Mobile data offloading is the use of complementary network technologies for delivering data originally targeted for cellular networks. For mobile operators the main purpose for the offloading is to prevent congestion of the cellular networks.

The main complementary network technologies used for the mobile data offloading are WiFi and Femtocells. Wi-Fi offloading is an emerging business domain with multiple companies entering to the market with proprietary solutions. Depending on the services to be offloaded and the business model there may be a need for interworking between WiFi and mobile cellular networks. Three solutions have been analyzed so far :

• Enhanced Generic Access Network (EGAN), a tight coupling architecture, specified by 3GPP (3rd Generation Partnership Project)
• Interworking Wireless LAN (IWLAN), a loose coupling architecture, specified by 3GPP
• Direct connection to the public Internet, the most straightforward way to offload data to the WiFi networks

There are three main initiation schemes of offloading procedures: WLAN scanning by ANDS (Access network discovery and selection function), user initiation or remotely-managed initiation.

Mobile data offloading for 3G/4G network using Femtocell technology is promoted by the industry Small Cell Forum.