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Publications

Publications by CTM

2009

Performance Analysis of Joint Radio Resource Management Strategies for Beyond 3G Networks

Authors
Del Monego, HI; Oliveira, JM; Ricardo, M;

Publication
THIRD INTERNATIONAL CONFERENCE ON NEXT GENERATION MOBILE APPLICATIONS, SERVICES, AND TECHNOLOGIES, PROCEEDINGS

Abstract
In beyond 3G networks the user will not be aware of the access network technology used to provide a telecommunications service. Heterogeneous network technologies will be seamlessly integrated in one "common" access network, enabling users to move around and continuously receive their subscribed services. In a commercial environment, this network evolution requires that a telecommunications operator jointly manages its networks resources to improve the service offered to the users and, at the same time, to increase its revenue. Starting from the UMTS and WLAN interconnection architecture defined by 3GPP, this paper analyzes the performance of a new joint radio resource management strategy, comparing it with two well-known strategies used in scenarios where both networks, the UMTS and the WLAN, are interconnected. The new strategy presented in the paper bases its decisions on criteria related to user mobility characteristics and the application characteristics. The strategy also introduces the possibility of renegotiating new calls and reallocating running calls from one access network to another. The performance analysis considers two traffic scenarios. One where only real-time applications are running and other which also introduces TCP applications. The comparison studies show the proposed strategy outperforms the other strategies in what concerns call blocking probability and applications QoS support. Besides, the proposed strategy tends to reduce the handoffs between networks.

2009

HEADER COMPRESSED VOIP IN IEEE 802.11

Authors
Fortuna, P; Ricardo, M;

Publication
IEEE WIRELESS COMMUNICATIONS

Abstract
Header compression techniques such as robust header compression can be used to reduce the overhead of IP-based traffic. Voice over IP may replace voice circuits in the next generations of wireless networks, and it is the type of traffic that benefits most from header compression because its packets have small pay-loads, IEEE 802.11 is a technology that will play an important role in the next generations of wireless networks. The study reported in this article shows that the maximum gain of the RoHC's U-mode when applied to VoIP over IEEE 802.11. is about 23 percent for medium or better voice quality. Values for the RoHC U-mode parameters over IEEE 802.11 are also suggested.

2009

Influence of parasitic capacitances in modeling and analysis of advanced floating gate memory devices

Authors
Moreira, A; Da Silva, JM; Tao, G;

Publication
Proceedings of the International Symposium on the Physical and Failure Analysis of Integrated Circuits, IPFA

Abstract
In this paper, we report the impact of the parasitic capacitances in the modeling and analysis of advanced floating gate (FG) non-volatile memory (NVM) devices, especially on the coupling ratio. Due to the poor accuracy of the existing capacitance model when compared to practice, an approach to include the parasitic capacitances has been established. Measurement results from two transistor (2T) Fowler-Nordheim (FN) tunneling operated flash memory show a good improvement in the model accuracy. The parasitic capacitances depend very much on the floating gate dimension, and the spacing to the neighboring elements in the flash cell array. The growing influence of the parasitic capacitances and the subsequent degradation of the existing model accuracy can be expected for the cells dimensions in future process technologies. With the accurate calculation method for the parasitic capacitances proposed in this paper, the cell characteristics can be more accurately modeled, andthe degradation of the cell can be accurately studied. ©2009 IEEE.

2009

ESTIMATION OF RF PA NONLINEARITIES AFTER CROSS-CORRELATING POWER SUPPLY CURRENT AND OUTPUT VOLTAGE

Authors
Veiga, R; Mota, P; da Silva, JM;

Publication
2009 IEEE 15TH INTERNATIONAL MIXED-SIGNALS, SENSORS, AND SYSTEMS TEST WORKSHOPS

Abstract
The present paper describes developments carried-out on estimating 1 dB compression and third-order intercept points after the cross-correlation between power supply dynamic current and output voltage of radio-frequency power amplifier. The underlining theory and a circuit that allows implementing this measurement on-chip are presented. Simulation results, including the analysis of optimum stimuli amplitudes and the Monte Carlo analysis to circuits' process variations are presented. These show that good accuracy can be obtained with relatively simple measurement conditions.

2009

Remote Patient Monitoring in Home Environments

Authors
Goncalves, P; Torres, J; Sobral, P; Moreira, R;

Publication
MOBILIZING HEALTH INFORMATION TO SUPPORT HEALTHCARE-RELATED KNOWLEDGE WORK

Abstract
The humanity is currently facing the difficulties of an aged society with an ever-growing predominance of chronic diseases and associated problems (e.g., mobility issues, possibility of falls, etc.). Traditional hospital or clinical internment is not an efficient answer both in terms of human, therapeutic or economical aspects. Alternatively, ambulatory and home healthcare are becoming preferred and predominant solutions. However, the typical home environment is not suited nor prepared for monitoring and helping to take care of elderly and/or disabled people. To overcome some of these issues, this paper proposes a wireless low cost hardware solution based on a microcontroller with several sensors (cf. temperature, oxymeter, 3-axis accelerometer) which allows monitoring several physiological parameters (e.g., temperature, heart bit, etc.) and infer human activities (e.g., standing, walking, falling, etc.) of home confined people. A similar platform with ambient temperature and light sensors was also created for monitoring the home environment. The collected data is pre-processed on the sensor nodes and then transmitted to a wireless gateway allowing the backend system to log the patient activity, his health condition as well as the living surroundings. Finally, a web application is provided to healthcare professionals for viewing, analyzing and statistically operating this information, thus empowering homecare.

2009

An interactive table: Comparison of vision algorithms for the detection of interactions [Um quadro interactivo: comparação de algoritmos de visão para detecção de interacções]

Authors
Soares, C; Torres, JM; Sobral, P; Moreira, RS;

Publication
Actas da 4a Conferencia Iberica de Sistemas e Tecnologias de Informacao, CISTI 2009

Abstract

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