Impact of Imperfect Channel State Information on Downlink Sum-Rate of Two user mmWave Non Orthogonal Multiple Access

Effect of imperfect channel state information on achievable data rates of a two user downlink non orthogonal multiple access scenario is considered in this paper. The optimum antenna array weight that steers the downlink beams towards the two users has been reported earlier based upon perfect knowledge of downlink channels at the base station. This antenna weight vector is no longer optimum as soon as the channel state information available with the base station becomes outdated. The effect of wrong angle of departure information and/or wrong channel gain information reduces the advantage of above access scheme over orthogonal multiple access scheme. How reduction in achievable data rate in a non orthogonal case depends on different transceiver parameters, such as the error in angle information, the absolute value of the angle of departure, number of antenna elements at the base station is shown in this paper.