CODING FOR MULTIPLE ANTENNAS

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CODING FOR MULTIPLE ANTENNAS WITH LINEAR AND
NONLINEAR (BLAST) INTERFACES
EZIO BIGLIERI (work done with
A. Nordio, G. Taricco, and A. Tulino)
DIMACS WORKSHOP, OCTOBER 2002
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OUTLINE

• SYSTEM MODEL AND BASIC ASSUMPTIONS
• LINEAR AND NONLINEAR RECEIVERS
• ZERO-FORCING AND MMSE BLAST
• ITERATIVE RECEIVER
• CODING FOR NONLINEAR RECEIVERS
• SIMULATION RESULTS

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SYSTEM MODEL

• mimo channel with t transmit and r
  receive antennas
• fading constant over N symbol intervals
• independent rayleigh fading channel
• perfect csi at receiver

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TX
RX
H
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SYSTEM MODEL
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INTRODUCING AN INTERLEAVER
Pairwise error probability with ML detection
E
E
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INTRODUCING AN INTERLEAVER
Spatial interference
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INTRODUCING AN INTERLEAVER
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INTRODUCING AN INTERLEAVER

• OPTIONS FOR REMOVING ?1
• r? ?

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INTRODUCING AN INTERLEAVER

• OPTIONS FOR REMOVING ?1
• r? ?
• Alamouti-type coding

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INTRODUCING AN INTERLEAVER

• OPTIONS FOR REMOVING ?1
• r? ?
• Alamouti-type coding
• Introducing a row-interleaver

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INTRODUCING AN INTERLEAVER
A random row interleaver yields
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LINEAR INTERFACE
Metric used
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NONLINEAR INTERFACE
reduce spatial interference
G



L
decoder
L has zero diagonal elements
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NONLINEAR INTERFACE
reduce spatial interference
G



L
decoder
L strictly upper triangular Allows t iterations
? BLAST L with zero diagonal elements ? ITERATIVE
RECEIVER
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BLAST INTERFACE
Use a soft estimate of the transmitted code word
X in the form
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BLAST algorithm step 1
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BLAST algorithm step 1
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BLAST algorithm step 1
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BLAST algorithm step 1
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BLAST algorithm step 2
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ZF BLAST
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ZF BLAST
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MMSE BLAST
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MMSE BLAST
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NONLINEAR ITERATIVE INTERFACE
A



L
decoder
estimate of spatial interference
L has zero diagonal elements L AH -
diag(AH)
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NONLINEAR ITERATIVE INTERFACE
estimate of spatial interference
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CODING FOR NONLINEAR INTERFACES
vertical coding coded symbols are spread across
TX antennas
encoder
. . .
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CODING FOR NONLINEAR INTERFACES
encoder
horizontal coding each TX antenna is encoded
separately
encoder
. . .
encoder
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CODING FOR NONLINEAR INTERFACES
vertical coding no preliminary decisions
available to increase the reliability of symbols
detected and used for cancellation
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CODING FOR NONLINEAR INTERFACES
horizontal coding interference cancellation is
limited by the weakest code
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CODING FOR NONLINEAR INTERFACES

horizontal vertical coding each TX antenna
transmits a subcode of a larger code

encoder
. . .

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SIMULATION RESULTS
(8,4,4) Extended Hamming code
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