Analysis of multi-lead QT dispersion by means of an algorithm implemented on Labview

QT dispersion measurement is significant in diagnostic ECG, and several methods are proposed in the literature to implement QT measurement. This study consists of two parts: The first part was the development of an algorithm to measure both QT interval and QT dispersion. To check the reliability of the algorithm, 25 single channel ECGs were recorded and their QT intervals were computed. On two subjects, three and four lead ECG data were recorded respectively and their QT dispersions were statistically analyzed. Another part of this study dealt with the effect of the electric dipole of the heart on QT dispersion. It was found that the mean and the standard deviation of the resulting QT dispersions were significantly smaller than those found in previous studies. In near and far field analysis, subjecting the data to a student\u27s T test revealed that both near and far field QT dispersion data were drawn from the same population

Renegotiation based dynamic bandwidth allocation for selfsimilar VBR traffic

The provision of QoS to applications traffic depends heavily on how different traffic types are categorized and classified, and how the prioritization of these applications are managed. Bandwidth is the most scarce network resource. Therefore, there is a need for a method or system that distributes an available bandwidth in a network among different applications in such a way that each class or type of traffic receives their constraint QoS requirements. In this dissertation, a new renegotiation based dynamic resource allocation method for variable bit rate (VBR) traffic is presented. First, pros and cons of available off-line methods that are used to estimate selfsimilarity level (represented by Hurst parameter) of a VBR traffic trace are empirically investigated, and criteria to select measurement parameters for online resource management are developed. It is shown that wavelet analysis based methods are the strongest tools in estimation of Hurst parameter with their low computational complexities, compared to the variance-time method and R/S pox plot. Therefore, a temporal energy distribution of a traffic data arrival counting process among different frequency sub-bands is considered as a traffic descriptor, and then a robust traffic rate predictor is developed by using the Haar wavelet analysis. The empirical results show that the new on-line dynamic bandwidth allocation scheme for VBR traffic is superior to traditional dynamic bandwidth allocation methods that are based on adaptive algorithms such as Least Mean Square, Recursive Least Square, and Mean Square Error etc. in terms of high utilization and low queuing delay. Also a method is developed to minimize the number of bandwidth renegotiations to decrease signaling costs on traffic schedulers (e.g. WFQ) and networks (e.g. ATM). It is also quantified that the introduced renegotiation based bandwidth management scheme decreases heavytailedness of queue size distributions, which is an inherent impact of traffic self similarity. The new design increases the achieved utilization levels in the literature, provisions given queue size constraints and minimizes the number of renegotiations simultaneously. This renegotiation -based design is online and practically embeddable into QoS management blocks, edge routers and Digital Subscriber Lines Access Multiplexers (DSLAM) and rate adaptive DSL modems

Impulse Radio Systems with Multiple Types of Ultra-Wideband Pulses

Spectral properties and performance of multi-pulse impulse radio ultra-wideband systems with pulse-based polarity randomization are analyzed. Instead of a single type of pulse transmitted in each frame, multiple types of pulses are considered, which is shown to reduce the effects of multiple-access interference. First, the spectral properties of a multi-pulse impulse radio system is investigated. It is shown that the power spectral density is the average of spectral contents of different pulse shapes. Then, approximate closed-form expressions for bit error probability of a multi-pulse impulse radio system are derived for RAKE receivers in asynchronous multiuser environments. The theoretical and simulation results indicate that impulse radio systems that are more robust against multiple-access interference than a "classical" impulse radio system can be designed with multiple types of ultra-wideband pulses.Comment: To be presented at the 2005 Conference on Information Sciences and System

Ultra Wideband Impulse Radio Systems with Multiple Pulse Types

In an ultra wideband (UWB) impulse radio (IR) system, a number of pulses, each transmitted in an interval called a "frame", is employed to represent one information symbol. Conventionally, a single type of UWB pulse is used in all frames of all users. In this paper, IR systems with multiple types of UWB pulses are considered, where different types of pulses can be used in different frames by different users. Both stored-reference (SR) and transmitted-reference (TR) systems are considered. First, the spectral properties of a multi-pulse IR system with polarity randomization is investigated. It is shown that the average power spectral density is the average of the spectral contents of different pulse shapes. Then, approximate closed-form expressions for the bit error probability of a multi-pulse SR-IR system are derived for RAKE receivers in asynchronous multiuser environments. The effects of both inter-frame interference (IFI) and multiple-access interference (MAI) are analyzed. The theoretical and simulation results indicate that SR-IR systems that are more robust against IFI and MAI than a "conventional" SR-IR system can be designed with multiple types of ultra-wideband pulses. Finally, extensions to multi-pulse TR-IR systems are briefly described.Comment: To appear in the IEEE Journal on Selected Areas in Communications - Special Issue on Ultrawideband Wireless Communications: Theory and Application

The Cramer-Rao bounds of hybrid TOA/RSS and TDOA/RSS location estimation schemes

In short range communications, the use of RSS measurements in conjunction with TOA or TDOA leads to enhanced estimation accuracy with respect to the case where only TOA or TDOA are used. In this article, we derive the Cramer-Rao Bound (CRB) for location estimation accuracy of two different hybrid schemes: TOA/RSS and TDOA/RSS. For short ranges, the hybrid schemes offer improved accuracy, particularly in the proximity of the reference devices

A hybrid location estimation scheme (H-LES) for partially synchronized wireless sensor networks

Heterogeneity is the key distinguishing characteristic of wireless sensor networks (WSN), compared to wireless cellular networks (WCN). It may appear in the form of communication ranges of sensor devices, synchronization and signal processing capabilities. In this article, we develop a hybrid location estimation scheme for heterogeneous WSNs with unsynchronized shortrange simple relays and mobile sensors nodes, and synchronized stations. Our scheme employs combination of time difference of arrival (TDOA) and received signal strength (RSS) measurements, whereby the TDOA is used to filter out the clock offset that appears due to the lack of synchronization. We quantify the estimation accuracy of the scheme by deriving the Cramer-Rao bound (CRB), and discuss the performance trade-off between the number of synchronized and non-synchronized devices involved

TOA Estimation with Different IR-UWB

In this paper, performances of stored-reference (SR), transmitted-reference (TR), and energy detection (ED) based time of arrival (TOA) estimation techniques are analyzed for impulseradio ultra-wideband (IR-UWB) systems. Various maximum likelihood estimation approaches are investigated under different observation models, and a new estimator that exploits the noise statistics and power delay profile of the channel is proposed. Simulation results show that ED and TR perform well if the sampling rate is much smaller than the Nyquist rate. Also, exploiting the channel and noise statistics considerably improves the accuracy of peak selection