On Pilot Design for Channel Estimation and MUI Reduction in Uplink OFDMA Systems

One of the major drawbacks of the orthogonal frequency division multiple access (OFDMA) system is the multi-user interference (MUI) induced by the carrier frequency offsets (CFOs). In sub-band based OFDMA systems, users occupy consecutive and non-overlapping frequency sub-bands. The pilots are usually placed on the edges of a sub-band for channel estimation. However, the channel estimation performance is seriously degraded by the MUI. Traditionally, the MUI is alleviated by inserting a guard sub-carrier between adjacent users. In this paper, a novel pilot architecture is proposed, where three pilots are placed on each edge of a sub-band and pilots of adjacent users are overlapped. The proposed architecture has the same bandwidth efficiency as that of the conventional guard sub-carrier insertion scheme and provides better channel estimation performance and MUI reduction.