802.15.4 and Zigbee
What is ZigBee?
Technological Standard Created for Control and Sensor Networks.
Based on the IEEE 802.15.4 Standard.
Centered in small radios.
Created by the ZigBee Alliance.
200+ members.
History.
May 2003: IEEE 802.15.4 completed.
December 2004: ZigBee specification ratified.
June 2005: public availability.
What Does ZigBee Do?
Designed for wireless controls and sensors.
Operates in Personal Area Networks (PAN’s) and device-to- device networks.
Connectivity between small packet devices.
Examples: control of lights, switches, thermostats, appliances, etc..
Zigbee?
Named for erratic, zig-zagging patterns of bees between flowers.
Symbolizes communication between nodes in a mesh network.
Network components “seen as analogous” to queen bee, drones, worker bees.
Network applications
ZigBee and Other Wireless Technologies
Features
Low power consumption.
Low cost.
Small packet.
Low offered message throughput.
Supports large network orders (<= 65k nodes).
Low to no QoS guarantees.
Flexible protocol design suitable for many applications.
Overview
Low Rate WPAN (LR-WPAN).
E.g. Sensor networks.
Simple and low cost.
Fully handshake protocol.
Low power consumption.
Years on lifetime using standard batteries.
Different topologies.
Star, peer-to-peer, combined.
Data rates: 20-250 kbps.
Low latency support.
Operates at different frequencies.
868 Mhz, 915 Mhz, 2.4 GHz.
Architecture
ZigBee Alliance
45+ companies: semiconductor manufacturers, IP providers, OEMs, etc.
Defining upper layers of protocol stack: from network to application, including application profiles.
First profiles published mid 2003.
IEEE 802.15.4 Working Group.
Defining lower layers of protocol stack: MAC and PHY.
Protocol Stack
How ZigBee Works
Topology.
Star.
Cluster Tree.
Mesh.
Network coordinator, routers, end devices.
2 or more devices form a PAN/WSN.
States of operation.
Active.
Sleep.
Devices.
Full Function Devices (FFD’s).
Reduced Function Devices (RFD’s).
Modes of operation.
Beacon.
Non-beacon.
Traffic types.
Intermittent.
Repetitive.
Periodic.
Traffic
Types
Data is periodic.
Application dictates rate (e.g. sensors).
Data is intermittent.
Application or stimulus dictates rate (optimum power savings), e.g. light switch.
Data is repetitive (fixed rate a priori).
Device gets guaranteed time slot (e.g. heart monitor).
Modes
Beacon mode
Beacon sent periodically.
Coordinator and end device can go to power save.
Lowest energy consumption.
Precise timing needed.
Beacon period (ms-m).
Non-Beacon mode
Coordinator/routers have to stay awake (robust power supply needed).
Heterogeneous network.
Asymmetric power.
Node-Types
ZigBee Coordinator (ZBC) (IEEE 802.15.4 FFD)
only one in a network.
initiates network.
stores information about the network.
all devices communicate with the ZBC.
routing functionality.
bridge to other networks.
ZigBee Router (ZBR) (IEEE 802.15.4 FFD)
optional component.
routes between nodes, network backbone.
extends network coverage.
manages local address allocation/de-allocation.
ZigBee End Device (ZBE) (IEEE 802.15.4 RFD)
optimized for low power consumption.
cheapest device type.
sensor would be deployed here.
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