rs). Because of their longer wavelengths, low-frequency signals travel farther than high-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. High-speed mobile data networks operate over a variety of spectrum, such as 600MHz, 700MHz, 2.1GHz, 2.6GHz and 39GHz. Higher frequencies require more closely spaced antennas because these signals fade over shorter distances. New 5th generation mobile services will be based on high-gigahertz frequencies such as 39GHz spectrum. For the most part, cells in urban areas cover a smaller area, resulting in many small cells with small antennas rather than large towers. Smaller, closely spaced cells are needed to support dense amounts of high-data-rate mobile traffic in metropolitan areas with high-pedestrian traffic. www.TechnicalPDF.com 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 frequency (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 allocated to one carrier in a region and the B Block to a different carrier for competing services in the same region. As new technologie