RE: stds-80220-requirements: Max Tolerable Delay Spread, 4.2.3
All,
My initial question was to seek a valid rationale for establishing a Maximum
Tolerable
Delay Spread (MTDS) as a specific, standalone requirement and not to
question whether it should
be a basis for evaluating various MBWA proposals. As Khurram mentioned,
their studies
have shown that there are some, though few, scenarios where the delay spread
can be in
excess of 5 microseconds. So, if Neka's proposal was accepted, I assume
that addressing
those scenarios wouldn't be a requirement for an MBWA AI. The Channel
Modelling CG is
considering different environments that have will have different profiles
for delay spread. Ultimately, this will feed into the evaluation criteria
and the various MBWA proposals will be
assessed based on their performance in these different environments. So, I
don't see that
it is necessary for a specific MTDS requirement to be established in the
Requirements document
because it will be included in the evaluation criteria as a consequence of
the channel modelling
work.
Fundamentally, I agree with Bob Love's point (and Jim Mollenaur's prior
presenation) about
the benefit establishing simple requirements. Moreover, philosophically
speaking, I believe
the requirements document should be written at a high enough level to
capture the essential
requirements in a way that is meaningful to a broad audience. My personal
litmus test for
what should be in the requirements document is whether it is essential to
the definition of
the MBWA AI, whether it is "visible" to the end customer or operator, and
whether it would not
otherwise naturally flow from another higher level requirement.
Requirements on specific parameters
that flow from higher level requirements would become a part of the
evaluation criteria within the
context of there necessity to support the higher level requirement. For
example, setting a
requirement of 5 microseconds for MTDS in the requirements document is not
as meaningful as
having it flow out of the work on channel models that would establish that
this is a necessary requirement for the MBWA to perform successfully in a
specific operational scenario.
In summary, I believe that it would be more appropriate for the MTDS, and
other such parameters,
to be addressed in the context of channel modelling and the evaluation
criteria, and not in the
Requirements Document. This allows all proposals to be assessed subsequently
on a common basis in a meaningful context.
Best regards,
Joanne
-----Original Message-----
From: Sheikh, Khurram P [GMG] [mailto:khurram.p.sheikh@mail.sprint.com]
Sent: Wednesday, July 30, 2003 1:15 PM
To: Neka Hicks; Joanne Wilson
Cc: Stds-80220-Requirements (E-mail)
Subject: RE: stds-80220-requirements: Max Tolerable Delay Spread, 4.2.3
Neka
I agree with your rationale and max tolerable delay is an important
parameter quantifying our statement for support of the different
environments for an MBWA system.
I know the channel modeling experts group will come up with the channel
models complying with the requirement of support of the system in
different environments i.e. urban, suburban rural etc. Can anyone from
that group give insight as to what would be the max tolerable delay
spread for the scenarios in the requirements document?
In our testing at Sprint, we have seen delay spreads in excess of 5
microseconds in some cases (although the percentage of those channels is
very small).
Thanks
Khurram P. Sheikh
Chief Technology Advisor
Sprint- Broadband Wireless
Tel (SM): 650-513-2056
Tel(KC): 913-762-1645
Mobile: 650-906-8989
khurram.p.sheikh@mail.sprint.com
-----Original Message-----
From: Neka Hicks [mailto:nhicks@Clearwire.com]
Sent: Wednesday, July 30, 2003 9:11 AM
To: 'Joanne Wilson'
Cc: Stds-80220-Requirements (E-mail)
Subject: RE: stds-80220-requirements: Max Tolerable Delay Spread, 4.2.3
Joanne,
Several contributions from participants in the channel modeling group
have
included proposed channel models for different environments including
rural,
suburban, and urban/dense-urban. Urban/dense-urban channel models
reflect
the highest delay spread, and 5 micro-seconds is typically accepted as a
suitable value for this type of environment. If the system is going to
work
under these conditions, then it must be able to tolerate a delay spread
of
atleast 5 micro-seconds.
-----Original Message-----
From: Joanne Wilson [mailto:joanne@arraycomm.com]
Sent: Tuesday, July 29, 2003 5:24 PM
To: Neka Hicks; Stds-80220-Requirements (E-mail)
Subject: RE: stds-80220-requirements: Max Tolerable Delay Spread, 4.2.3
Neka,
You have provided a rationale for your proposal,
"The maximum tolerable delay spread should be specified so that
it
can be
determined whether various vendor proposals can meet this
criteria."
which I don't believe to be a valid reason for establishing such a
requirement.
Can you provide any other reasoning for this proposal? I would expect
the
rationale to explain why such a requirement would be essential for the
802.20 MBWA
to achieve it performance objectives.
Best regards,
Joanne Wilson
ArrayComm, Inc.
joanne@arraycomm.com
-----Original Message-----
From: owner-stds-80220-requirements@majordomo.ieee.org
[mailto:owner-stds-80220-requirements@majordomo.ieee.org]On Behalf Of
Neka Hicks
Sent: Tuesday, July 29, 2003 3:19 PM
To: Stds-80220-Requirements (E-mail)
Subject: stds-80220-requirements: Max Tolerable Delay Spread, 4.2.3
All,
Here's a contribution regarding max tolerable delay spread:
<<clearwire contribution 072803 - max tolerable delay spread.doc>>
Neka C. Hicks
Director of Network Engineering
Clearwire Technologies
469-737-7555 (office)
817-706-2548 (cell)