Marjan Abbasi Mosleh - Department of Electrical Engineering K. N. Toosi University of Technology Tehran, Iran
Seyyed MohammadMahdi Shahabi - Department of Electrical Engineering K. N. Toosi University of Technology Tehran, Iran
Mohsen Ghasimi - Department of Electrical Engineering K. N. Toosi University of Technology Tehran, Iran
Mehrdad Ardebilipour - Department of Electrical Engineering K. N. Toosi University of Technology Tehran, Iran

This paper investigates the multi-user precoding in downlink transmission of a massive multiple input multiple output (MIMO) system. To this end, a constant envelope precoding (CEP) structure is utilized for the sake of decreasing the implementation cost as well as increasing the hardwareefficiency. In the following, in order to reduce the overhead imposed by sharing the channel coefficients among the BS and users, an efficient construction is proposed, where, exploiting the statistics of the channel features, such as the angle of arrival (AoA), only the partial channel state information (CSI) is exchanged. Moreover, utilizing semi-definite relaxation (SDR), a convex realization for the outgoing problem is devised, inwhich the corresponding scheme leads to the global optimum. Numerical results demonstrate, from the downlink rate per userpoint of view, the performance of the proposed method confronts a negligible drop compared to the perfect CSI case, while theoverall overhead of the system is significantly reduced.

Massive MIMO, Channel State Information Precoding