Late Decision Expected on Protection Value for FSS Systems

Difference of opinion over the value is the major unresolved technical issue, a HAPS proponent said. Satellite and HAPS proponents have been divided over a wide range of issues on the systems (CD June 14/10 p12). Lockheed Martin, Northrop Grumman, AeroVironment, Boeing, NASA and Stratocomm have done various tests or are developing solutions for commercial and defense purposes, the proponent said. A November ITU-R meeting will debate proposed values for the power flux density (PFD) limit, he said.

The value, if agreed upon, would be used in an ITU-R recommendation for HAPS modeling associated with the WRC-12 agenda item on identifying two 80 MHz channels in the range of 5850-7075 MHz for gateway links to support operations in the fixed and mobile services. Gateway links are needed for reaching other service links, including possibly international mobile telecommunications (IMT), the international standard for advanced wireless communications, the HAPS proponent said. The gateway link would be compatible with and spur IMT systems for underdeveloped, underserved and rural areas, he said. Discussion is focusing on the range of 6440-6520 MHz (down), and 6560-6640 MHz (up).

One recent hiccup for the HAPS camp was the inclusion by U.S. satellite interests of an additional spot beam classification into a table with the derivation of equivalent PFD values to protect geostationary satellite receivers, the proponent said. The value for the spot beam, -183.9 dBW/m2/4 kHz, is more stringent than the values for the other beams, he said. That referred to -163.7 for a global beam, -167.7 for a hemispheric beam, -172.7 for a semi-hemispheric and -177.7 for a regional beam.

An initially proposed value of -213 dBW/m2/4 kHz was later revised down to -177 dBW/m2/4 kHz in submissions by the U.S. and South Korea, the proponent said. “This is clearly a major mistake” pointed out by South Korea and other participants in an ITU-R meeting on fixed wireless systems, he said.

The PFD from the emissions of an individual transmitting HAPS gateway station at the geostationary orbital (GSO) arc shouldn’t exceed a certain, not-yet-agreed-upon threshold to protect receiving FSS stations. So said the last report from the chairman of the ITU-R group developing the HAPS modeling recommendation. The proposed options for the threshold are -177.8 dBW/m2/4 kHz and -183.9 dBW/m2/4 kHz, the proponent said. Intelsat and a U.S. satellite consultant in July reiterated the desired -183.9 dBW/m2/4 kHz value and was preparing to ask the ITU-R working group developing the HAPS recommendation to adopt it. The U.S. WRC-12 position on the agenda item is for no identification of frequencies for gateway links. The value is needed to protect “extensive and dense use” of the band by incumbent users, satellite consultant Don Jansky said.

There’s an outstanding difference of 6 dB, the proponent said. The chairman’s report said an “error” was put forward by an ITU-R satellite working group addressing the concerns. The chairman’s report notes a 30 dB correction from the satellite group’s initial assessment of the interference impact from a transmitting HAPS gateway station into a receiving FSS space station, the proponent said. A HAPS proponent said the analysis used by satellite interests to calculate the value for the other types of beams can’t be extended to spot beams, we've learned. HAPS proponents said satellite interests must provide more detail to derive the needed PFD value. A satellite executive said a new methodology would then need to be submitted to ITU-R for consideration. Approval of a new methodology would likely delay a decision on the value until after WRC-12.

HAPS systems aim to provide fixed and mobile services, and access to Internet, without having to build out towers, the proponent said. “Clearly, satellite services are too expensive.” A number of HAPS systems are in various stages of development, trial and testing, he said.

The WRC-12 preparatory report has two approaches for addressing the agenda item, the HAPS proponent said. The no-change approach is driven by space interests who don’t want new entrants in the Radio Regulations, he said. The second approach is driven by the HAPS community, he said. The proposed regulations will lay down the conditions for use, including additional opt-in footnotes for administrations, he said. The changes are for an identification of spectrum, not an allocation, he said.

The proposed changes will spur national regulatory decisions to use new technologies in domestic networks, the HAPS proponent said, including an alternative to fixed point-to-point relays. The option for a footnote will enable administrations to allow introduction of new technology provided it meets requirements for protecting other services, he said. Australia, Bangladesh, Lebanon and some African countries have publicly supported the systems in ITU or other meetings, the proponent said. Some have said they would like to add their names to a regulatory footnote for HAPS gateway links in the proposed frequencies. More interest will likely emerge before the start of the January conference, the proponent said. The WRC-12 will consider approving a regulatory provision for countries that want to use the systems.

Opponents of HAPS systems suggest using higher bands for the gateway links for connecting with public service networks to reach worldwide fixed and mobile services and other platforms, and for providing reliable access to the Internet, the proponent said. The WRC-12 preparatory report says: “HAPS gateway links may be able to make use of the existing identified spectrum in the bands 47.2-47.5 GHz and 47.9-48.2 GHz.” The gateway links, like feeder links for a satellite system, can’t use higher bands because propagation isn’t as dependable, he said. The 47 and 48 GHz bands aren’t suitable for instant, constant, fixed and mobile service in an environment with rain fade, the proponent said.