Yatindra Nath Singh

A Review of Indoor Optical Wireless Systems

Optical wireless communication offers a viable alternative to radio frequency (RF) communication for indoor use and other applications where high performance links are needed. These systems use infrared technology (IR), which has significant advantages over RF. This paper presents a review of the most significant issues related to infrared communication technology, which will enable the realization of future high performance and cost-effective indoor optical wireless systems. Several possible configurations for indoor optical wireless systems, modulation and multi-access techniques are presented as well as their advantages and limitations discussed.

p-Cycles: An overview

One of the most promising techniques of network protection i.e. p-Cycles (pre-planned, preconfigured-cycles) is reviewed in this paper. In this paper we provide a survey of the main work on p-cycles to date. The characteristics of p-cycles and various types of protection provided by them are discussed. Finally, some possible extensions or enhancements of the p-cycle concept are discussed.

WDM-based optical packet switch architectures

We have compared different loop buffer switch architectures in terms of their functionality. Some of these architectures have already been proposed with only their description and operation. The performance evaluation of the switches has been done in terms of packet loss probability for random and bursty traffic. A new architecture has been proposed, which incorporates the good features of the existing architectures.

Design Analysis of Optical Loop Memory

This paper describes the fiber optic loop buffer-based switch in which contention is resolved in the time and wavelength domain. In the loop buffer, tunable wavelength converters (TWCs) are placed in place of semiconductor optical amplifiers (SOAs) as in conventional loop buffer-based architectures. The placement of TWCs inside the buffer facilitate simultaneous read/write operation and dynamic re-allocation of wavelengths and improves the switch performance significantly. It is a well known fact that the re-circulating type buffer structure suffers from circulation limit (maximum revolutions that data can take in the buffer) due to the loss and noise accumulation in the switch. This paper presents a mathematical model to obtain a maximum number of allowed circulations of the data in loop buffer-based switch architecture. This model is derived for various configurations (transparent, noisy, and regenerative) of TWC. The detrimental effect of crosstalk and four wave mixing are shown, and the affect of dispersion on the maximum allowed bit rate is discussed. The minimum length of the loop is also evaluated. Finally, the bounded region is shown (bit rate versus number of wavelengths graph) where memory can work efficiently.

Exact and approximate analytical modeling of an FLBM-based all-optical packet switch

This paper develops both exact and approximate models for the analysis of an all-optical packet switch based on a fiber-loop buffer memory (FLBM). The switch structure and operation is based on the fully shared buffer architecture of the Research and Development in Advanced Communications in Europe - ATM Optical Switching (RACE-ATMOS) project , which uses individual wavelengths to store fixed-length packets in the fiber-loop buffer. An exact model of the switch has been developed , which can be used to determine the blocking performance of the switch and obtain both its throughput and packet loss characteristics. It has been used to study the switch performance under different loading conditions and for different values of the key design parameters of the switch. This model is difficult to use for studying large switches of this kind because of computational complexities. To tackle this problem, an approximate queuing model has also been presented, which may be used to study the performance of large switches of this kind. The results obtained by the two methods are compared to confirm that the approximate model works well under typical loading conditions of the switch.

Nonlinear Spread of Rumor and Inoculation Strategies in the Nodes With Degree Dependent Tie Strength in Complex Networks

In earlier rumor spreading models, at each time step nodes contact all of their neighbors. In more realistic scenario it is possible that a node may contact only some of its neighbors to spread the rumor. Therefore it is must in real world complex networks, the classic rumor spreading model need to be modified to consider the dependence of rumor spread rate on the degree of the spreader and the informed nodes. We have given a modified rumor spreading model to accommodate these facts. This new model, has been studied for rumor spreading in complex networks in this work. Nonlinear rumor spread exponent

Feedback fiber delay lines and AWG based optical packet switch architecture

\alpha

Sparse converter placement in WDM networks and their dynamic operation using path-metric based algorithms

and degree dependent tie strength exponent

Rumor spreading and inoculation of nodes in complex networks

\beta

Two-tiered wireless sensor networks - base station optimal positioning case study

in any complex network gives rumor threshold as some finite value. In the present work, the modified rumor spreading model has been studied in scale free networks. It is also found that if