Mobile communication method and mobile station

The present invention notifies of an EARFCN in an equivalent band by means of an SIB 5 while minimizing the increase in overhead. A mobile communication method according to the present invention includes: a step in which a radio base station eNB in a cell #1 notifies, by means of the SIB 5, of a band #2 and an equivalent band #21 that can be supported in a cell #2 adjacent to the cell #1; and a step in which a mobile station UE assumes that access in the cell #2 is prohibited when having determined that the mobile station does not support the band #2 and the equivalent band #21.

TECHNICAL FIELD

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

BACKGROUND ART

Each cell in an LTE (Long Term Evolution) scheme is configured to support a single band (a frequency band).

On the other hand, a mobile station UE is configured to be able to perform connection processing only in a cell that supports a band supported by the mobile station itself (or a band that has passed an authentication test).

That is, the mobile station UE is configured to not be able to perform the connection processing in a cell that does not support the band supported by the mobile station itself (or the band that has passed the authentication test).

Moreover, an “equivalent band” can be applied in an LTE scheme. Each cell can support a plurality of bands by applying the equivalent band.

Here, a band is configured to overlap with an equivalent band of that band.

Furthermore, a radio base station eNB in the LTE scheme is configured to notify of a target EARFCN (E-UTRA Absolute Radio Frequency Channel Number) for inter-frequency measurement to perform a cell reselection process, by means of an information element “InterFreqCarrierFreqInfo” included in an SIB (System Information Block)5.

CITATION LIST

SUMMARY OF INVENTION

The maximum number of information elements “InterFreqCarrierFreqInfo” that can be set within an information element “InterFreqCarrierFreqList” is eight, according to the specification of the existing LTE scheme.

There is however assumed a case where the number of information elements “InterFreqCarrierFreqInfo” that can be set within the information element “InterFreqCarrierFreqList” exceeds eight when each cell supports the plurality of bands by applying the “equivalent band” as described above.

In such case, it is not preferred to increase the number of information elements “InterFregCarrierFreqInfo” that can be set within the information element “InterFreqCarrierFreqList” in terms of an increase in overhead.

The present invention has been provided in consideration of the aforementioned problem. An object of the present invention is to provide a mobile station and a mobile communication method by which the SIB 5 can notify of an EARFCN of an equivalent band while minimizing the increase in the overhead.

A first characteristic of the present invention is the mobile communication method including: a step in which a radio base station in a first cell notifies, by means of broadcast information, of a radio frequency channel number within a band supported in a second cell adjacent to the first cell as well as an equivalent band of the band; and a step in which a mobile station assumes that access in the second cell is prohibited when having determined that the mobile station does not support the band and the equivalent band.

The second characteristic of the present invention is the mobile station including: a reception unit which receives the broadcast information from the radio base station in the first cell, the broadcast information notifying of the band supported in the second cell adjacent to the first cell as well as the equivalent band of the band; and a determination unit which is configured to assume that access in the second cell is prohibited when having determined that the mobile station does not support the band and the equivalent band.

DESCRIPTION OF EMBODIMENT

(Mobile Communication System According to First Embodiment of the Present Invention)

A mobile communication system according to a first embodiment of the present invention will be described with reference toFIGS. 1 to 7. In all figures provided to describe the present embodiment, a component having the same function is assigned the same reference numeral so that redundant description of such component will be omitted.

As illustrated inFIG. 1, the mobile communication system according to the present embodiment includes a radio base station eNB#1and a radio base station eNB#2.

The radio base station eNB#1manages a cell #1while the radio base station eNB#2is configured to manage a cell #2. The radio base station eNB#1and the radio base station eNB#2are connected to each other by an X2 interface.

Here, the cell #1supports a band #19 as well as bands #5/#26 as equivalent bands, whereas the cell #2supports a band #2 as well as a band #21 as an equivalent band.

The band #5 and the bands #19/#26 are configured to overlap one another while the band #2 and the band #21 are configured to overlap each other, but the bands #5/#19/#26 are not configured to overlap with the bands #2/#21.

Note that in the present embodiment, a mobile station UE is in a standby state in the cell #1subordinate to the radio base station eNB#1.

The configurations of the radio base station eNB#1and the radio base station eNB #2being fundamentally the same, the configuration of the radio base station eNB#1will be described below as a representative configuration.

As illustrated inFIG. 2, the radio base station eNB#1includes a management unit11and a broadcast information transmission unit12.

The management unit11is configured to manage a band configuration used in the radio base station eNB#1(or the cell #1).

The management unit11may also be configured to manage a band configuration used in the radio base station eNB #2(or the cell #2) adjacent to the radio base station eNB#1.

The broadcast information transmission unit12is configured to transmit broadcast information such as an MIB (Master Information Block) and SIBs 1 to 8 in the cell #1.

For example, the broadcast information transmission unit12is configured to refer to the band configuration managed by the management unit11to notify of the band #5 supported in the cell #1by means of an information element “freqBandIndicator” included in the SIB 1 and notify of the bands (hereinafter referred to as equivalent bands) #5/#26 supported in the cell #1as equivalent bands, by means of an information element “addiFreqBandIndicatorList” included in the SIB 1 as illustrated inFIG. 3.

The broadcast information transmission unit12is further configured to refer to the band configuration managed by the management unit11to notify of carrier frequency information pertaining to the equivalent bands #5/#26 supported in the cell #1, by means of an information element “addiFreqInfoList” included in the SIB 2 as illustrated inFIG. 4.

Furthermore, the broadcast information transmission unit12is configured to refer to the band configuration managed by the management unit11to notify of a target EARFCN for the inter-frequency measurement provided to perform a cell reselection process within the band #2 supported in the cell #2, by means of an information element “dl-CarrierFreq” within an information element “InterFreqCarrierFreqInfo” included in the SIB 5 as illustrated inFIG. 5.

Furthermore, the broadcast information transmission unit12is configured to refer to the band configuration managed by the management unit11to notify of the equivalent band #21 supported in the cell #2, by means of an information element “addiFreqBandIndicatorList” within the information element “InterFreqCarrierFreqInfo” included in the SIB 5 as illustrated inFIG. 5.

The mobile station UE according to the present embodiment includes a reception unit21, a determination unit22, and a standby processing unit23as illustrated inFIG. 6.

The reception unit21is configured to receive the broadcast information (such as the MIB and the SIBs 1 to 8) transmitted by the radio base station eNB#1.

Here, the reception unit21is configured to acquire information related to the band #19 and the equivalent bands #5/#26 that are supported in the cell #1, from the SIB 1.

The reception unit21is also configured to acquire uplink carrier frequency information related to the band #19 and the equivalent bands #5/#26 that are supported in the cell #1, from the SIB 2.

Moreover, the reception unit21is configured to acquire information related to the band #2 and the equivalent band #21 that are supported in the cell #2, from the SIB 5.

The determination unit22is configured to determine whether or not the band #19 and the equivalent bands #5/#26 supported in the cell #1and received by the reception unit are supported by the mobile station UE.

The determination unit22is configured to assume that access is prohibited in the cell #1when having determined that the mobile station UE does not support the band #19 and the equivalent bands #5/#26 supported in the cell #1.

The determination unit22is also configured to determine whether or not the band #2 and the equivalent bands #21 supported in the cell #2and received by the reception unit are supported by the mobile station UE.

The determination unit22is configured to assume that access in the cell #2is prohibited when having determined that the mobile station UE does not support the band #2 and the equivalent band #21 supported in the cell #2.

The standby processing unit23is configured to perform a standby process on the basis of the determination result made by the determination unit22.

That is, the standby processing unit23is configured to search for a cell with a different frequency without performing the standby process in a cell regarded by the determination unit22as the cell to which access is prohibited (a barred cell).

An example of an operation of the mobile station UE according to the present embodiment will be described below with reference toFIG. 7.

As illustrated inFIG. 7, the mobile station UE that is on standby in the cell #1determines, in step S101, whether or not the band specified by the information elements “freqBandIndicator” and “addiFreqBandIndicatorList” included in the SIB 1 received in the cell #1is supported by the mobile station UE.

The mobile station UE continues to be on standby in the cell #1and ends the present operation when the determination is “YES”.

When the determination is “NO”, on the other hand, the present operation proceeds to step S102where the mobile station UE assumes that access to the cell #1is prohibited.

In step S103, the mobile station UE determines whether or not the band corresponding to the EARFCN specified by the information element “dl-CarrierFreq” included in the SIB 5 received in the cell #1as well as the band specified by the information element “addiFreqBandIndicatorList” are supported by the mobile station UE.

The mobile station UE here performs this determination on all bands included in the information element “addiFreqBandIndicatorList”.

The mobile station UE performs the cell reselection process on a cell #1and ends the present operation when the determination is “YES”.

When the determination is “NO”, on the other hand, the present operation proceeds to step S104where the mobile station UE assumes that access to the cell #1is prohibited and searches for a cell with a different frequency.

According to the mobile communication system in the first embodiment of the present invention, the mobile station UE can properly perform the inter-frequency measurement to perform the cell reselection process without increasing the number of information elements “InterFregCarrierFreqInfo” that can be set within the information element “InterFreqCarrierFreqList” included in the SIB 5, even when each cell can support a plurality of bands by applying the “equivalent band”.

Modified Example 1

Now, a mobile communication system according to Modified Example 1 of the present invention will be described with reference toFIG. 8while focusing on what is different from the mobile communication system according to the first embodiment described above.

In Modified Example 1, a broadcast information transmission unit12in a radio base station eNB is configured to refer to a band configuration managed by a management unit11to notify of an equivalent band supported in each cell adjacent to a cell #1, by means of an information element “InterFreqNeighCellList” within an information element “InterFreqCarrierFreqInfo” included in an SIB 5 as illustrated inFIG. 8.

The mobile communication system according to Modified Example 1 can notify of a different equivalent band for each cell even when each cell adjacent to the cell #1supports a different equivalent band.

The aforementioned characteristic of the present embodiment may also be expressed as follows.

A first characteristic of the present embodiment is a mobile communication method including: a step in which the radio base station eNB in the cell #1(a first cell) notifies, by means of the SIB 5 (broadcast information), of the band #2 (a band) and the equivalent band #21 (an equivalent band) that can be supported in the cell #2(a second cell) adjacent to the cell #1; and a step in which the mobile station UE assumes that access in the cell #2is prohibited when having determined that the mobile station supports neither the band #2 nor the equivalent band #21.

A second characteristic of the present embodiment is the mobile station UE including: the reception unit21which is configured to receive the SIB 5 from the radio base station eNB in the cell #1, the SIB 5 notifying of the band #2 and the equivalent band #21 that can be supported in the cell #2; and the determination unit22which is configured to assume that access in the cell #2is prohibited when having determined that the mobile station does not support the band #2 and the equivalent band #21.

Note that the operation of the radio base station eNB and the mobile station UE described above may be implemented by hardware, a software module executed by a processor, or a combination of the both.

The software module may be provided in a storage medium of an arbitrary format such as 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 register, a hard disk, a removable disk, or a CD-ROM.

The storage medium is connected to the processor so that the processor can read/write information from/to the storage medium. The storage medium may also be integrated into the processor. The storage medium and the processor may be provided in an ASIC, which may be provided in the radio base station eNB and the mobile station UE. Moreover, the storage medium and the processor may be provided in the radio base station eNB and the mobile station UE as a discrete component.

While the present invention has been described in detail by using the aforementioned embodiments, it is apparent for those skilled in the art that the present invention is not limited to the embodiments described herein. The present invention can be implemented as revisions and modified aspects without departing from the spirit and the scope of the present invention provided by the description of claims. Accordingly, the description herein is provided for the purpose of illustration and not intended to have any restrictive meaning to the present invention.

Note that the entire content of Japanese Patent Application No. 2012-008010 (filed on Jan. 18, 2012) is herein incorporated by reference.

INDUSTRIAL APPLICABILITY

As described above, the present invention can provide the mobile station and the mobile communication method by which the EARFCN of the equivalent band can be notified by means of the SIB 5 while minimizing the increase in overhead.

REFERENCE SIGNS LIST