Abstracts / 2009
A Cross-Layer Approach for Data Replication and Gathering in Decentralized Long-Living Wireless Sensor Networks
9th International Symposium on Autonomous Decentralized Systems, Athens, March 23-25, 2009, Greece
Kurzinfo: Realizing highly reliable wireless sensor networks with a long lifetime is a challenging task. A long lifetime is normally achieved by low duty cycles and rare activity. High reliability requires the replication of data to cope with dying nodes, network fragmentation, etc. These problems become even harder to tackle in networks with no wired sink (decentralized networks), which can synchronize the nodes and store data. We thoroughly investigated the challenges and present a reasonable approach, which adopts cross-layer rendezvous and data dissemination schemes. Our protocol can achieve very good results for lifetime, efficient replication handling and data gathering in decentralized sensor networks. Off-the-shelf sensor nodes based on our approach offer a lifetime of two years. However, our simulation results reveal that very long sleep phases may lead to increased power consumption, which is not expected.
Completely Distributed Low Duty Cycle Communication for Long-Living Sensor Networks
7th IEEE / IFIP International Conference on Embedded and Ubiquitous Computing (EUC-9), Vancouver, August 29 - 31, 2009, Canada
Kurzinfo: A lifetime of several years for wireless sensor nodes can be achieved if their activity period is minimized. This can be done by using low duty cycle protocols. One of the challenges of these low duty cycle protocols is the synchronization of wake-up times. This becomes even more demanding if a wired central sink, which takes care of the schedule, is missing and communication links are unreliable. In this paper, we present our own Distributed Low Duty Cycle MAC (DLDC-MAC) protocol, which achieves a lifetime of two years using off-the-shelf sensor nodes. Our protocol synchronizes wake-up times of nodes in a fully decentralized way, even when plenty of transmitted packets get lost. We evaluated this in a real world scenario with 10 sensor nodes working for 14 days in our office space. Interestingly, the experiment showed that direct communication over long distances led to very high packet error rate, sometimes higher than 30%. In that case, multi-hop transmission delivered data with much higher reliability, with packet error rate close to 0%.
On Prolonging Sensornode Gataway Lifetime by Adapting its Duty Cycle
WWIC 2009, 7th International Conference on Wired / Wireless Internet Communications, Twente, May 27 - 29, 2009, The Netherlands
Kurzinfo: In this paper we discuss the lifetime of an battery powered device which acts as a gateway between a wireless sensor network and a standard network. The wireless communication standards used are IEEE802.15.4 and IEEE802.11g. The two parameters which are of ut- most importance but also contradicting each other are communication delay and lifetime of the gateway node. Our results clearly show that duty cycling i.e. switching off the gateway node improves its lifetime. Depending on the radio modules used the lifetime can be increased from seven hours up to 3 months using only 3 AA batteries. Our results also proove that prolonging the sleep intervals beyond a certain limit (about 10 seconds for a typical WLAN PC card) does not longer improve the lifetime but only worsens the delay.
An UWB Receiver Front-End for Low Data Rate Wireless Personal Area Networks
IEEE MTT-S International Microwave Workshop on Wireless Sensing, Local Positioning, and RFID, Cavtat, September 24 - 25, 2009, Croatia
Kurzinfo: This paper describes front-end components of the monolithic integrated impulse radio (IR) Ultra-wide band (UWB) receiver. The receiver is intended for the use in Low Data Rate (LDR) Wireless Personal Area Networks (WPAN) which is defined by the IEEE 802.15.4a standard. In order to assure compliance with the standard, receiver RF front-end components are designed towards higher degree of integration, low cost and low power consumption operation. The receiver operates in the higher UWB band and is able to cover channels from 5 to 9 of the IEEE 802.15.4a standard, which corresponds to the frequency range from 6 to 8.25 GHz. The circuit was fabricated in 0.25 μm SiGe:C BiCMOS technology.
Customizing Sensor Nodes and Software for Individual Pervasive Health Applications
Proceedings 3rd International Conference on Pervasive Computing Technologies for Healthcare, 2009
Kurzinfo: In this paper we introduce the idea of realizing pervasive health care applications by tailoring the underlying hardware and software to the needs of this specific application. We illustrate the feasibility of our idea by discussing an generalized approach form combining different harware components as well as a generalized approach for adapting specific software components.
A High Band Impulse Radio UWB Transmitter for Communication and Localization
Proc. ICUWB 2009, Vancouver, Sep. 2009, Canada
Kurzinfo: This paper describes a monolithic integrated transmitter intended for impulse radio (IR) Ultra-wide band (UWB) applications including indoor communication and indoor localization. The transmitter operates in the higher UWB band centered at 7.68 GHz and it is optimized for a pulse bandwidth of about 1.5 GHz. The transmitter generates single pulses with a repetition rate of 60 MHz and utilizes pulse position modulation (8-PPM) for data communication. A dedicated time-of-arrival (TOA) measurement extension supports precise indoor localization in conjunction with an appropriate UWB receiver. The demonstrated spatial ranging resolution is about 3.9 centimeter under line-of-sight conditions.
Performance and Design of IR-UWB Transceiver Baseband for Wireless Sensors
Proc. ICUWB 2009, Vancouver, Sep. 2009, Canada
Kurzinfo: Using UWB for wireless short range, low rate communication has been attracting growing interest due to its low power consumption and very high bandwidth. Moreover, it is able to offer accurate localization in the range of few centimeters. Recognising these qualities, it is desirable to design IR-UWB transceiver which can draw minimum possible power when it is applied for battery driven wireless sensors. For this reason in this paper, baseband design and performance of IR-UWB transceiver based on the standard IEEE.802.15.4a was investigated with particular emphasis on reducing power consumption. Synchronization algorithm that achieves 16 ns is presented and its performance is very promising offering nearly 100% synchronization for as low SNR as 8 dB. Different resolutions of analogue to digital converter (ADC) are investigated to find out the optimum with respect to power consumption and performance. 4 bit ADC was found to be the most optimal for the sample rate of 62.4 MHz. BER performance of pulse position modulation was evaluated under realistic channel conditions with multipath components.
Adaptive pruning of Event Decision Trees for energy efficient collaboration in event-driven WSN
Accepted for Third International Workshop on Information Fusion and Dissemination in Wireless Sensor Networks, in conjunction with MobiQuitous'09, 2009
Kurzinfo: Wireless Sensor Networks (WSN) are considered to be the key-enabler for low cost highly distributed applications in the area of homeland security, healthcare, environmental monitoring etc. A necessary prerequisite is reliable and efficient event detection. This paper introduces a novel approach for event configuration and in network processing, called Event Decision Trees (EDT). An EDT enables every node to self-divide event queries according to its resources. EDT autonomously adapt to the tasks assigned, even though it requires to organize collaboration between nodes to deliver expected results. The effort for maintaining EDT in WSN is evaluated by mathematical analysis and simulations. Our results show that the proposed lease-based mechanism for maintaining even producer/consumer pairs in an EDT outperforms even idealized Acknowledgmentbased approaches.
An Engineering Approach for Secure and Safe Wireless Sensor and Actuator Networks for Industrial Automation Systems
14th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA), Palma, 2009, Spain
Kurzinfo: Wireless communication and smart sensors and actuators pose means to sustainably improve automation technology. Unfortunately they also cause an abundance of new challenges regarding security and safety of the system. After introducing the security concepts, this paper discusses an engineering methodology to cope with security requirements in context of industrial automation. Two practical examples demonstrate how the solutions even for pretty similar scenarios can differ significantly. The proposed development flow promises a reliable objective engineering of proper system solutions. Key concepts of the flow are a holistic goal description and an iterative composition algorithm that inherently applies and extends existing knowledge.
Implicit Sleep Mode Determination in Power Management of Event-driven Deeply Embedded Systems
7th International Conference on Wired / Wireless Internet Communications, University of Twente, 2009, The Netherlands
Kurzinfo: Energy consumption is a crucial factor for the lifetime of many embedded systems, especially wireless sensor networks. Most modern microcontrollers provide various low power sleep modes. Utilizing them can lead to great energy savings. In this paper we present an approach for power management in embedded systems, based on the event-driven operating system Reflex. The implicit power management is mostly hardware independent, lightweight and efficiently chooses the optimal power saving mode of the microprocessor automatically.
Combining for cooperative WLANs -- A reality check based on prototype measurements
Proc. IEEE Workshop on Cooperative Mobile Networks (CoCoNET2), collocated with IEEE ICC
Kurzinfo: Many cooperative relaying systems combine signals received over multiple paths. For this task, .in literature usually Maximum Ratio Combining (MRC), or one of its derivatives, is assumed. We show that these complex techniques are not required in Wireless Local Area Network (WLAN) scenarios with slowly fading channels. Instead, simply selecting the "best" decoded packet achieves similar performance. This Packet Selection Combining (PSC) is more practical than MRC as it is independent on channel-knowledge, does not limit the choice of the modulation scheme, and avoids complex Physicallayer (PHY) implementation. Our real-time transceiver prototype demonstrates PSC's feasibility; measurements in an indoor scenario show its high performance and validate our theoretical results.
Improving Network Coded Cooperation by Soft Information
In Proc. IEEE International Workshop on Wireless Network Coding (WiNC2009)
Kurzinfo: Bit-wise XOR network coding has been shown to perform well in cooperative wireless transmission because of its simple coding operation and and overall robustness increase due to combining of several messages. Our aim is to develop a cooperation protocol that uses basic and easy to implement operations but still combines the messages well and achieves good performance. For this purpose, we modify the conventional network-coded cooperation protocol to work with soft information using low complexity operations. We analyze the performance by first deriving a closed form Bit Error Rate (BER) approximation and then verify its correctness by simulation. Both analytic and simulation results show that the BER approximation is accurate and that the new protocol gains about 5 dB in an indoor scenario with mobility. We conclude that soft information should be used whenever possible, and that it works especially well in the proposed combining scheme with network coding.