Adaptive feedback bit allocation for coordinated multi-point transmission systems

The problem of adaptive feedback bit allocation for two different Coordinated Multi-Point (CoMP) transmission schemes, namely Joint Transmission (JT) and Coordinated Beamforming (CBF), is studied here. We formulate the average rate maximization problem in which channel information to the serving and interfering base stations is quantized with different resolution. Unlike previously proposed solutions, we show that it is possible to solve the optimization problem without decomposing it in two terms (desired signal and interference). The proposed adaptive bit allocation algorithm is evaluated through simulations for a realistic cellular layout, where users are placed exclusively in the cell edge, and results are averaged over different positions to avoid placement biasing. The gains of the proposed method vary from 5% to 50% showing that adaptive feedback allocation is an effective method to improve throughput performance in CoMP systems.