ZebraNet Rolf Kristensen & Torben Jensen s s022359

Introduction to ZebraNet Tracking of Zebra behaviour at Mpala Research Center, Kenya Tracking of Zebra behaviour at Mpala Research Center, Kenya Wireless sensor nodes Wireless sensor nodes Sensor network Sensor network High mobility within the sensor nodes and the base station High mobility within the sensor nodes and the base station

Goals GPS position samples taken every three minutes GPS position samples taken every three minutes Activity log taken for 3 minutes every hour Activity log taken for 3 minutes every hour 1 year of operation 1 year of operation Operation over a wide range of open land Operation over a wide range of open land No fixed base stations No fixed base stations High data homing rate (close to 100 pct.) High data homing rate (close to 100 pct.) A weight of max 1,4 to 2,3 kg A weight of max 1,4 to 2,3 kg

A day in the life of a zebra Two kinds of Zebras Two kinds of Zebras –Grevy’s zebra Forms large loosely-bounded herds Forms large loosely-bounded herds –Plains zebra More common More common Forms tight-knit uni-male multi-female ”harems” Forms tight-knit uni-male multi-female ”harems” Possible to add collar just to the male Possible to add collar just to the male From time to time meet up with other zebras to form herds, for an example at water holes From time to time meet up with other zebras to form herds, for an example at water holes

A day in the life of a zebra Movement patterns Movement patterns –Grazing –Graze-walking –Fast-moving Zebras spend most day grazing and head for water about once a day Zebras spend most day grazing and head for water about once a day Zebras tend not to have long periods of motionless sleep Zebras tend not to have long periods of motionless sleep

Collar design Generally weight and power consumption are very important issues Generally weight and power consumption are very important issues Two kinds of radio Two kinds of radio –Short range (100 m) for communicating between the nodes –Long range (8 km) for communicating with the base station

Collar design Energy issues Energy issues –Battery recharged by solar power –Battery must be able to operate five days without being recharged –Traditional acid batteries are too heavy, so a lithium-ion battery must be used Space is conserved using a system, where the nodes delete old data as newer arrives Space is conserved using a system, where the nodes delete old data as newer arrives

Collar design 30 position samples per hour, 24 hours a day 30 position samples per hour, 24 hours a day 6 hours for searching for peer nodes and transferring data over the short- range radio 6 hours for searching for peer nodes and transferring data over the short- range radio 3 hours for searching for the base station using long-range radio (overlapping with short range to minimize CPU usage) 3 hours for searching for the base station using long-range radio (overlapping with short range to minimize CPU usage)

Possible network protocols Flooding network protocol Flooding network protocol –Simple –Given that the Zebras move extensively there is a high data homing rate –Large amount of data (requires large bandwidth, large storage and much energy)

Possible network protocols History based network protocol History based network protocol –Works with a system ranking nodes depending on whether they have been close to the base station or not –Data is transfered to the neighbour that has the highest hierachy ranking –If the network changes too dynamically this does not work well –If sucessfull, the requirements for bandwidth, storage and energy are lower

Experimental results Tests performed in software Tests performed in software –Simulating 400 square km map –Zebra movement based on actual moving patterns –Each zebra independently selects speed and direction –Once per day the zebra goes to get water

Experimental results Direct or indirect connectivity Direct or indirect connectivity –Direct connectivity requires a radio range of 12 km for 100 pct. network coverage –Indirect connectivity requires a radio range of 2 km for 100 pct. network coverage –Thus indirect connectivity is necessary, since energy consumption is heavier the longer the radio range is

Experimental results Protocol evaluations, given that there are no constraints Protocol evaluations, given that there are no constraints –Direct transmission is considered, but requires long data range (11 km) –Flooding and history both require only 6 km radio range to achieve 100 pct. sucess rate

Experimental results Protocol evaluations given constraints Protocol evaluations given constraints –Storage constraints Flood and history perform better than direct transmission. Flood and history perform better than direct transmission. History performs the best, because of storage limitations for flooding History performs the best, because of storage limitations for flooding –Bandwidth constraints With low radio range, and thus few neighbour nodes, flooding performs best, but as radio range increases history performs better due to less redundant data With low radio range, and thus few neighbour nodes, flooding performs best, but as radio range increases history performs better due to less redundant data

Experimental results Energy tradeoffs Energy tradeoffs –At long ranges flooding is very energy expensive, as it sends vast amounts of redundant data –History fares a lot better, being only 1.04 times as expensive as direct transmission at a radio range of 15 km –Flooding only makes sense with low radio ranges and low connectivity

Experimental results Final design choices Final design choices –Short-range radio 100 m 100 m 19,2 Kbps 19,2 Kbps –Long-range radio 8 km 8 km 2,4 Kbps 2,4 Kbps

Experimental results Final design choices Final design choices –640 KB flash memory There can be stored 300 collar-days There can be stored 300 collar-days –66 ampere-hours energy consumption per month –Simulation results in a 83 pct. success rate