Cellular Network Infrastructure » Radio Access Network » OsmoBTS

I have noticed that after changing BS-AG-BLKS-RES configuration from 1 to 2 or 3 from Osmo-NITB. The DSP starts to complain about unexpected burst as shown below.

[ERROR] : GsmL1_PhDataReq() : Unexpected burst (Invalid sapi) [Sapi = 6, Expected = 7]
[ERROR] : GsmL1_PhDataReq() : Unexpected burst (Invalid sapi) [Sapi = 6, Expected = 7]
[ERROR] : GsmL1_PhDataReq() : Unexpected burst (Invalid sapi) [Sapi = 6, Expected = 7]
[ERROR] : GsmL1_PhDataReq() : Unexpected burst (Invalid sapi) [Sapi = 6, Expected = 7]
[ERROR] : GsmL1_PhDataReq() : Unexpected burst (Invalid sapi) [Sapi = 6, Expected = 7]

Looking at ph_date_req function in src/osmo-bts-litecell15/l1_if.c, one can clearly see that the BTS always uses B0 for AGCH SAPI (line 392) leading to the DSP complaints about wrong SAPI for AGCH.

According to GSM 05.02, Section 7 Table 5 of 5, the number of blocks used AGCH must change according to BS-AG-BLKS-RES requested from BSC.