How many devices we can pair via Bluetooth of BLE to Android?

Question

How many devices can be connected to at one time via Bluetooth using the BLE firmware on Android?

Answer 1

A search of the Android Bluetooth Firmware source shows the following:

Max concurrent active synchronous connections (BTA_GATTC_CONN_MAX):

• 4 on Android 4.3
• 7 on Android 4.4+

Max concurrent active notifications (BTA_GATTC_NOTIF_REG_MAX):

• 4 on Android 4.3
• 7 on Android 4.4
• 15 on Android 5.0+

As a comparison my experience with iOS is that 8 devices can be connected at at time.

I tried connecting more than 7 devices the other day on Android 7.1 and Bluetooth stopped responding. Starting and stopping didn't help; the only thing that fixed it was restarting the device.

After working with several apps that connect to 4+ devices I can say from experience that these numbers are theoretical. Depending on each individual device and its hardware you'll have an easier or harder time connecting to and maintaining a connection to the maximum number of BLE devices.

Answer 2

Follow Bluetooth at Wikipedia,

A master Bluetooth device can communicate with a maximum of seven devices in a piconet (an ad-hoc computer network using Bluetooth technology), though not all devices reach this maximum.

You need know Master/Slave in Bluetooth first.

I think the good answer depend on your aim.

You're right when you know "can communicate with how many devices" depend on Hardware (Bluetooth Chip). Bluetooth chip on Apple iPhone 4, 5 or Samsung Galaxy S3, S4 ... totally different with Basic Bluetooth Chip.

In my case :

I'm working with Firmware side related to BLE.

His peripheral device has used Basic Bluetooth Chip since it did not has enough memory to store many capacities as many features, likes Bluetooth chip on Apple iPhone 4, 5 or Samsung Galaxy S3, S4 ....

Therefore, his peripheral device only paired with one device in one time.

Thanks,

Answer 3

Both of the answers here are wanting so I thought I should add one:

There are connection limitations built in to the different BLE hardware. I think the lowest I've encountered is 3 connections at once and the highest was about 12-13 connections. These were limitations due to the design of the hardware and had nothing to do with the OS being used, though. Usually the limitation is due to the fact that the hardware has to keep track of certain data and there's a limited amount of memory in the hardware.

So, I don't know specifically for Android, but it doesn't make much sense for a limitation to be imposed at the OS level. Likely when you try to make a connection, and you've reached the limit due to the hardware, you should receive some sort of error/exception preventing the new connection. I think there's actually a "connection limit" error in Bluetooth, but some hardware gives other exceptions like "out of resources". Again, I'm not sure how that gets reflected on the Android level.

Answer 4

I come into BLE development without any knowledge in Classic Bluetooth development and I really don't know what "pair" means in BLE. Isn't that something only exists in Classic Bluetooth?

If you are talking about connection, when Android 4.3 first came out I made a few test on the SDK on Nexus 7 2013. The maximum number of devices it can connect is 4. I didn't test if this number changes in 4.4, but I can confirm it will not be anything less than 4.