A High Performance HF Orthogonal Spread Spectrum Iterative Demodulation and Decoding Method

Abstract

A high-performance short-wave orthogonal spread spectrum iterative demodulation and decoding method, including sampling the received signal at a chip rate after passing through a matched filter, correlating the sampled data with the local orthogonal spread spectrum sequence, and using the correlation value to perform non-coherent The demodulated output bit soft value; the bit soft value is used as the input of high-performance coding and decoding for iterative decoding; the decoding and decision output bits are used to reconstruct the orthogonal spread spectrum modulation signal, and realize the channel estimation of the path; the channel estimation restores the path Phase information, to achieve coherent demodulation of orthogonal spread spectrum; according to this process, iterative demodulation and decoding, until the iteration stops, output information bits. This method proposes the iterative demodulation and decoding structure of the orthogonal spread spectrum system; it improves the reliability of the demodulation bit soft value, and fully utilizes the performance of channel coding and decoding; at the same time, the iterative process further improves the accuracy of channel estimation, positive Cross-spread demodulation performance and decoding performance, thereby improving the transmission performance of the existing short-wave communication system.

Description

technical field [0001] The invention relates to a reliable short-wave data communication transmission technology, in particular to a high-performance orthogonal spread spectrum iterative demodulation and decoding method. Background technique [0002] The short-wave channel presents the characteristics of multipath fading, and the spread spectrum technology can effectively resist the influence of fading, and has certain anti-interference ability. Compared with direct sequence spread spectrum, multi-ary orthogonal spread spectrum can avoid the limitation of bandwidth on binary numbers, and can support high-ary numbers without additional insertion of cyclic prefix or training sequence, improving transmission efficiency, and according to digital communication theory, When the binary number of multi-ary orthogonal spread spectrum modulation tends to infinity, the performance close to Shannon's limit signal-to-noise ratio can be obtained. Therefore, multi-ary system orthogonal sp...

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Problems solved by technology

[0003] In order to improve the transmission performance of the orthogonal spread spectrum system, an iterative decoding and demodulation method of joint channel estimation is proposed. However, since the multi-ary orthogonal spread spectrum system does not have a dedicated pilot channel similar to the mobile communication CDMA system, and the short-wave channel is a typical For time-varying fading channels, the traditional demodulation method often adopts non-coherent demodulation, which reduces the reliability of bit soft values ​​compared with coherent demodulation; in iterative demodulation and decoding, the modulation positive is reconstructed through decision feedback Cross-spread signal is used for channel estimation, and considering the time-varying nature of the channel, the channel estimated by two orthogonal spread-spectrum symbols before and after is used as the channel estimation in the current symbol period, which improves the channel estimation accuracy and realizes coherent demodulation. Lay a solid foundation

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