Wireless Sensor Network Technologies – Agilla, Deluge, Mate

With continual funding of wireless sensor network research at the university level, a number of tools have surfaced which merit review. In the area of in-network reprogramming, there is Agilla. Agilla is a middleware program that provides a mobile-agent paradigm which allows a node to migrate its code and state across a wireless sensor network. Agilla is based on TinyOS and allows a wireless sensor network to be reprogrammed with a minimal of computational and communication resources. While it’s a university-level research tool, it does start to create a list of functions and features a robust wireless sensor network program should have.

Another key tool is called Deluge which reprograms an entire wireless sensor network by copying a new image into each node’s ROM in an energy/communication efficient way. You can download a copy here.

Boston University came up with an improved version of Deluge which they called NOSY (Network Observation SYstem) which combines Deluge with a variable report rate for adjusting the nodes report rate, remote control so one can program individual nodes, and a watchdog timer for rebooting nodes that haven’t responded within a certain amount of time.

A team at Berkeley came up with an improved cryptography scheme for Deluge. The paper here describes how an “advertisement” message is sent to the network with a hash code that references a second message which also contains a hash code that references the third message, and so on. This way the network can authorize a stream of messages rather than one message at a time.

Mate is a virtual machine designed for sensor networks which uses complex programs in a small amount of code (< 100 bytes). Mate code can be broken up and packetized for distribution throughout the network. It’s a byte code interpreter that encapsulates 24 instructions per packet. Each command is routed to its destination node and processed at the node automatically. Mate uses a stack architecture similar to FORTH which was also a memory efficient structure for handling data and operands. Events fall into three categories: clock timers, message reception, and message send requests. Operands fall into three categories: values, sensor readings, and messages. Future uses of Mate focus on application-specific flavors.

Research into Wireless Sensor Networks reveals a variety of software efforts – some at the node level, and some at the application level, but from this review it’s clear there is a layer of middleware software that will be key to enabling robust applications.

Best regards,
Hall T.