NTT DoCoMo in Japan, one the world's leading mobile providers, recently announced a prototype wireless network that could send data packets at 2.5 gigabits per second -- fast enough to download a DVD movie in two seconds -- to a mobile device traveling at 20 kilometers per hour. DoCoMo's demonstration gives a glimpse into the two types of technologies that will most likely be adopted to increase bandwidth and range: MIMO, a type of technology applied to network base stations and mobile devices, and QAM, which loads more data on radio waves.
MIMO (multiple input, multiple output) uses multiple antennas to send and receive data, as well as specific coding that scrambles and unscrambles the signals produced by those antennas. Most MIMO routers have two or three antennas. In DoCoMo's demonstration, the router as well as the receiver used six antennas to produce rates of 2.5 gigabits per second. Tripling the number of antennas on a MIMO access point and receiver can triple the amount of bandwidth of the network.
DoCoMo also tweaked a commonly used form of signal modulation called QAM (quadrature amplitude modulation), which increases the number of bits that a single radio wave contains. DoCoMo used an advanced form of QAM that adjusted the amplitude and phase of each wave to 64 different levels instead of the usual 4 levels.
One of the main challenges to get this into commercial products is that sorting through data that come from different paths can be processor intensive, which can quickly drain a battery -- not good news for mobile device users. There is also issues of signal loss from the QAM technique. There is also the cost to roll out a major network upgrade.
There are cheap silicon ships for shorter range 2 gbps networks