Wireless Ad-Hoc Sensor Networks for Monitoring Endangered Plant Species Edo Biagioni University of Hawaii at Manoa Also Kim Bridges, Brian Chee, Anders Host-Madsen, Galen Sasaki, and many more, including Chen, Fan, Morton, Xie, and DARPA

Overview An ecological wireless sensor network Overall challenges Current solutions Future solutions

Protecting Endangered Plants Hard to do without knowing plants' needs, so Study the environment See how the plants are doing Use sensors and hi- res cameras

Challenges Energy: batteries, solar, wind Sleep, wake up, transmit, go back to sleep Low bit-rate, but over a wide area Low cost, unobtrusive ● Fading: bad geometry, plants (2.4GHz) ● Collisions and Congestion ● Sensors: sunlight, rain, wind Issues common to most sensor networks! Issues common to most sensor networks!

The PODS project Hawaii: endangered species “capital” Microclimates: rapid weather changes Pods communicate over many hops with internet-connected base station Assembly of COTS hardware (IPAQ w/ Linux), Custom software, protocols: MOR, Lusus Transmission range typically ~ Power -4

Pod placement Intensive deployment where plant grows Also interested in where the plant does not grow Connection to the internet is also a line of sensors Many interesting topologies [Biagioni and Sasaki, 2003] Sub-region

Ad-hoc Wireless Communication: Multipath On-Demand Routing Protocol provides routing information as well as transport for data (IP) packets Multiple paths with retransmission perform well in the face of congestion – good performance means low power Application-level broadcast supports synchronization Low or high mobility

Sensor Network Architecture More powerful pods form a “backbone”, may have better communications and sensors (cameras), may be always on Smaller sensors are cheaper, use less energy, may have less range and lower speed Two-tiered (or multi-tiered) architecture

Protocol for Simple Nodes Lusus Routing on a gradient towards base station or nearest high-level node Link-layer reliability Joining separate data into one packet Low speed serial radios PIC microcontroller

Application-Level Data Protocol: SNDT Features:ReliableLow-overheadEncryption Faster than using SSH/TCP to transfer small amounts of data Rate-limited transmission

11 Cooperative Diversity Anders Host-Madsen Ad-hoc networks Users communicate directly with each other Interference Among Different connections Fading due to distance – Fading

12 Cooperative TDMA Nodes use TDMA multiple-access While a transmitter is passive, it can act as relay One node transmits first and the other helps, then switch

Research Plan Anders Host-Madsen Results Fading Relay channel capacity (with J. Zhang, ASU) Theoretical bounds for 4-node cooperative diversity NSF funding Current MIMO Relay Channel (with J. Zhang, ASU) Multinode relay channel Construction of experimental 4-node network Practical coding methods for the relay channel Future Low power regime Experimentation on wireless testbed Generalization to larger networks Routing/clustering Application to environmental sensor network

Open Research Issues Theoretical models for wireless ad-hoc network performance Practical, reproducible performance tests Lessen power needs by moving away from COTS (or by COTS moving closer) Micropower generation and conservation Wireless that works well near the ground

Wireless Ad-Hoc Network Performance In typical multi-hop networks, at most 1 out of 3 nodes can transmit at any time Interference range is usually greater than transmission range Fading varies over time, and it is hard to reproduce any actual test “Quantum” testing: observe what actually happens, run in actual environments

Power Research Issues COTS keeps getting lower power, smaller, cheaper Microcontrollers can do 90% of the job at a fraction of the (cost, size, weight) Solar works well, expensive, hard to conceal Wind works sometimes, hard to conceal

Future Work More applications: science, agriculture, even tourism Better visualization of data Evaluation with larger actual networks Protocol improvements Better, lower power, less conspicuous, cheaper sensors and cameras

Summary Experience building, deploying wireless ad-hoc sensor networks Multi-tiered sensor network architecture Power may cost more than computer+sensor Most protocols work (e.g. MANET), but some (e.g. MOR) may work better Cooperative diversity improves range in a flexible manner Performance testing is difficult but essential