 be considered 4G, but other standards bodies do the actual development work of how these recommendations will be implemented. The ITU-R specified that 4G technologies must support 100Mbps downlink transmissions from the network to the user. Standards bodies developing LTE and WiMAX defined differ- ing ways that 4G protocols reach that speed. The two different standards bodies that developed 4G protocols areas follows. LTE Advanced: 3GPP. WiMAX 2: the Institute of Electrical and Electronics Engineers (IEEE). WiMAX 2 is also called WirelessMAN-Advanced. According to the ITU-R definition, which was published in November 2010, all 4G technologies must meet certain capabilities. Although High-Speed Packet Access Plus (HSPA+)-a WCDMA-evolved third-generation (3G) protocol-does not meet all of these requirements, it does have more capabilities than other 3G services. You can find more information about HSPA+ in the next section. The key 4G criteria are as follows. Data rates of 100Mbps downlink speeds for mobile devices such as those in cars or trains, and 1Gbps downlink speeds for low-mobility devices. Low mobility refers to devices used in fixed locations or portable only within a building. Internetworking with services based on international mobile telecommunica- tions (IMT), based on earlier 3G protocols, and with services transmitted on fixed, landline networks. An all-IP packet infrastructure. Fourth-Generation Advanced Mobile Services Internet Protocol version 6 (IPv6) addressing, which has more addresses than IPv4. The capability to support mobile TV. Efficient use of spectrum. Worldwide roaming compatibility between mobile 4G devices. Internetworking refers to the fact that 4G devices can seamlessly be handed over between cell sites that use 3G and 4G protocols without transmission interruptions. Roaming with earlier generations of these protocols is also supported. A large number of manufacturers compete with one another to supply 4G net- works. These include Alcatel-Lucent, Ericsson, Fujitsu, Huawei, Motorol