Vinod Chandra

A fail-safe interlocking system for railways

A new approach to the design of microprocessor-based failsafe systems for railways that was used to design the FIRM architecture is described. The approach involves assigning appropriate levels of safety to system functions, depending on how critical they are, instead of using the same safety standard for all functions. The FIRM (short for failsafe interlocking system for railways using microprocessors) architecture uses a pair of processors that operate in a see-saw mode, with one or more pairs kept on standby. The installation and testing of an engineering prototype of the architecture that was fabricated for Indian Railways are discussed.<<ETX>>

Reliability and safety analysis of fault tolerant and fail safe node for use in a railway signalling system

Abstract In this paper, we propose a Markov Reliability model for a transputer based fail safe and fault tolerant node for use in a network of distributed safety critical railway signalling systems. Using the Markov model we quantify the reliability and safety in terms of Probability of being in unsafe state, Probability of Safe shutdown during the useful life period and last phase of bath-tub curve. A fault analysis of the fail safe and fault tolerant node addressing Byzantine (malicious) faults with an extension of Byzantine Generals problem is given.

Transputer-based fault-tolerant and fail-safe node for dual ring distributed railway signalling systems

Abstract Railway signalling systems are based on fault-tolerant and fail-safe techniques to provide high reliability and safety. Transputers offer multiple communication links and provide a high degree of parallelism and are being used in safety-critical and fault-tolerant applications. We propose a fault-tolerant and fail-safe node using transputers for a local area network with dual ring topology to be used in distributed railway signalling systems. The proposed scheme uses a new technique of leadership based on rotation amongst the transputers of the node. Aspects of safe shutdown, recovery, reconfiguration and clock synchronization of the fault-tolerant and fail-safe node are addressed. Formal specifications of the fail-safe node and the simulation of the proposed technique are also given.

4×4 Optical data vortex switch fabric: Fault tolerance and network reliability analysis

Reliability and fault tolerant capability are the important factors for very large size interconnection networks. In this paper, we propose a more fault tolerant 4×4 data vortex switch fabric. Also, we analyse fault tolerance and network reliability of the novel architecture.

Experimental validation of multiple gain combiner in single-relay cooperative FSO communication systems

In this paper, we have proposed a new combining technique named as multiple gain combiner (MGC) for single-relay cooperative FSO communication systems. The first objective of this paper is to test the experimental feasibility of single-relay cooperative FSO communication system. The next objective is to ascertain the performance of a cooperative FSO link in the presence of simulated fading effect generated by means of modified optical chopper. The last objective is to determine the performance improvement of our proposed MGC combining method over conventional equal gain combining method. Bit error rate performance of the relay system is tested for single-relay cooperative FSO link under weak and strong fading conditions simulated with the modified optical chopper, which shows that the significant performance improvement can be obtained with the use of cooperative diversity. Rsoft-Optsim with MATLAB® co-simulation results show the same trend of performance for the same level of fading present in the system, thereby validating the fading mechanism as obtained by means of modified optical chopper.

4×4 optical data vortex switch fabric: BER analysis

In this paper we present the performance of 4×4 optical data vortex optical interconnection network in view of BER characteristics. Cascading of SOA based switching nodes is simulated.

Evaluation of All Routes and Terminal Reliability in the Data Vortex All Optical Switch for High Performance Computing

In this paper, we have given a detail procedure to determine all-possible paths for all source - destination pairs in the data vortex all optical switch, and the terminal pair reliability performance of the switch has been obtained, using a simple analytical method. The paths found can also have applications for the study of survivability and quality of service implementations in the switch. The reliability expression is useful for evaluating the performance of the data vortex switch for a given reliability requirement and to provide the quantitative comparisons with other interconnection networks.