Performance analysis of selection cooperative networks over asymmetric fading channels

The performances of selection cooperation are investigated over asymmetric fading channels where the source-relay and the relay-destination channels experience Nakagami-m and Rayleigh fading,respectively.Decode-and-forward(DF)protocol is adopted and the Nth best relay is selected from M available relays.Probability density function(PDF)for the instantaneous signal-to-noise ratio(SNR)at the destination is derived first.Then,it is used to derive the exact expressions for outage probability and average symbol error rate(SER).The results hold for arbitrary M or N.Finally,simulations are carried out to verify the correctness of our theoretical analysis and results show that M and N almost have the same effect on the performance of outage probability and SER.

Effective capacity of cognitive radio systems in asymmetric fading channels

As known that the effective capacity theory offers a methodology for exploring the performance limits in delay constrained wireless networks, this article considered a spectrum sharing cognitive radio （CR） system in which CR users may access the spectrum allocated to primary users （PUs）. Particularly, the channel between the CR transmitter （CR-T） and the primary receiver and the channel between the CR-T and the CR receiver （CR-R） may undergo different fading types and arbitrary link power gains. This is referred to as asymmetric fading. The authors investigated the capacity gains achievable under a given delay quality-of-service （QoS） constraint in asymmetric fading channels. The closed-form expression for the effective capacity under an average received interference power constraint is obtained. The main results indicate that the effective capacity is sensitive to the fading types and link power gains. The fading parameters of the interference channel play a vital role in effective capacity for the looser delay constraints. However, the fading parameters of the CR channel play a decisive role in effective capacity for the more stringent delay constraints. Also, the impact of multiple PUs on the capacity gains under delay constraints has also been explored.