Parviz Kermani

MENTOR: an algorithm for mesh network topological optimization and routing

The problem of obtaining a minimum cost topology for a mesh network given matrices specifying the cost of links between all pairs of nodes and the internode requirements is considered. A heuristic algorithm which works in terms of general network design principles and uses utilization as a figure of merit is presented. The procedure is applicable to a wide variety of networks, especially to the problem of obtaining starting topologies for other network design procedures. The algorithms computational complexity is shown to be of order N/sup 2/, a significant improvement over currently used algorithms and fast enough to be embedded in the inner loop of other more general design procedures, e.g., node selection procedures. Computational experience is presented which shows that the procedure is fast and simple and yields solutions of a quality competitive with other much slower procedures. >

Balanced media access methods for wireless networks

Fairness algorithms and access methods enable non-zero channel access for wireless communication systems operating in a random access channel environment. Fair access to a random access channel for each station in a wireless network is assured by each station calculating a priority or probability for accessing the channel based on logical connections among certain stations, based on other stations perception of the channel and based on each calculating stations own perception of the channel properties.

Adaptive allocation of resources and call admission control for wireless ATM using genetic algorithms

In wireless ATM-based networks, admission control is required to reserve resources in advance for calls requiring guaranteed services. In the case of a multimedia call, each of its substreams (i.e., video, audio, and data) has its own distinct quality of service (QoS) requirements (e.g., cell loss rate, delay, jitter, etc.). The network attempts to deliver the required QoS by allocating an appropriate amount of resources (e.g., bandwidth, buffers). The negotiated QoS requirements constitute a certain QoS level that remains fixed during the call (static allocation approach). Accordingly, the corresponding allocated resources also remain unchanged. We present and analyze an adaptive allocation of resources algorithm based on genetic algorithms. In contrast to the static approach, each substream declares a preset range of acceptable QoS levels (e.g., high, medium, low) instead of just a single one. As the availability of resources in the wireless network varies, the algorithm selects the best possible QoS level that each substream can obtain. In case of congestion, the algorithm attempts to free up some resources by degrading the QoS levels of the existing calls to lesser ones. This is done, however, under the constraint of achieving maximum utilization of the resources while simultaneously distributing them fairly among the calls. The degradation is limited to a minimum value predefined in a user-defined profile (UDP). Genetic algorithms have been used to solve the optimization problem. From the user perspective, the perception of the QoS degradation is very graceful and happens only during overload periods. The network services, on the other hand, are greatly enhanced due to the fact that the call blocking probability is significantly decreased. Simulation results demonstrate that the proposed algorithm performs well in terms of increasing the number of admitted calls while utilizing the available bandwidth fairly and effectively.

Locating application data across service discovery domains

The bulk of proposed pervasive computing devices such as PDAs and cellular telephones operate as thin clients within a larger infrastructure. To access services within their local environment, these devices participate in a service discovery protocol which involves a master directory that registers all services available in the local environment. These directories typically are isolated from each other. Devices that move across service discovery domains have no access to information outside their current local domain. In this paper we propose an application-level protocol called VIA that enables data sharing among discovery domains. Each directory maintains a table of active links to other directories that share related information. A set of linked directories forms a data cluster that can be queried by devices for information. The data cluster is distributed, self-organizing, responsive to data mobility, and robust to failures. Using application-defined data schemas, clusters organize themselves into a hierarchy for efficient querying and network resource usage. Through analysis and simulation we describe the behavior of VIA under different workloads and show that the protocol overhead for both maintaining a cluster and handling failures grows slowly with the number of gateways.

Security Issues in M-Commerce: A Usage-Based Taxonomy

M-commerce is a new area arising from the marriage of electronic commerce with emerging mobile and pervasive computing technology. The newness of this area--and the rapidness with which it is emerging--makes it diffcult to analyze the technological problems that m-commerce introduces--and, in particular, the security and privacy issues. This situation is not good, since history has shown that security is very diffcult to retro-fit into deployed technology, and pervasive m-commerce promises (threatens?) to permeate and transform even more aspects of life than e-commerce and the Internet has. In this paper, we try to begin to rectify this situation: we offer a preliminary taxonomy that unifies many proposed m-commerce usage scenarios into a single framework, and then use this framework to analyze security issues.

Approaches to building self healing systems using dependency analysis

Typical distributed transaction environments are a heterogeneous collection of hardware and software resources. An example of such an environment is an electronic store front where users can launch a number of different transactions to complete one or more interactions with the system. One of the challenges in managing such an environment is to figure out the root cause of a performance or throughput problem that manifests itself at a user access point, and to take appropriate action, preferably in an automated way. Our paper addresses this problem by analyzing the dependency relationship among various software components. We also provide a theoretical insight into how a set of transactions can be generated to pinpoint the root cause of a performance problem that is manifested at the user access point.

An adaptive quality of service channel borrowing algorithm for cellular networks

A multimedia call consists of three main sub-streams (i.e. video, audio and data) each with its own distinct quality of service (QoS) requirements (e.g. packet loss rate, delay tolerance, and jitter). These requirements constitute a specific fixed QoS level. In contrast to static approaches, we propose an adaptive QoS platform in which each sub-stream declares a preset range of acceptable QoS levels (e.g. maximum, acceptable, minimum) instead of just a single level. This range of QoS levels is pre-defined in a user-defined profile (UDP). In this paper, we propose a channel borrowing algorithm based on such adaptive QoS platform. In our proposed algorithm, an acceptor cell that has used all its channels can borrow from any neighbouring (donor) cell as long as this donor cell has some channels available after satisfying a minimum QoS (minQ) level defined in the UDP. A donor cell that is assigning QoS levels (to calls under its coverage) higher than the minQ levels will declare those channels as available for borrowing by other acceptor cells. The criteria for choosing the free channel include not only the number of free channels, but also the QoS levels in the donor cell. The criteria are also extended to include the effect of channel locking on the number of free channels, and the QoS levels on the locked cells. The algorithm is not triggered unless it does not cause any call dropping in either the donor cell, or the cells affected by call blocking. In the meantime, the call blocking rate is significantly decreased while the offered load increases. Copyright

ELM-N: e-learning media navigator

E-learning or learning via the Web is now changing the way universities and coprporations offer education and training. Rather than using conventional means for remotely distributing and delivering courses and classroom lectures, universities and enterprises are moving towards Web-based academic and training offerings. While content acquisition and distribution can be automated in a systematic fashion, research challenges remain in the area of personalized content delivery, access, and augmented interaction. Automated content indexing and annotation for easy and efficient access and navigation of various media elements associated with the course material become key takss in flexible content delivery and use. E-Learning Media Navigator (ELM-N) from IBM Research is a system with which a user can access and interact with online courses presented as audiovisual material, along with related slides and white broad contents in a time-synchronized fashion. In this demonstration, the system capabilities and research technologies behind them will be presented.

Next-generation indoor infrared LANs: issues and approaches

The design issues for the next-generation wireless infrared systems are discussed. An advanced infrared system is proposed to provide reliable high-speed short-range wireless communication throughout indoor environments. In the physical layer, the range of communication is extended for L-PPM infrared links by using repetition rate coding, which greatly increases the symbol capture probability at the receiver. Repetition rate coding is used in an adaptive way to update the data rate over a channel based on the channel parameters. The receiver symbol capture characteristics and signal-to-noise ratio gain due to the use of a repetition rate scheme are presented. The infrared media access control layer must be designed to establish fair and robust communications over the proposed physical layer. The fairness problem is described in detail, including the impact of the topology on the performance of the wireless system. Balanced media access methods are presented as a solution to the fairness problem. The link access control layer uses retransmission to provide reliable connections over infrared links.

A generic bandwidth allocation scheme for multimedia substreams in adaptive networks using genetic algorithms

In this paper we propose a generic call admission control scheme based on genetic algorithms. The scheme is applied to a wireless network using an adaptive resource allocation framework. A multimedia connection is represented in terms of three substreams (video, audio and data) each with a pre-specified range of acceptable quality of service (QoS) requirements. This range of requirements make the application adaptive in the sense that each of its substreams specify to the network a number of acceptable QoS levels instead of just a single one. For example, MPEG-based video can be transmitted at different levels of varying qualities. As resource availability in the wireless network changes, the control scheme selects the best possible QoS level that each substream can obtain for a certain period of time. In case of congestion, the control scheme attempts to free up some wireless resources by degrading the QoS of existing calls to a lesser level in order to accommodate new calls. This is done, however, under the constraint of achieving maximum utilization of the resources; and sharing them fairly among the calls. The degradation in the QoS is limited to a minimum value for each multimedia substream defined in a user-defined profile. From the user perspective, the perception of the QoS degradation is very graceful and happens only during over-load periods. The network services, on the other hand, are greatly enhanced due to the fact that the call blocking probability is significantly decreased. Genetic algorithms have been used to solve the optimization problem. Simulation results for a wireless ATM network demonstrate that the proposed scheme performs well in terms of increasing the number of calls admitted while effectively utilizing the available bandwidth fairly among the calls.