When prime real estate is too expensive or unavailable, the natural tendency is to look for reasonable alternatives. This same dynamic applies to space segment in satellite communications. Ku-band is divided into two major spectrum segments: conventional and extended. The conventional segment is exclusive to the FSS sector, while the extended segment is shared by other services. Cost and unavailability in conventional Ku-band have pushed users to look for options in the extended Ku-band.

Conventional and Extended Ku-Band

The conventional Ku-band is confined to 14.0-14.5 GHz in the uplink and 11.70-12.20 GHz in the downlink. This is a total of 1000 MHz for uplink and downlink combined — 500 MHz each way.

Extended Ku-band is not quite so symmetrical. In fact, for a long time, only the downlink had an extended component, with no corresponding extended bandwidth on the uplink. This changed in the mid-1990s when the U.S. Federal Communications Commission (FCC) allocated uplink bandwidth to fixed satellite services in extended Ku-band. The uplink portion rests in the 13.75-14.0GHz segment. This part of the electromagnetic spectrum traditionally was allocated to radiolocation services (i.e., finding the position of something through radio waves). Now, FSS players share this band with radiolocation on a co-primary basis.

Rationale for Extended Ku-Band Allocation

Why allocate additional spectrum to the extended Ku-band? One reason was to balance the uplink and downlink, however, U.S. global competitiveness and the efficient use of resources were the primary rationale. International satellites had been offering services in the extended Ku-band for years and, thus, provided options not available from U.S. satellites. The drive to promote U.S. economic growth by making its satellites more competitive in the international arena was a primary driver for the extended Ku-band allocation. There also was the idea that if a satellite was to be in orbit using a scarce geostationary arc slot, it might as well be used to provide all possible services. A satellite that can offer more bandwidth is more efficient because its cost per channel decreases.

Applying for Extended Ku-Band

Because fixed satellite and radiolocation services have co-primary rights, a downside of extended Ku-band is that frequency coordination is necessary. In fact, radiolocation services in this band primarily are government sites, and frequency coordination with the government is not known for lightning speed. Rather, it is a lengthy and time-consuming process requiring the performance of certain technical studies. Returning to the analogy of the not-so-prime real estate, think of extended Ku-band as buying a parcel of land with an easement through the middle of the property. Accordingly, it would have to be priced attractively, or there would have to be few other options for you to agree to buy it. Other restrictions in the extended Ku-band include a minimum Earth station diameter of 4.5 meters as well as limitations on transmit power. On top of that, RF equipment must be specially outfitted to operate in extended Ku-band.

There is a 50MHz uplink slot in extended Ku-band that deserves particular attention. This is the 13.75–13.80 GHz segment used by the Tracking and Data Relay Satellite System (TDRSS), a space-to-space link operated by NASA, and users intending to use this 50MHz slot also must coordinate with the space agency.

Conclusion

Extended Ku-band increases space segment availability, promotes satellite efficiency, and makes better use of scarce orbital slots. No one should be discouraged from making extended Ku-band part of their network plans, however, if you intend to use extended Ku-band, you should plan accordingly for dealing with all of the restrictions and contingencies that might come with it.

Raul Magallanes runs a Houston-based law firm focusing on telecommunications law.
He may be reached at +1 (281) 317-1397 or by email at raul@ rmtelecomlaw.com.