Tethering on 3.0
I've been trying out tethering over USB for a few days now, but today I found a Bluetooth dongle I had lying around (from a Logitech keyboard/mouse set I don't use anymore), and decided to test out Bluetooth tethering as well.
It took me a minute to figure out how to set the Bluetooth dongle to just "regular dongle" mode instead of having it dedicated to just look for the Logitech keyboard/mouse. After that, Vista automatically installed the Bluetooth drivers. I enabled Bluetooth on my iPhone 3G, and then my computer detected the iPhone. I created a "Personal Area Connection" with the iPhone and this shows up in Network Connections, where other LAN and Wi-Fi connections are. The whole process was so easy I actually don't remember all the steps, if anyone needs them. I just remember typing a passcode into my iPhone that appeared on my computer to authenticate it.
The first way I thought of to test the speed of the connection was to use a BitTorrent client with enough torrents queued up to max out my connection. Before I disabled it, my 6 megabit cable modem connection was being maxed out. Over Bluetooth tethering, I was getting 0.70 Mb/s (megabits per second) down through my BitTorrent client.
Then I tried a test through speedtest.net and got 0.69 Mb/s down and 0.18 Mb/s up. The speeds I've gotten running tests in Mobile Safari or with the speedtest.net iPhone app match these speeds pretty closely, so I think these speeds are just how fast the 3G speeds are in my area.
Then I tested USB tethering, to see if there was a difference between the two. After several tests on both Bluetooth and USB, they were both getting about the same range of speeds. The conclusion I get from this is that the limitations for tethering speeds come from the 3G network, not Bluetooth or USB, and it shouldn't matter which you use when you decide to tether. I guess if you have a USB-to-dock-connector cord with you, you might as well use it, because then you can charge the iPhone's battery at the same time.
What's really cool is that you can still use the iPhone as usual while it's in tethering mode, so one person could checking their email on the iPhone while sharing their 3G internet over Bluetooth to a laptop, where someone else could be surfing the web. I was surprised that tethering mode didn't appear to slow anything down on the iPhone, because I figured tethering would tie up some of the resources of RAM and the processor, but everything still worked smoothly.
Anyways, I'm eager to hear whether people think about tethering, like whether they will use tethering very often, whether Bluetooth or USB is preferred (and why), and anything else on the subject.