Bluetooth 2.0 and the Nokia N93

There is web 2.0, mobile web 2.0 and, believe it or not, Bluetooth 2.0… One of the main benefits of the new version is the enhanced data rates (EDR) feature which promises data rates of up to 2.1 MBit/s. That’s quite a step from the 0.7 MBit/s of previous versions of the standard. To test the higher data rates in action I performed some speed measurements between a notebook with an Anycom Bluetooth 250 USB stick and a Nokia N93.

While measurements between two Bluetooth 2.0 USB sticks might actually show higher transfer speeds than between a notebook and a mobile phone, I nevertheless decided to go for this test setup as I use Bluetooth mostly between such devices for file transfers and to connect my notebook to the Internet via the mobile phone and the 3G network.

The test setup:

• Mobile phone: A Nokia N93, firmware V 10.0.025
• Notebook: Anycom BT200/250 Bluetooth 2.0 USB stick with Widcom Stack V 5.1.0.2100
• File for transfer: A 34 minutes 64 kbit/s MP3 podcast with a file size of 15 MB (16.142.336 bytes)
• For reference tests: A Nokia 6680 with a Bluetooth 1.x chipset

From the notebook to the N93

This is a typical side-loading scenario, i.e. a user downloads a podcast from the Internet to the PC and then sends it via Bluetooth the mobile device. Over Bluetooth the 34 minute podcast was transfered to the N93 in 120 seconds. The resulting transfer speed was thus 16.142.336 bytes / 120 seconds = 134.5 kByte/s. That’s about half of the theoretical maximum speed Bluetooth 2.0+EDR offers with 272.25 kByte/s (2178 kbit/s). Nevertheless, the transfer was about twice as fast as what could be achieved with previous Bluetooth versions.

From the N93 to the notebook

I also transfer a lot of files from the mobile phone to the notebook, mostly images and videos. In order to better compare transmission speeds of both directions I used the same file to test the reverse direction. In this direction, the file was transfered to the notebook in 110 seconds. The resulting transfer speed was thus 16.142.336 bytes / 110 seconds = 146,78 kByte/s.

Bluetooth and the Nokia 6680

To compare the improvement, I ran the same tests once more with a Nokia 6680, a S60 2nd edition phone and predecessor of the Nokia N70. It uses a Bluetooth 1.x stack and the transfer of the file from the notebook to the mobile phone took 273 seconds. That’s a transfer speed of 57.4 kByte/s. In the other direction the file transfer took 313 seconds which corresponds to a transfer speed of about 50 kByte/s.

Summary

While end users won’t care much for the transmission speeds, the time required to transfer a file between two devices is quite important. Compared to the 273 seconds (4.5 minutes) it takes to transfer the file to the 6680, the 110 seconds (slightly less than 2 minutes) required to send the file to the N93 is a vast improvement. There is also still potential to increase the speed further as the transfer rates are far below the theoretical maximum. When using Bluetooth 2.0 capabilities to the fullest, the transfer time could be reduced from 2 minutes to around 1 minute for the 34 minute podcast file.

With file sizes especially of video files getting larger and larger due to the improved capabilities offered by new phones, it is only a matter of time before it becomes impractical to transfer such large files even over an optimized Bluetooth 2.0 connection. Also, 3G network features such as HSDPA with data transfer rates of up to 3.6 MBit/s today and 7.2 MBit/s in the future, Bluetooth definitely becomes the bottleneck.

It is time to think about alternatives. Many of today’s N-series phones already have a built in wireless LAN (wifi) adapter. Adding access point functionalities to the phone as suggested in this blog entry would surely remove this bottleneck.