JP3376387B2 - Broadcast communication channel allocation method and broadcast channel allocation apparatus in base station of cellular 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 broadcast channel assignment method and broadcast channel assignment apparatus in a base station of a cellular mobile communication system.

[0002]

2. Description of the Related Art In a conventional mobile communication system for business such as public service, in order to accommodate a large number of mobile terminal stations moving in a wide area, a plurality of zones (cells) formed by a plurality of base stations are required. In general, a cellular mobile communication system covering a service area is provided. By the way, in the commercial mobile communication system,
There is also individual communication for one mobile terminal station, but there is a high frequency of simultaneous communication between the command station and a plurality of mobile terminal stations.

FIG. 4 is an explanatory view showing a conventional communication system in the case where simultaneous communication is introduced in a cellular mobile communication system. In the figure, 1 to 7 are cells, 11 is a general command station, 12 _{1 to} 12 ₇ are base stations of cells ₁ to ₇ , 13 to ₁
Reference numeral 8 is a mobile terminal station, and 19 is a ground wire system. The cover area consists of cells 1-7. One base station 12 _{1 to} 12 ₇ is installed in each of the cells 1 to ₇ .

The mobile terminal stations 13-18 are the nearest base station 1
Two_Four~ 12₇Is wirelessly connected to. Usually the base station 12₁
~ 12₇A pilot signal is being transmitted from the
The terminal stations 13 to 18 are based on the received power of this pilot signal.
Know the cell that is located in the area, that is, the nearest base station.
It Here, the base station 12₁~ 12₇Is a mobile terminal station 13-1
When making a wireless connection to the 8 as described later with reference to FIG.
The base station 12₁~ 12₇Currently used from the channel
Free channels that do not meet the specified interference conditions.
Allocate additional channels. In addition, each base station 12₁~ 1
Two₇Is connected to the simultaneous command station 11 by the ground wire system 19.
Has been done. As a form of mobile communication, for example, each mobile
Base station 12 of the cell in which the terminal station is located ₁~ 12₇Via
One-to-one individual communication between mobile terminal stations 13-18
And the general command station 11 to the base station 12₁~ 12₇Via
One-to-N simultaneous communication with mobile terminal stations 13 to 18 in the area
There is faith. With simultaneous communication, voice and non-
Transmit audio data to multiple parties at once.

In the conventional commercial mobile communication system, the same channel is assigned to each simultaneous communication from each base station to a plurality of or a single mobile terminal station for each zone where the mobile terminal station exists. It was This method has an advantage that the number of required channels can be reduced, that is, even when a plurality of mobile terminal stations exist in one zone, only one channel need be allocated instead of a plurality of channels. While individual communication based on bidirectional simultaneous communication uses a pair of upstream and downstream channels, the basic information flow of simultaneous communication is only on the downstream channel (base station → terminal station). In the following description, for simplification, it is assumed that the simultaneous communication uses the upstream and downstream paired channels, and this paired channel is simply expressed as one channel. In the conventional system in which the simultaneous communication shown in FIG. 4 is introduced, the base stations 12 ₄ , 12 ₅ ,
12 ₇ to a plurality of or a single mobile terminal stations 14 to 16,
One channel to 18 is allocated.

[0006] A simultaneous communication method for transmitting the same communication content to a plurality of mobile terminal stations from the simultaneous command station 11 via the base stations 12 _{1 to} 12 ₇ by using one channel is used as a general broadcast method. Since they are similar, they are called “broadcast mode simultaneous communication” here. Mobile terminal stations 13 and 17
In the individual communication (marked), one channel of the cells 4 and 6 is required for each mobile terminal station 13 and 17. For example, cell 4
Then, the mobile station 13 needs the fifth channel CH4-5 of the base station 12 ₄ . In cell 6, mobile terminal station 1
For 7, the seventh channel CH6-7 of the base station 12 ₆ is required.

On the other hand, the mobile terminal stations 14, 15, 1
In the simultaneous communication to 6, 18 (marked with Δ in the figure), only one channel is required for one simultaneous communication in the serving cell of each mobile terminal station. For example, in the cell 4, there are two target mobile terminal stations 14 and 15 for the simultaneous communication a, but the base station 1
Only 2 ₄ 2nd channel CH4-2 is used. When the target mobile terminal station 18 of the simultaneous communication a is also in the cell 7, the base station 12 ₇ uses only the second channel CH7-2 regardless of the number of the target mobile terminal stations. . When another simultaneous communication b is performed, for example, the simultaneous communication b
In the cell 5 in which the target mobile terminal station 16 of No. 1 is located, the base station 12 ₅ , regardless of the number of simultaneous target mobile terminal stations,
Only channel CH5-1 is used.

In the above-described cellular mobile communication system, in recent years, base stations distant from each other in distance, that is, base stations with small radio wave interference, automatically allocate the same frequency channel and reuse the frequency, and Various advanced methods of increasing the number of mobile terminals that can be accommodated per hit are being studied. ARP method (Autonomous
Reuse Partitioning: There is an automatic frequency reuse partitioning method. This ARP method is, for example, T. Kanai "Autonomous
Reuse Partitioning in Cellular System "Proceedin
It is known as gs of IEEE VTC92 1992/6.

In the ARP system, each base station 12 _{1 to} 12 ₇ receives the CIR on the empty channel in accordance with the search order while the common channel search order common to all base stations 12 _{1 to} 12 ₇ is determined. (Carrier to Interference Ratio: Desired wave to interference wave level ratio) In this method, channels that satisfy the threshold Th are searched and assigned. Therefore, how to introduce the simultaneous communication in the ARP method becomes a problem.
The ARP method will be outlined.

The ARP-based channel allocation process consists of the following three procedures. (1) A free channel search order common to all base stations is determined in advance. For example, channel 1
→ Channel 2 → Channel 3 → Channel 4 → ... (2) When a call occurs and a channel allocation request is made, the nearest base station searches for a channel in the order of (1) above and allocates the first free channel satisfying a predetermined reception CIR threshold to the call.
(3) If all the channels owned by the base station are searched, but there is no free channel satisfying the CIR threshold, the call is lost (channels cannot be allocated and communication cannot be performed).

FIG. 5 is a flowchart showing a conventional ARP system channel allocation processing procedure in the base station.
i is a channel (number) and is also a free channel search counter variable. N is the number of channels held by the base station, and Th is a predetermined reception CIR threshold. When a call is generated from the mobile terminal station and a channel allocation request is made, the serving base station sets the initial value of the empty channel search order to i in S23.
= 0, and the empty channel search counter variable i is incremented by 1 in S24. In S25, it is determined whether the channel i of the base station is unused. For example, the base station
Since there is a table in which the usage status of each owned channel is registered, it is determined by referring to this table. If it is not used, the process proceeds to S27, and if it is in use, the process proceeds to S26.

In S27, the total interference wave level I from all other terminal stations using the same channel i is measured. In S28, the desired wave level C from the mobile terminal station which has requested the channel allocation is measured. For example, the reception level of the call request signal from the mobile terminal station received on the control channel is set to the desired wave level C. In S29, CIR
Is greater than or equal to a predetermined threshold Th, and the predetermined threshold
If Th or more, the process proceeds to S30, and if less than the predetermined threshold Th, the process proceeds to S26. In S30, the free channel i of the base station is allocated, and the channel allocation processing ends. That is, channel i is unused and
The first channel that satisfies a predetermined CIR threshold is assigned to the mobile terminal station that requested the channel assignment.

Further, in the above description, only the uplink from the mobile terminal station to the base station has been specifically described. For the downlink as well, the measurement values of the total interference wave level I and the desired wave level C at the mobile terminal station are reported to the base station through the control channel, and the measurement corresponding to S27 and S28 is performed. At the same time each threshold Th
Although it is determined whether or not the above is the case, the detailed description is omitted.

On the other hand, in S26, it is determined whether the channel i is equal to the number N of channels held by the base station. If they are equal, the process proceeds to S31, and there is no free channel to be allocated, so that the call loss or forced disconnection is performed. Loss of call means that communication is not possible because a channel is not assigned when a call occurs.Forced disconnection means that the mobile terminal station moves to another cell after the channel has been normally assigned in another cell. It means that communication cannot be performed because it cannot be assigned. When the channel i is not equal to the number N of channels in S26, it is possible that there are still empty channels. Therefore, the process is returned to S24, i is incremented by 1, and the same process is repeated. It should be noted that channel allocation is performed by the same procedure when the incoming mobile terminal station is called.

In the above-mentioned ARP system, each of the base stations 12 ₁ to ₁ 1
In 2 _7, on the basis of the common search order all base stations, a free channel to be allocated candidates are searched exactly the same order. Therefore, the channels in the earliest search order are assigned more frequently, and the interference wave level increases accordingly. Therefore, since a high desired wave level is required to obtain a sufficient CIR that is equal to or higher than the threshold Th, the mobile terminal station close to the base station will use such a channel in the quick search order. As a result, the channels in the earliest search order inevitably have cells 1-7.
In this case, many are allocated to mobile terminal stations close to the base stations 12 _{1 to} 12 ₇ . On the other hand, a channel with a slow search order has a low interference wave level because it is not frequently assigned. As a result, a channel with a slow search order can obtain a sufficient CIR that is equal to or higher than the threshold Th even at a weak desired wave level.
In each cell 1-7, inevitably, the base station 12 ₁ to 12 ₇
Will be assigned to a mobile terminal station far away from.

Due to this phenomenon, each of the base stations 12 ₁ to 12 ₁
Channel ₇ can allocate the channel with the minimum CIR margin without the need to rearrange the retained channels according to interference level I. This produces an effective frequency reuse pattern. The ARP frequency reuse pattern in each cell is automatically as shown in FIG. 6, and high system capacity is achieved.

FIG. 6 is a schematic explanatory view of the ARP system.
41 in the figure₁~ 41_FiveIs a set of multiple cells that are
It is Le. 42₁~ 42_FiveIs each cell 41₁~ 41_FiveIn the center of
It is a base station. Channels CH1 to CH4 (frequency channels
Each cell 41₁~ 41_FivePhases automatically assigned to
The search order is set in the order of this number for different channels
Has been done. For each channel CH1 to CH4,
A reuse arrangement is shown. D1 to D4 are reuse distances
Therefore, each channel CH1 to CH4 is
It is the distance between Le. 43₁₁, 43_{twenty one}, 43₃₁, 43
₄₁Is in cell 41₁Of the moving end using CH1 to CH4
It is the ring where the terminal station exists, and R1 to R4 are half of this ring.
Is the diameter. 43 ₁₂, 43_{twenty three}, 43₃₄, 43₄₅Is that
Cell 41₂~ Cell 41_FiveIn channels 1 to 4
This is a ring-shaped area where the mobile terminal station to be used exists.

[0018] As described above, in each cell 41 ₁ to 41 _5, usage patterns of the channel CH1~CH4 is generated in a ring shape, as those search order channel CH1~CH4 is earlier,
Used in the ring close to the base station. Moreover, each channel CH1 to CH4 has a minimum reuse distance according to the strength of the desired wave level, that is, the distance R1 to R4 from the base station of the mobile terminal station.
It is reused in D1 to D4, and the smaller the ring-shaped area, the shorter the reuse distance. That is, D1 / R1
= D2 / R2 = D3 / R3 = D4 / R4 (D1 to D4: each ring 43 ₁₁ to 4
3 ₄₁ reuse distance, channels CH 1 to CH 4 are assigned to each ring 43 ₁₁ to 43 ₄₁ ). In this way, the ARP method makes good use of the “far-and-far effect”, in which the desired wave level becomes higher for mobile terminal stations nearer the base station, and the Reuse Partitioni
ng (frequency reuse pattern) is being generated.

On the other hand, in the broadcast mode broadcast communication, as described above, for one broadcast communication, for each broadcast cell in which the mobile terminal station is present, the broadcast mode from the base station to one or a plurality of mobile terminal stations is used. Are assigned the same channel. FIG. 7 is a flowchart of a channel allocation process when a broadcast mode simultaneous channel allocation method is simply introduced to the conventional ARP method in a base station in which a simultaneous target mobile terminal station is located. In the figure, the same processing steps as those in FIG. j is a simultaneous communication channel number when the same simultaneous communication is already being performed in the base station zone, k is a counter variable for the number of simultaneous target mobile terminal stations, and m is the number of simultaneous target mobile terminal stations located in the own cell. Is.

In contrast to FIG. 5, S21, S22, S3
2, the processing of S51 to S55 is added. When a broadcast call is issued from the broadcast command station, and each base station in which the broadcast target mobile terminal station is located receives a channel assignment instruction, each base station starts the broadcast channel assignment process and The same channel for broadcast mode is assigned to a plurality (or single) simultaneous target mobile terminal stations located in the cell of.
Incidentally, by the periodic location registration of the mobile terminal station, each base station and the simultaneous command station know in advance which mobile terminal station is in each cell. I also know. If different simultaneous communications from the simultaneous command station, for example, simultaneous communications a and b, perform the simultaneous channel assignment processing shown in FIG. 7 for each of the simultaneous communications a and b.

In S21, the simultaneous variable mobile terminal station number counter variable k is set to 0, and in S22, the value of k is incremented by 1. In S51, it is determined whether or not the same simultaneous communication (for example, simultaneous communication a) on the channel j has already been performed in the base station zone. If the same simultaneous communication is in progress, the process is newly advanced to S52. If it is not the same broadcast, the process proceeds to S23 because it is a new channel assignment for the base station, and a blank channel search by the same ARP algorithm as in FIG. 5 is started for broadcast, and at the last S30, If an empty channel i can be assigned, this channel i is used as a channel for one simultaneous communication (simultaneous communication a), and this i becomes j.
When there are a plurality of broadcasts a and b, a channel j is set for each broadcast.

The description is returned to S52. In S52,
The channel i at this time is set as j, and in the next S53,
Similar to S27, the total interference wave level I from all other terminal stations using the same channel j is measured. Next S54
In S, as in S28, the desired wave level C from the terminal making the channel allocation request is measured. In next S55, it is determined whether or not the CIR is equal to or larger than the predetermined threshold Th. If it is equal to or more than the threshold value Th, the channel that has already been subjected to the same simultaneous communication in the base station zone satisfies the CIR condition. Therefore, the process proceeds to S30, and the channel i (= j ) Is assigned.

When the CIR is less than the threshold Th in the previous S55, the CIR of the broadcast mode broadcast communication channel does not satisfy the threshold Th for the broadcast target mobile terminal station. And the call is lost or forced to disconnect. When the process of S30 or S31 ends, the process proceeds to S32, and the simultaneous target mobile terminal station number counter variable k indicates the number m of simultaneous target mobile terminal stations located in the own cell.
It is determined whether or not. If they are equal, the process is terminated, but if they are not equal, there is still another target mobile terminal station, and the process is returned to S22.

The above-mentioned ARP system is based on the principle that a free channel of the base station is searched for and assigned according to the distance between the mobile terminal station and the base station (in other words, the strength of the radio wave received by the base station). However, in the combination of the above-described ARP method and broadcast mode simultaneous channel assignment, when a plurality of mobile terminal stations are present in one cell, the same broadcast mode is set regardless of the distance between each mobile terminal station and the base station. 1 channel is allocated. Therefore, there is a problem in that the principle of the ARP system that allocates channels according to the distance between the mobile terminal station and the base station is rather disturbed, and the frequency reuse effect is reduced.

Therefore, a simulation was carried out in which the ARP system was simply assigned one channel for the broadcast mode of the simultaneous communication. FIG. 8 is an explanatory diagram of simulation specifications. The terms radio wave propagation, channel, call time distribution, call hold time, generated call volume (erl is Erlang, which is the unit of call volume), and movement are values generally used in cellular mobile communication systems. , Is often used as a standard model for simulation in the art. The other items apply specifications based on the system assumed in this evaluation. The cell section assumes a relatively large cell called a large zone. The simulation term represents the time condition on the simulation performed. In the item of the number of terminals targeted for simultaneous broadcast, it is assumed that simultaneous communication is performed to five terminal stations in the area, and the ratio of simultaneous calls to the total number of calls (individual calls + simultaneous calls) that occur in the area Is evaluated by changing the ratio of simultaneous calls from 0.1% to 10%. However, in order to evaluate the overall performance of the system under the same conditions, the amount of calls generated (individual call + simultaneous call) is constant in all areas even if the ratio of the number of simultaneous calls changes.

FIG. 9 is an explanatory diagram of the cell configuration and the call distance distribution which are the premise of this simulation. In the figure, the horizontal axis is the distance r from the center of the cover area, and the vertical axis is the call density P.
(r). The call distance distribution may be either an ideal uniform distribution or an exponential distribution in which the call density exponentially decreases from the urban area to the suburbs, for example. I am evaluating. In the exponential distribution, 95% of the total call volume is included in the coverage area. κ
Is the traffic taper.

The evaluation result of the above-mentioned simulation is
It is shown in FIG. 3 together with the evaluation result of the simulation in the method of the present invention. FIG. 3 is a diagram showing a simple broadcast mode simultaneous channel allocation method and an evaluation result of simulation of the first embodiment of the present invention. FIG. 3A shows a case where the call density has a uniform distribution, and FIG.
Is the case where the call density is exponentially distributed. In both cases, individual calls and simultaneous calls are evaluated. The horizontal axis represents the ratio of simultaneous calls, and the vertical axis represents (call loss rate + forced disconnection rate). The call loss rate is the ratio of the total number of calls that could not be communicated because there was no available channel to the base station closest to the mobile terminal station at the time of call generation.
The forced disconnection rate is an overall ratio of the number of calls that could not be communicated because the mobile terminal station moved after the normal channel allocation once and the nearest base station of the moving destination did not have a free channel.
(Call loss rate + forced disconnection rate) is an index indicating the performance of the entire system. The smaller the (call loss rate + forced disconnection rate) is, the larger the rate that each communication can be normally serviced under a constant number of channels. In other words, if the same (call loss rate + forced disconnection rate), a larger call volume can be accommodated and the frequency reuse effect can be obtained.

In FIG. 3A, [broadcast mode simultaneous]
In the case of individual calls / broadcast calls, (call loss rate + forced disconnection rate) deteriorates as the number of broadcast calls increases. That is, as the proportion of simultaneous calls to which the same one channel is allocated for the broadcast mode increases, the principle of the ARP system that allocates channels according to the distance between the mobile terminal station and the base station is disturbed, and frequency reuse is performed. It can be seen that the effect is reduced. Figure 3
In (b), in [Broadcast Mode Simultaneous], the (call loss rate + forced disconnection rate) of individual calls / broadcast calls itself is worse than that in FIG. 3 (a), and as the ratio of the number of simultaneous calls increases (call loss rate + forced disconnection rate). The deterioration of) is more remarkable. This is because in the non-uniform call distribution, the density of the interference wave that causes the partition is not uniform, so that the partition is not clearly generated, and the ARP original frequency reuse effect is reduced.

[0029]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is a base of a cellular mobile communication system capable of allocating channels for simultaneous communication without degrading system performance. A broadcast channel allocation method and a broadcast channel allocation device in a station are provided.

[0030]

In order to achieve the above object, the invention of claim 1 is a broadcast communication channel allocation method in a base station of a cellular mobile communication system for allocating channels of individual communication based on the ARP system. The base station receives the broadcast channel allocation request to the target mobile terminal station of the broadcast in the cell of the base station, based on the same ARP system as the individual communication,
A procedure of searching and allocating an empty channel having a desired wave-to-interference level ratio equal to or higher than a threshold value in a common channel search order common to all base stations of the cellular mobile communication system is located in the cell of the base station. This is performed for each mobile terminal station targeted for simultaneous communication. Channel allocation according to the ARP method for each target mobile terminal station results in a larger number of required channels than a simple broadcast mode broadcast channel allocation aiming at the effect of reducing the number of used channels. However, regarding the reuse of the channel of the mobile communication system, the effect of maintaining the ARP system is more remarkable even for the simultaneous communication, and the same system
The overall system performance (call loss rate + forced disconnection rate) in terms of the number of channels is superior to simple broadcast mode broadcast channel allocation. As described above, there is a problem in the case where the broadcast mode simultaneous communication channel allocation is simply applied to the ARP system which originally exhibits the channel reuse effect for individual communication, that is, regardless of the distance between each mobile terminal station and the base station. It is possible to avoid the disturbance of the ARP method principle due to the allocation of the same channel and the deterioration of the channel reuse effect accompanying it, specifically, the deterioration of (call loss rate + forced disconnection rate), etc. A large capacity and stable mixed individual / broadcast communication cellular mobile communication system can be realized. In addition, the broadcast channel is not simply assigned to an empty channel, but is assigned to an empty channel whose desired wave-to-interference level level is equal to or higher than the threshold value, so that the transmission quality of the broadcast channel is secured as in the case of individual communication. There is.

According to the second aspect of the present invention, the desired wave level at the base station reception, the same level to interference wave level ratio, the same level to noise level ratio, or their statistical value, that is, each mobile terminal station, A method for allocating a simultaneous communication channel in a base station of a cellular mobile communication system, which searches for a free channel of the base station and allocates a channel for individual communication according to various quantities based on the distance of the base station,
The base station receives a broadcast channel allocation request to a target mobile terminal station for broadcast communication existing in a cell of the base station, based on the same channel assignment scheme as the individual communication, based on the base station. A procedure for searching for and assigning an empty channel of the base station according to the quantities based on the distance between the target mobile terminal station and the base station in the cell, This is performed for each mobile terminal station to be communicated. Therefore, there is a problem when the broadcast mode simultaneous channel allocation is simply applied to the channel allocation method that originally exerts the channel reuse effect for individual communication, that is, the same channel regardless of the distance between each mobile terminal station and the base station. It is possible to avoid the disturbance of the principle of the channel allocation method and the accompanying deterioration of the channel reuse effect due to the allocation of the, and to realize a stable individual / broadcast mixed cellular mobile communication system with a large user accommodation capacity.

According to the third aspect of the invention, the ARP
A method for allocating a broadcast communication channel in a base station of a cellular mobile communication system that allocates individual communication channels based on a method, wherein the base station is a target mobile terminal station for broadcast communication in a cell of the base station. At the time of receiving the simultaneous communication channel allocation request, based on the same ARP method as the individual communication, a desired channel-to-interference level ratio is set in an empty channel search order common to all base stations of the cellular mobile communication system. , A procedure for searching and assigning an empty channel having a threshold value or more to each of the target mobile terminal stations of the simultaneous communication existing in the cell of the base station, and in the cell of the base station 1 at the time of receiving a broadcast channel allocation request to the target mobile terminal station for broadcast broadcast
For each of the one simultaneous broadcast, a procedure for searching and allocating the same empty channel having a desired wave-to-interference wave level ratio equal to or greater than a threshold value is performed for each of the target mobile terminal stations in the cell of the base station. And a second procedure performed according to the load situation of the cellular mobile communication system.
Therefore, the first procedure for avoiding a problem when simply applying broadcast mode simultaneous channel allocation and the broadcast mode simultaneous channel allocation are applied to the ARP system which originally exerts the channel reuse effect for individual communication. The second procedure for reducing the number of channels used can be selectively applied according to the frequency distribution of broadcast calls in the coverage area of the cellular mobile communication system. Even if it fluctuates with time, by switching and applying the first and second procedures accordingly, it is possible to realize a stable individual / simultaneous communication mixed cellular mobile communication system with a large user accommodation capacity. Also,
Not only in the first procedure but also in the second procedure, the simultaneous communication channel is not simply assigned to the empty channel, but is assigned to the empty channel whose desired wave-to-interference level ratio is equal to or higher than the threshold value. In addition, the transmission quality of the simultaneous communication channel is also secured.

In the invention according to claim 4, in the broadcast channel allocation method in the base station of the cellular mobile communication system according to claim 3, the first and second procedures are the cellular mobile communication. It is selectively applied to each of the base stations according to the load status of the system. Therefore, the broadcast channel allocation method can be selected for each base station according to the distribution frequency of broadcast calls in the coverage area of the cellular mobile communication system.

According to the invention of claim 5, ARP is used.
A broadcast channel assigning device in a base station of a cellular mobile communication system that assigns individual communication channels based on a system, the broadcast channel assigning to a mobile terminal station targeted for broadcast in a cell of the base station A channel allocation request receiving means for receiving a request, and a free channel search common to all base stations of the cellular mobile communication system based on the same ARP system as the individual communication when the broadcast channel allocation request is received. In order, a means for performing a process of searching and allocating an empty channel having a desired wave-to-interference wave level ratio equal to or higher than a threshold value is provided to each of the target mobile terminal stations in the cell of the base station for broadcast communication. It is a thing. Therefore, it is possible to avoid the trouble when simply applying the broadcast mode simultaneous channel allocation to the ARP method that originally exerts the channel reuse effect for individual communication, has a large user accommodation capacity, and is stable individual / simultaneous communication mixed cellular A mobile communication system can be realized.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described with reference to the drawings.
An embodiment will be described. FIG. 1 shows a first embodiment of the present invention.
It is an explanatory view showing a communication system in a state. In the figure, the same as Figure 4.
Like parts are designated by the same reference numerals and description thereof is omitted. This fruit
The mode of operation is that a general communication call a occurs at the general command station 11.
Each base station 12 _Four, 12₇Channel allocation for simultaneous communication
When instructed, each base station responds to this broadcast.
Even if the principle of ARP method is maintained, the target of simultaneous communication in the area
For each mobile terminal station
Channels that satisfy the desired wave-to-interference level ratio are allotted
Of. In other words, each base station 12_Four, 12₇smell
One broadcast communication a from the broadcast command station 11 is
Pseudo equivalent to individual communication independent for each mobile terminal station
Therefore, the same AR as individual communication is used for the channel allocation.
The P method will be applied. For example, in cell 4
Base station 12_FourIs the mobile terminal that is the target of the simultaneous communication a
Assign channel CH4-1 to station 14 and then broadcast
Channel CH4 to the mobile terminal station 15 which is the target of signal a
Channel CH4-2 different from 1 is assigned.

FIG. 2 is a flow chart showing the channel allocation processing procedure of the first embodiment of the present invention in the base station in which the target mobile terminal stations are located. In the figure, the same processing steps as those in FIGS. 5 and 7 are designated by the same reference numerals, and the description thereof will be omitted. Compared with FIG. 5, S21, S
The processings 22 and S32 are added to introduce the simultaneous target mobile terminal station number counter variable k and the number m of simultaneous target mobile terminal stations existing in the own cell. Compared with FIG. 7, S51-
The process of S55 is deleted. When a simultaneous communication call occurs, the simultaneous command station 11 issues a channel allocation instruction to the base stations 12 _{1 to} 12 _{7 in which} the simultaneous target mobile terminal station is located. It should be noted that by periodically registering the location of the mobile terminal stations 13 to 18, the base stations 12 _{1 to} 12 ₇ and the general command station 11 are
Since the mobile terminal stations 13 to 18 residing in the cells 1 to 7 are known in advance, the simultaneous target mobile terminal stations 14, 15, 16 and 18 residing in the cells 1 to 7 are also known. When there are different simultaneous communications a and b from the simultaneous command station, the illustrated simultaneous communication channel assignment processing is performed for each of the simultaneous communications a and b. The base stations 12 _{1 to} 12 ₇ , which have received the channel allocation instruction from the general command station, start the general channel allocation processing shown in FIG. K = 0 in S21
As a result, k is sequentially increased by 1 in S22, the target mobile terminal station is sequentially changed, ARP channel search / allocation or call loss processing is repeated, and finally, in S32, k is compared with m. When k is less than m, the process returns to S22.

That is, for each of the simultaneous target mobile terminal stations located in the own cell, similarly to the flowchart of FIG. 5, based on the principle of the ARP method, the reception CIR threshold value on the empty channel is set in accordance with a predetermined search order. A procedure for searching and allocating a satisfying channel is performed, and the channel allocation process of the simultaneous communication in the base station is completed. The above-described channel allocation processing is performed in a short time as compared with the time interval of simultaneous / individual call occurrence.

The improvement of the system performance according to the above-described first embodiment of the present invention will be described below by using the evaluation result of the simulation. The assumed specifications of the ARP type cellular mobile communication system are as shown in the above-described explanatory diagram of FIG. 8, and the entire system is obtained by taking the cell configuration and the call density distribution shown in FIG. 9 described above. Has a fixed number of channels.

FIG. 3 shows the result of the simulation evaluation. FIG. 3A shows the case where the call density has a uniform distribution. As described above, the horizontal axis represents the ratio of simultaneous calls, that is, the ratio of the total number of calls (individual calls + simultaneous calls) that occur in the coverage area, and the vertical axis represents the overall system performance. It is (call loss rate + forced disconnection rate) as an index. In the method of the present invention, both (individual / broadcast call), the (call loss rate + forced disconnection rate) is improved as compared with the already described [broadcast mode burst], and moreover, (call loss rate + forced disconnection rate) The cutting rate) does not deteriorate. This indicates that the adverse effect on the original frequency reuse effect of the ARP method due to the simultaneous call is avoided.

FIG. 3B shows a case where the call density has an exponential distribution. Both the vertical axis and the horizontal axis are the same as in FIG.
In [Invention method simultaneous], ARP is affected by non-uniform call distribution.
Since the original frequency reuse effect is reduced, FIG.
The (call loss rate + forced disconnection rate) is worse than the case. However, it is improved as a whole compared to [broadcast mode simultaneous] shown in FIG. 3B, and (call loss rate + forced disconnection rate) is not deteriorated due to an increase in the ratio of simultaneous calls. Therefore, it is verified that even if the call density has an exponential distribution, the broadcast channel allocation according to the present invention maintains the principle of the ARP system and avoids the reduction of the frequency reuse effect by broadcast communication.

In the first embodiment described above, the entire cellular mobile communication system, that is, all base stations 12
_In a state in which the common channel search order common to _{1 to} 12 ₇ is determined, each base station 12 _{1 to} 12 ₇ searches for and allocates a channel satisfying the reception CIR threshold in the empty channel according to the search order. The example was based on the ARP method. However, the channel allocation method for automatically reusing frequency channels is not limited to the ARP method. For example, in recent years, an empty channel is obtained according to various quantities based on the distance between each mobile terminal station and the base station, which are obtained from the desired wave level, the interference wave level ratio, the noise level ratio, or the statistical value thereof at the reception of the base station. Various channel allocation methods for searching and allocating channels have been studied and proposed.

In the second embodiment of the present invention, when simultaneous communication is carried out in the above-mentioned other channel allocation system,
As in the case of assuming the ARP method, it is intended to avoid the reduction of frequency reuse effect due to simultaneous communication. That is, for each of the simultaneous target mobile terminal stations located in the own cell, a channel is allocated based on a channel allocation method in which frequencies are reused according to a principle different from the ARP method, and a channel for simultaneous communication at the base station is allocated. The allocation process ends.

In the above description, an example in which the method for allocating channels for simultaneous communication according to the present invention is applied to the entire system in a fixed and dedicated manner has been described, but the present invention is not limited to this. The distance distribution of the call density of the actual system is not limited to the simple uniform distribution without time fluctuation or the exponential distribution as shown in FIG. In other words, due to the occurrence of a disaster etc.
For example, it may occur intensively only in a specific cell. The third embodiment of the present invention includes the first and second procedures, and the first and second procedures are selectively applied according to the load status of the cellular mobile communication system.

In the first procedure, similarly to the first embodiment of the present invention described with reference to FIG. 2, a broadcast channel allocation request to a target mobile terminal station for broadcast in the area is received. At this point, based on the ARP method, a procedure for searching and assigning an empty channel whose CIR is equal to or greater than the threshold Th in the free channel search order that is common to all base stations To do. The second procedure is for one simultaneous communication as described with reference to FIG.
The procedure for searching for and assigning the same free channel whose CIR is greater than or equal to the threshold value Th is performed for each target mobile terminal station of the simultaneous communication in the area.

For example, as described above, the second procedure is temporarily applied when the simultaneous communication calls from the general command station are locally concentrated. As a result, it becomes possible to perform simultaneous communication on a large number of simultaneous target mobile terminal stations concentrated in a specific cell using only one channel for broadcast mode. If the call returns to normal and the calls are widely distributed throughout the coverage area, the first procedure is applied. In this way, both procedures are selectively applied to all base stations according to the call load status of the system. The load condition of the cellular mobile communication system and the selection of the procedure can be performed by a control station (not shown in FIGS. 1 and 4). It should be noted that the flow chart of FIG. 7 is not always necessary for realizing the second procedure. This flow can be variously modified.

In an actual system, there are cases where broadcast calls from the broadcast command center are concentrated in cells of a plurality of local cities scattered in the coverage area. In the fourth embodiment of the present invention, the first and second procedures described in the third embodiment are provided, and the first and second procedures are performed according to the load situation of the cellular mobile communication system. It is applied selectively for each cell. That is, the broadcast mode 1 channel allocation procedure is applied to a base station of a cell where calls are concentrated in a simultaneous communication and the call density is high, and a base station in an area where calls are widely distributed is broadcast based on the ARP method. Apply an independent channel allocation procedure to each target station. As a result, the two procedures are mixed and applied to the entire cellular mobile communication system. Such monitoring of the load condition of the cellular mobile communication system and selection of the procedure can be performed by a control station (not shown in FIGS. 1 and 4).

The above-described third and fourth embodiments are ARP
The explanation was given based on the method. However, in the third and fourth embodiments, as in the above-described second embodiment, an empty channel is searched for and assigned according to various quantities based on the distance between each mobile terminal station and the base station. , Can also be applied when a channel allocation method different from the ARP method is assumed.

Further, in the above description, in each of the embodiments, frequency channels are assigned on the premise of FDMA (frequency division multiple access). But TD
Even when allocating time-division channels on the premise of MA (time-division multiple access), if the same time-division channel is used in base stations of different cells, interference will occur with adjacent cells. Even in such a case, since the above-mentioned principle of the ARP system can be applied, the broadcast channel allocation method and broadcast channel allocation method in the base station of the cellular mobile communication system of the present invention are TDMA (time division multiple access). It is also applicable when allocating time division channels on the assumption that

[0049]

As described above, according to the present invention,
By maintaining the ARP system principle even for the simultaneous communication and allocating the channels, it is possible to avoid the reduction of the channel reuse effect caused by simply introducing the broadcast mode simultaneous communication. In addition, similar to the ARP method, other channel allocation methods, which are based on the principle of allocating channels for individual communication by searching for a vacant channel according to various amounts based on the distance between each mobile terminal station and the base station, can be used for simultaneous communication. On the other hand, by maintaining the principle of the system, it is possible to avoid the reduction of the channel reuse effect caused by simply introducing the broadcast mode simultaneous communication. As a result, it becomes possible to provide the simultaneous communication service to a large number of users with sufficient transmission quality in the cellular mobile communication system.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a communication system according to a first embodiment of this invention.

FIG. 2 is a flow chart showing a channel allocation processing procedure of the first embodiment of the present invention in a base station in which a target mobile terminal station is located.

FIG. 3 is a diagram showing a simple broadcast mode simultaneous channel allocation method and an evaluation result of simulation of the first embodiment of the present invention.

FIG. 4 shows a conventional cellular mobile communication system,
It is explanatory drawing which shows a communication system when a broadcast mode simultaneous communication channel allocation is simply introduced.

FIG. 5 is a flowchart showing a conventional ARP channel allocation procedure in the base station.

FIG. 6 is a schematic explanatory diagram of an ARP method.

FIG. 7 is a flowchart of channel allocation processing when a broadcast mode simultaneous channel allocation method is simply introduced to the ARP method in a base station in which a simultaneous target mobile terminal station is located.

FIG. 8 is an explanatory diagram of simulation specifications.

FIG. 9 is an explanatory diagram of a cell configuration and a distance distribution of call density, which are prerequisites for this simulation.

[Explanation of symbols]

1 to 7 ... Cell, 11 ... Simultaneous command station, 12 _{1 to} 12 ₇ ... Base station of each cell ₁ to ₇ , 13 to 18 ... Mobile terminal station, 19 ... Ground wire system

Claims (5)

(57) [Claims] 1. A broadcast channel allocation method in a base station of a cellular mobile communication system for allocating individual communication channels based on the ARP system, wherein the base station broadcasts in a cell of the base station. At the time of receiving a broadcast channel allocation request to the target mobile terminal station, a desired channel search order common to all base stations of the cellular mobile communication system is selected based on the same ARP system as the individual communication. The procedure for searching and assigning empty channels whose wave-to-interference level ratio is greater than or equal to the threshold
A method for allocating a broadcast channel in a base station of a cellular mobile communication system, which is performed for each target mobile terminal station of the broadcast that is in the cell of the base station. 2. A desired wave level at the reception of a base station, a same level to an interference wave level ratio, a same level to a noise level ratio, or statistics thereof, that is, various quantities based on a distance between each mobile terminal station and a base station. , A simultaneous communication channel allocation method in a base station of a cellular mobile communication system for allocating an individual communication channel by searching for an empty channel of the base station, wherein the base station is located in a cell of the base station. At the time of receiving a broadcast channel allocation request to the target mobile terminal station for broadcast communication, based on the same channel assignment method as the individual communication, with the target mobile terminal station for broadcast communication existing in the cell of the base station. The target mobile terminal of the simultaneous communication located in the cell of the base station is a procedure for searching for and assigning an empty channel of the base station according to the various amounts based on the distance from the base station. Of performed for each broadcast communication channel allocation method in a base station of a cellular mobile communication system, characterized in that. 3. A broadcast channel allocation method in a base station of a cellular mobile communication system for allocating a channel for individual communication based on the ARP system, wherein the base station broadcasts in a cell of the base station. At the time of receiving a broadcast channel allocation request to the target mobile terminal station, a desired channel search order common to all base stations of the cellular mobile communication system is selected based on the same ARP system as the individual communication. A first procedure of performing a procedure of searching and allocating an empty channel having a wave-to-interference level ratio of a threshold value or more for each of the target mobile terminal stations of the simultaneous communication existing in the cell of the base station; At the time of receiving a broadcast channel allocation request to a target mobile terminal station for broadcast communication existing in a cell of a base station, a desired wave-to-interference wave level ratio for one broadcast communication A procedure of searching for and allocating the same free channel equal to or more than a threshold value to each of the target mobile terminal stations of the simultaneous communication existing in the cell of the base station; The second procedure is selectively applied according to the load situation of the cellular mobile communication system, wherein the base station of the cellular mobile communication system is assigned a simultaneous communication channel. 4. The method according to claim 3, wherein the first and second procedures are selectively applied to each of the base stations according to a load status of the cellular mobile communication system. Method for allocating simultaneous communication channels in a base station of the cellular mobile communication system of. 5. A broadcast channel allocating device in a base station of a cellular mobile communication system for allocating a channel for individual communication based on the ARP system, the mobile terminal station being a target of broadcast communication existing in a cell of the base station. Channel assignment request receiving means for receiving a broadcast channel assignment request to all the base stations of the cellular mobile communication system based on the same ARP system as the individual communication at the time of receiving the broadcast channel assignment request. In the common empty channel search order, a process of searching and allocating an empty channel whose desired wave-to-interference level is equal to or higher than a threshold value is performed on each of the target mobile terminal stations of the simultaneous communication existing in the cell of the base station. A simultaneous communication channel assigning device in a base station of a cellular mobile communication system, comprising: