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HTC One A9: The first Sprint Handset to support uplink 2x CA




by Andrew J. Shepherd

Sprint 4G Rollout Updates

Thursday, November 12, 2015 - 3:07 PM MST


Yes, you read that correctly. Thanks to the mid range Qualcomm Snapdragon 617 (MSM8952), the HTC One A9 is the first Sprint handset to include a modem that supports uplink 2x CA (carrier aggregation). That comes on die via the X8 LTE modem, which is a Category 7 LTE baseband, capable of aggregating up to 40 MHz FDD/TDD 2x CA on both the uplink and downlink. Now, before anyone gets too excited, Sprint has no imminent plans to enable uplink 2x CA at the network level. So, the uplink 2x CA support is mostly a proof of concept novelty.


If you have been reading The Wall at S4GRU for a while, you probably know where this is headed. It is another in our classic series of FCC OET (Office of Engineering and Technology) RF authorization analysis articles. We do not dwell on processor benchmarks, screen qualities, etc. If you want that info, read reviews or visit the HTC tech specs site. Instead, we cut right to the heart of what a cellphone is -- a cellular RF device -- and rundown its lab tested cellular RF performance.


The One A9 filed its FCC OET authorizations over a month ago, but with Sprint selling the handset as we speak and HTC shipping the unlocked Sprint variant next week, we should take a look. Let us start with the band/class support:

  • CDMA2000 Band Class 0/1/10
  • GSM 850/900/1800/1900
  • W-CDMA Band 1/2/4/5
  • LTE Band 2/4/5/12/25/26/41

The Sprint and CCA/RRPP band support is expected at this point. But all of the GSM/W-CDMA band support info comes directly from the HTC tech specs. I state that explicitly because there is no testing of domestic GSM/W-CDMA in the FCC OET documents. Barring a Class II Permissive Change filing with the FCC, the GSM/W-CDMA support purely is for international roaming. While the Sprint variant One A9 can be unlocked or even purchased unlocked, it is not authorized for use on AT&T or T-Mobile -- unless you can live with no GSM/W-CDMA, only band 2/4/5/12 LTE.


For an unlocked One A9, HTC proactively has addressed the to/from Sprint provider switch issue by including that in its one time courtesy UH OH Protection program:


Switching carriers is a lot easier with an unlocked HTC One A9. You'll be able to switch carriers at will with the HTC One A9 unlocked edition. Simply insert your activated AT&T or T-Mobile SIM to begin using your HTC One A9. Verizon LTE compatibility will also be supported via a software update at a later date. Sprint compatibility requires separate hardware - customers switching to or from Sprint will need to switch to a compatible device, which is provided free of charge as part of the UH OH Protection program.


In other words, want to switch from Sprint to AT&T, T-Mobile, or VZW with your unlocked One A9? HTC will swap out for the other domestic variant. Want to switch from AT&T, T-Mobile, or VZW to Sprint with your unlocked One A9? HTC will swap out for the Sprint variant. While on the subject of the AT&T, T-Mobile, and VZW variant, it is 3GPP only, thus VoLTE only for voice on VZW. HTC even acknowledges that fact:


Verizon LTE compatibility will be added via a software update. The HTC One A9 is the first CDMA-less device to support both voice and data services over LTE, providing individuals with the flexibility to use the same device on multiple carrier networks. To ensure the best experience for our customers on the Verizon network, we are conducting more extensive testing and certification. We expect availability to be delayed but we are actively working with Verizon to make it available as quickly as possible.


The other domestic variant has some further relevance as we delve into the FCC authorized lab tested ERP/EIRP performance of the Sprint variant.


The FCC OET documents, per usual, do not disclose an antenna diagram. But they do note that the One A9 uses a dual antenna system -- antenna 0 and antenna 1, presumably top and bottom or vice versa. The handset will switch between the antennas at will based upon varying signal metrics. Much like Apple with the iPhone, HTC has implemented this dual antenna setup since the debut of the One M7 in 2013. In this case, however, the dual antennas are still single radio path, so SVLTE is not supported.


Now, for the main attraction, let us look at the Sprint variant One A9 radiated power figures. I may sound like a broken record, but the usual clauses about lab testing versus real world performance and uplink versus downlink always apply. The figures represent my best averaged and rounded estimates of maximum uplink ERP/EIRP test results provided to the FCC OET in the authorization filings for the device. See below:

  • Band Class 0: 17 dBm
  • Band Class 1: 22 dBm
  • Band Class 10: 18 dBm
  • Band 2: 16-19 dBm
  • Band 4: 13-16 dBm
  • Band 5: 14-16 dBm
  • Band 12: 14 dBm
  • Band 25: 17-19 dBm
  • Band 26: 16-17 dBm
  • Band 41: 21-22 dBm

The CDMA2000 performance is good, about average. And the band 41 output is along the same lines. That is about the best S4GRU can say regarding the tested results of the One A9. It does not quite hit the lows of the VZW variant Samsung Galaxy Note 3 -- the most anemic RF test results that S4GRU has ever seen in any notable handset -- but the One A9 is not far off. The band 4 output that maxes out as low as 13 dBm, for example, is very weak. It is mid band spectrum that needs greater EIRP. The positive is that band 4 roaming never may be a factor with this handset. And band 2/25 is a bit better, though still at least 4-5 dB below the desired level.


Now, back to the other domestic variant headed to AT&T, T-Mobile, and VZW. The picture does not get much rosier. Comparing the 3GPP bands in common, the other domestic variant is superior by 2-7 dB in band 2, 6-9 dB in band 4, 2-4 dB in band 5, and 2 dB in band 12. Wow, those are big differences nearly across the board. The Sprint variant does get one minor victory -- it is 1-2 dB better in band 41 than the other domestic variant is in band 7, as both band 41 and band 7 operate in the same BRS/EBS 2600 MHz spectrum.


What happened, HTC? The Sprint variant seems to have gotten shortchanged. Was that a compromise to optimize band 41 by 1-2 dB? We can hope for better returns in real world performance. But early returns from lab tested performance are not good.


Sources: FCC, HTC, Qualcomm

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Any guesses when a fully capable (new and vastly improved) Sprint version will be offered by Sprint to current users?

Would there be a feature advantage worth upgrading from HTC One M9?

Or just wait for a full bodied dual CA / dual band 25 capable version?

For the most part, I am fairly satisfied with the M9.

Thank you for your comments.

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Is there any reason to question the FCC's testing if there is that much of a varience between the multiple models?


The FCC does not do the testing.  The manufacturers or their contracted labs do the RF testing.  If HTC thought the results were in error, it would not submit them to the FCC.



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So with the X8 and X10, when is Sprint going to enable 3x2CA??


I am unsure what you meant by "3x2CA."  Did you intend to write 3x CA?


The X8 LTE modem does not support 3x CA.  The X10 LTE modem does, but it is unlikely that any of the current round of Snapdragon 808/810 handsets have the requisite hardware for 3x CA.  Rather, that will come with the next round of handsets utilizing the Snapdragon 820 with X12 LTE modem.



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