diff --git a/include/osmocom/bsc/Makefile.am b/include/osmocom/bsc/Makefile.am
index a5d7d18..17e8bd3 100644
--- a/include/osmocom/bsc/Makefile.am
+++ b/include/osmocom/bsc/Makefile.am
@@ -3,6 +3,7 @@
 	abis_nm.h \
 	abis_om2000.h \
 	abis_rsl.h \
+	acc_ramp.h \
 	arfcn_range_encode.h \
 	bsc_msc.h \
 	bsc_msg_filter.h \
diff --git a/include/osmocom/bsc/acc_ramp.h b/include/osmocom/bsc/acc_ramp.h
new file mode 100644
index 0000000..cb063bf
--- /dev/null
+++ b/include/osmocom/bsc/acc_ramp.h
@@ -0,0 +1,149 @@
+/* (C) 2018 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * Author: Stefan Sperling <ssperling@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <osmocom/core/timer.h>
+#include <osmocom/gsm/protocol/gsm_04_08.h>
+
+/*!
+ * 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.
+ */
+
+#define ACC_RAMP_STEP_SIZE_MIN 1 /* allow at most 1 new ACC per ramp step */
+#define ACC_RAMP_STEP_SIZE_DEFAULT ACC_RAMP_STEP_SIZE_MIN
+#define ACC_RAMP_STEP_SIZE_MAX 10 /* allow all ACC in one step (effectively disables ramping) */
+
+#define ACC_RAMP_STEP_INTERVAL_MIN 30	/* 30 seconds */
+#define ACC_RAMP_STEP_INTERVAL_MAX 600	/* 10 minutes */
+
+/*!
+ * Data structure used to manage ACC ramping. Please avoid setting or reading fields
+ * in this structure directly. Use the accessor functions below instead.
+ */
+struct acc_ramp {
+	struct gsm_bts *bts; /*!< backpointer to BTS using this ACC ramp */
+
+	bool acc_ramping_enabled; /*!< whether ACC ramping is enabled */
+
+	/*!
+	 * Bitmask which keeps track of access control classes that are currently denied
+	 * access. The function acc_ramp_apply() uses this mask to modulate bits from
+	 * octets 2 and 3 in RACH Control Parameters (see 3GPP 44.018 10.5.2.29).
+	 * Ramping is only concerned with ACCs 0-9. While any of the bits 0-9 is set,
+	 * the corresponding ACC is barred.
+	 * ACCs 11-15 should always be allowed, and ACC 10 denies emergency calls for
+	 * all ACCs from 0-9 inclusive; these ACCs are ignored in this implementation.
+	 */
+	uint16_t barred_accs;
+
+	/*!
+	 * This controls the maximum number of ACCs to allow per ramping step (1 - 10).
+	 * The compile-time default value is ACC_RAMP_STEP_SIZE_DEFAULT.
+	 * This value can be changed by VTY configuration.
+	 * A value of ACC_RAMP_STEP_SIZE_MAX effectively disables ramping.
+	 */
+	unsigned int step_size;
+
+	/*!
+	 * Ramping step interval in seconds.
+	 * This value depends on the current BTS channel load average, unless
+	 * it has been overriden by VTY configuration.
+	 */
+	unsigned int step_interval_sec;
+	bool step_interval_is_fixed;
+	struct osmo_timer_list step_timer;
+};
+
+/*!
+ * Return true if ACC ramping is currently enabled, else false.
+ * \param[in] acc_ramp Pointer to acc_ramp structure.
+ */
+static inline bool acc_ramp_is_enabled(struct acc_ramp *acc_ramp)
+{
+	return acc_ramp->acc_ramping_enabled;
+}
+
+/*!
+ * Return the current ACC ramp step size.
+ * \param[in] acc_ramp Pointer to acc_ramp structure.
+ */
+static inline unsigned int acc_ramp_get_step_size(struct acc_ramp *acc_ramp)
+{
+	return acc_ramp->step_size;
+}
+
+/*!
+ * Return the current ACC ramp step interval (in seconds)
+ * \param[in] acc_ramp Pointer to acc_ramp structure.
+ */
+static inline unsigned int acc_ramp_get_step_interval(struct acc_ramp *acc_ramp)
+{
+	return acc_ramp->step_interval_sec;
+}
+
+/*!
+ * If the step interval is dynamic, return true, else return false.
+ * \param[in] acc_ramp Pointer to acc_ramp structure.
+ */
+static inline bool acc_ramp_step_interval_is_dynamic(struct acc_ramp *acc_ramp)
+{
+	return !(acc_ramp->step_interval_is_fixed);
+}
+
+/*!
+ * Return bitmasks which correspond to access control classes that are currently
+ * denied access. Ramping is only concerned with those bits which control access
+ * for ACCs 0-9, and any of the other bits will always be set to zero in these masks, i.e.
+ * it is safe to OR these bitmasks with the corresponding fields in struct gsm48_rach_control.
+ * \param[in] acc_ramp Pointer to acc_ramp structure.
+ */
+static inline uint8_t acc_ramp_get_barred_t2(struct acc_ramp *acc_ramp)
+{
+	return ((acc_ramp->barred_accs >> 8) & 0x03);
+};
+static inline uint8_t acc_ramp_get_barred_t3(struct acc_ramp *acc_ramp)
+{
+	return (acc_ramp->barred_accs & 0xff);
+}
+
+/*!
+ * Potentially mark certain Access Control Classes (ACCs) as barred in accordance to ACC ramping.
+ * \param[in] rach_control RACH control parameters in which barred ACCs will be configured.
+ * \param[in] acc_ramp Pointer to acc_ramp structure.
+ */
+static inline void acc_ramp_apply(struct gsm48_rach_control *rach_control, struct acc_ramp *acc_ramp)
+{
+	rach_control->t2 |= acc_ramp_get_barred_t2(acc_ramp);
+	rach_control->t3 |= acc_ramp_get_barred_t3(acc_ramp);
+}
+
+void acc_ramp_init(struct acc_ramp *acc_ramp, bool enable, struct gsm_bts *bts);
+int acc_ramp_set_step_size(struct acc_ramp *acc_ramp, unsigned int step_size);
+int acc_ramp_set_step_interval(struct acc_ramp *acc_ramp, unsigned int step_interval);
+void acc_ramp_set_step_interval_dynamic(struct acc_ramp *acc_ramp);
+void acc_ramp_start(struct acc_ramp *acc_ramp);
+void acc_ramp_abort(struct acc_ramp *acc_ramp);
diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 07e5478..3c65c9c 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -26,6 +26,7 @@
 #include <osmocom/abis/e1_input.h>
 #include <osmocom/bsc/meas_rep.h>
 #include <osmocom/bsc/bsc_msg_filter.h>
+#include <osmocom/bsc/acc_ramp.h>
 
 struct mgcp_client_conf;
 struct mgcp_client;
@@ -948,6 +949,9 @@
 	/* do we use static (user-defined) system information messages? (bitmask) */
 	uint32_t si_mode_static;
 
+	/* access control class ramping */
+	struct acc_ramp acc_ramp;
+
 	/* exclude the BTS from the global RF Lock handling */
 	int excl_from_rf_lock;
 
@@ -976,6 +980,7 @@
 	/* Periodic channel load measurements are used to maintain T3122. */
 	struct load_counter chan_load_samples[7];
 	int chan_load_samples_idx;
+	uint8_t chan_load_avg; /* current channel load average in percent (0 - 100). */
 };