Osmocom Packet control Unit (PCU): Network-side GPRS (RLC/MAC); BTS- or BSC-colocated https://osmocom.org/projects/osmopcu
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 
osmo-pcu/src/gprs_rlcmac_sched.cpp

542 lines
17 KiB

/* PDCH scheduler
*
* Copyright (C) 2012 Andreas Eversberg <jolly@eversberg.eu>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* 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 General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <gprs_bssgp_pcu.h>
#include <gprs_rlcmac.h>
#include <pcu_l1_if.h>
#include <bts.h>
#include <tbf.h>
#include <tbf_ul.h>
#include <gprs_debug.h>
#include <gprs_ms.h>
#include <rlc.h>
#include <sba.h>
#include <pdch.h>
#include "pcu_utils.h"
extern "C" {
#include <osmocom/core/gsmtap.h>
}
struct tbf_sched_candidates {
struct gprs_rlcmac_tbf *ul_ass;
struct gprs_rlcmac_tbf *dl_ass;
struct gprs_rlcmac_tbf *nacc;
struct gprs_rlcmac_ul_tbf *ul_ack;
};
static void get_ctrl_msg_tbf_candidates(const struct gprs_rlcmac_pdch *pdch,
struct tbf_sched_candidates *tbf_cand)
{
struct gprs_rlcmac_ul_tbf *ul_tbf;
struct gprs_rlcmac_dl_tbf *dl_tbf;
struct llist_item *pos;
llist_for_each_entry(pos, &pdch->trx->ul_tbfs, list) {
ul_tbf = as_ul_tbf((struct gprs_rlcmac_tbf *)pos->entry);
OSMO_ASSERT(ul_tbf);
/* this trx, this ts */
if (!ul_tbf->is_control_ts(pdch->ts_no))
continue;
if (tbf_ul_ack_rts(ul_tbf))
tbf_cand->ul_ack = ul_tbf;
if (tbf_dl_ass_rts(ul_tbf))
tbf_cand->dl_ass = ul_tbf;
if (tbf_ul_ass_rts(ul_tbf))
tbf_cand->ul_ass = ul_tbf;
/* NACC ready to send. TFI assigned is needed to send messages */
if (ul_tbf->is_tfi_assigned() && ms_nacc_rts(ul_tbf->ms()))
tbf_cand->nacc = ul_tbf;
/* FIXME: Is this supposed to be fair? The last TBF for each wins? Maybe use llist_add_tail and skip once we have all
states? */
}
llist_for_each_entry(pos, &pdch->trx->dl_tbfs, list) {
dl_tbf = as_dl_tbf((struct gprs_rlcmac_tbf *)pos->entry);
OSMO_ASSERT(dl_tbf);
/* this trx, this ts */
if (!dl_tbf->is_control_ts(pdch->ts_no))
continue;
if (tbf_dl_ass_rts(dl_tbf))
tbf_cand->dl_ass = dl_tbf;
if (tbf_ul_ass_rts(dl_tbf))
tbf_cand->ul_ass = dl_tbf;
/* NACC ready to send. TFI assigned is needed to send messages */
if (dl_tbf->is_tfi_assigned() && ms_nacc_rts(dl_tbf->ms()))
tbf_cand->nacc = dl_tbf;
}
}
static struct gprs_rlcmac_ul_tbf *sched_select_uplink(struct gprs_rlcmac_pdch *pdch, bool require_gprs_only)
{
struct gprs_rlcmac_ul_tbf *tbf;
uint8_t i, tfi;
/* select uplink resource */
for (i = 0, tfi = pdch->next_ul_tfi; i < 32;
i++, tfi = (tfi + 1) & 31) {
tbf = pdch->ul_tbf_by_tfi(tfi);
/* no TBF for this tfi, go next */
if (!tbf)
continue;
/* no UL resources needed, go next */
/* we don't need to give resources in FINISHED state,
* because we have received all blocks and only poll
* for packet control ack. */
if (tbf->state_is_not(TBF_ST_FLOW))
continue;
if (require_gprs_only && tbf->is_egprs_enabled())
continue;
/* use this USF (tbf) */
/* next TBF to handle resource is the next one */
pdch->next_ul_tfi = (tfi + 1) & 31;
return tbf;
}
return NULL;
}
struct msgb *sched_app_info(struct gprs_rlcmac_tbf *tbf) {
struct gprs_rlcmac_bts *bts;
struct msgb *msg = NULL;
if (!tbf || !tbf->ms()->app_info_pending)
return NULL;
bts = tbf->bts;
if (bts->app_info) {
LOGP(DRLCMACSCHED, LOGL_DEBUG, "Sending Packet Application Information message\n");
msg = msgb_copy(bts->app_info, "app_info_msg_sched");
} else
LOGP(DRLCMACSCHED, LOGL_ERROR, "MS has app_info_pending flag set, but no Packet Application Information"
" message stored in BTS!\n");
tbf->ms()->app_info_pending = false;
bts->app_info_pending--;
if (!bts->app_info_pending) {
LOGP(DRLCMACSCHED, LOGL_DEBUG, "Packet Application Information successfully sent to all MS with active"
" TBF\n");
msgb_free(bts->app_info);
bts->app_info = NULL;
}
return msg;
}
static struct msgb *sched_select_ctrl_msg(struct gprs_rlcmac_pdch *pdch, uint32_t fn,
uint8_t block_nr, struct tbf_sched_candidates *tbfs)
{
struct msgb *msg = NULL;
struct gprs_rlcmac_tbf *tbf = NULL;
struct gprs_rlcmac_tbf *next_list[] = { tbfs->ul_ass,
tbfs->dl_ass,
tbfs->ul_ack,
tbfs->nacc };
uint8_t ts = pdch->ts_no;
/* Send Packet Application Information first (ETWS primary notifications) */
msg = sched_app_info(tbfs->dl_ass);
if (!msg) {
for (size_t i = 0; i < ARRAY_SIZE(next_list); ++i) {
tbf = next_list[(pdch->next_ctrl_prio + i) % ARRAY_SIZE(next_list)];
if (!tbf)
continue;
/*
* Assignments for the same direction have lower precedence,
* because they may kill the TBF when the CONTROL ACK is
* received, thus preventing the others from being processed.
*/
if (tbf == tbfs->ul_ass && tbf->ul_ass_state_is(TBF_UL_ASS_SEND_ASS_REJ))
msg = tbf_ul_ass_create_rlcmac_msg(tbfs->ul_ass, fn, ts);
else if (tbf == tbfs->ul_ass && tbf->direction == GPRS_RLCMAC_DL_TBF)
msg = tbf_ul_ass_create_rlcmac_msg(tbfs->ul_ass, fn, ts);
else if (tbf == tbfs->dl_ass && tbf->direction == GPRS_RLCMAC_UL_TBF)
msg = tbf_dl_ass_create_rlcmac_msg(tbfs->dl_ass, fn, ts);
else if (tbf == tbfs->ul_ack)
msg = tbf_ul_ack_create_rlcmac_msg(tbfs->ul_ack, fn, ts);
else if (tbf == tbfs->nacc) {
msg = ms_nacc_create_rlcmac_msg(tbf->ms(), tbf, fn, ts);
}
if (!msg) {
tbf = NULL;
continue;
}
pdch->next_ctrl_prio = (pdch->next_ctrl_prio + 1) % ARRAY_SIZE(next_list);
break;
}
}
if (!msg) {
/*
* If one of these is left, the response (CONTROL ACK) from the
* MS will kill the current TBF, only one of them can be
* non-NULL
*/
if (tbfs->dl_ass) {
tbf = tbfs->dl_ass;
msg = tbf_dl_ass_create_rlcmac_msg(tbfs->dl_ass, fn, ts);
} else if (tbfs->ul_ass) {
tbf = tbfs->ul_ass;
msg = tbf_ul_ass_create_rlcmac_msg(tbfs->ul_ass, fn, ts);
}
}
/* any message */
if (msg) {
if (!tbf) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_ERROR, "FN=%" PRIu32
" Control message to be scheduled, but no TBF\n", fn);
msgb_free(msg);
return NULL;
}
tbf->rotate_in_list();
LOGPDCH(pdch, DRLCMACSCHED, LOGL_DEBUG, "FN=%" PRIu32
" Scheduling control message at RTS for %s\n",
fn, tbf_name(tbf));
rate_ctr_inc(rate_ctr_group_get_ctr(tbf->ms()->ctrs, MS_CTR_DL_CTRL_MSG_SCHED));
return msg;
}
/* schedule PACKET PAGING REQUEST, if any are pending */
msg = pdch->packet_paging_request();
if (msg) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_DEBUG, "FN=%" PRIu32
" Scheduling paging request message at RTS\n", fn);
return msg;
}
return NULL;
}
static inline enum tbf_dl_prio tbf_compute_priority(const struct gprs_rlcmac_bts *bts, struct gprs_rlcmac_dl_tbf *tbf,
uint8_t ts, uint32_t fn, int age)
{
const gprs_rlc_dl_window *w = static_cast<gprs_rlc_dl_window *>(tbf->window());
unsigned long msecs_t3190 = osmo_tdef_get(the_pcu->T_defs, 3190, OSMO_TDEF_MS, -1);
unsigned long dl_tbf_idle_msec = osmo_tdef_get(the_pcu->T_defs, -2031, OSMO_TDEF_MS, -1);
int age_thresh1 = msecs_to_frames(200);
int age_thresh2 = msecs_to_frames(OSMO_MIN(msecs_t3190/2, dl_tbf_idle_msec));
if (tbf->is_control_ts(ts) && tbf->need_poll_for_dl_ack_nack())
return DL_PRIO_CONTROL;
if (tbf->is_control_ts(ts) && age > age_thresh2 && age_thresh2 > 0)
return DL_PRIO_HIGH_AGE;
if ((tbf->state_is(TBF_ST_FLOW) && tbf->have_data()) || w->resend_needed() >= 0)
return DL_PRIO_NEW_DATA;
if (tbf->is_control_ts(ts) && age > age_thresh1 && tbf->keep_open(fn))
return DL_PRIO_LOW_AGE;
if (!w->window_empty())
return DL_PRIO_SENT_DATA;
return DL_PRIO_NONE;
}
/* Check if next data block of a TBF can be encoded in GMSK [(M)CS1-4]. */
static bool can_produce_gmsk_data_block_next(struct gprs_rlcmac_dl_tbf *tbf, enum tbf_dl_prio prio)
{
const gprs_rlc_dl_window *w;
/* GPRS TBFs can always send GMSK */
if (!tbf->is_egprs_enabled())
return true;
switch (prio) {
case DL_PRIO_CONTROL:
/* Control blocks are always CS-1 */
return true;
case DL_PRIO_NEW_DATA:
/* We can send any new data (no block generated yet) using any
* MCS. However, we don't (yet) support resegmenting already
* sent blocks (NACKed blocks in this case) into lower MCS of
* the same family. See OS#4966 */
w = static_cast<gprs_rlc_dl_window *>(tbf->window());
return w->resend_needed() < 0;
default:
return false;
}
}
static struct msgb *sched_select_dl_data_msg(struct gprs_rlcmac_bts *bts, struct gprs_rlcmac_pdch *pdch,
uint32_t fn, uint8_t block_nr, enum mcs_kind req_mcs_kind,
bool *is_egprs)
{
struct msgb *msg = NULL;
struct gprs_rlcmac_dl_tbf *tbf, *prio_tbf = NULL;
enum tbf_dl_prio prio, max_prio = DL_PRIO_NONE;
uint8_t ts = pdch->ts_no;
uint8_t i, tfi, prio_tfi;
int age;
/* select downlink resource */
for (i = 0, tfi = pdch->next_dl_tfi; i < 32;
i++, tfi = (tfi + 1) & 31) {
tbf = pdch->dl_tbf_by_tfi(tfi);
/* no TBF for this tfi, go next */
if (!tbf)
continue;
/* no DL TBF, go next */
if (tbf->direction != GPRS_RLCMAC_DL_TBF)
continue;
/* no DL resources needed, go next */
if (tbf->state_is_not(TBF_ST_FLOW)
&& tbf->state_is_not(TBF_ST_FINISHED))
continue;
/* If a GPRS (CS1-4) Dl block is required, skip EGPRS(_GSMK) tbfs: */
if (req_mcs_kind == GPRS && tbf->is_egprs_enabled())
continue;
age = tbf->frames_since_last_poll(fn);
/* compute priority */
prio = tbf_compute_priority(bts, tbf, ts, fn, age);
if (prio == DL_PRIO_NONE)
continue;
/* If a GPRS (CS1-4/MCS1-4) Dl block is required, downgrade MCS
* below instead of skipping. However, downgrade can only be
* done on new data BSNs (not yet sent) and control blocks. */
if (req_mcs_kind == EGPRS_GMSK && !can_produce_gmsk_data_block_next(tbf, prio)) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_DEBUG, "FN=%" PRIu32
" Cannot downgrade EGPRS TBF with prio %d for %s\n",
fn, prio, tbf_name(tbf));
continue;
}
/* get the TBF with the highest priority */
if (prio > max_prio) {
prio_tfi = tfi;
prio_tbf = tbf;
max_prio = prio;
}
}
if (prio_tbf) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_DEBUG, "FN=%" PRIu32
" Scheduling data message at RTS for DL TFI=%d prio=%d mcs_mode_restrict=%s\n",
fn, prio_tfi, max_prio, mode_name(req_mcs_kind));
/* next TBF to handle resource is the next one */
pdch->next_dl_tfi = (prio_tfi + 1) & 31;
/* generate DL data block */
msg = prio_tbf->create_dl_acked_block(fn, ts, req_mcs_kind);
*is_egprs = prio_tbf->is_egprs_enabled();
}
return msg;
}
static const uint8_t rlcmac_dl_idle[23] = {
0x47, /* control without optional header octets, no polling, USF=111 */
0x94, /* dummy downlink control message, paging mode 00 */
0x2b, /* no persistance level, 7 bits spare pattern */
0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b,
0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b, 0x2b
};
static struct msgb *sched_dummy(void)
{
struct msgb *msg;
msg = msgb_alloc(23, "rlcmac_dl_idle");
if (!msg)
return NULL;
memcpy(msgb_put(msg, 23), rlcmac_dl_idle, 23);
return msg;
}
static inline void tap_n_acc(const struct msgb *msg, struct gprs_rlcmac_bts *bts, uint8_t trx, uint8_t ts,
uint32_t fn, enum pcu_gsmtap_category cat)
{
if (!msg)
return;
switch(cat) {
case PCU_GSMTAP_C_DL_CTRL:
bts_do_rate_ctr_inc(bts, CTR_RLC_SENT_CONTROL);
bts_send_gsmtap(bts, PCU_GSMTAP_C_DL_CTRL, false, trx, ts, GSMTAP_CHANNEL_PACCH, fn, msg->data,
msg->len);
break;
case PCU_GSMTAP_C_DL_DATA_GPRS:
case PCU_GSMTAP_C_DL_DATA_EGPRS:
bts_do_rate_ctr_inc(bts, CTR_RLC_SENT);
bts_send_gsmtap(bts, cat, false, trx, ts, GSMTAP_CHANNEL_PDTCH, fn, msg->data,
msg->len);
break;
case PCU_GSMTAP_C_DL_DUMMY:
bts_do_rate_ctr_inc(bts, CTR_RLC_SENT_DUMMY);
bts_send_gsmtap(bts, PCU_GSMTAP_C_DL_DUMMY, false, trx, ts, GSMTAP_CHANNEL_PACCH, fn, msg->data,
msg->len);
break;
default:
break;
}
}
int gprs_rlcmac_rcv_rts_block(struct gprs_rlcmac_bts *bts,
uint8_t trx, uint8_t ts,
uint32_t fn, uint8_t block_nr)
{
struct gprs_rlcmac_pdch *pdch;
struct tbf_sched_candidates tbf_cand = {0};
struct gprs_rlcmac_tbf *poll_tbf;
struct gprs_rlcmac_ul_tbf *usf_tbf = NULL;
struct gprs_rlcmac_sba *sba;
uint8_t usf;
struct msgb *msg = NULL;
uint32_t poll_fn;
enum pcu_gsmtap_category gsmtap_cat = PCU_GSMTAP_C_DL_DUMMY; /* init: make gcc happy */
bool tx_is_egprs = false;
bool require_gprs_only;
enum mcs_kind req_mcs_kind; /* Restrict CS/MCS if DL Data block is to be sent */
if (trx >= 8 || ts >= 8)
return -EINVAL;
pdch = &bts->trx[trx].pdch[ts];
if (!pdch->is_enabled()) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_INFO, "Received RTS on disabled TS\n");
return -EIO;
}
/* store last frame number of RTS */
pdch->last_rts_fn = fn;
/* require_gprs_only: Prioritize USF for GPRS-only MS here,
* since anyway we'll need to tx a Dl block with CS1-4 due to
* synchronization requirements. See 3GPP TS 03.64 version
* 8.12.0
*/
require_gprs_only = (pdch->fn_without_cs14 == MS_RESYNC_NUM_FRAMES - 1);
if (require_gprs_only) {
LOGP(DRLCMACSCHED, LOGL_DEBUG, "TRX=%d TS=%d FN=%d "
"synchronization frame (every 18 frames), only CS1-4 allowed",
trx, ts, fn);
req_mcs_kind = GPRS; /* only GPRS CS1-4 allowed, all MS need to be able to decode it */
} else {
req_mcs_kind = EGPRS; /* all kinds are fine */
}
/* polling for next uplink block */
poll_fn = rts_next_fn(fn, block_nr);
/* check for sba */
if ((sba = pdch_ulc_get_sba(pdch->ulc, poll_fn))) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_DEBUG, "Received RTS for PDCH: "
"FN=%d block_nr=%d scheduling free USF for "
"single block allocation at FN=%d\n", fn, block_nr, sba->fn);
/* else, check uplink resource for polling */
} else if ((poll_tbf = pdch_ulc_get_tbf_poll(pdch->ulc, poll_fn))) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_DEBUG, "Received RTS for PDCH: FN=%d "
"block_nr=%d scheduling free USF for polling at FN=%d of %s\n",
fn, block_nr, poll_fn, tbf_name(poll_tbf));
/* If POLL TBF is UL and already has a USF assigned on this TS,
* let's set its USF in the DL msg. This is not really needed,
* but it helps understand better the flow when looking at
* pcaps. */
if (poll_tbf->direction == GPRS_RLCMAC_UL_TBF && as_ul_tbf(poll_tbf)->m_usf[ts] != USF_INVALID)
usf_tbf = as_ul_tbf(poll_tbf);
/* else, search for uplink tbf */
} else if ((usf_tbf = sched_select_uplink(pdch, require_gprs_only))) {
LOGPDCH(pdch, DRLCMACSCHED, LOGL_DEBUG, "Received RTS for PDCH: FN=%d "
"block_nr=%d scheduling USF=%d for %s, expect answer on UL FN=%d\n",
fn, block_nr, usf_tbf->m_usf[pdch->ts_no], tbf_name(usf_tbf), poll_fn);
pdch_ulc_reserve_tbf_usf(pdch->ulc, poll_fn, usf_tbf);
}
/* If MS selected for USF is GPRS-only, then it will only be
* able to read USF if dl block uses GMSK (CS1-4, MCS1-4) */
if (usf_tbf && req_mcs_kind == EGPRS && ms_mode(usf_tbf->ms()) != EGPRS)
req_mcs_kind = EGPRS_GMSK;
get_ctrl_msg_tbf_candidates(pdch, &tbf_cand);
/* Prio 1: select control message */
if ((msg = sched_select_ctrl_msg(pdch, fn, block_nr, &tbf_cand))) {
gsmtap_cat = PCU_GSMTAP_C_DL_CTRL;
}
/* Prio 2: select data message for downlink */
else if((msg = sched_select_dl_data_msg(bts, pdch, fn, block_nr, req_mcs_kind, &tx_is_egprs))) {
gsmtap_cat = tx_is_egprs ? PCU_GSMTAP_C_DL_DATA_EGPRS :
PCU_GSMTAP_C_DL_DATA_GPRS;
}
/* Prio 3: send dummy control message if need to poll or USF */
else {
/* If there's no TBF attached to this PDCH, we can submit an empty
* data_req since there's nothing to transmit nor to poll/USF. This
* way we help BTS energy saving (on TRX!=C0) by sending nothing
* instead of a dummy block. The early return is done here and
* not at the start of the function because the condition below
* (num_tbfs==0) may not be enough, because temporary dummy TBFs
* created to send Imm Ass Rej (see handle_tbf_reject()) don't
* have a TFI assigned and hence are not attached to the PDCH
* TS, so they don't show up in the count below.
*/
const unsigned num_tbfs = pdch->num_tbfs(GPRS_RLCMAC_DL_TBF)
+ pdch->num_tbfs(GPRS_RLCMAC_UL_TBF);
bool skip_idle = (num_tbfs == 0);
#ifdef ENABLE_DIRECT_PHY
/* In DIRECT_PHY mode we want to always submit something to L1 in
* TRX0, since BTS is not preparing dummy bursts on idle TS for us */
skip_idle = skip_idle && trx != 0;
#endif
if (!skip_idle && (msg = sched_dummy())) {
/* increase counter */
gsmtap_cat = PCU_GSMTAP_C_DL_DUMMY;
} else {
msg = NULL; /* submit empty frame */
}
}
if (tx_is_egprs && pdch->has_gprs_only_tbf_attached()) {
pdch->fn_without_cs14 += 1;
} else {
pdch->fn_without_cs14 = 0;
}
/* Used to measure the leak rate, count all blocks */
gprs_bssgp_update_frames_sent();
if (msg) {
/* msg is now available */
bts_do_rate_ctr_add(bts, CTR_RLC_DL_BYTES, msgb_length(msg));
/* set USF */
OSMO_ASSERT(msgb_length(msg) > 0);
usf = usf_tbf ? usf_tbf->m_usf[ts] : USF_UNUSED;
msg->data[0] = (msg->data[0] & 0xf8) | usf;
/* Send to GSMTAP */
tap_n_acc(msg, bts, trx, ts, fn, gsmtap_cat);
}
/* send PDTCH/PACCH to L1. msg=NULL accepted too (idle block) */
pcu_l1if_tx_pdtch(msg, bts, trx, ts, bts->trx[trx].arfcn, fn, block_nr);
return 0;
}