arXiv subjects

Evangelos Papapetrou

Publications and source records attributed to Evangelos Papapetrou.

5 recordsLinked to original sources

arXiv2026

A Tutorial on Controlling Metasurfaces from the Network Perspective

Metasurfaces have emerged as transformative electromagnetic structures for wireless communications, enabling the real-time control over wave propagation, yielding potential for improved data rates, privacy, energy efficiency and even precise environmental sensing. This tutorial offers a perspective on controlling metasurfaces by treating them as components of a larger networked system. Towards this end, we first review the physical principles of metasurfaces and their various applications, followed by an exploration of manufacturing approaches for creating these structures. Then, aligning with standard network layer concepts, we describe the modeling of metasurfaces as wave routers, enabling us to describe systems of metasurfaces using graph theory. This approach enables the development of a performance objective framework for optimizing these systems, while classes of heuristic and path-finding-driven algorithms are discussed as practical solvers. The paper also examines the integration of metasurfaces with communication systems, by presenting their overall workflow, discussing its relation to ongoing standardization efforts, as well as defining a context for their integration to network simulators, using Omnet++ as a driving example. Finally, the paper explores future directions for research in this field, identifying graph-theoretic, standardization and integration challenges, relating to several networking disciplines including AI-driven applications.

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arXiv2021

A Replication Strategy for Mobile Opportunistic Networks based on Utility Clustering

Dynamic replication is a wide-spread multi-copy routing approach for efficiently coping with the intermittent connectivity in mobile opportunistic networks. According to it, a node forwards a message replica to an encountered node based on a utility value that captures the latter's fitness for delivering the message to the destination. The popularity of the approach stems from its flexibility to effectively operate in networks with diverse characteristics without requiring special customization. Nonetheless, its drawback is the tendency to produce a high number of replicas that consume limited resources such as energy and storage. To tackle the problem we make the observation that network nodes can be grouped, based on their utility values, into clusters that portray different delivery capabilities. We exploit this finding to transform the basic forwarding strategy, which is to move a packet using nodes of increasing utility, and actually forward it through clusters of increasing delivery capability. The new strategy works in synergy with the basic dynamic replication algorithms and is fully configurable, in the sense that it can be used with virtually any utility function. We also extend our approach to work with two utility functions at the same time, a feature that is especially efficient in mobile networks that exhibit social characteristics. By conducting experiments in a wide set of real-life networks, we empirically show that our method is robust in reducing the overall number of replicas in networks with diverse connectivity characteristics without at the same time hindering delivery efficiency.

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arXiv2016

Analyzing the Synergy between Broadcast Polling and Piggybacking in WiMAX Networks

In this work we present a model for analyzing the combined use of broadcast polling and piggybacking in Worldwide Interoperability for Microwave Access (WiMAX) networks. For an accurate analysis of piggybacking, the model focuses on the realistic case of limited up-link bandwidth and non-trivial queueing capability at the subscriber stations. We first model the activity of a subscriber station using a Markov chain and its queue as an M/G/1 system with vacations in order to facilitate the analysis of the piggyback mechanism. We then derive a set of fixed point equations that describe not only the contention process at the network level but also bandwidth allocation to contending and piggybacked requests. Our model uses a minimal set of assumptions and is generic in the sense that it is customizable through a set of parameters. It can also reproduce the system performance in both saturated and non-saturated conditions. After validating our analysis through extensive simulations, we shed light on the aspects of the synergy between broadcast polling and piggybacking and unveil the pros and cons of using the latter.

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arXiv2016

Revisiting XOR-based Network Coding for Energy Efficient Broadcasting in Mobile Ad Hoc Networks

Network coding is commonly used to improve the energy efficiency of network-wide broadcasting in wireless multi-hop networks. In this work, we focus on XOR-based broadcasting in mobile ad hoc networks with multiple sources. We make the observation that the common approach, which is to benefit from the synergy of XOR network coding with a CDS-based broadcast algorithm, suffers performance breakdowns. After delving into the details of this synergy, we attribute this behavior to an important mechanism of the underlying broadcast algorithm, known as the "termination criterion". To tackle the problem, we propose a termination criterion that is fully compatible with XOR coding. In addition to that, we revisit the internals of XOR coding. We first enhance the synergy of XOR coding with the underlying broadcast algorithm by allowing each mechanism to benefit from information available by the other. In this way, we manage to improve the pruning efficiency of the CDS-based algorithm while at the same time we come up with a method for detecting coding opportunities that has minimal storage and processing requirements compared to current approaches. Then, for the first time, we use XOR coding as a mechanism not only for enhancing energy efficiency but also for reducing the end-to-end-delay. We validate the effectiveness of our proposed algorithm through extensive simulations on a diverse set of scenarios.

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arXiv2014

Deterministic Broadcasting and Random Linear Network Coding in Mobile Ad Hoc Networks

Network coding has been successfully used in the past for efficient broadcasting in wireless multi-hop networks. Two coding approaches are suitable for mobile networks; Random Linear Network Coding (RLNC) and XOR-based coding. In this work, we make the observation that RLNC provides increased resilience to packet losses compared to XOR-based coding. We develop an analytical model that justifies our intuition. However, the model also reveals that combining RLNC with probabilistic forwarding, which is the approach taken in the literature, may significantly impact RLNC's performance. Therefore, we take the novel approach to combine RLNC with a deterministic broadcasting algorithm in order to prune transmissions. More specifically, we propose a Connected Dominating Set (CDS) based algorithm that works in synergy with RLNC on the "packet generation level". Since managing packet generations is a key issue in RLNC, we propose a distributed scheme, which is also suitable for mobile environments and does not compromise the coding efficiency. We show that the proposed algorithm outperforms XOR-based as well as RLNC-based schemes even when global knowledge is used for managing packet generations.

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