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BR-112020006250-B1 - First Base Station and State Control Method in a First Base Station

BR112020006250B1BR 112020006250 B1BR112020006250 B1BR 112020006250B1BR-112020006250-B1

Abstract

In one aspect of the present invention, a first base station for communication with the user equipment together with a second base station according to dual connectivity includes a data storage unit configured to store data to be transmitted from the first base station to the user equipment; a receiving unit configured to receive from the second base station information indicating whether there is data to be transmitted from the second base station to the user equipment; and a state control unit configured to, when information is received indicating that data to be transmitted from the second base station to the user equipment exists, prevent the user equipment from releasing a radio resource or transitioning to a discontinuous receiving state, even if the amount of data to be transmitted stored in the data storage unit is less than or equal to a predetermined limit.

Inventors

  • Teruaki Toeda
  • Anil Umesh
  • Tooru Uchino
  • Akihito Hanaki
  • Hiroshi OU

Assignees

  • NTT DOCOMO, INC

Dates

Publication Date
20260310
Application Date
20171117

Claims (6)

  1. 1. First base station (101; 102), configured to support distributed communication between base stations, characterized in that it comprises: a receiving unit (140) configured to receive from a second base station information indicating whether there is data to be transmitted from a second base station to a terminal (200); a transmission buffer (120) configured to store data to be transmitted to the terminal (200) that are distributed by the second base station; and a control unit (130) configured to perform discontinuous receive control (DRX) for the terminal (200), based on the received information indicating whether there is data to be transmitted from the second base station to the terminal (200), wherein the control unit (130) is configured to control the transmission of downlink control information in the PDCCH to prevent the terminal from transitioning to a discontinuous receive state.
  2. 2. First base station (101; 102), according to claim 1, characterized in that the control unit (130) is configured to, when the received information indicates that the data to be transmitted from the second base station to the terminal (200) exists, prevent the terminal (200) from transitioning to a discontinuous reception state, even if an amount of data to be transmitted stored in the transmission buffer is less than or equal to a predetermined threshold, and the control unit (130) is configured to, when the received information indicates that the data to be transmitted from the second base station to the terminal (200) does not exist and when the amount of data to be transmitted stored in the transmission buffer is less than or equal to the predetermined threshold, cancel the impediment of the terminal (200) from transitioning to the discontinuous reception state.
  3. 3. First base station (101; 102), according to claim 1 or 2, characterized in that the control unit (130) is configured to prevent a time management timer, when terminal (200) transitions to the discontinuous reception state, from expiring by transmitting downlink control information to terminal (200).
  4. 4. First base station (101; 102), according to any one of claims 1 to 3, characterized in that the distributed communication includes at least one of dual LTE-NR connectivity, dual inter-DU connectivity and dual connectivity using a plurality of nodes.
  5. 5. First base station (101; 102), according to any one of claims 1 to 4, characterized in that the data to be transmitted from a core network to the terminal (200) are allocated to the first base station and the second base station via an X2 interface, an Xn interface or an F1 interface.
  6. 6. State control method in a first base station (101; 102) that supports distributed communication between base stations, the method characterized in that it comprises the steps of: receiving from a second base station information indicating whether there is data to be transmitted from a second base station to a terminal (200); wherein the data to be transmitted to the terminal (200) which are distributed by the second base station are stored in a transmission buffer (120) of the first base station; and performing discontinuous receive control (DRX) for the terminal (200), based on the information received indicating whether there is data to be transmitted from the second base station to the terminal (200), wherein the transmission of downlink control information in the PDCCH to prevent the terminal from transitioning to a discontinuous receive state is controlled.

Description

TECHNICAL FIELD [001] The present invention relates to a base station and a state control method. TECHNICAL BACKGROUND [002] In the Third Generation Partnership Project (3GPP), standards for a new radiocommunication system referred to as a New Radio Access Technology (NR) system are currently under discussion as successors to a Long Term Evolution (LTE) system or an LTE-Advanced system. [003] In the NR system, dual LTE-NR connectivity (LTE-NR DC) or dual multi-RAT connectivity (MR DC) is expected to be introduced, wherein data is split between an LTE base station (eNB) and an NR base station (gNB), and then the split data is transmitted or received simultaneously by these base stations, as with dual connectivity in an LTE system (see Non-Patent Document 1). As illustrated in Fig. 1, for example, in LTE-NR DC, downlink data to the user equipment (UE) is allocated to an LTE base station (eNB) and an NR base station (gNB) via an X2 interface or an Xn interface, and then the data is transmitted simultaneously from these base stations to the user equipment. [004] Additionally, as illustrated in Fig. 2, dual connectivity between NR systems is also under discussion. Specifically, downlink data for user equipment (UE) is allocated by an NR base station (central unit (CU)) to a plurality of base stations (distributed units (DUs)) via an F1 interface, and then the data is simultaneously transmitted from these base stations to the user equipment. [State of the Art Documents] [Non-Patent Document] [005] [Non-Patent Document 1] 3GPP TS38.425 V0.2.0 (2017-10) DISCLOSURE OF THE INVENTION [PROBLEM(S) TO BE SOLVED BY THE INVENTION] [006] In a radio communication system, timing advance (TA) control is performed in order to adjust the timing between a base station and the user equipment. According to TA control, the user equipment releases a radio resource when a TA command is not received. [007] In addition, discontinuous reception control (DRX) is also performed in order to save battery consumption of user equipment or similar. According to DRX control, the user equipment transitions to a DRX state when data is not transmitted or received between a base station and the user equipment for a long time. [008] In dual connectivity, TA control and DRX control are performed independently between each base station and user equipment. For this reason, even if data is transmitted or received between a base station and user equipment, it may be possible for a radio resource to be released or the user equipment to transition to an DRX state on the part of another base station. In this situation, when the data to be transmitted from both base stations to the user equipment is generated, it is necessary to transition to a state in which the user equipment can receive the data, which consequently causes a delay in data transmission. [009] It is an objective of the present invention to reduce the delay in data transmission caused by TA control and DRX control, performed independently between each base station and the user equipment in dual connectivity. [METHODS FOR SOLVING THE PROBLEM(S)] [010] In one aspect of the present invention, a first base station is provided for communication with the user equipment together with a second base station in accordance with dual connectivity, including: a data storage unit configured to store data to be transmitted from the first base station to the user equipment; a receiving unit configured to receive from the second base station information indicating whether there is data to be transmitted from the second base station to the user equipment; and a state control unit configured to, when information is received indicating that data to be transmitted from the second base station to the user equipment exists, prevent the user equipment from releasing a radio resource or transitioning to a discontinuous receiving state, even if the amount of data to be transmitted stored in the data storage unit is less than or equal to a predetermined threshold. [ADVANTAGEOUS EFFECTS OF THE INVENTION] [011] According to the present invention, it is possible to reduce the delay in data transmission caused by TA control and DRX control, performed independently between each base station and the user equipment in dual connectivity. BRIEF DESCRIPTION OF THE FIGURES [012] Fig. 1 is a schematic diagram illustrating dual LTE-NR connectivity. [013] Fig. 2 is a schematic diagram illustrating the inter-DU dual connectivity. [014] Fig. 3 is a schematic diagram illustrating a radio communication system according to an embodiment of the present invention. [015] Fig. 4 is a diagram illustrating an example where the delay in data transmission is caused by dual connectivity. [016] Fig. 5 is a first diagram illustrating the state control of the user equipment in a radio communication system according to an embodiment of the present invention. [017] Fig. 6 is a second diagram illustrating the user equipment state control in a radio comm