Multi-channel Tracking with Different Fading Rates in an OFDM-PLNC Network

Abstract

In this paper, we address the problem of tracking the time varying/frequency selective fading channels with different fading rates in a decode-and-forward physical layer network coding (PLNC) structure. Since, in a PLNC system multi users send their information to the relay, simultaneously, the relay needs to estimate the uplink multi-channels, simultaneously, to be able to extract the network coded signal from superimposed signals. Different fading rates of channels due to different velocities of mobile users in a PLNC system make the channel tracking problem more complex. Providing an algorithm to simultaneous track multi-channels in such a system is the main object of this paper. To this end, a time domain channel tracking algorithm based on sum–product rules is derived, where, both frequency and time selectivity characteristics of the channels are taken into account. In order to stabilize against the frequency selectivity property of the channels, orthogonal frequency division multiplexing is also considered in this system. High accuracy, no phase ambiguity, and stability in fast fading conditions are some advantages of the proposed approach. The performance of the algorithm in the existence of channel coding has been also considered and compared with the non-coded channel system.