Use Fitlet to Analyze and Improve Your Wireless Network

Application notes using fitlet. Credit goes to user Hassellbear for publishing more than enough cool application notes to justify a dedicated sub-forum.

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hassellbear
Posts: 106
Joined: Mon May 28, 2012 12:25 pm

Use Fitlet to Analyze and Improve Your Wireless Network

Post by hassellbear »

Overview

Recently, it seems that devices connected to my 2.4 GHz wireless network are operating more slowly than they used to. Since this is not a desirable situation, I set out to see if any improvements in wireless performance are possible.




Some Theory

Often, poor wireless network performance is the result of some form of interference. Such interference can generally be divided into 4 classifications. These are:

1. Adjacent Channel Interference
Adjacent-Channel.jpg
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Adjacent Channel Interference occurs when WiFi devices set to adjacent, overlapping channels operate in close physical proximity to one another. As WiFi devices have grown in popularity and number, adjacent channel interference has become an ever growing issue.

In the 2.4 GHz ISM Band, the 11 available WiFi Channels are spaced 5 MHz apart. Generally, each Channel is 20 MHz wide, so with 5 MHZ Channel Spacing some overlap is possible and most likely probable.

In order to have the high wireless data throughput, RF bandwidth is a necessity. When devices operate on different WiFi channels which overlap, the effective bandwidth of these overlapping channels is reduced, and by extension the bandwidth dependent data throughput is reduced. The result can be noticeably degraded performance of WiFi devices. The image shown below shows significant signal overlap.

Overlapping Channels
LinSSID_2.4GHz.png
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Typically, channels 1, 6, and 11 are used more often than the other channels because they don't overlap each other and their use thus avoids the problems of adjacent channel interference. However, when every wireless router in your neighborhood is set to either channel 1, 6, or 11, other problems can occur. The following image shows how confining routers to channels 1, 6, and 11 avoids overlap.

Non-Overlapping Channels
1-6-11.png
1-6-11.png (58.37 KiB) Viewed 5152 times

hassellbear
Posts: 106
Joined: Mon May 28, 2012 12:25 pm

Use Fitlet to Analyze and Improve Your Wireless Network

Post by hassellbear »

2. Co-Channel Interference
Co-Channel.jpg
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Co-Channel Interference occurs when closely spaced wireless access points operate on the same channel/frequency. In this situation, there isn't just a few MHz of overlap as there is when adjacent channels overlap, there is a full 20 MHz of overlap. It is for this reason that co-channel interference has the potential to be even more problematic than adjacent channel interference. It is also for this reason that I am not entirely convinced that the industry recommendation of herding everyone onto channels 1, 6, or 11 is always the best approach for mitigating interference issues.

Take for instance the following WiFi spectrum graph. Since the Access Points are clustered on channels 1, 6, and 11, no adjacent-channel interference exists. However, there are 4 APs on channel 6 and 3 Aps on channel 11, so those channels potentially are experiencing co-channel interference. Only the single access point on channel 1 is potentially free from interference.
1-6-11.png
1-6-11.png (58.37 KiB) Viewed 5150 times

3. Non-Wifi Devices
Other.jpeg
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Many non-WiFi devices operate in the 2.4 GHz and 5 GHz bands. Such devices include cordless phones, radio controlled models, wireless microphones, wireless video systems, and a myriad of other items. From the perspective of WiFi, such devices compete for bandwidth and are sources of noise. As such, non-wifi devices operating at similar freqencies to WiFi have the potential to degrade performance.

hassellbear
Posts: 106
Joined: Mon May 28, 2012 12:25 pm

Use Fitlet to Analyze and Improve Your Wireless Network

Post by hassellbear »

4. Many Devices Connected to Access Point
Lots-Of-Devices.jpg
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Any given wireless access point has a maximum data bandwidth. Every device connected to that access point must share the available bandwidth, so in general the performance of each connected device suffers as more devices come online. In this case, the solution is to use multiple access points and divide the client devices between them.





Fitlet To The Rescue

When equipped with the simple hardware and software listed below, Fitlet can be a great tool for use in diagnosing and improving your wireless network.

LinSSID
LinSSID.jpeg
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LinSSID is a great open-source software tool for visualizing your WiFi environment. It provides a wealth of data including a graphical display of channel usage and signal strength and a table which lists access point data such as AP manufacturers, mac addresses, signal strengths, types of encryption used, etc. LinSSID will quickly show you where adjacent-channel and co-channel interference issues exist. LinSSID supports both 2.4 GHZ and 5 GHz, so it is a great tool for Fitlets which are equipped with dual-band wireless adapters.

The following website shows how to obtain and install LinSSID in Linux Mint.

http://www.itworld.com/article/2708192/ ... nd-13.html


Airview2
Airview2.jpeg
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Airview2 is a great, low-cost spectrum analyzer tool for the 2.4 GHz ISM band - which includes WiFi. Unlike LinSSID which only displays WiFi signals, Airview2 displays all signals present in the 2.4 GHz band. As a result, it is useful for identifying interference caused by non-wifi devices.

Airview2 works very well with Ftilet. For more information see:

http://www.fit-pc.com/forum/viewtopic.php?f=153&t=5712

hassellbear
Posts: 106
Joined: Mon May 28, 2012 12:25 pm

Use Fitlet to Analyze and Improve Your Wireless Network

Post by hassellbear »

Analyzing and Diagnosing My WiFi Situation Using Fitlet

Using Ftilet, LinSSID, and Airview2, I was able to quickly gain a sense of my WiFi situation. The images shown below tell the story.

LinSSID @ 2.4 GHz
LinSSID_2.4GHz.png
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LinSSID @ 5 GHz
LinSSID_5GHz.png
LinSSID_5GHz.png (137.21 KiB) Viewed 5144 times
Airview2 @ 2.4 GHz
AirView Spectrum Analyzer_2.4 GHz.png
AirView Spectrum Analyzer_2.4 GHz.png (103.55 KiB) Viewed 5144 times

Findings

1. In my location, the 2.4 GHz band is crowded. LinSSID has identified 12 Access Points in my immediate vicinity. Airview2 also indicates significant signal activity in the band. It is likely that some of what Airview2 is showing represents non-WiFi activity by other devices.

2. The 5 Ghz band is practically empty. LinSSID is only detecting my wireless router in this band (SSID: 1adam12-2, Color: purple).

3. In the 2.4 GHz band my router is operating on channel 3 (SSID: 1adam12-1, Color: red) and is experiencing 15 MHz of overlap with other nearby APs, so adjacent-channel interference is a distinct possibility.


Planned Course of Action

1. Move all dual band capable WiFi client devices from crowded 2.4 GHz band to un-crowded 5 GHz band.

2. Experiment with changing 2.4 GHz AP channel. However, based on the LinSSID 2.4 GHz graph shown above, changing the channel to 1, 6, or 11 may result in co-channel interference which is worse than the adjacent-channel interference I am experiencing on channel 3.




Conclusions

1. The proliferation of 2.4 GHz devices is rapidly leading to overcrowding of the band in crowded, urban areas.

2. At present, 5 Ghz offers a good alternative to 2.4 GHz

3. Fitlet is a great tool for such analysis.

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