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Impact of transmission techniques in asymmetric RF/FSO system over Nakagami- <i>m</i> and gamma-gamma fading channels with pointing errors
摘要： In this paper, the performance of transmission techniques on the fixed‐gain amplify‐and‐forward–based asymmetric radio frequency/free space optical (RF/FSO) communication system is studied. The RF link and FSO link are, respectively, modeled by the Nakagami‐m and Gamma‐Gamma fading channels under the effect of zero boresight and non‐zero boresight pointing errors subject to heterodyne detection. Maximum ratio transmission (MRT) and orthogonal space‐time block coding (OSTBC) techniques are the transmission scenarios considered at the system source while selection combining is used for reception at the relay and destination for the signal detection. Moreover, a unified cumulative density distribution (CDF) of end‐to‐end signal‐to‐noise ratio is derived for the system. By utilizing this channel statistical CDF, the closed‐form expressions for the outage probability and average bit error rate for the M‐ary phase shift keying modulation are then obtained for the system. The analysis presented illustrates that both the atmospheric turbulence and pointing error significantly degrade the system performance. Based on this, the MRT transmission technique offers a better performance compared with the OSTBC techniques under the same system conditions. The accuracy of the analytical results is verified by Monte‐Carlo simulations.
关键词： transmit diversity,free space optical,Nakagami‐m fading,pointing errors,atmospheric turbulence
更新于2025-09-09 09:28:46
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Joint user and relay selection for relay-aided RF/FSO systems over Exponentiated Weibull fading channels
摘要： In this paper, we investigate the performance of joint user and relay selection scheme for a multi-user relayed network over mixed radio-frequency (RF) and free space optical (FSO) system. In this set-up, the non-line-of-sight (NLOS) RF link is modeled with Rayleigh fading whereas the LOS FSO path is modeled with Exponentiated Weibull (EW) distribution. We assume that the multiple users at source terminal communicate with the destination over multiple decode and forward relays which are located at the rooftops of the buildings to provide a perfect LOS path. In the proposed scheme, all users send pilot signals to the destination through relay terminals and the latter jointly selects the best user and relay based on the maximization of the end-to-end signal-to-noise ratio (SNR). To quantify the performance of the proposed scheme, closed form outage and error probability are derived. Moreover, asymptotic analysis is performed to obtain important system parameters including fading severity, number of users and relays in the system. Finally, Monte-Carlo (MC) simulations are carried out the verify the performance of the considered scheme.
关键词： Exponentiated Weibull fading channel,Joint user and relay selection,Free space optical communication,relay aided transmission
更新于2025-09-04 15:30:14