by Andrew J. Shepherd
Sprint 4G Rollout Updates
Friday, May 8, 2015 - 12:15 PM MDT
Update: A week after the Sprint variant LG G4 original authorization documents were released at the FCC OET and S4GRU published this RF performance article, a Class II Permissive Change filing was added to the G4's docket. In writing the article last week, we did not detect anything amiss with the original filing, so this represents an optional change, which the filing discloses as hardware modification affecting the main antenna. Interestingly, none of the previous antenna gain figures have been altered, but the ERP/EIRP figures have increased or decreased. See the smoothed and averaged differences below:
- Band class 0: -1 dB
- Band class 10: -2 dB
- Band 4: -3 dB
- Band 5: -2 dB
- Band 12: -2 dB
- Band 26: -2 dB
- Band 41: +2 dB
So, you win some, you lose some. Overall, the Sprint variant G4 has become weaker in tested RF performance. Those negative differences, however, are limited mostly to lower frequencies in the 700-1700 MHz range. The 1900 MHz range is unaffected, and the 2600 MHz range is increased. The other win is that a Class II filing before a device is released generally means that release is imminent. Look for the G4 on shelves and online soon.
Yes, I know it is no longer May 4th. And we are not in a Samsung Galaxy far, far away. But this is episode IV in the LG G handset series, just four days removed from May 4th. That should be enough of the number four to satisfy anyone. Even if this isn't the Motorola Droid you're looking for, is the LG G4 a new hope for a flagship Sprint handset this spring?
S4GRU staff has been watching the FCC OET (Office of Engineering and Technology) authorization database over the past week as different G4 variants were revealed. The VZW variant came earlier in the week, and the Sprint variant ZNFLS991 documents were uploaded yesterday. Of course, we are going to write an article about it, so let us get started.
Right away, the G4 adheres to what has become the standard Sprint variant configuration: tri band LTE, non SVLTE, single RF path with e/CSFB. Additionally, it covers the CCA/RRPP LTE bands. And it was tested for domestic GSM/W-CDMA bands -- phone unlockers rejoice. Finally, it does officially support downlink carrier aggregation as its lone Release 10 feature. More on CA later.
Next, it is fairly well known and somewhat controversial that the G4 opted not for the top of the line Qualcomm Snapdragon 810 but for the lesser Snapdragon 808, taking some performance hits in graphics and memory departments, for example. S4GRU does not involve itself in that debate -- that is not the place of this cellular RF focused article. But the chipset choice is relevant because both the Snapdragon 808 and Snapdragon 810 incorporate the same Category 9 X10 LTE baseband on die. So, rest assured, the choice of the Snapdragon 808 does not lessen any RF capabilities.
On that topic, if you need a refresher on the new Qualcomm LTE baseband naming/numbering scheme, see this sidebar from our earlier article on the HTC One M9 and Samsung Galaxy S6:
As an aside, Qualcomm is changing up its baseband modem branding and numbering schemes. Previously, branding was Gobi and numbering was, to use one example, MDM9625 for standalone modem chipsets. Then, many Snapdragon processor chipsets also included the same modems on die -- a la the Snapdragon 800, aka MSM8974, which integrated the same stack as in the standalone MDM9625. Branding is now changing universally to Snapdragon and numbering, to use just one example again, will follow the X10 LTE pattern. That last example is the Snapdragon 810's brand new LTE category 9 modem, which has no standalone modem precursor. But other rebranded and renumbered examples with their standalone precursors include the Snapdragon X5 LTE (MDM9625), Snapdragon X7 LTE (MDM9635), and Snapdragon X12 LTE (MDM9645).
Back to discussion of CA support, we have stated previously that FCC OET authorization filings are not required to disclose downlink CA -- because that is only reception, not transmission. But the G4 filing does include an explicit attestation letter, stating its inclusion of downlink CA. What the G4 filing does not divulge is specifically 2x or 3x downlink CA support in band 41. For various reasons, S4GRU believes the former, that the G4 is capable of band 41 2x CA.
First, the Snapdragon X10 LTE baseband natively supports up to 60 MHz of 3x downlink CA. However, that requires some help. An RF transceiver sits ahead of the baseband, and presently, the Qualcomm WTR3925 can handle 2x CA -- but 3x CA necessitates the inclusion of a second transceiver. See this excerpt from an AnandTech article on the new Snapdragon chipsets:
Enabling 3x LTE CA requires two RF transceiver front ends: Qualcomm's WTR3925 and WTR3905. The WTR3925 is a single chip, 2x CA RF transceiver and you need the WTR3905 to add support for combining another carrier.
Moreover, the other G4 variants that support CA are explicitly limited to 2x CA, suggesting that all variants are using the single WTR3925 transceiver. This is all educated conjecture, barring a teardown of the Sprint variant that probably will never happen. But if you are waiting on 3x CA, that likely will require a next generation Qualcomm transceiver to do 3x CA all in one.
Finally, straight from the horse's mouth, Sprint CTO Stephen Bye stated the following in a recent FierceWireless article:
Bye said that in the fourth quarter of 2014 Sprint started seeding its device base with phones that can take advantage of 2x20 carrier aggregation in the 2.5 GHz band, and now has seven such models in the market, though he declined to say how many actual devices that translates into or what percentage of the subscriber base has a device capable of using the technology. Some of the models include the Samsung Galaxy S6 and S6 Edge and HTC One M9, he said.
Now, honestly, most read our FCC OET authorization articles for ERP/EIRP figures and analysis. So, without further ado, here are the numbers:
- Band class 0: 22 dBm
- Band class 1: 26 dBm
- Band class 10: 23 dBm
- Band 2: 25 dBm
- Band 4: 24 dBm
- Band 5: 22 dBm
- Band 12: 17 dBm
- Band 25: 25 dBm
- Band 26: 22 dBm
- Band 41: 23 dBm
For reference, the above figures represent our best averaged and rounded estimates of max uplink ERP/EIRP -- with uniquely Sprint frequencies receiving heavier weighting, if possible, in band class 10, band 25, and band 26. Of course, the usual disclaimers about lab testing versus real world performance apply.
As for analysis, max RF output looks quite healthy across the board, comparing very favorably with that of the One M9 and soundly thrashing that of the disappointing Galaxy S6. In particular, the power output for CDMA2000 band classes is a good 3 dB higher than most.
Note, if you are using the smart cover for wireless charging, though, ERP/EIRP is affected roughly -1 dB across the board. I am not a fan of wireless charging because of the power inefficiency involved, but the RF loss from the smart cover on the G4 appears considerably less than what we have seen from some previous handsets.
If there is any caveat about the G4's RF capabilities, that would be its antenna gain, broken down by frequency range as follows:
- 700 MHz: -5.9 dBi
- 800 MHz: -7.1 dBi
- 1700 MHz: -5.2 dBi
- 1900 MHz: -3.5 dBi
- 2600 MHz: 1.7 dBi
Except for 2600 MHz, all are negative, significantly negative. And for comparison, again except for 2600 MHz, the VZW variant antenna gain in all bands tracks about 3 dB higher. The head scratcher, however, is that the lab performance between the two variants is remarkably similar, despite the differences in antenna gain.
We have seen something like this before -- an LG handset that showed strong lab power output yet weak real world performance. Remember the LG Viper? That is the challenge in interpreting lab results. Low output always indicates weak performance. However, high output can be a mixed bag. But LG has a pretty good Sprint track record since the Viper, as the LG Optimus G, LG G2, and LG G3 were all at least average to good in the real world. And the LG manufactured Nexus 5 was practically a Jedi knight for its RF performance at the time.
In the end, only many trials on Dagobah will tell if the G4 lives up to its powerful promise. Use the 4th, LG, use the 4th.
Source: FCC, AnandTech, FierceWireless