Performance analysis of hybrid satellite-terrestrial networks over generalized fading channels

Abstract

In the past few decades, wireless communication technologies have witnessed the rapid development of mobile devices and their involvement in various aspects of our day-to-day life. This evolution eventually demands the high-speed transmission and seamless connectivity anytime at anyplace. In this context, satellite-based communication systems have become popular by rendering a terrestrial experience with broadband access to mobile users. Indeed, the integration of satellite and terrestrial networks has been envisioned to realize the desirable traits. Recently, hybrid satellite-terrestrial networks (HSTNs) have received tremendous research attention owing to their advantage of providing high-speed connectivity to portable and mobile devices. The performance of HSTNs can be further improved by exploiting cooperative communication technology which may extend the satellite coverage, especially in remote areas. Hence, it is viable to incorporate cooperative techniques into HSTNs to improve the overall system performance and reliability. To meet this, terrestrial cooperative techniques have been uni ed with the HSTNs, thereby, formed relayassisted HSTNs, referred to as hybrid satellite-terrestrial relay networks (HSTRNs). Despite the various advantages, HSTNs are associated with di erent practical issues such as outdated channel state information (CSI), co-channel interference (CCI), security attacks, etc. In this thesis, we aim to comprehensively analyze the performance of HSTNs over generalized fading channels to address the design objectives of the future wireless networks. Firstly, we discuss statistical characterization of the land mobile satellite (LMS) channel model and analyze the performance of LMS systems using the physical layer security (PLS) technique. We investigate the performance of an interference-limited single-user LMS system in the presence of an eavesdropper. For the performance assessment, we derive an accurate expression of secrecy outage probability (SOP) by considering multiple CCI signals over Nakagami-m fading at the user destination node. We also conduct asymptotic secrecy outage analysis to reveal more insights and extract diversity order of the considered LMS system. We further investigate the performance of a single-user LMS system with an eavesdropper by employing an unmanned aerial vehicle-based friendly jammer. Here, we derive analytical and asymptotic SOP expressions and depict the impact of jammer along with various key parameters on performance of the considered LMS system. Then, we consider an amplify-and-forward (AF) relay assisted multi-user HSTRN by employing a multi-antenna satellite. In this system design, we investigate the impact of outdated CSI and CCI under uncorrelated and correlated shadowed-Rician fading channels of satellite links. Herein, we employ opportunistic user scheduling of multiple users with outdated CSI over Nakagami-m fading channels of pertinent links and consider CCI at the relay. For the performance assessment of this system, we rst derive novel and accurate analytical expressions of outage probability. We also perform asymptotic analysis to investigate the diversity order of the considered system. We further derive ergodic capacity expressions by making use of the moment generating function transform. Thereafter, we derive tight closed-form analytical and asymptotic expressions of the average symbol error probability for the considered system. The derived analytical expressions provide e cient tools to characterize the impact of CCI, outdated CSI, and antenna correlation on the system performance of HSTRNs. Our analysis for this system leads to various interesting insights into achievable performance gains. We illustrate that the considered systems can achieve full diversity as long as the interference power level remains low, otherwise the performance remarkably deteriorates. In addition, we depict that the advantage of multi-user diversity cannot be realized when the CSI is outdated. Moreover, we highlight the advantages of a multi-antenna satellite and reveal that the achievable diversity gain of the considered HSTRN is not a ected by correlation in satellite antennas. Next, we turn our focus on the secrecy performance analysis of HSTRNs. By adopting shadowed-Rician fading for satellite links and Nakagami-m fading for terrestrial links, we investigate the PLS performance of di erent HSTRN con gurations with single eavesdropper and multiple eavesdroppers scenarios. With a singleeavesdropper scenario, we explore the con gurations of multi-user HSTRNs and multi-relay HSTRNs. We examine the performance of multi-user HSTRNs in the presence of a single eavesdropper. Herein, by employing opportunistic scheduling of terrestrial users, we derive the analytical SOP expression. For the multi-relay HSTRNs, we propose optimal and partial relay selection schemes and derive novel closed-form SOP expressions. Based on our results, we herein manifest that the optimal relay selection scheme outperforms partial relay selection scheme. Further, we investigate the PLS performance in HSTRNs with multiple eavesdroppers scenario. Speci cally, we consider an AF relay based single-relay single-user HSTRN with independent and non-identically distributed multiple colluding eavesdroppers. For the secrecy performance assessment of this system, we derive the SOP and ergodic secrecy capacity (ESC) expressions. We next analyze a more generalized multiuser multi-relay HSTRN con guration with multiple eavesdroppers. For this overall setup, we conduct a comprehensive PLS analysis for two di erent wiretapping scenarios, i.e., non-colluding and colluding eavesdroppers under AF and decode-andforward relaying protocols. Herein, we present opportunistic user-relay selection criteria and then derive accurate analytical and asymptotic expressions of the SOP to reveal useful insights. We also obtain the ESC expressions under AF relaying protocol for both the wiretapping scenarios. Our results enlighten that the achievable diversity order remains una ected by the number of eavesdroppers and scenarios of wiretapping. Above all, the theoretical ndings in thesis address various technical design aspects of HSTNs and eventually provide useful guidelines for their possible applications in the future wireless networks.