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bluetooth


Wireless personal area network (PAN) standard that enables data connections between electronic devices such as desktop computers, wireless phones, electronic organizers and printers in the 2.4 GHz range at 720kbps within a 30-foot range. Bluetooth depends on mobile devices equipped with a chip for sending and receiving information.

Overview of Operation

Radio

The Bluetooth RF (physical layer) operates in the unlicensed ISM band at 2.4GHz. The system employs a frequency hop transceiver to combat interference and fading, and provides many FHSS carriers. RF operation uses a shaped, binary frequency modulation to minimize transceiver complexity. The symbol rate is 1 Megasymbol per second (Msps) supporting the bit rate of 1 Megabit per second (Mbps) or, with Enhanced Data Rate, a gross air bit rate of 2 or 3Mb/s. These modes are known as Basic Rate and Enhanced Data Rate respectively.

Radio Channel

During typical operation, a physical radio channel is shared by a group of devices that are synchronized to a common clock and frequency hopping pattern.

Piconet Consists of Master and Slave Devices

One device provides the synchronization reference and is known as the master. All other devices are known as slaves. A group of devices synchronized in this fashion form a piconet. This is the fundamental form of communication for Bluetooth wireless technology.

Frequency Hopping and Adaptive Frequency Hopping (AFH)

Devices in a piconet use a specific frequency hopping pattern which is algorithmically determined by certain fields in the Bluetooth specification address and clock of the master. The basic hopping pattern is a pseudo-random ordering of the 79 frequencies in the ISM band. The hopping pattern may be adapted to exclude a portion of the frequencies that are used by interfering devices. The adaptive hopping technique improves Bluetooth technology co-existence with static (non-hopping) ISM systems when these are co-located.

Time Slots and Packets – Full Duplex Transmission

The physical channel is sub-divided into time units known as slots. Data is transmitted between Bluetooth enabled devices in packets that are positioned in these slots. When circumstances permit, a number of consecutive slots may be allocated to a single packet. Frequency hopping takes place between the transmission or reception of packets. Bluetooth technology provides the effect of full duplex transmission through the use of a time-division duplex (TDD) scheme.

Link and Channel Management Protocols

Control Layers

Above the physical channel there is a layering of links and channels and associated control protocols. The hierarchy of channels and links from the physical channel upwards is physical channel, physical link, logical transport, logical link and L2CAP channel.

Physical Links

Within a physical channel, a physical link is formed between any two devices that transmit packets in either direction between them. In a piconet physical channel there are restrictions on which devices may form a physical link. There is a physical link between each slave and the master. Physical links are not formed directly between the slaves in a piconet.

Logical Links

The physical link is used as a transport for one or more logical links that support unicast synchronous, asynchronous and isochronous traffic, and broadcast traffic. Traffic on logical links is multiplexed onto the physical link by occupying slots assigned by a scheduling function in the resource manager.

Link Manager Protocol (LMP)

A control protocol for the baseband and physical layers is carried over logical links in addition to user data. This is the link manager protocol (LMP). Devices that are active in a piconet have a default asynchronous connection-oriented logical transport that is used to transport the LMP protocol signaling. For historical reasons this is known as the ACL logical transport. The default ACL logical transport is the one that is created whenever a device joins a piconet. Additional logical transports may be created to transport synchronous data streams when this is required.
The link manager function uses LMP to control the operation of devices in the piconet and provide services to manage the lower architectural layers (radio layer and baseband layer). The LMP protocol is only carried on the default ACL logical transport and the default broadcast logical transport.

L2CAP

Above the baseband layer the L2CAP layer provides a channel-based abstraction to applications and services. It carries out segmentation and reassembly of application data and multiplexing and de-multiplexing of multiple channels over a shared logical link. L2CAP has a protocol control channel that is carried over the default ACL logical transport. Application data submitted to the L2CAP protocol may be carried on any logical link that supports the L2CAP protocol.

Bluetooth Radio

Scope

Bluetooth devices operate in the unlicensed 2.4 GHz ISM (Industrial Scientific Medical) band. A frequency hop transceiver is applied to combat interference and fading.
Two modulation modes are defined. A mandatory mode, called Basic Rate, uses a shaped, binary FM modulation to minimize transceiver complexity. An optional mode, called Enhanced Data Rate, uses PSK modulation and has two variants: ?/4-DQPSK and 8DPSK. The symbol rate for all modulation schemes is 1 Ms/s. The gross air data rate is 1 Mbps for Basic Rate, 2 Mbps for Enhanced Data Rate using ?/4-DQPSK and 3 Mbps for Enhanced Data Rate using 8DPSK.
For full duplex transmission, a Time Division Duplex (TDD) scheme is used in both modes. This specification defines the requirements for a Bluetooth radio for the Basic Rate and Enhanced Data Rate modes.

Frequency Bands and Channel Arrangement

The Bluetooth system operates in the 2.4 GHz ISM band. This frequency band is 2400 – 2483.5 MHz.
The 79 RF channels are ordered from channel number 0-78 and are spaced 1 MHz beginning at 2402 GHz.

Regulatory Range RF Channels
.400-2.4835 GHz f=+k MHz, k=0,…,78

In order to comply with out-of-band regulations in each country, a guard band is used at the lower and upper band edge.

Lower Guard Band Upper Guard Band
2 MHz 3.5 MHz

1. * Minimum output power at maximum power setting.
** The lower power limit Pmin<-30dBm is suggested but is not mandatory, and may be chosen according to application needs.

Power class 1 devices implement power control. The power control is used for limiting the transmitted power over +4 dBm. Power control capability under +4 dBm is optional and could be used for optimizing the power consumption and overall interference level.

Devices with power control capability optimizes the output power in a physical link with LMP commands (see Link Manager Protocol). It is done by measuring RSSI and reporting back if the transmission power shall be increased or decreased if possible.

Modulation Characteristics

The Modulation is GFSK (Gaussian Frequency Shift Keying) with a bandwidthbit period product BT=0.5.

Spurious Emissions

In-band spurious emissions shall be measured with a frequency hopping radio transmitting on one RF channel and receiving on a second RF channel; this means that the synthesizer may change RF channels between reception and transmission, but always returns to the same transmit RF channel. There will be no reference in this document to out of ISM band spurious emissions; the equipment manufacturer is responsible for compliance in the intended country of use.

Radio Frequency Tolerance

The transmitted initial center frequency shall be within ±75 kHz from Fc.

Enhanced Data Rate


A key characteristic of the Enhanced Data Rate mode is that the modulation scheme is changed within the packet. The access code and packet header, as defined in Table 6.1 in the Baseband Specification, are transmitted with the Basic Rate 1 Mbps GFSK modulation scheme, whereas the subsequent synchronization sequence, payload, and trailer sequence are transmitted using the Enhanced Data Rate PSK modulation scheme.

EDR Modulation Characteristics

During access code and packet header transmission the Basic Rate GFSK modulation scheme is used. During the transmission of the synchronization sequence, payload, and trailer sequence a PSK type of modulation with a data rate of 2 Mbps or optionally 3 Mbps is used.

Receiver Characteristics

Sensitivity Level

The actual sensitivity level is defined as the input level for which a raw bit error rate (BER) of 0.1% is met. The receiver sensitivity shall be below or equal to –70 dBm with any Bluetooth transmitter

Interference Performance

The interference performance on Co-channel and adjacent 1 MHz and 2 MHz shall be measured with the wanted signal 10 dB over the reference sensitivity level. For interference performance on all other RF channels the wanted signal shall be 3 dB over the reference sensitivity level.

Out-of-Band Blocking

The out-of-band suppression (or rejection) shall be measured with the wanted signal 3 dB over the reference sensitivity level. The interfering signal shall be a continuous wave signal. The BER shall be ? 0.1%.

Intermodulation Characteristics

The reference sensitivity performance, BER = 0.1%, shall be met under the following conditions:
The wanted signal shall be at frequency f0 with a power level 6 dB over the reference sensitivity level.A static sine wave signal shall be at a frequency f1 with a power level of –39 dBm.A Bluetooth modulated signal (see Section 4.1.7 on page 43) shall be at f2 with a power level of -39 dBm.

Enhanced Data Rate

EDR Actual Sensitivity Level

The actual sensitivity level shall be defined as the input level for which a raw bit error rate (BER) of 0.01% is met. The requirement for a Bluetooth ?/4-DQPSK and 8DPSK Enhanced Data Rate receiver shall be an actual sensitivity level of –70 dBm or better. The receiver shall achieve the –70 dBm sensitivity level with any Bluetooth transmitter compliant to the Enhanced Data Rate transmitter
specification.

EDR BER Floor Performance

The receiver shall achieve a BER less than 0.001% at 10 dB above the reference sensitivity level.

Interference Performance

The interference performance for co-channel and adjacent 1 MHz and 2 MHz channels shall be measured with the wanted signal 10 dB above the reference sensitivity level. On all other frequencies the wanted signal shall be 3 dB above the reference sensitivity level.

How Bluetooth Technology Works

Bluetooth wireless technology is a short-range communications system intended to replace the cables connecting portable and/or fixed electronic devices. The key features of Bluetooth wireless technology are robustness, low power, and low cost. Many features of the core specification are optional, allowing product differentiation.
The Bluetooth core system consists of an RF transceiver, baseband, and protocol stack. The system offers services that enable the connection of devices and the exchange of a variety of data classes between these devices.
Overview of Operation
Architecture – Radio
Architecture – Baseband
Architecture – Link Manager Protocol (LMP)
Architecture – Host Controller Interface (HCI)
Architecture – Logical Link Control and Adaptation Protocol (L2CAP)
Core System Architecture
Data Transport Architecture
Communications Topology

More links
Official Bluetooth website
Bluetooth Designer
Web site dedicated purely to the designers of Bluetooth wireless technology products.
Bluetooth Developer Corner
Bluetooth Qualification Program Website
Bluetooth Resource Center
Bluetooth Tutorial – Specifications, from palowireless.
Bluetooth Weblog
Covering the Bluetooth industry.
BlueZ
The overall goal of this project is to make an implementation of the Bluetooth™ wireless standards specifications for Linux.
A Mobile-Care System Integrated with Bluetooth Blood Pressure and Pulse Monitor,
and Cellular Phone

Article by Ren-Guey Lee, Chun-Chieh Hsiao, Chun-Chung Chen and Ming-Shiu Liu.
Engadget
Article – Switched On: The Blossoming of Bluetooth, by Peter Rojas.
Evaluation of Bluetooth as a Replacement for Cables in Intensive Care and Surgery
By Mats K. E. B. Wallin, MD MSc, and Samson Wajntraub, MSc.
GNOME Bluetooth Subsystem
In development as a prototype by Edd Dumbill, with the intention of being submitted to the GNOME desktop project. The software is free, licensed under the GPL.
GSM World
Article – What is Bluetooth?
Hewlett-Packard Development Company, L.P.
Compatibility matrix for Bluetooth wireless technology.
How Bluetooth Works
Article from HowStuffWorks, Inc., by Curt Franklin.
mPhone Ltd
Bluetooth mobile phones, Bluetooth accessories.
Socket Communications
Offers complete Bluetooth solutions which cordlessly connect your Windows handheld, notebook or PC to other Bluetooth enhanced devices.
Syncing the Treo 650 with Bluetooth
Article from the Linux Journal, by Dovid Kopel.
TDK Systems
Bluetooth products and accessories for wireless networking.

Transmitter Characteristics

The Bunker
Article: Security Briefs – Serious flaws in Bluetooth security lead to disclosure of personal data, by Adam Laurie, Ben Laurie.
Wi-Fi Planet
Article – Minimizing Bluetooth Interference, By Jim Geier.
Wireless Developer Network
An Introduction to Bluetooth By David Blankenbeckler.