diff --git a/gprs_gb/BSSGP_Helper_Functions.ttcn b/gprs_gb/BSSGP_Helper_Functions.ttcn
index 9c8af92..731d2ab 100644
--- a/gprs_gb/BSSGP_Helper_Functions.ttcn
+++ b/gprs_gb/BSSGP_Helper_Functions.ttcn
@@ -1,3 +1,6 @@
 module BSSGP_Helper_Functions {
-	external function f_BSSGP_preprocess_pdu(in octetstring inp) return octetstring;
+	external function f_BSSGP_expand_len(in octetstring inp) return octetstring;
+	external function f_BSSGP_compact_len(in octetstring inp) return octetstring;
+	external function f_NS_expand_len(in octetstring inp) return octetstring;
+	external function f_NS_compact_len(in octetstring inp) return octetstring;
 };