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

[Jorge Capelo]

Caro colega João Gonçalves Costa
c/c Flávio PY2ZX

Não sendo eu entendido em modos digitais, tenho curiosidade e queria
perguntar-lhe se o ROS usa o protocolo de algum dos modos digitais já
existentes (entendo que é da família dos FSKs), apenas tendo a capacidade de
lidar com estas espantosamente baixas relações sinal-ruído  ou é um novo
modo em si mesmo (o modo 'ROS'...). Isto é, se a comunicação só é possível
entre correspondentes usando o programa ROS, ou será possível por exemplo
entre o HRD e ROS, por ex.? Cordialmente, obrigado.
73.
Jorge Capelo
CT2JVH
Lisboa


2010/2/22 João Gonçalves Costa <joao.a.costa  ctt.pt>

> 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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