Fixing "Dropped Call" Issues on Long, High Bridges
Users on long bridges all over the world have a well known common cellular quality-of-service problem; in many cases the call is dropped at some point in the middle of the bridge.
Usually, this is due to the fact that the high, central section of the bridge is exposed to many surrounding BTSs resulting in multiple strong signals being received by the handset.
In such a case, creating a dominant signal which is significantly higher than the other carriers is the solution.
Installing a regular wide angle antenna to cover the bridge is the wrong solution.
Although the signal over the bridge might be high, the wide spread beam will cause interferences on the other bank of the river.
The correct solution is to install a very narrow beam, high gain directional cellular BTS antenna for this application thus minimizing interferences on the opposite bank.
This solution has been implemented on many bridges worldwide. The one shown below is the newly built bridge in Vladivostok, Far Eastern Russia. This bridge is about 2km long and 65m high above water level.
Installing a single VEGA very high gain antenna with 5⁰ beam width on one end of the bridge created a dominant signal enabling high quality, no dropped call service all along the bridge and minimum added interference.
As shown below, 1800 and 2100 MHz carriers were multiplexed into the VEGA antenna for customer’s best capacity and service.
Drive test team reported excellent QoS.