1. Field of the Invention
The present invention relates to a wireless communication system supporting multiple carriers between a mobile station and a base station and, more particularly, to a communication method using carrier switching with respect to a mobile station which cannot simultaneously process multiple carriers.
2. Description of the Related Art
3GPP (3rd Generation Partnership Project) LTE (long term evolution) and IEEE (Institute of Electrical and Electronics Engineers) 802.16m is being developed as a candidate of a next-generation wireless communication system. The 802.16m standard involves two aspects of continuity of the past of modification of the existing 802.16e standard and continuity of the future of a standard for a next-generation IMT-Advanced system. Thus, the 802.16m standard is required to meet advanced requirements for the IMT-Advanced system while maintaining compatibility with the 802.16e standard-based mobile WiMAX while maintaining compatibility with the 802.16e standard-based mobile WiMAX system.
In general, a wireless communication system uses one bandwidth for a data transmission. For example, a 2nd-generation wireless communication system uses a bandwidth of 200 KHz to 1.25 MHz, and a 3rd-generation wireless communication system uses a bandwidth of 5 MHz to 10 MHz. In order to support an increasing transmission capacity, the recent 3GPP LTE or 802.16m extends the bandwidth to 20 MHz or higher. The extension of the bandwidth to increase the transmission capacity seems inevitable, but the support of a wide bandwidth even for a case in which a required service level is low causes unnecessary power consumption.
Thus, a multi-carrier system allowing for a transmission and/ore reception of data at a broadband through a plurality of carriers by defining a carrier having one bandwidth and a center frequency has been emerged. The multi-carrier system supports both a narrowband and a broadband by using one or more carriers. For example, when one carrier corresponds to a 5 MHz bandwidth, the multi-carrier system supports a maximum 20 MHz bandwidth by using four carriers.
The IEEE 802.16m system supports an enhanced multicast broadcast service (E-MBS). The E-MBS is a point-to-multipoint system in which data packets are simultaneously transmitted from one source to a plurality of destinations. Broadcasting refers to the capability of transmitting contents to every user. Multicasting refers to contents destined for a particular group of users subscribed to receive a particular service. Static multicasting and dynamic multicasting may be supported.
In the multi-carrier system, namely, in the system in which a plurality of uplink carriers and a plurality of downlink carriers are in use, when a mobile station cannot process the plurality of carriers, an effective switching method is required to smoothly provide an E-MBS service.