| Abstract |
Wireless sensor networks are emerging as a new computing paradigm, where a number of autonomous miniature devices, capable of communicating via wireless, cooperate with each other in order to share and exchange information. The power of wireless sensor networks lies in the ability to deploy a large number of tiny nodes, that monitor and adapt to their environment, assembling and configuring themselves. Researchers are envisioning applications where tens, hundrends, or maybe thousands of nodes, carrying the appropriate sensory equipment, can be placed close to the phenomenon, allowing remote control and interaction by humans without demanding any intervention in the field. Early efforts in this area focused on building the devices themselves and on understanding network issues. An issue that has not received as much attention is generic runtime system support. In this thesis, we present CORMOS, a communication-oriented operating system and runtime environment for wireless sensor networks. CORMOS is tailored: (i) to provide easy-to-use abstractions and treat communication as a first class citizen rather than an extension, (ii) to be highly modular with unified application and system interfaces, and (iii) to deal with sensor limitations on concurrency, memory, and power. CORMOS uses a unified interface for system and application modules, that is, handlers that communicate with events. It uses the event and path abstractions to integrate remote communication with processing in a transparent manner, eliminating the need for a separate messaging mechanism. New protocols, such as routing and reliable transmission may be added to the system as new modules, as can user applications. CORMOS scheduler makes it easy for applications to schedule events and hides from applications the existence of timer-based asynchronous events. Finally, we also plan to use CORMOS to guide the design of sensor prototypes and components. In this thesis, we describe the design of CORMOS, discuss various design alternatives, and provide a prototype implementation on various networked sensor platforms. We investigate how runtime systems can facilitate the integration of ad-hoc networking protocols as runtime modules, by providing various routing algorithms and a retransmission scheme that guarantees delivery at the data link level. Furthermore, we present preliminary results for system resource requirements. We find that the runtime system and a simple network stack can fit in 5.5 KBytes of program memory, occupying about 250 Bytes of RAM. The system is able to process events at a rate of 2500 events/sec. When communicating over the radio transceiver, CORMOS achieves a maximum rate of 20 packets/sec.
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CORMOS: A Communication-Oriented Runtime System for Wireless Sensor Networks
