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bts: bts_snd_dl_ass(): clarify the meaning of last_rts_fn + 21216 

Change-Id: I8127e17607426443bb95b42873b580fc9f400af9
This commit is contained in:
Vadim Yanitskiy 2022-10-26 20:34:44 +07:00
parent 3547d64061
commit 153cb7f47d
1 changed files with 5 additions and 2 deletions
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src/bts.cpp
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@ -1083,8 +1083,11 @@ void bts_snd_dl_ass(struct gprs_rlcmac_bts *bts, struct gprs_rlcmac_tbf *tbf)
LOGPTBF(tbf, LOGL_INFO, "TX: START Immediate Assignment Downlink (PCH)\n");
bitvec *immediate_assignment = bitvec_alloc(22, tall_pcu_ctx); /* without plen */
bitvec_unhex(immediate_assignment, DUMMY_VEC); /* standard '2B'O padding */
/* use request reference that has maximum distance to current time,
* so the assignment will not conflict with possible RACH requests. */
/* 3GPP TS 44.018, section 9.1.18.0d states that the network shall code the
* Request Reference IE, e.g. by using a suitably offset frame number, such
* that the resource reference cannot be confused with any CHANNEL REQUEST
* message sent by a mobile station. Use last_rts_fn + 21216 (16 TDMA
* super-frame periods, or ~21.3 seconds) to achieve a decent distance. */
LOGP(DRLCMAC, LOGL_DEBUG, " - TRX=%d (%d) TS=%d TA=%d\n",
trx_no, tbf->trx->arfcn, ts_no, tbf->ta());
plen = Encoding::write_immediate_assignment(&bts->trx[trx_no].pdch[ts_no],