A method for implementing a multi-relay frequency hopping link

Abstract

The present invention relates to a method for realizing a multi-relay frequency hopping link. The link adopts time division multiple access technology, and time slots are planned according to the number of relay nodes required in the link, so as to realize the multi-relay frequency hopping link while avoiding collision. The relay link process is divided into three stages: initial synchronization, data transmission and service synchronization. After the initial synchronization stage, the master node, relay node and slave node are synchronized, a relay system is established, and a protocol frame carrying time information is sent at a fixed frequency to complete the synchronous access of the relay node and the slave node in the frequency hopping relay link; in the data transmission stage, the master node and the slave node perform frequency hopping data transmission, and in the service synchronization stage, the time information of the entire link is regularly maintained to reduce the time error and ensure the stability of the link. The time information of all nodes in the link is the same as that of the master node, and the frequency hopping is only related to the time information. The method uses the protocol frame to maintain the operation of the entire link; and uses the time slot count and the time frame count to distinguish the communication status of each node. The frequency hopping relay system can increase or decrease the number of relay nodes according to the actual distance, which is suitable for ultra-long-distance frequency hopping data transmission, and increases the coverage and stability of the entire system.

Description

Technical Field

[0001] The present invention relates to a method for realizing frequency hopping links of multiple relay radio stations based on time division multiple access technology, and belongs to the field of spread spectrum communication. Frequency hopping communication is one of the most commonly used spread spectrum communication methods. It has the characteristics of fast, safe, accurate, uninterrupted, anti-interception, and anti-interference. It is widely used in the field of military communications, especially in the field of unmanned aerial vehicles, and is an indispensable communication method for modern electronic warfare. Background Art

[0002] Frequency hopping communication is a communication method in which the carrier frequency of the transmission signal between the sender and the receiver changes pseudo-randomly. Frequency hopping relay communication is one of the more commonly used communication methods of frequency hopping communication. Collaborative communication technology is a "virtual" MIMO technology. It can enable multiple radio stations to share antenna resources after multiple single-antenna terminals are connected, thereby breaking through equipment limitations and achieving multi-antenna transmission similar to traditional MIMO systems. In collaborative communication, the node that helps users transmit through certain protocols is called a relay. The existence of relays can not only improve system performance, but also eliminate network coverage blind spots and increase coverage area, significantly improving system throughput, link reliability, energy efficiency and other performance indicators of wireless communication systems. Researching collaborative communication technology and applying it to frequency hopping communication systems has great benefits for the coverage range and communication quality of frequency hopping networks.

[0003] The multi-relay frequency hopping link based on time division multiple access technology proposed by the present invention has the master node, relay node and slave node in the link having the same real-time clock and using the master node time information as the time reference for synchronization. At the same time, all nodes in the link are divided into fixed time slots to avoid collision, and the communication status of each node is distinguished by using time slot count and time frame count, and a regular service synchronization method is adopted to maintain the stability and continuity of the entire link. Summary of the invention

[0004] 1. A method for implementing a multi-relay frequency hopping link, using a chain structure control, with a master node, a slave node and multiple relay nodes in the link, and the implementation method is as follows:

[0005] 1.1 All nodes are set with fixed addresses and divided into time slots according to equal intervals. The addresses and time slots are mapped to each other. The master node uses instructions to control the relay nodes and slave nodes to access the network, synchronize time, and communicate data in turn.

[0006] 1.2 Initial synchronization stage, after all nodes are powered on, they are in the first time slot frequency of the initial synchronization frame (called F0 frequency): at this time, the master node sends the synchronization data frame, the remaining time slots of the initial synchronization frame are in an idle state, and the last time slot of the initial synchronization frame is in a receiving state. The master node detects whether there is feedback from the relay node. If no feedback is received, the detection process is repeated until the relay node is captured, completing the initial synchronization stage;

[0007] 1.3 After the relay node and the slave node are powered on, they are in the receiving state at frequency F0. The relay node receives the initial synchronization frame from the master node or the relay node, then calibrates its own real-time clock to align with the master node time information, and reloads the initial synchronization frame for forwarding. Multiple relay nodes continue to forward until the slave node receives the initial synchronization frame. At this time, the time information of all nodes in the entire frequency hopping relay system is consistent with the master node, and the frequency hopping relay system enters the synchronization feedback stage;

[0008] 1.4 Synchronization feedback stage: the slave node sends a slave node synchronization feedback frame in the next time slot after receiving the initial synchronization frame and completing the time information alignment. After receiving the slave node synchronization feedback frame, the relay node determines that the slave node has completed the time information alignment, and then sends the relay node synchronization feedback frame. After receiving the relay node synchronization feedback frame, the next relay node continues to forward the synchronization feedback frame. When the master node receives the relay node synchronization feedback frame, it indicates that the initial synchronization is successful. After completing two initial synchronizations successfully, the frequency hopping relay system enters the data sending state;

[0009] 1.5 Effective data transmission stage, all nodes hop frequency once per time slot, and the frequency hops according to a unified pseudo-random sequence; every time a time slot is passed in the frequency hopping relay system, the time slot counter increases by 1, and every time the master node and the slave node complete a data communication, the data transmission time frame increases by 1. When the time frame counter counts to N, it is cleared to enter the service synchronization time frame;

[0010] 1.6 The master node reads its own time information in the service synchronization phase and sends a service synchronization frame in the next time slot. After receiving the service synchronization frame, the relay node and the slave node calibrate their own time again to complete the service synchronization. After the service synchronization is completed, it returns to the data transmission phase;

[0011] 1.7 The master node is in the data transmission state in the first time slot of each data transmission time frame, and is in the data reception state in the last time slot; the relay node and the slave node forward the received data and send the data frame containing their own valid data according to the time slot mapped by their own address;

[0012] 2. The initial synchronization frame, slave node / relay node synchronization feedback frame, service synchronization frame and relay system data frame in 1.2, 1.3, 1.4, 1.5 and 1.6 above have the following functions:

[0013] 2.1 The initial synchronization frame carries the master node time information and frequency information and is sent on an independent channel to complete the time synchronization and frequency synchronization of the link. The slave node / relay node synchronization feedback frame contains the feedback information of the relay node and the slave node, and informs the master node that the relay link is successfully established;

[0014] 2.2 The service synchronization frame carries the master node time information and regularly calibrates the relay nodes and slave nodes in the link; the relay system data frame contains dynamic length valid data;

[0015] 3. The time slot counter in 1.5 above counts the communication time slots in the three stages of initial synchronization time frame, data transmission time frame and service synchronization time frame. When the counter reaches M, one time synchronization or data communication is completed, the number of time slots is reset, and the number of time frames is accumulated;

[0016] 4. The number of M time slots in the above 3 depends on the number of relay nodes in the frequency hopping relay system, and the number of N time frames in the above 1.6 depends on the maximum number of data frames required to be transmitted by each node; the communication status of each node in the frequency hopping relay system link is switched according to the changes of the time slot counter and the time frame counter.

[0017] The present invention has the following advantages:

[0018] 1. Reasonable division of time slots can prevent data loss due to communication status of the entire frequency hopping relay system.

[0019] 2. Use service synchronization frame timing to calibrate the relay nodes and slave nodes in the link, which can reduce clock drift errors and improve network robustness;

[0020] 3. The relay system data frame contains dynamic length valid data, which improves the flexibility of system application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the timing diagram of the frequency hopping relay system.

[0022] Figure 2 Figure 2 shows the initial synchronization process of the frequency hopping relay system.

[0023] Figure 3 Diagram of the data transmission and service synchronization process of the frequency hopping relay system

[0024] Figure 4 Frame format diagram DETAILED DESCRIPTION

[0025] The following is a further description of the implementation of the present invention in conjunction with the accompanying drawings:

[0026] Figure 1This is the timing diagram of the frequency hopping relay system. The frequency hopping relay link is divided into three stages: initial synchronization, data transmission, and service synchronization. Each communication state of the frequency hopping relay system is designed as a relay time frame, including the initial synchronization relay time frame, the data transmission relay time frame, and the service synchronization relay time frame. Among them, the initial synchronization process includes 2 relay time frames, the data transmission process includes N relay time frames, and the number of N depends on the transmission rate required by the relay system; the service synchronization process includes 1 relay time frame. Each time frame contains a fixed number of M time slots, and the number of M time slots depends on the number of relay radio stations in the frequency hopping relay system.

[0027] Figure 2 This is the initial synchronization flow chart of the frequency hopping relay system. The method used by the frequency hopping relay system synchronization algorithm to complete the capture is the independent channel method. After the master node, relay node, and slave node are powered on, they are all at frequency F0. The master node sends a synchronization data frame at frequency F0 in the first time slot of the first time frame. The remaining time slots of the first time frame are in an idle state. The master node is in a receiving state in the Mth time slot of the second time frame. It detects whether there is feedback from the relay node. If no feedback is received, the broadcast process is repeated until the relay node is captured. If feedback from the relay node is received, the entire initial synchronization process is repeated. After completing two initial synchronizations, the data transmission and reception follow-up phase is entered. Among them, the value of time slot M is obtained by formula 1, and x is the number of relay radio stations in the frequency hopping relay system.

[0028] M=2*(x+1) (Formula 1)

[0029] The master node reads its own time information, packages and sends the initial synchronization frame, and sends it through the RF chip. After the relay node or slave node is turned on, it is in the receiving state at frequency F0. In the first time frame and the first time slot, relay station 1 receives the initial synchronization frame from the master node. After receiving it, the relay station reads the information and if it is determined to be an initial synchronization frame, calibrates its own real-time clock to align with the master node. In this way, the master node and relay station 1 can enter the next time slot at the same time and complete the time slot alignment; in the first time frame and the second time slot, relay station 1 sends the initial synchronization frame. If relay station 2 or the slave node receives it, relay station 2 reads the received information and determines it as an initial synchronization frame, calibrates its own real-time clock to align with relay station 1, and continues to broadcast the initial synchronization frame in the next time slot until the slave node receives it. The slave node reads the received information and determines it as an initial synchronization frame, calibrates its own real-time clock to align with relay station x, and sends a synchronization feedback frame, and the frequency hopping relay system enters the synchronization feedback stage.

[0030] In the synchronization feedback stage, the slave node sends a synchronization feedback frame in the next time slot after receiving the initial synchronization frame. After relay station x receives the synchronization feedback frame, it broadcasts it in the next time slot. After relay station x-1 receives the synchronization feedback frame, it continues to broadcast the synchronization feedback frame in the next time slot until the host receives the synchronization feedback frame, indicating that the first initial synchronization is successful.

[0031] In order to prevent synchronization problems, the above process needs to be repeated, and the initial synchronization frame is sent again or the synchronization feedback frame is received to perform the initial synchronization and synchronization confirmation phase, which is used to calibrate the time again. The master node, relay node, and slave node transmit and receive at the same frequency. If the master node receives feedback twice in a row, the system enters the data communication phase. The purpose of the two initial synchronizations is to effectively prevent interference at a certain frequency from causing the entire system to fail to synchronize.

[0032] In the figure, four time nodes are used to represent the process of establishing the relay link system. Node A indicates that the first relay node receives the time information of the master station and completes synchronization. Node B indicates that all nodes in the link have completed time synchronization. Node C indicates that the relay link system completes an initial synchronization. Node D indicates that two initial synchronizations are successful and the initial synchronization process is completed.

[0033] Figure 3 The figure is a diagram of the data transmission and service synchronization process of the frequency hopping relay system. The master node, relay node, and slave node of the frequency hopping relay system start to send and receive data with the same frequency hopping pattern. If there is no data communication in the receiving or sending time slot, the master node, relay node, and slave node only change the time slot according to their respective real-time clocks and use the frequency hopping pattern to change the frequency. Since the time information of all nodes in the system is the same as the frequency hopping pattern, as long as the communication logic of all node time slots corresponds to each other, the time and frequency synchronization of the entire system can be maintained. The host sends in the 1st time slot and receives in the Mth time slot of the data transmission time frame, and the slave receives in the x+1th time slot of the data transmission time frame and sends in the x+2th time slot. Assume that relay station n (n≤x) receives in the a1th and a2th time slots and sends in the b1th and b2th time slots. Where a1, a2, b1, and b2 are given by formula 2.

[0034] a1=n

[0035] b1=n+1

[0036] a2=Mn

[0037] b2=M-n+1 (Formula 2)

[0038] The master node and the relay node, the relay node and the relay node, and the relay node and the slave node transmit data and perform frequency hopping through fixed time slots, without the need for handshake signals to confirm the frequency hopping at all times, so that all nodes in the link are liberated, and the carrying frequency value is generated according to the pseudo-random sequence based on the time TOD information.

[0039] Due to various factors such as program running and distance, the real-time clocks of the master node, relay node, and slave node may produce errors. As the communication time increases, the time slots of all nodes in the link may be offset, causing the nodes in the link to lose synchronization. Regular service synchronization can correct the time slot deviations of the master node, relay node, and slave node caused by the communication time, so that the frequency hopping relay link data can be transmitted continuously and stably. After testing, the master node needs to enter the service synchronization stage every N time frames to calibrate the time information of the relay system. The relay receives the service synchronization frame in the first time slot of the Nth time frame. The service synchronization principle is the same as the initial synchronization. The host reads its own time information and sends it in a time slot. After receiving the service synchronization frame, the relay node and the slave node calibrate their own time again to complete the service synchronization. During service synchronization, the master node does not need to receive feedback from the relay node or the slave node. After the service synchronization is completed, it returns to the data transmission state.

[0040] In the figure, three time nodes are used to represent the data transmission phase and service synchronization phase of the relay link system. Node A represents the start of the data transmission phase, node B represents the start of the service synchronization phase, and node C represents the start of the next data transmission phase, and so on.

[0041] Figure 4 There are four types of communication protocol frames in the frequency hopping relay communication system, namely, initial synchronization frame, slave node / relay node synchronization feedback frame, service synchronization frame, and relay system data frame. The four protocol frames all include an 8-byte preamble, a 2-byte synchronization word, and a 1-byte frame type. Among them, the preamble format is 32 consecutive bits of "1010", and the preamble detection threshold is set to 20 bits, allowing 12-bit errors in the frame header in wireless communication to enhance the fault tolerance of the protocol frame; the synchronization word indicates the starting position of the data in the protocol frame; the frame types of the four protocol frames are initial synchronization frame: 0x02, synchronization feedback frame: 0x03, service synchronization frame: 0xA1, and relay system data frame 0xA2.

[0042] The hours, minutes, seconds, time slots, and timer values ​​of the initial synchronization frame are the values ​​of the real-time frame, which are combined into time information. Since the frequency hopping relay system will enter the communication state and perform frequency hopping after the initial synchronization is completed, the initial synchronization frame also contains the frequency hopping frequency value of the next time slot. The starting value of the frequency hopping pattern is the same as the frequency value. CRC check is used to check the initial synchronization frame.

[0043] The relay node feedback frame contains an ID number, and the slave feedback frame contains an ID number at the end of the frame. The master node determines whether the entire relay link is connected by receiving the feedback frame. CRC check is used to check the feedback frame.

[0044] The time information of the service synchronization frame is the same as that of the initial synchronization frame. The master node sends the service synchronization frame after every N data transmission time frames. The purpose is to synchronize the entire frequency hopping relay system again after the N data transmission phases of the relay system are completed to ensure the stability of the system. CRC check is used to check the service synchronization frame.

[0045] The relay system data frame is used for data transmission in the frequency hopping relay system. The CRC check determines whether the data frame is valid. The ID information determines whether it is the information required by the node. If the determination is successful, the data content carried by the data frame is uploaded to the SCI channel of the main control chip.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for implementing a multi-relay frequency hopping link, using a chain structure control, with a master node, a slave node and multiple relay nodes in the link, and the implementation method is as follows: 1.1 All nodes are set with fixed addresses and divided into time slots according to equal intervals. The addresses and time slots are mapped to each other. The master node uses instructions to control the relay nodes and slave nodes to access the network, synchronize time and communicate data in turn. The master node, relay node and slave node in the link have the same real-time clock and synchronize with the master node time information as the time reference; 1.2 Initial synchronization stage, after all nodes are powered on, they are in the first time slot frequency of the initial synchronization frame: at this time, the master node sends the synchronization data frame, and the remaining time slots of the initial synchronization frame are idle. The master node is in the receiving state in the last time slot of the initial synchronization frame to detect whether there is feedback from the relay node. If no feedback is received, the detection process is repeated until the relay node is captured, completing the initial synchronization stage; 1.3 Relay node 1 is in the receiving state in the first time slot of the first time frame. If it determines that the received information is the initial synchronization frame from the master node, it calibrates its own real-time clock to align with the master node; This allows the master node and relay node 1 to enter the next time slot at the same time, completing time slot alignment; In the 2nd time slot of the 1st time frame, relay node 1 sends an initial synchronization frame. If relay node 2 receives the information and determines it as an initial synchronization frame, it calibrates its own real-time clock to align with relay node 1 and continues to broadcast the initial synchronization frame in the next time slot until the slave node receives the initial synchronization frame. The slave node reads the received information and determines it as the initial synchronization frame, calibrates its own real-time clock to align with the relay node x, and sends a synchronization feedback frame. The frequency hopping relay system enters the synchronization feedback stage; 1.4 Synchronization feedback stage: the slave node sends a slave synchronization feedback frame in the next time slot after receiving the initial synchronization frame and completing the time information alignment. After the relay node x receives the synchronization feedback frame, it broadcasts it in the next time slot. After the relay node x-1 receives the synchronization feedback frame, it continues to broadcast the synchronization feedback frame in the next time slot until the master node receives the synchronization feedback frame, indicating that the first initial synchronization is successful. Then the master node sends the initial synchronization frame again, that is, repeats 1.2, 1.3 and the above process. If the master node receives the synchronization feedback frame again, that is, after completing two consecutive initial synchronizations successfully, it enters the frequency hopping relay system data sending state; otherwise, it continues the synchronization process of 1.2, 1.3, and 1.

4. 1.5 Effective data transmission phase, all nodes hop frequency once in each time slot and send and receive data with the same frequency hopping pattern. If there is no data communication in the receiving or sending time slot, all nodes only change the time slot according to their own real-time clocks and use the frequency hopping pattern to change the frequency; the master sends in the 1st time slot and receives in the Mth time slot of the data transmission time frame, and the slave receives in the x+1th time slot and sends in the x+2th time slot of the data transmission time frame; every time a time slot is passed in the frequency hopping relay system, the time slot counter increases by 1, and every time the master node and the slave node complete a data communication, the data transmission time frame increases by 1. When the time frame counter counts to N, it is reset to enter the service synchronization time frame; 1.6 The master node reads its own time information in the service synchronization phase and sends a service synchronization frame in the next time slot. After receiving the service synchronization frame, the relay node and the slave node calibrate their own time again to complete the service synchronization. The master node needs to enter the service synchronization phase every N time frames, and the relay node receives the service synchronization frame in the first time slot of the Nth time frame. The service synchronization principle is basically the same as the initial synchronization. The difference is that the master node does not need to receive feedback from the relay node or the slave node in the service synchronization. After the service synchronization is completed, it returns to the next data transmission phase. 1.7 The master node is in the data sending state in the first time slot of each data transmission frame and in the data receiving state in the last time slot; the relay node and the slave node forward the received data and send the data frame containing their own valid data according to the time slot mapped by their own address.

2. The method for implementing a multi-relay frequency hopping link according to claim 1, characterized in that: The initial synchronization frame, slave node / relay node synchronization feedback frame, service synchronization frame and relay system data frame in 1.2, 1.3, 1.4, 1.5 and 1.6 above have the following functions: 2.1 The initial synchronization frame carries the master node time information and the frequency hopping value of the next time slot. The starting value of the frequency hopping pattern is the same as the frequency value. It is sent on an independent channel to complete the time synchronization and frequency synchronization of the link. The slave node / relay node synchronization feedback frame contains the feedback information and ID number of the relay node and the slave node. The master node determines whether the relay link is connected by receiving the feedback frame. 2.2 The service synchronization frame carries the time information of the master node. The master node sends a service synchronization frame after every N data transmission time frames to regularly calibrate the relay nodes and slave nodes in the link. The relay system data frame contains dynamic length valid data, which is used for data transmission in the frequency hopping relay system. The CRC check is used to determine whether the data frame is valid, and the ID information is used to determine whether it is the information required by the node. If the determination is successful, the data content carried by the data frame will be uploaded to the SCI channel of the main control chip.

3. The method for implementing a multi-relay frequency hopping link according to claim 1, characterized in that: The time slot counter in 1.5 above counts the communication time slots in the three stages of initial synchronization time frame, data transmission time frame and service synchronization time frame. When the count reaches M, one time synchronization or data communication is completed, the number of time slots is reset and the number of time frames is accumulated.

4. The method for implementing a multi-relay frequency hopping link according to claim 3, characterized in that The number of M time slots is obtained by formula 1: M=2*(x+1), where x is the number of relay nodes in the frequency hopping relay system. Each time frame contains a fixed number of M time slots. The number of N time frames in the aforementioned 1.6 depends on the maximum number of data frames required to be transmitted by each node, wherein the initial synchronization process includes 2 relay time frames, and the data transmission process includes N relay time frames; the communication status of each node in the frequency hopping relay system link is switched according to the changes of the time slot counter and the time frame counter.

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