Spatial multiplexing
It is a transmission technique in MIMO wireless communication to transmit independent and separately encoded data signals, so called streams, from each of the multiple transmit antennas.
Therefore, the space dimension is reused, or multiplexed, more than one time. If the transmitter is equipped with Nt antennas and the receiver has Nr antennas, the maximum spatial multiplexing order (the number of streams) is Ns = min(Nt,Nr) if a linear receiver is used.
This means that Ns streams can be transmitted in parallel, leading to a Ns increase of the spectral efficiency (the number of bits per second and per Hz that can be transmitted over the wireless channel). Encoding In a MIMO system with Nt transmitter antennas and Nr receiver antennas, the input-output relationship can be described as where is the Ns×1 vector of transmitted symbols, are the Nr×1 vectors of received symbols and noise respectively, is the Nr×Nt matrix of channel coefficients and is the Nt×Ns linear precoding matrix.
A precoding matrix is used to precode the symbols in the vector to enhance the performance. The column dimension Ns of can be selected smaller than Nt which is useful if the system requires Ns(≠Nt) streams because of sevral reasons. Examples of the reasons are as follws: either the rank of the MIMO channel or the number of receiver antennas is smaller than the number of transmit antennas.
It is a transmission technique in MIMO wireless communication to transmit independent and separately encoded data signals, so called streams, from each of the multiple transmit antennas.
Therefore, the space dimension is reused, or multiplexed, more than one time. If the transmitter is equipped with Nt antennas and the receiver has Nr antennas, the maximum spatial multiplexing order (the number of streams) is Ns = min(Nt,Nr) if a linear receiver is used.
This means that Ns streams can be transmitted in parallel, leading to a Ns increase of the spectral efficiency (the number of bits per second and per Hz that can be transmitted over the wireless channel). Encoding In a MIMO system with Nt transmitter antennas and Nr receiver antennas, the input-output relationship can be described as where is the Ns×1 vector of transmitted symbols, are the Nr×1 vectors of received symbols and noise respectively, is the Nr×Nt matrix of channel coefficients and is the Nt×Ns linear precoding matrix.
A precoding matrix is used to precode the symbols in the vector to enhance the performance. The column dimension Ns of can be selected smaller than Nt which is useful if the system requires Ns(≠Nt) streams because of sevral reasons. Examples of the reasons are as follws: either the rank of the MIMO channel or the number of receiver antennas is smaller than the number of transmit antennas.
History of MIMO
1975,1976
A.R. Kaye and D.A. George and W. van van Etten
created earliest ideas
1984,1986
Jack Winters and Jack Salz
published several papers on beamforming
1993
Arogyaswami Paulraj and Thomas Kailath
proposed the concept of Spatial Multiplexing using MIMO
1994
Patent No. 5,345,599 issued 1994 on Spatial Multiplexing
1996
Greg Raleigh and Gerard J. Foschini refine new approaches to MIMO
technology
1998
Bell Labs was the first to demonstrate a laboratory prototype of SM
2006
MIMO-OFDMA based solutions for IEEE 802.16e WIMAX broadband mobile
standard.
Local
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