F_n ＝[0,1,…N_rf-max ]wherein F is_n For radio frame number, N_{rf_max} A maximum of 10ms frame number for one continuous reception of radio frequency.

When F_n At 128 or less, step 102 is performed, wherein F_n ＝F_n +1, when F_n If 128, then step 109 is performed directly;

step 102, downsampling the sampled data to a first preset sampling rate at 8-1-mm intervals,

denoted as d '= [ d ]'₀ ,d′₁ ,…,d′₂₃₉₉ ,…]；

Step 103, for the radio frame number F_n Within the 8 times downsampled data, from the offset τ position, 187 sample data in 11 OFDMA symbols are taken for autocorrelation calculation, and a vector composed of the data taken each time is expressed as:

wherein,,

i＝0～186,L_NPSS for the data of the sample points in question,

r_τ,l ＝[r_τ,17l ,r_τ,17l+1 ,…,r_τ,17l+16 ],l＝0～10

τ＝subFrameNum*240+m,subFrameNum∈[0,1,…9],m∈[49,53]；

the GNSS global navigation service enables the radio frequency front end to provide data with 1ms of air interface alignment;

104, calculating the autocorrelation result for the tau-fetch data set according to the offset

τ＝subFrameNum*240+m,subFrameNum∈[0,1,…9],m∈[49,53]，

Wherein F is_n For sliding the 10ms index of the autocorrelation, it is initialized to 0 at the beginning of the autocorrelation process, k denotes the different ofdma symbol intervals, s_l For the substitution code coverage set 1, -1, -1,1} mth element;

step 105, according to the autocorrelation result

Inter-frame combination is performed, and the reliability of NPSS detection can be further improved by using inter-frame accumulation. The method comprises the following steps:

τ＝subFrameNum*240+m,subFrameNum∈[0,1,…9],m∈[49,53]；

step 106, combining the different relevant OFDMA symbol intervals k, with the specific formula:

τ＝subFrameNum*240+m,subFrameNum∈[0,1,…9],m∈[49,53]

the vector after combination is obtained, and the specific formula is as follows:

step 107, according to the absolute value of the vector and the decision and time offset estimation according to the correlation peak,

the maximum correlation peak is:

average power of noise is

Wherein the method comprises the steps of

τ＝subFrameNum*240+m,subFrameNum∈[0,1,…9],m∈[49,53]

The decision formula is P_peak >P_noise *Th_AR ,Th_AR Is an autocorrelation decision threshold;

if so, judging that NPSS exists.

When the decision is established, the time offset is estimated as: TO_AR240KHz ＝τ_peak ；

Step 108, performing decimal frequency offset estimation according to the maximum correlation peak:

step 109, the autocorrelation section ends and decides whether to perform the following cross-correlation process according to the decision result.

Preferably, in any of the foregoing embodiments, step 2 specifically includes:

the step 2 specifically comprises the following steps:

Further elaboration of the calculation of the data such as the frequency offset is performed through coarse cross-correlation.

It should be noted that the first sampling data is sampling data that may include NPSS;

as shown in fig. 3, the specific operation method of step 2 may refer to the following:

step 201, data corresponding to a sampling rate of 240khz after 8 times downsampling of data with a sampling rate of 1.92MHz from a radio frequency front end is:

d″＝[d″₀ ,d″₁ ,…,d″₂₃₉₉ ，…]

wherein:

F_n ＝F_n +1,F_n initial value is 0, when F_n When 68 is smaller or smaller, step 202 is executed, when F_n >68, step 210 is performed;

step 202, extracting data containing the primary synchronization signal in step 201 according to sliding autocorrelation timing, and the specific formula is as follows:

step 203, for d_τ,k According to FO_AR240KHz The decimal frequency offset correction is carried out, and the specific formula is as follows:

λ_k counting the input points corresponding to the received data at a sampling rate of 1.92M;

step 204, generating a local time domain primary synchronization signal sequence according to a protocol synchronization signal generation formula, wherein the specific formula is as follows:

d_local_k ,k∈[0,1,2,…,188]；

step 205, performing integer frequency offset compensation on the time domain primary synchronization signal sequence, and specifically adopting the following formula:

step 206, calculating coarse cross-correlation, and recording the result as

F_n Representing the number of wireless frames, k is more than or equal to 0 and less than or equal to 188, -N_ifo ≤τ≤N_ifo ,N_ifo ＝2,i＝-1,0,1；

Step 207, inter-frame accumulation of coarse cross-correlation, and the specific formula is as follows:

F_n representing radio frame number, -N_ifo ≤τ≤N_ifo ,N_ifo ＝2,i＝-1,0,1；

Step 208, performing a decision of the primary synchronization signal according to the result in step 207, and specifically the following formula is:

if the following equation is satisfied, it is determined that the primary synchronization signal has been successfully detected and further confirmed,

sumMax32*Th_CR > sumE, sumMax32 is the first 32 energy summations of the ordered sequence, sumE is the total energy summations;

step 209, updating the time offset and the frequency offset of the judgment result, wherein the specific formula is as follows:

the updated time bias is: TO_CR240KHz ＝TO_AR240KHz +τ_out，

The updated frequency offset is: FO (FO)_CR240KHz ＝FO_AR240KHz +IFO，

Wherein the coarse integer frequency offset result is

Step 210, the coarse synchronization cross-correlation section ends and determines whether to perform the following fine synchronization cross-correlation procedure.

Preferably, in any of the foregoing embodiments, step 3 specifically includes:

It should be noted that, as shown in fig. 4, the specific operation method of step 3 may refer to the following:

step 301, the data corresponding to 1.92Mhz sampling rate from the rf front end is:

d″＝[d″₀ ,d″₁ ,…,d″₁₉₁₉₉ ]，

F_n ＝F_n +1,F_n initial value is 0, when F_n When 64 is smaller or smaller, step 302 is performed, when F_n At > 64, step 308 is performed;

step 302, extracting data containing a primary synchronization signal from the data corresponding to the sampling rate of 1.92Mhz, wherein the specific formula is as follows:

step 303, generating a local time domain primary synchronization signal sequence according to a generation formula of the protocol primary synchronization signal, wherein the specific formula is as follows:

d_local_k ,k∈[0,1,2,…,1507]；

step 304, performing frequency offset compensation on the generated data of the primary synchronization signal, where a specific formula is as follows:

step 305, calculating a fine cross-correlation for the data in step 302 and step 304 respectively, and specifically the following formula is as follows:

step 306, performing conjugate differential product on the fine cross-correlation value, and the specific formula is as follows:

CR_τ ＝conj(CR_τ,half0 ).*CR_τ,half1 ；

step 307, accumulating the numerical value and the history value after the conjugate difference product, and the specific formula is as follows:

wherein->

The initial value is 0;

jump to step 301 for execution;

step 308, updating calculation of time offset and frequency offset,

wherein,,

-24≤τ≤24。

the reader will appreciate that in the description of this specification, a description of terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

The present invention is not limited to the above embodiments, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the present invention, and these modifications and substitutions are intended to be included in the scope of the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.

Claims

1. A method of computing in a time-frequency synchronization process, comprising:

step 3, if the NPSS exists according to the signal-to-noise ratio and the coarse cross-correlation calculation result, carrying out two-section fine cross-correlation calculation on the received sampling data and the NPSS sequence which is locally generated and subjected to frequency offset compensation obtained in the step 2 under a second preset sampling rate, carrying out conjugate difference calculation on the two-section fine cross-correlation calculation result, carrying out wireless frame-to-frame combination on the conjugate difference calculation result, and calculating final time offset and frequency offset according to the wireless frame-to-frame combination result;

wherein, step 1 specifically comprises:

step 101, dividing the received sampling data into intervals at equal intervals according to a radio frame with a preset length, executing step 102 when the number of a first radio frame is smaller than a first preset number, and executing step 109 when the number of the first radio frame is larger than the first preset number; step 102, downsampling the received data to a first preset sampling rate;

2. The method according to claim 1, wherein step 2 specifically comprises:

step 204, generating a first local time domain NPSS signal sequence according to a protocol;

step 205, performing integer frequency offset compensation on the local time domain NPSS signal sequence; step 206, performing coarse cross-correlation calculation according to the decimal frequency offset compensated received data and the integer frequency offset compensated local generation sequence;

step 207, performing inter-frame accumulation on the result of the coarse cross-correlation calculation; step 208, sorting and judging whether the NPSS exists according to the accumulation result of the step 207;

step 209, updating the time offset and the frequency offset according to the accumulation sequencing result in step 208; and step 210, judging whether to execute the step 3 according to the calculation result of the coarse cross correlation.

3. The method according to claim 2, wherein the step 3 specifically comprises:

step 306, performing conjugate difference product calculation on the result of the two sections of fine cross-correlation calculation; step 307, performing wireless inter-frame accumulation on the result of the conjugate difference product calculation and the history value;