WO2016037571A1

WO2016037571A1 - A method and apparatus for clock synchronization

Info

Publication number: WO2016037571A1
Application number: PCT/CN2015/089261
Authority: WO
Inventors: 周海军; 赵毅; 刘刚
Original assignee: 电信科学技术研究院
Priority date: 2014-09-10
Filing date: 2015-09-09
Publication date: 2016-03-17
Also published as: CN105472722B; CN105472722A

Abstract

Disclosed are a method and apparatus for clock synchronization used for reducing clock synchronization cost and avoiding resource waste. The method comprises: a first D2D terminal accessing a cellular network receiving D2D correlation information sent by a network side, establishing downlink synchronization with the network side, and reaching synchronization level 2b; when determining that the cellular network has already obtained a UTC authorization and the location measurement error of the cellular network is less than a preset threshold, applying a distance calibration method or an uplink synchronization calibration method to perform clock synchronization with the network side; when determining that the cellular network has already obtained the UTC authorization, but the location measurement error of the cellular network is not less than the preset threshold, or when determining that the cellular network has not obtained the UTC authorization yet, applying the preset calibration method to perform clock synchronization with a device whose synchronization level meets preset conditions, and reaching synchronization level 2a. In this way, in the case of fast variation of network topology and enormous network scale, the cost of clock synchronization performed by each D2D terminal is decreased and resource waste is avoided.

Description

Clock synchronization method and device

The present application claims priority to Chinese Patent Application No. 2014-10458108.5, entitled "A Clock Synchronization Method and Apparatus", filed on September 10, 2014, the entire contents of which is incorporated herein by reference. .

Technical field

The present invention relates to vehicle networking technologies, and in particular, to a clock synchronization method and apparatus.

Background technique

The D2D (Device-to-Device) communication system is a short-distance communication service that enables direct transmission of data between terminals. At present, the combination of the D2D communication system and the cellular communication system can increase the spectrum efficiency of the cellular communication system, reduce the terminal transmission power, and shorten the delay. The vehicle networking system uses vehicles as the basic information unit, and uses advanced sensing technology, information acquisition technology, access technology, transmission technology, and networking technology to comprehensively perceive roads and traffic, and realize large-scale and large-scale between multiple systems. The interaction of capacity data to provide traffic efficiency and traffic safety to networks and applications. The Internet of Vehicles has node characteristics, mobility characteristics, and data flow characteristics. Its mobile characteristics are characterized by fast changes in network topology and fast node movement. During the high-speed movement of the terminal, some terminals may be under cellular coverage, and some terminals are outside the cellular coverage. Therefore, when the cellular base station performs D2D resource scheduling, the performance of the synchronous system is reduced, which directly leads to a decrease in communication quality, and even Make the communication system inoperable.

In the prior art, the clock synchronization solution in the D2D resource scheduling scenario of the cellular base station is roughly classified into two types: a distributed synchronization scheme and a centralized synchronization scheme.

The distributed synchronization scheme means that each terminal determines the clock of the terminal according to the timing of the surrounding terminals. For example, there are three terminals A, B, and C in the system. Each terminal occupies one time slot. A, B, and C transmit data sequentially. First, A sends data, and B receives A signal after receiving A signal. The clock is its own transmit clock; C receives the A and B signals and receives the A and B signals. For its own transmit clock; A receives the B and C signals, and receives the B and C signals with a clock average of A's transmit clock, and so on.

However, each terminal needs to send a preamble with a synchronization indication function to indicate the transmission clock of the next terminal when transmitting data, which results in a large synchronization overhead.

The centralized synchronization scheme refers to: terminals with similar geographical locations form a terminal cluster, each terminal cluster selects a cluster head based on a certain protocol, and other terminals in the terminal cluster form a clock source based on the clock and frequency of the cluster head, and the terminal The clock that the other terminals in the cluster send signals is determined by the clock source of the cluster head.

However, in the Internet of Vehicles environment, the network scale is large, the coverage of each cluster head is limited, and the network topology changes rapidly. This will inevitably lead to a large number of cluster heads, and the clock between the cluster head and the cluster head is easily inconsistent, resulting in a clock between terminals. Unable to synchronize, resulting in wasted resources. The current technology is not able to coordinate the clock between cluster heads.

Summary of the invention

The embodiment of the invention provides a clock synchronization method and device, which are used to reduce clock synchronization overhead and avoid resource waste.

The embodiment of the invention provides a clock synchronization method, including:

The first device to the device D2D terminal accessing the cellular network receives the D2D association system information sent by the network side, and establishes downlink synchronization with the network side, and enters the synchronization level 2b;

If the first D2D terminal determines, according to the received D2D association system information, that the cellular network has obtained the UTC timing of the Coordinated Time, and the position measurement error of the cellular network is lower than the preset threshold, the distance calibration mode or the uplink synchronization calibration mode is used to complete the network side. Clock synchronization, entering synchronization level 2a;

or,

If the first D2D terminal determines, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determines that the cellular network does not obtain the UTC grant, the preset calibration mode is adopted. , completes synchronization with the clock of the device whose synchronization level meets the preset condition, and enters the synchronization level 2a.

In this way, when the network topology changes rapidly and the network scale is large, each D2D terminal can be reduced. The overhead of clock synchronization is implemented to avoid waste of resources.

Preferably, the first D2D terminal enters the synchronization level 2b, and indicates that the first D2D terminal is only capable of receiving data and cannot transmit data;

The first D2D terminal enters the synchronization level 2a, indicating that the first D2D terminal is capable of receiving data and is also capable of transmitting data.

Preferably, if the first D2D terminal determines that the cellular network has obtained the UTC grant according to the received D2D association system information, and the location measurement error of the cellular network is lower than the preset threshold, the distance calibration method or the uplink synchronization calibration manner is used to complete the network. The clock on the side is synchronized and enters the synchronization level 2a, including:

If the first D2D terminal can obtain the uplink clock on the network side, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

If the first D2D terminal fails to obtain the uplink clock of the network side, the base station location information is further obtained based on the D2D association system information, and then based on the distance between the first D2D terminal and the base station, the distance calibration method is used to complete the network side The clock is synchronized and enters synchronization level 2a.

Preferably, if the first D2D terminal completes the clock synchronization with the network side by using the uplink synchronous calibration mode, the first D2D terminal adopts the first conventional cyclic prefix CP subframe structure and the clock after the clock synchronization process and the clock synchronization is completed. Performing information interaction between one of the two conventional CP subframe structures and the extended CP subframe structure;

If the first D2D terminal performs the clock synchronization with the network side by using the distance calibration mode, the first D2D terminal adopts the first regular CP subframe structure, the second regular CP subframe structure, and the clock synchronization process and after the clock synchronization is completed. Extending one of the CP sub-frame structures for information interaction;

among them,

The first conventional CP subframe structure is: each subframe includes one special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, and the length of the GP is 460Ts. The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, and the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is Degree is 72Ts;

The second regular CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts. The AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where The AGCT does not support time and frequency synchronization, and each data symbol has a length of 164 Ts.

Preferably, if the first D2D terminal determines, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determines that the cellular network does not obtain the UTC grant, then the method is adopted. The preset calibration mode completes the synchronization with the clock of the device whose synchronization level meets the preset condition, and enters the synchronization level 2a, including:

The first D2D terminal receives the dedicated pilot code sent by the second D2D terminal that is timed by the UTC, determines the downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the first D2D terminal and the second D2D terminal. The distance between the two is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the first D2D terminal obtains the location information of the base station according to the D2D association system information, based on the distance between the first D2D terminal and the base station, the clock synchronization with the network side is completed by using the distance calibration mode or the uplink synchronization calibration mode, and the synchronization level 2a is entered. ;

or,

If the position measurement error of the cellular network is not lower than the preset threshold, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

The first D2D terminal receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC. a downlink clock of the terminal, and based on the distance between the first D2D terminal and the second D2D terminal, correcting the downlink clock by using a distance calibration manner, completing clock synchronization with the second D2D terminal, and entering a synchronization level 2a;

or,

The first D2D terminal receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and adopts a zero calibration mode. The clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered.

Preferably, if the first D2D terminal receives the dedicated pilot code sent by the second D2D terminal, and completes the clock synchronization with the second D2D terminal by using the distance calibration mode, the first D2D terminal completes the clock synchronization process and the clock synchronization. After that, the second regular CP subframe structure is used for information interaction;

If the first D2D terminal completes the clock synchronization with the network side by using the distance calibration method based on the distance between the first D2D terminal and the base station, the first D2D terminal adopts the extended CP subframe after the clock synchronization process and the clock synchronization is completed. Structure for information interaction;

If the first D2D terminal detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the first D2D terminal and the second D2D terminal, performs the distance calibration method on the downlink clock of the second D2D terminal. Correcting, after the clock synchronization with the second D2D terminal is completed, the first D2D terminal adopts a first regular CP subframe structure, a second regular CP subframe structure, and an extended CP subframe structure in the clock synchronization process and after the clock synchronization is completed. One of them performs information interaction;

If the first D2D terminal detects the data sent by the UTC authorized second D2D terminal, and completes the correction of the downlink clock of the second D2D terminal by using the zero calibration mode, and completes the clock synchronization with the second D2D terminal, the first D2D After the clock synchronization process and the clock synchronization are completed, the terminal uses the extended CP subframe structure to perform information interaction;

among them,

The first conventional CP subframe structure is: each subframe includes 1 special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, the length of the GP is 460Ts, the AGCT The length is 636Ts, wherein the AGCT does not support the same time and frequency. Step, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second conventional CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts, where The AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where AGCT does not support time and frequency synchronization, and each data symbol has a length of 164Ts.

Preferably, after the first D2D terminal enters the synchronization level 2a, the clock synchronization is re-completed according to the set period. If the clock synchronization is not completed within the first set duration, the synchronization level 2b is entered;

After obtaining the UTC authorization, the first D2D terminal enters the synchronization level 1, and reacquires the UTC authorization according to the set period. If the UTC authorization is not obtained within the second set time period, the synchronization level 2a is entered.

Preferably, after the first D2D terminal enters the synchronization level 2b, if the second D2D terminal synchronization message of the synchronization level 1 is received, the synchronization level 2a is directly entered or the clock synchronization with the second D2D terminal is completed by using the distance calibration mode. After that, the synchronization level 2a is entered.

Preferably, when the first D2D terminal determines that the pilot power of the received base station is less than a preset value, the data receiving window is used to blindly detect the pilot signal and data sent by the third D2D terminal outside the coverage of the cellular network, when detecting When the pilot signal transmitted by the third D2D terminal of the synchronization level 3 is received, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe structure in the self-organizing mode and the coverage of the cellular network are adopted. The D2D terminal performs data transmission and reception, and assists the third D2D terminal of the synchronization level 3 to adopt the distance calibration mode or the uplink clock synchronization calibration mode to complete the clock synchronization with the first D2D terminal, and enters the synchronization level 2, wherein the cellular network There is a synchronization level 1, a synchronization level 2, a synchronization level 3, and a synchronization level 4 outside the coverage, and the synchronization level 2a in the default coverage of the first D2D terminal is equivalent to the synchronization level 2 outside the coverage of the cellular network, such that Can reduce the processing complexity of the D2D terminal.

A clock synchronization device includes:

a receiving unit, configured to receive D2D association system information sent by the network side, and establish downlink synchronization with the network side, and enter synchronization level 2b;

a first sending unit, configured to determine, according to the received D2D associated system information, that the cellular network has obtained the UTC timing of the Coordinated Time, and when the position measurement error of the cellular network is lower than a preset threshold, using a distance calibration method or an uplink synchronization calibration manner The clock on the network side is synchronized and enters the synchronization level 2a;

or,

a second sending unit, configured to determine, according to the received D2D association system information, that the cellular network has obtained UTC timing, but when the location measurement error of the cellular network is not lower than a preset threshold, or when determining that the cellular network does not obtain UTC grant, Set the calibration mode to complete the synchronization with the clock of the device whose synchronization level meets the preset condition, and enter the synchronization level 2a.

In this way, when the network topology changes rapidly and the network size is large, the overhead of clock synchronization of each D2D terminal can be reduced, and resource waste is avoided.

Preferably, the device enters a synchronization level 2b, indicating that the device is only capable of receiving data and is unable to transmit data;

The device enters synchronization level 2a, characterizing that the device is capable of receiving data and is also capable of transmitting data.

Preferably, according to the received D2D association system information, it is determined that the cellular network has obtained UTC timing, and the location measurement error of the cellular network is lower than a preset threshold, and the distance synchronization mode or the uplink synchronization calibration manner is used to complete clock synchronization with the network side. Entering the synchronization level 2a, the first sending unit is specifically configured to:

If the first sending unit can obtain the uplink clock on the network side, use the uplink synchronous calibration mode to complete the clock synchronization with the network side, and enter the synchronization level 2a;

or,

If the first sending unit fails to obtain the uplink clock of the network side, further obtaining base station location information based on the D2D associated system information, and then performing distance calibration based on the distance between the clock synchronization device and the base station. The clock on the network side is synchronized and enters the synchronization level 2a.

Preferably, if the first sending unit completes the clock synchronization with the network side by using the uplink synchronous calibration mode, the first sending unit adopts the first regular cyclic prefix CP during the clock synchronization process and after the clock synchronization is completed. Performing information interaction by one of a frame structure, a second regular CP subframe structure, and an extended CP subframe structure;

If the first sending unit completes the clock synchronization with the network side by using the distance calibration mode, the first sending unit adopts the first regular CP subframe structure and the second regular CP during the clock synchronization process and after the clock synchronization is completed. Information interaction between one of a subframe structure and an extended CP subframe structure;

among them,

The first conventional CP subframe structure is: each subframe includes one special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, and the length of the GP is 460Ts. The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

Preferably, according to the received D2D association system information, it is determined that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or, if the cellular network is determined not to receive the UTC grant, the preset calibration manner is adopted. And completing the synchronization with the clock of the device whose synchronization level meets the preset condition, and entering the synchronization level 2a, where the second sending unit is specifically configured to:

The second sending unit receives the dedicated pilot code sent by the second D2D terminal that is timed by the UTC, determines the downlink clock of the second D2D terminal according to the dedicated pilot code, and synchronizes the clock based on the clock. The distance between the second D2D terminal and the second D2D terminal is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the second sending unit obtains the location information of the base station according to the D2D association system information, based on the distance between the clock synchronization device and the base station, the distance synchronization mode or the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter Synchronization level 2a;

or,

The second sending unit receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and based on the The distance between the clock synchronization device and the second D2D terminal is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

The second sending unit receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when the data sent by the second D2D terminal authorized by the UTC is detected, and adopts zero. The calibration mode is completed in synchronization with the clock of the second D2D terminal, and enters the synchronization level 2a.

Preferably, if the second sending unit receives the dedicated pilot code sent by the second D2D terminal, and completes the clock synchronization with the second D2D terminal by using the distance calibration mode, the second sending unit is in the clock synchronization process. After the clock synchronization is completed, the second regular CP subframe structure is used for information interaction;

If the second sending unit completes the clock synchronization with the network side by using the distance calibration method based on the distance between the clock synchronization device and the base station, the second sending unit performs the clock synchronization process and after the clock synchronization is completed. Using the extended CP sub-frame structure for information interaction;

If the second sending unit detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the clock synchronization device and the second D2D terminal, using the distance calibration method to the downlink clock of the second D2D terminal Performing a correction to complete clock synchronization with the second D2D terminal, the first D2D terminal adopts a first regular CP subframe structure, a second regular CP subframe structure, and an extended CP subframe after clock synchronization and clock synchronization are completed. One of the structures performs information interaction;

If the second sending unit detects the data sent by the second D2D terminal authorized by the UTC, and completes the correction of the downlink clock of the second D2D terminal by using the zero calibration mode, and completes the clock synchronization with the second D2D terminal, The second sending unit uses the extended CP subframe structure to perform information interaction during the clock synchronization process and after the clock synchronization is completed;

among them,

Preferably, after entering the synchronization level 2a, the clock synchronization is re-completed according to the set period. If the clock synchronization is not completed within the first set duration, the synchronization level 2b is entered;

After obtaining the UTC authorization, the synchronization level 1 is entered, and the UTC authorization is re-acquired according to the set period. If the UTC authorization is not obtained within the second set duration, the synchronization level 2a is entered.

Preferably, after entering the synchronization level 2b, if the second D2D terminal synchronization message of the synchronization level 1 is received, the synchronization level 2a is directly entered or the clock synchronization with the second D2D terminal is completed by using the distance calibration mode. Enter sync level 2a.

Preferably, when it is determined that the pilot power of the received base station is less than a preset value, the data receiving window is used to blindly detect the pilot signal and data sent by the third D2D terminal outside the coverage of the cellular network, when the synchronization level 3 is detected. When the pilot signal transmitted by the third D2D terminal, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe structure in the self-organizing mode and the third D2D outside the coverage of the cellular network are adopted. The terminal performs data transmission and reception, and assists the third D2D terminal of the synchronization level 3 to adopt the distance calibration mode or the uplink clock synchronization calibration mode to complete the clock synchronization with the device, and enters the synchronization level 2, wherein the coverage of the cellular network exists. Synchronization level 1, synchronization level 2, synchronization level 3, and synchronization level 4, and the synchronization level 2a within the default cellular coverage of the device is equivalent to synchronization level 2 outside the coverage of the cellular network.

A clock synchronization device includes:

a receiving port, configured to receive D2D association system information sent by the network side, and establish downlink synchronization with the network side, and enter synchronization level 2b;

The sending port is configured to determine, according to the received D2D associated system information, that the cellular network has obtained the UTC timing of the Coordinated Universal Time, and when the position measurement error of the cellular network is lower than the preset threshold, the distance calibration mode or the uplink synchronous calibration manner is used to complete the network side. Clock synchronization, entering synchronization level 2a;

Or, configured to determine, according to the received D2D association system information, that the cellular network has obtained UTC timing, but when the location measurement error of the cellular network is not lower than a preset threshold, or when determining that the cellular network does not obtain UTC grant, adopt a preset calibration manner. , completes synchronization with the clock of the device whose synchronization level meets the preset condition, and enters the synchronization level 2a.

Preferably, the synchronization level 2b is entered to indicate that the device is only capable of receiving data and is unable to transmit data; entering the synchronization level 2a, indicating that the device is capable of receiving data, and is also capable of transmitting data.

Preferably, determining, according to the received D2D association system information, that the cellular network has obtained the UTC grant, And the position measurement error of the cellular network is lower than the preset threshold, and the clock synchronization with the network side is completed by using the distance calibration mode or the uplink synchronization calibration mode, and the synchronization level 2a is entered, and the transmission port is specifically used for:

If the sending port can obtain the uplink clock of the network side, the clock synchronization with the network side is completed by using the uplink synchronous calibration mode, and the synchronization level 2a is entered;

or,

If the sending port fails to obtain the uplink clock of the network side, the base station location information is further obtained based on the D2D associated system information, and then based on the distance between the first D2D terminal and the base station, the distance calibration method is used to complete the network side The clock is synchronized and enters synchronization level 2a.

Preferably, if the sending port completes the clock synchronization with the network side by using the uplink synchronous calibration mode, the first normal cyclic prefix CP subframe structure is adopted in the clock synchronization process and after the clock synchronization is completed. Performing information interaction between one of the two conventional CP subframe structures and the extended CP subframe structure;

If the sending port completes the clock synchronization with the network side by using the distance calibration mode, the sending port adopts a first regular CP subframe structure, a second conventional CP subframe structure, and after clock synchronization is completed. Extending one of the CP sub-frame structures for information interaction;

among them,

The extended CP subframe structure is: each subframe includes one special symbol and 12 data symbols. The special symbols include GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, wherein the AGCT does not support time and frequency synchronization, and each data symbol has a length of 164Ts.

Preferably, according to the received D2D association system information, it is determined that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or, if the cellular network is determined not to receive the UTC grant, the preset calibration manner is adopted. And completing the synchronization with the clock of the device whose synchronization level meets the preset condition, and entering the synchronization level 2a, where the sending port is specifically used to:

The transmitting port receives a dedicated pilot code sent by the second D2D terminal that is timed by the UTC, determines a downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the between the sending port and the second D2D terminal. The distance is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the sending port obtains the location information of the base station according to the D2D association system information, based on the distance between the sending port and the base station, the clock synchronization with the network side is completed by using the distance calibration mode or the uplink synchronization calibration mode, and the synchronization level 2a is entered. ;

or,

The sending port receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and sends the downlink clock based on the sending The distance between the port and the second D2D terminal is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

The sending port receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and adopts a zero calibration mode. The clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered.

Preferably, if the sending port receives the dedicated pilot code sent by the second D2D terminal, After the calibration mode is completed and the clock is synchronized with the second D2D terminal, the sending port uses the second regular CP subframe structure for information interaction during the clock synchronization process and after the clock synchronization is completed.

If the sending port completes the clock synchronization with the network side by using the distance calibration method based on the distance between the first D2D terminal and the base station, the transmitting port uses the extended CP subframe during the clock synchronization process and after the clock synchronization is completed. Structure for information interaction;

If the sending port detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the sending port and the second D2D terminal, correct the downlink clock of the second D2D terminal by using a distance calibration manner, After the clock synchronization with the second D2D terminal is completed, the first D2D terminal adopts a first regular CP subframe structure, a second regular CP subframe structure, and an extended CP subframe structure in the clock synchronization process and after the clock synchronization is completed. One for information interaction;

If the sending port detects the data sent by the second D2D terminal authorized by the UTC, and performs the correction of the downlink clock of the second D2D terminal by using the zero calibration mode to complete the clock synchronization with the second D2D terminal, the sending After the clock synchronization process and the clock synchronization are completed, the port uses the extended CP subframe structure for information interaction;

among them,

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where The AGCT does not support time and frequency synchronization, the length of each data symbol It is 164Ts.

A D2D terminal includes at least: a transceiver, a processor, and a memory;

The processor is configured to determine that the D2D terminal is a first D2D terminal, establish downlink synchronization with the network side according to the D2D association system information sent by the received network side, and enter a synchronization level 2b; according to the received D2D association system The information determines that the cellular network has obtained the UTC timing of the Coordinated Universal Time, and the position measurement error of the cellular network is lower than the preset threshold, and the clock synchronization with the network side is completed by using the distance calibration mode or the uplink synchronous calibration mode, and the synchronization level 2a is entered;

or,

Determining, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determining that the cellular network does not obtain the UTC grant, using a preset calibration manner, completing and The clock synchronization of the device whose synchronization level meets the preset condition enters the synchronization level 2a.

Preferably, the D2D terminal enters a synchronization level 2b, indicating that the D2D terminal can only receive data and cannot send data;

The D2D terminal enters a synchronization level 2a, which indicates that the D2D terminal can receive data and can also transmit data.

Preferably, if the processor determines that the cellular network has obtained the UTC grant according to the received D2D association system information, and the location measurement error of the cellular network is lower than a preset threshold, the distance calibration method or the uplink synchronization calibration manner is used to complete the network. The clock synchronization on the side enters the synchronization level 2a, and the processor is specifically used to:

If the processor can obtain the uplink clock on the network side, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

If the processor fails to obtain the uplink clock of the network side, further obtaining base station location information based on the D2D association system information, and then performing distance calibration on the network side based on the distance between the D2D terminal and the base station. The clock is synchronized and enters synchronization level 2a.

Preferably, the processor is further configured to: if the processor completes clock synchronization with the network side by using an uplink synchronization calibration manner, the processor adopts the first process during the clock synchronization process and after the clock synchronization is completed. Performing information interaction by one of a regular CP subframe structure, a second regular CP subframe structure, and an extended CP subframe structure;

If the processor completes the clock synchronization with the network side by using the distance calibration mode, the processor adopts a first regular CP subframe structure, a second conventional CP subframe structure, and a clock synchronization process and after clock synchronization is completed. Extending one of the CP sub-frame structures for information interaction;

among them,

The second regular CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, and the length of the GP is 460Ts, the AGCT The length of the AGCT is 1732Ts, wherein the AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

Preferably, if the processor determines, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determines that the cellular network does not obtain the UTC grant, then the method is adopted. The preset calibration mode is completed to synchronize with the clock of the device whose synchronization level meets the preset condition, and enters the synchronization level 2a, and the processor is specifically configured to:

The processor receives a dedicated pilot code sent by a second D2D terminal that is timed by UTC, determines a downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the first D2D terminal and the second D2D The distance between the terminals is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the processor obtains the location information of the base station according to the D2D association system information, based on the distance between the first D2D terminal and the base station, the distance synchronization mode or the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter synchronization. Level 2a;

or,

The processor receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and based on the Describe the distance between the first D2D terminal and the second D2D terminal, correct the downlink clock by using a distance calibration method, complete the clock synchronization with the second D2D terminal, and enter the synchronization level 2a;

or,

The processor receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when the data sent by the second D2D terminal authorized by the UTC is detected, and adopts zero The calibration mode is completed in synchronization with the clock of the second D2D terminal, and enters the synchronization level 2a.

Preferably, the processor is further configured to: if the processor receives the dedicated pilot code sent by the second D2D terminal, and completes clock synchronization with the second D2D terminal by using a distance calibration manner, After the clock synchronization process and the clock synchronization are completed, the first D2D terminal uses the second regular CP subframe structure to perform information interaction;

If the processor performs clock synchronization with the network side by using a distance calibration method based on the distance between the first D2D terminal and the base station, the first D2D terminal adopts the clock synchronization process and after the clock synchronization is completed. Extending the CP subframe structure for information interaction;

And if the processor detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the first D2D terminal and the second D2D terminal, using the distance calibration method to the second The downlink clock of the D2D terminal is corrected to complete clock synchronization with the second D2D terminal, and the first D2D terminal adopts a first conventional CP subframe structure and a second regularity during clock synchronization and after clock synchronization is completed. One of a CP subframe structure and an extended CP subframe structure performs information interaction;

If the processor detects the data sent by the second D2D terminal authorized by the UTC, and completes the correction of the downlink clock of the second D2D terminal by using a zero calibration manner, completing the clock with the second D2D terminal. Synchronization, the first D2D terminal uses an extended CP subframe structure for information interaction during clock synchronization and after clock synchronization is completed;

among them,

The first conventional CP subframe structure is: each subframe includes 1 special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, the length of the GP is 460Ts, the AGCT The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

Preferably, the D2D terminal further comprises: after the D2D terminal enters the synchronization level 2a, re-completes clock synchronization according to a set period, and if the clock synchronization is not completed within the first set time period, the synchronization is entered. Level 2b; and,

After obtaining the UTC authorization, the D2D terminal enters the synchronization level 1, and reacquires the UTC authorization according to the set period. If the UTC authorization is not obtained within the second set time period, the synchronization level 2a is entered.

Preferably, after the D2D terminal enters the synchronization level 2b, if the second D2D terminal synchronization message of the synchronization level 1 is received, the synchronization level 2a is directly entered or the clock synchronization with the second D2D terminal is completed by using the distance calibration mode. After that, the synchronization level 2a is entered.

Preferably, the D2D terminal further comprises: when the processor determines that the received pilot power of the base station is less than a preset value, and adopts a data reception window to blindly detect a third D2D terminal sent outside the coverage of the cellular network. The frequency signal and the data, when the pilot signal transmitted by the third D2D terminal of the synchronization level 3 is detected, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the sub-organization mode is used. The frame structure and the D2D terminal outside the coverage of the cellular network perform data transmission and reception, and assist the synchronization of the third D2D terminal of the level 3 by using a distance calibration mode or an uplink clock synchronization calibration mode to complete clock synchronization with the first D2D terminal, and enter synchronization. Level 2, wherein there is a synchronization level 1, a synchronization level 2, a synchronization level 3, and a synchronization level 4 outside the coverage of the cellular network, and the synchronization level 2a in the default coverage of the first D2D terminal is equivalent to the coverage of the cellular network. Synchronization level 2 outside the range.

DRAWINGS

1 is a schematic diagram of clock adjustment in an embodiment of the present invention;

2 is a synchronization process of a D2D terminal according to an embodiment of the present invention;

3 is a structural diagram of a radio frame in an embodiment of the present invention;

4 is a structural diagram of a self-organizing subframe in the prior art;

FIG. 5 is a structural diagram of a conventional CP subframe structure (1) according to an embodiment of the present invention;

6 is a structural diagram of a conventional CP subframe structure (2) according to an embodiment of the present invention;

FIG. 7 is a structural diagram of an extended CP subframe according to an embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a clock synchronization apparatus according to an embodiment of the present invention; FIG.

FIG. 9 is a schematic structural diagram of another clock synchronization apparatus according to an embodiment of the present invention; FIG.

FIG. 10 is a schematic structural diagram of a D2D terminal according to an embodiment of the present invention.

detailed description

In the embodiment of the present invention, the device is divided into different synchronization levels according to the synchronization state of the devices in the D2D communication system, and the low-level D2D terminals are in a high-level state, in order to reduce the cost of the clock synchronization of the D2D terminal. The device (which can be a base station or other D2D terminal) completes clock synchronization as a reference.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

When the D2D terminal is within the coverage of the cellular network, the synchronization level is defined as four levels for convenience of description, as described below, but is not limited to these descriptions:

It is assumed that the base station supporting the vehicle networking communication obtains the whole network synchronization, and always has a GPS (Global Positioning System) clock source, and can obtain the Universal Time Coordinated (UTC) timing, so that the base station crystal oscillator has The stability is high and the transmission power is large, so the base station can provide a synchronization source with a large coverage and high stability of the terminal under the coverage of the cell, and the synchronization level of the base station is defined as level 0;

Assuming that the D2D terminal can obtain the UTC grant, the synchronization level of the D2D terminal is defined as the synchronization level 1;

Assuming that the D2D terminal cannot obtain UTC timing, but can obtain high-precision positioning information or establish uplink synchronization with the base station, the D2D terminal can perform timing compensation based on distance calibration or uplink synchronization calibration, and the D2D terminal can receive data and transmit data. The synchronization level of such a D2D terminal is defined as a synchronization level 2a;

Assuming that the D2D terminal cannot obtain the UTC grant, and temporarily cannot perform timing compensation based on the distance calibration or the uplink synchronization calibration, the D2D terminal can only receive data and cannot transmit data, and the synchronization level of the D2D terminal is defined as the synchronization level 2b.

The specific process of the above D2D terminal for timing calibration to achieve clock synchronization is as follows:

Referring to FIG. 1 , the clock of the D2D terminal receiving the base station signal is t1; the positionable D2D terminal estimates that the distance to the base station is d; C is the speed of light; the corrected clock of the D2D terminal is t0; and the predicted signal delay of the D2D terminal is Τ1, that is, t0=t1-τ1, where t1 is the time of the received signal calculated by the D2D terminal.

If the D2D terminal cannot obtain the UTC timing, but can obtain high-precision positioning information, the D2D terminal can perform timing compensation based on the distance calibration to complete the clock synchronization, τ1=d/C, that is, t0=t1-d/C;

If the D2D terminal cannot obtain UTC grant time and cannot obtain high-precision positioning information, but can perform uplink synchronization with the base station, the D2D terminal can perform timing compensation based on uplink synchronization to complete clock synchronization, τ1=(t2-t1)/2 Wherein, t2 is the synchronized uplink transmission clock, and the D2D terminal sends the uplink signal to the base station, and then receives the downlink signal fed back by the base station. Therefore, the difference between t2 and t1 is the sum of the transmission delays of the signal round-trip, and the D2D terminal pre- The one-way signal delay τ1 can be calculated as half the sum of the transmission delays, that is, t0=t1-(t2-t1)/2.

The above synchronization levels are, in descending order, synchronization level 0, synchronization level 1, synchronization level 2a, synchronization level 2b, and the synchronization level of one D2D terminal is determined by the highest synchronization level that can be obtained. For example, a D2D terminal can obtain UTC timing, high-precision positioning information, or uplink synchronization with a base station, and the D2D terminal has a synchronization level of 1, and its transmission clock is UTC. The clock is decided.

The synchronization accuracy of the D2D terminal with the synchronization level of 1 and the synchronization level of 2a is higher than that of the D2D terminal of the synchronization level 2b.

Assuming that the error of the final horizontal positioning accuracy of the D2D terminal can be controlled within 1.5 meters, and the error of the distance between the GPS receiving and the RF end of the base station can also be controlled within 1.5 meters, the D2D terminal of the synchronization level 2a based on the distance calibration is used for timing compensation. The synchronization accuracy can be controlled within the order of μs. Therefore, the D2D terminal of the synchronization level 1 and the synchronization level 2a can obtain higher time synchronization precision, and the security overhead can be greatly reduced with the assistance of the cellular, thereby enabling frequency division communication.

However, the synchronization accuracy of the D2D terminal of the synchronization level 2b is lower than that of the D2D terminal of the synchronization level 2a. For example, when the cell coverage radius is above 900 m, the D2D terminal signal propagation delay of the synchronization level 2b within the cell coverage may be more than 3 μs. At this time, the D2D terminal of the synchronization level 2b can only receive data, and cannot pass the D2D chain. The road sends data.

Based on the definition of the synchronization level, in the embodiment of the present invention, when the clock synchronization is implemented in the vehicle network, the network side first needs to notify the terminal side of the D2D association system information in the broadcast message, where the D2D association system information includes at least the following content. : time-frequency resources carrying synchronization information, location information of the base station, current timing state of the cellular network (ie, whether UTC timing is obtained), and positioning accuracy (eg, an error of less than 1.5 meters). Optionally, the timing state may be recorded by using 1 bit, and 1 or 0 respectively indicates whether UTC grant is received; and the positioning accuracy may also be recorded by 1 bit, and the location information broadcasted by the base station and the radio frequency unit of the base station are respectively indicated by 1 or 0. Whether the distance difference between the actual positions (ie, the positioning error) is less than a certain threshold (for example, this threshold Lb can take 1.5 meters). If the cellular network determines that the current timing state and the positioning accuracy are not 11 (ie, the network side does not receive UTC timing and the position error is higher than 1.5 meters), it is necessary to indicate which kinds of synchronization modes the D2D terminal can enter into the synchronization level 2a.

Further, in the broadcast message, the subframe structure used by the D2D terminal to select different synchronization modes needs to be notified. In this embodiment, three subframe structures are designed for different synchronization modes. They are called a regular CP (Cyclic Prefix) subframe structure (1), a regular CP subframe structure (2), and an extended CP subframe structure, respectively.

A specific design manner of the three subframe structures will be given in the following embodiments, and only the subframe structure name is given here to facilitate the description of the subsequent embodiments.

Referring to FIG. 2, in the embodiment of the present invention, a specific process for implementing clock synchronization by a D2D terminal is as follows:

Step 200: The first D2D terminal accessing the cellular network receives the D2D association system information sent by the network side, and establishes downlink synchronization with the network side, and enters the synchronization level 2b.

In the embodiment of the present invention, the first D2D terminal entering the synchronization level 2b is defined as being able to receive data only and cannot transmit data, but the definition of the synchronization level 2b is not limited thereto, and can be widely defined as the synchronization accuracy does not meet certain requirements. The synchronization accuracy with respect to the synchronization level 2a is low.

After starting up, the first D2D terminal first needs to detect whether there is a cellular network signal, and when it is determined that there is a cellular network signal, select a camped cell (same mechanism as the cellular network), and read the D2D association of the cellular network sent by the network side. System information, and downlink synchronization (obtaining downlink clock t1) is established through Downlink Pilot Time Slot (DwPTS) of the cellular network, and frequency synchronization is established through downlink pilot signals of the cellular network. At this time, the synchronization level of the first D2D terminal is 2b, and only downlink data can be received, and uplink data cannot be transmitted.

The first D2D terminal of the synchronization level 2b may first receive the downlink data based on the downlink clock, and establish a signal receiving window. Further, the receiving window may be adjusted according to actual needs, for example, tentative forward or backward adjustment. The time position of the receiving window.

The following is discussed in the case where the first D2D terminal obtains the UTC timing and the error condition of the cellular network location measurement: if the first D2D terminal determines that the cellular network has obtained the UTC grant according to the received D2D associated system information, step 210 is performed; A D2D terminal determines, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determines that the cellular network does not obtain the UTC grant, and then performs step 220.

Step 210: If the first D2D terminal determines that the cellular network has obtained the UTC grant according to the received D2D association system information, and the location measurement error of the cellular network is lower than the preset threshold, the distance calibration mode or the uplink synchronization calibration manner is used to complete the network side. The clock is synchronized and enters the synchronization level 2a.

In the embodiment of the present invention, the D2D terminal entering the synchronization level 2a is defined as being capable of receiving data, and also The data can be transmitted, but the definition of the synchronization level 2a is not limited thereto, and can be broadly defined as the synchronization accuracy satisfies a certain requirement, and the synchronization accuracy is higher than the synchronization level 2b.

When the cellular network obtains the UTC grant and the location measurement error of the cellular network is lower than the preset threshold, the first D2D terminal of the synchronization level 2b can enter the synchronization level 2a by the following two methods:

(1) If the first D2D terminal can obtain the uplink clock on the network side, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and the synchronization level 2a is entered. In this case, the position measurement error of the cellular network is not required to be low. At the preset threshold.

Specifically, if the first D2D terminal can implement uplink synchronization with the network side, the uplink clock t2 can be obtained, and the transmission clock t0=(t1+t2)/2 of the terminal on the D2D link, that is, t0=t1-( T2-t1)/2, the first D2D terminal enters the synchronization level 2a.

Each terminal has an internal clock, and the downlink clock refers to a starting point of a subframe (with a duration of 1 ms) determined based on the received downlink downlink pilot signal, for example, in an LTE (Long Term Evolution) system. The length of the field is 5 ms, and the interval between the time when the network side transmits the downlink pilot signal and the starting point of the subframe is fixed. Therefore, the D2D terminal detects the downlink pilot signal to determine the subframe of the network side. Start position, thus completing the downlink synchronization.

Similarly, when the first D2D terminal completes the uplink synchronization, the time of the subframe in which the terminal side transmits the service data can be known, and the interval of the starting point of each subframe is also fixed. The uplink clock refers to the starting point of every 1 ms determined based on the uplink synchronization.

The clock t0 of the terminal on the D2D link is defined as the starting point of the subframe when the D2D data is transmitted, so that t0=(t1+t2)/2, that is, t0=t1-(t2-t1)/2.

In this case, the D2D terminal can perform the clock synchronization process and the flow after the clock synchronization is completed by using one of the conventional CP subframe structure (1), the normal CP subframe structure (2), and the extended CP subframe structure.

(2) if the first D2D terminal fails to obtain the uplink clock on the network side, and the location measurement error of the cellular network is lower than the preset threshold, the base station location information is further obtained based on the D2D association system information, and the first location is obtained according to the self-positioning result. Location information of a D2D terminal, and according to the bits of both The information is used to calculate the distance from the first D2D terminal to the base station, and then the distance synchronization with the network side is completed based on the distance, and the synchronization level 2a is entered.

The clock t0=t1-Lbu/C of the terminal on the D2D link, where Lbu is the distance from the first D2D terminal to the base station, and C is the speed of light.

Further, when the first D2D terminal cannot obtain its own location information, or the positioning accuracy of the base station does not meet the requirement (that is, the accurate location information of the base station cannot be obtained), the first D2D terminal cannot achieve uplink synchronization by using the distance calibration mode, and cannot The distance calibration method is used to enter the synchronization level 2a.

Step 220: If the first D2D terminal determines, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determines that the cellular network does not obtain the UTC grant, then the pre- The calibration mode is set to complete the synchronization with the clock of the device whose synchronization level meets the preset condition, and enter the synchronization level 2a.

Specifically, when the first D2D terminal learns that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than the preset threshold, or determines that the cellular network does not obtain the UTC grant, the following four manners may be adopted but not limited to the following: Synchronization level 2a is performed.

(1) When the first D2D terminal learns that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than the preset threshold, or determines that the cellular network does not obtain the UTC grant, the second D2D terminal that receives the UTC grant is received. Sending a dedicated pilot code, obtaining a downlink clock of the second D2D terminal according to the dedicated pilot code, and correcting the downlink clock by using a distance calibration manner based on a distance between the first D2D terminal and the second D2D terminal, The clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered.

A dedicated pilot code is added to the data transmitted by the second D2D terminal (ie, the synchronization level 1 D2D terminal) that obtains the UTC timing, such that the first D2D terminal that does not obtain the UTC timing (ie, the current synchronization level 2b D2D terminal) a second D2D terminal that can receive UTC grants (ie After the dedicated pilot code transmitted by the D2D terminal of the synchronization level 1 is determined, the downlink clock of the second D2D terminal of the synchronization level 1 (ie, the time of receiving the D2D signal of the synchronization level 1) is determined based on the pilot code, and then based on the two D2D terminals. The distance between the distances is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered.

For example, t0=tu1-Luu1/C, Luu1 is the distance of the first D2D terminal of the synchronization level 2b to the second D2D terminal of the synchronization level 1, which can be obtained by measurement, and tu1 is received by the first D2D terminal of the synchronization level 2b. The downlink clock of the second D2D terminal of the synchronization level 1 is, and the distance from the second D2D terminal of the synchronization level 1 to the first D2D terminal of the synchronization level 2b is Luu1.

In this case, the D2D terminal can perform the clock synchronization process and the process after the clock synchronization is completed by using the conventional CP subframe structure (2).

(2) When the first D2D terminal learns that the cellular network does not obtain the UTC grant, but the location measurement error of the cellular network is lower than the preset threshold, if the first D2D terminal obtains the location information of the base station according to the D2D associated system information, The distance between a D2D terminal and the base station is synchronized with the clock on the network side by using the distance calibration method or the uplink synchronous calibration mode, and enters the synchronization level 2a.

Specifically, when the clock synchronization with the network side is completed by using the distance calibration method, the formula t0=t1-Lbu/C is adopted, where Lbu is the distance between the first D2D terminal and the base station, and C is the speed of light.

Alternatively, the uplink synchronization calibration mode can also be used to complete the clock synchronization with the network side. Since the first D2D terminal can obtain the location information of the base station according to the D2D association system information, that is, the location of the first D2D terminal and the base station is accurate, then The signal propagation delay is calculated based on the position, and then the uplink transmission time can be derived. In this case, the formula t0=(t1+t2)/2 can be used, where t1 is the downlink clock and t2 is the uplink clock.

In this case, since the base station does not obtain the UTC grant time, the accuracy is reduced relative to the UTC grant time, so a larger CP is required, and the first D2D terminal needs to adopt the extended CP subframe structure to perform the clock synchronization process and the clock. The process after the synchronization is completed.

(3) When the position measurement error of the cellular network is not lower than the preset threshold, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

(4) The first D2D terminal is based on the downlink synchronization established with the base station (because it is the synchronization level 2b The D2D terminal, therefore, the first D2D terminal has completed downlink synchronization with the network side), receives data transmitted by other D2D terminals, and acquires data when detecting data transmitted by the second D2D terminal of the synchronization level 1 authorized by UTC The downlink clock of the second D2D terminal is based on the distance between the first D2D terminal and the second D2D terminal, and the clock synchronization with the second D2D terminal is completed by using the distance calibration mode, and the synchronization level 2a is entered.

Specifically, after completing the downlink synchronization with the base station, the first D2D terminal detects the data sent by the other D2D terminal by using the initial receiving window, and when determining the data sent by the second D2D terminal that detects the synchronization level 1, the formula t0=tu1- Luu1/C completes clock synchronization, where Luu1 is the distance from the first D2D terminal of synchronization level 2b to the second D2D terminal of synchronization level 1, which can be obtained by measurement, and tu1 is the synchronization received by the first D2D terminal of synchronization level 2b. a downlink clock of the second D2D terminal of level 1, the distance from the second D2D terminal of the synchronization level 1 to the first D2D terminal of the synchronization level 2b is Luu1, and the first D2D terminal of the synchronization level 2b can support after completing the clock synchronization. Frequency division communication.

In this case, the D2D terminal needs to perform the clock synchronization process and the flow after the clock synchronization is completed by using one of the conventional CP subframe structure (1), the normal CP subframe structure (2), and the extended CP subframe structure.

(5) The first D2D terminal is based on the downlink synchronization established with the base station (due to the D2D terminal of the synchronization level 2b, therefore, the first D2D terminal has completed the downlink synchronization with the network side), and receives the data sent by the other D2D terminal, When the data sent by the second D2D terminal of the synchronization level 1 authorized by the UTC is detected, the downlink clock of the second D2D terminal is acquired, and the clock synchronization with the second D2D terminal is completed by using the zero calibration mode, and the synchronization level 2a is entered.

Specifically, after completing the downlink synchronization with the base station, the first D2D terminal detects the data sent by the other D2D terminal by using the initial receiving window, and when determining the data sent by the second D2D terminal that detects the synchronization level 1, the formula t0=tu1 is used to complete the data. Clock synchronization, wherein tu1 is the downlink clock of the second D2D terminal of the synchronization level 1 received by the first D2D terminal of the synchronization level 2b. In this case, it can also be considered that the correction of the downlink clock is performed by the distance calibration method or the uplink clock calibration method, and the correction value is zero.

In this case, since no correction value is adopted, the clock synchronization accuracy is not high, so that the first D2D terminal needs to use an extended CP subframe structure for information interaction to determine the orthogonality of the transmitted and received signals.

Further, in each of the foregoing synchronization processes, if the D2D terminal uses the regular CP subframe structure (2), different synchronization levels may be identified by different pilot codes in the subframe.

On the other hand, when the cellular network does not obtain UTC authorization, when performing the clock synchronization process of (1)-(5) above, a dedicated message is required between the D2D terminals to indicate the synchronization level of the D2D terminal, and the dedicated message can be The control channel bearer can also be carried in the data channel.

After the first D2D terminal enters the synchronization level 2a, the clock synchronization needs to be re-completed according to the set period. If the clock synchronization is not completed within the set duration, the synchronization level 2b is entered.

Specifically, after the first D2D terminal enters the synchronization level 2a, it is required to update t0 according to the interval (100 ms), that is, periodically re-execute the clock synchronization process, if, within N seconds (eg, N=1), the first D2D If the terminal cannot complete the update to t0, it enters the synchronization level 2b.

Correspondingly, the D2D terminal (synchronization level 2a, 2b) within the coverage of the cellular network will immediately enter the synchronization level 1 after receiving the UTC grant, but if the UTC grant is not obtained within the set duration (eg, x1), then the entry is made. Synchronization level 2a.

In addition, the D2D terminal entering the synchronization level 1 within the coverage of the cellular network can be notified by the network to send a synchronization message through a high layer message.

Specifically, after the first D2D terminal enters the synchronization level 2b, if the second D2D terminal synchronization message of the synchronization level 1 is received, the synchronization level 2a is directly entered or the clock synchronization with the second D2D terminal is completed by using the distance calibration mode. , enter the synchronization level 2a. And through the network configuration, you can directly enter the specific environment of the synchronization level 2a.

The specific design manner of the frame structure used in the embodiment of the present invention will be described below with reference to the accompanying drawings.

The frame structure refers to the structure of the radio frame, which is used to constrain the transmission time parameter of the data to ensure the correct execution of data transmission and reception. In the car network D2D system, a radio frame is composed of a broadcast subframe and a plurality of service subframes, wherein the broadcast subframe is mainly used for providing a frequency synchronization reference signal and transmitting by the base station. Some system-level broadcast messages, the service subframe is used to carry the security message sent by the D2D terminal.

Since the transmission period of the secure service in the Internet of Vehicles is 100 ms, the length of the radio frame is also set to 100 ms. That is, subframe 0 is a broadcast subframe, and subframes 1 to 99 are service subframes. In order to be as consistent as possible with LTE, the LTE chip is multiplexed, and the length of each subframe is set to 1 ms.

Referring to FIG. 3, for the radio frame structure, the radio frame length is 100 subframes.

In a cellular-assisted system, a certain terminal may be in three working modes: strict synchronization mode, discovery mode, and self-organizing mode, specifically:

Under the coverage of the cellular network, and the pilot receiving power of the cell is greater than or equal to Pd (ie, the preset receiving power threshold), the D2D terminal belongs to the strict synchronization mode, and the D2D terminal in the strict synchronization mode is in the synchronization level 1 and the synchronization. At the level 2a, data is transmitted and received in accordance with a strictly synchronized subframe structure; at the synchronization level 2b, data is received in accordance with a strictly synchronized subframe structure. Data transmission and reception with frequency division is supported in strict synchronization mode.

Under the coverage of the cellular network, and the pilot received power of the cell is less than Pd, the D2D terminal belongs to the discovery mode. The discovery mode terminal needs to receive strictly synchronized subframe structure data and self-organized subframe structure data at the same time. When the D2D terminal in the discovery mode and the synchronization level is 1 or 2a receives the pilot code other than the synchronization level 2a, the data is transmitted using the self-organized subframe structure. Otherwise, the data is transmitted using the strictly synchronized subframe structure. . The self-organized sub-frame structure is as shown in FIG. 4: each sub-frame contains 1 special symbol and 12 data symbols, and the special symbol includes GP (Generic programming) and automatic Gain Control (Automatic Gain Control). Training, AGCT), when the AGCT code supports time and frequency synchronization, the length of the AGCT is 1732 Ts (about 112.8 us), of which 50 us is used for AGC processing.

The terminal outside the coverage of the cellular network only performs data transmission and reception using a self-organized subframe structure. If the D2D terminal does not detect the cellular network signal within a preset time, the self-organized synchronization mode is adopted. The specific synchronization method is:

The D2D terminal synchronization level of the external coverage of the cellular network is divided into four levels, namely, synchronization level 1, synchronization level 2, synchronization level 3, and synchronization level 4. The D2D terminal sets a timer to perform conversion between synchronization levels by a preset threshold.

After obtaining the UTC grant time, the D2D terminal clears the timer x and restarts the timer for timing. When the timer x is less than the preset threshold value x1, the D2D terminal enters the synchronization level 1;

The D2D terminal entering the synchronization level 1 does not obtain the UTC grant when the preset threshold x1 reaches the time limit, then the timer is cleared, and the timer is restarted for timing. The timer x is less than the preset threshold x2. Time, the D2D terminal enters synchronization level 2,

or,

The terminal of the synchronization level 2 or the synchronization level 3 or the synchronization level 4 (synchronization level 4, that is, the out-of-synchronization state), if the signal of the synchronization level 1 is received and synchronized with it (here synchronization means that the reception clock of the synchronization level 1 will be received) Determined as its own transceiver timing clock), the timer is cleared, and the timer is restarted for timing. When the timer x is less than the preset threshold x2, the D2D terminal enters the synchronization level 2,

or,

The D2D terminal of the synchronization level 3, if there are D2D terminals of the synchronization levels 2 and 3, and the timing advance of the D2D terminal of the surrounding synchronization level 3 is 1 μs or more higher than the D2D terminal of the surrounding synchronization level 2, Then clear the timer, and restart the timer to time, when the timer x is less than the preset threshold x2, the D2D terminal enters the synchronization level 2;

The D2D terminal of the synchronization level 2 does not obtain the synchronization with the D2D terminal of the synchronization level 1 when the preset threshold value x2 reaches the time limit, and the D2D terminal enters the synchronization level 2,

or,

The D2D terminal of the synchronization level 4 (ie, the D2D terminal in the out-of-synchronization state) clears the timer, and starts the timer to perform timing. When the preset threshold value x4 reaches the time limit, the synchronization level 3 is entered;

After the D2D terminal is powered on, the timer is cleared and the timer x is started for timely. If the D2D terminal does not receive the cellular network information, it is not synchronized with the D2D terminal of the synchronization level 1, 2 or 3, and the x is in the preset gate. Within the limit x4, the D2D terminal is in an out-of-synchronization state.

When the D2D terminal resynchronization level 1, synchronization level 2, and synchronization level 3 are described, transmission and reception of service data can be performed.

The design of the strict synchronization frame structure will be given below.

In the design of the subframe structure, two types are designed according to the length of the Cyclic Prefix (CP). Basic subframe structure: regular CP subframe (1) and regular CP subframe (2).

Referring to FIG. 5, the conventional CP subframe (1) is structured as follows: each subframe includes one special symbol and 13 data symbols, and the effective data portion length of each data symbol is 1024 Ts, and the special symbol includes GP and AGCT. The length of the GP is 460Ts, and the length of the AGCT used for AGC processing is 636Ts. The AGCT does not support time and frequency synchronization. The length of the first and eighth data symbols is 80Ts (5.208μs), and the remaining 11 data. The length of the symbol is 72Ts (4.6875μs).

Referring to FIG. 6, the conventional CP subframe (2) is structured as follows: each subframe includes one special symbol and 12 data symbols, and the effective data portion length of each data symbol is 1024 Ts, and the special symbol includes GP and For AGC processed by AGC, the length of GP is 460Ts, and the length of AGCT is 1732Ts (112.8μs). Among them, AGCT supports time and frequency synchronization. The length of the first and eighth data symbols is 80Ts, and the remaining 10 data symbols. The length is 72Ts.

Referring to FIG. 7, the extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, and the effective data portion length of each data symbol is 1024 Ts, and the special symbol includes GP and is used for AGC processing. For AGCT, the length of GP is 460Ts (30μs), the length of AGC needs to be compressed to 41.9μs, and the length of AGCT is 644Ts. Among them, AGCT does not support time and frequency synchronization, and the length of each data symbol is 164Ts (10.68μs).

In the above embodiment, the clock synchronization mode of the D2D terminal in the coverage of the cellular network is described in detail. In practical applications, there are some D2D terminals outside the coverage of the cellular network, so that D2D terminals within the coverage of the cellular network need to search for D2D terminals outside the coverage of the cellular network when certain conditions are met. To discover such D2D terminals and assist them in completing clock synchronization.

The specific process is: when the first D2D terminal (synchronization level 1 or 2a) in the coverage of the cellular network determines that the pilot power of the received base station is less than a certain preset value (for example, Pd), not only needs to follow the general cellular network coverage. The mode of the internal D2D terminal receives the data of other D2D terminals within the coverage of the cellular network, and also needs to use the data receiving window to blindly detect the pilot signal transmitted by the D2D terminal (hereinafter referred to as the third D2D terminal) outside the coverage of the cellular network ( For example, the preamble), and detecting the data transmitted by it, when the pilot signal transmitted by the third D2D terminal of the synchronization level 3 is detected, the self-organizing mode is adopted. The sub-frame structure under the formula performs data transmission and reception with the third D2D terminal of the synchronization level 3, and assists the third D2D terminal of the synchronization level 3 to complete the clock synchronization with the first D2D terminal by using the distance calibration method or the uplink clock synchronization calibration manner. Entering synchronization level 2, wherein there is synchronization level 1 (ie, obtaining UTC authorization), synchronization level 2, synchronization level 3, and synchronization level 4 (ie, out-of-synchronization state) outside the coverage of the cellular network, and determining the synchronization level of each D2D terminal Compared with the method described in the existing ad hoc network, the synchronization level 2a in the default coverage of the first D2D terminal is equivalent to the synchronization level 2 outside the coverage of the cellular network, and therefore, only the third level of the synchronization level 3 is assisted. The three D2D terminals can complete the clock synchronization.

In an alternative manner of the foregoing specific process, after the third D2D terminal assisting the synchronization level 3 completes the clock synchronization with the first D2D terminal, further, if the third D2D terminal of the auxiliary level 3 adopts the distance calibration mode Synchronization with the clock of the first D2D terminal completes the synchronization level 2. The remaining steps are consistent with the specific implementation process described above, and are not described here.

The first D2D terminal (synchronization level 1 or 2a) within the coverage of the cellular network uses a self-organized subframe structure for data transmission if a third D2D terminal other than the coverage of the cellular network is found during the discovery process. The first D2D terminal of the synchronization levels 1 and 2a adds a synchronization pilot code to the transmitted data when the data is transmitted using the self-organized subframe structure, and the synchronization pilot code includes synchronization information indicating the synchronization level 2a, the cellular The third D2D terminal outside the network coverage regards the synchronization level 2a of the pilot code as the synchronization level 2, and the processing is mainly for reducing the processing complexity of the D2D terminal.

In summary, the third D2D terminal outside the coverage of the cellular network needs to work without the assistance of the base station because the downlink synchronous clock of the base station cannot be obtained. In this case, because the security overhead is large, frequency division processing is not required, and only time division multiple access is used, so that the arrival time of the received signal can be calculated in real time, and the length of the GP between different third D2D terminals is large. Therefore, the requirements for clock synchronization accuracy are very low. The third D2D terminal outside the coverage of the cellular network needs to increase the detection of the pilot code including the synchronization level 2a when detecting the pilot code, and equate the synchronization level 2a with the synchronization level 2 in order to reduce the D2D processing complexity.

Based on the foregoing embodiment, referring to FIG. 8, in the embodiment of the present invention, the D2D terminal includes a receiving unit 800, a first sending unit 810, and a second sending unit 820.

The receiving unit 800 is configured to receive D2D association system information sent by the network side, and establish downlink synchronization with the network side, and enter synchronization level 2b;

The first sending unit 810 is configured to determine, according to the received D2D association system information, that the cellular network has obtained the UTC timing of the Coordinated Time, and the location measurement error of the cellular network is lower than the preset threshold, and the distance calibration mode or the uplink synchronization calibration manner is used. Synchronize with the clock on the network side and enter synchronization level 2a;

or,

The second sending unit 820 is configured to determine, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or if the cellular network is determined not to obtain the UTC grant, the pre- Set the calibration mode to complete the synchronization with the clock of the device whose synchronization level meets the preset condition, and enter the synchronization level 2a.

Preferably, according to the received D2D association system information, it is determined that the cellular network has obtained UTC timing, and the location measurement error of the cellular network is lower than a preset threshold, and the distance synchronization mode or the uplink synchronization calibration manner is used to complete clock synchronization with the network side. Entering the synchronization level 2a, the first sending unit 810 is specifically configured to:

If the first sending unit 810 can obtain the uplink clock on the network side, the uplink synchronization calibration mode is used to complete the clock synchronization with the network side, and enter the synchronization level 2a;

or,

If the first sending unit 810 fails to obtain the uplink clock of the network side, the base station location information is further obtained based on the D2D associated system information, and then based on the distance between the first D2D terminal and the base station, the distance calibration method is used to complete the network side. The clock is synchronized and enters the synchronization level 2a.

Preferably, if the first sending unit 810 performs clock synchronization with the network side by using the uplink synchronization calibration mode, the first sending unit 810 adopts the first conventional CP subframe structure and the clock synchronization and clock synchronization. Performing information interaction between one of the two conventional CP subframe structures and the extended CP subframe structure;

If the first sending unit 810 completes the clock synchronization with the network side by using the distance calibration mode, the first sending unit 810 adopts the first regular CP subframe structure and the second regular CP subframe in the clock synchronization process and after the clock synchronization is completed. One of the structure and the extended CP subframe structure for information interaction;

among them,

The first conventional CP subframe structure is: each subframe includes 1 special symbol and 13 data symbols, the special symbol includes a guard slot GP and an automatic gain control code AGCT, the length of the GP is 460Ts, and the length of the AGCT is 636Ts, where , AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second conventional CP subframe structure is: each subframe includes one special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts, wherein the AGCT supports time and frequency synchronization. The length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe contains 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, wherein the AGCT does not support time and frequency synchronization. Each data symbol has a length of 164Ts.

Preferably, according to the received D2D association system information, it is determined that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or, if the cellular network is determined not to receive the UTC grant, the preset calibration manner is adopted. The clock synchronization of the device that meets the preset condition with the synchronization level is completed, and the synchronization level 2a is entered. The second sending unit 820 is specifically configured to:

The second sending unit 820 receives the dedicated pilot code sent by the second D2D terminal that is timed by the UTC, determines the downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the second sending unit 820 and the second D2D terminal. The distance between the two is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the second sending unit 820 obtains the location information of the base station according to the D2D association system information, based on the distance between the second sending unit 820 and the base station, the distance synchronization mode or the uplink synchronization calibration mode is used to complete the clock synchronization with the network side, and the synchronization is entered. Level 2a;

or,

The second sending unit 820 receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and is based on the second The distance between the sending unit 820 and the second D2D terminal is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

The second sending unit 820 receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when the data transmitted by the second D2D terminal authorized by the UTC is detected, and adopts zero calibration. The mode completes synchronization with the clock of the second D2D terminal, and enters the synchronization level 2a.

Preferably, if the second sending unit 820 receives the dedicated pilot code sent by the second D2D terminal, and completes the clock synchronization with the second D2D terminal by using the distance calibration mode, the second sending unit 820 during the clock synchronization process and the clock. After the synchronization is completed, the second regular CP subframe structure is used for information interaction;

If the second sending unit 820 completes the clock synchronization with the network side by using the distance calibration method based on the distance between the first D2D terminal and the base station, the second sending unit 820 adopts the extended CP during the clock synchronization process and after the clock synchronization is completed. Subframe structure for information interaction;

If the second sending unit 820 detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the second sending unit 820 and the second D2D terminal, performs the distance calibration method on the downlink clock of the second D2D terminal. Correcting, after the clock synchronization with the second D2D terminal is completed, the first D2D terminal adopts a first regular CP subframe structure, a second regular CP subframe structure, and an extended CP subframe structure in the clock synchronization process and after the clock synchronization is completed. One of them performs information interaction;

If the second sending unit 820 detects the data sent by the second D2D terminal authorized by the UTC, And performing the correction of the downlink clock of the second D2D terminal by using the zero calibration mode to complete the clock synchronization with the second D2D terminal, and then the second sending unit 820 adopts the extended CP subframe structure during the clock synchronization process and after the clock synchronization is completed. Perform information exchange;

among them,

Preferably, when it is determined that the pilot power of the received base station is less than a preset value, the data receiving window is used to blindly detect the pilot signal and data sent by the third D2D terminal outside the coverage of the cellular network, when the synchronization level 3 is detected. When the pilot signal transmitted by the third D2D terminal, or the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe structure in the self-organizing mode and the third D2D terminal of the synchronization level 3 are adopted. Data transmission and reception, and assist in the synchronization of level 3 third D2D terminal Using the distance calibration method or the uplink clock synchronous calibration mode, the clock synchronization with the device is completed, and the synchronization level 2 is entered, wherein the synchronization level 1, the synchronization level 2, the synchronization level 3, and the synchronization level 4 exist outside the coverage of the cellular network, and The synchronization level 2a within the default cellular coverage of the device is equivalent to the synchronization level 2 outside the coverage of the cellular network.

Based on the foregoing embodiment, referring to FIG. 9, in the embodiment of the present invention, the D2D terminal includes a receiving port 900 and a sending port 910, where:

The receiving port 900 is configured to receive D2D association system information sent by the network side, and establish downlink synchronization with the network side, and enter synchronization level 2b;

The sending port 910 is configured to determine, according to the received D2D association system information, that the cellular network has obtained the UTC timing of the Coordinated Universal Time, and the location measurement error of the cellular network is lower than a preset threshold, and complete the network with the distance calibration mode or the uplink synchronization calibration mode. The clock on the side is synchronized and enters the synchronization level 2a;

Preferably, according to the received D2D association system information, it is determined that the cellular network has obtained UTC timing, and the location measurement error of the cellular network is lower than a preset threshold, and the distance synchronization mode or the uplink synchronization calibration manner is used to complete clock synchronization with the network side. Enter synchronization level 2a, and send port 910 specifically. Used for:

If the sending port 910 can obtain the uplink clock of the network side, the clock synchronization with the network side is completed by using the uplink synchronous calibration mode, and the synchronization level 2a is entered;

or,

If the sending port 910 fails to obtain the uplink clock of the network side, the base station location information is further obtained based on the D2D associated system information, and then the distance synchronization between the first D2D terminal and the base station is used to complete the clock synchronization with the network side. Enter sync level 2a.

Preferably, if the sending port 910 performs the clock synchronization with the network side in the uplink synchronous calibration mode, the sending port 910 adopts the first regular CP subframe structure and the second regular CP sub-phase during the clock synchronization process and after the clock synchronization is completed. One of a frame structure and an extended CP subframe structure performs information interaction;

If the sending port 910 performs the clock synchronization with the network side in the distance calibration mode, the transmitting port 910 adopts the first regular CP subframe structure, the second regular CP subframe structure, and the extended CP during the clock synchronization process and after the clock synchronization is completed. One of the sub-frame structures performs information interaction;

among them,

Preferably, the cellular network has obtained the UTC grant according to the received D2D association system information, but the location measurement error of the cellular network is not lower than a preset threshold, or the cellular network is determined not to obtain UTC. When the timing is given, the clock synchronization of the device that meets the preset condition with the synchronization level is completed by using the preset calibration mode, and the synchronization level 2a is entered, and the transmission port 910 is specifically used for:

The sending port 910 receives the dedicated pilot code sent by the second D2D terminal that is timed by the UTC, determines the downlink clock of the second D2D terminal according to the dedicated pilot code, and uses the distance based on the distance between the sending port 910 and the second D2D terminal. The calibration mode corrects the downlink clock, completes synchronization with the clock of the second D2D terminal, and enters the synchronization level 2a;

or,

If the sending port 910 obtains the location information of the base station according to the D2D associated system information, based on the distance between the sending port 910 and the base station, the distance synchronization mode or the uplink synchronous calibration mode is used to complete the clock synchronization with the network side, and enter the synchronization level 2a;

or,

The sending port 910 receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and based on the sending port 910 and The distance between the second D2D terminals is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

The sending port 910 receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and completes the zero calibration mode. Synchronizing with the clock of the second D2D terminal, the synchronization level 2a is entered.

Preferably, if the sending port 910 receives the dedicated pilot code sent by the second D2D terminal, and completes the clock synchronization with the second D2D terminal by using the distance calibration mode, the sending port 910 is in the process of clock synchronization and after the clock synchronization is completed. Performing information interaction using a second conventional CP subframe structure;

If the sending port 910 is based on the distance between the first D2D terminal and the base station, and performing clock synchronization with the network side in the distance calibration mode, the transmitting port 910 performs the extended CP subframe structure after the clock synchronization process and the clock synchronization is completed. Information exchange;

If the sending port 910 detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the sending port 910 and the second D2D terminal, correcting the downlink clock of the second D2D terminal by using the distance calibration manner, and completing The clock synchronization of the second D2D terminal, the first D2D terminal adopts one of a first conventional CP subframe structure, a second regular CP subframe structure, and an extended CP subframe structure during clock synchronization and after clock synchronization is completed. Perform information exchange;

If the sending port 910 detects the data sent by the second D2D terminal authorized by the UTC, and performs the correction of the downlink clock of the second D2D terminal by using the zero calibration mode to complete the clock synchronization with the second D2D terminal, the sending port 910 is After the clock synchronization process and the clock synchronization are completed, the extended CP sub-frame structure is used for information interaction;

among them,

Preferably, when determining that the pilot power of the received base station is less than a preset value, the data receiving window is used to blindly detect the pilot signal and data sent by the third D2D terminal outside the coverage of the cellular network, when detecting When the pilot signal transmitted by the third D2D terminal of the synchronization level 3 is received, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe structure in the self-organizing mode and the coverage of the cellular network are adopted. The third D2D terminal performs data transmission and reception, and assists the third D2D terminal of the synchronization level 3 to complete the clock synchronization with the first D2D terminal by using the distance calibration mode or the uplink clock synchronization calibration mode, and enters the synchronization level 2, wherein the cellular network There is a synchronization level 1, a synchronization level 2, a synchronization level 3, and a synchronization level 4 outside the coverage, and the synchronization level 2a in the device default cellular coverage is equivalent to the synchronization level 2 outside the coverage of the cellular network.

In summary, in the embodiment of the present invention, the first D2D terminal accessing the cellular network receives the D2D association system information sent by the network side, establishes downlink synchronization with the network side, enters the synchronization level 2b, and determines that the cellular network has obtained the UTC grant time and The position measurement error of the cellular network is lower than the preset threshold, and the distance calibration mode or the uplink synchronous calibration mode is used to complete the synchronization with the network side clock, enter the synchronization level 2a, and determine that the cellular network has obtained the UTC timing, but the position measurement error of the cellular network Not less than the preset threshold, or determining that the cellular network is not UTC-granted, using a preset calibration method to complete the synchronization with the clock of the device whose synchronization level meets the preset condition, and entering the synchronization level 2a, so that the network topology changes rapidly. When the network scale is large, the overhead of clock synchronization of each D2D terminal can be reduced, and resource waste is avoided.

Based on the clock synchronization method and apparatus provided by the foregoing embodiments, the embodiment of the present application provides a D2D terminal. As shown in FIG. 10, the D2D terminal includes: a transceiver 1000, a processor 1002, and a memory 1004, and further includes a bus interface. 1006 and user interface 1008;

The processor 1002 is configured to determine that the D2D terminal is a first D2D terminal, and establish downlink synchronization with the network side according to the received D2D association system information sent by the network side, and enter a synchronization level 2b;

Determining, according to the received D2D association system information, that the cellular network has obtained UTC timing of the Coordinated Time, and the location measurement error of the cellular network is lower than a preset threshold, and performing clock synchronization with the network side by using a distance calibration method or an uplink synchronization calibration manner. Enter synchronization level 2a;

or,

Determining, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determining that the cellular network does not obtain UTC When the time is given, the preset calibration mode is used to complete the synchronization of the clock with the device whose synchronization level meets the preset condition, and enter the synchronization level 2a.

The memory 1004 is configured to store one or more executable programs for configuring the processor 1002.

In FIG. 10, the bus architecture may include any number of interconnected buses and bridges, specifically linked by one or more processors represented by processor 1002 and various circuits of memory represented by memory 1004. The bus architecture can also link various other circuits such as peripherals, voltage regulators, and power management circuits, which are well known in the art and, therefore, will not be further described herein. Transceiver 1000 can be a plurality of components, including a transmitter and a receiver, providing means for communicating with various other devices on a transmission medium. The processor 1002 is responsible for managing the bus architecture and general processing, and the memory 1004 can store data used by the processor 1002 in performing operations. Bus interface 1006 provides an interface. For different user equipments, the user interface 1008 may also be an interface capable of externally connecting the required devices, including but not limited to a keypad, a display, a speaker, a microphone, a joystick, and the like.

Preferably, if the processor 1002 determines that the cellular network has obtained UTC timing according to the received D2D association system information, and the position measurement error of the cellular network is lower than a preset threshold, the distance calibration method or the uplink synchronization calibration method is used to complete and The clock synchronization on the network side enters the synchronization level 2a, and the processor 1002 is specifically configured to:

If the processor 1002 can obtain the uplink clock on the network side, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

If the processor 1002 fails to obtain the uplink clock of the network side, the base station location information is further obtained based on the D2D association system information, and based on the distance between the D2D terminal and the base station, the distance calibration method is used to complete the network side. The clock is synchronized and enters the synchronization level 2a.

Preferably, the processor 1002 is further configured to: if the processor 1002 completes clock synchronization with the network side by using an uplink synchronization calibration manner, the processor 1002 adopts a first regular CP subframe during clock synchronization and after clock synchronization is completed. Information interaction between the structure, the second regular CP subframe structure, and the extended CP subframe structure;

If the processor 1002 completes the clock synchronization with the network side by using the distance calibration mode, the processor 1002 adopts the first regular CP subframe structure, the second regular CP subframe structure, and the extended CP during the clock synchronization process and after the clock synchronization is completed. One of the sub-frame structures performs information interaction;

among them,

Preferably, if the processor 1002 determines, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determines that the cellular network does not obtain the UTC grant, the pre-preparation is adopted. The calibration mode is set to complete the synchronization with the clock of the device whose synchronization level meets the preset condition, and enters the synchronization level 2a, and the processor 1002 is specifically configured to:

The processor 1002 receives the dedicated pilot code sent by the second D2D terminal that is timed by the UTC, determines the downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the first D2D terminal and The distance between the second D2D terminals is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the processor 1002 obtains the location information of the base station according to the D2D association system information, based on the distance between the first D2D terminal and the base station, the distance synchronization mode or the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level. 2a;

or,

The processor 1002 receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and based on the The distance between the first D2D terminal and the second D2D terminal is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

The processor 1002 receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when the data transmitted by the second D2D terminal authorized by the UTC is detected, and adopts zero calibration. The mode completes synchronization with the clock of the second D2D terminal, and enters the synchronization level 2a.

Preferably, the processor 1002 is further configured to: if the processor 1002 receives the dedicated pilot code sent by the second D2D terminal, and completes clock synchronization with the second D2D terminal by using a distance calibration manner, After the clock synchronization process and the clock synchronization are completed, the first D2D terminal uses the second regular CP subframe structure to perform information interaction;

If the processor 1002 completes the clock synchronization with the network side by using the distance calibration method based on the distance between the first D2D terminal and the base station, the first D2D terminal adopts an extension during the clock synchronization process and after the clock synchronization is completed. The CP subframe structure performs information interaction;

If the processor 1002 detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the first D2D terminal and the second D2D terminal, the second D2D is adopted in a distance calibration manner. The downlink clock of the terminal is corrected to complete clock synchronization with the second D2D terminal, and the first D2D terminal adopts a first regular CP subframe structure and a second regular CP during clock synchronization and after clock synchronization is completed. Information interaction between one of a subframe structure and an extended CP subframe structure;

If the processor 1002 detects the data sent by the second D2D terminal authorized by the UTC, and completes correcting the downlink clock of the second D2D terminal by using a zero calibration manner, completing clock synchronization with the second D2D terminal. And the first D2D terminal uses the extended CP subframe structure to perform information interaction during the clock synchronization process and after the clock synchronization is completed;

among them,

After obtaining the UTC authorization, the D2D terminal enters the synchronization level 1 and restarts according to the set period. Obtaining the UTC authorization, if the UTC authorization is not obtained within the second set duration, the synchronization level 2a is entered.

Preferably, the D2D terminal further includes: when the processor 1002 determines that the received pilot power of the base station is less than a preset value, the data receiving window is used to blindly detect the pilot transmitted by the third D2D terminal outside the coverage of the cellular network. Signal and data, when the pilot signal transmitted by the third D2D terminal of the synchronization level 3 is detected, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe in the self-organizing mode is adopted. The structure and the D2D terminal outside the coverage of the cellular network perform data transmission and reception, and assist the synchronization of the third D2D terminal of the level 3 by using a distance calibration mode or an uplink clock synchronization calibration mode to complete clock synchronization with the first D2D terminal, and enter a synchronization level. 2, wherein there is a synchronization level 1, a synchronization level 2, a synchronization level 3, and a synchronization level 4 outside the coverage of the cellular network, and the synchronization level 2a in the default coverage of the first D2D terminal is equivalent to the coverage of the cellular network. Synchronization level 2 outside.

Those skilled in the art will appreciate that embodiments of the present invention can be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the invention can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) including computer usable program code.

The present invention has been described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (system), and computer program products according to embodiments of the invention. It will be understood that each of the processes and/or blocks in the flowcharts and/or block diagrams, and the flows in the flowcharts and/or block diagrams can be implemented by computer program instructions. And/or a combination of boxes. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine for the execution of instructions for execution by a processor of a computer or other programmable data processing device. Means for implementing the functions specified in one or more of the flow or in a block or blocks of the flow chart.

The computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device. The apparatus implements the functions specified in one or more blocks of a flow or a flow and/or block diagram of the flowchart.

These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device. The instructions provide steps for implementing the functions specified in one or more of the flow or in a block or blocks of a flow diagram.

While the preferred embodiment of the invention has been described, it will be understood that Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and the modifications and

It is apparent that those skilled in the art can make various modifications and variations to the embodiments of the invention without departing from the spirit and scope of the embodiments of the invention. Thus, it is intended that the present invention cover the modifications and modifications of the embodiments of the invention.

Claims

A clock synchronization method, comprising:

The first device to the device D2D terminal accessing the cellular network receives the D2D association system information sent by the network side, and establishes downlink synchronization with the network side, and enters the synchronization level 2b;

If the first D2D terminal determines, according to the received D2D association system information, that the cellular network has obtained the UTC timing of the Coordinated Time, and the position measurement error of the cellular network is lower than the preset threshold, the distance calibration mode or the uplink synchronization calibration mode is used to complete the The clock on the network side is synchronized and enters the synchronization level 2a;

or,

If the first D2D terminal determines, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determines that the cellular network does not obtain the UTC grant, the preset is adopted. The calibration mode completes the synchronization with the clock of the device whose synchronization level meets the preset condition, and enters the synchronization level 2a.
The method of claim 1 wherein

The first D2D terminal enters a synchronization level 2b, and indicates that the first D2D terminal is only capable of receiving data and cannot send data;

The first D2D terminal enters a synchronization level 2a, which indicates that the first D2D terminal can receive data and can also transmit data.
The method according to claim 1, wherein the synchronizing with the clock on the network side by using the distance calibration method or the uplink synchronization calibration manner, and entering the synchronization level 2a, includes:

If the first D2D terminal can obtain the uplink clock on the network side, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

If the first D2D terminal fails to obtain the uplink clock of the network side, further obtain base station location information based on the D2D association system information, and then perform distance calibration based on the distance between the first D2D terminal and the base station. The mode completes synchronization with the clock on the network side and enters the synchronization level 2a.
The method of claim 1 further comprising:

If the first D2D terminal completes the clock synchronization with the network side by using the uplink synchronization calibration mode, the first D2D terminal adopts the first regular cyclic prefix CP subframe structure and the clock after the clock synchronization process and the clock synchronization is completed. Performing information interaction between one of the two conventional CP subframe structures and the extended CP subframe structure;

If the first D2D terminal completes the clock synchronization with the network side by using the distance calibration mode, the first D2D terminal adopts the first regular CP subframe structure and the second regular CP during the clock synchronization process and after the clock synchronization is completed. Information interaction between one of a subframe structure and an extended CP subframe structure;

among them,

The first conventional CP subframe structure is: each subframe includes one special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, and the length of the GP is 460Ts. The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second regular CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts. The AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where The AGCT does not support time and frequency synchronization, and each data symbol has a length of 164 Ts.
The method according to claim 1, wherein the step of synchronizing with the clock of the device whose synchronization level meets the preset condition is completed by using a preset calibration manner, and the synchronization level 2a is entered, including:

The first D2D terminal receives a dedicated pilot code sent by the second D2D terminal that is UTC-granted, determines a downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the first D2D terminal and the Describe the distance between the second D2D terminals, using the distance calibration method for the downlink time The clock is corrected, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the first D2D terminal obtains the location information of the base station according to the D2D association system information, based on the distance between the first D2D terminal and the base station, the distance calibration mode or the uplink synchronization calibration mode is used to complete the clock with the network side. Synchronize, enter synchronization level 2a;

or,

If the position measurement error of the cellular network is not lower than the preset threshold, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

The first D2D terminal receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and Determining, by the distance calibration method, the downlink clock based on the distance between the first D2D terminal and the second D2D terminal, completing the clock synchronization with the second D2D terminal, and entering the synchronization level 2a;

or,

The first D2D terminal receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and The clock synchronization with the second D2D terminal is completed in a zero calibration manner, and the synchronization level 2a is entered.
The method of claim 5, further comprising:

After the first D2D terminal receives the dedicated pilot code sent by the second D2D terminal, and completes clock synchronization with the second D2D terminal by using a distance calibration manner, the first D2D terminal is in the process of clock synchronization. After the clock synchronization is completed, the second regular CP subframe structure is used for information interaction;

If the first D2D terminal completes the clock synchronization with the network side by using the distance calibration method based on the distance between the first D2D terminal and the base station, the first D2D terminal is in the process of clock synchronization and after the clock synchronization is completed. , using an extended CP subframe structure for information interaction;

And if the first D2D terminal detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the first D2D terminal and the second D2D terminal, using the distance calibration method Correcting a downlink clock of the second D2D terminal to complete clock synchronization with the second D2D terminal, wherein the first D2D terminal adopts a first conventional CP subframe structure and a clock synchronization process and after clock synchronization is completed. Performing information interaction between one of the two conventional CP subframe structures and the extended CP subframe structure;

If the first D2D terminal detects the data sent by the second D2D terminal authorized by the UTC, and completes correcting the downlink clock of the second D2D terminal by using a zero calibration manner, completing the second D2D terminal The clock synchronization is performed, and the first D2D terminal uses an extended CP subframe structure for information interaction during clock synchronization and after clock synchronization is completed;

among them,

The first conventional CP subframe structure is: each subframe includes one special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, and the length of the GP is 460Ts. The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second regular CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts. The AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where The AGCT does not support time and frequency synchronization, and each data symbol has a length of 164 Ts.
The method of any of claims 1-6, further comprising:

After the first D2D terminal enters the synchronization level 2a, the clock synchronization is re-completed according to the set period. If the clock synchronization is not completed within the first set duration, the synchronization level 2b is entered;

After obtaining the UTC authorization, the first D2D terminal enters the synchronization level 1, and reacquires the UTC authorization according to the set period. If the UTC authorization is not obtained within the second set time period, the synchronization level 2a is entered.
The method of any of claims 1-6, further comprising:

After the first D2D terminal enters the synchronization level 2b, if the second D2D terminal synchronization message of the synchronization level 1 is received, the synchronization level 2a is directly entered or the clock synchronization with the second D2D terminal is completed by using the distance calibration mode. Enter sync level 2a.
The method of any of claims 1-6, further comprising:

When the first D2D terminal determines that the pilot power of the received base station is less than a preset value, the data receiving window is used to blindly detect the pilot signal and data sent by the third D2D terminal outside the coverage of the cellular network;

When the pilot signal transmitted by the third D2D terminal of the synchronization level 3 is detected, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe structure and the cellular network in the self-organizing mode are adopted. The D2D terminal that is out of coverage performs data transmission and reception, and assists the third D2D terminal of the synchronization level 3 to complete the synchronization with the clock of the first D2D terminal by using the distance calibration mode or the uplink clock synchronization calibration mode, and enters the synchronization level 2, where There is synchronization level 1, synchronization level 2, synchronization level 3 and synchronization level 4 outside the coverage of the cellular network, and the synchronization level 2a in the default coverage of the first D2D terminal is equivalent to the synchronization outside the coverage of the cellular network. Level 2.
A clock synchronization device, comprising:

a receiving unit, configured to receive D2D association system information sent by the network side, and establish downlink synchronization with the network side, so that the device enters the synchronization level 2b;

a first sending unit, configured to determine, according to the received D2D associated system information, that the cellular network has obtained the UTC timing of the Coordinated Universal Time, and when the position measurement error of the cellular network is lower than a preset threshold, using a distance calibration mode or an uplink synchronization calibration manner Completing the synchronization with the clock on the network side, so that the device enters the synchronization level 2a;

or,

a second sending unit, configured to determine, according to the received D2D association system information, that the cellular network has been Obtaining the UTC timing, but when the position measurement error of the cellular network is not lower than the preset threshold, or determining that the cellular network does not obtain the UTC grant, the preset calibration mode is used to complete the clock synchronization of the device that meets the preset condition with the synchronization level. The device is brought into synchronization level 2a.
The device of claim 10, comprising:

The device enters a synchronization level 2b, indicating that the device is only capable of receiving data and is unable to transmit data;

The device enters synchronization level 2a, characterizing that the device is capable of receiving data and is also capable of transmitting data.
The apparatus according to claim 10, wherein, according to the received D2D associated system information, it is determined that the cellular network has obtained UTC timing, and the location measurement error of the cellular network is lower than a preset threshold, and the distance calibration mode or uplink is adopted. The synchronous calibration mode is synchronized with the clock on the network side. When the synchronization level 2a is entered, the first sending unit is specifically configured to:

If the first sending unit can obtain the uplink clock on the network side, use the uplink synchronous calibration mode to complete the clock synchronization with the network side, and enter the synchronization level 2a;

or,

If the first sending unit fails to obtain the uplink clock of the network side, further obtaining base station location information based on the D2D associated system information, and then performing distance calibration based on the distance between the clock synchronization device and the base station. The clock on the network side is synchronized and enters the synchronization level 2a.
The device of claim 10, further comprising:

If the first sending unit completes the clock synchronization with the network side by using the uplink synchronization calibration mode, the first sending unit adopts the first regular cyclic prefix CP subframe structure and the clock after the clock synchronization process and the clock synchronization is completed. Performing information interaction between one of the two conventional CP subframe structures and the extended CP subframe structure;

If the first sending unit completes the clock synchronization with the network side by using the distance calibration mode, the first sending unit adopts the first regular CP subframe structure and the second regular CP during the clock synchronization process and after the clock synchronization is completed. Information interaction between one of a subframe structure and an extended CP subframe structure;

among them,

The first conventional CP subframe structure is: each subframe includes one special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, and the length of the GP is 460Ts. The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second regular CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts. The AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where The AGCT does not support time and frequency synchronization, and each data symbol has a length of 164 Ts.
The device according to claim 10, wherein, according to the received D2D associated system information, it is determined that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or the cellular network is determined not to be determined. When the UTC grant is obtained, the clock synchronization of the device that meets the preset condition with the synchronization level is completed by using a preset calibration mode. When the synchronization level 2a is entered, the second sending unit is specifically configured to:

The second sending unit receives a dedicated pilot code sent by the second D2D terminal that is timed by the UTC, determines a downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the clock synchronization apparatus and the The distance between the second D2D terminals is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the second sending unit obtains the location information of the base station according to the D2D association system information, the clock synchronization with the network side is completed by using a distance calibration method or an uplink synchronization calibration manner based on the distance between the clock synchronization device and the base station. , enter the synchronization level 2a;

Or,

If the position measurement error of the cellular network is not lower than the preset threshold, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

The second sending unit receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and The distance clock is corrected according to the distance between the clock synchronization device and the second D2D terminal, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

The second sending unit, according to the downlink synchronization established with the base station, receives the data sent by the other D2D terminal, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC And the clock synchronization with the second D2D terminal is completed in a zero calibration manner, and the synchronization level 2a is entered.
The device of claim 14 further comprising:

After the second sending unit receives the dedicated pilot code sent by the second D2D terminal, and completes clock synchronization with the second D2D terminal by using a distance calibration manner, the second sending unit is in the clock synchronization process. After the clock synchronization is completed, the second regular CP subframe structure is used for information interaction;

If the second sending unit completes the clock synchronization with the network side by using the distance calibration method based on the distance between the clock synchronization device and the base station, the second sending unit performs the clock synchronization process and after the clock synchronization is completed. Using the extended CP sub-frame structure for information interaction;

And if the second sending unit detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the clock synchronization device and the second D2D terminal, using the distance calibration method The downlink clock of the second D2D terminal is corrected to complete the clock synchronization with the second D2D terminal, and the first D2D terminal adopts the first conventional CP subframe structure and the second after the clock synchronization process and the clock synchronization is completed. Performing information interaction between one of a regular CP subframe structure and an extended CP subframe structure;

If the second sending unit detects the data sent by the second D2D terminal authorized by the UTC, and completes correcting the downlink clock of the second D2D terminal by using a zero calibration manner, completing the second D2D terminal The clock is synchronized, and the second sending unit uses the extended CP subframe structure to perform information interaction during the clock synchronization process and after the clock synchronization is completed;

among them,

The first conventional CP subframe structure is: each subframe includes one special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, and the length of the GP is 460Ts. The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second regular CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts. The AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where The AGCT does not support time and frequency synchronization, and each data symbol has a length of 164 Ts.
The device of any of claims 10-15, further comprising:

After entering the synchronization level 2a, the clock synchronization is re-completed according to the set period, and if the clock synchronization is not completed within the first set duration, the synchronization level 2b is entered;

After obtaining the UTC authorization, the synchronization level 1 is entered, and the UTC authorization is reacquired according to the set period. If the UTC authorization is not obtained within the second set duration, the synchronization level 2a is entered.
The method of any of claims 10-15, further comprising:

After entering the synchronization level 2b, if the second D2D terminal synchronization message of the synchronization level 1 is received, the synchronization level 2a is directly entered or the clock synchronization with the second D2D terminal is completed by the distance calibration method, and then the synchronization level 2a is entered. .
The device of any of claims 10-15, further comprising:

When it is determined that the pilot power of the received base station is less than a preset value, the data receiving window is used to blindly detect the pilot signal and data sent by the third D2D terminal outside the coverage of the cellular network, and when the third D2D of the synchronization level 3 is detected. When the pilot signal sent by the terminal, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe structure in the self-organizing mode is used to transmit and receive data to and from the terminal outside the coverage of the cellular network, and The third D2D terminal assisting the synchronization level 3 adopts the distance calibration mode or the uplink clock synchronization calibration mode to complete the clock synchronization with the device, and enters the synchronization level 2, wherein the synchronization level 1 and the synchronization exist outside the coverage of the cellular network. Level 2, synchronization level 3, and synchronization level 4, and the synchronization level 2a within the default cellular coverage of the device is equivalent to synchronization level 2 outside the coverage of the cellular network.
A D2D terminal, comprising: at least: a transceiver, a processor, and a memory;

The processor is configured to determine that the D2D terminal is a first D2D terminal, establish downlink synchronization with the network side according to the D2D association system information sent by the received network side, and enter a synchronization level 2b; according to the received D2D association system The information determines that the cellular network has obtained the UTC timing of the Coordinated Universal Time, and the position measurement error of the cellular network is lower than the preset threshold, and the clock synchronization with the network side is completed by using the distance calibration mode or the uplink synchronous calibration mode, and the synchronization level 2a is entered;

or,

Determining, according to the received D2D association system information, that the cellular network has obtained the UTC grant, but the location measurement error of the cellular network is not lower than a preset threshold, or determining that the cellular network does not obtain the UTC grant, using a preset calibration manner, completing and The clock synchronization of the device whose synchronization level meets the preset condition enters the synchronization level 2a.
The D2D terminal of claim 19, wherein

The D2D terminal enters a synchronization level 2b, indicating that the D2D terminal can only receive data and cannot send data;

The D2D terminal enters a synchronization level 2a, which indicates that the D2D terminal can receive data and can also transmit data.
The D2D terminal according to claim 19, wherein the distance synchronization with the network side is completed by using a distance calibration method or an uplink synchronization calibration method, and the synchronization level 2a is entered. The processor is specifically configured to:

If the processor can obtain the uplink clock on the network side, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

If the processor fails to obtain the uplink clock of the network side, further obtaining base station location information based on the D2D association system information, and then performing distance calibration on the network side based on the distance between the D2D terminal and the base station. The clock is synchronized and enters synchronization level 2a.
The D2D terminal of claim 19, wherein the processor is further configured to:

If the processor completes clock synchronization with the network side by using an uplink synchronization calibration mode, the processor adopts a first regular CP subframe structure and a second conventional CP subframe structure during clock synchronization and after clock synchronization is completed. And interacting with one of the extended CP subframe structures;

If the processor completes the clock synchronization with the network side by using the distance calibration mode, the processor adopts a first regular CP subframe structure, a second conventional CP subframe structure, and a clock synchronization process and after clock synchronization is completed. Extending one of the CP sub-frame structures for information interaction;

among them,

The first conventional CP subframe structure is: each subframe includes one special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, and the length of the GP is 460Ts. The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second regular CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts. The AGCT supports time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes one special symbol and 12 data symbols. The special symbols include GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, wherein the AGCT does not support time and frequency synchronization, and each data symbol has a length of 164Ts.
The D2D terminal according to claim 19, wherein the clock synchronization of the device that meets the preset condition with the synchronization level is completed by using a preset calibration manner, and the synchronization level 2a is entered. The processor is specifically configured to:

The processor receives a dedicated pilot code sent by a second D2D terminal that is timed by UTC, determines a downlink clock of the second D2D terminal according to the dedicated pilot code, and is based on the first D2D terminal and the second D2D The distance between the terminals is corrected by the distance calibration method, and the clock synchronization with the second D2D terminal is completed, and the synchronization level 2a is entered;

or,

If the processor obtains the location information of the base station according to the D2D association system information, based on the distance between the first D2D terminal and the base station, the distance synchronization mode or the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter synchronization. Level 2a;

or,

If the position measurement error of the cellular network is not lower than the preset threshold, the uplink synchronization calibration mode is used to complete the synchronization with the network side clock, and enter the synchronization level 2a;

or,

The processor receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when detecting the data sent by the second D2D terminal authorized by the UTC, and based on the Describe the distance between the first D2D terminal and the second D2D terminal, correct the downlink clock by using a distance calibration manner, complete the clock synchronization with the second D2D terminal, and enter the synchronization level 2a;

or,

The processor receives the data sent by the other D2D terminal based on the downlink synchronization established with the base station, and acquires the downlink clock of the second D2D terminal when the data sent by the second D2D terminal authorized by the UTC is detected, and adopts zero The calibration mode is completed and synchronized with the clock of the second D2D terminal. Enter sync level 2a.
The D2D terminal of claim 23, wherein the processor is further configured to:

After the processor receives the dedicated pilot code sent by the second D2D terminal, and completes clock synchronization with the second D2D terminal by using a distance calibration manner, the first D2D terminal is in clock synchronization and clock synchronization. After completion, the second regular CP subframe structure is used for information interaction;

If the processor performs clock synchronization with the network side by using a distance calibration method based on the distance between the first D2D terminal and the base station, the first D2D terminal adopts the clock synchronization process and after the clock synchronization is completed. Extending the CP subframe structure for information interaction;

And if the processor detects the data sent by the second D2D terminal authorized by the UTC, and based on the distance between the first D2D terminal and the second D2D terminal, using the distance calibration method to the second The downlink clock of the D2D terminal is corrected to complete clock synchronization with the second D2D terminal, and the first D2D terminal adopts a first conventional CP subframe structure and a second regularity during clock synchronization and after clock synchronization is completed. One of a CP subframe structure and an extended CP subframe structure performs information interaction;

If the processor detects the data sent by the second D2D terminal authorized by the UTC, and completes the correction of the downlink clock of the second D2D terminal by using a zero calibration manner, completing the clock with the second D2D terminal. Synchronization, the first D2D terminal uses an extended CP subframe structure for information interaction during clock synchronization and after clock synchronization is completed;

among them,

The first conventional CP subframe structure is: each subframe includes 1 special symbol and 13 data symbols, and the special symbol includes a guard slot GP and an automatic gain control code AGCT, the length of the GP is 460Ts, the AGCT The length of the AGCT is 636Ts, wherein the AGCT does not support time and frequency synchronization, the length of the first and eighth data symbols is 80Ts, and the length of the remaining 11 data symbols is 72Ts;

The second conventional CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 1732Ts, where The AGCT supports time and frequency synchronization, 1st and 8th data The length of the symbol is 80Ts, and the length of the remaining 10 data symbols is 72Ts;

The extended CP subframe structure is: each subframe includes 1 special symbol and 12 data symbols, the special symbol includes GP and AGCT, the length of the GP is 460Ts, and the length of the AGCT is 644Ts, where AGCT does not support time and frequency synchronization, and each data symbol has a length of 164Ts.
The D2D terminal according to any one of claims 19 to 24, further comprising:

After the D2D terminal enters the synchronization level 2a, the clock synchronization is re-completed according to the set period. If the clock synchronization is not completed within the first set duration, the synchronization level 2b is entered;

After obtaining the UTC authorization, the D2D terminal enters the synchronization level 1, and reacquires the UTC authorization according to the set period. If the UTC authorization is not obtained within the second set time period, the synchronization level 2a is entered.
The D2D terminal according to any one of claims 19 to 24, further comprising:

After the D2D terminal enters the synchronization level 2b, if the second D2D terminal synchronization message of the synchronization level 1 is received, the D2D terminal directly enters the synchronization level 2a or completes the synchronization with the clock of the second D2D terminal by using the distance calibration mode, and then enters the synchronization. Level 2a.
The D2D terminal according to any one of claims 19 to 24, further comprising:

When the processor determines that the pilot power of the received base station is less than a preset value, the data receiving window is used to blindly detect the pilot signal and data sent by the third D2D terminal outside the coverage of the cellular network, when the synchronization level 3 is detected. When the pilot signal transmitted by the third D2D terminal is used, or when the signal transmitted by the third D2D terminal other than the coverage of the cellular network is detected, the subframe structure in the self-organizing mode is used to perform the D2D terminal outside the coverage of the cellular network. Transmitting and transmitting data, and assisting in synchronizing the third D2D terminal of the level 3 by using a distance calibration method or an uplink clock synchronization calibration manner, completing clock synchronization with the first D2D terminal, and entering synchronization level 2, wherein the coverage of the cellular network is out of range There is a synchronization level 1, a synchronization level 2, a synchronization level 3, and a synchronization level 4, and the first D2D terminal defaults to a cellular network overlay. The synchronization level 2a within the coverage range is equivalent to the synchronization level 2 outside the coverage of the cellular network.