HTC Thunderbolt Review: The First Verizon 4G LTE Smartphone
by Brian Klug on April 27, 2011 12:12 AM EST- Posted in
- Smartphones
- HTC
- Verizon
- LTE
- 4G
- Android
- HTC Thunderbolt
- Mobile
- MDM9600
- MSM8655
A Tale of Two Cellular Radios
I suppose now is as good a time as any to delve into the dual transceiver situation on the Thunderbolt. The two transceivers I speak of are the MSM8655’s built in cellular baseband (like all Qualcomm SoCs, you get a modem for free), and the MDM9600 which sits at the heart of every single other Verizon LTE product except the LG VL600 data card, which uses LG’s own L2000 chipset. If you want the short story, the Thunderbolt fully supports simultaneous CDMA2000-1x voice and 3G EVDO or 4G LTE data. The way this is done should already be somewhat obvious - the MSM8655 gives the Thunderbolt a continual free CDMA 1x connection for voice, SMS, and slow data, and the MDM9600 does all the 3G EVDO and 4G LTE data heavy lifting. What this boils down to is real SVDO (Simultaneous Voice Data Optimized) and SVLTE (Simultaneous Voice and Long Term Evolution data).
You can see proof of this in the Thunderbolt’s EPST menus, where there’s a second additional field marked “9k” which clearly is for the MDM9600 (9600, 9k, ahh right).
This situation also starts to become clear when you pry the battery cover off the back of the phone. Getting the battery cover off is incredibly difficult the first time. I swear I almost broke the thing the first time I did it. There are seriously more than ten plastic clips and guides which hold the door securely in position.
The Thunderbolt comes by default with a 1400 mAh, 3.7 VDC (5.18 Whr) battery (the official extended battery is 2750 mAh, 3.7 VDC, 10.18 Whr, as an aside). If you remove the battery, you can access the Thunderbolt’s USIM which slides out long ways first in a metal carrier. This is the first time I’ve seen a SIM door insert this way, but it works.
While we're talking about SIMs, Verizon's is technically both a CSIM and USIM. CDMA credentials are on the SIM (CSIM) as well as the credentials for LTE (USIM). The way the term SIM is abused lately for anything resembling one will likely continue, but if you're going to be pedantic, it's really both. Anyhow, as a result, you can finally swap devices on Verizon without having to call support, give them an ESN, and wait for routing tables to switch everything over. I haven't personally tried it since I don't have two Thunderbolts, but Verizon does advertise this is as a notable feature that finally brings full device portability. This is a huge feature if you intend to swap between devices a lot.
The reason why it’s held on so securely makes sense the second you get it off - there are two antennas back here built into the door. The reason for such a stiff and beefy door is so that no fewer than four independent contacts need to be held in good electrical contact. Count them - two contacts for the top right connector, another for top left, and another for wireless induction charging if you go with the extended battery combo.
Though we never reviewed it formally, the myTouch 4G was the first time I saw HTC start to go down the modular antenna route, with a similarly detachable (internal) antenna board. The Thunderbolt does the same thing here, yet builds it into the battery door. Likewise, the HTC Desire HD does the same thing, as does the upcoming Sensation. It isn’t just Apple that gets creative with antennas now and then, HTC deserves some credit too.
The antenna on the left is for GPS and even bears a marking to that effect on the flex board. The one on the right is for the MDM9600 and thus works for data on LTE and EVDO. There are two holes which punch clean through to the opposite side, clearly to ensure good contact with whatever antenna is built into this battery door.
There are two more antennas on the Thunderbolt, bringing the grand total to four. There’s one in the flex style we’re used to seeing which curves around the back and is for WiFi and BT, and another at the bottom right where we’re used to seeing them for CDMA 1x.
CDMA 1x Antenna at the bottom, Source: FCC
That’s a bit of a simplification too. If you’ve read anything about LTE or our other piece on it, you should know by now that a large part of the specification is mandatory multiple antenna support. At least on Verizon’s LTE network all devices need to be category 2 or 3, which means they must incorporate MIMO. The HTC Thunderbolt’s UL MIMO configuration is 1x2, meaning it has 1 transmit antenna and 2 receive antennas. The RF chains for both the MSM8655 and MDM9600 basebands are independent, however the two share an Rx antenna at the bottom in the traditional spot. This antenna serves as 1x voice Tx/Rx for the MSM8655, and EVDO/LTE Rx for the MDM9600.
The one at the top is EVDO/LTE Tx/Rx for the MDM9600. You can verify this yourself if you pry the back cover off the phone while in an LTE or EVDO data session - it goes away and you promptly fall back to slow 1x data. Pretty cool though.
I spent a lot of time on the phone with Qualcomm talking about the radios in the Thunderbolt and LTE in general. I ended up learning a ton more about the number of design challenges involved with making SVDO and SVLTE work for the first time and gained an appreciation for even more complexities than I expected.
First off, since this is the first phone (I’m aware of) with dual cellular transceivers that can be active at the same time, Qualcomm and HTC had to work with the FCC to establish proper testing to making sure the Thunderbolt meets FCC SAR (Specific Absorption Rate) requirements. Remember that although the HTC EVO 4G could have conceivably supported simultaneous 4G WiMAX and 1x voice, the feature was disabled and to my knowledge hasn’t ever been enabled. It’s for this reason - until the Thunderbolt no proper procedure for characterizing dual transceiver phones existed. (Update: Apparently the EVO does support simultaneous WiMAX data and 1x voice, thanks everyone!)
Architecting a dual-transciever cellular system that works properly with FCC SAR requirements necessitated some communication and logic between the MDM9600 and MSM8655 basebands. This is noted in addition in the FCC report for the Thunderbolt:
Although the RF circuits are independent for both transmitters, the chipset solution incorporated SVDO/SVLTE implementation does include electrical connections between the voice and data transmitters such that the device can coordinate the transmit power of both transmitters. That said, the transmitters operate independently in the sense that they independently support voice or data connection without interaction between the modems or signaling from the WWAN network.
It’s an edge case, but imagine a situation where you’re at cell’s edge transacting both LTE data and 1x voice. In that circumstance, SAR could theoretically exceed legal limits. To keep this from happening, that communication link between the MDM9600 and MSM8655 lets the Thunderbolt know the power and link budgets for both and allocate accordingly by reducing throughput on the data link. There are a whopping 17 Tx configurations that the Thunderbolt needs to support all while maintaining legal power budgets.
I tested endlessly trying to detect any 4G LTE speed degradation at the cell edge while on a voice call but never could notice anything appreciable.
This wouldn't be a complete review without a measurement to show whether the Thunderbolt is prone to deathgrip. Luckily thanks to the antenna diversity we've outlined, the Thunderbolt really isn't. I've done the due diligence of measuring the handset in our usual positions in both 3G and 4G environments.
Signal Attenuation Comparison in dB - Lower is Better | ||||||||
Cupping Tightly | Holding Naturally | Holding in Case | On an Open Palm | |||||
HTC Thunderbolt - LTE | 5.3 | 2.5 | - | 4.4 | ||||
HTC Thunderbolt - EVDO | 6.5 | 0.8 | - | 7.2 | ||||
Verizon iPhone 4 | 16.5 | 15.5 | 9.0 | 7.9 | ||||
LG Optimus 2X | 13.7 | 9.3 | - | 5.9 | ||||
Nexus S | 13.3 | 6.1 | - | 4.3 | ||||
Droid 2 | 11.5 | 5.1 | - | 4.5 | ||||
BlackBerry Torch | 15.9 | 7.1 | - | 3.7 | ||||
Dell Streak | 14.0 | 8.7 | - | 4.0 | ||||
Droid X | 15.0 | 5.1 | - | 4.5 | ||||
AT&T iPhone 4 | 24.6 | 19.8 | 7.2 | 9.2 | ||||
iPhone 3GS | 14.3 | 1.9 | 3.2 | 0.2 | ||||
HTC Nexus One | 17.7 | 10.7 | 7.7 | 6.7 |
The Thunderbolt has noticeably less attenuation when held in a 4G LTE scenario, no doubt thanks in part to the fact that it's fully leveraging MIMO and also on a 700 MHz carrier. I was surprised to see that make any measurable difference. I also saw a considerable amount of variance before the number settled down, which to me definitely indicates some DSP deciding on what link it can reliably hang onto in LTE coverage. In 3G EVDO the picture isn't as complicated, again attenuation is low until you put flesh over both antennas like what happens when it's on an open palm.
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hans007 - Wednesday, April 27, 2011 - link
i live in the bay and bought the tbolt.and WOW its like 10-20 mbps down. its insane fast. not to mention having used t-mobile before this (and i also used virgin mobile for about 3 weeks... which uh was pretty uneven honestly) the verizon network is bar none better than either of those (i dont use at&t but i hear it is horrible up here)
7Enigma - Wednesday, April 27, 2011 - link
I will second the request for a permanent post # for referencing. I know the embedded message makes this more difficult but it could simply be the start of a string gets a post number and followups a second number (or letter as rarely do comments get over 20+ replies). I know I've given up several times when I want to go back to an older article to see if the author responded to one of my comments and can't find it without reading every single one.Hopefully something like this can be implemented in the near future as the comment system has really been the only thing lacking on Anandtech compared to other hardware review sites.
Brian Klug - Wednesday, April 27, 2011 - link
We've been looking to add some features lately, I'll be sure to bring comment permalinking up. It might be a little while, but I totally agree.-Brian
CrystalBay - Wednesday, April 27, 2011 - link
Yea , nice job Brian...Omid.M - Wednesday, April 27, 2011 - link
Brian,Does it have dual mics, i.e. for noise cancellation?
I'm surprised at how many phones don't have this or at least don't advertise it.
@moids
Brian Klug - Wednesday, April 27, 2011 - link
Indeed it does, there's one up at the top near the headset jack which is used for noise cancellation. I found suppression to be very good. You can see the mic port here: http://www.anandtech.com/Gallery/Album/1039#21The problem with audio sounding strange when recording videos is still present, though HTC is going to fix this in an update soon, I'm told.
-Brian
SRHelicity - Wednesday, April 27, 2011 - link
Great review, Brian! As another commenter noted, this review is thorough and detailed. Good stuff!pandemonium - Wednesday, April 27, 2011 - link
It got me really thinking about the basis of why Verizon and Sprint are pushing their LTE out.With how fast smart phones are being adopted by the general public, they better get a faster move on with their LTE coverage. I can't imagine not being able to simultaneously use data and voice being on a widely covered UMTS service compared to the lacking LTE coverage and the need for a dual transceiver device.
softdrinkviking - Wednesday, April 27, 2011 - link
sorry to hear you were sick, brian. i know how it can be to get the double knockout, not so fun. :(nice to see this kind of form factor in the mix as it is exactly what i'm looking for.
do you, or anyone reading know if there are any similar designs around with a better screen? (ips)
i wonder what the refresh of the Dell streak 5" will add up to, if it's ever coming out?
Stuka87 - Wednesday, April 27, 2011 - link
Why is it so many (if not all) of the 4G phones out there are freaking huge?!Is this just a way of trying to move them farther up market, or what? I know there are people that want a larger device. But really, I like the smaller form factors. I would never even consider getting this device because of its size.