Method and system for MSK iterative demodulation by combining LDPC code

Abstract

The invention discloses a method for MSK iterative demodulation by combining an LDPC code, which comprises the following steps of: performing orthogonal down-conversion, low-pass filtering, carrier frequency offset rough estimation and compensation on received signals in turn, then storing processing results in a first-stage buffer, and simultaneously performing differential demodulation on data after compensation; performing frame synchronization head-related detection on the data after the differential demodulation, and after a frame synchronization head is detected in the related detection, using a control switch to perform carrier phase offset rough estimation and compensation and simultaneously perform an SNR estimation on the data in the first-stage buffer; storing the data after the carrier phase offset compensation into a second-stage buffer; and reading the data in the second-stage buffer to perform LDPC code assisted iterative carrier and timing synchronization and compensation, performing MSK coherent demodulation and LDPC encoding on the data after the LDPC code assisted iterative carrier and timing synchronization and compensation in turn, and outputting an encoding result decision. The technical scheme provided by the invention realizes quick demodulation and encoding functions under ultra-low SNR by using the system and the method for the MSK iterative demodulation by combining the LDPC code.

Description

technical field [0001] The invention relates to the technical field of digital communication, in particular to a joint LDPC code MSK iterative demodulation method and system. Background technique [0002] In deep space communication, the extremely low SNR first makes the demodulation of the receiver face severe synchronization problems. Under extremely low SNR, traditional synchronization using finite pilot or decision-oriented will not work effectively, and iterative synchronization combined with channel codes can effectively solve this problem. Joint demodulation and decoding have been typical applications in deep space communications. For example, JPL has simulated 1 / 31 code rate Turbo code and code-assisted synchronization, achieving reliable communication with an SNR as low as -15.8dB. But this scheme also has the problem of high implementation complexity. [0003] Iterative synchronization can feed back the soft information obtained in channel code decoding to the ca...

AI Technical Summary

Problems solved by technology

Moreover, since the convergence range of the decoding-assisted demodulation algorithm is relatively narrow, it is necessary to use a traditional low-complexity demodulation algorithm to perform a rough estimation to speed up the implementation process of joint demodulation and decoding.

In addition, the implementation complexity of the existing joint demodulation and decoding algorithm is still relatively high. The main reason is that the soft information feedback feedback in the decoding iteration process is not excavated from a deeper level, and the soft information is simply used in the traditional algorithm. Judgment basis for mid-judgment feedback occasions

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