To provide a configuration to prevent the separation impossibility of two mobile users using the same channel.

According to the SDMA(Spatial Division Multiple Access) method, a beam forming device (32) used in each base station in a GSM(Global System for Mobile communication) is designed to spatially separate many users using the same channel permitted in a cell/sector by generating proper beam patterns (26, 28) to each of the many users using the same channel. However, there is a case that a CIR(Carrier to Interference Ratio) of one of the mobile users using the same channel monitored in a base station BS is deteriorated than a preset threshold. In this case, re-assignment of a channel is instructed to the user. Thus, it is possible for the same number of users in each cell/sector that the channel can be reused more strictly or the number of the users using the same channel in each cell/sector can be increased.