https://www.science.smith.edu/~jcardell/Courses/EGR328/Readings/WSNSurvey2.pdf

Wireless sensor network survey

Wireless sensor networks are composed of large numbers of tiny networked devices that communicate untethered. For large scale networks, it is important to be able to download code into the network dynamically. We present Contiki, a lightweight operating system with support for dynamic loading and replacement of individual programs and services. Contiki is built around an event-driven kernel but provides optional preemptive multithreading that can be applied to individual processes. We show that dynamic loading and unloading is feasible in a resource constrained environment, while keeping the base system lightweight and compact.

/pdf/contiki-a-lightweight-and-flexible-operating-system-for-tiny-17ra90mhum.pdf

Contiki - a lightweight and flexible operating system for tiny networked sensors

In this paper we present X-MAC, a low power MAC protocol for wireless sensor networks (WSNs). Standard MAC protocols developed for duty-cycled WSNs such as BMAC, which is the default MAC protocol for TinyOS, employ an extended preamble and preamble sampling. While this “low power listening” approach is simple, asynchronous, and energy-efficient, the long preamble introduces excess latency at each hop, is suboptimal in terms of energy consumption, and suffers from excess energy consumption at nontarget receivers. X-MAC proposes solutions to each of these problems by employing a shortened preamble approach that retains the advantages of low power listening, namely low power communication, simplicity and a decoupling of transmitter and receiver sleep schedules. We demonstrate through implementation and evaluation in a wireless sensor testbed that X-MAC’s shortened preamble approach significantly reduces energy usage at both the transmitter and receiver, reduces per-hop latency, and offers additional advantages such as flexible adaptation to both bursty and periodic sensor data sources.

X-MAC: A Short Preamble MAC Protocol for Duty-Cycled Wireless Sensor Networks ; CU-CS-1008-06

In this paper we present X-MAC, a low power MAC protocol for wireless sensor networks (WSNs). Standard MAC protocols developed for duty-cycled WSNs such as BMAC, which is the default MAC protocol for TinyOS, employ an extended preamble and preamble sampling. While this "low power listening" approach is simple, asynchronous, and energy-efficient, the long preamble introduces excess latency at each hop, is suboptimal in terms of energy consumption, and suffers from excess energy consumption at nontarget receivers. X-MAC proposes solutions to each of these problems by employing a shortened preamble approach that retains the advantages of low power listening, namely low power communication, simplicity and a decoupling of transmitter and receiver sleep schedules. We demonstrate through implementation and evaluation in a wireless sensor testbed that X-MAC's shortened preamble approach significantly reduces energy usage at both the transmitter and receiver, reduces per-hop latency, and offers additional advantages such as flexible adaptation to both bursty and periodic sensor data sources.

/pdf/x-mac-a-short-preamble-mac-protocol-for-duty-cycled-wireless-3g39p5984w.pdf

X-MAC: a short preamble MAC protocol for duty-cycled wireless sensor networks

Solid-state disks (SSDs) have the potential to revolutionize the storage system landscape. However, there is little published work about their internal organization or the design choices that SSD manufacturers face in pursuit of optimal performance. This paper presents a taxonomy of such design choices and analyzes the likely performance of various configurations using a trace-driven simulator and workload traces extracted from real systems. We find that SSD performance and lifetime is highly workload-sensitive, and that complex systems problems that normally appear higher in the storage stack, or even in distributed systems, are relevant to device firmware.

/pdf/design-tradeoffs-for-ssd-performance-s4jiko38c9.pdf

Design tradeoffs for SSD performance

The MANTIS MultimodAl system for NeTworks of In-situ wireless Sensors provides a new multithreaded cross-platform embedded operating system for wireless sensor networks. As sensor networks accommodate increasingly complex tasks such as compression/aggregation and signal processing, preemptive multithreading in the MANTIS sensor OS (MOS) enables micro sensor nodes to natively interleave complex tasks with time-sensitive tasks, thereby mitigating the bounded buffer producer-consumer problem. To achieve memory efficiency, MOS is implemented in a lightweight RAM footprint that fits in less than 500 bytes of memory, including kernel, scheduler, and network stack. To achieve energy efficiency, the MOS power-efficient scheduler sleeps the microcontroller after all active threads have called the MOS sleep() function, reducing current consumption to the µA range. A key MOS design feature is flexibility in the form of cross-platform support and testing across PCs, PDAs, and different micro sensor platforms. Another key MOS design feature is support for remote management of in-situ sensors via dynamic reprogramming and remote login.

/pdf/mantis-os-an-embedded-multithreaded-operating-system-for-297bti43zu.pdf

MANTIS OS: an embedded multithreaded operating system for wireless micro sensor platforms

Time synchronization in a wireless sensor network is critical for accurate timestamping of events and fine-tuned coordination of wake/sleep duty cycles to reduce power consumption. This paper proposes TSync, a novel lightweight bidirectional time synchronization service for wireless sensor networks. TSync's bidirectional service offers both a push mechanism for accurate and low overhead global time synchronization as well as a pull mechanism for on-demand synchronization by individual sensor nodes. Multi-channel enhancements improve TSync's performance. We deploy a GPS-enabled framework in live sensor networks to evaluate the accuracy and overhead of TSync in comparison with other in-situ time synchronization algorithms.

TSync: a lightweight bidirectional time synchronization service for wireless sensor networks

The MANTIS MultimodAl system for NeTworks of In-situ wireless Sensors provides a new multithreaded embedded operating system integrated with a general-purpose single-board hardware platform to enable flexible and rapid prototyping of wireless sensor networks. The key design goals of MANTIS are ease of use, i.e. a small learning curve that encourages novice programmers to rapidly prototype novel sensor networking applications in software and hardware, as well as flexibility, so that expert researchers can leverage or develop advanced software features and hardware extensions to suit the needs of advanced research in wireless sensor networks.

/pdf/mantis-system-support-for-multimodal-networks-of-in-situ-1zepc7w80h.pdf

MANTIS: system support for multimodAl NeTworks of in-situ sensors

An efficient and reliable file storage system is important to micro sensor nodes so that data can be logged for later asynchronous delivery across a multi-hop wireless sensor network. Designing and implementing such a file system for a sensor node faces various challenges. Sensor nodes are highly resource constrained in terms of limited runtime memory, limited persistent storage, and finite energy. Also, the flash storage medium on sensor nodes differs in a variety of ways from the traditional hard disk, e.g. in terms of the limited number of writes for a flash memory unit. We present the design and implementation of ELF, an efficient log-structured flash-based file system tailored for sensor nodes. ELF is adapted to achieve memory efficiency, low power operation, and tailored support for common types of sensor file operations such as appending data to a file. ELF's log-structured approach achieves wear levelling across flash memory pages with limited write lifetimes. ELF also uniquely provides garbage collection capability as well as reliability for micro sensor nodes. A performance evaluation of an implementation of ELF based on TinyOS and MICA2 sensor motes is presented.

/pdf/elf-an-efficient-log-structured-flash-file-system-for-micro-516k65btad.pdf

ELF: an efficient log-structured flash file system for micro sensor nodes

By spreading the workload across a sensor network, load balancing reduces hot spots in the sensor network and increases the energy lifetime of the sensor network. In this paper, we design a node-centric algorithm that constructs a load-balanced tree in sensor networks of asymmetric architecture. We utilize a Chebyshev Sum metric to evaluate via simulation the balance of the routing trees produced by our algorithm. We find that our algorithm achieves routing trees that are more effectively balanced than the routing based on breadth-first search (BFS) and shortest-path obtained by Dijkstra's algorithm.

Hui Dai

Papers

MANTIS OS: an embedded multithreaded operating system for wireless micro sensor platforms

TSync: a lightweight bidirectional time synchronization service for wireless sensor networks

MANTIS: system support for multimodAl NeTworks of in-situ sensors

ELF: an efficient log-structured flash file system for micro sensor nodes

A node-centric load balancing algorithm for wireless sensor networks