Hybrid satellite–terrestrial networks toward 6G : key technologies and open issues

Future wireless networks will be required to provide more wireless services at higher data rates and with global coverage. However, existing homogeneous wireless networks, such as cellular and satellite networks, may not be able to meet such requirements individually, especially in remote terrain, including seas and mountains. One possible solution is to use diversified wireless networks that can exploit the inter-connectivity between satellites, aerial base stations (BSs), and terrestrial BSs over inter-connected space, ground, and aerial networks. Hence, enabling wireless communication in one integrated network has attracted both the industry and the research fraternities. In this work, we provide a comprehensive survey of the most recent work on hybrid satellite–terrestrial networks (HSTNs), focusing on system architecture, performance analysis, design optimization, and secure communication schemes for different cooperative and cognitive HSTN network architectures. Different key technologies are compared. Based on this comparison, several open issues for future research are discussed

Impact of CCI on performance analysis of downlink satellite-terrestrial systems: outage probability and ergodic capacity perspective

The evolution of non-orthogonal multiple access (NOMA) has raised many opportunities for massive connectivity with less latency in signal transmissions at great distances. We aim to integrate NOMA with a satellite communications network to evaluate system performance under the impacts of imperfect channel state information and co-channel interference from nearby systems. In our considered system, two users perform downlink communications under power-domain NOMA. We analyzed the performance of this system with two modes of shadowing effect: heavy shadowing and average shadowing. The detailed performance was analyzed in terms of the outage probability and ergodic capacity of the system. We derive closed-form expressions and performed a numerical analysis. We discover that the performance of two destinations depends on the strength of the transmit power at the satellite. However, floor outage occurs because the system depends on other parameters, such as satellite link modes, noise levels, and the number of interference sources. To verify the authenticity of the derived closed-form expressions, we also perform Monte-Carlo simulations.Web of Science20221art. no. 7

System Modelling and Design Aspects of Next Generation High Throughput Satellites

Future generation wireless networks are targeting the convergence of fixed, mobile and broadcasting systems with the integration of satellite and terrestrial systems towards utilizing their mutual benefits. Satellite Communications (Sat- Com) is envisioned to play a vital role to provide integrated services seamlessly over heterogeneous networks. As compared to terrestrial systems, the design of SatCom systems require a different approach due to differences in terms of wave propagation, operating frequency, antenna structures, interfering sources, limitations of onboard processing, power limitations and transceiver impairments. In this regard, this letter aims to identify and discuss important modeling and design aspects of the next generation High Throughput Satellite (HTS) systems. First, communication models of HTSs including the ones for multibeam and multicarrier satellites, multiple antenna techniques, and for SatCom payloads and antennas are highlighted and discussed. Subsequently, various design aspects of SatCom transceivers including impairments related to the transceiver, payload and channel, and traffic-based coverage adaptation are presented. Finally, some open topics for the design of next generation HTSs are identified and discussed.Comment: submitted to IEEE Journa

Komunikace na milimetrových vlnách v 5G a dalších sítích: Nové systémové modely a analýza výkonnosti

The dissertation investigates different network models, focusing on three important features for next generation cellular networks with respect to millimeter waves (mmWave) communications: the impact of fading and co-channel interference (CCI), energy efficiency, and spectrum efficiency. To address the first aim, the dissertation contains a study of a non-orthogonal multiple access (NOMA) technique in a multi-hop relay network which uses relays that harvest energy from power beacons (PB). This part derives the exact throughput expressions for NOMA and provides a performance analysis of three different NOMA schemes to determine the optimal parameters for the proposed system’s throughput. A self-learning clustering protocol (SLCP) in which a node learns its neighbor’s information is also proposed for determining the node density and the residual energy used to cluster head (CH) selection and improve energy efficiency, thereby prolonging sensor network lifetime and gaining higher throughput. Second, NOMA provides many opportunities for massive connectivity at lower latencies, but it may also cause co-channel interference by reusing frequencies. CCI and fading play a major role in deciding the quality of the received signal. The dissertation takes into account the presence of η and µ fading channels in a network using NOMA. The closed-form expressions of outage probability (OP) and throughput were derived with perfect successive interference cancellation (SIC) and imperfect SIC. The dissertation also addresses the integration of NOMA into a satellite communications network and evaluates its system performance under the effects of imperfect channel state information (CSI) and CCI. Finally, the dissertation presents a new model for a NOMA-based hybrid satellite-terrestrial relay network (HSTRN) using mmWave communications. The satellite deploys the NOMA scheme, whereas the ground relays are equipped with multiple antennas and employ the amplify and forward (AF) protocol. The rain attenuation coefficient is considered as the fading factor of the mmWave band to choose the best relay, and the widely applied hybrid shadowed-Rician and Nakagami-m channels characterize the transmission environment of HSTRN. The closed-form formulas for OP and ergodic capacity (EC) were derived to evaluate the system performance of the proposed model and then verified with Monte Carlo simulations.Dizertační práce zkoumala různé modely sítí a zaměřila se na tři důležité vlastnosti pro buňkové sítě příští generace s ohledem na mmW komunikace, kterými jsou: vliv útlumu a mezikanálového rušení (CCI), energetická účinnost a účinnost spektra. Co se týče prvního cíle, dizertace obsahuje studii techniky neortogonálního vícenásobného přístupu (NOMA) v bezdrátové multiskokové relay síti využívající získávání energie, kde relay uzly sbírají energii z energetických majáků (PB). Tato část přináší přesné výrazy propustnosti pro NOMA a analýzu výkonnosti se třemi různými schématy NOMA s cílem určit optimální parametry pro propustnost navrženého systému. Dále byl navržen samoučící se shlukovací protokol (SLCP), ve kterém se uzel učí informace o sousedech, aby určil hustotu uzlů a zbytkovou energii použitou k výběru hlavy shluku CH pro zlepšení energetické účinnosti, čímž může prodloužit životnost sensorové sítě a zvýšit propustnost. Za druhé, přístup NOMA poskytl mnoho příležitostí pro masivní připojení s nižší latencí, NOMA však může způsobovat mezikanálové rušení v důsledku opětovného využívání kmitočtů. CCI a útlum hrají klíčovou roli při rozhodování o kvalitě přijímaného signálu. V této dizertace je brána v úvahu přítomnost η a µ útlumových kanálů v síti užívající NOMA. Odvozeny jsou výrazy v uzavřené formě pro pravděpodobnost výpadku (OP) a propustnost s dokonalým postupným rušením rušení (SIC) a nedokonalým SIC. Dále se dizertace zabývá integrací přístupu NOMA do satelitní komunikační sítě a vyhodnocuje výkonnost systému při dopadech nedokonalé informace o stavu kanálu (CSI) a CCI. Závěrem disertační práce představuje nový model pro hybridní družicově-terestriální přenosovou síť (HSTRN) založenou na NOMA vícenásobném přístupu využívající mmWave komunikaci. Satelit využívá NOMA schéma, zatímco pozemní relay uzly jsou vybaveny více anténami a aplikují protokol zesilování a předávání (AF). Je zaveden srážkový koeficient, který je uvažován jako útlumový faktor mmWave pásma při výběru nejlepšího relay uzlu. Samotné přenosové prostředí HSTRN je charakterizováno pomocí hybridních Rician a Nakagami-m kanálů. Vztahy pro vyhodnocení výkonnosti systému navrženého modelu vyjadřující ergodickou kapacitu (EC) a pravděpodobnost ztrát (OP) byly odvozeny v uzavřené formě a následně ověřeny pomocí simulační numerické metody Monte Carlo.440 - Katedra telekomunikační technikyvyhově

5G embraces satellites for 6G ubiquitous IoT : basic models for integrated satellite terrestrial networks

Terrestrial communication networks mainly focus on users in urban areas but have poor coverage performance in harsh environments, such as mountains, deserts, and oceans. Satellites can be exploited to extend the coverage of terrestrial fifth-generation (5G) networks. However, satellites are restricted by their high latency and relatively low data rate. Consequently, the integration of terrestrial and satellite components has been widely studied, to take advantage of both sides and enable the seamless broadband coverage. Due to the significant differences between satellite communications (SatComs) and terrestrial communications (TerComs) in terms of channel fading, transmission delay, mobility, and coverage performance, the establishment of an efficient hybrid satellite-terrestrial network (HSTN) still faces many challenges. In general, it is difficult to decompose a HSTN into a sum of separate satellite and terrestrial links due to the complicated coupling relationships therein. To uncover the complete picture of HSTNs, we regard the HSTN as a combination of basic cooperative models that contain the main traits of satellite-terrestrial integration but are much simpler and thus more tractable than the large-scale heterogeneous HSTNs. In particular, we present three basic cooperative models, i.e., model X, model L, and model V, and provide a survey of the state-of-the-art technologies for each of them. We discuss future research directions towards establishing a cell-free, hierarchical, decoupled HSTN. We also outline open issues to envision an agile, smart, and secure HSTN for the sixth-generation (6G) ubiquitous Internet of Things (IoT)

Security-Reliability Tradeoffs for Satellite-Terrestrial Relay Networks with a Friendly Jammer and Imperfect CSI

peer reviewedThis article proposes and analyzes the reliability and security tradeoff for a satellite-terrestrial (SatTer) relay system. Herein, a satellite sends confidential information to multiple ground users with the help of a relay base station (BS) in the presence of multiple eavesdroppers trying to wiretap the information. In particular, a friendly jammer is deployed near the relay BS to improve secure transmissions. Moreover, the nonidentical Rayleigh fading channels and imperfect channel state information are adopted for a general system model. Then, we consider both amplify-and-forward (AF) and decode-and-forward (DF) relaying strategies to give a full picture of the benefits of each method. In this context, we derive the closed-form expressions of the outage probability and intercept probability corresponding to AF- and DF-based relaying schemes, which is a high challenge and has not been investigated before. Then, Monte-Carlo simulations are conducted to evaluate the correctness of the mathematical analysis and the effectiveness of the proposed methods. Furthermore, the security and reliability trade-off of the SatTer system and the influences of various system parameters (e.g., satellite's transmit power, channel estimation errors, relay's transmit power, fading severity parameter, the average power of light-of-sight, and satellite's multipath components) on the system performance are shown