F. Hernandez

A transmission power self-optimization technique for wireless sensor networks

Wireless sensor networks (WSNs) are generally used to monitor hazardous events in inaccessible areas. Thus, on one hand, it is preferable to assure the adoption of the minimum transmission power in order to extend as much as possible the WSNs lifetime. On the other hand, it is crucial to guarantee that the transmitted data is correctly received by the other nodes. Thus, trading off power optimization and reliability insurance has become one of the most important concerns when dealing with modern systems based on WSN. In this context, we present a transmission power self-optimization (TPSO) technique for WSNs. The TPSO technique consists of an algorithm able to guarantee the connectivity as well as an equally high quality of service (QoS), concentrating on the WSNs efficiency (Ef ), while optimizing the transmission power necessary for data communication. Thus, themain idea behind the proposed approach is to trade offWSNs Ef against energy consumption in an environment with inherent noise. Experimental results with different types of noise and electromagnetic interference (EMI) have been explored in order to demonstrate the effectiveness of the TPSO technique.

Measuring clock-signal modulation efficiency for Systems-on-Chip in electromagnetic interference environment

As IC technology scales down, signal integrity issues such as power supply noise and clock skews are becoming one of the major concerns of gigahertz system-on-chip (SoC) design. Considering that one of the most important mechanisms to degrade signal integrity is electromagnetic interference (EMI), this paper analyzes the effectiveness of a clock duty-cycle (CDC) modulation technique to enhance SoC signal integrity with respect to power/ground voltage transients induced by EMI. The technique is based on a clock stretching logic (CSL) block, which monitors abnormal power grid activity and increases CDC accordingly. Practical experiments based on the implementation of a 32-bit soft-core pipeline processor in an FPGA IC were performed and illustrate the circuit robustness enhancement to power line fluctuations while maintaining at-speed clock rate. These experiments were conducted according to the IEC 62.132-2. Normative for measurement of radiated electromagnetic immunity (TEM-cell method).

Evaluating the Effects of Combined Total Ionizing Dose Radiation and Electromagnetic Interference

Although measurement methods for Electromagnetic (EM) immunity and Total Ionizing Dose (TID) radiation are highly standardized, little effort has been made though, to evaluate the behavior of embedded systems under the combined effects. Considering realistic environment conditions only the measurement of these effects can guarantee reliable embedded systems for critical applications. A configurable platform to evaluate the effects of TID radiation and EM Interference (EMI) on embedded systems is presented. Experiments illustrate the consequences regarding delay and fault occurrence probability as well as current consumption and minimum power supply.

Experimental assessment of using network coding and cooperative diversity techniques in IEEE 802.15.4 wireless sensor networks

The use of wireless sensor networks (WSN) to support critical monitoring applications is becoming a relevant topic of interest. These networks allow a highly flexible approach to data monitoring and, consequently, a major breakthrough for several application domains, from industrial control applications to large building domotics and health care applications. One of the major impairments of using wireless networks to support critical monitoring applications is the electromagnetic noise, which may increase the packet loss ratio to unacceptable values. In this paper, we assess different techniques of cooperative communication and network coding that can be useful to mitigate the aforementioned problem. These techniques may be implemented in WSN nodes in conformance with the IEEE 802.15.4 standard, to reduce the impact of electromagnetic interferences upon the packet loss ratio. In this paper, we report an experimental assessment of the network coding and cooperative diversity techniques, where the network is subjected to a controlled electromagnetic interference inside of an anechoic chamber. The experimental results show that, by using these techniques, it is possible to increase the success rate of communication in typical electromagnetic noisy environments.

Configurable platform for IC combined tests of total-ionizing dose radiation and electromagnetic immunity

The roadmap for standardization of electromagnetic (EM) immunity measurement methods has reached a high degree of success with the IEC 62.132 proposal. The same understanding can be taken from the MIL-STD-883H for total ionizing dose (TID) radiation. However, no effort has been performed to measure the behavior of electronics operating under the combined effects of both, EM noise and TID radiation. For secure embedded systems and systems-on-chip (SoC) devoted to critical applications, these combined-effect measurements are mandatory. In this paper, we present a configurable platform devoted for combined tests of EM immunity and TID radiation measurements of prototype embedded systems. The platform attends the IEC 62.132–2 (for radiated EM noise), IEC 61.0004–17 and IEC 61.0004–29 (for conducted EM disturbance) and 1019.8 method for TID Test Procedure of MIL-STD-883H.

Evaluating a Transmission Power Self-Optimization Technique for WSN in EMI Environments

Wireless Sensor Networks (WSNs) can be used to monitor hazardous and inaccessible areas. The WSN is composed of several nodes each provided with its separated power supply, e.g. battery. Working in hardly accessible places it is preferable to assure the adoption of the minimum transmission power in order to prolong as much as possible the WSN’’s lifetime. Though, we have to keep in mind that the reliability of the data transmitted represents a crucial requirement. Therefore, power optimization and reliability have become the most important concerns when dealing with modern systems based on WSN. In this context, we propose to evaluate the effectiveness of a Transmission Power Self-Optimization (TPSO) technique for WSNs in an Electromagnetic Interference (EMI) Environment. The TPSO technique consists of an algorithm able to guarantee an equally high Quality of Service (QoS), concentrating on the WSN’’s Efficiency (Ef), while optimizing the transmission power necessary for data communication. Thus, the main idea behind our approach is to reach a trade-off between Ef and energy consumption in an environment with inherent noise.

Evaluating the use of a platform for combined tests of total ionizing dose radiation and Electromagnetic immunity

Although measurement methods for Electromagnetic (EM) immunity and Total Ionizing Dose (TID) radiation are highly standardized, no effort has been made to evaluate the behavior of embedded systems under the combined effects. Considering realistic environment conditions only the measurement of these effects can guarantee reliable embedded systems for critical applications. A configurable platform to evaluate the effects of TID radiation and EM Interference (EMI) on embedded systems is presented. Experiments illustrate the consequences regarding delay and fault occurrence probability as well as current consumption and minimum power supply.

Power-supply instability aware clock signal modulation for digital integrated circuits

As IC technology scales down, interconnect issues are becoming one of the major concerns of gigahertz system-on-chip (SoC) design. Voltage distortion (power supply noise) and delay violations (signal and clock skews) dramatically contribute to signal integrity loss. As a consequence, performance degradation, reliability problems and ultimately, functional error occur. In this paper, we propose a new methodology to enhance SoC signal integrity with respect to power/ground voltage transients, without degrading its performance. The underlying principle of the proposed methodology is to dynamically adapt the clock duty-cycle (CDC) according to the signal propagation delay through the logic whose power supply voltage is being disturbed. The methodology is based on a clock stretching logic (CSL) block, which monitors abnormal power grid activity and increases clock duty-cycle accordingly. Moreover, a model to accurately quantify CDC stretching as a function of VDD/Gnd fluctuations is proposed. Practical experiments based on the implementation of a 32-bit pipeline processor in a FPGA IC were performed and demonstrate the circuit robustness enhancement to power line fluctuations while maintaining at-speed clock rate.

Electromagnetic compatibility in active telephone sets

Dramatic growth has taken place in modern telecommunication equipment. AM and FM radio transmitter power is very high and it affects telephone set performance. In the worst case subscribers sited near transmission towers cannot hear the other talking party nor even dial the desired number. Usually they have to switch their sets to pulse dial mode in order to communicate. Three Mercosur Institutions (CITEI, IIE and ANTEL) have joint efforts to solve the problems existing in the PTTs outside plant (OSP). The results define measurement techniques and threshold values needed to achieve an adequate electromagnetic compatibility in active telephone sets and also determine a technical procedure for proper OSP construction. This paper describes the measurement techniques, test procedures and limits values used in the Mercosur region.