Cellular frequencies in the United States are allocated by the US Federal Communications Commission. As cellular mobile telephone technology has evolved over time, periodically bands of frequencies are reassigned from other radio services. Companies wishing to provide cellular services in a geographic region compete for the right to license radio spectrum in spectrum auctions. Different cellular companies in the same region may use different levels of cellular technology and different parts of the radio spectrum. In addition to radio frequencies used to connect handsets with cellular base stations, other parts of the radio spectrum are used to interconnect base stations and the wired telephone network. Some frequency bands may be vulnerable to interference by existing services in adjacent frequency bands, such as UHF television broadcasting. United States Carrier Bands Distribution and regulation The usage of frequencies within the United States is regulated by the Federal Communications Commission (FCC). When distributing initial spectrum licenses in a band the FCC divides the US geographically into a number of areas. A mobile operator (or other interested party) must bid on each area individually. A license owner can use any technology within the licensed area and frequency range subject only to the band rules defining various analog limits. A license owner can also partition the license (split geographically) or disaggregate it (split the whole licensed frequency range into two sub-ranges). Whole, partitioned, and disaggregated licenses can be sold to virtually any other entity. The Cellular band occupies 824–849 MHz and 869–894 MHz ranges. To issue cellular licenses, the FCC divided the U.S. into 734 geographic markets called Cellular Market Areas (CMAs) and divided the 40 MHz of spectrum into two, 20 MHz amounts referred to as channel blocks; channel block A and channel block B. A single license for the A block and the B block were made available in each market. The B block of spectrum was awarded to a local wireline carrier that provided landline telephone service in the CMA. The A block was awarded to non-wireline carriers. In 1986, the FCC allocated an additional 5 MHz of spectrum for each channel block, raising the total amount of spectrum per block to the current total of 25 MHz. The wireline/non-wireline distinction for Cellular Service licensees no longer exists. The 1850–1990 MHz PCS band is divided into six frequency blocks (A through F). Each block is between 10 MHz and 30 MHz in