A low complexity distributed beamforming method

Abstract

The application belongs to the technical field of communication systems, and discloses a low-complexity distributed beam forming method, which comprises the following steps: selecting a plurality of single-antenna distributed nodes in a communication system to form a transmitting end, and taking a single-antenna target node as a receiving end node; and adjusting the phase angles of the transmitting nodes to maximize the signal power at the target node, so as to realize distributed beam forming. Compared with the traditional beam forming method, the method is more clear and simple in the process under the premise of ensuring the efficiency of beam forming; compared with the commercial beam forming method, the implementation of the method is simpler and the overall robustness is stronger, which is conducive to engineering implementation and popularization, and overcomes the problems of large calculation amount and high engineering difficulty of the multi-node beam forming method in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of communication system technology, specifically relating to a low-complexity distributed beamforming method. Background Technology

[0002] Distributed beamforming is primarily used in ad hoc network communication systems, which consist of multiple independent, freely movable nodes. These nodes can communicate without the aid of base stations or other external equipment. It is widely applied in military communications, emergency rescue, and field communications. With the continuous development of communication technology, military communications place increasingly higher demands on the performance of ad hoc networks, primarily including stealth, reliability, and high speed. Therefore, it is necessary to propose a simple and easily implemented distributed cooperative beamforming method.

[0003] Patent CN201110281702.8 proposes an optimal beamforming design method under conditions of limited backhaul link capacity and limited power for each base station, while patent CN202080065130.7 proposes an idea that different nodes can cooperate to relay messages to remote radio nodes that cannot be reached through simple communication protocols. The cooperation methods provided by these patents are overly complex and impractical for engineering implementation. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a low-complexity distributed beamforming method. This method is simple, reliable, and easy to implement, which can not only effectively improve collaboration efficiency, but more importantly, facilitate engineering implementation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A low-complexity distributed beamforming method includes the following steps:

[0007] Multiple single-antenna distributed nodes with a single antenna in the communication system are selected to form the transmitting end, and the receiving end node is a single target node;

[0008] By adjusting the phase angle of each transmitting node at the transmitting end using multiple initial phase angle transmission signals, the signal power at the target node is maximized, thereby achieving distributed beamforming.

[0009] Furthermore, the carrier frequencies of multiple distributed nodes are fully synchronized.

[0010] Furthermore, the number of distributed nodes is greater than or equal to 2.

[0011] Furthermore, by adjusting the phase angle of each transmitting node, the received signal power at the target node is maximized, thereby achieving distributed beamforming, which includes the following steps:

[0012] The phase angle of the k-th transmitting node is optimized by fixing the phase angles of the remaining N-1 transmitting nodes, and the optimal phase angle of the k-th transmitting node is obtained when the received signal power at the target node is maximized; k is from 1 to N, and N is the number of transmitting nodes;

[0013] The phase angle values ​​of the transmitting nodes other than node k are adjusted to obtain the optimal phase angle values ​​of the remaining N-1 transmitting nodes when the received signal power at the target node is maximized, thereby realizing distributed beamforming of multiple transmitting nodes.

[0014] Furthermore, when optimizing the phase angle of the k-th transmitting node, the k-th transmitting node transmits signals with initial phase angles of 0, π / 2, and π.

[0015] Furthermore, the received signal power at the target node |r(φ)| 2 Calculated using the following formula:

[0016]

[0017] In the formula: α n It is the signal power value of the nth transmitting node, α l φ is the signal power value of the l-th transmitting node. n It is the emission phase angle of the nth emission node, φ l It is the transmission phase angle of the l-th transmitting node, l≠n, N is the number of transmitting nodes, and j represents the imaginary unit.

[0018] Furthermore, the received signal r(φ) at the target node is calculated using the following formula:

[0019]

[0020] In the formula: φ=[φ1,φ2,...,φ N ] T These are the phase angle values ​​for each transmitting node, where φ1 is the transmission phase angle of the first transmitting node, φ2 is the transmission phase angle of the second transmitting node, and φ... N It is the emission phase angle of the Nth emission node, α n It is the signal power value of the nth transmitting node.

[0021] Furthermore, the optimal phase angle of the k-th transmitting node is calculated using the following formula:

[0022] φ m,k =∠(C(0)-C(π)+j(2C(π / 2)-C(0)-C(π)))

[0023] In the formula, C(0) is the phase angle φ' of the k-th transmitting node. m,kThe received signal power at the target node is taken when the phase angle is 0; C(π / 2) is the phase angle φ' of the k-th transmitting node. m,k The received signal power at the target node is when the phase angle is π / 2; C(π) is the phase angle φ' of the k-th transmitting node. m,k When the phase angle is π, the received signal power at the target node is φ' m,k For the m-th iteration, the phase angle of the k-th transmitting node is given, where j is the imaginary unit.

[0024] Furthermore, the phase angle φ' of the k-th transmitting node m,k When the phase angle is 0, the received signal power C(0) at the target node and the phase angle φ' of the k-th transmitting node are taken. m,k The received signal power C(π / 2) at the target node and the phase angle φ' of the k-th transmitting node when the phase angle is π / 2. m,k When the phase angle is π, the received signal power C(π) at the target node is calculated by the following formula:

[0025]

[0026]

[0027]

[0028] In the formula, A is the real value of the dynamic change of the received signal power of the target node, and B is the lower limit of the received signal power of the target node.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention adjusts the phase angle of each transmitting node at the transmitting end by using multiple initial phase angle transmission signals to maximize the signal power at the target node and achieve distributed beamforming. Compared with traditional beamforming methods, this method is clearer and simpler while ensuring beamforming efficiency. It is also simpler to implement than commercial beamforming methods and has stronger overall robustness, which is conducive to engineering implementation and promotion. It overcomes the problems of large computational load and high engineering difficulty in existing multi-node beamforming methods.

[0031] Furthermore, in this invention, by selecting one transmitting node and fixing the other nodes, the selected transmitting node is controlled to transmit signals with various different initial phase angles. This allows the receiving node to determine which phase angle the current node should transmit to maximize the receiving gain. The operation process is similar for nodes other than the selected transmitting node. Through iteration, distributed beamforming of multiple transmitting nodes can be finally obtained. The method is simpler and easier to implement in engineering. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of multi-node beamforming.

[0033] Figure 2 The invention underwent 100 Monte Carlo experiments, and the power synthesis effect of 20 nodes after 10 iterations using the beamforming method of the invention is shown in the figure.

[0034] Figure 3 The invention underwent 100 Monte Carlo experiments, and the power synthesis effect of 100 nodes after 10 iterations using the beamforming method of the invention is shown in the figure.

[0035] Figure 4 This is a flowchart illustrating the implementation of the multi-node beamforming method of the present invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Addressing the drawback of existing beamforming algorithms requiring large computational loads, the present invention proposes a simple and effective beamforming method. The specific steps are as follows:

[0037] First, see Figure 1 In a communication system, N distributed nodes are selected, assuming their carrier frequencies are perfectly synchronized. The transmitter consists of N single-antenna transmitting nodes, and the receiver is a single target node. The phase angle φ of each transmitting node is adjusted... n To maximize the signal power at the target node, the signals transmitted by N nodes are focused at the target node. Here, N is an integer greater than or equal to 2. The focus of the signals transmitted by the N nodes at the target node, i.e., the received signal at the target node, can be expressed as:

[0038]

[0039] In the formula: φ=[φ1,φ2,...,φ N ] T These are the phase angle values ​​for each transmitting node, where φ1 is the transmitting phase angle of the first node, φ2 is the transmitting phase angle of the second node, and φ... N α is the emission phase angle of the Nth node, where N is the number of transmitting nodes and is an integer greater than or equal to 2. n This is the signal power value of the nth transmitting node, where n ranges from 1 to N. j represents the imaginary unit.

[0040] The received signal power at the target node can be expressed as:

[0041]

[0042] In the formula: n and l represent two independent transmitting nodes, α l It is the signal power value of the l-th (l≠n) transmitting node, α n It is the signal power value of the nth transmitting node, φ nIt is the emission phase angle of the nth emission node, φ l It is the phase angle of the l-th transmitting node.

[0043] Adjusting the phase angle of each transmitting node to maximize the received signal power at the target node, thus achieving point focusing at the target node, is modeled as an optimization problem, and the following equation is solved:

[0044]

[0045] Next, an alternating optimization approach is used to solve the above optimization problem so that the received signal power of the N transmitting nodes at the target node is maximized.

[0046] See Figure 4 Assume that the current alternating optimization requires a total of M iterations. Each iteration adjusts from the first initial launch node to the Nth launch node, with the initial state being m = 1 and k = 1, meaning the initial iteration count is m = 1 and the initial node is k = 1. Before iteration, the initial phase angles of the N launch nodes are φ0 = [φ1, φ2, ..., φ]. N ] T Since 1 is less than N+1, the process of counting nodes will continue.

[0047] The first step is to process the first transmitting node. If k=1, the initial phase angles of all nodes are not updated.

[0048] The second step is to fix the phase angle values ​​of the remaining transmitting nodes except for the first node, i.e., φ. 1,1 =[φ1' ,1 ,φ2,...,φ N ] T , where φ1' ,1 It is the phase angle value of the first iteration of the first launch node;

[0049] The third step is to control the first transmitting node at a phase angle φ1' ,1 =0,π / 2,π transmit signals. The target node calculates the optimal initial phase angle φ of the first transmitting node using three different received power values. 1,1 Next, the node number k = k + 1, meaning the current node number is 2. Since 2 is less than N + 1, the node counting loop will begin.

[0050] The first step is to adjust the phase angle of the second transmitting node and update the phase angle value of the first transmitting node to φ1 = φ. 1,1 ;

[0051] The second step is to fix the phase angle values ​​of the remaining transmitting nodes, except for the second node, i.e., φ. 1,2 =[φ1,φ1' ,2 ,...,φ 20 ], where φ1' ,2It is the phase angle value of the first iteration of the second launch node;

[0052] The third step is to control the second transmission node at a phase angle φ1' ,2 =0,π / 2,π transmit signals. The target node calculates the optimal initial phase angle φ of the second transmitting node using three received power values. 1,2 The operation for other transmitting nodes is similar to the above steps. When k = k + 1 = N + 1, the iteration for the current node number is stopped, and the iteration number m = m + 1 is performed. That is, the current iteration number is 2, and 2 is less than M + 1. The current node number k is updated to 1, and the phase angle φ of the Nth transmitting node is updated at the same time. N =φ 1,N The phase angle of the N transmitting nodes is φ 1,N =[φ1,φ1,...,φ 1,N ]=φ1=[φ1,φ1,...,φ N Then repeat the above node number loop process. When m = m + 1 = M + 1, exit the current iteration loop and obtain the optimal phase angle value φ for the current N transmitting nodes. M =[φ1,φ2,...,φ M,N ] T =[φ M,1 ,φ M,2 ,...,φ M,N ] T .

[0053] Considering the optimized phase angle of the k-th transmitting node in the m-th iteration, the phase angles of the remaining N-1 transmitting nodes (l≠k) are fixed, where m∈[0,M] is the iteration number and k∈[1,N] is the k-th transmitting node. At this point, the objective function for optimizing the phase angle of the k-th transmitting node in the m-th iteration is |r m,k (φ m,k )| 2 Let φ' be a phase angle of the k-th transmitting node m,k A sine wave, where φ m,k =[φ1,φ2,...,φ' m,k ,φ k+1 ,φ k+2 ,φ N ] T Let φ' be the phase angle of each current transmitting node. m,k Let φ' be the phase angle of the k-th transmitting node in the m-th iteration. m,k Values ​​can be obtained:

[0054]

[0055]

[0056]

[0057] Parameters D and B are both real numbers. To simplify the angle values, substitute the parameters above into the formula to obtain:

[0058]

[0059] Simplified to:

[0060]

[0061] In the formula: C(φ') m,k ) is the current received signal power of the target node, which will change with the phase angle φ' of the k-th transmitting node. m,k Dynamically changing, A is the real value of the dynamic change of the signal power received by the target node, and B is the lower limit of the signal power received by the target node, which is a fixed real value.

[0062] When determining the optimal phase angle of the k-th transmitting node, the k-th transmitting node is allowed to transmit signals with three different initial phase angles. The target receiving node then determines the received signal power based on the phase angle φ' of the k-th transmitting node. m,k The changes in phase angle are analyzed to obtain the optimal phase angle value for the k-th transmitting node under the current condition. The specific process is as follows:

[0063] Let the phase angle of the k-th transmitting node be φ' m,k Taking three phase angles of 0, π / 2, and π respectively, the received signal power at the target node can be expressed as follows:

[0064]

[0065]

[0066]

[0067] The target receiving node thus determines the received signal power as a function of the phase angle φ' of the k-th transmitting node. m,k The changes in phase angle are analyzed to obtain the optimal phase angle value of the k-th transmitting node in the m-th iteration.

[0068] The solution can be obtained from the received signal power at the target node:

[0069]

[0070]

[0071] when Then, the optimal phase angle of the k-th transmitting node in the m-th iteration can be obtained:

[0072] φ m,k=∠(C(0)-C(π)+j(2C(π / 2)-C(0)-C(π)))

[0073] Next, update the phase angle information of the current k-th transmitting node, that is, let φ k =φ m,k This yields the phase angle information φ of other transmitting nodes optimized for the phase angle of transmitting node k+1. m,k+1 =[φ1,φ2,...,φ k ,φ' m,k+1 ,φ k+2 ,φ N ] T Following the method described above, the phase angle φ' of the (k+1)th transmitting node is... m,k+1 Adjustments are made, and the operations of other nodes are the same as described above. After N operations, the optimal phase angle value φ of each transmitting node is obtained under the current iteration number. m Simultaneously, the optimal phase angle φ of the transmitted signals from the N nodes obtained in the previous iteration is used. m Using these initial phase angle values ​​for the next iteration of N transmitting nodes, the above process is repeated for a total of M iterations to obtain the final optimal phase angle value φ for the N transmitting nodes. M =[φ1,φ2,...,φ M,N ] T =[φ M,1 ,φ M,2 ,...,φ M,N ] T Phase angle enables distributed beamforming across N transmitting nodes.

[0074] Example 1

[0075] The specific parameters are set as follows: there are 20 transmitting nodes, each with a single antenna, and the initial phase angle of transmission is φ. 0,1 ,φ 0,2 ....φ 0,20 All of them are random numbers in the range [0, 2π] (Note: φ) m,n In this case, m is the iteration number. Let the initial phase angle of the first iteration be φ0 = [φ1, φ2, ..., φ0]. 20 ],φ1=φ 0,1 ,φ2=φ 0,2 ,...,φ 20 =φ 0,20 First, adjust the phase angle of the first transmitting node, and then control the phase angles of the second to twentieth transmitting nodes to be the initial phase angle value φ. 0,2 ,φ 0,3 ....φ 0,20 That is, the current phase angle is φ 1,1 =[φ' 1,1 ,φ2,...,φ 20Adjust φ' 1,1 (φ' 1,1 For φ' m,k (For the case where m=1, k=1, the process is similar to the steps above.) The phase angle of the first transmitting node is transmitted using three phase angles: 0, π / 2, and π. Based on the three power values ​​received, the receiving node can determine the optimal phase angle φ of the first transmitting node in the first iteration. 1,1 Next, adjust the phase angle of the second transmitting node to control the phase angle of the first transmitting node to be φ1 = φ 1,1 The initial transmission phase angles from the 3rd to the 20th node are the initial phase angle values, i.e., the current phase angle is φ. 1,2 =[φ1,φ' 1,2 ,...,φ 20 Similarly, adjust the launch phase angle φ' of the second launch node. 1,2 Transmitting with three phase angles of 0, π / 2, and π, the receiving node can determine the optimal phase angle φ of the second transmitting node in the first iteration based on the three received power values. 1,2 By performing the same operation on the remaining nodes, the optimal phase angle value φ1 for each transmitting node in the first iteration can be obtained. Then, using the optimal phase angle values ​​of each transmitting node obtained in the first loop as the initial phase angle values, the above operation process is repeated again, iterating 10 times to ensure that all 20 transmitting nodes reach the final optimal phase angle value φ1. 10 =[φ1,φ2,...,φ 20 ]=[φ 10,1 ,φ 10,2 ,...,φ 10,20 This enables distributed beamforming across 20 transmission nodes.

[0076] Figure 2 and Figure 3 The results of beamforming experiments with 20 and 100 transmitting nodes are shown respectively. The horizontal axis represents the number of iterations, and the vertical axis represents the received power value of the target node. It can be seen that in 100 experiments, using the low-complexity distributed beamforming method of this invention, the received power value of the target node reached its maximum after 10 iterations. This demonstrates that the method of this invention can achieve distributed beamforming of multiple nodes with relatively low complexity.

Claims

1. A low-complexity distributed beamforming method, characterized in that, Includes the following steps: The transmitter is composed of multiple single-antenna distributed nodes in a communication system, and the receiver is a single target node; the carrier frequencies of the multiple distributed nodes are completely synchronized; the number of distributed nodes is greater than or equal to 2. By adjusting the phase angle of each transmitting node at the transmitting end using multiple initial phase angle transmission signals, the signal power at the target node is maximized, thereby achieving distributed beamforming. Distributed beamforming is achieved by adjusting the phase angle of each transmitting node to maximize the received signal power at the target node. This includes the following steps: For the first The phase angle of the transmitting node is optimized, while the rest are fixed. The phase angle of the transmitting nodes is used to obtain the maximum received signal power at the target node. Optimal phase angle of the transmitting node; From 1 to , This is the number of transmitting nodes; For the node The phase angle values ​​of the external transmitting nodes are adjusted to obtain the maximum received signal power at the target node when the phase angle values ​​of the other nodes are maximized. The optimal phase angle value of each transmitting node is used to achieve distributed beamforming of multiple transmitting nodes; For the first When optimizing the phase angle of the transmitting node, the first The transmitting node transmits signals with initial phase angles of 0, π / 2, and π. No. The optimal phase angle of the transmitting node is calculated using the following formula: In the formula, For the first Phase angle of the transmitting node The received signal power at the target node when the phase angle is 0; For the first Phase angle of the transmitting node The received signal power at the target node when the phase angle is π / 2; For the first Phase angle of the transmitting node When the phase angle is π, the received signal power at the target node is... For the first The iteration, the The phase angle of the transmitting node, where j is the imaginary unit.

2. The low-complexity distributed beamforming method according to claim 1, characterized in that, Received signal power at the target node Calculated using the following formula: In the formula: It is the first The signal power value of the transmitting node, It is the first The signal power value of the transmitting node, It is the first The transmission phase angle of the transmitting node, It is the first The transmission phase angle of the transmitting node, , It represents the number of transmitting nodes, and j represents the imaginary unit.

3. The low-complexity distributed beamforming method according to claim 2, characterized in that, Received signal at the target node Calculated using the following formula: In the formula: These are the phase angle values ​​of each transmitting node. It is the launch phase angle of the first launch node. It is the launch phase angle of the second launch node. It is the first The transmission phase angle of the transmitting node, It is the first The signal power value of the transmitting node.

4. The low-complexity distributed beamforming method according to claim 3, characterized in that, No. Phase angle of the transmitting node When the phase angle is 0, the received signal power at the target node , No. Phase angle of the transmitting node The received signal power at the target node when the phase angle is π / 2 and the Phase angle of the transmitting node The received signal power at the target node when the phase angle is π Calculated using the following formula: In the formula, A is the real value of the dynamic change of the received signal power of the target node, and B is the lower limit of the received signal power of the target node.

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