Wireless Armenia

Imagine you have a typical modern living room with typical modern materials in it. There’s an entertainment system with stereo, DVD-player, satellite TV receiver and TV, there is also a wireless phone and a PC. All this systems use Bluetooth, and each forms its own piconet to talk between the main unit and peripheral.
Wireless phone is only Bluetooth transmitter to the base and the other in the phone. The Producer programmed each unit with an address that falls in the range of addresses it has established for a specific type of device. When the base is firstly switched on, it sends radio signals asking a response from any device with an address in a certain range. Since the phone has an address from the range, it gives response, and the tiny network is formed. Now, even if one of these devices should receive a signal from another system, it will ignore that because it is not on line. Computer and entertainment system go through similar procedures, creating a connection between the addresses in the range of established producers. Once installed the network, systems begin talking among themselves. Each piconet hops randomly through the available frequencies, so that all the piconets are completely separated from each other.
So the living room has established three separate networks, each of which consists of devices that know the address of transmitters it should listen and address of the receiver, it must talk to. So if every network is changing its frequency many times in the second place, it is unlikely that all two networks will be on the same frequency at the same time. If you find that they, as a result of confusion will only cover a tiny fraction of a second, and software designed to correct such errors weeds out of confusing information and gets on with the business network.

Bluetooth-network transmits data via in low power of radio waves. He communicates at a frequency of 2.45 gigahertz (actually between 2.402 GHz and 2.480 GHz, to be exact). This frequency band was set aside by international agreement for the use of industrial, scientific and medical destination (ISM).
The number of devices which you can use already is using the same radio frequency. Baby monitors, garage-door openers, and a new generation of wireless phones all use frequencies in the ISM. Make sure that Bluetooth and these other devices do not interfere with each other, was an essential part of the design process.
One of the ways, Bluetooth devices do not interfere with other systems, sending a very weak signal of about 1 m W. For comparison, the most powerful mobile phones can transmit a signal to 3 Watts. Low-power Bluetooth device within the range of about 10 meters (32 feet), cutting the chances of interference between your computer and a portable telephone or television. Even at low power, Bluetooth does not require line of sight between the communicating devices. The walls in your house will not stop Bluetooth signal, making the standard useful for controlling several devices in different rooms.
Simultaneously Bluetooth can connect up to eight devices. With all of these devices in the same 10-meters (32 feet) radius, you would think they interfere with each other, but this is unlikely. Bluetooth uses a technique called spread-spectrum frequency hopping, which makes it rare for more than one device to transmit on one frequency at the same time. In this technique, the device will use 79 individual, randomly chosen frequencies within a specified range, going from one to another on a regular basis. In the case of Bluetooth, the transmitters change frequencies 1,600 times per second, meaning that more devices can make full use of the limited slice of spectrum. Since each transmitter uses Bluetooth spread spectrum transmission automatically, it is unlikely that two transmitters will be on the same frequency at the same time. The same method makes less the risk that portable phones or baby monitors will disrupt Bluetooth devices, since any intervention at a particular frequency will last only a fraction of a second.

Bluetooth has a small area for  networking  to another side  by eliminating the need for user intervention and to maintain an extremely low power to conserve battery power. Imagine that you are on your Bluetooth-enabled cell phone, standing next the door of  your house. You say the man at the other side  to call you back after  five minutes, so you can go in your house  and put your things away. While  you enter to your house the map that you received on your mobile from your car’s Bluetooth-enabled GPS system is automatically sent to your  Bluetooth-enabled computer, because your mobile  has already  taken  the Bluetooth signal from your computer and automatically sent the data that you intended for  transfer . After five minutes, when your friend again calls you, your Bluetooth-enabled home phone rings instead of your mobile .The  person called the same number  by the same number, but your home phone picked up Bluetooth signals from mobile and automatically redirects the call, because it  knew   that you are  at home. And each transmission signal to your mobile  and from your mobile phone consumes just 1 MW of power, so that your mobile phone charge is virtually independent of all this activity.

From the beginning, Bluetooth is a networking standard that works on two levels:
• Ensures agreement at the physical level – Bluetooth is a radio frequency standard.
• It provides agreement at the protocol level, where products have to agree on when bits are transmitted, how many will be sent at a time, and as part of a conversation can be sure that the message is the same as the message sent.
The biggest advantage of Bluetooth is  that it is wireless, inexpensive and automatic. There are other ways to get around using wires, including infrared. Infrared (IR) refers to light waves of low frequency than human eyes can receive and interpret. Infrared is used in most remote control systems. Infrared communications are fairly reliable and do not cost a lot to be built into the device, but there are a couple of drawbacks. First, infrared is a “line of sight” technology. For example, you must specify the remote at the TV or DVD player to make things happen. A second drawback is that infrared is almost always “one to one” technology. You can transfer data between your desktop and laptop, but not  your laptop and PDA at the same time. (See how remote control works for  learning  more about infrared link.)
These two qualities of infrared are actually advantageous in some things. Because infrared transmitters and receivers must be aligned with each other, interference between devices is uncommon. Of course  nature of infrared communications is useful in that you can be sure that the message goes only to the recipient, even in a room full of infrared receivers.
Bluetooth is designed to circumvent the problems that comes  with infrared systems. Older Bluetooth 1.0 standard maximum transmission rate of 1 MB per second (Mbps), while Bluetooth 2.0 can manage up to 3 Mbps. Bluetooth 2.0 is backward compatible with 1.0 devices.
Let’s find out how Bluetooth-network works.
Why is it called Bluetooth?
Harald Bluetooth was king of Denmark at the end of 900. He succeed  to unite Denmark and part of Norway into one kingdom then  disseminated Christianity in  Denmark. He left a large monument, Jelling rune stone, in memory of his parents. He was killed in 986 during a battle with his son, Svend Forkbeard. The choice of this name for the standard indicates how important companies from Scandinavia (countries, including Denmark, Sweden, Norway and Finland) have the communications industry, even though he says little about how the technology works.