1. Jan Dohl Fabian Diehm Patrick Grosa
Faculty of Computer Science Chair of Computer Networks, Wireless Sensor Networks, Dr. W. Dargie
ZigBee
Jan Dohl Fabian Diehm Patrick Grosa
Dresden,

2. ZigBee – Short range comunication
Structure
Introduction
Concepts
Architecture
Implementation
Evaluation
Reference
TU Dresden,
ZigBee – Short range comunication

3. ZigBee – Short range comunication
Introduction
TU Dresden,
ZigBee – Short range comunication

4. ZigBee – Short range comunication
Introduction
What is ZigBee?
• Specification of protocols for small, low-power radios
History
May 2003: IEEE completed
December 2004: ZigBee specification ratified
June 2005: public availability
ZigBee-Alliance
Companies developing and promoting the standard
150+ members
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ZigBee – Short range comunication

5. ZigBee Alliance - Members
and many more....
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ZigBee – Short range comunication

6. ZigBee – Short range comunication
Concepts
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ZigBee – Short range comunication

7. Why do we need another WPAN standard?
Decreasing
Power consumption
ZigBee: 10mA <==> BT: 100mA
Production costs
In the beginning of 2005
ZigBee: 1.1 $ <==> BT: 3 $
Development costs
Codesize ZB/codesize BT = ½
Bit-error-rate (BER)
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ZigBee – Short range comunication

8. Why do we need another WPAN standard?
picture taken from [9]
TU Dresden,
ZigBee – Short range comunication

9. Why do we need another WPAN standard?
Increasing
Sensitivity
ZigBee: -92dbm(0,63pW) <==> BT: -82dbm(6,2pW)
flexibility
No. of supported nodes
ZigBee: (in a mesh) <==> BT: 7 (in a star)
Security
ZigBee: AES (128bit) <==> BT: SAFER (64/128bit)
Latency requirements
ZigBee: optional guaranteed time slot
Range
ZigBee: up to 75 m in LOS condition <==> BT: 10 m
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ZigBee – Short range comunication

10. ZigBee – Short range comunication
Usage Scenarios
Industrial & commercial
Consumer electronics
Toys & games
PC & periphals
Personal health care
home/building automation
Just everything you can imagine for wireless sensor nodes or in general short range communications
TU Dresden,
ZigBee – Short range comunication

11. ZigBee Frequency Bands
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ZigBee – Short range comunication

12. ZigBee – Short range comunication
ZigBee Protocol Stack
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ZigBee – Short range comunication

13. ZigBee – Short range comunication
Protocol Stack
picture taken from [10]
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ZigBee – Short range comunication

14. ZigBee – Short range comunication
ZigBee Profiles
Profiles:
Definition of ZigBee-Profiles
describes a common language for exchanging data
defines the offered services
device interoperatbility across different manufacturers
Standard profiles available from the ZigBee Alliance
profiles contain device descriptions
unique identifier (licensed by the ZigBee Alliance)
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ZigBee – Short range comunication

15. ZigBee – Short range comunication
Architecture
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ZigBee – Short range comunication

16. ZigBee – Short range comunication
ZigBee Node-Types
ZigBee Coordinator (ZBC) (IEEE FFD)
only one in a network
initiates network
stores information about the network
all devices communicate with the ZBC
routing functionality
bridge to other networks
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ZigBee – Short range comunication

17. ZigBee – Short range comunication
ZigBee Node-Types
ZigBee Router (ZBR) (IEEE FFD)
optional component
routes between nodes
extends network coverage
manages local address allocation/de-allocation
TU Dresden,
ZigBee – Short range comunication

18. ZigBee – Short range comunication
ZigBee Node-Types
ZigBee End Device (ZBE) (IEEE RFD)
optimized for low power consumption
cheapest device type
communicates only with the coordinator
sensor would be deployed here
TU Dresden,
ZigBee – Short range comunication

19. Addressing/Discovering ZigBee Nodes
Addressing ZigBee Nodes:
optimized unique 64 bit address (IEEE )
16 bit network address (65536 devices)
256 sub addresses for subunits
Device Discovery
unicast (NWK id known), broadcast (NWK id unknown)
ZBC-/ZBR-Response: IEEE address + NWK address + all known network addresses
Binding
creating logical links between 2 or more end devices
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ZigBee – Short range comunication

20. Addressing/Binding ZigBee Endpoints
picture taken from [11]
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ZigBee – Short range comunication

21. ZigBee – Short range comunication
Traffic-Types
1. Data is periodic
application dictates rate
2. Data is intermittent
application or stimulus dictates rate (optimun power savings)
3. Data is repetitive (fixed rate a priori)
device gets guaranteed time slot
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ZigBee – Short range comunication

22. ZigBee – Short range comunication
Traffic-Modes
1. Beacon mode:
beacon send periodically
Coordinator and end device can go to sleep
Lowest energy consumption
Pricise timing needed
Beacon period (ms-m)
picture taken from [1]
TU Dresden,
ZigBee – Short range comunication

23. ZigBee – Short range comunication
Beacon-Mode
picture taken from [8]
TU Dresden,
ZigBee – Short range comunication

24. ZigBee – Short range comunication
Traffic-Modes
1. Non-Beacon mode:
coordinator/routers have to stay awake (robust power supply needed)
heterogeneous network
asymmetric power
picture taken from [1]
TU Dresden,
ZigBee – Short range comunication

25. ZigBee – Short range comunication
Topologies
Mesh-Topology
picture taken from [7]
TU Dresden,
ZigBee – Short range comunication

26. ZigBee – Short range comunication
Topologies
Tree-Topology
picture taken from [7]
TU Dresden,
ZigBee – Short range comunication

27. ZigBee – Short range comunication
Implementation
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ZigBee – Short range comunication

28. ZigBee – Short range comunication
PHY layer
2400MHz Band specs
4 Bits per symbol
DSSS with 32 Bit chips
O-QPSK modulation
Sine halfwave impulses
Medium
Bit to
Symbol
Symbol to
Chip
QPSK
Mod.
Binary Data
picture taken from [4]
TU Dresden,
ZigBee – Short range comunication

29. ZigBee – Short range comunication
PHY layer
868/915 MHz Band specs
1 Bit per symbol
Differential encoding
DSSS with 15 Bit Chips
BPSK modulation
RC impulses (roll-off = 1)
Medium
Diff.
Encoder
Bit to
Chip
BPSK
Mod.
Binary Data
TU Dresden,
ZigBee – Short range comunication

30. ZigBee – Short range comunication
PHY layer
General specs and services
Error Vector Magnitude (EVM) < 35%
-3dBm minimum transmit power (500µW)
Receiver Energy Detection (ED)
Link Quality Indication (LQI)
Use ED & LQI to reduce TX-power
Clear Channel Assessment (CCA) with 3 modes
Energy above threshold
Carrier sense only
Carrier sense with energy above threshold
TU Dresden,
ZigBee – Short range comunication

31. ZigBee – Short range comunication
PHY layer
PHY Protocol Data Unit (PPDU) frame structure
Frame to be sent via radio
Preamble for chip and symbol synchronization
Contains either data or data acknowlegement
Packet size Octets
Contains MAC Protocol Data Unit (MPDU)
table taken from [1]
TU Dresden,
ZigBee – Short range comunication

32. ZigBee – Short range comunication
MAC layer
Channel access specification
Beacon/Nonbeacon
Define Superframe structure
Slotted/unslotted CSMA-CA
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ZigBee – Short range comunication

33. ZigBee – Short range comunication
MAC layer
Managing PANs
Channel scanning (ED, active, passive, orphan)
PAN ID conflict detection and resolution
Starting a PAN
Sending beacons
Device discovery
Device association/disassociation
Synchronization (beacon/nonbeacon)
Orphaned device realignment
TU Dresden,
ZigBee – Short range comunication

34. ZigBee – Short range comunication
MAC layer
Transfer handling
Transaction based (indirect transmission)
Beacon indication
Polling
Transmission, Reception, Rejection, Retransmission
Acknowleded
Not acknowledged
GTS management
Allocation/deallocation
Usage
Reallocation
Promiscous mode
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ZigBee – Short range comunication

35. ZigBee – Short range comunication
MAC layer
Frame security
Provided security features
Access control
Data encryption
Frame integrity
Sequential freshness
Avaiable security modes
Unsecured mode
ACL mode
Secured mode
Avaiable security suites
AES-CTR
AES-CCM
AES-CBC-MAC
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ZigBee – Short range comunication

36. ZigBee – Short range comunication
MAC layer
How far have we come? 4 1 6 5 2 7 3
Problem: How do 6 and 7 talk to coordinator 0?
Solution: Routing (NWK Layer)
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ZigBee – Short range comunication

37. ZigBee – Short range comunication
NWK layer
Distributed address assignment
Tree structure or self managed by higher layer
16Bit network space divided among child routers
Child routers divide there space again for their children
Depends on:
Maximum child count per parent
Maximum child-routers per parent
Maximum network depth
TU Dresden,
ZigBee – Short range comunication

38. ZigBee – Short range comunication
NWK layer
Distributed address assignment - Example
Cm=2 ; Rm=2 ; Lm=2 1 ? 2 6 4 5
TU Dresden,
ZigBee – Short range comunication

39. ZigBee – Short range comunication
NWK layer
Routing cost
Metric to compare „goodness“ of routes
Base: Link cost between 2 neighbors
Path cost = sum of link costs along the path
Link cost determination:
Link quality indication from PHY
Statistical measures
TU Dresden,
ZigBee – Short range comunication

40. ZigBee – Short range comunication
NWK layer
Route discovery
Find or update route between specific source and destination
Started if no active route present in routing table
Broadcast routing request (RREQ) packets
Generates routing table entries for hops to source
Endpoint router responds with Routing response (RREP) packet
Routes generated for hops to destination
Routing table entry generated in source device
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ZigBee – Short range comunication

41. ZigBee – Short range comunication
NWK layer
Route discovery
RREQ
RREP 2 1 3 5 2 1 4
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ZigBee – Short range comunication

42. ZigBee – Short range comunication
NWK layer
Routing
Check if routing table entry exists
Initiate route discovery if possible
Hierarchical routing as fallback
Route maintenance
Track failed deliveries to neighbors
Initiate route repair when threshold reached
Careful with network load!
In case of total connectivity loss:
Orphaning procedure
Re-association with network
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ZigBee – Short range comunication

43. ZigBee – Short range comunication
Application Level
picture taken from [11]
TU Dresden,
ZigBee – Short range comunication

44. ZigBee – Short range comunication
Application Level
picture taken from [11]
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ZigBee – Short range comunication

45. ZigBee – Short range comunication
Application Layer
Application Support Sub-layer (APS):
interface to NWK-layer (offers general set of functions)
Data transmission, binding and security management
picture taken from [1]
TU Dresden,
ZigBee – Short range comunication

46. ZigBee – Short range comunication
Application Level
picture taken from [11]
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ZigBee – Short range comunication

47. ZigBee – Short range comunication
Application Layer
Application Framework:
Specifies Datatypes
Devices describe themselves by ZigBee descriptor:
frequency band
power description
application flags
application version
serial number
manufacturer
...
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ZigBee – Short range comunication

48. ZigBee – Short range comunication
Application Layer
Supported Data-types
table taken from [1]
TU Dresden,
ZigBee – Short range comunication

49. ZigBee – Short range comunication
Application Level
picture taken from [11]
TU Dresden,
ZigBee – Short range comunication

50. ZigBee – Short range comunication
Application Layer
ZigBee defined Objects (ZDO):
provides common function for applications
Initializes APS, NWK-Layer and Security Service Specification
offers services like device-/service-descovery, binding and security management
assembles information about the network
for ZBC/ZBR -> e.g. binding table
picture taken from [1]
TU Dresden,
ZigBee – Short range comunication

51. ZigBee – Short range comunication
Evaluation
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ZigBee – Short range comunication

52. ZigBee – Short range comunication
Pros and Cons
Pros
good extension of existing standards
supported by many companies
low power consumption
low cost
easy implemented (Designer concentrates on end application)
flexible network structure
Cons
Not many end devices available yet
Single point of failure (centralized architecture)
TU Dresden,
ZigBee – Short range comunication

53. ZigBee – Short range comunication
Gadget example
Pantech & Curitel P1 phone
Only a prototype
control electrical appliances
Check temperature & humidity
Sending messages in case of trespass
picture taken from [9]
TU Dresden,
ZigBee – Short range comunication

54. ZigBee – Short range comunication
References
TU Dresden,
ZigBee – Short range comunication

55. ZigBee – Short range comunication
References
[1] ZigBee Specifications v1.0
[2] “Designing with and ZigBee”, Presentation Slides, available on ZigBee.org
[3] “ZigBee Tutorial”,
[4] IEEE Specification
[5] “Network Layer Overview”, Presentation Slides, Ian Marsden, Embedded Systems Show, Birmingham, October 12th, 2006, r00ZB_MG_Network_Layer_Overview.pdf, available on ZigBee.org
[6] “Designing a ZigBee Network”, Presentation Slides, David Egan, Ember Corporation, ESS 2006, Birmingham, r00ZG_MG_Network_Design.pdf, available on ZigBee.org
[7] “ZigBee Architecture Overview”, Presentation Slides, Oslo, Norway June 2005, ZigBee_Architecture_and_Specifications_Overview.pdf, available on ZigBee.org
[8] “Low Power Consumption Features of the IEEE /ZigBee LR-WPAN Standard”,
[9] “ZigBee Home Automation Mobile from Pantech”,
[10] “Basic Lecture - ZigBee”
[11] “Introduction to the ZigBee Application Framework”, Presentation Slides, ZigBee Open House, San Jose, June 15th, 2006, r06ZB_AFG-Overview-ZigBee-Open-House.pdf, available on ZigBee.org
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ZigBee – Short range comunication

56. ZigBee – Short range comunication
Thank you
for
your attention!
TU Dresden,
ZigBee – Short range comunication