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CODING FOR MULTIPLE ANTENNAS WITH LINEAR AND NONLINEAR (BLAST) INTERFACES

DIMACS WORKSHOP, OCTOBER 2002

EZIO BIGLIERI(work done with A. Nordio, G. Taricco, and A. Tulino)

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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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H

TX RX

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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

A

Metric used:

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NONLINEAR INTERFACE

G +

L decoder

+ –

reduce spatial interference

L has zero diagonal elements

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NONLINEAR INTERFACE

G +

L decoder

+ –

reduce spatial interference

L strictly upper triangular: Allows t iterations BLASTL with zero diagonal elements ITERATIVE RECEIVER

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Use a soft estimate of the transmitted code word X in the form

BLAST INTERFACE

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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

...encoder

vertical coding:

coded symbols are spread across TX antennas

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...

horizontal coding:

each TX antenna is

encoded separately

encoder

encoder

encoder

CODING FOR NONLINEAR INTERFACES

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...encoder

vertical coding:

no preliminary decisions available

to increase the reliability of symbols

detected and used for cancellation

CODING FOR NONLINEAR INTERFACES

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horizontal coding:

interference cancellation

is limited by the weakest code

...

encoder

encoder

encoder

CODING FOR NONLINEAR INTERFACES

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horizontal + vertical coding:

each TX antenna transmits

a subcode of a larger code

...

encoder

CODING FOR NONLINEAR INTERFACES

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SIMULATION RESULTS

(8,4,4) Extended Hamming code

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