Publications

A Mechanism for Mobile Data Offloading to Wireless Mesh Networks

Authors: Apostolos Apostolaras, George Iosifidis, Kostas Chounos, Thanasis Korakis and Leandros Tassiulas

Journal: IEEE Transactions on Wireless Communications, vol. 15, no. 9, pp. 5984-5997, Sept. 2016

Abstract: As the growth of mobile data traffic places significant strain on cellular networks, plans for exploiting underutilized network resources become increasingly attractive. In this paper, we propose, design, and evaluate a data offloading architecture, where mobile users are offloaded to mesh networks, which are built and managed by residential users. Such networks are often developed in the context of community networks or, recently, as commercial services. Mobile network operators can lease capacity from these networks and offload traffic to reduce their servicing costs. We introduce an analytical framework that determines the offloading policy, i.e. which mobile users should be offloaded, based on the energy cost induced to the cellular base stations. Accordingly, we design a minimum-cost servicing policy for the mesh networks. Clearly, such architectures are realizable only if the mesh nodes agree with each other to jointly serve the offloaded traffic. To achieve this, we employ the Shapley value rule for dispensing the leasing payment among the mesh nodes. We evaluate this paper by simulating the operation of the LTE-A network, and conducting test bed experiments for the mesh network. The results reveal significant savings for eNBs power consumption and reimbursements for mesh users. 

Index Terms — Mobile data offloading, mesh networks, network economics, Shapley value.

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Forging Client Mobility with OpenFlow: an experimental study

Authors: Nikos Makris, Kostas Choumas, Christos Zarafetas, Thanasis Korakis and Leandros Tassiulas

Conference: WCNC 2016, Doha, Qatar, April 2016

Abstract:The wide proliferation of IEEE 802.11 compatible devices and the provisioning of costless Internet connectivity in most cases, have created fertile ground for investigating seamless client mobility and handoff management from a cellular technology to any wireless access point available. Although handoffs and client mobility are currently addressed by the IEEE 802.21 standard along with mobility management protocols such as Mobile IPv6, yet no remarkable efforts exist for the wide deployment of such solutions. Moreover, the adoption of such architectures requires considerable changes in the mobile node’s networking stack. In this work, we propose a Software Defined Networking technology inspired scheme for managing client mobility among heterogeneous wireless networks, by adopting changes only on the network edges. Our solution is compatible with the existing IPv4 and IPv6 addressing solutions. By employing the OpenFlow technology on the border of our network with the Internet, we manage to keep both ends of the network aware of any topology changes, and thus preserve any already established connections, resulting in a seamless handoff process. We evaluate our technique in a real network setup, by employing WiFi and LTE technologies and benchmark it using higher layer protocols with multi-homing features, namely Stream Control Transmission Protocol and Multipath TCP.

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Semantic Coordination Protocol for LTE and Wi-Fi Coexistence

Authors: Milorad Tosic, Valentina Nejkovic, Filip Jelenkovic, Nenad Milosevic, Zorika Nikolic, Nikos Makris and Thanasis Korakis

Conference: EUCNC 2016, Athens, Greece, June 2016

Abstract:In this paper, we address the challenges in facilitating the intra-band coexistence of WiFi and LTE technologies in multi-RAT networks and propose a semantic coordination protocol that improves the communication performance among inter-network devices. Effective communication in LTE networks is a critical task to achieve as the heterogeneity of the devices and coexisting technologies arises. This paper introduces an internetwork spectrum coordination across Wi-Fi and LTE systems based on an ontological framework as a possible solution for improved coexistence. We develop and evaluate our approach under real-world settings. The results we obtained using the proposed semantic coordination protocol have shown significant gains for both the under-study Wi-Fi and LTE networks.

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Reduction of Collisions and Regret in Time Sharing Schemes for Opportunistic Spectrum Access

Authors: Dimitris Giatsios, Thanasis Korakis, Leandros Tassiulas and Iordanis Koutsopoulos

Conference: NETGCOOP 2014, Trento, Italy, 29-31 October, 2014

Abstract: We examine decentralized learning and access algorithms for opportunistic spectrum access with multiple users. Several distributed algorithms have been proposed for this problem, mainly as an application of corresponding algorithms for the multiarmed bandit problem, which are provably order optimal in terms of regret. However, none of them pays particular attention to reducing collisions among users caused by lack of message exchanges. The effect of such collisions becomes more observable as the number of users increases, causing a considerable amount of added regret, despite retaining the optimal order. Focusing on time division fair sharing schemes based on the idea of orthogonal offsets, we propose a simple algorithm for detecting offset collisions and trying to resolve them as quickly as possible, inspired from persistent distributed schemes for multiple access. We demonstrate the improved performance achieved by our algorithm by means of simulations.