Bluetooth operates in the 2.4 GHz ISM band and utilizes 74 MHz
of the spectrum. This range varies across different countries,
based on government regulations. Bluetooth uses a combination of
several standards to ensure a robust connection. A
frequency-hopping scheme is used to avoid radio interference
and add a level of security to RF connections by using a different
frequency within the available ISM band for each data packet
transmission. Each piconet is defined by its unique
frequency-hopping pattern that is defined by an algorithm based on
the master device address.
Time Division Duplex (TDD) is actually a fancy way of
describing the fact that the radio unit does not transmit and
receive at the same time. TDD means that the radio must set itself
to transmit for one time slot, and then switch itself to receive
for the next time slot.
Speech Coding (CVSD) is the particular voice data
transmission algorithm used by Bluetooth - it's simply a way
of digitally encoding the characteristics of analog data. Bluetooth
also uses small data packets, which are protected with Forward
Error Correction (FEC) or Automatic Repeat Request (ARQ), and
Cyclic Redundancy Check (CRC) for error correction. More
information on these algorithms is available at AnywhereYouGo.com
or in the Bluetooth Core Specifications.
Bluetooth devices may communicate at a range of 10 meters. This
range may be extended to 100 meters when using a scatternet
topology to transmit messages, or by increasing the radio unit's
transmission power.
Bluetooth devices may communicate at a speed of up to 1 Mbps,
and may maintain simultaneous voice and data connections. Data
connections may be synchronous or asynchronous, with data rates of
432 Kbps and 721 Kbps respectively. Up to three simultaneous voice
connections may be maintained at a data rate of 64 Kbps. Voice
connections are always synchronous.
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