Error Rate and Ergodic Capacity of RF-FSO System with Partial Relay Selection in the Presence of Pointing Errors

TL;DR

This paper analyzes the error rate and capacity of a dual-hop RF-FSO relay system with partial relay selection using outdated CSI, considering atmospheric turbulence and pointing errors, and provides novel analytical expressions validated by simulations.

Contribution

It introduces new analytical formulas for BER and ergodic capacity of RF-FSO systems with partial relay selection under pointing errors and outdated CSI, extending prior work.

Findings

Temporal correlation significantly affects BER performance.

FSO link conditions strongly influence overall system capacity.

Analytical results match Monte Carlo simulations accurately.

Abstract

This paper presents an analysis of a multiple dual-hop relaying system, which is composed of km-class radio frequency (RF)-free-space optical (FSO) links. Partial relay selection based on outdated channel state information (CSI) is employed in order to select active relay for further transmission. Amplify-and-forward relaying protocol is utilized. The RF links are assumed to be subject to Rayleigh fading, and the FSO links are influenced by both Gamma-Gamma atmospheric turbulence and pointing errors. On the basis of our previously derived expression for cumulative distribution function of the equivalent signal-to-noise ratio of the whole system, we derive novel analytical expressions for the average bit-error rate (BER) and ergodic capacity that are presented in terms of the Meijer's G-function and extended generalized bivariate Meijer's G-function, respectively. The numerical results are confirmed by Monte Carlo simulations. Considering the effect of time-correlation between outdated CSI and actual CSI related to the RF channel at the time of transmission, the average BER and the ergodic capacity dependence on various system and channel parameters are observed and discussed. The results illustrate that the temporal correlation between outdated and actual CSI has strong effect on system performance, particularly on BER values, when FSO hop is influenced by favorable conditions. Keywords: Bit error rate, ergodic capacity, free-space optical systems, partial relay selection, radio frequency systems.