Emanuel M. Popovici

Energy-Efficient Low Duty Cycle MAC Protocol for Wireless Body Area Networks

This paper presents an energy-efficient medium access control protocol suitable for communication in a wireless body area network for remote monitoring of physiological signals such as EEG and ECG. The protocol takes advantage of the static nature of the body area network to implement the effective time-division multiple access (TDMA) strategy with very little amount of overhead and almost no idle listening (by static, we refer to the fixed topology of the network investigated). The main goal is to develop energy-efficient and reliable communication protocol to support streaming of large amount of data. TDMA synchronization problems are discussed and solutions are presented. Equations for duty cycle calculation are also derived for power consumption and battery life predictions. The power consumption model was also validated through measurements. Our results show that the protocol is energy efficient for streaming communication as well as sending short bursts of data, and thus can be used for different types of physiological signals with different sample rates. The protocol is implemented on the analog devices ADF7020 RF transceivers.

Nano-Power Wireless Wake-Up Receiver With Serial Peripheral Interface

We designed, implemented, tested and measured an ultra low power Wake Up Receiver (WUR), intended for use in Wireless Body Area Networks (WBAN). Gaussian On-Off Keying (GOOK) and Pulse Width Modulation (PWM) are used to modulate and encode, respectively, the preamble signal. The receiver incorporates a decoder to enable Serial Peripheral Interface (SPI). WUR was also comprehensively tested for power consumption and robustness to RF interference from wireless devices commonly found in the vicinity of persons utilising WBAN technology. Our results and comparative evaluation demonstrate that the achieved listening power of 270nW for the Wake Up Receiver is significantly lower power consumption than for the other state-of-the-art. The proposed preamble detection scheme can significantly reduce false wake ups due to other wireless devices in a WBAN. Additionally, SPI significantly reduces the overall power consumption for packet reception and decoding.

Energy-Efficient TDMA-Based MAC Protocol for Wireless Body Area Networks

Body Area Networks (BAN) are a specific type of Network structure. They are spread over a very small area and their available power is heavily constrained. Hence it is useful to have gateway points in the network, such as nodes carried around the belt, that are less power constrained and can be used for network coordination. This network structure can result in very low transmission power/range for the sensors and effective TDMA timing control. This paper presents an energy-efficient MAC protocol for communication within the Wireless Body Area Network. The protocol takes advantage of the fixed nature of the Body Area Network to implement a TDMA strategy with very little communication overhead, long sleep times for the sensor transceivers and robustness to communication errors. The protocol is implemented on the Analog Devices ADF7020 RF transceivers.

An FPGA implementation of a GF(p) ALU for encryption processors

Abstract Secure electronic and internet transactions require public key cryptosystems to establish and distribute shared secret information for use in the bulk encryption of data. For security reasons, key sizes are in the region of hundreds of bits. This makes cryptographic procedures slow in software. Hardware accelerators can perform the computationally intensive operations far quicker. Field-Programmable Gate Arrays are well-suited for this application due to their reconfigurability and versatility. Elliptic Curve Cryptosystems over GF( p ) have received very little attention to date due to the seemingly more attractive finite field GF(2 m ). However, we present a GF( p ) Arithmetic Logic Unit which can perform 160-bit arithmetic at clock speeds of up to 50 MHz.

Extended Wireless Monitoring Through Intelligent Hybrid Energy Supply

This paper presents the design, implementation, and characterization of a hardware platform applicable to wireless structural health monitoring (WSHM). The primary design goal is to devise a system capable of persistent operation for the duration of the life cycle of a target structure. It should be deployable during the construction phase and reconfigurable thereafter, suitable for continuous long-term monitoring. In addition to selecting the most energy efficient useful components to ensure the lowest possible power consumption, it is necessary to consider sources of energy other than, or complementary to, batteries. Thus, the platform incorporates multisource energy harvesting, electrochemical fuel cell (FC), energy storage, recharging capability, and intelligent operation through real-time energy information exchange with the primary controller. It is shown that, with appropriate integration, the device will have sufficient energy to operate perpetually in a distributed WSHM application. This conclusion is demonstrated through experimental results, simulations, and empirical measurements that demonstrate the high-efficiency energy conversion of the harvesters (up to 86%) and low-power characteristics of the platform (less than 1 mW in sleep mode). It is shown that energy autonomy is comfortably achievable for duty cycles up to 0.75%, meeting the demands of the application, and up to 1.5%, invoking the FC.

A Low Cost, Highly Scalable Wireless Sensor Network Solution to Achieve Smart LED Light Control for Green Buildings

Reducing energy demand in the residential and industrial sectors is an important challenge worldwide. In particular, lights account for a great portion of total energy consumption, and unfortunately a huge amount of this energy is wasted. Light-emitting diode (LED) lights are being used to light offices, houses, industrial, or agricultural facilities more efficiently than traditional lights. Moreover, the light control systems are introduced to current markets, because the installed lighting systems are outdated and energy inefficient. However, due to high costs, installation issues, and difficulty of maintenance; existing light control systems are not successfully applied to home, office, and industrial buildings. This paper proposes a low cost, wireless, easy to install, adaptable, and smart LED lighting system to automatically adjust the light intensity to save energy and maintaining user satisfaction. The system combines motion sensors and light sensors in a low-power wireless solution using Zigbee communication. This paper presents the design and implementation of the proposed system in a real-world deployment. Characterization of a commercial LED panel was performed to evaluate the benefit of dimming for this light technology. Measurements of total power consumption over a continuous six months period (winter to summer) of a busy office were acquired to verify the performance and the power savings across several weather conditions scenarios. The proposed smart lighting system reduces total power consumption in the application scenario by 55% during a six month period and up to 69% in spring months. These figures take also into account individual user preferences.

Efficient hardware for the tate pairing calculation in characteristic three

In this paper the benefits of implementation of the Tate pairing computation on dedicated hardware are discussed. The main observation lies in the fact that arithmetic architectures in the extension field GF(36m) are good candidates for parallelization, leading to a similar calculation time in hardware as for operations over the base field GF(3m). Using this approach, an architecture for the hardware implementation of the Tate pairing calculation based on a modified Duursma-Lee algorithm is proposed.

Hardware Implementation of

Low density parity check (LDPC) codes over GF(2m) are an extension of binary LDPC codes with significantly higher performance. However, the computational complexity of the encoders/decoders for these codes is also higher. Hence there is a substantial lack of hardware implementations for LDPC over GF(2m) codes. This paper proposes a novel variation of the belief propagation algorithm for GF(2m) LDPC codes. The new algorithm results in a reduced hardware complexity when implemented in VLSI. The serial architecture of the novel decoding algorithm and two other algorithms for LDPC over GF(2m) are implemented on an FPGA. The results show that the proposed algorithm has substantial advantages over existing methods. We show that the implementation of LDPC over GF(2m) decoder is feasible for short to medium length codes. The additional complexity of the decoder is balanced by the superior performance of GF(2m) LDPC codes.

{\rm GF}(2^{m})

Nodes in wireless sensor networks (WSNs) typically have limited power supply and networks are often expected to be functional for extended periods. Therefore, the minimization of energy consumption and the maximization of network lifetime are key objectives in WSN. This paper proposes an overlay, energy optimized, sensor network to extend the functional lifetime of an energy-intensive sensor network application. The overlay network consists of additional nodes that exploit recent advances in energy harvesting and wake-up radio technologies, coupled with an application specific, complementary, ultra-low power sensor. The experimental results and simulations demonstrate that this approach can ensure survivability of energy-inefficient sensor networks. Simulating applications using energy-intensive video cameras and air quality sensors, combined with the proposed overlayed ultra-low power sensor network, demonstrates that this approach can increase functional lifetime toward perpetual operation and is suitable for WSN applications in which complementarity exists between the required energy-intensive sensors and low-cost sensors that can be used as triggers.

LDPC Decoders

This paper presents the design, implementation and characterization of an energy-efficient smart power unit for a wireless sensor network with a versatile nano-Watt wake up radio receiver. A novel Smart Power Unit has been developed featuring multi-source energy harvesting, multi-storage adaptive recharging, electrochemical fuel cell integration, radio wake-up capability and embedded intelligence. An ultra low power on board microcontroller performs maximum power point tracking (MPPT) and optimized charging of supercapacitor or Li-Ion battery at the maximum efficiency. The power unit can communicate with the supplied node via serial interface (I2C or SPI) to provide status of resources or dynamically adapt its operational parameters. The architecture is very flexible: it can host different types of harvesters (solar, wind, vibration, etc.). Also, it can be configured and controlled by using the wake-up radio to enable the design of very efficient power management techniques on the power unit or on the supplied node. Experimental results on the developed prototype demonstrate ultra-low power consumption of the power unit using the wake-up radio. In addition, the power transfer efficiency of the multi-harvester and fuel cell matches the state-of-the-art for Wireless Sensor Networks.