LLR-based interference suppression for the physical downlink control channel of LTE-A

Due to spectrum constraints most of cellular networks are deployed in frequency reuse one. In that scenario co-channel interference from neighboring cells becomes a limiting factor for the performance of all downlink physical channels. Therefore, the problem of interference suppression is being considered as one of the most important issues of modern wireless communication systems. In Long-Term Evolution Advanced (LTE-A) systems, several interference suppression techniques are introduced to cope with interference issues of the physical downlink data channel. However, the key problem of interference suppression for the physical downlink control channel (PDCCH), which carries downlink and uplink scheduling information, is not sufficiently addressed in LTE-A systems. In principle, receiver structures employed for interference suppression for the data channel can be reused to decode control channel transmissions. However, a number of issues specific only to the control channel (e.g., per subcarrier interference power boosting and random interference hit from the neighboring cell) should be considered in the design of interference suppression algorithms. In this paper, we investigate the performance of Log-Likelihood Ratio (LLR)-based interference suppression for the physical downlink control channel of LTE-A. The simulation results show that the proposed LLR calculation scheme provides remarkable error rate performance improvement compared to the conventional LLR calculation scheme.