Reconfigurable Antenna Multiple Access for 5G mmWave Systems

TL;DR

This paper introduces RAMA, a new multiple access technique for 5G mmWave systems using reconfigurable antennas, which outperforms NOMA by avoiding inter-user interference and optimizing power allocation.

Contribution

The paper proposes RAMA, a novel interference-free multiple access method for reconfigurable antennas, with analytical and numerical validation showing superior sum rate performance over NOMA.

Findings

RAMA outperforms NOMA in sum rate with partial CSI for symmetric channels.

RAMA achieves higher rates than NOMA with full CSI for both channel types.

RAMA is interference-free and adaptable to channel information availability.

Abstract

This paper aims to realize a new multiple access technique based on recently proposed millimeter-wave reconfigurable antenna architectures. To this end, first we show that integration of the existing reconfigurable antenna systems with the well-known non-orthogonal multiple access (NOMA) technique causes a significant degradation in sum rate due to the inevitable power division in reconfigurable antennas. To circumvent this fundamental limit, a new multiple access technique is proposed. The technique which is called reconfigurable antenna multiple access (RAMA) transmits only each user's intended signal at the same time/frequency/code, which makes RAMA an inter-user interference-free technique. Two different cases are considered, i.e., RAMA with partial and full channel state information (CSI). In the first case, CSI is not required and only the direction of arrival for a specific user is used. Our analytical results indicate that with partial CSI and for symmetric channels, RAMA outperforms NOMA in terms of sum rate. Further, the analytical result indicates that RAMA for asymmetric channels achieves better sum rate than NOMA when less power is assigned to users that experience better channel quality. In the second case, RAMA with full CSI allocates optimal power to each user which leads to higher achievable rates compared to NOMA for both symmetric and asymmetric channels. The numerical computations demonstrate the analytical findings.