Wireless Facility Components
Wireless infrastructure is highly integrated into the mosaic of urban and rural communities. An essential aspect of wireless communications is the requirement that antennas be elevated at a height above average terrain (HAAT or AAT) enough to propagate and receive line-of-sight radio signals to and from the coverage area.1 To accomplish this, structures are used to elevate and position antennas for the specific coverage objectives. Efforts to blend antennas into the surrounding landscape have resulted in stealth structural design to screen or block antennas from view.
Stealth-designed structures include flag poles and architecturally designed bell towers with antennas and waveguides placed inside the structure, fiberglass façades that block the view of rooftop antennas from the ground, and antennas painted to match the external color of a building. Monopole-style structures have evolved into designs such as coniferous trees with antennas embedded in the branches. In stealth examples, the process of positioning and designing antenna structures has become an art form, in addition to an application of high technology to real estate development.
Antenna Structure Types
Antenna structures fabricated for the communications industry are designed to meet industry standards.1 The primary types of antenna structures used for macro cell sites are lattice-style guyed towers, self-support communications towers (SSTs), specialized poles called monopoles, rooftops and sides of multi-story buildings, water tanks and towers, structures that carry electric power lines, grain elevators, windmills, smokestacks, and billboards. Microcell site facilities more commonly use the interior walls and ceilings of multi-story buildings, street light poles, traffic signals, sign poles, kiosks, posts, arches, and utility poles. Each type of communications tower has its own economics. It is more practical to use poles in urban areas where shorter antenna elevations are proposed, less ground space is available, or jurisdiction officials require stealth pole design.
All cell sites have elevated antenna and waveguide (coaxial or fiber-optic cable) connecting the antenna to radios and telecommunications demarcation boxes. On macro cell sites, the associated equipment is on-site.1 For microcell sites the associated equipment is mostly off-site. Whether on-site or off-site, radio transmitters/receivers or transceivers combined with power equipment, grounding system, and environmental controls, known as HVAC (heating, ventilation, and air conditioning) equipment, compose the associated equipment. The power equipment includes electric meters, a power transfer switch, a power cut-off switch, battery backup, and a backup generator.
On-site telecommunication interconnects link off-site fiber-optic cable transport service to on-site radio transmitters/receivers for transmission of communications traffic to the site from outside locations and from the site to destinations on the internet or in the public switched telephone network. Microwave radio systems serve as an alternative to contracting outside fiber-optic transport service providers to link the site to the internet and the public switched telephone network.
Some wireless carriers use microwave systems for backhaul to bypass the costs associated with contracting the fiber-optic transport service or to save on local telephone company (telco) transport costs. Microwave systems add additional elevated antennas, coax on the antenna structure, and microwave radios to the associated equipment on the site. A remote site’s microwave system works with similar systems on other sites of the carrier to route traffic to locations in their wireless network where the cost of external transport is reduced.
Mobile Switching Centers
This book does not focus on mobile switching centers (MSCs), which serve an integral purpose for wireless carriers and other telecommunications companies. These are also referred to as hubs with respect to small cell sites and distributed antenna systems. These computerized facilities manage and route all forms of communications traffic utilized in the wireless system throughout the public switched telephone network, the internet, and the cloud. For many network switches and system hubs, antenna systems and associated equipment are integral to the utility and function of the facility. As with equipment shelters at wireless cell sites, switches, and hubs are known for being windowless, environmentally-controlled buildings or rooms. They consume massive amounts of power from the local utility and have emergency standby power. A large pipe of telecommunications capacity for connections to the rest of the public switched telephone network, the internet, and the cloud is a basic requirement at switches, hubs, and data centers.