Elevators are usually composed of thick metal sheets. After the elevator doors are closed, will form a Faraday cage which shielding electromagnetic and radio frequencies efficiently.
And elevator always located in the middle position of the building, so mobile phone signal loss a lot after passing through the walls inside a building. The tunnel effect in elevator shaft will reduce cellular signal transmission also. Thus, elevator needs to do mobile phone coverage.
Below are the five common solutions to help to achieve a good cell phone signal coverage in elevator cages. Please choose the coverage solution according to your country’s regulations and coverage requirements.
First of all, you need to install an outdoor antenna on the roof of the building to capture mobile phone signals. Then connect the outdoor antenna to the cell phone signal booster with coaxial cable. Finally and most important part is to install the indoor antenna(s) in a suitable location to rebroadcast amplified mobile phone signals to the elevator cage.
Solution 1) Omni antenna in the middle of elevator shaft
The first basic coverage solution is to install an omnidirectional antenna in the midst of the elevator shaft. The omnidirectional antenna transmits amplified mobile phone signals from the mobile phone signal booster. The disadvantage of this solution is if elevator cage is far away from the omnidirectional antenna will not receive amplified cell phone signals.
Solution 2) Directional logarithm or yagi antenna in each 3~5 floors
The second and mostly used coverage solution is installing multiple directional antennae in each of 3 or 5 floors. Directional antenna points down direction. The directional antenna transmits amplified mobile phone signals from the mobile phone signal booster.
Solution 3) Ceiling or Omni antenna in roof of elevator cage
This solution requires installing an omnidirectional antenna in the ceiling of the elevator. This omnidirectional antenna connects to mobile phone signal booster via coaxial cable.
Solution 4) Ceiling or panel antenna in elevator halls of each floor
The fourth coverage solution is easier to install and no need authorization or permission. It's similar to install repeater system in a building, and ceiling antennas install near the elevator's entrance on each floor. The ceiling antenna rebroadcasts amplified mobile phone signals to user passes through.
Solution 5) Radiating leaky coaxial cable in the elevator shaft
The final solution is to use the radiating leaky cable in the elevator shaft. It's the most efficient signal coverage plan and very easy to operate. However since the radiating leaky cable is too expensive so not used widely.