Estimating the quality of a link is a key primitive in WSNs, as upper layers use this piece of information in making performance-critical decisions. State-of-the-art estimators extract a single sample of the link state per packet. Thus, improving the accuracy through multiple samples requires multiple packets, resulting in a significant energy and traffic overhead and delay.To address this issue, this paper proposes Rep, a novel sampling scheme able to extract the link quality from the packet repetitions of low-power preamble sampling MACs. The experiments show that Rep reduces the energy and traffic used for link estimation by one order of magnitude, and increases the speed of the process by one order of magnitude, while maintaining state-of-the-art accuracy.

The WiseSkin project aims at creating artificial skin that allows human patients with prosthetic limbs to regain their sense of touch. The system in charge of transferring the tactile information is based on a wireless sensor network with stringent adaptability, latency, energy and rehability constraints. This paper proposes a communication protocol aimed at enabling the WiseSkin wireless sensor network to operate under these constraints. The proposed design was chosen following the comparative evaluation of several solutions for two key issues in event-triggered low power systems: i) the energy-latency tradeoff and ii) concurrent transmissions. The evaluation was based on both analytical models and testbed experiments. In conclusion, we propose the use of concurrent transmissions in event-driven multi-hop wireless sensor networks with sporadic traffic surges. The choice is mainly driven by its superior energy efficiency, compared to traditional collision avoiding schemes, a principle with general apphcabihty in the domain of Cyber-Physical Systems.

Radio Tomographic Imaging in Wireless Sensor Networks aims at locating people while using only a network of inexpensive nodes. This system already has enabled "see-through-walls" applications. Nevertheless, the vast majority of surveyed techniques use only the Received Signal Strength Indication as input information, while overlooking the Link Quality Indication.

Latest research in composite metrics has shown potential to improve the delivery rate and the power consumption of wireless sensor networks. Nevertheless, leveraging this potential in collection applications brings significant challenges such as: collecting multiple samples of the metric, isolating the quality of the uplink, and returning the link quality information to the nodes that need it for taking routing decisions. This work addresses these challenges by proposing a novel exploration mechanism: WiseNE. The results show that WiseNE can provide the link quality information required by the Triangle Metric (a promising composite metric). Moreover, they confirm this metric's potential to combine the strengths of the signal-to-noise ratio, the link quality indication and the packet reception ratio, for predicting the quality of the links, both inside an office and in outdoor environments. The study concludes that WiseNE can enable novel composite metrics and proposes a series of next steps in order to significantly reduce its control overhead.

The SFly project is an EU-funded project, with the goal to create a swarm of autonomous vision controlled micro aerial vehicles. The mission in mind is that a swarm of MAV's autonomously maps out an unknown environment, computes optimal surveillance positions and places the MAV's there and then locates radio beacons in this environment. The scope of the work includes contributions on multiple different levels ranging from theoretical foundations to hardware design and embedded programming. One of the contributions is the development of a new MAV, a hexacopter, equipped with enough processing power for onboard computer vision. A major contribution is the development of monocular visual SLAM that runs in real-time onboard of the MAV. The visual SLAM results are fused with IMU measurements and are used to stabilize and control the MAV. This enables autonomous flight of the MAV, without the need of a data link to a ground station. Within this scope novel analytical solutions for fusing IMU and vision measurements have been derived. In addition to the realtime local SLAM, an offline dense mapping process has been developed. For this the MAV's are equipped with a payload of a stereo camera system. The dense environment map is used to compute optimal surveillance positions for a swarm of MAV's. For this an optimiziation technique based on cognitive adaptive optimization has been developed. Finally, the MAV's have been equipped with radio transceivers and a method has been developed to locate radio beacons in the observed environment.

Network dynamics, such as mobility and increase in network load, can influence the performance of a Wireless Sensor Network (WSN). In this paper, we introduce a method which exploits design-time knowledge of the application scenario dynamics to construct a proactive run-time reconfiguration approach. The approach anticipates for the impact that predefined dynamic events can have on the performance of the WSN by switching between various modes of operation defined at design-time. A mode defines the values for the controllable parameters of the network protocol stack. Our approach explicitly differentiates between parameters that can be adapted locally, per node, and those that should be considered globally for the whole WSN. Design-time definition of modes results in a very low run-time overhead as we only require detection of the mode to use and a low overhead synchronization to change global parameters. The approach is made robust by using a recovery approach for nodes unaware of their global mode after, for example, (re-)joining the network. Experiments with an office monitoring deployment and extensive simulations of a cow-health monitoring scenario show that our approach can easily be adopted by practical WSN deployments and results in a significant reduction in resource usage, e.g., power consumption in our examples, at a very low run-time overhead cost.

New technologies can help to develop preventive healthcare, thereby leading to significant life quality improvements. Medical Body Area Networks are expected to become a key element in tomorrow's medical IT infrastructure by enabling the long term collection and analysis of health parameters. For this vision to become a reality, several challenges must be addressed. This work focuses on the technological aspects of ultra low power consumption, low latency and packet error rate. We consider and evaluate state of the art technologies currently under evaluation by the IEEE Standard Association 802.15.6 task group on body area networks, using detailed network simulation models, which have been calibrated with hardware measurements whenever possible and with MATLAB communication link simulations otherwise. We observe that the expected power consumption levels are similar for all considered platforms, and that they are determined mainly by the medium access control protocol. Trade-offs between communications latency, throughput and power consumption are identified. The performance of the Ultra Wideband Impulse Radio system is clearly impacted by its lack of carrier sensing capability. We conclude that the existing technologies are mature enough and that the remaing obstacles to widespread adoption are organizational and societal.

This poster presents an innovative dual-mode medium access control scheme that combines the ultra low power MAC protocol WiseMAC with the wireless sensor networking standard IEEE 802.15.4. Each network device can independently and autonomously switch between the two modes depending on its residual energy resources and the current application traffic. We observe that this approach can reduce the power consumption and the average latency by almost two orders of magnitude.

The IEEE 802.15.4 standard is gaining momentum in the field of wireless sensor networks. The IEEE 802.15.4A draft specification proposes an impulse radio ultra wide band physical layer. This technology aims at being robust against mul-tipath propagation and multi user interference. In the context of body area networks, the impact of multi user interference must be evaluated precisely. It is modeled here with the pulse collision model adapted to the draft standard. Numerical simulations show remarkable performance for communications between two distant groups of devices. While still acceptable, results were less encouraging when considering a large grid of devices. This suggests a sensitivity to near-far interference.

The WiseNET system includes an ultra low-power system-on-chip (SoC) hardware platform and WiseMAC, a low power medium access control protocol (MAC) dedicated to duty-cycled radios. Both elements have been designed to meet the specific requirements of wireless sensor networks and are particularly well suited to ad-hoc and hybrid networks. The WiseNET radio offers dual-band operation (434-MHz and 868-MHz) and runs from a single 1.5-V battery. It consumes only 2.5-mW in receive mode with a sensitivity smaller than−108-dBm at a BER of 10−3 and for a 100-kb/s data rate. In addition to this low-power radio, the WiseNET system-on-chip (SoC) also includes all the functions required for data acquisition, processing and storage of the information provided by the sensors. Ultra-low power consumption with the WiseNET system is achieved thanks to the combination of the low power consumption of the transceiver and the high energy efficiency of the WiseMAC protocol. The WiseNET solution consumes more than 250 times less power than comparable solutions based on the IEEE 802.15.4 standard.

Despite early attempts to use Ethernet in the industrial context, only recently has it attracted a lot of attention as a support for industrial communication. A number of vendors are offering industrial communication products based on Ethernet and TCP/IP as a means to interconnect field devices to the first level of automation. Others restrict their offer to communication between automation devices such as programmable logic controllers and provide integration means to existing fieldbuses. This paper first details the requirements that an industrial network has to fulfill. It then shows how Ethernet has been enhanced to comply with the real-time requirements in particular in the industrial context. Finally, we show how the requirements that cannot be fulfilled at layer 2 of the OSI model can be addressed in the higher layers adding functionality to existing standard protocols.

This work proposes wiseMAC(wireless sensor MAC) for the downlink of infrastructure wireless sensor networks. WiseMAC is a novel energy efficient medium access control protocol based on synchronized preamble sampling. The trade-off between power consumption and delay is analyzed, focusing on low traffic. WiseMAC is compared analytically with the power management protocol used in the IEEE 802.15.4 ZigBee standard. It is shown that WiseMAC can provide a significantly lower power consumption for the same delay.

WiseMAC is a medium access control protocol designed for the WiseNET™ wireless sensor network. It is based on CSMA and uses the preamble sampling technique to minimize the power consumed when listening to an idle medium. A unique feature of this protocol is to exploit the knowledge of the sampling schedule of its direct neighbors in order to use a wake-up preamble of minimized size. This scheme allows not only to reduce the transmit and the receive power consumption, but also brings a drastic reduction of the energy wasted due to overhearing. Backoff and medium reservation schemes have been selected to provide fairness and collision avoidance. WiseMAC requires no set-up signaling, no network-wide time synchronization and is adaptive to the traffic load. It provides an ultra-low average power consumption in low traffic conditions and a high energy efficiency in high traffic conditions.

This paper presents the delay performances of two-way transactions implemented on top of the Bluetooth HCI layer. The two-way transaction, formally called the Send Data with Acknowledge (SDA) service primitive, is a fundamental building block for real-time protocols. We analyze its delay performances under packet loss probability caused by a number of co-located interfering piconets. We first present a probabilistic treatment of the performance of a Bluetooth piconet under co-channel interference from other Bluetooth piconets. An upper bound on the packet error rate is analytically derived. Simulation results validating the theoretical results are shown. The obtained packet error rate bounds are then applied to the problem of deadline for two-way transactions. The probability that a deadline will be met is introduced, as well as the value of the deadline in function of the desired probability that the deadline will be met.

No abstract available.

The Producer/Consumer (P/C) has been used to model communication in networks. The model states that in a system there is a producer of a given information and one or more consumers of this information. With this model different kinds of communication failures may occur. In this paper with the help of the adapted synchronous model (ASM), we show two methods for formally verifying the necessary conditions to avoid buffer overwrites in the P/C model. Specifically, we explore the constraints on communication parameters in distributed periodic control and more generally, we demonstrate how behavioral properties can be analyzed using formal methods.

Control applications constitute an important class of real-time systems. Such applications have specific temporal requirements that have to be taken into account during the system design. One such requirement is data temporary consistency. This paper gives an overview of the temporal consistency problem and addresses implementation issues for a distributed real-time system that is configured according to a producer/consumer communication model. Solutions are proposed that provide simple mechanisms for maintaining temporal consistency. Finally, a software architecture consisting of temporally homogeneous buffers is presented.>