5.6 Elevator Coverage
Mobile users inside a building expect a good quality coherent service level throughout the building, the elevators included. It is a major challenge to service elevators with RF coverage, and requires special consideration. Most elevator lift-cars are a virtual metal enclosure with very high RF attenuation, often exceeding 60 dB. The speed of the elevator adds to the challenge, especially in very high buildings with high-speed express elevators. However, the demand for mobile coverage inside elevators is growing, primarily motivated by the normal requirement for voice and data coverage everywhere. The mobile is also considered as an extra security line by the users, even though there is an emergency phone installed inside most lifts. Therefore mobile coverage inside elevators is a must.
There are several options on how to provide mobile coverage in the elevator; the optimum approach depends on the individual solution and the constraints of the actual elevator installation. The best mobile performance is achieved if the RF design is done so that there will only be one dominant cell covering the elevators throughout the building, thereby avoiding handovers inside the lift. However providing sufficient coverage inside the lift-car can be a challenge and sometimes close to impossible, due to the metallic enclosure of the lift-car.
In small to medium-sized buildings it might be preferable not to have a dedicated cell for the elevator only, but to use one of the ...