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WirelessRudy
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802.11n 5Ghz-Only-N versus 5Ghz a/n

Tue Mar 23, 2010 10:24 pm

Can anyone tell me if these two option are any different in MT?

Even if both ends of 'n' link radio have 5Ghz-Only-N mode in the wireless status both still shows "5Ghz a/n"


Does this mean "Greenfield" mode is not an option in MT?
Is MT "5Ghz-Only-N" mode actually same as "Greenfield" mode?

Asked this question in main 802.11n topic before but nobody seems to be able to answer this.
 
angboontiong
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Re: 802.11n 5Ghz-Only-N versus 5Ghz a/n

Tue Mar 30, 2010 6:23 pm

Mikrotik expert can say something here 8) ?
 
WirelessRudy
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Re: 802.11n 5Ghz-Only-N versus 5Ghz a/n

Tue Mar 30, 2010 7:39 pm

Following from support upon my questions:

Q; By switching to Only-N mode in MT-ROS, do we just tell the AP/station not to associate with legacy radio?
A; "onlyn mode means that AP requires connecting customers to support basic 11n MCS. This requirement can not be fulfilled by "legacy" radios therefore they will not be accepted."

Conclusion: "legacy" radio's are not allowed to associate with "Only-N" running AP. Nothing more, nothing less...

Q; What is the difference then between Only-N and a/n?
A; a/n does not require connecting device to support 11n MCS. onlyn does.

Why status in peer still shows "a/n" while radio is in "Only-N" mode was also my question but is not cleared in this. A software bug?

Q; I understood from your answer that MT-ROS and/or MT radio are not supporting HT or Greenfield mode?
A; There is no such "HT mode" in 802.11n terminology (mixing "HT" with "Greenfield" is obvious misinterpretation or misunderstanding). You should refer to 802.11n for thorough description of what is understood with term HT device. As stated above devices under RouterOS do not use greenfield preamble.

Hmm, I have been reading several articles (white papers) from within the industry (including the "802.11n-primer" presented at MUM in Poland) and they all consider "HT" the same as "Greenfield" mode.

My last remark in email with support was:
"The bottom line is that the promoted 300Mb throughput for the 802.11n protocol is a very theoretical one, not only for MT but all vendors, unless clear radio spectrum is possible and radio uses Greenfield."

Reply of support on this statement was:
"As is 54Mbps for "legacy" devices. It only refers to max rate at which transmission is encoded. And therefore it should not be mixed with "throughput". Throughput is a function of transmission rate and all overheads

(preables, interfame spaces, retransmissions, etc)."

Signed by Uldis.
+++++

Although some minor issues are cleared still a lot to be learned, both for me as for MT it looks to me!
 
Mplsguy
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Re: 802.11n 5Ghz-Only-N versus 5Ghz a/n

Tue Mar 30, 2010 8:58 pm

Why status in peer still shows "a/n" while radio is in "Only-N" mode was also my question but is not cleared in this. A software bug?
only-n is not really a special hardware mode. It is the same as a/n, except it does not accept legacy clients. When station connects to AP it is not distinguishing between those two modes, therefore displays "a/n". This approach is the same as "only-g" mode (it is also never seen in registration table), that has been there pretty long and it seems is not causing any confusion.
Hmm, I have been reading several articles (white papers) from within the industry (including the "802.11n-primer" presented at MUM in Poland) and they all consider "HT" the same as "Greenfield" mode.
802.11n has whole paragraph describing what is "HT device" and ability to support greenfield preamble is just one (by the way optional) feature.
 
WirelessRudy
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Re: 802.11n 5Ghz-Only-N versus 5Ghz a/n

Tue Mar 30, 2010 11:55 pm

Why status in peer still shows "a/n" while radio is in "Only-N" mode was also my question but is not cleared in this. A software bug?
only-n is not really a special hardware mode. It is the same as a/n, except it does not accept legacy clients. When station connects to AP it is not distinguishing between those two modes, therefore displays "a/n". This approach is the same as "only-g" mode (it is also never seen in registration table), that has been there pretty long and it seems is not causing any confusion.
Well, it confused me when coming to understand the full working ´n´. Probably the b/g mode works so much more smooth and without problems I never looked into any discrepancies in these. By raising this discussion I finally have cleared the confusion at my end. :D Isn't that what this forum or the help desk is all about?
Hmm, I have been reading several articles (white papers) from within the industry (including the "802.11n-primer" presented at MUM in Poland) and they all consider "HT" the same as "Greenfield" mode.
802.11n has whole paragraph describing what is "HT device" and ability to support greenfield preamble is just one (by the way optional) feature.
OK, that can well be true. But in seeking more info and explanation we all tend to read white papers and visit MUM's to see how the guru's think it works. If they talk (and this is written down) that both are the same who am I to question? If I can't take info given in whitepapers or MT presentations any more where does that leave us?
 
Mplsguy
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Re: 802.11n 5Ghz-Only-N versus 5Ghz a/n

Wed Mar 31, 2010 8:39 am

OK, that can well be true. But in seeking more info and explanation we all tend to read white papers and visit MUM's to see how the guru's think it works. If they talk (and this is written down) that both are the same who am I to question? If I can't take info given in whitepapers or MT presentations any more where does that leave us?
I guess you always have to take it with a grain of salt. And turn to standard whenever such an in depth knowledge is necessary.

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