In the U.S., you need special licenses to broadcast radio-frequency signals in most cases. Examples of licensed broadcasting include radio stations and cell-phone networks. Some devices, operating at low power and in specific frequency bands are exempt from licensing requirements. Such devices include radio-controlled toys, portable phones, baby monitors and Wi-Fi routers. Routers use the Wi-Fi radio frequency bands to establish wireless computer networks and control their traffic. Many of their operating characteristics depend on what bands they use and how.
The Two Frequency Bands
Wi-Fi routers are allowed to operate on the 2.4 and 5 GHz radio frequency bands. The 2.4 GHz band ranges from 2.412 – 2.472 GHz, divided up into 13 channels. The 5 GHz band goes from 5.180 – 5.825 GHz and has 23 channels. Most other unlicensed devices share the 2.4 GHz band and have a range of about 300 feet. If you're in an apartment building, there may be too many devices for the available channels, and 2.4 GHz routers may see a lot of interference. That slows them down and reduces their range. The 5 GHz band has more channels and fewer competing devices.
The 802.11 IEEE wireless standard governs Wi-Fi transmissions of all kinds. The standard has several versions. The 802.11a standard operated on the 5GHz band but did not see wide adoption. The 802.11b was the first widespread standard used for routers and Wi-Fi. The 802.11g standard, with higher speeds, replaced it. Both ran exclusively on the 2.4 GHz band. As the 2.4 GHz band interference became more of a problem, suppliers developed routers that could use both the 2.4 GHz and 5 GHz bands. The standards for these routers are 802.11n and the newer 802.11ac. The highest speeds are available on the 5 GHz band.
Normal Internet browsing is fast on single-band routers operating on the 2.4 GHz band. Most of these routers run at close to 54Mbps, which is the 802.11g speed. Older devices still run at the 802.11b speed of 11Mbps, and you can notice a slowing down of your connection when using these devices. The new 802.11n routers have a speed of 600 Mbps under ideal conditions and 802.11ac routers can transmit in the Gigabit range. These routers are ideal for streaming HD video and downloading large files quickly. The older, slower routers may give poor results for these applications that require high speeds.
Dual-Band vs. Single-Band
Suppliers address the problem of operating with two bands in one of three ways. They may offer single-band routers that run at a slower speed, are the least expensive and operate on the 2.4 GHz band. They may offer dual-band routers that operate either at 2.4 GHz and a slower speed for older devices, or at 5 GHz if all your devices are 802.11n or 802.11ac. Finally, they may offer simultaneous dual-band routers that operate at both frequencies at the same time, accommodating older devices where necessary and delivering high speeds where possible. These routers are about twice the price as single-band routers, as they are actually two routers in one.
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