Mode Selection-Based Channel Feedback Reduction Schemes for Opportunistic Scheduling in OFDMA Systems

In this paper, we present two new feedback schemes, namely the network mode selection-based feedback (NMF) and the user mode selection-based feedback (UMF), that reduce the feedback load needed for opportunistic scheduling in the OFDMA downlink system. The two schemes are designed to select either the selective feedback (SF) mode which feeds back the fine-grained condition of a part of the channels or the bit-map based feedback (BF) mode which feeds back the coarse-grained condition of all the channels using 1 bit for each channel, depending on the channel conditions of the users. Specifically, the NMF scheme makes the BS determine the more desirable feedback mode by predicting and comparing the average total throughputs of the two modes for the given statistical channel characteristics of the users. The UMF scheme makes each user determine its own feedback mode based on both its channel realization and the recommendation of the network. Numerical results reveal that the proposed NMF and UMF schemes achieve significant performance gain over the existing feedback reduction schemes with similar feedback load.