2. In 1994, Ericsson Mobile Communications began to examine
alternatives to cables linking accessories with their mobile
phones. This study produced the initial specification
for wireless technology, with the Bluetooth SIG founded in
February 1998 by the core promoters:
Ericsson Mobile Communications AB.
Nokia Mobile Phones.
3. The Bluetooth logo is the combination of “H” and “B,” the
initials of Harald “ blatand” literally means Bluetooth,
written in the ancient letters used by Vikings, which are called
4. Bluetooth is a method for data communication that uses
short-range radio links to replace cables between computers
and their connected units .
Bluetooth is a standardized protocol for sending and
receiving data via a 2.4GHz Industrial, Scientific and Medical
There are three key features of Bluetooth
5. For the majority of countries the ISM band
used by Bluetooth is available from 2.40-2.4835 GHz. In this
band Bluetooth uses Frequency Hopping Spread Spectrum
(FHSS)techniques in order to improve its immunity from
It has 79 RF channels with a channel spacing of 1 MHz.
Base frequency starts at 2402 MHz then the frequency of the
channels, f, can be expressed as:
f =2402 + n MHz
where, n, is the channel number with an integer value in the
range of 0 to 78
6. In this FHSS scheme there are 1600 hops per second, which is
hop every 625 µs.
The frequency hopping implements time division multiplexing
as shown in Figure .
The basis of the scheme has the Master device transmitting in
the first 625 us slot, k, and here the Slave receives. In the next
slot k = 1 the Slave is permitted to transmit and the master
7. Bluetooth devices exist in small ad-hoc network configuration
with the ability to operate as either master or the slave .
The configurations can be
which is the simplest configuration with one master and one
It is called a Piconet, based on up to 7 slaves clustered around
a single Master.
Scatternets are two or more independent and non-
synchronized piconets that communicate with each other by
making bridge nodes.
8. The role of the master is to control the available bandwidth
between the slaves, it calculates and allocates how often to
communicate with each slave and locks them into the appropriate
frequency hopping sequence.
In addition to hop sequence control, the master is responsible for
transmit control by dividing the network into a series of time slots
amongst the net members, as part of a Time Division Multiplexing
9. Bluetooth carries communication traffic over two types of air
interface links defined as
Asynchronous Connection Less (ACL) or Synchronous
Connection Oriented (SCO)
Packet constructed of a 72 bit access code, a 54 bit packet
header, a 16 bit CRC and
Non time critical data
Same access code and header as ACL packets
ARQ (Automatic Repeat reQuest) and SEQ (SEQuence)
flags redundant since flow control and re-transmissions
do not apply
Cyclic Redundancy Code (CRC) field is absent
Payload fixed at 30 bytes, with source data of 10, 20 or 30
Symmetric synchronous services
Slot reservation at fixed intervals
Power: Classes, Control and Saving
12. The Core Specification contains a software protocol stack
similar to the more familiar Open Systems Interconnect (OSI)
standard reference model for communication
The radio modulates and demodulates data for transmitting
and receiving over the air. The operating band of the radio is
divided into 1 MHz spaced channels with a chosen
modulation scheme of Gaussian Frequency Shift Keying
Baseband and Link Controller
They are responsible for controlling the physical links via the
radio, assembling the packets and controlling the frequency
13. Link Manager (LM)
It controls and configures links to other devices.
Host Controller Interface (HCI)
It handles communication between host and the module.
The standard defines the HCI command packets that the
host uses to control the module, the even packets used by
the host to inform lower protocol layers of changes, the data
packets for voice and data traffic between host and module
and the transport layer used by the HCI packets.
The transport layer can be USB(H2), RS232 (H3), UART (4) or a
robust proprietary standard such as BCSP (BlueCoreSerial
14. Logical Link Control and Adaptation (L2CAP)
It is a multiplexer, adapting data from higher layers and
converting between different packet sizes.
The next 4 layers could be grouped as communication interfaces.
These are RFCOMM (Radio Frequency Communication port)
which provides an RS232 like serial interface.
Wireless Application Protocol (WAP) and OBject EXchange
(OBEX) are responsible for providing interfaces to other
The final member of this rough grouping is the Telephony Control
protocol Specification (TCS) providing telephony
Service Discovery Protocol (SDP) lets devices discover the
services available on another Bluetooth device
16. Creating a Bluetooth connection between two devices is a
multi-step process involving three progressive states:
Inquiry – If two Bluetooth devices know absolutely nothing
about each other, one must run an inquiry to try
to discover the other. One device sends out the inquiry
request, and any device listening for such a request will
respond with its address, and possibly its name and other
Paging (Connecting) – Paging is the process of forming a
connection between two Bluetooth devices. Before this
connection can be initiated, each device needs to know the
address of the other (found in the inquiry process).
17. Connection – After a device has completed the paging
process, it enters the connection state. While connected, a
device can either be actively participating or it can be put into
a low power sleep mode.
Active Mode – This is the regular connected mode, where the
device is actively transmitting or receiving data.
Sniff Mode – This is a power-saving mode, where the device
is less active. It’ll sleep and only listen for transmissions at a
set interval (e.g. every 100ms).
Hold Mode – Hold mode is a temporary, power-saving mode
where a device sleeps for a defined period and then returns
back to active mode when that interval has passed. The
master can command a slave device to hold.
18. Park Mode – Park is the deepest of sleep modes. A master
can command a slave to “park”, and that slave will become
inactive until the master tells it to wake back up.
Bonding and Pairing
When two Bluetooth devices share a special affinity for each
other, they can be bonded together. Bonded
devices automatically establish a connection whenever
they’re close enough.
Bonds are created through one-time a process called pairing.
When devices pair up, they share their addresses, names,
and profiles, and usually store them in memory. The also
share a common secret key, which allows them to bond
whenever they’re together in the future.
Pairing usually requires an authentication process where a
user must validate the connection between devices. The flow
of the authentication process varies and usually depends on
the interface capabilities of one device or the other.
19. The short-range connections of data and voice could mean
the emergence of applications suitable for:
Access points allowing mobile devices connection to services
e.g. telephone network(PSTN) or LAN services
Mobile phone link to Laptop PCs
Mobile phone connections to wireless headsets
PDA, palmtop and desktop PC inter accessibility for file and