Bluetooth Tech - Parag K. ITPA09

7/29/2019 Bluetooth Tech - Parag K. ITPA09

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Bluetooth - A path towards an IT revolution

Parag K. Rabade1

1 Microsoft IT Academy Centre, Pune, INDIA

e-mail:[email protected]

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 communicationsprotocol primarily designed for low power consumption, with a short range

(power-class-dependent: 1 meter, 10 meters, 100 meters) based on low-cost

transceivermicrochipsin each device.

Keywords: piconet, spread-spectrum frequency hopping, adaptive frequencyhopping, 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 Bltand (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 withthe 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.
mailto:[email protected]:[email protected]:[email protected]://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Meterhttp://en.wikipedia.org/wiki/Meterhttp://en.wikipedia.org/wiki/Transceiverhttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Integrated_circuitmailto:[email protected]://en.wikipedia.org/wiki/Personal_area_networkhttp://en.wikipedia.org/wiki/Meterhttp://en.wikipedia.org/wiki/Transceiverhttp://en.wikipedia.org/wiki/Integrated_circuit


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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


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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 thendetermine 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 apiconet. 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.


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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, whichdefines 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:

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

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

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


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2. 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.

3. Link Manager Protocol (LMP): A Bluetooth devices 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).

4. Host Controller Interface (HCI): Next in the protocol stack, above the

LMP is the Host Controller Interface (HCI), which is there to allow


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command line access to the Baseband Layer and LMP for control and to

receive status information. Its made up of three parts:

a. The HCI firmware, which is part of the actual Bluetooth

hardware;

b. The HCI driver, which is found in the software of the Bluetooth

device, and

c. The Host Controller Transport Layer, which connects the

firmware to the driver.

5. 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. TheL2CAP 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.

6. RFCOMM (Radio frequency communication): Above L2CAP, the

RFCOMM protocol is what actually makes upper layer protocols thinktheyre communicating over a RS232 wired serial interface, so theres no

need for applications to know anything about Bluetooth.

7. 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: Whenset 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.


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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 deviceA sends the Passkey to Bluetooth device B.

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

automatically.

6. Bluetooth deviceA 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:

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

b. Steal the packets used to resend the PIN;

c. 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:

a. Security Mode 1: non-secure;

b. Security Mode 2: service level enforced security;

c. 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


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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
http://progtutorials.tripod.com/Bluetooth_Technology.htmhttp://progtutorials.tripod.com/Bluetooth_Technology.htmhttp://progtutorials.tripod.com/Bluetooth_Technology.htm

Bluetooth Tech - Parag K. ITPA09

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