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Beginner

Some newbie Aironet Q's

Hi there,

I've been trying to fix some problems with a stadium aironet setup and was hoping someone could help me with some Q's.

1. Is there a way of setting the access points so they are optimised for signal strength rather than distance - these only need to work in the immediate vicinity of the gates. Is this what the "power" setting is for?

2. Is the "clean air" setting likely to be of any help to me?

Thanks for any help with this.

-H

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Accepted Solutions
Cisco Employee

Re: Some newbie Aironet Q's

Here is how the count works.

You have 3 2.4 Ghz antennas and 3 5ghz antennas.

You see 5 check boxes but you are in the menu "802.11b/g". You will see 5 other checkboxes for the same AP on the 802.11a menu (or vice versa).

The AP can simultaneously receive through the 3 antennas but only transmit through 2 (out of 3). So you can select which antennas are receiving for 2.4 ghz (3 checkboxes) and which ones are receiving (only 2 checkboxes, that makes 5 for 2.4Ghz). Same for 5ghz.

Nicolas

9 REPLIES 9
Hall of Fame Community Legend

Re: Some newbie Aironet Q's

2. Is the "clean air" setting likely to be of any help to me?

CleanAir WON'T help because the 1250 doesn't support this technonogy.  Only the 3500 series support CleanAir.

3. Why do the aironets have 2.4GHz and 5Ghz antenna?

Simple question but very difficult to understand your intention.  Are you asking WHY an AP has both 2.4 Ghz and 5.0 Ghz antenna or radio modules?

Re: Some newbie Aironet Q's

Hi ,

1)Yes increasing power is defiently an option for increase of signal strenght and coverage area

Please take a look at the lnk,it explains manually assignment of power and Channel

http://www.cisco.com/en/US/docs/wireless/controller/7.0/configuration/guide/c70rrm.html#wp1099018

I would suggest use RRM instead which should take of problems like 'Coverage hole ' and 'signal strenght ' issue's.

http://www.cisco.com/en/US/docs/wireless/controller/7.0/configuration/guide/c70rrm.html#wp1097550

2)Yes 1250 series donot support clean air

4)If using non-802.11n rates then one antenna on port "A". If using 802.11n rates then at least two antennas on ports "A" and "B".  as per this link

http://www.cisco.com/en/US/docs/wireless/access_point/1250/installation/guide/125h_c1.html#wp1055162

Let me know if you need more detailed information

Regards,

Sharath K.P.

Please dont forget to rate the posts which answered your question and mark it as answered or was helpfull

Beginner

Re: Some newbie Aironet Q's

Thanks for the info - really helpful.

I have set the neighboring AP to be on different channels. RRM is also setup.

I'm still not clear about the antenna. At the moment the access points have just 2 antenna on the left hand side ports.(i.e. 1x 2.4Ghz & 1x 5Ghz). The other 4 antenna ports do not have an antenna connected.

The handsets use 802.11g - am I therefore right in assuming we are only using 1 of the 2 connected antennas - the 2.4 GHz antenna. Should I therefore disable the antenna ports that do not have antenna connected?

Will there be any improvement if I buy additional 2.4 GHz antennas?

Thanks again - I hope this makes sense!

Cheers,

H

Cisco Employee

Re: Some newbie Aironet Q's

Currently your access points is sending signal out of all 2.4Ghz and receiving through all those ports as well, but there is only one antenna connected. This can lead to severe issue. So I'd advise that you either put the remaining 2 antennas on the 2.4 ghz ports or you disable these 2 ports from the WLC (Go to "wireless", 802.11/bg radios list, configure the one of the ap, you should have checkboxes to enable disable antennas.

Nicolas

Beginner

Re: Some newbie Aironet Q's

Thanks Nicolas. I really appreciate the help.

I am a little confused as there are 6 antenna points but only 5 checkboxes - I have attached a screenshot to show you what I mean.

Should I only enable the "A" antenna points?

And just to confirm if the handsets are using 802.11g there is no point buying additional 5Ghz antenna?

-Huw

Enthusiast

Re: Some newbie Aironet Q's

Huw -

The reason for only 5 check boxes has to do with the way .11n works.  One way for increasing throughput is to make use of reflected signals.  When a radio puts out a signal, the waves bounce off of hard objects and generally end up creating another copy of its signal.  This copy is out of phase, travels a different path to the receiver, and is out of time synchronization.  For a non-802.11n client or AP, this copy shows up as noise or a reduced signal depending on what phase it is in.  Therefore, with two Tx antennas and three Rx antennas, the AP can now make use of this characteristic of radio physics by using one of the two Tx antennas to intentionally generate another copy of the signal and send it out milliseconds behind the original.  However, it can use this second signal to encode DIFFERENT data.  Using complex hardware and software, the AP can put this signal back together properly and decode the data.  The three Rx antennas help more than just two because the AP is stationary, and it's not known from which direction and at what angle the copy of the signal will come in at.  Although there's a total of six antennas (three for 2.4 GHz and three for 5 GHz), as the controller GUI indicates only 2 are used for Tx and three for Rx at any one time.

To comment on your signal strength vs. coverage question, I'm not sure what antennas you're using, but if they are omni directional, you might benefit from some directional antennas.  They have a smaller footprint, but are often higher gain.  If the area of use is a rather sectional area, this might work out for you.

As for the mobile computers being only 802.11g, then you would not benefit from adding any 5 GHz antennas.  You might want to consider turning the 5 GHz radios off, unless you plan to offer some kind of connectivity to clients that are 5 GHz capable.  Furthermore, with only one radio active, the 1250 AP can then be powered by 48v PoE (15.4 W) as opposed to the 56v PoE (30+ W) supplied by the special power injector for 1250s.

Regards,
Scott

Beginner

Re: Some newbie Aironet Q's

Thanks Scott. I have ordered extra 2.4 Ghz antennas.

I'm still curious as how you disable individual antennas - i.e. there are 5 check boxes but 6 antenna. Or am I looking in the wrong place?

-H

Cisco Employee

Re: Some newbie Aironet Q's

Here is how the count works.

You have 3 2.4 Ghz antennas and 3 5ghz antennas.

You see 5 check boxes but you are in the menu "802.11b/g". You will see 5 other checkboxes for the same AP on the 802.11a menu (or vice versa).

The AP can simultaneously receive through the 3 antennas but only transmit through 2 (out of 3). So you can select which antennas are receiving for 2.4 ghz (3 checkboxes) and which ones are receiving (only 2 checkboxes, that makes 5 for 2.4Ghz). Same for 5ghz.

Nicolas

Beginner

Re: Some newbie Aironet Q's

Now I understand. Cheers.

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