Report - Master Telecommunications Plan (MTP) (Wireless Facilities)

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APPENDIX A. WIRELESS TECHNOLOGY PRIMER It is both appropriate and prudent that the development of policies governing the location, height, and design of wireless telecommunication facilities consider technical requirements. This section is designed to introduce the basic principals and concepts of wireless telecommunications. Wireless Transmissions The most common wireless device is a portable or hand -held phone, more commonly referred to as a cell phone. This device receives and transmits radio signals from/to an antenna mounted on a tower or other structure. Wireless calls (transmissions) are transmitted through the air via radio waves at various frequencies. Cellular transmissions differ from television and radio transmissions in that cellular transmissions depend on a network of cell sites spread out over the service area whereas television and radio rely on one tower to provide service throughout a large region. The area covered by an antenna set is commonly referred to as a cell. The signal is routed to switching equipment that selects the channel and monitors the signal strength. In telephone applications, the signal normally is connected to the conventional or landline public telephone system (loop exchange carrier). If the communication device is moving, the signal is passed on to an antenna in an adjoining cell and the call continues uninterrupted. Figure 15 shows a typical honeycomb cell network configuration in which cell sites are linked to provide coverage over large geographical areas. The mobile telephone switching office (MTSO) in the center cell is the central office for the entire cellular system and is linked to the public switched telephone network (PSTN), which allows calls to be made over landlines from/to mobile units. Figure 15. Generalized cellular network configuration Source: Mark Brose, June 1997 Wireless networks are engineered to locate antennas spaced just far enough apart to provide the coverage needed. Antennas spaced too closely will cause signal overlap and create interference problems. Antennas spaced too far apart will create "gaps" or "holes" in the coverage and will result in calls being "dropped" as a traveler moves beyond the range of the antenna handling the call. Each cell can handle a limited number of conversations at one time. When the signal traffic in a cell reaches capacity, additional cells are required to provide additional system capacity. The network described above represents a typical configuration for a single wireless service provider. Each service provider operates a discrete network of sites, which operate at different frequencies and are developed based upon each carrier's unique service requirements. In addition to technical design requirements, the location and height of an antenna support structure is determined by other factors including underlying local zoning, the ability to secure a land lease, and public sentiment. In many cases the same site or structure may be utilized by multiple service providers, however the antennas and other equipment being used can not be shared[9]. The planning of cell networks is highly proprietary and collaboration among competitors in locating sites is a rarity, if it occurs at all. Licensing The FCC, through public auction, sells spectrum by geographical region. The federal government protects against interference problems from occurring by awarding exclusive use of separate, specific frequencies to each station in a region. Frequency is a finite, limited resource