Performance of Two-Way Channel Estimation Technique for Multi-User Distributed Antenna Systems with Spatial Precoding

This paper investigates the performance of a multiuser distributed antenna system (DAS) with spatial precoding in which mobile stations (MSs) just send back the received signals along with their training sequences. In this method, base stations (BSs) can obtain the channel state information of both the uplink and downlink without estimating the channels in MSs. This two-way multiple-input multiple-output (MIMO) channel estimation technique have been proposed and mathematically analyzed in the literature. However, implementation aspects of this method, such as forward gain and dynamic range, are not studied yet. In this paper, these aspects are investigated in order to confirm its feasibility in a multi-user DAS where a precoder is employed in BSs. Computer simulation results are presented to demonstrate the required hardware specs for an amplify and forward (AF) operation in MSs by examining the bit error rate (BER) performance. It is shown that an 8-bit A/D converter together with a fixed gain amplifier brings almost no degradation to the BER performance. Furthermore, a performance comparison with a vector feedback method is given.