Transcript Document

Submission Title: [What You Should Know about the ZigBee Alliance]
Date Submitted: [24 September 2003
Source: [Jon Adams] Company [Motorola]
Address [2100 E Elliott Rd, Tempe AZ 85254]
Voice:[480-413-3439], FAX: [480-413-4433], E-Mail:[[email protected]]
Re: [Sensors Expo Workshop]
Abstract: [Description of measures used to enhance reliability in IEEE 802.15.4/ZigBee]
Purpose: [Point of discussion for the Sensors Expo]
Notice: This document has been prepared to assist the ZigBee Alliance. It is offered as a basis for
discussion and is not binding on the contributing individual(s) or organization(s). The material in this
document is subject to change in form and content after further study. The contributor(s) reserve(s) the right
to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution will be posted in the member area of
the ZigBee web site.
Copyright 2002 The ZigBee Alliance, Inc.
What You Should Know about the
“Wireless that simply works”
Sensors Expo
24 September 2003
Anaheim Convention Center, Anaheim CA
Sensors Expo
September 24, 2003
Bob Heile, Chairman, Zigbee
Alliance
Copyright 2002 The ZigBee Alliance, Inc.
Mission Statement
To enable reliable, cost-effective, lowpower, wirelessly networked,
monitoring and control products based
on an open global standard.
Copyright 2002 The ZigBee Alliance, Inc.
The ZigBee Alliance Solution
• Targeted at home and building automation and
controls, consumer electronics, PC peripherals,
medical monitoring, and toys
• Industry standard through application profiles
running over IEEE 802.15.4 radios
• Primary drivers are simplicity, long battery life,
networking capabilities, reliability, and cost
• Alliance provides interoperability and
certification testing
Copyright 2002 The ZigBee Alliance, Inc.
History
Proposals Proposal ZigBee Alliance
formed
Initial MRD RSI/TRD
v0.2 to IEEE
ZigBee
IEEE 802.15.4
PAR
Proposals
1998
1999
2000
2001
Copyright 2002 The ZigBee Alliance, Inc.
Reviews
2002
Stand.
Complete
Promoter Companies
Copyright 2002 The ZigBee Alliance, Inc.
Membership Classes
• Promoters
– founding members of ZigBee, who form the
Board of Directors. There are currently 5
promoters + 1 chairperson
• Participants
– members who generally wish to make technical
contributions and/or serve on the Technical
Group committees. These members have early
access to specifications, and they may also
chair working group subcommittees. They are
in a position to help shape the ZigBee
technology for industrial applications and the
connected home.
Copyright 2002 The ZigBee Alliance, Inc.
Working Groups
• Architecture
• Application Framework
• Network
• Security
• Interoperability
• Marketing
Copyright 2002 The ZigBee Alliance, Inc.
The Wireless Market
GRAPHICS INTERNET
HI-FI
AUDIO
STREAMING
VIDEO
DIGITAL
VIDEO
MULTI-CHANNEL
VIDEO
>
LONG
TEXT
SHORT
< RANGE
802.11b
LAN
802.11a/HL2 & 802.11g
Bluetooth 2
ZigBee
PAN
Bluetooth1
LOW
< DATA RATE
>
HIGH
Copyright 2002 The ZigBee Alliance, Inc.
Applications
security
HVAC
AMR
lighting control
access control
BUILDING
AUTOMATION
patient
monitoring
fitness
monitoring
CONSUMER
ELECTRONICS
TV
VCR
DVD/CD
remote
ZigBee
PERSONAL
HEALTH CARE
asset mgt
process control
environmental
energy mgt
Wireless Control that
Simply Works
INDUSTRIAL
CONTROL
RESIDENTIAL/
LIGHT
COMMERCIAL
CONTROL
Copyright 2002 The ZigBee Alliance, Inc.
PC &
PERIPHERALS
mouse
keyboard
joystick
security
HVAC
lighting control
access control
lawn & garden irrigation
Development of the Standard
APPLICATION
ZIGBEE STACK
SILICON
• ZigBee Alliance
– 50+ companies: semiconductor
mfrs, IP providers, OEMs, etc.
Customer – Defining upper layers of
protocol stack: from network to
application, including
ZigBee
application profiles
Alliance
IEEE
– First profiles published mid
802.15.4
2003
• IEEE 802.15.4 Working Group
– Defining lower layers of protocol
stack: MAC and PHY scheduled
for release in April
Copyright 2002 The ZigBee Alliance, Inc.
Frequencies and Data Rates
2.4 GHz
BAND
COVERAGE
DATA RATE
ISM
Worldwide
250 kbps
16
Europe
20 kbps
1
Americas
40 kbps
10
868 MHz
915 MHz
ISM
Copyright 2002 The ZigBee Alliance, Inc.
# OF CHANNEL(S)
Stack Reference Model
End developer applications,
designed using application profiles
Application interface designed using
general profile
Topology management, MAC
management, routing, discovery
protocol, security management
Channel access, PAN maintenance,
reliable data transport
Transmission & reception on the
physical radio channel
ZA1
ZA2
…
ZAn
IA1
API
IAn
UDP
IP
ZigBee NWK
802.2 LLC
MAC (SSCS)
IEEE 802.15.4 MAC (CPS)
IEEE 802.15.4 PHY
Copyright 2002 The ZigBee Alliance, Inc.
Protocol Stack Features
• Microcontroller utilized
• Full protocol stack <32 k
• Simple node-only
stack ~4k
• Coordinators
require extra RAM
– Node device database
– Transaction table
– Pairing table
Customer
APPLICATIONS
APPLICATION INTERFACE
SECURITY
ZigBee
Alliance
NETWORK LAYER
Star/Cluster/Mesh
MAC LAYER
MAC LAYER
PHY LAYER
2.4 GHz
915MHz
Application
Copyright 2002 The ZigBee Alliance, Inc.
IEEE
802.15.4
868 MHz
ZigBee Stack
Silicon
ZigBee and Bluetooth
Competitive or
Complementary?
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
Optimized for different applications
• Bluetooth
• ZigBee
– Larger packets over small
– Smaller packets over
network
large network
– Ad-hoc networks
– Mostly Static
networks with many,
– File transfer
infrequently used
– Screen graphics, pictures,
devices
hands-free audio, Mobile
– Home automation,
phones, headsets, PDAs,
toys, remote controls,
etc.
etc.
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
Address Different Needs
• Bluetooth is a
cable replacement
for items like
Phones, Laptop
Computers,
Headsets
• Bluetooth expects
regular charging
– Target is to use
<10% of host
power
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
Address Different Needs
• ZigBee is better for
devices Where the
battery is ‘rarely’
replaced
– Targets are :
• Tiny fraction of host power
• New opportunities where
wireless not yet used
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
ZigBee
Air interface
Bluetooth
• FHSS
• DSSS- 11 chips/
symbol
• 1 M Symbol / second
• 62.5 K symbols/s
• Peak Information Rate
• 4 Bits/ symbol
~720 Kbit / second
• Peak Information Rate
~128 Kbit/second
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
Voice
Application Interface
Network Layer
Service
Discovery
Protocol
(Serial Port)
L2CAP
Host Control Interface
Link Manager
MAC Layer
MAC Layer
Link Controller
Baseband
RF
PHY Layer
ZigBee
Stack
Fax
Telephony OBEX
Control
RFCOMM
Protocol
Data Link Layer
Silicon
Dial-up
Networking
Application
vMessage
Intercom
Headset
Cordless
Group Call
vCard
vCal
vNote
User Interface
Application
Silicon
Zigbee
Bluetooth
Stack
Applications
Bluetooth
Protocol Stack Comparison
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
Timing Considerations
ZigBee:
• Network join time = 30ms typically
• Sleeping slave changing to active = 15ms typically
• Active slave channel access time = 15ms typically
Bluetooth:
• Network join time = >3s
• Sleeping slave changing to active = 3s typically
• Active slave channel access time = 2ms typically
ZigBee protocol is optimized for
timing critical applications
Copyright 2002 The ZigBee Alliance, Inc.
Initial Enumeration
ZigBee
Bluetooth
Coordinator
Coordinator
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
AIR INTERFACE
PROTOCOL STACK
BATTERY
DEVICES/NETWORK
LINK RATE
RANGE
Bluetooth
ZigBee
FHSS
DSSS
250 kb
28 kb
rechargeable non-rechargeable
8
255
1 Mbps
250 kbps
~10 meters (w/o pa) ~30 meters
Comparison Overview
Copyright 2002 The ZigBee Alliance, Inc.
An Application Example
Battery Life & Latency in a Light Switch
• Wireless Light switch –
– Easy for Builders to Install
• A Bluetooth Implementation
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.
Copyright 2002 The ZigBee Alliance, Inc.
Light switch using Bluetooth
• Option 1: use counter to predict hop
frequency reached by light
– The two devices must stay within 60 us (~1/10 of
a hop)
– With 30ppm crystals, devices need to
communicate once a second to track each other's
clocks.
– Assume this could be improved by a factor of 100
then devices would need to communicate once
every 100 seconds to maintain synchronization.
– => 900 communications / day with no information
transfer + perhaps 4 communications on demand
– 99.5% Battery Power wasted
Copyright 2002 The ZigBee Alliance, Inc.
Light switch using Bluetooth
• Option 2: Inquiry procedure to locate
light each time switch is operated
– Bluetooth 1.1 = up to 10 seconds typical
– Bluetooth 1.2 = several seconds even if
optimized
– Unacceptable latency
Copyright 2002 The ZigBee Alliance, Inc.
Light switch using ZigBee
• With DSSS interface, only need to
perform CSMA before transmitting
– Only 200 µs of latency
– Highly efficient use of battery power
ZigBee offers longer battery
life and lower latency than a
Bluetooth equivalent.
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee and Bluetooth
Conclusion
• ZigBee targets applications not
addressable by Bluetooth or any other
wireless standard
• ZigBee and Bluetooth complement for a
broader solution
Copyright 2002 The ZigBee Alliance, Inc.
Agenda
• What are IEEE 802.15.4 and ZigBee?
– IEEE802.15.4 – Packet Radio made simple
– ZigBee and the ZigBee Alliance
• Sensors and ZigBee, a natural pairing
– What’s Important
• Reliability and Robustness
• Cost, Size and Extreme Battery Life
– How it compares to other protocols
• Available Silicon and Platforms
– Motorola’s 802.15.4/ZigBee Platform Combo
• Summary / Q&A
Copyright 2002 The ZigBee Alliance, Inc.
A Primer to both 802.15.4 and ZigBee
Jon Adams
Director, Technology Strategy
Motorola Wireless and Mobile Systems
Tempe, Arizona
Copyright 2002 The ZigBee Alliance, Inc.
IEEE 802.15.4 Standard
Copyright 2002 The ZigBee Alliance, Inc.
IEEE 802.15.4 Basics
• 802.15.4 is a simple packet data protocol for lightweight
wireless networks
– Channel Access is via Carrier Sense Multiple Access with collision
avoidance and optional time slotting
– Message acknowledgement and an optional beacon structure
– Multi-level security
– Three bands, 27 channels specified
• 2.4 GHz: 16 channels, 250 kbps
• 868.3 MHz : 1 channel, 20 kbps
• 902-928 MHz: 10 channels, 40 kbps
– Works well for
• Long battery life, selectable latency for controllers, sensors, remote
monitoring and portable electronics
– Configured for maximum battery life, has the potential to last as
long as the shelf life of most batteries
Copyright 2002 The ZigBee Alliance, Inc.
Introduction to the IEEE
802.15.4 Standard
• IEEE 802.15.4 standard released May
2003
– Semiconductor manufacturers
• Sampling Transceiver ICs and platform
hardware/software to Alpha Customers now
– Users of the technology
• Defining application profiles for the first products,
an effort organized by the ZigBee Alliance
Copyright 2002 The ZigBee Alliance, Inc.
IEEE 802.15.4 standard
• Includes layers up to and including Link Layer Control
– LLC is standardized in 802.1
• Supports multiple network topologies including Star,
Cluster Tree and Mesh
• Features of the MAC:
Association/dissociation, ACK,
frame delivery, channel access
mechanism, frame validation,
guaranteed time slot management,
beacon management, channel scan
• Low complexity: 26 primitives
versus 131 primitives for
802.15.1 (Bluetooth)
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee Application Framework
Networking App Layer (NWK)
Data Link Controller (DLC)
IEEE 802.15.4 LLC
IEEE 802.2
LLC, Type I
IEEE 802.15.4 MAC
IEEE 802.15.4
868/915 MHz PHY
IEEE 802.15.4
2400 MHz PHY
IEEE 802.15.4 MAC Overview
•
Employs 64-bit IEEE & 16-bit short addresses
– Ultimate network size can reach 264 nodes (more than we’ll probably
need…)
– Using local addressing, simple networks of more than 65,000 (2^16) nodes
can be configured, with reduced address overhead
•
Three devices specified
– Network Coordinator
– Full Function Device (FFD)
– Reduced Function Device (RFD)
•
•
•
•
•
•
•
Simple frame structure
Reliable delivery of data
Association/disassociation
AES-128 security
CSMA-CA channel access
Optional superframe structure with beacons
GTS mechanism
Copyright 2002 The ZigBee Alliance, Inc.
IEEE 802.15.4 Device Types
• Three device types
– Network Coordinator
• Maintains overall network knowledge; most sophisticated of the three
types; most memory and computing power
– Full Function Device
• Carries full 802.15.4 functionality and all features specified by the
standard
• Additional memory, computing power make it ideal for a network router
function
• Could also be used in network edge devices (where the network
touches the real world)
– Reduced Function Device
• Carriers limited (as specified by the standard) functionality to control
cost and complexity
• General usage will be in network edge devices
• All of these devices can be no more complicated than the
transceiver, a simple 8-bit MCU and a pair of AAA batteries!
Copyright 2002 The ZigBee Alliance, Inc.
Data Frame format
•
•
•
•
•
One of two most basic and important structures in 15.4
Provides up to 104 byte data payload capacity
Data sequence numbering to ensure that all packets are tracked
Robust frame structure improves reception in difficult conditions
Frame Check Sequence (FCS) ensures that packets received are
without error
Copyright 2002 The ZigBee Alliance, Inc.
Acknowledgement Frame
Format
• The other most important structure for 15.4
• Provides active feedback from receiver to sender that
packet was received without error
• Short packet that takes advantage of standardsspecified “quiet time” immediately after data packet
transmission
Copyright 2002 The ZigBee Alliance, Inc.
MAC Command Frame format
• Mechanism for remote control/configuration of
client nodes
• Allows a centralized network manager to
configure individual clients no matter how
large the network
Copyright 2002 The ZigBee Alliance, Inc.
Beacon Frame format
•
•
•
Beacons add a new level of functionality to a network
Client devices can wake up only when a beacon is to be broadcast,
listen for their address, and if not heard, return to sleep
Beacons are important for mesh and cluster tree networks to keep all
of the nodes synchronized without requiring nodes to consume
precious battery energy listening for long periods of time
Copyright 2002 The ZigBee Alliance, Inc.
MAC Options
• Two channel access mechanisms
– Non-beacon network
• Standard ALOHA CSMA-CA communications
• Positive acknowledgement for successfully received packets
– Beacon-enabled network
• Superframe structure
– For dedicated bandwidth and low latency
– Set up by network coordinator to transmit beacons at
predetermined intervals
» 15ms to 252sec (15.38ms*2n where 0  n  14)
» 16 equal-width time slots between beacons
» Channel access in each time slot is contention free
– Three security levels specified
• None
• Access control lists
• Symmetric key employing AES-128
Copyright 2002 The ZigBee Alliance, Inc.
Frequencies and Data Rates
• The two PHY bands (UHF/Microwave) have
different physical, protocol-based and
geopolitical characteristics
– Worldwide coverage available at 2.4GHz at 250kbps
– 900MHz for Americas and some of the Pacific
– 868MHz for European-specific markets
Copyright 2002 The ZigBee Alliance, Inc.
ISM Band Interference and
Coexistence
• Potential for interference exists in every ISM band, not
just 2.4GHz
• IEEE 802.11 and 802.15.2 committees are addressing
coexistence issues
• ZigBee/802.15.4 Protocol is very robust
– Clear channel checking before transmission
– Backoff and retry if no acknowledgement received
– Duty cycle of a ZigBee-compliant device is usually
extremely low
– It’s the “cockroach that survives the nuclear war”
• Waits for an opening in otherwise busy RF spectrum
• Waits for acknowledgements to verify packet reception at
other end
Copyright 2002 The ZigBee Alliance, Inc.
PHY Performance
802.15.4 has excellent
performance in low
SNR environments
Copyright 2002 The ZigBee Alliance, Inc.
IEEE1451.5 Sensor Group
Wireless Criteria
• A survey was conducted mid-2002 on the characteristics
of a wireless sensor network most important to its users
• In order of importance, these characteristics are
1.
2.
3.
4.
5.
6.
7.
8.
Data Reliability
Battery Life
Cost
Transmission Range
Data Rate
Data Latency
Physical Size
Data Security
• How would you modify these requirements, if at all?
Copyright 2002 The ZigBee Alliance, Inc.
Reliability and Robustness
throughout the stacks of IEEE
802.15.4 and ZigBee
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
• Consistently perform a given task
to the desired result despite all
changes of environmental behavior
• Without fail
• A necessary ingredient of trust
• “When the sensor measures its
environment; the controller always
knows that same value”
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
• The wireless medium is not a
protected environment like the
wired medium, but rather, it is
fraught with degradations,
disruptions, and pitfalls such as
dispersion, multipath, interference,
frequency dependent fading,
sleeping nodes, hidden nodes, and
security issues.
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
• Each of these degradations and
disruptions can be mitigated by
various mechanisms within the ISO
layers; but not all mechanisms are
compatible with all other mechanisms
or may negatively impact critical
performance attributes
• The system must be optimized for
the best performance in a realistic
environment
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
• In addition to the previous
disruptions there is the case of
sending messages to devices that
are not receiving, e.g. they’re in
the “sleep” mode. When this
happens the message needs to be
buffered by another device that is
able to send the message when
the sleeping device wakes up.
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
Interferer
Router
Multipath
XX
Sleeping Node
Network
Coordinator
Hidden Node
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
• IEEE 802.15.4 has built upon the
successes of previous IEEE 802
standards by selecting those
mechanisms proven to ensure
good reliability without seriously
degrading system and device
performance.
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
ISO Layers:
• PHY: Direct Sequence with
Frequency Agility (DS/FA)
• MAC: ARQ, Coordinator buffering
• Network: Mesh Network (redundant
routing)
• Application Support Layer: Security
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
PHY Layers:
• Direct sequence: allows the radio to
reject multipath and interference by use
of a special “chip” sequence. The more
chips per symbol, the higher its ability
to reject multipath and interference.
• Frequency Agility: ability to change
frequencies to avoid interference from a
known interferer or other signal source.
Copyright 2002 The ZigBee Alliance, Inc.
IEEE 802 Direct Sequence
IEEE
802.
11
Chips/ 11
Symbol
11b
15.4
(900)
15.4
(2.4)
11
15
32
• As can be seen from above,
IEEE802.15.4/ZigBee has more
processing gain (chips/symbol)
than its predecessors
Copyright 2002 The ZigBee Alliance, Inc.
Direct Sequence and
Frequency Agility
Interferer
Over the Air
2.4 GHz
PHY
Desired Signal
After DS correlation
Channels 11-26
2.4 GHz
5 MHz
2.4835 GHz
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
MAC:
• ARQ (acknowledgement request) is
where a successful transmission is
verified by replying with an
acknowledge (ACK). If the ACK is not
received the transmission is sent again
• Coordinator buffering is where the
network coordinator buffers messages
for sleeping nodes until they wake again
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
Network:
• Mesh Networking: allows various
paths of routing data to the
destination device. In this way if a
device in the primary route is not
able to pass the data, a different
valid route is formed, transparent
to the user.
Copyright 2002 The ZigBee Alliance, Inc.
Reliability: Mesh Networking
ZigBee Coordinator (FFD)
ZigBee Router (FFD)
ZigBee End Device (RFD or FFD)
Mesh Link
Star Link
Copyright 2002 The ZigBee Alliance, Inc.
Reliability
Application Support Sub-layer(APS):
• Security: supports reliability by
keeping other devices from
corrupting communications.
• The APS configures the security
emplaced in the MAC layer and
also adds some of its own.
Copyright 2002 The ZigBee Alliance, Inc.
Robustness
• Let’s define robustness as the
ability to tolerate significant
degrading phenomena in the
physical medium
• Multipath and interference are
probably the most significant
degradations to the channel model.
Copyright 2002 The ZigBee Alliance, Inc.
Robustness
• Frequency hopping is a method that
allows the radio to periodically
change channels to over time
minimize the effect of a “bad”
channel. While this technique is
very effective in some circumstances
it creates other problems such as
latency, network uncertainty for
sleeping nodes, loss of the product
bandwidth x time, etc.
Copyright 2002 The ZigBee Alliance, Inc.
Robustness
• Direct Sequence with Frequency
Agility (DS/FA) combines the best
features of DS and FH without
most of the problems caused by
frequency hopping because
frequency changes aren’t
necessary most of the time, rather
they’re appropriate only on an
exception basis.
Copyright 2002 The ZigBee Alliance, Inc.
Robustness
The 802.11 Working Group couldn’t
agree upon which of the following
PHYs was the best: FH, IR, or DS.
So all three were standardized and
left to the market to decide.
Of the three PHYs; DS was the clear
market winner. DS provided
sufficient robustness with higher
overall performance.
Copyright 2002 The ZigBee Alliance, Inc.
Robustness
• Excess robustness does not
achieve higher performance,
rather it typically costs
performance
Copyright 2002 The ZigBee Alliance, Inc.
Conclusion
• IEEE 802.15.4/ZigBee have
addressed reliability throughout
the ISO stack with proven
mechanisms to minimize the
uncertainty of the wireless medium
Copyright 2002 The ZigBee Alliance, Inc.
Examples
Copyright 2002 The ZigBee Alliance, Inc.
Transceiver Comparisons
• Instantaneous Power Consumption
– 15.4 Transceivers are “similar” to Bluetooth Transceivers
• 802.15.4
– OQPSK with shaping
– Max data rate 250kbps over the air
– 2Mchips/s over the air Direct Sequence Spread Spectrum (62.5ksps*32
spread)
– -90 dBm sensitivity
– 40ppm xtal
• Bluetooth
– FSK
– Max data rate 720kbps over the air
– 1Msps over the air Frequency Hop Spread Spectrum (79 channels @ 1600
hps)
– -85dBm sensitivity
– 20ppm xtal
• Instantaneous power consumption will be similar for the raw
transceivers without protocol
• Bluetooth’s frequency hop makes it extremely difficult to
create extended networks without large synchronization cost
Copyright 2002 The ZigBee Alliance, Inc.
Protocol Makes the Difference
• 15.4 Protocol was developed for very different reasons than
Bluetooth
– 802.15.4
• Very low duty cycle, very long primary battery life applications
• Static and dynamic star and mesh network structures with potentially a
very large number (>>65534) of client units, low latency available but
not necessary
• Ability to remain quiescent for long periods of time without
communicating to the network
– Bluetooth
• Moderate duty cycle, secondary battery operation where battery lasts
about the same as master unit
• Wire replacement for consumer devices that need moderate data rates
with very high QoS and very low, guaranteed latency
• Quasi-static star network structure with up to 7 clients (and ability to
participate in more than one network simultaneously)
• Generally used in applications where either power is cycled (headsets,
cellphones) or mains-powered (printers, car kits)
• Protocol differences can lead to tremendous optimizations in
power consumption
Copyright 2002 The ZigBee Alliance, Inc.
Applications
• Industrial Control/Monitoring Space
– Asset Management
• Basic identification
– Device ID, Device PN/SN, Device source/destination, etc.
• Asset “health”
– Temperature, humidity, shock, fuel levels, etc.
– Nearly any parameter can be monitored given an appropriate sensor
– Asset Tracking
• Location tracking through two-way communication
– Simplest form is communication/identification when passes a checkpoint
» Same as other RFID tagging systems
– More sophisticated “what other devices can it hear/communicate with?”
– Other options include ranging (time of flight) and SNR measurement
» Has the potential for very precise location measurement
– The wireless network uses protocol gateways to move
command/monitor data between the end devices and the network
data management center
Copyright 2002 The ZigBee Alliance, Inc.
Product Examples
Warehouses, Fleet management, Factory,
Supermarkets, Office complexes
•
•
•
•
•
•
•
•
Gas/Water/Electric meter, HVAC
Smoke, CO, H2O detector
Refrigeration case or appliance
Equipment management services & PM
Security services
Lighting control
Assembly line and work flow, Inventory
Materials processing systems (heat, gas flow,
cooling, chemical)
Temp.
Sensor
Database
Gateway
Energy, diagnostics, e-Business
services
•
Gateway or Field Service links to
sensors & equipment
–
•
Monitored to suggest PM, product updates,
status changes
Nodes link to PC for database storage
–
PC Modem calls retailer, Service Provider, or
Corp headquarters
Corp headquarters remotely monitors assets,
billing, energy management
–
Field Service
or mobile
worker
Security
Sensor
Mfg Flow
Back End
Server
Telephone
Cable line
Materials
handling
HVAC
Copyright 2002 The ZigBee Alliance, Inc.
Service
Provider
Corp
Office
Retailer
Home & Diagnostics
Examples
SOHO
•
Retailer
Dealer
Service
Provider
Customers
•
Back End
Server
Server
Telephone
Cable line
Field
Service
AC or
heat
Pump
•
Gateway(s)
Mobile clients link to PC for database
storage
– PC links to peripherals, interactive
toys
– PC Modem calls retailer, SOHO,
Service Provider
Gateway links to security system,
temperature sensor, AC system,
entertainment, health.
Gateway links to field sales/service
PC &
peripherals
Entertainment
Temp.
Sensor
Body
monitor
Security
Sensor
Data Communication
Two way
Copyright 2002 The ZigBee Alliance, Inc.
White goods
HID Scenario: Wireless
Keyboard
• Scenario Parameters
– Battery-operated keyboard
• Part of a device group including a mouse or trackball,
sketchpad, other human input devices
• Each device has a unique ID
• Device set includes a USB to wireless interface dongle
– Dongle powered continuously from computer
• Keyboard does not have ON/OFF switch
• Power modes
– Keyboard normally in lowest power mode
– Upon first keystroke, wakes up and stays in a “more
aware” state until 5 seconds of inactivity have passes,
then transitions back to lowest power mode
Copyright 2002 The ZigBee Alliance, Inc.
Keyboard Usage
• Typing Rates
– 10, 25, 50, 75 and 100 words per
minute
• Typing Pattern
– Theoretical: Type continuously until
battery is depleted
• Measures total number of hours based
upon available battery energy
Copyright 2002 The ZigBee Alliance, Inc.
Wireless Keyboard Using
802.15.4
• 802.15.4 Operation Parameters
• Star network
• Non-beacon mode (CSMA-CA)
• USB Dongle is a PAN Coordinator Full Functional
Device (FFD)
• Keyboard is a Reduced Function Device (RFD)
• Power Modes
– Quiescent Mode used for lowest power state
» First keystroke latency is approx 25ms
– Idle mode used for “more aware” state
» Keystroke latency 8-12 ms latency
Copyright 2002 The ZigBee Alliance, Inc.
Wireless Keyboard Using
802.15.4
• 802.15.4 Chipset Parameters
• Motorola 802.15.4 Transceiver and
HCS08 MCU
• Battery operating voltage 2.0 – 3.6 V
– All required regulation internal to ICs
– Nearly all available energy usable with end of
life voltage at 2.0 volts
Copyright 2002 The ZigBee Alliance, Inc.
Wireless Keyboard Using
Bluetooth
• Bluetooth Operation Parameters
• Piconet network
• USB Dongle is piconet Master
• Keyboard is a piconet Slave
• Power Modes
– Park mode used for lowest power state
» 1.28 second park interval
» First keystroke latency is 1.28s
– Sniff mode used for “more aware” state
» 15ms sniff interval
» 15ms latency
Copyright 2002 The ZigBee Alliance, Inc.
Wireless Keyboard Using
Bluetooth
• Bluetooth Chipset Parameters
• CSR BlueCore 2 –External + Flash + Regulator
• Battery Operating Voltage 2.7 – 3.6 Vdc
– Requires external regulator for best performance
– Only 19 to 30 percent of available battery life
usable with 2.7V cutoff voltage
• Power Consumption (estimated)
– Park Mode @ 1.28 s interval: 0.05mA avg
– Sniff Mode @ 15ms interval: 8mA avg
– NOTE: I do not assume a deep sleep mode since
wake up time of 4 to 30 seconds seems
unacceptable
Copyright 2002 The ZigBee Alliance, Inc.
BT vs. 15.4 Keyboard
Comparison
Bad Hunt n’
Peck
802.15.4: Approx
38 days
BT: Approximately
5 operating days
By the way,
WirelessUSB looks
much like BT
Copyright 2002 The ZigBee Alliance, Inc.
Medical Sensor Scenario
Assumptions
• Environment
– Battery-operated sensor body-worn with either body-worn or
facility-mounted coordinator
– Sensor
• Running 100% of time
• Intelligent enough to output a digital waveform that at a minimum
signals a detected heart beat
• For the course of this study, assume that only the leading edge of this
pulse contains information (I.e., heartbeat event occurred)
• Power consumption is 10uA (WAG; immaterial to wireless connection
but will consume wireless connection's battery)
– Network Coordinator
• Provides a regular RF beacon to which the sensor synchronizes
• Expect to hear from the sensor during communications windows
relative to beacon interval
• Power Source
– Battery-operated if body-worn cellphone or other network access device
– Mains-powered if part of a hospital infrastructure
Copyright 2002 The ZigBee Alliance, Inc.
802.15.4/ZigBee Operation
Mode
•
802.15.4/ZigBee Mode
– Network environment using Guaranteed Time Slot (GTS)
– Network beacons occurring either every
• 960ms or 61.44s (closest values to 1 and 60 s)
• Guaranteed time slot occurs at some predetermined point in the beacon interval
•
Sensor has two ongoing processes
– Heartbeat time logging
– Transmit heartrate and other information (8 bytes total)
• Instantaneous heartrate (1/timeinterval between last two pulses,1ms precision)
• Running average heartrate (1/time interval between last twenty pulses, 1ms
precision)
• Sensor average temperature (0.1C precision)
• Sensor average battery state (0.1V precision)
heartbeat
GTS
Beacon
time
Copyright 2002 The ZigBee Alliance, Inc.
Medical Sensor Scenario
• Low Power, Low Latency
– RF XCVR IC is essentially off (leakage currents
predominating) in normal state
– MCU is capable of responding immediately to an interrupt
• MCU onboard 32kHz time clock is running
• Heartbeat sensor is capable of generating an interrupt signal
for MCU
• System is in a multisensor environment where all
sensors are assigned guaranteed timeslots (GTS) for
communications
• Scenario 1
– Beacon interval is 960ms (15ms*2^6)
• Scenario 2
– Beacon interval is 61.44s (15ms*2^12)
• Assume that retries are not necessary due to GTS
– Reasonable if we assume RF environment is well-controlled
Copyright 2002 The ZigBee Alliance, Inc.
General Schematic
Vcc
Vcc
802.15.4
XCVR
SPI
IRQ/
RESET
16.000MHz
4
3Vdc
SPI
MCU
INT
OSC1
Plus about 10-12 small value
capacitors, resistors excluding any
special components for heartbeat
sensor)
OSC2
IRQ
32.768kHz
Heartbeat
Sensor
Copyright 2002 The ZigBee Alliance, Inc.
Sensor Battery Type
• Lithium coin primary battery
– Tadiran Lithium type TL-2186
• http://www.tadiran.com/pdf/tl-2186.pdf
– 400 mAh nominal capacity (0.5mA
constant to 2.0V)
– 3.6V BOL, 2.0V EOL
Copyright 2002 The ZigBee Alliance, Inc.
Two Processes
• Process 1
– Each heartbeat forces the MCU to respond to the sensor interrupt
– From MCU interrupt to completion of processing
• Approximately 980 microseconds
• Approximately 3E-8 mAh consumed per heartbeat
• Process 2
– Each 960ms or 61.44s the system synchronizes to network and
transmits the information
– From MCU beacon wakeup to completion of transmission
• Approximately 56ms (varies depending on beacon interval and
assigned guaranteed time slot)
• Approximately 3E-4 mAh consumed per transmission event
• Constant Idle Currents
– 10 microamp sensor
– Leakage currents in RF XCVR IC and MCU oscillator/Time base
reference (~ microamps)
Copyright 2002 The ZigBee Alliance, Inc.
802.15.4/ZigBee vs Bluetooth
Li-Coin Cell Battery Life
(Beacon Interval vs Heartrate vs Days)
900
At beacon interval ~60s,
15.4/ZigBee battery life
approx 750 days
800
700
802.15.4/ZigBee superior
at all beacon intervals
greater than 0.246s
500
60
72
86
400
Bluetooth 33 days
(park300
mode @ 1.28s)
104
At beacon interval ~1s,
124
15.4/ZigBee battery life
149
nearly 136 days 179
200
BT@72bps
100
Beacon Interval (sec)
Copyright 2002 The ZigBee Alliance, Inc.
251.986
125.993
62.996
31.498
15.749
3.937
1.969
0.984
0.492
0.246
0.123
0.062
0.031
0.015
0
7.875
Days
600
Conclusion
• Bluetooth and 802.15.4 transceiver physical
characteristics are very similar
• Protocols are substantially different and designed for
different purposes
• 802.15.4 designed for low to very low duty cycle static
and dynamic environments with many active nodes
• Bluetooth designed for high QoS, variety of duty cycles,
moderate data rates in fairly static simple networks with
limited active nodes
• Bluetooth costs and system performance are in line with
3rd and 4th generation products hitting market while 1st
generation 15.4 products will be appearing only late this
year
Copyright 2002 The ZigBee Alliance, Inc.
More Information
• ZigBee Alliance web site
– http://www.ZigBee.org
• IEEE 802.15.4 web site
– http://www.ieee802.org/15/pub/TG4.html
• Articles
– “Meet the ZigBee Standard”, Sensors Mag June 2003
http://www.sensorsmag.com/articles/0603/14/
– “ZigBee Vital in Industrial Applications”, EETimes, 29
July 2003
http://www.eetimes.com/story/OEG20030727S0002
Copyright 2002 The ZigBee Alliance, Inc.
Motorola 802.15.4/ZigBee™
Platform for Low Data Rate
Wireless Jon Adams
Director,
Architecture
and Systems
Motorola
American
Association of
Wireless
and
Railroads
Automatic
Equipment
Broadband
Identification
Conference
Systems
Group
Pittsburgh,
PA 17 June
Copyright 2002 The ZigBee Alliance,
Inc.
jta @
System Simplicity and
Flexibility
Motorola RF Packet Radio
Motorola 8-Bit MCU
Copyright 2002 The ZigBee Alliance, Inc.
Motorola 802.15.4 / ZigBee™
solution
• Features
– 2.4 GHz Band, -90 dBm RX sensitivity at 1% PER
• IEEE spec is –85 dBm
– Power supply 2.0-3.6 V w/ on-chip regulator, logic interface 1.7 to
3.3
• Runs off a single Li or 2 alkaline cells
– Complete RF transceiver data modem – antenna in, fully
packetized data out
– Data and control interface via standard SPI at 4 to 8 MHz
– 802.15.4 MAC
– A large number of Motorola’s substantial line of HC08 MCUs will
interoperate with the data modem chip
• Often 802.15.4 functionality can be added to existing systems simply
by including the modem chip and reprogramming an existing MCU that
may already be in the application
– HC08 RAM/FLASH configurations from 384B/4kB to 2kB/60kB
depending upon application SW needs
Copyright 2002 The ZigBee Alliance, Inc.
Motorola’s RF Data Modem
Transceiver (1)
• Designed for the IEEE 802.15.4 and ZigBee™ standards
–
–
–
–
–
–
–
Operates in the 2.4 GHz ISM band available worldwide
Cost effective CMOS design
Low external components, no T/R switch required
On-chip low noise amplifier
0dBm (1.0 mW) PA, step adjustable to –30dBm
Integrated VCO, no external components
Full spread-spectrum encoding and decoding compatible
with 802.15.4
– RX sensitivity of –90 dBm at 1% PER, better than
specification
– Engineered to support 250 kBit/s O-QPSK data in 5.0 MHz
channels, per the IEEE 802.15.4 specification
– No line-of-sight limitations as with infrared (IR)
Copyright 2002 The ZigBee Alliance, Inc.
Motorola’s RF Data Modem
Transceiver (2)
• Designed to run DIRECTLY off two alkaline AA or AAA cells, or
one Lithium cell
– 2.0 to 3.6 V with on-chip voltage regulator
– Can use the full capacity of the battery (to end of life ~1.0V per
cell)
• Buffered transmit and receive data packets for simplified use
with low-end microcontrollers
• SPI data and control interface, operates up to 8MHz
• Designed to support peer to peer and star topologies
• On-board timers to support optional Superframe/Guaranteed
Time Slots for low latency transfer
• Will support optional Zigbee™ Network layer software
• Application-configurable power-saving modes that take best
advantage of battery operation
– RX/TX > Idle > Doze > Hibernate > Off
Copyright 2002 The ZigBee Alliance, Inc.
Scalability to Address Specific Needs
802.15.4 is a guest in existing microcontrollers
Applicationspecific interfaces
802.15.4 PHY Compliant Transceiver
RF Transceiver IC
RF Transmitter
Digital
Processing
RF Transmitter
>32kB FLASH 8-Bit
Microcontroller
Application
SPI
Digital
Processing
RF Transmitter
Zigbee NWK
15.4 RFD MAC
32kB FLASH 8-Bit
Microcontroller
RF Transceiver IC
RF Receiver
Application
15.4 FFD MAC
RF Transceiver IC
RF Receiver
Zigbee NWK
SPI
Digital
Processing
Application
15.4 RFD MAC
12kB FLASH 8-Bit
Microcontroller
RF Transceiver IC
RF Receiver
RF Transmitter
SPI
Digital
Processing
Application
Direct SPI Calls
3kB FLASH (min) 8-Bit
Microcontroller
Copyright 2002 The ZigBee Alliance, Inc.
System Complexity and Cost
RF Receiver
SPI
Motorola’s 802.15.4 Platform
Advantages
•
Total System Solution
– Single source for platform solution
• Integrated Circuits, Reference Designs, Modules, Stack Software, Development
Systems
•
Key technology enhancements provide for a superior solution
– Adjacent channel rejection
• Improvements in noisy environment
– High Sensitivity Radio Solution
• 5 dBm beyond spec – longer range
– Extended Temperature Operating Range
• -40°C to +85°C for industrial and automotive applications
– Operating voltage range optimized for alkaline or lithium primary cells
• 2.0 Vdc to 3.6 Vdc, disposable
– Adjustable TX Output power
• Improved coexistence for short range applications, improved battery life
•
IEEE and ZigBee™ Alliance membership
– Technology and standards driver
– Early access to new technology
Copyright 2002 The ZigBee Alliance, Inc.
Copyright 2002 The ZigBee Alliance, Inc.
Backups
Copyright 2002 The ZigBee Alliance, Inc.
Tracking Global Shipments
Securely 1
• High value consumer electronics shipment from
Singapore to Chicago (sea leg)
– Container loaded with high-value electronics in Singapore,
container’s transponder reads all the traditionally RFIDtagged material inside the container
– Loaded on ship at harbor, crane/ship communicates with
container’s transponder confirming loading, contents and
security and providing it information on ship’s network
– As ship proceeds across Pacific, environmental and
security data regularly collected from container’s
transponder, ensuring the safety of the contents and
providing ability for shipper/contents owner to proactively
respond to container malfunction/security breach
– Offloading at Long Beach, container transponder
communicates with crane to validate contents/point of
origin/container security and provides it information on
train’s network
Copyright 2002 The ZigBee Alliance, Inc.
Tracking Global Shipments
Securely 2
• High value consumer electronics shipment from
Singapore to Chicago (rail leg)
– Transloaded onto COFC train at Los Angeles harbor, crane
verifies contents, container ID and car number location
match to train manifest and provides it information on
train’s network
– Conveying flatcar establishes link with loaded container,
communicates “loaded” status forward to locomotive
computer
– Train leaves for Chicago; along way, locomotive continues
to request and receive regular updates from container and
relay entire train status to Ops
• Railroad provides the just-in-time information via internet to
the shipper/receiver
– Train arrives Chicago, container offloaded at yard, crane
communicates with container and verifies contents, source,
and security and provides it information on truck’s network
Copyright 2002 The ZigBee Alliance, Inc.
Tracking Global Shipments
Securely 3
• High value consumer electronics shipment from
Singapore to Chicago (road leg)
– Road tractor/trailer combo moving container to final
destination has transponder that communicates with
container, and verifies contents, source, destination, and
security
– Container arrives at destination (big box retail store
distribution) where employees verify for the final time the
contents, source, destination and container security before
signing off on delivery
• Shipment protected at all times on journey
• Mishandling, smuggling, homeland security issues all
contained with this simple yet very sophisticated system
Copyright 2002 The ZigBee Alliance, Inc.
Associating and disassociating
from a ZigBee network
• PAN Coordinator
– Enters enumeration or learn mode
– allows new nodes onto the network
for a defined amount of time (typical
may be a few seconds)
– If during this time there is a request
to join the network, a new node will
be able to do so
Copyright 2002 The ZigBee Alliance, Inc.
Are gateway products
available?
• Gateway Products have high value
for entry into established markets
– Alliance companies are developing
gateway products
– Will enable interconnection between
ZigBee networks and other home,
building automation, and industrial
networks
Copyright 2002 The ZigBee Alliance, Inc.
What are the international
regulations?
• ZigBee-compliant products
– Adhere to all relevant international
standards, including FCC, ETSI and
ARIB
Copyright 2002 The ZigBee Alliance, Inc.
How reliable is the ZigBee
technology?
• Reliability is a combination of
– RF Communications Link
• Clear channel detection
• Interference energy detection
• Frequency agility
– Protocol
•
•
•
•
•
Error detection/correction
Collision avoidance
Guaranteed Time Slots
Packet data acknowledgement
Packet data freshness
– Standardized and open protocol that has strong
certification and interoperability
Copyright 2002 The ZigBee Alliance, Inc.
What are some examples of
ZigBee applications?
• Well suited to a wide range of applications in every
industry
• Any application that could benefit from interoperability,
or that matches the fundamental RF characteristics of
the IEEE 802.15.4 standard would benefit from a
ZigBee solution. Examples include:
–
–
–
–
–
–
–
–
Wireless home security
Remote thermostats for air conditioner
Remote lighting, drape controller
Call button for elderly and disabled
Universal remote controller to TV and radio
Wireless keyboard, mouse and game pads
Wireless smoke, CO detectors
Industrial and building automation and control (lighting,
etc.)
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee vs. Proprietary
Solutions
• Main advantages
– Product interoperability
– Vendor independence
– Expectation of increased product innovation as a
result of the industry standardization of the physical
radio and logical networking layers
– No more having to invest resources to create a new
proprietary solution from scratch every time
– Companies now can leverage these industry
standards to instead focus their energies on finding
and serving customers
Copyright 2002 The ZigBee Alliance, Inc.
Adding ZigBee technology to
existing appliances
• Yes!
– Best suited to new design white goods
• Brings communications functionality from the appliance
to the manufacturer
– Some existing white goods may not be adaptable to
ZigBee application
– The opportunities for adding value through
integrating ZigBee into white goods is tremendous
• Improving service after the sale with high visibility into
product once sold
• Improved warranty coverage with ongoing functionality
data available to the manufacturer
• Potential for reduced energy costs by controlling
energy usage during peak periods
Copyright 2002 The ZigBee Alliance, Inc.
What security issues are
there and how will they be
solved?
• Security and data integrity
– Key benefits of the ZigBee technology
– ZigBee leverages the security model
of the IEEE 802.15.4 RF standard
• Extends this capability with robust
encryption options
• Can be tailored to the specific needs of
the networked device
Copyright 2002 The ZigBee Alliance, Inc.
How is ZigBee related to
IEEE 802.15.4?
• ZigBee takes full advantage of
– A powerful physical radio specified by
IEEE 802.15.4
• ZigBee adds
– Logical network and application
software
• ZigBee is based on the IEEE
802.15.4 RF standard, and the
Alliance is working closely with the
IEEE to ensure an integrated and
Copyright 2002 The ZigBee Alliance, Inc.
When will products be
available?
• Timetable
– IEEE 802.15.4 specification is
expected to be ratified in 1Q2003
– Standards-based silicon (868/915Mhz
and 2.4GHz) available shortly
thereafter
– ZigBee members are building
interoperable network, security and
application profiles on top of the IEEE
802.15.4 standard and this important
work is already underway
Copyright 2002 The ZigBee Alliance, Inc.
How big is the low data rate
wireless market expected to
be?
• The low data rate market is
currently estimated at 150M units
per year, according to ABI
– Market is completely proprietary, as
no industry standard has existed
before now that addressed the unique
needs of this market
– Impact of industry standardization on
the hardware and software layers is
expected to at least triple the size of
the current market within a few years
– Key market accelerators include an
Copyright 2002 The ZigBee Alliance, Inc.
What are the advantages of
joining the ZigBee Alliance?
• Membership provides
– Access to, and ability to influence,
this emerging standard
– Early access to the standard
specifications and to other companies
with complementary skills and
capabilities
– Ability to network with other leading
edge companies committed to
providing interoperable wireless
products and networks
Copyright 2002 The ZigBee Alliance, Inc.
How easy is it to develop
ZigBee-compliant products?
• ZigBee obviates the need for
development of RF or protocol
stacks
– Physical solution is ready for
integration into the end application
– Easy and cost-effective embedding of
ZigBee-compliant wireless networking
capabilities into products through the
introduction of small, low power,
wireless modules
– Availability of standards-based
Copyright 2002 The ZigBee Alliance, Inc.
Who is supporting the ZigBee
Alliance now?
• A rapidly growing list of industry
leaders worldwide has committed
to providing ZigBee-compliant
products and solutions
• Five promoter companies
– Honeywell, Invensys, Mitsubishi,
Motorola and Philips
• Nearly 40 (and growing every
month) participant companies
– Semiconductor manufacturers,
Copyright 2002 The ZigBee Alliance, Inc.
History
Proposals Proposal ZigBee Alliance
formed
Initial MRD RSI/TRD
v0.2 to IEEE
ZigBee
IEEE 802.15.4
PAR
Proposals
1998
1999
2000
2001
Copyright 2002 The ZigBee Alliance, Inc.
Reviews Expected
completion
2002
When will the preliminary
specification become
available?
• The IEEE 802.15.4 specification
– Physical, Media Access and Data Link
Layers
• Formal approval received in May 2003
• ZigBee Specification
– Network, security and application
profile layers
• Preliminary drafts available now
• Final specifications expected beginning in
the summer of 2003
Copyright 2002 The ZigBee Alliance, Inc.
Development of the Standard
• IEEE 802.15.4
Working Group
– Defining lower
layers of protocol
stack: MAC and
PHY scheduled for
release in April
• ZigBee Alliance
– 50+ companies:
semiconductor
mfrs, IP providers,
OEMs, etc.
– Defining upper
Copyright 2002 The ZigBee Alliance, Inc.
APPLICATION
Customer
ZIGBEE STACK
SILICON
ZigBee
Alliance
IEEE
802.15.4
•
How does ZigBee protocol
compare to the Bluetooth
protocol?
Stack sizes
– ZigBee stack is around 28Kbyte
– Bluetooth stack varies, but can be 250K
– Lower cost and lower power consumption
• System ability for truly long-sleep times
– Ultra-low power consumption is a key system design
aspect of the ZigBee technology
– Allows long lifetime non-rechargeable battery
powered devices versus rechargeable devices for
Bluetooth
– Example: the transition from sleep mode to data
transition is much faster in ZigBee than for Bluetooth
• Networking capabilities
– ZigBee can support at least 255 devices per network
– BT up to 8
• Radios are “similar”
Copyright 2002 The ZigBee Alliance, Inc.
How does ZigBee protocol
compare to the Bluetooth
protocol?
• Range for ZigBee products
– ~30 meters in a typical installation
– compared to ~10 meters for
Bluetooth products (without power
amplifier)
• ZigBee networks have very low
duty cycles
– Probability of interference and packet
loss in Bluetooth networks is very low
– If Bluetooth network causes the loss
of a ZigBee packet, the ZigBee
Copyright 2002 The ZigBee Alliance, Inc.
Why do we need both
technologies?
• Bluetooth wireless technology
– Well focused towards voice
applications and higher data rate
applications (cell phones, headsets,
etc.)
• The ZigBee technology
– Best suited for control and monitoring
applications
– Low data rates
– Low power
– Low costs
Copyright 2002 The ZigBee Alliance, Inc.
Comparing ZigBee to Existing
Technologies
• Other present offerings
– Proprietary technologies or
– Little or no networking capability
• Requires regular readers positioned at strategic points
• Tags cannot talk to similar devices
• Tags cannot independently network
– Asymmetric transceiving capability
• Primary function is traditional RFID tag
• Illuminate tag with plenty of RF, tag responds with ID,
maybe some small amount of fixed data
• Some tags now have simple transmitters and internal
batteries, but functionality is very minimal
• No practical sensors and little memory
Copyright 2002 The ZigBee Alliance, Inc.
Choosing ZigBee technology
over other protocols
• Choose ZigBee when
– Your application requires a standards-based wireless
network solution
– Simple to develop and deploy
– Flexible networking that can automatically (or under
network control) adjust to fit the physical plant
characteristics
– Optimized for applications requiring
•
•
•
•
•
•
Low cost
Low data rate
Long battery life
Robust security
High data reliability
Product interoperability
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee Topology Models
Mesh
Star
ZigBee coordinator
ZigBee Routers
ZigBee End Devices
Cluster Tree
Copyright 2002 The ZigBee Alliance, Inc.
Non-Beacon vs Beacon
Modes
• Non-Beacon Mode
– A simple, traditional multiple access system used in simple peer
and near-peer networks
– Think of it like a two-way radio network, where each client is
autonomous and can initiate a conversation at will, but could
interfere with others unintentionally
– However, the recipient may not hear the call or the channel might
already be in use
• Beacon Mode
– A very powerful mechanism for controlling power consumption in
extended networks like cluster tree or mesh
– Allows all clients in a local piece of the network the ability to know
when to communicate with each other
– Here, the two-way radio network has a central dispatcher who
manages the channel and arranges the calls
• As you’ll see, the primary value will be in system power
consumption
Copyright 2002 The ZigBee Alliance, Inc.
Example of Non-Beacon
Network
• Commercial or home security
– Client units (intrusion sensors, motion detectors, glass break
detectors, standing water sensors, loud sound detectors, etc)
• Sleep 99.999% of the time
• Wake up on a regular yet random basis to announce their continued
presence in the network (“12 o’clock and all’s well”)
• When an event occurs, the sensor wakes up instantly and transmits the
alert (“Somebody’s on the front porch”)
– The ZigBee Coordinator, mains powered, has its receiver on all the
time and so can wait to hear from each of these stations
• Since ZigBee Coordinator has “infinite” source of power it can allow
clients to sleep for unlimited periods of time to allow them to save
power
Copyright 2002 The ZigBee Alliance, Inc.
Example of Beacon Network
• Now make the ZigBee Coordinator battery-operated also
– All units in system are now battery-operated
– Client registration to the network
• Client unit when first powered up listens for the ZigBee Coordinator’s
network beacon (interval between 0.015 and 252 seconds)
• Register with the coordinator and look for any messages directed to it
• Return to sleep, awaking on a schedule specified by the ZigBee
Coordinator
• Once client communications are completed, ZigBee coordinator also
returns to sleep
– This timing requirement potentially impacts the cost of the timing
circuit in each end device
– Longer intervals of sleep mean that the timer must be more accurate or
– Turn on earlier to make sure that the beacon is heard, increasing receiver
power consumption, or
– Improve the quality of the timing oscillator circuit (increase cost) or
– Control the maximum period of time between beacons to not exceed 252
seconds, keeping oscillator circuit costs low
Copyright 2002 The ZigBee Alliance, Inc.
Growing the Network
•
•
•
In a beacon-environment, growing the network means keeping the
overall network synchronized
According to pre-existing network rules, the joining network’s PAN
Coordinator is probably demoted to Router, and passes along
information about its network (as required) to the PAN coordinator
Beacon information passed from ZigBee Coordinator to now-Router,
router knows now when to awake to hear network beacon
Joining Network
Existing
network’s
Coordinator
Demoted to
router
New link established
Copyright 2002 The ZigBee Alliance, Inc.
ZigBee Alliance
Promoters
Participants
And more each month…
Copyright 2002 The ZigBee Alliance, Inc.
Mission Statement
ZigBee Alliance members are defining
global standards for reliable, costeffective, low power wireless
applications. The ZigBee Alliance is a
rapidly growing, non-profit industry
consortium of leading semiconductor
manufacturers, technology providers,
OEMs and end users worldwide.
Copyright 2002 The ZigBee Alliance, Inc.
The Wireless Market
GRAPHICS INTERNET
HI-FI
AUDIO
STREAMING
VIDEO
DIGITAL
VIDEO
MULTI-CHANNEL
VIDEO
LAN
TEXT
802.11a/HL2 & 802.11g
ZigBee
<
RANGE
>
802.11b
PAN
Bluetooth 2
Bluetooth1
LOW
< DATA RATE
>
HIGH
Copyright 2002 The ZigBee Alliance, Inc.
802.15.4 and the
• IEEE 802.15.4
– Composed of many of the individuals and companies that
make up the ZigBee Alliance
– Developed the basic PHY and MAC standard with the
requirement that 15.4 be simple and manageable and that
high-level functionality (networking, security key
management, applications) be considered
• The ZigBee Alliance is
– A consortium of end users and solution providers, primarily
responsible for the development of the 802.15.4 standard
– Developing applications and network capability utilizing the
802.15.4 packet delivery mechanism
– Addresses application and interoperability needs of a
substantial part of the market
Copyright 2002 The ZigBee Alliance, Inc.
What is the ZigBee Alliance?
• Organization defining global standards for
reliable, cost-effective, low power wireless
applications
• A rapidly growing, worldwide, non-profit
industry consortium of
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–
–
–
Leading semiconductor manufacturers
Technology providers
OEMs
End-users
• Sensors are one of the reasons for ZigBee!
Copyright 2002 The ZigBee Alliance, Inc.
What is ZigBee technology?
• Cost-effective, standards-based wireless
networking solution
• Developed for and targets applications that
need
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–
–
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Low to moderate data rates and low duty cycles
Low average power consumption / long battery life
Security and reliability
Flexible and dynamic network topologies
• Star, cluster tree and mesh networks
– Interoperable application frameworks controlled by
an industry alliance to ensure
interoperability/compatibility
Copyright 2002 The ZigBee Alliance, Inc.
The ZigBee Alliance Solution
• Targeted at
–
–
–
–
–
–
Industrial and Commercial control/monitoring systems
Wireless sensor systems
Home and Building automation and controls
Medical monitoring
Consumer electronics
PC peripherals
• Industry standard through application profiles
• Primary drivers
–
–
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Simplicity
Long battery life
Networking capabilities
Reliability
Low cost
• Alliance member companies provide interoperability and
certification testing
Copyright 2002 The ZigBee Alliance, Inc.
Why do we need ZigBee
technology?
• ONLY standards-based technology that
– Addresses the unique needs of most remote
monitoring and control and sensory network
applications
– Enables the broad-based deployment of
wireless networks with low cost, low power
solutions
– Provides the ability to run for years on
inexpensive primary batteries for a typical
monitoring application
Copyright 2002 The ZigBee Alliance, Inc.
What kind of battery life can
a user expect?
• ZigBee protocol was designed from the ground
up to support
– very long life battery applications
• Users can expect
– Near-shelf life in a typical monitoring application
• Battery life is ultimately a function of
– battery capacity and application usage
• Many industrial applications are in harsh
thermal environments
– Batteries may include alkalines or Li-primaries
– Other forms of power generation might include solar,
mechanical, piezoelectric
Copyright 2002 The ZigBee Alliance, Inc.
Part 3: The Application Space
for 802.15.4/ZigBee
monitors
sensors
automation
control
monitors
diagnostics
sensors
INDUSTRIAL &
COMMERCIAL
CONSUMER
ELECTRONICS
TV
VCR
DVD/CD
remote
ZigBee
PERSONAL
HEALTH CARE
consoles
portables
educational
LOW DATA-RATE
RADIO DEVICES
TOYS &
GAMES
HOME
AUTOMATION
Copyright 2002 The ZigBee Alliance, Inc.
PC &
PERIPHERALS
security
HVAC
lighting
closures
mouse
keyboard
joystick
ZigBee and The ZigBee
Alliance
Copyright 2002 The ZigBee Alliance, Inc.