A novel modeling and interim channel estimation method for AF cooperative relay systems

This paper presents the use of interim channel state information (CSI) at the destination node (DN) to substantially improve the bit error rate (BER) performance of two hop amplify and forward (AF) cooperative relay systems. In order to facilitate the estimation of it without employing computationally expensive processing at the relays, we propose a new model for relaying which we denote as multi input multi output (MIMO) mimicking (MM) AF model. In this model, we consider a generic AF system with one source node (SN), one DN and M relay nodes (RN). The model works well with any space time coding (STC) technique. The MM AF model helps estimating the interim channel by means of a predefined pilot enhancement matrix (PEM) at RN and the corresponding overall channel estimation performed at DN from the pilots broad casted from SN. The channel estimation algorithm is based on linear least square estimation (LSE) technique. The performance advantages of this new model and estimation technique are substantiated through simulation studies and are compared with that of a relevant method available in the literature.