Dissertation > Industrial Technology > Radio electronics, telecommunications technology > Communicate > Communication theory > Information Theory

Coded Modulation with Low Density Parity Check Code

Author LiSaiZuo
Tutor ZhangNaiTong
School Harbin Institute of Technology
Course Information and Communication Engineering
Keywords LDPC codes BP algorithm Coded Modulation High soft demodulation Phase Noise
CLC TN911.2
Type Master's thesis
Year 2010
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Code modulation technique is a method of channel coding and modulation for the design as a whole joint error control techniques to simultaneously obtain diversity gain and coding gain , thereby improving the efficiency of the communication system and the power spectrum transmission spectral efficiency. Low Density Parity Check (LDPC: Low-density parity-check) codes with the Turbo code decoding performance and an excellent decoding a high throughput may make it become the mainstream of communication systems ( such as a wireless system, a wired communication system deep space communications systems, satellite communications, storage systems, etc. ) is one of several channel coding , this paper studies currently has broad application prospects IEEE802.16e systems . In order to improve the transmission efficiency , while to obtain a higher coding gain , consider an LDPC code having a high spectral efficiency modulation combined. LDPC codes in a deep understanding of the principles and their effective encryption algorithm based on this research is based on LDPC codes via coded modulation system , build a Gaussian channel LDPC codes combined with high order modulation QAM bit interleaved coded modulation (BICM: Bit Interleaver Code Modulation) system model and the high-order QAM modulation with LDPC combination of multi -level coded modulation (MLC: Multilever Code Modulation) system model . By studying the higher order modulation characteristics of unequal error protection (UEP: Unequal Error Protection), conducted a set of signals based on MLC system partitioning programs as well as the design of component codes . Based on the high-end soft demodulation in-depth study , we propose a reduced complexity approximate demodulation algorithms, simulation results show that its performance is close to the standard demodulation algorithm . Based on LDPC coding and modulation system, the phase noise of the channel (Phase Noise) will cause the rotation of the received signal constellation points and vague , thus causing distortion of the received signal . This paper started from the demodulation scheme gives an improved high-end soft demodulation scheme , changing the demodulation of the decision regions to reduce the adverse effects of phase noise . This demodulation scheme is applied BICM system simulation and achieve good results . Based on the phase noise channel demodulation scheme MLC systems research will be the main direction of the future .

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