E-Quality workshop

ABSTRACTS

Eitan Altman, INRIA, Sophia-Antipolis, France

New Insights from a Fixed Point Analysis of Single Cell IEEE 802.11 WLANs

We present in this talk an analysis of the throughput of the wireless local area network IEEE 802.11. Our starting point is a fixed point approach that does not require a Markov chain analysis; it is derived directly from renewal arguments. Uniqueness of the fixed point is established. Simple and general throughput formulas are provided. It is shown that the throughput of any flow will be bounded by the one with the smallest transmission rate. The aggregate throughput is bounded by the reciprocal of the harmonic mean of the transmission rates. We study in particular the asymptotic regime with a large number of nodes. We finally use our analysis to optimize the system's performance.

Joint work with Anurag Kumar, Daniele Miorandi and Munish Goyal

Sem Borst, Technische Universiteit Eindhoven, the Netherlands

Flow-level performance and user mobility in wireless data networks

Channel conditions in wireless networks exhibit huge variations across space and time, giving rise to vast random fluctuations in the feasible transmission rates. Channel-aware scheduling strategies provide an effective mechanism for improving throughput performance by exploiting such rate variations, and have been extensively investigated at packet level for a static user configuration. In this talk, we explore the performance implications at flow level for a dynamic user population, taking into consideration rate variations on a slower time scale and wide-range user mobility as well.

First of all, we present simple necessary conditions for flow-level stability, and prove that these are in fact (near-)sufficient for a wide family of utility-based scheduling strategies. It is further shown how the flow-level performance of the Proportional Fair scheduling strategy may be evaluated by means of a multi-class Processor-Sharing model with state-dependent service rate. In addition, we examine the impact of rate variations on a slower time scale, and establish that two limit regimes, termed fluid and quasi-stationary regime, yield explicit, insensitive performance bounds.

Finally, we turn attention to a network of several base stations with hand-offs of active sessions governed by wide-range user mobility. It is demonstrated that mobility increases the capacity region, not only in case of globally optimal scheduling, but also when each of the base stations adheres to a local fair sharing discipline.

Wim Coenen, VOSKO networking, Gouda, The Netherlands

Wireless Local Area Networks in large enterprise environments

Around 2004 a new generation of WLAN-systems was developed by a couple of specific founded companies as WLANs (conform IEEE 802.11) up to that moment did not scale and were not easy to manage in large environments. This new generation of WLAN-systems is now widely adopted by the networking market and is deployed in an increasing amount of enterprise environments.

To raise budget for the installation of such a large WLAN in enterprise environments, like hospitals, airports, universities, etc., the use as a data only wireless network is often not enough. When the same network however can also be used for inhouse telephony, it becomes more interesting to complete the business case. The addition of location based services over WLAN becomes a third important application to install and use a large WLAN.

All these different kind of applications with their specific requirements using a shared and limitted bandwidth network (compared to wired LANs) demand some kind of Quality of Service to perform as required. Vosko Networking designs, installs, secures and maintains large LANs and WLANs in the Netherlands. We will share all kind of issues we've come across during the recent design and installation cycles of large WLANs at Amsterdam Airport Schiphol, ErasmusMC and other Dutch Hospitals, Universities, High Schools and other Dutch enterpises.

Maurits de Graaf, Thales Communications, Huizen, The Netherlands

Network lifetime problems in personal communication systems

Thales Nederland BV - Land & Joint Systems (TNL) manufactures and supplies a.o. integrated communications systems for civil and military organisations. Since 2004 TNL is strongly involved in the development of personal communication systems: wearable voice and data systems that can be used by e.g. emergency services to exchange situational awareness information. TNL is based in Huizen and has around 250 employees. Quality of service plays an important role at almost all communication system layers and ranges from Dynamic Noise Reduction to improve speech quality in noisy environments to additions to routing protocols for ad-hoc networks to take link quality into account in route computations. A currently active line of research is on weight reduction for personal communication systems. As the weight of batteries contributes significantly to the total weight of the system, it is essential to increase the network lifetime (the 'network lifetime' is the time a network can perform its function until the first node runs of power). In the presentation we discuss recent work in this area that has been carried out in cooperation with the University of Twente in the Casimir project: Average analysis of a transmit power assignment algorithm, efficient selection of Multipoint Relay Nodes in an OLSR based network, and optimisation of the network lifetime in a specific type radio network.

Geert Heijenk, University of Twente, Enschede, The Netherlands

Is there anybody out there? - Discovering your environment in mobile ad-hoc networks

Mobile ad-hoc networks can provide for information exchange between devices if a communication infrastructure is not available or cost-effective. Such a networks should organize and configure itself spontaneously and automatically. For that purpose, it is important that mobile devices can learn about the other devices in their environment, and the services they can provide.

We present a novel approach to perform service discovery in an ad-hoc network based on the use of attenuated Bloom filters. In this approach, neighboring devices exchange advertisements, which provide a highly compressed summary of services they know of up to a certain number of hops away. Neighbors use these advertisements to supplement their knowledge of the environment, and to direct query messages, if they are in need for a certain service. The use of attenuated Bloom filters to summarize service availability in advertisements minimizes the amount of data to be exchanged at the cost of a small probability of false positives. Results obtained using an analytical performance model and a simulation model show that the approach is effective and very resource efficient for discovery processes in networks with mobile, resource-constrained nodes and wireless links.

Jan de Jongh TNO-ICT, Delft, The Netherlands

Emulating Mobility and the Wireless Medium in Ad Hoc Networks

The dynamic connectivity topology of wireless ad hoc networks and its performance-related effects are studied mostly through mathematical modeling techniques like simulation and exact or approximate analysis. In this presentation we introduce an ad hoc network emulator developed at TNO ICT. The emulator replaces the wireless medium of a real-world ad hoc network with a model-driven constellation of RF attenuators, leaving the rest of the system intact. Compared to aforementioned purely mathematical techniques, emulation leads to fewer modeling errors and can be used, for instance, for stress-testing actual products and protocols. The emulator supports several fading effects and has a wide frequency range.

In the presentation we will discuss the pros and cons of emulation, highlight some of the main design concerns, provide a feature overview of the emulator, and present past and ongoing research using the emulator.

Sindo Nunez - Queija CWI, Amsterdam, the Netherlands

Title and abstract t.b.a.

Eric Smeitink, KPN, The Netherlands

Comparing WiMAX and 3G technology for mobile broadband deployment

Abstract t.b.a.

Dirk Staehle, Universitaet Wuerzburg, Germany

Performance Models for the UMTS Enhanced Uplink

Abstract t.b.a.

Johan Trouwborst T-Mobile, The Netherlands

Challenges & Evolution of Quality of Service in mobile networks

The fundamental scope of Quality of Service is to achieve the optimum level of quality as provided to - and perceived by - the end-user.
In nowadays telecom industry there are multiple services requiring different network conditions to achieve an acceptable level of quality for each service, again from a customer perspective. Implementation of Quality of Service and its configuration can be therefore seen as key-enabler to provide each service with the best level of quality achievable. The better Quality of Service is implemented, the more a network operator can differentiate himself on the market with the best performing delay-sensitive and bandwidth-consuming services (each service type having its specific qualities and conditions).

In first place, this presentation briefly summarizes the importance of Quality of Service for the T-Mobile Netherlands organization.
The technology view on Quality of Service will be further discussed, addressing some actual challenges concerning QoS implementation today.
Potential solutions for today's QoS implementation challenges will be discussed by means of the expected evolution of Quality of Service in the mobile network.

The presentation will be closed with some room for discussion and sharing opinions.

Made / updated on 24-02-2009
Maintained by L. Coolen