A Low-Complexity Design for Rate-Splitting Multiple Access in Overloaded MIMO Networks

Rate-Splitting Multiple Access (RSMA) is a robust multiple access scheme for multi-antenna wireless networks. In this work, we study the performance of RSMA in downlink overloaded networks, where the number of transmit antennas is smaller than the number of users. We provide analysis and closed-form solutions for optimal power and rate allocations that maximize max-min fairness when low-complexity precoding schemes are employed. The derived closed-form solutions are used to propose a low-complexity RSMA system design for precoder selection and resource allocation for arbitrary number of users and antennas under perfect Channel State Information at the Transmitter (CSIT). We compare the performance of the proposed design with benchmark designs based on Space Division Multiple Access (SDMA) to show that the proposed low-complexity RSMA design achieves a significantly higher performance gain in overloaded networks

A Proof of Concept for OTFS Resilience in Doubly-Selective Channels by GPU-Enabled Real-Time SDR

Orthogonal time frequency space (OTFS) is a modulation technique which is robust against the disruptive effects of doubly-selective channels. In this paper, we perform an experimental study of OTFS by a real-time software defined radio (SDR) setup. Our SDR consists of a Graphical Processing Unit (GPU) for signal processing programmed using Sionna and TensorFlow, and Universal Software Radio Peripheral (USRP) devices for air interface. We implement a low-latency transceiver structure for OTFS and investigate its performance under various Doppler values. By comparing the performance of OTFS with Orthogonal Frequency Division Multiplexing (OFDM), we demonstrate that OTFS is highly robust against the disruptive effects of doubly-selective channels in a real-time experimental setup.Comment: ACCEPTED for 2023 IEEE Global Communications Conference: Wireless Communication

Power Budgeting of LEO Satellites: An Electrical Power System Design for 5G Missions

Although Geostationary-Equatorial-Orbit (GEO) satellites have achieved significant success in conducting space missions, they cannot meet the 5G latency requirements due to the far distance from the earth surface. Therefore, Low-Earth-Orbit (LEO) satellites arise as a potential solution for the latency problem. Nevertheless, integrating the 5G terrestrial networks with LEO satellites puts an increased burden on the satellites’ limited budget, which stems from their miniature sizes, restricted weights, and the small available surface for solar harvesting in the presence of additional required equipment. This paper aims to design the Electrical Power System (EPS) for 5G LEO satellites and investigate altitudes that meet the latency and capacity requirements of 5G applications. In this regard, accurate solar irradiance determination for the nadir-orientation scenario, Multi-Junction (MJ) solar cells modeling, backup batteries type and number, and designing highly-efficient converters are addressed. Accordingly, the power budgeting of the 5G LEO satellite can be achieved based on defining the maximum generated power and determining the satellite’s subsystem power requirements for 5G missions. In the sequel, the measured and simulated values of the electrical V-I characteristics of an MJ solar panel are compared to validate the model by using a Clyde Space solar panel that reaches a maximum power generation of approximately $1~W$ at ( $I_{MPP}=0.426\,\,A$ , $V_{MPP}=2.35\,\,V$ ). Moreover, a synchronous boost converter circuit is designed based on commercial off-the-shelf elements

Satellite-Based Non-Terrestrial Networks in 5G: Insights and Challenges

Non-terrestrial networks (NTNs) will become an indispensable part of future wirelessnetworks. Integration with terrestrial networks will provide new opportunities for both satellite andterrestrial telecommunication industries and therefore there is a need to harmonize them in a unifiedtechnological framework. Among different NTNs, low earth orbit (LEO) satellites have gained increasingattention in recent years and several companies have filed federal communication commission (FCC)proposals to deploy their LEO constellation in space. This is mainly due to several desired features suchas large capacity and low latency. In addition, recent successful LEO network deployments such as Starlinkhave motivated other companies. In the past satellite and terrestrial wireless networks have been evolvingseparately but now they are joining forces to enhance coverage and connectivity experience in the futurewireless networks. The 3rd Generation Partnership Project (3GPP) is one of the dominating standardizationbodies that is working on various technical aspects to provide ubiquitous access to the 5G networks withthe aid of NTNs. Initial steps have been taken to adopt 5G state of the art technologies and concepts andharmonized them with the conditions met in non-terrestrial networks. In this article, we review some ofthe important technical considerations in 5G NTNs with emphasis on the radio access network (RAN) partand provide some simulation based results to assess the required modifications and shed light on the designconsideration