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Tooway Modem RM4100

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spikey
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May 21st, 2012 at 8:27pm  
How do I find the Forward link speed on modem RM4100, I can see the RX SNR which is 13 dB in the modem/ tria settings but can't see anything related to Forward ?

or is it displayed as something else or is it not important if you have RX SNR of 12 to 13 dB

Spikey
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« Last Edit: May 22nd, 2012 at 1:41pm by Eric Johnston »  
 
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Eric Johnston
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Reply #1 - May 22nd, 2012 at 1:37pm  
I don't know what is the forward link speed or bit rate, but my guess is about 60 to 70 Mbit/s to the remote sites. Assuming 30 Msps carriers, 8PSK and 3/4 FEC rate = 67.5 Mbit/s.

Does anyone have a 500 MHz wide spectrum picture of the Tooway downlink ?
What is the carrier plan in each beam ?

Claimed capacity is about 450 Mbit/s per 500 MHz wide beam. Probably up to about 24000 customers per beam.

If your site RX SNR is 12 to 13 dB that sounds good to me. If you are a beam centre and it is clear sky you might get a bit higher.

Best regards, Eric.
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spikey
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Reply #2 - May 22nd, 2012 at 9:32pm  
Thanks eric.

Does the RX SNR 12 to 13db I'm getting include both the Forward & receive signal figures, or if not what actualy is the RXSNR ?

Cheers
Spikey
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Eric Johnston
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Reply #3 - May 22nd, 2012 at 10:43pm  
The RX C/N you are measuring at your remote terminal site refers to your reception of the outlink downstream carrier from the large gateway earth station.

You can only see measurments made at your terminal.

When your terminal transmits a brief burst, that upstream burst is received at the gateway earth station, where its C/N is measurable at the hub.

The hub can obtain your site measurement remotely and the hub operator can then obtain weekly graphs of the C/N in both directions like that below:
...

The term C/N means carrier to noise ratio.  Within the bandwidth of the carrier, say 32 MHz, the noise power and the signal power are compared.  A 13 dB C/N means that the signal is 20 times as powerful as the noise. Most of the noise comes from your LNB front end transistor and some from the satellite uplink receive pre-amplifier.

Best regards, Eric.
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spikey
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Reply #4 - May 23rd, 2012 at 6:27am  
Thanks for the graph eric, on the basic modem that I mentioned earlier how can I find the upstream db figures, I can see the downstream which I have been told is the 13db. Or has anyone got the same RM4100

rgds
Sp
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Eric Johnston
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Reply #5 - May 23rd, 2012 at 9:32am  
At the remote site you cannot measure your upstream C/N.  It does not exist at your site. It exists at the teleport hub receiver.

The hub operator can see the hub C/N measurement and also by remote messaging (from the site to the hub) get the C/N measurement of the outlink made at your site.

You can only see receive C/N measurements made at your site.

Your modem transmits a signal and the power of the modem transmit signal is displayed.  Also, the transmit power from the TRIA is also displayed. See this example of "TRIA status screen"
...
The power out from the modem is -27.6 dBm
The power out from the TRIA  is +31.0 dBm  (1.259 watt)
The difference (+58.6 dB) is the gain of the TRIA minus the cable loss.
Best regards, Eric.
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spikey
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Reply #6 - May 26th, 2012 at 4:14pm  
Thanks for the info Eric, shame we can't see the forward link though after activation.

spikey
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