Posted by: Waern | March 14, 2009

Technology Rant: Bluetooth is not a Proximity Technology

We are not the only research group that have come up with the ‘great’ idea that Bluetooth can be used for proximity detection, like finding out when other players are close by.

Bluetooth is a particular standard for wireless communication between devices that are within meters from each other. For example, Bluetooth is used between your mobile phone and your wireless earphones. There is a bit of security built into the standard too. To make your wireless earphones connect to your mobile, you have to first register them with the mobile.

The neat thing is that all Bluetooth devices (that are on) will continuously broadcast a unique identifier to other devices in their vicinity. At least on Symbian phones you can write a small program that scans your environment for bluetooth IDs . This has been the basis of a lot of cool game ideas, such as Insectopia and Hot Potato.

The problem is that Bluetooth isn’t really optimised for the device detection phase. The typical use of Bluetooth is to establish a fairly stable connection between two devices that need to communicate a fair bit of data. Proximity-based games are not in the least interested in communication – instead they want  a fast and reliable way to detect nearby devices, and this is precisely what Bluetooth doesn’t offer. Device detection is often both slow and erratic. This is fine when Bluetooth is used as it is supposed to be used: you are prepared to wait half a minute for your earphones to connect.  But, if you are to catch another player as he runs by you, the detection needs to be done  in seconds. The device manufacturers are also trying to extend the range of Bluetooth, perhaps up to as much as one hundred meters. This will make it fairly useless as a proximity detection technology.

momentum031-scaled1The technology you should be using for proximity technology is RFID, even though it’s not available in phones. The Thumin glove from Momentum contained an RFID reader, and used Bluetooth to stay connected to a mobile phone and communicate the readings. You could actually play Tag using Thumin gloves, something that would be completely impossible with Bluetooth.


  1. Though if taking on a seamful design principle Bluetooth proximity can work quite well, but you need to be aware of it’s quirks to design it well.

    Probably what we had most problem with in Momentum was to optimize how we did the proximity scans to be done within reasonable time. We tried to use as much knowledge as possible all the time to avoid scanning for devices that would not make sense from a gameplay perspective, like players from your fractions since it would not affect that players actions. And then utilize the server side as well to collect information from all players. But it is not easy and you can never expect it to be reliable to 100%.

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