New generic transmit power handling

In order to support transmit power reduction by thermal management
as well as the variety of new internal / external PA configurations
of BTSs, we need a slightly more complex system.

Also, as at high power a single dB can be quite a big difference,
we are now doing all computations in milli-dB(m), i.e. 1/10000 bel.

Ramping is now used both for up and down ramping, as that is useful in
cases where you want to gracefully shut down a cell by shrinking its
radius, gradually handing over subscribers to neighboring cells.

Furthermore, this code is becoming part of the 'common' codebase, as it
is not really specific to how sysmobts is working.

The user can specify a single aggregate value for external system
gain/attenuation.  Let's say you have 1dB loss of antenna cable, so you
can put that as 'user-gain -1' into the config, which means that a
'transmit power of 20dBm' will be compensatet for that and the TRX is
instructed to output 21dBm to compensate the cable loss.  Similarly,
external PAs can be described by a positive user-gain.

One of the next steps will be to communicate those values and the
nominal power capability of the specific BTS to the BSC, so the BSC will
automatically show correct signal levels in the VTY and log files.

The code includes provisions for future extensions regarding
* an external and an internal PA with calibration tables
* a thermal attenuation setting to be controlled by the site manager

1 files changed, 74 insertions, 0 deletions

diff --git a/include/osmo-bts/tx_power.h b/include/osmo-bts/tx_power.h
new file mode 100644
index 00000000..c5d6f2ba
--- /dev/null
+++ b/include/osmo-bts/tx_power.h
@@ -0,0 +1,74 @@
+#pragma once
+
+#include <stdint.h>
+#include <osmocom/core/timer.h>
+
+/* our unit is 'milli dB" or "milli dBm", i.e. 1/1000 of a dB(m) */
+#define to_mdB(x)	(x * 1000)
+
+/* PA calibration table */
+struct pa_calibration {
+	int gain_mdB[1024];		/* gain provided at given ARFCN */
+	/* FIXME: thermal calibration */
+};
+
+/* representation of a RF power amplifier */
+struct power_amp {
+	/* nominal gain of the PA */
+	int nominal_gain_mdB;
+	/* table with calibrated actual gain for each ARFCN */
+	struct pa_calibration calib;
+};
+
+/* Transmit power related parameters of a transceiver */
+struct trx_power_params {
+	/* specified maximum output of TRX at full power, has to be
+	 * initialized by BTS model at startup*/
+	int trx_p_max_out_mdBm;
+
+	/* intended current total system output power */
+	int p_total_tgt_mdBm;
+
+	/* actual current total system output power, filled in by tx_power code */
+	int p_total_cur_mdBm;
+
+	/* current temporary attenuation due to thermal management,
+	 * set by thermal management code via control interface */
+	int thermal_attenuation_mdB;
+
+	/* external gain (+) or attenuation (-) added by the user, configured
+	 * by the user via VTY */
+	int user_gain_mdB;
+
+	/* calibration table of internal PA */
+	struct power_amp pa;
+
+	/* calibration table of user PA */
+	struct power_amp user_pa;
+
+	/* power ramping related data */
+	struct {
+		/* maximum initial Pout including all PAs */
+		int max_initial_pout_mdBm;
+		/* temporary attenuation due to power ramping */
+		int attenuation_mdB;
+		unsigned int step_size_mdB;
+		unsigned int step_interval_sec;
+		struct osmo_timer_list step_timer;
+	} ramp;
+};
+
+int get_p_max_out_mdBm(struct gsm_bts_trx *trx);
+
+int get_p_nominal_mdBm(struct gsm_bts_trx *trx);
+
+int get_p_target_mdBm(struct gsm_bts_trx *trx, uint8_t bs_power_ie);
+int get_p_target_mdBm_lchan(struct gsm_lchan *lchan);
+
+int get_p_trxout_target_mdBm(struct gsm_bts_trx *trx, uint8_t bs_power_ie);
+int get_p_trxout_target_mdBm_lchan(struct gsm_lchan *lchan);
+
+int get_p_trxout_actual_mdBm(struct gsm_bts_trx *trx, uint8_t bs_power_ie);
+int get_p_trxout_actual_mdBm_lchan(struct gsm_lchan *lchan);
+
+int power_ramp_start(struct gsm_bts_trx *trx, int p_total_tgt_mdBm, int bypass);