| 1. |
|
|
| 2. |
- Ali, Muneeb, et al.
(author)
-
Medium access control issues in sensor networks
- 2006. - 1
-
In: Computer communication review. - : Association for Computing Machinery (ACM). - 0146-4833 .- 1943-5819. ; 36, s. 33-36
-
Journal article (peer-reviewed)abstract
- Medium access control for wireless sensor networks has been a very active research area for the past couple of years. The sensor networks literature presents an alphabet soup of medium access control protocols with almost all of the works focusing only on energy efficiency. There is much more innovative work to be done at the MAC layer, but current efforts are not addressing the hard unsolved problems. Majority of the works appearing in the literature are "least publishable incremental improvements" over the popular S-MAC [1] protocol. In this paper we present research directions for future medium access research. We identify some open issues and discuss possible solutions.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Boano, Carlo Alberto, et al.
(author)
-
Hot Packets : A systematic evaluation of the effect of temperature on low power wireless transceivers
- 2013
-
In: Proc. 5th Extreme Conference on Communication. - New York : ACM Press. - 9781450321716 ; , s. 7-12
-
Conference paper (peer-reviewed)abstract
- Temperature is known to have a significant effect on the performance of radio transceivers: the higher the temperature, the lower the quality of links. Analysing this effect is particularly important in sensor networks because several applications are exposed to harsh environmental conditions. Daily or hourly changes in temperature can dramatically reduce the throughput, increase the delay, or even lead to network partitions. A few studies have quantified the impact of temperature on low-power wireless links, but only for a limited temperature range and on a single radio transceiver. Building on top of these preliminary observations, we design a low-cost experimental infrastructure to vary the onboard temperature of sensor nodes in a repeatable fashion, and we study systematically the impact of temperature on various sensornet platforms. We show that temperature affects transmitting and receiving nodes differently, and that all platforms follow a similar trend that can be captured in a simple first-order model. This work represents an initial stepping stone aimed at predicting the performance of a network considering the particular temperature profile of a given environment.
|
|
| 7. |
- Boano, Carlo Alberto, et al.
(author)
-
JAG: Reliable and Predictable Wireless Agreement under External Radio Interference
- 2012. - 9
-
Conference paper (peer-reviewed)abstract
- Wireless low-power transceivers used in sensor networks typically operate in unlicensed frequency bands that are subject to external radio interference caused by devices transmitting at much higher power.communication protocols should therefore be designed to be robust against such interference. A critical building block of many protocols at all layers is agreement on a piece of information among a set of nodes. At the MAC layer, nodes may need to agree on a new time slot or frequency channel, at the application layer nodes may need to agree on handing over a leader role from one node to another. Message loss caused by interference may break agreement in two different ways: none of the nodes uses the new information (time slot, channel, leader) and sticks with the previous assignment, or-even worse-some nodes use the new information and some do not. This may lead to reduced performance or failures. In this paper, we investigate the problem of agreement under external radio interference and point out the limitations of traditional message-based approaches. We propose JAG, a novel protocol that uses jamming instead of message transmissions to make sure that two neighbouring nodes agree, and show that it outperforms message-based approaches in terms of agreement probability, energy consumption, and time-to-completion. We further show that JAG can be used to obtain performance guarantees and meet the requirements of applications with real-time constraints.
|
|
| 8. |
|
|
| 9. |
- Boano, Carlo Alberto, et al.
(author)
-
Making Sensornet MAC Protocols Robust Against Interference
- 2010. - 10
-
Conference paper (peer-reviewed)abstract
- Radio interference may lead to packet losses, thus negatively affecting the performance of sensornet applications. In this paper, we experimentally assess the impact of external interference on state-of-the-art sensornet MAC protocols. Our experiments illustrate that specific features of existing protocols, e.g., hand-shaking schemes preceding the actual data transmission, play a critical role in this setting. We leverage these results by identifying mechanisms to improve the robustness of existing MAC protocols under interference. These mechanisms include the use of multiple hand-shaking attempts coupled with packet trains and suitable congestion backoff schemes to better tolerate interference. We embed these mechanisms within an existing X-MAC implementation and show that they considerably improve the packet delivery rate while keeping the power consumption at a moderate level.
|
|
| 10. |
|
|
| 11. |
- Boano, Carlo Alberto, et al.
(author)
-
Mitigating the Adverse Effects of Temperature on Low-Power Wireless Protocols
- 2014. - 7
-
Conference paper (peer-reviewed)abstract
- Research and industrial installations have shown that the on-board temperature of wireless sensor nodes deployed outdoors can experience high fluctuations over time with a large variability across the network. These variations can have a strong impact on the efficiency of low-power radios and can significantly affect the operation of communication protocols, often compromising network connectivity. In this paper, we show the adverse effects of temperature on communication protocols and propose techniques to increase their resilience. First, we experimentally show that fluctuations of the on-board temperature of sensor nodes reduce the efficiency of data link layer protocols, leading to a substantial decrease in packet reception rate and to a considerable increase in energy consumption. Second, we investigate the reasons for such performance degradation, and show that high on-board temperatures reduce the effectiveness of clear channel assessment, compromising the ability of a node to avoid collisions and to successfully wake-up from low-power mode. After modelling the behaviour of radio transceivers as a function of temperature, we propose two mechanisms to dynamically adapt the clear channel assessment threshold to temperature changes, thus making data link layer protocols temperature-aware. An extensive experimental evaluation shows that our approaches considerably increase the performance of a network in the presence of temperature variations commonly found in real-world outdoor deployments, with up to 42% lower radio duty-cycle and 87% higher packet reception rate.
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Boario, Carlo Alberto, et al.
(author)
-
TempLab : A testbed infrastructure to study the impact of temperature on wireless sensor networks
- 2014
-
In: IPSN 2014 - Proceedings of the 13th International Symposium on Information Processing in Sensor Networks (Part of CPS Week). - : IEEE Computer Society. - 9781479931460 ; , s. 95-106
-
Conference paper (peer-reviewed)abstract
- Temperature has a strong impact on the operations of all electrical and electronic components. In wireless sensor nodes, temperature variations can lead to loss of synchronization, degradation of the link quality, or early battery depletion, and can therefore affect key network metrics such as throughput, delay, and lifetime. Considering that most outdoor deployments are exposed to strong temperature variations across time and space, a deep understanding of how temperature affects network protocols is fundamental to comprehend flaws in their design and to improve their performance. Existing testbed infrastructures, however, do not allow to systematically study the impact of temperature on wireless sensor networks. In this paper we present TempLab, an extension for wireless sensor network testbeds that allows to control the on-board temperature of sensor nodes and to study the effects of temperature variations on the network performance in a precise and repeatable fashion. TempLab can accurately reproduce traces recorded in outdoor environments with fine granularity, while minimizing the hardware costs and configuration overhead. We use TempLab to analyse the detrimental effects of temperature variations (i) on processing performance, (ii) on a tree routing protocol, and (iii) on CSMA-based MAC protocols, deriving insights that would have not been revealed using existing testbed installations.
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Dunkels, Adam, 1978-
(author)
-
Programming Memory-Constrained Networked Embedded Systems
- 2007
-
Doctoral thesis (other academic/artistic)abstract
- Ten years after the Internet revolution are we standing on the brink of another revolution: networked embedded systems that connect the physical world with the computers, enabling new applications ranging from environmental monitoring and wildlife tracking to improvements in health care and medicine. 98% of all microprocessors sold today are used in embedded systems. Those systems have much smaller amounts of memory than PC computers. An embedded system may have as little has a few hundred bytes of memory, which makes programming them a challenge.This thesis focus on three topics regarding programming memory-constrained networked embedded systems: the TCP/IP for memory-constrained networked embedded systems, simplifying event-driven programming of memory-constrained systems, and dynamic loading of program modules in my Contiki operating system for memory-constrained systems. I show that the TCP/IP protocol stack can, contrary to previous belief, be used in memory-constrained embedded systems by implementing two small TCP/IP protocol stacks, lwIP and uIP.I present a novel programming mechanism called protothreads that I show significantly reduce the complexity of event-driven programming for memory-constrained systems. Protothreads provide a conditional blocked wait mechanism on top of event-driven systems with a much smaller memory overhead than full multithreading; each protothread requires only two bytes of memory.I show that dynamic linking of native code in standard ELF object code format is doable and feasible for wireless sensor networks by implementing a dynamic linker in the Contiki operating system. The results show that the energy overhead of dynamic linking of ELF files mainly is due to the ELF file format and not due to the dynamic linking mechanism as such.The impact of the research in this thesis has been and continues to be large. The software I have developed as part of this thesis is currently used by hundreds of companies in embedded devices in such diverse systems as car engines and satellites. The papers in this thesis are included as required reading in advanced courses on networked embedded systems and wireless sensor networks.
|
|
| 19. |
- Oppermann, Felix Jonathan, et al.
(author)
-
Design and compilation of an object-oriented macroprogramming language for wireless sensor networks
- 2014
-
In: Proceedings - Conference on Local Computer Networks, LCN. - : IEEE Computer Society. ; , s. 574-582
-
Conference paper (peer-reviewed)abstract
- Wireless sensor network (WSN) programming is still largely performed by experts in a node-centric way using low-level languages such as C. Although numerous higher-level abstractions exist, each simplifying a specific aspect of distributed programming, real applications often require to combine multiple abstractions into a single program. Using current programming frameworks, this represents a difficult task. In previous work, we therefore defined a conceptual framework that facilitates abstraction composition by defining sound compositional rules among few fundamental abstraction categories. The framework is extensible: programmers can add new abstractions within the boundaries determined by the compositional rules. In this paper we describe the design of a language - called MPL - that instantiates this conceptual framework. To support the extensible nature of the framework, the language is object-oriented, which allows programmers to add new abstractions by inheriting from existing classes that implement predefined interfaces. We modeled the syntax after Java, to make it more palatable to inexperienced embedded programmers. Compared to Java, we modified the language to enable efficient execution on WSN devices. We designed and implemented a compiler that translates MPL language into executable C code, which spares the overhead of a virtual machine. By comparing MPL implementations against functionally-equivalent Contiki/C implementations of several benchmark applications, we determined that the performance overhead of MPL is limited, and yet the programming task is simplified.
|
|
| 20. |
- Tranquillini, Stefano, et al.
(author)
-
Process-Based Design and Integration of Wireless Sensor Network Applications
- 2012. - 13
-
Conference paper (peer-reviewed)abstract
- Wireless Sensor and Actuator Networks (WSNs) are distributed sensor and actuator networks that monitor and control real-world phenomena, enabling the integration of the physical with the virtual world. They are used in domains like building automation, control systems, remote healthcare, etc., which are all highly process-driven. Today, tools and insights of Business Process Modeling (BPM) are not used to model WSN logic, as BPM focuses mostly on the coordination of people and IT systems and neglects the integration of embedded IT. WSN development still requires significant special-purpose, low-level, and manual coding of process logic. By exploiting similarities between WSN applications and business processes, this work aims to create a holistic system enabling the modeling and execution of executable processes that integrate, coordinate, and control WSNs. Concretely, we present a WSN-specific extension for Business Process Modeling Notation (BPMN) and a compiler that transforms the extended BPMN models into WSN-specific code to distribute process execution over both a WSN and a standard business process engine. The developed tool-chain allows modeling of an independent control loop for the WSN.
|
|
| 21. |
|
|
| 22. |
|
|
