We have intentionally denoted the baseband section as a large box. This section will perform the
signal processing techniques discussed so far in this book. Specifically the algorithms include: symbol
timing recovery, demodulation, FEC, equalization, frequency offset estimation/compensation,
DC offset compensation, automatic gain control, and so on. We have chosen to emphasize the analog
front end (AFE) control signals such as AGC, AFC, and DC Offset. Since an ADC is placed in the
data path the received signal will have a fixed dynamic range. A control signal is used to adjust the
Gain Control Amplifier (GCA) in the RF front end to keep the signal within the operating dynamic
range. This correction signal will be used to compensate for path loss and time varying phenomenon
such as shadowing [40].
The frequency offset control signal (i.e., AFC) will be sent to the AFE to compensate for residual
frequency offsets due to tolerances in the crystal oscillators used in the design. In addition to the fact
that large frequency offsets degrade performance, wireless standards dictate certain frequency uncertainties
be met. For example, in the WCDMA standard a certain offset uncertainty should be achieved
(i.e., 0.
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