mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-18 01:52:05 -05:00
A few more editorial tweaks, and more text.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6354 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Joe Taylor
parent
b22f1c6d2e
commit
8ba09d5175
@ -139,15 +139,21 @@ WSJT-X
|
||||
\emph default
|
||||
, widely used for amateur weak-signal communication with JT65 and other
|
||||
specialized digital modes.
|
||||
The program is freely available and licensed under the GNU General Public
|
||||
License.
|
||||
The program is freely available
|
||||
\begin_inset CommandInset citation
|
||||
LatexCommand cite
|
||||
key "wsjt"
|
||||
|
||||
\end_inset
|
||||
|
||||
and licensed under the GNU General Public License.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
The JT65 protocol specifies transmissions that normally start one second
|
||||
into a UTC minute and last for 46.8 seconds.
|
||||
Receiving software therefore has up to several seconds to decode a message,
|
||||
before the operator sends a reply at the start of the next minute.
|
||||
Receiving software therefore has up to several seconds to decode a message
|
||||
before the start of the next minute, when the operator sends a reply.
|
||||
With today's personal computers, this relatively long time available for
|
||||
decoding a short message encourages experimentation with decoders of high
|
||||
computational complexity.
|
||||
@ -158,7 +164,7 @@ The JT65 protocol specifies transmissions that normally start one second
|
||||
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 5 orders of magnitude.
|
||||
complexity 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
|
||||
@ -405,7 +411,7 @@ probabilistic
|
||||
\begin_inset CommandInset citation
|
||||
LatexCommand cite
|
||||
after "Chapter 10"
|
||||
key "key-1"
|
||||
key "lc2004"
|
||||
|
||||
\end_inset
|
||||
|
||||
@ -1224,17 +1230,21 @@ Calculate the hard-decision Hamming distance
|
||||
\begin_inset Formula $X$
|
||||
\end_inset
|
||||
|
||||
between the candidate codeword and the received symbols, the corresponding
|
||||
soft distance
|
||||
between the candidate codeword and the received symbols, along with the
|
||||
corresponding soft distance
|
||||
\begin_inset Formula $d_{s}$
|
||||
\end_inset
|
||||
|
||||
, and the quality metric
|
||||
and the quality metric
|
||||
\begin_inset Formula $u$
|
||||
\end_inset
|
||||
|
||||
.
|
||||
If
|
||||
|
||||
\end_layout
|
||||
|
||||
\begin_layout Enumerate
|
||||
If
|
||||
\begin_inset Formula $u$
|
||||
\end_inset
|
||||
|
||||
@ -1242,8 +1252,8 @@ Calculate the hard-decision Hamming distance
|
||||
\begin_inset Formula $u_{1}$
|
||||
\end_inset
|
||||
|
||||
as
|
||||
\begin_inset Formula $u_{2}$
|
||||
by setting
|
||||
\begin_inset Formula $u_{2}=u_{1}$
|
||||
\end_inset
|
||||
|
||||
and then set
|
||||
@ -1262,11 +1272,11 @@ If
|
||||
\begin_inset Formula $d_{s}<d_{0}$
|
||||
\end_inset
|
||||
|
||||
, go to step 10.
|
||||
, go to step 11.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Enumerate
|
||||
If the number of trials is less than the timeout limit
|
||||
If the number of trials is less than the timeout limit
|
||||
\begin_inset Formula $T,$
|
||||
\end_inset
|
||||
|
||||
@ -1287,7 +1297,7 @@ If
|
||||
\begin_inset Formula $r<r_{1},$
|
||||
\end_inset
|
||||
|
||||
go to step 10.
|
||||
go to step 11.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Enumerate
|
||||
@ -1382,18 +1392,18 @@ The FT algorithm is completely general: with equal sensitivity it recovers
|
||||
much
|
||||
\emph default
|
||||
smaller list of messages (say, a few thousand messages or less) that we
|
||||
can guess may be among the most likely ones to be received.
|
||||
can guess might be among the most likely ones to be received.
|
||||
One such situation exists when making short ham-radio contacts that exchange
|
||||
minimal information including callsigns, signal reports, perhaps Maidenhead
|
||||
locators, and acknowledgments.
|
||||
On the EME path or on a VHF or UHF band with limited geographical coverage,
|
||||
On the EME path or a VHF or UHF band with limited geographical coverage,
|
||||
the most likely received messages often originate from callsigns that have
|
||||
been decoded before.
|
||||
Saving a list of previously decoded callsigns and associated locators makes
|
||||
it easy to generate lists of hypothetical messages and their corresponding
|
||||
codewords at very little computational expense.
|
||||
The resulting candidate codewords can be tested in the same way as those
|
||||
generated by the probabilistic method described in Setcion
|
||||
generated by the probabilistic method described in Section
|
||||
\begin_inset CommandInset ref
|
||||
LatexCommand ref
|
||||
reference "sec:The-decoding-algorithm"
|
||||
@ -1456,14 +1466,10 @@ For hinted decoding we again invoke a ratio threshold test, but in this
|
||||
\begin_inset Formula $r_{2}$
|
||||
\end_inset
|
||||
|
||||
can be a more relaxed limit than the
|
||||
\begin_inset Formula $r_{1}$
|
||||
\end_inset
|
||||
|
||||
used in the FT algorithm.
|
||||
For the limited subset of messages that operator experience suggests to
|
||||
can be a more relaxed limit than that used in the FT algorithm.
|
||||
For the limited subset of messages suggested by operator experience to
|
||||
be likely, hinted decodes can be obtained at lower signal levels than required
|
||||
for those obtained from the full universe of
|
||||
for the full universe of
|
||||
\begin_inset Formula $2^{72}$
|
||||
\end_inset
|
||||
|
||||
@ -1511,9 +1517,9 @@ reference "sec:Appendix:SNR"
|
||||
\end_inset
|
||||
|
||||
.
|
||||
Examples of both presentations are included in the following discussion,
|
||||
Examples of both types of plot are included in the following discussion,
|
||||
where we describe simulations carried out to compare performance of FT
|
||||
with other algorithms, and with theoretical expectations.
|
||||
with other algorithms and with theoretical expectations.
|
||||
We have also used simulations to establish suitable default values for
|
||||
the acceptance parameters
|
||||
\begin_inset Formula $X_{0},$
|
||||
@ -1599,7 +1605,7 @@ As expected, the soft-decision algorithms, FT and KV, are about 2 dB better
|
||||
\begin_inset Formula $T=10^{5}$
|
||||
\end_inset
|
||||
|
||||
is small enough to be practical on most of today's home computers.
|
||||
is small enough to be practical on today's home computers.
|
||||
|
||||
\end_layout
|
||||
|
||||
@ -1631,9 +1637,17 @@ Word error rates as a function of
|
||||
\end_inset
|
||||
|
||||
the signal-to-noise ratio per information bit.
|
||||
Theory: theoretical prediction for the hard-decision BM decoder.
|
||||
The remaining curves represent simulation results on an AWGN channel for
|
||||
the BM, KV, and FT decoders.
|
||||
The curve labeled
|
||||
\begin_inset Quotes eld
|
||||
\end_inset
|
||||
|
||||
Theory
|
||||
\begin_inset Quotes erd
|
||||
\end_inset
|
||||
|
||||
shows a theoretical prediction for the hard-decision BM decoder.
|
||||
Remaining curves represent simulation results on an AWGN channel for the
|
||||
BM, KV, and FT decoders.
|
||||
The KV algorithm was executed with complexity coefficient
|
||||
\begin_inset Formula $\lambda=15$
|
||||
\end_inset
|
||||
@ -1643,7 +1657,7 @@ Word error rates as a function of
|
||||
WSJT
|
||||
\emph default
|
||||
programs.
|
||||
The FT alrithm was run with timeout setting
|
||||
The FT algorithm used timeout setting
|
||||
\begin_inset Formula $T=10^{5}.$
|
||||
\end_inset
|
||||
|
||||
@ -1743,18 +1757,18 @@ name "fig:WER2"
|
||||
\end_inset
|
||||
|
||||
Percent of JT65 messages copied as a function of SNR in 2500 Hz bandwidth.
|
||||
Solid lines with filled circles are results from the FT decoder; numbers
|
||||
adjacent to the curves specify values of the timeout parameter
|
||||
\begin_inset Formula $T.$
|
||||
Numbers adjacent to curves specify values of timeout parameter
|
||||
\begin_inset Formula $T$
|
||||
\end_inset
|
||||
|
||||
The dotted line with open squares is the KV decoder with complexity coefficient
|
||||
|
||||
for the FT decoder.
|
||||
Open circles and dotted line show results for the KV decoder with complexity
|
||||
coefficient
|
||||
\begin_inset Formula $\lambda=15$
|
||||
\end_inset
|
||||
|
||||
.
|
||||
Results from the BM algorithm are shown with a dashed line and crosses.
|
||||
Results for the BM algorithm are plotted with crosses and dashed line.
|
||||
\end_layout
|
||||
|
||||
\end_inset
|
||||
@ -1768,12 +1782,12 @@ Percent of JT65 messages copied as a function of SNR in 2500 Hz bandwidth.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Timeout parameter
|
||||
Parameter
|
||||
\begin_inset Formula $T$
|
||||
\end_inset
|
||||
|
||||
is the maximum number of symbol-erasure trials allowed for a particular
|
||||
attempt at decoding a received word.
|
||||
in the FT algorithm is the maximum number of symbol-erasure trials allowed
|
||||
for a particular attempt at decoding a received word.
|
||||
Most successful decodes take only a small fraction of the maximum allowed
|
||||
number of trials.
|
||||
Figure
|
||||
@ -1784,18 +1798,20 @@ reference "fig:N_vs_X"
|
||||
\end_inset
|
||||
|
||||
shows the number of stochastic erasure trials required to find the correct
|
||||
codeword vs.
|
||||
the number of hard-decision errors in the received word, for a run with
|
||||
1000 simulated transmissions at
|
||||
codeword as a function of
|
||||
\begin_inset Formula $X,$
|
||||
\end_inset
|
||||
|
||||
the number of hard-decision errors in the received word.
|
||||
This run used 1000 simulated transmissions at
|
||||
\begin_inset Formula $\mathrm{SNR}=-24$
|
||||
\end_inset
|
||||
|
||||
dB, just slightly above the decoding threshold.
|
||||
The timeout parameter was
|
||||
\begin_inset Formula $T=10^{5}$
|
||||
dB, just slightly above the decoding threshold, and the timeout parameter
|
||||
was
|
||||
\begin_inset Formula $T=10^{5}.$
|
||||
\end_inset
|
||||
|
||||
for this run.
|
||||
No points are shown for
|
||||
\begin_inset Formula $X\le25$
|
||||
\end_inset
|
||||
@ -1808,7 +1824,7 @@ reference "fig:N_vs_X"
|
||||
|
||||
\end_inset
|
||||
|
||||
shows that the FT algorithm decoded received words with as many as
|
||||
shows that the FT algorithm decodes received words with as many as
|
||||
\begin_inset Formula $X=43$
|
||||
\end_inset
|
||||
|
||||
@ -1910,8 +1926,18 @@ reference "fig:Psuccess"
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
(*** A little more description is needed here, along with new data for the
|
||||
DS curves.***)
|
||||
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 hinted decoding.
|
||||
Simulated Doppler spreads of 0.2 Hz actually increased the FT and DS decoding
|
||||
rates slightly at SNRs close to the decosing threshold, presumably because
|
||||
with the low-rate JT65 code signal peaks can be enough to produce good
|
||||
copy.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
(*** New data will be used for the DS curves.
|
||||
***)
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
@ -1955,8 +1981,16 @@ Deep Search
|
||||
|
||||
) algorithm.
|
||||
Numbers adjacent to the curves are the simulated Doppler spreads in Hz.
|
||||
The curve labeled Sync illustrates the dependence of proper time and frequency
|
||||
synchronization in the decoder presently implemented in
|
||||
The curve labeled
|
||||
\begin_inset Quotes eld
|
||||
\end_inset
|
||||
|
||||
Sync
|
||||
\begin_inset Quotes erd
|
||||
\end_inset
|
||||
|
||||
illustrates the rate of correct time and frequency synchronization in the
|
||||
decoder presently implemented in program
|
||||
\emph on
|
||||
WSJT-X
|
||||
\emph default
|
||||
@ -1982,6 +2016,55 @@ Summary
|
||||
Still to come ...
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Possible ideas:
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Tie it in to
|
||||
\emph on
|
||||
WSJT-X
|
||||
\emph default
|
||||
and
|
||||
\emph on
|
||||
MAP65
|
||||
\emph default
|
||||
.
|
||||
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Mention two-pass decoding.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Experience with FT on crowded HF bands.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Maybe one screen shot, or partial screen shot of the
|
||||
\begin_inset Quotes eld
|
||||
\end_inset
|
||||
|
||||
Band Activity
|
||||
\begin_inset Quotes erd
|
||||
\end_inset
|
||||
|
||||
window?
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Some EME results needed!
|
||||
\end_layout
|
||||
|
||||
\begin_layout Standard
|
||||
Something about the code repository and how to build
|
||||
\emph on
|
||||
WSJT-X
|
||||
\emph default
|
||||
.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Bibliography
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
@ -1992,9 +2075,11 @@ key "kv2001"
|
||||
|
||||
“Algebraic soft-decision decoding of Reed-Solomon codes,” R.
|
||||
Köetter and A.
|
||||
Vardy, IEEE Trans.
|
||||
Inform.
|
||||
Theory, Vol.
|
||||
Vardy,
|
||||
\emph on
|
||||
IEEE Transactions on Information Theory
|
||||
\emph default
|
||||
, Vol.
|
||||
49, Nov.
|
||||
2003.
|
||||
\end_layout
|
||||
@ -2003,13 +2088,32 @@ key "kv2001"
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
label "2"
|
||||
key "wsjt"
|
||||
|
||||
\end_inset
|
||||
|
||||
|
||||
\emph on
|
||||
WSJT Home Page
|
||||
\emph default
|
||||
: http://www.physics.princeton.edu/pulsar/K1JT/.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Bibliography
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
label "3"
|
||||
key "lhmg2010"
|
||||
|
||||
\end_inset
|
||||
|
||||
"Stochastic Chase Decoding of Reed-Solomon Codes", Camille Leroux, Saied
|
||||
Hemati, Shie Mannor, Warren J.
|
||||
Gross, IEEE Communications Letters, Vol.
|
||||
Gross,
|
||||
\emph on
|
||||
IEEE Communications Letters
|
||||
\emph default
|
||||
, Vol.
|
||||
14, No.
|
||||
9, September 2010.
|
||||
\end_layout
|
||||
@ -2017,7 +2121,7 @@ key "lhmg2010"
|
||||
\begin_layout Bibliography
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
label "3"
|
||||
label "4"
|
||||
key "lk2008"
|
||||
|
||||
\end_inset
|
||||
@ -2026,7 +2130,9 @@ key "lk2008"
|
||||
Decoding," Soo-Woong Lee and B.
|
||||
V.
|
||||
K.
|
||||
Vijaya Kumar, IEEE
|
||||
Vijaya Kumar,
|
||||
\emph on
|
||||
IEEE
|
||||
\begin_inset Quotes eld
|
||||
\end_inset
|
||||
|
||||
@ -2034,25 +2140,31 @@ GLOBECOM
|
||||
\begin_inset Quotes erd
|
||||
\end_inset
|
||||
|
||||
2008 proceedings.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Bibliography
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
label "4"
|
||||
key "lc2004"
|
||||
|
||||
\end_inset
|
||||
|
||||
Error Control Coding, 2nd edition, Shu Lin and Daniel J.
|
||||
Costello, Pearson-Prentice Hall, 2004.
|
||||
2008 proceedings
|
||||
\emph default
|
||||
.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Bibliography
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
label "5"
|
||||
key "lc2004"
|
||||
|
||||
\end_inset
|
||||
|
||||
|
||||
\emph on
|
||||
Error Control Coding, 2nd Edition
|
||||
\emph default
|
||||
, Shu Lin and Daniel J.
|
||||
Costello, Pearson-Prentice Hall, 2004.
|
||||
\end_layout
|
||||
|
||||
\begin_layout Bibliography
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
label "6"
|
||||
key "ls2009"
|
||||
|
||||
\end_inset
|
||||
@ -2066,7 +2178,11 @@ Stochastic Erasure-Only List Decoding Algorithms for Reed-Solomon Codes,
|
||||
\end_inset
|
||||
|
||||
Chang-Ming Lee and Yu T.
|
||||
Su, IEEE Signal Processing Letters, Vol.
|
||||
Su,
|
||||
\emph on
|
||||
IEEE Signal Processing Letters,
|
||||
\emph default
|
||||
Vol.
|
||||
16, No.
|
||||
8, August 2009.
|
||||
\end_layout
|
||||
@ -2074,12 +2190,12 @@ Stochastic Erasure-Only List Decoding Algorithms for Reed-Solomon Codes,
|
||||
\begin_layout Bibliography
|
||||
\begin_inset CommandInset bibitem
|
||||
LatexCommand bibitem
|
||||
label "6"
|
||||
label "7"
|
||||
key "karn"
|
||||
|
||||
\end_inset
|
||||
|
||||
Berlekamp-Massey decoder written by Phil Karn, http://www.ka9q.net/code/fec/
|
||||
Berlekamp-Massey decoder written by Phil Karn, KA9Q: http://www.ka9q.net/code/fec/
|
||||
\end_layout
|
||||
|
||||
\begin_layout Section
|
||||
@ -2202,9 +2318,9 @@ reference "eq:Eb_Es"
|
||||
|
||||
:
|
||||
\begin_inset Formula
|
||||
\[
|
||||
\mathrm{SNR}_{2500}=1.23\times10^{-3}\frac{E_{b}}{N_{o}}.
|
||||
\]
|
||||
\begin{equation}
|
||||
\mathrm{SNR}_{2500}=1.23\times10^{-3}\frac{E_{b}}{N_{o}}.\label{eq:SNR2500}
|
||||
\end{equation}
|
||||
|
||||
\end_inset
|
||||
|
||||
@ -2213,9 +2329,9 @@ If all quantities are expressed in dB, then:
|
||||
|
||||
\begin_layout Standard
|
||||
\begin_inset Formula
|
||||
\[
|
||||
\mathrm{SNR}_{2500}=(E_{b}/N_{o})_{\mathrm{dB}}-29.1\,\mathrm{dB}.
|
||||
\]
|
||||
\begin{equation}
|
||||
\mathrm{SNR}_{2500}=(E_{b}/N_{o})_{\mathrm{dB}}-29.1\,\mathrm{dB}=(E_{s}/N_{0})_{\mathrm{dB}}-29.7\,\mathrm{dB}.\label{eq:SNR_all_types}
|
||||
\end{equation}
|
||||
|
||||
\end_inset
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user