Wi-Fi and 3G are both types of wireless data networks, providing high-speed Internet service for laptops, desktop PCs, smartphones and tablets. Although Wi-Fi enjoys an advantage in terms of raw speed, a 3G connection offers greater mobility; your devices get service across a much wider area. Many mobile devices can access either kind of network automatically, depending on which has the stronger signal.
Wi-Fi is a trade name for the 802.11 standard adopted by the Institute for Electrical and Electronics Engineers. The original version of Wi-Fi, introduced in 1997, had a maximum speed of one million bits per second. Subsequent improvements to Wi-Fi have increased the speed to over 300 Mbps; proposals for future Wi-Fi standards exceed 1 Gbps. Wi-Fi specifications don’t distinguish between upload and download speeds; other factors, such as the plan you purchase from your Internet service provider, affect uploads. 3G covers many technologies developed at different times, all of which have different data speeds. At the low end, general packet radio service delivers speeds up to 171 Kbps. A newer standard, Evolution-Data Only, has a peak download speed of 3.1 Mbps, averaging 1.2 Mbps; uploads are slower, with a maximum of 1.8 Mbps and averaging about 470 Kbps.
The numbers given in wireless speed specifications represent maximum possible rates; they assume a strong signal, clear weather and light network traffic. As conditions deteriorate and more users share the network, actual speeds can drop dramatically; this is true for both 3G and Wi-Fi technologies. The quality of a wireless service provider's infrastructure also figures heavily into your day-to-day experience of the network's speed: a company with more equipment in an area can provide greater speeds than one which has more customers than their system can handle.
As you move farther from a wireless network's antenna, the signal strength fades, limiting your ability to get a connection, and its maximum possible speed. Wi-Fi ranges vary from 150 feet for the oldest versions to 230 feet for 802.11n, the current version as of September 2012. A single Wi-Fi access point is sufficient for a coffee shop, but larger organizations need multiple access points. 3G covers a much wider area; service providers already have multiple cell towers servicing cities, towns and major highways.
A 3G connection's speed depends on if you are stationary or moving. In a moving car, for example, your connection may not be better than 348 kbps; standing or walking, the connection improves to 2 Mbps. As you move, the signal you receive from one cell tower increases and another decreases; the network continuously maintains your connection though the constant adjustments affect data speed. These issues don't apply to Wi-Fi, because its range is limited to a few hundred feet.
Many desktop PCs have a permanent connection to one Wi-Fi network signal. A mobile device, such as a smartphone or netbook, switches between different networks during a typical day. Early in the morning, for example, your smartphone may use your home Wi-Fi network. When you leave for work, the phone loses the Wi-Fi signal and switches automatically to 3G. Upon reaching your office, the phone locates the Wi-Fi signal there and connects to it. Along the way, the speed of your connection increases and decreases according to the type of connection, network traffic and how fast you move.
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