Cell Search Time Comparison Using Hierarchical and Non-Hierarchical Synchronization Channels in OFDM Based Evolved UTRA Downlink

This paper presents a performance comparison of the initial cell search time and neighboring cell search time using hierarchical and non-hierarchical synchronization channel (SCH) structures in order to establish the optimum SCH structure in the evolved UTRA downlink. Computer simulation results show that in a 19-cell configuration, the cell search time at the 90% cumulative distribution function using the hierarchical SCH structure is less than half that using the non-hierarchical SCH structure in a neighboring cell search under low signal-to-interference plus noise power ratio conditions, although both structures achieve almost the same cell search time in the initial cell search. This is due to the cross-correlation based SCH symbol timing detection in the hierarchical SCH structure, which is affected less by noise than auto-correlation based detection in the non-hierarchical SCH structure. Thus, we conclude that the hierarchical SCH structure is more appropriate than the non-hierarchical SCH structure based on the cell search time performance especially in the neighboring cell search.