falconia has uploaded this change for review.
TRAU encode: fix handling of OSMO_TRAU16_FT_IDLE
GSM 08.60 sections 3.4 and 3.5.5 (renumbered to 5.4 and 5.5.5 in
3GPP TS 48.060) define a special frame type called Idle Speech Frame.
It is not clear if any historical BSS vendor actually implemented
these special frames - Nokia documentation explicitly mentions how
they were deemed unnecessary and omitted from implementation - but
libosmotrau includes support for this frame type.
Looking at the referenced spec sections, we can see the designers'
intent: the idle speech frame is just like FRv1 speech frames,
but with different UL/DL frame type codes in C1..C5 and with all
Dn bits replaced with constant-1 filler. Following this design
intent on the part of GSM spec authors, the philophically correct
behavior for osmo_trau_frame_encode() with regard to this frame type
should be to handle it exactly the same as OSMO_TRAU16_FT_FR
(support both DL and UL output, timing alignment in DL, possibility
of changing C6..C21 and T-bits), but don't look at fr->d_bits[],
fill constant 1s in their place instead.
However, the behavior of the encoding function for this frame type
prior to the present change was not like this at all: instead it
would emit a constant (once and for all) frame of 320 bits that was
always for DL no matter which direction was requested, would not
allow time alignment, and would not allow any C-bits to be controlled
by upper layers.
At the present time there is no code anywhere in Osmocom that feeds
OSMO_TRAU16_FT_IDLE to osmo_trau_frame_encode() - thus we don't have
to maintain backward bug compatibility, and we can fix this design bug.
Change-Id: Ibcc9e8628a56c6f089264c9d6b0dd27a1d5a7b60
---
M src/trau/trau_frame.c
1 file changed, 23 insertions(+), 44 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/libosmo-abis refs/changes/43/39643/1
diff --git a/src/trau/trau_frame.c b/src/trau/trau_frame.c
index fb98247..74f4526 100644
--- a/src/trau/trau_frame.c
+++ b/src/trau/trau_frame.c
@@ -522,52 +522,31 @@
return 0;
}
-static struct osmo_trau_frame fr_idle_frame = {
- .type = OSMO_TRAU16_FT_IDLE,
- .dir = OSMO_TRAU_DIR_DL,
- .t_bits = { 1, 1, 1, 1 },
-};
-#define TRAU_FRAME_BITS (40*8)
-static ubit_t encoded_idle_frame[TRAU_FRAME_BITS];
-static int dbits_initted = 0;
-
-/*! \brief return pointer to global buffer containing a TRAU idle frame */
-static ubit_t *trau_idle_frame(void)
-{
- /* only initialize during the first call */
- if (!dbits_initted) {
- /* set all D-bits to 1 */
- memset(&fr_idle_frame.d_bits, 0x01, 260);
-
- memset(&fr_idle_frame.c_bits, 0x01, 25); /* spare are set to 1 */
- /* set Downlink Idle Speech Frame pattern */
- fr_idle_frame.c_bits[0] = 0; /* C1 */
- fr_idle_frame.c_bits[1] = 1; /* C2 */
- fr_idle_frame.c_bits[2] = 1; /* C3 */
- fr_idle_frame.c_bits[3] = 1; /* C4 */
- fr_idle_frame.c_bits[4] = 0; /* C5 */
- /* set no Time Alignment pattern */
- fr_idle_frame.c_bits[5] = 0; /* C6 */
- fr_idle_frame.c_bits[6] = 0; /* C7 */
- fr_idle_frame.c_bits[7] = 0; /* C8 */
- fr_idle_frame.c_bits[8] = 0; /* C9 */
- fr_idle_frame.c_bits[9] = 0; /* C10 */
- fr_idle_frame.c_bits[10] = 0; /* C11 */
- /* already set to 1, but maybe we need to modify it in the future */
- fr_idle_frame.c_bits[11] = 1; /* C12 (UFE), good frame */
- fr_idle_frame.c_bits[15] = 1; /* C16 (SP), no DTX */
-
- encode16_fr(encoded_idle_frame, &fr_idle_frame, false);
- dbits_initted = 1; /* set it to 1 to not call it again */
- }
- return encoded_idle_frame;
-}
-
/* TS 08.60 Section 3.4 */
static int encode16_idle(ubit_t *trau_bits, const struct osmo_trau_frame *fr)
{
- memcpy(trau_bits, trau_idle_frame(), 40*8);
- return 40 * 8;
+ const ubit_t *cbits5;
+
+ if (fr->dir == OSMO_TRAU_DIR_UL)
+ cbits5 = ft_idle_up_bits;
+ else
+ cbits5 = ft_idle_down_bits;
+
+ encode_sync16(trau_bits);
+
+ /* C1 .. C5 */
+ memcpy(trau_bits + 17, cbits5 + 0, 5);
+ /* C6 .. C15 */
+ memcpy(trau_bits + 17 + 5, fr->c_bits + 5, 15 - 5);
+ /* all 1s in the place of D-bits */
+ memset(trau_bits + 32, 1, 310 - 32);
+ /* C16 .. C21 */
+ memcpy(trau_bits + 310, fr->c_bits + 15, 6);
+ /* T1 .. T4 */
+ memcpy(trau_bits + 316, fr->t_bits, 4);
+
+ /* handle timing adjustment */
+ return encode16_handle_ta(trau_bits, fr);
}
/* TS 08.60 Section 3.3.1 */
@@ -1276,12 +1255,12 @@
case OSMO_TRAU16_FT_EFR:
case OSMO_TRAU16_FT_HR:
case OSMO_TRAU16_FT_AMR:
+ case OSMO_TRAU16_FT_IDLE:
/* timing alignment may happen: increased space requirement */
if (n_bits < 2 * 40 * 8 - 1)
return -ENOSPC;
break;
case OSMO_TRAU16_FT_OAM:
- case OSMO_TRAU16_FT_IDLE:
case OSMO_TRAU16_FT_DATA_HR:
case OSMO_TRAU16_FT_DATA:
case OSMO_TRAU16_FT_D145_SYNC:
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