2 * Copyright 2002-2005, Instant802 Networks, Inc.
3 * Copyright 2005, Devicescape Software, Inc.
4 * Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
5 * Copyright 2007-2008, Stefano Brivio <stefano.brivio@polimi.it>
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/netdevice.h>
13 #include <linux/types.h>
14 #include <linux/skbuff.h>
15 #include <linux/debugfs.h>
16 #include <net/mac80211.h>
17 #include "ieee80211_rate.h"
19 #include "rc80211_pid.h"
22 /* This is an implementation of a TX rate control algorithm that uses a PID
23 * controller. Given a target failed frames rate, the controller decides about
24 * TX rate changes to meet the target failed frames rate.
26 * The controller basically computes the following:
28 * adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
31 * adj adjustment value that is used to switch TX rate (see below)
32 * err current error: target vs. current failed frames percentage
34 * err_avg average (i.e. poor man's integral) of recent errors
35 * sharpening non-zero when fast response is needed (i.e. right after
36 * association or no frames sent for a long time), heading
38 * CP Proportional coefficient
39 * CI Integral coefficient
40 * CD Derivative coefficient
42 * CP, CI, CD are subject to careful tuning.
44 * The integral component uses a exponential moving average approach instead of
45 * an actual sliding window. The advantage is that we don't need to keep an
46 * array of the last N error values and computation is easier.
48 * Once we have the adj value, we map it to a rate by means of a learning
49 * algorithm. This algorithm keeps the state of the percentual failed frames
50 * difference between rates. The behaviour of the lowest available rate is kept
51 * as a reference value, and every time we switch between two rates, we compute
52 * the difference between the failed frames each rate exhibited. By doing so,
53 * we compare behaviours which different rates exhibited in adjacent timeslices,
54 * thus the comparison is minimally affected by external conditions. This
55 * difference gets propagated to the whole set of measurements, so that the
56 * reference is always the same. Periodically, we normalize this set so that
57 * recent events weigh the most. By comparing the adj value with this set, we
58 * avoid pejorative switches to lower rates and allow for switches to higher
59 * rates if they behaved well.
61 * Note that for the computations we use a fixed-point representation to avoid
62 * floating point arithmetic. Hence, all values are shifted left by
67 /* Adjust the rate while ensuring that we won't switch to a lower rate if it
68 * exhibited a worse failed frames behaviour and we'll choose the highest rate
69 * whose failed frames behaviour is not worse than the one of the original rate
70 * target. While at it, check that the new rate is valid. */
71 static void rate_control_pid_adjust_rate(struct ieee80211_local *local,
72 struct sta_info *sta, int adj,
73 struct rc_pid_rateinfo *rinfo)
75 struct ieee80211_sub_if_data *sdata;
76 struct ieee80211_supported_band *sband;
77 int cur_sorted, new_sorted, probe, tmp, n_bitrates, band;
78 int cur = sta->txrate_idx;
80 sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
81 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
83 n_bitrates = sband->n_bitrates;
85 /* Map passed arguments to sorted values. */
86 cur_sorted = rinfo[cur].rev_index;
87 new_sorted = cur_sorted + adj;
91 new_sorted = rinfo[0].rev_index;
92 else if (new_sorted >= n_bitrates)
93 new_sorted = rinfo[n_bitrates - 1].rev_index;
98 /* Ensure that the rate decrease isn't disadvantageous. */
99 for (probe = cur_sorted; probe >= new_sorted; probe--)
100 if (rinfo[probe].diff <= rinfo[cur_sorted].diff &&
101 rate_supported(sta, band, rinfo[probe].index))
104 /* Look for rate increase with zero (or below) cost. */
105 for (probe = new_sorted + 1; probe < n_bitrates; probe++)
106 if (rinfo[probe].diff <= rinfo[new_sorted].diff &&
107 rate_supported(sta, band, rinfo[probe].index))
111 /* Fit the rate found to the nearest supported rate. */
113 if (rate_supported(sta, band, rinfo[tmp].index)) {
114 sta->txrate_idx = rinfo[tmp].index;
121 } while (tmp < n_bitrates && tmp >= 0);
123 #ifdef CONFIG_MAC80211_DEBUGFS
124 rate_control_pid_event_rate_change(
125 &((struct rc_pid_sta_info *)sta->rate_ctrl_priv)->events,
126 sta->txrate_idx, sband->bitrates[sta->txrate_idx].bitrate);
130 /* Normalize the failed frames per-rate differences. */
131 static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
133 int i, norm_offset = pinfo->norm_offset;
134 struct rc_pid_rateinfo *r = pinfo->rinfo;
136 if (r[0].diff > norm_offset)
137 r[0].diff -= norm_offset;
138 else if (r[0].diff < -norm_offset)
139 r[0].diff += norm_offset;
140 for (i = 0; i < l - 1; i++)
141 if (r[i + 1].diff > r[i].diff + norm_offset)
142 r[i + 1].diff -= norm_offset;
143 else if (r[i + 1].diff <= r[i].diff)
144 r[i + 1].diff += norm_offset;
147 static void rate_control_pid_sample(struct rc_pid_info *pinfo,
148 struct ieee80211_local *local,
149 struct sta_info *sta)
151 struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
152 struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
153 struct ieee80211_supported_band *sband;
160 unsigned long period;
162 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
163 spinfo = sta->rate_ctrl_priv;
165 /* In case nothing happened during the previous control interval, turn
166 * the sharpening factor on. */
167 period = (HZ * pinfo->sampling_period + 500) / 1000;
170 if (jiffies - spinfo->last_sample > 2 * period)
171 spinfo->sharp_cnt = pinfo->sharpen_duration;
173 spinfo->last_sample = jiffies;
175 /* This should never happen, but in case, we assume the old sample is
176 * still a good measurement and copy it. */
177 if (unlikely(spinfo->tx_num_xmit == 0))
178 pf = spinfo->last_pf;
180 pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
181 pf <<= RC_PID_ARITH_SHIFT;
184 spinfo->tx_num_xmit = 0;
185 spinfo->tx_num_failed = 0;
187 /* If we just switched rate, update the rate behaviour info. */
188 if (pinfo->oldrate != sta->txrate_idx) {
190 i = rinfo[pinfo->oldrate].rev_index;
191 j = rinfo[sta->txrate_idx].rev_index;
193 tmp = (pf - spinfo->last_pf);
194 tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);
196 rinfo[j].diff = rinfo[i].diff + tmp;
197 pinfo->oldrate = sta->txrate_idx;
199 rate_control_pid_normalize(pinfo, sband->n_bitrates);
201 /* Compute the proportional, integral and derivative errors. */
202 err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf;
204 err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
205 spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
206 err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;
208 err_der = (pf - spinfo->last_pf) *
209 (1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
210 spinfo->last_pf = pf;
211 if (spinfo->sharp_cnt)
214 #ifdef CONFIG_MAC80211_DEBUGFS
215 rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
219 /* Compute the controller output. */
220 adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
221 + err_der * pinfo->coeff_d);
222 adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);
226 rate_control_pid_adjust_rate(local, sta, adj, rinfo);
229 static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
231 struct ieee80211_tx_status *status)
233 struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
234 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
235 struct ieee80211_sub_if_data *sdata;
236 struct rc_pid_info *pinfo = priv;
237 struct sta_info *sta;
238 struct rc_pid_sta_info *spinfo;
239 unsigned long period;
240 struct ieee80211_supported_band *sband;
242 sta = sta_info_get(local, hdr->addr1);
243 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
248 /* Don't update the state if we're not controlling the rate. */
249 sdata = IEEE80211_DEV_TO_SUB_IF(sta->dev);
250 if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
251 sta->txrate_idx = sdata->bss->max_ratectrl_rateidx;
255 /* Ignore all frames that were sent with a different rate than the rate
256 * we currently advise mac80211 to use. */
257 if (status->control.tx_rate != &sband->bitrates[sta->txrate_idx])
260 spinfo = sta->rate_ctrl_priv;
261 spinfo->tx_num_xmit++;
263 #ifdef CONFIG_MAC80211_DEBUGFS
264 rate_control_pid_event_tx_status(&spinfo->events, status);
267 /* We count frames that totally failed to be transmitted as two bad
268 * frames, those that made it out but had some retries as one good and
270 if (status->excessive_retries) {
271 spinfo->tx_num_failed += 2;
272 spinfo->tx_num_xmit++;
273 } else if (status->retry_count) {
274 spinfo->tx_num_failed++;
275 spinfo->tx_num_xmit++;
278 if (status->excessive_retries) {
279 sta->tx_retry_failed++;
280 sta->tx_num_consecutive_failures++;
281 sta->tx_num_mpdu_fail++;
283 sta->last_ack_rssi[0] = sta->last_ack_rssi[1];
284 sta->last_ack_rssi[1] = sta->last_ack_rssi[2];
285 sta->last_ack_rssi[2] = status->ack_signal;
286 sta->tx_num_consecutive_failures = 0;
287 sta->tx_num_mpdu_ok++;
289 sta->tx_retry_count += status->retry_count;
290 sta->tx_num_mpdu_fail += status->retry_count;
292 /* Update PID controller state. */
293 period = (HZ * pinfo->sampling_period + 500) / 1000;
296 if (time_after(jiffies, spinfo->last_sample + period))
297 rate_control_pid_sample(pinfo, local, sta);
303 static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
304 struct ieee80211_supported_band *sband,
306 struct rate_selection *sel)
308 struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
309 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
310 struct ieee80211_sub_if_data *sdata;
311 struct sta_info *sta;
315 sta = sta_info_get(local, hdr->addr1);
317 /* Send management frames and broadcast/multicast data using lowest
319 fc = le16_to_cpu(hdr->frame_control);
320 if ((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
321 is_multicast_ether_addr(hdr->addr1) || !sta) {
322 sel->rate = rate_lowest(local, sband, sta);
328 /* If a forced rate is in effect, select it. */
329 sdata = IEEE80211_DEV_TO_SUB_IF(dev);
330 if (sdata->bss && sdata->bss->force_unicast_rateidx > -1)
331 sta->txrate_idx = sdata->bss->force_unicast_rateidx;
333 rateidx = sta->txrate_idx;
335 if (rateidx >= sband->n_bitrates)
336 rateidx = sband->n_bitrates - 1;
338 sta->last_txrate_idx = rateidx;
342 sel->rate = &sband->bitrates[rateidx];
344 #ifdef CONFIG_MAC80211_DEBUGFS
345 rate_control_pid_event_tx_rate(
346 &((struct rc_pid_sta_info *) sta->rate_ctrl_priv)->events,
347 rateidx, sband->bitrates[rateidx].bitrate);
351 static void rate_control_pid_rate_init(void *priv, void *priv_sta,
352 struct ieee80211_local *local,
353 struct sta_info *sta)
355 /* TODO: This routine should consider using RSSI from previous packets
356 * as we need to have IEEE 802.1X auth succeed immediately after assoc..
357 * Until that method is implemented, we will use the lowest supported
358 * rate as a workaround. */
359 struct ieee80211_supported_band *sband;
361 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
362 sta->txrate_idx = rate_lowest_index(local, sband, sta);
365 static void *rate_control_pid_alloc(struct ieee80211_local *local)
367 struct rc_pid_info *pinfo;
368 struct rc_pid_rateinfo *rinfo;
369 struct ieee80211_supported_band *sband;
372 #ifdef CONFIG_MAC80211_DEBUGFS
373 struct rc_pid_debugfs_entries *de;
376 sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
378 pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
382 /* We can safely assume that sband won't change unless we get
384 rinfo = kmalloc(sizeof(*rinfo) * sband->n_bitrates, GFP_ATOMIC);
390 /* Sort the rates. This is optimized for the most common case (i.e.
391 * almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
393 for (i = 0; i < sband->n_bitrates; i++) {
395 rinfo[i].rev_index = i;
396 if (pinfo->fast_start)
399 rinfo[i].diff = i * pinfo->norm_offset;
401 for (i = 1; i < sband->n_bitrates; i++) {
403 for (j = 0; j < sband->n_bitrates - i; j++)
404 if (unlikely(sband->bitrates[rinfo[j].index].bitrate >
405 sband->bitrates[rinfo[j + 1].index].bitrate)) {
406 tmp = rinfo[j].index;
407 rinfo[j].index = rinfo[j + 1].index;
408 rinfo[j + 1].index = tmp;
409 rinfo[rinfo[j].index].rev_index = j;
410 rinfo[rinfo[j + 1].index].rev_index = j + 1;
417 pinfo->target = RC_PID_TARGET_PF;
418 pinfo->sampling_period = RC_PID_INTERVAL;
419 pinfo->coeff_p = RC_PID_COEFF_P;
420 pinfo->coeff_i = RC_PID_COEFF_I;
421 pinfo->coeff_d = RC_PID_COEFF_D;
422 pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
423 pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
424 pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
425 pinfo->norm_offset = RC_PID_NORM_OFFSET;
426 pinfo->fast_start = RC_PID_FAST_START;
427 pinfo->rinfo = rinfo;
430 #ifdef CONFIG_MAC80211_DEBUGFS
431 de = &pinfo->dentries;
432 de->dir = debugfs_create_dir("rc80211_pid",
433 local->hw.wiphy->debugfsdir);
434 de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR,
435 de->dir, &pinfo->target);
436 de->sampling_period = debugfs_create_u32("sampling_period",
437 S_IRUSR | S_IWUSR, de->dir,
438 &pinfo->sampling_period);
439 de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR,
440 de->dir, &pinfo->coeff_p);
441 de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR,
442 de->dir, &pinfo->coeff_i);
443 de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR,
444 de->dir, &pinfo->coeff_d);
445 de->smoothing_shift = debugfs_create_u32("smoothing_shift",
446 S_IRUSR | S_IWUSR, de->dir,
447 &pinfo->smoothing_shift);
448 de->sharpen_factor = debugfs_create_u32("sharpen_factor",
449 S_IRUSR | S_IWUSR, de->dir,
450 &pinfo->sharpen_factor);
451 de->sharpen_duration = debugfs_create_u32("sharpen_duration",
452 S_IRUSR | S_IWUSR, de->dir,
453 &pinfo->sharpen_duration);
454 de->norm_offset = debugfs_create_u32("norm_offset",
455 S_IRUSR | S_IWUSR, de->dir,
456 &pinfo->norm_offset);
457 de->fast_start = debugfs_create_bool("fast_start",
458 S_IRUSR | S_IWUSR, de->dir,
465 static void rate_control_pid_free(void *priv)
467 struct rc_pid_info *pinfo = priv;
468 #ifdef CONFIG_MAC80211_DEBUGFS
469 struct rc_pid_debugfs_entries *de = &pinfo->dentries;
471 debugfs_remove(de->fast_start);
472 debugfs_remove(de->norm_offset);
473 debugfs_remove(de->sharpen_duration);
474 debugfs_remove(de->sharpen_factor);
475 debugfs_remove(de->smoothing_shift);
476 debugfs_remove(de->coeff_d);
477 debugfs_remove(de->coeff_i);
478 debugfs_remove(de->coeff_p);
479 debugfs_remove(de->sampling_period);
480 debugfs_remove(de->target);
481 debugfs_remove(de->dir);
488 static void rate_control_pid_clear(void *priv)
492 static void *rate_control_pid_alloc_sta(void *priv, gfp_t gfp)
494 struct rc_pid_sta_info *spinfo;
496 spinfo = kzalloc(sizeof(*spinfo), gfp);
500 spinfo->last_sample = jiffies;
502 #ifdef CONFIG_MAC80211_DEBUGFS
503 spin_lock_init(&spinfo->events.lock);
504 init_waitqueue_head(&spinfo->events.waitqueue);
510 static void rate_control_pid_free_sta(void *priv, void *priv_sta)
512 struct rc_pid_sta_info *spinfo = priv_sta;
516 static struct rate_control_ops mac80211_rcpid = {
518 .tx_status = rate_control_pid_tx_status,
519 .get_rate = rate_control_pid_get_rate,
520 .rate_init = rate_control_pid_rate_init,
521 .clear = rate_control_pid_clear,
522 .alloc = rate_control_pid_alloc,
523 .free = rate_control_pid_free,
524 .alloc_sta = rate_control_pid_alloc_sta,
525 .free_sta = rate_control_pid_free_sta,
526 #ifdef CONFIG_MAC80211_DEBUGFS
527 .add_sta_debugfs = rate_control_pid_add_sta_debugfs,
528 .remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
532 MODULE_DESCRIPTION("PID controller based rate control algorithm");
533 MODULE_AUTHOR("Stefano Brivio");
534 MODULE_AUTHOR("Mattias Nissler");
535 MODULE_LICENSE("GPL");
537 int __init rc80211_pid_init(void)
539 return ieee80211_rate_control_register(&mac80211_rcpid);
542 void rc80211_pid_exit(void)
544 ieee80211_rate_control_unregister(&mac80211_rcpid);
547 #ifdef CONFIG_MAC80211_RC_PID_MODULE
548 module_init(rc80211_pid_init);
549 module_exit(rc80211_pid_exit);