Soutenance de thèse Sarkis Moussa

Soutenance de thèse Sarkis Moussa

Friday, June 30, 2023. 2pm

Place: thesis room (salle des thèses) at the Hannah Arendt campus.

For those unable to attend, here is the BBB link for the video conference:


Architecture and Protocols for Public Safety Users in the 5G Cellular Networks


Public Safety Networks (PSNs) are wireless communication systems designed to meet the needs of emergency responders, including firefighters, police, and many other Public Safety (PS) agencies. These networks are used to prevent or respond to incidents that pose a threat to people or property. Traditionally, these PSNs were supported by reliable, but low-rate radio technologies that provide limited services such as voice communication among Public Safety Users (PSUs). Consequently, their capability to take advantage of recent developments in wireless networks and broadband applications was restricted. At the forefront of wireless communication technologies, 5th Generation (5G) and beyond Cellular Networks (CNs), are ideal for this purpose due to their advanced infrastructure and tailored techniques developed for broadband services. Their capacity for high data transmission, low latency in data exchange, and ability to support a significant number of connected devices make them perfectly suited to overcome the limitations associated with PSNs.


Integrating PSNs into 5G can significantly improve the performance of PSUs. It enables PS agencies to respond more effectively to emergencies, improve communication among first responders, and access critical information in real-time. In this regard, the objective of this thesis is to develop models and architecture that guarantee effective communication among PSUs through the use of cellular resources. We consider different scenarios, including situations where resources are solely dedicated to PSUs and where resources are shared with primary users. In these scenarios, Non-Orthogonal Multiple Access (NOMA) technique and Device-to-Device (D2D) communication ensure an efficient allocation of limited resources for a larger number of PSUs. Additionally, in this thesis, we explore scenarios where cellular resources are not available (e.g. when the Base Station (BS) is not accessible). We develop strategies to maintain the continuous functioning of PSUs in such situations using the Multi-access Edge Computing (MEC) system.


To accomplish these objectives, we first focus on the formulation of a resource allocation problem in the in-band overlay D2D communication. The rationale for using the overlay mode is to guarantee the availability of Resource Blocks (RBs) that are dedicated exclusively to PSUs, minimizing therefore the interference between Cellular Users (CUs) and PSUs. Furthermore, we consider the NOMA technique for radio access, which allows multiple PSUs to share the same RBs, improving thereby the system performance in terms of spectral efficiency, achieved throughput, and number of PSUs accessing the network. This is achieved by implementing a heuristic that groups the PSUs that will share the same resources, so that the total amount of bandwidth used is minimized. We then allocate sufficient power to each PSU using the Particle Swarm Optimization (PSO) algorithm.


As a second approach, we propose a novel scheme for the underlay D2D communication scenario. This scheme also relies on the NOMA technique and is based on a mixed integer nonlinear programming problem for sum throughput maximization. It takes into account the power budget, the users required rates, and the Successive Interference Cancellation (SIC) constraints. Since the maximization problem is computationally challenging, we design a heuristic algorithm that selects the appropriate CUs to share their resources with the PS clusters. Then, given this selection, we compute the optimal power allocation in each PS cluster using the Lagrange multiplier method.


During a disaster, the infrastructure might get damaged, in particular, BSs, resulting in the disruption of PSUs’ access to the core network. To address this critical issue and ensure the continuous availability of PS services under any circumstances, we investigate the use of the Proximity-based Services (ProSe) standard which plays a crucial role in enabling D2D communication in licensed and unlicensed spectrum.

Accordingly, we propose and validate a new architecture for PSNs using the Simu5G network simulator. This architecture uses the NOMA technique and places both, the ProSe function and the ProSe application server, in the MEC system that is installed in a relay station. This approach guarantees network availability for as many PSUs as possible, and enables them to access the required information with minimal latency in the licensed spectrum, while they continue to operate in the unlicensed spectrum securely and efficiently

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