UMTS/GSM Interoperability

Overview:

The UMTS/GSM Interoperability course identifies some of the issues that arise when users are allowed to roam between 2G and 3G networks using dual mode terminals. Focus is on terminal/SIM capabilities, broadcast control parameters, QoS issues and the risk of calls being dropped during handovers between different radio access technologies (RATs).

System Information parameters for controlling the cell re-selection and reporting behaviour of the UE in a mixed 2G/3G environment are examined. On the Core Network side the course explains interworking between 2G and 3G networks, e.g. protocol conversion and mapping of QoS and security parameters.

The course also discusses how releases 5, 6 and 7 of GSM/UMTS will/might affect interoperability.

Pre-requisites:

General knowledge of the UMTS systemas well as the GSM/GPRS system is required. For background knowledge, we recommend the Apis course GSM/UMTS/EPS System Overview.

Course contents:

Introduction to Interoperability

• Mixed 2G/3G network topology and interfaces

• GERAN in Iu Mode

• Possible interoperability problems (e.g. QoS, security, different protocol versions and limited UE capabilities)

ME/SIM Capabilities

• Selection of PLMN and radio access technology

• Provision/retrieval of classmark information

• Interaction between ME and SIM/USIM

Inter-RAT Measurements

• System Information parameters relevant for interoperability between 2G and 3G networks

• Cell re-selection between 2G and 3G cells

• Network Assisted Cell Change feature

• MS/UE inter-RAT measurement reporting and control

Security Mechanisms

• GSM vs UMTS authentication and key agreement

• Conversion between quintets and triplets when using different combinations of ME/SIM/RAN/CN releases

QoS Handling

• 2G vs 3G QoS mechanisms for CS and PS services (negotiation, parameters, limitations etc.)

Handover Scenarios

• Signalling flows for handover for,/to UTRAN to/from GSM BSS, including failed handover cases, for CS and PS services

• Handover related timers in MSC, SGSN, RAN and MS/UE

• Impact of handover on specific CS services (e.g. multimedia)

• Impact of handover on QoS for PS connections

Core Network Interworking (during a handover)

• 2G/3G protocol conversion and fallback mechanisms

• Forwarding (and buffering) of data between CN nodes

• Distribution of classmark information between CN nodes

• Mapping between 2G and 3G QoS parameters

• Conversion and distribution of security parameters

Other interworking concepts

• Interworking between GERAN/UTRAN and EPS (evolved Packet System)

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