mohatta2015.pdf
signal processing from power amplifier operation control point of view
signal processing from power amplifier operation control point of view
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THE LITERATURE 185<br />
8.6 THE LITERATURE<br />
The idea of providing a "transmitted reference" for channel estimation and coherent<br />
demodulation can be found in [Rus64, Wal64, Hin65]. The approach has evolved<br />
to transmitting periodic pilot symbols, known as Pilot Symbol Assisted Modulation<br />
(PSAM) [Cav91]. The section on channel estimation and tracking is based<br />
on [ArsOlb, Bot03a]. How to divide energy between pilot and traffic symbols is<br />
examined in [Wal64, Hin65, Bus66]. An overview of sequence design for channel<br />
estimation can be found in [CheOO, Tong04].<br />
For ML detection of the traffic symbols, MMSE channel estimation using the<br />
transmitted reference should be employed [Rus64j. MMSE channel estimation also<br />
arises out of the estimator-correlator receiver for ML detection in the absence of a<br />
transmitted reference [Pri56, Kai60j. For MLSD, per-survivor processing is developed<br />
in [Ses94b, Rah95j. The fact that the Viterbi algorithm and the tree search<br />
are no longer equivalent is shown in [Chu96j.<br />
A survey of A/D conversion approaches is provided in [Wal99]. Quantization of<br />
soft information is examined in [Rag93a, Ony93].<br />
Adaptive equalization designs for the US TDMA system can be found in [Pro91J.<br />
PROBLEMS<br />
The idea<br />
8.1 It was shown that when estimating c, one would like the property that S\ So +<br />
s 2 Si is zero. Given that so = +1 and si = —1, what is the value of s 2 to achieve<br />
this?<br />
8.2 Consider estimated d.<br />
a) Substitute the models for r¡ and r 2 into the expression for d<br />
b) What is the property of so, si and s 2 such that the main path doesn't<br />
interfere with estimating dl<br />
c) Is it the same property that prevents the delayed path from interfering<br />
with estimating c?<br />
8.3 Consider noise power estimation.<br />
a) Substitute the models for n and r 2 into the expression for σ 2 . Assume<br />
that c = c and d = d and simplify the expression as much as possible.<br />
b) Does the result make sense? Why?<br />
8.4 Consider the case where we only need a one-tap equalizer (wi = 0) and<br />
direct adaptation. The error signal in the LMS algorithm simplifies to e m — ê m —<br />
W2{m)r m . Suppose r m is positive.<br />
a) What IS Srn .<br />
b) If w 2 is positive but too large, what is the sign of e m ?<br />
c) When w 2 is updated, will it be made larger or smaller?<br />
8.5 Consider MMSE DFE and determining the weights for the forward filter.
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