Where does the long-established TIA-898 fit in among the many different and confusing testing specs cluttering today�s lab benches?
The TIA-898 (C.S0031) Signaling Conformance test specification has been a staple of cdma2000� handset test labs for several years and through several revisions. Recently, unfamiliar documents have shown up on lab benches in place of the standard TIA-898 document. They have caused some anxiety, affected some resources, and triggered a lot of confusion.
Is TIA-898 still relevant? What are all the relevant standards? Which standards are being used and why? Are there more changes to come, and if so, when?
TIA-898 has grown bulky and encompasses test cases that cover different areas. As cdma2000 continues to mature and evolve, the test requirements contained in TIA-898 have become too diverse to be categorized within a single document.
It is rare for any one person to be involved with all the related categories of handset testing. For an engineer assigned to either short messaging services (SMS) or interoperability testing (inter-op), the mass of documents has made it difficult to discern which tests are truly relevant.
The original intent of TIA-898 was to standardize the specification created by the CDG System Test Team known as CDG-57, Stage 2 Interoperability Testing for cdma2000 Mobiles. The specification was created to validate the interoperability or interaction between a handset and a vendor-specific implementation of network equipment. Since many of the cases also provided a good baseline for testing messaging, they have become the basis for cases executed on network-emulating test equipment.
Because all of the procedures are described in a single document, engineers can inadvertently spend time on irrelevant testing. Some of the tests in TIA-898 are for the handset while others verify elements of the network. Some tests aim toward testing signaling conformance while others are better suited to inter-op.
This, in turn, causes confusion regarding which test cases are most appropriate for which purposes. No clear delineation within TIA-898 tells the engineer which tests are best suited to the task at hand.
For example, an engineer uses a network emulator to test a new cell phone design. In this case, performing call-forwarding tests per TIA-898 provides little value. In fact, most of the functionality tested by a call-forwarding test is network based.
When all of these procedures are defined within a single document, it becomes difficult to tell which tests are best suited for a particular stage of the product life cycle. In addition, some test cases need revision fairly often while others have been stable for quite some time. The overlay services tests are over-the-air service provisioning (OTASP), SMS, and data services. They fit into the latter category.
In response, the 3GPP2�s TSG-C SWG4.2 Subcommittee decided to break the document into more manageable and logical groupings. This resulted in these separate specifications for signaling conformance testing:
� Signaling Conformance Test Specification for cdma2000 Spread-Spectrum Systems
� Signaling Conformance Test Specification for OTASP
� Signaling Conformance Test Specification for SMS
� Signaling Conformance Test Specification for Data Services
The committee also defined a specification for interoperability named the Interoperability Specification for cdma2000 Air Interface.
To add to the confusion, the wireless industry seems to have no clear preference regarding the use of the 3GPP2 or TIA numbering system for the new test specifications. The specifications C.S0043, C.S0044, C.S0060, C.S0061, and C.S0062 are the same as TIA-1035, TIA-1036, TIA-1044, TIA-1045, and TIA-1046, respectively (Table 1).
The new C.S0043/TIA-1035 is the signaling conformance specification for the core air interface and provides those cases used for testing general signaling. C.S0044/TIA-1036 includes the cases used in testing MS/network interoperability. C.S0060/TIA-1044 is specific to OTASP, C.S0061/TIA-1045 is for SMS, and C.S0062/TIA-1046 outlines the testing of data services.
Figure 1 shows how the TIA-898 specification was split into several new specifications. Even though the documents clearly match specific test purposes, there are new sources of confusion.
Some of the test cases overlap and appear in multiple specifications. As an example, the test case call forwarding with dynamic threshold appears in both TIA-1035 and TIA-1036 as well as in TIA-898. This case may be used with real network equipment for interoperability testing per TIA-1036 or with a network emulator for testing signaling conformance on the device per TIA-1035.
Other test cases may appear verbatim or with subtle differences in two or more specs. TIA-898 and TIA-1035 include tests named soft handoff with dynamic threshold. TIA-1035 is a little more rigorous.
The TIA-898 test is executed by sending a handoff message to the mobile device. TIA-1035 uses an extended handoff direction message, a general handoff direction message, and a universal handoff direction message.
As another example, both documents include a test case named signaling message encryption on forward traffic channel. This time, TIA-1035 is less restrictive. It allows for the use of a channel assignment message (CAM) or an extended channel assignment message (ECAM). With this test case, TIA-898 specifies the use of the CAM.
To add to the confusion, not all of the new documents were released at the same time. The air interface signaling conformance and inter-op specs were published in October 2004. The OTASP, SMS, and data services specs were released incrementally over the next couple of years. As of Q4 2006, TIA-1046 has not been formalized, and without a data services specification, many engineers have gravitated back to TIA-898 as the de facto standard.
Lab-Based Handset Testing
For most lab-based device testing, best practices include staying with the signaling conformance specifications. These are the mobile station (MS)-centric tests in TIA-1035, TIA-1044, TIA-1045, and TIA-1046.
Sometimes engineers may run inter-op on network-emulating test equipment. If the intent is to get an idea of functionality before going to the interoperability lab, this is the standard procedure. However, it can amount to severe stress on the test equipment.
As an example, the TIA-898 Test 8.2.4 Unknown Destination Address states, �The base station shall route the short message to the Message Center. A Data Burst Message shall be sent to the MS indicating an unknown address.�
There is no requirement to test functionality of the MS, yet this test is performed in handset testing labs every day. The TIA-1035 spec does a good job of segregating tests meant for MSs from those for network testing, so you don�t waste time debugging network issues.
In addition, the TIA-898 spec does include some test cases that have become less relevant over time. For example, TIA-898 incorporates test cases for temporary mobile subscriber identity (TMSI) and priority access and channel assignment (PACA) as well as the power-up function (PUF). Only in rare cases is there value in performing these tests.
The best way to control the environment is to automate testing with a well-calibrated automated system. Automation is not only about resource conservation. There is a lot of value in the unbiased nature of an automated system and the development and verification of a procedure.
This problem, as complex as it may sound, can be solved. At best, dealing with references with errors can consume a lot of time. At worst, it can lead to erroneous test results in an area where a single error can affect hundreds of thousands of consumers.
What About Inter-op?
TIA-1036 outlines the tests necessary for inter-op between an MS and network equipment. This kind of testing normally is performed in a specialized lab using real network elements.
In some cases, it does make sense to check for potential device issues before going into the inter-op lab. For this reason, there still is some call for running TIA-1036 tests with network-emulating test equipment.
Four other specifications are a superset of all test requirements included in TIA-1036. In other words, if the device has passed TIA-1035, TIA-1044, TIA-1045, and TIA-1046, then it is more than prepared for the inter-op lab. TIA-1036 testing based on network-emulating equipment should be reserved for those rare cases where a device must be submitted to the inter-op lab before the standard signaling conformance tests have been done.
What About CTIA and CCF?
The CDMA Certification Forum (CCF) currently recommends using the TIA-898 specification for conformance testing and TIA-1036 for inter-op. However, the forum expects signaling conformance testing to transition over to the new documents by the end of 2006. In the interest of unifying the focus of test specifications, the CTIA-The Wireless Association� has wisely announced its intention to have its test plan point to the CCF plans and documents.
Conclusion
These new specifications are the result of a substantial collaborative effort by representatives from chipset manufacturers, test equipment makers, handset makers, network equipment manufacturers, and operators. It is important to remember that standards work is a contributive process, and contributions to the committee are always welcome.
As the industry searches for efficiencies in critical areas, it becomes more and more important to properly focus efforts during testing. Due to the recent proliferation of high-end data-oriented devices, there is renewed pressure on both operators and device manufacturers to guarantee efficient service under a lot of realistic conditions. By electing to reclassify signaling conformance specifications by purpose, the 3GPP2 is taking on a big job to ensure that wireless subscribers can depend on products and services no matter how rapidly the technology evolves.
About the Author
Kurt Bantle is a solution architect for Spirent�s Wireless and Positioning Division. He has more than 20 years of handset testing experience and chairs the 3GPP2�s TSG-C SWG4.2 Working Group. Mr. Bantle also is active in several industry standards bodies such as the CDG, CCF, and CTIA. Spirent Communications, 541 Industrial Way West, Eatontown, NJ 07724, 404-266-2060 ext. 17, e-mail: [email protected]
December 2006