Duplex distortion models for limited feedback MIMO communication

The use of limited feedback in multiple-input multiple-output (MIMO) wireless communications has grown in interest over the last few years. Research has shown that feedback can be used to increase achievable data rates and add resilience against fading. Most of the work to this point, however, has ignored the data rate overhead associated with feedback. Models that do not consider feedback overhead are valid in wireless systems with ever present control channels, but they fail to capture the data rate cost of feedback when control channels are not present. In this paper, we present a new system model, called a duplex model, that captures the true loss (or cost) of feedback. A new distortion function for use with codebook design follows from the duplex system model. This system model is used to derive bounds on the amount of feedback needed under different antenna, signal-to-noise ratio, and bandwidth assumptions. Simulation results show the necessity of taking feedback into account.