Source: https://patents.google.com/patent/US20090270105A1/en
Timestamp: 2018-12-11 07:59:30
Document Index: 580493841

Matched Legal Cases: ['art 20', 'art 20', 'art 40', 'art 50', 'art 50', 'art 60']

US20090270105A1 - Wireless communication terminal, wireless communication network system and handover timing determining method - Google Patents
Wireless communication terminal, wireless communication network system and handover timing determining method Download PDF
US20090270105A1
US20090270105A1 US12443726 US44372607A US2009270105A1 US 20090270105 A1 US20090270105 A1 US 20090270105A1 US 12443726 US12443726 US 12443726 US 44372607 A US44372607 A US 44372607A US 2009270105 A1 US2009270105 A1 US 2009270105A1
US12443726
US8311540B2 (en )
In recent years, various wireless communication devices such as WLAN (Wireless Local Area Network) have been installed in apparatuses such as a personal computer, a peripheral device, a mobile telephone, a game machine, and home electronics. Among them, in a mobile apparatus such as a note type personal computer, the mobile telephone, and the game machine, there is a case that a user moves while executing an application. For example, a situation in which the user moves while making a call by using the mobile telephone can be easily imagined.
The generation of the handover involves the following situation. Until the wireless communication terminal performs a data communication with a network through the base station, several processes are required such as negotiation for a connection, an authentication process as necessary, and a process of reserving a communication band. For example, there is a case that considerable processes and times are required, depending on a kind of the authentication process. Usually, these processes are required in not only the first connection to the base station but also switching of the base station in the handover. In short, in case of a wireless LAN, when the connection is switched between wireless LAN access points, a considerable connection destination switching time is required. It should be noted that while the connection destination is switched, the data communication is not performed through a newly-connected base station, until the completion of the switching of the connection.
For this reason, a technique of controlling the timing of the handover on the basis of the communication state of an application being executed currently is described in Japanese Patent Application Publications (JP-P2001-36936A and JP-P2005-101930A).
In the mobile wireless terminal described in Japanese Patent Application Publication (JP-P2001-36936A), a silence period in speech communication is detected in order to prevent the discontinuity of the speech communication, and a threshold level with respect to a reception signal level (received electric field intensity or the like) is set to be higher than a usual level in the silence period so as to make the handover easier, and reversely, the threshold level is set to the usual level in a non-silence period so as to make the handover difficult.
Also, in the mobile communication terminal described in Japanese Patent Application Publication (JP-P2005-101930A), a handover condition based on a throughput (a reception rate) for each kind of an application is added in addition to the usual handover threshold level based on a communication quality, in order to perform the handover in a suitable period based on the application being executed currently. Specifically, only when a reception signal level representing the level of a reception signal from the base station currently in communication is lower than a preset handover threshold level and the reception rate satisfies a handover condition which is preset to the application.
According to the technique described in Japanese Patent Application Publication (JP-P2001-36936A), it is easy to perform the handover in the silence period, as compared with other periods. Thus, when a user performs speech communication by a mobile wireless terminal while moving, a probability in which the handover is performed in the silence period becomes high. However, the handover threshold level in a period other than the silence period remains at a usual level. Therefore, the control is switched to the handover as soon as the reception signal level becomes equal to or less than a handover threshold level during the speech communication. That is, the handover is easily performed at an improper timing in the application currently in execution.
On the contrary, according to the technique described in Japanese Patent Application Publication (JP-P2005-101930A), the switching to the handover is controlled depending on an establishment or not of a handover condition according to the communication state of an application currently in execution. Thus, it is possible to prevent the handover from being easily performed at an improper timing for the application currently in execution. However, even if the reception signal level continues to be much lower than the handover threshold level, the wireless communication terminal continues to wait for the handover condition according to the communication state of the application currently in execution. Therefore, there is a fear that the wireless communication terminal becomes a situation in which the handover cannot be performed anymore.
With reference to FIG. 12B, as an operation of the wireless communication terminal 100 of the present invention, a handover timing determining method of the present invention contains the following steps S1, S2, S3 and S4. This handover timing determining method determines a timing when the handover control for switching from the first base station to the second base station in response to the connection request is performed to the wireless communication terminal connected to the first base station. At the step S1, the first detecting section 110 determines whether or not the first handover condition is established. At the step S2, if the first handover condition is established (Step S1—YES), the second detecting section 120 determines whether or not the second handover condition is established. At the step S3, if the second handover condition is not established (Step S2—NO), the third detecting section 130 determines whether or not the third handover condition is established. At the step S4, the determining section 140 determines any one of: the timing (Steps S1—YES, S2—YES) when the first and second handover conditions are both established; and the timing (Steps S1—YES, S2—NO, and S3—YES) when the first and third handover conditions are both established, as the timing of the switching to the handover control. Thus, the communication control section 150 performs the handover control.
The base station 2 is configured to perform a function as a base station based on IEEE 802.11 that is the standard of the wireless LAN, and performs a connection negotiation in response to a connection negotiation request from the wireless communication terminal 1 and performs an operation of relaying the data communication between the wireless communication terminal 1 and a communicating apparatus (not shown) connected to the network 4, after the completion of the connection negotiation. Specifically, a connection negotiation procedure based on the IEEE 802.11 is performed in the outline as follows.
The wireless communication terminal 1 is configured to perform a function as a terminal based on the IEEE 802.11 and can communicate with a communicating apparatus connected to the network 4 through the base station 2 or 3 by using an Internet protocol (IP). Specifically, the wireless communication terminal 1 transmits an authentication frame to the base station to be connected. When the authentication frame including the authentication result is transmitted from the base station based on the IEEE 802.11, the wireless communication terminal 1 receives this and transmits an association frame to notify that the connection to the base station is performed. Subsequently, when the association frame including the ID to identify the wireless communication terminal is transmitted from the base station, the wireless communication terminal 1 receives this. After that, as necessary, the authentication based on the IEEE 802.1X and the exchange of the keys to safely perform the communication are performed, which results in the completion of the connection negotiation. Thus, the data communication with the base station and the data communication through the base station can be performed. Also, the wireless communication terminal 1 has a security function based on IEEE 802.11i when the further reinforcement of the security is required, and has an admission control function (a call admission control and the like) and a QoS (Quality of Service) function (a band insurance function and the like) based on IEEE 802.11e when the communication quality is required to be secured; and an optimizing function of the authentication based on IEEE 802.11r and the exchange of the keys when the high speed handover is required during the data communication. As necessary, the wireless communication terminal 1 may be configured to perform a function as a terminal based on the rules of the IEEE 802.11 other than the IEEE 802.11i, the IEEE 802.11e and the IEEE 802.11r.
When performing the network communication through the base station 2 or the base station 3, the wireless communication terminal 1 performs the connection negotiation with the base station 2 or the base station 3 by using a wireless physical layer. As necessary, there may be a case that the authenticating process is additionally executed. On the completion of the connection negotiation, the network communication can be performed through the base station.
FIG. 2 is a block diagram showing the configuration of the wireless communication terminal 1 in FIG. 1 according to the first exemplary embodiment. With reference to FIG. 2, the wireless communication terminal 1 contains a wireless communication interface section 30, one or more applications 10, a communication control section 20, a handover permission instructing section 40, a handover permission determining section 50, a user preference data input section 70, a user preference data storage section 80 and a connection destination determining section 60. The application 10 is a communication application for performing a data communication through the wireless communication interface section 30, and it itself issues the instructions with regard to the handover. The communication control section 20 executes a connecting process to the network through the wireless communication interface section 30, a monitoring process of a reception signal level, and a transmitting/receiving process of data between the application 10 and the wireless communication interface section 30. The handover permission instructing section 40 outputs a handover permission notice and inhibition notice based on data with regard to the handover from the application 10. The handover permission determining section 50 determines permission or inhibition of the handover based on the handover permission notice and the inhibition notice from the handover permission instructing section 40 and a stay time period during which the handover permission determining section 50 is set to a handover inhibition state. The user preference data input section 70 inputs an identifier name of a connection destination base station, a priority for it and a network data. The user preference data storage section 80 holds a data supplied from the user preference data input section 70 or a pre-stored data. The connection destination determining section 60 is connected to the communication control section 20, the handover permission determining section 50 and the user preference data storage section 80, and determines the base station to which the wireless communication terminal is to be connected, and then issues the connection request on the communication control section 20.
The communication control section 20 has a part 20A corresponding to the first detecting section 110 and a part 20B corresponding to the communication control section 150. The handover permission instructing section 40 has a part 40A corresponding to the second detecting section 120. The handover permission determining section 50 has a part 50A corresponding to the third detecting section 130 and a part 50B corresponding to the determining section 140. The connection destination determining section 60 has a part 60A corresponding to the determining section 140.
The application 10 is a communication application program for performing the data communication through the wireless communication interface section 30. A kind of the application 10 is not limited. However, the application 10 is desired to be a connectionless communication using, especially, UDP (User Datagram Protocol), which is especially effective in a speech communication application, a television telephone application and a video reception application, which require real time properties. Moreover, the application 10 has a function of controlling the handover permission instructing section 40 to instruct the handover permission or inhibition to the handover permission determining section 50 at a timing based on the communication content in the application itself. For example, when the application 10 is the speech communication application, the application 10 determines the speech interval and the silence interval in the speech communication, outputs a handover inhibition instruction in response to start of the speech interval and outputs a handover permission instruction in response to end of the speech interval.
The communication control section 20 has a function of executing the connecting process to the network 4 in response to the request from the connection destination determining section 60. Specifically, the communication control section 20 has a function of executing a series of processes such as retrieval of a base station, the connection negotiation with the base station, and the encoding and decoding of data, and a function of notifying the retrieval result of the base station to the connection destination determining section 60. Moreover, the communication control section 20 holds a threshold level set by the connection destination determining section 60. The communication control section 20 has a function of comparing the threshold level with the reception signal level periodically obtained by the wireless communication interface section 30, and outputting a notice to the connection destination determining section 60 when the reception signal level is lower than the threshold level. It should be noted than threshold levels other than the threshold level set by the connection destination determining section 60 may be stored in advance.
Moreover, the connection destination determining section 60 is responsible for determining the switching of the connection from the current connection destination to a different base station, when there is a base station connected through the wireless communication interface section 30. The connection destination determining section 60 sets a threshold level in the wireless communication interface section 30 to the communication control section 20, as necessary. When receiving a reception signal level lowered notice indicating that the reception signal level of the reception signal from the communication control section 20 to the wireless communication interface section 30 becomes lower than the threshold level, the connection destination determining section 60 outputs the handover permission notice request to the handover permission determining section 50, to notify its fact at the time of the switching to the handover permission, in order to determine the permission or inhibition of the handover.
When receiving the handover permission notice from the handover permission determining section 50, the connection destination determining section 60 starts the handover process. This handover process is a process of retrieving the connectable base stations, acquiring the retrieval result of the base stations, and determining the connection destination base station having a high priority through the comparison between the retrieval result and a connection destination identification name held by the user preference data storage section 80, and also issuing the connection request for the selected base station to the communication control section 20 and then connecting to a new base station. This is similar to a process of firstly connecting to the base station. At this time, basically, the handover destination candidates do not include the base station currently in connection in which the reception signal level is reduced, in a case other than a next case. The case where the handover destination candidates include the base station currently in connection is a case where the transiently reduced reception signal level is recovered to a degree that exceeds the threshold level when the handover permission notice is received from the handover permission determining section 50. In this case, the handover process may be stopped and the base station currently in connection may be used in its original state.
At first, the wireless communication terminal 1 retrieves the base stations to be connected to the network 4 and acquires the retrieval result. The retrieval result and the list of the base station identification names which are stored in the user preference data storage section 80 of the wireless communication terminal 1 and arranged in the order of priorities are compared in the order of higher priority. When there is a coincident base station, the connection to the base station is determined, and the connection negotiation with the base station is performed, to allow the data communication. For example, the base station 2 is determined, and the connection negotiation with the base station 2 is performed. Thus, the wireless communication terminal 1 can communicate with an apparatus on the network 4 through the base station 2 (C1 and C2 in FIG. 5).
The handover permission determining section 50 is set to the handover permission state when it is active (Step B1 in FIG. 4) and waits for the handover permission notice or inhibition notice from the handover permission instructing section 40, and the handover permission notice request from the connection destination determining section 60 (Steps B2 to B4 in FIG. 4). When receiving the handover inhibition notice from the handover permission instructing section 40, the handover permission determining section 50 is set to the handover inhibition state (Step B3 in FIG. 4). After that, when receiving the handover permission notice, the handover permission determining section 50 is set to the handover permission state (Step B4 and Step B1 in FIG. 4).
When receiving the handover permission notice request from the connection destination determining section 60, the handover permission determining section 50 initializes a timer, which counts the staying time period in the handover inhibition state to “0” (Step B6 in FIG. 4) and then checks the handover state kept (Step B7 in FIG. 4). When the handover state is the handover permission state, the handover permission determining section 50 issues the handover permission notice to the connection destination determining section 60 (Step B11 in FIG. 4, C6 in FIG. 5). If at the step B7, the handover state is the inhibition state, while counting up the timer for each predetermined time (Step B9 in FIG. 4), the handover permission determining section 50 waits for the handover permission instruction from the handover permission instructing section 40 (Step B8 in FIG. 4, C6 in FIG. 5). When receiving the handover permission instruction, the handover permission determining section 50 issues the handover permission notice to the connection destination determining section 60 at that time (Step B11 in FIG. 4, C6 in FIG. 5). Also, when the timer exceeds a preset timeout value (Step B10 in FIG. 4), the handover permission determining section 50 issues the handover permission notice to the connection destination determining section 60 without any handover permission instruction from the handover permission instructing section 40 (Step B11 in FIG. 4, C6 in FIG. 5). When issuing the handover permission notice, the handover permission determining section 50 is set to the initial handover permission state and returns to the initial state (Step B1 in FIG. 4).
When receiving the handover permission notice from the handover permission determining section 50, the connection destination determining section 60 starts the handover process (Steps A4, A5 in FIG. 3, C7 in FIG. 5). Here, the handover process starts with the retrieval of the base station, similarly to the first connection, and then performs the determination of the connection destination base station based on the user preference data and the connection negotiation to the base station. Consequently, the handover process to the new base station is completed (Step A6 in FIG. 3, C8 in FIG. 5). For example, it is supposed that, the wireless communication terminal is firstly connected to the base station 2 and performs a data communication, and then performs retrieval of the base stations after the reception of the handover permission notice, and as the result of the comparison with the user preference data, the wireless communication terminal is connected to the base station 3. In such a case, the wireless communication terminal 1 performs the connection negotiation with the base station 3 and starts the data communication (C7, C8 in FIG. 5). The wireless communication terminal 1 may release the connection to the base station 2 and stop the data communication, as necessary, prior to the connection negotiation with the base station 3.
Next, when the handover permission determining section 50 receives the handover permission notice request (D8-1) in FIG. 6, the handover permission determining section 50 waits for the switching to the handover permission state, since the handover permission determining section 50 is in the handover inhibition state at present. When receiving the handover permission instruction (D6) from the handover permission instructing section 40, the handover permission notice (D8-2) is issued to the connection destination determining section 60, since the handover permission determining section 50 is set to the handover permission state at that time. Thus, the wireless communication terminal 1 starts the handover process when the handover permission instruction is issued, without starting the handover process until the application 10 issues the handover permission instruction, after the generation of the lowering in the reception signal level. However, if the wireless communication terminal 1 continues to wait for the handover permission instruction anymore when the timer exceeds a timeout value because the handover permission instruction is not issued for a long time, the reception signal level is lowered to a level corresponding to the data communication disabled state so that the handover cannot be performed. Therefore, the handover permission notice is issued to the connection destination determining section 60 without any handover permission instruction.
Also, in the foregoing descriptions, the application 10 is configured to issue the handover permission and inhibition instructions during the speech communication. However, it can be used in a control plane during the signaling to make a speech call, namely, other than a data plane. For example, in the speech communication application, when the speech communication is started, SIP (Session Initiation Protocol) is used to perform preparation of the speech communication. This is to call up a partner in making the call and perform the negotiation of a speech CODEC (COmpression/DECompression) to be used. For example, when transmitting an INVITE packet to start the speech communication, the wireless communication terminal 1 receives a [100 Trying] packet indicating continuation of a process from an SIP server, and receives a [180 Ringing] packet indicating an in-call state from the partner and receives a [200 OK] packet indicating that the partner answers the call and then returns an ACK packet implying a reception confirmation for it. Consequently, the preparation of the execution of the speech communication is completed.
Also, in the wireless communication system according to the first exemplary embodiment of the present invention, in case of a video data receiving application or speech data receiving application, it is possible to preliminarily determine a period during which the handover is permitted or inhibited, such as a case that a period between the broadcasts is determined to be the handover permission interval, based on a predetermined broadcast program (a picture distribution program or a speech distribution program). As a result, it is possible to perform the base station retrieval at a higher precision by effectively using the handover permission interval. Moreover, the effect is obtained in which the wireless communication terminal can suitably perform the handover on the base station whose communication state is better.
The communication control section 20 in this exemplary embodiment further holds another threshold level. In order to clarify a difference from the threshold level in the first exemplary embodiment, the threshold level in the first exemplary embodiment is referred to as a threshold level A, and another threshold level added in the second exemplary embodiment is referred to as a threshold level B. When the threshold level B is set to a value at which the data communication can be barely performed, the maximum effect can be obtained. However, the threshold level B may be set to a value slightly greater than the above value by a margin. The communication control section 20 compares the reception signal level, which is periodically obtained from the wireless communication interface section 30, with the threshold levels A and B. When the reception signal level becomes lower than the threshold level A, the communication control section 20 notifies it to the connection destination determining section 60, and when the reception signal level becomes lower than the threshold level B, notifies it to the connection destination determining section 60. The threshold level B is lower than the threshold level A. It should be noted that the threshold levels A and B may be held in advance, other than a case that they are set by the connection destination determining section 60.
In the communication control section 20 in the wireless communication terminal 1, when the movement of the terminal 1 causes the lowering of the reception signal level (F1 in FIG. 8) from the base station currently in connection, a reception signal level lowered notice A is issued to the connection destination determining section 60 at the timing (F2 in FIG. 8) at which the reception signal level becomes lower than the threshold level A set for the communication control section 20. Moreover, a reception signal level lowered notice B is issued to the connection destination determining section 60 at the timing (F3 in FIG. 8) when the reception signal level becomes lower than the threshold level B set for the communication control section 20.
The wireless communication system according to the second exemplary embodiment of the present invention is configured in such a manner that in addition to the threshold level A, the threshold level B lower than it is set, and when the reception signal level becomes equal to or less than the threshold level A, the communication control section 20 in the wireless communication terminal 1 starts the control of the switching to the handover, under the condition issuance of the handover permission instruction from the application 10, and when the handover permission instruction is inhibited from being issued from the application 10 due to any reason, forcedly performs the switching to the handover when the reception signal level becomes equal to or less than the threshold level. Accordingly, it is possible to prevent the occurrence of the situation that the handover cannot be performed because the reception signal level from the base station is reduced to a level corresponding to the data communication disabled state.
The operation of the wireless communication system according to the fourth exemplary embodiment of the present invention will be described below in detail. It should be noted that a process indicated in this exemplary embodiment is attained when the CPU in the computer configuring the wireless communication terminal 1 transfers the programs in the recording medium 90 onto the RAM and executes them.
It should be noted that the wireless communication interface section 30A and the wireless communication interface section 30B are possible to use various communication methods using radio communications such as WLAN, a mobile telephone network, WiMAX (Worldwide Interoperability for Microwave Access, another name IEEE 802.16e), Bluetooth, PHS (Personal Handyphone System). Both of them are possible to use any combination of the above radio communications. Moreover, the number of wireless communication interface sections is not limited to two, and additional wireless communication interface sections may be contained.
Also, when the handover is performed between the plurality of wireless communication interface sections under the situation that the data communication is performed in the wireless communication interface section previously in connection, the connection of the wireless communication interface previously in connection is continued, until new data communication can be performed after the completion of the connection of the wireless communication interface section for a new connection. Thus, the period during which the data communication is impossible is minimized.
a communication control section connected with a first base station, and configured to perform a handover control to switch from said first base station to a second base station in response to a connection request;
a first detecting section configured to detect whether or not a reception signal level indicating a level of a received signal from a base station currently in connection as said first base station reduces to be equal to or lower than a first threshold level;
a second detecting section configured to detect whether or not a communication situation of a communication application program currently in communication is a situation suitable for handover;
a third detecting section configured to detect whether or not a predetermined handover forcedly performing condition is established; and
a determining section configured to determine whether or not the handover control is necessary, based on detection results of said first to third detecting sections and outputting a connection request when the handover control is determined to be necessary.
2. The wireless communication terminal according to claim 1, wherein said determining section determines that switching to the handover control is necessary when the reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than the first threshold level and the communication situation of the communication application program currently in communication becomes suitable for handover, or when the reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than the first threshold level and the handover forcedly performing condition is established.
3. The wireless communication terminal according to claim 2, wherein the handover forcedly performing condition is established when a passage time exceeds a preset time after said reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than the first threshold level.
4. The wireless communication terminal according to claim 2, wherein the handover forcedly performing condition is established when the reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than a second threshold level which is lower than the first threshold level.
5. The wireless communication terminal according to claim 1, wherein said second detecting section is provided in said communication application program, and
the communication application program detects whether or not the communication situation of the communication application program is suitable for the handover, by said second detecting section.
6. The wireless communication terminal according to claim 1, wherein said second detecting section is provided in a handover instructing application program different from said communication application program, and
the handover instructing application program detects whether or not the communication situation of the communication application program is suitable for the handover, by said second detecting section.
7. The wireless communication terminal according to claim 1, wherein when the communication application program is a speech communication application program, said second detecting section detects a silence period during data communication as a period suitable for the handover.
8. The wireless communication terminal according to claim 1, wherein said second detecting section detects a period other than a period for a process of a control protocol of the communication application program as a period suitable for the handover.
9. The wireless communication terminal according to claim 8, wherein the control protocol is a signaling protocol for a call control.
10. The wireless communication terminal according to claim 8, wherein the control protocol is a protocol to secure a communication path with VPN.
11. The wireless communication terminal according to claim 1, wherein when the communication application program is a software program which receives a content program distributed based on a predetermined content program list the program, said second detecting section detects whether or not the communication situation is suitable for the handover, based on the content program list.
12. The wireless communication terminal according to claim 1, wherein said second detecting section determines whether or not the communication situation is suitable for the handover, based on an operation situation of a physical button of said wireless communication terminal or a virtual button.
13. The wireless communication terminal according to claim 1, wherein said communication control section switches said first base station which is connected through one wireless communication interface section to said second base station, as the handover control.
14. The wireless communication terminal according to claim 1, wherein said communication control section switches said first base station which is connected through one wireless communication interface section to said second base station which is connected through another wireless communication interface section, as the handover control.
a wireless communication terminal, which comprises:
a determining section configured to determine whether or not the handover control is necessary, based on detection results of said first to third detecting sections and outputting a connection request when the handover control is determined to be necessary,
wherein said wireless communication terminal is connected with a first base station of said plurality of base station and a connection destination is switched from said first base station to a second base station of said plurality of base stations, when a handover control is performed.
16. A method of determining a timing of a handover control to a wireless communication terminal for switching from a first base station to a second base station in response to a connection request, comprising:
17. The method according to claim 16, wherein said determining comprises:
18. The method according to claim 17, wherein the handover forcedly performing condition is established when a passage time exceeds a preset time after said reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than the first threshold level.
19. The method according to claim 17, wherein the handover forcedly performing condition is established when the reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than a second threshold level which is lower than the first threshold level.
20. A computer-readable recording medium in which a computer-readable program is stored to realize a method of determining a timing of a handover control to a wireless communication terminal which performs the handover control for switching from a first base station to a second base station in response to a connection request, wherein the method comprises:
21. The computer-readable recording medium according to claim 20, wherein said determining comprises:
22. The computer-readable recording medium according to claim 20, wherein the handover forcedly performing condition is established when a passage time exceeds a preset time after said reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than the first threshold level.
23. The computer-readable recording medium according to claim 21, wherein the handover forcedly performing condition is established when the reception signal level of the received signal from said base station currently in connection reduces to be equal to or lower than a second threshold level which is lower than the first threshold level.
US12443726 2006-10-11 2007-10-05 Wireless communication terminal, wireless communication network system and handover timing determining method Active 2029-08-02 US8311540B2 (en)
JP2006277120A JP4983195B2 (en) 2006-10-11 2006-10-11 Wireless communication terminal, a wireless communication network system, a handover timing determining process
JP2006-277120 2006-10-11
US20090270105A1 true true US20090270105A1 (en) 2009-10-29
US8311540B2 US8311540B2 (en) 2012-11-13
US12443726 Active 2029-08-02 US8311540B2 (en) 2006-10-11 2007-10-05 Wireless communication terminal, wireless communication network system and handover timing determining method
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