Research On Turbo Equalization

In recent years, the mobile communication has witnessed a rapid growth, from 1G system to 3G system, then to the 4G system that is being designed. The goal is the same one: to improve the system capacity and promote the quality of service. When the high rate data is transmitted through bandlimited channels in mobile communications, the intersymbol interference (ISI) caused by channel distortion and multipath propagation will bring decoding error. It needs to adopt appropriate techniques to remove or reduce this kind of interference. Equalization is the technique that is used to suppress intersymbol interference.The research on Turbo codes has been a hot spot in the area of error-correction in recent years. Turbo equalization is an iterative receiver algorithm repeating equalization and channel decoding to improve receiver performance. In general, turbo equalization algorithms combine equalization and soft output channel decoding in an iterative process. As equalization and decoding are performed several times, the complexity of the receiver increases respectively. In this paper, we propose a kind of reduced complexity turbo equalization, which uses hard instead of soft output channel decoding. So we call it based on hard output channel decoding Turbo equalization. We propose three kinds of based on hard output decoding Turbo equalization: the first one uses the hard decision Viterbi decoding algorithm, the second one uses the soft decision Viterbi decoding algorithm and the third one uses the soft-in-hard-out Viterbi decoding algorithm. Simulation shows that the implementation complexity is reduced significantly at negligible performance loss compared to the soft-in-soft-out decoding Turbo equalization. And the implementation complexity of these three kinds of Turbo equalization is similar, but the performance of the last is the best.