Non-identical Weibull Fading Channels Research Articles

Performance analysis of amplify-and-forward relaying over Weibull-fading channels with multiple antennas

Amplify-and-forward (AF) relaying with multi-branch dual-hop relays in independent non-identical Weibull fading channels with multiple antennas at the destination is addressed. The authors consider orthogonal relaying and study conventional cooperative systems where all relays participate in the relaying phase as well as opportunistic cooperative systems where only the best relay participates in the relaying phase. An expression for the approximate probability density function (PDF) of the total instantaneous signal-to-noise ratio (SNR) at the destination is derived. Subsequently, expressions for the asymptotic average error rate and the outage probability are presented. The results provided are fairly simple and general for arbitrary values of the fading severity parameters. It is shown that opportunistic relaying does not necessarily outperform the conventional approach in terms of coding gain under equal energy allocation as in the Rayleigh fading case. Simulation results verify the tightness of the proposed analytical expressions in the high SNR region.

Selection Diversity Receivers Over Nonidentical Weibull Fading Channels

The performance of selection combining (SC) receivers operating over independent, but not necessarily identically distributed, Weibull fading channels is studied. A novel closed form expression for the moments of the SC output signal-to-noise ratio (SNR) is derived, which is used to study the corresponding average output SNR and amount of fading. Second-order statistical parameters such as the average level crossing rate and average fade duration at the output of the SC are also obtained in closed form. Moreover, the average symbol error probability for several coherent and noncoherent modulations schemes as well as the Shannon capacity are extracted in terms of the tabulated Meijer's G-function. Simulations are also performed to validate the proposed formulation.

Performance Analysis of a Class of GSC Receivers Over Nonidentical Weibull Fading Channels

The performance of a class of generalized-selection combining (GSC) receivers operating over independent but nonidentically distributed Weibull fading channels is studied. We consider the case where the two branches with the largest instantaneous signal-to-noise ratio (SNR), from a total of L available, GSC(2, L) are selected. By introducing a novel property for the product of moments of ordered Weibull random variables, convenient closed form expressions for the moments of the GSC(2,L) output SNR are derived. Using these expressions, important performance criteria, such as average output SNR and amount of fading, are obtained in closed form. Furthermore, employing the Pade/spl acute/ approximants theory and the moment-generating function approach, outage and bit-error rate performance are studied. An attempt is also made to identify the equivalency between the Weibull and the Rice fading channel, which is typically used to model the mobile satellite channel. We present various numerical performance evaluation results for different modulation formats and channel conditions. These results are complemented by equivalent computer simulated results which validate the accuracy of the proposed analysis.

Equal-gain and maximal-ratio combining over nonidentical Weibull fading channels

We study the performance of L-branch equal-gain combining (EGC) and maximal-ratio combining (MRC) receivers operating over nonidentical Weibull-fading channels. Closed-form expressions are derived for the moments of the signal-to-noise ratio (SNR) at the output of the combiner and significant performance criteria, for both independent and correlative fading, such as average output SNR, amount of fading and spectral efficiency at the low power regime, are studied. We also evaluate the outage and the average symbol error probability (ASEP) for several coherent and noncoherent modulation schemes, using a closed-form expression for the moment-generating function (mgf) of the output SNR for MRC receivers and the Pade/spl acute/ approximation to the mgf for EGC receivers. The ASEP of dual-branch EGC and MRC receivers is also obtained in correlative fading. The proposed mathematical analysis is complimented by various numerical results, which point out the effects of fading severity and correlation on the overall system performance. Computer simulations are also performed to verify the validity and the accuracy of the proposed theoretical approach.