(19)
(11)EP 1 892 851 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
27.05.2015 Bulletin 2015/22

(21)Application number: 07114678.1

(22)Date of filing:  21.08.2007
(51)International Patent Classification (IPC): 
H04B 7/06(2006.01)

(54)

Apparatus and method for transmitting/receiving feedback information in a multi-user MIMO system, as well as system thereof

Vorrichtung und Verfahren für Sendung und Empfang von Rückmeldungsinformationen in einem MIMO-System mit mehreren Benutzern und System dafür

Appareil, procédé et système pour la transmission/réception d'informations de retour dans un système MIMO multi-utilisateurs


(84)Designated Contracting States:
DE FR GB NL

(30)Priority: 21.08.2006 US 838869 P
23.03.2007 KR 20070028905

(43)Date of publication of application:
27.02.2008 Bulletin 2008/09

(73)Proprietors:
  • Samsung Electronics Co., Ltd.
    Suwon-si, Gyeonggi-do, 443-742 (KR)
  • Seoul National University Industry Foundation
    Seoul (KR)

(72)Inventors:
  • Lee, Byong-Ok c/o Seoul National University Industry Foundation
    Seoul (KR)
  • Lee, Kwang-Bok c/o Seoul National University Industry Foundation
    Seoul (KR)
  • Park, Chang-Soon c/o Samsung Electronics Co., Ltd.
    Gyeonggi-do (KR)

(74)Representative: Grünecker Patent- und Rechtsanwälte PartG mbB 
Leopoldstraße 4
80802 München
80802 München (DE)


(56)References cited: : 
EP-A- 1 750 399
US-A1- 2005 201 296
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The present invention relates generally to a multi-transmission/reception antenna system, known as a Multiple Input Multiple Output (MIMO) system. More particularly, the present invention relates to a transmission/reception apparatus and method for reducing the amount of feedback information transmitted from a plurality of receivers in a multi-user MIMO system, and a system thereof.

    [0002] Generally, the Beyond 3rd Generation (3G) system, that is, the 4th Generation (4G) system, refers to a system in which both a wireless network and core network provide characteristics of ubiquitous & seamless connection, high data rate, openness, and network convergence. The 4G system is designed to enable high-capacity data transmission, targeting the high data rate.

    [0003] The 4G system should have a complex network configuration other than a single-network configuration. That is, the 4G system should have an integrated configuration of satellite network, wireless Local Area Network (LAN), Digital Audio Broadcast (DAB) network, Digital Video Broadcast (DVB) network, and the like. The integration of all types of networks enables multiple transceivers (for example, base stations and terminals) to simultaneously exchange data or signals using MIMO. This multi-user MIMO system arranges M antennas in a transmitter (or base station) and N antennas in receivers (or terminals). The transceivers can increase their data rate by exchanging signals using the antennas arranged in this manner.

    [0004] To provide a multi-user MIMO service through the multiple antennas provided between transceivers, a transmitter needs Channel Quality Information (CQI) from multiple receivers. Therefore, the transmitter sends a request for feedback information including CQI, to the receivers. The transmitter requires more CQIs from the receivers in order to use multi-carrier technology and multi-antenna technology.

    [0005] However, the increase in the amount of feedback information, or CQls, increases not only throughput of the transceivers but also the required amount of resources, thereby causing a degradation of the entire system performance. In the conventional method proposed to address the drawbacks, the users having a CQI greater than a predetermined threshold are allowed to feed back their CQls. Since the users having a better channel state perform CQI feedback, the method can reduce feedback overhead to some extent. However, because the users feed back

    [0006] CQIs without any processing, the method may still suffer from the feedback overhead.

    [0007] US 20057201296 A1 refers to a request channel quality feedback and to a wireless communication network that provides packet data services to mobile stations. A mobile station includes a transceiver connected to an antenna via a multiplexer. The transceiver may comprise a multiple input, multiple output, MIMO, transceiver. A radio based station, RBS, communicates with a plurality of mobile stations. The RBS transmits packet data to the mobile stations over a shared forward packet data channel. The mobile stations measure the channel quality on the forward link and send channel quality information on reverse link overhead channels to the RBS. The channel quality information may comprise a channel quality indicator, CQI, in 1xEV-DV and HSPDA systems. The RBS assigns slot times and data rates for a mobile station based on the channel quality feedback from the mobile station. When the number of mobile stations designed to the shared forward packet data channel, F-PDCH, is large, the feedback of channel quality information consumes significant reverse link resources and consequently reduces significantly reverse link capacity. When channel conditions between a mobile station and the RBS are unfavorable, a mobile station is not likely to be scheduled to receive data on the F-PDCH because a scheduler at the RBS will favor those mobile stations with better channel conditions. Using a discontinuous technique, the mobile station can determine dynamically in response to changing channel conditions whether to send channel quality feedback. The RBS may instruct the mobile station to send channel feedback information only if certain quality criteria are met. When the mobile station is in a discontinuous transmission mode for the reverse link overhead channels, the mobile station performs channel quality measurements and generates CQI values normally. Before sending CQI values to the RBS, the mobile station compares the generated CQI values with the CQI threshold provided by the RBS. If the generated CQI value is less than the threshold, the mobile station suspends or suppresses CQI reporting. As long as the generated CQI value remains below the CQI threshold, the mobile station will not send the CQI report to the RBS. The mobile station will resume CQI reporting when channel conditions improve so that the generated CQI values meet the CQI threshold.

    [0008] Accordingly, there is a need for an improved transmission and reception apparatus and method for increasing system performance by reducing the amount of feedback information needed in a multi-user MIMO system.

    [0009] An aspect of exemplary embodiments of the present invention is to address at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, the object of the present invention is to provide a transmission/reception apparatus and method for increasing system performance by reducing the amount of feedback information in a multi-user MIMO system, and a system thereof.

    [0010] This object is solved by the subject matter of the independent claims.

    [0011] According to one aspect of exemplary embodiments of the present invention, there is provided a transmitter for receiving feedback information in a Multiple Input Multiple Output (MIMO) system. The transmitter includes a channel state detector for receiving channel setting information from a receiver after transmitting a reference Channel Quality Information (CQI) to the receiver, and detecting a channel state of the receiver depending on information depending on the received channel setting information, and a controller for controlling beamforming of a plurality of antennas using the detected channel state, wherein the reference CQI is a threshold used for setting channels of the receivers to an Activation or Inactivation state, and the channel setting information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the channels.

    [0012] According to another aspect of exemplary embodiments of the present invention, there is provided a feedback information reception method of a transmitter in a Multiple Input Multiple Output (MIMO) system. The feedback information reception method includes determining a reference Channel Quality Information (CQI) to be applied to a plurality of channels of a receiver; transmitting the determined reference CQI to the receiver; and receiving setting information of the channels from the receiver, wherein the reference CQI is a threshold used for setting channels of the receivers to an Activation or Inactivation state, and the setting information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the channels.

    [0013] According to further another aspect of exemplary embodiments of the present invention, there is provided a receiver for transmitting feedback information in a Multiple Input Multiple Output (MIMO) system. The receiver includes a channel quality measurer for measuring a Channel Quality Information (CQI) of each stream received from a transmitter, a controller for comparing the measured CQI of the stream with a reference CQI received from the transmitter and setting a corresponding channel according to the comparison result, and a transmission unit for transmitting the comparison result to the transmitter, wherein the reference CQI is a threshold used for setting a channel of the stream to an Activation or Inactivation state, and the channel state information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the stream.

    [0014] According to yet another aspect of exemplary embodiments of the present invention, there is provided a feedback information transmission method of a receiver in a Multiple Input Multiple Output (MIMO) system. The feedback information transmission method includes receiving a reference Channel Quality Information (CQI) from a transmitter, comparing the received reference CQI with a CQI of a stream received from the transmitter, generating channel state information according to the comparison result, and transmitting the channel state information to the transmitter, wherein the reference CQI is a threshold used for setting a channel of the stream to an Activation or Inactivation state, and the channel state information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the stream.

    [0015] Preferred embodiments are defined in the dependent claims.

    [0016] According to one embodiment there is provided a CQI transmission/reception apparatus and method for feeding back CQI with one bit per channel in a multi-user MIMO system, and a system thereof.

    [0017] According to another embodiment there is provided a transmitter for determining a reference CQI using CQIs received from multiple receivers for a case when the transmitter has knowledge of statistical distribution of the CQIs, and for another case when the transmitter has no knowledge of statistical distribution of the CQIs, and a feedback information reception apparatus and method of the transmitter.

    [0018] According to still another embodiment there is provided a receiver for comparing a reference CQI received from a transmitter with a CQI of a received stream and setting Activation (ON) and/or Inactivation (OFF) of a corresponding channel, according to the comparison result, and a feedback information transmission apparatus and method of the receiver.

    [0019] The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

    FIG. 1 is a diagram illustrating a configuration of a multi-user MIMO system according to an exemplary embodiment of the present invention;

    FIG. 2 is a flowchart illustrating a feedback method in a multi-user MIMO system according to an exemplary embodiment of the present invention;

    FIG. 3 is a block diagram illustrating an exemplary Activation/Inactivation switching feedback technique in a multi-user MIMO system according to an exemplary embodiment of the present invention;

    FIG. 4 is a block diagram illustrating a feedback information reception apparatus of a transmitter in a multi-user MIMO system according to an exemplary embodiment of the present invention;

    FIG. 5 is a flowchart illustrating a feedback information transmission/reception method of a transmitter in a multi-user MIMO system according to an exemplary embodiment of the present invention;

    FIG. 6 is a block diagram illustrating a feedback information transmission/reception apparatus of a receiver in a multi-user MIMO system according to an exemplary embodiment of the present invention;

    FIGs. 7A and 7B are flowcharts illustrating a feedback information transmission apparatus of a receiver in a multi-user MIMO system according to an exemplary embodiment of the present invention.



    [0020] Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures.

    [0021] The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of exemplary embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. Also, descriptions of well known functions and configurations are omitted for clarity and conciseness.

    [0022] In the following description, exemplary embodiments of the present invention provide a multi-user MIMO system that increases system performance by reducing the amount of feedback information. Further, exemplary embodiments of the present invention provide a transmitter for determining a reference CQI for a case when the transmitter has knowledge of statistical distribution of CQIs and for another case when the transmitter has no knowledge of the statistical distribution of CQIs, and a method according thereto. In addition, exemplary embodiments of the present invention provide a receiver for comparing a reference CQI received from a transmitter with a CQI of a received stream, setting Activation (ON) and/or Inactivation (OFF) of a corresponding channel, and transmitting the set channel state information to the transmitter, and a method according thereto.

    [0023] FIG. 1 is a diagram illustrating a configuration of a multi-user MIMO system according to an exemplary embodiment of the present invention.

    [0024] Referring to FIG. 1, the multi-user MIMO system, according to an exemplary embodiment of the present invention, includes a transmitter (or base station) 100 and a plurality of receivers (or terminals) 200 and 300.

    [0025] The transmitter includes a user selector 150 and a unitary beamforming unit 160. The transmitter 100 performs a precoding process on a plurality of input user data User1, User2, ···, Userk, and broadcasts the precoded user data via a plurality of transmission antennas. The receivers each receive the data broadcasted via a plurality of reception antennas, and store or reproduce the received data.

    [0026] Accordingly, the transmitter provides a multi-user MIMO service between transceivers in the system, and broadcasts a reference CQI to the receivers in order to reduce the amount of feedback information. The reference CQI is a threshold used for setting channels of the receivers to an Activation or Inactivation state. Upon receipt of the reference CQI, the receivers each compare the received reference CQI with a CQI of a channel corresponding to a stream received later, set the corresponding channel to Activation/Inactivation (that is, ON/OFF) according to the comparison result, and transmit Activation/Inactivation signal or ON/OFF-signal to the transmitter. The Activation signal indicates the case where a CQI of a corresponding communication channel is greater than or equal to the reference CQI, and the Inactivation signal indicates the case where the CQI of the corresponding communication channel is less than the reference CQI.

    [0027] Upon receipt of the Activation/Inactivation signals from the receivers, the transmitter generates a channel matrix based on the received Activation/Inactivation signals, and transmits a stream to the receivers using the generated channel matrix.

    [0028] To perform this operation, the transmitter may appropriately set the reference CQI according to the system environment. A setting method can be divided into a method A in which the transmitter sets the reference CQI in the case when the transmitter has knowledge of statistical distribution, and a method B in which the transmitter sets the reference CQI in the case when the transmitter has no knowledge of the statistical distribution.

    [0029] In addition, the transmitter can group the receivers according to CQI. That is, the transmitter can group the receivers that have a poor CQI as they are located in a cell boundary area or a shadow area, or can group the receivers having a good CQI.

    [0030] FIG. 2 is a flowchart illustrating a feedback method in a multi-user MIMO system according to an exemplary embodiment of the present invention.

    [0031] Referring to FIG. 2, a transmitter and a receiver both have a plurality of antennas, and provide/receive a multi-user MIMO service via the antennas. In the multi-antenna system including multi-antenna transceivers, the transmitter transmits a plurality of streams to the receiver in step S100. The streams can be transmitted to the receiver via one or more than one antenna.

    [0032] Upon receipt of the streams from the transmitter, the receiver feeds back in step S102 to the transmitter the feedback information including quality of a channel corresponding to the stream having the highest channel gain among the received streams. The feedback information includes index information of the stream having the best quality among the streams and a CQI given at that time.

    [0033] Thereafter, in step S104, the transmitter transmits a reference CQI to all receivers in the cell. The reference CQI can be measured or determined by the transmitter or the receiver for smooth signal exchange between transceivers, or can be flexibly set for high system performance. The reference CQI value can be commonly applied to all receivers, or can be separately applied to each receiver or each receiver group. A technique of determining the reference CQI value will be described below. Upon receiving the reference CQI in step S104, the receiver compares in step S106 the received reference CQI with a CQI of a communication channel using the stream received via each antenna included in the receiver. The CQI of the communication channel for each individual antenna can be measured depending on a pilot signal that the transmitter periodically transmits, or can be measured depending on the streams received from the transmitter. After measuring the CQI of the communication channel for each antenna in this manner, the receiver can periodically measure channel quality separately for each antenna included therein.

    [0034] After comparing the received reference CQI with the CQI of the channel corresponding to the stream received separately for each antenna in step S106, the receiver sets a channel state according to the comparison result in step S108. Herein, the phrase 'setting the channel state' refers to setting Activation/Inactivation of a transmission/reception channel according to the comparison result. A process of setting the channel state to Activation means a process of connecting the transmitter to the channel of the corresponding antenna to perform communication, and a process of setting the channel state to Inactivation means a process of releasing (or disconnecting) the channel of the corresponding antenna from the transmitter to disable the communication, or setting the reference CQI to a CQI of the corresponding stream.

    [0035] The Activation indicates that a CQI value of a corresponding stream can be used as a preset CQI value because the CQI value of the corresponding stream is greater than or equal to the preset CQI value. The Inactivation indicates that a CQI value of a corresponding stream cannot be used as a preset CQI value because the CQI value of the corresponding stream is less than the preset CQI value, or that the CQI value cannot participate in stream scheduling. For example, if a CQI value of a specific stream is a natural number greater than the reference CQI (that is, its real value is equal to the reference CQI, but is greater than the reference CQI by a decimal fraction value), the decimal fraction value-removed natural number (that is, an integer being identical to the reference CQI) is set as a CQI of the corresponding stream.

    [0036] In this manner, if the CQI of the communication channel is greater than or equal to the reference CQI, the receiver sets the channel state to the Activation. However, if the CQI of the communication channel is less than the reference CQI, the receiver sets the channel state to the Inactivation.

    [0037] After step S108, the receiver transmits to the transmitter an Activation/Inactivation signal indicating the set channel state in step S110. The number of the Activation/Inactivation signals can be one according to the receiver, or can be equal to the number of antennas according to the channel states of the antennas included in the receiver. The Activation/Inactivation signal has a 1-bit size.

    [0038] Upon receipt of the Activation/Inactivation signals from multiple receivers, the transmitter transmits streams to more than one receiver using channels corresponding to the received Activation/Inactivation signals and performs multi-user MIMO service according to the Activation/Inactivation signal received for each receiver in step S112.

    [0039] FIG. 3 is a block diagram illustrating an exemplary Activation/Inactivation switching feedback technique in a multi-user MIMO system according to an embodiment of the present invention.

    [0040] Referring to FIG. 3, a receiver receives multiple streams from a transmitter, and detects a stream having the greatest CQI among the received streams. As shown in the drawing, assume that a CQI of a first stream is 1.5, a CQI of a second stream is 4, a CQI of a third stream is 2.5, and a CQI of a fourth stream is 2. The receiver transmits the highest CQI=4 among the received CQI values to the base station. Thereafter, upon receipt of a reference CQI detected by multiple techniques from the transmitter, the receiver compares the received reference CQI with CQIs of the multiple streams, and then transmits an Activation/Inactivation signal based on the comparison result to the transmitter. That is, as shown in the drawing, the receiver transmits an Inactivation signal to the transmitter, for the first stream with CQI=1.5; transmits an Activation signal to the transmitter, for the third stream with CQI=2.5; and transmits an Activation signal to the transmitter, for the fourth stream with CQI=2. A description of the Activation/Inactivation switching feedback technique for reducing the amount of feedback information in the multi-user MIMO system has been described below, and a transceiver applied to the system will be described below.

    [0041] FIG. 4 is a block diagram illustrating a feedback information reception apparatus of a transmitter in a multi-user MIMO system according to an exemplary embodiment of the present invention.

    [0042] Referring to FIG. 4, the transmitter includes a channel state detector 110 for detecting a channel state for each individual receiver depending on CQIs received from multiple receivers, a controller 120 for controlling precoding and multi-output of streams to be transmitted via multiple antennas according to the detected channel state, a coding and modulation unit 130 for coding and modulating the multiple stream, and a multi-output unit 140 for multi-outputting the coded/modulated multiple streams via multiple antennas.

    [0043] In addition, the transmitter includes a memory (not shown) for storing reference CQIs to be applied to multiple receivers, and storing channel state information received from the multiple receivers. Further, the controller 120 includes therein a module for determining a reference CQI using the method A or the method B described below, and transmitting the reference CQI to the receivers.

    [0044] The transmitter first sets a reference CQI value using any one of the following two methods A and B.

    [0045] A method of determining a reference CQI by the transmitter can be divided into two methods A and B for a case where the transmitter has knowledge of statistical distribution of CQls and for another case where the transmitter has no knowledge of statistical distribution of CQls.

    A. Statistical Distribution of CQIs is Known



    [0046] The transmitter, when it has knowledge of statistical distribution of CQIs, can determine a reference CQI using Equation (1).



    [0047] In Equation (1), CQIreference denotes a reference CQI, and α denotes a CQI acceptance rate indicating a probability that the transmitter will determine a given CQI as Activation, and is previously set by the transmitter. That is, the transmitter can set a given CQI to Activation by adjusting the probability α. For example, in Equation (1), α=0.7 means that a ratio of CQIs greater than the reference CQI (CQIreference) to all CQIs is set to 70%. The transmitter can determine the reference CQI by adjusting the probability α in this manner.

    [0048] The probability α can depend on the number of users, or the number of antennas included in each of receivers. That is, for a small number of users, the transmitter can set a high probability α to set a low reference CQI value, and for a large number of users, the transmitter can set a low probability α to set a high reference CQI value, thereby increasing system performance. The probability α is adjustable in this manner. The transmitter can perform communication with multiple users or multiple antennas by setting a low reference CQI.

    B. Statistical Distribution of CQIs is Unknown



    [0049] The transmitter, when it has no knowledge of statistical distribution of CQIs, can adjust a reference CQI using a ratio of Activations received from multiple users or multiple antennas. For example, if the ratio of Activations received from the users is high, the transmitter increases the reference CQI value. In contrast, if the Activation ratio is low, the transmitter decreases the reference CQI value, thereby increasing the system performance.

    [0050] Equation (2) can be used by the transmitter to adjust a reference CQI value according to time when the transmitter has no knowledge of statistical distribution of CQIs.



    [0051] With use of Equation (2), the transmitter can calculate a reference CQI to be used at a specific time t+1. In Equation (2),

    denotes a reference CQI to be used at a time t+1, αtarget denotes an Activation ratio targeted by the system, and α(1) denotes a ratio of Activations that more than one receiver has actually reported at a time t. In addition, w denotes a constant used for determining a possible change in the reference CQI according to time.

    [0052] In this manner, with use of Equation (2), the transmitter can achieve the Activation ratio targeted by the system at a specific time, even though the transmitter has no knowledge of statistical distribution of CQIs.

    [0053] After determining the reference CQI in this manner, the controller 120 transmits the reference CQI to the receiver.

    [0054] Thereafter, the transmitter transmits streams to the receiver, and the receiver transmits CQls of the streams to the transmitter depending on the received streams. The channel state detector 110, included in the transmitter, receives the CQIs of the individual streams from the receiver. The CQIs are received from multiple receivers, and include information on the channels that the receivers have set depending on the received streams. That is, the CQI includes ON-information indicating that the channel is set to Activation, and includes OFF-information indicating that the channel is set to Inactivation.

    [0055] Upon receipt of the information indicating Activation or Inactivation of the channel state, the transmitter detects channel states of multiple antennas included in the receiver, and provides the detection result to the controller 120. The controller 120 controls transmission of multiple streams. That is, to transmit multiple input streams to the multiple receivers, the controller 120 precodes the multiple input streams, and generates a channel matrix depending on Activation and/or Inactivation signals received from the receivers. In addition, the controller 120 forms a beam of antennas included in the transmitter to transmit the precoded streams to the receivers via the multi-output unit 140. Thereafter, the controller 120 transmits streams to the receivers through the beamforming antennas.

    [0056] FIG. 5 is a flowchart illustrating a feedback information transmission/reception method of a transmitter in a multi-user MIMO system according to an exemplary embodiment of the present invention.

    [0057] Referring to FIG. 5, the transmitter assumes that a threshold, a reference CQI to be applied to a receiver, has already been set. The reference CQI, as described above, can be set using at least one of the foregoing methods A and B, or can be set by a user of the receiver.

    [0058] As shown in the drawing, the transmitter transmits streams to the receiver in step S200. The transmission streams can be transmitted via one antenna of the transmitter one by one, or can be simultaneously transmitted via multiple antennas of the transmitter. In this manner, the transmission streams from the transmitter are transmitted to more than one receiver. Upon receipt of the streams, the receiver measures channel quality separately for each individual antenna or channel depending on the received streams. Thereafter, the receiver detects the highest quality value among the measured qualities, that is, detects a CQI value of the stream having the highest channel gain among the received streams, and transmits the detected quality value to the transmitter. Upon receipt of the CQI of the stream with the highest channel gain from the receiver, the transmitter transmits the reference CQI to the receiver in steps S202 and S204.

    [0059] The reference CQI can be previously set in the transmitter separately for each receiver, or can be determined using at least one of the methods A and B. In addition, the reference CQI is adjustable according to channel transmission conditions, system conditions, and priorities of receivers.

    [0060] The reference CQI is applied to the remaining streams except for the highest-channel gain stream corresponding to the CQI value received in step S202. That is, upon receipt of the reference CQI, the receiver compares the CQIs of the remaining streams with the received reference CQI, and then transmits the comparison result to the transmitter. The remaining streams can be received at the receiver via one antenna, or can be received via multiple antennas separately for the individual streams.

    [0061] For example, as a result of the comparison between the reference CQI value and a CQI for each of the remaining streams, if the reference CQI value is less than the CQI of each stream, the receiver transmits an Activation signal to the transmitter. However, if the reference CQI value is greater than or equal to the CQI of each stream, the receiver transmits an Inactivation signal to the transmitter.

    [0062] Upon receipt of the Activation/Inactivation signal, that is, channel state information, from the receiver in step S206, the transmitter performs antenna beamforming according to the received channel state information in step S208. The process of performing antenna beamforming includes indicating that the transmitter can use antennas having higher channel quality or higher data rate, among the multiple antennas included therein.

    [0063] After performing antenna beamforming in step S208, the transmitter transmits streams to the receiver via the beamforming antennas in step S210.

    [0064] FIG. 6 is a block diagram illustrating a feedback information transmission/reception apparatus of a receiver in a multi-user MIMO system according to an exemplary embodiment of the present invention.

    [0065] Referring to FIG. 6, the receiver 200 includes a channel quality measurer 210 for measuring quality of each individual channel depending on streams received from a transmitter, a controller 220 for comparing the measured quality value, that is, measured CQI, of each channel with a reference CQI, a memory 230 for storing the reference CQI and the comparison result value from the controller 220, a multi-reception unit 240 for multi-receiving the streams received from the transmitter, and a decoding and demodulation unit 250 for decoding and demodulating the received streams. In addition, the receiver includes a transmission unit (not shown) for transmitting the comparison result to the transmitter.

    [0066] Although a description of the following operation will be made herein based on one receiver, it will be understood by those skilled in the art that the operation can also be applied to all receivers that have received the reference CQI from the transmitter, or all receivers located in the coverage area of the transmitter. In addition, according to exemplary embodiments of the present invention, the receiver generates feedback information, and transmits the generated feedback information to the transmitter.

    [0067] Referring to FIG. 6, it is assumed that the transmitter provides a MIMO service to the receiver. For the MIMO service, the transmitter and the receiver both can include a plurality of antennas. That is, the receiver receives a stream via each of the antennas.

    [0068] The channel quality measurer 210 measures qualities (that is, CQls) of downlink channels depending on the streams received separately via the individual antennas. Alternatively, the channel quality measurer 210 can measure a CQI depending on the stream having the best channel quality among all the received streams. The channel quality measurer 210 transmits the CQls measured separately for the individual streams to the controller 220. Upon receipt of the measured CQls, the controller 220 compares each of the measured CQls with a reference CQI value. The reference CQI, received from the transmitter, is a threshold used for determining whether to set Activation or Inactivation for the antennas included in the receiver.

    [0069] After comparing the CQI of each stream with the reference CQI value in this manner, if the reference CQI is greater than or equal to the CQI of the stream, the controller 220 sets the channel, over which the stream was received, to Inactivation (that is, OFF mode). The controller 220 stores the resulting Inactivation signal in the memory 230. However, if the reference CQI is less than the CQI of the stream, the controller 220 sets the channel, over which the stream was received, to Activation (that is, ON mode). Similarly, the controller 220 stores the resulting Activation signal in the memory 230.

    [0070] The controller 220 can store the Activation or Inactivation signal in the memory separately for each individual stream on a one-by-one basis, or can store the Activation or Inactivation signals for all streams in the memory at a time after completion of the comparison for all streams.

    [0071] After completion of the comparison for each stream or all streams, the controller 220 transmits the Activation and/or Inactivation signal(s) stored in the memory 230 to the transmitter.

    [0072] A method of transmitting the Activation/Inactivation signals in the receiver according to an exemplary embodiment of the present invention can be divided into a method C of transmitting an Activation/Inactivation signal generated separately for each individual stream on a one-by-one basis, and a method D of transmitting Activation/Inactivation signals for all streams at a time.

    C. Activation/Inactivation Signal Generated Separately for Each Stream is Transmitted One by One



    [0073] With reference to FIG. 7A, a detailed description will now be made of a feedback information transmission/reception method of a receiver in a multi-user MIMO system according to an exemplary embodiment of the present invention.

    [0074] Upon receipt of a reference CQI from the transmitter, the receiver compares the received reference CQI with a CQI for each stream received from the transmitter in steps S300 and S302. The stream can be received via one antenna of the receiver, or can be received via multiple antennas included in the receiver. The reference CQI is commonly applied to every stream.

    [0075] If the received reference CQI is greater than or equal to the CQI of the stream received from the transmitter, the receiver sets the channel, over which the stream was received, to Inactivation in steps S304 and S306. The process of setting the channel to the Inactivation includes indicating that the receiver will no longer receive the stream from the transmitter over the corresponding channel. To avoid additional reception of the stream, the receiver generates an Inactivation signal (that is, OFF signal) depending on the setting result given in step S306.

    [0076] However, if the received reference CQI value is less than the CQI of the stream received from the transmitter in step S304, the receiver sets the channel, over which the stream was received, to Activation in steps S304 and S310. After setting the channel to Activation in step S310, the receiver generates an Activation signal (that is, ON signal) according to the setting result in step S312.

    [0077] In step S314, the receiver transmits to the transmitter the Activation or Inactivation signal generated in steps S308 and S312. After step S314, the receiver checks in step S316 whether the processes of steps S04 to S314 have been completely performed on all streams. That is, for every received stream, the receiver compares the reference CQI with the CQI of each stream. If the comparison between the reference CQI and the CQI of every stream have not been completed yet in step S316, the receiver returns to step S304.

    D. Activation/Inactivation Signals of All Streams are Transmitted at a Time



    [0078] With reference to FIG. 7B, a detailed description will now be made of a feedback information transmission/reception method of a receiver in a multi-user MIMO system according to an exemplary embodiment of the present invention.

    [0079] Referring to FIG. 7B, the proposed method of transmitting Activation/Inactivation signals of all streams at a time in the receiver is equivalent to the method of FIG. 7A in terms of the processes of steps S300 to S306 and S310.

    [0080] In FIG. 7B, after comparing the received reference CQI with a CQI of a corresponding stream, if the received reference CQI in step S400 is greater than or equal to the CQI of the stream, the receiver sets the channel, over which the stream was received, to Inactivation in steps S402 to S406. After setting the stream-received channel to Inactivation in step S406, the receiver stores, in step S408, in a memory the Inactivation signal which is generated independently for each stream according to the setting result. However, if the received reference CQI is less than the CQI of the stream, the receiver sets the channel, over which the stream was received, to Activation in step S410. After setting the stream-received channel to Activation in step S410, the receiver stores in step S412 in the memory the Activation signal which is generated independently for each stream according to the setting result.

    [0081] After performing the processes of steps S404 to S412 on all streams, the receiver transmits in step S414 to the transmitter the Activation/Inactivation signals stored in the memory.

    [0082] As is apparent from the foregoing description, according to exemplary embodiments of the present invention, the receiver, even though it receives multiple streams from the transmitter, transmits to the transmitter the Activation and/or Inactivation information of the channel separately for each individual stream, thereby contributing to a reduction in the total amount of feedback information. The reduction in the amount of feedback information can contribute to an increase in the system performance and an increase in the throughput of transceivers.

    [0083] While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.


    Claims

    1. A transmitter for receiving feedback information in a MIMO system, comprising:

    a channel state detector (110) for receiving channel setting information from a receiver (200, 300) after transmitting a reference channel quality information, CQI, to the receiver, and detecting a channel state of the receiver depending on information on the received channel setting information; and

    a controller (120) for controlling beam forming of a plurality of antennas using the detected channel state,

    wherein the reference CQI is a threshold used for setting channels of the receivers to an Activation or Inactivation state, and the channel setting information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the channels.


     
    2. The transmitter of claim 1, wherein the reference CQI is determined differently for a first case where the transmitter (100) has knowledge of statistical distribution of CQIs received from multiple receivers and for a second case where the transmitter (100) has no knowledge of the statistical distribution of the CQIs.
     
    3. The transmitter of claim 2, wherein in the first case, the reference CQI is determined when a probability that the reference CQI will be less than a CQI corresponding to the statistical distribution is substantially equal to a preset channel activation ratio.
     
    4. The transmitter of claim 2, wherein in the second case, the reference CQI at a specific time, t+1, is determined by subtracting a channel activation ratio targeted by the transmitter from an actual activation ratio received from more than one receiver at a specific time t, multiplying the subtraction result value by a value used for determining a possible change in the reference CQI according to time, and adding the reference CQI used at the specific time t to the multiplication result value.
     
    5. The transmitter of one of claims 1 to 4, wherein the channel setting information comprises information indicating activation and/or inactivation states according to the channel state of the receiver.
     
    6. A feedback information reception method of a transmitter (100) in a MIMO system, the method comprising:

    determining a reference channel quality information, CQI, to be applied to a plurality of channels of a receiver (200, 300);

    transmitting (S104) the determined reference CQI to the receiver (200, 300); and

    receiving setting information of the channels from the receiver (200, 300),

    wherein the reference CQI is a threshold used for setting channels of the receivers to an Activation or Inactivation state, and the setting information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the channels.


     
    7. The feedback information reception method of claim 6, further comprising:

    upon receipt of the setting information, detecting a channel state for each antenna of the receiver, and forming an antenna beam of the transmitter (100) using the detected channel state for each antenna.


     
    8. The feedback information reception method of claim 6 or 7, wherein the reference CQI is determined differently for a first case where the transmitter (100) has knowledge of statistical distribution of CQIs received from multiple receivers and for a second case where the transmitter has no knowledge of the statistical distribution of the CQIs.
     
    9. The feedback information reception method of claim 8, wherein in the first case, the reference CQI is determined when a probability that the reference CQI will be less than a CQI corresponding to the statistical distribution is substantially equal to a preset channel activation ratio.
     
    10. The feedback information reception method of claim 8 or 9, wherein in the second case, the reference CQI at a specific time, t+1, is determined by subtracting a channel activation ratio targeted by the transmitter from an actual activation ratio received from more than one receiver at a specific time t, multiplying the subtraction result value by a value used for determining a possible change in the reference CQI according to time, and adding the reference CQI used at the specific time t to the multiplication result value.
     
    11. The feedback information reception method of one of claims 6 to 10, wherein the setting information comprises information indicating activation and/or inactivation states according to a channel state of the receiver.
     
    12. The feedback information reception method of claim 8, wherein in the first case, the reference CQI is calculated using the following equation;


    where CQIreference denotes a reference CQI, and α denotes a previously stored probability that the transmitter will determine a given CQI as activation.
     
    13. The feedback information reception method of claim 8, wherein in the second case, the reference CQI is calculated using the following equation;


    where

    denotes a reference CQI to be used at a time t+1, αtarget denotes an activation ratio targeted by the system, α(t) denotes an activation ratio that more than one receiver has reported at the time t, and w denotes a constant used for determining a possible change in the reference CQI according to time.
     
    14. A receiver for transmitting feedback information in a MIMO system, comprising:

    a channel quality measurer (210) for measuring a channel quality information, CQI, of each stream received from a transmitter (100);

    a controller (220) for comparing the measured CQI of the stream with a reference CQI received from the transmitter (100), and setting a corresponding channel according to the comparison result; and

    a transmission unit for transmitting channel state information, based on the comparison result to the transmitter (100),

    wherein the reference CQI is a threshold used for setting a channel of the stream to an Activation or Inactivation state, and the channel state information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the stream.


     
    15. The receiver of claim 14, wherein the controller (220) is adapted to set a channel of the stream to an activation state, if the CQI of the stream is at least one of greater than and equal to the reference CQI.
     
    16. The receiver of claim 14 or 15, wherein the controller (220) is adapted to set a channel of the stream to an inactivation state, if the CQI of the stream is less than the reference CQI.
     
    17. The receiver of claim 14, wherein the controller (220) is adapted to generate channel state information according to the comparison result and to transmit the channel state information to the transmitter (100).
     
    18. The receiver of claim 17, wherein the channel state information is 1 bit in size.
     
    19. A feedback information transmission method of a receiver in a MIMO system, comprising:

    receiving a reference channel quality information, CQI, from a transmitter (100);

    comparing (S302, S402) the received reference CQI with a CQI of a stream received from the transmitter (100); and

    generating channel state information according to the comparison result, and transmitting (S314, S414) the channel state information to the transmitter (100),

    wherein the reference CQI is a threshold used for setting a channel of the stream to an Activation or Inactivation state, and the channel state information comprises Activation/Inactivation signals indicating Activation and/or Inactivation states of the stream.


     
    20. The feedback information transmission method of claim 19, further comprising:

    Setting (S306, S406, S310, S410) a corresponding channel to at least one of activation and inactivation according to the comparison (S304, S404) between the received reference CQI and the CQI of the stream.


     
    21. The feedback information transmission method of claim 19 or 20, wherein the channel state information indicates that a channel over which the stream is received, is set to inactivation, if the reference CQI is at least one of greater than and equal to the CQI of the stream.
     
    22. The feedback information transmission method of one of claims 19 to 21, wherein the channel state information indicates that a channel, over which the stream is received, is set to activation, if the reference CQI is less than the CQI of the stream.
     
    23. A MIMO system for transmitting/receiving channel quality information, CQI, comprising:

    a transmitter (100) according to one of the claims 1 to 5, wherein said transmitter (100) is further adapted to transmit multiple streams and the reference CQI to a receiver, and upon receipt of channel state information from the receiver, to form an antenna beam depending on the received channel state information; and

    the receiver (200, 300) for comparing the reference CQI with a CQI of the stream, setting a corresponding channel to at least one of activation and inactivation, according to the comparison result, generating channel state information, and transmitting the channel state information to the transmitter (100).


     
    24. The MIMO system of claim 23, wherein the transmitter (100) is further adapted to determine the reference CQI when a probability that the reference CQI will be less than a CQI corresponding to statistical distribution is equal to a preset channel activation ratio, and to determine the reference CQI by subtracting a channel activation ratio targeted by the transmitter from an actual activation ratio received from more than one receiver at a specific time, t+1, to multiply the subtraction result value by a value used for determining a possible change in the reference CQI according to time, and to add the reference CQI used at the specific time t to the multiplication result value.
     
    25. The MIMO system of claim 23 or 24, wherein the transmitter (100) is further adapted to group at least one of receivers that have a poor CQI as they are located in a cell boundary area or a shadow area and receivers having a good CQI, and then to transmit a common reference CQI to the receiver group.
     
    26. A channel quality information, CQI, transmission/reception method in a MIMO system, the method comprising:

    determining the reference CQI using a CQI received from a receiver, and transmitting the reference CQI to the receiver, according to claim 6;

    upon receipt of the reference CQI, comparing the reference CQI with a CQI of a stream received from the transmitter; and

    setting a channel, over which the stream is received, to at least one of an activation state and an inactivation state, according to the comparison result, and transmitting information of the set channel to the transmitter.


     
    27. The CQI transmission/reception method of claim 26, wherein the reference CQI is at least one of determined when a probability that the reference CQI will be less than a CQI corresponding to statistical distribution is equal to a preset channel activation ratio and determined by subtracting a channel activation ratio targeted by the transmitter from an actual activation ratio received from more than one receiver at a specific time, t+1, multiplying the subtraction result value by a value used for determining a possible change in the reference CQI according to time, and adding the reference CQI used at the specific time t to the multiplication result value.
     


    Ansprüche

    1. Sender zum Empfangen von Rückmeldungsinformationen in einem MIMO-System, umfassend:

    einen Kanalzustandsdetektor (110) zum Empfangen von Kanalsetzinformationen von einem Empfänger (200, 300) nach dem Senden von Bezugs-Kanalqualitätsinformationen, CQI, an den Empfänger und zum Erfassen eines Kanalzustands des Empfängers in Abhängigkeit von Informationen in den empfangenen Kanalsetzinformationen, und

    eine Steuereinrichtung (120) zum Steuern der Strahlbildung einer Vielzahl von Antennen unter Verwendung des erfassten Kanalzustands,

    wobei die Bezugs-CQI ein Schwellwert sind, der für das Setzen von Kanälen der Empfänger zu einem Aktivierungs- oder Inaktivierungszustand verwendet werden, und wobei die Kanalsetzinformationen Aktivierungs-/Inaktivierungssignale umfassen, die Aktivierungs- und/oder Inaktivierungszustände der Kanäle angeben.


     
    2. Sender nach Anspruch 1, wobei die Bezugs-CQI verschieden für einen ersten Fall, in dem der Sender (100) über Wissen zu der statistischen Verteilung der von mehreren Empfängern empfangenen CQIs verfügt, und für einen zweiten Fall, in dem der Sender (100) nicht über Wissen zu der statistischen Verteilung der CQIs verfügt, bestimmt werden.
     
    3. Sender nach Anspruch 2, wobei in dem ersten Fall die Bezugs-CQI bestimmt werden, wenn eine Wahrscheinlichkeit dafür, dass die Bezugs-CQI kleiner als die CQI in Entsprechung zu der statistischen Verteilung sind, im Wesentlichen gleich einem zuvor gesetzten Kanalaktivierungsverhältnis ist.
     
    4. Sender nach Anspruch 2, wobei in dem zweiten Fall die Bezugs-CQI zu einem spezifischen Zeitpunkt, t+1, bestimmt werden, indem ein durch den Sender angestrebtes Kanalaktivierungsverhältnis von einem tatsächlichen Aktivierungsverhältnis, das von mehr als einem Empfänger zu einer spezifischen Zeit t empfangen wird, subtrahiert wird, der Subtraktionsergebniswert mit einem Wert, der für das Bestimmen einer möglichen Änderung in den Bezugs-CQI in Übereinstimmung mit der Zeit verwendet wird, multipliziert wird und die zu der spezifischen Zeit t verwendeten Bezugs-CQI zu dem Multiplikationsergebniswert addiert werden.
     
    5. Sender nach einem der Ansprüche 1 bis 4, wobei die Kanalsetzinformationen Informationen umfassen, die Aktivierungs- und/oder Inaktivierungszustände in Übereinstimmung mit dem Kanalzustand des Empfängers angeben.
     
    6. Verfahren zum Empfangen von Rückmeldungsinformationen eines Senders (100) in einem MIMO-System, wobei das Verfahren umfasst:

    Bestimmen von Bezugs-Kanalqualitätsinformationen, CQI, für das Anwenden auf eine Vielzahl von Kanälen eines Empfängers (200, 300),

    Senden (S104) der bestimmten Bezugs-CQI an den Empfänger (200, 300), und

    Empfangen von Setzinformationen der Kanäle von dem Empfänger (200, 300),

    wobei die Bezugs-CQI ein Schwellwert sind, der für das Setzen von Kanälen der Empfänger zu einem Aktivierungs- oder Inaktivierungszustand verwendet wird, und wobei die Setzinformationen Aktivierungs-/Inaktivierungssignale umfassen, die Aktivierungs- und/oder Inaktivierungszustände der Kanäle angeben.


     
    7. Verfahren zum Empfangen von Rückmeldungsinformationen nach Anspruch 6, das weiterhin umfasst:

    nach dem Empfangen der Setzinformationen, Erfassen eines Kanalzustands für jede Antenne des Empfängers, und Bilden eines Antennenstrahls des Senders (100) unter Verwendung des erfassten Kanalzustands für jede Antenne.


     
    8. Verfahren zum Empfangen von Rückmeldungsinformationen nach Anspruch 6 oder 7, wobei die Bezugs-CQI verschieden für einen ersten Fall, in dem der Sender (100) über Wissen zu der statistischen Verteilung der von mehreren Empfängern empfangenen CQIs verfügt, und für einen zweiten Fall, in dem der Sender nicht über Wissen zu der statistischen Verteilung der CQIs verfügt, bestimmt werden.
     
    9. Verfahren zum Empfangen von Rückmeldungsinformationen nach Anspruch 8, wobei in dem erstem Fall die Bezugs-CQI bestimmt werden, wenn eine Wahrscheinlichkeit dafür, dass die Bezugs-CQI kleiner als eine CQI in Entsprechung zu der statistischen Verteilung sind, im Wesentlichen gleich einem zuvor gesetzten Kanalaktivierungsverhältnis ist.
     
    10. Verfahren zum Empfangen von Rückmeldungsinformationen nach Anspruch 8 oder 9, wobei in dem zweiten Fall die Bezugs-CQI zu einem spezifischen Zeitpunkt, t+1, bestimmt werden, indem ein durch den Sender angestrebtes Kanalaktivierungsverhältnis von einem tatsächlichen Aktivierungsverhältnis, das von mehr als einem Empfänger zu einer spezifischen Zeit t empfangen wird, subtrahiert wird, der Subtraktionsergebniswert mit einem Wert, der für das Bestimmen einer möglichen Änderung in den Bezugs-CQI in Übereinstimmung mit der Zeit verwendet wird, multipliziert wird und die zu der spezifischen Zeit t verwendeten Bezugs-CQI zu dem Multiplikationsergebniswert addiert werden.
     
    11. Verfahren zum Empfangen von Rückmeldungsinformationen nach einem der Ansprüche 6 bis 10, wobei die Setzinformationen Informationen umfassen, die Aktivierungs- und/oder Inaktivierungszustände in Übereinstimmung mit dem Kanalzustand des Empfängers angeben.
     
    12. Verfahren zum Empfangen von Rückmeldungsinformationen nach Anspruch 8, wobei in dem ersten Fall die Bezugs-CQI unter Verwendung der folgenden Gleichung berechnet werden:


    wobei CQIreference Bezugs-CQI wiedergibt und α eine zuvor gespeicherte Wahrscheinlichkeit dafür, dass der Sender bestimmte CQI als eine Aktivierung bestimmt, wiedergibt.
     
    13. Verfahren zum Empfangen von Rückmeldungsinformationen nach Anspruch 8, wobei in dem zweiten Fall die Bezugs-CQI unter Verwendung der folgenden Gleichung berechnet werden:


    wobei

    Bezugs-CQI für die Verwendung zu einer Zeit t+1 wiedergibt, αtarget ein durch das System angestrebtes Aktivierungsverhältnis angibt, α(t) ein Aktivierungsverhältnis wiedergibt, das mehr als ein Empfänger zu der Zeit t berichtet haben, und w eine für das Bestimmen einer möglichen Änderung in den Bezugs-CQI in Übereinstimmung mit der Zeit verwendete Konstante wiedergibt.
     
    14. Empfänger zum Senden von Rückmeldungsinformationen in einem MIMO-System, umfassend:

    einen Kanalqualitätsmesser (210) zum Messen von Kanalqualitätsinformationen, CQI, jedes von einem Sender (100) empfangenen Stroms,

    eine Steuereinrichtung (220) zum Vergleichen der gemessenen CQI des Stroms mit von dem Sender (100) empfangenen Bezugs-CQI und zum Setzen eines entsprechenden Kanals in Übereinstimmung mit dem Vergleichsergebnis, und

    eine Sendeeinheit zum Senden von Kanalzustandsinformationen basierend auf dem Vergleichsergebnis an den Sender (100),

    wobei die Bezugs-CQI ein Schwellwert sind, der für das Setzen eines Kanals des Stroms zu einem Aktivierungs- oder Inaktivierungszustand verwendet wird, und wobei die Kanalzustandinformationen Aktivierungs-/Inaktivierungssignale, die Aktivierungs- und/oder Inaktivierungszustände des Stroms angeben, umfassen.


     
    15. Empfänger nach Anspruch 14, wobei die Steuereinrichtung (220) ausgebildet ist, um einen Kanal des Stroms zu einem Aktivierungszustand zu setzen, wenn die CQI des Stroms größer oder gleich den Bezugs-CQI sind.
     
    16. Empfänger nach Anspruch 14 oder 15, wobei die Steuereinrichtung (220) ausgebildet ist, um einen Kanal des Stroms zu einem Inaktivierungszustand zu setzen, wenn die CQI des Stroms kleiner als die Bezugs-CQI sind.
     
    17. Empfänger nach Anspruch 14, wobei die Steuereinrichtung (220) ausgebildet ist, um Kanalzustandsinformationen in Übereinstimmung mit dem Vergleichsergebnis zu erzeugen und die Kanalzustandsinformationen an den Sender (100) zu senden.
     
    18. Empfänger nach Anspruch 17, wobei die Kanalzustandsinformationen 1 Bit groß sind.
     
    19. Verfahren zum Senden von Rückmeldungsinformationen eines Empfängers in einem MIMO-System, umfassend:

    Empfangen von Bezugs-Kanalqualitätsinformationen, CQI, von einem Sender (100),

    Vergleichen (S302, S402) der empfangenen Bezugs-CQI mit den CQI eines von dem Sender (100) empfangenen Stroms, und

    Erzeugen von Kanalzustandsinformationen in Übereinstimmung mit dem Vergleichsergebnis und Senden (S314, S414) der Kanalzustandsinformationen an den Sender (100),

    wobei die Bezugs-CQI ein Schwellwert sind, der für das Setzen eines Kanals des Stroms zu einem Aktivierungs- oder Inaktivierungszustand verwendet wird, und wobei die Kanalzustandsinformationen Aktivierungs-/Inaktivierungssignale, die Aktivierung- und/oder Inaktivierungszustände des Stroms angeben, umfassen.


     
    20. Verfahren zum Senden von Rückmeldungsinformationen nach Anspruch 19, weiterhin umfassend:

    Setzen (S306, S406, S310, S410) eines entsprechenden Kanals zu wenigstens einer Aktivierung oder Inaktivierung in Übereinstimmung mit dem Vergleich (S304, S404) zwischen den empfangenen Bezugs-CQI und den CQI des Stroms.


     
    21. Verfahren zum Senden von Rückmeldungsinformationen nach Anspruch 19 oder 20, wobei die Kanalzustandsinformationen angeben, dass ein Kanal, über den der Strom empfangen wird, zu einer Inaktivierung gesetzt wird, wenn die Bezugs-CQI größer oder gleich den CQI des Stroms sind.
     
    22. Verfahren zum Senden von Rückmeldungsinformationen nach einem der Ansprüche 19 bis 21, wobei die Kanalzustandsinformationen angeben, dass ein Kanal, über den der Strom empfangen wird, zu einer Aktivierung gesetzt wird, wenn die Bezugs-CQI kleiner als die CQI des Stroms sind.
     
    23. MIMO-System zum Senden/Empfangen von Kanalqualitätsinformationen, CQI, umfassend:

    einen Sender (100) nach einem der Ansprüche 1 bis 5, wobei der Sender (100) weiterhin ausgebildet ist, um mehrere Ströme und die Bezugs-CQI an einen Empfänger zu senden und um beim Empfang von Kanalzustandsinformationen von dem Empfänger einen Antennenstrahl in Abhängigkeit von den empfangenen Kanalzustandsinformationen zu bilden, und

    den Empfänger (200, 300) zum Vergleichen der Bezugs-CQI mit den CQI des Stroms, zum Setzen eines entsprechenden Kanals zu wenigstens einer Aktivierung oder Inaktivierung in Übereinstimmung mit dem Vergleichsergebnis, zum Erzeugen von Kanalzustandsinformationen und zum Senden der Kanalzustandsinformationen an den Sender (100).


     
    24. MIMO-System nach Anspruch 23, wobei der Sender (100) weiterhin ausgebildet ist, um die Bezugs-CQI zu bestimmen, wenn eine Wahrscheinlichkeit dafür, dass die Bezugs-CQI kleiner als eine CQI in Entsprechung zu einer statistischen Verteilung sind, gleich einem zuvor gesetzten Kanalaktivierungsverhältnis ist, und um die Bezugs-CQI zu bestimmen, indem ein durch den Sender angestrebtes Kanalaktivierungsverhältnis von einem tatsächlichen Aktivierungsverhältnis, das von mehr als einem Empfänger zu einer spezifischen Zeit t+1 empfangen wird, subtrahiert wird, der Subtraktionsergebniswert mit einem Wert, der für das Bestimmen einer möglichen Änderung in den Bezugs-CQI in Übereinstimmung mit der Zeit verwendet wird, multipliziert wird und die zu der spezifischen Zeit t verwendeten Bezugs-CQI zu dem Multiplikationsergebniswert addiert werden.
     
    25. MIMO-System nach Anspruch 23 oder 24, wobei der Sender (100) weiterhin ausgebildet ist, um wenigstens Empfänger, die schlechte CQI aufweisen, weil sie sich in einem Zellengrenzbereich oder einem Schattenbereich befinden, und Empfänger mit guten CQI zu gruppieren und dann gemeinsame CQI an die Empfängergruppe zu senden.
     
    26. Verfahren zum Senden/Empfangen von Kanalqualitätsinformationen, CQI, in einem MIMO-System, wobei das Verfahren umfasst:

    Bestimmen der Bezugs-CQI unter Verwendung der von einem Empfänger empfangenen CQI und Senden der Bezugs-CQI an den Empfänger nach Anspruch 6,

    nach dem Empfang der Bezugs-CQI, Vergleichen der Bezugs-CQI mit den CQI eines von dem Sender empfangenen Stroms, und

    Setzen eines Kanals, über den der Strom empfangen wird, zu wenigstens einem Aktivierungszustand oder Inaktivierungszustand in Übereinstimmung mit dem Vergleichsergebnis und Senden von Informationen des gesetzten Kanals an den Sender.


     
    27. Verfahren zum Senden/Empfangen von CQI-Informationen nach Anspruch 26, wobei die Bezugs-CQI wenigstens bestimmt werden, wenn die Wahrscheinlichkeit dafür, dass die Bezugs-CQI kleiner als die CQI in Entsprechung zu einer statistischen Verteilung sind, gleich einem zuvor gesetzten Kanalaktivierungsverhältnis ist, und bestimmt werden, indem ein durch den Sender angestrebtes Kanalaktivierungsverhältnis von einem tatsächlichen Aktivierungsverhältnis, das von mehr als einem Empfänger zu einer spezifischen Zeit t+1 empfangen wird, subtrahiert wird, der Subtraktionsergebniswert mit einem Wert, der für das Bestimmen einer möglichen Änderung in der Bezugs-CQI in Übereinstimmung mit der Zeit verwendet wird, multipliziert wird und die zu der spezifischen Zeit t verwendeten Bezugs-CQI zu dem Multiplikationsergebniswert addiert werden.
     


    Revendications

    1. Émetteur destiné à recevoir une information de retour dans un système MIMO, comprenant :

    un détecteur d'état de canal (110) pour recevoir une information de réglage de canal depuis un récepteur (200, 300) après transmission au récepteur d'une information de qualité de canal de référence, CQI, et détecter un état de canal du récepteur dépendant d'une information sur l'information de réglage de canal reçue ; et

    un contrôleur (120) pour commander la formation de faisceau d'une pluralité d'antennes utilisant l'état de canal détecté,

    dans lequel la CQI de référence est constituée d'un seuil utilisé pour régler les canaux des récepteurs dans un état d'activation ou d'inactivation, et l'information de réglage de canal comprend des signaux d'activation/inactivation indiquant les états d'activation et/ou d'inactivation des canaux.


     
    2. Émetteur selon la revendication 1, dans lequel la CQI de référence est déterminée différemment pour un premier cas où l'émetteur (100) possède la connaissance de la répartition statistique des CQI reçues depuis des récepteurs multiples et pour un second cas où l'émetteur (100) ne possède aucune connaissance de la répartition statistique des CQI.
     
    3. Émetteur selon la revendication 2, dans lequel, dans le premier cas, la CQI de références est déterminée lorsque la probabilité pour que la CQI de référence soit inférieure à une CQI correspondant à la répartition statistique est sensiblement égale à un taux d'activation de canal fixé à l'avance.
     
    4. Émetteur selon la revendication 2, dans lequel, dans le second cas, la CQI de référence à un temps spécifique t+1 est déterminée en soustrayant le taux d'activation de canal ciblé par l'émetteur d'un taux d'activation réel reçu depuis plusieurs récepteurs à un temps spécifique t, en multipliant la valeur du résultat de la soustraction par une valeur utilisée pour déterminer un changement possible de la CQI de référence en fonction du temps, et en additionnant la CQI de référence utilisée au temps spécifique t avec la valeur du résultat de la multiplication.
     
    5. Émetteur selon l'une des revendications 1 à 4, dans lequel l'information de réglage de canal comprend une information indiquant les états d'activation et/ou d'inactivation en fonction de l'état de canal du récepteur.
     
    6. Procédé de réception d'information de retour d'un émetteur (100) dans un système MIMO, le procédé comprenant :

    la détermination d'une information de qualité de canal de référence, CQI, destinée à être appliquée à une pluralité de canaux d'un récepteur (200, 300) ;

    la transmission (S104) au récepteur (200, 300) de la CQI de référence déterminée ; et

    la réception d'informations de réglage des canaux depuis le récepteur (200, 300),

    dans lequel la CQI de référence est constituée d'un seuil utilisé pour régler les canaux des récepteurs dans un état d'activation ou d'inactivation, et l'information de réglage comprend des signaux d'activation/inactivation indiquant les états d'activation et/ou d'inactivation des canaux.


     
    7. Procédé de réception d'information de retour selon la revendication 6, comprenant en outre :

    lors de la réception de l'information de réglage, la détection d'un état de canal pour chaque antenne du récepteur, et la formation d'un faisceau d'antennes de l'émetteur (100) en utilisant l'état de canal détecté pour chaque antenne.


     
    8. Procédé de réception d'information de retour selon la revendication 6 ou 7, dans lequel la CQI de référence est déterminée différemment pour un premier cas où l'émetteur (100) possède la connaissance de la répartition statistique des CQI reçues depuis des récepteurs multiples et pour un second cas où l'émetteur (100) ne possède aucune connaissance de la répartition statistique des CQI.
     
    9. Procédé de réception d'information de retour selon la revendication 8, dans lequel, dans le premier cas, la CQI de référence est déterminée lorsque la probabilité pour que la CQI de référence soit inférieure à une CQI correspondant à la répartition statistique est sensiblement égale à un taux d'activation de canal fixé à l'avance.
     
    10. Procédé de réception d'information de retour selon la revendication 8 ou 9, dans lequel, dans le second cas, la CQI de référence à un temps spécifique t+1 est déterminée en soustrayant le taux d'activation de canal ciblé par l'émetteur d'un taux d'activation réel reçu depuis plusieurs récepteurs à un temps spécifique t, en multipliant la valeur du résultat de la soustraction par une valeur utilisée pour déterminer un changement possible de la CQI de référence en fonction du temps, et en additionnant la CQI de référence utilisée au temps spécifique t avec la valeur du résultat de la multiplication.
     
    11. Procédé de réception d'information de retour selon l'une des revendications 6 à 10, dans lequel l'information de réglage comprend une information indiquant les états d'activation et/d'inactivation en fonction de l'état de canal du récepteur.
     
    12. Procédé de réception d'information de retour selon la revendication 8, dans lequel, dans le premier cas, la CQI de référence est calculée en utilisant l'équation suivante :


    où CQIreference représente une CQI de référence, et α représente une probabilité mémorisée précédemment pour que l'émetteur détermine une CQI donnée comme activation.
     
    13. Procédé de réception d'information de retour selon la revendication 8, dans lequel dans le second cas, la CQI de référence est calculée en utilisant l'équation suivante :




    représente une CQI de référence destinée à être utilisée au temps t+1, αtarget représente un taux d'activation ciblé par le système, α(t) représente un taux d'activation que plusieurs récepteurs ont rapportés au temps t et w représente une constante utilisée pour déterminer un changement possible de la CQI de référence en fonction du temps.
     
    14. Récepteur destiné à transmettre une information de retour dans un système MIMO, comprenant :

    un mesureur de qualité de canal (210) pour mesurer une information de qualité de canal, CQI, de chaque flux reçu depuis un émetteur (100) ;

    un contrôleur (220) pour comparer la CQI mesurée du flux avec une CQI de référence reçue depuis l'émetteur (100) et régler un canal correspondant en fonction du résultat de la comparaison ; et

    une unité de transmission pour transmettre à l'émetteur (100) une information d'état de canal, en se basant sur le résultat de la comparaison,

    dans lequel la CQI de référence est constituée d'un seuil utilisé pour régler un canal du flux dans un état d'activation ou d'inactivation et l'information d'état de canal comprend des signaux d'activation/inactivation indiquant les états d'activation et/d'inactivation du flux.


     
    15. Récepteur selon la revendication 14, dans lequel le contrôleur (220) est adapté à régler un canal du flux dans un état d'inactivation, si la CQI du flux est au moins supérieure ou égale à la CQI de référence.
     
    16. Récepteur selon la revendication 14 ou 15, dans lequel le contrôleur (220) est adapté à régler un canal du flux dans un état d'inactivation, si la CQI du flux est inférieure à la CQI de référence.
     
    17. Récepteur selon la revendication 14, dans lequel le contrôleur (220) est adapté à générer une information d'état de canal en fonction du résultat de la comparaison et à transmettre à l'émetteur (100) l'information d'état de canal.
     
    18. Récepteur selon la revendication 17, dans lequel la taille d'une information d'état de canal est de 1 bit.
     
    19. Procédé de transmission d'une information de retour d'un récepteur dans un système MIMO, comprenant :

    la réception d'une information de qualité de canal de référence, CQI, depuis un émetteur (100) ;

    la comparaison (S302, S402) de la CQI de référence reçue avec une CQI d'un flux reçu depuis l'émetteur (100) ; et

    la génération d'une information d'état de canal en fonction du résultat de la comparaison, et la transmission (S314, S414) à l'émetteur (100) de l'information d'état de canal,

    dans lequel la CQI de référence est constituée d'un seuil utilisé pour régler un canal du flux dans un état d'activation ou d'inactivation, et l'information de réglage de canal comprend des signaux d'activation/inactivation indiquant les états d'activation et/ou d'inactivation du flux.


     
    20. Procédé de transmission d'une information de retour selon la revendication 19 comprenant en outre :

    le réglage (S306, S406, S310, S410) d'un canal correspondant à au moins une parmi l'activation et l'inactivation en fonction de la comparaison (S304, S404) entre la CQI de référence reçue et la CQI du flux.


     
    21. Procédé de transmission d'une information de retour selon la revendication 19 ou 20, dans lequel l'information d'état de canal indique qu'un canal sur lequel le flux est reçu est réglé à inactivation, si la CQI de référence est au moins supérieure ou égale à la CQI du flux.
     
    22. Procédé de transmission d'une information de retour selon l'une des revendications 19 à 21, dans lequel l'information d'état de canal indique qu'un canal sur lequel le flux est reçu est réglé à inactivation, si la CQI de référence est inférieure à la CQI du flux.
     
    23. Système MIMO pour transmettre/recevoir une information de qualité de canal, CQI, comprenant :

    un émetteur (100) selon l'une des revendications 1 à 5, dans lequel ledit émetteur (100) est adapté en outre à transmettre des flux multiples et la CQI de référence à un récepteur, et lors de la réception d'une information d'état de canal depuis le récepteur, à former un faisceau d'antennes en fonction de l'information d'état de canal reçue ; et

    le récepteur (200, 300) pour comparer la CQI de référence avec la CQI du flux, régler un canal correspondant à au moins une parmi l'activation et l'inactivation, en fonction du résultat de la comparaison, générer une information d'état de canal et transmettre l'information d'état de canal à l'émetteur (100).


     
    24. Système MIMO selon la revendication 23, dans lequel l'émetteur (100) est adapté en outre à déterminer la CQI de référence lorsque la probabilité pour que la CQI de référence soit inférieure à une CQI correspondant à une répartition statistique est égale à un taux d'activation de canal fixé à l'avance, et à déterminer la CQI de référence en soustrayant un taux d'activation de canal ciblé par l'émetteur d'un taux d'activation réel reçu depuis plusieurs récepteurs à un temps spécifique t, à multiplier la valeur du résultat de la soustraction par une valeur utilisée pour déterminer un changement possible de la CQI de référence en fonction du temps, et à additionner la CQI de référence utilisée au temps spécifique t avec la valeur du résultat de la multiplication.
     
    25. Système MIMO selon la revendication 23 ou 24, dans lequel l'émetteur (100) est adapté en outre à regrouper au moins l'un des récepteurs ayant une mauvaise CQI lorsqu'il est situé dans une zone de limite de cellule ou dans une zone d'ombre et des récepteurs ayant une bonne CQI, puis à transmettre une CQI de référence commune au groupe de récepteurs.
     
    26. Procédé d'émission/réception d'informations de qualité de canal, CQI, dans un système MIMO, le procédé comprenant :

    la détermination de la CQI de référence en utilisant une CQI reçue depuis un récepteur et la transmission au récepteur selon la revendication 6 de la CQI de référence ;

    lors de la réception de la CQI de référence, la comparaison de la CQI de référence avec la CQI d'un flux reçu depuis l'émetteur ; et

    le réglage d'un canal, sur lequel le flux est reçu, au moins dans un état parmi un état d'activation et un état d'inactivation, en fonction des résultats de la comparaison et la transmission à l'émetteur d'une information du canal réglé.


     
    27. Procédé d'émission/réception de CQI selon la revendication 26, dans lequel la CQI de référence est au moins une CQI déterminée lorsque la probabilité pour que la CQI soit inférieure à une CQI correspondant à une répartition statistique est égale à un taux d'activation de canal fixé à l'avance et déterminée en soustrayant un taux d'activation de canal ciblé par l'émetteur d'un taux d'activation réel reçu depuis plusieurs récepteurs à un temps spécifique t+1, en multipliant la valeur du résultat de la soustraction par une valeur utilisée pour déterminer un changement possible de la CQI de référence en fonction du temps, et en additionnant la CQI de référence utilisée au temps spécifique t avec la valeur du résultat de la multiplication.
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description