Faster Throughput on WCDMA

Fixing unintended attenuation is only one part of what’s new however, the other part of the story is faster cellular connectivity for users on WCDMA/UMTS carriers. Users who are using the 4S on CDMA (like Sprint or Verizon) won’t see a performance difference since this is still the same EVDO Rev.A.

The iPhone 4 used an Intel/Infineon X-Gold 618 which supported HSDPA 7.2 and HSUPA 5.76. The MDM6610 inside the 4S supports HSDPA 14.4 and HSUPA 5.76, alongside a number of 3GPP Rel.7 features which are colloquially known as HSPA+. I talked about this extensively in another piece when there was some confusion about whether or not the 4S is HSPA+ - which it is.

iPhone Cellular Speeds
Property iPhone 3G/3GS iPhone 4 (GSM/UMTS) iPhone 4 (CDMA) iPhone 4S
Baseband Infineon X-Gold 608 Infineon X-Gold 618 Qualcomm MDM6600 Qualcomm MDM6610
HSDPA Cat.8 - 7.2 Mbps Cat.8 - 7.2 Mbps N/A Cat.10 - 14.4 Mbps
HSUPA None - 384 Kbps WCDMA only Cat.6 - 5.76 Mbps N/A Cat.6 - 5.76 Mbps
EVDO N/A N/A 1x/EVDO Rev.A 1x/EVDO Rev.A

The previous X-Gold 618 baseband was a nice improvement over the iPhone 3G/3GS’ X-Gold 608, which lacked HSUPA, but in a world where most WCDMA carriers are at least running HSDPA 14.4, it’s nice to finally have an iPhone with something faster than HSDPA 7.2. I’ve done lots of testing inside my Tucson, AZ market (which is “4G” HSPA+ on AT&T’s coverage viewer) with both the 4 and the 4S, and have built a very good feel for the 4’s performance. As a reminder, if you’re in the USA, those dark blue areas represent HSPA+ coverage areas with AT&T’s upgraded backhaul. In practice these are at least HSDPA 14.4.

Left: iPhone 4 Limited to ~6.1 Mbps down, Right: iPhone 4S (same location) hitting ~9 Mbps

With line of sight to an AT&T NodeB inside my HSPA+ market I’m used to seeing a maximum downstream throughput on the iPhone 4 of almost exactly ~6.1 Mbps, which is about right for the 4’s HSDPA 7.2 maximum when you include overhead. The nice straight line in that result should clue you in that downstream throughput on the 4 was being gated by the baseband. On the 4S, in this same location, I’ve been able to get 9.9 Mbps when the cell isn’t loaded at night (I didn't grab a screenshot of that one, for some reason). It’s nice to finally not be gated by the baseband anymore on an iDevice. Having a faster baseband is part of the reason the 4S’s cellular performance is much better, the other half is receive diversity which helps the 4S push these high throughput rates, and also dramatically improve performance at cell edge.

I did some drive testing with the 4 and 4S side by side and targeted areas that I know have pretty poor signal strength. The 4S is shown in yellow, the 4 in blue.

You can see how downstream throughput gets a nice shift up, and the average changes as well, from 2.28 Mbps on the 4 to 2.72 Mbps on the 4S. The maximum in this sample increases from 6.25 to 7.62 Mbps as well. It isn’t a huge shift, but subjectively I’ve noticed the 4S going a lot faster in areas that previously were difficult for the 4.

We’ve also run the usual set of standalone tests on the 4S on AT&T in my market of Tucson, AZ, in Anand’s market of Raleigh, NC, and on Verizon in Raleigh, NC. Though we don’t have a Sprint 4S yet, we hope to do a more serious 4S carrier comparison here in the US when we get one. First up is AT&T which is of course HSPA+ in both of our testing markets.


Verizon EVDO

iPhone 4S Speedtest Comparison
Carrier AT&T Verizon
  Avg Max Min Avg Max Min
Downstream (Mbps) 3.53 9.94 0.24 0.82 2.05 0.07
Upstream (Mbps) 1.17 1.86 0.009 0.38 0.96 0.003
Latency (ms) 137 784 95 177 1383 104
Total Tests 457 150
Air Interface HSPA+
(HSDPA 14.4/HSUPA 5.76)

For the CDMA carriers, the 4S shouldn’t (and doesn’t) bring any huge improvement to data throughput because the CDMA 4 had both receive diversity and MDM66x0. For users on GSM/UMTS, however, the 4S does make a difference again thanks to the inclusion of those two new features.

One of the things I noticed was absent on the CDMA iPhone 4 was the 3G toggle. It does indeed make some sense to not include this in a CDMA 1x/EVDO scenario since power draw is about the same between the two air interfaces, however, the absence of this toggle has carried over to the 4S regardless of whether the phone is activated on a CDMA2000 or UMTS/GSM network. That’s right, you can go under Settings -> General -> Network, and there’s no longer any 3G Data toggle which you can disable and fall onto EDGE (2G) with now.

Left: iPhone 4S (no 3G toggle), Right: iPhone 4 (3G toggle)

It’s likely that this is absent to accommodate the multi-mode nature of the 4S (and thus the lowest common denominator CDMA mode), however the absence of this toggle makes getting connected in congested areas more difficult. In some markets, (I’m looking at you, AT&T in Las Vegas), EDGE is often the only way to get any connectivity, even without a major convention going on. Not having that 3G toggle makes manually selecting that less-used but more reliable connection impossible now, to say nothing of the potential battery savings that this would afford (and that we sadly can’t test now).

There’s one last tangential question about HSPA+ on the 4S, specifically on AT&T. I’ve left this to the end since it doesn’t impact non-US 4S users, but the last question is whether the 4S is actually on HSPA+. For a while, I was concerned that AT&T would continue using the wap.cingular APN on the 4S which seems shaped to around 7.2 Mbps HSDPA. I’m glad to report that AT&T hasn’t continued using wap.cingular on its 4S data plans, instead using “phone” which is a newer APN that allows for HSPA+ (above 7.2 Mbps) rates. You can check this yourself under PDP Context Info on the 4S in field test.

Improved Baseband - No Deathgrip The A5 Architecture & CPU Performance


View All Comments

  • Davabled - Monday, October 31, 2011 - link

    With Field test enabled, do numbers closer to zero indicate a better connection? (I'm referring to the numbers that replace the bars in the upper left corner) Reply
  • Anand Lal Shimpi - Monday, October 31, 2011 - link

    Correct :)

    Take care,
  • Formul - Monday, October 31, 2011 - link

    why the huge drop from iPad 2 to iPhone 4S in the GL benchmark pro? its only about 30% performance .... any explanation? Reply
  • Anand Lal Shimpi - Monday, October 31, 2011 - link

    Because the number was incorrect :-P Fixed now :)

    Take care,
  • ZebuluniteX - Monday, October 31, 2011 - link

    Great review as always Anand!

    In addition to the GL benchmark pro results Formul mentioned, I was also surprised to see the Motorola Droid RAZR for some reason do far better than other Gingerbread-based Android smartphones. It is listed as using different version of Android (2.3.5 vs 2.3.4 or older), but given that very similar results were shown between the iPhone 4S and Honeycomb-running Galaxy Tab 8.9 in your 'iPhone 4S Preliminary Benchmarks' article (where the 4S was a bit slower than the Galaxy Tab in SunSpider, and marginally faster in BrowserMark), I'm guess those are just mislabeled Galaxy Tab results. Is that the case?
  • Anand Lal Shimpi - Monday, October 31, 2011 - link

    Thank you - be sure to thank Brian Klug as well, he really did the bulk of the heavy lifting here. I just popped in to talk about silicon and battery life.

    The RAZR numbers are what we ran at the RAZR announcement:

    The improvement is likely due to an updated browser from Motorola. I included those numbers effectively as a placeholder until Ice Cream Sandwich arrives :)

    Take care,
  • ZebuluniteX - Tuesday, November 01, 2011 - link

    Ah, thanks for the clarification, I missed that article. Hmm, that's interesting that, apparently, Motorola "ported" Honeycomb or Ice Cream Sandwich's browser optimizations to Gingerbread (or at least I assume that's what happened)...

    I'm in the market for a smartphone, and while I was leaning towards the 4S since I already am in the Apple ecosystem via an iPod Touch 2G, before pulling the trigger I wanted to read the Anandtech take on it. The review was excellent as always - thanks again to both you and Brian!
  • Formul - Monday, October 31, 2011 - link

    that was fast! i knew something was not right as there was no mention of this in the text :-)

    thanks for another great review, keep up the good work! :-)
  • zanon - Monday, October 31, 2011 - link

    The article wrote "The expectation that Apple will always deliver more than just a hardware upgrade is likely what made Siri a 4S exclusive."
    While only time will tell for sure, it seems quite possible that graduated ramp up had a bigger role to play here. As you say, most of the heavy duty lifting for Siri is going on server-side, and in turn local processing needs aren't too bad. However, the natural flip side of that of course is that the server-side infrastructure is required for the service to work at all, and resources aren't unlimited there either. Even with it limited purely to 4S users, Siri still had some availability problems in the first few days as millions activated and tried to user it simultaneously. It's not hard to imagine what would have happened if every single one of the tens of millions able to upgrade to iOS 5 *also* tried to start using it immediately. Apple has built a huge data center and that's all well and good, but nothing substitutes for actual working experience when it comes to massive software services.

    By limiting the initial rollout, Apple can do performance profiling, get an idea of average loads after initial "let's try it" dies down, and so forth. Staggering a rollout also means being able to plan for the general load rather then suffering the classic and well known double-bind of
    A) Building for a peak load, and ending up being left with a lot of extraneous hardware that barely gets used.
    B) Building for the average, then suffering from embarrassing and headline generating outages for a week or two.

    It's true they could just decide to keep it 4S only, but given they are still selling the iPhone 4, and probably make plenty of profit on that now very mature device, I think there is a decent chance they'll roll it out to a wider audience down the road.

    Also, a few typos:
    Page 2:
    I think the phrase is "pretty much par for the *course* for Apple..." rather then "par for the case".

    Pg 9, WiFi:
    "...newest WLAN, Bluetooth, and FM *cobo* chip" should I think be "combo".

    Pg 15:
    ...4S, without a (big blank, presumably some sentence was supposed to go here?)

    Pg 16:
    "aren't simply *academical*" should be "academic".

    Again, great review, thank you.
  • Anand Lal Shimpi - Monday, October 31, 2011 - link

    That's a very good point, I will add it to the discussion. The sinister view is to assume Apple did it to differentiate, the balanced view takes into account infrastructure, which is exactly what you did here :)

    And thanks for the corrections :)

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