GPRS challenges mobile network operators.
General packet radio service (GPRS) networks are an example of the new challenges in the test field for network operators. GPRS is an important improvement on the path from second- to third-generation (3G) mobile communications systems. An overlay to existing global system for mobile communications (GSM) networks, GPRS lays the foundation for universal mobile telecommunication service (UMTS) and 3G systems that are based on packet-switched architectures.
To support the new features introduced by GPRS, the existing GSM network must be enhanced with the addition of a new set of network elements, such as packet control unit (PCU), the serving GPRS support nodes (SGSN) and the gateway GPRS support nodes (GGSN). This new system is totally based on a packet-switched approach, and it is usually linked to other packet data networks like the Internet, X.25 network or other GPRS networks.
Monitoring, performance testing, simulation and emulation are crucial steps in the process of verifying the functionality and efficiency of individual GPRS network elements or an operator's entire network. The new requirements added by the GPRS layer introduce new challenges for operators. In particular, each element must be verified for interoperability. The combination and interworking of network elements and new features require new tests, which must cover the following:
* extended protocols on eight different signaling, and six different combined signaling and data interfaces inside the GPRS system;
* monitoring on multiple interfaces with different protocol stacks to obtain an overview of the whole system;
* simulation, emulation, data generation and analysis of multiple interfaces and protocol stacks;
* performance measurements;
* finding problems caused by the mobility in PDNs, for example, changing bandwidth on the air interface and its subsequent influence on the TCP/IP connection performance; and
* interworking or circuit-switched and packet-switched network components on, for example, location updates and short message services.
Test requirements fall into four areas:
1 Physical-layer testing: Most testers designed for physical-layer testing also contain protocol display and testing for Layer 2.
2 Circuit-switch testing: Seeing the signaling protocols and checking the switched circuits is necessary.
3 Packet-switched testing: This can be separated into the testing of the network layers (up to Layer 3 in the ISO OSI model).
4 Interworking between circuit-switched and packet-switched networks should also be checked.
The ideal protocol test system for GPRS should include all physical interfaces and all Layer 2 variants; all protocols for GSM and GPRS; the ability to monitor and simulate multiple interfaces in parallel because of the system's complex behavior; and the ability to monitor a particular condition in the network, trace it and make it available as a predefined configuration for easy and effective simulation test in the test plant.
The recommended test platform should include monitoring and simulation tools, combined with emulation and packet generation and checking capabilities. Due to the GPRS network environment, a standard interface to user applications with IP data is also recommended.
Because GPRS is the most important step to the UMTS 3G system, the protocol tester must be ready to address this technology. In particular, the protocol test instrument will have to be able to handle asynchronous transfer mode (ATM) exchanges with different interfaces, since the ATM interface will be incorporated into GPRS as the basic connection for UMTS.
Higher data transmission rates will also be achieved in next-generation systems by enhanced data rates for GSM evolution. UMTS increases speed and combines communications services, such as terrestrial mobile communications, wireless local loop, satellite-based mobile communications and wireless multimedia services.
When taking a look at the future and at 3G networks, a protocol tester will have to be able to handle higher bandwidths with new transport technologies like ATM, extended interworking features, and such new services as wireless multimedia applications. With the current and expected issues associated with GPRS protocol testing, mobile network operators need instruments that will provide both for the future and the here and now.
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