Samsung Droid Charge Review - Droid Goes LTE

Cellular and 4G LTE

We’ve now talked about the cellular architecture of the HTC Thunderbolt and LG Revolution, it’s now the Droid Charge’s turn. The Thunderbolt has the privilege of being the sole 4G LTE smartphone capable of doing simultaneous voice and data on both 3G EVDO and 4G LTE. The LG Revolution and Droid Charge can both transact voice and data at the same time only when connected to 4G LTE. 

The Charge does this with a very interesting combination of two basebands. 4G LTE connectivity is accomplished with Samsung’s very own CMC220 baseband, which is a category 3 device (same as Qualcomm’s MDM9600, and LG’s L2000) - 50 Mbps / 100 Mbps for upstream and downstream respectively on 20 MHz channels.

Like all the other devices, the Charge uses Verizon’s 4G LTE network on its 700 MHz spectrum, in LTE Band 13. We’ve talked extensively about Verizon’s 4G LTE network architecture in an exploratory piece already, but for a quick refresher Verizon currently is using 10 MHz channels with FDD, and has a total of 22 MHz of bandwidth. Even in markets where Verizon has licenses for additional spectrum, currently only upper C is being used. This is my first time seeing Samsung’s CMC220 on Verizon. 

What’s particularly curious about the Charge is that there’s no Qualcomm baseband for CDMA2000. Both 1x and EVDO are handled by VIA Telecom’s CPB7.1 baseband. This is very interesting, as it’s the first time in a long while I’ve seen something other than Qualcomm used for a CDMA2000 baseband inside the United States, though in China Via Telecom is apparently a major player. For comparison, the Samsung Fascinate used Qualcomm’s QSC6085 baseband. This combination of things makes the Charge one interesting and unique device from a cellular perspective. 

We don’t have to disassemble anything either, as the FCC has some nice shots of the Charge’s main PCB showing both basebands sitting pretty next to Hummingbird and its PoP LPDDR2. Center bottom is the VIA Telecom 7.1 (you can even make out VIA), and above it is the Samsung CMC220. 

Before we get to performance, let’s also go over what the Charge exposes for controlling these two radios. Inside Wireless & Network and Mobile Networks is a system selection toggle. Tap this and you can change from “LTE automatic” to “CDMA mode.” The former lets the Charge hand up to LTE whenever it is available, the latter forces the Charge to only use EVDO and 1x data. If you’re in an LTE market and want to save some power, this is handy. However, there’s no ‘LTE only’ mode that would force the Charge to hang onto LTE a bit longer, although its behavior wouldn’t offer any power savings. 

I was very impressed with the way the Charge hands over from EVDO to LTE most of the time, and never found myself want for more low-level control. In this regard, Samsung has done a nice job keeping data sessions working across the two basebands. My only complaint is that every once in a while, the LTE data session sometimes stalls briefly – sometimes for a a few seconds, other times for a few minutes. When that happens, you’ll see the uplink green arrow blink, but no orange downlink arrow. Rebooting the device fixes things. 

I seem to have developed the bad habit of taking so long with devices that they see their first firmware update and fixes. Then issues that I’ve identified in the launch software are addressed, and I have to go re-test everything to find what new issues have appeared in their stead. The Charge received its first major update last week, which both fixed the broken WiFi hotspot functionality (which previously stopped working exactly when May ended), and also changed the Charge’s bars to closely mimic those of Android 2.3. 

The update purports to improve handover between 3G EVDO and 4G LTE, improve call time battery life, improve call quality, enhance browser performance, and also improve GPS fix times among other things. I honestly couldn’t detect a measurable improvement in handover (the stall issue I mentioned still persists), and as I’ll show later call time battery life is better by a very small margin. I’ll talk more about the other changes in their respective sections. 

One subtle difference I noticed is that I can’t update the PRL on the Droid Charge the same way I could on the Thunderbolt. Dialing *228 to do an over the air PRL download yields the following:

It appears that we now have confirmation that both LTE and CDMA are using the USIM/CSIM in the device for both their roaming capabilities and cellular identities. I asked Vivek to do the same on his LG Revolution evaluation unit and he saw the same behavior. Back with the Thunderbolt, the OTA download would appear to complete happily just like any other CDMA handset. Regardless, in theory, you should now be able to swap SIMs (and thus your number, account, and service) between at least three handsets on Verizon – wow, that’s one sentence I wouldn’t have ever believed I’d write a year ago.