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Wireless Personal Area Networks
1. Wireless Personal Area
Networks
CS5440 Wireless Access Networks
Dilum Bandara
Dilum.Bandara@uom.lk
Some slides extracted from ZigBee by J. Dohl, F. Diehm, & P. Grosa and
ZigBee by E. Ünal CSE 401 Special Topics In Computer Networks
5. Bluetooth – IEEE 802.15.1
Developed by Ericson
Now managed by Bluetooth Special Interest Group
2.4 – 2.48 GHz ISM band
Range – 10 m
Bandwidth – 2.1 Mbps (shared) (version 2.0)
Version 4.0
Includes Classic Bluetooth, Bluetooth high speed & Bluetooth low
energy protocols
Bluetooth high-speed based on Wi-Fi
Classic Bluetooth based on legacy Bluetooth protocols
Low power consumption
Found in mobile phones, laptops, computer peripherals,
printers, etc. 5
6. Bluetooth Applications
Cable replacement
Phone to PC connection
Connecting computing devices
Digital imaging
Smart car systems
Multiparty data exchange
Exchange business cards, calendar events
Share presentation material
Synchronize information between multiple terminals
Play multi-player games
Personal trusted device
Reliable e-commerce transactions
Local value added services
Locking & access control 6
Stick N Find
7. Bluetooth Piconet
Through master
No slave-to-slave communication
Up to 7 active slaves 255 parked slaves 7
Source: www.techrepublic.com/article/secure-your-bluetooth-
wireless-networks-and-protect-your-data/6139987
8. Bluetooth Scatternet
By connecting 2+
piconets
No direct support at
Baseband Layer
8
Source: www.techrepublic.com/article/secure-your-bluetooth-
wireless-networks-and-protect-your-data/6139987
12. Bluetooth Applications/Profiles
Set of application protocols
Definitions of possible applications & specify general
behaviors
Resides on top of Bluetooth core specification &
(optionally) additional protocols
Example profiles
Hands-Free Profile (HFP)
Basic Printing Profile (BPP)
Audio/Video Remote Control Profile (AVRCP)
File Transfer Profile (FTP)
Human Interface Device Profile (HID)
Personal Area Networking Profile (PAN)
Generic Object Exchange Profile (GOEP)
OBEX
12
13. Other Key Layers
Link Management Protocol (LMP)
Set-up & control of radio link between 2 devices
Logical Link Control & Adaptation Protocol (L2CAP)
Multiplex multiple logical connections between 2 devices using
different higher-level protocols
Provides segmentation & reassembly of on-air packets
Service Discovery Protocol (SDP)
Allows a device to discover services offered by other devices, &
their associated parameters
Baseband layer
Physical layer
Manages physical channels & links
Error correction, data whitening, hop selection, & security
13
14. Physical Channel
Required to use spread spectrum technology as
it’s in ISM band
79 RF channels spaced 1 MHz apart
Channel – frequency range in which communication
occurs
Frequency hoping
Channel represented by a pseudo-random hopping
sequence hopping through 79 channels
Piconet – all devices use same channel
Hopping sequence is unique for the piconet & is determined
by device address (BD_ADDR) of master
14
15. Physical Channel (Cont.)
Traffic controlled by master
Master clock used for all timing & scheduling activities
Master transmissions at even slots, slaves always at odd
slots
Packet extended over up to 5 slots
15
16. Packets
Access code
Used for timing synchronization, offset compensation, paging &
inquiry
Header
Contains information for packet acknowledgement, packet
numbering for out-of-order packet reordering, flow control, slave
address, & error check for header
Payload
Can contain either voice field, data field, or both
16
17. ZigBee
By ZigBee Alliance
Very low power consumption long battery life
Low data rate
Low complexity circuits & small size low cost
17
18. ZigBee Applications
Telecom
Services
m-commerce
info services
object interaction
(Internet of Things)
ZigBee
Wireless Control that
Simply Works
TV
VCR
DVD/CD
remote
security
HVAC
lighting control
access control
irrigation
PC&
Peripherals
asset mgt
process
control
environmental
energy mgt
Personal
Health Care
security
HVAC
AMR
lighting control
access control
patient
monitoring
fitness
monitoring
18
Source: http://zigbee.org/
19. ZigBee Protocol Stack
IEEE 802.15.4 covers
physical layer & MAC
layer of low-rate
WPAN
ZigBee adds network
construction,
application services,
& more on top of
IEEE 802.15.4
19
Source: www.sena.com/products/industrial_zigbee/zigbee_summary.php
20. IEEE 802.15.4 Devıce Types
LR-WPAN devices defined by IEEE 802.15.4
1. Full Functional Device (FFD)
Can work as a PAN coordinator, as a coordinator, or
as a simple device
Can communicate with either another FFD or a RFD
2. Reduced Functional Device (RFD)
For applications that don’t need to transmit large
volumes of data & have to communicate only with a
specific FFD
20
22. ZigBee Topologies (Cont.)
1. Star Topology
Pros
Easy to synchronize
Low latency
Cons
Small scale
2. Mesh/P2P Topology
Pros
Robust multi-hop
communication
Multi-path communication
Flexible network
Lower latency
Cons
Route discovery is costly
Needs to store routing
table
22
23. ZigBee Topologies (Cont.)
3. Cluster Tree Topology
Pros
Low routing cost
Multi-hop communication
Scalable
Cons
Route reconstruction is costly
Latency may be quite long
Root node becomes a single point of failure
23
25. PHY Protocol Data Unit (PPDU)
2 different services
Data service
Controls radio
Management service
Energy detection in the channel
Clear channel assesment before sending messages
Link Quality Indication (LQI) for received packets
Preamble for chip & symbol synchronization
Frame size 8-127 Octets 25
26. MAC Layer
2 services
Data service
Tx & Rx MPDUs
Management service
If coordinator
Manages network beacons, PAN association & disassociation,
frame validation, & acknowledgment
CSMA/CA for channel access
Support device security
26
27. Traffic-Modes – Device to PAN
Coordinator
Beacon mode
Beacon send periodically
Coordinator & end device
can go to sleep
Lowest energy
consumption
Precise timing needed
Beacon period (ms-min)
27
Source: IEEE 802.15.4 Standard (2006)
28. Traffic-Modes – Device to PAN
Coordinator (Cont.)
Non-Beacon mode
Coordinator/routers have
to stay awake
Heterogeneous network
Asymmetric power
28
Source: IEEE 802.15.4 Standard (2006)
29. Data Transfer From PAN Coordınator
29
Source: IEEE 802.15.4 Standard (2006)
30. MAC Layer – Managing PANs
Channel scanning
Active, passive
PAN ID conflict detection & resolution
Starting a PAN
Sending beacons
Device discovery
Device association/disassociation
Synchronization (beacon/nonbeacon)
Orphaned device realignment
30
31. MAC Layer – Frame Security
Provided security features
Access control
Data encryption
Frame integrity
Sequential freshness
Available security modes
Unsecured mode
ACL mode
Secured mode
Available security suites
AES-CTR
AES-CCM
AES-CBC-MAC
31
32. Network Layer
Distributed address assignment
Tree structure or self managed by higher layer
16-bit network space divided among child routers
Child routers divide their space again for their children
Depends on
Maximum child count per parent
Maximum child-routers per parent
Maximum network depth
32
33. Network Layer (Cont.)
Route discovery
Find or update route between specific source &
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
33
35. Network Layer (Cont.)
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
35
36. ZigBee Profiles
Describes a common language for exchanging
data
Defines offered services
Device interoperability across different
manufacturers
Standard profiles available from the ZigBee
Alliance
Profiles contain device descriptions
Unique identifier (licensed by the ZigBee Alliance)
36
37. ZigBee vs. Bluetooth
Feature(s) Bluetooth ZigBee
Power Profile days years
Complexity complex Simple
Nodes/Master 7 64000
Latency 10 seconds 30 ms – 1s
Range 10m 70m ~ 300m
Extendibility no Yes
Data Rate 1 Mbps 250 Kbps
Security 64bit, 128bit 128bit AES &
Application Layer 37
38. ZigBee vs. BluetoothSHORT<RANGE>LONG
LOW < DATA RATE > HIGH
PAN
LAN
Text Graphic
s
Internet Hi-fi
Audio
Streaming
Video
Digital
Video
Multi-channel
Video
802.15.1
Bluetooth1
802.15.1
Bluetooth 2
802.15.4
ZigBee
802.11b
802.11a/HL2 & 802.11g
38
39. Ultra-Wideband
Short-range technology for high-speed WPANs
3.1 – 10.6 GHz, 15 MHz channels (up to 5)
10 m
Applications – Cell phones, HDTV, DVD players, audio
players, etc.
39
Source: www.ice.rwth-aachen.de/index.php?id=630&tx_felogin_pi1[forgot]=1&tx_iceprojects_pi1[uid]=155
40. Ultra-Wideband (Cont.)
Emit large no of very-short pluses over a wide
bandwidth
Few nanoseconds or less
Gains few 100s of Mbps
Channel capacity proportional to used bandwidth
No specific frequency allocation
Operate on frequency band allocated to other
technologies
Secure
Like other spread spectrum technologies
40
41. Protocol Stack
Wireless USB, Wireless IP, Bluetooth over UWB, &
IEEE1394 over UWB can be operated over a common
radio platform
41
Source: http://research.nokia.com/page/244
42. Summary
Bluetooth
Spread Spectrum
Moderate rate, short-range (10 m)
ZigBee
Low rate, low power, short range (10 m – 100 m)
Ultra-Wideband
High rate, very-short range
42
Editor's Notes
Device participating in both piconets can relay data between members of both ad hoc networks. However, the basic bluetooth protocol does not support this relaying - the host software of each device would need to manage it
Sdp – service discovery protocol
TCS (Telephone Control protocol Specification
Mobilkommunikation
SS 1998
HVAC (heating, ventilation, and air conditioning
Automatic Meter Reading (AMR)
GTS – guaranteed time slots
Transmission from a Coordinator to a Device
The coordinator has data to be transmitted to the device. It indicates this in the pending address fields of its beacon. Devices tracking the beacons, decode the pending address fields. If a device finds its address listed among the pending address fields, it realizes it has data to be received from the coordinator. It issues a Data-Request Command to the coordinator. The coordinator replies with an acknowledgement. If there is data to be sent to the device, it would transmit the data. If acknowledgements are not optional, the device would respond with an acknowledgement.