Max TX power for BT/BLE Beacon

[CS_SD]

Hi,

I am developing a small beacon application using the nRF 52805 device, and the intent is that it will send advertising packets at a slow rate, to indicate to a partner device that it is in proximity of the beacon. Think of it as a crude geofencing implementation.

BT hardware is not my strong suite, and I was wondering what the best way is to boost the signal of the beacon, and what the maximum amplification is that I will be able to get doing that. I am also curious on the impact of this on the power consumption of the beacon, as we intent to drive it with a coin cell battery like a CR2032 and want it to last for around a year.

In general, will it be better to have one beacon with a strong amplification of the signal, or deploying multiple beacons and create  a mesh network.

Thanks, and looking forward to suggestions/input.

[Bendik Heiskel]

Hi,

The nRF52805 have a max TX power of 4dBm. By adding a front end module(FEM), like the nRF21540, you can add 20dB gain. The max TX power with the nRF21540 will be 20dBm due to the amplifier saturating at a max of 20dBm.

But adding a FEM will increase the max power consumption significantly, so you will no be able to run it of a CR2032 battery for very long.

In this case it's probably better to use multiple beacons with a mesh network.

 

Best regards,

Bendik

[CS_SD]

Thanks for the answer, and sorry for the delay in replying.
Are there other solutions you can propose that maybe have better on-chip TX power with tradeoff for power consumption without having to go to the external FEM. We are open to adding two CR2032 batteries and increase the TX power, but still need to get 1 year of battery life out of our beacon. Our goal is to have maximum physical reach between the beacon and device looking for it within a house or an apartment.
Also, is there a way to increase the advertising period to be for example every 10s, looking the gap.h file in the Zephyr codebase, the maximum slow interval value is 1.2s

#define BT_GAP_ADV_SLOW_INT_MIN 0x0640 /* 1 s */
#define BT_GAP_ADV_SLOW_INT_MAX 0x0780 /* 1.2 s */

Can you also advise me where in the Zephyr/Nordic SDK code I can see the current Tx Power setting and how can I adjust it.

Thanks

[CS_SD]

any thoughts on this?