of transmitting D2D synchronization signals, namely, all idle peer synchronization terminals transmit D2D synchronization signals in a long period. The specific implementation steps are shown in fig. 3, and specifically include:

step 310: transmission/detection configuration C for acquiring D2D synchronous signal by IC terminal_lAnd C_u。

Wherein C is_lAnd C_uConfigured for long period transmission/detection and basic period respectivelyAnd a sending/detecting configuration, wherein partial parameters in the two configurations can be the same, and the two configurations can also be completely the same. C_lAnd C_uMay be broadcast by the cellular network or some D2D central control node, or defined directly by the standard.

Step 320: the IC terminal detects the signal of the cellular network and judges whether the IC terminal is positioned at the edge of a cellular network cell, if so, the step 330 is executed, otherwise, the step is repeatedly executed; or, the IC terminal determines whether a D2D synchronization signal detection indication of the base station is received, if so, determines to execute step 330, otherwise, repeats the step.

The specific manner of determining whether the IC terminal is located at the cell edge of the cellular network may adopt various existing manners, such as: based on whether the detected reference signal received power of the cellular network is less than a certain threshold TH_ccTo determine when the received power is less than TH_ccWhen the IC terminal is located at the edge of the cellular network cell, determining that the IC terminal is located at the edge of the cellular network cell; the reference signal detected by the I C terminal may include one or more of a primary synchronization channel signal, a secondary synchronization channel signal, and a cell reference signal of a cell of the cellular network. The reference signal received power may be the result of one detection or the average of the detection results over a period of time. TH_ccMay be configured by the cellular network or some D2D central control node, or defined directly by the standard.

Step 330: if it is determined in step 320 that the IC terminal is located at the edge of the cell, the IC terminal selects a window w in the primary synchronization terminal transmission window for each long period_l,iIn the window w_l,iDetecting a synchronous signal of a synchronous terminal at the same level; or, the IC terminal receives the eNB D2D synchronization signal detection indication, and selects the window w_l,iAnd detecting the synchronous signals of the synchronous terminals at the same level.

Wherein w_l,iIs a period P_lInner fundamental period P_u,iMiddle delta_lCorresponding transmission window, Δ_lTime offset of a transmission window of a primary synchronization terminal in a basic transmission/detection period, wherein i isA certain value between 0 and M-1 represents an index of the basic period in the long period, and M is the number of basic periods included in the long period. The manner in which i is determined (i.e., window w)_l,iThe selection method of (1) may be a random selection or other selection methods, and the present application does not limit the method of determining the value of i by the IC terminal. P_lTo configure C_lThe decided transmission/detection window period, i.e., the long period.

Step 340: if the IC terminal is in the window w_l,iFails to detect the synchronization signal from the same-level synchronization terminal, the IC terminal is set to have the period P_lWindow w at each cycle_l,iSending D2D synchronization signal, otherwise continuing in window w_l,iDetecting a synchronous signal of a synchronous terminal at the same level; or reporting the detection result to the base station, determining whether to send the D2D synchronous signal according to the base station indication, and if so, sending the synchronous signal in the period P_lWindow w at each cycle_l,iSending D2D synchronization signal, otherwise continuing in window w_l,iThe synchronization signal of the synchronous terminal of the same level is detected.

Here, when the IC terminal is in the window w_l,iWhen the synchronous signal from the synchronous terminal of the same level is not detected, the fact that no other IC terminal is in the window w in the coverage range of the synchronous signal of the IC terminal is shown_l,iSending a D2D synchronization signal, the IC terminal may be in the window w_l,iThe D2D synchronization signal is transmitted for synchronization by the D2D synchronization signal at a secondary synchronization terminal within the coverage of the IC terminal synchronization signal.

Preferably, the IC terminal may determine whether the received power of the synchronization signal is less than TH_cdAnd judging whether the synchronous signals from the synchronous terminals at the same level are successfully detected. The received power may be Δ_lCorresponding to the detection result of the power of the synchronizing signal of a synchronous terminal of the same level in the sending window, or a period of time T_cdInner delta_lThe average value of the detection results of the power of the synchronization signals of the same synchronization terminal in the corresponding sending window. T is_cdMay be one long period or a plurality of long periods, or other values configured by the cellular network or some D2D central control node, orA value defined directly by the standard. TH_cdMay be configured by the cellular network or some D2D central control node (e.g., via cell broadcast messaging), or may be defined directly by the standard.

Or, the IC terminal may directly report the detection result of the synchronization signal to the base station in step 330 without determining the receiving power of the synchronization signal by itself, and determine whether to send the D2D synchronization signal according to an instruction issued by the base station.

The IC terminal may determine the transmission window w of the mth long period after the transmission of the D2D sync signal_l,iTransmitting D2D synchronous signal, and transmitting window w in each long period_l,iThe D2D sync signal is repeatedly transmitted. As such, the IC terminal only transmits the D2D synchronization signal in one window per long period, which is called a sparse mode.

Step 350: if the IC terminal transmits the D2D synchronization signal in a sparse manner, the IC terminal is in the window w_l,iThe sending window of the second-stage synchronous terminal in the basic period detects the D2D synchronous signal from the next-stage synchronous terminal and in the basic period P_u,jMiddle delta_lCorresponding transmission window w_l,jAnd detecting the synchronous signals of the synchronous terminals at the same level.

The IC terminal transmits the D2D synchronization signal in a sparse manner for synchronization to the next-stage synchronization terminal. The secondary synchronization terminal can be used to perform self-synchronization if it detects the D2D synchronization signal sent by the IC terminal. Meanwhile, the OOC terminal that detects the D2D sync signal of the IC terminal transmits the D2D sync signal in a transmission window corresponding to the OOC terminal in response to the D2D sync signal transmitted by the IC terminal. Therefore, the IC terminal can determine whether the next-stage sync terminal receives the self-transmitted D2D sync signal by detecting the D2D sync signal in the transmission window of the next-stage sync terminal.

In this embodiment, the detection window of the upper synchronization terminal is the sending window of the lower synchronization terminal, and therefore, in this step, the window w is the window w_l,iCorresponding to the detection window, i.e. w_l,iAnd detecting the D2D synchronous signal of the next-stage synchronous terminal in the sending window of the second-stage synchronous terminal of the basic period for determining whether the next-stage synchronous terminal receives the synchronous signal sent by the IC terminal. J is more than or equal to 0 and less than or equal to M-1, and j is not equal to i.

The IC terminal detects the D2D synchronous signal of the next stage in the transmission window of the synchronous terminal of the next stage, and further detects the D2D synchronous signal of the next stage in the window w_l,iOther primary synchronous terminal transmitting window w_l,jThe D2D sync signal of the peer sync terminal is detected.

Step 360: the IC terminal detects the D2D synchronous signal according to the next synchronous terminal and w_l,jThe detection result of the synchronization signal of the peer synchronization terminal D2D adjusts the transmission method of the synchronization signal of D2D.

Preferably, the IC terminal may determine whether the received power of the synchronization signal is greater than TH_ddIt is determined whether the D2D sync signal of the next or peer sync terminal is successfully detected. For the next-stage sync terminal D2D sync signal detection, the received power may be the window w_l,iThe detection result of the power of the synchronization signal of the next-stage synchronization terminal in the corresponding detection window, or a period of time T_ddInner window w_l,iAnd averaging the power detection results of the synchronization signals of the next-stage synchronization terminal in the corresponding detection window. For the synchronization signal detection of the peer synchronization terminal D2D, the received power may be a window w_l,jThe result of detecting the power of the synchronization signal of a peer synchronization terminal in the corresponding transmission window, or a period of time T_ddInner window w_l,jAnd averaging the power detection results of the synchronization signals of the next-stage synchronization terminal in the corresponding detection window.

If the IC terminal detects the D2D sync signal from the next-stage sync terminal, indicating that there is a second-stage sync terminal synchronized with the D2D sync signal of the IC terminal, the terminal increases the transmission density of the D2D sync signal, and transmits the D2D sync signal in the transmission window of the first-stage sync terminal that is idle in a long period, i.e., in each long period P_lWindow of { w_lSending D2D synchronization signal, wherein{w_lIs composed of w_l,iAnd w_l,jThe transmission window of the synchronization signal of the peer synchronization terminal D2D is not detected. As such, the IC terminal may send the D2D synchronization signal in multiple windows per long period, which is referred to as a dense mode.

Step 370: if the IC terminal sends D2D synchronization signals in a dense manner, the IC terminal is in the same state as w_lAnd detecting the D2D synchronous signal from the next-stage synchronous terminal by the sending window of the corresponding second-stage synchronous terminal.

Similar to sparsely transmitting D2D synchronization signals, the IC terminals are at { w }_lDetecting a D2D synchronization signal from a next-stage synchronization terminal by a sending window of a corresponding secondary synchronization terminal, and determining whether a D2D synchronization signal received by the secondary synchronization terminal and sent by the IC terminal exists.

Step 380: if the IC terminal is in { w }_lIf the sending windows of all the secondary synchronous terminals corresponding to the IC terminal cannot detect the D2D synchronous signals from the next-stage synchronous terminal, the IC terminal sends D2D synchronous signals in a sparse mode, and the steps 350 to 380 are repeated; otherwise, continue with { w_lAnd detecting the D2D synchronous signal from the next-stage synchronous terminal by the sending window of the corresponding second-stage synchronous terminal.

Preferably, the IC terminal may determine whether the received power of the synchronization signal is less than TH_ddIt is determined whether the D2D sync signal of the next-stage sync terminal is successfully detected. The received power may be w_lThe detection result of the power of the synchronization signal of the next-stage synchronization terminal in the corresponding detection window, or a period of time T_ddInner { w_lAnd f, averaging the detection results of the power of the synchronization signal of the next-stage synchronization terminal in the corresponding detection window. Preferably, the position of the transmission window for transmitting the D2D synchronization signal in the IC terminal sparse mode is the same as that in step 340.

This embodiment ends up with the fact that if the IC terminal is at the cell edge of the cellular network and there are no other IC terminals around it sending D2D syncs in the same basic cycleThen the IC terminal will have a long period P_lThe D2D sync signal is continuously transmitted and the transmission density of the D2D sync signal is increased after the feedback from the next-stage sync terminal is detected. This approach, while increasing the power consumption of the IC terminals transmitting the D2D synchronization signals, is beneficial in reducing the complexity of the OOC terminals detecting the synchronization signals.

Example two:

in this embodiment, the target terminal may successfully detect the synchronization source of the cellular network cell, that is, the IC terminal. The terminal will detect a trigger sync signal from the OOC terminal according to a certain period and upon detecting the trigger sync signal, start transmitting a D2D sync signal. The IC terminal transmitting the D2D sync signal will detect the D2D sync signal from the next-stage sync terminal, and if the D2D sync signal of the next-stage sync terminal is not detected, the IC terminal will stop the transmission of the D2D sync signal. The specific implementation steps are shown in fig. 4, and include:

step 410: transmission/detection configuration C for acquiring D2D synchronous signal by IC terminal_IC。

Wherein C is_ICThe structure of the transmission/detection arrangement is the same as in the previous embodiment for the transmission/detection arrangement, in particular, the transmission/detection arrangement here may define only one period P_IC。C_ICMay be broadcast by a cellular network system message or defined directly by the standard.

Step 420: the IC terminal detects the trigger synchronization signal.

The trigger synchronization signal is a signal in a sequence form transmitted by the secondary synchronization terminal, and the carrier frequency of the trigger synchronization signal is the same as the detection frequency of the IC terminal, i.e., specified by the transmission/detection configuration. The specific design of the trigger synchronization signal is not limited in the present application, the specific format, transmission mode, and the like of the trigger synchronization signal can be set by the system, the D2D synchronization terminal is known, and the IC terminal detects the trigger synchronization signal according to the set format and transmission mode.

For example, whereas the D2D sync signal transmission/detection configuration indicates a detection window for a primary sync terminal (i.e., IC terminal), it may be set that the trigger has a trigger sync signal transmission within the corresponding detection window for the IC terminal, and accordingly, the IC terminal may be at Δ_cCorresponding detection window w_cDetecting a trigger synchronization signal, Δ_cTo be configured by C_ICDetermining the time offset, w, corresponding to the detection window of the primary synchronization terminal_c∈{w_1cWhere { w }_1cIs configuration C_ICAnd determining a set of primary synchronous terminal detection windows.

Step 430: if the IC terminal detects a trigger sync signal, the IC terminal is set to have a period P_ICD2D synchronization signal is sent and step 440 is executed, otherwise, step 420 is returned to.

When the IC terminal detects the trigger synchronization signal, it indicates that a secondary synchronization terminal exists in the coverage of the IC terminal synchronization signal and wants to perform synchronization processing by means of the D2D synchronization signal of the IC terminal, so in this step, after the trigger synchronization signal is detected, the IC terminal periodically transmits the D2D synchronization signal. Here period P_ICTo configure C_ICThe determined transmission/detection window period, in which case the transmission detection configuration defines only one transmission/detection window period, as follows.

Preferably, the IC terminal may determine whether the received power of the trigger sync signal is greater than a threshold TH_ctAnd judging whether the trigger synchronous signal is successfully detected. The received power may be a trigger synchronization signal power detection result, or a period of time T_bdAverage value of the detected trigger synchronization signal power. T is_bdMay be one period or multiple periods (multiple periods may not be consecutive), or other cellular networks or some D2D central control node configuration or standard defined value. TH_ctThe values may be configured by the cellular network or some D2D central control node (such as through cell broadcast messaging), or defined directly by the standard.

The IC terminal synchronizes the transmission window of the terminal at a level after a number of times from the satisfaction of the above condition (e.g., m and w after the satisfaction of the above condition)_cCorresponding transmission window) w_tUp-transmitting D2D synchronous signal, and transmitting window w in each period_tThe D2D sync signal is repeatedly transmitted. Where m may be equal to 1, or some random value, or some standard definition or cellular network cell broadcast or some D2D central control node configured value. The above-mentioned detection window w_cAnd a transmission window w_tIs represented by C_ICAnd (4) determining.

Step 440: if the IC terminal is in period P_ICThe D2D sync signal is transmitted, the IC terminal starts at the r-th period after the first transmission, at delta_cThe corresponding next-stage sync terminal transmission window detects the D2D sync signal from the next-stage sync terminal.

Similarly to the embodiment, after the IC terminal transmits the D2D synchronization signal, the D2D signal of the next-stage synchronization terminal is detected in the transmission window of the next-stage synchronization terminal to determine whether there is a D2D synchronization signal transmitted by the next-stage synchronization terminal to receive and utilize the IC terminal. Where r may be equal to 0 (indicating the period of the first transmission of the D2D synchronization signal), or some random value, or some standard definition or cellular network cell broadcast or some D2D central control node configuration.

Step 450: if the IC terminal fails to detect the D2D synchronization signal from the next-level synchronization terminal through the detection of the step 440, the IC terminal stops transmitting the D2D synchronization signal and repeats the steps 420-450; otherwise, the step 440 is returned to continue sending the D2D synchronization signal.

When the IC terminal fails to detect the D2D synchronization signal of the next-stage synchronization terminal, it is demonstrated that there is no D2D synchronization signal received and utilized by the secondary synchronization terminal in the IC terminal's synchronization signal coverage area. In this case, the D2D sync signal need not be transmitted again.

Preferably, the IC terminal is connected according to the detected next-stage synchronizing signalWhether received power is less than TH_ddIt is determined whether the D2D sync signal of the next-stage sync terminal is successfully detected. The received power may be Δ_cThe detection result of the power of the synchronization signal of the next-stage synchronization terminal in the corresponding detection window, or a period of time T_ddInner delta_cAnd averaging the power detection results of the synchronization signals of the next-stage synchronization terminal in the corresponding detection window.

To this end, the embodiment is completed, in which the IC terminal starts sending the D2D sync signal only after detecting the trigger sync signal, which is beneficial to reduce the power consumption of the IC terminal, but the complexity of detecting the sync signal by the OOC terminal is relatively high.

Example three:

in this embodiment, the target terminal cannot detect the synchronization source of the cellular network cell, that is, the target terminal is an OOC terminal. The OOC terminal will detect the D2D synchronization signal transmitted by the D2D terminal in a manner similar to cell search in a cellular network system, and for the D2D terminal that detects the D2D synchronization signal, if the terminal is a non-final terminal and is far away from the edge of the D2D synchronization signal coverage, or the terminal is a final terminal, the terminal will transmit the D2D synchronization signal in a certain idle window with a long period; if the terminal is a non-final terminal and is at the edge of the D2D synchronous signal, the terminal will send D2D synchronous signal in a certain idle window with long period, and start to detect the synchronous signal of the next-stage synchronous terminal in the next-stage synchronous terminal sending window corresponding to the idle window, the terminal will increase the sending density of D2D signal after detecting the synchronous signal of the next-stage synchronous terminal, and send D2D synchronous signal in all idle peer terminal sending windows within a long period. The specific implementation steps are shown in fig. 5, and include:

step 510: sending/detecting configuration C for OOC terminal to obtain D2D synchronous signal_lAnd C_u。

Wherein C is_lAnd C_uThe two configurations are respectively a long period transmission/detection configuration and a basic transmission/detection configuration, and partial parameters in the two configurations may be the same, or the two configurations may be completely the same. C_lAnd C_uMay be broadcast by the cellular network or some D2D central control node, or defined directly by the standard.

Step 520: OOC terminal supports each carrier cf according to configuration C_lThe D2D sync signal is detected.

Wherein CF belongs to CF, and CF is a set of carrier frequency bands supported by the UE. The OOC terminal may store carrier frequency information of surrounding cellular network cells, prioritize different cellular network cells according to access or measurement time, cell signal quality, and the like, and perform D2D synchronization signal detection on corresponding carriers according to the priority order. The OOC terminal detects the D2D synchronization signal on each carrier in the same way, and the following description will take one carrier cf as an example.

Step 530: if the OOC terminal is at time T_OOCWhen the D2D synchronization signal is detected on the internal carrier cf, the OOC terminal selects the window w in which the synchronization signal with the highest level is located from all the windows in which the synchronization signal is detected_k,iAccording to configuration C_lAt the window w_k,iCorresponding next-stage synchronous terminal sending window w_t,iDetecting the synchronization signal of the terminal of the same level D2D, and continuing to execute step 540; if the OOC terminal is at time T_OOCFailing to detect any D2D sync signal, step 531 is performed.

Wherein, when the OOC terminal is at time T_OOCWhen the D2D sync signal is internally detected, the D2D sync signal may be detected in one or more windows, and the OOC terminal needs to select the window w in which the sync signal with the highest synchronization level is located from all the windows in which the D2D sync signal is detected_k,i。

Window w_k,iIndicates the window where the highest level synchronization signal is selected, where k indicates the synchronization level when the window is used as the transmission window, and i indicates the synchronization level in the window w_k,iBasic period index of where, w_t,iIs a long period P_lInner window w_k,iIn the basic period P_u,iAnd the transmission window corresponding to the medium k +1 level synchronous terminal.

OOC terminal selects window w_k,iThen, the D2D sync signal detected in the window is used as the D2D sync signal transmitted by the upper sync terminal, and the sync process can be performed by using the sync signal. The upper synchronization terminal may be an IC terminal or an upper OOC terminal.

In addition, similarly to the embodiment, the previous synchronization terminal a, after transmitting the D2D synchronization signal, detects the D2D synchronization signal of the next synchronization terminal through the transmission window of the next synchronization terminal, thereby determining whether there is a D2D synchronization signal that the next synchronization terminal receives and transmits with the terminal a. In this case, as long as the next-stage synchronization terminal sends the D2D synchronization signal as feedback, all the next-stage synchronization terminals that receive the D2D synchronization signal of the previous-stage synchronization terminal are not required to send, and therefore, in this step, after detecting the D2D synchronization signal of the previous-stage synchronization terminal, the OOC terminal detects the D2D synchronization signal of the peer-stage synchronization terminal to determine whether the D2D synchronization signal needs to be sent as a response for the previous-stage synchronization terminal to send the D2D synchronization signal.

Preferably, the OOC terminal can be based on the window w_k,iWhether the detected power of the D2D synchronization signal is greater than TH_ddIt is determined whether the D2D sync signal was successfully detected. An OOC terminal located at the edge of the coverage area of the synchronization signal of the upper synchronization terminal is referred to as an NDB terminal, whereas an OOC terminal located at the edge of the coverage area of the synchronization signal far from the upper synchronization terminal is referred to as an FDB terminal. For example, if the OOC terminal is in window w_k,iThe detected D2D synchronous signal detection power is less than a certain threshold TH_bWherein TH is_dd≤TH_bIf the OOC terminal is located at the edge of the coverage range of the synchronization signal of the upper synchronization terminal, the OOC terminal is called an NDB terminal, otherwise, the OOC terminal is called an FDB terminal. The received power may beWindow w_k,iThe detected power of the primary D2D sync signal, or a period of time T_ddInner window w_k,iAverage value of the D2D sync signal power detection result. TH_dd≤TH_bBoth values may be configurable by the cellular network or some D2D central control node (e.g., via cell broadcast messaging), or defined directly by the standard.

Step 531: OOC terminal according to configuration C_lBasic period P in each long period_u,iiThe independent D2D synchronization signals are sent in a sparse manner.

When the OOC terminal is in the set time T_OOCAfter not detecting any D2D synchronization signal, the OOC terminal uses itself as a synchronization source to send an independent D2D synchronization signal for synchronization of other OOC terminals in the coverage of the OOC terminal synchronization signal.

Wherein, P_u,iiFrom configuration C_uIs defined as a long period P_lAnd one of M basic periods, wherein i is a specific value between 0 and M-1, and the method for determining the value of ii by the OOC terminal is not limited in the application. Preferably, the OOC terminal is in the basic period P_u,iiThe transmission window of the first-stage or second-stage synchronous terminal of (1) transmits the synchronous signal. P_lTo configure C_lThe decided transmission/detection window period. T is_OOCMay be defined directly by the standard or may be configured by the cellular network or some D2D central control node (e.g., via cell broadcast messaging).

Step 540: the OOC terminal determines the synchronization level of the OOC terminal and determines the synchronization level according to the window w_t,iAnd transmitting or detecting the corresponding D2D synchronization signal according to the corresponding configuration as a result of the detected synchronization signal of the terminal with the same level D2D.

The OOC terminal is at window w according to step 530_k,iDetects the D2D synchronization signal, extracts the level of the last synchronization terminal of the OOC terminal, and determines the synchronization level of the OOC terminal. Then, according to the synchronization level of the window w_t,iResult of detected synchronization signal of terminal of same level D2D, send orThe D2D sync signal is detected.

Specifically, the OOC terminal transmits the D2D synchronization signal in its corresponding transmission window, typically for one of two purposes: 1. transmitting a D2D synchronization signal, which is used for responding to the synchronization signal transmitted by the superior synchronization terminal; 2. the D2D sync signal is transmitted so that the next-stage sync terminal can perform synchronization using the D2D sync signal.

For the above two purposes, the D2D synchronization signal transmission can be performed under the following conditions:

1. if the OOC terminal is the final terminal and the terminal is in the window w_t,iThe D2D synchronization signal of the terminal at the same level is not successfully detected, which means that no other terminal at the same level responds to the synchronization signal of the terminal at the upper level, and therefore, the OOC terminal needs to send the D2D synchronization signal in a sparse manner, that is, the OOC terminal is in the window w of each long period_t,iThe D2D synchronization signal is sent in a sparse manner. Wherein, when the detected power of the synchronization signal from the peer D2D terminal is less than the threshold TH_ddIt can be considered that the D2D synchronization signal of the peer terminal is not successfully detected.

2. If the OOC terminal is an NDB terminal, it is indicated that the OOC terminal is located in an edge area covered by a synchronization signal of a superior synchronization terminal, and a D2D synchronization signal may need to be provided for a next-stage terminal; if the OOC terminal is not only the NDB terminal but also the non-final terminal, and the terminal is in the window w_t,iThe detected power of the synchronization signal from the peer D2D terminal is less than the threshold TH_bAlthough there is a peer D2D terminal sending a synchronization signal, the OOC terminal is located at the edge of the coverage area of the peer synchronization terminal sending the synchronization signal, and needs to provide a D2D synchronization signal for the next terminal, and then the OOC terminal is in a window w of each long period_t,iThe D2D synchronization signal is sent in a sparse manner.

3. If the OOC terminal is an FDB terminal, it indicates that the OOC terminal is far from the edge area covered by the synchronization signal of the upper synchronization terminal, so that it is not necessary to provide a D2D synchronization signal for other terminals within the coverage range of the synchronization signal; if the OOC terminal is not onlyFDB terminal, also non-final terminal, and the terminal is in window w_tIf the synchronization signal of the peer synchronization terminal is not detected, it means that no other peer synchronization terminal responds to the D2D synchronization signal of the previous synchronization terminal, and therefore, the OOC terminal needs to send the D2D synchronization signal in a sparse manner to respond to the D2D synchronization signal sent by the previous synchronization terminal, that is, the OOC terminal is in a window w of each long period_t,iThe D2D synchronization signal is sent in a sparse manner. Wherein, when the OOC terminal detects that the power of the synchronization signal from the peer D2D terminal is less than the threshold TH_ddMeanwhile, the OOC terminal is considered to have not detected the synchronization signal of the peer D2D terminal.

The received power may be a window w_t,iThe detected power of the primary D2D sync signal, or a period of time T_ddInner window w_t,iAverage value of the D2D sync signal power detection result.

If the OOC terminal cannot satisfy any one of the above-mentioned 3 conditions, the synchronization signal detection of the terminals synchronized at the same level in step 530 is repeatedly performed.

In the above D2D synchronization signal transmission performed by satisfying 3 conditions, the D2D synchronization signal transmission satisfying the 1 st and 3 rd conditions is a transmission performed in response to the upper synchronization terminal, and the D2D synchronization signal transmission satisfying the 2 nd condition is a transmission performed for providing a synchronization signal to the other synchronization terminal, so that it is necessary to further confirm whether the lower synchronization terminal receives the corresponding synchronization signal and to increase the transmission density when it receives the synchronization signal, for the D2D synchronization signal performed by the 2 nd condition, similarly to steps 350 to 380 in the first embodiment. The specific operation is as shown in steps 550-580 below.

Step 550: if the OOC terminal is an NDB terminal and a non-final terminal, and the D2D synchronization signal is sent in a sparse manner, the OOC terminal is in a window w_t,iThe corresponding detection window detects the D2D synchronous signal from the next stage synchronous terminal and in the basic period P_u,jMiddle delta_tCorresponding transmission window w_t,jDetecting synchronization signals of synchronous terminals of same level。

The corresponding relation between the sending window and the detecting window is configured by C_lAnd (4) determining. J is more than or equal to 0 and less than or equal to M-1, and j is not equal to i.

Step 560: if the OOC terminal is an NDB terminal and transmits the D2D synchronization signal in a sparse manner, the terminal detects the D2D synchronization signal of the next-stage synchronization terminal according to the detection result and w_t,jThe detection result of the synchronization signal of the peer synchronization terminal D2D adjusts the transmission method of the synchronization signal of D2D.

Preferably, the terminal may determine whether the received power of the synchronization signal is greater than TH_ddIt is determined whether the D2D sync signal of the next or peer sync terminal is successfully detected. For the next-stage sync terminal D2D sync signal detection, the received power may be the window w_t,iThe detection result of the power of the synchronization signal of the next-stage synchronization terminal in the corresponding detection window, or a period of time T_ddInner window w_t,iAnd averaging the power detection results of the synchronization signals of the next-stage synchronization terminal in the corresponding detection window. For the synchronization signal detection of the peer synchronization terminal D2D, the received power may be a window w_t,jThe result of detecting the power of the synchronization signal of a peer synchronization terminal in the corresponding transmission window, or a period of time T_ddInner window w_t,jAnd averaging the power detection results of the synchronization signals of the next-stage synchronization terminal in the corresponding detection window.

If the terminal detects the D2D synchronization signal from the next-stage synchronization terminal, the terminal will detect the D2D synchronization signal in each long period P_lWindow of { w_tSending D2D sync signals in a dense manner, where w_tIs composed of w_t,iAnd w_t,jThe transmission window of the synchronization signal of the peer synchronization terminal D2D is not detected.

Step 570: if an OOC terminal transmits D2D synchronization signals in a dense manner, the OOC terminal is in a state of being associated with w_tThe corresponding detection window detects the D2D synchronization signal from the next-stage synchronization terminal.

Step 580: if the OOC terminal transmits the D2D synchronization signal in a dense manner and fails to detect the D2D synchronization signal from the next-stage synchronization terminal, the OOC terminal transmits the D2D synchronization signal in a sparse manner and repeats steps 550 to 580.

Preferably, the IC terminal may determine whether the received power of the synchronization signal is greater than TH_ddIt is determined whether the D2D sync signal of the next-stage sync terminal is successfully detected. The received power may be w_tThe detection result of the power of the synchronization signal of the next-stage synchronization terminal in the corresponding detection window, or a period of time T_ddInner { w_tAnd f, averaging the detection results of the power of the synchronization signal of the next-stage synchronization terminal in the corresponding detection window. The position of the transmission window in which the OOC terminal transmits the D2D sync signal is the same as in step 540.

To this end, the embodiment is that the behavior of the OOC terminal corresponds to the behavior of the IC terminal in the first embodiment, and this way has the greatest advantage that the OOC terminal can reuse the search function of the current cellular network cell to search for the D2D synchronization signal, and can simplify the implementation of the D2D terminal.

Example four:

in this embodiment, the target terminal cannot detect the synchronization source of the cellular network cell, that is, the target terminal is an OOC terminal. The OOC terminal will detect the D2D sync signal transmitted by the D2D terminal in a manner similar to cell search in a cellular network system, and when it cannot detect any D2D sync signal, will initiate a trigger sync signal transmission procedure to trigger a potential IC terminal to transmit a D2D sync signal. The specific implementation steps are shown in fig. 6, and include:

step 600: OOC terminal obtaining D2D signal transmission/detection configuration C_OC。

Wherein C is_OCFor the transmission/detection configuration, the structure of the transmission/detection configuration is the same as that in the foregoing embodiment, including a long-period transmission/detection configuration and a basic-period transmission/detection configuration, C_OCIt can be defined directly by the standard or configured by some D2D central control node.

Step 610: OOC terminal supports each carrier cf according to configuration C_OCThe D2D sync signal is detected.

Step 611: if the OOC terminal is at time T_OOCWhen the D2D sync signal is detected, the OOC terminal performs transmission/detection of the D2D sync signal in steps 520 to 580 in the third embodiment of the transmission/detection scheme.

Step 620: if the OOC terminal is at time T_OOCAnd if no D2D synchronization signal is detected, the OOC terminal sends a trigger synchronization signal and a D2D synchronization signal on a carrier cf in a time division mode.

The trigger synchronous signal is a signal in a certain sequence form sent by a secondary synchronous terminal, and the carrier frequency of the trigger synchronous signal is the same as the detection frequency of the IC terminal and is determined by the sending/detecting configuration. Like the embodiment, the present application does not limit the specific design of the trigger synchronization signal.

After the trigger synchronization signal and the detection D2D synchronization signal are sent in a time division manner, the following steps are executed according to the detection result of the D2D synchronization signal:

step 621: if the OOC terminal is at time T_trIf the D2D synchronous signal is not detected, the OOC terminal follows the configuration C_OCBasic period P in each long period_u,iThe sending window of the primary or secondary synchronous terminalThe port transmits the independent D2D synchronization signal in a sparse manner and transmits/detects the D2D synchronization signal as per steps 350 through 380 in embodiment one.

Wherein, T_trMay be defined directly by the standard or may be configured by the cellular network or some D2D central control node (e.g., via cell broadcast messaging). When the processing is performed according to steps 350 to 380 in the first embodiment, the main body of the execution operation is replaced by the OOC terminal.

Step 630: if the OOC terminal is at time T_trWhen the D2D sync signal is detected, the OOC terminal should stop the trigger sync signal transmission and D2D sync signal detection in the time division manner, and perform the D2D sync signal transmission/detection according to steps 520 to 580 in the third embodiment of the transmission/detection scheme.

This embodiment is finished, and in this embodiment, the behavior of the OOC terminal corresponds to the behavior of the IC terminal in the second embodiment, which is beneficial to reducing the power loss of the IC terminal. However, the OOC terminal needs to transmit the trigger synchronization signal at a different carrier frequency to trigger the IC terminal, which increases the implementation complexity of the OOC terminal.

Example five:

in this embodiment, the target terminal may successfully detect the synchronization source of the cellular network cell, that is, the IC terminal. The terminal firstly judges whether the terminal is positioned at the edge of the cellular network cell according to the detected strength of the downlink reference signal of the cellular network cell, further detects the power of the D2D synchronous signal of the same-level synchronous terminal for the IC terminal positioned at the edge of the cellular network cell, and starts to send the D2D reference signal with a long period in the sending/detecting configuration if the detected power of the synchronous signal is less than a certain set threshold. The IC terminal may also start detecting the D2D synchronization signal of the peer synchronization terminal by receiving the indication from the base station, report the detection result to the base station, and determine whether to send the D2D synchronization signal according to the indication from the base station. The specific implementation steps are shown in fig. 7, and specifically include:

step 710: transmission/detection configuration C for acquiring D2D synchronous signal by IC terminal_lAnd C_u。

Wherein C is_lAnd C_uThe two configurations are respectively a long period transmission/detection configuration and a basic period transmission/detection configuration, and partial parameters in the two configurations may be the same, and the two configurations may also be completely the same. C_lAnd C_uMay be broadcast by the cellular network or some D2D central control node, or defined directly by the standard.

Step 720: the IC terminal detects the signal of the cellular network, judges whether the IC terminal is located at the edge of the cellular network cell, if so, executes step 730, otherwise, repeatedly executes the step; or judging whether a synchronous signal detection instruction of the base station is received, if so, executing step 730, otherwise, repeatedly executing the step.

Step 730: if it is determined in step 720 that the IC terminal is located at the edge of the cell or receives an indication that the eNB performs measurement, the IC terminal selects a window w in the primary synchronization terminal transmission window of each long period_l,iIn the window w_l,iThe synchronization signal of the synchronous terminal of the same level is detected.

Wherein w_l,iIs a period P_lInner fundamental periodP_u,iMiddle delta_lCorresponding transmission window, Δ_lThe time offset of the transmission window of the primary synchronous terminal in the basic transmission/detection period is shown, wherein i is a certain specific value between 0 and M-1 and represents the index of the basic period in the long period, and M is the number of the basic periods in the long period. The manner in which i is determined (i.e., window w)_l,iThe selection method of (1) may be a random selection or other selection methods, and the present application does not limit the method of determining the value of i by the IC terminal. P_lTo configure C_lThe decided transmission/detection window period, i.e., the long period.

Step 740: if the IC terminal is in the window w_l,iFails to detect the synchronization signal from the same-level synchronization terminal, the IC terminal is set to have the period P_lWindow w at each cycle_l,iSending a D2D synchronization signal, otherwise, repeatedly executing the step 730; or reporting the measurement result to the base station, determining whether to send D2D synchronous signal according to the base station indication, if so, sending the signal in the period P_lWindow w at each cycle_l,iThe D2D sync signal is sent, otherwise step 730 is repeated.

Preferably, the IC terminal may determine whether the received power of the synchronization signal is less than TH_cdAnd judging whether the synchronous signals from the synchronous terminals at the same level are successfully detected. The received power may be Δ_lCorresponding to the detection result of the power of the synchronizing signal of a synchronous terminal of the same level in the sending window, or a period of time T_cdInner delta_lThe average value of the detection results of the power of the synchronization signals of the same synchronization terminal in the corresponding sending window. T is_cdMay be one long period or multiple long periods, or may be otherwise defined by the cellular networkA value configured by a network or some D2D central control node, or a value defined directly by a standard. TH_cdMay be configured by the cellular network or some D2D central control node (e.g., via cell broadcast messaging), or may be defined directly by the standard.

Or, the IC terminal may directly report the detection result of the synchronization signal to the base station in step 730 without determining the receiving power of the synchronization signal by itself, and determine whether to send the D2D synchronization signal according to an instruction issued by the base station.

To this end, the embodiment ends, in which if an IC terminal is at the edge of a cell of a cellular network and no other IC terminal around transmits a D2D synchronization signal in the same basic period, the IC terminal will always transmit a long period P_lThe D2D synchronization signal is continuously transmitted. This approach, while increasing the power consumption of the IC terminals transmitting the D2D synchronization signals, is beneficial in reducing the complexity of the OOC terminals detecting the synchronization signals.

Example six:

in this embodiment, the target terminal cannot detect the synchronization source of the cellular network cell, that is, the target terminal is an OOC terminal. The OOC terminal will detect the D2D synchronization signal transmitted by the D2D terminal in a manner similar to cell search in a cellular network system, and for the D2D terminal that detected the D2D synchronization signal, after obtaining synchronization timing using the D2D synchronization signal, if the terminal is a non-final terminal and is at the edge of the D2D synchronization signal, the terminal will transmit the D2D synchronization signal in a certain idle window with a long period. The specific implementation steps are shown in fig. 8 and include:

step 810: sending/detecting configuration C for OOC terminal to obtain D2D synchronous signal_lAnd C_u。

Step 820: OOC terminal supports each carrier cf according to configuration C_lThe D2D sync signal is detected.

Step 830: if the OOC terminal is at time T_OOCDetecting a D2D synchronization signal on the intrinsic carrier cf, and continuing to execute step 840; if the OOC terminal is at time T_OOCIf no D2D sync signal is detected, step 831 is performed.

Window w_k,iIndicates the window where the highest level synchronization signal is selected, where k indicates the synchronization level when the window is used as the transmission window, and i indicates the synchronization level in the window w_k,iThe basic period index of the position.

The OOC terminal is at window w according to step 830_k,iThe detected D2D synchronization signal is detected, and the level of the synchronization terminal at the upper level of the OOC terminal is extracted, so that the synchronization level of the OOC terminal is determined.

Preferably, the OOC terminal can be based on the window w_k,iWhether the detected power of the D2D synchronization signal is greater than TH_ddIt is determined whether the D2D sync signal was successfully detected. An OOC terminal located at the edge of the coverage area of the synchronization signal of the upper synchronization terminal is referred to as an NDB terminal, whereas an OOC terminal located at the edge of the coverage area of the synchronization signal far from the upper synchronization terminal is referred to as an FDB terminal. For example, if the OOC terminal is in window w_k,iThe detected D2D synchronous signal detection power is less than a certain threshold TH_bWherein TH is_dd≤TH_bIf the OOC terminal is located at the edge of the coverage range of the synchronization signal of the upper synchronization terminal, the OOC terminal is called an NDB terminal, otherwise, the OOC terminal is called an FDB terminal. The received power may be a window w_k,iThe detected power of the primary D2D sync signal, or a period of time T_ddInner window w_k,iAverage value of the D2D sync signal power detection result. TH_dd≤TH_bBoth values may be configurable by the cellular network or some D2D central control node (e.g., via cell broadcast messaging), or defined directly by the standard.

Step 831: OOC terminal according to configuration C_lBasic period P in each long period_u,jThe independent D2D synchronization signals are sent in a sparse manner.

When the OOC terminal is in the set time T_OOCAfter not detecting any D2D synchronous signal, the OOC terminal takes itself as a synchronous source to sendIndependent D2D synchronization signals are sent for synchronization of other OOC terminals within the OOC terminal synchronization signal coverage.

Wherein, P_u,jFrom configuration C_uIs defined as a long period P_lAnd in one of M basic periods, j is a specific value between 0 and M-1, and the method for determining the value of j by the OOC terminal is not limited in the application. Preferably, the OOC terminal is in the basic period P_u,jThe transmission window of the primary or secondary synchronization terminal of (1) transmits the synchronization signal. P_lTo configure C_lThe decided transmission/detection window period. T is_OOCMay be defined directly by the standard or may be configured by the cellular network or some D2D central control node (e.g., via cell broadcast messaging).

Step 840: and the OOC terminal detects the corresponding D2D synchronous signal according to the corresponding configuration according to the synchronous level and the state of the OOC terminal.

Specifically, the OOC terminal transmits the D2D synchronization signal in its corresponding transmission window in order that the next-stage synchronization terminal can perform synchronization using the D2D synchronization signal.

For the above purpose, if the OOC terminal is an NDB terminal and is a non-final terminal, it indicates that the OOC terminal is located in an edge area covered by a synchronization signal of an upper synchronization terminal, and it may be necessary to provide a D2D synchronization signal for a next terminal. The OOC terminal selects a window w in each long-period transmission window corresponding to its synchronization level_l,iiIn the window w_l,iiThe synchronization signal of the synchronous terminal of the same level is detected.

Wherein w_l,iiIs a period P_lInner fundamental period P_u,iiMiddle delta_lCorresponding transmission window, Δ_lIs the time offset of the sending window corresponding to the synchronization level of the OOC terminal in the basic sending/detecting period, wherein ii is a certain value between 0 and M-1, which represents the index of the basic period in the long period, and M is the number of the basic periods included in the long period. The determination of the specific ii (i.e. window w)_l,iiMay be a random selection)Or other alternatives, the present application is not limited to the manner in which the OOC terminal determines the value of ii. P_lTo configure C_lThe decided transmission/detection window period, i.e., the long period.

If the OOC terminal is an FDB terminal and is a non-final terminal, the terminal continuously detects its own state and performs the operation of the NDB non-final terminal in this step when it is converted into an NDB terminal.

If the OOC terminal is the final terminal, the application does not limit the operation after the OOC terminal detects the D2D synchronization signal.

Step 850: if the OOC terminal is a non-final NDB terminal, and is at w_l,iiFailing to detect the synchronization signal from the peer D2D terminal, the OOC terminal is in the window w of each long period_l,iiThe D2D synchronization signal is sent in a sparse manner.

Can be in the window w_l,iiThe detected receiving power of the synchronous signal is less than threshold TH_bIt is determined that the synchronization signal from the peer D2D terminal was not detected. The received power may be a window w_l,iiThe detected power of the primary D2D sync signal, or a period of time T_ddInner window w_t,iAverage value of the D2D sync signal power detection result.

If the OOC terminal cannot satisfy the above condition, the synchronization signal detection of the terminal synchronized at the same level in step 540 is repeatedly performed.

Example seven:

in this embodiment, the target terminal may successfully detect the synchronization source of the cellular network cell, that is, the IC terminal. The terminal firstly judges whether the terminal is positioned at the edge of a cellular network cell according to the detected strength of the downlink reference signal of the cellular network cell, further detects the power of a D2D synchronous signal of a synchronous terminal at the same level for an IC terminal positioned at the edge of the cellular network cell, and starts to send the D2D reference signal at a specific sending/detecting window by a long period in sending/detecting configuration if the detected power of the synchronous signal is less than a certain set threshold. Thereafter, the IC terminal continues to detect the D2D synchronization signal in other transmission/detection windows outside the above-described transmission/detection window, and stops transmission of the synchronization signal when the D2D synchronization signal is detected or is far from the cell edge. The specific implementation steps are shown in fig. 9 and include:

step 910: transmission/detection configuration C for acquiring D2D synchronous signal by IC terminal_lAnd C_u。

Wherein C is_lAnd C_uThe two configurations are respectively a long period transmission/detection configuration and a basic period transmission/detection configuration, and partial parameters in the two configurations may be the same, and the two configurations may also be completely the same. C_lAnd C_uMay be broadcast by the cellular network or some D2D central control node, or defined directly by the standard. In this embodiment, C_uCorresponding period length of P_u，C_lCorresponding period P_l＝N×P_u. Where 1 ≦ N, configured by the base station or defined by the standard.

The position of the transmission/detection window is determined by the offset delta and the basic period P_uIt is uniquely determined that subframe n (0 ≦ n < 10240) is the transmission/detection window if the following conditions are met:

mod(n-Δ，P_u)＝0；

example C_lAnd C_uThe corresponding delta values in (a) are equal, i.e. the set of transmission/detection windows belonging to the long period is a subset of the set of transmission/detection windows belonging to the short period.

Step 920: the IC terminal detects the signal of the cellular network, judges whether the IC terminal is located at the edge of the cellular network cell, if yes, step 930 is executed, otherwise, the step is executed repeatedly; or determining whether a D2D synchronization signal detection indication of the base station is received, if yes, performing step 930, otherwise, repeating the step.

Step 930: if it is determined in step 920 that the IC terminal is located at the edge of the cell or an indication of D2D synchronization signal detection by the eNB is received, the IC terminal detects the synchronization signal of the peer synchronization terminal in the transmission/detection window determined in step 910.

Step 940: if the IC terminal fails to detect a synchronization signal from a peer synchronization terminal in the transmission/detection window, the IC terminal performs a synchronization operation with a period P_lSending a D2D synchronization signal, otherwise, repeatedly executing the process of detecting the synchronization signal in the step 930; or reporting the measurement result to the base station, determining whether to send D2D synchronous signal according to the base station indication, if so, sending the signal in the period P_lThe D2D sync signal is sent, otherwise the process of detecting the sync signal in step 930 is repeated.

Here, when the IC terminal fails to detect the synchronization signal from the peer synchronization terminal in the transmission/detection window, it is explained that no other IC terminal is transmitting the D2D synchronization signal within the coverage of the IC terminal synchronization signal, and the IC terminal is in the period P_lSending D2D sync signals for use in ICThe secondary synchronization terminals within the coverage of the terminal synchronization signal are synchronized by the D2D synchronization signal.

Preferably, the IC terminal may determine whether the received power of the synchronization signal is less than TH_cdAnd judging whether the synchronous signals from the synchronous terminals at the same level are successfully detected. The received power may be a power detection result of a synchronization signal of a peer synchronization terminal in the transmission/detection window, or a period of time T_cdAverage value of the synchronous signal power detection results of the synchronous terminals in the same level in the sending/detecting window. T is_cdIt may be a long period or a plurality of long periods, or other values configured by the cellular network or some D2D central control node, or values defined directly by the standard. TH_cdMay be configured by the cellular network or some D2D central control node (e.g., via cell broadcast messaging), or may be defined directly by the standard.

Or, the IC terminal may directly report the detection result of the synchronization signal to the base station in step 930 without determining the receiving power of the synchronization signal by itself, and determine whether to send the D2D synchronization signal according to an instruction issued by the base station.

The IC terminal may determine the transmission window w of the mth long period after the transmission of the D2D sync signal_lTransmitting D2D synchronous signal, and transmitting window w in each long period_lThe D2D sync signal is repeatedly transmitted. As such, the IC terminal only transmits the D2D synchronization signal in one window per long period, which is called a sparse mode. Wherein a transmission window w_lThe sub-frame number n corresponding to the sub-frame in which it is located_lSatisfies the following conditions:

mod(n_l-Δ，P_l) 0; or mod (n)_l-Δ-N_ID×P_u，P_l)＝0；

Wherein N is_IDMod (RNTI, N), which is the ID of the IC terminal in the cell.

Step 950: if the IC terminal is in the transmission/detection window w_lWith a period of P_lTransmitting the D2D synchronization signal, the terminal is in the transmission/detection windowAnd detecting the synchronous signal of the peer synchronous terminal, and stopping the transmission of the D2D synchronous signal after detecting the synchronous signal of the peer synchronous terminal. If the synchronization signal of the peer sync terminal is not detected, steps 940 and 950 are continuously performed.

Wherein,sub-frame number ń corresponding to the sub-frame in which it is located_lSatisfies the following conditions:

mod(ń_l-Δ，P_u) 0 and ń_l≠n_l；

To this end, the embodiment ends, in which if an IC terminal is at the edge of a cell of a cellular network and no other IC terminal around transmits a D2D synchronization signal in the same basic period, the IC terminal will transmit a long period P_lThe D2D sync signal is transmitted, and the transmission of the D2D sync signal is stopped after a terminal transmitting the D2D sync signal in a short period appears around. When the cell edge has no terminal transmitting the synchronization signal in a short period, this way can provide timing for other D2D terminals outside the cell coverage, and avoid the interference caused to the terminals in the cell when the D2D terminal performs D2D communication in an asynchronous (relative to the cell) manner.

The foregoing is a specific implementation of the method for implementing D2D terminal synchronization in this application. The application also provides a D2D terminal device, which can be used for implementing the synchronization method. Fig. 10 is a basic configuration diagram of a D2D terminal device in the present application. As shown in fig. 10, the terminal device includes: the system comprises a cellular network synchronization source detection unit, a configuration receiving unit, an IC terminal synchronization unit and an OOC terminal synchronization unit.

The device comprises a cellular network synchronization source detection unit, an IC terminal synchronization unit and an OOC terminal synchronization unit, wherein the cellular network synchronization source detection unit is used for detecting a synchronization source of a cellular network, when the synchronization source is detected, the IC terminal synchronization unit is indicated to carry out synchronization processing, and when the synchronization source is not detected, the OOC terminal synchronization unit is indicated to carry out synchronization processing.

And the configuration receiving unit is used for receiving the transmission/detection configuration of the D2D synchronous signal. The sending/detecting configuration includes sending/detecting period, sending window and detecting window corresponding to each stage of synchronous terminal.

And the IC terminal synchronization unit is used for transmitting/detecting the D2D synchronization signal according to the transmission/detection configuration after receiving the notification of the cellular network synchronization source detection unit. The processing method in the first embodiment and the second embodiment may be specifically adopted.

And the OOC terminal synchronization unit is used for transmitting/detecting the D2D synchronization signal according to the transmission/detection configuration after receiving the notification of the cellular network synchronization source detection unit. The processing method in the third embodiment and the fourth embodiment can be specifically adopted.

It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.

In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for supporting D2D terminals to realize synchronization is characterized by comprising the following steps:

2. The method of claim 1, wherein the IC terminal transmitting/detecting the D2D synchronization signal comprises:

a1, when the IC terminal is at the edge of the cellular network cell or receives the D2D synchronous signal detection indication of the base station, the IC terminal selects a window w in the sending window of each long period of the same synchronous terminal according to the sending/detection configuration of the D2D synchronous signal_l,iIn the window w_l,iDetecting a D2D synchronization signal of a peer synchronization terminal; when the IC terminal determines that the D2D synchronization signal of the peer synchronization terminal is not detected, or when the IC terminal reports the D2D synchronization signal detection result of the peer synchronization terminal to the base station and receives a D2D synchronization signal transmission instruction of the base station, execute step a 2; the period of the sending/detecting configuration is divided into a long period and a basic period, the long period comprises M basic periods, M is a positive integer, i is a long period P_lI is the identity of the long period in the transmission/detection configuration;

a2 in the window w_l,iD2D synchronization signal is sent for the secondary synchronization terminal to synchronize.

3. The method of claim 1, wherein the IC terminal transmitting/detecting the D2D synchronization signal comprises:

a1, when the IC terminal is located at the edge of the cellular network cell or receives the D2D synchronous signal detection indication of the base station, the IC terminal detects the D2D synchronous signal of the same synchronous terminal at each sub-frame n of the long period according to the transmission/detection configuration of the D2D synchronous signal; when the IC terminal determines that the D2D synchronization signal of the peer synchronization terminal is not detected, or when the IC terminal reports the D2D synchronization signal detection result of the peer synchronization terminal to the base station and receives a D2D synchronization signal transmission instruction of the base station, execute step a 2; wherein mod (n- Δ, P)_u) The period of the transmission/detection configuration is divided into long periods P, 0_lAnd a basic period P_uLong period of timePeriod P_lComprising N fundamental periods P_uL is the identification of the long period in the sending/detecting configuration, and delta is the deviation of a preset long period detecting window;

4. The method of claim 3, wherein after performing step a2, the method further comprises: the IC terminal is in the sending/detecting windowDetecting a synchronous signal of a peer synchronous terminal, and stopping the sending of the D2D synchronous signal after detecting the synchronous signal of the peer synchronous terminal; when the synchronization signal of the peer synchronization terminal is not detected, returning to step a 2;

5. The method of claim 2 or 3, wherein determining the IC terminal is located at the cell edge of the cellular network comprises:

6. The method of claim 2, wherein after step a2, the method further comprises:

7. The method of claim 6, wherein the increasing the transmission density of the D2D synchronization signals comprises: the IC terminal is arranged in the window w_l,iAnd the sending window w of the D2D synchronous signal of the other peer synchronous terminal is not detected_l,jSending the D2D synchronization signal; wherein j is an index of the transmission window of the D2D synchronization signal of the other peer synchronization terminal in the long period l.

8. The method as claimed in claim 6 or 7, wherein after increasing the transmission density of the D2D sync signals, the IC terminal detects the D2D sync signal of the next-stage sync terminal in the transmission window of the second-stage sync terminal in the basic period in which the window for transmitting the D2D sync signal is located, and returns to step a2 when the D2D sync signal of the next-stage sync terminal is not detected in the transmission windows of all the corresponding second-stage sync terminals.

9. The method of claim 1, wherein the IC terminal sending a D2D synchronization signal comprises: the IC terminal detects the trigger synchronous signal sent by the secondary synchronous terminal, and then the IC terminal sends the trigger synchronous signal with the period P indicated in the sending/detecting configuration_ICFor the period, the D2D synchronization signal is transmitted in the transmission window of the primary synchronization terminal.

10. The method of claim 9, wherein the IC terminal detects the trigger synchronization signal at each detection window of a primary synchronization terminal in accordance with the transmit/detect configuration.

11. The method of claim 9, wherein after the D2D synchronization signal is transmitted in the transmission window of the primary synchronization terminal, the method further comprises: and the IC terminal detects the D2D synchronous signal of the next-level synchronous terminal in a detection window corresponding to the sending window of the first-level synchronous terminal, and stops sending the D2D synchronous signal after the D2D synchronous signal of the next-level synchronous terminal cannot be detected.

12. The method of claim 1, wherein the OOC terminal sending/detecting D2D synchronization signals comprises:

13. The method of claim 12, wherein for any carrier when the OOC terminal is at a set time T_OOCAnd after the D2D synchronous signals are detected on any carrier, the OOC terminals are synchronized according to the D2D synchronous signal with the highest level in the detected D2D synchronous signals.

14. The method of claim 13, wherein after detecting the D2D synchronization signal on any of the carriers, the method further comprises:

b1, the OOC terminal selects the window w of the highest level synchronizing signal in the detected D2D synchronizing signals_k,iAccording to the window w_k,iThe level information k in the detected D2D synchronization signal determines that the synchronization level is k +1 and the synchronization level is k +1Window w_k,iThe OOC terminal in the basic period has the same level of sending window w_t,iDetecting a D2D synchronization signal of a terminal of the same level as the OOC terminal; the period of the sending/detecting configuration is divided into a long period and a basic period, the long period comprises M basic periods, M is a positive integer, and i is an index of the basic period in which the window of the highest-level synchronization signal is detected;

15. The method of claim 14, wherein after step b3, the method further comprises:

16. The method of claim 15, whichThe method for improving the transmission density of the D2D synchronous signals is characterized by comprising the following steps: the OOC terminal is at the window w_t,iAnd the sending window w of the D2D synchronous signal of the other peer synchronous terminal is not detected_t,jSending the D2D synchronization signal; wherein j is an index of the transmission window of the D2D synchronization signal of the other peer synchronization terminal in the long period l.

17. The method of claim 15 or 16, wherein after increasing the transmission density of the D2D sync signals, the OOC terminal detects the D2D sync signal of the next-stage sync terminal in the transmission window of the next-stage sync terminal in the basic period of the window where the D2D sync signal is transmitted, and returns to step b3 when the D2D sync signal of the next-stage sync terminal is not detected by the transmission windows of all the corresponding next-stage sync terminals.

18. The method of claim 13, wherein after detecting the D2D synchronization signal on any of the carriers, the method further comprises:

c2 if in the window w_l,iiIf no D2D synchronization signal of the terminal of the same level as the OOC terminal is detected, the OOC terminal is in the window w of each long period l_l,iiA D2D synchronization signal is sent.

19. The method of claim 12, wherein for any carrier, when the OOC terminal does not detect any D2D sync signal on any carrier within a set time, the OOC terminal selects a window w in the transmission window of each long period l primary or secondary sync terminal according to the D2D sync signal transmission/detection configuration_l,iIn the window w with a period of l_l,iSending an independent D2D synchronization signal for the next-stage synchronization terminal to synchronize; the period of the sending/detecting configuration is divided into a long period and a basic period, wherein the long period comprises M basic periods, M is a positive integer, and i is an index of the basic period in the long period.

20. The method of claim 12, wherein for any carrier when the OOC terminal is at a set time T_OOCWhen no D2D synchronous signal is detected on any carrier, the OOC terminal sends a trigger synchronous signal and a detection D2D synchronous signal on any carrier in a time division mode, and if the set time T is after the trigger synchronous signal is sent_trD2D synchronous signals are not detected, and the step D is executed;

21. The method of claim 20, wherein after step d, the method further comprises:

the OOC terminal transmits/detects the configuration according to the D2D synchronous signal in the window w_l,iDetecting the D2D synchronous signal of the next-stage synchronous terminal in the sending window of the second-stage or third-stage synchronous terminal of the basic period, and dividing the window w_l,iThe sending windows of other peer synchronizing terminals detect the D2D synchronizing signal of the peer synchronizing terminal; when the D2D synchronous signal of the next-stage synchronous terminal is detected, the transmission density of the D2D synchronous signal is increased.

22. The method of claim 21, wherein increasing the transmission density of the D2D synchronization signals comprises: the OOC terminal is at the window w_l,iAnd the sending window w of the D2D synchronous signal of the other peer synchronous terminal is not detected_l,jSending the D2D synchronization signal; wherein j is the long period P of the sending window of the D2D synchronization signal of the other peer synchronization terminal not detected_lThe index in (1).

23. The method of claim 21 or 22, wherein after increasing the transmission density of the D2D sync signals, the OOC terminal detects the D2D sync signal of the next-stage sync terminal in the transmission window of the secondary or tertiary sync terminal in the basic period of the window for transmitting the D2D sync signals, and returns to step D when the D2D sync signal of the next-stage sync terminal is not detected in the transmission windows of all corresponding secondary or tertiary sync terminals.

24. The method according to claim 14, 15 or 16, wherein for any carrier when the OOC terminal is at a set time T_OOCWhen any D2D synchronous signal is not detected on any carrier, the OOC terminal sends a trigger synchronous signal and a detection D2D synchronous signal on any carrier in a time division mode, and if the trigger synchronous signal and the detection D2D synchronous signal are sentSet time T after sending the trigger synchronous signal_trAnd D2D synchronous signals are detected, the OOC terminal stops sending the trigger synchronous signals and the detection D2D synchronous signals on any carrier in a time division mode, and steps b 1-b 3 are executed.

25. A D2D terminal device, characterized in that the device comprises: the system comprises a cellular network synchronization source detection unit, a configuration receiving unit, an IC terminal synchronization unit and an OOC terminal synchronization unit;