Wednesday, November 7, 2018

OnePlus 6T shows its pluses, minuses in FCC RF tests

The OnePlus 6T (variant A6013, FCC ID 2ABZ2-A6013) had its authorization documents uploaded to the FCC OET database early last week in conjunction with the OnePlus launch event in New York.  Typically, I would not run analyses of lab tested RF and write blog posts about mobile handsets that are intended for sale primarily outside of the US.  In fact, such devices and variants, while almost always FCC authorized for use in the US, often are not RF optimized for domestic LTE bands -- but I digress, as that is the intended subject of a future article.

Back to the OnePlus 6T, though, it presents something of a paradigm shift.  Not only is T-Mobile selling the One Plus 6T directly but also VZW has certified it as an LTE only device for use on its network.  That really puts the OnePlus 6T on similar footing to that of the Pixel 3/XL.  So, in light of those developments, let us take a look at its certified RF testing lab report submitted to the FCC OET.

First, a quick rundown of a few gigabit LTE capabilities drawn from the FCC filings and the OnePlus 6T tech specs page:
  • Downlink 5x CA, uplink 2x CA
  • Downlink 256-QAM, uplink 64-QAM
  • Downlink 4x4 MIMO (operational bands undisclosed, likely limited to mid and high band)
Also, because many who read my iPhone XS/Max articles (1, 2, 3) had difficulty understanding my graphs and accepting my factual analyses, let me reiterate some of my standard boilerplate:
RF power figures below represent best averaged and rounded estimates of maximum uplink EIRP test results provided to the FCC OET in individual device authorization filings.  Or in the case of ERP low band test measurements submitted in the filings, that ERP has been converted manually to EIRP for level comparison purposes.  Caveats about lab testing versus real world capability and uplink transmission versus downlink reception always apply.
Uplink transmission, folks, not downlink reception.  Uplink transmission.

Now, on to the graphs...

Radiated power figures for the OnePlus 6T look okay, nothing great, nothing terrible.  The pluses are the mid band figures, which do reach or exceed 200 mW.  The low band figures are not exactly minuses, as most do closely approach 200 mW.  And due to low band antenna efficiency, we just do not see low band output above 200 mW that often.

The biggest minus here would be the high band EIRP.  Because of high band path loss and antenna efficiency characteristics, we would prefer to see high band radiated power above 200 mW.  Furthermore, the OnePlus 6T does not indicate support for HPUE on band 41 or otherwise.  Honestly, though, that minus may be rendered irrelevant for use in the US.  Bands 7 and 38 are not deployed here.  Band 41 effectively is a Sprint exclusive, and the OnePlus 6T shows no signs of being added to Sprint's device whitelist.  Lastly, band 30 always will be power constrained, since it must limit adjacent channel interference with nearby satellite radio operations.

As a sidenote, I also have included uplink 2x CA figures in this graph.  The gist is that EIRP does not increase with uplink CA but remains basically the same.  Each uplink carrier is reduced in power by 3 dB (50 percent) to maintain the same total EIRP across both combined uplink carriers (half power × double bandwidth = equivalent total power).  As I like to point out, uplink CA does not come without a cost.  And uplink CA may not be operational near cell edge, where uplink radiated power will be most stressed.

I have not included a conducted power graph.  Just be aware that conducted power targets for all tested bands fall within 23-24 dBm -- the only exception is band 71 at a slightly greater 24.5 dBm.  The takeaway is that the OnePlus 6T appears to be using primarily 24 dBm as its conducted power target.  That is well within the +/-2 dB margin of the 23 dBm standard for Power Class 3.  And while conducted power is slightly elevated, it is not excessively so.  As we will see next, the OnePlus 6T offers decent antenna gain, mitigating power loss, such that conducted power can remain in the 23-24 dBm range.

Technically, this main antenna gain graph is a composite of two antennas.  The OnePlus 6T does not support simultaneous transmission, but it does contain multiple antennas.  Antennas 1 and 2 both cover low and mid band, while antenna 3 does so for high band.  Thus, the graph above is a combination of antenna 1 below 2 GHz and antenna 3 above 2 GHz, since each of those two antennas is the primary or highest gain antenna for its respective bands.  To conclude, antenna gain across the board is negative, albeit minimally so, and that contributes to fairly consistent radiated power output -- with a few pluses and minuses along the way.

Source: FCC OET