Channel equalization in narrowband mobile peer-to-peer networks using superimposed pilots

Two most significant channel training methods in wireless communications are superimposed (SI) and time-division multiplexed (TDM) training. Assuming a fixed user bit rate in narrowband system with scarce capacity resources, SI based training enables utilization of lower coding rate. Moreover, only a slight difference in coding rates is shown to have a considerable effect on system performance. This paper introduces a novel channel estimation structure for the SI scheme. The structure improves the quality of initial channel estimates by exploiting the coarsely estimated information symbols, which are obtained through expectation maximization (EM) algorithm. The simulations show that in the presented narrowband peer-to-peer environment, SI training based channel estimation may provide significant benefits over the conventional TDM pilot scheme.