Summary of osmo-pcu failures/defects

Andreas Eversberg andreas at
Wed Nov 27 08:06:00 UTC 2013

Holger Hans Peter Freyther wrote:
> Are you referring to "Acknowledge state array V(B) for GPRS
> TBF Mode"?
yes, the protocol sends all unacknowledged blocks in a loop until all
blocks are acknowledged and the tbf is complete.
> With statistics in place it appears that for CS4 close to 50% of the
> sent RLC blocks are re-sends. Is that what you expected when implementing
> it?
if there is a continuous download (opening a web page), there should be
almost no re-sends unless the window stalls or the download is complete.
in case of a ping with several small tbfs, there are re-sends due to the
delay between PCU and the radio interface: the PCU sends the final block
of a tbf (polling bit set) and then waits for PACKET DOWNLINK ACK/NACK.
higher delay will cause more re-sends for each tbf at the end, so
smaller tbf will cause more percentage of re-sends.

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