diff --git a/lib/decoding/osmocom/coding/gsm0503_coding.h b/lib/decoding/osmocom/coding/gsm0503_coding.h
new file mode 100644
index 0000000..83cdbd5
--- /dev/null
+++ b/lib/decoding/osmocom/coding/gsm0503_coding.h
@@ -0,0 +1,46 @@
+#pragma once
+
+#include <stdint.h>
+#include <osmocom/core/bits.h>
+
+#define GSM0503_GPRS_BURSTS_NBITS	(116 * 4)
+#define GSM0503_EGPRS_BURSTS_NBITS	(348 * 4)
+#define NUM_BYTES(N) ((N + 8 - 1) / 8)
+
+
+
+int gsm0503_xcch_encode(ubit_t *bursts, uint8_t *l2_data);
+int gsm0503_xcch_decode(uint8_t *l2_data, sbit_t *bursts,
+	int *n_errors, int *n_bits_total);
+
+int gsm0503_pdtch_encode(ubit_t *bursts, uint8_t *l2_data, uint8_t l2_len);
+int gsm0503_pdtch_decode(uint8_t *l2_data, sbit_t *bursts, uint8_t *usf_p,
+	int *n_errors, int *n_bits_total);
+
+int gsm0503_tch_fr_encode(ubit_t *bursts, uint8_t *tch_data, int len,
+	int net_order);
+int gsm0503_tch_fr_decode(uint8_t *tch_data, sbit_t *bursts, int net_order,
+	int efr, int *n_errors, int *n_bits_total);
+
+int gsm0503_tch_hr_encode(ubit_t *bursts, uint8_t *tch_data, int len);
+int gsm0503_tch_hr_decode(uint8_t *tch_data, sbit_t *bursts, int odd,
+	int *n_errors, int *n_bits_total);
+
+int gsm0503_tch_afs_encode(ubit_t *bursts, uint8_t *tch_data, int len,
+	int codec_mode_req, uint8_t *codec, int codecs, uint8_t ft,
+	uint8_t cmr);
+int gsm0503_tch_afs_decode(uint8_t *tch_data, sbit_t *bursts,
+	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
+	uint8_t *cmr, int *n_errors, int *n_bits_total);
+
+int gsm0503_tch_ahs_encode(ubit_t *bursts, uint8_t *tch_data, int len,
+	int codec_mode_req, uint8_t *codec, int codecs, uint8_t ft, uint8_t cmr);
+int gsm0503_tch_ahs_decode(uint8_t *tch_data, sbit_t *bursts, int odd,
+	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
+	uint8_t *cmr, int *n_errors, int *n_bits_total);
+
+int gsm0503_rach_encode(ubit_t *burst, uint8_t *ra, uint8_t bsic);
+int gsm0503_rach_decode(uint8_t *ra, sbit_t *burst, uint8_t bsic);
+
+int gsm0503_sch_encode(ubit_t *burst, uint8_t *sb_info);
+int gsm0503_sch_decode(uint8_t *sb_info, sbit_t *burst);