GeoMote:Geographic Network

Architecture for Sensor Networks

Joe Polastre<polastre@cs.berkeley.edu>

Rachel Rubin<rrubin@cs.berkeley.edu>

Motivation

• Sensor Network Data is typically interpreted based on a sensor’s location

• Current multihop beacon-based routing– Requires too much overhead– Only allows multihop to one node

• Routing by shortest number of hops results in large distance between hops

• Sensors often overloaded with participating in the network; not enough time to sense!

Goals

• Separate client sensing functions from network functions

• Enable clients with geographic information

• Provide a generalized architecture suitable for all client communications

• Maintain the same or less overhead in the geographic network architecture as in traditional multihop architectures

Applications of Geographic Services

• Geographic Multicast (GeoCast)

• Nearest Neighbor Service Discovery

• Geographic Network Reprogramming and Reconfiguration

• Low Power Pursuer/Evader Games

Low-Power Pursuer Evader

Evader

Components

• Allow Geographic Architecture to be plugable service for client applications

GENERIC_COMM

Localization

Location Services / Routing

Client Application

Why Use Location?

• Permits messages to be sent between any two nodes in the network

• Gives routing algorithms an additional parameter to analyze

• Provides additional information to client applications

GeoCast Architecture

Three Layer Architecture:• GeoHosts• GeoGateways• GeoRouters

Designed for powerful Internet workstations

(Julio Navas, Tomasz Imielinski, 1997)

GeoHosts

• Endpoints of the network

• Run client processes

• Initiate message transfer

• Determines if a packet is destined for its current geographic region

GeoGateways

• Entry and exit points of the network

• Communicate with GeoRouters and GeoHosts through broadcast messages

• Cover a given region specified by a radius

GeoRouters

• Perform intelligent routing and message delivery tasks

• Know the location of nearby GeoRouters and GeoGateways

• Route packets to GeoRouters and GeoGateways to deliver the packet to the destination geographic region

Geographic Routing Architecture

ClientProcess

ClientProcess

Direct Message

Router

Host

Gateway

Event

Event

Geographic vs. Internet Architecture

• Geographic (sensor)– Routers may never

talk to Hosts and vice versa

– Gateways are entry/exit points but have no routing info

– Broadcast medium dependant on distance from source

• Internet– Functions of the

gateway and router are typically merged

– Gateways perform routing functions and are entry/exit points

– Broadcast medium dependant on physical network

Network Hierarchy

• 2 layers– Simple

Implementation• Layer 1: Hosts• Layer 2: Routers

– Reduced Overhead– Less hops per

packet from source to destination

• n layers– More Complex– Can dedicate nodes

to specific network functions

– Allows optimization of resource usage

Its not obvious what the optimum number of network layers is.

Geographic Routing

• Naïve Method: Route to “closest” router

• Probabilistic Algorithms– Local Search

• Directed Diffusion (Estrin et al)

• Beam Forming (Algorithms, Antennae)

Experimental ResultsPacket Throughput

Experimental ResultsNumber of Hops

Future Work / Ideas

• Utilize the wireless broadcast medium to allow intermediate nodes to cache and aggregate data passively

• Evaluate and design new routing algorithms that leverage location information

• Collect and analyze results for controlled large-scale experiments

http://www.cs.berkeley.edu/~polastre/cs262/