CN109639385B - Broadband diversity synchronization method and system based on CAZAC sequence - Google Patents

Broadband diversity synchronization method and system based on CAZAC sequence Download PDF

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CN109639385B
CN109639385B CN201811641949.4A CN201811641949A CN109639385B CN 109639385 B CN109639385 B CN 109639385B CN 201811641949 A CN201811641949 A CN 201811641949A CN 109639385 B CN109639385 B CN 109639385B
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diversity
cazac sequence
energy
synchronization
total energy
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CN109639385A (en
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姚璐
姚玉征
魏强
卢圣龙
程敏敏
朱正毅
赵利凯
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Shanghai Institute of Microwave Technology CETC 50 Research Institute
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0602—Systems characterised by the synchronising information used
    • H04J3/0605—Special codes used as synchronising signal
    • 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]
    • H04J13/0059—CAZAC [constant-amplitude and zero auto-correlation]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0602—Systems characterised by the synchronising information used
    • H04J3/0605—Special codes used as synchronising signal
    • H04J3/0608—Detectors therefor, e.g. correlators, state machines

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Abstract

The invention provides a broadband diversity synchronization method and a system based on a CAZAC sequence, comprising the following steps: CAZAC sequence determination step: determining a required CAZAC sequence; broadband diversity synchronization determination: and according to the determined CAZAC sequence, obtaining a synchronous position through broadband diversity synchronous operation. According to the invention, the diversity synchronization technology is adopted, so that the synchronization precision stability under the condition of low signal-to-noise ratio is improved, and the communication performance of the whole communication system can be effectively ensured; the timing precision, stability and reliability of the wireless communication receiving end can be effectively improved.

Description

Broadband diversity synchronization method and system based on CAZAC sequence
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a wideband diversity synchronization method and system based on a CAZAC (constant Amplitude zero auto-correlation) sequence.
Background
Synchronization is a very important issue in wireless communication systems, especially in digital communication systems. In a digital communication system, an OFDM (Orthogonal Frequency Division Multiplexing) technology has the advantages of high Frequency band utilization rate, multipath fading resistance and the like, but is more sensitive to synchronization errors than a single carrier technology. Once the synchronization is inaccurate, the induced inter-symbol interference (ISI) and inter-subcarrier interference (ICI) will greatly diminish the advantages of OFDM, so the synchronization is crucial for the implementation of OFDM receivers. The synchronization in the OFDM mainly comprises three parts of timing synchronization, carrier frequency synchronization and sampling clock synchronization, wherein the timing synchronization is most important. Since the other two synchronizations and channel estimation will not be mentioned once the timing synchronization is inaccurate.
To solve the synchronization problem, there are in principle two types of methods. The first method is to use a method of inserting auxiliary synchronization information, that is, to insert synchronization information in the frequency domain or the time domain, and this method is fast in time for establishing synchronization, but occupies frequency resources and power resources of the communication system. The second method is to directly extract the synchronization information from the received signal without using auxiliary synchronization information, and the method has long synchronization establishment time but saves the frequency resource and the power resource occupied by the system.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a broadband diversity synchronization method and system based on a CAZAC sequence.
The invention provides a broadband diversity synchronization method based on a CAZAC sequence, which comprises the following steps:
CAZAC sequence determination step: determining a required CAZAC sequence;
broadband diversity synchronization determination: and according to the determined CAZAC sequence, obtaining a synchronous position through broadband diversity synchronous operation.
Preferably, the CAZAC sequence akThe determination method comprises the following steps:
Figure BDA0001931282370000021
wherein k is 0,1, …, N-1; n is the sequence length; r is any positive integer coprime to N; e is; j is.
Preferably, the step of determining the wideband diversity synchronization comprises:
a cross-correlation operation sub-step: performing moving recursive summation calculation according to the energy of the received signal, averaging the energy values after the recursive summation, and calculating a threshold value;
the sub-step of the enhanced diversity operation: dividing the energy value obtained by the moving recursive summation calculation into n diversity, performing cross-correlation operation on the energy value in each diversity to obtain the total energy of each diversity, and performing summation operation on the total energy of all the diversity;
normalizing the operation sub-step: and normalizing the total energy of each diversity and the total energy of all the diversity, and comparing the normalized result with the threshold value to obtain the synchronous position.
Preferably, the moving recursive summation calculation includes:
mn+1＝mn+|rn+1|2-|rn-L+1|2
wherein the content of the first and second substances,
Figure BDA0001931282370000022
rnto receive signals, omeganAs noise, snIs a signal, mnCumulative sum at window length L for received signal energy, CnIs a CAZAC sequence, C* nIs sequence CnConjugation of (1).
Preferably, the result D is normalizednComprises the following steps:
Dn＝|Bn|2/|An|2；
wherein, BnFor the total energy of all diversities, AnIs the total energy of each diversity.
The invention provides a wide band diversity synchronization system based on CAZAC sequence, comprising:
CAZAC sequence determination module: determining a required CAZAC sequence;
a broadband diversity synchronization determining module: and according to the determined CAZAC sequence, obtaining a synchronous position through broadband diversity synchronous operation.
Preferably, the CAZAC sequence CkThe determination method comprises the following steps:
Figure BDA0001931282370000023
wherein k is 0,1, …, N-1; n is the sequence length; r is any positive integer coprime to N; e is; j is.
Preferably, the wideband diversity synchronization determining module includes:
a cross-correlation operation submodule: performing moving recursive summation calculation according to the energy of the received signal, averaging the energy values after the recursive summation, and calculating a threshold value;
the enhanced diversity operation submodule: dividing the energy value obtained by the moving recursive summation calculation into n diversity, performing cross-correlation operation on the energy value in each diversity to obtain the total energy of each diversity, and performing summation operation on the total energy of all the diversity;
a normalization operation submodule: and normalizing the total energy of each diversity and the total energy of all the diversity, and comparing the normalized result with the threshold value to obtain the synchronous position.
Preferably, the moving recursive summation calculation includes:
mn+1＝mn+|rn+1|2-|rn-L+1|2
wherein the content of the first and second substances,
Figure BDA0001931282370000031
rnto receive signals, omeganAs noise, snIs a signal, mnCumulative sum at window length L for received signal energy, CnIs a CAZAC sequence, C* nIs sequence CnConjugation of (1).
Preferably, the result D is normalizednComprises the following steps:
Dn＝|Bn|2/|An|2；
wherein, BnFor the total energy of all diversities, AnIs the total energy of each diversity.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the diversity synchronization technology is adopted, so that the synchronization precision stability under the condition of low signal-to-noise ratio is improved, and the communication performance of the whole communication system can be effectively ensured; the timing precision, stability and reliability of the wireless communication receiving end can be effectively improved.
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Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a graph of wideband diversity synchronization algorithm performance;
FIG. 3 is a performance diagram of a wideband diversity synchronization algorithm in a Gaussian white noise channel;
FIG. 4 is a performance diagram of a wideband diversity synchronization algorithm in a fading channel;
fig. 5 is a comparison of bit error rate curves using different rates under gaussian channel conditions.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1, the wideband diversity synchronization method based on CAZAC sequence provided by the present invention includes the following steps:
step 1: determining a CAZAC sequence;
step 2: wideband diversity synchronization is determined.
Wherein, step 1 includes the following steps:
step 1.1: the method for determining the required CAZAC sequence is that the CAZAC sequence is called as constant envelope zero autocorrelation sequence, and the implementation process is as follows:
Figure BDA0001931282370000041
wherein k is 0,1, …, N-1, and N is the sequence length. r is any positive integer coprime to N.
CAZAC sequences have the following properties:
a) constant envelope property. The amplitude of any CAZAC sequence is constant, and the characteristic can ensure that each frequency point in a corresponding broadband experiences the same excitation, thereby facilitating the realization of unbiased estimation in coherent detection;
b) ideal periodic autocorrelation properties. For any CAZAC original sequence and the sequence after cyclic shift are not correlated, the autocorrelation peak value is sharp;
c) good cross-correlation properties. Namely, the cross-correlation values of different CAZAC root sequences are close to zero, and the receiving end can accurately carry out coherent detection;
d) low peak-to-average ratio. The amplitude of the CAZAC sequence is constant, the ratio of the peak power to the mean power of the time domain signal is low, and the nonlinear distortion of the power amplifier can be reduced;
e) after Fourier transformation/inverse Fourier transformation, the CAZAC sequence is still obtained.
The method for determining the broadband diversity synchronization in the step 2 comprises the following steps:
step 2.1: traditional cross-correlation operation based on CAZAC sequence
Measuring the energy of the received signal is one of the simplest packet detection algorithms. When no data packet arrives, the signal r is receivednIn which only noise, i.e. rn＝ωn(ii) a And when a data packet arrives, a signal r is receivednIn which the component of the signal, i.e. r, is addedn＝sn+ωn，snIs a signal; cnIs a CAZAC sequence, C* nIs sequence CnConjugation of (1). Therefore, packet detection can be performed according to the change of the received signal energy value. To avoid the impact of sudden loud noise, a decision variable mnThe sum of the window lengths L selected to receive the signal energy may be expressed as
Figure BDA0001931282370000051
In fact, mnIs a moving sum of the received signal energy, also called a sliding window, whose basic principle is that at each time n the sum adds a new value while discarding a previous value. The following equation is the calculation of this moving recursive sum
mn+1＝mn+|rn+1|2-|rn-L+1|2(3)
As can be seen from the above formula, the use of the moving recursive summation simplifies the complex multiplication operation and is easier to implement. To avoid the influence of sudden loud noise, i.e. the received energy fluctuates to some extent at the maximum under the influence of noise, m isn+1And during summation, averaging the data subjected to recursive summation to calculate a threshold value of the data.
Step 2.2: enhanced diversity operation
While conventional packet energy detection compares the energy obtained in step 2.1 with a threshold to obtain the position of synchronization, in wideband diversity synchronization step 2.1 constitutes only a subset of diversity operation. Dividing the energy value in 2.1 into n diversity, and performing cross-correlation operation on the energy value in each diversity to obtain the total energy A of each diversityn。
Figure BDA0001931282370000052
Summing the total energy of each diversity
Figure BDA0001931282370000053
Where H is the different coefficients taken for the different subsets.
Step 2.3: normalization operation
Normalizing the energy of each diversity obtained in step 2.2 with the energy of the total diversity to obtain DnThen useObtained DnThe value is compared with a set threshold value to obtain a synchronous position.
Dn＝|Bn|2/|An|2(6)
As can be seen from the simulation results of fig. 2 to fig. 5, the concept of diversity technology is used, the synchronization performance is better, and the synchronization position obtained by the wideband diversity synchronization operation is more accurate and stable than the synchronization position obtained by the conventional steps.
On the basis of the wideband diversity synchronization method based on the CAZAC sequence, the invention also provides a wideband diversity synchronization system based on the CAZAC sequence, which comprises the following steps:
CAZAC sequence determination module: determining a required CAZAC sequence;
a broadband diversity synchronization determining module: and according to the determined CAZAC sequence, obtaining a synchronous position through broadband diversity synchronous operation.
Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, units provided by the present invention as pure computer readable program code, the system and its various devices, modules, units provided by the present invention can be fully implemented by logically programming method steps in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system and various devices, modules and units thereof provided by the invention can be regarded as a hardware component, and the devices, modules and units included in the system for realizing various functions can also be regarded as structures in the hardware component; means, modules, units for performing the various functions may also be regarded as structures within both software modules and hardware components for performing the method.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (6)

1. A wideband diversity synchronization method based on CAZAC sequence is characterized by comprising the following steps:
CAZAC sequence determination step: determining a required CAZAC sequence;
broadband diversity synchronization determination: according to the determined CAZAC sequence, obtaining a synchronous position through broadband diversity synchronous operation;
the CAZAC sequence akThe determination method comprises the following steps:
Figure FDA0002448737500000011
wherein k is 0,1, …, N-1; n is the sequence length; r is any positive integer coprime to N; e is frequency deviation; j is an imaginary unit;
the wideband diversity synchronization determining step includes:
a cross-correlation operation sub-step: performing moving recursive summation calculation according to the energy of the received signal, averaging the energy values after the recursive summation, and calculating a threshold value;
the sub-step of the enhanced diversity operation: dividing the energy value obtained by the moving recursive summation calculation into n diversity, performing cross-correlation operation on the energy value in each diversity to obtain the total energy of each diversity, and performing summation operation on the total energy of all the diversity;
normalizing the operation sub-step: and normalizing the total energy of each diversity and the total energy of all the diversity, and comparing the normalized result with the threshold value to obtain the synchronous position.
2. The CAZAC sequence-based wideband diversity synchronization method according to claim 1, wherein the moving recursive summation calculation comprises:
mn+1＝mn+|rn+1|2-|rn-L+1|2
wherein the content of the first and second substances,
Figure FDA0002448737500000012
rn＝sn+ωn；
rnto receive signals, omeganAs noise, snIs a signal, mnCumulative sum at window length L for received signal energy, CnIs a CAZAC sequence, C* nIs sequence CnConjugation of (1).
3. The CAZAC sequence-based wideband diversity synchronization method according to claim 2, wherein the result of normalization DnComprises the following steps:
Dn＝|An|2/|Bn|2；
wherein, BnFor the total energy of all diversities, AnIs the total energy of each diversity.
4. A wide band diversity synchronization system based on CAZAC sequences, comprising:
CAZAC sequence determination module: determining a required CAZAC sequence;
a broadband diversity synchronization determining module: according to the determined CAZAC sequence, obtaining a synchronous position through broadband diversity synchronous operation;
the CAZAC sequence CkThe determination method comprises the following steps:
Figure FDA0002448737500000021
wherein k is 0,1, …, N-1; n is the sequence length; r is any positive integer coprime to N; e is frequency deviation; j is an imaginary unit;
the broadband diversity synchronization determining module includes:
a cross-correlation operation submodule: performing moving recursive summation calculation according to the energy of the received signal, averaging the energy values after the recursive summation, and calculating a threshold value;
the enhanced diversity operation submodule: dividing the energy value obtained by the moving recursive summation calculation into n diversity, performing cross-correlation operation on the energy value in each diversity to obtain the total energy of each diversity, and performing summation operation on the total energy of all the diversity;
a normalization operation submodule: and normalizing the total energy of each diversity and the total energy of all the diversity, and comparing the normalized result with the threshold value to obtain the synchronous position.
5. The CAZAC sequence-based wideband diversity synchronization system according to claim 4, wherein the moving recursive summation computation comprises:
mn+1＝mn+|rn+1|2-|rn-L+1|2
wherein the content of the first and second substances,
Figure FDA0002448737500000022
rn＝sn+ωn；
rnto receive signals, omeganAs noise, snIs a signal, mnCumulative sum at window length L for received signal energy, CnIs a CAZAC sequence, C* nIs sequence CnConjugation of (1).
6. The CAZAC sequence-based wideband diversity synchronization system according to claim 5, wherein the result of normalization DnComprises the following steps:
Dn＝|An|2/|Bn|2；
wherein, BnFor the total energy of all diversities, AnIs the total energy of each diversity.
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CN103188196A (en) * 2011-12-31 2013-07-03 中国电子科技集团公司第五十研究所 Synchronized method of orthogonal frequency division multiplexing system
CN103532898A (en) * 2013-04-22 2014-01-22 上海数字电视国家工程研究中心有限公司 OFDM training symbol generation and synchronization method based on CAZAC sequence

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