Microwave Mobile Communications
Microwave Mobile Communications
Adaptive Modulation over Nakagami Fading Channels
Wireless Personal Communications: An International Journal
Wireless Communications
IEEE Transactions on Wireless Communications
Multiuser OFDM with adaptive subcarrier, bit, and power allocation
IEEE Journal on Selected Areas in Communications
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In the OFDMA downlink, obtaining Channel State Information (CSI) from users is necessary for the Base Station (BS) to optimize network performance by intelligently allocating resources and scheduling mobile stations (MS). However, the overhead of obtaining CSI is a large burden and therefore, schemes to reduce CSI are necessary for a realizable system. By considering a MS's coherence time Δtcoh and coherence bandwidth Bcoh, and exploiting this redundancy in the MS's CSI, the amount of feedback can be tailored to the specific user's profile and greatly decreased. Typically, reducing feedback results in more uncertainty in CSIT and performance degradation. However, in the proposed scheme, the CSIT's deviation from the true channel state is bounded, and thus can provide robust scheduling. Specifically, two BS schemes are suggested that either fix the average BER or the average outage probability regardless of user mobility or delay spread.