WO2003036836A1 - Procede et dispositif de capture de synchronisation par abaissement dans le systeme de communication amrc - Google Patents

Procede et dispositif de capture de synchronisation par abaissement dans le systeme de communication amrc Download PDF

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Publication number
WO2003036836A1
WO2003036836A1 PCT/CN2001/001486 CN0101486W WO03036836A1 WO 2003036836 A1 WO2003036836 A1 WO 2003036836A1 CN 0101486 W CN0101486 W CN 0101486W WO 03036836 A1 WO03036836 A1 WO 03036836A1
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WO
WIPO (PCT)
Prior art keywords
synchronization
signal
code
preamble sequence
frame
Prior art date
Application number
PCT/CN2001/001486
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English (en)
Chinese (zh)
Inventor
Chen Ji
Daoben Li
Yongsheng Zhang
Liwen Shi
Original Assignee
Linkair Communications,Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Linkair Communications,Inc. filed Critical Linkair Communications,Inc.
Priority to PCT/CN2001/001486 priority Critical patent/WO2003036836A1/fr
Priority to CNA018228577A priority patent/CN1493124A/zh
Publication of WO2003036836A1 publication Critical patent/WO2003036836A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7075—Synchronisation aspects with code phase acquisition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0007—Code type
    • H04J13/004—Orthogonal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
    • H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
    • H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
    • H04B2201/70701—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation featuring pilot assisted reception

Definitions

  • the present invention relates to the technical field of wireless spread spectrum communication and the technical field of digital mobile communication, and in particular, to a method and an apparatus for downlink synchronization acquisition in a wireless spread spectrum communication system. Background of the invention
  • CDMA technology is being widely used in wireless communication systems. Because of its unique advantages such as large capacity, soft capacity, soft handover, high voice quality and low transmit power, as well as anti-interference and privacy, CDMA systems have developed rapidly and become the technology of choice for third-generation cellular communication systems.
  • CDMA is a modulation and multiple access technology based on spread-spectrum communications.
  • signals used by different users to transmit information are not distinguished by different frequencies or time slots, but by different coding sequences.
  • the receiver correlator can select a signal using a predetermined pattern among a plurality of CDMA signals. Other signals using different code patterns cannot be demodulated because they are different from the code patterns generated locally by the receiver.
  • a base station transmitter or a mobile station transmitter uses a spreading code to spread the digital information
  • the receiving device uses a local spreading code to despread the spread spectrum signal to find useful information.
  • Synchronization means that the local spreading code and the received spreading code are completely consistent in structure, frequency, and phase.
  • a CDMA system is unique to spreading code synchronization. Therefore, the synchronization problem of the spread spectrum system is more complicated than the general digital communication system.
  • a clock source with high accuracy and stability is used in the transmitter and receiver. Many frequency and phase instabilities can be removed. However, objectively, there are many uncertain factors that cannot be estimated in advance, especially in mobile communications. These uncertain factors are random and cannot be compensated in advance. They can only be eliminated by a synchronous system. Therefore, the synchronization system is indispensable and very important in the CDMA system.
  • the synchronization of the spreading code is divided into two steps: First, capturing, that is, coarsely adjusting the frequency and phase of the local spreading code, so that the phase difference between the local spreading code and the receiving spreading code is less than one symbol width Tc.
  • the second is tracking, which automatically adjusts the phase of the local spreading code to accurately synchronize the frequency and phase of the received spreading code. Therefore, as the transmission rate requirements for digital mobile communication systems become higher and higher, and the capacity becomes larger, the requirements for synchronization accuracy become higher and higher.
  • the bit synchronization, chip synchronization, symbol synchronization, and frame synchronization of the system must be guaranteed to achieve the despreading of the spread spectrum signal and the correct reception and processing of the signal.
  • a spread spectrum multiple address code coding technology a coding method for a spread spectrum multiple access code is disclosed.
  • the frequency code has good auto-correlation and cross-correlation characteristics.
  • a spreading code is simply referred to as a LA code.
  • the LA code consists of polarized basic pulses with a normalized amplitude and width of 1.
  • the number of basic pulses depends on the number of users required.
  • the actual factors such as the number of orthogonal pulse compression codes used, the number of orthogonal frequencies that can be used, the system bandwidth, and the maximum signal transmission rate of the system are determined.
  • the intervals of the basic pulses on the time coordinate are different and different.
  • the pulse positions and pulse polarities are arranged and coded at different intervals. Taking the above design, it provides a clear and fast design method for the spread spectrum address code for the spread spectrum technology and digital multiple access technology.
  • the characteristics of this LA code are: first: the main peaks of the autocorrelation function are equal to the number of basic pulses, and also the number of orthogonal codewords in the code group; second: the subpeaks of the autocorrelation and cross-correlation functions are only + 1 ,-1 and 0 are three possible values.
  • the LA code can be used to identify different cells. The description about the encoding method of the spread spectrum multiple access code is omitted here, and the document is incorporated herein by reference.
  • the inventor Li Daoben and the invention name "A Spread Spectrum Multiple Access Coding Method with Zero Correlation Window", a spread spectrum
  • the address code is called the LS code. Since the LS code is composed of the C code and the S code, it is also called the CS code.
  • the method for generating the LS code (CS code) is described in detail in PCT / CN00 / 00028. be omitted.
  • the designed spread-spectrum multi-address code with "zero correlation window" has the following two characteristics: First: The auto-correlation function of each spread-spectrum address code is zero except for the origin, that is, it has the most ideal characteristics.
  • each spreading address code is completely orthogonal to any non-zero delay except for the zero delay.
  • the cross-correlation function between spread-spectrum address codes has a "zero correlation window" near the origin. From the perspective of orthogonality, the relative delay between the spreading address codes is completely orthogonal when the relative delay is smaller than the width of the "zero correlation window".
  • the above-mentioned method for generating the LS code is a method for designing a spread spectrum address code, so that the correlation function of the newly formed spread spectrum address code forms a "no interference window (IFW)" near the origin, thereby making the corresponding bidirectional Synchronous CDMA systems do not have the fatal near-far effect in traditional CDMA systems, that is, there is no multiple-access interference (MAI) and inter-symbol interference (ISI), which lays the foundation for establishing a large-capacity wireless digital communication system.
  • MAI multiple-access interference
  • ISI inter-symbol interference
  • the multi-user interference and neighboring cell interference and the high-speed mobile fading environment in the mobile communication system increase the difficulty of synchronization. Therefore, there must be a high-precision synchronous capture method, which can quickly and accurately realize synchronous capture, and meet the requirements of the system.
  • downlink synchronization capture method mentioned in the application number PCT / CN00 / 00142 and the invention name "Downlink Synchronization Capture Method in Code Division Multiple Access System" is mainly through the use of broadcast channels and matched filtering. And sliding related technologies. The implementation of this method includes the following steps:
  • a broadcast channel is added to the downlink, and a unique code is placed in a fixed time slot in the broadcast channel frame; when the mobile station broadcast channel receiver detects the unique code, the frame positioning information can be determined.
  • the broadcast channel synchronization loop In order to overcome the influence of the multipath fading channel, the broadcast channel synchronization loop first finds the position of the energy concentration where the main peak of each symbol appears, and then determines the decision time of the broadcast channel receiver for each symbol according to the position. Correctly, when the unique code matching filter detects the unique code, it can give an accurate synchronization information.
  • an object of the present invention is to provide a new method and device for downlink synchronization capture in a code division multiple access communication system.
  • a downlink synchronization capture method in a commercial CDMA system based on a LA and LS spread-spectrum address coding method includes the following steps: Prefix the data segment with a fixed-length preamble sequence; choose different spreading code sequences that are as orthogonal to each other as possible for the preamble sequence and the traffic channel; execute the preamble sequence codeword on the baseband sampled signal at the receiver Matching filtering to obtain I and Q signals; calculate the signal energy value by performing a square operation on the I and Q signals; accumulate all the sampled values in the data length of a frame; take the largest value in the data length of a frame Sampling values, capturing the maximum energy correlation peak; and estimating the accurate arrival time of the preamble sequence based on the captured maximum energy correlation peak, thereby achieving forward chip synchronization and frame synchronization.
  • the invention also provides a device for performing downlink synchronization acquisition in a commercial CDMA communication system based on the LA and LS spread-spectrum address coding methods.
  • the device includes a matched filter for sampling the baseband at the receiving end.
  • the signal performs filtering that matches the preamble sequence code word to obtain I and Q signals; a device that calculates the signal energy value by performing a square operation on the I and Q signals; accumulates all of the data length of a frame Accumulation device of sampling values; a device that takes the maximum sampling value within one frame of data to capture the maximum energy-related peak; and the maximum energy-related peak that is captured to estimate the accurate arrival time of the pre-synchronization sequence to achieve forward Device for chip synchronization and frame synchronization.
  • the downlink synchronization capture method of the present invention is mainly realized by a matched filter using a preamble sequence.
  • the method adopted by the present invention is to add a fixed-length preamble sequence before a given length of data segment, and select a spreading code of the data segment and the preamble sequence to make the signal of the data segment and the preamble sequence as orthogonal as possible.
  • the maximum energy-related peak is captured through a matched filter of the pre-synchronization sequence, thereby achieving chip and frame synchronization capture.
  • FIG. 1 is a frame structure used for implementing the method of the present invention.
  • FIG. 2 is a schematic diagram of the overall signal processing of a synchronization capture device designed according to the method of the present invention.
  • FIG. 3 is a schematic diagram of a synchronization detection module for maximum correlation window of captured energy according to the present invention.
  • FIG. 4 is a schematic diagram of a preamble sequence designed according to the method of the present invention.
  • Figure 5 shows the auto-correlation and cross-correlation characteristics using the LS code as a preamble sequence according to the method of the present invention.
  • the frame structure includes a preamble sequence and a data segment sequence (0, the preamble sequence and the data segment sequence are time-multiplexed.
  • the preamble sequence ( ⁇ ) and the data segment signal (0
  • the preamble sequence and data segment signals can use different LS code group and LA code group, and ⁇ 0 has the autocorrelation characteristic of the impact form, which can also be achieved by LS code and LA code.
  • FIG. 2 the figure shows a schematic diagram of the overall signal processing of the synchronization capture device.
  • the parts before the synchronization detection device 207 are similar to the conventional spread-spectrum communication system. Those skilled in the art can easily understand that details will not be described again.
  • This synchronization capture device includes an analog down-converter 201, a band-pass filter 202, a digital-to-analog converter A / D203, a digital down-converter 204, a down-sampler 205, a matched filter 206, and a synchronization detection device 207.
  • the analog down conversion converter 201 down converts the received radio frequency signal RF into an intermediate frequency analog signal.
  • the output of the down-converter 201 is provided to a band-pass filter 202, which performs band-pass filtering on the input intermediate frequency analog signal, and the band-pass filtered intermediate frequency analog signal is provided to the analog A-to-digital converter A / D203 converts into a digital signal containing Nsl samples in each symbol, obtains the baseband signal through digital down-converting converter 204, and a downsampler 205 samples the input baseband signal so that each symbol With Ns2 samples, the sampling result is input to the matched filter 206 that matches the preamble sequence, and the I and Q values output by the matched filter 206 are sent to the synchronization detection device 207.
  • FIG. 3 shows a schematic diagram of a synchronization detection module of the present invention.
  • the received signal often contains several multipath delay components with different propagation delays and channel fading.
  • the capture energy is used in commercial CDMA systems based on the LA and LS spread-spectrum address coding methods. Method of maximum correlation window.
  • the I and Q channels are squared in the arithmetic unit 301, the signal energy values are calculated, and then N are performed in the module 302
  • the maximum value is taken within a frame of data length, and the position of the maximum value is determined. The determined maximum position is used to capture the maximum energy correlation window, thereby obtaining frame positioning information, and obtaining frame positioning. After that, an accurate phase of the spreading code can be obtained, and the signal despreading processing and timing tracking can be performed.
  • the downlink service channel of the data segment is superimposed on 32 independent code channels, and each code channel uses a 128-bit LS code. Therefore, a code sequence should be found in the preamble sequence in each cell, and the 32 LS codes used by the traffic channel should be as orthogonal to each other as possible.
  • the receiver performs matching filtering on the preamble sequences of different cells, and selects the one with the strongest energy as the correct selected cell. Therefore, the preamble sequences of neighboring cells should also have better mutual interaction.
  • the relevant characteristics are as orthogonal as possible to avoid interference between neighboring cell pre-synchronization sequences, so as to correctly extract synchronization information and perform cell selection.
  • the preamble sequences of different cells use different LA interval gaps and the preamble sequence codeword sequences constructed by the LA polarity, which have better autocorrelation and cross-correlation characteristics, and the presync structured in this way
  • the sequence and data segment downlink traffic channels also have good cross-correlation characteristics.
  • a method for constructing a preamble sequence using the LS + LA code in a LAS-CDMA system is given below in conjunction with FIG. 3 and FIG. 4.
  • the first symbol sequence This symbol sequence will be spread using a short LS code.
  • the gray area in the figure is the interval between two adjacent symbols. The interval is generated according to the LA arrangement.
  • FIG 4 is given in the structure of a short code LS, assume that the total code length of 81 ⁇ , pre-gap length interval I ⁇ C code length 2L 15 in spaced opposed gap length code length 2L 13 S ⁇ 21, rear spacer
  • the gap length is added to the code with a protective interval gap of the same length as the C code and the S code.
  • the purpose of the gap is to prevent the C code and the S code from colliding, thereby providing a zero correlation window as large as possible for auto-correlation and cross-correlation.
  • the zero correlation window is-2L1-2L1.
  • composition of LA Composition of LA:
  • the LA code can be regarded as a concatenation method of the LS code.
  • each cell uses the same LS code set, so different cells need to use different LAs to distinguish them.
  • the interval between two LA code spread symbols in a LA sequence is the LA interval Gap, and the sequence of the sequential LA interval Gap is called the LA array.
  • the selection of symbol, ... is called LA polarity.
  • LS + LA code preamble sequence with excellent auto-correlation and cross-correlation characteristics.
  • Figure 5 shows the auto-correlation and cross-correlation characteristics of 4 preamble synchronization sequences using 8 symbols in each of which a total of 43 chip long gap gaps are added between 32-bit LS code spreading symbols.
  • Tables 1 and 2 show the selection methods of the LA interval and LA polarity of the four preamble sequences, respectively.
  • the auto-correlation of the preamble sequence 1 and the cross-correlation characteristics with the preamble sequences 2, 3, and 4 are shown in order.
  • the chip amplitude is taken to be 1.
  • the maximum side peak amplitude of the auto-correlation and cross-correlation is 1/8 of the main peak of the auto-correlation, and the energy difference is about 18 dB.
  • the main peak can be easily distinguished, whether it is auto-correlation There is still cross correlation, and there are zero correlation windows of -2L1 _ 2L1.
  • Preamble sequences 2, 3, 4 have the same characteristics as sequence 1. Table 1: LA permutations
  • the transmission power of the preamble sequence can be increased to be equivalent to the signal power of the data channel service channel at full load.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Dans un système de communication mobile numérique, en particulier dans le système de communication AMRC, ce qui est le plus important est d'obtenir une synchronisation précise. Pour permettre la capture rapide et exacte d'une synchronisation de bribe et d'une synchronisation de trame, il est proposé, selon l'invention, d'utiliser un système qui capture la fenêtre de corrélation maximum d'énergie pour l'acquisition d'une information de synchronisation par insertion d'une séquence de synchronisation de préfixe. La présente invention concerne également un procédé de constitution de la séquence de synchronisation de préfixe dans le canal descendant multicellulaire du système AMRC commercial, fondé sur le mode impliquant le codage d'adresse et l'étalement du spectre LA et LS. Le récepteur utilise un filtre adapté au mot de code de séquence de synchronisation de préambule pour effectuer la capture de la synchronisation par abaissement.
PCT/CN2001/001486 2001-10-18 2001-10-18 Procede et dispositif de capture de synchronisation par abaissement dans le systeme de communication amrc WO2003036836A1 (fr)

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Application Number Priority Date Filing Date Title
PCT/CN2001/001486 WO2003036836A1 (fr) 2001-10-18 2001-10-18 Procede et dispositif de capture de synchronisation par abaissement dans le systeme de communication amrc
CNA018228577A CN1493124A (zh) 2001-10-18 2001-10-18 Cdma通信系统下行链路同步捕获方法和装置

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100372247C (zh) * 2004-04-26 2008-02-27 北京天碁科技有限公司 移动终端的下行同步监测装置与方法及其应用
CN107276708A (zh) * 2016-04-08 2017-10-20 深圳超级数据链技术有限公司 定时同步方法、装置和系统
CN116683983A (zh) * 2023-08-02 2023-09-01 北京融为科技有限公司 Tdma突发通信的捕获跟踪方法、装置及设备

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0832547A (ja) * 1994-07-20 1996-02-02 Oki Electric Ind Co Ltd 同期捕捉方法
EP0887946A2 (fr) * 1997-06-24 1998-12-30 Nec Corporation Circuit de capture synchrone pour communication à accès multiple par multiplexage de code
CN1260651A (zh) * 1998-12-08 2000-07-19 皇家菲利浦电子有限公司 接收机,cdma电信系统和接收机与这样系统的发送站的同步方法
US6160037A (en) * 1997-07-10 2000-12-12 Ciba Specialty Chemicals Corporation Reactive extrusion of latent pigments

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0832547A (ja) * 1994-07-20 1996-02-02 Oki Electric Ind Co Ltd 同期捕捉方法
EP0887946A2 (fr) * 1997-06-24 1998-12-30 Nec Corporation Circuit de capture synchrone pour communication à accès multiple par multiplexage de code
US6160037A (en) * 1997-07-10 2000-12-12 Ciba Specialty Chemicals Corporation Reactive extrusion of latent pigments
CN1260651A (zh) * 1998-12-08 2000-07-19 皇家菲利浦电子有限公司 接收机,cdma电信系统和接收机与这样系统的发送站的同步方法

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100372247C (zh) * 2004-04-26 2008-02-27 北京天碁科技有限公司 移动终端的下行同步监测装置与方法及其应用
CN107276708A (zh) * 2016-04-08 2017-10-20 深圳超级数据链技术有限公司 定时同步方法、装置和系统
CN107276708B (zh) * 2016-04-08 2020-01-07 深圳光启合众科技有限公司 定时同步方法、装置和系统
CN116683983A (zh) * 2023-08-02 2023-09-01 北京融为科技有限公司 Tdma突发通信的捕获跟踪方法、装置及设备
CN116683983B (zh) * 2023-08-02 2023-11-17 北京融为科技有限公司 Tdma突发通信的捕获跟踪方法、装置及设备

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