ECE MIMO PPT PDF

MULTIPLE INPUT MULTIPLE OUTPUT SYSTEMS (MIMO) Content  Introduction  What is MIMO?  Spatial Diversity and Spatial Multiplexing  MEMO capacity on fading channels  Benefits of MIMO  Drawbacks of MIMO  Conclusion Introduction MIMO Systems:  use multiple inputs and multiple o...

MULTIPLE INPUT MULTIPLE OUTPUT SYSTEMS (MIMO) Content  Introduction  What is MIMO?  Spatial Diversity and Spatial Multiplexing  MEMO capacity on fading channels  Benefits of MIMO  Drawbacks of MIMO  Conclusion Introduction MIMO Systems:  use multiple inputs and multiple outputs from a single channel  are defined by Spatial Diversity and Spatial Multiplexing What is MIMO? As we know MIMO is multiple antenna technology in which more than one antennas are used at transmitter and receiver stations. Spatial Diversity and Spatial Multiplexing  Spatial Diversity ◦ Signal copies are transferred from multiple antennas or received at more than one antenna ◦ redundancy is provided by employing an array of antennas, with a minimum separation of λ/2 between neighbouring antennas  Spatial Multiplexing ◦ the system is able to carry more than one data stream over one frequency, simultaneously Why MIMO?  There is always a need for increase in performance in wireless systems ◦ Significant increase in spectral efficiency and data rates ◦ High Quality of Service (QoS) ◦ Wide coverage, etc.  Wireless channel that we are using is very unfriendly ◦ Suffers from Co–channel interference and signal level fading ◦ It provides a limited bandwidth ◦ power falls off with distance MIMO System solutions  By using Multiple Output Multiple Input (MIMO) systems ◦ Diversity gain mitigates the fading and increases coverage and improves QoS ◦ Multiplexing gain increases capacity and spectral efficiency with no additional power or bandwidth expenditure ◦ Array gain results in an increase in average receive SNR.  Spatial Diversity and Spatial Multiplexing can be conflicting goals Spatial Multiplexing  MIMO channels can be decomposed into a number of R parallel independent channels → Multiplexing Gain ◦ Principle: Transmit independent data signals from different antennas to increase the throughput, capacity. Source: An Overview of MIMO Systems in Wireless Communications www.iet.ntnu.no/projects/beats/Documents/mimo.pdf MEMO capacity on fading channels  The capacity increase can be seen by comparing MEMO systems with SISO, SIMO, and MISO systems ◦ SISO:capacity is given by Shannon’s classical formula: C B log (1  snr h 2 ) 2 Where B is the BW and h is the fading gain ◦ SIMO (with M transmitting antennas), the capacity is given by m 2 C B log (1  snr   h ) 2 n n 1 ◦ MISO (with M transmitting antennas), the capacity is given by  snr  N 2 C B log (1     h ) 2  N  n 1 n MEMO capacity on fading channels  The capacity for MIMO systems can have the following forms (Assuming Tx antennas = Rx antennas = N): A) If the channel is not known at the transmitter:  Es  2 C  N log (1    h ) 2  2 n  N  ◦ Where Es is the total power, σ2 is noise level of AWGN ◦ Hence the power is equally shared by each channel ◦ The capacity grows linearly with the number of antennas B) If the channel is known at the transmitter N  En  2  C   log (1    h ) n1  2  2  n     MEMO capacity on fading channels  With the channel known at the transmitter, the total power allocation the each channel will be based on watterfilling. ◦ Watterfilling: Strong Sub-channel, with low noise power level will be assigned with a higher signal power. Illustrating Watterfilling Where σN2 = σ2 / │hn2│ Source: MIMO Systems and Transmit Diversity, www.comm.utoronto.ca/~rsadve/Notes/DiversityTransmit.pdf Average capacity of a MIMO Rayleigh fading channel [] 60 55 50 45 40 Average Capacity [bits/sec/Hz] 35 30 25 20 15 10 5 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 SNR [dB] N=1 M=1 N=2 M=1 N=1 M=2 N=2 M=2 N=2 M=4 N=2 M=6 N=4 M=4 N=8 M=8 Source: Space-time Diversity Codes for Fading Channels, Spatial Diversity  Improves the signal quality and achieves a higher SNR at the receiver-side  Principle of diversity relies on the transmission of structured redundancy xi yi MIMO Diversity and Reliability  The performance improvement in SNR and error probability for MIMO can be compared with SISO, SIMO, and MISO  The detailed calculationy for hxSNR  n and Pe is shown in ◦ SISO: 2 1 E hx 2 Pe  SNR(h)  SNR h and SNR En 2 1 2 yi hi x  ni , i 1,2, N ◦ Receive Diversity (SIMO): N 1 2 Pe  SNR(h) SNR h and  SNR  N i 1    2  MIMO Diversity and Reliability  The values for SNR and Pe for: M ◦ Transmit Diversity (MISO): y  hjx j  n j 1 M yi  hij xj  ni M 1 j 1 2 Pe  SNR(h) SNR hj and  SNR  M j 1 1    2  ◦ Transmit/Receive Diversity (MIMO):  The received signal at antenna i will be:  H is the channel fading matrix SNR H 2 1 2 Pe  MN SNR( H ) SNR H and  SNR  min{N , M }  1    2 min{N , M }  Benefits of MIMO ➨There is lower susceptibility of tapping by unauthorized persons due to multiple antennas and algorithms. ➨The systems with MIMO offers high QoS (Quality of Service) with increased spectral efficiency and data rates. ➨The wide coverage supported by MIMO system helps in supporting large number of subscribers per cell. ➨The MIMO based system is widely Drawbacks of MIMO ➨The hardware resources increase power requirements. Battery gets drain faster due to processing of complex and computationally intensive signal processing algorithms. This reduces battery lifetime of MIMO based devices. ➨MIMO based systems cost higher compare to single antenna based system due to increased hardware and advanced software requirements. Conclusion  The capacity of Receive or Transmit Diversity grows logarithmically with the number of antennas  Capacity of MEMO increases linearly with the number of antennas  Using Spatial Diversity: ◦ The SNR increases and Pe decreases when using MIMO  Spatial Multiplexing and Spatial Diversity are conflicting objectives Reference  www.google.com  www.wikipedia.com  www.studymafia.org THANKS