Been working with a very unique environment for the past year where the implemented WLAN CCI is so high without any clients it had to have a re-design. (actually fork lift out…that is a whole other story). From a WLAN implementation perspective it not just about signal strength as some think.
For instance the low cost of 802.11 access points makes it tempting to deploy them with very high density. An example, some WLAN networks are being deployed with an access point in every room. This type of deployment has the benefit of increasing the capacity of the network by allowing “spatial reuse” of the spectrum. It somewhat makes sense that by having more APs in the area of deployment, it’s more likely that a client will be able to operate successfully even when interference is present.
However, when you deploy a dense network of access points, it’s necessary to reduce the transmit signal power of each of the access points. If you don’t reduce the power, the access points generate interference to each other, a phenomenon known as co-channel interference. While a wireless voice over IP network might have sufficient signal strength, having a high CCI will drastically degrade the quality of the user experience as the WLAN network is loaded. It is the same as trying to have a quiet conversation with someone next to you at a rock concert. See below basic requirements for wireless voice over IP.
A typical WLAN design for voice over IP must ensure a minimum of -67dBm signal strength on the edge of coverage cell with a SNR of +25dB in all areas where a wireless voice over IP phone is used. There should be -19dBm separation between similar non-overlapping channels. (Example: a client on channel 2 at -67dBm or better should not hear another channel 1 with a reading of -84dBm.) Idle channel utilization must below 10% and % metrics should be defined for loading. The packet error rate (PER) should be no higher than 1% (or a success rate of 99%).
