Figure 1 Basic Network Structure of R99
3GPP standard versions include R99, R4, R5, R6 and R7.
R99 version was frozen formally in Mar, 2000, and refreshes once every three months.
Current commercial version of R99 is based on the version of June, 2001, for in later version, the number of CR is decreasing rapidly and there are no larger modifications and non-compatible upgrade.
R4 version was frozen in Mar, 2001.
It passed in Mar, 2002 and is stable currently. R5 version was frozen in June, 2002 and is stable currently.
Most R5 versions that providers support are the version of June, 2004. R6 version was frozen in June, 2005 and may be stable in a year.
At present, R7/LTE has started up and its functional features are still in initial phase.
R99 and R4 versions are put into commercial use maturely. R6 version protocols are in developing status.
Basic Network Structure Based on R99
The R99 is the first phase version of 3GPP in 3G network standardization.
The R99 was already frozen in June 2001, and subsequent revision is made on the R4. The basic configuration structure of the R99 is illustrated in Figure 1.
To guarantee the investment interests of telecom operators, the network structure of the R99 is designed with 2G/3G compatibility fully in mind, for smooth evolution to 3G.
Therefore, the core network in the basic network structure remains unchanged.
To support 3G services, some NEs are added with appropriate interface protocols, and the original interface protocols are also improved by different degrees.
Network Structure Based on UMTS R4
Same as the R99 network, the basic structure of the R4 network consists of the core network and wireless access network, and there are the CS domain and PS domain on the core network side.
The basic NE entities and the interfaces are largely inherited from the definitions of entities and interfaces of the R99 network.
The network entities with the same definitions as the R99 network remain unchanged in basic functionality, and the related protocols are also similar.
Compared with the R99, the R4 network structure has tremendous changes in the structure of the CS domain of the core network, while those of the PS domain of the core network and of the UTRAN also remain the same.
According to the idea of separation between call control, bearer and bearer control, the network entity (G) MSC of the CS domain of the R99 network evolves to the MGW and (G) MSCServer in the R4 stage, with R-SGW and T-SGW added.
In addition, related interfaces are also changed, with the Mc interface added between the MGW and MSC Sever, the Nc interface between the MSC Sever and GMSC Sever, and the Nb interface between MGWs, and the Mh interface between the MR-MGW and HLR.
Figure 2 Basic Network Structure of the R4