文章标题

MIMO System

• System utilizing multiple transmit and multiple receive antennas are commonly knowns as Multiple Input Multiple Output(MIMO) Systems
• Performance improvements from multiple antennas at both transmitter and receiver
  
  • Array Gain —> SNR improvement
  • Diversity Gain —> fading mitigating
  • Spatial Multiplexing Gain —> channel capacity
  • Interference Reduction / Avoidance

Spatial Multiplexing

• In rich scattering environments, independent data signals transmitted from different antennas can be uniquely decoded to yield an increase in channel capacity
  -

Capacity - now multipath is good

• Recall SISO capacity in one-path
  
  • C=B*log_2(1+|h|^2 * SNR)
• Now, MIMO channel capacity for N transmit antennas
  
  • C=B*log_2 det[I + (SNR/N) HH^H]
  • C=N_ss*log_2 (1+SNR)

MIMO Channel Model

-

• y(n)=Hd(n)+w(n)
• where
  
  • y(n): M x 1 received vector
  • H: M x N channel Matrix with E{|H(k,l)|^2}=1
  • d(n): N x 1 data vector with E{d(n)d(n)^H}=P***I_N***
  • w(n): M x 1 noise vector with E{w(n)w(n)^H}= ρ^2 I_M

MIMO Receivers

• 
  
  • z = G^H * y = G^H * H * d + G^H * w
• MF(matched filter): G^H = H^H
• LS(Least Square) or ZF(zero-forcing): G^H=(H^H* H)^(-1)* H^H
• MMSE: G^H=(H^H * H+(1/Θ)I_N)^(-1) * H^H
  = H^H(H H^H +(1/Θ) I _N)^(-1)

MIMO System

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