EmberNet – Wireless Networks for Industrial Systems

Presented by Ryan WuApril 11, 2003

Some slides and figures courtesy EmberNet, Rob Poor and Cliff Bowman

Motivation

Traditional Wireless Systems for Industry Point-to-Point Point-to-Multipoint

Pros v.s. Cons Structure, planning, signal failures…

New approach: Wireless Mesh Network

To meet the need

The network does not require sophisticated planning and site mapping to achieve reliable communication

Self-configuring, no human assistance needed Devices are able to transmit without moving Low error rate Low cost (energy and $ )

Mesh Network: At least two nodes with two or more

paths between them (Redundancy) E.g. Internet backbone

Pros: Reliability; Adaptability; Scalability

Cons:? Mesh Network v.s. Peer-to-

Peer?

Wireless Mesh Network

Outline Communication Architecture Ember Technology (Nodes and

Gateway) Gradient Routing and Service Discovery

Communication-Mesh Network

IEEE 802.15.4 (WPAN) Low rate (250,40,20 kbps at

2.4G/868/915MHz) Low power (goal: 3 AA for years)

Antennas: 1000 feet in open air, 20dBM No clear support for network diagnosis Loss retransmission at higher layer…

Ember Networks EmberNet nodes

embedded wireless networking peripheral

900MHz/2.4GHz 3.81 x 5.59 x .76 cm

EmberNet gateways

192 MHz,32 MB SDRAM, Intrinsyc Linux 4.1

Distribution

EmberNet Nodes EmberNet SPI: Synchronous serial hardware interface Host API provides a simple, consistent interface to the

routing, discovery, and service management in the EmberNet Protocol Stack on the EmberNet Node

EmberNet Gateway 10 Base-T Ethernet port 16MB Flash, 32 MB SDRAM, diskless Intrinsyc Linux 4.1 Distribution EmberNet Protocol Stack, EmberNet View, Apache HTTP

Server

Design and Programming Distributed task and messaging Match to available resources (compute,

space, etc. ) Exception-based (event driven) msg Reliability? (when multi-hops…)

Ad Hoc Routing Things to consider:

Energy Scalability And ?

Traditional routing protocols Distance vector approach Link state approach

Gradient Ad Hoc Routing Each node is also a router ”Cost” as a measurement, advertising to

others Only the neighboring ones that can delivery at

a lower cost will relay the msg

More details of GRAd

And more … A service point of view

Services are destinations for messages Service descriptions not unique: (need

nodeID) Change nodeID to represent devices

added/lost replaced Discovery: send msg with discovery flag Processors could filter messages and drop

the not matched ones…

And more: Discussion Pros of GRAd

Conceptually simple Loop free (gradient like) Limited data to keep at each node And?

Cons of Grad Scalability ? Problems with broadcast ? Interference and Collision ? Others ?

Discussions Compared with ”smart dust” ? Compared with ”TinyOS” ? Other Comments ?

Reference White Paper of EmberNet Gradient Routing in Ad Hoc Networks IEEE 802.15.4 http://www.ieee802.org/15/pub/TG4.html www.ember.com