JP2003174664A - Multiple controller, wireless base station, and time slot allocation revising method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless base station that can easily perform a new connection. <P>SOLUTION: The wireless base station 100 that allocates a mobile station to a plurality of time slots divided by time division and makes wireless communication with a plurality of mobile stations through time division multiplex and space multiplex, is provided with a control section 80 that tries to change the allocation in a way of reserving a free time slot to which no mobile station is allocated. <P>COPYRIGHT: (C)2003,JPO

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, with the increase in mobile stations such as PHS and mobile phones, social demand for effective use of frequency resources is increasing. One of the methods for responding to this request is communication using a space division multiplexing method in combination with the conventional time division multiplexing method.
FIG. 14 is a diagram showing the relationship between the time division multiplexing method and the spatial multiplexing method described above.

In the time division multiplex system, one mobile station is assigned to each of a plurality of time slots divided by time division for communication. The above-mentioned time slot is divided into a control time slot (hereinafter referred to as “control slot”) and a call time slot (hereinafter referred to as “call slot”). As seen, three call slots are prepared for one control slot.

Similarly, as a slot for transmission,
Three speech slots are prepared for one control slot, and one frame is composed of a total of eight slots including the four receiving slots. The spatial multiplexing method is
This is a method in which a radio base station performs multiplexing by using one frequency at the same time between a plurality of mobile stations in different directions and the radio base station by controlling the directivity of an antenna.

That is, in the spatial multiplexing system, two or more mobile stations are assigned to one communication slot for communication.
Therefore, it is necessary that the radio waves of the spatially multiplexed mobile stations arrive at the radio base station from different directions, and the mobile stations existing in the same directivity pattern formed by the adaptive array antenna described above have mutually The transmitted radio waves interfere and communication becomes difficult.

FIG. 15 is a diagram showing a state of new connection in a conventional radio base station. Note that, here, the description will be made by taking the receiving slot as an example, and it is assumed that the transmitting slot is also assigned the same mobile station as the receiving slot. Usually, the radio base station preferentially performs time division multiplexing so that the communication quality does not depend on the positional relationship of the mobile stations so that the communication quality is good.

That is, the radio base station first allocates a mobile station requesting a new connection to a speech communication slot to which no mobile station is allocated (hereinafter referred to as "empty slot"), and then, for example, As shown from time t ₀ onward in FIG. 15, when there are no empty slots, spatial multiplexing is performed, and two or more mobile stations are assigned to one speech slot and communication is attempted.

At this time, the radio base station predicts the communication quality between each mobile station and the radio base station, and selects a call slot to be assigned so that the communication quality above a predetermined threshold can be secured. To do. More specifically, the radio base station predicts communication quality as follows. Each radio base station stores a spatial correlation value threshold value J _t and an electric field strength ratio threshold value K _t , which are set to predetermined values in advance.

The radio base station notifies the mobile station which has already been allocated, based on the communication state using the receiving speech slot, and the mobile station which has made a new connection request, the notification of this request. The data necessary for the above-mentioned evaluation of communication quality is sampled based on the state of communication by the control slot for reception used in the above. Based on the data thus obtained, the radio base station calculates a response vector indicating the direction in which each mobile station exists, and calculates the spatial correlation value J _X between the two calculated response vectors.

Further, the electric field strengths of the two mobile stations are measured, and the electric field strength ratio K _X (D wave level ratio) between the measured electric field strengths of the two mobile stations is calculated. Here, the electric field intensity ratio K _X is assumed to be a value greater than 0 and 1 or less, and when the calculated electric field intensity ratio K _X is 1 or more, the reciprocal thereof is used. And
When the spatial correlation value J _X of the response vector is smaller than or equal to the spatial correlation value threshold J _t (condition 1), and the electric field strength ratio K _X between the two electric field strengths is the electric field strength ratio threshold K _t. When it is greater than or equal to (condition 2), it is considered that the communication quality between the radio base station and the mobile station is good, so the radio base station communicates with the mobile station by the spatial multiplexing method.

On the other hand, when the condition 1 is not satisfied or 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. In the meantime, another call slot is used for communication or new connection is rejected.

[0012]

However, as the number of mobile stations connected increases, the number of spatial multiplexing increases, so that the number of comparison targets of the above conditions increases for mobile stations requesting new connection. However, there is a problem in that it becomes more difficult to establish the conditions for connection, and the number of opportunities for new connection decreases.

Further, even if the above two conditions are satisfied, for example, as shown at time t ₁ in FIG.
When multiplexing is actually performed, the call quality may not be able to ensure a predetermined level, and in such a case, the allocation to this call slot has to be canceled (hereinafter referred to as "return"). One of the reasons why such switching back occurs is that the accuracy of the data sampled from the mobile station that has made the new connection request is low.

In other words, as described above, for the mobile station that has made a request for a new connection, the data necessary for evaluating the communication quality is obtained based on the communication state of the control slot for reception. Since the sampling time in the control slot for communication is limited to an extremely short time compared to the communication slot for reception, in unstable communication conditions, the communication quality evaluation result may be better or worse than it actually is. Therefore, there is a possibility that a valid judgment cannot be made.

Further, when the mobile station is moving at high speed,
It is desirable to determine the speech slot to be spatially multiplexed after grasping the movement direction, etc., but the data obtained using the control slot for reception has a very short sampling time, so it is necessary to grasp the movement direction. There is a problem that time series data cannot be collected sufficiently. Then, this invention is made | formed in view of the said problem, and an object of this invention is to provide the wireless base station which can be connected easily at the time of a new connection.

It is another object of the present invention to provide a multiplex control device which is provided in the above-mentioned radio base station and executes the processing for achieving the above-mentioned object. It is another object of the present invention to provide a time slot allocation changing method and program for achieving the above object.

[0017]

In order to achieve the above object, a radio base station according to the present invention assigns a mobile station to any one of a plurality of time slots divided by time division, performs time division multiplexing and A wireless base station that wirelessly communicates with a plurality of mobile stations by spatial multiplexing, and generates or maintains a state in which there are low multiplex time slots with a spatial multiplex number N that is less than the spatial multiplex limit number. To do
It is characterized by comprising time slot allocation changing means for attempting to change the allocation.

Further, the multiplexing control apparatus according to the present invention is provided in a radio base station that performs radio communication with a plurality of mobile stations by time division multiplexing and spatial multiplexing, and has a low spatial multiplexing number N which is less than the spatial multiplexing limit number. It is characterized in that the spatial multiplexing is controlled so as to generate a state in which multiple time slots exist or maintain the state. Further, the time slot assignment changing method according to the present invention assigns a mobile station to a plurality of time slots divided by time division, and performs radio communication with a plurality of mobile stations by time division multiplexing and space multiplexing, A time slot allocation changing method for changing the allocation, comprising a time slot allocation step of attempting to change the allocation so as to secure a low multiplex time slot in which no mobile station has been allocated. To do.

Further, the program according to the present invention assigns a mobile station to a plurality of time slots divided by time division, and performs radio communication with the plurality of mobile stations by time division multiplexing and space multiplexing. A program for changing the allocation, in which the allocation of mobile stations is 1
The method is characterized by causing a computer to execute a time slot allocation step that attempts to change the allocation so as to secure a low multiplex time slot that has not been performed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A radio base station 100 as a first embodiment of the present invention will be described. The radio base station 100 uses a time division multiplexing system (TDMA / TDD, Time Di) defined by the PHS standard.
vision Multiple Access / Ti
PHS by me Division Duplex)
A mobile station (hereinafter referred to as a mobile station) is wirelessly connected, and in addition to the time division multiplexing, spatial multiplexing is further performed to communicate with the mobile station. (Configuration of Radio Base Station 100) FIG. 1 is a functional block diagram of the radio base station 100 according to the first embodiment of the present invention.

The radio base station 100 includes antenna units 11-1.
4, radio units 21 to 24, signal processing unit 50, modem unit 6
0, baseband unit 70, control unit 80, and information storage unit 9
It consists of zero. (1) Baseband unit 70 The baseband unit 70 is connected to the exchange through the ISDN line.

The baseband unit 70 receives the packet data through the ISDN line, extracts the traffic information from the received packet data, performs the TDMA modulation process and the spatial multiplexing process, and performs the 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 is performed by 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 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 a maximum of four signals for each channel. Therefore, by TDMA modulation processing and spatial multiplexing processing, multiplexing is performed by up to 16 channels in one TDMA / TDD frame.

One of the four transmission time slots is
It is a control slot for transmission, and the remaining three are speech slots for transmission. Also, one of the four reception time slots is a control slot for reception, and
The remaining three are call slots for reception. The baseband unit 70 also receives a plurality of baseband signals from the modem unit 60 via a maximum of 16 channels in one TDMA / TDD frame and generates packet data from the plurality of received baseband signals. Then, the generated packet data is output via the ISDN line. (2) Modem Unit 60 The modem unit 60 receives the π / 4 shift QP from the signal processing unit 50.
SK (Quadrature Phase Shift)
The baseband signal modulated by Keying is received, the modulated baseband signal is demodulated to generate a baseband signal, and the generated baseband signal is output to the baseband unit 70.

Further, the modem section 60 includes a baseband section 7
The baseband signal is received from 0, 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 section 60 performs the modulation and the demodulation in parallel for 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 table 200, a quality index value table 300, a communication quality prediction table 400, an ideal threshold value table 420, and a switching source selection table 60.
Has 0. (Threshold Value Table 200) FIG. 2 is a diagram showing a logical configuration of a threshold value table 200 which is a table for storing threshold values used for communication quality judgment.

The threshold value table 200 comprises a spatial correlation value threshold value J _t , an electric field strength ratio threshold value K _t , and a fading threshold value P _t . The spatial correlation value threshold value J _t is a threshold value relating to the spatial correlation value J _X obtained from the response vector of the communicating mobile station and the response vector of the new mobile station. The electric field strength ratio threshold value K _t is a ratio of the electric field strength of the signal received from the mobile station during communication to the electric field strength of the signal received from the new mobile station, that is, the electric field strength ratio K _X.

The fading threshold P _t is a threshold for changing speed of the spatial correlation value J _X between the communicating mobile station and the new mobile station, that is, the fading value P _X. The fading value P _X is the amount of change in the spatial correlation value J _X per unit time. It is estimated that the larger the fading value P _X is, the higher the relative moving speed between the mobile stations is, and thus the possibility of deviating from the range of the directivity pattern formed by each of the antenna units 11 to 14 is high. At the same time as
That is, it is not suitable for spatial multiplexing on the same speech slot. (Quality index value table 300) Quality index value table 30
0 indicates each TDMA / TD, as shown in FIG. 3 as an example.
Mobile station response vector 30 using four channels that are spatially multiplexed for each time slot in the D frame
There are n areas for storing four sets of 3 and electric field strength 304.

Here, n = (the number of TDMA / TDD frames) × 4 (the number of time slots in the frame). As shown as an example in FIG. 3, for the time slot with the time slot number 301 of “1”, the response vector of the mobile station using the channel with the spatial multiplexing number 302 of “1” is “R1”, and the electric field strength is , “I1”, the response vector of the mobile station using the channel with spatial multiplexing number 302 of “2” is “R2”, and the electric field strength is
Since the channels with "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. (Communication Quality Prediction Table 400) In the first embodiment, a call slot to which only one mobile station is assigned and a mobile station assigned to this call slot are set as communication quality of assigned mobile stations. Channel switching (hereinafter referred to as "forced TCH switching") that is performed regardless of the call source, while the target of forced TCH switching is the mobile station that is the source of this switching and the call that is assumed to be the switching destination. It is determined based on the prediction result of the communication quality with all the mobile stations assigned to the slot.

Here, the above-mentioned allocation of mobile stations is carried out for one reception speech slot and one transmission speech slot constituting one channel, but these two speech slots are paired. Therefore, the call slot will be described below as indicating both the receiving call slot and the transmitting call slot.
Here, for the sake of convenience, a call slot to which n (n is an integer of 1 or more) mobile stations is assigned is referred to as an n-multiplex slot for convenience, and the number of spatial multiplexing in this case (hereinafter, "space It is assumed that it is n.

As shown in FIG. 4A, consider a case where all three communication slots are one multiplex slot. FIG. 4B is a diagram showing the communication quality prediction table 400 for determining the switching destination in the forced TCH switching created by the control unit 80 in such a case.

As shown as an example in FIG. 4B, the communication quality prediction table 400 has a spatial correlation value J calculated based on two response vectors between two mobile stations.
_X , a fading value P _X indicating the rate of change of the spatial correlation value J _X , and an electric field strength ratio K _X between the two mobile stations are shown. Furthermore, in the communication quality prediction table 400, when there are two or more combinations of the above-mentioned two mobile stations, the above-mentioned spatial correlation value J _X , electric field strength ratio K _X, and fading value P _X are relative in each of the above-mentioned combinations. Point A, point B, and point C indicating the order of the general evaluation results are also shown.

A combination 401 represents a set of two mobile stations which are targets of evaluation of communication quality prediction when the forced TCH switching is carried out. The spatial correlation value 402 indicates the spatial correlation value J _X , which is an index indicating the closeness between two mobile stations. point
(A) 403 shows the above-mentioned spatial correlation values J _X in order from those closer to the ideal value of this spatial correlation value J _X to those farther from it.

The electric field strength ratio 404 indicates the electric field strength ratio K _X which is the ratio of the electric field strengths of the two mobile stations. Point (B) 4
Reference numeral 05 denotes each of the electric field strength ratios K _X described above, in order from those closer to the ideal value of the electric field strength ratio (hereinafter referred to as “ideal value of electric field strength ratio”) K _R to those farther away. .

The fading value 406 indicates the fading value P _X which is the amount of change in the spatial correlation value J _X per unit time. Point (C) 407 is each fading value mentioned above.
The order of P _X from the one close to the ideal value of this fading value P _X to the one far from it is added. The total point 408 indicates a value obtained by adding the values of point A, point B, and point C for each combination described above.

Thus, when the spatial multiplexing number is 2 or less,
The above-described communication quality prediction may be performed for each combination indicated by the combination 401 in FIG. However, it is considered that the frequency at which the spatial multiplexing number becomes 2 or less is actually small, and as shown in FIG. 5A, when the forced TCH switching is performed, the spatial multiplexing number becomes 3 or more. There are many.

FIG. 5B shows such a case.
The communication quality prediction table 500 created by the control unit 80 in place of the communication quality prediction table 400 is shown. In the communication quality prediction table 500, the values from the combination 501 to the total points 508 are the same as the values from the combination 401 to the total points 408 in FIG.

The multi-space method 510 is provided for the purpose of explanation, and is not actually stored as data, but indicates a combination in which a mobile station of one multiplex slot is assigned to one or more communication slots. Here, the combination of mobile stations assigned to the same call slot can be regarded as belonging to the same group.

If the new spatial multiplexing is performed by the forced TCH switching, the communication quality of all mobile stations belonging to the group of the spatially multiplexed call slots may be affected. To select, it is necessary to predict the communication quality on a group basis. The quality evaluation group 511 indicates a number that identifies such a group. (Threshold ideal value table 420) The threshold ideal value table 420 includes a spatial correlation value threshold J _t , an electric field intensity ratio threshold K _t , a fading threshold P _t , and these thresholds. An ideal value of spatial correlation value J _R , an ideal value of electric field strength ratio K _R, and an ideal value of fading P _{R corresponding} to each are stored in advance.

The spatial correlation value J _X between the spatial correlation value threshold value J _t and the ideal spatial correlation value value J _R (including these two values).
And the field strength ratio threshold K _t and the ideal value of the field strength ratio K
_{In the combination} having the electric field intensity ratio K _{X in R} (including these two values) and the fading value P _{X in} the fading threshold P _t and the ideal fading value P _R (including these two values), It is determined that there is no communication quality problem.

The ideal value 410 represents a set of the spatial correlation value ideal value J _R , the electric field intensity ratio ideal value K _R, and the fading ideal value P _R. The threshold value 411 indicates a set of the spatial correlation value threshold value J _t , the electric field strength ratio threshold value K _t, and the fading threshold value P _t . The switching source selection table 600 is a table for selecting a switching source when there are a plurality of one-multiplex slots, that is, when there are a plurality of call slots that can be a switching source in forced TCH switching, and is a one-multiplex slot. The priority and the number of retries are associated with each of the call slots. (4) Signal Processing Unit 50 The signal processing unit 50 includes a signal adjustment unit 51, a response vector calculation unit 53, an RSSI detection unit 54, and a communication failure detection unit 55. Specifically, the programmable DSP (D
It is realized by the digital signal processor. (Signal Adjusting Unit 51) The signal adjusting unit 51 includes wireless units 21 to 2
4 receives signals from each of the TDMA / TDD
In the four reception time slots in the frame, the radio unit 21 reduces the error with respect to the signal to be received in the portion where the content of the received signal is known in advance.
By adjusting the amplitude and phase of each transmission / reception signal of No. 24 to No. 24, a directivity pattern is formed for each mobile station, and as a result, a 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 that they are transmitted only to desired mobile stations.
Output to 4. (RSSI detection unit 54) The RSSI detection unit 54 is
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 is detected for the mobile station for which the link channel is not established. Output to 80. In addition, regarding the mobile station in which the link channel is established, the detected electric field strength is set to the quality index value table 300
Of the time slot and the spatial multiplex number.

The RSSI detector 54 performs the above-mentioned detection when there is a link channel allocation request from the mobile station. (Response vector calculation unit 53) Response vector calculation unit 53
Is based on the signal received from the radio units 21 to 24 and the signal adjusted by the signal adjusting unit 51 for each time slot in each TDMA / TDD frame, and the direction of the mobile station communicating in the time slot. A response vector containing information is calculated as shown below.

Mobile station a, mobile station b, mobile station c, mobile station d
From the wireless units 21 to 2 respectively.
4 for the signals X1, X2, X3 and X4 received and the signals Aa, Ab, Ac and Ad to be ideally received from the mobile station a, mobile station b, mobile station c, mobile station d, X1 = h1aAa + h1bAb + H1cAc + h1dAd X2 = h2aAa + h2bAb + h2cAc + h2dAd X3 = h3aAa + h3bAb + h3cAc + h3dAd = X4 = h4aAa + h4bAd + h4aAh + h4bAb + h4bAb + h4bAb + h4bAb + h4bAd + h4a
a, h2a, h3a, h4a) is calculated.

Here, Ra is the response vector of the mobile station a. Logically, the signal X1 received by the radio unit 21
By correlating with the signal Aa that should 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 not possible for the mobile station to know Aa over the entire signal. Since it is possible, h1a is asymptotically obtained by using the signal Ua of the mobile station a separated by the signal adjusting unit 51 instead of Aa.

The signals h2a, h3a and h4a are also obtained by correlating the signals received by the respective radio units and the separated signal Ua of the mobile station a. The response vectors Rb, Rc, and Rd of the mobile station b, the mobile station c, and the mobile station d are calculated in the same manner. The response vector calculation unit 53 writes the calculated response vector in the quality index value table 300 in the area specified by the spatial multiplexing number for identifying the time slot and the spatial multiplexing channel for the mobile station with the established link channel. .

The calculated response vector is output to the control unit 80 for the mobile station for which the link channel is not established. The response vector calculation unit 53 performs the above calculation when the mobile station makes a link channel allocation request. (Communication failure detection unit 55) The communication failure detection unit 55 monitors the wireless communication status of all the mobile stations in communication, and when a problem occurs in the wireless communication of these mobile stations, the control unit 8 immediately notifies that fact.
It has the function of notifying 0. (5) Antenna Units 11 to 14 and Radio Units 21 to 24 The antenna units 11 to 14 are adaptive array antennas.

The antenna units 11 to 14 are connected to the radio units 21 to 24, respectively. The wireless unit 21 includes a transmitting unit 111 including a high power amplifier and the like, and a receiving unit 112 including a low noise amplifier and the like. The transmitter 111
The low-frequency signal input from the signal processing unit 50 is converted into a high-frequency signal, amplified to the transmission output level, and the antenna unit 1
Output to 1. The transmission unit 111 adjusts the transmission output by controlling the gain of the high power amplifier or the like according to the instruction from the control unit 80. The receiving unit 112 includes the antenna unit 11
The high frequency signal received by is converted into a low frequency signal, amplified, and output to the signal processing unit 50.

Since the radio units 22, 23 and 24 have the same structure as the radio unit 21, their description will be omitted. (6) Control Unit 80 The control unit 80 is specifically a ROM (Read Only Memory) in which a microprocessor, a timer, and a computer program (hereinafter, program) are recorded.
y) and RAM (Random A) used for work
access memory) and the like, and the microprocessor achieves its function by executing the program recorded in the ROM.

The control unit 80 controls the overall operation of the radio base station 100. (Empty slot reservation process) The control unit 80 carries out the following empty slot reservation process so as to constantly reserve an empty slot while executing a switching source selection process and a communication quality prediction process which will be described later.

That is, the control unit 80 determines whether or not there is an empty slot and no speech slot to which only one mobile station is assigned when the allocation state of the mobile station to the speech slot changes. If there is such a call slot, forced TCH switching is performed to change the allocation of this mobile station to another call slot, and an attempt is made to secure an empty slot.

This is not the conventional channel switching in which the mobile station is conventionally assigned to another speech slot due to the deterioration of the communication quality between the accommodated mobile station and the radio base station 100, but the accommodated mobile station. And the switching is performed regardless of the communication quality between the wireless base stations 100. Further, the control unit 80, when attempting the above-mentioned forced TCH switching, collects a plurality of data necessary for predicting the communication quality of the assigned mobile station over a time period of a timer value t1 second,
Based on these data, that is, the spatial correlation value J _X , the electric field strength ratio K _X, and the fading value P _X , it is determined whether the communication quality of the set level or higher can be secured.
After determining whether the communication band of the ISDN line going from 0 to the external exchange is empty, the feasibility of performing the forced TCH switching is determined.

By the way, in general, as the number of spatially multiplexed signals increases, the communication quality of mobile stations assigned to the same speech slot tends to decrease. This is because radio waves are received at the same frequency and the same call slot, so even if they are received by a directional antenna such as an adaptive array antenna, they may be affected by radio wave interference, etc. .

That is, the communication quality of the mobile station assigned to one multiplex slot, that is, the mobile station which is the switching source in the forced TCH switching, is the communication quality of the mobile station assigned to the two, three and four multiplex slots. Is better than
It is considered that the accuracy of the response vector and the electric field strength obtained under such circumstances is high. Furthermore, since the 1-multiplex slot is a call slot and data is received until the call ends, sufficient time can be secured to accurately calculate the fading value P _X described above.

As a result of the forced TCH switching, the frequency with which empty slots are secured increases. Further, the control unit 80 has no empty slot when the allocation state of the mobile station to the call slot is changed, and
When there are two or more multiplex slots, the following switching source selection processing is executed to determine the speech slot to be the switching source.

Further, the control unit 80 has the baseband unit 7
Monitor the traffic on the ISDN line connecting to 0. (Switching Source Selection Process) FIG. 6 is a diagram for explaining a switching source selection process for determining a speech slot to be a switching source in the above-described forced TCH switching.

When the above-mentioned forced TCH switching is to be carried out, the control unit 80 generates a switching source selection table 600 for determining the call slot to be the switching source, and stores it in the information storage unit 90. Then, each time the above-mentioned forced TCH switching ends unsuccessfully, the contents of the switching source selection table 600 are updated to determine the call slot to be the next switching source, and after waiting for the timer value t2 seconds, again. , Try to secure empty slot.

This standby is executed for the purpose of giving an instruction such as channel switching from the radio base station 100 to the mobile station within a range not exceeding the limit of the response ability of the mobile station. As a trigger for executing the empty slot reservation process, one of the mobile stations newly connected to the empty slot (hereinafter, referred to as “Case 1”), which is allocated to 2, 3 or 4 multiple slots becomes an empty slot. When the allocation has been changed (hereinafter referred to as “Case 2”) and all call slots are in the spatial multiplex state of 2 or more, the result of the call being terminated and the connection being released in 2 of these multiplex slots One is a multiplex slot (hereinafter referred to as “case 3”).

FIG. 6 is a diagram showing a switching source selection table 600 for determining a speech slot and a mobile station which are switching sources. Here, the update status of this table associated with the empty slot reservation process will be described by taking the above-mentioned case 1 and case 2 as an example. The control unit 80 controls the case 1 and the case 2 for one multiplex slot to which the mobile station whose allocation state to the call slot has finally changed is assigned, and in the case 3, the mobile station whose connection has been terminated. Is stored in the switching source selection table 600 by associating 1 which is the highest priority with the 1 multiplex slot to which was assigned.

When the empty slot securing process is executed, the control unit 80 recognizes one multiplex slot associated with the highest priority as the call source switching slot. The reason for prioritizing in this way is that mobile stations already in communication are
This is for avoiding selecting the mobile station of the switching source, which is predicted to deteriorate the communication quality at the time of forced TCH switching, so as not to make the user in the call as uncomfortable as possible.

By the way, when there is one multiplex slot other than the call slot with the highest priority, the control unit 80
Assigns a priority from a small slot number to a large slot number, which is a unique number that is associated with each other to identify each call slot. Further, the number of retries is set to 3 as a default value and stored in the switching source selection table 600 with respect to one multiplex slot to which the above-described priority order is associated.

The above is the processing immediately before the empty slot reservation processing is executed by the control unit 80, and is the processing for specifying the call slot and the mobile station which are the switching sources. Then, in the communication quality prediction table 400, the control unit 80 has the smallest total number of points among the combinations including the mobile station that is the switching source, that is, the combination that is expected to obtain the highest communication quality. And the call slot to which the mobile station that is not the switching source among the mobile stations included in the combination is assigned is determined as the call slot of the switching destination.

Based on the mobile station and the call slot of the switching source and the call slot of the switching destination thus determined, the control unit 80 carries out the forced TCH switching. This forced TC
When the H switching is successful, the control unit 80 ends the switching source selection process. On the other hand, when the above-mentioned forced TCH switching fails due to poor communication quality or the like, the priority value of the one-multiplex slot that is the switching source is changed to the lowest priority value, and in the switching source selection table 600, The number of retries associated with one multiplex slot is decremented by one, and the priority value of another one multiplex slot is increased.

As a result of repeating such processing,
The number of retries associated with one multiplex slot is 0
In this case, the control unit 80 excludes this one-multiplex slot from the candidates for the one-multiplex slot of the switching source. Further, in accordance with this exclusion, the control unit 80 reviews the priority order so as to fill the hole of the priority order of the excluded one multiplex slot. (Communication Quality Prediction Process) The control unit 80 predicts communication quality as follows.

The control unit 80 receives from the response vector calculation unit 53, for example, the response vector Ra of the mobile station a which is about to newly perform wireless communication or is already in communication,
The response vector Rx of the existing mobile station X is read from the area identified by the time slot number that identifies the time slot of the quality index value table 300, and the response vector Rx between the mobile station a and the mobile station X is read as follows. The spatial correlation value Ja is calculated.

[0063]

[Equation 1]

Next, the control unit 80 receives the above-mentioned electric field intensity Ia of the mobile station a from the RSSI detection unit 54, and from the area identified by the time slot number identifying the relevant time slot of the quality index value table 300, The electric field strength Ix of the mobile station X is read out, and the electric field strength ratio Ka is calculated by Ka = Ia / Ix. Here, in the case of Ka> 1, it is calculated by Ka = Ix / Ia.

Next, the calculated spatial correlation value Ja and the spatial correlation value threshold value J _t stored in the threshold value table 200.
Compare with. In addition, the calculated electric field intensity ratio Ka and the electric field intensity ratio threshold K _t stored in the threshold table 200.
Compare with. When Ja ≦ Jt and Ka ≧ Kt, it is determined that spatial multiplexing is possible, and in other cases, spatial multiplexing is impossible.

When a plurality of (2 to 3) mobile stations are already communicating by spatial multiplexing, the control unit 80
The above determination process is performed for each mobile station. Further, the control unit 8
For 0, the fading value Pa, which is a temporal change of the above spatial correlation value Ja, is calculated by Pa (t _n ) = (Ja (t _n ) -Ja (t _p )) / (t _n -t _p ).

Here, Ja (t _n ) is the spatial correlation value calculated from the response vector at the current time t _n , and Ja (t _n ).
_p ) is a spatial correlation value calculated from the response vector of the previous frame at time t _p . Note that the above-mentioned timer value t1 and t _n and t _p have a relationship of t1 ≧ (t _n −t _p ).

As described above, the control unit 80 controls the spatial correlation value.
Ja, the electric field intensity ratio Ka, and the fading value Pa are obtained and stored in the communication quality prediction table 400 or the quality prediction table 500. In addition, the control unit 80 finally determines whether or not to perform the forced TCH switching based on the prediction result of the communication quality of the group including the mobile station determined as the switching source by the switching source selection processing described above. To do.

That is, in the above group combination, if even one group has a threshold crack, the control unit 80 determines that the combination belonging to this group is
Stop implementing forced TCH switching. (Process at New Connection) The control unit 80 performs a process at new connection as follows.

That is, when a new connection is requested from the mobile station, the control unit 80 determines whether or not there is an empty slot, and if there is an empty slot, assigns the mobile station requesting the new connection to this empty slot. . On the other hand, if there are no empty slots,
The control unit 80 attempts connection in the same procedure as the conventional one. That is, the control unit 80 attempts to assign the mobile station that has requested the new connection to the already assigned call slot.

At this time, the control unit 80 determines whether the communication quality of the assigned mobile station and the mobile station of the new connection can be ensured at the set level or higher based on the spatial correlation value J _X and the electric field strength ratio K _X. Then, the feasibility of the new connection is determined. (Processing during communication) The control unit 80
Perform processing during communication.

When the control unit 80 determines that the communication quality is poor, the control unit 80 controls the mobile station to switch the communication slot. Further, when it is determined that a handover has occurred, control is performed to switch to the wireless channel of the transfer destination cell. 2 Operation of Radio Base Station 100 The operation of the radio base station 100 will be described. (1) Operation of vacant slot reservation process The vacant slot reservation process will be described with reference to the flowchart shown in FIG.

The control unit 80 waits for the number of users in the call slot to change (step S301), and when the number of users in the call slot changes, there is no empty slot in all the call slots and there is one multiplex slot. It is determined whether or not (step S302), and if these conditions are not satisfied, the process ends. On the other hand, when these conditions are satisfied, the control unit 80 substitutes 1 into the value M indicating the number of times the forced TCH switching is tried (step S303), and sets the value of the timer to the time t1 second (step S304).

Then, the control unit 80 waits for the set time of the timer (step S305), and during this period, collects the response vector and the electric field strength of each mobile station necessary for predicting the communication quality. . When the set time of the timer has passed, the control unit 80 determines whether there is a state change in all call slots (step S306). No, and there is one multiplex slot, the process returns to step S302.

On the other hand, when there is no state change in all the communication slots, the control unit 80 determines whether or not the value of M is 1 (step S307). If the value of M is 1, the above-mentioned step S3 is performed.
In 03, the highest priority is given to the 1 multiplex slot accommodating the mobile station that has caused the change, and the default value of the number of retries N is set (step S308). It is determined whether or not (step S309), and if there is, a priority is assigned to another one multiplex slot in ascending order of slot number which is the identification number associated with this communication slot, and the number of retries. The default value of N is set (step S310).

After the above steps are executed, if the value of M is not 1 in the above step S307, or if there is no other 1 multiplex slot in the above step S309, the control unit 80 determines the highest priority. The mobile station of 1 multiplex slot is set as the compulsory TCH switching source (step S
311), forced TC for the call slot of the switching destination candidate
Predict communication quality when H switching is performed (step S
312), a call slot of a switching destination candidate in which the highest communication quality is expected, that is, a call slot to which a mobile station other than the mobile station of the switching source in a combination with a small total number of points is assigned is used as a switching slot of the switching destination. A selection is made (step S313).

Then, the control unit 80, in the communication quality prediction table 400 or 500, for all combinations in the group to which the combination targeted for forced TCH switching belongs, the spatial correlation value, the electric field strength ratio K _X, and the fading value. It is determined whether P _X clears each threshold value corresponding to these (step S314), and when clearing,
ISD from the baseband unit 70 to the external exchange
It is determined whether or not there is a vacancy in the communication band of the N line (step S315), and if there is no vacancy, the process ends.

The reason for carrying out such control is that it is meaningless if a new call cannot be connected even if this control is carried out, and the purpose is to prevent the possibility of unnecessary performance deterioration. On the other hand, when there is an empty space, the control unit 80 controls the forced TCH.
The switching is tried (step S316) and the compulsory TCH is performed.
It is determined whether the switching is successful (step S317),
If successful, the process ends.

When the forced TCH switching has failed, the control unit 80 decrements the number of retries associated with this switching source, that is, the multiplex slot by 1 (step S318). Then, when the above-described decrement is performed, or when it is not cleared in the determination in step S314, the control unit 80
Changes the rank associated with the one multiplex slot that is the switching source to the lowest rank (step S319),
Force T for the mobile station in the call slot where the number of retries is 0
It is excluded from the candidates for the CH switching source (step S320), 0
It is determined whether or not there is a call slot associated with the number of retries other than, that is, a candidate to be a switching source (step S321). If there is no candidate to be a switching source, the control unit 80 To finish.

On the other hand, when there is a candidate to be the switching source, the control unit 80 sets the value of the timer to the time t2 seconds, and sets the value obtained by incrementing the current value of M by 1 as the new value of M. (Step S322), the process returns to step S305 of waiting for the set time of the timer. The steps corresponding to the above communication quality prediction process are S304, S
305, S313 and S314.

FIG. 8 is a diagram showing a time-series change in the status of allocation to the mobile station to the communication slot when such empty slot reservation processing is carried out. When the empty slot can be secured, the control unit 80 allocates only one mobile station to one communication slot without performing spatial multiplexing. Time t0
In the above, since the mobile station was assigned to the remaining 1 empty slot, there was no empty slot in all call slots,
At the same time, the control unit 80 determines that there is one multiplex slot, and starts the empty slot securing process. As a result, at time t1, the mobile station assigned to slot 3 moves to slot 1. Then, as shown from t4 to t6, by accommodating the mobile station that makes the new connection request in the newly created empty slot, the empty slot securing process is repeatedly executed. Become.

Eventually, as shown at t7, after allocating four mobile stations to each of slot 1 and slot 2 and allocating the mobile station to the remaining one empty slot, the empty slot can no longer be generated. . In this case, a connection similar to the conventional one is tried thereafter. In addition,
Up to four spatial multiplexing can be performed in one speech slot, but the number of mobile stations that can be spatially multiplexed varies depending on the positional relationship between the spatially multiplexed mobile stations. Therefore, as shown at t20, three slots are used in slot 1. The mobile station has 4 mobile stations in slot 2 and 1 in slot 3.
Even when three mobile stations are respectively assigned, a normal connection may occur.

As described above, according to the first embodiment, the radio base station 100 constantly carries out forced TCH switching so as to secure an empty slot, so that the frequency at which an empty slot is secured is secured. , And assigning a mobile station requesting a new connection to this empty slot facilitates the new connection. Incidentally, in the first embodiment,
In the empty slot securing process, an empty slot having a spatial multiplexing number of 0 is generated, but the spatial multiplexing number is M (M is
A slot (hereinafter, referred to as a “low multiplexing slot”) of 1 or more and less than the limit spatial multiplexing number (4 in the first embodiment) may be generated.

By making the value of M as small as possible and assigning it to the mobile station requesting a new connection to this low multiplex slot, the frequency of smooth connection without causing a problem in communication quality. Will increase. In addition, in the first embodiment, the wireless base station 100
Is wirelessly connected to the PHS mobile station, but the present invention is not limited to this, and any wireless communication system such as a mobile phone that uses both time division multiplexing and space multiplexing can be used.

Further, although the number of antennas in the first embodiment is four, the number of antennas is not limited to this and may be any number. In that case, when the number of antennas is L, the maximum spatial multiplexing number is L. In addition, in FIG. 6, the case 1 and the case 2 have been described as an example, but whether or not the change in the state as in the case 2 is a trigger for executing the forced TCH switching can be freely set by the user setting. May be changed to.

Further, in the first embodiment, the communication quality in the case of performing the forced TCH switching is based on the three values of the spatial correlation value J _X , the electric field strength ratio K _X and the fading value P _X. Although the prediction is performed, the quality prediction may be performed based on factors other than these. In that case,
In the first embodiment, for example, in FIG.
“He” indicates only one combination assuming that the same quality prediction result as when “to slot 3” is obtained. However, even if the same mobile station combination is used, the switching target is different. When the predicted value of the communication quality is different, it is necessary to predict the communication quality by performing more detailed case classification in consideration of the difference of the switching targets.

For example, it is convenient that the transmission timings from the spatially multiplexed mobile stations to the radio base station 100 are slightly deviated in order to separate the signals of the mobile stations. Therefore, the radio base station 100 instructs the mobile stations so that the transmission timings of the spatially multiplexed mobile stations do not overlap. However, the speed of response of the mobile station to this instruction is different for each mobile station, and assigning a mobile station with a fast response to another slot is not a problem, but a mobile station with a slow response is assigned to another slot. Allocating seems to be a problem.

Thus, for example, when the speed of response is taken into consideration as a factor of communication quality prediction, it is necessary to carry out more detailed case classification as described above to predict the communication quality. Further, although not described in the first embodiment, when the user allocation changes due to other influences during the activation of the empty slot reservation process, for example, the existing user has ended the call, the existing user has deteriorated performance, etc. And force T
When a phenomenon such as CH switching or an existing user moving to another base station due to handover occurs, the control unit 80
May interrupt the real empty slot reservation process by interrupting.

In this case, if the allocation of the new mobile station satisfies the condition for performing the empty slot securing process, that is, the condition that there is no empty slot in all the speech slots and that there is one multiplex slot, the control unit 80 starts the empty slot securing process again from the beginning. On the other hand, when the above conditions are not satisfied, the control unit 80 does not execute the empty slot securing process.

When the mobile station requesting a new connection makes a connection request again, the control unit 80 may terminate the empty slot reservation process and perform normal channel switching according to the request from the terminal. Further, the content of the empty slot reservation processing executed by the control unit 80 in the first embodiment is merely an example, and processing for constantly performing forced TCH switching so as to reserve an empty slot. If

FIG. 9 is a flowchart of the empty slot reservation process, which exemplifies such a different case, and describes the operation contents of only important parts. The difference between FIG. 9 and FIG. 7 will be described with reference to FIG. 7. Forced TC is performed from step S308 to step S311 in FIG.
The difference is that the call slot and the mobile station that are the switching source of the H switching are determined.

The flowchart of FIG. 9 will be described below. The control unit 80 waits for the number of users in the call slot to change (step S601), and when the number of users in the call slot changes, there is no empty slot in all the call slots and whether there is one multiplex slot or not. Is determined (step S602), and if these conditions are not satisfied, the process ends.

On the other hand, when these conditions are satisfied, the control unit 80 waits for the time set by the timer (step S6).
03), during this period, the response vector and electric field strength of each mobile station necessary for predicting the communication quality are collected. When the set time of the timer has passed, the control unit 80 determines whether or not there is a state change in all call slots (step S6).
04), if there is a state change in all the call slots, the process returns to step S602 to determine whether or not there is a vacant slot in all the call slots and there is one multiplex slot.

On the other hand, when there is no state change in all the communication slots, the control unit 80 ranks the groups of the switching source mobile station and the switching destination mobile station with good communication quality, that is, from the one with the smallest total points. The number of retries N for each group.
The default value of is set (step S605). This step S605 is a step corresponding to steps S308 to S311 in FIG. 7, and in the first embodiment, the switching source of the first forced TCH is an opportunity to change the number of users in the call slot. Even if it is a mobile station and there is another multiplex slot, the priority order of these communication slots is merely given to the slot number order, whereas in the first embodiment, the communication quality prediction is performed. The switching source is determined with emphasis on communication quality, that is, the switching source of the forced TCH is determined in ascending order of the total points in the table 400 or 500.

That is, the control unit 80 forces the combination of mobile stations whose total number of points is the minimum to be T.
The CH is switched (step S606). And
The control unit 80 clears the threshold values corresponding to the spatial correlation value, the electric field intensity ratio K _X, and the fading value P _X for all the combinations in the group to which the combination targeted for forced TCH switching belongs. It is determined whether or not (step S607), when clearing, the forced TCH switching is tried (step S608), it is determined whether or not the forced TCH switching is successful (step S609), and if successful, the processing is ended. To do.

When the forced TCH switching fails, the control unit 80 decrements the number of retries associated with one switching source slot in the switching source selection table 600 by one (step S
610). When the above-described decrement is performed, or when it is not cleared in the determination in step S607, the control unit 80 is the switching source 1
The order associated with the multiplex slot is changed to the lowest order (step S611), and the mobile station of the call slot for which the number of retries is 0 is excluded from the switching source candidates for forced TCH switching (step S612), and other than 0. It is determined whether there is a call slot associated with the number of retries, that is, a candidate to be a switching source (step S61).
3) If there is no switching source candidate, the control unit 80
Ends the process.

On the other hand, when there is a candidate to be the switching source, the control unit 80 returns to step S606 in which the combination of mobile stations having the minimum total points is the target of the forced TCH switching. As described above, the method of determining the mobile station as the switching source of the forced TCH switching may be different from that of the flowchart of FIG. 7.

FIG. 10 is a diagram showing an example of empty slot reservation processing different from FIGS. 7 and 9. Control unit 80
Waits for the number of users in the call slot to change (step S701), and when the number of users in the call slot changes, there are no empty slots in all the call slots, and 1
It is determined whether there are multiple slots (step S70).
2) If the above conditions are not satisfied, the process ends.

On the other hand, when these conditions are satisfied, the control unit 80 waits for the time set by the timer (step S7).
03), during this period, the response vector and electric field strength of each mobile station necessary for predicting the communication quality are collected. When the set time of the timer has passed, the control unit 80 determines whether or not there is a state change in all call slots (step S7).
04), if there is a state change in all call slots, the process returns to step S702 to determine whether or not there are no empty slots in all call slots and there is one multiplex slot.

On the other hand, when there is no state change in all the communication slots, the control section 80 ranks the groups of the switching source mobile station and the switching destination mobile station with good communication quality, that is, from the one with the smallest total points. The number of retries N for each group.
The default value of is set (step S705). The control unit 80 sets the combination of mobile stations having the minimum total number of points as the target of forced TCH switching (step S706).

Then, the control unit 80 determines that the spatial correlation value, the electric field strength ratio K _X, and the fading value P _X correspond to all combinations in the group to which the combination targeted for forced TCH switching belongs. It is determined whether or not the threshold value is cleared (step S707). When the threshold value is cleared, the forced TCH switching is tried (step S708),
It is determined whether the forced TCH switching has succeeded (step S709), and if successful, the process ends.

When the forced TCH switching fails, the control unit 80 decrements the number of retries associated with this call slot in the switching source selection table 600 by 1 (step S710). That is, the process of changing the rank associated with one multiplex slot that is the switching source to the lowest rank, which is performed in the flowchart in FIG. 9, is not performed.

As a result, the number of retries becomes 0 again due to the spatial multiplexing condition in which the forced TCH switching has failed.
This is when the forced TCH switching is tried. When the above decrement is performed, or step S70
If it is not cleared in the determination in 7, the control unit 80 excludes the mobile station of the communication slot for which the number of retries is 0 from the switching source candidates for forced TCH switching (step S711), and the number of retries other than 0 corresponds. It is determined whether or not there is a call slot attached, that is, a candidate to be a switching source (step S712), and if there is no candidate to be a switching source, the process ends.

On the other hand, if there is a candidate to be the switching source, the control unit 80 returns to step S706 in which the combination of mobile stations having the smallest total points is the target of the forced TCH switching. Further, in the first embodiment, the forced TCH switching is constantly carried out so as to secure an empty slot. However, when a new connection is requested, the empty slot securing process is started to secure the empty slot. May be secured.

In this case, the content of the determination in step S301 of FIG. 6 is not that the number of users in the call slot has changed, but whether or not a new connection request has been made. Further, in the flowchart of FIG. 6, the set value of the number of retries N is set uniformly for one multiplex slot, but different numbers of times may be set individually.

Further, in the first embodiment, the number of retries N is associated with the call slot that is the switching source, but it may be associated with the call slot that is the switching destination. (Second Embodiment) A radio base station 100 as a second embodiment of the present invention will be described.

As in the first embodiment, the radio base station in the second embodiment wirelessly connects to the mobile station by the time division multiplexing method defined by the PHS standard, and in addition to the time division multiplexing, In addition, the wireless base station further performs spatial multiplexing to communicate with the mobile station, has a functional unit similar to that of FIG. 1, and has different contents of processing performed by the control unit 80. Here, the control unit 8 that executes a process different from that of the first embodiment
0 will be described.

In the first embodiment, the control unit 80
When the state of mobile station allocation to a call slot changes, if there is no empty slot and there is a call slot to which only one mobile station is allocated, the empty slot reservation process is performed to establish a new connection. In the second embodiment, the control unit 80 preferentially allocates the mobile station requesting the new connection to one or more multiplex while the mobile station requesting the request is preferentially assigned to the empty slot. It is different in that it is assigned to a call slot, that is, priority is given to spatial multiplexing.

More specifically, when a new connection is requested from the mobile station, the control unit 80 first determines whether or not there is one or more speech slots to which the mobile station can be assigned, and If there is such a call slot, an attempt is made to assign a mobile station. At that time, the control unit 80 carries out a process corresponding to the communication quality prediction process in the first embodiment as shown below.

That is, the control unit 80 predicts the communication quality based on the spatial correlation value J _X , the electric field intensity ratio K _X and the fading value P _X. Here, since the fading value P _X is the change amount of the spatial correlation value J _X per unit time as described above, it is usually calculated based on the spatial correlation value J _X obtained in different speech slots. It

However, since the mobile station requesting a new connection is not communicating using the call slot at the time of requesting a connection, the fading value for this mobile station is
P _X cannot but be calculated from the spatial correlation value J _X obtained using only the control slot for reception. That is, the fading value P _X is the spatial correlation value J _X obtained in the first half of the control slot.
And the spatial correlation value J _X obtained in the latter half.

This is data sampled at extremely short time intervals, and the accuracy of calculating the fading value P _X is inferior to that when the communication is performed using the communication slot. Therefore, consideration is given to canceling the allocation of this mobile station only when the fading value P _X is obviously large. Therefore, the fading threshold P _t is
The values are more relaxed than the spatial correlation value threshold value J _t and the electric field strength ratio threshold value K _t . When the fading value P _X regarding the mobile station requesting the connection is equal to or less than the fading threshold P _t and the allocation is attempted to one or more multiple slots of the mobile station requesting the new connection, the control unit 80 sets an empty When there are slots, the spatial correlation value threshold value J _t and field strength ratio threshold value K _t used for prediction of communication quality are set to higher threshold values than those when there are no empty slots. Is used to determine whether to allocate the mobile station requesting this new connection to one or more multiplex slots.

The reason for using the high-level threshold value is that the fading value P _X is excluded from the evaluation items used for communication quality prediction as compared with the first embodiment, so that the communication quality prediction accuracy decreases. However, when a mobile station requesting a new connection is actually assigned to one or more multiplex slots, it is possible to avoid the occurrence of poor communication quality. On the other hand, when an attempt is made to allocate to one or more multiple slots of the mobile station requesting the new connection described above, if there is no empty slot, the control unit 80 uses the threshold value of the normal level to allocate this new connection. It is determined whether the requesting mobile station is assigned to one or more multiplex slots.

That is, when there is no empty slot, connection is attempted as usual. FIG. 11 is a diagram showing a time-series change in the allocation status of mobile stations to call slots when the above processing is performed. At time t0, the mobile station requests a new connection,
The control unit 80 attempts to spatially multiplex the mobile station in slot 1 so that the spatial multiplexing number increases.

At this time, at this point, there are two empty slots, and there is room for allocation when the spatial multiplexing of the mobile station requesting a new connection is not successful. Therefore, the control unit 80 The threshold value used for determining whether or not spatial multiplexing to slot 1 is set is set to a higher level than usual. At time t0, the determination as to whether spatial multiplexing is possible is OK even if such a threshold value is used.

At time t1, the mobile station requests a new connection, and the control unit 80 attempts to spatially multiplex this in slot 1. Also in this case, since there are two empty slots at this time, the control unit 80 determines that the threshold value used for determining whether or not spatial multiplexing to slot 1 is possible is
Set to a higher level than usual.

However, in the above determination, it is determined that spatial multiplexing cannot be performed, so that the slot 2 is assigned at time t2. By repeating such processing, slot 1 and slot 2 are gradually filled. The mobile station is requesting a new connection, and the control unit 80 attempts spatial multiplexing in the order of slot 1 and slot 2, but it is not successful.

Therefore, the control unit 80 assigns the mobile station to slot 3, which is an empty slot. After that, since there are no empty slots, the slot allocation procedure similar to the conventional one is followed. That is, the control unit 80 multiplexes the mobile station into the call slot in which the communication quality is predicted to be the best.

In this case, the control unit 80 sets a normal level value as the threshold value used for determining whether or not spatial multiplexing is possible. This is because there is no empty slot for which allocation is surely successful, and as a result of setting the threshold value to a high level, it is determined not to be impossible in all spatial multiplexing availability determinations.

FIG. 12 is a diagram showing an example of such normal level and high level threshold values. The threshold table 900 shows the normal level, the high level threshold, and the ideal value at the spatial correlation value threshold value J _t and the electric field strength ratio threshold value K _t , and further sets the fading threshold value P _t . This table is shown in advance, and this table is stored in the information storage unit in advance.

A threshold value (normal level) 901 indicates a normal level threshold value, and a threshold value (high level) 902.
Indicates a high level threshold, which is a stricter value than the normal level threshold, and the ideal value 903 indicates an ideal value. Here, the spatial correlation value 904 indicates the spatial correlation value threshold value J _t , the electric field strength ratio 905 indicates the electric field strength ratio threshold value K _t , and the fading value 906 indicates the fading threshold value P _t . ing.

Radio base station 10 in the second embodiment
Operation of 0 FIG. 13 is a flowchart showing a process of preferentially performing spatial multiplexing on a mobile station requesting a new connection in the second embodiment. The control unit 80 waits until a new connection request is made (step S801), and when the new connection request is made, determines whether or not there is an empty slot (step S802).

If there is an empty slot, the control unit 80
It is determined whether or not there is a speech slot that has room for spatial multiplexing in the above multiplex slots (step S8).
03) In the case of the above-mentioned multiplex slots, and there is a communication slot with room for spatial multiplexing, the control unit 80
Determines a high-level threshold as a threshold used for prediction of communication quality (step S804), and determines whether communication quality that clears this threshold is expected (step S805).

When this threshold value is cleared, the control unit 8
In 0, the mobile station that has requested the new connection is assigned to the above-mentioned one or more multiplex slots (step S806), and the process is terminated. On the other hand, in step S803 for determining whether there is a speech slot having one or more multiplexing slots and space for spatial multiplexing remaining, if such a speech slot does not exist, a high level threshold is set. Step S for determining whether or not the communication quality to be cleared is expected
When it is not possible to clear such a high level threshold in 805, the control unit 80 allocates the mobile station requesting a new connection to an empty slot.

Further, in the case where the above-mentioned new connection request is made and it is judged in step S802 whether or not there is an empty slot, if there is no empty slot, the controller 80
Is the threshold of the normal level used as a threshold used for prediction of communication quality (step S808), determines whether communication quality that clears this threshold is expected (step S809), and clears it. In this case, the mobile station requesting the new connection is assigned to the call slot other than the empty slot (step S810).

On the other hand, if it is not cleared, the control unit 80
Refuses the connection to the mobile station requesting a new connection (step S811). As described above, according to the second embodiment, in the radio base station 100, the spatial multiplexing is actively performed at the time of a new connection, so that the chances that an empty slot remains without being used increases. .

Further, when determining whether or not spatial multiplexing is possible, if there is an empty slot, the above-mentioned determination is performed using a high level threshold value, so that more reliable spatial multiplexing can be realized. Even when it is determined that multiplexing is not possible, an empty slot is prepared, so that a smooth connection can be made by assigning a mobile station requesting a new connection to this empty slot.

In the second embodiment, the forced TCH is used.
The case where the communication quality of the mobile station assigned to the newly spatially multiplexed call slot becomes poor as a result of the switching is not described, but in such a case, the first implementation In the same manner as the above form, the forced TCH switching may be stopped and the spatial multiplexing may be attempted with another speech slot as the switching destination.

[0129]

As is apparent from the above description, the multiplex control device according to the present invention is provided in a wireless base station that wirelessly communicates with a plurality of mobile stations by time division multiplexing and spatial multiplexing.
The present invention is characterized in that the spatial multiplexing is controlled so as to generate a state in which a low multiplexing time slot having a spatial multiplexing number N which is less than the spatial multiplexing limit number exists or to maintain the state.

Thus, in the new connection, the new connection can be easily implemented by further spatially multiplexing the low multiplexing time slot. That is, since the number of spatial multiplexing is small in the low-multiplex time slot, the spatial multiplexing condition is relaxed and the connection can be made more easily. A radio base station according to the present invention is a radio base station that assigns a mobile station to any of a plurality of time slots divided by time division, and performs radio communication with a plurality of mobile stations by time division multiplexing and space multiplexing. A time slot allocation changing means for attempting to change the allocation so as to generate a state in which there are low multiplex time slots of the spatial multiplexing number N which is less than the spatial multiplexing limit number, or to maintain the state. A time slot allocation changing method according to the present invention is characterized in that a mobile station is allocated to a plurality of time slots divided by time division, and wireless communication is performed with the plurality of mobile stations by time division multiplexing and space multiplexing. A method of changing a time slot allocation in a base station, wherein no allocation of mobile stations is performed. The method according to the present invention is characterized by including a time slot allocation step for attempting to change the allocation so as to secure a heavy time slot, and the program according to the present invention allocates a mobile station to a plurality of time slots divided by time division, In a radio base station that performs radio communication with a plurality of mobile stations by time division multiplexing and space multiplexing, a program for changing the allocation, which secures a low multiplex time slot in which no mobile station is allocated And causing the computer to execute a time slot allocation step for attempting to change the allocation as described above.

By using the low multiplex time slot as an allocation destination for new connection,
New connections are easily implemented. That is, similar to the above, in the low multiplex time slot, the number of spatial multiplexes is small, so the spatial multiplex condition is relaxed and connection can be made more easily. Further, the number of N may be 0.

As a result, a time slot that can be connected is secured without performing spatial multiplexing. Further, the time slot allocation changing means may realize the state by generating the low multiplex time slot. As a result, even if there is no low-multiplex time slot, the low-multiplex time slot is secured by newly generating the low-multiplex time slot.

Further, the plurality of time slots include a first time slot to which only one mobile station is allocated and a second time slot to which one or more mobile stations are allocated, and the time slot allocation change The means is
The generation may be performed by changing the allocation of the first mobile station from the first time slot to the second time slot so that the first time slot is a low multiplex time slot.

With this, a low multiplex time slot is generated only by changing the allocation of one mobile station,
Low multiplex time slots are reserved. Further, there are a plurality of the second time slots, and further, assuming that the allocation of the first mobile station is changed from the first time slot to the second time slot, the second time after the change is made. One of the communication quality predicting means for determining the predicted communication quality of all mobile stations assigned to the slot and the second time slot in which the predicted communication quality exceeds a predetermined communication quality Allocation destination determining means for determining the allocation destination of the station may be provided.

As a result, a low multiplex time slot is generated while ensuring a predetermined communication quality. Further, the allocation destination determining means may further determine, as the allocation destination, a second time slot in which the best predicted communication quality is obtained. As a result, the communication quality when the allocation of the first mobile station to the second time slot is changed is further improved.

Further, the communication quality predicting means ranks the predicted communication qualities for the respective second time slots, and the allocation destination determining means determines the second time slot having the highest priority as the allocation destination. You may. This makes it possible to easily identify the time slot in which the best predicted communication quality can be obtained.

[0137] Further, it further comprises communication quality evaluation means for evaluating the current communication quality of the allocated mobile station in the present situation, and the time slot allocation changing means further executes the change, and then the second allocation destination. If there is at least one mobile station whose current communication quality is lower than a predetermined communication quality among mobile stations assigned to a time slot, the state before the change may be restored.

As a result, the low multiplex time slot is ensured while giving priority to the current communication quality. Further, with the restoration, correction means for correcting the rank of the second time slot which is the allocation destination immediately before the restoration to the lowest rank is provided, and the allocation destination determining means is provided when the correction is made. The second time slot having the highest priority may be newly determined as the allocation destination, and the time slot allocation changing means may further execute the change to the new allocation destination.

This increases the chances of ensuring low multiplex time slots. The time slot allocation changing means may stop the change when the restoration is repeated a predetermined number of times or more. This allows
It is possible to avoid repeating the useless change for a slot in which the current communication quality is unlikely to exceed the predetermined communication quality.

Furthermore, when the number of times of performing the change to the same second time slot becomes a predetermined number of times or more,
Excluding means for excluding the second time slot from the target of determination of the allocation destination, and the time slot allocation changing means may cancel the change when there is no target of the allocation destination due to the exclusion. Good.

As a result, the change is made until the restoration is repeated a predetermined number of times or more for all the second time slots. Further, there are a plurality of first time slots, and among the plurality of first time slots, the one in which the allocation state of the mobile station has changed at the time closest to the present time is the allocation source of the first mobile station. The time slot allocation changing means may change the allocation of the one mobile station from the selected allocation source to the allocation destination.

As a result, the mobile station with good communication quality in which the allocation state has not changed is maintained in its current state, and the temporary deterioration in communication quality which may occur when the allocation is changed can be avoided. In other words, it is considered that the communication quality of mobile stations whose allocations have been changed originally has temporarily deteriorated.For such mobile stations, the allocations are further changed and communication quality is re-established. Even if the communication quality temporarily deteriorates, the time interval of the deterioration of the communication quality is very short, and the user feels that the communication quality deteriorates only once, which is advantageous.

[0143] Further, it further comprises communication quality evaluation means for evaluating the current communication quality of the allocated mobile station in the present situation, and the time slot allocation changing means further executes the change, and then the second allocation destination. If there is at least one mobile station whose current communication quality is lower than a predetermined communication quality among mobile stations assigned to a time slot, the state before the change may be restored.

As a result, the current communication quality is maintained above the predetermined communication quality. Further, each of the plurality of time slots is associated with an identifier for identifying each time slot, and further, with storage means that stores a rank corresponding to each of the identifiers, with the restoration,
And an order correction unit for correcting the order of the identifier associated with the first time slot, which is the allocation source immediately before the restoration, to the lowest order, and the allocation source selection unit is provided when the correction is made. , A first time slot associated with the highest-ranked identifier is selected as the allocation source, and the time slot allocation changing means further changes the newly selected allocation source to the allocation destination. May be carried out.

As a result, the allocation change is repeatedly executed until the current communication quality equal to or higher than the predetermined communication quality is secured. In addition, the time slot allocation changing means, when the restoration is repeated a predetermined number of times or more,
The change may be canceled. As a result, it is possible to avoid repeating the useless change for a slot in which the current communication quality is unlikely to exceed the predetermined communication quality.

Further, for each first time slot, there is provided counting means for counting the number of changes made with the first time slot as the allocation source, and the counted number of changes is a predetermined number or more. In some cases, an allocation source excluding unit that excludes the first time slot that is the target of the count from the selection target of the allocation source is provided, and the time slot allocation changing unit eliminates all the allocation source targets by the exclusion. In that case, the change may be stopped.

As a result, it is possible to set the upper limit number of times that the change is allowed for each first time slot. Further, the time slot assignment changing means may try the change when a new connection request arrives from a mobile station other than the plurality of mobile stations. As a result, if the other mobile station is assigned to the low multiplex time slot, a more reliable new connection can be realized.

Further, the time slot allocation changing means may try the change by preferentially assigning the slot other than the low multiplex time slot to the other mobile station. If there is already a low multiplex time slot, this leaves this low multiplex time slot intact.

Further, the slots other than the low-multiplex time slot may be the second time slot to which one or more mobile stations are assigned. If there is already a low multiplex time slot, this allows the second time slot to be assigned to the other mobile station,
The other mobile station is connected while maintaining the state of this low multiplex time slot.

Further, the time slot allocation changing means carries out the change when the predicted communication quality for all the mobile stations allocated to the second time slot under the assumption of the change is equal to or higher than a predetermined communication quality. However, if the predicted communication quality of any of the mobile stations is lower than a predetermined communication quality and a low multiplex time slot already exists, the low multiplex time slot is newly replaced in place of the second time slot. Carry out the change as the allocation destination, and if the predicted communication quality of any of the mobile stations is less than a predetermined communication quality, and if the low multiplex time slot does not exist, stop the change, The connection of another mobile station may be refused.

As a result, the above-mentioned change is performed with priority given to ensuring communication quality rather than making a new connection. Further, the communication quality prediction means, when the low multiplex time slot does not exist, sets the threshold value indicating the predetermined communication quality as a first threshold value, and sets the low multiplex time slot. If there is a
The second threshold may be set to be stricter than the threshold of.

As a result, while the low multiplex time slot is secured, the predicted communication quality of the mobile station assigned to the second time slot is improved. Further, it further comprises communication quality evaluation means for evaluating the current communication quality of the allocated mobile station in the present situation, and the time slot allocation changing means further executes the change and then sets the second time slot of the allocation destination. If at least one of the assigned mobile stations has the current communication quality lower than a predetermined communication quality, the state before the change may be restored.

As a result, the current communication quality higher than the predetermined communication quality is secured. Further, the time slot allocation changing means may try the change when the number of mobile stations to which the allocation is made fluctuates.
As a result, the change is performed not only for new connections but also when the number of mobile stations to which the allocation is made fluctuates, so that the frequency of ensuring lower multiplex time slots increases.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a radio base station according to a first embodiment.

FIG. 2 is a diagram showing a logical configuration of a threshold table.

FIG. 3 is a diagram showing a logical configuration of a quality index value table.

FIG. 4A is a diagram showing the allocation status of mobile stations in each slot. (B) is a figure which shows the logical structure of a communication quality prediction table.

FIG. 5A is a diagram showing the allocation status of mobile stations in each slot. (B) is a figure which shows the logical structure of a communication quality prediction table.

FIG. 6 is a diagram illustrating a switching source selection process.

FIG. 7 is a diagram showing an empty slot securing process.

FIG. 8 is a diagram showing a time-series change in allocation status of mobile stations to slots when the empty slot reservation process is performed.

FIG. 9 is a flowchart showing an empty slot reservation process.

FIG. 10 shows an empty slot reservation process different from FIGS. 7 and 9.
It is a figure which shows an example.

FIG. 11 is a diagram showing a process of preferentially performing spatial multiplexing on a mobile station requesting a new connection in the second embodiment.

FIG. 12 is a diagram showing an example of a normal level threshold value and a high level threshold value according to the second embodiment.

FIG. 13 is a flowchart showing a process of preferentially performing spatial multiplexing on a mobile station requesting a new connection in the second embodiment.

FIG. 14 is a diagram showing a relationship between a time division multiplexing method and a spatial multiplexing method.

FIG. 15 is a diagram showing a state of new connection in a conventional radio base station.

[Explanation of symbols]

11, 12, 13, 14 Antenna part 21 Radio section 21, 22, 23, 24 Radio section 50 Signal processing unit 51 Signal Conditioning Section 53 Response vector calculator 54 RSSI detector 55 Communication failure detector 60 Modem section 70 Baseband section 80 Control unit 90 Information storage unit 100 wireless base stations 111 Transmitter 112 Receiver

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshiharu Doi             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Shogo Nakao             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Tadayoshi Ito             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F term (reference) 5K067 AA11 BB04 CC01 EE02 EE10                       FF02 JJ02 JJ12 JJ35 JJ74                       KK03

Claims (26)

[Claims] 1. A state in which there is a low multiplex time slot of a spatial multiplex number N, which is less than the spatial multiplex limit number, is provided in a wireless base station that wirelessly communicates with a plurality of mobile stations by time division multiplex and spatial multiplex. Or a spatial multiplexing control device that controls the spatial multiplexing so that the state is maintained. 2. A radio base station which allocates a mobile station to any of a plurality of time slots divided by time division and performs radio communication with a plurality of mobile stations by time division multiplexing and space multiplexing, wherein the space multiplexing limit is set. It is characterized by comprising time slot allocation changing means for attempting to change the allocation so as to generate a state in which there are low multiplex time slots of a spatial multiplexing number N which is less than the number, or to maintain the state. Wireless base station. 3. The radio base station according to claim 2, wherein the number of N is 0. 4. The radio base station according to claim 3, wherein the time slot allocation changing means realizes the state by generating the low multiplex time slot. 5. The plurality of time slots include a first time slot to which only one mobile station is allocated and a second time slot to which one or more mobile stations are allocated, and the time slot allocation change The means changes the allocation of the first mobile station from the first time slot to the second time slot, thereby making the first time slot a low multiplex time slot and performing the generation. The described wireless base station. 6. A plurality of the second time slots are provided, and further, when it is assumed that the allocation of the first mobile station is changed from the first time slot to the second time slot, after the change is made, Communication quality predicting means for respectively obtaining predicted communication quality for all mobile stations assigned to the second time slot; and one of the second time slots for which the predicted communication quality exceeds a predetermined communication quality, The wireless base station according to claim 5, further comprising: an allocation destination determining unit that determines an allocation destination of one mobile station. 7. The radio base station according to claim 6, wherein the allocation destination determining unit further determines, as the allocation destination, a second time slot in which the best predicted communication quality is obtained. 8. The communication quality predicting means ranks the predicted communication qualities of respective second time slots, and the allocation destination determining means determines the second time slot having the highest priority as the allocation destination. The radio base station according to claim 7, wherein 9. Further comprising communication quality evaluation means for evaluating the current communication quality of the allocated mobile station in the present situation, wherein the time slot allocation changing means further executes the change, and then the second of the allocation destinations. The mobile station assigned to the time slot, if any one of the mobile stations whose current communication quality is lower than a predetermined communication quality exists, the state before the change is restored. 8. The radio base station according to item 8. 10. Further, in accordance with the restoration, correction means for correcting the rank of the second time slot which is the allocation destination immediately before the restoration to the lowest rank is provided, and the allocation destination determining means is configured to correct the correction. When made
10. The second time slot having the highest priority is newly determined as the allocation destination, and the time slot allocation changing means further implements the change to the new allocation destination. Wireless base station. 11. The radio base station according to claim 10, wherein the time slot allocation changing means cancels the change when the restoration is repeated a predetermined number of times or more. 12. An excluding means for excluding the second time slot from the target of determination of the allocation destination when the number of times of performing the change to the same second time slot is equal to or more than a predetermined number of times, 12. The radio base station according to claim 11, wherein the time slot allocation changing unit executes the change stop when the target of the allocation destination disappears due to the exclusion. 13. A plurality of first time slots exist, and among the plurality of first time slots, the one in which the allocation state of the mobile station has changed at a time closest to the present time is the one mobile station. Allocation source selecting means for selecting as an allocation source, the timeslot allocation changing means changes the allocation of the one mobile station from the selected allocation source to the allocation destination. Item 6. The radio base station according to item 6. 14. Further comprising communication quality evaluation means for evaluating the current communication quality of the allocated mobile station in the current situation, wherein the time slot allocation changing means further executes the change, and then the second of the allocation destinations. The mobile station assigned to the time slot, if any one of the mobile stations whose current communication quality is lower than a predetermined communication quality exists, the state before the change is restored. 13. The radio base station according to item 13. 15. Each of the plurality of time slots is associated with an identifier for identifying each time slot, and further, a storage unit that stores a rank corresponding to each of the identifiers, and the recovery unit Along with this, there is provided a rank modifying means for modifying the rank of the identifier associated with the first time slot, which was the allocation source immediately before the restoration, to the lowest rank, and the allocation source selecting means makes the modification. When
The first time slot associated with the highest-ranked identifier is selected as the allocation source, and the time slot allocation changing means further changes the newly selected allocation source to the allocation destination. The radio base station according to claim 14, which is implemented. 16. The radio base station according to claim 15, wherein the time slot assignment changing means cancels the change when the restoration is repeated a predetermined number of times or more. 17. Further, for each first time slot, a counting means for counting the number of changes made by the first time slot as the allocation source is provided, and the counted number of changes is a predetermined number or more. In some cases, an allocation source excluding unit that excludes the first time slot that is the target of the counting from the selection target of the allocation source is provided, and the time slot allocation changing unit eliminates all the objects of the allocation source by the exclusion. 17. The radio base station according to claim 16, wherein when the change occurs, the change is stopped. 18. The time slot assignment changing means attempts the change when a request for a new connection arrives from a mobile station other than the plurality of mobile stations. Wireless base station. 19. The radio base station according to claim 18, wherein the time slot allocation changing unit tries to change the slot other than the low multiplex time slot by preferentially setting it as the allocation destination of the another mobile station. Station. 20. The radio base station according to claim 19, wherein the slots other than the low-multiplex time slots are the second time slots to which one or more mobile stations are assigned. 21. The time slot allocation changing means implements the change when the predicted communication quality of all mobile stations allocated to the second time slot under the assumption of the change is equal to or higher than a predetermined communication quality. Then
When the predicted communication quality of any of the mobile stations is lower than a predetermined communication quality and a low multiplex time slot already exists, the low multiplex time slot is newly assigned instead of the second time slot. If the change is implemented as a destination, the predicted communication quality of any of the mobile stations is less than a predetermined communication quality, and the low multiplex time slot does not exist, the change is canceled and the other 21. The radio base station according to claim 20, wherein the connection of the mobile station is rejected. 22. When the low multiplex time slot does not exist, the communication quality predicting means sets the threshold value indicating the predetermined communication quality as a first threshold value, and the low multiplex time slot exists. In this case, the wireless base station according to claim 21, wherein the threshold value is set to a second threshold value that is stricter than the first threshold value. 23. The communication quality evaluation means for evaluating the current communication quality of the allocated mobile station in the present situation, wherein the time slot allocation changing means further executes the change, and then the second allocation destination. The mobile station assigned to the time slot, if any one of the mobile stations whose current communication quality is lower than a predetermined communication quality exists, the state before the change is restored. 22. The radio base station according to 22. 24. The time slot allocation changing means attempts the change when the number of mobile stations to which the allocation is made fluctuates.
The described wireless base station. 25. In a radio base station that allocates a mobile station to a plurality of time slots divided by time division and performs radio communication with a plurality of mobile stations by time division multiplexing and space multiplexing, time slot allocation for changing the allocation. A method of changing a time slot allocation, comprising a time slot allocation step of attempting to change the allocation so as to secure a low multiplex time slot in which no mobile station has been allocated. 26. A program for changing the allocation in a radio base station that allocates a mobile station to a plurality of time slots divided by time division and performs radio communication with a plurality of mobile stations by time division multiplexing and space multiplexing. A program for causing a computer to execute a time slot allocation step for attempting to change the allocation so as to secure a low multiplex time slot in which no mobile station has been allocated.