CN109586879B

CN109586879B - Method and equipment for selecting synchronous source of multi-carrier bypass communication

Info

Publication number: CN109586879B
Application number: CN201810438003.1A
Authority: CN
Inventors: 张世昌; 李迎阳; 王轶
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2017-09-28
Filing date: 2018-05-09
Publication date: 2023-06-20
Anticipated expiration: 2038-05-09
Also published as: EP3689053A4; KR102617246B1; CN109586879A; KR20200049889A; EP3689053A1

Abstract

The invention discloses a method for selecting a synchronous source of multi-carrier bypass communication, which comprises the following steps: selecting a synchronization source according to the states of User Equipment (UE) on a plurality of carriers; the selected synchronization source is used as a reference synchronization source for the UE on all carriers. Compared with the prior art, the method and the device for detecting the synchronous source based on the cell coverage attribute of the equipment have the advantages that the priority order is determined according to the cell coverage attribute of the equipment based on the carrier set, and the strategy is adopted on each carrier to detect and acquire the synchronous source, so that the same equipment can refer to the same synchronous source on all carriers in the carrier set to realize time synchronization, the influence caused by in-band interference and half duplex limitation is obviously reduced, and the communication efficiency and the transmission performance of a bypass communication system are effectively improved.

Description

Method and equipment for selecting synchronous source of multi-carrier bypass communication

Technical Field

The present invention relates to the field of wireless communications technologies, and in particular, to a method and apparatus for selecting a synchronization source for multi-carrier bypass communication.

Background

In the 3GPP standard, a direct communication link between UEs (User equipment) is called bypass (sidlink). Similar to the uplink and downlink, there are control channels and data channels on the bypass, the former being called PSCCH (Physical Sidelink Control Channel, bypass control channel) and the latter being called PSSCH (Physical Sidelink Shared Channel, bypass data channel). The PSCCH is used to indicate a time-frequency domain resource location of PSSCH transmission, a modulation coding scheme, a priority of data carried in the PSSCH, and the like, and the PSSCH is used to carry data. In the current 3GPP standard, bypass communications include D2D (device-to-device direct communication) and V2X (vehicle-to-outside communication).

For UEs participating in bypass communication, when certain conditions are met, SLSS (Sidelink Synchronization Signal, bypass synchronization signal) needs to be sent on synchronization resources configured by the cell or preconfigured by the UE to provide a synchronization signal source at the subframe level for other UEs. Meanwhile, for a UE performing bypass communication on a certain carrier, a corresponding reference synchronization source needs to be selected according to the state in which it is currently located.

In order to increase the system data transmission rate and system capacity, bypass carrier aggregation techniques are required to allow the UE to transmit V2X data on multiple carriers. In the bypass carrier aggregation, each V2X service may correspond to one or more carriers therein, and the UE access layer determines a correspondence between the service and the carrier according to information provided by a UE higher layer. When the bypass carrier aggregation technology is adopted, a plurality of bypass carriers may belong to the same frequency band, in-band interference (In-band transmission) exists between the plurality of bypass carriers, and if a sufficient interval does not exist between the plurality of carriers belonging to the same frequency band, the UE cannot simultaneously perform transmission and reception operations on the plurality of carriers at the same time, that is, half duplex limitation exists between the plurality of carriers. Therefore, bypass carrier aggregation requires alignment of sub-frame boundaries of multiple carriers belonging to the same frequency band, thereby reducing the effects of in-band interference and half-duplex limitation.

In existing V2X systems, the selection of the reference synchronization source is performed independently on each V2X communication carrier, and in the case where there are multiple carriers, existing synchronization mechanisms cannot guarantee time synchronization between the multiple carriers. In view of the foregoing, it is desirable to provide a method and apparatus for selecting a synchronization source for multi-carrier bypass communication that can solve the above-mentioned problems.

Disclosure of Invention

The invention aims at: the method and the equipment for selecting the multi-carrier bypass communication synchronous source can effectively improve the transmission performance of the bypass communication system.

In order to achieve the above object, the present invention provides a method for selecting a synchronization source for a multi-carrier bypass communication, comprising the steps of:

selecting a synchronization source according to the states of User Equipment (UE) on a plurality of carriers;

the selected synchronization source is used as a reference synchronization source for the UE on all carriers.

Preferably, determining the cell coverage attribute of the UE on all carriers according to the cell coverage states of the UE on a plurality of carriers;

and selecting a synchronization source according to the cell coverage attribute of the UE on all carriers.

Preferably, the selecting a synchronization source according to the status of the UE on a plurality of carriers includes:

Determining the priority order of the synchronization sources according to the states of the UE on a plurality of carriers;

and selecting one synchronous source according to the priority order.

Preferably, determining the priority order of the synchronization sources according to the states of the UE on the plurality of carriers includes:

determining the cell coverage attribute of the UE on all carriers according to the cell coverage states of the UE on a plurality of carriers;

and determining the priority order of the synchronization sources according to the cell coverage attribute of the UE on all carriers.

Preferably, the determining the cell coverage attribute of the UE on all carriers according to the cell coverage states of the UE on the multiple carriers includes:

if one carrier exists in the plurality of carriers, the UE is in the cell coverage area on the carrier, and the cell coverage attribute of the UE on all the carriers is determined to be cell full coverage user equipment ICUE;

if the UE is out of the coverage area of the cell on all the carriers and the available carrier list v2x-InterFreqInfoList of the vehicle-to-outside communication in the system message or the RRC reconfiguration message is received by the UE and contains at least one carrier in all the carriers, determining that the coverage attribute of the cell of the UE on all the carriers is cell partial coverage user equipment PCUE;

otherwise, determining that the cell coverage attribute of the UE on all carriers is the cell coverage-free user equipment OCUE.

and determining the priority order of the UE to select the synchronization source according to the states of the UE on the plurality of carriers, the preferable types of the synchronization sources of the UE on all the carriers and the signal strength of the synchronization sources.

Preferably, the determining the priority order of the synchronization sources according to the states of the UE on the plurality of carriers includes:

determining the cell coverage attribute of the UE on all carriers according to the states of the UE on a plurality of carriers;

determining a synchronization source optimization type of the UE on all carriers according to the cell coverage attribute of the UE on all carriers;

and determining the priority order of the UE to select the synchronization source according to the cell coverage attribute of the UE on all the carriers and the synchronization source preference type of the UE on all the carriers or according to the cell coverage attribute of the UE on all the carriers, the synchronization source preference type of the UE on all the carriers and the synchronization source signal strength.

Preferably, the determining the preferred type of the synchronization source of the UE on all carriers according to the cell coverage attribute of the UE on all carriers includes:

if the cell coverage attribute of the UE on all the carriers is cell full coverage user equipment ICUE, determining that the preferred type of the synchronization source of the UE on all the carriers is the same as that of the carrier X, wherein the cell coverage state of the UE on the carrier X is ICUE;

If the cell coverage attribute of the UE on all the carriers is cell Partial Coverage User Equipment (PCUE), determining that the preferable type of the synchronization source of the UE on all the carriers is the same as that of the carrier Y, wherein the cell coverage state of the UE on the carrier Y is PCUE, the priority of the carrier Y is highest or the index value is minimum, and the priority of the carrier Y is indicated by a high layer;

if the cell coverage attribute of the UE on all carriers is no cell coverage user equipment ocu, determining that the preferred type of the synchronization source of the UE on all carriers is the same as carrier Z, wherein the priority of carrier Z is highest or the index value is smallest, and the priority of carrier Z is indicated by a higher layer.

Preferably, the determining the priority order of the UE selecting the synchronization source according to the cell coverage attribute of the UE on all carriers and the synchronization source preference type of the UE on all carriers includes: recording all carriers as a carrier set G;

if the cell coverage attribute of the first UE is ICUE in the carrier set G, the preferred type of the synchronization source of the first UE is a base station, and it is determined that the priority order of the first UE selection synchronization source is that the primary carrier of the first UE cell coverage state in the carrier set G is ICUE, the secondary carrier of the first UE cell coverage state in the carrier set G is ICUE, and other carriers of the first UE cell coverage state in the carrier set G are sequentially arranged from high to low; or (b)

If the cell coverage attribute of the first UE is ICUE on the carrier set G, the preferred type of the synchronization source of the first UE is GNSS, it is determined that the priority order of the synchronization source selected by the first UE is GNSS, the second UE sends a bypass synchronization signal SLSS on the carrier in the carrier set G, and the bypass synchronization signal sequence slssid=0, and the base stations are sequentially arranged from high to low; or (b)

If the cell coverage attribute of the first UE is PCUE on the carrier set G, the preferred type of the synchronization source of the first UE is GNSS, it is determined that the priority order of the synchronization source selected by the first UE is GNSS, the second UE transmitting SLSS on the carrier in the carrier set G and slssid=0, and the base stations are sequentially arranged from high to low; or (b)

If the cell coverage attribute of the first UE is ocu on the carrier set G, the preferred type of the synchronization source of the first UE is a base station, determining that the priority order of the first UE for selecting the synchronization source is that the second UE, GNSS, which sends SLSS on the carrier in the carrier set G and slssid=0, sends SLSS on the carrier in the carrier set G and sends SLSS on the carrier in the carrier set G, and other second UEs are sequentially arranged from high to low; or (b)

If the cell coverage attribute of the first UE is ocus on the carrier set G, the preferred type of the synchronization source of the first UE is GNSS, it is determined that the priority order of the first UE selection synchronization source is GNSS, a second UE transmitting a bypass broadcast channel PSBCH on the carrier in the carrier set G and having a coverage status indication field index of TRUE, or a second UE transmitting SLSS on the carrier in the carrier set G and a subframe indicated by a pre-configured parameter 3 rd synchronization signal transmission subframe offset sync indicator3, a second UE transmitting a PSBCH on the carrier in the carrier set G and having an index field index of FALSE, and other second UEs transmitting SLSS on the carrier in the carrier set G are sequentially arranged from high to low;

The first set is a set of SLSSIDs providing SLSSID selection when sending SLSS for UEs within cell coverage.

Preferably, the determining the priority order of the UE selecting the synchronization source according to the cell coverage attribute of the UE on all carriers and the synchronization source preference type of the UE on all carriers includes: recording all carriers as a carrier set G, if the cell coverage attribute of the first UE is ICUE on the carrier set G, the preferred type of the synchronization source of the first UE is GNSS, and determining that the priority order of the synchronization source selection of the first UE is that the following items are orderly arranged from high to low:

GNSS；

a second UE transmitting SLSS and slssid=0 on a carrier in carrier set G, or a second UE transmitting SLSS and slssid=0 on a carrier a in carrier set G, a second UE transmitting SLSS and slssid=0 on a carrier a, or a second UE transmitting SLSS and slssid=0 on a carrier a in carrier set G, a cell coverage attribute of the first UE being ICUE or PCUE, a priority indicated by a higher layer of carrier a being highest;

reference cells.

Preferably, the determining the priority order of the UE selecting the synchronization source according to the cell coverage attribute of the UE on all carriers and the synchronization source preference type of the UE on all carriers includes: recording all carriers as a carrier set G, if the cell coverage attribute of the first UE is PCUE on the carrier set G, the preferred type of the synchronization source of the first UE is GNSS, and determining that the priority order of the first UE for selecting the synchronization source is that the following items are orderly arranged from high to low:

GNSS；

A second UE transmitting SLSS and slssid=0 on a carrier in carrier set G, or a second UE transmitting SLSS and slssid=0 on a carrier a in carrier set G, wherein a cell coverage attribute of a first UE on carrier a is PCUE, or a second UE transmitting SLSS and slssid=0 on carrier a in carrier set G, wherein a cell coverage attribute of a first UE on carrier a is PCUE, a priority indicated by a higher layer is highest;

reference cells.

Preferably, the determining the priority order of the UE selecting the synchronization source according to the cell coverage attribute of the UE on all carriers and the synchronization source preference type of the UE on all carriers includes: recording all carriers as a carrier set G, if the cell coverage attribute of the first UE is OCUE on the carrier set G, the preferred type of the synchronization source of the first UE is a base station, and determining that the priority order of the first UE for selecting the synchronization source is that the following items are orderly arranged from high to low:

a second UE that sends SLSS and SLSSID as a first set on carrier a in carrier set G, sends PSBCH and index threshold of PSBCH as TRUE on carrier a;

a second UE which sends SLSS on carrier A in carrier set G, sends PSBCH on carrier A, and has a PSBCH index threshold value of FALSE, wherein SLSSID is the first set;

GNSS；

A second UE that sends SLSS and slssid=0 on carrier a in carrier set G, sends PSBCH on carrier a with an inCoverage threshold of TRUE, or sends SLSS and slssid=0 on carrier a in carrier set G and on a subframe indicated by a preconfigured parameter syncOffsetIndicator 3;

a second UE that sends SLSS and slssid=0 on carrier a in carrier set G and on a subframe indicated by a 1 st synchronization signal sending subframe offset syncOffsetIndicator1 or a 2 nd synchronization signal sending subframe offset syncOffsetIndicator2 of a preconfigured parameter, sends PSBCH on carrier a and has an inCoverage threshold value of FALSE;

other second UEs transmitting SLSS on carriers in carrier set G;

Preferably, the determining the priority order of the UE selecting the synchronization source according to the cell coverage attribute of the UE on all carriers and the synchronization source preference type of the UE on all carriers includes: recording all carriers as a carrier set G, if the cell coverage attribute of the first UE is OCUE on the carrier set G, the preferred type of the synchronization source of the first UE is GNSS, and determining that the priority order of the synchronization source selection of the first UE is that the following items are orderly arranged from high to low:

GNSS；

A second UE that sends SLSS on carrier a in carrier set G, SLSSID as a first set or slssid=0, PSBCH on carrier a and the inCoverage threshold of PSBCH is TRUE, or a second UE that sends SLSS on carrier a in carrier set G and on a subframe indicated by a preconfigured parameter syncOffsetIndicator3 and slssid=0;

a second UE that transmits SLSS and SLSSID as a first set on carrier a in carrier set G, transmits PSBCH and inCoverage threshold of PSBCH as FALSE on carrier a, or transmits SLSS and slssid=0 on carrier a and sub-frame indicated by preconfigured parameter syncOffsetIndicator1 or syncOffsetIndicator2, transmits SLSS and inCoverage threshold of PSBCH as FALSE on carrier a, or transmits slssid=169 on carrier a in carrier set G, transmits PSBCH and inCoverage threshold of PSBCH as FALSE on carrier a;

other second UEs transmitting SLSS on carriers in carrier set G;

Preferably, the selecting a synchronization source according to the priority order includes: and detecting SLSS signals in all SLSSID ranges on all carriers, or detecting SLSS signals in all SLSSID ranges on the carrier with the highest corresponding service priority or the smallest index, or detecting SLSS signals in all SLSSID ranges on the carrier corresponding to the service which is needed to be received to the UE, and selecting a synchronous source according to the priority order, wherein the priority of the service corresponding to the carrier is indicated by a high layer.

Preferably, the selecting a synchronization source according to the priority order includes: and selecting the detected synchronization source with the highest priority according to the priority sequence, and selecting the UE type synchronization source corresponding to the SLSS with the largest S-RSRP value if a plurality of the detected UE type synchronization sources with the highest priority exist.

Preferably, the selecting a synchronization source according to the priority order includes: and selecting the detected synchronization source with the highest priority according to the priority sequence, and if a plurality of the detected UE type synchronization sources with the highest priority exist, selecting the UE type synchronization source with the highest S-RSRP intensity or selecting the UE type synchronization source with the highest S-RSRP intensity on the carrier with the highest corresponding service priority, wherein the priority of the carrier corresponding to the service is indicated by a high layer.

In order to achieve the above object, the present invention also provides a user equipment, including:

a synchronous source selecting module for selecting a synchronous source according to the states of the User Equipment (UE) on a plurality of carriers;

and applying a synchronization source module to use the selected synchronization source as a reference synchronization source of the UE on all carriers.

Compared with the prior art, the technical effects of the invention include but are not limited to: according to the state of the device on a plurality of carriers, a synchronization source is selected, and the strategy is adopted on each carrier to detect and acquire the synchronization source, so that the same device can refer to the same synchronization source on all carriers in a carrier set to realize time synchronization, the influence caused by in-band interference and half duplex limitation is obviously reduced, and the communication efficiency and transmission performance of a bypass communication system are effectively improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a flow chart of a method of selecting a synchronization source for a multi-carrier bypass communication in accordance with the present invention;

fig. 2 is a block diagram of a multi-carrier bypass communication synchronization source selection device of the present invention.

Detailed Description

Embodiments of the present disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for the purpose of illustrating the present disclosure and are not to be construed as limiting the present disclosure.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. The term "and/or" as used herein includes all or any element and all combination of one or more of the associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As used herein, a "terminal" or "terminal device" includes both a device of a wireless signal receiver having no transmitting capability and a device of receiving and transmitting hardware having receiving and transmitting hardware capable of bi-directional communication over a bi-directional communication link, as will be appreciated by those skilled in the art. Such a device may include: a cellular or other communication device having a single-line display or a multi-line display or a cellular or other communication device without a multi-line display; a PCS (PerSonal CommunicationS Service, personal communication system) that may combine voice, data processing, facsimile and/or data communication capabilities; a PDA (PerSonal Digital ASSiStant ) that can include a radio frequency receiver, pager, internet/intranet access, web browser, notepad, calendar and/or GPS (Global PoSitioning SyStem ) receiver; a conventional laptop and/or palmtop computer or other appliance that has and/or includes a radio frequency receiver. As used herein, "terminal," "terminal device" may be portable, transportable, installed in a vehicle (aeronautical, maritime, and/or land-based), or adapted and/or configured to operate locally and/or in a distributed fashion, to operate at any other location(s) on earth and/or in space. The "terminal" and "terminal device" used herein may also be a communication terminal, a network access terminal, and a music/video playing terminal, for example, may be a PDA, a MID (Mobile Internet Device ), and/or a mobile phone with a music/video playing function, and may also be a smart tv, a set top box, and other devices.

In the disclosed bypass communication system technology, for UEs participating in bypass communication, in order to achieve synchronization at subframe level between different UEs, the UEs satisfy certain conditions, such as: upon receiving a specific signaling indication from a base station (eNB), or when it is located at the cell edge, or outside the cell Coverage (In Coverage) and using GNSS (Global Navigation Satellite System ) as a reference synchronization source, the UE needs to send an SLSS (Sidelink Synchronization Signal, bypass synchronization signal) on a synchronization resource configured by the cell or preconfigured by the UE, where the SLSS includes a PSSS (Primary Sidelink Synchronization Signal, primary bypass synchronization signal) and a SSSS (Secondary Sidelink Synchronization Signal, secondary bypass synchronization signal), the PSSS employs a root sequence with length 62 or a ZC (Zadoff-Chu) sequence with indexes 26 and 37, and the SSSS is composed of two m sequences with length 31, and the two m sequences are uniquely determined by indexes corresponding to the SSSS.

Within the SLSS transmission subframe, the SLSS occupies 4 frequency division multiple access SC-FDMA symbols in the subframe, and the remaining SC-FDMA symbols, except for the first and last SC-FDMA symbols, will be used for transmission of PSBCH (bypass broadcast channel) and its demodulation reference signals. Wherein the PSBCH is used for carrying information such as a side subframe number, a system bandwidth, a cell TDD configuration, a synchronization source state and the like.

Meanwhile, for a UE performing bypass communication on a certain carrier, a corresponding reference synchronization source needs to be selected according to the state in which it is currently located. Specifically, in D2D communication, if the UE is under coverage of a cell on a carrier currently performing bypass communication, the UE selects the cell as a reference synchronization source, that is, obtains time-frequency synchronization information through a primary synchronization signal, a secondary synchronization signal and a system message of the cell. If the UE is out of coverage of the cell on the carrier currently performing bypass communication, the UE searches SLSSs transmitted by other UEs on the current carrier, selects the UE capable of transmitting the SLSSs with the highest detected priority as a reference synchronization source, and if a plurality of UEs with the highest priority exist, preferentially selects the UE with the highest demodulation reference signal receiving power (S-RSRP, sidelnk-Reference Signal Receiving Power) of the transmitted PSBCH.

In V2X communication, if the UE is in the Cell coverage (hereinafter, the UE in the Cell coverage will be referred to as an iceue) on the carrier currently performing bypass communication, or the carrier currently performing bypass communication is included in V2X-interfacinfolist (hereinafter, the UE in the above state will be referred to as a PCUE, and UEs other than the iceue and the PCUE will be collectively referred to as an oce) of a system message 21 (SystemInformationBlockType 21) or an RRC reconfiguration message (RRCConnectionReconfiguration) transmitted from a Serving Cell or a Primary Cell (Primary Cell):

If the carrier is the preferred reference synchronization source for the base station (i.e., typeTxSync for the carrier is configured as eNB or gNB), the UE selects one cell as the reference synchronization source;

if the carrier reference synchronization source is of a preferred type GNSS (i.e. typeTxSync for the carrier is configured as GNSS), the UE selects GNSS as the reference synchronization source if the UE is able to detect reliable GNSS signals; otherwise (the UE cannot detect a reliable GNSS signal), the UE detects an SLSS with slssid=0 on the carrier, and if an SLSS with strength meeting the requirement can be detected, the UE that sends the SLSS is selected as a reference synchronization source; if the UE detects neither reliable GNSS signals nor reliable SLSS with slss=0, the UE selects a cell as a reference synchronization source.

Further, in V2X communication, if the carrier on which the UE is currently performing bypass communication is out of cell coverage and the preferred type of carrier reference synchronization source is GNSS (i.e., the synchronization priority for the carrier is configured as GNSS in the pre-configuration of the UE), the UE selects GNSS as the reference synchronization source.

Furthermore, in existing V2X communication (refer to V2X communication defined in 3GPP release 14, hereinafter, the same), if the UE is out of cell coverage on the carrier currently performing bypass communication, the UE detects all possible SLSSIDs on the current carrier. If the UE has selected another UE as the reference synchronization source at this time, when the UE detects a new UE with higher S-RSRP or the UE can detect a reliable GNSS and the GNSS has a higher priority than the current reference synchronization source UE, the UE considers that any UE is not selected as the reference synchronization source at present; if the UE has selected GNSS as the reference synchronization source at this time, the UE considers that GNSS is not currently selected as the reference synchronization source when the UE detects a UE whose S-RSRP strength satisfies the requirement and whose priority is higher than GNSS or a reliable GNSS is not detected.

For UEs that do not select any UE as a reference synchronization source and that do not select GNSS as a reference synchronization source, if one or more reference synchronization source UEs that meet the strength requirements can be detected, or reliable GNSS signals can be detected, if the current carrier prefers to use eNB as a reference synchronization source, the UEs select synchronization sources in the following priority order:

first priority: the SLSSID belongs to the first set and the value of the inCoverage field in PSBCH is TRUE. Wherein the first set is a set of SLSSIDs from which SLSSIDs can be selected for UE within the coverage of the cell. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Second priority: the SLSSID belongs to the first set and the value of the inCoverage field in the PSBCH is FALSE. Wherein the first set is a set of SLSSIDs from which SLSSIDs can be selected for UE within the coverage of the cell. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Third priority: and (5) GNSS.

Fourth priority: slssid=0, and the value of the inCoverage field in PSBCH is TRUE UE; alternatively, slssid=0, and the UE of the SLSS is transmitted in a subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Fifth priority: slssid=0, the value of the inCoverage field in psbch is FALSE, and the UE of the SLSS is transmitted in the subframe indicated by the preconfigured parameter syncOffsetIndicator1 or syncOffsetIndicator 2. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Sixth priority: other types of reference synchronization source UEs. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

For UEs that do not select any UE as a reference synchronization source and that do not select GNSS as a reference synchronization source, if one or more reference synchronization source UEs that are strength-compliant or reliable GNSS signals can be detected, if the current carrier prefers GNSS as the reference synchronization source, the UE selects the synchronization source in the following priority order:

first priority: and (5) GNSS.

Second priority: the SLSSID belongs to a first set, and the value of an index domain in PSBCH is the UE of TRUE, wherein the first set is the SLSSID set from which SLSSID can be selected for UE in the coverage area of a cell to send SLSSS; alternatively, slssid=0, and the value of the inCoverage field in PSBCH is TRUE UE; alternatively, slssid=0, and the UE of the SLSS is transmitted in a subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Third priority: the SLSSID belongs to a first set, and the value of an inCoverage domain in the PSBCH is FALSE; or, slssid=0, the value of the inCoverage field in the psbch is FALSE, and the UE of the SLSS is sent in the subframe indicated by the preconfigured parameter syncOffsetIndicator1 or syncOffsetIndicator 2; alternatively, slssid=169, and the value of the inCoverage field in psbch is FALSE. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Fourth priority: other types of reference synchronization source UEs. If there are a plurality of UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

As can be seen from the above description, in the existing V2X system, for a UE performing V2X communication on a certain carrier, the manner of selecting a synchronization source is related to the state of the UE on the current carrier, for example, the UE is an ICUE, a PCUE or an oce on the current carrier, the UE preferentially uses a GNSS as the synchronization source or an eNB as the synchronization source on the current carrier, and the signal strength of the synchronization source that the UE has selected on the current carrier.

The method and the device for selecting the synchronous source of the multi-carrier bypass communication can be applied to time synchronization between different terminals in a multi-carrier bypass communication system, and particularly can be applied to the process of selecting and reselecting the synchronous source of a V2X system.

Referring to fig. 1, the method for selecting a synchronization source for a multi-carrier bypass communication of the present disclosure includes the following steps:

step 101, selecting a synchronization source according to the states of User Equipment (UE) on a plurality of carriers;

step 102, use the selected synchronization source as a reference synchronization source for the UE on all carriers.

For example, the method of the present disclosure may be broken down into the following steps:

step 201 (not labeled in the figure) determines the cell coverage attribute of the UE based on the carrier set G.

The UE determines the carrier set G according to its own pre-configuration information, specific rules, or received configuration information sent by the base station, for example, the carrier set G may be composed of a plurality of carriers belonging to the same frequency band and usable for bypass communication. The number of carriers in the carrier set G is not greater than the total number of carriers available for bypass communication, either configured by the base station or preconfigured by the UE. If the UE determines the carrier set G through the pre-configuration, preferably, the positions and the number of the subframes pre-configured on each carrier of the carrier set G for transmitting the SLSS and the PSBCH are the same.

The reference synchronization source preference type may be the same for all carriers in carrier set G. That is, if the UE determines the carrier set G by receiving configuration information of the base station, a value for each carrier typeTxSync in the carrier set G may be the same in the configuration information, or for all carriers in the carrier set G may correspond to the same typeTxSync configuration parameter. If the first UE determines the carrier set G through the pre-configuration information, the value of each carrier synchronization priority in the pre-configuration information may be the same for the carrier set G, or the value of each carrier synchronization priority in the pre-configuration information may correspond to the same synchronization priority configuration parameter for all carriers in the carrier set G. If the first UE determines the carrier set G according to a specific rule, for example, consider carriers belonging to the same frequency band as the carrier set G, the first UE may consider that the values of typeTxSync or synchronization of all carriers in the carrier set G are the same as the typeTxSync or synchronization of one carrier in the carrier set G.

In the carrier set G, each carrier corresponds to a unique carrier index, and the index value may be equal to the order in which the carriers occur in the configuration signaling or the pre-configuration signaling.

Step 202 (not labeled in the figure) determines a synchronization source preference type of the UE based on the carrier set G according to the cell coverage attribute.

Step 203 (not labeled in the figure), determining the priority order of the UE selecting the synchronization source according to the cell coverage attribute and the synchronization source preference type.

Step 204 (not labeled in the figure) selects a synchronization source for the UE according to the priority order.

After determining the reference synchronization source of the UE on the carrier set G, all carriers in the carrier set G determine a subframe boundary according to the reference synchronization source, and may further determine a bypass system frame number (DFN, direct Frame Number) and a subframe number according to the reference synchronization source.

In order to facilitate understanding of the disclosure, the foregoing technical solutions of the disclosure are further described below in terms of modes of interaction between devices by means of several embodiments in connection with specific application cases, which are specifically described below.

Example 1

In this embodiment, the first UE determines, according to the status on each carrier in the carrier set G, whether the cell coverage attribute currently based on the carrier set G, i.e. belongs to the ICUE, the PCUE or the ocu in the carrier set G. Specifically, if there is such a carrier in the carrier set G on which the first UE is within the coverage of the cell, the first UE belongs to the ICUE in the carrier set G; if the first UE is out of the coverage area of the cell on any carrier in the carrier set G, and the v2x-inter freqlnfo list in the system message 21 or RRC reconfiguration message sent by the serving cell or the primary cell and received by the first UE includes at least one carrier in the carrier set G, the first UE belongs to the PCUE in the carrier set G; otherwise, the first UE belongs to the ocu in the carrier set G.

If the first UE belongs to the ICUE on the carrier set G, the preferred type of the synchronization source of the first UE on all carriers in the carrier set G is the same as the configuration of the carrier X in the carrier set G, where the carrier X satisfies: the first UE is an ICUE on carrier X. If the first UE belongs to the PCUE on the carrier set G, the preferred type of the synchronization source of the first UE on all carriers in the carrier set G is the same as the configuration of the carrier Y in the carrier set G, where the carrier Y satisfies: the first UE is a PCUE on carrier Y; if the first UE belongs to the PCUE on a plurality of carriers in the carrier set G, the carrier Y is the carrier with the highest priority or the smallest index value of the corresponding services in the carriers, where the priority of the corresponding services of the carrier is indicated by the UE higher layer (relative to the access layer). If the first UE belongs to the ocu on the carrier set G, the preferred type of the synchronization source of the first UE on all carriers in the carrier set G is the same as the configuration of the carrier Z in the carrier set G, where the carrier Z satisfies: the carrier with the highest priority or the lowest index value, wherein the priority of the carrier corresponding to the traffic is indicated by the UE higher layer (relative to the access layer).

If the first UE is an ICUE on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is a base station, the first UE selects one reference cell as a reference synchronization source for all carriers on the carrier set G.

According to one implementation of this embodiment, the first UE selects the reference cell as follows:

if there is a primary carrier in carrier set G (Primary frequency) and the first UE is an ICUE on the primary carrier, the primary carrier cell is selected as the reference cell.

If there is no primary carrier in the carrier set G, or the first UE is PCUE or oce on the primary carrier contained in the carrier set G, however, the carrier set G contains one or more secondary carriers (Secondary frequency), and the first UE is icen on the one or more secondary carriers, then the secondary carrier cell with the highest RSRP or priority is selected as the reference cell.

If the carrier set G contains neither the primary carrier nor the secondary carrier, or neither the primary carrier nor the secondary carrier in the carrier set G is the icle, but the UE belongs to the icle in one or more other carriers in the carrier set G, the first UE selects the cell corresponding to the carrier with the strongest RSRP or highest priority from the carriers as the reference cell.

Preferably, in this embodiment, if the first UE uses the cell corresponding to the carrier a as the reference cell of the carrier B, and the first UE is an ICUE on both the carrier a and the carrier B, where a is not equal to B, the first UE determines the subframe boundary of the carrier B only according to the carrier a, and performs downlink measurement on the carrier a and the carrier B respectively.

According to another implementation of this embodiment, the first UE selects the reference cell as follows:

if the first UE belongs to the ICUE on one or more carriers in the carrier set G, the first UE selects a cell corresponding to the carrier with the highest corresponding service priority as a reference cell, or the first UE selects a cell corresponding to the carrier with the highest RSRP as a reference cell.

Example two

As another possible implementation of the disclosure, on the basis of the first embodiment, if the first UE is an ICUE on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is a GNSS, the first UE selects the GNSS as the reference synchronization source of all carriers in the carrier set G if the first UE can detect reliable GNSS signals.

If the first UE cannot detect a reliable GNSS signal, the first UE selects a second UE with ID 0 of a transmitted SLSS as a reference synchronization source for all carriers in the carrier set G. Then, according to an implementation manner of this embodiment, the first UE detects SLSS with slssid=0 on all carriers in the carrier set G, and if SLSS with slssid=0 that the S-RSRP strength meets the requirement can be detected, the first UE selects the second UE that sends the SLSS as a reference synchronization source for all carriers in the carrier set G. Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect SLSS with the S-RSRP strength satisfying the slssid=0 on all carriers in the carrier set G, the first UE selects a reference cell as a reference synchronization source of all carriers in the carrier set G, where the manner of selecting the reference cell by the first UE is the same as in the first embodiment.

If the first UE cannot detect a reliable GNSS signal, according to another implementation manner of this embodiment, the first UE detects an SLSS with an slssid=0 on a part of carriers of the carrier set G, where the first UE belongs to the ICUE and/or the PCUE, and if an SLSS with an slssid=0 that satisfies the S-RSRP strength can be detected, the first UE selects a second UE that sends the SLSS as a reference synchronization source for all carriers in the carrier set G. Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect SLSS with the S-RSRP strength satisfying the slssid=0 on the above part of carriers, the first UE selects a reference cell as a reference synchronization source of all carriers in the carrier set G; or the first UE further detects SLSSs with slssid=0 on other carriers in the carrier set G, if SLSSs with S-RSRP strength meeting the requirement can be detected, the first UE selects the second UE that sends the SLSS as a reference synchronization source of all carriers in the carrier set G, otherwise, the first UE selects a reference cell as a reference synchronization source of all carriers in the carrier set G, where the first UE selects the reference cell in the same manner as in the first embodiment.

If the first UE does not detect a reliable GNSS signal, according to a further implementation of the present embodiment, the first UE detects SLSS with slssid=0 on one reference carrier of the carrier set G, where the first UE belongs to the ICUE and/or the PCUE, and where the priority of the traffic corresponding to the reference carrier is highest when the first UE belongs to the ICUE and/or the PCUE on multiple carriers of the carrier set G. If an SLSS with an S-RSRP strength satisfying the required slssid=0 can be detected, the first UE selects the second UE that transmits the SLSS as a reference synchronization source for all carriers in the carrier set G. Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect an SLSS with the S-RSRP strength satisfying the requirement slssid=0 on the reference carrier, the first UE selects a cell corresponding to the reference carrier as a reference synchronization source of all carriers in the carrier set G.

If the first UE does not detect a reliable GNSS signal, according to a further implementation of the present embodiment, the first UE detects SLSS with slssid=0 on one or more carriers in the carrier set G that at least meet one of the following conditions:

1. the first UE detects PSCCH and PSSCH on the carrier;

2. the first UE performs channel detection (sensing) on the carrier;

3. the service PPPP level corresponding to the carrier wave is 0;

4. the corresponding business PPPP level of the carrier wave is 0 or 1;

5. the value of the service PPPP corresponding to the carrier is smaller than a specific threshold, wherein the threshold can be defined by a standard, preconfigured, or configured by a base station;

6. the carrier is a carrier indicated by a base station or indicated by a pre-configuration signaling, which has to perform PSCCH and PSSCH reception;

7. the traffic corresponding to the carrier needs to be received back to the UE (i.e., V2X UE of 3GPP Rel-14).

If the first UE can detect an SLSS with an S-RSRP strength satisfying the slssid=0, the first UE selects a second UE that transmits the SLSS as a reference synchronization source for all carriers in the carrier set G.

Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect SLSS with the S-RSRP strength satisfying the slssid=0 on the above part of carriers, the first UE selects a reference cell as a reference synchronization source of all carriers in the carrier set G; or the first UE further detects SLSSs with slssid=0 on other carriers in the carrier set G, if SLSSs with S-RSRP strength meeting the requirement can be detected, the first UE selects the second UE that sends the SLSS as a reference synchronization source of all carriers in the carrier set G, otherwise, the first UE selects a reference cell as a reference synchronization source of all carriers in the carrier set G, where the first UE selects the reference cell in the same manner as in the first embodiment.

If the first UE currently has a plurality of aggregated bypass communication carriers, a set of the plurality of aggregated carriers is C, and the first UE uses a certain synchronization source Ry on a carrier Y in the set C as a reference synchronization source, then:

according to one implementation of the present application, if the first UE satisfies the SLSS and PSBCH transmission conditions on carrier Y, then the first UE is considered to satisfy the SLSS and PSBCH transmission conditions on all carriers in carrier set C. If Ry is a UE transmitting SLSS and PSBCH, when the first UE transmits SLSS and PSBCH on a certain carrier Z of the carrier set C, the SLSS ID transmitted by the first UE on the carrier Z is SDz, where SDz may be equal to SD, where SD is determined by the first UE according to the SLSS ID and PSBCH content transmitted by Ry in a manner defined in the existing standard (3 GPP standard 36.331 version e 40), and preferably, in this case, the first UE considers that the SLSS ID value configured on each carrier in the carrier set C for SLSS transmission is the same (i.e. the slssid value contained in the v2x-SyncConfig configuration parameter set containing txdiameter parameters); SDz may be equal to sd+Δ, where Δ is the difference between the SLSS ID value configured on carrier Z for SLSS transmission and the SLSS ID value configured on carrier Y for SLSS transmission. If Ry is a UE transmitting SLSS and PSBCH, when determining the content of the PSBCH transmitted on carrier Z, the first UE sets the value of the Bandwidth domain sl-Bandwidth in the PSBCH to the Bandwidth of carrier Z, and may set the reserved bit domain syncinfofreserved to the value of the domain configured on carrier Z.

According to another implementation manner of the present application, for any carrier K in the carrier set C, the first UE selects a synchronization source with the highest priority on the carrier K as the SLSS and PSBCH transmission reference synchronization source Ssp, and then determines, according to the measured S-RSRP of the Ssp transmission signal, whether the SLSS and PSBCH transmission conditions are satisfied on the carrier Z. If the Ssp is a UE transmitting the SLSS and the PSBCH, when the first UE transmits the SLSS and the PSBCH on the carrier K, a method of the first UE determining the SLSS ID transmitted on the carrier K according to the SLSS ID and the PSBCH content transmitted by the Ssp may be the same as defined in the existing standard (3 GPP standard 36.331 release e 40), and a method of the first UE determining the PSBCH content transmitted on the carrier K according to the SLSS ID and the PSBCH content transmitted by the Ssp may be the same as defined in the existing standard (3 GPP standard 36.331 release e 40). It should be clarified that the SLSS and PSBCH transmission reference synchronization source is different from the reference synchronization source of the UE on all carriers defined in step 102, the former is only used to determine whether or not to transmit the SLSS and PSBCH on the current carrier and, if so, to determine the value of the SLSS ID and the content of the PSBCH, and not to determine the timing of the UE transmitting the PSSCH and PSCCH on all aggregated carriers.

Preferably, if the first UE currently has a plurality of aggregated bypass communication carriers and the UE satisfies the SLSS and PSBCH transmission conditions on one or more of the carriers, then:

according to the first implementation manner of the present application, the first UE should send the SLSS and the PSBCH on the SLSS and PSBCH sending resources corresponding to all carriers meeting the conditions, if at a certain moment, the number of carriers that the first UE needs to send the SLSS and the PSBCH simultaneously exceeds the number of currently available sending radio frequency links of the UE, or the first UE does not have the capability of sending bypass signals simultaneously on multiple carriers, the UE should preferentially ensure the sending of the SLSS and the PSBCH on the carrier corresponding to the high priority service, and discard the sending of the SLSS and the PSBCH on the carrier corresponding to the low priority service.

According to a second implementation of the present application, if the first UE satisfies the SLSS and PSBCH transmission conditions on one or more carriers, the first UE transmits the SLSS and PSBCH only on carriers where the corresponding service PPPP is less than a certain specific threshold, which is defined by the standard, configured or preconfigured by the base station.

According to a third implementation manner of the present application, the first UE should send the SLSS and the PSBCH on the SLSS and PSBCH sending resources corresponding to all carriers meeting the conditions, if at a certain moment, the number of carriers that the first UE needs to send the SLSS and the PSBCH simultaneously exceeds the number of currently available sending radio frequency links of the UE, or the first UE does not have the capability of sending bypass signals simultaneously on multiple carriers, the UE should randomly select X carriers for sending the SLSS and the PSBCH, where X is the number of carriers that the UE can currently send the SLSS and the PSBCH simultaneously; preferably, if the carrier wave of the SLSS and PSBCH needs to be transmitted simultaneously, which contains the carrier wave where the reference synchronization source currently selected by the UE is located, the first UE must transmit the SLSS and PSBCH on the carrier wave, and then randomly select X-1 from other carrier waves needing to transmit the SLSS and the PSBCH for transmitting and PSBCH.

According to a fourth implementation of the present application, the first UE sends SLSS and PSBCH at least on the carrier on which the traffic that the UE (referred to as V2X UE of Rel-14) receives after the need exists.

According to a fifth implementation manner of the present application, the first UE should send the SLSS and the PSBCH on the SLSS and PSBCH sending resources corresponding to all carriers meeting the conditions, and if at a certain moment, the number of carriers that the first UE needs to send the SLSS and the PSBCH simultaneously exceeds the number of currently available sending radio frequency links of the UE, or the first UE does not have the capability of sending bypass signals simultaneously on multiple carriers, the UE selects R carriers to send the SLSS and the PSBCH from the carriers meeting the SLSS and PSBCH sending conditions. The value of R and the R carriers selected should satisfy:

the value of R is not more than the number of radio frequency links of the first UE;

2. moreover, the R carriers should at least include a carrier Cr, where Cr is the carrier on which the first UE refers to the synchronization source if the carrier on which the first UE refers to the synchronization source meets the SLSS and PSBCH transmission conditions, and otherwise, the carrier Cr is an empty set (i.e., does not represent any carrier);

3. moreover, the first UE supports simultaneous transmission on the R carriers;

4. and the first UE does not support simultaneous transmission on any R+1 carriers including carrier Cr in the carriers meeting SLSS and PSBCH transmission conditions, or R+1 is larger than the number of radio frequency links of the first UE.

If the above conditional carrier combinations are satisfied and the R carriers included in each combination are not identical, the first UE selects one carrier combination for transmitting the SLSS and the PSBCH based on its own implementation method or randomly selects one carrier combination among the plurality of carrier combinations satisfying the condition for transmitting the SLSS and the PSBCH.

Example III

As another possible implementation of the disclosure, on the basis of the first embodiment, if the first UE is a PCUE on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is an eNB, the first UE selects a primary Cell (PCell) or a Serving Cell (Serving Cell) as a reference synchronization source for all carriers in the carrier set G.

If the first UE is a PCUE on the carrier set G, and the preferred type of synchronization source of the UE on the carrier set G is GNSS, and the first UE is able to detect reliable GNSS signals, the first UE uses GNSS as the reference synchronization source for all carriers in the carrier set G.

If the first UE is a PCUE on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is GNSS, but the first UE does not detect reliable GNSS signals, then according to an implementation of this embodiment, the first UE detects SLSSs with slssid=0 on all carriers of the carrier set G, and if SLSSs with slssid=0 that the S-RSRP strength meets the requirement can be detected, the first UE selects the second UE that transmits the SLSS as the reference synchronization source of all carriers in the carrier set G. Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect SLSS with the S-RSRP strength satisfying the slssid=0 on all carriers in the carrier set G, the first UE selects a primary Cell (PCell) or a Serving Cell (Serving Cell) as a reference synchronization source for all carriers in the carrier set G.

If the first UE is PCUE on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is GNSS, but the first UE cannot detect reliable GNSS signals, according to another implementation of this embodiment, the first UE detects SLSS with slssid=0 on a part of carriers of the carrier set G, the first UE belongs to PCUE on the part of carriers, and if SLSS with slssid=0 that satisfies the S-RSRP strength can be detected, the first UE selects the second UE that transmits the SLSS as the reference synchronization source of all carriers in the carrier set G. Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect SLSS with the S-RSRP strength satisfying the slssid=0 on all carriers in the carrier set G, the first UE selects a primary Cell (PCell) or a Serving Cell (Serving Cell) as a reference synchronization source for all carriers in the carrier set G.

If the first UE is a PCUE on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is GNSS, however the first UE does not detect reliable GNSS signals, according to a further implementation of the present embodiment, the first UE detects SLSS with slssid=0 on one reference carrier of the carrier set G, on which the first UE belongs to the PCUE, and when the first UE belongs to the PCUE on multiple carriers of the carrier set G, the traffic priority corresponding to the reference carrier is highest. If an SLSS with an S-RSRP strength satisfying the required slssid=0 can be detected, the first UE selects the second UE that transmits the SLSS as a reference synchronization source for all carriers in the carrier set G. Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect SLSS with the S-RSRP strength satisfying the required slssid=0 on the reference carrier, the first UE selects a primary Cell (PCell) or a Serving Cell (Serving Cell) as a reference synchronization source for all carriers in the carrier set G.

If the first UE is a PCUE on the set of carriers G and the preferred type of synchronization source of the UE on the set of carriers G is GNSS, however the first UE does not detect reliable GNSS signals, then according to a further implementation of the present embodiment the first UE detects SLSS with slssid=0 on one or more carriers in the set of carriers G that at least meet one of the following conditions:

1. the first UE detects PSCCH and PSSCH on the carrier;

2. the first UE performs channel detection (sensing) on the carrier;

3. the service PPPP level corresponding to the carrier wave is 0;

4. the corresponding business PPPP level of the carrier wave is 0 or 1;

If the first UE can detect an SLSS with an S-RSRP strength satisfying the slssid=0, the first UE selects a second UE that transmits the SLSS as a reference synchronization source for all carriers in the carrier set G. Preferably, if the first UE can detect a plurality of SLSSs with slssid=0 on one or more carriers, the first UE preferentially selects the SLSS with the largest S-RSRP value; or, the second UE with the highest S-RSRP strength in the second UE with the high priority is preferentially selected as a reference synchronization source of all carriers in the carrier set G, where the second UE with the high priority refers to the second UE with the value of the index field in the transmitted PSBCH being TRUE, or the second UE that sends the SLSS in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If the first UE does not detect SLSS with the S-RSRP strength satisfying the slssid=0 on the above part of carriers, the first UE selects a reference cell as a reference synchronization source of all carriers in the carrier set G; or the first UE further detects SLSSs with slssid=0 on other carriers in the carrier set G, if SLSSs with S-RSRP strength meeting the requirement can be detected, the first UE selects the second UE that sends the SLSS as a reference synchronization source of all carriers in the carrier set G, otherwise, the first UE selects a reference cell as a reference synchronization source of all carriers in the carrier set G, where the first UE selects the reference cell in the same manner as in the first embodiment.

Preferably, if the first UE currently has a plurality of aggregated bypass communication carriers and the UE satisfies the SLSS and PSBCH transmission conditions on one or more carriers therein, according to an implementation of the present application, the first UE should transmit the SLSS and PSBCH on the SLSS and PSBCH transmission resources corresponding to all carriers that satisfy the conditions, and if at a certain moment, the number of carriers that the first UE needs to simultaneously transmit the SLSS and the PSBCH exceeds the number of transmission radio frequency links currently available to the UE, or the first UE does not have the capability of simultaneously transmitting the bypass signals on a plurality of carriers, the UE should preferentially ensure the transmission of the SLSS and the PSBCH on the carrier corresponding to the high priority service and discard the transmission of the SLSS and the PSBCH on the carrier corresponding to the low priority service. According to another implementation of the present application, if the first UE satisfies the SLSS and PSBCH transmission conditions on one or more carriers, the first UE transmits the SLSS and PSBCH only on carriers where the corresponding service PPPP is less than a certain threshold, which is defined by the standard, configured or preconfigured by the base station. According to still another implementation manner of the present application, the first UE should send the SLSS and the PSBCH on the SLSS and PSBCH sending resources corresponding to all carriers meeting the condition, and if at a certain moment, the number of carriers that the first UE needs to send the SLSS and the PSBCH simultaneously exceeds the number of currently available sending radio frequency links of the UE, or the first UE does not have the capability of sending bypass signals simultaneously on multiple carriers, the UE should randomly select X carriers for sending the SLSS and the PSBCH, where X is the number of carriers that the UE can currently send the SLSS and the PSBCH simultaneously; preferably, if the carrier wave of the SLSS and PSBCH needs to be transmitted simultaneously, which contains the carrier wave where the reference synchronization source currently selected by the UE is located, the first UE must transmit the SLSS and PSBCH on the carrier wave, and then randomly select X-1 from other carrier waves needing to transmit the SLSS and the PSBCH for transmitting and PSBCH. According to yet another implementation of the present application, the first UE transmits the SLSS and PSBCH at least on the carrier on which the traffic that the UE (referred to as V2X UE of Rel-14) receives after the presence.

3. moreover, the first UE supports simultaneous transmission on the R carriers;

Example IV

As another possible implementation of the disclosure, on the basis of the first embodiment, if the first UE is an oce on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is an eNB, the first UE may detect SLSS within all SLSSIDs on all carriers of the carrier set G, or the first UE may detect SLSS within all SLSSIDs on one or more carriers in the carrier set G that at least one of the following conditions is satisfied:

1. the first UE detects PSCCH and PSSCH on the carrier;

2. the first UE performs channel detection (sensing) on the carrier;

3. the service PPPP level corresponding to the carrier wave is 0;

4. the corresponding business PPPP level of the carrier wave is 0 or 1;

If the first UE can detect one or more reference synchronization source UEs with satisfactory strength on one or more carriers or can detect reliable GNSS signals, the first UE selects one reference synchronization source as a reference synchronization source for all carriers in the carrier set G according to the following priority order (the first priority to the sixth priority are arranged in order from high to low):

First priority: and transmitting the SLSS on one or more carriers detected by the first UE, wherein the SLSSID belongs to a first set, and the value of an index domain in the corresponding PSBCH is a second UE of TRUE. Wherein the first set is a set of SLSSIDs from which SLSSIDs can be selected for UE within the coverage of the cell. If a plurality of second UEs meeting the conditions are provided, the second UE with the highest S-RSRP strength is the highest priority; or the second UE with the highest S-RSRP on the carrier with the highest corresponding service priority is the highest priority.

Second priority: and transmitting the SLSS on one or more carriers detected by the first UE, wherein the SLSSID belongs to a first set, and the value of an index domain in the corresponding PSBCH is a second UE of FALSE. Wherein the first set is a set of SLSSIDs from which SLSSIDs can be selected for UE within the coverage of the cell. If a plurality of UEs satisfying the above conditions exist, the second UE with the highest S-RSRP strength is the highest priority; or the second UE with the highest S-RSRP on the carrier with the highest corresponding service priority is the highest priority.

Third priority: and (5) GNSS.

Fourth priority: transmitting SLSS and slssid=0 on one or more carriers detected by the first UE, and the value of the index field in the corresponding PSBCH is the second UE of TRUE; or, the second UE that sends SLSS and slssid=0 in the subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If there are a plurality of second UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Fifth priority: and transmitting the SLSS on one or more carriers detected by the first UE, wherein SLSSID=0, the value of an inCoverage domain in the corresponding PSBCH is FALSE, and transmitting the second UE of the SLSS in a subframe indicated by a pre-configuration parameter syncOffsetIndexter 1 or syncOffsetIndexter 2. If there are a plurality of second UEs satisfying the above condition, the UE with the highest S-RSRP strength is the highest priority.

Sixth priority: other types of reference synchronization source UEs of the SLSS are transmitted on one or more carriers detected by the first UE. If a plurality of UEs meeting the above conditions exist, the UE with the highest S-RSRP strength is the highest priority; or the second UE with the highest S-RSRP on the carrier with the highest corresponding service priority is the highest priority.

According to a third implementation manner of the present application, the first UE should send the SLSS and the PSBCH on the SLSS and PSBCH sending resources corresponding to all carriers meeting the conditions, if at a certain moment, the number of carriers that the first UE needs to send the SLSS and the PSBCH simultaneously exceeds the number of currently available sending radio frequency links of the UE, or the first UE does not have the capability of sending bypass signals simultaneously on multiple carriers, the UE should randomly select X carriers for sending the SLSS and the PSBCH, where X is the number of carriers that the UE can currently send the SLSS and the PSBCH simultaneously; preferably, if the carrier wave of the SLSS and PSBCH needs to be transmitted simultaneously, which contains the carrier wave where the reference synchronization source currently selected by the UE is located, the first UE must transmit the SLSS and PSBCH on the carrier wave, and then randomly select X-1 from other carrier waves needing to transmit the SLSS and PSBCH for transmitting the SLSS and the PSBCH.

3. moreover, the first UE supports simultaneous transmission on the R carriers;

Example five

As another possible implementation of the disclosure, on the basis of the first embodiment, if the first UE is an oce on the carrier set G and the preferred type of synchronization source of the UE on the carrier set G is GNSS, then when the first UE does not detect reliable GNSS signals, the first UE may detect SLSS within all SLSSIDs on all carriers of the carrier set G, or the first UE may detect SLSS within all SLSSIDs on one or more carriers in the carrier set G that at least one of the following conditions is satisfied:

1. the first UE detects PSCCH and PSSCH on the carrier;

2. the first UE performs channel detection (sensing) on the carrier;

3. the service PPPP level corresponding to the carrier wave is 0;

4. the corresponding business PPPP level of the carrier wave is 0 or 1;

If the first UE can detect one or more reference synchronization source UEs with satisfactory strength on one or more carriers or can detect reliable GNSS signals, the first UE selects one reference synchronization source as a reference synchronization source for all carriers in the carrier set G according to the following priority order (the first priority to the fourth priority are arranged in order from high to low):

first priority: and (5) GNSS.

Second priority: transmitting an SLSS on one or more carriers detected by a first UE, wherein the SLSSID belongs to a first set, and the value of an index domain in a corresponding PSBCH is a second UE of TRUE, wherein the first set is an SLSSID set from which the SLSSID can be selected for transmitting the SLSS for the UE in a cell coverage area; or, sending SLSS and slssid=0 on one or more carriers detected by the first UE, and the value of the index field in the corresponding PSBCH is the second UE of TRUE; alternatively, the SLSS is sent on one or more carriers detected by the first UE and slssid=0, and the second UE of the SLSS is sent in a subframe indicated by the preconfigured parameter syncOffsetIndicator 3. If a plurality of second UEs meeting the conditions are provided, the second UE with the highest S-RSRP strength is the highest priority; or the second UE with the highest S-RSRP on the carrier with the highest corresponding service priority is the highest priority.

Third priority: transmitting the SLSS on one or more carriers detected by the first UE, wherein the SLSSID belongs to a first set, and the value of an index domain in the corresponding PSBCH is a second UE of FALSE; or, the SLSS is sent on one or more carriers detected by the first UE, where slssid=0, the value of the index field in the corresponding PSBCH is FALSE, and the second UE of the SLSS is sent in a subframe indicated by the preconfigured parameter syncOffsetIndicator1 or syncOffsetIndicator 2; or, the SLSS is sent on one or more carriers detected by the first UE, and slssid=169, and the value of the index field in the corresponding PSBCH is the second UE of FALSE. If a plurality of UEs meeting the above conditions exist, the UE with the highest S-RSRP strength is the highest priority; or the second UE with the highest S-RSRP on the carrier with the highest corresponding service priority is the highest priority.

Fourth priority: and transmitting the other types of reference Synchronization Source (SSs) of the SLSS to the second UE on one or more carriers detected by the first UE. If a plurality of second UEs meeting the conditions are provided, the UE with the highest S-RSRP strength is the highest priority; or the second UE with the highest S-RSRP on the carrier with the highest corresponding service priority is the highest priority.

According to yet another implementation of the present application, if Ry is a UE transmitting SLSS and PSBCH, the first UE considers that the SLSS and PSBCH transmission conditions are satisfied on all carriers except carrier Y in set C. When the first UE transmits the SLSS and the PSBCH on a certain carrier Z in the carrier set C, the SLSS ID transmitted by the first UE on the carrier Z is SDz, where SDz may be equal to SD, where SD is determined by the first UE according to the SLSS ID transmitted by Ry and the PSBCH content in a manner defined in the existing standard (3 GPP standard 36.331 version e 40), and preferably, in this case, the first UE considers that the SLSS ID value configured on each carrier in the carrier set C for SLSS transmission is the same (i.e. the SLSS value contained in the v2x-SyncConfig configuration parameter set containing the txps parameters); SDz may be equal to sd+Δ, where Δ is the difference between the SLSS ID value configured on carrier Z for SLSS transmission and the SLSS ID value configured on carrier Y for SLSS transmission. If Ry is a UE transmitting SLSS and PSBCH, when determining the content of the PSBCH transmitted on carrier Z, the first UE sets the value of the Bandwidth domain sl-Bandwidth in the PSBCH to the Bandwidth of carrier Z, and may set the reserved bit domain syncinfofreserved to the value of the domain configured on carrier Z.

According to still another implementation manner of the present application, for any carrier K in the carrier set C, the first UE selects a synchronization source with the highest priority on the carrier K as the SLSS and PSBCH transmission reference synchronization source Ssp, and then determines, according to the measured S-RSRP of the Ssp transmission signal, whether the SLSS and PSBCH transmission conditions are satisfied on the carrier Z. If the Ssp is a UE transmitting the SLSS and the PSBCH, when the first UE transmits the SLSS and the PSBCH on the carrier K, a method of the first UE determining the SLSS ID transmitted on the carrier K according to the SLSS ID and the PSBCH content transmitted by the Ssp may be the same as defined in the existing standard (3 GPP standard 36.331 release e 40), and a method of the first UE determining the PSBCH content transmitted on the carrier K according to the SLSS ID and the PSBCH content transmitted by the Ssp may be the same as defined in the existing standard (3 GPP standard 36.331 release e 40). It should be clarified that the SLSS and PSBCH transmission reference synchronization source is different from the reference synchronization source of the UE on all carriers defined in step 102, the former is only used to determine whether or not to transmit the SLSS and PSBCH on the current carrier and, if so, to determine the value of the SLSS ID and the content of the PSBCH, and not to determine the timing of the UE transmitting the PSSCH and PSCCH on all aggregated carriers.

3. moreover, the first UE supports simultaneous transmission on the R carriers;

Example six

As another possible implementation of the present disclosure, in the present embodiment, the first UE first selects one reference carrier in the carrier set G. According to the first implementation manner of the present embodiment, the reference carrier is the carrier with the highest corresponding service priority in the carrier set G; according to a second implementation manner of the present embodiment, if the first UE belongs to the ICUE and/or the PCUE on one or more carriers in the carrier set G, the reference carrier is the carrier with the highest corresponding service priority, otherwise, the reference carrier is the carrier with the highest corresponding service priority in the carrier set G.

The first UE performs reference synchronization source selection on the reference carrier in the manner of the disclosed technique described above, and uses the selected reference synchronization source as a reference synchronization source for all carriers in the carrier set G.

Referring to fig. 2, an apparatus for multi-carrier bypass communication synchronization source selection of the present disclosure includes:

Preferably, the selecting a synchronization source according to the cell coverage attribute of the UE on all carriers includes:

determining priority order of the UE to select the synchronization source according to the cell coverage attribute of the UE on all carriers and the synchronization source preference type of the UE on all carriers or according to the cell coverage attribute of the UE on all carriers, the synchronization source preference type of the UE on all carriers and the synchronization source signal strength;

and selecting one synchronous source according to the priority order.

GNSS；

reference cells.

GNSS；

reference cells.

GNSS；

other second UEs transmitting SLSS on carriers in carrier set G;

GNSS；

other second UEs transmitting SLSS on carriers in carrier set G;

Preferably, the selecting a synchronization source according to the cell coverage attribute of the UE on all carriers includes: and detecting SLSS signals in all SLSSID ranges on all carriers, or detecting SLSS signals in all SLSSID ranges on the carrier with the highest corresponding service priority or the smallest index, and selecting a synchronous source according to the cell coverage attribute of the UE on all carriers, wherein the priority of the corresponding service of the carrier is indicated by a higher layer.

Preferably, the selecting a synchronization source according to the priority order includes: and arranging the detected signals from high to low according to the priority order, if more than two second UEs meeting the conditions are detected on the highest level of priority of the arrangement result, selecting the second UE corresponding to the SLSS with the largest S-RSRP value, or selecting the second UE with the largest S-RSRP value in the second UEs with high priority as a synchronous source of the first UE, wherein the second UE with high priority comprises the second UE which transmits PSBCH on the corresponding carrier and has the coverage threshold of TRUE, and the second UE which transmits SLSS on the corresponding carrier and the subframe indicated by the preconfigured parameter syncOffsetindicator 3.

Preferably, the selecting a synchronization source according to the priority order includes: and arranging the detected signals from high to low according to the priority order, and if more than two second UEs meeting the conditions are detected on the highest-level priority of the arrangement result, selecting the second UE with the highest S-RSRP intensity or selecting the second UE with the highest S-RSRP intensity on the carrier with the highest corresponding service priority as a synchronization source of the first UE, wherein the corresponding service priority of the carrier is indicated by a high layer.

Example seven

Since the backward UE can only recognize the resource reservation interval of not less than 20, if the new UE sets the resource reservation interval to a value of less than 20, for example, 10, the effect of resource reservation cannot be achieved when the new UE and the backward UE operate in the same resource pool.

To solve the above-mentioned problem, a method for setting SCI1 is provided in this embodiment, where the physical layer of the transmitting UE sets the values of the relevant domains in SCI1 according to the values of the resource reservation interval (Resource reservation interval) and the new transmission and retransmission resource time interval (Time gap between initial transmission and retransmission) in the bypass Grant (Sidelink Grant) configured by the higher layer (MAC layer). Preferably, if the value of the resource reservation interval in the bypass grant of the higher layer configuration is not less than 20, the UE sets the resource reservation interval field (Resource reservation field) and the new transmission and retransmission resource time interval field (Time gap between initial transmission and retransmission field) in SCI1 in the same manner as defined in 3GPP standard 36.213V14.3.0.

If the value of the resource reservation interval in the bypass grant of the higher layer configuration is 10, according to an implementation manner of the present embodiment, the transmitting UE sets four bits of the resource reservation interval field in SCI1 to 1100, i.e. the corresponding resource reservation interval value is 20, and sets four bits of the new transmission and retransmission resource time interval field to 1010, i.e. the corresponding time interval is 10. In addition, a first bit, a second bit, a third bit and a fourth bit in a Reserved bit field (Reserved bits) are set to values of a new transmission and retransmission resource time interval in bypass grant of a higher layer configuration, a fifth bit in the Reserved bit field is set to 1 for indicating that a current resource reservation interval is 10, wherein the first bit, the second bit, the third bit, the fourth bit and the fifth bit are some 5 idle bits in Reserved bits in SCI 1. Preferably, in this way, the new transmission and retransmission resource time interval k should satisfy-9.ltoreq.k.ltoreq.9. For the receiving UE, the location where the UE transmitting SCI1 transmits the PSSCH and the location where the PSSCH resource is reserved should be determined according to the received resource reservation interval field in SCI1, the new transmission and retransmission resource time interval field, the values of the first bit, the second bit, the third bit, the fourth bit and the fifth bit in the reserved bit field, and the corresponding meanings.

If the value of the resource reservation interval in the bypass grant of the higher layer configuration is 10, according to another implementation manner of the present embodiment, the transmitting UE sets four bits of the resource reservation interval field in SCI 1 to 1100, i.e. the corresponding resource reservation interval value is 20, and sets four bits of the new transmission and retransmission resource time interval field to 1010, i.e. the corresponding time interval is 10. In addition, a first bit, a second bit and a third bit in a Reserved bit field (Reserved bits) are set to values of a new transmission and retransmission resource time interval in bypass grant of a higher layer configuration, a fourth bit in the Reserved bit field is set to 1 for indicating that a current resource reservation interval is 10, wherein the first bit, the second bit, the third bit and the fourth bit are some 4 idle bits in Reserved bits in SCI 1. Preferably, in this way, the new transmission and retransmission resource time interval k should satisfy-7.ltoreq.k.ltoreq.7, or-8.ltoreq.k.ltoreq.8. For the receiving UE, the location where the UE sending SCI 1 sends the PSSCH and the location where the PSSCH resource is reserved should be determined according to the received resource reservation interval field in SCI 1, the new transmission and retransmission resource time interval field, the values of the first bit, the second bit, the third bit and the fourth bit in the reserved bit field, and the corresponding meanings.

The method can indicate the next reservation through the new transmission and retransmission resource time interval domain in SCI 1, and indicates the new transmission and retransmission resource time interval by using four additional bits in reserved bits, thereby avoiding the occupation of resources reserved by the new UE with a time interval smaller than 20 to the UE. In addition, the fifth bit in the reserved bits can indicate the real new transmission and retransmission resource time interval of the new UE, so that the new UE can correctly receive and measure the PSSCH transmitted by the transmitting UE.

As can be seen from the above detailed description of the present disclosure, the present disclosure has at least the following advantageous technical effects compared to the prior art: the optimal reference synchronization source is selected as the unified reference synchronization source of the plurality of carriers according to the state of the UE on the plurality of carriers, so that the influence caused by in-band interference and half-duplex limitation is obviously reduced, the interference of bypass communication on cellular communication is avoided, and the data transmission rate and the system capacity of the bypass communication system are effectively improved.

Those skilled in the art will appreciate that the present disclosure includes reference to apparatus for performing one or more of the operations described herein. These devices may be specially designed and constructed for the required purposes, or may comprise known devices in general purpose computers. These devices have computer programs stored therein that are selectively activated or reconfigured. Such a computer program may be stored in a device (e.g., a computer) readable medium or any type of medium suitable for storing electronic instructions and respectively coupled to a bus, including, but not limited to, any type of disk (including floppy disks, hard disks, optical disks, CD-ROMs, and magneto-optical disks), ROMs (Read-Only memories), RAMs (Random AcceSS Memory, random access memories), EPROMs (EraSable Programmable Read-Only memories), EEPROMs (Electrically EraSable Programmable Read-Only memories), flash memories, magnetic cards, or optical cards. That is, a readable medium includes any medium that stores or transmits information in a form readable by a device (e.g., a computer).

It will be understood by those within the art that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by computer program instructions. Those skilled in the art will appreciate that these computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing method to perform the functions specified in the block diagrams and/or block or blocks of the flowchart of the present disclosure, by the processor of the computer or other programmable data processing method.

Those of skill in the art will appreciate that the various operations, methods, steps in the flow, actions, schemes, and alternatives discussed in the present disclosure may be alternated, altered, combined, or eliminated. Further, other steps, measures, schemes in various operations, methods, flows that have been discussed in this disclosure may also be alternated, altered, rearranged, split, combined, or deleted. Further, steps, measures, schemes in the prior art with various operations, methods, flows disclosed in the present disclosure may also be alternated, altered, rearranged, decomposed, combined, or deleted.

The foregoing is only a partial embodiment of the present disclosure, and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present disclosure, and such modifications and adaptations are intended to be comprehended within the scope of the present disclosure.

Claims

1. A method performed by a first user equipment, UE, for transmitting multicarrier bypass communication synchronization information, the method comprising the steps of:

selecting a reference synchronization source;

setting a value of a bandwidth parameter in a physical bypass broadcast channel, PSBCH, to be transmitted on a second carrier, in case the second UE is selected as a reference synchronization source on the first carrier;

a bypass synchronization signal SLSS and a PSBCH comprising bandwidth parameters are sent on a second carrier,

wherein the first carrier and the second carrier are different.

2. The method of claim 1, wherein the value of the bandwidth parameter is set to a value of a preconfigured bandwidth and the reserved bit field of the PSBCH is set to a preconfigured value on the second carrier.

3. The method as recited in claim 1, further comprising:

the SLSS is selected with the same SLSSID as the SLSS received from the second UE on the first carrier.

4. The method of claim 1, wherein the first UE is outside of cell coverage.

5. The method of claim 1, wherein the selecting the reference synchronization source comprises:

determining a priority order of a reference synchronization source according to the states of the first UE on a plurality of carriers;

and selecting a reference synchronous source according to the priority order.

6. The method of claim 5, wherein the determining the priority order of reference synchronization sources based on the status of the first UE on the plurality of carriers comprises:

determining the cell coverage attribute of the first UE on all carriers according to the states of the first UE on a plurality of carriers;

determining a reference synchronization source preferred type of the first UE on all carriers according to the cell coverage attribute of the first UE on all carriers;

and determining the priority order of the reference synchronization sources according to the cell coverage attribute of the first UE on all carriers and the reference synchronization source preference type of the first UE on all carriers or according to the cell coverage attribute of the first UE on all carriers, the reference synchronization source preference type of the first UE on all carriers and the reference synchronization source signal strength.

7. The method of claim 6, wherein the determining the reference synchronization source preference type for the first UE on all carriers based on the cell coverage attribute for the first UE on all carriers comprises:

if the cell coverage attribute of the first UE on all carriers is cell full coverage user equipment ICUE, determining that the reference synchronous source optimization type of the first UE on all carriers is the same as that of carrier X, wherein the cell coverage attribute of the first UE on carrier X is ICUE;

if the cell coverage attribute of the first UE on all carriers is cell partial coverage user equipment PCUE, determining that the preferred type of the reference synchronization source of the first UE on all carriers is the same as that of carrier Y, wherein the cell coverage attribute of the first UE on carrier Y is PCUE, the priority of carrier Y is highest or the index value is smallest, and the priority of carrier Y is indicated by a higher layer;

if the cell coverage attribute of the first UE on all carriers is no cell coverage user equipment ocu, determining that the preferred type of the reference synchronization source of the first UE on all carriers is the same as carrier Z, where the priority of carrier Z is highest or the index value is smallest, and the priority of carrier Z is indicated by a higher layer.

8. The method of claim 6, wherein the determining the priority order of reference synchronization sources based on the cell coverage attribute of the first UE on all carriers and the reference synchronization source preference type of the first UE on all carriers comprises:

recording all carriers as a carrier set G;

if the cell coverage attribute of the first UE is ICUE and the preferred type of the reference synchronization source of the first UE is a base station, determining that the priority order of the reference synchronization source is that the primary carrier of the first UE cell coverage state is ICUE in the carrier set G, the secondary carrier of the first UE cell coverage state is ICUE in the carrier set G, and the priority of other carriers of the first UE cell coverage state is ICUE in the carrier set G are sequentially arranged from high to low; or (b)

If the cell coverage attribute of the first UE is ICUE and the preferred type of the reference synchronization source of the first UE is GNSS, determining that the priority order of the reference synchronization source is GNSS, sending a bypass synchronization signal SLSS on a carrier in the carrier set G, and arranging the priorities of the second UE and the base station in sequence from high to low, where the bypass synchronization signal slssid=0; or (b)

If the cell coverage attribute of the first UE is PCUE and the preferred type of the reference synchronization source of the first UE is GNSS on the carrier set G, determining that the priority order of the reference synchronization source is GNSS, and transmitting SLSS on the carrier in the carrier set G, and the priorities of the second UE and the base station with slssid=0 are sequentially arranged from high to low; or (b)

If the cell coverage attribute of the first UE is ocu and the preferred type of the reference synchronization source of the first UE is a base station, determining that the priority order of the reference synchronization source is that the priority order of the second UE, GNSS, which sends SLSS on the carrier in the carrier set G and slssid=0, of the second UE, which sends SLSS on the carrier in the carrier set G and SLSSID of the first set, and the priority order of the other second UEs, which sends SLSS on the carrier in the carrier set G, are sequentially arranged from high to low; or (b)

If the cell coverage attribute of the first UE is ocu and the preferred type of the reference synchronization source of the first UE is GNSS, determining that the priority order of the reference synchronization source is GNSS, transmitting a second UE with a bypass broadcast channel PSBCH and a coverage status indication field index field of PSBCH of TRUE on the carrier in the carrier set G, or transmitting a second UE with SLSS on the carrier in the carrier set G and a subframe indicated by a subframe offset sync offsetindicator3 in the 3 rd synchronization signal transmission of the preconfiguration parameter, transmitting a second UE with a PSBCH and an inCoverage field of PSBCH of FALSE on the carrier in the carrier set G, and transmitting other second UEs with SLSS on the carrier in the carrier set G are sequentially arranged from high to low;

9. The method of claim 6, wherein the determining the priority order of reference synchronization sources based on the cell coverage attribute of the first UE on all carriers and the reference synchronization source preference type of the first UE on all carriers comprises:

recording all carriers as a carrier set G;

if on the carrier set G, the cell coverage attribute of the first UE is ICUE, and the preferred type of the reference synchronization source of the first UE is GNSS, it is determined that the priority order of the reference synchronization source is that the priorities of the following items are sequentially arranged from high to low:

GNSS；

a second UE that transmits SLSS and slssid=0 on a carrier in carrier set G, or a second UE that transmits SLSS and slssid=0 on a carrier a in carrier set G, wherein a cell coverage attribute of the first UE on carrier a is ICUE or PCUE, or a second UE that transmits SLSS and slssid=0 on carrier a in carrier set G, wherein a cell coverage attribute of the first UE on carrier a is ICUE or PCUE, a priority of carrier a indicated by a higher layer is highest;

reference cells.

10. The method of claim 6, wherein the determining the priority order of reference synchronization sources based on the cell coverage attribute of the first UE on all carriers and the reference synchronization source preference type of the first UE on all carriers comprises:

Recording all carriers as a carrier set G;

if on the carrier set G, the cell coverage attribute of the first UE is PCUE, and the preferred type of the reference synchronization source of the first UE is GNSS, it is determined that the priority order of the reference synchronization source is that the priorities of the following items are sequentially arranged from high to low:

GNSS；

a second UE transmitting SLSS and slssid=0 on a carrier in carrier set G, or a second UE transmitting SLSS and slssid=0 on a carrier a in carrier set G, wherein a cell coverage attribute of the first UE on carrier a is PCUE, or a second UE transmitting SLSS and slssid=0 on carrier a in carrier set G, wherein a cell coverage attribute of the first UE on carrier a is PCUE, a priority indicated by a higher layer of carrier a is highest;

reference cells.

11. The method of claim 6, wherein the determining the priority order of reference synchronization sources based on the cell coverage attribute of the first UE on all carriers and the reference synchronization source preference type of the first UE on all carriers comprises:

recording all carriers as a carrier set G;

if the cell coverage attribute of the first UE is ocu and the preferred type of the reference synchronization source of the first UE is a base station on the carrier set G, determining that the priority order of the reference synchronization source is that the priorities of the following items are sequentially arranged from high to low:

GNSS；

a second UE transmitting SLSS and slssid=0 on carrier a in carrier set G, transmitting PSBCH on carrier a with an inCoverage threshold of TRUE, or transmitting SLSS and SLSS id=0 on carrier a in carrier set G and on a subframe indicated by a preconfigured parameter syncOffsetIndicator 3;

other second UEs transmitting SLSS on carriers in carrier set G;

12. The method of claim 6, wherein the determining the priority order of reference synchronization sources based on the cell coverage attribute of the first UE on all carriers and the reference synchronization source preference type of the first UE on all carriers comprises:

Recording all carriers as a carrier set G;

if the cell coverage attribute of the first UE is oce and the preferred type of the reference synchronization source of the first UE is GNSS on the carrier set G, determining that the priority order of the reference synchronization source is that the priorities of the following items are sequentially arranged from high to low:

GNSS；

a second UE that sends SLSS on carrier a in carrier set G, SLSSID as a first set or SLSS id=0, PSBCH on carrier a and the inCoverage threshold of PSBCH is TRUE, or a second UE that sends SLSS on carrier a in carrier set G and on a subframe indicated by a pre-configured parameter syncOffsetIndicator3 and slssid=0;

Other second UEs transmitting SLSS on carriers in carrier set G;

13. The method of claim 11, wherein the selecting a reference synchronization source according to the priority order comprises at least one of:

detecting SLSS signals in the range of all SLSSIDs on all carriers, and selecting a reference synchronous source according to the priority order;

detecting SLSS signals in all SLSSID ranges only on the carrier wave with the highest corresponding service priority, and selecting a reference synchronous source according to the priority order;

detecting SLSS signals in all SLSSID ranges only on carriers corresponding to the service received by the UE in the need of backward, and selecting a reference synchronous source according to the priority order;

wherein, the priority of the service corresponding to the carrier is indicated by the higher layer.

14. The method of claim 9, wherein the selecting a reference synchronization source according to the priority order comprises:

selecting the reference synchronous source with the highest detected priority according to the priority sequence;

and under the condition that a plurality of UE type reference synchronization sources with the highest priority are detected, selecting the UE type reference synchronization source with the highest S-RSRP intensity, or selecting the UE type reference synchronization source with the highest S-RSRP intensity on the carrier with the highest corresponding service priority, wherein the priority of the service corresponding to the carrier is indicated by a high layer.

15. A first user equipment, UE, for transmitting multi-carrier bypass communication synchronization information, comprising:

a memory; and

a processor configured to perform the method of any of claims 1-14.