Wireless communication network system, wireless communication apparatus, mobile terminal, connection-target switch determining method, and connection-target change determining method

A wireless communication network system includes: a mobile terminal that transmits a switching request for requesting to switch a connection target from a currently connected first wireless communication apparatus to a second wireless communication apparatus mounted on a mobile body; and a wireless communication apparatus that determines permission or prohibition that the mobile terminal switches the connection target from its own apparatus to the second wireless communication apparatus, based on permission/prohibition setting of the connection target switching from the first wireless communication apparatus to the second wireless communication apparatus in accordance with a type of the first wireless communication apparatus.

FIELD

The present invention relates to a wireless communication apparatus mounted on a mobile body, a wireless communication apparatus installed at a predetermined position, and a wireless communication network system including a mobile terminal.

BACKGROUND

In recent years, wireless communication provides not only voice communication but also various services such as access to the Internet, delivery of streaming broadcasts, and delivery of contents containing music and videos.

In order to provide these services anywhere with high quality, introduction of a relay station that relays communication between a terminal and a base station is studied in LTE (Long Term Evolution) Advanced, which is a next-generation standard of 3GPP (3rd Generation Partnership Project). The high-quality service here refers to, for example, a service that is provided to a wide connection area with high throughput.

PATENT DOCUMENT

The relay station includes: a fixed relay station the installation site of which is fixed; and a mobile relay station that serves to improve processing during high-speed movement and is mounted on a mobile body.

FIG. 34is a diagram illustrating an example of a wireless communication network system including a mobile relay station. In the case where the mobile relay station is used in a switching process for a base station or a relay station to which a mobile terminal is connected, the following problem is expected to occur.

The wireless communication network system illustrated inFIG. 34includes a base station P1, a mobile relay station P2installed in a train P50, and a mobile terminal P4. The mobile terminal P4is located in a cell of the base station P1, and is located along a railway track on which the train P50passes.

(1) The mobile terminal P4is connecting to the base station P1to communicate with the other party. The mobile relay station P2is located sufficiently far from the mobile terminal P4, and hence, for the mobile terminal P4, the reception quality of a signal from the base station P1is better than the reception quality of a signal from the mobile relay station P2.

(2) A distance between the mobile terminal P4and the mobile relay station P2becomes smaller along with the movement of the train P50, and the mobile terminal P4enters a cell of the mobile relay station P2. When the mobile terminal P4enters the cell of the mobile relay station P2, for the mobile terminal P4, the reception quality of the signal from the mobile relay station P2becomes better than the reception quality of the signal from the base station P1. At the timing at which the reception quality of the signal from the mobile relay station P2becomes better than the reception quality of the signal from the base station P1, the mobile terminal P4starts a process of switching its connection target from the base station P1to the mobile relay station P2.

(3) As the mobile relay station P2moves away from the mobile terminal P4along with the movement of the train P50, the mobile terminal P4comes out of the cell of the mobile relay station P2. When the mobile terminal P4comes out of the cell of the mobile relay station P2, for the mobile terminal P4, the reception quality of the signal from the mobile relay station P2decreases to be exceeded by the reception quality of the signal from the base station P1. At the timing at which the reception quality of the signal from the base station P1becomes better than the reception quality of the signal from the mobile relay station P2, the mobile terminal P4starts a process of switching its connection target from the mobile relay station P2back to the base station P1.

Also with regard to cell selection when the mobile terminal P4is in a stand-by state, a cell is selected again on the basis of the reception qualities of signals similarly to (1) to (3) described above. Note that the reception quality of a signal may be determined from, for example, the power level of a pilot signal from each station.

However, the switching of the connection target of the mobile terminal P4as (1) to (3) described above is not preferable for the mobile terminal P4that is stably connected to the base station P1.

In the case where the mobile terminal P4is making communication, there occurs a period during which the communication is instantly interrupted due to the switching of the connection target. Such an instant interruption of the communication leads to unfavorable influences such as a decrease in throughput and an instant interruption of speech communication. In addition, for the network side such as the base station P1and the mobile relay station P2, unnecessary communication occurs, so that the network load is increased.

In the case where the mobile terminal P4is in a stand-by state, calling of this terminal may be missed during the execution of cell selection, and an incoming call may be delayed. In addition, electric power is consumed for the execution of unnecessary cell selection, so that a battery duration of the mobile terminal P4shortens.

Accordingly, in wireless communication networks using mobile relay stations as the example illustrated inFIG. 34, the connection target of a mobile terminal may not be efficiently switched in some cases.

SUMMARY

An aspect of the present invention relates to a wireless communication network system. The wireless communication network system includes: a mobile terminal that transmits a switching request for switching connection target from a currently connected first wireless communication apparatus to a second wireless communication apparatus mounted on a mobile body; and a wireless communication apparatus that determines permission or prohibition of the connection target switching of the mobile terminal from its own apparatus to the second wireless communication apparatus, based on permission/prohibition setting of switching the connection target from the first wireless communication apparatus to the second wireless communication apparatus in accordance with a type of the first wireless communication apparatus.

Another aspect of the present invention relates to a wireless communication apparatus. The wireless communication apparatus includes: a storing unit that holds permission/prohibition setting of switching connection target: from a first wireless communication apparatus to which a mobile terminal is currently connected; to a second wireless communication apparatus mounted on a mobile body, in accordance with a type of the first wireless communication apparatus; and a determining unit that determines, when receiving a switching request from the mobile terminal, permission or prohibition of the connection target switching of the mobile terminal from its own apparatus to the second wireless communication apparatus, based on the permission/prohibition setting.

Another aspect of the present invention relates to a wireless communication apparatus. The wireless communication apparatus is a first wireless communication apparatus mounted on a first mobile body, the first wireless communication apparatus including a determining unit that does not permit a mobile terminal that connects to the first wireless communication apparatus to switch its connection target from the first wireless communication apparatus to a second wireless communication apparatus mounted on a second mobile body, and permits the mobile terminal to switch its connection target from the first wireless communication apparatus to a third wireless communication apparatus that is not mounted on a mobile body.

Another aspect of the present invention relates to a mobile terminal. The mobile terminal includes: a storing unit that holds permission/prohibition setting of connection target change from a currently connected first wireless communication apparatus to a second wireless communication apparatus mounted on a mobile body in accordance with a type of the first wireless communication apparatus; and a determining unit that determines permission or prohibition of the connection target change from the first wireless communication apparatus to the second wireless communication apparatus, based on the permission/prohibition setting held in the storing unit.

Another aspect of the present invention relates to a connection-target switch determining method and a connection-target change determining method for the wireless communication network system, the wireless communication apparatus, and the mobile terminal described above.

The object and advantage of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.

DESCRIPTION OF EMBODIMENTS

Hereinafter, modes for carrying out the present invention (hereinafter, referred to as embodiments) are described with reference to the drawings. Configurations of the embodiments described below are given as examples, and the present invention is not limited to the configurations of the embodiments.

First Embodiment

FIG. 1is a diagram illustrating a configuration example of a wireless communication network system. A wireless communication network system100illustrated inFIG. 1includes: a base station1; a mobile relay station2installed in a train50as a mobile body; a fixed relay station3installed in a train station at which the train50stops; and mobile terminals4A,4B, and4C.

The base station1relays communication between a mobile terminal located in its own cell and a terminal with which the mobile terminal communicates. The base station1also relays communication between a mobile terminal located in a cell of the mobile relay station2and a terminal with which the mobile terminal communicates, via the mobile relay station2. The base station1also relays communication between a mobile terminal located in a cell of the fixed relay station3and a terminal with which the mobile terminal communicates, via the fixed relay station3.

The fixed relay station3is a relay station installed in the train station at which the train50stops. The fixed relay station3covers areas that are unreachable in a communicable level of a signal from the base station1, for example, undergrounds and areas far from the base station1. The fixed relay station3relays communication between the mobile terminal in the cell of the fixed relay station3and the base station1. It is preferable that the fixed relay station3be installed in a boarding/exiting facility for a mobile body such as the train station at which the train50stops.

The mobile relay station2is a relay station mounted on the train50. A cell range of the mobile relay station2is, for example, a range that roughly covers the train50. In the case where the mobile relay station2enters the cell of the base station1, the mobile relay station2relays communication with the base station1, of the mobile terminal that connects to the mobile relay station2.

The mobile terminal4A is a mobile terminal that is located along a railway track on which the train50passes. InFIG. 1, the mobile terminal4A is located in the cell of the base station1, and is not in the cells of the mobile relay station2and the fixed relay station3.

The mobile terminal4B is a mobile terminal owned by a passenger in the train50. That is, the mobile terminal4B is located inside of the train50. InFIG. 1, the mobile terminal4B is located in the cell of the base station1, and is located also in the cell of the mobile relay station2. The mobile terminal4B receives radio signals from both the base station1and the mobile relay station2. The reception quality of the signal that the mobile terminal4B receives from the mobile relay station2is better than the reception quality of the signal from the base station1, and hence, at the time of communication, the mobile terminal4B connects to the mobile relay station2to make communication.

The mobile terminal4C is a mobile terminal located inside of the train station at which the train50stops. The mobile terminal4C is located in the cell of the base station1, and is located also in the cell of the fixed relay station3. The mobile terminal4C receives radio signals from both the base station1and the fixed relay station3. The reception quality of the radio signal that the mobile terminal4C receives from the fixed relay station3is better than the reception quality of the radio signal from the base station1, and hence the mobile terminal4C connects to the fixed relay station3to make communication.

During communication and in a stand-by state, the mobile terminals4A,4B, and4C receive a signal from at least one of the base station1, the mobile relay station2, and the fixed relay station3, and periodically measure the reception quality of the signal from each station. On the basis of the measurement result of the reception quality of the signal, the mobile terminals4A,4B, and4C each select a station that is a transmission source of a signal having the best reception quality, as a station to be used for communication. Accordingly, inFIG. 1, at the time of communication, the mobile terminal4A selects the base station1and connects thereto. The mobile terminal4B selects the mobile relay station2and connects thereto. The mobile terminal4C selects the fixed relay station3and connects thereto. In the case where the station that is the transmission source of the signal having the best reception quality has changed in accordance with a change in radio wave conditions due to the movement of the mobile terminal itself or the like, the mobile terminals4A,4B, and4C each select another station (or the cell) to be used for communication.

Switching of the connection target station by the mobile terminal during communication is referred to as handover. Selecting of another connection target station (or cell) by the mobile terminal in a stand-by state is hereinafter referred to as reselection. A station that is selected as the connection target of the mobile terminal is hereinafter referred to as selected station. A station that is selected as a handover target or a reselection target is hereinafter referred to as transfer target candidate station. The base station, the mobile relay station, and the fixed relay station are collectively referred to as “station”. The base station, the mobile relay station, and the fixed relay station correspond to the “wireless communication apparatus” according to one of the aspects of the present invention. The base station and the fixed relay station correspond to the “fixed apparatus” according to one of the aspects of the present invention. The mobile relay station corresponds to the “mobile apparatus” according to one of the aspects of the present invention.

Note that, for simplicity of description, it is assumed inFIG. 1that the mobile terminals4A,4B, and4C do not move.

In the wireless communication network system100illustrated inFIG. 1, for example, the following restrictions can be provided for the handover and reselection of the cellular phones4A,4B, and4C.

(Restriction 1) The mobile terminal4A the selected station of which is the base station1is prohibited from making the handover and the reselection from the base station1to the mobile relay station2. This is because the mobile terminal4A can communicate with the base station1without the intermediation of the relay station and such unfavorable handover and reselection from the base station1to the mobile relay station2cause an instant interruption or an increase in network load.

(Restriction 2) The mobile terminal4B the selected station of which is the mobile relay station2can make the handover and the reselection from the mobile relay station2to the base station1in the case where the reception quality of the signal from the base station1is the best. When the mobile terminal4B communicates directly with the base station1without the intermediation of the mobile relay station2, more stable communication can be established in terms of throughput and the like. Hence, in the case where the reception quality from the base station1is better, the selected station is switched to the base station1. In addition, when the reception quality of the signal from the mobile relay station2becomes the best as the train50moves away from the base station1, the mobile terminal4B can make the handover and the reselection from the base station1back to the mobile relay station2. Similarly, the mobile terminal4B can make the handover and the reselection from the mobile relay station2to the fixed relay station3, and further can make the handover or the reselection from the fixed relay station3back to the mobile relay station2.

(Restriction 3) The mobile terminal4C the selected station of which is the fixed relay station3can make the handover and the reselection from the fixed relay station3to the mobile relay station2, in reaction to the approach of the train50. The fixed relay station3is a station installed in the train station. In addition, the owner of the mobile terminal4C the selected station of which is the fixed relay station3may get on the train50. Accordingly, in order to continue the communication even when the owner of the mobile terminal4C gets on the train50, the mobile terminal4C can make the handover and the reselection from the fixed relay station3to the mobile relay station2in the case where the reception quality from the mobile relay station2is better. With this configuration, even in the case where the owner of the mobile terminal4C does not get on the train50, the mobile terminal4C may make the handover and the reselection to the mobile relay station2in reaction to the approach of the train50. In order to continue the communication even when the train50has moved away from the train station, the mobile terminal4C can make the handover and the reselection from the mobile relay station2back to the fixed relay station3in the case where the reception quality from the fixed relay station3becomes better.

(Restriction 4) The mobile terminal4B the selected station of which is the mobile relay station2is prohibited from making the handover and the reselection to another mobile relay station. For example, this is because, inFIG. 1, even if the mobile terminal4B makes the handover to another mobile relay station mounted on a train (not illustrated) that passes by the train50, the time of connection to the another mobile relay station is short.

InFIG. 1, also in the case where a base station is installed at the train station instead of the fixed relay station3, Restriction 3 is applied to the base station. That is, even if the fixed relay station3inFIG. 1is a base station, the restriction of (Restriction 1) to (Restriction 4) is put on the wireless communication network system100. Accordingly, the type of station is as described below.

(Type 1) A base station or a fixed relay station installed near a boarding/exiting facility for a mobile body such as a train station and a bus stop

(Type 2) A base station or a fixed relay station other than Type 1

(Type 3) A mobile relay station

Examples of the mobile body include a train, a bus, and an automobile. Note that, in the case where the base station or the fixed relay station is not particularly distinguished by Type 1 and Type 2, the base station or the fixed relay station is simply referred to as base station or fixed relay station.

FIG. 2is a table in which (Restriction 1) to (Restriction 4) are put in order. That is,FIG. 2is a table illustrating restriction on the handover and the reselection in the wireless communication network system100. InFIG. 2, changes of the selected station of the mobile terminal are categorized into Cases (a) to (e), and description is given for each case.

(a) a Change of the Selected Station from a Base Station or a Fixed Relay Station to a Base Station or a Fixed Relay Station

The handover and the reselection from a base station or a fixed relay station to a fixed relay station or a base station occur due to the movement of a mobile terminal, and thus are naturally permitted.

(b) a Change of the Selected Station from the Base Station or the Fixed Relay Station of Type 1 to a Mobile Relay Station

The handover and the reselection from the base station or the fixed relay station (Type 1) installed near the boarding/exiting facility for the mobile body to a mobile relay station are permitted according to (Restriction 3).

(c) a Change of the Selected Station from the Base Station or the Fixed Relay Station of Type 2 to a Mobile Relay Station

The handover and the reselection from the base station or the fixed relay station of Type 2 to a mobile relay station are permitted according to (Restriction 1) and (Restriction 2), in the case where a history of connection to the mobile relay station as the transfer target candidate station exists before connection to the currently selected station.

(d) A change of the selected station from a mobile relay station to a base station and a fixed relay station

The handover and the reselection from a mobile relay station to a base station and a fixed relay station are permitted according to (Restriction 2).

(e) A change of the selected station from a mobile relay station to a mobile relay station

The handover and the reselection from a mobile relay station to a mobile relay station are not permitted according to (Restriction 4).

According to the example illustrated inFIG. 2, in the wireless communication network system, in the case where the transfer target candidate station is a base station or a fixed relay station, the handover and the reselection are permitted without any condition. On the other hand, in the case where the transfer target candidate station is a mobile relay station, the permission or prohibition of the handover and the reselection is determined depending on the type of the currently selected station and the connection history.

The handover is a process in which a mobile terminal switches its connection target during communication via a base station, a fixed relay station, or a mobile relay station, and hence the permission or prohibition of the handover can be determined by any of the stations and the mobile terminal. On the other hand, the reselection is a process performed when a mobile terminal is in a stand-by state, and thus is closed to the mobile terminal.

In the first embodiment, description is given of the case where the permission or prohibition of the handover is determined by the stations.

Hereinafter, the mobile terminals4A,4B, and4C are simply referred to as “mobile terminal4” unless the mobile terminals4A,4B, and4C are particularly distinguished from one another.

<Operation Example when Handover is Made from Base Station to Fixed Relay Station>

FIG. 3is a diagram illustrating an operation example when the mobile terminal executes the handover from the base station to the fixed relay station. In the example illustrated inFIG. 3, inFIG. 1, the mobile terminal4A makes the handover from the base station1to the fixed relay station3.

The mobile terminal4A is making communication while the base station1is its selected station. In addition, the fixed relay station3relays the communication between the base station1and the mobile terminal4A.

The mobile terminal4A periodically executes a detection process of neighboring stations and a measurement process of the reception quality of signals from the neighboring stations (OP1). The mobile terminal4A determines whether or not the reception quality of the signal from the base station1as the currently selected station is the best (OP2).

If the reception quality of the signal from the base station1is the best (OP2: Yes), the processing returns to OP1.

If there is a station having a reception quality better than that of the signal from the base station1(OP2: No), the mobile terminal4A determines to make the handover to a station having the best reception quality. In the example illustrated inFIG. 3, the reception quality of the signal from the fixed relay station3is the best for the mobile terminal4A, and hence the mobile terminal4A determines to make the handover from the base station1to the fixed relay station3.

The mobile terminal4A transmits a measurement report for requesting the handover to the fixed relay station3, to the currently connected base station1(OP3). The measurement report transmitted by the mobile terminal4A includes, for example: the identification number of each station detected by the mobile terminal4A; and the identification number of the transfer target candidate station.

Upon the reception of the measurement report, the base station1transmits a handover request for requesting the handover, to the fixed relay station3as the transfer target candidate station included in the measurement report (OP4). The handover request is a message for inquiring of the transfer target candidate station whether or not the handover is possible. The fixed relay station3as the transfer target candidate station that has received the handover request permits the handover, and transmits a handover request ACK to the base station1(OP5).

If a response is returned from the fixed relay station3, the base station1transmits a handover command to the mobile terminal4A, and thus instructs the mobile terminal4A to execute the handover (OP6). Upon the reception of the handover command, the mobile terminal4A executes the handover from the base station1to the fixed relay station3(OP7). Upon the completion of the handover, the mobile terminal4A issues a handover complete, to thereby report the completion of the handover to the fixed relay station3(OP8).

Upon the reception of the handover complete by the fixed relay station3, a session is established between the mobile terminal4A and the fixed relay station3.

<Operation Example when Reselection is Made from Base Station to Fixed Relay Station>

FIG. 4is a diagram illustrating an operation example when the mobile terminal executes the reselection from the base station to the fixed relay station. In the example illustrated inFIG. 4, inFIG. 1, the mobile terminal4A makes the reselection from the base station1to the fixed relay station3.

The mobile terminal4A periodically executes a detection process of neighboring stations and a measurement process of the reception quality of signals from the neighboring stations (OP11). The mobile terminal4A determines whether or not the reception quality of the signal from the base station1as the currently selected station is the best (OP12).

If the reception quality of the signal from the base station1is the best (OP12: Yes), the processing returns to OP11.

If there is a station having a reception quality better than that of the signal from the base station1(OP12: No), the mobile terminal4A determines to change the selected station to a station having the best reception quality. In the example illustrated inFIG. 4, the reception quality of the signal from the fixed relay station3is the best, and hence the mobile terminal4A determines to make the reselection from the base station1to the fixed relay station3.

The mobile terminal4A acquires notifying information from the fixed relay station3as the transfer target candidate station (OP13), and executes the reselection from the base station1as the currently selected station to the fixed relay station3(OP14).

<<Configuration Example of Mobile Terminal>>

FIG. 5is a diagram illustrating a configuration example of the mobile terminal4. The mobile terminal4includes a receiving antenna41, a radio unit42, a layer 1 processing unit43, a layer 2 processing unit44, a radio resource controlling unit45, an application layer processing unit46, and a transmitting antenna47. These units are each implemented by software components or hardware components or by the combination thereof (see the section [Others]).

The mobile terminal4receives a signal transmitted by the base station1, the mobile relay station2, or the fixed relay station3through the receiving antenna41. The reception signal received by the receiving antenna41is down-converted by the radio unit42from a radio-frequency signal to a baseband signal and is outputted to the layer 1 processing unit43.

The layer 1 processing unit43executes a process that is performed in a physical layer corresponding to a layer 1 in LTE, on the inputted baseband signal. The layer 1 processing unit43includes a demodulating unit431, a decoding unit432, a coding unit433, and a modulating unit434.

The demodulating unit431receives the baseband signal from the radio unit42, and performs a demodulation process on the received baseband signal. The demodulating unit431performs the demodulation process according to, for example, an OFDMA (Orthogonal Frequency Division Multiplexing Access) system. The demodulating unit431includes a measuring unit431a, an FFT (Fast Fourier Transformation) unit431b, and a demodulation executing unit431c.

The measuring unit431aperforms cell search and level measurement on the basis of the received baseband signal. The FFT unit431bexecutes fast Fourier transformation on an OFDMA symbol, and performs transformation from a time-domain signal to a frequency-domain signal. The demodulation executing unit431cdemodulates the inputted signal (a multilevel-modulated symbol according to, for example, QPSK (Quadrature Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation), and 64QAM), and thus obtains data. The demodulation executing unit431coutputs the obtained data to the decoding unit432.

The decoding unit432performs a decoding process on the inputted data. The decoding unit432includes a de-rate matching unit432a, an HARQ (Hybrid Automatic Repeat reQuest) combining unit432b, a turbo decoding unit432c, and a CRC (Cyclic Redundancy Check) unit432d.

The de-rate matching unit432arestores data that has been expanded or reduced, in accordance with an allocated physical channel resource, and outputs the restored data to the HARQ combining unit432b. The HARQ combining unit432bcombines retransmitted data through an HARQ retransmission process, to thereby perform error recovery. The HARQ combining unit432boutputs the data obtained by the error recovery to the turbo decoding unit432c. The turbo decoding unit432cdecodes the inputted turbo encoded data, and outputs the decoded data to the CRC unit432d. The CRC unit432dchecks whether or not the data inputted by the turbo decoding unit432cis correct, and outputs the result to the layer 2 processing unit44.

The coding unit433performs a coding process on a transmission data. The coding unit433includes a CRC adding unit433a, a turbo coding unit433b, and a rate matching unit433c.

The turbo coding unit433bperforms turbo coding on the transmission data inputted by the CRC adding unit433a, and outputs the resultant data to the rate matching unit433c.

The rate matching unit433cexpands or reduces the transmission data inputted by the turbo coding unit433b, in accordance with an allocated physical channel resource. The rate matching unit433coutputs the expanded or reduced transmission data to the modulating unit434.

The modulating unit434performs a modulation process on the transmission data inputted by the coding unit433. The modulating unit434applies, for example, SC-FDMA (Single Carrier Frequency Division Multiple Access) to the transmission data. The modulating unit434includes a modulation executing unit434a, a DFT (Discrete Fourier Transform) unit434b, a subcarrier mapping unit434c, and an IFFT (Inverse FFT) unit434d.

The modulation executing unit434aperforms multilevel modulation on the transmission data inputted by the coding unit433. The modulation executing unit434aoutputs the multilevel-modulated symbol to the DFT unit434b.

The DFT unit434bperforms discrete Fourier transform on the symbol inputted by the subcarrier modulation executing unit434a. The DFT unit434boutputs the symbol that has been subjected to the discrete Fourier transform, to the subcarrier mapping unit434c.

The subcarrier mapping unit434callocates the symbol inputted by the DFT unit434b, to a physical channel resource designated by the network. The subcarrier mapping unit434coutputs the symbol allocated to the physical channel resource, to the IFFT unit434d.

The IFFT unit434dperforms inverse fast Fourier transformation on the symbol that is inputted by the subcarrier mapping unit434cand is allocated for each physical channel. The IFFT unit434outputs the symbol that has been subjected to the inverse fast Fourier transformation, to the radio unit42.

The baseband signal outputted by the layer 1 processing unit43is transformed by the radio unit42into a radio-frequency signal, and is transmitted through the antenna47.

The layer 2 processing unit44performs data coupling/decoupling in accordance with respective formats of an MAC (Media Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer included in a layer 2 in LTE. In addition, the layer 2 processing unit44also performs retransmission control and ordering of data.

The radio resource controlling unit45is in charge of radio resource control and entire apparatus control on the basis of the data inputted by the layer 2 processing unit44. The radio resource controlling unit45includes a connection controlling unit451, a measurement controlling unit452, and a mobility controlling unit453.

The connection controlling unit451performs an outgoing call/incoming call process, establishment and opening of a call and the like. The measurement controlling unit452manages and reports a measurement target cell, and controls a measurement threshold of the handover. The mobility controlling unit453controls the handover and the like. The detail of the mobility controlling unit453is described later.

The application layer processing unit46performs an upper layer process such as data processing corresponding each user.

FIG. 6is a diagram illustrating a configuration example of the mobility controlling unit453of the mobile terminal4. The mobility controlling unit453of the mobile terminal4includes a measurement value acquiring unit61, a first reselection determining unit62, a second reselection determining unit63, a reselection executing unit64, a handover executing unit65, and a storing unit66.

The storing unit66holds: a mobile relay station connection history of the mobile terminal4; the identification numbers of neighboring stations detected by the mobile terminal4; information on a mobile relay station list; and cell transfer permission/prohibition setting of each station neighboring the mobile terminal4, the information and the cell transfer permission/prohibition setting being included in notifying information delivered by the base station. The mobile relay station list is, for example, a list of the identification numbers of mobile relay stations in the wireless communication network100, and is one of pieces of information included in the notifying information delivered by each station.

FIG. 7is a table illustrating an example of the mobile relay station connection history. The mobile relay station connection history stores the identification number of a mobile relay station that is last selected as the selected station. In the initial state of the mobile relay station connection history, a history of connection to the mobile relay station does not exist, and the setting value is Invalid. The identification number of the mobile relay station registered in the mobile relay station connection history is deleted when this mobile relay station is not detected any more by neighborhood monitoring of the mobile terminal. Upon the deletion of the identification number of the mobile relay station, the setting value becomes Invalid.

FIG. 7illustrates a change in information that is set to the mobile relay station connection history when the mobile terminal4makes the handover or the reselection in order of the fixed relay station3, the mobile relay station2, the base station1, the mobile relay station2, and a fixed relay station3b(not illustrated inFIG. 1) in the example illustrated inFIG. 1.

(1) For example, it is assumed that the mobile terminal4does not have a history of connection to any mobile relay station and that the fixed relay station3is selected as the selected station. In this case, Invalid is set to the mobile relay station connection history of the mobile terminal3.

(2) The train50approaches the train station, the user who owns the mobile terminal4gets on the train50, and the mobile terminal4makes the handover or the reselection to the mobile relay station2. At this time, the identification number of the mobile relay station2is set to the mobile relay station connection history.

(3) Further, in the case where the mobile terminal4makes the handover or the reselection to the base station1due to the movement of the train50, because the transfer target is not a mobile relay station, the mobile relay station connection history regarding the mobile relay station2is held.

(4) After that, when the mobile terminal4connects again to the mobile relay station2, the mobile relay station connection history is updated with the identification number of the mobile relay station2(in this case, overwritten and updated).

(5) After that, the user who owns the mobile terminal4gets off the train, and the mobile terminal4makes the handover or the reselection to the fixed relay station3b. When the mobile terminal4moves sufficiently away from the train50on which the mobile relay station2is mounted, the mobile relay station2is not detected any more, and hence the identification number of the mobile relay station2is deleted from the mobile relay station connection history. Invalid is set to the mobile relay station connection history.

In this way, the information on the last connected mobile relay station is held in the mobile relay station connection history.

FIG. 8is a diagram illustrating an example of the cell transfer permission/prohibition setting. The cell transfer permission/prohibition setting is, for example, setting of the permission or non-permission of the handover and the reselection from each station to a mobile relay station, the setting being made in advance to each station by an administrator or the like of the wireless communication network. The cell transfer permission/prohibition setting of each station is one of pieces of information contained in the notifying information delivered by each station.FIG. 8illustrates the cell transfer permission/prohibition setting for each type of station.

The base station and the fixed relay station (Type 1) installed near the boarding/exiting facility for the mobile body are permitted to make the handover and the reselection to a mobile relay station according to the table illustrated inFIG. 2. Accordingly, the cell transfer permission/prohibition setting of the fixed relay station3inFIG. 1is “Permitted”.

The base station and the fixed relay station (Type 2) other than Type 1 are not permitted to make the handover and the reselection to a mobile relay station according to (Restriction 1). Accordingly, the cell transfer permission/prohibition setting of the base station1inFIG. 1is “Not Permitted”.

A mobile relay station is not permitted to make the handover and the reselection to a mobile relay station according to the table illustrated inFIG. 2. Accordingly, the cell transfer permission/prohibition setting of the mobile relay station2inFIG. 1is “Not Permitted”.

The measurement value acquiring unit61obtains, as its input, a measurement result of each station neighboring the mobile terminal4, the measurement result being obtained by the measuring unit431aof the layer 1 processing unit43. On the basis of a measurement result of the reception quality of a signal from each station, the measurement value acquiring unit61determines a station having the best measurement result as the transfer target candidate station, in the case where the measurement result exceeds a predetermined threshold. The predetermined threshold is, for example, a measurement threshold of the handover managed by the measurement controlling unit452of the radio resource controlling unit45. The measurement value acquiring unit61reports the transfer target candidate station to the handover executing unit65and the first reselection determining unit62.

The handover executing unit65is activated upon communication start of the mobile terminal4. When the transfer target candidate station is reported by the measurement value acquiring unit61during the communication of the mobile terminal4, the handover executing unit65determines whether or not the transfer target candidate station is the same as the currently selected station. If the transfer target candidate station is different from the currently selected station, that is, if the station having the best reception quality of the signal has changed, the handover executing unit65determines to make the handover to the transfer target candidate station. The handover executing unit65generates a measurement report for requesting the execution of the handover to the transfer target candidate station, and transmits the measurement report to the currently selected station. The measurement report includes: the identification numbers of the neighboring stations whose signal is detected by the mobile terminal4; the identification number of the transfer target candidate station; the mobile relay station connection history and the like, on the basis of the information held in the storing unit66.

Upon the completion of the handover, in the case where the transfer target station that has newly become the selected station is a mobile relay station, the handover executing unit65updates the mobile relay station connection history in the storing unit66with the identification number of the mobile relay station.

If the transfer target candidate station is reported by the measurement value acquiring unit61during a stand-by state of the mobile terminal4, the first reselection determining unit62determines whether or not the transfer target candidate station is the same as the currently selected station. If the transfer target candidate station is different from the currently selected station, the first reselection determining unit62starts a reselection process in cooperation with the second reselection determining unit63.

The first reselection determining unit62determines whether or not the currently selected station and the transfer target candidate station are mobile relay stations, and determines the permission or prohibition of the reselection from the currently selected station to the transfer target candidate station. As a result of the determination, if the reselection from the currently selected station to the transfer target candidate station is possible, the first reselection determining unit62instructs the reselection executing unit64to execute the reselection.

In the case where the permission or prohibition of the reselection is not determined by the first reselection determining unit62, the second reselection determining unit63determines the permission or prohibition of the reselection from the currently selected station to the transfer target candidate station, on the basis of the mobile relay station connection history. As a result of the determination, if the transfer from the currently selected station to the transfer target candidate station is possible, the second reselection determining unit63instructs the reselection executing unit64to execute the reselection.

Upon the reception of the instruction to execute the reselection from the first reselection determining unit62or the second reselection determining unit63, the reselection executing unit64executes the reselection from the currently selected station to the transfer target candidate station. At the time of the completion of the reselection, in the case where the station that has newly become the selected station is a mobile relay station, the reselection executing unit64updates the mobile relay station connection history in the storing unit66with the identification number of the mobile relay station.

The first reselection determining unit62and the second reselection determining unit63correspond to the “determining unit” according to one of the aspects of the present invention.

FIG. 9is a diagram illustrating a flow example of a reselection determination process of the mobile terminal4. At the timing at which a station having the best reception quality of the signal changes during a stand-by state of the mobile terminal4, the mobile terminal4starts the reselection determination process with the station having the best reception quality being as the transfer target candidate station. That is, if the transfer target candidate station inputted by the measurement value acquiring unit61is different from the currently selected station, the first reselection determining unit62starts the reselection determination process.

The first reselection determining unit62determines whether or not the transfer target candidate station is a mobile relay station (OP21). The first reselection determining unit62compares the mobile relay station list held in the storing unit66with the identification number of the transfer target candidate station, to thereby determine whether or not the transfer target candidate station is a mobile relay station.

If the transfer target candidate station is not a mobile relay station (OP21: No), the reselection is permitted regardless of the type of the currently selected station (seeFIG. 2). The first reselection determining unit62instructs the reselection executing unit64to execute the reselection from the currently selected station to the transfer target candidate station. The reselection executing unit64that has received the instruction executes the reselection from the currently selected station to the transfer target candidate station (OP26b), and ends the reselection determination process.

If the transfer target candidate station is a mobile relay station (OP21: Yes), the reselection to the mobile relay station as the transfer target candidate station is restricted depending on the type of the currently selected station (seeFIG. 2). If the currently selected station is the base station and the fixed relay station (Type 1) installed near the boarding/exiting facility for the mobile body, the reselection from the currently selected station to the mobile relay station (transfer target candidate station) is permitted. If the currently selected station is the base station and the fixed relay station (Type 2) other than Type 1, the permission or prohibition of the reselection from the currently selected station to the mobile relay station (transfer target candidate station) is determined in accordance with the mobile relay station connection history. If the currently selected station is a mobile relay station, the reselection from the mobile relay station (currently selected station) to the mobile relay station (transfer target candidate station) is not permitted.

Accordingly, if the transfer target candidate station is a mobile relay station (OP21: Yes), the first reselection determining unit62determines whether or not the transfer from the currently selected station to the transfer target candidate station (mobile relay station) is possible (OP22). That is, the first reselection determining unit62determines whether or not the cell transfer permission/prohibition setting of the currently selected station held in the storing unit66is “Permitted”.

If the cell transfer permission/prohibition setting of the currently selected station is “Permitted” (OP22: Yes), this means that the currently selected station is the base station and the fixed relay station (Type 1) installed near the boarding/exiting facility for the mobile body. In this case, the first reselection determining unit62instructs the reselection executing unit64to execute the reselection from the currently selected station to the mobile relay station (transfer target candidate station). The reselection executing unit64that has received the instruction executes the reselection from the currently selected station to the mobile relay station (transfer target candidate station) (OP26a). Upon the completion of the reselection, the reselection executing unit64updates the mobile relay station connection history in the storing unit66with the identification number of the mobile relay station as the transfer target (OP27). Upon the completion of the update of the mobile relay station connection history, the reselection determination process is ended.

If the cell transfer permission/prohibition setting of the currently selected station is “Not Permitted” (OP22: No), this means that the currently selected station is any of: the base station and the fixed relay station (Type 2) other than Type 1; and a mobile relay station. In this case, the permission or prohibition of the reselection is determined depending on whether or not the mobile relay station held in the mobile relay station connection history is coincident with the transfer target candidate station (seeFIG. 2). Accordingly, the processing moves from the first reselection determining unit62to the second reselection determining unit63, and the second reselection determining unit63refers to the mobile relay station connection history in the storing unit66. The second reselection determining unit63determines whether or not the mobile relay station held in the mobile relay station connection history is coincident with the transfer target candidate station (OP25).

If the mobile relay station in the mobile relay station connection history is not coincident with the transfer target candidate station (OP25: No), the second reselection determining unit63determines the non-permission of the reselection, and stops the reselection determination process (OP24). This ends the reselection determination process.

If the mobile relay station in the mobile relay station connection history is coincident with the transfer target candidate station (OP25: Yes), the second reselection determining unit63determines the permission of the reselection, and instructs the reselection executing unit64to execute the reselection. The reselection executing unit64that has received the instruction executes the reselection from the currently selected station to the mobile relay station (transfer target candidate station) (OP26a). Upon the completion of the reselection, the reselection executing unit64updates the mobile relay station connection history in the storing unit66with the identification number of the mobile relay station as the transfer target (OP27). Upon the completion of the update of the mobile relay station connection history, the reselection determination process is ended.

Through the process in OP25, for example, the mobile terminal4B inFIG. 1can make the reselection from the mobile relay station2to the base station1, and further can make the reselection from the base station1to the mobile relay station2. Note that, in the flow illustrated inFIG. 9, a change of the selected station between mobile relay stations is not permitted, and hence information on a mobile relay station as the transfer target in such a change of the selected station between mobile relay stations is not set to the mobile relay station connection history. For this reason, even in the case where the currently selected station is a mobile relay station and where the transfer target candidate station is another mobile relay station, it is determined in OP22that the transfer from the selected station is not possible, it is determined in OP25that the mobile relay station connection history is not coincident with the transfer target candidate station, and the reselection is stopped in OP24. Accordingly, in the flow illustrated inFIG. 9, the reselection from a mobile relay station to another mobile relay station is not executed.

<<Configuration Example of Base Station>>

FIG. 10is a diagram illustrating a configuration example of the base station1. The base station1includes a receiving antenna11, a radio unit12, a layer 1 processing unit13, a layer 2 processing unit14, a radio resource controlling unit15, and a transmitting antenna16. The layer 1 processing unit13includes a demodulating unit131, a decoding unit132, a coding unit133, and a modulating unit134. The demodulating unit131includes an FFT unit131a, a subcarrier demapping unit131b, an IDFT (Inverse DFT) unit131c, and a demodulation executing unit131d. The decoding unit132includes a de-rate matching unit132a, an HARQ combining unit132b, a turbo decoding unit132c, and a CRC unit132d. The coding unit133includes a CRC adding unit133a, a turbo coding unit133b, and a rate matching unit133c. The modulating unit134includes a modulation executing unit134a, a subcarrier mapping unit134b, and an IFFT unit134c. The radio resource controlling unit15includes a connection controlling unit151, a measurement controlling unit152, and a mobility controlling unit153. These units are each implemented by software components or hardware components or by the combination thereof (see the section [Others]).

The processing units of the base station1perform processes similar to those of the corresponding processing units (seeFIG. 5) with the same names of the mobile terminal4, and hence description of the processing units is omitted. In the base station1, unlike the mobile terminal4, users are multiplexed by the subcarrier mapping unit134blocated before the input of the IFFT unit134clocated before transmission of physical channel data. Meanwhile, on the reception side of physical channel data, users are separated by the subcarrier demapping unit131b. A set of the IDFT unit131c, the demodulation executing unit131d, the de-rate matching unit132a, the HARQ combining unit132b, the turbo decoding unit132c, and the CRC unit132dis provided for each user. Similarly, a set of the CRC adding unit133a, the turbo coding unit133b, the rate matching unit133c, the modulation executing unit134a, and the subcarrier mapping unit134bis provided for each user. In the base station1, data is subjected to a coding process and a modulation process and to a demodulation process and a decoding process on a user basis. In addition, the base station1is connected to an upper node.

FIG. 11is a diagram illustrating a configuration example of the mobility controlling unit153of the base station1. The mobility controlling unit153of the base station1includes a handover controlling unit71, a storing unit72, and a notifying information updating unit73.

The notifying information updating unit73updates notifying information for reporting information on neighboring base stations to the mobile terminal4, and delivers the updated information to the mobile terminal4. The notifying information updating unit73delivers, to the mobile terminal, the notifying information including: the identification number of its own station; information on stations in neighboring cells including the cell in which the mobile terminal4is located; the cell transfer permission/prohibition setting of each station; and the mobile relay station list. The information on the base stations in the neighboring cells is, for example, used frequency of each station. In addition, the notifying information updating unit73updates the mobile relay station list when receiving a request of registration into the mobile relay station list from the mobile relay station or receiving an update report of the mobile relay station list from another station. The notifying information updating unit73updates the notifying information including the updated mobile relay station list, and delivers the updated information to the mobile terminal. At the same time, the notifying information updating unit73delivers the update report of the mobile relay station list to base stations and fixed relay stations under the base station1. Each time the notifying information is updated, the notifying information updating unit73stores the updated notifying information into the storing unit72.

The storing unit72holds the type of its own station, the cell transfer permission/prohibition setting of its own station, the mobile relay station list, components of the notifying information and the like. The type of its own station held in the storing unit72is information for identifying which of the base station, the fixed relay station, and the mobile relay station its own station is.

The handover controlling unit71controls the handover of the mobile terminal4. The handover controlling unit71includes a first handover determining unit711, a second handover determining unit712, and a handover executing unit713.

When the first handover determining unit711receives a measurement report that triggers the handover from the mobile terminal4that connects to its own station as the selected station through the layer 2 processing unit14, the first handover determining unit711starts a handover determination process. The first handover determining unit711determines whether or not the transfer target candidate station of the mobile terminal4that is a transmission source of the measurement report is a mobile relay station, and determines the permission or prohibition of the handover from its own station as the currently selected station to the transfer target candidate station. As a result of the determination, if the handover from its own station to the transfer target candidate station is possible, the first handover determining unit711instructs the handover executing unit713to execute the handover.

In the case where the handover is not permitted by the first handover determining unit711, the second handover determining unit712determines the permission or prohibition of the handover on the basis of the mobile relay station connection history of the mobile terminal4included in the measurement report. As a result of the determination, if the mobile terminal4can make the handover from its own station to the transfer target candidate station, the second handover determining unit712instructs the handover executing unit713to execute the handover.

Upon the reception of the instruction to execute the handover to the transfer target candidate station from the first handover determining unit711and the second handover determining unit712, the handover executing unit713executes the handover to the transfer target candidate station. The handover executing unit713transmits, to the transfer target candidate station, a handover request for requesting the execution of the handover of the mobile terminal4that is a transmission source of the measurement report. If a handover request ACK as a response is returned from the transfer target candidate station, the handover executing unit713transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4that is a request source of the handover.

The first handover determining unit711and the second handover determining unit712correspond to the “determining unit” according to one of the aspects of the present invention.

FIG. 12is a diagram illustrating a flow example of the handover determination process of the base station1. Upon the reception of a measurement report from the mobile terminal4that connects to its own station as the selected station, the base station1starts the handover determination process.

The first handover determining unit711determines whether or not the transfer target candidate station of the mobile terminal4included in the measurement report is a mobile relay station (OP31). The first handover determining unit711compares the mobile relay station list held in the storing unit72with the identification number of the transfer target candidate station included in the measurement report, to thereby determine whether or not the transfer target candidate station is a mobile relay station.

If the transfer target candidate station is not a mobile relay station (OP31: No), the handover of the mobile terminal4from its own station (base station1) to the transfer target candidate station is permitted (seeFIG. 2). The first handover determining unit711instructs the handover executing unit713to execute the handover to the transfer target candidate station of the mobile terminal4. The handover executing unit713that has received the instruction executes the handover to the transfer target candidate station of the mobile terminal4(OP36). A detailed process in OP36by the handover executing unit713is as follows. The handover executing unit713transmits a handover request for requesting the handover, to the transfer target candidate station of the mobile terminal4. If a handover request ACK as a response is returned from the transfer target candidate station of the mobile terminal4, the handover executing unit713transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4, and ends the handover determination process.

If the transfer target candidate station is a mobile relay station (OP31: Yes), the handover to the mobile relay station as the transfer target candidate station is restricted depending on the type of the currently selected station of the mobile terminal4(seeFIG. 2).

Accordingly, if the transfer target candidate station is a mobile relay station (OP31: Yes), the first handover determining unit711determines whether or not the transfer from its own station as the currently selected station of the mobile terminal4to the transfer target candidate station (mobile relay station) is possible (OP32). That is, the first handover determining unit711determines whether or not the cell transfer permission/prohibition setting of its own station held in the storing unit72is “Permitted”.

If the cell transfer permission/prohibition setting of its own station as the currently selected station of the mobile terminal4is “Permitted” (OP32: Yes), the handover to the mobile relay station as the transfer target candidate station of the mobile terminal4is permitted. Note that, in the case where its own station is the base station (Type 1) installed near the boarding/exiting facility for the mobile body, the cell transfer permission/prohibition setting is set to “Permitted”. In this case, the first handover determining unit711instructs the handover executing unit713to execute the handover from its own station to the mobile relay station (transfer target candidate station). The handover executing unit713that has received the instruction executes the handover from its own station to the mobile relay station (transfer target candidate station) (OP36).

If the cell transfer permission/prohibition setting of its own station is “Not Permitted” (OP32: No), this means that its own station is the base station (Type 2) other than Type 1 or a mobile relay station. In this case, the permission or prohibition of the handover is determined depending on whether or not the mobile relay station held in the mobile relay station connection history of the mobile terminal4is coincident with the transfer target candidate station (seeFIG. 2). Accordingly, the processing moves from the first handover determining unit711to the second handover determining unit712, and the second handover determining unit712refers to the mobile relay station connection history of the mobile terminal4included in the measurement report.

The second handover determining unit712determines whether or not the mobile relay station held in the mobile relay station connection history is coincident with the transfer target candidate station (OP35).

If the mobile relay station held in the mobile relay station connection history of the mobile terminal4is not coincident with the transfer target candidate station (OP35: No), the second handover determining unit712determines the non-permission of the handover, and stops the handover determination process (OP34). This ends the handover determination process.

If the mobile relay station held in the mobile relay station connection history of the mobile terminal4is coincident with the transfer target candidate station (OP35: Yes), the second handover determining unit712determines the permission of the handover, and instructs the handover executing unit713to execute the handover. The handover executing unit713that has received the instruction executes the handover from its own station to the mobile relay station (transfer target candidate station) (OP36).

Through the process in OP35, for example, the mobile terminal4B inFIG. 1can make the handover from the mobile relay station2to the base station1, and further can make the handover from the base station1back to the mobile relay station2.

<<Configuration Example of Fixed Relay Station>>

FIG. 13is a diagram illustrating a configuration example of the fixed relay station3. The fixed relay station3is wirelessly connected to the mobile terminal4and the base station1. A connection method between the fixed relay station3and the mobile terminal4is the same as a connection method between the base station1and the mobile terminal4. A connection method between the fixed relay station3and the base station1is the same as the connection method between the mobile terminal4and the base station1assuming that the fixed relay station3behaves like the mobile terminal4with respect to the base station1. Accordingly, the fixed relay station3has the configuration of the base station1and the configuration of the mobile terminal4.

The fixed relay station3includes receiving antennas31aand31d, transmitting antennas31band31c, radio units32and39, layer 1 processing units33and38, layer 2 processing units34and37, a radio resource controlling unit35, and a data reconstructing unit36. These units are each implemented by software components or hardware components or by the combination thereof (see the section [Others]).

The layer 1 processing unit33includes a demodulating unit331, a decoding unit332, a coding unit333, and a modulating unit334. The demodulating unit331includes an FFT unit331a, a subcarrier mapping unit331b, an IDFT unit331c, and a demodulation executing unit331d. The decoding unit332includes a de-rate matching unit332a, an HARQ combining unit332b, a turbo decoding unit332c, and a CRC unit332d. The coding unit333includes a CRC adding unit333a, a turbo coding unit333b, and a rate matching unit333c. The modulating unit334includes a modulation executing unit334a, a subcarrier mapping unit334b, and an IFFT unit334c.

A set of the IDFT unit331c, the demodulation executing unit331d, the de-rate matching unit332a, the HARQ combining unit332b, the turbo decoding unit332c, and the CRC unit332dis provided for each user. Similarly, a set of the CRC adding unit333a, the turbo coding unit333b, the rate matching unit333c, the modulation executing unit334a, and the subcarrier mapping unit334bis provided for each user.

The radio resource controlling unit35includes a connection controlling unit351, a measurement controlling unit352, and a mobility controlling unit353.

The layer 1 processing unit38includes a coding unit381, a modulating unit382, a demodulating unit383, and a decoding unit384. The coding unit381includes a CRC adding unit381a, a turbo coding unit381b, and a rate matching unit381c. The modulating unit382includes a modulation executing unit382a, a DFT unit382b, a subcarrier mapping unit382c, and an IFFT unit382d. The demodulating unit383includes an FFT unit383aand a demodulation executing unit383b. The decoding unit384includes a de-rate matching unit384a, an HARQ combining unit384b, a turbo decoding unit384c, and a CRC unit384d.

The processing units included in the fixed relay station3perform processes similar to those of the corresponding processing units with the same names of the mobile terminal4(seeFIG. 5) and the base station1(seeFIG. 10), and hence description of the processing units is omitted.

The fixed relay station3includes the data reconstructing unit36. In the case where the fixed relay station3relays pieces of data transmitted from the mobile terminals4to the base station1, the fixed relay station3collectively transmits the pieces of data from a plurality of users (the plurality of mobile terminals4). In the case where the fixed relay station3relays pieces of data transmitted from the base station1to the mobile terminals4under the fixed relay station3, the fixed relay station3separates and processes the pieces of data for each mobile terminal4. Accordingly, in the case of relaying the pieces of data transmitted from the mobile terminals4to the base station1, the data reconstructing unit36performs data reconstruction for putting together the pieces of data from the plurality of users. In addition, in the case of relaying the pieces of data transmitted from the base station1to the mobile terminals4, the data reconstructing unit36performs data reconstruction for separating the pieces of data for each mobile terminal4.

The configuration of the mobility controlling unit353of the fixed relay station3is the same as that of the mobility controlling unit153of the base station1illustrated inFIG. 11, and the fixed relay station3executes the handover determination process illustrated inFIG. 12similarly to the base station1.

<<Configuration Example of Mobile Relay Station>>

FIG. 14is a diagram illustrating a configuration example of the mobile relay station2. Because the mobile relay station2itself makes a cell transfer, the mobile relay station2includes: a measuring unit283cthat measures neighboring cells; and a mobility controlling unit254that controls the cell transfer of the mobile relay station2itself. Except that, the configuration of the mobile relay station2is the same as that of the fixed relay station3.

The mobile relay station2includes receiving antennas21aand21d, transmitting antennas21band21c, radio units22and29, layer 1 processing units23and28, layer 2 processing units24and27, a radio resource controlling unit25, and a data reconstructing unit26.

The layer 1 processing unit23includes a demodulating unit231, a decoding unit232, a coding unit233, and a modulating unit234. The demodulating unit231includes an FFT unit231a, a subcarrier mapping unit231b, an IDFT unit231c, and a demodulation executing unit231d. The decoding unit232includes a de-rate matching unit232a, an HARQ combining unit232b, a turbo decoding unit232c, and a CRC unit232d. The coding unit233includes a CRC adding unit233a, a turbo coding unit233b, and a rate matching unit233c. Further, the modulating unit234includes a modulation executing unit234a, a subcarrier mapping unit234b, and an IFFT unit234c.

A set of the IDFT unit231c, the demodulation executing unit231d, the de-rate matching unit232a, the HARQ combining unit232b, the turbo decoding unit232c, and the CRC unit232dis provided for each user. Similarly, a set of the CRC adding unit233a, the turbo coding unit233b, the rate matching unit233c, the modulation executing unit234a, and the subcarrier mapping unit234bis provided for each user.

The radio resource controlling unit25includes a connection controlling unit251, a measurement controlling unit252, a mobility controlling unit253, and the mobility controlling unit254. The mobility controlling unit253controls the handover and the like of the mobile terminal4under the mobile relay station. The mobility controlling unit254controls the handover and the like of the mobile relay station itself.

The layer 1 processing unit28includes a coding unit281, a modulating unit282, a demodulating unit283, and a decoding unit284. The coding unit281includes a CRC adding unit281a, a turbo coding unit281b, and a rate matching unit281c. The modulating unit282includes a modulation executing unit282a, a DFT unit282b, a subcarrier mapping unit282c, and an IFFT unit282d. The demodulating unit283includes an FFT unit283a, a demodulation executing unit283b, and the measuring unit283c. The decoding unit284includes a de-rate matching unit284a, an HARQ combining unit284b, a turbo decoding unit284c, and a CRC unit284d.

The processing units other than the mobility controlling units253and254included in the mobile relay station2perform processes similar to those of the corresponding processing units with the same names of the fixed relay station3(seeFIG. 13), and hence description of the processing units is omitted.

FIG. 15is a diagram illustrating a configuration example of the mobility controlling unit253of the mobile relay station2. The mobility controlling unit253of the mobile relay station2includes a handover controlling unit91, a storing unit92, and a notifying information generating unit93.

The storing unit92holds the identification number of its own station, the preset cell transfer permission/prohibition setting of its own station, and the mobile relay station list. “Not Permitted” is set to the cell transfer permission/prohibition setting of the mobile relay station2(seeFIG. 8).

For example, when receiving the update report of the mobile relay station list from another station, the notifying information generating unit93delivers notifying information including the mobile relay station list held in the storing unit92, to the mobile terminal4under the mobile relay station2.

Upon the reception of a measurement report from the mobile terminal4that connects to its own station through the layer 2 processing unit24, the handover controlling unit91executes a process relating to the handover of the mobile terminal4. The handover controlling unit91includes a handover determining unit911and a handover executing unit912.

The handover determining unit911determines whether or not the transfer target candidate station of the mobile terminal4included in the measurement report is a mobile relay station. If the transfer target candidate station is a mobile relay station, the handover determining unit911does not permit the handover of the mobile terminal4on the basis of the cell transfer permission/prohibition setting of its own station, abandons the measurement report, and stops the handover determination process. If the transfer target candidate station is not a mobile relay station, the handover determining unit911permits the handover of the mobile terminal4, and instructs the handover executing unit912to execute the handover of the mobile terminal4. The handover determining unit911corresponds to the “determining unit” according to one of the aspects of the present invention.

Upon the reception of the instruction to execute the handover of the mobile terminal4from the handover determining unit911, the handover executing unit912transmits a handover request for requesting the execution of the handover, to the transfer target candidate station. If a handover request ACK is received from the transfer target candidate station, the handover executing unit912transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4, and ends the handover determination process.

FIG. 16is a diagram illustrating a flow example of the handover determination process of the mobile relay station2. Upon the reception of the measurement report from the mobile terminal4that connects to its own station, the mobile relay station2starts the handover determination process.

The handover determining unit911of the mobile relay station2determines whether or not the transfer target candidate station of the mobile terminal4included in the measurement report is a mobile relay station (OP41). The handover determining unit911compares the mobile relay station list held in the storing unit92with the identification number of the transfer target candidate station included in the measurement report, to thereby determine whether or not the transfer target candidate station is a mobile relay station.

If the transfer target candidate station is a mobile relay station (OP41: Yes), the handover from its own station (mobile relay station) is not permitted on the basis of the cell transfer permission/prohibition setting (seeFIG. 8). The handover determining unit911abandons the measurement report, and stops the handover determination process (OP43).

If the transfer target candidate station is not a mobile relay station (OP41: No), the handover from its own station is permitted. The handover determining unit911instructs the handover executing unit912to execute the handover to the transfer target candidate station. Upon the reception of the instruction, the handover executing unit912transmits a handover request for requesting the handover, to the transfer target candidate station (OP42). If a handover request ACK is received from the transfer target candidate station, the handover executing unit912transmits a handover command to the mobile terminal4, and thus gives an instruction to execute the handover. This ends the handover determination process.

<Registration Process of Mobile Relay Station into Mobile Relay Station List>

FIG. 17is a diagram illustrating an example of a registration process of the mobile relay station2into the mobile relay station list in the example illustrated inFIG. 1, the registration process being performed when the mobile relay station2is newly added. In the example illustrated inFIG. 1, it is assumed that the fixed relay station3is under the base station1. It is also assumed that the mobile relay station2is powered on in the cell of the base station1.

When the mobile relay station2is powered on, the mobile relay station2detects the base station1as an upper station to which its own station is to connect. The radio resource controlling unit25of the mobile relay station2transmits a registration request of the mobile relay station list to the base station1(OP52). The registration request of the mobile relay station list includes the identification number and the cell transfer permission/prohibition setting of its own station.

The notifying information generating unit93of the mobile relay station2generates notifying information including the mobile relay station list held in the storing unit92, and delivers the notifying information to the mobile terminal4under the mobile relay station2(OP53).

Upon the reception of the registration request of the mobile relay station list, the notifying information updating unit73of the base station1registers the identification number of the mobile relay station2into the mobile relay station list, and thus updates the mobile relay station list (OP54).

Upon the completion of the update of the mobile relay station list, the notifying information updating unit73of the base station1transmits an update report of the mobile relay station list to stations including the fixed relay station3under the base station1(OP55). The update report of the mobile relay station list is a message for reporting information on the additionally registered mobile relay station2to the stations under the base station1. The notifying information updating unit73of the base station1updates the notifying information with the updated mobile relay station list, and delivers the updated information to the mobile terminal4under the base station1(OP56).

The fixed relay station3that has received the update report of the mobile relay station list updates the mobile relay station list (OP57). The fixed relay station3updates the notifying information with the updated mobile relay station list, and delivers the updated information to the mobile terminal4under the fixed relay station3(OP58).

In this way, the information on the newly added mobile relay station2is delivered through the wireless communication network system100.

Operation Example 1

Example Case in which Mobile Terminal4A Makes Handover from Base Station1to Mobile Relay Station2

FIG. 18is a diagram for describing Operation Example 1. Note that a wireless communication network system100illustrated inFIG. 18is similar to the wireless communication network system100illustrated inFIG. 1. InFIG. 18, the mobile terminal4A is located in the cell of the base station1, and is connecting to the base station1to make communication. The mobile relay station2is moving in the cell of the base station1, and relays connection between the mobile terminal located in its own cell and the base station1.

In Operation Example 1, the following example is described. That is, in reaction to the approach of the mobile relay station2, the mobile terminal4A that is connecting to the base station1to make communication transmits a request of the handover to the mobile relay station2, and the base station1determines the permission or prohibition of the handover of the mobile terminal4A. In the wireless communication network system100, the handover of the mobile terminal4A from the base station1to the mobile relay station is prohibited, and hence the base station1does not permit the handover of the mobile terminal4A to the mobile relay station.

FIG. 19is a diagram illustrating a flow of Operation Example 1. It is assumed that the mobile relay station connection history of the mobile terminal4A does not have a history of connection to the mobile relay station2before the mobile terminal4A connects to the base station1, that is, is in its initial state (Invalid).

The mobile terminal4A detects neighboring stations, and measures the reception quality of a signal from each station (OP61). On the basis of a result of the measurement, the mobile terminal4A determines whether or not the reception quality of the signal from the base station1as the currently selected station is the best (OP62). InFIG. 18, when the mobile relay station2approaches the mobile terminal4A due to the movement of the train50, the reception quality of the signal from the mobile relay station2may become better than that of the signal from the base station1in some cases. If the reception quality of the signal from the mobile relay station2becomes better, the mobile terminal4A determines that the reception quality from the mobile relay station2is the best (OP62: No).

Because the station having the best reception quality has changed, the mobile terminal4A transmits a measurement report for requesting the handover, to currently connected the base station1(OP63). The measurement report at this time includes: the terminal identification number of the mobile terminal4A itself; the identification number of the mobile relay station2as the transfer target candidate station; and the mobile relay station connection history held by the mobile terminal4A.

Upon the reception of the measurement report from the mobile terminal4A, the base station1executes the handover determination process of the mobile terminal4A (OP64). The handover determination process of the base station1according to Operation Example 1 is performed in the following manner with reference toFIG. 12.

The base station1(first handover determining unit711) determines whether or not the transfer target candidate station is a mobile relay station, on the basis of the measurement report received from the mobile terminal4A (FIG. 12, OP31). Because the transfer target candidate station is the mobile relay station2(FIG. 12, OP31: Yes), the processing proceeds to OP32.

The base station1(first handover determining unit711) determines whether or not the handover from its own station to the mobile relay station2is possible, on the basis of the cell transfer permission/prohibition setting of its own station (FIG. 12, OP32). The base station1is a base station installed in a location other than the boarding/exiting facility (train station) on the route of the train50, and hence the cell transfer permission/prohibition setting of the base station1is “Not Permitted” (seeFIG. 8). Accordingly, the handover from the base station1to the mobile relay station2is not permitted (FIG. 12, OP32: No), and the processing proceeds to OP35.

The base station1(second handover determining unit712) determines whether or not the mobile terminal4A has ever connected to the mobile relay station as the transfer target candidate, on the basis of the mobile relay station connection history contained in the measurement report (FIG. 12, OP35). Because the mobile relay station connection history of the mobile terminal4A does not have a history of connection to the mobile relay station (FIG. 12, OP35: No), the base station1abandons the measurement report, and ends the handover determination process (FIG. 12, OP34).

Accordingly, as a result of the handover determination process of the base station1, the handover of the mobile terminal4A from the base station1to the mobile relay station2is not permitted, and the mobile terminal4A does not execute the handover, and continues the communication while keeping the connection to the base station1. The mobile relay station connection history of the mobile terminal4A remains in its initial state (Invalid) because the handover has not been executed.

In this way, it is possible to prevent the mobile terminal4A from making the handover: from the base station1to which to the mobile terminal4A can be stably connected; to the mobile relay station2. As a result, an instant interruption of communication of the mobile terminal4A can be avoided, the network load can be reduced, and efficient communication can be provided.

Operation Example 2

Example Case in which Mobile Terminal4B Makes Handover in Order of Mobile Relay Station2→Base Station1→Mobile Relay Station2

FIG. 20is a diagram for describing Operation Example 2. Note that a wireless communication network system100illustrated inFIG. 20is similar to the wireless communication network system100illustrated inFIG. 1. InFIG. 20, the mobile terminal4B is a terminal owned by a passenger of the train50, and is connecting to the mobile relay station2to make communication. The mobile relay station2is moving in the cell of the base station1, and relays connection between the mobile terminal4B located in its own cell and the base station1.

In Operation Example 2, the following example is described. That is, when the train50passes near the base station1, the mobile terminal4B makes the handover to the base station1. Further, when the train50moves away from the base station1, the mobile terminal4B makes the handover back to the mobile relay station2.

FIG. 21AandFIG. 21Bare diagrams each illustrating a flow of Operation Example 2. The mobile terminal4B is connected to the mobile relay station2, and the mobile relay station connection history holds the identification number of the mobile relay station2.

The mobile terminal4B periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP71). As a result of the measurement, the mobile terminal4B determines whether or not the reception quality of the signal from the mobile relay station2as the selected station is the best (OP72). InFIG. 20, when the mobile relay station2approaches the base station1due to the movement of the train50, the reception quality of the signal from the base station1may become better than that of the signal from the mobile relay station2in some cases. In this case, the mobile terminal4B determines that the reception quality from the base station1is the best (OP72: No).

Because the station having the best reception quality has changed, the mobile terminal4B transmits a measurement report for requesting the handover, to the currently connected mobile relay station2(OP73). The measurement report at this time includes: the terminal identification number of the mobile terminal4B itself; the identification number of the base station1as the transfer target candidate station; and the mobile relay station connection history held by the mobile terminal4B.

Upon the reception of the measurement report from the mobile terminal4B, the mobile relay station2executes the handover determination process of the mobile terminal4B (OP74). The handover determination process of the mobile relay station according to Operation Example 2 is performed in the following manner with reference toFIG. 16.

The mobile relay station2(handover determining unit911) determines whether or not the transfer target candidate station is a mobile relay station, on the basis of the measurement report received from the mobile terminal4B (FIG. 16, OP41). Because the transfer target candidate station is the base station1(FIG. 16, OP41: No), the handover from the mobile relay station2to the base station1is permitted (seeFIG. 2).

The mobile relay station2transmits a handover request for requesting the handover of the mobile terminal4B, to the base station1as the transfer target candidate station (FIG. 16, OP42;FIG. 21A, OP75).

Upon the reception of the handover request from the mobile relay station2, the base station1transmits a handover request ACK representing the permission of the handover of the mobile terminal4B, to the mobile relay station2(OP76).

Upon the reception of the handover request ACK from the base station1, the mobile relay station2transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4B (OP77).

Upon the reception of the handover command, the mobile terminal4B executes the handover from the mobile relay station2to the base station1(OP78). Upon the transmission of a handover complete from the mobile terminal4B to the base station1as the transfer target (OP79), the handover is completed, and the mobile terminal4B connects to the base station1to make communication. At this time, because the handover is not made to a mobile relay station, the mobile relay station connection history of the mobile terminal4B is not changed, and keeps holding the identification number of the mobile relay station2.

As the train50moves away from the base station1, reception environments of the mobile terminal4B change, and the reception quality from the mobile relay station2becomes better than that from the base station1.

The mobile terminal4B periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP80), and determines that the reception quality from the mobile relay station2is better than that from the base station1(OP81: No).

Because the station having the best reception quality has changed, the mobile terminal4B transmits a measurement report for requesting the handover, to the currently connected base station1(OP82). The measurement report at this time includes: the terminal identification number of the mobile terminal4B itself; the identification number of the mobile relay station2as the transfer target candidate station; and the mobile relay station connection history held by the mobile terminal4B. The mobile relay station connection history of the mobile terminal4B at this time stores the identification number of the last connected mobile relay station2.

Upon the reception of the measurement report from the mobile terminal4B, the base station1executes the handover determination process of the mobile terminal4B (OP83). The handover determination process of the base station1according to Operation Example 2 is performed in the following manner with reference toFIG. 12.

The base station1(first handover determining unit711) determines whether or not the transfer target candidate station is a mobile relay station, on the basis of the measurement report received from the mobile terminal4B (FIG. 12, OP31). Because the transfer target candidate station is the mobile relay station2(FIG. 12, OP31: Yes), the processing proceeds to OP32.

The base station1(first handover determining unit711) determines whether or not the handover from its own station to the mobile relay station is possible, on the basis of the cell transfer permission/prohibition setting of its own station (FIG. 12, OP32). The cell transfer permission/prohibition setting of the base station1is “Not Permitted” (seeFIG. 8), and hence the handover from the base station1to the mobile relay station is not permitted (FIG. 12, OP32: No).

The base station1(second handover determining unit712) determines whether or not the mobile terminal4B has ever connected to the transfer target candidate station, on the basis of the mobile relay station connection history included in the measurement report (OP35). Because the last connected mobile relay station2is stored in the mobile relay station connection history of the mobile terminal4B (FIG. 12, OP35: Yes), the base station1permits the handover of the mobile terminal4B to the mobile relay station2.

The base station1transmits a handover request for requesting the handover of the mobile terminal4B, to the mobile relay station2as the transfer target candidate station (FIG. 12, OP36;FIG. 21B, OP84).

Upon the reception of the handover request from the base station1, the mobile relay station2transmits a handover request ACK representing the permission of the handover of the mobile terminal4B, to the base station1(OP85).

Upon the reception of the handover request ACK from the mobile relay station2, the base station1transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4B (OP86).

Upon the reception of the handover command, the mobile terminal4B executes the handover from the base station1to the mobile relay station2(OP87). Because the handover target of the mobile terminal4B is a mobile relay station, the mobile relay station connection history is overwritten and updated with the identification number of the mobile relay station2. Upon the transmission of a handover complete from the mobile terminal4B to the base station1as the transfer target (OP88), the handover is completed, and the mobile terminal4B connects to the mobile relay station2to make communication.

In this way, even in the case where the cell transfer permission/prohibition setting of the base station1is “Not Permitted”, if the mobile relay station connection history of the mobile terminal4B has the same mobile relay station as the transfer target candidate station, that is, if the last connected mobile relay station is coincident with the transfer target candidate station, the handover from the base station1to the mobile relay station2is permitted. As a result, the mobile terminal4B that connects to the mobile relay station2can make the handover from the mobile relay station2to the base station1, and further can make the handover from the base station1back to the mobile relay station2.

Operation Example 3

Example Case in which Mobile Terminal4C Makes Handover from Fixed Relay Station3to Mobile Relay Station2

FIG. 22is a diagram for describing Operation Example 3. Note that a wireless communication network system100illustrated inFIG. 22is similar to the wireless communication network system100illustrated inFIG. 1. InFIG. 22, the mobile terminal4C is located in the cell of the fixed relay station3, and is connecting to the fixed relay station3to make communication. The fixed relay station3is located in the cell of the base station1, and relays connection between the mobile terminal4C located in its own cell and the base station1.

In Operation Example 3, the following example is described. That is, when the mobile relay station2approaches the fixed relay station3, the fixed relay station3determines the permission or prohibition of the handover of the mobile terminal4C to the mobile relay station2, the mobile terminal4C connecting to the fixed relay station3to make communication. In the wireless communication network system100, the handover of the mobile terminal4C from the fixed relay station3to the mobile relay station2is permitted, and hence the mobile terminal4C can make the handover to the mobile relay station2.

FIG. 23is a diagram illustrating a flow of Operation Example 3. It is assumed that the mobile terminal4C does not have a history of connection to a mobile relay station before the mobile terminal4C connects to the fixed relay station3and that the mobile relay station connection history is in its initial state (Invalid).

The mobile terminal4C periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP91). InFIG. 22, when the mobile relay station2approaches the mobile terminal4C due to the movement of the train50, the reception quality of the signal from the mobile relay station2may become better than that of the signal from the fixed relay station3in some cases. As a result of the measurement, the mobile terminal4C determines that the reception quality of the signal from the mobile relay station2is better than that from the fixed relay station3as the selected station (OP92: No).

The mobile terminal4C transmits a measurement report for requesting the handover, to the currently connected fixed relay station3(OP93). The measurement report at this time includes: the terminal identification number of the mobile terminal4C itself; the identification number of the mobile relay station2as the transfer target candidate station; and the mobile relay station connection history held by the mobile terminal4C.

Upon the reception of the measurement report from the mobile terminal4C, the fixed relay station3executes the handover determination process of the mobile terminal4C (OP94). The handover determination process of the fixed relay station3according to Operation Example 3 is performed in the following manner with reference toFIG. 12.

The fixed relay station3(first handover determining unit711) determines that the transfer target candidate station is a mobile relay station, on the basis of the measurement report received from the mobile terminal4C (FIG. 12, OP31: Yes).

Next, the fixed relay station3(first handover determining unit711) determines whether or not the handover from its own station to the mobile relay station2is possible, on the basis of the cell transfer permission/prohibition setting of its own station (FIG. 12, OP32). Because the fixed relay station3is the fixed relay station (Type 1) installed near the boarding/exiting facility (train station) for the train50, the cell transfer permission/prohibition setting of the fixed relay station3is “Permitted” (seeFIG. 8). Accordingly, the handover from the fixed relay station3to the mobile relay station2is permitted (FIG. 12, OP32: Yes).

The fixed relay station3transmits a handover request for requesting the handover of the mobile terminal4C, to the mobile relay station2as the transfer target candidate station (FIG. 12, OP36;FIG. 23, OP95). The handover request is transmitted to the mobile relay station2via the base station1.

Upon the reception of the handover request from the fixed relay station3, the mobile relay station2transmits a handover request ACK representing the permission of the handover of the mobile terminal4C, to the fixed relay station3(OP96).

Upon the reception of the handover request ACK from the mobile relay station2via the base station1, the fixed relay station3transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4C (OP97).

Upon the reception of the handover command, the mobile terminal4C executes the handover from the fixed relay station3to the mobile relay station2(OP98). Because the handover target of the mobile terminal4C is a mobile relay station, the identification number of the mobile relay station2is stored for update in the mobile relay station connection history. Upon the transmission of a handover complete from the mobile terminal4C to the mobile relay station2as the transfer target (OP99), the handover is completed, and the mobile terminal4C connects to the mobile relay station2to make communication.

In this way, the mobile terminal4C that connects for communication to the fixed relay station3installed near the boarding/exiting facility (train station) for the train50can make the handover from the fixed relay station3to the mobile relay station2.

Operation Example 4

Example Case in which Mobile Terminal4A Makes Reselection from Base Station1to Mobile Relay Station2

In Operation Example 4, the following example is described. That is, inFIG. 18, the mobile terminal4A in a stand-by state, the selected station of which is the base station1, determines the permission or prohibition of the reselection to the mobile relay station2, in reaction to the approach of the mobile relay station2. In the wireless communication network system100, the reselection of the mobile terminal4A from the base station1to the mobile relay station2is not permitted, and hence the mobile terminal4A does not execute the reselection to the mobile relay station2.

FIG. 24is a diagram illustrating a flow of Operation Example 4. The mobile terminal4A is in a stand-by state, and the selected station thereof is the base station1. It is assumed that the mobile terminal4A does not have a history of connection to the mobile relay station2before the mobile terminal4A connects to the base station1and that the mobile relay station connection history is in its initial state (Invalid).

The mobile terminal4A executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP101). As a result of the measurement, the mobile terminal4A determines whether or not the reception quality of the signal from the base station1as the selected station is the best (OP102). InFIG. 18, when the mobile relay station2approaches the mobile terminal4A due to the movement of the train50, the reception quality of the signal from the mobile relay station2may become better than that of the signal from the base station1in some cases. In this case, the mobile terminal4A determines that the reception quality from the mobile relay station2is the best (OP102: No).

Because the station having the best reception quality has changed, the mobile terminal4A executes the reselection determination process (OP103). The reselection determination process of the mobile terminal4A according to Operation Example 4 is performed in the following manner with reference toFIG. 9.

The mobile terminal4A (first reselection determining unit62) determines whether or not the transfer target candidate station is a mobile relay station (FIG. 9, OP21). Because the transfer target candidate station is the mobile relay station2(FIG. 9, OP21: Yes), the mobile terminal4A (first reselection determining unit62) determines whether or not the reselection from the currently selected station to the mobile relay station is possible (FIG. 9, OP22). The currently selected station of the mobile terminal4A is the base station1. Because the base station1is the base station (Type 2) installed at a position sufficiently away from the boarding/exiting facility (train station) for the train50, the cell transfer permission/prohibition setting of the base station1is “Not Permitted”. Accordingly, the mobile terminal4A (first reselection determining unit612) determines that the reselection from the base station1to the mobile relay station2is not permitted (FIG. 9, OP22: No).

The mobile terminal4A (first reselection determining unit612) determines whether or not the mobile relay station to which the mobile terminal4A last connects is coincident with the mobile relay station2as the transfer target candidate station, on the basis of the mobile relay station connection history held in the storing unit66(FIG. 9, OP25). The mobile relay station connection history of the mobile terminal4A holds Invalid, and does not have a history of connection to the mobile relay station (OP25: No). Hence, the mobile terminal4A (first reselection determining unit612) ends the reselection determination process (FIG. 9, OP24).

Accordingly, as a result of the reselection determination process of the mobile terminal4A, the reselection from the base station1to the mobile relay station2is not permitted, and the mobile terminal4A does not execute the reselection. In addition, because the reselection has not been made, the mobile relay station connection history of the mobile terminal4A is not changed, and keeps holding Invalid.

In this way, it is possible to avoid the reselection: from the base station1to which the mobile terminal4A can be stably connected; to the mobile relay station2and to enhance the network efficiency.

Operation Example 5

Example Case in which Mobile Terminal4B Makes Reselection in Order of Mobile Relay Station2→Base Station1→Mobile Relay Station2

In Operation Example 5, the following example is described. That is, inFIG. 20, when the train50passes near the base station1, the mobile terminal4B in a stand-by state makes the reselection to the base station1, and further makes the reselection back to the mobile relay station2.

FIG. 25AandFIG. 25Bare diagrams each illustrating a flow of Operation Example 5. The currently selected station of the mobile terminal4B is the mobile relay station2, and the identification number of the mobile relay station2is held in the mobile relay station connection history.

The mobile terminal4B periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP111). As a result of the measurement, the mobile terminal4B determines whether or not the reception quality of the signal from the mobile relay station2as the selected station is the best (OP112). InFIG. 20, when the mobile relay station2approaches the base station1due to the movement of the train50, the reception quality of the signal from the base station1may become better than that of the signal from the mobile relay station2in some cases. In this case, the mobile terminal4B determines that the reception quality from the base station1is the best (OP112: No).

Because the station having the best reception quality has changed, the mobile terminal4B executes the reselection determination process (OP113). The reselection determination process of the mobile terminal4B according to Operation Example 5 is performed in the following manner with reference toFIG. 9.

The mobile terminal4B (first reselection determining unit62) determines whether or not the transfer target candidate station is a mobile relay station (FIG. 9, OP21). Because the transfer target candidate station is the base station1(FIG. 9, OP21: No), the reselection from the mobile relay station2to the base station1is permitted.

The mobile terminal4B acquires notifying information from the base station1as the transfer target candidate station (OP114), and executes the reselection from the mobile relay station2as the currently selected station to the base station1(FIG. 9, OP26;FIG. 25A, OP115). The reselection target is the base station1, which is not a mobile relay station, and hence the mobile relay station connection history is not changed, and keeps holding the identification number of the mobile relay station2.

As the train50moves away from the base station1, reception environments of the mobile terminal4B change, and the reception quality from the mobile relay station2becomes better than that from the base station1.

The mobile terminal4B periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP116), and determines that the reception quality from the mobile relay station2is better than that from the base station (OP117: No).

Because the station having the best reception quality has changed from the base station1to the mobile relay station2, the mobile terminal4B executes the reselection determination process (OP118). The reselection determination process of the mobile terminal4B according to Operation Example 5 is performed in the following manner with reference toFIG. 9.

The mobile terminal4B (first reselection determining unit62) determines whether or not the transfer target candidate station is a mobile relay station (FIG. 9, OP21). The transfer target candidate station is the mobile relay station2(FIG. 9, OP21: Yes), and the cell transfer permission/prohibition setting of the base station1as the currently selected station is “Not Permitted” (FIG. 9, OP22: No).

The mobile terminal4B (second reselection determining unit63) determines whether or not the last connected mobile relay station is coincident with the mobile relay station2as the transfer target candidate station, on the basis of the mobile relay station connection history held in the storing unit66(FIG. 9, OP25). The identification number of the last connected mobile relay station2is stored in the mobile relay station connection history of the mobile terminal4B, and the last connected mobile relay station2is coincident with the transfer target candidate station (FIG. 9, OP25: Yes). Hence, the mobile terminal4B permits the reselection to the mobile relay station2.

The mobile terminal4B acquires notifying information from the mobile relay station2as the transfer target candidate station (OP119), and executes the reselection from the base station1as the currently selected station to the mobile relay station2(FIG. 9, OP26;FIG. 25B, OP120). Upon the completion of the reselection, the mobile terminal4B overwrites and updates the mobile relay station connection history with the identification number of the mobile relay station2(FIG. 9, OP27).

In this way, even in the case where the cell transfer permission/prohibition setting of the base station1is “Not Permitted”, if the mobile relay station held in the mobile relay station connection history of the mobile terminal4B is coincident with the mobile relay station as the transfer target candidate station, the reselection from the base station1to the mobile relay station2is permitted. As a result, the mobile terminal4B that connects to the mobile relay station2can make the reselection from the mobile relay station2to the base station1, and further can make the reselection from the base station1back to the mobile relay station2.

Operation Example 6

Example Case in which Mobile Terminal4C Makes Reselection from Fixed Relay Station3to Mobile Relay Station2

In Operation Example 6, the following example is described. That is, in the example illustrated inFIG. 22, when the mobile relay station2approaches the fixed relay station3, the mobile terminal4C in a stand-by state makes the reselection from the fixed relay station3to the mobile relay station2. In the wireless communication network system100, the reselection of the mobile terminal4C from the fixed relay station3to the mobile relay station2is permitted, and hence the mobile terminal4C can make the reselection to the mobile relay station2.

FIG. 26is a diagram illustrating a flow of Operation Example 6. It is assumed that the mobile terminal4C does not have a history of connection to the mobile relay station before the mobile terminal4C connects to the fixed relay station and that the mobile relay station connection history is in its initial state (Invalid).

The mobile terminal4C periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP121). InFIG. 22, when the mobile relay station2approaches the mobile terminal4C due to the movement of the train50, the reception quality of the signal from the mobile relay station2may become better than that of the signal from the fixed relay station3in some cases. As a result of the measurement, the mobile terminal4C determines that the reception quality of the signal from the mobile relay station2is better than that from the fixed relay station3as the selected station (OP122: No).

The mobile terminal4C executes the reselection determination process (OP123). The reselection determination process of the fixed relay station3according to Operation Example 6 is performed in the following manner with reference toFIG. 9.

The mobile terminal4C (first reselection determining unit62) determines whether or not the transfer target candidate station is a mobile relay station (FIG. 9, OP21). Because the transfer target candidate station is the mobile relay station2(FIG. 9, OP21: Yes), the mobile terminal4C (first reselection determining unit62) determines whether or not the reselection from the fixed relay station3as the currently selected station to the mobile relay station2is possible. Because the fixed relay station3is the fixed relay station (Type 1) installed near the boarding/exiting facility (train station) for the train50, the cell transfer permission/prohibition setting of the fixed relay station3is “Permitted” (seeFIG. 8). Accordingly, the reselection from the fixed relay station3to the mobile relay station2is permitted (FIG. 9, OP22: Yes).

The mobile terminal4C acquires notifying information from the mobile relay station2as the transfer target candidate station (OP124), and executes the reselection from the fixed relay station3as the currently selected station to the mobile relay station2(FIG. 9, OP26;FIG. 26, OP125). Upon the completion of the reselection, because the reselection target of the mobile terminal4C is the mobile relay station, the mobile terminal4C updates the mobile relay station connection history with the identification number of the mobile relay station2(FIG. 9, OP27).

In this way, the mobile terminal4C in a stand-by state, the selected station of which is the fixed relay station3(Type 1) installed near the boarding/exiting facility for the train50, can make the reselection from the fixed relay station3to the mobile relay station2.

Operations and Effects of First Embodiment

In the first embodiment, the permission or prohibition of the cell transfer from a base station and a fixed relay station to a mobile relay station is set depending on whether or not the station is installed near a boarding/exiting facility for a mobile body of public transportation, such as a train and a bus, the mobile body passing in a given route. As a result, for example, the mobile terminal4A illustrated inFIG. 1can avoid unfavorable processing, such as the handover and the reselection from the base station1to the mobile relay station2, so that the network load is reduced.

In addition, in the case where the last connected mobile relay station is coincident with the mobile relay station as the transfer target candidate station, the cell transfer from a base station and a fixed relay station that is not installed near a boarding/exiting facility for a mobile body to a mobile relay station is permitted. As a result, for example, the mobile terminal4B illustrated inFIG. 1can make the handover from the mobile relay station2to the base station1, and further can make the handover from the base station1back to the mobile relay station2, along with the movement of the train50.

According to the disclosed wireless communication network system, the connection target of a mobile terminal can be efficiently switched.

In the first embodiment, the base station1, the mobile relay station2, and the fixed relay station3each determine the permission or prohibition of the handover of the mobile terminal4from its own station to another station. In the case where the mobile relay station2and the fixed relay station3do not have a processing capacity that is high enough to determine the permission or prohibition of the handover, the base station1may determine the permission or prohibition of the handover in a unified manner. This can be achieved by the configuration in which the base station1acquires the cell transfer permission/prohibition setting of each station from notifying information and the like and receives a measurement report from a mobile terminal via the mobile relay station2or the fixed relay station3.

Second Embodiment

In the first embodiment, the handover determination process is performed by stations such as the base station, the fixed relay station, and the mobile relay station. In the second embodiment, the handover determination process is performed by the mobile terminal. In the second embodiment, description common to that of the first embodiment is omitted.

<<Configuration Example of Mobility Controlling Unit of Mobile Terminal>>

FIG. 27is a diagram illustrating a configuration example of the mobility controlling unit453of the mobile terminal4. The mobility controlling unit453of the mobile terminal4includes the measurement value acquiring unit61, the first reselection determining unit62, the second reselection determining unit63, the reselection executing unit64, the handover executing unit65, and the storing unit66that are described in the first embodiment, and further includes a first handover determining unit67and a second handover determining unit68.

Upon the report of a transfer target candidate station from the measurement value acquiring unit61, the first handover determining unit67determines whether or not the transfer target candidate station is the same as the currently selected station. In the case where the transfer target candidate station is different from the currently selected station, that is, in the case where the station having the best reception quality of the signal has changed, the first handover determining unit67starts a handover determination process. The first handover determining unit67determines whether or not the transfer target candidate station is a mobile relay station, and determines the permission or prohibition of the handover from the currently selected station to the transfer target candidate station. As a result of the determination, in the case where the handover from the currently selected station to the transfer target candidate station is possible, the first handover determining unit67instructs the handover executing unit65to execute the handover.

In the case where the handover is not permitted by the first handover determining unit67, the second handover determining unit68determines the permission or prohibition of the handover on the basis of the mobile relay station connection history held in the storing unit66. As a result of the determination, in the case where the handover from the currently selected station to the transfer target candidate station is possible, the second handover determining unit68instructs the handover executing unit65to execute the handover.

The first handover determining unit67and the second handover determining unit68correspond to the “determining unit” according to one of the aspects of the present invention.

FIG. 28is a diagram illustrating a flow example of the handover determination process of the mobile terminal4. In the case where the station having the best reception quality has changed as a result of the measurement of the reception quality from each station that is acquired by the measurement value acquiring unit61, the mobile terminal4starts the handover determination process.

The first handover determining unit67determines whether or not the transfer target candidate station is a mobile relay station (OP131). The first handover determining unit67compares the mobile relay station list held in the storing unit66with the identification number of the transfer target candidate station, to thereby determine whether or not the transfer target candidate station is a mobile relay station.

If the transfer target candidate station is not a mobile relay station (OP131: No), the handover from the currently selected station is permitted (seeFIG. 2). The first handover determining unit67determines the permission of the handover, and instructs the handover executing unit65to execute the handover. The handover executing unit65that has received the instruction transmits a measurement report for requesting the handover from the currently selected station to the transfer target candidate station, to the currently selected station (OP136b), and ends the handover determination process.

If the transfer target candidate station is a mobile relay station (OP131: Yes), the handover to the mobile relay station as the transfer target candidate station is restricted depending on the type of the currently selected station of the mobile terminal4(seeFIG. 2).

Accordingly, if the transfer target candidate station of the mobile terminal4is a mobile relay station (OP131: Yes), the first handover determining unit67determines whether or not the transfer from the currently selected station to the transfer target candidate station (mobile relay station) is possible (OP132). That is, the first handover determining unit67determines whether or not the cell transfer permission/prohibition setting of the currently selected station held in the storing unit66is “Permitted”.

If the cell transfer permission/prohibition setting of the currently selected station is “Permitted” (OP132: Yes), the handover to the mobile relay station as the transfer target candidate station is permitted. This means that the selected station is the base station or the fixed relay station (Type 1) installed near the boarding/exiting facility for the mobile body. The first handover determining unit67determines the permission of the handover, and instructs the handover executing unit65to execute the handover. The handover executing unit65that has received the instruction transmits a measurement report for requesting the handover from the currently selected station to the transfer target candidate station, to the currently selected station (OP136a).

If the cell transfer permission/prohibition setting of the currently selected station is “Not Permitted” (OP132: No), this means that the currently selected station is a mobile relay station or is the base station or the fixed relay station (Type 2) other than Type 1. In this case, the permission or prohibition of the handover is determined depending on whether or not the mobile relay station to which the mobile terminal4last connects is coincident with the transfer target candidate station (seeFIG. 2). Accordingly, the processing moves from the first handover determining unit67to the second handover determining unit68, and the second handover determining unit68refers to the mobile relay station connection history held in the storing unit66. The second handover determining unit68determines whether or not the mobile relay station to which the mobile terminal4last connects is coincident with the transfer target candidate station (OP135). If the mobile relay station to which the mobile terminal4last connects is not coincident with the transfer target candidate station (OP135: No), the second handover determining unit68determines the non-permission of the handover, and stops the handover determination process (OP134). This ends the handover determination process.

If the mobile relay station to which the mobile terminal4last connects is coincident with the transfer target candidate station (OP135: Yes), the second handover determining unit68determines the permission of the handover, and instructs the handover executing unit65to execute the handover. The handover executing unit65that has received the instruction transmits a measurement report for requesting the handover from the currently selected station to the transfer target candidate station, to the currently selected station (OP136a).

Upon the completion of the handover, the handover executing unit65updates the mobile relay station connection history in the storing unit66with the identification number of the mobile relay station as the transfer target, in the case where the transfer target candidate station is a mobile relay station (OP137). Upon the completion of the update of the mobile relay station connection history, the handover determination process is ended.

The mobile terminal4holds the identification number and the cell transfer permission/prohibition setting of each neighboring station on the basis of the notifying information from each station, and thus can determine the permission or prohibition of the handover. The handover determination process is performed not by the stations but by the mobile terminal, and hence the transmission of a wasteful measurement report can be avoided in the case where the handover is not permitted, so that the network load can be reduced.

<<Configuration Example of Mobility Controlling Units of Base Station and Fixed Relay Station>>

FIG. 29is a diagram illustrating a configuration example of the mobility controlling units153and353of the base station1and the fixed relay station3.

The mobility controlling units153and353each include the handover executing unit713, the storing unit72, and the notifying information updating unit73.

Upon the reception of a measurement report from the mobile terminal4, the handover executing unit713transmits a handover request for requesting the handover, to the transfer target candidate station.

The storing unit72and the notifying information updating unit73are as described in the first embodiment, and hence description thereof is omitted.

<<Configuration Example of Mobility Controlling Unit of Mobile Relay Station>>

FIG. 30is a diagram illustrating a configuration example of the mobility controlling unit253of the mobile relay station2. The mobility controlling unit253of the mobile relay station2includes the handover executing unit912, the notifying information generating unit93, and the storing unit92.

Upon the reception of a measurement report from the mobile terminal4, the handover executing unit912transmits a handover request for requesting the handover, to the transfer target candidate station.

The storing unit92and the notifying information generating unit93are as described in the first embodiment, and hence description thereof is omitted.

Operation Example 7

Example Case in which Mobile Terminal4A Makes Handover from Base Station1to Mobile Relay Station2

In Operation Example 7, the following example is described. That is, in the wireless communication network system100illustrated inFIG. 18, the mobile terminal4A itself that is connecting to the base station1to make communication determines the permission or prohibition of the handover, in reaction to the approach of the mobile relay station2. In the wireless communication network system100, the handover of the mobile terminal4A from the base station1to the mobile relay station is prohibited, and hence the mobile terminal4A does not permit its own handover to the mobile relay station.

FIG. 31is a diagram illustrating a flow of Operation Example 7. It is assumed that the mobile terminal4A does not have a history of connection to the mobile relay station2before the mobile terminal4A connects to the base station1and that the mobile relay station connection history is in its initial state (Invalid).

The mobile terminal4A detects neighboring stations, and measures the reception quality of a signal from each station (OP141). As a result of the measurement, the mobile terminal4A determines whether or not the reception quality of the signal from the base station1as the selected station is the best (OP142). InFIG. 18, when the mobile relay station2approaches the mobile terminal4A due to the movement of the mobile body50, the reception quality of the signal from the mobile relay station2may become better than that of the signal from the base station1in some cases. Accordingly, the mobile terminal4A determines that the reception quality from the mobile relay station2is the best (OP142: No).

The mobile terminal4A executes the handover determination process (OP143). The handover determination process of the mobile terminal4A according to Operation Example 7 is performed in the following manner with reference toFIG. 28.

The mobile terminal4A (first handover determining unit67) determines whether or not the transfer target candidate station is a mobile relay station (FIG. 28, OP131). Because the transfer target candidate station is the mobile relay station2(FIG. 28, OP131: Yes), the mobile terminal4A (first handover determining unit67) determines whether or not the handover from the base station1as the currently selected station to the mobile relay station2is possible (FIG. 28, OP132). Because the base station1is the base station (Type 2) installed at a position sufficiently away from the boarding/exiting facility (train station) for the train50, the cell transfer permission/prohibition setting of the base station1is “Not Permitted” (seeFIG. 8). Accordingly, the handover from the base station1to the mobile relay station2is not permitted (FIG. 28, OP132: No), and the processing proceeds to OP135.

The mobile terminal4A (second handover determining unit68) determines whether or not the last connected mobile relay station is coincident with the mobile relay station as the transfer target candidate station, on the basis of the mobile relay station connection history held in the storing unit66(FIG. 28, OP135). Because the mobile relay station connection history of the mobile terminal4A does not have a history of connection to the mobile relay station (FIG. 28, OP135: No), the mobile terminal4A ends the handover determination process (OP134).

Accordingly, as a result of the handover determination process of the mobile terminal4A, the handover from the base station1to the mobile relay station2is not permitted, and the mobile terminal4A does not execute the handover, and continues the communication while keeping the connection to the base station1.

In this way, it is possible to prevent the mobile terminal4A from making the handover: from the base station1to which to the mobile terminal4A can be stably connected; to the mobile relay station2, so that efficient communication can be provided. In addition, the mobile terminal4A itself determines the permission or prohibition of the handover, and hence the transmission of a wasteful measurement report can be avoided in the case where the handover is not permitted.

Operation Example 8

Example Case in which Mobile Terminal4B Makes Handover in Order of Mobile Relay Station2→Base Station1→Mobile Relay Station2

In Operation Example 8, the following example is described. That is, in the example illustrated inFIG. 20, when the train50passes near the base station1, the mobile terminal4B makes the handover to the base station1, and further makes the handover back to the mobile relay station2.

FIG. 32AandFIG. 32Bare diagrams each illustrating a flow of Operation Example 8. The mobile terminal4B is connected to the mobile relay station2, and the mobile relay station connection history holds the identification number of the mobile relay station2.

The mobile terminal4B periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP151). InFIG. 20, when the mobile relay station2approaches the base station1due to the movement of the train50, the reception quality of the signal from the base station1may become better than that of the signal from the mobile relay station2in some cases. As a result of the measurement, the mobile terminal4B determines that the reception quality from the base station1is better than the reception quality of the signal from the mobile relay station2as the selected station (OP152: No).

Because the station having the best reception quality has changed, the mobile terminal4B executes the handover determination process (OP153). The handover determination process of the mobile relay station according to Operation Example 8 is performed in the following manner with reference toFIG. 28.

The mobile terminal4B (first handover determining unit67) determines whether or not the transfer target candidate station is a mobile relay station (FIG. 28, OP131). Because the transfer target candidate station is the base station1(FIG. 28, OP131: No), the handover from the mobile relay station2to the base station1is permitted (seeFIG. 2).

The mobile terminal4B transmits a measurement report for requesting the handover, to the currently connected mobile relay station2(OP154). The measurement report at this time includes: the terminal identification number of the mobile terminal4B itself; and the identification number of the base station1as the transfer target candidate station.

Upon the reception of the measurement report from the mobile terminal4B, the mobile relay station2transmits a handover request for requesting the handover of the mobile terminal4B, to the base station1as the transfer target candidate station (OP155).

Upon the reception of the handover request from the mobile relay station2, the base station1transmits a handover request ACK representing the permission of the handover of the mobile terminal4B, to the mobile relay station2(OP156).

Upon the reception of the handover request ACK from the base station1, the mobile relay station2transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4B (OP157).

Upon the reception of the handover command, the mobile terminal4B (handover executing unit65) executes the handover from the mobile relay station2to the base station1(OP158). Upon the transmission of a handover complete from the mobile terminal4B to the base station1as the transfer target (OP159), the handover is completed, and the mobile terminal4B connects to the base station1to make communication. At this time, because the handover target is the base station1, which is not a mobile relay station, the mobile relay station connection history is not changed, and the identification number of the mobile relay station2is held without any change.

After that, as the train50moves away from the base station1, reception environments of the mobile terminal4B change, and the reception quality from the mobile relay station2becomes better than that from the base station1.

The mobile terminal4B periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP160), and determines that the reception quality from the mobile relay station2is better than that from the base station (OP161: No).

The mobile terminal4B (first handover determining unit67) executes the handover determination process (OP162). The handover determination process of the mobile terminal4B according to Operation Example 8 is performed in the following manner with reference toFIG. 28.

The mobile terminal4B (first handover determining unit67) determines whether or not the handover from the currently selected station (base station1) to the mobile relay station2is possible, on the basis of the cell transfer permission/prohibition setting held in the storing unit66(FIG. 28, OP131and OP132). Because the cell transfer permission/prohibition setting of the base station1is “Not Permitted” (seeFIG. 8), the handover from the base station1to the mobile relay station2is not permitted (FIG. 28, OP132: No).

The mobile terminal4B (second handover determining unit68) determines whether or not the last connected mobile relay station is the mobile relay station2as the transfer target candidate station, on the basis of the mobile relay station connection history held in the storing unit66(FIG. 28, OP135). Because the mobile relay station connection history of the mobile terminal4B stores the mobile relay station2as the last connected mobile relay station (FIG. 28, OP135: Yes), the mobile terminal4B permits the handover to the mobile relay station2.

The mobile terminal4B transmits a measurement report for requesting the handover, to the currently connected base station1(FIG. 28, OP136a;FIG. 32B, OP163). The measurement report at this time includes: the terminal identification number of the mobile terminal4B itself; and the identification number of the mobile relay station2as the transfer target candidate station.

Upon the reception of the measurement report from the mobile terminal4A, the base station1transmits a handover request for requesting the handover of the mobile terminal4B, to the mobile relay station2as the transfer target candidate station (OP164).

Upon the reception of the handover request from the base station1, the mobile relay station2transmits a handover request ACK representing the permission of the handover of the mobile terminal4B, to the base station1(OP165).

Upon the reception of the handover request ACK from the mobile relay station2, the base station1transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4B (OP166).

Upon the reception of the handover command, the mobile terminal4B executes the handover from the base station1to the mobile relay station2(OP167). The mobile terminal4B overwrites and updates the mobile relay station connection history with the identification number of the mobile relay station2(FIG. 28, OP137). Upon the transmission of a handover complete from the mobile terminal4B to the mobile relay station2as the transfer target (OP168), the handover is completed, and the mobile terminal4B connects to the mobile relay station2to make communication.

Operation Example 9

Example Case in which Mobile Terminal4C Makes Handover from Fixed Relay Station3to Mobile Relay Station2

In Operation Example 9, the following example is described. That is, in the example illustrated inFIG. 22, when the mobile relay station2approaches the fixed relay station3, the mobile terminal4C during communication determines the permission or prohibition of the handover to the mobile relay station2. In the wireless communication network system100, the handover of the mobile terminal4C from the fixed relay station3to the mobile relay station2is permitted, and hence the mobile terminal4C can make the handover to the mobile relay station2.

FIG. 33is a diagram illustrating a flow of Operation Example 9. It is assumed that the mobile terminal4C does not have a history of connection to the mobile relay station before the mobile terminal4C connects to the fixed relay station3and that the mobile relay station connection history is in its initial state (Invalid).

The mobile terminal4C periodically executes a detection process of neighboring stations and a measurement process of the reception quality of a signal from each station (OP171). InFIG. 22, when the mobile relay station2approaches the mobile terminal4C due to the movement of the train50, the reception quality of the signal from the mobile relay station2becomes better than that of the signal from the fixed relay station3. As a result of the measurement, the mobile terminal4C determines that the reception quality of the signal from the mobile relay station2is better than that from the fixed relay station3as the selected station (OP172: No).

The mobile terminal4C executes the handover determination process (OP173). The handover determination process of the fixed relay station3according to Operation Example 9 is performed in the following manner with reference toFIG. 28.

The mobile terminal4C (first handover determining unit67) determines that the transfer target candidate station is a mobile relay station (FIG. 28, OP131: Yes).

Next, the mobile terminal4C (first handover determining unit67) determines whether or not the handover from the currently selected station to the mobile relay station2is possible, on the basis of the cell transfer permission/prohibition setting (FIG. 28, OP132). Because the fixed relay station3is the fixed relay station (Type 1) installed near the boarding/exiting facility for the train50, the cell transfer permission/prohibition setting of the fixed relay station3is “Permitted” (seeFIG. 8). Accordingly, the handover from the fixed relay station3to the mobile relay station2is permitted (FIG. 28, OP132: Yes).

The mobile terminal4C transmits a measurement report for requesting the handover, to the currently connected fixed relay station3(FIG. 28, OP136a;FIG. 33, OP174). The measurement report at this time includes: the terminal identification number of the mobile terminal4C itself; and the identification number of the mobile relay station2as the transfer target candidate station.

The fixed relay station3transmits a handover request for requesting the handover of the mobile terminal4C, to the mobile relay station2as the transfer target candidate station (OP175). The handover request is transmitted to the mobile relay station2via the base station1.

Upon the reception of the handover request from the fixed relay station3, the mobile relay station2transmits a handover request ACK representing the permission of the handover of the mobile terminal4C, to the fixed relay station3(OP176).

Upon the reception of the handover request ACK from the mobile relay station2via the base station1, the fixed relay station3transmits a handover command for giving an instruction to execute the handover, to the mobile terminal4C (OP177).

Upon the reception of the handover command, the mobile terminal4C executes the handover from the fixed relay station3to the mobile relay station2(OP178). Because the handover target of the mobile terminal4C is the mobile relay station, the identification number of the mobile relay station2is stored for update in the mobile relay station connection history (FIG. 28, OP137). Upon the transmission of a handover complete from the mobile terminal4C to the mobile relay station2as the transfer target (OP179), the handover is completed, and the mobile terminal4C connects to the mobile relay station2to make communication.

In this way, even in the case where the mobile terminal4C determines the permission or prohibition of the handover, the mobile terminal4C can make the handover from the fixed relay station3to the mobile relay station2.

Operations and Effects of Second Embodiment

The mobile terminal itself determines the permission or prohibition of the handover, and hence the transmission of a wasteful measurement report can be avoided in the case where the handover is not permitted, so that the network band occupation can be reduced.

<Regarding Hardware Components and Software Components>

The hardware components refer to a hardware circuit, and examples thereof include a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a gate array, the combination of logical gates, a signal processing circuit, and an analog circuit.

The software components refer to parts (fragments) that implement the above-mentioned functions in the form of software, and do not refer to a concept that limits languages, development environments, and the like that implement the software. Examples of the software components include a task, a process, a thread, a driver, firmware, a database, a table, a function, a procedure, a subroutine, a predetermined part of a program code, a data structure, a sequence, a variable, and a parameter. These software components are implemented on one or more memories (one or more processors (for example, a CPU (Central Processing Unit) and a DSP (Digital Signal Processor)).

Note that the above-mentioned embodiments do not limit a method of implementing the above-mentioned processing units, and hence the processing units may be each implemented by the hardware components or the software components or by the combination thereof according to a method that can be achieved by a normal technical person who belongs to the technical field of the present invention.