ARLA/CLUSTER: Novo software ROS - é possível recuperar sinais a -35dB SNR!

[João Gonçalves Costa]

ROS 
Enviado por: "PY2ZX" py2zx.ham  gmail.com   py2zx 
Dom, 21 de Fev de 2010 3:40 pm 


Olá pessoal,

Informações na zsvhf e debate no qrz.com sobre o novo software ROS que
trabalha em Spread Spectrum. Segundo o manual é possível recuperar um
sinal a -35 dB SNR!

Flávio PY2ZX

====================================
Date: Sun, 21 Feb 2010 12:45:46 +0200
From: "Derek" <derek  fotogravett.com>
Subject: Re: [ZSVHF] New Digital mode

ROS is a digital communications software based on Spread Spectrum
techniques. It is designed to fully optimize the power available and
make contacts in the toughest conditions, for HF, EME or Meteor Scatter.
The software has two Symbol Rates: 16 and 1 baud (the latter aimed at
weak signals until -35 dbs of S/N) and can automatically synchronize any
Symbol Rate. ROS also automatically reply to the operators that include
an email in any of your messages, reporting on the parameters of the
received signal.

The decoding is done in real time, even in the case of 1 baud, and
automatically synchronizes in frequency within a range of + -200 Hz. So,
ROS simplifies the work of the operators.

Hardware & Software Requirements

. a SSB transceiver connected to an antenna
. a computer with WindowsT.
. 700 MHz or faster CPU and 32 MB of available RAM
. Monitor with at least 1024 x 768 resolution
. a 16 bit sound card
. a serial port radio interface (to use PTT).

Download manuals and software here.

http://rosmodem.wordpress.com/

73's ZS5Y
===================================

Recorded at University of Twente (Netherlands) Web SDR:
http://websdr.ewi.utwente.nl:8901/

2205z ROS: PA3FWM, one hour ago has place the first offcial QSO with
ROS, and it was received at this SDR. Thank you
2205z PA3FWM: Ah, I had seen your repeated advertisements for your
experiment, so it's nice to know that it worked out!
2206z ROS: It was a historical moment. It was on 7065 LSB

The First QSO
18 February 2010, at 20:56 UTC took place the First Official QSO with
ROS from Vitoria (Spain) to University of Twente (Netherlands) covering
a distance of 1265 Km. on 7.065 Mhz. The first Ham Radio Operator to get
it was EA2LE.

The First Automatic Reply
ROS notification: EATEST has received your Radio Message
********** Please don't reply to this email ********************
EATEST has received your Radio Message sent at: 21:03 UTC
Received Message: 'CQ CQ CQ de EA2LE EA2LE EA2LE pse k My email is:
<ea2le  ure.es> <ea2le  ure.es> <ea2le  ure.es>'
Operator Info:
Callsign: EATEST
Name: Jose Alberto Nieto Ros
E-mail: nietoros  hotmail.com
QTH: La Aljorra-Cartagena SPAIN
Locator: IM97lq
Station: web SDR
ROS Version: 1.6.1 beta
Signal Info:
Symbol Rate: 16 bauds
Frame Acquisition: 20/20
Final Acquisition: 15/16
Frequency Shift: -39,1 Hz
Symbol Errors detected by Viterbi: 2/50
Metric: 0 dB
Vumeter Level: -8 dB
CPU Usage: 20 %

Download the ROS beta Software and give it a try, sounds cool.
http://rosmodem.wordpress.com/
Requires WinRaR or similar Rar unzipper.
=====

I have pretty good evidence: For starters, if you use the supplied WAV
file on the website (labeled as a test sample of -35 dB S/N), you get
-35dB S/N. This noise has fairly high peaks and some good troughs.

I've been playing with Audacity and playing recording of the mode and
noise at the same time, and I've gotten at least -31dB with fairly
reliable copy. I used the white noise generator in Audacity, and read
the "Metric" scale in ROS. Audacity's "white noise" is a worse-case
scenario - absolutely NO nulls or peaks. I would say -31dB in this
scenario is pretty darn good, considering real-life noise will wax and
wain over time.

-31dB is beyond WSPR mode, and ROS is real-time, whereas WSPR requires
~2 minutes to decode before you can read it.

KE7HQY
--------------
Up on the wide open spaces of VHF it may not be a problem but there just
isn't enough space for digimodes that wide on HF. Fine when it's just a
couple of experimenters using it, but the more who use it where are they
all going to go?
Julian, G4ILO
--------------
That's true if, and only if, the baud (a.k.a. signaling) rate equals the
bit rate. According to Shannon-Hartley, the maximum error-free bit rate
that can be sent on a noisy channel with a bandwidth of 2.2K Hz and a
signal-to-noise ratio of -35dB is 1 bps.

Shannon-Hartley formula...

S/N = 10^(dB/10)
S/N = 10^(-35/10) ~= 0.000316
C = 2200 * (log(1 + 0.000316) / log(2)) ~= 1 bps

N3RQ
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