packets per connInterval

[Sebastien]

Hi,

I would know how many packets per connInterval the nRF52832 and BLE stack are able to manage ?

I see that Android can manage a maximum of 4 packets.per connection interval.

The maximum packet size for Notification at 7.5ms conn Interval is 21 Bytes. It means that this 21*4 packets = 84 Bytes evry 7.5 ms ?

If we have two slaves, that it means that we divide by two the throuhput?

If I understand correctly we can increase payload size to 255 bytes but to do this we must increase conn interval ?

If something change if we change the BLE bit rate from 1Mbps to 2Mbps ? Could you increase the number of packet per conn interval?

Thanks.

Regards,

  Sebastien Riccardi

[MartinBL]

Hi

I suggest that you read this blog post: https://www.novelbits.io/bluetooth-5-speed-maximum-throughput/

I would know how many packets per connInterval the nRF52832 and BLE stack are able to manage ?
The SoftDevice may transfer as many packets as can fit within the connection event as specified by the event length for the connection. Please refer to the Softdevice Specification: Bluetooth Low Energy data throughput.

I see that Android can manage a maximum of 4 packets.per connection interval.
It depends on the BLE chip set being used and the BLE stack implementation and varies from device to device. Here is a relevant (but somewhat old) blog post: https://punchthrough.com/blog/posts/maximizing-ble-throughput-on-ios-and-android

If we have two slaves, that it means that we divide by two the throuhput?
Yes, they will share the bandwidth of the central. 

If something change if we change the BLE bit rate from 1Mbps to 2Mbps ? Could you increase the number of packet per conn interval?
Yes. But not all devices support 2Mbps mode.

[Sebastien]

When you have 2 slaves, they share the bandwidth of the central.

It seems that they share 1 over 2 conn intervall. Is it not possible that they share packets in a same intervall ?

[MartinBL]

Sorry, what I wrote was ambiguous. 

First off, in the BLE world we usually refer to "central" and "peripheral" roles rather than "master" and "slave" roles.

BLE uses a TDMA scheme when a central is connected to two or more peripherals, so the central's bandwidth is split (i.e. divided in two) between the two peripherals. This is simply because the central can only transmit data to one peripheral at a time. It is not possible for both peripherals to receive the same packets from the central. You can read more about how it works and how to configure the bandwidth here: Scheduling.