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Bug #4966
openosmo-pcu: gprs+egprs multiplex: Allow selecting original 8-PSK dl block during retransmission for GMSK-required DL block
Status:
New
Priority:
Normal
Assignee:
-
Target version:
-
Start date:
01/21/2021
Due date:
% Done:
0%
Spec Reference:
Description
DUring GPRS+EGPRS multiplexing on a PDCH, if a GPRS-only phone is using the PDCH, there a re some constraints that must be followed by the PCU scheduler so that they are able to receive the DL blocks. That is namely:
- At least 1 GMSK block must be sent every 18th block
- If USF targes the GPRS-only phone, GMSK must be used
That means, for instance, when the scheduler looks for a GMSK DL block candidate to sent (due to above restrictions), it skips selecting DL blocks for TBFs which are waiting for retransmission of 8PSK blocks (MCS>4), meaning it may end up sending a Dummy Block sometimes.
Under that circumstances, we should do a 2nd pass over the TBFs and downgrade the ready-to-be-transmitted 8PSK DL block to a MCS of the same family which is MCS <= 4), that is, in practice, splitting the data in 2 blocks containing same BSN but different SPB to identify first/second subblocks.
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