From Certification to Commercialization
Global wireless subscriptions are expected to exceed 5 billion in 2010.1 Consumer purchases of new services and smartphones in the developed world as well as accelerating purchases of wireless devices for basic communications in the developing world are driving this huge demand.
The consumers behind these subscriptions are serviced by networks using a wide variety of regionally based communications standards including GSM, W-CDMA, 1xRTT, 1xEV-DO, and most recently LTE. Along with this wide range of networks, an equally broad selection of wireless devices is available from basic voice devices to tablet PCs with integrated data connections and even wireless telematics options from automobile manufacturers.
Across this large number of subscribers, networks, and devices, consumers are united in their expectations that the wireless devices they use should function flawlessly at all times. This includes applications such as roaming in a foreign country, browsing the worldwide web while in a voice call, or using GPS-based maps augmented by ratings or other local feedback. Certification testing and carrier-specific testing of these wireless devices prior to commercialization provide a high level of confidence that these devices will meet customer expectations under all possible conditions.
Test Requirements for Wireless Devices
Prior to initial deployment of a new wireless device, a network operator typically will require that the device be verified through one of several certification bodies and against other unique carrier-specific tests. The intent of performing both of these categories of tests is to guarantee that a device will interoperate with a number of networks under a variety of scenarios.
In addition to certification and carrier-specific testing, a device must receive regulatory approval from a local or regional government authority like the FCC in the United States or EU in Europe although a large part of this testing burden has shifted to GCF and PTCRB since deregulation in the 1990s. The types of testing required to get a new wireless device into the consumer market are summarized in Figure 1.
For 3G W-CDMA and upcoming 4G LTE networks, the network operator usually would require that device manufacturers obtain certification by the GCF or PTCRB. The CC of both organizations are similar since they include a group of tests to check conformance of the device to technical requirements known as CTs. The CTs incorporate RF and protocol conformance tests from the 3GPP, application tests from the OMA, radiated spurious, and other similar RF and protocol-based tests.
CT Case Origins and the Validation Process
The 3GPP organization is responsible for originating standards for wireless technologies such as GSM, W-CDMA, and LTE. The CT standards for a specific technology such as LTE are originated in a subcommittee within 3GPP called RAN5. However, the focus for LTE CT is on TS 36.521-1 for RF CT including Transmit/Receive, Performance, and Channel State Reporting; TS 36.521-3 for RRM; and TS 36.523-1 for protocol CT.
While the CT definitions are written (typically called prose), 3GPP provides a software implementation of the test case for protocol CT. These test cases are written in TTCN language and called an ATS. The ATS is created, reviewed, and debugged by a consortium of companies in the test industry working under the auspices of the ETSI and supplies a vendor-independent reference for the test cases. The ATS for LTE is provided in TS 36.521-3.
GCF and PTCRB do not automatically adopt all tests defined by 3GPP for a specific technology. Instead, the GCF WIs and PTCRB RFT documents are defined for a particular feature such as HSDPA or Rel. 7 MIMO. Typically, a number of related test cases from TX, RX, RRM, and protocol conformance categories are selected for use in a given WI/RFT as agreed by members of the organization.
For LTE, there are both FDD and TDD variants to fit a carrier’s local spectrum allocation, so LTE WIs have been arranged within the GCF as follows:
WI-080 E-UTRA RF Rel. 8 FDD
WI-081 E-UTRA Protocol Rel. 8 FDD (P1 & P2)
WI-082 EPC Protocols Rel. 8 FDD (P1 & P2)
WI-083 E-UTRA Protocol Rel. 8 FDD (P3 & P4)
WI-084 EPC Protocols Rel. 8 FDD (P3 & P4)
WI-090 E-UTRA RF Rel. 8 TDD
WI-091 E-UTRA Protocol Rel. 8 TDD (P1 & P2)
WI-092 EPC Protocols Rel. 8 TDD (P1 & P2)
WI-093 E-UTRA Protocol Rel. 8 TDD (P3 & P4)
WI-094 EPC Protocols Rel. 8 TDD (P3 & P4)
For PTCRB, RFT 076 has been defined for LTE and includes RF, RRM, and protocol CT tests for FDD only.
Although RF CT and protocol CT test cases are separated into individual WIs for LTE, for other technologies, there also are WIs that combine RF and protocol CT into a single WI. In addition, due to the large number of LTE Protocol test cases, GCF and PTCRB have categorized each test case as Priority 1, 2, 3, or 4 based on criticality for initial network deployment. The intent is that the industry would complete work on Priority 1 and 2 test cases such as WI-081 and WI-082 prior to starting work on Priority 3 and 4 like WI-083 and WI-084.
Following the definition of a WI, a system manufacturer would implement the test cases in the WI on its own test platforms, with an individual platform receiving a unique test platform number from GCF and PTCRB. Protocol test cases must be implemented in TTCN per the 3GPP definition while RF test cases may be implemented in a language at the manufacturer’s discretion.
After a group of test cases is finished and operation is verified, the system manufacturer then commissions an authorized test lab to validate the test cases. Typically, two wireless devices from different manufacturers using different chipsets are required in this process although some single-device validations have been allowed in the early stages of LTE deployment due to limited device availability. Following successful execution of a test case, the authorized test lab submits a validation report to GCF or PTCRB for analysis and subsequent approval.
The status of a validated test case can change and is not static. Categories have been defined to signify validation status and applicability of a test case ranging from Category A (validated and required for certification) to Category P (not validated). Changes in category can be due to changes in the prose or ATS version of the test case from 3GPP RAN5, downgrades due to test case problems, upgrades based on previously downgraded tests, and many additional combinations subject to highly detailed procedural rules for the relevant certification organization.
Validations provided by GCF and PTCRB are for a test case executed on a specific test platform. The test platform itself is never validated by either GCF or PTCRB, only the capability of the test platform to execute the specific test case correctly.
Historically, GCF and PTCRB have differed in regional focus, with PTCRB associated with the North American market and GCF with markets in EMEA and Asia. However, there no longer is a regional distinction commencing with LTE since operators may align with either of these organizations moving forward.
Device Certification and Validated Test Cases
Both the GCF and PTCRB maintain databases of device CC that are updated periodically as WIs and RFTs are added and other modifications are made. For GCF, this is called the GCF CC Database while for PTCRB it is referred to as NAPRD.
For GCF, the trigger for a new WI to be used for certification of a wireless device typically is when 80% of the test cases in the WI have been validated and are available on a single test platform. At this time, the WI has reached CEC and becomes mandatory for certification testing.
The 80% rule considers the total number of test cases validated by all test system manufacturers vs. the total number of test cases in the WI. For LTE, the target is to reach CEC for WI-080, 081, and 082 by Q4 2010.
When a wireless device is submitted for certification, the manufacturer must provide a variety of information to either GCF or PTCRB, including PICS and the name of the authorized lab at which the certification will be performed. Applicable WIs will be selected based on the PICS, and certification testing will be performed. Since CC and NAPRD document applicability overlap in time, the manufacturer may be given the choice of which document to use for certification depending on timing in the update cycle.
|1xRTT||1x (single carrier) radio transmission technology|
|3GPP||Third-Generation Partnership Project|
|4G||fourth generation of cellular test standards|
|ATS||automatic test suite|
|CEC||certification entry criteria|
|EMEA||Europe, Middle East, and Africa|
|EPC||enhanced packet core|
|ETSI||European Technical Standard Institute|
|E-UTRA||enhanced universal mobile telephone system|
|EV-DO||evolution data optimized|
|GCF||Global Certifi cation Forum|
|GSM||global system for mobile communications|
|HSDPA||high-speed downlink packet access|
|MIMO||multiple input, multiple output|
|NAPRD||North American Program Reference Document|
|OMA||Open Mobile Alliance|
|PICS||Protocol Implementation Conformance Statement|
|PTCRB||PCS Type Certifi cation Review Board|
|RFT||request for test|
|RRM||radio resource management|
|TS||technical specifi cation|
|TTCN||testing and test control notation|
|W-CDMA||wideband code division multiple access|
In the event that a carrier needs to buy a device prior to inclusion of the WI in the CC or NAPRD, the carrier can purchase it without testing or define a carrier-specific test plan to verify functionality and interoperability of the device. A carrier-specific test plan also may be necessary if the carrier feels that testing of a certain feature or function is needed and no corresponding tests are provided by 3GPP. Finally, a carrier may decide to use a carrier-specific test plan if there is a need to verify compatibility with a unique carrier network configuration different from the reference configuration used for CT.
Currently, the test industry is focused on meeting GCF CEC for WI-080, 081, and 082 in Q4 2010 as well as providing the same test cases for PTCRB. Consequently, there may be features and functions for which testing is desired but for which test coverage defined in these WIs is limited to less than what a carrier desires.
For example, a carrier may wish to test LTE throughput at the maximum data rate under an exhaustive set of conditions, assuming that the data rates provided by LTE to the consumer are a crucial part of the carrier’s marketing strategy. As a secondary example, a carrier may wish to test LTE handoffs to the pre-existing 2G or 3G network in a different fashion than defined in 3GPP, assuming that call reliability is crucial to the carrier’s marketing strategy.
If a carrier does decide to write a unique test plan for verification of devices, a procedure must be defined to validate the test cases in the plan on more than one wireless device. In addition, there must be a method to notify wireless device suppliers to the carrier when a test case has been validated on a specific manufacturer’s test platform. Lastly, authorized test labs must be enabled to provide test services to the same wireless device suppliers using validated test cases on the same platforms.
Platforms for LTE RF and Protocol CT
Anritsu has introduced some instruments and systems to support LTE CT as this technology is deployed around the world.
The ME7873L LTE RF Conformance Test System for GCF-validated LTE test cases uses the MD8430A Signaling Tester as an LTE network simulator and is configured from company-developed test instruments, interface hardware, and software. It handles TRX, performance, and RRM test cases with the UE in a test call or no-call test mode. LTE bands currently supported include 1 to 14 and 17.
A drag-and-drop interface helps create test sequences, and many modes beyond strict CT testing are supported, including a search mode for receive and performance tests, automatic termination and retry for failed tests, a signaling log viewer, and simple call processing parameter changes for efficient R&D and certification tests.
Testing of 3GPP TS 36.521-1 Chapter 6 Transmitter Characteristics, Chapter 7 Receiver Characteristics, Chapter 8 Performance Requirements, Chapter 9 Reporting of Channel State Information, and TS 36.521-3 RRM is accommodated with the ME7873L. Support for TDD and Inter-RAT tests including LTE to GSM, UMTS, and CDMA2000 is planned.
The ME7832L LTE UE Protocol Conformance Test System is based on 3GPP TS36.523 for GCF/PTCRB Terminal Certification and uses the MD8430A LTE Signaling Tester as the base-station simulator. It handles all GCF and PTCRB-supported LTE bands. Factory integration of the MD8430A LTE Signaling Tester and the GCF Protocol Conformance Test Toolkit into the ME7832L facilitates setup and maintenance and includes cabling, software installation, and system-level correction. The ME7832L also features the Intelligent Test Sequencer with a drag-and-drop GUI, a TTCN3 viewer and editor, and future LTE inter-RAT capability to/from UTRAN/GERAN and CDMA2000.
1. “ITU Sees 5 Billion Mobile Subscriptions Globally in 2010,” Barcelona, Feb. 15, 2010.
About the Author
Mike Barrick is the business development manager for the wireless test portfolio at Anritsu Co. and has 20 years of experience within the test and measurement industry. Throughout his career, Mr. Barrick has held a variety of positions including marketing, application engineering, and sales. He has a B.S.E.S. from Baylor University, an M.S.E.E. from University of Texas, and MBA credit-hours at Baylor University. Anritsu Co., Americas Sales Region Headquarters, 1155 E. Collins Blvd., Suite 100, Richardson, TX 75081, 972-644-1777, e-mail: firstname.lastname@example.org