To achieve insights about the impact of amplified loop interference, we consider a dual-hop fullduplex (FD) massive multiple-input multiple-output (MIMO) amplify-and-forward (AF) relaying system in terms of achievable ergodic rates for each user pair as well as spectrum and energy efficiencies. It is assumed that the base station (or relay) is equipped with M Rx receive antennas and M Tx transmit antennas, while all sources and destinations have a single antenna. For such FD massive MIMO AF relaying systems, the closedform expressions of the lower bounds of achievable ergodic rates are derived first with a finite number of receive and transmit antennas at base station. Then, the asymptotic performance analysis is performed by considering three different power-scaling schemes: 1

Summary In this paper, the cognitive relay cooperation (CRC) wireless communication systems are investigated over Nakagami‐m fading channels. The decode‐and‐forward (DF) relay is employed to assist the communications between cognitive source and destination. Especially, to achieve full diversity order, we consider the case in which there is a direct path between cognitive source and destination. Besides the interference at primary users (PUs) created by secondary users (SUs), the interference at SUs created by PUs is also considered. For the interested CRC systems, we first achieve the exact expression for the CDF of the equivalent end‐to‐end signal‐to‐interference ratio (SIR) of CRC systems. Then, with the exact CDF, the exact average symbol error ratio (SER) and outage performance of CRC systems are achieved. The derivation is of significance, by which we can obtain a detailed knowledge about CRC systems. Though a single integral included in the derivation, it can be calculated numerically by employing some mathematical tools such as Matlab. At the same time, to obtain the insight and highlight the effect of system parameters on the considered CRC systems, by using the high SIR approximation, we obtain the asymptotic closed‐form expression of CDF as well as the ones of average SER and outage probability. From the asymptotic results, we can find the main factors that dominate the performance of CRC systems. The presented simulation results for outage probability and average SER show the derivations and simulations are in agreement. Moreover, in high SIR the achieved asymptotic results match well the exact ones. As a result, in high SIR we can employ the asymptotic closed‐form solutions to evaluate the exact performance of CRC systems. This can reduce greatly the implementation complexity. Besides this, the simulations also show that the diversity order is dominated by the fading severities of the secondary systems, i.e. the diversity order be proportional to the summation of the minimum fading severity between the two hops and that of the direct link. In contrast, the parameters of the primary systems only affect the coding gain, not the diversity gain. Copyright © 2014 John Wiley & Sons, Ltd.

To obtain an insight about the effect of channel parameters on buffer-aided relay selection systems, the max-link selection (MLS) schemes are investigated over independent and non-identically distributed (i.ni.d) Rayleigh fading channels. Specially, by employing Markov chain, the authors first model the state transition matrix and outage probability. Secondly, they obtain the closed-form expressions of the corresponding statistic properties. The presented results show: (i) when the relaying channels are asymmetric (but the source-relay links are independent and identically distributed fading, so does the relay-destination links), the MLS scheme outperforms the traditional best relay selection (T-BRS) and max-max best relay selection (MM-BRS) schemes. However, when the relaying links are unbalanced severely, the MLS scheme does not provide diversity gain over the T-BRS and MM-BRS schemes; and (ii) For the more general i.ni.d fading case, it is observed that the MLS schemes can be inferior to the MM-BRS schemes. The derivations of this work have values for reference. For example, by using the achieved statistic properties they can further perform the investigation on the delay for the buffer-aided MLS relaying systems over i.ni.d fading channels, which is a critical issue of buffer-aided relay selection systems.

75 effect of μ on the first-order and second-order performances is different greatly. For the first-order performance, the performance gap is negligible when the value of μ is relatively large. However, for the second-order one, the gap is distinct. I n t h i s p a p e r, t h e authors investigate the first-order and second-order performances of cognitive opportunistic relaying systems with the available maximum transmit power and tolerate maximum interference power limits.