WifiNigel

[Note: The information in this white paper has been superseded. Check out my updated white paper:  http://wifinigel.blogspot.co.uk/2018/05/updated-white-paper-on-license-exempt.html ] I decided it was time to update my white paper detailing the use of the 5GHz band here in the UK for wireless LANs. I've tidied a few things up and added some information around 802.11ac channel planning within the constraints of UK 5GHz spectrum. You can download the whitepaper from here: PDF download Google docs Scribd

One thing that keeps me awake at night is the whole concept of Co-channel interference in WiFi networks (well, that and acid reflux) . I'm always concerned by it's presence in a Wireless LAN, how to detect it, how to avoid it and how to measure its effect. In this article I share a tip I picked up from a recent Cisco webinar to determine the general level of utilization of an AP's channel. I also look at how this may give us a clue about the level of CCI in a Cisco wireless network. Background Co-channel interference (CCI), co-channel contention (CCC)...whatever you want to call it (I'm growing quite fond of the term "Co-channel Chatter"), is a blight in many WiFi networks. In all but the most isolated and carefully designed of wireless LANs, it lurks, waiting to disrupt the efficient operation of our WiFi network. As the number of WiFi networks rises, AP channel-widths increase (with newer WiFi standards) and the population of WiFi devices explodes,...

There's a well known rule of thumb when planning wireless LAN networks which states that for every 6dB increase in AP transmit power, the coverage distance of the AP doubles, This is obviously assuming there are no obstacles to limit or reduce coverage - it assumes a clear path and considers the effect of Free Space Path Loss (FSPL). Nonetheless, it is a useful rule of thumb for planning. Although doubling coverage with 6dB is useful, I thought it might be interesting to look at the effect of increasing power by other increments too, to see the (theoretical) effect on coverage. Background Quite a few articles, web pages and wireless LAN text books quote the following rule of thumb when considering the effect of increasing the transmit power of an access point. For every increase of 6 dB, the coverage distance doubles. For every decrease of 6 dB, the coverage distance is cut in half. Here is an example of such an article: http://www.cisco.com/c/en/us/support/docs/wir...