JP2003179965A - Communication channel assigning device and radio base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio base station for assigning a communication channel to a mobile station so that the increase of mobile stations to fall into uncommunicable state in future can be suppressed in a certain degree. <P>SOLUTION: The radio base station uses a plurality of time division slots by a time division multiplex system, and uses together a spatial multiplex system for multiplexing the communication signals of a plurality of mobile stations to each of the time division slots. When newly connecting a mobile station or when communication channel switching is required, concerning each of the time division slots, various kinds of parameters indicating a communication quality calculated on the basis of measurements concerning that time division slot are compared with thresholds and an assignment possibility decision is performed to decide whether that time division slot can be assigned to that mobile station or not. In the assignment possibility decision, a limit threshold is used for requesting a high quality to the time division slot of a high multiplex degree (the number of mobile stations to assign) (S16), a default threshold is used for making a low quality satisfactory for the other time division slot (S17), and the assignment to the time division slot of the high multiplex degree is suppressed by the low quality. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a spatial multiplexing system (P
ath Division MultipleAccess
A wireless base station wirelessly connected to a plurality of PHS (Personal Handyphone System) mobile terminals, mobile phones, and other wireless telephone devices (hereinafter referred to as "mobile stations") by the ss: PDMA method, in particular, mobile stations. The present invention relates to a technique for selecting a communication channel to be assigned to each.

[0002]

2. Description of the Related Art Conventionally, in a radio base station that wirelessly communicates with a plurality of mobile stations, a time division multiplexing (TDM) method is used to allocate a communication channel to each mobile station by effectively utilizing frequency resources.
A / TDD, Time Division Multi
ple Access / Time Division
Duplex) is used, and spatial multiplexing is used for effective use of further frequency resources.

In the spatial multiplexing system, the wireless base station is
For a plurality of mobile stations existing in different directions, by forming a directional pattern using an adaptive array device,
It is a method of communicating at the same time with the same frequency. The adaptive array device is provided with a plurality of antennas fixedly installed, and by dynamically adjusting the amplitude and phase of the transmission / reception signal with respect to each antenna, the antenna as a whole has a directivity for transmission and reception. A signal that dynamically forms the characteristic pattern and that reduces the transmission strength and reception sensitivity in the direction of other mobile stations that are being multiplexed while increasing the transmission strength and reception sensitivity in the direction of the desired mobile station. The control for removing the mutual interference is performed.

For example, a radio base station which multiplexes signals from a maximum of four mobile stations at the same time at the same frequency by the spatial multiplexing method, and a periodic fixed time is defined by four transmission time slots by the time division multiplexing method. It is divided into a total of eight reception time slots and four, and three of four transmission / reception time slot pairs, which are a set of transmission time slots and reception time slots, are bidirectionally communicated with up to four mobile stations. Channel (TC)
A radio base station to be assigned as H) is being researched and developed.

By the way, conventionally, TC based on communication channel allocation at the time of new connection of a mobile station in a radio base station, or deterioration of communication quality of a mobile station to which communication channel allocation has been performed, etc.
The communication channel allocation when H switching is required is such that the transmission / reception time slots are transmission / reception time slots that are the allocation candidates when the availability determination is made as the allocation candidates in the order of priority determined by some standard. The slot is assigned to a new mobile station or a mobile station that needs TCH switching.

The conventional assignability determination is a determination as to whether or not communication with a certain quality is possible in a transmission / reception time slot that is an assignment candidate, and a fixed parameter is fixed in advance for each of a plurality of parameters that affect the communication quality. If it is possible to perform communication with a certain level of communication quality even if it is not of high quality, it is determined that allocation is possible.

As the above-mentioned parameter used in the assignment availability determination, for example, the maximum value of the DDR values among the mobile stations spatially multiplexed in the same transmission / reception time slot (hereinafter referred to as "worst DDR value"). There is. Here, DDR (Desired to Desired)
Ratio is a number indicating the ratio of the received power levels between mobile stations, and is a ratio of the magnitudes of reception response vectors for two mobile stations (adjusted by exchanging the divisor and dividend so that the number becomes 1 or more). ). The reception response vector is a number indicating the propagation path of the signal from the mobile station to the radio base station. This DDR is one index that greatly affects the communication quality, and under the situation where the worst DDR value is large, it becomes difficult for the radio base station to separate signals from each mobile station, and the communication quality deteriorates. In the judgment, if the worst DDR value is larger than a predetermined threshold value, it is judged that the allocation is impossible.

That is, in conventional communication channel allocation to a mobile station when a new connection is made by a radio base station or when TCH switching is required, communication with a certain level of communication quality is possible for the time being based on the above-mentioned allocation availability judgment. The transmission / reception time slot determined to be assigned to that mobile station.

[0009]

However, in the conventional communication channel allocation at the time of new connection by the radio base station,
The following problems that occur when a radio base station allocates a transmission / reception time slot that is already used for communication with one or more other mobile stations to a new mobile station cannot be solved.

That is, in this case, there occurs a situation in which the communication quality of one or more mobile stations already communicating with the radio base station is deteriorated in the transmission / reception time slot to which a new mobile station is assigned, , If there are a large number of mobile stations targeted for spatial multiplexing in the transmission / reception time slot, that is, if the degree of multiplexing is high, it is technically difficult to eliminate interference between mobile stations, so it is possible to achieve a certain level of communication quality. Even if the communication is possible, the communication quality will deteriorate, and there is an increased risk that the communication quality of many mobile stations will fall to the incommunicable state in the future due to future movement of mobile stations and other factors. The problem arises.

Further, in the conventional communication channel allocation by the radio base station when TCH switching is required, the transmission / reception time which the radio base station has already used for communication with one or more other mobile stations is set for the mobile station to be TCH switched. If you assign a slot,
When viewed as a whole of the mobile stations with which the wireless base station is communicating, a situation may naturally occur in which the number of mobile stations whose communication quality deteriorates. As a result, there arises a problem that the communication quality of many mobile stations is likely to be lowered to an incommunicable state in the future.

Therefore, the present invention has been made in view of the above problems, and when a new connection is made or TCH switching is required,
An object of the present invention is to provide a radio base station, a communication channel allocation device, and the like that allocate communication channels to mobile stations so as to suppress the increase in the number of mobile stations that will be unable to communicate in the future to some extent.

[0013]

In order to solve the above problems, a communication channel allocation device according to the present invention uses a time division multiplexing system and a space multiplexing system for allocating any of a plurality of time slots to a mobile station. In a case where it is assumed that the time slot is assigned to the mobile station for one or more time slots in order to determine the time slot to be assigned to the mobile station, the radio base station wirelessly communicating with the plurality of mobile stations. Based on the evaluation value indicating the communication quality related to the time slot, it is determined whether or not the time slot can be assigned to the mobile station, and the time slot is determined by the mobile station. , The number of mobile stations assigned to each time slot is When it will be uniform degree is increased, and not than when increasing, and performs so as to suppress the determination that the assignable.

Here, "to suppress the determination that allocation is possible" means, for example, whether or not a time slot related to a certain multiplicity such as multiplicity 4 can be allocated to a mobile station. According to the case depending on the non-uniformity of the multiplicity, the strict determination is made on the premise that two determination levels, that is, a normal determination and a strict determination are used properly. In this determination method, whether or not the same mobile station can be assigned a time slot relating to a specific multiplicity is determined normally even if the situation of the mobile station and that of the time slot are exactly the same. However, it is premised that the criterion for communication quality can be switched based on two criteria, that is, normal and strict, such that a strict determination may result in non-allocation.

With the above configuration, when the number of mobile stations assigned to a time slot such as a transmission / reception time slot, that is, the variation in the multiplicity among the time slots increases, it is determined whether or not the assignment is possible, compared to other cases. Since the allocation availability judgment will be performed by a suppressive judgment method such as comparison using a strict threshold equivalent to a high communication quality, when allocation is performed according to the result of the allocation availability judgment, It is possible to suppress to some extent the degree of non-uniformity of the multiplicity in the case where the degree is higher than that before allocation. This leads to suppressing the multiplicity in each time slot to a low level, and according to the present invention, the increase in the number of mobile stations which cannot be separated because the signals of each mobile station cannot be separated due to the high multiplicity. It becomes possible to suppress.

A radio base station according to the present invention is a radio base station that wirelessly communicates with a plurality of mobile stations by a time division multiplexing method and a spatial multiplexing method in which any of a plurality of time slots is assigned to the mobile station. For each of the one or more time slots, the time slot is allocated based on the evaluation value indicating the communication quality of the time slot when it is assumed that the time slot is allocated to one mobile station that requires allocation. A deciding means for deciding whether or not it can be assigned to a mobile station, and an allocating means for allocating one time slot determined by the deciding means to be allocable to one mobile station requiring the allocation. And the determining means determines whether or not the time slot can be assigned to the mobile station assigned to the time slot. The total number, when greater than a predetermined reference number, than when less than a predetermined reference number, and carrying out to suppress the determined assignable with.

As a result, the assignability determination for a time slot with a high degree of multiplicity is performed by a restraint determination such as a comparison using a strict threshold value corresponding to a higher communication quality than the assignment availability determination for a time slot with a low degree of multiplicity. As a result, the multiplicity in each time slot can be suppressed to a low level, and the increase in the number of mobile stations that will be in a communication-disabled state in the future when a new connection is made or when TCH switching is required is suppressed to some extent. It becomes possible to do.

A radio base station according to the present invention is a radio base station that wirelessly communicates with a plurality of mobile stations by a time division multiplexing method and a spatial multiplexing method in which any of a plurality of time slots is assigned to the mobile station. For each of the one or more time slots, based on the evaluation value indicating the communication quality of the time slot when it is assumed that the time slot is assigned to one mobile station that requires communication channel switching, To a mobile station that requires the communication channel switching, and a determination unit that determines whether or not it can be assigned to the mobile station, and one time slot that is determined to be assignable by the determination unit Allocating means for allocating the time slot, the determining means determines whether or not the time slot can be allocated,
When the total number of mobile stations assigned to the time slot in the above assumption is larger than the total number of assigned mobile stations in the time slot originally assigned to one mobile station requiring the communication channel switching, It is characterized in that the determination that allocation is possible is performed more than when it is smaller than the total number of mobile stations related to the original time slot.

Thus, when TCH switching is required,
It is possible to suppress to some extent an increase in the degree of multiplicity unevenness after TCH switching compared to before TCH switching, and as a result, it is possible to suppress to some extent the number of mobile stations that will fall into the incommunicable state in the future. become.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A radio base station according to an embodiment of the present invention will be described below with reference to the drawings. <Structure> FIG. 1 is a block diagram showing a structure of radio base station 100 according to the embodiment of the present invention.

The radio base station 100 uses a time division multiplexing method (TDMA / TDD, Time Division) that uses a plurality of transmission / reception time slots defined by the PHS standard.
Multiple Access / Time Divi
This is a radio base station that wirelessly connects to mobile stations by spatially multiplexing signals of up to four mobile stations at the same frequency by using a spatial multiplexing scheme based on the adaptive array technology in addition to the zone duplex system.

That is, the radio base station 100 uses the time division multiplexing method to transmit 8 TDMA frames each having a period of 5 ms.
It is equally divided into four transmission time slots and four reception time slots, and three sets of four transmission / reception time slots, which are sets of transmission time slots and reception time slots, are each divided into a maximum of four. Two-way communication channel (Traffic Channel: TC) for mobile stations
H), that is, it has a function of spatially multiplexing signals of up to four mobile stations for communication, and as shown in the figure, adaptive array antennas 1a1 to 1an, radio units 2a1 to 2an, and signal processing. A unit 3, a modem unit 4, a baseband unit 5 and a control unit 6 are provided.

The spatial multiplexing system is based on the radio base station 100.
Is a method for performing communication at the same time at the same frequency by forming different directivity patterns for a plurality of mobile stations existing in different directions. The adaptive array antennas 1a1 to 1an, the radio units 2a1 to 2an, and the signal The processing unit 3 and the control unit 6 dynamically adjust the amplitude and the phase of the transmission / reception signal for each antenna,
It is realized by dynamically forming directivity patterns for transmission and reception. The adaptive array technology in this spatial multiplexing system is described in detail in "Special Issue on Adaptive Signal Processing in Spatial Domain and Its Application Technology" (Journal of the Institute of Electronics, Information and Communication Engineers VOL. J75-B-2 No. 11). .

The baseband unit 5 sends and receives a plurality of signals, that is, baseband signals of voice or data, between the modem unit 4 and a plurality of telephone lines connected via a telephone switching network. The modem unit 4 provides a π for the digitized baseband signal between the signal processing unit 3 and the baseband unit 5.
/ 4 shift QPSK (Quadrature Phase
e Shift Keying) has the function of performing modulation and demodulation. This modulation and demodulation can be spatially multiplexed up to 4 in one transmitting or receiving time slot.
It is performed in parallel for one baseband signal.

The signal processing unit 3 includes user-specific signal processing units b1 to bn for separating and extracting a signal of a specific mobile station, and D.
The DR calculation unit 14 and the control regarding the formation of the directional pattern under the control of the control unit 6, that is, each radio unit 2a1.
Each spatially multiplexed signal input from 2an (hereinafter,
It is called "multiplex signal". Based on the above), the user-specific signal processing units b1 to bn calculate a weight vector which is a coefficient for adjusting the amplitude and the phase, weight each multiplexed signal, separate and extract the received signal from each mobile station, and extract the modem. Control is performed to generate a signal weighted for spatial multiplexing so that the transmission signal input to the unit 4 and input from the modem unit 4 can be transmitted to a desired mobile station, and output to each radio unit 2a1 to 2an. Part, specifically, programmable D
SP (Digital Signal Process)
or)). Here, the weight vector is a minimum mean square error method (Minimum Mean).
Square Error: MMSE). Specifically, the sum of the error between the value obtained by multiplying each multiplexed signal input to each antenna by the weight vector for that antenna and the known reference signal, that is, the preamble or unique word based on the PHS standard, is minimized. Then the weight vector is calculated.

It is to be noted that only the communication on the communication channel (TCH) forms the directional pattern by the spatial multiplexing method for transmission / reception, and the communication on the other control channels is basically performed by the spatial multiplexing method. Instead of using it, the same control processing as that of a general PHS radio base station is performed. Each of the user signal processing units b1 to bn sends reception response vectors H1 to Hn, which are coefficients indicating the propagation path of a signal from a specific mobile station to a wireless base station, to the DDR calculation unit 14, and also the DDR calculation unit 14 Is a DDR (Desired) used as an index used for control or the like for appropriately separating signals from each mobile station based on the reception response vectors H1 to Hn.
to Desired Ratio) and notifies the control unit 6 of this.

This DDR indicates the ratio of the received power level of the radio wave from one spatially multiplexed mobile station to the received power level of the radio wave from one of the other spatially multiplexed mobile stations. Become. The DDR will be described later in detail. The wireless unit 2a1 includes a transmitter 11 including a high power amplifier and the like, and a receiver 12 including a low noise amplifier and the like. The transmission unit 11 converts a signal input from the signal processing unit 3 from a low frequency to a high frequency, amplifies the signal to a transmission output level, and outputs the amplified signal to the antennas 1a1 to 1an. In response to an instruction from the control unit 6. , Has a function of adjusting the transmission output by controlling the gain of the high power amplifier. The receiving unit 12 has a function of converting a signal received by the antennas 1 a 1 to 1 an from a high frequency to a low frequency, amplifying the signal, and outputting the amplified signal to the signal processing unit 3. The wireless units 2a2-2
an is equivalent to the wireless unit 2a1.

The control unit 6 is a CPU as hardware.
(Central Processing Unit)
And a memory 16 and the like, which has a function of controlling each unit of the radio base station 100 by executing a program in the CPU by the CPU, and has a function of allocating a set of transmission / reception time slots to the mobile station. Including part 15.

The communication channel allocator 15 attempts to allocate a set of transmission / reception time slots to a mobile station in response to a new connection request from the mobile station, and also reduces the communication quality of the mobile station already in communication. When a communication channel (TCH) needs to be switched, such as when an error occurs, the mobile station has a function of attempting to allocate a set of transmission / reception time slots different from the original transmission / reception time slot,
New channel allocation for determining whether or not a certain transmission / reception time slot can be allocated to the new or mobile station requiring TCH switching by referring to a threshold value table 20 in the memory 16 that defines threshold values for communication quality Processing or switching channel allocation processing.

The new channel assignment process and the switching channel assignment process are performed so that the transmission / reception time to be assigned should be suppressed to some extent so as to suppress an increase in the non-uniformity between the transmission / reception time slots of the number of mobile stations assigned to all the transmission / reception time slots. Is the process of defining slots,
These processes will be described in detail later. Note that the allocation result by the communication channel allocation unit 15 is recorded in the memory 16, and based on this allocation result, the control unit 6 performs control for communicating with a plurality of mobile stations to which the same transmission / reception time slot is allocated by the spatial multiplexing method. Run. Further, the control unit 6 receives the DDR from the signal processing unit 3, and
Transmission power control etc. are performed according to DR.

The user-specific signal processing unit b1 will be described in detail below. FIG. 2 is a block diagram showing the configuration of the user-specific signal processing unit b1. The user-specific signal unit b1 extracts a signal from a specific mobile station and transmits it to the modem unit 4, and a reception response vector H1 which is a coefficient indicating a propagation path of the signal from the specific mobile station to the radio base station. Of the input ports 20a1 to 20an and the switch circuits 21a1 to 21a as shown in FIG.
an, multipliers 22a1-22an, multipliers 23a1-2
3an, an adder 24, a memory 25, a determination unit 26, and a weight vector control unit 27.

Here, the input ports 20a1 to 20an
Is a multiplex signal X ₁ (t) to X input from each radio unit.
_n (t) is received, and the switch circuit 21a1
21 an is a switch that can be switched between transmission and reception under the control of the control unit 6. Multipliers 22a1-22
an are, each multiplexed signal input from the input port 20A1～20an, a weight vector W ₁₁ to _W-n1 given by the weight vector control unit 27 multiplies each is intended to convey to the adder 24, the adder 24 adds the signals transmitted from the multipliers 22a1 to 22an,
The provisional reception signal Y ₁ (t) is transmitted to the determination unit 26.

The decision unit 26 determines the Y ₁ input from the adder.
The extraction signal S is corrected by correcting the phase value of (t) to be a value that is the closest to that value and is an integral multiple of π / 4.
_It has a function of obtaining _r1 (t), outputting S _r1 (t) to the modem unit 4, and transmitting it to the weight vector control unit 27. The extracted signal S _r1 (t) corresponds to the received signal from a specific mobile station.

The memory 25 previously stores, for example, a start symbol, a preamble, a unique word, etc. defined by the PHS standard as reference signals, and
The weight vectors W _{11 to} W _n1 calculated by the weight vector control unit 27 are stored. The weight vector control unit 27 refers to the reference signal previously stored in the memory 25, and uses the reference signal d (t) and the signal S _r1 (t) input from the determination unit 26 to switch the switch circuit 21a1.
.About.21an from each of the multiplex signals X ₁ (t) to X transmitted from the input ports 20a1 to 20an at a certain time t.
_The weight vectors W _{11 to} W _n1 to be multiplied are calculated at the next time (t + 1) for _n (t). Thus the weight vector control unit 27 on the basis of the signal S _r1 output to the previous modem unit 4 (t-1), each weight vector W ₁₁ to _W-n1 to be given to the multiplier 22a1~22an at the present time (t) Will be decided.

Further, the weight vector control unit 27
Each multiplexed signal transmitted from the power ports 20a1 to 20an
X₁(T) to X_n(T) and the signal input from the determination unit 26.
Issue S _r1From (t), the reception response vector H₁And calculate
It has a function of notifying the DDR calculation unit 14. Multiplier 23a
1 to 23an are extracted signals S_r1For mobile stations related to (t)
Transmission signal S_t1(T) is input from the modem unit 4.
And S_t1S for (t)_r1Wait time using (t)
Each weight vector calculated by the cuttle control unit 27
W ₁₁~ W_n1And each transmitted signal obtained by multiplying
Each wireless unit is connected via the switch circuits 21a1 to 21an.
It is what is sent.

<Weight Vector Calculation Method> The following is performed by the user-specific signal processing units b1 to bn for extracting each extraction signal S _ri (t) (i = 1, 2, 3, ..., M). Weight vector W _ji (j = 1, 2, 3, ...,
The calculation of n) will be described. In order to simplify the description, calculation of the weight vector W _j1 in the user-specific signal processing unit b1 will be described as an example with the multiplicity m = 2 and the number of antennas n = 2.

[Equation 1] Y ₁ (t) = W ₁₁ (t) X
₁ (t) + W ₂₁ (t) X ₂ (t) As shown in Equation 1, the user-specific signal processing unit b1 outputs the multiplexed signals X ₁ (t) and X ₂ (t) output from the wireless units. For each of the weight vectors W ₁₁ (t), W
_The temporary reception signal Y ₁ (t), which is the sum of the values multiplied by ₂₁ (t), is obtained, and the extraction signal S _r1 (t), which is the result of the phase correction by the determination unit 26, is output.

It should be noted that t indicates the time when the signal arrives, and P
It shows the elapsed time within the reception time slot in units of time for receiving one symbol in the HS standard. Therefore,
Multiple signals X ₁ (t), X ₂ (t), weight vector W ₁₁
(T), W ₂₁ (t), etc. are signal sequences in which the value of t is 1, 2, ... Also, the multiplexed signals X ₁ (t), X
₂ (t), weight vector W ₁₁ (t), W ₂₁ (t),
The temporary reception signal Y ₁ (t) and the extraction signal S _r1 (t) are
It has a phase and can be represented by a complex number.

Weight vectors W ₁₁ (t) and W ₂₁ (t)
, The weight vector control unit 27 minimizes the error between the reference signal d (t) and the extraction signal S _r1 (t) by the least mean square error method. So that within the predetermined range, W ₁₁ (t), W ₂₁
By varying and adjusting the value of (t),
W ₁₁ (t + 1) and W ₂₁ (t + 1) are calculated for each unit time.

[Equation 2] e (t) = d (t) -S
_{r1 (t) ≒ d (t} ) -Y 1 (t) = d (t) - (W
₁₁ (t) X ₁ (t) + W ₂₁ (t) X ₂ (t)) W ₁ (t + 1) and W ₂ (t + 1) are extracted signals S _r1 (t)
W ₁₁ (t) and W ₂₁ (t) are corrected so as to reduce the error e (t) between the reference signal d (t) and the reference signal d (t). The value of the weight vector converges to a constant value with the passage of time, and the extraction signal S _r1 (t) is accurate at the receiving stage of the main data, which is the communication content transmitted following the preamble, unique word, etc. Becomes After the communication is started, the value of the weight vector finally obtained in the previous reception time slot may be used as the initial value of the weight vector for the next reception time slot.

<Reception Response Vector Calculation Method> Next, the reception response vector calculation processing by the weight vector control unit 27 will be described using the above example. Between the signals S _{r1 ′} (t) and S _{r2 ′} (t) transmitted by the two mobile stations and the respective multiplexed signals X ₁ (t) and X ₂ (t), The relationship is established.

[Equation 3] X ₁ (t) = h ₁₁ S _{r1 ′} (t) +
h ₂₁ S _{r2 ′} (t) + n ₁ (t) [Equation 4] X ₂ (t) = h ₁₂ S _{r1 ′} (t) + h ₂₂ S
_{r2 ′} (t) + n ₂ (t) Note that h _ij is a complex number that represents the propagation path from the i-th mobile station to the j-th antenna, and is the first when n adaptive array antennas are used. The reception response vector corresponding to the i-th mobile station is generally h _i1 , h _i2 ,.
···, which is a vector H _i whose components are h _in . Also, n ₁
(T) and n ₂ (t) are noises.

User-specific signal processing section b of the radio base station 100
The extracted signal S _r1 (t) separated by 1 and the signal S _{r1 ′} (t) that is the signal transmitted by the first mobile station can properly receive the transmitted signal and perform separation and extraction appropriately. If so, they are equal. The weight vector control unit 27
Using the complex conjugate S _r1 ^* (t) of the extracted signal S _r1 (t) and the reception signals X ₁ (t) and X ₂ (t), the reception response is expressed by the following equations 5 and 6. The components h ₁₁ and h ₁₂ of the vector H ₁ are calculated.

[Equation 5] h ₁₁ = E [X ₁ (t) S _r1 ^* (t)] [Equation 6] h ₁₂ = E [X ₂ (t) S _r1 ^* (t)] Here, E is an ensemble It represents an average, and means an average value at t = 1, 2, ..., N for a certain period. For example, when n is 100, the average value in 100 symbol periods is calculated.

The extracted signals S _r1 (t) and S _r2 (t) are normally obtained, and the mobile station signals S _{r1 ′} (t) from the two mobile stations are obtained.
In a state where it can be regarded as equivalent to S _{r2 ′} (t), S _{r1 ′} (t) and S _{r2 ′} (t) are replaced with S _r1 (t) and S _r2 (t) in the equations 3 and 4, respectively. S on both sides
By multiplying _r1 ^* (t) and taking the ensemble average, the following equations 7 and 8 are obtained.

[Equation 7] E [X ₁ (t) S _r1 ^* (t)] =
E [h ₁₁ S _r1 (t) S _r1 ^* (t)] + E [h ₁₂ S
^{_{r2 (t) S r1 * (}} t)] + E [n 1 (t) S r1 * (t)] [ Number _{8] E [X 2 (t} ) S r1 * (t)] = E [h 21 S r1
(T) S _r1 ^* (t)] + E [h ₂₂ S _r2 (t) S
^{_{r1 * (t)] + E}} [n 2 (t) S r1 * (t)] where a _{E [S r1 (t) S} r1 * (t)] = 1, also essentially each mobile station Signal transmitted from S _{r1 ′} (t)
And S _{r2 ′} (t) have no correlation, and the signal S _{r1 ′} (t) has no correlation with the noise component, so E (S _r2 (t) S _r1
^* (T)) = 0, E [n ₁ (t) S _r1 ^* (t)] = 0, E
[N ₂ (t) S _r1 ^* (t)] = 0.

Therefore, from Equations 7 and 8, Equations 5 and 6
Can be derived. By this, the influence of the noise component is removed mathematically. The weight vector control unit 27 in the user-specific signal processing unit b1 calculates h ₁₁ and h ₁₂ by performing the calculations shown in Formulas 5 and 6, and calculates the reception response vector H ₁ including h ₁₁ and h ₁₂ as components. Calculate and DD
It is output to the R calculation unit 14. Similarly to output the DDR calculating unit 14 calculates the reception response vector H ₂ to H _n also each other user-specific signal processing unit B2～bn.

<DDR Calculation Method> The DDR calculation unit 14
Based on the two reception response vectors, for example, D ₁ / D ₂ which is the reception power level ratio of the _first mobile station to the second mobile station is calculated as shown in the following Expression 9. [Equation 9] D ₁ / D ₂ = | H ₁ | ² / | H ₂ | ² = (| h ₁₁ |
^{_{2 + | h 12 | 2)}} / (| h 21 | 2 + | h 22 | 2) the received power level ratio between two such mobile station is DDR.

For convenience of explanation, two components are used here.
However, in reality, m m
User-specific signal processing unit bi (i = 1, 2, ..., M)
Is h _i1, H_i2, H_i3, H_i4Received response vector containing
Tol H_iIs calculated and output to the DDR calculation unit 14,
The calculation unit 14 determines the reception time for each reception time slot.
Between the mobile stations that are multiplexed in
Ask for DDR. For example, if the DDR value is 1 or more
Therefore, the above D1 and D2 are determined and the DDR is calculated.
Therefore, the DDR calculation unit 14
Worst DDR which is the maximum value of DDR calculated by
The value is specified and the worst DDR value is sent to the control unit 6. Well
Also, the DDR calculation unit determines the received power level for each mobile station.
D₁, D₂Etc. and reception response vector H₁, H₂Etc. to the control unit 6
Send out.

<Threshold Table> The threshold table 20 used in the new channel allocation processing and the switching channel allocation processing by the communication channel allocation unit 15 will be described below. FIG. 3 is a diagram showing a configuration and an example of contents of the threshold table 20. The threshold table 20 is a table in which the multiplicity 510, the worst DDR threshold 520, and the worst correlation threshold 530 are associated with each other for two or more multiplicities, and the worst DDR threshold 520 and the worst correlation threshold 530 have default values. And the limit value are included.

The worst DDR threshold 520 is a threshold for comparison with the worst DDR value for the reception time slot, and when the worst DDR value is larger than the worst DDR threshold, the communication quality of a certain level in the reception time slot. It is presumed that cannot be maintained. The worst correlation threshold value 530 is a threshold value for comparison with the worst correlation value for the reception time slot, and when the worst correlation value is larger than the worst correlation threshold value, a certain level of communication quality cannot be maintained in the reception time slot. It is estimated that Here, the worst correlation value is the maximum value of the correlation values in all combinations when two of the mobile stations multiplexed in the reception time slot are combined, and the correlation value S is a set of each movement. It indicates the correlation between the reception response vectors of the stations, and is a value obtained by the following Expression 10.

[Equation 10] Correlation value S = (| H ₁ · H ₂ |)
/ (| H ₁ || H ₂ |) From this equation 10, the correlation value S between the first mobile station and the second mobile station is obtained. Here, the numerator of the fraction is the inner product of the received response vector H ₁ and H _2, the denominator is the product of the received response vector H ₁ and H ₂ each size. The worst DDR threshold 520 and the worst correlation threshold 530 are used for determining whether or not a certain transmission / reception time slot can be assigned to a certain mobile station, and the worst DDR value calculated by the measurement is the worst DDR. When it is larger than the threshold value, it is determined that the allocation is impossible, and when the worst correlation value calculated by the measurement is larger than the worst correlation threshold value, it is determined that the allocation is impossible. It should be noted that in the new channel allocation processing and the switching channel allocation processing, which will be described later, the allocation availability determination is performed using one of the default value and the limit value.

There are two levels of communication quality, a low level determined by a default value and a high level determined by a limit value. The low level is a level indicating that communication is possible, and the high level is a level indicating communication having a communication quality relatively higher than that of the low level. It should be noted that the default value and the limit value are numerical values obtained as a result of an experiment, which are predetermined as thresholds representing low level and high level, respectively, and are set in advance.

In the example shown in FIG. 3, for example, when the multiplicity is 2, for the worst DDR value, the default value indicates that if the worst DDR value is 15 dB or less, the communication quality is at a low level or higher. Depending on the limit value
If the worst DDR value is 11.25 dB or less, it indicates that the communication quality is at a higher level. It should be noted that the limit value being 0 means that it is determined that it is always impossible to assign when the assignability determination is performed using the limit value. Therefore, in the example of FIG. 3, when the multiplicity is 4, it is always determined that the allocation is impossible if the allocation availability determination is performed using the limit value.

<Operation> The new channel allocation processing and the switching channel allocation processing by the communication channel allocation unit 15 will be described below. The control unit 6 of the radio base station 100 causes the communication channel allocation unit 15 to perform a new channel allocation process that attempts to allocate a set of transmission / reception time slots to the mobile station in response to a new connection request from the mobile station, and When communication channel (TCH) switching is required for a mobile station that is already communicating, such as when the communication channel (TCH) needs to be switched, that mobile station has a set of transmission / reception times other than the original transmission / reception time slot. A switching channel allocation process that attempts to allocate a slot is performed, and according to the allocation result, the signal processing unit 3 and the like are controlled so that the mobile station communicates with other mobile stations in a specific transmission / reception time slot as a spatial multiplexing target. .

FIG. 4 is a flowchart showing a new channel allocation process by the communication channel allocation unit 15. When a connection request from a new mobile station is received using one transmission / reception time slot other than the communication channel or another control channel, the new channel allocation processing is performed by executing the software. However, if there is a transmission / reception time slot to which no mobile station is assigned, that is, if there is an empty transmission / reception time slot, the new transmission / reception time slot is assigned to the new mobile station,
The following processing is not performed.

First, the communication channel allocator 15 sets the number N of allocation trials, which is a variable for controlling the number of allocation trials, to 0.
(Step S11), the multiplicity and the worst DDR value for each transmission / reception time slot are calculated, and the minimum multiplicity M is calculated (step S12). The multiplicity of each transmission / reception time slot is recorded in the memory 16 by the control unit 6 for each transmission / reception time slot, and the recorded content is updated whenever the allocation is changed. Further, the worst DDR value in each reception time slot, the reception response vector for each mobile station, and the reception power level are received by the control unit 6 from the DDR calculation unit 14 and stored in the memory 16.
It is recorded inside. Therefore, step S12 is realized by acquiring the required multiplicity and the worst DDR value from the memory 16 and specifying the minimum value among the multiplicities.

Subsequent to step S12, the communication channel allocator 15 determines the order of performing the new allocation availability determination for each transmission / reception time slot by giving priority to the one with the highest multiplicity, and at this time, the transmission / reception with the same multiplicity. As for the time slot, the corresponding one having the smallest worst DDR value is preferentially determined (step S13). Communication channel allocation unit 15
Stores information indicating the determined priority in the memory 16 for each transmission / reception time slot.

Then, the communication channel allocation unit 15 focuses on the transmission / reception time slot of the first order (step S1).
4) It is determined whether or not the multiplicity of the transmission / reception time slot of interest is greater than the minimum multiplicity M, and if it is larger, a threshold table is used to determine whether or not the transmission / reception time slot of interest can be assigned to the new mobile station. The determination is made using the limit values for the worst DDR threshold and the worst correlation threshold within 20 (step S16), and if not large, it is determined whether the transmission / reception time slot of interest can be assigned to the new mobile station.
The determination is performed using the default values for the worst DDR threshold and the worst correlation threshold in the threshold table 20 (step S
17).

In step S16 or S17, the communication channel allocation unit 15 determines the reception power level and the reception response vector of the new mobile station calculated by the DDR calculation unit 14 in one transmission / reception time slot other than the communication channel. The worst DDR value and the worst correlation value related to the transmission / reception time slot when the transmission / reception time slot of interest is assigned to the new mobile station are obtained by using Whether or not the allocation is possible is performed by comparing each threshold value which is the limit value or the default value in the threshold table 20.

When it is determined that the allocation is possible (step S18) as a result of the allocation availability determination in step S16 or step S17, the communication channel allocation unit 15 allocates the transmission / reception time slot of interest to the new mobile station ( In step S23), the new channel allocation process ends. As a result, the control unit 6 transmits information indicating the allocation result to the new mobile station through the control channel so as to communicate with the new mobile station using the allocated transmission / reception time slot.

Further, step S16 or step S17
If it is determined that the allocation is impossible, the communication channel allocation unit 15 determines that the allocation trial number N is
It is determined whether or not the number of transmission / reception time slots that can be used as a communication channel is less than or equal to a predetermined trie threshold value (step S1).
9) If it is not smaller, error processing is performed to inform the control unit 6 that allocation is not possible (step S22), and the new channel allocation processing ends. As a result, the control unit 6 transmits the information indicating that the connection is impossible to the new mobile station through the control channel.

If, in step S19, the number N of allocated tries is smaller than the threshold value of the tries, the communication channel allocation unit 15 increases the number N of allocated tries by 1 (step S19).
20), based on the information indicating the priorities stored in the memory 16, pay attention to the transmission / reception time slot of the next order (step S21), and the process returns to step S15. With such a new channel allocation process, it is determined that the new mobile station can be allocated to the transmission / reception time slot of the lowest multiplicity, if the communication quality of the low level is satisfied. In the assignment availability judgment of whether or not it can be assigned to the transmission / reception time slot of higher multiplicity, it is not determined that it can be assigned unless the communication quality of a high level is satisfied. Considering the fact that it is technically difficult to separate and extract the signals of each mobile station when the multiplicity of the mobile stations can be suppressed to a certain extent and the multiplicity is high, this will eventually result in an incommunicable state in the future. It can be understood that the increase in the number of mobile stations that fall into the range can be suppressed to some extent.

FIG. 5 is a flowchart showing the switching channel allocation processing by the communication channel allocation unit 15. When there is a mobile station that requires TCH switching due to deterioration of communication quality (hereinafter referred to as “switch target mobile station”),
This switching channel allocation processing is performed by executing the software. However, if there is a transmission / reception time slot to which no mobile station is assigned, that is, if there is a vacant transmission / reception time slot, the vacant transmission / reception time slot is assigned to the switching target mobile station. Not done.

First, the communication channel allocator 15 sets the number N of allocation trials, which is a variable for controlling the number of allocation trials, to 0.
(Step S31), and the multiplicity and worst DDR value for each transmission / reception time slot are obtained (step S32). However, the worst DDR value of the transmission / reception time slot (hereinafter referred to as “original slot”) to which the switching target mobile station was originally assigned is calculated excluding the switching target mobile station. This step S32 is performed by the memory 16
From the memory 16 and the received power level of each mobile station other than the switching target mobile station in the original slot, and based on this, the worst DDR value related to the original slot. It is realized by calculating

Subsequent to step S32, the communication channel allocating unit 15 determines the order of determining whether or not allocation is possible for each transmission / reception time slot other than the original time slot, preferentially the one with the highest multiplicity. For the same transmission / reception time slot having the same number, the corresponding one having the smallest worst DDR value is preferentially determined (step S33). The communication channel allocation unit 15 stores information indicating the determined priority order in the memory 16 for each transmission / reception time slot.

Then, the communication channel allocation unit 15 focuses on the transmission / reception time slot of the first order (step S3).
4) Compare the multiplicity of the transmission / reception time slot of interest + 1, that is, the multiplicity of the transmission / reception time slot of interest with the post-switching assumption, and the multiplicity of the original slot (step S35) to assume the post-switching When the multiplicity of the transmission / reception time slot of interest in the case is larger than the multiplicity of the original slot, the switching target mobile station
Whether or not the transmission / reception time slot of interest can be assigned is determined using the limit values for the worst DDR threshold and the worst correlation threshold in the threshold table 20 (step S3
8) On the contrary, if the multiplicity of the transmission / reception time slot of interest is smaller than that of the original slot in the case after switching, it is possible to allocate the transmission / reception time slot of interest to the switching target mobile station. Whether or not it is determined using the default values for the worst DDR threshold and the worst correlation threshold in the threshold table 20 (step S39).

Further, in step S35, when the multiplicity of the transmission / reception time slot of interest and the multiplicity of the original slot are equal when the post-switching is assumed,
The communication channel assigning unit 15 obtains the worst DDR value related to the transmission / reception time slot on the assumption that the transmission / reception time slot of interest is assigned to the switching target mobile station (step S36), and the worst of the original slot obtained in step S32. It is determined whether or not the DDR value is smaller than the worst DDR value related to the transmission / reception time slot calculated in step S36 (step S37), and if smaller, determination of allocation availability using the limit value in step S38 as a threshold value. Process, if not small, step S
Allocation availability determination processing is performed using the default value of 39 as the threshold value.

In step S36, the communication channel allocation unit 15 focuses on the switching target mobile station using the reception power level of the switching target mobile station calculated by the DDR calculation unit 14 in the original slot. The worst DDR value related to the transmission / reception time slot is calculated assuming that the transmission / reception time slot is assigned. When it is determined that the allocation is possible as a result of the allocation availability determination in step S38 or step S39 (step S40),
The communication channel allocation unit 15 allocates the transmission / reception time slot of interest to the switching target mobile station (step S
45), and ends the switching channel allocation process. As a result, the control unit 6 transmits information indicating the allocation result to the switching target mobile station through the control channel so that communication is performed using the allocated transmission / reception time slot.

Further, step S38 or step S39
If it is determined that the allocation is impossible, the communication channel allocation unit 15 determines that the allocation trial number N is
It is determined whether or not the number of transmission / reception time slots that can be used as a communication channel is -1 or less, or less than a predetermined trie threshold (step S41). If not, allocation is determined. An error process is performed to inform the control unit 6 that it is not possible (step S4
4) The switching channel allocation processing is ended. in this case,
The control unit 6 does not control the TCH switching for the switching target mobile station because it is less likely to cause a communication disconnection than when switching the transmission / reception time slot assigned to the switching target mobile station.

If, in step S41, the number N of assigned tries is smaller than the threshold of tries, the communication channel assigning unit 15 increases the number N of assigned tries by 1 (step S41).
42), based on the information indicating the priorities stored in the memory 16, pay attention to the transmission / reception time slot of the next order (step S43), and return to the process of step S35. By such switching channel allocation processing, the mobile station to be switched is
In the assignment availability judgment of whether or not it can be assigned to the transmission / reception time slot of the multiplicity lower than the original slot, it is determined that it can be assigned if the communication quality of the low level is satisfied, but to the transmission / reception time slot of the multiplicity higher than the original slot. In the assignment availability determination of whether or not it can be assigned, it is not determined as assignable unless a high level communication quality is satisfied, and as a result, the dispersion of the multiplicity between the transmission and reception time slots after the assignment is suppressed to some extent. As a result, it is possible to suppress the increase in the number of mobile stations that will be in a communication impossible state in the future to some extent.

<Supplement> The radio base station according to the present invention has been described above based on the embodiment, but it goes without saying that the present invention is not limited to this embodiment. That is, (1) In the present embodiment, the wireless base station and the mobile station in the PHS system have been described as examples, but the present invention is not limited to the PHS system, and any communication system that employs the spatial multiplexing method can be used as described above. It is possible to use a control method related to allocation of various communication channels.

(2) In the present embodiment, the worst DDR is used to determine whether or not the transmission / reception time slot can be assigned to the mobile station.
Calculate the index and the worst correlation value based on the measured values,
Although it was decided to compare with the threshold, the index used for the allocation availability determination is not limited to these, for example, using the indices such as fading rate, received power level, transmission timing difference, instantaneous error, the threshold is determined in advance. Alternatively, each index value may be calculated based on the measured value, and each index value may be compared with each threshold value to determine whether or not allocation is possible. Here, the fading speed is an index indicating the correlation between the past reception response vector of the mobile station and the current reception response vector, and the transmission timing difference is a timing at which the radio base station slightly transmits the transmission timing to each mobile station. The difference between the transmission timings when the communication is performed with a shift is made, and the instantaneous error is the number of times of data error detection within a predetermined unit time in the near past.

(3) In the switching channel allocation processing shown in this embodiment, the default value is set when the multiplicity is larger than that of the original slot after the allocation of the transmission / reception time slot of the allocation availability determination target is assumed. By using the limit value, which is a stricter judgment condition, as the threshold,
Compared with the case where the transmission / reception time slot of the allocation availability judgment target after allocation is smaller than the original slot and the multiplicity is smaller than that of the original slot, it is decided that allocation is possible only when the communication quality at a higher level is satisfied. However, in addition to this, as in step S15 of the new channel allocation processing, the multiplicity of the transmission / reception time slot of the allocation availability determination target is
If the multiplicity of the transmission / reception time slots excluding the original slot is greater than the lowest multiplicity, the limit value is used as a threshold value to determine whether or not allocation is possible. In this case, it may be possible to use the default value as a threshold value to determine whether or not allocation is possible.

Further, in the switching channel allocation processing and the new channel allocation processing, when the multiplicity of the transmission / reception time slot of the allocation availability determination is larger than the predetermined fixed value of 3 etc., the limit value is used as the threshold value. It is also possible to determine whether the allocation is possible or not, and if it is smaller than the predetermined value, use the default value as a threshold value to make the determination of allocation.

(4) In the threshold value table 20 illustrated in FIG. 3 in the present embodiment, if the multiplicity is 4, the limit value is 0, and the limit value is a threshold value. Although the allocation is prohibited in such a case that the limit value is disabled and the limit value is substantially applied, the content example of FIG. 3 is merely an example. May be set to 0, or a value larger than 0 may be used as the threshold even when the multiplicity is 4.

(5) In the new channel allocation processing and the switching channel allocation processing shown in this embodiment, the transmission / reception time slot having a high multiplicity is selected from the viewpoint of efficiency in determining the order of the allocation availability determination. Prioritize
Worst case for transmit / receive time slots with equal multiplicity D
Although the one with the smaller DR value is prioritized, for example, between the transmission / reception time slots having the same multiplicity, the one with a smaller serial number predetermined for the transmission / reception time slots may be prioritized. The order may be determined only by the serial number regardless of the worst DDR value.

(6) Steps S36 and S37 in the switching channel allocation processing shown in this embodiment are omitted,
When the multiplicity of the transmission / reception slot of interest + 1 and the multiplicity of the original slot are equal, the process of step S38 may be performed, or the process of step S39 may be performed. (7) A computer program for causing the CPU in the wireless base station to execute the new channel allocation processing or the switching channel allocation processing by the communication channel allocation unit 15 shown in the present embodiment is recorded in a recording medium or various communication channels. It can also be distributed and distributed via the Internet. Such recording media include IC cards, optical disks, flexible disks, ROMs and the like. The distributed and distributed computer program is used by being recorded in a memory or the like of the wireless base station, and the CPU of the wireless base station executes the computer program to allocate a new channel as shown in this embodiment. A process or a switching channel allocation process is realized.

[0079]

As is apparent from the above description, the communication channel assigning apparatus according to the present invention uses a time division multiplexing method and a spatial multiplexing method for allocating any of a plurality of time slots to a mobile station. A time slot provided in a radio base station that wirelessly communicates with a station, and for each of one or more time slots, the time slot is assumed to be assigned to the mobile station in order to determine the time slot to be assigned to the mobile station. Based on the evaluation value indicating the communication quality according to the above, it is determined whether the time slot can be assigned to the mobile station, and the time slot is assigned to the mobile station. Then, the degree of non-uniformity among the time slots of the number of mobile stations assigned to all time slots When will increase, and not than when increasing, and performs so as to suppress the determination that the assignable.

As a result, when the number of mobile stations allocated to the time slot such as the transmission / reception time slot, that is, the variation in the multiplicity among the time slots increases, the allocation availability judgment is performed in a higher level than in other cases. Since it is determined whether or not allocation is possible by a restraint determination method such as comparison using a strict threshold equivalent to the communication quality of, when performing allocation according to the result of the allocation determination, It is possible to suppress to some extent an increase in the degree of non-uniformity of the multiplicity of the above.

It should be noted that suppressing the degree of unevenness of the multiplicity among the time slots leads to suppressing the multiplicity in each time slot to be low. By the way, the multiplicity is different from the worst DDR value and other indicators relating to communication quality in that it does not change over time unless the communication channel allocation is changed. Note that, for example, the worst DDR
The value can be changed by the movement of the mobile station or can be improved by the transmission power control of the radio base station. In addition, the higher the degree of multiplexing, the more difficult it is technically to separate and extract the signals of each mobile station.

From these points of view, from a comprehensive and long-term perspective, the multiplicity is considered to be a factor that exerts a particularly great influence on the communication quality, and when a new connection is made or TCH switching is required, communication channel allocation is performed. As a result, the present invention that suppresses the multiplicity in each time slot to a low level
The effect of suppressing the increase in the number of mobile stations that will be unable to communicate in the future to some extent is obtained.

The radio base station according to the present invention is a radio base station that wirelessly communicates with a plurality of mobile stations by a time division multiplexing method and a spatial multiplexing method in which any of a plurality of time slots is assigned to the mobile station. For each of the one or more time slots, the time slot is allocated based on the evaluation value indicating the communication quality of the time slot when it is assumed that the time slot is allocated to one mobile station that requires allocation. A deciding means for deciding whether or not it can be assigned to a mobile station, and an allocating means for allocating one time slot determined by the deciding means to be allocable to one mobile station requiring the allocation. And the determining means determines whether or not the time slot can be assigned to the mobile station assigned to the time slot. The total number, when greater than a predetermined reference number, than when less than a predetermined reference number, and carrying out to suppress the determined assignable with.

As a result, the determination as to whether or not a time slot with a high degree of multiplicity can be assigned is performed by a restraint determination such as comparison using a strict threshold value corresponding to a higher communication quality than the determination as to whether or not a time slot with a low degree of multiplicity can be assigned. As a result, the multiplicity in each time slot can be suppressed to a low level, and the increase in the number of mobile stations that will be in a communication-disabled state in the future when a new connection is made or when TCH switching is required is suppressed to some extent. The effect is obtained.

Further, the one mobile station requiring the allocation is a mobile station which newly starts communication with the radio base station, and the judging means is the mobile station allocated to the time slot among all the time slots. The allocation availability determination may be performed after the total number of timeslots having the smallest total number is determined as the predetermined reference number.

As a result, at the time of new connection, the tendency is that the time slot with the lowest multiplicity is assigned to the new mobile station, and the increase in the number of mobile stations that will be in the incommunicable state in the future due to the addition of new mobile stations is suppressed to some extent. The effect is obtained. Also, the radio base station, by measurement, a data acquisition unit that acquires data as a basis for calculating the evaluation value indicating the communication quality of communication with a mobile station in a certain time slot, and a comparison target with the evaluation value. As the first
And a second threshold value representing a second communication quality higher than the first communication quality in advance, and the determination means is acquired by the data acquisition means. The evaluation value is calculated from the data obtained, and based on the evaluation value, the assignment permission / inhibition determination for the time slot is performed, and in the assignment permission / inhibition determination, when the total number of mobile stations related to the time slot is larger than a predetermined reference number. The suppression of determining that the allocation is possible is performed by comparing the evaluation value of the time slot with the second threshold value and determining that the allocation is possible only when the second communication quality is satisfied, If the total number of mobile stations related to the time slot is less than or equal to a predetermined reference number, the evaluation of the time slot and the first threshold value are compared to determine whether or not to perform the first communication. May be performed by determining only assignable and if it meets the quality.

As a result, two types of thresholds, that is, a threshold for requesting high communication quality and a threshold for requesting low communication quality, are used in advance as thresholds used for comparison with the index indicating communication quality in the determination of availability of allocation at the time of new connection. If it is determined based on the experimental result, it becomes possible to easily control the time slot allocation with an emphasis on multiplicity. Further, a radio base station according to the present invention is a radio base station that wirelessly communicates with a plurality of mobile stations by a time division multiplexing method that allocates any of a plurality of time slots to a mobile station, and a spatial multiplexing method,
For each of the one or more time slots, based on the evaluation value indicating the communication quality related to the time slot when it is assumed that the time slot is assigned to one mobile station that requires communication channel switching, A determination unit that determines whether or not it can be assigned to a mobile station, and one time slot that is determined to be assignable by the determination unit is assigned to one mobile station that requires the communication channel switching. Allocation means, the determination means, the total number of mobile stations allocated to the time slot in the case of the allocation availability determination of the time slot, the one mobile station requiring the communication channel switching Greater than the total number of assigned mobile stations in the originally assigned timeslot Sometimes, than when smaller total number of mobile station according to the original time slots, and performs so as to suppress the determined assignable with.

As a result, when TCH switching is required,
It is possible to suppress to some extent an increase in the degree of multiplicity unevenness after TCH switching compared to before TCH switching, and as a result, to some extent suppress the situation in which the number of mobile stations that will fall into a communication-disabled state in the future increases. To be Further, the determination means is further configured such that the total number of mobile stations assigned to the time slot in the case where the assignment availability determination for the time slot is assumed is based on one mobile station requiring the communication channel switching. When it is equal to the total number of allocated mobile stations in the allocated time slot, the first worst DDR value, which is the maximum value of the difference in the received power level between the mobile stations in the allocated time slot in the above-mentioned case, is If it is larger than the second worst DDR value in the original time slot, the same suppression as the above suppression may be performed.

As a result, the TCH switching can prevent the switching to the direction in which the communication condition is worse than that before the switching to some extent, and as a result, the number of mobile stations which will be in the communication disabled state in the future is increased. The effect of suppressing to some extent can be obtained. Also, the radio base station, by measurement, a data acquisition unit that acquires data as a basis for calculating the evaluation value indicating the communication quality of communication with a mobile station in a certain time slot, and a comparison target with the evaluation value. And a storage unit that stores in advance a first threshold value representing the first communication quality and a second threshold value representing the second communication quality higher than the first communication quality. The evaluation value is calculated from the data acquired by the acquisition means, the allocation availability determination is performed for the time slot based on the evaluation value, and in the allocation availability determination, the mobile station related to the time slot in the case of the assumption. Is greater than the total number of mobile stations in the original time slot, the suppression of determining that allocation is possible is It is performed by comparing the evaluation value related to the mobile slot with the second threshold value and determining that the allocation is possible only when the second communication quality is satisfied, and the allocation availability determination is performed on the time slot in the case where the assumption is made. When the total number of such mobile stations is smaller than the total number of mobile stations related to the original time slot, the first threshold is compared by comparing the evaluation value related to the assumed time slot with the first threshold, and the first communication quality is satisfied. Only in such a case, it may be determined by determining that allocation is possible.

As a result, two types of thresholds, a threshold requesting a high communication quality and a threshold requesting a low communication quality, are used as the thresholds used for comparison with the index indicating the communication quality in the determination of allocation availability when TCH switching is required. If it is determined in advance based on the experimental result, it is possible to determine whether or not the allocation is possible by switching between the two types of thresholds according to the multiplicity and the like, so that it is possible to easily control the time slot allocation with an emphasis on the multiplicity. Become.

Further, the determining means further determines, when the total number of mobile stations assigned to the time slot in the case of the assumption is higher than a predetermined number in the assignment availability determination of the time slot, the time slot is assigned. It may be determined to be impossible. As a result, it becomes impossible to switch to a certain degree of multiplicity at the time of TCH switching, so that it is possible to prevent, to some extent, the mobile station already in communication from becoming incommunicable due to TCH switching.

The evaluation value related to the time slot may be the worst DDR value which is the maximum difference in the received power levels among the mobile stations assigned to the time slot. As a result, by comparing the worst DDR value, which is an index that affects communication quality, with a predetermined threshold value, it becomes possible to perform the allocation availability determination so as to obtain a preferable result in terms of communication quality.

Further, the determining means may suppress the determination that the allocation is possible in the allocation availability determination for the time slot by determining that the allocation is impossible without determining the allocation possible. . As a result, allocation cannot be performed at a relatively high multiplicity,
It becomes possible to prevent the mobile station which is already in communication from becoming incommunicable to some extent.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a radio base station 100 according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a user-specific signal processing unit b1.

FIG. 3 is a diagram showing a configuration and an example of contents of a threshold table 20.

FIG. 4 is a flowchart showing a new channel allocation process by the communication channel allocation unit 15.

5 is a flowchart showing a switching channel allocation process by the communication channel allocation unit 15. FIG.

[Explanation of symbols]

1a1 to 1an Adaptive array antenna 2a1-2an wireless unit 3 Signal processing unit 4 Modem section 5 Baseband section 6 control unit 11 Transmitter 12 Receiver 14 DDR calculator 15 Communication channel allocation unit 16 memory 20 threshold table 26 Judgment section 27 Weight vector controller 100 wireless base stations

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeo Miyata             1-1 Sanyo-cho, Daito-shi, Osaka Sanyo Teleco             Communications 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) 5K022 FF00                 5K028 AA02 AA11 BB06 CC05 DD01                       DD02 LL02 RR01                 5K067 AA23 BB04 BB21 CC01 CC04                       DD11 DD42 EE02 EE10 GG03                       HH11 HH22 JJ02 JJ12 JJ17                       JJ21 JJ74

Claims (13)

[Claims] 1. A time slot to be assigned to a mobile station, which is provided in a radio base station that wirelessly communicates with a plurality of mobile stations by a time division multiplexing method and a spatial multiplexing method for allocating any of a plurality of time slots to the mobile station. For each of the one or more time slots, the time slot is assigned to the mobile station based on an evaluation value indicating the communication quality of the time slot assuming that the time slot is assigned to the mobile station. If the time slot is assigned to the mobile station, the number of mobile stations assigned to each time slot is not determined in the time slot. When the degree of uniformity increases, it is determined that it can be allocated rather than when it does not increase. A communication channel allocating device, characterized in that 2. A radio base station that wirelessly communicates with a plurality of mobile stations according to a time division multiplexing method and a spatial multiplexing method, in which any one of a plurality of time slots is assigned to the mobile station. , Whether it is possible to allocate the time slot to the mobile station based on the evaluation value indicating the communication quality related to the time slot when it is assumed that the time slot is allocated to one mobile station requiring allocation. And a allocating unit that allocates one time slot determined to be allocable by the deciding unit to one mobile station that requires the allocating, the deciding unit, In the assignment availability judgment for the time slot, the total number of mobile stations assigned to the time slot is larger than a predetermined reference number. A radio base station, characterized in that the determination that allocation is possible is performed more occasionally than when the number is equal to or less than a predetermined reference number. 3. The one mobile station that requires the allocation is a mobile station that newly starts communication with a radio base station, and the determination unit is a mobile station that is allocated to the time slot among all the time slots. 3. The radio base station according to claim 2, wherein the allocation availability determination is performed after the total number of timeslots having the smallest total number is determined as the predetermined reference number. 4. The data acquisition unit, which obtains data as a basis for calculating the evaluation value indicating the communication quality of communication with a mobile station in a certain time slot by measurement, the evaluation value, and And a storage unit that stores in advance a first threshold value that represents the first communication quality and a second threshold value that represents the second communication quality that is higher than the first communication quality. , Calculating the evaluation value from the data acquired by the data acquisition means, based on the evaluation value, to determine the allocation availability of the time slot, in the allocation availability determination, the total number of mobile stations related to the time slot Is greater than a predetermined reference number, the suppression of the determination that the allocation is possible is performed by comparing the evaluation value of the time slot with the second threshold to determine the second communication quality. If the total number of mobile stations related to the time slot is less than or equal to a predetermined reference number, then the evaluation value and the first threshold value related to the time slot are determined. 4. The radio base station according to claim 3, wherein the radio base station is compared with the radio base station and is determined to be allocatable only when the first communication quality is satisfied. 5. A radio base station that wirelessly communicates with a plurality of mobile stations by a time division multiplexing method and a spatial multiplexing method, in which any one of a plurality of time slots is assigned to the mobile station, and for each of one or more time slots. , It is possible to assign the time slot to the mobile station based on the evaluation value indicating the communication quality of the time slot assuming that the time slot is assigned to one mobile station that requires communication channel switching. A determination unit that determines whether or not allocation is possible, and an allocation unit that allocates one time slot determined to be allocatable by the determination unit to one mobile station that requires the communication channel switching, The determining means assigns the assignment availability determination for the time slot to the time slot in the case where the assumption is made. When the total number of assigned mobile stations is larger than the total number of assigned mobile stations in the time slot to which one mobile station that requires the communication channel switching was originally assigned, the movement related to the original time slot is moved. A radio base station, characterized in that the determination that allocation is possible is performed more than when the total number of stations is smaller. 6. The determination means is further configured such that the total number of mobile stations assigned to the time slot in the case where the assignment availability determination for the time slot is assumed is one mobile station requiring the communication channel switching. When the total number of allocated mobile stations in the originally allocated time slot is equal to, the first worst DDR, which is the maximum difference in the received power level between the mobile stations in the allocated time slot in the above-mentioned case
The value is the second worst DD in the original timeslot
The radio base station according to claim 5, wherein if it is larger than the R value, the same suppression as the suppression is performed. 7. The radio base station obtains data, which is a basis for calculation of the evaluation value indicating communication quality of communication with a mobile station in a certain time slot, by measurement, the evaluation value, And a storage unit that stores in advance a first threshold value that represents the first communication quality and a second threshold value that represents the second communication quality that is higher than the first communication quality. , Calculating the evaluation value from the data acquired by the data acquisition means, based on the evaluation value, the allocation availability determination for the time slot, in the allocation availability determination, the time slot in the case of the assumption When the total number of such mobile stations is larger than the total number of mobile stations related to the original time slot, the suppression of determining that the allocation is possible is based on the above assumption. Evaluation value and the second according to that the time slot
It is determined by comparing with a threshold value that allocation is possible only when the second communication quality is satisfied, and the allocation availability determination is based on the above-mentioned assumption that the total number of mobile stations related to the time slot is the original one. When it is smaller than the total number of mobile stations related to the time slot, it is determined that the allocation is possible only when the first communication quality is satisfied by comparing the evaluation value related to the time slot in the above-described case with the first threshold value. The wireless base station according to claim 5, wherein 8. The determination means further determines, in the assignment availability determination of a time slot, if the total number of mobile stations assigned to the time slot in the case of assumption is higher than a predetermined number, the time slot is assigned. The radio base station according to claim 7, wherein the radio base station is determined to be impossible. 9. The evaluation value related to a time slot is a worst DDR value which is the maximum value of the difference in received power levels between mobile stations assigned to the time slot. The described wireless base station. 10. The determination means, in the assignment availability determination of a time slot, suppresses the determination that the allocation is possible by determining that the allocation is not possible without determining that the allocation is possible. Claim 2 or 5
The described wireless base station. 11. A CP in a radio base station that wirelessly communicates with a plurality of mobile stations by a time division multiplexing method and a spatial multiplexing method for allocating any of a plurality of time slots to the mobile station.
A computer program for causing U to perform a communication channel allocation control process, wherein the communication channel allocation control process is performed for one or more time slots in order to determine a time slot to be allocated to a mobile station. Allocation availability determination processing for determining whether or not the time slot can be assigned to the mobile station based on an evaluation value indicating the communication quality of the time slot when the slot is assigned to the mobile station. In the assignment availability determination process for a time slot, if the time slot is assigned to the mobile station, the degree of non-uniformity between the time slots of the number of mobile stations assigned to each time slot increases. Suppress the determination that allocation is possible when Computer program, characterized in that it comprises a control that. 12. The assignment availability determination process for a time slot is performed by calculating the total number of mobile stations assigned to each time slot when the total number of mobile stations assigned to the time slot is larger than a predetermined reference number. The computer program according to claim 11, further comprising control for treating that the degree of non-uniformity is increased and suppressing the determination that the allocation is possible than when the number is less than or equal to a predetermined reference number. 13. The communication channel allocation control process is a process for determining a time slot to be allocated to one mobile station that requires communication channel switching, and the time slot is defined for each of one or more time slots. The allocation availability determination processing for a time slot includes an allocation availability determination processing for determining whether it is possible to assign to one mobile station that requires communication channel switching, and the allocation availability determination processing for a time slot is assigned to the time slot in the case where the assumption is made. When the total number of mobile stations associated with the original time slot is greater than the total number of assigned mobile stations in the time slot originally assigned to the one mobile station requiring the communication channel switching, the total number of mobile stations related to the original time slot. It includes a control that suppresses the determination that allocation is possible than when it is smaller. According to claim 11 of a computer program to.