Add functions for extended RACH coding
Add support for extended RACH (11 bit) according 3GPP TS 45.003 ยง5.3.2:
* convolutional code with puncturing
* encoding/decoding routines
* corresponding tests
Change-Id: I85a34a82d5cd39a594ee89d91a2338226066ab5d
Related: OS#1548
diff --git a/src/coding/gsm0503_coding.c b/src/coding/gsm0503_coding.c
index cacc612..f3b319a 100644
--- a/src/coding/gsm0503_coding.c
+++ b/src/coding/gsm0503_coding.c
@@ -2824,13 +2824,47 @@
* b(0) = MSB of PLMN colour code
* b(5) = LSB of BS colour code
*/
-static int rach_apply_bsic(ubit_t *d, uint8_t bsic)
+static inline void rach_apply_bsic(ubit_t *d, uint8_t bsic, uint8_t start)
{
int i;
/* Apply it */
for (i = 0; i < 6; i++)
- d[8 + i] ^= ((bsic >> (5 - i)) & 1);
+ d[start + i] ^= ((bsic >> (5 - i)) & 1);
+}
+
+static inline int16_t rach_decode(const sbit_t *burst, uint8_t bsic, bool is_11bit)
+{
+ ubit_t conv[17];
+ uint8_t ra[2] = { 0 }, nbits = is_11bit ? 11 : 8;
+ int rv;
+
+ osmo_conv_decode(is_11bit ? &gsm0503_rach_ext : &gsm0503_rach, burst, conv);
+
+ rach_apply_bsic(conv, bsic, nbits);
+
+ rv = osmo_crc8gen_check_bits(&gsm0503_rach_crc6, conv, nbits, conv + nbits);
+ if (rv)
+ return -1;
+
+ osmo_ubit2pbit_ext(ra, 0, conv, 0, nbits, 1);
+
+ return is_11bit ? osmo_load16le(ra) : ra[0];
+}
+
+/*! Decode the Extended (11-bit) RACH according to 3GPP TS 45.003
+ * \param[out] ra output buffer for RACH data
+ * \param[in] burst Input burst data
+ * \param[in] bsic BSIC used in this cell
+ * \returns 0 on success; negative on error (e.g. CRC error) */
+int gsm0503_rach_ext_decode(uint16_t *ra, const sbit_t *burst, uint8_t bsic)
+{
+ int16_t r = rach_decode(burst, bsic, true);
+
+ if (r < 0)
+ return r;
+
+ *ra = r;
return 0;
}
@@ -2842,18 +2876,12 @@
* \returns 0 on success; negative on error (e.g. CRC error) */
int gsm0503_rach_decode(uint8_t *ra, const sbit_t *burst, uint8_t bsic)
{
- ubit_t conv[14];
- int rv;
+ int16_t r = rach_decode(burst, bsic, false);
- osmo_conv_decode(&gsm0503_rach, burst, conv);
+ if (r < 0)
+ return r;
- rach_apply_bsic(conv, bsic);
-
- rv = osmo_crc8gen_check_bits(&gsm0503_rach_crc6, conv, 8, conv + 8);
- if (rv)
- return -1;
-
- osmo_ubit2pbit_ext(ra, 0, conv, 0, 8, 1);
+ *ra = r;
return 0;
}
@@ -2865,15 +2893,33 @@
* \returns 0 on success; negative on error */
int gsm0503_rach_encode(ubit_t *burst, const uint8_t *ra, uint8_t bsic)
{
- ubit_t conv[14];
+ return gsm0503_rach_ext_encode(burst, *ra, bsic, false);
+}
- osmo_pbit2ubit_ext(conv, 0, ra, 0, 8, 1);
+/*! Encode the Extended (11-bit) or regular (8-bit) RACH according to 3GPP TS 45.003
+ * \param[out] burst Caller-allocated output burst buffer
+ * \param[in] ra11 Input RACH data
+ * \param[in] bsic BSIC used in this cell
+ * \param[in] is_11bit whether given RA is 11 bit or not
+ * \returns 0 on success; negative on error */
+int gsm0503_rach_ext_encode(ubit_t *burst, uint16_t ra11, uint8_t bsic, bool is_11bit)
+{
+ ubit_t conv[17];
+ uint8_t ra[2] = { 0 }, nbits = 8;
- osmo_crc8gen_set_bits(&gsm0503_rach_crc6, conv, 8, conv + 8);
+ if (is_11bit) {
+ osmo_store16le(ra11, ra);
+ nbits = 11;
+ } else
+ ra[0] = (uint8_t)ra11;
- rach_apply_bsic(conv, bsic);
+ osmo_pbit2ubit_ext(conv, 0, ra, 0, nbits, 1);
- osmo_conv_encode(&gsm0503_rach, conv, burst);
+ osmo_crc8gen_set_bits(&gsm0503_rach_crc6, conv, nbits, conv + nbits);
+
+ rach_apply_bsic(conv, bsic, nbits);
+
+ osmo_conv_encode(is_11bit ? &gsm0503_rach_ext : &gsm0503_rach, conv, burst);
return 0;
}