CN103532899B - Time domain OFDM synchronizing symbol generates and demodulation method, data frame transmission method - Google Patents
Time domain OFDM synchronizing symbol generates and demodulation method, data frame transmission method Download PDFInfo
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Abstract
A kind of time domain OFDM synchronizing symbol generates and demodulation method, data frame transmission method, and wherein the generation method of time domain OFDM synchronizing symbol includes generating CAZAC sequence and its shift sequence；Shift sequence based on CAZAC sequence and CAZAC sequence forms frequency-domain OFDM synchronizing symbol；Frequency-domain OFDM synchronizing symbol is carried out Fourier inversion and synchronizes training symbol to form time domain OFDM；Time domain OFDM is synchronized training symbol and is divided into Part I symbol and Part II symbol, and respectively this two parts symbol is multiplied by mutually with fixing frequency deviation the prefix forming time domain OFDM synchronizing symbol and suffix；Suffix based on the prefix of time domain OFDM synchronizing symbol, OFDM synchronization training symbol and time domain OFDM synchronizing symbol forms time domain OFDM synchronizing symbol.The technical program reduces the complexity that OFDM symbol generates, and reduces demodulated complex degree and improve demodulation parameter performance.
Description
Technical field
The present invention relates to wireless communication technology field, particularly to generation method and demodulation method, the data frame transmission method of a kind of time domain OFDM synchronizing symbol.
Background technology
OFDM (OFDM) is a kind of efficient modulation technique, it is possible not only to opposing frequency selective fading, and there is the higher availability of frequency spectrum, it is widely used in radio standard, such as DAB (digital audio broadcasting, DigitalAudioBroadcast), DVB-T (ground digital television broadcast, DigitalVideoBroadcast-Terrestrial) and the second filial generation standard DVB-T2 (second filial generation ground digital television broadcast) that is recently proposed.
The shortcoming of OFDM is that timing offset and frequency shift (FS) is very sensitive, if system exists timing error, it will cause intersymbol interference and data phase to rotate；If there is frequency shift (FS), the orthogonality between system subcarrier can be destroyed, and causes cochannel interference.Therefore, at OFDM receiving terminal, it is necessary to realize high-precision Time And Frequency and synchronize.
Realize high-precision synchronization, it is necessary to design the algorithm that can resist noisy channels synchronizing symbol and correspondence.nullBased on synchronizing symbol P1 in DVB-T2 system，DVBdocumentA133 file " ImplementationGuidelinesforaSecondGenerationDigitalTerre strialTelevisionBroadcastingSystem (second filial generation ground system of digital television broadcast enforcement manual，DVB-T2) " give the purpose of synchronizing symbol P1 design and give timing frequency deviation algorithm for estimating CBS method based on relative theory，CBS method is furtherd investigate by DobladoJG et al. in " CoarsetimesynchronizationforDVB-T2 (DVB-T2 system time domain slightly synchronizes) "，Point out owing to timing metric function exists flat-top，The timing accuracy that this algorithm provides under Gaussian channel is not high.There is more scholar that CBS method is improved subsequently, as provided timing frequency deviation to estimate in conjunction with maximum likelihood estimate, although simulation results show the method performance is more excellent, but method of maximum likelihood complexity is higher, and the number of correlator and the number of sliding filter are the twice of desirable value in CBS method.ViemannA et al. does relevant unit in " Implementation-friendlysynchronizationalgorithmforDVB-T2 (the DVB-T2 synchronized algorithm being easily achieved) " is to CBS method and counting of glide filter is modified, timing metric function is three sharp-pointed horns, and net synchronization capability has had bigger lifting.
The synchronized algorithm of above-mentioned document, all the time with CBS method for framework, does not change P1 synchronizing symbol structure.P1 symbol has its inherent shortcoming: carry parameter few, only comprises FFT size and SISO/MISO pattern, still needs to calculate protection gap size after synchronization；Generate complexity, the computing such as including DBPSK modulation, scrambling, zero padding, inverse FFT；Need to likely sequence be relevant to the sequence received obtains optimum matching point by local during receiving terminal demodulation parameter information, it is necessary to adopting the correlator of big quantity, computation complexity is significantly high.LifengHe et al. proposes new synchronizing symbol in " PreambleDesignUsingEmbeddedSignalingforOFDMBroadcastSyst emsBasedonReduced-ComplexityDistanceDetection (the frame head method for designing of the information of carrying based on distance of OFDM broadcast system low complex degree) ", 0 sequence length in frequency-domain structure is utilized to carry information, but it is relevant to do difference for sliding window to local sequence with 256 in its demodulating process, operand is still very big, therefore completing the P1 function realized with low complex degree is the major issue in digital TV communication systems.
Summary of the invention
The demodulation method operand that the problem that this invention address that is existing OFDM synchronizing symbol is very big, and complexity is higher.
For solving the problems referred to above, the embodiment of the present invention provides a kind of generation method of time domain OFDM synchronizing symbol, comprising the steps: to generate the shift sequence of CAZAC sequence and described CAZAC sequence, wherein said CAZAC sequence includes root parameter, the shift sequence of described CAZAC sequence includes shift parameters；Shift sequence based on described CAZAC sequence and described CAZAC sequence forms frequency-domain OFDM synchronizing symbol；Described frequency-domain OFDM synchronizing symbol is carried out Fourier inversion and synchronizes training symbol to form time domain OFDM；This time domain OFDM is synchronized training symbol and is divided into Part I symbol and Part II symbol, and respectively this two parts symbol is multiplied by mutually with fixing frequency deviation the prefix forming time domain OFDM synchronizing symbol and suffix；Suffix based on the prefix of described time domain OFDM synchronizing symbol, OFDM synchronization training symbol and time domain OFDM synchronizing symbol forms time domain OFDM synchronizing symbol.
The embodiment of the present invention additionally provides a kind of demodulation method to the time domain OFDM synchronizing symbol that said method generates, comprising the steps: to receive time domain OFDM synchronizing symbol, wherein said time domain OFDM synchronizing symbol generation method of time domain OFDM synchronizing symbol described in claim 1 obtains；Related operation is utilized to process to determine OFDM symbol timing point and fraction frequency offset value to the time domain OFDM synchronizing symbol received；From this time domain OFDM synchronizing symbol, intercept time domain OFDM according to determined OFDM symbol timing point and synchronize training symbol；Demodulate this time domain OFDM and synchronize the CAZAC sequence on training symbol correspondence frequency domain to solve root parameter and to determine integer-times frequency offset value；The shift sequence of CAZAC sequence is intercepted according to determined integer-times frequency offset value；The shift sequence of the CAZAC sequence that demodulation intercepts is to determine shift parameters；Corresponding system parameter message is determined based on described root parameter and shift parameters.
Compared with prior art, technical solution of the present invention has the advantages that
The generation method of the time domain OFDM synchronizing symbol provided according to embodiments of the present invention, utilizes the shift sequence of CAZAC sequence and this CAZAC sequence generated directly to fill at frequency domain and forms frequency-domain OFDM synchronizing symbol, reduce the complexity that OFDM symbol generates.Further; the shift sequence of CAZAC sequence and this CAZAC sequence carries root parameter and shift parameters, so that receiving terminal obtains the system parameter messages such as the size of the such as Fourier transformation that system is carried, the size protecting interval and input and output mode by solving the two parameter.
The demodulation method of the time domain OFDM synchronizing symbol provided according to embodiments of the present invention, from receiving in the process demodulating root parameter and shift parameters in time domain OFDM synchronizing symbol, have only to can be realized by two correlation operators, reduce demodulated complex degree and improve demodulation parameter performance.Further, it is estimated that integer-times frequency offset value in the process demodulating root parameter, follow-up work amount is decreased.
The data frame transmission method provided according to embodiments of the present invention, is filled with null sequence in the frequency-domain OFDM synchronizing symbol of generation between the shift sequence of CAZAC sequence and described CAZAC sequence, the impact of carrier wave leakage occurs reducing ofdm system.Further, in frequency-domain OFDM synchronizing symbol, also it is filled with virtual subnet carrier wave, to tackle the frequency shift (FS) occurred between sending and receiving end in ofdm system, it is ensured that owing to frequency deviation affects effective subcarrier all in midbandwidth.
Accompanying drawing explanation
Fig. 1 is the schematic flow sheet of the embodiment of the generation method of a kind of time domain OFDM synchronizing symbol of the present invention；
Fig. 2 is the structural representation of a kind of OFDM synchronizing symbol that the generation method of the time domain OFDM synchronizing symbol utilizing the present invention generates；
Fig. 3 is the schematic flow sheet of the embodiment of the demodulation method of a kind of time domain OFDM synchronizing symbol of the present invention；
Fig. 4 be the time domain OFDM synchronizing symbol of the present invention demodulation method in determine OFDM symbol timing point and the schematic flow sheet of fraction frequency offset value；
Fig. 5 is that the present invention demodulates, with existing time domain OFDM synchronizing symbol, the schematic diagram that error rate performance compares；
Fig. 6 is the schematic diagram of the present invention and the mean square error Performance comparision of existing time domain OFDM synchronizing symbol timing offset；
Fig. 7 is the schematic diagram of the present invention and the mean square error Performance comparision of existing time domain OFDM synchronizing symbol frequency deviation；
Fig. 8 is the structural representation of a kind of data frame transmission method frequency domain OFDM synchronizing symbol of the present invention.
Detailed description of the invention
Inventor have found that the demodulation method operand of existing OFDM synchronizing symbol is very big, complexity is higher.
For the problems referred to above, inventor is through research, it is provided that a kind of generation method of time domain OFDM synchronizing symbol and demodulation method thereof.The technical program reduces the complexity that time-domain OFDM symbol generates, and also reduces demodulated complex degree simultaneously and improves demodulation parameter performance.
Understandable for enabling the above-mentioned purpose of the present invention, feature and advantage to become apparent from, below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in detail.
As shown in Figure 1 be the schematic flow sheet of embodiment of generation method of a kind of time domain OFDM synchronizing symbol of the present invention.Generation method with reference to Fig. 1, OFDM synchronizing symbol comprises the steps:
Step S11: generating the shift sequence of CAZAC sequence and described CAZAC sequence, wherein said CAZAC sequence includes root parameter, the shift sequence of described CAZAC sequence includes shift parameters；
Step S12: the shift sequence based on described CAZAC sequence and described CAZAC sequence forms frequency-domain OFDM synchronizing symbol；
Step S13: described frequency-domain OFDM synchronizing symbol is carried out Fourier inversion to form time domain OFDM and synchronize training symbol；
Step S14: this time domain OFDM is synchronized training symbol and is divided into Part I symbol and Part II symbol, and respectively this two parts symbol is multiplied by mutually with fixing frequency deviation the prefix forming time domain OFDM synchronizing symbol and suffix；
Step S15: the suffix based on the prefix of described time domain OFDM synchronizing symbol, OFDM synchronization training symbol and time domain OFDM synchronizing symbol forms time domain OFDM synchronizing symbol.
Below in conjunction with specific embodiment, the generation method of above-mentioned time domain OFDM synchronizing symbol is described in detail.
In the present embodiment, as described in step S11, generating the shift sequence of CAZAC sequence and described CAZAC sequence, wherein said CAZAC sequence includes root parameter, the shift sequence of described CAZAC sequence includes shift parameters.
Specifically, CAZAC sequence can be Zadoff-Chu sequence, and expression formula isWherein M is sequence length, k=0,1 ... and, M-1, j is ordinal number unit, and r is root parameter.Wherein, the value of described root parameter is relatively prime for the length M positive integer with described CAZAC sequence.In actual applications, the value of described root parameter should as far as possible close to the length of described CAZAC sequence.
The shift sequence of CAZAC sequence isWherein, λ is shift parameters, represents CAZAC sequential shift λ position.Wherein, the value of described shift parameters is less than the length of described CAZAC sequence, and the difference of adjacent two values of this shift parameters is in preset range.Described preset range is [1,20].
nullSystem is according to different r values and λ value carrying system parameter information，System parameter message includes FFT size、Protection gap size、SISO/MISO pattern，Wherein SISO represents single-input single-output、MISO represents multiple input single output pattern，Necessary clear and definite input and output mode during data is extracted in rear end，It is transformed into frequency domain (doing FFT) from time domain and needs the protection interval of clear and definite FFT size and correspondence，A concrete system is given below and carries the example of parameter，" the Framingstructure that above-mentioned parameter value proposes according to ETSI，Channelcodingandmodulationforasecondgenerationdigitalter restrialtelevisionbroadcastingsystem (DVB-T2) " (frame structure of second filial generation ground system of digital television broadcast (DVB-T2)、Channel Coding and Modulation) standard setting，As shown in table 1，This parameter value does not affect the generality of the present invention.
The value of table 1 parameters information
As described in step S12, the shift sequence based on described CAZAC sequence and described CAZAC sequence forms frequency-domain OFDM synchronizing symbol.
In the present embodiment, the frequency-domain structure of OFDM synchronizing symbol is Sk=[zk,ak,ok,bk,zk].Wherein, k is frequency domain sample point；zkFor virtual subnet carrier wave, length is p, and this virtual subnet carrier wave is 0 sequence；okBeing 0 sequence, length is u, u=[80,450]；The frequency-domain structure S of whole OFDM synchronizing symbolkThere are 1024 sampled points.
As described in step S13, described frequency-domain OFDM synchronizing symbol is carried out Fourier inversion to form time domain OFDM and synchronize training symbol.It will be appreciated by those skilled in the art that frequency domain data converts to time domain data generally can adopt the mode of Fourier inversion to change.Wherein, the concrete conversion regime of Fourier inversion is referred to prior art and realizes, and does not repeat them here.
As described in step S14, this time domain OFDM is synchronized training symbol and is divided into Part I symbol and Part II symbol, and respectively this two parts symbol is multiplied by mutually with fixing frequency deviation the prefix forming time domain OFDM synchronizing symbol and suffix.
In the present embodiment, to the length of described Part I symbol and Part II symbol and be not construed as limiting, but the length sum of Part I symbol and Part II symbol is required to be time domain OFDM and synchronizes the length of training symbol.Then, this two parts symbol being multiplied by the prefix forming time domain OFDM synchronizing symbol and suffix respectively with fixing frequency deviation mutually, wherein, fixing frequency deviation is set in advance, and this fixing frequency deviation is ej2πk/N, wherein N is 512.
In a preferred embodiment, this step can be realized by following manner:
This time domain OFDM is synchronized training symbol and is divided into front and back two parts symbol that length is equal, and first half symbol is multiplied by mutually with fixing frequency deviation the prefix forming OFDM synchronizing symbol and latter half symbol is multiplied by mutually with fixing frequency deviation the suffix forming OFDM synchronizing symbol.
As shown in step S15, the suffix based on the prefix of described time domain OFDM synchronizing symbol, OFDM synchronization training symbol and time domain OFDM synchronizing symbol forms time domain OFDM synchronizing symbol.
Such as, OFDM synchronizing symbol time domain main structure is A, A is SkObtaining after Fourier inversion, if the first half of A is A1, latter half is A2, and fixing frequency deviation is ej2πk/N, then spatial structure is sn=[A1ej2πn/N,A1,A2,A2ej2πn/N], snThere are 2048 sampled points.
The structural representation of the OFDM synchronizing symbol according to the present embodiment formation is referred to shown in Fig. 2.In fig. 2, respectively illustrating the structure of frequency-domain OFDM synchronizing symbol and the structure of time domain OFDM synchronizing symbol, wherein, time domain OFDM synchronizing symbol is to be obtained after Fourier inversion processes by frequency-domain OFDM synchronizing symbol.
As shown in Figure 3 be the schematic flow sheet of embodiment of demodulation method of a kind of time domain OFDM synchronizing symbol of the present invention.In the present embodiment, described time domain OFDM synchronizing symbol is that the generation method of the time domain OFDM synchronizing symbol shown in above-mentioned Fig. 1 obtains.
With reference to Fig. 3, the demodulation method of time domain OFDM synchronizing symbol comprises the steps:
Step S21: receive time domain OFDM synchronizing symbol；
Step S22: utilize related operation to process to determine OFDM symbol timing point and fraction frequency offset value to the time domain OFDM synchronizing symbol received；
Step S23: intercept time domain OFDM from this time domain OFDM synchronizing symbol according to determined OFDM symbol timing point and synchronize training symbol；
Step S24: demodulate this time domain OFDM and synchronize the CAZAC sequence on training symbol correspondence frequency domain to solve root parameter and to determine integer-times frequency offset value；
Step S25: intercept the shift sequence of CAZAC sequence according to determined integer-times frequency offset value；
Step S26: the shift sequence of the CAZAC sequence that demodulation intercepts is to determine shift parameters；
Step S27: determine corresponding system parameter message based on described root parameter and shift parameters.
Below in conjunction with specific embodiment, the demodulation method of above-mentioned time domain OFDM synchronizing symbol is described in detail.
As described in step S21, receive time domain OFDM synchronizing symbol.
Such as, receiving signal is rk=sk-θej2πεk/N+ωk, wherein skRepresenting and send signal kth moment sample value, θ represents symbol timing deviation, and ε represents frequency offseting value after subcarrier spacing normalization, ωkRepresent the additive white Gaussian noise kth moment sample value in transmission channel.
As described in step S22, related operation is utilized to process to determine OFDM symbol timing point and fraction frequency offset value to the time domain OFDM synchronizing symbol received.
Specifically, in the present embodiment, this step specifically includes following steps:
Step S221: eliminate the frequency deviation value corresponding to the prefix of this time domain OFDM synchronizing symbol and suffix respectively.
Step S222: respectively the Part I symbol in the prefix training symbol Tong Bu with time domain OFDM eliminating the time domain OFDM synchronizing symbol of frequency deviation value is made related operation to obtain first kind related operation value, and the Part II symbol in the suffix training symbol Tong Bu with time domain OFDM eliminating the time domain OFDM synchronizing symbol of frequency deviation value is made related operation to obtain Equations of The Second Kind related operation value；
Step S223: obtain the first associated averages and the second associated averages after respectively this first kind related operation value and Equations of The Second Kind related operation value being made moving average；
Step S224: the maximum of the maximum and this second associated averages that are based respectively on this first associated averages determines the first synchronizing symbol timing point and the second synchronizing symbol timing point；
Step S225: the argument being based respectively on argument corresponding to the peak-peak of this first associated averages corresponding with the peak-peak of this second associated averages determines the first fraction frequency offset value and the second fraction frequency offset value；
Step S226: the minima in the first synchronizing symbol timing point and the second synchronizing symbol timing point is defined as OFDM symbol timing point, and the meansigma methods of the first fraction frequency offset value and the second fraction frequency offset value is defined as fraction frequency offset value.
Here can in conjunction with the demodulation method of OFDM synchronizing symbol as shown in Figure 4 is determined OFDM symbol timing point and the schematic flow sheet of fraction frequency offset value.
To the s receivednThe first half of (having 2048 data) the fixing frequency deviation that disappears is relevant uk=rk+N(rke-j2πk/N)*, wherein rkRepresent and receive signal, in the present embodiment, synchronize training symbol with corresponding time domain OFDM after taking conjugate complex number after the prefix of time domain OFDM synchronizing symbol is eliminated frequency deviation value and obtain u as related operationk.Further, by correlated results ukU ' is obtained after moving averagek, then the first synchronizing symbol timing point is θ1=argmax (max (abs (u'))), the first fraction frequency offset value is f1=angle (u'(θ1))。
To the s receivednThe latter half of (having 2048 data) the fixing frequency deviation that disappears is relevant vk=rk+2N(rk+3Ne-j2πk/N)*, in the present embodiment, synchronize training symbol with corresponding time domain OFDM after taking conjugate complex number after the suffix of time domain OFDM synchronizing symbol is eliminated frequency deviation value and obtain v as related operationk.Further, by correlated results vkV ' is obtained after moving averagek, then the second synchronizing symbol timing point is θ2=argmax (max (abs (v'))), the second fraction frequency offset value is f2=angle (v'(θ2))。
When the OFDM symbol timing point of estimating system and fraction frequency offset value, OFDM symbol timing point takes the first synchronizing symbol timing point and the minima of the second synchronizing symbol timing point, fraction frequency offset value is the first fraction frequency offset value and the meansigma methods of the second fraction frequency offset value, compensate in system again after estimating system fraction frequency offset value, such that it is able to compensate subsequently received time domain OFDM synchronizing symbol.
Intercepting temporal center part A according to above-mentioned synchronization timing result, wherein temporal center part A includes the A in time-domain OFDM symbol structure as shown in Figure 21+A2Part, obtains frequency domain data Y after Fourier transformation.
Wherein YaFor the M point CAZAC sequence that frequency domain intercepts from k point, a is local optional CAZAC root sequence, CAZAC root sequence described here and CAZAC sequence, takes different root parameter r and can obtain different CAZAC root sequences in CAZAC sequence expression formula, L is sliding scale, Da=argmax (Ra) the corresponding sequence obtaining maximum is CAZAC root sequence, has namely solved r value.Da-pBeing integer-times frequency offset value, p is both sides virtual subnet carrier wavelength.
According to integer-times frequency offset value, the ideal position of the shift sequence of CAZAC sequence offsets Da-pPoint, intercepts the shift sequence of CAZAC sequence.
According to Rb=fft (b*Yb), wherein YbThe shift sequence of the CAZAC sequence for intercepting, b is the shift sequence of locally known CAZAC sequence, Db=argmax (Rb), then DbIt is the shift parameters of b.In actual applications, it is also possible to by DbWith d modulo operation (i.e. DbModd), according to the residual value calculated, revise DbValue, finally estimates λ.
Further; according to the CAZAC sequence demodulated and shift sequence (r value and λ value) thereof; corresponding table 1 obtains the system parameter message that system is carried, and this system parameter message includes the size of Fourier transformation, the size protecting interval and input and output mode (such as SISO pattern and MISO pattern).
Inventor also utilizes the demodulation method of the time domain OFDM synchronizing symbol that the technical program provides to carry out emulation experiment.This emulation experiment carries out in following experimental situation:
nullThis experiment has carried out Computer Simulation for the synchronizing symbol based on CAZAC sequential design described in detailed description of the invention and parametric demodulation thereof，Here with DVBdocumentA133 file " ImplementationGuidelinesforaSecondGenerationDigitalTerre strialTelevisionBroadcastingSystem (second filial generation ground system of digital television broadcast enforcement manual，DVB-T2) the training symbol P1 provided in " is reference marks，Using ViemannA et al. timing frequency deviation scheme proposed in " Implementation-friendlysynchronizationalgorithmforDVB-T2 (the DVB-T2 synchronized algorithm being easily achieved) " as the Synchronos method of reference.
Simulation parameter is provided that simulated environment is DVB-T2 system, system bandwidth is 8M, OFDM subcarrier number is 1024, Cyclic Prefix is 64, intercarrier is divided into 8.929KHZ, 1024 sampled point correspondence 112us, data modulation is 16QAM, CAZAC sequence M=334, r=333, in shift sequence, displacement point λ is with 9 for interval, virtual subnet variable number is p=132, length u is 92, adds 166KHZ frequency deviation, channel is the RayleighChannel (Rayleigh channel) of definition in DVB-T2, and sets synchronizing symbol that the present invention proposes as C1.
Experiment content is as follows with experimental result:
Experiment one: the emulation of demodulation error rate performance
Demodulation error rate described in detailed description of the invention, under Rayleigh channel, has been emulated by this experiment, and after setting synchronization, timing offset is as 4, and decimal overtones band 0.01 subcarrier of residue, integer-times frequency offset remains 18 subcarriers, and result is as shown in Figure 5.
The demodulation error rate of the present invention is far below the P1 symbol in T2 system, more excellent 1dB than P1 demodulation performance.
Experiment two: the emulation of timing offset MSE performance
Timing offset MSE described in detailed description of the invention, under Rayleigh channel, has been emulated by this experiment, and result is as shown in Figure 6.
Timing offset MSE value of the present invention is close with P1 timing offset MSE value, finally all tends to 80.
Experiment three: the emulation of frequency deviation variance performance
Frequency deviation variance described in detailed description of the invention, under Rayleigh channel, has been emulated by this experiment, and result is as shown in Figure 7.
Frequency deviation variance of the present invention, less than P1, estimates excellent about the 1dB of performance than P1 frequency deviation.
The time domain OFDM synchronizing symbol that the present invention proposes generates simple, and thick net synchronization capability substantially increases parametric demodulation performance while being not less than P1.
The embodiment of the present invention additionally provides a kind of data frame transmission method.Wherein, at least including frequency-domain OFDM synchronizing symbol in the Frame of formation, this frequency-domain OFDM synchronizing symbol can be arranged at the frame head part of Frame.As shown in Figure 8 be the structural representation of a kind of data frame transmission method frequency domain OFDM synchronizing symbol of the present invention.
With reference to Fig. 8, described frequency-domain OFDM synchronizing symbol includes:
CAZAC sequence 11, described CAZAC sequence shift sequence 12.
It is filled in the null sequence 13 between the shift sequence 12 of described CAZAC sequence 11 and described CAZAC sequence.In the present embodiment, between the shift sequence 12 of described CAZAC sequence 11 and described CAZAC sequence, why fill the null sequence 13 of certain length (concrete length can set according to actual needs), it it is the impact that carrier wave leakage occurs to reduce ofdm system, namely the time domain OFDM synchronizing symbol (being obtained after Fourier inversion by frequency-domain OFDM synchronizing symbol) generated is sent to receiving terminal process and bigger DC component above occurs at zero-frequency point (in other words low frequency position) by transmitting terminal, is not suitable for transmitting terminal modulation data.
With continued reference to Fig. 8, described frequency-domain OFDM synchronizing symbol also includes being filled in the virtual subnet carrier wave (such as virtual subnet carrier wave 14a, 14b) on the sequence both sides being made up of described CAZAC sequence 11, the shift sequence 12 of described CAZAC sequence and described null sequence 13.In practice, this virtual subnet carrier wave is null sequence.
Skilled artisan understands that, frequency between transmitting terminal and receiving terminal is likely to and asynchronous in an ofdm system, and when frequency shift (FS) is bigger, if being not provided with the virtual subnet carrier wave of certain length, when receiving terminal intercepts sequence from the time domain OFDM synchronizing symbol received, it is possible to described CAZAC sequence or the shift sequence of described CAZAC sequence cannot be truncated to exactly.Therefore, in the present embodiment, the effect filling virtual subnet carrier wave is for tackling the frequency shift (FS) occurred between sending and receiving end in ofdm system, it is ensured that owing to frequency deviation affects effective subcarrier all in midbandwidth.
Described CAZAC sequence 11 is Zadoff-Chu sequence, and its expression formula can beWherein M is sequence length (M is even number), k=0,1 ... and, M-1, j is ordinal number unit, and r is root parameter.Or the expression formula of described CAZAC sequence 11 can also beWherein M is sequence length (M is odd number), k=0,1 ... and, M-1, j is ordinal number unit, and r is root parameter.
In the present embodiment, the value of described root parameter r is relatively prime for the length M positive integer with described CAZAC sequence.
Correspondingly, the expression formula of the shift sequence 12 of described CAZAC sequence isWherein, M is sequence length (M is even number), and λ is shift parameters；Or the expression formula of the shift sequence 12 of described CAZAC sequence can also beWherein M is sequence length (M is odd number), and λ is shift parameters.
In the present embodiment, the value of described shift parameters λ is less than the length of described CAZAC sequence, and the difference of adjacent two values of this shift parameters is in preset range.Described preset range is [1,20].
System is according to different r values and λ value carrying system parameter information, and receiving terminal can pass through to demodulate r value after receiving time domain OFDM synchronizing symbol and λ value obtains the system parameter messages such as the size of the such as Fourier transformation that system is carried, the size protecting interval and input and output mode.
Compared to prior art, the frequency-domain OFDM symbol that the present embodiment provides adopts the shift sequence of CAZAC sequence and this CAZAC sequence directly fill at frequency domain and form frequency-domain OFDM synchronizing symbol, reduce the complexity that OFDM symbol generates.
Although the present invention is with preferred embodiment openly as above; but it is not for limiting the present invention; any those skilled in the art are without departing from the spirit and scope of the present invention; may be by the method for the disclosure above and technology contents and technical solution of the present invention is made possible variation and amendment; therefore; every content without departing from technical solution of the present invention; according to any simple modification, equivalent variations and modification that above example is made by the technical spirit of the present invention, belong to the protection domain of technical solution of the present invention.
Claims (8)
1. the generation method of a time domain OFDM synchronizing symbol, it is characterised in that comprise the steps:
Generating the shift sequence of CAZAC sequence and described CAZAC sequence, wherein said CAZAC sequence includes root parameter, the shift sequence of described CAZAC sequence includes shift parameters；
Shift sequence based on described CAZAC sequence and described CAZAC sequence forms frequency-domain OFDM synchronizing symbol；
Described frequency-domain OFDM synchronizing symbol is carried out Fourier inversion and synchronizes training symbol to form time domain OFDM；
This time domain OFDM is synchronized training symbol and is divided into Part I symbol and Part II symbol, and respectively this two parts symbol is multiplied by mutually with fixing frequency deviation the prefix forming time domain OFDM synchronizing symbol and suffix；
Suffix based on the prefix of described time domain OFDM synchronizing symbol, OFDM synchronization training symbol and time domain OFDM synchronizing symbol forms time domain OFDM synchronizing symbol.
2. the generation method of time domain OFDM synchronizing symbol as claimed in claim 1, it is characterised in that the value of described root parameter is the positive integer relatively prime with the length of described CAZAC sequence.
3. the generation method of time domain OFDM synchronizing symbol as claimed in claim 1, it is characterised in that the value of described shift parameters is less than the length of described CAZAC sequence, and the difference of adjacent two values of this shift parameters is in preset range.
4. the generation method of time domain OFDM synchronizing symbol as claimed in claim 3, it is characterised in that described preset range is [1,20].
5. the generation method of time domain OFDM synchronizing symbol as claimed in claim 1, it is characterized in that, described this time domain OFDM is synchronized training symbol it be divided into Part I symbol and Part II symbol, and respectively this two parts symbol is multiplied by mutually with fixing frequency deviation the prefix of formation OFDM synchronizing symbol and suffix comprises the steps:
This time domain OFDM is synchronized training symbol and is divided into front and back two parts symbol that length is equal, and first half symbol is multiplied by mutually with fixing frequency deviation the prefix forming OFDM synchronizing symbol and latter half symbol is multiplied by mutually with fixing frequency deviation the suffix forming OFDM synchronizing symbol.
6. the demodulation method to the time domain OFDM synchronizing symbol that the generation method of time domain OFDM synchronizing symbol described in claim 1 obtains, it is characterised in that comprise the steps:
Receive time domain OFDM synchronizing symbol；
Related operation is utilized to process to determine OFDM symbol timing point and fraction frequency offset value to the time domain OFDM synchronizing symbol received；
From this time domain OFDM synchronizing symbol, intercept time domain OFDM according to determined OFDM symbol timing point and synchronize training symbol；
Demodulate this time domain OFDM and synchronize the CAZAC sequence on training symbol correspondence frequency domain to solve root parameter and to determine integer-times frequency offset value；
The shift sequence of CAZAC sequence is intercepted according to determined integer-times frequency offset value；
The shift sequence of the CAZAC sequence that demodulation intercepts is to determine shift parameters；
Corresponding system parameter message is determined based on described root parameter and shift parameters.
7. the demodulation method of time domain OFDM synchronizing symbol as claimed in claim 6, it is characterised in that described utilize related operation to process the time domain OFDM synchronizing symbol received to determine that OFDM symbol timing point and fraction frequency offset value comprise the steps:
Eliminate the frequency deviation value corresponding to the prefix of this time domain OFDM synchronizing symbol and suffix respectively；
Respectively the Part I symbol in the prefix training symbol Tong Bu with time domain OFDM eliminating the time domain OFDM synchronizing symbol of frequency deviation value is made related operation to obtain first kind related operation value, and the Part II symbol in the suffix training symbol Tong Bu with time domain OFDM eliminating the time domain OFDM synchronizing symbol of frequency deviation value is made related operation to obtain Equations of The Second Kind related operation value；
The first associated averages and the second associated averages is obtained after respectively this first kind related operation value and Equations of The Second Kind related operation value being made moving average；
The maximum of the maximum and this second associated averages that are based respectively on this first associated averages determines the first synchronizing symbol timing point and the second synchronizing symbol timing point；
The argument being based respectively on argument corresponding to the peak-peak of this first associated averages corresponding with the peak-peak of this second associated averages determines the first fraction frequency offset value and the second fraction frequency offset value；
Minima in first synchronizing symbol timing point and the second synchronizing symbol timing point is defined as OFDM symbol timing point, and the meansigma methods of the first fraction frequency offset value and the second fraction frequency offset value is defined as fraction frequency offset value.
8. the demodulation method of time domain OFDM synchronizing symbol as claimed in claim 6, it is characterised in that described system parameter message includes the size of Fourier transformation, the size protecting interval and input and output mode.
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| CN106603456A (en) * | 2014-03-28 | 2017-04-26 | 上海数字电视国家工程研究中心有限公司 | Generation method of preamble symbol and generation method of frequency-domain OFDM symbol |
| CN105024963A (en) * | 2014-04-30 | 2015-11-04 | 上海数字电视国家工程研究中心有限公司 | Frequency domain OFDM symbol generation method and preamble symbol generation method |
| CN105991266B (en) * | 2015-01-30 | 2019-12-13 | 上海数字电视国家工程研究中心有限公司 | Preamble symbol generation method, reception method, generation device, and reception device |
| CN105991500B (en) * | 2015-02-12 | 2019-07-02 | 上海数字电视国家工程研究中心有限公司 | The method of reseptance and device of leading symbol |
| CN105024952B (en) * | 2014-04-29 | 2019-03-19 | 上海数字电视国家工程研究中心有限公司 | The generation method of frequency-domain OFDM symbol and the generation method of leading symbol |
| CA3212005A1 (en) | 2014-04-16 | 2015-10-22 | Shanghai National Engineering Research Center Of Digital Television Co., Ltd. | Preamble symbol generation and receiving method, and frequency-domain symbol generation method and device |
| US11071072B2 (en) * | 2014-04-16 | 2021-07-20 | Shanghai National Engineering Research Center Of Digital Television Co., Ltd. | Preamble symbol receiving method and device |
| CN106789810A (en) * | 2014-05-28 | 2017-05-31 | 上海数字电视国家工程研究中心有限公司 | The generation method of leading symbol in physical frame |
| CN106850485A (en) * | 2014-06-12 | 2017-06-13 | 上海数字电视国家工程研究中心有限公司 | The generation method of frequency-domain OFDM symbol |
| CN105262710B (en) * | 2014-07-10 | 2020-12-22 | 上海数字电视国家工程研究中心有限公司 | Receiving and processing method of frequency domain OFDM symbol |
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| CN115208725B (en) * | 2022-05-07 | 2024-02-02 | 中国人民解放军国防科技大学 | Method, device and medium for combining OFDM synchronization and information modulation |
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