It is impractical to survey the entire oceanic regions 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 this environment, ATC must rely on pilot position reports as the primary means for separating traffic. Fixes on oceanic routes are mandatory reporting points. Pilots must submit a position report when crossing these fixes. ATC plots the location of aircraft and may issue speed instructions, altitude assignments, or course changes, but they can not issue radar vectors.
In the real 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 are the INMARSAT satellite network and the use of the HF "SELCAL" system to alert pilots with a "ping".
Once inside the Oceanic FIR and established on the oceanic route, position reports will be compulsory. That means when you cross each waypoint forming the oceanic route, you are required to submit a position report to the FSS.
The report consists of the following elements:
* The fix you just crossed and time you crossed it
* Estimated time to next fix and fix name
* Airspeed / Mach number
* Optional - winds aloft direction & speed, and outside air temperature (OAT).
Here's an example of a pilots submitting a position report:
AAL1028: "San Francisco Radio, AAL1028. Position on 131.95."
KZAK_FSS: "AAL1028, San Francisco Radio. Go ahead."
AAL1028: "AAL1028 is position DEROK at 17:15 Zulu, FL360. Estimating DANKA at 17:55 Zulu, DUFFE next. Mach point 84, ground speed 510. Over.
KZAK_FSS: "AAL1028, San Francisco Radio, copy position."
To separate traffic on the oceanic routes, ATC has several methods for insuring separation. The two most likely that will be used, are to separate you vertically by assigning or changing your cruise altitude, or adjusting your airspeed by specifying a mach number. You may also be given time restrictions, such "Cross <fix> at or after <time>."
the SELCAL system was devised to free pilots from having to monitor the HF frequency over the long over water flight. Aircraft are assigned a unique SELCAL code during the flight. The code is an electronic "out-of-band" signal that is transmitted on the HF frequencies. The aircraft is equipped with a SELCAL decoder that recognizes its assigned SECAL code and alerts the pilot with a "ding" sound. The pilot then turns up the radio and listens for a message to him.