Abstract: A wireless LAN mobile station is capable of decreasing the frequency of handovers. The wireless LAN mobile stations 1-1 to 1-N are configured to calculate the number of executing the handover processes in unit time and change a threshold value serving as a criterion for executing the handover process on the basis of the calculated number of handovers.

Abstract: A wireless LAN mobile station stores a threshold value serving as a criterion for executing a handover process and which is increased on the basis of other conditions in addition to a received signal strength indicator (RSSI) so as to facilitate the execution of the handover process and expedite the breaking of association with the current association device, thereby allowing the wireless LAN mobile station to make an association with an optimal association device.

Abstract: When a basic amino acid is produced by culturing a microorganism having an ability to produce the basic amino acid in a liquid medium under an aerobic condition to produce and accumulate the basic amino acid in the medium, pH of the medium is controlled to be 6.5-9.0 during the culture, and 7.2-9.0 at the end of the culture, and a culture period where 2 g/L or more of hydrogencarbonate ions and/or carbonate ions exist in the medium is secured during the culture by controlling pressure in a fermentation tank to be a positive pressure during the fermentation, or supplying carbon dioxide gas or a mixed gas containing carbon dioxide gas to the medium, so that the hydrogencarbonate ions and/or carbonate ions should serve as counter ions of cations mainly consisting of the basic amino acid.