6 Iur Interface Protocols
25.4203GPPRelease 17TSUTRAN Iur interface general aspects and principles
6.1 General
There shall exist a clear separation between the Radio Network Layer and the Transport Layer. Therefore, the radio network signalling and Iur data streams are separated from the data transport resource and traffic handling as shown in Figure 2. Data transport resource and traffic handling is controlled by Transport Signalling. The Transport Signalling is carried by a Signalling Bearer over the Iur interface.
Figure 2: Separation of Radio Network Protocols and transport over Iur
6.2 Radio Signalling Protocols
6.2.1 RNSAP Protocol
The protocol responsible for providing signalling information across the Iur interface is called the Radio Network Subsystem Application Part (RNSAP). A subset of RNSAP is used over the Iur-g interface.
The RNSAP is terminated by the two RNCs inter-connected via the Iur interface RNSAP Procedure Modules. In addition, the RNSAP is terminated by a RNC and a BSS supporting Iu mode inter-connected via the Iur-g interface (TR 43.930 [17]). For 1.28Mcps TDD, the RNSAP may be terminated by a RNC and a BSS supporting A/Gb mode inter-connected via the Iur-g interface.
RNSAP procedures are divided into four modules as follows:
1. RNSAP Basic Mobility Procedures;
2. RNSAP Dedicated Procedures;
3. RNSAP Common Transport Channel Procedures;
4. RNSAP Global Procedures;
5. RNSAP MBMS Procedures.
The Basic Mobility Procedures module contains procedures used to handle the mobility within UTRAN as well as to handle mobility in case of UTRAN/GERAN interworking.
The Dedicated Procedures module contains procedures that are used to handle DCHs, [FDD – F-DPCH,] E-DCH, [TDD – DSCH, USCHs] and HS-DSCH between two RNSs. If procedures from this module are not used in a specific Iur, then the usage of DCH, [FDD – F-DPCH,] E-DCH, [TDD – DSCH, USCH] and HS-DSCH traffic between corresponding RNSs is not possible.
The Common Transport Channel Procedures module contains procedures that are used to control common transport channel data streams (excluding the DSCH, HS-DSCH, E-DCH and USCH) over Iur interface.
The Global Procedures module contains procedures that are not related to a specific UE. The procedures in this module are in contrast to the above modules involving two peer CRNCs. The procedures in this module are also used in cases involving one RNC and one BSS.
The MBMS Procedures module contains procedures that are specific to MBMS and used for cases that cannot be handled by other modules.
6.3 User Plane Frame Protocols
6.3.1 Iub/Iur DCH Frame Protocol
There are two types of Iub/Iur DCH FP frames:
– DCH data frame;
– DCH control frame.
The contents of the Iub/Iur DCH data frame include:
– Transport Block Sets;
– Quality estimate.
The contents of the Iur DCH control frame include:
– Measurement reports;
– Power control information;
– Synchronisation information.
For a more detailed description of the Iur/Iub DCH frame protocol refer to ‘UTRAN Iur & Iub Interface User Plane Protocol for DCH Data Streams’ TS 25.427 [1].
6.3.2 Iur DSCH Frame Protocol [TDD]
There are two types of Iur DSCH FP frames:
– DSCH data frame;
– DSCH control frames.
The contents of the Iur DSCH data frame include:
– MAC-c/sh SDUs;
– User Buffer Status.
The contents of the Iur DSCH control frame include:
– Flow control Information (UL);
– Capacity Request Information (DL).
For a more detailed description of the Iur DSCH frame protocol refer to ‘UTRAN Iur Interface User Plane protocols for Common Transport Channel Data Streams’ TS 25.425 [2].
6.3.3 Iur USCH Frame Protocol [TDD]
There is one type of Iur USCH FP frames:
– USCH data frame.
The contents of the Iur USCH data frame include:
– MAC-c/sh SDUs.
For a more detailed description of the Iur USCH frame protocol refer to ‘UTRAN Iur Interface User Plane protocols for Common Transport Channel Data Streams’ TS 25.425 [2].
6.3.4 Iur RACH Frame Protocol
For a more detailed description of the Iur RACH framing protocol refer to ‘UTRAN Iur Interface User Plane protocols for Common Transport Channel Data Streams’ TS 25.425 [2].
6.3.5 Iur FACH Frame Protocol
For a more detailed description of the Iur FACH framing protocol refer to ‘UTRAN Iur Interface User Plane protocols for Common Transport Channel Data Streams’ TS 25.425 [2].
6.3.6 Iur HS-DSCH Frame Protocol
There are two types of Iur HS-DSCH FP frames:
– HS-DSCH data frame;
– HS-DSCH control frames.
The contents of the Iur HS-DSCH data frame include:
– MAC-d PDUs;
– User Buffer Status.
The contents of the Iur HS-DSCH control frame include:
– Flow control Information (UL);
– Capacity Request Information (DL).
For a more detailed description of the Iur HS-DSCH frame protocol refer to ‘UTRAN Iur Interface User Plane protocols for Common Transport Channel Data Streams’ TS 25.425 [2].
6.3.7 Iur E-DCH Frame Protocol
There is one type of Iur E-DCH FP frames:
– E-DCH data frame;
The contents of the Iur E-DCH data frame include:
– Mac-es PDUs (multiplexed);
– Number of HARQ retransmissions;
– CFN and Sub frame number.
For a more detailed description of the Iur E-DCH frame protocol refer to ‘UTRAN Iur Interface User Plane Protocols for DCH Data Streams’ TS 25.427 [1].
6.4 Mapping of Frame Protocols onto transport bearers
DCH One Iur DCH data stream is carried on one transport bearer except in the case of co-ordinated DCHs in which case a set of co-ordinated DCHs are multiplexed onto the same transport bearer.
[TDD – DSCH One Iur DSCH data stream is carried on one transport bearer.]
HS-DSCH One Iur HS-DSCH data stream is carried on one transport bearer.
E-DCH One Iur E-DCH data stream is carried on one transport bearer. For each E-DCH data stream, a transport bearer must be established over the Iur interface.
[TDD – USCH One Iur USCH data stream is carried on one transport bearer.]
RACH Multiple RACH data streams may be carried on one transport bearer.
FACH Multiple FACH data streams may be carried on one transport bearer.
RACH and FACH data streams for one UE are carried on same transport bearer.