Jahan Hassan

Optimising expanding ring search for multi-hop wireless networks

Expanding ring search (ERS) is a widely used technique to reduce broadcast overhead in multi-hop wireless networks (e.g., ad-hoc and sensor networks). ERS works by searching successively larger areas in the network centred around the source of broadcast. Network-wide broadcast is initiated only if L successive searches fail. This paper explores if there exists an optimal L that would minimise the broadcast cost of ERS. A theoretical model is developed to analyse the expected broadcast cost as a function of L. Using this model, we show that an optimal L exists for any random network topology. The analytical results are validated through extensive numerical experiments that consider a large number of random network topologies of varying sizes and hop lengths. By tuning the parameter L to the optimum value, broadcast cost can be reduced up to 52% depending on the topology.

Trust-Based Fast Authentication for Multiowner Wireless Networks

In multiowner wireless networks, access points (APs) are owned and operated by different administrations, leading to significant authentication delays during handoff between APs. We propose to exploit the trust between the owners of neighboring APs for reducing the authentication delay. In the proposed authentication scheme, neighboring APs that trust each other share the security key for the visiting node to avoid lengthy authentication routines each time the visiting node switches APs. The performance of the proposed trust-based authentication scheme is evaluated using a Markov model. Using numerical experiments, we first study a basic scenario where mobile nodes are not aware of the trust networks that exist in a given neighborhood. Subsequently, we consider an advanced scenario where a mobile node functionality is augmented to discover the trust network so as to minimize roaming beyond the trusted APs. We find that, even with the basic implementation, the average number of full authentications needed for a roaming mobile reduces linearly as the likelihood of two neighboring APs trusting each other increases. With the advanced implementation, our experiments show that quadratic reduction is achieved. The Markov model is validated using discrete event simulation.

On the optimization trade-offs of expanding ring search

In decentralized and unstructured networks, such as peer-to-peer and Ad-hoc wireless networks, broadcasting of queries is frequently used for obtaining required information. However, because of the inherent overhead of broadcasting in terms of bandwidth, energy, and processing power consumption, various techniques are used to minimize those overhead. Expanding Ring Search (ERS) is one such technique. Although ERS helps to reduce the overhead of broadcasting, it does not reduce the expected locating time. In this paper, we analyze the locating time and overhead that are two contradicting metrics of ERS performance.

Universal network of small wireless operators (UNSWo)

The recent auctioning of wireless bandwidth in various countries indicates that the service provided by Telcos over these networks will be very expensive. A new type of architecture is currently evolving as a low cost alternative cellular wireless service by allowing the users to play the role of a wireless network operator. Some users of the current Internet may install a low cost base station based on their needs and interconnection between these base stations will form a grid of wireless Internet. This paper provides a survey on related work that either uses ad-hoc mobile networking or a combination of fixed and wireless networking. Finally we present an alternate architecture and describe new issues that arise from this new type of architecture.

Managing Quality of Experience for Wireless VOIP Using Noncooperative Games

We model the users quality of experience (QoE) in a wireless voice over IP (VoIP) service as a function of the amount of effort the user has to put to continue her conversation. We assume that users would quit or terminate an ongoing call if they have to put more efforts than they could tolerate. Not knowing the tolerance threshold of each individual user, the service provider faces a decision dilemma of whether to fix the network problem immediately whenever he detects a user effort in the VoIP system, or ignore it with the hope that the user may still continue the call anyway. In this paper, we formulate the providers dilemma as a non-cooperative game between the provider and the VoIP user experiencing a deteriorating QoE. We demonstrate that providers implementing the equilibrium solutions can expect to not only increase their revenues, but also reduce the number of cases when users quit out of frustration thus minimizing potential churning. We also discuss conditions under which a sophisticated user may or may not benefit from faking unwarranted efforts with a goal of receiving a better service from the provider. Finally, we conduct a subjective experiment of VoIP over WiFi, which verifies the key model assumption that perceptual quality is negatively correlated to the amount of effort the user has to put to continue the call.

Cell hopping: a lightweight architecture for wireless communications

We propose a novel lightweight cellular wireless network architecture called cell hopping. Unlike traditional cellular networks, cell hopping has base stations interconnected by wireless inter-base station links, WIBLs. WIBLs support all routing and switching in cell hopping networks, obviating the need for costly core networks (or a costly switching infrastructure). Cell hopping utilizes an unlicensed frequency and presents a low-cost, rapidly deployable solution for mobile communications. We discuss various technical challenges that must be addressed before cell hopping can become a reality. In particular, we concentrate on location management. We propose an on-demand location management technique that completely eliminates the need for location databases and periodic updates by mobile stations. We provide a few variations of the location management scheme, and compare their performance through simulation.

Performance analysis of expanding ring search for multi-hop wireless networks

Expanding ring search (ERS) is a powerful technique used frequently in multi-hop wireless networks for optimising the broadcast cost of searching. How many times to search using ERS, i.e., the search threshold L, is an interesting open question. Various work found in the literature reports an arbitrary value of the search threshold. In this paper, we analyse the impact of L on the performance of ERS by modeling three different regular network topologies - circular, grid, and hexagonal. We have also carried out a pilot study on nonregular (random) topologies. Our analysis of regular topologies suggests that although it is possible to reduce the network-wide broadcast overhead with ERS by carefully selecting parameter L, the overhead reduction is only marginal. We, however, find that for random topologies, ERS may be very effective in reducing broadcast overhead. We also present guidelines for selecting L for both regular and non-regular topologies.

Improving quality of experience for network services

In pursuit of new revenue opportunities and improving market competitiveness, network service providers are offering new value-added services, such as voice over IP (VoIP), video on demand (VoD), IPTV, and so on. With the increased competition, improving the quality of the offered services as perceived by the users, commonly referred to as the quality of experience (QoE), becomes very important as well as a significant challenge to the service providers with a goal to minimize the customer churn yet maintaining their competitive edge.In pursuit of new revenue opportunities and improving market competitiveness, network service providers are offering new value-added services, such as voice over IP (VoIP), video on demand (VoD), IPTV, and so on. With the increased competition, improving the quality of the offered services as perceived by the users, commonly referred to as the quality of experience (QoE), becomes very important as well as a significant challenge to the service providers with a goal to minimize the customer churn yet maintaining their competitive edge.

Improving quality of experience for network services [Guest Editorial]

In pursuit of new revenue opportunities and improving market competitiveness, network service providers are offering new value-added services, such as voice over IP (VoIP), video on demand (VoD), IPTV, and so on. With the increased competition, improving the quality of the offered services as perceived by the users, commonly referred to as the quality of experience (QoE), becomes very important as well as a significant challenge to the service providers with a goal to minimize the customer churn yet maintaining their competitive edge.In pursuit of new revenue opportunities and improving market competitiveness, network service providers are offering new value-added services, such as voice over IP (VoIP), video on demand (VoD), IPTV, and so on. With the increased competition, improving the quality of the offered services as perceived by the users, commonly referred to as the quality of experience (QoE), becomes very important as well as a significant challenge to the service providers with a goal to minimize the customer churn yet maintaining their competitive edge.

Guest editorial: improving quality of experience for network services

In pursuit of new revenue opportunities and improving market competitiveness, network service providers are offering new value-added services, such as voice over IP (VoIP), video on demand (VoD), IPTV, and so on. With the increased competition, improving the quality of the offered services as perceived by the users, commonly referred to as the quality of experience (QoE), becomes very important as well as a significant challenge to the service providers with a goal to minimize the customer churn yet maintaining their competitive edge.In pursuit of new revenue opportunities and improving market competitiveness, network service providers are offering new value-added services, such as voice over IP (VoIP), video on demand (VoD), IPTV, and so on. With the increased competition, improving the quality of the offered services as perceived by the users, commonly referred to as the quality of experience (QoE), becomes very important as well as a significant challenge to the service providers with a goal to minimize the customer churn yet maintaining their competitive edge.