The Oceanic Environment is not serviced by Radar, therefore the only way ATC can provide you with separation, is by every aircraft telling them where they precisely are. To facilitate this, certain reporting procedures are put in place.
The primary difference between flying in this airspace and land-based ARTCC/FIRs is that it is impractical to survey the entire region with radar. Thus air traffic control is accomplished with time-honored non-radar procedures that were honed in the 1940s and 50s before radar coverage was common.
In the real-world environment, the primary communications means are over HF frequencies as opposed to normal land based VHF frequencies. This band is capable of much greater distance, but is highly susceptible to natural interference. Other methods of communications used in the real world are the INMARSAT satellite network and the use of the HF “SELCAL” system to alert pilots with a “ping”.