Stevan Jovica Marinkovic

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.

Power management techniques for Wireless Sensor Networks: A review

During recent years, Wireless Sensor Networks captured the imagination of many researchers with number of applications growing rapidly. Power consumption is (most often) the dominant constraint in designing such systems. This constraint has multi-dimensional implications such as battery type and size, energy harvester design, lifetime of the deployment, etc. Energy neutral system implementation is the ultimate goal in wireless sensor networks and represents a hot topic of research. Several recent advances promise significant reduction of the overall sensor network power consumption. These advances include novel sensors and sensor interfaces, low power wireless transceivers, low power processing, etc. Power optimization techniques have to explore a large design search space. This paper reviews a number of system level power management methodologies for Wireless Sensor Networks which use ultra low power wake-up radio receivers.

Nano-power Wake-Up Radio circuit for Wireless Body Area Networks

We developed, implemented and tested a Nano-power Wake Up Radio mainly intended for Wireless Body Area Networks (WBANs), but it can be also used in other types of low power wireless networks. The radio was tested for power consumption and robustness to communication interferences from a wireless devices commonly found around the person carrying a WBAN. Results show that our radio has significantly lower power consumption when idle listening (470nW) than other state-of-the-art radios. We also developed passive filtering method that can, along with our preamble detection method, significantly reduce power for false wake ups in a WBAN.

Network Coding for Efficient Error Recovery in Wireless Sensor Networks for Medical Applications

Modern medical wireless systems present a challenge where communication reliability is crucial, but the resources are limited, since medical devices carried on a patient need to be small. We propose, simulate and analyze one relay network, and show that network coding along with redundancy can be used as a very efficient error recovery mechanism that greatly improves network reliability at very low computational and hardware cost. Thus, network coding can be an interesting method for reliability improvement in medical systems such as Wireless Body Area Networks (WBAN). A network coding scheme is proposed and simulated, and the optimal method according to that scheme is analyzed. Practical and fast decoding algorithm is presented. We then simulate the proposed network and the optimal method and compare it with the regular redundant network. Simulations show great improvement compared to regular redundant transfer, for very small computational cost. Finally, we simulate and show that the proposed network is still functional and operational even in case where one relay point is off.

Wake-up radio receiver based power minimization techniques for wireless sensor networks

In a short period of time Wireless Sensor Networks (WSN) captured the imagination of many researchers with the number of applications growing rapidly. The applications span large domains including mobile digital health, structural and environmental monitoring, smart home, energy efficient buildings, agriculture, smart cities, etc. WSN are also an important contributor to the fast emerging Internet of Things infrastructure. Some of the design specifications for WSN include reliability, accuracy, cost, deployment versatility, power consumption, etc. Power consumption is (most often) the dominant constraint in designing such systems. This constraint has multi-dimensional implications such as battery type and size, energy harvester design, lifetime of the deployment, intelligent sensing capability, etc. Power optimization techniques have to explore a large design search space. Energy neutral system implementation is the ultimate goal in wireless sensor networks ensuring a perpetual/greener use and represents a hot topic of research. Several recent advances promise significant reduction of the overall sensor network power consumption. These advances include novel sensors and sensor interfaces, low energy wireless transceivers, low power processing, efficient energy harvesters, etc. This paper reviews a number of system level power management methodologies for Wireless Sensor Networks. Especially, the paper is focusing on the promising technology of nano-Watt wake-up radio receiver and its combination with mature power management techniques to achieve better performance. Some of the presented techniques are then applied in the context of low cost and battery powered toy robots.

Ultra low power signal oriented approach for wireless health monitoring.

In recent years there is growing pressure on the medical sector to reduce costs while maintaining or even improving the quality of care. A potential solution to this problem is real time and/or remote patient monitoring by using mobile devices. To achieve this, medical sensors with wireless communication, computational and energy harvesting capabilities are networked on, or in, the human body forming what is commonly called a Wireless Body Area Network (WBAN). We present the implementation of a novel Wake Up Receiver (WUR) in the context of standardised wireless protocols, in a signal-oriented WBAN environment and present a novel protocol intended for wireless health monitoring (WhMAC). WhMAC is a TDMA-based protocol with very low power consumption. It utilises WBAN-specific features and a novel ultra low power wake up receiver technology, to achieve flexible and at the same time very low power wireless data transfer of physiological signals. As the main application is in the medical domain, or personal health monitoring, the protocol caters for different types of medical sensors. We define four sensor modes, in which the sensors can transmit data, depending on the sensor type and emergency level. A full power dissipation model is provided for the protocol, with individual hardware and application parameters. Finally, an example application shows the reduction in the power consumption for different data monitoring scenarios.

Implementation and testing of a secure fall detection system for Body Area Networks

As the average age of the people in the Western world increases, so does the number of orthopaedic medical treatments due to falls. A method for better treatment of this type of injuries consists of early and accurate fall detection. We present an implementation and test of the system for accurate fall detection. First, a number of tests were performed to get thresholds for distinguishing falls from fall-like or normal behaviour. Then, the algorithm was implemented and tested on Biomobius, a technology platform, which allows researcher to rapidly develop sophisticated technology solutions for biomedical research. Sensors for gathering the acceleration data were part of the Tyndall Mote, a wireless sensor platform designed at Tyndall National Institute, Cork. Data is transmitted wirelessly to the PC. Therefore, since security has to be also considered in such medical systems, an encryption system is also implemented and tested on a low power microprocessor.

Combined methods to extend the lifetime of power hungry WSN with multimodal sensors and nanopower wakeups

During recent years, there has been a growing interest on wireless sensor networks (WSNs) and on the opportunities opened by this technology. Since the energy consumption is a bottleneck in WSNs, reducing it has a significant impact on the applicability of this technology. Typically, the energy consumed by wireless communication and by power-hungry sensors as CMOS imagers or Gas sensors, is dominant over the power required for computation or other activities of the node. Hence, an efficient management of the resources leading to a reduction of unnecessary communication and minimizing the use of power-hungry sensor while keeping the same performance is desirable to extend the life-time of the network. In this paper we address the challenges of exploiting wake-up receivers and heterogeneous sensors in WSN applications to reduce the average power consumption of individual nodes. In particular, we show how to configure a WSN which includes Pyroelectric InfraRed (PIR) sensors, smart camera sensors and a nano-Watt wake up radio as secondary radio receiver to efficiently extend the autonomy of the system. The evaluation of the proposed approach shows a significant reduction of the activity of the primary radio and of the high power sensor while keeping the same accuracy. We prototyped and tested the nodes, and used their characterization to demonstrate through simulations the power consumption reduction and the life-time extension of the network in a typical surveillance application.