6 Iur Interface Protocols

3GPP43.130GSM/EDGE Iur-g interfaceRelease 16Stage 2TS

6.1 General

There shall exist a clear separation between the Radio Network Layer and the Transport Layer. Therefore, the radio network signalling is separated from the data transport resource and traffic handling as shown in Figure 3. This separation is also present in the Iur interface (see 3GPP TS 25.420 [4]).

Since the Iur-g does not carry user data information, neither data transport resources nor Transport Signalling are present on this interface. These elements, present in the Iur interface but not in the Iur-g, are shown in dotted lines in Figure 3.

Figure 3: Separation of Radio Network Protocols and transport over Iur-g.

The following Table lists all stage 3 specifications that are used for Iur-g interface:

Table 1: Stage 3 Iur-g interface specifications

Spec. No

Spec. Name

TS 25.401

UTRAN Overall Description

TS 25.420

UTRAN Iur Interface: General Aspects and Principles

TS 25.421

UTRAN Iur interface Layer 1

TS 25.422

UTRAN Iur Interface Signalling Transport

TS 25.423

UTRAN Iur Interface RNSAP Signalling

6.2 Functions of the Iur-g interface protocols

The list of functions on the Iur-g interface is the following:

Paging. This function allows the SBSS/SRNC to page a MS/UE in a GRA/URA or a cell in the DBSS/DRNS;

Relocation Execution. This function allows the SBSS/SRNC to finalise a Relocation previously prepared via other interfaces;

Reporting of General Error Situations. This function allows reporting of general error situations, for which function specific error messages have not been defined.

Measurements on Common Resources. This function allows an BSS/RNC to request from another BSS/RNC to initiate measurements on Common Resources. The function also allows the requested BSS/RNC to report the result of the measurements.

Radio Resource Reserve Handover. This function allows the SRNC to request allocation of radio resources in the TBSS prior to the HANDOVER REQUEST message is received from the Core Network.

6.3 Iur-g Interface protocol structure

The Iur interface protocol architecture consists of two functional layers:

Radio Network Layer: it defines the procedures related to the interaction of two BSSs or between a BSS and an RNC within a PLMN. The radio network layer consists of a Radio Network Control Plane and a Radio Network User Plane. The functionality of the Radio Network User Plane of the Iur-g interface is null.

Transport Layer: it consists of two planes:

a) Transport Network Control Plane: it defines procedures for establishing physical connections between two BSSs or between a BSS and an RNC within a PLMN. The functionality of the Transport Network Control Plane of the Iur-g interface is null.

b) Transport Network User Plane: it provides means for the transport of the Radio Network Layer information.

Figure 4: Iur-g interface protocol structure.

6.4 Radio signalling protocols

The protocol responsible for providing signalling information across the Iur-g interface is a sub-set of the Radio Network Subsystem Application Part (RNSAP) (see 3GPP TS 25.423 [5]). This subset of RNSAP is terminated by two BSSs or by the BSS and RNC inter-connected via the Iur-g interface.

The subset of RNSAP procedures applicable to the Iur-g interface are divided into two modules as follows:

1. RNSAP Basic Mobility Procedures: these procedures are used to handle the mobility within GERAN or between GERAN and UTRAN.

2. RNSAP Global Procedures: these procedures are not related to a specific MS. The procedures in this module are in contrast to the above module involving two peer CBSSs or a CBSS and a CRNC.