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why do we need 20% overlap for voice deployment and how to verify the overlap percentage in heat map

vinodjad1234
Explorer
Explorer

Hi Experts, 

As per cisco recommendation for voice deployment, we need to have 20% cell overlap. I was going site survey documents however I was not able to get the answer for below questions : 

1) Why cell overlap should be 20% in voice deployment , why not 30% or 10% ?  

2) Once we get site survey report with heat map , how to verify the cell overlap percentage ? 

It would be really great if someone could share details about this.

2 Replies 2

ali aqrabawi
Participant
Participant

i'm not site survey expert but i will share my thoughts :

1) Why cell overlap should be 20% in voice deployment , why not 30% or 10% ?  

30% could be considered very high which may resulting in interference with adjacent neighbor  channels ,,   

2) Once we get site survey report with heat map , how to verify the cell overlap percentage ? 

this is smth i would like to know , but i would say that if i get -67 at the AP edge cells and farther the client will find an AP with RSSI > -67 , then i would say this is a 20% channel overlapping or so .

mohanak
Cisco Employee
Cisco Employee

The recommended AP cell overlap for VoWLAN deployments at 2.4GHz, is 20 percent. The purpose of the 20 percent overlap is to ensure that a VoWLAN handset can detect and connect to alternative APs, when it is close to the cell boundary. This should allow a VoWLAN client to change AP associations with a minimum of interruption to a call, by minimizing the amount of data rate shifting and retransmission at a cell boundary for a given VoWLAN client.

Refer link : https://learningnetwork.cisco.com/thread/77284

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