Mica A Wireless Platform for Deeply Embedded Networks

Mica: A Wireless Platform for Deeply Embedded Networks Jason Hill and David Culler Presented by Arsalan Tavakoli

Requirements for Wireless Embedded Networks Platform n Low power consumption n Protocol processing must be optimized for ultra-low power consumption, not high data rates No reliance on pre-deployed infrastructure network Must be suited to wide-variety of applications

Conventional Wireless Platforms n Cell Phones n n Wireless Ethernet (802. 11 b) n n Expensive, single application, pre-deployed infrastructure High power consumption Bluetooth n Master-slave format with 8 max connections limits large, efficient deployments

Mica Platform n n Runs Tiny. OS operating system Facilitates cross-layer optimization through interconnected interfaces Does not require use of pre-defined protocols Minimal power consumption

Mica Sensor Node

Mica Architecture Diagram

Atmel Microcontroller n n n Runs at 4 Mhz with 4 MIPS 128 KB flash program memory 4 KB static RAM One external universal asynchronous receiver transmitter (UART) One serial (SPI) port

TR 1000 Radio Transceiver n n n Communication rates up to 115 Kb/s Unobstructed communication range of approximately 200 feet Operating System: n n Controls radio transmission strength Can sense strength of the receive signal

Expansion Connector n 51 -pin Connector for attaching sensor boards to increase sensing capabilities: n n n Temperature Barometric Pressure Magnetic Fields Light Passive Infrared Frequency (Motion) Acoustic

Other Components n n Coprocessor – Allows for wireless dynamic reprogramming DS 2401 – Provides unique ID 4 Mb External Flash – Stores data logs and temporarily holds program images Dc-Dc Boost Converter – Provides constant 3. 3 V power supply

Tiny. OS Operating System n n Designed at UC Berkeley specifically for sensor networks Event-based operating system Component-based structure allows application customization No blocking or waiting

Packet Transmission and Reception

Hardware Accelerators n Buffer Accelerator n n Shared memory buffer between bit-parallel data path and bit-serial radio channel Synchronization Accelerator n n Captures exact timing of incoming packet (within one clock cycle) Information available to application software

RF Wake-Up n n Ultralow-power Network Wake-Up Signal Nodes turn off radios to conserve energy Wake-up call is long RF pulse Nodes wake up periodically to check for wake-up signal

Time Synchronization n Primitive time synchronization scheme discussed n n n Allows pair-wise synchronization Sender stamps packet as it is being transmitted Receiver stamps packet as it is received, and computes difference

Localization n RF Signal Strength falls off with distance With knowledge of sender’s transmit power level, receiver can approximate distance Localization through acoustic pulses

Application Classes n n Applications with low-duty cycle, low data-rate, long latency, static topology, and long expected lifetime Applications with highly dynamic senseand-control networks with high datarates, latency limits, and highly mobile nodes