7925 Cell Overlap Thresholds (Maximums)

[n.lavender]

Hi Chaps,

Although the 7925 deployment guide recommends an overlap of 15-20% for adjacent cells, is there a min/maximum % figure that will still allow the phones to work. This is really to cover off previous data deployments where overlap is greater or less than these figures, and to remedy would involve a moderate amount of moves/changes.

Thanks,

Nick

[Scott Fella]

The overlap helps ensure the -65dbi coverage in a way. So really it depends on your existing data survey and deployment. If your existing survey and deployment was for -75 or -72 at the edges of each cell, you will have to look at the rssi and SNR in those overlap areas. Can it be an issue... Yes and no. It will depend on your rssi and SNR the phone has during a call and during a roam. I see install where a data grade survey was done and a couple years down the road they implemented voice. So work fine and some don't. So it's really hard to say. If you had a post survey done, they can show you where the coverage might be lacking and these would be the area of concern.

Thanks,

Scott Fella

Sent from my iPhone

[n.lavender]

Thanks for the reply.

I'm more concerned about the possibility of too much overlap. For instance if you have a low spot of coverage and require an additional AP... This could then push overlap at -67dbm to say 30-50% in some circumstances.

I've seen some installations that have the 7925 with a high density of APs with no issue although others do.

It's definetly an interesting one as theres no real requirements stated other than the 15-20% overlap & -67dbm.

Thanks,

Nick

[migilles]

It all depends on how many SSIDs you have enabled / amount of traffic generated on that channel.

Just beacon traffic can reduce channel capacity and increase collisions which can lead to retries for data frames, etc.

The 15-20% is the bare minimum to allow for seamless roaming; enough time to discover the neighbors, etc.

In critical environments, that # will be increased as it is suggested to have dual APs at -67 dBm with the 25 dB SNR available.

[n.lavender]

OK, It would seem the best  route is to  define a minimum 15-20% overlap as appose to any maximum. They are using a few ssids on b/g serving phones/barcode scanners so co-channel will need to be taken into consideration.

Cheers Guys.