Wireless systems for automotive, communication between two devices

[Yaroooo]

I want to ask system, and related products, advises about a wireless product inside a car.

Inside my country each device, added to the machine aftermarket, become part of it and is subject under automotive regulation. So, about electronics products, each one should be certificated under EMI/EMC/FCC/CE to be legally installed inside of car. In this case, used already certified modules is a huge advice despite price. But since quantities are very low, price shouldn't be a problem.

The communication would be between two devices and will be always active if car have battery connected through key. This two devices are fixed and installed in two point of the car and a plus, but unnecessary, there can be a possible connection with a smartphone to set some parameters. Key feature is not a big data transfer, there are only some parameters every some ms, but reliability of connection that should be never lost or recovered very fast if this happens. Distance is very near, about 1-1.5m of distance, inside cockpit.

So, I've found several modules, ATWINC WiFi, Microchip BT, nrF bluetooth and several devices with different operative frequencies and protocols.

I'd like to ask, about your experience, some advice:
- Should I concentrate about find a product that is reliable? Maybe dedicated for automotive that not necessarily uses wifi/BT standards?
- Is the above question something that I should not aware of because current modules are already reliable so WiFi/BT modules are already my solution?
- Should be the possibility of Smartphone connection strictly separated (additional module) because may create association problems? Maybe WiFi modules, that support several connection, a better solution?
- Are there advised products?
- About EMI/EMC, are WiFi and BT frequency easier to pass EMI/EMC compatibility?


I'm sorry if I'm vague on some points, but right now nothing is defined and I need to, with your suggestion and documentation on google, make my ideas more clear. About application, is sensor application. I need to constantly read data from one wireless sensor and send this data to a central unit. If data are not recived or there's huge delays, my central unit will create an safety alarm.

Thanks for any advice.

[Scrts]

We've used TI Bluetooth CC25xx devices on safety related automated parking feature for Mercedes. Works reliably.

[sokoloff]

Have you considered integrating with an existing CAN bus on the vehicle? That’s almost surely how the OEM would have done it and with reasonable reason. 

I’m not sure if the exact app or how integrated this is, of course. I’m just making sure you’ve considered and (maybe) rejected the idea of hard wiring.

[Yaroooo]

Have you considered integrating with an existing CAN bus on the vehicle? That’s almost surely how the OEM would have done it and with reasonable reason. 

I’m not sure if the exact app or how integrated this is, of course. I’m just making sure you’ve considered and (maybe) rejected the idea of hard wiring.

Yes, this an additional detail we've already considered. The answer is that we don't want to perform any invasive change on car. This means we're allowed to get only power from battery, but any other kind of signal, bus or signal manipulations must be left untouched. This should electrically less invasive as possible solution.

Also we've already hardwired solution (not trough car signals), but an evolution should be a wireless communication between the sensor and central unit.