BLE MTU higher but speed is the same

Question

I'm playing around with CoreBluetooth in iOS 7, and have successfully got two devices sending quite a large amount of data between each other (one is the central, one is the peripheral).

Between an iPhone 5 and 4S I had an MTU of 20 bytes, and between an iPhone 5s and iPhone 5 I had an MTU of 132 bytes. The size is much larger, so I assumed fewer individual messages would be sent and therefore the overall time of the transfer would decrease.

Unfortunately the time remains pretty much the same in both scenarios (around 15 seconds). Was my original assumption incorrect or is there something I may be doing wrong?

Answer 1

L2CAP has MTU of 20 bytes. If you want to send data of more than 20 bytes, it is sent in multiple packets. Most likely the 132 bytes are being sent in 7 packets at the same rate as 7 20-byte packets. So the throughput is the same.