Hybrid Adaptive/non-Adaptive Multi-User OFDMA Systems in the Presence of User-Specific Imperfect Channel Knowledge
In this paper, a hybrid multi-user OFDMA scheme which considers different user demands regarding channel access and user-specific imperfect Channel Quality Information (CQI) is analytically described and evaluated. The considered hybrid scheme offers two possible modes to serve the user: firstly, via a non-adaptive mode which applies a discrete Fourier transform proceeding to exploit frequency diversity and, thus, does not require any CQI at the transmitter. Secondly, via an adaptive mode this performs an adaptive resource allocation and link adaptation. Since this adaptation to the channel is done based on CQI, the adaptive mode is prone to imperfect CQI which results from estimation errors or time delays.