Initial DS/SS code synchronization by two-dimensional techniques and MIMO systems

Serial multi-dwell probability tests, based on noncoherent correlation from a number of data blocks, are usually adopted for the initial code acquisition in the radio access of 3G mobile communications. The test sequentially searches for the most likely codes and their optimum timing shift as reliable candidates for code (and code offset) acquisition. The constant false alarm rate (CFAR) criterion is adopted to determine the threshold value. The paper extends the analysis to the case of smart antennas and MIMO systems, involving 2D spatio-temporal signal processing and two-dwell procedures. In particular, we preliminarily discuss the spatial coverage of customers, assuming an adaptive management of call admission from distinct angular sectors. The main novelty of the presented procedure is twofold: a two-dwell acquisition technique is performed to save the mean acquisition time with respect to one-dwell acquisition techniques; the searching procedure is driven from the estimates of the local signal-to-interference-plus-noise ratio (SINR), reducing again the mean acquisition time. The analytic performance is expressed by using the generalized-Q functions. An application to typical mobile environments is provided. The obtained results evidence the effectiveness of the analyzed spatio-temporal two-dwell procedures.