Regression in osmo-pcu with UHD trx ?

Pierre Baudry pierre.baudry at diateam.net
Fri May 27 16:02:28 UTC 2016


Hi all,

I have a Osmocom setup running with a Ettus B200

I noticed that since several weeks that osmo-pcu did not work as good as
previously.

The latest "good" revision I am aware of is commit
d87e1d6ab747423d3668c74d16201a5d967accf0 (2015/12/14)

I tried again today with commit 2fcfc29020c81891d7888ddc7ddbcd866bcd406d
(2016/05/24) and not a single handset could establish data communication

Reading osmo-pcu logs show that T6169 timeouts during TBF assignment :

> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:479 MS requests UL TBF on RACH, so we provide one:
> Fri May 27 15:51:38 2016 DRLCMAC <0002> tbf.cpp:672 ********** TBF starts here **********
> Fri May 27 15:51:38 2016 DRLCMAC <0002> tbf.cpp:674 Allocating UL TBF: MS_CLASS=0/0
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_ms.cpp:114 Creating MS object, TLLI = 0x00000000
> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:407 Searching for first unallocated TFI: TRX=0
> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:417  Found TFI=0.
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:525 Slot Allocation (Algorithm B) for unknown class (assuming 12)
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:560 - Rx=4 Tx=4 Sum Rx+Tx=5  Tta=2 Ttb=1  Tra=2 Trb=1 Type=1
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:157 - Skipping TS 0, because not enabled
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:579 - Possible DL/UL slots: (TS=0)".CCCCCCC"(TS=7)
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:940 - Selected UL slots: (TS=0)"...U...."(TS=7), single
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:966 Using single slot at TS 3 for UL
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:990 - Reserved DL/UL slots: (TS=0)"...C...."(TS=7)
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_rlcmac_ts_alloc.cpp:1017 - Assigning UL TS 3
> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:1481 PDCH(TS 3, TRX 0): Attaching TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=NULL), 1 TBFs, USFs = 01, TFIs = 00000001.
> Fri May 27 15:51:38 2016 DRLCMAC <0002> tbf.cpp:385 - Setting Control TS 3
> Fri May 27 15:51:38 2016 DRLCMAC <0002> gprs_ms.cpp:267 Attaching TBF to MS object, TLLI = 0x00000000, TBF = TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=NULL)
> Fri May 27 15:51:38 2016 DRLCMAC <0002> tbf.cpp:625 Allocated TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=NULL): trx = 0, ul_slots = 08, dl_slots = 00
> Fri May 27 15:51:38 2016 DRLCMAC <0002> ./tbf.h:291 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=NULL) changes state from NULL to FLOW
> Fri May 27 15:51:38 2016 DRLCMAC <0002> tbf.cpp:409 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=FLOW) starting timer 3169.
> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:523 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=FLOW) [UPLINK] START
> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:527 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=FLOW) RX: [PCU <- BTS] RACH qbit-ta=0 ra=0x7b, Fn=1607859 (28,33,19)
> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:529 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=FLOW) TX: START Immediate Assignment Uplink (AGCH)
> Fri May 27 15:51:38 2016 DRLCMAC <0002> bts.cpp:542  - TRX=0 (128) TS=3 TA=0 TSC=3 TFI=0 USF=0
> Fri May 27 15:51:38 2016 DRLCMAC <0002> ./tbf.h:291 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=FLOW) changes state from FLOW to WAIT ASSIGN
> Fri May 27 15:51:43 2016 DRLCMAC <0002> tbf.cpp:819 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=WAIT ASSIGN) timer 3169 expired.
> Fri May 27 15:51:43 2016 DRLCMAC <0002> tbf.cpp:874 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=WAIT ASSIGN) T3169 timeout during transsmission
> Fri May 27 15:51:43 2016 DRLCMAC <0002> tbf.cpp:893 - Assignment was on CCCH
> Fri May 27 15:51:43 2016 DRLCMAC <0002> tbf.cpp:899 - No uplink data received yet
> Fri May 27 15:51:43 2016 DRLCMAC <0002> tbf.cpp:879 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=WAIT ASSIGN) will be freed due to timeout
> Fri May 27 15:51:43 2016 DRLCMAC <0002> tbf.cpp:334 TBF(TFI=0 TLLI=0x00000000 DIR=UL STATE=WAIT ASSIGN) free


Every element of the stack is running with today's revision on master
(cheers for making it happen without specific branches by the way).

With the same setup with
osmo-pcu at d87e1d6ab747423d3668c74d16201a5d967accf0, I get solid data
rates around 40 Kbits/s.

I haven't seen anybody on the mailing list experiencing the same
behavior, making me believe that it could be specific to osmo-bts-trx /
osmo-trx users.

Can somebody confirm or reproduce this attitude ?

I will try to provide more logs and a pcap capture as soon as I get
hands back on the hardware.


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