Network Improvements

The iPhone continues to be an AT&T exclusive in the US. With the iOS 4 upgrades the iPhone 4 supports tethering over Bluetooth or USB. The feature is an extra $20 per month on top of your existing iPhone data plan and it also deducts bandwidth from the 2GB you get with the data plan. It's not a coincidence that AT&T timed the release of its iPhone tethering option with the move away from unlimited data plans. You don't have to give up your existing unlimited data plan if you don't want to, however if you want to enable tethering you have to sign up for the new $25/2GB plan.

I'm not a huge fan of iPhone tethering right now because despite paying for the service and having full signal strength on AT&T, I'm getting horrible transfer rates while trying to upload this article. I had to sign up for airport WiFi to get it live, thanks AT&T. When it does work however, it works well. As you'll see later you can easily get multiple Mbps out of AT&T's network in areas with good coverage. That easily equals the lower end of what you'd see from WiMAX today. As I've mentioned before however, it's really hit or miss with AT&T. The network is either great or totally unusable, while its competitors are generally more consistent but never quite as fast. I'd say that there's a good chance Apple will bring the iPhone to Verizon, it's just a matter of when.

Cost of Ownership Comparison
  AT&T iPhone 4 Sprint EVO 4G Verizon HTC Droid Incredible
Cost of Device $199 w/ 2 year contract $199 w/ 2 year contract after $100 MIR $199 w/ 2 year contract
Plan with 900 Minutes, Unlimited SMS/Data $104.99/mo, unlimited SMS, 2GB data $99.99/mo, unlimited SMS, unlimited data, 4G $109.98/mo, unlimited SMS, unlimited data
Tethering + $20/mo + $29.99/mo + $25/mo*
Total Monthly + Tethering $124.99/mo $129.98/mo $134.98/mo
Total Cost of Ownership over 2 Years $2718.76 $2598.76 after $100 MIR $2838.52
Total Cost of Ownership over 2 Years w/ Tethering $3198.76 $3318.52 after $100 MIR $3438.52

AT&T's plans are actually reasonably priced if you don't go over the data limits. A $15/mo data plan will get you 200MB of transfers per month and $25 will give you 2GB. For users like my parents the 200MB option is great. Even for me personally, 2GB is fine. I tend to peak at 700MB per month, but that's because at the office I'm almost always on my desktop or connected via WiFi. It's unclear how tethering is going to change this for me. Our own Brian Klug on the other hand easily pushes more than 2GB of transfers per month. So AT&T's rate switch is either going to save you a few bucks per month or make you really unhappy.

The iPhone 4 brings HSUPA class 6 for upload speeds of up to 5.76 megabits/s to the platform. This is a 15 fold improvement over the 384 kilobits/s maximum of the iPhone 3G and 3GS, which I routinely see. Not all AT&T markets are updated to HSUPA, and in practice I saw uploads of around 1.5 megabits/s, in line with class 2 or class 3 HSUPA.

Downstream HSDPA speeds remain unchanged from the 3GS, supporting up to 7.2 megabit/s HSDPA. I'm lucky since my market is HSDPA 7.2, as I routinely see speedtests of 5 megabits/s or above very late at night when there isn't very much plant load. I haven't seen any measurable increase in speeds over the 3GS, except in locations with very low signal as noted before.


My fastest iPhone 4 speedtest so far

Even Anand in one of the slowest 3G cities in the US saw significant improvements with the iPhone 4. AT&T's network in general seems to be improving. While the best he'd been able to achieve was around 1Mbps a year ago, these days he can break 2.5Mbps down during the evenings.


iPhone 4 speedtest in Raleigh, NC

WiFi speeds have also improved, as Apple has added 802.11n in the 2.4 GHz band. 5 GHz support remains absent, something which would have likely complicated antenna design even further. Interestingly enough, the BCM4329 WiFi and Bluetooth SoC does contain 802.11a 5 GHz support, the reason it's disabled is again likely due to antenna design constraints. The Broadcom SoC also includes an FM tuner and transmitter, though support for either remains and sadly (given Apple's historical lack of FM radio support) will remain such. Bluetooth 2.1 EDR is there as well.

The iPhone 4 seems to connect at 802.11n rates of 72 megabits/s in best case, far from the maximum without channel bonding of 150 megabits/s. This is still a welcome improvement from the 802.11b/g in the iPhone 3GS, which seemed to never connect above b rates in practice. As an aside, mobile devices using 802.11b rates (modulated using DSSS) are a huge contributing factor to WiFi congestion at conferences - I've even seen DSSS modulated rates (and thus 802.11b devices) explicitly disallowed from connecting to APs at conferences. It's a welcome improvement to see iPhone bringing N support.


A typical WiFi test result

However, even on my 25/4 DOCSIS 3 cable connection, I could only squeeze out a maximum of 8.5 megabits/s down and 8.0 megabits/s up while connected at 72 megabits/s best case. This was using the speedtest.net app to a local test location. I tried with an Airport Extreme (new generation), a WRT600N running DD-WRT, and a WRT54GL-TM running Tomato. All three showed similar results capping out around 8 megabits/s down when I could run tests in excess of 30 megabits down on my desktop. This is probably more of a CPU bottleneck appearing than anything else.

Update:

I thought there was something wrong with my WiFi performance, turns out the iPhone 4 is indeed faster than a palty 8 megabits/s. ;)

There were a number of comments by folks who were able to run speedtest.net and get throughput above 10 or 11 megabits/s. Testing earlier today on a much faster connection, I managed to get something in line with their numbers:

Early today, the folks at DigitalSociety also managed to get much faster WiFi speeds in the neighborhood of 20 megabits/s, way higher than my meager 8 megabits/s. To do so, they loaded an MP3 in safari stored on a local webserver and watched network utilization. I wish I had thought of this, because it's perfect. In the past, the speedtest.net app always used to saturate my connection over WiFi. My only explanation is that the application performs slower over WiFi in iOS 4 than it did in iOS 3, something Anand noted as well. Thanks for all the heads up messages, everyone!

I set up a similar test to DigitalSociety's. I opened an 85 MB PDF stored on my local web server in the browser of each device and watched network utilization using bwm-ng. I tested with an Airport Extreme connected over gigabit to my webserver with no other network utilization. I took the average of 5 runs on the iPad, iPhone 4, iPhone 3GS, and my AT&T Nexus One running Froyo 2.2 (which is 802.11n). The results are much, much more in line with earlier expectations.

The iPhone 4 comes close to but can't quite best the iPad, though the difference is minimal. I did notice that the iPad associates at the same 72 megabits/s connection speed as the iPhone 4. Thankfully, the iPhone 4 easily bests the iPhone 3GS. Finally, although the AT&T Nexus One associates at an 802.11n rate of 65 megabits/s, it's slower than the iPhone 3GS. I have a feeling the device is writing the PDF into flash, whereas the iOS devices are loading it into memory.

The Real Story on iPhone 4's Antenna Screen - Retina Display
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  • scarnie - Thursday, July 1, 2010 - link

    See my article here: http://bit.ly/5pxjgk

    Basically, the iPhone 4 is about 33% faster than the 3GS (600MHz) and 25% slower than iPad (1GHz) putting it squarely at 800MHz.

    Cheers,

    Stu
  • heri16 - Thursday, July 1, 2010 - link

    Since it has been confirmed that Apple would not be able to beat physics, the best way for them is to issue a firmware update to hide the signal loss in terms of bars (GASP!) . Since after-all, calls won't be dropped at one bar, why make us all worry?

    From my tests, attenuation by water-containing bodies is always a problem to RF. My best way around has been using micro-strip circular polarized antennas to reduce the effect. I've been using such antennas to cut 2.4Ghz signals through dense trees, which have "waterly" leaves. It also works better in rainy conditions compared to linear antennas.

    (My tests shows reduction in attenuation by 70% in dbm units for my modded 2.4Ghz enterprise router through those same trees.) This will work since our hands/bodies are "waterly" too.

    My suggestion to Apple to is have both thin circular-polarized micro-strip antennas embedded in the back surface, and linear polarized antennas at the sides, and diversity-RF controllers to get improved best-case and worst-case performance.

    I'm not sure whether an iphone accessory maker can create the same fix through a paper-thin antenna plugged in.
  • heri16 - Thursday, July 1, 2010 - link

    Here are some links to help understand the iphone RF fix.

    http://en.wikipedia.org/wiki/Circular_polarization
    http://en.wikipedia.org/wiki/Microstrip_antenna
  • NordicNINE - Thursday, July 1, 2010 - link

    I finished up work & school for the day and just popped down to relax. Brought up my favorite tech news site and started the recorded DVR shows. I pulled up this article and then the recording of the new Futurama started up.
  • Xeeros - Friday, July 2, 2010 - link

    Not to nitpick but The Incredible has 8GB internal PLUS the microSD which Verizon gives you a 2GB stick so it would be 10GB stock as they now package the SD card in the phone. Had a Launch unit and the refresher that says Droid on the box versuses the HTC incredible box. ONly difference was my store gave me a card for the 2GB and now its pre-packaged. To be honest most review sites that have it listed in comparison have it labeled this way, so probably not your fault.
  • sporadic - Friday, July 2, 2010 - link

    A question though:
    When you ran your PDF download tests were you using any encryption or was this on an open network?
  • dhvanii - Friday, July 2, 2010 - link

    This is a great article on i4 antenna and DL reception. I have a few questions.
    1. if you take 1.5 MHz channel bandwidth, then the lowest signal strength measurable should be around -112 dBm. But this WCDMA and so if it is 4.5 MHz the lowest RSSI should be -107 dBm. Add to that a 4-6 dB noise figure and the lowest RSSI should be around -100 dBm. How is the device reporting -113 dBm for 3G ? Is that only for GSM reception where it is 200 KHz channel bandwidth and so theoretical lowest is around -120 dBm ?
    2. How about UL ? What is the Max Tx Power of this device ? 23 dBm ? How is that affected by this antenna glitch. Radio link protocols requiring UL acks for DL packets will definitely get affected by this poor antenna performance if UL is also affected.
    Thanks again for your detailed analysis.
  • navderek - Friday, July 2, 2010 - link

    Well I'm glad we agree...to be honest I did not read the entire article, but only the section about the antenna issues with the handset.

    I did not see you bring up the point of CQI, nor did I see you mention that RSSI is really not a good measure for network coverage / quality (when used alone). Perhaps you've mentioned it in other articles, and if so a link to those would have been warranted for charities sake.

    Have you ever considered writing up an article about how the air interface works? I think everyone would be much further ahead if they had a good basic understanding of the air interface and how the handset communicates with the BTS...especially now with so many networks competing it would put a little more power into the consumers hands to judge the quality of the network rather than rely on their silly marketing adds and crappy signal strength bar displays.

    Finally, you said that at -107dB the iPhone4 "deals just fine" with it. Do you have data to back that up? What kind of data rates were you getting? I'd be surprised if you could even hit 1MB/s.

    Just so you know, I work for TELUS Mobility in Canada. We have the first TRUE "all IP" network running in North America. We launched back at the end of 2009 with a 3.5G network. In my area we use NSN equipment and in practical use you can easily get sustained data rates greater than 10MB/s (downlink, theoretical = 21MB/s). We are also talking latencies of less than 50ms and almost no jitter....how did we do this? Well we are the only company in North America to have built the network from the ground up using IP transport all the way to the radios. We have fiber going to every single tower which serves only this 1 network (we have 2 others to manage as well, PCS / iDEN). :-) I'm not trying to prop-up my company or anything, but just giving a hint as to why other carriers such as AT&T have so many problems with their "patchwork" network which still most likely uses legacy copper circuits multiplexed and converted into IP packets...this puts significant strain on the core to keep up with the demands.

    If people understood the air interface protocols in a general and basic sense at least they could judge the quality of this part of the network and then focus on looking into the other parts...I just find it frustrating that most people who don't understand how it works tend to give the network a "basket" rating based on simple RSSI measurements which does not really give much insight except as to how much radiation your standing in.
  • zmslink - Friday, July 2, 2010 - link

    So the net effect is that iPhone 4 drops fewer calls then the 3GS despite losing as much as 24dB when held "incorrectly," but does that signal loss affect battery life much?
  • davidcjones - Friday, July 2, 2010 - link

    It is amazing how someone can do such detailed research to get to the bottom of this!

    Thanks for your hard work. Of course, I am distressed that people are so inclined to run to the courts to file class action suits before they actually investigate the issue in detail...

    David Jones
    Jericho, VT

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