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Publications

Publications by CTM

2011

Network infrastructure extension using 802.1D-based wireless mesh networks

Authors
Campos, R; Duarte, R; Sousa, F; Ricardo, M; Ruela, J;

Publication
WIRELESS COMMUNICATIONS & MOBILE COMPUTING

Abstract
Ubiquitous Internet access is becoming a major requirement for end-users due to the increasing number of services and applications supported over the Internet. Extending the coverage of current Wi-Fi infrastructures installed in companies, universities and cities, has been considered a solution to help in fulfilling this requirement, namely when it comes to wireless and nomadic Internet access. This paper describes and analyses a new and simple solution, called Wi-Fi network Infrastructure eXtension (WiFIX), aimed at extending current Wi-Fi infrastructures. WiFIX is based on standard IEEE 802.1D bridges and a single-message protocol that is able to self-organize the network, and it only requires software changes in IEEE 802.11 access points (APs); no changes to IEEE 802.11 stations are needed. Overhead analysis and experimental results show both the higher efficiency of the solution compared to the IEEE 802.11s draft standard and its good performance as far as data throughput, delay and packet loss are concerned. Copyright (C) 2010 John Wiley & Sons, Ltd.

2011

Developing aircraft photonic networks - An overview of the European DAPHNE project

Authors
Proudley, GM; Brownjohn, N; Baptista, J; Bacou, A; Salgado, HM; Clausen, A; Deimel, P; Farries, M; Gauchy, S; Kopacek, I; Lee, A; Napier, B; Traversone, M; Vincent, J; Zimmermann, A;

Publication
2011 IEEE Avionics, Fiber- Optics and Photonics Technology Conference, AVFOP 2011

Abstract
DAPHNE (Developing Aircraft PHotonic NEtworks) is a 3-year European FP7 project (started September 2009). The aim of DAPHNE is to exploit terrestrial optical networking technology (with associated performance advantages) in future aircraft and systems. The consortium comprises fifteen partners (from seven nations) ranging from major air framers (both fixed and rotary wing) through component and equipment manufacturers and leading European universities. The project is coordinated by Airbus. © 2011 IEEE.

2011

Signal Processing Techniques for Transmission Impairments Compensation in Optical Systems

Authors
Oliveira, JMB; Pessoa, LM; Salgado, HM; Darwazeh, I;

Publication
2010 12TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)

Abstract
We discuss recent developments in signal processing techniques for post-compensation of fiber dispersion and nonlinear distortion in both coherent and radio-over-fiber optical systems.

2011

Compact Printed Monopole Antenna With Chip Inductor for WLAN

Authors
Luo, Q; Pereira, JR; Salgado, HM;

Publication
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS

Abstract
One compact printed monopole antenna with a chip inductor for dual-band WLAN is presented. The proposed antenna has a two-armed structure and an electrically small size. The equivalent circuit structure of the chip inductor is studied and a simplified circuit structure is proposed. This simplified circuit structure was introduced into the electromagnetic (EM) simulation model by assigning a boundary condition, and the experimental results show that with this model, the simulation can provide an accurate prediction of the antenna radiation performance. The measurement results show that the proposed monopole antenna has a VSWR 2: 1 bandwidth over 2.41-2.49 and 5.2-5.6 GHz with omnidirectional radiation patterns. The simulation results suggest that the proposed antenna has a directivity around 1.5 dB at both bands with relatively high radiation efficiency. The antenna is designed and optimized by using Ansoft HFSS.

2011

A Photon Counting Estimates Distribution of the Average Number of Photons in Coherent Pulses

Authors
De Sousa e Castro, JCDE; Salgado, HM;

Publication
2011 13TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)

Abstract
A statistical model linking the probability of detecting photons in a photon counting experiment to the average number of input photons is used to analytically derive an error distribution of the estimates of the average number of photons in coherent input pulses. The estimates distribution determines the required number of experimental count runs required for an acceptable measurement error, for any value of the average number of input photons. An expression for the minimum detectable power by photon counting is obtained, fully capturing the effect of the photon counting statistics thereby completing an earlier analysis.

2011

Clock Recovery of an Injection-Locked Resonant Tunneling Diode Microwave-Photonics Oscillator

Authors
Romeira, B; Pessoa, LM; Salgado, HM; Silva, S; Figueiredo, JML;

Publication
2011 13TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)

Abstract
We show experimental results of clock recovery from return-to-zero (RZ) format data by using injection locking of a free-running optoelectronic oscillator (OEO) circuit, which consists of a resonant tunneling diode (RTD) oscillator integrated circuit with both a detector and optical source. Error free extraction of a clock signal from the RTD-OEO is shown under both optical and electrical injection. The clock recovery performance at similar to 1.25 Gb/s is analyzed in terms of timing jitter, phase noise and locking bandwidth.

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