WO2006032191A1 - Procede d'etalement et de desetalement ameliorant les performances de synchronisation d'un systeme ofdm - Google Patents

Procede d'etalement et de desetalement ameliorant les performances de synchronisation d'un systeme ofdm Download PDF

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Publication number
WO2006032191A1
WO2006032191A1 PCT/CN2005/001481 CN2005001481W WO2006032191A1 WO 2006032191 A1 WO2006032191 A1 WO 2006032191A1 CN 2005001481 W CN2005001481 W CN 2005001481W WO 2006032191 A1 WO2006032191 A1 WO 2006032191A1
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WO
WIPO (PCT)
Prior art keywords
ofdm system
ofdm
code
orthogonal spreading
synchronization performance
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Application number
PCT/CN2005/001481
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English (en)
Chinese (zh)
Inventor
Yu Zhang
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Founder 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.)
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Publication of WO2006032191A1 publication Critical patent/WO2006032191A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0007—Code type
    • H04J13/0055—ZCZ [zero correlation zone]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0003—Code application, i.e. aspects relating to how codes are applied to form multiplexed channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/0007—Code type
    • H04J13/004—Orthogonal

Definitions

  • the present invention relates to a method for improving synchronization performance of an OFDM (Orthogonal Frequency Division Multiplexing) system by using an orthogonal spreading code having an Interference Free Window (IFW) characteristic, which belongs to mobile communication.
  • OFDM Orthogonal Frequency Division Multiplexing
  • IFN Interference Free Window
  • OFDM is a high-speed transmission technology in a wireless environment. It can meet both high-speed and anti-interference requirements. It not only greatly improves the frequency band utilization, provides higher data throughput, but also effectively suppresses multipath interference.
  • the field of high-speed mobile communication has great advantages. Therefore, it is widely estimated that OFDM technology will become one of the core technologies of the fourth generation mobile communication (4G).
  • FIG. 1 is a basic graph of a typical OFDM system.
  • the input data stream is transformed into a parallel low-speed data stream by serial/parallel conversion.
  • Each parallel data stream is separately modulated by a different carrier frequency.
  • OFDM technology has many advantages, it also has many technical difficulties to overcome in the specific implementation.
  • the most important technical difficulty is that the OFDM system is sensitive to carrier frequency deviation and phase noise, and the synchronization requirements are very high. This is because the deviation of the carrier frequency and the noise cause interference between the subchannels, so that the strict orthogonality between the subchannels by the OFDM technique cannot be satisfied. If each subchannel cannot be strictly orthogonal, strong inter-channel interference will occur, which will seriously degrade the performance of the entire OFDM system.
  • OFDM synchronization algorithms such as ESPRIT synchronization algorithm and ML estimation algorithm, are proposed.
  • these algorithms have their own advantages and disadvantages, and they cannot solve the problem fundamentally. And using these algorithms will undoubtedly increase the computational burden of the entire system.
  • zero-interference window also known as the zero-correlation window
  • the cross-correlation function is also ideal within a certain offset range (inside the window), that is, there is no peak at all. There is only a sparse peak outside the window, as shown in Figure 2.
  • the object of the present invention is to provide a spreading/de-spreading operation by using an orthogonal spreading code having a zero-interference window characteristic to form a zero-interference window arranged in frequency, thereby overcoming the adjacent A method of improving the synchronization performance of an OFDM system by mutual interference of orthogonal subcarriers.
  • a method for improving synchronization performance of an OFDM system characterized by:
  • the information symbols are spread using an orthogonal spreading code having a zero interference window characteristic; and then the information symbol is despread by the orthogonal spreading code at the receiving end.
  • the acyclic autocorrelation sequence and the acyclic cross-correlation sequence of the orthogonal spreading code have at least one zero correlation window within a certain range of displacement.
  • the orthogonal spreading code is a LAS code.
  • the orthogonal spreading code is a CCK code.
  • the transmission information is encoded into at least one group, and each group is segmented according to the number of modulation bits of one OFDM subcarrier, and the bit constellation required for each segment is modulated according to the OFDM subcarrier. Mapping rules are mapped to complex symbols.
  • each group of user information is separately encoded, and each group of user information is segmented according to the number of modulation bits of one OFDM subcarrier, and each segment is based on an OFDM sub
  • the bit constellation mapping rules required for carrier modulation are mapped to complex symbols.
  • all data subcarriers in the OFDM are grouped, the number of subcarriers in each group is the length of the orthogonal spreading code, and the subcarriers in the same group are adjacent in frequency. .
  • frequency domain equalization processing is first performed, and despreading processing is performed by using the orthogonal spreading code.
  • the frequency domain equalization processing may adopt a pilot subcarrier method used by an OFDM system, or may use a FSm codeword in a CDMA system as a pilot channel for channel estimation and compensation.
  • the invention utilizes orthogonal spreading codes with zero interference window characteristics to improve OFDM system
  • the step performance method makes full use of the zero-interference window characteristic of the specific orthogonal spreading code, effectively overcomes the influence of carrier frequency offset, noise and other factors on the synchronization performance of the OFDM system, and lays a foundation for the popularization and application of the OFDM system. basis.
  • the method further broadens the application range of the orthogonal spreading code with zero interference window characteristics.
  • FIG. 1 is a basic structural diagram of a typical OFDM system in the prior art.
  • Figure 2 is a schematic diagram of the correlation function of the LAS-CDMA address code, showing the zero-interference window provided by the orthogonal spreading code.
  • FIG. 3 is a schematic diagram of a spread spectrum modulation process at a transmitting end in an OFDM system employing the method of the present invention.
  • FIG. 4 is a schematic diagram of a despreading process at the receiving end in an OFDM system employing the method of the present invention.
  • Figure 5 is a block diagram showing the structure of a system simulation station for verifying the performance of the method of the present invention.
  • orthogonal spread spectrum codes having zero interference window characteristics are commonly used in two types of LAS codes and CCK codes.
  • the LAS code is first proposed by Mr. Li Daoben in the invention entitled "A Spread Spectrum Multiple Access Coding Method with Zero Correlation Window" under the patent number ZL 00801970. 3, and is used as a coding scheme for the LAS-CDMA system.
  • the LAS code is composed of an LS code and an LA code, wherein the LS code is a basic multi-user access sequence family, and the LA family functions to expand the number of access sequence families.
  • the LS code is synthesized by the C code and the S code.
  • the C code and the S code have the same autocorrelation peak and complementary extra peak characteristics.
  • the LS code formed after synthesis is all zeros outside the autocorrelation peak, LS
  • the cross-correlation between sequences in the code family is all zero.
  • the LA code is a three-level code, which is composed of an orthogonal code having L orthogonal spreading codes (taking + 1 and a 1 value), and then inserting a string of 0s of different lengths between the respective symbols. .
  • the LAS code composed of the LS code and the LA code composite has a zero correlation window characteristic, and the width of the zero correlation window can be pre-designed.
  • CCK code complementary code keying
  • LAS code complementary code keying
  • CCK code complementary code keying
  • the zero correlation window characteristic of LAS code is better than CCK code, because its zero correlation window is not only a large number, but also the width is controllable.
  • the most important thing is that the number of code words satisfying the zero correlation window condition is much larger than the CCK code. This has a direct meaning for the actual application, that is, to ensure that the number of available users or the user's data transmission rate is much larger than the CCK code, so in the following specific embodiments, the orthogonal expansion with zero correlation window characteristics
  • the frequency code is taken as an example of the LAS code.
  • the arrangement of the zero correlation window in the frequency domain can overcome the mutual interference of adjacent subcarriers, thereby improving the synchronization performance of the OFDM system. This is the basic principle of the method of the invention.
  • the method of the present invention firstly spreads the information symbol with a CDMA orthogonal spreading code having a zero interference window before the OFDM modulation at the transmitting end; and then uses the FFT after the receiving end performs the FFT transformation.
  • the orthogonal spreading code despreads the information symbols.
  • the following process is divided into two stages of transmitting end spread spectrum modulation and receiving end despreading.
  • the length of the LAS orthogonal spreading code is first defined as 2N, and N is a natural number.
  • the N spreading sequences are FS1, FS2, ..., FSN, and the number of modulation bits per OFDM subcarrier is M, and M is also a natural number.
  • FIG. 3 is a schematic diagram of a spread spectrum modulation process at a transmitting end in an OFDM system employing the method of the present invention.
  • the transmitted information is encoded into N groups, which are respectively recorded as S 1 ; S 2 , ..., S N , and each group is segmented by length M bits, which is divided into Segment j, mapping the bit constellation mapping rules required for each segment of M bits according to OFDM subcarrier modulation to complex symbols: S n , S 12 , ..., S 21 , S 22 , ..., S N1 , S N2 , ...Sy , where S denotes the jth symbol of the i-th group.
  • the above process shown in the figure may have another meaning, that is, after N sets of different user information are separately encoded, each group of user information is segmented according to the length M bits, and is divided into j segments, and is described above.
  • the bit constellation mapping is performed in the same way, and the complex symbols can also be obtained: Su, S 12 , ..., S 21 , S 22 , ..., S N1 , S N2 , ...Sy, where Sy is the ith The jth symbol of the user.
  • each complex symbol is spread using the aforementioned LAS orthogonal spreading code, and the spreading sequence used for the i-th symbol is F.
  • All data subcarriers in OFDM are grouped: d, C 2 , ..., C k , ..., the number of subcarriers per group is the length of the spreading sequence 2N : C u , C i2 , ..., C i2N , and the subcarriers in the same group are adjacent in frequency.
  • Each group of subcarriers in the OFDM is modulated with modulation data sequences DD 2 , ..., D k , ..., respectively, where d ik is modulated onto C ik .
  • K denotes that the subcarriers of all the transmitted data of OFDM are divided into K segments, and each segment transmits exactly one LAS codeword carrying a plurality of modulated data.
  • FIG. 4 is a schematic diagram of a despreading process at the receiving end in an OFDM system using the method of the present invention.
  • the receiving end first performs conventional processing such as frequency offset correction, clock synchronization, frame synchronization, and de-cyclic prefix processing on the received baseband complex signal.
  • the FFT calculation is performed on the complex signal subjected to the above processing, and then frequency domain equalization processing is performed to obtain data drik modulated by each subcarrier, and the subcarrier number of the subcarrier and the transmitting end are identical.
  • the data sequence Srij is then subjected to subsequent processing such as bit map decoding.
  • the processed data becomes the received information after being reassembled.
  • the key to the improvement of the synchronization performance of the OFDM system by the above-mentioned spread spectrum modulation and despreading operation is that the spread spectrum sequence has zero interference window characteristics, that is, its non-cyclic autocorrelation sequence and acyclic cross-correlation sequence have a certain displacement range. Zero related window.
  • the LAS orthogonal spreading code is an ideal spreading sequence that satisfies the above conditions.
  • the system synchronization needs to be synchronized to the zero window offset to make the correlation value after de-spreading zero.
  • this can be done by synchronizing OFDM itself. Simply put, the sender must know the correspondence between the chip and the subcarrier of the LAS code, but the receiver needs to know the correspondence to despread. This synchronization has been provided by the frame synchronization requirements of the OFDM system itself.
  • the method for improving the synchronization performance of an OFDM system by using the orthogonal spreading code with zero interference window characteristic is not only theoretically reasonable, but also proves that it has satisfactory improvement of the synchronization performance of the OFDM system through simulation calculation. effect.
  • Figure 5 is a block diagram showing the structure of a system simulation station for verifying the performance of the method of the present invention.
  • the simulation system consists of three types: two spread spectrum OFDM systems and one common OFDM system.
  • the spread spectrum sequences of the two spread spectrum systems are M sequence and LAS-Code spread spectrum respectively; while the ordinary OFDM system has no spread spectrum and despread two modules.
  • the results of the simulation calculation are obtained by comparing the received constellation diagrams.
  • the parameters used in the simulation are:
  • LAS— Code code group (1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23 25, 27, 29, 31)
  • the zero correlation window is 7.
  • 6a is a normal OFDM system
  • FIG. 6b is an M-sequence spread-spectrum MC-CDMA
  • FIG. 6c is an LAS-Code spread-spectrum MC-CDMA.
  • 7a is a normal OFDM system
  • FIG. 7b is M-sequence spread-spectrum MC-CDMA
  • FIG. 7c is LAS-Code spread-spectrum MC-CDMA.
  • Figure 8a shows a conventional OFDM system
  • Figure 81 is a frame of -4 sequence spread-spectrum MC-CDMA
  • Figure 8c is a LAS-Code spread-spectrum MC-CDMA.
  • the received signals of all OFDM systems produce a large amount of rotation, while the received signals are divergent.
  • This phase rotation is tolerable because it does not generate errors and can be corrected using equalization methods.
  • the divergence of the received signal is unbearable because it will result in a bit error.
  • This situation has the most serious impact on the common OFDM system, and the MC-CDMA system after the M-sequence spread spectrum improves the problem to some extent, but it is obviously more serious than the case without frequency offset, so that it exists in the system. In the case of noise, errors are also relatively easy to occur.
  • the MC-CDMA system after LAS-Code spread spectrum has significantly improved this performance, and the received signal hardly diverges. This shows that the LAS-coded-OFDM system has strong resistance to system frequency offset.
  • 9a is a normal OFDM system
  • FIG. 9b is an M-sequence spread-spectrum MC-CDMA
  • FIG. 9c is an LAS-Code spread-spectrum MC-CDMA.
  • the method is characterized by spreading the LAS orthogonal spreading code before the IFFT of the transmitting end OFDM, and then spreading the symbol with the LAS orthogonal spreading code after the terminating FFT.
  • the advantage of OFDM is preserved, and the destruction of the orthogonality of subcarriers due to high-speed motion and the like is eliminated by the despreading of the LAS orthogonal spreading code of the next stage.
  • the LS orthogonal spreading code despreading can further reduce the influence of noise, that is, the gain of general CDMA can be obtained while retaining the characteristics of OFDM technology.
  • OFDM plus CDMA can also be networked with the characteristics of CDMA, this can make up for the shortcomings of OFDM in networking.

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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

Procédé d'étalement et de désétalement améliorant les performances de synchronisation d'un système OFDM consistant à étaler les symboles d'information avec les codes d'étalement orthogonaux ayant les propriétés de fenêtre exemptes d'interférences avant la modulation du système OFDM; à désétaler ensuite au niveau du récepteur les symboles d'information au moyen des codes d'étalement orthogonaux après la transformée de fourrier rapide. Le procédé tire sensiblement profit des codes d'étalement orthogonaux ayant des propriétés de fenêtre exempte d'interférences, résout efficacement les facteurs d'influence de déviation d'une fréquence porteuse, le bruit, etc. pour les performances de synchronisation du système OFDM, établit la fondation technique pour étendre et appliquer ultérieurement le système OFDM. Le procédé élargit en outre la fourchette d'application des codes d'étalement orthogonaux ayant les propriétés de fenêtre exempte d'interférences.
PCT/CN2005/001481 2004-09-21 2005-09-16 Procede d'etalement et de desetalement ameliorant les performances de synchronisation d'un systeme ofdm WO2006032191A1 (fr)

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CN 200410009597 CN1753394B (zh) 2004-09-21 2004-09-21 改善ofdm系统同步性能的解扩频方法
CN200410009597.2 2004-09-21

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111835668A (zh) * 2020-08-05 2020-10-27 成都盟升科技有限公司 一种简化的msk扩频系统非相干解扩解调方法
CN112671683A (zh) * 2020-12-16 2021-04-16 清华大学 一种分段连续调频波的信号调制解调方法及系统

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101355539B (zh) * 2007-07-24 2012-05-09 重庆无线绿洲通信技术有限公司 多载波同步cdma传输方法
CN101692664B (zh) * 2009-10-13 2012-02-08 清华大学 一种采用非连续载波干涉码的多载波无线传输方法
CN107276740B (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
CN107276951B (zh) * 2016-04-08 2021-08-06 深圳光启合众科技有限公司 载波同步方法和装置
CN109217968B (zh) * 2018-08-17 2020-04-28 盐城工学院 一种基于相移键控技术的采用cdma技术的近距离无线网络
CN108964827B (zh) * 2018-08-17 2020-04-28 盐城工学院 一种基于频移键控的采用cdma技术的近距离无线网络

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004002038A1 (fr) * 2002-06-25 2003-12-31 Koninklijke Philips Electronics N.V. Mt-cdma utilisant des codes d'etalement avec des fenetres exemptes de parasites
WO2004023752A1 (fr) * 2002-08-29 2004-03-18 Siemens Aktiengesellschaft Procede et dispositif d'emission permettant la transmission de donnees dans un systeme a porteuses multiples

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1138428C (zh) * 2001-06-11 2004-02-11 华为技术有限公司 移动通信同步系统的同步码选择方法

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004002038A1 (fr) * 2002-06-25 2003-12-31 Koninklijke Philips Electronics N.V. Mt-cdma utilisant des codes d'etalement avec des fenetres exemptes de parasites
WO2004023752A1 (fr) * 2002-08-29 2004-03-18 Siemens Aktiengesellschaft Procede et dispositif d'emission permettant la transmission de donnees dans un systeme a porteuses multiples

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111835668A (zh) * 2020-08-05 2020-10-27 成都盟升科技有限公司 一种简化的msk扩频系统非相干解扩解调方法
CN111835668B (zh) * 2020-08-05 2023-03-31 成都盟升科技有限公司 一种简化的msk扩频系统非相干解扩解调方法
CN112671683A (zh) * 2020-12-16 2021-04-16 清华大学 一种分段连续调频波的信号调制解调方法及系统
CN112671683B (zh) * 2020-12-16 2023-07-25 清华大学 一种分段连续调频波的信号调制解调方法及系统

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