Showing posts from 2015

Measuring Obstruction Losses For WLAN Predictive Modelling

I recently attended the Ekahau Certified Survey Engineer (ECSE) training course, presented by Keith Parsons. In addition to learning about using Ekahau Site Survey  (ESS), Keith also shared some valuable insights in to best practice wireless LAN design and surveying techniques. One of these insights was a best practice approach to measuring loss through obstructions and attenuation areas, such as doors, walls and warehouse racking, when gathering data for a WLAN predictive model.  In this article, I’ll share the details of that approach and some mistakes you might be making in your own measuring approach. Please visit the Ekahau blog site to see my guest posting for the full details on this topic.

Do Cisco AP LEDs Ever Flash Once Disabled?

A quick post about an interesting question on Twitter about disabling indicator LEDs on Cisco APs: There are often times when a customer would like the LEDs disabled on Cisco APs. Examples include education and healthcare environments when the LEDs may be perceived as being annoying or distracting if left illuminated. The LED may be disabled by two methods: CLI :  config ap led-state disable <ap name> WLC GUI (AireOs): Wireless > All APs > [Select AP] > Advanced > Led State (see screen-shot below) Fig. Disable AP LED from WLC GUI However, once the AP indicator LED has been disabled, does it remain disabled at all times? I setup this up in my lab and did a quick test with an AP3600 running code on the WLC. I tested 4 scenarios to see if the AP lamps remains extinguished, or would become illuminated. Here are the results: Normal operation: LED off AP lost contact with the WLC: LED off AP power cycled: Flashing LED during boot seq

Wi-Fi EIRP Calculator

As a Wi-Fi engineer, there are a number of occasions when it is useful to understand the EIRP ("Effective Isotropically Radiated Power) of a system. (I'll leave to you to read this Wikipedia link for an EIRP explanation). This is often a requirement when using external antennas on an access point or perhaps using tools (e.g. survey software) which require you to account for the various gains and losses in a system. Calculating EIRP is crucial to understand the power level that will actually end up radiating out of your antenna. This is often for reasons of regulatory compliance, coverage considerations or perhaps matching the power of client devices. As this is something I seem to have to do on a fairly regular basis, I thought I'd knock up an EIRP calculator to add to my website . To calculate the EIRP of a system, enter the AP transmit power, the loss of any cable and connectors  and the gain of the antenna. Note that if you are using an AP with an internal anten

Wi-Fi Power Level Convertors and Lookup Tables

I put this page together so that I have one place to come to for my Wi-Fi power conversion utilities and lookup tables. Hope you find it useful.( Note : you will need Javascript enabled to use these calculators) Check out my other Wi-Fi RF calculators: link Milliwatt to dBm Convertor Enter a value in milliwatts and hit the 'Convert' button to see the dBm conversion: Enter milliwatt value: (mW) dBm Conversion: ---- (dBm) dBm to Milliwatt Convertor Enter a value in dBm and hit the 'Convert' button to see the milliwatt conversion: Enter dBm value:  (dBm) mW Conversion  : ---- (mW)   dBm & Milliwatt Lookup Tables mW to dBm Lookup Table dBm to mW Lookup Table mW dBm dbm mW 1 0 0 1 2 3 1 1.3 3 4.8 2 1.6 4 6 3 2 5 7 4 2.5 10 10 5 3.2 15 11.8 6 4 20 13 7 5 25 14 8 6.3 30 14.8 9 7.9 35 15.4 10 10 40 16 11 12.6 45 16.5 12 15.8 50 17 13 20 55 17.4 14 25.1 60 17.8 15 31.6 65 18.1 16 39.8 70 18.5 17 50.1 75

What Are Sticky Clients?

One term you'll often hear banded about when talking with Wi-Fi professionals is "sticky clients". I thought it might be worth spending a few moments exploring what is meant by "sticky clients", why they are generally considered to be a bad thing in Wi-Fi networks and some approaches to mitigate them. Background Many folks dealing with Wi-Fi networks often talk about the "sticky" characteristics of wireless clients when discussing client roaming within a W-iFi network. In an ideal world, we'd like to have access points providing ubiquitous coverage across our desired area providing high-quality, consistent client coverage where-ever we go. In this wonderful land of rainbows and unicorns, our clients would gracefully roam from AP to AP, detecting and associating with their closest AP throughout the coverage area to ensure their best connection speed at all times. Unfortunately, the real world doesn’t quite reflect this roaming-client