Anjana Jain

Performance Evaluation of Wireless Network in Presence of Hidden Node: A Queuing Theory Approach

Hidden node is a fundamental problem that affects any wireless network where nodes cannot hear each other and leads to data packet collision. IEEE 802.11 wireless networks employ RTS/CTS mechanism for avoiding DATA packet collision .The main design assumption in this method is that all the nodes in the vicinity of a sender and a receiver must hear the RTS and CTS packets. They also defer their transmission appropriately. In this paper first scenarios are discussed which leads to DATA packet collision. In the later part of the paper an analytical model is developed by taking queuing and retransmissions. Expression for probability of packet collision is then derived. Finally detail simulation is performed. Analytical and simulation results are compared as well as the variation of packet error is calculated. Results are presented which show the variation of packet error with the variation of service time and packet arrival rate. These results can be used in future for the evaluation of throughput and delay of the system.

A New Scheme of ICI Self-Cancellation in OFDM System

The Performance of the Orthogonal Frequency Division Multiplexing (OFDM) is degrade due to Doppler frequency or frequency drift between transmitter and receiver oscillator which causes frequency offset and leads to Inter-Carrier-Interference (ICI). In this paper, we present a new scheme of self-cancellation for ICI mitigation in OFDM system and compared with the existing methods of self-cancellation in terms of carrier-to-interference ratio (CIR) and bit-error rate (BER). The simulation result shows that the proposed scheme outperforms the existing methods.

Monte Carlo Simulation Based Error Performance Analysis of DS-CDMA System

With the growing interest in integration of voice, data and video traffic in wireless communication networks, CDMA emerged as an attractive access technique. The performance of wireless system is deteriorated in presence of multipath fading environment. Hence, the error performance analysis is a fundamental requirement to deploy CDMA system. The Bit Error Rate (BER) is one of the error performance parameter in communication systems. This paper presents estimation of BER as function of Eb/No (bit energy to noise power spectral density ratio) using Monte Carlo simulation technique. The simulation includes the effects of Additive White Gaussian Noise, multipath and Multiple Access Interference (MAI). Direct Sequence Spread spectrum with BPSK modulation is used for the simulation. The Ricean fading channel with various factor K is considered. Results are presented in form of graphs which show the effect of different Ricean factor K on BER. These elegant results can be used for evaluating the system capacity, designing power control algorithms and appropriate channel coding techniques for CDMA.

Stochastic Modeling and Performance Evaluation of Fading Channel for Wireless Network Design

Characterization of temporal variations in wireless channel impairments plays an important role in the design of a reliable and efficient mobile communication system. Such channels are termed as fading channels since various random phenomena in the propagation path result in fading of the received signal envelope. Simulation models are often used to estimate channel behavior due to higher complexity in developing analytical models for such channels. In this paper, Finite State Markov Model is developed for the evaluation of multi-path fading channel. Cumulative states and frequency duration analysis approach is used for computing rate of transition between satisfactory states and outage states, and outage time, of the channel. Simulation results obtained for Rayleigh channel are then used to find correspondence between fade depth and outage time for a sample system. These results may be used in the estimation of bit error rate and deciding optimum sampling instant of the received signal. It will also assist in selection of appropriate channel code and interleaver design for a future wireless networks with enhanced channel capacity.

A study of peak to average power ratio for different companding techniques in VLC-OFDM system

VLC-OFDM is proposed to be used as the transmission technique in 5G mobile communication. VLC-OFDM produces the non-linear distortion due to non linear characteristics of LEDs and the PAPR of multiple sub-carrier modulation. The mitigation of non-linear distortion in VLC system is presently focused by many researchers, as it degrades system performance. Since the technique used in VLC system is OFDM so the system suffers the drawbacks of OFDM as well as VLC. Therefore, the non-linearity in the VLC-OFDM is quite severe. Hence, three companding techniques(A-law, μ-law, advanced A-law) can be implemented to remove the PAPR issue. Comparatively, advance A-law provides lower PAP ratio. This paper proposes these three non-linear companding techniques for reducing PAPR in VLC-OFDM system.

Negotiation based adaptive distributed power control algorithm in wireless communication system

In wireless communication networks, transmitter power control can play an important role in various communication scenario, like power control, throughput and quality of service (QoS). It is essential to find effective means of power control point-to-point, broadcasting and multi-casting. We consider the problem of unicast or point-to point (peer to peer) communication in wireless networks in the presents of other nodes. In the proposed work the feasibility of admitting new nodes while maintaining the quality of service (QoS) in terms of signal to interference ratio (SIR) and bit error rate (BER). Between two nodes the SIR is maintained by adjusting the transmitter power levels at each transmitting node while BER is maintained by using adaptive modulation techniques. Distributed power control (DPC) is a effective technique to achieve this. Unlike centralized power control, DPC should be able to adjust the power levels of each transmitted node using local measurements, so that all nodes will maintain the desire SIR. Adaptive modulation is used to increase the spectrum efficiency and to provide different level of service to users. Proposed idea results in increased throughput, QoS and effective uses of power. Simulation has been presented to this work.

Throughput comparison for Cognitive Radio network under various conditions of primary user and channel noise signals

Spectrum scarcity is increasing with the growing demand of number of wireless technologies and services. Cognitive Radio (CR) techniques have become reliable solution for solving spectral congestion problem. For utilization of unused electromagnetic spectrum in a cognitive radio network, it is necessary for secondary users to monitor the available spectrum (allocated to primary users) and identify the free spectrum (spectrum holes). In this paper primary user signal and channel noise conditions are discussed. Earlier literature has worked on one of these conditions. What are these conditions? Primary user signal and channel noise can be real valued signal or complex valued signal. There modulation schemes may also be different. In this paper classification of primary user signal and channel noise is discussed. The probability of false alarm, probability of detection and throughput of secondary network (user) is calculated and a comparison of throughput of secondary user for different conditions of primary user signal and channel noise is being presented.

Modern error correcting codes for 4G and beyond: Turbo codes and LDPC codes

Modern error correcting codes are used in 4G and are proposed for future wireless cellular networks for achieving improved channel error correcting capability. Turbo codes, and their improved variants with better error correcting capabilities, and LDPC codes are near Shannon limit channel codes and are used in such systems. This paper focuses on error correcting codes used in present and future generations of mobile communication systems for improving system performance. These systems have higher data rates and low energy per bit. The comparative performance evaluation of Turbo codes and LDPC codes and their suitability for future cellular network is explored in the paper. This comparison will be useful in the selection of error correcting codes for future mobile communication systems.

Higher order statistics for discrete Weibull fading channel: An alternate formulation

Higher order fading statistics for continuous process has been modeled and explored for various existing channels such as Rayleigh, Ricean and Nakagami-m, to a great extent. The inherent randomness in wireless channels is one of emerging and open research topic, and as this randomness is highly correlated therefore discrete model have been proposed earlier. In this paper, an alternative formulation of higher order statistics such as level crossing rate and average fade duration in terms of cumulative distribution function and its bivariate function is presented for discrete Weibull fading channel sampled at a certain sampling interval, and is expressed in terms of Marcum-Q function. To reliably characterize the fading severity, close-form expressions for the LCR and AFD are given along with numerical examples to illustrate the exactness of proposed expressions.

Performance analysis of decode and forward cooperative diversity networks with threshold scheme

Cooperative diversity technique is used for achieving high data rate and low BER with low transmit power. The paper proposes a new scheme for selection of first relay having SNR above a predefined threshold level in cooperative diversity network, based on geometric distribution. Closed form expression for outage probability is derived for independent and identically distributed channels with decode and forward protocol. Numerical results show that the proposed scheme not only minimizes resource requirements but also improves the overall outage probability over previously proposed schemes for cooperative diversity network.