Troubleshooting wireless networks with WiFi Explorer

Wireless networks are everywhere and we use them everyday. However, there are many factors that influence the performance of wireless networks and getting the most out of them is not an easy task. In this post, I’ll try to summarize the most important aspects that need to be considered when optimizing a wireless network and how you can use WiFi Explorer to diagnose connectivity or stability issues.

Keep in mind that if any configuration changes are required, you must have them done in the access point or router itself. If necessary, please refer to your device’s User Manual for instructions on how to change the configuration of your wireless network.

Band and Range

Let’s talk first about the band. The band is the set of frequencies used by the radio device to communicate wirelessly. Most of the devices we use daily can operate in one of two different bands: 2.4 GHz or 5 GHz. Most modern devices and wireless network adapters, including the built-in Wi-Fi card in modern Mac computers, can operate in dual-mode, in other words, can operate using the two bands simultaneously. Older models, however, as well as older wireless clients such as iPhone 4 and 4S only run in 2.4 GHz.

Because 2.4 GHz has a wider range (the lower the frequency, the wider the range), it is suitable for deployments where there are too many obstacles (e.g. walls) in between the access point and the client device. It is also the only choice if you need to connect older devices. On the other hand, 5 GHz is a good alternative when there’s a need for higher throughput (e.g. streaming your favorite shows in Netflix) and the distance between devices is shorter.

If you are troubleshooting or setting up a new wireless network, make sure you know which band is supported by the different wireless devices to ensure they can connect to the network using the frequency of your choice. Also, consider the requirements of your wireless network and decide whether you need a wider coverage or higher throughput.

WiFi Explorer can help you verify that your network is operating in 2.4 GHz, 5 GHz or dual-mode, particularly if you’re using the same name (SSID) for both wireless networks.

You can also determine which frequency and channel other networks nearby are using and determine if it is necessary to change or adjust your configuration to mitigate possible interference. Interference is in fact, the most common cause for performance and stability problems in wireless networks, so let’s talk about it next.

Interference

In wireless communications, the signals of multiple transmitters can overlap and interfere with each other, resulting in poor signal quality. It’s like when you’re in a room full of people and you’re listening to a conversation where everybody is talking at the same time. Imagine also that there’s a loud song playing. This would be considered background noise and it can degrade the signal quality as well.

To understand better the concept of interference, we need to talk about channels. A channel is the specific frequency range used by two communicating stations to pass information between them. In 2.4 GHz, there are 11 to 14 channels. The number of channels available on each frequency band differ because of different country regulations. In the US, for example, channels 12, 13 and 14 in the 2.4 GHz band cannot be used.

Each channel has a width and a separation. In 2.4 GHz, the width varies from 20 to 30 MHz and the center frequency is separated by 5 MHz. This definition of a channel means that adjacent channels will overlap. Imagine two persons next to each other talking about two different things, as loud as they can. We will hardly understand either of them! In technical terms, the presence of multiple 2.4 GHz access points and clients transmitting in the same, adjacent channels will have a great impact in the performance of your wireless network and may result in degraded throughput and added latency. So, when configuring a wireless network, it is important you choose the less congested, non-overlapping channel.

In the US, the 2.4 GHz band has only three non-overlapping channels. These channels are 1, 6, and 11. In most of the other countries, channels 1, 5, 9 and 13 can be considered non-overlapping channels and are recommended as the best options for setting up a wireless network. In the figure below, the network “vanet” is centered at channel 11, one of the less congested, non-overlapping channels.

The case in the 5 GHz band is a little different. Networks in the 5 GHz have better performance and are less impacted by interference because most of the wireless devices such as video baby monitors, cordless phones, microwave ovens, and Bluetooth devices transmit in the 2.4 GHz frequency range. There are also many fewer wireless clients in the 5 GHz band and plenty of non-overlapping channels (up to 23 depending on country regulations). At my house, for example, only my own 5 GHz network (SSID: vanet) is found.

If your wireless network is experiencing connectivity and stability issues, make sure you choose the less crowded, non-overlapping channel available. Also consider using a 5 GHz configuration if your access point and wireless clients support it.

You can quickly check for conflicting or overlapping channels in WiFi Explorer. Launch WiFi Explorer and select the 2.4 GHz Channels view for the 2.4 GHz band or the 5 GHz Channels view for the 5 GHz band in WiFi Explorer. There you can observe how the channels are being allocated and used by nearby networks.

Note that signal strength is also an important factor. There may be networks transmitting in the same channel but with such a weak signal that they will probably not impact the performance of your network. Following the talking persons example, it’s like having these persons talking between them very quietly. You will probably be able to catch a conversation with someone who is talking using a normal tone of voice. But remember, a DJ is playing a loud song while you talk, something you need to deal with as well.

Signal Quality

WiFi Explorer helps you determine the relation between the signal and the noise levels to determine the quality of your wireless connection. Looking at the signal strength is not enough. By comparing the signal strength to the background noise levels you will have a more accurate estimation of the quality of the connection. You can measure the signal quality of your connection by monitoring the signal-to-noise ratio (SNR) of the wireless network.

To monitor the SNR of the wireless network in WiFi Explorer, select a wireless network from the list, switch to the Network Details tab, and then choose SNR. If your wireless network is experiencing connectivity and stability issues, make sure SNR is above 25 dB. In general, follow these simple rules:

• If SNR is lower than 25 dB and signal strength is below 40% (-70 dBm), then you may need to move closer and remove any possible obstructions between your computer and the router to see if the signal level increases.
• If SNR is lower than 25 dB and noise is above 10% (-90 dBm), then you may need to check any active electronics nearby the computer or the router, and make sure they are turned off or disconnected to see if the noise level decreases.

Make sure you measure SNR at different locations to ensure all spots from where you need to connect offer a good signal quality. If there are problematic locations, move the access point or consider using a wireless repeater, also known as range extenders.

Channel Bonding

Finally, let’s talk about channel bonding. In the 802.11n wireless standard, channel bonding allows for using two 20 MHz-wide channels simultaneously for higher data rates. Just for a second, imagine you have two mouths and two pair of ears. Well, if this were true, you would probably have the the ability to communicate or process double the information at once (no more of these strange examples, I promise).

Channel bonding renders a channel width of 40 MHz: 20 MHz from a primary channel plus 20 MHz from a secondary channel, and this is why channel bonding is also known as 40 MHz channel mode. The secondary channel is always the immediate non-overlapping channel above or below the primary channel. This configuration is indicated with the following notation: ch,+1 if the secondary channel is above the primary channel (ch) or ch,-1 if the secondary channel is below. Most routers and access points have an option to automatically choose the channel width (20 MHz or 40 MHz), so if you’re not sure what’s the best channel mode configuration, choose the automatic mode.

In WiFi Explorer, you can check the channel width by selecting a wireless network from the list and then switching to the Network Details view, but note that even if you specifically choose 40 MHz in your router’s configuration, the channel width in WiFi Explorer may be reported as 20/40 MHz. The reason is that some routers operating with 40 MHz channels will downgrade to 20 MHz channels if necessary (i.e. when using a 40 MHz channel width will cause significant overlap with signals from nearby networks, degrading the performance of the networks involved).

Conclusion

Many factors can influence the performance of wireless networks, and even after network configurations are optimized, circumstances can change, resulting again in degraded performance and connectivity issues. The good thing is that, if you’re familiar with the concepts I’ve just described, WiFi Explorer can help you quickly determine the best configuration for your wireless network to mitigate stability problems and to increase throughput. You can find more about WiFi Explorer here.