How does shorter connection interval reduces the transmission latency in BLE communication?

[Subhanshu Sahu]

I have read that choosing shorter connection interval reduces the communication latency at the cost of increased power consumption. 

But shorter connection interval will lead to increase in number of connection interval for sending a message. As per my understanding this should increase the communication latency.

So how communication latency is reduced on choosing shorter connection interval?

[Jørgen Holmefjord]

Hi,

In BLE, you are only allowed to send data on the connection interval, as this is the only time both sides of the link have their radio enabled. If you have a long connection interval, you will have to wait longer before the next connection event arrives before you can send data. With a shorter connection interval, the next connection event will come faster and you will be able to send the data quicker, giving lower latency.

The drawback with lower connection interval is like you said, higher current consumption. The device needs to wakeup before all connection events to transmit/receive an empty packet indicating to the other device that it is still there and keeping the link active.

Best regards,
Jørgen