Full-Band CQI Feedback by Haar Compression in OFDMA Systems

Implementation of an efficient CQI feedback mechanism is the focus of the study presented in this paper. OFDMA-based systems such as 3 GPP Long Term Evolution (LTE) downlink and WiMax require an accurate CQI feedback to allow effective operation of the adaptive modulation and coding. Besides accuracy, such mechanism should impose only a low overhead when using uplink resources for conveying the CQI information. Unlike the Best-M CQI feedback algorithms where only the M highest CQI´s and their locations are reported, a full-band feedback method compresses the whole CQI vector and transmits the compressed vector in the uplink channel. In this paper, application of the Haar transform for a full-band CQI report is investigated and its performance is compared against Discrete Cosine Transform (DCT)-based compression schemes. Full-band Haar CQI feedback offers a flexible process for CQI feedback that can be easily adapted to different operating scenarios. Key features of Haar compression are incremental update and very low complexity for compression and decompression. Simulation results indicate that the full-band Haar scheme achieves significantly higher throughput than the DCT-based schemes at low speeds and about the same performance at higher speeds.