Coded Modulation with Low Density Parity Check Code
|School||Harbin Institute of Technology|
|Course||Information and Communication Engineering|
|Keywords||LDPC codes BP algorithm Coded Modulation High soft demodulation Phase Noise|
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 .