I suppose to do remote keyless entry (RKE) for door opening as a commercial product, there is DC motor which drive the door to open or close (receiver side), on transmitter side (remote) three button for 'OPEN' ,'CLOSE' and 'STOP'.
I'm new to RF, but I completed this project using a cheap 433 MHz transmitter and receiver model, and made compact size remote with that tx module, both tx and rx module is interfaced with ATmega88PA SMD package. For data processing I used the USART protocol for data transmission.
I'm using 3 V coin cell battery so it has a low range of transmission, but I overcome this with the antenna set, and now I'm getting the expected range (not bad).
The problem comes here: It is interfering with other 433 MHz. There is a water level controller in my company, and it will transmit data continuously for 30 min from the water tank to motor control room. During that time my receiver is not taking my signal since my remote is powered with 3 V, and that water level controller is powered with 9 V using HOLTECH encoder also.
So it's not good idea for selecting modules for commercial products. I want an RF IC for overcoming these problem. It should have its own protocol, since I wasted a month with these modules. It should be easy to configure.