JP2013214983A - Mobile communication system, mobile station, base station, and handover method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve seamless handover between base stations using different frequency bands.SOLUTION: In response to start of handover from a base station 14-1 to a base station 14-2 by a mobile station 12, the base station 14-2 determines an ANCH 2 to be allocated to the mobile station 12 in a frequency band the base station 14-2 is using, and notifies the mobile station 12 of the determined ANCH 2 via a CCH (S100-S102). If the frequency difference between an ANCH 1 and the ANCH 2 is equal to or less than a frequency bandwidth the mobile station 12 uses, the mobile station 12 shifts its frequency band in use from the frequency band in use of the base station 14-1 to a frequency band including the ANCH 1 and ANCH 2 (S108). After that, the mobile station 12 establishes connection with the base station 14-2 via the ANCH 2 (S110-S120), then disconnects connection with the base station 14-1 (S122), and further shifts its frequency band in use to the frequency band of the base station 14-2 (S124).

Description

  The present invention relates to a mobile communication system, a mobile station, a base station, and a handover method.

  In a mobile communication system, a mobile station may perform a handover for switching a connection destination from one base station to another base station due to movement between cells or deterioration of communication quality. Among handovers, those that can smoothly switch the connection destination while maintaining the communication state of the application are called seamless handovers.

  For example, XGP (eXtended Global Platform) known as next-generation PHS also defines seamless handover (see Non-Patent Document 1).

“ARIB STD-T95 Version 1.2“ OFDMA / TDMA TDD Broadband Wireless Access System (Next Generation PHS) ””, March 18, 2009, Japan Radio Industry Association

  In general, in seamless handover, a mobile station needs to perform wireless communication simultaneously with both a connected base station and a connected base station so that data communication is not interrupted (so that the communication state of an application is maintained). .

  However, in a mobile communication system such as the XGP, different use frequency bands may be set for adjacent base stations for the purpose of avoiding interference. In this case, it is not easy for a mobile station with a limited usable frequency bandwidth to perform radio communication simultaneously with both a connected base station and a connected base station in handover.

  The present invention has been made in view of the above problems, and provides a mobile communication system, a mobile station, a base station, and a handover method capable of realizing seamless handover between base stations using different frequency bands. With the goal.

  In order to solve the above-described problem, a mobile communication system according to the present invention uses a first base station that uses a first frequency band and a second frequency band that is different from the first frequency band. A mobile communication system including a base station and a mobile station assigned by the first base station to a first control channel belonging to the first frequency band, wherein the first base station The used frequency band of the connected mobile station includes the first frequency band and a common channel defined at the first frequency band side end in the second frequency band, and the second frequency band In response to the start of handover from the first base station to the second base station by the mobile station, the base station assigns a second control channel to be assigned to the mobile station in the second frequency band. Control channel determining means for determining from the control channel; Means for notifying the mobile station of the second control channel determined by the channel determination means via the common channel, the mobile station including the first control channel and the second base When the frequency difference from the second control channel notified from the station is equal to or smaller than the use frequency bandwidth of the mobile station, the use frequency band of the mobile station includes the first and second control channels. First frequency band shifting means for shifting to a band, and after the use frequency band of the mobile station is shifted by the first frequency band shifting means, the second base station via the second control channel Means for establishing a connection; and second frequency band shifting means for further shifting the use frequency band of the mobile station to the second frequency band after the connection with the second base station is established. And characterized by That.

  In the present invention, when the mobile station performs handover from the first base station to the second base station, the frequency band used by the mobile station is changed from the first frequency band used by the first base station to the second base station. Instead of switching directly to the second frequency band used by the mobile station, the common frequency channel defined by the first frequency band side end in the second frequency band is used to change the frequency band used by the mobile station in two stages. shift. Here, the use frequency band of the mobile station connected to the first base station includes the first frequency band and the common channel.

  That is, in the present invention, the first control channel assigned from the first base station (connected base station) and the second base station (connected base station) are notified through the common channel. When the frequency difference with the second control channel is equal to or smaller than the use frequency bandwidth of the mobile station, first, the mobile station uses its own use frequency band as the frequency band including the first frequency band and the common channel. To the frequency band including the first and second control channels (first shift).

  At this time, since the use frequency band of the mobile station is in a frequency band including the first and second control channels, the mobile station transmits the first and second control channels via the first and second control channels, respectively. Wireless communication can be performed simultaneously with both base stations. Therefore, after the first shift, the mobile station establishes a connection with the second base station via the second control channel. During this time, the mobile station maintains data communication via the first control channel assigned by the first base station.

  When the connection between the mobile station and the second base station is established, the mobile station further shifts its own use frequency band to the second frequency band (second shift). Thereafter, the mobile station disconnects the connection with the first base station and continues data communication via the second control channel assigned by the second base station. In this way, the mobile station completes the handover from the first base station to the second base station without interrupting data communication.

  Thus, according to the present invention, seamless handover between base stations using different frequency bands can be realized.

  In the aspect of the present invention, the first frequency shift means may be configured such that a frequency difference between the first control channel and a second control channel notified from the second base station is equal to that of the mobile station. Shifting the used frequency band of the mobile station so that the second frequency band side end in the used frequency band of the mobile station is equal to the frequency of the second control channel when the frequency band is equal to or smaller than the used frequency band width. May be.

  According to this aspect, since the shift amount (first shift amount) of the used frequency band of the mobile station is minimized, the first base station allocates a communication channel belonging to the first frequency band to the mobile station. The number of communication channels released by the first shift can be reduced. For this reason, a more seamless handover can be realized.

  In the aspect of the present invention, the mobile station may be configured such that a frequency difference between the first control channel and the second control channel notified from the second base station is a frequency band used by the mobile station. Reassignment requesting means for requesting the second base station to reallocate a control channel via the common channel so that the frequency difference is less than or equal to the use frequency bandwidth of the mobile station when the frequency difference is greater than the width. The control channel allocating means further includes a new second control channel different from the second control channel notified to the mobile station in response to a control channel reassignment request from the mobile station. It may be determined from the frequency band.

  According to this aspect, the frequency difference between the first control channel allocated from the first base station and the second control channel notified from the second base station via the common channel is the mobile station's frequency difference. Even if it is larger than the used frequency bandwidth, the frequency difference can be made smaller than the used frequency bandwidth of the mobile station by reassigning the second control channel. For this reason, seamless handover between base stations using different frequency bands can be realized.

  In one aspect of the present invention, when the mobile station starts a handover from the first base station to the second base station, the mobile station sets the frequency of the first control channel via the common channel. Means for notifying the second base station of identification information to be shown, wherein the control channel determining means is configured to determine whether the frequency difference from the first control channel is based on the identification information notified from the mobile station. You may determine a said 2nd control channel from the empty channels which are below the use frequency bandwidth of the said mobile station.

  According to this aspect, the frequency difference between the first control channel allocated from the first base station and the second control channel notified from the second base station via the common channel is the mobile station's frequency difference. It is possible to prevent the usage frequency band from being exceeded.

  Also, in one aspect of the present invention, the control channel determination unit is configured such that the frequency difference with the first control channel is less than or equal to a use frequency bandwidth of the mobile station based on identification information notified from the mobile station. A certain idle channel whose frequency is closest to the frequency of the first control channel may be determined as the second control channel.

  According to this aspect, since the shift amount (first shift amount) of the used frequency band of the mobile station can be reduced, the first base station moves the communication channel belonging to the first frequency band. When assigned to a station, the number of communication channels released by the first shift can be reduced. For this reason, a more seamless handover can be realized.

  Also, the mobile station according to the present invention performs handover from the first base station using the first frequency band to the second base station using the second frequency band different from the first frequency band. The use frequency band of the mobile station connected to the first base station is a mobile station at the first frequency band side end in the first frequency band and the second frequency band. A first control channel belonging to the first frequency band assigned from the first base station and via the common channel in response to the start of the handover. When the frequency difference with the second control channel belonging to the second frequency band notified from the second base station is equal to or smaller than the used frequency bandwidth of the mobile station, the used frequency band of the mobile station Including the first and second control channels A first frequency band shift means for shifting to a frequency band; and after the use frequency band of the mobile station is shifted by the first frequency band shift means, the second base station via the second control channel And a second frequency band shifting means for further shifting the use frequency band of the mobile station to the second frequency band after the connection with the second base station is established. It is characterized by including.

  The base station according to the present invention is a base station using a second frequency band different from the first frequency band used by another base station, and is connected to the other base station. The frequency band used by the station includes the first frequency band and a common channel defined at the first frequency band side end in the second frequency band, and the first frequency band belonging to the first frequency band. A second control channel assigned to the mobile station in response to the start of a handover from the other base station to the base station by the mobile station assigned by the other base station. Control channel determining means for determining from among the frequency bands, means for notifying the mobile station of the second control channel determined by the control channel determining means via the common channel, and use of the mobile station Before the frequency band After being shifted to a frequency band including the first and second control channels, characterized in that it comprises a means for establishing a connection with the mobile station via the second control channel.

  Further, the handover method according to the present invention includes a first base station that uses a first frequency band, a second base station that uses a second frequency band different from the first frequency band, and A mobile communication system including a mobile station assigned by the first base station with a first control channel belonging to a first frequency band, wherein the handover method is connected to the first base station The use frequency band of the mobile station includes the first frequency band and a common channel defined at the first frequency band side end in the second frequency band, and the mobile station uses the first frequency band. Control in which the second base station determines a second control channel to be allocated to the mobile station from the second frequency band in response to the start of handover from the base station to the second base station Channel decision step and before A second base station notifying the mobile station of the second control channel determined in the control channel determination step via the common channel; the first control channel; and the second control channel When the frequency difference from the second control channel notified from the base station is less than or equal to the use frequency bandwidth of the mobile station, the use frequency band of the mobile station includes the first and second control channels. A first frequency band shifting step that shifts to a frequency band; and after the use frequency band of the mobile station is shifted in the first frequency band shifting step, the mobile station transmits the first frequency band via the second control channel. Establishing a connection with the second base station, and after the connection between the mobile station and the second base station is established, further shifting the frequency band used by the mobile station to the second frequency band. First Characterized in that it comprises a frequency band shifting step.

It is a figure which shows the structure of the mobile communication system which concerns on Embodiment 1-3 of this invention. It is a figure which shows the radio | wireless channel structure in the mobile communication system which concerns on Embodiment 1-3. It is a figure which shows the relationship between the use frequency band of a base station, and the use frequency band of a mobile station in the radio channel structure shown to FIG. 2A. It is a functional block diagram of the mobile station which concerns on Embodiment 1-3. It is a functional block diagram of the base station which concerns on Embodiment 1-3. 6 is a sequence diagram illustrating an example of a handover method according to Embodiment 1. FIG. 6 is a sequence diagram illustrating another example of a handover method according to Embodiment 1. FIG. It is a figure which shows an example of the relationship between the use frequency band of the base station of a connection and a connection destination, the use frequency band of a mobile station, and PRU (ANCH1, EXCH) which the connected base station allocates to the mobile station. is there. It is a figure which shows PRU (ANCH2) which the base station of the connection destination allocated to the mobile station from the state shown to FIG. 6A. It is a figure which shows the use frequency band (1st shift) of the mobile station shifted to the frequency band containing ANCH1 and ANCH2 from the state shown to FIG. 6B. In the state shown in FIG. 6C, after the connection between the mobile station and the connection destination base station is established, the use frequency band of the mobile station further shifted to the use frequency band of the connection destination base station (second shift) FIG. It is a figure which shows ANCH2 which the base station of the connection destination allocated to the mobile station from the state shown to FIG. 6A. FIG. 6E is a diagram showing that the use frequency band of the mobile station cannot be shifted to a frequency band including both ANCH1 and ANCH2 from the state shown in FIG. 6E. FIG. 6B is a diagram showing ANCH2 newly allocated by the connection-destination base station in response to the ANCH2 reallocation request from the mobile station from the state shown in FIG. 6E. It is a figure which shows the use frequency band (1st shift) of the mobile station shifted to the frequency band containing ANCH1 and ANCH2 from the state shown to FIG. 6G. After the connection between the mobile station and the connection destination base station is established in the state shown in FIG. 6H, the use frequency band of the mobile station further shifted to the use frequency band of the connection destination base station (second shift) FIG. 6 is a sequence diagram illustrating an example of a handover method according to Embodiment 2. FIG. It is a figure which shows an example of the relationship between the use frequency band of the base station of a connection and a connection destination, the use frequency band of a mobile station, and PRU (ANCH1, EXCH) which the connected base station allocates to the mobile station. is there. It is a figure which shows the range of PRU which the base station of a connection destination should allocate as a new ANCH2 to a mobile station in the state shown to FIG. 8A. It is a figure which shows ANCH2 which the base station of the connection destination allocated to the mobile station from the state shown to FIG. 8A. It is a figure which shows the use frequency band (1st shift) of the mobile station shifted to the frequency band containing ANCH1 and ANCH2 from the state shown to FIG. 8C. In the state shown in FIG. 8D, after the connection between the mobile station and the connection destination base station is established, the use frequency band of the mobile station further shifted to the use frequency band of the connection destination base station (second shift). FIG. 10 is a sequence diagram illustrating an example of a handover method according to Embodiment 3. FIG. It is a figure which shows an example of the relationship between the use frequency band of the base station of a connection and a connection destination, the use frequency band of a mobile station, and PRU (ANCH1, EXCH) which the connected base station allocates to the mobile station. is there. It is a figure which shows PRU (ANCH2) which the base station of the connection destination allocated to the mobile station from the state shown to FIG. 10A. FIG. 10B is a diagram showing that the use frequency band of the mobile station cannot be shifted to a frequency band including both ANCH1 and ANCH2 from the state shown in FIG. 10B. FIG. 10B is a diagram showing a range of PRUs to which a connected base station should allocate as a new ANCH1 in the state shown in FIG. 10B. FIG. 10B is a diagram showing ANCH1 newly allocated by the connected base station in response to a request to reassign ANCH1 from the mobile station from the state shown in FIG. 10B. It is a figure which shows the use frequency band (1st shift) of the mobile station shifted to the frequency band containing ANCH1 and ANCH2 from the state shown to FIG. 10E. After the connection between the mobile station and the connection destination base station is established in the state shown in FIG. 10F, the use frequency band of the mobile station further shifted to the use frequency band of the connection destination base station (second shift) FIG.

Hereinafter, Embodiments 1 to 3 of the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
FIG. 1 is a diagram showing a configuration of a mobile communication system 10 according to Embodiment 1 of the present invention. As shown in FIG. 1, the mobile communication system 10 includes a plurality of mobile stations 12 (only one is shown here) and a plurality of base stations 14 (here, only adjacent base stations 14-1 and 14-2). And). Here, it is assumed that the cell 16-1 of the base station 14-1 and the cell 16-2 of the base station 14-2 partially overlap.

  Each base station 14 uses an OFDMA (Orthogonal Frequency Division Multiple Access) method and a TDMA / TDD (Time Division Multiple Access / Time Division Duplex) method. Wireless communication with each of the mobile stations 12 located in the cell 16.

  FIG. 2A is a diagram showing a radio channel configuration in the mobile communication system 10. As shown in the figure, in the mobile communication system 10, a TDMA frame having a predetermined time width (here, 5 ms) is divided into an upstream subframe (2.5 ms) and a downstream subframe (2.5 ms). Each frame is equally divided into a plurality of time slots (here, Slot 1 to Slot 4). In addition, a plurality of OFDMA subchannels (here, Sch1 to Sch17) are defined in a predetermined frequency band. The minimum unit of the radio channel that the base station 14 assigns to the mobile station 12 is called a PRU (Physical Resource Unit), and each PRU is either a time slot (Slot 1 to Slot 4) or a sub channel (Sch 1 to Sch 17). , Belonging to. In addition, it is determined that each PRU is identified by consecutive PRU numbers (1, 2, 3,...) Starting from 1, for example, in both the uplink subframe and the downlink subframe. It is supposed to be used in upper and lower pairs. In other words, the PRU is defined to be assigned symmetrically.

  In the mobile communication system 10, different use frequency bands are set in the adjacent base stations 14 for the purpose of avoiding interference. Here, as shown in FIG. 2B, Sch1 to Sch9 (width 8.1 MHz) are set as the use frequency band of the base station 14-1, and Sch9 to Sch17 (width 8.4) as the use frequency band of the base station 14-2. 1 MHz) is set.

  Among these, Sch1, Sch9, and Sch17 are defined as CCH (Common Channel) shared by one or more mobile stations 12. This is a radio channel configuration called “dual CCH” in which two subchannels for CCH are arranged in the use frequency band of each base station 14 so that the reception gain in CCH increases. For this reason, the use frequency band of the base station 14-1 and the use frequency band of the base station 14-2 overlap with each other in the Sch9 defined as the CCH.

  On the other hand, PRUs belonging to Sch2 to Sch8 and Sch10 to Sch16 are used as ICH (Individual Channel) individually assigned to each mobile station 12. In principle, one ICH is assigned to each mobile station 12 as an individual control channel and is mainly used for transmission of control information. One or more communication channels are assigned to each mobile station 12 and mainly communication data. EXCH (Extra Channel) and the like used for transmission. The base station 14 can change the PRU (particularly EXCH) assigned to the mobile station 12 as ICH for each frame or every plurality of frames.

  Further, the usable frequency bandwidth of the mobile station 12 is limited to the frequency bandwidth (8.1 MHz) for nine subchannels that is the same as the usable frequency bandwidth of the base stations 14-1 and 14-2. For this reason, when the mobile station 12 is connected to the base station 14-1, the use frequency of the mobile station 12 is set to Sch1 to Sch9, which are use frequency bands of the base station 14-1. When the mobile station 12 is connected to the base station 14-2, the use frequency of the mobile station 12 is set to Sch9 to Sch17, which are use frequency bands of the base station 14-2. In addition, since the use frequency band of the base station 14-1 and the use frequency band of the base station 14-2 overlap in CCH (Sch9), the use frequency band of the mobile station 12 connected to the base station 14-1 Includes the CCH (Sch9) located at the upper end of the use frequency band of the base station 14-2 (the use frequency band side end of the base station 14-1).

  However, in the mobile communication system 10, when the mobile station 12 performs a handover from the base station 14-1 to the base station 14-2, the used frequency band of the mobile station 12 is Sch1 which is the used frequency band of the base station 14-1. Instead of directly switching from Sch9 to Sch9 to Sch17, which is the frequency band used by the base station 14-2, the CCH (the frequency band used by the base station 14-1 and the frequency band used by the base station 14-2 overlap) Using Sch9), the used frequency band of the mobile station 12 is shifted in two steps. Thereby, the mobile station 12 can perform a seamless handover between the base stations 14-1 and 14-2 using different frequency bands.

  Below, based on FIG. 3 and FIG. 4, the structure with which the mobile station 12 and the base station 14 are provided in order to implement | achieve a seamless handover is demonstrated concretely.

  FIG. 3 is a functional block diagram of the mobile station 12. As shown in FIG. 3, the mobile station 12 includes an antenna 20, a radio communication unit 22, a baseband unit 24, a signal processing unit 26, and a control unit 28 (a message analysis unit 30, a handover control unit 32, a frequency band shift unit 34). , The message generation unit 36).

  The antenna 20 receives a radio signal from the base station 14 and outputs the received radio signal to the radio communication unit 22. Further, the antenna 20 transmits a radio signal supplied from the radio communication unit 22 to the base station 14.

  The wireless communication unit 22 includes a low noise amplifier, a power amplifier, a frequency converter, a band pass filter, an A / D converter, and a D / A converter. The radio communication unit 22 amplifies the radio signal input from the antenna 20 with a low noise amplifier, down-converts the signal to an intermediate frequency signal, converts the signal to a digital signal, and outputs the digital signal to the baseband unit 24. Further, the radio communication unit 22 converts the digital signal input from the baseband unit 24 into an analog signal, then up-converts it to a radio signal, amplifies it to a transmission output level with a power amplifier, and then supplies the signal to the antenna 20 .

  Note that the frequency converter of the wireless communication unit 22 changes the reference frequency multiplied by the down-conversion target signal or the up-conversion target signal in accordance with an instruction from the control unit 28 (frequency band shift unit 34) described later. Switch the used frequency band.

  The baseband unit 24 includes an FFT (Fast Fourier Transform) unit, an IFFT (Inverse Fast Fourier Transform) unit, a serial-parallel converter, and a parallel-serial converter. The baseband unit 24 subjects the digital signal input from the wireless communication unit 22 to serial / parallel conversion, GI (Guard Interval) removal, fast Fourier transform, parallel / serial conversion, and the like, and performs signal processing on the obtained complex symbol sequence. To the unit 26. Further, the baseband unit 24 subjects the complex symbol sequence input from the signal processing unit 26 to serial / parallel conversion, inverse fast Fourier transform, addition of GI, parallel / serial conversion, and the like, and the obtained digital signal is transmitted to the wireless communication unit. 22 to output.

  The signal processing unit 26 is configured by a DSP (Digital Signal Processor), for example. The signal processing unit 26 performs demodulation, decoding, error detection, and the like on the complex symbol sequence input from the baseband unit 24 and outputs the obtained reception data to the control unit 28. In addition, the signal processing unit 26 adds error detection codes, encodes, modulates the transmission data input from the control unit 28 and the message addressed to the base station 14, and based on the obtained complex symbol sequence. The data is output to the band unit 24.

  The control unit 28 is constituted by, for example, a CPU and a program for controlling the operation of the CPU, and controls each unit of the mobile station 12. In particular, the control unit 28 functionally includes a message analysis unit 30, a handover control unit 32, a frequency band shift unit 34, and a message generation unit 36, and controls the handover operation of the mobile station 12.

  The message analysis unit 30 extracts various messages from the base station 14 from the reception data input from the signal processing unit 26, and analyzes the contents of the messages. For example, the message analysis unit 30 acquires an LCH (Link Channel) assignment response message from the base station 14 from the received data, and the PRU assigned to the mobile station 12 as an ANCH (Dedicated Control Channel) from the LCH assignment response message. A number (information for identifying an ANCH time slot and subchannel) is acquired. The message from the base station 14 extracted from the received data includes an LCH reassignment response message, a link setup response message, a function extension response message, a connection response message, an ANCH / CSCH switching instruction message in addition to the LCH assignment response message. and so on.

  The handover control unit 32 controls the handover operation of the mobile station 12. For example, when the mobile station 12 performs a handover from the base station 14-1 to the base station 14-2, the handover control unit 32 sends an LCH allocation request to the base station 14-2, a shift of the used frequency band of the mobile station 12, Each unit of the mobile station 12 is instructed to establish connection with the base station 14-2, disconnect connection with the base station 14-1, and the like.

  When the mobile station 12 performs handover, the frequency band shift unit 34 sends the reference frequency of the frequency converter to the radio communication unit 22 so that the use frequency band of the mobile station 12 is shifted in two steps according to the instruction of the handover control unit 32. Is changed (described later).

  The message generator 36 generates a message addressed to the base station 14 and outputs the message to the signal processor 26. Messages addressed to the base station 14 include an LCH allocation request message, an LCH reassignment request message, a link setting request message, a function extension request message, a connection request message, an ANCH / CSCH switching request message, an ANCH / CSCH switching confirmation message, and the like. .

  FIG. 4 is a functional block diagram of the base station 14. As shown in FIG. 4, the base station 14 includes an antenna 40, a wireless communication unit 42, a baseband unit 44, a signal processing unit 46, and a control unit 48 (message analysis unit 50, line quality detection unit 52, channel determination unit 54). , The message generation unit 56).

  The antenna 40 receives a radio signal from the mobile station 12 and outputs the received radio signal to the radio communication unit 42. Further, the antenna 40 transmits a radio signal supplied from the radio communication unit 42 to the mobile station 12.

  The wireless communication unit 42 includes a low noise amplifier, a power amplifier, a frequency converter, a band pass filter, an A / D converter, and a D / A converter. The radio communication unit 42 amplifies the radio signal input from the antenna 40 with a low noise amplifier, down-converts it to an intermediate frequency signal, further converts it to a digital signal, and outputs the digital signal to the baseband unit 44. The wireless communication unit 42 converts the digital signal input from the baseband unit 44 into an analog signal, then up-converts the signal into a wireless signal, amplifies the signal to a transmission output level with a power amplifier, and then supplies the signal to the antenna 40. .

  The baseband unit 44 includes an FFT unit, an IFFT unit, a serial / parallel converter, and a parallel / serial converter. The baseband unit 44 performs serial-parallel conversion, GI removal, fast Fourier transform, parallel-serial conversion, and the like on the digital signal input from the wireless communication unit 42, and outputs the obtained complex symbol to the signal processing unit 46. . Further, the baseband unit 44 subjects the complex symbol sequence input from the signal processing unit 46 to serial / parallel conversion, inverse fast Fourier transform, addition of GI, parallel / serial conversion, and the like, and the obtained digital signal is transmitted to the wireless communication unit. Output to 42.

  The signal processing unit 46 is configured by a DSP, for example. The signal processing unit 46 performs demodulation, decoding, error detection, and the like on the complex symbol sequence input from the baseband unit 44 and outputs the obtained reception data to the control unit 48. In addition, the signal processing unit 46 adds error detection codes, encodes, modulates the transmission data input from the control unit 48 and the message addressed to the mobile station 12, and based on the obtained complex symbol sequence. The data is output to the band unit 44.

  The control unit 48 includes, for example, a CPU and a program that controls the operation of the CPU, and controls each unit of the base station 14. In particular, the control unit 48 functionally includes a message analysis unit 50, a channel quality detection unit 52, a channel determination unit 54, and a message generation unit 56, and determines the PRU (ANCH, EXCH, etc.) to be allocated to the mobile station 12. Do.

  The message analysis unit 50 extracts various messages from the mobile station 12 from the received data input from the signal processing unit 46 and analyzes the contents of the messages. The message from the mobile station 12 extracted from the received data includes an LCH assignment request message, an LCH reassignment request message, a link setting request message, a function extension request message, a connection request message, an ANCH / CSCH switching request message, an ANCH / CSCH. There is a switching confirmation message.

  The channel quality detection unit 52 detects a channel quality value representing the channel quality of each PRU belonging to the used frequency band of the base station 14 based on the complex symbol sequence input from the baseband unit 44 via the signal processing unit 46. To do. Examples of the line quality value detected by the line quality detection unit 52 include RSSI (Received Signal Strength Indication) detected by carrier sense (interference wave measurement) and SNR (Signal to Noise Ratio). Power ratio).

  The channel determination unit 54 includes a channel quality value detected by the channel quality detection unit 52, a PRU availability, an amount of data transmitted to and received from the mobile station 12, a communication type (voice communication, packet communication, etc.), movement The PRU to be allocated to the mobile station 12 is determined based on the contract information of the station 12 (information relating to the upper limit number of PRUs that can be allocated to the mobile station 12). For example, the channel determination unit 54 determines a PRU to be allocated to the mobile station 12 as an ANCH (Dedicated Control Channel) based on the LCH allocation request message from the mobile station 12. Further, the channel determination unit 54 determines one or more PRUs to be assigned to the mobile station 12 as EXCH (communication channel) for each frame or a plurality of frames. Furthermore, the channel determination unit 54 changes the PRU assigned to the mobile station 12 as an ANCH based on the ANCH / CSCH switching request message from the mobile station 12.

  The message generator 56 generates a message addressed to the mobile station 12 and outputs the message to the signal processor 46. The message addressed to the mobile station 12 includes an LCH assignment response message including the number of the PRU assigned to the mobile station 12 as an ANCH, an LCH reassignment response message, a link setup response message, a function extension response message, a connection response message, an ANCH / CSCH switching instruction message.

  Next, based on FIGS. 5A, 5B, and 6A to 6I, the mobile station 12 and the base station 14-1 when the mobile station 12 performs a handover from the base station 14-1 to the base station 14-2. 14-2 will be specifically described.

  FIG. 5A is a sequence diagram illustrating an example of a handover method according to the first embodiment. FIG. 5B is a sequence diagram illustrating another example of the handover method according to the first embodiment. Here, before the handover, the used frequency band of the connected base station 14-1, the used frequency band of the connected base station 14-2, the used frequency band of the mobile station 12, and the base station 14-1 It is assumed that the PRU (ANCH1, EXCH) assigned to the mobile station 12 has the relationship shown in FIG. 6A.

  As shown in FIG. 5A, when the mobile station 12 starts a handover to the base station 14-2, the used frequency band of the CCH (the base station 14-1 and the used frequency band of the base station 14-2 overlap). An LCH allocation request message is transmitted to the connection destination base station 14-2 via (Sch9) (S100).

  In response to the LCH assignment request message from the mobile station 12, the base station 14-2 determines a PRU (ANCH2) to be assigned to the mobile station 12 as an ANCH. Specifically, the channel determination unit 54 of the base station 14-2 determines ANCH2 based on the channel quality value detected by the channel quality detection unit 52, the PRU availability, and the like. Then, the base station 14-2 transmits an LCH allocation response message including the determined PRU number of ANCH2 to the mobile station 12 via the CCH (S102).

  Next, the mobile station 12 determines that the frequency difference between the ANCH1 allocated from the base station 14-1 and the ANCH2 notified from the base station 14-2 in S102 is the frequency band used by the local station (8.1 MHz). ) Determine whether or not:

  Here, as shown in FIG. 6B, when the frequency difference between ANCH1 and ANCH2 is equal to or smaller than the use frequency bandwidth of the mobile station 12, the mobile station 12 uses its own use frequency band as a frequency band including ANCH1 and ANCH2. (S108: first shift). Specifically, the frequency band shift unit 34 of the mobile station 12 causes the radio communication unit 22 to change the reference frequency of the frequency converter so that the use frequency band of the mobile station 12 is shifted to a frequency band including ANCH1 and ANCH2. .

  In the first shift, as shown in FIG. 6C, the lower end of the use frequency band of the mobile station 12 (the use frequency band side end of the base station 14-2) is set equal to the frequency of the ANCH2 (Sch12). It is desirable to shift the use frequency band of the mobile station 12. By doing so, the shift amount (first shift amount) of the used frequency band of the mobile station 12 is minimized, so that the number of EXCHs (communication channels) released by the first shift can be reduced. it can.

  At the time of S108, since the use frequency band of the mobile station 12 is in a frequency band including ANCH1 and ANCH2, the mobile station 12 is connected to both the base station 14-1 and the base station 14-2 via the ANCH1 and ANCH2, respectively. At the same time, wireless communication can be performed (see FIG. 6C). Therefore, after the first shift, the mobile station 12 establishes a connection with the base station 14-2 via the ANCH2. That is, the mobile station 12 sends a link setup request message (S110), a link setup response message (S112), a function extension request message (S114), a function extension response message (S116), a connection request message (S118), and a connection response message. A connection with the base station 14-2 is established by transmitting and receiving (S120) via the ANCH2. During this time, the mobile station 12 maintains data communication via the ANCH 1 and the EXCH remaining without being released by the first shift (see FIG. 6C).

  When the connection with the base station 14-2 is established, the mobile station 12 disconnects the connection with the base station 14-1 via the ANCH1 (S122). As a result, all the PRUs assigned to the mobile station 12 as ANCH1 and EXCH are released. Subsequently, as shown in FIG. 6D, the mobile station 12 further shifts its own use frequency band to Sch9 to Sch17 that are use frequency bands of the base station 14-2 (S124: second shift). Specifically, the frequency band shift unit 34 of the mobile station 12 causes the radio communication unit 22 to change the reference frequency of the frequency converter so that the use frequency band of the mobile station 12 is shifted to Sch9 to Sch17.

  Thereafter, the mobile station 12 continues data communication via the ANCH 2 and the EXCH newly assigned from the base station 14-2. In this way, the mobile station 12 completes the handover from the base station 14-1 to the base station 14-2 without interrupting data communication, that is, seamlessly.

  On the other hand, as shown in FIG. 6E, the frequency difference between the ANCH 1 assigned from the base station 14-1 and the ANCH 2 notified from the base station 14-2 in S102 is a used frequency band of the mobile station 12. When it is larger than the width, the use frequency band of the mobile station 12 cannot be shifted to a frequency band including both ANCH1 and ANCH2 (see FIG. 6F). For this reason, the mobile station 12 requests the base station 14-2 to reassign ANCH2 via the CCH (Sch9) so that the frequency difference is equal to or less than the use frequency bandwidth of the local station. That is, as shown in FIG. 5B, the mobile station 12 transmits an LCH reassignment request message to the connected base station 14-2 via the CCH (S104).

  In response to the LCH reassignment request message from the mobile station 12, the base station 14-2 determines a new ANCH2 different from the ANCH2 notified to the mobile station 12 from the Sch10 to Sch16. Then, the base station 14-2 transmits an LCH reassignment response message including the newly determined PRU number of ANCH2 to the mobile station 12 via the CCH (S106). The mobile station 12 may repeat the transmission of the LCH reassignment request message (S106) until the frequency difference between ANCH1 and ANCH2 is equal to or less than the use frequency bandwidth of the local station.

  Then, as shown in FIG. 6G, when the frequency difference between ANCH1 and ANCH2 becomes equal to or less than the usable frequency bandwidth of the mobile station 12 due to the reassignment of ANCH2, as shown in FIG. 6H, the mobile station 12 The frequency band is shifted to a frequency band including ANCH1 and ANCH2 (S108: first shift).

  After the first shift, the mobile station 12 establishes a connection with the base station 14-2 via the ANCH2 (S110 to S120). When the connection with the base station 14-2 is established, the mobile station 12 disconnects the connection with the base station 14-1 via the ANCH1 (S122). Subsequently, as shown in FIG. 6I, the mobile station 12 further shifts the use frequency band of its own station to Sch9 to Sch17, which are use frequency bands of the base station 14-2 (S124: second shift).

Thus, according to the mobile communication system 10 according to the first embodiment, the frequency difference between the ANCH 1 allocated from the base station 14-1 and the ANCH 2 notified from the base station 14-2 is Even if it is larger than the used frequency bandwidth, the mobile station 12 can make the frequency difference equal to or smaller than the used frequency bandwidth of its own station by requesting the base station 14-2 of the connection destination to reassign ANCH2. . For this reason, the mobile station 12 can perform a seamless handover from the base station 14-1 using Sch1 to Sch9 to the base station 14-2 using Sch9 to Sch17.
[Embodiment 2]
The mobile communication system 10 according to Embodiment 2 of the present invention has the same system configuration and radio channel configuration as the mobile communication system 10 according to Embodiment 1 described above.

  That is, as shown in FIG. 1, the mobile communication system 10 according to the second embodiment includes a plurality of mobile stations 12 (only one is shown here) and a plurality of base stations 14 (here adjacent base stations 14- 1 and 14-2 only).

  In the mobile communication system 10 according to the second embodiment, the radio channel configuration shown in FIG. 2A is defined. Further, as shown in FIG. 2B, for the purpose of avoiding interference, Sch1 to Sch9 (width 8.1 MHz) are set as the used frequency band of the base station 14-1, and Sch9 to Sch2 as the used frequency band of the base station 14-2. It is assumed that Sch17 (width 8.1 MHz) is set (Sch1, Sch9, and Sch17 are defined as CCH). Further, the usable frequency bandwidth of the mobile station 12 is assumed to be the same frequency bandwidth (8.1 MHz) for nine subchannels as the usable frequency bandwidth of the base stations 14-1 and 14-2.

  Further, as shown in FIG. 3, the mobile station 12 according to the second embodiment includes an antenna 20, a radio communication unit 22, a baseband unit 24, a signal processing unit 26, and a control unit 28 (message analysis unit 30, handover control unit). 32, a frequency band shift unit 34, and a message generation unit 36).

  Further, as shown in FIG. 4, the base station 14 according to the second embodiment includes an antenna 40, a wireless communication unit 42, a baseband unit 44, a signal processing unit 46, and a control unit 48 (message analysis unit 50, line quality detection). Unit 52, channel determination unit 54, and message generation unit 56).

  However, in the second embodiment, unlike the first embodiment, when the mobile station 12 starts a handover from the base station 14-1 to the base station 14-2, the mobile station 12 is assigned from the base station 14-1. Identification information indicating the frequency of the existing ANCH (ANCH1) is notified to the base station 14-2 via the CCH (Sch9). Then, based on the identification information notified from the mobile station 12, the base station 14-2 uses an empty PRU (for example, any mobile station 12) whose frequency difference from the ANCH 1 is equal to or less than the use frequency bandwidth of the mobile station 12. Are assigned, and the ANCH (ANCH2) to be assigned to the mobile station 12 is determined from among the PRUs whose interference wave level is not more than a predetermined value. This is to prevent the frequency difference between ANCH1 and ANCH2 from exceeding the use frequency bandwidth of the mobile station 12.

  Thus, there is a slight difference between Embodiment 1 and Embodiment 2 in the control of the handover operation by the control unit 28 of the mobile station 12 and the determination of the ANCH by the channel determination unit 54 of the base station 14. is there.

  In the following, centering on this difference, the mobile station 12 and the base station when the mobile station 12 performs handover from the base station 14-1 to the base station 14-2 based on FIG. 7 and FIGS. 8A to 8E. The operation of 14-1 and 14-2 will be described.

  FIG. 7 is a sequence diagram illustrating an example of a handover method according to the second embodiment. Here, before the handover, the used frequency band of the connected base station 14-1, the used frequency band of the connected base station 14-2, the used frequency band of the mobile station 12, and the base station 14-1 It is assumed that the PRU (ANCH1, EXCH) assigned to the mobile station 12 has the relationship shown in FIG. 8A.

  As shown in FIG. 7, when starting a handover to the base station 14-2, the mobile station 12 transmits an LCH allocation request message to the connected base station 14-2 via the CCH (S200). This LCH allocation request message includes identification information indicating the frequency of ANCH1. As the identification information indicating the frequency of ANCH1, for example, the ANCH1 frequency itself, the PRU number of ANCH1 (information for identifying the time slot and subchannel of ANCH1), and the like are used.

  In response to the LCH assignment request message from the mobile station 12, the base station 14-2 determines ANCH2 to be assigned to the mobile station 12. Specifically, the channel determination unit 54 of the base station 14-2 determines the ANCH1 based on the identification information included in the LCH allocation request message, the channel quality value detected by the channel quality detection unit 52, the availability of the PRU, and the like. ANCH2 is determined from empty PRUs (see the thick line frame in FIG. 8B) whose frequency difference is less than or equal to the used frequency bandwidth of the mobile station 12.

  Here, the channel determination unit 54 may determine an empty PRU whose frequency is closest to the frequency of ANCH1 (see the hatched portion in FIG. 8B) as ANCH2. In this way, the shift amount (first shift amount) of the used frequency band of the mobile station 12 can be reduced, so the number of EXCH (communication channels) released by the first shift is reduced. can do. Here, as shown in FIG. 8C, it is assumed that one of the empty PRUs whose frequency is closest to the frequency of ANCH1 is determined as ANCH2.

  Thereafter, the base station 14-2 transmits an LCH allocation response message including the determined PRU number of ANCH2 to the mobile station 12 via the CCH (S202).

  In the second embodiment, since the frequency difference between ANCH1 allocated from the base station 14-1 and ANCH2 notified from the base station 14-2 in S202 is equal to or less than the use frequency bandwidth of the mobile station 12, The station 12 shifts its use frequency band to a frequency band including ANCH1 and ANCH2 (S204: first shift).

  In the first shift, as shown in FIG. 8D, the lower end of the use frequency band of mobile station 12 (the end of the use frequency band of base station 14-2) is equal to the frequency (Sch10) of ANCH2. It is desirable to shift the use frequency band of the mobile station 12. In this way, the shift amount (first shift amount) of the used frequency band of the mobile station 12 can be minimized. Incidentally, in the example shown in FIG. 8D, the number of EXCHs released by the first shift is zero.

  After the first shift, the mobile station 12 establishes a connection with the base station 14-2 via the ANCH2 (S206 to S216). When the connection with the base station 14-2 is established, the mobile station 12 disconnects the connection with the base station 14-1 via the ANCH1 (S218). Subsequently, as shown in FIG. 8E, the mobile station 12 further shifts its own use frequency band to Sch9 to Sch17, which are use frequency bands of the base station 14-2 (S220: second shift).

Thus, according to the mobile communication system 10 according to the second embodiment, it is possible to prevent the frequency difference between ANCH1 and ANCH2 from exceeding the use frequency bandwidth of the mobile station 12. For this reason, the mobile station 12 can seamlessly perform handover from the base station 14-1 using Sch1 to Sch9 to the base station 14-2 using Sch9 to Sch17 earlier.
[Embodiment 3]
The mobile communication system 10 according to Embodiment 3 of the present invention has the same system configuration and radio channel configuration as the mobile communication system 10 according to Embodiment 1 described above.

  That is, as shown in FIG. 1, the mobile communication system 10 according to the third embodiment includes a plurality of mobile stations 12 (only one is shown here) and a plurality of base stations 14 (here adjacent base stations 14- 1 and 14-2 only).

  In the mobile communication system 10 according to the third embodiment, the radio channel configuration shown in FIG. 2A is defined. Further, as shown in FIG. 2B, for the purpose of avoiding interference, Sch1 to Sch9 (width 8.1 MHz) are set as the used frequency band of the base station 14-1, and Sch9 to Sch2 as the used frequency band of the base station 14-2. It is assumed that Sch17 (width 8.1 MHz) is set (Sch1, Sch9, and Sch17 are defined as CCH). Further, the usable frequency bandwidth of the mobile station 12 is assumed to be the same frequency bandwidth (8.1 MHz) for nine subchannels as the usable frequency bandwidth of the base stations 14-1 and 14-2.

  Further, as shown in FIG. 3, the mobile station 12 according to the third embodiment includes an antenna 20, a radio communication unit 22, a baseband unit 24, a signal processing unit 26, and a control unit 28 (message analysis unit 30, handover control unit). 32, a frequency band shift unit 34, and a message generation unit 36).

  Further, as shown in FIG. 4, the base station 14 according to the third embodiment includes an antenna 40, a radio communication unit 42, a baseband unit 44, a signal processing unit 46, and a control unit 48 (message analysis unit 50, line quality detection). Unit 52, channel determination unit 54, and message generation unit 56).

  However, in the third embodiment, unlike the first embodiment, when the mobile station 12 performs a handover from the base station 14-1 to the base station 14-2, the ANCH (ANCH1) allocated from the base station 14-1; If the frequency difference between the ANCH (ANCH2) notified from the base station 14-2 via the CCH (Sch9) is larger than the used frequency bandwidth of the mobile station 12, the mobile station 12 A reassignment of ANCH1 is requested not to the connected base station 14-2 but to the connected base station 14-1 so as to be equal to or less than the used frequency bandwidth. Then, the base station 14-1 determines a new ANCH 1 different from the ANCH 1 assigned to the mobile station 12 in response to the reassignment request of the ANCH 1 from the mobile station 12.

  Thus, there is a slight difference between Embodiment 1 and Embodiment 3 in the control of the handover operation by the control unit 28 of the mobile station 12 and the determination of the ANCH by the channel determination unit 54 of the base station 14. is there.

  In the following, centering on this difference, the mobile station 12 and the base station when the mobile station 12 performs handover from the base station 14-1 to the base station 14-2 based on FIG. 9 and FIGS. 10A to 10G. The operation of 14-1 and 14-2 will be described.

  FIG. 9 is a sequence diagram illustrating an example of a handover method according to the third embodiment. Here, before the handover, the used frequency band of the connected base station 14-1, the used frequency band of the connected base station 14-2, the used frequency band of the mobile station 12, and the base station 14-1 Assume that PRUs (ANCH1, EXCH) allocated to the mobile station 12 have the relationship shown in FIG. 10A.

  As shown in FIG. 9, when starting a handover to the base station 14-2, the mobile station 12 transmits an LCH allocation request message to the connected base station 14-2 via the CCH (S300).

  In response to the LCH assignment request message from the mobile station 12, the base station 14-2 determines ANCH2 to be assigned to the mobile station 12. Specifically, the channel determination unit 54 of the base station 14-2 determines ANCH2 based on the channel quality value detected by the channel quality detection unit 52, the PRU availability, and the like. Then, the base station 14-2 transmits an LCH assignment response message including the determined PRU number of ANCH2 to the mobile station 12 via the CCH (S302).

  Next, the mobile station 12 determines that the frequency difference between the ANCH1 allocated from the base station 14-1 and the ANCH2 notified from the base station 14-2 in S302 is the used frequency bandwidth (8.1 MHz) of its own station. ) Determine whether or not:

  Here, as shown in FIG. 10B, when the frequency difference between ANCH1 and ANCH2 is larger than the use frequency band width of the mobile station 12, the use frequency band of the mobile station 12 is shifted to a frequency band including both ANCH1 and ANCH2. It cannot be done (see FIG. 10C). For this reason, the mobile station 12 requests the base station 14-1 to reassign ANCH1 so that the frequency difference is equal to or less than the use frequency bandwidth of the mobile station. That is, the mobile station 12 transmits an ANCH / CSCH switching request message to the connected base station 14-1 via the ANCH 1 (S304). This ANCH / CSCH switching request message includes identification information indicating the frequency of ANCH2. As identification information indicating the frequency of ANCH2, for example, the ANCH2 frequency itself, the PRU number of ANCH2 (information for identifying the time slot and subchannel of ANCH2), and the like are used.

  In response to the ANCH / CSCH switching request message from the mobile station 12, the base station 14-1 determines a new ANCH1 different from the ANCH1 assigned to the mobile station 12 from the Sch2 to Sch8. Specifically, the channel determination unit 54 of the base station 14-1 determines the identification information included in the ANCH / CSCH switching request message, the channel quality value detected by the channel quality detection unit 52, the availability status of the PRU, and the like. , ANCH1 is determined from among the empty PRUs (see the bold line frame in FIG. 10D) whose frequency difference from ANCH2 is equal to or less than the used frequency bandwidth of the mobile station 12.

  Thereafter, the base station 14-1 transmits an ANCH / CSCH switching response message including the newly determined PRU number of ANCH1 to the mobile station 12 via the ANCH1 assigned to the mobile station 12 (S306). Here, it is assumed that the PRU shown in the thick line frame in FIG. 10E is determined as a new ANCH1. The mobile station 12 that has received the ANCH / CSCH switching response message from the base station 14-1 returns an ANCH / CSCH switching confirmation message to the base station 14-1 via the new ANCH1 (S308).

  When the frequency difference between the ANCH 1 reassigned from the base station 14-1 and the ANCH 2 notified from the base station 14-2 in S302 is equal to or smaller than the use frequency bandwidth of the mobile station 12, the mobile station 12 Is shifted to a frequency band including ANCH1 and ANCH2 (S310: first shift).

  In the first shift, as shown in FIG. 10F, the lower end of the use frequency band of the mobile station 12 (the use frequency band side end of the base station 14-2) is equal to the frequency (Sch13) of the ANCH2. It is desirable to shift the use frequency band of the mobile station 12. By doing so, the shift amount (first shift amount) of the used frequency band of the mobile station 12 is minimized, so that the number of EXCHs (communication channels) released by the first shift can be reduced. it can.

  After the first shift, the mobile station 12 establishes a connection with the base station 14-2 via the ANCH2 (S312 to S322). When the connection with the base station 14-2 is established, the mobile station 12 disconnects the connection with the base station 14-1 via the ANCH1 (S324). Subsequently, as shown in FIG. 10G, the mobile station 12 further shifts its own use frequency band to Sch9 to Sch17 that are use frequency bands of the base station 14-2 (S326: second shift).

Thus, according to the mobile communication system 10 according to the third embodiment, the frequency difference between the ANCH 1 assigned from the base station 14-1 and the ANCH 2 notified from the base station 14-2 is Even when it is larger than the used frequency bandwidth, the mobile station 12 can request the base station 14-1 being connected to reassign ANCH1, thereby making the frequency difference equal to or smaller than the used frequency bandwidth of the own station. . For this reason, the mobile station 12 can perform a seamless handover from the base station 14-1 using Sch1 to Sch9 to the base station 14-2 using Sch9 to Sch17.
[Summary]
According to the mobile communication system 10 according to the first to third embodiments described above, seamless handover between the base stations 14 using different frequency bands can be realized.

  In addition, this invention is not limited to the said Embodiment 1-3.

  For example, the radio channel configuration may be different from the radio channel configuration shown in FIG. 2A. Further, the relationship between the use frequency band of the base station 14 and the use frequency band of the mobile station 12 may be different from the relationship shown in FIG. 2B. In particular, the use frequency band of the base station 14-1 and the use frequency band of the base station 14-2 do not need to overlap at a frequency defined as a CCH (common channel) (radio channel configuration called dual CCH). The use frequency band of the mobile station 12 connected to the base station 14-1 is the same as the use frequency band (first frequency band) of the base station 14-1 and the connection destination base station 14 -2 used frequency band (second frequency band) in the use frequency band (the second frequency band) and the CCH defined at the first frequency band side end may be satisfied.

  Further, the present invention is not limited to the mobile communication system adopting the OFDMA scheme and the TDMA / TDD scheme, and the first base station using the first frequency band and the second frequency different from the first frequency band. The present invention is applicable to all mobile communication systems including a second base station that uses a band and a mobile station that performs handover from the first base station to the second base station.

10 mobile communication systems, 12 mobile stations, 14 base stations, 16 cells, 20, 40 antennas, 22, 42 radio communication units, 24, 44 baseband units, 26, 46 signal processing units, 28, 48 control units, 30, 50 message analysis unit, 32 handover control unit, 34 frequency band shift unit, 36, 56 message generation unit, 52 channel quality detection unit, 54 channel determination unit.

Claims (4)

A first base station using a first frequency band; a second base station using a second frequency band different from the first frequency band; and a first base station belonging to the first frequency band A mobile communication system comprising a mobile station assigned a control channel from the first base station,
The use frequency band of the mobile station connected to the first base station includes the first frequency band and a common channel defined at the first frequency band side end in the second frequency band. Including,
The second base station is
A control channel for determining a second control channel to be allocated to the mobile station from the second frequency band in response to the start of handover from the first base station to the second base station by the mobile station A determination means;
Means for notifying the mobile station via the common channel of a second control channel determined by the control channel determination means,
The mobile station
When the frequency difference between the first control channel and the second control channel notified from the second base station is less than or equal to the use frequency bandwidth of the mobile station, the use frequency band of the mobile station First frequency band shifting means for shifting to a frequency band including the first and second control channels;
Means for establishing a connection with the second base station via the second control channel after the use frequency band of the mobile station is shifted by the first frequency band shifting means;
Second frequency band shifting means for further shifting the use frequency band of the mobile station to the second frequency band after the connection with the second base station is established;
A mobile communication system. A mobile station that performs a handover from a first base station that uses a first frequency band to a second base station that uses a second frequency band different from the first frequency band,
The use frequency band of the mobile station connected to the first base station includes the first frequency band and a common channel defined at the first frequency band side end in the second frequency band. Including,
A first control channel assigned from the first base station, belonging to the first frequency band, and notified from the second base station via the common channel according to the start of the handover, When the frequency difference from the second control channel belonging to the second frequency band is equal to or smaller than the use frequency bandwidth of the mobile station, the use frequency band of the mobile station is set to the first and second control channels. First frequency band shifting means for shifting to a frequency band including:
Means for establishing a connection with the second base station via the second control channel after the use frequency band of the mobile station is shifted by the first frequency band shifting means;
Second frequency band shift means for further shifting the use frequency band of the mobile station to the second frequency band after connection with the second base station is established;
A mobile station characterized by comprising: A base station using a second frequency band different from the first frequency band used by another base station,
The use frequency band of the mobile station connected to the other base station includes the first frequency band and a common channel defined at the first frequency band side end in the second frequency band. Including
The first control channel belonging to the first frequency band is allocated to the mobile station in response to the start of handover from the other base station to the base station by the mobile station allocated from the other base station. Control channel determining means for determining a second control channel from the second frequency band;
Means for notifying the mobile station of the second control channel determined by the control channel determination means via the common channel;
Means for establishing a connection with the mobile station via the second control channel after a use frequency band of the mobile station is shifted to a frequency band including the first and second control channels;
A base station comprising: A first base station using a first frequency band; a second base station using a second frequency band different from the first frequency band; and a first base station belonging to the first frequency band A mobile station assigned a control channel from the first base station, and a handover method in a mobile communication system comprising:
The use frequency band of the mobile station connected to the first base station includes the first frequency band and a common channel defined at the first frequency band side end in the second frequency band. Including,
In response to the start of handover from the first base station to the second base station by the mobile station, the second base station assigns a second control channel to the mobile station to the second frequency. A control channel determination step for determining from within the band;
The second base station notifying the mobile station of the second control channel determined in the control channel determination step via the common channel;
When the frequency difference between the first control channel and the second control channel notified from the second base station is less than or equal to the use frequency bandwidth of the mobile station, the use frequency band of the mobile station Shifting to a frequency band including the first and second control channels; and
After the use frequency band of the mobile station is shifted in the first frequency band shift step, the mobile station establishes a connection with the second base station via the second control channel;
A second frequency band shifting step of further shifting the use frequency band of the mobile station to the second frequency band after the connection between the mobile station and the second base station is established;
A handover method comprising:

Images