Showing papers by "Indian Institute of Management Calcutta published in 2003"

A network-aware MAC and routing protocol for effective load balancing in ad hoc wireless networks with directional antenna

Abstract: Use of directional antenna in the context of ad hoc wireless networks can largely reduce radio interference, thereby improving the utilization of wireless medium. Our major contribution in this paper is to devise a routing strategy, along with a MAC protocol, that exploits the advantages of directional antenna in ad hoc networks for improved system performance. In this paper, we have illustrated a MAC and routing protocol for ad hoc networks using directional antenna with the objective of effective load balancing through the selection of maximally zone disjoint routes. Zone-disjoint routes would minimize the effect of route coupling by selecting routes in such a manner that data communication over one route will minimally interfere with data communication over the others. In our MAC protocol, each node keeps certain neighborhood status information dynamically in order that each node is aware of its neighborhood and communications going on in its neighborhood at that instant of time. This status information from each node is propagated periodically throughout the network. This would help each node to capture the approximate network status periodically that helps each node to become topology-aware and aware of communications going on in the network, although in an approximate manner. With this status information, each intermediate node adaptively computes routes towards destination. The performance of the proposed framework has been evaluated on QualNet Network Simulator with DSR (as in QualNet) as a benchmark. Our proposed mechanism shows four to five times performance improvement over DSR, thus demonstrating the effectiveness of this proposal.

Gender differences in self-construal: how generalizable are Western findings?

Abstract: The authors used the Twenty Statements Test in 2 studies to investigate gender and country differences in the spontaneous self-descriptions of 811 college students from Hong Kong, India, Nepal, Nigeria, and Zimbabwe and 136 secondary school students from Taiwan and Hong Kong. The authors performed statistical analysis and found no significant gender differences in the percentage of responses classified as belonging to the idiocentric self in either study. However, the authors found significant Country effects in both studies for responses classified as representing the idiocentric self and some aspects of the collective self, and the authors found significant Country x Gender effects involving all 4 categories of the idiocentric self and the collective self for the college students. These findings raise questions about the generalizability of Western findings that males are more likely to espouse an independent conception of self than females. However, as the authors predicted, females were more likely to use small group self-descriptions than their male peers.

The Dynamics of Organizational Information Security

Abstract: In recent times, it has become evident that information security is not achieved through technology alone. Rather, it depends on a complex interplay among technology, organizational and managerial issues, and events in the external environment. Senior management attention, training, and sound operating procedures are just as important as firewalls and virtual private networks in arriving at a robust security posture. In this paper, we represent the interactions among these technical and organizational drivers using the system dynamics methodology, to develop a high level model of organizational information security. Since the basic system dynamics construct is the feedback loop, our model is able to expose the counteracting mechanics that work to reinforce and erode security, respectively. By doing so, it can inform the process of crafting an appropriate level of security—a problem facing most organizations. Since the model is based on simulation, it is also possible to test what-if scenarios of how the security posture of the organization would fare under different levels of external threats and management policies.

Availability of a periodically inspected system, maintained under an imperfect-repair policy

Abstract: A periodically inspected system is maintained through a fixed number of imperfect-repairs before being replaced or perfectly repaired. The lifetime distribution of the system in its new and imperfectly repaired states is arbitrary. The times required for imperfect repairs and for perfect repair or replacement are random. The repaired system is restored to operation at the next scheduled inspection time. The system availability function is expressed as the weighted average of the survival functions and their shifts, and gives the limiting average availability.

Anticipating internet diffusion

Abstract: Understanding the sociotechnical aspects of Internet growth helps anticipate Internet diffusion, even in countries with vastly different socioeconomic conditions and telecommunication infrastructures.

An adaptive framework for QoS routing through multiple paths in ad hoc wireless networks

Abstract: We propose an adaptive framework for computing multiple paths in temporal and spatial domains to transmit a large volume of data packets from a source s to a destination d in ad hoc wireless networks The objective is to achieve quality of service (QoS) by minimizing end-to-end delay for packet delivery We consider two aspects in this framework The first aspect is to perform preemptive route rediscoveries before the occurrence of route errors while transmitting a large volume of data from s to d This helps us to find out dynamically a series of possible paths in temporal domain to complete the data transfer The second aspect is to select multiple paths in spatial domain for data transfer at any instant of time, and to distribute the data packets in sequential blocks over those paths in order to reduce congestion and end-to-end delay A notion of link stability and path stability is also defined, and a unified mechanism is proposed to address the above two aspects that relies on evaluating a path based on link and path stability Our solution method uses Lagrangean relaxation and subgradient heuristics to solve an optimization formulation of the problem in order to compute the paths and the corresponding data distribution, both in temporal and spatial domains Simulation experiments demonstrate that the proposed framework helps in significantly reducing the end-to-end delay and the required number of route-rediscoveries

Improving End-to-End Delay through Load Balancing with Multipath Routing in Ad Hoc Wireless Networks Using Directional Antenna

Abstract: Multipath routing protocols are distinguished from single-path protocol by the fact that they use several paths to distribute traffic from a source to a destination instead of a single path. Multipath routing may improve system performance through load balancing and reduced end-to-end delay. However, two major issues that dictate the performance of multipath routing – how many paths are needed and how to select these paths. In this paper, we have addressed these two issues in the context of ad hoc wireless networks and shown that the success of multipath routing depends on the effects of route coupling during path selection. Route coupling, in wireless medium, occurs when two routes are located physically close enough to interfere with each other during data communication. Here, we have used a notion of zone-disjoint routes to minimize the effect of interference among routes in wireless medium. Moreover, the use of directional antenna in this context helps to decouple interfering routes easily compared to omni-directional antenna.

A rotational sector-based, receiver-oriented mechanism for location tracking and medium access control in ad hoc networks using directional antenna

Abstract: The use of directional antenna in wireless ad hoc networks potentially increases simultaneous communication by directing the transmitting and receiving beams towards the receiver and transmitter node as compared to omni-directional antenna, where nodes in the vicinity of a communication are kept silent. However, in order to implement effective directional MAC protocol using directional antenna, a node should know how to set its transmission direction to transmit a packet to its neighbors and to avoid transmission in other directions where data communications are already in progress. So, it becomes imperative to have a mechanism at each node to track the locations of its neighbors and to know the communication status of neighboring nodes. In this paper, we propose a receiver-centric approach for location tracking and MAC protocol. The performance evaluation on QualNet network simulator indicates that our protocol is highly efficient with increasing number of communications and increasing data rate.

Optimal Design of Timetables to Maximize Schedule Reliability & Minimize Energy Consumption, Rolling Stock and Crew Deployment

Abstract: We have developed a non-linear multi-objective model for optimal design of railway timetables. The objectives of the model are to maximize schedule reliability and minimize energy consumption, rolling stock and crew deployment. Metrics have been derived for each of these objectives. AHP is used to determine the relative weights of the objectives, while GCA & TOPSIS techniques are used for optimization, which is demonstrated on a test case.

Probability matching priors for predicting a dependent variable with application to regression models

Abstract: In a Bayesian setup, we consider the problem of predicting a dependent variable given an independent variable and past observations on the two variables. An asymptotic formula for the relevant posterior predictive density is worked out. Considering posterior quantiles and highest predictive density regions, we then characterize priors that ensure approximate frequentist validity of Bayesian prediction in the above setting. Application to regression models is also discussed.

A Power-Efficient MAC Protocol with Two-Level Transmit Power Control in Ad Hoc Network Using Directional Antenna

Abstract: The use of directional antenna in wireless ad hoc networks largely reduces radio interference, thereby improving the utilization of wireless medium and consequently the network throughput, as compared to omni-directional antenna, where nodes in the vicinity of communication are kept silent. In this context, researchers usually assume that the gain of directional antennas is equal to the gain of corresponding omni-directional antenna. However, for a given amount of input power, the range R with directional antenna will be much larger than that using omni-directional antenna. In this paper, we propose a two-level transmit power control mechanism in order to approximately equalize the transmission range R of an antenna operating at omni-directional and directional mode. This will not only improve medium utilization but also help to conserve the power of the transmitting node during directional transmission. The performance evaluation on QualNet network simulator clearly indicates the efficiency of our protocol.

Tuning the quality parameters of a firewall to maximize net benefit

Abstract: A firewall protects the informational assets of an organization from intruders. Incoming message packets are filtered by the firewall before being forwarded to their destinations inside the organization. In the process, a fraction q1 of benign (i.e., desirable or harmless) packets and a fraction q2 of intrusive (i.e., undesirable or harmful) packets get blocked. Ideally, we should have q1 = 0 and q2 = 1, but in practice q1 and q2 are functionally related. Since the firewall has a non-zero service time, it also causes a delay because packets get queued for service. Thus by using a firewall an organization incurs a cost, but there is also a corresponding benefit. This study considers the simple case when a single firewall is in use. We do an economic analysis and derive a mathematical expression for the net benefit. We then maximize it by tuning the quality parameters q1 and q2 appropriately.

How Valuable is Credit Card Lending

Abstract: Standard methodology for valuing interest-dependent assets is by now well established, with the Heath-Jarrow-Morton (HJM) model being one of the most widely-used approaches. However, despite representing a significant portion of many banks9 portfolios, credit card loans as an asset class have not been brought into the standard valuation framework. Like a bond position, valuing a bank9s credit card loan portfolio involves projecting the levels of future interest rates. But a portfolio of credit card loans also has several special features not shared by bonds. One is that the total loan face value shows long-run growth, but also short-term fluctuation, reflecting both seasonal effects and interest rate changes. A second is that the profitability, and hence the capitalized value, of the loan portfolio depends on the difference between the rate earned on the loans and the rate the bank must pay to fund those loans, so both rates need to be modeled. In this article, Chatterjea, Jarrow, Neal, and Yildirim offer a general modeling approach for valuing a bank9s credit card loan portfolio within an extended HJM paradigm, and then illustrate how it works by fitting it to the credit card portfolios of five different banks.

Location management in mobile wireless networks

Abstract: Location management schemes are essentially based on users' mobility and incoming call rate characteristics. The network mobility process has to face strong antagonism between its two basic procedures: location update (or registration) and paging. The location update procedure allows the system to keep location knowledge more or less accurately in order to find the user in case of an incoming call, for example. Location registration also is used to bring the user's service profile near its location and allows the network to rapidly provide the user with services. The paging process achieved by the system consists of sending paging messages in all cells where the mobile terminal could be located. A detailed description of the means and techniques for user location management in present cellular networks is addressed.A network must retain information about the locations of endpoints in the network in order to route traffic to the correct destinations. Location tracking (also referred to as mobility tracking or mobility management) is the set of mechanisms by which location information is updated in response to endpoint mobility. In location tracking, it is important to differentiate between the identifier of an endpoint (i.e., what the endpoint is called) and its address (i.e., where the endpoint is located). Mechanisms for location tracking provide a time-varying mapping between the identifier and the address of each endpoint. Most location tracking mechanisms may be perceived as updating and querying a distributed database (the location database) of endpoint identifier-to-address mappings. In this context, location tracking has two components: (1) determining when and how a change in a location database entry should be initiated; and (2) organizing and maintaining the location database. In cellular networks, endpoint mobility within a cell is transparent to the network, and hence location tracking is only required when an endpoint moves from one cell to another. Location tracking typically consists of two operations: (1) updating (or registration), the process by which a mobile endpoint initiates a change in the location database according to its new location; and (2) finding (or paging), the process by which the network initiates a query for an endpoint's location (which also may result in an update to the location database). Most location tracking techniques use a combination of updating and finding in an effort to select the best trade-off between update overhead and delay incurred in finding. Specifically, updates are not usually sent every time an endpoint enters a new cell, but rather are sent according to a predefined strategy so that the finding operation can be restricted to a specific area. There is also a trade-off, analyzed formally between the update and paging costs.Location management methods are most adapted and widely used in current cellular networks, e.g., GSM, IS-54. IS-95, etc. The location management methods are broadly classified into two groups. The first group includes all methods based on algorithms and network architecture, mainly on the processing capabilities of the system. The second group contains the methods based on learning processes, which require the collection of statistics on subscribers' mobility behavior, for instance.

Live bio-sensor nodes for invisible pervasive computing

Abstract: The focal point of this paper pivots on a most plausible proposition to develop a model via which live biological entities can be visualized as components of a wireless sensor network. Inherent distributed communication methodologies present among such chosen organisms are exploited to provide the interaction mechanism between the nodes of the sensor network. The related functional specifications of the bio-sensors and their related rationale have been discussed. The sensor network thus developed is used as a tool for implementing Pervasive Computing. Salient benefits of using Bio-sensor nodes over electronic sensors have been discussed.

An efficient technique for dynamic lightpath establishment in survivable local/metro WDM optical networks

Abstract: Providing a reliable and fast connection to a user is one of the challenging issues in a survivable IPover WDM optical network. A dynamic lightpath establishment (DLE) strategy along with a path protection technique may be used to address the issue. In this strategy, a primary lightpath is established when a request for communication from a node comes, and it is released when the communication is over. To protect the primary lightpath, there will also be a backup lightpath. Thus, DLE with path protection is the problem of establishing a pair of primary and backup lightpaths on a call request within a reasonable amount of time. This problem is a variant of the classical Routing and Wavelength Assignment (RWA) problem in the WDM optical network literature. It can be formulated as a combinatorial optimization problem and, in this paper, we have proposed a heuristic search technique, developed based on Best-First Search. We have tested the performance of our technique with respect to the lightpath establishment time (LET) and call blocking probability (CBP) and compared it with the performance of another well-known technique namely Mixed Integer Linear Programming (MILP). We have also studied the performance of our technique with respect to CBP and LET when there are multiple calls to admit. A significant performance gain is noticed in all the above cases.

Organizational Memory in Group Decision Making: Use of Constructive Group Conflict

Abstract: The increased use of information technology (IT) support for group decision making has augmented the need for research on the performance of groups using such support The use of organizational memory in IT supported group decision making has been discussed in the recent literature Proponents of the use of organizational memory have cautioned against the biases that memory may introduce in the decision making process Prior research has shown that group conflict can be constructively used Using extant literature this paper develops a theoretical framework and hypothesizes that induced group conflict can be used to mitigate any biases organizational memory may produce

Adoption of enterprise resource planning software by organizations in India: a managerial framework

Abstract: Enterprise Resource Planning (ERP) systems are designed to integrate various functions and processes, and are used by organizations as the first-level transaction processing systems in their information architecture. Although many studies have been conducted and reported on ERP implementation cases in the developed countries, there is not much literature on the experiences of companies in Asia and other parts of the developing world. These organizations confront issues that are significantly different from those faced by companies in the developed world, because of differences in the sophistication of IT use, and cultural and social contexts. This chapter describes a three-stage model for analyzing the deployment of ERP in developing countries, based on an empirical study of ERP implementation exercises in Indian organizations. Each stage describes a specific aspect of the implementation process. The specific characteristics of each stage and their implications for managers have also been discussed.

Internet Auctions: Some Issues and Problems

Abstract: Recent advances in client-server, web-server and networking technology have made it possible to hold auctions over the Internet. The popularity of such auctions has grown very rapidly in the last few years, giving a new impetus to the study and analysis of auctions. Apart from technological problems, there are a variety of implementational, economic, and behavioral aspects that need to be studied. In this paper we describe a few representative issues, and outline promising quantitative and computer-based approaches that can lead to solutions. The three issues we examine are timed bids, forecasting of final bid values in incomplete auctions, and last-minute bidding. These and other related features of Internet auctions could have a major impact in the near future on the volume of business transactions over the Internet.

Vision for the Future

Abstract: What distinguishes modern humankind from others is our collective ability to build more complex tools and communities. In previous eras, these amplified muscle power. In the last half century, a new kind of tool has emerged, which is known as Information Technology (IT). Its impact on society is now only dimly understood. PervComp, with its focus on users and their tasks rather than on computing devices and technology, provides an attractive vision for the future of IT. PervComp will redefine it not only by developing innovative new technologies, but also by applying expertise in human-centred systems to evaluate how well IT leverages and enhances human interaction and intellectual activity.

Wireless Access Technology

Abstract: As discussed in Chapter 2, access in PervNet will preferably be wireless to accommodate end-user mobility. After learning backbone technologies, those will be used in PervNet, in the previous chapter, the focus is now on the wireless access technologies that may find places in PervNet.

Modified algorithm for efficient reasoning in qualitative belief networks

Abstract: This paper introduces a computational framework for reasoning in Qualitative Belief Network (QBN) that derives its basis from inductive inference and reasoning. QBNs are essentially based on Bayesian Belief Networks (BBN), except that here the numerical probabilities of BBN are replaced by qualitative symbols. The relationships among the symbols provide a leeway to get good solutions with a qualitative approach to data utilization. The reasoning algebra is based on the usage of sign tables to propagate a belief through the QBN, in a guided approach to discover the causes in the causal relationships in QBN. This algorithm is also ideally suited to a distributed environment as it can absorb queries from multiple sources. The basis of this paper is the work done by Marek J. Druzdzel and the propagation algorithm that was proposed by him and Max Henrion for QBNs [5]. Their algorithm had problems in dealing with situations that might arise in normal circumstances e.g. the degrees of Belief in a particular event. In this paper, we have addressed the above issues and extended the reasoning algorithm by adding more levels in Belief by utilizing certain logical implications derived from basic rules of reasoning. Our algorithm also handles the issue of interactive processing and reasoning thereby making it capable of being used in a distributed platform. Given any data model, this approach helps in efficient reasoning of a solution which may not be directly evident from the singular belief in QBN. We have also implemented this algorithm to handle real life situations and the results thus obtained are in keeping with our expectations.