I am King Harold Bluetooth
who unified warring
Viking Tribes in the
10th Century. In the 21st
Century a wireless Bluetooth
network is named after me
CSCD 439/539 Wireless Networks and Security
Lecture 7 Bluetooth
Fall 2007
Who is Bluetooth?
• Harald Blaatand “Bluetooth” II
– King of Denmark 940-981 AC
– Harald Bluetooth was first
Christian king of Denmark
– He united Denmark under his
rule in the mid-900's
– Similarly, Bluetooth seeks to
unite personal computing
devices wirelessly
How did Bluetooth start?
• In 1994 – need for low power consumption
wireless devices to substitute for cable
• Ericsson – driving force behind Bluetooth
– Pre-Cell phone
– 1998, Ericsson, Nokia, IBM, Toshiba, Intel
formed the Bluetooth Special Interest Group
(SIG)
– 1999 – Release of Bluetooth protocol
– 2002 – IEEE adopted Bluetooth standard,
802.15 working group
Bluetooth Vision
• Vision of Bluetooth
– Personal connectivity space
• Bubble that follows you around
• Connect personal devices anytime one enters
bubble sphere
• Connectivity is spontaneous, accommodate
devices of diverse power and capacity
– Laptops, phones, PDA’s, cameras …
• Users don’t even need to be aware of Bluetooth
connection
Bluetooth Vision
• Idea is …
– Connections will be done seamlessly without
need for installations and software drivers
– Devices can discover other Bluetooth-enabled
devices
• Determine its capabilities and applications,
and establish connections for data
exchange
• User doesn’t need to be highly skilled
Bluetooth Applications
More prevalent applications of Bluetooth include:
• Wireless communication between a mobile phone and a
hands-free headset or car kit
• Wireless communications with PC input and output
devices, the most common being the mouse, keyboard
and printer
• For controls where infrared was traditionally used
• Sending small advertisements from Bluetooth enabled
advertising hoardings to other, discoverable, Bluetooth
devices
• Seventh-generation game consoles
– Nintendo Wii, Sony PlayStation 3
– Use Bluetooth for their wireless controllers
• Receiving commercial advertisements ("spam") via a
kiosk, e.g. at a movie theatre or lobby
What does Bluetooth do for
you?
Landline
Cable
Replacement
Data/Voice
Access Points
Personal Ad-hoc
Networks
Ultimate Headset
Cordless Computer
General Description
• Bluetooth operates in unlicensed Industrial
Scientific Medical (ISM) band at 2.4 GHz
– Which ensures worldwide communication
compatibility
– ISM band is open to anyone, systems operating on
this band must deal with unpredictable sources of
interference,
– Microwave ovens, baby monitors and 802.11 wireless
networks
• Reduce interference, Bluetooth uses Frequency
Hopping Spread Spectrum (FHSS) technology
Frequency Hopping Spread
Spectrum (FHSS)
• Works like this …
– During a connection, radio transceivers hop from one
channel to another
– One packet is sent on a channel, two devices then
retune their frequencies (hop) to send the next packet
on a different channel.
• So, if one frequency channel is blocked, limited disturbance
to the Bluetooth communication
– Allows several Bluetooth networks to run concurrently
without interrupting one other
– Link rate: 1 Mbps, but with overhead, this reduces to
721 kbps
– Range for Bluetooth:
• 10m, can reach up to 100m depending on the power class of
the device
Adaptive Frequency Hopping
(AFH)
• Bluetooth version 2.0 + EDR uses an enhanced
technology called: Adaptive Frequency Hopping (AFH)
– AFH allows Bluetooth devices to measure quality of wireless
signal
– Determines if there are bad channels present on specific
frequencies due to interference from other wireless devices.
– If bad channels present on a specific frequency, Bluetooth device
will adjust its hopping sequence to avoid them
– As a result, the Bluetooth connection is stronger, faster, and
more reliable
Definitions - Piconet
• A network of devices connected in an ad
hoc fashion using Bluetooth technology
– A piconet is formed when at least two devices,
such as a portable PC and a cellular phone,
connect
• Can support up to eight devices
• When piconet is formed, one device acts as the
master while the others act as slaves
• A piconet is sometimes called a PAN
– Personal Area Network
Definitions - Scatternet
• Scatternet is …
– A group of independent and non-synchronized
piconets that share at least one common
Bluetooth device
– Bluetooth devices must have point-tomultipoint capability to engage in scatternet
communication
– There may be a maximum of 10 fully loaded
piconets in a scatternet
– Scatternet is a more recent use of Bluetooth
Piconets
• Two or more Bluetooth units sharing the same
channel form a piconet
– Slaves in a piconet can only have links to the master
– Slaves cannot directly transmit data to one another
– Master acts as a switch for the piconet and all traffic
must pass through master
– Any device can be either a master or a slave within a
piconet and they can change roles at any point in a
connection when a slave wants to take over a
master's role
Piconets
• Every Bluetooth device has its own clock and
can be uniquely identified by its Bluetooth device
address
– Slaves in a piconet use master's Bluetooth device
address and clock to determine the frequency
hopping sequence
– Slaves synchronize with master's clock for duration of
the connection
– Master also controls when devices transmit data,
since slaves can only transmit when scheduled by a
master
– Master controls how total available bandwidth is
distributed among the slaves
Scatternets
• A set of two or more interconnected
piconets form scatternets (More recent
development)
– A Bluetooth unit can be a slave in two or more
piconets, but it can be a master in only one
– Devices that participate in two or more
piconets may act as gateways, forwarding
traffic from one piconet to another
Scatternets and Piconets
Bluetooth Protocols
• Bluetooth protocols contain standard
procedures for connections and data
exchange between Bluetooth devices
– Bluetooth protocol stack (See next slide)
Bluetooth Protocol Stack
The Link
Controller is
responsible for
establishing and
maintaining links
between
Bluetooth units
The Radio is
the interface
between the
on-air channel
medium and
the Baseband
Link Manager
Protocol (LMP)
handles piconet
management and
link configuration. It
also includes link
security
The Baseband layer
is responsible for
channel coding and
decoding
Digitizes signals
received by the
radio for passing up
the stack and it
formats the data it
receives from the
Link Controller for
transmission over
the channel
Bluetooth Protocol Stack
Host Controller
Interface (HCI)
defines uniform
methods for
accessing and
controlling lower
layers of the protocol
stack, namely
baseband and the
link manager
RFCOMM protocol
defines a transport
protocol for emulating
RS-232 serial ports.
Service Discovery
Protocol (SDP)
defines procedures
for discovering
services of other
devices as well as
determining the
characteristics of
those services.
Logical Link Control
and Adaptation
Protocol (L2CAP)
provides connectionoriented and
connectionless data
services to the other
higher level protocol
layers
Bluetooth Protocol Stack
• Telephony Control Protocol
Specification (TCS) defines
call control signaling for
establishing speech and
data calls between
Bluetooth devices, provides
them with telephony
services
• Object Exchange Protocol
(OBEX) is for object data
exchange over infrared (IR)
links
• Wireless Application
Protocol (WAP) includes
interoperability requirements
for Bluetooth
Connecting with Bluetooth
• Say we want a laptop connecting wirelessly to a mobile
phone to use dial-up networking.
– Process is shown in following slide
– First, Bluetooth device looks for devices that it might connect to
• Step 1 - the Inquiry Process.
• Inquiring device, A, sends out an inquiry packet or repeated inquiry
packets and waits to receive responses back
• Discoverable devices in range respond to an inquiry by sending a
Frequency Hop Synchronization (FHS) packet, which contains all
the information device A needs to connect to the responding device,
including the Bluetooth device's address, page scan modes, and
clock offset
• All devices that respond to the inquiry are reported to the host
controller of device A.
• List of all devices discovered is presented to the user - is
application-dependent
Connecting with Bluetooth
Step 1
Connecting with Bluetooth
• At this point, A knows which devices are in
range, but it doesn’t know which devices support
dial-up
– Step 2 - Using information retrieved from inquiry, A
now attempts to connect to different devices that
responded to its inquiry in order to find out what
services they support
– Depending on the application, device A may either
1) Establish links to all devices that responded to its inquiry and
get information about their services and later on reconnect
with one that supports dial-up networking; or
2) Upon seeing that a device supports dial-up networking,
directly proceed to setting up a connection with that device
without finding out the services from the rest of the devices in
the list.
In following slide, second option is adopted.
Connecting with Bluetooth
Step 2
Connecting with Bluetooth
• Step 2 continued
– Device A wants to find out services of a device, so, device A
sends out paging packets
– Connectable device will respond and a baseband link can be
established between the two devices
– Following that, a L2CAP connection will be established before
they can exchange service information. Information exchange is
handled by Service Discovery Protocol
– Device B responds, “I have dial-up networking service”
– RFCOMM connection can then be established across the
already existing L2CAP link
– After this, a dial-up networking connection can then be
established on top of the RFCOMM connection
– Laptop can then start using the cell phone to access the phone
network without any cables being needed for connections
Example Bluetooth Networks
• In a modern living room,
– An entertainment system with a stereo, a DVD
player, a satellite TV receiver and a television,
plus a cordless telephone and a personal
computer
– Each system uses Bluetooth, and each forms
its own piconet to talk between the main unit
and peripheral
Example Bluetooth Networks
• Cordless telephone has one Bluetooth transmitter in the
base and another in the handset.
• Manufacturer has programmed each unit with an
address that falls into a range of addresses it has
established for a particular type of device
• When base is first turned on
– Sends radio signals asking for a response from any units with an
address in a particular range
– Since handset has an address in range, it responds, and a tiny
network is formed
• Even if one of these devices should receive a signal from
another system, it will ignore it since it’s not from within
the network
Example Bluetooth Networks
• Computer and entertainment system go through
similar routines, establishing networks among
addresses in ranges established by
manufacturers.
• Once the networks are established, the systems
begin talking among themselves
• Each piconet hops randomly through the
available frequencies, so all of the piconets are
completely separated from one another
Bluetooth Profiles
• Bluetooth enabled devices must use and
understand certain Bluetooth "profiles" in order
to use Bluetooth technology to connect to one
another
– These profiles define the possible applications that a
Bluetooth enabled device can support.
• In order for one Bluetooth device to connect to
another
– Both devices must share at least one of the same
Bluetooth profiles
Bluetooth Profiles
• Bluetooth profiles define possible applications
and describe how Bluetooth technology is to be
used for each specific device
– For example
• File Transfer profile is used to define how devices like a PDA
will use Bluetooth Technology to transfer files to other
devices like another PDA, cell phone, or computer
– When a Bluetooth device is developed
• Manufacturer assigns (In accordance with the Bluetooth
SIG's requirements) specific Bluetooth profiles for that device
to use in order to establish applications which will work with
other Bluetooth devices
Bluetooth Challenges
• Two challenges faced by Bluetooth include: Scheduling
algorithms for scatternets and interference with other
wireless technologies
• The first issue concerns the development of effective
scheduling algorithms for Bluetooth scatternets
– As discussed previously, a Bluetooth unit can only be active in
one piconet but it can be a member in a number of piconets
– Hence, a unit that participates in multiple piconets needs to
divide its time among the different piconets
– To schedule communication with such units, their availability in
other piconets needs to be taken into consideration
• This then becomes a scatternet-wide coordination problem
which can easily become a bottleneck in scatternet
organization
Bluetooth Challenges
• Second issue is interference problems with
IEEE 802.11 wireless networks
– Because both IEEE 802.11 and Bluetooth wireless
networks operate on the same frequency band, it is
expected that some interference will occur when
these two networks are present in the same
environment
– Simulations and experiments have shown that
significant packet losses and access delays do occur
• Some co-existence mechanism may need to be
developed to reduce the performance degradation
when these two technologies are present in one
area
802.11 vs. Bluetooth
• Where interference issues occur interesting to
look at intersections in 802.11b wireless local
area network (WLAN) technology and Bluetooth
– Could we just use 802.11b in place of Bluetooth?
• Although IEEE 802.11b was originally designed
for providing network access, can also operate
in ad hoc mode
– Possible to form ad hoc personal area networks
(PANs) which is where Bluetooth shines
– Because widespread use of IEEE 802.11b standard
even in small handheld devices,
• Concern that this technology might surpass Bluetooth in
terms of usage and acceptance even in PANs.
802.11 vs. Bluetooth
Media Access Control
Neighbor Discovery
Multihop PAN's
Bluetooth
Based on controlling unit
Master
IEEE 802.11b
Random-accessoriented
Standardized discovery
using INQUIRY process
No defined way to
discover unknown
devices (may use
broadcasting
Straightforward
no piconet
architecture,
all nodes are peers
Involves scatternets
interconnected piconets
Summary
• Bluetooth is a global, RF-based (ISM band: 2.4GHz),
short-range, connectivity technology & solution for
portable, personal devices
– it is not just a radio
– create piconets on-the-fly (appr. 1Mbps)
• piconets may overlap in time and space for high aggregate bandwidth
• The Bluetooth spec comprises
– a HW & SW protocol specification
– usage case scenario profiles and interoperability requirements
• 1999 Discover Magazine Awards finalist
• To learn more: http://www.bluetooth.com
• Holiday on Monday!!!
• Take-home Midterm
– Due: Wed. November 14