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Can We Really Understand Device Data Performance Without MIMO Over-the-Air Testing?

My faithful smartphone from the last 2 years finally gave up last week, putting me in the market for a replacement.  Considering myself to be fairly tech savvy, I perused a long list of worthy contenders, all loaded with the latest and the greatest features. Being a part of the wireless test industry, I know that the success of these features relies heavily on data performance, which in turn translates to good antenna performance. How could I be reasonably sure that I will actually get the data performance that I think I will get from these smartphones?

MIMO_OTA_Testing

This thought was triggered in part because of my recent involvement in a Signals Research Group benchmark study on MIMO Over The Air (OTA) testing. The study was comprehensive in the true sense - spanning fifteen different commercial phones over a wide price range and encompassing three different band configurations including low, mid and high. For a better understanding of the impact of modem implementations, devices across four different modem suppliers were thrown into the mix.  In addition, the study also involved collaboration with two independent test labs which allowed comparison of results of reference devices. This ability to compare the performance of reference devices was invaluable as it allowed us to verify the consistency of results. The greater the consistency of results across test labs, the better off we are in terms of predictability of end-user experience.

The test methodology for this study involved evaluating MIMO performance of a device under test (DUT) in a radiated environment using an anechoic chamber. An anechoic chamber minimizes interference from external signals on the DUT while a network emulator and a channel emulator connected to the chamber create various channel conditions, mimicking a MIMO environment, including the expected signal to interference conditions. Multiple antenna probes serve to create a radiated signal profile for the DUT while preserving the spatial aspects. Performance is evaluated by rotating the DUT in a variety of orientations and measuring the data performance. Thus the emulation environment is very close to what a mobile device would experience in the real world.   Measuring the throughput in a variety of orientations in its actual form factor makes the test methodology very realistic.

Findings from the study were truly eye opening; some lower-priced devices unexpectedly performed better and some devices performed several orders of magnitude better than others at similar Signal to Noise (SNR) values.

MIMO_OTA_Testing

The industry is moving towards enforcing MIMO OTA performance testing fairly rapidly. As discussed in my previous blog, the CTIA test plan v1.0 was published a couple of months ago and requires testing with a MIMO OTA anechoic chamber. Test labs and solution vendors gear up to become  authorized by the CTIA for this version of the MIMO OTA test plan which is expected to be mandated soon. 

Ron Borsato, Principal Architect at Spirent Communications and co-chair of the CTIA OTA working group, believes that this will be the first significant milestone in what he sees as a constant evolution of test methodology– “The CTIA is striving to develop OTA-based test cases that look to characterize antenna performance not just with Transmission Mode 3(TM3) which the recent SRG study was based on but for Transmission Mode 2(TM2) which considers cell edge conditions as well.”

The antenna performance insights that MIMO OTA testing delivers are beneficial to all – be it the handset manufacturer looking to get the best performance from his device in its final form factor, or the operator looking to evaluate device performance from the perspective of an end-user, or the chipset manufacturer trying to ensure that his solution meets or exceeds performance expectations.

Spirent is committed to supporting the industry in the field of MIMO OTA testing. As a follow up to this study, we will be hosting a join webinar with the Signals Research Group focusing on MIMO OTA test methodology, in addition to taking a deeper dive into the study highlights and the CTIA Test Plan which will be topped off with an interactive Q&A session. Watch our On-Demand webinar if you have not already and have your questions on MIMO answered.  

From a personal front, the study was just the push I needed to zero in on my next smartphone- hopefully, it will live up to my expectations. 

 
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