OFDM Transmission scheme for asynchronous two-way multi-relay cooperative networks with analog network coding

For two-way relaying assisted by analog network coding, most investigation so far is based on perfect synchronization assumption. In contrast, in this paper we consider the more practical asynchronism assumption, and develop a new OFDM transmission scheme that is robust to the lack of synchronization in both timing and carrier frequency. In our scheme, the relays´ signals are constructed by fusing several OFDM symbols received from the source nodes transmissions. The source node receivers can successfully demodulate the received OFDM signals after mitigating effectively multiple carrier frequency offsets and multiple timing phase offsets. Simulations are conducted to demonstrate its superior performance. This scheme has the same bandwidth efficiency as the conventional OFDM transmission, and can achieve the same relaying gain as the existing multiple relay transmissions. By relieving the stringent synchronization requirement, this scheme leads to simplified relay design, which makes it more practical to exploit multiple relays in two-way relaying networks.