JP2013106258A - Mobile communication method and radio base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a probability of a successful transition of a mobile station to a connected state within a coverage area of a CSG cell, even when a coverage area of a macrocell and the coverage area of the CSG cell at least partially overlap with each other.SOLUTION: The mobile communication method comprises: a step in which a radio base station eNB #1 communicates a random access preamble #1 used in a macrocell #1 and a window size for random access response reception #1 to a radio base station HeNB #1; and a step in which the radio base station HeNB #1, upon detecting a random access preamble #1, performs processing for reducing influence of interference on a random access response to the random access preamble #1 during a time period for random access response reception determined by the window size for random access response reception #1.

Description

  The present invention relates to a mobile communication method and a radio base station.

  As shown in FIG. 5, in a LTE (Long Term Evolution) mobile communication system, a coverage area by a macro cell # 1 under the radio base station eNB # 1 and a CSG (Closed Subscriber Group) cell under the radio base station HeNB # 1 A case where the coverage areas by # 1 are formed so as to overlap at least partially may be assumed.

3GPP TS36.300

  However, in such a case, the mobile station UE that is in the standby state (IDLE state) in the macro cell # 1 and does not have the access right to the CSG cell # 1 is connected from the standby state in the coverage area by the CSG cell # 1. When attempting to make a transition to the connected state (Connected state), there is a problem that reception of the downlink control signal in the macro cell # 1 may fail due to interference from the CSG cell # 1, and the transition may end in failure. It was.

  In particular, in the random access procedure (Random Access Procedure) performed in performing such a transition, a random access response signal is transmitted from the radio base station eNB # 1 to the mobile station UE without performing HARQ (Hybrid-HARQ) control. In this case, the mobile station UE is likely to fail to receive the random access response signal.

  Therefore, the present invention has been made in view of the above-described problems, and even if the coverage area by the macro cell and the coverage area by the CSG cell overlap at least partially, the coverage area by the CSG cell An object of the present invention is to provide a mobile communication method and a radio base station that can improve the success probability of transition to a connection state of a mobile station.

  The first feature of the present invention is that the mobile communication system is configured such that a coverage area by a cell under the first radio base station and a coverage area by a cell under the second radio base station overlap at least partially. A communication method, wherein the first radio base station uses a random access preamble used in a cell under the first radio base station and a reception window size for random access response to the second radio base station. And when the second radio base station detects the random access preamble, the random access is received within a random access response reception period determined based on the random access response reception window size. To reduce the effect of interference on the random access response to the preamble And summarized in that a step of performing management.

  According to a second aspect of the present invention, there is provided a mobile communication system configured such that a coverage area by a cell under the first radio base station and a coverage area by a cell under the second radio base station overlap at least partially. A radio base station that functions as a first radio base station, and for the second radio base station, a random access preamble used in a cell under the first radio base station and reception for a random access response The gist is to include a transmission unit configured to notify the window size.

  A third feature of the present invention is that in a mobile communication system formed so that a coverage area by a cell under the first radio base station and a coverage area by a cell under the second radio base station overlap at least partially. A radio base station functioning as a second radio base station, and a random access preamble used in a cell under the first radio base station and a reception window size for a random access response from the first radio base station And a random access preamble within a reception period for random access response that is determined based on the reception window size for random access response when the random access preamble is detected. Reduce the impact of interference on random access responses to And summarized in that and a control unit configured to perform processing of fit.

  As described above, according to the present invention, even if the coverage area by the macro cell and the coverage area by the CSG cell overlap at least partially, the connection state of the mobile station within the coverage area by the CSG cell It is possible to provide a mobile communication method and a radio base station that can improve the success probability of transition to.

1 is an overall configuration diagram of a mobile communication system according to a first embodiment of the present invention. FIG. 3 is a functional block diagram of a radio base station eNB # 1 according to the first embodiment of the present invention. FIG. 3 is a functional block diagram of a radio base station HeNB # 1 according to the first embodiment of the present invention. It is a figure for demonstrating the RACH procedure used with the mobile communication system which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the conventional mobile communication system.

(Mobile communication system according to the first embodiment of the present invention)
A mobile communication system according to a first embodiment of the present invention will be described with reference to FIGS. In the present embodiment, an LTE mobile communication system will be described as an example of the mobile communication system according to the present embodiment, but the present invention is also applicable to mobile communication systems other than the LTE system.

  As shown in FIG. 1, the mobile communication system according to the present embodiment manages a radio base station eNB # 1 that manages a macro cell # 1 and a CSG cell (or may be called a femto cell) # 1. And a radio base station HeNB # 1.

  In the mobile communication system according to the present embodiment, the coverage area by the macro cell # 1 and the coverage area by the CSG cell are formed so as to overlap at least partially geographically. Specifically, as shown in FIG. 1, the mobile communication system according to the present embodiment is configured such that the coverage area by the CSG cell # 1 is included in the coverage area by the macro cell # 1.

  As illustrated in FIG. 2, the radio base station eNB # 1 includes a RACH (Random Access Channel) procedure execution unit 11 and a transmission unit 12.

  The RACH procedure execution unit 11 is configured to execute the RACH procedure with the mobile station UE in a standby state in the macro cell # 1.

  For example, when receiving a random accelerator preamble from the mobile station UE, the RACH procedure executing unit 11 is configured to transmit a random access response to the mobile station UE.

  Further, the RACH procedure execution unit 11 is configured to transmit “Contention Resolution” to the mobile station UE when receiving “Scheduled Transmission” from the mobile station UE.

  The transmission unit 12 is configured to notify the radio base station HeNB # 1 of the random access preamble # 1 and the random access response reception window size # 1 used in the macro cell # 1.

  As illustrated in FIG. 3, the radio base station HeNB # 1 includes a reception unit 21, a control unit 22, and a transmission unit 23.

  The receiving unit 21 is configured to receive various signals from the radio base station eNB # 1.

  Specifically, the reception unit 21 acquires the random access preamble # 1 and the random access response reception window size # 1 used in the macro cell # 1 from the radio base station eNB # 1 at a predetermined timing. It is configured.

  For example, the reception unit 21 acquires the random access preamble # 1 and the reception window size # 1 for random access response when setting a connection between the radio base station eNB # 1 and the radio base station HeNB # 1. Alternatively, the random access preamble # 1 and the random access response reception window size # 1 may be periodically acquired.

  The receiving unit 21 is configured to detect the random access preamble # 1 used in the macro cell # 1.

  When the reception unit 21 detects the random access preamble # 1, the control unit 22 performs the random access preamble # 1 within the random access response reception period determined based on the random access response reception window size # 1. Is configured to perform processing for reducing the influence of interference on the random access response.

  For example, as shown in FIG. 4, the random access response reception period starts after 3 subframes from the time when the random accelerator preamble # 1 is transmitted and has a time length corresponding to the random access response reception window size # 1. It is a period.

  In the example of FIG. 4, the random access response reception period is a period from subframe # 3 to subframe # 12. Here, in subframe # 0, random accelerator preamble # 1 is transmitted, and reception window size # 1 for random access response is assumed to be 10 subframes long.

  For example, in the above-described process, the data transmitted via the downlink data signal for the connected mobile station UE in the CSG cell # 1, for example, PDSCH (Physical Downlink Shared Channel), in the reception period for the random access response described above. Signal scheduling may be performed so that downlink control signals in the CSG cell # 1, for example, CRS (Cell-Specific Reference Signal), P-SS (Primary Synchronization Signal), and S-SS ( Processing for reducing transmission power, such as Secondary Synchronization Signal), may be used.

  The transmission unit 23 is configured to transmit a scheduling signal, a downlink data signal, a downlink control signal, and the like for the connected mobile station UE in the CSG cell # 1.

  Hereinafter, with reference to FIG. 1, in the mobile communication system according to the present embodiment, when a mobile station UE that does not have an access right to the CSG cell # 1 is in a standby state (IDLE state) in the macro cell # 1. In the coverage area by CSG cell # 1, an operation of attempting to transition from the standby state to the connected state (Connected state) will be described.

  As shown in FIG. 1, when the mobile station UE transmits the random access preamble # 1 used in the macro cell # 1 (subframe # 0 shown in FIG. 4), in step S101A, the radio base station eNB # 1 receives the random access preamble # 1, and in step S101B, the radio base station HeNB # 1 detects that the random access preamble # 1 is transmitted.

  Here, the radio base station HeNB # 1 receives a random access response reception period (sub-range shown in FIG. 4) determined based on a random access response reception window size # 1 (10 subframe length in the example of FIG. 4). In the frames # 3 to # 12), as a process for reducing the influence of interference on the random access response to the random access preamble # 1, scheduling of the downlink data signal for the connected mobile station UE is performed in the CSG cell # 1. At least one of a process for preventing transmission and a process for reducing the transmission power of the downlink control signal in CSG cell # 1 is performed.

  In step S102, the radio base station eNB # 1 transmits a random access response to the random access preamble # 1 without performing HARQ control.

  Here, since the above-described processing is performed by the radio base station HeNB # 1, the mobile station UE performs CSG cell # 1 during the random access response reception period (subframes # 3 to # 12 shown in FIG. 4). Therefore, the possibility of successful reception of such a random access response is increasing.

  According to the mobile communication system according to the present embodiment, even when the coverage area by the macro cell and the coverage area by the CSG cell overlap at least partially, in the reception period for the random access response, the macro cell # 1 stands by. Since the influence of interference from the CSG cell # 1 on the mobile station UE in the state is small, the possibility of success of the RACH procedure is increased. Therefore, the connection state of the mobile station UE is reached within the coverage area by the CSG cell # 1. The success probability of the transition can be improved.

  The characteristics of the present embodiment described above may be expressed as follows.

  The first feature of the present embodiment is that the coverage area by the macro cell # 1 under the radio base station eNB # 1 (first radio base station) and the CSG cell # under the radio base station HeNB # 1 (second radio base station) 1 is a mobile communication method in a mobile communication system that is formed so that at least part of the coverage area by 1 is overlapped, and the radio base station eNB # 1 is in macrocell # 1 with respect to the radio base station HeNB # 1 The process of notifying the used random access preamble # 1 and the reception window size # 1 for random access response, and when the radio base station HeNB # 1 detects the random access preamble # 1, the random access response The reception period for the random access response determined based on the reception window size # 1 (the subframe in FIG. 4). In over beam # 3 to # 12), and summarized in that a step of performing processing for reducing the influence of interference on the random access response for the random access preamble # 1.

  In the first feature of the present embodiment, the above-described process is a process for preventing scheduling of the downlink data signal for the connected mobile station UE in the CSG cell # 1 within the reception period for the random access response described above. It may be.

  In the first feature of the present embodiment, the above-described process may be a process of reducing the transmission power of the downlink control signal in the CSG cell # 1 within the above-described random access response reception period.

  A second feature of the present embodiment is that the coverage area by the macro cell # 1 under the radio base station eNB # 1 and the coverage area by the CSG cell # 1 under the radio base station HeNB # 1 are at least partially overlapped. Random access preamble # 1 used in macro cell # 1 and reception window size for random access response for radio base station eNB # 1 in the mobile communication system being used The gist of the present invention is to include a transmission unit 12 configured to notify # 1.

  The third feature of the present embodiment is that the coverage area by the macro cell # 1 under the radio base station eNB # 1 and the coverage area by the CSG cell # 1 under the radio base station HeNB # 1 are at least partially overlapped. Radio base station HeNB # 1 in the mobile communication system being used, and from the radio base station eNB # 1, the random access preamble # 1 used in the macro cell # 1, and the reception window size # 1 for the random access response Within the reception period for random access response determined based on the reception window size # 1 for random access response when detecting the random access preamble # 1 and the reception unit 21 configured to acquire the random access preamble # 1 For random access response to access preamble # 1 And summarized in that and a control unit 22 that is configured to perform processing for reducing the influence of interference that.

  The operations of the radio base station eNB # 1 / HeNB # 1 and the mobile station UE described above may be implemented by hardware, may be implemented by a software module executed by a processor, or a combination of both May be implemented.

  The software module includes a RAM (Random Access Memory), a flash memory, a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM), an EEPROM (Electronically Erasable and Programmable ROM, a hard disk, a registerable ROM, a hard disk). Alternatively, it may be provided in a storage medium of an arbitrary format such as a CD-ROM.

  Such a storage medium is connected to the processor so that the processor can read and write information from and to the storage medium. Further, such a storage medium may be integrated in the processor. Such a storage medium and processor may be provided in the ASIC. Such an ASIC may be provided in the radio base station eNB # 1 / HeNB # 1 or the mobile station UE. Further, the storage medium and the processor may be provided in the radio base station eNB # 1 / HeNB # 1 or the mobile station UE as a discrete component.

  Although the present invention has been described in detail using the above-described embodiments, it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

eNB # 1, HeNB # 1 ... radio base station UE ... mobile station 11 ... RACH procedure execution unit 12, 23 ... transmitting unit 21 ... receiving unit 22 ... control unit

Claims (5)

A mobile communication method in a mobile communication system formed such that a coverage area by a cell under the first radio base station and a coverage area by a cell under the second radio base station overlap at least partially,
The first radio base station notifying the second radio base station of a random access preamble used in a cell under the first radio base station and a reception window size for random access response;
When the second radio base station detects the random access preamble, the random access response to the random access preamble is received within the random access response reception period determined based on the random access response reception window size. And a step of performing a process for reducing the influence of interference.   The processing is processing for preventing scheduling of a downlink data signal for a connected mobile station in a cell under the second radio base station within the reception period for the random access response. Item 2. The mobile communication method according to Item 1.   The mobile communication method according to claim 1, wherein the process is a process of reducing transmission power of a downlink control signal in a cell under the control of the second radio base station within the reception period for the random access response. A radio functioning as the first radio base station in a mobile communication system formed such that a coverage area by a cell under the first radio base station and a coverage area by a cell under the second radio base station overlap at least partially. A base station,
A transmitter configured to notify the second radio base station of a random access preamble used in a cell under the first radio base station and a reception window size for a random access response; A radio base station. A radio functioning as the second radio base station in a mobile communication system formed such that a coverage area by a cell under the first radio base station and a coverage area by a cell under the second radio base station overlap at least partially. A base station,
A receiving unit configured to obtain, from the first radio base station, a random access preamble used in a cell under the first radio base station, and a reception window size for random access response;
In order to reduce the influence of interference on the random access response with respect to the random access preamble within the reception period for the random access response determined based on the reception window size for the random access response when the random access preamble is detected A radio base station comprising: a control unit configured to perform processing.

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