Switched-based reduced feedback OFDM multi-user opportunistic scheduling

We consider in this paper the problem of opportunistic scheduling of users employing orthogonal frequency division multiplexing (OFDM) with adaptive modulation and coding under the constraint that all sub-carriers are assigned to a single user during one time slot. We first present an optimal scheme which schedules the user with the best instantaneous channel conditions in order to maximize the system sum-capacity. The optimality of this scheme comes at the expense of a full feedback load and high number of channel estimations. In an attempt at simplifying the complexity of the system, we then present and study the performance of two switched-based scheduling schemes. Extensive and detailed numerical results are performed to illustrate the capacity-feedback tradeoff of the three schemes under consideration. These results show the switched-based scheduling schemes reduce considerably the number of channel estimations and the feedback load with a negligible loss in sum-capacity.