BROADBAND COMMUNITIES is the leading source of information on digital and broadband technologies for buildings and communities. Our editorial aims to accelerate the deployment of Fiber-To-The-Home and Fiber-To-The-Premises.
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MAY/JUNE 2016 | www.broadbandcommunities.com | BROADBAND COMMUNITIES | 43 elevator doors provides coverage to the elevator cars. However, modern elevator construction and speed and the increasing numbers of elevators in each bank make this method more and more unpredictable. Because signal strength loss from a lobby antenna through a set of elevator doors can be as high as 30 dB, the signal may be adequate only when the elevator is directly adjacent to the lobby. Tis makes meeting building service requirements very difcult. Some design choices create further challenges. For example, elevators that cover only part of a building and bypass certain foors make coverage between foors for the entire elevator journey almost impossible. High-rise buildings with multiple wireless sectors require handofs between the coverage areas as the elevator passes through the diferent zones. As a mobile device travels from zone to zone, these multiple handofs lead to an increased possibility of dropped calls inside the elevator. Finally, attempting to provide wireless service from an elevator lobby can be expensive because equipment dedicated to providing elevator coverage is needed on every foor. ANTENNAS AT THE TOP OR BOTTOM OF ELEVATOR SHAFTS Te second traditional solution is to mount antennas at the top or bottom of an elevator shaft. Typically, high-gain antennas radiate high power to food the area with coverage. Because radio signals attenuate as the car moves farther from the antenna, this solution is most efective in mid-rise buildings, in which elevator shafts are relatively short. A NEW COVERAGE SOLUTION A third way to provide wireless coverage inside elevators is to mount a remote antenna on the roof of each elevator car. Tis solution addresses the shortfalls of the traditional elevator coverage methods already discussed. It creates a dedicated zone of wireless service that travels with the car as it moves up and down through the elevator shaft. Tis eliminates device hunting or handof from one wireless zone to another as the car moves from foor to foor – the mobile device always remains within the same coverage zone. In addition, it eliminates wireless signal attenuation caused by locating antennas away from the car – either at the top or bottom of a shaft or in an elevator lobby – and thereby guarantees a strong signal. With this solution, consistent wireless performance is ensured regardless of whether an elevator is on the bottom foor, on the top foor, somewhere in between or moving between foors. An elevator car–mounted antenna solution requires appropriate cabling infrastructure, remote unit size, feeder hub fexibility and multifrequency support. Te distributed antenna system (DAS) that supplies an on-car remote unit must use a fber optic cabling infrastructure from end to end. Te 1/2-inch coaxial cabling that traditional DAS solutions use is too heavy and infexible to be installed along with the other cables that connect an elevator to its electrical power source. In contrast, fber is light and fexible, and it supports distances of up to 2 kilometers, so it has ample performance and reach to deliver multicarrier wireless signals to an elevator car, even in the tallest buildings. Te remote unit must be small enough and light enough to mount on the roof of an elevator car. Many DAS solutions on the market today use chassis-based remote units that are too large and heavy. Te feeder hub that drives the remote units must be as scalable and fexible as possible. Ideally, installers would mount this hub at the top of an elevator bank or in an adjacent wiring closet and use it to drive individual remotes on the tops of multiple elevators. A scalable hub should be modular and able to drive at least eight remotes. Finally, the remote units must support multiple frequencies and services. Diferent mobile operators use diferent frequencies, such as 850/1900 MHz, 700 MHz LTE and 2100 MHz AWS, and predicting which frequencies will be needed inside elevator cars in busy buildings is impossible. In addition, mobile operators license new frequencies every few years. If possible, a remote unit should not only support all current frequencies but also accommodate new services in the future without requiring a hardware upgrade. Te system shouldn't have to be physically upgraded each time a new frequency appears (which is a common occurrence). In addition, the system should accommodate public safety services. Supporting multiple frequencies and services will signifcantly reduce the total cost of ownership of an elevator coverage system. In short, the ideal solution for wireless coverage within elevators is an all-fber DAS that uses small remote units, has fexible and scalable hubs and has a wideband architecture that supports current and future frequencies without requiring hardware upgrades. Wireless coverage inside elevators has usually required overprovisioning of remote antennas in areas near the elevator doors, generally resulting in a costly, suboptimal solution. A car- mounted remote antenna system delivers superior coverage and performance at a reasonable cost, ensuring happy building owners, tenants and visitors. v John Spindler joined Zinwave as vice president of marketing and product management in November 2015 and has more than 30 years of product management and marketing experience in the wireless and telecommunications industries. Contact him at john.spindler@ zinwave.com. Distributed antenna systems for elevator car– mounted units require fber optic cabling from end to end.