Invisible beacon (Peripheral) at Ultra low power and able to make DFU over the air from Reader (Central)

[srijan12]

Hello, 

I am developing a new application for Asset Tracking, whose general architecture is the common one - where Beacons are mounted on asset and the Reader scan for Advertisement data. The architecture is clear and simple but with 3 special requirements that I am curious about - 

1) Hidden. The Beacons will not be paired with any Reader. They will advertise freely and periodically and reader will detect the data. However, any general Laptop or Mobile phone should not be able to see it. I guess that can be controlled by "BLE_GAP_ADV_FLAGS GAP Advertisement Flags". Is this correct? If not, what is the way to hide them from naive hackers?

2) Very low power. We want to develop a beacon with life of 3 years on a coin cell, advertising interval can be kept as 5 minutes. Is it practical? If yes, kindly guide me as how we can do it and the corner cases. If no, what is the practical limit if we use an Energizer (brand) coin cell?

3) DFU OTA. Having achieved 1) and 2) can I send a signal to the sleeping Beacon from the Reader so it wakes up and I can put it in Device Firmware Upgrade (over the air) mode? Can one NRF51 program another NRF51 over the air?

Please shed some light on these tricky cases.  

[Hung Bui]

Hi, 

 

For new application we suggest you to start your development with nRF52 series. nRF51 is older and we stopped development of any new feature with this series. The nRF52810 has very similar price range to nRF51 and offer much better features and lower power consumption. 

1. Bluetooth Advertising is public and can be scanned by any BLE device. So it's not possible to make your beacon packet visible to your scanner but not other BLE scanner. What you can do is to encrypt your data and use resolvable address (address that 's regenerate periodically) to protect your privacy. You can consider using EID with EddyStone ,have a look here.

2. Yes, it's practical. We had seen our customer made their beacons with 10 years battery life. It's just how big the battery can be :) You can calculate your power consumption base on the interval here. A 2450/2477 coincell battery with 600mAh/1000mAh should be enough for your application to last 3 year+ with 1 second interval. 

 

3. You would need to advertise not only in beacon mode but also in normal mode once in a while to wait for the command to tell your device to enter DFU mode. This will result of little bit more power consumption.