Showing papers by "Stephen McLaughlin published in 2007"

Long-term outcomes of patients with localized rectal cancer treated with chemoradiation or radiotherapy alone because of medical inoperability or patient refusal.

Abstract: The standard management of rectal cancer continues to be defined by the results of randomized, clinical trials exploring the optimal timing and use of adjuvant chemotherapy and radiation therapy in relation to surgery. The patient with rectal cancer who is elderly and/or has significant comorbidities and the patient who refuses surgery are clinical contexts for which there is limited current data to guide decision making. A retrospective analysis was performed at six Australian centers of patients with rectal cancer treated with radiation therapy or chemoradiation alone because of excessive operative risk or patient refusal of surgery. We identified 48 patients treated between August 1998 and June 2005 with a median age of 76 (range, 49–94) years. Twenty-four patients (50 percent) were considered medically inoperable and 24 patients refused surgery. Treatment was with chemoradiation (with 5-fluorouracil) in 36 patients and radiotherapy alone in 12 patients; 93 percent completed the planned therapy. A clinical complete response was seen in 56 percent and a partial response in 30 percent of patients. At a median follow-up of 49 months, 18 patients have disease progression, including 10 of 24 in the medically inoperable group and 8 of 24 in the refused surgery group. Of the 25 deceased patients, 16 died from progressive disease and 9 from noncancer causes. Chemoradiation or radiotherapy alone is a safe alternative that results in significant progression-free and overall survival times in patients who are considered medically inoperable or refuse to undergo surgery. Ultimately, however, many patients will progress.

Layered BP Decoding for Rate-Compatible Punctured LDPC Codes

Abstract: Rate-compatible punctured LDPC codes have shown to perform well over a wide variety of code rates, both theoretically and practically. However it has been reported that the belief propagation (BP) decoding for these codes converges slower than for unpunctured codes. Layered BP algorithm is a modified BP algorithm that accelerates the decoding convergence by means of sequential scheduling of check node updates. In this letter, we propose an efficient scheduling of check node updates for rate-compatible punctured LDPC codes that performs well. We show that the convergence speed of the proposed scheduling outperforms conventional (random) scheduling and conventional BP decoding. Performance improvements become more distinctive with the growing fraction of punctured bits

Enhanced Empirical Mode Decomposition using a Novel Sifting-Based Interpolation Points Detection

Abstract: Empirical mode decomposition (EMD) is a signal analysis method which has received much attention lately due its performance in a number of applications The main disadvantage ntage of EMD is that it is lacking a theoretical foundation and therefore, our understanding of it have come through intuition and experimental validation This drawback has significantly limited the potential for improvements to the method itself In other words, the version of EMD currently used by most researchers is roughly the same as that proposed 9 years ago In this paper, a novel version of EMD is proposed which exhibits significantly improved decomposition performance This new development exploits the results of a study on EMD concerning the optimized configuration of EMD with respect to criteria for selection of interpolation points

Towards a Tailored Sensor Network for Fire Emergency Monitoring in Large Buildings

Abstract: Presentation by Dr. Rochan R. Upadhyay at IEEE-WRECOM on joint work carried out with Dr. Athanasia Tsertou.

Constellation Shaping using LDPC Codes

Abstract: It is well-known that a Gaussian source distribution is required for maximum information transfer across a Gaussian channel. In a coded modulation system an equiprobable symbol constellation loses at most 1.53 dB when compared to a Gaussian source. To bridge this shaping gap, a code can be used to make the source distribution more Gaussian over an expanded constellation that results in lower average transmitted energy. Trellis shaping uses convolutional codes and the Viterbi algorithm for minimizing the transmitted energy. In this work, we propose trellis shaping using low-density parity-check codes as the shaping codes. We show that the 2-state min-sum algorithm over the Tanner graph can be used to efficiently implement the energy minimization. This is a more than 4-fold decrease in complexity over 4-state convolutional code-based trellis shaping. Using one of our simple shaping codes, we have observed a shaping gain of up to 0.65 dB (with CER = 1.26; PAPR = 3.86) (as compared with CER=1.41 and PAPR=3.3 for convolutional-code based trellis shaping with similar shaping gain). This encouraging result indicates that more complex LDPC-based approaches will do even better. We also present simulation results to show that constellation shaping provides similar gains over wireless channels under slow fading conditions.

Scalable Fault Diagnosis in IP Networks using Graphical Models: A Variational Inference Approach

Abstract: In this paper we investigate the fault diagnosis problem in IP networks. We provide a lower bound on the average number of probes per edge using variational inference technique proposed in the context of graphical models under noisy probe measurements. To obtain the bounds, we construct a graphical model using Bayesian networks. The advantages of the variational inference technique are the explicit choices of a simplifying conjugate function and a computationally tolerable approximation to address the intractable detection problem for large networks. We propose an entropy lower (EL) bound by drawing similarities between the coding problem over binary symmetric channel and the diagnosis problem and compare it against the variational lower bound. In addition, we discuss scalable and non-scalable scenarios in the presence of noise. Simulation results demonstrate that indeed the variational inference technique can provide a linear growth of the average number of probes per edge as a function of the network size.

Fast Decoding of Rate-Compatible Punctured LDPC Codes

Abstract: While rate-compatible punctured low-density parity-check (RCP-LDPC) codes offer high flexibility in terms of code rate at a relatively low cost in implementation complexity, they are reported to require more decoding iterations than unpunctured LDPC codes. In this paper1 we consider layered belief propagation decoding and propose efficient check node layering that significantly accelerates the decoding convergence of RCP-LDPC codes. We show that the proposed layering outperforms both random layering and conventional BP decoding. The performance improvements become more distinctive at high rates and they come at no additional implementation cost.

Investigation of the Empirical Mode Decomposition Based on Genetic Algorithm Optimization Schemes

Abstract: Empirical mode decomposition (EMD) has lately received much attention due to the many interesting features that exhibits. However it lacks a strong theoretical basis which would allow a performance analysis and hence the enhancement and optimization of the method in a systematic way. In this paper, an investigation of EMD is attempted in an alternative way. The interpolation points and the piecewise interpolating polynomials for the formation of the upper and lower envelopes of the signal are optimized based on a genetic algorithm framework revealing important characteristics of the method which where previously hidden. As a result, novel directions for both the performance enhancement and the theoretical investigation of the method are unveiling.

Post-Error Correcting Code Modeling of Burst Channels Using Hidden Markov Models With Applications to Magnetic Recording

Abstract: We present two approaches for modeling burst channels using hidden Markov models (HMMs). The first method is based on the maximum-likelihood approach and improves on the computational efficiency of earlier methods. We present new algorithms for scaling and for determining the model parameters by using smart search techniques. We then generalize a gap length analysis and apply it to modeling HMMs. The algorithms are low-complexity and memory-efficient. Finally, we present simulation results for modeling errors in magnetic storage channels and show how this can be used for evaluating decoder failure rates by using Wolf's method, from real observed data

Error analysis of ultrasonic tissue doppler velocity estimation techniques for quantification of velocity and strain

Abstract: Recent work in the field of Doppler tissue imaging has focused mainly on the quantification of results involving the use of techniques of strain and strain-rate imaging. These results are based on measuring a velocity gradient between two points, a known distance apart, in the region-of-interest. Although many recent publications have demonstrated the potential of this technique in clinical terms, the method still suffers from low repeatability. The work presented here demonstrates, through the use of a rotating phantom arrangement and a custom developed single element ultrasound system, that this is a consequence of the fundamental accuracy of the technique used to estimate the original velocities. Results are presented comparing the performance of the conventional Kasai autocorrelation velocity estimator with those obtained using time domain cross-correlation and the complex cross-correlation model based estimator. The results demonstrate that the complex cross-correlation model based technique is able to offer lower standard deviations of the velocity gradient estimations compared with the Kasai algorithm.

Implementable wireless access for B3G networks. I. MIMO mimo channel measurement, analysis, and modeling [Topics in Radio Communications]

Abstract: Within Mobile VCE, a team of several leading U.K. universities, in dose association with major manufacturers and international telecom operators from the mobile industry, have been addressing the challenging task of designing transceiver structures for beyond 3G networks. Innovative approaches led to a plethora of cross-layer optimized technologies of low complexity and high robustness, allowing for the much promised multimedia-centric services over future wireless networks. This article presents a comprehensive overview of the research conducted within Mobile VCE's Core Wireless Access Research Programme, a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article, the first of four, MIMO channel measurements, analysis, and modeling are presented, which were then utilized to develop compact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user space-time coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry's in-house research program, significant extensions of this work are now in hand, within Mobile VCE's own core activity, aimed at securing major improvements in delivery efficiency in future wireless systems through cross-layer operation

Implementable wireless access for B3G networks. II. MIMO receiver architectures [Topics in Radio Communications]

Abstract: This article presents a comprehensive overview of the research conducted within Mobile VCE's Core Wireless Access Research Programme, a key focus of which has naturally been on MIMO transceivers. The article, the second of four, provides a follow on from the first article, which dealt with MIMO channels and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In Part I MIMO channel measurements, analysis, and modeling were presented, which were then utilized to develop compact and distributed antenna arrays. This article reports parallel activities into low-complexity MIMO single-user space-time coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. Also, overall B3G system designs have been suggested for beamformed multilayer CDMA-based networks

Knowledge management - Achieving success with KM

Abstract: For any business to survive and compete in today's globally competitive market place the concept of knowledge creation and transfer must be understood and embraced across the organisation. In the case of organisations where driving innovation is vital to the success of the business, the development and implementation of an effective knowledge management strategy is an absolute necessity.

From gigabytes to bytes: automated denoising and feature identification in electron tomograms of intact bacterial cells

Abstract: Advances in automated data acquisition in electron tomography have led to an explosion in the amount of data that can be obtained about the spatial architecture of a variety of biologically and medically relevant objects with resolutions in the "nano" range of 10-1000 nm. The development of methods to automatically analyze the vast amounts of information contained in these tomograms is a major challenge since the electron tomograms are intrinsically very noisy. A fundamental step in the automatic analysis of large amounts of data for statistical inference is to segment relevant 3D features in cellular tomograms. Procedures for segmentation must work robustly and rapidly in spite of the low signal to noise ratios inherent to biological electron microscopy. This work first evaluates various non-linear denoising techniques on tomograms recorded at cryogenic temperatures. Using datasets of bacterial tomograms as an example, we demonstrate that non-linear diffusion techniques significantly improve the fidelity of automated feature extraction. Our approach represents an important step in automating the efficient extraction of useful information from large datasets in biological tomography, and facilitates the overall goal of speeding up the process of reducing gigabyte-sized tomograms to relevant byte-sized data.

Wideband Unshielded-Twisted-Pair (UTP) Cable Measurements and Modeling for Multiple-Input–Multiple-Output (MIMO) Systems

Abstract: The study of multiple-input-multiple-output (MIMO) systems over unshielded-twisted-pair (UTP) cables relies on or assumes models of the cable's transmission and crosstalk parameters. Several cable models have been proposed; however, there has been a lack of wide-scale line surveys to verify the applicability of these models. This paper presents the results of wideband-crosstalk and transmission-parameter measurements on UTP cables conducted at the laboratories of BTExact. The measurement results are then used to verify Joffe's MIMO channel model, which is one of the two available but mathematically equivalent models. It is shown that crosstalk estimates from measurements taken on very short cable lengths fail to account for the effects from the pair and bundle twisting. Model parameters measured on longer cable pieces yield more realistic frequency-dependent model predictions; these are, however, distorted at high frequencies due to resonance effects. In general, the model tends to overestimate far-end crosstalk and underestimate near-end crosstalk.

Hybrid wireless communication system and communicating method thereof

Abstract: A complex wireless communication system and a communication method thereof are provided to increase data rates decrease interference in executing communication by using respectively different communication methods. A base station divides available frequency resources by a frame unit and executes communication. At the switching time of each frame, switching is made between real-time service mode and non-real time mode. The base station executes up-link or down-link communication with terminals within a cellular communication zone in an FDD(Frequency Division Duplex) method every frame in real-time service mode. In the non-real time service mode of each frame, the base station executes up-link or down-link communication with terminals in an Ad-hoc method, based on a TDD(Time Division Duplex) method.

Packet Scheduling in Wireless Systems using MIMO Arrays and VBLAST Architecture

Abstract: In this paper, we investigate different packet scheduling techniques applied in MIMO to maximize spectral efficiency and to provide fairness among users. We investigate the performance of various schemes based on exploiting the VBLAST (Vertical Bell Labs Space Time) architecture and proportional fair (PF) scheduling. New algorithms using MIMO antennas and the VBLAST architecture are proposed to improve the performance of the PF scheme. Computer simulations are conducted to compare the different scheduling schemes in terms of cell throughputs and outage capacities. The degree of fairness (in terms of time delay and data rates) among the users for these schemes is also investigated.

Implementable wireless access for B3G networks. III. Complexity reducing transceiver structures [Topics in Radio Communications]

Abstract: This article presents a comprehensive overview of some of the research conducted within Mobile VCE's Core Wireless Access Research Programme, a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article MIMO channel measurements, analysis, and modeling, which were presented previously in the first article in this series of four, are utilized to develop compact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user space-time coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry's in-house research program, significant extensions of this work are now in hand, within Mobile VCE's own core activity, aiming toward securing major improvements in delivery efficiency in future wireless systems through cross-layer operation

MIMO Cooperative Diversity in a Transmit Power Limited Environment

Abstract: This paper considers a fading relay channel where the total transmit power used is constrained to be equal to that of the standard single-hop channel. The relay channel used operates in what is termed as MIMO cooperative diversity mode, where the source transmits to both relay and destination terminals in the first instance. Both the source and relay then transmit to the destination in the second instance. Initially the cooperative diversity framework is introduced to consider system constraints so a direct and fair comparison with the single-hop case can be made. In-particular a power constraint is placed on the system and the optimal transmit power levels are derived and presented. The derived technique for finding the optimal transmit power levels is then used to demonstrate the advantages of using cooperative diversity in a wireless network. The results presented show that MIMO cooperative diversity offers a 3.4 dB increase in spectral efficiency at 5 % outage, with no additional cost incurred in transmit time, power or bandwidth.

Implementable Wireless Access for B3G Networks - III: Complexity Reducing Transceiver Structures

Abstract: This article presents a comprehensive overview of some of the research conducted within Mobile VCE’s Core Wireless Access Research Programme, 1 a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article MIMO channel measurements, analysis, and modeling, which were presented previously in the first article in this series of four, are utilized to develop compact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user spacetime coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry’s in-house research program, significant extensions of this work are now in hand, within Mobile VCE’s own core activity, aiming toward securing major improvements in delivery efficiency in future wireless systems through crosslayer operation.

Gigabytes to Bytes: Automated Denoising and Feature Extraction as Applied to the Analysis of HIV Architecture and Variability using Electron Tomography

Abstract: Advances in automated data acquisition in electron tomography have led to an explosion in the amount of data that can be obtained about the spatial architecture of a variety of biologically and medically relevant objects with sizes in the "nano" range of 10-1000 nm. The development of methods to analyze the vast amounts of information contained in these tomograms is a major challenge since the electron tomograms are intrinsically noisy. A fundamental step in the automatic analysis of large amounts of data for statistical inference is to segment 3D features in cellular tomograms that can work robustly and rapidly despite of low signal to noise ratios inherent to biological electron microscopy. This work evaluates various denoising techniques on tomograms obtained using dual-axis simultaneous iterative reconstruction (SIRT) technique. Using three-dimensional images of HIV in infected human macrophages as an example, we demonstrate that transform domain-denoising techniques significantly improve the fidelity of automated feature extraction. Importantly, our approaches represent an vital step in automating the efficient extraction of useful information from large datasets in biological tomography, and facilitate the overall goal of speeding up the process of reducing gigabyte-sized tomograms to byte-sized data.

Implementable wireless access for B3G networks. IV. Resource management issues [Topics in Radio Communications]

Abstract: In this article the fourth in a series of four offers as a compilation of material which has been presented in detail elsewhere (see references within the article). In this article the focus is on resource management based methods for B3G mobile communications systems. As well as feeding into the industry's in-house research program, significant extensions of this work are now in hand, within Mobile VCE's own core activity, aiming towards securing major improvements in delivery efficiency in future wireless systems through cross-layer operation