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encoding: Add bitvec based write_packet_uplink_ack 

The current write_packet_uplink_ack implementation is based on the
CSN.1 encoder which makes it difficult to do the bitmap encoding for
EGPRS.

Add a new implementation based on bitvec functions to create the
PACKET UPLINK ACK/NACK messages.

Sponsored-by: On-Waves ehf
This commit is contained in:
Jacob Erlbeck 2015-12-22 14:58:34 +01:00
parent 580edbc326
commit 37005a165d
2 changed files with 179 additions and 0 deletions
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176
src/encoding.cpp
View File

@ -516,6 +516,182 @@ void Encoding::write_packet_uplink_ack(struct gprs_rlcmac_bts *bts,
}
}
static void write_packet_ack_nack_desc_gprs(
struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
gprs_rlc_ul_window *window, bool is_final)
{
char rbb[65];
window->update_rbb(rbb);
rbb[64] = 0;
LOGP(DRLCMACUL, LOGL_DEBUG, "- V(N): \"%s\" R=Received "
"I=Invalid\n", rbb);
bitvec_write_field(dest, wp, is_final, 1); // FINAL_ACK_INDICATION
bitvec_write_field(dest, wp, window->ssn(), 7); // STARTING_SEQUENCE_NUMBER
for (int i = 0; i < 64; i++) {
/* Set bit at the appropriate position (see 3GPP TS 04.60 9.1.8.1) */
bool is_ack = (rbb[i] == 'R');
bitvec_write_field(dest, wp, is_ack, 1);
}
}
static void write_packet_uplink_ack_gprs(
struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
struct gprs_rlcmac_ul_tbf *tbf, bool is_final)
{
bitvec_write_field(dest, wp, tbf->current_cs() - 1, 2); // CHANNEL_CODING_COMMAND
write_packet_ack_nack_desc_gprs(bts, dest, wp, &tbf->m_window, is_final);
bitvec_write_field(dest, wp, 1, 1); // 1: have CONTENTION_RESOLUTION_TLLI
bitvec_write_field(dest, wp, tbf->tlli(), 32); // CONTENTION_RESOLUTION_TLLI
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Timing Advance
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Power Control Parameters
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Extension Bits
bitvec_write_field(dest, wp, 0, 1); // fixed 0
bitvec_write_field(dest, wp, 1, 1); // 1: have Additions R99
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Extended Timing Advance
bitvec_write_field(dest, wp, 1, 1); // TBF_EST (enabled)
bitvec_write_field(dest, wp, 0, 1); // 0: don't have REL 5
};
static void write_packet_ack_nack_desc_egprs(
struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
gprs_rlc_ul_window *window, bool is_final)
{
int urbb_len = 0;
int crbb_len = 0;
int len;
bool bow = true;
bool eow = true;
int ssn = window->mod_sns(window->v_q() + 1);
int num_blocks = window->mod_sns(window->v_r() - window->v_q());
int esn_crbb = window->mod_sns(ssn - 1);
int rest_bits = dest->data_len * 8 - wp;
if (num_blocks > 0)
/* V(Q) is NACK and omitted -> SSN = V(Q) + 1 */
num_blocks -= 1;
if (num_blocks > window->ws())
num_blocks = window->ws();
if (num_blocks > rest_bits) {
eow = false;
urbb_len = rest_bits;
/* TODO: use compression, start encoding bits and stop when the
* space is exhausted. Use the first combination that encodes
* all bits. If there is none, use the combination that encodes
* the largest number of bits (e.g. by setting num_blocks to the
* max and repeating the construction).
*/
} else if (num_blocks > rest_bits - 9) {
/* union bit and length field take 9 bits */
eow = false;
urbb_len = rest_bits - 9;
/* TODO: use compression (see above) */
}
if (urbb_len + crbb_len == rest_bits)
len = -1;
else if (crbb_len == 0)
len = urbb_len + 15;
else
len = urbb_len + crbb_len + 23;
/* EGPRS Ack/Nack Description IE */
if (len < 0) {
bitvec_write_field(dest, wp, 0, 1); // 0: don't have length
} else {
bitvec_write_field(dest, wp, 1, 1); // 1: have length
bitvec_write_field(dest, wp, len, 8); // length
}
bitvec_write_field(dest, wp, is_final, 1); // FINAL_ACK_INDICATION
bitvec_write_field(dest, wp, bow, 1); // BEGINNING_OF_WINDOW
bitvec_write_field(dest, wp, eow, 1); // END_OF_WINDOW
bitvec_write_field(dest, wp, ssn, 11); // STARTING_SEQUENCE_NUMBER
bitvec_write_field(dest, wp, 0, 1); // 0: don't have CRBB
/* TODO: Add CRBB support */
LOGP(DRLCMACUL, LOGL_DEBUG,
" - EGPRS URBB, len = %d, SSN = %d, ESN_CRBB = %d, "
"SNS = %d, WS = %d, V(Q) = %d, V(R) = %d%s%s\n",
urbb_len, ssn, esn_crbb,
window->sns(), window->ws(), window->v_q(), window->v_r(),
bow ? ", BOW" : "", eow ? ", EOW" : "");
for (int i = urbb_len; i > 0; i--) {
/* Set bit at the appropriate position (see 3GPP TS 04.60 12.3.1) */
bool is_ack = window->m_v_n.is_received(esn_crbb + i);
bitvec_write_field(dest, wp, is_ack, 1);
}
}
static void write_packet_uplink_ack_egprs(
struct gprs_rlcmac_bts *bts, bitvec * dest, unsigned& wp,
struct gprs_rlcmac_ul_tbf *tbf, bool is_final)
{
bitvec_write_field(dest, wp, 0, 2); // fixed 00
bitvec_write_field(dest, wp, 2, 4); // CHANNEL_CODING_COMMAND: MCS-3
// bitvec_write_field(dest, wp, tbf->current_cs() - 1, 4); // CHANNEL_CODING_COMMAND
bitvec_write_field(dest, wp, 0, 1); // 0: no RESEGMENT (nyi)
bitvec_write_field(dest, wp, 1, 1); // PRE_EMPTIVE_TRANSMISSION, TODO: This resembles GPRS, change it?
bitvec_write_field(dest, wp, 0, 1); // 0: no PRR_RETRANSMISSION_REQUEST, TODO: clarify
bitvec_write_field(dest, wp, 0, 1); // 0: no ARAC_RETRANSMISSION_REQUEST, TODO: clarify
bitvec_write_field(dest, wp, 1, 1); // 1: have CONTENTION_RESOLUTION_TLLI
bitvec_write_field(dest, wp, tbf->tlli(), 32); // CONTENTION_RESOLUTION_TLLI
bitvec_write_field(dest, wp, 1, 1); // TBF_EST (enabled)
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Timing Advance
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Packet Extended Timing Advance
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Power Control Parameters
bitvec_write_field(dest, wp, 0, 1); // 0: don't have Extension Bits
write_packet_ack_nack_desc_egprs(bts, dest, wp, &tbf->m_window, is_final);
bitvec_write_field(dest, wp, 0, 1); // fixed 0
bitvec_write_field(dest, wp, 0, 1); // 0: don't have REL 5
};
void Encoding::write_packet_uplink_ack(
struct gprs_rlcmac_bts *bts, bitvec * dest,
struct gprs_rlcmac_ul_tbf *tbf, bool is_final)
{
unsigned wp = 0;
LOGP(DRLCMACUL, LOGL_DEBUG, "Encoding Ack/Nack for %s "
"(final=%d)\n", tbf_name(tbf), is_final);
bitvec_write_field(dest, wp, 0x1, 2); // Payload Type
bitvec_write_field(dest, wp, 0x0, 2); // Uplink block with TDMA framenumber (N+13)
bitvec_write_field(dest, wp, is_final, 1); // Suppl/Polling Bit
bitvec_write_field(dest, wp, 0x0, 3); // Uplink state flag
bitvec_write_field(dest, wp, 0x9, 6); // MESSAGE TYPE Uplink Ack/Nack
bitvec_write_field(dest, wp, 0x0, 2); // Page Mode
bitvec_write_field(dest, wp, 0x0, 2); // fixed 00
bitvec_write_field(dest, wp, tbf->tfi(), 5); // Uplink TFI
if (tbf->is_egprs_enabled()) {
/* PU_AckNack_EGPRS = on */
bitvec_write_field(dest, wp, 1, 1); // 1: EGPRS
write_packet_uplink_ack_egprs(bts, dest, wp, tbf, is_final);
} else {
/* PU_AckNack_GPRS = on */
bitvec_write_field(dest, wp, 0, 1); // 0: GPRS
write_packet_uplink_ack_gprs(bts, dest, wp, tbf, is_final);
}
LOGP(DRLCMACUL, LOGL_DEBUG,
"Uplink Ack/Nack bit count %d, max %d, message = %s\n",
wp, dest->data_len * 8,
osmo_hexdump(dest->data, dest->data_len));
}
unsigned Encoding::write_packet_paging_request(bitvec * dest)
{
unsigned wp = 0;

3
src/encoding.h
View File

@ -58,6 +58,9 @@ public:
static void write_packet_uplink_ack(struct gprs_rlcmac_bts *bts, RlcMacDownlink_t * block, struct gprs_rlcmac_ul_tbf *tbf,
uint8_t final);
static void write_packet_uplink_ack(
struct gprs_rlcmac_bts *bts, bitvec * dest,
struct gprs_rlcmac_ul_tbf *tbf, bool is_final);
static int write_paging_request(bitvec * dest, uint8_t *ptmsi, uint16_t ptmsi_len);