Studying the Sum Capacity of Mobile Multiuser Diversity Systems with Feedback Errors and Delay

To achieve multiuser diversity gains, resource allocation relies on accurate and timely feedback of the users´ channel states. This feedback suffers from transmission errors and delay which can heavily degrade the sum capacity of a scheduled multiuser downlink. The order of this capacity loss and its interdependency to relevant scenario factors is characterized in this paper. From studying a simple sum capacity-maximizing scheduler, we conclude that in many mobile scenarios the upper bound of the achievable data rate is primarily defined by the feedback delay. This makes reducing feedback delay to one of the most important challenges in designing future wireless systems.