In the UMTS (Universal Mobile Telecommunications System) network, the specifications of long term evolution (LTE) have been drafted for the purpose of further increasing high speed data rates, providing lower delays and so on (see non-patent literature 1). In LTE, as multiple-access schemes, a scheme that is based on OFDMA (Orthogonal Frequency Division Multiple Access) is used in downlink channels (downlink), and a scheme that is based on SC-FDMA (Single Carrier Frequency Division Multiple Access) is used in uplink channels (uplink). Also, successor systems of LTE (also referred to as, for example, “LTE-advanced” or “LTE enhancement” (hereinafter referred to as “LTE-A”)) have been developed for the purpose of achieving further broadbandization and increased speed beyond LTE, and the specifications thereof have been drafted (Rel. 10/11).
In relationship to LTE-A systems, a HetNet (Heterogeneous Network), in which small cells (for example, pico cells, femto cells and so on), each having local a coverage area of a radius of approximately several tens of meters, are formed within a macro cell having a wide coverage area of a radius of approximately several kilometers, is under study. Also, in relationship to HetNets, a study is in progress to use carriers of different frequency bands between macro cells and small cells, in addition to carriers of the same frequency band.
Furthermore, for future radio communication systems (Rel. 12 and later versions), a study is in progress to introduce a new mechanism for small cell discovery. To be more specific, a user terminal detects the detection/measurement signal that is transmitted from a small cell, and establishes synchronization, conducts measurements and so on. Note that this detection/measurement signal may be referred to as the “discovery reference signal” (DRS). When a channel state measurement signal (for example, the CSI-RS (Channel State Information Reference Signal) is included in the DRS, the user terminal detects and measures this channel state measurement signal based on the timing of synchronization.