diff --git a/gprs_gb/BSSGP_Helper_Functions.ttcn b/gprs_gb/BSSGP_Helper_Functions.ttcn
new file mode 100644
index 0000000..9c8af92
--- /dev/null
+++ b/gprs_gb/BSSGP_Helper_Functions.ttcn
@@ -0,0 +1,3 @@
+module BSSGP_Helper_Functions {
+	external function f_BSSGP_preprocess_pdu(in octetstring inp) return octetstring;
+};