Angle-of-Departure-Aided Opportunistic Space-Division Multiple Access

In this paper, a novel transmission technique for the multiple-input multiple-output (MIMO) broadcasting directional channels is introduced. During the training period, the base station sends a set of mutually orthogonal signals which enables each user to estimate the angle-of-departure of the anticipated strongest beam and the corresponding SNR. Then, the base station uses the reported angles-of-departure and SNRs to select a subgroup of users for data transmission in such a way that the sum capacity is maximized. Compared to the opportunistic space-division multiple access with beam selection algorithm, the advantage of the proposed algorithm is that it provides throughput gains up to 95% with low to medium number of users, under the same number of feedback bits. In addition to our new proposed algorithm, we introduce a modified version of the opportunistic space-division multiple access with beam selection algorithm, which shows a significant throughput improvement when evaluated using directional channel models such as WINNER.