Communication Theory Lab

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Now showing 1 - 5 of 983
  • Article

    HAPS in the Non-Terrestrial Network Nexus: Prospective Architectures and Performance Insights

    (IEEE Communications Society, 2023) Lou, Zhengying; Belmekki, Baha Eddine Youcef; Alouini, Mohamed-Slim; King Abdullah University of Science and Technology (KAUST); Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division
  • Article

    On the Peak AoI of UAV-Assisted IoT Networks: A Stochastic Geometry Approach

    (Institute of Electrical and Electronics Engineers (IEEE), 2023-09-28) Qin, Yujie; Kishk, Mustafa Abdelsalam; Alouini, Mohamed-Slim; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; Department of Electronic Engineering, Maynooth university, Maynooth, Ireland

    In this paper, we analyze the peak age of information (PAoI) in UAV-assisted internet of thing (IoT) networks, in which the locations of IoT devices are modeled by a Matérn cluster process (MCP) and UAVs are deployed at the cluster centers to collect the status updates from the devices. Specifically, we consider that IoT devices can either monitor the same physical process or different physical processes and UAVs split their resources, time or bandwidth, to serve the devices to avoid inter-cluster interference. Using tools from stochastic geometry, we are able to compute the mean activity probability of IoT devices and the conditional success probability of an individual device. We then use tools from queuing theory to compute the PAoI under two load models and two scenarios for devices, respectively. Our numerical results show interesting system insights. We first show that for a low data arrival rate, increasing the number of correlated devices can improve the PAoI for both load models. Next, we show that even though the time-splitting technique causes higher interference, it has a limited impact on the mean PAoI, and the mean PAoI benefits more from the time-splitting technique. This is because of the nature of UAV communication, especially at places where devices (users) are spatially-clustered: shorter transmission distances and better communication channels, comparing the links established by the cluster UAV and serving devices (users) to links established by interferers.

  • Article

    Parallel FSO-RF Transmissions for High-Throughput Remote Access with Satellite Communications

    (Institute of Electrical and Electronics Engineers (IEEE), 2023-09-26) Samy, Ramy; Yang, Hong-Chuan; Rakia, Tamer; Alouini, Mohamed-Slim; ECE, KAUST, Thuwal, Saudi Arabia; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; electrical and computer engineering, University of Victoria, Victoria, Canada; University of Victoria, Victoria, Canada; Avionics department, Military Technical College, Cairo, Egypt

    Mixed usage of radio frequency (RF) and free space optical (FSO) transmissions can improve the reliability and throughput of future satellite communication (Satcom) systems. To overcome the rate limitation of conventional hybrid implementations, we propose parallel FSO and RF transmissions to explore their complementary properties in beamwidth and bandwidth. In particular, RF transmissions serve the users over a large geographical area, while the FSO link is employed to increase the throughput to a particular hot-spot area with higher capacity demand through an access point. Independent data streams are adaptively sent over both links to satisfy capacity and availability requirements. To highlight the significant potential of parallel FSO-RF transmissions, we analytically derive the sum capacity outage probability. The obtained expression is validated by Monte Carlo simulations. Furthermore, we derive an asymptotic expression to obtain diversity gain and to provide further insights into the behavior of the proposed system. The presented results demonstrate the potential of parallel FSO and RF Satcom over existing solutions.

  • Article

    HAP-enabled Communications in Rural Areas: When Diverse Services Meet Inadequate Communication Infrastructures

    (Institute of Electrical and Electronics Engineers (IEEE), 2023-09-25) Zhang, Yongqiang; Kishk, Mustafa Abdelsalam; Alouini, Mohamed-Slim; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; Electronic Engineering Department, Maynooth University, Maynooth, Ireland

    The high altitude platform (HAP) network has been regarded as a cost-efficient solution for providing network access to rural or remote areas. Apart from network connectivity, rural areas are predicted to have demands for diverse real-time intelligent communication services, such as smart agriculture and digital forestry. The effectiveness of real-time decision-making applications depends on the timely updating of sensing data measurements used in generating decisions. As a performance metric capable of quantifying the freshness of transmitted information, the age of information (AoI) can evaluate the freshness-aware performance of the process of updating sensory data. However, unlike urban areas, the available communication resources in rural areas may not allow for maintaining dedicated infrastructures for different types of services, e.g., conventional non-freshness-aware services and freshness-aware real-time services, thereby requiring the proper resource allocation among different services. In this article, we first introduce the anticipated services and discuss the advances of rural networks. Next, a case study on the efficient resource allocation across heterogeneous services characterized by AoI and data rate in HAP networks is presented. We also explore the potential of employing the free-space optical (FSO) backhaul framework to enhance the performance of multi-layer HAP networks. To strike a balance between the AoI and data rate, we develop both static and deep reinforcement learning (DRL)-based dynamic resource allocation schemes to allocate the communication resources provided by HAP networks. The simulation results show that the proposed dynamic DRL-based method outperforms the heuristic algorithm and can surpass the performance ceiling achieved by the proposed static allocation scheme. In particular, our presented method can improve performance by nearly 2.5 times more than the ant colony optimization (ACO) method in terms of weighted sum performance improvements. Some insights on system design and promising future research directions are also given.

  • Article

    Precoding for High Throughput Satellite Communication Systems: A Survey

    (Institute of Electrical and Electronics Engineers (IEEE), 2023-09-20) Khammassi, Malek; Kammoun, Abla; Alouini, Mohamed-Slim; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division

    With the expanding demand for high data rates and extensive coverage, high throughput satellite (HTS) communication systems are emerging as a key technology for future communication generations. However, current frequency bands are increasingly congested. Until the maturity of communication systems to operate on higher bands, the solution is to exploit the already existing frequency bands more efficiently. In this context, precoding emerges as one of the prolific approaches to increasing spectral efficiency. This survey presents an overview and a classification of the recent precoding techniques for HTS communication systems from two main perspectives: 1) a problem formulation perspective and 2) a system design perspective. From a problem formulation point of view, precoding techniques are classified according to the precoding optimization problem, group, and level. From a system design standpoint, precoding is categorized based on the system architecture, the precoding implementation, and the type of the provided service. Further, practical system impairments are discussed, and robust precoding techniques are presented. Finally, future trends in precoding for satellites are addressed to spur further research.