cooperative_relay

  CR [1] is a promising solution to the problem of spectrum scarcity in wireless communications. The basic idea of CR is to allow secondary (unlicensed) users (SUs) to opportunistically utilize the spectrum of PUs (licensed), provided that the SU transmission do not harmfully affect the PUs. In this paper, we focus on the underlay CR approach, where the SUs access the spectrum occupied by the PUs, given that the interference they cause to the PUs is less than a certain threshold such that the Quality-of-Service (QoS) of the PUs can be ensured