aboutsummaryrefslogtreecommitdiffstats
path: root/include/osmocom/bsc/acc_ramp.h
blob: a02db15b72e7c9ab3cfacd0c0069575a641f3c0a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
/* (C) 2018 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/>.
 *
 */

#ifndef _ACC_RAMP_H_
#define _ACC_RAMP_H_

#include <stdbool.h>
#include <stdint.h>

#include <osmocom/core/timer.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.
 */

enum acc_ramp_step_size {
	ACC_RAMP_STEP_SIZE_MIN = 1, /* allow at most 1 new ACC per ramp step */
	ACC_RAMP_STEP_SIZE_DEFAULT = ACC_RAMP_STEP_SIZE_MIN,
	ACC_RAMP_STEP_SIZE_MAX = 10, /* allow all ACC in one step (disables ramping) */
};

enum acc_ramp_step_interval {
	ACC_RAMP_STEP_INTERVAL_MIN = 1,		/* 1 second */
	ACC_RAMP_STEP_INTERVAL_DEFAULT = 60,	/* 1 minute */
	ACC_RAMP_STEP_INTERVAL_MAX = 600,	/* 10 minutes */
};

struct acc_ramp {
	struct gsm_bts *bts; /* backpointer to BTS using this ACC ramp */

	/*
	 * Bitmasks which keep track of access control classes that are currently denied
	 * access. These masks should be used to modulate bits from octets 2 and 3 of
	 * the RACH Control Parameters (see 3GPP 44.018 10.5.2.29).
	 * While a bit in these masks is set, the corresponding ACC is barred.
	 * Note that t2 contains bits for classes 11-15 which should always be allowed,
	 * and a bit which denies emergency calls for all ACCs from 0-9 inclusive.
	 * Ramping is only concerned with those bits which control access for ACCs 0-9.
	 */
	uint8_t barred_t2;
	uint8_t barred_t3;

	/*
	 * 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.
	 */
	enum acc_ramp_step_size 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;
};

/*
 * Initialize the acc_ramp data structure.
 * Storage for this structure must be provided by the caller.
 *
 * The BTS which uses this ACC ramp must be provided as well.
 *
 * If 'bts->acc_ramping_enabled' is true, all ACCs are denied by default.
 * A subsequent call to acc_ramp_start() will begin the ramping process.
 *
 * If 'bts->acc_ramping_enabled' is false, all ACCs will be allowed by default,
 * and there is no need to do anything else.
 */
void acc_ramp_init(struct acc_ramp *acc_ramp, struct gsm_bts *bts);

/* Change the ramping step size. Returns negative on error (step_size out of range), else zero. */
int acc_ramp_set_step_size(struct acc_ramp *acc_ramp, enum acc_ramp_step_size step_size);

/*
 * Change the ramping step interval to a fixed value. Unless this function is called,
 * the interval is automatically scaled to the BTS channel load average.
 */
int acc_ramp_set_step_interval(struct acc_ramp *acc_ramp, unsigned int step_interval);

/*
 * Clear a previously set fixed ramping step interval, so that the interval
 * is again automatically scaled to the BTS channel load average.
 */
void acc_ramp_set_step_interval_dynamic(struct acc_ramp *acc_ramp);

/*
 * Begin the ramping process. This initially sets all ACCs to denied, and then
 * performs at least one ramping step to allow 'step_size' ACCs.
 * If 'step_size' is ACC_RAMP_STEP_SIZE_MAX, all ACCs will be allowed immediately,
 * i.e. ACC ramping becomes a no-op.
 */
void acc_ramp_start(struct acc_ramp *acc_ramp);

/* Abort the ramping process. If the process has already finished, this function has no effect. */
void acc_ramp_abort(struct acc_ramp *acc_ramp);

/*
 * Return bitmasks which correspond to access control classes which 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.
 */
static inline uint8_t acc_ramp_get_barred_t2(struct acc_ramp *acc_ramp)
{
	return (acc_ramp->barred_t2 & 0x03);
};

static inline uint8_t acc_ramp_get_barred_t3(struct acc_ramp *acc_ramp)
{
	return acc_ramp->barred_t3;
}

#endif /* _ACC_RAMP_H_ */