Transcript Bluetooth - Department of Telematics

Bluetooth
 Introduction


Why Bluetooth
History
 The Bluetooth Technology

The Bluetooth Stack
 Bluetooth in ad hoc networks
Introduction
 Why Bluetooth?






Cable replacement between devices.
Supported by major companies.
Open Specification
Low power consumption
Connection can be initiated without user interaction.
Devices can be connected to multiple devices at the same
time.
History
 The technology was born in 1994.
 The first version was released July 1999.
 The Bluetooth name comes from the Danish
Viking Harald Blåtand.
The Bluetooth Technology
 The Bluetooth Stack:
Radio
 Bluetooth devices operate on 2.4 GHz
Industrial Scientific Medical band (ISM
band).
 Unlicensed in most countries.
 Interferences from:




Other radio frequency short-range techniques
Wireless local area networks (IEEE 802.11)
Random noise generators (microwave ovens)
Other Bluetooth units
Radio (cont.)
 Techniques to minimize packet loss:



Frequency Hopping
Adaptive power control
Short data packets
Frequency Hopping
 Uses FHSS (Frequency Hopping Spread
Spectrum)


Divides the ISM-band into 79 1-Mhz channels.
Communication between devices switches between
available channels.
Frequency Hopping (cont.)
Power Control
 Three power classes defined with max output power
from 1 mW (Class 1) to 100 mW (Class 3).
 Devices may be implementet with power control


Optimize power consumption
Decrease interference
Bluetooth Packet Structure
Baseband
 Responsible for channel coding/decoding, timing
and managing a Bluetooth link.
 Master/slave




Devices in a connection are either master or slave.
Communication is only possible between a master and its
slaves.
A master and the slaves are named piconets.
Scatternet; multiple piconets connected together.
Piconets and Scatternet
The Link Manager
 Responsible for establishing, supervising and tear
down connections and logical links.
 Link controller states introduced to carry out these
tasks.
 States:




Standby
Inquiry / Inquiry Scan
Page / Page Scan
Connection
The Link Manager (cont.)
 Inquiry

Used to detect all devcies in an unknown environment.
 Page / Page Scan


Describes how connection is established.
Have to know the address of the other devices. Is usually
achieved through inquiry.
 Connection


Master and slaves are synchronized.
Connection is established.
Inquiry / Inquiry Scan
Page / Page Scan
Host Controller Interface (HCI)
 Provided to ease the partition of the
Bluetooth Stack across two processors.
 Some systems will implement the baseband
and link manager on the Bluetooth device
and higher levels on the host processor.
 The HCI is provided as an interface between
these parts.
Logical Link Control and
Adaption (L2CAP)
 Deals with




multiplexing of different services
segmentation
reassembling of packets
Quality of Service
Profiles
 Provide interoperability between devices
from different manufacturers for specific
services and use cases.
 A profile defines


a selection of messages and procedures
gives an unambiguous description of
communication between two devices.
Bluetooth in ad hoc networks
 Bluetooth network infrastructure is of
dynamic ad-hoc type.
 It is constantly changing and depending on
the movement of the devices.
Bluetooth in ad hoc networks
(cont.)
 Temporary networks.
 Connect ”on-the-fly”.
 Small wireless network called ”personal
area network” (PAN).
 Provide voice, data, eliminate cables, bridge
networks.
 Supports PDAs, mobile phones, printers,
faxes, microphones.
Bluetooth in ad hoc networks
(cont.)
 The master can support up to 7 devices in its
network.
 Devices use the same frequency, but can be
in multiple networks.
Security
 Bluetooth provides security only over the
radio link, from each device to all other
devices.
 Three security specifications:



Confidentiality
Authentication
Authorization
Bluetooth in the future
 Bluetooth was originally intended to be a
cable replacement,
 but, has evolved to become an infrastructure
for Personal Area Network (PAN)
 2001: 10 million devices produced
 2003: 70 million!