3G technologies like GPRS and CDMA2000 are wireless wide area network (WAN) technologies, suitable for connecting mobile devices to carrier base stations -- the base station provides entry into the carrier's wireless network, and from there into the Internet or public switched telephone network. Think of 3G as the wireless equivalent of ISDN or DSL.
There are many underlying technical reasons why these two technologies are suitable for different applications, but here are a few key differences:
- Wi-Fi reaches only 300+ feet from the station to the access point, and is most often used indoors. 3G connects stations that are within miles of a base station (cellular tower), used most often outdoors.
- Wi-Fi bandwidth ranges from 11 Mbps to 54 Mbps, depending upon the actual standard. 3G services deliver about 40-70 Kbps today, even though they promise to deliver better than 1 Mbps in the future.
- Wi-Fi uses unlicensed spectrum, which means that anyone (you or I) can install a wireless LAN. 3G uses licensed spectrum, which means that only public carriers that purchase the spectrum can install a wireless WAN and offer commercial service to the public.
People begin to think of these technologies as competing when they consider running the same application over both. For example, voice over Wi-Fi could be a less expensive alternative to voice over GPRS, but only when the mobile device is close enough to a Wi-Fi access point. Carriers are a bit troubled by that possibility because they'd lose revenue. That is, unless carriers get into the business of providing Wi-Fi public access -- which companies like Verizon and SprintPCS are starting to do right now!
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