ZigBee / IEEE 802.15.4

ZigBee / IEEE 802.15.4
ZigBee /
IEEE 802.15.4
ZigBee Alliance:
http://www.ZigBee.org
IEEE 802.15.4:
http://www.ieee802.org/15/pub/TG4.html
The Wireless Market
INTERNET/AUDIO
LONG
TEXT
>
RANGE
MULTI-CHANNEL
DIGITAL VIDEO
802.11b
802.11a/HL2 & 802.11g
ZigBee
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SHORT
COMPRESSED
VIDEO
Bluetooth 2
802.15.3/WIMEDIA
Bluetooth1
LOW
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ACTUAL THROUGHPUT
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HIGH
2
The Wireless Market (2)
3
What Is the ZigBee Alliance?
■  An organization with a mission to define reliable, cost-effective, low-power,
wirelessly networked, monitoring and control products based on an open global
standard
■  Alliance provides
► 
► 
► 
Upper layer stack and application profiles
Compliance and certification testing
Branding
■  Result is a set of interoperable solutions recognizable in the market
■  Eight promoter companies
► 
Ember, Freescale, Honeywell, Invensys, Mitsubishi, Motorola, Philips and
Samsung
■  A rapidly growing list (Over 120 participants) of industry leaders worldwide
committed to providing ZigBee-compliant products and solutions
► 
Companies include semiconductor manufacturers, wireless IP providers,
OEMs, and end-users
4
Why Do We Need ZigBee Technology?
■  No standard approach today that addresses the
unique needs of most remote monitoring and
control applications
► 
► 
► 
Enables the broad-based deployment of reliable
wireless networks with low-complexity, low-cost
solutions
Provides the ability to run for years on inexpensive
primary batteries for a typical monitoring application
Capable of inexpensively supporting robust mesh
networking technologies
5
How Is ZigBee Related to IEEE 802.15.4?
■  ZigBee takes full advantage of a physical radio
and MAC layers specified by IEEE 802.15.4 (lower
layers)
■  ZigBee adds logical network, security and
application software (higher layers)
■  ZigBee continues to work closely with the IEEE to
ensure an integrated and complete solution for the
market
6
Zigbee target markets
7
Applications
security
HVAC
AMR
lighting control
access control
patient
monitoring
fitness
monitoring
BUILDING
AUTOMATION
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
PC &
PERIPHERALS
mouse
keyboard
joystick
security
HVAC
lighting control
access control
lawn & garden irrigation
8
HVAC Energy Management
■  Hotel energy management
► 
Major operating expense for hotel
s  Centralized HVAC management
allow hotel operator to make sure
empty rooms are not cooled
► 
► 
► 
Retrofit capabilities
Battery operated t-stats can be
placed for convenience
Personalized room settings at
check-in
9
Home/Light Commercial Spaces
10
Industrial/Commercial Spaces
■  Warehouses, Fleet management, Factory, Supermarkets,
■ 
■ 
■ 
■ 
■ 
■ 
■ 
■ 
Office complexes
Gas/Water/Electric meter, HVAC
Smoke, CO, H2O detector
Refrigeration case or appliance
Equipment management services & Preventative maintenance
Security services
Lighting control
Assembly line and work flow, Inventory
Materials processing systems (heat, gas flow, cooling,
chemical)
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
Temp.
Sensor
Database
Gateway
Security
Sensor
Mfg Flow
Back End
Server
Telephone
Cable line
Materials
handling
HVAC
Service
Provider
Corp
Office
Retailer
11
Asset Management
■  Within each container, sensors
form a mesh network
■  Multiple containers in a ship
form a mesh to report sensor
data
■  Increased security through on-
truck and on-ship tamper
detection
■  Faster container processing.
Manifest data and sensor data
are known before ship docks
at port
12
ZigBee IP stack diagram
Application
Security
ZigBee SE 2.0
ZigBee IP
stack
Network
Managemen
t
(ND, RPL)
TCP
UDP
IPv6
Stack
Security
6lowpan adaptation
802.15.4 MAC
802.15.4 PHY
13
Frequencies and Data Rates (2006)
2.4GHz
BAND
COVERAGE
DATA RATE
# of CHANNELS
ISM
Worldwide
250kbps
16
Europe
20kbps,
100kbps,
250kbps
1
Americas
250kbps,
40kbps
10
868 MHz
915MHz
ISM
14
Basic Network Characteristics
■  65,536 network (client) nodes
■  Optimized for timing-critical applications
► 
Network join time:30 ms (typ)
► 
Sleeping slave changing to active: 15 ms (typ)
► 
Active slave channel access time: 15 ms (typ)
Network coordinator
Full Function node
Reduced Function node
Communications flow
Virtual links
15
Comparison of Key Features of
Complementary Protocols
Feature(s)
IEEE 802.11b
Bluetooth
ZigBee
Power Profile
Hours
Days
Years
Complexity
Very Complex
Complex
Simple
Nodes/Master
32
7
64000
Latency
Enumeration up to 3
Seconds
Enumeration up to 10
seconds
Enumeration 30ms
Range
100 m
10m
70m-300m
Extendibility
Roaming Possible
No
YES
Data Rate
11Mbps
1 Mbps
250Kbps
Security
Authentication Service Set
ID (SSID), WEP
64 bit, 128 bit
128 bit AES and Application
Layer user defined
16
Why ZigBee?
■  Reliable and self healing
■  Supports large number of nodes
■  Easy to deploy
■  Very long battery life
■  Secure
■  Low cost
■  Can be used globally
17
IEEE 802.15.4 Tutorial
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
►  Three
security
bands, 27 channels specified
s  2.4 GHz: 16 channels, 250 kbps
s  868.3 MHz : 1 channel, 20 kbps (BPSK) / 100 kbps (O-QPSK), 250
kbps (ASK)
s  902-928 MHz: 10 channels, 40 kbps (BPSK) / 250kbps (ASK or O-
QPSK)
►  Works
well for
s  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
19
802.15.4 General Characteristics
Data rates of 250 kb/s, 100 kb/s 40 kb/s and 20 kb/s.
Star or Peer-to-Peer operation.
Support for low latency devices.
CSMA-CA channel access.
Dynamic device addressing.
Fully handshaked protocol for transfer reliability.
Low power consumption.
Frequency Bands of Operation, either:
ü 16
channels in the 2.4GHz ISM band;
ü Or
10 channels in the 915MHz ISM band
and 1 channel in the European 868MHz band.
802.15.4 Architecture
Upper Layers
Other LLC
IEEE 802.2 LLC
IEEE 802.15.4 MAC
IEEE 802.15.4
868/915 MHz
PHY
IEEE 802.15.4
2400 MHz
PHY
IEEE 802.15.4 PHY Overview
Operating Frequency Bands
868MHz / 915MHz
PHY
2.4 GHz
PHY
2.4 GHz
Channel 0
Channels 1-10
868.3 MHz
902 MHz
Channels 11-26
2 MHz
928 MHz
5 MHz
2.4835 GHz
22
IEEE 802.15.4 PHY Overview
Packet Structure
PHY Packet Fields
• 
• 
• 
• 
Preamble (32 bits) – synchronization
Start of Packet Delimiter (8 bits)
PHY Header (8 bits) – PSDU length
PSDU (0 to 1016 bits) – Data field
Preamble
Start of
Packet
Delimiter
6 Octets
PHY
Header
PHY Service
Data Unit (PSDU)
0-127 Octets
23
IEEE 802.15.4 PHY Overview
Modulation/Spreading
2.4 GHz PHY
• 
• 
• 
• 
250 kb/s (4 bits/symbol, 62.5 kBaud)
Data modulation is 16-ary orthogonal modulation
16 symbols are orthogonal set of 32-chip PN codes
Chip modulation is O-QPSK at 2.0 Mchips/s
868MHz/915MHz PHY
•  Symbol Rate
•  868 MHz Band: 250 kb/s (20 bit/symbol, 12.5 kBaud),
100 kb/s (4 bit/symbol, 25 Kbaud), 20 kb/s (1 bit/symbol,
20 kBaud)
•  915 MHz Band: 250 kb/s (5 bit/symbol, 50 Kbaud or 4
bit/symbol, 62.5 Kbaud), 40 kb/s (1 bit/symbol, 40
kBaud)
•  Data modulation is BPSK with differential encoding
•  Spreading code is a 15-chip m-sequence
•  Chip modulation is BPSK , ASK or O-QPSK at
•  868 MHz Band: 300 or 400 kchips/s
•  915 MHz Band: 600, 1600 or 1000 kchips/s
24
IEEE 802.15.4 PHY Overview
Common Parameters
Transmit Power
•  Capable of at least .5 mW
Transmit Center Frequency Tolerance
•  ± 40 ppm
Receiver Sensitivity (Packet Error Ratio <1%)
•  <-85 dBm @ 2.4 GHz band
•  <-92 dBm @ 868/915 MHz band
RSSI Measurements
•  Packet strength indication
•  Clear channel assessment
•  Dynamic channel selection
25
IEEE 802.15.4 PHY Overview
PHY Primitives
PHY Data Service
•  PD-DATA – exchange data packets between MAC and PHY
PHY Management Service
• 
• 
• 
• 
PLME-CCA – clear channel assessment
PLME-ED - energy detection
PLME-GET / -SET– retrieve/set PHY PIB parameters
PLME-TRX-ENABLE – enable/disable transceiver
26
PHY Performance
802.15.4 has excellent
performance in low
SNR environments
Bluetooth
Working
zone BER
27
IEEE 802.15.4 MAC Overview
Design Drivers
•  Extremely low cost
•  Ease of implementation
•  Reliable data transfer
•  Short range operation
■  Very low power consumption
Simple but flexible protocol
28
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
►  Full
Coordinator
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
■  Optional GTS mechanism
29
IEEE 802.15.4 MAC Overview
Device Classes
■ 
■ 
Full function device (FFD)
► 
Any topology
► 
Network coordinator capable
► 
Talks to any other device
Reduced function device (RFD)
► 
Limited to star topology
► 
Cannot become a network coordinator
► 
► 
Talks only to a network coordinator
Very simple implementation
30
Topology Models
Star
Mesh
PAN coordinator
Full Function Device
Reduced Function Device
Cluster Tree
31
IEEE 802.15.4 MAC Overview
Star Topology
PAN
Coordinator
Master/slave
Full function device
Communications flow
Reduced function device
32
IEEE 802.15.4 MAC Overview
Peer-Peer (Mesh) Topology
Point to point
Full function device
Cluster tree
Communications flow
33
IEEE 802.15.4 MAC Overview
Combined Topology
Clustered stars - for example,
cluster nodes exist between rooms
of a hotel and each room has a
star network for control.
Full function device
Communications flow
Reduced function device
34
Mesh Networking
Coordinator (FFD)
Router (FFD)
End Device (RFD or FFD)
Mesh Link
Star Link
35
Cluster Tree
36
Star Network Key Attributes
§  Simplicity
§  Low Cost
§  Long Battery Life
§  Single Point of Failure
Node
Controller
Repeater (optional)
37
Mesh Network Key Attributes
§  Reliability
§  Extended Range
§  No Battery Life
§  Routing Complexity
Router Node
Controller
38
Hybrid Network Key Attributes
§  Flexibility
§  Reliability/Range of Mesh
§  Battery Life of Star
§  Design Complexity
Router Node
Node
Controller
39
IEEE 802.15.4 MAC Overview
Addressing
■  All devices have 64 bit IEEE addresses
■  Short addresses can be allocated
■  Addressing modes:
►  Network
+ device identifier (star)
►  Source/destination
identifier (peer-peer)
40
IEEE 802.15.4 MAC Overview
General Frame Structure
PHY Layer
MAC
Layer
Payload
Synch. Header
(SHR)
MAC Header
(MHR)
MAC Service Data Unit
(MSDU)
MAC Footer
(MFR)
MAC Protocol Data Unit (MPDU)
PHY Header
(PHR)
PHY Service Data Unit (PSDU)
4 Types of MAC Frames:
•  Data Frame
•  Acknowledgment
Frame
•  MAC Command Frame
•  Beacon Frame
41
Data Frame format
■  One of two most basic and important structures in 802.15.4
■  Provides up to 104 byte data payload capacity
■  Data sequence numbering to ensure that packets are tracked
■  Robust structure improves reception in difficult conditions
■  Frame Check Sequence (FCS) validates error-free data
42
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 standards-specified “quiet time” immediately after
data packet transmission
43
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
44
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
45
Frame Control field
46
IEEE 802.15.4 MAC Overview
Optional Superframe Structure
GTS 2
Contention Access
Period
GTS 1
Contention Free Period
15ms * 2n
where 0 ≥ n ≥ 14
Network beacon
Contention period
Guaranteed
Time Slot
Transmitted by network coordinator. Contains network information,
frame structure and notification of pending node messages.
Access by any node using CSMA-CA
Reserved for nodes requiring guaranteed bandwidth
47
IEEE 802.15.4 MAC Overview
Traffic Types
■ 
Periodic data
► 
■ 
Intermittent data
► 
■ 
Application defined rate (e.g. sensors)
Application/external stimulus defined rate (e.g. light switch)
Repetitive low latency data
► 
Allocation of time slots (e.g. mouse)
48
IEEE 802.15.4 MAC Overview
MAC Data Service
Recipient
MAC
Originator
MAC
MCPS-DATA.request
Originator
Recipient
Channel
access
Data frame
Acknowledgement
(if requested)
MCPS-DATA.indication
MCPS-DATA.confirm
49
IEEE 802.15.4 PHY Overview
MAC Primitives
MAC Data Service
•  MCPS-DATA – exchange data packets between MAC and PHY
•  MCPS-PURGE – purge an MSDU from the transaction queue
•  MAC Management Service
• 
• 
• 
• 
• 
• 
• 
• 
• 
• 
• 
MLME-ASSOCIATE/DISASSOCIATE – network association
MLME-SYNC / SYNC-LOSS - device synchronization
MLME-SCAN - scan radio channels
MLME- COMM-STATUS – communication status
MLME-GET / -SET– retrieve/set MAC PIB parameters
MLME-START / BEACON-NOTIFY – beacon management
MLME-POLL - beaconless synchronization
MLME-GTS - GTS management
MLME-RESET – request for MLME to perform reset
MLME-ORPHAN - orphan device management
MLME-RX-ENABLE - enabling/disabling of radio system
50
802.15.4 MAC Layer Specs
■  CSMA-CA (like 802.11) channel access scheme
■  Unlike 802.11 no RTS/CTS mechanism (due to relatively low data rate collisions are much
less likely)
■  Different Modes of Operation Depending on Nature of Traffic
► 
Periodic Transmissions
s  Beacon Mode
► 
Intermittent Transmissions
s  Disconnection Mode, node not attached to network when it doesn't need to
communicate (energy savings!)
► 
Low Latency Transmissions
s  Guaranteed Time Slot (GTS), allows for device to get an assigned time slot in super frame (a TDMA
scheme)
■  16 bit short addressing scheme or 64bit long addressing scheme
■  Four MAC frame types:
► 
Beacon Frame
► 
Data Frame
► 
ACK Frame
► 
MAC Command Frame
51
Non-Beacon Mode (Unslotted CSMA-CA)
Coordinator always active,
Coordinator
Node
Data frame
Node with low duty cycle
Coordinator
Node
Data Request
Acknowledgement
Acknowledgement
(opcional)
Data frame
Acknowledgement
Data to Coordinator
Data from Coordinator
52
Beacon Mode (Slotted CSMA-CA)
Nodes synchronized with Coordinator
Coordinator
Node
Beacon
Data frame
Coordinator
Node
Beacon
Data Request
Acknowledgement
Acknowledgement
(opcional)
Data frame
Acknowledgement
Data to Coordinator
Data from Coordinator
53
Peer-Peer Transfer
Nodes synchronized with each other
Node 1
Node 2
Data frame
Acknowledgement
54
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