Using Cyclic Prefix to Mitigate Carrier Frequency and Timing Asynchronism in Cooperative OFDM Transmissions

While OFDM is a good modulation scheme for cooperative transmissions, the difficulty of synchronizing carrier frequencies of distributed transmitters presents one of the primary challenges. In this paper we show that cyclic prefix (CP) can be used not only to resolve the timing asynchronism, which is well-known, but also to mitigate the carrier frequency offsets (CFO) among the transmitters. Depending on the CP length, CFO can be mitigated or removed completely, which indicates an interesting trade-off between bandwidth efficiency and cooperation overhead.