JP2000316183A - Mobile communication system and channel assignment method in the same system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce or eliminate radio wave interference between adjacent radio bases in a system and to improve effective frequency use of the system by assigning a channel in which the radio wave interference is not generated to communication of the radio base station based on information of the radio wave interference between radio base stations. SOLUTION: Radio base stations 1 to 5 form service areas 101 to 105. When there is a call from mobile radio equipment in the service area 101, the base station 1 which receives the call transmits an assignment demand signal of a communication channel to a controller. The controller which receives a demand signal assigns a speech channel and a time slot to be communicated with the mobile radio equipment. In the case, the controller does not give interference interruption to communication of nearby base stations 2, 4 and 5 which are already progressing at this point of time and, on the contrary, assigns a radio channel and the time slot which do not receive interference interruption from communication of the nearby base stations 2, 4 and 5 to communication of the mobile radio equipment itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio base station of a mobile communication system using a time-division multiplexed digital signal. Methods and systems for implementing low traffic channel assignments. More specifically, a plurality of wireless base stations belonging to the same system exist in a service area, and a plurality of nearby wireless base stations exist in each service area. (Other mobile phones, mobile data terminals, etc. have different names, but hereafter collectively referred to as mobile radios.) When good wireless communication is performed, a control device that collectively manages each radio base station collects and stores in advance. If the same radio channel and the same time slot are assigned to the same base station at the same time based on the obtained information, interference may occur. The present invention relates to a communication channel allocating method and system for reducing or eliminating such interference as much as possible and effectively using the frequency of the system.

[0002]

2. Description of the Related Art In mobile communication systems, service areas are expanding as information communication and users (subscribers) are rapidly expanding. To cope with the sudden increase in subscribers,
Effective use of frequency is essential. As a technical solution, there is a digitization of a signal format, and there is a method of narrowing a service area of one radio base station and increasing a frequency reuse rate in different places. As a system in which the service area of one radio base station is extremely narrow with a radius of about 100 meters, in Japan, for example, 1.9 GHz
There are digital cordless telephone systems that use bandwidth. Although the communication capacity of the entire system is required to be considerably large, the required communication capacity per radio base station is considerably reduced as a result of narrowing the service area controlled by one radio base station. However, it is natural that the number of required radio base stations included in the system has become considerably large.

[0003] Specifically, for example, a digital cordless telephone system is taken as an example. Unlike other cellular systems, the radio base stations in this system are not strictly designed in advance so that the locations of the radio base stations are not mutually interfered, and therefore the distance between the radio base stations is different. As a result, if the same radio channel and the same time slot are allocated to the same time at a plurality of adjacent radio base stations, interference may occur.

However, since the number of wireless channels allocated to the system is large, radio interference can be avoided with a simple technique, and the problem did not become apparent. The communication frequency is 37 radio channels x 4 (slot)
= 148 communication channels (8 communication channels TDMA-TD)
D (Time Division Multiple A)
access Time Division Dupl
ex)), while the communication capacity per wireless base station, that is, the communication traffic used simultaneously, is sufficient for about 4 or 8 traffic channels. For this reason, each radio base station monitors interference power at any time without particularly limiting the communication channels that can be allocated, and assigns a communication channel with a low interference level to the communication channel to maintain good communication. Can be handled.

[0005] However, T, which is a kind of digital signal format adopted from the viewpoint of further effective use of frequency, is used.
DMA / CDMA (Time Division Mu)
single Access / Code Divis
In ion multiple access), the following technical problems have occurred, and the solution has to be solved.

[0006]

In a system using a time-division multiplexed digital signal (TDMA / CDMA), a communication channel is allocated to each base station in units of time slots from the viewpoint of interference canceller technology. Thus, the control of the communication channel allocation can be simplified, and the capacity can be increased. However, since the distance between the wireless base stations in the system is not always uniform, it is not possible to determine a base station that may cause interference in the same system and a base station that does not cause interference. Therefore, if the assignment is performed indiscriminately as described above, the possibility of occurrence of interference becomes large, and it becomes difficult to maintain good communication.

Accordingly, the present invention provides means for reducing or eliminating radio interference generated between adjacent radio base stations in the above-mentioned system and improving the effective use of the frequency of the system.

First, at the time of system installation, each radio base station follows an instruction from a control device that supervises control of the system,
Transmit the signal using the common control channel. However, in order to prevent a plurality of wireless base stations from transmitting the common control channel at the same time, the control device designates and executes the wireless base station to be transmitted for each time. In accordance with this designation, each nearby radio base station receives the transmitted signal of the common control channel and notifies the control device of its own radio base station number and reception level. However, when the transmission power of the common control channel transmitted from the radio base station differs for each radio base station, the transmission power level is also included in the signal of the common control channel and transmitted.

FIG. 2 is a diagram showing an example of a radio wave reception level between radio base stations in a mobile communication system. The control device can create and store a reception level table between the respective radio base stations as shown in FIG. 2 by sequentially performing the above operation for each of the radio base stations. The details of FIG. 2 will be described later. As described below, this table is used when the control device allocates a communication channel in the same radio channel to be used by the subordinate radio base station, that is, when allocating a certain code in a time slot, when performing a communication channel allocation without interference. used.

The operation when the above-described means is applied to a system will be described.

When a call is made from a mobile radio located in a service area of a certain radio base station, a control device for controlling the call allocates a communication channel with which the radio base station communicates with the mobile radio. However, at this time, good communication is maintained without interfering with other communications that are proceeding simultaneously at the time of communication and conversely, preventing interference from other communications with respect to own communication. This is the maximum requirement for communication control.

That is, in a mobile communication system using a time-division multiplexed digital signal, a call signal is transmitted using a control channel from one mobile radio located in a service area of a radio base station to which the system belongs. Suppose you came. The wireless base station receiving this transmits this information to the control device. The control device that has received this signal stores the radio channel in use by this radio base station and nearby radio base stations, the usage status of the speech channel included in each time slot in the radio channel, and stores the radio channel. FIG.
The presence or absence of a communication channel that is not likely to cause interference is examined using the table of FIG.

As a result, if it can be recognized that there is a communication channel in which no interference is likely to occur, the method of giving the most effective frequency utilization as a system is examined and executed. Will be.

[0014] As a result of the above examination, if there is no communication channel in which interference is not likely to occur, it is determined whether to accept the call in consideration of the importance of the mobile radio which requested the call. consider. As a result, in the case of a mobile wireless device having a high degree of importance, it is necessary to minimize the occurrence of interference and obstruction to other communications, and to study and execute a method for improving the effective frequency utilization as a system. .

[0015]

An invention according to claim 1 is a mobile communication system provided with a plurality of radio base stations, wherein radio interference between the radio base stations with respect to communication of the radio base stations is provided. Channel assigning means for assigning a channel in which the radio wave interference does not occur based on the information of (1).

According to a second aspect of the present invention, in the mobile communication system according to the first aspect, the system has a plurality of radio channels, each radio channel has a plurality of speech channels, and the channel allocating means. Is characterized in that, when there is a radio channel not used by any radio base station, an arbitrary communication channel within the radio channel is allocated.

According to a third aspect of the present invention, in the mobile communication system according to the first or second aspect, the system has a plurality of radio channels, and each radio channel has a plurality of speech channels. The allocating means does not include any radio channel that does not use any radio base station, but includes, in the radio channel, a communication channel that does not use any radio base station.
A communication channel that does not cause the radio wave interference is allocated.

According to a fourth aspect of the present invention, in the mobile communication system according to any one of the first to third aspects, the system has a plurality of radio channels, and each radio channel has a plurality of speech channels. Each of the communication channels can be multiplexed into two or more by code or frequency, and the channel allocating means has no radio channel that is not used by any radio base station. If there is no communication channel in which no interference occurs, a combination of a code or a frequency in which the radio interference does not occur and a communication channel is assigned.

According to a fifth aspect of the present invention, in the mobile communication system according to any one of the first to fourth aspects, the channel allocating unit uses a channel other than a radio base station other than a radio base station to which a channel is allocated. The present invention is characterized in that a channel to be allocated is determined in consideration of an influence on channel use.

According to a sixth aspect of the present invention, in the mobile communication system according to any one of the first to fifth aspects, the channel allocating means is provided when there is no channel in which the radio wave interference does not occur. A mobile communication system characterized in that when it is necessary to assign, based on information on the radio interference between the radio base stations, a channel in which the generated radio interference is small is allocated.

According to a seventh aspect of the present invention, in the mobile communication system according to any one of the first to sixth aspects, the information on radio wave interference between the radio base stations includes a common control channel between the radio base stations. It is characterized by the reception level of a radio wave when a signal is transmitted and received by using the signal.

The invention according to claim 8 is a channel allocation method in a mobile communication system having a plurality of radio base stations, wherein information on radio interference between the radio base stations with respect to communication of the radio base stations is provided. , A channel in which the radio interference does not occur is assigned.

According to the above configuration, radio interference can be reduced as much as possible in the mobile communication system, the subscriber capacity can be increased as a system, and a service of good communication quality can be provided to the user. .

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a diagram showing a configuration example of a mobile communication system including a plurality of radio base stations (for example, a digital cordless telephone system for business use). In this case, four radio base stations 71 to 74 are shown, and these are PBX
The lines are concentrated to the control device 70 having the equal control function. Each wireless base station has service areas 171 to 174, and the service areas are gathered to form a service area of the system. Numerals 81 to 88 in the figure denote mobile wireless devices (mobile phone (data) devices, mobile terminals). The mobile radio can freely move to the service areas 171 to 174 of another radio base station while communicating within the service areas 171 to 174.

FIG. 2 is a diagram showing an example of the reception level of radio waves between radio base stations in a mobile communication system as described above. That is, each radio base station 1 to use for communication
For each of the five radio channels, each of the radio base stations 1 to 5 is provided with a control device that comprehensively controls each of the radio base stations 1 to 5 in advance. It reports the information of. Here, the transmission power is assumed to be known, but the transmission power and the reception level may be reported together. The number in each column in the figure indicates the magnitude of the amount of interference, and the larger the numerical value, the greater the amount of interference. A blank column means that the interference amount could not be measured at all, and indicates that there is no interference relationship. Note that, for example, the transmission of the radio base station 1 and the radio base station 4
The difference between the measured interference amount at the time of reception and the measured value at the time of transmission of the radio base station 4 and the reception of the radio base station 1 indicates that there is a measurement error between the radio base station 1 and the radio base station 4. I have. The similar thing is that there is an interference relationship when the radio base station 5 transmits and the radio base station 1 receives, but when the radio base station 1 transmits and the radio base station 5 receives, the measured value of the interference amount is obtained. No, this is because the effective radiated power level of the radio base station 1 is low,
This indicates that no interference has occurred in the wireless base station 5.

FIG. 3 is a diagram showing an image of an example of a frame structure used in a mobile communication system using a time-division multiplexed digital signal. The horizontal axis represents the time axis, and one frame has 16 time slots. The vertical axis represents codes or frequencies. This figure shows an example in which the number of codes or frequencies in the vertical axis direction is 8, and eight communication channels are multiplexed.

FIG. 4 is a diagram showing an example of the arrangement of radio base stations in a digital cordless telephone system for business use. 5 in the figure
Ellipses represent each of the radio base stations 1 to
5 shows the service area No. 5. Each of the wireless base stations 1 to 5 is indicated by a rectangle. In FIG. 4, the overlap of the ellipses indicates that the service areas overlap, but in the overlapped area, the radio signals transmitted from each of the wireless base stations 1 to 5 that control the area may indicate interference. Is shown. Although not shown, a large number of mobile radios exist in the service area of the system and are in a communication or standby state. Although not shown, the system includes a control device for controlling all the radio base stations 1 to 5 shown in FIG. 4 and is connected to each of the radio base stations 1 to 5 by a transmission line. ing. The result of FIG. 2 described above can be considered as a measurement example in the case where the radio base station arrangement is as shown in FIG.

FIG. 5 is a diagram showing an example of a communication channel used in each radio base station of FIG. That is, the communication channel used between each mobile radio device and the service area of each of the radio base stations 1 to 5 is displayed.

FIG. 6 is a diagram showing an example of a communication channel used in each radio base station of FIG. 4 at the time of traffic congestion.

Hereinafter, the system shown in FIG. 4 will be described as an example. It is assumed that a call is made from a mobile wireless device (not shown) existing in the service area of the wireless base station 1 using a control channel. The radio base station 1 receiving this signal transmits a communication channel assignment request signal to the control device. The control device receiving this signal specifies the communication channel and time slot with which the radio base station should communicate with the mobile radio. Start the assignment operation. In this case, the control device does not interfere with other communications already in progress at this time, and conversely, does not interfere with the communication of the mobile radio itself from other communications, It is determined whether a time slot can be assigned. If the call traffic in the service area is not congested, the following process is performed.

The controller uses the radio channel in use by the nearby radio base station, the used speech channel in the radio channel, that is, the used time slot and the table in FIG. 2 to cause interference. Investigate the existence of wireless and communication channels that are not possible. as a result,
When a plurality of wireless channels are provided in the system, if there is a wireless channel 2 which is not used at all and traffic traffic is low, an arbitrary traffic channel within the wireless channel 2, for example, the traffic channel 1 is allocated. .

In the above case, since the radio channel 2 is not used at all by the radio base stations 2, 4 and 5 around the radio base station 1, the assignment to the radio base station 1 is arbitrary. No interference occurs even if any communication channel, that is, any time slot is assigned. Therefore,
This is the case where assignment of time slots is easy and causes the least problem.

Next, a description will be given of the assignment of a time slot which should be noted. This is the case when the communication traffic in the vicinity of the calling mobile radio device is slightly congested. In this case, even if the system has multiple radio channels,
There will be no completely unused radio channels. Therefore, the control device cannot provide a wireless channel having no interference relation regardless of the communication state of the wireless base station in the vicinity. That is, it is possible to solve the problem as to which time slot should be given to avoid interference.

For the sake of simplicity, the radio channel number to be allocated is set to 1, the number of time slots that can be allocated in the radio channel 1 is set to 4, and the multiplicity in the time slot is set to 1
And It is assumed that these use states are as shown in FIG. In the figure, ○ indicates that the channel is in use, ☆ indicates that the channel is unused, that is, it is an idle channel, so that if there is a new call, it can be used, and Δ indicates that channel. Is not used, but if used, there is a possibility that interference may occur in the speech channel being used by the adjacent radio base station, indicating that it is practically unusable. The state of each of the wireless base stations 1 to 5 in FIG. 5A can be described as follows.

In the radio base station 1, the communication channel 1 is in use, the communication channel 4 is idle, and the communication channels 2 and 3 cannot be used.

In the radio base station 2, the communication channel 4 is idle, and the communication channels 1, 2, and 3 cannot be used.

In the radio base station 3, the communication channels 1 and 2 are in use, and the communication channels 3 and 4 are idle.

In the radio base station 4, the communication channel 2 is in use, the communication channels 3 and 4 are idle, and the communication channel 1 is unavailable.

In the radio base station 5, the communication channel 3 is in use, the communication channels 2 and 4 are idle, and the communication channel 1 is unavailable.

In the above state, it is assumed that a new call originates from a mobile radio within the service area of the radio base station 5. The control device that has received the call request from the radio base station 5 examines which communication channel to give to the radio base station 5 is optimal in view of the entire system, that is, determines whether the system has the highest frequency effective use and executes it. Will do. The method will be described below. After examining the call channel that can be assigned by the radio base station 5, the control device recognizes that the call channel 2 or 4 can be assigned. Therefore, if the communication channel 2 is allocated, the effect on the adjacent radio base stations 1 and 2 is shown in FIG. The meaning of this figure is as follows.

A new communication channel 2 at the radio base station 5
(Indicated by □ in the figure), the radio base station 1,
There is no interference at all stations of 2, 3 or all of the radio base stations 4, and the available idle speech channels owned by each radio base station do not change to unusable due to a new call. .

On the other hand, if the communication channel 4 is allocated, the effect on the adjacent radio base station is as shown in FIG. The meaning of this figure is as follows.

A new communication channel 4 at the radio base station 5
Even if (が in the figure) is started to be used, no interference has occurred in all the stations currently in communication, but the idle communication channel 4 cannot be used in the radio base stations 1 and 2 (FIG. 5).
(A) changes to (△) in (a). As a result, there is no available communication channel in the wireless base station 2, and it becomes impossible to cope with the occurrence of a new call. In addition, since the idle communication channel 4 cannot be used in the radio base station 1, it is impossible to cope with the occurrence of a new call unless the currently used communication channel 1 becomes idle.

The above is an example, and the number of time slots of the radio channel is limited to four, and the multiplicity is 1. However, the actual number of time slots is 8 or 16, and the multiplicity is 8 channels. And a large number of them, which is more complicated than the above, but the basics of the method of assigning the communication channel are the same as above. Further, the number of radio base stations in an actual system is often not less than 10 and cannot be limited to 5 as in the above example, but the considerations in the control device are exactly the same as in this example. As described above, it has been clarified that the assignment of the communication channel in the control device has a large effect on the increase in the capacity of the communication traffic in the entire system, and therefore plays a large role in improving the effective use rate of the frequency.

Further, when a new mobile radio device makes a call to a place where the call traffic in the system is congested (or when a mobile radio device in the system service area receives a call) The channel allocation method of the control device will be described. FIG. 6 shows a call situation in the service area in such a case. In this case, the meaning of the numbers in each column is the same as in FIGS. 5 (a) to 5 (c). That is,
The state shown in FIG. 6 is a state in which call traffic is full in all the radio base stations 1 to 5, and a state in which a new call can not be accepted without interference to another channel.
In such a state, the control device should accept or not. A normal subscriber would reject the call acceptance (rejection by busy tone). However, what if the caller is an important subscriber or an emergency call? In this case, rejection of call acceptance is inappropriate, and it is conceivable to accept the call by forced termination of another general subscriber who is currently talking on the phone. In this case, a call is accepted by allowing some interference. However, this acceptance also depends on the implementation method,
It is possible to minimize the occurrence of interference with others, which will be described below.

It is assumed that a new call is made from a mobile radio located in the service area of the radio base station 2. Which of the unavailable idle speech channels 1 to 3 should the controller allocate? In this study, the following cases 1 and 2 are considered, and the effects of the results on the entire system are also different.

Case 1: When the communication channel 1 is assigned by the radio base station 2, the interference amount to the radio base station 1 is 30 dB
u, the amount of interference with the wireless base station 3 is 13 dBu, the amount of interference with the wireless base station 5 is 8 dBu (however, there is no actual harm because it cannot be used), and no amount of interference with the wireless base station 4 results.

Case 2: When the communication channel 2 or 3 is allocated by the radio base station 2, the amount of interference with the radio base station 1 is 3
0dBu (however, there is no actual harm because it cannot be used), the interference amount to the wireless base station 3 is 13dBu, the interference amount to the wireless base station 5 is 8dBu, and the interference amount to the wireless base station 4 is no result.

Therefore, in this case, a large interference disturbance of 30 dBu is applied to the communication actually performed by the wireless base station 1 in case 1, but 8 dBu is applied to the communication performed by the wireless base station 5 in case 2. It will give a fairly small interference. However, in both cases 1 and 2, the amount of interference with the radio base station 3 gives a slightly large interference of 13 dBu, but this is unavoidable. Therefore, it is optimal for the radio base station 2 to allocate the communication channel 2 or 3.

The above is an example, and the number of time slots of the radio channel is limited to four and the multiplicity is one.
However, since the actual number of time slots is 8 or 16, and the multiplicity is as large as 8 channels, it is more complicated than the above, but the basic method of assigning the communication channel is the same as above. is there. Further, the number of wireless base stations in an actual system is often not less than 10 and is often 5 as in the above example.
Although it cannot be limited to a station, the considerations in the control device are exactly the same as in this example. As described above, it has been clarified that the assignment of the communication channel in the control device has a large effect on the increase in the capacity of the communication traffic in the entire system, and therefore plays a large role in improving the effective use rate of the frequency.

Hereinafter, the method of FIG. 1 will be described with reference to the flowchart of the system operation shown in FIG. 7, and the control device suitable for the call traffic state in the system described above will be described with reference to the flowcharts of the system operation shown in FIGS. A communication channel assignment method will be described.

FIG. 7 is a flowchart for obtaining a radio wave reception level between radio base stations in a mobile communication system.

Hereinafter, a case where the procedure shown in FIG. 7 is applied to the system shown in FIG. 4 will be described as an example. It is assumed that the control device and the radio base stations 1, 2, 3, 4, and 5 of the system in FIG. 4 have started operation but have not yet actually operated the system. In the control device, the subordinate radio base stations 1 to 5
For all of the above, performing signal transmission at a specified transmission power level using a common control channel according to the allocated time timing, and measuring the reception level of a signal transmitted from a peripheral wireless base station, Is transmitted (S10). Each of the radio base stations 1 to 5 receiving the signal from the control device transmits the signal on the common control channel at the given time timing, and measures the reception level of the signal transmitted from the peripheral radio base station. Execute (S20). The signal transmitted from each radio base station includes the I
In addition to D (identification information), the transmission power level of the common control channel is also included.

Next, the control device requests all the subordinate radio base stations 1 to 5 to transmit the above measurement result at the reception level to the control device at the assigned time timing (S30). Each of the radio base stations 1 to 5 receiving this instruction transmits each reception level to the control device at the given time timing (S40). The control device that has received these reception levels from the radio base stations 1 to 5 creates and stores the reception levels between the respective radio base stations (S50).

FIG. 2 is completed by the above-described process, and the control device 10 can start system operations such as calling and receiving using FIG.

Next, a description will be given of the operation of the system when the traffic traffic state in the system is rather high and attention must be paid to the communication channel assignment of the control device.

FIG. 8 is a flowchart showing the operation of the system when the traffic traffic state in the system is rather high and attention must be paid to the communication channel assignment of the control device. System control device, radio base stations 1, 2, 3, 4,
It is assumed that many mobile radios in the service area including the mobile communication devices 5 and 5 have already started the system operation. It is assumed that the call traffic in the system is in the state shown in FIG. At this time, it is assumed that a new call is originated from the mobile radio and a call signal is transmitted on the uplink control channel (S210). This signal is received by the nearest wireless base station 5 and transmits a request signal for traffic channel assignment to the control device (S220). When the control device, which has received the call channel assignment request from the radio base station 5, determines the call traffic in the service area of the system, FIG.
Recognizing that it is in the state shown in (a), the study of the communication channel used by the radio base station 5 is started with reference to FIG. 2 (S230). As a result, it is found that the communication channel 2 or 4 is possible without causing interference to the communication channel used by the nearby radio base station. However, when the communication channel 2 is given, as shown in FIG. 5B, the nearby radio base stations 1, 2
There is no change in the state of the idle channel owned by the communication channel 4, but when the communication channel 4 is given, the state of the idle channel owned by the nearby wireless base stations 1 and 2 becomes available as shown in FIG. It turns out that it changes into unusable.
Therefore, it is not wise to provide the communication channel 4 and it is determined that the communication channel 2 should be provided.

Then, the radio base station 5 is notified that the communication channel 2 is to be provided (S240). Upon receiving this communication, the radio base station 5 sends a call channel 2 to the mobile radio.
Is instructed to be used (S250). The mobile wireless device transmits a dial signal on the call channel 2 according to the instruction signal (S260). This signal is received by the wireless base station 5 and transferred to the control device (S270). The control device transfers the data to the communication network side (S280), and transmits it to the called telephone in the communication network. However, the communication network and the called telephone are not shown. With the above process, the setting of the transmission path between the calling party and the called party is completed, and when the called party hangs up the telephone, the call is started (S290).

Further, a description will be given of the allocation of a communication channel when the communication traffic in the system is in a congested state as shown in FIG.

FIG. 9 is a flow chart showing a system operation of allocating a communication channel when communication traffic in the system is in a congested state. Many mobile radios in the service area are communicating with each radio base station facing each other, and as a result, when a new call occurs in the service area, the control device interferes with other calls. It recognizes that it is not possible to grant a communication channel without having. It is assumed that a new call request is issued from a mobile radio located in the service area of the radio base station 2 in such a call traffic state. What to do if a new call request comes from an important subscriber The operation in such a case will be described with reference to the flowchart of the system operation shown in FIG. System control device, radio base station 1,
Many mobile radios in the service area, including 2, 3, 4, and 5, have already started operating the system.

At this time, it is assumed that a new call is generated from the mobile radio and a call signal is transmitted on the uplink control channel (S410). This signal is received by the nearest wireless base station 2 and transmits a request signal for traffic channel assignment to the control device (S420). The control device, which has received the call channel assignment request from the radio base station 2, examines the call traffic in the service area of the system and recognizes that the state is as shown in FIG. Since the subscriber is a subscriber, a slight interference is allowed with reference to FIG.

As a result, the radio base station 2 recognizes that there is an unusable communication channel 1, 2 or 3 which is an idle channel. Among them, it is examined which channel is given to minimize the interference and disturbance given to the communication of the nearby radio base station (S430). Therefore, when investigating the case where the communication channel 1 is given, it is found that the adjacent wireless base station 1 has 30 dBu and the wireless base station 3 has 13 dBu.
u, and 8 dBu of interference to the radio base station 5. However, there is no actual harm to the radio base station 5 since the communication channel 1 is an unusable channel. Next, when investigating the case where the communication channel 2 or 3 is given, there is no actual harm to the radio base station 1 because it is an unusable channel. However, 13 dB to the wireless base station 3
u, and 8 dBu of interference to the radio base station 5. By comparing and examining the above results, the radio base station 1
It is not appropriate to use the communication channel 1 which gives an interference of as large as 30 dBu to the radio base station 5 which has a small amount of interference of 8 dBu and the communication channel 2 or 3 which gives the radio base station 3 an amount of interference of 13 dBu. It is concluded that the use has low system-wide interference. Therefore, it is determined that the communication channel 2 should be given.

Then, the radio base station 2 is notified that the communication channel 2 is to be provided (S440). Upon receiving this communication, the wireless base station 2 sends a call channel 2 to the mobile wireless device.
Is instructed to be used (S450). The mobile radio transmits a dial signal on the call channel 2 according to the instruction signal (S460). This signal is received by the wireless base station 2 and transferred to the control device (S470). The control device transfers the information to the communication network side (S480), and transmits it to the called telephone in the communication network. However, the communication network and the called telephone are not shown. With the above process, the setting of the transmission path between the calling party and the called party is completed, and when the called party hangs up the telephone, the call is started (S490).

As described above, even when the call traffic in the system is in a congested state, the call is accepted for the important subscriber, and the occurrence of some interference between itself and other communication is acknowledged. In addition, minimizing the amount of the interference as much as possible increases the reliability of system operation and leads to effective use of frequency.

In the present embodiment, the case where the multiplicity according to the code or frequency in the communication channel (time slot) is 1 has been described as an example. Even if there is no unused radio channel and there is no communication channel in the radio channel where radio wave interference does not occur even if the radio channel is allocated, changing the code or frequency and assigning the combination of the code or frequency and the communication channel Radio interference can be avoided.

[0067]

According to the present invention, in order to cope with the needs for wireless use, which is increasing more and more in the future, further effective use of frequencies is required, while a low-cost system is required. As a result, like a digital cordless telephone system, there is a tendency that installation of a wireless base station is performed without much consideration of radio wave propagation characteristics. In such a system in which the radio base stations are arranged, when the traffic of the communication in the service area increases, the communication performed between the radio base station and the mobile radio in the same system is changed to the radio base station in the vicinity. Between the communication between the station and the mobile radio,
Mutual interference may occur. As a result, the communication quality is degraded and the effective frequency utilization is reduced. On the other hand, if the present invention is applied, it is possible to prevent radio interference occurring between adjacent wireless base stations in the same system beforehand, or even when the call traffic in the system is congested, the present invention can be applied. By applying the above, it is possible to provide a communication channel for a new call with as little interference as possible. As a result, it is possible to improve the communication quality and the effective use of the frequency of the system by increasing the number of simultaneous callers in the system,
The effect of the present invention is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a mobile communication system including a plurality of wireless base stations.

FIG. 2 is a diagram illustrating an example of a reception level of a radio wave between wireless base stations in a mobile communication system.

FIG. 3 is a diagram showing an image of a frame configuration example used in a mobile communication system using a time-division multiplexed digital signal.

FIG. 4 is a diagram showing an example of an arrangement of wireless base stations in a digital cordless telephone system for business use;

FIG. 5 is a diagram illustrating an example of a communication channel used in each wireless base station in FIG. 4;

FIG. 6 is a diagram illustrating an example of a communication channel used in each wireless base station in FIG. 4 at the time of traffic congestion.

FIG. 7 is a flowchart for obtaining a radio wave reception level between radio base stations in a mobile communication system.

FIG. 8 is a flow chart showing the operation of the system when the traffic traffic state in the system is rather high and attention needs to be paid to the communication channel assignment of the control device.

FIG. 9 is a flowchart showing a system operation of a communication channel assignment when the communication traffic in the system is in a congested state.

[Explanation of symbols]

 1 to 5, 71 to 74 Radio base station 70 Controller 81 to 88 Mobile radio 101 to 105 Service area of radio base station

Continued on the front page F term (reference) 5K022 EE02 EE11 EE21 EE31 FF01 5K028 AA02 BB06 CC02 CC05 DD01 DD02 HH02 LL02 LL42 PP04 5K033 AA05 AA07 CA12 CB01 DA01 DA19 DB17 EA02 5K067 AA03 AA11 CC04 DD19 DD23 DD23 DD23 JJ12 JJ17 LL11

Claims (8)

[Claims] 1. A mobile communication system comprising a plurality of radio base stations, wherein a channel in which said radio base station does not generate radio interference is determined based on radio interference information between said radio base stations. A mobile communication system comprising channel assignment means for assignment. 2. The mobile communication system according to claim 1, wherein the system has a plurality of radio channels, each radio channel has a plurality of communication channels, and said channel allocating means is any radio base station. A mobile communication system characterized in that, when there is a wireless channel that is not being used, any communication channel within the wireless channel is allocated. 3. The mobile communication system according to claim 1, wherein the system has a plurality of radio channels, each of the radio channels has a plurality of communication channels, and the channel allocating means is any one of the radio channels. If there is no wireless channel that is not used by the base station, but there is a communication channel that is not used by any of the wireless base stations in the wireless channel, a call in which the radio interference does not occur is included in the communication channel. A mobile communication system characterized by allocating a channel. 4. The mobile communication system according to claim 1, wherein a plurality of radio channels are provided in the system, each radio channel has a plurality of communication channels, and each communication channel has a code or a code. It is possible to multiplex to two or more according to the frequency, and the channel allocating means has no radio channel that is not used by any radio base station,
A mobile communication system, wherein if there is no communication channel in which the radio interference does not occur even if the radio channel is allocated, a combination of a code or a frequency and a communication channel in which the radio interference does not occur is allocated. 5. The mobile communication system according to claim 1, wherein said channel allocating means comprises:
A mobile communication system characterized in that a channel to be allocated is determined in consideration of an influence on a channel usage by a radio base station other than the radio base station to which the channel is allocated by channel allocation. 6. The mobile communication system according to claim 1, wherein the channel assignment unit comprises:
When there is no channel in which the radio interference does not occur, and when it is necessary to allocate a channel, a channel in which the generated radio interference is small is allocated based on information on the radio interference between the radio base stations. Mobile communication system. 7. The mobile communication system according to claim 1, wherein information on radio interference between the radio base stations is transmitted and received between the radio base stations using a common control channel. A mobile communication system characterized by a radio wave reception level. 8. A channel allocation method in a mobile communication system including a plurality of radio base stations, wherein the radio interference with respect to the communication of the radio base stations is based on radio interference information between the radio base stations. A channel assignment method in a mobile communication system, wherein a channel that does not occur is assigned.