Does data packet size affects current/power consumption during data transmission?

[sushil]

I am sending 13 bytes of data from my BLE application. Will the current consumption reduce after i limit that data to 4 bytes?

[Pål Håland]

Hi sushil

That depends, it is better to send most of the data in one burst compared to many small data transmissions. If those additional 9 bytes is not necessary, then you will save some power by only transmitting those 4 bytes.

(you would save ~9us transmission time at arround 16uA)

But if you transmit all those data in smaller burst, then you have a bigger overlay of data transmitted.

BR Pål

[junsoo337]

Dear Pål.

i would like to ask you for "you would save ~9us transmission time at arround 16uA". can i get the information about consumption ratio of transmission power per bytes size? (ex. max 20byte, and half size, quarter size..)

thank you

[Pål Håland]

I was actually wrong when I said 9 saved microseconds, it should be 9*8us = 72us (1us per bit). For the nRF52 you can see radio current consumption in the infocenter. Calculating it for a packet would be 10 bytes LL header, 4 bytes l2cap header, and 3 bytes ATT header. Then you can add the calculations for the remaining data bytes.

[junsoo337]

thank you Pål. if so, you mean ,payload size is 9 bytes, then 72us => about 16uA? right?

[Hung Bui]

@junsoo: I assume we are talking about the average current here. The average current depends not only the packet size but also how frequently you send the packets. We provided a power profiling tool here for calculation that. It's for nRF52, but you may have a rough idea how it would affect if you calculated it for nRF51.

[junsoo337]

thank you Hung. it seems to be helpful. thanks