TECHNICAL FIELD

The present invention relates to a terminal, a radio communication method, a base station, and a system in next-generation mobile communication systems.

BACKGROUND ART

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 latency and so on (see non-patent literature 1). Also, the specifications of LTE-A (also referred to as “LTE-advanced,” “LTE Rel. 10,” “LTE Rel. 11,” “LTE Rel. 12” or “LTE Rel. 13”) have been drafted for further broadbandization and increased speed beyond LTE (also referred to as “LTE Rel. 8” or “LTE Rel. 9”), and successor systems of LTE (also referred to as, for example, “FRA (Future Radio Access),” “5G (5th generation mobile communication system),” “NR (New Radio),” “NX (New radio access),” “FX (Future generation radio access),” “LTE Rel. 14,” “LTE Rel. 15” or later versions) are under study.

In LTE Rel. 10/11, carrier aggregation (CA) to integrate multiple component carriers (CC) is introduced in order to achieve broadbandization. Each CC is configured with the system bandwidth of LTE Rel. 8 as 1 unit. In addition, in CA, multiple CCs under the same radio base station (eNB (eNodeB)) are configured in a user terminal (UE (User Equipment)).

Meanwhile, in LTE Rel. 12, dual connectivity (DC), in which multiple cell groups (CGs) formed with different radio base stations are configured in a UE, is also introduced. Each cell group is comprised of at least 1 cell (or CC). In DC, since multiple CCs of different radio base stations are integrated, DC is also referred to as “inter-eNB CA.”

Also, in existing LTE systems (for example, LTE Rel. 8 to 13), synchronization signals (PSS/SSS), broadcast channel (PBCH) and so on which a user terminal uses in initial access procedures are allocated, on a fixed basis, in fields that are determined in advance. By detecting the synchronization signals in cell search, the user terminal can establish synchronization with the network, and, furthermore, identify the cell (for example, cell ID) at which the user terminal should connect with. Furthermore, the user terminal can acquire system information by receiving the broadcast channel (PBCH and SIB) after the cell search.

CITATION LIST

Non-Patent Literature

Non-Patent Literature 1: 3GPP TS 36.300 “Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall Description; Stage 2”

SUMMARY OF INVENTION

Technical Problem

Future radio communication systems (for example, 5G, NR, etc.) are expected to realize various radio communication services so as to fulfill mutually varying requirements (for example, ultra high speed, large capacity, ultra-low latency, etc.). For example, regarding 5G/NR, studies are in progress to provide radio communication services, referred to as “eMBB (enhanced Mobile Broad Band),” “IoT (Internet of Things),” “mMTC (massive Machine Type Communication),” “M2M (Machine To Machine),” and “URLLC (Ultra Reliable and Low Latency Communications).”

In addition, 5G/NR is expected to support flexible use of numerologies and frequencies, and realize dynamic frame configurations. Here, “numerology” refers to communication parameters in the frequency direction and/or the time direction (for example, at least one of the subcarrier spacing (subcarrier interval), the bandwidth, the symbol duration, the time duration of CPs (CP duration), the subframe duration, the time duration of TTIs (TTI duration), the number of symbols per TTI, the radio frame configuration, the filtering process, the windowing process, and so on).

When cells that use different numerologies than existing LTE systems (also referred to as “NR/5G-cell”) are supported, it is likely that a user terminal communicates by using a number of cells including these NR/5G-cells (for example, by using CA and/or DC). However, how to control communication using multiple cells including NR/5G-cells is not decided.

The present invention has been made in view of the above, and it is therefore an object of the present invention to provide a user terminal and a radio communication method, whereby communication to use a number of cells, including cells that use different numerologies than existing LTE systems, can be controlled properly.

Solution to Problem

According to one aspect of the present invention, a user terminal has a receiving section that receives, from the first cell, information about synchronization between the first cell and the second cell and/or information about a configuration of a synchronization signal block in the second cell, and a control section that controls a processes for connecting with the second cell based on the information about synchronization and/or the information about the configuration of the synchronization signal block.

Advantageous Effects of Invention

According to the present invention, communication to use a number of cells, including cells that use different numerologies than existing LTE systems, can be controlled properly.

