On the value of transmitter information

Coherent signaling over a fading channel requires the receiver to have knowledge of the current fading state (CSIR). In order to proactively prevent outages, the transmitter requires knowledge of the fading state (CSIT) to perform power control. Typically, the channel state is estimated by using a training signal, and the channel state information contains some error. In this work, we examine the performance of a symmetric, single-input, multiple-output (SIMO) channel in which both the transmitter and the receiver have independent, imperfect estimates of the channel. We give expressions for mutual information and outage probability, and we use those expressions to evaluate the diversity order of the system for a constant target rate. We show that diversity order is dominated by the transmitter error and that the diversity order is equal to that of a system with perfect CSIR.