Bluetooth Personal Area Network:
An Investigation of new networking technology

By: Kan Leung (9717375)

 

 

Introduction

Why use the word "Bluetooth"?

History of Bluetooth

Who owns Bluetooth?

Specification of Bluetooth

Benefit of Bluetooth technology

Products already exist in the market

Major development in recent months

Conclusion

Appendix I: The different layer of the Bluetooth Protocol

Bibliography

 

 

Introduction
Bluetooth is the code name for a personal area network (PAN) technology that makes it extremely easy to connect a mobile computing device to wireless phones and modems. It is a short-range radio technology that allows virtually any digital device telecommunications, personal computing, networking automotive, and consumer electronic - to communicate without wrestling with numerous cords or cables. Bluetooth wireless technology is set to revolutionize the way we communicate and how we connect device. Cables become a thing of the past thanks to the robust, low-cost Bluetooth chips.

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Why use the word "Bluetooth"?
The name of Bluetooth comes from a Dutch ruler " Harald Bluetooth " in late 900 A.D. who ruled and united greater part of Denmark and Norway during his reign. This is what this technology is trying to archieve, uniting devices through Bluetooth.

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History of Bluetooth
The idea that resulted in the Bluetooth wireless technology was born in 1994 when Ericsson Mobile Communications decided to investigate the feasibility of a low-power, low-cost radio interface between mobile phones and their accessories. The idea was that a small radio built into both the cellular telephone and the laptop would replace the cumbersome cable used today to connect the two devices. The radio technology showed possibilities to become a universal bridge to existing data networks, a peripheral interface, and a mechanism to form small private ad hoc groupings of connected devices away from fixed network infrastructures.

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Who owns Bluetooth?
Bluetooth is a specification for a wireless technology. The open specification for this innovative technology "Bluetooth" is being developed through the combined contribution of the members of the Bluetooth Special Interest Group (SIG). Ericsson, Toshiba, IBM, Nokia and Intel, which are the five major founding companies, have combined their individual expertise to create Bluetooth towards a technology standard. The SIG was formed in early 1998 and each of the companies was responsible in difference parts. By signing a zero cost agreement, companies can join the SIG and qualify for a royalty-free licence to build products based on the Bluetooth technology.

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Specification of Bluetooth
Bluetooth is a radio system that consists of three parts, hardware, software framework and interoperability requirements. The end result is of this is a low-cost, low-power, short-range radio link for mobile devices and for WAN/LAN access points. Bluetooth's technical details are fairly basic. The radios will operate in the 2.4-GHz ISM (Industrial, Scientific and Medical) Band. Bluetooth uses frequency-hopping techniques to keep communication flowing even in spaces that are "noisy." Calling for support of both synchronous and asynchronous communication, Bluetooth's synchronous bands are geared to carry relatively high-quality voice, while the asynchronous communication will support data at slightly more than 700 Kbps. Distance is limited to about 10 meters. Advanced error-correction methods are used to protect data, encryption and authentication routines for user's privacy and the technology provides a high transmission rate. The Bluetooth wireless technology supports both point-to-point and point-to-multipoint connections. With the current specification, up to seven 'slave' devices can be set to communicate with a 'master' radio in one device. The detail layers of the Bluetooth protocol are described in Appendix I. It is beyond the scope of this paper.

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Benefit of Bluetooth technology
The radio transmitter/receiver are expected to cost approximately $20 at first and could drop to $5 thereafer. Thus, including the technology in most handheld devices won't break the businessperson's budget and will probably accommodate the consumer's budget, too. Of course, any device capable of incorporating this technology must have some sort of general-purpose CPU able to run the lightweight networking and data-link protocols that govern Bluetooth transmission. People can have quick and immediate access to mobile devices without connecting them with wires. Once the devices are within the ten meters boundary, the devices will be connected automatically. It also provides a fast and secure transmission of voice and data even when the devices are not within line of sight. Bluetooth-enabled devices can exchange information and synchronize with one another automatically. It is a perfect replacement for cables.

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Products already exist in the market
Motorola produces a first capable mobile phone calls Motorola Timeport 270, which combines with the new Smart Module accessory and Bluetooth PC card and completes the premier package of initial Bluetooth solution. This mobile phone has all the Bluetooth benefits that descript above. The phone has integrated hands-free speakerphone, four-way navigation "Joy stick" which offers greater ease in scrolling through menus and accessing information from the Internet, large graphical display which enhances presentation of WAP Internet content and Short Message Service (SMS) content.
For computer components, IBM produces a Bluetooth PC card, which "provides mobile professionals with the ultimate in short-range wireless connectivity between ThinkPad systems and other Bluetooth-enabled devices, such as IBM compatible PCs, mobile phones and PDA." The new Bluetooth PC card eliminates the need for expensive proprietary cables and it operates in the license-free 2.4 GHz radio frequency spectrums. This can also used for file transfer, ad hoc networking, device synchronization, peripheral connectivity and Internet Bridge.

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Major development in recent months
"The three-in-one phone" is one of the new products that benefit from Bluetooth. The idea of the three-in-one phone is very simple. When people are at home, the phone will function as a cordless phone and people only need to pay fixed line charge. When people go out, the phone will function as a mobile phone and they need to pay cellular charge. However when people's phone comes within range of another mobile phone with built-in Bluetooth wireless technology, or in a bluetooth wireless network, the phone can be used "as a walkie-talkie" with no telephone charge.
Bluetooth can also be used as "interactive conference". During meetings or conferences, people can transfer their particular documents with selected participants and exchange electronic business cards automatically without any "wired" connection. In daily application, Bluetooth can offer premises-based information specific to where people are at the moment. If people are in a large store and wondering what items are on sale, they just need to turn on their PDA then Bluetooth connection will give them a specific offer based on their location in the store. In business, people no longer require to use cable when setting up a presentation in the future. By having Bluetooth, printer can automatically deliver printouts and audience can watch the presentation on their own Bluetooth-enable laptops simultaneously.
Bluetooth can also be used as "automatic synchronizer". Before the development of Bluetooth technology, it takes more times for people to update or enter the information they want into each of their devices. However now Bluetooth can work as an automatic synchronizer to transfer information to people's desktop, mobile computer, PDA and mobile phone. When people enter to their office, the address list, calendar and the to-do-list in their notebook will be updated to automatically.

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Conclusion
The development of Bluetooth is a creative and useful idea that benefits many people. This technology allows a variety of devices, such as PCs, laptops, mobile phones, personal digital assistants and printers, to communicate with each other without cables or hard wiring. Today many companies are still working in the development of Bluetooth devices and they spend lots of money in this new development. They hope that Bluetooth can be applied world widely. The success of Bluetooth will benefits all the users in the future.

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Appendix I: The different layers of Bluetooth Protocol:

Bluetooth Stack

Application
JINI
WAP
SDP
TCP/IP
RFCOMM
L2CAP
ACL
SCO
Baseband
Bluetooth Radio


The above diagram shows the different layers of the Bluetooth protocol and how they interact. The Bluetooth system has four basic parts: a radio (RF section) that receives and transmits data and voice; a baseband or link control unit that processes the transmitted or received data; link management software that manages the transmission; and supporting application software.
The Bluetooth radio is the lowest defined layer of Bluetooth specification. Bluetooth radio is a short-distance, low-power radio that operates in the unlicensed spectrum of 2.4 GHz. It uses nominal antenna power of 0dBm. For 0dBm, the range is 10 meters, which means equipment must be within 10 meters to each other to communicate using the Bluetooth standard. Data is transmitted at a maximum gross rate of up to 1 Mbps. Communication protocol overhead limits the practical data rate to a little over 721 kbps. Bit error rate will be increase and the achievable data rate will be decrease when there is interference during transmission or equipment is out of range. Interference with Bluetooth devices is inevitable since other type of equipment, such as microwave ovens and LANs, shares the 2.4 GHz frequencies. In order to address the issue, specification group employs frequency-hopping spread-spectrum techniques. Bluetooth uses 79 hop frequencies spaced 1 MHz apart in the frequency range of 2.402 to 2.480 GHz. The hop rate is 1,600 hops per second. If transmission encounters interference, it waits for the next frequency hop and re-transmits on a new frequency.
The Baseband is the physical layer of the Bluetooth. The baseband is the hardware that turns received radio signal into a digital form, which can be processed by the host application. It also converts digital or voice data into a form that can be transmitted by using a radio signal. The Baseband processor handles all the tasks that performed by the packets. Each packet contains information about where it is coming from, what frequency it is using and where it is going. Besides, it contains information on how the data was compressed, the order in which the packets were transmitted and information used to verify the effectiveness of the transmission. When the data is received, baseband will check for accuracy and extracted from the packet. On the other hand, baseband also takes care of converting data from one form to another, such as from voice to digital data. It will compress the data, put it into packets and take it out of packets, assigning identifiers and error correction information. Then it will reverse the entire process for data that is received. The baseband function becomes the link controller. The Bluetooth link is used as a data transmission. The Bluetooth standard supports two types of link: synchronous connection-oriented links (SCO) and asynchronous connectionless links (ACL). SCO is used primarily for voice communications and ACL is used for packet data. Each types of link support 16 different packets that are used depending on the application. Any two devices in a Bluetooth system may use either link type and may change link types during a transmission. Bluetooth has five logical channels that are used to transfer different types of information. They are Control Channel (LC), Link Manager (LM), UA, UI and US. LC and LM are used in the link level, but US, UI and US are used to carry asynchronous, isosynchronous and synchronous user information. These two links are the third layer of Bluetooth specification.
Link management (LM) is the forth layer of Bluetooth specification. The link manager software runs on a microprocessor and manages the communication between Bluetooth devices. Each Bluetooth devices has it own link manager. When one of the devices discovers other remote link managers, then it can communicate with them through the Link Manager Protocol (LMP) to handle link setup, negotiate features, authenticate QoS and to encrypt and adjust data rate on link. To perform its service provider role, the LM uses the services of the underlying Link Controller (LC). LC is a supervisory function that handles all of the Bluetooth baseband functions and supports the link manager. It is responsible to send and receive data and it is able to identify the sending device and perform authentication and ciphering functions. It will determine what type of frame to use on a slot-by-slot basis. It directs how devices will listen for transmissions from other devices or put devices into various power-save modes according to the Bluetooth-specified procedures. Each packet uses a single 625 timeslot but it can be extend to cover up to five slots. Bluetooth supports an asynchronous data channel, three synchronous voice channels at 64 kbps and simultaneous asynchronous data and synchronous voice channels. The asynchronous channel can support an asymmetric link of 721 kbps in either direction, 57.6 kbps in the return direction and 432.6 kbps for symmetric link.
The last basic part of Bluetooth system is application software. The application software is set in the device that operates an application over the Bluetooth protocol stack. This software allows the mobile phone, PDA or keyboard to do its job. In order to interoperate with each Bluetooth devices, all of them must have compatible sections in their Bluetooth stack. Therefore, all Bluetooth-certified devices must contain the basic four parts in accordance with the standard. Besides the requirement of basic four parts that described above, Host Controller Interface (HCI), Logical Link Control and Adaptation Protocol (L2CAP), RFCOMM Protocol and Service Discovery Protocol (SDP) are also needed. The basic four parts that described above show how Bluetooth works. The rest parts of the Bluetooth Stack are also very significant.
The HCI provides a command interface to the baseband controller and link manager. It can access to hardware status and control registers, but more importantly, it provides a uniform method of accessing the Bluetooth baseband capabilities. The HCI is functionally broken up into three separate parts, which are HCI Firmware, HCI Driver and Host Controller Transport Layer. HCI Firmware is located on the Host Controller that means HCI-enabled Bluetooth device. By accessing baseband commands, link manager commands, hardware status registers, control registers and event registers, it implements the HCI commands for Bluetooth hardware. HCI Driver is located on the Host that means the HCI-enabled Software Unit. The HCI events will send asynchronous notifications to Host when something occurs. Then the Host will collect the received event packet to determine which event occurred. Host Controller Transport Layer is used to communicate with HCI Driver and Firmware. It is an intermediate layers and it has ability to transfer data without intimate knowledge of the data being transferred. There are three different Host Controller Layers. They are USB, UART and RS232.
The Logical Link Control and Adaptation Layer Protocol (L2CAP) is layered over the Based Protocol and belongs to data link layer. It provides connection-oriented and connectionless data services to upper layer protocols. It contains protocol multiplexing capability, segmentation and reassembly operation, and group abstractions. It allows higher-level protocols and applications to receive and transmit L2CAP data packets and the length can up to 64 kilobytes.

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Bibliography

1. "Bluetooth-enabled products finally hit market", Dec. 18, 2000

2. Bluetooth: What is the Potential? Analysts disagree", April 15, 1999

3. Bluetooth - Special Interest Group Announces Release of the Bluetooth 1.0, July 26, 1999

4. "Brush Up on Bluetooth", June 28, 1999

5. "Mobile Devices: Bluetooth demands system tools", March 20, 2001

6. www.bluetooth.com

7. www.ericsson.com

8. www.ibm.com

9. www.motorola.com

10. www.palowireless.com

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