| Multiple-input Multiple-output Communications |
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Information AboutMultiple-input Multiple-output Communications |
| CATEGORIES ABOUT MULTIPLE-INPUT MULTIPLE-OUTPUT COMMUNICATIONS | |
| wireless communications | |
| ieee 802 | |
| information theory | |
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Wireless MIMO communication exploits phenomena such as Multipath Propagation to increase data Throughput and range, or reduce Bit Error rates, rather than attempting to eliminate effects of multipath propagation as traditional SISO (Single-Input Single-Output) communication systems seek to do. MIMO can also be used in conjunction with OFDM , and will be part of the IEEE 802.11n High-Throughput standard, which is expected to be finalized in mid 2006 . HISTORY OF MIMO IN RADIO COMMUNICATIONS Jack Winters at Bell Laboratories filed a patent on wireless communications using multiple antennas in 1984 . Jack Salz, also of Bell Laboratories, published a paper on MIMO in 1985, based on Winters' research. Winters and many others published articles on MIMO in the period from 1986 to 1995 . Notably, Dr Winters is now Chief Scientist at Motia Inc. which produces a 'beamforming amplifier' chip, that is designed to operate independently of any MIMO implementation. In 1996 , Greg Raleigh and Gerard J. Foschini invented new approaches to MIMO which increased its efficiency. Greg Raleigh is the founder of Airgo Networks , which claims to be the inventor of MIMO OFDM, offering a "pre-n" chipset called "True MIMOTM". However, it is unlikely that hardware based on this chipset will be compatible with other devices once the 802.11n standard is ratified. MIMO AND INFORMATION THEORY It has been shown that the Channel Capacity (a theoretical upper bound on system throughput) for a MIMO system is increased as the number of antennas is increased, proportional to the minimum number of transmit and receive antennas. This basic result in Information Theory is what led to a spurt of research in this area. BENEFITS OF MIMO MIMO, as used by the expected 802.11n standard, will offer up to eight times the coverage, and up to six times the speed, of current 802.11g networks. A few wireless networking manufacturers have released "pre-N" hardware in anticipation of an eventual standard. On January 19, 2006, the IEEE 802.11n Working Group approved the EWC's specification as the draft approval of 802.11n. THE FUTURE OF WIRELESS NETWORKS The 802.11n ("MIMO") standard is still being discussed, but one prototype can offer up to (under optimal conditions) 250 Mbit /second. This is over four times the speed of existing 802.11g hardware. Other new enhancements will include the arrival of 802.11e and 802.11i . 802.11e will prioritize important information on the network (e.g. a voice message takes precedence over email or a webpage). 802.11i will increase security by using WPA2 . MIMO has just been added to the latest draft version of Mobile WiMAX ( 802.16e ). SEE ALSO EXTERNAL LINKS
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