JPH05130668A - Communication system - Google Patents

Abstract

PURPOSE:To detect a biased traffic state in a cell and to previously suppress interference with an adjacent cell by grasping the number of talking terminals of mobile body communication terminals in each distance from a base station for each cell and controlling the number of talking terminals in each distance in a communication system allowing adjacent cells to use the same frequency. CONSTITUTION:Transmitters 111 to 11k and receivers 121 to 12k corresponding to respective channels in a talking transceiver 10 are connected to an antenna 4 through an antenna sharing device 2. A receiving signal outputted through the antenna 4 and the device 2 is inputted to the receiver 12 corresponding to the received channel through a receiver input signal line. When an originating request from a movible body communication terminal or terminating request from a terminal is outputted, a base station control circuit 1 in the base station measures a distance between the objective terminal and the base station and judges whether a new terminal can be connected or not based upon the number of talking terminals sorted in accordance with the distance and the information on the upper limit number of talking enabled terminals.

Description

Detailed Description of the Invention

[0001]

The present invention relates to, for example, a so-called CDM.
The present invention relates to a communication system, such as A (code division multiple access) system, which performs mobile communication by using the same frequency in adjacent cells.

[0002]

2. Description of the Related Art A cell structure in a conventional mobile communication system is shown in FIG.

In FIG. 13, each cell CL is an area in which the base station BS is in charge of connecting mobile communication terminals M _A and M _M , which are arranged in mobile units such as automobiles and people, by radio lines. is there.

Here, the area (cell CL) in which the base station BS and the radio line can be connected is a feature (building, etc.) when the antenna arranged in the base station BS is, for example, an omnidirectional antenna. ) Except for the influence of etc., it becomes almost circular. Basically, as shown in FIG. 13 above, the circle (each cell C
Generally, L) are arranged so as to overlap each other.

As a schematic representation of the structure of each cell CL, for example, a regular hexagonal structure as shown in FIG. 14 is often used. However, the boundary of each cell CL as shown in FIG. 14 is not as clear as the illustrated example due to the influence of the above-mentioned features.

Here, for example, the conventional analog system and T
In a DMA (Time Division Multiple Access) type mobile communication system, for example, in order to avoid mutual interference between cells CL using the same frequency, the cell CL radius of 4 to
The base stations BS are separated from each other by about 5 times.

On the other hand, for example, in a so-called CDMA (code division multiple access) system mobile communication system, a plurality of mobile communication terminals can use the same frequency in the same area, and the adjacent cells are included. All cells are designed to use the same frequency.

That is, in this CDMA system, a specific code is assigned to each line, a modulated wave of the same carrier frequency is spectrum-spread by this code and transmitted to the same repeater. This is a multiple access method for identifying the line, and is also called the SSMA method. Further, in this CDMA system, since the repeater band is limited, the transmission capacity per repeater is FDMA.
It is smaller than the (frequency division multiple access) method and the TDMA (time division multiple access) method. This is because the band of the repeater is narrow and a sufficient processing gain cannot be obtained, and the number of channels is limited by the interference noise between the carriers. On the other hand, the CDMA system is characterized in that it does not require an initial connection process and can communicate directly for each call as long as the codes are decided on each other, and that it is excellent in confidentiality and interference resistance.

In other words, since the so-called spread spectrum technique is used in the CDMA communication, for example, the signal of the mobile communication terminal M other than the mobile communication terminal M of interest viewed from the base station BS, or the focus of interest. The signal transmitted from the base station BS to another mobile communication terminal M as seen from the mobile communication terminal M is characterized in that it is regarded as noise of a considerably low level. Therefore, a plurality of mobile communication terminals M can use the same frequency even in one cell CL. This means that the same frequency can be used even in the adjacent cells CL.

[0010]

By the way, each cell CL
When calculating the degree of interference (interference) between cells, cell CL
It is general and appropriate to estimate the line capacity on the assumption that the mobile communication terminals M are uniformly present in the network.

When the distance between the base stations BS using the same frequency is large as in the analog system or the TDMA system described above, the influence is small even if the distribution of the mobile communication terminals M in each cell CL is biased. ..

However, when the same frequency is used in the adjacent cells CL as in the case of the CDMA system, if the distribution of the mobile communication terminals M in each cell CL is biased, the influence as described later will occur. Cannot be ignored.

Here, FIG. 15 shows an example in which the mobile communication terminals M are uniformly present. Further, for example, the number of mobile communication terminals M is limited so that each neighboring cell (cells shown in B to G in the figure) CL does not affect the base station BS _A of the cell CL _A shown in the figure. And

On the other hand, FIG. 16 shows a cell CL _{A in} the drawing.
2 shows the expected arrangement of the mobile communication terminals M when the traffic is concentrated in (the mobile communication terminals in the connected state are concentrated in the peripheral portion of the cell). In this case, the mobile communication terminal M in communication in the adjacent cell CL of the cell CL _A.
Are biased toward the cell CL _A side in the figure, and this cell CL _A
It is expected that many mobile communication terminals M other than the above approach the base station BS _A of the cell CL _A.

Here, since the strength of the radio wave is usually inversely proportional to the third to fourth power of the distance from the transmission point, the mobile communication terminal M of the adjacent cell CL approaches the base station BS _A of the cell CL _A. it is the base station BS _a of the cell CL _a means to undergo significant interference from terminals in neighboring cells CL.

[0016] Therefore, in the case of FIG. 16, the cell CL _A and when comparing the degree of interference that each adjacent cell CL is subjected, the cell CL _A base station BS _A and the adjacent cells CL
Distance from the mobile communication terminal M is smaller than that when the adjacent cell CL is focused (for example, the adjacent cell C shown in B in the figure).
L is smaller than the distance between the mobile communication terminal in each cell adjacent to the neighboring cell of the base station BS and in the diagram B of) for, received the cell CL _A Gayori strong interference, resulting in the cell It may happen that the number of mobile communication terminals M that can be used in CL _A is considerably smaller than that of each neighboring cell CL.

In an extreme case, one cell communication terminal M cannot be used because the interference is too great in the cell CL _A.

That is, the peak of the communication traffic is in the cell CL _A , and the number of mobile communication terminals M that can be used in this cell CL _A is lower than that in the surrounding area, while the line capacity in the cell CL _A is desired to be further increased. This is a big problem in the system.

As described above, in the CDMA system,
Even if it can be said that the same frequency can be used, the degree of interference given to other mobile communication terminals M is only small, and due to the imbalance of communication traffic (there is a terminal that is busy talking depending on the region), the line capacity. There may be a problem that is significantly lower than originally planned.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and communication capable of detecting an unbalanced traffic state in a cell to prevent interference with adjacent cells in advance. The purpose is to provide a system.

[0021]

The communication system of the present invention is proposed to achieve the above-mentioned object, and includes a plurality of base stations each provided with a cell, and one or more mobile communication terminals. Consisting of a mobile communication terminal existing in the cell and performing communication via the base station, in the communication is a communication system using the same frequency in adjacent cells, the base station, There is a distance measuring means for measuring the distance between the base station and the mobile communication terminal connected at the same frequency, and there is a request for a call from the mobile communication terminal or a call to the mobile communication terminal. In this case, the distance measuring means measures the distance between the target mobile communication terminal and the base station, and the number of mobile communication terminals in communication classified by the distance and the mobile communication terminal capable of making a call Number limit By the broadcast, in which so as to determine whether the connection of a new mobile communication terminal.

That is, in the present invention, so-called CDMA is used.
In a communication system using the same frequency in adjacent cells as in the method, the base station for each cell grasps the number of mobile communication terminals by distance from the base station, and controls the number of communication terminals by this distance. By limiting the number of call terminals in a large distance range (around the cell), it is possible to reduce interference with adjacent cells and prevent a significant decrease in line capacity. ing.

In other words, in the present invention, the base station has a distance measuring means for measuring the distance from the base station of a terminal (a mobile communication terminal making a call) connected at the same frequency. Creates traffic information classified by, when a call from the mobile communication terminal or a request for an incoming call to the mobile communication terminal is received, the distance between the target mobile communication terminal and the base station is measured, Based on information on the upper limit of the number of call terminals (mobile communication terminals in communication) classified by distance and the number of mobile communication terminals that can make a call, it is determined whether a new mobile communication terminal can be connected. in this way,
By limiting the number of terminals around the cell in particular, interference with adjacent cells is reduced.

In the communication system of the present invention,
The base station has a jamming condition measuring means for measuring the occurrence condition of jamming in the same frequency, and when there is a request from the mobile communication terminal to make a call or an incoming call to the mobile communication terminal, the jamming occurs. The situation measuring means measures the occurrence situation of the interference at the target frequency, and judges whether or not a new mobile communication terminal can be connected based on the measurement result.

That is, according to the present invention, in a communication system in which the same frequency is used in adjacent cells such as a CDMA system, the base station of each cell checks the interference situation in the frequency band used and simultaneously uses terminals in adjacent cells. By issuing a request regarding the number limit and limiting the number of mobile communication terminals to which adjacent cells are connected in response to this request, it is possible to reduce interference between cells and prevent the line capacity from being significantly reduced. I have to.

In other words, according to the present invention, the base station has the function of monitoring the received power level of the used channel and determining the interference level from the adjacent cell. By issuing a request to limit the number of communication terminals and limiting the number of mobile communication terminals to which the adjacent cell connects in response, it is possible to prevent the line capacity from being significantly reduced due to the interference from the adjacent cell.

[0027]

According to the communication system of the present invention, the base station uses the distance measuring means to perform targeted mobile communication when the mobile communication terminal makes a call or a call is received from the mobile communication terminal. The distance between the terminal and this base station is measured, and based on the information on the number of mobile communication terminals in a call and the upper limit of the number of mobile communication terminals that can be called classified by the distance, the connection of a new mobile communication terminal is determined. Whether the connection is impossible or not is judged, and if the connection is impossible, the connection of a new mobile communication terminal is restricted. Therefore, it is possible to reduce interference with adjacent cells and prevent the line capacity from remarkably decreasing.

Further, according to the communication system of the present invention, the base station is targeted by the jamming condition measuring means when there is a request from the mobile communication terminal for an outgoing call or an incoming call to the mobile communication terminal. Measure the occurrence status of interference at the frequency, judge whether or not to connect a new mobile communication terminal based on this measurement result, and if the connection is not possible, limit the connection of the new mobile communication terminal. There is. Therefore, it is possible to reduce interference between cells and prevent the line capacity from significantly decreasing.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

The communication system of this embodiment is the same as that shown in FIG.
As shown in 3, a plurality of base stations BS each provided with a cell CL and one or more mobile communication terminals M (M _A , M _M ).
The mobile communication terminal M existing in the cell CL communicates via the base station BS, and uses the same frequency in the adjacent cell CL during this communication (that is, for example, the CDMA system is used). ) In a communication system, as shown in FIG. 1, the base station BS has a built-in distance measuring means for measuring the distance between the mobile communication terminal M connected at the same frequency and the base station BS. When the mobile communication terminal M requests or receives a call to the mobile communication terminal M, the distance measuring means of the base station control circuit 1 causes
The distance between the target mobile communication terminal M and the base station BS is measured, and information on the upper limit of the number of mobile communication terminals in a call and the number of mobile communication terminals capable of making a call, which are previously classified by the distance, Thus, it is determined whether or not a new mobile communication terminal M can be connected.

Here, prior to the description of the configuration of the base station BS shown in FIG. 1, the outline of the present invention will be described.

FIG. 2 shows the distribution of the mobile communication terminals M in the cell CL.

In FIG. 2, assuming that the distance between the mobile communication terminal M and the base station BS is x, and if the mobile communication terminal M is uniformly distributed in the cell CL, the distance x and the mobile communication are calculated. The relationship of the number of terminals y is as shown in FIG.

That is, in FIG. 3, as the distance x increases, the number y of mobile communication terminals increases in proportion to the increase in the circumference of the radius x corresponding to this distance.

Further, since the number n of mobile communication terminals making a call takes a discrete value, the number n of communication terminals when the distance x is equally divided is as shown in FIG. 4, for example.

Here, if the long-time average is taken, for example, the number n of communication terminals will show a uniform increasing tendency with respect to the distance x as shown in FIG. Since the number of communication terminals is small, it can be considered that the number n of communication terminals usually fluctuates as shown in FIG. 5 in a short time.

In addition, the adjacent cell (cell C in FIG.
When each mobile communication terminal has a biased distribution, such as each cell adjacent to L _A ) CL, move to a location where the distance x of each adjacent cell CL from each base station BS is large as shown in FIG. The body communication terminals M are concentrated.

Here, the distance x from the base station BS and the degree of interference with the adjacent cell CL become very large as the distance x becomes large.

There are two factors for this. The first factor is that the received power is inversely proportional to the third to fourth power of the distance from the transmission point, so that when the mobile communication terminal M approaches the adjacent cell CL, it causes interference. The second factor is that each base station BS has a mobile communication terminal M within its cell CL.
The transmission power of the mobile communication terminal M is controlled so that the reception power becomes the same level even if the distance from the mobile communication terminal M is different. Therefore, the transmission power of the mobile communication terminal M becomes very large as the distance from the base station BS increases. Is to be. That is, this means that the mobile communication terminal M in a call state around the cell CL.
Means that dominates the state of interference.

From the above, according to the present invention, as shown in FIG. 7, the number of mobile communication terminals (the number of communication terminals n) is limited as the distance x from the base station BS increases. FIG. 7 shows the number of mobile communication terminals N1, N2, N3, N4, and N5 that are allowed for communication by dividing the distance x from the base station BS into five, for example. The method of dividing the distance is not limited to five divisions, and does not have to be evenly divided. Further, logarithmic division or another method may be adopted.

Further, since the interference with the adjacent cell CL is small near the base station BS, a larger number of mobile communication terminals M can be accommodated as compared with the peripheral portion of the cell CL.

Table 1 shows these information together with information on the number of mobile communication terminals currently in communication, and the base station BS uses the traffic information separated by such distance x as a table. I have it.

[0043]

[Table 1]

In Table 1, the number of mobile communication terminals N1, N2, N3, N4, N5 that can communicate is determined to some extent by calculation. However, the number of mobile communication terminals N1, N2, N3, N4, N5 that can talk
Is preferably (empirically) set in accordance with the attenuation of the radio wave due to the influence of a feature or the like.

Returning to FIG. 1 again, the base station BS shown in FIG. 1 is capable of transmitting and receiving a plurality of frequencies (for example, k channels). That is, the base station BS of FIG. 1 is not limited to only one channel because it corresponds to the CDMA system, and when the frequency band to be used is gradually increased, for example, when switching from an existing system. Has a system that can use multiple channels. Therefore, the transmitters 11 ₁ , ...
_The receivers 12 ₁ , ..., 12 _k are connected to the antenna 4 via the antenna sharing device 2. Even in this case, the adjacent cells CL still use the same frequency.

Here, only the first channel (1CH) will be described. The antenna 4 and the antenna sharing device 2
The reception signal output via the above is input to the receiver 12 ₁ for the channel (1CH) via the receiver input signal line. The signal RS ₁ demodulated by the receiver 12 ₁ is sent to the base station control circuit 1 via the receiver output signal line. The signal transmitted through the base station control circuit 1 is connected to the public network from the terminal 5 through various wireless control stations.

On the other hand, the transmission signal sent from the public network to the terminal 5 via various wireless control stations is transmitted through the base station control circuit 1 and the transmitter input signal line (transmission signal TS ₁ ). It is input to the transmitter 11 ₁ for the channel (1CH). The transmission signal modulated by the transmitter 11 ₁ is input to the antenna sharing device 2 via the transmitter output signal and is transmitted from the antenna 4.

The description of the other transmitters and receivers of the call transmitting / receiving apparatus 10 will be omitted because they are similar to the above.

Further, in the base station control circuit 1, as described above, when there is a request from the mobile communication terminal M to make an outgoing call or an incoming call to the mobile communication terminal, the built-in distance measuring means The distance between the mobile communication terminal M, which is the target of the call or the call, and the base station BS is measured,
At the same time, whether or not a new mobile communication terminal can be connected is determined based on the number of mobile communication terminals currently in a call and the information on the upper limit of the number of mobile communication terminals that can be called, which are classified according to the distance. ..

That is, the base station control circuit 1 prepares traffic information classified by the distance from the base station BS to the mobile communication terminal M in the call, and at the same time, sets the target of the call or the call. The distance between the mobile communication terminal M and the base station BS is measured, and a new mobile communication terminal is created based on the information about the upper limit of the number of communication terminals classified according to the distance and the number of mobile communication terminals that can communicate. It is determined whether M can be connected.

The specific configuration and operation of the base station control circuit 1 will be described later with reference to FIG. 8, but the transmission signal TS _c from the base station control circuit 1 is transmitted / received by the control transmission / reception device 2.
It is sent to the antenna sharing device 2 via the transmitter 23 of 0. Further, the received signal is sent to the base station control circuit 1 via the receiver 24 of the control transceiver 20 (signal RS _c ).

FIG. 8 shows a block diagram of one channel of the base station control circuit 1.

In the configuration of FIG. 8, since communication is performed with a plurality of mobile communication terminals M on one channel, a plurality (j) of encoders 40 ₁ , ..., 40 _j and a plurality of decoders 41 are provided. _1,..., and a 41 _j.

[0054] Each encoder 40 _1, ..., 40 _j and the decoder 41 _1, ..., a 41 _j sets will be connected to a plurality of mobile communication terminal M and 1: 1.

Further, for example, terminals 51 ₁ , ..., 51 _j
Transmitting a call signal from the radio network base station which is supplied via the ET _1, · · ·, ET _j is sent to the encoder 40 ₁ via the control unit 43. The output of this encoder 40 ₁ is combined with the outputs of other encoders by the adder 53,
It is sent to the transmitter shown in FIG. 1 via the terminal 54.

Further, the output of the receiver of FIG. 1 supplied through the terminal 55 is the decoders 41 ₁ , ..., 41.
distributed to _j . These decoders 41 ₁ , ..., 41
Each received call signal DT ₁ , ..., DT from _j
j is sent to the control unit 43 and finally the terminals 52 ₁ , ...
.., 52 _j to the radio network controller.

Here, as described above, in the base station control circuit 1, there are two possible distance measuring means for obtaining the distance between the base station BS and the mobile communication terminal M.

The first distance measuring means is the mobile communication terminal M.
Is a means for measuring the distance by using the power control information.

That is, since the received power at the base station BS is controlled to be constant, the base station BS controls so that the output of the mobile communication terminal M increases as the distance from the base station BS increases. Specifically, the decoders 41 ₁ , ..., 41 _j
The decoded state of the signal in the signal is (the decoded signal DS ₁ , ...
, DS _j ) is sent to the control unit 43, and the control unit 4
3 controls the output to the mobile communication terminal M based on the information (decoded signals DS ₁ , ..., DS _j ). In other words, the control unit 43 causes the decoder 41 ₁ , ...
Using the information on the decoding state of the signal at 41 _j ,
It is possible to know how far the mobile communication terminal M is from the base station BS.

Further, the second distance measuring means is a transmission signal (signals TS ₁ , ..., TS in FIG. 1) from the base station BS.
It is means for measuring the distance of the mobile communication terminal M depending on how much the received signal from the mobile communication terminal M is delayed with respect to _j ).

In this case, for example, the encoders 40 ₁ , ...
· ·, 40 _j and the decoder 41 _1, ..., respectively, from 41 _j transmits a call signal ET _1, ..., synchronization signal SE ₁ of ET _j, ..., SE _j and receive speech signal DT _1, ·
.., SD _j synchronizing signals SD ₁ , ..., SD _j, and delay measuring circuits 4 corresponding to these synchronizing signals, respectively.
2 _1, ..., are input to 42 _j, these delay measuring circuit 42 _1, ..., by measuring the delay time of both the synchronization signal 42 _j, and sends it to the control unit 43. At this time, the control unit 4
In 3, the distance is calculated based on the information of each delay time, the distribution of the mobile communication terminals M in the cell CL is controlled, and the interference to the adjacent cell CL is reduced.
It is generally more accurate to measure the delay time as described above.

That is, in the base station control circuit 1 of FIG. 1 described above, the control unit 4 of FIG.
Received signal RS _c from the mobile communication terminal M input to 3
Based on the above, the distance between the base station BS and the mobile communication terminal M is obtained as described above, and the control signal of the mobile communication terminal M obtained by the control unit 43 based on this distance is the transmission signal. It is adapted to be sent to the transmitter 23 as TS _c .

FIG. 9 shows a flowchart of the operation of the control unit 43 shown in FIG.

Here, the control unit 43 has the table of Table 1 above, and how many mobile communication terminals M are in communication (communication) in each distance band (a belt-shaped place connecting the same distance). Have to figure out. For that purpose, it is necessary to measure not only when the mobile communication terminal M is connected but also the distance of the mobile communication terminal M during a call from the base station BS. Also,
When the mobile communication terminal M during the call moves (when the distance band is changed), the above table must be updated.

That is, in the flow chart of FIG. 9, if there is a call from the mobile communication terminal M or a request for an incoming call to the mobile communication terminal M in step S1, a call is being made in the cell CL in step S2. It is checked whether the number of mobile communication terminals M can be increased. In the case of the CDMA communication, the data error rate gradually increases as the number of mobile communication terminals is increased. Therefore, in this step S2, the mobile communication is performed so as not to exceed the error rate allowed in the system design. The number of terminals is limited. As a method of checking whether or not the number of mobile communication terminals M in communication in this step S2 can be increased, specifically, a method of judging by the number of mobile communication terminals in communication in the cell CL and a base station BS Of the mobile communication terminals M until the error rate reaches a certain value. In step S2, the determination is made using any of these methods.

If it is determined in step S2 that the number of mobile communication terminals M cannot be increased any more, the process proceeds to step S7, and in step S7 the request source (caller After notifying the former)
In step S6, the processing of the outgoing / incoming call request ends.

If it is determined in step S2 that the addition is possible, the process proceeds to step S3 and this step S3 is performed.
In step 3, the line is temporarily connected to the mobile communication terminal M to measure the distance of the mobile communication terminal M, and the number of mobile communication terminals Mi existing in the range to which the connected mobile communication terminal M belongs The upper limit number Ni of body communication terminals is taken out from the table of Table 1.

After that, in step S4, the number Mi of mobile communication terminals is compared with the upper limit number Ni. If Mi <Ni is not satisfied in this step S4 (No), the number of mobile communication terminals M cannot be increased. In step S7, the request source is notified that connection cannot be established due to congestion of the wireless line in the same manner as described above in step S7, and the process is terminated (step S
6).

If Mi <Ni is determined in step S4 (Yes), the number of mobile communication terminals M can be increased. Make a connection. Furthermore, this step S5
Then, the mobile communication terminal M connected to the table of Table 1 above.
After adding the information of (3), the process proceeds to step S6 to end the processing of the outgoing / incoming call request.

As described above, according to this embodiment, the cell C
By adding the determination of whether or not the mobile communication terminal M can be added according to the distance from the base station BS to the determination of the entire L, it is possible to prevent interference with the adjacent cell CL in advance.

Further, in the communication system of the present invention, as shown in FIG. 10 of another embodiment system described below, the base station BS has a built-in interference condition measuring means for measuring the occurrence condition of interference at the same frequency. When the mobile communication terminal M requests or receives an incoming call to the mobile communication terminal M, the interference measuring means in the base station control circuit 6 is provided. It is also possible to measure the occurrence status of interference at a target frequency and determine whether or not a new mobile communication terminal M can be connected based on the measurement result. In FIG. 10, the same components as those in FIG. 1 described above are designated by the same reference numerals.

That is, the base station control circuit 6 of the present invention is
It has a function of monitoring the received power level of the used channel and determining the interference level from the adjacent cell CL, and when this interference level is above a certain level, it issues a request to the adjacent cell CL to limit the number of communication terminals, In response to this, the cell CL limits the number of mobile communication terminals to be connected.

In FIG. 10, the base station BS is
Transmission and reception of a plurality of frequencies (for example, k channels) can be performed. That is, the base station BS of FIG.
However, since it corresponds to the above CDMA system, it is not limited to one channel, and a plurality of channels can be used when the frequency band to be used is gradually increased, for example, when switching from an existing system. It is a system. Therefore, the transmitter 11 ₁ of each channel of the call transceiver device 10, · · ·, 11 _k
, And the receivers 13 ₁ , ..., 13 _k are connected to the antenna 4 via the antenna sharing device 2. Even in this case, the adjacent cells CL still use the same frequency.

Here, only the first channel (1CH) will be described. The antenna 4 and the antenna sharing device 2
The received signal output via the above is input to the receiver 13 ₁ for the channel (1CH) via the receiver input signal line. The signal RS ₁ demodulated by the receiver 13 ₁ is sent to the base station control circuit 6 via the receiver output signal line. The signal via the base station control circuit 6 is connected to the public network from the terminal 5 through various wireless control stations.

On the other hand, the transmission signal sent from the public network to the terminal 5 via various wireless control stations is transmitted through the base station control circuit 6 and the transmitter input signal line (transmission signal TS ₁ ). It is input to the transmitter 11 ₁ for the channel (1CH). The transmission signal modulated by the transmitter 11 ₁ is input to the antenna sharing device 2 via the transmitter output signal and is transmitted from the antenna 4.

The other transmitters and receivers of the call transmitting / receiving apparatus 10 are the same as those described above, and the description thereof will be omitted.

Here, from the receivers 13 ₁ , ..., 13 _{k of the} other embodiment shown in FIG. 10, signals (power level measurement signals EL ₁ ,.
.., EL _k ) are taken out. That is, in the base station control circuit 6 of the other embodiment, it becomes possible to know the interference level from the power level measurement signals EL ₁ , ..., EL _k .

[0078] For example, as shown in FIG. 16 described above, the mobile communication terminal M of the cell CL _A in the drawing A the same frequency are also used, therefore, in the received power level is the cell CL _A The mobile communication terminal M used in the above is included. Here, the reception power level of the mobile communication terminal M in the cell CL _A can be separately measured by the base station BS _A , and accordingly, from the reception power level, the cell CL can be measured.
The level of interference from the external cell CL can be known by subtracting the amount (reception power level) of the mobile communication terminal M in _A. That is, in CDMA communication, the base station B
In S, the received signal strength from the mobile communication terminal M in the cell CL is controlled to be substantially constant, and the received power for the mobile communication terminal M in the cell CL can be calculated only by the number of units in use. Is.

When the base station control circuit 6 makes a request for an outgoing call from the mobile communication terminal M or an incoming call to the mobile communication terminal M based on the reception power level obtained as described above. First, the occurrence status of the interference at the target frequency is measured, and based on the measurement result, it is determined whether or not the new mobile communication terminal M can be connected.

FIG. 11 shows a flowchart of the operation in the base station BS _A of the cell CL _A shown in A of FIG.

Here, the disturbing level is the same cell CL _A from the disturbing level information output from each receiver shown in FIG.
It is a value calculated by subtracting the amount of the mobile communication terminal M in the above. Also, this base station BS _A will have the number of mobile communication terminals connected to the base station BS of the adjacent cell CL limited according to the state of the channel. Prepare it and call it the limit level below.

In the flowchart of FIG. 11, after the start in step S11 (when the operation of the base station BS _A is started), the limit level is 0 (minimized) as an initial setting in step S12. In this state, the limitation of the number of mobile communication terminals to the adjacent cell CL is not required, and the adjacent cell CL also follows the upper limit of the number of mobile communication terminals determined in each cell CL (when the restriction level is 0). Mobile communication terminal M
Are making connections.

Next, in step S13, the interference level is checked. When the disturbance level is higher than the set value P1 in step S13 (Yes), it means that the cell CL _A is strongly disturbed by the adjacent cell CL. In this case (Yes), the process proceeds to step S14, and it is checked in step S14 whether the limit level has reached the maximum. If it is determined in step S14 that the limit level has reached the maximum (Yes), the limit cannot be further strengthened, and no processing is performed, and the process returns to the check of the disturbance level in step S13.

If it is determined in step S14 that the limit level has not reached the maximum (No), the process proceeds to step S15, the limit level is increased in step S15, and then the number of mobile communication terminals is increased in step S16. Request the restriction to the adjacent cell CL.

After step S16, step S1
7 waits for responses from all of the adjacent cells CL,
When the response to the end of restriction strengthening has been received from all L, the process returns to the interference level check in step S13.

If it is determined in step S13 that the interference level is lower than the set value P1 (No), the process proceeds to step S18, and in step S18, it is determined whether the interference level is higher than the set value P2. Find out. If it is determined to be large in step S18 (Yes), there is no need to strengthen or relax the restriction, and the process returns to step S13 without any processing.

When it is determined in step S18 that the value is smaller than the set value P2 (No), the interference from the adjacent cell CL is very small, and therefore the process proceeds to step S19 and the limit level is set in step S19. Check if can be lowered (minimum).

If it is already at the minimum level in this step S19 (Yes), the process returns to step S13. If it is determined in step S19 that the minimum level is not reached (N
o), the process proceeds to step S20, and this step S20
After lowering the restriction level in step S21, the adjacent cell CL is requested to relax the restriction in step S21.

After step S21, step S
In step S22, the process waits for responses from all of the adjacent cells CL, and when the response of restriction relaxation completion is received from all of the adjacent cells CL, the process returns to step S13.

The above-mentioned restriction level may be one step.

FIG. 12 shows a flowchart of the operation of the adjacent cell CL in response to one restriction strengthening or relaxation request.

Here, the adjacent cell CL is always waiting for a command regarding the limit level. In each cell CL, the number of mobile communication terminals used in the cell CL is controlled according to the restriction level, and when the mobile communication terminals M are used more than the number of mobile communication terminals corresponding to the restriction level. Limits the outgoing call request from the mobile communication terminal M and the incoming call request to the mobile communication terminal M to be equal to or less than the number of mobile communication terminals corresponding to the restriction level. On the contrary, when the number of mobile communication terminals is small with respect to the restriction level and there is a request for outgoing or incoming, the request is accepted within the range of the number of mobile communication terminals corresponding to the restriction level. In the other embodiments described above, the number of mobile communication terminals that can be used in the cell CL is limited to a small number as the restriction level increases.

In FIG. 12, when a command is received from the adjacent cell CL in step S31, it is checked in step S32 whether the restriction should be strengthened or relaxed. This step S
When the restriction is strengthened in 32 (restriction), step S3
3, the level of restriction is increased in step S33.

After step S33, step S3
Then, in step S34, it is checked whether or not the restriction has been completed. If it is less than the number of mobile communication terminals corresponding to the restriction level (Yes) in step S34, the process immediately proceeds to the determination of step S35. In addition, this step S
At 34, if the number of mobile communication terminals at the restriction level is exceeded (No), the end of call disconnection of the mobile communication terminal M progresses and waits until the number of mobile communication terminals corresponding to the restriction level is reached, and then step Proceed to S35.

In the step S35, the completion of the restriction is reported to the base station BS which has received the command, and the process is ended (step S36).

If it is determined in step S32 that the restriction is relaxed, the process proceeds to step S37, the restriction level is lowered in step S37, and then step S38.
Check whether the restrictions were relaxed in.

In this step S38, if there is no request for outgoing or incoming call (Yes), and if there is a request (No), the request is permitted within the range of the restriction level, and then restricted in step S39. A report of completion of implementation of the mitigation is sent to the partner base station BS that received the command, and the process for one restriction command is completed (step S36).

In the description of the other embodiments described above, the case where the cell CL _A is requested to limit the number of mobile communication terminals to be used to the adjacent cell CL when there is interference from the adjacent cell CL I explained, but all cells CL
Needless to say, can take the position of the cell CL _{A and} the position of the adjacent cell CL. Therefore, one cell CL in FIG. 16 described above is also a neighboring cell CL of the other six cells CL, and receives a command regarding the limitation of the number of mobile communication terminals from the six cells CL. Also, a plurality of cells CL
In the case of simultaneous restriction from the above, the maximum restriction level sent from each cell CL will be used for control.

Furthermore, in the above-mentioned other embodiments, for the sake of convenience of explanation, the description has been made in the form of control between the cell stations CL of the base stations BS. Here, normally, a plurality of base stations BS are generally controlled by a radio network controller. Thus the central cell C
When a total of seven L and adjacent cells CL are in one line control station, all control is performed in the radio line control station, and when a plurality of line control stations are spread, a plurality of line control stations are connected. However, control processing should be performed.

Incidentally, the above-mentioned conventional analog system and TD
Although the reception power is also measured in the equipment of the base station BS of the MA communication system, the purpose of them is to monitor the transmission power of the mobile communication terminal M using that frequency. The embodiment of the present invention is different in that it is used as a disturbance level.

As described above, in this other embodiment, a traffic state that is biased in the cell CL (a state in which the mobile communication terminals M in the connected state are concentrated in the peripheral portion of the cell CL) is detected beforehand. It becomes possible to prevent interference with the adjacent cell CL. Further, by measuring the received power level and limiting the number of mobile communication terminals in the adjacent cells CL based on the measured received power level, it is possible to prevent the communication capacity of each cell CL from significantly decreasing.

[0102]

As described above, in the communication system of the present invention, when the base station requests the call from the mobile communication terminal or the call to the mobile communication terminal, the distance measuring means allows The distance between the target mobile communication terminal and the base station is measured, and a new mobile unit is obtained based on the number of mobile communication terminals in a call and the information about the upper limit of the number of mobile communication terminals that can be called, which are classified by the distance. By determining whether or not the communication terminal can be connected, it is possible to reduce interference with adjacent cells and prevent the line capacity from significantly decreasing.

In addition, in the communication system of the present invention,
When the base station makes a call from the mobile communication terminal or receives a call to the mobile communication terminal, the jamming situation measuring means measures the jamming situation at the target frequency, and the measurement result Since it is determined whether or not a new mobile communication terminal can be connected, the interference between cells can be reduced and the line capacity can be prevented from significantly decreasing.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a base station of a communication system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a distribution of base stations and mobile communication terminals in a cell according to the embodiment.

FIG. 3 is a diagram showing a relationship between a distance from a base station and the number of mobile communication terminals according to an embodiment.

FIG. 4 is a diagram showing the relationship between the distance from the base station and the number of communication terminals when the mobile communication terminals of the embodiment have a uniform distribution.

FIG. 5 is a diagram showing the relationship between the distance from the base station and the number of call terminals when the distribution of mobile communication terminals of the embodiment varies.

FIG. 6 is a diagram showing the relationship between the distance from the base station and the number of communication terminals when the distribution of mobile communication terminals in the embodiment is concentrated in the peripheral portion of the cell.

FIG. 7 is a diagram showing a distance from a base station and an upper limit of the number of terminals according to the embodiment.

FIG. 8 is a block circuit diagram showing a specific configuration of a base station control circuit of the base station of the embodiment.

FIG. 9 is a flowchart of an operation of limiting the number of mobile communication terminals in a cell in the example.

FIG. 10 is a block circuit diagram showing a configuration of a base station of a communication system according to another embodiment of the present invention.

FIG. 11 is a flowchart of the operation in the cell CL _A in another example.

FIG. 12 is a flowchart of operations of neighboring cells in another embodiment.

FIG. 13 is a diagram showing mobile communication and a cell structure.

FIG. 14 is a diagram showing a regular hexagonal cell structure.

FIG. 15 is a diagram showing an example in which mobile communication terminals are distributed.

FIG. 16 is a diagram showing an example in which mobile communication terminals are biased.

[Explanation of symbols]

1, 6 ・ ・ ・ ・ Base station control circuit 2 ・ ・ ・ ・ ・ ・ Antenna sharing device 4 ・ ・ ・ ・ ・ ・ ・ Antenna 10 ・ ・ ・ ・ ・ ・ Communication transmission / reception Device 11 _{1 to} 11 _k , 23 ..... Transmitter 12 _{1 to} 12 _k , 13 _{1 to} 13 _k , 24 ... Receiver

Claims (2)

[Claims] 1. A plurality of base stations each provided with a cell,
A mobile communication terminal consisting of one or more mobile communication terminals and existing in the cell communicates via the base station, and at the time of communication, in a communication system using the same frequency in adjacent cells, The base station has a distance measuring means for measuring the distance between the mobile communication terminal and the base station connected at the same frequency, and the transmission from the mobile communication terminal or to the mobile communication terminal. When there is a request for incoming call, the distance measuring means measures the distance between the target mobile communication terminal and the base station, and the number of mobile communication terminals in communication classified by the distance and the call A communication system characterized by determining whether or not a new mobile communication terminal can be connected based on information on the upper limit of the number of possible mobile communication terminals. 2. A plurality of base stations each provided with a cell,
A mobile communication terminal consisting of one or more mobile communication terminals and existing in the cell communicates via the base station, and at the time of communication, in a communication system using the same frequency in adjacent cells, The base station has a jamming condition measuring means for measuring a jamming condition in the same frequency, and when there is a request from the mobile communication terminal to make a call or receive a call to the mobile communication terminal, the jamming occurs. A communication system characterized in that the situation measuring means measures the occurrence situation of interference at a target frequency and judges whether or not a new mobile communication terminal can be connected.