JP5066071B2 - Base station apparatus and control method for base station apparatus - Google Patents

Description

  The present invention relates to a base station apparatus and a control method for the base station apparatus.

  In a wireless communication system including a plurality of base station devices and a plurality of mobile station devices, a communication channel that is a communication path is set in a predetermined frequency band used by the base station device and the mobile station device, respectively. Use to communicate.

  Among such wireless communication systems, in wireless communication systems that perform autonomous distributed communication channel assignment, the mobile station apparatus measures the interference wave level called carrier sense for the communication channel to be used when assigning communication channels. The communication channel having the interference wave level equal to or lower than a predetermined value is selected and notified to the base station apparatus to determine the allocation of the communication channel used by the base station apparatus.

  This is to prevent communication on the communication channel because the communication quality may deteriorate when the interference wave level of the communication channel to be used is large. As a result, the user can communicate with a certain amount of throughput and QoS (Quality of Service) guaranteed.

In Patent Document 1, the number of times of performing carrier sense is reduced by setting a threshold based on the presence / absence of a frequency band in which the interference wave level is lower than the carrier sense level (threshold) in the previous carrier sense and the past carrier sense level. The configuration to be shown is shown.
JP-A-8-322077

  FIG. 6A is a diagram illustrating a relationship between the interference wave level and the threshold when the interference wave level does not exceed the threshold. FIG. 6B is a diagram illustrating a relationship between the interference wave level and the threshold when the interference wave level exceeds the threshold.

  When the base station apparatus and the mobile station apparatus start communication, at least a part of the communication channel that can obtain the result shown in FIG. 6A is assigned to communication. A communication channel that obtains a result as shown in FIG. 6B is not assigned to communication.

  By the way, in recent years, a broadband wireless communication system called orthogonal frequency division multiple access (OFDMA) has attracted attention in order to transmit a large amount of information more efficiently.

  However, in such a broadband wireless communication system, since the usable frequency band per user is very wide, there is a possibility that communication channels used by a plurality of users communicating with adjacent base station apparatuses compete with each other. To be high. Therefore, when channel assignment based on carrier sense is performed, if user A who started communication is assigned many communication channels, one or a plurality of users B, C, D... It becomes difficult to acquire the number of communication channels for efficient communication.

  Thus, when autonomous distributed communication channel assignment is performed in a broadband wireless communication system, communication channel assignment to a plurality of users may not be performed properly. As a result, some users can perform efficient communication with guaranteed throughput and QoS, while other users may lose throughput and be unable to maintain QoS.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a base station apparatus that controls allocation of frequency bands (communication channels).

  The base station apparatus according to the present invention includes an interference wave level measurement unit that measures an interference wave level in a predetermined frequency band that can be used for a neighboring base station apparatus, and an interference wave level measured by the interference wave level measurement unit. Band allocation means for allocating a frequency band less than the threshold for communication with the mobile station apparatus, a value indicating the width of the frequency band allocated by the band allocation means, and the width of the target frequency band set in the base station apparatus And a threshold value determining means for determining the threshold value based on the indicated value.

  According to the present invention, by adjusting the value indicating the width of the target frequency band set in the base station apparatus, frequency band allocation performed in the base station apparatus is controlled. In each of the plurality of base station apparatuses, the frequency band (communication channel) distribution between the base station apparatuses is also controlled by appropriately setting a value indicating the target of the allocated frequency band width (number of communication channels). Is done.

  Further, in the base station apparatus according to the present invention, the predetermined frequency band includes a plurality of communication channels, and the interference wave level measuring unit measures an interference wave level in each of the plurality of communication channels, and the band The assigning means assigns a communication channel whose interference wave level is less than the threshold value to communication with the mobile station apparatus, and a value indicating the width of the target frequency band is the number of communication channels assigned by the band assigning means. The threshold value determining means determines the threshold value based on the number of communication channels allocated by the band allocating means and the target communication channel number.

  According to the present invention, by adjusting the target number of communication channels set in the base station apparatus, the allocation of communication channels included in the frequency band performed in the base station apparatus is controlled.

  Furthermore, in the base station apparatus according to the present invention, each of the plurality of communication channels includes any one of a plurality of subchannels included in the predetermined frequency band and any of a plurality of time slots included in a predetermined time period. , Is specified by.

  According to the present invention, by adjusting the target number of communication channels set in the base station apparatus, assignment of communication channels specified by the subchannel and time slot performed in the base station apparatus is controlled. The

  In the base station apparatus according to the present invention, the value indicating the width of the target frequency band is the same value as the value set in the adjacent base station apparatus.

  According to the present invention, the frequency bandwidth allocated in the base station apparatus according to the present invention is controlled to be equal to the frequency bandwidth allocated in the adjacent base station apparatus.

  In the base station apparatus according to the present invention, the value indicating the width of the target frequency band is determined based on a distribution target of the frequency band between the base station apparatus and the adjacent base station apparatus. .

  According to the present invention, the frequency bandwidth allocated in the base station apparatus according to the present invention is controlled such that the frequency band allocation between the base station apparatus and the adjacent base station apparatus approaches the allocation target. .

  The base station apparatus control method according to the present invention includes an interference wave level measurement step for measuring an interference wave level in a predetermined frequency band that can be used for a neighboring base station apparatus, and the interference wave level measurement step. A bandwidth allocation step for allocating a frequency band whose interference wave level is less than a threshold for communication with a mobile station device, a value indicating the width of the frequency band allocated in the bandwidth allocation step, and a target set in the base station device And a threshold value determining step for determining the threshold value based on a value indicating the width of the frequency band.

  A base station apparatus according to the present embodiment will be described. FIG. 1 is a diagram showing a configuration of base station apparatus 101 according to the present embodiment. When the base station apparatus 101 determines the start of communication with the mobile station apparatus, the base station apparatus 101 includes one of a plurality of subchannels included in a predetermined frequency band that can be used for a neighboring base station apparatus and a plurality of subchannels included in a predetermined time period. And at least one of a plurality of communication channels (PRU, Physical Resource Unit; physical resource unit, communication resource) specified by these time slots and assigns them to the communication.

  FIG. 5 is a diagram illustrating an example of a PRU. In FIG. 5, each of the areas defined by subchannels and time slots is a PRU.

  FIG. 2 is a diagram showing a communication system 201 including the base station apparatus 101 according to the present embodiment. In the communication system 201, the communicable range 207 of the base station apparatus 101 and the communicable range 206 of the adjacent base station apparatus 202 overlap, and the base station apparatuses 101 and 202 are included in a PRU included in a predetermined frequency region. Among these, the PRU that is not used by itself performs carrier sense for measuring the interference wave level, and at least one of the PRUs having the interference wave level smaller than the threshold is used for communication with any of the mobile station apparatuses 203, 204, and 205. assign.

  Base station apparatus 101 according to the present embodiment determines this threshold according to the number NRU of PRUs used by itself.

  The base station apparatus 101 includes a reception RF processing unit 102, a reception baseband signal processing unit 103, a PRU allocation control unit 104, a transmission baseband signal processing unit 105, a transmission RF processing unit 106, a memory 107, and an antenna 108. The reception baseband signal processing unit 103, the PRU allocation control unit 104, and the transmission baseband signal processing unit 105 are configured by, for example, a CPU or a DSP, and the reception RF processing unit 102 and the transmission RF processing unit 106 are configured by, for example, semiconductor circuits.

  The memory 107 stores data used in the base station apparatus 101, parameters for controlling the operation of the base station apparatus 101, and the like.

  The antenna 108 transmits a signal output from the transmission RF processing unit 106 as a radio wave. Further, the antenna 108 receives a signal transmitted from a mobile station apparatus that is a communication partner of the base station apparatus 101 and outputs the signal to the reception RF processing unit 102.

  Reception RF processing section 102 performs amplification processing and down-conversion processing on the signal input from antenna 108, and outputs the obtained signal to reception baseband signal processing section 103.

  The reception baseband signal processing unit 103 performs synchronization processing, AD conversion, demodulation processing, and the like on the signal input from the reception RF processing unit 102 to generate reception data.

  The transmission baseband signal processing unit 105 performs modulation processing, DA conversion, and the like on the transmission data transmitted by the base station apparatus 101, and outputs the obtained signal to the transmission RF processing unit 106. Here, in the modulation processing, modulation is performed on a signal corresponding to the PRU notified from the PRU allocation control unit 104 described later.

  The transmission RF processing unit 106 performs processing such as up-conversion on the signal input from the transmission baseband signal processing unit 105, and outputs the obtained signal to the antenna 108.

  When the base station apparatus 101 starts communication with the mobile station apparatus, the PRU allocation control unit 104 executes a PRU allocation operation that allocates a PRU used for the communication.

  The PRU allocation control unit 104 changes the threshold based on the number of PRUs NRU used by the base station apparatus 101. This will be described in detail below.

  The PRU allocation control unit 104 includes a default PRU allocation threshold setting unit 109, an operational PRU allocation threshold calculation unit 110, a PRU allocation unit 111, a target PRU number setting unit 112, a PRU number comparison unit 113, a PRU number counting unit 114, and carrier sense processing. Part 115.

  When the PRU allocation operation in the PRU allocation control unit 104 is started, the carrier sense processing unit 115 starts using the PRUs included in a predetermined frequency band from the signal before the demodulation process in the reception baseband signal processing unit 103. The carrier sense for measuring the interference wave level in the PRU that is not used by itself is performed, and the measurement result is output to the PRU allocation unit 111.

  The PRU allocating unit 111 refers to the measurement result input from the carrier sense processing unit 115, and selects at least one of the PRUs whose interference wave level is less than the PRU allocation threshold input from the operation PRU allocation threshold calculating unit 110 described later. Assigned to communication with the mobile station apparatus, and notifies the transmission baseband signal processing unit 105 of the assigned PRU.

  Further, the PRU allocation unit 111 outputs an allocation result notification indicating the allocation result to the PRU number counting unit 114 described later. Further, the PRU allocation unit 111 outputs an allocation stop notification to the PRU number counting unit 114 when communication using a certain PRU is completed.

  The default PRU allocation threshold setting unit 109 sets the initial value Td of the PRU allocation threshold at an arbitrary timing before starting the PRU allocation operation in the PRU allocation control unit 104. This Td is the same value as the value set in the adjacent base station apparatus 202.

  The target PRU number setting unit 112 sets a target PRU number NRUt that is a target of the number of PRUs allocated by the PRU allocation unit 111 at an arbitrary timing before the PRU allocation operation in the PRU allocation control unit 104 is started. This NRUt is the same value as the value set in the adjacent base station apparatus 202.

  The PRU count unit 114 counts the number of PRUs NRUc allocated by the PRU allocation unit 111. The PRU count section 114 counts the NRUc based on the allocation result notification and the allocation stop notification input from the PRU allocation section 111 and outputs the obtained NRUc to the PRU count comparison section 113.

The PRU number comparison unit 113 is a PRU that is a difference between the target PRU number NRUt set by the target PRU number setting unit 112 and the number NRUc of PRUs allocated by the PRU allocation unit 111 input from the PRU number counting unit 114. The number difference value NRUd is calculated, and the obtained NRUd is output to the operational PRU allocation threshold value calculation unit 110. NRUd is expressed by equation (1).
NRUd = NRUt−NRUc (1)

The operational PRU allocation threshold value calculation unit 110 calculates the PRU allocation threshold T based on the number of PRUs NRUc allocated by the PRU allocation unit 111 and the target number of PRUs NRUt that is the target of the number of PRUs allocated by the PRU allocation unit 111. Is calculated. The operational PRU allocation threshold calculation unit 110 uses the initial value Td of the PRU allocation threshold set by the default PRU allocation threshold setting unit 109 and the PRU number difference value NRUd input from the PRU number comparison unit 113 as follows: 2), the PRU allocation threshold T used in the PRU allocation control unit 104 is calculated. Here, α is a positive coefficient determined empirically from simulation or the like, and is stored in the memory 107.
T = Td + α × NRUd (2)

  From the equation (1), the PRU number difference value NRUd becomes smaller as the PRU number NRUc used is larger in a range not exceeding NRUt. Also, from equation (2), the PRU allocation threshold T decreases as NRUd decreases. That is, T decreases as NRUc increases. In other words, T increases as the number of PRUs used by the base station apparatus 101 increases, and the condition for newly allocating PRUs becomes stricter.

  FIG. 3 is a diagram illustrating a relationship between an interference wave level and a threshold (PRU allocation threshold) in a certain PRU. In the base station apparatus 101, the PRU allocation threshold decreases as the NRU increases. When the interference wave level as shown in FIG. 3 is measured, this PRU is assigned when NRU = 0 or NRU = 10, but is not assigned when NRU = 20. That is, as the NRU increases, the conditions for assigning the PRU become stricter.

  Next, calculation of the PRU allocation threshold T performed in the base station apparatus 101 will be described using a flowchart.

  FIG. 4 is a flowchart showing the calculation process of the PRU allocation threshold T performed in the base station apparatus 101. When the base station apparatus 101 determines to start communication with a mobile station apparatus, the calculation process of the PRU allocation threshold T is started.

  First, the PRU number comparison unit 113 acquires the number NRUc of PRUs currently used for communication by the base station apparatus 101 from the PRU number counting unit 114 (S401).

  Next, the PRU number comparison unit 113 is a difference between the target PRU number NRUt set by the target PRU number setting unit 112 and the number NRUc of PRUs used for communication by the base station apparatus 101 acquired in S401. A certain PRU number difference value NRUd is calculated (S402).

  The operation PRU allocation threshold calculation unit 110 then sets the initial value Td of the PRU allocation threshold set by the default PRU allocation threshold setting unit 109, α stored in the memory 107, and the PRU number difference value calculated in S402. A PRU allocation threshold T is calculated from NRUd (S403).

  Thus, the calculation process of the PRU allocation threshold T is completed, and PRU allocation is performed using the calculated PRU allocation threshold T.

  With the above configuration, by adjusting the target PRU number NRUt set in the base station apparatus 101, PRU allocation performed in the base station apparatus is controlled. Also, by setting NRUt to the same value as the value set in the adjacent base station apparatus 202, the number of PRUs allocated in the base station apparatus 101 is equal to the number of PRUs allocated in the adjacent base station apparatus 202. It is controlled to become.

  It is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the present embodiment, the configuration in which the PRU is allocated using the carrier sense result is shown, but the present invention is also applied to the base station apparatus that allocates the frequency band and the base station apparatus that allocates a plurality of communication channels included in the frequency band. The invention is applicable. In the base station apparatus to which the frequency band is allocated, the value indicating the width of the frequency band allocated for communication by the base station apparatus is used for calculating the PRU allocation threshold T instead of the number of PRUs allocated by the PRU allocation unit 111. Thus, a value indicating the width of the target frequency band is used instead of the target PRU number NRUt. In the base station apparatus that allocates a plurality of communication channels included in the frequency band, the PRU allocation threshold T is calculated in place of the number of PRUs allocated by the PRU allocation unit 111, instead of the communication channel allocated for communication by the base station apparatus. The target communication channel number is used instead of the target PRU number NRUt.

  Further, in the present embodiment, the target PRU number NRUt is configured to be the same as the value set in the adjacent base station apparatus 202, but a value different from that in the adjacent base station apparatus 202 may be set. In this case, the NRUt is determined based on, for example, a PRU allocation target between the base station apparatus 101 and the adjacent base station apparatus 202.

  Further, in the present embodiment, the initial value Td of the PRU allocation threshold is the same as the value set in the adjacent base station apparatus 202, but a value different from that in the adjacent base station apparatus 202 is set. Also good. In this case, Td is determined based on, for example, a PRU allocation target between the base station apparatus 101 and the adjacent base station apparatus 202.

  In the present embodiment, the PRU allocation threshold is calculated when the base station apparatus 101 determines the start of communication with the mobile station apparatus. However, the PRU allocation threshold may be periodically performed or the PRU may be periodically calculated. It is good also as a structure performed whenever a number changes.

It is a figure which shows the structure of the base station apparatus which concerns on embodiment of this invention. It is a figure which shows the communication system containing the base station apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship between an interference wave level and threshold value (PRU allocation threshold value) in a certain PRU. It is a flowchart which shows the calculation process of the PRU allocation threshold value T performed with the base station apparatus which concerns on embodiment of this invention. It is a figure which shows an example of PRU. It is a figure which shows the relationship between an interference wave level and a threshold value when an interference wave level does not exceed a threshold value. It is a figure which shows the relationship between an interference wave level and a threshold value when an interference wave level exceeds a threshold value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 Base station apparatus, 102 Reception RF processing part, 103 Reception baseband signal processing part, 104 PRU allocation control part, 105 Transmission baseband signal processing part, 106 Transmission RF processing part, 107 Memory, 108 Antenna, 109 Default PRU allocation threshold Setting unit, 110 operational PRU allocation threshold calculation unit, 111 PRU allocation unit, 112 target PRU number setting unit, 113 PRU number comparison unit, 114 PRU number counting unit, 115 carrier sense processing unit, 201 communication system, 202 base station device, 203 mobile station apparatus, 204 mobile station apparatus, 205 mobile station apparatus, 206 communicable range, 207 communicable range.

Claims (6)

Interference wave level measuring means for measuring an interference wave level in a predetermined frequency band that can be used in a neighboring base station apparatus;
Band allocating means for allocating a frequency band whose interference wave level measured by the interference wave level measuring means is less than a threshold to communication with a mobile station device;
Threshold determining means for determining the threshold based on a value indicating the width of the frequency band allocated by the band allocation means and a value indicating the width of the target frequency band set in the base station apparatus;
A base station apparatus comprising: The base station apparatus according to claim 1,
The predetermined frequency band includes a plurality of communication channels,
The interference wave level measuring means measures an interference wave level in each of the plurality of communication channels;
The band allocating unit allocates a communication channel in which the interference wave level is less than the threshold value for communication with the mobile station device,
The value indicating the width of the target frequency band is a target number of communication channels that is a target of the number of communication channels allocated by the band allocation unit,
The threshold determination means determines the threshold based on the number of communication channels allocated by the band allocation means and the target communication channel number;
A base station apparatus. The base station apparatus according to claim 2,
Each of the plurality of communication channels includes one of a plurality of subchannels included in the predetermined frequency band, and one of a plurality of time slots included in a predetermined time period.
Specified by
A base station apparatus. In the base station apparatus in any one of Claim 1 to 3,
The value indicating the width of the target frequency band is the same value as the value set in the adjacent base station device,
A base station apparatus. In the base station apparatus in any one of Claim 1 to 3,
The value indicating the width of the target frequency band is determined based on an allocation target of the frequency band between the base station apparatus and the adjacent base station apparatus.
A base station apparatus. An interference wave level measurement step of measuring an interference wave level in a predetermined frequency band that can be used by a neighboring base station device;
A bandwidth allocation step for allocating a frequency band in which the interference wave level measured in the interference wave level measurement step is less than a threshold to communication with a mobile station device;
A threshold value determining step for determining the threshold value based on a value indicating a width of a frequency band allocated in the band allocation step and a value indicating a width of a target frequency band set in the base station device;
A control method for a base station apparatus.

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