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http://dx.doi.org/10.6109/jkiice.2011.15.12.2534

Performance Analysis Based On Log-Likelihood Ratio in Orthogonal Code Hopping Multiplexing Systems Using Multiple Antennas  

Jung, Bang-Chul (경상대학교 정보통신공학과, 해양산업연구소)
Sung, Kil-Young (경상대학교 정보통신공학과, 해양산업연구소)
Shin, Won-Yong (미국 하버드 대학교)
Publication Information
Journal of the Korea Institute of Information and Communication Engineering / v.15, no.12, 2011 , pp. 2534-2542 More about this Journal
Abstract
In this paper, we show that performance can be improved by using multiple antennas in the conventional orthogonal code hopping multiplexing (OCHM) scheme, which was proposed for accommodating a larger number of users with low channel activities than the number of orthogonal codewords used in code division multiple access (CDMA)-based communication systems through downlink statistical multiplexing. First, we introduce two different types of OCHM systems together with orthogonal codeword allocation strategies, and then derive their mathematical expression for log-likelihood ratio (LLR) values according to the two different schemes. Next, when a turbo encoder based on the LLR computation is used, we evaluate performance on the frame error rate (FER) for the aformentioned OCHM system. For comparison, we also show performance for the existing symbol mapping method using multiple antennas, which was used in 3GPP standards. As a result, it is shown that our OCHM system with multiple antennas based on the proposed orthogonal codeword allocation strategy leads to performance gain over the conventional system---energy required to satisfy a target FER is significantly reduced.
Keywords
Multiple antennas; log-likelihood ratio (LLR); orthogonal code hopping multiplexing (OCHM); frame error rate (FER);
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