WO2017096543A1 - 基于反向补偿机制的最佳中继位置的搜寻方法及系统 - Google Patents

基于反向补偿机制的最佳中继位置的搜寻方法及系统 Download PDF

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WO2017096543A1
WO2017096543A1 PCT/CN2015/096740 CN2015096740W WO2017096543A1 WO 2017096543 A1 WO2017096543 A1 WO 2017096543A1 CN 2015096740 W CN2015096740 W CN 2015096740W WO 2017096543 A1 WO2017096543 A1 WO 2017096543A1
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mobile relay
relay
communication performance
bit information
performance
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French (fr)
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谢宁
陈敬坤
王晖
林晓辉
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Shenzhen University
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Shenzhen University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22—Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management

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  • the invention belongs to the technical field of wireless communications, and in particular relates to a search method and system for optimal relay position of a mobile relay based on a reverse compensation mechanism.
  • the communication relay is used to forward information sent between different nodes, which expands the communication range and improves the performance of the communication system.
  • Terrestrial radio communications are easily obstructed and shielded by obstacles, and aircraft, satellites, and unmanned aerial vehicles (UAVs) can act as communication relays because airborne relays can effectively interact with each other in rugged mountains or urban areas. The two sides of the communication establish a connection.
  • UAVs unmanned aerial vehicles
  • the existing algorithms for mobile relay location search mainly include: as shown in FIG. 1a, the location information of the source end (S) and the destination end (D) is measured based on the GPS, and the mobile relay uses the information to search for the most. Good relay position; as shown in Figure 1b, the Distremum Seeking Control (ESC) algorithm based on disturbance; the algorithm based on airborne multi-antenna.
  • the existing mobile relay location search algorithm can make the mobile relay find the best relay location, but these algorithms or applicable scopes also have certain deficiencies and defects, mainly reflected in: (1) communication relay depends on GPS It is vulnerable to attack, and may also suffer from GPS spoofing or interference, which may cause relay communication failure.
  • the communication parties do not have GPS function or the GPS device is damaged, such as natural disaster causing GPS device damage.
  • DOA signal arrival angle
  • the technical problem to be solved by the present invention is to provide a search method and system for optimal relay position based on a reverse compensation mechanism, which aims to solve the problem that the existing search algorithm for the optimal communication position of the mobile relay is easy. Suffering from GPS spoofing or interference, communication relay fails, estimation error is easy to occur, and the complexity and algorithm complexity of the mobile relay communication device are increased.
  • the present invention is implemented in such a manner that the optimal relay position searching method based on the reverse compensation mechanism includes the following steps:
  • Step A The mobile relay is in the current position of the fixed track, receives the test signal sent from the source end, and is amplified and forwarded to the destination end;
  • Step B The destination end calculates communication performance according to the received signal, and then generates single-bit information feedback to the mobile relay according to the calculation result; the single-bit information includes information about whether the received signal performance is improved;
  • Step C The mobile relay calculates a next time position according to the single bit information of the feedback and moves to the next time position;
  • the mobile relay further comprises: initializing at any starting position of the fixed track, and recording the initial position in the memory as the known optimal position.
  • step B specifically includes:
  • the destination end is initialized according to the first received signal, and the communication performance is calculated according to the received signal, and the communication performance is saved in the memory as the known best communication performance, and the communication performance includes the signal to noise ratio strength and error. Rate; when the destination receives a new signal, calculates new communication performance, compares the new communication performance with the known best communication performance stored in the memory, and generates single-bit information feedback to the mobile relay according to the comparison result. At the same time, after determining the improvement of the receiving performance, the known best communication performance in the memory is updated.
  • step C specifically includes: the mobile relay calculates a random disturbance step according to the single bit information, and introduces a correction factor, and then the mobile relay performs a motion step and a direction on a fixed track according to the calculation result. Move the position and return to step A.
  • step C specifically includes:
  • Step C1 the mobile relay records its known optimal position ⁇ (n), and n represents the nth time slot;
  • Step C2 the mobile relay transforms a motion step according to the single bit information, and the transformed motion step includes a random disturbance step and a correction factor;
  • Step C3 the mobile relay calculates the next time position according to the transformed motion step, then moves to the next time position, returns to step A, continues to receive the test signal transmitted from the source, and amplifies and forwards to the destination. end;
  • Step C4 the mobile relay updates the known optimal position according to the fed single bit information and stores, calculates the motion step and direction to determine the next time position and moves to the next time position.
  • step C4 specifically includes:
  • Step C41 The mobile relay determines the single bit information.
  • Step C42 When it is determined that the performance of the received signal is improved, the correction factor is cleared.
  • Step C43 When it is determined that the performance of the received signal is not improved, the mobile relay returns to the position of the previous time slot, and the correction factor is modified to be the inverse of the motion step of the previous time slot.
  • the present invention also provides a search system for optimal relay position based on a reverse compensation mechanism, including a source, a mobile relay, and a destination:
  • the source end is configured to send a test signal to the mobile relay
  • the mobile relay is configured to receive a test signal sent from the source end to be amplified and then forwarded to the destination end at a current position of the fixed track;
  • the destination end is configured to calculate communication performance according to the received signal, and then generate single-bit information feedback to the mobile relay according to the calculation result; and the single-bit information includes information about whether the receiving performance is improved;
  • the mobile relay is further configured to calculate a next time position according to the fed single bit information and move to the next time position, and amplify the test signal sent by the source end and transmit the test signal to the target in real time. The end of the calculation is performed until the optimal relay position is finally determined.
  • the mobile relay is also used to initialize at any position of the fixed track and record the initialization position as the known best position in the memory.
  • the destination end calculates communication performance according to the received signal, and stores the communication performance in a memory as a known optimal communication performance, the communication performance includes a signal to noise ratio strength and a bit error rate; the destination end receives a new one.
  • the signal is calculated to calculate new communication performance, the new communication performance is compared with the known best communication performance saved in the memory, and single-bit information is generated and fed back to the mobile relay according to the comparison result, and after determining the reception performance is improved , update the known best communication performance in memory.
  • the mobile relay calculates a random disturbance step according to the single bit information, and introduces a correction factor, and then the mobile relay performs a positional movement on the fixed track according to the calculation result, and real time moves in a fixed track.
  • the test signal sent by the source is amplified and transmitted to the destination for calculation until the optimal relay position is finally determined.
  • the present invention has the beneficial effects that the search method and the search system provided by the present invention can improve the performance of the relay communication, and do not need to obtain the location information of the source end and the destination end, and do not need multiple antennas, and the mobile relay only utilizes The single-bit information fed back at the destination can find the best relay communication position within a given range of motion trajectories.
  • FIG. 1 is a flow chart of an optimal relay location searching method using a drone as a mobile relay provided by the prior art.
  • FIG. 2 is a flowchart of a method for searching for an optimal relay position based on a reverse compensation mechanism according to an embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a search system based on a reverse compensation mechanism for using an unmanned aerial vehicle as an optimal relay position for a mobile relay according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a signal to noise ratio distribution in a search process using an unmanned aerial vehicle as an optimal position of a mobile relay according to an embodiment of the present invention.
  • FIG. 5 is a schematic diagram of a time slot and a signal to noise ratio of a search process using a drone as an optimal location for a mobile relay according to an embodiment of the present invention.
  • FIG. 6 is a diagram showing a bit error rate distribution diagram of a mobile relay using a drone as a mobile relay according to an embodiment of the present invention.
  • FIG. 7 is a schematic diagram of a time slot and a bit error rate of a search process using a drone as an optimal location of a mobile relay according to an embodiment of the present invention.
  • the shortcomings and defects of the optimal relay location search algorithm for existing drones are: (1) The source (S) and destination (D) need to use their own GPS function to measure their location information and send the information. For mobile relay, relying on GPS function is vulnerable to attack and interference, resulting in location search failure; (2) For communication devices without GPS function or GPS damage, some existing algorithms are unusable; (3) more onboard Antennas increase the complexity of mobile relays compared to single antennas, and inevitably have angle estimation errors, which also increases the complexity of the algorithm.
  • the algorithm provided by the invention uses the airborne single antenna, and does not need to know the position information of the source end (S) and the destination end (D), and can still find the optimal relay position within the predetermined motion trajectory range, and the applicable scene is expanded.
  • the use of drones as mobile relays using the descending step perturbation positive and negative feedback mechanism to control the drone automatically search for the best relay position, can effectively improve the performance of the communication system.
  • the present invention provides a method for searching for an optimal relay position based on a reverse compensation mechanism as shown in FIG. 2, the steps including:
  • the mobile relay is in the current position of the fixed track, receives the test signal sent from the source end and performs amplification, and then forwards the amplified test signal to the destination end.
  • the mobile relay is placed anywhere on the fixed circular track and initialized, and the initialization position is recorded as the most known in memory. A good position, receiving the test signal transmitted from the source and amplifying, and then forwarding the amplified test signal to the destination.
  • the destination end calculates communication performance according to the received signal, and then generates single-bit information and feeds back to the mobile relay according to the calculation result.
  • the single-bit information includes information about whether the received signal performance is improved.
  • the destination end is initialized according to the first received signal, and the communication performance is calculated according to the received signal, and the communication performance is saved in the memory as the known best communication performance, and the communication performance includes the letter. Noise ratio strength and bit error rate; when the destination receives a new signal, it calculates new communication performance, compares the new communication performance with the known best communication performance stored in the memory, and generates single-bit information feedback based on the comparison result.
  • the mobile relay while determining the improved reception performance, updates the known best communication performance in the memory. Specifically, in actual use, the single-bit information generally indicates that the reception performance is improved by 1, and 0 indicates that the reception performance is not improved, and vice versa.
  • the mobile relay calculates a next time position according to the fed single bit information and moves to the next time position; and repeatedly performs steps S1 to S3 until the optimal relay position is finally determined.
  • the mobile relay calculates a random disturbance step according to the single bit information, and introduces a correction factor, and then the mobile relay performs a positional movement on the fixed track according to the calculation result, and the motion step and direction are changed. And return to step S1.
  • step S3 specifically includes:
  • the mobile relay records its known optimal position ⁇ (n), and n represents an nth time slot;
  • the mobile relay transforms a motion step according to the single bit information, and the transformed motion step includes a random disturbance step size ⁇ (n) and a correction factor ⁇ (n);
  • the mobile relay calculates a next time position according to the transformed motion step, then moves to the next time position, returns to step S1, continues to receive and amplifies the test signal transmitted from the source, and transmits the signal to the destination. end;
  • the mobile relay updates the known best location according to the single-bit information of the feedback and stores the The motion step and direction are calculated to determine the next moment position and move to the next moment position.
  • step S4 further includes:
  • S341 The mobile relay determines the single bit information.
  • the mobile relay may be a drone, a balloon, a satellite, or an airplane.
  • the unmanned aerial vehicle is used as a mobile relay, and the present invention is further described in conjunction with FIG. 3 to FIG.
  • a search system based on a descending step perturbation positive and negative feedback algorithm for using an unmanned aerial vehicle as an optimal relay position of a mobile relay including a source end and a mobile relay, is provided.
  • the destination end the source end is configured to send the test signal to the mobile relay; the mobile relay is used to receive the test signal sent from the source end to be amplified at the current position of the fixed track, and then forward the amplified test signal to the destination end
  • the destination end is configured to calculate communication performance according to the received signal, and then generate single-bit information feedback to the mobile relay according to the calculation result; the single-bit information includes information about whether the reception performance is improved.
  • the mobile relay is further configured to calculate a next time position according to the single bit information of the feedback and move to the next time position, and amplify the test signal sent by the source end in real time and transmit the test signal to the destination end for calculation. Until the final relay position is finally determined.
  • the three coordinate variables in the cylindrical coordinate system are (r, ⁇ , z).
  • r is the radius of motion of the drone on the xoy plane
  • ⁇ is the angle rotated from the x-axis in the counterclockwise direction to oR' i from the positive z-axis
  • oR' i is the drone in the xy plane
  • the mapping, z is the height of the drone.
  • the drone moves on a circle with a height of z and a radius of r.
  • the coordinates of the center of the circle o (0, 0, z), the coordinates of the source end S (x s , y s , z s ), the coordinates of the destination end D (x) d , y d , z d ).
  • the coordinates of the drone at time n are R(r, ⁇ (n), z), then the coordinates of the drone at time n+1 are R(r, ⁇ (n+1), z).
  • the communication distance between the source R and the destination D is the relay distance R (r, ⁇ (n), z) at time n:
  • x denotes the signal transmitted by S
  • P S denotes the transmission power of S
  • n 1 is an additive white Gaussian noise satisfying E[
  • 2 ] N 01 . Is the free space path loss of the first hop channel.
  • G is the gain of the drone to the signal
  • n 2 is the additive white Gaussian noise satisfying E[
  • 2 ] N 02 . Is the free space path loss of the second hop channel.
  • the gain G is as follows:
  • ⁇ 1 and ⁇ 2 are as follows:
  • the method for searching for the optimal relay position of the mobile relay based on the reverse compensation mechanism specifically includes:
  • n represents a time slot.
  • the destination (D) measures the new received signal communication performance (signal-to-noise ratio, bit error rate, and later uses signal-to-noise ratio to represent communication performance), SNR strength SNR(n), and updates the most in memory.
  • the destination then feeds back single-bit information to the drone to indicate whether the received signal performance strength is increased.
  • the drone updates its known best position ⁇ (n) based on the single-bit information returned from the feedback.
  • the update rules are as follows:
  • the mobile relay location search simulation is shown in Figure 4:
  • Position coordinates of the source (S): (x s , y s , z s ) (0, -700, 1);
  • the horizontal axis represents ⁇ (n), and the vertical axis represents the end-to-end signal-to-noise ratio ⁇ end of the relay position corresponding to ⁇ (n);
  • Position coordinates of the source (S): (x s , y s , z s ) (0, -700, 1);
  • Fig. 5 shows the number of time slots spent in the mobile relay searching for the best position
  • the vertical axis represents the end-to-end signal-to-noise ratio ⁇ end , and it can be seen that the 6 dB position is found when the 40th time slot is searched.
  • the best relay position was found in the 50th time slot, which is the maximum point in Figure 4.
  • Position coordinates of the source (S): (x s , y s , z s ) (0, -700, 1);
  • the horizontal axis represents ⁇ (n)
  • the vertical axis represents the end-to-end error rate of the relay position corresponding to ⁇ (n).
  • Position coordinates of the source (S): (x s , y s , z s ) (0, -700, 1);
  • the horizontal axis represents the number of time slots spent in searching for the best position of the mobile relay
  • the vertical axis represents the end-to-end error rate
  • the invention belongs to the field of wireless communication technologies and can be applied to search for an optimal relay location point and improve the performance of relay communication.
  • This method is applicable to fixed relay motion tracks.
  • Potential application scenarios include the construction of temporary communication systems and communication connections at disaster sites.

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Abstract

本发明适用于无线通信技术领域，提供了基于反向补偿机制的移动中继最佳中继位置的搜寻方法，步骤包括：A，移动中继在固定轨道的当前位置，接收来自源端发送的测试信号并进行放大后转发给目的端；B，目的端根据接收到的信号计算通信性能，然后根据计算结果生成单比特信息反馈给所述移动中继；C，所述移动中继根据反馈的单比特信息计算下一时刻位置并移动到所述下一时刻位置；重复执行步骤A-C，直至最终确定最佳中继位置。本发明提供的搜寻方法和搜寻系统可提高中继通信的性能，且无需获得源端和目的端的位置信息，无需多天线，移动中继只利用目的端反馈的单比特信息就能在给定运动轨迹范围内找到最佳的中继通信位置。

Description

基于反向补偿机制的最佳中继位置的搜寻方法及系统 技术领域
本发明属于无线通信技术领域，尤其涉及一种基于反向补偿机制的移动中继的最佳中继位置的搜寻方法及系统。
背景技术
通信中继用来转发不同的节点之间发出的信息，扩大了通信范围，提高了通信系统的性能。陆地无线电通信很容易被障碍物遮挡和屏蔽，飞机、卫星及无人机(Unmanned Aerial Vehicles，UAVs)可以充当通信中继，因为机载中继可以在崎岖的山区或市区有效地为需要相互通信的双方建立起连接。近年来，使用无人机作为通信中继的问题已吸引不少学者的关注和研究，同时其应用也十分广泛。
现有的应用于移动中继位置搜寻的算法主要有：如图1a所示，基于GPS去测量源端(S)和目的端(D)的位置信息，移动中继再利用该信息去搜寻最佳中继位置；如图1b所示，基于扰动的极值搜索控制(Extremum Seeking Control，ESC)算法；基于机载多天线的算法。现有的移动中继位置搜寻算法都可以使移动中继找到最佳的中继位置，但是这些算法或适用范围也存在一定的不足和缺陷，主要体现在：(1)通信中继依赖于GPS容易受到攻击，也可能遭受GPS欺骗或干扰而导致中继通信失败，更重要的是，在很多特殊情况下通信双方没有GPS功能或者GPS设备已损坏，如自然灾害导致GPS设备损坏。(2)使用机载多天线对信号到达角(DOA)进行估计来搜寻最佳中继位置，容易出现估计误差，且增加了无人机通信设备的复杂度和算法复杂度。
发明内容
本发明所要解决的技术问题在于提供一种基于反向补偿机制的最佳中继位置的搜寻方法及系统，旨在解决现有以无人机作为移动中继的最佳通信位置的搜寻算法容易遭受GPS欺骗或干扰而导致通信中继失败，容易出现估计误差，且增加了移动中继通信设备的复杂度和算法复杂度的问题。
本发明是这样实现的，基于反向补偿机制的最佳中继位置的搜寻方法，步骤包括：
步骤A，移动中继在固定轨道的当前位置，接收来自源端发送的测试信号并进行放大后转发给目的端；
步骤B，目的端根据接收到的信号计算通信性能，然后根据计算结果生成单比特信息反馈给所述移动中继；所述单比特信息包括接收信号性能是否提高的信息；
步骤C，所述移动中继根据反馈的单比特信息计算下一时刻位置并移动到所述下一时刻位置；
重复执行步骤A-C，直至最终确定最佳中继位置。
进一步地，所述步骤A之前还包括：移动中继在固定轨道的任意起始位置进行初始化，并在内存中将初始化位置记录为已知最佳位置。
进一步地，步骤B具体包括：
所述目的端根据第一次接收到信号进行初始化，根据接收的信号计算通信性能，将所述通信性能保存在内存中作为已知最佳通信性能，所述通信性能包括信噪比强度和误码率；当目的端接收新的信号后计算新的通信性能，将新的通信性能与内存中保存的已知最佳通信性能进行比较，根据比较结果生成单比特信息反馈至所述移动中继，同时在确定接收性能提高后，更新内存中的已知最佳通信性能。
进一步地，步骤C具体包括：所述移动中继根据所述单比特信息计算随机扰动步长，同时引入修正因子，然后所述移动中继根据计算结果变换运动步长和方向在固定轨道上进行位置移动，并返回步骤A。
进一步地，步骤C具体包括：
步骤C1，所述移动中继记录其已知最佳位置θ(n)，n表示第n个时隙；
步骤C2，所述移动中继根据所述单比特信息变换运动步长，变换后的运动步长包括随机扰动步长和修正因子；
步骤C3，所述移动中继根据变换后的运动步长计算下一时刻位置，然后移动至所述下一时刻位置，返回步骤A，继续接收来自源端发射的测试信号，并放大转发至目的端；
以
Figure PCTCN2015096740-appb-000001
表示所述下一时刻位置，以δ(n)所述随机扰动步长，ξ(n)表示所述修正因子，则：
Figure PCTCN2015096740-appb-000002
步骤C4，所述移动中继根据反馈的单比特信息更新已知最佳位置并存储，计算运动步长和方向以确定下一时刻位置并移动到该下一时刻位置。
进一步地，所述步骤C4具体包括：
步骤C41：移动中继对所述单比特信息进行判断；
步骤C42：在判断为接收信号性能提高时，修正因子清零。
步骤C43：在判断为接收信号性能未提高时，移动中继返回上一时隙的位置，修正因子修改为上一时隙的运动步长的相反数。
本发明还提供了基于反向补偿机制的最佳中继位置的搜寻系统，包括源端、移动中继和目的端：
所述源端，用于发送测试信号至所述移动中继；
所述移动中继，用于在固定轨道的当前位置，接收来自源端发送的测试信号进行放大后转发给目的端；
所述目的端，用于根据接收到的信号计算通信性能，然后根据计算结果生成单比特信息反馈给所述移动中继；所述单比特信息包括接收性能是否提高的信息；
所述移动中继还用于根据反馈的单比特信息计算下一时刻位置并移动到所述下一时刻位置，并实时将所述源端发送的测试信号进行放大后传输至所述目 的端进行计算，直至最终确定最佳中继位置。
进一步地，移动中继还用于，在固定轨道的任意位置进行初始化，并在内存中将初始化位置记录为已知最佳位置。
进一步地，所述目的端根据接收的信号计算通信性能，将所述通信性能保存在内存中作为已知最佳通信性能，所述通信性能包括信噪比强度和误码率；目的端接收新的信号后计算新的通信性能，将新的通信性能与内存中保存的已知最佳通信性能进行比较，根据比较结果生成单比特信息反馈至所述移动中继，同时在确定接收性能提高后，更新内存中的已知最佳通信性能。
进一步地，所述移动中继根据所述单比特信息计算随机扰动步长，同时引入修正因子，然后所述移动中继根据计算结果变换运动步长和方向在固定轨道上进行位置移动，并实时将所述源端发送的测试信号进行放大后传输至所述目的端进行计算，直至最终确定最佳中继位置。
本发明与现有技术相比，有益效果在于：本发明提供的搜寻方法和搜寻系统可提高中继通信的性能，且无需获得源端和目的端的位置信息，无需多天线，移动中继只利用目的端反馈的单比特信息就能在给定运动轨迹范围内找到最佳的中继通信位置。
附图说明
图1是现有技术提供的以无人机作为移动中继的最佳中继位置搜寻方法的流程图。
图2是本发明实施例提供的一种基于反向补偿机制的最佳中继位置的搜寻方法的流程图。
图3是本发明实施例提供的一种基于反向补偿机制的以无人机作为移动中继的最佳中继位置的搜寻系统的结构示意图。
图4是本发明实施例提供的使用无人机作为移动中继最佳位置的搜寻过程中的信噪比分布示意图。
图5是本发明实施例提供的使用无人机作为移动中继最佳位置的搜寻过程所花时隙与达到信噪比的示意图。
图6是本发明实施例提供的使用无人机作为移动中继在固定轨道上的误码率分布图。
图7是本发明实施例提供的使用无人机作为移动中继最佳位置的搜寻过程所花时隙与达到误码率的示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
针对现有无人机最佳中继位置搜寻算法的不足和缺陷，即：(1)源端(S)和目的端(D)需要利用自身的GPS功能测量自己的位置信息并把该信息发送给移动中继，依赖GPS功能容易受到攻击和干扰而导致位置搜寻失败；(2)对于没有GPS功能或者GPS已损坏的通信设备，现有的一些算法是无法使用的；(3)机载多天线相比于单天线增加了移动中继的复杂性，且不可避免的会有角度估计误差，同时也增加了算法的复杂性。本发明提供的算法使用机载单天线，且无需知道源端(S)和目的端(D)的位置信息，依然能够在预定运动轨迹范围内找到最佳的中继位置，适用场景扩大。而使用无人机作为移动中继，利用下降步长扰动正负反馈机制去控制无人机自动搜寻最佳中继位置，能有效地提升通信系统性能。
基于上述原理，本发明提供了如遇2所示的一种基于反向补偿机制的最佳中继位置的搜寻方法，步骤包括：
S1，移动中继在固定轨道的当前位置，接收来自源端发送的测试信号并进行放大后，将放大测试信号转发给目的端。在本步骤中，移动中继在固定的圆形轨道上的任意位置，并进行初始化，并在内存中将初始化位置记录为已知最 佳位置，接收来自源端发射的测试信号并放大，然后将放大后的测试信号转发给目的端。
S2，目的端根据接收到的信号计算通信性能，然后根据计算结果生成单比特信息反馈给所述移动中继；所述单比特信息包括接收信号性能是否提高的信息。在本步骤中，所述目的端根据第一次接收到信号进行初始化，根据接收的信号计算通信性能，将所述通信性能保存在内存中作为已知最佳通信性能，所述通信性能包括信噪比强度和误码率；当目的端接收新的信号后计算新的通信性能，将新的通信性能与内存中保存的已知最佳通信性能进行比较，根据比较结果生成单比特信息反馈至所述移动中继，同时在确定接收性能提高后，更新内存中的已知最佳通信性能。具体的，在实际使用过程中，所述单比特信息一般用1表示接收性能提高，0表示接收性能未提高，反之亦然。
S3，所述移动中继根据反馈的单比特信息计算下一时刻位置并移动到所述下一时刻位置；重复执行步骤S1至S3，直至最终确定最佳中继位置。在本步骤中，所述移动中继根据所述单比特信息计算随机扰动步长，同时引入修正因子，然后所述移动中继根据计算结果变换运动步长和方向在固定轨道上进行位置移动，并返回步骤S1。
进一步地，步骤S3具体包括：
S31，所述移动中继记录其已知最佳位置θ(n)，n表示第n个时隙；
S32，所述移动中继根据所述单比特信息变换运动步长，变换后的运动步长包括随机扰动步长δ(n)和修正因子ξ(n)；
S33，所述移动中继根据变换后的运动步长计算下一时刻位置，然后移动至所述下一时刻位置，返回步骤S1，继续接收并放大来自源端发射的测试信号，并传输至目的端；
以
Figure PCTCN2015096740-appb-000003
表示所述下一时刻位置，以δ(n)所述随机扰动步长，ξ(n)表示所述修正因子，则：
Figure PCTCN2015096740-appb-000004
S34，所述移动中继根据反馈的单比特信息更新已知最佳位置并存储，计 算运动步长和方向以确定下一时刻位置并移动到该下一时刻位置。
进一步地，步骤S4还进一步的包括：
S341：移动中继对所述单比特信息进行判断；
S342：在判断为接收信号性能提高时，修正因子清零。
S343：在判断为接收信号性能未提高时，移动中继返回上一时隙的位置，修正因子修改为上一时隙的运动步长的相反数。
在具体实施过程中，移动中继可以是无人机、气球、卫星或者飞机等，在本实施例中，以无人机作为移动中继，结合图3至图8对本发明进行进一步的阐述。
如图3所示，为本发明实施例提供的一种基于下降步长扰动正负反馈算法的以无人机作为移动中继的最佳中继位置的搜寻系统，包括源端、移动中继和目的端：源端，用于发送测试信号至移动中继；移动中继，用于在固定轨道的当前位置，接收来自源端发送的测试信号进行放大后，将放大测试信号转发给目的端；目的端，用于根据接收的信号计算通信性能，然后根据计算结果生成单比特信息反馈给所述移动中继；所述单比特信息包括接收性能是否提高的信息。所述移动中继还用于根据反馈的单比特信息计算下一时刻位置并移动到该下一时刻位置，并实时将所述源端发送的测试信号进行放大后传输至所述目的端进行计算，直至最终确定最佳中继位置。
如图3所示，柱坐标系中的三个坐标变量是(r，θ，z)。其中r为无人机在xoy平面上的运动半径，θ为从正z轴来看自x轴按逆时针方向转到oR′i所转过的角，oR′i为无人机在xy平面的映射，z为无人机的高度。在
本实施例中：
①、变步长δ(n)＝±δ0，δ(n)＝+δ0表示逆时针方向移动，δ(n)＝-δ0表示顺时针方向移动。
②、无人机在高度为z，半径为r的圆周上移动，圆心坐标o(0，0，z)，源端坐标S(xs，ys，zs)，目的端坐标D(xd，yd，zd)。
③、无人机在n时刻的坐标为R(r，θ(n)，z)，那么无人机在n+1时刻的坐标为R(r，θ(n+1)，z)。
④、柱坐标系(r，θ，z)与空间直角坐标系(x，y，z)的转换关系如下：
Figure PCTCN2015096740-appb-000005
⑤、n时刻中继R(r，θ(n)，z)离源S与目的端D的通信距离分别是：
Figure PCTCN2015096740-appb-000006
(2)移动中继通信过程：
第一跳通信：源端(S)到无人机(R)
Figure PCTCN2015096740-appb-000007
x表示S发射的信号，PS表示S的发射功率，n1是满足E[|n1|2]＝N01的加性高斯白噪声。
Figure PCTCN2015096740-appb-000008
是第一跳信道的自由空间路径损耗。
第二跳通信：无人机(R)到目的端(D)
Figure PCTCN2015096740-appb-000009
G是无人机对信号的增益，n2是满足E[|n2|2]＝N02的加性高斯白噪声。
Figure PCTCN2015096740-appb-000010
是第二跳信道的自由空间路径损耗。
其中增益G如下：
Figure PCTCN2015096740-appb-000011
由公式(2)得端到端的信噪比为：
Figure PCTCN2015096740-appb-000012
其中γ1、γ2如下：
Figure PCTCN2015096740-appb-000013
详细的，在一个时隙里，对于移动中继来说，如果某一次的扰动(如：δ(n)＝δ0)导致了性能的下降，那么通常反向的扰动(δ(n)＝-δ0)将带来性能的提升。本实施例中，基于反向补偿机制的移动中继最佳中继位置的搜寻方法具体包括：
1)无人机在内存中记录其已知最佳位置θ(n)，每个迭代时隙增加一个随机扰动步长δ(n)＝±δ0，引入修正因子ξ(n)，δ0为本算法的扰动步长，n表示时隙。
2)无人机计算它的下一时刻位置：
Figure PCTCN2015096740-appb-000014
3)目的端(D)测量新的接收信号通信性能(信噪比、误码率，以后都用信噪比来表示通信性能)，信噪比强度SNR(n)，并且更新内存中的最佳接收信号信噪比强度，更新规则为SNRbest(n+1)＝max(SNRbest(n)，SNR(n))。随后目的端反馈单比特信息给无人机，以此表明接收信号性能强度是否提高。
4)无人机根据反馈回来的单比特信息，更新自己的已知最佳位置θ(n)，更新规则如下：
if SNR(n)＞SNRbest(n)
θ(n+1)＝θ(n)+δ(n)+ξ(n)；
ξ(n+1)＝0；
else                      (6)
θ(n+1)＝θ(n)；
ξ(n+1)＝-δ(n)；
end
移动中继位置搜寻仿真如图4所示：
初始步长：
Figure PCTCN2015096740-appb-000015
(1)以信噪比为基准表示通信性能的好坏，也就是公式(4)；
源端(S)的位置坐标：(xs，ys，zs)＝(0，-700，1)；
目的端(D)的位置坐标：(xd，yd，zd)＝(30，600，1)；
无人机的位置坐标：(r，θ(n)，z)＝(500，θ(n)，30)；
图4横轴表示θ(n)，纵轴表示与θ(n)相对应的该中继位置的端到端信噪比γend；
(2)以信噪比为基准表示通信性能的好坏，也就是公式(4)；
源端(S)的位置坐标：(xs，ys，zs)＝(0，-700，1)；
目的端(D)的位置坐标：(xd，yd，zd)＝(30，600，1)；
无人机的位置坐标：(r，θ(n)，z)＝(500，θ(n)，30)；
图5横轴表示移动中继搜寻最佳位置过程中花费的时隙数，纵轴表示端到端信噪比γend，可以看到在搜寻到第40个时隙时就找到了6dB的位置，在第50个时隙找到了最佳的中继位置，也就是图4中的极大值点。
(3)以误码率为基准表示通信性能的好坏：
源端(S)的位置坐标：(xs，ys，zs)＝(0，-700，1)；
目的端(D)的位置坐标：(xd，yd，zd)＝(30，600，1)；
无人机的位置坐标：(r，θ(n)，z)＝(500，θ(n)，30)；
图6中横轴表示θ(n)，纵轴表示与θ(n)相对应的该中继位置的端到端误码率。
(4)以误码率为基准表示通信性能的好坏；
源端(S)的位置坐标：(xs，ys，zs)＝(0，-700，1)；
目的端(D)的位置坐标：(xd，yd，zd)＝(30，600，1)；
无人机的位置坐标：(r，θ(n)，z)＝(500，θ(n)，30)；
图7中，横轴表示移动中继搜寻最佳位置过程中花费的时隙数，纵轴表示端到端误码率，可以看到在搜寻到第55个时隙时算法收敛结束，也就是找到了 图6中的极小值点。
本发明属于无线通信技术领域，可以被应用来搜寻最佳中继位置点，提高中继通信的性能。本方法适用固定的中继运动轨道。潜在的应用场景有：临时通信系统的搭建、灾害现场的通信连接等。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 基于反向补偿机制的最佳中继位置的搜寻方法，其特征在于，所述搜寻方法的步骤包括：
    步骤A，移动中继在固定轨道的当前位置，接收来自源端发送的测试信号并进行放大后转发给目的端；
    步骤B，目的端根据接收到的信号计算通信性能，然后根据计算结果生成单比特信息反馈给所述移动中继；所述单比特信息包括接收信号性能是否提高的信息；
    步骤C，所述移动中继根据反馈的单比特信息计算下一时刻位置并移动到所述下一时刻位置；
    重复执行步骤A-C，直至最终确定最佳中继位置。
  2. 如权利要求1所述的搜寻方法，其特征在于，所述步骤A之前还包括：移动中继在固定轨道的任意起始位置进行初始化，并在内存中将初始化位置记录为已知最佳位置。
  3. 如权利要求1所述的搜寻方法，其特征在于，步骤B具体包括：
    所述目的端根据第一次接收到信号进行初始化，根据接收的信号计算通信性能，将所述通信性能保存在内存中作为已知最佳通信性能，所述通信性能包括信噪比强度和误码率；当目的端接收新的信号后计算新的通信性能，将新的通信性能与内存中保存的已知最佳通信性能进行比较，根据比较结果生成单比特信息反馈至所述移动中继，同时在确定接收性能提高后，更新内存中的已知最佳通信性能。
  4. 如权利要求1所述的搜寻方法，其特征在于，步骤C具体包括：所述移动中继根据所述单比特信息计算随机扰动步长，同时引入修正因子，然后所述移动中继根据计算结果变换运动步长和方向在固定轨道上进行位置移动，并返回步骤A。
  5. 如权利要求4所述的搜寻方法，其特征在于，步骤C具体包括：
    步骤C1，所述移动中继记录其已知最佳位置θ(n)，n表示第n个时隙；
    步骤C2，所述移动中继根据所述单比特信息变换运动步长，变换后的运动步长包括随机扰动步长δ(n)和修正因子ξ(n)；
    步骤C3，所述移动中继根据变换后的运动步长计算下一时刻位置，然后移动至所述下一时刻位置，返回步骤A，继续接收来自源端发射的测试信号，并放大转发至目的端；
    以
    Figure PCTCN2015096740-appb-100001
    表示所述下一时刻位置，则：
    Figure PCTCN2015096740-appb-100002
    步骤C4，所述移动中继根据反馈的单比特信息更新已知最佳位置并存储，计算运动步长和方向以确定下一时刻位置并移动到该下一时刻位置。
  6. 如权利要求5所述的搜寻方法，其特征在于，所述步骤C4具体包括：
    步骤C41：移动中继对所述单比特信息进行判断；
    步骤C42：在判断为接收信号性能提高时，修正因子清零。
    步骤C43：在判断为接收信号性能未提高时，移动中继返回上一时隙的位置，修正因子修改为上一时隙的运动步长的相反数。
  7. 基于反向补偿机制的最佳中继位置的搜寻系统，其特征在于，所述搜寻系统包括源端、移动中继和目的端：
    所述源端，用于发送测试信号至所述移动中继；
    所述移动中继，用于在固定轨道的当前位置，接收来自源端发送的测试信号进行放大后转发给目的端；
    所述目的端，用于根据接收到的信号计算通信性能，然后根据计算结果生成单比特信息反馈给所述移动中继；所述单比特信息包括接收性能是否提高的信息；
    所述移动中继还用于根据反馈的单比特信息计算下一时刻位置并移动到所述下一时刻位置，并实时将所述源端发送的测试信号进行放大后传输至所述目的端进行计算，直至最终确定最佳中继位置。
  8. 如权利要求7所述的搜寻系统，其特征在于，移动中继还用于，在固定 轨道的任意位置进行初始化，并在内存中将初始化位置记录为已知最佳位置。
  9. 如权利要求7所述的搜寻系统，其特征在于，所述目的端根据第一次接收到信号进行初始化，根据接收的信号计算通信性能，将所述通信性能保存在内存中作为已知最佳通信性能，所述通信性能包括信噪比强度和误码率；当目的端接收新的信号后计算新的通信性能，将新的通信性能与内存中保存的已知最佳通信性能进行比较，根据比较结果生成单比特信息反馈至所述移动中继，同时在确定接收性能提高后，更新内存中的已知最佳通信性能。
  10. 如权利要求7所述的搜寻系统，其特征在于，所述移动中继根据所述单比特信息计算随机扰动步长，同时引入修正因子，然后所述移动中继根据计算结果变换运动步长和方向在固定轨道上进行位置移动，并实时将所述源端发送的测试信号进行放大后传输至所述目的端进行计算，直至最终确定最佳中继位置。
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