Iteration carrier synchronization method used under condition of extremely low signal to noise ratio

A carrier synchronization and signal-to-noise ratio technology, applied in digital transmission systems, electrical components, error prevention, etc., and can solve problems such as synchronization difficulties

Inactive Publication Date: 2011-05-25
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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Problems solved by technology

[0003] Aiming at the difficulty of synchronization under extremely low SNR conditions, this paper proposes an LDPC-Hadamard code-assisted iterative carrier synchronization algorithm

Method used

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  • Iteration carrier synchronization method used under condition of extremely low signal to noise ratio
  • Iteration carrier synchronization method used under condition of extremely low signal to noise ratio
  • Iteration carrier synchronization method used under condition of extremely low signal to noise ratio

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Embodiment Construction

[0061] ◆Sender:

[0062] 1. LDPC-Hadamard code encoder

[0063] Pass the 504-bit source information bit sequence b through the LDPC-Hadamard encoder, and output the 6048-bit LDPC-Hadamard code word C. The row weight of the check matrix of the LDPC code is 6, and the column weight is 3.

[0064] 2. BPSK modulation

[0065] Codeword C is modulated into BPSK signal s according to the following rules, namely 0→1, 1→-1.

[0066] ◆Receiving end:

[0067] At the receiving end, the specific operation process of joint decoding and synchronization is as follows: Figure 4 As shown, the maximum number of iterations is set to 20. In the case of this code length (N=6048), the synchronization convergence range of the algorithm proposed in this paper is |ΔfT|≤2.5*10 -5 , |θ|≤25°, so before using this algorithm, the received signal needs to be roughly synchronized so that the residual frequency offset and phase offset are within this convergence range. In the convergence range, when th...

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Abstract

The invention provides a low density parity code (LDPC)-Hadamard code-assisted iteration carrier synchronization scheme, which can realize accurate synchronization and correct decoding even under the condition of extremely low signal to noise ratio. In the scheme, two modules, namely a LDPC-Hadamard code decoder and a carrier synchronizer are provided, wherein the carrier synchronizer estimates frequency offset and phase offset by using soft information output by the decoder, performs carrier compensation on a received signal by using estimated values of the frequency offset and the phase offset, transmits a compensated signal to the decoder for decoding and outputs soft information. After iteration is performed repeatedly, carrier synchronization and LDPC-Hadamard code decoding can be realized at the same time. The biggest advantage of the scheme is that: a low-bit-rate code (an LDPC-Hadamard code) is taken as an error correcting code, so that accurate carrier synchronization and correct decoding can be realized under the condition of extremely low signal to noise ratio. A coding and decoding structure of the LDPC-Hadamard code is mainly introduced, and an LDPC-Hadamard code-assisted iteration carrier synchronization method is provided in combination with the decoding structure of the LDPC-Hadamard code. At last, an embodiment is given.

Description

technical field [0001] The present invention relates to two key technologies in the digital communication system, that is, carrier synchronization and error correction coding. Especially in the condition of extremely low signal-to-noise ratio, the design of iterative decoding joint carrier estimation scheme. Background technique [0002] Error-correcting codes with strong error-correcting capabilities, such as Turbo codes and LDPC codes, have excellent theoretical performance, but there is often a large gap in performance in practical applications. This is mainly because the system synchronization accuracy decreases with the decrease of the signal-to-noise ratio. When the signal-to-noise ratio is very low, traditional synchronization algorithms can no longer work normally. In recent years, a code-assisted iterative carrier synchronization method has been proposed. It combines carrier synchronization with a SISO decoder, using the soft information output by the decoder for ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/26H04L25/02H04L1/00
Inventor 唐发建史治平张忠培晏辉
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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