Information from
Johnson Consulting

  1. What is "Bluetooth"?

  2. How could Bluetooth be used?

  3. Basic Bluetooth functions

  4. How does Bluetooth work?

  5. Establishing network connections

  6. What kind of traffic can Bluetooth handle?

  7. What about competing technologies?

  8. What about radiation; is it dangerous?

  9. What is Bluetooth´s growth potential?

  10. What is Bluetooth´s prestanda?

  11. What about Bluetooth´s security?

  12. Bluetooth definitions

  13. How networks are formed and controlled

  14. What´s the advantage of frequency-hopping?

  15. How timeslots are used

Bluetooth - An Overview

What kind of traffic can Bluetooth handle?

Bluetooth is specifically designed to provide low-cost, robust, efficient, high capacity, ad hoc voice and data networking with the following characteristics:
  1. 1 Mb/sec. transmission/reception rate exploits maximum available channel bandwidth.
  2. Fast frequency hopping avoids interference.
  3. Adaptive output power minimizes interference.
  4. Short data packets maximize capacity during interference.
  5. Fast acknowledge allows low coding overhead for links.
  6. CVSD (Continuous Variable Slope Delta Modulation) voice coding enables operation at high bit-error rates.
  7. Flexible packet types supports a wide application range.
  8. Relaxed link budget supports low-cost single chip integration.
  9. Transmission/reception interface tailored to minimize electric current consumption.

The Bluetooth technology was not planned to be just a physical wireless medium offering merely a platform for high-level protocols and applications. The aim is to provide something more, with immediate device-interoperability as soon as the first Bluetooth products hit the market. But this can only be achieved if all the communication blocks, including radios, protocols and applications, are accurately defined and can interoperate.

Sound Transmissions

Bluetooth uses either a 64 kb/s log PCM format (A-law or m-law) or a 64 kb/s CVSD (Continuous Variable Slope Delta Modulation). The CVSD-format uses an adaptive delta modulation algorithm with syl-labic companding. The voice coding on the line interface should have a quality equal to or better than the quality of 64 kb/s log PCM.

LOG PCM CODEC
Since the voice channels on the air-interface can support a 64 kb/s information stream, a 64 kb/s log PCM traffic can be used for transmission, using either A-law or m-law compression. If the line interface uses A-law and the air interface uses m-law or vice versa, a conversion from A-law to m-law is performed. The compression method follows ITU-T recommendations G. 711.

CVSD CODEC
A more robust format for voice over the air interface is a delta modulation. This modulation scheme follows the waveform where the output bits indicate whether the prediction value is smaller or larger then the input waveform. To reduce slope overload effects, syllabic companding is applied: the step size is adapted according to the average signal slope. The input to the CVSD encoder is 64 ksamples/second linear PCM.

CVSD Waveform Coding

CVSD audio quality

For Bluetooth audio quality the requirements are put on the transmitter side. The 64 ksamples/s linear PCM input signal must have negligible spectral power density above 4 kHz. A set of reference input signals are encoded by the transmitter and sent through a reference decoder (available on the website).

The power spectral density in the 4-32 kHz band of the decoded signal at the 64 ksample/s linear PCM output, should be more than 20 dB below the maxi-mum in the 0-4 kHz range.

Fitting into the Environment

Connection speeds of up to 721kbps are possible, providing users with network performance that it is not much slower than a shared Lan. In theory, Bluetooth can be added to the network backbone to simplify hot-desking. It can also allow users to synchronise address books and e-mail messages with mobile devices without having to worry about plugging in devices.

But while Bluetooth will allow uses to connect to mobile devices without needing to carry external cables, current devices such as mobile phones will need adapters to work with Bluetooth.

 At the CeBIT-fair in Hannover, Germany in March, 2001, the Singapore-based company Sunderland Technologies introduced a Bluetooth-module for the Palm V-series. When the Wave Clip Bluetooth module is switched on, Palm V can communicate with other Bluetooth-units within a 9 meters radius.
Copyright © 2001, Johnson Consulting
Last Updated: 2007-01-02
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