Definitions

• "Third generation," or 3G, refers to the cellular phone technology that replaced "second generation" or 2G technology. The introduction of 3G provided smartphone users with faster connections that made mobile video -- and mobile video conferencing -- possible. "Fourth generation," or 4G, technology supersedes 3G technology in terms of connection speed. The technology allows for more advanced smartphone functionality, including HD video streaming. Unlike 3G and 4G, Wi-Fi is a trademarked wireless networking technology established by the Wireless Fidelity Alliance. Wi-Fi relies on the IEEE 802.11 networking standard used for smartphones, computers and other devices.
  
  

Function

• 3G, 4G and Wi-Fi technologies use radio waves to send and receive data. Specifically, the technologies can convert binary code -- a series of "1"s and "0"s -- into radio waves for transmission and can convert those radio waves back into binary code once a smartphone, or other device, receives the transmissions. 3G and 4G technologies have even more in common, as both rely on networks that divide geographic regions into smaller areas known as cells. Each cell uses a specific set of radio channels or radio frequencies, which a localized cell phone tower or antenna broadcasts. When a smartphone user changes locations, the user can remain connected with 3G or 4G by picking up the broadcasts of another cell. By offering a wider bandwidth, or range of frequencies, 4G signals are able to carry more data, which is why 4G offers more advanced services than 3G. Unlike 3G and 4G, Wi-Fi does not rely on a network of connected cells. Instead, Wi-Fi uses a router to establish a local area network, or LAN, that broadcasts signals within a specific geographic range. Once a user moves beyond that range, his smartphone, or other device, cannot send and receive radio waves.
  
  

Speed

• 3G remains the slowest among Internet connectivity technologies, a result of its narrow bandwidth. 4G and Wi-Fi operate at similar speeds. While 3G offers a maximum data transfer rate of 3 megabits per second, 4G and Wi-Fi can both provide data transfer rates of 100 Mbps and above. To put this into perspective, Practical E-commerce notes that downloading a 100 MB file with 3G could take approximately seven minutes, while downloading that same file with 4G or Wi-Fi takes approximately 30 seconds.
  
  

Uses

• Service providers use 4G networks specifically for delivering Internet data, whereas 3G networks carry voice data and Internet data. Even with a 4G smartphone, a 3G network still delivers the voice data, while the faster 4G network provides the Internet connectivity. Like 4G, Wi-Fi is used specifically for Internet connectivity. While 4G and Wi-Fi offer the same speed, 4G has the advantage of being "always-on," meaning a user can access the Internet via a 4G network regardless of his location provided he stays in range of a cell phone tower. In contrast, accessing the Internet with Wi-Fi requires that a user be in range of a router, which limits mobility.