A Lighter Shade of Bluetooth

It seems I've found yet another use for my extant XP box. Besides being my always-on file server, it's now an improvised Bluetooth access point for my 2210. Besides being far easier to setup than I expected (far easier than my experiences with Bluetooth on RedHat, it was relatively cheap (EUR 59) and has an equivalent range to my old peer-to-peer Wi-Fi network (before I got my first Linksys access point).

Why Bluetooth (the nearly-dead wireless technology of the century)? Well, here's my usual bulleted list of reasons:

• The 2210 has it built-in:
  • No need to fish around for my CF card
  • Lower battery drain
  • Two-click activation (and deactivation) from the Today screen
• More than enough bandwidth to fetch e-mail headers, RSS, etc., even full e-mail messages to read while on transit.
• Despite being involved with Wi-Fi for years now, I was curious as to whether Bluetooth:
  • Was at all usable beyond a 10m radius.
  • Was easy enough to set up for "simpler" connections
  • Poses any real threat to the services I develop, given the new long-range radio designs

The answer, thanks to the Conceptronic CBT100U shown above, is yes - sort of. Bluetooth-enabled Pocket PCs are extremely simple to set up - against an XP server. I couldn't find a way to enable LAN Access via a Mac, but I confess I wasn't too motivated to try hard, since my PC is the only thing turned on 24/7, and I wasn't going to fire up my Mac every morning to get my news...

Blue LAN

I had already mentioned the fact that my 2210 could access the net via an ActiveSync connection - which is a PPP-like shim over a "serial" port. But it turns out that it incorporates a Bluetooth LAN client, and that the excellent Bluetooth software provided with the Conceptronic adapter creates a new network interface and provides Internet Connection Sharing (i.e., NAT, DHCP and a DNS relay) on top of it to client devices.

Setup was a bit fiddly for one reason only - like any "easy" Windows products, it is full of irritating wizards, and it took me a while to click through all of them, figure out I needed to click something three steps back, overshooting, and finally clicking through to the end.

Despite all the wizards, setting up Bluetooth LAN Access is not for novices, however. I'm an old hand at configuring any kind of network, so I just jumped through the appropriate hoops as the wizards prompted me to pick an interface to enable Internet Connection Sharing, pick security settings and input PINs on both devices, but newbies will have a lot of difficulties.

In short, it's not as easy as setting up Bluetooth on the Mac - not by a long shot - but it is easy. I'll have to investigate more about Mac OS X Bluetooth support, since I can see no reason for it not to provide LAN Access as well (as far as I remember, it is an entirely different service profile than the usual serial port access).

This is where this particular adapter comes in. I had already used the older, less powerful model, and was curious as to what real improvement the "100m" rating brought.

It turns out the difference was very significant indeed - I have yet to read the full specs, but empirical testing shows it to be roughly equivalent in range to a 50mW radio like those found in Wi-Fi cards. I had excellent reception on my 2210 over a relatively wide range (at least 30m in an open space office) but since the radios aren't symmetrical (the iPAQ's of course, is much weaker), I lost connectivity (ping timeouts) beyond 20m (which means there is some reception gain involved on the adapter side, but not enough to compensate for the iPAQ's weaker Bluetooth radio).

At home, I sill had a strong signal through three (brick and concrete) walls, and actual connectivity through two (which was quite amazing for Bluetooth).

Since the Bluetooth status panel only provided a "1 to 5" bar graph, I have no "real" dBm measurements. Apologies to my colleagues and fellow network geeks (who will probably be interested in those), but there are no power ratings on either the casing or the adapter's documentation.

Well, it's no Wi-Fi. Pretty obvious, right? Actually, it feels more (in overall latency and thoroughput) like an ISDN connection.

Even at close range (line of sight, less than 10m away from the adapter) there was a bit more latency involved (as confirmed by pinging the server). I suspect this might have more to do with chipset or bus limitations on the Pocket PC itself than the medium, but plugging in my SanDisk card confirmed that Wi-Fi soundly trounces Bluetooth on page load times (roughly two to five times faster at least). It is fast, mind you, but quantifying it (without a bunch of tools I don't have installed on my Pocket PC) is tough.

It is, however, more than fast enough for me to check my e-mail via ADSL, even with SSL thrown in. I can't honestly say the delay is noticeable.

If, like me, you have a Bluetooth-enabled Pocket PC and commute to work, get one of these adapters - you'll appreciate having e-mail, AvantGo and whatnot with you as you go out the door (I can always use GPRS, but this is way faster - I practically only use it now to follow-up on interesting links while on the move).

There are identical ones from other manufacturers - apparently all based on the same chipset - so feel free to shop around.

Oh, and do drop me a line if you know more about Mac OS X support for Bluetooth services (or have pointers to Apple docs on what lies below the application-level services). Besides LAN access, headsets, audio relay and the like seem very interesting.

(Not that I'm partial to slowly microwaving my temples with a Bluetooth handset, but I like to broaden my horizons.)