Overview :: Wi-Fi Diagnostic Tools

"Using the (802.11) infrastructure to troubleshoot the infrastructure..."

Wouldn't it be great if radio transmissions were free from interference from other devices operating in the same frequency range? However, the reality is that in the public ISM bands many wireless devices must coexist. The ISM bands represent portions of the frequency spectrum that have been set aside by the FCC for unlicensed, low-power, short-range operation. Examples of devices operating on ISM bands are cordless phones, wireless networks, Bluetooth devices, security cameras and systems, baby monitors, game controllers and cordless keyboards and mice for PCs -- in addition, microwave ovens and certain types of fusion lighting emit energy in the 2.4 GHz range. When installing or trouble-shooting a wireless network that must coexist with potential sources of interference, it is most useful to understand how these transmissions can affect wireless communication. And in order to gain that insight we need to use certain diagnostic tools.

With wireless systems it is very difficult to predict the propagation of radio waves and detect the presence of interfering signals without the use of test equipment. Radio waves don't travel the same distance in all directions -- instead walls, doors, elevator shafts, people, and other obstacles offer varying degrees of attenuation, which cause the Radio Frequency (RF) radiation pattern to be irregular and unpredictable. In order to achieve optimal reliability and throughput for your Wi-Fi ( 802.11) wireless network it is necessary to measure sources of interference that impact negatively on its performance.

Until recently there have been two primary techniques employed to troubleshoot wireless networks -- network discovery and RF spectrum analysis. Network discovery is also commonly referred to as network site survey and Wi-Fi scanning. In addition to supporting network discovery and RF spectrum analysis, we have introduced innovative tools that broaden the range of troubleshooting techniques currently available. We refer to these new strategies as 'Wi-Fi Channel Analysis' and 'Connection Performance Analysis'. In addition to briefly describing these strategies here, we will also touch upon two additional techniques -- RF signal generation and 802.11 packet injection. Though these latter two techniques are not directly related to detecting RF interference, in many cases they can be applied to help troubleshoot wireless networks.

When it comes to offering Wi-Fi diagnostic tools, Nuts About Nets is not alone in the marketplace. Where we distinguish ourselves is our emphasis on finding the best Wi-Fi channel that will provide optimal throughput performance -- using low-cost, PC-based diagnostic tools. There are expensive tools out there to help you measure a variety of RF metrics that only an RF engineer has a clue what they mean and the implications of their values. But when it comes to networks -- wired or wireless -- ultimately, what we care about most is throughput performance. 802.11 (i.e. Wi-Fi) is a robust standard that includes a variety of protocols that help it communicate wirelessly with other devices. Unless one has intimate knowledge of the 802.11 standard and its inner workings, then it is not possible to predict how an 802.11 network will behave when you are armed solely with RF measurements. This is why we focus on performance metrics -- because these more accurately predict how your wireless network will actually perform.

WiFi Diagnostic Tools :: Climb Mountain

Here is a brief summary of the 'pros' and 'cons' of 4 troubleshooting strategies (network discovery, RF spectrum analysis, WiFi channel analysis, and WiFi connection analysis):

Network Discovery:
Advantages:
    Inexpensive
Disadvantages:
    Of limited use since it only detects beacon packets transmitted by 802.11 access points. It does not "see" or measure RF energy transmitted by non-802.11 devices (which dominate the RF environment) or, even, actively transmitting 802.11 stations.

RF Spectrum Analysis:
Advantages:
    Detects all RF transmissions within a frequency band.
    Based on the transmission pattern you might be able to identify the source of the interference.
Disadvantages:
    Expensive -- since it requires proprietary hardware.
    When it detects RF interference in the 2.4x or 5.x GHz ISM bands, it can not predict how this will affect 802.11 devices or WiFi network performance -- since it knows nothing about the 802.11 standard nor how its underlying protocols work to mitigate potential sources of interference.

WiFi Channel Analysis:
Advantages:
    Inexpensive -- uses off-the-shelf 802.11 devices.
    Measures RF interference through the eyes of an 802.11 device -- hence, can better predict how an 802.11 Wi-Fi network will actually perform in the current environment.
    Can quantify the expected performance for each Wi-Fi channel, thereby allowing you to choose the optimal channel.
Disadvantages:
    Of limited use when attempting to identify the source of interference.

Connection Analysis:
Advantages:
    Inexpensive -- uses off-the-shelf 802.11 devices or your built-in 802.11 adapters.
    Measures throughput performance of your 802.11 devices when connected to a Wi-Fi network -- which is the ultimate metric when it comes to troubleshooting a network.
Disadvantages:
    Of limited use when attempting to identify the source of interference.

The following table shows a rough comparison of the different troubleshooting strategies. In addition to the four mentioned above, we've also included RF channel / signal generation and 802.11 packet injection, since they are useful techniques that can also aid in finding and solving wireless problems.

	Detects 802.11 Access Points	Measures All RF Energy	Quantifies Effect of RF Interference On Each WiFi Channel	Quantifies Throughput Performance (i.e. Data Rate)	Locate "Dead Spots"	Measure Quality of Tx and Rx	Tools
Network Discovery	yes						NetSurveyor
RF Spectrum Analysis		yes					Sleuth Series
WiFi Channel Analysis			yes				Eagle Series
Connection Performance Analysis				yes			NetSurveyor Professional
RF Channel / Signal Generation					yes		AirHORN
802.11 Packet Injection					yes	yes	WifiCopper