A new scalable decoder for linear space-time block codes with intersymbol interference

Space-time codes represent a key technology for future broadband wireless communication systems. A class of space-time block codes according to Wittneben and Kuhn (see VTC 2002 - Spring) is used which can lead to intersymbol interference (ISI) due to an optimized diversity performance. Therefore ISI compensation is an important task of the decoding process of these codes. Several known ISI compensation methods can be applied for example MMSE equalization or parallel or serial ISI cancellation. In this paper a new scalable ISI cancellation method is presented, that by using a posteriori information achieves almost the performance of the maximum likelihood decoder but with a much lower complexity. The key idea is to use estimated a posteriori probabilities to determine the order of the cancellation process. In each iteration the decoder jointly decodes a variable number of symbols, which meet a specified probability threshold. By varying the threshold, the decoder is scalable in such a way that the complexity of the decoder - and consequently the available data flow rate - can be adapted in a wide range to the requests of the transmission, to a given node complexity or a required quality of service.