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Nstreme2 can be 100% FDD?

Posted: Thu Mar 11, 2010 6:01 pm
by asterisco
Hi

I'm planning a point 2 point link working as FDD with a pair of cards (one for each direction on both ends). I plan to use Nstreme2 for that link.

The question is that for legal aspects I must assure that the link is fully FDD (frequency division duplex) : each channel is used exclusively in one direction. I understand that with Nstreme protocol we can disable CSMA and specially the ACK that sends the receiver to the transmitter. Is this true?. If the receiver ACK can't be disabled, from a legal point of view, the channel is being used as TDD (time division duplex).

Thanks,
Antonio

Re: Nstreme2 can be 100% FDD?

Posted: Thu Mar 11, 2010 10:40 pm
by andreacoppini
don't know if it would help, but you could use tx-a/rx-b to get around legal issues. You would still be running in TDD mode and tx and rx will be in the same frequency (since you will be using 1 card), but you can use a bigger antenna on the rx side since that antenna (should) never transmit.

Re: Nstreme2 can be 100% FDD?

Posted: Thu Mar 11, 2010 11:52 pm
by KillerOPS
i did some nstreme links with broken cm9 cards, using only the tx part or the rx part of them (broken diversity chip) and it worked flawless. And it's exactly what you need.

Re: Nstreme2 can be 100% FDD?

Posted: Fri Mar 12, 2010 12:20 am
by aaa
If you have broken diversity swich all direction is shorted to ground.Any usage is not possible.

Re: Nstreme2 can be 100% FDD?

Posted: Fri Mar 12, 2010 12:27 am
by changeip
can someone post a pic of a diversity switch? I'd like to test some on my SR9 cards but have no idea where they are.

Re: Nstreme2 can be 100% FDD?

Posted: Fri Mar 12, 2010 8:07 am
by 0ldman
If you have broken diversity swich all direction is shorted to ground.Any usage is not possible.
Typically, if you have a broken diversity chip you see a 20dB signal loss and it makes no difference whether you choose port a or b.

I've got a couple out there that took a minor lightning hit and lost the diversity chip. Still works quite well for those customers who's signal would normally be in the -30 to -40 range, puts them right in the sweet spot.

Re: Nstreme2 can be 100% FDD?

Posted: Fri Mar 12, 2010 9:42 am
by aaa
If you can make photo without RF shield , I can show you diversity swich. You can test with multimeter like on all other card. Later if someone is interesting I can try make short movie how replace diversity swich. Only I need find some camera :))

can someone post a pic of a diversity switch? I'd like to test some on my SR9 cards but have no idea where they are.

Re: Nstreme2 can be 100% FDD?

Posted: Fri Mar 12, 2010 9:48 am
by andreacoppini
http://www.vallstedt-networks.de/Forum/ ... php?t=1355

It's in German so I have no idea what they're talking about, but the diversity chip is the small chip between the antenna connectors in the first pic.

I think the forum explains how to remove the diversity chip since further down the thread there is a similar pic with the diversity chip removed

Re: Nstreme2 can be 100% FDD?

Posted: Fri Mar 12, 2010 10:09 am
by asterisco
don't know if it would help, but you could use tx-a/rx-b to get around legal issues. You would still be running in TDD mode and tx and rx will be in the same frequency (since you will be using 1 card), but you can use a bigger antenna on the rx side since that antenna (should) never transmit.
Hi,

thanks for the response. The question is to confirm the "should" never transmit. If it really never transmits I can put a 50ohm load in the tx-a connector.

Regards
Antonio

Re: Nstreme2 can be 100% FDD?

Posted: Fri Mar 12, 2010 11:46 am
by andreacoppini
don't know if it would help, but you could use tx-a/rx-b to get around legal issues. You would still be running in TDD mode and tx and rx will be in the same frequency (since you will be using 1 card), but you can use a bigger antenna on the rx side since that antenna (should) never transmit.
Hi,

thanks for the response. The question is to confirm the "should" never transmit. If it really never transmits I can put a 50ohm load in the tx-a connector.

Regards
Antonio
I meant using tx-a/rx-b on a single card, in other words, NOT using Nstreme2.

Re: Nstreme2 can be 100% FDD?

Posted: Sat Mar 13, 2010 9:42 pm
by Mplsguy
each channel is used exclusively in one direction. I understand that with Nstreme protocol we can disable CSMA and specially the ACK that sends the receiver to the transmitter. Is this true?. If the receiver ACK can't be disabled, from a legal point of view, the channel is being used as TDD (time division duplex).
For nstreme-dual (the one that uses 2 wireless cards - one for tx and one for rx) you can be sure that receiving interface is not transmitting, all feedback is sent over transmit interface. ACKs, as in regular 802.11 are not used and therefore are not getting sent.

Re: Nstreme2 can be 100% FDD?

Posted: Sat Mar 13, 2010 9:49 pm
by andreacoppini
Interesting. This should be in the official documentation, as there's no definitive answer in the docs.

Re: Nstreme2 can be 100% FDD?

Posted: Sun Mar 14, 2010 11:59 am
by asterisco
For nstreme-dual (the one that uses 2 wireless cards - one for tx and one for rx) you can be sure that receiving interface is not transmitting, all feedback is sent over transmit interface. ACKs, as in regular 802.11 are not used and therefore are not getting sent.
[/quote]

Ok. Thank you. This was exactly I need!!

Regards
Antonio