Jagjit Singh Malhotra

Performance Evaluation of MAC- and PHY-Protocols in IEEE 802.11 WLAN

This work evaluates and compares the performance of IEEE 802.11 WLAN scenario by evaluating QoS parameters such as medium access delay, end to end delay and re-transmission attempts at data rate of 2Mbps by means of different mechanisms in PHY- & MAC-layers. The Point coordination function (PCF) and Distribution Coordination Function (DCF) of MAC layer together with mechanism used in Physical layer i.e. Frequency hopping- and Direct sequence- spread spectrum (FHSS & DSSS) are reported and investigated to provide better QoS using OPNET simulator.

Statistical Analysis of FSO Links Employing Multiple Transmitter/Receiver Strategy over Double-Generalized and Gamma–Gamma Fading Channel Using Different Modulation Techniques

Abstract Free space optical (FSO) communication links have recently received lot of attention as high bandwidth and cost-effective access technique. However, the transmission medium, i. e. atmosphere, itself is a major spoilsport factor as atmospheric turbulence may lead to fading. The legacy of spatial diversity techniques which have already proven their worth as effective mechanism to counter channel fading in radio links has also been extended to FSO links in this paper. A mathematical model to evaluate error rate performance of FSO links over strong turbulent conditions using gamma–gamma and double-generalized gamma channel model for different modulation techniques has also been included. It was observed that higher modulation techniques such as binary phase shift keying (BPSK) and differential phase shift keying (DPSK) allow superior error performance as compared to on–off keying (OOK) links, and this performance further enhances with incorporation of spatial diversity techniques. However, across different diversity options, explained in this paper, BPSK–MISO links were the best choice for turbulent conditions.

Gain profile analysis in fiber optical parametric amplifiers using SBS technique

In this paper experimental verification of optical fiber based parametric amplification has been studied over different modulation formats. Based on principle of parametric amplification, which is essentially a non linear phenomena, these fiber amplifiers offer discrete amplification along with greater use of bandwidth without any major compromise on usable gain and vice versa. We have demonstrated the gain profile of fiber optical parametric amplifier using SBS (Stimulated Brillouin Scattering) control mechanism which is based on SBS power pump, which in turn determines the gain of lumped amplifier. Different modulation formats like amplitude modulation, frequency modulation and phase modulation were investigated, both with and without the parametric amplification over given length of fiber. During performance evaluation it was observed that FM and PM modulated data responded with considerable increase in gain with activation of SBS pump, while the similar gain improvement was found to be missing in AM modulated data.

Performance Evaluation and PMD Tolerance of PM-QPSK at 100 Gbit/s in Dispersion Managed 64 Channel Long Haul DWDM Optical Communication Link

Abstract In this paper, performance investigations on PM-QPSK modulation format in a terabit capacity, long haul DWDM optical communication link resulted in high Q2(dB) of 20.71 and low BER of the order of 10−28 proving the suitability of PM-QPSK. It is reported here that PM-QPSK is quite resilient against PMD effects as the variation in PMD_seed value from 0–50 at PMD_Coefficient of 0.1 and 1.0 resulted in minimum Q2(dB) of 18.7 and maximum BER of 10−18.