All spectrum in the US and generally internationally is controlled by each country's equivalent of the FCC.  In some cases and some countries portions of the spectrum are set aside for general use such as license-free networks.  Part of the spectrum in most countries is controlled for military use, public safety and commercial services.  Only the entities so entitled may use the frequency bands they have rights to.  Considering the wide variety of International differences in other areas of public policy, radio spectrum is remarkably homogenous. 

In each country, there are portions of the spectrum set aside for commercial purposes.  Some examples of this are broadcast TV spectrum in the 700 MHz range in the US recently auctioned for broadband wireless use, or PCS cellular spectrum widely licensed across the US at 1.9 GHz.  In Europe and much of Asia, the 3.5 GHz spectrum range is used for broadband wireless, but not in the US.  This particular spectrum range could be described as the worldwide de-facto broadband wireless spectrum due to its commonality in so many countries.  In virtually all cases only the spectrum licensee can build infrastructure and offer services across its spectrum range.  This allows much higher power output without interference across the band, facilitating improved QOS.  In the US, the most readily usable licensed broadband wireless spectrum is at 2.5 GHz.  There is also licensed spectrum at 2.3 GHz and 1.9 GHz that could be used for broadband wireless commercial service delivery. 

Among the most sought after spectrum currently available in the US (and widely available internationally also) is the 2.5 GHz range.  This is very effective for the delivery of point to multi point signal to many users.  The spectrum range supports robust bandwidth capability and with licensed power allotments and WiMAX technology it supports NLOS capability and far reduced or eliminated truck roll installations.  Users can often self-install.  There are two types of 2.5 GHz licenses.  One is broadband radio service (BRS), the commercial version of the license.  These licenses can be owned by commercial companies and bought and sold basically at will.  The second is educational broadband service (EBS) which can only be owned by educational or religious type organizations with a scholastic mission.  In the US, the Catholic Church is a major holder of this spectrum.  These licenses can be leased for use by commercial entities.  In the US, Sprint/Nextel control about seventy percent of the BRS/EBS licenses .  Clearwire controls approximately another fifteen percent---with the balance held by several smaller block holders.  In fact, Clearwire and Sprint concluded a deal shifting some of Clearwire's licenses in metropolitan areas to Sprint in exchange for a larger number of rural or smaller tier city licenses prior to the two companies agreeing to merge their combined 2.5 GHz assets; a deal which should close late in 2008. 

There are special rules for a type of licensed spectrum for certain point to point links whereby multiple spectrum holders can co-exist in the same area and use licensed spectrum.  This type of PTP link is typically used for robust interference free backhaul.  It features highly focused, high gain antennas that deliver very tight beam signals.  In almost all cases, many users can be accommodated without interference.  There is spectrum in the US for this purpose at 900 MHz, 2.0 GHz, 6 GHz, 11 GHz, 18 GHz, 23 GHz and 39 GHz.  Any company that can pass the frequency coordination process (to ensure minimum or no interference) can purchase a PTP license in these bands.  It should be noted that the FCC for various reasons rarely approves PTP licenses in the 900 MHz or 2.0 GHz range.  The sweet spot for industry due to cost and capability factors seems to be the 18 GHz range, particularly when used with Ethernet radios versus packet switched technologies. 

For many years prior to the advent of fiber optic cable the nation's Telcos used 6 GHz and 11 GHz links primarily to backhaul phone service across the US.