Two-way relaying with network coding for frequency-selective fading channels

In this paper, we present a design method of physical layer network coding for reliable two-way relaying in frequency-selective fading channels. We consider a two-stage protocol: At the first stage, two terminals simultaneously transmit data packets towards a relaying node. The relay maps the received signal into a discrete constellation using appropriate network coding, after which it is broadcasted to the terminals at the second stage. In our previous work, it has been revealed that network coding should be adaptively changed according to the channel state information, and unconventional signalling such as 5QAM can improve throughput for some channel conditions. In this paper, our design method of network coding is improved for the case of frequency-selective fading channels.