Dr. Anargyros J. Roumeliotis receives the Dimitris N. Chorafas Prize 2022

Dr. Anargyros J. Roumeliotis is awarded the prestigious Dimitris N. Chorafas Foundation Prize for the year 2022 for his PhD thesis “Optimization Algorithms for High Throughput Wireless and Satellite Networks”. The Dimitris N. Chorafas Prize 2022 is meant to reward outstanding scientific contributions within the doctoral education.

Dr. Anargyros J. Roumeliotis has received his PhD from the School of Electrical and Computer Engineering of the NTUA on 16/6/2022 with supervisor Professor Athanasios D. Panagopoulos.

PhD Summary: Considering the urgent demand for high speed internet, multimedia and broadband applications in accordance with the ever growing amount of data that each user needs, wireless networks have to make appropriate resource management in this demanding communication environment. Furthermore, satellite networks are a viable solution, either alone or in cooperation with 5G cellular systems, supporting the backhaul links of the operators or offloading the traffic. Moreover, satellite systems are useful to providing services in rural or remote areas, such as in maritime and aeronautical fields. Here it must be noted that the European Commission’s Digital Agenda states that all European household and citizens must be able to have high speed broadband services anywhere and at any time. Thus, assuming the need for “smart” resource allocation to have worldwide network coverage, my research contributes significantly towards this direction.

Particularly, having in mind that the satellite operators have to guarantee an acceptable quality of service for users, they have to utilize their network in the best way. This means that their gateways, located in different regions, that can provide specific offered capacities related with atmospheric attenuation, have to serve the demands of users’ beams, translated the latter through their requested capacities. From the view of the system’s design, its performance is quantified through appropriate performance metrics by solving optimization problems. Under these assumptions, we provide appropriate and efficient pairings among the gateways and users based on widely accepted metrics from literature, such as the losses, rate matching and satisfaction ratio and proposing also a new metric that is the dissatisfaction ratio. The latter can be used to model future resource allocation problems that cannot be solved with respect to the satisfaction ratio.

Considering the fast variations of channel propagation conditions and users’ demands, i.e. the fast changes in offered and requested capacities, the proposed pairing schemes are efficient and can be applied for real-time scenarios. On the other hand the corresponding exhaustive optimal scheme, exploring all possible pairs, has prohibitive time complexity. Moreover, the proposed pairing schemes can be applied in realistic cases where the gateways are less than the users. In this case the network operators can exploit their existent infrastructure in the best way.

Furthermore, through the conducted research, some useful results have been extracted for the satellite system’s operators that have to be considered in the network’s implementation. Especially, focusing on gateways-satellite links, a design dilemma for the system is to give priority to the maximization of the "worst" user’s satisfaction ratio or the overall system’s satisfaction, because the optimal pairs for the first result in minimization of second and vice versa. Additionally, another important design point is that if there are disallowed pairs in the system, i.e. some gateways-users pairs are impossible, then the system’s performance is worsen. Finally, examining the performance of nth order rate matching, the minimization of rate matching with higher nth order results in more fair results among the users in terms of their absolute differences among their requested and offered capacities. These aforementioned points can help the network operators to decide appropriately having in mind the users’ demands.

Finally, one of most important characteristics of the research is the case that the presented robust and efficient pairing algorithms are directly applied to other wireless networks except from the satellite systems. Hence, the presented mechanisms and results of aforementioned studies can help not only the satellite system’s engineers, but also the wireless network operators generally.

Brief CV and Publications of Dr. Anargyros J. Roumeliotis