Wireless connection: possible alternatives

Dear all,

For my project I have the arduino uno connected via serial to a RPi which has a wi-fi connection. Unfortunately these are placed outside, protected by humidity but subject to low temperatures.

While arduino it seems to work fine (atmega328 should work between -40°C and 85°C) I'm not that sure about RPi and about my wi-fi adapter (which died at 0°C).
Now I would like to move RPi inside and have the Arduino outside, but cannot have a long serial cable.
The distance would be around 10m with one wall in the middle.

So far I identified the following alternatives:

  • VirtualWire: using 433MHz modules (signal seems to arrive since I also have remote plugs at the same frequency). The RPi would be connected to an additional arduino to get the signal. Possible interference with 433MHz

  • NRF24L01+: (these) are 3.3V, but input (not VCC) should be tollerant 5V (datasheet). It seems that multiple nodes can be added in future in case of need. Possible interference with wi-fi.
    Can I use these also if I have other things connected via SPI? For CE and CSN can I use any digital pin?

  • Bluetooth: (JY-MCU). Not clear if I'm able to cover the range with this (considering the wall). Can I connect it to the RPi using any bluethooth adapter and use it like if it is a serial connection?

  • New wifi adapter for RPi: but not sure if the RPi resists below 0°C.

Which option do you suggest?
Do you have any other ideas/pro/cons?

Thank you for your support,

I'll be watching the responses with interest & if we could add to the above query "what would be the best solution if one wanted to use it for a networked application with a Master to 1+ Slaves"
Regards all

Why don't you use an RN-XV module on the Arduino? It's Wifi you might ommit the Raspberry Pi completely (you didn't specify what you use it for). The datasheet says it's operating down to -40°C. This way at least you don't need another device for the RaspPi.