MIMO is a wireless communications technology that actually uses multipath propagation to its advantage. What is Multipath? I’m glad you asked.
After transmission, radio signals bounce and reflect off objects along their path to a receiver. As a result, many different paths to a particular receiver are possible - each arriving at the receiver at slightly different times. Traditionally, these signals arriving at different times would actually interfere with one another and prevent the receiver from being able to recover the original signal.
MIMO on the other hand, uses these varying paths to carry even more information than previously possible. Essentailly, each different path to the receiver is used to carry different parts of the signal. At the receiver, each part is recombined by the MIMO algorithms into the original signal. Think of it as a form of Inverse Multiplexing. Start with a 100Mbps data stream, separate it into 10 different 10 Mbps data streams and transmit each stream at the same time - only along different paths to the receiver - where the 10 Mbps streams are recombined into the 100 Mbps stream.
MIMO is the basis of the IEEE 802.11n specification for WLANs having at least 100M bit/sec throughput. Additionally, MIMO, in conjunction with OFDM, are the bellweathers of the 802.16 wireless standard.
MIMO doubles the spectral efficiency compared with that of current WLANs. The maximum data rate for 802.11g and 802.11a networks is 54M bit/sec, though actual throughput is closer to 20M to 30M bit/sec. Current MIMO techniques can boost raw WLAN throughput to greater than 100M bit/sec. Some even tout systems that can support up to 250 Mbps.
Here is a listing of some currently available products that support MIMO technology.
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