The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Orthogonal Frequency Division Multiplexing (OFDM) is becoming widely deployed in fourth generation (4G) wireless communications systems. Synchronization between a transmitter and receiver is required for coherent demodulation of OFDM symbols, but this process is extremely fragile and susceptible to attacks from malicious third parties. Carrier frequency offset estimation and correction in particular...
This work presents chaos synchronization and parameter adaptation using P-C complete replacement scheme. Finally this scheme is applied to secure communication. The advantage of proposed scheme is shown based on the fact that there is no need for controller at the receiver side which is the basic requirement in most of the existing chaotic communication schemes. Only coupling is sufficient to achieve...
With the improving evolution in VLSI technology most of the digital circuits are becoming SOCs. However most of the SOC systems are synchronous designs and the issues like clock skew, power consumption and EMI are related to clock network. Asynchronous circuits can offer benefits like reduced power and improved performance. However implementing whole design with asynchronous design style is a challenge...
Wireless sensor networks (WSNs) have received a lot of attention recently due to their enormous potential in different applications. As in all distributed systems, time synchronization is very important in a sensor network since the design of many protocols and implementation of applications require precise time. In this article, we first gave some basic background knowledge about time synchronization...
Recently many channel hopping algorithms have been studied to guarantee rendezvous for Cognitive Radio Networks (CRNs). These algorithms propose rendezvous methods without using common control channels (CCCs) to avoid the limitations such as single point of failure, low scalability, and jamming attacks. In particular, the Jump-Stay based channel hopping rendezvous (JSR) algorithms provide guaranteed...
Efficient utilization of wireless bandwidth is a critical, if not the key, component of the wireless network architectures that balance availability and access. Cognitive Radio Networks (CRNs) are an important part of the solution to this problem. Common control channels (CCCs) for rendezvous in CRNs have limitations such as single point of failure, low scalability, and susceptibility to jamming attacks...
Continuous phase modulation (CPM) is a widely used modulation scheme in communication systems. However, difficulties arise with the design of CPM receivers, due to the nonlinear nature of CPM. One popular solution to this problem is to linearize CPM with pulse amplitude modulation (PAM) representation. In this paper, a reduced-complexity superbaud timing recovery method is proposed for PAM-based multi-h...
Low power listening (LPL) has been widely adopted to save energy in wireless sensor networks. However, LPL is ineffective in adapting to dynamic networks with asymmetric traffic patterns, as it sets a network-wide check interval. As a result, nodes with low data traffic waste significant energy resources doing idle listening. This problem is particularly exacerbated in multi-radio networks where majority...
In this paper, we present an algorithm for joint decoding of the modulo-2 sum of the bits transmitted from two unsynchronized transmitters using Physical Layer Network Coding (PLNC). We address the problems that arise when the boundaries of the signals do not align with each other and when the channel parameters are slowly varying and are not known to the receiver at the relay node. Our approach first...
Pseudolites are one of the most promising technologies for indoor localization because they can directly use off-the-shelf GPS/GNSS receivers with minor change of their firmware. However, pseudolites have some fundamental issues such as near-far, multipath, and synchronization problems. Many of these issues derive from using more than one transmitter and trilateration. In this paper, we propose a...
Pseudolite system is good alternative for indoor navigation in where GPS signal can not reach. There are two types of pseudolite system. The one is synchronous system and the other is asynchronous system. For the asynchronous system, user requires RF link to be provided augmentation data for timing and reference station for monitoring timing offsets of pseudolites. For the synchronous system, User...
This paper addresses the development of a new generation of lightweight intelligent buoys. These buoys are used to support underwater acoustic positioning systems, but were also designed to be elements of portable coastal observatories for short term deployments. We will present the main features of a buoy prototype including the physical structure, the computational system and algorithms developed...
In this paper, we propose and analyze a new GPS positioning algorithm. Our algorithm uses the direct linearization technique to reduce the computation time overhead. We invoke the general least squares method in order to achieve optimality in the situation when the trilateration system of equations becomes over-determined. We systematically evaluate our new algorithms and show that they indeed take...
Impulse radio ultra-wideband offers the potential of high data rate communication and accurate ranging with low power. However, synchronisation of impulse radio systems is known to be difficult. To be able to detect pulses with low energy, the receiver needs to combine multiple pulses. Traditionally, coherent and non-coherent signal combination are used. The vectorial sum of the samples used for coherent...
This paper presents an energy efficient way to detect a UWB Impulse Radio (UWB-IR) signal relying on a Time Hopping sequence with a non coherent receiver. This detection is performed in a periodic manner, observing the received signal on the mean pulse repetition period basis. It allows to derive a simple requirement on the THSs design, to fit our detection scheme. Compared to a straightforward busy...
The double time difference of arrival (DTDOA) approach applying in the mobile ad hoc network can effective avoid the synchronization problem. This paper investigates the performance of techniques for DTDOA node localisation in mobile ad hoc network by using root of quadratic equation and Gauss-Newton algorithm in NLOS environments. The validity of DTDOA method is demonstrated in an example of a simple...
Precise time synchronization is the precondition of precise navigation in radio navigation system, high frequency stability cesium atomic clock is used in this system as frequency reference and GPS time receiver is used. To solve the problem of system synchronize error caused by low quality of GPS time receiver in short time, shift average method and Kalman filter is introduced in this paper. The...
An adaptive control method and a structural acceleration method are introduced for estimating the unknown parameter when a time series for a scalar function of the variables of a nonlinear dynamical model is given. The methods are shown to work when the scalar function explicitly depends on a variable with the evolution equation in which the parameter appears explicitly, and the structural acceleration...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
This paper presents a fuzzy state tracking control scheme for chaotic synchronized secure communication based on the T-S fuzzy model of chaos. The conditions for dealing with the stability of the overall synchronization error system are proved by utilizing Lyapunov stability theory, and formulated into linear matrix inequalities (LMIs) afterwards. The structure of the controller is simply linear without...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.