Patent Application
20120289282
The present invention relates to a mobile station device, a mobile communication system, and a program.
Priority is claimed on Japanese Patent Application No. 2010-005821, filed Jan. 14, 2010, the content of which is incorporated herein by reference.
Regarding W-CDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), and LTE-A (LTE-Advanced), introduction of a small Home (e)NodeB has been considered for expansion of service areas, personal use, or the like. Cells served by the Home (e)NodeB include an open cell to which all users are allowed access, a CSG cell (Closed Subscriber Group cell) which allows specific users to access thereto, and a hybrid cell having both characteristics of the open cell and the CSG cell. Currently, the standardization thereof is in progress by 3GPP (3rd Generation Partnership Project). Requirements for the CSG cells are defined on the eighth section of Non-Patent Document 1.
If a UE (User Equipment), which has failed to camp on the best ranked cell determined to be the most adequate cell to be reselected as a result of measuring neighboring cells, camps on a cell having the same frequency as that of the best rank cell and performs communication with that cell, this communication causes interference with communication performed in the best ranked cell. As a method of solving such an interference problem, an IFRI (Intra Frequency Reselection Indicator) for the best ranked cell to prohibit a UE from camping on a cell having the same frequency as that of the best ranked cell for a predetermined duration has been introduced in the 3GPP (see, for example, RRC messages on section 6.2 of Non-Patent Document 2).
The IFRI is an indicator of whether to allow reselection of a cell having the same frequency as that of the best ranked cell in case that the best ranked cell is a CSG cell, and a user fails to camp on that cell because the user is not allowed access thereto even though that cell is the best ranked call. The IFRI is reported by broadcast information. If the IFRI indicates “not allowed,” that is, if it is prohibited to camp on a cell having the same frequency, a UE is forcibly caused to reselect a cell having a different frequency (inter-frequency cell). In case that the best ranked cell is a CSG cell, however, if the IFRI is applied to a UE failing to camp on that cell, all other CSG cells having the same frequency (intra frequency CSG cells) are excluded from cells to be reselected, thereby causing deterioration of service quality in some cases.
To solve this problem, Non-Patent Document 3 has proposed a method of delaying application of the IFRI until a timer expires. Thereby, the best ranked cell might be changed while a UE is in motion, and therefore there is a possibility that the UE will camp on a new best ranked cell.
If a timer expires while it is still prohibited to camp on the best ranked cell, however, a UE applies the IFRI and reselects a cell having a different frequency in order to avoid interference.
Regarding the technology disclosed in Non-Patent Document 3, however, a mobile station device does not apply IFRI immediately after receiving the IFRI from a CSG cell, and delays the application timing using a timer. Thereby, it is possible to camp on another cell having the same frequency and to make it easier to find another intra frequency CSG cell. However, if, by the time the timer expires, communication, such as verbal communication, is initiated with another cell having the same frequency (such as a macro cell) as that of the CSG cell to which the IFRI has been reported, interference from a mobile station device performing communication with the macro cell to the CSG cell to which the IFRI has been reported occurs.
The present invention has been made in view of such situations. An object of the present invention is to provide a mobile station device, a mobile communication system, and a program, which can prevent interference from occurring while it is prohibited to reselect a base station device having the same frequency.
(1) The present invention has been made to solve the above problem. One embodiment of the present invention is a mobile station device configured to wirelessly communicate with a plurality of base station devices. In case that a base station device selected as a base station device to be reselected is a base station device on which the mobile station device is prohibited to camp, and has reported an indication of prohibition to reselect a base station device using the same frequency, the mobile station device is configured to delay application of the indication of prohibition, and to apply the indication of prohibition when the mobile station device performs transmission.
(2) Additionally, regarding the mobile station device according to another aspect of the present invention, in case that the mobile station device delays application of the indication of prohibition and performs transmission, the mobile station device is configured to select a base station device targeted for the transmission, from among a plurality of base station devices using frequencies different from the frequency used by the base station device selected as the base station device to be reselected.
(3) Additionally, regarding the mobile station device according to another aspect of the present invention, the mobile station device is configured not to apply the indication of prohibition in case that the base station device selected as the base station device to be reselected is a base station device on which the mobile station device is allowed to camp.
(4) Additionally, regarding the mobile station device according to another aspect of the present invention, the transmission from the mobile station device is based on a paging signal from a base station device on which the mobile station device currently camps.
(5) Additionally, regarding the mobile station device according to another aspect of the present invention, the transmission from the mobile station device is based on a request for communication with the base station device, which is made by the mobile station device.
(6) Additionally, regarding the mobile station device according to another aspect of the present invention, in case that the mobile station device delays application of the indication of prohibition and a predetermined duration elapses, the mobile station device is configured to apply the indication of prohibition.
(7) Additionally, regarding the mobile station device according to another aspect of the present invention, in case that the base station device selected as the base station device to be reselected is a base station device on which the mobile station device is prohibited to camp, and has reported the indication of prohibition to reselect a base station device using the same frequency, and in case that a transmission request is made from the mobile station device, and the transmission request is made by a user operating the mobile station device, the mobile station device is configured to give the user a notification that transmission is impossible.
(8) Further, another aspect of the present invention is a mobile communication system including: a plurality of base station devices; and a mobile station device configured to wirelessly communicate with a plurality of base station devices. In case that a base station device selected as a base station device to be reselected is a base station device on which the mobile station device is prohibited to camp, and has reported an indication of prohibition to reselect a base station device using the same frequency, the mobile station device is configured to delay application of the indication of prohibition, and to apply the indication of prohibition when the mobile station device performs transmission.
(8) Moreover, another aspect of the present invention is a program causing a computer of a mobile station device configured to wirelessly communicate with a plurality of base station devices to execute: a process of, in case that a base station device selected as a base station device to be reselected is a base station device on which the mobile station device is prohibited to camp, and has reported an indication of prohibition to reselect a base station device using the same frequency, delaying application of the indication of prohibition and applying the indication of prohibition when the mobile station device performs transmission.
According to the present invention, while it is prohibited to reselect a base station device having the same frequency, the indication of prohibition is not applied until the mobile station device performs transmission, thereby preventing interference from occurring.
Hereinafter, a first embodiment of the present invention is explained.
The communication request detector 141 detects a request for transmission to a base station device by receiving an input by user operation via the UI unit 16, such as operation of sending a mail or operation of making a phone call. The communication processor 142 performs a process of communicating with a base station device via the transmitter 12 and the receiver 13. Regarding transmission data of transmission data and reception data to be subjected to the communication process, the UI unit 16 generates the transmission data based on an input by user operation and an input of information. Reception data received from the receiver 13 is output to the UI unit 16. The paging signal detector 143 detects that the receiver 13 has received a paging signal from a base station device. The camp-on controller 144 determines a base station device to be camped on while the mobile station device 10 is in the idle mode. Then, the camp-on controller 144 sets a reception frequency and the like so that the receiver 13 receives a paging signal from the base station device.
For simplification of explanation, it has been explained here that determination of whether or not to perform reselection of a cell and determination of a cell to be reselected are performed based on the reception level as the exclusive criterion. However, determination of whether or not to perform reselection of a cell and determination of a cell to be reselected may be performed according to 3GPP TS 36.304 (LTE), TS 25.304 (User equipment (UE) procedures in idle mode and procedures for cell reselection in connected mode), in consideration of not only the reception level, but also other conditions, such as priority according to frequency, the cell type, or the moving speed of a mobile station.
If it is determined that reselection of a cell is not to be performed (Sa2—No), the camp-on controller 144 returns to step Sa1 to periodically perform cell search.
On the other hand, if it is determined that reselection of a cell is to be performed (Sa2—Yes), the camp-on controller 144 sets the transmission frequency for the base station device to the receiver 13 so that the receiver 13 receives a signal including broadcast information from the base station device determined as the best ranked cell, as a result of the cell search. Then, the camp-on controller 144 obtains the broadcast information received by the receiver 13 (Sa3). Here, the best ranked cell means a cell having the highest value that is an evaluation criterion for determining a cell to be reselected. Based on the obtained broadcast information, the camp-on controller 144 determines whether or not the best ranked cell is a CSG cell (Sa4). For example, if the mobile communication system according to the first embodiment is an LTE system, whether or not the best ranked cell is a CSG cell is determined based on csg-Indication and csg-Identity which are information elements of SystemInformationBlockType1 included in the broadcast information.
If it is determined that the best ranked cell is a CSG cell, the camp-on controller 144 determines whether or not the mobile station device 10 has been registered on a base station device serving that CSG cell (Sa5). For example, the camp-on controller 144 reads a CSG list from the storing unit 15. If information indicating a base station device serving the CSG cell is included in the CSG list, the camp-on controller 144 determines that the registration has been made. If the information is not included, the camp-on controller 144 determines that the registration has not been made. For example, this CSG list is previously set by a user.
If it is determined in step Sa4 that the best ranked cell is not a CSG cell (Sa4—No), and if it is determined in step Sa5 that the mobile station device 10 has been registered (not unregistered) (Sa5—No), the camp-on controller 144 reselects the base station device determined to be the best ranked cell, and camps on the base station device (Sa10). Additionally, the camp-on controller 144 clears the IFRI information stored by the storing unit 15, and returns to step Sa1. On the other hand, if it is determined in step Sa5 that the mobile station device 10 has not been registered (Sa5—Yes), the camp-on controller 144 reads the IFRI from the broadcast information obtained in step Sa3, and determines whether or not the IFRI is set to be “not allowed” (prohibiting a cell having the same frequency from being reselected) (Sa6). If it is determined that the IFRI is not set to be “not allowed” (Sa6—No), and if a cell determined to be the second best ranked cell is not a cell currently camped on, the camp-on controller 144 reselects a base station device serving that cell, and camps on the base station device (Sa11). Additionally, the camp-on controller 144 clears the IFRI information stored by the storing unit 15, and returns to step Sa1.
If it is determined in step Sa6 that the IFRI is set to be “not allowed” (Sa6—Yes), the camp-on controller 144 causes the storing unit 15 to store IFRI information indicating that the IFRI is set to be “not allowed,” and information indicating the frequency for the best ranked cell (Sa7). Further, the camp-on controller 144 determines whether or not the mobile station device 10 is camping on a cell (Sa8). For example, if it is determined that the mobile station device 10 is not camping on a cell, for example, at the time immediately after the power-on (Sa8—No), the camp-on controller 144 reselects the base station device determined to be the second best ranked cell as a result of the cell search, camps on that base station device (Sa9), and then returns to step Sa1. If it is determined that the mobile station device 10 is camping on a cell (Sa8—Yes), the camp-on controller 144 returns to step Sa1.
If it is determined that the IFRI has been set to be “not allowed” (Sb2—Yes), the paging signal detector 143 reads the frequency used for the best ranked cell, which the camp-on controller 144 has caused the storing unit 15 to store in step Sa1 shown in
If it is determined in step Sc2 that the IFRI has been set to be “not allowed” (Sc2—Yes), the communication request detector 141 reads the frequency for the best ranked cell that the camp-on controller 144 has caused the storing unit 15 to store in step Sa7 shown in
In other words, firstly, the camp-on controller 144 performs cell search, and determines to perform reselection of a cell in step Sat (Sa2—Yes). Thus, the best ranked cell, that is, the base station device selected as a base station device to be reselected, is the CSG base station device 31. For this reason, the camp-on controller 144 determines in step Sa4 that the best ranked cell is the CSG cell (Sa4—Yes). Further, in step Sa5, the CSG base station device 31 selected as a base station device to be reselected is not included in the CSG list. For this reason, the camp-on controller 144 determines that the base station device is a base station device that the mobile station device 10 cannot camp on, that is, a base station device having not been registered (Sa5—Yes). Moreover, the CSG base station device 31 has reported the IFRI=not allowed, and therefore has reported in step Sa6 an indication which prohibits reselection of a base station device using the same frequency. In other words, the camp-on controller 144 determines that the IFRI is set to be “not allowed” (Sa6—Yes). Then, the camp-on controller 144 determines in step Sa8 that the mobile station device is camping on (Sa8—Yes), and returns back to step Sa1 to repeat cell search. In other words, even if “not allowed” is reported, a base station device having a frequency different from the frequency determined as “not allowed” is not immediately reselected.
On the other hand, the paging signal detector 143 operates according to the flowchart shown in
If a receipt of the paging signal is detected while the mobile station device 10 is present in the cell served by the CSG base station device 31, it is determined in step Sb2 that the IFRI has been set to be “not allowed” (Sb2—Yes), and the IFRI is applied. In other words, a frequency other than the frequency for the best ranked cell (CSG base station device 31) stored by the storing unit 15 is not searched until “not allowed” is reported by the IFRI. Then, a transfer to the best ranked cell determined as a result of the search is performed, and communication is initiated. Also in case that a communication request is detected, the IFRI is applied similarly.
As explained above, even if “not allowed” is reported, a base station device having a frequency different from the frequency determined as “not allowed” is not immediately reselected, and application of the indication “not allowed” is delayed until a receipt of the paging signal is detected.
In case that the mobile station device 10, by delaying application of indication, moves to the point P2 outside the CSG base station device 31 or the point P3 inside the cell served by the CSG base station device 32 while performing those monitoring processes, the best ranked cell is the base station device 21 or 22, or the CSG base station device 32 as a result of the cell search in step Sa1 shown in
Here, the transfer to the cell performed in steps Sb3 and Sc3 may be performed by a procedure similar to that of the reselection in the idle mode, or by a procedure similar to the handover procedure after the mobile station device 10 enters a connected mode.
Additionally, the timing of clearing the IFRI information may be set to the time the base station device having transmitted the IFRI constituting the IFRI information becomes the non-best ranked cell as a result of the cell search in step Sa1, that is, the time the best ranked cell is changed from the result of the previous cell search.
Further, it has been explained that the camp-on controller 144 causes the storing unit 15 to store the frequency for the best ranked cell. However, CSG_ID may be stored instead of storing the frequency, and the frequency may be obtained from broadcast information.
Thus, the IFRI to be transmitted from the mobile station device 10 causing interference is monitored at the time of communication. If “not allowed” is reported, a transfer to a cell having a different frequency is forcibly performed according to the IFRI, thereby preventing unnecessary interference from affecting the base station device having reported the IFRI. Additionally, when a paging signal is not received or when a communication request is not made (i.e., there is no calling), it is possible to leave as many opportunities as possible to search other base stations including a base station device using the same frequency (specifically, the CSG base station device).
Regarding Non-Patent Document 3, if the timer expires, reselection with respect to the same frequency is limited for a predetermined duration similarly to Non-Patent Document 4, and therefore a base station device using a different frequency is reselected. For this reason, reselection cannot be made even if accessible intra frequency CSG cells are present at a near place, thereby occasionally causing deterioration of service quality. According to the present invention, however, the timing of applying the indication of prohibition corresponds to the time a mobile station initiates transmission. For this reason, the mobile station camps on the cell having the same frequency irrespective of the expiration of the timer, thereby preventing deterioration of service quality.
Hereinafter, a second embodiment of the present invention is explained with reference to the drawings. A mobile communication system according to the second embodiment differs from that of the first embodiment in that a mobile station device 10a is included in lieu of the mobile station device 10.
On the other hand, it is determined in step Sd1 that “not allowed” is set (Sd2—Yes), the timer unit 145a reads a frequency for the best ranked cell stored by the storing unit 15, sets a frequency other than the read frequency to the receiver 13, and performs cell search that causes the receiver 13 to measure the reception level of a signal received from a neighboring base station device. For example, the timer 145a sets to the transmitter 12 and the receiver 13, a transmission and reception frequency for the best ranked cell determined as a result of that cell search, and performs a transfer to that cell (Sd3). Then, the timer unit 145a clears the IFRI information stored by the storing unit 15 (Sd4), and terminates the process.
Here, also in the second embodiment, a paging signal is received, and if an incoming call is received, operation similar to that shown in
Additionally, if similar conditions are met and if a communication request from the mobile station device 10a is detected, operation similar to that shown in
Thus, even in a case that the timer unit 145 controls its timer to leave as many as possible opportunities to search other base station devices including a base station device using the same frequency (specially, the CSG base station device) until the timer value expires even if the IFRI information indicates “not allowed”, IFRI to be transmitted from the base station device 10 causing interference is monitored at the time of communication. Then, if “not allowed” is reported, a transfer to a cell using a different frequency is forcibly performed according to the IFRI, thereby preventing unnecessary interference with the base station device having reported the IFRI. When a paging signal is not received (i.e., there is no incoming call) or when a communication request is not made (i.e., there is no outgoing call), it is possible to leave as many as possible opportunities to search other base stations including a base station device using the same frequency (specifically, the CSG base station device).
Hereinafter, a third embodiment of the present invention is explained with reference to the drawings. A mobile communication system according to the third embodiment differs from that of the first embodiment in that a mobile station device 10b is included in lieu of the mobile station device 10.
Thus, the IFRI to be transmitted from the mobile station device 10 causing interference is monitored at the time of communication, and if “not allowed” is reported, the notification that transmission is impossible is given to a user according to the IFRI, and communication is not performed, thereby preventing unnecessary interference.
Additionally, a computer-readable recording medium may store a program for implementing the functions of: the controller 14 shown in
Further, the “computer-readable recording medium” indicates a storage device, which includes a portable medium such as a flexible disc, a magneto-optical disc, a ROM, and a CD-ROM, and a storage device such as a hard disk built in the computer system. Additionally, the “computer-readable recording medium” may include a medium that dynamically stores a program for a short period of time, such as a communication line used when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. Additionally, the “computer readable recording medium” may include a medium that stores a program for a predetermined period of time, such as a volatile memory built in a computer system serving as a server or client when the program is transmitted via a network such as the Internet or a communication line such as a telephone line. Moreover, the program may be a program for implementing part of the aforementioned functions. Further, the program may be a program that can implement the aforementioned functions in combination with a program already recorded in the computer system.
Embodiments of the present invention have been explained above in detail with reference to the drawings. However, the specific configuration is not limited thereto. Various modifications may be made without departing from the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-005821 | Jan 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/050342 | 1/12/2011 | WO | 00 | 7/25/2012 |
