Performance Analysis of Optimum Zero-Forcing Beamforming with Greedy User Selection

In this letter, an exact performance analysis is presented on the sum rate of zero-forcing beamforming with a greedy user selection algorithm in a downlink system. Adopting water-filling power allocation, we derive a compact form for the joint probability density function of the scheduled users' squared subchannel gains when a transmitter with multiple antennas sends information to at most two scheduled users with each having a single antenna. The analysis is verified by numerical results.