Sandra E. M. Dudley

Toward terabit-per-second capacities over multimode fiber links using SCM/WDM techniques

This paper outlines the progress made on the use of subcarrier multiplexing (SCM) for high-speed datacommunications links over multimode fiber. Results include the demonstration of penalty-free transmission of 2.5 Gb/s data over worst case multimode fiber (MMF). A complete link demonstration of an SCM transmission system is reported, based on a quadrature phase-shift keying modulator and demodulator capable of a record 5.1 Gb/s per subcarrier data transmission. Superior performance compared with conventional baseband modulation techniques is shown. It is also demonstrated that when SCM is combined with dense wavelength-division multiplexing (WDM), aggregate data capacity of 200 Gb/s is feasible. Preliminary results demonstrate the possibility of 20-GHz WDM channel spacings, which if scaled show the potential for 1-Tb/s aggregate rates with a bandwidth-length product of 3 Tb/s/spl middot/km.

Do TETRA (Airwave) base station signals have a short-term impact on health and well-being? A randomized double-blind provocation study.

Background “Airwave” is the new communication system currently being rolled out across the United Kingdom for the police and emergency services, based on the Terrestrial Trunked Radio Telecommunications System (TETRA). Some police officers have complained about skin rashes, nausea, headaches, and depression as a consequence of using their Airwave handsets. In addition, a small subgroup in the population self-report being sensitive to electromagnetic fields (EMFs) in general. Objectives We conducted a randomized double-blind provocation study to establish whether short-term exposure to a TETRA base station signal has an impact on the health and well-being of individuals with self-reported “electrosensitivity” and of participants who served as controls. Methods Fifty-one individuals with self-reported electrosensitivity and 132 age- and sex-matched controls participated in an open provocation test; 48 sensitive and 132 control participants went on to complete double-blind tests in a fully screened semianechoic chamber. Heart rate, skin conductance, and blood pressure readings provided objective indices of short-term physiological response. Visual analog scales and symptom scales provided subjective indices of well-being. Results We found no differences on any measure between TETRA and sham (no signal) under double-blind conditions for either controls or electrosensitive participants, and neither group could detect the presence of a TETRA signal at rates greater than chance (50%). When conditions were not double blind, however, the self-reported electrosensitive individuals did report feeling worse and experienced more severe symptoms during TETRA compared with sham. Conclusions Our findings suggest that the adverse symptoms experienced by electrosensitive individuals are due to the belief of harm from TETRA base stations rather than to the low-level EMF exposure itself.

A semantic-enhanced trajectory visual analytics for digital forensic

With the increasing application of GPS devices, trajectory data have been frequently adopted in digital forensics because it can encompass spatial and temporal aspects of suspects’ movements. However, a lack of semantic information causes difficulty of linking the trajectories with the activities of suspects. Using the situation of a kidnapping, this paper proposes a semantic-enhanced method in trajectory analysis, which categorizes the daily activities of suspects into different semantic types by connecting trajectory data with transaction data. In the meantime, we present an interactive visualization system with four inner-linked views to provide a collaborative visual analytics of trajectory and transaction data in multiple perspectives. In the case study, the kidnapping investigation is used to demonstrate how the system works on the routine pattern analysis of suspects, the detection of abnormal behaviors, and the association exploration among suspects and their abnormal behaviors.Graphical abstract

Ultrabroadband Wireless–Optical Transmission Links Using Axial Slot Leaky Feeders and Optical Fiber for Underground Transport Topologies

This paper describes a hybrid leaky feeder/fiber-optic transmission system for use in underground transportation networks. The system has a 1.6-Gb/s throughput and features an ultrawideband axial slot leaky feeder, which is based on a standard semirigid coaxial cable as a fixed antenna. Patch antennas with a 4-GHz center frequency and a 1-GHz, -10-dB bandwidth are proposed for the rolling stock. This highest reported data rate was achieved by combining two 800-Mb/s in-phase and quadrature (I and Q) phase-shift keying (PSK) modulated data streams. A specially designed carrier and data synchronization system provided a convenient interface to a 1.3/1.5-mum diplex single-mode fiber-remoting network. The measured 2.4- to 6-GHz leaky feeder bandwidth allows multiradio multiband wireless mesh networking and, therefore, low-contention gigabit rolling stock data communications.

A complete 5 Gb/s throughput quadrature subcarrier system featuring zero-latency carrier and data synchronization

We have demonstrated a complete quadrature subcarrier system with 5 Gb/s throughput suitable for within-building multimode fibre applications. By using a 5.1 GHz pilot tone and referencing the data to a prescaled version of the carrier, a zero-latency synchronisation scheme has been realised which is scaleable to higher data rates and upgrades to existing infrastructure.

Bi-directional, 480Mbps, ultra-wideband, radio-over-fibre transmission using a 1310/1564nm reflective electro-absorption transducer and commercially-available components

We present the first experimental demonstration of a bi-directional, reflective, electro-absorption transducer-based, 480 Mbps UWB-wireless/optical transmission system. A -21.4 dB error vector magnitude was observed over 1 km of single mode fibre.

HACH: Heuristic Algorithm for Clustering Hierarchy protocol in wireless sensor networks☆

Wireless sensor networks (WSNs) require energy management protocols to ef ciently use the energy supply constraints of battery-powered sensors to prolong its network lifetime. This paper proposes a novel Heuristic Algorithm for Clustering Hierarchy (HACH), which sequentially performs selection of inactive nodes and cluster head nodes at every round. Inactive node selection employs a stochastic sleep scheduling mechanism to determine the selection of nodes that can be put into sleep mode without adversely a ecting network coverage. Also, the clustering algorithm uses a novel heuristic crossover operator to combine two di erent solutions to achieve an improved solution that enhances the dis- tribution of cluster head nodes and coordinates energy consumption in WSNs. The proposed algorithm is evaluated via simulation experiments and compared with some existing algorithms. Our protocol shows improved performance in terms of extended lifetime and maintains favourable performances even under di erent energy heterogeneity settings.

A new approach for event detection using k-means clustering and neural networks

In composite event detection systems such as fire alarms, the two foremost goals are speed and accuracy. One way to achieve these goals is by performing data aggregation at central nodes. This helps reduce energy consumption and redundancy. In this paper we present a new hybrid approach that involves the use of k-means algorithm with neural networks, an efficient supervised learning algorithm that extracts patterns and detects trends that are hidden in complex data. Previous research on event detection concentrates majorly on the use of feed forward neural network and other classifiers such as naive Bayes and decision tree alone for modern fire detection applications. In our approach presented here, we combine k-means with neural networks and other classifiers in order to improve the detection rate of event detection applications. To demonstrate our approach, we perform data aggregation on normalized multi-dimensional fire datasets in order to remove redundant data. The aggregated data forms two clusters which represent the two class labels (actual outputs) with the aid of k-means clustering. The resulting data outputs are trained by the Feed Forward Neural Network, Naive Bayes, and Decision Trees. This approach was found to significantly improve fire detection performance.

Low-power optical feeder for VDSL over twisted pair for last mile access networks

In this paper, we describe an ultra-low-power optoelectronic very-high-data-rate digital subscriber line (VDSL) system, enabling broadband access to the home over 10 km of optical fiber and 1 km of twisted pair. The cabinet/distribution point interface has a footprint of just 3 /spl times/ 3 /spl times/ 1 cm, and consumes only 165 mW. A quadrature-amplitude-modulation (QAM) scheme was used for system tests with 10 Mb/s full duplex achieved, and up to 40-dB up/downstream channel isolation is obtained using hybrid transformers.

480Mbit/s UWB bi-directional radio over fiber CWDM PON using ultra-low cost and power VCSELs

Radio-over-fiber (RoF) schemes offer the possibility of permitting direct access to native format services for the domestic user. A low power requirement and cost effectiveness are crucial to both the service provider and the end user. Here, we present an ultra-low cost and power RoF scheme using direct modulation of commercially-available 1344 nm and 1547 nm VCSELs by band-group 1 UWB wireless signals (ECMA-368) at near broadcast power levels. As a result, greatly simplified electrical-optical-electrical conversion is accomplished. A successful demonstration over a transmission distance of 20.1 km is described using a SSMF, CWDM optical network. EVMs of better than -18.3 dB were achieved.