Null Sub-Carrier Aided Reference Symbol Mapping for Improved Channel Estimation in 3GPP LTE Downlink

In this paper, a new reference symbol mapping scheme is proposed to improve downlink channel estimation performance over the standard reference symbol mapping scheme defined in the 3GPP LTE standard. The proposed scheme is based on the concept of guarding reference symbols (i.e., pilot symbols) with null sub-carriers. This helps mitigate the effect of inter-carrier interference (ICI) at pilot sub-carriers. In addition, the proposed scheme allows the ICI gain parameters to be estimated via a simple estimator. To assess the relative merits of the proposed reference symbol mapping scheme over the standard scheme, we compare normalized mean square error and uncoded bit error rate performances of the two schemes under different mobile user speeds. These comparisons show excellent performance improvements achieved by the proposed scheme over the standard one at high mobile user speeds.