Publications

Characterizing the Impact of Interference through Spectral Analysis on Commercial 802.11 Devices

Authors: Kostas Chounos, Stratos Keranidis, Thanasis Korakis and Leandros Tassiulas

Conference: IEEE ICC 2017, Paris, France, May 2017

Abstract: Performance experienced by end-users supporting the popular 802.11 protocol is significantly degraded in densely populated urban areas,mainly due to the extensive spectrum sharing and the resulting 802.11 impairments such as "hidden-terminals", overlapping channel interference, etc. Moreover, as the unlicensed spectrum is also home for other wireless technologies and a large range of RF devices, the experienced channel conditions further deteriorate due to cross-technology interference. While the various resulting phenomena can be efficiently mitigated by isolating affected links from interference sources over spectrum, 802.11 networks currently lack unified mechanisms for characterizing the impact of different interference sources across the available channel configurations. In this work, we take advantage of spectral measurements available at the PHY-layer of commercial 802.11 equipment, in order to develop a highly accurate spectral analysis mechanism that is able to quantify the impact of interference on WLAN performance. The developed distributed mechanism concurrently operates on all network nodes and characterizes the band of interest with minimal overhead. Through the implementation of our approach on commercial 802.11n chipsets and its detailed experimental evaluation, we showcase its applicability in characterizing the impact of spectrum congestion and interference in a unified way, towards driving efficient spectrum adaptation decisions.

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Paris Metro Pricing for 5G HetNets

Authors: Virgilios Passas, Vasileios Miliotis, Nikos Makris, Thanasis Korakis and Leandros Tassiulas

Conference: GLOBECOM 2016, Washington DC, USA, December 2016

Abstract: Heterogeneous network access has been proposed as a solution for the continuously deteriorating congestion problem of cellular infrastructures. In this paper we focus on a multi-Radio Access Technology (RAT) environment and we provide a solution based on the Paris Metro Pricing (PMP) scheme, which was first applied in Paris metro. The concept of this pricing scheme was to provide differentiated service classes for customers who desired to avoid being congested, while maintaining the same wagons, characterized only by a different ticket price. The proposed solution extends the classic PMP policy by inducing dynamic prices formed by the congestion of each available technology. We investigate the performance of our dynamic PMP scheme taking into consideration a mobility model of the interested users. Through simulations and testbed experimentation we provide evaluation results on the average throughput, the acceptance capability of the incoming users and how these performance metrics are affected under different mobility conditions.

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Experimental Evaluation of Functional Splits for 5G Cloud-RANs

Authors: Nikos Makris, Pavlos Basaras, Thanasis Korakis, Navid Nikaein and Leandros Tassiulas

Conference: ICC 2017, Paris, France, May 2017

Abstract: Centralized RAN processing has been identified as one of the major enablers for 5G mobile network access. By moving the baseband units (BBU) to the Cloud, multiple instances can be instantiated on the fly, serving several Remote Radio Head (RRH) units. The goal is to satisfy the existing demand of particular geographical areas, whereas drastically reducing the overall CAPEX and OPEX costs of the mobile operators. In this work, we present an experimental study of real Cloud-RAN deployments, with respect to different functional splits. We use as a reference architecture the 3GPP LTE stack, and argue about the functional split applicability in contemporary networks. We evaluate Layer 2 functional splits, that can be used for the convergence of multiple heterogeneous wireless technologies in an all-in-one unit. By deploying our approach in a real testbed setup, we extract the backhaul network transfer requirements for the different splits and present our experimental findings, compared with the respective simulation results.

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Measuring LTE and WiFi Coexistence in Unlicensed Spectrum

Authors: Nikos Makris, Agorastos Dimitrios Samaras, Virgilios Passas, Thanasis Korakis and Leandros Tassiulas

Conference: EuCNC 2017, Oulu, Finland, June 2017

Abstract: The exponential growth in mobile services demand, along with the scarce licensed spectrum in the sub-6GHz bands, mandate the exploitation of bands other than the traditionally used by mobile broadband technologies. An example of such operation is the opportunistic access of the unlicensed bands by the LTE technology, as a means to increase the delivered end-user capacity and enhancing the overall quality of experience. In this paper, we present some extensive testbed measurements used for modeling the coexistence of LTE and WiFi technologies when operating within the same unlicensed environment. The experiments deal with different bandwidth settings for both the WiFi and LTE technologies, when LTE is operating closely or inside the primary or secondary channels of IEEE 802.11, taking into account the different threshold values for the Clear Channel Assessment functions that WiFi entails. We present exhaustive experimental measurements, collected under a real testbed setup, and present a cognitive algorithm for minimizing the impact of the two technologies to each other.

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