Bluetooth is easily the best in wireless handheld
technology. When it comes to learning, Bluetooth
can get quite complicated. To help you, you'll find
the key learning points of Bluetooth below:
1. Bluetooth is an energy efficient, low
overhead communication protocol that's ideal for
interdevice communications.
2. Unlike infrared, Bluetooth doesn't require
a line of sight.
3. Depending on the implementation, Bluetooth
can have a range of up to 100 meters.
4. The specification of Bluetooth consists of
a Foundation Profile Document and a Foundation Core
Document.
5. The protocol stack for Bluetooth consists
of core protocols, cable protocols, and even adapted
protocols.
6. The transmitter operates around the 2.4
GHz frequency band.
7. The data channel will change frequency, or
hops, 1,600 times in a second, between the 79 allocated
channels in the ISM band.
8. Bluetooth utilizes a spread spectrum
frequency hopping RF characteristic to ensure that
independant networking operates when the other
devices are in range.
9. A piconet is formed when one or more
devices open up a channel of communication.
10. A piconet can have a master and up to
seven slaves.
11. Communication of the interdevice is
based on the concepts of channels.
12. All Bluetooth devices are capable of
transmitting voice.
13. The channel has a total capacity of
1 MB per second.
14. There are two types of channels with
Bluetooth - SCO (Synchronous Connection Oriented) and
ACL (Asynchronous Connectionless).
15. The SCO channels are time oriented, and
are therefore primarily used for transferring time
critical data such as voice.
16. ACL channels are normally used for
communicating data.
17. Data contained in a packet can be up to
2,745 bits in length.
18. In a single piconet, there can be up
to three SCO links containing 64,000 bits a second
each.
19. To avoid collision and timing problems,
SCO links are reserved slots that are set up by
the master.
20. The masters can support up to three
SCO links with either one, two, or three slaves.
21. The slots that aren't reserved for SCO
links can be used as ACL links.
22. The LMP (Link Management Protocol)
will handle link level security, error corrections,
and the establishment of communications links.
23. The LMP packets will have priority
over user packets that originate and form the
L2CAP layer.
24. The L2CAP layer will ensure an
acceptable quality of service.
25. No more than one ACL link can exist
at the L2CAP layer.
Tuesday, October 14, 2008
Sunday, October 12, 2008
How Bluetooth Works
Bluetooth devices will normally operate at 2.4 GHZ
in the license free, globally available ISM radio
band. The advantage to this band includes worldwide
availability and compatibility. A disadvantage to
this however, is that the devices must share this
band with other RF emitters. This includes
automobile security systems, other wireless devices,
and other noise sources, such as microwaves.
To overcome this challenge, Bluetooth employs a
fast frequency hopping scheme and therefore uses
shorter packets than other standards within the
ISM band. This scheme helps to make Bluetooth
communication more robust and more secure.
Frequency hopping
Frequency hopping is basically jumping from frequency
to frequency within the ISM radio band. After a
bluetooth device sends or receives a packet, it
and the device (or devices) it's communicating with
hop to another frequency before the next packet is
sent. This scheme offers three advantages:
1. Allows Bluetooth devices to use the
entirety of the available ISM band, while never
transmitting from a fixed frequency for more than a
short period of time. This helps insure that
Bluetooth conforms to the ISM restrictions on the
transmission quantity per frequency.
2. Ensures that any interference won't
last long. Any packet that doesn't arrive safely
to its destination can be resent to the next
frequency.
3. Provides a base level of security as
it's very hard for an eavesdropping device to predict
which frequency the Bluetooth devices will use
next.
The connected devices however, must agree upon the
frequency they will use next. The specification
in Bluetooth ensures this in two ways. First, it
defines a master and slave type relationship between
bluetooth devices. Next, it specifies an algorithm
that uses device specific information when
calculating the frequency hop sequences.
A Bluetooth device that operates in master mode can
communicate with up to seven devices that are set in
slave mode. To each of the slaves, the master
Bluetooth device will send its own unique address
and the value of its own internal clock. The
information sent is then used to calculate the
frequency hop sequences.
Because the master device and each of the slave
devices use the same algorithm with the same initial
input, the connected devices will always arrive
together at the next frequency that they have agreed
upon.
As a replacement for cable technology, it's no
wonder that Bluetooth devices are usually battery
powered, such as wireless mice and battery powered
cell phones. To conserve the power, most devices
operate in low power. This helps to give Bluetooth
devices a range of around 5 - 10 meters.
This range is far enough for wireless communication
but close enough to avoid drawing too much power
from the power source of the device.
in the license free, globally available ISM radio
band. The advantage to this band includes worldwide
availability and compatibility. A disadvantage to
this however, is that the devices must share this
band with other RF emitters. This includes
automobile security systems, other wireless devices,
and other noise sources, such as microwaves.
To overcome this challenge, Bluetooth employs a
fast frequency hopping scheme and therefore uses
shorter packets than other standards within the
ISM band. This scheme helps to make Bluetooth
communication more robust and more secure.
Frequency hopping
Frequency hopping is basically jumping from frequency
to frequency within the ISM radio band. After a
bluetooth device sends or receives a packet, it
and the device (or devices) it's communicating with
hop to another frequency before the next packet is
sent. This scheme offers three advantages:
1. Allows Bluetooth devices to use the
entirety of the available ISM band, while never
transmitting from a fixed frequency for more than a
short period of time. This helps insure that
Bluetooth conforms to the ISM restrictions on the
transmission quantity per frequency.
2. Ensures that any interference won't
last long. Any packet that doesn't arrive safely
to its destination can be resent to the next
frequency.
3. Provides a base level of security as
it's very hard for an eavesdropping device to predict
which frequency the Bluetooth devices will use
next.
The connected devices however, must agree upon the
frequency they will use next. The specification
in Bluetooth ensures this in two ways. First, it
defines a master and slave type relationship between
bluetooth devices. Next, it specifies an algorithm
that uses device specific information when
calculating the frequency hop sequences.
A Bluetooth device that operates in master mode can
communicate with up to seven devices that are set in
slave mode. To each of the slaves, the master
Bluetooth device will send its own unique address
and the value of its own internal clock. The
information sent is then used to calculate the
frequency hop sequences.
Because the master device and each of the slave
devices use the same algorithm with the same initial
input, the connected devices will always arrive
together at the next frequency that they have agreed
upon.
As a replacement for cable technology, it's no
wonder that Bluetooth devices are usually battery
powered, such as wireless mice and battery powered
cell phones. To conserve the power, most devices
operate in low power. This helps to give Bluetooth
devices a range of around 5 - 10 meters.
This range is far enough for wireless communication
but close enough to avoid drawing too much power
from the power source of the device.
Effective Way Using Bluetooth
The amazing technology of Bluetooth presents a great
way of exchanging data between two wireless devices.
Unlike telephones, there are no wires or messy
leads to worry about. You can enjoy wireless
communications with short distances of up to thirty
feet.
Bluetooth also offers interoperability, meaning that
you can use your portable Bluetooth device to connect
with existing Bluetooth points. This way, you won't
have to carry a data lead or CDs of drivers around
with you everywhere you go. You can enjoy the best
of wireless without having to worry about installing
your software.
With today's Bluetooth, you can use your PDA and cell
phone to surf the net or check emails as you travel.
If you are in the business field, this can be very
beneficial, especially if you like to check your
email throughout the day. Bluetooth will enable you
to check your email no matter where you are - which
is great news for those who like to travel.
Bluetooth will also enable to you to transfer files
as well, such as MP3 and photo to and from your mobile
device. Bluetooth dominates the world of short range
wireless, enabling you to do more than you may
have thought possible.
One of the best things to Bluetooth and something
everyone loves is the wireless headset. Bluetooth
offers wire free headsets for your cell phone or
computer, which is great for those who like to walk
around or talk on the phone in the car, without
having to worry about your hands getting in the way.
To make things even better, you can use a Bluetooth
GPS device for satellite navigation on your PDA,
laptop, or mobile. If you travel - this can be
really great to have.
way of exchanging data between two wireless devices.
Unlike telephones, there are no wires or messy
leads to worry about. You can enjoy wireless
communications with short distances of up to thirty
feet.
Bluetooth also offers interoperability, meaning that
you can use your portable Bluetooth device to connect
with existing Bluetooth points. This way, you won't
have to carry a data lead or CDs of drivers around
with you everywhere you go. You can enjoy the best
of wireless without having to worry about installing
your software.
With today's Bluetooth, you can use your PDA and cell
phone to surf the net or check emails as you travel.
If you are in the business field, this can be very
beneficial, especially if you like to check your
email throughout the day. Bluetooth will enable you
to check your email no matter where you are - which
is great news for those who like to travel.
Bluetooth will also enable to you to transfer files
as well, such as MP3 and photo to and from your mobile
device. Bluetooth dominates the world of short range
wireless, enabling you to do more than you may
have thought possible.
One of the best things to Bluetooth and something
everyone loves is the wireless headset. Bluetooth
offers wire free headsets for your cell phone or
computer, which is great for those who like to walk
around or talk on the phone in the car, without
having to worry about your hands getting in the way.
To make things even better, you can use a Bluetooth
GPS device for satellite navigation on your PDA,
laptop, or mobile. If you travel - this can be
really great to have.
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