Abstract
In this paper, we provide the theoretical framework for the performance comparison of reconfigurable intelligent surfaces (RISs) and amplify-and-forward (AF) relaying wireless systems. In particular, after statistically characterizing the end-to-end (e2e) wireless channel coefficient of the RIS-assisted wireless system, in terms of probability density function (PDF) and cumulative density function (CDF), we extract novel closed-form expressions for the instantaneous and average e2e signal-to-noise ratio (SNR) for both the RIS-assisted and AF-relaying wireless systems. Building upon these expressions, we derive the diversity gain of the RIS-assisted wireless system as well as the outage probability (OP) and symbol error rate (SER) for a large variety of Gray-mapped modulation schemes of both systems under investigation. Additionally, the diversity order of the RIS-assisted wireless system is presented as well as the ergodic capacity (EC) of both the RIS-assisted and AF-relaying wireless systems. Likewise, high-SNR and high-number of metasurfaces (MS) approximations for the SER and EC for the RIS-assisted wireless system are reported. Finally, for the sake of completeness, the special case in which the RIS is equipped with only one MS is also investigated. For this case, the instantaneous and average e2e SNR are derived, as well as the OP, SER and EC. Our analysis is verified through respective Monte Carlo simulations, which reveal the accuracy of the presented theoretical framework. Moreover, our results highlight that, in general, RIS-assisted wireless systems outperform the corresponding AF-relaying ones in terms of average SNR, OP, SER and EC.
Highlights
The evolution of the wireless world towards the beyond fifth generation (B5G) era comes with higher reliability, data-rates and traffic demands, which is driven by innovative applications, such as unmanned mobility, three dimensional (3D) media, augmented and virtual reality [1]–[4]
In order to compare the reconfigurable intelligent surfaces (RISs)-assisted wireless system with the corresponding AF-relaying one, we provide the analytical framework for the derivation of the average e2e signal-to-noise ratio (SNR), outage probability (OP), symbol error rate (SER), and ergodic capacity (EC) of the AF-relaying wireless system.Note that the probability density function (PDF) and cumulative density function (CDF) of the e2e SNR of the AF-relaying wireless system has been initially presented in [37], to the best of the authors knowledge, this is the first time that closed-form expressions for the average e2e SNR, SER, and EC are reported in the technical literature
RESULTS & DISCUSSION This section is focused on verifying the theoretical framework through respective Monte Carlo simulations and reporting the RIS-assisted wireless system performance in comparison with the ones of the corresponding AF-relaying wireless system, in terms of e2e SNR, OP, SER and EC
Summary
The evolution of the wireless world towards the beyond fifth generation (B5G) era comes with higher reliability, data-rates and traffic demands, which is driven by innovative applications, such as unmanned mobility, three dimensional (3D) media, augmented and virtual reality [1]–[4]. In [14], the values of the PSs, which were created by the MSs, were optimized in a RIS-assisted single-user multiple-input-single-output (MISO) wireless system, whereas, in [28], the authors solved the same problem, in a more realistic scenario, in which the RIS consisted by a finite number of discrete PSs. in [29], optimal linear precoder, power allocation and RIS phase matrix designs that used the large-scale statistics channel knowledge and aimed at maximizing the minimum signal-to-noise-plus-interference ratio (SINR) at the base-station were reported. The results are accurate only for scenarios in which the RIS consists of a large number of MSs. In [34], Jung et al provided an asymptotic analysis of the uplink sum-rate of a RIS-assisted system, assuming that the established channels follow Rician distribution. This is the first time that the generalized SER and EC expressions, which refer the single-MS RIS system, are presented in the literature
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