WO2017096540A1 - 基于连续负反馈变步长的最佳中继位置搜寻方法及系统 - Google Patents

基于连续负反馈变步长的最佳中继位置搜寻方法及系统 Download PDF

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WO2017096540A1
WO2017096540A1 PCT/CN2015/096737 CN2015096737W WO2017096540A1 WO 2017096540 A1 WO2017096540 A1 WO 2017096540A1 CN 2015096737 W CN2015096737 W CN 2015096737W WO 2017096540 A1 WO2017096540 A1 WO 2017096540A1
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Prior art keywords
relay
communication performance
location
negative feedback
mobile relay
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English (en)
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

Definitions

  • the present invention relates to the field of communications technologies, and in particular, to an optimal relay location searching method and system based on continuous negative feedback variable step size.
  • Communication relay can be used to forward information sent between different nodes, expand the communication range, and improve the performance of the communication system.
  • UVAs Terrestrial radiocommunication is easily obscured and shielded by obstacles, and aircraft, satellites, and drones (UVAs) can act as communication relays because airborne relays can effectively establish for both parties in need of communication in rugged mountains or urban areas. connection.
  • UVAs drones
  • the existing algorithms for UAV relay position search mainly include: measuring the position information of the ground communication unit by using GPS and searching for the optimal relay position by the drone; the perturbation-based extreme value search control algorithm, based on the machine Algorithms for carrying multiple antennas, etc.
  • the existing UAV relay position search algorithm can make the UAV find the best relay position on its own basis, but these algorithms or applicable scopes also have certain deficiencies and defects, mainly reflected in:
  • the ground communication unit needs to use its own GPS function to measure its own location information and send the information to the drone, relying on the GPS function to be vulnerable to attack and interference, resulting in location search failure;
  • the airborne multi-antenna increases the complexity of the drone compared to the single antenna, and inevitably has an angle estimation error, which also increases the complexity of the algorithm.
  • the embodiment of the invention provides an optimal relay position searching method based on continuous negative feedback variable step size And the system is used to solve the problem that the location information of the source end and the destination end must be known in the prior art to determine the limitation of use and the error caused by the relay position.
  • Step A The mobile relay receives the test signal sent from the source end at an arbitrary position on the fixed track, and amplifies and forwards the signal to the destination end;
  • Step B The destination end receives the signal sent by the mobile relay and calculates the current communication performance, where the communication performance includes: a signal to noise ratio and a bit error rate, and according to the calculation result and the saved known best Comparing communication performance of the relay location, and generating one-bit information to the mobile relay, the one-bit information indicating a comparison result between the current communication performance and the saved communication performance of the known optimal relay location, Said that the best relay position is the best tested communication performance;
  • Step C the mobile relay records current location information, and moves to the next location according to the one-bit information and the random disturbance step and the correction factor, and returns to step A until finally determining the optimal relay location.
  • the optimal relay position is: a location with the best communication performance within a preset search duration, or a location where the mobile relay moves the entire fixed track with the best communication performance, or the communication performance is satisfied.
  • the system sets the required location.
  • the search system includes a mobile relay, a source end, and a destination end;
  • the mobile relay receives the test signal sent from the source end at an arbitrary position of the fixed track, and amplifies and forwards the test signal to the destination end;
  • a signal sent by the mobile relay and calculating a current communication performance, where the communication performance includes: a signal to noise ratio and a bit error rate, and according to the calculation result and the saved known optimal relay position
  • the communication performance is compared, and a bit of information is fed back to the mobile relay, the one-bit information representing a comparison of the current communication performance with the saved communication performance of the known best relay location, the known The best relay location is the location with the best communication performance tested;
  • the mobile relay records the current location information, and moves to the next location according to the one-bit information, the random disturbance step and the correction factor, and performs the reception of the test signal sent from the source again, and amplifies and forwards to the location Describe the destination end step until the optimal relay position is finally determined, the optimal relay position is: a location with the best communication performance within a preset search duration, or the mobile relay moves the entire fixed location The location where the communication performance is best at the time of the track, or the position where the communication performance satisfies the system setting requirements.
  • the embodiment of the present invention has the following advantages: receiving a test signal through a mobile relay, and transmitting to the destination end for calculation and comparison of communication performance between the current location and the known optimal relay location, according to the purpose
  • the comparison result of the end feedback and the random disturbance step size and the correction factor are moved to the next relay position, and the step of performing the mobile relay receiving signal is returned, and by repeating the above process, the mobile relay can continuously move to the step based on the step size.
  • the method can improve the performance of the relay communication, and does not need to obtain the location information of the source end and the destination end, and does not require multiple antennas. Only the destination end needs to feed back one bit of information to the mobile relay for search control, and the optimal relay position point can still be determined within the predetermined trajectory range, thereby expanding the applicable range.
  • FIG. 1 is a schematic diagram of a communication model of an optimal relay position determining system according to an embodiment of the present invention
  • FIG. 2 is a schematic diagram of a flow of a mobile relay optimal relay location searching method based on a continuous negative feedback variable step size according to an embodiment of the present invention
  • FIG. 3 is a simulation diagram of a correspondence relationship between a moving angle of a mobile relay and a signal to noise ratio of a signal according to an embodiment of the present invention
  • FIG. 4 is a simulation diagram of a correspondence relationship between a number of slots and a signal to noise ratio according to an embodiment of the present invention
  • FIG. 5 is a simulation diagram of a correspondence relationship between a moving angle and a signal to noise ratio when determining an optimal relay position by a bit error rate according to an embodiment of the present invention
  • FIG. 6 is a simulation diagram of the correspondence between the number of slots and the error rate when the optimal relay position is determined by the bit error rate according to the embodiment of the present invention.
  • FIG. 7 is a schematic diagram showing the structure of a mobile relay optimal relay position searching system based on a continuous negative feedback variable step size according to an embodiment of the present invention.
  • an embodiment of a communication model of an optimal relay location determining system includes: a source end, a mobile relay, and a destination end.
  • R i denotes a mobile relay
  • S denotes a source
  • D denotes a destination.
  • the source end and the destination end may be two different terrestrial communication units, and the terrestrial communication unit may be various types of wireless communication transceiving devices, such as a mobile phone, a terminal, a base station, etc., or may be other mobile devices. Following.
  • the source end is used as the signal transmitting end
  • the destination end is taken as the signal receiving end as an example.
  • both the source end and the destination end can serve as the signal transmitting end and the signal receiving end.
  • the parameters of the cylindrical coordinate system used by the relay are moved in a three-dimensional coordinate system, and the coordinates are (r, ⁇ , z), where r is the radius of motion of the mobile relay on the xoy plane, that is, R i '. O represents the origin of the cylindrical coordinates.
  • the mobile relay operation has a fixed orbit, and it moves along a predetermined orbit with a radius of r. Therefore, in the embodiment of the present invention, it is an optimal relay for finding a mobile relay on a circle formed by radius r. position.
  • ⁇ is the angle rotated from the x-axis counterclockwise to oR′ i from the positive Z-axis
  • z is the height of the mobile relay.
  • the coordinates of the mobile relay in the tth time slot are (r, ⁇ (t), z), and the coordinates in the t+1th time slot are (r, ⁇ (t+1), z. ).
  • the communication distances of the mobile relays (r, ⁇ (t), z) from the source end (x s , y s , z s ) and the destination end (x d , y d , z d ) are respectively :
  • d 1 represents the communication distance between the mobile relay and the source end
  • d 2 represents the communication distance between the mobile relay and the destination end
  • Step A The mobile relay receives the test signal sent from the source end at any position of the fixed track, and amplifies and forwards it to the destination end.
  • the source end sends a test signal for testing communication performance to the mobile relay, and the mobile relay will amplify the test signal after receiving the test signal, and forward the amplified signal.
  • the test signal sent by the source is not exactly the same as the test signal received by the mobile relay, and the mobile relay receives the test signal. After that, the received test signal will be amplified, and therefore, the signal received by the mobile relay is not the same as the signal transmitted by the mobile relay.
  • the mobile relay initializes its own location information before the mobile relay starts searching.
  • the source sends a test signal to the mobile relay, and the mobile relay forwards the received test signal to the destination.
  • the step of forwarding actually includes amplifying and forwarding the signal, so that the destination calculates the initial communication performance. And save as the initial record of the destination.
  • the test signal is a signal for testing communication performance, which can help the mobile relay to search for the optimal relay position, and can carry data for testing communication performance in the signal, and search for the best in the mobile relay.
  • the source Before the location, the source sends the test signal, and only finds the best in the mobile relay. After the relay location, the source will send really useful data.
  • Step B The destination end receives the signal sent by the mobile relay and calculates the current communication performance, where the communication performance includes a signal to noise ratio, a bit error rate, and according to the calculated result and the saved known optimal relay position. The communication performance is compared, and one bit of information is generated and fed back to the mobile relay.
  • the destination end calculates the communication performance, including calculating the signal-to-noise ratio or the bit error rate of the current communication, and performing the calculated communication performance of the communication performance with the saved known optimal relay position.
  • the known optimal relay position is the best tested communication performance
  • the signal-to-noise ratio of the known optimal relay position is all signal signals that have been calculated by the destination before the t-th time slot.
  • the maximum value of the noise ratio, or the bit error rate of the known optimal relay position is the minimum value of the bit error rate in all signals that have been calculated by the destination before the t-th time slot.
  • the one-bit information represents a comparison result between the current communication performance and the saved communication performance of the known optimal relay position, that is, the one-bit information includes
  • the source end receives information about whether the communication performance corresponding to the signal from the mobile relay is improved.
  • the one-bit information may be the signal-to-noise ratio of the test signal received by the destination end and the best saved on the destination end.
  • the comparison result of the signal-to-noise ratio of the known position may also be a comparison result of the error rate of the test signal received at the destination end and the bit error rate of the best known position saved on the destination end.
  • the comparison result may be that the communication performance of the current location is better than the communication performance of the known optimal relay location, or may be a communication performance that is inferior to the known optimal relay location.
  • the comparison result is transmitted in the form of one-bit information.
  • the bit information 1 can be set in advance to indicate that the current communication performance is improved compared to the known optimal relay position, and the bit information 0 indicates that the current communication performance of the signal is the most known.
  • the communication performance of the good relay location has decreased.
  • the comparison result can also be set by other forms, which is not limited herein.
  • the following is an example of calculating the communication performance as the signal-to-noise ratio, and the source terminal, the mobile relay, and the destination end are involved in the communication process in the embodiment of the present invention.
  • the parameters are as follows:
  • x is the test signal transmitted by the source
  • P S is the transmit power of the source
  • n 1 is the additive white Gaussian noise of the first hop communication
  • y R is the test signal received by the mobile relay
  • N 01 is the Gaussian white.
  • the power of noise n 1 , E represents the mathematical expectation value
  • L S represents the free space path loss from the source to the mobile relay
  • ⁇ represents the wavelength of the wave used by the source to transmit the test signal
  • d 1 represents the source and the mobile The distance between the relays.
  • d 1 can be calculated by moving the relay and the coordinates of the source end in the three-dimensional coordinate system.
  • Calculating the following parameters related to the mobile relay-forwarded test signal received by the destination including:
  • the destination receives the test signal sent from the mobile relay:
  • y D represents the test signal transmitted by the mobile terminal received by the destination
  • x represents the test signal sent by the source
  • P S represents the transmit power of the source
  • n 1 represents the additive white Gaussian noise of the first hop communication
  • E Indicates the mathematical expectation value
  • L S represents the free-space path loss from the source to the mobile relay
  • ⁇ represents the wavelength used by the mobile relay to amplify the forward test signal
  • d 2 represents the distance between the mobile relay and the destination
  • L R, D represents the free space path loss of the mobile relay to the destination
  • G represents the gain of the mobile relay to the received test signal, ie the relay gain
  • P R represents the transmit power of the mobile relay
  • n 2 represents the mobile relay
  • N 02 represents the power of the Gaussian white noise n 2 .
  • ⁇ is used to indicate the wavelength used by the mobile relay to amplify and forward the test signal and the wavelength used by the source to transmit the test signal, because the wavelength used by the mobile relay to amplify the forward test signal and the wavelength used by the source to transmit the test signal may be the same. wavelength.
  • the destination calculates the signal-to-noise ratio of the received test signal as follows:
  • SNR represents the signal-to-noise ratio of the test signal received by the destination
  • P S represents the transmit power of the source
  • G represents the gain of the mobile relay to the received signal
  • L S, R represents the source to the mobile relay. That is, the free space path loss of the first hop communication
  • L R, D represents the mobile relay to the destination end, that is, the free space path loss of the second hop communication
  • N 01 represents the power of the Gaussian white noise n 1 of the first hop communication
  • N 02 represents the power of the second hopping Gaussian white noise n 2 .
  • the mobile relay only needs to forward the test signal after receiving the test signal, the test signal still has fading and noise interference during the transmission process, in order to ensure that the destination end can receive a better signal.
  • the mobile relay will amplify the received test signal, ie increase the gain G.
  • the destination end can calculate the signal to noise ratio of the received test signal according to the manner of 3) above.
  • the initial position of the known optimal relay position recorded by the destination is randomly given before the search for the optimal relay position is performed, and the initial value of the signal-to-noise ratio is the signal-to-noise ratio of the initial position.
  • Step C The mobile relay records current location information, and according to the one-bit information, a random perturbation step The long and correction factors move to the next position and return to step A until the optimal relay position is finally determined.
  • the mobile relay After receiving the one-bit information including the comparison result sent by the destination end, the mobile relay determines the next relay position according to the comparison result, the random disturbance step size and the correction factor, and moves to the next relay position. At the t+1th time slot, the process returns to step A.
  • the mobile relay can continuously search for the optimal relay position by the cyclic process described above by the present invention, and after determining the optimal relay position, the above cyclic search process will be stopped.
  • the random perturbation step size represents a step size of the mobile relay random perturbation.
  • the correction factor is a parameter used to correct the random disturbance step size so that the mobile relay moves to the next relay position closer to the optimal relay position.
  • the one-bit information indicates that the current communication performance is greater than the communication performance of the known optimal relay position, that is, the signal-to-noise ratio of the communication signal of the current location is greater than the signal noise of the communication signal of the known optimal relay position.
  • the communication error rate of the current location is less than the communication error rate of the known optimal relay location, the current location is recorded as the known optimal relay location, and a disturbance step is randomly moved to move to the next A relay position, that is, determined and moved to the next relay position according to the first correction factor value and the random disturbance step.
  • the first correction factor has a value of zero. When the current communication performance is better than the communication performance of the known optimal relay position, the value of the correction factor is cleared, and therefore, the value of the correction factor, that is, the first correction factor value is 0.
  • the mobile relay If the one-bit information indicates that the current communication performance is less than the communication performance of the known optimal relay position, that is, the signal-to-noise ratio of the communication signal of the current location is smaller than the signal-to-noise ratio of the communication signal of the known optimal relay position, or If the communication error rate of the current location is greater than the communication error rate of the known optimal relay location, the mobile relay first returns to the previous location, and then randomly moves one disturbance step to move to the next relay location. That is, determining and moving to the next relay position according to the random disturbance step and the second correction factor value, the value of the second correction factor being the opposite of the previous random disturbance step.
  • the current communication performance is lower than the communication performance of the known optimal relay position, indicating that the positional movement in the t-th slot causes the performance of the signal to deteriorate.
  • the destination end will not update the known optimal relay position and has Knowing the signal-to-noise ratio of the best relay position, and in order to cancel the position shift in the t-th slot, the mobile relay will return to the relay position where the t-1 time slot is located, that is, in the t-th time slot, The mobile relay returns the relay position at the t-1th slot, while determining the next relay position, because it is known that the random disturbance step added in the t-1th slot will bring performance degradation.
  • the value of the second correction factor is the mobile relay at the t-th
  • the inverse of the random perturbation step size increased by 1 slot that is, if the random perturbation step size of the mobile relay increases by ⁇ 0 in the t-1th slot, the mobile relay will increase the negative ⁇ in the tth time slot.
  • the mobile relay increases the random disturbance step size to negative ⁇ 0 , then in the first For the t-slot, the mobile relay will increase the modified step size of ⁇ 0 , which is the increase or decrease of the step size for the mobile relay to move due to the deterioration of the communication performance.
  • the mobile relay records the known best relay position, which is represented by ⁇ (t) and t represents the number of time slots. Take Representing the relay position of the next time slot, ⁇ (t) represents the random disturbance step size, and ⁇ (t) represents the correction factor, then:
  • the random disturbance step is used to indicate the magnitude of the movement angle on the circumference when the mobile relay moves once.
  • the random perturbation step its positive and negative are random, positive and negative represent the direction, and the random perturbation step can determine whether the mobile relay moves counterclockwise or clockwise.
  • the reduction ratio of the random disturbance step is preset in the mobile relay, and the random disturbance step used to start the mobile relay is the initial given step size, and in the process of searching for the optimal relay position, the preset is gradually followed.
  • the scale reduces the absolute value of the disturbance step until the end of the search is determined by determining the optimal relay position.
  • the setting of the random disturbance step enables the mobile relay to move to different relay positions, and the destination end calculates the signal-to-noise ratio or the bit error rate of the test signal transmitted by the mobile relay at different relay positions. And compare the calculated result with the recorded signal-to-noise ratio or bit error rate of the known best relay position, The comparison result is fed back to the mobile relay, and the mobile relay determines the next relay location and continues to search for the optimal relay location so that the mobile relay can get closer and closer to the optimal relay location and determine.
  • the destination end updates the relay position of the mobile relay in the t-th slot to the known best.
  • the location is relayed and the communication performance at the t-th slot is updated to the communication performance of the known best relay location.
  • the communication performance of the known optimal relay location held in the destination end is the best communication performance tested, and in the process of constantly updating the communication performance of the known optimal relay location, the known most The good relay location will also be getting closer and closer to the optimal relay location.
  • the destination end updates the known best received signal communication performance in the memory according to the calculated comparison result between the current communication performance and the saved communication performance of the known optimal relay position, that is, if the comparison result is current
  • the communication performance of the location is improved compared to the communication performance of the known optimal relay location, and the mobile relay records the relay location at the t-th slot as the known optimal relay location and updates the in-memory
  • the best received signal communication performance is known.
  • the mobile relay when the signal to noise ratio of the signal is greater than the signal to noise ratio of the known optimal relay position, the mobile relay will remain in the relay position of the tth time slot, and move to the next one. In the case of the position, the mobile relay moves with the relay position in the t-th slot as the starting point.
  • the mobile relay determines the next relay position as follows:
  • ⁇ (t+1) represents the position of the mobile relay in the t+1th slot
  • ⁇ (t) represents the known optimal relay position
  • ⁇ (t) represents the random disturbance step
  • a continuous negative feedback counter is also provided in the embodiment of the invention, and the continuous negative feedback counter is used to determine the optimal relay position.
  • the continuous negative feedback counter is used to describe the continuous number of communication performances of the current location in the process of searching for the optimal relay location, the communication performance of the current location is smaller than the known optimal relay location, that is, each mobile relay is receiving
  • the comparison result is that the signal-to-noise ratio of the communication signal of the current location is smaller than the signal-to-noise ratio of the communication signal of the known optimal relay position, or the error rate of the communication signal of the current location In the case of a bit error rate of a communication signal larger than the known optimum relay position, the value of the continuous negative feedback counter is increased.
  • the comparison result is that the signal-to-noise ratio of the test signal of the current location is greater than the signal-to-noise ratio of the signal of the known optimal relay position, or the error rate of the test signal of the current location is smaller than the known optimal relay position.
  • the signal error rate, the value of the correction factor is cleared, and the value of the continuous negative feedback counter is cleared;
  • the comparison result is that the signal-to-noise ratio of the test signal of the current position is smaller than the signal-to-noise ratio of the signal of the known optimal relay position, or the error rate of the test signal of the current position is greater than the signal error of the known optimal relay position.
  • the code rate is then returned to the relay position where the t-1th slot is located, the mobile relay adds 1 to the continuous negative feedback counter, and sets the value of the correction factor to the last random perturbation step. The opposite is true.
  • the mobile relay Determining whether the value of the continuous negative feedback counter reaches a preset continuous negative feedback threshold, where the meaning reached is greater than or equal to. If the value of the continuous negative feedback counter reaches the continuous negative feedback threshold, the current random disturbance step is not suitable. For further precise search, the random disturbance step size should be appropriately reduced, then the mobile relay will reduce the random disturbance step size according to the preset ratio, and at the same time clear the continuous negative feedback counter, and return to the execution step C to move to the next one. Following the step of position, it can be understood that the mobile relay optimal relay position search based on the continuous negative feedback step size will be performed thereafter according to the newly determined random disturbance step. If the value of the continuous negative feedback counter does not reach the continuous negative feedback threshold, it indicates that the current random disturbance step size can be used, and then returns to the step of moving to the next relay position in step C.
  • the negative feedback counter is set because during the process of searching for the optimal relay position, when the mobile relay is around the optimal relay position, a random disturbance step occurs whether clockwise or counterclockwise. Longer will make the transmission performance worse, that is, the signal-to-noise ratio of the signal is smaller than the signal-to-noise ratio of the known optimal relay position. Therefore, when the value of the negative feedback counter reaches the preset threshold, the mobile relay will reduce its The step size of the movement, by changing the step size, reduces the error between the relay position where the mobile relay is located and the optimal relay position.
  • the relay position where the mobile relay is located can be made. Get closer and closer to the best relay location and complete the search for the best relay location.
  • the test signal is received by the mobile relay, and sent to the destination end for calculation and comparison of the communication performance of the current location and the known optimal relay location, according to the comparison result of the destination end feedback and the random disturbance step.
  • the mobile relay can gradually approach the most in the process of continuously moving to the next relay position based on the step size.
  • the relay position is determined, and the optimal relay position is determined.
  • This method can improve the performance of the relay communication, and does not need to obtain the location information of the source end and the destination end, does not need multiple antennas, and only needs the destination end to feed back one bit of information to the mobile. Following the search control, it is still possible to determine the optimal relay position within the predetermined trajectory range and expand the scope of application.
  • the initial step size is:
  • FIG. 3 is a simulation diagram of a correspondence relationship between a moving angle of a mobile relay and a signal to noise ratio of a signal according to an embodiment of the present invention.
  • the horizontal axis represents the moving angle of the mobile relay
  • the vertical axis represents the end-to-end signal-to-noise ratio of the relay position corresponding to the moving angle of the mobile relay
  • the end-to-end refers to the source to the destination. end.
  • FIG. 4 is a simulation diagram of the correspondence between the number of slots and the signal to noise ratio according to an embodiment of the present invention.
  • the schematic diagram refers to different letters corresponding to different time slots in the process according to the technical solution described in the present invention. Noise ratio.
  • 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 signal-to-noise ratio of the signal
  • the strength of the communication performance can also be described by the error rate, and the technical idea similar to that in the embodiment of the present invention can be used to determine the optimal relay position by using the error rate.
  • FIG. 5 is a simulation diagram of a correspondence relationship between a moving angle of a mobile relay and a signal to noise ratio of a signal when determining an optimal relay position by using a bit error rate according to an embodiment of the present invention.
  • the horizontal axis represents the angle of the mobile relay in the column coordinates
  • the ordinate represents the end-to-end error rate of the relay position corresponding to the angle, that is, the bit error rate from the source end to the destination end.
  • FIG. 6 is a simulation diagram of the correspondence between the number of slots and the error rate when the optimal relay position is determined by the error rate according to the embodiment of the present invention.
  • the horizontal axis represents the mobile relay.
  • the number of time slots is searched for the best relay position, and the vertical axis represents the end-to-end bit error rate.
  • the BER convergence ends when the 70th time slot is searched, that is, the pole in Figure 6. Small value points.
  • the effect of searching for the optimal relay position according to the idea of the technical solution of the present invention is the same using the bit error rate or the signal to noise ratio, and therefore, other types of communication performances other than the bit error rate or the signal to noise ratio are utilized.
  • the technical solution for determining the optimal relay position according to the idea in the technical solution of the present invention also belongs to the protection scope of the embodiment of the present invention.
  • FIG. 7 is a schematic diagram of a structure of a mobile relay optimal relay location search system based on a continuous negative feedback variable step size according to an embodiment of the present invention, including:
  • the mobile relay 701 receives the test signal sent from the source end 702 at any position of the fixed track, and amplifies and forwards it to the destination end 703.
  • the destination end 703 receives the signal sent by the mobile relay 701 and calculates the current communication performance.
  • the communication performance includes: a signal-to-noise ratio and a bit error rate, and compares the calculated result with the saved communication performance of the known optimal relay position, and generates one-bit information fed back to the mobile relay, the one bit
  • the information represents a comparison result of the communication performance of the current communication performance and the saved known optimal relay position, that is, the one-bit information includes information on whether the received signal communication performance is improved, and the known optimal relay position is tested. The best location for communication performance.
  • the mobile relay 701 records the current location information and moves to the next according to the one-bit information, the random disturbance step size, and the correction factor. Position and execute again at any position on the fixed track, receive the test signal sent from the source 702, and amplify the step of forwarding to the destination 703, repeating the loop until the optimal relay position is finally determined, the best middle
  • the following position is: the location with the best communication performance within the preset search duration, or the location where the mobile relay moves the complete communication track with the best communication performance, or the communication performance meets the system setting requirements. .
  • the mobile relay 701 records the current location as the known optimal relay position, and randomly moves a disturbance step to Move to the next relay position, that is, determine and move to the next relay position according to the first correction factor value and the random disturbance step.
  • the first correction factor has a value of zero.
  • the value of the correction factor is cleared, and therefore, the value of the correction factor, that is, the first correction factor value is 0.
  • the mobile relay 701 If the one-bit information indicates that the current communication performance is less than the communication performance of the known optimal relay position, the mobile relay 701 first returns to the previous position, and then randomly moves one disturbance step to move to the next relay position. That is, determining and moving to the next relay position according to the random disturbance step and the second correction factor value, the value of the second correction factor being the opposite of the previous random disturbance step.
  • ⁇ (t) represents the current position
  • ⁇ (t) represents the random disturbance step size
  • ⁇ (t) represents the correction factor
  • the continuous negative feedback counter is used to describe the number of consecutive times that the mobile relay 701 is worse than the saved known best relay position during the search for the optimal relay position.
  • the mobile relay 701 When it is judged that the communication performance of the current communication performance is worse than the saved known optimal relay position, the mobile relay 701 returns to the position of the previous time slot, and at the same time, the value of the continuous negative feedback counter is incremented by 1, the correction factor setting Is the opposite of the last random disturbance step, and judges that the value of the continuous negative feedback counter is Whether the preset continuous negative feedback threshold is reached.
  • the random disturbance step is scaled down, and the continuous negative feedback counter is cleared and returned to the next relay position. If it is determined that the value of the continuous negative feedback counter does not reach the preset continuous negative feedback threshold, then the step of moving to the next relay position is returned.
  • the destination 703 updates the known best received signal communication performance in the memory according to the calculated comparison result between the current communication performance and the saved communication performance of the known optimal relay position.
  • the test signal is received by the mobile relay, and sent to the destination end for calculation and comparison of the communication performance of the current location and the known optimal relay location, according to the comparison result of the destination end feedback and the random disturbance step.
  • the mobile relay can gradually approach the most in the process of continuously moving to the next relay position based on the step size.
  • the relay position is determined, and the optimal relay position is determined.
  • This method can improve the performance of the relay communication, and does not need to obtain the location information of the source end and the destination end, does not need multiple antennas, and only needs the destination end to feed back one bit of information to the mobile. Following the search control, it is still possible to determine the optimal relay position within the predetermined trajectory range and expand the scope of application.

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Abstract

本发明提供了基于连续负反馈变步长的最佳中继位置搜寻方法及系统，该方法包括：移动中继将接收到的源端发送的信号放大转发给目的端，使得目的端将该测试信号的通信性能强度与保存的已知最佳中继位置的通信性能强度进行对比，并将该对比结果用一比特信息反馈给移动中继，移动中继根据这一比特信息，计算随机扰动步长及修正因子，由此确定下一个中继位置，并移动到该下一个中继位置，再次执行接收源端发送的用于测试通信性能的测试信号的步骤，直至确定最佳中继位置。该方法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，且只需要目的端反馈一比特信息给移动中继进行搜寻控制，依然可在预定轨迹范围内确定最佳中继位置点，扩大了适用范围。

Description

基于连续负反馈变步长的最佳中继位置搜寻方法及系统 技术领域
本发明涉及通信技术领域，尤其涉及基于连续负反馈变步长的最佳中继位置搜寻方法及系统。
背景技术
通信中继可以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。
陆地无线电通信容易被障碍物遮挡和屏蔽，飞机、卫星及无人机(UVAs)可以充当通信中继，因为机载中继可以在崎岖的山区或者市区有效地为需要互相通信的双方建立起连接。这些年来，使用无人机作为通信中继的问题已经吸引不少学者的关注和研究，同时其应用也十分广泛。
现有的应用于无人机中继位置搜寻的算法主要有：利用GPS测量地面通信单元的位置信息并被无人机利用搜寻最佳中继位置；基于扰动的极值搜索控制算法，基于机载多天线的算法等等。现有的无人机中继位置搜寻算法，在各自的基础上都可以使无人机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、地面通信单元需要利用自身的GPS功能测量自己的位置信息并把该信息发送给无人机，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设备已损坏的地面通信单元，现有的一些算法是无法使用的，因此，现有的算法的使用受限；
3、机载多天线相比于单天线增加了无人机的复杂性，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。
发明内容
本发明实施例提供了一种基于连续负反馈变步长的最佳中继位置搜寻方法 及系统，用于解决现有技术中须获知源端和目的端的位置信息才能够确定中继位置带来的使用受限和误差大等问题。
本发明实施例提供的基于连续负反馈变步长的最佳中继位置搜寻方法，包括：
步骤A，移动中继在固定轨道的任意位置上，接收来自源端发送的测试信号，并放大转发至目的端；
步骤B，所述目的端接收所述移动中继发来的信号并计算本次通信性能，所述通信性能包括：信噪比和误码率，并根据计算结果与已保存的已知最佳中继位置的通信性能进行比较，以及生成一比特信息反馈至所述移动中继，所述一比特信息表示当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，所述已知最佳中继位置为已测试的通信性能最好的位置；
步骤C，所述移动中继记录当前位置信息，并根据所述一比特信息及随机扰动步长和修正因子移动到下一个位置，并返回步骤A，直至最终确定最佳中继位置，所述最佳中继位置为：在预设的搜寻时长内通信性能最好的位置，或者，所述移动中继移动完整个所述固定轨道时通信性能最好的位置，或者，所述通信性能满足系统设定要求的位置。
本发明实施例提供的基于连续负反馈变步长的最佳中继位置搜寻系统，包括：
所述搜寻系统包括移动中继、源端和目的端；
其中，所述移动中继在固定轨道的任意位置上，接收来自所述源端发送的测试信号，并放大转发至所述目的端；
所述目的端接收所述移动中继发来的信号并计算本次通信性能，所述通信性能包括：信噪比和误码率，并根据计算结果与已保存的已知最佳中继位置的通信性能进行比较，以及生成一比特信息反馈至所述移动中继，所述一比特信息表示当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，所述已知最佳中继位置为已测试的通信性能最好的位置；
所述移动中继记录当前位置信息，并根据所述一比特信息、随机扰动步长和修正因子移动到下一个位置，并再次执行接收来自所述源端发送的测试信号，并放大转发至所述目的端的步骤，直至最终确定最佳中继位置，所述最佳中继位置为：在预设的搜寻时长内通信性能最好的位置，或者，所述移动中继移动完整个所述固定轨道时通信性能最好的位置，或者，所述通信性能满足系统设定要求的位置。
从以上技术方案可以看出，本发明实施例具有以下优点：通过移动中继接收测试信号，并发送给目的端进行当前位置和已知最佳中继位置的通信性能的计算和比较，根据目的端反馈的比较结果以及随机扰动步长和修正因子，移动到下一个中继位置，并返回执行移动中继接收信号的步骤，通过循环上述的过程使得移动中继能够在基于步长不断移动到下一个中继位置的过程中，逐渐接近最佳中继位置，并确定最佳中继位置，该方法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，且只需要目的端反馈一比特信息给移动中继进行搜寻控制，依然可在预定轨迹范围内确定最佳中继位置点，扩大了适用范围。
附图说明
图1为本发明实施例中最佳中继位置确定系统的通信模型的示意图；
图2为本发明实施例中基于连续负反馈变步长的移动中继最佳中继位置搜寻方法的流程的一个示意图；
图3为本发明实施例中移动中继的移动角度与信号的信噪比的对应关系的仿真图；
图4为本发明实施例中时隙数与信噪比的对应关系的仿真图；
图5为本发明实施例中以误码率确定最佳中继位置时，移动角度与信噪比之间的对应关系的仿真图；
图6为本发明实施例中以误码率确定最佳中继位置时，时隙数与误码率之间的对应关系的仿真图。
图7为本发明实施例中基于连续负反馈变步长的移动中继最佳中继位置搜寻系统的结构的示意图。
具体实施方式
为更进一步阐述本发明为实现预定发明目的所采取的技术手段及功效，以下结合附图及较佳实施例，对依据本发明的具体实施方式、结构、特征及其功效，详细说明如后。
请参阅图1，为本发明实施例中最佳中继位置确定系统的通信模型的实施例，包括：源端，移动中继及目的端。
在图1中，Ri表示移动中继，S表示源端，D表示目的端。
其中，源端和目的端可以是两个不同的地面通信单元，该地面通信单元可以是各种类型的无线通信收发设备，例如可以是手机、终端、基站等等，或者还可以是其他移动中继。
在本发明实施例中，是以源端作为信号发射端，目的端作为信号接收端为例进行描述的，在实际应用中，源端和目的端均可以作为信号发射端和信号接收端。
如图1所示，在三维坐标系中移动中继采用的柱坐标系的参数，且其坐标为(r，θ，z)，其中r为移动中继在xoy平面上的运动半径，即Ri′。O表示柱坐标的原点。
移动中继运行是有固定轨道的，它沿着预定轨道以r为半径进行运动，因此，在本发明实施例中，是在以r为半径构成的圆上寻找移动中继的最佳中继位置。其中，θ为从正Z轴来看自x轴逆时针方向转到oR′i所转过的角，z则表示移动中继的高度。
在本发明实施例中，移动中继在第t时隙的坐标为(r，θ(t)，z)，在第t+1时隙的坐标为(r，θ(t+1)，z)。
其中，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 PCTCN2015096737-appb-000001
在第t时隙，移动中继(r，θ(t)，z)离源端(xs，ys，zs)及目的端(xd，yd，zd)的通信距离分别是：
Figure PCTCN2015096737-appb-000002
其中，d1表示移动中继与源端之间的通信距离，d2表示移动中继与目的端之间的通信距离。
需要说明的是，三维坐标系中的原点是固定的，因此，可以确定移动中继的运动轨迹的半径和高度。下面将详细描述本发明实施例中基于连续负反馈变步长的最佳中继位置搜寻方法的实施例，请参阅图2，包括：
步骤A、移动中继在固定轨道的任意位置上，接收来自源端发送的测试信号，并放大转发至目的端。
在第t时隙，源端将向移动中继发送用于测试通信性能的测试信号，且移动中继在接收到该测试信号之后将对该测试信号进行放大，并将放大后得到的信号转发给目的端，需要说明的是，由于信号在传输过程中存在衰减及噪声，源端发送的测试信号，与移动中继接收到的测试信号不是完全一样的，且移动中继在接收到测试信号之后，还将对接收到的测试信号进行放大处理，因此，移动中继接收到的信号与移动中继发送的信号也不是一样的。
需要说明的是，在移动中继开始搜寻之前，移动中继初始化其自身的位置信息。源端向移动中继发送一个测试信号，移动中继将把接收到的测试信号转发给目的端，其中该转发的步骤实际包含了对信号的放大及转发，使得该目的端计算初始通信性能，并保存为该目的端的初始记录。
其中，测试信号是用于测试通信性能的信号，能够帮助移动中继搜寻到最佳中继位置，可以在该信号中携带用来测试通信性能的数据，且在移动中继搜寻到最佳中继位置之前，源端发送的都是测试信号，只有在移动中继找到最佳 中继位置之后，源端才将发送真正有用的数据。
步骤B、该目的端接收该移动中继发来的信号并计算本次通信性能，该通信性能包括信噪比、误码率，并根据计算结果与已保存的已知最佳中继位置的通信性能进行比较，以及生成一比特信息反馈至该移动中继。
目的端接收到该信号之后计算本次通信性能，包括计算本次通信的信噪比或误码率，将计算出来的本次通信性能与已保存的已知最佳中继位置的通信性能进行比较，该已知最佳中继位置为已测试的通信性能最好的位置，该已知最佳中继位置的信噪比为在第t时隙之前目的端已计算得到的所有信号中信噪比的最大值，或者，该已知最佳中继位置的误码率为在第t时隙之前目的端已计算得到的所有信号中误码率的最小值。
进一步地，根据比较结果生成一比特信息反馈至该移动中继，该一比特信息表示当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，也即该一比特信息包括源端接收来自移动中继的信号对应的通信性能是否提高的信息，具体地，该一比特信息可以是该目的端接收到的该测试信号的信噪比与该目的端上已保存的最佳已知位置的信噪比的对比结果，也可以是为该目的端接收到的该测试信号的误码率与该目的端上已保存的最佳已知位置的误码率的对比结果。该比较结果可以是当前位置的通信性能优于该已知最佳中继位置的通信性能，也可以是劣于该已知最佳中继位置的通信性能。
该比较结果通过一比特信息的形式发送，例如，可以预先设置比特信息1表示当前通信性能比已知最佳中继位置的通信性能有提高，比特信息0表示信号的当前通信性能比已知最佳中继位置的通信性能有下降。在实际应用中，还可以通过其他的形式设置比较结果，此处不作限定。
为了更好的理解本发明实施例中的技术方案，下面将以计算通信性能为信噪比为例，详细介绍本发明实施例中源端、移动中继及目的端在通信过程中涉及到的参数，如下：
1)第一跳通信过程：源端至移动中继；
计算移动中继接收到源端发送的信号相关的以下参数，包括：
移动中继接收到的信号：
Figure PCTCN2015096737-appb-000003
平均功率：E[|n1|2]＝N01
空间自由路径损耗：
Figure PCTCN2015096737-appb-000004
其中，x表示源端发射的测试信号，PS表示源端的发射功率，n1表示第一跳通信的加性高斯白噪声，yR表示移动中继接收到的测试信号，N01表示高斯白噪声n1的功率，E表示求数学期望值，LS，R表示从源端至移动中继的自由空间路径损耗，λ表示源端发送测试信号使用的波的波长，d1表示源端与移动中继之间的距离。
其中，d1可以通过移动中继和源端在三维坐标系中的坐标计算得到。
2)第二跳通信过程：移动中继至目的端；
计算与目的端接收到的移动中继转发的测试信号有关的的以下参数，包括：
目的端接收到来自移动中继发送的测试信号：
Figure PCTCN2015096737-appb-000005
平均功率：E[|n2|2]＝N02
自由空间路径损耗：
Figure PCTCN2015096737-appb-000006
增益：
Figure PCTCN2015096737-appb-000007
其中，yD表示目的端接收到的移动中继发送的测试信号，x表示源端发送的测试信号，PS表示源端的发射功率，n1表示第一跳通信的加性高斯白噪声，E表示求数学期望值，LS，R表示源端至移动中继的自由空间路径损耗，λ表示移动中 继放大转发测试信号使用的波长，d2表示移动中继与目的端之间的距离，LR，D表示移动中继至目的端的自由空间路径损耗，G表示移动中继给接收到的测试信号的增益，即中继增益，PR表示移动中继的发射功率，n2表示移动中继发送接收到的测试信号的过程中的第二跳通信的加性高斯白噪声，N02表示高斯白噪声n2的功率。
其中，用λ表示移动中继放大转发测试信号使用的波长和源端发送测试信号使用的波长，是因为移动中继放大转发测试信号使用的波长和源端发送测试信号使用的波长可以是相同的波长。
3)目的端计算接收到的测试信号的信噪比，如下：
Figure PCTCN2015096737-appb-000008
其中，SNR表示目的端接收到的测试信号的信噪比，PS表示源端的发射功率，G表示移动中继给接收到的信号的增益，LS，R表示从源端至移动中继，即第一跳通信的自由空间路径损耗，LR，D表示移动中继至目的端，即第二跳通信的自由空间路径损耗，N01表示第一跳通信的高斯白噪声n1的功率，N02表示第二跳高斯白噪声n2的功率。
需要说明的是，虽然移动中继接收到测试信号之后只需要对其进行转发，但是该测试信号在传输的过程中还是会有衰落及噪声的干扰，为了确保目的端能够接收到较好的信号，移动中继将对接收到的测试信号进行放大，即增加增益G。
在本发明实施例中，目的端可按照上述3)的方式计算接收到的测试信号的信噪比。
在未进行最佳中继位置的搜寻之前，目的端记录的已知最佳中继位置的初始位置是随机给定的，且信噪比的初始值为初始位置的信噪比。
步骤C、该移动中继记录当前位置信息，并根据该一比特信息、随机扰动步 长和修正因子移动到下一个位置，并返回步骤A，直至最终确定最佳中继位置。
移动中继在接收到目的端发送的包含比较结果的一比特信息之后，根据该比较结果、随机扰动步长和修正因子确定下一个中继位置，且移动到下一个中继位置。在第t+1时隙时，返回执行步骤A。移动中继可通过本发明上述描述的循环过程不断搜索最佳中继位置，且在确定最佳中继位置之后，将停止上述循环搜索过程。
随机扰动步长表示移动中继随机扰动的一个步长。
修正因子是用于修正随机扰动步长的参数，使得移动中继移动到下一个中继位置更接近最佳中继位置。
具体地，若该一比特信息表示当前通信性能大于该已知最佳中继位置的通信性能，即当前位置的通信信号的信噪比大于该已知最佳中继位置的通信信号的信噪比，或当前位置的通信误码率小于该已知最佳中继位置的通信误码率，则将当前位置记录为已知最佳中继位置，并随机移动一个扰动步长以移动到下一个中继位置，即根据第一修正因子值和该随机扰动步长确定及移动到下一个中继位置。该第一修正因子值为0。当前通信性能优于该已知最佳中继位置的通信性能时，修正因子的值是作清零处理的，因此，此时修正因子的值，即第一修正因子值为0。
若该一比特信息表示当前通信性能小于该已知最佳中继位置的通信性能，即当前位置的通信信号的信噪比小于该已知最佳中继位置的通信信号的信噪比，或当前位置的通信误码率大于该已知最佳中继位置的通信误码率，则该移动中继先返回到上一次的位置，再随机移动一个扰动步长以移动到下一个中继位置，即，根据该随机扰动步长和第二修正因子值确定及移动到下一个中继位置，该第二修正因子的值为上一次随机扰动步长的相反数。当前通信性能小于已知最佳中继位置的通信性能，表明在第t时隙的位置移动导致信号的性能变差，此种情况下，目的端将不更新已知最佳中继位置及已知最佳中继位置的信噪比，且为了抵消在第t时隙的位置移动，移动中继将返回在t-1时隙所处的中 继位置，即，在第t时隙，将移动中继返回在第t-1时隙所处的中继位置，同时在确定下一个中继位置时，因为知道在第t-1时隙增加的随机扰动步长将带来性能变差的后果，则向第t-1时隙移动的相反方向移动则可避免出现相同的情况，且可能带来通信性能变好的效果，因此，第二修正因子的值为移动中继在第t-1时隙增加的随机扰动步长的相反数，即若在第t-1时隙，移动中继增加的随机扰动步长为δ0，则在第t时隙，移动中继将增加负δ0的修正步长，若在t-1时隙，移动中继增加的随机扰动步长为负δ0，则在第t时隙，移动中继将增加δ0的修正步长，该修正步长是指由于通信性能变差，对移动中继要移动的步长所作的增减量。
移动中继记录已知最佳中继位置，该已知最佳中继位置用θ(t)表示，t表示时隙数。以
Figure PCTCN2015096737-appb-000009
表示下一时隙的中继位置，δ(t)表示所述随机扰动步长，ξ(t)表示该修正因子，则：
Figure PCTCN2015096737-appb-000010
其中，该随机扰动步长用于表示移动中继一次移动时，在圆周上的移动角度的大小。随机扰动步长为δ(t)＝±δ0，其中δ(t)表示该随机扰动步长，且当δ(t)＝δ0时表示移动中继将逆时针方向上移动一个步长δ0，当δ(t)＝-δ0时，表示移动中继将顺时针方向上移动一个步长δ0，反之亦然，即也可以设置为当δ(t)＝-δ0时表示移动中继将逆时针方向上移动一个步长δ0，当δ(t)＝δ0时，表示移动中继将顺时针方向上移动一个步长δ0。在使用该随机扰动步长时，其正负是随机的，正负代表方向，通过随机扰动步长可确定移动中继是逆时针方向上移动还是顺时针方向上移动。
移动中继中预先设置了随机扰动步长的缩小比例，开始移动中继使用的随机扰动步长是初始给定步长，且在搜索最佳中继位置的过程中，逐渐按照该预置的比例减小扰动步长的绝对值，直到确定最佳中继位置结束搜索。
通过随机扰动步长的设置，使得移动中继能够移动到不同的中继位置，并由目的端计算该移动中继在不同的中继位置时传输的测试信号的信噪比或误码率，并将计算结果与记录的已知最佳中继位置的信噪比或误码率进行比较，将 比较结果反馈给移动中继，由移动中继确定下一个中继位置并继续搜索最佳中继位置，使得移动中继能够越来越靠近最佳中继位置并确定。
本实施例中，若比较结果为本次通信性能比已知最佳中继位置的通信性能有所提高，则目的端将移动中继在第t时隙的中继位置更新为已知最佳中继位置，且将在第t时隙的通信性能更新为已知最佳中继位置的通信性能。其中，该目的端中保存的已知最佳中继位置的通信性能为已测试的最好的通信性能，且在不断更新已知最佳中继位置的通信性能的过程中，该已知最佳中继位置也将越来越接近最佳中继位置。
进一步地，目的端根据计算得到的该当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，更新内存中的已知最佳接收信号通信性能，即若比较结果为当前位置的通信性能比已知最佳中继位置的通信性能有所提高，则移动中继将在第t时隙所处的中继位置记录为已知最佳中继位置，并更新内存中的已知最佳接收信号通信性能。
在本发明实施例中，当信号的信噪比大于已知最佳中继位置的信噪比时，移动中继将在第t时隙的中继位置保留下来，且在移动到下一个中继位置时，移动中继是以在第t时隙的中继位置为起点进行移动的。
即在信号的信噪比大于已知最佳中继位置的信噪比的情况下，移动中继按照如下方式确定下一个中继位置：
θ(t+1)＝θ(t)+δ(t)
其中，θ(t+1)表示在第t+1时隙移动中继的位置，θ(t)表示已知最佳中继位置，δ(t)表示随机扰动步长。
本发明实施例中还设置了连续负反馈计数器，使用该连续负反馈计数器来确定最佳中继位置。该连续负反馈计数器用于描述移动中继在搜寻最佳中继位置的过程中，当前位置的通信性能小于已知最佳中继位置的通信性能的连续次数，即每次移动中继在接收到比较结果为当前位置的通信信号的信噪比小于已知最佳中继位置的通信信号的信噪比，或者，为当前位置的通信信号的误码率 大于已知最佳中继位置的通信信号的误码率的情况下，都将连续负反馈计数器的值增加。
具体地，若比较结果为当前位置的测试信号的信噪比大于已知最佳中继位置的信号的信噪比，或，当前位置的测试信号的误码率小于已知最佳中继位置的信号误码率，则将该修正因子的值清零，以及将连续负反馈计数器的值清零；
若比较结果为当前位置的测试信号的信噪比小于已知最佳中继位置的信号的信噪比，或，当前位置的测试信号的误码率大于已知最佳中继位置的信号误码率，则在将移动中继返回在第t-1时隙所处的中继位置，移动中继将连续负反馈计数器加1，并将该修正因子的值设置为上一次的随机扰动步长的相反数。
判断连续负反馈计数器的值是否达到预先设置的连续负反馈阈值，此处达到的含义为大于或等于，若连续负反馈计数器的值达到该连续负反馈阈值，说明当前的随机扰动步长不适合进一步的精确搜寻，应该适当缩小该随机扰动步长，则移动中继将按照预置的比例缩小该随机扰动步长，同时将连续负反馈计数器清零，并返回执行步骤C中移动到下一个中继位置的步骤，可以理解的，此后将将按照新确定的随机扰动步长进行基于连续负反馈变步长的移动中继最佳中继位置搜寻。若连续负反馈计数器的值未达到该连续负反馈阈值，说明还可继续使用当前的随机扰动步长，则返回执行步骤C中移动到下一个中继位置的步骤。
在本发明实施例中，设置负反馈计数器是因为在搜寻最佳中继位置的过程中，移动中继在处于最佳中继位置周围时，会出现无论顺时针还是逆时针移动一个随机扰动步长都将使得传输性能变差，即信号的信噪比小于已知最佳中继位置的信噪比，因此，当负反馈计数器的值在达到预先设置的阈值之后，移动中继将减少其移动的步长，通过改变步长，来缩小移动中继所处的中继位置与最佳中继位置之间的误差。
在本发明实施例中，在本发明实施例中，通过设置负反馈计数器及按照预先设置的步长缩小比例减小随机扰动步长，能够使得移动中继所处的中继位置 越来越接近最佳中继位置，并完成最佳中继位置的搜索。
在本发明实施例中，通过移动中继接收测试信号，并发送给目的端进行当前位置和已知最佳中继位置的通信性能的计算和比较，根据目的端反馈的比较结果以及随机扰动步长，移动到下一个中继位置，并返回执行移动中继接收信号的步骤，通过循环上述的过程使得移动中继能够在基于步长不断移动到下一个中继位置的过程中，逐渐接近最佳中继位置，并确定最佳中继位置，该方法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，且只需要目的端反馈一比特信息给移动中继进行搜寻控制，依然可在预定轨迹范围内确定最佳中继位置点，扩大了适用范围。
为了更好的理解本发明实施例中的技术方法，下面介绍利用本发明实施例中的技术方案确定最佳中继位置，如下：
在以信噪比为基准表示通信性能强弱的情况下，
初始步长为：
Figure PCTCN2015096737-appb-000011
源端的坐标位置为：(xs，ys，zs)＝(0，-700，1)；
目的端的坐标位置为：(xd，yd，zd)＝(30，600，1)；
移动中继的坐标位置为：(r，θ(n)，z)＝(500，θ(n)，30)。
请参阅图3，为本发明实施例中移动中继的移动角度与信号的信噪比的对应关系的仿真图。在图3中，横轴表示移动中继的移动角度，纵轴表示与移动中继的移动角度对应的该中继位置的端到端的信噪比，该端到端是指从源端至目的端。
请参阅图4，为本发明实施例中时隙数与信噪比的对应关系的仿真图，该示意图是指在按照本发明描述的技术方案的过程中，不同的时隙对应的不同的信噪比。
在图4中，横轴表示移动中继搜寻最佳位置过程中花费的时隙数，纵轴表示信号的信噪比，可以看到在搜寻到第25个时隙时就找到7dB的位置，在第40 个时隙找到最佳中继位置，也就是图4中的极大值点。
在本发明实施例中，还可以以误码率来描述通信性能的强弱，且能够采用和本发明实施例中相似的技术思想来利用误码率确定最佳中继位置。
请参阅图5，为本发明实施例中，利用误码率确定最佳中继位置时，移动中继的移动角度与信号的信噪比之间的对应关系的仿真图。
在图5中横轴表示移动中继的在柱坐标中的角度，纵坐标表示与该角度对应的中继位置的端到端误码率，即，从源端至目的端的误码率。
请参阅图6，为本发明实施例中，以误码率确定最佳中继位置时，时隙数与误码率之间的对应关系的仿真图，在图6中横轴表示移动中继搜寻最佳中继位置花费额时隙数，纵轴表示端到端的误码率，从图6中可以看到，搜寻到第70个时隙时误码率收敛结束，即图6中的极小值点。
基于上述描述，利用误码率或信噪比按照本发明技术方案中的思想搜寻最佳中继位置的效果是一样的，因此，在利用误码率或者信噪比以外的其他类型的通信性能参数按照本发明技术方案中的思想确定最佳中继位置的技术方案也属于本发明实施例的保护范围。
请参阅图7，为本发明实施例中的基于连续负反馈变步长的移动中继最佳中继位置搜寻系统的结构的示意图，包括：
移动中继701、源端702及目的端703；
其中，移动中继701在固定轨道的任意位置上，接收来自源端702发送的测试信号，并放大转发至目的端703，目的端703接收移动中继701发来的信号并计算本次通信性能，该通信性能包括：信噪比和误码率，并根据计算结果与已保存的已知最佳中继位置的通信性能进行比较，以及生成一比特信息反馈至该移动中继，该一比特信息表示当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，即，该一比特信息包括接收信号通信性能是否提高的信息，该已知最佳中继位置为已测试的通信性能最好的位置。移动中继701记录当前位置信息，并根据该一比特信息、随机扰动步长和修正因子移动到下一 个位置，并再次执行在固定轨道的任意位置上，接收来自源端702发送的测试信号，并放大转发至目的端703的步骤，反复循环，直至最终确定最佳中继位置，该最佳中继位置为：在预设的搜寻时长内通信性能最好的位置，或者，该移动中继移动完整个该固定轨道时通信性能最好的位置，或者，该通信性能满足系统设定要求的位置。
具体地，若该一比特信息表示当前通信性能大于该已知最佳中继位置的通信性能，移动中继701将当前位置记录为已知最佳中继位置，并随机移动一个扰动步长以移动到下一个中继位置，即根据第一修正因子值和该随机扰动步长确定及移动到下一个中继位置。该第一修正因子值为0。当前通信性能优于该已知最佳中继位置的通信性能时，修正因子的值是作清零处理的，因此，此时修正因子的值，即第一修正因子值为0。
若该一比特信息表示当前通信性能小于该已知最佳中继位置的通信性能，则移动中继701先返回到上一次的位置，再随机移动一个扰动步长以移动到下一个中继位置，即，根据该随机扰动步长和第二修正因子值确定及移动到下一个中继位置，该第二修正因子的值为上一次随机扰动步长的相反数。
其中，以
Figure PCTCN2015096737-appb-000012
表示所述下一时隙的中继位置，θ(t)表示当前位置，δ(t)表示所述随机扰动步长，ξ(t)表示所述修正因子，则：
Figure PCTCN2015096737-appb-000013
t表示时隙数。
在移动中继701判断当前通信性能比已保存的已知最佳中继位置的通信性能提高时，即，在判断为接收信号性能提高时，将该修正因子的值和连续负反馈计数器的值清零，该连续负反馈计数器用于描述移动中继701在搜寻最佳中继位置的过程中，当前位置的通信性能比已保存的已知最佳中继位置差的连续次数。
在判断当前通信性能比已保存的已知最佳中继位置的通信性能差时，移动中继701返回上一时隙的位置，同时，将该连续负反馈计数器的值加1，该修正因子设置为上一次随机扰动步长的相反数，并判断该连续负反馈计数器的值是 否达到预设的连续负反馈阈值。
若判断该连续负反馈计数器的值达到该预设的连续负反馈阈值，则按比例缩小该随机扰动步长，同时将该连续负反馈计数器清零并返回移动到下一个中继位置的步骤，若判断该连续负反馈计数器的值未达到预设的连续负反馈阈值，则返回移动到下一个中继位置的步骤。
进一步地，目的端703根据计算得到的所述当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，更新内存中的已知最佳接收信号通信性能。
在本发明实施例中，通过移动中继接收测试信号，并发送给目的端进行当前位置和已知最佳中继位置的通信性能的计算和比较，根据目的端反馈的比较结果以及随机扰动步长，移动到下一个中继位置，并返回执行移动中继接收信号的步骤，通过循环上述的过程使得移动中继能够在基于步长不断移动到下一个中继位置的过程中，逐渐接近最佳中继位置，并确定最佳中继位置，该方法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，且只需要目的端反馈一比特信息给移动中继进行搜寻控制，依然可在预定轨迹范围内确定最佳中继位置点，扩大了适用范围。
本领域普通技术人员可以理解实现上述实施例方法中的全部或部分步骤是可以通过程序来指令相关的硬件完成，所述的程序可以存储于一种计算机可读存储介质中，上述提到的存储介质可以是只读存储器，磁盘或光盘等。
以上对本发明所提供的基于连续负反馈变步长的最佳中继位置搜寻方法及系统进行了详细介绍，对于本领域的一般技术人员，依据本发明实施例的思想，在具体实施方式及应用范围上均会有改变之处，综上所述，本说明书内容不应理解为对本发明的限制。

Claims (10)

  1. 一种基于连续负反馈变步长的最佳中继位置搜寻方法，其特征在于，所述搜寻方法步骤包括：
    步骤A，移动中继在固定轨道的任意位置上，接收来自源端发送的测试信号，并放大转发至目的端；
    步骤B，所述目的端接收所述移动中继发来的信号并计算本次通信性能，所述通信性能包括：信噪比和误码率，并根据计算结果与已保存的已知最佳中继位置的通信性能进行比较，以及生成一比特信息反馈至所述移动中继，所述一比特信息表示当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，所述已知最佳中继位置为已测试的通信性能最好的位置；
    步骤C，所述移动中继记录当前位置信息，并根据所述一比特信息、随机扰动步长和修正因子移动到下一个位置，并返回步骤A，直至最终确定最佳中继位置，所述最佳中继位置为：在预设的搜寻时长内通信性能最好的位置，或者，所述移动中继移动完整个所述固定轨道时通信性能最好的位置，或者，所述通信性能满足系统设定要求的位置。
  2. 如权利要求1所述的搜寻方法，其特征在于，所述方法还包括：
    以yR表示所述移动中继接收到的所述测试信号，则：
    Figure PCTCN2015096737-appb-100001
    其中x表示所述源端发射的所述测试信号，PS表示所述源端的发射功率，LS，R表示所述源端到所述移动中继的第一跳通信的自由空间路径损耗，n1表示表示所述第一跳通信的加性高斯白噪声；
    进行最佳中继位置搜寻前，所述移动中继初始化其位置信息，并接收来自所述源端发射的所述测试信号并放大转发至目的端；
    所述目的端计算初始通信性能，并保存为初始记录。
  3. 如权利要求1所述的搜寻方法，其特征在于，所述方法还包括：
    以yD表示所述目的端接收到的所述移动中继发送的信号，则：
    yD＝yRGLR，D+n2，其中，其中yR表示所述移动中继接收到的所述测试信号，G表示中继增益，LR，D表示所述移动中继到所述目的端的第二跳通信的自由空间 路径损耗，n2表示所述第二跳通信的加性高斯白噪声。
  4. 如权利要求1所述的搜寻方法，其特征在于，所述步骤C中根据所述一比特信息、随机扰动步长和修正因子移动到下一个位置，包括：
    若所述一比特信息表示当前通信性能大于所述已知最佳中继位置的通信性能，则将当前位置记录为已知最佳中继位置，则根据所述随机扰动步长和第一修正因子值确定及移动到下一个中继位置，所述第一修正因子值为0；
    若所述一比特信息表示当前通信性能小于所述已知最佳中继位置的通信性能，则所述移动中继先返回到上一次的位置，再根据所述随机扰动步长和第二修正因子值确定及移动到下一个中继位置，所述第二修正因子值为上一次随机扰动步长的相反数；
    其中，以t表示时隙数，
    Figure PCTCN2015096737-appb-100002
    表示所述下一时隙的中继位置，θ(t)表示已知最佳中继位置，δ(t)表示所述随机扰动步长，ξ(t)表示所述修正因子，则：
    Figure PCTCN2015096737-appb-100003
  5. 如权利要求4所述的搜寻方法，其特征在于，所述方法还包括：
    在当前通信性能比已保存的已知最佳中继位置的通信性能提高时，则将所述修正因子的值和连续负反馈计数器的值清零，所述连续负反馈计数器用于描述所述移动中继在搜寻最佳中继位置的过程中，当前位置的通信性能比已保存的已知最佳中继位置的通信性能差的连续次数；
    在当前通信性能比已保存的已知最佳中继位置的通信性能差时，在所述移动中继返回上一时隙的位置的同时，将所述连续负反馈计数器的值加1，并将所述修正因子的值设置为上一次随机扰动步长的相反数，以及判断所述连续负反馈计数器的值是否达到预设的连续负反馈阈值；
    若判断所述连续负反馈计数器的值达到所述预设的连续负反馈阈值，则按预置的比例缩小所述随机扰动步长，同时将所述连续负反馈计数器清零并返回步骤C中的移动到下一个中继位置；
    若判断所述连续负反馈计数器的值未达到预设的连续负反馈阈值，则返回 步骤C中的移动到下一个中继位置。
  6. 如权利要求5所述的搜寻方法，其特征在于，所述方法还包括：
    所述目的端根据计算得到的所述当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，更新内存中的已知最佳中继位置的通信性能。
  7. 一种基于连续负反馈变步长的最佳中继位置搜寻系统，其特征在于，所述搜寻系统包括移动中继、源端和目的端；
    其中，所述移动中继在固定轨道的任意位置上，接收来自所述源端发送的测试信号，并放大转发至所述目的端；
    所述目的端接收所述移动中继发来的信号并计算本次通信性能，所述通信性能包括：信噪比和误码率，并根据计算结果与已保存的已知最佳中继位置的通信性能进行比较，以及生成一比特信息反馈至所述移动中继，所述一比特信息表示当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，所述已知最佳中继位置为已测试的通信性能最好的位置；
    所述移动中继记录当前位置信息，并根据所述一比特信息、随机扰动步长和修正因子移动到下一个位置，并再次执行接收来自所述源端发送的测试信号，并放大转发至所述目的端的步骤，直至最终确定最佳中继位置，所述最佳中继位置为：在预设的搜寻时长内通信性能最好的位置，或者，所述移动中继移动完整个所述固定轨道时通信性能最好的位置，或者，所述通信性能满足系统设定要求的位置。
  8. 如权利要求7所述的搜寻系统，其特征在于，
    若所述一比特信息表示当前通信性能大于所述已知最佳中继位置的通信性能，则所述移动中继将当前位置记录为已知最佳中继位置，则根据所述随机扰动步长和第一修正因子值确定及移动到下一个中继位置，所述第一修正因子值为0；
    若所述一比特信息表示当前通信性能小于所述已知最佳中继位置的通信性能，则所述移动中继先返回到上一次的位置，再根据所述随机移动步长和第二 修正因子值确定及移动到下一个中继位置，所述第二修正因子的值为上一次随机扰动步长的相反数；
    其中，以t表示时隙数，
    Figure PCTCN2015096737-appb-100004
    表示所述下一时隙的中继位置，θ(t)表示已知最佳中继位置，δ(t)表示所述随机扰动步长，ξ(t)表示所述修正因子，则：
    Figure PCTCN2015096737-appb-100005
  9. 如权利要求7或8所述的搜寻系统，其特征在于，
    在所述移动中继判断当前通信性能比已保存的已知最佳中继位置的通信性能提高时，将所述修正因子的值和连续负反馈计数器的值清零，所述连续负反馈计数器用于描述所述移动中继在搜寻最佳中继位置的过程中，当前位置的通信性能比已保存的已知最佳中继位置的通信性能差的连续次数；
    在判断当前通信性能比已保存的已知最佳中继位置的通信性能差时，在所述移动中继返回上一时隙的位置的同时，将所述连续负反馈计数器的值加1，并将所述修正因子的值设置为上一次随机扰动步长的相反数，以及判断所述连续负反馈计数器的值是否达到预设的连续负反馈阈值；
    若判断所述连续负反馈计数器的值达到所述预设的连续负反馈阈值，则所述移动中继按比例缩小所述随机扰动步长，同时将所述连续负反馈计数器清零并返回移动到下一个中继位置的步骤；
    若判断所述连续负反馈计数器的值未达到预设的连续负反馈阈值，则所述移动中继返回移动到下一个中继位置的步骤。
  10. 如权利要求9所述的搜寻系统，其特征在于，
    所述目的端根据计算得到的所述当前通信性能与已保存的已知最佳中继位置的通信性能的比较结果，更新内存中的已知最佳中继位置的通信性能。
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