Performance of LDPC Coded OFDM/DS Under Fading and Jamming Environment

Seo, Dong-Cheul; Lee, Woo-Chan; Kim, Jong-Hun

Journal of the Korea Institute of Military Science and Technology 2008;11(5):23-33.

Dong-Cheul Seo, Woo-Chan Lee, Jong-Hun Kim

Korea Military Academy

페이딩과 재밍 환경에서 LDPC 부호화된 OFDM/DS 시스템의 성능

서동철, 이우찬, 김종훈

육군사관학교

Abstract

In this paper, we verify the performance of LDPC coded OFDM/DS system by Monte-Carlo simulation of BER on Eb/No. The simulation results show that LDPC coded OFDM/DS has a strong anti-jamming characteristic over pulse-noise jammer and partial-band noise jammer. The performance of LDPC coded OFDM/DS system is evaluated on both faded waveforms and non-faded waveforms. For non-faded waveforms, high coding gain is attained due to LDPC, even when waveforms have short PN sequence and JSR is only 5dB. Especially, the increase in the repeated number of LDPC decoding enhances coding gain. However, faded waveforms cannot achieve sufficient average effect when PN sequence is short. High coding gain of faded waveforms can be achieved by extending length of PN sequence. In addition, we compare LDPC coded OFDM/DS system with Convolutional coded OFDM/DS system. The simulation results illustrate that when LDPC coded OFDM/DS system with short PN sequence has sufficient average effects, the system shows lower BER than Convolutional coded OFDM/DS system with long PN sequence.

Key Words: LDPC(Low Density Parity Code), OFDM(Orthogonal Frequency Division Multiplexing), PN(Pseudo-Noise), JSR(Jammer to Signal power Ratio), DS(Direct Sequence), BER(Bit Error Rate), Eb/No(Energy Per Bio to Noise Spectral Density Ratio)