WO2007105276A1

WO2007105276A1 - Radio base station

Info

Publication number: WO2007105276A1
Application number: PCT/JP2006/304771
Authority: WO
Inventors: Keiichi Teshirogi
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2006-03-10
Filing date: 2006-03-10
Publication date: 2007-09-20

Abstract

A line control section (6) of a radio base station (1b) refers to a frequency table in which a radio frequency weighted according to the number of successes and failures of the past allocation is registered, selects a candidate to which a radio frequency for the communication of a mobile station (2b) is allocated on the basis of the weight, and changes the weight of the radio frequency of the allocated candidate in the frequency table according to the successes or the failures of the allocation.

Description

Specification

Wireless base station

Technical field

[0001] The present invention relates to a radio base station of a DCA (Dynamic Channel Assignment) type mobile communication system.

Background art

[0002] In a mobile communication system using a conventional DCA scheme, when a radio base station allocates a radio frequency for a mobile station call, carrier sense for interference wave detection is performed within a certain time. Based on the result of this carrier sense, the radio base station employs a frequency with a disturbance wave level lower than a certain threshold as a radio frequency for a call (for example, see Non-Patent Document 1).

[0003] Non-Patent Document 1: Second Generation Cordless Telephone System Standards Version 3.3, Radio Industries Association, 1995 (pages 21-25, Figure 3.1)

[0004] In a conventional mobile communication system, a radio base station performs interference wave detection again on a radio frequency that is a candidate for allocation immediately before allocating a radio frequency for a call, thereby preventing interference. Assign a radio frequency with a low wave level. For this reason, the tendency that the same frequency is used in each base station becomes strong. In this case, the following problems may occur.

[0005] For example, when the distance between base stations becomes out of sight due to a building or the like, the intensity of the radio waves of the other base station power received by one base station is reduced, but the mobile station side sees from these base stations. Some places are located throughout. In this case, when the same radio frequency is assigned for a call by each base station, interference occurs in the communication area of these base stations.

[0006] The present invention has been made to solve the above-described problems, and achieves autonomously optimal radio frequency allocation and improves communication quality by reducing interference in a communication area. The object is to obtain a radio base station capable of

Disclosure of the invention

The radio base station according to the present invention is weighted according to the number of successful and unsuccessful assignments. When allocating the frequency table in which the radio frequency is registered and the radio frequency for mobile station communication, the frequency table is referred to, and based on this weighting, the radio frequency assignment candidate for communication is selected and assigned. The weighting of the radio frequency of the allocation candidate is changed according to the success or failure.

[0008] Thereby, an optimum frequency with less interference is preferentially assigned to the call channel, and the call connection rate can be improved. In addition, it is possible to improve the communication quality by selecting a frequency that is unlikely to cause handover or switching of the call channel.

Brief Description of Drawings

FIG. 1 is a diagram showing a mobile communication system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a radio base station in FIG. 1.

FIG. 3 is a block diagram showing a configuration of the mobile station in FIG. 1.

FIG. 4 is a flowchart showing a flow of radio frequency allocation by the mobile communication system of the first embodiment.

FIG. 5 is a flowchart showing a radio frequency allocation flow of the mobile communication system according to the second embodiment of the present invention.

FIG. 6 is a diagram showing frequency tables in which the frequency assignment success and failure times in the past are classified by time zone.

FIG. 7 is a flowchart showing a flow of radio frequency allocation by the mobile communication system of the third embodiment.

FIG. 8 is a flowchart showing a flow of radio frequency allocation by the mobile communication system of the fourth embodiment.

FIG. 9 is a flowchart showing a flow of radio frequency allocation by the mobile communication system of the fifth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, in order to describe the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1. FIG. 1 is a diagram showing a mobile communication system according to Embodiment 1 of the present invention, which is a DCA mobile communication system including a plurality of radio base stations. In FIG. 1, mobile communication system power according to Embodiment 1 is composed of radio base stations la and lb and mobile stations 2a and 2b. The communication area 3a is served from the radio base station la, and the communication area 3b is served from the radio base station lb. Further, in the example of FIG. 1, the building 5 exists at the position of line of sight from each radio base station la, lb, and the area between the radio base stations la, lb is out of line of sight.

[0011] Mobile stations 2a and 2b embodied by a mobile phone or the like are connected by a frequency division multiple access (FDMA) system. In addition, the mobile station 2b is located in an area 4 (hatched in the figure) where the communication areas 3a and 3b of the wireless base stations la and lb overlap and is waiting in the communication area 3b.

In other words, in FIG. 1, the force between the radio base stations la and lb is out of line of sight due to the building 5. On the mobile station 2b side, the radio base stations la and lb are in line of sight. In such a case, conventionally, there is a possibility that the same radio frequency is allocated to the mobile station 2b from the radio base station la, lb to cause interference. On the other hand, in the present invention, as will be described later, even in the case of FIG. 1, the radio base station lb force autonomously assigns an optimal radio frequency, and reduces interference in area 4. Can do.

FIG. 2 is a block diagram showing a configuration of the radio base station in FIG. In FIG. 2, the radio base stations la and lb include a line control unit 6, a radio communication control unit 7, a radio resource management unit 8, a time measurement unit 9, a wired resource management unit 10, and a wired communication control unit 11. The line control unit 6 is a component that performs line control for the mobile stations 2a and 2b in the communication areas 3a and 3b, and has a frequency table in which radio frequencies used for allocation are registered.

[0014] As an operation of the line control unit 6, for example, a layer 3 (network layer) connection is performed with a base station control device (not shown) that controls the radio base stations la and lb and the mobile stations 2a and 2b. Further, the line control unit 6 performs radio frequency and time slot assignment, wired line assignment, handover necessity determination and handover for the mobile stations 2a and 2b.

[0015] Further, the line control unit 6 according to the first embodiment manages the history of success and failure of radio frequency allocation, and succeeds in past frequency allocation in assigning radio frequencies for mobile station calls. And radio frequency allocation based on weighting according to the number of failures [0016] The radio communication control unit 7 is a configuration unit that controls radio communication with the mobile stations 2a and 2b, and includes layer 1 (physical layer) and layer 2 (data link layer) with the mobile stations 2a and 2b. Control the connection. It also detects interference waves in wireless communication with the mobile stations 2a and 2b. The radio resource management unit 8 performs radio resource management such as radio channel usage status and interference wave status due to carrier sense.

[0017] The time measurement unit 9 measures the time in the radio base stations la and lb. The wired resource management unit 10 manages the wired resources of the radio base stations la and lb, and manages, for example, the usage status of the wired line and the status of the line quality. The wired communication control unit 11 is a component that controls wired communication with the base station control device, and controls layer 1 (physical layer) and layer 2 (data link layer) connection with the base station control device.

FIG. 3 is a block diagram showing a configuration of the mobile station in FIG. The mobile stations 2 a and 2 b include a radio communication control unit 12, a radio resource management unit 13, and a line control unit 14. The radio communication control unit 12 is a component that controls radio communication with the radio base stations la and lb, and performs layer 1 (physical layer) and layer 2 (data link layer) connection with the radio base stations la and lb. Control. It also detects interference waves in wireless communication with the wireless base stations la and lb.

[0019] The radio resource management unit 13 manages the state of interference waves due to carrier sense. The line control unit 6 is a layer 3 (network layer) connection with the radio base stations la and lb, a radio frequency request to the radio base stations la and lb based on the detection result of the interference wave by the radio communication control unit, and a hand Determine whether or not over is necessary and perform handover.

Next, the operation will be described.

FIG. 4 is a flowchart showing a flow of radio frequency allocation by the mobile communication system of the first embodiment, and will be described in detail with reference to this figure.

In the following, the case where the radio frequency of the call channel is assigned to the mobile station 2b located in the area 4 by the radio base station lb will be described.

When the mobile station 2b makes / receives a call from the standby state, the line control unit 14 of the mobile station 2b communicates with the radio base station lb via the control channel connected by the radio communication control unit 12 to the communication channel (TCH : Traffic Channel) allocation request message. [0021] When the radio communication control unit 7 of the radio base station lb receives the call channel assignment request message from the mobile station 2b (step ST1), the line control unit 6 of the radio base station lb It is determined whether or not the frequency allocation is the first power (step ST2). At this time, if it is determined to be the first time, the line control unit 6 randomly assigns the frequency in the frequency table as the assignment candidate frequency for the call of the mobile station 2b (step ST3).

[0022] If it is not the first time, search the frequency table for the most weighted frequency (highest allocation priority) and determine whether there is only one frequency (step ST15 )

[0023] Here, if there is one frequency with the highest weighting, line controller 6 selects that frequency as an allocation candidate, and proceeds to the processing of step ST4. On the other hand, when there are a plurality of weights having the highest weight, the frequency that is the candidate for allocation is also selected at random among the plurality of frequencies having the same weight (step ST16).

[0024] When the allocation candidate radio frequency is selected by at least one of step ST3, step ST15, or step ST16, the radio resource management unit 8 of the radio base station lb Perform carrier sense for jamming detection (step ST4). Radio communication control unit 7 monitors the status of jamming waves due to carrier sense of radio resource management unit 8 and detects the presence or absence of jamming waves for the radio frequency (step ST5).

[0025] At this time, when an interference wave is detected by the radio communication control unit 7, the line control unit 6 adds the number of times of radio frequency allocation failure in the frequency table (step ST13), and further weights the frequency. Is changed (step ST14). Thereafter, by returning to the processing of step ST2, the allocation is most likely to be successful based on the above-mentioned weighting, and the frequency is selected again and carrier sense is performed.

[0026] In step ST5, when the radio communication control unit 7 does not detect an interference wave with respect to the radio frequency, the line control unit 6 notifies the mobile station 2b of the frequency of the allocation candidate to the mobile station 2b. In response to this, a frequency allocation notification message is sent (step ST6).

[0027] When the radio resource management unit 13 of the mobile station 2b receives the frequency assignment notification message from the radio base station lb, the radio resource management unit 13 performs carrier sense for detecting the interference wave. Wireless communication controller 12 Then, the state of the interference wave by the carrier sense of the radio resource management unit 13 is monitored to detect the presence or absence of the interference wave for the radio frequency.

[0028] Here, if an interference wave is not detected by the radio communication control unit 12, the channel control unit 14 of the mobile station 2b notifies the radio base station lb that the frequency can be allocated. Do. Also, when an interference wave is detected at the corresponding frequency, a notification is given to the radio base station lb that the frequency cannot be assigned.

[0029] The radio communication control unit 7 of the radio base station lb receives an assignment result for the frequency from the mobile station 2b (step ST7). In response to this result, the line control unit 6 of the radio base station lb determines whether or not the radio frequency can be assigned (step ST8). At this time, if the radio frequency can be assigned, the line control unit 6 assigns the radio frequency to the speech channel of the mobile station 2b (step ST9).

[0030] Thereafter, the line control unit 6 adds the number of successful allocations of the radio frequency in the frequency table (step ST10), and changes the weighting of the frequency (step ST11). For example, a change is made to increase the weighting of the radio frequency (increase the weighting value). When the radio frequency is assigned to the call channel as described above, the call of the mobile station 2b is started (step ST12).

[0031] On the other hand, if the radio frequency assignment is not possible in step ST8, circuit controller 6 adds the number of radio frequency assignment failures in the frequency table (step ST13), and further Change the weighting of (step ST14). For example, a change is made to lower the weight of the radio frequency (decrease the weight value).

[0032] Thereafter, returning to the processing of step ST2, the above-described processing is repeated, whereby the frequency at which allocation is most likely to be successful is selected based on the weighting according to the number of successful and failed allocations. 2b is notified.

[0033] It should be noted that the initial value of frequency weighting in the frequency table is 0, that is, an equal state with no weighting. By repeating the processing of step ST11 and step ST14, weighting according to the success or failure of frequency allocation Changed to

[0034] In addition, the radio frequency weighting in the frequency table can be changed by subtracting 1 from the existing weighting every time allocation fails and adding 1 every time allocation succeeds. In addition, With allocation success as the main criterion, if the allocation is successful, a number greater than 1, for example, 2 may be added. If allocation failure is the main criterion, a number greater than 1 for each allocation failure. For example, 2 may be subtracted. Note that such a weighting change method may be changed as appropriate in accordance with the communication environment, the communication status for each hour, and the like.

[0035] According to the first embodiment, the mobile station 2b is present at a line-of-sight position from each radio base station la, lb that is out of line of sight due to the building 5, such as the area 4 shown in FIG. Even so, the optimum radio frequency for the communication channel for calls is autonomously allocated.

[0036] As described above, according to the first embodiment, the line control unit 6 of the radio base station lb has registered the frequency with which the radio frequency weighted according to the number of past allocation successes and failures is registered. Refer to the table and select a radio frequency allocation candidate for communication of mobile station 2b based on this weighting, and change the radio frequency weighting of the allocation candidate in the frequency table according to the success or failure of the allocation. . As a result, the radio frequency that is most likely to be successfully allocated is selected as an allocation candidate based on the weighting according to the number of past allocation successes and failures. Therefore, the optimal radio frequency can be autonomously allocated from the radio base station lb to the mobile station 2b, and interference in the communication area 4 can be reduced.

[0037] Embodiment 2.

The radio base station and mobile station according to the second embodiment have the same configurations as those shown in FIGS. 2 and 3 described in the first embodiment. The difference from the above embodiment is that the radio network controller of the radio base station has a plurality of frequency tables in which the frequency of past frequency allocation successes and failures is classified according to time zones. Refer to the frequency table corresponding to the current time in the frequency table.

Next, the operation will be described.

FIG. 5 is a flowchart showing a radio frequency allocation flow of the mobile communication system according to the second embodiment of the present invention. The flow of operation will be described in detail with reference to this figure. In the following description, the case where the radio frequency of the communication channel is assigned to the mobile station 2b located in the area 4 by the radio base station lb will be described.

[0039] First, when the mobile station 2b performs outgoing / incoming calls from a standby state, the line control of the mobile station 2b is performed. The unit 14 sends a call channel allocation request message to the radio base station lb via the control channel connected by the radio communication control unit 12.

[0040] When the radio communication control unit 7 of the radio base station lb receives the call channel assignment request message from the mobile station 2b (step STla), the line control unit 6 of the radio base station lb Based on the measured current time, select and refer to the frequency table corresponding to the current time from the multiple frequency tables that classify the frequency of successful and failed past frequency assignments by time zone (step ST2a).

[0041] Fig. 6 is a diagram showing a frequency table in which the frequency assignment success and failure times in the past are classified by time zone. Fig. 6 (a) shows the daytime frequency table and Fig. 6 (b). Shows the morning and evening frequency table, and Fig. 6 (c) shows the night frequency table. In the example shown in the figure, the amount of traffic in the middle of these time periods is during the daytime when the nighttime traffic volume is the highest during morning and evening traffic volume than in other time zones. In this way, the traffic volume of communication generally changes depending on the time of day. For example, it starts to increase at around 7am, reaches a peak at around 10am, then decreases once and then around in the evening. It shows a change over time, such as increasing again and gradually decreasing thereafter.

That is, since the number of radio frequencies used and the usage time change with the passage of time, the assignable frequencies may change depending on the time zone. In the example of FIG. 6, the frequency fl is easily assigned at night as shown in FIG. 6 (c), but the frequency f3 is easily assigned in the morning and evening, which is not the frequency fl, as shown in FIG. 6 (b). Therefore, in the second embodiment, the frequency table is divided according to the time zone to increase the probability of successful frequency allocation.

[0043] Returning to the explanation of FIG. 5, the line control unit 6 of the radio base station lb refers to the frequency table corresponding to the current time, and determines whether or not the current frequency allocation is the first power in the base station lb. Determine (step ST3a). At this time, if it is determined that it is the first time, the line control unit 6 randomly assigns allocation candidate frequencies for the call of the mobile station 2b (step ST4a).

The subsequent processing from step ST5a to step ST17a is similar to the processing up to step ST16 in step ST4 force in FIG. 4 shown in the first embodiment, and detailed description thereof is omitted. In step ST12a and step ST15a, refer to step ST2a. The frequency weighting of the frequency table corresponding to the illuminated current time is changed.

[0045] As described above, according to the second embodiment, the frequency table corresponding to the current time is referred to from among a plurality of frequency tables in which the frequency assignment successes and failures in the past are classified according to time zones. Therefore, the allocation is most likely to succeed, and the frequency is set as a candidate for the allocation frequency. As a result, an optimal radio frequency can be allocated from the radio base station lb to the mobile station 2b according to changes in the time zone.

[0046] Embodiment 3.

The radio base station and mobile station according to the third embodiment have the same configurations as those shown in FIGS. 2 and 3 described in the first embodiment. The difference from the above embodiment is that when the channel control unit of the radio base station changes the weighting of the frequency in the frequency table, the increase in the weighting is increased for the new allocation success in time. Therefore, if the old allocation is successful, the increase in weight is reduced. In addition, the decrease in weighting is increased for new allocation failures in time, and the decrease is decreased for allocation failures that are older in time.

Next, the operation will be described.

FIG. 7 is a flowchart showing a radio frequency allocation flow of the mobile communication system according to the third embodiment of the present invention. The flow of operation will be described in detail with reference to this figure. In the following description, the case where the radio frequency of the call channel is assigned to the mobile station 2b located in the area 4 by the radio base station lb will be described.

[0048] First, when the mobile station 2b performs outgoing / incoming calls from a standby state, the line control unit 14 of the mobile station 2b communicates with the radio base station lb via the control channel connected by the radio communication control unit 12. To send a call channel assignment request message.

[0049] When the radio communication control unit 7 of the radio base station lb receives the call channel assignment request message from the mobile station 2b (step STlb), the line control unit 6 of the radio base station lb transmits to the own base station 1b. Then, it is determined whether or not the current frequency allocation is the first time (step ST2b). At this time, if it is determined that it is the first time, the line control unit 6 randomly allocates the frequency of the allocation candidate for the call of the mobile station 2b (step ST3b).

[0050] The subsequent processing from step ST4b to step STIOb is the same as the processing up to step ST10 because the step ST4 force in FIG. 4 shown in the first embodiment is the same as the processing up to step ST10. Is omitted.

[0051] When the number of successful radio frequency assignments is added in step STIOb, the line control unit 6 refers to the frequency assignment success history in the frequency table, and a predetermined time has elapsed since the current successful assignment. The frequency with new allocation success in time is increased, and the change (increase) is increased so that the frequency becomes higher than the frequency with the old allocation success after a predetermined time. Change the frequency weighting in the frequency table.

[0052] On the other hand, the line control unit 6 reduces the change (increase) to the frequency that has passed a predetermined time since the current successful allocation and has succeeded in the old allocation, The frequency weighting in the frequency table is changed so that the weighting is lower than the frequency for which new allocation was successful for a time less than the predetermined time. The above processing corresponds to step ST11b.

[0053] When the processing of step ST1 lb is completed, the time measurement unit 9 of the radio base station lb performs time measurement (step ST12b). Using the time of this measurement result, the line control unit 6 performs calibration if the time is set. Thereafter, the mobile station 2b starts a call (step ST13b).

[0054] If a jamming wave is detected in step ST5b, or if it is determined in step ST8b that the mobile station 2b force is also not frequency-assignable, the line control unit 6 of the radio base station lb In step ST14b, the frequency allocation failure count is added in step ST14b.

[0055] Thereafter, the line control unit 6 refers to the allocation success history of the frequency in the frequency table, and the allocation failure power this time has not passed the predetermined time, and the frequency at which a new allocation failure has occurred in time. Increases the amount of change (decrease), and changes the frequency weighting in the frequency table so that the weighting is lower than the frequency at which a predetermined time or more has passed and there was an old allocation failure.

[0056] On the other hand, the line control unit 6 reduces the amount of change (decrease) to the frequency where the allocation failure power this time has been more than a predetermined time and there is an old allocation failure in time, The frequency weighting in the frequency table is changed so that the weighting is higher than the frequency where there was a new allocation failure in time less than the predetermined time. The above processing corresponds to step ST15b. Note that the predetermined time for changing the increment (decrease) of the weighting is, for example, considering the fluctuation status of the communication traffic amount, and the allocation success of a certain frequency. The fluctuation of the communication traffic amount is as small as possible. Time is selected. This is a force that can be expected to be different from the communication status that has already been successfully allocated and the probability of successful allocation will be reduced if the communication traffic volume changes over time from the communication status that has been successfully allocated. . In addition, the predetermined time may be set in units of 24 hours, for example, in units of one week, months, days of the week, etc., depending on fluctuations in the amount of communication traffic.

[0058] When the process of step ST15b is completed, the time measurement unit 9 of the radio base station lb performs time measurement (step ST16b). On the basis of the time of this measurement result, the line controller 6 returns to the processing from step ST2b, and assigns a high (or low) weight to a new allocation success (or failure) in time and an old allocation success (or failure). Is assigned a low (or high) weight, and the frequency that is most likely to be successfully assigned is selected as a candidate for the assigned frequency based on this weight.

[0059] As described above, according to the third embodiment, when changing the weighting of the frequency in the frequency table, the change is changed in accordance with the passage of time of success and failure of the frequency assignment. It is possible to autonomously assign the optimum radio frequency to the station 2b and to increase the success probability of radio frequency assignment to the mobile station.

[0060] Embodiment 4.

Mobile stations 2a and 2b of the mobile communication system according to the fourth embodiment are connected by a time division multiple access (TDM A) method. The radio base station according to the fourth embodiment has the same configuration as that shown in FIG. The difference from the above embodiment is that, in the frequency table, the line control unit of the radio base station responds to the combination of the radio frequency and the time slot to which it is assigned according to the number of successful assignments and failures in the past. The most appropriate time slot and radio frequency combination is selected based on this weight.

Next, the operation will be described.

FIG. 8 is a flowchart showing a flow of radio frequency allocation by the mobile communication system according to the fourth embodiment, which will be described in detail with reference to this figure. In the following, the case where the radio frequency of the call channel is assigned to the mobile station 2b located in the area 4 by the radio base station lb will be described.

[0062] First, when the mobile station 2b performs outgoing / incoming calls from the standby state, the line control unit 14 of the mobile station 2b communicates with the radio base station lb via the control channel connected by the radio communication control unit 12. To send a call channel assignment request message.

[0063] When the radio communication control unit 7 of the radio base station lb receives the call channel assignment request message from the mobile station 2b (step STlc), the line control unit 6 of the radio base station lb Then, it is determined whether or not the current frequency allocation is the first time (step ST2c). At this time, if it is determined that it is the first time, the line control unit 6 randomly assigns a candidate time slot and frequency for the call of the mobile station 2b (step ST3c).

[0064] If it is not the first time, search the frequency table for a combination of time slot and frequency with the highest weight (highest allocation priority) and whether there is only one such combination. (Step ST15c). Here, if there is one combination with the highest weight, the line control unit 6 selects the combination as an allocation candidate, and proceeds to the processing of step ST4c.

[0065] On the other hand, when there are a plurality of combinations of time slots and frequencies with the highest weighting, a combination that is a candidate for allocation is randomly selected from a plurality of frequencies having the same weighting (step ST16c).

[0066] When the allocation candidate time slot and frequency combination is selected by at least one of step ST3c, step ST15c, or step ST16c, the radio resource management unit 8 of the radio base station lb The carrier sense of the interference wave detection is executed for the radio frequency assigned above (step ST4c). Radio communication control unit 7 monitors the status of the jamming wave due to carrier sense of radio resource management unit 8 and detects the presence or absence of the jamming wave for the radio frequency (step ST5c).

[0067] At this time, when an interference wave is detected by the radio communication control unit 7, the line control unit 6 adds the time slot in the frequency table and the number of times of radio frequency allocation failure (step ST13c), Furthermore, the weighting for the time slot and frequency combination is changed (step ST14c). After this, by returning to the processing of step ST2c, weighting is performed. Based on this, the assignment is most likely to succeed! / Career sense is performed by selecting the combination of time slot and frequency again.

[0068] In step ST5c, when the radio communication control unit 7 does not detect an interference wave with respect to the radio frequency, the line control unit 6 notifies the mobile station 2b of the time slot and frequency of the allocation candidate, A time slot and frequency assignment notification message is sent to station 2b (step ST6c).

[0069] When the radio resource management unit 13 of the mobile station 2b receives the allocation notification message from the radio base station lb, the radio resource management unit 13 performs carrier sense for detecting the interference wave. The radio communication control unit 12 monitors the status of jamming waves due to carrier sense of the radio resource management unit 13, and detects the presence or absence of jamming waves for the radio frequency allocated on the time slot.

Here, if no interference wave is detected by the radio communication control unit 12, the line control unit 14 notifies the radio base station lb that a frequency can be allocated on the time slot. Do. Also, when an interference wave is detected at the relevant frequency, a notification is given to the radio base station lb that it is impossible to assign a frequency on the relevant time slot.

[0071] The radio communication control unit 7 of the radio base station lb receives a result of assignment or disapproval of the frequency from the mobile station 2b (step ST7c). In response to this result, the channel control unit 6 of the radio base station lb determines whether or not radio frequencies can be allocated on the time slot (step ST8c). Here, when the radio frequency can be assigned on the time slot, the line control unit 6 assigns the radio frequency to the speech channel on the time slot (step ST9c).

[0072] Thereafter, the line control unit 6 adds the number of successful allocations of the time slot and the radio frequency in the frequency table (step STIOc), and changes the weighting of the combination of the time slot and the frequency (step STl lc). For example, the weighting of the combination of the time slot and the frequency is increased (the weighting value is increased). As described above, when a radio frequency is assigned to the call channel in the time slot, the call of the mobile station 2b is started (step ST12c).

[0073] On the other hand, in step ST8c, if radio frequency allocation on the time slot is impossible, the line control unit 6 The number of radio frequency allocation failures is added (step ST13c), and the weight of the combination of the time slot and the frequency is changed (step ST14c). For example, the weighting of the combination of the time slot and the frequency is lowered (the weighting value is decreased).

[0074] After that, returning to the processing of step ST2c and repeating the above-described processing, the allocation is most likely to succeed based on the weighting according to the number of successful allocations and the number of failures. The combination is selected and notified to the mobile station 2b.

[0075] It should be noted that the initial value of the weighting of the combination of the time slot and the frequency in the frequency table is 0, that is, an equal state without weighting, and by repeating the processing of step STl lc and step ST14 c, The weight is changed according to the failure.

[0076] In addition, for changing the weighting of the combination of the time slot and the radio frequency in the frequency table, it is conceivable that the existing weighting is subtracted by 1 every time allocation fails and 1 is added every time allocation succeeds. Other than this, if allocation is the main criterion, if allocation is successful, a number greater than 1, for example, 2 may be added. If allocation failure is the main criterion, it will be greater than 1 for each allocation failure. A number, for example 2, may be subtracted. Note that such weighting change method should be changed as appropriate according to the communication environment and communication conditions for each hour.

[0077] Furthermore, when the second embodiment is applied, a plurality of frequency tables in which the number of past allocation successes and failures is classified according to time zones are provided, and a combination of time slots and frequencies is selected. A frequency table corresponding to the current time may be referred to. Further, the third embodiment may be applied to change the weighting of the combination of the time slot and the frequency in the frequency table in accordance with the allocation success and failure times.

[0078] According to the above-described Embodiment 4, the mobile station 2b exists at a line-of-sight position from each radio base station la, lb that is out of line-of-sight by the building 5 as in the area 4 shown in FIG. However, the optimal time slot and frequency for the communication channel for calls are allocated autonomously.

[0079] As described above, according to the fourth embodiment, the line controller 6 determines that the past allocation has been successful. Based on the weighting according to the number of failures, the frequency table power is selected as a candidate for allocation, which is the combination of time slot and frequency that is most likely to be allocated successfully. As a result, a radio frequency can be allocated from the radio base station lb to the mobile station 2b in an optimum time slot.

[0080] Embodiment 5.

The radio base station according to the fifth embodiment has the same configuration as that of FIG. 2 shown in the first embodiment. The difference from the above embodiment is that, when the channel control unit of the radio base station performs handover or switching of the call channel (TCH) while communicating with the mobile station, the frequency table weights the frequency. After the change, the frequency allocation is temporarily disabled.

Next, the operation will be described.

FIG. 9 is a flowchart showing a flow of radio frequency allocation by the mobile communication system of the fifth embodiment, which will be described in detail with reference to this figure.

In the following, a case will be described in which, in the communication area 3a shown in FIG. 1, the radio base station la and the mobile station 2a satisfy the conditions for occurrence of handover or TCH switching by receiving an interference wave on the radio channel during communication.

[0082] The line control unit 6 of the radio base station la receives an interference wave during communication with the mobile station 2a (step STld), and the communication quality of the radio line deteriorates or the reception level decreases. If the conditions for occurrence of hand-over or TCH switching are satisfied (step ST2d), V is assigned to the communication channel for mobile station 2a in the frequency table, and the number of radio frequency assignment failures is added (step ST3d).

[0083] Next, line control unit 6 temporarily disables assignment of the radio frequency with the changed weight to the communication channel in the frequency table (step ST4d). When handover is switched to TCH, communication at the radio frequency assigned to the previous call channel has been affected by disturbance interference. If such a radio frequency is reassigned to the call channel, interference may occur again.

[0084] Therefore, until the call using the radio frequency is terminated, the assignment of the frequency to the mobile station 2a is temporarily prohibited. This prevents interference from occurring again. It should be noted that other mobile stations (eg, mobile station 2b) that were weak during communication are located at different locations, and may not interfere with the jamming waves. This does not limit the allocation for the other mobile stations.

[0085] After the lapse of the allocation prohibition time, the line control unit 6 of the radio base station la searches the frequency table for the highest weighted (highest allocation priority) frequency, and determines whether the frequency is one or not. Is determined (step ST5d).

Here, if there is one frequency with the highest weighting, channel controller 6 selects that frequency as an allocation candidate, and proceeds to the processing of step ST6d. On the other hand, if there are multiple frequencies with the highest weight, a frequency that is a candidate for allocation is randomly selected from the multiple frequencies having the same weight (step ST17d), and the process proceeds to step ST6d. .

[0087] When an allocation candidate frequency is selected by the processing of step ST5d or step ST17d, the radio resource management unit 8 of the radio base station la performs carrier sense for interference wave detection on the allocated radio frequency. Execute (Step ST4d). Radio communication control unit 7 monitors the status of the jamming wave due to carrier sense of radio resource management unit 8 and detects the presence or absence of the jamming wave for the radio frequency (step ST7d).

[0088] At this time, when an interference wave is detected by the radio communication control unit 7, the line control unit 6 adds the number of times of allocation failure of the radio frequency (step ST15d), and further, in the frequency table, the frequency Change the weighting of (step ST16d). Thereafter, by returning to the processing of step ST5d, the allocation is most likely to be successful based on the weighting, and the frequency is selected again to perform carrier sense.

[0089] In step ST7d, if the radio communication control unit 7 does not detect an interference wave with respect to the radio frequency, the line control unit 6 notifies the mobile station 2a of the frequency of the allocation candidate to the mobile station 2a. A frequency allocation notification message is sent (step ST8d

) o

[0090] When the radio resource management unit 13 of the mobile station 2a receives the frequency allocation notification message from the radio base station la, the radio resource management unit 13 performs carrier sense for detecting an interference wave. The radio communication control unit 12 monitors the state of the jamming wave due to carrier sense of the radio resource management unit 13 and The presence or absence of an interference wave with respect to the radio frequency is detected.

Here, if no interference wave is detected by radio communication control unit 12, channel control unit 14 notifies radio base station la that the frequency can be allocated. When an interference wave is detected at the frequency, the radio base station la is notified that the frequency cannot be allocated.

[0092] Radio communication control unit 7 of radio base station la receives a result of assignability or impossibility of the frequency from mobile station 2a (step ST9d). Based on this result, the line control unit 6 of the radio base station la determines whether or not the radio frequency can be assigned (step STIOd). At this time, if the radio frequency can be assigned, the line control unit 6 assigns the radio frequency to the call channel (step ST1 Id).

[0093] Thereafter, the line control unit 6 adds the number of successful allocations of the radio frequency in the frequency table (step ST12d), and changes the weighting of the frequency (step ST13d). For example, a change is made to increase the weighting of the frequency (increase the weighting value!). When the radio frequency is assigned to the call channel as described above, the call of mobile station 2a is started (step ST14d).

[0094] On the other hand, in step STIOd, if the radio frequency allocation is not possible, circuit controller 6 adds the number of radio frequency allocation failures in the frequency table (step ST15d), and further Change the weighting of (step ST16d). For example, change the frequency combination to lower the weight (decrease the weight value).

[0095] Thereafter, returning to the processing of step ST5d and repeating the above-described processing, the frequency that is most likely to be successfully allocated is selected based on the weighting according to the number of successful and unsuccessful allocations, and the mobile station 2a To be notified.

[0096] As described above, according to the fifth embodiment, when a handover or switching of a communication channel occurs due to an interference wave during communication with a mobile station, the frequency is weighted in the frequency table. After the change, the frequency allocation is temporarily disabled. This prevents reassignment of the frequency that was interfered by the jamming wave as the frequency after switching during handover or switching of the call channel, and increases the probability of successful frequency assignment. be able to.

[0097] It should be noted that when the embodiment 5 is applied to the embodiment 4 and an interference wave is received during the communication between the radio base station la and the mobile station 2a, the radio frequency of the speech channel of the mobile station 2a is set. You may pause the process assigned to the time slot!

Industrial applicability

As described above, since the radio base station according to the present invention can reduce interference in an area where communication areas of a plurality of radio base stations overlap, a DCA mobile communication system having a plurality of radio base stations Suitable for

Claims

The scope of the claims

[1] A frequency table in which radio frequencies weighted according to the number of successful and unsuccessful assignments are registered;

When allocating radio frequencies for communication of mobile stations, the frequency table is referred to, the radio frequency candidates for communication are selected based on the weights, and the allocation candidates are selected according to the success or failure of the allocation. And a line control unit that changes the weighting of the radio frequency.

[2] Has multiple frequency tables classified according to past allocation time zones,

2. The radio base station according to claim 1, wherein the line control unit refers to a frequency table corresponding to a current time from among the plurality of frequency tables when assigning a radio frequency for communication of the mobile station.

[3] The radio base station according to claim 1, wherein, when changing the weighting of the radio frequency, the line control unit changes the weighting according to an increment and a decrement corresponding to the lapse of allocation time.

4. The radio base station according to claim 1, wherein the line control unit temporarily stops assignment of radio frequency for communication when receiving an interfering wave during communication with the mobile station.

[5] A frequency table in which combinations of time slots and radio frequencies weighted according to the number of successful and unsuccessful assignments are registered;

When allocating radio frequencies for mobile station communication on a time slot, the frequency table is referred to, the allocation candidates for the combination are selected based on the weights, and the allocation candidates are determined according to the success or failure of the allocation. And a line control unit that changes the weight of the combination.

[6] Has multiple frequency tables classified according to the time slot of time slot and radio frequency combination allocation,

6. The line control unit refers to a frequency table corresponding to a current time from among the plurality of frequency tables when assigning a radio frequency for communication of a mobile station on a time slot. Wireless base station.

[7] The line controller is responsible for changing the weighting of the combination of time slot and radio frequency. 6. The radio base station according to claim 5, wherein the weighting is changed in accordance with an increment and a decrement corresponding to an elapsed time of allocation.

6. The radio base station according to claim 5, wherein the line control unit temporarily stops assignment of a combination of a time slot and a radio frequency when receiving an interference wave during communication with the mobile station.