Wireless entertainment may soon lead to an upswing in the telecommunications market. In large part, its commercial success will depend upon the quality and usability of new mobile terminals. To run increasingly sophisticated games and other entertainment applications, mobile terminals must be web-enabled. In addition, they have to support new software environments, interfaces, and multimedia features. Hardware features, including RF power and battery life, also must be optimized. Meanwhile, software and hardware development must face the challenges of evolving standards, complex protocol stacks, embedded applications, and even mobile location technology.

The manufacturers that develop mobile terminals have to ensure that all of these components work together before they take a product to market. They must submit their final designs to rigorous conformance and interoperability testing. Yet they also need to avoid the high cost of last-minute design changes. Manufacturers must therefore recognize the need for early and continuous testing during the product design and integration processes. Thankfully, a new generation of test instruments makes it easier to verify the advanced features, protocol implementations, and integration of software at each stage of the mobile terminal's development.

In first- and second-generation wireless communication systems, only one connection path went from the mobile terminal to the cellular network. That single path handled all calls, including any data application that was carried along with the voice information. Beginning with GPRS, however, a second connection path was added. This path allowed data transfer to and from the Internet. The link to any 2.5G or 3G mobile terminal now carries control and messaging functions for both sets of services.

To support the growing number of data applications together with voice and voice-related services, today's mobile terminals contain numerous components and subsystems. They range from audio components and traditional hardware, such as RF circuitry (combiners, filters, oscillators, mixers, and power amplifiers), to specialized chip sets. Also included are the following: protocol stacks, data-communication software, display drivers, a complex user interface, mechanical packaging, and the battery.

With the introduction of Internet connectivity and packet data transmission, the industry has witnessed a huge increase in the amount of embedded software in mobile terminals. In earlier-generation cellular phones, software consisted mainly of RF signaling protocols. Those protocols were used to control phone operation.

Today, a larger percentage of the embedded code is devoted to the multiple layers of data-communication protocols (FIG. 1). In 2.5G and 3G mobile terminals, an application stack has been added in parallel with existing signaling protocols. The application protocols allow mobile terminals to run embedded software, such as web browsers and Java engines. They also provide modem capability for transmitting and receiving data. Such capability might be needed, for example, between a handset and the Internet in order to download a web page or game.

A growing trend is to design chip sets, protocol stacks, and applications independently of the wireless terminal. Often, this design approach relies on different vendors for each specialized component. Although every component may be individually tested and certified, product developers must ensure that these components provide a desired level of performance when assembled. What happens to the mobile terminal if a short message or a voice call comes in while a user is playing a game? How is the mobile affected if it passes under a bridge while the user is downloading a web page? It is critical to understand and validate the mobile terminal's performance under real-world conditions.

Typically, product developers verify the performance of data-communication software by stressing the device under test. They then measure parameters, such as lost data packets, data throughput, and delays. This technique requires real Internet-protocol (IP) data traffic. In a wireless environment, that traffic is found in a live network. Unfortunately, it's not practical to test a mobile terminal in a commercial operation. The obvious reasons include inconvenience and a lack of environmental control.

Protocol software is more commonly verified using the large, script-based systems that were developed for conformance testing. A test script provides the exact sequence of protocol messages that must be exchanged between a wireless terminal and the network in order to implement a specific feature. Scripts can be written to test any possible scenario. The message exchanges between the wireless terminal and the network are spelled out line by line. The conformance test system steps through the messages sequentially. When an unexpected response occurs, it sends an alert.

Generally, scripted tests are required to demonstrate conformance to a particular standard. Each standard has a specified number of tests that were developed by the relevant governing organization as part of the minimum performance requirements. Product developers can augment that set with additional tests for their particular circumstances.