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!

[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

[Øyvind Karlsen]

For maximum range I would go with either nRF51 or nRF52 series, these have higher sensitivity, which means longer range. The SDK is also more recent (and in my opinion better), which makes development easier. Gazell and ESB are still supported for these newer chips, and you will get better performance in all categories.

The sensitivity of the radio is dependent on how much information you transfer per second, higher sensitivity is achieved by averaging over a larger amount of time to reduce noise. This means that higher sensitivity -> lower transfer rate, which in turn means that higher range means lower data rate. Gazell is essentially a more sophisticated version of ESB, in fact it is built on top of ESB, and has some features like guaranteeing that packets are transmitted, in other words a full link layer.

Best regards,

Øyvind