Then we can write the differential detector
output as d(t) X(t) j Y(t).
(6.108)
(6.109)
Taking the expectation operation reveals the following which can be used to determine the presence
of delay spread ((t) that is the differential modulation symbol).
(6.110)
This consists of the sum of the autocorrelations of the channel response weighted by the
modulation.
6.5.5 Eye Opening Statistics
This fifth quality estimation technique is based on the symbol eye opening at the output of the demodulator.
It is well known that the received signal??™s eye diagram is indicative of the quality of the received
signal and in turn the quality of the channel. In this CQE we will assume the normal operation is to have
a received signal with an opened eye diagram. Hence the block diagram shown in Fig. 6.39 is used to
convey the idea of using the averaged eye opening power to provide a CQE.5
E5d(t)6 Rh1
(T ) # ejf(t) Rh2
(T ) # ejf(tt)
5h1(t T ) # s(t T ) h2(t t T ) # s(t t T )6*
d(t) 5h1(t) # s(t) h2(t t) # s(t t)6 d(t) r(t) # r*(t T)
Yk Qk # Ik1 Qk1 # Ik
Xk Ik # Ik1 Qk # Qk1
Zh2 Z2
Zh1 Z2 Threshold
Zh1 Z2
Zh2 Z2 Threshold
RECEIVER DIGITAL SIGNAL PROCESSING 329
5 United States Patent #5,159,282.
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