Kontinuerlig bedömning och eliminering av interferens i ett mobilt landradiosystem

摘要

In a land mobile radio system including at least one base site having a system for interconnecting a plurality of radio channel units with a plurality of directional antennas and/or antenna beams, the base site further includes an interference avoidance system for controlling communications between each radio channel unit of the base site and mobile radio units communicating with the base site so as to avoid causing potential interference at the operating frequency of each radio channel unit at other base sites. The interference avoidance system monitors potential interference at the operating frequency of each radio channel unit on each antenna beam. If potential interference exists on an antenna beam determined to be the antenna beam best suited for transmitting and receiving signals at the operating frequency of the radio channel unit, a determination is made if adjacent antenna beams have reduced chance of potential interference and sufficient signal strength for communication and therefore are better suited for transmitting signals at the operating frequency of the radio channel unit. To further enhance interference avoidance, a comparison is made of the signal strength of received signals at the operating frequency of the radio channel unit with one or more threshold values to assess the proximity of the mobile radio unit to the base site, and the transmission signal strength for signals transmitted from the radio channel unit to the mobile radio unit are controlled based on the proximity assessment.