Himanshu B. Soni

Lifetime prolonging in LEACH protocol for wireless sensor networks

The expeditious transformation of hardware technology has empowered the reinforcement of small, inexpensive, static and dynamic powerful sensor nodes, which are capable of sensing, computation and wireless communication on wide range of frequency with various modulation technique. This revolutionizes the implementation of wireless sensor network for considerable dimensions like overseeing some geographic area and parameter collection task. However, a limited energy constraint presents a major challenge such vision to become reality. In this paper we have attempted to explain how the wireless sensor networks are formed and how the various nodes present in those networks act as interdependent communicating nodes. LEACH (Low Energy Adaptive Clustering Hierarchy) [2] is one of the popular cluster-based structures, which has been widely proposed in wireless sensor networks. We are proposing the iLeach protocol (Improved Low-Energy Adaptive Clustering Hierarchy) and comparing to LEACH protocol. Lifetime of sensors is evaluated in terms of FND (First Node Dies) and HND (Half of the Nodes Die) [11] which will take care for the reliability and power efficiency of a wireless sensor network.

Peak to Average Power Ratio (PAPR) reduction in OFDM for a WLAN network using SLM technique

Orthogonal Frequency Division Multiplexing (OFDM) is a spectrally efficient multicarrier modulation technique for high speed data transmission over multipath fading channels. OFDM modulation schemes offer many advantages for multicarrier transmission at high data rates over time dispersive channels, particularly in mobile applications. One of the main issues of OFDM is high Peak-to-Average Power Ratio (PAPR) of the transmitted signal which adversely affects the complexity of power amplifiers. SeLected Mapping (SLM) technique is one of the promising PAPR reduction techniques for OFDM. This paper analyzes the capability of the existing SLM technique in reducing the effect of Peak-to-Average Power Ratio. The approach is very flexible and works with arbitrary numbers of subcarriers and without restriction on the type of modulation applied in them. The analysis is on a network model designed by WLAN 802.11a standard using MATLAB, a mathematical simulation software tool. As a performance measure for the PAPR reduction, we study the probability that the PAPR of an OFDM data block exceeds a given threshold, which is the Complementary Cumulative Distribution Function (CCDF) of PAPR.

Low complexity scheme for carrier frequency offset estimation in orthogonal frequency division multiple access uplink

Maximum likelihood (ML) carrier-frequency offset estimation for orthogonal frequency-division multiple access uplink is a complex multi-parameter estimation problem. The ML approach is a global optima search problem, which is prohibitive for practical applications because of the requirement of multidimensional exhaustive search for a large number of users. There are a few attempts to reduce the complexity of ML search by applying evolutionary optimisation algorithms. In this study, the authors propose a novel canonical particle swarm optimisation (CPSO)-based scheme, to reduce the computational complexity without compromising the performance and premature convergence. The proposed technique is a two-step process, where, in the first step, low resolution alternating projection frequency estimation (APFE) is used to generate a single better positioned particle for CPSO, followed by an actual CPSO procedure in second step. The mean square error performance of the proposed scheme is compared with existing low complexity algorithms namely APFE and linear particle swarm optimisation with mutation. Simulation results presented in this study show that the new scheme completely avoids premature convergence for a large number of users as high as 32.

Path scheduling for multiple mobile actors in wireless sensor network

ABSTRACT In wireless sensor network (WSN), energy is the main constraint. In this work we have addressed this issue for single as well as multiple mobile sensor actor network. In this work, we have proposed Rendezvous Point Selection Scheme (RPSS) in which Rendezvous Nodes are selected by set covering problem approach and from that, Rendezvous Points are selected in a way to reduce the tour length. The mobile actors tour is scheduled to pass through those Rendezvous Points as per Travelling Salesman Problem (TSP). We have also proposed novel rendezvous node rotation scheme for fair utilisation of all the nodes. We have compared RPSS with Stationery Actor scheme as well as RD-VT, RD-VT-SMT and WRP-SMT for performance metrics like energy consumption, network lifetime, route length and found the better outcome in all the cases for single actor. We have also applied RPSS for multiple mobile actor case like Multi-Actor Single Depot (MASD) termination and Multi-Actor Multiple Depot (MAMD) termination and observed by extensive simulation that MAMD saves the network energy in optimised way and enhance network lifetime compared to all other schemes.

Performance evaluation of GMSK modulated signal under Rician channel model

In this paper we have presented an effect of Rician channel model which is used to model the wireless channels. We have evaluated its channel effect on Minimum Shift keying modulation technique. We have also considered the Gaussian Minimum Shift keying modulation (GMSK) and carried out simulation with Rayleigh channel for comparison purpose. We have carried out simulation with MATLAB.

Performance Evaluation of DS-CDMA Based OFDM Multiuser System for Ultra Wideband (UWB) Communication

Here we have considered multiuser communication scenario with ultra wideband (UWB) communication. We propose two schemes for downlink communication, which are DS-CDMA based OFDM systems. For both the schemes, performance is compared with TH-PPM UWB. Performance of both the schemes is evaluated with additive white Gaussian noise (AWGN) channel. We have considered effect of higher spreading factor for AWGN channel. Also, we investigate performance of both the schemes under fading channel with different numbers of multipath components.

Energy efficient policy selection in wireless sensor network using cross layer approach

The authors have addressed the issue of energy saving in packet retransmission by reducing the packet loss in the first attempt. They have formulated the problem as Markov decision process and mapped the system into various states based on system dynamics like channel gain, buffer space, battery energy and harvested energy. In wireless sensor network, adaptive policy management is the best approach to work out with the variation of system states in a dynamically changing environment. The policies are defined regarding various controllable parameters like transmission power, modulation scheme, and transmission rate. The solution is sought regarding best policy selection as per the individual state of the system. They have evaluated the performance of the proposed optimum transreceiver scheme by extensive simulations with existing schemes like optimum energy allocation, adaptive modulation and adaptive power management for the various performance metrics like net bit rate and energy consumption in retransmission of packets for different system states.

Carrier frequency offset estimation & compensation in AMC OFDM

Sensitivity to Carrier Frequency Offset (CFO) is a well known issue in Orthogonal Frequency Division Multiplexing (OFDM). The recent wireless standards, which propose OFDM as modulation technique, prefer to use it with Adaptive Modulation and Coding (AMC). Inter carrier interference (ICI) created by CFO disturbs the selection of modulation order and channel coding rate in AMC. Effect of CFO on OFDM with AMC is studied in this work. The survey of Fractional CFO (FCFO) estimation techniques is presented in this paper. The optimal but complex to implement method for CFO estimation-the ML estimation is applied to OFDM with AMC. Efforts are made to reduce its complexity while actual implementation. Performance comparison of original and reduced complexity methods are presented based on accuracy and complexity.

Comparative study of various antenna selection techniques under MIMO for multiuser DS-CDMA based OFDM System for UWB communication

The use of Multiple Element Antenna (MEA) at transmitter and receiver side provides possibility of significant rise in the throughput of a fading channel. Recent research shows that use of multiple antenna elements improves the performance when large number of pair of transmit-receive antennas are available from which subset of antenna is selected based on the channel realization. In this paper we have considered the MEA system for improving the capacity of system. We have combined MEA system with DS-CDMA based OFDM System for Ultra wideband (UWB) communications and ensured the performance. We have considered DS-CDMA based OFDM system model with Multiuser Interference (MUI) and without MUI. Here, we have considered the different antenna selection techniques for improving performance of the system. In this paper we have considered the optimal and suboptimal antenna selection criterion with DS-CDMA based OFDM system.

E-shaped patch antenna analysis for multiple applications

An ‘E’ patch antenna is designed and analyzed. The antenna is designed to function in multiple bands in the frequency range of 1–4 GHz depending on the geometric specifications of antenna. It covers applications including GSM 1800, P-GSM, E-GSM, GSM-R, GPS, UMTS and Wi-MAX. E-patches of different dimensions of area 604mm2, 1600mm2 and 1720mm2 are analyzed. At each band, obtained corresponding VSWR is near to 1. The proposed antenna provides good return loss S11 and impedance behavior. Far-field radiation pattern, Impedance pattern and 3D gain have been analyzed.