bts: add IMMEDIATE ASSIGNMENT via PCH transmission
In situations where the PCU is co-located to the BSC, the IMMEDIATE ASSIGNMENT
for downlink TBFs must be sent via RSL and the BSC also must instruct the BTS
to transmit the IMMEDIATE ASSIGNMENT via PCH instead of AGCH. Eventually the
BSC must sent a confirmation message (follow-up patch) where the TLLI is used
as an identifer.
This new method will eventually replace the previous method that uses
the MAC block as an identifier. To remain compatible with older versions
of osmo-bsc, we will keep the old method until osmo-bts is migrated as
well.
This patch also requires new features to be added to the PCU socket
interface the version number of the protocol is incremented from 0x0a to
0x0b. Version 0x0a will remain compatible and use the old method, while
version 0x0b will use the new method introduced with this patch.
Change-Id: I2a78651593323e8b9627c39918d949a33497b70f
Related: OS#5198
diff --git a/src/bts.cpp b/src/bts.cpp
index 33ad4a6..504ba27 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -1103,7 +1103,6 @@
void bts_snd_dl_ass(struct gprs_rlcmac_bts *bts, const struct gprs_rlcmac_dl_tbf *tbf)
{
- uint16_t pgroup = ms_paging_group(tbf_ms(tbf));
int plen;
const struct gprs_rlcmac_pdch *pdch;
@@ -1129,7 +1128,10 @@
GSM_L1_BURST_TYPE_ACCESS_0);
if (plen >= 0) {
bts_do_rate_ctr_inc(bts, CTR_IMMEDIATE_ASSIGN_DL_TBF);
- pcu_l1if_tx_pch(bts, immediate_assignment, plen, pgroup);
+ if (the_pcu->pcu_if_version >= 0x0b)
+ pcu_l1if_tx_pch_dt(bts, immediate_assignment, plen, tbf->imsi(), tbf->tlli());
+ else
+ pcu_l1if_tx_pch(bts, immediate_assignment, plen, ms_paging_group(tbf_ms(tbf)));
}
bitvec_free(immediate_assignment);
diff --git a/src/gprs_pcu.h b/src/gprs_pcu.h
index a9e40ea..ca52c30 100644
--- a/src/gprs_pcu.h
+++ b/src/gprs_pcu.h
@@ -134,6 +134,8 @@
struct si_cache *si_cache; /* ARFC+BSIC -> CGI PS cache */
struct osmo_timer_list update_stats_timer; /* Used to update some time_cc stats periodically */
+
+ uint8_t pcu_if_version;
};
diff --git a/src/pcu_l1_if.cpp b/src/pcu_l1_if.cpp
index 6c4ed22..14cc778 100644
--- a/src/pcu_l1_if.cpp
+++ b/src/pcu_l1_if.cpp
@@ -294,6 +294,24 @@
pcu_tx_data_req(bts, 0, 0, PCU_IF_SAPI_PCH, 0, 0, 0, data, sizeof(data));
}
+/* Send a block via the paging channel and require a confirmation by the receiving end */
+void pcu_l1if_tx_pch_dt(struct gprs_rlcmac_bts *bts, bitvec *block, int plen, const char *imsi, uint32_t tlli)
+{
+ /* NOTE: This is in practice only used to transmit IMMEDIATE ASSIGNMENT messages through the paging channel and
+ * it is not guaranteed to work with other message types. The prepended TLLI will be used as an identifier in
+ * the confirmation message. */
+
+ struct gsm_pcu_if_pch_dt pch_dt;
+
+ pch_dt.tlli = tlli;
+ strcpy(pch_dt.imsi, imsi);
+
+ pch_dt.data[0] = (plen << 2) | 0x01;
+ bitvec_pack(block, pch_dt.data + 1);
+
+ pcu_tx_data_req(bts, 0, 0, PCU_IF_SAPI_PCH_DT, 0, 0, 0, (uint8_t*)&pch_dt, sizeof(pch_dt));
+}
+
int pcu_tx_neigh_addr_res_req(struct gprs_rlcmac_bts *bts, const struct neigh_cache_entry_key *neigh_key)
{
struct msgb *msg;
@@ -734,14 +752,22 @@
if (llist_count(&the_pcu->bts_list) > 1)
LOGP(DL1IF, LOGL_ERROR, "more than one BTS regsitered at this PCU. This PCU has only been tested with one BTS! OS#5930\n");
- if (info_ind->version != PCU_IF_VERSION) {
- fprintf(stderr, "PCU interface version number of BTS (%u) is "
- "different (%u).\nPlease re-compile!\n",
+ LOGP(DL1IF, LOGL_DEBUG, "Info indication received:\n");
+
+ /* NOTE: The classic way to confirm an IMMEDIATE assignment is to send the whole MAC block payload back to the
+ * PCU. So it is the MAC block itsself that serves a reference for the confirmation. This method has certain
+ * disadvantages so it was replaced with a method that uses the TLLI as a reference ("Direct TLLI"). This new
+ * method will replace the old one. The code that handles the old method will be removed in the foreseeable
+ * future. (see also OS#5927) */
+ if (info_ind->version == 0x0a) {
+ LOGP(DL1IF, LOGL_NOTICE, "PCUIF version 10 is deprecated. OS#5927\n");
+ } else if (info_ind->version != PCU_IF_VERSION) {
+ fprintf(stderr, "PCU interface version number of BTS/BSC (%u) is different (%u).\nPlease use a BTS/BSC with a compatble interface!\n",
info_ind->version, PCU_IF_VERSION);
exit(-1);
}
- LOGP(DL1IF, LOGL_DEBUG, "Info indication received:\n");
+ the_pcu->pcu_if_version = info_ind->version;
if (!(info_ind->flags & PCU_IF_FLAG_ACTIVE)) {
LOGP(DL1IF, LOGL_NOTICE, "BTS not available\n");
diff --git a/src/pcu_l1_if.h b/src/pcu_l1_if.h
index e7080d5..1827d84 100644
--- a/src/pcu_l1_if.h
+++ b/src/pcu_l1_if.h
@@ -149,6 +149,7 @@
void pcu_l1if_tx_agch(struct gprs_rlcmac_bts *bts, bitvec *block, int len);
void pcu_l1if_tx_pch(struct gprs_rlcmac_bts *bts, bitvec *block, int plen, uint16_t pgroup);
+void pcu_l1if_tx_pch_dt(struct gprs_rlcmac_bts *bts, bitvec *block, int plen, const char *imsi, uint32_t tlli);
#endif
#ifdef __cplusplus