MIMO (Multiple-Input Multiple-Out-put)

MIMO (Multiple-Input Multiple-Out-put) system is a core technology used in 802.11n. IEEE 802.11n is the following 802.11b \ a \ g after the new wireless LAN technology, the speed up to 600Mbps. Meanwhile, the proprietary MIMO technology improves the performance of existing 802.11a/b/g networks. The technology was first used by Marconi in 1908's, which uses multiple antennas to suppress fading. According to the number of receive antennas at both ends, as opposed to ordinary SISO (Single-Input Single-Output) systems, MIMO can also include SIMO (Single-Input Multi-ple-Output) systems, and MISO (Multiple-Input Single-Output) systems. Outline Multiple Input Multiple Output MIMO said. Read / maimo / or / mimo /, usually Americans former British read the latter, international research expert in this field are more read / maimo /. Typically used for IEEE 802.11n, but it can also be used for other 802.11 technologies. MIMO spatial diversity is sometimes called, because it uses more space channel transmit and receive data. Only site (mobile) or access point (AP) only when the deployment support MIMO MIMO. Advantage MIMO can increase the advantages of wireless range and performance. Connected to the old site 802.11g 802.11n access point to a higher speed connection to the longer distances. For example, if you use the old site, from 25 feet away from the access point is connected to the speed of 1Mbps; use of the site when the speed of 802.11n MIMO is 2Mbps. To 2Mbps range, allows users to maintain connectivity at greater distances. Radio signals transmitted is reflected, will produce more than one signal. Each signal is a spatial stream. Single-input single-output (SISO) a current or old system can only send or receive one spatial stream. MIMO allows multiple antennas to transmit and receive multiple spatial stream. It allows the antenna to transmit and receive. Old access point to the old client - send and receive only one spatial stream MIMO MIMO access point to the client - both send and receive multiple spatial streams Can be seen at this time of the channel capacity increases with the number of antennas increases linearly. MIMO channel that can be used to improve wireless channel capacity is doubled, without increasing the bandwidth and the antenna transmit power case, spectrum efficiency can increase exponentially. The use of MIMO technology can improve the channel capacity, but also can improve the reliability of the channel, reducing the error rate. The former is the use of MIMO channels provide spatial multiplexing gain, which is provided the use of MIMO channel spatial diversity gain. Spatial multiplexing gain of the algorithm are the BLAST algorithm at Bell Labs, ZF algorithm, MMSE algorithm, ML algorithm. ML decoding algorithm has good performance, but the complexity of large, real-time requirements for higher wireless communications can not meet the requirements. ZF algorithm is simple and easy to implement, but require a higher channel SNR. Optimal performance and complexity is the BLAST algorithm. The algorithm is actually using the ZF algorithm with interference de derived. Another current research focus areas of MIMO technology is space-time coding. Common space-time code free-time block codes, space-time trellis codes. The main idea of ​​space-time code is the use of space and time coding to achieve a certain degree of spatial diversity and time diversity, thereby reducing the channel bit error rate.