More thoughts for section 7.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6378 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
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Steven Franke 2016-01-10 01:20:03 +00:00
parent 5a3e9842c4
commit ede606e746

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@ -2242,7 +2242,169 @@ MAP65
\end_layout
\begin_layout Standard
Mention two-pass decoding.
Mention two-pass decoding - could use Fig
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:spectrogram"
\end_inset
as a case study.
The table below is for the data shown in Fig
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:spectrogram"
\end_inset
.
Maybe less confusing if the third row was deleted.
\begin_inset Float table
wide false
sideways false
status open
\begin_layout Plain Layout
\align center
\begin_inset Tabular
<lyxtabular version="3" rows="5" columns="2">
<features rotate="0" tabularvalignment="middle">
<column alignment="center" valignment="top">
<column alignment="center" valignment="top">
<row>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
Case
\end_layout
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
# decodes
\end_layout
\end_inset
</cell>
</row>
<row>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
one-pass, BM
\end_layout
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
9
\end_layout
\end_inset
</cell>
</row>
<row>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
one-pass, FT
\end_layout
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
12
\end_layout
\end_inset
</cell>
</row>
<row>
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
two-pass, BM
\end_layout
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
12
\end_layout
\end_inset
</cell>
</row>
<row>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
two-pass, FT
\end_layout
\end_inset
</cell>
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text
\begin_layout Plain Layout
21
\end_layout
\end_inset
</cell>
</row>
</lyxtabular>
\end_inset
\end_layout
\begin_layout Plain Layout
\begin_inset Caption Standard
\begin_layout Plain Layout
The effect of soft-symbol decoding combined with signal subtraction on the
data shown in Figure
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:spectrogram"
\end_inset
.
\end_layout
\end_inset
\end_layout
\begin_layout Plain Layout
\end_layout
\end_inset
\end_layout
\begin_layout Subsubsection*
@ -2250,8 +2412,14 @@ Experience with FT on crowded HF bands:
\end_layout
\begin_layout Standard
(Re the following paragraph and Figure 5 - just playing around with ideas
- feel free to change, delete, etc.)
(Re the following paragraph and Figure
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:spectrogram"
\end_inset
- just playing around with ideas - feel free to change, delete, etc.)
\end_layout
\begin_layout Standard
@ -2269,19 +2437,28 @@ moonbounce
reflection paths at HF.
Use on HF was not originally an intended application for the mode, but
at present HF use accounts for the largest number of 2-way contacts.
Figure 5 is a spectrogram with frequency in Hz on the horizontal axis showing
JT65 activity during a one-minute time-segment (JT65 transmissions start
at the beginning of a minute and last for approximately 47 s).
Figure
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:spectrogram"
\end_inset
is a spectrogram with frequency in Hz on the horizontal axis showing JT65
activity during a one-minute time-segment (JT65 transmissions start at
the beginning of a minute and last for approximately 47 s).
The data was collected in the 20m amateur band during daytime under crowded
band conditions.
With some straightforward signal processing to demodulate the signals and
produce soft-symbol data for the FT decoder it is possible to extract and
decode 21 messages from the data summarized in Figure 5, and this is achieved
with a relatively small timeout parameter
decode 21 messages from the data summarized in Figure 5.
This is achieved with a relatively small timeout parameter
\begin_inset Formula $T=1000$
\end_inset
.
and in spite of the fact that the 200 Hz-wide 65-FSK (sync plut 64-FSK)
signals overlap, with as many as 4 signals superposed in some parts of
the spectrum.
Using exactly the same pre-processing, but without soft-symbol information
the errors-only BM decoder is able to decode only 12 messages.
@ -2310,6 +2487,12 @@ status open
\begin_inset Caption Standard
\begin_layout Plain Layout
\begin_inset CommandInset label
LatexCommand label
name "fig:spectrogram"
\end_inset
A spectrogram showing one minute of data collected under crowded band conditions
on 20m during daytime hours.
WSJT-X extracted 21 JT65 messages in approximately the same bandwidth required