Reconfigurable architecture of a hybrid synchronisation algorithm for LTE

Time and frequency synchronisation are significant parts of the cell-search procedure and one of the first processing blocks within a mobile communication system. Particularly for an OFDM transmission within an initial synchronisation process, the algorithm has to deal with carrier frequency offsets up to several subcarrier spacings. To be able to still operate under those conditions, the cell-search procedure consists of different processing steps, combined in a hybrid algorithm. Beside good performance properties, hybrid algorithms lead to a high computational demand and implementation effort. To overcome these challenges, flexible architectures, which are able to select the most suitable algorithm during runtime, are the base for an efficient hardware realization. In this paper, as an example, we are introducing an hybrid initial synchronisation algorithm for an LTE-system, which still operates under the effect of a carrier frequency offset greater than the subcarrier spacing. Consecutively, we are showing a reconfigurable architecture as well as the results of an FPGA implementation of the time synchronisation part of that algorithm. The architecture is able to switch between different correlators, namely a reverse-auto, a cross- and a CP-based auto-correlation during runtime, which enables a flexible and low complexity realization of the computational complex synchronisation process.