Ashok Jhunjhunwala

The role of technology in telecom expansion in India

It is not viable to expand the telecom network in India substantially at the prevalent level of per-line investment. However, systems based on new technologies, many developed in India, promise to more than halve the investment required. This article looks at the telecom scenario, the new technologies, the Indian products based on these technologies, and the cost reductions they promise. The provision of widespread Internet service with low access tariff is an important aspect of the new approach.

Wavelength reassignment algorithms for all-optical WDM backbone networks

In this paper, we consider the problem of enhancing the blocking performance, in the circuit-switched wide-area optical wavelength-division multiplexed (WDM) networks with no wavelength conversion at the nodes. The limitation of such a no conversion network is the wavelength continuity constraint (wcc) which requires the same wavelength on all the hops of the path. Whenever there is a session request, a lightpath has to be established in the network. If the lightpath could not be established, lightpath request rejection or call blocking occurs. As each lightpath is a substantial revenue and is long-lived, lightpath request rejection is highly unfavorable in the optical backbone networks. An optimal optical network is the one with wavelength conversion capability at the nodes. In these conversion networks, blocking occurs due to capacity exhaustion on the links and not due to wcc. Hence these networks have the lowest possible blocking probability (Pb) achievable for any given network. Our aim is to see if one can achieve this near optimal blocking performance in no conversion networks by using our proposed wavelength reassignment algorithms. In the reassignment technique, when the new call gets blocked due to wcc, the already established calls or lightpaths are wavelength reassigned, so as to create a wavelength-continuous route in order to accommodate the new call. During wavelength reassignment, the routes for all the calls remain the same, i.e. no rerouting is done. We have proposed two heuristic reassignment algorithms namely, MOLC and Random and have studied their performance on some standard backbone optical networks. Simulation results show that in these example networks, our proposed reassignment algorithm can mostly remove the blocking due to the wcc and can achieve the wavelength conversion performance.

Solar-dc Microgrid for Indian Homes: A Transforming Power Scenario

It is well established that access to energy is closely linked with socioeconomic development. India houses the largest share of the worlds population deprived of electricity with about 237 million people lacking access (International Energy Agency). At the same time, in India, many households that do have access to electricity lack an uninterrupted and quality power supply. A recent study conducted by the Council for Energy, Environment, and Water (CEEW) across six states (Bihar, Jharkhand, Madhya Pradesh, Uttar Pradesh, West Bengal, and Odisha), found that about 50% of the households had no electricity despite having a grid connection. This indicates that there is an immediate need to address the quality, affordability, and reliability of the power supply in addition to extending the grid footprint.

Mobile payment architectures for India

Mobile payments are a new and alternative payment method. Instead of using traditional methods like cash, cheque, or credit cards, a customer can use a mobile phone to transfer money or to pay for goods and services. Mobile payments have numerous advantages over traditional payment methods. Apart from their apparent flexibility, they enable consumers who do not have easy access to banking facilities to participate readily in financial transactions. Unfortunately, existing mobile payment solutions in India are not interoperable; i.e. they only offer services for merchants registered with them and do not allow the transfer of money to, or between, users of other payment providers. This limitation reduces the widespread adoption of mobile payments. In this paper, we propose new mobile payment architectures that support interoperability. A key technical aspect of the mobile payment process is to lookup customer details, for which we propose the following three design options: (1) a central database, (2) a peer-to-peer query, or (3) a hierarchical lookup. These options are evaluated using relevant metrics such as the complexity of implementation and scalability with respect to system size. Based on our evaluation we recommend that initially the peer-to-peer design is chosen, and once the technology is more widespread, the central database option should be adopted.

Re-Routing at Critical Nodes to Enhance Performance of Wavelength Reassignment in All-Optical WDM Networks Without Wavelength Conversion

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 . 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.

Wireless in Local Loop: Some Key Issues

Wireless links are emerging as a superior alternative to the copper pair for the local loop in telephony. However, to provide for sufficient subscriber density with a reasonable bandwidth allocation, a micro-cellular architecture is a must. Further, the wireless local loop system is best interfaced as a remote access unit to an exchange. The V5.2 standard provides a convenient protocol for interfacing in this manner to all exchanges.

Proposed high speed packet switch for broadband integrated networks

The design of a high speed, broadband packet switch with two priority levels for application in integrated voice/data networks is presented. The packet switch can efficiently cope with 128 byte packets converging on it from eight 140 Mbit/s dynamic time division multiplexed fibre optic links. The packet switch throughput varies with the load and traffic composition, and the delay experienced by voice and data packets is within 300 @ms and 3 ms, respectively. The design is implemented by task-sharing in a multi-processor configuration. The design of the packet switch, including its subsystems, is detailed here.

Load balanced routing to enhance the performance of optical backbone networks

In this paper, we identify the topological and routing technique constraints on the performance of optical backbone WDM networks with wavelength conversion at the nodes and propose techniques to over come this constraints so that the network performance is enhanced. For any session request, a lightpath has to be established on the shortest path between the node pairs. As each lightpath is a substantial revenue and long-lived, the network operator would like no lightpath request rejection (call blocking) or would like to accommodate more calls in the network before he has to upgrade his network. Hence given a network, we are proposing an analytical method to identify the critical links of the network which will cause early blocking, for the fixed shortest path routing. Once the critical links are identified, we would like to analyse the physical location of these critical links on the network topology and propose a new fixed routing technique namely, restricted routing by which the performance is enhanced as it balances the load uniformly among the links. In this routing technique, not all the calls have the shortest path. We compare the performance of the restricted routing with the optimal performance where all the links have equal blocking probability. The analysis is carried out on some of the standard backbone networks and the results show that by the restricted routing there is a significant performance improvement.

Electrifying India: Using solar dc microgrids

According to a recent report by the International Energy Agency [1], although India is the second most populous country on earth, it ranks far behind other countries in terms of per capita electricity consumption and carbon footprint. As shown in Table 1, India is well below the world average in both per capita electricity consumption and carbon footprint indices. However, with an ambitious plan for rapid growth and economic development, India is poised to quickly increase its carbon footprint and become a major contributor to preventing global climate change.

Solar-DC deployment experience in off-grid and near off-grid homes: Economics, technology and policy analysis

India is a power deficit country and one third of its homes are off grid or near off grid. This paper presents an efficient and affordable Solar DC solution for powering such homes. Though several solutions have emerged in the past for powering these homes, those have been expensive and energy inefficient. These solutions rely on several DC to AC and AC to DC conversions, to feed the widely used AC home loads, thus, wasting a large chunk of the expensive power. The proposed Solar DC solution for off-grid homes (OGH) is developed to use the generated PV power efficiently. With this solution, the panel and battery size is reduced by 2 to 2.5 times and the cost to power a house is reduced to nearly half the cost of the existing solutions. The paper also presents a techno-economic comparison between the proposed OGH solution with some existing solar systems.