WifiNigel

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

When designing WiFi networks, a crucial part of the design process is the wireless survey. This may be a traditional ‘AP on a stick’ survey or may be an off-site, ‘desktop’, predictive survey. In amongst the variety of variables that need to be considered, including coverage and capacity, there is one crucial item that is easy to forget: how does the designed wireless network look from the point of view WiFi clients that will actually use the network? Background Best practice for wireless surveying usually dictates that prior to completing a survey for a new WiFi deployment design, a pre-survey questionnaire will be supplied to your customer. This document will ask about the environment that the network is to be deployed into. It will include information such as physical building characteristics, cabling and switch infrastructure, health and safety considerations, access arrangements etc.   In addition, the pre-survey questionnaire will also request information from the custo

Whilst working with Cisco ISE recently, I became aware of a setting within the product that could be a major ‘gotcha’ if you aren’t aware of it. We’ll take a very quick look at it in this article. Background Tucked away in the depths of the Cisco ISE menu structure is a rather innocent-looking configuration setting under the ‘Anomalous Client Detection’ section of the System Settings. The option I’m referring to can be found in the following location in ISE 1.2: Administration > System> Settings > Protocols > RADIUS The screenshot below shows the settings page I am discussing: The settings on this page have been provided to protect ISE in the face of an onslaught of misbehaving or mis-configured clients that may flood it with authentication traffic (and hence RADIUS traffic). In larger environments, this could become an issue and affect ISE’s performance. Suppress Anomalous Clients The tick-box ‘Suppress Anomalous Clients’ provides a very