surrey dl 2

1-1 Asahidai, Nomi, Ishikawa 923-1292, Japanhttp://www.jaist.ac.jp/is/labs/matsumoto-lab

Tad Matsumoto, Fellow, IEEEVisiting Fellow, Royal Academy of Engineering in UK

Japan Advanced Institute of Science and Technology (JAIST)[email protected]

Paradigm Shift in Turbo Processing:From P2P to Networks

Centre for Wireless Communications, University of [email protected]

P.O.Box 4500, University of Oulu FIN-90014, FINLAND

School of Information Science

Symbol Duration T

･･･

･･･

τ1G

･･･

･･･

τ

First path

Last Path

2G

τ

･･

･･

3Gτ<<T No inter-symbol interference (ISI)

τ≒T only minor ISI τ>>T Severe ISI

Single Carrier Signaling：Time Domain Behavior

Tx Rx

Delay Spread τ

“0” “1” “1” “0”

“0” “1” “1” “0”

“0” “1” “1” “0”

“0” “1” “1” “0”

Characterized by Multipath Propagation

School of Information Science

Single carrier signaling is Green!:The number of the signal points increases exponentially!

What happens if there are a lot more multipath components?

Single Carrier Signaling：Time Domain Behavior

2 x 2 MIMO setup QPSK signal transmitted over 20 pathpropagation channel!

Principle of MIMO SC-MMSE Turbo equalization

Soft symbols constructed from decoder feedback

s

[ ])(2 kbλ

[ ])(1 kbλ

Block-wise Time Domain MIMO SC-MMSE Equalizer: My 2002 Equation

wherediag denotes a diagonal matrix constructed by its argument elements

Computational complexity is dominated by the matrix inversion Σ−1.

Tx antennaSoft symbols constructed from decoder feedback

Covariance of the soft cancellation output

[ ] [ ]{ }22 ˆ)ˆ)(ˆ( ssEdiagssssE H −=−−=Λ

Complexity: O[N3(L+K)3]Problematic!!!

Soft Cancellation Output

Frame Length

Number of Receive AntennasPath Length

Finally, the equalizer output vector is given by:

Diagonal Block

By Exploiting Beneficial Properties of Frequency Domain Processing, it Ends up with

My 2005 Equation (Green!!!)

( )[ ]FΞIΔΞΞΞFΓ fm

fHffHm

Hm diag 12 −

+≈ σ

(2x2 MIMO)

Now, analysis, including EXIT analysis, is EASY!

Number of Users = U, Each user uses 2 Tx antennas and Rx uses 4 antenns.(Multi-user MIMO) Frame length = 512

Complexity is at a logarithm order of the frame length K and is Independent of the

Path Number L!

2002

2005