Bluetooth Learning Points and concepts
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.
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Bluetooth Working
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 onder that Bluetooth devices are usually battery owered, such as wireless mice and battery powered cell phones. To conserve the power, most devices perate in low power. This helps to give Bluetooth devices a range of around 5 - 10 meters.
This range is far enough for wireless communication put close enough to avoid drawing too much power from the power source of the device.
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Bluetooth connecting people
Constantly evolving, the technology of Bluetooth started off as a basic wireless connection standard but has since then been adapted and proven with many different uses and functions.
A good example is Bluetooth for cell phones. It enables mobile users to connect to their hands free headset without using wires. Bluetooth technology will also allow mobile phone users to connect with their hands free kit as well.
Another handy use of Bluetooth is file sharing. It allows the sharing of files between two cell phones, between a cell phone and computer, which makes the sharing of files a snap. If you have a cell phone and computer, you can easily transfer data between the two.
Say for example you wanted to put an MP3 on your phone from your computer you could do it easily with Bluetooth. All you would need is a Bluetooth adapter for your computer. It doesn’t stop with the swapping of files either,as you can use your computer and phone to synchronise phone books, send SMS messages, and much more.
Although Bluetooth may be dandy for cell phones, it also comes in handy for the home office as well. Utilizing Bluetooth is a great way to set up a home office - two computers, a printer, and even a scanner. They all can be connected using Bluetooth technology with effective ranges of up to 10 meters.
The technology and devices of Bluetooth will be around for years and years to come. As years go by, Bluetooth will provide even better wireless solutions for different applications. Even though Bluetooth has a short range, it has that short range for a reason. Bluetooth is easily the best in wireless technology - which it continues to
prove time and time again.
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