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Random Access Success Rate

paraHO - 16th August 2011  (20:20 GMT)

Hi Pix - thanks. Just can't keep away from the forum ;-)

pix - 16th August 2011  (17:04 GMT)

hi paraHO,

glad to see you are still around !


paraHO - 16th August 2011  (12:30 GMT)

'Um' is an acronym for "User Mobile"

pix - 15th August 2011  (08:03 GMT)

Hello and welcome to internet.

Wikipedia / Um interface
"It is called Um because it is the mobile analog to the U interface of ISDN."


Ramlakhan Anvit - 14th August 2011  (23:58 GMT)

Hi all.
What is the meaning of Um interface, thus what does it stands for. I know it interfaces the MS and BTS. But what is the meaning of U and m in Um interface.


pix - 6th March 2008  (16:06 GMT)

you're right, a RACH on a BCCH is not "failed" even though there is a poor BSIC-BCCH plan.

in my opinion, the only problem could be a RACH sent on a BCCH frequency that is used as well few kilometers away. In this situation, the second cell might receive this RACH with a distance > "rach timing advance".

Bilal - 6th March 2008  (14:30 GMT)

Got the answer. But it creates another confusion.

Successful Random Accesses are all except failed random accesses.The failed random access counter is incremented for a Random access received with too high TA, values that are not used or in case of "software file congestion".

That means every RACH attempt with less than max TA and defined cause value is a successful Random Access. But Ericsson says poor BSIC planning can be a cause of bad Random Access Success Rate, how is this? Even a phantom RACH intended for another cell must have a valid cause value and hence it must be treated as a Successful Random Access.Any idea?

Pix - 6th March 2008  (14:12 GMT)

That's the thing, we don't have those in alcatel.

Let's try to guess.. the MS starts with a channel request on RACH, the "Channel Required" reaches the BSC, and then is counted as a "random access attempt".

The BSC sends a Channel Activation to the BTS, if the SDCCH is not congested. Counted as a "SDCCH Request".

The BTS replies with a Channel Activation Ack (not counted)

Then the BSC sends a Immediate Assign Command, counted as a "SDCCH allocated".

Maybe in your formula, this is the ratio CHANNEL ACTIVATION / CHANNEL REQUIRED ?

I really cannot be sure... this indicator is not provided by alcatel. it can be computed manually though.

Bilal - 6th March 2008  (11:59 GMT)

You can give the Alcatel's definition for it, I don't think there will be much difference :)

Pix - 6th March 2008  (11:45 GMT)

you need to find an ericsson guy... i'm the alcatel guy :)

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