Troubleshooting Wireless Networks with WiFi Explorer

Wireless networks are everywhere, and we use them every day. However, many factors influence their performance, and getting the most from them is not always easy. In this article, I’ll summarize the most important considerations when optimizing a wireless network. I’ll also explain how WiFi Explorer can help diagnose connectivity and stability problems.

Keep in mind that you must make any configuration changes on the access point or router itself. If necessary, consult your device’s user manual for instructions on changing its wireless settings.

Band and Range

Let’s start with the frequency band. A band is a range of frequencies that a radio device uses for wireless communication. Most devices operate in one of two Wi-Fi bands: 2.4 GHz or 5 GHz. Many modern devices and wireless adapters, including the built-in Wi-Fi adapters in modern Macs, support both bands. Older models and clients, such as the iPhone 4 and 4S, support only 2.4 GHz.

Because 2.4 GHz generally provides a wider range, it can work well in deployments with many obstacles, such as walls, between the access point and client device. It is also the only choice when connecting older devices that do not support 5 GHz. By contrast, 5 GHz is a good option when you need higher throughput—for example, when streaming video—and the distance between devices is shorter.

When setting up or troubleshooting a wireless network, identify the bands supported by each client device. This step helps ensure that every device can connect on the band you intend to use. You should also consider the network’s requirements and decide whether wider coverage or higher throughput matters more.

WiFi Explorer can help you confirm whether your network operates on 2.4 GHz, 5 GHz, or both. This information is particularly useful when both bands use the same network name, or SSID.

You can also see the channels and frequencies used by nearby networks. With that information, you can decide whether adjusting your configuration might reduce interference. Because interference commonly causes wireless performance and stability problems, let’s examine it next.

Interference

In wireless communication, signals from multiple transmitters can overlap and interfere with one another, reducing signal quality. Imagine trying to follow a conversation in a crowded room where everyone is talking at once. Now imagine that loud music is also playing. The music represents background noise, which can further degrade your ability to understand the conversation.

To better understand interference, we first need to discuss channels. A channel is the frequency range used by two stations to exchange information. The 2.4 GHz band provides between 11 and 14 channels, depending on local regulations. In the United States, for example, Wi-Fi devices cannot use channels 12, 13, or 14.

Each channel has a defined width and center frequency. In the 2.4 GHz band, channel widths range from 20 to 30 MHz, while adjacent center frequencies are separated by 5 MHz. As a result, adjacent channels overlap. Imagine two people standing next to each other and talking loudly about different subjects. You would have difficulty understanding either conversation.

Similarly, access points and clients transmitting on the same or adjacent 2.4 GHz channels can significantly affect wireless performance. The result may include lower throughput and higher latency. When configuring a wireless network, choose the least congested non-overlapping channel available.

The 2.4 GHz band has three non-overlapping channels in the United States: 1, 6, and 11. In many other countries, channels 1, 5, 9, and 13 may also serve as non-overlapping choices. In the figure below, the network “vanet” is centered on channel 11, one of the least congested non-overlapping channels.

The situation differs in the 5 GHz band. Networks there often experience less interference because many common devices—including video baby monitors, cordless phones, microwave ovens, and Bluetooth devices—operate in the 2.4 GHz range. The 5 GHz band also tends to have fewer wireless clients and offers many more non-overlapping channels, with as many as 23 depending on local regulations. At my house, for example, WiFi Explorer finds only my own 5 GHz network, “vanet.”

If your network has connectivity or stability problems, look for the least crowded non-overlapping channel. You should also consider using 5 GHz if both the access point and client devices support it.

WiFi Explorer makes it easy to identify conflicting or overlapping channels. Launch the app and select the 2.4 GHz Channels view or the 5 GHz Channels view. These views show how nearby networks allocate and use the available channels.

Signal strength also matters. A network may use the same channel as yours but have such a weak signal that it has little effect on performance. Returning to the conversation analogy, imagine that the other people are speaking very quietly. You can probably still understand someone talking to you at a normal volume. However, you must also account for the loud music—the background noise—in the room.

Signal Quality

WiFi Explorer can help you evaluate signal quality by comparing signal strength with the noise level. Signal strength alone does not tell the whole story. The relationship between signal and background noise provides a better estimate of connection quality. This relationship is called the signal-to-noise ratio, or SNR.

To monitor SNR in WiFi Explorer, select a wireless network, open the Network Details tab, and choose SNR. If your network has connectivity or stability problems, aim for an SNR above 25 dB. In general, follow these guidelines:

• If the SNR is below 25 dB and signal strength is below 40% (-70 dBm), move closer to the router and remove possible obstructions. Then check whether the signal level improves.
• If the SNR is below 25 dB and noise is above 10% (-90 dBm), inspect active electronic devices near the computer or router. Turn them off or disconnect them temporarily, then check whether the noise level decreases.

Measure SNR in several locations to confirm that every area where you need connectivity has adequate signal quality. If you find problem areas, move the access point or consider using a wireless repeater, also known as a range extender.

Channel Bonding

Finally, let’s discuss channel bonding. In 802.11n, channel bonding combines two 20 MHz channels to support higher data rates. Imagine, for a moment, that you had two mouths and two pairs of ears. You could probably communicate or process twice as much information at once. That is the last strange analogy, I promise.

Channel bonding produces a 40 MHz channel: 20 MHz from the primary channel and another 20 MHz from the secondary channel. For this reason, it is also known as 40 MHz channel mode. The secondary channel sits immediately above or below the primary channel. The notation ch,+1 indicates that the secondary channel is above the primary channel, while ch,-1 indicates that it is below. Most routers and access points can select a 20 or 40 MHz channel width automatically. If you are unsure which configuration to use, choose the automatic mode.

In WiFi Explorer, you can check channel width by selecting a network and opening the Network Details view. Even if you configure the router to use 40 MHz, WiFi Explorer may report the width as 20/40 MHz. Some routers operating with 40 MHz channels fall back to 20 MHz when necessary. For example, they may do so when a 40 MHz channel would overlap significantly with nearby networks and degrade performance.

Conclusion

Many factors influence wireless network performance. Even after you optimize a network’s configuration, conditions can change and cause new performance or connectivity problems. Once you understand the concepts described above, WiFi Explorer can help you identify potential causes, adjust the network configuration, improve stability, and increase throughput. You can learn more about WiFi Explorer here.