When a Wi-Fi router transmits information over the air, it does so by vibrating electromagnetic waves, similarly to traditional radios or cellular phones. Because we can’t see information being transmitted through the air, we often don’t realize that the air space is divided into several bands, all assigned to specific applications. There are also different wireless transmission frequencies, primarily 2.4 GHz and 5 GHz, and different standards for wireless networking.
These standards are defined by the IEEE 802.11 specification for implementing wireless local area network computer communication in the 900 MHz and 2.4, 3.6, 5, and 60 GHz frequency bands. The slowest commonly used standard is called 802.11b, and it has a maximum raw data rate of 11 Mbit/s. Currently, the fastest standard is 802.11ac, and it has a maximum raw data rate of up to 1300 Mbit/s under ideal conditions.
If you have a fast home connection and a router that supports it but purchase a USB Wi-Fi adapter that supports, for example, only the 802.11g standard, which operates at a maximum raw data rate of 54 Mbit/s, you won’t be able to achieve maximum download and upload speeds. Similarly, if your home wireless network is broadcasted on the 5 GHz frequency and your USB Wi-Fi adapter only supports the 2.4 GHz you won’t be able to connect to your home network at all.
In the current day and age, with thousands of new strains of malware being released every single day, it’s also vital to pay attention to wireless security standards. Your USB WiFi adapter should support the WEP, WPA, and WPA2 protocols, and it should be manufactured by a company that supports its products long after the initial release, constantly working on security updates even for products that are no longer available for sale.