Management of channel quality reporting in highly loaded LTE networks

In LTE networks, with many active users per cell, frequency utilization is high and significant QoS performance gains are possible through frequency selective scheduling. In order to realize this, the scheduler requires rich and frequent reporting of the channel quality or state such that the channel response in the frequency domain can be accurately tracked. CQI (Channel Quality Indicator) measurements support this for the downlink. However, with many active users it is not practical to configure such reporting for all users simultaneously. In this paper, we investigate how best to configure CQI reporting in these circumstances. We demonstrate the advantages from requesting CQI on all regular PUSCH (physical uplink shared channel) transmissions (piggybacking), whilst at the same time issuing grants for PUSCH transmissions carrying CQI but no MAC PDU for targeted users only (boosting). Targeting of cell edge users during their FTP file transfers demonstrates a transfer delay reduction of 10% at 75% RB utilization, with one boost per TTI per cell, in system simulation.