Efficient Blind Detection for OFDM Systems in Selective Fading Channels

Abstract

With blind detection, one can enhance the throughput of communications. However, not all blind algorithms can be applied in time-varying or frequency-selective fading channels. Furthermore, blind algorithms usually have higher complexity. In this paper, we first propose a general principle by which one can build a metric for blind detection from any pilot-assisted channel response (CR) estimation algorithm. By this principle and based on the least-squares-fitting (LSF) pilot-assisted CR estimation, we derive a metric for blind detection and propose an efficient blind data detection algorithm. The proposed algorithm is operated on a block of received symbols that are along subchannels or along time slots; therefore, the proposed blind detection can be applied in frequency-selective or time-varying fading channels. With the proposed tree search method, the proposed algorithm attains the same error performance as a previous blind detection algorithm based on the same metric, although the complexity is greatly reduced. We further apply the channel prediction to obtain a better initial block in the tree search, such that the complexity can be further reduced. A range-reduced scheme is also proposed to give a tradeoff between performance and complexity. In the fast time-varying channel, we can combine the proposed blind detection with an intersubchannel interference (ICI) self-reduction algorithm.