a plurality of base stations in respective adjacent or neighboring cells, wherein the respective base stations are capable of communicating and share a channel on a space, time, and/or frequency basis;

wherein each base station that has a multi-user detection function determines that a first mobile station outside a local cell thereof approaches a boundary with a neighboring cell based on detection of a transmitted signal from the first mobile station for identifying a user, and said base station mixes and synthesizes a synthesized signal including user data for a second mobile station within the local cell and control information for the first mobile station outside the local cell and outputs the synthesized signal at a frequency;

wherein the multi-user detection function applies a successive interference cancellation technique to distinguish a first signal transmitted at the frequency by the first mobile station from a second signal transmitted at the same frequency by the second mobile station,

the synthesized signal being used to perform a handoff of the first mobile station from a base station corresponding to the neighboring cell to the base station corresponding to the local cell without conducting any communication other than communication with a mobile station.