Power Control

All the decorrelation processes rely on coded channel streams being visible at the
demodulator at similar received power levels (energy per bit) ideally within 1 dB of
each other.
For every slot, the handset has to obtain channel estimates from the pilot bits, estimate
the signal to interference ratio, and process the power control command (Transmission
Power Control, or TPC), that is, power control takes place every 660 μs, or 1500
times per second. This is fast enough to track fast fading for users moving at up to 20
kmph. Every 10 ms, the handset decodes the Transport Format Combination Indicator
(TFCI) which gives it the bit rate and channel decoding parameters for the next 10-ms
frame. Data rates can change every 10 ms (dynamic rate matching) or at the establishment
or teardown of a channel stream (static matching). The coding can change
between 1/3 convolutional coding, 1/3 convolutional coding with additional block
coding, /or turbo coding.
Power control hardware implementation will be similar to the detection methods
outlined in Chapter 2 but the methods need to comprehend additional dynamic range
and faster rates of change. The power control function also needs to be integrated with
the linearization process.