Publications

New Channel Allocation Techniques for Power Efficient WiFi Networks

Authors: Vasileios Miliotis, Apostolos Apostolaras, Thanasis Korakis, Zhifeng Tao, Leandros Tassiulas

Conference: W-Green 2010, PIMRC 2010, Istanbul, Turkey September 2010

Energy efficiency becomes evergreen than ever before. Over the last few years a significant research in wireless communications, aiming to enhance communications efficiency subject to constraint of power consumption, has given rise to optimization techniques of power control and management in wireless networks. Although the initial target was the utilization of resources in order to exploit communications services, the benefits of this effort, underlying the green perspective, are now opening eyes out to research community for a more green matter of conscience in use of communication equipment and devices. Towards this direction and affected by a green sensitivity in terms of wasting useful resources, we propose a system model for infrastructure WiFi networks aiming to reduce the consumed power, by introducing a scheme for channel allocation to Wireless LANs under energy conserving criteria.

Download paper: wgreen2010_AllocationTechniquesforPowerEfficientWifiNetworks

TLQAP: Topology and Link Quality Assessment Protocol For Efficient Node Allocation onWirelessTestbeds

Authors: Dimitris Syrivelis, Angelos-Christos Anadiotis, Apostolos Apostolaras,Thanasis Korakis, Leandros Tassiulas

Conference: WinTech 2009, Beijing, China, September 2009

In this paper we present Topology and Link Quality Assessment Protocol (TLQAP), which we have implemented as a wireless testbed management framework component, that is used to inspect link quality between wireless testbed nodes and appropriately map them to user experiment requirements. TLQAP is mainly an OSI layer 2 design for fixed location, non RF-isolated wireless testbed deployments, which assesses interconnection topology and link quality by estimating packet delivery ratio (PDR) and transmission delay at each node for all requested channel, rate and transmission power combinations. Moreover, TLQAP builds a measurement history log and creates a channel utilization profile, in the context of each testbed node, for all the nearby testbed external devices that operate independently in the region and are not under the management framework control. The analysis of this information enables TLQAP to choose the channels that have the highest probability of being free during an experiment. TLQAP OSI layer 2 component has been implemented in the click modular router framework and the controller component has been integrated with OMF management framework for wireless testbeds. To outline TLQAP benefits, we have performed experiments on our ORBIT node testbed and we compare it to an existing ap- plication level measuring tool.

Download paper: wintech09_TLQAP

Contention and Traffic Load-aware Association in IEEE 802.11 WLANs: Algorithms and Implementation

Authors: Stratos Keranidis, Thanasis Korakis, Iordanis Koutsopoulos and Leandros Tassiulas

Conference: WinMee 2011, Princeton NJ, USA, May 2011

Efficient association of a station with the appropriate access point has always been a challenging problem. The standard approach of considering only the Received Signal Strength, has recently been substituted by more efficient schemes that consider channel conditions, cell population etc. However, in spite of the large variety of approaches, several factors that determine to a large extent user throughput after association with an access point have been overlooked. In this work, we propose innovative metrics on which association should be based. First, we capture the contention from one-hop and interference from two-hop neighbors that is inherent in IEEE 802.11 WLAN environments. Second we include the PHY transmission rate and show preference to higher rates that reduce the above effects. Third, unlike most relevant approaches, we define an activity factor that reveals the anticipated activity due to backlogged traffic. We devise an association protocol suite, through which messages containing the information above are passed between the AP and the user to support association decisions for the uplink and downlink. We implement the proposed mechanism using the MAD-WiFi open source driver and moreover show through experiments in a wireless testbed that it significantly improves user performance in real conditions.

Download presentation: Keranidis_Association_WinMee_Presentation_2011.pdf

Download paper: Keranidis_Association_WinMee_Paper_2011.pdf

Various Detection Techniques and Platforms for Monitoring Interference Condition in a Wireless Testbed

Authors: Wei Liu, Stratos Keranidis, Michael Mehari, Jono Vanhie-Van Gerwen, Stefan Bouckaert, Opher Yaron and Ingrid Moerman

Conference: LNCS of the Workshop in Measurement and Measurement Tools 2012, Aalborg, Denmark, May 2012

Abstract: Recently the constant growth of the wireless communication technology has caused a huge demand for experimental facilities. Hence many research institutes setup public accessible experimental facilities, known as testbeds. Compared to the facilities developed by individual researchers, a testbed typically offers more resources, more flexibilities. However, due to the fact that equipments are located remotely and experiments involve more complex scenarios, the required complexity for analysis is also higher. A deep insight on the underlying wireless environment of the testbed becomes necessary for comprehensive analysis. In this paper, we present a framework and associated techniques for monitoring the wireless environment in an OMF enabled testbed. The framework utilizes most common resources in the testbed, such as WIFI nodes, as well as some high-end software-defined radio platforms. Information from both physical layer and network layer are taken into account. Further more we explored the added value of distributed sensing system. The performance is mainly analyzed experimentally

Download paper: Keranidis_Monitoring_LNCS_2012_paper.pdf