1. 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.

2. 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

3. 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.

4. 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.

5. 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

6. 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.

7. 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.

8. 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.

9. 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

10. 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.

11. 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.

12. Discussion