CS294-1 Reading Aug 28, 2003 Jaein Jeong Habitat Monitoring: Application Driver for Wireless Communications Technology CS294-1 Reading Aug 28, 2003 Jaein Jeong Good afternoon. We are going to present localization using DOT3 wireless sensors.

Outline Introduction How to achieve low duty-cycle operation Challenges for sensor network Habitat monitoring How to achieve low duty-cycle operation Frisbee Model Time Synchronization Tiered Architecture for scalability Hardware and software platforms

Introduction The rise of sensor/actuator network Thanks to the micro-sensor and low-power wireless communications. Challenges for sensor network Need for good physical models. Increased dynamics. Energy constraints. Scaling challenges.

Principles for habitat monitoring. Self-configuration. The ability to operate autonomously. Sheer number of nodes can’t depend on manual configuration. Sensor nodes should adjust to the environment dynamics. Self-assembly / healing, localization, time synchronization, etc. Energy efficiency. Techniques are needed to reduce power consumption for longevity. Filtering and in-network processing reduces communication traffic (e.g. seismic sensor & camera). Ability to wake-up nodes in response to interesting events.

Frisbee Model Motivation Frisbee Model Not all the sensors need to be active. Save energy by waking up only the nececessry ones. Frisbee Model Only a region of sensors are active (frisbee). Active region can move. Power saving by making sensors asleep outside the frisbee

Frisbee Model: Localized Algorithms for Defining Frisbee Boundary Nodes that have detected the target wake up neighbors. Query the nodes already awake to determine speed and direction. After a certain amount of time, the nodes time out and sleep.

Time Synchronization Sensor 1 Sensor 2 Sensor 3 ε The clock of each sensor is synchronized within a bound ε. Rationale Suppression duplication for data aggregation. Scheduled wake-ups (e.g. TDMA). Detection of speed and direction of phenomena. Application specific variables Precision of time synchronization. Frequency to fix. Sensor network density.

Time Synchronization Methods Universal Time A single time signal is broadcast to all nodes. Example: WWVB, GPS Pros: best for eliminating accumulated error. Cons: requires more resources (HW, power). Depends on infrastructure (e.g. WWVB). Peer-to-peer time distribution. NTP establishes a federation of synced nodes. Works with no external time source. Works over existing comm. Infrastructure. Can be synced with external time source.

Tiered Architecture Idea Advantages Use different levels of hardware platforms to make an efficient system. Analogous to memory hierarchy. “Sensors” : more expensive, larger, but faster “Tags” : more limited, but smaller, cheaper Advantages Lower cost  More densely deployable. Lower power  Longevity Smaller form factor  More easily deployable. Sensors L1 Cache Tags L2 Cache Motes Main Memory Tiered architecture of sensors Memory hierarchy of desktop systems

Hardware Platforms Prototype radio controller for “tag” platform COTS Mote UC Berkeley PC104-based sensor node “High end” node compatible with desktop PCs. Lower cost w.r.t. laptops Fast μ-processor (66MHz), large memory (16MB), Radio. “velcroable” device Master, radio, sensor and DSP module Under development Smallest device in tiers Envisioned to be the size of dusts.

Software Radiometrix Device Drivers Emlog Parapin Linux device driver for RPC. Emlog Linux kernel module that displays the most recent output from a process. Useful for logging and debugging. Parapin A tool helps writing C code to control parallel port.

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