Digital Design of Communication Systems - Digital Design of Signal Processing Systems: A Practical Approach - page 570

dmax = Max of Autocorrelation function

Requirs delay of
strongest
channel tap

Delivers the estimate of the
frequency to be compensated

Theta = Frequency Estimate
Limited to +-L/2 carrier spacing

Frequency
Compensation

Fine
Frequency

Channel
Estimation

Coarse
Frequency

Coarse
Timing Block

Fine Timing

Theta = Coarse frequency Estimate

dmax = coarse timing point

Operates by
channel
Inversion

Data without
training Sequence

Remove
Cyclic Prefix

S/P FFT Equalization

FEC Decoder Slicer

Convolution and Reed Solomon Decoding

Figure 13.43 Block diagram of complete OFDM receiver

then the received signal can be written as:

r ¼ e j W ðÞS h þn

where

WðÞ = diag 1 ; e j 2 pv=N ; e j 2 p 2 v=N ; ...; e j 2 pðN 1 Þv=N

n = n ½ ðÞn 0 ðÞ...nðN 1 1 Þ

2
4

3
5

s ðÞ s ð ... s k þ 1 ð Þ

s ðÞ s ðÞ... s k þ 2 ð Þ

:
:
:

S ð 13 : 1 Þ

sN 1 ð Þ sN 2 ð Þ ... sNk ð Þ

1} are the samples of the training sequence with cyclic
prefix, n is the noise vector, v is the frequency offset, and r is the received signal. The channel
estimation using coarse frequency offset can be written as:

Here, {s(k): k ¼ -N g ,-N g þ 1, ... , N

1

h ¼ S H S

S H W H ðÞr