Bluetooth introduction

Bluetooth introduction

Brief Introduction to Bluetooth
Bluetooth is a short range wireless technology. It operates in the license free ISM (Industrial, Scientific, and Medical) band at 2.4 GHz. It is a WPAN (Wireless Personal Area Network) data net and was originally developed as a cable replacement when connecting different devices, such as PC's, printers and mobile phones, and not at least between different products from different manufactures.
It was developed as an open standard in 1994 after a proposal made by Sven Mattisson and Jaap Haartsen from Ericsson. It was later in 1998 formalized by Bluetooth SIG (Special Interest Group).
The Bluetooth technology got its name after the Danish King Harald Blåtand (in Danish) (911-987). He introduced Christianity in Denmark and united the Scandinavian countries. He was King of Denmark and Norway from 958-985 and son of King Gorm den Gamle and Queen Thyra.
Bluetooth SIG
Bluetooth SIG is the controlling group behind Bluetooth. They drive the continued development of the Bluetooth standard.
Originally in 1998:
Ericsson, Nokia, IBM, Intel and Toshiba
Later also: Motorola, Lucent, Microsoft and 3COM
Today 2009:
Agere Systems, Ericsson, Intel, Lenovo, Microsoft, Motorola, Nokia and Toshiba
You can read more about Bluetooth SIG here.
Bluetooth Trade Mark and Logo
Bluetooth trade mark and logo is registered by Bluetooth SIG.

 

Bluetooth Protocol
The Bluetooth protocol has a layered architecture. At the bottom is the embedded part of the protocol also denoted as the "lower part" and contains the layers:
Radio
Baseband
LMP (Link Manager Protocol) containing LC (Link Control) and LM (Link Manager)
HCI lower part (Host Control Interface)
At the top is the host part of the protocol and contains the layers:
HCI upper part (Host Control Interface)
L2CAP (Logical Link Control and Adaptation Protocol)
RFCOMM (Radio Frequency Communication)
SDP (Service Discovery Protocol)
On top again are the different profiles. The profiles describe different use case functions. They are standardized and describe the requirements to the different layers of the protocol. They are a very vital part of the Bluetooth specification:
GAP - Generic Access Profile
SDAP - Service Discovery Application Profile
CTP - Cordless Telephony Profile
SPP - SerialPort Profile
HS - Headset Profile
DNP - Dial-up Networking Profile
FP - Fax Profile
LAP - LAN (Local Area Network) Access Profile
OPP - Object Push Profile
FTP - File Transfer Profile
etc.
Bluetooth Technology:
Bluetooth has the following characteristics:
2.4 GHz (2400 – 2483.5 MHz) in the license free ISM band
79 channels of 1 MHz, divided into slots of 625 µs
Data packets 1 – 5 slots
GFSK (Gaussian Frequency Shift Keying) modulation
Version 1.1/1.2: 1 Mbps, data rate ~700 kbps
Version 2.0/2.1 EDR (Enhanced Data Rate): 3Mbps, data rate 2.1 Mbps
Master – slave system
Encryption (SAFER+ algorithm)
FHSS (Frequency-Hopping Spread Spectrum) – hops 1600 times/second in a pseudo random pattern (robust)
AFH (Adaptive Frequency Hopping) was introduced with version 1.2 – noisy (interference) channels are removed from the hopping pattern for a period
Low power consumption capability
Next version:
The Bluetooth specification version 3.0 was supposed to use UWB (Ultra Wideband technology) with data rate ~480Mbps (60MB pr. second) for high speed transport. In April 21, 2009 UWB was dropped and 802.11 (WIFI) added instead. Main new feature is AMP (Alternate MAC/PHY) and the addition of 802.11 with ~24Mbps data rate as a high speed transport.
You can read more about Bluetooth here and more about Bluetooth radio technique here
Find Devices in the Vicinity - Discovery Process
When you want to discover another Bluetooth device the discovering device must be in Inquiry Mode and the other one in Inquiry Scan Mode and be visible (discoverable).
During Inquiry it hops 3200 times/second on only 32 out of the 79 channels
Uses LAP (Lower Address Parts) from GIAC (General Inquiry Access Code)
Up to 10.24 seconds to find another device (noise free environment)
Connect two Devices - Pairing Process
When you want to make a connection to another Bluetooth device it must be in Page Mode and the other one in Page Scan Mode.
During Paging it hops 3200 times/second
No PIN code or passkeys are transmitted over the air
After initial PIN code it uses 56 or 128 bit encryption

 

Bluetooth Topology:
Bluetooth supports different network topologies:
Piconet
Scatternet
Master/slave topology
Up to 7 active devices on a master and 255 devices inactive (park mode)

 

Figure: Agilent Technologies

Bluetooth Security

The Bluetooth security is extremly high:

Unique Bluetooth address assigned by IEEE (it cannot be changed in the device)
Pseudo-random frequency hopping (79 channels/1600 times/second)
Authentication
Encryption (SAFER+ algorithm, up to 128 bit)
Device can be hidden (non-discoverable)
Transmit Power
Bluetooth supports 3 transmit power classes:
Class 1: 1 mW - 100 mW / (0 dBm - 20 dBm 100 meter
Class 2: 0.25 mW - 2.5 mW / –6 dBm - +4 dBm 20 meter
Class 3: 1 mW / 0 dBm max power 1 meter
Quality Of Service
A lot has been done to ensure the QoS (Quality Of Service) in the Bluetooth technology. If a sufficient QoS cannot be guarantied, it is not possible to ensure that data are send correctly. Since Bluetooth operates in the license free ISM band is it also important that adequate robustness is available to ensure coexistence with other technologies in the same frequency band e.g. WLAN and Zigbee etc.
The main technologies Bluetooth uses to secure high QoS and robustness are:
FHSS (Frequency-Hopping Spread Spectrum) - hops 1600 times/second in a pseudo random scheme – ensures that the impact of noise blocking one or more channels are minimized and gives a higher robustness
AFH (Adaptive Frequency Hopping) – noisy (interference) channels are removed from the hopping scheme for a period of time
Dynamic power control - (sends only with sufficient power to ensure QoS (Quality of Service) not more
ACL (data) connection has ARQ (Automatic Repeat Request) to repeat corrupt data
22 Bluetooth channels "hops" on one WLAN channel (WLAN has 13 channels)
Distribution
Today Bluetooth is widely distributed and is used daily by many users around the world. Bluetooth has the endorsement from many major electronic companies. Bluetooth is here to stay:
Number of sold Bluetooth chip sets:
317 millions in 2005
555 millions in 2006 and encreasing (decreasing prices)
Number of sold mobile phones with Bluetooth:
238 millions in 2006, 25% of all sold mobile phones (53% in 2008 prognoses)
722 millions in 2010 59% (prognoses)
Links
See links on Bluetooth News.

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