JP4956484B2 - Mobile communication terminal, communication system, and handover method - Google Patents

Description

  The present invention relates to a mobile communication terminal that performs handover, a communication system, and a handover method.

  In the mobile communication terminal, a handover process for switching the communication from one base station to another base station is performed, and a cell search for searching for another base station is performed prior to the handover process.

For example, the following Patent Document 1 (Japanese Patent Laid-Open No. 2006-287663) discloses a cell search based on a transmission timing difference notified from a base station in order to shorten a cell search time and reduce power consumption of a mobile station. It describes that cell search is performed with a limited range.
JP 2006-287663 A

  However, Patent Document 1 does not consider the propagation delay from the base station to the mobile station, and there is a limit to efficient cell search.

  Therefore, in order to solve the above-described problems, an object of the present invention is to provide a mobile communication terminal, a communication system, and a handover method that can perform a cell search more efficiently.

  In order to solve the above-described problem, the mobile communication terminal of the present invention performs a cell search for the second base station and the first communication means for executing the first communication method via the first base station. A second communication means for executing a second communication method different from the first communication method via the second base station searched by the cell search, and the first communication means , When the transmission timing of the head data transmitted from the second base station and the propagation delay amount in the first base station are received, the cell is determined based on the received transmission timing and propagation delay amount. Control means for setting a search start time and controlling the cell search by the second communication means from the start time.

  According to the present invention, when the first communication means receives the transmission timing of the head data of the second communication means and the propagation delay amount in the first communication means, the received transmission timing and propagation delay amount are received. Based on the above, it is possible to set a cell search start time and perform a cell search by the second communication means from the start time. Thereby, the cell search time can be limited, and the power consumption and CPU load required for the cell search can be reduced.

  Further, the mobile communication terminal of the present invention further comprises a calculation means for calculating a maximum propagation delay time in the second base station based on the cell size information of the second base station, and the second communication means Preferably, the end time of the cell search time is determined based on the maximum propagation delay time calculated by the calculating means, and the cell search is executed until the end time.

  According to the present invention, the cell search time can be limited by determining the end time of the cell search time based on the calculated maximum propagation delay time and executing the cell search until the end time. It is possible to reduce the power consumption and CPU load required.

  The mobile communication terminal of the present invention further includes an acquisition unit that acquires a maximum propagation delay time based on cell size information from the second base station, and the second communication unit is acquired by the acquisition unit. Preferably, the end time of the cell search time is determined based on the maximum propagation delay time, and the cell search is executed until the end time.

  According to the present invention, the cell search time can be limited by determining the end time of the cell search time based on the acquired maximum propagation delay time and executing the cell search until the end time. It is possible to reduce the power consumption and CPU load required.

  The mobile communication terminal of the present invention further comprises notification means for notifying the first base station of functional information indicating that the second communication method can be executed, wherein the first base station It is preferable to transmit the transmission timing of the head data of the second base station and the propagation delay amount in the first base station in response to the notification by the notification means.

  According to this invention, it is possible to notify the first base station of function information indicating that the second communication method can be executed, and the first base station can receive various information based on the function information. Can be transmitted to the mobile communication terminal. Therefore, only necessary terminals can be notified of information for shortening the cell search, and efficient processing can be realized.

  In addition, the mobile communication terminal of the present invention performs a cell search for the first communication means for executing the first communication method and the second base station via the first base station, and the cell search. Second communication means for executing a second communication method different from the first communication method via the second base station searched by the first base station and the second base station Synchronizing means for synchronizing with timing, transmission time of head data received by the first communication means and time information synchronized by the synchronizing means, and transmission timing received by the first communication means or in advance Control means for setting a start time at the time of cell search based on a predetermined transmission timing and controlling the cell search by the second communication means.

  According to the present invention, when the transmission time of the head data received by the first communication means and the transmission timing of the head data transmitted from the second base station are received, the received transmission time is synchronized. The start time of the cell search is set based on the received time information and the received or predetermined transmission timing, and control is performed so that the cell search by the second communication means is performed. Thereby, it is not necessary to consider the propagation delay, and the processing can be simplified. In addition, the cell search time can be limited, and the power consumption and CPU load required for the cell search can be reduced.

  By the way, the present invention can be described as an invention of a mobile communication terminal as described above, and can also be described as an invention of a communication system and a handover method as follows. These are substantially the same inventions only in different categories, and exhibit the same actions and effects.

  That is, a communication system according to the present invention includes the mobile communication terminal described above, a first base station that can execute the first communication method, and a second base station that can execute the second communication method. Has been.

  In addition, the handover method of the present invention executes a cell search for the first communication means for executing the first communication method and the second base station via the first base station, and by the cell search. A handover method in a mobile communication terminal comprising: a second communication unit that executes a second communication method different from the first communication method via the searched second base station; In the communication means, a reception step of receiving the transmission timing of the head data transmitted from the second base station and a propagation delay amount in the first base station, and the transmission timing and propagation delay received in the reception step A cell search step of setting a cell search start time based on the amount, and performing a cell search by the second communication means from the start time. .

  In addition, the handover method of the present invention executes a cell search for the first communication means for executing the first communication method and the second base station via the first base station, and by the cell search. In a handover method in a mobile communication terminal comprising: a second communication unit that executes a second communication method different from the first communication method via the searched second base station; A synchronization step for synchronizing with timings in the base station and the second base station, a reception step for receiving at least a transmission time of the head data received in the first communication means, and a transmission received in the reception step Time and time information synchronized in the synchronization step, and transmission timing received by the first communication means or predetermined time And set the start time for the cell search based on the transmission timing, and a, a cell search step of performing cell search according to the second communication means.

  According to the present invention, the cell search time can be limited, and the power consumption and CPU load required for the cell search can be reduced.

  Embodiments of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a conceptual diagram showing a concept of a communication system 10 in the present embodiment. As shown in FIG. 1, a communication system 10 includes a so-called 3G (3 ^RD GENERATION) communication area, that is, a 3G base station 200 constituting a mobile communication network, and a WiMAX (worldwide interoperability for microwaveaccess) communication area. The base station 300 is comprised. The mobile communication terminal 100 can execute both the 3G communication method and the WiMAX communication method, and can perform communication by switching each communication method according to the communication area. For example, when the mobile communication terminal 100 moves from the 3G communication area to the WiMAX communication area as indicated by an arrow a, the mobile communication terminal 100 performs a process of switching from the 3G communication method to the WiMAX communication method.

  That is, the mobile communication terminal 100 performs communication using the mobile communication network by connecting to the 3G base station 200. When moving to the WiMAX communication area, the mobile communication terminal 100 performs handover processing on the WiMAX base station 300, Communication by WiMAX can be executed by communication connection. The handover process is executed by performing a cell search based on the notification from the WiMAX base station 300. The outline will be described below.

  First, the transmission timing in the 3G communication system and the transmission timing in the WiMAX communication system, which are the prerequisites, will be described. FIG. 2 is an explanatory diagram showing the relationship between the transmission timing of the 3G communication system and the transmission timing of the WiMAX communication system. The 3G base station 200 that executes the 3G communication method and the WiMAX base station 300 that executes the WiMAX communication method have different data forms as shown in FIG.

That is, as illustrated in FIG. 2B, the 3G base station 200 executes the 3G communication scheme, and performs downlink and uplink individually. On the other hand, as shown in FIG. 2A, the WiMAX base station 300 transmits data by the WiMAX communication method, and alternately performs uplink and downlink. As is apparent from FIG. 2, in the 3G communication method and the WiMAX communication method, a time difference Δt _off that is a time lag occurs at the leading frame position in the downlink and uplink. Therefore, even if the mobile communication terminal 100 moves from the 3G communication area to the WiMAX communication area, performs a handover process, and performs a base station switching process, the switching process waits for the difference. That is, when performing handover processing in the WiMAX communication system, it is necessary to perform a cell search for searching for a base station to be switched to. By this cell search, the beginning of each frame in the WiMAX communication system (preamble portion) Since the handover process is executed by detecting, the cell search is performed for a longer time as the above-described deviation is larger. If cell search is performed for a long time, power consumption, CPU load, etc. are applied, which is not preferable. In the present embodiment, this cell search is to be performed efficiently, and the cell search is to be started later by the difference.

In order to perform cell search later by the amount of the difference, the mobile communication terminal 100 notifies the mobile communication terminal 100 of the time difference Δt _off from the 3G base station 200, so that the mobile communication terminal 100 uses the top frame received in the 3G communication system as a reference. The cell search can be started later by Δt _off . Here, it represents the temporal position of the first frame by 3G communication system and t _0.

By the way, it is generally known that a propagation delay occurs in a transmission frame transmitted from the 3G base station 200 to the mobile communication terminal 100. In the present embodiment, the cell search start time can be further delayed based on this propagation delay. FIG. 3 is an explanatory diagram showing the concept of propagation delay. 3A shows actual transmission timings in the 3G base station 200 and the WiMAX base station 300, and FIG. 3B shows actual reception timings in the mobile communication terminal 100. As shown in FIG. 3A, the start of the frame (WiMAX frame) transmitted from the base station 300 with respect to the transmission timing t ₀ indicating the start position of the frame (3G frame) transmitted from the 3G base station 200. The position is t ₀ + Δt _off .

Further, due to the propagation delay, as shown in FIG. 3B, the mobile communication terminal 100 receives the _signals delayed by the propagation delay time T _delay1 . Actually, the timing when the 3G frame is received is t ₀ + T _{delay 1} , and the timing when the WiMAX frame is received is t ₀ + Δt _off + T _{delay 1} .

  Therefore, the cell search needs to be started earlier than the received timing.

  Further, in order to efficiently perform a cell search for the WiMAX base station 300 that performs WiMAX communication, it is necessary to appropriately set the end time. The concept will be described with reference to FIG. FIG. 4 is an explanatory diagram showing a positional relationship between the mobile communication terminal 100 and the WiMAX base station 300. As shown in FIG. 4, the mobile communication terminal 100x is located in the vicinity of the WiMAX base station 300, and the mobile communication terminal 100y is located at the cell edge (near the boundary line) on the communication area line of the WiMAX base station 300. Show. Considering the propagation delay, it takes more time for the mobile communication terminal 100y to reach the signal transmitted from the base station 300 than to the mobile communication terminal 100x.

FIG. 5 shows propagation delays in the mobile communication terminal 100x and the mobile communication terminal 100y. As shown in FIG. 5, when referenced to the transmission timing _{t 0} of 3G base stations 200 of the 3G communication system, the mobile communication terminal 100x, becomes _{t o} + _{Δt off} + _{T delay_x} reception timing, the mobile communication terminal 100y, _{t o} + Δt _off + T _{delay_y} is the reception timing. Therefore, the position where the reception timing in the position of the mobile communication terminal 100y is the maximum propagation delay time T _md.

Therefore, the cell search end time should be determined in consideration of the maximum propagation delay time T _md . Considering these, the cell search timing is set to be between t _o + Δt _off −T _{delay 1} and t _o + Δt _off + T _md as shown in FIG. Can do.

  Below, the structure and operation | movement of the portable communication terminal 100 and base station 200 for performing such a required minimum cell search are demonstrated.

  FIG. 7 is a block diagram illustrating functions of the mobile communication terminal 100 of the communication system 10 according to the present embodiment. The mobile communication terminal 100 includes an antenna 101a, a transmission / reception unit 101 (first communication unit), a control unit 102 (propagation delay measurement unit 103, a neighboring base station information acquisition unit 104 (acquisition unit), and a notification unit 105 (notification unit). Control unit), antenna 106a, transmission / reception unit 106 (second communication unit), control unit 107 (cell search unit 108, cell search time calculation unit 109 (calculation unit): control unit), and external interface 110 Has been. This mobile communication terminal 100 is configured by hardware described below.

  FIG. 8 is a hardware configuration diagram of the mobile communication terminal 100. As shown in FIG. 8, the mobile communication terminal 100 shown in FIG. 8 physically includes a CPU 11, a RAM 12 and a ROM 13 as main storage devices, an input device 14 such as a keyboard and mouse as input devices, a display, and the like. The computer system includes an output device 15, a communication module 16 that is a data transmission / reception device such as a network card, and an auxiliary storage device 17 such as a hard disk. Each function described in FIG. 7 has the input device 14, the output device 15, and the communication module 16 under the control of the CPU 11 by reading predetermined computer software on the hardware such as the CPU 11 and the RAM 12 shown in FIG. This is realized by reading and writing data in the RAM 12 and the auxiliary storage device 17. Hereinafter, each functional block will be described based on the functional blocks shown in FIG.

  The transmission / reception unit 101 is a part that performs communication connection with the 3G base station 200 via the antenna 101a, and is a part that executes communication using the 3G communication method.

  The control unit 102 is a part that executes and controls the 3G communication method in the mobile communication terminal 100, and includes a propagation delay measurement unit 103, a neighboring base station information acquisition unit 104, and a notification unit 105.

  Here, the propagation delay measuring unit 103 is a part used to measure the propagation delay between the mobile communication terminal 100 and the 3G base station 200. For example, the 3G base station 200 measures RTT (Round Trip Time). In this case, it is a part that makes a response to the transmission from the 3G base station 200.

The neighboring base station information acquisition unit 104 is a part that acquires base station information of the WiMAX base station 300 that can execute the neighboring WiMAX communication notified from the 3G base station 200. Here, as base station information, presence / absence of base station 300 capable of performing WiMAX communication, preamble transmission timing in base station 300 (that is, time difference Δt _off between the top frame in 3G communication and the top frame in WiMAX communication) , Cell size information R indicating the cell radius of WiMAX base station 300, transmission power of WiMAX base station 300, maximum propagation delay time T _md at the cell edge of WiMAX base station 300, and 3G measured by propagation delay measurement unit 203 A propagation delay time T _delay1 between the mobile communication terminal 100 and the 3G base station 200 in the communication area is acquired.

  The notification unit 105 is a part that notifies the 3G base station 200 of function information indicating that the WiMAX communication method is supported. Upon receiving this, the 3G base station 200 transmits base station information for efficiently performing a cell search to the mobile communication terminal 100 via the transmission / reception unit 101.

  The transmission / reception unit 106 is a part that communicates with the WiMAX base station 300 capable of performing WiMAX communication via the antenna 106a.

  The control unit 107 controls and executes the WiMAX communication method in the mobile communication terminal 100, and controls the transmission / reception unit 106 to perform cell search based on the base station information acquired by the control unit 102. The control unit 107 includes a cell search unit 108 and a cell search time calculation unit 109.

The cell search unit 108 is a part that performs control to search for the base station 300 using the transmission / reception unit 106. The cell search unit 108 performs cell search according to the cell search start time t ₀ + Δt _off −T _delay1 and the cell search end time t ₀ + Δt _off + T _md calculated by the cell search time calculation unit 109. That is, when the head of a transmission frame transmitted from the 3G base station 200 is detected, the cell search unit 108 corrects the time difference Δt _off and T _delay1 based on the detected time point, and calculates the start time.

The cell search time calculation unit 109 is a part that calculates the time for executing the cell search in order to efficiently perform the cell search, and is a part that calculates the start time and end time of the cell search. Specifically, the cell search time calculation unit 109 transmits the transmission timing t _{0 of the first} frame in the 3G communication system, the time difference Δt _off of the transmission timing of the first frame in the WiMAX communication system with respect to this transmission timing, and the propagation delay time in the 3G communication area. T _delay1 , cell size information R of WiMAX base station 300 is calculated, cell search start time is set to t ₀ + Δt _off −T _{delay 1} based on these information, and cell search end time is set to t ₀ + Δt _off + T _md . . Here, although indicated as transmission timing t ₀ , this is conceptually described. Actually, every time a transmission frame transmitted from the 3G base station 200 is detected as described above, A time indicated by Δt _off −T _delay1 with respect to the detection time is a start time, and Δt _off + T _md is an end time. A plurality of transmission frames are transmitted, and a cell search is performed from the start time to the end time determined here every time the head of the transmission frame is detected.

T _md is the maximum propagation delay time and is calculated based on the cell size information R. For example, when the cell radius is indicated as the cell size information R, the cell search time calculation unit 109 calculates the maximum propagation delay time T _md by dividing the radius by the speed of light (the speed of light). can do. Further, a mapping table that defines a propagation delay time corresponding to the size of the cell size information R may be provided, and the maximum propagation delay time T _md corresponding to the cell size information R may be calculated. Incidentally, in the cell search time calculating unit 109 may be configured to receive the maximum propagation delay time T _md calculated in WiMAX base station 300 without calculating the maximum propagation delay time T _md.

  The external interface 110 includes an operation part for the user to operate the mobile communication terminal 100, a display for displaying information to the user, and the like.

  FIG. 9 is a block diagram illustrating functions of the base station 200 configuring the communication system 10 of the present embodiment. As illustrated in FIG. 9, the base station 200 includes an antenna 201 a, a transmission / reception unit 201, a control unit 202 (propagation delay measurement unit 203, neighboring base station information notification unit 204), and an NW interface 205. Each function will be described below.

  The transmission / reception unit 201 is a part that performs communication connection to the mobile communication terminal 100 via the antenna 201a, and is a part that transmits various types of information and receives information from the mobile communication terminal 100.

  The control unit 202 is a part that controls the base station, and includes a propagation delay measurement unit 203 and a neighboring base station information notification unit 204. Among these, the propagation delay measuring unit 203 is a part that measures the propagation delay with the mobile communication terminal 100, for example, a part that measures RTT (Round Trip Time), and the transmission / reception unit 201 is the mobile communication terminal. By calculating the time to transmit data to 100 and receive the response, the propagation delay time can be calculated.

When the neighboring base station information notification unit 204 receives from the portable communication terminal 100 functional information indicating that the WiMAX communication method is supported via the transmission / reception unit 201, the neighboring base station information notification unit 204 notifies the propagation delay measurement unit 203 to that effect. In addition, this is a part for notifying the mobile communication terminal 100 of the propagation delay time T _delay1 measured here and the base station information regarding the WiMAX base station 300 via the transmission / reception unit 201. Here, the presence or absence of the WiMAX base station 300, the transmission timing of the preamble portion in the WiMAX base station 300 (that is, the time difference Δt _off which is the time difference between the top frame in 3G communication and the top frame in WiMAX communication), the cell of the WIMAX base station 300 The size information R, the transmission power of the WiMAX base station 300, the maximum propagation delay time at the cell edge of the WiMAX base station 300, and the propagation delay time T _delay1 measured in the propagation delay measurement unit 203 are notified. These _pieces of information (excluding the propagation delay time T _delay1 ) are information acquired in advance via the NW interface 205 and stored in a memory (not shown).

  Furthermore, the neighboring base station information notification unit 204 transmits to the mobile communication terminal 100 instruction information for performing a cell search together with the above base station information. The mobile communication terminal 100 can perform a cell search by receiving the instruction information.

  The NW interface 205 is a part connected to a network, and the 3G base station 200 is connected to an exchange, a subscriber storage server, an authentication server, another base station, etc. constituting mobile communication via the NW interface 205. .

Processing between the mobile communication terminal 100 and the 3G base station 200 configured as described above will be described. FIG. 10 is a sequence diagram showing processing with the mobile communication terminal 100 and the 3G base station 200. In the mobile communication terminal 100, the notification unit 105 notifies that the WiMAX communication system is supported (S01). In the 3G base station 200, when the fact is received, the propagation delay measuring unit 203 measures the propagation delay time _Tdelay1 (S02).

When the propagation delay time T _delay1 is measured, an instruction to perform cell search for the WiMAX base station 300, the measured propagation delay time T _delay1 and the base station information of the WiMAX base station 300 are _{displayed in the} neighboring base station information notification unit 204. (S03). When receiving these pieces of information, the mobile communication terminal 100 performs a cell search for the WiMAX base station 300. In performing this cell search, it is necessary to perform the minimum necessary cell search. Detailed processing for performing the minimum cell search will be described with reference to FIG. FIG. 11 is a flowchart illustrating a process for calculating a period for performing cell search in the mobile communication terminal 100.

Base station information regarding the WiMAX base station 300 is received by the neighboring base station information acquisition unit 104 from the 3G base station 200 via the transmission / reception unit 201. Specifically, transmission timing t ₀ + Δt _off of the preamble portion of the transmission frame in the WiMAX base station 300, propagation delay time T _delay1 in the 3G communication area, and cell size information R of the WiMAX base station 300 are received as base station information. (S101).

Based on the cell size information R among the received information, the maximum propagation delay time T _md is calculated by the cell search time calculation unit 109 (S102). Then, the cell search start time t ₀ + Δt _off −t _delay1 and the cell search end time t ₀ + Δt _off + t _md are calculated by the cell search time calculation unit 109 (S103, S104).

In accordance with the calculated start time and end time, the cell search unit 108 performs cell search (S105). When the WiMAX base station 300 is found by the end time (S106: YES), a communication connection is made to the found WiMAX base station 300 (S107). If the WiMAX base station 300 is not found by the end time (S106: NO), the cell search start time is reached again, that is, when the head of the next transmission frame in the 3G communication system is detected, Δt _off A cell search is performed after _suspending -T _delay1 . (S105).

  By narrowing down the time for cell search in this way, power consumption can be reduced and CPU load can be reduced without performing unnecessary cell search.

  Next, a modification of the communication system 10 according to the present embodiment will be described. According to this modification, in the above-described embodiment, the cell search time is calculated in the mobile communication terminal 100, but the 3G base station 200a calculates the cell search time, and the mobile communication terminal 100a is calculated in the 3G base station 200. The cell search is to be performed based on the cell search time. Each configuration will be described below.

  FIG. 12 is a block diagram illustrating functions of the mobile communication terminal 100a which is a modified example. As shown in FIG. 12, the mobile communication terminal 100a includes an antenna 101a, a transmission / reception unit 101, a control unit 102 (a propagation delay measurement unit 103, a cell search time acquisition unit 104x, a notification unit 105), an antenna 106a, a transmission / reception unit 106, and a control. A unit 107 (cell search unit 108) and an external interface 110 are included. The mobile communication terminal 100 includes a cell search time acquisition unit 104x instead of the cell search time calculation unit 109, as compared with the above-described embodiment.

  The cell search time acquisition unit 104x is a part that acquires the cell search time calculated in the 3G base station 200a via the transmission / reception unit 101. The cell search unit 108 can perform a cell search according to the cell search time acquired by the cell search time acquisition unit 104x.

  Next, the 3G base station 200a capable of calculating the cell search time will be described. FIG. 13 is a block diagram illustrating functions of a 3G base station 200a which is a modified example. The 3G base station 200a of this modification includes an antenna 201a, a transmission / reception unit 201, a control unit 202 (propagation delay measurement unit 203, cell search time calculation unit 206, cell search instruction unit 207), and an NW interface 205. Yes. Each configuration will be described below.

The cell search time calculation unit 206 calculates the cell search time. By performing the same processing as the cell search time calculation unit 109 in the above-described embodiment, the cell search start time t ₀ + Δt _off −t _delay1 , and The cell search end time t ₀ + Δt _off + t _md can be calculated.

  The cell search instruction unit 207 receives the cell search time (start time, end time) calculated by the cell search time calculation unit 206 and instruction information indicating that a cell search is to be performed via the transmission / reception unit 201, and the mobile communication terminal 100a. It is a part to send to.

  Processing of the communication system 10 including the mobile communication terminal 100a and the 3G base station 200a configured as described above will be described.

  FIG. 14 is a sequence diagram illustrating processing of the communication system 10 according to the modification of the present embodiment. The mobile communication terminal 100 notifies the 3G base station 200a that WiMAX is supported (S201). In the 3G base station 200a, the propagation delay time is measured by the propagation delay measuring unit 203 (S202), and the cell search time calculating unit 206 calculates the start time and end time of the cell search (S203). The cell search start time and end time calculated here are transmitted to the mobile communication terminal 100a by the cell search instruction unit 207 together with instruction information indicating that the cell search is to be performed (S204).

  According to this modification, the function of calculating the cell search time can be provided on the 3G base station 200a side, the cell search can be performed efficiently, and the function of the mobile communication terminal 100a is simplified. be able to.

  Next, a second modification will be described. FIG. 15 is a block diagram illustrating functions of the 3G base station 200b in the second modification. In the second modification, the 3G base station 200b has the function of the WiMAX base station 200a. That is, the 3G base station 200b includes the antenna 201a, the transmission / reception unit 201, the control unit 202 (propagation delay measurement unit 203, neighboring base station information notification unit 204), and the NW interface 205 that are configured in the 3G base station 200. In addition, it includes an antenna 208a, a WiMAX receiving unit 208, and a neighboring WiMAX base station detecting unit 209.

  The WiMAX receiving unit 208 is a part that receives base station information of a WiMAX base station (not shown) located in the vicinity of the 3G base station 200b. The WiMAX receiving unit 208 may output a request for base station information to a neighboring WiMAX base station and receive the base station information as a response to the request, or periodically from a neighboring WiMAX base station. You may make it receive the base station information transmitted to.

  The neighboring WiMAX base station detecting unit 209 detects the base station information received by the WiMAX receiving unit 208, and outputs the detected base station information to the neighboring base station information notifying unit 204. The neighboring base station information notification unit 204 can transmit the base station information detected by the neighboring WiMAX base station detection unit 209 to the mobile communication terminal 100.

  In this way, the 3G base station 200b can collect base station information of WiMAX base stations located in the vicinity.

  Next, a third modification will be described. In the third modification, the 3G base station 200 can measure or acquire an absolute time without error, and uses this time to calculate a cell search time.

  FIG. 16 is a block diagram illustrating functions of the mobile communication terminal 100c according to the third modification. As shown in FIG. 16, in addition to the configuration of the mobile communication terminal 100 (excluding the cell search time calculation unit 109 and the propagation delay measurement unit 103), the mobile communication terminal 100c includes a cell search time calculation unit 109a, an antenna 111a, A GPS receiver 111 and a time synchronization processing unit 112 are provided. That is, the mobile communication terminal 100c includes an antenna 101a, a transmission / reception unit 101, a control unit 102 (neighboring base station information acquisition unit 104, a notification unit 105), an antenna 106a, a transmission / reception unit 106, and a control unit 107 (cell search unit 108, cell search). The time calculation unit 109a), the external interface 110, the antenna 111a, the GPS receiver 111, and the time synchronization processing unit 112 (synchronization means) are configured.

  The GPS receiver 111 is a part that receives radio waves from GPS satellites and also receives time information via the antenna 111a. This time information is information representing a highly accurate time with no error.

  The time synchronization processing unit 112 is a part that performs synchronization processing based on time information received by the GPS receiver 111. Here, the time synchronization processing is performed based on the time information acquired by the GPS receiver 111. However, the present invention is not limited to this, and highly accurate time information is acquired from the 3G base station 200. Any other method may be used as long as it measures or acquires an absolute time with no error. In that case, the GPS function becomes unnecessary.

The cell search time calculation unit 109a is a part that calculates the cell search time based on the transmission frame received from the 3G base station 200 received by the transmission / reception unit 101 via the antenna 101a. For example, the cell search time calculating unit 109a acquires the transmission timing t ₁ of the transmission frame based on the time information included in the transmission frame transmitted from the 3G base station 200. This transmission timing t ₁ is information representing the transmission time of the transmission frame, and is highly accurate time information without error. Note that the transmission timing t ₁ may be those stored in advance in the mobile communication terminal 100c (e.g. cell search time calculating unit 109a or the memory which is separately configured (not shown)), in advance in which case the using the transmission timing t ₁ stored cell search time calculating unit 109a calculates the cell search time.

On the other hand, the neighboring base station information acquisition unit 104 receives base station information (time difference Δt _off , cell size information R) from the 3G base station 200 before calculating the cell search time. Then, the cell search time calculation unit 109a calculates the cell search start time t ₁ + Δt _off using the transmission timing t ₁ and the time difference Δt _off . On the other hand, the cell search time calculation unit 109a calculates a cell search end time t ₁ + Δt _off + t _md .

Here, the cell search time using the absolute time will be described with reference to FIG. FIG. 17 is an explanatory diagram showing the relationship between the transmission time t ₁ and the time difference Δt _off in the mobile communication terminal 100. FIG. 17 shows that the preamble portion of the transmission frame is detected (transmitted) from the WiMAX base station 300 at the position of the time difference Δt _off with reference to the transmission time t ₁ managed in the mobile communication terminal 100. Has been.

As described above, in the mobile communication terminal 100c, when the absolute time can be measured or acquired, the cell search may be performed by shifting the time difference Δt _off from the transmission timing included in the 3G frame. There is no need to consider the delay. Similarly, for the cell search end time, there is no need to consider the propagation delay in the 3G communication area, and the end time t ₁ + Δt _off + T _md can be obtained by simply adding the maximum propagation delay time T _md in the WiMAX base station 300. Can be calculated.

This operation will be described with reference to FIG. FIG. 18 is a flowchart showing the operation of the mobile communication terminal 100c of the third modification. The neighboring base station information acquisition unit 104 acquires base station information from the 3G base station 200. Here, the time difference Δt _off indicating the shift in transmission timing and the cell size information R are acquired (S301). The cell search time calculation unit 109a calculates the maximum propagation delay time T _md based on the cell size information R (S302), and the cell search time calculation unit 109a calculates the start time and end time of the cell search. (S303, S304)

  Then, the cell search unit 108 performs a cell search according to the calculated start time and end time (S305). When the WiMAX base station 300 is found by this cell search, connection processing is performed (S307). If the WiMAX base station 300 is not found until the end time, the cell search is performed after the start time is reached again (S305).

  Next, operational effects of the mobile communication terminal 100 of the present embodiment, the mobile communication terminals 100a, 100c, the 3G base station 200b, which are modifications thereof, and the communication system 10 including these mobile communication terminals will be described.

In the mobile communication terminal 100 of the present embodiment, the time difference Δt _off indicating the transmission timing of the head data of the WiMAX base station 300 from the 3G base station 200 via the transmission / reception unit 101, and the propagation delay time T _delay1 in the 3G base station 200 Is received. Then, the cell search time calculating unit 109, based on the received transmission timing and transmission delay time, and calculates the start time _{t 0} + _{Δt off} -t _delay1 cell search, cell search unit 108 from the start time, A cell search can be performed using the transceiver 106. Thereby, the cell search time can be limited, and the power consumption and CPU load required for the cell search can be reduced.

  Note that the mobile communication terminal 100a which is a modification includes a cell search time acquisition unit 104x instead of the cell search time calculation unit 109, and instead of calculating the cell search time, the cell search time is calculated from the 3G base station 200a. The cell search time may be set by some method, and the cell search may be performed based on the set cell search start time.

  Further, as shown in the second modification, the 3G base station 200b includes a neighboring WiMAX base station detection unit 209, acquires base station information of the neighboring WiMAX base station 300, and uses this information as the mobile communication terminal 100. You may make it transmit to.

Further, in the mobile communication terminal 100 of the present embodiment, the cell search time calculation unit 109 causes the neighboring base station information acquisition unit 104 to acquire the cell size information R of the WiMAX base station 300 via the transmission / reception unit 101, and the cell search time The calculation unit 109 calculates the maximum propagation delay time T _md based on the cell size information R. The cell search time calculation unit 109 calculates a cell search time end time t ₀ + t _delay1 + T _md based on these _{pieces of} information. The cell search unit 108 can limit the cell search time by executing the cell search until the end time, and can reduce power consumption and CPU load required for the cell search.

  Further, in the mobile communication terminal 100 of the present embodiment, the 3G base station 200 notifies the 3G base station 200 of function information indicating that the WiMAX communication method can be executed, so that the 3G base station 200 responds to the function information. Various base station information can be transmitted to the mobile communication terminal 100. Therefore, only necessary terminals can be notified of information for shortening the cell search, and efficient processing can be realized.

Further, in the mobile communication terminal 100c which is the third modification, the time synchronization processing unit 112 uses the GPS receiver 111 so that there is no error so as to synchronize with the timing of the 3G base station 200 and the WiMAX base station 300. Synchronous processing is performed so as to keep time with high accuracy. When the transmission / reception unit 101 receives the transmission time t ₁ of the head data from the 3G base station 200, the cell search time calculation unit 109 a receives the various base station information and the time information measured and the transmission / reception unit 101. time difference Delta] t _off indicating the transmission timing of the leading data of the WiMAX base station 300, or to set the start time for the cell search _{t 1} + Δt _off based on pre-stored time difference Delta] t _off. The cell search unit 108 can perform a cell search for the WiMAX base station 300. Thereby, it is not necessary to consider the propagation delay, and the processing can be simplified. In addition, the cell search time can be limited, and the power consumption and CPU load required for the cell search can be reduced.

It is a conceptual diagram which shows the concept of the communication system 10 in this embodiment. It is explanatory drawing which shows the relationship between the transmission timing of a 3G communication system, and the transmission timing of a WiMAX communication system. It is explanatory drawing which shows the concept of a propagation delay. 3 is an explanatory diagram showing a positional relationship between a mobile communication terminal 100 and a WiMAX base station 300. FIG. It is explanatory drawing which shows the propagation delay in the mobile communication terminal 100x and the mobile communication terminal 100y. It is explanatory drawing which shows a cell search period. It is a block diagram which shows the function of the mobile communication terminal 100 of the communication system 10 of this embodiment. 2 is a hardware configuration diagram of a mobile communication terminal 100. FIG. It is a block diagram which shows the function of the base station 200 which comprises the communication system 10 of this embodiment. It is a sequence diagram which shows a process with the mobile communication terminal 100 and 3G base station 200. FIG. 5 is a flowchart showing a process for calculating a period for performing a cell search in portable communication terminal 100. It is a block diagram which shows the function of the mobile communication terminal 100a which is a modification. It is a block diagram which shows the function of 3G base station 200a which is a modification. It is a sequence diagram which shows the process of the communication system 10 in the modification of this embodiment. It is a block diagram which shows the function of 3G base station 200b in a 2nd modification. It is a block diagram which shows the function of the mobile communication terminal 100c in a 3rd modification. It is an explanatory view showing the relationship between the transmission time _{t 1} and the time difference Delta] t _off in the portable communication terminal 100. It is a flowchart which shows operation | movement of the mobile communication terminal 100c of a 3rd modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Communication system, 100 ... Mobile communication terminal, 100a ... Mobile communication terminal, 100c ... Mobile communication terminal, 100x ... Mobile communication terminal, 100y ... Mobile communication terminal, 101 ... Transmission / reception part, 101a ... Antenna, 102 ... Control part, 103 ... Propagation delay measurement unit 104 ... Neighboring base station information acquisition unit 104x ... Cell search time acquisition unit 105 ... Notification unit 106 ... Transmission / reception unit 106a ... Antenna 107 ... Control unit 108 ... Cell search unit 109 ... Cell search time calculation unit, 109a ... cell search time calculation unit, 110 ... external interface, 111 ... receiver, 111a ... antenna, 112 ... time synchronization processing unit, 200 ... 3G base station, 200a ... 3G base station, 200b ... 3G Base station 201 ... Transmission / reception unit 201a ... Antenna 202 ... Control unit 203 ... Propagation delay measurement unit 20 ... neighbor base station information notification unit, 205 ... interface, 206 ... cell search time calculating section, 206 ... receiver, 300 ... base station.

Claims (8)

First communication means for executing the first communication method via the first base station,
A second communication that performs a cell search for the second base station and executes a second communication method different from the first communication method via the second base station searched by the cell search. Means,
When the transmission timing of the head data transmitted from the second base station and the propagation delay amount in the first base station are received by the first communication means, the received transmission timing and propagation delay A mobile communication terminal comprising: a control unit configured to set a cell search start time based on the amount and to perform a cell search by the second communication unit from the start time. Based on the cell size information of the second base station, further comprising a calculating means for calculating a maximum propagation delay time in the second base station,
The second communication unit determines an end time of the cell search time based on the maximum propagation delay time calculated by the calculation unit, and executes the cell search until the end time. The portable communication terminal as described. An acquisition means for acquiring a maximum propagation delay time based on cell size information from the second base station;
The second communication unit determines an end time of the cell search time based on the maximum propagation delay time acquired by the acquiring unit, and executes the cell search until the end time. 2. The mobile communication terminal according to 2. A notification means for notifying the first base station of function information indicating that the second communication method can be executed;
The first base station transmits a transmission timing of head data of the second base station and a propagation delay amount in the first base station in response to the notification by the notification unit. Item 4. The mobile communication terminal according to any one of Items 1 to 3. First communication means for executing the first communication method via the first base station,
A second communication that performs a cell search for the second base station and executes a second communication method different from the first communication method via the second base station searched by the cell search. Means,
Synchronization means for synchronizing with timings in the first base station and the second base station;
A cell based on the transmission time of the head data received by the first communication means and the time information synchronized by the synchronization means, and the transmission timing received by the first communication means or a predetermined transmission timing And a control means for setting a start time at the time of search and controlling to perform a cell search by the second communication means.   The mobile communication terminal according to any one of claims 1 to 5, a first base station capable of executing a first communication method, a second base station capable of executing a second communication method, A communication system comprising: A first communication means for executing the first communication method via the first base station and a cell search for the second base station, and the second base station searched by the cell search A handover method in a mobile communication terminal comprising: a second communication unit that executes a second communication method different from the first communication method via
In the first communication means, a reception step of receiving a transmission timing of head data transmitted from the second base station and a propagation delay amount in the first base station;
A cell search step of setting a cell search start time based on the transmission timing and propagation delay amount received in the reception step, and performing a cell search by the second communication means from the start time;
A handover method comprising: A first communication means for executing the first communication method via the first base station and a cell search for the second base station, and the second base station searched by the cell search A handover method in a mobile communication terminal comprising: a second communication unit that executes a second communication method different from the first communication method via
A synchronization step for synchronizing with timings in the first base station and the second base station;
A reception step of receiving at least the transmission time of the head data received in the first communication means;
Based on the transmission time received in the reception step and the time information synchronized in the synchronization step, and the transmission timing received by the first communication means or a predetermined transmission timing, the start time at the time of cell search is determined. A cell search step for setting and performing a cell search by the second communication means;
A handover method comprising:

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