WO2014146435A1 - Distributed beamforming system and carrier synchronization method of transmitting antennas at source end thereof - Google Patents

Distributed beamforming system and carrier synchronization method of transmitting antennas at source end thereof Download PDF

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Publication number
WO2014146435A1
WO2014146435A1 PCT/CN2013/086813 CN2013086813W WO2014146435A1 WO 2014146435 A1 WO2014146435 A1 WO 2014146435A1 CN 2013086813 W CN2013086813 W CN 2013086813W WO 2014146435 A1 WO2014146435 A1 WO 2014146435A1
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Prior art keywords
base station
carrier
information
base stations
synchronization signal
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PCT/CN2013/086813
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French (fr)
Chinese (zh)
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谢宁
王晖
林晓辉
曾捷
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深圳大学
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Publication of WO2014146435A1 publication Critical patent/WO2014146435A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements

Definitions

  • the present invention belongs to the field of wireless communication technologies, and in particular, to a distributed beamforming system and a carrier synchronization method for each transmitting antenna at the source end.
  • Distributed beamforming technology is a wireless communication technology that can significantly improve the power efficiency of the system. It integrates independent antennas distributed in multiple cells into a virtual antenna array (each antenna has its own crystal oscillator, and only Knowing their local time), each antenna in the antenna array sends the same signal to the destination node, and these signals are coherently merged at the destination node.
  • the distributed beamforming technology can obtain higher directional transmission characteristics than the traditional antenna array, and can obtain a larger receiving signal-to-noise ratio than the single antenna system (Signal Noise Ratio (SNR) gain, its application involves multi-cell cooperative network, multi-user wireless communication system, wireless sensor network (Wireless Sensor) Network, WSN), Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division) Multiplexing, OFDM) - Multiple-Input Multiple-Output (MIMO), 3G Long Term Evolution (Long Term) Evolution, LTE) and many other fields.
  • SNR Signal Noise Ratio
  • each source node has an independent local oscillator, the location of the source node, and the difference in channel transmission state, so that the signal of each source node reaches a phase offset when it reaches the destination node.
  • the merged and recombined signals are destroyed. Therefore, the source must synchronize the transmit carriers.
  • Source-side carrier synchronization is a key technology in distributed beamforming.
  • the carrier synchronization determines whether the destination receiving performance is good or bad. The less the synchronization occupation time, the better the system performance.
  • the open-loop methods applicable to the distributed beamforming technology and synchronizing the carriers in the prior art mainly include a time division duplex round-trip carrier synchronization method and a two-way carrier synchronization method.
  • the received uplink signal is transmitted back and forth in the base station of the transmitting end, thereby estimating the phase information of each base station to achieve synchronization
  • the disadvantages of this method are mainly: (1) occupying more time slots, for M
  • the system consisting of root antennas requires 2M-1 time slots to achieve synchronization of all base stations.
  • This method can only achieve carrier phase synchronization, and can not achieve accurate synchronization of carrier frequency.
  • This method before the antenna transmits signals Synchronization cannot be achieved, synchronization must be started after receiving the uplink signal from the destination end, and the delay of the system is increased; the latter method uses the time-division bidirectional transmission between the base stations to estimate the phase of the received signal, thereby realizing the base station.
  • Carrier synchronization but this method occupies a large number of slots. For a system composed of M antennas, 2M-2 slots are required to achieve synchronization of all base stations.
  • the first technical problem to be solved by the present invention is to provide a carrier synchronization method for each transmitting antenna at the source end of a distributed beamforming system, which aims to realize phase and frequency synchronization of carriers of each transmitting antenna at the source end and reduce synchronization occupation. Time slot overhead.
  • the present invention is implemented as a carrier synchronization method for each transmit antenna at a source end of a distributed beamforming system, the distributed beamforming system includes a source end and a destination end, and the source end has a plurality of base stations, each of which The base station only covers the base stations adjacent to both sides thereof, and the plurality of base stations include a synchronization signal generating base station;
  • the carrier synchronization method includes the following steps:
  • Step A The synchronization signal generation base station initializes the synchronization signal in the first time slot and broadcasts the synchronization signal to the base stations adjacent to both sides thereof, and the intermediate base station estimates the phase offset of the channel between the adjacent base stations on both sides;
  • the intermediate base station is a base station that is farthest from the base station of the synchronization signal generating base station;
  • Step B the synchronization signal generating base station and the intermediate base station have two signal transmission paths, and the synchronization signal generation base stations adjacent to the two sides of the base station respectively transmit one time along each of the two signal transmission paths according to the two signal transmission paths.
  • the synchronization signal is forwardly broadcasted to the intermediate base station, and during the entire forward broadcast transmission, each base station in the same direction as the synchronization signal transmission path performs carrier information estimation according to the received synchronization signal.
  • Step C The intermediate base station superimposes the synchronization signals transmitted on the two signal transmission paths, and then reversely transmits the superposed synchronization signals along the two signal transmission paths respectively, and the adjacent base stations on both sides of the intermediate base station Extracting, by the superimposed synchronization signal, a signal transmitted by the path of the opposite party, and performing carrier information estimation according to the extracted signal, to obtain respective second carrier estimation information including carrier frequency and phase information; and then both sides of the intermediate base station
  • the neighboring base station reversely transmits the extracted signal to the synchronization signal generating base station, and each base station in the same direction as the synchronization signal transmission path in the transmission process performs carrier information estimation according to the received extracted signal, and obtains respective carrier-containing carriers.
  • Step D The base station on both sides of the intermediate base station calculates the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and the remaining base stations estimate information according to the first carrier,
  • the two carrier estimation information is used to calculate the synchronized carrier information.
  • a second technical problem to be solved by the present invention is to provide a distributed beamforming system including a source end and a destination end, the source end having a plurality of base stations, each base station covering only base stations adjacent to both sides thereof;
  • the plurality of base stations include a synchronization signal generating base station, and the synchronization signal generating base station is configured to initialize a synchronization signal in a first time slot and broadcast the synchronization signal to a base station adjacent to both sides thereof; the synchronization signal generates a base station and There are two signal transmission paths between the intermediate base stations, and the intermediate base station is the base station farthest from the base station of the synchronization signal generation; the synchronization signal generation base stations adjacent to the two sides of the base station respectively follow the two signal transmission paths And transmitting the synchronization signal forward to the intermediate base station in a manner of transmitting one station per time slot; and the intermediate base station is configured to superimpose the synchronization signals transmitted on the two signal transmission paths, and then superimposing The synchronization signal is further reversely transmitted along the two signal transmission paths to the synchronization signal generating base station;
  • a phase offset estimation unit is included in the intermediate base station and adjacent base stations on both sides thereof; and the phase offset estimation unit is configured to estimate the intermediate base station and the two sides thereof when the synchronization signal generation base station starts broadcasting The phase offset of the channel between the neighboring base stations;
  • Each base station includes a first carrier information estimating unit, a second carrier information estimating unit, and a synchronization information calculating unit; the first carrier information estimating unit is configured to transmit a path with the synchronization signal during the entire forward broadcast transmission process.
  • Each base station in the same direction performs carrier information estimation according to the received synchronization signal, and obtains respective first carrier estimation information including carrier frequency and phase information;
  • the unit is configured to extract, from the superposed synchronization signal, a signal transmitted by the path of the opposite party, and perform carrier information estimation according to the extracted signal to obtain respective second carrier estimation information including carrier frequency and phase information;
  • the base stations adjacent to the two sides of the base station reversely transmit the extracted signals to the synchronization signal generating base station, and each base station in the same direction as the synchronization signal transmission path in the transmission process performs carrier information estimation according to the received extracted signals, and obtains respective signals.
  • Second carrier estimation information including carrier frequency and phase information
  • the synchronization information calculation unit in the base station on both sides of the intermediate base station is configured to calculate the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and calculate synchronization information in the remaining base stations.
  • the unit calculates the synchronized carrier information according to the first carrier estimation information and the second carrier estimation information.
  • the present invention fully utilizes the broadcast characteristics of the wireless link, and achieves accurate synchronization of the carrier frequency and phase of the distributed beamforming system by precise time slot control and channel estimation, and the present invention is greatly reduced compared with the conventional carrier synchronization method.
  • the synchronization overhead reduces the time slot required for synchronization from 2M-1 to M (where M is the number of source base stations), thereby increasing the effective communication time of the system.
  • FIG. 1 is a schematic diagram of signal flow when a base station having an odd number of ring structures at a source end is provided in a distributed beamforming system according to the present invention
  • FIG. 2 is a schematic diagram of signal flow when a base station having an even number of ring structures at a source end is provided in the distributed beamforming system provided by the present invention
  • FIG. 3 is a schematic diagram of signal flow when a base station having an odd number of linear structures at a source end is provided in the distributed beamforming system provided by the present invention
  • FIG. 4 is a schematic diagram of signal flow when a base station having an even number of linear structures at a source end is provided in the distributed beamforming system provided by the present invention
  • FIG. 5 is a schematic structural diagram of a distributed beamforming system provided by the present invention.
  • each base station at the source has at least one antenna, and each antenna provides services in its own coverage area and has its own crystal oscillator, each antenna uses its own local time.
  • the received signal and the processed signal can realize accurate time slot control, and estimate the phase offset information caused by the frequency and phase of the received signal and the channel delay.
  • each base station at the source end only covers the base stations adjacent to both sides thereof, and can be implemented by setting an appropriate signal transmission distance, and includes a synchronization signal generating base station in a plurality of base stations, and the synchronization signal generating base station can be One (such as a ring structure) can also be two (such as a linear structure), as described below.
  • the carrier pass method provided by the present invention includes the following steps:
  • Step A The synchronization signal generation base station initializes the synchronization signal in the first time slot and broadcasts the synchronization signal to the base stations adjacent to both sides thereof, and the intermediate base station estimates the phase offset of the channel between the adjacent base stations on both sides.
  • the intermediate base station is the base station farthest from the base station of the synchronization signal generation.
  • the distance synchronization signal generating base station has two farthest base stations, and any one of them can serve as an intermediate base station.
  • the base stations in the system composed of M base stations are numbered, which are BS 1 , BS 2 , ..., BS M in sequence, and any base station (assuming BS 1 ) initializes the synchronization signal and broadcasts the synchronization signal to the surroundings.
  • the sync signal can only be received by its two adjacent base stations.
  • the synchronization signal generating base station has two signal transmission paths between the base station and the farthest base station, and the synchronization signal generation base station adjacent to both sides of the base station can forward the synchronization signal to the intermediate base station along the two signal transmission paths.
  • the synchronization signal received by the next base station is the periodic extension of the synchronization signal sent by the previous base station, and the phase is delayed, and the frequency remains basically unchanged.
  • the method utilizes the broadcast characteristics of the wireless link
  • the synchronization signals broadcast by the two base stations arrive at the intermediate base station at the same time.
  • the processing method at this time is that the three base stations involved estimate the phase offset information caused by the channel delay between the neighboring base stations, and the two base stations that broadcast the synchronization signal receive the intermediate base station broadcast backhaul.
  • the received synchronization signal is subtracted by the received signal.
  • the processed synchronization signal is the phase of the synchronization signal broadcasted by the previous time slot plus the channel delay phase as the signal of the new phase, and the intermediate base station Do similar processing.
  • the number of base stations that need to perform channel estimation is different, and the number of slots occupied by the channel estimation is also different.
  • the channel estimation of the initial broadcast synchronization signal can be used to reduce the number of time slots occupied by the entire synchronization process; for the case where the number of base stations is not more than 6, additional time is needed to avoid interference.
  • the gap is used for channel estimation.
  • the number of base stations is M
  • Step B the synchronization signal generating base station has two signal transmission paths between the base station and the farthest base station, and the synchronization signal generates a manner in which the base stations adjacent to the two sides of the base station respectively transmit one station along each of the two signal transmission paths according to each time slot.
  • the synchronization signal is forwardly broadcasted to the intermediate base station, and during the entire forward broadcast transmission process, each base station performs carrier information estimation according to the received synchronization signal to obtain respective first carrier estimates including carrier frequency and phase information. information.
  • any base station (assuming BS1) initializes the synchronization signal and broadcasts the synchronization signal to the surroundings.
  • the synchronization signal can only be received by its two adjacent base stations and used to estimate the respective carrier frequency and phase information. At this time, the other base stations ignore the signal.
  • the two base stations broadcast the synchronization signals received in the previous time slot, are received by the respective neighboring base stations, and are used for carrier information estimation.
  • This synchronization signal will be transmitted simultaneously along the paths BS 1 , BS 2 , ..., BS M/2 and the paths BS M , B SM-1 , ..., BS M/2 until reaching the intermediate node, at which time along the signal transmission path
  • the base station in the direction uses the received synchronization signal to estimate the frequency and phase information of the carrier to obtain the first carrier estimation information, and the base station in the opposite direction of the signal transmission path directly ignores the received synchronization signal.
  • Step C The intermediate base station superimposes the synchronization signals transmitted on the two signal transmission paths, and then reversely transmits the superposed synchronization signals to the synchronization signal generation base station along the two signal transmission paths, respectively, and transmits the entire reverse broadcast process.
  • Each base station performs carrier information estimation according to the received superimposed synchronization signal, and obtains respective second carrier estimation information including carrier frequency and phase information.
  • the intermediate node After the synchronization signal broadcast is transmitted to the intermediate node, the intermediate node transmits the sum broadcast of the synchronization signals from the two paths, and the signal is received and processed by the adjacent nodes of the intermediate node, and then transmitted simultaneously along the opposite path. Until the synchronization signal is broadcast back to the initially transmitted base station, the base station along the signal transmission path uses the received synchronization signal to estimate the frequency and phase information of the carrier, thereby obtaining the second carrier estimation information. The base station in the opposite direction of the signal transmission path directly ignores the received synchronization signal.
  • Step D The base station on both sides of the intermediate base station calculates the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset, and the remaining base stations calculate according to the first carrier estimation information and the second carrier estimation information. Carrier information after synchronization.
  • each base station has first carrier estimation information and second carrier estimation information (the base station that initially transmits the synchronization signal has only one set of frequency and phase estimation information, and the other group of frequency and phase information is the frequency and phase at the time of initial transmission. And the three base stations in the middle also have phase estimation information, each base station adds two frequencies as the synchronized frequency, and phase adds as the synchronized phase, thereby realizing carrier synchronization of all base stations in the system.
  • Step C1 When the number of source base stations is an odd number, after receiving the superimposed synchronization signal sent by the intermediate base station, receiving the superimposed synchronization signal as one of the adjacent base stations on both sides of the intermediate base station The signal received in the previous time slot which is reduced by 2 times the phase offset is used as a subtraction difference, and then the carrier information is estimated according to the difference, and the respective second carrier including the carrier frequency and phase information is obtained. Estimated information;
  • Step C2 When the number of the source base stations is an even number, after receiving the superimposed synchronization signal sent by the intermediate base station, receiving the superimposed synchronization signal as one of the adjacent base stations on both sides of the intermediate base station The signal received in the previous time slot which is reduced by 2 times the phase offset is used as a subtraction difference, and then the carrier information is estimated according to the difference, and the respective second carrier including the carrier frequency and phase information is obtained.
  • the neighboring base stations on both sides of the intermediate base station broadcast the respective extracted signals separately in different time slots, and the intermediate base station estimates the carrier information for the two extracted signals received at this time to obtain two phase estimation values and
  • the two frequency estimates are obtained by subtracting the corresponding phase offsets from the two phase estimates as their first and second carrier phase estimation information, and the frequency estimation values are first and second carrier frequency estimation information.
  • step D all the base stations add the frequency in the first carrier estimation information and the frequency in the second carrier estimation information as the synchronized carrier frequency, and the phase and the second carrier in the first carrier estimation information.
  • the phase addition in the estimation information is used as the carrier frequency after synchronization.
  • Embodiment 1 An odd number of base stations at the source end form a closed loop structure, and the synchronization signal generation base station is any one of the base stations in the closed loop structure, as shown in FIG. 1 .
  • Step A specifically includes the following steps: Step A1: In the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station.
  • the solid line indicates the transmission process of the synchronization signal between the base stations. Each time the signal transmitted is the periodic extension of the signal of the previous time slot, and the broken line indicates the process of channel estimation.
  • a time slot TS 1 is required for Channel estimation (base station BS [M/2]+1 estimates the channel phase between BS [M/2]+1 and BS [M/2]+2 , respectively, BS [M/2]+3 estimates BS [M /2] +3 and channel [M/2]+2 channel phase), where TS i represents the ith time slot, BS i represents the ith base station, and the symbol '[ ] ' indicates rounding, the same below .
  • Step A specifically includes the following steps: Step A2, in the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station; in the second time slot, the intermediate base station estimates the The phase offset of the channel with the neighboring base station on one side; in the last time slot of the reverse broadcast transmission, the intermediate base station estimates the phase offset of the channel between it and the neighboring base station on the other side.
  • Step A2 specifically includes the following steps: Step A2, in the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station; in the second time slot, the intermediate base station estimates the The phase offset of the channel with the neighboring base station on one side; in the last time slot of the reverse broadcast transmission, the intermediate base station estimates the phase offset of the channel between it and the neighboring base station on the other side.
  • the solid line indicates the transmission process of the synchronization signal between the base stations, and each transmitted signal is a periodic extension of the previous time slot signal, and a broken line indicates the channel estimation process.
  • three time slots are needed for the channel. Estimate (in TS 1 time slot, BS M/2 , BS M/2+2 estimate the channel phase between each and BS M/2+1 ; in TS 2 time slot, BS M/2+1 estimates its and BS Channel phase between M/2+2 ; BS M/2+1 estimates the channel phase between it and BS M/2 in the TS M time slot).
  • Embodiment 3 A plurality of base stations at the source end can form a linear structure, and the synchronization signal generates base stations at both ends of the linear structure of the base station.
  • the number of base stations shown in FIG. 3 may be an odd number of base stations, or an even number shown in FIG.
  • the base station is different from the ring structure in that the synchronization signals generated by the base station at the two ends may be the same or different.
  • Step A specifically includes the following steps: Step A3, in the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station. For the case of FIG.
  • the thin solid line indicates the transmission process of the synchronization signal between the base stations, and each transmitted signal is a periodic extension of the previous time slot signal, and a thick solid line indicates the channel estimation process.
  • the slot TS 1 is used for channel estimation (the base station BS [M/2] estimates the channel phase between BS [M/2] and BS [M/2] +1 , respectively, BS [M/2] + 2 estimates BS [ M/2]+2 and channel [M/2]+1 channel phase), the dotted line indicates that the base station BS [M/2] is separated from the BS [M/2]+2 by two time slots.
  • the thin solid line indicates the transmission process of the synchronization signal between the base stations, and the signal transmitted each time is the cycle extension of the previous time slot signal, and the thick solid line indicates the process of channel estimation.
  • the slot TS1 is used for channel estimation (the base station BS [M/2] estimates the channel phase between BS [M/2] and BS [M/2]+1 , respectively, BS [M/2]+2 estimates BS [M /2] +2 and channel [M/2] +1 channel phase), the dashed line indicates that the intermediate base station receives the synchronization signals from the adjacent two base stations, respectively.
  • the present invention fully utilizes the broadcast characteristics of the wireless link, and achieves precise synchronization of the carrier frequency and phase of the distributed beamforming system through accurate time slot control and channel estimation.
  • the essence of the invention is to spread the synchronization signal.
  • the path is divided into two, and then the base station on the two paths respectively records the phase delay information of the other path, and exchanges the local time information of the base station by means of the synchronization signal transmitted between the base stations, thereby realizing the global synchronization of the system carrier.
  • each base station subtracts the phase of the uplink signal from the phase after synchronization. This difference is used as the phase of the downlink signal, and the frequency after synchronization is subtracted from the frequency of the uplink signal.
  • the frequency of the signal (the frequency after synchronization is approximately twice the frequency of the upstream signal), so that when the downlink signal arrives at the terminal, it is always synchronized.
  • the invention greatly reduces the synchronization overhead, and reduces the time slot required for synchronization from 2M-1 to M (where M is the number of source base stations), thereby increasing the effective communication time of the system.
  • FIG. 5 shows the structural principle of the distributed beamforming system provided by the present invention, and for the convenience of description, only the parts related to the present invention are shown.
  • FIG. 5 is only described by taking an example of a base station with an odd number of ring arrangements at the source end. It should be understood that the remaining even number of ring-shaped base stations, and odd and even linearly arranged base stations have the same principle.
  • the distributed beamforming system includes a source end and a destination end, and the source end has a plurality of base stations BS 1 to BS M , and each base station covers only base stations adjacent to both sides thereof.
  • the plurality of base stations including the base station generating a synchronization signal BS 1, the base station BS 1 generates a synchronization signal in a first time slot for synchronization initialization signal and on both sides thereof adjacent to the base station broadcasts a synchronization signal; generating a synchronization signal the base station BS 1 and its farthest
  • the synchronization signal is forwardly transmitted to the intermediate base station BS (M/2)+2 ; and the intermediate base station BS (M/2)+2 is used to transmit the synchronization signals transmitted on the two signal transmission paths.
  • the superimposed synchronization signals are again reversely transmitted along the two signal transmission paths to the synchronization signal generating base station BS 1 .
  • a phase offset estimation unit is included in the intermediate base station BS (M/2)+2 and its adjacent base stations BS (M/2)+1 and BS (M/2)+3 ; phase offset The quantity estimating unit is configured to estimate the intermediate base station BS (M/2)+2 and its adjacent base stations BS (M/2)+1 and BS (M/2)+3 when the synchronization signal generating base station starts broadcasting.
  • Each base station includes a first carrier information estimating unit, a second carrier information estimating unit, and a synchronization information calculating unit; the first carrier information estimating unit is configured to receive each base station according to the received forward broadcast transmission process.
  • the synchronization signal performs carrier information estimation to obtain respective first carrier estimation information including carrier frequency and phase information; and the second carrier information estimating unit is configured to perform, in the entire reverse broadcast transmission process, each base station according to the received superposition the synchronization signal information to estimate the carrier, to obtain the respective second carrier information comprises carrier frequency and the estimated phase information; generating a base station BS the base station BS farthest sides.
  • the synchronization information calculation unit in M/2)+1 and BS (M/2)+3 is configured to calculate the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and the remaining base stations
  • the synchronization information calculation unit in the calculation calculates the synchronized carrier information based on the first carrier estimation information and the second carrier estimation information.
  • the plurality of base stations at the source end may form a closed loop structure, and the synchronization signal generation base station is any one of the closed loop structures.
  • the number of base stations at the source end is an odd number, in the first time slot, the neighboring base stations BS (M/2)+1 and BS (M/2)+3 on both sides of the intermediate base station BS (M/2)+2
  • the phase offset estimation unit estimates the phase offset of the channel with the intermediate base station BS (M/2)+2 , respectively.
  • the phase offset estimation unit in the intermediate base station BS (M/2)+2 estimates the The phase offset of the channel between the adjacent base stations BS (M/2)+1 and BS (M/2)+3 on one side; the phase offset in the intermediate base station in the last time slot of the reverse broadcast transmission
  • the quantity estimating unit estimates the phase offset of the channel between it and the neighboring base station on the other side.
  • the plurality of base stations at the source end may form a linear structure, and the synchronization signal generates base stations at both ends of the linear structure of the base station; in the first time slot, the adjacent base stations BS on both sides of the intermediate base station BS (M/2)+2 (
  • the phase shift amount estimating unit in M/2)+1 and BS (M/2)+3 estimates the phase shift amount of the channel with the intermediate base station, respectively.
  • the adjacent base stations BS (M/2)+1 and BS (M/2)+3 of the intermediate base station BS (M/2)+2 are respectively in two
  • the broadcast transmission of the synchronization signal is performed in different time slots.
  • the synchronization information calculation unit in all the base stations is configured to add the frequency in the first carrier estimation information and the frequency in the second carrier estimation information as the synchronized carrier frequency, and compare the phase in the first carrier estimation information.
  • the phase addition in the second carrier estimation information is used as the carrier frequency after synchronization.
  • the present invention is applicable to the field of wireless communication technologies, and in particular, to carrier synchronization of a distributed time division duplex system, a multi-cell communication system, a cooperative communication system, a distributed adhoc/mesh network, and the like.

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Abstract

The present invention is applicable to the technical field of wireless communications, and provides a distributed beamforming system and a carrier synchronization method of transmitting antennas at a source end thereof. In the present invention, transmitting antennas at a source end can accurately control timeslots, and can estimate frequencies and phases on received signals, and can estimate phase shift information caused by channel time delay. In the present invention, a broadcasting characteristic of a wireless link is fully utilized, and accurate synchronization of carrier frequencies and phases of a distributed beamforming system is implemented by using accurate timeslot control and channel estimation. Compared with the conventional carrier synchronization method, the present invention greatly reduces the synchronization overhead, and time slots needed for synchronization is decreased to from 2M-1 to M (M being the number of source-end base stations), thereby increasing the effective communications time of the system.

Description

分布式波束合成系统及其源端各发送天线的载波同步方法  Distributed beamforming system and carrier synchronization method of each transmitting antenna at its source end Technical FieldTechnical Field
本发明属于无线通信技术领域，尤其涉及一种分布式波束合成系统及其源端各发送天线的载波同步方法。  The present invention belongs to the field of wireless communication technologies, and in particular, to a distributed beamforming system and a carrier synchronization method for each transmitting antenna at the source end.
Background ArtBackground Art
分布式波束合成技术是一种能够显著提高系统功率效率的无线通信技术，它把分布在多个小区的独立的天线组成虚拟的天线阵（其中每个天线都有各自的晶体振荡器，且只知道自己的本地时间），天线阵中的每个天线向目的节点发送相同的信号，这些信号在目的节点相干合并。由于虚拟天线阵的可扩展性和稳健性，使得分布式波束合成技术相对于传统天线阵能够获得更高的定向传输特性，相对于单天线系统能够获得更大的接收信噪比(Signal Noise Ratio，SNR)增益，其应用涉及多小区协作网络、多用户无线通信系统、无线传感器网络(Wireless Sensor Network，WSN)、正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)-多入多出(Multiple-Input Multiple-Output,MIMO)、3G 长期演进(Long Term Evolution, LTE)等众多领域。但是由于网络中源节点的异构性，即每个源节点都有独立的本地振荡器、源节点的位置以及信道传输状态的差异，使得各个源节点的信号到达目的节点时产生相位偏移，破坏信号的合并重组，因此，源端必须对发送载波进行同步处理。Distributed beamforming technology is a wireless communication technology that can significantly improve the power efficiency of the system. It integrates independent antennas distributed in multiple cells into a virtual antenna array (each antenna has its own crystal oscillator, and only Knowing their local time), each antenna in the antenna array sends the same signal to the destination node, and these signals are coherently merged at the destination node. Due to the scalability and robustness of the virtual antenna array, the distributed beamforming technology can obtain higher directional transmission characteristics than the traditional antenna array, and can obtain a larger receiving signal-to-noise ratio than the single antenna system (Signal Noise Ratio (SNR) gain, its application involves multi-cell cooperative network, multi-user wireless communication system, wireless sensor network (Wireless Sensor) Network, WSN), Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division) Multiplexing, OFDM) - Multiple-Input Multiple-Output (MIMO), 3G Long Term Evolution (Long Term) Evolution, LTE) and many other fields. However, due to the heterogeneity of the source nodes in the network, that is, each source node has an independent local oscillator, the location of the source node, and the difference in channel transmission state, so that the signal of each source node reaches a phase offset when it reaches the destination node. The merged and recombined signals are destroyed. Therefore, the source must synchronize the transmit carriers.
源端载波同步是分布式波束合成中的关键技术，载波同步与否决定目的端接收性能的好坏，同步占用时间越少系统性能越好。现有技术中适用于分布式波束合成技术、并对载波进行同步的开环方法主要有基于时分双工的往返载波同步法和双向载波同步法。前一种方法把接收到的上行信号在发送端基站中往返传输，以此来估计每个基站的相位信息实现同步，这种方法的缺点主要有（1）占用的时隙较多，对于M根天线组成的系统需要2M-1个时隙实现所有基站同步，（2）这种方法只能实现载波相位的同步，不能实现载波频率的精确同步，（3）这种方法在天线发送信号之前不能实现同步，必须在接收完来自目的端的上行信号后才能开始同步，增大了系统的延时；后一种方法利用同步信号在基站间的分时双向传输来估算接收信号相位，从而实现基站的载波同步，但这种方法占用的时隙数较多，对于M根天线组成的系统需要2M-2个时隙实现所有基站同步。Source-side carrier synchronization is a key technology in distributed beamforming. The carrier synchronization determines whether the destination receiving performance is good or bad. The less the synchronization occupation time, the better the system performance. The open-loop methods applicable to the distributed beamforming technology and synchronizing the carriers in the prior art mainly include a time division duplex round-trip carrier synchronization method and a two-way carrier synchronization method. In the former method, the received uplink signal is transmitted back and forth in the base station of the transmitting end, thereby estimating the phase information of each base station to achieve synchronization, and the disadvantages of this method are mainly: (1) occupying more time slots, for M The system consisting of root antennas requires 2M-1 time slots to achieve synchronization of all base stations. (2) This method can only achieve carrier phase synchronization, and can not achieve accurate synchronization of carrier frequency. (3) This method before the antenna transmits signals. Synchronization cannot be achieved, synchronization must be started after receiving the uplink signal from the destination end, and the delay of the system is increased; the latter method uses the time-division bidirectional transmission between the base stations to estimate the phase of the received signal, thereby realizing the base station. Carrier synchronization, but this method occupies a large number of slots. For a system composed of M antennas, 2M-2 slots are required to achieve synchronization of all base stations.
Technical ProblemTechnical Problem
本发明所要解决的第一个技术问题在于提供一种分布式波束合成系统的源端各发送天线的载波同步方法，旨在实现源端各发送天线的载波的相位、频率同步并减少同步占用的时隙开销。 The first technical problem to be solved by the present invention is to provide a carrier synchronization method for each transmitting antenna at the source end of a distributed beamforming system, which aims to realize phase and frequency synchronization of carriers of each transmitting antenna at the source end and reduce synchronization occupation. Time slot overhead.
Technical SolutionTechnical Solution
本发明是这样实现的，一种分布式波束合成系统的源端各发送天线的载波同步方法，所述分布式波束合成系统包括源端和目的端，所述源端具有多个基站，每个基站仅覆盖其两侧相邻的基站，所述多个基站中包括同步信号产生基站；所述载波同步方法包括下述步骤：The present invention is implemented as a carrier synchronization method for each transmit antenna at a source end of a distributed beamforming system, the distributed beamforming system includes a source end and a destination end, and the source end has a plurality of base stations, each of which The base station only covers the base stations adjacent to both sides thereof, and the plurality of base stations include a synchronization signal generating base station; the carrier synchronization method includes the following steps:
步骤A，同步信号产生基站在第一时隙初始化同步信号并向其两侧相邻的基站广播所述同步信号，同时中间基站估算与其两侧相邻基站之间的信道的相位偏移量；所述中间基站为距离所述同步信号产生基站最远的基站；Step A: The synchronization signal generation base station initializes the synchronization signal in the first time slot and broadcasts the synchronization signal to the base stations adjacent to both sides thereof, and the intermediate base station estimates the phase offset of the channel between the adjacent base stations on both sides; The intermediate base station is a base station that is farthest from the base station of the synchronization signal generating base station;
步骤B，所述同步信号产生基站与中间基站之间具有两条信号传递路径，所述同步信号产生基站的两侧相邻的基站分别沿所述两条信号传递路径按照每个时隙传递一站的方式、将所述同步信号正向广播传递至中间基站，并且在整个正向广播传递过程中，与同步信号传递路径相同方向上的每个基站均根据接收到的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第一载波估算信息；Step B, the synchronization signal generating base station and the intermediate base station have two signal transmission paths, and the synchronization signal generation base stations adjacent to the two sides of the base station respectively transmit one time along each of the two signal transmission paths according to the two signal transmission paths. In the manner of the station, the synchronization signal is forwardly broadcasted to the intermediate base station, and during the entire forward broadcast transmission, each base station in the same direction as the synchronization signal transmission path performs carrier information estimation according to the received synchronization signal. Obtaining respective first carrier estimation information including carrier frequency and phase information;
步骤C，中间基站将所述两条信号传递路径上传递过来的同步信号进行叠加，然后将叠加后的同步信号再分别沿所述两条信号传递路径逆向传递,中间基站两侧相邻的基站从所述叠加后的同步信号中提取出对方路径传递过来的信号,并根据所提取的信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息;然后中间基站两侧相邻的基站将提取的信号逆向传递至所述同步信号产生基站,传递过程中与同步信号传递路径相同方向上的每个基站均根据接收到的提取信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息； Step C: The intermediate base station superimposes the synchronization signals transmitted on the two signal transmission paths, and then reversely transmits the superposed synchronization signals along the two signal transmission paths respectively, and the adjacent base stations on both sides of the intermediate base station Extracting, by the superimposed synchronization signal, a signal transmitted by the path of the opposite party, and performing carrier information estimation according to the extracted signal, to obtain respective second carrier estimation information including carrier frequency and phase information; and then both sides of the intermediate base station The neighboring base station reversely transmits the extracted signal to the synchronization signal generating base station, and each base station in the same direction as the synchronization signal transmission path in the transmission process performs carrier information estimation according to the received extracted signal, and obtains respective carrier-containing carriers. Second carrier estimation information of frequency and phase information;
步骤D，中间基站两侧的基站根据所述第一载波估算信息、第二载波估算信息、所述相位偏移量来计算同步后的载波信息，其余基站根据所述第一载波估算信息、第二载波估算信息来计算同步后的载波信息。Step D: The base station on both sides of the intermediate base station calculates the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and the remaining base stations estimate information according to the first carrier, The two carrier estimation information is used to calculate the synchronized carrier information.
本发明所要解决的第二个技术问题在于提供一种分布式波束合成系统，包括源端和目的端，所述源端具有多个基站，每个基站仅覆盖其两侧相邻的基站；A second technical problem to be solved by the present invention is to provide a distributed beamforming system including a source end and a destination end, the source end having a plurality of base stations, each base station covering only base stations adjacent to both sides thereof;
所述多个基站中包括同步信号产生基站，所述同步信号产生基站用于在第一时隙初始化同步信号并向其两侧相邻的基站广播所述同步信号；所述同步信号产生基站与中间基站之间具有两条信号传递路径，所述中间基站为距离所述同步信号产生基站最远的基站；所述同步信号产生基站的两侧相邻的基站分别沿所述两条信号传递路径按照每个时隙传递一站的方式、将所述同步信号正向广播传递至中间基站；而中间基站用于将所述两条信号传递路径上传递过来的同步信号进行叠加，然后将叠加后的同步信号再分别沿所述两条信号传递路径逆向传递至所述同步信号产生基站；The plurality of base stations include a synchronization signal generating base station, and the synchronization signal generating base station is configured to initialize a synchronization signal in a first time slot and broadcast the synchronization signal to a base station adjacent to both sides thereof; the synchronization signal generates a base station and There are two signal transmission paths between the intermediate base stations, and the intermediate base station is the base station farthest from the base station of the synchronization signal generation; the synchronization signal generation base stations adjacent to the two sides of the base station respectively follow the two signal transmission paths And transmitting the synchronization signal forward to the intermediate base station in a manner of transmitting one station per time slot; and the intermediate base station is configured to superimpose the synchronization signals transmitted on the two signal transmission paths, and then superimposing The synchronization signal is further reversely transmitted along the two signal transmission paths to the synchronization signal generating base station;
在中间基站及其两侧相邻的基站中均包括一相位偏移量估算单元；所述相位偏移量估算单元用于在所述同步信号产生基站开始广播时，估算中间基站与其两侧相邻基站之间的信道的相位偏移量；A phase offset estimation unit is included in the intermediate base station and adjacent base stations on both sides thereof; and the phase offset estimation unit is configured to estimate the intermediate base station and the two sides thereof when the synchronization signal generation base station starts broadcasting The phase offset of the channel between the neighboring base stations;
每个基站中均包括一第一载波信息估算单元、第二载波信息估算单元和同步信息计算单元；所述第一载波信息估算单元用于在整个正向广播传递过程中，与同步信号传递路径相同方向上的每个基站均根据接收到的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第一载波估算信息；中间基站两侧相邻的基站中的第二载波信息估算单元用于从所述叠加后的同步信号中提取出对方路径传递过来的信号,并根据所提取的信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息;然后中间基站两侧相邻的基站将提取的信号逆向传递至所述同步信号产生基站,传递过程中与同步信号传递路径相同方向上的每个基站均根据接收到的提取信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息； Each base station includes a first carrier information estimating unit, a second carrier information estimating unit, and a synchronization information calculating unit; the first carrier information estimating unit is configured to transmit a path with the synchronization signal during the entire forward broadcast transmission process. Each base station in the same direction performs carrier information estimation according to the received synchronization signal, and obtains respective first carrier estimation information including carrier frequency and phase information; second carrier information estimation in adjacent base stations on both sides of the intermediate base station The unit is configured to extract, from the superposed synchronization signal, a signal transmitted by the path of the opposite party, and perform carrier information estimation according to the extracted signal to obtain respective second carrier estimation information including carrier frequency and phase information; The base stations adjacent to the two sides of the base station reversely transmit the extracted signals to the synchronization signal generating base station, and each base station in the same direction as the synchronization signal transmission path in the transmission process performs carrier information estimation according to the received extracted signals, and obtains respective signals. Second carrier estimation information including carrier frequency and phase information;
中间基站两侧的基站中的同步信息计算单元用于根据所述第一载波估算信息、第二载波估算信息、所述相位偏移量来计算同步后的载波信息，其余基站中的同步信息计算单元根据所述第一载波估算信息、第二载波估算信息来计算同步后的载波信息。The synchronization information calculation unit in the base station on both sides of the intermediate base station is configured to calculate the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and calculate synchronization information in the remaining base stations. The unit calculates the synchronized carrier information according to the first carrier estimation information and the second carrier estimation information.
Advantageous EffectsAdvantageous Effects
本发明充分利用了无线链路的广播特性，通过精确地时隙控制以及信道估算来实现分布式波束合成系统的载波频率和相位上的精确同步，与传统载波同步方法相比，本发明大大减少了同步开销，使同步所需时隙从2M-1降低到M（其中M为源端基站个数），从而增加了系统的有效通信时间。 The present invention fully utilizes the broadcast characteristics of the wireless link, and achieves accurate synchronization of the carrier frequency and phase of the distributed beamforming system by precise time slot control and channel estimation, and the present invention is greatly reduced compared with the conventional carrier synchronization method. The synchronization overhead reduces the time slot required for synchronization from 2M-1 to M (where M is the number of source base stations), thereby increasing the effective communication time of the system.
Description of DrawingsDescription of Drawings
图1是本发明提供的分布式波束合成系统中源端有奇数个环形结构的基站时的信号流向示意图；1 is a schematic diagram of signal flow when a base station having an odd number of ring structures at a source end is provided in a distributed beamforming system according to the present invention;
图2是本发明提供的分布式波束合成系统中源端有偶数个环形结构的基站时的信号流向示意图；2 is a schematic diagram of signal flow when a base station having an even number of ring structures at a source end is provided in the distributed beamforming system provided by the present invention;
图3是本发明提供的分布式波束合成系统中源端有奇数个线性结构的基站时的信号流向示意图；3 is a schematic diagram of signal flow when a base station having an odd number of linear structures at a source end is provided in the distributed beamforming system provided by the present invention;
图4是本发明提供的分布式波束合成系统中源端有偶数个线性结构的基站时的信号流向示意图；4 is a schematic diagram of signal flow when a base station having an even number of linear structures at a source end is provided in the distributed beamforming system provided by the present invention;
图5是本发明提供的分布式波束合成系统的架构原理图。FIG. 5 is a schematic structural diagram of a distributed beamforming system provided by the present invention.
Mode for InventionMode for Invention
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。The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
本发明提供的分布式波束合成系统中，源端的每个基站至少具有一天线，且每个天线在各自的覆盖区域中提供服务并拥有各自的晶体振荡器，每个天线都使用各自的本地时间接收信号和处理信号，能够实现精确的时隙控制，并对接收信号进行频率和相位以及信道延时造成的相位偏移信息进行估算。In the distributed beamforming system provided by the present invention, each base station at the source has at least one antenna, and each antenna provides services in its own coverage area and has its own crystal oscillator, each antenna uses its own local time. The received signal and the processed signal can realize accurate time slot control, and estimate the phase offset information caused by the frequency and phase of the received signal and the channel delay.
本发明中，源端的每个基站仅覆盖其两侧相邻的基站，具体可以通过设置合适的信号发送距离来实现，并且在多个基站中包括同步信号产生基站，此同步信号产生基站可以为一个（如环形结构），也可以为两个（如线性结构），具体见下文内容。In the present invention, each base station at the source end only covers the base stations adjacent to both sides thereof, and can be implemented by setting an appropriate signal transmission distance, and includes a synchronization signal generating base station in a plurality of base stations, and the synchronization signal generating base station can be One (such as a ring structure) can also be two (such as a linear structure), as described below.
本发明提供的载波通方法包括以下步骤：The carrier pass method provided by the present invention includes the following steps:
步骤A，同步信号产生基站在第一时隙初始化同步信号并向其两侧相邻的基站广播同步信号，同时中间基站估算与其两侧相邻基站之间的信道的相位偏移量。 Step A: The synchronization signal generation base station initializes the synchronization signal in the first time slot and broadcasts the synchronization signal to the base stations adjacent to both sides thereof, and the intermediate base station estimates the phase offset of the channel between the adjacent base stations on both sides.
其中，中间基站为距离所述同步信号产生基站最远的基站，当源端有奇数个基站时，距离同步信号产生基站有两个最远的基站，其中任意一个均可作为中间基站。假设对M个基站组成的系统中的基站进行编号，依次为BS1、BS2，…，BSM，某一时隙，任意基站（假设BS1）初始化同步信号并向周围广播此同步信号，此同步信号只能被它相邻的两个基站接收。这样，同步信号产生基站与其最远的基站之间具有两条信号传递路径，同步信号产生基站的两侧相邻的基站可沿两条信号传递路径将同步信号正向广播传递至中间基站，在传递过程中，下一基站接收到的同步信号是上一基站发送的同步信号的周期延拓，具体表现在相位会有所延迟，而频率则基本维持不变。 The intermediate base station is the base station farthest from the base station of the synchronization signal generation. When the source end has an odd number of base stations, the distance synchronization signal generating base station has two farthest base stations, and any one of them can serve as an intermediate base station. Suppose that the base stations in the system composed of M base stations are numbered, which are BS 1 , BS 2 , ..., BS M in sequence, and any base station (assuming BS 1 ) initializes the synchronization signal and broadcasts the synchronization signal to the surroundings. The sync signal can only be received by its two adjacent base stations. In this way, the synchronization signal generating base station has two signal transmission paths between the base station and the farthest base station, and the synchronization signal generation base station adjacent to both sides of the base station can forward the synchronization signal to the intermediate base station along the two signal transmission paths. During the transmission process, the synchronization signal received by the next base station is the periodic extension of the synchronization signal sent by the previous base station, and the phase is delayed, and the frequency remains basically unchanged.
因为本方法利用的是无线链路的广播特性，在同步信号处理过程中，会出现两个基站广播的同步信号同时到达中间基站的情况。此时的处理方法是，涉及到的这三个基站估算出与自己相邻基站间，由于信道延时造成的相位偏移信息，广播出同步信号的两个基站在接收到中间基站广播回传的同步信号后，用此接收信号减去各自处理后的同步信号，这个处理后的同步信号是，用前一时隙广播出去的同步信号相位加上信道延时相位作为新相位的信号，中间基站做类似处理。根据基站数量的奇偶性，需要进行信道估算的基站数不同，则信道估算占用的时隙数也不同。对于基站数量大于６的情况，可以利用最初广播同步信号的时隙进行信道估算，从而减少整个同步过程所占用的时隙数；对于基站数不大于６的情况，为了避免干扰则需要额外的时隙用于信道估算。当基站数为Ｍ时，根据具体的Ｍ值不同，需要的时隙数分别为：（１）Ｍ＞６，需要Ｍ个时隙实现同步，（２）M<=6 , 近似需要Ｍ＋１个时隙实现同步。 Because the method utilizes the broadcast characteristics of the wireless link, during the synchronization signal processing, there may be a case where the synchronization signals broadcast by the two base stations arrive at the intermediate base station at the same time. The processing method at this time is that the three base stations involved estimate the phase offset information caused by the channel delay between the neighboring base stations, and the two base stations that broadcast the synchronization signal receive the intermediate base station broadcast backhaul. After the synchronization signal, the received synchronization signal is subtracted by the received signal. The processed synchronization signal is the phase of the synchronization signal broadcasted by the previous time slot plus the channel delay phase as the signal of the new phase, and the intermediate base station Do similar processing. According to the parity of the number of base stations, the number of base stations that need to perform channel estimation is different, and the number of slots occupied by the channel estimation is also different. For the case where the number of base stations is greater than 6, the channel estimation of the initial broadcast synchronization signal can be used to reduce the number of time slots occupied by the entire synchronization process; for the case where the number of base stations is not more than 6, additional time is needed to avoid interference. The gap is used for channel estimation. When the number of base stations is M, the number of required slots is different according to the specific M value: (1) M>6, M slots are required to achieve synchronization, and (2) M<=6 , approximately requires M+1 time slots to achieve synchronization.
步骤B，同步信号产生基站与其最远的基站之间具有两条信号传递路径，同步信号产生基站的两侧相邻的基站分别沿两条信号传递路径按照每个时隙传递一站的方式、将同步信号正向广播传递至中间基站，并且在整个正向广播传递过程中，每个基站均根据接收到的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第一载波估算信息。 Step B, the synchronization signal generating base station has two signal transmission paths between the base station and the farthest base station, and the synchronization signal generates a manner in which the base stations adjacent to the two sides of the base station respectively transmit one station along each of the two signal transmission paths according to each time slot. The synchronization signal is forwardly broadcasted to the intermediate base station, and during the entire forward broadcast transmission process, each base station performs carrier information estimation according to the received synchronization signal to obtain respective first carrier estimates including carrier frequency and phase information. information.
如上文，某一时隙，任意基站（假设BS1）初始化同步信号并向周围广播此同步信号，此同步信号只能被它相邻的两个基站接收，并用于估算各自的载波频率和相位信息，此时，其他基站忽略此信号，在下一时隙，这两个基站把前一时隙接收到的同步信号广播转发出去，被各自相邻的基站接收，并用于载波信息估计。这个同步信号将沿着路径BS1，BS2，…,BS M/2 和路径BS M ，B SM-1 ，…,BS M/2 同时传递，直到到达中间节点，此时沿着信号传递路径方向上的基站利用接收到的同步信号，估算载波的频率和相位信息，从而得到第一载波估算信息，而在信号传递路径相反方向上的基站则直接忽略接收到的同步信号。As described above, in a certain time slot, any base station (assuming BS1) initializes the synchronization signal and broadcasts the synchronization signal to the surroundings. The synchronization signal can only be received by its two adjacent base stations and used to estimate the respective carrier frequency and phase information. At this time, the other base stations ignore the signal. In the next time slot, the two base stations broadcast the synchronization signals received in the previous time slot, are received by the respective neighboring base stations, and are used for carrier information estimation. This synchronization signal will be transmitted simultaneously along the paths BS 1 , BS 2 , ..., BS M/2 and the paths BS M , B SM-1 , ..., BS M/2 until reaching the intermediate node, at which time along the signal transmission path The base station in the direction uses the received synchronization signal to estimate the frequency and phase information of the carrier to obtain the first carrier estimation information, and the base station in the opposite direction of the signal transmission path directly ignores the received synchronization signal.
步骤C，中间基站将两条信号传递路径上传递过来的同步信号进行叠加，然后将叠加后的同步信号再分别沿两条信号传递路径逆向传递至同步信号产生基站，并且在整个逆向广播传递过程中，每个基站均根据接收到的叠加后的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息。 Step C: The intermediate base station superimposes the synchronization signals transmitted on the two signal transmission paths, and then reversely transmits the superposed synchronization signals to the synchronization signal generation base station along the two signal transmission paths, respectively, and transmits the entire reverse broadcast process. Each base station performs carrier information estimation according to the received superimposed synchronization signal, and obtains respective second carrier estimation information including carrier frequency and phase information.
当同步信号广播传递至中间节点后，中间节点把来自两条路径上的同步信号的总和广播传递出去，此信号经中间节点的相邻节点接收、处理后，再沿着相反的路径同时传递，直到同步信号再次广播回传到初始发送的基站为止，与之前类似，沿着信号传递路径方向上的基站利用接收到的同步信号，估算载波的频率和相位信息，从而得到第二载波估算信息，而在信号传递路径相反方向上的基站则直接忽略接收到的同步信号。 After the synchronization signal broadcast is transmitted to the intermediate node, the intermediate node transmits the sum broadcast of the synchronization signals from the two paths, and the signal is received and processed by the adjacent nodes of the intermediate node, and then transmitted simultaneously along the opposite path. Until the synchronization signal is broadcast back to the initially transmitted base station, the base station along the signal transmission path uses the received synchronization signal to estimate the frequency and phase information of the carrier, thereby obtaining the second carrier estimation information. The base station in the opposite direction of the signal transmission path directly ignores the received synchronization signal.
步骤D，中间基站两侧的基站根据第一载波估算信息、第二载波估算信息、相位偏移量来计算同步后的载波信息，其余基站根据第一载波估算信息、第二载波估算信息来计算同步后的载波信息。 Step D: The base station on both sides of the intermediate base station calculates the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset, and the remaining base stations calculate according to the first carrier estimation information and the second carrier estimation information. Carrier information after synchronization.
这时，每个基站都有第一载波估算信息、第二载波估算信息（初始发送同步信号的基站只有一组频率和相位估算信息，另一组频率和相位信息是初始发送时的频率和相位），而中间的三个基站还具有相位估算信息，每个基站把两个频率相加作为同步后的频率，相位相加作为同步后的相位，从而实现系统中所有基站的载波同步。 At this time, each base station has first carrier estimation information and second carrier estimation information (the base station that initially transmits the synchronization signal has only one set of frequency and phase estimation information, and the other group of frequency and phase information is the frequency and phase at the time of initial transmission. And the three base stations in the middle also have phase estimation information, each base station adds two frequencies as the synchronized frequency, and phase adds as the synchronized phase, thereby realizing carrier synchronization of all base stations in the system.
进一步地，对于中间基站及其两侧相邻的基站，还需多一个信道估算过程，根据源端基站个数的奇偶来执行下述步骤C1或C2： Further, for the intermediate base station and its neighboring base stations, one more channel estimation process is required, and the following steps C1 or C2 are performed according to the parity of the number of source base stations:
步骤C1，当源端基站个数为奇数时，对于中间基站两侧相邻的基站中的一个，在接收到中间基站发送过来的叠加后的同步信号后，将所述叠加后的同步信号作为被减数、延迟了2倍所述相位偏移量的上一时隙接收到的信号作为减数做差，然后根据差值进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息； Step C1: When the number of source base stations is an odd number, after receiving the superimposed synchronization signal sent by the intermediate base station, receiving the superimposed synchronization signal as one of the adjacent base stations on both sides of the intermediate base station The signal received in the previous time slot which is reduced by 2 times the phase offset is used as a subtraction difference, and then the carrier information is estimated according to the difference, and the respective second carrier including the carrier frequency and phase information is obtained. Estimated information;
步骤C2，当源端基站个数为偶数时，对于中间基站两侧相邻的基站中的一个，在接收到中间基站发送过来的叠加后的同步信号后，将所述叠加后的同步信号作为被减数、延迟了2倍所述相位偏移量的上一时隙接收到的信号作为减数做差，然后根据差值进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息；然后中间基站两侧相邻的基站把各自提取处理后的信号分开不同时隙广播出去，中间基站对此时接收到的两个提取的信号进行载波信息估算得到两个相位估算值和两个频率估算值，利用两个相位估算值分别减去对应的所述相位偏移量作为其第一和第二载波相位估算信息，频率估算值为第一和第二载波频率估算信息。 Step C2: When the number of the source base stations is an even number, after receiving the superimposed synchronization signal sent by the intermediate base station, receiving the superimposed synchronization signal as one of the adjacent base stations on both sides of the intermediate base station The signal received in the previous time slot which is reduced by 2 times the phase offset is used as a subtraction difference, and then the carrier information is estimated according to the difference, and the respective second carrier including the carrier frequency and phase information is obtained. Estimating the information; then the neighboring base stations on both sides of the intermediate base station broadcast the respective extracted signals separately in different time slots, and the intermediate base station estimates the carrier information for the two extracted signals received at this time to obtain two phase estimation values and The two frequency estimates are obtained by subtracting the corresponding phase offsets from the two phase estimates as their first and second carrier phase estimation information, and the frequency estimation values are first and second carrier frequency estimation information.
进一步地，步骤D具体为，所有基站将第一载波估算信息中的频率和第二载波估算信息中的频率相加作为同步后的载波频率，将第一载波估算信息中的相位和第二载波估算信息中的相位相加作为同步后的载波频率。 Further, in step D, all the base stations add the frequency in the first carrier estimation information and the frequency in the second carrier estimation information as the synchronized carrier frequency, and the phase and the second carrier in the first carrier estimation information. The phase addition in the estimation information is used as the carrier frequency after synchronization.
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面以三个实施例、四种情况进行描述。 In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description is made in three embodiments and four cases.
实施例一：源端的奇数个基站形成一闭环结构，同步信号产生基站为闭环结构中的任意一个基站，如图1所示。步骤A具体包括以下步骤：步骤A1，在第一时隙，中间基站的两侧相邻基站，分别估算与中间基站之间的信道的相位偏移量。图1中，实线表示同步信号在各基站间的传递过程，每一次传递的信号都是前一时隙信号的周期延拓，虚线表示信道估算的过程，此时需要一个时隙TS1用于信道估算（分别是基站BS[M/2]+1估算BS[M/2]+1与BS[M/2]+2之间的信道相位， BS[M/2]+3估算BS[M/2]+3与BS[M/2]+2之间的信道相位）,这里TS i 表示第i个时隙， BS i 表示第i个基站，符号' [ ] '表示取整,下同。Embodiment 1: An odd number of base stations at the source end form a closed loop structure, and the synchronization signal generation base station is any one of the base stations in the closed loop structure, as shown in FIG. 1 . Step A specifically includes the following steps: Step A1: In the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station. In Fig. 1, the solid line indicates the transmission process of the synchronization signal between the base stations. Each time the signal transmitted is the periodic extension of the signal of the previous time slot, and the broken line indicates the process of channel estimation. In this case, a time slot TS 1 is required for Channel estimation (base station BS [M/2]+1 estimates the channel phase between BS [M/2]+1 and BS [M/2]+2 , respectively, BS [M/2]+3 estimates BS [M /2] +3 and channel [M/2]+2 channel phase), where TS i represents the ith time slot, BS i represents the ith base station, and the symbol '[ ] ' indicates rounding, the same below .
实施例二：源端的偶数个基站形成一闭环结构，同步信号产生基站为闭环结构中的任意一个基站，如图2所示。步骤A具体包括以下步骤：步骤A2，在第一时隙，中间基站的两侧相邻基站，分别估算与中间基站之间的信道的相位偏移量；在第二时隙，中间基站估算其与一侧的相邻基站之间的信道的相位偏移量；在逆向广播传递的最后一个时隙，中间基站估算其与另一侧的相邻基站之间的信道的相位偏移量。图2中，实线表示同步信号在各基站间的传递过程，每一次传递的信号都是前一时隙信号的周期延拓，虚线表示信道估计的过程，此时需要三个时隙用于信道估算（在TS1时隙，BSM/2、BSM/2+2 估算各自与BSM/2+1之间的信道相位； 在TS2时隙，BSM/2+1估算其与BSM/2+2之间的信道相位； 在TSM时隙，BSM/2+1估算其与BSM/2之间的信道相位）。Embodiment 2: An even number of base stations at the source end form a closed loop structure, and the synchronization signal generation base station is any one of the closed loop structures, as shown in FIG. 2 . Step A specifically includes the following steps: Step A2, in the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station; in the second time slot, the intermediate base station estimates the The phase offset of the channel with the neighboring base station on one side; in the last time slot of the reverse broadcast transmission, the intermediate base station estimates the phase offset of the channel between it and the neighboring base station on the other side. In FIG. 2, the solid line indicates the transmission process of the synchronization signal between the base stations, and each transmitted signal is a periodic extension of the previous time slot signal, and a broken line indicates the channel estimation process. In this case, three time slots are needed for the channel. Estimate (in TS 1 time slot, BS M/2 , BS M/2+2 estimate the channel phase between each and BS M/2+1 ; in TS 2 time slot, BS M/2+1 estimates its and BS Channel phase between M/2+2 ; BS M/2+1 estimates the channel phase between it and BS M/2 in the TS M time slot).
实施例三：源端的多个基站可形成一线性结构，同步信号产生基站为线性结构的两端的基站，此时可以是图3所示的奇数个基站，也可以是图4所示的偶数个基站,与环形结构不同的是,两端的同步信号产生基站所产生的同步信号可以相同也可以不同。步骤A具体包括以下步骤：步骤A3，在第一时隙，中间基站的两侧相邻基站，分别估算与中间基站之间的信道的相位偏移量。对于图3的情况，细实线表示同步信号在各基站间的传递过程，每一次传递的信号都是前一时隙信号的周期延拓，粗实线表示信道估算的过程，此时需要一个时隙TS1用于信道估算（分别是基站BS[M/2]估算BS[M/2]与BS[M/2]+1之间的信道相位， BS[M/2]+2估算BS[M/2]+2与BS[M/2]+1之间的信道相位），虚线表示基站BS[M/2]与BS[M/2]+2分开两个时隙想周围广播传递同步信号，当一个基站广播信号时，另一个基站处于侦听状态但不做任何处理，从而避免了信号同时到达中间节点。对于图4的情况，细实线表示同步信号在各基站间的传递过程，每一次传递的信号都是前一时隙信号的周期延拓，粗实线表示信道估算的过程，此时需要一个时隙TS1用于信道估算（分别是基站BS[M/2]估算BS[M/2]与BS[M/2]+1之间的信道相位， BS[M/2]+2估算BS[M/2]+2与BS[M/2]+1之间的信道相位），虚线表示中间基站分别接收来自相邻的两个基站的同步信号。 Embodiment 3: A plurality of base stations at the source end can form a linear structure, and the synchronization signal generates base stations at both ends of the linear structure of the base station. In this case, the number of base stations shown in FIG. 3 may be an odd number of base stations, or an even number shown in FIG. The base station is different from the ring structure in that the synchronization signals generated by the base station at the two ends may be the same or different. Step A specifically includes the following steps: Step A3, in the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station. For the case of FIG. 3, the thin solid line indicates the transmission process of the synchronization signal between the base stations, and each transmitted signal is a periodic extension of the previous time slot signal, and a thick solid line indicates the channel estimation process. The slot TS 1 is used for channel estimation (the base station BS [M/2] estimates the channel phase between BS [M/2] and BS [M/2] +1 , respectively, BS [M/2] + 2 estimates BS [ M/2]+2 and channel [M/2]+1 channel phase), the dotted line indicates that the base station BS [M/2] is separated from the BS [M/2]+2 by two time slots. Signal, when one base station broadcasts a signal, the other base station is in the listening state but does not do any processing, thereby avoiding the signal reaching the intermediate node at the same time. For the case of FIG. 4, the thin solid line indicates the transmission process of the synchronization signal between the base stations, and the signal transmitted each time is the cycle extension of the previous time slot signal, and the thick solid line indicates the process of channel estimation. The slot TS1 is used for channel estimation (the base station BS [M/2] estimates the channel phase between BS [M/2] and BS [M/2]+1 , respectively, BS [M/2]+2 estimates BS [M /2] +2 and channel [M/2] +1 channel phase), the dashed line indicates that the intermediate base station receives the synchronization signals from the adjacent two base stations, respectively.
需要注意的是，对于线性奇数的情况，当基站线性分布时，BS1、BS M 同时初始化同步信号，并向周围空间广播，这两个同步信号的频率和相位不一定是相等的，而当基站环形分布时，只有基站BS1初始化同步信号，并向周围空间广播，即中间基站的两侧相邻基站分别在两个不同时隙进行同步信号的广播传递。It should be noted that, in the case of linear odd numbers, when the base station is linearly distributed, BS 1 and BS M simultaneously initialize the synchronization signal and broadcast to the surrounding space, and the frequencies and phases of the two synchronization signals are not necessarily equal, but when When the base station is circularly distributed, only the base station BS 1 initializes the synchronization signal and broadcasts to the surrounding space, that is, the adjacent base stations on both sides of the intermediate base station respectively perform broadcast transmission of the synchronization signals in two different time slots.
综上，本发明充分利用了无线链路的广播特性，通过精确地时隙控制以及信道估算来实现分布式波束合成系统的载波频率和相位上的精确同步，其原理实质是将同步信号的传播路径分为两条，然后将两条路径上基站分别记录保存对方路径的相位延迟信息，通过同步信号在基站之间传递的方式交换基站的本地时间信息，从而实现系统载波的全局同步。系统载波实现全局同步后，每个基站用同步后的相位减去上行链路信号相位，这个差值作为下行信号的相位，而同步后的频率减去上行链路信号频率，这个差值作为下行信号的频率（一般同步后的频率近似上行信号频率的2倍），这样当下行信号到达终端时，总是同步的。与传统载波同步方法相比，本发明大大减少了同步开销，使同步所需时隙从2M-1降低到M（其中M为源端基站个数），从而增加了系统的有效通信时间。 In summary, the present invention fully utilizes the broadcast characteristics of the wireless link, and achieves precise synchronization of the carrier frequency and phase of the distributed beamforming system through accurate time slot control and channel estimation. The essence of the invention is to spread the synchronization signal. The path is divided into two, and then the base station on the two paths respectively records the phase delay information of the other path, and exchanges the local time information of the base station by means of the synchronization signal transmitted between the base stations, thereby realizing the global synchronization of the system carrier. After the system carrier realizes global synchronization, each base station subtracts the phase of the uplink signal from the phase after synchronization. This difference is used as the phase of the downlink signal, and the frequency after synchronization is subtracted from the frequency of the uplink signal. This difference is used as the downlink. The frequency of the signal (the frequency after synchronization is approximately twice the frequency of the upstream signal), so that when the downlink signal arrives at the terminal, it is always synchronized. Compared with the traditional carrier synchronization method, the invention greatly reduces the synchronization overhead, and reduces the time slot required for synchronization from 2M-1 to M (where M is the number of source base stations), thereby increasing the effective communication time of the system.
图5示出了本发明提供的分布式波束合成系统的结构原理，为了便于描述，仅示出了与本发明相关的部分。图5仅以源端奇数个环形排列的基站为例进行描述，应当理解，其余偶数个环形排列的基站，以及奇、偶个线性排列的基站原理相同。 Fig. 5 shows the structural principle of the distributed beamforming system provided by the present invention, and for the convenience of description, only the parts related to the present invention are shown. FIG. 5 is only described by taking an example of a base station with an odd number of ring arrangements at the source end. It should be understood that the remaining even number of ring-shaped base stations, and odd and even linearly arranged base stations have the same principle.
参照图5，本分布式波束合成系统包括源端和目的端，源端具有多个基站BS1至BSM，每个基站仅覆盖其两侧相邻的基站。多个基站中包括同步信号产生基站BS1，同步信号产生基站BS1用于在第一时隙初始化同步信号并向其两侧相邻的基站广播同步信号；同步信号产生基站BS1与其最远的基站BS（M/2）+2之间具有两条信号传递路径，同步信号产生基站BS1的两侧相邻的基站BS2和BSM分别沿两条信号传递路径按照每个时隙传递一站的方式、将同步信号正向广播传递至中间基站BS（M/2）+2；而中间基站BS（M/2）+2用于将两条信号传递路径上传递过来的同步信号进行叠加，然后将叠加后的同步信号再分别沿两条信号传递路径逆向传递至同步信号产生基站BS1。Referring to FIG. 5, the distributed beamforming system includes a source end and a destination end, and the source end has a plurality of base stations BS 1 to BS M , and each base station covers only base stations adjacent to both sides thereof. The plurality of base stations including the base station generating a synchronization signal BS 1, the base station BS 1 generates a synchronization signal in a first time slot for synchronization initialization signal and on both sides thereof adjacent to the base station broadcasts a synchronization signal; generating a synchronization signal the base station BS 1 and its farthest There are two signal transmission paths between the base stations BS (M/2)+2 , and the base stations BS 2 and BS M adjacent to the two sides of the synchronization signal generating base station BS 1 are respectively transmitted along each of the two signal transmission paths. In one station mode, the synchronization signal is forwardly transmitted to the intermediate base station BS (M/2)+2 ; and the intermediate base station BS (M/2)+2 is used to transmit the synchronization signals transmitted on the two signal transmission paths. Superimposed, and then the superimposed synchronization signals are again reversely transmitted along the two signal transmission paths to the synchronization signal generating base station BS 1 .
在中间基站BS（M/2）+2及其两侧相邻的基站BS（M/2）+1和BS（M/2）+3中均包括一相位偏移量估算单元；相位偏移量估算单元用于在同步信号产生基站开始广播时，估算中间基站BS（M/2）+2及其两侧相邻的基站BS（M/2）+1和BS（M/2）+3之间的信道的相位偏移量；A phase offset estimation unit is included in the intermediate base station BS (M/2)+2 and its adjacent base stations BS (M/2)+1 and BS (M/2)+3 ; phase offset The quantity estimating unit is configured to estimate the intermediate base station BS (M/2)+2 and its adjacent base stations BS (M/2)+1 and BS (M/2)+3 when the synchronization signal generating base station starts broadcasting. The phase offset of the channel between;
每个基站中均包括一第一载波信息估算单元、第二载波信息估算单元和同步信息计算单元；第一载波信息估算单元用于在整个正向广播传递过程中，每个基站均根据接收到的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第一载波估算信息；第二载波信息估算单元用于在整个逆向广播传递过程中，每个基站均根据接收到的叠加后的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息；距离同步信号产生基站BS1最远的基站BS（M/2）+2的两侧的基站BS（M/2）+1和BS（M/2）+3中的同步信息计算单元用于根据第一载波估算信息、第二载波估算信息、相位偏移量来计算同步后的载波信息，其余基站中的同步信息计算单元根据第一载波估算信息、第二载波估算信息来计算同步后的载波信息。Each base station includes a first carrier information estimating unit, a second carrier information estimating unit, and a synchronization information calculating unit; the first carrier information estimating unit is configured to receive each base station according to the received forward broadcast transmission process. The synchronization signal performs carrier information estimation to obtain respective first carrier estimation information including carrier frequency and phase information; and the second carrier information estimating unit is configured to perform, in the entire reverse broadcast transmission process, each base station according to the received superposition the synchronization signal information to estimate the carrier, to obtain the respective second carrier information comprises carrier frequency and the estimated phase information; generating a base station BS the base station BS farthest sides. 1 (M / 2) +2 a synchronization signal from the base station BS ( The synchronization information calculation unit in M/2)+1 and BS (M/2)+3 is configured to calculate the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and the remaining base stations The synchronization information calculation unit in the calculation calculates the synchronized carrier information based on the first carrier estimation information and the second carrier estimation information.
进一步地，源端的多个基站可形成一闭环结构，同步信号产生基站为闭环结构中的任意一个基站。当源端的基站个数为奇数时，在第一时隙，中间基站BS（M/2）+2的两侧相邻基站BS（M/2）+1和BS（M/2）+3中的相位偏移量估算单元，分别估算与中间基站BS（M/2）+2之间的信道的相位偏移量。当源端的基站个数为偶数时，在第一时隙，中间基站BS（M/2）+2的两侧相邻基站BS（M/2）+1和BS（M/2）+3中的相位偏移量估算单元，分别估算与中间基站之间的信道的相位偏移量；在第二时隙，中间基站BS（M/2）+2中的相位偏移量估算单元估算其与一侧的相邻基站BS（M/2）+1和BS（M/2）+3之间的信道的相位偏移量；在逆向广播传递的最后一个时隙，中间基站中的相位偏移量估算单元估算其与另一侧的相邻基站之间的信道的相位偏移量。Further, the plurality of base stations at the source end may form a closed loop structure, and the synchronization signal generation base station is any one of the closed loop structures. When the number of base stations at the source end is an odd number, in the first time slot, the neighboring base stations BS (M/2)+1 and BS (M/2)+3 on both sides of the intermediate base station BS (M/2)+2 The phase offset estimation unit estimates the phase offset of the channel with the intermediate base station BS (M/2)+2 , respectively. When the number of base stations at the source end is even, in the first time slot, the neighboring base stations BS (M/2)+1 and BS (M/2)+3 on both sides of the intermediate base station BS (M/2)+2 a phase offset estimation unit that estimates a phase offset of the channel with the intermediate base station; and a second phase slot, the phase offset estimation unit in the intermediate base station BS (M/2)+2 estimates the The phase offset of the channel between the adjacent base stations BS (M/2)+1 and BS (M/2)+3 on one side; the phase offset in the intermediate base station in the last time slot of the reverse broadcast transmission The quantity estimating unit estimates the phase offset of the channel between it and the neighboring base station on the other side.
进一步地，源端的多个基站可形成一线性结构，同步信号产生基站为线性结构的两端的基站；在第一时隙，中间基站BS（M/2）+2的两侧相邻基站BS（M/2）+1和BS（M/2）+3中的相位偏移量估算单元，分别估算与中间基站之间的信道的相位偏移量。Further, the plurality of base stations at the source end may form a linear structure, and the synchronization signal generates base stations at both ends of the linear structure of the base station; in the first time slot, the adjacent base stations BS on both sides of the intermediate base station BS (M/2)+2 ( The phase shift amount estimating unit in M/2)+1 and BS (M/2)+3 estimates the phase shift amount of the channel with the intermediate base station, respectively.
进一步地，当源端的基站个数为奇数时，中间基站BS（M/2）+2的两侧相邻基站BS（M/2）+1和BS（M/2）+3分别在两个不同时隙进行同步信号的广播传递。Further, when the number of base stations at the source end is an odd number, the adjacent base stations BS (M/2)+1 and BS (M/2)+3 of the intermediate base station BS (M/2)+2 are respectively in two The broadcast transmission of the synchronization signal is performed in different time slots.
进一步地，所有基站中的同步信息计算单元用于将第一载波估算信息中的频率和第二载波估算信息中的频率相加作为同步后的载波频率，将第一载波估算信息中的相位和第二载波估算信息中的相位相加作为同步后的载波频率。 Further, the synchronization information calculation unit in all the base stations is configured to add the frequency in the first carrier estimation information and the frequency in the second carrier estimation information as the synchronized carrier frequency, and compare the phase in the first carrier estimation information. The phase addition in the second carrier estimation information is used as the carrier frequency after synchronization.
本发明适用于无线通信技术领域，特别是涉及分布式时分双工系统、多小区通信系统、协作通信系统、分布式adhoc/mesh网络等的载波同步。 The present invention is applicable to the field of wireless communication technologies, and in particular, to carrier synchronization of a distributed time division duplex system, a multi-cell communication system, a cooperative communication system, a distributed adhoc/mesh network, and the like.
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。 The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims (12)

  1. 一种分布式波束合成系统的源端各发送天线的载波同步方法，其特征在于，所述分布式波束合成系统包括源端和目的端，所述源端具有多个基站，每个基站仅覆盖其两侧相邻的基站，所述多个基站中包括同步信号产生基站；所述载波同步方法包括下述步骤：A carrier synchronization method for each transmitting antenna at a source end of a distributed beamforming system, characterized in that the distributed beamforming system includes a source end and a destination end, the source end has a plurality of base stations, and each base station only covers a base station adjacent to both sides thereof, wherein the plurality of base stations include a synchronization signal generating base station; and the carrier synchronization method includes the following steps:
    步骤A，同步信号产生基站在第一时隙初始化同步信号并向其两侧相邻的基站广播所述同步信号，同时中间基站估算与其两侧相邻基站之间的信道的相位偏移量；所述中间基站为距离所述同步信号产生基站最远的基站；Step A: The synchronization signal generation base station initializes the synchronization signal in the first time slot and broadcasts the synchronization signal to the base stations adjacent to both sides thereof, and the intermediate base station estimates the phase offset of the channel between the adjacent base stations on both sides; The intermediate base station is a base station that is farthest from the base station of the synchronization signal generating base station;
    步骤B，所述同步信号产生基站与中间基站之间具有两条信号传递路径，所述同步信号产生基站的两侧相邻的基站分别沿所述两条信号传递路径按照每个时隙传递一站的方式、将所述同步信号正向广播传递至中间基站，并且在整个正向广播传递过程中，与同步信号传递路径相同方向上的每个基站均根据接收到的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第一载波估算信息；Step B, the synchronization signal generating base station and the intermediate base station have two signal transmission paths, and the synchronization signal generation base stations adjacent to the two sides of the base station respectively transmit one time along each of the two signal transmission paths according to the two signal transmission paths. In the manner of the station, the synchronization signal is forwardly broadcasted to the intermediate base station, and during the entire forward broadcast transmission, each base station in the same direction as the synchronization signal transmission path performs carrier information estimation according to the received synchronization signal. Obtaining respective first carrier estimation information including carrier frequency and phase information;
    步骤C，中间基站将所述两条信号传递路径上传递过来的同步信号进行叠加，然后将叠加后的同步信号再分别沿所述两条信号传递路径逆向传递,中间基站两侧相邻的基站从所述叠加后的同步信号中提取出对方路径传递过来的信号,并根据所提取的信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息;然后中间基站两侧相邻的基站将提取的信号逆向传递至所述同步信号产生基站,传递过程中与同步信号传递路径相同方向上的每个基站均根据接收到的提取信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息； Step C: The intermediate base station superimposes the synchronization signals transmitted on the two signal transmission paths, and then reversely transmits the superposed synchronization signals along the two signal transmission paths respectively, and the adjacent base stations on both sides of the intermediate base station Extracting, by the superimposed synchronization signal, a signal transmitted by the path of the opposite party, and performing carrier information estimation according to the extracted signal, to obtain respective second carrier estimation information including carrier frequency and phase information; and then both sides of the intermediate base station The neighboring base station reversely transmits the extracted signal to the synchronization signal generating base station, and each base station in the same direction as the synchronization signal transmission path in the transmission process performs carrier information estimation according to the received extracted signal, and obtains respective carrier-containing carriers. Second carrier estimation information of frequency and phase information;
    步骤D，中间基站两侧的基站根据所述第一载波估算信息、第二载波估算信息、所述相位偏移量来计算同步后的载波信息，其余基站根据所述第一载波估算信息、第二载波估算信息来计算同步后的载波信息。Step D: The base station on both sides of the intermediate base station calculates the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and the remaining base stations estimate information according to the first carrier, The two carrier estimation information is used to calculate the synchronized carrier information.
  2. 如权利要求1所述的载波同步方法，其特征在于，所述源端的多个基站可形成一闭环结构，所述同步信号产生基站为闭环结构中的任意一个基站；The carrier synchronization method according to claim 1, wherein the plurality of base stations at the source end form a closed loop structure, and the synchronization signal generation base station is any one of the closed loop structures;
    当源端的基站个数为奇数时，步骤A具体包括以下步骤：步骤A1，在第一时隙，中间基站的两侧相邻基站，分别估算与中间基站之间的信道的相位偏移量；When the number of base stations at the source end is an odd number, step A specifically includes the following steps: Step A1, in the first time slot, neighboring base stations on both sides of the intermediate base station, respectively estimating a phase offset of the channel between the intermediate base station and the intermediate base station;
    当源端的基站个数为偶数时，步骤A具体包括以下步骤：步骤A2，在第一时隙，中间基站的两侧相邻基站，分别估算与中间基站之间的信道的相位偏移量；在第二时隙，中间基站估算其与一侧的相邻基站之间的信道的相位偏移量；在所述逆向广播传递的最后一个时隙，中间基站估算其与另一侧的相邻基站之间的信道的相位偏移量。When the number of base stations at the source end is even, step A specifically includes the following steps: Step A2, in the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station; In the second time slot, the intermediate base station estimates the phase offset of the channel between it and the neighboring base station on one side; in the last time slot of the reverse broadcast transmission, the intermediate base station estimates its neighboring relationship with the other side The phase offset of the channel between the base stations.
  3. 如权利要求1所述的载波同步方法，其特征在于，所述源端的多个基站可形成一线性结构，所述同步信号产生基站为线性结构的两端的基站；The carrier synchronization method according to claim 1, wherein the plurality of base stations at the source end form a linear structure, and the synchronization signal generates a base station whose base stations are both ends of a linear structure;
    步骤A具体包括以下步骤：步骤A3，在第一时隙，中间基站的两侧相邻基站，分别估算与中间基站之间的信道的相位偏移量。Step A specifically includes the following steps: Step A3, in the first time slot, the neighboring base stations on both sides of the intermediate base station respectively estimate the phase offset of the channel with the intermediate base station.
  4. 如权利要求3所述的载波同步方法，其特征在于，当源端的基站个数为奇数时，中间基站的两侧相邻基站分别在两个不同时隙进行同步信号的广播传递。The carrier synchronization method according to claim 3, wherein when the number of base stations at the source end is an odd number, the neighboring base stations on both sides of the intermediate base station respectively perform broadcast transmission of the synchronization signal in two different time slots.
  5. 如权利要求1所述的载波同步方法，其特征在于，所述步骤C包括下述步骤C1或C2： The carrier synchronization method according to claim 1, wherein said step C comprises the following steps C1 or C2:
    步骤C1，当源端基站个数为奇数时，对于中间基站两侧相邻的基站中的一个，在接收到中间基站发送过来的叠加后的同步信号后，将所述叠加后的同步信号作为被减数、延迟了2倍所述相位偏移量的上一时隙接收到的信号作为减数做差，然后根据差值进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息；Step C1: When the number of source base stations is an odd number, after receiving the superimposed synchronization signal sent by the intermediate base station, receiving the superimposed synchronization signal as one of the adjacent base stations on both sides of the intermediate base station The signal received in the previous time slot which is reduced by 2 times the phase offset is used as a subtraction difference, and then the carrier information is estimated according to the difference, and the respective second carrier including the carrier frequency and phase information is obtained. Estimated information;
    步骤C2，当源端基站个数为偶数时，对于中间基站两侧相邻的基站中的一个，在接收到中间基站发送过来的叠加后的同步信号后，将所述叠加后的同步信号作为被减数、延迟了2倍所述相位偏移量的上一时隙接收到的信号作为减数做差，然后根据差值进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息；然后中间基站两侧相邻的基站把各自提取处理后的信号分开不同时隙广播出去，中间基站对此时接收到的两个提取的信号进行载波信息估算得到两个相位估算值和两个频率估算值，利用两个相位估算值分别减去对应的所述相位偏移量作为其第一和第二载波相位估算信息，频率估算值为第一和第二载波频率估算信息。Step C2: When the number of the source base stations is an even number, after receiving the superimposed synchronization signal sent by the intermediate base station, receiving the superimposed synchronization signal as one of the adjacent base stations on both sides of the intermediate base station The signal received in the previous time slot which is reduced by 2 times the phase offset is used as a subtraction difference, and then the carrier information is estimated according to the difference, and the respective second carrier including the carrier frequency and phase information is obtained. Estimating the information; then the neighboring base stations on both sides of the intermediate base station broadcast the respective extracted signals separately in different time slots, and the intermediate base station estimates the carrier information for the two extracted signals received at this time to obtain two phase estimation values and The two frequency estimates are obtained by subtracting the corresponding phase offsets from the two phase estimates as their first and second carrier phase estimation information, and the frequency estimation values are first and second carrier frequency estimation information.
  6. 如权利要求1所述的载波同步方法，其特征在于，所述步骤D具体包括以下步骤：The carrier synchronization method according to claim 1, wherein the step D specifically comprises the following steps:
    步骤D1，所有基站将所述第一载波估算信息中的频率和第二载波估算信息中的频率相加作为同步后的载波频率，将所述第一载波估算信息中的相位和第二载波估算信息中的相位相加作为同步后的载波频率。Step D1: All base stations add the frequency in the first carrier estimation information and the frequency in the second carrier estimation information as the synchronized carrier frequency, and estimate the phase and the second carrier in the first carrier estimation information. The phase in the information is added as the carrier frequency after synchronization.
  7. 一种分布式波束合成系统，包括源端和目的端，所述源端具有多个基站，每个基站仅覆盖其两侧相邻的基站；其特征在于：A distributed beamforming system includes a source end and a destination end, the source end having a plurality of base stations, each base station covering only base stations adjacent to both sides thereof;
    所述多个基站中包括同步信号产生基站，所述同步信号产生基站用于在第一时隙初始化同步信号并向其两侧相邻的基站广播所述同步信号；所述同步信号产生基站与中间基站之间具有两条信号传递路径，所述中间基站为距离所述同步信号产生基站最远的基站；所述同步信号产生基站的两侧相邻的基站分别沿所述两条信号传递路径按照每个时隙传递一站的方式、将所述同步信号正向广播传递至中间基站；而中间基站用于将所述两条信号传递路径上传递过来的同步信号进行叠加，然后将叠加后的同步信号再分别沿所述两条信号传递路径逆向传递至所述同步信号产生基站；The plurality of base stations include a synchronization signal generating base station, and the synchronization signal generating base station is configured to initialize a synchronization signal in a first time slot and broadcast the synchronization signal to a base station adjacent to both sides thereof; the synchronization signal generates a base station and There are two signal transmission paths between the intermediate base stations, and the intermediate base station is the base station farthest from the base station of the synchronization signal generation; the synchronization signal generation base stations adjacent to the two sides of the base station respectively follow the two signal transmission paths And transmitting the synchronization signal forward to the intermediate base station in a manner of transmitting one station per time slot; and the intermediate base station is configured to superimpose the synchronization signals transmitted on the two signal transmission paths, and then superimposing The synchronization signal is further reversely transmitted along the two signal transmission paths to the synchronization signal generating base station;
    在中间基站及其两侧相邻的基站中均包括一相位偏移量估算单元；所述相位偏移量估算单元用于在所述同步信号产生基站开始广播时，估算中间基站与其两侧相邻基站之间的信道的相位偏移量；A phase offset estimation unit is included in the intermediate base station and adjacent base stations on both sides thereof; and the phase offset estimation unit is configured to estimate the intermediate base station and the two sides thereof when the synchronization signal generation base station starts broadcasting The phase offset of the channel between the neighboring base stations;
    每个基站中均包括一第一载波信息估算单元、第二载波信息估算单元和同步信息计算单元；所述第一载波信息估算单元用于在整个正向广播传递过程中，与同步信号传递路径相同方向上的每个基站均根据接收到的同步信号进行载波信息估算，得到各自的包含载波频率和相位信息的第一载波估算信息；中间基站两侧相邻的基站中的第二载波信息估算单元用于从所述叠加后的同步信号中提取出对方路径传递过来的信号,并根据所提取的信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息;然后中间基站两侧相邻的基站将提取的信号逆向传递至所述同步信号产生基站,传递过程中与同步信号传递路径相同方向上的每个基站均根据接收到的提取信号进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息； Each base station includes a first carrier information estimating unit, a second carrier information estimating unit, and a synchronization information calculating unit; the first carrier information estimating unit is configured to transmit a path with the synchronization signal during the entire forward broadcast transmission process. Each base station in the same direction performs carrier information estimation according to the received synchronization signal, and obtains respective first carrier estimation information including carrier frequency and phase information; second carrier information estimation in adjacent base stations on both sides of the intermediate base station The unit is configured to extract, from the superposed synchronization signal, a signal transmitted by the path of the opposite party, and perform carrier information estimation according to the extracted signal to obtain respective second carrier estimation information including carrier frequency and phase information; The base stations adjacent to the two sides of the base station reversely transmit the extracted signals to the synchronization signal generating base station, and each base station in the same direction as the synchronization signal transmission path in the transmission process performs carrier information estimation according to the received extracted signals, and obtains respective signals. Second carrier estimation information including carrier frequency and phase information;
    中间基站两侧的基站中的同步信息计算单元用于根据所述第一载波估算信息、第二载波估算信息、所述相位偏移量来计算同步后的载波信息，其余基站中的同步信息计算单元根据所述第一载波估算信息、第二载波估算信息来计算同步后的载波信息。The synchronization information calculation unit in the base station on both sides of the intermediate base station is configured to calculate the synchronized carrier information according to the first carrier estimation information, the second carrier estimation information, and the phase offset amount, and calculate synchronization information in the remaining base stations. The unit calculates the synchronized carrier information according to the first carrier estimation information and the second carrier estimation information.
  8. 如权利要求7所述的分布式波束合成系统，其特征在于，所述源端的多个基站可形成一闭环结构，所述同步信号产生基站为闭环结构中的任意一个基站；The distributed beamforming system according to claim 7, wherein the plurality of base stations at the source end form a closed loop structure, and the synchronization signal generating base station is any one of the closed loop structures;
    当源端的基站个数为奇数时，在第一时隙，中间基站的两侧相邻基站中的相位偏移量估算单元，分别估算与中间基站之间的信道的相位偏移量；When the number of base stations at the source end is an odd number, in the first time slot, the phase offset estimation unit in the neighboring base stations on both sides of the intermediate base station respectively estimates the phase offset of the channel with the intermediate base station;
    当源端的基站个数为偶数时，在第一时隙，中间基站的两侧相邻基站中的相位偏移量估算单元，分别估算与中间基站之间的信道的相位偏移量；在第二时隙，中间基站中的相位偏移量估算单元估算其与一侧的相邻基站之间的信道的相位偏移量；在所述逆向广播传递的最后一个时隙，中间基站中的相位偏移量估算单元估算其与另一侧的相邻基站之间的信道的相位偏移量。When the number of base stations at the source end is even, in the first time slot, the phase offset estimation unit in the neighboring base stations on both sides of the intermediate base station respectively estimates the phase offset of the channel with the intermediate base station; a second time slot, the phase offset estimation unit in the intermediate base station estimates a phase offset of the channel between the adjacent base station and one of the adjacent base stations; the phase in the intermediate base station in the last time slot of the reverse broadcast transmission The offset estimation unit estimates the phase offset of the channel between it and the neighboring base station on the other side.
  9. 如权利要求7所述的分布式波束合成系统，其特征在于，所述源端的多个基站可形成一线性结构，所述同步信号产生基站为线性结构的两端的基站；The distributed beamforming system according to claim 7, wherein the plurality of base stations at the source end form a linear structure, and the synchronization signal generates base stations at both ends of the linear structure;
    在第一时隙，中间基站的两侧相邻基站中的相位偏移量估算单元，分别估算与中间基站之间的信道的相位偏移量。In the first time slot, the phase offset estimation unit in the adjacent base stations on both sides of the intermediate base station estimates the phase offset of the channel with the intermediate base station, respectively.
  10. 如权利要求9所述的分布式波束合成系统，其特征在于，当源端的基站个数为奇数时，中间基站的两侧相邻基站分别在两个不同时隙进行同步信号的广播传递。The distributed beamforming system according to claim 9, wherein when the number of base stations at the source end is an odd number, the neighboring base stations on both sides of the intermediate base station respectively perform broadcast transmission of the synchronization signal in two different time slots.
  11. 如权利要求7所述的分布式波束合成系统，其特征在于，当源端基站个数为奇数时，对于中间基站两侧相邻的基站中的一个之中的第二载波信息估算单元，用于在接收到中间基站发送过来的叠加后的同步信号后，将所述叠加后的同步信号作为被减数、延迟了2倍所述相位偏移量的上一时隙接收到的信号作为减数做差，然后根据差值进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息；The distributed beamforming system according to claim 7, wherein when the number of source base stations is an odd number, for the second carrier information estimating unit of one of the adjacent base stations on both sides of the intermediate base station, After receiving the superimposed synchronization signal transmitted by the intermediate base station, the superimposed synchronization signal is used as a subtraction signal as a subtraction and a signal received in the previous time slot delayed by 2 times the phase offset. Making a difference, and then performing carrier information estimation according to the difference, and obtaining respective second carrier estimation information including carrier frequency and phase information;
    当源端基站个数为偶数时，对于中间基站两侧相邻的基站中的一个之中的第二载波信息估算单元，用于在接收到中间基站发送过来的叠加后的同步信号后，将所述叠加后的同步信号作为被减数、延迟了2倍所述相位偏移量的上一时隙接收到的信号作为减数做差，然后根据差值进行载波信息估算，得到各自的包含载波频率和相位信息的第二载波估算信息；然后中间基站两侧相邻的基站把各自提取处理后的信号分开不同时隙广播出去，中间基站对此时接收到的两个提取的信号进行载波信息估算得到两个相位估算值和两个频率估算值，利用两个相位估算值分别减去对应的所述相位偏移量作为其第一和第二载波相位估算信息，频率估算值为第一和第二载波频率估算信息。When the number of the source base stations is an even number, the second carrier information estimating unit of one of the neighboring base stations on both sides of the intermediate base station is configured to: after receiving the superimposed synchronization signal sent by the intermediate base station, The superimposed synchronization signal is used as a subtraction as a subtraction, and a signal received in the previous time slot delayed by 2 times the phase offset is used as a subtraction, and then the carrier information is estimated according to the difference, and the respective carrier signals are obtained. The second carrier estimation information of the frequency and phase information; then the neighboring base stations on both sides of the intermediate base station broadcast the respective extracted signals separately in different time slots, and the intermediate base station performs carrier information on the two extracted signals received at this time. Estimating two phase estimation values and two frequency estimation values, respectively subtracting the corresponding phase offset amount as the first and second carrier phase estimation information by using the two phase estimation values, and the frequency estimation value is the first sum. Second carrier frequency estimation information.
  12. 如权利要求7所述的分布式波束合成系统，其特征在于：所有基站将所述第一载波估算信息中的频率和第二载波估算信息中的频率相加作为同步后的载波频率，将所述第一载波估算信息中的相位和第二载波估算信息中的相位相加作为同步后的载波频率。The distributed beamforming system according to claim 7, wherein all base stations add the frequency in the first carrier estimation information and the frequency in the second carrier estimation information as the synchronized carrier frequency, The phase in the first carrier estimation information and the phase in the second carrier estimation information are added as the synchronized carrier frequency.
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