Method and device for sending and receiving time-frequency synchronization of V2X terminals

Abstract

The present application discloses a method and device for sending and receiving time-frequency synchronization of a V2X terminal, including: when the synchronization signal to be sent is the same as the synchronization signal of an existing D2D terminal, reusing the time-frequency resources of the D2D terminal configured in the cell to send the synchronization signal; when the synchronization signal to be sent is different from the synchronization signal of the existing D2D terminal, using the reconfigured time-frequency resources to send the synchronization signal; in the synchronization signal sent by the V2X terminal, the corresponding synchronization source type is indicated by the value of the SLSS sequence index and / or the PSBCH specified field. For the V2X terminal receiving the synchronization signal, the type of the synchronization source is determined according to the received synchronization signal, and the reference synchronization source is further selected according to the detected synchronization source according to the established priority. According to the present invention, it is possible to support time-frequency synchronization between terminals in a V2X communication environment with a relatively small modification cost to the prior art.

Description

[0001] This application is a divisional application of the invention patent application with the application date of December 1, 2016, application number 201611090382.7, and invention name "V2X terminal time and frequency synchronization sending and receiving processing method and device". Technical Field

[0002] The present application relates to the field of mobile communication technology, and in particular, to a method and device for sending and receiving time-frequency synchronized transmission between V2X terminals in a vehicle to vehicle / pedestrian / infrastructure / network communication system. Background Art

[0003] At present, device-to-device (D2D) communication technology has been accepted by the Third Generation Partnership Project (3GPP) standard due to its huge potential value in the fields of public safety and general civilian communications, and some functions have been standardized in 3GPP Rel-12, including mutual discovery of D2D terminals in cell coverage scenarios and broadcast communication between D2D terminals in cell coverage (IC, In Coverage) scenarios, cell partial coverage (PC, Partial Coverage) scenarios and no cell coverage (OC, Out of Coverage) scenarios.

[0004] According to the current 3GPP conclusion, for user terminals (UE) participating in D2D mutual discovery, in order to achieve subframe-level synchronization between D2D terminals in different cells, the UE sending the D2D discovery signal needs to send a sidelink synchronization signal (SLSS, Sidelink Synchronization Signal) on the synchronization resources configured in the cell when it receives the signaling indication from the base station (eNB) or when it is at the edge of the cell. The SLSS includes a primary sidelink synchronization signal (PSSS, Primary Sidelink Synchronization Signal) and a secondary sidelink synchronization signal (SSSS, Secondary Sidelink Synchronization Signal). The PSSS uses a ZC (Zadoff-Chu) sequence with a root sequence index of 26 and 37 and a length of 62. The SSSS consists of two m-sequences with a length of 31. The above two m-sequences are uniquely determined by the index corresponding to the SSSS (hereinafter referred to as the SSSS index). For UEs participating in D2D broadcast communications, in order to achieve subframe-level synchronization between the UEs sending broadcast signals and the UEs receiving broadcast signals, the UE (ICUE) sending broadcast communication signals and being within the cell coverage needs to send SLSS on the synchronization resources configured in the cell when it receives the signaling indication from the eNB or when it is located at the edge of the cell; in addition, in order for the UEs without cell coverage (OCUE) to obtain the system frame, system bandwidth, time division duplex (TDD) configuration and other information of the cell, the ICUE sending broadcast communication signals needs to send a D2D broadcast channel (PSBCH) to forward the above information to the OCUE.

[0005] The period of D2D synchronization resources is 40ms, centered on the cell carrier frequency, occupying 6 physical resource blocks (PRBs) and a length of one subframe. Among them, SLSS occupies 4 frequency division multiple access SC-FDMA symbols in the above subframe, and the remaining symbols, except for the last single carrier frequency division multiple access (SC-FDMA) symbol of the subframe used for protection interval, will be used for PSBCH transmission. SLSS from D2D mutual discovery UE and D2D broadcast communication UE will share the above synchronization resources for SLSS, that is, on some SLSS synchronization resources, if both the discovery UE and the communication UE meet the conditions for sending SLSS, the SLSS from the above two UEs will be accumulated on the same time-frequency resources.

[0006] OCUE participating in D2D broadcast communication needs to select a D2D synchronization source according to the strength of the D2D synchronization signal from the D2D synchronization source. Because there may be SLSS from the discovery UE on the SLSS resource, the above OCUE will measure the strength of the synchronization signal based on the demodulation reference signal of the PSBCH.

[0007] Because the D2D communication standardized in 3GPP Rel-12 / 13 is mainly aimed at low-speed terminals and services with low latency sensitivity and reception reliability requirements, the implemented D2D functions are far from meeting user needs. In the subsequent 3GPP versions, further enhancing the D2D functional framework has become a broad consensus among various communication terminal manufacturers and communication network equipment manufacturers. Among them, based on the current D2D broadcast communication mechanism, supporting direct low-latency and high-reliability communication between high-speed devices, between high-speed devices and low-speed devices, and between high-speed devices and stationary devices, such as vehicle to selected devices (V2X, Vehicle to Vehicle / Pedestrian / Infrastructure / Network), is one of the functions that need to be standardized first.

[0008] Currently, 3GPP has defined the V2X services that need to be supported. These services are all based on the geographical location of the UE (referred to as V2X terminal in this article, also referred to as VUE for short) that supports V2X communication services. In other words, VUE has the ability to receive Global Navigation Satellite System (GNSS) signals (including equivalent GNSS signals). Therefore, VUE can not only achieve time and frequency synchronization through eNB, but also through the crystal oscillator trained by GNSS signals. In addition, in actual traffic environments, there are blind spots of cellular networks and GNSS coverage, such as tunnels and underground parking lots. In order to support V2X communication services in such environments, VUE needs to forward synchronization signals based on eNB or GNSS. Therefore, in the V2X communication environment, there is currently no mature implementation solution for how to achieve the sending and receiving of V2X terminal time and frequency synchronization. Summary of the invention

[0009] The purpose of this application is to at least solve the above-mentioned technical defects, and in particular to provide a sending and receiving processing method and corresponding device for time-frequency synchronization of a V2X terminal.

[0010] The technical solution of the present invention is achieved in this way:

[0011] A transmission processing method supporting time-frequency synchronization of a vehicle and a selected device communication service V2X terminal, comprising:

[0012] When the synchronization signal to be sent by the V2X terminal is the same as the synchronization signal of the existing device-to-device D2D terminal, reusing the time-frequency resources configured in the cell for sending the synchronization signal of the D2D terminal to send the synchronization signal;

[0013] When the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal, the synchronization signal is sent using the reconfigured time-frequency resources;

[0014] In the synchronization signal sent by the V2X terminal, the corresponding synchronization source type is indicated by the bypass synchronization signal SLSS sequence index and / or the value of the D2D broadcast channel PSBCH designated field.

[0015] In a preferred embodiment, the V2X terminal is a controlled V2X terminal;

[0016] In the case where the synchronization signal to be sent by the V2X terminal is the same as the synchronization signal of the existing D2D terminal, the synchronization signal is sent by reusing the time-frequency resources configured in the cell for sending the synchronization signal of the D2D terminal, wherein the timing of sending the synchronization signal is:

[0017] When the value of the reference signal received power RSRP received by the V2X terminal relative to the base station eNB is lower than the syncTxThreshIC, or when the V2X terminal receives an SLSS sending indication from the eNB; wherein the syncTxThreshIC is a value determined by the commSyncConfig message containing the txParameters parameter in the commSyncConfigList message sequence in the system information block SIB18 system message of the eNB.

[0018] In a preferred embodiment, the V2X terminal is a controlled V2X terminal;

[0019] When the synchronization signal to be sent by the V2X terminal is the same as the synchronization signal of the existing D2D terminal: the root sequence index of the primary bypass synchronization signal PSSS in the SLSS sequence index in the synchronization signal is 26; the index value of the auxiliary bypass synchronization signal SSSS in the SLSS sequence index in the synchronization signal and the value of the reserved bit in PSBCH are determined by the commSyncConfig message containing the txParameters parameter in the commSyncConfigList message sequence of the SIB18 system message of the eNB.

[0020] In a preferred embodiment, the V2X terminal is an autonomous V2X terminal;

[0021] In the case where the synchronization signal to be sent by the V2X terminal is the same as the synchronization signal of the existing D2D terminal, the synchronization signal is sent by reusing the time-frequency resources configured in the cell for sending the synchronization signal of the D2D terminal, wherein the timing of sending the synchronization signal is:

[0022] If the reference synchronization source of the V2X terminal is a user terminal UE that sends SLSS, the timing is: when the value of the reference signal received power RSRP received by the V2X terminal from the current reference synchronization source is lower than the value corresponding to the syncTxThreshOoC in the pre-configuration information; wherein the RSRP is measured according to the demodulation reference signal DMRS of the PSBCH of the reference synchronization source;

[0023] If the reference synchronization source of the V2X terminal is a global navigation satellite system GNSS, the timing is: when the geographical location of the V2X terminal is within a triggering area, wherein the triggering area is determined by the V2X terminal through pre-configuration information.

[0024] In a preferred embodiment, the V2X terminal is an autonomous V2X terminal;

[0025] In the case where the synchronization signal to be sent by the V2X terminal is the same as the synchronization signal of the existing D2D terminal: if the reference synchronization source of the V2X terminal is GNSS, the root sequence index of the PSSS in the synchronization signal to be sent is 26, and the index value of the SSSS is randomly selected in the range of 0 to 167; if the reference synchronization source of the V2X terminal is a UE that sends SLSS and the UE uses the eNB as the reference synchronization source, the root sequence index of the primary bypass synchronization signal PSSS in the synchronization signal to be sent is 26, and the index value of the auxiliary bypass synchronization signal SSSS is the same as the SSSS index value sent by the reference synchronization source; if the V If the reference synchronization source of the V2X terminal is a UE that sends SLSS and the UE uses GNSS as the reference synchronization source, the root sequence index value of the PSSS in the synchronization signal to be sent is 37, and the index value of the SSSS is ID_r+168, where ID_r is the index value of the SSSS sent by the reference synchronization source; if the reference synchronization source of the V2X terminal is a synchronization source other than the above-mentioned synchronization source, the synchronization signal is not sent, or the root sequence index value of the PSSS in the synchronization signal to be sent is 37, and the index value of the SSSS is ID_r+168, where ID_r is the index value of the SSSS sent by the reference synchronization source.

[0026] In a preferred embodiment, the V2X terminal is a controlled V2X terminal;

[0027] In the case where the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal, the synchronization signal is sent using the reconfigured time-frequency resources, wherein the timing of sending the synchronization signal is:

[0028] If the V2X terminal uses GNSS as a reference synchronization source, the timing is: when the position of the V2X terminal is in a triggering area, wherein the triggering area is determined by the V2X terminal through receiving eNB configuration signaling or through pre-configuration;

[0029] If the V2X terminal uses the eNB as a reference synchronization source, the timing is: when the value of the RSRP received by the V2X terminal relative to the eNB is lower than the syncTxThreshIC, or when the V2X terminal receives an SLSS sending indication from the eNB; wherein the value of the syncTxThreshIC is determined according to the commSyncConfig message containing txParameters in the commSyncConfigList message sequence in the SIB18 system message of the eNB, or is determined according to a system message redefined by the V2X terminal.

[0030] In a preferred embodiment, the V2X terminal is a controlled V2X terminal;

[0031] In the case where the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal: the root sequence index of the PSSS in the synchronization signal is not equal to the root sequence index used for the PSSS, and is not equal to the root sequence index of the PSSS sent by the D2D terminal; the index value of the SSSS in the synchronization signal is determined by the V2X terminal according to the system message of the eNB, and the index value of the SSSS is not equal to the index value of the sequence of the SSSS sent by the D2D terminal; the value of the reserved bit in the PSBCH in the synchronization signal is determined by the V2X terminal according to the received eNB signaling.

[0032] In a preferred embodiment, the V2X terminal is a controlled V2X terminal;

[0033] In the synchronization signal sent by the V2X terminal, the corresponding synchronization source type is indicated by the value of the SLSS sequence index and / or the PSBCH specified field, specifically including:

[0034] If the V2X terminal uses the eNB as a reference synchronization source, the even or odd bits in the first N bits of the PSBCH reserved bits are set to a first specified value;

[0035] If the V2X terminal uses GNSS as a reference synchronization source, the even or odd bits in the first N bits of the PSBCH reserved bits are set to a second specified value;

[0036] The value of the inCoverage field in the PSBCH is set to TRUE to indicate that the V2X terminal is within the cell coverage.

[0037] In a preferred embodiment, the V2X terminal is an autonomous V2X terminal;

[0038] In the case where the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal, the synchronization signal is sent using the reconfigured time-frequency resources, wherein the timing for sending the synchronization signal is: when the geographical location of the V2X terminal is within the trigger area, wherein the trigger area is determined by the V2X terminal through pre-configuration information.

[0039] In a preferred embodiment, the V2X terminal is an autonomous V2X terminal;

[0040] In the case where the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal: if the reference synchronization source of the V2X terminal is a V2X terminal that sends SLSS and is located within the coverage of the cell, and the V2X terminal that sends SLSS uses the eNB as the reference synchronization source, then the index value of the SSSS in the synchronization signal to be sent is the same as the SSSS index value sent by the reference synchronization source; if the reference synchronization source of the V2X terminal is a V2X terminal that sends SLSS, and the V2X terminal uses GNSS as the reference synchronization source, then the SSSS in the synchronization signal to be sent is the same as the SSSS index value sent by the reference synchronization source. The index value of SS is a specific value, or the index value of SSSS is the same as the index value of SSSS sent by the reference synchronization source V2X terminal; if the reference synchronization source of the V2X terminal is GNSS, the index value of SSSS in the synchronization signal to be sent is a value randomly selected within the range of 336 to 503 or a subset of the above range, or is a specific value; if the V2X terminal cannot detect any synchronization source, the index value of SSSS in the synchronization signal to be sent is a specific value; if the reference synchronization source of the V2X terminal is a synchronization source other than the above synchronization source, the synchronization signal is not sent.

[0041] In a preferred embodiment, the V2X terminal is an autonomous V2X terminal;

[0042] In the synchronization signal sent by the V2X terminal, the corresponding synchronization source type is indicated by the value of the SLSS sequence index and / or the PSBCH specified field, specifically including:

[0043] If the V2X terminal uses GNSS as a reference synchronization source, an even or odd bit in the first N bits of the PSBCH reserved bits is set to a first specified value, and a specified bit in the PSBCH reserved bits other than the first N bits is set to TRUE;

[0044] If the V2X terminal uses a V2X terminal referenced to a GNSS as a reference synchronization source, an even or odd bit in the first N bits of the PSBCH reserved bits is set to a first specified value, and a specified bit in the PSBCH reserved bits other than the first N bits is set to FALSE;

[0045] If the V2X terminal uses the UE referenced to the eNB as a reference synchronization source, the even or odd bits in the first N bits of the PSBCH reserved bits are set to a second specified value;

[0046] The value of the inCoverage field in the PSBCH is set to false FALSE to indicate that the V2X terminal is out of cell coverage.

[0047] In a preferred embodiment, when the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal, the bypass synchronization signal SLSS sequence in the synchronization signal to be sent is different from the synchronization signal of the existing D2D terminal.

[0048] A receiving and processing method for time-frequency synchronization of a V2X terminal, comprising:

[0049] Detect the synchronization signal, and determine the corresponding synchronization source type according to the value of the SLSS sequence index and / or the PSBCH specified field in the detected synchronization signal;

[0050] From the synchronization source types determined in the previous step, select the synchronization source type with the highest priority as the reference synchronization source according to the specified synchronization source priority.

[0051] In a preferred embodiment, determining the corresponding synchronization source type according to the SLSS sequence index and / or the value of the PSBCH specified field in the detected synchronization signal specifically includes at least one of the following steps:

[0052] If the value of the inCoverage field in the PSBCH in the synchronization signal is TRUE, and the corresponding bit in the PSBCH reserved bit indicates that the transmitting V2X terminal sending the synchronization signal uses the eNB as the reference synchronization source, it is determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses the eNB as the reference synchronization source and is within the cell coverage;

[0053] If the value of the inCoverage field in the PSBCH in the synchronization signal is TRUE, and the corresponding bit in the PSBCH reserved bit indicates that the transmitting V2X terminal sending the synchronization signal uses GNSS as the reference synchronization source, it is determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses GNSS as the reference synchronization source and is within the cell coverage;

[0054] If the value of the inCoverage field in the PSBCH in the synchronization signal is FALSE, and the corresponding bit in the PSBCH reserved bit indicates that the transmitting V2X terminal sending the synchronization signal uses GNSS as the reference synchronization source, then further according to the index value of the SSSS of the synchronization signal, it is determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage, or a UE that indirectly uses GNSS as the reference synchronization source and is outside the cell coverage, or an independent UE;

[0055] If the value of the inCoverage field in the PSBCH in the synchronization signal is FALSE, and the corresponding bit in the PSBCH reserved bit indicates that the sending V2X terminal sending the synchronization signal uses the eNB as the reference synchronization source, then it is determined that the synchronization source corresponding to the synchronization signal is a UE that indirectly uses the eNB as the reference synchronization source and is outside the cell coverage.

[0056] In a preferred embodiment, the method further comprises:

[0057] If the VUE can detect the eNB on the carrier performing V2X communication, the eNB or GNSS is preferentially used as the reference synchronization source according to the eNB instruction; and / or the VUE determines the eNB as the reference synchronization source according to the physical cell ID and / or the operating frequency in the configuration signaling;

[0058] Alternatively, if the VUE is able to detect the configuration signaling of the eNB on a carrier other than the V2X communication carrier, and the configuration signaling includes the synchronization source priority configuration information on the current V2X communication carrier, the VUE preferentially selects the eNB or GNSS as the reference synchronization source according to the configuration of the eNB;

[0059] Alternatively, if the VUE cannot detect any eNB on all carriers but can detect a reliable GNSS synchronization signal, the GNSS is used as the reference synchronization source.

[0060] In a preferred embodiment, if the VUE cannot detect any eNB on all supported carriers and cannot receive reliable GNSS synchronization signals, but only detects synchronization signals sent by other UEs, the VUE selects the synchronization source with the highest detected priority as the reference synchronization source according to the following priorities a1 to a5, or priorities A1 to A5;

[0061] The following synchronization sources are ranked in descending order of priority from a1 to a5:

[0062] a1. A UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0063] a2. UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0064] a3. UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0065] a4. UE that indirectly uses the eNB as a reference synchronization source;

[0066] a5. Independent UE;

[0067] Alternatively, the following synchronization sources are ranked in descending order of priority from A1 to A5:

[0068] A1, UE that directly uses GNSS as the reference synchronization source;

[0069] A2, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0070] A3, UE that directly uses eNB as reference synchronization source;

[0071] A4, UE that indirectly uses eNB as reference synchronization source;

[0072] A5. Independent UE.

[0073] In a preferred embodiment, if the VUE can detect an eNB on a carrier, and the eNB configures the current V2X communication carrier to preferentially use the eNB as a reference synchronization source, and configures the physical cell ID and / or the operating carrier frequency corresponding to the eNB as the reference synchronization source, but the VUE cannot detect the configured reference synchronization source eNB, then the VUE selects the synchronization source with the highest detected priority as the reference synchronization source according to the following priorities b1 to b6, or c1 to c6, or d1 to d6;

[0074] The following synchronization sources are ranked in descending order of priority from b1 to b6:

[0075] b1, UE that directly uses eNB as reference synchronization source;

[0076] b2, UE that indirectly uses the eNB as a reference synchronization source;

[0077] b3, GNSS;

[0078] b4, UE that directly uses GNSS as the reference synchronization source;

[0079] b5, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0080] b6, independent UE;

[0081] Alternatively, the following synchronization sources are ranked in descending order of priority from c1 to c6:

[0082] c1, GNSS;

[0083] c2, a UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0084] c3, UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0085] c4, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0086] c5, UE that indirectly uses the eNB as a reference synchronization source;

[0087] c6, independent UE;

[0088] Alternatively, the following synchronization sources are ranked in descending order of priority from d1 to d6:

[0089] d1, GNSS;

[0090] d2, UE that directly uses GNSS as reference synchronization source;

[0091] d3, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0092] d4, UE that directly uses eNB as reference synchronization source;

[0093] d5, UE that indirectly uses eNB as reference synchronization source;

[0094] d6, independent UE.

[0095] In a preferred embodiment, if the VUE is able to detect an eNB on a carrier, and the eNB configures the current V2X communication carrier to prioritize GNSS as a reference synchronization source, but the VUE cannot detect a reliable GNSS signal, the VUE selects the synchronization source with the highest detected priority as the reference synchronization source according to the following priorities e1 to e6, or f1 to f6, or g1 to g5;

[0096] The following synchronization sources are ranked in descending order of priority from e1 to e6:

[0097] e1, UE that directly uses GNSS as reference synchronization source;

[0098] e2, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0099] e3, eNB;

[0100] e4, UE that directly uses eNB as reference synchronization source;

[0101] e5, UE that indirectly uses eNB as reference synchronization source;

[0102] e6, independent UE;

[0103] Alternatively, the following synchronization sources are ranked in descending order of priority from f1 to f6:

[0104] f1,eNB;

[0105] f2, a UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0106] f3, UE that indirectly uses the eNB as a reference synchronization source;

[0107] f4, UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0108] f5, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0109] f6, independent UE.

[0110] Alternatively, the following synchronization sources are ranked in descending order of priority from g1 to g5:

[0111] g1, a UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0112] g2, UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0113] g3, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0114] g4, UE that indirectly uses eNB as reference synchronization source;

[0115] g5, independent UE.

[0116] A transmission processing device for time-frequency synchronization of a V2X terminal, comprising:

[0117] A reuse synchronization transmission module is used to reuse the time-frequency resources configured in the cell for transmitting the synchronization signal of the D2D terminal to transmit the synchronization signal when the synchronization signal to be transmitted by the V2X terminal is the same as the synchronization signal of the existing D2D terminal;

[0118] A reconfigured synchronization transmission module is used to transmit the synchronization signal using the reconfigured time-frequency resources when the synchronization signal to be transmitted by the V2X terminal is different from the synchronization signal of the existing D2D terminal;

[0119] Among them, in the synchronization signal sent by the V2X terminal, the corresponding synchronization source type is indicated by the value of the SLSS sequence index and / or the PSBCH specified field.

[0120] A receiving and processing device for time-frequency synchronization of a V2X terminal, comprising:

[0121] A detection and judgment module is used to detect the synchronization signal and determine the corresponding synchronization source type according to the value of the SLSS sequence index and / or the PSBCH specified field in the detected synchronization signal;

[0122] The selection module is used to select the synchronization source type with the highest priority as the reference synchronization source from the synchronization source types determined by the detection and judgment module according to the specified synchronization source priority.

[0123] Compared with the prior art, the technical solution proposed in the present application is that for a V2X terminal that sends a synchronization signal, if the synchronization signal sent by the V2X terminal is the same as that of an existing D2D terminal, the time-frequency resources configured in the cell for sending D2D synchronization signals are reused to send synchronization signals, and the SLSS sequence is the same as that of the D2D terminal; otherwise, the V2X terminal sends a synchronization signal in a redefined or configured time-frequency resource, and uses a redefined or configured synchronization sequence, wherein the synchronization resources and synchronization sequence used are different from the time-frequency resources and synchronization sequence used by the D2D terminal to send the synchronization signal. In the above two methods, the type of reference synchronization source is distinguished by the reserved bits in the PSBCH. For a V2X terminal that receives a synchronization signal, the type of synchronization source is determined according to the received synchronization signal, and the reference synchronization source is further selected according to the detected synchronization source according to a predetermined priority. According to the method proposed in this embodiment, time-frequency synchronization between terminals in a V2X communication environment can be supported with minimal standard changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0124] Figure 1 This is a flowchart of a method for sending a synchronization signal according to the present application;

[0125] Figure 2 A flowchart of a method for receiving a synchronization signal of the present application;

[0126] Figure 3 A schematic diagram of a composition of a sending and processing device for time-frequency synchronization of the V2X terminal;

[0127] Figure 4 A schematic diagram of the composition of a receiving and processing device for time-frequency synchronization of the V2X terminal. DETAILED DESCRIPTION

[0128] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0129] First of all, in the V2X communication environment, the following three problems are mainly faced: under what circumstances should the V2X terminal forward the synchronization signal originated from the eNB or GNSS; on what physical resources and in what synchronization sequence should the V2X terminal carry the sent synchronization signal; for the V2X terminal that receives the synchronization signal in the V2X communication environment, what kind of synchronization signal needs to be prioritized to achieve synchronization in different environments.

[0130] In the V2X communication environment, due to the introduction of GNSS, V2X terminals need a new method to select the optimal synchronization source to achieve time and frequency synchronization in different environments. In order to support V2X terminals in cellular network and GNSS coverage blind areas to perform V2X communication, V2X terminals in cellular network or GNSS coverage need a new method to forward time and frequency information originating from eNB or GNSS. In order to solve the above problems, the present application proposes a sending processing and receiving processing method for realizing time and frequency synchronization of V2X terminals.

[0131] Among them, the core technical solution of the transmission processing method of the V2X terminal time-frequency synchronization is:

[0132] When the synchronization signal to be sent by the V2X terminal is the same as the synchronization signal of the existing D2D terminal, reusing the time-frequency resources configured in the cell for sending the synchronization signal of the D2D terminal to send the synchronization signal;

[0133] In the case where the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal, the synchronization signal is sent using the reconfigured time-frequency resources; in a preferred embodiment, in the case where the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal, the SLSS sequence in the synchronization signal is different from the synchronization signal of the existing D2D terminal;

[0134] In the synchronization signal sent by the V2X terminal, the corresponding synchronization source type is indicated by the value of the SLSS sequence index and / or the PSBCH specified field.

[0135] Correspondingly, the core technical solution of the receiving and processing method of the V2X terminal time-frequency synchronization is:

[0136] Detect the synchronization signal, and determine the corresponding synchronization source type according to the value of the SLSS sequence index and / or the PSBCH specified field in the detected synchronization signal;

[0137] From the synchronization source types determined in the previous step, select the synchronization source type with the highest priority as the reference synchronization source according to the specified synchronization source priority.

[0138] In the following, the V2X terminal is referred to as VUE for description.

[0139] like Figure 1 As shown, if used as a transmitter in VUE time-frequency synchronization, the method for VUE to send synchronization signals (including SLSS and PSBCH) includes the following steps in the time flow:

[0140] Step 110: VUE determines the specific sending conditions of SLSS / PSBCH, which include: the time-frequency resource location for sending SLSS / PSBCH, the SLSS sequence index (or the index set of the optional sequence) and the value of the designated field of PSBCH.

[0141] There are two specific situations here:

[0142] In the first case, the VUE attempts to receive the indication signaling of the eNB regarding the above-mentioned specific transmission condition information. If the VUE is able to receive the indication signaling of the eNB regarding the above-mentioned specific transmission condition information, the VUE determines the above-mentioned specific transmission condition information through the received indication signaling of the eNB. Such a VUE that determines the specific transmission condition according to the indication signaling of the eNB is referred to as a controlled VUE in this article. In the first case, the carrier frequency of the eNB may be the same as or different from the frequency at which the VUE performs V2X communication.

[0143] In the second case, if the VUE cannot receive the indication signaling of the eNB regarding the above-mentioned specific sending conditions, the VUE determines the above-mentioned specific sending condition information according to the pre-configuration. Such a VUE that determines the above-mentioned specific sending condition information according to the pre-configuration is referred to as an autonomous VUE in this article. Part of the above-mentioned specific sending condition information can also be directly set by the standard.

[0144] Step 120: When the SLSS / PSBCH transmission conditions are met, the VUE transmits corresponding SLSS and PSBCH in corresponding time-frequency resources.

[0145] For an autonomous VUE, if the autonomous VUE is in a non-independent state, that is, the autonomous VUE is synchronized to a reference synchronization source, the PSSS and SSSS indexes (PSSS index value is the index of the PSSS root sequence, the same below) in the SLSS sequence index sent by the VUE are related to the sequence of the PSSS index and SSSS index sent by the synchronization source referenced by the VUE; if the autonomous VUE is in an independent state, that is, it is not synchronized to any synchronization source, the PSSS and SSSS sequences in the SLSS sequence index sent by the VUE are autonomously selected by the VUE from the available sequence set.

[0146] like Figure 2As shown, if serving as a receiving end in VUE time-frequency synchronization, the method for VUE to select a reference synchronization source includes the following steps:

[0147] Step 210: The VUE detects the synchronization signal, and determines the type of the synchronization source that sends the synchronization signal according to the detected synchronization signal.

[0148] The above synchronization signals include downlink synchronization signals sent by eNB, GNSS signals sent by global navigation satellites, signals equivalent to GNSS sent by other global navigation devices, and SLSS and PSBCH signals sent by VUE. If the SLSS and PSBCH signals are sent by VUE, the present invention needs to determine the corresponding synchronization source type according to the value of the SLSS sequence index and / or PSBCH specified field therein.

[0149] The types of synchronization sources include: eNB, GNSS, UE that directly uses eNB as a reference synchronization source and is within the coverage of a cell (may be a VUE or a D2D terminal, the same below), UE that directly uses GNSS as a reference synchronization source and is within the coverage of a cell, UE that directly uses GNSS as a reference synchronization source and is outside the coverage of a cell, UE that indirectly uses eNB as a reference synchronization source, UE that indirectly uses GNSS as a reference synchronization source and is outside the coverage of a cell, and an independent UE.

[0150] The UE that directly uses eNB or GNSS as a reference synchronization source means that the UE can receive a reliable synchronization signal sent by an eNB or GNSS satellite. The UE that indirectly uses eNB or GNSS as a reference synchronization source means that the UE can receive a reliable synchronization signal sent by an external UE, and the external UE directly uses eNB or GNSS as a reference synchronization source. The independent UE refers to a UE that sends a synchronization signal according to its own crystal oscillator timing.

[0151] Step 220: The VUE selects the synchronization source with the highest detectable priority as the reference synchronization source.

[0152] The priority of the synchronization source may be related to the number of synchronization source types that the VUE can detect.

[0153] In order to facilitate the understanding of the present application, the above technical solution of the present application is further explained in the mode of interaction between devices in combination with specific application situations as follows:

[0154] Embodiment 1:

[0155] In the first embodiment, the UE is a controlled VUE, and the controlled VUE obtains the specific sending condition information of sending SLSS according to the instruction of eNB. VUE uses eNB or GNSS as the reference synchronization source and sends SLSS with this as the reference. In order to reduce the impact on cellular network communication and ensure backward compatibility, VUE reuses the time and frequency resources configured in the cell for D2D terminal SLSS transmission, and adopts the same synchronization sequence and PSBCH structure as D2D terminal. The specific implementation steps are as follows:

[0156] Step 310: VUE receives the indication signaling about specific sending condition information sent by eNB, and determines the specific sending condition of SLSS / PSBCH according to the indication signaling, and the specific sending condition includes: the time-frequency resource location for sending SLSS / PSBCH, the SLSS sequence index and the value of the designated domain of PSBCH.

[0157] Step 320: When the SLSS sending conditions are met, the VUE sends the corresponding SLSS and PSBCH in the corresponding time-frequency resources.

[0158] In the first embodiment, the timing of the VUE sending the synchronization signal is: when the received reference signal received power (RSRP) value relative to the eNB is lower than the syncTxThreshIC, or when the VUE receives the SLSS sending indication from the eNB, the VUE starts to send the SLSS and PSBCH. The VUE determines the value of the syncTxThreshIC by receiving the commSyncConfig message containing the txParameters in the commSyncConfigList message sequence in the SIB18 system message of the eNB.

[0159] In the first embodiment, the specific characteristics of the time-frequency resources for sending the synchronization signal include:

[0160] Time domain characteristics: The subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*SFN+sn)mod40=syncOffsetIndicator, where SFN is the system frame number corresponding to the above subframe, and sn is the subframe number of the above subframe. The VUE determines the value of syncOffsetIndicator by receiving the commSyncConfig message containing txParameters in the commSyncConfigList message sequence of the system information block (SIB) 18 system message of the eNB.

[0161] Frequency domain characteristics: The frequency domain position of sending SLSS is located at n PRBs in the center of the current carrier, where n is a value defined by the standard, for example, n=6.

[0162] In the first embodiment, the root sequence index of the PSSS is 26, and the VUE determines the index value of the SSSS and the value of the reserved bit in the PSBCH by receiving the commSyncConfig message containing txParameters in the commSyncConfigList message sequence of the SIB18 system message of the eNB.

[0163] In the first embodiment, according to the instruction of the eNB, the VUE may use the eNB as a reference synchronization source or use the GNSS as a reference synchronization source, and the VUE sets a specific bit in the PSBCH reserved bit to a corresponding value to distinguish the above two different states. For example, if the VUE uses the eNB as a reference synchronization source, the even (or odd) bits in the first N bits of the PSBCH reserved bit are set to a first specified value, such as 1 (or 0); if the GNSS is used as a reference synchronization source, the even or odd bits in the first N bits of the PSBCH reserved bit are set to a second specified value, such as the second specified value is the inverse of the first specified value, such as set to 0 (or 1). The value of N is specified by the standard.

[0164] At the same time, the VUE should set the inCoverage field in the PSBCH in the synchronization signal to true (TRUE) to indicate that the VUE is within the cell coverage.

[0165] At this point, the first embodiment ends. Through the method of the first embodiment, the VUE can reuse the time-frequency resources configured in the cell for sending the D2D terminal synchronization signal, which is conducive to reducing the impact of V2X communication on the cellular network communication in the cell. In addition, because the SLSS sent by the VUE is the same as the SLSS sent by the D2D terminal, the SLSS sent by the VUE can support the synchronization of the D2D terminal, and vice versa.

[0166] Embodiment 2:

[0167] In the second embodiment, the UE is an autonomous VUE, and the VUE obtains the corresponding information for sending SLSS according to the pre-configuration. The VUE can use other UEs or GNSS that send SLSS as the reference synchronization source, and use this as a reference to send SLSS and PSBCH. In order to reduce the impact on cellular network communications and ensure backward compatibility, the VUE reuses the time-frequency resources configured in the cell for D2D terminal SLSS transmission, and uses the same synchronization sequence and PSBCH structure as the D2D terminal. The specific implementation steps are as follows:

[0168] Step 410: VUE determines the specific transmission conditions of SLSS / PSBCH, sends the time-frequency resource location of SLSS / PSBCH, SLSS sequence index and the value of some fields of PSBCH.

[0169] Step 420: When the SLSS sending conditions are met, the VUE sends the corresponding SLSS and PSBCH in the corresponding time-frequency resources.

[0170] In the second embodiment, the timing of sending the synchronization signal is:

[0171] If the reference synchronization source of the VUE is a UE that sends SLSS, the VUE starts sending SLSS and PSBCH when the value of the RSRP received from the current reference synchronization source is lower than the value corresponding to the syncTxThreshOoC in the pre-configuration information, where the above RSRP is measured based on the demodulation reference signal (DMRS) of the PSBCH of the reference synchronization source.

[0172] If the reference synchronization source of the VUE is GNSS, the SLSS starts to be sent when the geographical location of the VUE is within the trigger area, wherein the VUE determines the scope of the trigger area through pre-configuration.

[0173] In the second embodiment, specific characteristics of the time-frequency resources for sending the synchronization signal include:

[0174] Time domain characteristics: The subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*DFN+sn)mod40=syncOffsetIndicator1 or (10*DFN+sn)mod 40=syncOffsetIndicator2, where DFN is the system frame number corresponding to the above subframe, sn is the subframe number of the above subframe, and the VUE determines the value of syncOffsetIndicator1 or syncOffsetIndicator2 through pre-configuration information. If the reference synchronization source of the current VUE is an external UE, that is, another UE (possibly a VUE or a D2D terminal), and the subframe position offset of the SLSS sent by the UE is syncOffsetIndicator1, then the subframe offset of the SLSS sent by the VUE should be syncOffsetIndicator2, and vice versa, that is, if the subframe position offset of the SLSS sent by the UE is syncOffsetIndicator2, then the subframe offset of the SLSS sent by the V2X terminal is syncOffsetIndicator1. If the current reference synchronization source of the VUE is GNSS, the VUE can select any one of syncOffsetIndicator1 and syncOffsetIndicator2 as the subframe offset for sending SLSS.

[0175] Frequency domain characteristics: The frequency domain position of sending SLSS is located at n PRBs in the center of the current carrier, where n is a value defined by the standard, for example, n=6.

[0176] In the second embodiment, if the reference synchronization source of the VUE is GNSS, the root sequence index of the PSSS is 26, and the index value of the SSSS is randomly selected in the range of 0 to 167. If the reference synchronization source of the VUE is a UE that sends SLSS and the UE uses eNB as the reference synchronization source, the root sequence index of the PSSS is 26, and the index value of the SSSS is the same as the index value of the SSSS sent by the reference synchronization source. If the reference synchronization source of the VUE is a UE that sends SLSS and the UE uses GNSS as the reference synchronization source, the root sequence index value of the PSSS is 37, and the index value of the SSSS is ID_r+168, where ID_r is the index of the SSSS sent by the reference synchronization source. If the reference synchronization source of the VUE is another synchronization source, then according to one method of this embodiment, the VUE does not need to perform step 420, and the PSSS root sequence index and SLSS index are empty; according to another method of this embodiment, the root sequence index value of the PSSS is 37, and the index value of the SSSS is ID_r+168, where ID_r is the index of the SSSS sent by the reference synchronization source.

[0177] In the second embodiment, the reference synchronization source of the VUE may be GNSS, or the reference synchronization source of the VUE may be a UE that sends SLSS, and the UE uses GNSS as the reference synchronization source; or the reference synchronization source of the VUE may be a UE that sends SLSS, and the UE uses eNB as the reference synchronization source. Therefore, the VUE needs to set a specific bit in the PSBCH reserved bit to a corresponding value for identification. For example, if the VUE uses GNSS as a reference synchronization source, the even (or odd) bits of the first N bits in the PSBCH reserved bits are set to a first specified value, such as 1 (or 0), and another specified bit in the PSBCH reserved bits other than the first N bits is set to true (TRUE), indicating that the VUE directly uses GNSS as a synchronization source, and the position of the above-mentioned specified bit is defined by the standard; if the VUE uses the VUE referenced to GNSS as a reference synchronization source, the even (or odd) bits of the first N bits in the PSBCH reserved bits are set to a first specified value, such as 1 (or 0), and another specified bit in the PSBCH reserved bits other than the first N bits is set to false (FALSE), indicating that the VUE indirectly uses GNSS as a synchronization source, and the position of the above-mentioned bit is defined by the standard; if the UE referenced to the eNB is used as the reference synchronization source, the even or odd bits of the first N bits in the PSBCH reserved bits are set to a second specified value; the second specified value may be the inverse of the first specified value, such as being set to 0 (or 1);. The value of N is defined by the standard.

[0178] The VUE shall set the inCoverage field in the PSBCH in the synchronization signal to FALSE to indicate that the VUE is out of cell coverage.

[0179] At this point, the second embodiment ends. In this embodiment, the autonomous VUE can reuse the pre-configured time-frequency resources for D2D terminal synchronization signal transmission, and for terminals that support both D2D and V2X communications, the number of synchronization signal transmissions can be reduced. In addition, similar to the first embodiment, the SLSS sent by the VUE is the same as the SLSS sent by the D2D terminal, so the SLSS sent by the VUE can support the synchronization of the D2D terminal, and vice versa.

[0180] Embodiment three:

[0181] In the third embodiment, the UE is a controlled VUE, and the VUE obtains the corresponding information for sending SLSS according to the instruction of the eNB. The VUE uses the eNB or GNSS as the reference synchronization source, and sends SLSS with this as the reference. In this embodiment, the PSBCH structure sent by the VUE may be different from that sent by the D2D terminal. In order to avoid mutual influence, the time-frequency resources and SLSS sequence of the VUE sending SLSS are different from those of the D2D terminal. The specific implementation steps are as follows:

[0182] Step 510: The VUE receives the eNB signaling to determine the specific transmission conditions of the SLSS / PSBCH, and sends the time-frequency resource location of the SLSS / PSBCH, the SLSS sequence index and the value of some fields of the PSBCH.

[0183] Step 520: When the SLSS sending conditions are met, the VUE sends the corresponding SLSS and PSBCH in the corresponding time-frequency resources.

[0184] In this third embodiment, the timing of sending the synchronization signal includes:

[0185] According to an implementation method (method 1) of this embodiment, when the VUE is located in the trigger area, SLSS and PSBCH are started to be sent, wherein the VUE determines the trigger area by receiving eNB configuration signaling or by pre-configuration. This application does not limit the configuration method of the trigger area.

[0186] According to another implementation method (method 2) of this embodiment, when the received RSRP value relative to the eNB is lower than syncTxThreshIC, or when the VUE receives an SLSS transmission indication from the eNB, the VUE starts to send SLSS and PSBCH. The VUE determines the value of syncTxThreshIC by receiving a commSyncConfig message containing txParameters in a commSyncConfigList message sequence in a SIB18 system message of the eNB, or a redefined system message.

[0187] According to another implementation method of the present application, if the VUE uses GNSS as a reference synchronization source, SLSS sending is triggered according to method one; if the VUE uses eNB as a reference synchronization source, SLSS sending is triggered according to method two.

[0188] In the third embodiment, the location characteristics of the time-frequency resources for sending SLSS / PSBCH include:

[0189] Time domain characteristics: The subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*SFN+sn)mod40=syncOffsetIndicator-v, where SFN is the system frame number corresponding to the above subframe, and sn is the subframe number of the above subframe. The VUE determines the value of syncOffsetIndicator-v by receiving the system message of the eNB. Preferably, syncOffsetIndicator-v is not equal to syncOffsetIndicator1 and syncOffsetIndicator2 in the second embodiment.

[0190] Frequency domain characteristics: The frequency domain position of sending SLSS is located at n PRBs in the center of the current carrier, where n is a specified value defined by the standard, for example, n=6.

[0191] In the third embodiment, the root sequence index of PSSS is defined by the standard and is not equal to the root sequence used for PSS, i.e., 25, 29 and 34, and is not equal to the root sequence of PSSS used for D2D terminal transmission, i.e., 26 and 37. VUE determines the index value of SSSS by receiving the system message of eNB, and the index value of SSSS is not equal to the sequence index of SSSS used for D2D terminal transmission, i.e., 0 to 335. VUE determines the value of the reserved bit in PSBCH by receiving eNB signaling.

[0192] In the third embodiment, according to the instruction of the eNB, the VUE may use the eNB as a reference synchronization source or use the GNSS as a reference synchronization source, and the VUE sets a specific bit in the PSBCH reserved bit to a corresponding value to distinguish the above two different states. For example, if the VUE uses the eNB as a reference synchronization source, the even (or odd) bits in the first N bits of the PSBCH reserved bit are set to a first specified value; such as set to 1 (or 0); if the GNSS is used as a reference synchronization source, the even (or odd) bits in the first N bits of the PSBCH reserved bit are set to a second specified value; the second specified value may be the inverse of the first specified value, such as set to 0 (or 1); the value of N is defined by the standard.

[0193] The VUE should set the inCoverage field in the PSBCH in the synchronization signal to TRUE to indicate that the V2X terminal is within the cell coverage.

[0194] At this point, the third embodiment ends. By using the method of the third embodiment, the time-frequency resources for the VUE to send SLSS / PSBCH are different from the time-frequency resources configured for the D2D terminal to send SLSS / PSBCH, which can avoid mutual interference caused by different PSBCH structures of the two. In addition, the SLSS sequence used by the VUE is different from that of the D2D terminal, which can avoid affecting the synchronization of the backward D2D terminal.

[0195] Embodiment 4:

[0196] In the fourth embodiment, the UE is an autonomous VUE, and the VUE obtains the corresponding information for sending SLSS according to the preconfiguration. The VUE can use other UEs or GNSS that send SLSS as the reference synchronization source, and use this as a reference to send SLSS and PSBCH. In this embodiment, the PSBCH structure sent by the VUE may be different from that sent by the D2D terminal. In order to avoid mutual influence, the time-frequency resources and SLSS sequence of the VUE sending SLSS are different from those of the D2D terminal. The specific implementation steps are as follows:

[0197] Step 610: The VUE determines the specific transmission conditions of SLSS / PSBCH, and transmits the time-frequency resource location of SLSS / PSBCH, the SLSS sequence index and the value of some fields of PSBCH.

[0198] Step 620: When the SLSS sending conditions are met, the VUE sends the corresponding SLSS and PSBCH in the corresponding time-frequency resources.

[0199] In the fourth embodiment, the timing of sending the synchronization signal is: when the geographical location of the VUE is within the triggering area, the VUE starts sending the synchronization signal, wherein the VUE determines the range of the triggering area through pre-configuration information, or the VUE cannot detect any synchronization source.

[0200] In this fourth embodiment, the specific characteristics of the time-frequency resources include:

[0201] Time domain characteristics: The subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*DFN+sn)mod40=syncOffsetIndicator-v1 or (10*DFN+sn)mod 40=syncOffsetIndicator-v2, where DFN is the system frame number corresponding to the above subframe, sn is the subframe number of the above subframe, and the VUE determines the value of syncOffsetIndicator-v1 or syncOffsetIndicator-v2 through pre-configuration information. Preferably, syncOffsetIndicator-v1 and syncOffsetIndicator-v2 are not equal to syncOffsetIndicator1 and syncOffsetIndicator2 in the second embodiment. If the current VUE's reference synchronization source is an external UE such as another UE (possibly a VUE or a D2D terminal), and the subframe position offset of the UE sending SLSS is syncOffsetIndicator-v1, then the subframe offset of the VUE sending SLSS should be syncOffsetIndicator-v2, and vice versa, that is, if the subframe position offset of the UE sending SLSS is syncOffsetIndicator-v2, then the subframe offset of the VUE sending SLSS should be syncOffsetIndicator-v1. If the current VUE's reference synchronization source is GNSS, the VUE can select one of syncOffsetIndicator-v1 and syncOffsetIndicator-v2 as the subframe offset for sending SLSS.

[0202] Frequency domain characteristics: The frequency domain position of sending SLSS is located at n PRBs in the center of the current carrier, where n is a value specified by the standard, for example, n=6.

[0203] In the fourth embodiment, if the reference synchronization source of the VUE is another VUE that sends SLSS and is located within the coverage of the cell, and the VUE that sends SLSS uses the eNB as the reference synchronization source, the index value of the SSSS is the same as the SSSS index value sent by the reference synchronization source. If the reference synchronization source of the VUE is another VUE that sends SLSS, and the VUE uses GNSS as the reference synchronization source, the index value of the SSSS is a specific value defined by a certain standard, such as 503, and the SSSS index value is only used for the above-mentioned type of VUE; or the index value of the SSSS is the same as the SSSS index value sent by the reference synchronization source VUE. If the reference synchronization source of the VUE is GNSS, the VUE randomly selects the index of the SSSS to be sent within the range of 336 to 503 or within a subset of the above range (e.g., 336 to 419 or 336 to 502), or a specific value defined by a certain standard, such as 502, and the SSSS index value is only used for the above-mentioned type of VUE. If the VUE cannot detect any synchronization source, the index value of the SSSS sent by the VUE is a specific value defined by a standard, such as 501. At this time, the SSSS index value is only used for the above-mentioned type of VUE. In the above case, the root sequence index of the PSSS sent by the VUE is defined by the standard and is not equal to the root sequence used for PSSS, that is, 25, 29 and 34, and is not equal to the root sequence used for PSSS sent by the D2D terminal, that is, 26 and 37. If the reference synchronization source of the VUE is another type of synchronization source, the VUE does not need to perform step 620, and the PSSS root sequence index and SLSS index are empty.

[0204] In the fourth embodiment, the reference synchronization source of the VUE may be GNSS, or the reference synchronization source of the VUE may be a VUE that sends SLSS, and the VUE uses GNSS as the reference synchronization source; or the reference synchronization source of the VUE may be a VUE that sends SLSS, and the VUE uses eNB as the reference synchronization source. Therefore, the VUE needs to set a specific bit in the PSBCH reserved bit to a corresponding value for identification. For example, if the VUE uses GNSS as a reference synchronization source, the even (or odd) bits of the first N bits in the PSBCH reserved bits are set to a first specified value, such as set to 1 (or 0), and another specified bit in the PSBCH reserved bits other than the first N bits is set to true (TRUE), indicating that the VUE directly uses GNSS as a synchronization source, and the position of the above-mentioned specified bit is defined by the standard; if the VUE uses the VUE referenced to GNSS as a reference synchronization source, the even (or odd) bits of the first N bits in the PSBCH reserved bits are set to a first specified value, such as set to 1 (or 0), and another specified bit in the PSBCH reserved bits other than the first N bits is set to false (FALSE), indicating that the VUE indirectly uses GNSS as a synchronization source, and the position of the above-mentioned bit is defined by the standard; if the VUE referenced to the eNB is used as the reference synchronization source, the even or odd bits of the first N bits in the PSBCH reserved bits are set to a second specified value, for example, the second specified value can be the inverse of the first specified value, such as set to 0 (or 1). The value of N is specified by the standard.

[0205] The VUE shall set the inCoverage field in the PSBCH to FALSE to indicate that the V2X terminal is out of cell coverage.

[0206] At this point, the fourth embodiment ends. In the fourth embodiment, the autonomous VUE uses a synchronization sequence different from that of the D2D terminal to send SLSS and PSBCH in different time-frequency resources, which can avoid interference with the SLSS and PSBCH sent by the D2D terminal.

[0207] Embodiment five:

[0208] In the fifth embodiment, VUE is a terminal that receives a synchronization signal. The fifth embodiment is a method for receiving and processing time-frequency synchronization of VUE. The specific steps for determining a reference synchronization source are as follows:

[0209] Step 710: The VUE detects a synchronization signal, and determines the type of the synchronization source according to the detected synchronization signal.

[0210] If the VUE detects SLSS and PSBCH, the VUE can determine the type of synchronization source according to the PSSS root sequence index of the SLSS, the SSSS index of the SLSS, the value of the reserved bit field in the PSBCH, and the value of inCoverage in the PSBCH. The specific determination method includes at least one of the following steps:

[0211] If the value of the inCoverage field in the PSBCH in the synchronization signal is TRUE, and the corresponding bit in the PSBCH reserved bit indicates that the sending VUE that sends the synchronization signal uses the eNB as the reference synchronization source, then it is determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses the eNB as the reference synchronization source and is within the cell coverage. For example, corresponding to the above embodiment, when the corresponding bit can be an even or odd bit in the first N bits of the reserved bit and is set to the first specified value, it is determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses the eNB as the reference synchronization source and is within the cell coverage.

[0212] If the value of the inCoverage field in the PSBCH in the synchronization signal is TRUE, and the corresponding bit in the PSBCH reserved bit indicates that the sending VUE that sends the synchronization signal uses GNSS as the reference synchronization source, then it is determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses GNSS as the reference synchronization source and is within the coverage of the cell. For example, corresponding to the above embodiment, when the corresponding bit can be an even or odd bit in the first N bits of the reserved bit and is set to the second specified value, it is determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses GNSS as the reference synchronization source and is within the coverage of the cell.

[0213] If the value of the inCoverage field in the PSBCH in the synchronization signal is FALSE, and the corresponding bit in the PSBCH reserved bit indicates that the sending VUE of the synchronization signal uses GNSS as the reference synchronization source, and then further based on the index value of the SSSS of the synchronization signal, it can be determined that the synchronization source corresponding to the synchronization signal is a UE that directly uses GNSS as a reference synchronization source and is outside the cell coverage, or a UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage, or an independent UE.

[0214] If the value of the inCoverage field in the PSBCH in the synchronization signal is FALSE, and the corresponding bit in the reserved bit of the PSBCH indicates that the sending VUE that sends the synchronization signal uses the eNB as the reference synchronization source, then it is determined that the synchronization source corresponding to the synchronization signal is a UE that indirectly uses the eNB as the reference synchronization source and is outside the cell coverage. For example, corresponding to the above embodiment, when the corresponding bit can be an even or odd bit in the first N bits of the reserved bit and is set to the second specified value, it is determined that the synchronization source corresponding to the synchronization signal is a UE that indirectly uses the eNB as the reference synchronization source and is outside the cell coverage.

[0215] Step 720: From the synchronization source types determined in the previous step, select the synchronization source type with the highest priority as the reference synchronization source according to the specified synchronization source priority.

[0216] There are three exceptions here: (1) If the VUE can detect the eNB on the carrier performing V2X communication, the eNB or GNSS will be prioritized as the reference synchronization source according to the eNB instruction. Preferably, if the eNB on the V2X communication carrier configures the current carrier to prioritize the eNB as the reference synchronization source, the configuration signaling should further include information such as the physical cell ID and / or operating frequency corresponding to the eNB as the reference synchronization source; the VUE determines the eNB as the reference synchronization source according to the physical cell ID and / or operating frequency in the configuration signaling; (2) If the VUE can detect the configuration signaling of the eNB on other carriers other than the V2X communication carrier, and the configuration signaling includes the synchronization source priority configuration information on the current V2X communication carrier, the VUE will prioritize the eNB or GNSS as the reference synchronization source according to the configuration of the eNB. At this time, the eNB as the synchronization source can be the eNB on the V2X communication carrier, the eNB that sends the configuration signaling, or the eNB on other carriers. Preferably, if the eNB configures a certain V2X communication carrier to prioritize the eNB as the reference synchronization source, the configuration signaling should further include information such as the physical cell ID and / or operating frequency corresponding to the eNB used as the reference synchronization source; (3) If the VUE cannot detect any eNB on all carriers but can detect a reliable GNSS synchronization signal, the GNSS is used as the reference synchronization source.

[0217] If the VUE cannot detect any eNB on all supported carriers and cannot receive reliable GNSS synchronization signals, but only detects synchronization signals sent by other UEs, the VUE selects the synchronization source with the highest priority detected as the reference synchronization source according to the following priorities a1 to a5, or priorities A1 to A5. The following synchronization sources are ranked from high to low in terms of priorities a1 to a5:

[0218] a1, a UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0219] a2, UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0220] a3, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0221] a4, UE that indirectly uses eNB as reference synchronization source;

[0222] a5, independent UE.

[0223] Alternatively, the following synchronization sources are ranked in descending order of priority from A1 to A5:

[0224] A1, UE that directly uses GNSS as the reference synchronization source;

[0225] A2, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0226] A3, UE that directly uses eNB as reference synchronization source;

[0227] A4, UE that indirectly uses eNB as reference synchronization source;

[0228] A5. Independent UE.

[0229] If the VUE is able to detect an eNB on a certain carrier, and the eNB configures the current V2X communication carrier to prioritize the eNB as a reference synchronization source, and configures the physical cell ID and / or operating carrier frequency corresponding to the eNB as the reference synchronization source, however, the VUE cannot detect the configured reference synchronization source eNB, then the following implementation methods one, two, or three may be used.

[0230] Implementation method 1: In order to ensure that VUE is synchronized to the timing of eNB first, VUE selects the synchronization source with the highest priority detected as the reference synchronization source according to the following priorities b1 to b6; the following synchronization sources are in descending order of priority from b1 to b6:

[0231] b1, UE that directly uses eNB as reference synchronization source;

[0232] b2, UE that indirectly uses the eNB as a reference synchronization source;

[0233] b3, GNSS;

[0234] b4, UE that directly uses GNSS as the reference synchronization source;

[0235] b5, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0236] b6, independent UE.

[0237] Implementation method 2: In order to make VUE synchronize to GNSS first and take into account the protection of cellular communication, VUE selects the synchronization source with the highest priority detected as the reference synchronization source according to the following priorities c1 to c6. The following synchronization sources are ranked from high to low in order of priority c1 to c6:

[0238] c1, GNSS;

[0239] c2, a UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0240] c3, UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0241] c4, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0242] c5, UE that indirectly uses the eNB as a reference synchronization source;

[0243] c6, independent UE.

[0244] Implementation method 3: In order to make VUE synchronize to GNSS first, VUE selects the synchronization source with the highest priority detected as the reference synchronization source according to the following priorities d1 to d6. The following synchronization sources are ranked from high to low in terms of priority d1 to d6:

[0245] d1, GNSS;

[0246] d2, UE that directly uses GNSS as reference synchronization source;

[0247] d3, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0248] d4, UE that directly uses eNB as reference synchronization source;

[0249] d5, UE that indirectly uses eNB as reference synchronization source;

[0250] d6, independent UE.

[0251] If the VUE is able to detect the eNB on a certain carrier, and the eNB configures the current V2X communication carrier to prioritize GNSS as the reference synchronization source, however, the VUE cannot detect a reliable GNSS signal, then the following implementation methods A, B, or C may be used.

[0252] Implementation method A: To ensure that VUE is synchronized to GNSS timing first, VUE selects the synchronization source with the highest priority detected as the reference synchronization source according to the following priorities e1 to e6. The following synchronization sources are in descending order of priority from e1 to e6:

[0253] e1, UE that directly uses GNSS as reference synchronization source;

[0254] e2, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0255] e3, eNB;

[0256] e4, UE that directly uses eNB as reference synchronization source;

[0257] e5, UE that indirectly uses eNB as reference synchronization source;

[0258] e6, independent UE.

[0259] Implementation method B: In order to make VUE synchronize to eNB first, VUE selects the synchronization source with the highest priority detected as the reference synchronization source according to the following priorities f1 to f6. The following synchronization sources are ranked from high to low in terms of priorities f1 to f6:

[0260] f1,eNB;

[0261] f2, a UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0262] f3, UE that indirectly uses the eNB as a reference synchronization source;

[0263] f4, UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0264] f5, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0265] f6, independent UE.

[0266] Implementation method C: In order to synchronize VUE to GNSS first and take into account the protection of cellular communication, VUE selects the synchronization source with the highest priority detected as the reference synchronization source according to the following priorities g1 to g5. The following synchronization sources are ranked from high to low in order of priority g1 to g5:

[0267] g1, a UE that directly uses the eNB as a reference synchronization source and is within the cell coverage, or a UE that directly uses the GNSS as a reference synchronization source and is within the cell coverage;

[0268] g2, UE that directly uses GNSS as the reference synchronization source and is outside the cell coverage;

[0269] g3, UE that indirectly uses GNSS as a reference synchronization source and is outside the cell coverage;

[0270] g4, UE that indirectly uses eNB as reference synchronization source;

[0271] g5, independent UE.

[0272] At this point, the fifth embodiment ends. According to the method of the fifth embodiment, the VUE can select the synchronization source with the highest accuracy as the reference synchronization source, which is beneficial to improving the performance of V2X communication.

[0273] Embodiment six:

[0274] In the sixth embodiment, the UE may be a controlled VUE or an autonomous VUE. If it is a controlled VUE, the VUE obtains the corresponding information for sending SLSS according to the instruction of the eNB, takes the eNB or GNSS as the reference synchronization source, and sends SLSS with this as the reference. If it is an autonomous VUE, the VUE obtains the corresponding information for sending SLSS according to the pre-configuration, and the VUE may take other UEs or GNSS that send SLSS as the reference synchronization source, and send SLSS and PSBCH with this as the reference. The specific implementation steps are as follows:

[0275] Step 810: VUE determines the specific transmission conditions of SLSS / PSBCH, sends the time-frequency resource location of SLSS / PSBCH, SLSS sequence index and the value of some fields of PSBCH.

[0276] For controlled VUE, the above information is obtained by receiving eNB signaling. For autonomous VUE, the corresponding information for sending SLSS is obtained according to pre-configuration.

[0277] Step 820: When the SLSS sending conditions are met, the VUE sends the corresponding SLSS and PSBCH in the corresponding time-frequency resources.

[0278] In the fifth embodiment, the timing of sending the synchronization signal includes:

[0279] According to an implementation method (method 1) of this embodiment, when the VUE is located in the trigger area, SLSS and PSBCH are started to be sent, wherein the VUE determines the trigger area by receiving eNB configuration signaling or by pre-configuration. This application does not limit the configuration method of the trigger area.

[0280] According to another implementation method (method 2) of this embodiment, when the received RSRP value relative to the eNB is lower than syncTxThreshIC, or when the VUE receives an SLSS transmission indication from the eNB, the VUE starts to send SLSS and PSBCH. The VUE determines the value of syncTxThreshIC by receiving a commSyncConfig message containing txParameters in a commSyncConfigList message sequence in a SIB18 system message of the eNB, or a redefined system message.

[0281] According to another implementation method of the present application, if the VUE uses GNSS as a reference synchronization source, SLSS sending is triggered according to method one; if the VUE uses eNB as a reference synchronization source, SLSS sending is triggered according to method two.

[0282] In the fifth embodiment, the location characteristics of the time-frequency resources for sending SLSS / PSBCH include:

[0283] Time domain characteristics:

[0284] If the VUE uses the eNB as the reference synchronization source (this is the controlled VUE), the subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*SFN+sn)mod 160=syncOffsetIndicator-v, where SFN is the system frame number corresponding to the above subframe, and sn is the subframe number of the above subframe. The VUE determines the value of syncOffsetIndicator-v by receiving the system message of the eNB. Preferably, mod(syncOffsetIndicator-v, 40) is not equal to syncOffsetIndicator1 and syncOffsetIndicator2 in the second embodiment.

[0285] For a controlled VUE with GNSS as the synchronization source, the subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*G-SFN+sn)mod 160=syncOffsetIndicator-v1. The VUE determines the value of syncOffsetIndicator-v1 by pre-configuration or receiving eNB signaling. Preferably, 0≤syncOffsetIndicator-v1<160. G-SFN represents the current system frame number determined by the UE based on GNSS timing. At this time, the SSSS index value used by the VUE should be 0, and the inCoverage domain is set to TRUE.

[0286] For an autonomous VUE with GNSS as the synchronization source (autonomous VUE1), and the VUE cannot read the PSBCH sent by the controlled VUE with GNSS as the synchronization source, the subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*G-SFN+sn)mod160=syncOffsetIndicator-v3, and the VUE determines the value of syncOffsetIndicator-v3 through pre-configuration. Preferably, 0≤syncOffsetIndicator-v3<160, and syncOffsetIndicator-v3 is not equal to syncOffsetIndicator-v1. G-SFN represents the current system frame number determined by the UE based on GNSS timing. At this time, the SSSS index value used by the VUE should be 0, and the inCoverage domain is set to FALSE. If the VUE can read the PSBCH sent by the controlled VUE with GNSS as the synchronization source, the subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*G-SFN+sn)mod160=syncOffsetIndicator-v1, and the VUE determines the value of syncOffsetIndicator-v1 through pre-configuration. At this time, the SSSS index value used by the VUE should be 0, and the inCoverage domain is set to TRUE.

[0287] For an autonomous VUE that uses a controlled VUE that uses GNSS as the synchronization source (i.e., a controlled VUE whose SSSS index value is 0 and the inCoverage domain is set to TRUE) (autonomous VUE2), the subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*G-SFN+sn)mod 160=syncOffsetIndicator-v2. The VUE determines the value of syncOffsetIndicator-v2 through pre-configuration. Preferably, 0≤syncOffsetIndicator-v2<160, and syncOffsetIndicator-v2 is not equal to syncOffsetIndicator-v1 and syncOffsetIndicator-v1. Among them, G-SFN represents the current system frame number determined by the UE based on GNSS timing. At this time, the SSSS index value used by the VUE should be 0, and the inCoverage domain is set to FALSE.

[0288] For autonomous VUE and autonomous VUE1 as synchronization source, the subframe position of the SLSS synchronization signal sent by VUE satisfies (10*G-SFN+sn)mod 160=syncOffsetIndicator-v2. VUE determines the value of syncOffsetIndicator-v2 through pre-configuration. Preferably, 0≤syncOffsetIndicator-v2<160, and syncOffsetIndicator-v2 is not equal to syncOffsetIndicator-v1 and syncOffsetIndicator-v1. G-SFN represents the current system frame number determined by UE according to GNSS timing. At this time, the SSSS index value used by VUE should be 168, and the inCoverage domain is set to FALSE.

[0289] For an autonomous VUE with autonomous VUE2 as the synchronization source, the subframe position of the SLSS synchronization signal sent by the VUE satisfies (10*G-SFN+sn)mod 160=syncOffsetIndicator-v1, and the VUE determines the value of syncOffsetIndicator-v1 through pre-configuration. G-SFN represents the current system frame number determined by the UE based on GNSS timing. At this time, the SSSS index value used by the VUE should be 168, and the inCoverage domain is set to FALSE.

[0290] Frequency domain characteristics:

[0291] The frequency domain position of sending SLSS is located at n PRBs in the center of the current carrier, where n is a specified value defined by the standard, for example, n=6.

[0292] By using the method of the fifth embodiment, the direct mutual interference between the controlled VUE with GNSS as the synchronization source and the autonomous VUE with GNSS as the synchronization source can be avoided, and the interference between the VUE with VUE1 as the synchronization source and the VUE with autonomous VUE2 as the synchronization source can be avoided.

[0293] Corresponding to the above method, the present invention also discloses a V2X terminal time-frequency synchronization transmission processing device. Figure 3 A schematic diagram of a composition of a sending processing device for time-frequency synchronization of the V2X terminal, the sending processing device comprising:

[0294] The reuse synchronization transmission module 301 is used to reuse the time-frequency resources configured in the cell for transmitting the synchronization signal of the D2D terminal to transmit the synchronization signal when the synchronization signal to be transmitted by the V2X terminal is the same as the synchronization signal of the existing device-to-device D2D terminal;

[0295] The reconfiguration synchronization transmission module 302 is used to use the reconfigured time-frequency resources to send the synchronization signal when the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal. In a preferred embodiment, when the synchronization signal to be sent by the V2X terminal is different from the synchronization signal of the existing D2D terminal, the SLSS sequence in the synchronization signal is different from the synchronization signal of the existing D2D terminal;

[0296] Among them, in the synchronization signal sent by the V2X terminal, the corresponding synchronization source type is indicated by the value of the SLSS sequence index and / or the PSBCH specified field.

[0297] Corresponding to the above method, the present invention also discloses a receiving and processing device for V2X terminal time-frequency synchronization, such as Figure 4 A schematic diagram of a composition of a receiving and processing device for time-frequency synchronization of the V2X terminal; the receiving and processing device includes:

[0298] The detection and judgment module 401 is used to detect the synchronization signal and determine the corresponding synchronization source type according to the value of the SLSS sequence index and / or the PSBCH specified field in the detected synchronization signal;

[0299] The selection module 402 is used to select the synchronization source type with the highest priority as a reference synchronization source from the synchronization source types determined by the detection and judgment module according to the specified synchronization source priority.

[0300] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0301] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0302] In addition, each embodiment of the present invention can be implemented by a data processing program executed by a data processing device such as a computer. Obviously, the data processing program constitutes the present invention. In addition, the data processing program usually stored in a storage medium is executed by directly reading the program out of the storage medium or by installing or copying the program to a storage device (such as a hard disk and / or memory) of the data processing device. Therefore, such a storage medium also constitutes the present invention. The storage medium can use any type of recording method, such as paper storage media (such as paper tape, etc.), magnetic storage media (such as floppy disks, hard disks, flash memory, etc.), optical storage media (such as CD-ROM, etc.), magneto-optical storage media (such as MO, etc.), etc.

[0303] Therefore, the present invention also discloses a storage medium, in which a data processing program is stored. The data processing program is used to execute any one of the embodiments of the above method of the present invention.

[0304] In addition, the method steps described in the present invention can be implemented by hardware in addition to data processing programs, for example, by logic gates, switches, application specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers, etc. Therefore, such hardware that can implement the method described in the present invention can also constitute the present invention.

[0305] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method performed by a terminal in a wireless communication system, the method include: determining configuration information for V2X communication, the configuration information comprising information indicating a priority associated with a synchronization source; determining whether the information is set to a global navigation satellite system GNSS or a base station; as well as If the information is set to GNSS and there is no reliable GNSS, selecting a synchronization reference from a plurality of synchronization signals detected by the terminal based on a priority order, The priority order includes: The priority of at least one first terminal synchronized to the GNSS is higher than the priority of the base station, The at least one first terminal includes a terminal using GNSS as a reference synchronization source, and / or a terminal using a third terminal as a reference synchronization source and being out of coverage, wherein the third terminal uses GNSS as a reference synchronization source.

2. The method according to claim 1, in, The priority of a terminal within the coverage area among the at least one first terminal is higher than the priority of a terminal outside the coverage area among the at least one first terminal.

3. The method according to claim 1, in, If the information is set to GNSS and there is a reliable GNSS, the reliable GNSS is selected as the reference synchronization source.

4. The method according to claim 1, in, The base station can be detected by the terminal as a synchronization reference.

5. The method of claim 1, wherein if the information is set as a base station, the priority order for selecting a synchronization reference is based on the following: At least one second terminal directly synchronized to the base station has a first priority; At least one second terminal indirectly synchronized to the base station has a second priority; GNSS has the third priority; At least one first terminal directly synchronized to the GNSS has a fourth priority; At least one first terminal indirectly synchronized to the GNSS has a fifth priority; and Other terminals have the sixth priority.

6. The method according to claim 5, in, At least one first terminal directly synchronized to the GNSS and within the coverage has a fourth priority.

7. The method according to claim 5, in, At least one first terminal directly synchronized to the GNSS and out of coverage has a fifth priority.

8. The method according to any one of claims 5 to 7, in, The priority of a terminal within the coverage area among the at least one second terminal is higher than the priority of a terminal outside the coverage area among the at least one second terminal.

9. A terminal in a wireless communication system, the terminal include: Transceiver; and The controller is configured as: determining configuration information for V2X communication, the configuration information comprising information indicating a priority associated with a synchronization source; determining whether the information is set to a global navigation satellite system GNSS or a base station; as well as If the information is set to GNSS and there is no reliable GNSS, selecting a synchronization reference from a plurality of synchronization signals detected by the terminal based on a priority order, The priority order includes: The priority of at least one first terminal synchronized to the GNSS is higher than the priority of the base station, The at least one first terminal includes a terminal using GNSS as a reference synchronization source, and / or a terminal using a third terminal as a reference synchronization source and being out of coverage, wherein the third terminal uses GNSS as a reference synchronization source.

10. The terminal according to claim 9, in, The priority of a terminal within the coverage area among the at least one first terminal is higher than the priority of a terminal outside the coverage area among the at least one first terminal.

11. The terminal according to claim 9, in, If the information is set to GNSS and there is a reliable GNSS, the reliable GNSS is selected as the reference synchronization source.

12. The terminal according to claim 9, in, The base station can be detected by the terminal as a synchronization reference.

13. The terminal according to claim 9, if the information is set as a base station, the priority order for selecting a synchronization reference is based on the following: At least one second terminal directly synchronized to the base station has a first priority; At least one second terminal indirectly synchronized to the base station has a second priority; GNSS has the third priority; At least one first terminal directly synchronized to the GNSS has a fourth priority; At least one first terminal indirectly synchronized to the GNSS has a fifth priority; and Other terminals have the sixth priority.

14. The terminal according to claim 13, in, At least one first terminal directly synchronized to the GNSS and within the coverage has a fourth priority.

15. The terminal according to claim 13, in, At least one first terminal directly synchronized to the GNSS and out of coverage has a fifth priority.

16. The terminal according to any one of claims 13 to 15, in, The priority of a terminal within the coverage area among the at least one second terminal is higher than the priority of a terminal outside the coverage area among the at least one second terminal.

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