Thank you very much "Roger That" for your reply. It really helped deepening my understanding. Let me ask a bit more to clear still hanging fog in my brain.
1. To display ADS-B data of the target on the ATM screen, does it need special atenna or is it just a software upgrade of existing SSR?
2. Regarding the name of the waypoint, now I get why it does matter. ADS-C downloads what's in the FMS and compare the route with the filed route in the ATM. Fair enough. However it still doesn't answer the issue that I raised.For the NAT HLA, all coordinates that commercial aircrafts use, there're univeral 5 digit names of those using agreed coding rules as described in ARINC424. So it is not a problem as long as this is used both in the FMS and ATM system.
Problem comes when using the random route which include coordinates like N0500.0 E13530.0 (Half degree on the Longitude). It is neither a whole number nor a half degree LAT coordinate that NAT HLA uses. From a pilot point of view, we file a flight plan using a coordinate and insert this coordinate into the FMS. When inserting this coordinate, FMS fix name is created either 7 digit (05N135E) by default which doesn't show half degree or any name defined by a pilot. As a result it can't be the same between ATM(N0500.0 E13530.0) and FMS(Either 05N135E or ABCDE).
I hope my point is well delivered and any input would be highly appreciated.