JP2001268006A - Wireless communication systems, base stations, mobile stations - Google Patents

Abstract

(57) [Problem] To avoid an increase in the size of a base station in a space division multiple access (SDMA) communication system. SOLUTION: The direction of arrival of a radio wave emitted from a base station to a mobile station, attitude measuring means for measuring a deviation of attitude from earth coordinates, and delay time measuring means for obtaining a distance between the mobile station and the base station. Based on these measurement results, the mobile station obtains a vector having the base station as the starting point and the mobile station as the ending point, notifies this vector to the base station, and directs the directivity of the base station toward the mobile station. Control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a mobile communication system using a space division multiple access system (SDMA).

[0002]

2. Description of the Related Art Generally, in a mobile communication system, communication between a base station and a plurality of mobile stations is performed using channels having different frequencies. According to this communication system, it is necessary to increase the number of frequency channels assigned to each mobile station in order to increase the number of mobile stations that can be stored in the same call zone. Since there is a limit to the number of frequency channels that can be assigned to each mobile station, there is also a limit to the number of mobile stations that can be accommodated in the same call zone.

[0003] From such a background, a technique has been considered in which a plurality of mobile stations can secure a call with a base station while sharing the same frequency channel. This technique is a space division multiple access system (SDMA). The space division multiple access system (SDMA) is a multiple access system (Mul) in which a base station forms different directivities for a plurality of mobile stations and simultaneously communicates with the plurality of mobile stations on the same frequency channel.
ti-Beam Adaptive Base-Sta
Tion Antennas for Cellula
r Land Mobile Radio System
m: S. C Swales, IEEE VTC, 198
9).

The space division multiple access system (SDM)
The mobile communication system using A) has not been put to practical use yet.
Therefore, the prior art described here is a prior art under development. As shown in FIG. 10, the base station BS directs the main beams B1 and B2 to the mobile stations MS1 and MS2 within the same call zone ZN, so that the mobile stations MS1 and MS2 can simultaneously operate on the same frequency channel. Can make calls. By increasing the number of main beams B1 and B2, it is possible to increase the number of mobile stations that can simultaneously talk while using the same frequency channel.

An important technique for constructing an SDMA wireless communication system is a directivity forming method for each mobile station. The base station needs to direct the main beams B1 and B2 toward the mobile station to be communicated, and to direct null (in the direction of zero gain) toward the mobile station that becomes another interference source. Several algorithms are known as a directivity forming method.
It is divided into two systems.

One is a method using a replica (reference signal) of a desired wave as prior knowledge. The MMSE which forms directivity by the least square method using the replica as a reference signal is used.
(RLS, LMS). One is a method using a direction of arrival (DOA) of a desired wave as prior knowledge, and algorithms called MSN and DCMP are known. In addition, there is also an algorithm called CMA, which forms a directivity blindly without using prior knowledge using the property of constant envelope of a signal. Also, instead of pointing the null to the interference wave, the main beam is directed to the desired wave, and a low-gain directivity pattern is formed in a direction other than the desired wave, thereby suppressing the interference wave by fixed beam forming. The method can also be used in SDMA, but also in this case, it is necessary to measure the direction of arrival (DOA) of the desired wave.

In a method of forming a directivity after measuring a direction of arrival (DOA) of a desired wave, a base station has conventionally measured the direction of arrival. As an algorithm for measuring the direction of arrival (DOA), the beamformer method, Capon
Method, linear prediction method, minimum norm method, MUSIC, ESPR
IT (for details, see "Adaptive signal processing by array antenna: Nobuyoshi Kikuma, Science and Technology Publishing Company").

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 11 shows an example of a radio base station used in a conventional SDMA radio communication system. In the SDMA system, since it is necessary to form directivity in a specific mobile station, a plurality of antennas are required. In FIG. 11, K array antenna elements AN1-A
The case where NK is provided is shown. These plurality of array antenna elements AN1 to ANK have N signal processing units 11A to 11A.
1N is connected. These N signal processing units 11A to 11A
1N, N traffic channel receivers 12A to 12N and N traffic channel transmitters 13A to 13N, one control channel receiver 14, and one control channel transmitter 15, A case is shown in which a radio base station capable of communicating with N mobile stations is constituted by N direction measurement means 16 and one system controller 17.

The N signal processing units 11A to 11N have the same number of complex weight multipliers B1 to BK as the number of array antenna elements AN1 to ANK, and adder / branch unit D, respectively.
And a weight control unit CC. The signal processing units 11A to 11N receive the array antenna element A during reception.
N1 to ANK operate as first signal processing means for forming reception directivity, and at the time of transmission, array antenna elements AN
It operates as second signal processing means for giving directivity to the radiation characteristics of 1 to ANK.

When operating as the first signal processing section, the complex amplitude X which is the output of the array antenna elements AN1 to ANK is used.
1 to XK are multiplied by complex weights W1 to WK by complex weight multipliers B1 to BK, and the adder / brancher D operates as an adder, and obtains sum outputs Y1 to YN as an addition result. By appropriately selecting the complex weights W1 to WK, the directivity of the array antenna elements AN1 to ANK can be changed. When operating as the second signal processing unit,
The addition and branching unit D operates as a branching unit. In this example, the transmission signal output from the communication channel transmitter 13A is K-divided, and the K-divided signals are subjected to complex weighting by complex weight multipliers B1 to BK. By multiplying W1 to WK and applying the complex amplitude multiplied by the complex weight to each of the array antenna elements AN1 to ANK, radio waves having directivity are emitted.

Next, a method of determining the directivity of the array antenna elements AN1 to ANK will be described. Each of the array antenna elements AN1 to ANK has, for example, a coupler J1 to JK.
The azimuth measuring means 16 is connected through. The azimuth measuring means 16 captures a control signal transmitted from a mobile station to each mobile station for each time slot, measures a phase difference between signals induced in each of the array antenna elements AN1 to ANK, and calculates a phase difference based on the phase difference. The arrival direction of the radio wave of each mobile station is determined.

When the direction of arrival of the radio wave is determined, the direction measuring means 16 inputs the direction information of each mobile station to the system controller 17, and causes the system controller 17 to transfer the weight information to each weight controller CC. Then, the directivity of each of the signal processing means 11A to 11N processing the signal of each mobile station is directed to the azimuth obtained by the measurement by the azimuth measuring means 16. The control channel receiver 14 and the control channel transmitter 15 are communication channel receivers 12A to 12N.
The operation timings of the communication channel transmitters 13A to 13N are time-divisionally operated. FIG. 12 shows this state. In the time slot T1, the control channel receiver 14
The control channel transmitter 15 operates to transmit and receive control signals to and from the mobile station. In the time slot T2, the communication channel receivers 12A to 12N and the communication channel transmitters 13A to 13N operate to form a communication line with each mobile station.

In a time slot in which the control channel receiver 14 and the control channel transmitter 15 operate, the weight controller CC sets only the complex weight W1 to 1, sets the other complex weights W2 to WK to zero, and sets the array antenna element to zero. A signal is given to only AN1, and transmission and reception are performed with omni-directionality.

[0014]

As described above, the SD
When trying to build a MA wireless communication system,
The base station determines the direction in which each mobile station exists by calculation, and determines the directivity. The algorithm for measuring the azimuth requires a considerable amount of calculation, so that the load on the base station is increased and the size of the apparatus is increased.
SUMMARY OF THE INVENTION An object of the present invention is to provide an SDMA wireless communication system having a simple configuration as a whole, avoiding an increase in the size of a base station, and to propose a base station and a mobile station used in the wireless communication system.

[0015]

According to the first aspect of the present invention, a control channel for transmitting signals for all mobile stations under the control of a base station, such as an incoming call signal and a broadcast signal, is omni-directional. Channels that transmit and receive signals and transmit signals intended for a specific mobile station, such as a speech channel and a control channel associated with the speech channel, are directed to the particular mobile station using space division multiple access technology. In a wireless communication system that performs transmission and reception with an aim, the mobile station is provided with vector operation means for obtaining a vector starting from the base station and ending at the own station. The vector operation means calculates the vector calculated by the vector operation means in the base station. And the base station proposes a wireless communication system that forms directivity for the mobile station based on this vector.

According to a second aspect of the present invention, in the wireless communication system according to the first aspect, the base station includes a multiplier for multiplying a complex amplitude of the array antenna by a complex weight according to a vector transmitted from the mobile station. The present invention proposes a base station configured to form directivity corresponding to each mobile station by taking the sum of the multiplication results. According to a third aspect of the present invention, in the wireless communication system according to the first aspect, the mobile station measures an arrival direction measuring means for measuring an arrival direction of a radio wave emitted from the base station, and measures a delay time of a radio wave emitted from the base station. Delay time measuring means, attitude measuring means for measuring the attitude of the own station with respect to a coordinate axis fixed to the earth, arrival direction measuring means, delay time measuring means, using the measurement results of the attitude measuring means to the base station as a starting point The present invention proposes a mobile station including a vector operation unit that calculates a vector having its own station as an end point, and a vector information transmission unit that transmits a vector calculated by the vector operation unit to a base station.

According to a fourth aspect of the present invention, in the wireless communication system according to the first aspect, the mobile station measures an absolute position of the own station with respect to a coordinate axis fixed to the earth; Vector calculation means for calculating a vector having a base station for communication as a start point and an end point for the own station from a map storing an area including an absolute position of the station and an absolute position and a map obtained from the absolute position measurement means; And a vector information transmitting means for transmitting the vector calculated by the vector calculating means to the base station.

According to a fifth aspect of the present invention, in the mobile station used in the wireless communication system according to the first aspect, a moving speed calculating means of the mobile station based on a difference between vectors of adjacent times and a fixed time by the moving speed calculating means. Equipped with a predicted position calculating means for predicting and calculating the position of the mobile station later, and vector information for converting the predicted position calculated by the predicted position calculating means into vector information and notifying the vector information to the base station, We propose a mobile station with such a configuration.

According to a sixth aspect of the present invention, in the mobile station used in the wireless communication system according to the first aspect, an absolute position measuring means for measuring an absolute position of the own station with respect to a coordinate axis fixed to the earth; Map information storage means for storing map information of an area including the position of the station; position prediction means for predicting the position of the mobile station after a certain period of time by referring to the travel path reserved in the map information storage means; The predicted position information predicted by the prediction means is converted into vector information,
A mobile station having a configuration including vector information transmitting means for transmitting to a base station is proposed.

[0020]

According to the radio communication system of the present invention, the mobile station individually obtains a vector starting from the base station and ending at each mobile station, and notifies the base station of this vector information. The base station forms directivity for each base station based on the transmitted vector information, so that the base station does not need to calculate and calculate the azimuth for each mobile station. As a result, there is an advantage that the burden on the base station can be reduced and the scale of the device can be reduced. Note that the mobile station needs to be provided with vector operation means. However, since this vector operation only requires vector operation relating to itself, the size of the mobile station does not increase.

[0021]

FIG. 1 shows an example of a base station used in a radio communication system according to the present invention. Parts corresponding to those in FIG. 11 are denoted by the same reference numerals. In the wireless communication system according to the present invention, a vector having a base station as a start point and a mobile station as an end point is measured and obtained on the mobile station side, and this vector information is transmitted from the mobile station to the base station. The directivity is controlled by the obtained vector information.

The vector information is transmitted from the mobile station via the control channel and is input to the complex weight calculating means 17A provided in the system controller 17. The complex weight calculation unit 17A calculates and calculates complex weights W1 to WK for each mobile station according to the vector information sent from the mobile station, and calculates the complex weights W1 to WK by the weight control unit CC.
To the complex weight multipliers B1 to BK to provide directivity to the reception characteristics and radiation characteristics of the array antenna elements AN1 to ANK.

FIG. 2 shows an embodiment of the mobile station according to the present invention. The mobile station according to the invention comprises a plurality of antenna elements BN
1 to BNK, and the plurality of antenna elements BN1 to BN
The signals induced by the NK are extracted by the couplers 21A to 21K, and the arrival direction of the radio wave is obtained by measuring the phase difference (time difference) of the control channel signal sent from the base station by the arrival direction measuring means 28. In the example shown in FIG. 2, a case is shown in which BN1 of the plurality of antenna elements BN1 to BNK is also used as a transmission and reception antenna for a communication channel, and BNK is also used as a transmission and reception antenna for a control channel. Arrival direction φ of radio wave measured by arrival direction measuring means 28
Calculating means 27 provided in the system controller 27
Input to A. The delay data from the delay time measuring means 29 is input to the vector calculating means 27A. The calculation of the delay data can be performed, for example, as follows. The base station transmits a radio wave that performs a frequency sweep in a predetermined frequency range. The mobile station obtains a phase difference between signals generated in the antenna elements BN1 to BNK of the radio wave whose frequency is swept. From the phase difference and the arrival direction of the radio wave measured by the arrival direction measurement means 28, the antenna element BN1
~ Complex weight W1 for giving BNK directivity
The propagation delay time of the radio wave is calculated from the WK (for details, see "Adaptive signal processing by array antenna: Nobuyoshi Kikuma" described above).

At the same time, the attitude measuring means 30 can be constituted by, for example, a magnet for detecting the north which is the reference coordinate axis of the earth. By specifying the north, east, south, and west directions using a magnet, it is possible to detect a deviation (posture) between the reference axis of the mobile station and the coordinate axes of the earth. 3 and 4
This is shown using. FIG. 3 shows delay time measuring means 2
9, the delay time τ between the base station BS and the mobile station MS
And the state in which the arrival direction φ of the radio wave from the base station BS is detected. XY shown in FIG. 3 indicates a reference axis in a horizontal plane given to the mobile station MS. That is, as shown in FIG.
The reference axis XY of the mobile station MS is determined by the arrangement of the antenna elements BN1 to BNK attached to S. In the example shown in FIG. 5, X is the direction in which the phase difference between the signals received by the antenna elements BN1 to BNK is maximum, and Y is the direction in which the phases of all the signals are the same.

The attitude measuring means 30 built in the mobile station MS obtains a deviation δ (see FIG. 4) between the reference axis XY of the mobile station MS and the coordinate axis NW indicating the north and east of the earth. The vector calculation means 27A obtains the distance γ from the delay time τ, and θ =
The vector information (γ, θ) is calculated by calculating φ + δ, and the vector information (γ, θ) is transmitted to the base station BS through the vector transmission means 31 and the control channel transmitter 26. The directionality of the directivity of AN1 to ANK is determined.

As is apparent from the above description, according to the radio communication system of the present invention, vector information including distance information is notified to the base station. The transmission power can be controlled according to the transmission power. FIG. 6 shows an embodiment of a mobile station proposed in claim 4 of the present invention. According to claim 4 of the present invention, for example, an absolute position measuring means 32 for measuring an absolute position (latitude, longitude) on the earth called GPS or the like, and an area including the position of the base station BS and the position of the own station are defined. A mobile station equipped with the stored map storage means 33 is proposed.

By inputting the position of the own station measured by the absolute position measuring means 32 into the map storage means 33, the coordinate information (X1, Y) of the own station shown in FIG.
1) and the coordinate information (X2, Y2) of the base station BS can be obtained. From this coordinate information, the vectors with the base station BS as the start point and the mobile station MS as the end point are (X1-X2, Y1-
Y2) is obtained. When this coordinate display is converted to polar coordinate display, station coordinates (γ, θ) shown in FIGS. 3 and 4 are obtained. This vector information is transmitted to the base station via the vector information transmitting means 31 and the control channel transmitter 26.

FIG. 8 shows an embodiment of the mobile station proposed in claim 5. In this embodiment, the mobile station shown in FIG. 2 is provided with a moving speed calculating means 27B and a predicted position calculating means 27C for calculating and predicting the position of the mobile station after a predetermined time based on the calculation result of the moving speed calculating means 27B. An example will be described. The moving speed calculator 27B calculates the moving speed of the mobile station MS from the difference between the vectors calculated at the close time intervals by the vector calculator 27A. The predicted position calculating unit 27C calculates the position of the mobile station after a predetermined time from the moving speed calculated by the moving speed calculating unit 27B, and calculates the predicted position. This predicted position is converted into vector information, and the vector information
1 to the base station via the control channel transmitter 26.

As described above, the predicted position of the mobile station is notified to the base station as vector information, and the base station stably tracks the moving mobile station by forming the directivity predictively based on the vector information. Can be. FIG. 9 shows an embodiment of the mobile station proposed in claim 6 of the present invention. Claim 6 shows an embodiment in which a position estimating means 34 is provided in a mobile station having a configuration equipped with the absolute position measuring means 32 shown in FIG.

In this case, since the travel route can be input in the map information storage means 33 in advance, the position of the mobile station after a predetermined time can be determined by referring to the planned travel route by the position prediction means 34. Can be predicted. By converting the predicted position into vector information and notifying the base station, the directivity formed in the base station can be accurately tracked in accordance with the movement of the moving object. In FIG. 8, the mobile station having the structure shown in FIG.
7B and the configuration provided with the predicted position calculation means 27C are shown, but the mobile station having the configuration provided with the absolute position measurement means 32 shown in FIG. 6 may be provided with the movement speed calculation means 27B and the predicted position calculation means 27C. It can be easily understood that the same operation and effect as described above can be obtained.

In the above-described embodiment, the complex weight W1 is used to determine the delay time of the radio wave between the base station and the mobile station.
In the description above, the weight multipliers B1 to BK (see FIG. 1) are connected to the antenna elements AN1 to ANK, and the complex weights W1 to WK are supplied to the weight multipliers B1 to BK. And each antenna element BN1
The complex amplitudes X1 to XK induced by .about.BNK are multiplied by the complex weights W1 to WK, and the mobile station side also performs antenna element AN1.
ANK can be used to provide directivity. In the case of such a configuration, there is obtained an advantage that the mobile station can improve the resistance to the multiplex wave of the speech channel.

[0032]

As described above, according to the radio communication system of the present invention, each mobile station measures the position of each mobile station, converts this position information into vector information, and notifies it to the base station. Since the base station does not need to measure the position for each mobile station, the burden on the base station can be reduced. Therefore, there is an advantage that the size of the base station can be prevented from increasing.

Further, in the present invention, a method is employed in which vector information starting from the base station and ending at the mobile station is notified to the base station, so that the base station can know the distance from each mobile station. Therefore, since power control can be performed in accordance with the distance, the base station achieves lower power compared to a case where the transmission power is output at a constant transmission power while the distance between the base station and the mobile station is short. be able to. Therefore, for example, in a battery-operated base station, the power consumption can be reduced, the charging interval to the battery or the number of times of replacement of the battery can be reduced, and there is an advantage that labor for maintenance can be saved. Furthermore, according to the configuration of the mobile station proposed in claims 5 and 6 of the present invention, the directivity of the base station can be directed to the predicted position even while the mobile station is moving. Therefore, even if the mobile station moves fast, the position of the mobile station is predicted at the elapse of a certain time, so that the directivity does not delay the movement of the mobile station, and the mobile station moves stably. Can be tracked.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining an embodiment of a base station proposed in claim 1 of the present invention.

FIG. 2 is a block diagram for explaining an embodiment of the mobile station proposed in claim 3 of the present invention.

FIG. 3 is a view for explaining the operation of an arrival direction measuring means used in the embodiment shown in FIG. 2;

FIG. 4 is a view for explaining the operation of an arrival direction measuring means and an attitude measuring means used in the embodiment shown in FIG. 2;

FIG. 5 is a perspective view for explaining the operation of an arrival direction measuring means used in the embodiment shown in FIG. 2;

FIG. 6 is a block diagram for explaining an embodiment of a mobile station proposed in claim 4 of the present invention.

FIG. 7 is a view for explaining the operation of the embodiment shown in FIG. 6;

FIG. 8 is a block diagram for explaining an embodiment of the mobile station proposed in claim 5 of the present invention.

FIG. 9 is a block diagram for explaining an embodiment of the mobile station proposed in claim 6 of the present invention.

FIG. 10 is a conceptual diagram for explaining a space division multiple access system to which the present invention is applied.

FIG. 11 is a block diagram for explaining a configuration of a conventional base station.

FIG. 12 is a timing chart for explaining the operation sequence of the base station shown in FIG. 11;

[Explanation of symbols]

 BS Base station MS Mobile station AN1 to ANK Array antenna element BN1 to BNK antenna element B1 to BK Weight multiplier CC Weight control unit W1 to WK Complex weight 11A to 11N Signal processing unit 12A to 12N, 23 Receiver for speech channel 13A to 13N, 24 Communication channel transmitter 14, 25 Control channel receiver 15, 26 Control channel transmitter 17 System controller 17A Complex weight calculator 21A to 21K Combiner 37A Vector calculator 27B Moving speed calculator 27C Predicted position Calculation means 28 Arrival direction measurement means 29 Delay time measurement means 30 Attitude measurement means 31 Vector information transmission means 32 Absolute position measurement means 33 Map storage means 34 Position prediction means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shuji Kubota 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation (reference) 5J021 AA05 AA06 AA11 AB01 DB02 FA13 FA16 FA32 GA02 HA10 JA07 5K067 AA11 CC01 DD20 DD27 EE02 EE10 EE53 HH21 HH23 JJ52 JJ56 KK02 KK03

Claims (6)

[Claims] A control channel for transmitting a signal for all mobile stations under the control of a base station, such as an incoming call signal and a broadcast signal, performs transmission and reception with omni-directionality. A channel for transmitting a signal intended for a specific mobile station such as an accompanying control channel is used in a wireless communication system that transmits and receives directivity to a specific mobile station using a space division multiple access technology. The mobile station is provided with vector calculation means for obtaining a vector having the base station as a start point and the own station as an end point,
A radio communication system wherein the vector calculated by the vector calculation means is notified to the base station, and the base station forms directivity for the mobile station based on the vector. 2. The wireless communication system according to claim 1, wherein the base station includes a multiplier that multiplies a complex amplitude of the array antenna by a complex weight according to a vector sent from the mobile station, and a sum of the multiplication results. A base station configured to form directivity corresponding to each mobile station by taking the following. 3. The wireless communication system according to claim 1, wherein the mobile station measures an arrival direction of a radio wave emitted by the base station, and a delay time that measures a delay time of a radio wave emitted by the base station. Measuring means, an attitude measuring means for measuring the attitude of the own station with respect to a coordinate axis fixed to the earth, and a base station as a starting point using the measurement results of the arrival direction measuring means, the delay time measuring means, and the attitude measuring means. A mobile station comprising: vector operation means for calculating a vector having a station as an end point; and vector information transmission means for transmitting the vector calculated by the vector operation means to a base station. 4. The radio communication system according to claim 1, wherein said mobile station comprises: an absolute position measuring means for measuring an absolute position of the own station with respect to a coordinate axis fixed to the earth; a position of a base station and an absolute position of the own station. A vector storing means for calculating a vector having a base station for communication as a start point and an end point for the own station based on the absolute position and the map obtained from the absolute position measuring means, A mobile station, comprising: vector information transmitting means for transmitting a vector calculated by an arithmetic means to a base station. 5. A mobile station used in the wireless communication system according to claim 1, wherein a moving speed calculating means for calculating a moving speed of the mobile station from a difference between the vectors at a close time; A predicted position calculating means for predicting and calculating the position of the mobile station later, and a vector information transmitting means for converting the predicted position calculated by the predicted position calculating means into vector information and notifying the vector information to the base station. A mobile station characterized in that it has a configuration. 6. A mobile station for use in a wireless communication system according to claim 1, wherein an absolute position measuring means for measuring an absolute position of the own station with respect to a coordinate axis fixed to the earth, and an area including a position of the base station and the own station. With reference to the map information storage means storing the map information of the above, and the travel route reserved in the map information storage means,
A position predicting means for predicting the position of the mobile station after a predetermined time; and a vector information transmitting means for converting the predicted position information predicted by the position predicting means into vector information and transmitting the vector information to the base station. A mobile station, characterized in that: