diff --git a/include/osmocore/gsm_utils.h b/include/osmocore/gsm_utils.h
index b611050d3..25360459a 100644
--- a/include/osmocore/gsm_utils.h
+++ b/include/osmocore/gsm_utils.h
@@ -27,6 +27,14 @@
 
 #include <stdint.h>
 
+struct gsm_time {
+	uint32_t	fn;	/* FN count */
+	uint16_t	t1;	/* FN div (26*51) */
+	uint8_t		t2;	/* FN modulo 26 */
+	uint8_t		t3;	/* FN modulo 51 */
+	uint8_t		tc;
+};
+
 enum gsm_band {
 	GSM_BAND_850	= 1,
 	GSM_BAND_900	= 2,
@@ -58,5 +66,19 @@ static inline int rach_max_trans_raw2val(int raw) {
 	return tbl[raw & 3];
 }
 
+#define	ARFCN_PCS	0x8000
+#define	ARFCN_UPLINK	0x4000
+
+enum gsm_band gsm_arfcn2band(uint16_t arfcn);
+
+/* Convert an ARFCN to the frequency in MHz * 10 */
+uint16_t gsm_arfcn2freq10(uint16_t arfcn, int uplink);
+
+/* Convert from frame number to GSM time */
+void gsm_fn2gsmtime(struct gsm_time *time, uint32_t fn);
+
+/* Convert from GSM time to frame number */
+uint32_t gsm_gsmtime2fn(struct gsm_time *time);
+
 void generate_backtrace();
 #endif
diff --git a/src/gsm_utils.c b/src/gsm_utils.c
index 174b2d499..4ee137c3c 100644
--- a/src/gsm_utils.c
+++ b/src/gsm_utils.c
@@ -1,7 +1,7 @@
 /*
  * (C) 2008 by Daniel Willmann <daniel@totalueberwachung.de>
  * (C) 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
- * (C) 2009 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2009-2010 by Harald Welte <laforge@gnumonks.org>
  *
  * All Rights Reserved
  *
@@ -268,3 +268,94 @@ void generate_backtrace()
 	free(strings);
 }
 #endif
+
+enum gsm_band gsm_arfcn2band(uint16_t arfcn)
+{
+	if (arfcn & ARFCN_PCS)
+		return GSM_BAND_1900;
+	else if (arfcn <= 124)
+		return GSM_BAND_900;
+	else if (arfcn >= 955 && arfcn <= 1023)
+		return GSM_BAND_900;
+	else if (arfcn >= 128 && arfcn <= 251)
+		return GSM_BAND_850;
+	else if (arfcn >= 512 && arfcn <= 885)
+		return GSM_BAND_1800;
+	else if (arfcn >= 259 && arfcn <= 293)
+		return GSM_BAND_450;
+	else if (arfcn >= 306 && arfcn <= 340)
+		return GSM_BAND_480;
+	else if (arfcn >= 350 && arfcn <= 425)
+		return GSM_BAND_810;
+	else if (arfcn >= 438 && arfcn <= 511)
+		return GSM_BAND_750;
+	else
+		return GSM_BAND_1800;
+}
+
+/* Convert an ARFCN to the frequency in MHz * 10 */
+uint16_t gsm_arfcn2freq10(uint16_t arfcn, int uplink)
+{
+	uint16_t freq10_ul;
+	uint16_t freq10_dl;
+
+	if (arfcn & ARFCN_PCS) {
+		/* DCS 1900 */
+		arfcn &= ~ARFCN_PCS;
+		freq10_ul = 18502 + 2 * (arfcn-512);
+		freq10_dl = freq10_ul + 800;
+	} else if (arfcn <= 124) {
+		/* Primary GSM + ARFCN 0 of E-GSM */
+		freq10_ul = 8900 + 2 * arfcn;
+		freq10_dl = freq10_ul + 450;
+	} else if (arfcn >= 955 && arfcn <= 1023) {
+		/* E-GSM and R-GSM */
+		freq10_ul = 8900 + 2 * (arfcn - 1024);
+		freq10_dl = freq10_ul + 450;
+	} else if (arfcn >= 128 && arfcn <= 251) {
+		/* GSM 850 */
+		freq10_ul = 8242 + 2 * (arfcn - 128);
+		freq10_dl = freq10_ul + 450;
+	} else if (arfcn >= 512 && arfcn <= 885) {
+		/* DCS 1800 */
+		freq10_ul = 17102 + 2 * (arfcn - 512);
+		freq10_dl = freq10_ul + 950;
+	} else if (arfcn >= 259 && arfcn <= 293) {
+		/* GSM 450 */
+		freq10_ul = 4506 + 2 * (arfcn - 259);
+		freq10_dl = freq10_ul + 100;
+	} else if (arfcn >= 306 && arfcn <= 340) {
+		/* GSM 480 */
+		freq10_ul = 4790 + 2 * (arfcn - 306);
+		freq10_dl = freq10_ul + 100;
+	} else if (arfcn >= 350 && arfcn <= 425) {
+		/* GSM 810 */
+		freq10_ul = 8060 + 2 * (arfcn - 350);
+		freq10_dl = freq10_ul + 450;
+	} else if (arfcn >= 438 && arfcn <= 511) {
+		/* GSM 750 */
+		freq10_ul = 7472 + 2 * (arfcn - 438);
+		freq10_dl = freq10_ul + 300;
+	} else
+		return 0xffff;
+
+	if (uplink)
+		return freq10_ul;
+	else
+		return freq10_dl;
+}
+
+void gsm_fn2gsmtime(struct gsm_time *time, uint32_t fn)
+{
+	time->fn = fn;
+	time->t1 = time->fn / (26*51);
+	time->t2 = time->fn % 26;
+	time->t3 = time->fn % 51;
+	time->tc = (time->fn / 51) % 8;
+}
+
+uint32_t gsm_gsmtime2fn(struct gsm_time *time)
+{
+	/* TS 05.02 Chapter 4.3.3 TDMA frame number */
+	return (51 * ((time->t3 - time->t2 + 26) % 26) + time->t3 + (26 * 51 * time->t1));
+}