Channel Adaptive CQI Reporting Schemes for UMTS High-Speed Downlink Packet Access

HSDPA (high-speed downlink packet access) is an evolved UMTS packet scheme that delivers increased user peak data rates and supports quality of service. A key technique supporting HSDPA is adaptive modulation and coding (AMC), in which the modulation scheme and the coding rate are changed adaptively according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) reporting scheme is directly related to the accuracy of AMC and the performance of HSDPA. In the current specification of HSDPA, each UE must periodically report to Node B the CQI. Hence, UE must report the same CQI value repeatedly when the channel quality is unchanged. Obviously, this is the waste of the UE's battery power. To solve this problem, we propose channel adaptive CQI reporting schemes in which UEs report the CQI value intelligently using information about channel quality. With the proposed schemes, the battery capacity of UEs can be conserved and the uplink interference can be lowered by filtering off redundant CQI reports or the transmission error rate can be lowered by fast CQI reports.