A carrier frequency synchronization method for device-to-device communication network

Device-to-device (D2D) communication has received considerable attention in recent years as one of the key technologies for future communication system. Among the typical D2D communication systems, FlashLinQ (FLQ) adopted single-tone orthogonal frequency division multiplexing (OFDM) transmission which enables wide-sense discovery by time domain spreading and very low peak to average power ratio (PAPR). Although synchronization based on a common external source (CES) is basically assumed in FLQ, a means to support devices when they are unable to use a CES is still necessary. In OFDM system, generally, carrier frequency offset (CFO) induces inter-carrier interference (ICI) which degrades overall system performance drastically. Especially in D2D system, ICI can be amplified due to not only different frequency selectivity but also different path losses between links. Accordingly, a precise estimation and compensation of CFO are very important. Therefore, in this paper, we propose a new CFO estimation method for OFDM based D2D system. In the proposed method, the estimation of CFO is obtained by using two correlation results in a symbol. The estimation procedure of the proposed method enables the independent estimation of CFO between links and the estimation range can be adaptively defined depending on the distance between the two windows. By numerical analysis and performance evaluation, we verified that the proposed method achieves precise estimation performance compared to the conventional method.