Hui Dai

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

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.

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

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. TSyncs 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 TSyncs 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.

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

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.

A node-centric load balancing algorithm for wireless sensor networks

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 Dijkstras algorithm.

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

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. ELFs 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.

Unifying micro sensor networks with the Internet via overlay networking [wireless networks]

Todays architecture for interconnecting wireless sensor networks (WSNs) and the Internet is based on treating a WSN as a separate entity from the Internet. Our approach to unifying sensor networks with the Internet is instead to decouple the relationship between the API-enforced database view and the gateway, making the gateway more general by introducing application-level overlay networking into the gateway. In our approach, sensor network packets, rather than being stopped at the gateway, are instead encapsulated into IP packets, and then directed from the gateway to any number of interested applications and services residing remotely on the Internet.

Poster abstract: mantis - system supports for m ultimod A l N e T works on In-Situ sensors

The <i>MANTIS</i> <i>M</i>ultimod<i>A</i>l system for <i>N</i>e<i>T</i>works 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.