6.36.4
RECEIVER DIGITAL SIGNAL PROCESSING 327
Pilot
Time Slot
Data Pilot Data
Time Slot
PER(k) PER(k + 1)
Pilot Data
Time Slot
PER(k + 2)
FIGURE 6.35 General time slot structure.
4 United States Patent # 5,159,282.
Demodulate
Pilot
Extract
PER +
Z??“Tslot
Time Slot
Averaged PER
r(k)
FIGURE 6.36 PER receiver block diagram.
6.5.2 Nonredundant Error Correction Based
This second quality estimation technique is based on the Nonredundant Error Correction (NEC)
demodulation technique presented in the early chapters. Recall the NEC demodulator calculates syndromes
in order to determine if an error is present. This CQE counts the number of times (or frequency)
the error signal is enabled. A simplified block diagram of the NEC-based CQE is given in
Fig. 6.37.
1DD +
Error Pattern
Detector
Detected Symbols
2DD
r(k)
Calculate
Syndrome
Error
Measure
Delay
CQE
FIGURE 6.37 Block diagram of an NEC-based CQE.
In Fig. 6.37, we show the basic elements of the NEC demodulator. The CQE output comes from
the block labeled error measure. Here, the error signal is counted to determine an estimate of the symbol
error rate and then produces the CQE output.
Since the CQE is now based on all the symbols in the time slot, a priori information is not needed.
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