CN111585935B - Integral demodulation method for continuous non-uniform multi-carrier signal - Google Patents
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2649—Demodulators
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
Abstract
The invention discloses an integral demodulation method of continuous non-uniform multi-carrier signals, belonging to the technical field of digital signal processing. The method adopts a serial sectional processing mode to cut a plurality of paths of continuous signal carriers into processing frames, and inputs the processing frames into a matched filtering module, a symbol timing synchronization module, a carrier phase synchronization module and a frame synchronization module in sequence, and realizes the continuous demodulation processing of signals through the reloading of module state information. The method greatly improves the demodulation path number of the demodulation baseband processor, and the advantage is obvious when the speed of a single-path carrier signal is low. The invention can be applied to FDMA networking or multi-system hybrid networking systems, and can greatly reduce the scale of central station equipment, so that the networking mode of the system is more flexible and the processing capability is stronger.
Description
Technical Field
The invention relates to the technical field of digital signal processing, in particular to an integral demodulation method of continuous non-uniform multi-carrier signals.
Background
When the traditional multi-path demodulation method faces continuous signals, a continuous processing framework is not broken through, and before a decoding frame is recovered, multi-path processing can be carried out only by adopting a method of stacking baseband processing modules in parallel. The parallel processing method is simple in design, but the resource consumption is greatly increased along with the increase of the number of processing paths, so that the parallel processing method is difficult to adapt to the application scene of large-scale low-speed signal networking.
Disclosure of Invention
In view of this, the present invention provides an overall demodulation method for continuous non-uniform multi-carrier signals, which can implement overall demodulation for non-uniform multi-channel continuous signals, and has the advantages of multiple processing paths, low implementation complexity, and reduced cost for a central station demodulation baseband processor.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for ensemble demodulation of a continuous non-uniform multi-carrier signal, comprising the steps of:
(1) cutting a plurality of paths of continuous signal carriers with different rates into processing frames according to time, wherein the processing frames of different carriers are distinguished by carrier numbers;
(2) inputting each processing frame into the same demodulation baseband processor in sequence, wherein the demodulation baseband processor performs matched filtering processing, symbol timing synchronization processing, carrier phase synchronization processing and frame synchronization processing on the input processing frame in sequence through an internal matched filtering module, a symbol timing synchronization module, a carrier phase synchronization module and a frame synchronization module;
(3) decoding the decoding block to be decoded obtained after frame synchronization processing to obtain a decoding result and finish the integral demodulation of the continuous non-uniform multi-carrier signal;
the processing mode of each module is as follows:
(201) acquiring a carrier number of a current processing frame from an externally input control parameter, namely a current carrier number;
(202) extracting the data cached at the end of the last processing frame of the current carrier number from the internal RAM of the module, restoring the module to the state at the end of the last processing frame of the current carrier number according to the cached data, and processing the current processing frame in the state, wherein the processing is the current processing;
(203) after the current processing is finished, caching data required by state recovery in an internal RAM of the module, and marking the cached data by using the current carrier number;
(204) and (5) resetting the module, waiting for the next processing frame to arrive, and re-executing the steps (201) to (204) by taking the next processing frame as the current processing frame.
Further, for the matched filtering module, the data buffered in step (203) is the last input data of the currently processed frame and the convolution calculation result of the currently processed frame, and the specific way of the current processing in step (202) is as follows:
multiplexing the last input data of the last processing frame of the current carrier number before the input data of the current processing frame, sequentially performing convolution operation on the multiplexed input data, multiplexing the last convolution calculation results of the last processing frame before the operation result, and taking the two multiplexed convolution calculation results as the processing result of the current processing.
Further, for the symbol timing synchronization module, the buffered data in step (203) is the last input data of the currently processed frame, the currently processed timing error estimation value and the intra-symbol snapshot count value, and the specific way of the current processing in step (202) is as follows:
multiplexing the last input data of the last processing frame of the current carrier number before the input data of the current processing frame, performing timing error recovery on the multiplexed input data by using a cached timing error estimation value, and selecting an optimal sampling point by using a cached intra-symbol snapshot count value for output; and meanwhile, carrying out timing error estimation by using the multiplexed input data to obtain a timing error estimation value.
Further, for the carrier phase synchronization module, the data cached in step (203) is the FFT frequency offset estimation result of the current processing frame and the values of shift registers at different stages in the phase feedback loop of the module, and the specific way of current processing in step (202) is:
recovering a phase feedback loop by using the values of all levels of shift registers in the cached phase feedback loop, performing frequency offset correction on the current processing frame by using the cached FFT frequency offset estimation result, and performing phase tracking on the current processing frame through the recovered phase feedback loop to obtain output data after phase synchronization processing; meanwhile, FFT frequency offset estimation is carried out by utilizing input data of the current processing frame, and an FFT frequency offset estimation result is obtained.
Further, for the frame synchronization module, the buffered data in step (203) is the last input data of the currently processed frame, and the specific way of the current processing in step (202) is as follows:
the last input data of the last processing frame of the current carrier number are multiplexed before the input data of the current processing frame, the unique code search operation is carried out on the multiplexed input data, the position exceeding the threshold is used as the initial position after frame synchronization, and the data is output from the initial position.
Furthermore, the matched filtering module, the symbol timing synchronization module, the carrier phase synchronization module and the frame synchronization module are all realized based on an FPGA.
Compared with the background technology, the invention has the following advantages:
1. the invention solves the path number limitation of the original continuous signal multipath receiving software and can support the integral demodulation of up to 32 paths of continuous signals.
2. The invention introduces the 'serial processing and module multiplexing' method in burst signal demodulation into continuous signal processing, and combines the thought of 'intermediate state parameter overloading', thereby realizing the processing mode of 'segmented cutting and sequential entering' of multi-path continuous signals.
3. The FDMA satellite communication system and the TDMA/FDMA hybrid networking satellite communication system realized by the invention can greatly reduce the equipment scale of the central station and obviously improve the networking flexibility of the system.
Drawings
Fig. 1 is a schematic block diagram of a demodulation baseband processor in an embodiment of the present invention.
Fig. 2 is a schematic diagram of a multi-channel continuous signal divided and then sequentially input to a demodulation baseband processor according to an embodiment of the present invention. Where 1, 2, and 3 denote carrier numbers, continuous data of the same carrier is divided into a plurality of pieces of data, and each piece of data is regarded as one processing frame.
Fig. 3 is a schematic diagram of a processing manner of each module in the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
A method for ensemble demodulation of a continuous non-uniform multi-carrier signal, comprising the steps of:
(1) the method comprises the steps of cutting a plurality of paths of continuous signal carriers with different rates into processing frames according to time, and distinguishing the processing frames of different carriers by carrier numbers.
(2) As shown in fig. 2, each processed frame is sequentially input to the same demodulation baseband processor. As can be seen from fig. 2, the processed frames of each carrier are mixed together and arranged into an input queue, which is sequentially input into the demodulation baseband processor for processing, thereby implementing alternate processing of different carriers.
(3) And decoding the decoding block to be decoded obtained after the frame synchronization processing to obtain a decoding result and finish the integral demodulation of the continuous non-uniform multi-carrier signal. The decoding process can be performed in various conventional manners, which are not described herein.
The demodulation baseband processor is shown in fig. 1, and includes a matched filtering module, a symbol timing synchronization module, a carrier phase synchronization module, and a frame synchronization module, and can sequentially perform matched filtering processing, symbol timing synchronization processing, carrier phase synchronization processing, and frame synchronization processing on an input processing frame; the matched filtering module, the symbol timing synchronization module, the carrier phase synchronization module and the frame synchronization module can be realized based on FPGA, and the specific functions of each module are as follows:
1) the matched filtering module carries out convolution operation to realize filtering processing, and the operation of bit truncation by a digital push filter is adopted, so that only the data at the tail of each storage frame needs to be cached, and the intermediate state of the caching operation is not needed;
2) the symbol timing synchronization module carries out timing error estimation and selects the optimal sampling time to output by utilizing the estimation result, the related estimation algorithm needs to cache the timing error estimation result and the snapshot count value, and demodulation data does not need to be cached;
3) the carrier phase recovery module realizes the correction of frequency and phase and needs to cache the FFT operation frequency offset estimation result used in the coarse synchronization process and the register values of all levels of a feedback loop utilized in the fine synchronization process;
4) the frame synchronization processing module realizes the positioning of the frame starting position and needs to buffer tail data and parameters such as a frame synchronization identifier, the starting position of the previous frame, the frame length, a unique code and the like.
The processing method of each module is shown in fig. 3. The processing flow of each module is similar, parameters and last input data (namely tail data) of a last processing frame are extracted according to carrier numbers, the parameters and the last input data are spliced with the input data of the current frame, algorithm processing is carried out under the control of the parameters, meanwhile, the tail data of the current frame are stored in a data cache, and the intermediate state value of the algorithm processing is stored in a parameter cache. Specifically, the processing procedure of each module comprises the following steps:
(201) acquiring a carrier number of a current processing frame from an externally input control parameter, namely a current carrier number;
(202) extracting the data cached at the end of the last processing frame of the current carrier number from the internal RAM of the module, restoring the module to the state at the end of the last processing frame of the current carrier number according to the cached data, and processing the current processing frame in the state, wherein the processing is the current processing;
(203) after the current processing is finished, caching data required by state recovery in an internal RAM of the module, and marking the cached data by using the current carrier number;
(204) and (5) resetting the module, waiting for the next processing frame to arrive, and re-executing the steps (201) to (204) by taking the next processing frame as the current processing frame.
Further, for the matched filtering module, the data buffered in step (203) is the last input data of the currently processed frame and the convolution calculation result of the currently processed frame, and the specific way of the current processing in step (202) is as follows:
multiplexing the last input data of the last processing frame of the current carrier number before the input data of the current processing frame, sequentially performing convolution operation on the multiplexed input data, multiplexing the last convolution calculation results of the last processing frame before the operation result, and taking the two multiplexed convolution calculation results as the processing result of the current processing.
Further, for the symbol timing synchronization module, the buffered data in step (203) is the last input data of the currently processed frame, the currently processed timing error estimation value and the intra-symbol snapshot count value, and the specific way of the current processing in step (202) is as follows:
multiplexing the last input data of the last processing frame of the current carrier number before the input data of the current processing frame, performing timing error recovery on the multiplexed input data by using a cached timing error estimation value, and selecting an optimal sampling point by using a cached intra-symbol snapshot count value for output; and meanwhile, carrying out timing error estimation by using the multiplexed input data to obtain a timing error estimation value.
Further, for the carrier phase synchronization module, the data cached in step (203) is the FFT frequency offset estimation result of the current processing frame and the values of shift registers at different stages in the phase feedback loop of the module, and the specific way of current processing in step (202) is:
recovering a phase feedback loop by using the values of all levels of shift registers in the cached phase feedback loop, performing frequency offset correction on the current processing frame by using the cached FFT frequency offset estimation result, and performing phase tracking on the current processing frame through the recovered phase feedback loop to obtain output data after phase synchronization processing; meanwhile, FFT frequency offset estimation is carried out by utilizing input data of the current processing frame, and an FFT frequency offset estimation result is obtained.
Further, for the frame synchronization module, the buffered data in step (203) is the last input data of the currently processed frame, and the specific way of the current processing in step (202) is as follows:
the last input data of the last processing frame of the current carrier number are multiplexed before the input data of the current processing frame, the unique code search operation is carried out on the multiplexed input data, the position exceeding the threshold is used as the initial position after frame synchronization, and the data is output from the initial position.
The following is a more specific example:
a method for ensemble demodulation of a continuous non-uniform multi-carrier signal, comprising the steps of:
(1) each path of continuous signals which are cut on a time axis are sequentially input into a matched filtering module according to carrier numbers to complete filtering processing, and noise information outside a signal bandwidth is filtered;
(2) each filtered carrier signal sequentially enters a symbol timing synchronization module for timing synchronization processing to obtain an optimal sampling point;
(3) each carrier signal which completes symbol timing synchronization enters a carrier phase recovery module in sequence to eliminate residual frequency offset and phase offset;
(4) after the carrier phase recovery is finished, all carrier signals sequentially enter a frame synchronization module to carry out frame header capture, and a decoding frame structure is recovered;
finally, each carrier decoding frame is buffered by FIFO and processed by a decoding module in sequence to complete the integral demodulation of the continuous non-uniform multi-carrier signal.
The matched filtering module obtains the filter order and tap coefficient of each stage according to the carrier number, extracts the last frame tail data of the carrier, and performs convolution operation before the processed frame. And cutting the convolution result according to the order of the filter, and outputting the result as matched filtering. The data at the end of the frame to be processed needs to be buffered so as to be extracted and used when the next frame to be processed of the carrier comes, and the depth of the buffer also depends on the order of the filter.
The symbol timing synchronization module extracts the carrier symbol timing error estimation result and the snapshot count value according to the carrier number, determines a snapshot output position according to the error value, and selects an optimal sampling point for the current processing frame data to output by taking the snapshot count value as a cycle counting initial value. Meanwhile, timing error estimation operation is required, and the estimation result is updated to a new error value in real time. At the end of this processing frame, the timing error estimate and snapshot count are cached.
And the carrier phase recovery module extracts the FFT frequency offset estimation result and register values of all levels of the feedback loop according to the carrier number, and performs down-conversion by using the frequency offset estimation result to complete coarse synchronization. And the data after coarse synchronization enters a feedback loop to carry out fine synchronization. Meanwhile, FFT operation is carried out on the processed frame data, and a new frequency offset estimation result is obtained. When the processing frame is finished, caching the new frequency offset estimation result and the register values of all levels of the feedback loop at the moment for the next call.
And the frame synchronization module extracts parameters such as last frame tail data, frame synchronization identification, the starting position of the previous frame, frame length, unique codes and the like according to the carrier number. Wherein the length of the tail data is the same as the frame synchronization unique code. And splicing the tail data and the processed frame data, and detecting the initial position. And when the frame synchronization mark is invalid, searching the frame starting position by taking the synchronization judgment threshold as a basis. When the frame synchronization mark is effective, the frame starting position is estimated according to the previous frame starting position and frame length count, and whether the synchronization state is kept is detected according to the desynchronization judgment threshold. When the frame processing is finished, the whole frame data and the series of parameters are buffered, and the frame synchronized data is output.
And the decoding module at the later stage performs decoding processing on the data subjected to frame synchronization processing, namely the decoding blocks to be decoded to obtain decoding results, so that the overall demodulation of the continuous non-uniform multi-carrier signal is completed.
In the method, each module uses the RAM of the module to realize the caching of the parameters and the tail data, and uses the carrier number as a control address to control the reading and writing of the parameters and the data related to the current processing frame. In addition, the buffer depth of the tail data is determined by the filter order and the frame synchronization unique word length, respectively.
In short, the invention cuts continuous signals, cuts multi-path continuous signal carriers into processing frames by adopting a serial sectional processing mode, and inputs the processing frames into a matched filtering module, a symbol timing synchronization module, a carrier phase synchronization module and a frame synchronization module in sequence, and realizes the continuous demodulation processing of the signals by reloading module state information. The serial processing mode adopted by the invention greatly improves the demodulation path number of the demodulation baseband processor, and the advantage is obvious when the speed of a single-path carrier signal is low.
The invention can be applied to the central station of FDMA networking system or TDMA, FDMA multi-system hybrid networking system, can make the system processing networking mode more flexible and have stronger processing capability, and can greatly reduce the equipment scale of the central station.
Claims (2)
1. A method for ensemble demodulation of a continuous non-uniform multi-carrier signal, comprising the steps of:
(1) cutting a plurality of paths of continuous signal carriers with different rates into processing frames according to time, wherein the processing frames of different carriers are distinguished by carrier numbers;
(2) inputting each processing frame into the same demodulation baseband processor in sequence, wherein the demodulation baseband processor performs matched filtering processing, symbol timing synchronization processing, carrier phase synchronization processing and frame synchronization processing on the input processing frame in sequence through an internal matched filtering module, a symbol timing synchronization module, a carrier phase synchronization module and a frame synchronization module;
(3) decoding the decoding block to be decoded obtained after frame synchronization processing to obtain a decoding result and finish the integral demodulation of the continuous non-uniform multi-carrier signal;
the processing mode of each module is as follows:
(201) acquiring a carrier number of a current processing frame from an externally input control parameter, namely a current carrier number;
(202) extracting the data cached at the end of the last processing frame of the current carrier number from the internal RAM of the module, restoring the module to the state at the end of the last processing frame of the current carrier number according to the cached data, and processing the current processing frame in the state, wherein the processing is the current processing;
(203) after the current processing is finished, caching data required by state recovery in an internal RAM of the module, and marking the cached data by using the current carrier number;
(204) resetting the module, waiting for the next processing frame to arrive, and taking the next processing frame as the current processing frame to execute the steps (201) - (204) again;
for the matched filter module, the data buffered in step (203) is the last input data of the currently processed frame and the convolution calculation result of the currently processed frame, and the specific way of the current processing in step (202) is as follows:
multiplexing the last input data of the last processing frame of the current carrier number before the input data of the current processing frame, sequentially carrying out convolution operation on the multiplexed input data, multiplexing the last convolution calculation results of the last processing frame before the operation results, and taking the two multiplexed convolution calculation results as the processing results of the current processing;
for the symbol timing synchronization module, the buffered data in step (203) is the last input data of the currently processed frame, and the currently processed timing error estimation value and the intra-symbol snapshot count value, and the specific way of the current processing in step (202) is as follows:
multiplexing the last input data of the last processing frame of the current carrier number before the input data of the current processing frame, performing timing error recovery on the multiplexed input data by using a cached timing error estimation value, and selecting an optimal sampling point by using a cached intra-symbol snapshot count value for output; meanwhile, timing error estimation is carried out by using the multiplexed input data to obtain a timing error estimation value;
for the carrier phase synchronization module, the data cached in step (203) is the FFT frequency offset estimation result of the current processing frame and the values of the shift registers at each stage in the phase feedback loop of the module, and the specific way of the current processing in step (202) is:
recovering a phase feedback loop by using the values of all levels of shift registers in the cached phase feedback loop, performing frequency offset correction on the current processing frame by using the cached FFT frequency offset estimation result, and performing phase tracking on the current processing frame through the recovered phase feedback loop to obtain output data after phase synchronization processing; meanwhile, performing FFT frequency offset estimation by using input data of a current processing frame to obtain an FFT frequency offset estimation result;
for the frame synchronization module, the buffered data in step (203) is the last input data of the currently processed frame, and the specific way of the current processing in step (202) is as follows:
the last input data of the last processing frame of the current carrier number are multiplexed before the input data of the current processing frame, the unique code search operation is carried out on the multiplexed input data, the position exceeding the threshold is used as the initial position after frame synchronization, and the data is output from the initial position.
2. The method of claim 1, wherein the matched filter module, the symbol timing synchronization module, the carrier phase synchronization module and the frame synchronization module are all implemented based on FPGA.
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