WO2004028037A1

WO2004028037A1 - Radio communication system

Info

Publication number: WO2004028037A1
Application number: PCT/JP2002/009704
Authority: WO
Inventors: Kazunari Kihira; Yoshitaka Hara; Takashi Sekiguchi
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2002-09-20
Filing date: 2002-09-20
Publication date: 2004-04-01

Abstract

A radio communication system comprising a radio base station for forming beams having a plurality of different directivities and a plurality of terminal stations for performing communication with the radio base station. Each terminal station comprises a means for estimating the ratio of the desired signal power to the interference signal power of an downstream line transmitted from a plurality of beams of the radio base station, a beam selecting means for selecting the optimum beam from the ratio of the desired signal power to the interference signal power, and a means for informing the selected beam number by using an upstream line from the terminal station to the radio base station. The radio base station comprises a transmission control means for transmitting information signals to the terminal station by using the beam corresponding to the beam number if there is the beam number informed from the terminal station.

Description

Description Wireless communication system

TECHNICAL FIELD The present invention relates to wireless communication between a wireless base station and a terminal station used for mobile communication and the like, and particularly achieves good information transmission efficiency by following a change in propagation path characteristics while reducing interference. A wireless communication system capable of Background art

In recent years, PDC (Personal Digital Cellular) and PHS (Personai Handy-phone

Wireless communication systems centering on mobile phones, such as the Mobile Phone System, have been recognized for their convenience and are spreading at a remarkable pace. On the other hand, with the increase in users, problems such as tight use of frequencies and deterioration of communication quality have arisen. In particular, the occurrence of multipath fading due to reflection and scattering at surrounding structures is a problem peculiar to wireless communication, and is a major factor in deterioration of communication quality. Conventionally, as a countermeasure, a radio base station adopts a sector configuration in which a plurality of directional antennas having different directivities are arranged, thereby sequentially selecting the antenna having the best reception state. Have been.

In addition, as a technique for further enhancing the functionality, a plurality of spatially orthogonal multiple stations are located according to the positions of multiple terminal stations unevenly distributed in the service area and the direction of arrival of signals transmitted from the terminal stations. Beams are formed and allocated for receiving signals from each terminal station.

Specifically, there is an adaptive array antenna that actively removes a signal from a terminal station (interfering station) that is present in an arbitrary direction and is different from the terminal station that desires communication. An adaptive array antenna is a signal processing system that uses a plurality of antenna elements to adjust the amplitude and phase of their received signals and combine them to suppress interference signals at the output. That is, in an environment where there is an interference signal that affects the communication quality, the beam is directed to the arrival direction of the desired signal, and the interference signal Operates so as to form a directional null for the arrival direction. Adjusting the amplitude and phase of the received signal is equivalent to complex weighting the output signals from the antenna elements # 1 to #N as shown in FIG.

For the downlink (base station transmission, terminal station reception) TDD (Time Division Duplex) method (a method in which the same frequency is used by time division for transmission and reception), the transmission and reception channel characteristics are In the case of a sector configuration, the antenna selected in the uplink (base station reception, terminal station transmission) can be used for the downlink as well, and when using an adaptive array antenna, By turning the directivity null toward the interfering station, suboptimal control can be performed.

On the other hand, FDD (Frequency Division

In the case of the (Duplex) method, transmission / reception propagation path characteristics are different, and good characteristics may not be obtained with the above method of determining the transmission method of the downlink from the received signal of the uplink. Therefore, information on the propagation path characteristics of the downlink is measured at the terminal station, and information necessary for controlling the transmission beam at the radio base station is extracted. Then, there is a feedback control method in which the information is inserted into an uplink transmission signal to notify the radio base station. In this case, it is possible to control the beam used for transmission on the radio base station side so that the reception state of the terminal station is always good irrespective of the difference between the transmission and reception frequencies, and the communication quality can be expected to be improved. ,

For example, in the conventional antenna selection control method, as shown in Fig. 15, pilot symbols for each beam (assuming N beams in the figure) are inserted into each slot in the downlink information symbol sequence. Send. The terminal station detects the N pilot symbol sequences transmitted from each beam, measures the received power of each, and broadcasts the beam number having the highest received power on the uplink, so that In the slot, the radio base station transmits information symbols using the selected beam.

Also, when an adaptive array antenna is applied, the information to be broadcast in the uplink includes the propagation path transfer coefficient for each antenna element of the radio base station and the estimation of the transmission weight at the terminal station. Is the weighting factor for each antenna element, o

In this way, the terminal station estimates the parameters related to the propagation path characteristics, Broadcasting to a radio base station using a transmission line enables beam control that follows fluctuations in propagation path characteristics even in systems with different uplink and downlink frequencies. However, in the conventional beam selection control method, as the number of beams increases, as shown in Fig. 15, the ratio of pilot symbols to information symbols in the entire slot increases, resulting in deterioration of information transmission efficiency in the downlink. Problem

On the other hand, when an adaptive array antenna is used, the channel transfer coefficient or weight coefficient broadcast from the terminal station is a complex number composed of amplitude and phase information, and each coefficient corresponding to the number of antenna elements is fed back in the uplink. The amount of information is increased. For example, when the number of bits per weighting coefficient is k and the number of beams is n, the amount of information to be fed back is also k * n bits. For example, it is necessary to insert this control signal into the uplink information symbol every slot, and the ratio of the control symbol to be inserted to the uplink information symbol is increased, so that the uplink information transmission efficiency is significantly reduced. there is a possibility.

Also, the technique of forming a null in the direction of the interfering station is an extremely effective method in ideal operation.However, considering the actual operation, the processing delay in the terminal station divided by the control delay due to feedback The effect of this is large, and there is a possibility that the interference suppression effect cannot be sufficiently obtained for the processing complexity.

An object of the present invention is to provide a wireless communication system which solves the above-mentioned problems and realizes improvement of communication quality while maintaining information transmission efficiency while being robust, that is, capable of responding to environmental changes.

Disclosure of the invention

The present invention relates to a radio communication system including a radio base station forming beams having a plurality of different directional directions and a plurality of terminal stations communicating with the radio base station, wherein each of the terminal stations is Means for estimating the ratio of desired signal power to interference signal power of the downlink transmitted from the plurality of beams of the station, and beam selecting means for selecting an optimal beam from the desired signal power to interference signal power ratio. Means for notifying the selected beam number using an uplink from the terminal station to the radio base station; Transmission control means for transmitting an information signal to the terminal station by using a beam corresponding to the beam number if there is the beam number broadcasted from the terminal station. A wireless communication system characterized by the following.

Further, the radio base station includes an array antenna configured by a plurality of antenna elements for forming a plurality of beams, and a beam forming apparatus that arbitrarily sets a beam shape according to an environment in which the radio base station is installed. Means are provided. Further, the transmission control means of the radio base station multiplexes and adds a known signal different for each of a plurality of beams formed by the radio base station to an information signal transmitted from the radio base station to the terminal station. The desired signal power to interference signal power ratio estimating means of the terminal station detects the known signal and estimates the desired signal power to interference signal power ratio.

Further, data symbols orthogonal to each other are used as the known signal.

Also, the radio communication system performs a communication of the CDMA communication system, and the transmission control means of the radio base station spreads the known signal by orthogonal codes, and outputs the spread known signal for each beam. The multiplexed signal is added to the information signal transmitted to the terminal station, and the desired signal power to interference signal power ratio estimating means of the terminal station detects the spread known signal, and It is characterized by estimating the interference signal power ratio.

Further, it is characterized in that the desired signal power to interference signal power ratio estimating means of the terminal station detects the known signal after R AKE combining and estimates the desired signal power to interference signal power ratio.

Further, the desired signal power to interference signal power ratio estimating means of the terminal station detects the known signal included in a path having the highest received power among the desired signal group received by the terminal station, and obtains the desired signal power. It is characterized by estimating an interference signal power ratio.

Also, the beam selection means of the terminal station selects all beams whose desired signal power to interference signal power ratio is larger than a set threshold, and the transmission control means of the radio base station uses these beams to transmit information. It is characterized by transmitting a signal.

In addition, a desired signal power to interference signal power ratio estimating means of the terminal station, a beam selecting means, In the notification means, and in the transmission control means of the radio base station, in the initial state of communication start, after determining the beam number using all beams, a beam corresponding to the beam number and a beam adjacent thereto are determined. And estimating the ratio of the power of the desired signal to the power of the interference signal in the downlink and sequentially updating the beam to be selected.

In the terminal station, a desired signal power to interference signal power ratio estimating means, a beam selecting means, a notifying means, and a transmission controlling means of the radio base station, wherein in the initial state of communication start, the terminal station uses all beams. To estimate the ratio of the desired signal power to the interference signal power in the downlink, and broadcast information on the angle range in a good reception state using the uplink to the radio base station. A plurality of beams formed in the specified range, estimating the ratio of the desired signal power to the interference signal power in the downlink, and sequentially updating the beams to be selected.

Further, the present invention is characterized in that the ratio of the desired signal power to the interference signal power in the downlink is periodically estimated using all the beams, and information on the angle range in which the reception state is good is updated.

Further, based on the angle range notified from the terminal station, a plurality of beams are re-formed within the range by using the allowed degree of freedom to the maximum extent.

Also, a plurality of array antennas for forming beams having a plurality of different directional directions are arranged at a distance such that the correlation characteristics of the propagation path can be ignored sufficiently, and a beam to be used for transmission is selected and transmitted. It is characterized by the following.

Further, a plurality of array antennas for forming beams having a plurality of different directional directions are arranged at a distance such that the correlation characteristics of the propagation path can be sufficiently ignored, and one optimal beam is selected from all the beams. It is characterized by transmitting. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram showing a configuration of a wireless base station of a wireless communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a terminal station in a wireless communication system according to an embodiment of the present invention.

FIG. 3 is a signal diagram of a transmission slot in a radio base station according to an embodiment of the present invention. Diagram showing an example of the format

FIG. 4 is a diagram showing an example of a specific configuration of each beam SIR estimator in FIG. 2,

FIG. 5 is a block diagram showing the configuration of a wireless base station of the wireless communication system according to the present invention provided with a plurality of array antennas,

FIG. 6 is a block diagram showing a configuration of a wireless base station of a wireless communication system according to another embodiment of the present invention.

FIG. 7 is a diagram showing an example of a specific configuration of the beam forming circuit of FIG. 6,

FIG. 8 is a diagram showing an example of a specific configuration of each beam SIR estimator of the terminal station in the CDMA communication system of the present invention.

FIG. 9 is a diagram showing another example of a specific configuration of each beam SIR estimator of the terminal station in the CDMA communication system of the present invention.

FIG. 10 is a diagram showing an example of a signal format of a transmission slot in a radio base station according to another embodiment of the present invention.

FIG. 11 is a diagram for explaining a transmission beam forming method in a radio base station according to another embodiment of the present invention,

FIG. 12 is a diagram for explaining a transmission beam forming method in a radio base station according to still another embodiment of the present invention.

FIG. 13 is a diagram for explaining a transmission beam forming method in a radio base station according to still another embodiment of the present invention.

FIG. 14 is a diagram for explaining a conventional wireless communication system,

FIG. 15 is a diagram for describing insertion of a pilot symbol for beam selection in a conventional antenna selection type control method. BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1

A radio communication system, a radio base station, and a terminal station according to an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are block diagrams each showing an example of the configuration of a wireless base station and a terminal station of a wireless communication system according to an embodiment of the present invention. An example of the slot signal format is shown. -It is a figure.

The radio base station in FIG. 1 includes a plurality of antenna elements (# 1 to #N) 101 to 103 having directivity in different directions, a duplexer 104 to 106, a transmitter (Tx) 107 to 109, and a receiver. (Rx) 110 to 112, a reception beam control circuit 113, a demodulator 114, a beam number detector 115, a modulator 116, a pilot symbol generator 117, and a beam switching circuit 118.

The terminal station in FIG. 2 includes an antenna element 141, a duplexer 142, a receiver (Rx) 143, a transmitter (Tx) 144, each beam SIR estimator 145, a beam selection circuit 146, and a modulator 147. Be composed.

An operation of the wireless communication system according to the embodiment of the present invention will be described. In the terminal station shown in FIG. 2, a signal received by an antenna 141 is input to a receiver (Rx) 143 via a duplexer 142. The receiver 143 converts: a received signal in an RF (Radio Frequency) band into a baseband digital signal. Each beam SIR estimator 145 detects a pilot symbol (known signal) of each beam multiplexed and inserted at the head of each slot as shown in FIG. 3 described later, and calculates a desired signal power for each beam. Estimate the interference signal power ratio (SIR: Signal-to-Interference Ratio).

As an example of a specific configuration of each beam SIR estimating section 145, a configuration as shown in FIG. 4 is cited. (1 to N) 155 to 157, SIR calculator (1 to N) 158 to: 160.

Pilot symbol generator 151 generates the same pilot symbol for each beam as that inserted into the transmission slot in the radio base station. In the correlators 152 to 154, a correlation operation is performed between these pilot symbols and the output signal from the receiver 143 to extract a desired signal component. After that, the timing detectors 155 to 157 detect the sample whose timing coincides with the pilot symbol included in the received signal, that is, the timing of the sample whose SIR is most improved, and then determine the timing of the detected timing. Using the samples, SIR calculators 158 to 160 derive the SIR of each beam. The SIR value of each of these beams is input to the subsequent beam selection circuit 146.

It should be noted that the SIR calculators 158 to 160 use multiple samples By performing the averaging process, it is possible to estimate an accurate value.

The beam selection circuit 146 selects a beam having the highest SIR. This is reported to the radio base station on the uplink. The procedure is to insert the information of the selected beam number into the information symbol to be transmitted, perform modulation processing in the modulator 147, and then transmit the signal to the transmitter (Tx The signal is converted into an RF band signal at) 144 and radiated from the antenna 141 via the duplexer 142.

In this way, the information fed back from the terminal station need only be the beam number, and thus has little effect on the transmission efficiency of the uplink. For example, when using eight beams, only three bits are required as control information. In addition, since the beam number is broadcast, no matter what shape the beam is used in the radio base station, it is not necessary for the terminal station to consider them, and the system expandability is excellent. A signal component including various information data such as voices transmitted from the radio base station is detected by a demodulator or the like. However, in the configuration example of FIG. This part has been omitted to make the features easier to understand.

On the other hand, in the radio base station of FIG. 1, the modulated signal transmitted from the terminal station is received by アンテナ antenna elements 101 to 103 having directivities in different directions, and is received by the duplexers 104 to 106. Via the receivers (Rx) 110 to 112 to convert the RF band signal into a base band digital signal.

The antenna element groups 101 to 103 have different directivities, and are set according to the communication range of the radio base station. For example, when 360 degrees around the entire circumference are covered by eight antenna elements, the beam width of each antenna element may be set to about 45 degrees and arranged evenly.

The reception beam control circuit 113 adjusts the amplitude and phase of the reception signal of each antenna element and combines them to obtain an output signal. At this time, the control means of the reception beam control circuit 113 uses various existing algorithms, for example, diversity combining techniques such as selective combining and maximum ratio combining, and an adaptive array that forms nulls for interference signals. Various control algorithms of the antenna are included.

The output signal after the array synthesis is demodulated by the demodulator 114, and the beam number detector At 115, the information of the selected beam number included in the received data is detected. In FIG. 1, the process of determining information symbols from the received data obtained from demodulator 114 is omitted in FIG. 1 to simplify the description and to make the features of the present invention easier to understand.

The transmission operation will be described. Pilot symbol generator 117 generates pilot symbols of the specified length by the number of beams to be formed, and modulates information symbols by modulator 116 and beam numbers detected by beam number detector 115 The information is input to the beam switching circuit 118 together with the information.

The beam switching circuit 118 creates a format transmission slot as shown in FIG. That is, an information symbol is added to the back of the pilot symbol of the beam corresponding to the beam number detected by the beam number detector 115 (FIG. 3 shows an example when Beam2 is selected). For other beams, either add nothing or insert a null symbol such as an all zero value. By performing multiplexing for simultaneously transmitting the transmission slots (N in this case) of these beams, it is possible to reduce the ratio of pilot symbols in the slot and prevent a reduction in transmission efficiency.

In the embodiment of the present invention, since the pilot symbols of each beam are multiplexed and transmitted at the same time, the correlation characteristic of each pilot symbol is as small as possible in consideration of the accuracy of SIR estimation at the terminal station. It is desirable to set each pilot symbol to be orthogonal.

For example, in the CDMA (Code Division Multiple Access) communication system, communication at the same time is enabled by identifying users by using spreading codes. By allocating orthogonal spreading codes to the pilot symbols of each beam and performing spreading processing, the present invention can be applied to the CDMA system, and an efficient transmission system can be realized.

Then, the signals are converted into RF band signals by transmitters (Tx) 107 to 109 and radiated by antenna elements 101 to 103 via duplexers 104 to 106.

In this way, the radio base station forms a plurality of beams, multiplexes and transmits signals orthogonal to each other from each, and selects and broadcasts the beam having the best reception state at the terminal station. Wireless communication using different frequencies for downlink and In a communication system, it is possible to maintain the information transmission efficiency and follow the fluctuation of the propagation path characteristics.

Further, as shown in FIG. 5, in the radio base station, a plurality of array antennas 10a and 10b-- consisting of antenna elements 101 to 103 are installed, and the intervals are set so that the propagation path characteristics are unrelated to each other. By performing the above control on each array antenna, it is possible to obtain a diversity effect. Array antennas 10a and 101 that form beams having a plurality of different directional directions may be used to select and transmit a beam to be used for transmission, or may be configured to transmit the whole (all) One of the optimal beams (with the highest SIR) may be selected and transmitted. The control section consisting of 104 to 118 in FIG. 1 may be provided individually for each array antenna, or one set may be provided in common and switched for connection.

Embodiment 2

Next, a radio base station according to another embodiment of the present invention will be described. FIG. 6 is a block diagram showing a configuration of a radio base station according to another embodiment of the present invention. The radio base station shown in FIG. 6 forms each beam by digital signal processing, and has a plurality of omnidirectional antenna elements (# 1 to #N) 121 to 123 and duplexers 124 to 126. Transmitter (Tx) 127 to 129, receiver (Rx) 130 to: 132, receive beam control circuit 133, demodulator 134, beam number detector 135, modulator 136, pilot symbol It comprises a generator 137, a beam switching circuit 138, and a beam forming circuit 139 for forming a plurality of beams by digital signal processing.

Explaining the specific operation, the elements other than the antenna elements (# 1 to #N) 121 to 123 and the beam forming circuit 139 are basically the same as the corresponding parts shown in FIG. Omitted.

Arbitrary N antenna elements 121 to 123 are each formed of a so-called non-directional antenna element having no directivity in a specific direction.

Subsequent operations are the same as those of the wireless base station in FIG. 1, except that the beam switching circuit 138 creates a transmission slot for each beam, and the beam forming circuit 139 performs digit signal processing. Form a beam with multiple pointing directions Element 121-: Transmitted by 123.

FIG. 7 shows an example of a specific configuration of the beam forming circuit 139. In FIG. 7, the beam forming circuit includes distributors (1 to L) 171 to 173, a weighting coefficient adder 174 for assigning weighting coefficients, and combiners (1 to N) 175 to 177. FIG. 7 shows an example in which the number of beams to be formed is L, but the number of beams L does not need to be the same as the number N of antenna elements. The transmission slot of each beam generated by the beam switching circuit 138 in FIG. 6 is distributed to N by the distributors 171 to 173.

Each of the distributed slots has its amplitude and phase components adjusted by complex weighting factors Wii (i = l, ..., N; j = l, ..., L) r74, and then the combiners (1 to Ν) Combined by 175 to Γ77 and multiplexed.

That, wij~w _N j corresponds to the weighting factor of the array antenna for beam j, by such a weighting coefficient L sets prepared performs beamforming in daisy evening Le stage.

These processes can be realized not only by a hardware as shown in FIG. 7 but also by software. Therefore, DFT (Discrete Fourier

Transform) and FFT (Fast Fourier Transform) can be used easily.

In this way, by forming each beam by the digital signal processing, that is, setting the beam shape, it is possible to freely re-form the beam according to the installation environment of the wireless base station and environmental fluctuations. Become.

Embodiment 3.

FIG. 8 shows an example of the configuration of each beam SIR estimator (see 145 in FIG. 2) of the terminal station according to the present invention in the CDMA communication system. Each beam SIR estimator 145a in FIG. 8 includes a spreading code generator 181, a MF (Matched Filter) (1-N) 182-: 184, and a path timing detector (1-N) 185. ~: 187, RAKE (1-N) combiners 188-190, and SIR calculators (1-N) 191-: 193.

The spreading code generator 181, MF (Matched Filter) 182-: 184, each path timing detector 185-187, and the SIR calculators 191-193 are composed of the pilot symbol generator 151 shown in FIG. , Correlator 152-154, Evening detector 155-: 157, SIR calculation unit 158-: Performs an operation similar to 160.

In the CDMA communication system, a spread code with a higher data rate than information symbols is spread over a wideband signal and transmitted. On the receiver side, the original information symbols are reproduced by performing correlation detection using the same spreading code as that used on the transmitting side (despreading process). At this time, the smaller the cross-correlation characteristic of the spreading code assigned to each user, the greater the interference suppression effect in the despreading process.

In the wireless communication system according to the embodiment of the present invention, this characteristic is used for beam selection processing in the terminal station. This will be specifically described below.

As described in Embodiment 1, when a terminal station receives a transmission slot in which a pilot symbol is spread using an orthogonal spreading code for each beam, the spreading code generator 181 shown in FIG. Generate the same spreading code as used in the station and input it to MF182 ~: 184. After performing correlation detection processing (despreading processing) between the received signal and the spreading code in MF182 ~: 184, the desired signal arriving through various propagation paths in each path timing detector 185 ~: 187 The delay timing of each path is detected. The RAKE combiners 188 to 190 perform RAKE combining for maximal ratio combining of each path component based on each path timing, and use the combined output to calculate the SIR value of each beam in the SIR calculators 191 to 193. presume.

By assigning orthogonal spreading codes to each beam in this way, a high interference suppression effect can be obtained at the time of correlation detection, and further accurate and most accurate by estimating the SIR of each beam using the RAKE-combined signal. Efficient selection of a beam becomes possible.

Embodiment 4.

FIG. 9 shows an example of the configuration of each beam SIR estimator of the terminal station in another embodiment of the present invention in the CDMA communication system. Each beam SIR estimator 145b in FIG. 9 includes a spreading code generator 201, MF (Matched Filter) (1 to N) 202 to 204, and a maximum path timing detector (1 to N) 205 to 207 and SIR calculators (1 to N) 208 to 210.

The spreading code generator 201, the MFs 202 to 204, and the SIR calculators 208 to 210 perform the same operations as the spreading code generator 181 in the third embodiment, the MFs 182 to 184, and the SIR calculators 191 to 193. Therefore, the description is omitted. Maximum path timing detectors 205 to 207 detect the timing of the path having the highest reception level among the paths of the desired signal arriving through various propagation paths. Then, based on the detected sample timing of the maximum path, the SIR calculators 208 to 210 estimate the SIR value of each beam.

By adopting a configuration in which only the path having the maximum reception level is detected, the timing detector can be simplified and the number of RAKE combiners can be reduced, so that the device configuration of the terminal station can be simplified.

Embodiment 5

In the above embodiment, the terminal station selects the beam with the best SIR. However, depending on the propagation path characteristics, a beam with a high SIR may occur due to multipath arriving from a distant angle. May exist multiple times. The beam selection method in such a case will be described.

The terminal station sets the target SIR as a threshold value in advance. The SIR of each beam is estimated using the pilot symbol in the transmission slot from the radio base station, and a plurality of beams having a value larger than the target SIR are selected. Each of these selected beam numbers is reported to the radio base station via the uplink, and the radio base station transmits information symbols using the plurality of beams.

FIG. 10 shows a transmission slot configuration in a radio base station according to the present embodiment. Multiplexing is performed to simultaneously transmit the transmission slots of these N beams. Fig. 10 shows an example in which J out of N beams are selected by the terminal station.The transmission slot of the selected beam and an information symbol must be added and multiplexed. Thus, it is possible to efficiently use a beam having a good propagation path characteristic. Embodiment 6

A method of forming a transmission beam in the radio base station according to the present embodiment will be described. FIG. 11 shows an example in which beams are formed at equal intervals in a horizontal plane. The selected beam 221 is a beam selected by the terminal station, and is used by the radio base station to transmit information symbols in the next slot. The adjacent beams 222 and 223 are beams adjacent thereto.

A system that feeds back some control information from a terminal station to a radio base station. In addition, the amount of information affects uplink information transmission efficiency. Therefore, it is desirable that the control information is as small as possible. This embodiment shows a method for realizing it.

A specific operation will be described. In the initial state of communication, it is assumed that a pilot symbol is transmitted using all beams, and that the beam number information selected by the terminal station is broadcast to the radio base station via the uplink. As described in the previous embodiment, the radio base station detects the selected beam number and creates a transmission slot. At this time, a transmission slot is not created using all beams, but a slot is created using only the selected beam 221 and the adjacent beams 222 and 223 adjacent thereto. Then, the beam to be selected is updated successively.

By doing so, the amount of processing at the radio base station can be reduced, and the beam selection processing at the terminal station and the number of control information symbols to be inserted into the uplink can be reduced. Note that Fig. 11 shows an example in the horizontal plane, but in the case of forming a beam also in the vertical plane, the beam configuration of each wireless base station is supported by using adjacent beams around the selected beam 221 it can.

Also, by determining the selected beam periodically using all the beams, it becomes possible to more accurately follow the change in the propagation path characteristics.

Embodiment 7

A method for forming another transmission beam in the radio base station according to the present embodiment will be described. FIG. 12 shows an example in which beams are formed at equal intervals in a horizontal plane. The selected beam group 225 is a set of beams selected by the terminal station in the initial state.

In the initial state of communication, the wireless base station transmits pilot symbols of all beams as described in the first embodiment. The terminal station estimates the SIR of each beam, and designates the selected beam group 255 from a favorable angle range of the SIR. At this time, the number of beams included in the selected beam group 255 is specified in advance.

As for the range setting of the beam group, there are a method of sliding one beam completely and a method of setting continuously.

The radio base station notified of this selected beam group information by the uplink transmits the pilot symbol using the beam in the selected beam group 225, and sequentially selects the beam. Update the process.

In addition, by periodically resetting the beam group to be used as described above, it becomes possible to follow a change in propagation path characteristics.

Embodiment 8

A method for forming another transmission beam in the radio base station according to the present embodiment will be described. FIG. 13 shows an example in which beams are formed at equal intervals in a horizontal plane. In Fig. 13, a is the initial state, and b is the beam group at the start of communication. The selected beam group 230 is a set of beams initially selected by the terminal station. The method of setting the selected beam group 230 is the same as that described in the seventh embodiment.

The radio base station densely reshapes the beam using the maximum allowed degree of freedom in the angular range of the selected beam group 230 broadcast from the terminal station. After the start of communication, the information symbols are transmitted using the reconstructed beam group 231.

By densely arranging the beams in the good SIR angle range in this way, it is possible to accurately follow the fluctuation of the propagation path characteristics.

Further, by periodically resetting the beam group to be used as described above, it becomes possible to follow a change in propagation path characteristics. Industrial potential

The wireless communication system of the present invention is useful as a device that improves communication quality while maintaining information transmission efficiency while being robust, that is, capable of responding to environmental changes.

Claims

The scope of the claims

1. In a wireless communication system including a wireless base station that forms beams having a plurality of different directional directions and a plurality of terminal stations that communicate with the wireless base station,

各 s3 each ¾

Means for estimating the ratio of desired signal power to interference signal power of the downlink transmitted from the plurality of beams of the radio base station,

Beam selection means for selecting an optimal beam from the desired signal power to interference signal power ratio;

Means for reporting the selected beam number using an uplink from the terminal station to the radio base station,

With

The wireless base station,

Transmission control means for transmitting an information signal to the terminal station using a beam corresponding to the beam number if the beam number is broadcast from the terminal station;

A wireless communication system comprising:

2. The radio base station arbitrarily sets an array antenna composed of a plurality of antenna elements for forming a plurality of beams and the beam shape according to an environment in which the radio base station is installed. 2. The wireless communication system according to claim 1, further comprising: a beam forming unit.

3. The transmission control means of the radio base station multiplexes and adds a known signal different for each of a plurality of beams formed by the radio base station to an information signal transmitted from the radio base station to the terminal station, The wireless communication system according to claim 1, wherein the desired signal power to interference signal power ratio estimating means of the terminal station detects the known signal and estimates a desired signal power to interference signal power ratio. .

4. The wireless communication system according to claim 1, wherein mutually orthogonal data symbols are used as the known signal.

5. The wireless communication system performs communication according to the CDMA communication method, and the transmission control means of the wireless base station spreads the known signal using orthogonal codes. A multiplexed known signal subjected to spread processing is added to an information signal to be transmitted to the terminal station, and the desired signal power to interference signal power ratio estimating means of the terminal station performs the spread processing on the known signal. 2. The wireless communication system according to claim 1, wherein a signal is detected, and a desired signal power to interference signal power ratio is estimated.

6. The desired signal power to interference signal power ratio estimating means of the terminal station detects the known signal after RAKE combining and estimates the desired signal power to interference signal power ratio. The wireless communication system according to claim 1.

7. The desired signal power to interference signal power ratio estimating means of the terminal station detects the known signal included in the path having the highest received power in the desired signal group received by the terminal station and outputs the desired signal. 2. The wireless communication system according to claim 1, wherein a power-to-interference signal power ratio is estimated.

8. The beam selection means of the terminal station selects all beams whose desired signal power to interference signal power ratio is larger than the set threshold, and the transmission control means of the radio base station uses these beams. The wireless communication system according to claim 1, wherein the wireless communication system transmits an information signal.

9. The desired signal power to interference signal power ratio estimating means of the terminal station, the beam selecting means, the notifying means, and the transmission controlling means of the radio base station, wherein in the initial state of communication start, the beam number is determined using all beams. Is determined, the desired signal power to interference signal power ratio of the downlink is estimated using the beam corresponding to the beam number and the beam adjacent thereto, and the beam to be sequentially selected is updated. The wireless communication system according to claim 1, wherein:

10. In the terminal station, the desired signal power to interference signal power ratio estimating means, the beam selecting means, the notifying means, and the transmission control means of the radio base station, in the initial state of communication start, Estimate the desired signal power to interference signal power ratio of the downlink by using, and broadcast the information of the good reception angle range using the uplink to the radio base station, and then select in the radio base station The plurality of beams formed in the specified range are used to estimate the ratio of the desired signal power to the interference signal power in the downlink, and the beam to be sequentially selected is updated. Wireless communication system.

11. The system according to claim 10, wherein the ratio of the desired signal power to the interference signal power in the downlink is periodically estimated using all beams, and information on an angle range in a good reception state is updated. A wireless communication system as described.

12. The method according to claim 10, wherein a plurality of beams are re-formed within the range based on the angle range notified from the terminal station by using an allowable degree of freedom to a maximum extent. The wireless communication system according to claim 1.

13 3. A plurality of array antennas that form beams having a plurality of different directional directions are arranged at a distance such that the correlation characteristics of the propagation path can be ignored sufficiently, and a beam to be used for transmission is selected, and transmission is performed. 2. The wireless communication system according to claim 1, wherein: