PCT and IOT in LTE Networks: A Study on Test Cases and Test Results

In order to produce communication devices compliant with the LTE standard, a terminal manufacturer must perform a series of tests before mass production. This work analyzes the test cases and results of LTE Protocol Conformance Test (PCT) and Interoperability Test (IOT) for the user equipment (UE). We conduct 175 PCT test cases from the 3GPP specifications and the results show a PCT pass ratio of about 80%. IOT consists of 9 test cases selected by the manufacturers based on an agreed set of important test cases; only a few Devices under Test (DUTs) fail the IOT. Further analysis reveals that there exists a many-to-many mapping between PCT cases and IOT cases: a total of 42 PCT cases, i.e., 24% of PCT, map to all 9 IOT cases, and a PCT case might also map to several IOT cases. On average, every IOT case maps to 13 different PCT cases. The PCT cases that do not have mapped counterparts in IOT are mostly Layer 2 test cases. This is because most of the IOT test flows use Layer 3 parameters to determine passing or not without changing the default Layer 2 parameters. Passing IOT does not warrant passing PCT since PCT has requirements that are more rigid.