Repeaters have to be employed in metros to meet the coverage requirements because leakage cables and free spaces are much more spoiled due to high frequency of 3G signal.

• 由于3G信号频率高,在地铁中的泄漏电缆损耗和空间损耗将大大增加,为了达到覆盖要求,必然要引入中继放大。