Osmocom Packet control Unit (PCU): Network-side GPRS (RLC/MAC); BTS- or BSC-colocated https://osmocom.org/projects/osmopcu
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osmo-pcu/src/rlc.cpp

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/*
* Copyright (C) 2013 by Holger Hans Peter Freyther
*
* 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 "bts.h"
#include "gprs_debug.h"
#include <rlc.h>
#include <stdbool.h>
#include <string.h>
#include <sys/types.h>
extern "C" {
#include <osmocom/core/utils.h>
#include <osmocom/core/bitvec.h>
#include <osmocom/core/logging.h>
#include "coding_scheme.h"
}
uint8_t *prepare(struct gprs_rlc_data *rlc, size_t block_data_len)
{
/* todo.. only set it once if it turns out to be a bottleneck */
memset(rlc->block, 0x0, sizeof(rlc->block));
memset(rlc->block, 0x2b, block_data_len);
/* Initial value of puncturing scheme */
rlc->next_ps = EGPRS_PS_1;
return rlc->block;
}
void gprs_rlc_v_b::reset()
{
for (size_t i = 0; i < ARRAY_SIZE(m_v_b); ++i)
mark_invalid(i);
}
void gprs_rlc_dl_window::reset()
{
m_v_s = 0;
m_v_a = 0;
m_v_b.reset();
}
int gprs_rlc_dl_window::resend_needed() const
{
for (uint16_t bsn = v_a(); bsn != v_s(); bsn = mod_sns(bsn + 1)) {
if (m_v_b.is_nacked(bsn) || m_v_b.is_resend(bsn))
return bsn;
}
return -1;
}
int gprs_rlc_dl_window::mark_for_resend()
{
int resend = 0;
for (uint16_t bsn = v_a(); bsn != v_s(); bsn = mod_sns(bsn + 1)) {
if (m_v_b.is_unacked(bsn)) {
/* mark to be re-send */
m_v_b.mark_resend(bsn);
resend += 1;
}
}
return resend;
}
/* Update the receive block bitmap */
uint16_t gprs_rlc_ul_window::update_egprs_rbb(uint8_t *rbb)
{
uint16_t i;
uint16_t bsn;
uint16_t bitmask = 0x80;
int8_t pos = 0;
int8_t bit_pos = 0;
for (i = 0, bsn = (v_q()+1); ((bsn < (v_r())) && (i < ws())); i++,
bsn = this->mod_sns(bsn + 1)) {
if (m_v_n.is_received(bsn)) {
rbb[pos] = rbb[pos] | bitmask;
} else {
rbb[pos] = rbb[pos] & (~bitmask);
}
bitmask = bitmask >> 1;
bit_pos++;
bit_pos = bit_pos % 8;
if (bit_pos == 0) {
pos++;
bitmask = 0x80;
}
}
return i;
}
int gprs_rlc_dl_window::count_unacked()
{
uint16_t unacked = 0;
uint16_t bsn;
for (bsn = v_a(); bsn != v_s(); bsn = mod_sns(bsn + 1)) {
if (!m_v_b.is_acked(bsn))
unacked += 1;
}
return unacked;
}
static uint16_t bitnum_to_bsn(int bitnum, uint16_t ssn)
{
return (ssn - 1 - bitnum);
}
void gprs_rlc_dl_window::update(struct gprs_rlcmac_bts *bts, const struct bitvec *rbb,
uint16_t first_bsn, uint16_t *lost,
uint16_t *received)
{
unsigned dist = distance();
unsigned num_blocks = rbb->cur_bit > dist
? dist : rbb->cur_bit;
unsigned bsn;
/* first_bsn is in range V(A)..V(S) */
for (unsigned int bitpos = 0; bitpos < num_blocks; bitpos++) {
bool is_ack;
bsn = mod_sns(first_bsn + bitpos);
if (bsn == mod_sns(v_a() - 1))
break;
is_ack = bitvec_get_bit_pos(rbb, bitpos) == 1;
if (is_ack) {
LOGP(DRLCMACDL, LOGL_DEBUG, "- got ack for BSN=%d\n", bsn);
if (!m_v_b.is_acked(bsn))
*received += 1;
m_v_b.mark_acked(bsn);
} else {
LOGP(DRLCMACDL, LOGL_DEBUG, "- got NACK for BSN=%d\n", bsn);
m_v_b.mark_nacked(bsn);
bts_do_rate_ctr_inc(bts, CTR_RLC_NACKED);
*lost += 1;
}
}
}
void gprs_rlc_dl_window::update(struct gprs_rlcmac_bts *bts, char *show_rbb, uint16_t ssn,
uint16_t *lost, uint16_t *received)
{
/* SSN - 1 is in range V(A)..V(S)-1 */
for (int bitpos = 0; bitpos < ws(); bitpos++) {
uint16_t bsn = mod_sns(bitnum_to_bsn(bitpos, ssn));
if (bsn == mod_sns(v_a() - 1))
break;
if (show_rbb[ws() - 1 - bitpos] == 'R') {
LOGP(DRLCMACDL, LOGL_DEBUG, "- got ack for BSN=%d\n", bsn);
if (!m_v_b.is_acked(bsn))
*received += 1;
m_v_b.mark_acked(bsn);
} else {
LOGP(DRLCMACDL, LOGL_DEBUG, "- got NACK for BSN=%d\n", bsn);
m_v_b.mark_nacked(bsn);
bts_do_rate_ctr_inc(bts, CTR_RLC_NACKED);
*lost += 1;
}
}
}
int gprs_rlc_dl_window::move_window()
{
int i;
uint16_t bsn;
int moved = 0;
for (i = 0, bsn = v_a(); bsn != v_s(); i++, bsn = mod_sns(bsn + 1)) {
if (m_v_b.is_acked(bsn)) {
m_v_b.mark_invalid(bsn);
moved += 1;
} else
break;
}
return moved;
}
void gprs_rlc_dl_window::show_state(char *show_v_b)
{
int i;
uint16_t bsn;
for (i = 0, bsn = v_a(); bsn != v_s(); i++, bsn = mod_sns(bsn + 1)) {
uint16_t index = bsn & mod_sns_half();
switch(m_v_b.get_state(index)) {
case GPRS_RLC_DL_BSN_INVALID:
show_v_b[i] = 'I';
break;
case GPRS_RLC_DL_BSN_ACKED:
show_v_b[i] = 'A';
break;
case GPRS_RLC_DL_BSN_RESEND:
show_v_b[i] = 'X';
break;
case GPRS_RLC_DL_BSN_NACKED:
show_v_b[i] = 'N';
break;
default:
show_v_b[i] = '?';
}
}
show_v_b[i] = '\0';
}
void gprs_rlc_v_n::reset()
{
for (size_t i = 0; i < ARRAY_SIZE(m_v_n); ++i)
m_v_n[i] = GPRS_RLC_UL_BSN_INVALID;
}
void gprs_rlc_window::set_sns(uint16_t sns)
{
OSMO_ASSERT(sns >= RLC_GPRS_SNS);
OSMO_ASSERT(sns <= RLC_MAX_SNS);
/* check for 2^n */
OSMO_ASSERT((sns & (-sns)) == sns);
m_sns = sns;
}
void gprs_rlc_window::set_ws(uint16_t ws)
{
LOGP(DRLCMAC, LOGL_INFO, "ws(%d)\n",
ws);
OSMO_ASSERT(ws >= RLC_GPRS_SNS/2);
OSMO_ASSERT(ws <= RLC_MAX_SNS/2);
m_ws = ws;
}
/* Update the receive block bitmap */
void gprs_rlc_ul_window::update_rbb(char *rbb)
{
int i;
for (i=0; i < ws(); i++) {
if (m_v_n.is_received((ssn()-1-i) & mod_sns()))
rbb[ws()-1-i] = 'R';
else
rbb[ws()-1-i] = 'I';
}
}
/* Raise V(R) to highest received sequence number not received. */
void gprs_rlc_ul_window::raise_v_r(const uint16_t bsn)
{
uint16_t offset_v_r;
offset_v_r = mod_sns(bsn + 1 - v_r());
/* Positive offset, so raise. */
if (offset_v_r < (sns() >> 1)) {
while (offset_v_r--) {
if (offset_v_r) /* all except the received block */
m_v_n.mark_missing(v_r());
raise_v_r_to(1);
}
LOGP(DRLCMACUL, LOGL_DEBUG, "- Raising V(R) to %d\n", v_r());
}
}
/*
* Raise V(Q) if possible. This is looped until there is a gap
* (non received block) or the window is empty.
*/
uint16_t gprs_rlc_ul_window::raise_v_q()
{
uint16_t count = 0;
while (v_q() != v_r()) {
if (!m_v_n.is_received(v_q()))
break;
LOGP(DRLCMACUL, LOGL_DEBUG, "- Taking block %d out, raising "
"V(Q) to %d\n", v_q(), mod_sns(v_q() + 1));
raise_v_q(1);
count += 1;
}
return count;
}
void gprs_rlc_ul_window::receive_bsn(const uint16_t bsn)
{
m_v_n.mark_received(bsn);
raise_v_r(bsn);
}
bool gprs_rlc_ul_window::invalidate_bsn(const uint16_t bsn)
{
bool was_valid = m_v_n.is_received(bsn);
m_v_n.mark_missing(bsn);
return was_valid;
}
static void gprs_rlc_data_header_init(struct gprs_rlc_data_info *rlc,
enum CodingScheme cs, bool with_padding, unsigned int header_bits,
const unsigned int spb)
{
unsigned int i;
unsigned int padding_bits = with_padding ? mcs_opt_padding_bits(cs) : 0;
rlc->cs = cs;
rlc->r = 0;
rlc->si = 0;
rlc->tfi = 0;
rlc->cps = 0;
rlc->rsb = 0;
rlc->usf = 0;
rlc->es_p = 0;
rlc->rrbp = 0;
rlc->pr = 0;
rlc->num_data_blocks = num_data_blocks(mcs_header_type(cs));
rlc->with_padding = with_padding;
OSMO_ASSERT(rlc->num_data_blocks <= ARRAY_SIZE(rlc->block_info));
for (i = 0; i < rlc->num_data_blocks; i++) {
gprs_rlc_data_block_info_init(&rlc->block_info[i], cs,
with_padding, spb);
rlc->data_offs_bits[i] =
header_bits + padding_bits +
(i+1) * num_data_block_header_bits(mcs_header_type(cs)) +
i * 8 * rlc->block_info[0].data_len;
}
}
void gprs_rlc_data_info_init_dl(struct gprs_rlc_data_info *rlc,
enum CodingScheme cs, bool with_padding, const unsigned int spb)
{
OSMO_ASSERT(mcs_is_valid(cs));
return gprs_rlc_data_header_init(rlc, cs, with_padding,
num_data_header_bits_DL(mcs_header_type(cs)), spb);
}
void gprs_rlc_data_info_init_ul(struct gprs_rlc_data_info *rlc,
enum CodingScheme cs, bool with_padding)
{
OSMO_ASSERT(mcs_is_valid(cs));
/*
* last parameter is sent as 0 since common function used
* for both DL and UL
*/
return gprs_rlc_data_header_init(rlc, cs, with_padding,
num_data_header_bits_UL(mcs_header_type(cs)), 0);
}
void gprs_rlc_data_block_info_init(struct gprs_rlc_data_block_info *rdbi,
enum CodingScheme cs, bool with_padding, const unsigned int spb)
{
unsigned int data_len = mcs_max_data_block_bytes(cs);
if (with_padding)
data_len -= mcs_opt_padding_bits(cs) / 8;
rdbi->data_len = data_len;
rdbi->bsn = 0;
rdbi->ti = 0;
rdbi->e = 1;
rdbi->cv = 15;
rdbi->pi = 0;
rdbi->spb = spb;
}
unsigned int gprs_rlc_mcs_cps(enum CodingScheme cs,
enum egprs_puncturing_values punct,
enum egprs_puncturing_values punct2, bool with_padding)
{
/* validate that punct and punct2 are as expected */
switch (cs) {
case MCS9:
case MCS8:
case MCS7:
if (punct2 == EGPRS_PS_INVALID) {
LOGP(DRLCMACDL, LOGL_ERROR,
"Invalid punct2 value for coding scheme %d: %d\n",
cs, punct2);
return -1;
}
/* fall through */
case MCS6:
case MCS5:
case MCS4:
case MCS3:
case MCS2:
case MCS1:
if (punct == EGPRS_PS_INVALID) {
LOGP(DRLCMACDL, LOGL_ERROR,
"Invalid punct value for coding scheme %d: %d\n",
cs, punct);
return -1;
}
break;
default:
return -1;
}
/* See 3GPP TS 44.060 10.4.8a.3.1, 10.4.8a.2.1, 10.4.8a.1.1 */
switch (cs) {
case MCS1: return 0b1011 +
punct % EGPRS_MAX_PS_NUM_2;
case MCS2: return 0b1001 +
punct % EGPRS_MAX_PS_NUM_2;
case MCS3: return (with_padding ? 0b0110 : 0b0011) +
punct % EGPRS_MAX_PS_NUM_3;
case MCS4: return 0b0000 +
punct % EGPRS_MAX_PS_NUM_3;
case MCS5: return 0b100 +
punct % EGPRS_MAX_PS_NUM_2;
case MCS6: return (with_padding ? 0b010 : 0b000) +
punct % EGPRS_MAX_PS_NUM_2;
case MCS7: return 0b10100 +
3 * (punct % EGPRS_MAX_PS_NUM_3) +
punct2 % EGPRS_MAX_PS_NUM_3;
case MCS8: return 0b01011 +
3 * (punct % EGPRS_MAX_PS_NUM_3) +
punct2 % EGPRS_MAX_PS_NUM_3;
case MCS9: return 0b00000 +
4 * (punct % EGPRS_MAX_PS_NUM_3) +
punct2 % EGPRS_MAX_PS_NUM_3;
default: ;
}
return -1;
}
void gprs_rlc_mcs_cps_decode(unsigned int cps,
enum CodingScheme cs, int *punct, int *punct2, int *with_padding)
{
*punct2 = -1;
*with_padding = 0;
switch (cs) {
case MCS1:
cps -= 0b1011; *punct = cps % 2; break;
case MCS2:
cps -= 0b1001; *punct = cps % 2; break;
case MCS3:
cps -= 0b0011; *punct = cps % 3; *with_padding = cps >= 3; break;
case MCS4:
cps -= 0b0000; *punct = cps % 3; break;
case MCS5:
cps -= 0b100; *punct = cps % 2; break;
case MCS6:
cps -= 0b000; *punct = cps % 2; *with_padding = cps >= 2; break;
case MCS7:
cps -= 0b10100; *punct = cps / 3; *punct2 = cps % 3; break;
case MCS8:
cps -= 0b01011; *punct = cps / 3; *punct2 = cps % 3; break;
case MCS9:
cps -= 0b00000; *punct = cps / 4; *punct2 = cps % 3; break;
default: ;
}
}
/*
* Finds the PS value for retransmission with MCS change,
* retransmission with no MCS change, fresh transmission cases.
* The return value shall be used for current transmission only
* 44.060 9.3.2.1 defines the PS selection for MCS change case
* cs_current is the output of MCS selection algorithm for retx
* cs is coding scheme of previous transmission of RLC data block
*/
enum egprs_puncturing_values gprs_get_punct_scheme(
enum egprs_puncturing_values punct,
const enum CodingScheme &cs,
const enum CodingScheme &cs_current,
const enum egprs_rlcmac_dl_spb spb)
{
/*
* 10.4.8b of TS 44.060
* If it is second segment of the block
* dont change the puncturing scheme
*/
if (spb == EGPRS_RLCMAC_DL_SEC_SEG)
return punct;
/* TS 44.060 9.3.2.1.1 */
if ((cs == MCS9) &&
(cs_current == MCS6)) {
if ((punct == EGPRS_PS_1) || (punct == EGPRS_PS_3))
return EGPRS_PS_1;
else if (punct == EGPRS_PS_2)
return EGPRS_PS_2;
} else if ((cs == MCS6) &&
(cs_current == MCS9)) {
if (punct == EGPRS_PS_1)
return EGPRS_PS_3;
else if (punct == EGPRS_PS_2)
return EGPRS_PS_2;
} else if ((cs == MCS7) &&
(cs_current == MCS5))
return EGPRS_PS_1;
else if ((cs == MCS5) &&
(cs_current == MCS7))
return EGPRS_PS_2;
else if (cs != cs_current)
return EGPRS_PS_1;
/* TS 44.060 9.3.2.1.1 ends here */
/*
* Below else will handle fresh transmission, retransmission with no
* MCS change case
*/
else
return punct;
return EGPRS_PS_INVALID;
}
/*
* This function calculates puncturing scheme for retransmission of a RLC
* block with same MCS. The computed value shall be used for next transmission
* of the same RLC block
* TS 44.060 10.4.8a.3.1, 10.4.8a.2.1, 10.4.8a.1.1
*/
void gprs_update_punct_scheme(enum egprs_puncturing_values *punct,
const enum CodingScheme &cs)
{
switch (cs) {
case MCS1 :
case MCS2 :
case MCS5 :
case MCS6 :
*punct = ((enum egprs_puncturing_values)((*punct + 1) %
EGPRS_MAX_PS_NUM_2));
break;
case MCS3 :
case MCS4 :
case MCS7 :
case MCS8 :
case MCS9 :
*punct = ((enum egprs_puncturing_values)((*punct + 1) %
EGPRS_MAX_PS_NUM_3));
break;
default:
break;
}
}