What is Bluetooth?
 Bluetooth technology is a peripheral that
connects to a variety of products in order to
provide wireless connections.
Why is it called “Bluetooth”?
 Harald Bluetooth was
king of Denmark in the
late 900s. He managed
to unite Denmark and
part of Norway into a
single kingdom then
introduced Christianity
into Denmark. He was
killed in 986 during a
battle with his son,
Svend Forkbeard.
 Choosing this name
for the standard
indicates how
important companies
from the Baltic
region (nations
including Denmark,
Sweden, Norway
and Finland) are to
the communications
industry, even if it
says little about the
way the technology
works.
History of Bluetooth
 Technology was born in Swedish town of
Lund in 1994
 Research facility was tied to the local
university
 The research that developed Bluetooth
came about by accident
History continued…
 In Feb. 1998, 5 companies
got together to and formed a
SIG further the university’s
research on Bluetooth and
May 20, 1998 it was publicly
announced as a marketable
product
 Bluetooth continued
to thrive, although it
didn’t evolve into it’s
current form until 4
companies joined the
original 5, these
include: Motorola,
Microsoft, Lucent and
3-Com
How Bluetooth Works
 Bluetooth communicates on a frequency of
2.45 gigahertz
 This frequency was allocated for industrial,
scientific and medical devices (ISM)
 This band also works for baby monitors,
garage-door openers, and the newer
cordless phones
Bluetooth and interference
 To prevent interference with other devices,
Bluetooth sends out minute signals of 1
milliwatt
 This only allows units to send out signals
for a distance of 10 meters, however this
is strong enough to go through a normal
wall
Spread-spectrum frequency
hopping
 In order to avoid crossing signals between
devices, Bluetooth utilizes frequency
hopping.
 Using 79 individual, random frequencies in
an area, the device hops from one to
another regularly.
How Bluetooth interacts
 When 2 Bluetooth
devices come within
the range of each
other, they
electronically speak to
each other to
determine whether
they have data to
share or if one will
control the other
Piconet
 The devices then set up a personal-area network
(PAN) or piconet.
 In a piconet
network, one device
is assigned the
master role, and up
to seven other
devices are
assigned to be
slaves.
 The master transmits in the even time slots,
slaves transfer in the odd time slots.
Piconet data channels
 Devices in a piconet connect through a
common data channel, which has a
capacity of 1 Mbps
 A channel is divided into time slots of 625
microseconds long
 Each data channel hops randomly 1,600
per second.
Channel Control
 There are two major states in channel control;
Standby and Connection
 Standby – the default low power state, only the
native clock runs, and there is no interaction with
the device
 Connection – master and slave exchange
packets using the master’s access code and
native clock
IF CONNECTION STATE IS ACTIVE…
Inquiry Phase
 Inquiry – enables a
Page Procedure
 Page – procedure
device to find other
devices within range.
where an actual
connection is made .
Inquiry Phase
 1. Unit sends out inquiry packets and receives
replies if anything is present
 2. Receiving unit is hopefully in scan state to
receive packets
 3. Receiving unit then switches to response
states and replies to sending source
Paging Procedure
 1. Source device pages
destination device(s)
 2. Destination receives the
page
 3. Destination replies to source
 4. Source sends an FHS packet
to destination
 5. Destination sends its second
reply to source
 6. Destination and source then
switch to source channel
parameters
Piconet modes
 Active Mode – Bluetooth actively participates
 Sniff Mode – slave listens to the piconet at
reduced rates, reducing its duty cycle
 Hold Mode – master unit can put a slave unit
into hold mode where only the internal timer is
running
 Park Mode – a device is still synched but not
actively participating in traffic
Piconet Packets
 Packets can be up to five time slots wide
 Data in the packets can be up to 2,754
bits in length
 Data is transferred in two types in
Bluetooth Devices: Sychnronous
connection oriented (SCO) or
asynchronous connectionless (ACL)
SCO link
 SCO link is a symmetric point-to-point link
between a master and slave
 Master maintains the link by using reserved slots
at regular intervals (circuit switch)
 Master can support up to 3 links, while slaves
can maintain 2-3
 SCO is mainly used for voice info transferred at
64/Kb
ACL link
 ACL is a point-to-multipoint link between
master and all the slaves in the network
 In the slots unused by the SCO, the
master can create a ACL link on a per-slot
basis to any slave (packet switch)
 Only a single ACL link can exist in a
piconet
Bluetooth Devices