66 msec in time duration. The bit fields in the time-slot structures are
defined as:
Guard 6 bits are allocated to the guard field to prevent uplink transmitted time-slot bursts from
overlapping.
WIRELESS TOPICS 3
1 2 3 4 5 6 1 2 6
1 Frame = 40 msec
1 2 3 4 5 6 1 2
45 Symbols
117 Symbols
Base Station
Transmit
Base Station
Receive
FIGURE 1.2 NADC uplink and downlink timing relationship.
Analog FM
Digital
17
C/I (dB)
Voice
Quality
13
FIGURE 1.3 Voice quality performance.
1 MOS voting has a 5-point rating with 5 excellent, 4 good, 3 fair, 2 poor, and 1 unacceptable.
We will use this standard to convey some important observations that were made when we evolved
the AMPS to Digital [5]. In Fig. 1.3, we plot the voice quality as a function of carrier to interference
ratio (C/I). There are quite a few ways that can be used in viewing the figure, we will present one.
The x-axis can be viewed as we move closer to the serving base station, the C/I increases. Continuing
along these lines, then moving away from the base station will produce a smaller C/I ratio, such as at
Ramp 6 bits are allocated to the ramp field to allow the mobile transmitter to gradually reach
its desired power level while maintaining emission mask requirements.
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