How many Bluetooth piconets can you fit in a room before they stop working? That's a question that a lot of people have asked—but, of course, there's no real answer because it's too imprecise! How big is the room? How are the piconets spaced out? Are they using power control? What profiles are they using, and how active are they? Well, maybe we can't answer the question as it stands, but we can make a few useful assumptions and then try to answer the question.
How Are Piconets Spaced, and Are They Using Power Control?
Figure 1 shows some Bluetooth devices in piconets. A couple are Class 1 devices, spaced at a distance that means they will have to use their powerful radios. There are two piconets mostly made up of low-power Class 3 devices: The one at the top includes a Class 1 slave, but because it's close to its master, it can turn down the power and behave as if it were another Class 3 device.
Piconets made up of devices with different power classes.
Then in the lower center we have a piconet with a pair of Class 2 devices, as well as a Class 3 device close to the Class 2 master. The Class 2 master will use more power to talk to the Class 2 slave because it's at a greater distance than the Class 3 slave.
So, if we spread out our devices a lot, they will use higher power and will interfere with each other more. Perhaps we should fill our room with tightly clustered piconets so that they can use the lowest possible amount of power and interfere with one another as little as possible.