Low-Bandwidth Channel Quality Indication for OFDMA Frequency Domain Packet Scheduling

In this paper we consider bandwidth-efficient means for the user equipment (UE) to conduct channel quality indication (CQI) for OFDMA frequency domain packet scheduling (FDPS). Using a UTRAN long-term evolution (LTE) system model, we find that a threshold-based CQI scheme can enable about 60% CQI bandwidth saving with less than 5-10% loss on system performance compared to near-ideal signaling. To sustain sufficient CQI reporting accuracy and high FDPS gain, we show that time- domain CQI averaging over multiple sub-frames is desirable although it lowers the mobility performance. Conducting the averaging on the UE side is most attractive from a signalling perspective. Combining averaging with lowered CQI reporting rate, FDPS can provide around 30-50% gain for LTE with a CQI reporting bandwidth as low as 10 kbit/s in a 20 MHz system (up to 3-5 km/h).