VIC2-2E/M E&M card and delay. Using with Motorola Astro Modem

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May 6th, 2010
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I am running a proprietary modem  signal across  Cisco VIC2-2E/M cards (with microwave for transport). 4 wire circuit.

The modem is a Motorola Astro Modem, it runs constantly. It is connected to a Motorola Quantar radio base station on one end, and a Motorola AstroTac 3000 comparator on the other. The Astro modems are constantly 'connected' to each other regardless if there is a radio signal or 'remote control' signal to transmit. When that happens, there are proprietary signalling done to determine if it is digital, analog, what channel etc.

The problem is the Astro modems keep losing the 'link'. I get constant timing errors and other errors I can't find what they are.

The delay on the circuit (this is what the Motorola equipment says) is about 98ms. That is right at the very edge of what it will function, I think 99 and it won't work. The delays isn't constant, but does change slightly from one test to another ( a couple of ms).

So it appears that there are delays in the Cisco transport. The IT person that runs the Cisco equipment says a 'ping' test shows very minimal delays (I recall something like 9ms, perhaps a bit more, but still much, much less).

Therefore I've theorized that the E&M cards are causing the delay- OR perhaps there are other settings that could minimize delays.

What settings in the E&M cards can be changed to optimize speed?

Please help!!!!

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Overall Rating: 4.7 (3 ratings)
paolo bevilacqua Thu, 05/06/2010 - 13:05
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The reduce delay,.you could only try reducing the sampling size, that is an option for codec command under dial-peer

However, I recommend you find a better way to connect these devices, rather than modem you could try synchonous or asynchronous emulation for example.

Mark Hollingsworth Thu, 05/06/2010 - 13:17
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Thanks for the idea.

Is that changed in the cards themselves? (I cannot do it, but can only ask the agency that is running the 'link' for us to change).

We cannot change the connection method, it is integral with the Motorola system we have. We have to work with what is there.

Thanks again,

I'll see what we can do.


paolo bevilacqua Fri, 05/07/2010 - 09:48
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That is a configuration command that any person of the trade should be able to understand and apply.

Please remember to rate useful posts clicking on the stars below.

Felipe Garrido Mon, 05/17/2010 - 12:47
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can you share the configuration of the voice gateways with teh E/M cards? I don' think the ports themselves would be injecting that much delay. How was the ping test performed? Did it simulate the payload size and CoS? 100 ms delay is not uncommon for a VoIP environment. It would be interesting to see if the playout delay buffers have been configured to account for the delay. Typically when two Cisco voice gateways detect a modem or fax call, the playout delay buffers will be increased and set to fixed values. If the modems are using proprietary signaling, it may be that the gateways aren't performing the switch to modem passthrough or even configured to do so.

If you can provide me with the following information, I can suggest some configuration that may help.

show version

show run

show voice dsp detail

show voice call summary

show voice port summary

Mark Hollingsworth Wed, 12/12/2012 - 17:18
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Sorry for the delay, I got busy with other projects and have not gotten back to solving this.

I cannot get the configuration, another agency owns the system.

They way I got the delay was given by the Motorola equipment. My assumption is it is measuring the time it is taking to make the drop with its proprietary signalling.

I can't do a Ping test, since I can't access the system. Plus the only card I have access to is E&M, so of course doesn't do ping natively.

Motorola give the 100ms latency, that could be a round trip, I really don't know (Moto is notorious for withholding information.).

I hope to get back to solving this- currently we are not using the Astro modems at all, but plain old audio. This limits the functionality quite a bit, so I really would like to get the Astro Modems working.

I will try and get as much info- and hopefully I can pass along some ideas for them to modify and optimize the link for us.

Oh yes, everything is running over a microwave link.

thanks for the help.


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