Nirmala Shenoy

A framework for seamless roaming across cellular and wireless local area networks

In the future, wireless and mobile users will have increased demands for seamless roaming across different types of wireless networks, quality of service guarantees, and support for a variety of services. This awareness has led to research activities directed toward intersystem and global roaming, and can be noticed in numerous products like multimode handsets, interworking gateways, and ongoing standards and research work on intersystem roaming. The authors of this article proposed a global mobility management framework to support seamless roaming across heterogeneous wireless networks. In this article we provide details on the use of the framework to support roaming across cellular and wireless local area networks. Highlights of the framework include a robust architecture for mobility management for varying user mobility spans, provisioning for QoS mapping, intersystem message translation, and mechanisms in the WLAN to support user-subscribed services. Performance aspects related to handoff delays, data redirection, and processing overheads are presented and discussed. Performance comparison of intersystem roaming between cellular and WLAN with and without the framework is presented.

A random walk mobility model for location management in wireless networks

This paper describes a new and simple random walk mobility model that simplifies the two-dimensional Markov chain based on the properties of symmetry and lumped process. Compared to various other approaches, the proposed approach significantly reduces the complexity of the model by reducing the computing states. Based on this model, the location update rate and dwell time can be easily derived. The regular Markov chain and the property of combining states are applied to derive the number of location updates and a modified absorbing Markov chain property can be used to derive the dwell time. Analytical performance results of the model were validated by simulation. Results show the relative error between analytical and simulation performances are within 1%. This is the first model of its kind that can be used for studying area-crossing rates. This model can be adapted to most mobility management studies for architectures.

A comparative study of mobility prediction in fixed wireless networks and mobile ad hoc networks

In this paper we have introduced a mobility prediction scheme that proposes the use of a new sector-based tracking of mobile users, with a sector-numbering scheme to predict user movements. The proposed scheme is applicable for both the fixed network and the ad hoc networking structures. Our study shows that accurate prediction is possible with reduced area of tracking for both types of networks.

Optimized rule-based delay proportion adjustment for proportional differentiated services

We present a novel method to adjust output queue delay proportion fairly among traffic classes of different priorities in relative differentiated services. The delay proportion adjustment is based on acceleration of incoming traffic in each class. It aims to reduce the undesirable effects of queue-delay propagation toward higher priority classes, caused by the introduction of bursty data into lower priority classes. We use a fuzzy controller to make the decision regarding the amount of proportion adjustment, as it is very flexible and adjustable. We suggest an efficient extension to the particle swarm optimization algorithm for the purpose of optimizing the fuzzy system. The simulation shows that the dependency of high-priority-class delay, which is a value that indicates quality-of-service of the traffic, on lower priority classes is significantly reduced by the proposed delay proportion adjustment.

An underwater sensor allocation scheme for a range dependent environment

A series of assumptions is typically made when designing a field of passive underwater sensors. One of the more glaring is range independence throughout an operational area. It is unlikely that a large water space will have uniform acoustic characteristics throughout, i.e., the performance of a sensor will vary based upon its physical location. In an area clearance scenario, where there is no apparent target for an adversary to gravitate towards, such as a ship or a port, it is difficult to determine where the field designer should allocate sensors so that their deployment locations can be planned efficiently. To intelligently allocate sensors, a field designer could first divide an area into sectors of relatively uniform acoustics, based upon variations in acoustic characteristics throughout the area. A prediction of how often a threat submarine will visit each sector can then be made in order to increase the fields detection capabilities. In this work, an area of interest is divided into sectors of varying geographic size and acoustic characteristics and the probability of visitation to each sector by a threat submarine is determined by solving a minimax matrix game. The Game Theory Field Design (GTFD) model is proposed, which allocates sensors to sectors of relatively uniform acoustics according to the visitation probabilities of an adversary, against adversaries of varying intelligence. In a comparison with two models that do not consider these visitation probabilities and only examine either acoustic characteristics or the size of the sectors, GTFD is shown to offer a significant improvement in terms of overall field detection capability against intelligent adversaries.

A framework for seamless roaming across heterogeneous next generation wireless networks

In the future, wireless and mobile users will have increased demands for seamless roaming across different types of wireless networks, quality of service guarantees and support of different types of services. This awareness has led to research activities directed towards inter-system and global roaming and can be noticed in the numerous products like multimode handsets, inter-working gateways and some ongoing standards and research work on signaling protocols for inter-system roaming. This article proposes a global mobility management framework. The framework is like an overlay network comprising of Inter-System Interface Control Units IICU to support inter-network communication and control for Location Management. The protocols and functions of this framework will be distributed and exist partly within the wireless networks and partly within the core-network. A hierarchy introduced among the IICUs will accommodate for the varying mobility coverage required by the mobile user. The IICU may be configured to perform various functions depending on its placement in the hierarchy of the framework. This approach aims to optimize across call set up delays, signaling traffic, database processing, handoff facilitation for seamless roaming and QoS mapping and negotiations as the user moves across different wireless networks. It avoids centralized database dependency with its associated single-point bottleneck and failures. We restrict our analysis of the framework to a 2-network and a 3-network roaming scenario. The presentation has been further restricted to cost and delay analysis of the location update and call delivery procedures. We have taken into account the signalling requirements when the mobile user roams across networks with and without an active call.

Review: A survey of identity and handoff management approaches for the future Internet

Since its inception almost 40years ago, the Internet has evolved and changed immensely. New technology solutions are desired to keep up with this unprecedented growth. Besides the traditional computing devices, different types of mobile devices need to be supported by the future Internet architecture. In this work, a survey of identity and handoff management solutions proposed in future Internet architectures is presented. Mobility protocols developed by the Internet Engineering Task Force initiatives are discussed to give the background on the user mobility support challenges with the current architecture. The next generation network architectures supported by global initiatives are presented and analyzed in terms of their support for seamless user and device mobility. Furthermore, this survey is extended to include the architectures proposed for wireless mesh networks, which are envisioned to be a part of the next generation networks with their self organizing and self configuring network characteristics.

Fuzzy system for adaptive network routing

In this paper we propose an adaptive routing using a fuzzy system. The traffic in the network is re-routed to nodes, which are less congested, or have spare capacity. Based on a set of fuzzy rules, link cost is dynamically assigned depending upon the present condition of the network. Distance vector algorithm, which is one of the shortest path routing algorithms is used to build the routing tables at each node in the network. The proposed fuzzy system determines the link cost given the present congestion situation measured via the delays experienced in the network and the offered load on the network. Delay in the links, was estimated by the time taken for the test packets to travel from the node to its neighbors. The delay information collected by the test packets and the number of packets waiting in the queue, are the two inputs to the fuzzy system. The output of the fuzzy system is the link cost. This algorithm was applied on a simulated NSFNET, the USA backbone, as well as to another test network with a different topology. Robustness and optimality of the proposed fuzzy system was tested by simulating various types of load patterns on these networks. Simulation studies showed that the performance of the fuzzy system was very close to or better than the best performance of the composite metric under different load conditions and topologies.

A tiered addressing scheme based on a floating cloud internetworking model

Scalability in inter-domain routing is becoming stressful as routing table sizes grow at very high rates. In this paper, we present a tiered addressing scheme to be implemented over a Floating Cloud Tiered internetworking model which uses tier based aggregation to address routing scalability. Analysis of the HD-ratio of the addressing scheme and its possible implementation on the AT&T network is presented.

Route robustness of a multi-meshed tree routing scheme for Internet MANETs

We propose a layer 2 routing and forwarding scheme called multi-meshed tree (MMT) routing for MANETs connected to Internet. The specifications of this scheme were drawn from unique features of Internet MANETs. Evaluation of the robustness of routes in this scheme is provided along with the route failure notification delays, which is an important performance parameter of this scheme. Where available we have substantiated our results with simulation data. The results clearly show the significance of the redundant routes offered by MMT