CN-116390219-B - Access synchronization and tracking method for TDMA self-organizing network broadband frequency hopping system

CN116390219BCN 116390219 BCN116390219 BCN 116390219BCN-116390219-B

Abstract

An access synchronization and tracking method for a TDMA self-organizing network broadband frequency hopping system belongs to the technical field of communication. The invention solves the problem that the synchronization and access of the broadband frequency hopping system in the TDMA self-organizing network scene can not be realized by adopting the prior method. The invention corresponds the frequency hopping time slot with the time slot of the TDMA self-organizing network, and completes the time synchronization and tracking correction process of the TDMA self-organizing network, and simultaneously completes the synchronous capturing and tracking of the frequency hopping system, thereby ensuring that the network access process is simpler, more convenient and faster. Through the synchronous symbols carried in each time slot, the receiver can accurately determine the positions of the symbols, complete the demodulation of signals and realize the transmission of information. Meanwhile, by the design of the front and rear guard intervals, the influence of different clock deviations and propagation delays in interconnection and interworking among nodes in the self-organizing network can be effectively dealt with. The method can be applied to synchronization and access of the broadband frequency hopping system in a TDMA self-organizing network scene.

Inventors

FANG XIAOJIE
Liao Zhuangzhuang
ZHANG TONG
ZHANG CHUANBIN
LI ZUNQI
SHA XUEJUN

Assignees

哈尔滨工业大学

Dates

Publication Date: 20260505
Application Date: 20230419

Claims (9)

The access synchronization and tracking method for the TDMA self-organizing network broadband frequency hopping system is characterized by comprising the following steps: Step 1, presetting M frequency hopping tables, wherein each frequency hopping table comprises a plurality of frequency hopping frequency points, and the duration time of each frequency point is t hop ; Taking the duration of each hop in frequency hopping as a time slot in the TDMA self-organizing network, namely taking the duration t hop of each frequency point as a time slot in the TDMA self-organizing network, taking N continuous time slots as a super-frame, and functionally dividing N time slots contained in the super-frame into 1 network management time slot, 1 access time slot and N-2 service time slots; Step 2, the structure in each time slot is divided into a front guard interval, a synchronous symbol, a reference symbol, a data symbol and a rear guard interval in sequence; Step 3, the nodes in the unaccessed network execute network time synchronization and access; For a node in a certain network to be accessed to the network, the specific process of performing network time synchronization and access is as follows: Step 31, the node to be accessed to the network waits at a random frequency point f w , and carries out sliding cross-correlation operation on the baseband data received at the frequency point and a local synchronous sequence until a sliding cross-correlation peak value is detected, and then step 32 is executed; Step 32, the node to be accessed to the network records the frequency point f w waiting currently and the time t p when the sliding cross correlation peak value is detected, and obtains the starting time t s of the time slot corresponding to the frequency point f w according to t p : t s ＝t p -Δt s,p wherein Δt s,p is the time difference between the time when the sliding cross-correlation peak is detected and the starting time of the time slot corresponding to the frequency point f w ; step 33, determining the positions of the synchronization symbol, the reference symbol and each data symbol in the baseband data received in step 31 according to the detected position of the sliding cross-correlation peak value, extracting the reference symbol and each data symbol, and sequentially performing FFT, channel estimation, channel equalization, constellation demodulation, channel decoding and CRC on the extracted data; If the CRC result is wrong, randomly changing the receiving frequency point of the node to be accessed to the network to be f' w , and jumping to execute the step 31; Step 34, obtaining the time slot where the data packet is located and the frequency hopping table specifically used by the current frequency hopping network according to the information in the frame header of the data packet with correct CRC check result; according to the frequency points of the data packet which are recorded in the step 32 and receive the correct CRC result, and combining with a frequency hopping table used by the current frequency hopping network, the node to be accessed to the network acquires the subsequent frequency hopping frequency points of the network; Calculating the starting time of each superframe according to the time t s obtained in the step 32 and the time slot where the data packet is located, and finishing preliminary correction of the self time and the time in the network according to the calculated starting time of each superframe by the node to be accessed to the network, namely aligning the self time with the calculated starting time of the superframe; Step 35, obtaining the time corresponding to the access time slot according to the calculated starting time of each superframe and the position of the access time slot in the superframe, and sending the access request information by using the frequency hopping frequency corresponding to the access time slot at the time corresponding to the access time slot; step 36, after receiving an access request from a node of the network to be accessed, the node in the network calculates a starting time t ra of an access time slot where the access request is located according to Δt s,p , and feeds back time information t ra as a part of an access request reply to the node of the network to be accessed; step 37, after receiving the access request reply, the node of the network to be accessed calculates the propagation delay delta t d and clock deviation delta t a between the node in the network and the node of the network to be accessed according to the time information t ra fed back in the access request reply and the time t rack of receiving the access request reply; correcting the clock bias according to the calculated delta t a to finish the access process; And 4, correcting clock deviation of the nodes in the accessed network in real time in the communication process.
2. The method for access synchronization and tracking in a TDMA ad hoc network broadband frequency hopping system according to claim 1, wherein said network management time slots are used for a cluster head node in the TDMA ad hoc network to broadcast network control information to other slave nodes.
3. The method for access synchronization and tracking in a TDMA ad hoc network broadband frequency hopping system according to claim 2, wherein said access time slots are used for nodes in the network to be accessed to initiate access requests.
4. The method for access synchronization and tracking in a TDMA ad hoc network broadband frequency hopping system according to claim 3, wherein said traffic slots are used for data traffic between nodes in the TDMA ad hoc network.
5. The method for synchronizing and tracking access of a TDMA ad hoc network broadband frequency hopping system according to claim 4, wherein said calculating propagation delay Δt d and clock deviation Δt a according to time information t ra fed back in access request reply and time t rack when receiving access request reply comprises the following steps: setting the time when the node to be accessed to the network sends the access request as t sa , and the time when the node in the network sends the access request reply as t sack , then Wherein Δt a represents the clock bias between the node in the network and the node of the network to be accessed, and Δt d represents the propagation delay between the node in the network and the node of the network to be accessed; And (3) solving to obtain:
6. The method for access synchronization and tracking in a TDMA ad hoc network broadband frequency hopping system according to claim 5, wherein the length of the post guard interval of said access slot is 2 times the length of the post guard interval of the other slots.
7. The method for access synchronization and tracking of TDMA ad hoc network broadband frequency hopping system according to claim 6, wherein said step 4 comprises the steps of: step 41, setting any one node in the network as a master node, and taking the rest nodes as slave nodes and taking the time of the master node as a reference; Step 42, in the communication process, each time the slave node receives the data of the master node, calculating the signal delay from the master node to the slave node according to the time when the data is received, and when the signal delay from the master node to the slave node exceeds a set range [ t 1 ,t 2 ], sending a time correction request by the slave node; Wherein t 1 is the difference between the propagation delay from the master node to the slave node and a preset threshold deltat m when the clock offset correction is performed last time, and t 2 is the sum of the propagation delay from the master node to the slave node and a preset threshold deltat m when the clock offset correction is performed last time; Step 43, after receiving the time correction request sent by the slave node, the master node records the time t rc when the time correction request is received, and feeds back the time information t rc as a part of the time correction request reply to the slave node which initiates the time correction request; step 44, after receiving the time correction request reply from the node, calculating the current propagation delay and clock deviation between the master node and the slave node according to the time t rc fed back in the time correction request reply and the time t r ′ ack receiving the time correction request reply; and the slave node corrects the clock deviation according to the calculated current clock deviation, and the time correction process is completed.
8. The method for access synchronization and tracking for a TDMA ad hoc network broadband frequency hopping system according to claim 7, wherein said threshold Δt m is not greater than min { t sp ,t ep -Δt d,max }, wherein t sp is a front guard interval length, t ep is a rear guard interval length, and Δt d,max is a maximum transmission delay.
9. The method for synchronizing and tracking access of a TDMA ad hoc network broadband frequency hopping system according to claim 8, wherein said calculating the current propagation delay and clock bias between the master node and the slave node according to the time t rc fed back in the time correction request reply and the time t' rack when receiving the time correction request reply comprises the following steps: Let the time of sending the time correction request by the slave node be t ' sa , and the time of sending the time correction request reply by the master node be t' sack Wherein Δt ' a represents the current clock bias between the master node and the slave node, and Δt' d represents the current propagation delay between the master node and the slave node; And (3) solving to obtain:

Description

Access synchronization and tracking method for TDMA self-organizing network broadband frequency hopping system Technical Field The invention belongs to the technical field of communication, and particularly relates to an access synchronization and tracking method for a TDMA self-organizing network broadband frequency hopping system. Background With the increasing demand for various high-rate communication services, wideband communication technologies, such as wideband OFDM technology, are increasingly used in wireless communication systems. In a military communication scenario, the communication system needs to not only meet the requirement of a higher communication rate, but also resist various malicious interferences of an adversary in a complex battlefield environment. Frequency hopping is also commonly used in various military communication systems as an effective means of combating interference. Meanwhile, with the application of unmanned aerial vehicle clusters in military, the end of a military communication network is gradually required to have stronger network self-organizing capability and strong network topology robustness. However, the synchronization and access of the broadband frequency hopping system in the TDMA self-organizing network scene can not be realized by adopting the existing method. Disclosure of Invention The invention aims to solve the problem that the synchronous and access of a broadband frequency hopping system in a TDMA self-organizing network scene can not be realized by adopting the existing method, and provides a synchronous and tracking method for the access of the TDMA self-organizing network broadband frequency hopping system. The wideband frequency hopping system of the present invention is a wideband communication system in which a communication frequency point combined with a frequency hopping technique continuously changes during communication. The technical scheme adopted by the invention for solving the technical problems is as follows: The method for synchronizing and tracking the access of the TDMA self-organizing network broadband frequency hopping system specifically comprises the following steps: Step 1, presetting M frequency hopping tables, wherein each frequency hopping table comprises a plurality of frequency hopping frequency points, and the duration time of each frequency point is t hop; Taking the duration of each hop in frequency hopping as a time slot in the TDMA self-organizing network, namely taking the duration t hop of each frequency point as a time slot in the TDMA self-organizing network, taking N continuous time slots as a super-frame, and functionally dividing N time slots contained in the super-frame into 1 network management time slot, 1 access time slot and N-2 service time slots; Step 2, the structure in each time slot is divided into a front guard interval, a synchronous symbol, a reference symbol, a data symbol and a rear guard interval in sequence; Step 3, the nodes in the unaccessed network execute network time synchronization and access; For a node in a certain network to be accessed to the network, the specific process of performing network time synchronization and access is as follows: Step 31, the node to be accessed to the network waits at a random frequency point f w, and carries out sliding cross-correlation operation on the baseband data received at the frequency point and a local synchronous sequence until a sliding cross-correlation peak value is detected, and then step 32 is executed; Step 32, the node to be accessed to the network records the frequency point f w waiting currently and the time t p when the sliding cross correlation peak value is detected, and obtains the starting time t s of the time slot corresponding to the frequency point f w according to t p: ts＝tp-Δts,p wherein Δt s,p is the time difference between the time when the sliding cross-correlation peak is detected and the starting time of the time slot corresponding to the frequency point f w; step 33, determining the positions of the synchronization symbol, the reference symbol and each data symbol in the baseband data received in step 31 according to the detected position of the sliding cross-correlation peak value, extracting the reference symbol and each data symbol, and sequentially performing FFT, channel estimation, channel equalization, constellation demodulation, channel decoding and CRC on the extracted data; If the CRC result is wrong, randomly changing the receiving frequency point of the node to be accessed to the network to be f' w, and jumping to execute the step 31; Step 34, obtaining the time slot where the data packet is located and the frequency hopping table specifically used by the current frequency hopping network according to the information in the frame header of the data packet with correct CRC check result; according to the frequency points of the data packet which are recorded in the step 32 and receive the correct CRC result, and