WiFi Performance

Apple hasn’t spared upgrading WLAN connectivity on the 4S, though the improvement isn’t quite as dramatic as what I was hoping for. The 4S uses BCM4330, Broadcom’s newest WLAN, Bluetooth, and FM combo chip (though the latter still isn’t used). We’ve seen this particular combo chip in the Samsung Galaxy S2, and no doubt BCM4330 will start popping up a lot more in places where its predecessor, BCM4329 was used, which was everything from the 3GS to the 4 and in virtually innumerable Android devices. BCM4330 brings Bluetooth 4.0 support, whereas BCM4329 was previously Bluetooth 2.1, and still includes the same 802.11b/g/n (2.4 GHz, single spatial stream) connectivity as the former, including only tuning 20MHz channels (HT20). I was hoping that the 4S would also include 5 GHz support, after seeing SGS2 include it, however the 4S still is 2.4GHz only.

Encircled in red: The iPhone 4S' 2.4 GHz WiFi+BT Antenna

In addition, the 4S locates the WiFi antenna in the same place as the CDMA iPhone 4. If you missed it back then, and have read the previous cellular connectivity section, you’re probably wondering where the WiFi and Bluetooth antennas went, given the absence of a stainless steel band for them. The answer is inside, printed on a flex board, like virtually everyone else does for their cellular antennas. It’s noted on the FCC-submitted schematic, but I also opened up the 4S I purchased and grabbed a picture.

Left: iPhone 4S with WiFi RSSI circled, Right: iPhone 4

Given the small size of this antenna, you might be led (deceptively) to think it has worse sensitivity or isotropy. It’s interesting to me that this is actually not the case. Subjectively, I measured slightly better received signal strength on the 4S compared to a 4 side by side, and upon checking the FCC documents learned the 4S’ WLAN antenna has a peak gain of –1.5 dBi compared to –1.89 dBi on the 4, making it better than the previous model. That said, the two devices have approximately the same EIRP (Equivalent Isotropically Radiated Power) for transmit when you actually work the math out.

WiFi Performance

Moving to a newer WLAN combo chip helps speed WiFi throughput up considerably in our test, though I’m starting to think that the bigger boost is actually thanks in part to a faster SoC. As a reminder, this test consists of a 100MB PDF hosted locally loaded over 802.11n (Airport Extreme Gen.5), throughput is measured on the server. On MobileSafari, the PDF document is loaded in its entirety before being rendered, so we’re really seeing WiFi throughput.


The iPhone 4 previously used a BCM4750 single chip GPS receiver, and shared the 2.4 GHz WiFi antenna as shown many times in diagrams. We reported with the CDMA iPhone 4 that Qualcomm’s GPS inside MDM6600 was being used in place of some discrete solution, and showed a video demonstrating its improved GPS fix. I suspected at the time that the CDMA iPhone 4 might be using GLONASS from MDM6600 (in fact, the MDM6600 amss actually flashed onto the CDMA iPhone 4 includes many GLONASS references), but never was able to concretely confirm it was actually being used.

MDM6610 inside the 4S inherits the same Qualcomm GNSS (Global Navigation Satellite System) Gen8 support, namely GPS and its Russian equivalent, GLONASS. The two can be used in conjunction at the same time and deliver a more reliable 3D fix onboad MDM6610, which is what the 4S does indeed appear to be using. GPS and GLONASS are functionally very similar, and combined support for GPS and GLONASS at the same time is something most modern receivers do now. There are even receivers which support the EU’s standard, Galileo, though it isn’t completed yet. This time around, Apple is being direct about its inclusion of GLONASS. The GPS inside MDM6610 fully supports standalone mode, and assisted mode from UMTS, GSM, OMA, and gpsOneXTRA.

Just like with the CDMA iPhone 4, I drove around and recorded a video to illustrate GPS performance, since unfortunately iDevices still don’t report direct GPS NMEA data. The 4S has a very constant error radius circle in the Maps application and shows little deviation while traveling, whereas the 4 sometimes wanders, changes horizontal accuracy, and velocity. In addition, the 4S GPS reports the present position in the proper lane the whole time as well, while the 4 is slightly shifted. I don’t think many people complained about the GPS performance on the 4, but both time to fix and overall precision are without a doubt improved over the GSM/UMTS 4. Subjectively, indoor performance seems much improved, and I’ve noticed that the iPhone 4S will report slightly better horizontal accuracy than the 4 (using MotionX-GPS on iOS) indoors. Unfortunately we can’t perform much more analysis since again real NMEA data isn’t presented on iOS, instead location is abstracted away using Apple’s location services APIs.

Noise Cancelation

The iPhone 4 included a discrete Audience noise processor and second microphone for doing some advanced common mode noise rejection. This reduced the amount of background noise audible to other parties when calling from a noisy environment, and is a feature that virtually all of this latest generation of smartphones has included. The 4S still includes that second microphone (up at the top, right next to the headset jack), though the discrete Audience IC is gone. It’s possible that Audience has been integrated into the A5 SoC itself, or elsewhere, or the 4S is using Qualcomm’s Fluence noise cancelation. I spent considerable time digging around and couldn’t find anything conclusive to indicate one possible situation over the other.

We recently started measuring noise rejection by placing a call between a phone under test and another phone connected to line-in on an audio card, then ramping volume up and talking into the handset. The 4S doesn’t get spared this treatment, and I’ve also included the 4 and 3GS (which has no such common mode noise rejection) for comparison.

iPhone 4S Noise Rejection Demonstration - GSM/UMTS - AT&T by AnandTech
iPhone 4 Noise Rejection Demonstration - GSM/UMTS - AT&T by AnandTech
iPhone 3GS Noise Rejection Demonstration - GSM/UMTS - AT&T by AnandTech

Subjectively, the 4S has further improved ambient noise rejection over the 4. I ran this test twice to make sure it wasn’t a fluke, and indeed the 4S subjectively has less noticeable ambient noise than the 4 even at absurd volume levels.

We’ve also placed the usual test calls to the local ASOS weather station and recorded the output. I can’t detect any difference in line-out quality of the voice call for better or worse, at least on GSM/UMTS. I’d expect the 4S to offer exactly the same quality on CDMA as the CDMA iPhone 4.

Apple iPhone 4S (GSM/UMTS) - ASOS Test Call by AnandTech

One thing I should note is that there does seem to be a bit more perceptible line noise on the 4S’ earpiece when on phone calls. It isn’t a huge difference, but there is definitely a bit more background noise on the 4S earpiece than the 4 in calls. The original 4S that Anand purchased had a noticeable and distracting amount of background noise, though swapping that unit out seems to have somewhat mitigated the problem (he still complains of audible cracking via the earpiece during calls). I’ve tested enough iPhone 4 handsets (and been through several) to know that there is a huge amount of variance in earpiece quality, (even going through one with an earpiece that sounded saturated/overmodulated at every volume setting), so I wager this might have been what was going on.

Siri Display


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: http://www.anandtech.com/show/4981/motorola-droid-...

    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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