Radio communication system and method therefor

A hand-over method comprising:

• generating time alignment information using a signal transmitted from a main base station in current communication with a mobile station and a signal transmitted from a sub base station in next communication with said mobile station;
• transmitting said time alignment information from said mobile station to said sub base station via said main base station;
• and
• performing a hand-over from said main base station to said sub base station after time alignment is performed at said sub base station.

A hand-over method comprising:

• comparing received power of data from another base station other than a main base station in current communication with a mobile station, using a first spread code, with a predetermined value;
• establishing said another base station as a sub base station when said received power of data from said another base station becomes higher than said predetermined value;
• transmitting same data as data to be transmitted to said mobile station by said main base station to said mobile station from said sub base station with a second spread code which is different from said first spread code;
• carrying out time alignment for said main base station and receiving time alignment information of said sub base station from said main base station when received power of data from said main base station is higher than received power of data from said sub station at said mobile station;
• and
• switching said first spread code to said second spread code for communicating with said sub base station when received power of data from said sub base station becomes higher than received power of data from said main base station at said mobile station.

A radio mobile station apparatus comprising:

• control circuitry that generates first time alignment information using a signal transmitted from a main base station in current communication with said mobile station and a signal transmitted from a sub base station in next communication with said mobile station, said first time alignment information for being transmitted from said mobile station to said main base station;
• and
• a decoder that decodes another signal transmitted from said main base station and a time aligned signal transmitted from said sub base station based on said first time alignment information,
• wherein said control circuitry carries out time alignment for said main base station when received power of data from said main base station is higher than received power of data from said sub station, and, when received power of data from said sub base station becomes higher than received power of data from said main base station, performs a hand-over from said main base station to said sub base station after performing time alignment for said sub base station.