CN103259573B - Wireless transmission method, wireless transmitter and wireless receiver - Google Patents

Abstract

The present invention provides a kind of wireless transmission method, wireless transmitter and wireless receiver. The transmission numbers of beams formed for transmitting this data stream, according to transmitting data fluxion, is controlled by wireless transmitter (1); Wireless receiver (2), among described transmission wave beam, selects to receive the transmission wave beam of any more than 1. By changing the transmission numbers of beams to be formed according to transmitting data fluxion like this such that it is able to when realizing many streaming based on the high-throughput characteristic of degree of association between low wave beam and single current time big directional gain.

Description

Wireless transmission method, wireless transmitter and wireless receiver

This application is the original application of the application date of February 2, 2006, the application number is 200680052201.X (international application number PCT/JP2006/301776), and the title of the invention is "wireless transmission method, wireless transmitter and wireless receiver" Divisional application.

technical field

The present invention relates to a wireless transmission method, a wireless transmitter, and a wireless receiver, and particularly relates to a wireless transmission technology suitable for use in multiple input and multiple output wireless transmission technologies that use multiple transceiver antennas for signal transmission in wireless communication systems such as mobile phones and wireless access. technology.

Background technique

In recent years, attention has been paid to MIMO (Multiple-Input Multiple-Output: Multiple-Input Multiple-Output) as a technology capable of effectively utilizing frequency bands for large-capacity (high-speed) data communication. MIMO refers to a technology that uses multiple antennas on both sides, that is, uses a transmitter with multiple antennas and a receiver with multiple antennas, transmits independent data streams from multiple antennas of the transmitter, and uses a transmission path ( channel) estimated value, from the signal received by each receiving antenna of the receiver, the multiple transmission signals (data streams) mixed on the transmission path are separated, and the transmission rate can be improved without expanding the frequency band.

FIG. 8 shows a configuration example of a conventional MIMO transmission system. The system shown in FIG. 8 is equivalent to the system shown in Fig. 1 of Non-Patent Document 1 described later, and is composed of a MIMO transmitter 100 and a MIMO receiver 200. The main parts are as follows: MIMO transmitter 100 has user selection unit 101, channel coder/modulator 102, beam selection unit 103, multi-beamformer (Multi-beamformer) 104, scheduler (Scheduler) 105, and multiple transmit antennas 106, and MIMO receiver 200 has multiple receive An antenna 201, a MIMO/SIMO demodulator 202, a channel decoder 203, a transmission beam measurement unit 204, and a transmission beam/stream determination unit 205 are configured.

In addition, in the MIMO transmitter 100, the user selection unit 101 selects one or more user data streams to be transmitted from among a plurality of sequences of user data streams under the control of the scheduler 105, and inputs them to the channel coder/modulator 102, the channel coding/modulator 102, under the control of the scheduler 105, implements necessary error correction coding such as Turbo coding at a specified coding rate, and the obtained bit sequence is mapped to a specified modulation method, such as QPSK ( QuadraturePhaseShiftKeying: Quadrature Phase Shift Keying) or 16QAM (QuadratureAmplitudeModulation: Quadrature Amplitude Modulation) and other signal point symbols (signals of data channels) for modulation. In addition, in this channel coder/modulator 102, in addition to the signal of the data channel, a signal of a pilot channel (pilot symbol) used for channel estimation, a signal of a control channel (control symbol) for transmitting control information, etc. Perform multiplexing.

The modulated data obtained in this way is input to the beam selection unit 103, and the beam selection unit 103 selects the beam to be transmitted from a plurality of fixed beams (multi-beams) formed by the multi-beam former 104 under the control of the scheduler 105. The modulated data is transmitted from the transmitting antenna 106 using the beams selected for transmitting the modulated data.

For example, assuming that the number of transmitting antennas 106 is 4, and the number of fixed beams that can be formed by the multi-beamformer 104 is at most 4 beams, when the number of streams to be transmitted is 4, all 4 beams are selected; When , select 2 beams from 4 beams; when 1, select 1 beam from 4 beams.

On the other hand, in the MIMO receiver 200, the wireless signal transmitted from the transmitting antenna 106 of the MIMO transmitter 100 is received by each receiving antenna 201, and is subjected to MIMO demodulation or SIMO (Single-InputMulti -Output: single input multiple output) demodulation to generate user data stream. That is, in the MIMO/SIMO demodulator 202, based on the channel estimation value (channel matrix) obtained by calculating the correlation between the received pilot symbol and the pilot replica, by using the channel correlation matrix The method of using the inverse matrix of the MLD (MaximumLikelihood Detection: Maximum Likelihood Estimation) algorithm, etc., separates the user data stream multiplexed for each transmission antenna 106, and generates demodulation data.

The obtained demodulated data is input to the channel decoder 203, and error correction decoding such as turbo decoding is performed in the channel decoder 203 to obtain decoded data of the user data stream received through the data channel.

In addition, each signal received by the receiving antenna 201 is also input to the transmission beam measurement unit 204, and the transmission beam measurement unit 204 measures a CQI value (ChannelQualityIndicator: Channel Quality Indicator), which is an index of reception quality, from the reception pilot symbol. , the transmission beam/stream determination unit 205 determines (selects) one or more beams with the best reception quality based on the obtained CQI value. Then, as feedback information to the MIMO transmitter 100 , information including the determined number of beams, corresponding CQI values, and beam IDs is generated and sent to the MIMO transmitter 100 .

The above feedback information is finally notified to the scheduler 105 of the MIMO transmitter 100, so that the scheduler 105 controls the user selection unit 101, the channel coder/modulator 102, and the beam selection unit 103 so that the MIMO receiver 200 (transmission beam/stream) determines The unit 205) determines (selects) beams of the number of beams (beam ID), and transmits the transmission user data stream as described above according to the coding rate and modulation method corresponding to the reported CQI value.

In addition, as disclosed in Patent Document 1 mentioned later, in the closed-loop MIMO transmission scheme in which precoding is performed on the transmitting side, it is also necessary to return the channel matrix and reception weights acquired on the receiving side as feedback information to the transmitting side. (weighting factor for multiple beams).

[Patent Document 1] Japanese Patent Laid-Open No. 2005-311902

[Non-Patent Document 1] 3GPPTSGRANWG1meeting#43 (R1-051438), "Multi-beam MIMO for EUTRADownlink", Fujitsu, November 2005

In order to improve the transmission rate of the MIMO multiplexing method, (1) higher SNR (SignaltoNoiseRatio: signal-to-noise ratio) and (2) low inter-antenna correlation (or low inter-beam correlation) are required. If this condition is not satisfied, the throughput characteristics of MIMO multiplexing will be greatly degraded, and the method of using MIMO diversification or directional beam transmission is more beneficial to the overall system throughput.

Here, in the prior art described above, the number of beams to be formed is constant (for example, fixed to the maximum number of beams that can be formed) regardless of the number of transmission streams (in other words, the beam width per beam (directivity Intensity) is constant), so the effect of MIMO multiplexing cannot be obtained through the selected beam, resulting in the degradation of throughput characteristics.

For example, based on the feedback information from the receiving side, if beams with high correlation (for example, mutually adjacent beams) are selected on the transmitting side, it will result in separation of user data streams on the receiving side, demodulation processing Ability to deteriorate. Therefore, as long as the beam with low correlation degree is boldly selected, the separation and the deterioration of the demodulation processing capability can be suppressed. Gain) The reception quality of a beam with good beam selection is poor.

Here, as described in the above-mentioned Patent Document 1, if the signal matrix or reception weight used by the receiving side is fed back to the transmitting side as the feedback information, it is possible to adjust and select inter-beam correlation or beam directivity, and it is possible to alleviate the problem. The aforementioned separation, degradation of demodulation processing capability, and degradation of reception quality lead to an increase in the amount of feedback information, and calculation processing is required for adjustment.

Contents of the invention

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to obtain good reception characteristics based on high throughput characteristics with low inter-beam correlation and high directivity gain balance without increasing the amount of feedback information in MIMO transmission .

In order to achieve the above object, the present invention is characterized by using the following wireless transmission method, wireless transmitter, and wireless receiver. which is,

(1) The wireless transmission method of the present invention, which can transmit data streams between a wireless transmitter having a plurality of transmitting antennas and a wireless receiver having a plurality of receiving antennas by using multi-beams, the wireless transmitting method is characterized in that , the wireless transmitter controls the number of transmission beams formed to transmit the data streams according to the number of data streams to be transmitted, and the wireless receiver selects and receives any one or more transmission beams among the transmission beams.

(2) Here, the radio transmitter preferably performs control such that the number of transmission beams is increased as the number of transmission data streams decreases.

(3) Furthermore, the radio receiver preferably selects and receives two or more of the transmission beams having a low correlation with each other when the number of transmission data streams is two or more.

(4) More preferably, the wireless receiver selects and receives non-adjacent transmission beams as the transmission beams with low correlation.

(5) In addition, the wireless transmitter multiplexes the pilot signal for each of the transmitting antennas, and performs beam transmission with a fixed weighting coefficient, and the wireless receiver measures the the level of the transmission beam, determine the number of transmission data streams and the transmission beam to be received based on the level measurement result, and notify the information related to the determined number of transmission data streams and the transmission beam For the radio transmitter, the radio transmitter controls the number of transmission beams based on the information notified from the radio receiver.

(6) In addition, the wireless transmitter multiplexes the pilot signal for each of the transmission beams, and performs beam transmission with a fixed weight coefficient, and the wireless receiver measures the voltage of the transmission beam according to the pilot signal. determining the number of transmission data streams and the transmission beams to be received based on the level measurement results thereof, and notifying the wireless transmitter of information related to the determined number of transmission data streams and the transmission beams , the wireless transmitter controls the number of transmission beams based on the information notified from the wireless receiver.

(7) In addition, the wireless transmitter multiplexes pilot signals for each of the transmission antennas, transmits beams with variable weighting coefficients, and combines information related to the weighting coefficients with the number of transmission beams The relevant information is reported to the wireless receiver, which measures the level of the transmission beam according to the pilot signal and the information related to the weighting coefficients reported from the wireless transmitter, and according to its electric The measured result and the information related to the number of transmission beams reported from the wireless transmitter, determine the number of transmission data streams and the transmission beams to be received, and compare the determined number of transmission data streams and The wireless transmitter is notified of information on the transmission beams, and the wireless transmitter controls the number of transmission beams based on the information notified from the wireless receiver.

(8) In addition, the wireless transmitter of the present invention can transmit data streams between it and a wireless receiver having multiple receiving antennas through multiple beams, and the wireless transmitter is characterized in that the wireless transmitter has : a plurality of transmission antennas; and a transmission beam number control unit configured to control the number of transmission beams formed to transmit the data streams based on the number of data streams to be transmitted from the transmission antennas.

(9) Here, the transmission beam number control unit is configured to perform control to increase the number of transmission beams as the number of transmission data streams decreases.

(10) In addition, the transmitter further includes: a first pilot multiplexing unit, which multiplexes pilot signals for each of the transmitting antennas; a first beamformer, which uses fixed weighting coefficients to perform beam transmission; and a first notification information receiving unit, which receives information related to the number of transmission data streams and transmission beams notified from the wireless receiver, wherein the information related to the number of transmission data streams and transmission beams is based on the following method Determination of the obtained level measurement result: In the wireless receiver, the transmission beam is measured according to the pilot signal and the weighting coefficient, and the transmission beam number control unit receives the first notification information according to the The information received by the unit controls the number of beams transmitted.

(11) Moreover, the transmitter is further equipped with: a second pilot multiplexing unit, which multiplexes pilot signals for each of the transmission beams; a first beamformer, which performs beam transmission by means of fixed weighting coefficients; and a second notification information receiving unit, which receives information related to the number of transmission data streams and transmission beams notified from the wireless receiver, wherein the information related to the number of transmission data streams and transmission beams is based on the following method Determination of the obtained level measurement result: In the wireless receiver, the transmission beam is measured according to the pilot signal, and the transmission beam number control unit is based on the information received by the second notification information receiving unit , to control the number of transmit beams.

(12) In addition, the transmitter also has: a first pilot multiplexing unit, which multiplexes pilot signals for each of the transmitting antennas; a second beamformer, which uses variable weighting coefficients to perform beam transmission a reporting unit that reports information related to the weighting coefficient and information related to the number of transmission beams to the wireless receiver; and a third notification information receiving unit that receives the information related to the wireless receiver notified from the wireless receiver Information related to the number of transmission data streams and transmission beams, wherein the information related to the number of transmission data streams and transmission beams is based on the level measurement result obtained by the following method and the number of transmission beams reported by the reporting unit The relevant information is determined, the method is: in the wireless receiver, according to the pilot signal and the information related to the weighting coefficient reported by the reporting unit, measure the transmission beam, the The number of sending beams control unit controls the number of sending beams according to the information received by the third notification information receiving unit.

(13) In addition, in the wireless receiver of the present invention, the wireless receiver can transmit data streams between it and a wireless transmitter having a plurality of transmitting antennas through multiple beams, and the wireless receiver is characterized in that the The wireless receiver includes: a plurality of receiving antennas; and a beam selection receiving control unit that, in accordance with the number of data streams to be transmitted by the wireless transmitter, controls the number of transmission beams formed to transmit the data streams, Select and receive any one or more transmission beams via the reception antennas.

(14) Here, the beam selection reception control unit selects and receives two or more of the transmission beams having a low mutual correlation when the number of the transmission data streams is two or more.

(15) In addition, the beam selection reception control unit selects and receives non-adjacent transmission beams as the transmission beams with a low degree of correlation.

(16) Furthermore, the radio transmitter multiplexes pilot signals for each of the transmission antennas, and transmits beams using fixed weighting coefficients, and the beam selection reception control unit includes: a first level measuring unit based on The pilot signal and the weighting coefficient measure the level of the transmission beam; the first determination unit determines the number of the transmission data streams to be received based on the level measurement result of the first level measurement unit. and the transmission beam; and a first notification section that notifies information on the number of transmission data streams and the transmission beam determined by the first determination section as the number of transmission beams in the wireless transmitter control information.

(17) In addition, the wireless transmitter multiplexes the pilot signal for each of the transmission beams and transmits the beams with a fixed weighting factor, and the beam selection reception control unit includes: a second level measurement unit based on The pilot signal measures the level of the transmission beam; the second determination unit determines the number of transmission data streams to be received and the transmission beam based on the level measurement result of the second level measurement unit. and a second notification section that notifies information on the number of transmission data streams and the transmission beams determined by the second determination section as control information of the number of transmission beams in the wireless transmitter.

(18) In addition, the wireless transmitter multiplexes pilot signals for each of the transmitting antennas, transmits beams with variable weighting coefficients, and combines information related to the weighting coefficients with the number of transmitting beams information reported to the wireless receiver, and the beam selection reception control unit includes: a third level measuring unit that, based on the pilot signal and the information on the weighting coefficient reported from the wireless transmitter, measuring the level of the transmission beam; a third determination unit that determines the number of transmission beams to be received based on the level measurement result of the third level measurement unit and the information related to the number of transmission beams reported from the wireless transmitter. the number of transmission data streams and the transmission beam; and a third notifying section that notifies information on the number of transmission data streams and the transmission beam determined by the third determination section as The control information of the number of transmission beams.

Invention effect

According to the present invention described above, at least any of the following effects can be obtained.

(1) Since the number of transmission beams to be formed (the number of beams of selectable transmission sources) is controlled (changed) in the transmitter according to the number of data streams to be transmitted, the feedback information from the receiver to the transmitter is not increased A good throughput characteristic (reception characteristic) can also be obtained.

(2) For example, when the number of transmission beams is increased as the number of transmission data streams decreases, the number of transmission source beams that can be selected increases as the number of transmission data streams decreases, so that high directivity gain can be obtained.

(3) In addition, when the number of transmission data streams is two or more, as long as two or more transmission beams with low correlation between receptions (for example, non-adjacent ones) are selected, it is possible to avoid The data stream separation performance is degraded, and high throughput characteristics based on low inter-beam correlation can be obtained.

Description of drawings

FIG. 1 is a diagram illustrating an outline of an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of the MIMO transmission system according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a focus on the configuration of a transmission beam ID/stream determination section and a known selectable beam memory shown in FIG. 2 .

FIG. 4 is a flowchart for explaining the operation (beam selection method) of the transmission beam ID/flow specifying unit shown in FIG. 3 .

FIG. 5 is a schematic diagram showing an example of selectable beams for explaining the operation of the MIMO transmission system shown in FIG. 2 .

FIG. 6 is a block diagram showing a configuration of a MIMO transmission system according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing the configuration of a MIMO transmission system according to a third embodiment of the present invention.

FIG. 8 is a block diagram showing the configuration of a conventional MIMO transmission system.

Mark description

1MIMO transmitter; 11 user selection unit; 12 channel coder/modulator; 13 beam selection unit; 14 multi-beam former; notification information receiving unit); 16-1~16-n transmitting antenna; 17-element pilot multiplexing unit (first pilot multiplexing unit); 17-1~17-n adder (multiplexing circuit); 17a beam Pilot multiplexing unit (second pilot multiplexing unit); 17a-1~17a-m adders (multiplexing circuit); 18 report information addition unit (reporting unit); 19a weight generation unit; 19b optional beam information Generating part; 2MIMO receiver; 20 beam selection receiving control unit; 21-1~21-M receiving antenna; 22 MIMO/SIMO demodulator; 23 decoder (channel decoder); 2. The third level measurement unit); 25 known pilot memory; 26 known transmission weight memory; 27 transmission beam ID/flow determination unit (first, second, third determination unit, first, second, 3rd notification part); 271 arrangement/level comparison part; 28 known selectable beam memory; 281 comparison beam ID table; 29 report information extraction part; 30-0～30-9 beam

detailed description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[A] Summary

First, an outline of an embodiment to be described below will be described using FIG. 1 . In this figure 1, 1 represents a MIMO transmitter equipped with multiple (here, 4) transmitting antennas, and 2 represents a MIMO receiver equipped with multiple receiving antennas, and these MIMO transmitters 1 and MIMO receivers 2 can be connected , using wireless MIMO transmission. In addition, the MIMO transmitter 1 can be applied, for example, as a base station apparatus of a mobile radio communication system, and the MIMO receiver 2 can also be applied as a mobile station apparatus (UE: User Equipment) of the system. Therefore, in the following description, the MIMO transmitter 1 may be expressed as the base station device 1 or the base station 1 , and the MIMO receiver 2 may be expressed as the mobile station device 2 or the mobile station 2 . And, for the detailed specifications, for example, Table (Table) A1 of the above-mentioned Non-Patent Document 1 is followed.

In addition, in this example, the base station apparatus 1 is configured to be able to change (control) the number of beams formed (beamforming) according to the number of user data streams to be transmitted (transmitted) (hereinafter, sometimes simply referred to as “transmission streams”), and to move The station apparatus 2 is configured to be able to select and receive any one or more beams among the multi-beams having the above-mentioned number of beams.

For example, when the base station 1 transmits a small number of streams, that is, the minimum is a single stream, the mobile station 2 selects, for example, the beam with the highest reception level among more beams formed by the base station 1 for reception. Also, as the number of transmission streams increases, selectable beam combinations are limited. When the number of sending streams is large, in the case of sending multiple streams corresponding to the maximum number of sending antennas, select the beam that the receiving element sends (it can also be interpreted as the number of selectable beams is only 1).

In addition, in FIG. 1 , the base station 1 shows (1) the case of four transmission streams, (2) the case of two streams, (3) the case of one stream, and the case of (1) , base station 1 forms one beam with each transmit antenna, and transmits four streams using this beam element, while mobile station 2 directly receives (without selecting a beam) the signal transmitted with one beam element; (2) Next, the base station 1 forms 4 beams and uses the 4 beams to transmit 2 streams. On the other hand, the mobile station 2 selects from the 4 beams to receive, for example, 2 beams with low inter-beam correlation; (3) In this case, the base station 1 forms 8 beams and transmits 1 stream using the 8 beams, while the mobile station 2 selects and receives 1 beam from among the 8 beams.

In this way, by changing the number of beams that can be selected as sources, that is, the number of transmission beams to be formed (beamforming), according to the number of transmission streams, it is possible to obtain as large a gain as possible in the case of a single stream, and to perform Beam selection makes the correlation between beams low, so that good throughput characteristics and directivity gain can be obtained.

Specific examples will be described in detail below.

[B] Explanation of the first embodiment

FIG. 2 is a block diagram showing the configuration of the MIMO transmission system according to the first embodiment of the present invention. The MIMO transmission system shown in FIG. 2 is configured by including a MIMO transmitter 1 and a MIMO receiver 2, and the main parts of each are as follows. : The MIMO transmitter 1 includes a user selection unit 11, a channel coder/modulator 12, a beam selection unit 13, a multi-beam former 14, a scheduler (beam control unit) 15, and a plurality of transmission antennas 16-1 to 16-n ( n is an integer of 2 or more), and an element-pilot multiplexing unit 17, and the MIMO receiver 2 has one or more receiving antennas 21-1 to 21-M (M is an integer of 1 or more, and may be M=n), MIMO/SIMO demodulator 22, decoder (channel decoder) 23, transmission beam measurement unit 24, known pilot memory 25, known transmission weight memory 26, transmission beam ID/stream determination unit 27 , and a known selectable beam memory 28 is formed. In addition, below, the MIMO transmitter 1 may be simply referred to as "transmitter 1" or "transmitter 1", and the MIMO receiver 2 may be simply referred to as "receiver 2" or "receiver 2".

Here, in the MIMO transmitter 1, the user selection unit 11 is used to select one or more user data streams to be transmitted from among a plurality of sequences of user data streams under the control of the scheduler 15; The modulator 12 is used to implement necessary error correction coding such as Turbo coding at a specified coding rate under the control of the scheduler 15, and map the obtained bit sequence to a specified modulation method, such as QPSK (QuadraturePhaseShiftKeying) or 16QAM (QuadratureAmplitudeModulation) Modulation is performed on symbols (signals of data channels) of equal signal points.

The beam selection unit 13 is under the control of the scheduler (beam control unit) 15, more specifically, according to the feedback information (information related to the transmission beam ID and transmission stream) from the receiving side 2, and passes through the multi-beam former 14 Among the formed plurality of beams (multi-beams), one or more beams are selected for transmitting the transmission stream (user data) coded and modulated by the channel coder/modulator 12 . In addition, the transmission beam ID (identification information) is uniquely determined (set) based on the transmission weight matrix W used in the multi-beamformer 14 described below (the same applies hereinafter).

The multi-beamformer (first beamformer) 14 is configured to form a multi-beam for transmitting the transmission stream according to a predetermined transmission weight matrix (weighting coefficient) W. In addition, in this example, the sending weight matrix W is fixed.

The component pilot multiplexing unit (first pilot multiplexing unit) 17 uses the respective adders (multiplexing circuits) 17-1 to 17-n of the transmitting antennas 16-1 to 16-n to transmit each transmitting antenna 16- i (i=1 to n), the orthogonal pilot signal (symbol) pi is multiplexed, and the orthogonal pilot signal pi is transmitted for each transmission antenna 16 - i (element).

The beam control unit (scheduler; means for controlling the number of transmission beams) 15 controls the beam selection in the above-mentioned beam selection unit 13, thereby controlling the number of transmission beams formed for transmitting the transmission stream according to the number of transmission streams. In this example, information related to the beam ID and the number of streams determined (selected) by the transmission beam ID/stream determination unit 27 on the receiving side 2 is received as feedback information, and based on this feedback information, the number of transmission streams and the number of streams used for transmission are controlled. Beams for this transmit stream (number of transmit beams formed).

On the other hand, in the receiver 2, the receiving antenna 21-j (j=1~M) is used to receive the beams transmitted from the transmitting antennas 16-i of the transmitter 1, and the MIMO/SIMO demodulator 22 controls each The signal received by the receiving antenna 21-j is subjected to MIMO demodulation or SIMO demodulation, and the channel estimation value (channel matrix) obtained by calculating the correlation between the pilot signal pi multiplexed on the received signal and the pilot copy , by using the inverse matrix of the channel correlation matrix or the method of using the MLD algorithm, etc., separate the user data streams multiplexed for each transmit antenna 16-i, and generate demodulated data.

The decoder 23 decodes the user data stream obtained by the MIMO/SIMO demodulator 22 using a decoding method corresponding to the encoding method at the transmitting side 1 .

The known pilot memory 25 pre-stores the replica signal (pilot replica) of the pilot signal pi, the known transmission weight memory 26 pre-stores the information of the transmission weight matrix W of the transmitting side 1, and the transmission beam measurement unit (first electronic The level measurement unit) 24 measures the level of each beam from the transmitter 1 based on the pilot replicas stored in the known pilot memory 25 and the information of the transmission weight matrix W stored in the known transmission weight memory 26 .

It is known that the selectable beam memory 28 stores information on selectable beams in advance, and in this embodiment, for example, as shown in FIG. 3 , it stores a comparison beam ID table 281 that associates the number of transmission streams with candidate beam IDs. In addition, in the comparison beam ID table 281 shown in FIG. 3 , when the number of transmission streams is 4, one beam with ID=0 as a beam candidate (candidate beam) can be selected; , the IDs of candidate beams are 2, 4, 6, 8 (or 1, 3, 5, 7), that is, 4 non-adjacent beams with even (or odd) IDs; In this case, the IDs of the candidate beams are nine beams of 1 to 9.

The transmission beam ID/flow determination unit (first determination unit) 27 determines that it should be passed as feedback information to The information (beam selection information) on the transmission beam ID (the number of transmission beams) and the number of transmission streams of the transmitter 1, in this example, as shown in FIG. In the level comparison unit 271, the measurement level (Level[ID]) of each beam (ID) measured by the transmission beam measurement unit 24, the threshold value (TH[k]) corresponding to the number of transmission streams (k), and the comparison beam The content of the ID table 281 checks the possibilities sequentially from the one with the larger number of transmission streams to specify the number of transmission streams and the beam ID at that time. In addition, FIG. 3 shows an example in which the maximum number of transmission streams is 4 (that is, k=1 to 4).

That is, the module 20 composed of the above-mentioned transmission beam measurement unit 24, known pilot memory 25, known transmission weight memory 26, transmission beam ID/flow determination unit 27, and known selectable beam memory 28 functions as follows: The role of the selective reception control unit: Select and receive any one or more transmission beams via the receiving antenna 21-j from among the transmission beams whose number of transmission beams formed for transmitting the transmission stream is controlled by the transmitter 1 according to the number of transmission streams. beam.

In addition, the information specified by the transmission beam ID/stream determination unit 27 is used as control information for the beam control unit 15 of the transmitter 1 to perform transmission beam control (the number of beams formed), and is passed through the transmission system of the receiver 2 (not shown). , Feedback (notification) to sender 1. Therefore, the transmitter 1 (beam control unit 15) operates according to the above-mentioned control information (feedback information), and controls the beam selection unit 13 and the multi-beam former 14 to increase the number of transmission beams as the number of transmission streams decreases. When the number of transmission streams is at the maximum value, the beam selection unit 13 and the multi-beam former 14 are controlled so that one beam with beam ID=0 performs element transmission.

Hereinafter, the operation (beam selection method) of the MIMO transmission system according to the present embodiment configured as described above will be described in detail.

First, the transmitter 1 multiplexes and transmits the orthogonal pilot signal pi for each transmission antenna 16 - i using a constant fixed weight as the multi-beam transmission weight (matrix) W. That is, under the control of the scheduler 15, the user selection unit 11 selects one or more user data streams to be transmitted from a plurality of sequences of user data streams, and inputs them to the channel coding/modulator 12; the channel coding/modulation Under the control of the scheduler 15, after performing necessary error correction coding such as Turbo coding at a specified coding rate, the obtained bit sequence is mapped to a symbol (data channel signal) for modulation.

The obtained modulated data is input to the beam selection unit 13, and the beam selection unit 13 selects only the fixed beam (multi-beam) formed by the multi-beam former 14 under the control of the scheduler 15 and the one to be transmitted. The number of beams corresponding to the number of streams is used to transmit the modulated data, and the modulated data is transmitted from the transmitting antenna 16 via the selected beams. At this time, each transmit antenna 16-i multiplexes the orthogonal pilot signal pi by each adder 17-i of the element-pilot multiplexing unit 17, and transmits the signal.

On the other hand, in the receiver 2, the multi-beam signals transmitted from the transmitter 1 are received by each receiving antenna 21-j, and are input to the MIMO/SIMO demodulator 22 and the transmission beam measuring unit 24, respectively. In the MIMO/SIMO demodulator 22, MIMO demodulation or SIMO demodulation is performed on the received signal from each receiving antenna 21-j to generate a user data stream. That is, according to the channel estimation value (signal matrix), the user data stream is separated to generate demodulation data.

The obtained demodulated data is subjected to error correction decoding such as Turbo decoding by the decoder 23 to obtain decoded data of the user data stream.

On the other hand, in the transmission beam measurement unit 24, based on the information of the known transmission weight W in the known pilot memory 25 and the known transmission weight W in the known transmission weight memory 26 (hereinafter sometimes expressed as transmission weight information W ), measure the level of each beam.

For example, express the transmitted data vector as X=[x1,…,xn], express the transmitted weight information (matrix) as W=[W1,…,Wm] (where m is the number of transmitted beams), and express the pilot vector Expressed as P=[p1,…,pn], channel information (matrix) is expressed as H=[H1,…,Hn], when the received signal of receiving side 2 is expressed as Y, Y is received in receiving side 2 =HP=HWX.

Therefore, in the transmission beam measurement unit 24, the channel information H of each element (transmission antenna 16-i) is obtained using the known pilot vector P, and further, HW is obtained using the known transmission weight information W, Accordingly, the channel information of each transmission beam can be obtained, and therefore, the level measurement for each beam can be performed based on the channel information.

Then, the obtained level measurement result (Level[ID]) for each beam (ID) is input to the transmission beam ID/flow determination unit 27, and the alignment/level comparison unit 271, based on the level measurement result, The threshold value (TH[k]) corresponding to the number of transmission streams (k) and the contents of the beam ID table 281 are compared, and the possibilities are checked sequentially from the one with the larger number of transmission streams to determine the number of transmission streams and the beam at that time ID.

That is, for example, as shown in FIG. 4 , when the maximum number of transmission streams is 4 streams (beam ID=0), the arrangement/level comparison unit 271 first compares the level measurement result Level[ID=0] of beam ID=0 And the threshold TH[k=4] corresponding to the number of sent streams k=4, check whether Level[ID=0]>TH[k=4] (the possibility that the number of sent streams is 4 streams) (step S1) . As a result, if Level[ID=0]>TH[k=4], the arrangement/level comparison unit 271 determines that the number of transmission streams k=4 and the beam ID=0 (from the Y path in step S1 to step S2) .

On the other hand, when Level[ID=0]≦TH[k=4], the array/level comparison unit 271 calculates the level measurement results Level[ID=1], Level[ID=2], Level[ Among ID=3] and Level[ID=4], select two IDs (IDmax1, IDmax2) with higher levels (from the N path of step S1 to step S3), and compare the measurement results of each level Level[ID= IDmax1], Level[ID=IDmax2] and the threshold TH[k=2] corresponding to the number of sent flows k=2, check whether the level measurement results Level[ID=IDmax1], Level[ID=IDmax2] are greater than the threshold TH [k=2] (possibility that the number of transmission streams is 2) (step S4).

As a result, if the level measurement results Level[ID=IDmax1] and Level[ID=IDmax2] are both greater than the threshold TH[k=2], the arrangement/level comparison unit 271 determines that the number of transmission streams k=2 and the beam ID = IDmax1, IDmax2 (from the Y path of step S4 to step S5).

On the other hand, if either or both of the level measurement results Level[ID=IDmax1] and Level[ID=IDmax2] is equal to or less than the threshold value TH[k=2], the array/level comparison unit 271 determines from the level measurement result Among Level[ID=1]～Level[ID9], select the largest ID as IDmax (from the N path of step S4 to step S6), and check whether the level measurement result Level[IDmax] is greater than the value corresponding to the number of sending flows k=1 Threshold TH[1] (possibility that the number of transmission streams is 1) (step S7 ).

As a result, if the level measurement result Level[IDmax] is greater than the threshold value TH[1], the arrangement/level comparison unit 271 determines that the number of transmission streams k=1 and the beam ID=IDmax (from the Y path in step S7 to step S8 ); if not, it is determined that there is no distribution of the number of transmission streams k and beam ID (from the N path of step S7 to step S9).

As described above, the transmission beam ID/flow determination unit 27 selects a beam ID with the highest reliability of channel information from among predetermined known selectable beams according to the number of streams for which a transmission request is made.

A specific example will be described using the schematic diagram shown in FIG. 5 . This FIG. 5 shows a case where the transmitter 1 performs multiple transmissions with a maximum number of transmission beams of 9 (beam ID=1, 2, ..., 9) with the number of transmission antennas n=4 and the number of transmission streams k=1 to 4. Beam transmission or element transmission (ID=0).

When the number of transmission streams k = 1, the receiver 2 selects the one with the highest reception level (reception quality) from all nine beams 30-1 to 30-9 (beam ID = 1 to 9) by the above algorithm Beams; when the number of transmission streams k=2, as known selectable beams, 4 beams 30-2, 30-4, 30-6, from even beam IDs (ID=2,4,6,8) 30-8 (or, it can also be one of 5 beams 30-1, 30-3, 30-5, 30-7, 30-9 of odd beam ID (ID=1, 3, 5, 7, 9) In , two beams with high reception levels are selected. That is, beam selection is performed under the constraint that the correlation between beams is low (non-adjacent). Furthermore, when the number of transmission streams is increased to k=4, the receiver 2 does not perform beam selection under the same restricted conditions, or extremely large (in the case of the maximum number of transmission streams) beam selection, but transmits using elements (beam ID=0) Receive 1 beam 30-0.

As described above, when the number of transmission streams is small, a beam is selected from a plurality of beams with different beam directions. Specifically, when the number k of transmission streams is more than 2 (MIMO transmission), a beam is selected from among orthogonal multi-beams (or multi-beams equivalent thereto) as multi-beams; when the number k of transmission streams is the maximum When the value is , beam selection is not performed, and one beam sent by the component is directly received; when the number of sending streams k is the minimum value (k=1) (SIMO transmission), the orthogonal multi-beam (or its equivalent) as a multi-beam beams), beams oriented in directions that complement the inter-beams are added to the selectable candidate beams, and a beam is selected from among more beams configured in such a manner that the gain does not decrease depending on the direction.

In addition, as described above, the information of the number of transmission streams k and the beam ID specified in the receiver 2 (transmission beam ID/stream determination unit 27) is sent back to the transmission system through the transmission system of the receiver 2 (not shown) as feedback information. Machine 1. That is, in this example, the transmission beam ID/flow determination unit 27 also functions as a first notification unit for sending information related to the determined number of transmission streams and transmission beams as 1 to notify the control information of the number of transmission beams formed in 1.

In the transmitting side 1, the above-mentioned feedback information from the receiving side 2 is notified to the beam control unit 15 through the receiving system of the transmitter 1 not shown in the figure, and the beam control unit 15 performs the user selection unit 11 and the channel coding according to the feedback information. The /modulator 12 and the beam selection unit 13 perform control to select the number of transmission streams and beams, and perform beam control of the transmission streams.

As described above, according to the present embodiment, the transmitting side 1 controls (changes) the number of candidate beams (the number of formed transmission beams) selectable by the receiving side 2 according to the number of transmission streams, so that, for example, when there is one stream , can get as much gain as possible through component transmission; when there are multiple streams, the beam with lower inter-beam correlation can be selected, and the amount of feedback information to transmitter 1 will not increase, high throughput based on low inter-beam correlation characteristics and high directivity gain equalization, can obtain good throughput characteristics (reception characteristics).

(C) Explanation of the second embodiment

FIG. 6 is a block diagram showing the configuration of a MIMO transmission system according to a second embodiment of the present invention. The MIMO transmission system shown in FIG. 6 also includes a MIMO transmitter 1 and a MIMO receiver 2. Compared with the configuration described above, the point of difference is that in the MIMO transmitter 1, instead of the element pilot multiplexing unit 17, the beam pilot is provided in the previous stage of the multi-beam former 14 (the subsequent stage of the beam selection unit 13). The multiplexing section 17a, and in the MIMO receiver 2, the known transmission weight memory 26 is not required in the module 20 functioning as a beam selection reception control unit. In addition, other constituent elements given the same reference numerals as those described above are the same as or identical to the constituent elements described above unless otherwise specified. Also, in this example, the transmission weight information W=[W1, . . . , Wm] of the multi-beamformer 14 is fixed as in the first embodiment.

Here, the beam-pilot multiplexing unit (second pilot multiplexing unit) 17 a includes adders (multiplexing circuits) 17 a - 1 to 17a-m, these adders 17a-1-17a-m multiplex the orthogonal pilot signals p1-pm for each of the multi-beams.

Therefore, even if the receiving side 2 (transmission beam measuring unit 25) does not know the transmission weight information W on the transmitting side 1 (even if the known transmission weight information memory 26 described above is not provided), it can be based on the known pilot The known pilot replica in the memory 25 can estimate the channel information of each transmission beam, and can perform the level measurement for each beam as in the first embodiment. That is, the transmission beam measurement unit 25 of this example functions as a second level measurement unit for measuring the level of the transmission beam based on the pilot signal (replica).

Therefore, in this example, in the transmission beam ID/flow determination section 27 (arrangement/level comparison section 271), the same method as the algorithm (steps S1-S9) described in FIG. The information in the beam memory 28 (compared with the beam ID table 281 ) performs beam selection according to the number of transmission streams (determines the beam ID and the number of transmission streams), and feeds back the information to the transmission side 1 .

That is, the transmission beam ID/flow determination unit 27 of this example functions as a second determination unit for The number of transmission streams and transmission beams to be received is determined, and the transmission beam ID/flow determination unit 27 also functions as a second notification unit for notifying the number of transmission streams and transmission beams related to the determined number of transmission streams and transmission beams. The information is notified as control information of the number of transmission beams of the transmitter 1 .

In addition, in this case, the beam control unit 15 of the transmitter 1 also functions as a second notification information receiving unit for receiving information based on the pilot signal transmitted in the receiver 2 as described above. The signal is information on the number of transmission streams and transmission beams notified from the receiver 2 that is determined based on the level measurement result of the transmission beam measurement, and the beam control unit 15 controls the number of transmission beams based on the reception information.

Therefore, in addition to obtaining the same effects and advantages as those of the first embodiment, in this example, the receiving side 2 does not need the known transmission weight memory 26, so the configuration and processing of the receiving side 2 can be simplified.

(D) Explanation of the third embodiment

FIG. 7 is a block diagram showing the configuration of a MIMO transmission system according to a third embodiment of the present invention. The MIMO transmission system shown in FIG. Compared with the configuration of the MIMO transmitter 1, the MIMO transmitter 1 is provided with a report information addition unit 18 at a subsequent stage of the multi-beam former 14, and is provided with a weight generation unit 19a and an optional beam information generation unit 19b. , on the other hand, in the MIMO receiver 2, in the module 20 which plays the role of the beam selection reception control unit, a report information extraction part 29 is also provided, and at the same time, there is no need for the known transmission weight memory 26 and the known selectable beam Memory 28 (compare beam ID table 281). In addition, other constituent elements given the same reference numerals as those described above are the same as or identical to the constituent elements described above unless otherwise specified.

Here, in the transmitter 1 , the weight generation unit 19 a adaptively generates transmission weight information W=[W1, . . . , Wm] used in the multi-beamformer 14 . That is, the beamformer 14 of this example functions as a second beamformer that performs beam transmission using variable transmission weight information W.

The selectable beam information generation unit 19b generates information on beams selectable by the receiving side 2 (beam selection constraints), for example, information corresponding to the contents of the comparative beam ID table 281 described in FIG. 3 .

That is, in this example, the transmission weight information W and information on beams selectable according to the transmission weight information W and the number of transmission streams (hereinafter referred to as selectable beam information) can be changed (controlled).

The report information addition unit (reporting unit) 18 needs to notify the receiving side 2 of these variable information, so it adds (multiplexes) to the transmission stream as information such as a (downlink) reporting channel to the receiving side 2 . In addition, the update period of the report information, that is, the update period of the transmission weight information W of the weight generator 19a and the update period of the selectable beam information of the selectable beam information generator 19b can be set according to the system.

On the other hand, in the receiver 2, the report information extraction unit 29 is used to extract the report information (transmission weight information W and selectable beam information) from the signal demodulated by the MIMO/SIMO demodulator 22, and the extracted The transmission weight information W among the report information of , is passed to the transmission beam measurement unit 24 , and the selectable beam information is passed to the transmission beam ID/flow determination unit 27 .

Therefore, the transmission beam measurement unit 24 of this example can estimate the signal of each beam based on the transmission weight information W reported from the transmitter 1 and extracted by the report information extraction unit 29 and the pilot copy of the known pilot memory 25 without requiring The known transmission weight memory 26 described above can measure the level for each beam in the same manner as in the first embodiment. That is, the transmission beam measurement unit 24 of this example functions as a third level measurement unit for measuring the level of the transmission beam based on the pilot signal and the transmission weight information W reported from the transmitter 1. level.

Furthermore, the transmission beam ID/flow determination unit 27 uses the selectable beam information extracted by the report information extraction unit 29, the level measurement result of the transmission beam measurement unit 24, and the threshold (TH[k] ), using the same method as the algorithm described in Figure 4 (steps S1-S9), select the beam corresponding to the number of transmission streams (determine the beam ID and the number of transmission streams), and feed back the information to the sending side 1 . This means that in the receiver 2 , information corresponding to the comparison beam ID table 281 described above can be constructed or updated based on the information extracted by the report information extraction unit 29 .

That is, the transmission beam ID/flow determination unit 27 of this example functions as a third determination unit for determining the level from the level measurement result of the transmission beam measurement unit 24 as the third level measurement unit and the The selectable beam information (information related to the number of transmission beams) reported by the transmitter 1 determines the number of transmission streams and transmission beams to be received, and the transmission beam ID/stream determination unit 27 also functions as a third notification unit, The third notification unit is used to notify information on the determined number of transmission streams and transmission beams as control information on the number of transmission beams in the transmitter 1 .

Furthermore, in the transmitter 1, the above-mentioned control information (feedback information) notified from the receiver 2 is received by the beam control unit 15, and transmit beam control is performed based on this information. That is, the beam control unit 15 of this example also functions as a third notification information receiving unit that receives the information reported by the pilot signal and the report information adding unit 18 in the receiver 2 as described above. The information about the number of transmission streams and transmission beams notified from the receiver 2 is determined based on the level measurement result of the transmission beam measurement and the selectable beam information reported by the report information addition unit 18 based on the transmission weight information W of the transmission beam. , the beam control unit 15 controls the number of transmission beams based on the reception information.

Therefore, in addition to obtaining the same effects and advantages as those of the first embodiment, in this example, the transmission weight information W and the selectable beam information can be adaptively changed according to the communication environment between the transmitter 1 and the receiver 2, Optimum beam selection according to the communication environment can be realized, and further improvement in throughput characteristics can be realized.

In addition, in the above example, both the transmission weight information W and the selectable beam information are reported to the receiving side 2 as variable information, but either one may be reported to the receiving side 2 as variable information.

Also, in this example, as in the second embodiment, a configuration may be employed in which orthogonal pilot signals are multiplexed and transmitted for each beam. In this case, as described above, the receiving side 2 does not need to know the transmission weight information W, so it is only necessary to report the selectable beam information to the receiving side 2 .

In addition, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within a range not departing from the gist of the present invention.

Industrial availability

As described above, according to the present invention, by changing the number of transmission beams to be formed (the number of transmission element beams selectable on the receiving side) according to the number of transmission streams, it is possible to achieve good performance with less feedback information for beam selection. Communication systems, that is, realize high-throughput characteristics based on low inter-beam correlation in multi-stream transmission and large directivity gain in single-stream transmission, so they are very useful in the field of wireless communication technology.

Claims (5)

1. A wireless transmitter capable of transmitting data streams to a wireless receiver, the wireless transmitter comprising: multiple transmit antennas; and A scheduler that performs control such that the number of candidate beams that can be selected for transmitting the data stream is increased based on the decrease in the number of data streams to be transmitted from the transmission antennas. 2. A wireless receiver capable of receiving data streams from a wireless transmitter having multiple transmit antennas, the wireless receiver comprising: receiving antenna; and a receiver that receives any one or more transmit beams transmitted by the wireless transmitter via the receive antenna; a determination unit that determines the number of transmission data streams and at least 1 transmission beam by the wireless receiver; and a notification unit that notifies the wireless transmitter from the wireless receiver of the information on the number of transmission data streams and the at least one transmission beam, The wireless transmitter performs control such that the number of candidate beams that can be selected for transmitting the data stream is increased based on the decrease in the number of data streams to be transmitted from the transmission antenna. 3. A method for transmitting a data stream, the method comprising the steps of: Control is performed such that the number of candidate beams that can be selected for transmitting the data stream is increased based on the decrease in the number of data streams to be transmitted from the plurality of transmission antennas. 4. A method for receiving a data stream from a wireless transmitter having a plurality of transmit antennas, the method comprising the steps of: receiving any one or more transmit beams transmitted by the wireless transmitter via a receive antenna; and determining the number of transmit data streams and at least one transmit beam; and notifying the wireless transmitter of information related to the number of transmit data streams and the at least 1 transmit beam, The wireless transmitter performs control such that the number of candidate beams that can be selected for transmitting the data stream is increased based on the decrease in the number of data streams to be transmitted from the transmission antenna. 5. A wireless communication system, the wireless communication system comprising: a wireless transmitter capable of transmitting a data stream; and a wireless receiver capable of receiving said data stream from said wireless transmitter, wherein The wireless transmitter includes: multiple transmit antennas; and a scheduler that performs control such that the number of candidate beams that can be selected for transmitting the data stream increases based on the decrease in the number of data streams that should be transmitted from the transmit antenna, The wireless receiver includes: receiving antenna; and a receiver that receives any one or more transmit beams transmitted by the wireless transmitter via the receive antenna; a determination unit that determines the number of transmission data streams and at least 1 transmission beam by the wireless receiver; and A notification unit that notifies the wireless transmitter from the wireless receiver of the information on the number of transmission data streams and the at least one transmission beam.