Also the receiver doesn??™t need to have time slot synchronization before calculating the CQE. This is
a useful property to exploit, especially if the receiver is asked to measure the quality of another link;
in this case it would immediately be able to perform this CQE task. Lastly, since the entire slot is
used in the calculation it is conceivable that fewer slots are needed to achieve the desired confidence
level in the measured quantity, when compared to techniques involving only the pilot bit field.
In Fig. 6.38 we plot the estimated error rate using the 1NEC demodulator receiver in an AWGN
channel. The CQE results follow reasonably well when compared to the conventional differential
detector.
328 CHAPTER SIX
1NEC-Based Channel Quality Estimation in AWGN
1.E??“01
1.E??“05
1.E??“04
1.E??“03
1.E??“02
4 5 6 10 11
Eb/No (dB)
Error Rate
Pb(DQPSK)-DD
1NEC
1NEC-CQE
7 8 9
FIGURE 6.38 1NEC-based channel quality estimation performance.
6.5.3 Channel Impulse Response Based
This third quality estimation technique is based on the receiver??™s knowledge of the Power Delay
Profile (PDP) or Channel Impulse Response (CIR). Regardless of the multiple access scheme used,
some form of channel delay spread information is estimated in the receiver.
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