SATWAYS - Satellite Integrated Facility Management and Radio over IP Gateway

The SATWAYS system has been fully developed, validated and documented. Prior to its deployment, the services provided by the SATWAYS system were rigorously tested in the lab and in an end-to-end manner under a variety of strenuous conditions representing extreme system and network loads.

The peak call setup delay that was recorded was 1.06 seconds, while the peak end-to-end delay equaled 392 msecs. The packet loss remained below 0.5% at all times, so the voice quality requirements that were put forth in the beginning of the project were covered. Consequently, the objective voice quality metrics indicated a very good quality of service. The remaining services (control/monitoring, video surveillance and weather monitoring) were also functionally and performance tested to prove that they operated as expected.

The system was installed at the heliport of Patmos and HCAA headquarters and the pilot phase was initiated at 20:00 Hours on September 18, 2008. In the meantime, the pilot trial experienced two long interruptions. On the 20th of January 2009, the ODU at HCAA headquarters failed and was finally replaced on the 6th of March 2009 due to supply chain problems. On the 18th of December 2009, the project partners were informed that the carrier the system was using could no longer be used, due to ESA release of HellasSat2 capacity, so SATWAYS was once more shut down. HCAA, together with inAccess Networks put a lot of effort in finding access to another carrier via the Hellenic Ministry of Transportation and Communications and they finally achieved their goal on the 30th of April 2010. The new carrier resides on a different transponder, such that a change of the RF head was required. The necessary components were purchased and installed. The SATWAYS system resumed operation on the 17th of May 2010 and the pilot testing phase was resumed to proceed with a final review on October 6, 2010. The carrier is still available to HCAA, so the pilot phase still continues.

With the invaluable help of HCAA, a user acceptance test plan was compiled, so that flight controllers could evaluate the operation of the system in operational conditions. The approach used was based on questionnaires inspired by the CARS (Controller Acceptance Rating Scale) method devised by USA’s Federal Aviation Authority to test new systems for radio communications in ATC. User ratings were impressive and revealed full compliance to the above mentioned requirements and proper operation of the QoS mechanisms which enforce them.

The users rated the system with an average of 8.67 on a scale from 1 to 10 (10 is best) regarding voice quality and an average of 1.44-1.61 on a scale from 1 to 10 (1 is best) regarding the effect of delay on their perception, effectiveness, timing, correct phraseology and speech rate. The SATWAYS system has been used numerous times for operational activities, however, the controllers were rating it in writing only when their workload was reduced and flight safety was not compromised by their actions.

It has to be noted that the SATWAYS system has been used and evaluated not only during the control of VFR flights (that is helicopters which were the original target), but also for IFR flights, i.e. speedy airplanes rushing through the Greek skies through extremely dense regions of our airspace. Taking into consideration that, to the best of the knowledge of the authors, there exist no publications that present a similar system or a similar trial, this outcome is considered truly original.

To put the SATWAYS project in a nutshell, the use of Radio over IP over satellite can be used in the ATC environment, in support of even the most demanding missions, such as control of a jumbo jet doing 950 km/h just 5 nautical miles away from another one, when delays can be lethal. The biggest reward was Report #18, within which the responsible controller wrote:

“This was a flight with destination the Patmos heliport. The frequency was checked upon departure from the heliport of Mykonos (translation note: another island about 45 miles West of Patmos) and throughout the flight until landing at the heliport of Patmos. At a distance of 15 nautical miles east of the RIPLI region (translation note: controller jargon for an area within the Greek airspace), the pilot reported a 5/5 radio communications quality and so did the flight controller with little noise. At 20 nautical miles west of Patmos and at a flight level of 1500 feet, both the pilot and controller reported a 5/5 quality. Beginning the descent to the Patmos heliport, both the transmission and reception were exceptional. On the ground, the communication quality was also exceptional and the flight plan has been closed using radio comms. The pilot has expressed to me his admiration, since traditionally this area had no radio coverage. I consider that the use of satellite communications is a success and covers our requirements for the heliport up to ground level”

“Albert Einstein once said imagination is more important than knowledge. We combined both, in the development of SATWAYS,” remarked Mr. Constantine Simaiakis, Chief of HCAA’s Communications, Navigation and Surveillance Division, Communications sector and responsible for the SATWAYS project on behalf of HCAA. “We are creating an anthropocentric system aiming at the provision of communication and a variety of other services both reliably and efficiently in the Air Traffic Management domain, in environments where legacy systems fail.”

Selected project dissemination includes a highlighted publication in the IEEE Communication Magazine, D&I series, August 2008 issue, introduced by a flattering editorial, which has already generated significant feedback, as well as a presentation in Space Application Days, Toulouse Space Show, France, April 22-25, 2008. Moreover, a research paper on E-model adaptation for satellite IP radio calls in Air Traffic Control is currently under evaluation by IEEE JSAC. Furthermore, a press release on the successful installation and operation of the system appeared on the ESA Telecom web news on 05 Nov 2008. A Springer book publication summarizing the most important results achieved throughout the SATWAYS project is also under preparation.

Figure 9: Antenna installation on top of the Athens International Airport approach tower at Hellenicon, Athens, together with Mr. Simeakis, HCAA representative for SATWAYS click for larger image

Figure 10: Heliport antenna assembly click for larger image

Figure 11: The heliport equipment rack click for larger image

Figure 12: The heliport VHF antenna and IP camera click for larger image

Figure 13: The heliport Vaisala AWS520 meteo station click for larger image