JP2780683B2 - Mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system for performing communication between a mobile station and a base station, and more particularly to a mobile communication system in which a free channel is selected from a plurality of communication channels commonly allocated to a plurality of base stations. The present invention relates to a mobile communication system that performs communication selectively.

[0002]

2. Description of the Related Art In a large-capacity mobile communication system such as an automobile telephone system, a service area is covered by a plurality of base stations, and the same channel is repeatedly used between base stations which do not cause interference. The frequency is used effectively. Such a system is called a cellular system.

[0003] As a channel allocation system used in each base station, there is a so-called dynamic channel allocation system in which a channel that does not cause interference is selected and used for each communication. Although the control method and the configuration of the device are slightly complicated, any channel can be used arbitrarily as long as interference does not occur, so that there is an advantage that the number of subscribers that can be accommodated can be increased. Allocation schemes are commonly employed.

FIG. 8 shows a flow of an operation for allocating channels according to a conventionally used dynamic channel method. A total of N (N arbitrary positive integers) channels are prepared for the communication channels common to each base station. Also, these N call channels include:
First to N-th channel numbers are assigned. The selection order for searching for an available channel is the same for each base station, and the search is performed in order of channel number from the first communication channel.

[0005] The base station periodically receives and stores the interference level of the idle channel. This value is Ups
(I). Here, "i" represents a channel number. Also, the transmission power of the mobile station and the transmission power of the base station are known. The transmission power of the mobile station is represented by Pms, and the transmission power of the base station is represented by Pbs. When a call request or a call request is generated, the base station stores the reception level of the call request signal or the call response signal received on the control channel as an uplink desired wave level (Dup) (step S101). Next, the transmission power of the mobile station (Pm
The value obtained by subtracting the desired uplink signal level (Dup) from s) is stored as the propagation loss between the base station and the mobile station (step S102). Here, the propagation loss is represented as L.

Since reversibility is established between the uplink from the mobile station to the base station and the downlink from the base station to the mobile station,
It is considered that the propagation loss on the uplink and the propagation loss on the downlink are the same. Therefore, a desired downlink level at the mobile station is obtained by subtracting the propagation loss (L) from the transmission power (Pbs) of the base station (step S103). Here, the desired downlink wave level is represented as Ddown. Since an empty channel is searched from the first communication channel, the channel number parameter (i) is initialized to "1" (step S104). Next, the desired upstream signal level (Dup)
Is subtracted from the uplink interference wave level (Ups (1)) of the first communication channel, which is measured regularly in advance. This value is the uplink desired wave to interference wave power ratio in the first communication channel. Then, it is compared with a predetermined value (CIRth) predetermined as a value of the uplink desired wave interference wave power ratio necessary to secure an appropriate communication state (step S).
105).

[0007] When the power ratio of the desired uplink signal to the interference signal is equal to or higher than the required value (step S105; Y), the base station instructs the mobile station to measure the downlink interference signal level of the first communication channel. Received from the mobile station (step S10
6). Here, the downlink interference wave level is represented by Udowns (i).
It is expressed as “I” corresponds to the channel number.
Then, the desired downlink signal-to-interference wave power ratio, which is a value obtained by subtracting the downlink interference wave level (Ddowns (1)) from the downlink desired wave level (Ddown), is compared with a required value (step S).
107). When the downlink desired wave to interference wave power ratio is equal to or more than the required value (step S107; Y), the first communication channel is allocated to the communication request (step S108).

[0008] If the uplink desired wave to interference wave power ratio or the downlink desired wave to interference wave power ratio is less than the required value (step S
105; N Step S107; N), it is checked whether or not search has been performed for all communication channels (step S109). If all the communication channels have not been checked (step S109; N), the channel number parameter (i) is increased by "1" (step S1).
10), and return to step S105. If a usable call channel is not found even after checking all call channels (step S109; Y), a call loss occurs (step S112), and the process ends (END).

As described above, in order from the first channel,
When an available free channel is selected, the frequency of use of the first communication channel becomes the highest, and the frequency of use gradually decreases toward the Nth communication channel. For this reason,
Regardless of which base station or mobile station measures the interference level of an empty channel, the interference level tends to increase as the position is closer to the first communication channel, and gradually decrease toward the Nth communication channel. appear.
This is called a reuse partition. In such a situation, if the selection is sequentially performed from the first communication channel, the communication channel having a small margin with respect to the required value of the desired signal to interference wave power ratio is preferentially allocated.

Since a mobile station near a base station has a high desired wave level, a communication channel having a high interference wave level and a high selection order is allocated to a mobile station near the base station. On the other hand, since the desired wave level becomes smaller for a mobile station far from the base station, there is a tendency that a communication channel with a lower selection order is assigned. Therefore, in any base station station, a communication channel with a higher selection order is assigned to a mobile station closer to the base station, and a communication channel with a lower selection order is assigned to a mobile station far from the base station.

[0011] That is, the relation of the distance between the mobile station and the base station with respect to the communication channel is the same for each base station. For this reason, a communication channel with a high selection order is frequently used repeatedly by mobile stations near the base station, and a communication channel with a low selection order is used by a mobile station far from the base station at a large repetition interval, and an efficient channel is used. Assignments can be made. A mobile communication system using such a dynamic channel system is disclosed in JP-A-4-351126.

[0012]

In such a dynamic channel system, a channel having a high selection order tends to be frequently used repeatedly, and a channel having a low selection order normally has a gradually repeated distance. It should be larger and less frequently used. However, when a simulation is actually performed, the frequency of use of channels after a certain selection order becomes almost equal.

FIG. 9 shows the relationship between the selection order and the frequency of use of the channel. The horizontal axis represents the selection order and the vertical axis represents the channel usage ratio. In the figure, up to the twentieth place, the use frequency increases as the selection order increases, but below that, there is almost no difference in the use frequency. As described above, after a certain selection order, channels are randomly used regardless of the selection order, and the reuse partition is not effective in a group of channels having a low selection order. Therefore, there is a problem that a channel group having a low selection order is not used efficiently.

An object of the present invention is to provide a mobile communication system capable of improving the frequency use efficiency of a channel having a low selection order.

[0015]

According to the present invention, a vacant channel is searched for from a plurality of communication channels commonly assigned to a plurality of base stations used for communication between a mobile station and a base station. aforementioned as search order when
A selection order storage means for storing a selection order predetermined for same between a plurality of base stations, arbitrarily defined, respectively by the base station as a search order when searching for unused channel from among a plurality of communication channels to the Priority communication means for storing the assigned priority, and searching for an empty channel having a desired wave-to-interference power ratio equal to or more than a prescribed value in accordance with the selection order stored in the selection order storage when communicating with the mobile station. A first vacant channel searching means, and a precedence storing means when the first vacant channel searching means cannot find a vacant channel within the range of the search order corresponding to the selection order and the use frequency of the communication channel. A second search for a vacant channel having a desired signal-to-interference power ratio equal to or greater than a specified channel value according to the stored priority order.
And free channel search means of, put in each of the base stations
The priority changing means for changing the priority order stored in the priority storage means in accordance with the frequency of use of each communication channel that, depending on the channel the first free channel search unit
Channels whose desired signal to interference wave power ratio exceeds the specified value
Is found by the first empty channel searching means.
Broadens the search range for available channels, and
Available channel by the second available channel search means
When found, the first available channel
Use search means to narrow the search range for available channels
The mobile communication system is provided with search range changing means for performing the search .

That is, according to the first aspect of the present invention, a search for an empty channel is performed first according to the same selection order determined among the base stations. A free channel cannot be found within the range of the so-called reuse partition effect in which the frequency of use of communication channels and the selection order correspond.
When it has, to search for an unused channel according to the priority order that is set individually for each base station. The priority is changed by each base station according to the frequency of use of the communication channel. As a result, for communication channels that have relatively high selection priority and do not benefit from reuse partitions,
Priority can be given according to their use frequency. As a result, a difference occurs in the frequency of use of these channels, and the efficiency of frequency use can be improved. Moreover, according to the present invention, empty channels are selected according to the selection order.
If you can find a flannel,
Search in the selection order to obtain the effect of the
The range is expanded. Conversely, empty channels
If a channel cannot be assigned,
Therefore, in order to increase the probability of searching,
The range to be searched is narrowed. As a result, the reuse
In the range where the effect of the
Out of this range, by priority
Thus, the scope of the search is gradually optimized.

According to the second aspect of the present invention, the search order when searching for an empty channel from among a plurality of communication channels commonly assigned to a plurality of base stations used for communication between a mobile station and a base station is described. A selection order storage unit that stores a selection order determined in advance identically among a plurality of base stations,
Priority order storage means for storing a priority order arbitrarily determined in the base station as a search order when searching for an empty channel from a plurality of communication channels; and a selection order storage for communication with the mobile station. First empty channel searching means for searching for an empty channel having a desired wave-to-interference power ratio equal to or greater than a prescribed value in accordance with the selection order stored in the means, and a communication channel having the highest priority by the first empty channel selecting means. When it is not possible to find an empty channel whose desired signal-to-interference power ratio is equal to or more than the specified value at the time when the search is performed, an empty channel whose desired signal-interference power ratio is equal to or more than the specified value is determined according to the priority stored in the priority order storage means. The second free channel search means to be searched and the priority storage means are stored in accordance with the frequency of use of each communication channel. A priority changing means for changing the priority and is provided in a mobile communication system.

That is, according to the second aspect of the present invention, a search for a free channel is first performed in accordance with the same selection order among base stations. If no empty channel can be found at the time of searching for the highest priority channel according to the selection order, an empty channel is searched according to the priority order instead of the selection order.
After selecting an empty channel, each base station changes the priority according to the frequency of use of the communication channel. As described above, after the communication channel with the highest priority, a search for an empty channel is performed according to the priority instead of the selection order. Channel allocation can be performed more efficiently than allocation. Further, by changing the priority according to the result of the selection, the frequency use efficiency can be further increased.

According to the third aspect of the invention, when the second free channel searching means finds an empty channel, the priority changing means raises the priority of the communication channel.

That is, according to the third aspect of the present invention, when a free channel is found by the search based on the priority, the priority of the channel is raised. As a result, the priority of a channel that is frequently used in a certain base station gradually increases. In the base station adjacent thereto, the interference wave level of those channels becomes higher. Therefore, a channel having a higher priority in one base station has a lower priority in an adjacent base station. As a result, between the adjacent base stations, the area of the communication channel that is frequently used in the channel group in which the reuse partition does not work can be separated according to the selection order, and the frequency use efficiency can be improved.

[0021]

[0022]

In the invention described in claim 4 , the priority changing means is configured to determine the priority when the first and second vacant channel searching means cannot find a vacant channel having a desired wave-to-interference-wave power ratio equal to or more than a specified value. The priority of the communication channel having a higher selection order than the selection order assigned to the highest communication channel is set higher, and an empty channel is found by the first empty channel searching means.
In this case, the priority of a communication channel having a higher selection order is set lower than the selection order assigned to the communication channel having the highest priority .

In other words , according to the fourth aspect of the present invention, when a call is lost because a free channel cannot be found ,
The priority of a communication channel having a higher selection order than the selection order assigned to the communication channel with the highest priority is set higher to increase the probability of being searched according to the priority order. On the other hand, an empty channel is found according to the selection order.
Then, by lowering the priority of the communication channel having a higher selection order than the selection order assigned to the communication channel having the highest priority, the probability of being searched according to the selection order is increased. Thereby, the boundary is optimized so that the search is performed by the selection order in the range where the effect of the reuse partition is obtained, and the search is performed by the priority order in the range where the effect of the reuse partition is not obtained.

[0025]

FIG. 1 illustrates an example of a service area of a mobile communication system according to an embodiment of the present invention. This mobile communication system has two types of search order when searching for an empty channel: a selection order common to each base station and a priority order arbitrarily set in each base station. The selection order is fixedly determined, whereas the priority order changes the order of the channel according to the frequency of use. Each base station
In the range where the reuse partition is effective, an empty channel is searched according to the selection order, and outside the range, the empty channel is selected according to the priority instead of the selection order.

The mobile communication system shown in FIG. 1 has an exchange 11 for connecting to a public telephone network, first and second base stations 12 and 13, and first and second mobile stations 14 and 15. It is composed of Here, for convenience of explanation, two base stations and two mobile stations are shown, but there are many base stations and mobile stations. Service areas 16 and 17 of each base station
Is generally called a cell. Assuming that communication is performed between the first base station 12 and the first mobile station 14 existing in the cell, a radio wave reaching the first base station from the first mobile station 14 Wave 21. Further, the radio wave transmitted from the first base station 12 and received by the first mobile station becomes the downlink desired wave 22.

On the other hand, the radio wave transmitted from the second mobile station and received by the first base station is an uplink interference wave 23, which is transmitted from the second base station and received by the first mobile station. The radio wave becomes the downstream interference wave 24. The signal level of the desired upstream signal 21, the signal level of the desired downstream signal 22, the signal level of the upstream interference wave 23, and the signal level of the downstream interference wave 24 are respectively represented by D
Up, Ddown, Dups, and Ddowns. When a call request is generated from the first mobile station 14 existing in the cell 16 of the first base station 12, the first base station 12 firstly follows a predetermined selection order,
A search is made for available vacant channels whose uplink and downlink desired wave-to-interference wave power ratios are equal to or greater than a required value.

If a free channel cannot be found in a higher rank where the reuse partition is effective even if the search is performed in accordance with the selection rank, a search for a free channel is performed in accordance with the priority instead of the selection rank. Here, the first and second base stations 12 and 13 have 100 common communication channels. In both the selection order and the priority order, the search order is assigned to all of these 100 communication channels. Also, channel numbers from 1 to 100 are assigned to each channel, and the order of selection and the order of the channel numbers match.

FIG. 2 shows an outline of the configuration of the base station. The base station includes an antenna 21 for transmitting and receiving radio waves. The antenna 21 is connected to a distributor 22 and separates or combines radio waves to be transmitted and received into a control channel and a communication channel. The distributor 22 includes a control channel transceiver circuit 23 for transmitting and receiving the control channel, traffic channel transceiver circuit 24 _{1-24 3} for transmitting and receiving in communication channel
Is connected. The control channel transceiver circuit 23 and communication channel transceiver circuit 24 _{1-24 3,} the reception level detection circuit 25 ₁ to 25 ₄ for measuring the level of the electromagnetic wave received by these are connected respectively. Further, communication channel transceiver circuit 24 _{1-24 3,} the channel selection circuit 2 for selecting a channel to be transmitted and received
6 is connected. Control channel transmitting / receiving circuit 23
Is the transmission and reception of various commands on the control channel,
It is connected to a control circuit 27 for instructing measurement of the reception level.

The base station includes a CPU (Central Processing Unit) 28 which plays a central role in controlling the base station, and receives level detection circuits 25 ₁ to 25 2 through its input / output ports.
5 ₄ , a channel selection circuit 26 and a control circuit 27 are connected. The CPU 28 has a ROM (Read Only Memory) in which a program and an initial value of a selection order and a priority order for selecting an empty channel are stored. Also, a RAM (random access memory) for temporarily storing data required for executing the program is provided. An area for storing the priority order is assigned to the RAM. The initial value is copied from the ROM to this area, and thereafter, according to the frequency of use of the channel, R
The priority stored in the AM is changed.

Communication channel transmitting / receiving circuits 24 _{1 to} 24 ₃
Are respectively connected to the exchange interface circuit 29. The exchange interface circuit 29 is connected to the exchange 11 shown in FIG. 1 by a communication cable 31, and data transmitted and received by the base station is time-division multiplexed and transmitted here.

FIG. 3 shows the flow of the procedure for selecting a free channel in the base station. It is assumed that a total of N (N arbitrary positive integer) channels are prepared for the communication channels in common to the respective base stations, and the first to N-th channel numbers are allocated. The selection order and the channel number are the same. The priority of the initial state is such that the 15th channel is the highest priority, and the priority is given in order of channel number, the next priority of the 100th channel is given to the 14th channel, and the priority is lower in the order of the 1st channel. It is becoming.

The base station periodically receives and stores the interference level of the idle channel. This value is Ups
(I). Here, i represents the selection order. Ups (i) represents the interference level of the channel whose selection order is “i”, that is, the interference level of the ith communication channel.

The transmission power (Pms) of the mobile station and the transmission power (Pbs) of the base station are known. When a call request or a call request occurs, the base station changes the reception level of the call request signal or the call response signal received on the control channel.
It is stored as the desired uplink wave level (Dup) (step S201). Next, a value obtained by subtracting the desired uplink signal level (Dup) from the transmission power (Pms) of the mobile station is stored as a propagation loss (L) between the base station and the mobile station (step S2).
02).

Since reversibility is established between the uplink from the mobile station to the base station and the downlink from the base station to the mobile station,
It is considered that the propagation loss of the uplink and the downlink is the same. Then, by subtracting the propagation loss (L) from the transmission power (Pbs) of the base station, the desired downlink signal level (Ddown) at the mobile station is obtained.
n) (step S203). Empty channels are first searched according to the selection order. First, the selection order parameter (i) is initialized to “1” (Step S)
204). That is, initialization is performed so that the channel having the selection order “1” is searched. Since the selection order and the channel number are the same, a search is first performed from the first call channel.

Next, it is checked whether or not the priority of the channel whose selection order is "i" is the highest (step S).
205). Here, the channel having the first priority has the fifteenth selection order. Therefore, while "i" is 15 or less (Step S205; N), selection is continued according to the selection order. When the channel of the selection order “i” is different from the channel of the first order (step S205; N), the channel of the desired uplink level (Dup) is
The uplink interference wave level (Ups (i)) of the channel, which is measured regularly in advance, is subtracted. This value is the power ratio of the desired uplink signal to the interference signal in the channel. Then, it is compared with a predetermined value (CIRth) predetermined as a value of the uplink desired wave interference wave power ratio necessary to secure an appropriate communication state (step S206).

If the uplink desired wave-to-interference wave power ratio is equal to or larger than the required value (step S206; Y), the base station informs the mobile station of the downlink interference wave level (Ddown) of the channel.
The measurement of (i)) is instructed, and the result is received from the mobile station (step S207). Then, the desired signal level (D
down) to downlink interference wave level (Ddowns)
The required value is compared with the downlink desired wave-to-interference wave power ratio obtained by subtracting (i)) (step S208). When the downlink desired wave-to-interference wave power ratio is equal to or greater than a required value (step S20)
8; Y), the i-th selected order channel is assigned to the call request (step S209). Then, the priority order is changed (step S210), and the process ends (END). The priority changing process will be described later in detail.

If the uplink desired wave to interference wave power ratio or the downlink desired wave to interference wave power ratio is less than the required value (step S
206; N Step S208; N), it is checked whether or not all the communication channels have been searched (Step S211). If all the communication channels have not been checked (step S211; N), the selection order parameter (i) is increased by "1" (step S212), and the process returns to step S205. If no usable communication channel is found even after checking all the communication channels (step S211; Y), the call is lost (step S213), and the priority is changed (step S210). End (end).

Until the priority order matches the highest priority channel, an empty channel is searched according to the selection order. In a range where the selection order is high to some extent, the effect of the reuse partition can be obtained by selecting an empty channel in accordance with the selection order commonly defined in each base station.

When the channel having the selection order "i" matches the channel having the first priority (step S2).
05; Y), channels are allocated according to priority (step S214). Then, after performing the priority change process (step S210), the process ends (end).

FIG. 4 shows a flow of processing for allocating empty channels according to priority. Before starting the search by priority, the priority parameter (j) is initialized to "1" (step S30).
1). Hereinafter, it is assumed that the measurement and calculation of the interference wave power and the like are performed on the channel of the priority indicated by the priority parameter (j). From the uplink desired wave level (Dup), the uplink interference wave level (Ups (j)) of the channel having the priority “j”, which has been periodically measured in advance, is subtracted to obtain an uplink desired wave to interference wave power ratio. This is compared with a required value (CIRth) (step S302).

When the uplink desired wave-to-interference wave power ratio is equal to or greater than the required value (step S302; Y), the base station provides the mobile station with the downlink interference wave level (Ddown (j)) of the channel.
, And receives the result from the mobile station (step S303). Then, the desired level of the descending wave (Ddow)
Then, a required value is compared with a downlink desired wave-to-interference wave power ratio, which is a value obtained by subtracting the downlink interference wave level (Ddowns (j)) from n) (step S304). When the downlink desired wave-to-interference wave power ratio is equal to or more than the required value (step S304; Y), the j-th priority channel is assigned to the call request (step S305).

If the uplink desired wave to interference wave power ratio or the downlink desired wave to interference wave power ratio is less than the required value (step S
302; N Step S304; N), it is checked whether or not search has been performed for all communication channels (step S306). If all the communication channels have not been checked (step S306; N), the priority parameter (j) is increased by "1" (step S307), and the process returns to step S302. If no usable communication channel is found even after checking all communication channels (step S306; Y), a call loss occurs (step S308), and the process ends (END).

As described above, the vacant channels having the desired-to-interference-wave power ratio equal to or more than the required value are searched in order from the highest priority channel. That is, if no empty channel can be found within the range in which the effect of the reuse partition can be obtained by the search according to the selection order, the empty channel is searched in the order according to the next priority. In FIG. 4, it was checked whether or not the desired wave-to-interference wave power ratio could be obtained to a required value or more for each channel according to the priority. However, in the process of searching by the selection order, the interference condition for the same channel has already been checked. There are cases. In this case, since it is clear that the desired wave-to-interference wave power ratio does not exceed the required value for the channel, the channel may be skipped without measuring the desired wave-to-interference wave power ratio.

FIG. 5 shows the flow of the channel assignment process based on the priority when the search is performed by skipping the searched channels in the search in the selection order.
In this figure, steps S408 and S409 are performed instead of step S307 in FIG. The other steps are the same as those in FIG. 4, and the description thereof will be appropriately omitted. If the desired wave-to-interference wave power ratio for the channel of the priority (j) cannot be obtained more than the required value (step S402; N, step S404; N), it is checked whether or not all channels have been searched (step S406). Here, when the search has been completed for all the channels (step S406; Y), a call loss occurs (step S407), and the process ends (end).

If the search has not been completed for all the channels, the priority parameter (j) is increased by 1 and the channel of the next priority is selected (step S).
408). It is checked whether or not this channel selection order is higher than the highest-order channel selection order (step S409). Channels with a higher priority than the highest priority channel have already been examined in the search process according to the priority, and it has been found that it is inappropriate to select a channel as a free channel. Therefore, when the selection order is higher than the selection order of the highest priority channel (step S4).
09; Y), the process returns to step S406 to avoid the determination of the overlapping interference condition.

If the priority of the channel is not higher than that of the highest priority channel (step S409; N), the process returns to step S402 to measure the power ratio of the desired wave to the interference wave for the channel. I do. By skipping in this manner, it is possible to avoid determination of overlapping interference conditions.

FIG. 6 shows the flow of processing in the priority change processing shown in FIG. First, it is checked whether or not an empty channel is assigned based on the priority (step S501). If they are not assigned by priority (step S501; N),
The process ends without changing the priority (end). If an empty channel is allocated according to the priority (step S501; Y), the priority of the allocated channel is increased (step S50).
2). The priority may be raised by increasing the priority of the assigned channel by one. Further, the priority of the assigned channel may be raised to the highest priority at once.

At the boundary between the order in which the reuse partition effect is obtained by the selection order and the order in which the effect is difficult to obtain, it is desirable to switch from the search based on the selection order to the search based on the priority order. Therefore, a process of changing the boundary point between the selection order and the priority order depending on whether an empty channel is allocated according to the priority order is added after the priority order change process shown in FIG.

FIG. 7 shows a flow of processing for changing the boundary at which the search is switched from the search based on the selection order to the search based on the priority order. This process is inserted after the priority change process (step S210) shown in FIG.
If a vacant channel cannot be found and the call is lost (step S601; Y), the selection probability based on the priority is increased (step S602). If it is not a call loss (step S601; N), it is determined whether or not the channel is assigned based on the priority (step S603). If the channel is assigned not according to the priority but according to the selection order (step S60)
3; N), increase the selection probability according to the selection order. When the channels are assigned according to the priority order (step S603; Y), the process is terminated without particularly changing the selection probability (end).

Increasing the selection probability by the selection order means, in other words, decreasing the selection probability by the priority order. To increase or decrease the selection probability, for example, the priority order of all the channels having a higher priority than the selection order of the channel with the highest priority may be increased by one.
Conversely, when reducing the selection probability, the water bath rankings of all channels lower than the selection priority of the channel with the highest priority are lowered one by one. Further, even if the priority of the channel having the highest selection priority is higher than that of the channel having the highest priority, the selection probability based on the priority can be increased. Conversely, by changing the priority of a channel having a lower selection priority than that of a channel having the highest priority to the highest priority, the selection probability based on the priority can be reduced.

As described above, by increasing or decreasing the selection probability in the priority order and the selection probability in the selection order, the boundary between the region selected in the selection order and the region selected in the priority order is assigned to the channel allocation status. It can be changed appropriately according to.

By increasing the priority of a channel assigned according to the priority, the channel can be easily selected in the next search, and the frequency of use can be increased. In the assignment according to the selection order, even in a range where there is no difference in the use frequency, a difference can be created in the use frequency of the channel by selecting using the priority order whose order is changed according to the use frequency. . In FIG. 1, a channel having a higher priority in a first base station is a first channel.
Use frequency of the base station increases. Since this channel is a channel having a high interference wave level in the second base station, a channel different from that of the first base station is easily selected in the second base station. That is, a channel with a higher priority in the first base station becomes a channel with a lower priority in the second base station. Since a situation is created in which channels used by adjacent base stations are separated from each other, channel use efficiency can be improved.

Even when the priorities at the time of initialization are given at random, as the channel is selected, the priorities corresponding to the frequency of use are gradually formed. In addition, in a range where the effect of the reuse partition can be sufficiently obtained in the selection order, it is not necessary to perform the selection based on the priority. Therefore, the priority may be given only to the remaining channels excluding the channels whose selection order is higher than a certain level. Good. When the priority is given to all the channels, it is necessary to initially set the selection order of the channel having the highest priority to a channel which is somewhat lower.

In the embodiment described above, the priority of the channel having the fifteenth priority is initially set to the highest priority, but the initial value of the priority may be other values. This is because appropriate priorities are formed autonomously as they are used.

[0056]

As described above, according to the first aspect of the present invention, the selection order determined identically among the base stations and the priority order individually changed at each base station according to the frequency of use of the communication channel. Search for available channels in combination. Accordingly, even to the communication channel groups ineffective the reuse partitioning in searches by selection order, it is possible to perform high channel allocation efficiency. In addition, since the priority is individually changed in each base station, there is no need to perform control communication between the base stations to change the priority, and the configuration of the mobile communication system is not complicated. Moreover, according to the present invention, empty channels are selected according to the selection order.
Depending on whether or not a channel was found
Since the box is increased or decreased, the range searched in the selection order
To the extent that the effects of the reuse partition can be obtained.
There is also an effect that it can be made to respond quickly.

According to the second aspect of the present invention, after the communication channel having the highest priority, an empty channel is searched according to the priority instead of the selection order. Channel allocation more efficient than random channel allocation can be performed for a group of unused channels. Further, by changing the priority according to the result of the selection, it is possible to further improve the frequency use efficiency.

[0058]

[0059]

According to the fourth aspect of the present invention, the search is performed in accordance with the selection order in the range where the effect of the reuse partition can be obtained, and the search is performed in accordance with the priority order in the range where the effect of the reuse partition cannot be obtained. , Has adapted its boundaries. As a result, the frequency use efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of a service area of a mobile communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an outline of a configuration of a base station.

FIG. 3 is a flowchart showing a flow of a procedure for selecting a free channel in a base station.

FIG. 4 is a flowchart showing a flow of a procedure for selecting an empty channel according to priority.

FIG. 5 is a flowchart showing a flow of a procedure for selecting an empty channel in a priority order when the determination of an overlapping interference condition is omitted.

FIG. 6 is a flowchart showing a processing flow in a priority change processing shown in FIG. 3;

FIG. 7 is a flowchart illustrating a flow of a process of changing a boundary at which a search is switched from a search based on a selection order to a search based on a priority order.

FIG. 8 is a flowchart showing a procedure for selecting an empty channel in a conventionally used mobile communication system.

FIG. 9 is an explanatory diagram showing a relationship between a selection order and a frequency of use of a channel.

[Explanation of symbols]

 12, 13 base station 14, 15 mobile station 16, 17 service area of each base station 23 control channel transmission / reception circuit 24 communication channel transmission / reception circuit 25 reception level detection circuit 26 channel selection circuit 28 CPU

Claims (4)

(57) [Claims] 1. A search order for searching for an empty channel from among a plurality of communication channels commonly assigned to a plurality of base stations used for communication between a mobile station and a base station, the search order between the plurality of base stations. A selection order storage means for storing a selection order predetermined in advance, and a priority order arbitrarily determined by the base station as a search order when searching for an empty channel from among the plurality of communication channels. Priority communication means for performing communication between a mobile station and a mobile station, and searching for a vacant channel having a desired signal-to-interference power ratio equal to or greater than a specified value in accordance with the selection order stored in the selection order storage means. Channel search means; and the first free channel search means, wherein the selected order and the frequency of use of the communication channel correspond to free channels within a search order range. A second free channel search unit that the signal to interference power ratio to find a free channel of more than the prescribed value according to the priority stored in the priority storage unit when it can not find a channel, each base station the priority changing means for changing the priority order stored in the priority storing means in accordance with the frequency of use of each communication channel in the desired signal Taihi by the first free channel search unit
An empty channel with an interference power ratio equal to or greater than the default value was found.
When the first available channel searching means
The search range of the channel is widened, and the second
When a free channel is found by the
Is an empty channel by the first empty channel searching means.
A mobile communication system comprising: a search range changing unit that narrows a range in which a cell is searched . 2. A search order for searching for an empty channel from among a plurality of communication channels commonly allocated to a plurality of base stations used for communication between a mobile station and a base station, the search order between the plurality of base stations. A selection order storage means for storing a selection order predetermined in advance, and a priority order arbitrarily determined by the base station as a search order when searching for an empty channel from among the plurality of communication channels. Priority communication means for performing communication between a mobile station and a mobile station, and searching for a vacant channel having a desired signal-to-interference power ratio equal to or greater than a specified value in accordance with the selection order stored in the selection order storage means. A desired signal to interference power ratio is defined at a point in time when the communication channel having the highest priority is searched by the channel searching means and the first free channel selecting means. When it is not possible to find an empty channel having a value equal to or more than the value, a second empty for searching for an empty channel having a desired signal-to-interference power ratio equal to or more than the prescribed value according to the priority order stored in the priority order storage means. A mobile communication system comprising: a channel search unit; and a priority change unit that changes a priority stored in the priority storage according to a frequency of use of each communication channel. Wherein the priority changing unit, idle channel is found by the second free channel search unit
Claim 1 or claim 2 mobile communication system, wherein increasing the priority of the communication channel when. 4. The apparatus according to claim 1, wherein said priority changing means includes means for changing the priority order.
And desired wave interference by the second available channel searching means
It is possible to find an empty channel whose wave power ratio exceeds the specified value.
If not possible, assign to the highest priority communication channel.
Communication channels with a higher selection order than the assigned selection order
Channel, and the first available channel
Priority when a free channel is found by search means
The selection assigned to the highest ranked communication channel
Priority of communication channels with higher selection priority than priority
3. The mobile communication system according to claim 2, wherein: