[ibis-macro] Re: Updated AMI Flow BIRD
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: <ibis-macro@xxxxxxxxxxxxx>
- Date: Wed, 29 Sep 2010 08:40:04 -0700
Ambrish,
First of all, I do not want to start entertaining multiple
versions of the draft in parallel, because we will lose
track of who changed what and things will go out of hand
very quickly. Let's please respond to each other's
suggestions before proposing another iteration of the
draft.
On the technical note, here are the technical problems I
have with this latest version of your draft:
1) The discussion under Step 3 explains what the two of
many options the EDA tool has when Tx GetWave_Exists=true
and Tx Init_Returns_Impulse=true (and when the Rx Init
contains an optimizer which we don't know since there
is no indicator for that). The second option states that
"In this case, the output of Step 3 will include only the
impulse response of the Rx filter." This discussion doesn't
mention any dependency on Rx GetWave_Exists. If you study
the flow diagram on slide 17 of Todd's presentation:
http://www.vhdl.org/pub/ibis/macromodel_wip/archive/20100713/toddwesterh
off/IBIS-AMI%20Flows/Flows_July2010-v2.pdf
you will notice that the deconvolution is only needed when
Rx GetWave_Exists is false. Since there is no mention of
this in the discussion under Step 3, you are instructing
the innocent reader to execute this deconvolution in
situations when it is really not needed.
2) Consider the case when Tx Init_Returns_Impulse=false
(and Tx GetWave_Exists=true). The whole discussion under
Step 3 does not apply, since there is no double counting.
So we would take the output of Step 3 as is for Step 6b.
In this case the output of Step 3 contains the channel
impulse response and the Rx filter. However we are doing
Step 5a in this case, which in your version says that:
"The output of Step 5a is convolved with the output of
Step 1 by the simulation platform." Recall that Step 1
is the channel impulse response, which is already present
in Step 3. A software implementation following these
instructions will generate incorrect results.
3) Editorial and specification clarity comments:
- The organization of the discussion of the various conditions
of Tx and Rx GetWave_Exists is sprinkled out in too many places
in this reference flow. It is very hard to keep track of what
the conditions are in the various steps and what to do as a result.
There is mention of Tx GetWave_Exists in Steps 3, 5a, 5b. There
is mention of Rx GetWave_Exists in Steps 5b, 6a, 6b. There is
implicit mention of Tx Init_Returns_Impulse in Step 3. I find
that it would be a lot easier to follow the discussion if these
conditions would be collected and discussed in one place all
together like I did it in my draft. That way the reader gets
a clear mental image of a 2x2 truth table.
- The first part of Step 5b talks about Tx GetWave_Exists=false
without mentioning Rx GetWave_Exists, which implies
that Rx GetWave_Exists can have any value. On the other
hand, the second part of 5b talks about what to do when
Rx GetWave_Exists is false, which implies that Step 5a is
only valid when Rx GetWave_Exists=true. Such language sounds
a little childish to me...
Thanks,
Arpad
==========================================================
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Ambrish Varma
Sent: Wednesday, September 29, 2010 8:17 AM
To: 'Fangyi Rao'; ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Updated AMI Flow BIRD
Hi Fangyi,
Sorry about that - You are correct. It was a result of a slight
oversight on my part.
I have fixed the wordings to correctly represent the scenario now.
Please let me know if there are any issues with this version.
Thanks,
Ambrish.
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com
-----Original Message-----
From: fangyi_rao@xxxxxxxxxxx [mailto:fangyi_rao@xxxxxxxxxxx]
Sent: Tuesday, September 28, 2010 7:46 PM
To: Ambrish Varma; ibis-macro@xxxxxxxxxxxxx
Subject: RE: [ibis-macro] Re: Updated AMI Flow BIRD
Hi, Ambrish;
Can you explain to me how the double-counting of channel impulse
response is fixed? Take the case Tx_GetWave_Exists=False and
Rx_GetWave_Exists=False.
Step 1 output: h_AC
Step 3 output: h_TE*h_AC*h_RE
Step 4 output: p(t) (bit stream)
Step 5b output: h_AC*p(t)
(new sentence "if Rx GetWave_Exists is also False, the output of Step 4
is convolved with the output of Step 1" you add to 5b.)
Step 6b: h_AC*p(t) * h_TE*h_AC*h_RE
("If the Rx GetWave_Exists is False, the output of Step 5 is convolved
with the output of Step 3")
So h_AC is counted twice. Did I miss something?
Thanks,
Fangyi
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Ambrish Varma
Sent: Tuesday, September 28, 2010 2:41 PM
To: IBIS-ATM
Subject: [ibis-macro] Re: Updated AMI Flow BIRD
Fangyi,
Thanks for pointing out the double counting in step 6 in section 3.2
during the call. I have added a sentence in step 5b that should fix the
issue. Please let me know if it addresses the issue you have raised.
Thanks,
Ambrish.
Ambrish Varma | Member of Consulting Staff
P: 978.262.6431 www.cadence.com
-----Original Message-----
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Monday, September 27, 2010 10:30 AM
To: IBIS-ATM
Subject: [ibis-macro] Re: Updated AMI Flow BIRD
Hello everyone,
In the attached version of the flow BIRD draft I added a few items at
the end to remove all mention of Use_Init_Output from the spec, and
added Walter's note below to the "Analysis path/data/that led to
specification" section. Please review this draft and lets vote
tomorrow.
Thanks,
Arpad
===============================================================
________________________________
From: Walter Katz [mailto:wkatz@xxxxxxxxxx]
Sent: Friday, September 24, 2010 1:32 PM
To: Muranyi, Arpad; IBIS-ATM
Subject: RE: [ibis-macro] Re: Updated AMI Flow BIRD
Arpad,
I think in the case of Use_Init_Output, we should remove all references
to Use_Init_Output in the body of the final 5.1 Version, and add
something like the following in a new IBIS Deprecation Section:
The parameter Use_Init_Output was an optional reserved parameter in IBIS
5.0. The use of Use_Init_Output has been deprecated in IBIS 5.1, and EDA
tools shall ignore the value of Use_Init_Output, and assume that models
operate according to the flows as described in IBIS 5.1. In IBIS 5.0,
Use_Init_Output only had application to time domain flows in conjunction
with dual models (Init_Returns_Impulse=True, and GetWave_Exists=True).
Existing dual models that assumed the logic of Use_init_Ouput=True as
specified in IBIS 5.0 may not work properly in the flows documented in
IBIS 5.1.
Walter
Walter Katz
303.449-2308
Mobile 303.883-2120
wkatz@xxxxxxxxxx
www.sisoft.com
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