JP3423268B2 - Wireless base station, mobile station and wireless communication system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive array type wireless base station for wirelessly connecting a plurality of mobile stations by spatial multiplexing.

[0002]

2. Description of the Related Art In recent years, with the increase in mobile stations such as PHS and mobile phones, social demand for effective use of frequency resources is increasing. One of the methods for responding to this request is communication by spatial multiplexing. The spatial multiplexing method is a method in which a radio base station uses a directional antenna for both transmission and reception, and
This is a method of multiplexing at the same time using one frequency.

An adaptive array device is used as a directional antenna used in the spatial multiplexing system. 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 of each antenna, the antenna as a whole,
A directivity pattern (also called an array antenna pattern) is dynamically formed for each of transmission and reception.

The adaptive array device can be easily installed because the individual antennas are fixedly installed, and the directivity pattern can be dynamically formed. Therefore, the adaptive array device is suitable for use in a radio base station that should follow the movement of a mobile station. It is particularly suitable and is being put to practical use in order to effectively use frequency resources. For details of the adaptive array antenna system, refer to "Special Issue on Adaptive Signal Processing in Spatial Domain and its Application Technology" (Journal of the Institute of Electronics and Communication Engineers, VOL.J75-B-II No.11N).
OVEMBER), detailed description is omitted here.

In order to maintain communication quality, the spatially multiplexed radio base station follows the movement of each mobile station to change the directivity pattern. Conventionally, this control is performed in order to reduce an error between a signal that is actually received and a signal that should be received for a portion whose signal content is known, for example, a UW (Unique Word) portion if the signal complies with the PHS standard. This is done by controlling the amplitude and phase of the signal transmitted and received by the antenna. By performing this control, as a result, the transmission strength and the reception sensitivity can be increased in the direction of the mobile station to be followed, and the transmission strength and the reception sensitivity can be reduced in the direction of the other spatially multiplexed mobile station. .

By the way, the frequencies of the carrier waves transmitted from each of the spatially multiplexed mobile stations are not completely the same because there is an error depending on the accuracy of the circuit elements and the circuit configuration. Therefore, in addition to the control of the directivity pattern, the signal of each mobile station is controlled by separating the signal of each mobile station from the signal received by the radio base station based on the difference in the frequency of the carrier wave. There is also a radio base station that more accurately extracts.

By performing such control, the communication quality is maintained in the radio base station using the conventional adaptive array antenna.

[0008]

However, according to the conventional control, the user's satisfaction with respect to noise and sound quality is not sufficient, and there is still a strong demand for improvement in communication quality. Furthermore, recently, because the frequency accuracy of the mobile station is improved and the carrier frequency difference is reduced by the improvement of the circuit element and the circuit configuration, the signal of each mobile station is calculated based on the carrier frequency difference in the radio base station. Control of separation is becoming difficult.

In view of the above problems, the present invention provides an adaptive array type wireless base station for wirelessly connecting a plurality of mobile stations through one communication channel by spatial multiplexing.
An object of the present invention is to provide a radio base station capable of further accurately separating the signal of each mobile station from the signal received by the base station and further improving the communication quality.

[0010]

In order to solve the above problems, a radio base station of the present invention is an adaptive array type radio base station for wirelessly connecting a plurality of mobile stations by spatial multiplexing, and each of the mobile stations There is provided notification means for notifying each mobile station of information that is a frequency that should be assigned to a station and that does not affect adjacent frequency bands and that corresponds to a different frequency. Here, the frequency band is a carrier wave of one frequency.
Is used to mean the frequency width of the communication channel. adjacent
The frequency band to be used is defined by the carrier waves of adjacent frequencies.
A communication channel for communication. Below, in this specification
The term frequency band is used in this sense.

The notifying means may notify, as the information, information for identifying the center frequency of the frequency band and the shift amount from the center frequency. A mobile station of the present invention is a mobile station wirelessly connected to a radio base station by spatial multiplexing, and receives from the radio base station information identifying a center frequency of a frequency band and a shift amount from the center frequency. The receiver includes a receiver and a transmitter that transmits a signal by using a carrier having a frequency obtained by adding the center frequency identified by the information and the shift amount.

A wireless communication system of the present invention is a wireless communication system comprising an adaptive array type wireless base station for wirelessly connecting a plurality of mobile stations by spatial multiplexing, and the plurality of mobile stations. The station is a frequency to be assigned to each of the mobile stations, the center frequency of the frequency band and the shift amount from the center frequency as information corresponding to different frequencies that do not affect adjacent frequency bands. The mobile station is provided with notifying means for notifying each mobile station of the respective identifying information, the mobile station is a receiving means for receiving from the radio base station information identifying each of the center frequency of the frequency band and the shift amount from the center frequency, And a transmitting unit that transmits a signal using a carrier having a frequency obtained by adding a center frequency identified by the information and a shift amount.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The radio base station according to the present embodiment uses time division multiplexing (TDMA / T) defined by the PHS standard.
DD, Time Division Multiple
Access / Time Division Dup
It is installed as a base station that wirelessly connects PHS mobile stations by the lex system, and performs spatial multiplexing in addition to the time division multiplexing to communicate with the mobile stations.

The mobile station in this embodiment is a PHS mobile station that is wirelessly connected to and communicates with the base station. <Overall Configuration of Radio Base Station> FIG. 1 is a block diagram showing the configuration of the radio base station 1. The radio base station 1 has an antenna 1
1 to 14, radio units 21 to 24, a signal processing unit 50, a modem unit 30, a baseband unit 40, and a control unit 60, the maximum four signals are spatially multiplexed and simultaneously communicated.

The baseband unit 40 transmits a plurality of signals (voice or data baseband signals) between a plurality of lines connected via a telephone switching network (not shown) and the signal processing unit 50.
Give and receive. In the present embodiment, four channels are multiplexed in one TDMA / TDD frame according to the PHS standard, and signals of up to four telephone lines to be spatially multiplexed per channel are processed in parallel. 1 TDMA / TD
The D frame has a cycle of 5 mS and is composed of four transmission time slots and four reception time slots which are formed by dividing each cycle into eight equal parts. One time slot for each of transmission and reception constitutes one channel by time division multiplexing.

The modem unit 30 has a π / 4 shift QPSK (Quadratur) between the signal processing unit 50 and the baseband unit 40 with respect to the digitized baseband signal.
rePhase Shift Keying)
Modulate and demodulate. This modulation and demodulation can be up to 4 TDMs spatially multiplexed in one time division channel.
This is done in parallel for A / TDD frames.

The signal processing unit 50 is specifically a programmable DSP (Digital Signal Pro).
, and each of the time slots in a maximum of four TDMA / TDD frames that are processed in parallel by the modem unit 30 so as to optimally transmit and receive the signal of each mobile station communicating in the time slot.
The amplitude and the phase of each transmission / reception signal of the radio units 21 to 24 are adjusted, and the reception signal is separated based on the frequency difference of the carrier wave.

This processing is performed by the signal processing unit 50 on the directional pattern forming parameter (hereinafter referred to as a directional pattern forming parameter) for reducing an error between a signal actually received by each mobile station and a signal to be received for a portion whose reception content is known in advance. , Weight vector) is calculated.
The weight vector is the adjustment amount of the amplitude and phase of the transmission / reception signal for each radio unit.

The radio section 21 includes a transmission section 211 including a high power amplifier and the like, and a reception section 21 including a low noise amplifier and the like.
2 and. The transmission unit 211 includes the signal processing unit 50.
The low frequency signal input from is converted into a high frequency signal, amplified to the transmission output level, and output to the antenna 11. The transmission unit 211 has a function of adjusting the transmission output by controlling the gain of the high power amplifier or the like according to an instruction from the control unit 60. The receiving unit 212 converts the high frequency signal received by the antenna 10 into a low frequency signal, amplifies and outputs the low frequency signal to the signal processing unit 50.

The radio section is provided for each antenna,
The radio units 22, 23, 24 have the same configuration as the radio unit 21, and therefore their explanations are omitted. The control unit 60 is specifically a CPU
(Central Processing Unit) and a memory, and the CPU controls the entire wireless base station according to a program in the memory.

The control unit 60, when allocating a link channel to a mobile station to be newly spatially multiplexed, has a carrier number for identifying the center frequency of the link channel and a different shift amount from the center frequency. An offset number for identifying a shift amount that is different from any shift amount notified to the mobile station that has already been spatially multiplexed and is within a deviation range that does not affect adjacent frequency bands is notified.

The correspondence between the center frequency and the carrier number and the correspondence between the shift amount and the offset number are predetermined and stored in the frequency table 61 and the offset table 62 provided in the control unit 60, respectively. Be present. FIG. 4 shows a specific example of the frequency table 61, and FIG. 5 shows a specific example of the offset table 62. The frequency table 61 holds a set of carrier number and center frequency MHz, and the offset table holds a set of offset number and shift amount KHz.

The control unit 60 uses the frequency management table 63 provided in the control unit 60 to set different shift amounts for mobile stations spatially multiplexed using communication channels of the same frequency band in the same time slot. decide. FIG. 6 shows a specific example of the frequency management table 63,
TD assigned and used for each mobile station in communication
The MA time slot number, carrier number, and offset number are recorded.

As an example, the control unit 60 notifies the mobile station of the carrier number and offset number using a link channel assignment message. FIG. 7 shows an example of the link channel allocation message, in which the carrier number is held in the fourth octet and the offset numbers are held in the fifth and fourth bits of the second octet. After receiving the link channel assignment message, the mobile station transmits using the carrier of the frequency obtained by adding the offset value identified by the offset number to the center frequency identified by the held carrier number. That is, each mobile station transmits using carrier waves of different frequencies.

According to this structure, in the radio base station,
The signal processing unit 50 serves to separate the signals of each mobile station based on the difference in carrier frequency. <Signal Adjustment Unit> FIG. 2 is a block diagram showing the 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.

The user processing units 51a to 51d and the radio units 21 to 24 are arranged to optimally transmit and receive the signal of the mobile station communicating in the time slot for each TDMA / TDD frame. The amplitude and the phase of each transmission / reception signal input / output between are adjusted. The adders 551 to 554 are user processing units 51 a to 5
The transmission signals adjusted by 1d are added for each radio unit and output to the radio units 21 to 24. <User Processing Unit> FIG. 3 is a block diagram showing the arrangement of the user processing unit 51a. The user processing unit 51a uses the multiplier 5
21 to 524, 581 to 584, an adder 59, a transmission / reception changeover switch 56, a reference signal generation unit 55, a reception frequency estimation unit 57, and a weight calculation unit 58.

The reception frequency estimator 57 estimates the carrier frequency of the received signal based on the received signal and outputs it to the reference signal generator 55. The reference signal generation unit 55 uses a portion of the received signal whose content is known, such as UW (Unique).
(e Word) part, a signal is generated when the signal is transmitted using the carrier having the frequency estimated by the reception frequency estimation unit 57.

The weight calculator 58 calculates the weight vector so that the total sum of the errors between the received signal and the signal generated by the reference signal generator 55 is minimized. Multiplier 5
21 to 524 and the adder 59 are connected to the individual radio units 21 to 21.
The amplitude and phase of the signal input from 24 are adjusted and added according to the weight vector calculated by the weight calculator 58.

The multipliers 581 to 584 adjust the amplitude and phase of the signal output to each radio section according to the weight vector calculated by the weight calculating section 58. <Details of Control Unit> Hereinafter, in the present embodiment, the control unit 60
The control operation performed by the above will be described with reference to the flowchart shown in FIG.

When receiving the link channel establishment request or the link channel establishment re-request from the mobile station (step S01, step S02), the control unit 60 links the time slot and carrier that can be assigned to the mobile station. Search for a channel (step S03). If there is no such link channel (step S04), a link channel allocation refusal is transmitted (step S05).
If there is a link channel that can be assigned, other mobile stations that are currently using the same carrier in the same time slot as the link channel are known by referring to the frequency management table 63 (step S06), and for any of them. The smallest offset number that is not applied is selected (step S07), and the time slot number, carrier number, and selected offset number are recorded in the unused mobile station number column of the frequency management table 63. (Step S08). After that, the respective numbers are stored in the link channel assignment message and transmitted (step S09).

Note that the control unit 60, after recording in the frequency management table, fails to establish a link channel due to a timeout, etc. outside the figure, or for link switching or channel disconnection. When the channel is released, the mobile station number column that used the link channel is returned to unused. <Overall Configuration of Mobile Station> FIG. 9 is a block diagram showing the configuration of the mobile station 2. The mobile station 2 includes a radio unit 71, a synthesizer unit 74, a modem unit 72, a TDMA processing unit 73, a voice processing unit 75, a speaker 76, a microphone 77, a display unit 78, a key unit 79, and a control unit 82. The station is notified of information for identifying the carrier frequency and the offset value from the frequency, and transmission is performed using the carrier of the frequency obtained by adding the shift amount to the designated frequency.

The radio section 71 communicates with a radio base station. The modem unit 72, between the radio unit 71 and the TDMA processing unit 73, is π / for the digitized baseband signal.
Modulation and demodulation are performed by 4-shift QPSK or the like. The synthesizer unit 74 generates a carrier wave having a frequency designated by the control unit 82 and supplies the carrier wave to the wireless unit.

The TDMA processing unit 73 controls a transmission time slot and a reception time slot used for transmission and reception among the time division multiplexed time slots. Voice processing unit 75
Converts a digital audio signal and an analog voice signal to each other, and inputs and outputs a voice signal through the speaker 76 and the microphone 77 and amplifies the voice signal.

The display unit 78 is a display device realized by a liquid crystal display panel or the like, and the key unit 79 is an input device having ten keys (numerical keys, * key and # key), on-hook key, off-hook key and the like. The control unit 82
Specifically, a CPU (Central Process)
ngUnit) and a memory, and the CPU controls the entire mobile station according to a program in the memory.

In particular, the control unit 82 has therein the same frequency table 83 and offset table 84 as those in the radio base station, and when the link channel allocation message is received from the radio base station, the carrier in the message is received. The center frequency and the shift amount identified by the number and the offset number are obtained by referring to the respective tables, and the value obtained by adding the shift amount to the center frequency is output to the synthesizer unit 74.

In the above description, the radio base station notifies the mobile station of the offset number using the link channel allocation message, but it may use other messages. In the above description, the radio base station notifies the offset number to the mobile station when allocating a link channel to a mobile station to be newly spatially multiplexed, but after starting communication by spatial multiplexing,
The notification may be issued when it is determined that the signal separation accuracy has deteriorated.

[0037]

The radio base station of the present invention is an adaptive array type radio base station that wirelessly connects a plurality of mobile stations by spatial multiplexing, and is a frequency to be assigned to each of the mobile stations and adjacent frequencies. A notification means is provided for notifying each mobile station of information that does not affect the band and that corresponds to different frequencies.

According to this structure, since the radio base station can instruct each mobile station of different frequencies that can be used in one frequency band, the radio base station can perform signal separation based on the difference in frequency. It is possible to instruct each mobile station to transmit an easier signal, which helps improve communication quality. The notifying unit may notify, as the information, information for identifying a center frequency of a frequency band and a shift amount from the center frequency.

According to this structure, the same effect as that of the above structure can be obtained. A mobile station of the present invention is a mobile station wirelessly connected to a radio base station by spatial multiplexing, and receives from the radio base station information identifying a center frequency of a frequency band and a shift amount from the center frequency. The receiver includes a receiver and a transmitter that transmits a signal by using a carrier having a frequency obtained by adding the center frequency identified by the information and the shift amount.

According to this configuration, each mobile station transmits signals using carrier waves of different frequencies that can be used in one frequency band in response to an instruction from the radio base station, so that the radio base station It is possible to further improve the communication quality by separating the signal received from the mobile station based on the frequency difference. A wireless communication system of the present invention is a wireless communication system including an adaptive array type wireless base station that wirelessly connects a plurality of mobile stations by spatial multiplexing, and a wireless communication system including the plurality of mobile stations. The center frequency of the frequency band and the shift amount from the center frequency are respectively identified as information corresponding to different frequencies that do not affect adjacent frequency bands and are frequencies to be assigned to the mobile stations. The mobile station is provided with notifying means for notifying the information to each mobile station, and the mobile station receives the information for identifying the center frequency of the frequency band and the shift amount from the center frequency from the radio base station, and the receiving means for receiving the information. And a transmitting unit that transmits a signal using a carrier having a frequency obtained by adding the identified center frequency and the shift amount.

With this configuration, the effects of the radio base station and the mobile station can be synergized to further improve the communication quality of the radio communication system.

[Brief description of drawings]

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

FIG. 2 is a functional block diagram of a signal processing unit.

FIG. 3 is a functional block diagram of a user processing unit.

FIG. 4 is an example of a frequency table.

FIG. 5 is an example of an offset table.

FIG. 6 is an example of a frequency management table.

FIG. 7 is an example of a link channel assignment message.

FIG. 8 is a flowchart showing a process of a control unit.

FIG. 9 is a functional block diagram of a mobile station in this embodiment.

[Explanation of symbols]

1 wireless base station 2 mobile stations 11-14 Antenna 21-24 Radio section 30 modem section 40 Baseband section 50 Signal processing unit 51a to 51d User processing unit 55 Reference signal generator 56 Send / receive switch 57 Reception frequency estimation unit 58 Weight calculator 59 adder 60 control 61 Frequency table 62 offset table 63 Frequency management table 71 radio section 72 Modem section 73 TDMA processing unit 74 Synthesizer part 75 Voice processing unit 76 speakers 77 Mike 78 Display 79 key part 82 Control unit 83 Frequency table 84 offset table 211 Transmitter 212 Receiver 521 to 524 multiplier 551-554 adder 561 to 564 transmission / reception changeover switch 581-584 multiplier

Claims (4)

(57) [Claims] 1. An adaptive array type wireless base station for wirelessly connecting a plurality of mobile stations by spatial multiplexing, which affects a communication channel using a carrier of a frequency that should be assigned to each of the mobile stations and is adjacent to the frequency. comprising a notification means for notifying each mobile station information identifying and different frequencies without causing the notification means, in a communication channel, wherein each mobile station is used as the information
The heart frequency and the shift amount from the center frequency are respectively
A radio base station characterized by notifying information for identification . 2. A plurality of mobile stations are wirelessly connected by spatial multiplexing.
A wireless base station of the adaptive array system, which is a frequency to be assigned to each of the mobile stations and is adjacent to the mobile station.
Does not affect communication channels that use carrier waves of
And notify each mobile station of information that identifies different frequencies.
That includes a notification means, the notification unit may continuously line the base station you and notifies information including the shift amount from <br/> center frequency of the communication channel each mobile station used as the information . 3. A mobile station wirelessly connected to a radio base station by spatial multiplexing, and receiving information for identifying the center frequency of a communication channel and the shift amount from the center frequency from the radio base station. And a transmitting unit that transmits a signal by using a carrier having a frequency obtained by adding a center frequency identified by the information and a shift amount. 4. A wireless communication system comprising an adaptive array type wireless base station for wirelessly connecting a plurality of mobile stations by spatial multiplexing, and a plurality of the mobile stations, wherein each of the wireless base stations comprises: From the center frequency of the communication channel used by each mobile station and the center frequency, as information for identifying the different frequencies that do not affect the communication channels that use the carriers of the adjacent frequencies each information identifying a shift amount includes a notifying means for notifying each mobile station, wherein each mobile station, each information identifying a shift amount from the center frequency and the center frequency of the previous SL communications channel The signal is transmitted using the receiving means for receiving from the radio base station and the carrier wave of the frequency added with the center frequency and the shift amount identified by the information. Wireless communication system, comprising a transmission unit.