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THOUGHT: Keep Bluetooth 2.0's EDR in your Mind
Posted by Arne Hess - on Monday, 30.04.07 - 14:46:25 CET under 09 - Thoughts - Viewed 26512x
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If you are a long time visitor of the::unwired and it's forerunners, you know that all the sites were about connectivity, especially about connectivity between devices. Was Arne's Windows CE Page back in 1998 about connecting a Windows CE based Handheld PC (H/PC) via IrDA with an IrDA enabled mobile phone to use the mobile phone as the modem for the H/PC, the focus and technology changed during the years and today it's about connecting a Notebook via Bluetooth with a Bluetooth enabled Windows Mobile Pocket PC or Smartphone to use the Windows Mobile smartphone as a modem for the PC.
That's all fine and in general, Bluetooth works pretty good (an exception is posted in my next column this week) but for sure you can also connect your PC/Notebook/Tablet PC using the USB sync cable. Nevertheless, I prefer to commute and travel as light as possible and since Bluetooth is also doing fine for sync, I rarely carry a sync cable with me.

Anyway, today's available technologies are simply great. When I started with Arne's Windows CE Page back in 1998 we had GSM with an "amazing" speed of 9.6 Kbps and IrDA with a bandwidth of 115 Kbps. So IrDA wasn't the bottleneck at all but it was GSM. Well, I haven't surfed the web too much with 9.6 Kbps but it was good enough already to receive and send E-Mails and back in the late 90's of the last century, you haven't received too much mails with huge attachments so it was not too bad for its time. However, even if preferred a wireless connection between my H/PC and my mobile phone (because cable solutions weren't available at this time anyway but came later), IrDA was always a little bit clumsy because it required a line of sight and basically it was impossible to use this data connection while commuting.
Therefore I awaited the availability of Bluetooth even more and I got my hands on one of the first Ericsson mobile phones with Bluetooth as well as I got some sample Anycom Bluetooth PC and CF cards before they were launched. Both worked together perfectly and I fell in love to Bluetooth from day one!

Now, 8 years later or so, I'm still a big fan and supported of Bluetooth and as the mobile networks and the Windows CE devices enhanced, also the Bluetooth standard enhanced - from version 1.0 in the beginning to 1.1/1.2 and 2.0 EDR. And even the next version is on the horizon already: Bluetooth 2.1 EDR .
But - there is a problem with today's Bluetooth standard and it's the bandwidth of Bluetooth connections. Remember - back in the 90's, when we had GSM 9.6 Kbps CSD (Circuit Switched Data) connections, IrDA was good enough with the available bandwidth of 115 Kbps and it was even good enough for GPRS (with its practical used bandwidth or around 56 Kbps). However for EDGE (which serves speed up to 200 Kbps), IrDA would be too slow already and the bottleneck wouldn't be the air interface anymore but the short range connection between the mobile phone and the PC; not to talk about UMTS with its possible 384 Kbps.
On the other hand, today's mostly used Bluetooth v2 version can be easily used for EDGE and UMTS connections since Bluetooth 1.x and 2.0 serves a theoretic bandwidth of 1 Mbps and with a available bandwidth of 721 Kbps. But now, with the introduction (and availability) of HSDPA, even Bluetooth - as we used it over the years - isn't sufficient anymore since we are talking about a 721 Kbps Bluetooth short range connection versus a 1.8/3.6/7.2 Mbps HSDPA wide area connection. Again a bottleneck but this time with an even bigger difference between the air interface and the short range interface.

The solution? Well, until Bluetooth 3 is released and widely available, the only available (wireless) solution is Bluetooth 2.x EDR. Since the introduction of Bluetooth 2.0+EDR (Enhance Data Rate), Bluetooth 2.0 EDR compliant devices serves a speed up to 3.0 Mbps as long as the Bluetooth stack supports the additional EDR technology which is - at least for today - good enough to use HSDPA at the already available 1.8 Mbps and also for HSDPA 3.6, the gap wouldn't be too big.
However, while many manufactures supports Bluetooth 2.0, not all of them also supports 2.0 EDR but if you plan to use your mobile phone as a modem for your PC, the EDR part is critical - otherwise you will not get the theoretically 3.0 Mbps which only EDR serves.
Thankfully, my new Fujitsu Siemens Tablet PC, I bought end of last year, supports Bluetooth 2.0 EDR but it looks like it supports it with the Toshiba Bluetooth stack only:

This was one reason for me, to switch back to the Toshiba Bluetooth stack since I haven't gotten the Windows Vista stack working with the EDR extension.

However, also the HSDPA-enabled Windows Mobile smartphone, you might want to use as your wireless modem, has to support Bluetooth 2.0 EDR, otherwise - even with Bluetooth 2.0 - you are again stuck with 721 Kbps only.

The problem is, that many manufactures offers Bluetooth 2.0 compliant devices but without supporting EDR! While 2.0 has other benefits as well (like a less battery draining power consumption), the full benefit is given with EDR only and both sides of the Bluetooth connection has to support it.

How does it looks in the real word? Well, bellow two screenshots I made with two different devices. On the left a Bluetooth 2.0 device without EDR support which gets a maximum connection of 1 Mbps. On the right a Bluetooth device with support of Bluetooth 2.0 EDR which gets a connection of 3 Mbps:

Okay, above we've seen now, that two different device - both Bluetooth 2.0 - but one without EDR and one with EDR are physically connected at different speeds. But how big is the difference in the daily use?
Well, I made a small bandwidth test to see if I get any differences and indeed - I got differences. I took two different Windows Mobile smartphones, both HSDPA-enabled and both connected to O2 Germany's HSDPA network (at least I got the [H] indicated which made me thinking I'm connected to HSDPA).
After, I connected each from my Bluetooth 2.0 EDR-enabled Notebook and made a couple of bandwidth test. In the results you can see the difference. On the left - HSDPA without EDR, on the right - HSDPA with EDR:

Well, that's a significant difference and it might shows best, what EDR provides in the daily use!

So here we go with a couple of advices:

  • If you plan to use your Notebook with a mobile phone as your HSDPA modem, make sure your (new) Notebook or Bluetooth dongle supports Bluetooth 2.0+EDR
  • If you plan to use a Notebook with your mobile phone as your HSDPA modem, make sure your mobile phone supports Bluetooth 2.0+EDR
  • Make sure that the Bluetooth stack supports Bluetooth 2.0+EDR as well

And the future since even 2.0 EDR isn't good enough for HSDPA 3.6 and 7.2 Mbps? Well, the Bluetooth SIG is already working on the Bluetooth 3.0 standard which is expected to boost Bluetooth to sufficient 480 Mbps. However, as long as 3.0 isn't released (and a release date isn't given yet), we have to stay with Bluetooth 2.x where EDR makes the difference.
So better keep it in mind the next time, you buy a new Notebook, Bluetooth dongle or mobile phone. And no - a Bluetooth 1.x enabled mobile phone shouldn't be an option anymore - especially not if the device is UMTS or even HSDPA!

Cheers ~ Arne

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