This paper investigates the performance limits of cognitive uplink Fixed Satellite Service (FSS) and terrestrial Fixed Service (FS) operating in 27.5-29.5 GHz for Ka-band. In light of standard International Telecommunications Union (ITU) recommendations and a rain fading channel model, we analyze the interference level at the FS receiver by considering the channel statistical properties, propagation losses and antenna patterns. By employing the interference constraint criterion at the FS, an analytical expression for the capacity of the cognitive uplink FSS is derived, which is useful in understanding the performance limits and the potential application of the considered coexistence scenario. Simulation results are carried out to verify the theoretical derivations, and highlight the impact of key parameters on the performance limits.

In this letter, we investigate the outage probability (OP) of amplify-and-forward hybrid satellite-terrestrial relay networks with a nonorthogonal multiple access (NOMA) scheme. By assuming that a single antenna satellite communicates with multiple multiantenna users simultaneously through the help of a single antenna relay and the NOMA scheme, we first derive the closed-form OP expressions for each NOMA user. Then, asymptotic OP expressions at the high signal-to-noise ratio regime are also obtained to evaluate the achievable diversity order and coding gain. Finally, simulations are provided to the validity of theoretical results, the superiority of introducing the NOMA scheme in satellite-terrestrial relay networks, and the effect of key parameters on the performance of NOMA users.

Satellite communication networks are expected to be indispensable as part of an integrated complement for the upcoming 5G networks, since they can provide the most comprehensive coverage and reliable connection for areas where are economically unviable and/or difficult to deploy terrestrial infrastructures. Meanwhile, power-domain non-orthogonal multiple access (NOMA), which can serve multiple users simultaneously within the same time/frequency block, has been viewed as another promising strategy used in the 5G network to provide high spectral efficiency and resource utilization. In this article, we introduce a general overview of the application of NOMA to various satellite architectures for the benefits of meeting the availability, coverage, and efficiency requirements targeted by 5G. The fundamental and ubiquitous features of satellite link budget are first reviewed. Then, the advantage and benefit of introducing the NOMA scheme in various satellite architectures, such as conventional downlink/uplink satellite networks, cognitive satellite terrestrial networks, and cooperative satellite networks with satellite/terrestrial relays, are provided, along with the motivation and research methodology for each scenario. Finally, this article reviews the potential directions for future research Index Terms—Power-domain non-orthogonal multiple access, satellite networks, cognitive satellite terrestrial networks, cooperative satellite terrestrial networks, 5G.

Allowing multiple users access simultaneously, a power-domain nonorthogonal multiple access (NOMA) scheme can provide enhanced resource utilization efficiency and has been viewed as a promising strategy in the satellite networks, to provide high quality-of-service for large number of users within limited spectrum and time resources. Taking into account the random location information of served users, imperfect channel state information (CSI), and antenna-pointing error, we study the ergodic capacity of a NOMA-based uplink satellite network in this article. Specially, we first develop a general framework for the NOMA-based system by applying standard recommendations, configurations, and channel characteristics. Then, the analytical expression for the achievable ergodic capacity of the considered network is derived. Finally, numerical simulations are provided to attest the validity of theoretical results and show the impact of various key parameters, such as location information, link quality, transmission power, imperfect CSI, and antenna-pointing error, on the considered network.

In this letter, we investigate the outage probability (OP) and ergodic capacity of downlink hybrid satellite terrestrial relay networks (HSTRNs) with a cooperative non-orthogonal multiple access (C–NOMA) scheme, in which a user with better channel condition acts as a relay node and forwards information to other users, thus alleviating the masking effect of users with poor channel conditions in heavy shadowing. Specifically, the exact analytical expression for the OP of the considered system is derived. Furthermore, the ergodic capacity expression is also developed to facilitate the performance evaluation of the proposed framework. Finally, simulations are provided to show the impact of key parameters on the considered system and the superiority of introducing the C–NOMA scheme to the HSTRNs.