SUM-RATE MAXIMIZATION AND SUM-POWER MINIMIZATION FOR 2-USER (2,2) DOWNLINK SYSTEMS USING GENERALIZED ZERO-FORCING

摘要

This paper analyzes a downlink system where a 2-antenna base station is sending independent signals to 2 2-antenna mobile users simultaneously in the same physical (time and frequency) channel. To multiplex the signals in spatial domain, we consider the use of orthogonal space-division multiplexing (OSDM) or broadly known as generalized zero-forcing (GZF) that allows the users to be completely separated before decoding. The main contribution of this paper is that we derive the optimal array processing solutions for both the sum-rate maximization problem subject to a fixed transmit power constraint, and the sum-power minimization problem subject to a fixed rate constraint. The capacity and signal-to-noise ratio (SNR) regions for the OSDM system are also derived, and results for dirty-paper coding (DPC) and time-division systems are provided for comparison.