Architectural Approaches (Part 1) Power Aware Distributed Systems Kickoff August 23, 2000

Sensor Node Baseline 1. Instrument a state-of-the-art sensor node to understand power consumption in current systems. Where can we expect significant latitude in power tradeoff? Which knobs have the greatest dynamic range? What baseline will we use for comparison? 2. Identify hardware knobs that can be provided by modules (radio and processor systems) that can be altered dynamically, and externally readable parameters (power, BER, signal strength, battery, etc.) that can be provided to a power-aware runtime system.

Rockwell WINS Nodes Rockwell WINS is a modular stack consisting of:  Power Board  StrongARM Board  Radio Board  Sensor Board This architecture is fairly representative of other sensor nodes in the community. We plan to adapt this node to allow module-level power instrumentation and logging both in the lab and in the field.

Module Isolation Insert a power isolation board between each module in the WINS stack. Signals are passed through, power supplies are isolated. Microcontroller provides power monitoring and power control from a host’s serial port. Event “snooping” may be possible to trigger data acquisition in the field. PADS Power Isolator StrongARM PADS Power Isolator Radio PADS Power Isolator Sensor Host Serial Port Battery Pack

Sensor Node Baseline 1. Instrument a state-of-the-art sensor node to understand power consumption in current systems. Where can we expect significant latitude in power tradeoff? Which knobs have the greatest dynamic range? What baseline will we use for comparison? 2. Identify hardware knobs that can be provided by modules (radio and processor systems) that can be altered dynamically, and externally readable parameters (power, BER, signal strength, battery, etc.) that can be provided to a power-aware runtime system.

Power Aware Research Platform Testbed Provide a highly instrumented open sensor network platform that conforms to open APIs and COTS hardware interfaces.  Must be inexpensive and easy to replicate.  Geared for lab and parking lot experiments, but rugged enough to take to field.  Leaning towards PC104+ standard. Integrate advanced power aware processing and communications technology into the PADS research platform as it becomes available in the PAC/C community.  Allow community to test new PAC/C technology in sensor networks without big leap into proprietary low-power commercial systems. Too power hungry! Expensive.

Node Options Rockwell WINS – StrongARM Stack  Advantage is that Rockwell is a team partner, but some sensitive components make it not entirely open source and easily replicable. BWRC Pico Node – StrongARM + Xilinx 4020  Similar to WINS. Intended to be open standard, but hardware and software not as mature. Sensoria WINS-NG – WinCE PDA + custom box  With the exception of PDA, box is closed to developers. MIT (Anantha Chakandrasan)  Focus is on voltage scaling and other in-the-lab power tradeoffs. Note: All of the above are CPU-centric architectures!

CPU-Centric Architectures Most nodes are CPU-centric in that the radio, GPS, and sensors are wired up to serial ports, A/D bus, and/or GPIOs on an embedded processor such as StrongARM. A processor must be present in every node. The CPU must wake up on any event and facilitate communications between any pair of modules (radio and sensor modules, for example). Is this the most power-efficient sensor node system model? Is there another approach which allows most of the sensor node to be turned off most of the time?

Distributed Microcontroller Model Make each module an independent actor on a multi-master serial bus such as I2C (400Kb, 4Mb*) or CAN (1Mb). Minimum module processing is a 25mA microcontroller. Migrate specific processing to the modules (microcontroller on seismic board, DSP on imager board, etc.). Create common command set for peer to peer communication and control of modules. A StrongARM may be used for application control, but it could distribute “event handlers” to microcontrollers on the modules and power down most of the time. I2C/CAN

Module Emulation Most existing sensor nodes have an external serial port. A distributed microcontroller architecture on a multi-master serial bus would make it much easier to integrate modules that don’t fit the form factor. Also enables simple module emulation and module testing from a workstation or laptop. I2C/CAN Serial Port Bridge Serial Port Bridge Laptop Serial GPS Unit

Distributed Microcontroller Model w/ Local Power Control

Distributed Microcontroller Model w/ Central Power