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
<
SHORT
COMPRESSED
VIDEO
Bluetooth 2
802.15.3/WIMEDIA
Bluetooth1
LOW
<
ACTUAL THROUGHPUT
>
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
IEEE 802.15.4 & ZigBee In Context
Application
Customer
► 
API
Security
► 
32- / 64- / 128-bit encryption
Network
ZigBee
Alliance
Star / Mesh / Cluster-Tree
IEEE
802.15.4
PHY
868MHz / 915MHz / 2.4GHz
Stack
Network, Security & Application
layers
Brand management
IEEE 802.15.4
MAC
Silicon
► 
“the software”
► 
► 
“the hardware”
Physical & Media Access Control
layers
App
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 (10 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
Network Layer Functions
■  Starting a network – able to establish a new network
■  Joining and Leaving Network – nodes are able to become
members of the network as well as quit being members
■  Configuration – Ability of the node to configure its stack to
operate in accordance with the network type
■  Addressing – The ability of a ZigBee coordinator to assign
addresses to devices joining the network
■  Synchronization – ability of a node to synchronize with
another node by listening for beacons or polling for data
■  Security – ability to ensure end-to-end integrity of frames
■  Routing – nodes can properly route frames to their
destination (AODV, etc.)
55
Application Support Layer Functions
■  Zigbee Device Object (ZDO) maintains what the device is
capable of doing and makes binding requests based on
these capabilities
■  Discovery – Ability to determine which other devices are
operating in the operating space of this device
■  Binding – Ability to match two or more devices together
based on their services and their needs and allow them to
communicate
56
Binding
EP – Endpoint (subunit of a node)
57
MicaZ,TinyOS, and Zigbee
58
Micaz Crossbow
■  MicaZ motes use the 802.15.4
standard defined in 2003
■  MicaZ motes do not use the
network and application layers
defined by the Zigbee Alliance’s
network and application layers
■  Zigbee upper layers had not
been finalized in time
■  MicaZ motes are using TinyOS
1.1.7 and Crossbow’s mesh
networking stack
59
MicaZ Network & Application layers
Network Layer:
■  Any Network Layer/ Routing Algorithm can be implemented
in TinyOS
► 
Many available already
Application Layer
■  open-source TinyOS supported
►  Applications
can be developed for use with TinyOS
60
More 802.15.4 Specs
■  MicaZ Power Consumption
► 
30 µW during sleep
► 
33 mW while active
■  MicaZ Lifetime
► 
~ 1 year (Zigbee specifies up to 2 years) (ATTN!)
■  MicaZ Range
► 
75 – 100 m (outdoors)
► 
20 – 30 m (indoors)
61
MICAz MOTE
■  IEEE 802.15.4
■  250 kbps radio
■  4KB SRAM
■  4KB Configuration EEPROM
■  128KB program flash memory
■  512KB measurement log flash memory (xbow estimates >
100000 samples)
■  10 bit Analog to Digital Converter
■  Red, Green, & Yellow LEDs
■  51-pin expansion connector
62
TinyOS
■  Open Source Operating System designed for MOTEs
■  Programs written in an extension of C called nesC
►  TinyOS
is event driven
►  nesC
- wire together components that handle events/fire
commands through interfaces to build an application (highly
modular)
■  Preinstalled (8 motes) Surge ad-hoc multi-hop (Destination-
Sequenced Distance Vector routing) software (xbow) written
in nesC
63
Simulation Tools
■  TOSSIM - TinyOS simulator
►  simulates
application code
more so than a network
simulation like ns2, Opnet
■  TinyViz - graphical interface
for TOSSIM
►  can
be extended with plug-
ins
64
Most important characteristics of WSN
Survey conducted mid-2002 on the characteristics of a
wireless sensor network most important to its users:
► 
Data Reliability
► 
Battery Life
► 
Cost
► 
Transmission Range
► 
Data Rate
► 
Data Latency
► 
Physical Size
► 
Data Security
65
Designing with 802.15.4 and ZigBee
IEEE 802.15.4 vs Bluetooth
Motorola 802.15.4 / ZigBee™ features
► 
2.4 GHz Band, -92 dBm RX sensitivity at 1% PER
s  IEEE requirement is at least –85 dBm
► 
Power supply 2.0-3.6 V w/ on-chip regulator, logic interface 1.7 to 3.3
s  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 MHz minimum
► 
802.15.4 MAC supplied
► 
Four new Motorola HCS08 MCUs will interoperate with the data
modem chip
s  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
67
System Simplicity and Flexibility
Motorola RF Packet Radio
Motorola 8-Bit MCU
68
Motorola’s 802.15.4 Platform Advantages
■  One-Stop-Shop Solution
► 
Single source for platform solution
s  Integrated Circuits, Reference Designs, Modules, Stack Software, Development Systems
■  Key technology enhancements provide for a superior solution
► 
Excellent adjacent channel rejection
s  No external filtering required under most conditions
► 
High Sensitivity Radio Solution
s  7 dBm better than spec – longer range
► 
Extended Temperature Operating Range
s  -40°C to +85°C for industrial and automotive applications
► 
Operating voltage range optimized for alkaline or lithium primary cells
s  2.0 Vdc to 3.6 Vdc, disposable
–  Nearly 100% of available battery life whether Alkaline or Lithium
–  Normal 2.7v EOL silicon systems can only get perhaps 30% of available alkaline
battery energy
► 
Adjustable TX Output power
s  Improved coexistence for short range applications
■  IEEE Participation and ZigBee™ Alliance leadership
► 
Technology and standards driver
► 
Early access to new technology
69
IEEE 802.15.4/ZigBee and Bluetooth
■  Instantaneous Power Consumption
► 
15.4 Transceivers are “similar” to Bluetooth Transceivers
s  802.15.4
–  O-QPSK with shaping
–  Max data rate 250kbps over the air
–  2Mchips/s over the air Direct Sequence Spread Spectrum (62.5ksps*32 spread)
–  -92 dBm sensitivity nominal
–  40ppm xtal
s  Bluetooth
–  FSK
–  Max data rate 720kbps over the air
–  1Msps over the air Frequency Hop Spread Spectrum (79 channels @ 1600 hps)
–  -83 to -84 dBm sensitivity nominal
–  20ppm xtal
■  Instantaneous power consumption will be similar for the raw transceivers
without protocol
■  Bluetooth’s FHSS makes it impractical to create extended networks without
large synchronization cost
70
IEEE 802.15.4 Protocol Built for the Mission
■  15.4 Protocol was developed for very different reasons than Bluetooth
► 
802.15.4
s  Very low duty cycle, very long primary battery life applications as well as mains-
powered
s  Static and dynamic mesh, cluster tree and star network structures with potentially a
very large number (>>65534) of client units, low latency available as required
s  Ability to remain quiescent for long periods of time without communicating to the
network
► 
Bluetooth
s  Moderate duty cycle, secondary battery operation where battery lasts about the
same as master unit
s  Wire replacement for consumer devices that need moderate data rates with very
high QoS and very low, guaranteed latency
s  Quasi-static star network structure with up to 7 clients (and ability to participate in
more than one network simultaneously)
s  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
71
Security Sensors
■  Battery Operation
►  2
AA Alkaline or 1 Li-AA cell
■  802.15.4/ZigBee Mode
►  Non-beacon network environment
■  Sensor process
►  RC Oscillator waking up MCU and
doing network check-in at some
interval
s  Many security systems have
between ~10 second and ~15
minute requirement
►  On a sensor event, device
immediately awakens and reports
in to network
Vcc
SPI
4
802.15.4
XCVR CLK
SPI
OSC1
Vcc
3Vdc
MCU
IRQ
16.000MHz
Security
Sensor
72
Security Sensor Timing
Battery-Powered
Sensor
Mains-Powered
Router
Interval timer
expires: Wake Up
Check-in only
~1640µs
Event and Get Data
~2300µs
256µs
CCAx2
192µs
RX>TX
~650µs
TX
RX
192µs
TX>RX
RX>TX
~350µs
ACK RX
ACK TX
OPT:
Pending ON
~650µs
RX Data
TX Data
Set Interval timer
Sleep
73
802.15.4 Security Sensor
Any check-in interval
exceeding ~14 sec allows
sensor to surpass alkaline
battery shelf life
Only at 15-min interval
does BT reach battery
shelf life
74
Body-Worn Medical Sensors
■  Heartbeat Sensor
►  Battery-operated
using CR2032 Li-
Coin cell
■  802.15.4/ZigBee Mode
►  Network environment using
Guaranteed Time Slot (GTS)
►  Network beacons occurring either
every
s  960ms or 61.44s (closest values
to 1 and 60 s)
■  Sensor has two ongoing processes
►  Heartbeat time logging
►  Transmit heartrate and other
information (8 bytes total)
s  Instantaneous and average
heart rate
s  Body temperature and battery
voltage
heartbeat
GTS
Beacon
time
Vcc
Vcc
802.15.4
XCVR
SPI
IRQ/
RESET
16.000MHz
4
SPI
3Vdc
MCU
INT
OSC1
OSC2
32.768kHz
IRQ
Heartbeat
Sensor
75
IEEE 802.15.4/ZigBee vs Bluetooth
At beacon interval ~60s,
15.4/ZigBee battery life
approx 416 days
802.15.4/ZigBee more
battery-effective at all
beacon intervals greater
than 0.246s
At beacon interval ~1s,
15.4/ZigBee battery life 85
days
Bluetooth 30 days
(park mode @ 1.28s)
76
Summary
■  IEEE 802.15.4 and ZigBee
►  Designer
concentrates on end application
s  Silicon vendors and ZigBee Alliance take care of transceiver, RF channel and
protocol
►  Reliable
and robust communications
►  Flexible network architectures
►  Very long primary battery life (months to years to decades)
►  Very inexpensive Bill Of Materials
►  Low system complexity for the OEM
■  More Information
►  Motorola:
www.motorola.com/zigbee
►  ZigBee: www.zigbee.org
77
Low Data Rate Wireless Evolution
First Stage
………
2002
2003
Second Stage
2004
2005
2006
Third Stage
2007
2008
2009+
§  Proprietary Dominates
§  Proprietary Fades
§  Standards Dominate
§  IEEE 802.15.4 Emerges
§  ZigBee Emerges
§  IEEE 1451.5 Emerges
§  System Integrator Focus
§  Semiconductor Focus
§  OEM Focus
§  Leading Edge OEMs
§  Early Adopter OEMs
§  Wireless Ubiquitous
§  $.1 - $1B Industry
§  $1 - $10B Industry
§  $10 - $100B+ Industry
§  $1,000 - $100 Unit Cost
§  $100 - $10 Unit Cost
§  $10 - $1 Unit Cost
78
Wireless Networking Standards
Market Name
Standard
Application Focus
GPRS/GSM
Wi-Fi™
Bluetooth™
ZigBee™
1xRTT/CDMA
802.11b
802.15.1
802.15.4
Wide Area Voice &
Data
Web, Email, Video
Cable Replacement
Monitoring & Control
System Resources
16MB+
1MB+
250KB+
4KB - 32KB
Battery Life (days)
1-7
.5 - 5
1-7
100 - 1,000+
Network Size
1
32
7
255 / 65,000
Bandwidth (KB/s)
64 - 128+
11,000+
720
20 - 250
Transmission Range
(meters)
1,000+
1 - 100
1 - 10+
1 - 100+
Success Metrics
Reach, Quality
Speed, Flexibility
Cost, Convenience
Reliability, Power,
Cost
79
IEEE 802.15.4 Key Features
  High
Data Reliability
Ø  DSSS,
bi-directional, message acknowledgement, low latency
Ø  Beacon
mode enables Guaranteed Time Slots (priority comm.)
  Advanced
Ø  Typical
 
Power Management
monitoring applications good for shelf life of battery
Inherent Data Security
Ø  Data
encryption, message authentication, packet freshness
  Protocol
Simplicity
Ø  Designed
for minimal cost & complexity
80
ZigBee Overview
  Specifications
Ø  Global
Managed by the ZigBee Alliance
consortium of OEMs, IC vendors & tech companies
Ø  Specify
device, network and service discovery / pairing
  Defining
Ø  Allows
Star, Mesh & Cluster-Tree Networks
users to balance system cost, reliability & battery life
  Defining
Ø  Extends
  Defining
Ø  Ensures
Security Management
32-, 64- & 128-bit AES encryption of 802.15.4
Application Profiles & Brand Compliance
product & application interoperability (e.g., AMR & DSM)
81
6LoWPAN Standard
82
6LoWPAN …
what it means for sensors
■  Low-Power Wireless Embedded devices can now be connected using
familiar networking technology,
►  like
ethernet
(but even where wiring is not viable)
►  and
like WiFi (but even where power is not plentiful)
■  all of these can interoperate in real applications
■  Interoperate with traditional computing infrastructure
■  Utilize modern security techniques
■  Application Requirements and Capacity Plan dictate how the network
is organized,
►  not
artifacts of the underlying technology
83
Web Services
XML / RPC / REST / SOAP / OSGI
HTTP / FTP / SNMP
Proxy / Gateway
Making sensor nets make sense
LoWPAN – 802.15.4
•  1% of 802.11 power, easier to
embed, as easy to use.
•  8-16 bit MCUs with KBs, not
MBs.
•  Off 99% of the time
TCP / UDP
IP
Ethernet
Sonet
802.11
802.15.4, …
IETF 6lowpan
84
Many Advantages of IP
■  Extensive interoperability
► 
Other wireless embedded 802.15.4 network devices
► 
Devices on any other IP network link (WiFi, Ethernet, GPRS, Serial lines, …)
■  Established security
► 
Authentication, access control, and firewall mechanisms
► 
Network design and policy determines access, not the technology
■  Established naming, addressing, translation, lookup, discovery
■  Established proxy architectures for higher-level services
► 
NAT, load balancing, caching, mobility
■  Established application level data model and services
► 
HTTP/HTML/XML/SOAP/REST, Application profiles
■  Established network management tools
► 
Ping, Traceroute, SNMP, … OpenView, NetManager, Ganglia, …
■  Transport protocols
► 
End-to-end reliability in addition to link reliability
■  Most “industrial” (wired and wireless) standards support an IP option
85
Key Factors for IP over 802.15.4
■  Header
►  Standard
IPv6 header is 40 bytes [RFC 2460]
►  Entire 802.15.4 MTU is 127 bytes [IEEE ]
►  Often data payload is small
■  Fragmentation
►  Interoperability
means that applications need not know the constraints of physical
links that might carry their packets
►  IP packets may be large, compared to 802.15.4 max frame size
►  IPv6 requires all links support 1280 byte packets [RFC 2460]
■  Allow link-layer mesh routing under IP topology
►  802.15.4
subnets may utilize multiple radio hops per IP hop
►  Similar to LAN switching within IP routing domain in Ethernet
■  Allow IP routing over a mesh of 802.15.4 nodes
►  Options
and capabilities already well-defines
►  Various protocols to establish routing tables
86
6LoWPAN – IP Header Optimization
Network IPv6 packet
40 Bytes
cls flowlen hops NH src IP dst IP
802.15.4 frame
net payload
3B
ctrl len src ID dst ID
hops
chk
6LoWPAN adaptation header
■  Eliminate all fields in the IPv6 header that can be derived from the 802.15.4
header in the common case
► 
Source address
: derived from link address
► 
Destination address
: derived from link address
► 
Length
: derived from link frame length
► 
Traffic Class & Flow Label
: zero
► 
Next header
: UDP, TCP, or ICMP
■  Additional IPv6 options follow as options
87
6LoWPAN Fragmentation
■  IP interoperability over many links => users not limited by frame size
■  IP datagrams that are too large to fit in a 802.15.4 frame are
fragmented into multiple frames
►  Self
describing for reassembly
Network IPv6 packet
IP header
net payload (e.g. 1500 bytes)
Multiple 802.15.4 frames
15.4 header
...
Fn
15.4 header F2 IP
15.4 header F1 IP
IP
chk
...
chk
chk
88
Conclusion
■  6LoWPAN turns IEEE 802.15.4 into the next IP-enabled link
■  Provides open-systems based interoperability among low-power devices
over IEEE 802.15.4
■  Provides interoperability between low-power devices and existing IP
devices, using standard routing techniques
■  Paves the way for further standardization of communication functions
among low-power IEEE 802.15.4 devices
■  Offers watershed leverage of a huge body of IP-based operations,
management and communication services and tools
■  Great ability to work within the resource constraints of low-power, low-
memory, low-bandwidth devices like WSN
89
Future convergence Zigbee/ 6LoWPAN
for Internet of Thinks
■  http://zachshelby.org/2009/02/20/zigbee-vs-ipv6/
90
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