Assessing extrema of empirical principal component functions

The difficulties of estimating and representing the distributions of functional data mean that principal component methods play a substantially greater role in functional data analysis than in more conventional finite-dimensional settings. Local maxima and minima in principal component functions are of direct importance; they indicate places in the domain of a random function where influence on the function value tends to be relatively strong but of opposite sign. We explore statistical properties of the relationship between extrema of empirical principal component functions, and their counterparts for the true principal component functions. It is shown that empirical principal component funcions have relatively little trouble capturing conventional extrema, but can experience difficulty distinguishing a ``shoulder'' in a curve from a small bump. For example, when the true principal component function has a shoulder, the probability that the empirical principal component function has instead a bump is approximately equal to 1/2. We suggest and describe the performance of bootstrap methods for assessing the strength of extrema. It is shown that the subsample bootstrap is more effective than the standard bootstrap in this regard. A ``bootstrap likelihood'' is proposed for measuring extremum strength. Exploratory numerical methods are suggested.Comment: Published at http://dx.doi.org/10.1214/009053606000000371 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

On an approach to provide space diversity to an ultra wideband time hopping pulse position modulated wireless communication system

The hypothesis question, which is addressed in this PhD dissertation, is how to use two transmission antennas in an Ultra Wide Band Time Hopping Pulse Position Modulation system to take advantage of space diversity in such a way as to not significantly degrade the communication link compared to using only one transmit antenna. In answering the hypothesis question, this dissertation proposes a novel technique, based on Space Time Spreading, to allow an Ultra Wideband Time Hopping Pulse Position Modulation system to obtain full advantage from space diversity using two transmit antennas and one receive antenna, showing how such a Multiple Input Multiple Output system is designed. This is achieved with the added advantage of transmitting the same two symbols simultaneously on each antenna link. This means that for the proposed system, should a fade occur on one of the two antenna links, the two symbols transmitted will still be received with a slight increased cost in average Bit Error Rate (BER) performance as Signal to Noise Ratio (SNR) or measured Eb/No is increased. Results are first provided for wideband Space Time Spreading in the presence of Multiple Access Interference when using two, four and eight transmit antennas. A system is developed in simulation using modules provided by MATLABs Simulink program. It is then shown that using low correlation Wysocki spreading code set results in an improved BER performance compared to the more often used Walsh Hadamard spreading code set. A Simulink Ultra Wide Band Pulse Position Modulation Single Input Single Output system is developed and validated against published peer reviewed material. This is then modified to consider the use of Space Time Spreading in a Single Input Single Output system and it is shown that improved performance over an Ultra Wide Band Pulse Position Modulated Single Input Single Output is possible. It is also shown that this improvement allows the transmission of two symbols in the same time that the original system only transmits one symbol. The thesis also investigates a system which uses two transmit antennas but a hard decision is made on a chip by chip basis. Its performance, compared to an equivalent Single Input Single Output comparable system, is suboptimal. It does, however, have the advantage that it sends two symbols in the same time that the equivalent Single Input Single output Ultra Wide Band Pulse Position Modulation system sends one, and its implementation is simpler to codify. Also, it has the feature that both symbols are sent simultaneously on each antenna link. The simulator is then modified to make a hard decision after all chips of a spreading sequence for two antennas are received and it is shown that this system, in simulation and analysis, has a similar performance to that for a comparable Single Input Single Output system with the added advantage that both antenna links send the same two symbols simultaneously. It is further demonstrated in simulation and analysis that such systems can be affected by Multiple Access Interference. In addition, it is shown, using simulation, that the choice of spreading sequence set does have an impact on the average BER performance of the proposed Space Time Spreading Time Hopping Ultra Wideband Pulse Position Modulation system. The thesis finally proposes some extensions using the developed simulator which are outlined in future work

On the Effect of Adjacent Sector Multiple Access Interference on Space Time Spreading Systems

Space Time Spreading systems are proposed as a method to enhance communications between the Base Station (BS) and Mobile Station (MS) by using multiple transmit antennas at the Base Station. This provides a form of transmit diversity when there are more than one transmitting antennas. Space Time Spreading systems have been shown to be efficient in their use of the limited number of orthogonal spreading sequences and to provide a diversity gain, which in the case of two transmitter antennas at the BS and one receiving antenna at the MS, is of order two. The paper looks at the effect of unsynchronized adjacent cell interference caused by scatterers causing the target MS to experience Multiple Access Interference (MAI) due to misaligned orthogonal codes from adjacent sectors in a sectorised cell (with 120 degree sectorisation). The study finds that adjacent MAI does adversely influence the Bit Error Rate (BER) of the target MS

Hand gesture recognition: An overview

Hand gesture recognition has been applied to many fields in recent years, especially in man-machine interaction (MMI) area, which is regarded as a more natural and flexible input. In this paper, an overview of hand gesture recognition research up to date is presented, which includes common stages of hand gesture recognition, common methods and technique of each stage, the state of the recent research and summaries of some successful hand gesture recognition models. 2013 IEEE

Electron density in the quiet solar coronal transition region from SoHO/SUMER measurements of S VI line radiance and opacity

Context: The sharp temperature and density gradients in the coronal transition region are a challenge for models and observations. Aims: We set out to get linearly- and quadratically-weighted average electron densities in the region emitting the S VI lines, using the observed opacity and the emission measure of these lines. Methods: We analyze SoHO/SUMER spectroscopic observations of the S VI lines, using the center-to-limb variations and radiance ratios to derive the opacity. We also use the Emission Measure derived from radiance at disk center. Results: We get an opacity at S VI line center of the order of 0.05. The resulting average electron density is 2.4 10^16 m^-3 at T = 2 10^5 K. This value is higher than the values obtained from radiance measurements. Conversely, taking a classical value for the density leads to a too high value of the thickness of the emitting layer. Conclusions: The pressure derived from the Emission Measure method compares well with previous determinations and implies a low opacity of 5 10^-3 to 10^-2. The fact that a direct derivation leads to a much higher opacity remains unexplained, despite tentative modeling of observational biases. Further measurements need to be done, and more realistic models of the transition region need to be used.Comment: 11 pages, 9 figure

The feasability of implementing a face recognition system based on Gabor filter and nearst nighbour techniques in an FPGA device for door control systems

Door access control systems based on face recognition are geared towards simplifying difficult face recognition problems in uncontrolled environments. Such systems are able to control illumination, offer neutral pose and improve the poor performance of many face recognition algorithms. Door access control systems control illumination and pose in order to overcome face recognition problems. While there have been significant improvements in the algorithms with increasing recognition accuracy, very little research has been conducted on implementing these in hardware devices. Most of the previous studies focused on implementing a simple principal component analysis in hardware with low recognition accuracy. In contrast, the use of a Gabor filter for feature extraction and the nearest neighbour method for classification were found to be better alternatives. Dramatic developments in field programmable gate arrays (FPGAs) have allowed designers to select various resources and functions to implement many complex designs. The aim of this paper is to present the feasibility of implementing Gabor filter and nearest neighbour face recognition algorithms in an FPGA device for face recognition. Our simulation using Xilinx FPGA platforms verified the feasibility of such a system with minimum hardware requirements

Novel receiver for correlated fading multi-antenna physical network coding TWRNs

Physical Network Coding (PNC) has recently been proposed for multi-antenna Two-Way Relay Networks (TWRNs) with independent fading channels because the total network throughput could be significantly improved. However, PNC for multi-antenna TWRNs with correlated fading channels has not been considered yet. This paper thus considers an important class of multi-antenna TWRNs with the following properties: single-antenna source nodes and two-antenna relay; distance between source nodes and the relay is significantly larger than that between antennas of the relay; and channels between source nodes and the relay are correlated. For such a system, we first propose a novel correlation model that facilitates an easy method to create fading channels with certain correlation properties. We then propose an ovelreceiver design for correlated fading TWRNs. Simulation results show that the proposed receiver design provides much better error performance than the well-known Log-Likelihood Ratio (LLR) algorithm proposed in the literature

Ultra Wideband Noise Channel Measurement using a Vector Network Analyzer

In this paper, we analyze the measurement of ultra wideband (UWB) noise channels in different indoor environments. All measurements are done using a vector network analyzer (VNA) which allows us to measure the noise channel transfer functions. We find that the noise power of the system is decreased by increasing the intermediate frequency (IF) bandwidth which leads to an increase in time taken to perform measurements of the channels. Also, we measure the environmental noise power and find that it is slightly affected by fluorescent light sources inside the measurement environments. In addition, we find that the environmental noise is decreased when enclosed in a Faraday cage (steel shed), within an intense multipath measurement environment. As secondary application, we show how a frequency detection device can be used to re-adjust a maladjusted frequency selection on a remote controller for a garage door, in presence of environmental noise power

Measurement of Ultra Wideband Channel Sounding Using a Vector Network Analyzer

In this paper, we analyze the measurement of ultra wideband (UWB) noise channels in different indoor environments. All measurements are done using a vector network analyzer (VNA) which allows us to measure the noise channel transfer functions. We find that the noise power of the system is decreased by increasing the intermediate frequency (IF) bandwidth which leads to an increase in time taken to perform measurements of the channels. Also, we measure the environmental noise power and find that it is slightly affected by fluorescent light sources inside the measurement environments. In addition, we find that the environmental noise is decreased when enclosed in a Faraday cage (steel shed), within an intense multipath measurement environment. We found that, the Environmental noise decreases slightly by using the LPDA antenna compared to using the Teardrop and Horn antennas. Our results show that the Horn antenna is less suitable for UWB channel measurements compared to the LPDA directional antennas because of lower S11 (Return Loss) values. While foromnidirectional antennas, the Teardrop antenna is much more suitable than the monocone antennas for UWB measurements (due to lower S11 values) and decreases the Environmental noise power. As secondary application, we show how a frequency detection device can be used to re-adjust a maladjusted frequency selection on a remote controller for a garage door, in presence of environmental noise power