Do Not Use Wi-Fi for Tethering your iPhone

Some of my friends asked whether they should use Wi-Fi, Bluetooth or USB when using their iPhone’s cellular data for Internet access on their computers.  In other words what is the best connection to use for Personal Hotspot. At a glance, Wi-Fi tethering should be faster than Bluetooth because of it’s higher theoretical data transfer rate. But using Wi-Fi for personal hotspot tend to drain your battery faster. Of course USB has the fastest transfer rate of the three but you need to carry the Apple’s 30-pin USB cable everywhere.

I’ve done some tests and concluded that you should prefer Bluetooth over Wi-Fi for personal hotspot. Why? Two reasons:

  • There isn’t any significant drop in real data transfer speed when you use Bluetooth for 3G cellular data access. This is because the typical  3G data plans gives significantly lower real throughput than what Bluetooth normally offers. I’m not talking about theoretical transfers here – I’m talking about the the real kilobytes per second of download and upload to your favorite Internet sites.
  • Bluetooth tethering can be initiated even when the iPhone is in standby with the screen turned off. Unlike Wi-Fi where you need to turn the phone on on when you need to tether. It’s a whole lot more convenient since you can keep the phone in your pocket and just initiate the connection from your laptop or iPad.

Of course it’s better to use USB tethering when your laptop is connected to an AC adapter since you can charge both the phone and your laptop at the same time. I carry a short (5 cm) iPhone-to-USB cable in my laptop bag just for this use.

Speed Tests

I did some tests of the connection speed of M1‘s cellular data connection performance and compare it untethered on the iPhone, tethered to Mac and tethered to an iPad. All tests were done by the SpeedTest application, with SpeedTest.net for iOS for testing on iPhone and iPad and their Flash-based version for testing on the Mac. Each test was done four times on each device which amounts to twenty test cases in total. Test devices were iPhone 4 (the older one), iPad 2, and Macbook Air (2011). It was done on a Thursday night at around 20:00 local time.

Bluetooth tethering has slightly lower response times than Wi-Fi when tethered to the Mac and iPad. However the variance is high and maybe this really need a re-test with more samples (which I don’t have the inclination to do at this point). The graph below shows the average response times in milliseconds and the error bars represent one standard deviation above or below the mean. In other words, the range within the error bars represent 68% probability assuming that the results were normally distributed.

 Tethering Ping Response Times Comparison between Bluetooth and Wi-Fi

However data transfer tests doesn’t show a significant difference between Bluetooth and Wi-Fi tethering. In the graph below you can see the average upload and download speeds between the various devices. The error bars represent one standard deviation or 68% probability of more test results will fall into that range. All values are in Mega-bits per second (there are eight bits to a byte and 1024 Kilobits per Megabit).

Tethering Data Transfer Rates Comparison between Bluetooth and Wi-Fi

You might be curious, what was the data plan that I subscribed to and used in these tests? I used the M1 iPhone Value plan that promises “Up to 14.4 Mbps” data transfer speed. You can see for yourself  that M1′s real data transfer of about 0.15 Mbps is vastly below the speed that they advertised – which is by the way the theoretical maximum of 3G data (that anybody can conveniently quote without testing nor needing to commit to an SLA).

M1 iPhone Plan

You can test these out yourself and see whether your cellular operator’s real data transfer rates are anywhere near Bluetooth 2.1′s theoretical limit of 2.1Mbps. Even if your favorite mobile operator is twice as fast as mine, you’ll come to the same conclusion that Bluetooth is the better choice for wireless tethering.

 

Tags: , , , , , ,

  • Ren Nakanote

    Very nice research done on this topic, I wish more would be done on this topic.  

    I hate how carriers advertise 4g 3g…I guess it may be their way to obfuscate true data speeds when compared to residential broadband carriers.

  • http://twitter.com/nellob Neil Brennan

    I used to use bluetooth for iPhone tethering, but some time in the last 6 months the second of your points stopped being true for me. Every time I try to tether via bluetooth, I have to turn bluetooth off and on again on the iPhone to get a connection. I’ve tried re-pairing etc. and nothing helps. Any thoughts would be helpful.

  • http://twitter.com/justinmchenry Justin McHenry

    Thanks for the great testing. Your conclusions are only valid on slower connections. We just got AT&T LTE in my town and and I did some testing. I could get 28 Mbps on Wifi tethering from an iPhone 5 to an iPad Mini. On bluetooth I was limited to 1Mbps. This makes since given the theoretical maximums for LTE versus those for Bluetooth.

    I am with you that Bluetooth tethering is easier to use and easier on your battery but it is just too slow to support modern high speed data connections.

  • basilsalad

    That’s what people are saying here in Singapore too — because LTE is new, not too many people have upgraded to LTE-capable devices and thus the network haven’t been congested and can approach its theoretical maximum speed. Unlike the 3G network that the “real” speed barely reach even a fifth of the maximum. It’ll be interesting to see when most people are on the LTE network whether it deteriorates the speed that you’re enjoying now.

    Sasmito Adibowo
    http://cutecoder.org

%d bloggers like this: