Bluetooth - A Path Towards an IT Revolution

Bluetooth, a small cheap radio chip designed by Ericsson, has entirely replaced the need for cables.

Abstract. Take a look around at any person working on a computer and you will find that his CPU is entangled with so many cables!!! One comes from the keyboard, another from the mouse, still another from the printer and so on. The cables are a mess. In order to make life simple and comfortable, Ericsson conceived the Bluetooth technology which means replacement for cables. Bluetooth is a standard for small, cheap radio-chip to be plugged into computers, printers, mobile phones etc. It is designed to replace the cables by getting the information carried by the cable and transmitting it at a special frequency to a receiver Bluetooth chip which will then give the information to the computer, phone etc. Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth is a standard and communications protocol primarily designed for low power consumption, with a short range (power-class-dependent: 1 meter, 10 meters, 100 meters) based on low-cost transceiver microchips in each device.

Keywords: piconet, spread-spectrum frequency hopping, adaptive frequency hopping, scatternet, Link Manager Protocol, Logical link control and adaptation protocol, Radio frequency communication, passkey, Bluejacking, Bluebugging, Bluesnarfing, eavesdrop.

1   Introduction

Bluetooth was named after a Danish Viking and King, Harald Blåtand (translated as Bluetooth in English), who lived in the latter part of the 10th century. He united and controlled Denmark and Norway. However a more popular, was that Old Harald had an inclination towards eating Blueberries, so much so his teeth became stained with the color, leaving Harald with a rather unique set of molars. Bluetooth is a specification for the use of low power radio communications to wireless phones, computers, and other network wireless devices over short distances.  The wireless signals that are transmitted by Bluetooth cover short distances of up to 30 feet, generally communicating less than 1 Mbps (Mega Byte per second). The technology is more popular with cell phones, as Bluetooth headsets are the way to go these days.  To use Bluetooth, your cell phone will need to have it enabled, or an infrared device somewhere on the phone. Certain mobile phone based chat clients can use bluetooth to communicate, with the benefit again of the mobile phone operators billing being totally cut out. Many video streaming mobile phones are equipped with Bluetooth. 

 

1.1   Why Bluetooth technology?

Wireless is improving safety as a result of eliminating wires you don't need. When traveling with your laptop or other wireless devices, you'll no longer have to worry about bringing connection cables.

  1. Bluetooth is actually inexpensive: The technology of Bluetooth is cheap for companies to implement, which results in lower costs for the company.

  2. Interoperability: Bluetooth is standardized wireless. Bluetooth will connect devices to each other, even if they aren't the same model.

  3. Low energy consumption: As a result of Bluetooth using low power signals, the technology requires very little energy and will use less battery or electrical power as a result.

  4. Low interference: Bluetooth devices almost always avoid interference from other wireless devices.  Bluetooth uses a technique known as frequency hopping, and also low power wireless signals.

  5. Sharing voice and data: The standard for Bluetooth will allow compatible devices to share data and voice communications.

  6. Instant PAN (Personal Area Network) you can connect up to seven Bluetooth devices to each other within a range of up to 30 feet, forming a piconet or PAN.  For a single room, you can also set up multiple piconets.

  7. The technology stays: Bluetooth technology is a world wide, universal wireless standard. A chain reaction will occur, making Bluetooth the standard for cutting edge wireless.

1.2   How Bluetooth works?

When the devices are using Bluetooth technology, they will communicate without wires. Devices in this “electronic conversation” know that the information is via a protocol. A protocol is a standard that controls or enables the connection, communication, and data transfer between two electrical devices. Bluetooth uses a standardized wireless protocol for devices to communicate. It forces devices to agree on when bits are sent, how many will be sent at a time, and how the devices in a conversation can be sure that the message received is the same as the message sent. Data can be transferred at a rate of up to one Megabyte per second. Bluetooth transmitters require minimal amounts of power. Bluetooth devices are able to avoid interference is through a technique known as spread-spectrum frequency hopping. By using the “hopping” method, a device will use one of 79 different, randomly chosen frequencies within an assigned range, and will frequently change frequencies from one to another. Bluetooth enabled devices, which all use the “hopping” method, change frequencies 1,600 times per second.

Bluetooth version 2.0 + EDR, the very latest of the Bluetooth specification versions, uses an enhanced technology called: Adaptive Frequency Hopping (AFH). AFH allows Bluetooth devices to measure the quality of the wireless signal and then determine if there are bad channels present on specific frequencies due to interference from other wireless devices. If bad channels are present on a specific frequency, the Bluetooth device will adjust its hopping sequence to avoid them. As a result, the Bluetooth connection is stronger, faster, and more reliable.

Bluetooth enabled devices must use and understand certain Bluetooth “profiles” in order to use Bluetooth technology to connect to one another. These profiles define the possible applications that a Bluetooth enabled device can support. In order for one Bluetooth device to connect to another, both devices must share at least one of the same Bluetooth profiles. Once the Bluetooth devices are all connected, a network is created.

Bluetooth devices create a Personal-area Network (PAN), or commonly called a piconet. Bluetooth piconets are designed to link up to eight different devices. A piconet can be as small as a two foot connection between a keyboard and computer, or it can encompass several devices over an entire room. Devices that are apart of a specific piconet, based on their profiles, use “Hopping” simultaneously so they stay in touch with one another and avoid other piconets that may be operating in the same room. In order to regulate communications one of the participating devices is assigned the role of “master” of the piconet, while all other units become “slaves”. Masters have the duty of directing and controlling communications, even between two slave devices.
Furthermore, in order to extend these networks, several piconets can be joined together in what is known as a scatternet. In theory, anyone with a compatible Bluetooth device is supposed to have the ability to hook up anywhere within that network and connect to another Bluetooth device.

2   Bluetooth Profiles

The Bluetooth SIG states, Bluetooth profiles are general behaviors through which Bluetooth enabled devices communicate with other devices. Bluetooth profiles define the possible applications and describe how Bluetooth technology is to be used for each specific device. When a Bluetooth device is developed, the manufacturer assigns specific Bluetooth profiles for that device to use in order to establish applications which will work with other Bluetooth devices. For example, if you want to use a Bluetooth headset with your Bluetooth enabled cell phone, both devices must use the Headset (HS) profile According to the Bluetooth SIG, every Bluetooth profile includes information on the following issues:

  1. Dependencies on other profiles.

  2. Recommended user interface formats.

  3. Particular parts of the Bluetooth protocol stack used by the profile.

Most Bluetooth devices are given just a few profiles. For example, a Bluetooth headset will use the Headset Profile, but not the LAN Access Profile.

2.1   Bluetooth Protocol Architecture

The architecture given in fig. 1 includes layers like:

  1. Radio Layer: Everything in Bluetooth runs over the Radio Layer, which defines the requirements for a Bluetooth radio transceiver, which operates in the 2.4GHz band. The radio layer defines the sensitivity levels of the transceiver, establishes the requirements for using Spread-spectrum Frequency Hopping and classifies Bluetooth devices into three different power classes:

    1. Power Class 1 – long range devices (100m),

    2. Power Class 2 – normal or standard range devices (10m), and

    3. Power Class 3 – short (10cm)-range operation

 

 

  1. Baseband Layer: The next “floor” in the Bluetooth protocol stack is the Baseband Layer as shown in fig.2, which is the physical layer of the Bluetooth. It is used as a link controller, which works with the link manager to carry out routines like creating link connections with other devices. It controls device addressing, channel control (how devices find each other) through paging and inquiry methods, power-saving operations, and also flow control and synchronization among Bluetooth devices.

 

 

  1. Link Manager Protocol (LMP): A Bluetooth device’s Link Manager Protocol (LM) carries out link setup, authentication, link configuration and other protocols. It discovers other LMs within the area and communicates with them via the Link Manager Protocol (LMP).

  2. Host Controller Interface (HCI): Next in the protocol stack, above the LMP is the Host Controller Interface (HCI), which is there to allow command line access to the Baseband Layer and LMP for control and to receive status information. It’s made up of three parts:

    1. The HCI firmware, which is part of the actual Bluetooth hardware;

    2. The HCI driver, which is found in the software of the Bluetooth device, and

    3. The Host Controller Transport Layer, which connects the firmware to the driver.

  3. Logical Link Control and Adaptation Protocol (L2CAP): Above the HCI level is the Logical Link Control and Adaptation Protocol (L2CAP), which provides data services to the upper level host protocols. The L2CAP plugs into the Baseband Layer and is located in the data link layer, rather than riding directly over LMP. It provides connection-oriented and connectionless data services to upper layer protocols. Protocol types are first identified in the L2CAP. Data services are provided here using protocol multiplexing, segmentation and reassembly operation, and group abstractions occur. L2CAP allows higher-level protocols and applications to send and receive data packets up to 64 kilobytes. The L2CAP spends a lot of its time handling segmentation and reassembly tasks.

  4. RFCOMM (Radio frequency communication): Above L2CAP, the RFCOMM protocol is what actually makes upper layer protocols think they’re communicating over a RS232 wired serial interface, so there’s no need for applications to know anything about Bluetooth.

  5. Service Discovery Protocol (SDP): Also relying on L2CAP is the Service Discovery Protocol (SDP). The SDP provides a way for applications to detect which services are available and to determine the characteristics of those services.

2.2   What is Bluetooth Pairing?

  1. Bluetooth device A looks for other Bluetooth devices in the area: When set to discoverable, Bluetooth device A will allow other Bluetooth devices to detect its presence and attempt to establish a connection. Undiscoverable devices can still communicate with each other but they have to initiate communication themselves.

  2. Bluetooth device A finds Bluetooth device B: Usually the discoverable device will indicate what type of device it is and its Bluetooth device name.

  3. Bluetooth Device A prompts you to enter a password (Passkey): Both users must agree on the Passkey and enter it into their device. The code can be anything you like as long as it is the same for both Bluetooth wireless devices. Most often, the passkey is zero.

  4. Bluetooth device A sends the Passkey to Bluetooth device B.

  5. When both Passkeys are the same, a trusted pair is formed. This happens automatically.

  6. Bluetooth device A and B are now paired and able to exchange data.

3   Bluetooth Security

Today, all communication technologies are facing the issue of privacy and identity theft. Bluetooth technology is no exception. There have been some Bluetooth cell phones that have been hacked into. According to the Bluetooth Special Interest Group (SIG), in order to break into a Bluetooth device, a hacker must:

  1. Force two paired Bluetooth devices to break their connection;

  2. Steal the packets used to resend the PIN;

  3. Decode the PIN.

One of the most basic levels of security for Bluetooth devices is the “pairing” process. Once Bluetooth devices pair with one another, they too are entirely secure.  Unfortunately experienced hackers have come up with a way to get around this basic level of security. There are three security modes for connecting Bluetooth devices:

  1. Security Mode 1: non-secure;

  2. Security Mode 2: service level enforced security;

  3. Security Mode 3: link level enforced security.

It is the company who develops each specific Bluetooth product that decides which security modes to use. For example, devices use two levels: “trusted device” and “distrusted device”. After a trusted device is connected to another device, it has unrestricted access to all services. However, if the problem is a result of the implementation of Bluetooth technology, then the SIG will work with the specific members in order to release patches and prevent future problems from occurring. Following security threats might arise.

  1. Bluejacking: It allows phone users to send business cards anonymously to one another using Bluetooth technology. To ignore bluejackers, simply reject the business card, or if you want to avoid them entirely, set your phone to non-discoverable mode.

  2. Bluesnarfing: This refers to a hacker who has gained access to data, which is stored on a Bluetooth enabled phone. It allows the hacker to make phone calls, send and receive text messages. It requires advanced equipment and expertise. To avoid this, set your phone to non-discoverable mode always.

  3. Bluebugging: It refers to a skilled hacker who has accessed a cell phone's commands using Bluetooth technology without the owner's permission or knowledge. To do so, the hacker must be within a 30 feet range.

4   Conclusion

The future success of Bluetooth remains to be seen, yet there are strong indicators that the technology will continue to grow. Manufacturers are constantly coming up with new ways to implement Bluetooth in various industries, including auto, medicine, restaurants, and more.

Future of Bluetooth is likely to succeed due to

  1. Broadcast Channel: This will drive the adoption of Bluetooth into mobile phones, and enable advertising models based around users pulling information from the information points

  2. Topology Management: enables the automatic configuration of the piconet topologies especially in scatternet situations that are becoming more common today.

  3. Alternate MAC PHY: enables the use of alternative MAC and PHY's for transporting Bluetooth profile data. The high speed alternate MAC PHY's will be used to transport the data.

  4. QoS improvements: enable audio and video data to be transmitted at a higher quality, especially when best effort traffic is being transmitted in the same piconet.

References

1.    Bluetooth end to end by Dee Bakker, Diane McMichael Gilste, Ron Glister, Wiley Publication.

2.    Bluetooth Profiles by Dean A Gratton, Prentice Hall Publication.

3.  Bluetooth Technology - http://progtutorials.tripod.com/Bluetooth_Technology.htm

Category: Papers

About Author

Parag Rabade

Parag currently works with the National Institute of Management and Administration in Kabul as Head of the ICT department with responsibilities that include curriculum development, faculty evaluation and training. He is a qualified chemical engineer and e-Commerce expert, and has over 22 years of experience in the fields of Education, Chemicals, Plastics, Textiles, HR and Logistics. A passionate teacher and mentor, he is also involved with research, and has seven conference papers to his name.

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