MLSD coupled with LMMSE channel estimation for OFDM in time-variant channels

For OFDM systems, high user mobility induces time-variation of channel response over symbol duration, causing orthogonality destruction and introducing intercarrier interference (ICI) among subcarriers. To enhance the performance, sequence detection schemes have been proposed with the availability of corresponding channel state information (CSI), which is generally obtained via channel estimation using some inserted preamble symbols. However, bandwidth efficiency is significantly degraded and long latency is introduced. In this work, without the need of inserting preamble symbols, we propose a linear minimum mean square error (LMMSE) channel estimation method coupled with the Viterbi-algorithm based maximum-likelihood sequence detection (MLSD) scheme to improve bandwidth efficiency and to minimize the detection latency. Hence this proposed scheme can be applied to real-time, delay-sensitive applications. Compared to other pilot-based ICI mitigation methods, our scheme has better performance, as well as better bandwidth efficiency.