Novel timing synchronization technique for public safety communication systems employing heterogeneous cognitive radio

A novel synchronization technique is proposed for a heterogeneous cognitive radio combining a public safety mobile communication system (PMCS) with a commercial mobile wireless communication system (CMWCS). Since the PMCS is crucial in public safety activities such as search-and-rescue operations, we have implemented a heterogeneous cognitive technique to improve the communication quality of the PMCS. To combine the PMCS with the CMWCS properly, the proposed synchronization technique enables not only the co-synchronization between the PMCS and the CMWCS but also the self-synchronization of the PMCS. In this paper, we especially focus on the PMCS´s self-synchronization that is one of the most difficult parts of our proposed cognitive radio system. The proposed technique is utilized for systems employing differentially encoded 7t/4-shift QPSK modulation. The synchronization can be achieved by correlating the envelopes calculated from the PMCS´s received signals with subsidiary information (SI) sent via the CMWCS. In this study, the performance of the proposed synchronization technique is evaluated by computer simulation.