Energy-efficient channel quality indication (CQI) feedback scheme for UMTS high-speed downlink packet access

Abstract

A major evolution of UMTS standard is the High Speed Downlink Packet Access (HSDPA). Several new tech- nologies are applied to HSDPA system. One of key techniques supporting HSDPA is the adaptive modulation and coding (AMC) in which the modulation scheme and the coding rate are adaptively changed according to the downlink channel quality reported by the user equipment (UE). Therefore, the channel quality indication (CQI) feedback scheme is directly related to the accuracy of AMC and the performance of HSDPA. This paper proposes an enhanced CQI feedback scheme that can be used when a proportional fair scheduling algorithm (PFA) is used as a packet scheduling algorithm. The enhanced CQI feedback scheme uses a dynamic threshold to filter off redundant CQI feedbacks. With the proposed scheme, the battery capacity of UE can be conserved, maintaining the performance of traditional CQI feedback scheme.