GPRS Rei5 Architecture

As shown in Figure 10.2, the GPRS mobile system consists of three main entities: Mobile Station (MS), Radio Access Network (RAN), and Core Network (CN). A mobile station refers to the mobile equipment on which a user executes mobile services and applications (i.e., voice services, SMS). A mobile station communicates with the base station that controls the radio channel within its coverage area (or a cell, so to speak). Multiple base station systems interconnect and form the network called RAN. RAN is responsible for providing the communication path between the Mobile Station and the Core Network. Furthermore, RAN also provides several key functions to support communication such as channel access, mobility management, and radio resource management. GERAN (GSM/EDGE Radio Access Network) is the RAN entity of GPRS (Rel-5).

Figure 10.2. GPRS Architecture

Figure 10.2. GPRS Architecture

Gsm Network Architecture

The Core Network connects the mobile network to the external network (i.e., [PSTN], Integrated Services Digital Network [ISDN], Internet). The core network comprises two domains: Circuit Switching (CS) domain and Packet Switching (PS) domain. The CS domain contains modules that support circuit switching services. As shown in Figure 10.2, the Mobile

Switching Center (MSC) resides in the CS domain. The PS domain contains the following main modules that support packet switching services: Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN). A voice signal (circuit switching traffic) travels between a mobile station and an external voice network (i.e., PSTN) through the Base Station System (BSS) and MSC. On the other hand, a data signal (packet switching traffic) travels between a mobile station and an external data network (i.e., Internet) through the BSS, SGSN, and GGSN. Home Subscriber Server (HSS) is a supporting module providing subscription-related information for both the CS and PS domains.

GERAN consists of multiple interconnected BSSs. Each BSS serves the mobile stations within its coverage area. The BSS connects to the CS domain of the core network through A and Iu-CS interfaces while the BSS connects to the PS domain of the core network through Gb and Iu-PS interfaces. Iu-CS and Iu-PS can be simply called Iu interface. The mobile station connects to the BSS through the Um interface. Each interface has its own protocol architecture that handles the communication between the pair systems.

Prior to Release 5, the BSS connects to the core network only via the A and Gb interfaces (no Iu interface). This core network is considered to be the second generation core network. 3GPP realizes a smooth migration from the second generation mobile system toward 3G's UMTS (Universal Mobile Telecommunications System). In UMTS, UTRAN (UMTS Terrestrial Radio Access Network) connects to the third generation core network through the Iu interface. Therefore, in order to align with UMTS, GPRS Release 5 includes Iu interface in addition to the existing A/Gb interfaces. Figure 10.3 illustrates the GPRS architecture for 2G and 3G core networks.

Figure 10.3. GPRS Architecture for 2G and 3G Systems

Figure 10.3. GPRS Architecture for 2G and 3G Systems

Gsm Network Structure Ran Pstn

The mobile station can be in one of two modes: A/Gb mode and Iu mode. The mode is determined by the generation of the core network (i.e., 2G or 3G) with which the mobile station associates (see Figure 10.3).

The standard allows three domains of operation for the mobile station in A/Gb mode:

• Class A domain of operation: The MS can operate both packet switching services and circuit switching services simultaneously.

• Class B domain of operation: The MS can operate either packet switching services or circuit switching service at one time.

• Class C domain of operation: The MS can only operate packet switching services.

Furthermore, the standard also defines three domains of operation for the mobile station in Iu mode:

• CS/PS domain of operation: The MS can operate both packet switching services and circuit switching services simultaneously. This domain is analogous to Class A of the A/ Gb mode.

• PS domain of operation: The MS can only operate packet switching services. This domain is analogous to Class C of the A/Gb mode

• CS domain of operation: The MS can only operate circuit switching services.

GPRS supports both Point-to-Point (PTP) and Point-to-Multipoint (PTM) services while supporting roaming of GPRS users between different carriers. The PTP can be used for accessing information on the Internet, messaging services, and conferencing applications. PTM can be used for delivering information, such as news and weather, to multiple locations or interactive conferencing applications.

GPRS Rel-5 added a new component as compared to previous GPRS releases, the Internet Multimedia Subsystem (IMS). IMS allows simultaneous access to multiple different types of realtime and non-real-time traffic. Real-time traffic includes voice, text, and video, and non-realtime traffic includes data, audio and video files, audio and voice streaming, text and multimedia messaging, emails, and Internet browsing.

IMS provides synchronization between the multiple components of a multimedia communication session. For example, a user can receive calls while continuing with web browsing. IMS lists key requirements for multimedia services. These requirements pertain to the user perspective. In addition, IMS lists requirements for security, addressing, support for roaming, emergency calls, mobile number portability, messaging, and Virtual Private Network (VPN) support.

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  • Feaven
    What is ps domain inwareless network?
    1 year ago

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