A Non-Hierarchical Cell Search Scheme

Cell search is the procedure by which a mobile terminal acquires time and frequency synchronization to the network and detects a cell identity. In this paper, we give a non-hierarchical scheme for OFDM systems, where cell-specific signals are concurrently used for synchronization and cell identification. By using time-domain symmetric signals, the symbol timing is accurately found by a reverse differential correlator. Once the timing is established and frequency offsets are estimated, detection of the transmitted synchronization sequence is done non-coherently by means of a differential decoder. The frame timing is obtained by letting different synchronization signals represent elements of cyclically unique codewords over a radio frame. The scheme can convey large amount of cell identities and numerical results show that it is robust to frequency offsets.