Add support for Access Control Class ramping.

Access Control Class (ACC) ramping is used to slowly make the cell
available to an increasing number of MS. This avoids overload at
startup time in cases where a lot of MS would discover the new
cell and try to connect to it all at once.

Ramping behaviour can be configured with new VTY commands:

  [no] access-control-class-ramping
  access-control-class-ramping-step-interval (<30-600>|dynamic)
  access-control-class-ramping-step-size (<1-10>)

(The minimum and maximum values for these parameters are hard-coded,
but could be changed if they are found to be inadequate.)

The VTY command 'show bts' has been extended to display the
current ACC ramping configuration.

By default, ACC ramping is disabled.

When enabled, the default behaviour is to enable one ACC per
ramping step with a 'dynamic' step interval. This means the
ramping interval (time between steps) is scaled to the channel
load average of the BTS, i.e. the number of used vs. available
channels measured over a certain amount of time.

Below is an example of debug log output with ACC ramping enabled,
while many 'mobile' programs are concurrently trying to connect
to the network via an osmo-bts-virtual BTS. Initially, all ACCs
are barred, and then only one class is allowed. Then the current
BTS channel load average is consulted for scheduling the next
ramping step. While the channel load average is low, ramping
proceeds faster, and while it is is high, ramping proceeds slower:

(bts=0) ACC RAMP: barring Access Control Class 0
(bts=0) ACC RAMP: barring Access Control Class 1
(bts=0) ACC RAMP: barring Access Control Class 2
(bts=0) ACC RAMP: barring Access Control Class 3
(bts=0) ACC RAMP: barring Access Control Class 4
(bts=0) ACC RAMP: barring Access Control Class 5
(bts=0) ACC RAMP: barring Access Control Class 6
(bts=0) ACC RAMP: barring Access Control Class 7
(bts=0) ACC RAMP: barring Access Control Class 8
(bts=0) ACC RAMP: barring Access Control Class 9
(bts=0) ACC RAMP: allowing Access Control Class 0
(bts=0) ACC RAMP: step interval set to 30 seconds based on 0% channel load average
(bts=0) ACC RAMP: allowing Access Control Class 1
(bts=0) ACC RAMP: step interval set to 354 seconds based on 59% channel load average
(bts=0) ACC RAMP: allowing Access Control Class 2
(bts=0) ACC RAMP: step interval set to 30 seconds based on 0% channel load average
(bts=0) ACC RAMP: allowing Access Control Class 3
(bts=0) ACC RAMP: step interval set to 30 seconds based on 0% channel load average

Change-Id: I0a5ac3a08f992f326435944f17e0a9171911afb0
Related: OS#2591

1 files changed, 113 insertions, 0 deletions

diff --git a/src/libbsc/bsc_vty.c b/src/libbsc/bsc_vty.c
index 36c849d5e..5ff9cb258 100644
--- a/src/libbsc/bsc_vty.c
+++ b/src/libbsc/bsc_vty.c
@@ -60,6 +60,7 @@
 #include <osmocom/bsc/handover_cfg.h>
 #include <osmocom/bsc/handover_vty.h>
 #include <osmocom/bsc/gsm_04_08_utils.h>
+#include <osmocom/bsc/acc_ramp.h>
 
 #include <inttypes.h>
 
@@ -343,6 +344,18 @@ static void bts_dump_vty(struct vty *vty, struct gsm_bts *bts)
 		VTY_NEWLINE);
 	vty_out(vty, "  Cell Reselection Hysteresis: %u dBm%s",
 		bts->si_common.cell_sel_par.cell_resel_hyst*2, VTY_NEWLINE);
+	vty_out(vty, "  Access Control Class ramping: %senabled%s",
+		acc_ramp_is_enabled(&bts->acc_ramp) ? "" : "not ", VTY_NEWLINE);
+	if (acc_ramp_is_enabled(&bts->acc_ramp)) {
+		if (!acc_ramp_step_interval_is_dynamic(&bts->acc_ramp))
+			vty_out(vty, "  Access Control Class ramping step interval: %u seconds%s",
+				acc_ramp_get_step_interval(&bts->acc_ramp), VTY_NEWLINE);
+		else
+			vty_out(vty, "  Access Control Class ramping step interval: dynamic%s", VTY_NEWLINE);
+	        vty_out(vty, "  enabling %u Access Control Class%s per ramping step%s",
+			acc_ramp_get_step_size(&bts->acc_ramp),
+			acc_ramp_get_step_size(&bts->acc_ramp) > 1 ? "es" : "", VTY_NEWLINE);
+	}
 	vty_out(vty, "  RACH TX-Integer: %u%s", bts->si_common.rach_control.tx_integer,
 		VTY_NEWLINE);
 	vty_out(vty, "  RACH Max transmissions: %u%s",
@@ -767,6 +780,15 @@ static void config_write_bts_single(struct vty *vty, struct gsm_bts *bts)
 		for (i = 0; i < 8; i++)
 			if ((i != 2) && (bts->si_common.rach_control.t2 & (0x1 << i)))
 				vty_out(vty, "  rach access-control-class %d barred%s", i+8, VTY_NEWLINE);
+	vty_out(vty, "  %saccess-control-class-ramping%s", acc_ramp_is_enabled(&bts->acc_ramp) ? "" : "no ", VTY_NEWLINE);
+	if (!acc_ramp_step_interval_is_dynamic(&bts->acc_ramp)) {
+		vty_out(vty, "  access-control-class-ramping-step-interval %u%s",
+			acc_ramp_get_step_interval(&bts->acc_ramp), VTY_NEWLINE);
+	} else {
+		vty_out(vty, "  access-control-class-ramping-step-interval dynamic%s", VTY_NEWLINE);
+	}
+	vty_out(vty, "  access-control-class-ramping-step-size %u%s", acc_ramp_get_step_size(&bts->acc_ramp),
+		VTY_NEWLINE);
 	for (i = SYSINFO_TYPE_1; i < _MAX_SYSINFO_TYPE; i++) {
 		if (bts->si_mode_static & (1 << i)) {
 			vty_out(vty, "  system-information %s mode static%s",
@@ -1858,6 +1880,11 @@ DEFUN(cfg_bts,
 		/* allocate a new one */
 		bts = gsm_bts_alloc_register(gsmnet, GSM_BTS_TYPE_UNKNOWN,
 					     HARDCODED_BSIC);
+		/*
+		 * Initalize bts->acc_ramp here. Else we could segfault while
+		 * processing a configuration file with ACC ramping settings.
+		 */
+		acc_ramp_init(&bts->acc_ramp, false, bts);
 	} else
 		bts = gsm_bts_num(gsmnet, bts_nr);
 
@@ -3210,6 +3237,88 @@ DEFUN(cfg_bts_pcu_sock, cfg_bts_pcu_sock_cmd,
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_bts_acc_ramping,
+      cfg_bts_acc_ramping_cmd,
+      "access-control-class-ramping",
+      "Enable Access Control Class ramping\n")
+{
+	struct gsm_bts *bts = vty->index;
+
+	acc_ramp_init(&bts->acc_ramp, true, bts);
+
+	/* ACC ramping takes effect when the BTS reconnects. */
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_bts_no_acc_ramping, cfg_bts_no_acc_ramping_cmd,
+      "no access-control-class-ramping",
+      NO_STR
+      "Disable Access Control Class ramping\n")
+{
+	struct gsm_bts *bts = vty->index;
+
+	if (acc_ramp_is_enabled(&bts->acc_ramp)) {
+		acc_ramp_abort(&bts->acc_ramp);
+		acc_ramp_init(&bts->acc_ramp, false, bts);
+		gsm_bts_set_system_infos(bts);
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_bts_acc_ramping_step_interval,
+      cfg_bts_acc_ramping_step_interval_cmd,
+      "access-control-class-ramping-step-interval (<"
+      OSMO_STRINGIFY_VAL(ACC_RAMP_STEP_INTERVAL_MIN) "-"
+      OSMO_STRINGIFY_VAL(ACC_RAMP_STEP_INTERVAL_MAX) ">|dynamic)",
+      "Configure Access Control Class ramping step interval\n"
+      "Set a fixed step interval (in seconds)\n"
+      "Use dynamic step interval based on BTS channel load\n")
+{
+	struct gsm_bts *bts = vty->index;
+	bool dynamic = (strcmp(argv[0], "dynamic") == 0);
+	int error;
+
+	if (dynamic) {
+		acc_ramp_set_step_interval_dynamic(&bts->acc_ramp);
+		return CMD_SUCCESS;
+	}
+
+	error = acc_ramp_set_step_interval(&bts->acc_ramp, atoi(argv[0]));
+	if (error != 0) {
+		if (error == -ERANGE)
+			vty_out(vty, "Unable to set ACC ramp step interval: value out of range%s", VTY_NEWLINE);
+		else
+			vty_out(vty, "Unable to set ACC ramp step interval: unknown error%s", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_bts_acc_ramping_step_size,
+      cfg_bts_acc_ramping_step_size_cmd,
+      "access-control-class-ramping-step-size (<"
+      OSMO_STRINGIFY_VAL(ACC_RAMP_STEP_SIZE_MIN) "-"
+      OSMO_STRINGIFY_VAL(ACC_RAMP_STEP_SIZE_MAX) ">)",
+      "Configure Access Control Class ramping step size\n"
+      "Set the number of Access Control Classes to enable per ramping step\n")
+{
+	struct gsm_bts *bts = vty->index;
+	int error;
+
+	error = acc_ramp_set_step_size(&bts->acc_ramp, atoi(argv[0]));
+	if (error != 0) {
+		if (error == -ERANGE)
+			vty_out(vty, "Unable to set ACC ramp step size: value out of range%s", VTY_NEWLINE);
+		else
+			vty_out(vty, "Unable to set ACC ramp step size: unknown error%s", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
+	return CMD_SUCCESS;
+}
+
 #define EXCL_RFLOCK_STR "Exclude this BTS from the global RF Lock\n"
 
 DEFUN(cfg_bts_excl_rf_lock,
@@ -4723,6 +4832,10 @@ int bsc_vty_init(struct gsm_network *network)
 	install_element(BTS_NODE, &cfg_bts_amr_hr_hyst3_cmd);
 	install_element(BTS_NODE, &cfg_bts_amr_hr_start_mode_cmd);
 	install_element(BTS_NODE, &cfg_bts_pcu_sock_cmd);
+	install_element(BTS_NODE, &cfg_bts_acc_ramping_cmd);
+	install_element(BTS_NODE, &cfg_bts_no_acc_ramping_cmd);
+	install_element(BTS_NODE, &cfg_bts_acc_ramping_step_interval_cmd);
+	install_element(BTS_NODE, &cfg_bts_acc_ramping_step_size_cmd);
 	/* See also handover commands added on bts level from handover_vty.c */
 
 	install_element(BTS_NODE, &cfg_trx_cmd);