Whole house coverage with RF

[Emil]

Due to BLE's low range, license costs and unneeded complexity, I am looking in to pure radio RF. I am curious about ESB and Gazelle, and which one is good for relatively simple but secure communication in a house. I am surprised that I didn't find this question before!

Is this even the right SoC for me, I would guess I can amplify the signal itself on both ends, bot not sure how to do / test that. I use NRF51-DK. Can I add some kind of an antenna booster on that without too much ado? I got recommended WIFI due to it's high signal power and license free use. But I guess NRF SoC can't do that. But does it even matter as long as you boost the signal?

In short, I want great range and reliability. It needs to work everywhere in a normally sized house, preferably also out on a porch or lawn. Speed and power usage during transmission does not matter as much. It will sleep, will send rarely. It is multiple devices communicating to a central. Perhaps 5-10 of them. Central has a working nrf24l01+ already.

Thanks!

[Dave_couling]

If you design the RF section well you should be able to cover a house with BLE. Using a stubby antenna, and proper placement should get you pretty close to WiFi coverage from my testing.

[Emil]

Thanks! Do you have any hints or tips to make such an RF part? The form factor will be small, but it should be possible to just twirl a wire around or something like that. Any idea on how to amplify and attach antenna to NRF51 DK? Also, will pure RF (Enhanced ShockBurst) give longer range with the same power usage?

Thanks!

[Dave_couling]

I can only comment on the BLE protocol. The stubby antenna used on the old DK kits are a good example of what antenna to use. I'm not sure amplification is necessary. Though the nRF52 has ~3dB better link budget. So thats something to look into. Front End PA's tend to consume more power then they are worth.

[Emil]

So no extra circuitry is necessary. Nice. That answers half my question. Is the stubby antenna the one with a small coaxial connector that fits on the dev board or something?

Thanks again :)

[Øyvind Karlsen]

Hi,

If you are going to use BLE, you are limited to a max EIRP of 10mW. The max allowed in the 2.4GHz ISM band is 36dBm or 4W. Range for a radio system is given by Friis transmission equation. For example usage see this thread.

Safe bet on range for BLE is 10-15m, however it depends on what kind of obstacles your signal sees, walls, people, wifi, and more. In order to get good range, your antenna and radio need to be tuned to each other, please see the general PCB design guidelines blog.

If you find that the range offered by BLE is too short, you can add a power amplifier(PA) to your design and use a proprietary protocol, such as gazell. A power amplifier is an additional component that will add cost to your project, there are a lot of commercial products available. Make sure that the PA is matched to the radio at the entry, and also the antenna at the exit, otherwise you will lose performance. A PA typically has some connection points, RF_in, RF_out and some sort of enable mechanism, for the nRF51 you can simply connect the VDD_PA(see product specification) pin which is active when the radio is in TX mode.

Nordic also offers help with RF-tuning of your solution, for more information you can submit a ticket through the MyPage support portal.

Your suggestion of making a mesh style network is also possible, for more information you can have a look at the mesh-network on github.

Hopefully this answers your questions, if anything is unclear, please ask!

Best regards,

Øyvind