FIG. 1 illustrates a wireless communication system according to one or more exemplary embodiments.

Referring to FIG. 1, the wireless communication system 10 is widely located to provide a variety of communication services such as a voice service and a packet data service. The wireless communication system 10 includes one or more evolved-NodeBs (eNBs) 11. Each eNB 11 provides a communication service to a predetermined cell, for example, cells 15a, 15b, and 15c. Here, the cell may be divided into a plurality of areas (also, referred to as sectors).

User equipment 12 (UE) may be located at a certain location or portable, and may also be referred to as different terms, including MS (mobile station), MT (mobile terminal), UT (user terminal), SS (subscriber station), wireless device, PDA (personal digital assistant), wireless modem, and handheld device. An eNB 11 may also be referred to as BS (Base Station), BTS (Base Transceiver System), Access Point, femto base station, Home nodeB, relay and the like. A cell inclusively refers to various coverage areas, such as mega cell, macro cell, micro cell, pico cell, and femto cell. A cell may be used as a term for indicating a frequency band that a BS provides, a coverage of a BS, or a BS.