IEEE 802.11 wireless networking is a convenient means to connect a device to a local network or the Internet. When deploying new devices, it is important to perform a basic frequency analysis and then adjust the deployment plans accordingly. One of the biggest concerns for wireless networking is maintaining a reliable connection. This can be difficult in densely populated areas where many other wireless networks are already in use or where interference is present. However, there is an easy method to avoid conflicts and poor signals: wireless frequency analysis.
Install a wireless scanner on a smart phone. Some good examples are WiFi Analyzer, WiFiFoFum, WiFi Manager, and Wi-Fi Analytics. With one of these apps, scan the area to detect whether or not there are existing wireless networks in either the 2.4 GHz or the 5 GHz bands. Take note of which channels are in use. In the 2.4 GHz band, you might notice that most networks default to channel 6. For any of the 11 channels available in the 2.4 GHz band (for the USA, 13 in Europe, 14 in Japan), the 3 channels above and below partially overlap and thus interfere with that channel. Select the channel which has none or the least amount of overlap with other existing networks. Note: any device supporting 802.11b, 11g, 11n, or 11ac can use the 2.4 GHz frequency.
If you have 802.11n or 11ac devices, then you can use the 5 GHz frequency. There are many more channels in the 5 GHz frequency band (although which specific channels varies by country), but unlike the 2.4 GHz band, most of these channels do not overlap. So, pick any 5 GHz channel that is not already in use.