MIMO (Multiple-Input Multiple-Out-put)

MIMO ( Multiple-Input Multiple-Out-put ) system is an application on the key technology of 802.11n. 802.11n IEEE following 802.11b \ a \ g new wireless LAN technology, speed up to 600Mbps. At the same time, proprietary MIMO technology can improve the existing 802.11a / B / G network performance. The technique was first proposed in 1908 by Marconi, which uses multiple antennas to suppress channel fading. According to the sending and receiving ends of antenna number, relative to the ordinary SISO ( Single-Input Single-Output ) system, MIMO can also include SIMO ( Single-Input Multi-ple-Output ) and MISO ( Multiple-Input Single-Output ) system.

Summary

MIMO said multiple input multiple output. Read / maimo / or / MIMO /, usually the former British Americans, read the latter, the study of international experts in the field and more are read / maimo /. Typically used for IEEE 802.11n, but can also be used for other 802.11 technology. MIMO is sometimes called the space diversity, because of its use of multiple spatial channels for transmitting and receiving data. Only site ( mobile ) or access point ( AP ) to support MIMO to deploy MIMO.

Advantage

MIMO has the advantage of being able to increase and improve the performance of wireless range. Connected to the old 802.11g access point 802.11n sites with higher speed connection to the farther distance. For example, if you use the old site, from a distance of 25 feet is connected to the access point speed is 1Mbps; and the use of 802.11n MIMO site speed for 2Mbps. To increase the range of 2Mbps, allows the user to farther distances remain connected.

The radio signals transmitted by reflection, will have a signal. Each signal is a spatial flow. The use of single input single output ( SISO ) of the current or the old system one can only send or receive a spatial flow. MIMO allows for multiple antenna for simultaneously transmitting and receiving a plurality of spatial flow. It allows the antenna to transmit and receive simultaneously.

The old access point to the old client - only to send and receive a space flow MIMO access point to the MIMO client - simultaneously transmitting and receiving multiple spatial flow can be seen, the channel capacity with the number of antennas increases linearly. That is to say you can use the MIMO channel increase the capacity of wireless channel, without increasing the bandwidth and transmitting power condition, spectrum utilization rate can be enhanced greatly.

The use of MIMO technology can improve the capacity of the channel, but also can improve the reliability of channel, reduce the error rate. The former is the use of MIMO channel provided spatial multiplexing gain, the latter is the use of MIMO channel to provide space diversity gain. Realization of spatial multiplexing gain algorithm mainly Baer lab BLAST algorithm, ZF algorithm, MMSE algorithm, ML algorithm. ML algorithm has good decoding performance, but the complexity of relatively large, for real-time wireless communication can not meet the requirements. ZF algorithm is simple and easy to implement, but the channel's SNR higher. The performance and complexity of the optimal BLAST algorithm. This algorithm is actually using the ZF algorithm with interference cancellation technology derived. At present, the field of MIMO technology another is the research hotspot of space-time coding. Common space time code with space-time block codes, space-time trellis codes. Space-time codes of the main idea is to use the space and time of the code to achieve a certain space diversity, time diversity, thereby reducing the channel bit error rate.