Nt1310 Unit 5 Application Of Mo System

The matrix elements are complex numbers that correspond to the attenuation and phase shift that the wireless communication channel introduces to the signal reaching the receiver with delay τ.
3.1.1 Benefits of MIMO Systems
3.1.1.1 Interference reduction and avoidance
Interference in wireless networks results from multiple users sharing time and frequency resources scheme. Interference may be mitigated in MIMO systems by exploiting the spatial dimension to increase the separation among users. Interference reduction and avoidance improve the coverage and range of a wireless network.
3.1.1.2 Spatial multiplexing
Spatial multiplexing offers a linear (in the number of transmit-receive antenna pairs or min increase in the transmission rate (or
Fading channel, signal experiences fade (i.e they fluctuate in their strength). When the signal power drops significantly, channel is said to be in deep fade. This gives rise to high BER. The diversity is used to combat fading channel. This involves providing replicas of the transmitted signal over time, frequency, or space.
3.1.1.4 Array gain
Array gain is the average increase in the SNR at the receiver that arises from the coherent combining effect of multiple antennas at the receiver antenna or transmitter antenna or both. Basically, multiple antenna require perfect channel knowledge either at the transmitter or receiver or both to achieve good array gain.
3.2 Orthogonal Space Time Block Code (OSTBC)
The transmit diversity scheme designed by Alamouti can be used only in a system with two transmit antenna. It turns out that this system belongs to a general class of codes named Space–Time Block Codes or, more precisely, the Orthogonal Space–Time Block Codes (OSTBC), since they are based on the theory of orthogonal designs. The authors of [4] introduced the theory of generalized orthogonal designs in order to create codes for an arbitrary number of transmit antennas.
The general idea behind Space–Time Block Codes construction is based on finding coding matrices X that can satisfy the following condition, ).
In other words, the sequences transmitted from two different antenna elements are orthogonal to each other for each transmission block. For real signal, it is possible to reach full rate. However, it has been proven in [4] that this statement is false for two-dimensional constellations, complex signals. The encoding and decoding approaches follow the pattern described in Alamouti’s method. For complex signals, the theory of orthogonal designs can be used to generate coding matrices that achieve a transmission rate of 1/2 for the cases of 3 and 4 transmission