Field of the Invention
The present invention relates to a wireless communication system, and more particularly, to a method for a UE to determine whether to report a measurement result based on a plurality of measurement report-triggering conditions, and a device supporting the same.
Related Art
3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) that is an advancement of UMTS (Universal Mobile Telecommunication System) is being introduced with 3GPP release 8. In 3GPP LTE, OFDMA (orthogonal frequency division multiple access) is used for downlink, and SC-FDMA (single carrier-frequency division multiple access) is used for uplink. The 3GPP LTE adopts MIMO (multiple input multiple output) having maximum four antennas. Recently, a discussion of 3GPP LTE-A (LTE-Advanced) which is the evolution of the 3GPP LTE is in progress.
A wireless communication system may need to estimate an uplink channel or downlink channel to transmit/receive data, to achieve system synchronization, and to feed back channel information. In a wireless communication system environment, fading occurs by multipath time delay. A process of recovering a transmitted signal by compensating for a signal distortion caused by drastic environmental changes by fading is referred to as channel estimation. Further, it is needed to measure a channel state with respect to a cell to which a user equipment (UE) belongs or another cell. For channel estimation or channel state measurement, channel estimation is generally performed using a reference signal (RS) known between a transmitter and a receiver.
A UE may perform measurement using the following three methods.
1) Reference signal received power (RSRP): RSRP indicates the average received power of all resource elements (REs) carrying CRSs transmitted over the entire band. Here, the UE may measure the average received power of all REs carrying channel state information (CSI) RSs instead of CRSs.
2) Received signal strength indicator (RSSI): RSSI indicates received power measured over the entire band. RSSI includes all of a signal, interference, and thermal noise.
3) Reference symbol received quality (RSRQ): RSRQ indicates a channel quality indicator (CQI) and may be determined as RSRP/RSSI depending on a bandwidth or a sub-band. That is, RSRQ refers to signal-to-interference-plus-noise-ratio (SINR). Since RSRP does not provide sufficient mobility information, RSRQ may be used instead of RSRP in a handover or cell reselection process.
RSRQ may be calculated by RSSI/RSSP. Alternatively, RSRQ may be calculated by N*RSSI/RSSP. Here, N may be a parameter (for example, the number of PRBs) or a function associated with a bandwidth in which RSSI is measured.