Mobile terminal and communication control method for urging a connected communication terminal to perform a handover

An object is to urge a communication terminal connecting (or belonging) to a mobile terminal, to carry out a handover. A cell phone 1 has a relay unit 15 for relaying data transmitted between a digital camera 5 and a network, and a relay controller 17 for controlling the relay unit 15, based on a location state in a wireless LAN 3 derived based on a reception situation of a beacon from a base station 3a of the wireless LAN 3 different from a mobile communication network 2. The relay controller 17 cancels a connection to the digital camera 5 when the mobile terminal is located inside an area of the wireless LAN 3.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile terminal with a data relay function, and a communication control method thereof.

2. Related Background Art

In general wireless LAN communication, an access point at public facilities or at home is connected through a broadband line to a network and a session is established between a communication terminal with a wireless LAN function and the access point to enable the communication terminal to implement communication with the network. Examples of such communication terminals with the wireless LAN function include personal computers, game machines, cell phones, and so on.

In a wireless LAN system, the communication terminal normally connects (or belongs) to an optimal access point according to conditions of radio waves sent from access points. A handover process is carried out with changeover to another optimal access point due to movement of the communication terminal. Patent Document 1 below describes a method of performing a reconnection process upon the handover in a short time even during quick movement of the communication terminal. This method is to temporarily set the number of retransmissions smaller than the preset number of retransmissions of connection cancellation information in transmission of the connection cancellation information from the communication terminal to a base station connected before the handover and thereby reduce a time from detection of a base station to be connected after the handover, to connection to the base station.Patent Document 1: Japanese Patent Application Laid-open No. 2005-323034

SUMMARY OF THE INVENTION

If the function of the access point is loaded on such a mobile terminal as a cell phone, the communication terminal can perform communication with the network through the mobile terminal even at places where there is neither a home wireless LAN nor a public wireless LAN. However, when a user uses the mobile terminal as an access point, the mobile terminal is usually placed near the communication terminal, and thus the communication terminal connected once to the mobile terminal continues to belong to the mobile terminal. As a result, even if the communication terminal moves into an area of a home wireless LAN or public wireless LAN, it will not be handed over to a base station of the wireless LAN and the mobile terminal will continuously transmit information (a beacon signal) necessary for communication.

The present invention has been accomplished in order to solve the above problem and an object of the present invention is to provide a mobile terminal capable of urging a communication terminal connecting (or belonging) thereto, to carry out a handover, and a communication control method thereof.

A mobile terminal according to the present invention is a mobile terminal comprising: relay means for relaying data transmitted between another communication terminal and a network; and control means for controlling the relay means, based on a location state in a radio communication network derived based on a reception situation of a signal from a base station of the radio communication network different from a mobile communication network, wherein the control means cancels a connection to the another communication terminal when the mobile terminal is located inside an area of the radio communication network.

A communication control method according to the present invention is a communication control method in a mobile terminal with relay means for relaying data transmitted between another communication terminal and a network, the communication control method comprising: a control step of controlling the relay means, based on a location state in a radio communication network derived based on a reception situation of a signal from a base station of the radio communication network different from a mobile communication network, wherein the control step is to cancel a connection to the another communication terminal when the mobile terminal is located inside an area of the radio communication network.

Since the mobile terminal and the communication control method as described above are configured to cancel the connection to the another communication terminal connecting to the mobile terminal, when the mobile terminal moves into the area of the radio communication network, the communication terminal stops belonging to the mobile terminal. The communication terminal is given a chance of the handover in this manner, whereby the communication terminal connecting (or belonging) to the mobile terminal is urged to carry out the handover.

The mobile terminal of the present invention is preferably configured as follows: it further comprises monitoring means for monitoring a connection request signal transmitted from the another communication terminal the connection to which was cancelled; the control means deactivates the relay means if a destination of the connection request signal monitored by the monitoring means is the base station of the radio communication network, and establishes a connection to the another communication terminal in order to relay data communication associated with the another communication terminal if the destination is the mobile terminal.

In this case, the monitoring means monitors to which access point the another communication terminal stopping belonging to the mobile terminal transmits the connection request signal. If the communication terminal requests the connection to the base station of the radio communication network, the relay means of the mobile terminal is deactivated; if the communication terminal requests the connection to the mobile terminal, the communication terminal is again connected to the mobile terminal. As the relay function (access point function) is operated only if a connection is again requested by the communication terminal the connection to which was cancelled, the power of the mobile terminal consumed for the relay function can be reduced.

Since these mobile terminal and communication control method are configured to cancel the connection to the another communication terminal connecting to the mobile terminal when the mobile terminal moves into the area of the radio communication network, the communication terminal connecting (or belonging) to the mobile terminal can be urged to carry out the handover.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the embodiments the mobile terminal according to the present invention is applied to a cell phone. In the description of the drawings identical or equivalent elements will be denoted by the same reference symbols, without redundant description.

First, configurations and functions of a cell phone according to an embodiment will be described usingFIGS. 1 and 2.FIG. 1is a drawing showing a functional configuration of the cell phone.FIG. 2is a drawing showing a hardware configuration of the cell phone.

As shown inFIG. 1, the cell phone1can communicate with a mobile communication network2through transmission and reception of signals to and from a base station2aforming the mobile communication network2. Furthermore, the cell phone1can also communicate with a wireless LAN3through transmission and reception of signals to and from a base station3aforming the wireless LAN3. It is noted herein that the wireless LAN3is a communication network different from the mobile communication network2. The mobile communication network2and the wireless LAN3are connected each to a backbone network4.

The cell phone is equipped with an access point function to relay data transmitted between a digital camera (another communication terminal)5and the network. The digital camera5is equipped with a wireless LAN function.

The cell phone1has the following functional components: first receiver11, first determiner12, second receiver13, second determiner14, relay unit (relay means)15, monitoring unit (monitoring means)16, and relay controller (control means)17.

As shown inFIG. 2, the cell phone1is composed of a CPU101to execute an operating system, an application program, and others, a main memory unit102composed of a ROM and a RAM, an auxiliary memory unit103composed of a memory or the like, a communication control unit104to perform data communication through the mobile communication network2or the wireless LAN3, a display unit105composed of a liquid crystal monitor or the like, and an operation unit106composed of input keys or the like. Each of the functions shown inFIG. 1is implemented by making predetermined software retrieved onto the CPU101and main memory unit102, operating the communication control unit104under control of the CPU101, and reading and writing data from and into the main memory unit102or the auxiliary memory unit103.

Referring back toFIG. 1, the first receiver11is a part that receives broadcast information (signal) from the base station2aof the mobile communication network2. The first receiver11outputs the received broadcast information to the first determiner12.

The first determiner12is a part that determines a location state of the cell phone1in the mobile communication network2, based on a reception situation of the signal from the base station2aof the mobile communication network2. For example, the first determiner12determines that the cell phone1is located inside the area of the mobile communication network2, if the first receiver11receives the broadcast information; otherwise, it determines that the cell phone1is located outside the area of the mobile communication network2. The first determiner12outputs the determination result as first location information to the relay controller17. The first location information is information indicative of whether the cell phone1is located in the mobile communication network2and, as described above, it is derived based on the reception situation of the broadcast information from the base station2aof the mobile communication network2.

The second receiver13is a part that receives a beacon (signal) from the base station3aof the wireless LAN3. The second receiver13outputs the received beacon to the second determiner14.

The second determiner14is a part that determines a location state of the cell phone1in the wireless LAN3, based on a reception situation of the signal from the base station3aof the wireless LAN3. For example, the second determiner14determines that the cell phone1is located inside the area of the wireless LAN3, if the second receiver13receives the beacon; otherwise, it determines that the cell phone1is located outside the area of the wireless LAN3. Then the second determiner14outputs the determination result as second location information to the relay controller17. The second location information is information indicative of whether the cell phone1is located in the wireless LAN3and, as described above, it is derived based on the reception situation of the beacon from the base station3aof the wireless LAN3.

The relay unit15is a part that relays data transmitted between the digital camera (another communication terminal)5and the network. The relay unit15initiates or terminates transmission of a beacon according to a control signal input from the relay controller17described below. When a connection is established between the cell phone1and the digital camera5by transmission of the beacon, the relay unit15becomes able to relay data transmitted between the digital camera5and the mobile communication network2and data transmitted between the digital camera5and the backbone network4. At this time, the cell phone1functions as an access point.

The relay unit15also functions to cancel the connection to the digital camera5and to deactivate the relay function in accordance with a control signal fed from the relay controller17. The relay unit15transmits a belonging cancellation message such as disauthentication (de-authentication) or disassociation to the digital camera5to cancel the connection to the digital camera5. However, the connection cancellation (belonging cancellation) method is not limited only to this. For example, the relay unit15may execute the connection cancellation by reducing the transmission power or by forcibly changing (or resetting) a radio setting such as a service set identifier (SSID).

The monitoring unit16is a part that monitors a connection request signal transmitted from the digital camera5the connection to which was cancelled. This connection request signal is specifically a probe request. The monitoring unit16receives the probe request, checks the SSID included in the request, and determines to which the digital camera5requests a connection. Since the probe request is a broadcast signal, the monitoring unit16can also monitor the probe request which the digital camera5transmitted to the wireless LAN3. The monitoring unit16generates connection request information indicative of a destination of the probe request (object requested to connect to the digital camera5) and outputs the connection request information to the relay controller17.

The relay controller17is a part that controls the relay unit15, based on a location state in the wireless LAN3derived based on a reception situation of the signal from the base station3aof the wireless LAN3. The relay controller17controls the relay unit15, based on the first location information and the second location information.

With input of the first location information indicative of the location inside the area of the mobile communication network2and input of the second location information indicative of the location outside the area of the wireless LAN3, the relay controller17determines that the relay unit is to be activated. Then the relay controller17generates a control signal for controlling the relay unit15to transmit a beacon, and outputs it to the relay unit15. This makes the relay unit15start transmission of the beacon or continue its transmission process. As a result, the access point function of the cell phone1is activated and the digital camera5becomes connectable to the network.

If the relay controller17receives input of the second location information indicative of the location inside the area of the wireless LAN3while the cell phone1connects to the digital camera5or while the digital camera5belongs to the cell phone1, it determines that the connection to the digital camera5is to be cancelled. Then the relay controller17generates a control signal for cancelling the connection to the digital camera5, and outputs it to the relay unit15. This makes the relay unit15cancel the connection to the digital camera5.

Thereafter, when the connection request information is fed from the monitoring unit16, the relay controller17controls the relay unit15, based on the signal. Specifically, when the input is the connection request information indicating that the digital camera5requests a connection to the base station3aof the wireless LAN3, the relay controller17determines that the access point function is to be deactivated. Then the relay controller17generates a control signal for deactivating the relay unit15, and outputs it to the relay unit15. On the other hand, when the input is the connection request information indicating that the digital camera5requests a connection to the cell phone1, the relay controller17determines that the cell phone is to connect to the digital camera5. Then the relay controller17generates a control signal for controlling the relay unit to transmit a beacon, and outputs it to the relay unit15. In this case, the access point function of the cell phone1is resumed and the relay unit15connects to the digital camera5in order to relay data communication associated with the digital camera5.

The below will describe the operation of the cell phone shown inFIG. 1and a communication control method according to the present embodiment, usingFIGS. 3 to 5.FIG. 3is a flowchart showing the operation of the cell phone.FIGS. 4 and 5are sequence diagrams showing cooperative operations among the cell phone, the digital camera, and the wireless LAN.

It is assumed that the cell phone1is connected to the digital camera5and that the cell phone1is functioning as an access point of the digital camera5(step S1). Thereafter, when the second determiner14determines that the cell phone1has moved into the area of the wireless LAN3(step S2; YES), the relay controller17determines that the connection to the digital camera5is to be cancelled, and the relay unit15executes the connection cancellation process, based on the determination (step S3, control step).

Thereafter, the monitoring unit16monitors the probe request transmitted from the digital camera (step S4) and judges the destination of the request. If the destination is the base station3aof the wireless LAN3(step S5; wireless LAN), the relay controller17determines that the access point function is to be deactivated, and the relay unit15is deactivated based on the determination (step S6). At this time, the digital camera5connects to the wireless LAN3and becomes able to execute data communication with the network through the wireless LAN3(step S7).

On the other hand, if the destination of the probe request is the cell phone1(step S5; cell phone), the relay controller17determines that the cell phone is to again connect to the digital camera5, and the relay unit15resumes the access point function (step S8). This makes the digital camera5belong to the cell phone1and allows the digital camera5to execute data communication with the network through the cell phone1.

When the digital camera5switches its access point from the cell phone1to the wireless LAN3, the processing as shown inFIG. 4is carried out. Specifically, while the cell phone1and the digital camera5connect to each other (step S11), these devices move into the area of the wireless LAN3(step S12), and, based on the determination of the relay controller17, the relay unit15sends a belonging cancellation message to the digital camera5(step S13, control step). This results in cancelling the connection between the cell phone1and the digital camera5.

Thereafter, the monitoring unit16monitors the probe request from the digital camera5(step S14). This monitoring operation is continuously executed during a period of time T until the destination of the probe request is figured out. Thereafter, the digital camera5sends the probe request to the base station3aof the wireless LAN3(step S15). This causes the digital camera5to connect to the wireless LAN3, thereby completing the handover (step S16). On the other hand, the relay controller17deactivates the relay unit15in the cell phone1(step S17).

When the digital camera5again uses the cell phone1as an access point, the processing as shown inFIG. 5is carried out. First, the processes of steps S21to S24are the same as those of steps S11to S14. The monitoring unit16continuously executes the monitoring process during a period of time T′ until the destination of the probe request is figured out. Thereafter, the digital camera5transmits the probe request to the cell phone1, e.g., for the reason of failure in connection to the wireless LAN3(step S25). Then the digital camera5again connects to the cell phone1(step S26).

In the present embodiment, as described above, when the cell phone1moves into the area of the wireless LAN3, the connection to the digital camera5connecting to the cell phone1is cancelled and thus the digital camera5stops belonging to the cell phone1. As the digital camera5is given a chance of a handover in this manner, the digital camera5connecting (or belonging) to the cell phone1is urged to carry out the handover.

According to the present embodiment, the cell phone1is configured to monitor the probe request transmitted from the digital camera5which stopped belonging to the cell phone1. If the digital camera5requests a connection to the base station3aof the wireless LAN3, the relay unit15of the cell phone1is deactivated; if the digital camera5requests a connection to the cell phone1, the cell phone again connects to the digital camera5. Since the relay function (access point function) is operated only when the connection is again requested by the digital camera5the connection of which was cancelled, the power of the cell phone1consumed for the relay function can be reduced. Furthermore, convenience is improved because the handover process of the digital camera5is automatically carried out.

The present invention was described above in detail based on the embodiment thereof. However, the present invention is not limited only to the above embodiment. The present invention can be modified in many ways as described below, without departing from the scope and spirit of the invention.

The above embodiment showed the example wherein the cell phone1determined the location situation in the wireless LAN3, but it is also possible to adopt a configuration wherein the digital camera5determines the location situation in the wireless LAN3and notifies the cell phone1of the determination result (equivalent to the second location information in the above embodiment). This configuration eliminates the need for the mobile terminal to determine the location situation in the radio communication network and thus reduces the load on the mobile terminal.

The above embodiment showed the wireless LAN3as the radio communication network, but there are no restrictions on the type of the radio communication network. For example, the present invention is also applicable to systems using WiMAX (Worldwide Interoperability for Microwave Access). Furthermore, there are no restrictions on the type of the mobile communication network, either. For example, the present invention is also applicable to systems using W-CDMA (Wideband Code Division Multiple Access), CDMA-2000, or LTE (Long Term Evolution).

The above embodiment showed the example of the cell phone1and the digital camera5as the mobile terminal and the another communication terminal, but there are no restrictions on the type of the mobile terminal, and the type of the communication terminal configured to communicate through the mobile terminal. For example, a personal digital assistant (PDA) can be the mobile terminal and a portable game machine or portable music player can be the another communication terminal.