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http://dx.doi.org/10.3837/tiis.2013.04.009

Selective Demodulation Scheme Based on Log-Likelihood Ratio Threshold  

Huang, Yuheng (Department of Electronics and Information Engineering, Huazhong University of Science &Technology)
Dong, Yan (Department of Electronics and Information Engineering, Huazhong University of Science &Technology)
Jo, Minho (Department of Computer and Communication, Korea University)
Liu, Yingzhuang (Department of Electronics and Information Engineering, Huazhong University of Science &Technology)
Publication Information
KSII Transactions on Internet and Information Systems (TIIS) / v.7, no.4, 2013 , pp. 767-783 More about this Journal
Abstract
This paper aims at designing a selective demodulation scheme based on Log-likelihood Ratio threshold (SDLT) instead of the conventional adaptive demodulation (ADM) scheme, by using rateless codes. The major difference is that the Log-likelihood ratio (LLR) threshold is identified as a key factor to control the demodulation rate, while the ADM uses decision region set (DRS) to adjust the bit rate. In the 16-QAM SDLT scheme, we deduce the decision regions over an additive white Gaussian channel, corresponding to the variation of LLR threshold and channel states. We also derived the equations to calculate demodulation rate and bit error rate (BER), which could be proven by simulation results. We present an adaptation strategy for SDLT, and compare it with ADM and adaptive modulation (AM). The simulation results show that our scheme not only significantly outperforms the ADM in terms of BER, but also achieves a performance as good as the AM scheme. Moreover, the proposed scheme can support much more rate patterns over a wide range of channel states.
Keywords
Selective demodulation; log-likelihood ratio; decision region; rateless codes;
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