Portable devices such as cell phones, palmtops, and laptops were quickly becoming an integral part of our daily lives. In most cases, these devices do not have compatible data communications interfaces, or if they do, the interface requires complicated cable connections and configuration procedures. Isn't it absolutely fantastic to connect your PC to share music, data and calendar information wirelessly? Or to wirelessly access phone numbers on your PDA from your cell phone. Driving without holding the device makes everything much safer and easier. Accessing the internet, print files from your computer and print photos taken from a digital camera without a single piece of wire in your office.
One obvious solution was to get rid of cables and use short-range, wireless, inexpensive cables universally adopted by device vendors to facilitate on-demand connectivity between devices. The marvel of engineering has given us the freedom to exchange data without using meters of wires and popularly known as Bluetooth. It all started in 1994, when Ericsson Mobile Communications began a utility evaluation of an inexpensive, low-power radio solution between cell phones and phone accessories. The idea was to build a small radio in both cell phones and laptops that would replace the cumbersome wires between them. Four years later, Ericsson, together with Nokia, IBM, Toshiba and Intel formed the Bluetooth Special Interest Group (SIG). These were the leading companies in the area of cell phones, notebooks and leaders in the digital technology market. With such big names in the field, it immediately caught the attention of the media and there were high expectations for the product. But many complexities and problems were faced initially. Then, in 1999, the first Bluetooth 1.0 specification was released, and a year later the 1.1 specification. Today, the Bluetooth SIG has 3,400 companies.
Bluetooth is a wireless technology standard for connecting fixed or mobile devices using short radio link. It aims to provide wireless communication with small size, minimum power consumption and low price. The technology was designed to be simple and the goal was to make it the standard in wireless connectivity. The name Bluetooth has a very interesting history. The Bluetooth SIG adopted the codename as a tribute to the 10th century Viking king Harald Blatand, who peacefully united several small kingdoms under his region that worked under different rules, the same as those of Bluetooth technology. Harald liked to eat blueberries, which gave his teeth the color that gave rise to his nickname “Bluetooth.” The symbol is also famous for its name and has a very interesting origin. The logo combines the representation of the Norse runes Hagalaz (transcribed by 'H') and Berkana (transcribed by 'B') in the same symbol. That is, HB as Harald Blatand.
Figure 1: Representative image of the Bluetooth symbol
What makes Bluetooth special when wireless technologies like IrDA and Wi-Fi existed?
Pitting these technologies against each other would be unfair, as they each have unique advantages and complement each other rather than compete with each other. Although IrDA supported wireless connectivity, they needed direct line-of-sight optical contact that supported one-to-one data exchange using infrared light. For example, a remote control and a television where we need to keep the remote control in the line of sight of the television. Likewise, Wi-Fi offers a means of wirelessly connecting one or more computers to each other and to a router so that we can access the Internet. It uses greater distances and also transfers data at faster rates, but Bluetooth offers a way to connect not just computers, but PDAs, headphones, headsets, printers, and other technologies to each other. The figure below represents the three networks.
Figure 2: Image showing different Bluetooth networks
“Wireless communication made easy”, a slogan used to address Bluetooth, but it is only for users and not developers. The demands of creating Bluetooth-enabled products are very challenging . It must be a flexible application topology so that switching can occur between the necessary devices. The power required by Bluetooth must be low as no one wants a short battery life. Size is an important feature during design. It should be small, so adding Bluetooth capability to a device shouldn't noticeably increase its size. Quality of service is supported for voice and last but not least, Bluetooth cannot cost more than cables.
The promise of Bluetooth – What it can do!!
The promise of Bluetooth is extremely ambitious. Originally conceived as a low-power, short-range technology to replace cables that interconnect devices such as printers, keyboards and mines. He has evolved his perceived potential to a much greater extent. It gave rise to the personal area network where everything related to the communication of voice and data information is accessible within the Personal Operating Space. There are several examples where the Bluetooth model has been used.
Figure 3: Summary of Bluetooth functions
As we can see initially Bluetooth was started in the mobile telephony area. All manufacturers have started implementing Bluetooth-enabled devices in phones. The reason behind this adoption was the use of wireless headphones with the phone, which means the phone can be used even if it is in a briefcase or in the trunk. It was used to make a cell phone or wireless modem to provide Dial-Up Networking that allows you to connect to the Internet without any physical telephone line. The laptop can automatically use the user's nearby cell phone to dial and connect to dial-up service. Peer-to-peer file exchange can be done without the presence of network infrastructure. For example, a salesperson can share electronic slide content with the public. Bluetooth allows automatic detection of Bluetooth devices in the room, allowing transfer. Data synchronization between devices is enabled via Bluetooth. For example, a Bluetooth-enabled desktop computer can wirelessly synchronize its contact list, task information, and calendar with a user's phone, PDA, or notebook. These days, HP is making printers and notebooks with built-in Bluetooth technology so they can automatically detect Bluetooth-enabled printers in your area and send documents wirelessly to the printer without going through lengthy networking and print setup processes.
How does bluetooth work?
Bluetooth is short-range communication that is simple, secure and available anywhere. Billions of devices, from cell phones and computers to medical devices and home entertainment products, are enabled with Bluetooth devices.
In simple terms, Bluetooth takes information normally carried by wire and transmits it on a special frequency to another Bluetooth device. The sending and receiving devices have the same Bluetooth receiver chip, which translates the data into wireless transmission and then back to normal, depending on the sender or receiver. Any Bluetooth device can be a master or slave depending on the application. Each device is equipped with a microchip (trans-receiver) that transmits and receives on the 2.4 GHz frequency that is available worldwide. In addition to information, three voice channels are available. Information can be exchanged at a speed of up to 1 megabit per second or 2 megabit per second in the Second Generation of this Technology). Frequency hopping enables inclusive communication without interference. The transmitted data is divided into packets and each packet is transmitted on one of 79 designated Bluetooth channels. Each channel has a bandwidth of 1 MHz. The first channel starts at 2402 MHz and continues to 2480 MHz in 1 MHz steps. It typically performs 800 hops per second, with Adaptive frequency hopping enabled. The master sets the jump sequence and the slaves synchronize with the master. A cluster is made up of a master and up to seven active slaves known as Pico networks. Slaves in a Pico network communicate only with the master. A dispersion network can be formed by connecting two or more Pico networks. When a device is present on more than one Pico network, it must time share and synchronize with the master of the Pico network it is currently communicating with. Bluetooth networks are much more diverse and dynamic. Because they are constantly forming and dissolving, Bluetooth devices move in and out of range, so there are unlimited ways to connect them. The figure below summarizes Bluetooth communication.
Figure 4: Bluetooth Communication Overview
With the basic understanding of information exchange in the Bluetooth system, we now move on to the specifications.
Frequency
Bluetooth operates in the 2.4 GHz frequency band. Although this band is available worldwide, it may differ in some countries. This is the 2.45 GHz scientific and medical industries (ISM*) frequency band. ISM* is open to any radio system and takes care of interference from monitors, garage door controls, cordless telephones and microwave ovens. Bandwidth bands in the United States and Europe are between 2,400 and 2,483.5 MHz and cover parts of France and Spain. The bandwidth range in Japan is between 2471 to 2497 MHz. Therefore, the system can be used worldwide because the radio transmitters cover 2400 and 2500 MHz and make it possible to select the appropriate frequency. ISM The Industrial, Scientific and Medical (ISM) radio bands were originally reserved internationally for the use of RF electromagnetic fields for industrial, scientific and medical purposes other than communications. In general, communications equipment must accept any interference generated by ISM equipment.
|
Country |
Frequency Range |
RF Channels |
|
|
Europe and USA |
2400-2483.5 MHz |
F =2402 +k MHz |
k = 0,……..,78 |
|
Japan |
2471-2497 MHz |
F=2473+ kMHz |
k=0,………22 |
|
Spain |
2445-2475 MHz |
F=2449+ kMHz |
K=0,………22 |
|
France |
2446.5-2483.5 MHz |
F =2454+ kMHz |
K=0,……..22 |
Table representing the frequency band of various countries.
Power
According to the emission power, the equipment is classified into 3 categories ranging from 1mW to 10mW. The receiving equipment must have at least 70dBm. The chips are incorporated into portable devices and are powered by batteries and therefore must have a minimum power consumption of up to 97% less than a cell phone so that the phone's battery lasts longer. If Bluetooth devices do not exchange information, they enter standby mode to save power. The transmission power used as specification is 1 mW for a range of 10 m, 100 mW for a range of up to 100 m.
|
Device power class |
Power Issued |
Range |
|
Class 1 |
100mW |
~ 100 meters |
|
Class 2 |
2.5mW |
~10m |
|
Class 3 |
1mW |
~1 meter |
Range
Connections have a maximum range of 10 meters, however with amplifiers it is possible to reach up to 100 meters, but creating some distortion is disruptive. It may not seem like much, but it is important to remember that these devices were created with the intention of being used indoors and at short distances.
Data type and customers
It can carry data and voice as an exchange. The different types of Bluetooth users can be computers, PDAs, cell phones, etc. There are many other places where Bluetooth is used. For example, cell phones, headphones, stereo headphones, audio adapter, printer, keyboard, GPS system and more.
Data transfer rate
It is one of the important features of the Bluetooth device. Data transfer rate is defined as the speed at which data is transmitted from one device to another. It generally ranges from 1 megabite to 24 megabite depending on the type of Bluetooth device version as shown below.
|
Version |
Data rate |
Maximum output application |
|
Version 1.2 |
1Mbit/s |
0.7Mbit/s |
|
Version 2.0 |
3 Mbit/s |
2.1 Mbit/s |
|
Version 3.0 |
24Mbit/s |
– |
Frequency Hopping
It is a method of transmitting radio signals by rapidly exchanging a carrier wave between many channels, using a pseudorandom sequence known to both the transmitter and the receiver. It is useful to avoid collisions where many devices use the same frequency to send the signal and avoid interference.
Because the ISM band is open to anyone, radio systems operating in this band must deal with a variety of unpredictable sources of interference, such as baby monitors, garage door openers, cordless telephones, and microwave ovens (the most common source). strong interference). Interference can be avoided using an adaptive scheme that finds an unused part of the spectrum, or it can be suppressed through spectrum spreading. In the United States, radios operating in the 2.45 GHz ISM band are required to apply spread spectrum techniques if their transmitted power level exceeds 0 dBm (2). Bluetooth radios use frequency hopping (FH) spread spectrum as they better support low-cost, low-power radio implementations. Furthermore, they deal better with close-range problems: a nearby jammer is effectively suppressed by the narrow channel filter, as long as the jammer's TX spectrum does not match the selected hopping channel. FH systems divide the frequency band into multiple hopping channels. During a connection, radio transceivers jump from one channel to another pseudo-randomly. The instantaneous (hop) bandwidth is small in FH radios, but spread is achieved across the entire frequency band. This results in low-cost narrowband transceivers with maximum interference immunity.
Figure 5: Frequency hopping on the Bluetooth network
Here we can see that the channel time is divided into 625uS slots. Each package can occupy 1, 3 or 5 slots. The hopping frequency remains constant within the package. The master uses the odd number of slots to send the packets and the slave uses even numbers.
Ad hoc network
Ad hoc network is a decentralized wireless network where it does not rely on pre-existing infrastructure such as routers, instead each device participates in routing, routing data to other nodes. An ad hoc network typically refers to any set of networks where all devices have equal status on a network and are free to associate with any other ad hoc network device within link range. Bluetooth also uses ad hop networking and is based on peer connectivity: a device carrying a Bluetooth radio can make a connection with any other device carrying a Bluetooth radio. There is no wired infrastructure with base stations or access points that can support call setup or provide low power consumption modes. In a Bluetooth system, the master device can connect up to seven other devices forming a network known as Pico net. For example, a computer can connect to seven different Bluetooth-enabled devices such as a mouse, printer, CD-player, keyboard, etc. The Pico network is a group of several devices that are in the same radio coverage where they share the same channel that is made up between two and eight other units. Two or more Bluetooth units sharing an FH channel form a Pico network. To regulate traffic on the channel, one of the participating units becomes the master of the Pico network. However, users on the same channel must share capacity. Since the channel capacity is only 1 MHz, as more and more users are added, the throughput per user quickly drops to less than 10 kb/s. The available spectral bandwidth is 79 MHz, but it cannot be used effectively when each unit must share the same 1 MHz skip channel. Therefore, another solution was adopted. Units that share the same area and are within range of each other can potentially establish ad hoc connections with each other. However, only units that actually want to exchange information share the same 1 MHz channel of a Pico network. This solution allows you to create several Pico networks with overlapping coverage areas. Each Pico network channel applies its own pseudorandom hopping sequence across the 79 MHz medium. Pico networks are uncoordinated and hop independently. Within the Pico network, participants must share 1 MHz, but multiple Pico networks share the entire 79 MHz, thus increasing capacity. A collection of multiple Pico networks is called a scattering network. A maximum of 10 Pico networks can be connected to form a scatter network. The figure below shows how the Pico network works.
Figure 6: Image representing a typical Bluetooth Ad Hoc network
Bluetooth Protocols
Bluetooth is not a single protocol, but is made up of different protocols, seven to be exact. Each of these protocols works on different parts of Bluetooth, completing the Bluetooth setup. Bluetooth hardware can be represented in a diagram with host, Bluetooth radio, link controller, and link manager.
Figure 7: Tile image summarizing the Bluetooth hardware
Each piece of hardware runs on certain protocols and combining them gives us a compact bluetooth device structure.
Figure 8: Figure showing the compact structure of the Bluetooth device
Protocols will be part of the next section. Cont……………
