CCI and SNR on Wireless Network

Lately, I´ve been looking for putting some light over some obscure subject in my head about CCI and SNR. We are planing to deploy a very large Wireless Network and consequently, we need to be prepared for very crowded spaces.
  It turns out that CCI , the short for Co-Channel Interference, is a natural consequence when it comes to deploy many Access Points in a relatively small area. There´s a equation related to crowded space that is not easy to solve. If you have a space in which you´ll have too much people on it, you consequently will need too many Access Points in order for accommodate all those peoples. This is known as "Coverage for performance".Once you try to accommodate too many Access Point together, you´ll have problem with CCI in the 2.4 frequency band or even 5.0 Gigahertz.
  The other factor is SNR. Well, SNR is the short for Signal to Noise Ratio and, as its name states, Ratio means a comparative value between to things. This things is Noise floor and Power.
  The fact is , when we are planing  wireless network, we have to have some north in order to ensure that the network will offer a good users experience . Once Wifi KPIs is not well defined as it is in mobile, SNR is considered to be a very good parameter when it comes to have a reliable network.
 When we go through papers, we often see value like -67 dBm RSSI ate the edge of the Cell and 35 dB SNR. An environment with such KPIs, is considered to be good for any kind of transmission over Wireless network.(Video, voice and data).
  Therefore, this is not the only one important  thing to consider. Actually, it is really easy to achieve a good SNR if you have the desired resource available. I mean, if you can spread out as many Access Point as necessary.

 You probably will get astonished if I said that one and only one Access Point installed at the right place and height can provide at least -90 dBm RSSI for a whole stadium. For sure this is just a curiosity, but you wont to be wrong in your design if you followed  the figure above. This is in fact, the correct deployment for a really good Wireless environment. As we can see, we have Cells with RSSI equal to -67 dBm at the edge and consequently, 35 dB SNR. We also have the necessary distance between cells accounting for 20 dBm in Signal Strength between two cell. This is necessary because, if an Access Point hears another Access Point with a signal strength greater than 19 dBm , this means both Access Point can transmit without to provoke CCI.
  The problem is that this cells will repeat over and over around an area and, most important, Access Point cells is not round like that. Considering the obstacle and others factors, at the end of the store, it is really complicate deploy 2.4 band and keep the network healthy.
 Back to CCI and SNR, the conclusion is that, we need to have a good SNR in the environment but this is not enough. A good SNR with a poor frequency reuse allowing for CCI, will result in users with five bars wireless client and poor wireless connection.
  I will explain CCI in another opportunity. By now, that´s all. Keep in mind that bad SNR will make you fail at all but, good SNR does not guarantee success.