Known issues of spatial multiplexing MIMO Spatial multiplexing MIMO - - PowerPoint PPT Presentation

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Known issues of spatial multiplexing MIMO

 Spatial multiplexing MIMO significantly improves

spectral efficiency, but:

 Suffers from inter-channel interference

resulting in high computational complex algorithms (e.g., Vertical – Bell Labs Layered Space Time (V-BLAST) algorithm)

 Requires inter-antenna synchronisation (IAS)  Requires multiple RF-chains ( expensive and

requires high energy)

 Suffers from error propagation

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Spatial Modulation: How does it work?

A(A) B(A) C(A) D(A) A(D) B(D) C(D) D(D) A (Tx1) B (Tx2) C (Tx3) D (Tx4) Signal Constellation Spatial Constellation Re Im Im Im Re Re

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SM Principle

A(C) B(C) C(C) D(C) A (Tx1) B (Tx2) C (Tx3) D (Tx4) Spatial Constellation Re Im Im Re t1 Signal Constellation Diagram C B D A B C

Spatial symbol Signal symbol Spatial symbol Signal symbol Spatial symbol Signal symbol

t1 t2 t3

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SM Principle

A(D) B(D) C(D) D(D) A (Tx1) B (Tx2) C (Tx3) D (Tx4) Spatial Constellation Re Im Im Re t2 Signal Constellation Diagram C B D A B C

Spatial symbol Signal symbol Spatial symbol Signal symbol Spatial symbol Signal symbol

t1 t2 t3

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SM Principle

A(B) B(B) C(B) D(B) A (Tx1) B (Tx2) C (Tx3) D (Tx4) Spatial Constellation Re Im Im Re t3 Signal Constellation Diagram C B D A B C

Spatial symbol Signal symbol Spatial symbol Signal symbol Spatial symbol Signal symbol

t1 t2 t3

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SM Complexity vs. Performance

Complexity Data Rate

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Key Advantages of SM

 SM entirely avoids inter–channel interference (ICI) and

requires no synchronisation between the transmit antennas.

 No constraints on the number of receive antennas or

transmit antennas.

 Achieves spatial multiplexing gains even for a single

receive antenna.

 Only a single RF chain is required at the transmitter.  Better robustness to channel estimation errors compared to

V-BLAST.

 Better robustness to channel correlation compared to V-

BLAST.

 Has been shown to outperform V-BLAST in terms of ABER.  The computational complexity is independent of the

number of transmit antennas.