Electronic Warfare Operation Can’t Be Cleared from 1755-1850 MHz Band, CSMAC Report Concludes

A Commerce Spectrum Management Advisory Committee working group concludes in a report slated to be presented Wednesday that satellite control systems and electronic warfare operations can peacefully co-exist with LTE operations in the 1755-1850 MHz band. But it also warns that electronic warfare (EW) systems can’t be cleared from the spectrum because of national security needs. The band is targeted by the wireless industry for clearance where possible and sharing where clearance won’t work. Carriers are focused in particular on the lower part of the band -- 1755-1780 MHz (CD June 19 p11).

Industry officials who are closely following CSMAC said the report is the first on the 1755-1780 MHz band to provide so much detail, though final reports of other CSMAC working groups are also expected to be presented at Wednesday’s meeting.

On electronic warfare, the report said research, development, test and evaluation (RDT&E) are important as are training and large force exercises (LFE) using the spectrum (http://1.usa.gov/12HxdQ2). The report said these training exercises can take place in the band on Department of Defense ranges on a non-interfering basis through coordination. “Relocation of EW systems from the 1755-1850 MHz band would leave U.S. forces unprotected and vulnerable from threats operating in this band and is therefore not a viable option,” the report said. The importance of EW capability “has been clearly demonstrated in current operations in Iraq and Afghanistan, where U.S. forces have successfully countered radio controlled improvised explosive devices ... saving countless lives and protecting vital operations.” The report notes that sharing will be complicated. “Enhancements to existing procedures must take place to enable commercial wireless broadband service while maintaining EW RDT&E, training and LFE capabilities in and around approved federal test and training ranges and operating areas.”

"With respect to potential harmful interference caused by LTE devices to satellite control systems (SATOPS), working group analysis found negligible interference predicted to all satellite programs except possibly a few experimental spacecraft based upon current deployment and operational assumptions,” the report said. “A power flux density of -179 dBW/Hz/m2 was determined to be a safe interference level for satellites in geostationary orbit. Specifying the protection level for geostationary orbit also protects satellites at other altitudes.” SATOPS ground stations also don’t pose a major problem for LTE base stations, the report said. “Analysis showed that the SATOPS ground stations only radiate a relatively small percentage of the time: 8-13 percent of the time in the lower portions of the band ... with higher radiating percentages in the upper ... portions of the band. Analysis found that when the SATOPS ground stations radiate, they only use a small fraction of the overall band (typically 0.2 to 4 MHz of the 1761-1842 MHz band) at any one time.”

The report also found there are a “number of technologies and techniques with significant potential to mitigate harmful interference when it does occur.” Rick Reaser of Raytheon, who presented an update on the group’s work at the June 18 CSMAC meeting, said the group just that day had gotten data back on interference between handsets and satellite receivers (CD June 19 p4).

The report also said NTIA should recommend that the FCC, in consultation with NTIA and other federal agencies, “develop methods for licensees in the 1761-1842 MHz band to demonstrate technologies or techniques that ensure commercial operations can accept interference from the satellite operations when operating within the zones where the nominal SATOPS power is expected to exceed the LTE interference threshold.” The FCC should also require that licenses that make use of the 1761-1842 MHz portion of the band provide a “technical showing of compatibility with satellite uplinks.”