Ashok Jhunjhunwala

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.

In planar bulk acoustic wave devices, an interdigital transducer (IDT) is generally used as the source of excitation. Grooves, which convert an incident SAW (surface acoustic wave) to bulk waves and vice versa, also have the potential to be used as an alternative (if secondary) source of excitation. A typical shallow rectangular groove etched into a crystalline substrate perpendicular to the propagation direction is considered. The groove is modeled as an interior perturbation to the substrate. Coupled-mode equations are developed and solved for the reflected SAW and the scattered bulk waves. The results are compared to those of the half-space geometry. The interior-perturbation approach produces a good match with earlier published results that used the boundary-perturbation method.

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.

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.

A recirculating, synchronous TDM (time division multiplexed) backbone loop operating at 1 Mbps that supports multiple 9600 baud point-to-point connections, and multiple low bit rate packet channels is described. Slots are deterministically allotted to groups of devices and any medium access protocol suitable for the ring topology can be used to regulate access to the transmission channel. Nodes on the backbone are interconnected through fiber optic or atmospheric optical links. The objective of the network is to satisfy the demands of a typical computing environment, viz., to offer a terminal distribution system and to simultaneously support multiple low bit rate packet channels. Devices communicate with the network through RS-232C serial lines.

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.

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

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.

This paper illustrates the Battery Life Cycle Tester with intelligent charging and discharging unit comprising of measurement, data logging, remote monitoring and communication sections for data acquisition and control. The life cycle tester switches between different charging and discharging modes making it compatible with all battery chemistries. The discharger comprises of an electronic load using MOSFETs operated in their linear region to dissipate power. The required charging/discharging profiles for various applications like electric vehicle motor load and urban drive cycle tests can be programmed via an RS485 link and the data collection is done through Ethernet with an onboard SD card for backup. The user can also set their own test profiles within given limits. The Battery Life Cycle tester is used to perform required charging and discharging profiles at the specified Depth of Discharge (DOD), temperature, State of charge (SOC), charge and discharge rates for the desired number of cycles and store the data for analysis.

This paper describes and discusses the setting up of a DSP Cloud Lab, a setup to execute programs remotely. The programs can be executed on a variety of DSP boards; they could be microprocessor assembly language programs or programs written in assembly language requiring powerful DSP boards or even DSP boards with an FPGA accelerator. The boards used are based on Blackfin Architecture. For a student / developer who writes codes and tests on it, it appears as if they have exclusive use of the boards. However, the boards are highly shared, enabling a large number of students / developers to use them simultaneously. This paper also discusses the design choices made at different stages and the extent to which it facilitates or restricts the use of the DSP boards for a developer. © 2013 IEEE.