JPH08223106A - Radio channel selection method for mobile communication system and base station equipment - Google Patents

Abstract

PURPOSE: To improve the frequency use efficiency without increasing the communication traffic in a control channel neither delaying the connection and securing a high allowable traffic when assigning a radio channel. CONSTITUTION: The CIR value of an up line is obtained by the reception level of a carrier coming from a mobile station PS2 as the connection object and the reception level of an interference wave coming from another mobile station PS1 through the same radio channel, and the CIR value of a down-line is obtained by estimation based on the reception level of a carrier coming from another base station PS1, and it is discriminated whether the radio channel can be used or not based on the CIR measured value of the up-line ana the CIR estimated value of the down-line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system such as an analog cordless telephone system, a digital cordless telephone system, a digital car / mobile telephone system, and particularly adopts an autonomous distributed dynamic allocation method as a wireless channel allocation method. The present invention relates to a radio channel selection method for a system and a base station device.

[0002]

2. Description of the Related Art In a mobile communication system having a plurality of base stations and a plurality of mobile stations, radio channels are repeatedly used in order to increase frequency utilization efficiency, separated by a distance equal to or less than an allowable value of interference. The radio channel allocation method used in such a mobile communication system includes fixed channel allocation (FCA).
Method and dynamic channel allocation (DCA: Dynamic
Channel Assignment) method.

In the FCA system, a plurality of wireless channels are fixedly allocated to each base station in advance, and the base station is allocated to itself when communicating with a mobile station. It selects and assigns an appropriate wireless channel from the. On the other hand, in the DCA method, when performing communication with a mobile station, each base station selects and allocates an appropriate wireless channel from all wireless channels possessed by the system. The DCA method does not require a line design as compared with the FCA method, and thus has an advantage that radio channels can be flexibly allocated according to the amount of communication.

By the way, when selecting a wireless channel by this DCA method, it is necessary to select a wireless channel whose interference is equal to or less than an allowable value, and it is necessary to consider so as not to affect other communication in use. There is. As a wireless channel selection method that satisfies these conditions, base stations that are not separated by a predetermined distance or more do not use the same wireless channel, or if there is another communication that uses the same wireless channel, this communication is selected. There is a method of selecting a wireless channel after confirming that it does not give interference.

In these selection methods, a base station which is going to select a radio channel communicates control signals with other base stations using the same radio channel, either directly or indirectly through the control station. To obtain information for selecting a wireless channel. However, when the number of base stations increases, the amount of communication by this control signal increases rapidly. Particularly in a micro cell system, the number of base stations is very large, and thus it is practically difficult to select a radio channel by such a method.

Therefore, as a wireless channel allocation method for the microcell system, adoption of an autonomous distributed DCA method which does not require control signal communication between base stations is being considered.

In the autonomous distributed DCA system, each base station selects a radio channel using only information obtained by itself without communicating with other base stations.
The selection of the wireless channel is performed as follows, for example. Here, a case will be described as an example in which the influence of interference is evaluated using the ratio CIR (Carrier to Interference Ratio) between the received wave level and the interference wave level.

That is, the information that can be used when selecting a radio channel by the autonomous distributed DCA method is limited to the information obtained by the own base station and the information obtained by the mobile station that communicates with the own base station. Therefore, it is not possible to directly evaluate the deterioration of CIR given to other communication using the same channel. For this reason, a method is used in which the probability that the CIR of other communications will deteriorate below a required value is selected by selecting a radio channel with a sufficient margin for CIR.

FIG. 6 is a diagram for explaining a radio channel selection method according to the autonomous distributed DCA system.
1 and the mobile station PS1 communicate with each other using a certain radio channel, the base station BS2 and the mobile station PS2 attempt to use the same radio channel. Although the number of communications using the same wireless channel is 1 here, the CIR can be similarly measured by adding a plurality of interference waves when the number of communications is plural.

First, C for both the uplink and the downlink
A method of measuring the IR to determine the availability of the wireless channel will be described. The base station BS2 respectively measures the reception level of the transmission wave of the mobile station PS2 and the interference wave level from another mobile station PS1 using the same channel, and compares these levels to determine the uplink level. Find the CIR. The mobile station PS2 receives the reception level of the transmission wave of the base station BS2 and other base stations BS that use the same channel.
The interference wave level from 1 is measured, and the CIR of the downlink is obtained by comparing these levels.
Then, the base station BS2 sets a radio channel in which both the uplink CIR and the downlink CIR satisfy the threshold values as usable channels.

The above determination method can be expressed as follows using mathematical expressions. That is, in FIG. 6, the base station BS
1, the distance between BS2 and D, base station BS1 and mobile station PS1
Is r1, the distance between the base station BS2 and the mobile station PS2 is r2, and the distance from the base station BS1 to the mobile station P2 is r1.
Propagation loss to S2 is L12, mobile station PS1 to base station B
Propagation loss to S2 is L21, mobile station PS2 to base station B
The propagation loss to S2 is L22. Then, the CIR of the uplink from the mobile station PS2 to the base station BS2 and the CIR of the downlink from the base station BS2 to the mobile station PS2 are respectively expressed by the following equations.

Uplink CIR = L21−L22 = 10αlog {(D + r1) / | r2 |} ...
(1) Downlink CIR = L12-L22 = 10αlog {(D-r2) / | r2 |} ...
(2) where α is a propagation constant.

Here, while communication (communication 1) is being performed between the base station BS1 and the mobile station PS1, communication (communication 2) is performed between the base station BS2 and the mobile station PS2 using the same channel. ) Is performed, assuming that the threshold value of the uplink CIR is THru [dB] and the threshold value of the downlink CIR is THrd [dB], r2 ≦ (D + r1) 10 ^{−THru / 10} (r2> 0 ) ^R2 ≧ − (D + r1) 10 ^{−THru / 10} (r2 <0) (3) r2 ≦ D (10 ^{THrd / 10} +1) ⁻¹ (r2> 0) r2 ≧ −D (10 ^{THrd / 10} −1) ^-1 (r2 <0) ... (4)

The base station BS2 uses the formula (3) and the formula (3) for each radio channel held by the system.
It is determined whether or not the condition of the expression (4) is satisfied at the same time, and if a wireless channel satisfying the condition is found, this wireless channel is assigned to the communication with the mobile station PS2.

Assuming that the transmission output levels of all the base stations BS1 and BS2 and the transmission output levels of all the mobile stations PS1 and PS2 are set to the same value, the propagation losses L22, L21, L12
Can be obtained from the reception level of the transmission wave and the reception level of the interference wave, respectively. Even if the transmission level differs for each base station or mobile station, the CIR
It is possible to ask for

Substituting a specific numerical value into the above equation yields the following. That is, suppose now that the CIR threshold is THr.
Assuming u = THrd = 20 dB, the range r2 in which the communication 2 is possible is expressed by | r2 | ≦ 0.10r1 + 0.10D ... [1] −0.11D ≦ from the above equations (3) and (4), respectively. r2 ≦ 0.09D ... [2]. FIG. 7 is a diagram showing this condition along the horizontal axis r1 and the vertical axis r2.

The mobile stations PS1 and PS2 are respectively [-0.
5, 0.5], the probability Pc that communication 2 is possible when communication 1 is present can be represented by the area of shaded area in FIG. 7, where Pc = 0. .174.

In the above-described method of determining whether or not the wireless channel can be used based on the CIRs of both the uplink and the downlink, it is possible to always reliably select the wireless channel in which both the CIRs of the uplink and the downlink satisfy the threshold value. , It is advantageous in securing high line quality. However, on the other hand, in order to evaluate the downlink, it is necessary to perform measurement at the mobile station PS2 and transfer the measurement result or the evaluation result to the base station BS2. Therefore, the base station BS2 and the mobile station P
There are drawbacks such as an increase in the amount of control data communication with S2 and a delay in connecting the wireless link.

Next, as a simpler method, the uplink C
A method of measuring only the IR and determining whether or not the wireless channel can be used will be described. The base station BS2 is the mobile station PS2.
, The level of the interference wave from another mobile station PS1 using the same channel is measured, and these levels are compared to determine the uplink C
Find the IR. Then, the wireless channel whose uplink CIR satisfies the threshold value is set as the usable channel.

The CIR of the above-mentioned uplink is the above-mentioned (1)
In the state where communication (communication 1) is performed between the base station BS1 and the mobile station PS1, the communication (communication (communication) is performed between the base station BS2 and the mobile station PS2 using the same channel. The condition for performing 2) is expressed as in the above equation (3). The base station BS2 determines whether or not the condition of the above expression (3) is satisfied for each radio channel held by the system, and when a radio channel satisfying the condition is found, the base station BS2 transmits this radio channel to the mobile station PS2. Assign to the communication of.

In the case of using the method of judging the availability of the radio channel based on only the CIR of the uplink, the communication 2
The range r2 in which is possible is given by the equation [1]. FIG. 8 is a diagram showing this condition on the horizontal axis r1 and the vertical axis r2.
The downlink threshold value which is not measured is indicated by a broken line. The establishment Pc that enables the communication 2 is Pc = 0.200, which is the C for both the uplink and the downlink described above.
The number is larger than the method (Pc = 0.174) for determining whether to use the wireless channel based on IR.

However, in the method of judging whether or not the wireless channel can be used based only on the CIR of the uplink, there is a region B where the CIR of the downlink does not satisfy the threshold as shown in FIG. Here, the minimum value of the CIR is calculated by using the equation (2), which is 15.1 dB, which is more than that of the method of determining the availability of the radio channel based on the CIR of both the uplink and the downlink. It is reduced by 9 dB. When selecting a wireless channel, if the same minimum CIR value as in the method of determining the availability of the wireless channel based on the CIRs of the uplink and the downlink is to be secured,
The uplink CIR must be set high. The CIR threshold value THru that satisfies this condition is THru = 24.4 dB from the above equation (3), which means that it must be set 4.4 dB higher.

When this condition is applied, the range r2 in which the communication 2 is possible is | r2 | ≦ 0.06r1 + 0.06D ... [1 ']. This condition is indicated by an arrow in FIG. At this time, the probability Pc that communication 2 is possible when communication 1 is present is Pc = 0.120, which is a method for determining whether or not the wireless channel can be used based on the CIRs of the uplink and the downlink. Decrease compared to.

As described above, according to the method for determining the availability of the radio channel based only on the CIR of the uplink, it is not necessary to measure the received wave in the mobile station PS2, and the base station BS2 and the mobile station PS2 are not required to be measured. Since it is not necessary to transfer control data between them, there is no fear of causing an increase in communication amount on the control channel or occurrence of connection delay. However, the downlink CIR may be less than the threshold. Therefore, in order to secure the same downlink CIR as in the case of measuring the CIR of the uplink and the CIR of the downlink described above, it is necessary to set the threshold value of the uplink CIR high. If the threshold value of the uplink CIR is set to be high, the distance between communications using the same channel will increase, so that the call capacity that can be accommodated in the mobile communication system will decrease and the frequency utilization efficiency will decrease.

[0025]

As described above,
When a wireless channel is selected using the autonomous distributed dynamic channel allocation method, there are two methods for determining whether or not the wireless channel can be used: a method based on both the CIR of the uplink and the downlink. There is a method of making a determination based on only the CIR. However, while the former has the advantage of ensuring high line quality, the base station BS
2 and the mobile station PS2, which leads to an increase in the amount of control data communication and a delay in connecting the wireless link.
On the other hand, the latter does not cause an increase in communication volume or connection delay in the control channel, but since the threshold value must be set high, the call capacity that can be accommodated in the system decreases and the frequency utilization efficiency decreases. It has drawbacks.

The present invention has been made by paying attention to the above circumstances, and an object thereof is to, when allocating a radio channel, prevent an increase in communication amount in the control channel and an occurrence of connection delay. Moreover, it is an object of the present invention to provide a radio channel selection method and a base station device for a mobile communication system, which can secure a large amount of call capacity and can improve frequency utilization efficiency.

[0027]

In order to achieve the above object, a radio channel selection method of the present invention is a method for selecting a radio channel for connecting a base station to be connected and a mobile station. Reception level of the carrier wave arriving from the mobile station of the connection target via any one of the wireless channels of the other wireless channel, and another mobile station and another base station via the same wireless channel as the arbitrary wireless channel. And the reception level of the carrier arriving from each of them is measured at the connection target base station, and the measured reception level of the carrier arriving from the connection target mobile station and the reception of the carrier arriving from the other mobile station. Based on the level and the reception wave-to-interference ratio of the uplink from the connection target mobile station to the connection target base station, the measured transfer target Based on the reception level of the carrier coming from the station and the reception level of the carrier coming from the other base station, the received wave-to-interference ratio of the downlink from the connection target base station to the connection target mobile station. Is determined, and whether or not to use the above-mentioned arbitrary radio channel is determined based on the obtained uplink received wave-to-interference wave ratio and downlink estimated reception wave-to-interference wave ratio.

On the other hand, in order to achieve the above object, the base station apparatus of the present invention comprises a reception level measuring means, first and second
The interference detection unit and the determination unit are included. And
In the reception level measuring means, when selecting a radio channel for connecting between one of the plurality of mobile stations,
The reception level of the carrier wave arriving from the mobile station of the connection target via any one of the plurality of radio channels, and other mobile stations and other mobile stations via the same radio channel as the any radio channel. The reception level of each carrier arriving from the base station device is measured, respectively, and the measured reception level of the carrier arriving from the mobile station of the connection target and the reception level of the carrier arriving from the other mobile station are measured. Then, the first interference detecting means obtains the ratio of the received wave to the interference wave of the uplink from the mobile station to be connected to the own base station apparatus, and the measured carrier wave from the mobile station to be connected is measured. Based on the reception level of the carrier and the reception level of the carrier wave arriving from the other base station device, the second interference detecting means detects the upper level from the own base station device. Estimate the received wave-to-interference ratio of the downlink toward the mobile station of the connection target, based on the obtained received wave-to-interference ratio of the uplink and the estimated received-to-interference ratio of the downlink This is to determine whether or not the wireless channel can be used.

Further, in the base station apparatus of the present invention, when the transmission levels of the plurality of base station apparatuses and the transmission levels of the plurality of mobile stations are set to the same value, the first interference detecting means is connected. From the reception level of the carrier coming from the target mobile station and the transmission level of the mobile station, the propagation loss of the transmission path from the mobile station to be connected to its own base station device is obtained, and it is also received from another mobile station. From the reception level of the carrier wave and the transmission level of the mobile station, obtain the propagation loss of the transmission path from the other mobile station to its own base station device, and from the mobile station to be connected based on the difference between these propagation losses. It is also characterized in that the ratio of the received wave to the interference wave on the uplink toward the own base station device is obtained.

Further, in the base station apparatus of the present invention, when the transmission levels of the plurality of base station apparatuses and the transmission levels of the plurality of mobile stations are respectively set to the same value, the second interference detecting means can be the connection target. From the reception level of the carrier arriving from the mobile station and the transmission level of the mobile station, the propagation loss of the transmission path from the mobile station to be connected to the own base station is calculated, and the carrier loss of the carrier arriving from another base station is calculated. From the reception level and the transmission level of the base station device, obtain the propagation loss of the transmission path from the other base station device to the own base station device, and from the own base station device based on the difference between these propagation losses. It is also characterized by estimating the received wave-to-interference ratio of the downlink toward the mobile station to be connected.

[0031]

As a result, according to the radio channel selection method and the base station device of the present invention, the ratio of the received wave to the interference wave (CI) in the downlink from the connection target base station device to the connection target mobile station is increased.
R) is estimated based on the reception level of the carrier wave that has arrived from another base station device using the same radio channel, and the radio channel of the radio channel is estimated based on the estimated downlink CIR and uplink CIR. Whether it can be used is determined.

Therefore, it becomes possible to determine whether or not the wireless channel can be used only by measuring the reception level in the base station apparatus, and measuring the reception level in the connection target mobile station and from the connection target mobile station to the base station apparatus. It is not necessary to transfer measurement data. For this reason, the increase in the communication volume and the occurrence of the connection delay in the control channel are reduced. Also,
Since the downlink CIR estimation value as well as the uplink CIR measurement value is used to determine whether or not the wireless channel can be used, a more accurate determination can be made as compared to the case of using only the uplink CIR measurement value. It becomes possible to do it. For this reason, it is not necessary to set a high threshold for CIR determination, which makes it possible to shorten the distance between communications using the same channel, thereby increasing the accommodable call volume of the mobile communication system. As a result, it is possible to improve the frequency utilization efficiency.

Further, when the transmission levels of the plurality of base station devices and the transmission levels of the plurality of mobile stations are set to the same value, the propagation loss of each transmission line can be easily obtained only from the reception level. As a result, it is possible to easily calculate the CIRs of the uplink and the downlink and, moreover, determine whether or not the wireless channel can be used.

[0034]

1 is a circuit block diagram showing the configuration of a base station of a mobile communication system according to an embodiment of the present invention.
In the figure, a radio frequency signal arriving from a mobile station (not shown) is received by an antenna 11 and then input to a reception unit 13 via a high frequency switch (SW) 12 of the radio unit 1. In the reception unit 13, the received radio frequency signal is mixed with the reception local oscillation signal generated from the frequency synthesizer 14 and frequency-converted into a reception intermediate frequency signal. The local oscillation frequency generated by the frequency synthesizer 14 is instructed by the control unit 6 according to the radio channel frequency. Further, the radio unit 1 is provided with a reception field strength detection unit (RSSI) 16. The received electric field strength detection unit 16 detects the received electric field strength of the wireless carrier waves arriving from the mobile station and other base stations, and the detected value is notified to the control unit 6 for wireless channel selection control described later.

The received intermediate frequency signal output from the receiver 13 is input to the demodulator 21 of the modem 2. The demodulation unit 21 digitally demodulates the received intermediate frequency signal, thereby reproducing the digital speech signal.
In the TDMA decoding unit 31 of the TDMA unit 3, the control unit 6
The digital call signal is decomposed for each time slot of the radio channel in accordance with the instruction of 1. and the decomposed digital call signal is input to the call section 4.

The call unit 4 uses a channel codec (CH-
CODEC 41 and a speech codec (SP-CO
DEC) 42. The digital speech signal output from the TDMA decoding unit 31 is first subjected to error correction decoding processing in the channel codec 41, and then input to the speech codec 42 for voice decoding processing. Then, the call signal reproduced by these decoding processes is sent from the line interface 5 having the hybrid circuit to the control station for mobile communication (not shown) via the wire line CL.

On the other hand, a call signal coming from the control station via the wired line CL is input to the speech codec 42 of the call section 4 via the line interface 5. Then, after speech coding processing is carried out by the speech codec 42, error correction coding is carried out by the channel codec 41 and the result is input to the TDMA encoding section 32 of the TDMA section 3.

The TDMA encoder 32 inserts the coded digital speech signal output from the channel codec 41 into the time slot assigned to the mobile station of the communication partner, and modulates the coded digital speech signal.
To enter. In the modulator 22, the carrier signal is digitally modulated by the encoded digital call signal, and the modulated carrier signal is input to the transmitter 15. The transmitter 15 mixes the modulated carrier signal with the transmitter local oscillation signal generated from the frequency synthesizer 14 to perform frequency conversion to the radio channel frequency instructed by the controller 6 and further to a predetermined transmission power level. Amplify to. Then, the radio frequency signal output from the transmitting unit 15 is transmitted to the antenna 11 via the high frequency switch 12.
Is transmitted from the mobile station to a mobile station (not shown).

By the way, the control unit 6 has, for example, a microcomputer as a main control unit, and in addition to a normal control function such as a radio channel connection control, a radio channel selection control means to which an autonomous distributed dynamic allocation system is applied. I have it.

This radio channel selection control means, when selecting a radio channel, the reception wave level from the mobile station to be connected, the interference wave reception level from another mobile station using the same radio channel, and The reception levels from other base stations using the same radio channel are respectively measured via the reception electric field strength detection unit 16. Then, the propagation loss of each transmission line is calculated from these reception level measurement values, and based on this propagation loss, the uplink C with the mobile station of the connection partner is calculated.
The IR is calculated and the downlink CIR is estimated.
Further, the CIR calculated value for the uplink and the CIR estimated value for the downlink are respectively compared with threshold values, thereby determining whether or not the wireless channel can be used.

Next, the radio channel selection control operation by the base station configured as described above will be explained. 2 and 3 are flowcharts showing the control procedure and control contents.

Now, for example, as shown in FIG. 5, the base station BS
1 and the mobile station PS1 communicate with each other using a certain radio channel, the base station BS2 and the mobile station PS2 attempt to use the same radio channel.

As shown in FIG. 2, the control unit 6 of the base station BS2 provisionally selects the radio channel in step 2a and designates it as the mobile station PS2 to be connected. Then, in this state, first in step 2b, the received wave level of the carrier wave coming from the mobile station PS2 to be connected is measured via the reception electric field intensity detection unit 16, and then in step 2c, the same radio channel is used. The reception level of the interference wave coming from the other mobile station PS1 is measured via the reception electric field strength detection unit 16, and further, the reception of the carrier coming from the other base station BS1 using the same radio channel in step 2d is received. The level is measured via the reception electric field strength detection unit 16.

Here, assuming that the transmission power levels of all the base stations of the system are equal and the transmission power levels of all the mobile stations are also equal, the propagation loss can be easily obtained from the measured values of the respective reception levels. . Therefore, base station B
In step 2e, the control unit 6 of S2 obtains the transmission loss L22 of the uplink from the connection target mobile station PS2 to its own base station BS2 from the received wave level of the carrier wave coming from the connection target mobile station PS2. , And the propagation loss L from another mobile station PS1 to its own base station BS2.
21 is obtained from the reception level of the interference wave coming from the other mobile station PS1, and the propagation loss Ld between the other base station BS1 and its own base station BS2 comes from the other base station BS1. Obtained from the reception level of the carrier wave.

When the propagation losses L22, L21, and Ld are obtained in this way, the control unit 6 first calculates the CIR of the uplink in step 2f, and further obtains the expression representing the call condition of the uplink in step 2g. That is, the uplink CIR is obtained by the above-mentioned equation (1), that is, the uplink CIR = L21−L22 = 10αlog {(D + r1) / | r2 |}.

Further, in a state where communication is being performed between the base station BS1 and the mobile station PS1, an uplink for newly performing communication between the base station BS2 and the mobile station PS2 using the same channel. The CIR condition in
It is represented by the equation (3), that is, r2 ≦ (D + r1) 10 ^{−THru / 10} (r2> 0) r2 ≧ − (D + r1) 10 ^{−THru / 10} (r2 <0).

Next, the control unit 6 estimates the CIR of the up link from the mobile station PS2 to the base station BS2 in step 2h, and further obtains the estimated call condition expression of the down link in step 2i. That is, the CIR of the uplink is the transmission loss L22 of the uplink and the other base station B.
It is estimated as follows from the propagation loss Ld between S1 and its own base station BS2. Downlink estimation CIR = Ld−L22 = 10αlog (D / | r2 |) (2 ′) In addition, while communication is being performed between the base station BS1 and the mobile station PS1, the same channel is used. Base station BS2
The CIR condition in the downlink for newly performing communication between the mobile station and the mobile station PS2 is the estimated CIR of the downlink ≧ CIR ≧
THrd, from the above formula (2 ′), r2 ≦ D · 10 ^{−THrd / 10} (r2> 0) r2 ≧ −D · 10 ^{−THrd / 10} (r2 <0) (4 ′) .

Next, as shown in FIG. 3, the control unit 6 judges whether or not the uplink satisfies the call enable condition based on the above equation (3) in step 3a, and further step 3
In b, it is determined whether or not the downlink satisfies the call enable condition based on the equation (4 ′). If it is determined that the conditions for both the uplink and the downlink are satisfied, the process proceeds to step 3c, where the wireless channel temporarily selected previously is officially selected and designated as the mobile station PS2, Terminates channel selection control.

On the other hand, if it is determined that the call enable condition is not satisfied on either the uplink or the downlink, the control unit 6 proceeds to step 3d, where all the systems have. It is determined whether or not there is any unselected wireless channel among the wireless channels.
Then, when the unselected wireless channel remains, the process proceeds to step 3e, where the next unselected wireless channel is tentatively selected and designated as the mobile station PS2, and then the process returns to step 2b of FIG. After that, the same control is executed.

When the availability of the wireless channel is determined in this way, the following effects are obtained. That is, the estimated downlink call condition expression, that is, the expression (4 ′) is
This is parallel to the downlink call condition expression obtained by actually measuring the reception level at the mobile station PS2, that is, the expression (4). Therefore, it is possible to determine whether or not the downlink can be used with an accuracy close to that in the actual measurement by merely changing the threshold THrd to some extent.

Substituting specific numerical values, the CI of the downlink
The following is a comparison with the case where R is actually measured.
That is, it is assumed that the CIR threshold value is set to THru = THrd = 20 dB. Then, the range r2 in which the communication 2 between the mobile station PS2 and the base station BS2 is established is the above-mentioned range r2.
It is given by | r2 | ≦ 0.10D ... [5] obtained from the equation (4 ′) and | r2 | ≦ 0.10r1 + 0.10D ... [1] obtained from the above equation (3). FIG. 4 is a diagram showing this condition along the horizontal axis r1 and the vertical axis r2. In the figure, the broken line shows the actual threshold value [2] of the downlink CIR that is not measured by the method of the present embodiment, and [5] obtained based on the above estimated CIR is close to this [2]. Becomes

Further, in the state where the communication 1 between the base station BS1 and the mobile station PS1 exists, a new communication 2 is performed between the base station BS2 and the mobile station PS2 using the same radio channel.
The probability Pc of performing is Pc = 0.175, which is almost equal to Pc = 0.174 when actually measured.

In the present embodiment, as shown in FIG. 4, there is a region C that does not satisfy the threshold value of the downlink CIR.
When the minimum CIR value is calculated using equation (2), it is 19.1 dB.
Is the minimum CIR value when actually measured, which is 2
It is 0.9 dB less than 0 dB.

Here, when selecting a radio channel,
Assuming that the same minimum CIR value as when actually measuring the uplink and downlink CIRs is required, the CIR threshold is set to 2
It must be set higher than 0 dB. But,
The threshold THrd that satisfies the condition is THrd = 20.9 dB from the above equation (4 ′), and it is almost unnecessary to set the threshold THrd high. At this time, r2 is | r2 | ≦ 0.09D ... [5 ′]. This condition [5 '] is shown in FIG.

Further, the probability Pc that communication 2 using the same wireless channel is possible in the presence of communication 1 is Pc = 0.164, and it is determined whether or not the wireless channel can be used by using only the uplink CIR. It is sufficiently higher than the case (Pc = 0.120).

That is, in the radio channel selection method of the present embodiment, the actually measured uplink CIR value and the downlink CIR value estimated based on the carrier reception level from another base station BS1 are used. Since it is determined whether or not the wireless channel can be used, the downlink CIR is not used and the uplink C
Accurate determination can be performed as compared with the case where determination is performed using only the IR value. Therefore, it is not necessary to set a high threshold value for CIR determination, which makes it possible to shorten the distance between communications using the same channel, thereby increasing and accommodating the call volume that can be accommodated by the system. Can improve frequency utilization efficiency.

Moreover, since the determination can be made only by the measurement at the base station BS2, the reception level at the connection target mobile station PS2 and the connection target mobile station PS2 to the base station BS
The transfer of the measurement data to 2 is unnecessary. For this reason, it is possible to reduce the increase in the communication volume in the control channel and the occurrence of connection delay.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the present invention is applied to the system in which the transmission power levels of the base stations and the mobile stations are equal to each other has been described as an example. it can. In this case, the transmission power level of the mobile station is transmitted to the base station, the propagation loss is obtained from the value and the reception level, and the mobile station reception level is obtained from the propagation loss and the transmission levels of other base stations. Then, the downlink CIR value can be obtained by comparing this reception level with the reception levels of other base stations measured by the base station.

The radio channel selection method of the present invention is
T that uses the same radio frequency for both uplink and downlink
This is particularly effective in a DD (Time Division Duplex) system. However, the present invention is not limited to this, and an FDD (Frequency Divi- cation) that uses different radio frequencies for the uplink and the downlink by installing equipment for measuring the signal level of the downlink with different frequencies in addition to the normal receiver.
It is also possible to apply to a sion duplex system.

In addition, the circuit configuration of the base station, the control procedure and control contents of the radio channel selection control means, the type of the mobile communication system, etc. can be variously modified and implemented without departing from the scope of the present invention.

[0061]

As described in detail above, in the wireless channel selection method of the present invention, when selecting a wireless channel for connecting between a base station to be connected and a mobile station, a plurality of wireless channels are selected. The reception level of the carrier arriving from the mobile station of the connection target via any wireless channel of, and the carrier respectively arriving from another mobile station and another base station via the same wireless channel as the arbitrary wireless channel And the reception level of each of them is measured at the connection target base station, and based on the measured reception level of the carrier coming from the connection target mobile station and the reception level of the carrier coming from the other mobile station. , The uplink received wave-to-interference ratio from the connection target mobile station to the connection target base station is obtained, and the carrier arriving from the measured connection target mobile station is obtained. Based on the reception level of the wave and the reception level of the carrier arriving from the other base station, to estimate the received wave-to-interference ratio of the downlink from the connection target base station to the connection target mobile station, Whether or not the above-mentioned arbitrary radio channel can be used is determined based on the obtained uplink received wave-to-interference wave ratio and downlink estimated reception-to-interference wave ratio.

Further, the base station apparatus of the present invention comprises the reception level measuring means, the first and second interference detecting means, and the judging means. Then, in the reception level measuring means, when selecting a radio channel for connecting to one of the plurality of mobile stations, the connection target of the connection target is set via any one of the plurality of radio channels. The reception level of the carrier arriving from the mobile station and the reception level of the carrier respectively arriving from another mobile station and another base station device via the same radio channel as the above arbitrary radio channel are measured, and this measurement is performed. On the basis of the reception level of the carrier wave arriving from the mobile station of the connection target and the reception level of the carrier wave arriving from the other mobile station of the connection target, the mobile station of the connection target performs its own operation by the first interference detection means. The ratio of the received wave to the interference wave on the uplink toward the base station device is obtained, and the measured reception level of the carrier wave arriving from the mobile station to be connected and the above Based of on the reception level of the carrier wave coming from the base station apparatus, the second
The interference detection means estimates the reception wave-to-interference wave ratio of the downlink from the own base station device to the mobile station to be connected, and estimates the obtained reception-to-interference ratio of the uplink and the downlink. Whether or not to use the above-mentioned arbitrary radio channel is determined based on the received wave-to-interference wave ratio.

Therefore, according to the radio channel selection method and the base station device of the present invention, when allocating the radio channel, the communication volume on the control channel does not increase and the connection delay does not occur, and the accommodable call volume increases. It is possible to provide a radio channel selection method and a base station device of a mobile communication system that can secure the frequency utilization efficiency.

[Brief description of drawings]

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

2 is a flowchart showing the first half of the procedure and contents of radio channel selection control by the control unit of the base station shown in FIG.

3 is a flowchart showing the latter half of the procedure and contents of radio channel selection control by the control unit of the base station shown in FIG.

FIG. 4 Uplink CIR and estimated downlink CIR
The figure which shows the characteristic of the line measurement at the time of making determination based on.

FIG. 5 is an explanatory diagram of a line to be measured for determining availability of a wireless channel according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a conventional line that is measured to determine whether or not a wireless channel can be used.

[FIG. 7] Conventional uplink CIR and downlink C
The figure which shows the characteristic of the line measurement in the case of making determination based on IR.

FIG. 8 is a diagram showing characteristics of line measurement in the case of performing determination based on only the uplink CIR in the related art.

[Explanation of symbols]

BS1, BS2 ... Base station PS1, PS2 ...
Mobile station 1 ... Radio unit 2 ... Modem unit 3 ... TDMA unit 4 ... Call unit 5 ... Line interface 6 ... Control unit 11 ... Antenna 12 ... High frequency switch 13 ... Reception unit 14 ... Frequency synthesizer 15 ... Transmission unit 16 ... Reception electric field strength Detection unit (RSSI) 21 ... Demodulation unit 22 ... Modulation unit 31 ... TDMA decoding unit 32 ... TDMA encoding unit 41 ... Channel codec (CH-CODEC) 42 ... Speech codec (SP-CODEC) L21, L22, Ld ... Propagation loss

Claims (4)

[Claims] 1. A mobile communication system having a plurality of base stations and a plurality of mobile stations, wherein an appropriate radio channel is selected from a plurality of radio channels between the base stations and the mobile stations. In the method of selecting a wireless channel for connection, a plurality of wireless channels are selected when selecting a wireless channel for connection between a base station and a mobile station of a connection target among the base stations and mobile stations. And the reception level of the carrier wave arriving from the mobile station of the connection target via any one of the wireless channels and the other mobile station and the other base station via the same wireless channel as the arbitrary wireless channel. Measuring the reception level of the carrier wave that has been received at the base station that is the connection target, and the reception level of the carrier wave that has arrived from the measured mobile station that is the connection target and that that has arrived from the other mobile station. Based on the received level of the carrier wave, the step of obtaining the ratio of the received wave to the interference wave of the uplink from the mobile station of the connection target to the base station of the connection target, and the measured arrival from the mobile station of the connection target Estimating a received wave-to-interference ratio on the downlink from the connection target base station to the connection target mobile station based on the reception level of the carrier wave and the reception level of the carrier wave arriving from the other base station. And a step of determining whether or not to use the arbitrary radio channel based on the ratio of the received wave to the interference wave of the uplink and the estimated ratio of the received wave to the interference wave of the downlink. System radio channel selection method. 2. A plurality of base station devices and a plurality of mobile stations are provided, and an appropriate wireless channel is selected from among a plurality of wireless channels between each of these base station devices and each of the mobile stations. In the base station device used in a mobile communication system to be connected, a reception level of a carrier wave arriving from the mobile station of the connection target via an arbitrary wireless channel of the plurality of wireless channels, and the arbitrary wireless channel Reception level measuring means for measuring the reception levels of the carriers respectively coming from other mobile stations and other base station devices via the same radio channel, and the connection measured by the reception level measuring means. Based on the reception level of the carrier wave arriving from the target mobile station and the reception level of the carrier wave arriving from the other mobile station, the mobile station of the connection target self First interference detection means for obtaining an uplink received wave-to-interference wave ratio toward the base station device, a reception level of a carrier wave arriving from the connection target mobile station measured by the reception level measurement means, and Second interference detection for estimating the received wave-to-interference ratio of the downlink from the own base station apparatus to the mobile station to be connected, based on the reception level of the carrier wave arriving from another base station apparatus Means for determining whether or not the arbitrary radio channel can be used based on the uplink received wave-to-interference wave ratio and the downlink estimated received wave-to-interference wave ratio obtained by the first and second interference detection means. A base station device of a mobile communication system, comprising: a determining unit for determining. 3. When the transmission levels of a plurality of base station devices and the transmission levels of a plurality of mobile stations are set to the same value, the first interference detection means is a carrier coming from a mobile station to be connected. From the reception level of the mobile station and the transmission level of the mobile station to obtain the propagation loss of the transmission path from the mobile station to be connected to the own base station device, and the reception level of the carrier wave arriving from another mobile station and the mobile station. The transmission loss of the transmission path from the other mobile station to its own base station device is obtained from the transmission level of the above, and based on the difference between these propagation losses, the mobile station of the connection target goes to its own base station device. The base station device of the mobile communication system according to claim 2, wherein a received wave-to-interference wave ratio of the line is obtained. 4. The second interference detection means, when the transmission levels of the plurality of base station devices and the transmission levels of the plurality of mobile stations are set to the same value, respectively, From the reception level of the mobile station and the transmission level of the mobile station, the propagation loss of the transmission path from the mobile station to be connected to the own base station device is obtained, and the reception level of the carrier wave arriving from another base station device and the base From the transmission level of the station device, obtain the propagation loss of the transmission path from the other base station device to the own base station device, and based on the difference between these propagation losses, the mobile station of the connection target from the own base station device The base station apparatus of the mobile communication system according to claim 2, wherein the received wave-to-interference wave ratio of the downlink going toward the terminal is estimated.