Precoding Design for Massive MIMO Systems with Sub-connected Architecture and Per-antenna Power Constraints

Conference: WSA 2018 - 22nd International ITG Workshop on Smart Antennas
03/14/2018 - 03/16/2018 at Bochum, Deutschland

Proceedings: ITG-Fb. 276: WSA 2018

Pages: 6Language: englishTyp: PDF

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Cao, Phuong Le; Oechtering, Tobias J.; Skoglund, Mikael (School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden)

This paper provides the necessary conditions to design precoding matrices for massive MIMO systems with a subconnected architecture, RF power constraints and per-antenna power constraints. The system is configured such that each RF chain serves a group of antennas. The necessary condition to design the digital precoder is established based on a generalized water-filling and joint sum and per-antenna optimal power allocation solution, while the analog precoder is based on a perantenna power allocation solution only. We study the analytically most interesting case where the power constraint on the RF chain is smaller than the sum of the corresponding per-antenna power constraints. For this, the optimal power is allocated based on two properties: Each RF chain uses full power and if the optimal power allocation of the unconstraint problem violates a per-antenna power constraint then it is optimal to allocate the maximal power for that antenna.