ZigBee

Market Application Landscape

Why ZigBee?

•    Standard in a fragmented market

–Many proprietary solutions, interoperability issues

•    Low Power consumption

–Users expect battery to last months to years!

•    Low Cost

•    High density of nodes per network

•    Simple protocol, global implementation

 

ZigBee -Target Markets

ZigBee Technology Adoption Curve

ZigBee Rate of Adoption

Standards Expectations

Market Size – Low Data Rate (No      )

Market Segmentation 2002 - 2006

Some Details - Home Controls

•    Energy Management is going to be a key aspect

 

•    Even if we are to ignore the Building Auto and Industrial Markets for a few minutes….

 

The Connected Home:

•     The features of a connected home exist today; they are not dreams of tomorrow. This home is connected in the sense that normally independent systems are linked to a centrally controlled system. In a connected home, your home computer, TV, lighting and heating controls, home security system and many appliances within the home can talk to each other via the Internet. These linked systems can be controlled through various devices, including your pager, cellular phone, TV, home PC, PDA, or even your automobile.

•     More specifically, the connected home offers the following: new forms of entertainment; anywhere, anytime communication with family, friends and coworkers; advanced home control and security; new ways to buy over the Internet; safe and secure e-mail and other communications; and always-on, high speed Internet access - all from reliable providers.

Internet Home Alliance Survey Findings
 Zigbee can provide or help provide 3 of the 5 top features customers want in a connected home

Connected Home Pilot Programs

Home Networking
Home appliances will complement additional Zigbee markets

Market Requirements

•    Global licence free ISM band operation

•    Unrestricted geographic use

•    RF penetration through walls & ceilings

•    Automatic/semi-automatic installation

•    Ability to add or remove devices

•    Possible voice support

Market Requirements, cont...

•    10k-115.2kbps data throughput

•    10-75m coverage range (home/garden)

•    Support for 32-255 nodes

•    Support for 4 critical devices

•    4-100 co-located networks

•    0.5-2 year battery life

•    Up to 5m/sec. (18kmph) permitted mobility

•    Module cost: $1.5-$2.5 in 2004/5!

ZigBee - General Characteristics

•    Data rates of 250 kbps and 20 kbps

•    Star topology, peer to peer possible

•    255 devices per network

•    CSMA-CA channel access

•    Optional Guaranteed Time Slot

•    Fully handshaked protocol for transfer reliability

•    Low power (battery life multi-month to years)

•    Dual PHY (2.4GHz and 868/915 MHz)

•    Extremely low duty-cycle (<0.1%)

•    Range: 10m nominal (1-100m based on settings)

•    Location Aware: Yes, but optional

 

ZigBee Alliance - IEEE - Customer Relationship

Range Estimation (Meters)

Network Topology

Other Network Forms

Supported Traffic Types

•    Periodic data

–Application defined rate

•    Intermittent

–Basic communication

•    Repetitive low latency data

–Allocation of guaranteed time slots

The Network Coordinator

•    Transmits network beacons

•    Sets up a network

•    Manages network nodes

•    Stores network node information

•    Routes messages between paired nodes

•    Receives constantly

The Network Node

•    Is generally battery powered

•    Searches for available networks

•    Transfers data from its application as necessary

•    Determines whether data is pending

•    Requests data from the network coordinator

 

•    Can sleep for extended periods

Stack System Requirements

•    8-bit mC, e.g. 80c51

•    Full protocol stack <32k

 

•    Simple node only stack ~4k

 

•    Coordinators require extra RAM

–node device database

–transaction table

–pairing table

The ZigBee Alliance

Some Participants

Standardization Challenge
How do we make a protocol a standard?

•    ZigBee Alliance created with companies who share a common vision

•    Alliance initiates need for low data rate W-PAN in IEEE, 802.15.4 is born

•    Both MAC and PHY proposals win vote in IEEE

•    Alliance is focussed on:

–Upper Layers of stack

–Interoperability

–Marketing

•    Keep initial participants limited until spec basics are defined

ZigBee vs Bluetooth

Competition or Complementary?

Bluetooth is Best

For :

 

•    Ad-hoc networks between capable devices

•    Handsfree audio

•    Screen graphics, pictures…

•    File transfer

Air Interface:

ZigBee

DSSS

11 chips/ symbol

62.5 K symbols/s

4 Bits/ symbol

 

Peak Information Rate

    ~128 Kbit/second

 

 

Bluetooth

FHSS

1 M Symbol / second

 

 

Peak Information Rate

    ~720 Kbit/second

ZigBee Protocol Stack
Size/Complexity

Bluetooth Protocol Stack Size/Complexity

Timing Considerations

Initial Enumeration

Power Considerations

ZigBee

•    2+ years from ‘normal’ batteries

•    Designed to optimise slave power requirements

 

Bluetooth

•    Power model as a mobile phone (regular charging)

•    Designed to maximise ad-hoc functionality

 

Battery Life & Latency in a Lightswitch

•    Bluetooth would either :

– keep a counter running so that it could predict which hop frequency the light would have reached or

–use the inquiry procedure to find the light each time the switch was operated.

To reduce latency, Bluetooth would:

•    The two devices must stay within 60 us (~1/10 of a hop)

•    30ppm crystals => could increase at 60us per second.

•    Devices communicate once a second to track each other's clocks.

•    Possibly could be improved by a factor of 100.

 

•     The devices would then need to communicate once every 100 seconds to maintain synchronisation.

 

•    => 900 communications / day with no information transfer

•    + perhaps 4 communications on demand

 

•    99.5% Battery Power wasted

To reduce power consumption, Bluetooth would

Light switch Conclusion

•    ZigBee radio using DSSS need only perform CSMA before transmitting, a delay of only 200 us (Radio wake up time)

 

•    In the case of a light switch, ZigBee offers longer battery life and lower latency than a Bluetooth equivalent.

Cost Standpoint

Solution Prices

Conclusion

•    ZigBee and Bluetooth are two solutions for two application areas

ZigBee in Building Automation

•    Existing solutions are either:

– Power Line Carrier based (PLC)

•Expensive ($15 - $40 BOM)

•Restricted to where there is existing power lines

•No mobility

•Interference from noisy inductance into the system (adding a fan, etc.)

•Security issues, PLC goes outside the home

•Interoperability is questionable

–Or proprietary

•Interoperability among various manufacturers

•Cost

•Existing RF solutions have limited capabilities

 

ZigBee - Bluetooth - PLC Comparison

Thank You