[Make-wifi-fast] Wiring up a wireless testbed

Bob McMahon bob.mcmahon at broadcom.com
Sat Nov 4 21:56:23 EDT 2017

Also, Ixia is selling a controllable RF system and it's in early stages.
Maybe contact them to see what the market is driving them to build?   My
guess is their asking price will exceed $100K and has huge margins relative
to bill of materials.

One could probably work with telemakus and build a few using their parts
and sell it for cheaper than the IXIA chassis and still make a nice profit.


On Sat, Nov 4, 2017 at 6:50 PM, Bob McMahon <bob.mcmahon at broadcom.com>

> Try telemakus <http://www.telemakus.com/> for variable attenuators and
> variable phase shifters.    Aeroflex works well to though are a bit more
> expensive, e.g. the 8331
> <http://weinschel.apitech.com/weinschel/pdfiles/wmod8331.pdf> is an
> example
> Power dividers, splitter/combiners and butler matrix devices are sold by
> multiple vendors.  Prices will vary. Unfortunately, prices aren't super
> low.  But usually it's worth the extra money to get a reliable and
> controllable test bed, particularly when one values their time into the
> equation.
> Bob
> On Sat, Nov 4, 2017 at 2:48 PM, Toke Høiland-Jørgensen <toke at toke.dk>
> wrote:
>> Bob McMahon <bob.mcmahon at broadcom.com> writes:
>> > A way I think about is to emulate the "system" in both range/power
>> > (attenuation) and in mixing (phase shifts)   It's a diagonal matrix for
>> > range feeding into an h-matrix for the mixing.  A butler matrix can be
>> used
>> > for the latter if variable phase control isn't required, e.g. you don't
>> > care about spatial stream relative powers.
>> >
>> > On adding energy for "random" noise, some knobs of concern are the
>> energy
>> > detect on the tx and signal floor for the rx.   These sources can be fed
>> > into the same h-matrix through their own d-matrices.  This won't replace
>> > field tests but helps get closer towards that while providing for repeat
>> > ability.
>> What equipment would it take to do something like that?
>> > Also, equally important by my judgment, though not related to wireless,
>> is
>> > to synchronize the clocks on the PCs.  An oven controlled oscillator and
>> > PTP works well towards that goal.
>> Yeah, already using PTP in my testbed; quite essential for measuring
>> one-way delay.
>> -Toke
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