JP3863792B2 - Wireless base station, communication method, and computer program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio base station that communicates with a plurality of terminal stations using a spatial multiplexing method, a communication method, and a computer program for realizing the radio base station, and more particularly to a technique for improving communication quality.
[0002]
[Prior art]
In recent years, with the increase of wireless information terminals including mobile phones, portable information communication devices, etc., social demands for effective use of frequency resources are increasing. There is a spatial multiplexing method as a technology that meets this demand.
The spatial multiplexing scheme is a scheme in which a radio base station performs communication at the same time with a plurality of terminal stations that exist in different directions on a carrier wave of the same frequency using an antenna having directivity.
[0003]
As an antenna having directivity used in this spatial multiplexing system, there is an adaptive array device. The adaptive array device includes a plurality of antenna elements fixedly installed, and dynamically changes the amplitude and phase of a transmission / reception signal for each antenna element, thereby directing the antenna as a whole for transmission and reception. Pattern (also referred to as an array antenna pattern).
[0004]
The adaptive array device not only increases the transmission intensity and reception sensitivity in the direction of the desired terminal station, but also decreases the transmission intensity and reception sensitivity in the direction of other terminal stations that are spatially multiplexed. Also do it.
The principle and operation of the adaptive array device are described in detail in “Adaptive signal processing by array antenna” (Nobuyoshi Kikuma, published by Science and Technology Publishing).
[0005]
In a conventional radio base station that communicates using a spatial multiplexing scheme, an adaptive array device including N antenna elements is controlled using a minimum mean square error (MMSE) scheme, and directivity during reception and transmission The contents of control when forming a pattern will be described.
The directivity pattern during reception is controlled so that the target signal obtained by adding after changing the amplitude and phase of the signal received through each antenna element is the received signal from the desired terminal station. In addition, it is control for finding an appropriate amount of change (also called weight).
[0006]
FIG. 9 is a conceptual diagram showing the contents of the control.
[Equation 1] y (t) = W (t−1) × X (t) = w ₁ (T-1) × x ₁ (T) + w ₂ (T-1) × x ₂ (T) + ... + w _N (T-1) × x _N (T)
Where t is time and x ₁ (T), x ₂ (T), ..., x _N (T) is a received signal actually obtained through each antenna element at each time, w ₁ (T-1), w ₂ (T-1), ..., w _N (T-1) is a weight corresponding to each antenna element at each time.
[0007]
The received signal and the weight are both analytical expressions (complex numbers), and the complex multiplication of both represents an operation for changing the amplitude and phase of the received signal. The time may be, for example, an elapsed time in a time slot in units of time for receiving one symbol in “Second Generation Cordless Telephone System Standard STD-28” (issued by the Japan Radio Industry Association). . The standard is hereinafter abbreviated as “PHS standard”.
[0008]
W (t) = [w ₁ (T), w ₂ (T), ..., w _N (T)] is a received signal vector whose element is a received signal for each antenna, and X (t) = [x ₁ (T), x ₂ (T), ..., x _N (T)] ^T Is a weight vector having a weight for each antenna as an element, and both are complex vectors.
The target signal y (t) is sequentially calculated by multiplying the received signal vector at each time by the weight vector at the immediately preceding time according to Equation 1.
[Equation 2] e (t) = d (t) −y (t) = d (t) −W (t−1) × X (t) where d (t) is a transmission sent from the terminal station. Of the signal, the signal content is defined in advance, for example, a signal of a preamble or a unique word for synchronization (UW: Unique Word) defined in the PHS standard (hereinafter referred to as “reference signal”), e (t) is an error at each time between the calculated target signal and the reference signal.
[0009]
A predetermined initial value is determined for the weight vector, and is corrected within a predetermined range so that the error calculated according to Equation 2 is minimized at each time. Theoretically, over time, the weight vector converges to a constant value, and the target signal y (t) is a signal transmitted by the desired terminal station.
Since the preamble and unique word constituting the reference signal are sent prior to the main data that is the communication content, the target signal obtained at the time of reception of the main data that is the communication content is the signal transmitted by the desired terminal station. Approximate.
[0010]
Note that after the communication is started, for example, a value finally obtained in the previous time slot may be used as the initial value of the weight vector in each time slot.
The directivity pattern control during transmission is performed by distributing the transmission signal to the desired terminal station to each antenna element, and assigning the final weight vector corresponding to each antenna element obtained during reception to the distributed signal. The content is that the signals obtained by the multiplication are transmitted simultaneously from the respective antenna elements. As a result, the directivity is directed toward the desired terminal station and a transmission gain is obtained, and interference signals transmitted toward the undesired terminal station are reduced.
[0011]
As described above, the conventional radio base station using the spatial multiplexing scheme, when receiving, adjusts a weight vector based on a signal received through a plurality of antenna elements and a reference signal such as a preamble or a unique word while receiving a desired terminal station. In the transmission, the directivity is directed to the desired terminal station using the weight vector at the time of transmission, thereby preventing interference and communicating with each terminal station while maintaining communication quality.
[0012]
In the above-described directivity pattern control, any terminal station transmits a common unique word defined in the PHS standard. Therefore, in rare cases, when reception timings from a plurality of terminal stations completely match, There is a problem that a wrong directivity pattern is formed by mistaking the received signals from the terminal stations.
In order to avoid this problem, a method in which individual terminal stations transmit individual unique words different from each other (hereinafter referred to as “individual UW method”) has been implemented.
[0013]
When a radio base station that communicates according to the individual UW method is requested to start communication using a control channel from a terminal station, an individual unique word that is not notified to other terminal stations is also transmitted using the control channel. Notify the new terminal station. The new terminal station transmits the notified unique word in the communication channel.
The cooperation between the radio base station and the terminal station adopting the individual UW scheme eliminates the mistaken reception signals when the reception timings from the respective terminal stations completely match.
[0014]
[Problems to be solved by the invention]
However, at present, since an individual UW terminal station and a common UW terminal station that transmits a common unique word defined in the PHS standard are used side by side, an actual wireless base station is used. A station needs to communicate with both of its terminal stations using a spatial multiplexing scheme.
[0015]
However, a radio base station adopting the above-described prior art individual UW system includes both an individual UW terminal station (abbreviated as an individual UW station) and a common UW terminal station (abbreviated as a common UW station). However, there is a problem that the directivity pattern may not be formed accurately when communicating with each other.
As an example, the conventional radio base station is not prevented from notifying one of the terminal stations that communicate using the spatial multiplexing method of the common unique word defined in the PHS standard, and thus is notified of the unique word. There is a problem that the received signals are mixed between the individual UW station and the common UW station.
[0016]
As another example, when a conventional radio base station performs communication using the spatial multiplexing method in each time division time slot using the time division multiplexing method together, communication is already performed. A time slot with the smallest number of terminal stations is assigned to a new terminal station. When there are a plurality of such time slots, a time slot in which a larger number of common UW stations are communicating is assigned to a new common UW station. Therefore, the problem of mistaking received signals among a plurality of common UW stations is promoted.
[0017]
On the contrary, since it does not prevent the time slot in which a smaller number of common UW stations are communicating from being assigned to a new individual UW station, a time slot that is advantageous to the common UW station that starts communication thereafter is left. I can't.
In view of the above problems, the present invention improves the accuracy of directivity pattern formation when communicating with an individual UW station and a common UW station side by side using a spatial multiplexing method, thereby improving communication accuracy. An object is to provide a radio base station and a communication method used in the radio base station.
[0018]
[Means for Solving the Problems]
In order to solve the above problem, the radio base station of the present invention is a radio base station that communicates with the terminal station using a code included in a received signal from the terminal station by a spatial multiplexing method, Code storage means for storing different codes of the maximum multiplexing number in the spatial multiplexing system, numbers indicating the ranks of the codes, and information indicating whether the codes are actually used for communication in association with each other; When the new terminal station starts communication, the new terminal station is a first type terminal station that transmits a signal including a common code, or transmits a signal including a code notified from the radio base station. The terminal type judging means for judging whether it is a type 2 terminal station, and, when it is judged that the new terminal station is a type 2 terminal station, the above information indicates that it is not actually used for communication. Notify the new terminal station of the rank code And a code notification section, code stored in the code storage means may have any except the sign of the lowest rank different from the common code.
[0019]
The radio base station also uses time division multiplexing, communicates with a terminal station in the spatial multiplexing method in each time slot, and further uses a time to be used for communication with the new terminal station. Time slot selection means for selecting a time slot having the smallest number of terminal stations transmitting signals including the common code in the time slot from the slot candidates, and the new terminal station is the first type terminal station If it is determined, it may comprise time slot notifying means for notifying the new terminal station that communication should be performed in the selected time slot.
[0020]
The radio base station also uses time division multiplexing, communicates with a terminal station in the spatial multiplexing method in each time slot, and further uses a time to be used for communication with the new terminal station. Time slot selection means for selecting a time slot having the largest number of terminal stations transmitting signals including the common code in the time slot from the slot candidates, and the new terminal station is a type 2 terminal station A time slot notifying means for notifying the new terminal station that communication should be performed in the selected time slot, the code storage means includes the different codes of the maximum multiplexing number, A number indicating the order of the code and information indicating whether the code is currently used for communication in each time slot are stored in association with each other, When it is determined that the new terminal station is a type 2 terminal station, the number notification means indicates the highest-order code indicated by the information that it is not currently used for communication in the notified time slot, You may notify to the said new terminal station.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
In addition to the time division multiple access (TDMA / TDD, Time Division Multiple Access / Time Division Duplex) scheme, the radio base station according to the present embodiment uses each of a plurality of frequency carriers defined by the PHS standard, This is a radio base station that spatially multiplexes up to four signals at the same frequency and wirelessly connects to a terminal station using a multiplexing scheme.
[0022]
In particular, the radio base station performs communication by mixing both a common UW station that transmits a common unique word defined by the PHS standard and an individual UW station that transmits a unique word specified by the radio base station. .
<Overall configuration>
FIG. 1 is a block diagram showing an overall configuration of radio base station 100 in the present embodiment.
[0023]
The radio base station 100 includes antennas 11 to 14, radio units 21 to 24, a signal processing unit 50, a modem unit 60, a baseband unit 70, a control unit 80, and a unique word storage unit 90.
The radio base station 100 multiplexes four channels in one TDMA / TDD frame according to the PHS standard, and processes signals of up to four communication lines to be spatially multiplexed per channel in parallel. One TDMA / TDD frame has a period of 5 mS and is composed of four transmission time slots and four reception time slots obtained by dividing each period into eight equal parts. Each time slot for transmission and reception constitutes one time division channel by time division multiplexing.
[0024]
The baseband unit 70 exchanges a plurality of signals (voice or data baseband signals) between a plurality of lines connected via a communication network and the signal processing unit 50.
The modem unit 60 has a function of modulating and demodulating the digitized baseband signal between the signal processing unit 50 and the baseband unit 70 by π / 4 shift QPSK (Quadrature Phase Shift Keying). This modulation and demodulation is performed in parallel for up to four TDMA / TDD frames spatially multiplexed in one time division channel.
[0025]
Under the control of the control unit 80, the signal processing unit 50 performs control related to directivity pattern formation, that is, separates and extracts received signals from each of the spatially multiplexed terminal stations input from the radio units 21 to 24. This is a part that performs control to generate a signal that is spatially multiplexed so that the transmission signal input from the modem unit 60 can be transmitted to a desired terminal station and output to the radio units 21 to 24. Specifically, it is realized by a programmable DSP (Digital Signal Processor).
[0026]
The control is performed by the MMSE method, specifically, for each time slot in a maximum of four TDMA / TDD frames processed in parallel by the modem unit 60 as follows. At the time of reception, each weight is adjusted so as to reduce an error between the received signal obtained by multiplying the signal actually received by each radio unit 21 to 24 with a weight corresponding to each radio unit and the reference signal. . At the time of transmission, a signal obtained by multiplying the transmission signal by the weight for each radio unit adjusted at the time of the previous reception is distributed to the corresponding radio units 21 to 24.
[0027]
Note that the directivity pattern for each terminal station is formed and transmitted / received using the spatial multiplexing method only for communication on the communication channel, and the spatial multiplexing method is not used for communication on the control channel.
The radio units 21 to 24 are all equivalent, and the radio unit 21 includes a transmission unit 111 including a high power amplifier and a reception unit 112 including a low noise amplifier.
[0028]
The transmission unit 111 converts the low-frequency signal input from the signal processing unit 50 into a high-frequency signal, amplifies the signal to a transmission output level, and outputs the signal to the antenna 11. In response to an instruction from the control unit 80, It has a function of adjusting the transmission output by controlling the gain of the power amplifier.
The receiving unit 112 has a function of converting a high frequency signal received by the antenna 11 into a low frequency signal, amplifying the signal, and outputting the amplified signal to the signal processing unit 50.
[0029]
Specifically, the control unit 80 includes a CPU (Central Processing Unit), a memory, and the like, and has a function of controlling each unit of the radio base station 100 when the CPU executes a program in the memory.
In addition, the unique word storage unit 90 includes unique word pattern information to be assigned to a plurality of individual UW stations to be spatially multiplexed, and unique word usage status information indicating the relationship between each unique word pattern and each terminal station to which the unique word pattern is assigned. Hold. This information will be described in detail later.
[0030]
FIG. 2 is a block diagram illustrating a configuration of the signal processing unit 50.
The signal processing unit 50 includes transmission / reception changeover switches 561 to 564, adders 551 to 554, and user processing units 51a to 51d.
Here, each of the user processing units 51a to 51d adjusts a weight vector so as to optimally transmit / receive a signal of a terminal station communicating in a time slot for each TSL / TDD frame for each time slot. Yes, it receives input signals X1 to X4 from each radio unit and outputs output signals Sa1 to Sa4 to each radio unit. That is, each of the user processing units 51a to 51d separates and extracts a signal from one spatially multiplexed terminal station and transmits it to the modem unit 60, and transmits a transmission signal to the terminal station transmitted from the modem unit 60. The originally generated signal is output to each radio unit.
[0031]
The transmission / reception changeover switches 561 to 564 are switched under the control of the control unit 80.
The adders 551 to 554 add output signals to the respective radio units adjusted by the user processing units 51 a to 51 d and output the added signals to the radio units 21 to 24.
FIG. 3 is a block diagram illustrating a configuration of the user processing unit 51a.
[0032]
The user processing unit 51a includes multipliers 521 to 524, multipliers 581 to 584, an adder 59, a transmission / reception selector switch 56, a reference signal generation unit 55, a weight calculation unit 58, and a weight storage unit 57.
Here, the reference signal generation unit 55 generates a start symbol (SS) and a preamble (PR) fixed in addition to the unique word according to the PHS standard, and a reference signal representing the unique word. At this time, for the unique word portion, a reference signal is generated so as to take the value of the unique word received from the control unit 80.
[0033]
The weight calculation unit 58 adjusts the weight vector by the MMSE method described above. The weight calculation unit 58 generates a reception signal and a reference signal generated by multiplying each of the reception signals X1, X2, X3, and X4 currently received by the radio units 21 to 24 by multiplying the corresponding weight vector. Each weight is adjusted so that the difference between the reference signal obtained from the unit 55 and the reference signal is reduced.
[0034]
That is, the weight calculation unit 58 represents the received signal as a sequence of numbers x1 (t), x2 (t), x3 (t), and x4 (t) that change according to time, and sets the corresponding weight to w1 (t ), W2 (t), w3 (t), and w4 (t), the received signal y (t) is obtained by the following equation (3). t is the time when the reception time of one symbol in the time slot of the PHS standard is the unit time.
[Formula 3] y (t) = w1 (t-1) * x1 (t) + w2 (t-1) * x2 (t) + w3 (t-1) * x3 (t) + w4 (t-1) * x4 (T)
A range in which the value of w (t−1) is determined in advance so that the difference e (t) between the received signal y (t) and the reference signal d (t) is minimized after the received signal y (t) is obtained. The weight value w (t) at the next time is set as the adjusted value. Note that e (t) is calculated by the following equation (4).
[Equation 4] e (t) = d (t) -y (t)
The weight storage unit 57 stores the weight for each radio unit calculated by the weight calculation unit 58 at the time of reception, and the multipliers 581 to 584 multiply the transmission signals given from the modem unit by the respective stored weights. Output.
<Data structure>
Hereinafter, the unique word pattern information and unique word usage information held in the unique word storage unit 90 will be described.
[0035]
FIG. 4 is a diagram illustrating an example of unique word pattern information. The unique word pattern information 200 includes a UW number 201 and a UW pattern value 202 in association with each other, UW pattern values P1 to P4 of the maximum spatial multiplexing number (here, four), and a UW number for identifying the UW pattern value. 1-4 are included. Specifically, P1 to P4 are 16-bit values represented by binary numbers such as “0011110101001100” and the like, and are different from each other. In particular, P4 is a common unique word value defined by the PHS standard.
[0036]
The UW number 201 also represents a rank when selecting a UW pattern value, where 1 represents the highest rank and 4 represents the lowest rank.
FIG. 5 is a diagram illustrating an example of unique word usage information. The unique word usage status information 300 includes a frequency number 301, a slot number 302, and UW notification status values 303 corresponding to the maximum number of spatially multiplexed terminal stations in association with each other.
[0037]
The frequency number 301 is a number that identifies the frequency of the carrier wave, and the slot number 302 is a number that identifies the time slot, and the combination of both identifies the communication channel. The UW notification status value 303 is a UW number notified to a communicating individual UW terminal station in a communication channel provided in the time slot using a carrier wave of the frequency, or a state in which no communication is performed with any terminal station. Indicates the value “empty”. It is also set to “4” when communicating with a common UW station.
[0038]
Note that the UW notification status value corresponding to a specific slot of a specific frequency in which communication is performed without using the spatial multiplexing method is not recorded. In the example shown in the figure, the time slot 1 using the carrier wave of the frequency 1 is a control channel in which only communication not using spatial multiplexing is performed, and the UW notification status value is not recorded.
<Operation>
Hereinafter, the operation of the radio base station 100 having the above-described configuration will be described in detail with respect to the link channel selection process and the unique word selection and notification process for each individual UW station, which are features of the present invention.
<Details of unique word notification processing>
FIG. 6 is a flowchart showing the operation of the radio base station 100 when a link channel establishment request is received from a terminal station to start a call or data communication. This operation is executed under the control of the control unit 80.
[0039]
When the control unit 80 receives a link channel establishment request from the terminal station via the control channel (step S01) or receives a link channel establishment re-request (step S02), the control unit 80 determines whether the terminal station is a common UW station. It is determined whether the station is a UW station (step S03).
As a specific example of the method for making this determination, the individual UW station sets a specific value different from the value set by the common UW station in a specific field in the link channel establishment request message and the link channel establishment re-request message. It is sufficient to determine that the terminal station is an individual UW station based on the value.
[0040]
The control unit 80 selects a link channel to be used for communication with the terminal station (step S04). One link channel is a communication channel specified by a set of a carrier frequency and a time slot, and is a unit for performing one set of multiplex communication by a spatial multiplexing method. Details of this processing will be described later.
When the link channel is not selected (step S05: no), control is performed so as to transmit a link channel assignment rejection notification to the terminal station (step S12).
[0041]
When the link channel is selected (step S05: yes), the following processing is performed depending on whether or not the terminal station is determined to be an individual UW station.
If it is an individual UW station (step S06: yes), the UW notification status value corresponding to the communication channel is referred to from the unique word usage information, and the highest rank (that is, the lowest) not used in the communication channel. The UW number is selected, and the unique word usage information is updated so that the selected UW number is indicated as the UW notification status value in the communication channel (step S07).
[0042]
According to this selection method, the UW pattern value of the maximum spatial multiplexing number is stored in the unique word pattern information and is different from the common UW pattern value except for the lowest rank UW pattern value. A common UW is designated for a station when all of the spatially multiplexed terminal stations are individual UW stations, and is limited to the individual UW station that started communication at the end. That is, when the common UW station is communicating, the common UW is not designated for the individual UW station.
[0043]
Transmitting the link channel assignment notification including information indicating the selected unique word and the frequency and time slot specifying the communication channel to the terminal station (step S08), and performing processing corresponding to the terminal station; The unique word notified to the terminal station is passed to the reference signal generation unit of the determined user processing unit (step S09). Thereby, the reference signal generation unit 55 in the user processing unit generates a signal that includes the value of the unique word and is scheduled to be transmitted from the terminal station as a reference signal. In addition, the user processing unit transmits the transmission data for the terminal station including the unique word.
[0044]
If it is a common UW station (step S06: no), a link channel assignment notification including information indicating the frequency and time slot specifying the communication channel is transmitted to the terminal station, and the lowest UW number is assigned to the communication channel. The unique word usage information is updated as indicated by the UW notification status value (step S10). A common unique word is passed to the reference signal generation unit of the user processing unit that is determined to perform processing corresponding to the terminal station (step S11).
<Details of link channel selection processing>
FIG. 7 is a flowchart showing the operation of the radio base station 100 when a link channel used for communication with a new terminal station is selected as a part of the unique word selection and notification process. This operation is executed under the control of the control unit 80.
[0045]
The control unit 80 uses the unique word usage status information 300 as a candidate for a link channel to be used for communication with a new terminal station. The UW notification status value 303 corresponding to each time slot of the carrier wave of each frequency is found by searching (step S21). Then, the following processing is performed according to the number of communication channels found.
[0046]
When one communication channel is found (step S22: 1), the communication channel is selected as a link channel.
When a plurality of communication channels are found (step S22: plural), if the new terminal station is an individual UW station (step S24: yes), the communication channel with the largest number of common UW stations in communication is selected as the link channel. (Step S25) If it is a common UW station (step S24: no), a communication channel with the smallest number of common UW stations in communication is selected as a link channel (step S26).
[0047]
If the corresponding communication channel is not found (step S22: none), the process returns to the unique word notification process without selecting a link channel.
Here, the control unit 80 searches for the minimum number of communication channels whose number of terminal stations in communication is less than the maximum number of spatial multiplexing and the number of communication channels to be used for communication with the new terminal station. Communication channels in which a noise level with a level exceeding a predetermined threshold is detected may be excluded from the candidates. Further, a communication channel in which a reception level difference between a new terminal station and a terminal station already in communication exceeds a predetermined threshold may be excluded from the candidates. In this case, even if there is a gain difference caused by the directivity of the adaptive array device, the two signals cannot be correctly separated.
<Relationship with link channel establishment sequence>
FIG. 8 is a diagram showing an outline of a link channel establishment sequence between the terminal station and the radio base station. The timing at which each process described above is performed in the sequence will be described with reference to FIG.
[0048]
As shown in the figure, when a link channel establishment request is received from a terminal station (S101), the radio base station performs the operation shown in FIG. 6, and the execution of step S03 determines whether the new terminal station is an individual UW station or a common UW station. It is determined whether it is a station, and the processing shown in FIG. 7 is called and executed from step S04, and a communication channel to be allocated is selected.
When it is determined as an individual UW station, a unique word to be used is selected by executing steps S07 and S08, and the carrier station frequency and time slot for specifying the unique word and the communication channel are selected for the terminal station. The link channel allocation notification including the instruction is transmitted (S102). In addition, after the notification, the unique word is included in the transmission data for the terminal station in the communication using the assigned communication channel.
[0049]
If it is determined that the station is a common UW station, a link channel assignment notification including a carrier frequency for specifying a communication channel and a time slot instruction is transmitted to the terminal station by executing steps S10 and S11 (S102).
As described above, in addition to the configuration of the common UW station according to the conventional PHS standard, the individual UW station changes the value of the unique word to the PHS standard when receiving a notification of the unique word from the radio base station. It is a terminal station having a function of transmitting / receiving communication data to / from a radio base station by using instead of a specified unique word.
<Specific examples of communication channel and unique word selection operations>
As a specific example, a communication channel and unique word selection operation when a link channel establishment request or the like is received from a new terminal station with the unique word usage information shown in FIG. 5 will be described.
[0050]
Here, the number of terminal stations in communication that are candidates for the link channel used for communication with the new terminal station is less than the maximum spatial multiplexing number, and the minimum number of communication channels is the slot 4 of frequency 1 and the frequency 2 Slot 1.
If the terminal station that has received a link channel establishment request or the like is a common UW station, slot 4 of frequency 1 with the number of common UW stations in communication being 0 is selected as the link channel, and the frequency number and the slot number are selected. Is instructed to the common UW station via the control channel by the link channel assignment notification, and the common UW station starts communication on the instructed link channel.
[0051]
If the terminal station that received the link channel establishment request or the like is an individual UW station, slot 1 of frequency 2 with the number of common UW stations in communication being 1 is selected as the link channel, and further used in the link channel. The smallest UW number 2 is selected, the frequency number, the slot number, and the UW number are instructed to the individual UW station via the control channel by the link channel assignment notification, and the individual UW station In the established link channel, communication is started using the unique word indicated by the UW number.
<Summary>
Thus, when the terminal station that has started communication is a common UW station, the radio base station 100 has already used the common UW from the communication channel candidates to be used for communication with the common UW station. Since there is no terminal station in communication or the channel with the smallest number is selected, the problem of mistaking received signals with other terminal stations using a common UW is reduced as much as possible.
[0052]
Further, when the terminal station that has started communication is an individual UW station, the number of terminal stations that are already in communication using the common UW is the largest among communication channel candidates to be used for communication with the individual UW station. Since a large number of channels are selected, channels that are advantageous in terms of communication quality with respect to the common UW station that starts communication thereafter can be left as much as possible. Even in this case, since the individual UW station is notified of a UW different from that of other terminal stations, there is no problem of mistaking the received signal.
[0053]
Also, since the individual UW station is notified of the unused UW of the highest rank in the communication channel, if the common UW station is already communicating, the common unique word is assigned to the individual UW as described above. The station will not be notified. Therefore, the problem of mistaking received signals between the individual UW station and the common UW station is solved.
<Other variations>
Although the present invention has been described based on the above embodiment, it is needless to say that the present invention is not limited to the above embodiment. The following cases are also included in the present invention.
(1) The present invention may be a method including the steps described in the embodiments. Further, these methods may be a computer program for realizing the method using a computer system, or may be a digital signal representing the program.
[0054]
Further, the present invention is a computer-readable recording medium on which the program or the digital signal is recorded, for example, a flexible disk, a hard disk, a CD-ROM, an MO, a DVD, a DVD-ROM, a DVD-RAM, a semiconductor memory, and the like. It is good.
Further, the present invention may be the computer program or the digital signal transmitted via an electric communication line, a wireless or wired communication line, a network represented by the Internet, or the like.
[0055]
The present invention is also a computer system including a microprocessor and a memory, wherein the memory stores the program, and the microprocessor operates according to the program stored in the memory, so that the method is performed. May be realized.
Further, the program or the digital signal may be recorded on the recording medium and transferred, or transferred via the network or the like, and executed in another independent computer system.
(2) In the present embodiment, the radio base station and the terminal station in the PHS system have been described as examples. However, the communication system performs communication using the spatial multiplexing method, and the codes transmitted individually by the terminal station In general, the present invention can be applied to any communication system that uses antennas to control antenna directivity for each terminal station.
(3) In this embodiment, the radio base station notifies the terminal station of the UW number specifying the unique word. However, the information to be notified is not limited to the UW number, and the unique word is specified. For example, the bit pattern itself that constitutes the unique word may be used as long as it is necessary information.
(4) Although not specifically shown in the present embodiment, the radio base station is unique so that when communication with the terminal station is terminated, the UW notification status value corresponding to the terminal station becomes “empty”. Update word usage information.
[0056]
【The invention's effect】
The radio base station of the present invention is a radio base station that communicates with the terminal station using a code included in a received signal from the terminal station in a spatial multiplexing scheme, and the maximum multiplexing number in the spatial multiplexing scheme The code storage means for storing the different codes, the number indicating the order of the codes, and the information indicating whether the codes are actually used for communication, and the new terminal station When started, the new terminal station is a first type terminal station that transmits a signal including a common code, or a second type terminal station that transmits a signal including a code notified from the radio base station. Terminal type determination means for determining whether or not the new terminal station is the second type terminal station, the highest-order code indicated by the information as not being actually used for communication Code notification means for notifying the terminal station, Code stored in said code storing means is characterized by any except the sign of the lowest priority is different from the common code.
[0057]
According to this configuration, when the radio base station newly starts communication with the type 2 terminal station and the type 1 terminal station is in communication, the radio base station has a predetermined common code for the type 2 terminal station. You will not be notified. As a result, when the first type terminal station and the second type terminal station are mixed and communicated using the spatial multiplexing method, the radio base station solves the problem of mistaking received signals between the two.
[0058]
The radio base station also uses time division multiplexing, communicates with a terminal station in the spatial multiplexing method in each time slot, and further uses a time to be used for communication with the new terminal station. Time slot selection means for selecting a time slot having the smallest number of terminal stations transmitting signals including the common code in the time slot from the slot candidates, and the new terminal station is the first type terminal station If it is determined, it may comprise time slot notifying means for notifying the new terminal station that communication should be performed in the selected time slot.
[0059]
According to this configuration, when the radio base station newly starts communication with the first type terminal station, there is no terminal station that is already in communication using the common code among the time slots that are candidates for use. Or notifies the first type terminal station of the least time slot and performs communication in the time slot. Thereby, the said radio base station reduces the problem which mixes a received signal between the said 1st type terminal station and the other terminal station which uses the said common code as much as possible.
[0060]
The radio base station also uses time division multiplexing, communicates with a terminal station in the spatial multiplexing method in each time slot, and further uses a time to be used for communication with the new terminal station. Time slot selection means for selecting a time slot having the largest number of terminal stations transmitting signals including the common code in the time slot from the slot candidates, and the new terminal station is a type 2 terminal station A time slot notifying means for notifying the new terminal station that communication should be performed in the selected time slot, the code storage means includes the different codes of the maximum multiplexing number, A number indicating the order of the code and information indicating whether the code is currently used for communication in each time slot are stored in association with each other, When it is determined that the new terminal station is a type 2 terminal station, the number notification means indicates the highest-order code indicated by the information that it is not currently used for communication in the notified time slot, You may notify to the said new terminal station.
[0061]
According to this configuration, when the wireless base station newly starts communication with the type 2 terminal station, the number of terminal stations already in communication using the common code among the time slots to be used is determined. The most time slot is notified to the second type terminal station, and communication is performed in the time slot. Thereby, the radio base station can leave as many time slots as possible in terms of communication quality with respect to the first type terminal station that starts communication thereafter. Even if it does in this way, since the code | symbol different from the other terminal station is notified to the said 2nd type | mold terminal station, the problem which mixes a received signal does not arise.
[0062]
Further, the radio base station uses a plurality of carrier waves, communicates with the terminal station by the spatial multiplexing method using each of the carrier waves, and further uses a carrier wave to be used for communication with the new terminal station. From the candidates, it is determined that the carrier selection means for selecting the carrier with the smallest number of terminal stations transmitting signals including the common code using the carrier, and that the new terminal station is the first type terminal station. In this case, a carrier wave notification means for notifying the new terminal station that communication should be performed using the selected carrier wave may be provided.
[0063]
According to this configuration, when the wireless base station newly starts communication with the first type terminal station, there is no terminal station that is already in communication using the common code among the carrier waves that are candidates for use. Alternatively, a minimum number of carrier waves are notified to the first type terminal station, and communication is performed using the carrier waves. As a result, the radio base station reduces as much as possible the problem of mistaking received signals between the first type terminal station and other terminal stations using a common code.
[0064]
Further, the radio base station uses a plurality of carrier waves, communicates with the terminal station by the spatial multiplexing method using each of the carrier waves, and further uses a carrier wave to be used for communication with the new terminal station. A carrier selection means for selecting a carrier having the largest number of terminal stations transmitting a signal including the common code by using the carrier, and a case where it is determined that the new terminal station is a type 2 terminal station. Carrier selection means for notifying the new terminal station that communication should be performed using the identified carrier wave, and the code storage means indicates the different codes of the maximum multiplexing number and the order of the codes A number and information indicating whether or not the code is currently used for communication by each carrier, and the code notification means is configured such that the new terminal station is a type 2 terminal station. When judged , By the information, the sign of the highest rank currently indicated as not being used for communication by the notified carrier, may notify the new terminal station.
[0065]
According to this configuration, when the wireless base station newly starts communication with the type 2 terminal station, the number of terminal stations already in communication using the common code among the carrier candidates to be used is the highest. A large number of carrier waves are notified to the second type terminal station, and communication is performed using the carrier waves. As a result, the radio base station can leave, as much as possible, a carrier wave that is advantageous in terms of communication quality with respect to the first type terminal station that starts communication thereafter. Even if it does in this way, since the code | symbol different from the other terminal station is notified to the said 2nd type | mold terminal station, the problem which mixes a received signal does not arise.
[0066]
The communication method of the present invention is a communication method in a radio base station that communicates with the terminal station by a spatial multiplexing method using a code included in a received signal from the terminal station, and the radio base station A code having a different maximum multiplex number in the spatial multiplexing scheme, a number indicating the order of the code, and information indicating whether or not the code is actually used for communication are stored in association with each other. All the codes except for the lowest-order code are different from the predetermined common code, and when the new terminal station starts communication, the new terminal station transmits a signal including the common code. A terminal type determining step for determining whether the terminal is a first type terminal station or a second type terminal station that transmits a signal including a code notified from the radio base station; and the new terminal station is a second type terminal If it is determined that the station The highest priority code indicated as not being currently used for communication by the broadcast, and a code notification step of notifying the new terminal station.
[0067]
When a radio base station that implements this communication method newly starts communication with a type 2 terminal station and the type 1 terminal station is in communication, a predetermined common code is assigned to the type 2 terminal station. There is no notification. Thus, when the first type terminal station and the second type terminal station are mixed and communicated using the spatial multiplexing method, the radio base station solves the problem of mistaking received signals between the two.
[0068]
The program of the present invention can be executed by a computer for controlling a radio base station that communicates with the terminal station using a code included in a received signal from the terminal station using a computer. The radio base station is a program that includes different codes of the maximum multiplexing number in the spatial multiplexing scheme, a number indicating the order of the codes, and information indicating whether or not the codes are actually used for communication. Are stored in association with each other, and the stored codes are different from the predetermined common code except for the lowest-order code, and when the new terminal station starts communication, the new terminal station Is a terminal type determination step for determining whether the signal is a first type terminal station that transmits a signal including the common code or a second type terminal station that transmits a signal including a code notified from the radio base station When, A code notification step of notifying the new terminal station of the highest-order code indicated by the information that it is not currently used for communication, when it is determined that the new terminal station is a type 2 terminal station; Run the computer.
[0069]
If the radio base station controlled using this program starts communication with the second type terminal station and the first type terminal station is in communication, the radio base station is in common with the second type terminal station. The code is not notified. Thus, when the first type terminal station and the second type terminal station are mixed and communicated using the spatial multiplexing method, the radio base station solves the problem of mistaking received signals between the two.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a radio base station in an embodiment.
2 is a block diagram showing a configuration of a signal processing unit 50. FIG.
FIG. 3 is a block diagram illustrating a configuration of a user processing unit 51a.
FIG. 4 is an example of unique word pattern information.
FIG. 5 is an example of unique word usage information
FIG. 6 is a flowchart showing a unique word notification process executed by a radio base station.
FIG. 7 is a flowchart showing link channel selection processing executed by the radio base station.
FIG. 8 is a link channel establishment sequence between a terminal station and a radio base station
FIG. 9 is a conceptual diagram showing control contents using the MMSE method of the adaptive array apparatus.
[Explanation of symbols]
11-14 Antenna
21-24 Radio section
50 Signal processor
51a to 51d User processing unit
55 Reference signal generator
56 Transmission / reception selector switch
57 Weight storage
58 Weight calculator
59 Adder
60 Modem part
70 Baseband part
80 Control unit
90 Unique word storage
100 radio base station
111 Transmitter
112 Receiver
521-524 multiplier
551-554 Adder
561-564 Transmission / reception selector switch
581-584 multiplier

Claims (7)

Using a code included in a received signal from a terminal station, a radio base station that communicates with the terminal station by a spatial multiplexing method,
Code storage means for storing a code having a different maximum number of multiplexing in the spatial multiplexing method, a number indicating the order of the code, and information indicating whether or not the code is actually used for communication When,
When the new terminal station starts communication, the new terminal station is a first type terminal station that transmits a signal including a common code, or a signal including a code notified from the radio base station. Terminal type determining means for determining whether the terminal station is a two-type terminal station;
When it is determined that the new terminal station is a type 2 terminal station, code notification means for notifying the new terminal station of the highest-order code indicated by the information that it is not currently used for communication; Prepared,
The radio base station characterized in that the codes stored in the code storage means are all different from the common code except for the lowest rank code. The radio base station uses time division multiplexing in combination, communicates with the terminal station in the spatial multiplexing scheme in each time slot, and
Time slot selecting means for selecting a time slot having the smallest number of terminal stations transmitting signals including the common code in the time slot from candidates of time slots to be used for communication with the new terminal station;
When it is determined that the new terminal station is a type 1 terminal station, it comprises time slot notifying means for notifying the new terminal station that communication should be performed in the selected time slot. Item 2. The radio base station according to Item 1. The radio base station uses time division multiplexing in combination, communicates with the terminal station in the spatial multiplexing scheme in each time slot, and
Time slot selection means for selecting a time slot having the largest number of terminal stations transmitting signals including the common code in the time slot from candidates of time slots to be used for communication with the new terminal station;
When it is determined that the new terminal station is a type 2 terminal station, the time slot notification means for notifying the new terminal station that communication should be performed in the selected time slot,
The code storage means associates the different codes of the maximum multiplex number, a number indicating the order of the codes, and information indicating whether or not the codes are currently used for communication in each time slot. Remember,
When it is determined that the new terminal station is a type 2 terminal station, the code notification means uses the information indicating the highest-order code indicated as not being used for communication in the notified time slot. The radio base station according to claim 1, notifying the new terminal station. The radio base station uses a plurality of carriers, and communicates with the terminal station by the spatial multiplexing method using the individual carriers.
Carrier wave selection means for selecting a carrier wave having the smallest number of terminal stations that transmit signals including the common code using the carrier wave from candidate carriers to be used for communication with the new terminal station;
A carrier wave notification means for notifying to the new terminal station that the new terminal station is to be communicated using the selected carrier wave when it is determined that the new terminal station is a type 1 terminal station. Item 2. The radio base station according to Item 1. The radio base station uses a plurality of carriers, and communicates with the terminal station by the spatial multiplexing method using the individual carriers.
Carrier wave selection means for selecting a carrier wave having the largest number of terminal stations transmitting signals including the common code by the carrier wave from carrier candidates to be used for communication with the new terminal station;
When it is determined that the new terminal station is a type 2 terminal station, carrier selection means for notifying the new terminal station that communication should be performed using the identified carrier wave,
The code storage means associates and stores the different codes of the maximum multiplex number, a number indicating the order of the codes, and information indicating whether the codes are currently used for communication by individual carriers. And
When it is determined that the new terminal station is a type 2 terminal station, the code notification means uses the information to indicate the highest-order code indicated as not currently being used for communication by the notified carrier wave, The radio base station according to claim 1, wherein notification is made to the new terminal station. Using a code included in a received signal from a terminal station, a communication method in a radio base station that communicates with the terminal station by a spatial multiplexing method,
The radio base station stores a code having different maximum multiplex numbers in the spatial multiplexing scheme, a number indicating the order of the code, and information indicating whether or not the code is actually used for communication. The stored code is different from the predetermined common code except for the lowest-order code,
When the new terminal station starts communication, the new terminal station is a first type terminal station that transmits a signal including a common code, or a signal including a code notified from the radio base station. A terminal type determination step of determining whether the terminal station is a type 2 terminal station;
If it is determined that the new terminal station is a type 2 terminal station, a code notification step of notifying the new terminal station of the highest-order code indicated by the information that it is not currently used for communication; A communication method characterized by comprising. A computer-executable program for controlling, using a computer, a radio base station that communicates with the terminal station by a spatial multiplexing method using a code included in a received signal from the terminal station,
The radio base station stores a code having different maximum multiplex numbers in the spatial multiplexing scheme, a number indicating the order of the code, and information indicating whether or not the code is actually used for communication. The stored code is different from the predetermined common code except for the lowest-order code,
When the new terminal station starts communication, the new terminal station is a first type terminal station that transmits a signal including a common code, or a signal including a code notified from the radio base station. A terminal type determination step of determining whether the terminal station is a type 2 terminal station;
If it is determined that the new terminal station is a type 2 terminal station, a code notification step of notifying the new terminal station of the highest-order code indicated by the information that it is not currently used for communication; A program that is executed by the computer.

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