Transmitter Optimization of Coordinated Multipoint Transmission without Zero-Forcing Constraints

Maximizing the total information rates of downlink coordinated multi-point (CoMP) transmission without zero-forcing (ZF) constraints is investigated. ZF can simplify the CoMP transmission problem, but the number of serviced users is limited by the number of antennas of all the coordinated base stations (BS). Without ZF constraints, more users can be serviced at the same time. In order to solve the problem efficiently, the information rate is first approximated using Taylor expansion. Then, maximizing the sum of information rates is transformed into a semidefinite programming (SDP) problem. Simulation results show that the proposed algorithm can work better when the number of the users is close to the total number of antennas of the base stations.