A few more minor edits.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6386 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
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Joe Taylor 2016-01-12 00:45:52 +00:00
parent ee997b1a96
commit 6c925494ec

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@ -164,9 +164,9 @@ The JT65 protocol specifies transmissions that normally start one second
and by a meaningful amount over the KV decoder.
In addition to its excellent performance, the new algorithm has other desirable
properties, not least of which is its conceptual simplicity.
Decoding performance and complexity scale in a convenient way, providing
steadily increasing soft-decision decoding gain as a tunable computational
complexity parameter is increased over more than five orders of magnitude.
Decoding performance and computational complexity scale in a convenient
way, providing steadily increasing soft-decision decoding gain as a tunable
parameter is increased over more than five orders of magnitude.
Appreciable gain is available from our decoder even on very simple (and
relatively slow) computers.
On the other hand, because the algorithm benefits from a large number of
@ -1636,11 +1636,11 @@ Otherwise, declare decoding failure and exit.
An acceptable hinted decode has been found.
Declare a successful result and return the saved codeword and the value
\begin_inset Formula $q=100*(u_{1}-bu_{2})$
\begin_inset Formula $q=100(u_{1}-bu_{2})$
\end_inset
as a confidence indicator.
By default we use
By default we use the value
\begin_inset Formula $b=1.12$
\end_inset
@ -1672,12 +1672,12 @@ Comparisons of decoding performance are usually presented in the professional
noise power spectral density.
For weak-signal amateur radio work, performance is more conveniently presented
as the probability of successfully decoding a received word plotted against
signal-to-noise ratio in a 2500 Hz reference bandwidth,
\begin_inset Formula $\mathrm{SNR}{}_{2500}$
\end_inset
.
The relationship between
, the signal-to-noise ratio in a 2500 Hz reference bandwidth, The relationship
between
\begin_inset Formula $E_{b}/N_{o}$
\end_inset
@ -1725,8 +1725,8 @@ Simulated results on the AWGN channel
\end_layout
\begin_layout Standard
Results of simulations using the BM, KV, and FT, decoding algorithms on
the JT65 code are presented in terms of word error rate versus
Results of simulations using the BM, KV, and FT decoding algorithms on the
JT65 code are presented in terms of word error rate versus
\begin_inset Formula $E_{b}/N_{o}$
\end_inset
@ -1905,10 +1905,10 @@ reference "fig:bodide"
.
It is apparent that the FT decoder produces more decodes than KV when
\begin_inset Formula $T=10^{4}$
\begin_inset Formula $T\gtrsim3000$
\end_inset
or larger.
.
As already noted in connection with Figure
\begin_inset CommandInset ref
LatexCommand ref
@ -2075,16 +2075,17 @@ Number of trials needed to decode a received word versus Hamming distance
\begin_inset Formula $X$
\end_inset
between the received word and the decoded codeword, for 1000 simulated
transmissions on an AWGN channel with no fading and
between the received word and the decoded codeword.
We used 1000 simulated transmissions on an AWGN channel with no fading,
and
\begin_inset Formula $\mathrm{SNR}{}_{2500}=-24$
\end_inset
dB or
\begin_inset Formula $E_{b}/N_{o}=5.1$
dB
\begin_inset Formula $(E_{b}/N_{o}=5.1$
\end_inset
dB.
dB).
\end_layout
@ -2126,13 +2127,9 @@ reference "fig:Psuccess"
These simulated Doppler spreads are comparable to those encountered on
HF ionospheric paths and also for EME at VHF and the lower UHF bands.
For comparison we note that the JT65 symbol rate is about 2.69 Hz.
\end_layout
\begin_layout Standard
It is interesting to note that while Rayleigh fading severely degrades the
success rate of the BM decoder, the penalties are much smaller with both
FT and
It is interesting to note that while Rayleigh fading severely degrades
the success rate of the BM decoder, the penalties are much smaller with
both FT and
\begin_inset Quotes eld
\end_inset
@ -2143,8 +2140,8 @@ Deep Search
decoding.
Simulated Doppler spreads of 0.2 Hz actually increased the FT and DS decoding
rates slightly at SNRs close to the decoding threshold, presumably because
with the low-rate JT65 code signal peaks can be enough to produce good
copy.
with the low-rate JT65 code signal peaks can provide the information needed
for good copy.
\end_layout
\begin_layout Standard
@ -2254,11 +2251,10 @@ reference "fig:JT65B_EME"
\emph on
WSJT-X,
\emph default
illustrating replies to an EME CQ from K1JT on 144.118 MHz using submode
JT65B.
illustrating replies to an EME CQ from K1JT on 144.118 MHz.
Speckled vertical lines on the waterfall at 1494 and 1515 Hz are the synchroniz
ing tones of signals from DL7UAE and SP6GWB.
Other visible speckles (barely above the noise) up to about 1693 Hz are
Other visible speckles (barely above the noise) up to about 1870 Hz are
data tones from these two stations.
Two lines of decoded text show that the estimated average signal strengths
were
@ -2313,10 +2309,6 @@ s vertical direction is one minute of time.
\end_inset
\end_layout
\begin_layout Plain Layout
\end_layout
\end_inset
@ -2325,7 +2317,7 @@ s vertical direction is one minute of time.
\end_layout
\begin_layout Standard
Figure
As another example, Figure
\begin_inset CommandInset ref
LatexCommand ref
reference "fig:spectrogram"
@ -2334,16 +2326,17 @@ reference "fig:spectrogram"
shows activity in submode JT65A during a single minute on the 20 m amateur
band.
At this time the band was crowded with overlapping signals; you can probably
count at least 19 distinct synchronizing tones (the speckled vertical lines
in the figure), and see that in some places as many as four signals overlap.
At this time the band was crowded with overlapping signals.
You can probably count at least 19 distinct synchronizing tones (the speckled
vertical lines in the figure), and can see that in some places as many
as four signals overlap.
After straightforward signal processing to demodulate the signals and produce
soft-symbol data for the FT decoder, program
\emph on
WSJT-X
\emph default
extracts and decodes 21 error-free messages from this recorded data segment.
This is achieved with a relatively small timeout parameter,
This result is achieved with a relatively small timeout parameter,
\begin_inset Formula $T=1000.$
\end_inset
@ -2351,8 +2344,8 @@ WSJT-X
The strongest signals (12 in this example) are sequentially decoded and
subtracted from the raw data after the first pass.
Another 9 signals are decoded in the second pass.
For comparison, the hard-decision BM decoder decodes only 12 messages from
this recording (9 in the first pass and 3 more in a second pass).
For comparison, the hard-decision BM decoder decodes a total of 12 messages
from this recording (9 in the first pass and 3 more in a second).
\end_layout
\begin_layout Standard
@ -2423,7 +2416,7 @@ key "karn"
\end_inset
, modified slightly so that the Reed-Solomon syndromes are computed only
once in our most time-consuming loop (steps 2 through 8 in Algorithm 1).
once in our most time-consuming loop (steps 2 through 8, Algorithm 1).
The FT algorithm is now an integral part of programs
\emph on
WSJT,