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Several classical timing synchronization schemes for OFDM systems have been proposed based on the correlation between identical parts of OFDM symbol. These schemes show poor performance due to the presence of plateau and significant side lobe. In this paper we design a new OFDM symbol based on a constant amplitude zero auto correlation sequence and proposed a modified timing metric for time synchronization. The performance of the proposed timing synchronization scheme is better than the classical techniques.

In compared to wired communication networks, the wireless communication networks suffer from various factors that affect the network performance. More specifically in case of ad hoc networks such as wireless sensor network (WSN), where the network exists without the support of fixed infrastructure the performance is greatly influenced by network size, traffic intensity, routing, etc. One of the key parameters to handle the traffic in between nodes of WSN is buffering of data packets. Thus, the selection of an appropriate size of buffer for the nodes belonging to a WSN of stipulated size is important so far as the performance of the network is concerned. This paper presents a study about the effect of buffer size on the performance such as packet delivery fraction and packet drop fraction. The results of the study are obtained through simulation of a static WSN of fixed size with randomly placed nodes.

Analysis of coverage and bit error rate (BER) for Wireless systems in a Nakagami fading channel have been reported in the literature. Most of the analysis considers the nodes to be static and the received power follows Gamma distribution. However, the nodes in Mobile Ad hoc Networks are mostly mobile. The mobility pattern of nodes is depicted using mobility models. In this paper, we consider the Random Direction mobility model to represent the mobility of mobile nodes. Due to mobility of nodes, the received power at the nodes does not follow Gamma distribution in a Nakagami fading environment. The probability density function and cumulative distribution function of the received power at the mobile nodes are derived in this paper. Subsequently, the coverage probability and average BER are derived. Furthermore, the effects of interference due to the presence of neighboring nodes on the coverage probability and average BER are investigated.

In order to combat the multipath fading effect in wireless communication the diversity technique is usually preferred which also improves data rate. The different diversity schemes and its impact on a static wireless network- based link performance is well discussed in literature. However, in the current scenario, wireless networks are highly dominated with the functionality of mobile nodes. This paper presents the diversity impact through the use of Maximal Ratio Combining (MRC) method on the signal power being received at the receiver node from a mobile transmitting node where the communication channel assumed to be of Rayleigh fading type. The node movement in the mobile network in this work is depicted through Random Direction (RD) mobility model so as to study the effect of diversity. A closed form mathematical expression of the Probability Density Function (PDF) for the received signal power is being derived in this work. Furthermore, the diversity impact is also analyzed for the performance metric such as outage probability.

Space diversity with different signal combining techniques is one of the method, which is widely used to reduce the effects of multipath fading. Analysis of the effects of diversity on the performance of the link for a wireless static network is well studied. However, in the recent times, most of the wireless applications are associated with the mobility of nodes. Thus the analysis of effects of space diversity with combining techniques is essential to understand the effects of diversity on the link of mobile networks. In this paper we considered random way point mobility model (Wang and Low (2013)) to describe mobility of nodes in a mobile network scenario and evaluate the outage and Average BER performance of the wireless link (Han et al. (2019)) [1] .

In a traditional method of timing synchronization in the OFDM system, data on regularly spaced subcarriers are transmitted. However, the concept of data transmission on regular spaced sub- carriers does not fulfil the requirement of cognitive radio (CR) system in achieving dynamic spectrum management, free from interference from the primary users. So, Non-Contiguous OFDM (NC-OFDM) is considered for CR to support high data rate transmission in a wireless environment, it overcomes multipath delay spread.NC-OFDM system has high spectrum efficiency, so it is useful for CR system. Several synchronization schemes have been explored for the OFDM system. However, these schemes are not appropriate for NC-OFDM system as these schemes do not use deactivated subcarriers. In this paper, a modified timing metric for the timing synchronization in NC-OFDM based CR system is proposed. The performance of the proposed timing synchronization scheme is compared with the traditional Park and Zhang schemes.

Several classical timing synchronization schemes have been proposed for the timing synchronization in OFDM systems based on the correlation between identical parts of OFDM symbol. These schemes show poor performance due to the presence of plateau and significant side lobe. In this paper we present a timing synchronization schemes with timing metric based on a Constant Amplitude Zero Auto Correlation (CAZAC) sequence. The performance of the proposed timing synchronization scheme is better than the classical techniques

Coarse frequency offset estimate and tracking of residual frequency offset are two crucial stages for frequency synchronization in OFDM based WLAN systems. An improved frequency offset estimation scheme is proposed for tracking residual offset. The estimation scheme is dependent on the position of an OFDM symbol in a frame.

A new timing synchronization scheme for Orthogonal Frequency Division Multiplexing (OFDM) based Wireless Local Area Networks (WLANs) is presented. Specifically, use of one long OFDM symbol in the frame format of IEEE802.11a is suggested for coarse timing synchronization. A new timing metric has been proposed which results in significant improvement in performance compared to the results reported.

Wireless links in a Mobile Ad Hoc Network (MANET) is unreliable. So the links in between the nodes in a MANET breaks frequently. Mobility of nodes in a MANET increases the level of unreliability of the link between the nodes. Failure of a link also leads to complete route failure and affect the performance of MANET. So, there is a need to study the effect of mobility of nodes that causes a link break or a route failure. This paper presents a theoretical approach to analyze the effects of velocity on the performance of MANET in terms of routing overhead and average end to end delay. The analytical results are also validated with simulation.

Now a days there is a remarkable growth in telecommunication technology which makes users of mobile electronic devices accessible to a communication network. These electronic devices are nothing but the nodes of the Mobile Ad hoc Network (MANET). Each node can move from one place to other during communication and this mobility is having its effect on performance of the network. Mobility changes when speed of the node and pause time with which it moves changes. Change in mobility causes break of link with neighboring nodes as a result of which the performance of a network may be reduced. A number of packets are dropped at different layers of the network. This paper describes the analysis of change in performance due to change in mobility and transmission power. The parameters describing the reason of variation in performance are (1) number of link breaks and (2) number of packet delivered. (3)End to end delay. The simulator we have used in our work for the calculation of performance matrices is GLOMOSIM. The performance comparison has also made between two types of on demand routing protocols AODV and DSR.

The digital channel equalizers are located in the front end of the receivers to avoid the effect of Inter-Symbol-Interference (ISI). In this paper, the equalization problem has been viewed as an optimization problem. In past the Least Mean Square Algorithm (LMS), Recursive least square (RLS), Artificial Neural Network (ANN) and Genetic Algorithm (GA) have been successfully employed for nonlinear channel equalization. The LMS, RLS and ANN techniques are derivative based and hence are chances that the parameters may fall to local minima during training. Though GA is a derivative free technique, it takes more converging time. We propose a novel equalization technique based on Differential Evolution (DE). DE is an efficient and powerful population based stochastic search technique for solving optimization problems over continuous space and hence the channel equalization performance is expected to be superior.

In recent years the rapid development in telecommunication technologies leads to a non linear growth in the number of users of mobile electronic gadgets accessible to a communication network. These electronic gadgets are nothing but the nodes of the MANET (Mobile Ad hoc Network) and thus the mobility of the nodes effects a much the performance of the network. A change in mobility can be meant as the change in speed of node during motion in the network or pause time at different points during its motion between a source and destination point in the network. Due to change in mobility link between neighbour nodes can break a number of times as a result of which the performance of a network may be hampered. Also a number of packets may be dropped at different layers of the network. One of the way of analyzing the performance of a MANET is by considering the packet delivery fraction (PDF). This paper describes a detailed analysis of performance affected due to change in mobility in different terrain area. The parameter describing the reason of variation in performance is the number of packets delivered. The simulator we have used in our work for the calculation of performance matric is GLOMOSIM. The performance comparison has also made considering two types of routing protocols AODV and DSR.

The increase in users of mobile electronic gadgets with communication facilities day by day all around the world is resulting growth in research on multi hop wireless network getting exponential in past few years. Mobile ad hoc network is the suitable one for providing communication between these users (known as nodes) in a network as far as the application and physical structure of the network is considered. The mobile ad hoc network being infrastructure less is flexible to form. However the existence of the network for a long duration depends on the lifetime individual nodes belongs to that network. The life time of a node depends on the battery power. Most of the power consumed in a node is because of transmission. Therefore it is important to know the effect of transmission power on the performance of network so that for specific applications the transmission power of nodes can be decided based on the network area and the number of possible nodes that to work in the network which can work for long duration. In this paper we have described the analysis of the effect of transmission power on the performance of network such as packet delivery fraction, routing load, average energy consumption per node and hop count. The analysis is made for a network with different number of sources and different transmission power of nodes for a fixed network area.

In recent years the rapid development in telecommunication technologies leads to a non linear growth in the number of users of mobile electronic gadgets accessible to a communication network. These electronic gadgets are nothing but the nodes of the MANET (Mobile Ad hoc Networks) and thus the mobility of the nodes effects a much the performance of the network. A change in mobility can be meant as the change in speed of node during motion in the network or pause time at different points during its motion between a source and destination point in the network. Due to change in mobility link between neighbor nodes can break a number of times as a result of which the performance of a network may be hampered. Also a number of packets may be dropped at different layers of the network. One of the ways of analyzing the performance of a MANET is by considering the packet delivery fraction. This paper describes a detailed analysis of performance affected due to change in mobility. The parameters describing the reason of variation in performance are number of link breaks and number of packet drops.

Frequency offset estimation is one of the crucial stages for frequency synchronization in OFDM based systems such as MB-OFDM UWB systems. A frequency offset estimation scheme is proposed for coarse frequency offset estimate. Variance of the proposed frequency offset estimated scheme is compared with the Cramer Rao Lower Bound (CRLB). BER performance of the proposed scheme is also reported.