WiMax vs. Long Term Evolution: Let the battle begin
- — 15 May, 2008 10:20
A group called the WiMax Forum, made up of more than 500 vendors and other members, has established itself as an authority to certify WiMax gear. In April, it announced the certification of eight WiMax products for use in the 2.3 GHz band, with products in the 2.5 GHz band expected to be certified later this year.
As for equipment manufacturers, Intel has invested billions of dollars in WiMax research and chip sets and showed off conceptual mobile Internet devices at the Consumer Electronics Show in January. Motorola, among a long list of manufacturers, has been a strong proponent of Sprint's WiMax initiative, but it also will be developing LTE technology.
How will LTE and WiMax perform? The big technology focus of both approaches has been on speed, or throughput, to the user. Theoretical maximums for WiMax are listed in textbooks at 70Mbit/sec., while an AT&T official boasted LTE will provide speed of 100Mbit/sec.
Such speeds would greatly enhance video transmissions and online gaming. For business users, they could offer lightning-fast access to enormous corporate data stores sent over encrypted channels. Some futurists believe both technologies could bring about wireless video phone calls, like the ones Dick Tracy receives on his watch. Today, by comparison, videoconferencing from a wired desktop is still relatively expensive and not always reliable without a high-speed wired connection.
The speeds expected by both LTE and WiMax are hard to nail down primarily because the technologies are just rolling out. Many factors will be taken into consideration, including whether a carrier plans to send the signals over a wireless channel that is 40 MHz in width, double the standard 20 MHz channel, noted analyst Philip Solis of ABI Research.
Speed to an end user is also dependent on how many users are connected to a cell tower, how far away they are, what frequency is used, the processing power of the user's device, and other factors.
A Verizon spokesman wouldn't offer any predictions on what speeds LTE could deliver. "I'm not saying anything on that," said the spokesman, Jeffrey Nelson. "Not theoretical or advertised speeds or what's proved out in the real world."
At Sprint, a spokesman said conservative estimates of the WiMax downlink speeds will be 2Mbit/sec. to 4Mbit/sec. on average on the Xohm WiMax network that Sprint is building, with 10Mbit/sec. peak downlink speeds. For uplinks, the speeds will average 1Mbit/sec. to 2Mbit/sec, depending on the processing power of the user's device.
The same, yet different
There are some notable technology differences between LTE and WiMax, but analysts said both approaches have much in common.
For example, both technologies provide the same approach for downlinks, and both have Multiple Input Multiple Output (MIMO), which means that information is sent over two or more antennas from a single cell site to improve reception. In tough transmission locations, such as a dense downtown area, MIMO could be a relatively inexpensive means of improving reception to users.
The downlinks from the cell tower to the end user in both LTE and WiMax are enhanced with OFDM (Orthogonal Frequency Division Multiplexing), a technology that supports sustained video and multimedia transmissions and is already being deployed in some non-LTE and -WiMax networks. It works by splitting up signals among multiple narrow frequencies, with bits of data sent at once in parallel. Needless to say, it is complex technology that will require sophisticated base stations, an added expense even for those carriers that see LTE as an upgrade path to GSM, analysts said.