Iterative Joint Channel Estimation and Decoding Using Superimposed Pilots in OFDM-WLAN

A preamble technique is used in present OFDM-based WLAN systems to accomplish synchronization and channel estimation. The preamble introduces transmission delay and wastes capacity, especially when a data packet is short. An alternative is a superimposed pilot technique which can provide similar BER vs. Eb/N0 performance by specially designed receiver and optimized system parameters. In this paper we study the conditions under which superimposed pilots can be successfully used for jointly estimating the channel and detecting data. It is shown that the transmission delay or throughput of wideband WLAN systems can be significantly improved when such a technique is employed at the price of higher complexity due to the iterative receive algorithm.