Fibre optics ethernet network for voice and data communication
In this paper, we present a variant of the Ethernet protocol that uses fibre optic media. By the use of periodic frames, the protocol caters to voice and data traffic, adapting to the number of voice calls. This protocol is thus suited for both office automation and industrial applications. We describe in detail how the proposed protocol can be implemented using inexpensive Ethernet VLSI chipsets with a little additional hardware. An extensive simulation study of the protocol shows that the framing imposes minimal additional overhead compared to the standard Ethernet. Under low loads, data delay is low while under heavy loads, voice performance is maintained at the expense of high data delays.
New Orientations for Bulk-Acoustic-Wave Devices
In recent years there has been a considerable interest in bulk-acoustic-wave (BAW) devices. Several new materials/orientations for which strong BAW response is predicted is presented. It is also found that a strong BAW response occurs at a frequency at which the pseudo-surface acoustic wave (PSAW) is expected to occur. © 1990 IEEE
Thin route optical fibre communication system for railway traffic control
Railway traffic Control requires dedicated point to point and point to multipoint circuits for communication over larger number of signal points spread along the track. A typical despatcher control section spreads over 200 kms with 30 to 40 signal points. Till mid 80s, such communication were economically provided by copper quad cable in electrified territory. Development in optical fibre technology has changed the scenario and fibre finds increasing use in Railway Telecommunication Network due to its distinctive advantages. However some of the railways' requirements are too specialized. These include omnibus circuits with large number of tappings, closely spaced repeaters, lineside emergency communication requirement, transmission of safety information and ability to provide on demand service. The technology of optical fibre therefore requires adoptions to meet these specialized requirements. In this paper we describe an optical fibre based Railway Communication system used by Indian Railways and conclude that even though large number of repeaters are used in the link, the performance quality is satisfactory and optical fibre based communications are economical in the railway environment. Reliability of the link can be improved through additional fibres or through alternate media. A hybrid solution based on optical fibre and copper cable is proposed to achieve economy without sacrificing quality and reliability.
Affordable fibre access network for developing countries
The most cost-effective type of access solutions available today are described. With a target cost of $300 for the total network, it is possible for the operator to expand the network very rapidly to a size many times the existing network and still earn adequate revenue. A fiber access network is becoming the operator's choice. Most private operators in India, implementing the network in different states, are planning to use such a solution to provide large-scale connectivity. It is very likely that India will soon have more fiber in the access network than that in any other country. Other developing countries, even with their own specificities, may choose such solutions because of economic reasons.
The design and flow control of a high speed, integrated, packet switched network
This paper proposes a packet switched broadband integrated network, for multi-rate services such as voice and data. A novel design of a high speed packet switch capable of catering to voice and data traffic is described. Some sources of traffic bottle-necks are identified, and methods of clearing the bottle-necks through flow control techniques are discussed. The design and flow control parameters are obtained through simulation, and the results are presented. The performance of the network and the packet switch is evaluated for various traffic characteristics through a second simulation, and the results are briefly presented. © 1992.
Design tool for symbolic substitution
A design tool that aids in designing, evaluating, and comparing various implementations of optical symbolic substitution is presented. A hierarchical, modular approach to design similar to that used in digital electronics is supported to facilitate the design of large complex systems. This tool is composed of a schematic capture unit, a simulator unit, and an evaluation unit. Starting with the definition of certain basic or integrated optical elements performing well-defined functions, a schematic capture unit helps to design specific functions. The simulator tool helps to verify the design and the evaluation tool determines its complexity. The usefulness of this design tool is demonstrated with an example design of a simple four-function arithmetic logic unit. © 1996 Society of Photo-Optical Instrumentation Engineers.
Theoretical Analysis of Planar Bulk-Acoustic-Wave Response
Interdigital Transducers (IDT’s) on a piezoelectric substrate launch, in addition to surface-acoustic waves (SAW’s), bulk-acoustic-waves (BAW’s) into the medium. Some of these BAW’s reach the output IDT after reflection from the bottom surface. Devices using this phenomenon are known as planar bulk-acoustic-wave devices and have gained considerable importance in recent years due to the fact that they operate at higher frequencies. A detailed theoretical analysis is presented for this device that results in a method for computing the bulk-acoustic-wave response for any orientation of any piezoelectric substrate. The BAW response for several devices for which experimental results are published, is computed using this method. The computed results are found to be in excellent agreement with the experimental ones. The analytical technique is also used to optimize one of these devices to achieve a lower value of insertion loss, by varying the separation between the two interdigital transducers. © 1990, IEEE
Fibre access networks for India and other developing countries
Copper based wired local loop has served us well for over 100 years. However much we may decry the copper for its bottlenecks today, it has served us so long due to the following (i) it is a passive network, which does not fail unless cable is cut, (ii) it carries power for subscriber terminals, (iii) it carries voice signals both ways, (iv) 56 kbps data can be carried in 4 kHz copper loop, (v) n-isdn, HDSL, ADSL, VDSL is enabling tens of Mbps data to be carried on the copper loop. It is such a loop that one wishes to replace with Fibre. How does fibre handle these issues? While fibre finds it difficult to provide one to one replacement of copper loop, and is still struggling to make a mark in the Access Network of developed world, a certain kind of Fibre Access Networks is suddenly becoming the way of deploying new telecom networks in developing countries. Fibre in the Loop today provides the most cost-effective solution for new deployment in urban areas; most Basic Services Operators in India plan to use this in major way. It is likely that in the next three to four years, more Fibre in Access Network will be deployed in India than in any other country in the world. This paper examines the issues involved in use of Fibre in the Access Network and suggest solution which are likely to make it the technology of choice for new operators.
Techniques for efficient symbolic substitution implementations using one-of-many coding
Two techniques for implementing symbolic substitution (SS) using one-of-many coding are presented. Both techniques involve simultaneous recognition of multiple rules and hence reduce the complexity of SS implementation. Based on these new implementations, some factors that influence simultaneous recognition of rules are identified. It is shown using illustrations that the one-of-many coding is an optimal coding technique in terms of complexity of implementation. © 1996 Society of Photo-Optical Instrumentation Engineers.