A New Downlink Control Channel Scheme for LTE

Abstract

To accommodate the realistic channel conditions better and thus improve the system throughput, 3GPP introduced the Physical Downlink Control Channel (PDCCH) in LTE. A downlink control information (DCI) message is generated and transmitted over the PDCCH. The User Equipment (UE) is required to perform blind decoding as it is not aware of the detailed control structure. However, blind decoding consumes a lot of UE's computational power, e.g. UE needs to do nearly 240 convolutional decodings on the dedicated search space (DSS) within about 0.15ms in the case of aggregation of 5 carriers. This is a big challenge for UE implementation in reality. In this paper, we propose a new downlink control channel scheme which can greatly reduce the PDCCH blind decoding complexity (from 240 to about 15 convolutional decodings) and power consumption. Another important benefit of this new scheme is that the DCI design can be much more flexible by the DCI index. Also, the new scheme can reduce the false alarm of PDCCH blind decoding and thus decrease the false uplink transmission and interference.