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Feature #6131

closed

Feature #5500: MS-Side GPRS RLC/MAC implementation

modem: Implement pkt-access-procedure retransmission

Added by pespin 7 months ago. Updated 5 months ago.

Status:
Resolved
Priority:
Normal
Assignee:
Category:
OsmocomBB modem (host)
Target version:
Start date:
08/02/2023
Due date:
% Done:

100%

Resolution:
Spec Reference:
Tags:

Description

Right now, RLC/MAC sends primitive L1CTL-RACH.request to lower layers to initiate a pkt-access-procedure. Lower layers (modem app, l1ctl) are in charge of doing the pkt-acces-procedure details, like RACH.req retransmission, or submit a failure to upper layers if all retransmission fail and no answer is received.

This is already implemented in "mobile" app around ./src/mobile/gsm48_rr.c.

We need to port some of that code to newer osmocom infra and put it in src/common/, so that it can be used by "modem" app and in the future also reused by mobile.

Actions #1

Updated by fixeria 6 months ago

  • Tags set to ARDC
  • Category changed from OsmocomBB Layer 3 (RR/MM/CC) to OsmocomBB modem (host)
  • Target version set to MS-side GPRS
Actions #2

Updated by fixeria 5 months ago

  • Status changed from New to In Progress
Actions #3

Updated by fixeria 5 months ago

  • Status changed from In Progress to Feedback
  • % Done changed from 0 to 80

We had a Jitsi call with pespin today, during which we agreed on the approach and found out that libosmo-gprs needs to be modified to not expect a specific RA, because it does change during retransmissions. I have implemented the actual retransmission as an additional state of the GRR-FSM, not employing the existing logic we have in gsm48_rr.c. The reason is that this would require a lot of refactoring and quite some integrating effort, so we better postpone this for later.

https://gerrit.osmocom.org/c/libosmo-gprs/+/34512 rlcmac: deal with RACH retransmissions (drop rach_req_ra) [NEW]
https://gerrit.osmocom.org/c/osmocom-bb/+/34513 modem: grr: clarify a comment in forward_to_rlcmac() [NEW]
https://gerrit.osmocom.org/c/osmocom-bb/+/34514 modem: grr: implement RACH.req retransmission [NEW]

Actions #4

Updated by fixeria 5 months ago

  • Status changed from Feedback to Resolved
  • % Done changed from 80 to 100

All patches have been merged.

Actions #5

Updated by fixeria 5 months ago

Found a problem while testing, fixed here:

https://gerrit.osmocom.org/c/osmocom-bb/+/34534 modem: fix grr_st_packet_access_action(): shift rr->cr_hist properly

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