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Re: stds-80220-ch-models: Delay-spread limitation


I'm not sure I fully understood the discussion which resulted in this proposed power
delay profile.  Could someone please clarify what this proposed power delay profile
would be used for?    (Thanks in advance.)

If the resulting profile is to be used as a starting point for our channel models, then
I'm not sure this is the right way to proceed. Simply deleting the taps beyond a
particular delay value would seem to violate the spirit of sticking with power delay
profiles that were derived based on large amounts of measured data.   The delay and
power values of this particular ITU model were characteristic of the measured vehicular
channels on which the model was based.  Real channels having no taps beyond 10usec would
probably have a different power delay profile than the proposed modified profile.
Therefore, there really is no scientific basis for using the proposed truncated profile
as the starting point for our channel models.   Deleting taps based on a relative power
threshold might make (somewhat) more sense to me, but that is obviously not what's being
done here.  (The deleted tap 4 has more power than the retained tap 3.)

On the other hand, if the idea here is to generate the specifics of a delay spread
requirement for the requirements document, does it make sense to have a specific power
delay profile for such a requirement (given that our MBWA channel models are not yet
specified)?   Wouldn't it be awkward to have one power delay profile in the requirements
document (for the delay spread requirement) and a different profile (or set of profiles)
in the channel modeling document?  Isn't there a better way of stating the requirement
that the MBWA system must operate well in terrestrial delay spread environments?

Best Regards,

- Fred

Fred W. Vook -- Motorola Labs -- Communication Systems Research Laboratory
1301 E. Algonquin Road, IL02-2912,  Schaumburg, IL  60196  USA

Marianna Goldhammer wrote:

> Hi,
> In support of 10us max. delay (Khurram proposal), following the
>  discussion in the Channel Models teleconference, here is the
> proposed modification of Vehicular Channel Model B, from ITU-R
> Rec. M-1225, page 28:
> - keep tap 1:                               0ns, -2.5dB
> - keep tap 2:                           300ns, 0dB
> - keep tap 3:                        8 900ns, -12.8dB
> - delete tap 4:                    12 900ns, -10dB
> - delete tap 5:                    17 100ns, -25.2dB
> - delete tap 6:                    20 000ns, -16dB
> Kind Regards,
> Marianna
>       Marianna Goldhammer
>       Director - Strategic Technologies
>     Alvarion, Ltd.
> 10 years of wireless expertise
>        21 HaBarzel Street
>        P.O.Box 13139, Tel Aviv 61131, Israel
>        Tel: (972)- 3 -6456241/6262
>        Fax: (972) -3 -6456204
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