JP3891436B2 - Communication control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication control apparatus that assigns a radio channel to a call that occurs during communication between a base station and a mobile station that constitute a radio zone.
[0002]
[Prior art]
In a cellular mobile communication system that provides a communication service by arranging a large number of base stations and forming a service area by a radio zone constituted by each base station, for the purpose of effectively using a limited radio frequency band, The same wireless channel is repeatedly used in wireless zones that are separated from each other, so-called wireless channel is repeatedly reused (see, for example, Non-Patent Document 1). In general, the system capacity and the communication quality are considered to have a trade-off relationship. For this reason, when the distance between the radio zones where the same radio channel is used is short, the frequency utilization efficiency is improved, so that the system capacity can be expanded, but the communication quality is lowered. For this reason, the distance between the radio zones in which the same radio channel is used cannot be reduced without limitation.
[0003]
Methods for realizing repetitive reuse of radio channels while satisfying communication quality are broadly divided into fixed channel assignment methods and dynamic channel assignment methods. The fixed channel assignment method is a method in which a radio wave propagation environment and traffic distribution are derived by actual measurement or theoretical calculation, and a radio channel is fixedly assigned to each base station. On the other hand, in the dynamic channel allocation method, when a radio channel is allocated to a call that has been generated, the amount of interference such as a carrier-to-interference power ratio (CIR) is measured and a base station corresponding to the call is measured. This is a method for determining in a station that a radio channel having an interference amount of a predetermined value or less can be used.
[0004]
FIG. 1 is a flowchart of a conventional dynamic channel allocation method. A radio control station that performs communication control related to channel allocation receives a radio channel allocation request from the mobile station when a call is generated by the mobile station (step 501). Next, the radio control station searches for an unused radio channel (hereinafter referred to as “empty channel”) from all the radio channels, and selects any one of the empty channels (step 502).
[0005]
Further, the radio control station measures the CIR of the selected radio channel (step 503) and determines whether the CIR is equal to or less than a predetermined value (step 504). If the CIR is less than or equal to the predetermined value, the radio control station assigns the radio channel selected in step 502 to the call that has been made (step 505). On the other hand, when the CIR exceeds the predetermined value, the radio control station repeats the operations after the search and selection (step 502) of the empty channel again.
[0006]
This dynamic channel allocation method can allocate radio channels to some degree of flexibility with respect to traffic temporal variation, spatial bias, and the like. Furthermore, since an unused radio channel is shared by the entire system and any base station can use the unused radio channel, a so-called grouping effect can be obtained. For this reason, the dynamic channel allocation method is said to have better frequency utilization efficiency than the fixed channel allocation method.
[0007]
[Non-Patent Document 1]
Shuichi Sasaoka, “Mobile Communications” Ohmsha, May 12, 2000, p. 129-130
[0008]
[Problems to be solved by the invention]
However, according to the above-described conventional dynamic channel allocation method, when a radio channel is allocated to a call generated by a mobile station, there is another center between radio channels arranged so as not to overlap at a predetermined frequency interval. When so-called interleaved channel arrangement is adopted in which radio channels are arranged, the frequency band of the radio channel and other radio channels adjacent to the radio channel overlap, so that the influence of interference by the adjacent radio channel is affected. Arise. Furthermore, when the mobile station moves away from the communication partner base station, in particular, the mobile station is communicating with another base station using a radio channel having the same frequency as the mobile station. When moving in the direction of approaching, the influence of interference caused by the radio channel of the same frequency increases. Such interference becomes a factor that degrades communication quality.
[0009]
As a method for preventing such deterioration in communication quality, there is a method in which the mobile station constantly measures the amount of interference during communication and switches to another radio channel with a small amount of interference when the amount of interference exceeds a predetermined value. is there. However, with this method, frequent channel switching may cause an increase in processing load on the system and a decrease in frequency utilization efficiency, or communication quality may deteriorate due to instantaneous interruptions that occur during channel switching. For this reason, an appropriate radio channel allocation method considering both frequency utilization efficiency and communication quality is desired by another method.
[0010]
Therefore, an object of the present application is to provide a communication control apparatus that enables appropriate radio channel assignment in consideration of both frequency utilization efficiency and communication quality.
[0011]
[Means for Solving the Problems]
  In order to solve the above problems, the present inventionAccording toIn a communication control apparatus that assigns a radio channel to a call that occurs during communication between a base station and a mobile station that constitute a radio zone, a plurality of groups each including a plurality of radio channels each having a predetermined frequency band Yes, according to the amount of traffic in communication between the base station and the mobile station, group information holding means for holding information of each group ranked according to the degree of interference between radio channels in the group, Radio channel allocating means for selecting a group according to the order and allocating an unused radio channel belonging to the selected group.
[0012]
  In addition, the present inventionAccording toThe radio channel allocating means selects groups in order from the top group when the traffic volume is equal to or greater than a predetermined value, and selects all groups when the traffic volume exceeds a predetermined value.
[0013]
In addition, the present inventionAccording toAnd an interference amount measuring means for measuring an interference amount of the radio channel, wherein the radio channel assigning means assigns a radio channel whose interference amount measured by the interference amount measuring means is a predetermined value or less.
[0014]
  In addition, the present inventionAccording toThe radio channel allocating unit makes a radio channel to be preferentially allocated among radio channels belonging to one group different between adjacent radio zones.
[0015]
  In addition, the present inventionAccording toAnd a traffic amount measuring means for measuring a traffic amount in communication between the base station and the mobile station.
[0016]
In the present invention, each group ranked according to the degree of interference between the radio channels in the group is selected according to the traffic volume in the communication between the base station and the mobile station, and the unassigned group belonging to the selected group is selected. Assigned radio channel for use. Therefore, when the traffic volume is small, priority is given to the communication quality over the frequency usage efficiency, whereas when the traffic volume is large, the frequency usage efficiency is given priority over the communication quality, and both the frequency usage efficiency and the communication quality are set. Appropriate radio channel assignment in consideration is possible.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 2 is a diagram illustrating a configuration example of the mobile communication system in the present embodiment. As shown in the figure, the mobile communication system 1 includes radio control stations 100-1 and 100-2 as communication control apparatuses (hereinafter, these radio control stations 100-1 and 100-2 are collectively referred to as “radio control”. Station 100 ") and base stations 200-1, 200-2, 200-3 and 200-4 (hereinafter these base stations 200-1, 200-2, 200-3 and 200-4 are collectively referred to as (Referred to as “base station 200” as appropriate), a radio zone 210-1 configured by the base station 200-1, a radio zone 210-2 configured by the base station 200-2, and a base station 200-3 A radio zone 210-4 configured by the radio zone 210-3 and the base station 200-4 (hereinafter, these radio zones 210-1, 210-2, 210-3, and 210-4 are collectively referred to as a radio zone 210-4). Appropriately referred to as “radio zone 210”), mobile stations 300-1 and 300-2 (hereinafter, these mobile stations 300-1 and 300-2 are collectively referred to as “mobile station 300”), and an exchange network 400.
[0019]
In FIG. 2, radio control station 100-1 places base stations 200-1 and 200-2 under control, and radio control station 100-2 places base stations 200-3 and 200-4 under control. Radio control stations 100-1 and 100-2 are connected by a switching network 400.
[0020]
The radio control station 100 includes a subordinate base station 200 and a mobile station 300 existing in the radio zone 210 constituted by the base station 200 (in FIG. 2, the mobile station 300-1 exists in the radio zone 210-2). In the communication with the mobile station 300-2 in the wireless zone 210-4), when a call originated or received by the mobile station 300 is generated, a radio channel is set for the call. assign.
[0021]
In this embodiment, the radio channel employs an interleave channel arrangement. FIG. 3 is a diagram illustrating an example of an interleave channel arrangement. In the figure, the odd-numbered radio channel (f₀₁, F₀₃, F₀₅... f₂₇) Are arranged at predetermined frequency intervals so that their frequency bands do not overlap each other. On the other hand, even-numbered radio channels (f₀₂, F₀₄... f₂₈) Is arranged at the center between odd-numbered radio channels, and even-numbered radio channels are arranged so that their frequency bands do not overlap each other at a predetermined frequency interval. Are arranged with a part of the frequency band overlapping. The radio control station 100 appropriately allocates radio channels adopting such an interleave channel arrangement in consideration of both frequency use efficiency and communication quality.
[0022]
FIG. 4 is a diagram illustrating a configuration example of the radio control station 100. As shown in the figure, the radio control station 100 includes a communication unit 102, a traffic amount measurement unit 104, a channel allocation unit 106, a group information holding unit 108, and an interference amount measurement unit 110.
[0023]
The communication unit 102 performs control related to communication between the base station 200 and the mobile station 300 and the switching network 400. The traffic amount measuring unit 104 measures the traffic amount in communication between the subordinate base station 200 and the mobile station 300 existing in the radio zone 210 formed by the subordinate base station 200. The measured traffic volume is sent to the channel allocation unit 106.
[0024]
The group information holding unit 108 is a plurality of groups including a plurality of radio channels each having a predetermined frequency band (hereinafter referred to as “channel group”), and is ranked according to the degree of interference between the radio channels in the group. Hold information for each group.
[0025]
FIG. 5 is a diagram illustrating correspondence between radio channels and channel groups when the radio channel arrangement is the interleave arrangement shown in FIG. As shown in FIG. 5, each wireless channel is classified into two channel groups, group A and group B. Specifically, each radio channel is counted from an odd-numbered radio channel (f₀₁, F₀₃, F₀₅... f₂₇) Are classified into group A, and even-numbered radio channels (f₀₂, F₀₄... f₂₈) Is classified into group B. As shown in FIG. 3, the odd-numbered radio channels are arranged so that the frequency bands do not overlap with each other when counted from the lower frequency band, and similarly, the even-numbered radio channels do not overlap with each other. Is arranged. Accordingly, the wireless channels belonging to the group A do not overlap in frequency band.
[0026]
The channel allocation unit 106 is configured to generate a call originating from the mobile station 300 in the radio zone 210 configured by the subordinate base station 200 or a call originating from the mobile station 300. A channel allocation request transmitted from the transmission source is received via the communication unit 102.
[0027]
Further, when the channel allocation unit 106 receives a channel allocation request, the channel allocation unit 106 allocates a radio channel to the generated call based on the information in the group information holding unit 108 described above.
[0028]
Specifically, the channel allocating unit 106 communicates between the subordinate base station 200 and the mobile station 300 existing in the radio zone 210 formed by the subordinate base station 200 from the traffic amount measuring unit 104. The traffic amount is received, and the traffic amount is compared with a predetermined value (first threshold). FIG. 6 is a diagram illustrating an example of a change in traffic volume. As shown in the figure, the traffic volume fluctuates over time, for example, increases during the daytime period and decreases during the nighttime period, and exceeds or does not exceed the first threshold. .
[0029]
When the traffic volume is less than or equal to the first threshold, there are many unused radio channels (empty channels), so it is desirable that communication quality be given priority over frequency utilization efficiency. Therefore, when the traffic amount is equal to or less than the first threshold, the channel allocation unit 106 is arranged so that the frequency bands do not overlap with each other as shown in FIG. A group including the channel is selected, and free channels belonging to the A group are searched. Then, the channel assignment unit 106 selects any of the free channels belonging to the group A. Further, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group A. In response to this instruction, the interference amount measuring unit 110 measures the CIR of the empty channel. The measured CIR is sent to the channel assignment unit 106. The channel allocation unit 106 determines whether or not the CIR of the free channel belonging to the selected group A is equal to or less than a predetermined value. Then, when the CIR is equal to or less than a predetermined value, the channel allocation unit 106 allocates an empty channel belonging to the selected group A to the call that has been generated.
[0030]
When the CIR of the free channel belonging to the selected group A exceeds a predetermined value, the channel assignment unit 106 selects another free channel belonging to the group A. Thereafter, the same processing as described above is performed. That is, the channel assignment unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group A. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, the channel allocation unit 106 allocates a free channel belonging to the selected group A to the generated call.
[0031]
Further, when the CIRs of all the empty channels belonging to the group A exceed a predetermined value, the channel allocation unit 106 selects the group B that is the channel group with the lower rank according to the degree of interference, and the group B Search for free channels belonging to. Then, the channel allocation unit 106 selects one of the free channels belonging to the group B. Further, the channel assignment unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group B. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, the channel allocation unit 106 allocates a free channel belonging to the selected group B to the generated call.
[0032]
In addition, when the CIR of the free channel belonging to the selected group B exceeds a predetermined value, the channel allocation unit 106 selects another free channel belonging to the group B. Thereafter, the same processing as described above is performed. That is, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group B. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, the channel allocation unit 106 allocates a free channel belonging to the selected group B to the generated call.
[0033]
As described above, when the traffic amount is equal to or less than the first threshold, the free channels belonging to the group A including a plurality of radio channels that are arranged so that the frequency bands do not overlap each other and have a small degree of mutual interference are included. Assigned with priority. Accordingly, communication quality is prioritized over frequency utilization efficiency.
[0034]
On the other hand, when the traffic volume exceeds the first threshold, since there are few empty channels, it is desirable to prioritize frequency utilization efficiency over communication quality. For this reason, when the traffic volume is equal to or less than the first threshold, the channel allocation unit 106 selects both the A group and the B group as shown in FIG. 7, and the free channels belonging to these A group and B group. Search for. Then, the channel assignment unit 106 selects one of the free channels belonging to the A group and the B group. Further, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group A or group B. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR of the free channel belonging to the selected group A or group B is equal to or less than a predetermined value, and if it is equal to or less than the predetermined value, belongs to the selected group A or group B Assign a free channel to the call that was made.
[0035]
If the CIR of the free channel belonging to the selected A group or B group exceeds a predetermined value, the channel allocation unit 106 selects another free channel belonging to the A group or the B group. Thereafter, the same processing as described above is performed. That is, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group A or group B. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or smaller than a predetermined value. If the CIR is equal to or smaller than the predetermined value, the free channel belonging to the selected group A or group B is assigned to the generated call. assign.
[0036]
As described above, when the traffic volume exceeds the first threshold value, the frequency bands overlap with each other, and although there is a possibility that a free channel having a high degree of mutual interference may be allocated, The number increases. Accordingly, priority is given to frequency utilization efficiency over communication quality.
[0037]
By the way, in the radio channel assignment process described above, when the radio zones 210 configured by the base stations 200 are adjacent to each other, the base stations 200 corresponding to the plurality of radio zones 210 that are close to each other and the base stations 210. There is a possibility that a radio channel having the same frequency band may be assigned to a call generated in communication with the mobile station 300 of the other communication partner even when the traffic volume is equal to or less than the first threshold value. . In such a case, it interferes with each other and causes deterioration in communication quality. For this reason, when the radio zones 210 configured by the base stations 200 are adjacent to each other, deterioration of communication quality is suppressed as follows.
[0038]
FIG. 8 is a diagram illustrating a configuration example of wireless zones adjacent to each other. This figure is a configuration example of a wireless zone when a cluster by 7-zone repetition is adopted. In the figure, one cluster is composed of seven wireless zones numbered 1 to 7. In these seven radio zones, radio channels having different frequency bands are used, thereby preventing deterioration in communication quality.
[0039]
Therefore, in order to prevent the use of radio channels having the same frequency band between radio zones in one cluster, there are 7 radio channels belonging to group A, which is a higher-order channel group according to the degree of interference. One group is associated with each radio zone as a group C radio channel.
[0040]
FIG. 9 is a diagram illustrating an example of a wireless channel belonging to the group C when the wireless zone is configured as illustrated in FIG. As shown in the figure, the radio channel (f₀₁, F₀₃, F₀₅... f₂₇) Are classified into seven and are associated with each wireless zone. For example, as a group C radio channel corresponding to radio zone 1, radio channel f₀₁And f₁₅And the wireless channel f as a wireless channel of the group C corresponding to the wireless zone 2₀₃And f₁₇Are associated.
[0041]
As described above, when the wireless channels belonging to the group A are classified and associated with each wireless zone one by one as the wireless channels of the group C, the channel assignment unit 106 performs wireless communication as follows. Assign channels.
[0042]
That is, when the traffic volume is equal to or less than the first threshold, the channel allocation unit 106, as shown in FIG. 10, has a wireless zone 210 in which there is a mobile station 300 that transmits or receives a call that is a target of wireless channel allocation. A group C corresponding to is selected, and an empty channel belonging to the group C is searched. Then, the channel assignment unit 106 selects one of the free channels belonging to the group C. For example, the radio zone is configured as shown in FIG. 8, the radio channel belonging to group C is configured as shown in FIG. 9, and a call originated or terminated by the mobile station 300 in the radio zone 1 is generated. Consider the case. In this case, the channel assignment unit 106 selects a group C corresponding to the wireless zone 1 shown in FIG.₀₁, F₁₅If at least one of the channels is an empty channel, the empty channel is selected.
[0043]
Furthermore, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group C. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR of the free channel belonging to the selected C group is equal to or less than a predetermined value. Assign to a call
[0044]
When the CIR of the free channel belonging to the selected group C exceeds a predetermined value, the channel allocation unit 106 selects another free channel belonging to the group C. For example, the channel allocation unit 106 selects a group C corresponding to the wireless zone 1 shown in FIG.₀₁Selected, but the available channel f₀₁If the CIR exceeds the predetermined value, another free channel f of the group C corresponding to the wireless zone 1₁₅If is a free channel, the free channel is selected.
[0045]
Thereafter, the same processing as described above is performed. That is, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group C. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, the channel allocation unit 106 allocates a free channel belonging to the selected group C to the generated call.
[0046]
If the CIRs of all the free channels belonging to the group C exceed a predetermined value, the channel assignment unit 106 searches for free channels belonging to the group A excluding the group C. Then, the channel allocation unit 106 selects any of the free channels belonging to the group A excluding the group C. For example, when the CIRs of all the free channels belonging to the C group corresponding to the wireless zone 1 shown in FIG. 9 exceed a predetermined value, the channel allocating unit 106 assigns free channels belonging to the A group excluding the C group. f₀₃, F₀₅, F₀₇, F₀₉, F₁₁, F₁₃, F₁₇, F₁₉, F_{2 1}, F₂₃, F₂₅, F₂₇If any of these is an empty channel, the empty channel is selected. Further, the channel assignment unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group A excluding group C. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, a free channel belonging to the selected A group excluding the C group is generated. Assign for calls.
[0047]
In addition, when the CIR of the free channel belonging to the selected group A excluding the group C exceeds a predetermined value, the channel allocating unit 106 selects other free channels belonging to the group A excluding the group C. select. Thereafter, the same processing as described above is performed. That is, the channel allocating unit 106 instructs the interference amount measuring unit 110 to measure the CIR of the free channel belonging to the selected group A minus the group C. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, a free channel belonging to the selected A group excluding the C group is generated. Assign for calls.
[0048]
If the CIRs of all the free channels belonging to the group A minus the group C exceed a predetermined value, the channel assignment unit 106 selects the group B and searches for a free channel belonging to the group B. . Then, the channel allocation unit 106 selects one of the free channels belonging to the group B. Further, the channel assignment unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group B. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, the channel allocation unit 106 allocates a free channel belonging to the selected group B to the generated call.
[0049]
In addition, when the CIR of the free channel belonging to the selected group B exceeds a predetermined value, the channel allocation unit 106 selects another free channel belonging to the group B. Thereafter, the same processing as described above is performed. That is, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group B. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, the channel allocation unit 106 allocates a free channel belonging to the selected group B to the generated call.
[0050]
As described above, when the traffic amount is equal to or less than the first threshold, the vacant channels belonging to the group A including a plurality of radio channels with a small degree of interference with each other are classified so as to be different between the adjacent radio zones 210. Free channels belonging to the group C are preferentially assigned. Therefore, communication quality is prioritized over frequency utilization efficiency, and it is possible to control the deterioration of communication quality by changing the available channels that are preferentially allocated between adjacent radio zones 210.
[0051]
On the other hand, when the traffic volume exceeds the first threshold, the channel allocation unit 106, as shown in FIG. 10, moves to the radio zone 210 where the mobile station 300 that originates or terminates a call that is the target of radio channel allocation exists. A corresponding group C is selected, and free channels belonging to the group C are searched. Then, the channel assignment unit 106 selects one of the free channels belonging to the group C. Furthermore, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group C. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR of the free channel belonging to the selected C group is equal to or less than a predetermined value. Assign to a call
[0052]
When the CIR of the free channel belonging to the selected group C exceeds a predetermined value, the channel allocation unit 106 selects another free channel belonging to the group C. Thereafter, the same processing as described above is performed. That is, the channel allocation unit 106 instructs the interference amount measurement unit 110 to measure the CIR of the free channel belonging to the selected group C. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocation unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, the channel allocation unit 106 allocates a free channel belonging to the selected group C to the generated call.
[0053]
Further, when the CIRs of all the free channels belonging to the C group exceed a predetermined value, the channel allocation unit 106 searches for free channels belonging to the A group excluding the C group and the B group. Then, the channel allocation unit 106 selects any one of the free channels belonging to the group A and the group B and the group B. Further, the channel allocating unit 106 instructs the interference amount measuring unit 110 to measure the CIR of the free channel belonging to the selected group A excluding group C or group B. In response to this instruction, the interference amount measurement unit 110 measures the CIR of the empty channel and sends it to the channel allocation unit 106. The channel allocating unit 106 determines whether or not the CIR is equal to or less than a predetermined value. If the CIR is equal to or less than the predetermined value, a channel obtained by removing the C group from the selected A group or a free channel belonging to the B group is determined. Assign for calls that have been made.
[0054]
As described above, when the traffic volume exceeds the first threshold, when the CIRs of all the empty channels belonging to the group C exceed a predetermined value, the frequency bands overlap each other, and the degree of mutual interference is large. Although there is a possibility that an empty channel is allocated, the number of radio channels that can be allocated increases. Accordingly, priority is given to frequency utilization efficiency over communication quality.
[0055]
When the traffic volume exceeds the first threshold, the channel allocation unit 106 may select both the group A and the group B and search for an empty channel belonging to the group A and the group B. . In this case, the channel assignment unit 106 selects any one of the free channels belonging to the A group and the B group. Furthermore, the channel allocating unit 106 acquires the CIR of the free channel measured by the interference amount measuring unit 110. If the CIR of the free channel is equal to or less than a predetermined value, the channel allocating unit 106 is assigned to the generated call. Assign to.
[0056]
Next, the operation of the radio control station 100 will be described with reference to the flowchart. FIG. 11 is a flowchart showing an operation of the radio control station 100 in which the dynamic channel allocation method of the present embodiment is adopted.
[0057]
When a call originated by the mobile station 300 in the radio zone 210 constituted by the subordinate base station 200 is generated, or when a call arrives by the mobile station 300, the radio control station 100 A channel allocation request transmitted from the transmission source is received (step 101).
[0058]
Next, the radio control station 100 measures the traffic volume in communication between the subordinate base station 200 and the mobile station 300 existing in the radio zone 210 formed by the subordinate base station 200 (step 102). .
[0059]
Further, the radio control station 100 selects a channel group in the priority order according to the measured traffic volume, searches for a free channel belonging to the channel group, and selects any free channel (step 103).
[0060]
Next, the radio control station 100 measures the CIR of the selected empty channel (step 104), and determines whether or not the CIR is equal to or less than a predetermined value (step 105). If the CIR is less than or equal to the predetermined value, the radio network controller 100 allocates the free channel selected in step 103 to the call that has been generated (step 106). On the other hand, when the CIR exceeds the predetermined value, the radio control station 100 repeats the operation after the selection of the channel group and the search and selection of the free channel belonging to the channel group (step 103).
[0061]
Thus, in this embodiment, the radio control station 100 has a traffic volume in communication between the subordinate base station 200 and the mobile station 300 existing in the radio zone 210 formed by the subordinate base station 200. When the value is equal to or less than the first threshold, a free channel belonging to the group A including a plurality of wireless channels having a small degree of mutual interference is preferentially assigned. Accordingly, communication quality is prioritized over frequency utilization efficiency. On the other hand, when the traffic volume exceeds the first threshold, the frequency bands overlap each other, and although there is a possibility that a free channel having a large degree of mutual interference may be allocated, the number of radio channels that can be allocated increases. . Accordingly, priority is given to frequency utilization efficiency over communication quality.
[0062]
In the above-described embodiment, when the traffic amount is equal to or less than the first predetermined value, the wireless channels belonging to the group A are preferentially assigned. However, the wireless channels belonging to the group B are mutually connected to the frequency band. Are not overlapping, and the degree of mutual interference is thought to be small. Therefore, radio channels belonging to group B may be preferentially assigned.
[0063]
In the above-described embodiment, as shown in FIG. 3, two channel groups of A group and B group are formed corresponding to the overlapping frequency bands of the two radio channels. When an arrangement is adopted in which the frequency bands of two or more radio channels overlap, a channel group including a plurality of radio channels arranged so that the frequency bands do not overlap with each other and the degree of interference with each other is small A channel group including other radio channels may be formed. Alternatively, a number of channel groups corresponding to the number of overlapping frequency bands may be formed.
[0064]
【The invention's effect】
According to the present invention, it is possible to perform appropriate radio channel assignment considering both frequency utilization efficiency and communication quality.
[Brief description of the drawings]
FIG. 1 is a flowchart of a conventional dynamic channel allocation method.
FIG. 2 is a diagram illustrating a configuration example of a mobile communication system.
FIG. 3 is a diagram illustrating an example of an interleave channel arrangement.
FIG. 4 is a diagram illustrating a configuration example of a radio control station.
FIG. 5 is a diagram illustrating a correspondence between a radio channel and a channel group.
FIG. 6 is a diagram showing fluctuations in traffic volume.
FIG. 7 is a diagram illustrating a first example of correspondence between traffic volume and group selection priority;
FIG. 8 is a diagram illustrating a configuration example of a wireless zone.
FIG. 9 is a diagram illustrating a correspondence between a radio zone and a radio channel.
FIG. 10 is a diagram illustrating a second example of correspondence between traffic volume and group selection priority;
FIG. 11 is a flowchart of the dynamic channel allocation method of the present embodiment.
[Explanation of symbols]
1 Mobile communication system
100-1, 100-2 Radio control station
102 Communication Department
104 Traffic volume measurement unit
106 Channel allocation unit
108 Channel information holding unit
110 Interference amount measurement unit
200-1, 200-2, 200-3, 200-4 Base station
210-1, 210-2, 210-3, 210-4 Wireless zone
300-1, 300-2 Mobile station
400 switching network

Claims (4)

In a communication control apparatus that assigns a radio channel to a call that occurs during communication between a base station and a mobile station constituting a radio zone,
Radio channels are radio channels arranged in an interleaved manner, and the radio channels are classified into groups so that frequency bands do not overlap each other,
A group information holding means for holding a plurality of groups each including a plurality of radio channels each having a predetermined frequency band, and holding information of each group ranked according to the degree of interference between the radio channels in the group;
Depending on the traffic volume in communication between the base station and the mobile station, when the traffic volume is a predetermined value or less, a plurality of radios are arranged so that the frequency bands do not overlap each other and the degree of mutual interference is small Radio channel allocating means for selecting a group including channels, selecting all groups when the traffic volume exceeds a predetermined value, and selecting empty channels belonging to these groups;
A communication control device comprising: The communication control device according to claim 1,
An interference amount measuring means for measuring an interference amount of the radio channel;
The radio channel allocating unit is a communication control apparatus that allocates a radio channel whose interference amount measured by the interference amount measuring unit is a predetermined value or less. In the communication control device according to claim 1 or 2,
The wireless channel assigning unit is a communication control device that makes a wireless channel preferentially assigned among wireless channels belonging to one group different between adjacent wireless zones. The communication control apparatus according to any one of claims 1 to 3,
A communication control device comprising: a traffic amount measuring means for measuring a traffic amount in communication between the base station and the mobile station.

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