JP2010226622A - Base station device and slot allocation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station device and slot allocation method in which reduction in frequency utilization efficiency caused by dealing with two mobile communication systems with different ways of slot allocation can be suppressed. <P>SOLUTION: A dual base station 10 is corresponding to both PHS and XGP with different ways of slot allocation and uses one of a plurality of slots included within a predetermined temporal cycle to communicate with one of PHS terminals 22 corresponding to PHS or one or more XGP terminals 24 corresponding to XGP. In response to a new connection request (S200) from an XGP terminal 24, the dual base station 10 performs a handover of a PHS terminal 22 communicating with the dual base station 10 to a PHS base station 12 (S202-S208). The dual base station 10 then assigns the XGP terminal 24 to a slot released by the handover of the PHS terminal 22 (S210). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a base station apparatus and a slot allocation method, and more particularly to a base station apparatus corresponding to two mobile communication systems having different slot allocation methods and a slot allocation method thereof.

  In an area where two different mobile communication systems coexist, a so-called dual-mode base station corresponding to both systems may be installed.

  For example, currently, PHS (Personal Handy-phone System, see Non-Patent Document 1) adopting a TDMA / TDD (Time Division Multiple Access / Time Division Duplex) system and OFDMA (Orthogonal) The introduction of base stations compatible with both XGP (eXtended Global Platform, see Non-Patent Document 2) employing the Frequency Division Multiple Access (Orthogonal Frequency Division Multiple Access) system and the TDMA / TDD system is being studied. In these systems, four sets of transmission / reception slots (hereinafter simply referred to as “slots”) are defined in a TDMA frame having a period of 5 ms. The PHS slot and the XGP slot are synchronized with each other.

“RCR STD-28“ Second Generation Cordless Telephone System ”5.3”, September 25, 2008, Japan Radio Industry Association “ARIB STD-T95“ OFDMA / TDMA TDD Broadband Wireless Access System ARIBSTANDARD 1.0 ”, December 12, 2007, Japan Radio Industry Association

  However, in a dual-mode compatible base station having only one radio (radio communication unit), frequency utilization efficiency may be reduced due to a difference in slot allocation between the two mobile communication systems.

  For example, in XGP, a plurality of OFDMA subchannels (2.5 GHz band) are defined in each slot, and the base station can assign one or more XGP terminals (XGP-compatible mobile stations) to each slot. On the other hand, in PHS, since the number of radio channels (1.9 GHz band) that can be used in each slot is limited to one, the base station assigns only one PHS terminal (PHS compatible mobile station) to each slot. I can't.

  For this reason, a base station that supports both PHS and XGP cannot further allocate an XGP terminal or another PHS terminal to a slot to which a PHS terminal is allocated, and cannot fully utilize radio resources in the slot. .

  An object of the present invention is to provide a base station apparatus and a slot allocation method capable of suppressing a decrease in frequency use efficiency due to the correspondence to two mobile communication systems having different slot allocation methods.

  In order to solve the above-described problem, a base station apparatus according to the present invention uses one of a plurality of slots included in a predetermined time period to provide a first mobile station apparatus corresponding to the first mobile communication system. A base station apparatus that communicates with one or more second mobile station apparatuses corresponding to one or a second mobile communication system, and in response to a request from the second mobile station apparatus, Handover instruction means for handing over the communicating first mobile station apparatus to another base station apparatus; means for allocating the second mobile station apparatus to a slot released by handover of the first mobile station apparatus; , Including.

  According to the present invention, in response to a request from the second mobile station device, the base station device hands over any of the first mobile station devices communicating with the base station device to another base station device. And assigning the second mobile station apparatus to the slot released by the handover. For this reason, the base station apparatus can suppress a decrease in frequency use efficiency due to the correspondence to two mobile communication systems with different slot allocation methods.

  In the aspect of the invention, the base station device further includes a frequency use efficiency acquisition unit that acquires the frequency use efficiency of the base station device, and the handover instruction unit sets the frequency use efficiency to a predetermined threshold value. If it falls below, the first mobile station apparatus is handed over to the other base station apparatus.

  According to this aspect, the base station apparatus maintains the wireless connection with the first mobile station apparatus as much as possible, and reduces the frequency utilization efficiency due to the correspondence to two mobile communication systems having different slot allocation methods. Can be suppressed.

  In this aspect, the frequency utilization efficiency may be determined based on the number of first mobile station devices communicating with the base station device, or the amount of data transmitted and received by the base station device May be determined based on

  Further, the request from the second mobile station apparatus may be a new connection request or a radio resource allocation addition request.

  In addition, the slot allocation method according to the present invention uses one of the plurality of slots included in a predetermined time period, one of the first mobile station apparatuses corresponding to the first mobile communication system, or the second A slot allocation method for a base station apparatus that communicates with one or more second mobile station apparatuses compatible with a mobile communication system, and communicates with the base station apparatus in response to a request from the second mobile station apparatus. Handing over the first mobile station device to another base station device, and allocating the second mobile station device to a slot released by the handover of the first mobile station device. It is characterized by.

It is a figure which shows the wireless communication apparatus located in the dual base station which concerns on embodiment of this invention, and its periphery. It is a figure which shows the channel structure of PHS and the channel structure of XGP. It is a figure which shows an example of the slot allocation by the dual base station which concerns on embodiment of this invention. It is a figure which shows an example of the slot allocation by the conventional dual base station. It is a figure which shows an example of the slot allocation by the dual base station which concerns on embodiment of this invention. It is a figure which shows an example of the slot allocation by the dual base station which concerns on embodiment of this invention. It is a functional block diagram of the dual base station which concerns on embodiment of this invention. It is a figure which shows the frequency utilization efficiency table memorize | stored in a memory | storage part. It is a flowchart which shows an example of the slot allocation process which concerns on embodiment of this invention. It is a sequence diagram which shows an example of the slot allocation process which concerns on embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a dual base station 10 according to an embodiment of the present invention and wireless communication devices located in the vicinity thereof. The dual base station 10 is compatible with both PHS (first mobile communication system) adopting the TDMA / TDD system and XGP (second mobile communication system) adopting the OFDMA system and the TDMA / TDD system. A base station that includes one or more PHS terminals 22 (here, only PHS terminals 22-1 and 22-2 are shown) and one or more XGP terminals 24 (here, only XGP terminals 24-1 to 24-4) And multiplex communication.

  Since the dual base station 10 is installed in an area where PHS and XGP coexist, a PHS base station 12 compatible with PHS and an XGP base station 14 compatible with XGP exist in the vicinity thereof.

  FIG. 2 is a diagram illustrating a PHS channel configuration and an XGP channel configuration. As shown in the figure, in PHS and XGP, four slots (four sets of transmission / reception slots) are defined in a TDMA frame having a period of 5 ms, and the PHS slot and the XGP slot are synchronized with each other.

  In XGP, a plurality of (for example, nine) OFDMA subchannels (hereinafter simply referred to as “subchannels”) belonging to the 2.5 GHz band are defined in each slot, and the dual base station 10 and the XGP base station 14 One or more XGP terminals 24 can be assigned to the. The minimum unit of the radio channel assigned to each XGP terminal 24 is called PRU (Physical Resource Unit) and belongs to one of four slots (Slot 1 to Slot 4) and one of a plurality of subchannels.

  On the other hand, in PHS, since the number of radio channels (1.9 GHz band) that can be used in each slot is limited to one, the dual base station 10 and the PHS base station 12 allocate only one PHS terminal to each slot. I can't. For this reason, the dual base station 10 cannot further allocate the XGP terminal 24 or another PHS terminal 22 to the slot to which the PHS terminal 22 is allocated.

  FIG. 3 is a diagram illustrating an example of slot allocation by the dual base station 10. In the example shown in the figure, the PHS terminal 22-1 is in slot 1, the XGP terminals 24-1 and 24-2 are in slot 2, the XGP terminals 24-3 and 24-4 are in slot 3, and the PHS terminal 22-2 is in slot 4. , Each assigned. Specifically, the XGP terminal 24-1 belongs to the four PRUs belonging to Slot 2 (denoted as XGP1), the XGP terminal 24-2 belongs to the five PRUs belonging to Slot 2 (denoted as XGP2), and the five PRUs belonging to Slot 3 (denoted as XGP2). XGP terminal 24-3 is assigned to XGP3), and XGP terminal 24-4 is assigned to four PRUs belonging to Slot 3 (denoted XGP4). Since Slots 1 and 4 are occupied by PHS terminals 22-1 and 22-2, other XGP terminals 24 cannot be assigned to Slots 1 and 4.

  If a conventional dual base station receives a new connection request from the XGP terminal 24 in the state shown in FIG. 3, the allocation of at least one PRU belonging to Slot 2 or Slot 3 is released and released as shown in FIG. The XGP terminal 24 is assigned to the PRU (denoted as XGP5). Alternatively, in the state shown in FIG. 3, a new connection request is not accepted. In any case, since the PHS terminals 22-1 and 22-2 are still assigned to the Slots 1 and 4, the XGP terminal 24 is not assigned to the empty PRU existing in the 2.5 GHz band of the Slots 1 and 4. .

  In contrast, when the dual base station 10 according to the present embodiment receives a new connection request from the XGP terminal 24 in the state illustrated in FIG. 3, the PHS is communicating with the dual base station 10 as illustrated in FIG. 5A. A handover is instructed to one of the terminals 22. When the PHS terminal 22 succeeds in the handover, the dual base station 10, as shown in FIG. 5B, at least one PRU (here, XGP5) belonging to the slot (here, Slot 1) released by the handover. The XGP terminal 24 is assigned to the notation.

  As described above, in response to a new connection request from the XGP terminal 24, the dual base station 10 transmits any of the PHS terminals 22 communicating with the dual base station 10 to the PHS base station 12 (or another dual base station). 10), the XGP terminal 24 is assigned to the slot released by the handover. In this way, the dual base station 10 suppresses a decrease in frequency utilization efficiency due to the correspondence to both PHS and XGP having different slot allocation methods.

  Below, the structure with which the dual base station 10 is provided in order to implement | achieve the said process is demonstrated.

  FIG. 6 is a functional block diagram of the dual base station 10. As shown in the figure, the dual base station 10 includes an antenna 30, a radio communication unit 32, a PHS processing unit 34, an XGP processing unit 36, a storage unit 38, and a control unit 40 (frequency utilization efficiency acquisition unit 42, handover instruction unit). 44 and a slot allocation unit 46).

  The antenna 30 receives a radio signal and outputs the received radio signal to the radio communication unit 32. Further, the antenna 30 transmits a radio signal supplied from the radio communication unit 32 to the PHS terminal 22 or the XGP terminal 24.

  The wireless communication unit 32 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 32 amplifies the radio signal input from the antenna 30 with a low noise amplifier, down-converts it to an intermediate frequency signal, and then outputs the digitally converted signal to the PHS processing unit 34 or the XGP processing unit 36 To do. The radio communication unit 32 converts the digital signal input from the PHS processing unit 34 or the XGP processing unit 36 into an analog signal, then up-converts the signal to a radio signal, amplifies it to a transmission output level with a power amplifier, and then transmits the antenna 30. To supply.

  Note that either the PHS terminal 22 or the XGP terminal 24 assigns the output destination of the digital signal output from the wireless communication unit 32 and the input source of the digital signal input to the wireless communication unit 32 to the slot where the signal is transmitted and received. It is switched according to whether it is done.

  The PHS processing unit 34 is configured by, for example, a DSP (Digital Signal Processor) and a program for controlling the operation of the DSP, and performs signal processing according to the PHS protocol on an input signal in accordance with an instruction from the control unit 40. That is, the PHS processing unit 34 performs signal processing such as demodulation and decoding according to the PHS protocol on the digital signal input from the wireless communication unit 32, and outputs the obtained reception data to the control unit 40. In addition, the PHS processing unit 34 performs signal processing such as modulation according to the PHS protocol on the transmission data input from the control unit 40, and outputs the obtained digital signal to the wireless communication unit 32.

  The XGP processing unit 36 is constituted by, for example, a DSP and a program for controlling the operation of the DSP, and performs signal processing according to the XGP protocol on the input signal in accordance with an instruction from the control unit 40. That is, the XGP processing unit 36 performs signal processing such as demodulation (including fast Fourier transform) and decoding according to the XGP protocol on the digital signal input from the wireless communication unit 32, and controls the obtained reception data. To the unit 40. Further, the XGP processing unit 36 performs signal processing such as modulation (including inverse fast Fourier transform) according to the XGP protocol on the transmission data input from the control unit 40, and the obtained digital signal is transmitted to the wireless communication unit. 32.

  The storage unit 38 is composed of, for example, a semiconductor memory element, and stores various control programs, parameters, tables, and the like used by the control unit 40. For example, the storage unit 38 includes a call management table for managing the allocation of slots and PRUs, PHS terminal capacity (0 to 4) and frequency utilization efficiency (here, so that the frequency utilization efficiency decreases as the PHS terminal capacity increases). Then, a frequency use efficiency table (see FIG. 7) and the like associated with 4 to 0) are stored.

  The control unit 40 includes, for example, a CPU (Central Processing Unit) and a program for controlling the operation of the CPU, and controls each unit of the dual base station 10. In particular, the control unit 40 functionally includes a frequency utilization efficiency acquisition unit 42, a handover instruction unit 44, and a slot allocation unit 46, and controls allocation of the PHS terminal 22 or the XGP terminal 24 to each of the four slots.

  The frequency usage efficiency acquisition unit 42 acquires the frequency usage efficiency of the dual base station 10. In the present embodiment, the frequency usage efficiency acquisition unit 42 acquires the frequency usage efficiency based on the number of PHS terminals 22 communicating with the dual base station 10 (the number of PHS terminals accommodated). Specifically, the frequency usage efficiency acquisition unit 42 selects the frequency usage efficiency from the frequency usage efficiency table based on the number of PHS terminals accommodated in the dual base station 10, and uses the selected frequency usage efficiency as the frequency of the dual base station 10. Obtained as usage efficiency.

  Note that the frequency usage efficiency acquisition unit 42 may calculate the frequency usage efficiency of the dual base station 10 based on the number of PHS terminals accommodated in the dual base station 10 without depending on the frequency usage efficiency table. The frequency utilization efficiency of the dual base station 10 may be calculated based on the amount of data transmitted / received by.

  In response to a new connection request from the XGP terminal 24, the handover instruction unit 44 instructs a handover to one of the PHS terminals 22 communicating with the dual base station 10. However, in this embodiment, even when the dual base station 10 receives a new connection request from the XGP terminal 24, if the frequency utilization efficiency of the dual base station 10 is equal to or higher than a predetermined threshold, the handover instruction unit 44 It is assumed that no handover is instructed to any of the terminals 22. That is, only when there is a new connection request from the XGP terminal 24 and the frequency usage efficiency of the dual base station 10 acquired by the frequency usage efficiency acquisition unit 42 falls below a predetermined threshold, the dual base station 10 One of the PHS terminals 22 communicating with the base station 10 is handed over to the PHS base station 12 or another dual base station 10.

  For example, if “3” is set as the predetermined threshold, the frequency utilization efficiency of the dual base station 10 is less than 3, that is, the PHS terminal accommodation number of the dual base station 10 is 2 or more (4 Only when two or more of the slots are occupied by the PHS terminal 22 (see FIG. 7), the dual base station 10 is connected to any of the PHS terminals 22 communicating with the dual base station 10. Since the handover is instructed, the frequency at which the handover instruction is issued to the PHS terminal 22 becomes more appropriate.

  The slot allocation unit 46 controls allocation of the PHS terminal 22 or the XGP terminal 24 to each of the four slots. In particular, in response to a new connection request from the XGP terminal 24, the handover instruction unit 44 instructs the handover to one of the PHS terminals 22 communicating with the dual base station 10, and when the handover is successful, the slot allocation unit 46 Assigns an XGP terminal 24 for a new connection to at least one PRU belonging to the slot released by the handover of the PHS terminal 22.

  The slot allocation unit 46 updates the call management table stored in the storage unit 38 every time the allocation of the PHS terminal 22 or the XGP terminal 24 to each of the four slots is changed.

  FIG. 8 shows a control unit 40 (frequency utilization efficiency acquisition unit 42, handover instruction unit 44, slot allocation unit) when the dual base station 10 receives an LCH (Link Channel) allocation request (new connection request) from the XGP terminal 24. FIG. 46 is a flowchart showing an example of slot allocation processing executed by 46).

  As shown in the figure, first, the control unit 40 confirms whether or not the dual base station 10 is communicating with the PHS terminal 22 (S100). Here, if the dual base station 10 is communicating with the PHS terminal 22 (S100: Y), the dual base station 10 is based on the number of PHS terminals 22 communicating with the dual base station 10 (PHS terminal accommodating number). Frequency utilization efficiency is acquired, and it is determined whether or not the acquired frequency utilization efficiency is equal to or greater than a predetermined threshold (S102).

  When the frequency utilization efficiency of the dual base station 10 is below a predetermined threshold (S102: N), the control unit 40 is configured so that a handover instruction is transmitted to any of the PHS terminals 22 communicating with the dual base station 10. A handover instruction message is generated, and the generated handover instruction message is output to the PHS processing unit 34 (S104). Thereafter, when the PHS terminal 22 instructing the handover succeeds in the handover (S106: Y), the control unit 40 releases the slot used by the PHS terminal 22 and releases it to the XGP terminal 24 that requests a new connection. An LCH allocation response designating any PRU belonging to the designated slot is transmitted (S108).

  On the other hand, when the dual base station 10 is not communicating with the PHS terminal 22 (S100: N), the dual base station 10 is communicating with the PHS terminal 22, but the frequency utilization efficiency of the dual base station 10 is equal to or higher than a predetermined threshold. In some cases (S102: Y), or when the PHS terminal 22 instructing handover in S104 fails in handover (S106: N), the control unit 40 is used for the XGP terminal 24 communicating with the dual base station 10. It is determined whether there is any releasable PRU (S110). Here, when there is a releasable PRU (S110: Y), the control unit 40 releases any releasable PRU used by the XGP terminal 24 communicating with the dual base station 10 (S112). Then, an LCH allocation response designating the released PRU is transmitted to the XGP terminal 24 seeking a new connection (S108).

  In S110, if there is no releasable PRU used for the XGP terminal 24 in communication with the dual base station 10 (S110: N), the control unit 40 determines the LCH for the XGP terminal 24 that requests a new connection. The allocation is rejected (S114).

  FIG. 9 shows the dual base station 10, the XGP terminal 24, and the PHS terminal 22 in communication with the dual base station 10 when the dual base station 10 receives an LCH Assignment Request from the XGP terminal 24. 2 is a sequence diagram illustrating an example of slot allocation processing performed between the PHS base station 12 located in the vicinity of the dual base station 10.

  As shown in the figure, when the dual base station 10 receives the LCH allocation request from the XGP terminal 24 (S200), the dual base station 10 performs the determinations of S100 and S102 shown in FIG. Here, when the frequency utilization efficiency of the dual base station 10 falls below a predetermined threshold, the dual base station 10 transmits a handover instruction (HO Indication) to any of the PHS terminals 22 communicating with the dual base station 10. (S202).

  The PHS terminal 22 that has received the handover instruction from the dual base station 10 receives the search results of the surrounding PHS base stations 12 acquired so far (the reception level of the notification signal periodically transmitted from each PHS base station 12). Etc.), the PHS base station 12 (which may be another dual base station 10) to be a handover destination is determined. Next, the PHS terminal 22 transmits a link establishment request (Link Establishment Request) to the PHS base station 12 determined as the handover destination (S204).

  Thereafter, when the PHS terminal 22 receives a link establishment assignment from the PHS base station 12 (S206), the PHS terminal 22 requests the dual base station 10 to disconnect the radio connection (Disconnect) ( S208).

  The dual base station 10 requested to disconnect the wireless connection from the PHS terminal 22 releases the slot used by the PHS terminal 22 and the slot released to the XGP terminal 24 that transmitted the LCH allocation request in S200. An LCH assignment response (LCH Assignment Response) designating any PRU belonging to is transmitted (S210).

  According to the embodiment described above, in response to a new connection request from the XGP terminal 24, the dual base station 10 connects any of the PHS terminals 22 communicating with the dual base station 10 to the surrounding PHS base stations 12. (Or another dual base station 10) is handed over, and the XGP terminal 24 is assigned to the slot released by the handover. For this reason, the dual base station 10 can suppress a decrease in frequency utilization efficiency due to the correspondence to both PHS and XGP having different slot allocation methods.

  The present invention is not limited to the above embodiment.

  For example, in the above description, an example in which the dual base station 10 determines whether or not to issue a handover instruction to the PHS terminal 22 based on the frequency usage efficiency has been described. Irrespective of this, the PHS terminal 22 may be instructed to perform handover, or it may be determined whether or not to issue a handover instruction based on other parameters that change according to the propagation path environment.

  In the above-described embodiment, an example in which the dual base station 10 issues a handover instruction to the PHS terminal 22 in response to a new connection request from the XGP terminal 24 is shown. However, the dual base station 10 receives the PRU ( A handover instruction may be issued to the PHS terminal 22 in response to an allocation addition request for (radio resource).

  Of course, the present invention is not limited to base stations that support both PHS and XGP, but can be widely applied to all base stations that support two mobile communication systems with different slot allocation methods.

  10 dual base stations, 12 PHS base stations, 14 XGP base stations, 22 PHS terminals, 24 XGP terminals, 30 antennas, 32 radio communication units, 34 PHS processing units, 36 XGP processing units, 38 storage units, 40 control units, 42 Frequency utilization efficiency acquisition unit, 44 handover instruction unit, 46 slot allocation unit.

Claims (7)

One of the first mobile station devices corresponding to the first mobile communication system or the second mobile station corresponding to the second mobile communication system using one of the plurality of slots included in the predetermined time period A base station device that communicates with one or more of the devices,
In response to a request from the second mobile station device, handover instruction means for handing over the first mobile station device communicating with the base station device to another base station device;
Means for allocating the second mobile station device to a slot released by a handover of the first mobile station device;
A base station apparatus comprising: The base station apparatus according to claim 1,
It further includes a frequency use efficiency acquisition means for acquiring the frequency use efficiency of the base station device,
The handover instructing means causes the first mobile station apparatus to be handed over to the other base station apparatus when the frequency utilization efficiency falls below a predetermined threshold;
A base station apparatus. The base station apparatus according to claim 2,
The frequency utilization efficiency is determined based on the number of first mobile station devices communicating with the base station device.
A base station apparatus. The base station apparatus according to claim 2,
The frequency utilization efficiency is determined based on the amount of data transmitted and received by the base station device,
A base station apparatus. In the base station apparatus in any one of Claim 1 to 4,
The request from the second mobile station device is a new connection request.
A base station apparatus. In the base station apparatus in any one of Claim 1 to 4,
The request from the second mobile station apparatus is a radio resource allocation addition request.
A base station apparatus. One of the first mobile station devices corresponding to the first mobile communication system or the second mobile station corresponding to the second mobile communication system using one of the plurality of slots included in the predetermined time period A slot allocation method for a base station device communicating with one or more of the devices, comprising:
In response to a request from a second mobile station device, handing over the first mobile station device communicating with the base station device to another base station device;
Allocating the second mobile station device to a slot released by handover of the first mobile station device;
A slot allocation method comprising:

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