Extendable CQI table design for higher order modulation in LTE downlink transmission

In this paper, we first propose a future-proof extendable channel quality indicator (CQI) table design method for LTE downlink transmission in order to support higher order modulation, i.e., 256 Quadrature Amplitude Modulation (QAM) in the current system. Meanwhile, a two-stage feedback scheme, which contains window-index feedback procedure and inside-index feedback procedure, is designed to support the extendable CQI table. In order to decrease the feedback overhead, an adaptively window-index update method is proposed. Due to this method, UE only needs to report the window-index once. Hence, the CQI feedback overhead is almost the same as that of the legacy one. Simulation results show that the cell edge UE throughput is obvious enhanced and there is no performance loss on the cell center UE by utilizing the extendable CQI table.