Low Complexity Channel Estimation for Novel Bi-Directional Relaying Schemes

In this paper we investigate the channel estimation and data transmission scheme for bi-directional relaying applied in cellular systems. We propose a novel pilot-aided transmission strategy to realize the efficient data exchange between Base Station (BS) and Mobile Station (MS) via a fixed Relay Node (RN). Based on the characteristics of the BS-RN link, the transmitted signals at the BS are pre-equalized. At the RN, part of the CSI is estimated and used to equalize the relayed signals. We then propose a semi-orthogonal pilot structure for channel estimation. With the proposed transmission scheme and pilot structure, the pilot number is reduced by half and the channel estimation at the MS has much low complexity. Simulation results show that the BER performance of the proposed scheme at the MS is a little better than the conventional scheme.