I would like to present you my self-made filter. It's called PortmannFilter. It can be used to smooth your RSSI data of an RF-Link reciever. Feel free to ask me questions and use it. But please declare in your project the usage of my filter.
The Arduino measures an analog signal from the RSSI pin of the reciever. Then it does the same again. Afterwards the PortmannFilter compares the two values and smoothes them and too low values are getting ignored.