Non-Coherent Cell-Free Large SIMO Using DMPSK

A cell-free non-coherent (NC) massive single-input-multiple-output (SIMO) system is proposed in a wireless uplink where a single-antenna user transmits to several multi-antenna access points (APs). NC detection using differential phase shift keying is the utilized detection technique in this system. It has the advantage that no channel state information (CSI) is required in the APs for signal reception, so it is beneficial with respect to coherent massive MIMO in stringent scenarios where channel state information has very low quality. Additionally, it outperforms the single-AP NC massive SIMO due to the increased number of antennas to average the received signal. The distribution of the received symbol of the NC multi-AP processing is analytically derived to show that several geographically distributed antennas result in a distribution with smaller variances. Several AP selection techniques to maximize the performance and minimize the complexity of the scheme are also proposed. Numerical results are provided to demonstrate the validity of the analysis and to show that the proposal outperforms both the coherent CF schemes in scenarios with stringent conditions and the single-AP NC massive SIMO.