Behold the Power of Testing

Protocol-analysis tools help ensure that subscribers get new features that they will love.

New features are the currency of competition. No sooner is a new service described in the press than consumers begin pressuring service providers to offer it immediately. In turn, service providers look to network-equipment manufacturers to provide equipment that answers those consumer demands.

A case in point is the 2.5G wireless feature set that delivers certain data-transmit/receive capabilities to wireless subscribers. These 2.5G features are the stepping stone to true 3G digital-wireless architectures in which voice, data and video traverse the entire network with equal ease.

The equipment manufacturer that is first to market with 2.5G-capable equipment has a huge advantage. In the time it takes to design and introduce a product that restores competitive parity, the market has moved on with a new set of customer demands.

Of course, this urgency is a reflection of the consumer market's demand for tangible new features in mobile telephony — features that provide data services to individual subscribers' handsets. Networks are being transformed, one element at a time, moving toward an ultimate goal of end-to-end packet-switching capability. Unfortunately, this process of network transformation is unable to keep pace with advancements in mobile-station capability. After all, the costs to service providers are huge, and the task can affect the quality of service that current subscribers receive. From the service provider's view, there's a pressing need for solutions that can speed up the upgrade cycle and minimize the impact on the operating network.

Virtually all new network features and technologies have their origins in rigorous standards developed within industry committees. These bodies include representatives from service providers, equipment manufacturers, infrastructure developers and test-equipment vendors. The "deliverable" of a standards committee is a practical, non-partisan definition of new protocols and implementation guidelines.

Obviously, the introduction of a new wireless capability, whether from the manufacturer's standpoint or that of the service provider, is a major strategic step. Yet one crucial requirement in the process of implementing new, standards-compliant features is easy to overlook. Committees can specify new protocols and engineers can design new hardware and software, but where is the proof that a new feature is fully compliant and ready for prime time in a practical, real-world sense?

This is a potential barrier to the realization of new mobile technologies. Just as network equipment must keep pace with wireless subscribers' service demands, so too must test and measurement equipment keep pace with changing protocols and standards. Implicitly, this means close, synergistic cooperation among test vendors and the design and installation technologists in the wireless industry.

Protocol Analyzers at Work
What happens when a brand new protocol stabilizes and new features must be brought to market as quickly as possible? Can the existing research and evaluation tools adapt to meet the new need? A major manufacturer of CDMA base stations and equipment recently concluded a design/evaluation project that paid off with the introduction of the industry's first IS-634-compliant product line. A cornerstone of this introduction was a protocol-analysis tool that had the "hooks" and the support to adapt quickly to the needs at hand.

The IS-634B protocol adds channel bundling, roaming information and other data-related 2.5G capabilities to CDMA networks. As the governing standard for the A interface between CDMA BSCs and mobile-station controllers (MSCs), IS-634B is poised to become, in some modified form, part of the eventual cdma2000 standard. Currently the protocol's main responsibility is to speed up data transactions between the BSC and MSC by bundling several channels into a packet for simultaneous transmission. As the remainder of the cdma2000 network infrastructure falls into place, the A-interface portion will integrate into the larger continuum from the BTS to the network cloud.

Equipment manufacturers need proper tools in the engineering lab to verify that IS-634B capabilities are correctly designed, and in the field for evaluation and trials. Service providers need similar instruments to confirm that the new features are correctly installed and to support routine troubleshooting.

Proving that new protocols and installations work as proposed is the job of a class of tools known as protocol analyzers, which connect to and monitor network interfaces. This is not a new class of instruments. However, continuing technical and market pressures are driving new requirements for protocol analyzers, and for the test-equipment vendors that provide them.

Ability to Adapt
One of the most important attributes of these measurement and monitoring instruments is flexibility — their ability to adapt to emerging standards and protocols. The tool must make it easy to develop a protocol stack for monitoring and decoding new data formats. Equally important, the same tool must offer the hardware capacity and connectivity to make protocol testing more cost-effective on a large scale.

Essential to this project was a flexible protocol-analysis tool with the base performance to handle the data rates and channel counts involved. The instrument has a built-in protocol-stack editor and a wealth of built-in protocol definitions (more than 150). These work together to expedite development of new protocols and message formats. The protocol analyzer exemplifies the kind of tools that underpin the fast-changing network-equipment market.

Two Sides of the Same Coin
The protocol analyzer can hasten the development of critical new network elements. But the instrument's utility doesn't end with the manufacturer's applications alone. It extends to the service provider's installation process and also plays a role in the continuing maintenance of new protocols and features. Here too, the analyzer can speed up the delivery of the data transmit/receive features that wireless subscribers want.

The installation acceptance process is a thorough "wringing out" of new equipment during and after installation. Of course, there's an assumption that the equipment vendor will strive in good faith to meet agreed-upon performance commitments. But an acceptance checklist ensures that nothing is overlooked and documents any discrepancies. Better to reach this kind of understanding at installation time than to sort it out months later.

Equipment vendors may elect to include recommendations for specific monitoring tools as part of the documentation accompanying newly installed network elements. Why? Because so much of the work already is done. As in the foregoing application example, the manufacturer and the test-equipment vendor's engineers already have put in the hours developing protocol stacks for the instrument. The tool and the test procedure have been thoroughly proved through months of use in exercising the new network equipment. And all of the test code, test results and development data is recorded in the context of that one platform.

This latter aspect is important. In most instances, the equipment vendor will install new capabilities such as IS-634 with the help of the same kind of protocol-analysis tools and procedures used to develop the product originally. That ensures consistency from design to implementation. Now imagine that an IS-634-compliant A interface is installed and accepted based on the protocol information from such an analyzer. But after a few months, the interface appears to be the source of dropped calls or other errors.

Now the service provider's maintenance team looks into the problem. This group, if not armed with the same tools used at installation/acceptance time, can produce test results that differ in form or style from those of the original instrument. Comparing the results with "known-good" reference screens and archived acceptance data may be difficult if not impossible. The maintenance team might have to start from scratch to identify the problem -- and meanwhile, mobile subscribers may be experiencing problems with their phone use.

If the maintenance group is able to go afield with the same type of test/monitoring platform used to develop and install the transceiver equipment originally, results can be compared with those of controlled tests in the service provider's I&M laboratory, or even with readings from the installation team's work months before. Some scaleable protocol analyzers lend themselves to both field and factory use, offering cost-effective configurations for field applications.

New wireless protocols are emerging steadily, in answer to wireless subscribers' demands for data communications on their handsets. Equipment manufacturers designing products — base stations, switches and transceiver elements — are challenged by the need to implement these protocols, and verify compliance with the new standards. A generation of powerful, self-contained protocol analyzers has arisen to help wireless-equipment engineers meet this challenge. The analyzers include graphical tools to simplify the creation of test routines and are scaleable to meet the needs of designers, installers and maintenance teams.

Newitts is Tektronix U.S. Design Center business development manager.