diff --git a/doc/hnb_cs_mt_sms.msc b/doc/hnb_cs_mt_sms.msc
new file mode 100644
index 0000000..8a1b808
--- /dev/null
+++ b/doc/hnb_cs_mt_sms.msc
@@ -0,0 +1,67 @@
+msc {
+	hscale = "3";
+	ue,hnb,hnbgw,cn;
+
+	cn box cn	[ label = "subscriber A send a SMS; signalling arrives at CN" ];
+
+	cn => hnbgw	[ label = "SCCP UDT (RANAP Paging Command)" ];
+	hnbgw => hnb	[ label = "RUA ConnectionlessTransfer (RANAP Paging Command)" ];
+	hnb => ue 	[ label = "RRC Paging" ];
+	
+	ue box hnb	[ label = "Radio Channel Establishment" ];
+	ue => hnb 	[ label = "RRC (CM PAGING RESP)" ] ;
+	hnb => hnbgw 	[ label = "RUA CONNECT (RANAP Initial UE Msg (CM PAGING RESP))" ];
+	hnbgw => cn	[ label = "SCCP CR (RANAP Initial UE Msg (CM PAGING RESP))" ];
+	cn >> hnbgw	[ label = "SCCP CC" ];
+
+	---		[ label = "Optional retrieval of IMSI (if not given in CM or retrived from VLR by TMSI)" ];
+	cn => hnbgw	[ label = "SCCP DT1 (RANAP DirectTransfer (MM IDENTITY REQ))" ];
+	hnbgw => hnb	[ label = "RUA DT (RANAP DirectTransfer (MM IDENTITY REQ))" ];
+	hnb => ue	[ label = "RRC (MM IDENTITY REQ)" ];
+	ue >> hnb	[ label = "RRC (MM IDENTITY RESP)" ];
+	hnb >> hnbgw	[ label = "RUA DT (RANAP DirectTransfer (MM IDENTITY RESP))" ];
+	hnbgw >> cn	[ label = "SCCP DT1 (RANAP DirectTransfer (MM IDENTITY RESP))" ];
+
+	---		[ label = "Mandatory activation of Integrity Protection" ];
+	cn => hnbgw	[ label = "SCCP DT1 (RANAP SecurityModeCommand (IK))" ];
+	hnbgw => hnb	[ label = "RUA DT (RANAP SecurityModeCommand (IK))" ];
+	hnb >> hnbgw	[ label = "RUA DT (RANAP SecurityModeResponse (IK))" ];
+	hnbgw >> cn	[ label = "SCCP DT1 (RANAP SecurityModeResponse (IK))" ];
+
+	cn => hnbgw	[ label = "SCCP DT1 (RANAP CommonID)" ];
+	hnbgw => hnb	[ label = "RUA DT (RANAP CommonID)" ];
+
+	---		[ label = "Optional Authentication" ];
+	cn => hnbgw	[ label = "SCCP DT1 (RANAP DirectTransfer (MM AUTH REQ))" ];
+	hnbgw => hnb	[ label = "RUA DT (RANAP DirectTransfer (MM AUTH REQ))" ];
+	hnb => ue	[ label = "RRC (MM AUTH REQ)" ];
+	ue >> hnb	[ label = "RRC (MM AUTH RESP)" ];
+	hnb >> hnbgw	[ label = "RUA DT (RANAP DirectTransfer (MM AUTH RESP))" ];
+	hnbgw >> cn	[ label = "SCCP DT1 (RANAP DirectTransfer (MM AUTH RESP))" ];
+
+	---		[ label = "Optional activation of Encryption" ];
+	cn => hnbgw	[ label = "SCCP DT1 (RANAP SecurityModeCommand (IK+CK))" ];
+	hnbgw => hnb	[ label = "RUA DT (RANAP SecurityModeCommand (IK+CK))" ];
+	hnb >> hnbgw	[ label = "RUA DT (RANAP SecurityModeResponse (IK+CK))" ];
+	hnbgw >> cn	[ label = "SCCP DT1 (RANAP SecurityModeResponse (IK+CK))" ];
+
+	cn => hnbgw	[ label = "SCCP DT1 (RANAP DirectTransfer (CP-DATA (RP-DATA (SMS DELIVER))))" ];
+	hnbgw => hnb	[ label = "RUA DT (RANAP DirectTransfer (CP-DATA (RP-DATA (SMS DELIVER))))" ];
+	hnb => ue	[ label = "RRC (CP-DATA (RP-DATA (SMS DELIVER)))" ];
+
+	ue => hnb	[ label = "RRC (CP-ACK)" ];
+	hnb => hnbgw	[ label = "RUA DT (RANAP DirectTransfer (CP-ACK))" ];
+	hnbgw => cn	[ label = "SCCP DT1 (RANAP DirectTransfer (CP-ACK))" ];
+	
+	ue => hnb	[ label = "RRC (CP-DATA (RP-ACK)" ];
+	hnb => hnbgw	[ label = "RUA DT (RANAP DirectTransfer (CP-DATA (RP-ACK)))" ];
+	hnbgw => cn	[ label = "SCCP DT1 (RANAP DirectTransfer (CP-DTA (RP-ACK)))" ];
+
+	cn => hnbgw	[ label = "SCCP DT1 (RANAP DirectTransfer (CP-ACK))" ];
+	hnbgw => hnb	[ label = "RUA DT (RANAP DirectTransfer (CP-ACK))" ];
+	hnb => ue	[ label = "RRC (CP-ACK)" ];
+
+	cn box cn	[ label = "MAP MT Forward SM to GMSC/SMSC" ];
+
+	cn box hnb	[ label = "RAB Release or Iu Release" ];
+}