Performance Enhancement of E-UTRA Uplink Control Channel in Fast Fading Environments

Hybrid automatic repeat request (HARQ) is employed for the 3GPP Evolved Universal Terrestrial Radio Access (E-UTRA) downlink. Each user equipment (UE) sends its ACK/NACK corresponding to the downlink data reception to the base station via a physical uplink control channel (PUCCH). The ACK/NACK signals from the UE are first code spread by the cyclic shift sequences, and then spread by the orthogonal cover sequences. The ACK/NACK signals from each UE are multiplexed by means of code division multiple access (CDMA), however, it is difficult for the conventional PUCCH code design to satisfy the required bit error rate (BER) of 10 3 in fast- fading environments because of inter-code interferences among the orthogonal cover sequences. In this paper, we propose a novel PUCCH code design which can suppress the effect of inter-code interferences among the orthogonal cover sequences. And the simulation evaluations confirm that the proposed code design can significantly improve the performance of the ACK/NACK signals via PUCCH especially in fast-fading environments.