Nous sommes désolé mais le présent article est seulement disponible en Anglais

First of all, I would like to explain why I am discouraging this initiative because it will result in a wireless network with a lot of contention providing poor performance.

  • The first argument against this approach is the fact that wireless networks such as 802.11 WiFi technology are basically share networks that share the medium in this case of wireless for communication. The challenge with such shared network is that only one wireless client at a time will communicate through the access point to other parts of the network. This means that other clients that want to communicate at the same time will have to wait until this particular client have finished before they can transmit. Further explanation on contention based wireless network can be review in the 802.11 arbitration white paper done by Marcus Burton CWNE#78 available at : http://www.cwnp.com/pdf/802.11_arbitration.pdf
  • The second argument against having two separate wireless networks come from the facts that if AP’s are operating on the same channel they will interfere against each other. In order to minimize interference same channel operation must be separated by at least 19 DBm of power.
  • Centrally coordinated wireless networks offer now better mitigation against interference with automated algorithm that will control channel frequency and power settings of all AP’s that have joined the controller. This technology and algorithm are improving but they are still not perfect in mitigating interference. The challenge is already present when having one wireless network that is designed for location, voice and data which involves a great quantity of access points operating at low power to mitigate interference. If we add a separate centrally coordinated wireless infrastructure that is not connected to the other controller they both will spend a lot of time changing frequency or reducing power in order to minimize interference. It will be even worse if the other network is not a centrally managed wireless network.
  • Another misconception of creating multiple SSID’s ( Service Set Identifier) or wireless network name is the fact that as mentioned earlier when operating in a particular frequency, multiple SSID’s will share the same bandwidth . Although it sounds that it is a different network, it actually create virtual networks on the same physical broadcast domain.
  • If the two wireless networks are close to each other and they operate in the 2,4GHz frequency, the challenge is even greater because only 3 channels are available without interference. The 5GHz would be a smarter choice but end users devices must be available in that particular band.
  • Also wireless channels do not provide infinite bandwidth and wifi devices share this bandwidth with other type of devices such as Bluetooth, wireless camera and microwave oven just to name a few in the 2,4 GHz band. Further details on WiFi interferences are available in the Cisco White Paper ( 20 myths of Wi-Fi interferences)
  • Another important aspect of wireless communication is the clients or wireless devices. The better they are (802.11n preferably), the better they will perform. MIMO technology and the wireless physical improvements of 802.11n standard provide a superior quality of communication and higher data rates.

Before deploying two separates wireless infrastructure in the same building, end user customers must align their wireless design as well as their deployment strategy. WiFi networks are license free and have a lot of advantages but they can be havoc if two entities decide to do their own networks in the same building sharing the same medium (i.e. wireless spectrum). FCC and Industry Canada will always recommend owner of license free wireless networks in the same vicinity to cooperate and align their strategy for their mutual benefits.