The complexity of mobile devices and networks continues to grow with the increasing application of technologies such as MIMO. Recognizing the importance of comprehensively testing devices that employ this technology, operators and manufacturers have worked with the industry to develop standardized over-the-air (OTA) test methodologies that fully evaluate both baseband modem performance and antenna design.
The main two groups working on the standardization of MIMO OTA testing methods and techniques areand . The year 2020 has witnessed tremendous achievements in MIMO OTA standards in both groups.
3GPP is taking the lead in 5G MIMO OTA testing
First, 3GPP RAN4 is spearheading the effort in 5G new radio FR1 and FR2 . This year brought the successful and (mostly) timely completion of the MIMO OTA Study Item (SI) . The timely completion was primarily due to all the lessons learned in 4G LTE MIMO OTA, where it took more than nine years to reach an agreement in both 3GPP RAN4 and CTIA. Despite the challenges brought by the pandemic (such as the inability to hold in-person meetings as before), companies focused on settling the MIMO OTA methodologies for FR1 and FR2 first. This was the main culprit for the 4G LTE standardization delay (the seemingly endless battle between reverberation and anechoic chambers).
Once the methodologies were settled, the details were fleshed out one by one, like the number of probes, the layout, the channel models, and the validation techniques (mostly borrowed from 4G LTE for FR1 and a few new for FR2, like PSP validation). Other important parts were deferred for the Work Item (WI) phase, like measurement uncertainty (MU). By the end of the summer, the RAN Plenary approved the successful conclusion of the SI embodied in TR38.827 and also approved the beginning of the WI, whose outcome will be captured in TS38.151.
Thus far, in the three RAN4 meetings after the WI phase began, companies are working toward settling details like a unified probe layout for FR2 and the lab alignment phase (where actual performance will be measured by a set of independent labs). It is expected that the WI will conclude by the end of the summer 2021. TS38.151 will contain performance requirements for several FR1 and FR2 operating frequency bands.
CTIA is broadening their MIMO OTA test plans to include 5G
As for CTIA, their MIMO OTA test plan version 1.2 will be mandatory on December 23, 2020. Though this plan is for 4G LTE only, CTIA has begun discussions about the requirements for 5G NR FR1 testing in the MIMO OTA Subgroup (MOSG). Initial indications point to a possible divergence in methodologies for FR1 with respect to 3GPP RAN4. CTIA has signaled the possible continuation of the use of the 4G LTE methodology that specifies 8 dual polarized probes. In contrast, the 3GPP RAN4 methodology specifies 16 dual polarized probes.
The year ahead promises a lot in terms of the MIMO OTA standardization process, with the anticipated issuance of 3GPP TS38.151 and CTIA continuing discussions to select methodologies for FR1 and FR2.
Trust Spirent expertise
Channel emulation is an essential part of MIMO OTA testing and Spirent experts are long-time contributors to the CTIA OTA and 3GPP RAN4 working groups. It is this industry-recognized expertise that is the foundation of Spirent’s test solutions spanning MIMO OTA and A-GNSS OTA test requirements.
For MIMO OTA, Spirent provides a robust channel emulation solution with the Vertex® platform. Vertex supports the current CTIA MIMO OTA Test Plan and the 3GPP RAN4 FR1 and FR2 methodologies.