Ashok Jhunjhunwala

Presence of Railway stations are essential for train traffic control (to enable crossings and precedence). Movement of trains at stations are controlled by Signals. In busy trunk routes, the running time of trains in station area is comparable to that between stations. Indian Railways use different signalling schemes to enable movement of trains in a safe manner. The signalling schemes play an important role in determining the action of the driver in terms of slowing down of trains and consequently on the throughput of the railway system. This paper examines the different schemes of signalling used currently and in recent past by Indian Railways from the point of view of information that they present to the train driver and the impact that it has on total throughput. The signalling schemes are compared using total signal entropy presented to the driver at each stage. Apart from theoretical computation of signal entropy, results of some experiments conducted on impact of signalling schemes on run time of trains are also presented.

Reassignment of calls to different wavelengths on blocking can be used in WDM networks without wavelength conversion to get almost the same performance as that of WDM networks with wavelength conversion for circuit switched traffic [11]. However, in a few networks, we did find that while the reassignment on blocking does improve the performance of WDM networks without wavelength conversion, the performance falls short of that of wavelength conversion networks. In this paper, we analyze the reasons for this behavior in these networks. On identifying certain critical nodes as a cause of this behavior, we propose a rerouting technique around the critical node. With a small amount of rerouting, this bottleneck can be removed and the performance of WDM networks without wavelength conversion becomes almost equal to that of networks with wavelength conversion, thus making the wavelength conversion (costly) feature, as redundant. In this paper, we also propose a technique to carry out seamless wavelength reassignment so as not to disrupt traffic during the wavelength reassignment process. © 2008 IEEE.

In this paper, we have proposed an analytical model that computes the blocking probability and the channel utilisation for a given load on the optical networks with wavelength conversion at the nodes. The computation has been carried out for fixed routing with uniform traffic distribution (UTD). When any link on a route blocks a call, the dropped call reduces the offered load on all other links invovled in the route. The overall blocking probability of the network is estimated using Erlang fixed point approximation with the reduced load on the links. The expression has been validated by comparing the results with that of simulation for a number of standard networks including 14 node NSFNET, 20 node ARPANET and 20 node INDIANET. We show that the analytical method performs well in the desired range of blocking probabilities and is applicable to any network topology. © 2008 by the IETE.

In this paper, we consider the problem of maximizing the time of first lightpath request rejection, T in the circuit-switched time division multiplexed (TDM) wavelength-routed (WR) optical WDM networks. TDM is incorporated into WDM, to increase the channel utilization when the carried traffic does not require the entire channel bandwidth. In TDM-WDM network, multiple sessions are multiplexed on each wavelength by assigning a sub-set of the TDM slots to each session. Thus, given a session request with a specified bandwidth, a lightpath has to be established by using the routing, wavelength and time-slot assignment (RWTA) algorithms. If the lightpath cannot be established, lightpath request rejection or call blocking occurs. As each lightpath is substantial revenue and long-lived, lightpath request rejection is highly unfavourable in the opitcal backbone networks. In this paper, we are proposing an intelligent routing, wavelength and time-slot reassignment algorithm for multi rate traffic demands, where, when a call gets blocked, the already established calls in the network are rerouted, wavelength and timeslot reassigned so as to accomodate the blocked call. Since we are talking of slow arrivals and long holding times for the lightpaths, it is possible to do this reassignment while provisioning a new call. Simulation based analyses are used to study the performance of the proposed reassignment algorithm. The results show that the proposed reassignment algorithm can be used to maximize the time of first call blocking, thereby accommodating more calls in the network before upgrading the network capacity. © 2006 IEEE.

After decades of very modest growth, telecom in India has taken off. While liberalisation of telecom sector created the conditions, the key to this take off has been a conscious effort in India to drive down the capital expenditure (CAPEX) of telecom infrastructure which made telecom affordable to large sections of Indian people. This paper discusses the role that Indian and Chinese telecom companies have played towards this reduction of per-line CAPEX and identifies technologies still dominated by the West. Telecom is now set to grow rapidly and India would achieve 200 million connections in less than a decade. However, this optimist situation is still, pretty much confined to urban areas. It is the growth of telecom and Internet infrastructure in rural areas, that have much greater potential. But harnessing of this potential requires special efforts. This paper presents a glimpse of how this could be made possible. © 2003 Taylor & Francis Group, LLC.

Porting MP3 decoder effectively on a given hardware platform ADSP-BF533 EZ KITLITE is discussed in this paper [1]. Data structure layout, proficient data placement and data memory/cache handling for porting MP3 decoder are discussed. Hardware features and advanced instructions are availed for effective implementation of MP3 modules to reduce the MIPS. Results show MP3 decoder implementation consumes 24 MIPS peak. © 2008 IEEE.

DesiCrew is a unique Business Process Outsourcing (BPO) initiative that provides high volume data related services at an affordable cost from rural areas across India. The model provides cost cutting alternatives to urban clients and new sources of income and employment to the villagers, by leveraging Internet technology. The DesiCrew central team in Chennai manages training of rural workforce, distribution and monitoring of work, quality control and client interaction all remotely. In this paper, we describe the Rural BPO model and one specific application, data entry of forms. We describe the software, Pegasus, developed for this purpose and explain the management of the distributed workforce. © 2007 International Federation for Information Processing.

Telecommunications in India has evolved greatly in the last two decades, and the number of lines has grown to over 100 million. However, these lines are disproportionate in the urban areas and are mainly low bandwidth wireless access links. Thus there is double challenge we are facing, namely how to take the Telecom revolution to the rural areas and how to take broadband to both the urban and rural parts of India. This article discusses these issues and how the TeNeT group at IIT Madras is trying to tackle some of the problems. Copyright © 2006 by the IETE.