KR20150042715A - Method for maintaining quality of wireless link - Google Patents

Abstract

Receiving a status information of a radio link between a terminal and a secondary base station from a secondary base station in a wireless communication system in which a master base station and a secondary base station are dual-connected to a terminal, Determining whether to release the secondary base station or the secondary base station, and reconfiguring the radio bearer setup of the master base station.

Description

[0001] The present invention relates to a method for maintaining quality of a wireless link,

The present invention relates to a method for maintaining the quality of a wireless link in a wireless communication system supporting dual connectivity.

 In order to deal with the transmission amount of explosively increasing wireless communication traffic, studies are being conducted to increase the communication capacity and to improve the cost performance by disposing small-sized low-cost cells over macro cells. In this regard, in 3GPP, Small Cell Enhancement (SCE) for small cells is under study item (SI) in Release 12.

On the other hand, a secondary cell is one type of small cell, and if there is a problem in the wireless link with the secondary cell, the quality of the service provided to the mobile station may deteriorate. Conventionally, when a problem occurs in a wireless link, a problem caused by a connection reset for a link in which a problem occurs is solved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of reconfiguring a radio bearer setup of a secondary base station or releasing a connection of a secondary base station to maintain link quality when a problem occurs in a radio link between the secondary base station and the terminal.

According to an aspect of the present invention, in a wireless communication system in which a master base station and a secondary base station are dual-connected to a terminal, a method of maintaining quality of a radio link of the master base station is provided. The radio link quality maintenance method includes: receiving status information of a radio link between a terminal and a secondary base station from a secondary base station; resetting the radio bearer of the secondary base station or releasing the secondary base station, And reconfiguring the radio bearer setup of the master base station.

According to an embodiment of the present invention, a radio bearer setup with a secondary base station is changed or a connection is released so as to prevent a service quality deterioration due to a delay time. The secondary base station according to the embodiment of the present invention can measure the state of the radio link between the terminal and the secondary base station and can quickly change the radio bearer setting or release the connection with the terminal when a radio link problem occurs.

1 is a view illustrating a double connection structure according to an embodiment of the present invention.
2 is a diagram illustrating an RRM function included in a secondary base station according to an embodiment of the present invention.
3 is a diagram illustrating reference signals transmitted from a terminal according to an embodiment of the present invention.
4 is a flowchart illustrating a system operation procedure when a quality of a dual-link wireless system deteriorates according to an exemplary embodiment of the present invention.
5 is a flowchart illustrating a system operation procedure when a quality of a dual-link wireless system deteriorates according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, a terminal is referred to as a mobile station (MS), a mobile terminal (MT), an advanced mobile station (AMS), a high reliability mobile station ), A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) AMS, HR-MS, SS, PSS, AT, UE, and the like.

Also, a base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) (RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, a high reliability relay station (HR) A femto BS, a home Node B, a HNB, a pico BS, a metro BS, a micro BS, ), Etc., and may be all or part of an ABS, a Node B, an eNodeB, an AP, a RAS, a BTS, an MMR-BS, an RS, an RN, an ARS, It may include a negative feature.

1 is a view illustrating a double connection structure according to an embodiment of the present invention.

Referring to FIG. 1, a UE is simultaneously connected to a master eNB (MeNB) and a secondary eNB (SeNB). The embodiments of the present invention can be applied to a system in which a macro cell and a small cell are simultaneously connected to a terminal through a wireless link. At this time, the core network may be connected to the master base station, and the master base station and the secondary base station may be connected to the non-ideal backhaul.

In the embodiment of the present invention, both the master base station and the secondary base station must be able to manage and provide radio resources themselves. Therefore, the secondary base station must also include a radio resource management (RRM) function related to radio resources.

2 is a diagram illustrating an RRM function included in a secondary base station according to an embodiment of the present invention.

Referring to FIG. 2, the RRM function included in the secondary base station includes a dynamic resource allocation function, a radio bearer control function, and a radio access control function.

The dynamic resource allocation function is a function of allocating packets in the user plane and the control plane based on the QoS requirements associated with the radio bearer, the channel quality for the terminal, the buffer status, interference conditions or limitations / And can allocate or release resources.

The radio bearer control function can set, maintain and release the bearer according to the setting for the radio bearer.

The radio access control function accepts a setup request for a new radio bearer based on resource conditions, QoS requirements, priority, QoS of an ongoing service, or QoS requirements according to a new radio bearer request, Or refused.

3 is a diagram illustrating reference signals transmitted from a terminal according to an embodiment of the present invention.

Referring to FIG. 3, in order to allocate a dynamic resource between a master base station and a secondary base station, a mobile station transmits a sounding reference signal (SRS) and feedback information on a downlink service Information, HARQ ACK / NACK). At this time, the terminals connected to the master base station and the secondary base station can monitor the quality of the radio link mainly on the downlink, but the secondary base station monitors the quality of the downlink through the feedback information on the downlink service, Link quality can be improved. Therefore, it is effective that the secondary base station monitors the state of the radio link and performs processing according to the degradation of the radio link quality.

In case of a problem of a wireless link between a secondary base station and a terminal, the secondary base station can provide additional wireless resources to the terminal in the dual connection structure. Therefore, instead of resetting the wireless connection in which quality degradation occurs, The radio bearer setup between the secondary base station and the terminal may be changed or the connection between the secondary base station and the terminal may be canceled so that the service quality is not deteriorated due to the delay time required for the resetting. At this time, the system operation due to the deterioration of the quality of the radio link detected by the secondary base station can be performed mainly by the master base station or the secondary base station.

4 is a flowchart illustrating a system operation procedure when a quality of a dual-link wireless system deteriorates according to an exemplary embodiment of the present invention.

First, when the secondary base station detects a radio link state in which the established service can not be efficiently provided, the secondary base station reports the state of the radio link between the secondary base station and the terminal to the master base station (SeNB Radio Status Report) (S401).

In step S402 and step S402 ', the master base station determines whether the radio bearer set in the secondary base station is reset or the secondary base station is released according to the QoS and the radio link state of the bearer set in the secondary base station.

When the master base station determines to reset the radio bearer (S402_1), the master base station transmits a secondary base station reconfiguration (SeNB Reconfiguration) message including the new bearer setup to the secondary base station (S402_2).

At this time, if the new bearer setting is acceptable in the secondary base station, the secondary base station permits bearer reconfiguration, performs resource control of the secondary base station, and transmits a secondary base station reconfiguration acknowledgment message (S402_3) to the master base station .

However, if the new bearer setting is unacceptable in the secondary base station, the secondary base station transmits a secondary base station rejection message (SeNB Reconfiguration Reject) message to the master base station. Upon receiving the secondary base station reconfiguration rejection message, the master base station transmits a secondary base station release message (SeNB Removal) message to the secondary base station (S402_3 ').

However, if the master base station determines to release the secondary base station, the master base station immediately transmits a secondary base station release message (SNB Removal) message to the secondary base station (S402 ').

When the radio bearer of the secondary base station is reset or the secondary base station is released, the master base station reconfigures the radio bearer setup of the master base station so that the service for the terminal can be maintained before or after the reset or release (S403) And transmits a radio resource control reconfiguration (RRC Connection Reconfiguration) message including the change to the RRC connection reconfiguration message (S404). Thereafter, the MS transmits a RRC Connection Reconfiguration Complete message to the master BS (S405).

5 is a flowchart illustrating a system operation procedure when a quality of a dual-link wireless system deteriorates according to another embodiment of the present invention.

The secondary base station detects a radio link state in which a service set by the secondary base station can not be efficiently provided (S501), and the secondary base station resets the radio bearer established in the secondary base station through radio resource management (RRM) (S502, S502 ').

When the secondary base station determines the reconfiguration of the secondary base station (i.e., reestablishment of the radio bearer) (S502_1), the secondary base station transmits a secondary base station reconfiguration (SeNB Reconfiguration) message including the new bearer setting to the master base station (S502_2). The master base station receiving the secondary base station reconfiguration message reconstructs the radio bearer setup of the master base station by reflecting the bearer configuration re-established by the secondary base station so that the service provided to the terminal can be maintained (S502_3) (Acknowledgment message transmission) (S502_4). The secondary base station receiving the grant message of the master base station can perform radio resource control (RRC) according to the new bearer setting (S502_5).

When the secondary base station determines to release (S502'_1), the secondary base station transmits a secondary base station release message to the master base station (S502'_2). Upon receiving the request from the secondary base station, the master base station reconfigures the radio bearer setup of the master base station so that the service provided to the terminal can be maintained regardless of the release of the secondary base station (S502'3), and releases the secondary base station (S502 ' _4).

After the radio bearer setup of the secondary base station is reconfigured or the secondary base station is released, the master base station transmits a RRC Connection Reconfiguration message including the changed radio bearer setup information (S503) (RRC Connection Reconfiguration Complete) message is received (S504).

As described above, according to an embodiment of the present invention, the radio bearer setup with the secondary base station is changed or the connection is released so as to prevent deterioration of service quality when the link quality between the secondary base station and the terminal is degraded. At this time, the secondary base station according to the embodiment of the present invention measures the state of the radio link between the terminal and the secondary base station, and can quickly change the radio bearer setup or release the connection with the terminal when a radio link problem occurs.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (1)

A method for maintaining quality of a radio link of a master base station in a wireless communication system in which a master base station (master eNB, MeNB) and a secondary base station (secondary eNB, SeNB)
Receiving status information of a wireless link between the terminal and the secondary base station from the secondary base station;
Determining a re-establishment of the radio bearer of the secondary base station or a release of the secondary base station based on the status information of the radio link, and
Reconfiguring the radio bearer setup of the master base station
Gt; a < / RTI > wireless link quality.

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