Feedback Reduction for Multiuser OFDM Systems

Feedback reduction in multiuser orthogonal frequency-division multiplexing (OFDM) systems has become an important issue due to the excessive amount of feedback required to use opportunistic scheduling, particularly when the number of users and carriers is large. In this paper, we propose a novel feedback-reduction scheme for efficient downlink scheduling. In the proposed scheme, each user determines the amount of feedback based on the so-called feedback efficiency in a distributed manner. The key idea is to give more of an opportunity for feedback to users who are more often scheduled. Simulation results demonstrate that the proposed scheme can substantially decrease the feedback load while achieving almost the same scheduling performance as in the case of full feedback. In addition, the proposed scheme offers unique advantages over existing ones. First, it is not tailored to a specific scheduling policy; thus, it has adaptability to the change of the underlying scheduling policy. Second, the total feedback load can be maintained below a target level, regardless of the number of users in the system.