  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.
