Cellular Connectivity

We’ve already outlined much of what there is to say about the combination of Qualcomm’s MDM6600 and Motorola’s on Wrigley LTE baseband inside the Droid Bionic review, but it still bears going over. Just like the Bionic, MDM6600 handles 1x voice and data, EVDO Rev.A 3G data, and Wrigley supplies LTE connectivity. In fact, the RAZR has a virtually identical cellular architecture to the Bionic, at least as far as I can tell. There’s the same Infineon transciever for LTE, Skyworks 700 MHz power amp, and combination MCP DRAM+NAND packages for the MDM6600 and Wrigley basebands.


Motorola Wrigley LTE baseband, Intel/Infineon transceiver, Skyworks PA encircled in blue, green, and red respectively. (Original image courtesy iFixit)

I wasn’t totally satisfied in the Bionic piece that I proved the Wrigley baseband was UE Category 2, so I did some more poking this time with the RAZR and found the same exact architecture for administration and configuration as previously. Wrigley is actually a very interesting little part, consisting of an ARM926EJ-S running at 380 MHz:

cat /proc/cpuinfo
Processor       : ARM926EJ-S rev 5 (v5l)
BogoMIPS        : 189.57
Features        : swp half thumb fastmult edsp java 
CPU implementer : 0x41
CPU architecture: 5TEJ
CPU variant     : 0x0
CPU part        : 0x926
CPU revision    : 5
Hardware        : Wrigley 3G DatacardLTE

Oddly enough there are many places where it refers to itself as a “3G Datacard” even though it’s clearly designed only to work with LTE. The thing is just running GNU Linux:

uname -a
Linux localhost 2.6.29-omap1 #2 Tue Oct 25 20:02:46 CDT 2011 armv5tejl GNU/Linux

The reality is that almost all black boxes inside mobile phones end up revealing something similar at their heart if you poke around enough. If we were counting the number of ARM parts onboard your average smartphone I wouldn’t be surprised to see at least 4 or 5 different ARM cores.

Anyhow, the RAZR doesn’t have a nice mib default xml file that nicely spells out the LTE UE category like the Bionic did, but the default set of mibs being set does include the Verizon EARFCN of 5230 which corresponds to LTE band 13. After lots of poking around, I found a way to query the UE category directly:

shell@(unknown):/system/bin$ iwaconfig -g -x 33163
MOID 0x818b  Name LTE_MGMT_RRC_UE_CATEGORY   MIB OID 
  value=2 [0x02]

So life is good and our earlier claims that Motorola Wrigley (with lots of TI references inside) is indeed LTE UE Category 2. As a reminder, other devices based on MDM9x00, LG L2000, and Samsung’s CMC220 are UE Category 3.

FCC UE Category for RAZR

Oddly enough, just like the Bionic the official FCC filing summary information for the LTE side of the RAZR erroneously states that it is UE Category 1. As usual we get the normal pretty diagram with the location of antennas, and interestingly enough the LTE antenna is up at the top on the RAZR instead of in a combined module at the very bottom.

FCC Diagram

We’ve been doing a pretty good job keeping track of cellular throughput by running a bunch of speedtests, getting that data off, and making some graphs. The RAZR isn’t spared this treatment at all, and I ran 510 tests on Verizon 4G LTE in my own market in Tucson AZ and while on a trip to Los Angeles, CA.

Downstream Stats (Mbps)
Avg: 14.701; Max: 36.267; Min: 0.068, StDev: 6.594
 
Upstream Stats (Mbps)
Avg: 6.912; Max: 20.719; Min: 0.084, StDev: 3.707
 
Latency Stats (ms)
Avg: 80.990; Max: 196; Min: 34, StDev: 17.499

Downstream Upstream Latency

The histograms themselves look a lot like what we’ve seen already out of Verizon’s 4G LTE network on other smartphones, which again uses 10 MHz FDD on LTE band 13. I’ve seen numerous other people hit speeds above 50 Mbps on category 3 devices in favorable network conditions, but obviously the RAZR being category 2 does preclude it hitting those speeds.

Like the Bionic, the RAZR also gives you a nice and easily accessible network option to use either LTE/CDMA or just CDMA. Unfortunately again there’s no way to force data on only LTE and avoid handing over, but in practice I rarely saw the RAZR do a hard handover unless network conditions completely precluded using LTE.

I was pleased with myself when I used the Bionic that it was possible to look at LTE signal power (RSCP) and the channel quality indicator (CQI) by just running logcat and grepping the radio status daemon that Motorola wrote for updating their bar visualization. Unfortunately in this newer version of Blur that logging debug output and functionality is no longer, and if you look closely you’ll also notice they went from 4 bars to 5. There’s another way to view those metrics but it involves having shell on the baseband and directly querying the MIBs that correspond to all the LTE signal quality figures of merit. It’s still possible but much more involved. The upside of course is that I was able to confirm the RAZR correctly reports those bars based on signal power and quality, unlike most of the other LTE handsets which just look at power.

Lastly, the Droid RAZR XT912 Motodev page notes that the phone has WCDMA 850/900/1900/2100 connectivity courtesy of the MDM6600. However, the shipping Droid RAZR has WCDMA disabled and corresponding lines commented out inside build.prop for the WCDMA components. Considering the existence of the RAZR XT910 (sans “Droid”) with WCDMA and GSM I think it’s fairly easy to predict that a world mode variant with LTE is coming sooner rather than later. I wouldn’t mind having a RAZR that works on AT&T WCDMA, that’s for sure.

WiFi, GPS, Audio and Speakerphone Camera - Stills and Video
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  • mfenn - Friday, December 16, 2011 - link

    Dunno how many times I have to say this, but etc. is short for "et cetera". Putting more than one period in it is just plain wrong. Reply
  • jordanclock - Sunday, December 18, 2011 - link

    Actually, when finishing a sentence with etc. it is correct to put a second period afterward, as the first one is to indicate an abbreviation and the second is to indicate the end of the sentence. It is acceptable to use just one period, but it is not incorrect to use two. Reply
  • BabelHuber - Friday, December 16, 2011 - link

    A question to the Anandtech guys:

    Why don't you ever lose a word about rSAp (remote SIM Access Profile)?

    I regularily use my phones in my car, where I want to use the built-in antenna when connecting my phone via bluetooth.

    Connecting via Handsfree is really a PITA: The speech quality is bad and the phone's battery is stressed.

    Hence for three years now I use rSAP, first in my Audi A5 and now in my BMW 5er (via the Snap-in adapter SAP from BMW).

    I still have my good old Nokia X6, this one does rSAp very well. Android, OTOH, does not support rSAP (neither does iOS), but AFAIK e.g. Samsung added rSAP-capabilities to the Galaxy line.

    I know that testing rSAP is not easy because of the different systems the various Auto makers use, but it would even be interresting if you could test it at least a little bit (e.g. checking if the Adress Book synchronization works or if one has to use the SIM card itself).

    A phone without rSAP is useless for me, but perhaps I am part of a small minority, who knows.

    Have you had any thoughts on rSAP?
    Reply
  • Conficio - Friday, December 16, 2011 - link

    Where are you located? I have not heard about that tech.

    But sounds very interesting. Especially as there is a big debate going on in the US about driving and using the phone.
    Reply
  • BabelHuber - Friday, December 16, 2011 - link

    I'm located in Germany, but I would think that rSAP is a global tech.

    It supported by VW/ Audi, Mercedes and BMW. For BMW, you need the 'Snap-in-adapter SAP', though.

    With rSAP, the phone is put to standby-mode, since the phone itself is in the car. The car gets the SIM-card-information via bluetooth and also reads the address book, then you use its built-in phone.

    It's a cool technology, the speech quality is very good, since the antenna of the car is used. Also there is almost no drag on the phone's battery, since it doesn't do anything at all.

    The downside is that you cannot stream music from your phone to the car's stereo, you also can't use E-Mail with rSAP.
    For me this is OK, though, I don't want to receive mails while driving and the car's stereo is fed by a USB-harddisk attached to it.
    Reply
  • introiboad - Tuesday, December 20, 2011 - link

    There is no technical reason for you not to be able to stream music even when using RSAP. They are 2 different profiles, RSAP and A2DP, and should be able to run in parallel. It's a limitation imposed by the car manufacturer, not by the spec. Reply
  • JonnyDough - Saturday, December 17, 2011 - link

    Its not really a debate. Using a cell while driving should be illegal. When you're operating a vehicle that can take someone's life in a 30mph crash then your eyes, hands, and mind should be focused on the task of driving. I learned that in driver's ed and I believe its still part of the test to get a driver's license. Driving is a privilege and so many of the younger generations today have such a sense of entitlement.. Reply
  • cheetahfox - Saturday, December 17, 2011 - link

    As someone who was nearly killed because the person that hit my car was changing the radio station; there will always be distractions in a car. If you feel that Cell phones should be illegal then you should also ban all radio's, gps, cd-players and ipods. Further you should also make all cars have a single seat. We can't let someone talking to you distract you. You should also have some way to measure if a car is being driven by someone that is sleepy. It's been shown over and over again the lack of sleep is worse that drunk driving. I propose a mandatory system of cameras that monitor the driver of a car and if they detect that the person in question is sleepy and not attentive enough that they slowly cut power to the car and force them to pull over for a 30 min nap.

    I am taking it to an extreme but if we should ban cell phones, we should really ban many other things. Things that we would never ban, like more than one person in a car. The problem isn't the device, it's the person using it. If the person driving is a distracted driver(for whatever reason) and they cause an accident it should be handled with existing laws.
    Reply
  • introiboad - Tuesday, December 20, 2011 - link

    Remote SIM access profile is part of the Bluetooth Specification, it's just one of the profiles defined by the Bluetooth SIG. Unfortunately, RSAP never took off in the same way that HFP (Handsfree Profile) which is the profile that nearly every other phone available uses when connecting to a car.
    One of the reasons may be that RSAP requires the car to come bundled with a GSM baseband/radio since it only obtains the SIM info from the phone and then uses it to place calls using its own. On the other hand HFP simply instructs the phone to place the call using the phone's own GSM radio and then transfers the sound to the car. So it's clearly cheaper to include in a car since the car manufacturer doesn't need to include a Bluetooth _and_ a GSM radio.
    Reply
  • introiboad - Tuesday, December 20, 2011 - link

    As far as I know, only Symbian and Bada phones implement RSAP. Reply

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