JP3338418B2 - Wireless base station - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio base station for performing radio communication with a plurality of mobile stations by spatial multiplexing.

[0002]

2. Description of the Related Art In recent years, social demands for effective use of frequency resources have increased with the increase in mobile stations such as PHSs and mobile phones. One of the methods for responding to this request is communication using a spatial multiplexing method. Spatial multiplexing means that a radio base station uses an adaptive array antenna that forms directivity for both transmission and reception, so that one frequency can be transmitted at the same time between a plurality of mobile stations and radio base stations in different directions at the same time. This is a method for multiplexing and communicating.

In the spatial multiplexing method, when one mobile station is already in communication and another mobile station is to be spatially multiplexed, the radio base station operates as follows.
It is determined whether to perform spatial multiplexing. Each radio base station stores a correlation value threshold value and a field intensity ratio threshold value each having a predetermined value set in advance.

[0004] Further, the radio base station calculates response vectors of a mobile station that is already communicating and a mobile station that is to newly communicate. Here, the response vector is information indicating the direction in which the mobile station exists. Next, a correlation value between the two calculated response vectors is calculated. Further, the electric field intensity of the two mobile stations is measured, and the electric field intensity ratio (D wave level ratio) between the two measured electric field intensities is calculated. Here, the electric field intensity ratio is greater than 0 and takes a value of 1 or less, and when the calculated electric field intensity ratio is 1 or more, the reciprocal thereof is used.

Next, when the correlation value of the response vector is smaller than or equal to the correlation value threshold (condition 1), and the electric field intensity ratio between the two electric field intensities is larger than or equal to the electric field intensity ratio threshold. (Condition 2) Since it is considered that the communication quality between the wireless base station and the mobile station is good, the wireless base station communicates with the mobile station by the spatial multiplexing method.

On the other hand, when the condition 1 is not satisfied or when the condition 2 is not satisfied, it is considered that the communication quality between the radio base station and the mobile station is not good. The communication is performed using another available communication channel, the communication is transferred to another wireless base station, or the communication is rejected. In this way, a certain communication quality is ensured between the radio base station and the mobile station while a certain traffic volume is secured.

[0007]

The communication quality between the radio base station and the mobile station differs depending on the communication environment and the communication state of the radio base station, but the radio base station is fixedly set. Since it is determined whether to perform spatial multiplexing using the correlation value threshold value and the electric field strength ratio threshold value, it is necessary to secure a constant traffic volume and maintain a constant communication between the radio base station and the mobile station. There is a problem that the relationship between quality assurance cannot be optimized.

[0008] In order to solve the above problems, the present invention provides:
It is an object of the present invention to provide a radio base station capable of optimizing a relationship between securing a certain amount of traffic and guaranteeing a certain communication quality between a radio base station and a mobile station.

[0009]

In order to achieve the above object, the present invention relates to a radio base station for performing radio communication by spatial multiplexing with a plurality of mobile stations, wherein a threshold value is stored in advance. Threshold value storing means, a first calculating means for calculating a quality index value indicating a communication quality between a mobile station newly performing wireless communication, and the calculated quality index value and the threshold value. Multiplexing determination means for determining whether or not to perform spatial multiplexing by comparing the values, and communication means for performing wireless communication by spatial multiplexing with the mobile station when it is determined to perform spatial multiplexing. A second calculating means for calculating a state index value indicating a communication environment state of the radio base station, and a threshold for updating a threshold value stored in the threshold value storing means according to the calculated state index value. Value updating means.

Here, the threshold value storage means previously stores a first threshold value and a second threshold value as threshold values, and the first calculation means stores the quality index value as A correlation value between a response vector of a mobile station that is already communicating and a mobile station that is newly trying to perform wireless communication, and an electric field intensity ratio between electric field intensities of the two mobile stations are calculated, Comparing the correlation value with the first threshold value, or comparing the electric field intensity ratio with the second threshold value to determine whether to perform spatial multiplexing, May be configured to update the first threshold value or the second threshold value stored in the threshold value storage means according to the calculated state index value.

[0011] Here, the multiplex judgment means, when the correlation value is smaller than or equal to the first threshold value, and when the electric field strength ratio is larger than or equal to the second threshold value, You may comprise so that it may determine to perform spatial multiplexing. Here, the first calculating means includes, as a state index value, an interference avoidance activation number indicating the number of times a communication channel of a mobile station performing wireless communication by spatial multiplexing is changed per unit time, Is determined by comparing the quality index value with the threshold value by the installation density of other radio base stations or by the multiplex determining means, and determining that spatial multiplexing is not to be performed. The threshold updating unit updates the threshold according to the calculated number of interference avoidance activations, the installation density, or the number of rejections as the state index value. May be configured.

Here, the threshold value updating means may be configured to periodically update the threshold value.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A radio base station 100 as one embodiment of the present invention will be described. Wireless base station 100
Is a time division multiplexing system (TDMA) defined by the PHS standard.
/ TDD, Time Division Multip
le Access / Time Division D
multiplex), and wirelessly connects to a PHS mobile station (hereinafter, referred to as mobile station), and performs spatial multiplexing in addition to the time division multiplexing to communicate with the mobile station. 1 Configuration of Radio Base Station 100 As shown in FIG.
1 to 14, a radio unit 21 to 24, a signal processing unit 50, a modem unit 60, a baseband unit 70, a control unit 80, and an information storage unit 90. (1) Baseband unit 70 The baseband unit 70 is connected to an exchange via an ISDN line.

The baseband unit 70 receives packet data via the ISDN line, extracts traffic information from the received packet data, performs TDMA modulation processing and spatial multiplexing processing, and performs processing through a plurality of channels. The extracted traffic information is decomposed into a plurality of baseband signals and output to the modem unit 60. Here, the TDMA modulation process includes one TD according to the PHS standard.
Four channels are multiplexed in the MA / TDD frame.
One TDMA / TDD frame is composed of four transmission time slots and four reception time slots. One time slot of each of the transmission time slot and the reception time slot constitutes one channel by time division multiplexing. Each time slot is 5 ms long.
Further, the spatial multiplexing process multiplexes up to four signals for each channel. Therefore, by the TDMA modulation processing and the spatial multiplexing processing, the data is multiplexed by a maximum of 16 channels in one TDMA / TDD frame.

The baseband unit 70 has one TD.
A plurality of baseband signals are received from the modem unit 60 via a maximum of 16 channels in the MA / TDD frame, packet data is generated from the plurality of received baseband signals, and the generated packet data is transmitted via the ISDN line. Output. (2) Modem unit 60 The modem unit 60 sends a π / 4 shift QP from the signal processing unit 50.
SK (Quadrature Phase Shift)
Keying), demodulates the modulated baseband signal, generates a baseband signal, and outputs the generated baseband signal to the baseband unit 70.

The modem unit 60 includes a baseband unit 7.
From 0, the baseband signal is received, the received baseband signal is modulated by π / 4 shift QPSK, and the modulated baseband signal is output to the signal processing unit 50.
The modem unit 60 performs the modulation and the demodulation in parallel on up to four TDMA / TDD frames spatially multiplexed in one time-division channel. (3) Information Storage Unit 90 The information storage unit 90 includes a threshold value table 200, a quality index value table 300, an information storage table 400, and a wireless base station table 500. (Threshold table 200) Threshold table 200
As shown in FIG. 2 as an example, the interference avoidance activation number 211 which is the state index value 201 indicating the communication environment state of the radio base station 100, the installation density 212, the rejection number 213,
A plurality of sets each including a correlation value threshold value 214 as the threshold value 202 and an electric field intensity ratio threshold value 215 are stored in advance.

Here, the interference avoidance activation number 211 is the sum of the communication channel switching number and the handover number. The communication channel switching count is the number of times per unit time that the radio base station instructs the mobile station to switch the communication channel when the communication quality is poor.
Day. For example, when interference is caused by an interference wave, a radio channel with less interference may be selected and switched even in the same cell. The number of handovers is the number of times that a handover occurs per unit time, and the handover is a radio channel of a destination cell when a mobile station traverses a plurality of cells during a call, even during a call. To switch to. Also, this occurs when there is no free channel in the own radio base station and the communication channel is switched to another radio base station.

The installation density 212 is the number of other wireless base stations installed near the wireless base station 100. The number of rejections 213 is the number of times per unit time that link channel assignment is rejected due to poor communication quality.
One day. The correlation value threshold value 214 is a threshold value relating to a correlation value between a response vector of a mobile station to which a communication channel has already been assigned and a response vector of a mobile station to be newly spatially multiplexed.

The electric field intensity ratio threshold value 215 is a threshold value relating to the ratio between the electric field intensity of a mobile station to which a communication channel has already been assigned and the electric field intensity of a mobile station that is newly spatially multiplexed. As shown in FIG. 2 as an example, the interference avoidance activation number 211 is “-10”, “11 to 50”, “51 to 1”.
00 "and" 101- ".
The installation density 212 has a range of two values of “−10” and “11”. The number of rejections 213 is “~ 1
0 "," 11-100 ", and" 101- ". By combining these ranges, the threshold value table 200 stores 24 state index values 201 in advance, and stores these 24 state index values 20.
24 threshold values 202 corresponding to 1 are set. (Quality index value table 300) Quality index value table 30
0 indicates each TDMA / TD as shown as an example in FIG.
For each time slot in the D frame, the response vector 30 of the mobile station using four spatially multiplexed channels
It has n areas for storing four sets of 3 and electric field strength 304.

Here, n = (number of TDMA / TDD frames) × 4 (number of time slots in a frame). As shown in FIG. 3 as an example, for a time slot whose time slot number 301 is “1”, a response vector of a mobile station using a channel whose spatial multiplexing number 302 is “1” is “R1”, and the electric field strength is , “I1”, the response vector of the mobile station using the channel whose spatial multiplexing number 302 is “2” is “R2”, and the electric field strength is
Since the channels of “I2” and the spatial multiplexing numbers 302 of “3” and “4” have not been used yet, the response vector and the electric field strength are “blank”, respectively. (Information storage table 400) Information storage table 400
As shown as an example in FIG. 4, the previous interference avoidance activation number Eb, the current interference avoidance activation number Et, and the current installation density D
t, the number of previous rejections Rb, the current number of rejections Rt, the correlation value threshold value Jt, the field intensity ratio threshold value Kt, and the multiplex flag F.

The previous number Eb of avoiding interference is 1
Indicates the number of interference avoidance activations counted in the preceding unit time. The current number of interference avoidance activations Et is the number of interference avoidance activations being counted in a unit time including the present time. The current installation density Dt is the number of other wireless base stations installed near the wireless base station 100 at the present time.

The previous rejection count Rb is the number of rejections counted in the unit time immediately before the current time. The current rejection count Rt is the number of rejections being counted in a unit time including the current time. The correlation value threshold value Jt is a threshold value relating to a correlation value between a response vector of a mobile station to which a communication channel has already been allocated and a response vector of a mobile station to be spatially multiplexed. It is used to determine whether

The electric field intensity ratio threshold value Kt is a threshold value relating to the ratio between the electric field intensity of a mobile station to which a communication channel has already been allocated and the electric field intensity of a mobile station to be newly spatially multiplexed. It is used to determine whether to perform. The multiplexing flag F indicates a result of determining whether to perform spatial multiplexing. When the multiplexing flag F is “1”, it indicates that spatial multiplexing is performed, and when the multiplexing flag F is “0”, it indicates that spatial multiplexing is not performed. (Wireless base station table 500) Wireless base station table 50
0 is a radio base station ID5 as shown as an example in FIG.
01 and an electric field strength 502 are provided.

The radio base station ID 501 is the radio base station ID
0 is an identifier for identifying another wireless base station, and the electric field strength 502 is the electric field strength of the wireless base station identified by the identifier. Wireless base station ID 501 and electric field strength 502
Are arranged and stored in descending order of electric field strength. (4) Signal Processing Unit 50 The signal processing unit 50 includes a signal adjustment unit 51, a response vector calculation unit 53, and an RSSI detection unit 54. Specifically, a programmable DSP (DigitalSign) is used.
al Processor). (Signal Adjusting Unit 51) The signal adjusting unit 51 includes the wireless units 21 to 2
4 from the respective TDMA / TDD
In the four reception time slots in the frame, the radio unit 21 is configured to reduce an error between a signal whose content is already known and a signal to be received.
~ 24, the directivity pattern is formed for each mobile station by adjusting the amplitude and phase of each transmission / reception signal, whereby the signal for each mobile station is obtained from the spatially multiplexed signals received from the radio units 21-24. Are separated and output to the modem unit 60, and the signals received from the modem unit 60 are spatially multiplexed so as to be transmitted only to the desired mobile stations, and the radio units 21 to 2
Output to 4. (RSSI detection unit 54) The RSSI detection unit 54
For each time slot in the MA / TDD frame, the electric field strength of the mobile station received by the radio units 21 to 24 in the time slot is detected, and the detected electric field strength for the mobile station with no established link channel is controlled by the control unit. Output to 80. Further, the detected electric field strengths of the mobile stations with established link channels are stored in the quality index value table 300.
In the area specified by the time slot and the spatial multiplexing number.

Further, the electric field strength of another radio base station is detected, and the detected electric field strength is written in the radio base station table 500 in the order of the electric field strength, together with the identifier for identifying the other radio base station. Note that the RSSI detector 54 performs the above detection when a link channel allocation request is issued from the mobile station. (Response Vector Calculator 53) Response Vector Calculator 53
Is based on the signal received from the radio units 21 to 24 and the signal adjusted by the signal adjustment unit 51 for each time slot in each TDMA / TDD frame, and indicates the direction of the mobile station communicating in the time slot. The response vector including the information is calculated as described below.

Mobile station a, mobile station b, mobile station c, mobile station d
Are transmitted by being spatially multiplexed from
4, the signals X1, X2, X3, and X4 and the signals Aa, Ab, Ac, and Ad that should be ideally received from the mobile stations a, b, c, and d are as follows. + H1cAc + h1dAd X2 = h2aAa + h2bAb + h2cAc + h2dAd X3 = h3aAa + h3bAb + h3cAc + h3dAd X4 = h4aA + h4Ab
a, h2a, h3a, h4a) are calculated.

Here, Ra is a response vector of the mobile station a. Logically, the signal X1 received by the radio unit 21
And the signal Aa to be ideally received from the mobile station a, the term of the signal of the other station is removed to obtain h1a, but it is impossible for the mobile station to know Aa over the entire signal. Since it is possible, h1a is asymptotically determined by using the signal Ua of the mobile station a separated by the signal adjustment unit 51 as a substitute.
h2a, h3a, and h4a are also obtained by correlating the signal received by each radio unit with the separated signal Ua of the mobile station a.

The response vectors Rb, Rc and Rd of the mobile stations b, c and d are calculated in the same manner. The response vector calculation unit 53 writes the calculated response vector for the mobile station with the established link channel in an area specified by the spatial multiplex number identifying the time slot and the spatial multiplex channel in the quality index value table 300. . For a mobile station for which a link channel has not been established, the calculated response vector is output to control section 80.

Note that the response vector calculation unit 53 performs the above calculation when there is a link channel allocation request from the mobile station. (5) Antenna units 11 to 14, radio units 21 to 24 The antenna units 11 to 14 are adaptive array antennas. The antenna units 11 to 14 are respectively
To 24.

The radio section 21 includes a transmitting section 111 including a high power amplifier and the like, and a receiving section 11 including a low noise amplifier and the like.
And 2. The transmission unit 111 includes the signal processing unit 50
Is converted to a high-frequency signal, amplified to a transmission output level, and output to the antenna unit 11.
The transmission unit 111 adjusts the transmission output by controlling the gain of the high-power amplifier in response to an instruction from the control unit 80. The receiving unit 112 converts the high-frequency signal received by the antenna 11 into a low-frequency signal, amplifies the signal, and amplifies the signal.
Output to 0.

The radio units 22, 23, and 24 have the same configuration as the radio unit 21, and a description thereof will be omitted. (6) Control Unit 80 Specifically, the control unit 80 includes a microprocessor, a ROM (Read Only Memory) in which a computer program (hereinafter, a program) is recorded, and a RAM (Random Acces) used for work.
s Memory), and the microprocessor achieves its functions by executing a program stored in the ROM.

The control unit 80 controls the overall operation of the radio base station 100. (State Index Value Calculation Process and Threshold Value Update Process) The control unit 80 performs a status index value calculation process and a threshold value update process including a correlation value threshold value and a field intensity ratio threshold value. ,
Repeat. The control unit 80 performs a process of calculating a state index value as described below.

The control unit 80 determines whether or not the current time is midnight. If the current time is midnight, the control unit 80 compares the current interference avoidance activation number Et in the information storage table 400 with the previous interference avoidance activation number. Copy to Eb, and copy current rejection count Rt to previous rejection count Rb. Next, 0 is set to the current interference avoidance activation number Et and the current rejection number Rt. Also, 240
The progress of the time (10 days) is monitored, and every 240 hours, the installation density Dt is calculated as follows.

The control unit 80 controls the radio base station table 500
, The pair of the wireless base station ID 501 and the electric field strength 502 are sequentially read, the read electric field strength 502 is compared with a predetermined electric field strength, and the number of cases where the read electric field strength 502 is greater than or equal to the predetermined electric field strength is counted. . The reading, comparison and counting are repeated in this manner. The count value thus obtained is defined as the installation density Dt.

The controller 80 updates the threshold value as follows. The control unit 80 determines that the current time is 3 am
It is determined whether it is time or not, and when it is 3:00 am, the previous interference avoidance activation number Eb, the current installation density Dt, and the previous rejection number Rb are read from the information storage table 400, and A range including the interference avoidance activation number Eb, the current installation density Dt, and the previous rejection number Rb is extracted from the state index value 201 of the threshold table 200, and the threshold value corresponding to the extracted state index value is extracted. 202 is read. The correlation value threshold value 214 and the electric field intensity ratio threshold value 215 included in the read threshold value 202 are overwritten with the correlation value threshold value Jt and the electric field intensity ratio threshold value Kt of the information storage table 400, respectively. . (Process at the time of establishing a link channel) The control unit 80 performs a process at the time of establishing a link channel as follows.

The control unit 80 performs a spatial multiplexing on a mobile station to be newly communicated by radio,
If another mobile station has not been spatially multiplexed in the candidate channel selected as having an empty slot, control is performed to allocate a link channel. If another mobile station is already spatially multiplexed, the control unit 8
When the multiplexing flag F is set to "1", the multiplexing decision processing is controlled as follows. If the multiplexing flag F is "0", it is determined whether to search for another candidate channel. If not, a value of 1 is added to the number of rejections Rt, and the allocation of the link channel is rejected. To control. When performing a search, control is performed so as to search for a candidate channel again. (Multiplexing determination process) The control unit 80 performs a multiplexing determination process as described below.

The control unit 80 calculates the response vector Ra of the mobile station a to be newly communicated by radio to the response vector calculation unit 5.
3 and reads the response vector Rx of the existing mobile station X from the area identified by the time slot number identifying the time slot in the quality index value table 300, and sets the response vector Ra and the response vector A correlation value Ja with the vector Rx is calculated.

[0038]

(Equation 1)

Next, the control unit 80 determines the electric field strength Ia of the mobile station a with which new wireless communication is to be performed by the RSSI detection unit 54.
From the area identified by the time slot number identifying the time slot in the quality index value table 300, and reads the electric field intensity Ix of the existing mobile station X, and calculates the electric field intensity ratio Ka by Ka = Ia / Ix. . Here, in the case of Ka> 1, it is calculated by Ka = Ix / Ia.

Next, the calculated correlation value Ja is compared with the correlation value threshold value Jt stored in the information storage table 400. Further, the calculated electric field intensity ratio Ka and the electric field intensity ratio threshold value Kt stored in the information storage table 400 are used.
Compare with When Ja ≦ Jt and Ka ≧ Kt, the multiplexing flag F is set to a value of 1; otherwise, the multiplexing flag F is set to a value of 0.

If communication has been performed with a plurality of (two or three) mobile stations by spatial multiplexing, the control unit 80
The above-described determination processing is performed for each mobile station. (Processing During Communication) The control unit 80
Perform processing during communication. The control unit 80 has poor communication quality,
When the radio base station determines that the mobile station is instructed to switch the communication channel, a value of 1 is added to the current interference avoidance activation number Et, and the mobile station is controlled to switch the communication channel. I do.

When it is determined that a handover has occurred, a value of 1 is added to the current interference avoidance activation number Et, and
Control is performed to switch to the wireless channel of the destination cell. 2 Operation of Radio Base Station 100 The operation of the radio base station 100 will be described. (1) Operations of State Index Value Calculation Processing and Threshold Value Update Processing Operations of the state index value calculation processing and threshold value update processing will be described with reference to the flowchart shown in FIG.

The control unit 80 performs a process of calculating a state index value (step S101), and performs a process of updating a threshold value including a correlation value threshold value and a field intensity ratio threshold value (step S102). repeat. Next, details of the process of calculating the state index value in step S101 of the flowchart shown in FIG. 6 will be described with reference to the flowchart shown in FIG.

The controller 80 determines whether or not the current time is midnight, and if it is 0:00 (step S12).
1) Copy the current interference avoidance activation number Et in the information storage table 400 to the previous interference avoidance activation number Eb, and copy the current rejection number Rt to the previous rejection number Rb (step S12).
2). Next, a value of 0 is set to the current interference avoidance activation number Et and the current rejection number Rt (step S123). The elapse of 240 hours (10 days) is monitored, and the installation density Dt is calculated every elapse of 240 hours (step S124) (step S125).

Next, details of the process of calculating the installation density Dt in step S125 of the flowchart shown in FIG. 7 will be described with reference to the flowchart shown in FIG. The control unit 80 sets a value of 0 to the variable i (step S14).
1) The radio base station ID is obtained from the radio base station table 500.
A set of the field 501 and the electric field strength 502 is sequentially read (step S142), and when the reading is completed (step S14).
3) Substitute the variable i for the installation density Dt (step S14)
6), the process of calculating the installation density Dt ends.

If the reading has not been completed (step S143), the read field strength is compared with the predetermined field strength. If the read field strength is greater than or equal to the predetermined field strength (step S144), the variable i Is added to (step S145), and the control returns to step S142. Otherwise (step S144), control is transferred to step S146.

Next, details of the threshold value updating process in step S102 of the flowchart shown in FIG. 6 will be described with reference to the flowchart shown in FIG. The control unit 80 determines whether or not the current time is 3:00 am, and if it is 3:00 am (step S161), the previous interference avoidance activation number Eb and the current installation density Dt are read from the information storage table 400. And the previous rejection count Rb (step S
162) The range including the read interference avoidance activation number Eb before reading, the current installation density Dt, and the previous rejection number Rb is defined as:
It extracts from the state index value 201 of the threshold value table 200, and reads out the threshold value 202 corresponding to the extracted state index value (step S163). Read threshold 2
02 is overwritten with the correlation value threshold value Jt of the information storage table 400 (step S164), and the electric field intensity ratio threshold value 215 included in the read out threshold value 202 is replaced with the information Overwrites the electric field intensity ratio threshold value Kt in the storage table 400 (step S16)
5). (2) Operation at the time of establishing a link channel The operation at the time of establishing a link channel will be described with reference to the flowchart shown in FIG.

The radio base station 100 receives a link channel establishment request from the mobile station (step S181), or the radio base station 100 receives a link channel establishment re-request from the mobile station (step S182).
Calculates a response vector (step S183), and the wireless base station 100 searches for a candidate channel (step S1).
84), if there is no candidate channel (step S18)
5) Reject link channel assignment to the mobile station (step S186).

If there is a candidate channel (step S18)
5) If another mobile station is not spatially multiplexed in the candidate channel selected as having an empty slot when a new mobile station to perform wireless communication is to be newly spatially multiplexed (step). S187),
A link channel is allocated to the mobile station (step S188). If another mobile station has already been spatially multiplexed (step S187), the control unit 80 performs multiplexing determination processing (step S189), and sets the multiplexing flag F set by the multiplexing determination processing to “1”. "(Step S190), a link channel is allocated to the mobile station (step S194).

If multiplexing flag F is "0" (step S190), control unit 80 determines whether to search for another candidate channel, and if not, rejects (step S191). A value of 1 is added to the number of times Rt (step S192), and assignment of a link channel to the mobile station is rejected (step S193). When the search is performed (step S191), the process returns to step S184, and the search from the candidate channel is repeated again.

Next, the details of the multiplexing decision processing in step S189 of the flowchart shown in FIG.
This will be described with reference to the flowchart shown in FIG. The control unit 80 receives the response vector Ra of the mobile station a to newly communicate with the wireless station from the response vector calculation unit 53 (step S221), and is identified by the time slot number for identifying the time slot in the quality index value table 300. The response vector Rx of the existing mobile station X is read out from the region (step S222), and the correlation value Ja between the response vector Ra and the response vector Rx is calculated (step S222).
223).

Next, the control unit 80 determines the electric field strength Ia of the mobile station a to be newly communicated by radio by using the RSSI detection unit 54.
(Step S224), reads the electric field strength Ix of the existing mobile station X from the area identified by the time slot number for identifying the time slot in the quality index value table 300 (step S225), and calculates the electric field strength ratio Ka. It is calculated (step S226).

Next, the controller 80 calculates the calculated correlation value Ja.
Is compared with the correlation value threshold value Jt stored in the information storage table 400, and the calculated electric field intensity ratio Ka is compared with the electric field intensity ratio threshold value Kt stored in the information storage table 400, When Ja ≦ Jt (Step S227) and Ka ≧ Kt (Step S228), the multiplexing flag F is set to a value of 1 (Step S229), and in other cases (Steps S227 and S228), the multiplexing flag F is set. Is set to a value of 0 (step S230). (3) Processing Operation During Communication The processing operation during communication will be described with reference to the flowchart shown in FIG.

If the control unit 80 determines that the communication quality is poor and the radio base station instructs the mobile station to switch the communication channel (step S251), the current interference avoidance activation number Et is set to a value of 1. (Step S25)
2) Control the mobile station to switch the communication channel (step S253). The control unit 80
When it is determined that a handover has occurred (step S254), a value of 1 is added to the current interference avoidance activation number Et (step S255), and control is performed so as to switch to the radio channel of the destination cell (step S256). ). 3. Conclusion When the TDMA communication radio base station 100 equipped with an adaptive array antenna performs path multiplexing radio channel allocation in the same time slot at the same frequency, the correlation value threshold of the response vector used when performing path multiplexing in the same slot. The value is adjusted, and the optimal path multiplexed radio channel is assigned according to the surrounding environment and the like. Further, path multiplex communication with better communication quality is performed using the ratio of the radio field intensity between mobile stations to be path multiplexed.

The radio base station 100 counts the number of activations for avoiding interference, counts the installation density of other radio base stations installed around the radio base station, and rejects the link channel assignment due to poor communication quality. The number of rejections is counted, and the correlation value threshold value and the electric field strength ratio threshold value are updated according to the counted interference avoidance activation number, the installation density, and the rejection number. 4. Other Modifications (1) In the above embodiment, the ratio of the electric field strengths of two mobile stations is used as the electric field strength ratio, but a digibel may be used. (2) When the multiplexing flag F is “0”, the control unit 80 counts the number of determinations when determining whether to search for another candidate channel, and determines the number of determinations based on the counted number of determinations. You may do it. For example, if the number of determinations is two or less, another candidate channel is searched. If the number of determinations is three or more, a value of 1 is added to the number of rejections Rt, and control is performed to reject link channel assignment. You may do it.

Further, when the multiplexing flag F is “0”, the control unit 80 may shift the control to another base station. (3) The unit time for counting the number of rejections, the number of communication channel switchings or the number of handovers may be a unit other than one day. For example, it may be one hour, 12 hours, three days, or the like.

Further, the number of rejections may be the number of rejections per fixed number of link establishment requests from the mobile station. (4) The control unit 80 sets the information storage table 40 at midnight.
The current interference avoidance activation number Et of 0 is replaced by the previous interference avoidance activation number E
b, the current number of refusals Rt is copied to the previous number of refusals Rb, and the current interference avoidance activation number Et and the current number of refusals Rt are set to 0, but of course other times may be used. . It may be performed several times a day. (5) The control unit 80 monitors the elapse of 240 hours (10 days) and calculates the installation density Dt every elapse of 240 hours, but the present invention is not limited to this 240 hours. It may be another time. (6) The controller 80 updates the threshold value at 3:00 am, but may be another time. It may be performed several times a day. Also, the information storage table 400
Of the current interference avoidance activation number Et of the previous collision avoidance activation number Eb
The current rejection count Rt is copied to the previous rejection count Rb, the current interference avoidance activation count Et and the current rejection count R
It may be performed at the same time as the time when a value of 0 is set to t. (7) According to the above embodiment, when the correlation value between the response vectors is smaller than or equal to the correlation value threshold value Jt, and the electric field intensity ratio is equal to the electric field intensity ratio threshold value Kt. If the values are larger or equal, spatial multiplexing is performed. FIGS. 13A to 13C show the correlation value on the horizontal axis and the electric field intensity ratio on the vertical axis, the relationship between the correlation value and the correlation value threshold value Jt, and the electric field intensity ratio and the electric field intensity ratio threshold value Kt.
FIG. In FIG. 13A, a rectangular area E10 (an area indicated by oblique lines) surrounded by a line segment L11, a line segment L12, a vertical axis and a horizontal axis is a portion corresponding to the above condition. When the correlation value and the electric field strength ratio are included in the area E10, spatial multiplexing is performed.

Here, the following may be performed. FIG.
As shown in FIG. 3B, an area E20 (an area indicated by oblique lines) surrounded by a curve L21 connecting the correlation value threshold value Jt and the electric field intensity ratio threshold value Kt, and a vertical axis and a horizontal axis is
It shows the relationship between the correlation value and the correlation value threshold value Jt and the relationship between the electric field intensity ratio and the electric field intensity ratio threshold value Kt. When the correlation value and the electric field intensity ratio are included in this area E20, Spatial multiplexing may be performed.

Further, as shown in FIG. 13C, a line segment L connecting the correlation value threshold value Jt and the electric field intensity ratio threshold value Kt.
31, a line segment L32, a line segment L33, a line segment L34, and a polygonal region E30 (region indicated by oblique lines) surrounded by a vertical axis and a horizontal axis indicate the relationship between the correlation value and the correlation value threshold value Jt. The relationship between the electric field intensity ratio and the electric field intensity ratio threshold value Kt is shown.
When it is included in 0, spatial multiplexing may be performed. (8) The RSSI detection unit 54 performs the above detection when a mobile station requests a link channel allocation, and the response vector calculation unit 53 performs the following when a mobile station requests a link channel allocation. Although the calculation is performed, the detection and the calculation may be performed when a synchronization burst is received from a mobile station or when a communication channel burst is received.

[0060]

As described above, the present invention relates to a radio base station for performing radio communication by spatial multiplexing with a plurality of mobile stations, wherein the threshold value is stored in advance. Storage means, first calculating means for calculating a quality index value indicating a communication quality between a mobile station which is to newly perform wireless communication, and comparing the calculated quality index value with the threshold value Multiplexing determining means for determining whether to perform spatial multiplexing, communication means for performing wireless communication by spatial multiplexing with the mobile station when spatial multiplexing is determined to be performed, and communication of the wireless base station. Second to calculate the state index value indicating the environmental state
A threshold value updating unit that updates a threshold value stored in the threshold value storing unit in accordance with the calculated state index value.

According to this configuration, the threshold value is updated by the state index value indicating the communication environment state of the radio base station.
There is an effect that spatial multiplexing can be appropriately performed according to the communication environment state of the wireless base station. For this reason, for each wireless base station, the relationship between securing a certain amount of traffic and guaranteeing a certain communication quality can be optimized between the wireless base station and the mobile station.

Here, the threshold value storing means previously stores a first threshold value and a second threshold value as threshold values, and the first calculating means stores the quality index value as A correlation value between a response vector of a mobile station that is already communicating and a mobile station that is newly trying to perform wireless communication, and an electric field intensity ratio between electric field intensities of the two mobile stations are calculated, Comparing the correlation value with the first threshold value, or comparing the electric field intensity ratio with the second threshold value to determine whether to perform spatial multiplexing, May be configured to update the first threshold value or the second threshold value stored in the threshold value storage means according to the calculated state index value.

According to this configuration, the correlation value between the response vectors of the mobile station that is already communicating and the mobile station that is newly trying to perform wireless communication, and the electric field intensity ratio between the electric field intensities of the two mobile stations, Since the quality index value indicates the communication quality, the communication quality between the mobile station and the radio base station can be accurately grasped. Here, the multiplexing determination unit performs spatial multiplexing when the correlation value is smaller than or equal to the first threshold value and when the electric field strength ratio is larger than or equal to the second threshold value. You may be comprised so that it may determine to perform.

According to this configuration, there is an effect that spatial multiplexing can be more appropriately performed according to the communication environment state of the radio base station. Here, the first calculating means includes, as a state index value, an interference avoidance activation number indicating the number of times a communication channel of a mobile station performing wireless communication by spatial multiplexing is changed per unit time, Is determined by comparing the quality index value with the threshold value by the installation density of other radio base stations or by the multiplex determining means, and determining that spatial multiplexing is not to be performed. The threshold updating unit updates the threshold according to the calculated number of interference avoidance activations, the installation density, or the number of rejections as the state index value. May be configured.

According to this configuration, since the number of activations for avoiding interference is used as the state index value indicating the communication environment state of the radio base station, the installation density of other radio base stations installed around the radio base station can be reduced. Because it is a state index value indicating the communication environment state of the base station, also, comparing the quality index value and the threshold value, by determining that spatial multiplexing is not performed,
Since the number of rejections of rejection of link channel assignment is used as a state index value indicating the communication environment state of the wireless base station, there is an effect that the communication environment state of the wireless base station can be accurately grasped.

Here, the threshold value updating means may be configured to periodically update the threshold value. According to this configuration, since the threshold value is periodically updated, there is an effect that spatial multiplexing can be appropriately performed using the regularly updated threshold value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a radio base station 100.

FIG. 2 shows an example of a threshold table 200.

FIG. 3 shows an example of a quality index value table 300.

FIG. 4 shows an example of an information storage table 400.

FIG. 5 shows an example of a wireless base station table 500.

FIG. 6 is a flowchart showing the operation of the control unit 80 for calculating a state index value and updating a threshold value.

FIG. 7 is a flowchart illustrating details of a process of calculating a state index value by a control unit.

FIG. 8 is a flowchart illustrating details of processing for calculating an installation density Dt by the control unit 80;

FIG. 9 is a flowchart illustrating details of a threshold updating process performed by the control unit;

FIG. 10 is a flowchart showing an operation of the wireless base station 100 when establishing a link channel.

FIG. 11 is a flowchart showing a multiplexing determination processing operation of the control unit 80;

FIG. 12 is a flowchart showing an operation of the radio base station 100 during communication.

FIG. 13 shows a relationship between a correlation value and a correlation value threshold value Jt, and a relationship between an electric field intensity ratio and an electric field intensity ratio threshold value Kt.
(A) indicates that spatial multiplexing is performed when the correlation value and the electric field strength ratio are included in the rectangular area E10. (B)
This indicates that spatial multiplexing is performed when the correlation value and the electric field strength ratio are included in the region E20. (C) When the correlation value and the electric field strength ratio are included in the polygonal area E30,
This indicates that spatial multiplexing is performed.

[Explanation of symbols]

 11 to 14 antenna unit 21 to 24 wireless unit 50 signal processing unit 51 signal adjustment unit 53 response vector calculation unit 54 RSSI detection unit 60 modem unit 70 baseband unit 80 control unit 90 information storage unit

Claims (5)

(57) [Claims] 1. A wireless base station that performs wireless communication by spatial multiplexing with a plurality of mobile stations, and newly attempts wireless communication with threshold storage means that stores a threshold in advance. First calculating means for calculating a quality index value indicating communication quality with a mobile station; and comparing the calculated quality index value with the threshold to determine whether to perform spatial multiplexing. Multiplex determining means, a communication means for performing wireless communication by spatial multiplexing with the mobile station when it is determined to perform spatial multiplexing, and a state index value indicating a communication environment state of the wireless base station. (2) A radio base station, comprising: a calculating means; and a threshold updating means for updating a threshold value stored in a threshold value storing means according to the calculated state index value. 2. The threshold value storage means stores a first threshold value and a second threshold value as threshold values in advance, and the first calculation means has already stored a quality index value as a threshold value. The correlation value between the response vector of the mobile station that is communicating and the mobile station that is to newly communicate wirelessly, and the electric field strength ratio between the electric field strengths of the two mobile stations are calculated. Comparing the correlation value with the first threshold value, or comparing the electric field intensity ratio with the second threshold value to determine whether to perform spatial multiplexing, The radio base station according to claim 1, wherein the first threshold value or the second threshold value stored in the threshold value storage means is updated according to the calculated state index value. 3. The multiplex judging means, when the correlation value is smaller than or equal to the first threshold value, and when the electric field strength ratio is larger than or equal to the second threshold value, The radio base station according to claim 2, wherein it is determined that multiplexing is performed. 4. The interference avoidance activation number indicating the number of times a communication channel of a mobile station performing wireless communication by spatial multiplexing is changed per unit time as a state index value, The density of other radio base stations installed in the base station, or the multiplexing judging means compares the quality index value with the threshold value to determine that spatial multiplexing is not to be performed, and thus links per unit time. Calculating the number of rejections for rejecting the channel assignment, the threshold value updating means updates the threshold value according to the calculated number of interference avoidance activations as the state index value, the installation density, or the number of rejections. The radio base station according to any one of claims 1 to 3, wherein: 5. The radio base station according to claim 1, wherein the threshold updating unit periodically updates the threshold.