SummaryIn this work, an amplify-and-forward variable-gain relayed mixed RF-FSO system is studied. The considered dual-hop system consists of a radio frequency (RF) link followed by a free space optical (FSO) channel. The RF link is affected by short-term multipath fading and long-term shadowing effects and is assumed to follow the generalized-K fading distribution that approximates accurately several important distributions often used to model communication channels.The FSO channel experiences fading caused by atmospheric turbulence that is modeled by the gamma-gamma distribution characterizing moderate and strong turbulence conditions. The FSO channel also suffers path loss and pointing error induced misalignment fading. The performance of the considered system is analyzed under the collective influence of distribution shaping parameters, pointing errors that result in misalignment fading, atmospheric turbulence, and path loss. The moment-generating function of the Signal power to noise power ratio measured end-to-end for this system is derived. The cumulative distribution function for the Signal power to noise power ratio present between the source and destination receiver is also evaluated. Further, we investigate the error and outage performance and the average channel capacity for this system. The analytical expressions in closed form for the outage probability, symbol and bit error rate considering different modulation schemes and channel capacity are also derived. The mathematical expressions obtained are also demonstrated by numerical plots.
KEYWORDSchannel capacity, fading, free space optical communication, probability of outage, radio frequency communication, symbol error rate
In this paper, we investigate the performance of a decode-and-forward relayed mixed radio frequency-free space optical (RF-FSO) dual-hop link. The transmitter to receiver link’s first-hop is a RF channel and the second-hop is a FSO channel. The RF link experiences long-term shadowing and short-term multi-path fading effects, while the FSO channel suffers atmospheric turbulence fading, path loss, and pointing error-induced misalignment fading. The performance of the system is analyzed considering the impact of these parameters. We model the RF link by generalized-K fading distribution and the atmospheric turbulence over the FSO link by the gamma–gamma fading. The expressions in closed form for the outage probability, symbol error rate for the system employing
$q$-ary PSK modulation schemes, and the channel capacity of the system are derived. The obtained numerical results are also depicted by numerical plots.
This paper presents the performance of a dual‐hop mixed radio frequency (RF)‐free space optical (FSO) system employing a hybrid‐decode/amplify‐and‐forward (HDAF) relaying protocol. The RF link forms the first hop and the FSO link is the second hop for the proposed system model. The assumption of the absence of the direct FSO and RF link between the source transmitter and the destination receiver ends is made for the analysis. The RF link is affected by short‐term multipath fading and long‐term shadowing phenomena and is characterized by the generalized‐K fading distribution, whereas the FSO link is modeled by the gamma‐gamma fading, representing moderate to strong turbulence scenarios. We assume pointing error‐induced misalignment fading to be significantly present over the FSO link. We analyze the outage probability for the system employing amplify‐and‐forward, decode‐and‐forward, and HDAF relaying protocols and show the benefits of using HDAF relaying in mixed RF‐FSO systems. The optimum relay position that results in the best outage performance is investigated. Furthermore, the bit error rate performance for a q‐ary phase shift keying (q‐PSK) modulated signal and the channel capacity for the proposed system employing HDAF relaying protocol are also evaluated. The expressions in closed form for the outage probability, bit error rate, and channel capacity are derived. The asymptotic outage and error performance at high signal‐to‐noise ratio is also evaluated. Furthermore, the performance of the system is demonstrated by numerical plots.
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