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 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 In deep space communication, the extremely low SNR firstly makes the demodulation of the receiver face severe synchronization problems. Under extremely low SNR, traditional synchronization using finite-length pilot or decision-directed will not work effectively, and iterative synchronization combined with channel codes can effectively solve this problem. Joint demodulation and decoding have been used in typical applications in deep space communication. For example, JPL simulated a Turbo code with a code rate of 1 / 31 and code-assisted synchronization, and achieved reliable communication with an SNR as low as -15.8dB. However, this scheme also has the problem of high implementation complexity. The iterative synchronization can feed back the soft information obtained in the channel code de...

AI Technical Summary

Problems solved by technology

The purpose of the present invention is to at least solve one of the above-mentioned technical defects, especially to solve the problem of receiving demodulation under the extremely low SNR condition of deep space communication. The above shortcomings and deficiencies caused by extremely low SNR provide a digital communication receiving system that can avoid the above shortcomings and deficiencies - MSK iterative demodulation system combined with LDPC codes

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