JP5330028B2 - Base station apparatus and channel allocation method - Google Patents

Description

  The present invention relates to a base station apparatus and a channel allocation method that allocate any one of a plurality of radio channels to a mobile station apparatus.

  A base station that performs carrier sense (interference wave measurement) on a plurality of radio channels and assigns a radio channel with as little interference as possible to a mobile station based on the result is known (see, for example, Patent Document 1). Specifically, one of the radio channels whose interference level (interference wave reception level) detected by the base station is less than a predetermined threshold is assigned to the mobile station.

JP 2008-72285 A

  In some mobile communication systems, in order to maintain the communication quality between the base station and the mobile station, the radio channel that the base station assigns to the mobile station according to the radio wave condition, traffic, etc. is changed appropriately during communication There is. However, in such a mobile communication system, when a base station assigns a radio channel based on the carrier sense result, a radio channel with less interference that is not used by any neighboring base station may not be assigned to the mobile station. .

  For example, in XGP (eXtended Global Platform: next-generation PHS), QS-MODE (high quality channel based on carrier sensing-mode) mainly used for bandwidth-guaranteed or low-delay type communication and mainly high-speed packet communication FM-MODE (Fast access channel based on MAP-Mode) is used. In QS-MODE, one of a plurality of radio channels called PRUs (Physical Resource Units) is assigned to a mobile station as a CRU (Circuit Switching Channel, control or communication) fixed in principle to PRU until the end of communication. On the other hand, in FM-MODE, one PRU is in principle PRU-fixed ANCH (Anchor Channel, for control) until communication is completed, and one or more PRUs are PRU-variable EXCH (Extra Channel, for control or communication) during communication. , Each of which is assigned to a mobile station. Since EXCH is PRU variable unlike CSCH and ANCH, PRU assigned to the mobile station as EXCH in the previous frame is released in the next frame and is used as an empty PRU that is not used by any base station. Sometimes.

  Even in this XGP, the base station assigns PRUs based on the carrier sense result. By estimating whether or not the PRU is used by the neighboring base station based on the interference level detected in each PRU, and assigning only the PRU estimated not to be used to the mobile station, the base station This is because it becomes possible to prevent interference with neighboring base stations.

  However, in the conventional carrier sense, although it is possible to estimate whether or not the PRU that is the previous frame is used in the neighboring base station, the PRU is a CSCH (fixed channel) of QS-MODE and FM-MODE. It cannot be determined whether the channel is used as ANCH (fixed channel) or FM-MODE EXCH (variable channel). For this reason, the base station must determine uniformly that the PRU is the PRU used for the neighboring base station even in the next frame. Then, even if the PRU is used as an EXCH and is a PRU that is released in the next frame due to an assignment change, the PRU is excluded from the assignment target to the mobile station.

  As described above, in the conventional mobile communication system, a radio channel with less interference that is not used by any neighboring base stations may not be allocated to the mobile station, and radio resources are effectively used. hard.

  An object of this invention is to provide the base station apparatus and channel allocation method which can utilize a radio | wireless resource effectively.

  In order to solve the above problems, a base station apparatus according to the present invention is a base station apparatus that allocates one of a plurality of radio channels to a mobile station apparatus, and detects a level of interference of each of the plurality of radio channels. A channel allocating unit that determines whether the radio channel can be allocated to the mobile station apparatus according to a type of interference wave in the radio channel in which an interference level equal to or greater than a predetermined threshold is detected by the carrier sensing unit; It is characterized by including.

  According to the present invention, the base station apparatus does not determine that a radio channel in which an interference level equal to or greater than a predetermined threshold is detected by carrier sense cannot be uniformly assigned to the mobile station apparatus. Whether to assign to the mobile station apparatus is determined according to the type of wave. For this reason, a radio channel that has not been allocated in the past even though it is usable can be allocated to the mobile station apparatus, and radio resources can be effectively utilized.

  Further, according to one aspect of the present invention, it further includes variable channel determination means for determining whether or not the interference wave is a signal related to a variable channel, and the channel allocation means includes interference equal to or greater than the threshold by the carrier sense means. When the interference wave in the radio channel whose level is detected is a signal related to the variable channel, it is determined that the radio channel can be assigned to the mobile station apparatus.

  According to this aspect, even if the interference channel is a radio channel in which an interference wave equal to or greater than the threshold is detected, if the interference wave is a signal related to a variable channel (a signal whose channel assignment can be appropriately changed during communication), the mobile station It becomes possible to assign to a device.

  In this aspect, the variable channel discrimination means is a signal related to the variable channel when the interference wave includes variable channel identification information indicating that the signal is related to the variable channel. May be determined.

  In addition, when the variable channel identification information includes a predetermined training symbol pattern, the variable channel discrimination unit calculates a correlation between the interference wave and the training symbol pattern, and based on the calculation result, the interference wave It may be determined whether or not is a signal related to the variable channel.

  Further, in one aspect of the present invention, the channel allocating unit determines that the radio channel whose interference level is less than the threshold value can be allocated in the determination when the radio channel cannot be allocated to the mobile station device. Is assigned to the mobile station apparatus.

  According to this aspect, the radio channel with the interference level less than the threshold is assigned to the mobile station apparatus with priority over the radio channel with the interference level greater than or equal to the threshold.

  Further, the channel allocation method according to the present invention includes a mobile station apparatus that detects an interference level of each of a plurality of radio channels and a type of interference wave in the radio channel in which an interference level equal to or greater than a predetermined threshold is detected. And determining whether or not the radio channel can be assigned to the mobile station apparatus, and allocating any of the radio channels determined to be assignable in the determination to the mobile station apparatus.

It is a figure which shows the structure of the mobile communication system which concerns on embodiment of this invention. It is a figure which shows an example of the channel structure which concerns on embodiment of this invention. It is a figure which shows an example of channel allocation. It is a functional block diagram of the base station which concerns on embodiment of this invention. It is a figure which shows an example of the carrier sense result memorize | stored in a memory | storage part. It is a flowchart which shows the carrier sense process which concerns on embodiment of this invention. It is a flowchart which shows the channel 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 showing a configuration of a mobile communication system 10 according to an embodiment of the present invention. As shown in the figure, the mobile communication system 10 includes a plurality of base stations 12 (only the base stations 12-1 and 12-2 are shown here) and a plurality of mobile stations 14 (here, the mobile stations 14-1 to 14-1). 14-5 only).

  The base station 12 uses the OFDMA (Orthogonal Frequency Division Multiple Access) method and the TDMA / TDD (Time Division Multiple Access / Time Division Duplex) method to cover area 16. Multiple communication is performed with a plurality of mobile stations 14 located in the network.

  In the mobile communication system 10, as shown in FIG. 2, half of one TDMA frame (5 ms) defined in the time direction is allocated to each of the uplink and the downlink, and half of the TDMA frame further includes four times. Divided equally into slots. In the frequency direction, 18 subchannels based on OFDMA are defined. The minimum unit of the radio channel is called PRU and belongs to one of the time slots (Slot1 to Slot4) and one of the subchannels (Sch1 to Sch18). Each of the 72 PRUs is defined to be identified by one of consecutive PRU numbers (PRU1, PRU2, PRU3,..., PRU72) starting from 1.

  As shown in FIG. 2, among these 72 PRUs, four PRUs (PRU1 to PRU4) belonging to the subchannel Sch1 are CCH (Common Channel) shared by one or more mobile stations 14. Used as On the other hand, the remaining 68 PRUs (PRU5 to PRU72) are used as ICH (Individual Channel) individually assigned to each mobile station 14.

  The base station 12 assigns at least one PRU to be assigned to the mobile station 14 out of 68 PRUs (ICH) based on the carrier sense result obtained so far for each 1 TDMA frame from the start of communication with the mobile station 14. Determine and communicate with the mobile station 14 via the PRU.

  In the mobile communication system 10, as in the above-described XGP (next generation PHS), QS-MODE mainly used for bandwidth-guaranteed or low-delay type communication and FM- mainly used for high-speed packet communication. MODE is specified. In QS-MODE, one of the 68 PRUs (ICH) is assigned to the mobile station 14 as a PSCH-fixed CSCH in principle until the end of communication. On the other hand, in FM-MODE, one PRU (ICH) moves as a PRU-fixed ANCH (for control) and one or more PRUs (ICH) as a PRU variable EXCH (for control or communication) until communication ends. Assigned to station 14.

  FIG. 3 is a diagram illustrating an example of channel assignment by the base station 12-2 to the mobile stations 14-3 to 14-5. In this example, one PRU is allocated as CSCH (CSCH3) to the mobile station 14-3 that performs communication by QS-MODE. On the other hand, one PRU is assigned as ANCH (ANCH4) and five PRUs are assigned as EXCH (EXCH4) to the mobile station 14-4 that performs communication by FM-MODE. Further, one PRU is assigned as ANCH (ANCH5) and three PRUs are assigned as EXCH (EXCH5) to the mobile station 14-5 that performs communication by FM-MODE.

  As described above, unlike the CSCH and ANCH, the channel assignment may be changed during communication in the EXCH. Therefore, the PRU assigned to the mobile station 14 as the EXCH in the previous frame is released in the next frame and is free. Sometimes it becomes a PRU. For this reason, in the example shown in FIG. 3, until the mobile stations 14-3 to 14-5 end the communication with the base station 12-2, the PRU allocation of the CSCH 3, ANCH 4, and ANCH 5 is not changed in principle, but the EXCH 4 and the EXCH 5 The PRU allocation may be changed as appropriate according to the radio wave condition, traffic, and the like.

  Therefore, the base station 12 according to the present embodiment does not determine that a PRU in which an interference level equal to or higher than a predetermined threshold is detected by carrier sense cannot be uniformly assigned to the mobile station 14, but does not determine an interference wave in the PRU. Whether to assign to the mobile station 14 is determined according to the type of the mobile station 14.

  For example, when the base station 12-1 (see FIG. 1) arranged around the base station 12-2 determines a PRU to be allocated to the mobile station 14-1, the base station 12-2 or its base station is determined in a certain PRU. Even if radio signals transmitted from the mobile stations 14-3 to 14-5 that communicate with 12-2 are detected as interference waves, the detected interference waves are signals related to PRU variable EXCH (variable channel). If there is, it is determined that the PRU can be assigned to the mobile station 14-1.

  For this reason, in the mobile communication system 10, PRUs that have been used but have not been assigned in the past can be assigned to the mobile station 14, and radio resources can be effectively utilized.

  Below, the structure with which the base station 12 is provided in order to implement | achieve the said process is demonstrated.

  FIG. 4 is a functional block diagram of the base station 12. As shown in the figure, the base station 12 includes an antenna 20, a radio module 30 (a radio communication unit 32, a baseband unit 34), a reception unit 40 (a reception level calculation unit 42, a correlation calculation unit 44), a transmission unit 50, The wireless control unit 60 (carrier sense control unit 62, channel allocation unit 64) and a storage unit 70 made of, for example, a semiconductor memory element are included.

  The antenna 20 receives a radio signal and outputs the received radio signal to the radio module 30. Further, the antenna 20 transmits a radio signal supplied from the radio module 30 to the mobile station 14.

  The radio module 30 includes a radio communication unit 32 and a baseband unit 34, and performs various conversions related to radio signals transmitted and received by the antenna 20.

  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 20 with a low noise amplifier, down-converts it to an intermediate frequency signal, and outputs the digitally converted signal to the baseband unit 34. Further, the radio communication unit 32 converts the digital signal input from the baseband unit 34 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 supplies the signal to the antenna 20. .

  The baseband unit 34 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 34 performs GI (Guard Interval) removal, serial parallel conversion, discrete Fourier transform, and the like on the digital signal input from the wireless communication unit 32, and subcarrier components of the obtained complex symbol sequence are subtracted. After concatenating for each channel, the complex symbol sequence concatenated for each subchannel is output to receiving section 40. Further, the baseband unit 34 is obtained by subjecting the complex symbol sequence divided for each mobile station 14 input from the transmission unit 50 to serial-parallel conversion, inverse discrete Fourier transform, parallel-serial conversion, addition of GI, and the like. The digital signal is output to the wireless communication unit 32.

  The receiving unit 40 further concatenates the complex symbol sequences connected for each sub-channel input from the radio module 30 for each mobile station 14, and from the complex symbol sequences concatenated for each mobile station 14 according to the symbol modulation scheme. After the received data is decoded, the decoded received data is output to the radio control unit 60. The receiving unit 40 includes a reception level calculating unit 42 and a correlation calculating unit 44, and performs processing related to carrier sense in accordance with instructions from the carrier sense control unit 62.

  The reception level calculation unit 42 calculates the reception level of each PRU based on the complex symbol sequence connected for each subchannel input from the wireless module 30. Here, the reception level of the PRU that is not assigned to any mobile station 14 by the own station (base station 12) is stored in the storage unit 70 in association with the PRU number as an interference level (interference wave reception level). (See FIG. 5). Note that PRU1 to PRU4 used as CCH may be excluded from reception level calculation targets.

  The correlation calculation unit 44, based on the complex symbol sequence connected for each subchannel input from the wireless module 30, detects a radio signal (interference wave) detected by the PRU that is not assigned to any mobile station 14 by the own station. ) Is a signal related to EXCH (variable channel). In the mobile communication system 10, it is specified that a signal related to EXCH includes a predetermined training symbol pattern indicating the signal. Therefore, the correlation calculation unit 44 calculates the correlation between the interference wave and the lane symbol pattern, and determines whether the interference wave is a signal related to EXCH based on the calculation result. Specifically, if the obtained correlation is equal to or greater than a predetermined value, the interference wave is a signal related to EXCH, that is, the PRU in which the interference wave is detected is used as an EXCH by neighboring base stations. Determined. It should be noted that a discrimination method different from the correlation calculation based on the training symbol pattern may be adopted for discrimination of the detected interference wave type.

  The result of determination by the correlation calculation unit 44 is stored in the storage unit 70. Specifically, as shown in FIG. 5, in association with the PRU number of the PRU where the interference wave is detected, flag information indicating whether or not the PRU is used as an EXCH by the neighboring base stations (for example, 0: Unknown, 1: used as EXCH) is stored in the storage unit 70.

  The transmission unit 50 performs symbol mapping (assignment of amplitude and phase) according to the modulation method specified by the radio control unit 60 on the transmission data to each mobile station 14 input from the radio control unit 60, The complex symbol sequence divided for each mobile station 14 is output to the radio module 30.

  The radio control unit 60 is constituted by, for example, a CPU and a program for controlling the operation of the CPU, and controls each unit of the base station 12. In particular, the radio control unit 60 functionally includes a carrier sense control unit 62 and a channel allocation unit 64, and performs carrier sense control, PRU allocation to the mobile station 14, and the like.

  The carrier sense control unit 62 controls the wireless module 30 and the reception unit 40 (reception level calculation unit 42, correlation calculation unit 44) in order to perform carrier sense.

  FIG. 6 is a diagram illustrating a carrier sense process started by an instruction from the carrier sense control unit 62. As shown in the figure, the reception level calculation unit 42 detects the interference level of each PRU that is not assigned to any mobile station 14 (S100).

  Next, the carrier sense control unit 62 determines whether or not the interference level is less than a predetermined threshold for each PRU (S102), and for PRUs whose interference level is less than the threshold (S102: Y), The interference level and flag information “0” are stored in the storage unit 70 in association with the PRU number (S104).

  On the other hand, for the PRU having the interference level equal to or higher than the threshold (S102: N), the carrier sense control unit 62 calculates the correlation between the interference wave detected by the PRU and the training symbol pattern for EXCH in the correlation calculation unit 44. (S106), it is determined whether or not the obtained correlation is a predetermined value or more (S108). Here, for a PRU having a correlation less than a predetermined value (S108: N), since it is estimated that the neighboring base station is a PRU that is not used as an EXCH, the carrier sense control unit 62 associates with the PRU number. Then, the interference level and the flag information “0” are stored in the storage unit 70 (S104). On the other hand, for a PRU having a correlation greater than or equal to a predetermined value (S108: Y), it is estimated that the neighboring base station is a PRU used as an EXCH. Therefore, the carrier sense control unit 62 sets the PRU number to The interference level and flag information “1 (used as EXCH)” are stored in the storage unit 70 in association with each other (S110).

  As described above, in the base station 12, in addition to the conventional carrier sense result, flag information indicating whether or not the PRU in which the interference wave is detected is the PRU used as the EXCH in the neighboring base station is recorded. (See FIG. 5).

  The channel allocation unit 64 allocates at least one of 68 PRUs (ICH) to the mobile station 14 for each frame from the start of communication with the mobile station 14 based on the carrier sense result acquired as described above.

  FIG. 7 is a flowchart showing channel allocation processing by the channel allocation unit 64. As shown in the figure, the channel allocation unit 64 refers to the carrier sense result stored in the storage unit 70 and is not allocated by itself (not allocated by the channel allocation unit 64) and has an interference level. It is determined whether there is a PRU that is less than a predetermined threshold (S200). Here, if there is a PRU that satisfies this condition (S200: Y), the channel allocation unit 64 allocates one of the PRUs to the mobile station 14 (S202).

  On the other hand, if there is no PRU that satisfies this condition (S200: N), the channel allocating unit 64 refers to the carrier sense result stored in the storage unit 70, and is not allocated by the own station and is the interference level as EXCH. Is stored (flag information is “1”) or not (S204). Here, if there is a PRU that satisfies this condition (S204: Y), the channel allocation unit 64 allocates one of the PRUs to the mobile station 14 (S206). On the other hand, if there is no PRU that satisfies this condition (S204: N), the channel allocation unit 64 determines that there is no PRU that can be allocated to the mobile station 14, and does not allocate a PRU.

  As described above, the channel allocating unit 64 allocates the PRU that is used as the EXCH to the neighboring base station and has the interference level equal to or higher than the threshold only when there is no PRU whose interference level is less than the threshold. I have to.

  According to the embodiment described above, the base station 12 does not determine that a PRU in which an interference level equal to or greater than a predetermined threshold is detected by carrier sense cannot be uniformly assigned to the mobile station 14, but the PRU Whether to assign to the mobile station 14 is determined according to whether or not the peripheral base station is used as EXCH (variable channel). For this reason, PRUs that have not been allocated in the past even though they can be used can be allocated to the mobile station 14, and radio resources can be effectively utilized.

  The present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, an example in which the present invention is applied to the base station 12 that performs multiplex communication with a plurality of mobile stations 14 using the OFDMA scheme and the TDMA / TDD scheme has been described. : A base station that employs a frequency division multiple access) system, and can be widely applied to all base stations that allocate one of a plurality of radio channels to mobile station apparatuses.

  DESCRIPTION OF SYMBOLS 10 Mobile communication system, 12 Base station, 14 Mobile station, 16 Cover area, 20 Antenna, 30 Wireless module, 32 Wireless communication part, 34 Baseband part, 40 Reception part, 42 Reception level calculation part, 44 Correlation calculation part, 50 Transmission unit, 60 radio control unit, 62 carrier sense control unit, 64 channel allocation unit, 70 storage unit.

Claims (4)

A base station device that assigns one of a plurality of radio channels to a mobile station device,
Carrier sense means for detecting an interference level of each of the plurality of radio channels;
Channel allocating means for determining whether or not the radio channel can be allocated to the mobile station device according to the type of interference wave in the radio channel in which an interference level equal to or higher than a predetermined threshold is detected by the carrier sensing means;
Variable channel discriminating means for discriminating whether or not the interference wave is a signal related to a variable channel;
Only including,
The channel allocating unit allocates the radio channel to the mobile station apparatus when an interference wave in the radio channel in which an interference level equal to or greater than the threshold is detected by the carrier sense unit is a signal related to the variable channel. Judge that it is possible,
The base station apparatus according to claim and this. The base station apparatus according to claim 1 ,
The variable channel discriminating unit discriminates that the interference wave is a signal related to the variable channel when variable channel identification information indicating that the signal is related to the variable channel is included in the interference wave.
A base station apparatus. The base station apparatus according to claim 2 ,
The variable channel identification information includes a predetermined training symbol pattern,
The variable channel determination means calculates a correlation between the interference wave and the training symbol pattern, and determines whether the interference wave is a signal related to the variable channel based on a result of the calculation.
A base station apparatus. A carrier sense step for detecting an interference level of each of a plurality of radio channels;
A channel assignment determination step of determining whether or not to assign the radio channel to the mobile station apparatus according to the type of interference wave in the radio channel in which an interference level equal to or greater than a predetermined threshold is detected;
A channel allocation step of allocating to the mobile station device any of the radio channels determined to be allocated in the determination;
A variable channel determining step for determining whether or not the interference wave is a signal related to a variable channel;
Only including,
When an interference wave in a radio channel in which an interference level equal to or higher than the threshold is detected in the carrier sense step is a signal related to the variable channel, in the channel assignment determination step, the radio channel is transmitted to the mobile station apparatus. Judge that allocation is possible,
Channel allocation method comprising the this.

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