Mobile madness defined

Does all this talk of WiMAX, 3G and 4G make your head spin? Here's a quick primer about what each technology really delivers:

• 3G networks are based on the International Telecommunication Union family of standards. Services typically include mobile wide-area wireless voice telephony, video calls and broadband wireless data. Additional features also include High-Speed Packet Access (HSPA) data transmission capabilities able to deliver speeds up to 14.4Mbps on the downlink and 5.8Mbps on the uplink.

• 4G generally refers to "the next generation of cellular" network that will follow 3G, the wireless broadband networks that are currently deployed through technologies such as HSPA. While true 3G technology has specific worldwide industry standards associated with it, 4G doesn't mandate specific technical network standards beyond the use of the IP protocol and packet-switching technology. Rather, it describes capabilities desirable in the next generation of mobile networks. For example, 4G networks — regardless of how they are constructed — will support IP multimedia applications and the ability for users to roam across dissimilar network infrastructures. 4G wireless technologies will be capable of providing between 100M and 1Gbps speeds both indoors and outdoors, with high quality and security features.

• WiMAX: Unlike 4G, WiMAX is a set of technical standards for a specific network. Mobile WiMAX, which is technically the IEEE's set of 802.16-2005 standards, will likely be the first available 4G alternative. But the terms aren't synonymous: Mobile WiMAX will be a type of 4G network, but not all 4G networks will be mobile WiMAX networks. WiMAX provides fixed , nomadic, portable and, soon, mobile wireless broadband connectivity without the need for direct line-of-sight with a base station. In a typical cell radius deployment of three to ten kilometers, systems can be expected to deliver capacity of up to 40 Mbps per channel, for fixed and portable access applications, according to the WiMAX Forum.

• LTE, which stands for Long Term Evolution, is considered the next big wave in 4G technology. Specifically, LTE is a modulation technique designed for GSM/UMTS-based technology that uses Orthogonal Frequency-Division Multiplexing (OFDM) and multiple-input and multiple-output, (MIMO). While LTE products aren't expected to hit the market until 2010 at the earliest, trial runs suggest that it is going to deliver very fast mobile broadband. During last week's CTIA Wireless conference, Japanese wireless carrier DoCoMo announced that its trial LTE system reached download speeds of up to 250Mbps. Previous LTE trial runs had achieved download speeds ranging from 45M to 144Mbps.