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7921 switching from 802.11g to 802.11a and vice versa

Unanswered Question
Jul 26th, 2007
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Does anyone know if a 7921 Cisco WiPhone can automatically switch from a 802.11g connection to an 802.11a connection moving from a g coverage area (2,4 GHz) to an a coverage area (5,0 GHz)?

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Overall Rating: 5 (1 ratings)
migilles Thu, 07/26/2007 - 12:19
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Yes if the phone is in one of the Auto modes, either Auto-RSSI, Auto-a, or Auto-b/g, then the phone can potentially roam to a different band. The roam will not be seamless as it will have to discover the channels in the new band. Also DFS channels on 5 GHz will need to be passively scanned.

So should expect a short outage when moving to a new band and on call. The call will be retained after moving to the new band.

f-genovese Fri, 07/27/2007 - 00:43
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Yes, I think the WiPhone works or in 802.11b/g or in 802.11a but not both at the same time (one active and the other in standby/scanning). So, the switching process from 802.11b/g to 802.11a causes an outage. I'd like to know if someone has tested if this possible roaming-outage is perceptible in a roaming inter-cell from 802.11a to 802..1b/g and viceversa, during a call.

migilles Fri, 07/27/2007 - 14:57
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So only 1 band is scanned during association period. If connected to 802.11a w/ Auto-A configured, then will not scan B/G until signal for 5 GHz for configured network is lost. So yes it will be noticeable, which is why I stated this type of roam is not seamless. Please set expectations correctly.

f-genovese Sat, 07/28/2007 - 01:58
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I was interested in roaming between b/g cells and a cells, 'cause I have to project an outdoor coverage for a campus. The indoor coverage is already present: there are more than 100 APs distributed over 3 buildings, using the 3 non-overlapping channel (ch 1, 6, 11 managed by 3 WLC4402-50-K9).

My goal was to use the 802.11a for the outdoor coverage to avoid the channels interference with the indoor signals. Moreover in 802.11a I could use 19 channels against only 3 non-overlapping channels of 802.11b/g.

The outdoor coverage in this campus was thought above all for WiPhones connectivity, so I think I can't use the solution I mentioned before, for the roaming trouble.

Thank you for your support,



Rob Huffman Sat, 07/28/2007 - 07:33
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Hi Michael,

Very good description of this functionality! 5 points for your great work :)

Take care,



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