3GPP declared a major milestone for 5G this past December by announcing the approval of the first 5G New Radio (NR) specifications. But even after that formal milestone, the members of 3GPP will spend at least the next six months finishing additional required details of the 5G specification.
While the specification for the radio are approaching completeness, the test specifications were barely started when the announcement was made. Test specifications are an important part of the overall 3GPP output as they are adopted by certification bodies to certify user equipment (UE). RAN5 is the working group within 3GPP which has the task of detailing the UE test specifications also known as conformance specifications. These specifications include the various well-known tests such as RF transmit and receive power, waveform quality, occupied bandwidth, adjacent channel leakage, etc. There are also protocol specifications that define the behavioral performance of signaling between the phone and network, yet to be written.
As of March 2018, 3GPP RAN5 had established the skeletons of the test specifications as well as significant detailing of some aspects of the specifications. These test specifications are pre-release documents and can be seen as very early due to the very frequent use of “TBD” (to be determined) and “FFS” (for future study)—these are known unknowns that are placeholders for future values.
User Equipment (UE) conformance specification; Part 1: Common test environment
Special conformance testing functions for User Equipment (UE)
User Equipment (UE) conformance specification; Applicability of RF and RRM test cases
UE conformance specification; Part 1: Protocol conformance specification; RAN5 doc
User Equipment (UE) conformance specification; Radio transmission and reception; Part 1: [Frequency] Range 1 Standalone
User Equipment (UE) conformance specification; Radio transmission and reception; Part 2: [Frequency] Range 2 Standalone
User Equipment (UE) conformance specification; Radio transmission and reception; Part 3: NR interworking between NR range1 + NR range2; and between NR and LTE;
User Equipment (UE) conformance specification; Radio transmission and reception; Part 4: Performance requirements;
5G UE test specifications produced by 3GPP RAN5 (source: ftp.3gpp.org/Specs/latest-drafts)
An interesting aspect of testing 5G, and a concern for the industry, is how to test beamforming in base stations and mobile phones while the system is actively scanning and tracking the 3-D sphere for energy. A new function defined for 5G NR that helps with this challenge is called “beamlock” (see specification 38.509). The beamlock function forces the UE to freeze the beamforming pattern of the UE so that testing can occur. The receive pattern and transmit beam patterns can be independently frozen. This test function is not meant to be used in regular operation . The presence of this function reinforces that the world is quite different when it comes to testing a beam-formed millimeter wave system-- the yet to be defined over-the-air (OTA) tests will be far different from past wireless generations. And it is certain to be a challenging task finding agreement on these tests given the highly varied opinions of RAN5 attendees and complex technical nature of the problem.
The early nature of the test standards coupled with the complexity of OTA suggests a substantial amount of work in order to complete the test specifications by 3GPP’s goal of the end of 2018. In order to achieve the goal, 3GPP RAN5 will continue its world tour, hosting 2018 meetings in Korea, Sweden and the United States. In addition, there will likely be many discussions over phone and email to complete the work.
As we look forward to the future, we await 3GPP’s detailing of the test specification, especially in the aforementioned area of OTA. With beamforming and tightly integrated device antennas, we expect the R&D, type approval, and production tests to have a dramatic increase in the amount of OTA testing compared to prior generations.
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