Terminal testing for network operators: the applications and limitations of a network simulator: Page 2 of 7

July 13, 2015 // By Francois Ortolan, Anritsu (EMEA)
Mobile phone subscribers care nothing about the complex mix of factors underlying the performance of their handset in the real world. By and large, if the user experiences a dropped call, or a low data download rate, or poor voice quality, he or she will blame the network operator. The real cause of the poor performance might be the handset, or the backhaul network - factors outside the direct control of the operator. To subscribers, this is irrelevant: they pay for mobile network service, and if they do not get it, the service provider must be at fault.
The use of a test bed alleviates some of these drawbacks. A test bed is an exact replica of a live network. Maintained as a dedicated test environment, isolated from the live network, this offers a controlled environment in which operators can test terminal performance in existing infrastructure and with the network features currently supported by the operator's live network.

A test bed provides a good means to test existing infrastructure before deploying new features on it, or to troubleshoot problems with radio resource management (RRM), or failures of interoperability. It suffers from limitations when the operator comes to test new mobile handsets, however. The product development cycles of handsets move much faster than those of network equipment. This means that new handsets are generally more advanced than an operator's infrastructure, and so a test bed might not be able to exercise many of the new features that handset users will wish to take advantage of. What is more, a test bed is composed of ordinary network equipment intended for use in a live network. This means that a test bed cannot offer features that would be helpful in a test environment, such as an automation interface for modifying operational parameters on the fly, or the ability to capture comprehensive logs.

A network simulator is the third type of test environment available to the operator. Because it is designed specifically for testing, it provides all the features that a test engineer would want, including a comprehensive automation framework and detailed logs. Any parameter, including all possible RF conditions, can easily be simulated. In addition, a simulator implements the latest network technology - for instance, the MD8475A from Anritsu today offers a comprehensive set of test cases for the latest LTE-Advanced standard (see Figure 1).

This means that a simulator is an ideal tool for a scientific comparison of a terminal's performance.

Figure 1: the MD8475A from Anritsu is a typical example of a network simulator that supports all mobile telephone standard technologies.

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