1 files changed, 273 insertions, 0 deletions
diff --git a/src/common/tx_power.c b/src/common/tx_power.c
new file mode 100644
index 00000000..e2bb9ed7
--- /dev/null
+++ b/src/common/tx_power.c
@@ -0,0 +1,273 @@
+/* Transmit Power computation */
+
+/* (C) 2014 by Harald Welte <laforge@gnumonks.org>
+ *
+ * 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 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/>.
+ *
+ */
+
+#include <stdint.h>
+#include <limits.h>
+#include <errno.h>
+
+#include <osmocom/core/utils.h>
+
+#include <osmo-bts/logging.h>
+#include <osmo-bts/gsm_data.h>
+#include <osmo-bts/bts_model.h>
+#include <osmo-bts/tx_power.h>
+
+static int get_pa_drive_level_mdBm(const struct power_amp *pa,
+		       int desired_p_out_mdBm, unsigned int arfcn)
+{
+	if (arfcn > ARRAY_SIZE(pa->calib.gain_mdB))
+		return INT_MIN;
+
+	/* FIXME: temperature compensation */
+
+	return desired_p_out_mdBm - pa->calib.gain_mdB[arfcn];
+}
+
+/* maximum output power of the system */
+int get_p_max_out_mdBm(struct gsm_bts_trx *trx)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+	/* Add user gain, internal and external PA gain to TRX output power */
+	return tpp->trx_p_max_out_mdBm + tpp->user_gain_mdB +
+			tpp->pa.nominal_gain_mdB + tpp->user_pa.nominal_gain_mdB;
+}
+
+/* nominal output power, i.e. OML-reduced maximum output power */
+int get_p_nominal_mdBm(struct gsm_bts_trx *trx)
+{
+	/* P_max_out subtracted by OML maximum power reduction IE */
+	return get_p_max_out_mdBm(trx) - to_mdB(trx->max_power_red);
+}
+
+/* calculate the target total output power required, reduced by both
+ * OML and RSL, but ignoring the attenutation required for power ramping and
+ * thermal management */
+int get_p_target_mdBm(struct gsm_bts_trx *trx, uint8_t bs_power_ie)
+{
+	/* Pn subtracted by RSL BS Power IE (in 2 dB steps) */
+	return get_p_nominal_mdBm(trx) - to_mdB(bs_power_ie * 2);
+}
+int get_p_target_mdBm_lchan(struct gsm_lchan *lchan)
+{
+	return get_p_target_mdBm(lchan->ts->trx, lchan->bs_power);
+}
+
+/* calculate the actual total output power required, taking into account the
+ * attenutation required for power ramping but not thermal management */
+int get_p_actual_mdBm(struct gsm_bts_trx *trx, int p_target_mdBm)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+
+	/* P_target subtracted by ramp attenuation */
+	return p_target_mdBm - tpp->ramp.attenuation_mdB;
+}
+
+/* calculate the effective total output power required, taking into account the
+ * attenutation required for power ramping and thermal management */
+int get_p_eff_mdBm(struct gsm_bts_trx *trx, int p_target_mdBm)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+
+	/* P_target subtracted by ramp attenuation */
+	return p_target_mdBm - tpp->ramp.attenuation_mdB - tpp->thermal_attenuation_mdB;
+}
+
+/* calculate effect TRX output power required, taking into account the
+ * attenuations required for power ramping and thermal management */
+int get_p_trxout_eff_mdBm(struct gsm_bts_trx *trx, int p_target_mdBm)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+	int p_actual_mdBm, user_pa_drvlvl_mdBm, pa_drvlvl_mdBm;
+	unsigned int arfcn = trx->arfcn;
+
+	/* P_actual subtracted by any bulk gaion added by the user */
+	p_actual_mdBm = get_p_eff_mdBm(trx, p_target_mdBm) - tpp->user_gain_mdB;
+
+	/* determine input drive level required at input to user PA */
+	user_pa_drvlvl_mdBm = get_pa_drive_level_mdBm(&tpp->user_pa, p_actual_mdBm, arfcn);
+
+	/* determine input drive level required at input to internal PA */
+	pa_drvlvl_mdBm = get_pa_drive_level_mdBm(&tpp->pa, user_pa_drvlvl_mdBm, arfcn);
+
+	/* internal PA input drive level is TRX output power */
+	return pa_drvlvl_mdBm;
+}
+
+/* calculate target TRX output power required, ignoring the
+ * attenuations required for power ramping but not thermal management */
+int get_p_trxout_target_mdBm(struct gsm_bts_trx *trx, uint8_t bs_power_ie)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+	int p_target_mdBm, user_pa_drvlvl_mdBm, pa_drvlvl_mdBm;
+	unsigned int arfcn = trx->arfcn;
+
+	/* P_target subtracted by any bulk gaion added by the user */
+	p_target_mdBm = get_p_target_mdBm(trx, bs_power_ie) - tpp->user_gain_mdB;
+
+	/* determine input drive level required at input to user PA */
+	user_pa_drvlvl_mdBm = get_pa_drive_level_mdBm(&tpp->user_pa, p_target_mdBm, arfcn);
+
+	/* determine input drive level required at input to internal PA */
+	pa_drvlvl_mdBm = get_pa_drive_level_mdBm(&tpp->pa, user_pa_drvlvl_mdBm, arfcn);
+
+	/* internal PA input drive level is TRX output power */
+	return pa_drvlvl_mdBm;
+}
+int get_p_trxout_target_mdBm_lchan(struct gsm_lchan *lchan)
+{
+	return get_p_trxout_target_mdBm(lchan->ts->trx, lchan->bs_power);
+}
+
+
+/* output power ramping code */
+
+/* The idea here is to avoid a hard switch from 0 to 100, but to actually
+ * slowly and gradually ramp up or down the power.  This is needed on the
+ * one hand side to avoid very fast dynamic load changes towards the PA power
+ * supply, but is also needed in order to avoid a DoS by too many subscriber
+ * attempting to register at the same time.  Rather, grow the cell slowly in
+ * radius than start with the full raduis at once.  */
+
+static int we_are_ramping_up(struct gsm_bts_trx *trx)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+
+	if (tpp->p_total_tgt_mdBm > tpp->p_total_cur_mdBm)
+		return 1;
+	else
+		return 0;
+}
+
+static void power_ramp_do_step(struct gsm_bts_trx *trx, int first);
+
+/* timer call-back for the ramp tumer */
+static void power_ramp_timer_cb(void *_trx)
+{
+	struct gsm_bts_trx *trx = _trx;
+	struct trx_power_params *tpp = &trx->power_params;
+	int p_trxout_eff_mdBm;
+
+	/* compute new actual total output power (= minus ramp attenuation) */
+	tpp->p_total_cur_mdBm = get_p_actual_mdBm(trx, tpp->p_total_tgt_mdBm);
+
+	/* compute new effective (= minus ramp and thermal attenuation) TRX output required */
+	p_trxout_eff_mdBm = get_p_trxout_eff_mdBm(trx, tpp->p_total_tgt_mdBm);
+
+	LOGP(DL1C, LOGL_DEBUG, "ramp_timer_cb(cur_pout=%d, tgt_pout=%d, "
+		"ramp_att=%d, therm_att=%d, user_gain=%d)\n",
+		tpp->p_total_cur_mdBm, tpp->p_total_tgt_mdBm,
+		tpp->ramp.attenuation_mdB, tpp->thermal_attenuation_mdB,
+		tpp->user_gain_mdB);
+
+	LOGP(DL1C, LOGL_INFO,
+		"ramping TRX board output power to %d mdBm.\n", p_trxout_eff_mdBm);
+
+	/* Instruct L1 to apply new effective TRX output power required */
+	bts_model_change_power(trx, p_trxout_eff_mdBm);
+
+	/* and do another step... */
+	power_ramp_do_step(trx, 0);
+}
+
+static void power_ramp_do_step(struct gsm_bts_trx *trx, int first)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+
+	/* we had finished in last loop iteration */
+	if (!first && tpp->ramp.attenuation_mdB == 0)
+		return;
+
+	if (we_are_ramping_up(trx)) {
+		/* ramp up power -> ramp down attenuation */
+		tpp->ramp.attenuation_mdB -= tpp->ramp.step_size_mdB;
+		if (tpp->ramp.attenuation_mdB <= 0) {
+			/* we are done */
+			tpp->ramp.attenuation_mdB = 0;
+		}
+	} else {
+		/* ramp down power -> ramp up attenuation */
+		tpp->ramp.attenuation_mdB += tpp->ramp.step_size_mdB;
+		if (tpp->ramp.attenuation_mdB >= 0) {
+			/* we are done */
+			tpp->ramp.attenuation_mdB = 0;
+		}
+	}
+
+	/* schedule timer for the next step */
+	tpp->ramp.step_timer.data = trx;
+	tpp->ramp.step_timer.cb = power_ramp_timer_cb;
+	osmo_timer_schedule(&tpp->ramp.step_timer, tpp->ramp.step_interval_sec, 0);
+}
+
+
+int power_ramp_start(struct gsm_bts_trx *trx, int p_total_tgt_mdBm, int bypass)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+
+	/* The input to this function is the actual desired output power, i.e.
+	 * the maximum total system power subtracted by OML as well as RSL
+	 * reductions */
+
+	LOGP(DL1C, LOGL_INFO, "power_ramp_start(cur=%d, tgt=%d)\n",
+		tpp->p_total_cur_mdBm, p_total_tgt_mdBm);
+
+	if (!bypass && (p_total_tgt_mdBm > get_p_nominal_mdBm(trx))) {
+		LOGP(DL1C, LOGL_ERROR, "Asked to ramp power up to "
+		     "%d mdBm, which exceeds P_max_out (%d)\n",
+		     p_total_tgt_mdBm, get_p_nominal_mdBm(trx));
+		return -ERANGE;
+	}
+
+	/* Cancel any pending request */
+	osmo_timer_del(&tpp->ramp.step_timer);
+
+	/* set the new target */
+	tpp->p_total_tgt_mdBm = p_total_tgt_mdBm;
+
+	if (we_are_ramping_up(trx)) {
+		if (tpp->p_total_tgt_mdBm <= tpp->ramp.max_initial_pout_mdBm) {
+			LOGP(DL1C, LOGL_INFO,
+				"target_power(%d) is below max.initial power\n",
+				tpp->p_total_tgt_mdBm);
+			/* new setting is below the maximum initial output
+			 * power, so we can directly jump to this level */
+			tpp->p_total_cur_mdBm = tpp->p_total_tgt_mdBm;
+			tpp->ramp.attenuation_mdB = 0;
+			power_ramp_timer_cb(trx);
+		} else {
+			/* We need to step it up. Start from the current value */
+			/* Set attenuation to cause no power change right now */
+			tpp->ramp.attenuation_mdB = tpp->p_total_tgt_mdBm - tpp->p_total_cur_mdBm;
+
+			/* start with the firsrt step */
+			power_ramp_do_step(trx, 1);
+		}
+	} else {
+		/* Set ramp attenuation to negative value, and increse that by
+		 * steps until it reaches 0 */
+		tpp->ramp.attenuation_mdB = tpp->p_total_tgt_mdBm - tpp->p_total_cur_mdBm;
+
+		/* start with the firsrt step */
+		power_ramp_do_step(trx, 1);
+	}
+
+	return 0;
+}