diff --git a/gprs_gb/BSSGP_Helper.cc b/gprs_gb/BSSGP_Helper.cc
index 8cf97d2..4665dcd 100644
--- a/gprs_gb/BSSGP_Helper.cc
+++ b/gprs_gb/BSSGP_Helper.cc
@@ -9,7 +9,7 @@
 
 /* convert a buffer filled with TLVs that have variable-length "length" fields (Osmocom TvLV) into a
  * buffer filled with TLVs that have fixed 16-bit length values (TL16V format) */
-static OCTETSTRING transcode_tlv_part(OCTETSTRING const &in)
+static OCTETSTRING expand_tlv_part(OCTETSTRING const &in)
 {
 	const unsigned char *in_ptr = (const unsigned char *)in;
 	int in_len = in.lengthof();
@@ -33,7 +33,7 @@
 			tl_length = 2;
 		} else {
 			/* E bit is not set, 15 bit length field */
-			if (in_len < 3) {
+			if (remain_len < 3) {
 				TTCN_error("Remaining input length insufficient for 2-octet length");
 				break;
 			}
@@ -67,12 +67,67 @@
 	return out;
 }
 
+/* convert a buffer filled with TLVs that have fixed-length "length" fields (Osmocom TL16V) into a
+ * buffer filled with TLVs that have variable-length values (TvLV format) */
+static OCTETSTRING compact_tlv_part(OCTETSTRING const &in)
+{
+	const unsigned char *in_ptr = (const unsigned char *)in;
+	int in_len = in.lengthof();
+	int ofs = 0;
+	uint16_t data_len;
+	OCTETSTRING out(0, (const unsigned char *)"");
+
+	while (ofs < in_len) {
+		int remain_len = in_len - ofs;
+		int tl_length;
+
+		if (remain_len < 3) {
+			TTCN_error("Remaining input length (%d) insufficient for Tag+Length", remain_len);
+			break;
+		}
+
+		data_len = (in_ptr[ofs+1] << 8) | in_ptr[ofs+2];
+
+		/* Tag + 16bit length */
+		uint8_t hdr_buf[3];
+		hdr_buf[0] = in_ptr[ofs+0];
+
+		if (data_len <= 0x7f) {
+			/* E bit is set, 7-bit length field */
+			hdr_buf[1] = 0x80 | data_len;
+			tl_length = 2;
+		} else {
+			/* E bit is not set, 15 bit length field */
+			hdr_buf[1] = data_len >> 8;
+			hdr_buf[2] = data_len & 0xff;
+			tl_length = 3;
+		}
+		if (in_len < 3 + data_len) {
+			TTCN_error("Remaining input length insufficient for TLV value length");
+			break;
+		}
+
+		OCTETSTRING tlv_hdr(tl_length, hdr_buf);
+		out += tlv_hdr;
+
+		if (data_len) {
+			/* append octet string of current TLV to output octetstring */
+			OCTETSTRING tlv_val(data_len, in_ptr + ofs + 3);
+			out += tlv_val;
+		}
+
+		/* advance input offset*/
+		ofs += data_len + 3;
+	}
+
+	return out;
+}
+
 #define BSSGP_PDUT_DL_UNITDATA	0x00
 #define BSSGP_PDUT_UL_UNITDATA	0x01
 
-/* expand all the variable-length "length" fields of a BSSGP message (Osmocom TvLV) into 
- * statlc TL16V format */
-OCTETSTRING f__BSSGP__preprocess__pdu(OCTETSTRING const &in)
+/* expand all the variable-length "length" fields of a BSSGP message (Osmocom TvLV) into statlc TL16V format */
+OCTETSTRING f__BSSGP__expand__len(OCTETSTRING const &in)
 {
 	const unsigned char *in_ptr = (const unsigned char *)in;
 	int in_len = in.lengthof();
@@ -90,7 +145,65 @@
 	OCTETSTRING prefix(static_hdr_len, in_ptr);
 	OCTETSTRING tlv_part_in(in_len - static_hdr_len, in_ptr + static_hdr_len);
 
-	return prefix + transcode_tlv_part(tlv_part_in);
+	return prefix + expand_tlv_part(tlv_part_in);
+}
+
+OCTETSTRING f__BSSGP__compact__len(OCTETSTRING const &in)
+{
+	const unsigned char *in_ptr = (const unsigned char *)in;
+	int in_len = in.lengthof();
+	uint8_t pdu_type = in_ptr[0];
+	uint8_t static_hdr_len = 1;
+
+	if (pdu_type == BSSGP_PDUT_DL_UNITDATA || pdu_type == BSSGP_PDUT_UL_UNITDATA)
+		static_hdr_len = 8;
+
+	if (in_len < static_hdr_len)
+		TTCN_error("BSSGP message is shorter (%u bytes) than minimum header length (%u bytes) for msg_type 0x%02x",
+				in_len, static_hdr_len, pdu_type);
+
+	/* prefix = non-TLV section of header */
+	OCTETSTRING prefix(static_hdr_len, in_ptr);
+	OCTETSTRING tlv_part_in(in_len - static_hdr_len, in_ptr + static_hdr_len);
+
+	return prefix + compact_tlv_part(tlv_part_in);
+}
+
+/* expand all the variable-length "length" fields of a NS message (Osmocom TvLV) into statlc TL16V format */
+OCTETSTRING f__NS__expand__len(OCTETSTRING const &in)
+{
+	const unsigned char *in_ptr = (const unsigned char *)in;
+	int in_len = in.lengthof();
+	uint8_t pdu_type = in_ptr[0];
+	uint8_t static_hdr_len = 1;
+
+	if (in_len < static_hdr_len)
+		TTCN_error("NS message is shorter (%u bytes) than minimum header length (%u bytes) for msg_type 0x%02x",
+				in_len, static_hdr_len, pdu_type);
+
+	/* prefix = non-TLV section of header */
+	OCTETSTRING prefix(static_hdr_len, in_ptr);
+	OCTETSTRING tlv_part_in(in_len - static_hdr_len, in_ptr + static_hdr_len);
+
+	return prefix + expand_tlv_part(tlv_part_in);
+}
+
+OCTETSTRING f__NS__compact__len(OCTETSTRING const &in)
+{
+	const unsigned char *in_ptr = (const unsigned char *)in;
+	int in_len = in.lengthof();
+	uint8_t pdu_type = in_ptr[0];
+	uint8_t static_hdr_len = 1;
+
+	if (in_len < static_hdr_len)
+		TTCN_error("NS message is shorter (%u bytes) than minimum header length (%u bytes) for msg_type 0x%02x",
+				in_len, static_hdr_len, pdu_type);
+
+	/* prefix = non-TLV section of header */
+	OCTETSTRING prefix(static_hdr_len, in_ptr);
+	OCTETSTRING tlv_part_in(in_len - static_hdr_len, in_ptr + static_hdr_len);
+
+	return prefix + compact_tlv_part(tlv_part_in);
 }
 
 }