Robust Channel Estimation and Detection for Uplink Control Channel in 3GPP-LTE

In this paper, we present improved channel estimation and detection methods applicable for control channel in 3GPP-LTE. The physical uplink control channel (PUCCH) carries the vital information to the evolved-Node-B (eNB) such as Hybrid-ARQ (HARQ) ACK/NACK corresponding to the downlink assignment and channel quality information (CQI) for resource allocation. A robust detection of control channel helps in supporting higher data rates with low latency to the user-equipments (UEs). The PUCCH is a narrow-band code multiplexed channel and hence the inter-user interference becomes the performance limiting factor. This interference becomes severe in the presence of timing errors (leading to loss in code orthogonality) and near-far problem. The improved receiver presented in this paper employ the complex exponential functions for channel estimation and a joint minimum mean squared error (MMSE) data detection and hence are robust to timing errors and near-far problem. Also, we exploit the pilot structure for reducing the complexity of the joint channel estimation. Simulation results provided shows that the proposed receiver breaks the error floor encountered in the single user receiver.