I encourage all to find source documents for questions like this. Some of the info posted by others are not accurate. Even the link I include on this post is very general in nature. Instead, your regulatory agency and company Ops Specs are better sources.
"P-RNAV capability can be achieved using inputs from DME/DME or GNSS.
Many existing aircraft can achieve P-RNAV capability without additional onboard equipment."
http://www.ecacnav.com/downloads/P-R...20notices).pdf
As Perfomance Based Navigation continues deployment in Europe and around the globe, you will see additional equipment requirements. Perhaps it is of interest to you that PBN requires certification of avionics, pilots, and pilot training programs.