▲ Application Note COMPUTING TELECOM Testing the UMTS Iu Interface VIDEO ▲ Protocol Testing in the 3G Wireless Network This application note describes protocol tests for the UMTS Iu interface between the Radio Network Controller (RNC) and the Core Network (CN). It is the first in a series of documents on third-generation (3G) wireless networks. Each note addresses one of the new network interfaces and provides guidelines for equipment designers, manufacturers, operators and maintenance personnel to meet the measurement challenges with testing solutions. Examples are given in this document for testing: • Messaging and procedures on the Radio Access Network (RANAP) • Mobile Radio Interface Layer 3 (CC/MM/GPRS MM/GPRS SM) • Traffic channel signaling (AAL2 layer3) • Tunneling (GTP-U). Due to space limitations, only brief descriptions are presented here. Complete detailed information needed to perform these and other tests can be found in the user handbooks for the K1297 and K1205 Protocol Testers and in other training materials. Please contact Tektronix sales support to obtain the most recent information. Testing the UMTS Iu Interface Testing the UMTS Iu Interface ▲ ▲ Application Note Application Note Table of Contents 1. Introduction – The Iu Interface and All traffic over the Iu interface uses the Asynchronous Transfer Mode (ATM) as Protocols 1. INTRODUCTION – THE Iu INTERFACE AND PROTOCOLS ..................................................................................................................................................3 the physical transport technology, regardless of the data source. As a result, all data will be segmented into 53-byte ATM-cells and transported 1.1. TRANSPORT PROTOCOLS FOR THE CONTROL PLANE ........................................................................................................................................3 asynchronously. This document describes test applications for the Iu interface as it was defined 1.2. TRANSPORT PROTOCOLS FOR THE USER PLANE ..............................................................................................................................................3 by 3GPP at the end of 1999 (UMTS Rel. ‘99). Change requests have been 1.3. CONTROL PROTOCOLS FOR CALL CONTROL, SESSION AND MOBILITY MANAGEMENT..........................................................................................4 introduced and new features have been proposed every three months since 1.1. Transport Protocols for the Control Plane 1.4. PROTOCOLS FOR USER TRAFFIC ....................................................................................................................................................................4 that definition was adopted, so it is possible that there will be revisions in more 2. MEASUREMENT CHALLENGES AND SOLUTIONS ............................................................................................................................................................4 recent releases of the standard. Transport protocols for the control plane consist of the SSCS signaling 2.1. SELECTING THE APPROACH – MONITORING , SIMULATION, EMULATION, CONFORMANCE....................................................................................4 protocols (SSCOP and SSCF) as they are used in broadband networks to The Iu interface is defined in the 3GPP document series TS25.410-419. Iu is 2.1.1. Monitoring ............................................................................................................................................................................4 ensure the signaling links between network nodes with numbered subdivided into two different interfaces: Iu-CS for the circuit switched domain 2.1.2. Simulation ............................................................................................................................................................................5 datagrams. Loss of signaling messages can be detected and and Iu-PS for the packet switched domain. Figures 1 and 2 show the protocol retransmitted. SCCP is used to setup specific connections for the 2.1.3. Emulation ..............................................................................................................................................................................5 stacks for each of the Iu interfaces. different control signaling protocols, enabling both connectionless and 2.1.4. Conformance Testing. ............................................................................................................................................................5 connection-oriented communications. Iu normally uses the connection- 2.2. CONFIGURING THE TEST EQUIPMENT ..............................................................................................................................................................6 The protocols can be grouped according to their usage into: oriented mode. 2.2.1. Hardware Connection Issues....................................................................................................................................................6 • transport protocols for control plane 2.2.2. Setting the Operating Parameters ............................................................................................................................................7 • transport protocols for user plane MTP3b handles the routing and traffic management function for upper 2.2.3. Defining Protocol Stacks ........................................................................................................................................................7 • control protocols for call, session, mobility management layer protocols. It delivers messages to the destination point and manages the load sharing mechanism for the operation. MTP3b is 2.2.4. Defining Emulation Parameters ................................................................................................................................................8 • protocols for user traffic responsible for routing messages within a network with one operator; 2.3. TESTING AAL2 LAYER 3 ..................................................................................................................................................................................9 SCCP routes messages beyond the board of an operator. While the 2.3.1. Simulation of AAL2 layer 3 ......................................................................................................................................................9 connections between the RNC and Core Network nodes are shown here Radio Transport User User Network Network Plane Plane 2.3.2. Emulation of AAL2 layer 3 ....................................................................................................................................................11 Control Control Data Voice as point-to-point, these connections could also be incumbent networks Plane Plane Services Services CC/MM/GPRS MM/GPRS SM TAF consisting of several interim nodes. 2.4. TESTING RANAP AND DMTAP ........................................................................................................................................................................12 AMR Codec RANAP AAL2L3 RLP Iu UP 2.5. TESTING OF THE GTP-U PROTOCOL ..............................................................................................................................................................13 SCCP STC MTP3-b The most logical approach for Iu-PS would be to use the IP protocol stack 3. CONCLUSION ..............................................................................................................................................................................................................14 SSCF-UNI SSCOP to transport the control signaling information. For this reason, the Internet 4. APPENDIX I ................................................................................................................................................................................................................15 AAL5 AAL2 ATM Engineering Task Force (IETF) has proposed to replace SSCS and MTP3b 4.1. RECOMMENDED DOCUMENTS AND STANDARDS ............................................................................................................................................15 with M3UA and SCTP protocols on top of UDP/IP. Since this protocol stack ▲ 4.2. GLOSSARY ..................................................................................................................................................................................................16 Figure 1: Iu-CS protocol stack is still under development, there are no application tests for it in this release of the note. 5. APPENDIX II – UMTS – Entering the Third Generation of Mobile Networks ................................................................................................................20 Radio Network Transport Network User Plane Control Plane Control Plane CC/MM/GPRS MM/GPRS SM IP 1.2. Transport Protocols for the User Plane RANAP Iu UP SCCP MTP3-b M3UA GTP-U SSCF-NNI SCTP UDP SSCOP IP/UDP IP All signaling traffic for the control plane at the Iu interface is based on AAL5 AAL5 AAL type 5. Signaling messages are packet data with variable lengths. ATM However, transport protocols for the user plane use both AAL5 and AAL2 (AAL5 for packet data, AAL2 for circuit-switched transmission). ▲ Figure 2: Iu-PS protocol stacks 2 www.tektronix.com/commtest www.tektronix.com/commtest