When troubleshooting an 802.11 network it is not possible to predict how it will behave when you are armed solely with RF measurements. This is why we focus on performance metrics and IMMI technology -- because they more accurately predict how your wireless network will actually perform. Though RF spectrum analysis remains a popular tool for troubleshooting interference-related problems, IMMI technology holds greater promise since it excels at computing the best Wi-Fi channel -- that is, the channel with the greatest available bandwidth and least affected by RF interference from other wireless devices. IMMI technology employs 802.11 hardware and sees the RF environment through the same eyes as the wireless devices in your network. There is a new mantra brewing -- "Using the (802.11) infrastructure to troubleshoot the infrastructure..." People understand this to mean that when it comes to troubleshooting 802.11 networks, then 802.11 devices make better diagnostic tools than spectrum analyzers. And that’s because a spectrum analyzer knows nothing about the 802.11 standard, its internal protocols, or the methods it employs to mitigate interference from other wireless devices.
Our latest product WifiBuilder employs IMMI technology to quantify the available throughput performance of each channel. Not only does this allow you to determine the best channel, but also to predict (in a quantitative way) the increase or decrease you’d expect by reconfiguring an access point to use a different channel. IMMI relies on off-the-shelf 802.11 devices and the protocols inherent in the 802.11 standard. The software uses the 802.11 device to query each channel for its available bandwidth. That value is affected by RF interference from other devices in the neighborhood. So, on one hand, it is like a spectrum analyzer in that it measures RF interference. But, on the other, it differs in that the measurements are channel centric. The benefits of the channel-centric results are significant and can't be understated. It is no longer necessary to interpret RF measurements or deduce from a spectrum trace which channel will provide the best performance -- IMMI ranks the channels from best-to-worst based on their available bandwidth. In this way an access point can be reconfigured to always use the best channel.
If your goal is to hunt down interfering wireless devices, then an RF spectrum analyzer is still the tool of choice. But consider this -- it turns out in practice most Wi-Fi problems are solved by changing to a better channel. This is because: (a) the interfering device may belong to someone else and you have no control over it; (b) the interfering device may be perfectly legitimate in its own right (e.g. a wireless security system); (c) it is time-consuming and challenging to track down the source of interference -- RF waves bounce off of walls and objects, making it difficult to determine from which direction the source actually emanates. When your goal is reformed to one of simply determining the best Wi-Fi channel under the current conditions, then a tool that uses IMMI is a better choice.
White Paper: Wi-Fi Diagnostics and Optimizing Performance Through IMMI Technology
|Spectrogram chart from WifiEagle Channel Analyzer. The RF signal is generated by AirHORN.||Spectrum trace from AirSleuth 2.4 GHz RF spectrum analyzer. The RF signal is generated by AirHORN.|
The WifiBuilder hardware is a simultaneous, dual-band 802.11N wireless router manufactured by Linksys / Cisco. The original operating system has been replaced with an embedded, linux variant and 802.11 software stack licensed from Atheros, a leading developer of wireless networking systems and whose 802.11 chipsets dominate enterprise-level wireless routers. The operating system on the AP was further customized to include software that implements IMMI technology. Running this customized version of linux, the WifiBuilder AP supports diagnostic applications that are run from your Windows desktop or laptop machine. These diagnostic applications are used for installing, troubleshooting and monitoring 802.11 wireless networks. That is, in addition to being used as your normal AP for wireless network communication, WifiBuilder is designed to be used as a diagnostic tool -- performing data acquisition and communicating with a Windows application that analyzes the results and displays them using graphical charts. When the WifiBuilder AP is left in-place as your normal AP then its diagnostic capabilities are always available when the need arises. Alternatively, the WifiBuilder AP can also be used as a standalone diagnostic tool -- just connect it directly to your PC via ethernet cable.
Standalone Diagnostic Tool
A family of PC-based, diagnostic applications are being developed for the WifiBuilder AP. These applications run on Windows machines and are used to analyze and display real-time data as it is acquired from WifiBuilder. The first of these applications is Profiler24x Channel Analyzer -- additional applications will be available soon.
- Profiler24x Channel Analyzer
- Profiler5x Channel Analyzer (coming soon)
- ClientMonitor (coming soon)