1. Lecture 41 IEEE 802.15.4/ZigBee Dr. Ghalib A. Shah
Wireless Networks
Lecture 41
IEEE /ZigBee
Dr. Ghalib A. Shah

2. Outlines Overview of ZigBee IEEE 802.15.4
Whats is ZigBee, Zigbee in Wireless World, Architecture, Characteristics
IEEE
Basics, Type of Devices
Topology, Addressing
Phy Layer
Channel Access Mechanisms
Slotted/Unslotted CSMA/CA
Data Transfer Model
Superframe Structure

3. Last Lecture IP Over Bluetooth Bluetooth Security WPAN Standards
IEEE Overview
Topology
Coordination
Starting a Piconet
Handing over control of piconet
Creating child piconet
Ending a Piconent
Association/Disassociation
Medium Access (Superframe)
Channel Time Management
Power management
MAC Frame format

4. What is 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
The alliance provides interoperability, certification testing, and branding.

5. IEEE 802.15.4: What is ZigBee? A standard for mesh networking
Reliability through meshed connectivity
Designed for low power applications
Very long battery life
Low data rate
20-250Kb/sec (depending on band)
Very Secure
AES-128 encryption available
Self configuring
Allows ad hoc networks
Ease of installation and configuration

6. ZigBee in the wireless world
Chart Copyright ZigBee Alliance 2004

7. ZigBee/IEEE 802.15.4 Market Feature
Low power consumption
Low cost
Low offered message throughput
Supports large network orders (<= 65k nodes)
Low to no QoS guarantees
Flexible protocol design suitable for many applications

8. LIGHT COMMERCIAL CONTROL
ZigBee Target Markets
Security
HVAC
AMR
Lighting Control
Access Control
BUILDING
AUTOMATION
CONSUMER ELECTRONICS TV
VCR
DVD/CD
RF Remotes
PC & PERIPHERALS
PERSONAL HEALTH CARE
ZigBee
Wireless Control that
Simply Works
Patient monitoring
Fitness monitoring
INDUSTRIAL
CONTROL
RESIDENTIAL/
LIGHT COMMERCIAL CONTROL
Security
HVAC
Lighting Control
Access Control
Lawn & Garden
Irrigation
Asset Mgt
Process Control
Environmental
Energy Mgt
Chart Copyright ZigBee Alliance 2004

9. ZigBee/ Architecture

10. ZigBee/802.15.4 Technology: General Characteristics
Data rates of 250 kbps , 20 kbps and 40kpbs.
Star or Peer-to-Peer operation.
Support for low latency devices.
CSMA-CA channel access.
Dynamic device addressing.
16 channels in the 2.4GHz ISM band, 10 channels in the 915MHz ISM band and one channel in the European 868MHz band.

11. IEEE Basics
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

12. IEEE 802.15.4 Device Types There are two different device types :
A full function device (FFD)
A reduced function device (RFD)
The FFD can operate in three modes serving
Device
Coordinator
PAN coordinator
The RFD can only operate in a mode serving:

13. FFD vs RFD Full function device (FFD) Reduced function device (RFD)
Any topology
Network coordinator capable
Talks to any other device
Reduced function device (RFD)

14. Star Topology Network Network coordinator coordinator Master/slave
Full Function Device (FFD)
Reduced Function Device (RFD)
Communications Flow

15. Peer-Peer Topology Full Function Device (FFD) Communications Flow
Point to point
Tree
Full Function Device (FFD)
Communications Flow

16. Combined Topology Full Function Device (FFD)
Reduced Function Device (RFD)
Communications Flow

17. Extending ZigBee Networks
ZED (ZigBee Extension Device)
A ZigBee router with a wire interface
Joins two or more radio disjoint PANs
Provides a “wormhole” within a single PAN
A low cost, high reliability link within the radio network
“Extends” the ZigBee network layer

18. Device Addressing
Each independent PAN will select a unique PAN identifier
Addressing modes:
star: Network (64 bits) + device identifier (16 bits)
peer-to-peer: Source/destination identifier (64 bits)

19. IEEE 802.15.4 PHY Overview PHY functionalities:
Activation and deactivation of the radio transceiver
Energy detection within the current channel
Link quality indication for received packets
Clear channel assessment for CSMA-CA
Channel frequency selection
Data transmission and reception

20. IEEE 802.15.4 PHY Overview Operating Frequency Bands 868MHz/ 915MHz
2.4 GHz
868.3 MHz
Channel 0
Channels 1-10
Channels 11-26
GHz
928 MHz
902 MHz
5 MHz
2 MHz

21. Frequency Bands and Data Rates
The standard specifies two PHYs :
868 MHz/915 MHz direct sequence spread spectrum (DSSS) PHY (11 channels)
1 channel (20Kb/s) in European 868MHz band
10 channels (40Kb/s) in 915 ( )MHz ISM band
2450 MHz direct sequence spread spectrum (DSSS) PHY (16 channels)
16 channels (250Kb/s) in 2.4GHz band

22. General Radio Specifications
Transmit Power
Capable of at least –3dBm
Receiver Sensitivity
-85 dBm (2.4GHz) / -91dBm (868/915MHz)
Link quality indication
The measurement may be implemented using
Signal to noise ratio estimation
Receiver energy detection

23. Channel Access Mechanism
Two type channel access mechanism, based on the network configuration:
In non-beacon-enabled networks  unslotted CSMA/CA channel access mechanism
In beacon-enabled networks  slotted CSMA/CA channel access mechanism
The super frame structure will be used.

24. CSMA/CA Algorithm
Each device shall maintain three variables for each transmission attempt
NB: number of slots the CSMA/CA algorithm is required to backoff while attempting the current transmission.
BE: the backoff exponent which is related to how many backoff periods a device shall wait before attempting to assess a channel
CW: (a special design)

25. Data Transfer Model Data transferred from device to coordinator
Network Device
Coordinator
Network Device
Beacon
Data
Data
Acknowledgement
Acknowledgement
(Optional)
(Optional)
Communication to a coordinator
In a beacon-enabled network
Communication to a coordinator
In a non beacon-enabled network

26. Data Transfer Model Data transferred from coordinator to device
Beacon
Coordinator
Network Device
Data Request
Acknowledgement
Data
Communication from a coordinator
In a beacon-enabled network

27. Data Transfer Model Data transferred from coordinator to device
Network Device
Data Request
Acknowledgement
Data
Acknowledgement
Communication from a coordinator
in a non beacon-enabled network

28. Superframe

29. Superframe Structure (cont.)
In CFP, a GTS may consist of multiple slots, all of which are assigned to a single device, for either transmission (t-GTS) or reception (r-GTS).
GTS = guaranteed time slots
In CAP, the concept of slots is not used.
Each “contention slot” is of 20 symbols long.