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RE: [10GBASE-T] question about the complexity reduction of MIMO


A few points of clarification:

Chart 20 considers only echo and next and is based on SISO processing, which is not our proposal.  Throwing in fext cancellation and equalizers makes the complexity higher.  So, I agree with you, it would be difficult to justify feasibility with this type of architecture, hence the need to be clever.

After discussing things like MIMO, MUD and parallel structures, chart 25 compares the complexity of the proposal with 1000BASE-T accounting for all the major receiver blocks.  Personally, a 6x increase in complexity for a 10x increase in throughput doesn't seem that out of whack given expected technological advances in architectures and algorithms.

I am not sure what your concerns are about the number of PAM levels.  I assume it is word widths.  At most its an extra bit which is a small fraction compared to the multiplier factors we were just considering.  It is a little confusing, though, that you have the distance between constellation points in PAM10 being two while for PAM5, it is one. 


-----Original Message-----
From: Rao, Sailesh []
Sent: Wednesday, January 22, 2003 3:18 PM
To: William Jones; P.J. Sallaway
Subject: RE: [10GBASE-T] question about the complexity reduction of MIMO


	On Page 20 of your January tutorial presentation, you show that the
DSP complexity of the receiver in your proposal will be >40X the DSP
complexity of 1000BASE-T receivers in the market, assuming scalar
operations. It would be very difficult to justify the technical feasibility
of your proposal on this basis.

	On Page 25, you are claiming that there are MIMO realizations
possible that would render the complexity of the Matrix-Vector
multiplication (with a 4X4 matrix, and a 4X1 vector) needed for your
receiver to be equal to 1.5X that of a 1000BASE-T scalar operation, and
therefore the DSP complexity of your receiver is only 6X that of commercial
1000BASE-T receivers. Aside from the matrix-scalar distinction, since the
4X1 vector in your receiver uses 4 10-level symbols ranging over [-9, +9]
and since the 1000BASE-T scalar uses 5-level symbols ranging over [-2, +2],
this appears too good to be true.

	Can you please clarify your claims? 


-----Original Message-----
From: William Jones [] 
Sent: Tuesday, January 21, 2003 10:10 PM
To: P.J. Sallaway
Subject: RE: [10GBASE-T] question about the complexity reduction of MIMO


Answering your question first, the metric used in the tutorial was

Regarding your comment, I agree that the complexity of a realization is a
concern for the group, but, not the realization itself.  This distinction
avoids excessive consideration for vendor dependent issues which was what I
was trying to get at.  So, I think it is not whether MIMO can achieve a 4x
or 16x reduction, but rather, that there exists at least one possible
realization of a particular technology that can achieve an acceptable level
of complexity. In the tutorial, we made the comparison to a multi-port
1000BASE-T part.  One can then argue feasibility by extension to a realized

This leads to a question for the group.  What strategy or steps are needed
to get to an agreement on technical feasibility?  


-----Original Message-----
From: P.J. Sallaway []
Sent: Tuesday, January 21, 2003 10:24 AM
To: William Jones
Subject: RE: [10GBASE-T] question about the complexity reduction of MIMO


I believe the complexity of a practical realization is important to the
group as we look at the feasibility of 10 gigabits/second over Cat-5 and
the role that different line codes play.

I am curious as to what complexity measure you are using when discussing
the 16x reduction using MIMO.  Is it power dissipation for a given
technology?  Multiplies per second?  Gate count?



On Mon, 2003-01-20 at 13:44, William Jones wrote:
> Xiaopeng
> I would claim the maximum is a 16x reduction.  So, a practical realization
is in the range 4x to 16x.  Our approach is somewhere around 7x.  Note, a
MIMO realization is not unique.  But, this is not a concern for the study
> Bill  
> -----Original Message-----
> From: []
> Sent: Monday, January 20, 2003 10:24 AM
> To: William Jones
> Cc:
> Subject: [10GBASE-T] question about the complexity reduction of MIMO
> Bill,
> I have a quick question about MIMO.  In your presentation, you stated that
> the MIMO architecture can help to reduce the DSP complexity from 10 to
> For a 4x4 MIMO system, the maximum complexity reduction is 4 times if I am
> not wrong.   In this extreme case, a one-channel DSP engine can be reused
> for 4 channels without any modification.  However even in such a case, the
> DSP complexity is still 2.5.
> Xiaopeng
P.J. Sallaway <>
Myrica Networks Inc.