19 Apr
2010
19 Apr
'10
3:40 p.m.
Even if two MS collide with the same random number at the same time,
and one RACH burst overpowers the other enough to be detected and
decoded, the L2 contention resolution procedure will usually prevent
a complete failure, at lease for one of the MS.
On Apr 18, 2010, at 11:14 PM, Dieter Spaar wrote:
Hello Holger,
On Mon, 19 Apr 2010 12:37:12 +0800, "Holger Freyther"
<zecke(a)selfish.org> wrote:
David A. Burgess
Kestrel Signal Processing, Inc.
The other problem is with the 20 paging requests every two seconds
I'm
creating a RACH DoS for my BTS to a point that I think (didn't
bother to
do the easy math, and I don't have the spec here right now) we
have two
MS picking the same random number. At least the symptom is that
even if
we assign a channel, it gets closed down with a RF Failure.
I wonder how frequently it happens with 20 MS that a RACH is sent
on the
same frame and with the same random number. There are at least 16
possible
random numbers for the "Answere to Paging" Channel Request and
there are
27 frames in the MF to chooses from (in the "Combined Configuration").
Do you use the same phones for testing and does the RF Failure happen
frequently (this probably would mean a bad random number generator in
this phone firmware) ? Also I would expect that two RACH burst will
disturb each other, at least in a testing environment where all the
MS have the same distance to the BTS and send with the same power.
Best regards,
Dieter
--
Dieter Spaar, Germany
spaar(a)mirider.augusta.de