A carrier phase synchronization method in distributed coherent communication

Abstract

The application discloses a carrier phase synchronization method in distributed coherent communication, comprising the following steps: n transmitters independently generate initial values of carrier phase correction values randomly; each transmitter independently generates a phase disturbance value within a certain value range, generates two symbols after correcting a local carrier phase with the carrier phase correction value, adds a phase disturbance to one of the two symbols, and simultaneously transmits the two symbols; a sum signal of the n transmitter signals is received by a receiver, average power of the two symbols corresponding to the sum signal is calculated respectively, and the average power values are fed back to the transmitters; the transmitters calculate correction amounts reflecting the change trend of the average power, multiply the correction amounts by a step factor to obtain adjustment amounts of the phase correction values, and update the local phase correction values. The application improves the convergence speed of the carrier phase synchronization, greatly saves the synchronization time, has good convergence stability and convergence precision, and greatly improves the synchronization effect compared with traditional synchronization algorithms.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, specifically a carrier phase synchronization method in distributed coherent communication. Background Technology

[0002] In recent years, communication technology has developed rapidly, and wireless communication, as the most widely used communication method, has received high attention and developed rapidly. Among them, distributed coherent communication is an important technology. Distributed transmit beams send common information from multiple transmitting nodes, and their signals are superimposed at the receiver. In this scheme, the transmitters cooperate to form a network and converge their transmitted signals to the target node. This structure allows multiple small omnidirectional antennas to achieve the effect of a single high-power, highly directional antenna, thus greatly improving energy efficiency and achieving the same reception effect with less power.

[0003] The basic idea of ​​distributed communication technology is that multiple nodes share transmission resources. These nodes are geographically dispersed, and the transmitted information is transmitted to the receiving end through independent channels. By ensuring the coherence of the transmitted signals from each node at the receiving end through technological means, the strength of the received signal can be significantly improved. Compared with a single-antenna system, under the same total transmit power, the signal power at the receiving end of a distributed communication system is greatly increased, and energy efficiency is multiplied. It can be seen that the nodes of a distributed communication system actually form a virtual antenna array, breaking through the limitations of traditional communication technologies on antenna equipment. This makes it a promising technology for applications such as cellular mobile networks and wireless sensor networks.

[0004] In earlier research, distributed coherent beamforming was mostly presented as an established premise without specifying concrete implementation methods. Distributed coherent communication has received increasing attention in recent years, leading to the proposal of numerous methods for its implementation. The core issue in achieving distributed coherent communication is distributed coherent beamforming, which involves transmitting signals by forming a virtual antenna array using multiple nodes. The implementation of distributed beamforming relies on the synchronization of each communication node, including frequency and phase synchronization. Significant progress has been made in the study of phase synchronization in distributed coherent communication, such as closed-loop structures (explicit channel feedback, 1-bit feedback, round-trip feedback, bidirectional feedback, etc.) and open-loop structures (precise ranging of nodes to spontaneously form a distributed array). These techniques reflect different trade-offs between synchronization overhead, channel feedback, and system complexity.

[0005] Among the various phase synchronization methods mentioned above, most methods struggle to achieve a balance between simplicity and accuracy. Open-loop structures are mostly based on precise ranging of each transmitting node, and they have stringent requirements for ranging accuracy, making them quite difficult to implement. In closed-loop structures, round-trip feedback and bidirectional feedback offer better accuracy, but the systems are more complex and lack reliability. The 1-bit feedback method has received the most attention due to its simplicity and scalability, but its slow convergence speed is a significant drawback that limits its application.

[0006] Chinese Patent Publication No. CN103988449A discloses a method for operating a slave transmitter to achieve coherent transmission with a master transmitter. This method compensates for frequency and phase differences between transmitters by appropriately precoding the synchronization signal transmitted by one of the master transmitters, received by a corresponding receiver, before modulating one or more transmitters. This method can quickly establish frequency and phase synchronization between nodes, but the system is relatively complex, and the transmitted synchronization signal is affected by the estimation accuracy and channel environment, which may lead to synchronization failure. Summary of the Invention

[0007] The purpose of this invention is to provide a carrier phase synchronization method in distributed coherent communication.

[0008] The technical solution for achieving the objective of this invention is as follows: Firstly, this invention provides a carrier phase synchronization method in distributed communication, comprising the following steps:

[0009] Step 1: There are n transmitters that have achieved carrier frequency synchronization. Each transmitter independently and randomly selects a carrier phase correction value.

[0010] Step 2: Each transmitter independently and randomly generates a phase perturbation value δ. i , i = 1, ..., n, δ i ∈(R min R max ), with the corrected value Corrected local carrier generation signal; each transmitter transmits two symbols S 1· S2, where the carrier S1 is not subject to phase perturbation, and its corresponding phase is... A phase disturbance is added to the S2 carrier, and its carrier phase is... phase in the expression i Let be the initial phase of the carrier wave for the i-th transmitter; each transmitter transmits this signal to the receiver simultaneously.

[0011] Step 3: The receiver receives the combined signal of the signals transmitted by n transmitters, calculates the average power of symbols S1 and S2 respectively, which are P1 and P2, and broadcasts P1 and P2 to each transmitter.

[0012] Step 4: After receiving the power information fed back from the receiver, each transmitter calculates the carrier phase correction value based on the average power P1 and P2 in the feedback information and the local phase disturbance value δ. The adjustment amount is used to update the phase correction value;

[0013] Step 5: Determine whether the phase synchronization process has converged. If it has not converged, return to step 2. If it has converged, the algorithm ends.

[0014] In a second aspect, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method described in the first aspect.

[0015] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in the first aspect.

[0016] Compared with the prior art, the significant advantages of this invention are: 1) The convergence speed of phase adjustment in this invention is greatly improved compared with the traditional algorithm; 2) The feedback overhead of this invention is small, only two average power values ​​need to be transmitted, and there is no need to transmit a large amount of z synchronization information; 3) This invention achieves a combination of algorithm simplicity and effectiveness. The algorithm steps are simple, there are no complicated formula calculations, and the convergence speed and convergence accuracy are both good.

[0017] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a flowchart of a carrier phase synchronization method in distributed coherent communication proposed in this invention.

[0019] Figure 2 This is a graph showing the iterative results of a classic 1-bit feedback algorithm implementation example.

[0020] Figure 3 This is a graph showing the iterative results of an implementation example of the algorithm proposed in this invention.

[0021] Figure 4 This is a received signal demodulation constellation diagram of a distributed coherent communication system using the carrier phase synchronization algorithm proposed in this invention. Detailed Implementation

[0022] Combination Figure 1 This invention proposes a carrier phase synchronization method in distributed coherent communication, comprising the following steps:

[0023] Step 1. There are n transmitters that have achieved carrier frequency synchronization. Each transmitter independently and randomly selects a carrier phase correction value.

[0024] Step 2. Each transmitter independently and randomly generates a phase perturbation value δ. i , i = 1, ..., n, δ i ∈(R min R max ), with the corrected value The corrected local carrier generation signal consists of two symbols, S1 and S2, transmitted by each transmitter. S1 carrier is not subject to phase perturbation, and its corresponding carrier phase is... A phase disturbance is added to the S2 carrier, and its carrier phase is... phase in the expression i This is the initial phase of the carrier wave for the i-th transmitter; each transmitter simultaneously transmits this signal to the receiver; the specific steps are as follows:

[0025] Step 2-1. Determine the range of values ​​for the random phase perturbation (R). min R max Each transmitter randomly generates a phase perturbation value δ within this range. i The range of values ​​is manually selected; a range that is too large or too small will cause significant fluctuations in the average power value during the iteration process. In this invention, the range was ultimately selected through simulation testing.

[0026] Step 2-2. Each transmitter sends two symbols S1 and S2. The expression for the S1 carrier in the i-th transmitter is:

[0027]

[0028] Where fc is the carrier frequency, phase i Let i be the initial phase of the carrier wave of the i-th transmitter. Let be the carrier phase correction value for the i-th transmitter;

[0029] A random phase perturbation δ is added to the carrier of S2. i Its expression is:

[0030]

[0031] Where fc is the carrier frequency, phase i Let i be the initial phase of the carrier wave of the i-th transmitter. Let δ be the carrier phase correction value for the i-th transmitter. i Let be the random phase perturbation value of the i-th transmitter;

[0032] Steps 2-3: Each transmitter simultaneously transmits the signal to the receiver;

[0033] Step 3. The receiver receives the combined signal from the signals transmitted by n transmitters, calculates the average power of each of the two symbols, and broadcasts it back to each transmitter. The specific steps are as follows:

[0034] After receiving the composite signal from n transmitters, the receiver calculates the average signal power P1 and P2 for each of the two symbols. P1 is the average power of the signal with phase perturbation added, and P2 is the average power of the signal without phase perturbation added. The power information P1 and P2 is then fed back to each transmitter for carrier phase correction. Update;

[0035] Step 4. Each transmitter calculates its own phase correction adjustment based on the average power of the received signal fed back. The specific steps are as follows:

[0036] Step 4-1. Each transmitter obtains the average signal power P1 and P2 of two symbols from the feedback signal;

[0037] Step 4-2. Each transmitter calculates the change in received power θ under a unit radian change, using the following formula:

[0038]

[0039] Where δ i For the random phase perturbation generated by the i-th transmitter, θ i The received power change is calculated for the i-th transmitter. This invention utilizes the power change trend to update the phase adjustment value along the direction of power increase to achieve the ideal phase that maximizes the received power. This change θ reflects the power change trend of the i-th transmitter near its current phase adjustment value. Based on this, the phase adjustment value is corrected in the direction that increases the received power, but due to δ... i The randomness of the value means that the change θ obtained by this formula will fluctuate within a large range, which will adversely affect the iteration. Therefore, the range of this value is restricted. If the change value is between (-β, β), the original value is retained; if it is greater than β, β is used; if it is less than -β, -β is used. In this way, the trend of change is preserved while avoiding excessively large values ​​from affecting the iteration. β is a manually selected value. Taking a larger β will speed up the convergence speed in the early stage of the iteration, but it will also increase the power fluctuation after convergence and reduce the convergence stability. Taking a smaller β will improve the stability after convergence, but it will also reduce the convergence speed. After simulation testing, β is selected as 1. At this value, both the convergence speed and convergence stability are good.

[0040] Step 4-3. Multiply the change θ by the step size factor α as the adjustment amount for the carrier phase correction value of each transmitter, and update the carrier phase correction value:

[0041]

[0042] in Let be the carrier phase correction value for the i-th transmitter. The step size factor α is a manually selected value that relates to the convergence speed and accuracy. Generally, it is taken as a larger value in the early stage of iteration to speed up the convergence and a smaller value in the later stage of iteration to increase the iteration accuracy. After simulation testing, the value of α for the i-th iteration is selected as . Where i is the number of iterations and j is the number of transmitters. α decreases as i increases. Since the number of iterations required increases with the number of receivers, the formula introduces the number of receivers j to constrain the rate of decrease of α, preventing it from decreasing too quickly and causing the iteration to fail to converge to the vicinity of the optimal value.

[0043] Step 5. Determine whether the phase synchronization process has converged. If it has not converged, return to step 2. If it has converged, the algorithm ends.

[0044] The invention will be further described in detail below with reference to examples.

[0045] Example

[0046] The simulation involves three transmitters transmitting signals, and the analytical expression for the transmitted signal carrier wave is:

[0047]

[0048]

[0049]

[0050] Where the carrier frequency fc is 400MHz, and phase is the initial phase of the carrier for each transmitter, which is a randomly generated value within (0, 2π). This refers to the phase correction value for each transmitter. Each transmitter updates its local phase correction value iteratively. This ensures that the signals transmitted by each transmitter are coherent at the receiver.

[0051] Simulations were conducted to test the convergence of the proposed algorithm and the classic 1-bit feedback algorithm under three transmitter scenarios. The iterative results of this invention are as follows: Figure 3 As shown, for the case of three transmitters, the algorithm proposed in this invention reaches approximately the theoretical maximum value after 25 iterations and successfully converges in subsequent iterations. The iterative results of the classic 1-bit feedback algorithm are as follows: Figure 2 As shown, the traditional algorithm only reaches the theoretical maximum value after 80 iterations. The algorithm proposed in this invention is superior to the classic 1-bit feedback algorithm in terms of convergence speed, and its stability after convergence is basically the same as that of the 1-bit algorithm. Therefore, the overall effect is better than the 1-bit algorithm.

[0052] The received signal constellation diagram of the distributed communication system using the carrier phase synchronization algorithm proposed in this invention is as follows: Figure 4 As shown in the figure, the demodulation effect on the received signal is good, which confirms the effectiveness of the algorithm.

Claims

1. A carrier phase synchronization method in distributed coherent communication, characterized in that, Includes the following steps: Step 1: There are n transmitters that have achieved carrier frequency synchronization. Each transmitter independently and randomly selects a carrier phase correction value. Step 2: Each transmitter independently and randomly generates a phase perturbation value δ. i , i = 1, ..., n, δ i ∈(R min R max ), with the corrected value Corrected local carrier generation signal; Each transmitter emits two symbols S 1· S2, where the carrier S1 is not subject to phase perturbation, and its corresponding phase is... A phase disturbance is added to the S2 carrier, and its carrier phase is... phase in the expression i Let be the initial phase of the carrier wave of the i-th transmitter; each transmitter transmits this signal to the receiver simultaneously. Step 3: The receiver receives the combined signal of the signals transmitted by n transmitters, calculates the average power of symbols S1 and S2 respectively, which are P1 and P2, and broadcasts P1 and P2 to each transmitter. Step 4: After receiving the power information fed back by the receiver, each transmitter calculates the carrier phase correction value based on the average power P1 and P2 in the feedback information and the local phase disturbance value δ. The adjustment amount is used to update the phase correction value; Step 5: Determine whether the phase synchronization process has converged. If it has not converged, return to step 2. If it has converged, the algorithm ends.

2. The carrier phase synchronization method in distributed coherent communication according to claim 1, characterized in that, Step 2: Each transmitter randomly generates a phase perturbation and generates a transmission signal. The specific steps are as follows: Step 2-1, determine the range of values ​​for the random phase perturbation (R). min R max Each transmitter randomly generates a phase perturbation value δ within this range. i ,in Step 2-2: Each transmitter sends two symbols S1 and S2. The expression for the carrier symbol S1 in the i-th transmitter is: Where fc is the carrier frequency; The carrier of symbol S2 has a random phase perturbation δ added. i Its expression is: Steps 2-3: Each transmitter simultaneously transmits the signal to the receiver.

3. The carrier phase synchronization method in distributed coherent communication according to claim 1, characterized in that, Step 3: The receiver receives the combined signal from the signals transmitted by n transmitters, calculates the average signal power of each of the two symbols, and broadcasts it back to each transmitter. Specifically: After receiving the composite signal from n transmitters, the receiver calculates the average signal power P1 and P2 for each of the two symbols. P1 is the average power of the signal with phase perturbation added, and P2 is the average power P of the signal without phase perturbation added. The power information P1 and P2 are then fed back to each transmitter for carrier phase correction. Update.

4. The carrier phase synchronization method in distributed coherent communication according to claim 1, characterized in that, Step 4: Each transmitter calculates its own phase correction adjustment based on the average power P1 and P2 of the received signal feedback. The specific steps are as follows: Step 4-1: Each transmitter obtains the average power P1 and P2 of the two symbols from the feedback signal; Step 4-2: Each transmitter calculates the change in received power θ per unit radian change, using the following formula: Where δ i For the random phase perturbation generated by the i-th transmitter, θ i The change in received power per unit radian is calculated for the i-th transmitter; if the change value is between (-β, β), the original value is retained; if it is greater than β, β is used; if it is less than -β, -β is used. Step 4-3: Multiply the change θ by the step size factor α as the adjustment amount for the carrier phase correction value of each transmitter, and update the carrier phase correction value: in This is the carrier phase correction value for the i-th transmitter.

5. The carrier phase synchronization method in distributed coherent communication according to claim 4, characterized in that, β is 1.

6. The carrier phase synchronization method in distributed coherent communication according to claim 4, characterized in that, In the i-th iteration, α takes the value of Where i is the number of iterations and j is the number of transmitters.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method as described in any one of claims 1-6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-6.

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