ters) long. Higher-frequency 10-gigahertz wavelengths measure 1.78 inches (3 centimeters). Because of their longer wavelengths, low-frequency signals travel farther than higher-frequency signals. Their longer lengths allow them to better withstand physical barriers such as rain and other solid materials. Thus, low frequencies can penetrate walls, buildings, and similar obstacles better than high frequencies. For these reasons, broadcast services such as those for traditional TV and for TV broadcasts designed for mobile devices typically use lower frequencies. Finite Spectrum for Wireless Networks In the United States, analog TV, formerly in the 700MHz band, was relocated to another portion of the spectrum for digital TV. Most of the 700MHz frequencies were allocated to mobile carriers to build high-capacity Long-Term Evolution (LTE) mobile networks. High-speed mobile data networks operate over a variety of spectrum, such as 700 MHz, 2.1GHz, and 2.6GHz. Higher frequencies require more closely spaced antennas because these signals fade over shorter distances. Spectrum Blocks Governments allocate spectrum in chunks of frequency bands that are measured in ranges of, for example, 12-, 15-, 22-, and 30MHz. The size of the spectrum band is determined by subtracting the lowest frequency of the range from the highest fre- quency (highest frequency minus lowest frequency). For example, if an organization is granted the rights to use the spectrum band from 785MHz to 800MHz, it has the right to a 15MHz band (800 - 785 = 15). Spectrum bands, which are set aside for specific services, are divided into blocks designated by letters of the alphabet. For example, within the 700MHz band (between 700MHz and 799MHz), the A block refers to a different block or range of frequencies within this larger range of frequencies than the B Block. The A Block might be allo- cated to one carrier in a region and the B Block to a different carrier to offer competing services in the same region. The Federal Communications Commission (FCC) auctioned