CN109728827B - Sequence assisted acquisition low signal-to-noise ratio TPC coding and decoding system - Google Patents
Sequence assisted acquisition low signal-to-noise ratio TPC coding and decoding system Download PDFInfo
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Abstract
A sequence assisted capturing low signal to noise ratio TPC coding and decoding system firstly generates a TPC coding auxiliary sequence at a sending end, segments the obtained TPC coding auxiliary sequence, respectively carries out FFT and IFFT transformation on each segment of data, crossly stores the data after the FFT transformation and the IFFT transformation in front of a corresponding TPC coding data frame, outputs the data to up-conversion and transmits the data, then carries out sliding sampling on an AD sampling signal at a receiving end through a low pass filter, searches for the maximum value to obtain the frame head position and Doppler frequency offset of the TPC coding auxiliary sequence after the FFT transformation and the IFFT transformation, compensates to a data clock, and sends the TPC coding data frame to a TPC decoder.
Description
Technical Field
The invention relates to a sequence assisted acquisition low signal-to-noise ratio TPC coding and decoding system, which is mainly used for quickly acquiring under a low signal-to-noise ratio, recovering original data and verifying the system performance of a receiver.
Background
With the use and development of measurement and control satellites and deep space exploration, the problem of low signal-to-noise ratio acquisition brought by remote communication is increasingly prominent; in addition, due to the limitation of transmitter power, the cost of modifying and verifying the hardware such as an antenna on the mature model products is high; the fast acquisition of signals under the environment of low signal-to-noise ratio is a key technology to be solved by a measurement and control system.
Disclosure of Invention
The technical problem solved by the invention is as follows: the defects of the prior art are overcome, and a sequence assisted acquisition low signal-to-noise ratio TPC coding and decoding system is provided, which can perform self-adaptive discrimination on a signal to noise ratio, thereby realizing rapid acquisition and tracking.
The technical solution of the invention is as follows: a sequence assisted acquisition low signal-to-noise ratio (TPC) coding and decoding system comprises a TPC coding sequence generation module and a TPC decoding sequence auxiliary module, wherein:
a TPC coding sequence generation module, which is deployed at the transmitter end of a TPC coding and decoding system, generates a TPC coding auxiliary sequence by adopting a local clock and a local time timer according to the frequency deviation and the signal-to-noise ratio of a receiver, segments the TPC coding auxiliary sequence, supplements 0 to each segment of data to enable the segments to be equal in length, then respectively carries out FFT and IFFT on each segment of data, and stores the data after the FFT and IFFT are crossed before corresponding TPC coding data frames, and then outputs the data to up-conversion and transmits the data;
the TPC decoding sequence auxiliary module is deployed at a receiver end of a TPC coding and decoding system, an AD sampling signal passes through a low-pass filter, then the low-pass signal is subjected to sliding sampling by a matching clock, the maximum value is searched to obtain the frame header position and Doppler frequency offset of the TPC coding auxiliary sequence after FFT and IFFT conversion, the frame header position and Doppler frequency offset are compensated to a data clock, the TPC coding data frame is sent to a TPC decoder, and when the error rate does not meet the requirement of the TPC coding and decoding system after the iterative search of the TPC decoder, the TPC coding auxiliary sequence after the FFT and IFFT conversion and the TPC coding data frame are subjected to exclusive OR division and then sent to the decoder for multiple iterations until the error rate meets the requirement of the TPC coding and decoding system after the iterative search of the TPC decoder.
The local clock adopts 110M, and the local time timer adopts 64-bit wide.
After the data of each section is supplemented with 0, the data length of each section is 2N.
The TPC coding frame comprises a TPC coding auxiliary sequence and a TPC coding data frame after FFT transformation and IFFT transformation.
The matching clock of the TPC decoding sequence auxiliary module is 1/N of the data rate Ts of the TPC coding and decoding system.
The TPC coding sequence generation module generates an auxiliary sequence according to the frequency offset, the signal-to-noise ratio and the TPC coding, and the used data rate, the data frame format, the TPC coding matrix and the length can be configured.
A coding and decoding method for sequence assisted acquisition low signal-to-noise ratio (TPC) comprises the following steps:
(1) Generating a TPC coding auxiliary sequence at a transmitter end of a TPC coding and decoding system by adopting a local clock and a local time timer according to the frequency offset and the signal-to-noise ratio of a receiver;
(2) Segmenting the obtained TPC coding auxiliary sequence, complementing 0 for each segment of data until the length of each segment of data is equal, then respectively carrying out FFT and IFFT transformation on each segment of data, storing the data after the FFT and IFFT transformation in front of the corresponding TPC coding data frame in a crossed manner, and then outputting the data to up-conversion and transmitting;
(3) And (3) an AD sampling signal passes through a low-pass filter at a receiver end of the TPC coding and decoding system, then the low-pass signal is subjected to sliding sampling by taking 1/N of the data rate Ts of the TPC coding and decoding system as a matched clock, the maximum value is searched to obtain the frame head position and Doppler frequency offset of the TPC coding auxiliary sequence after FFT conversion and IFFT conversion, the frame head position and Doppler frequency offset are compensated to the data clock, the TPC coding data frame is sent to a TPC decoder, if the error rate does not meet the TPC coding and decoding system requirement after the TPC decoder is subjected to iterative search, the TPC coding auxiliary sequence after FFT conversion and IFFT conversion and the TPC coding data frame are subjected to exclusive OR and then are sent to the decoder for multiple iterations until the error rate meets the TPC coding and decoding system requirement after the TPC decoder is subjected to iterative search.
The local clock adopts 110M, and the local time timer adopts 64-bit wide.
And (2) segmenting the obtained TPC coding auxiliary sequence, and complementing 0 for each segment of data until the length of each segment of data is 2N.
And (4) in the step (3), the matching clock is 1/N of the data rate Ts of the TPC coding and decoding system.
Compared with the prior art, the invention has the advantages that:
(1) The invention utilizes the characteristics of the auxiliary sequence to uniformly calibrate the information after TPC coding from the time dimension, and has the advantage of less occupied spacecraft system resources;
(2) The gain of the invention in long-time data communication is stable, depends on the signal-to-noise ratio and frequency offset and the rate of a data source, and can realize different system performances according to the hardware resource conditions of a transmitter and a receiver;
(3) The auxiliary sequence generation method realizes accurate recovery of data in different signal-to-noise ratio environments.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a schematic diagram of a TPC coding sequence generation module of the present invention;
fig. 3 is a schematic diagram of an auxiliary module of the TPC decoding sequence according to the present invention.
Detailed Description
The invention overcomes the defects of the prior art, provides a sequence assisted acquisition low signal-to-noise ratio TPC coding and decoding system, and can adaptively judge the signal-to-noise ratio of a signal, thereby realizing rapid acquisition and tracking. A sequence assisted acquisition low signal-to-noise ratio (TPC) coding and decoding system comprises a TPC coding sequence generation module and a TPC decoding sequence auxiliary module, wherein:
the TPC coding sequence generation module is deployed at the transmitter end of the TPC coding and decoding system, and generates a TPC coding auxiliary sequence by adopting a local clock and a local time timer according to the frequency offset and the signal-to-noise ratio of a receiver, wherein the local clock adopts 110M, and the local time timer adopts 64-bit width; segmenting the TPC coding auxiliary sequence, complementing 0 for each segment of data until the length of each segment of data is 2N, then respectively carrying out FFT and IFFT transformation on each segment of data, cross-storing the data after the FFT and IFFT transformation in front of a corresponding TPC coding data frame, and then outputting the data to the upper frequency conversion and transmitting; the TPC coding frame comprises a TPC coding auxiliary sequence and a TPC coding data frame after FFT and IFFT transformation;
the TPC decoding sequence auxiliary module is deployed at a receiver end of a TPC coding and decoding system, an AD sampling signal passes through a low-pass filter, then the low-pass signal is subjected to sliding sampling by taking 1/N of the data rate Ts of the TPC coding and decoding system as a matching clock, the maximum value is searched to obtain the frame head position and Doppler frequency offset of the TPC coding auxiliary sequence after FFT and IFFT conversion, the frame head position and Doppler frequency offset are compensated to the data clock, the TPC coding data frame is sent to a TPC decoder, if the error rate does not meet the TPC coding and decoding system requirement (10-6) after iterative search of the TPC decoder, the TPC coding auxiliary sequence after FFT and IFFT conversion and the TPC coding data frame are subjected to exclusive OR and then sent to the decoder for multiple iterations until the error rate meets the TPC coding and decoding system requirement (10-6) after iterative search of the TPC decoder.
A coding method for sequence assisted acquisition of low signal-to-noise ratio (TPC) comprises the following steps:
(1) Generating a TPC coding auxiliary sequence at a transmitter end of a TPC coding and decoding system by adopting a local clock and a local time timer according to the frequency offset and the signal-to-noise ratio of a receiver, wherein the local clock adopts 110M, and the local time timer adopts 64-bit wide;
(2) Segmenting the obtained TPC coding auxiliary sequence, supplementing 0 to each segment of data until the length of each segment of data is 2N, then respectively carrying out FFT and IFFT transformation on each segment of data, and cross-storing the data after the FFT and IFFT transformation in front of the corresponding TPC coding data frame, and then outputting the data to an upper frequency converter and transmitting the data; the TPC coding frame comprises a TPC coding auxiliary sequence and a TPC coding data frame after FFT and IFFT transformation;
(3) An AD sampling signal is processed by a low-pass filter at a receiver end of a TPC coding and decoding system, then the signal after low-pass is subjected to sliding sampling by taking 1/N of the data rate Ts of the TPC coding and decoding system as a matching clock, the maximum value is searched to obtain the frame head position and Doppler frequency offset of a TPC coding auxiliary sequence after FFT (fast Fourier transform) and IFFT (inverse fast Fourier transform), the frame head position and Doppler frequency offset are compensated to the data clock, a TPC coding data frame is sent to a TPC decoder, and if the error rate does not meet the requirements of the TPC coding and decoding system after iterative search of the TPC decoder (10) -6 ) Dividing the TPC coding auxiliary sequence subjected to FFT (fast Fourier transform) and IFFT (inverse fast Fourier transform) and the TPC coding data frame into XOR (exclusive OR) and sending the XOR to a decoder for multiple iterations until the error rate meets the TPC coding and decoding system requirement after the TPC decoder is iteratively searched (10) -6 )。
As shown in fig. 1, a signal source in the TPC code sequence generating module in the present invention is compressed by a high definition image through a DSP, and then output to an FPGA for buffering, and data is encoded by row and column TPC, and the TPC encoded data is divided into a plurality of segments according to a required signal-to-noise ratio, and after each segment is xored with an auxiliary sequence generated by local clock control, FFT and IFFT transformation are performed, and after being divided by a number of points and stored in a cross manner before the TPC encoded data, the TPC encoded data is transmitted to a wireless channel through a modulator and an up-conversion.
The TPC decoding sequence auxiliary module is converted to a baseband through a down converter, signals converted into 140M are sampled and cached by AD9239 company, the auxiliary sequence is detected, corresponding frequency offset relation is calculated when the in-place detection timing begins, a data clock is generated from the frequency offset relation and sent to a TPC decoder, data recovered by the TPC decoder is compared with original data, and the system error rate is counted.
Fig. 2 shows the structure of an embodiment of the TPC code sequence generating module of the present invention. The auxiliary sequence is generated by timing control of a local clock and local time, and a time control counter adopts 64-bit wide, so that the data discrimination of the receiver under long-time work can be ensured. Meanwhile, the data after TPC coding is controlled by the signal-to-noise ratio to be segmented, the segmented data is supplemented with the power of N from 0 to 2, FFT and IFFT conversion is respectively carried out, then the FFT and IFFT data are stored in front of the TPC coding frame in a crossed mode, multiplied by a DDS generated carrier wave 25M and input to an AD9148 chip, the AD9148 chip is configured with an internal phase-locked loop from SPI to be multiplied by 165M, and after sampling, a 140M intermediate frequency signal is output and output to up-conversion.
Fig. 3 shows the structure of an embodiment of the TPC decoding sequence assistance block in the present invention. The DDS generates 30M cos theta and sin theta, which are multiplied by the AD sampled signals respectively, and the high frequency components are eliminated through a low pass filter. And (2) performing sliding sampling on the low-pass signal by taking N divided by 1 data rate Ts as a matching clock, searching a maximum value at a position where timing occurs accurately, comparing whether a frame header position is searched according to the setting of a threshold value, calculating the frequency offset at the moment, compensating to the data clock, sending data into a TPC decoder, and if an error code exists after iterative search of the TPC decoder, performing exclusive OR on the auxiliary sequence and the data with the error code in the TPC decoder, and then sending the auxiliary sequence and the data into the decoder for iteration.
In summary, the invention firstly assists the sequence to improve the TPC decoding gain, and the calculation and combination of the data bit timing start and the frequency offset, secondly, the data segmentation after the TPC coding only needs to meet the capture minimum sensitivity of the signal under the environment, and finally, the simulation generation of interference and noise is convenient for the construction of a test system, and the system performance can be rapidly verified.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (10)
1. A sequence assisted acquisition low signal-to-noise ratio (TPC) coding and decoding system is characterized by comprising a TPC coding sequence generation module and a TPC decoding sequence auxiliary module, wherein:
a TPC coding sequence generation module, which is deployed at the transmitter end of a TPC coding and decoding system, generates a TPC coding auxiliary sequence by adopting a local clock and a local time timer according to the frequency deviation and the signal-to-noise ratio of a receiver, segments the TPC coding auxiliary sequence, supplements 0 to each segment of data to enable the segments to be equal in length, then respectively carries out FFT and IFFT on each segment of data, and stores the data after the FFT and IFFT are crossed before corresponding TPC coding data frames, and then outputs the data to up-conversion and transmits the data;
the TPC decoding sequence auxiliary module is deployed at a receiver end of a TPC coding and decoding system, an AD sampling signal passes through a low-pass filter, then the low-pass signal is subjected to sliding sampling by a matching clock, the maximum value is searched to obtain the frame header position and Doppler frequency offset of the TPC coding auxiliary sequence after FFT and IFFT conversion, the frame header position and Doppler frequency offset are compensated to a data clock, the TPC coding data frame is sent to a TPC decoder, and when the error rate does not meet the requirement of the TPC coding and decoding system after the iterative search of the TPC decoder, the TPC coding auxiliary sequence after the FFT and IFFT conversion and the TPC coding data frame are subjected to exclusive OR division and then sent to the decoder for multiple iterations until the error rate meets the requirement of the TPC coding and decoding system after the iterative search of the TPC decoder.
2. The system of claim 1, wherein the sequence assisted acquisition TPC coding system comprises: the local clock adopts 110M, and the local time timer adopts 64-bit wide.
3. The system of claim 2, wherein the sequence assisted acquisition TPC coding system further comprises: after the data of each section is supplemented with 0, the data length of each section is 2N.
4. A sequence assisted acquisition TPC coding system according to claim 1 or 2, wherein: the TPC coding frame comprises a TPC coding auxiliary sequence and a TPC coding data frame after FFT transformation and IFFT transformation.
5. A sequence assisted acquisition TPC coding system according to claim 1 or 2, wherein: the matching clock of the TPC decoding sequence auxiliary module is 1/N of the data rate Ts of the TPC coding and decoding system.
6. A sequence assisted acquisition TPC coding system according to claim 1 or 2, wherein: the TPC coding sequence generation module generates an auxiliary sequence according to the frequency offset, the signal-to-noise ratio and the TPC coding, and the used data rate, the data frame format, the TPC coding matrix and the length can be configured.
7. A coding and decoding method for sequence assisted acquisition (TPC) with low signal-to-noise ratio is characterized by comprising the following steps:
(1) Generating a TPC coding auxiliary sequence at a transmitter end of a TPC coding and decoding system by adopting a local clock and a local time timer according to the frequency offset and the signal-to-noise ratio of a receiver;
(2) Segmenting the obtained TPC coding auxiliary sequence, complementing 0 for each segment of data until the length of each segment of data is equal, then respectively carrying out FFT and IFFT transformation on each segment of data, storing the data after the FFT and IFFT transformation in front of the corresponding TPC coding data frame in a crossed manner, and then outputting the data to up-conversion and transmitting;
(3) And (3) an AD sampling signal passes through a low-pass filter at a receiver end of the TPC coding and decoding system, then the low-pass signal is subjected to sliding sampling by taking 1/N of the data rate Ts of the TPC coding and decoding system as a matched clock, the maximum value is searched to obtain the frame head position and Doppler frequency offset of the TPC coding auxiliary sequence after FFT conversion and IFFT conversion, the frame head position and Doppler frequency offset are compensated to the data clock, the TPC coding data frame is sent to a TPC decoder, if the error rate does not meet the TPC coding and decoding system requirement after the TPC decoder is subjected to iterative search, the TPC coding auxiliary sequence after FFT conversion and IFFT conversion and the TPC coding data frame are subjected to exclusive OR and then are sent to the decoder for multiple iterations until the error rate meets the TPC coding and decoding system requirement after the TPC decoder is subjected to iterative search.
8. The method of claim 7, wherein the sequence assisted acquisition TPC coding method with low snr is characterized by: the local clock adopts 110M, and the local time timer adopts 64-bit wide.
9. The method of claim 8 wherein the code encoding is performed by a sequence assisted acquisition (TPC) with low SNR, wherein: and (2) segmenting the obtained TPC coding auxiliary sequence, and complementing 0 for each segment of data until the length of each segment of data is 2N.
10. The method of claim 9, wherein the TPC coding is based on a sequence assisted acquisition low snr TPC coding method, wherein: and (4) the matching clock in the step (3) is 1/N of the data rate Ts of the TPC coding and decoding system.
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