Transmission Control with Imperfect CSI in Channel-Aware Slotted ALOHA Networks

The impact of imperfect channel state information (CSI) on the transmission control of channel-aware slotted ALOHA networks is studied in this work. By taking into consideration the statistics of the channel estimation error to maximize the achievable stable throughput, we obtain the optimal transmission control policy that determines the transmission probability, rate, and power that should be adopted under different channel states. Specifically, with imperfect CSI, we find that high transmission probabilities should be assigned to channel states that allow for high probability of successful transmission (which may be affected by the estimation errors), but rate allocation must be performed more conservatively (compared to the case with perfect CSI) in order to avoid transmission errors due to imprecise channel estimates. The policies are first developed for,single carrier systems and then extended to multi-carrier systems with maximum per-user power constraints. The asymptotic maximal stable throughput is analyzed for both the single and multiple carrier systems as the number of users goes to infinity. We observe that, with error in the channel estimate, the proposed transmission control policy that takes into consideration the error statistics may significantly increase the throughput compared to strategies that are derived under the perfect CSI assumption.