An OFDM-based distributed transmission scheme for uncoordinated transmitters without carrier frequency and timing synchronization

Distributed transmission involving multiple uncoordinated transmitters has become a popular subject in wireless communications, such as cooperative transmissions, relaying, distributed MIMO, network coding, multi-access and multiuser detection. One of the major challenges for implementing distributed transmissions is the difficulty of synchronizing carrier frequency and timing of the distributed transmitters. In this paper we propose a new OFDM-based transmission scheme that does not require carrier frequency and timing synchronization. Specifically, by exploiting jointly OFDM cyclic prefixes (CP), spreading and scrambling techniques, the receiver can mitigate multiple carrier frequency offsets and timing offsets successfully. This comes at no loss of bandwidth efficiency or power efficiency. In contrast, by allowing multiple OFDM symbols to share a CP, the bandwidth efficiency can even be higher than that of conventional OFDM. This scheme can support most of the existing distributed or cooperative transmission frameworks.