Active Roaming?

vining

This new set up feature under the TPs wireless settings:
From MVP8400i manual

Active Roaming on
Channels 1,6,11
When enabled, the device is actively roaming on the channels 1, 6, and 11.
Of all the frequency channels that are assigned for wireless, only three are
nonoverlapping frequencies that do not interfere with each other.
Nonoverlapping channels to avoids the interferences that affect the signal.

I going to assume that this feature was put in to allow the wireless connection to dis associate w/ one WAP and re-associate w/ a stronger WAP which has been a problem with some of the older panels. I know AMX is hell bent on channels 1,6 & 11 but the rest of the world isn't. I generally use 1,4,8 & 11 on large projects and place the WAPS where close channel numbers are at greater distances from each other so that when I start repeating my channels I worry about close channels number but offset that fact based on the distance between them. This works better on large jobs w/ 6 or more WAPS than using 1,6 & 11. Now with this in mind I can't take advantage of the roaming feature. Also in large projects w/ ajoining overlapping wireless networks from neighboring offices or residences you cant change the channels and use say just two waps 3 & 9 because the neighbors are using 1,6 or 11. Again screwed.

Active roaming should be active roaming and cover the entire range. This may already be the case but the above except from the manual would lead one to believe otherwise.

maxifox

Vining,

Would you please shed some light on why do you prefer this set of channels - {1, 4, 8, 11} to {1, 6, 11}? Is that because it is giving more flexibility in proper frequency distribution for large projects or something else? Thank you.

vining

My thinking is that if the APs are side by side the 22mhz speration would be required to avoid stepping on each other but when they are spread apart as in a normal installation the roll off would decrease the amount of frequency seperation required and allow the 1, 4, 8, 11 spacing. Obviously at the same time you put adjacent channels at the furthest distances from each other to maximize the roll off. This will allow the addiotnal channel.

If you set up you wi-fi netwrok on the same SSID and on different channels and use the the primary channels 1, 6 & 11 you'll have to repeat these channels in a large house so you try to keep repeat channels as far as part as possible to minimize interference but often you can't get them far enough where a, they don't affect each other or b, your TP is the middle where it can see both on the same channel clearly. Not sure if locking on to one MAC address will really help when it's receiving same channel RF from two APs at the same time. I can't see the tranceiver being able to differentiate between the two.

On a large house I also try to avoid repeating channels and if I use channel 1 on the far end of the house I'd like to use channel 2 on the other end when repeating just so there is some seperation since you can never really be assured that from the point you connecting from you won't be able to see both channels if they are indeed the same. Maybe doors that werre closed while testing are now open and the RF is propagating down the hallway better, or something? RF acts different on a daily basis.

Another reason I don't like being locked into 1, 6 & 11 for roaming (not that it works great anyway) is that if you're in an office environment, condos or beach front community where different folks are clustered together in a close proximity to each you often need to adjust your channels to avoid being on the same channel as your neighbors. So if I have neighbors using 1 & 6 I might want to use 4 & 10 but now I can't roam.

If your in the classroom and they tell you to use 1, 6 & 11 that's fine but when you get to the real world you find that the classroom teachings don't always make sense.

ericmedley

I've found the roaming to be more trouble than it's worth. It roams when it is not needed. Just because the currently associated WAP might have fallen to 'good' and one far away is 'very good' doesn't mean it should reassociate.

my 2 cents.

DHawthorne

WAP's use a spread spectrum technology. The stated frequency for a channel is only the center point; it actually covers a fair range on either side of that frequency. 1, 6 and 11 are the only non-overlapping channels in the USA-designated range. If you have neighbors using 1 and 6, and you are using 4 and 10, then your channel 4 is stepping on the channel 1 and your channel 10 is stepping on the 6.

It's not that AMX is insisting on those channels, its the manufacturers themselves: http://documentation.netgear.com/reference/fra/wireless/WirelessNetworkingBasics-3-05.html .

ericmedley

DHawthorne wrote: »

WAP's use a spread spectrum technology. The stated frequency for a channel is only the center point; it actually covers a fair range on either side of that frequency. 1, 6 and 11 are the only non-overlapping channels in the USA-designated range. If you have neighbors using 1 and 6, and you are using 4 and 10, then your channel 4 is stepping on the channel 1 and your channel 10 is stepping on the 6.

It's not that AMX is insisting on those channels, its the manufacturers themselves: http://documentation.netgear.com/reference/fra/wireless/WirelessNetworkingBasics-3-05.html .

To further illustrate Dave's point, I thought I'd throw up a spectrum plot that illustrates just how wide each channel is. You'll see that each channel spreads out well into it's neighboring channles at almost the same db gain.

vining

ericmedley wrote:

You'll see that each channel spreads out well into it's neighboring channles at almost the same db gain.

Yes, the center frequency of each channel is seperated by 5Mhz but the bandwidth of each channel is 22Mhz so they actually overlap the 2 channels left & right of the center frequency at almost full power.

If you use the 1, 6 & 11 channels then the center frequencies are 25Mhz apart and you get 3Mhz of dead space in between.

You weren't supposed to notice that the roll off is not as pronouced as my thinking would prefer and I should have mentioned that as well but it should still be enough to squeeze in another channel if the WAP spacings are far enough apart.

DHawthorne wrote:

1, 6 and 11 are the only non-overlapping channels in the USA-designated range.

True but that's only a fair statement when measuring side by side with all WAPs at their peak db levels. When your WAPs are spread apart and the db level drops off to 1/2 power (3db) or less your frequency seperation increases.

DHawthorne wrote:

If you have neighbors using 1 and 6, and you are using 4 and 10, then your channel 4 is stepping on the channel 1 and your channel 10 is stepping on the 6.

Yes, you will still be stepping on your neighbors and they on you but it will be much better to be on 4 & 10 then on 1 & 6 or 6 & 11. If you're dead on the same frequencies your deifinitely going to be dropping the majority of your packets and hanging up your TP.

DHawthorne wrote:

It's not that AMX is insisting on those channels, its the manufacturers themselves

Agreed but AMX is the one that won't support roaming on channels other than 1, 6 & 11.