The overall data rate for the radio channel is
270kb/s.
This is split into B full rate or 16 half rate traffic
channels, plus the signaling channels.
The coding is complex in order to have the maximum chance to
detect and correct the errors encountered in a typical propagation path.
The output of the speech coder is encrypted,
coded and interleaved in a sophisticated way to allow Forward
Error Correction to be applied.
The data is then sent as bursts in time slots of
577µs, each containing 116 encrypted bits.
There are 8 or 16 of these time slots per TDMA frame, and
the receive and transmit time slots are staggered so that the mobile station is not
receiving at the same instant as it is transmitting, thus simplifying the filtering
requirements.
With this scheme, there can be at least one spare slot
between transmit and receive, leaving time for the synthesizer to change frequency
(whether or not hopping is employed).
The receiver also monitors adjacent cell for one time slot
each frame to determine their signal strength to optimize a possible handover,