Matched filter bound optimization for multiuser downlink transmit beamforming

This paper is devoted to the optimization of the matched filter bounds (MFB) of different co-channel users, using adaptive antenna arrays at base stations for downlink transmit beamforming in cellular mobile communication systems. We mainly consider time division multiple access (TDMA) frequency division duplexing (FDD) based systems. Note that in the case of time division duplexing (TDD), under terrain assumptions the downlink channel can be assumed to be practically the same as the uplink channel. On the contrary, when using FDD, the downlink channel can not be directly observed and estimated. That makes FDD based systems most difficult to deal with, although the proposed criteria and methods are general and suitable for both FDD and TDD. Problem formulations are provided for both spatial division multiple access (SDMA) and non-SDMA spectrum reuse techniques. Novel analytical solutions and algorithms are derived, implementation issues are discussed and simulations are provided in order to compare different approaches.