JP4490462B2 - Apparatus and method for transmitting and receiving feedback information in multi-user MIMO system and system therefor - Google Patents

Description

  The present invention relates to a MIMO (Multiple Input Multiple Output) system and method, and more particularly, to a transmission / reception apparatus and method for transmitting / receiving feedback information in a multi-user MIMO system that reduces the amount of feedback information transmitted from a plurality of receivers, and the system. Is.

  In general, systems after the third generation, that is, the fourth generation system, all ubiquitous and seamless connection between the wireless network and the core network (Core Network), high data transmission rate, openness, network Refers to a system that has the feature of network convergence. Such a fourth generation system is designed to allow large-capacity data transmission by focusing on a high data transmission rate.

  This fourth generation system must have a complex network configuration rather than a single network. That is, the fourth generation system is integrated into a satellite network, a wireless local area network (LAN), a digital audio broadcast (DAB) network, and a digital video broadcast (DVB) network. Must be. When all the networks are integrated in this way, a plurality of transceivers (for example, a base station and a terminal) can simultaneously transmit and receive data or signals using MIMO. In this multi-user MIMO system, M antennas are arranged in a transmitter (or a base station), and N antennas are arranged in a receiver (or a terminal). Thus, the transmission rate can be increased by transmitting and receiving signals using the arranged antennas.

  In order to provide a multi-user MIMO service through a plurality of antennas provided between transmitters and receivers, a transmitter requires channel quality information (hereinafter referred to as “CQI”) from a plurality of receivers. Accordingly, the transmitter requests feedback information including CQI from a plurality of receivers. The transmitter also requires a larger amount of CQI from multiple receivers in order to use multi-carrier, multi-antenna technology.

  However, this increase in the amount of feedback information or CQI increases not only the throughput of the transceiver but also the required amount of resources, thereby reducing the overall system performance. As a conventional method for overcoming such a problem, a method in which only a user having a CQI higher than a predetermined threshold value feeds back the CQI has been proposed. This is because only a user with a relatively good channel state performs CQI feedback, so that the feedback overhead can be reduced to some extent. However, since the CQI is fed back as it is, there is a problem that the feedback overhead still exists. .

Accordingly, there is a need for an improved transceiver device and method that improves system performance by reducing the amount of feedback information required in a multi-user MIMO system.
Dongwoo Kim and In-Ho Lee, “On Capacity of Quality-Based Channel-State Reporting in Mobile Systems With Greedy Transmission Scheduling”, IEEE Transactions on Communications, vol.54, NO.6 JUN. 2006.

  Accordingly, in order to solve the above-described problems of the prior art, an object of the present invention is to provide a transmission / reception apparatus and method in a multi-user MIMO system and a system thereof that improve system performance by reducing the amount of feedback information. There is to do.

  Another object of the present invention is to provide a CQI transmission / reception apparatus and method in a multi-user MIMO system for feeding back CQI with 1 bit per channel, and a system therefor.

  Furthermore, the object of the present invention is to use the CQI received from a plurality of receivers to set the reference CQI for the case where the transmitter knows the statistical distribution of the CQI and the case where the transmitter does not know the statistical distribution. It is an object of the present invention to provide a transmitter for determining, and an apparatus and method for receiving feedback information of the transmitter.

  An object of the present invention is to compare a reference CQI received from a transmitter with a CQI of a received stream, and set the activation (ON) and / or deactivation (OFF) of the corresponding channel according to the comparison result. And a feedback information transmitting apparatus and method for the receiver.

  In order to achieve the above object, the present invention provides a transmitter for receiving feedback information in a multiple input multiple output (MIMO) system, wherein a reference CQI (Channel Quality Information) is provided to the receiver. A channel state detector that receives channel setting information from the receiver after transmission and detects a channel state of the receiver according to the received channel setting information; and a plurality of antennas using the detected channel state. And a control unit for controlling beam forming.

  The present invention is also a method for receiving feedback information of a transmitter in a MIMO system, the step of determining a reference CQI to be applied to a plurality of channels of the receiver, and the determined reference CQI to the receiver. And transmitting the channel setting information from the receiver.

  Further, the present invention is a receiver for transmitting feedback information in a MIMO system, the channel quality measuring unit for measuring the CQI of each stream received from the transmitter, the CQI of the stream and the receiver received from the transmitter. And a control unit that sets a corresponding channel according to the comparison result, and a transmission unit that transmits the comparison result to a transmitter.

  The present invention is a method for transmitting feedback information of a receiver in a MIMO system, wherein a step of receiving a reference CQI from a transmitter and comparing the received reference CQI with a CQI of a stream received from the transmitter And generating channel state information according to the comparison result and transmitting the channel state information to the transmitter.

  The present invention has an effect of reducing the amount of overall feedback information by transmitting channel activation and / or deactivation information to each transmitter even when the receiver receives a plurality of streams from the transmitter. . Further, by reducing the amount of feedback information, there is an effect that the system performance can be improved and the processing amount of the transceiver can be increased.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  In the following technical field, it will be obvious that various modifications can be made without departing from the technical idea of the embodiments of the present invention. In addition, when it is determined that a specific description regarding a known function or configuration related to the present invention makes the gist of the present invention unclear, a detailed description thereof will be omitted.

  In the following description, embodiments of the present invention provide a multi-user MIMO system that improves system performance by reducing the amount of feedback information. Embodiments of the present invention also provide a transmitter and method thereby for determining a reference CQI with and without knowing the statistical distribution of CQI. In the embodiment of the present invention, the reference CQI received from the transmitter is compared with the CQI of the received stream to set the active (ON) and / or inactive (OFF) of the corresponding channel. A receiver and method for transmitting channel state information to a transmitter are provided.

  FIG. 1 shows a configuration of a multi-user MIMO system according to an embodiment of the present invention.

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

The transmitter includes a user selection unit 150 and a unitary beamforming unit 160. The transmitter 100 performs a precoding process on a plurality of input user data User ₁ , User ₂ ,..., User _k , and broadcasts precoded user data through a plurality of antennas. Each receiver receives data broadcast through a plurality of receiving antennas, and stores or reproduces the received data.

  Therefore, the transmitter provides multi-user MIMO service between the transceivers in this system and broadcasts the reference CQI to the receiver to reduce the amount of feedback information. The reference CQI is a threshold used to set the receiver channel to an active or inactive state. When receiving this reference CQI, each receiver compares the received reference CQI with the CQI of the channel corresponding to the stream received thereafter, and activates / deactivates the corresponding channel according to the comparison result (ie, ON / OFF) and transmit the active / inactive signal or ON / OFF signal to the transmitter. The activation signal indicates a case where the CQI of the corresponding communication channel is greater than or equal to the reference CQI, and the inactivation signal indicates a case where the CQI of the corresponding communication channel is smaller than the reference CQI.

  Upon receiving active / inactive signals from multiple receivers, the transmitter generates a channel matrix based on the received active / inactive signals, and uses the generated channel matrix to stream to multiple receivers. Is transmitted.

  In order to perform such an operation, the transmitter must set the reference CQI appropriately according to the system environment. The setting method is divided into a method A for setting the reference CQI when the transmitter knows the statistical distribution and a method B for setting the reference CQI when the transmitter does not know the statistical distribution.

  Also, the transmitter can group receivers according to CQI. That is, the transmitter may be located in a cell boundary region or shadow region, and group receivers having bad CQI, or group receivers having good CQI.

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

  Referring to FIG. 2, the transmitter and the receiver have a plurality of antennas, and multi-user MIMO services are provided / received through these antennas. In a multi-antenna system including a plurality of antennas, the transmitter transmits a plurality of streams to the receiver (step S100). This stream can be transmitted to the receiver through one or more antennas.

  When a plurality of streams are received from the transmitter in this way, the receiver feeds back feedback information including the quality of the channel corresponding to the stream having the highest channel gain among the received streams to the transmitter. (Step S102). This feedback information includes index information of the stream having the highest quality among these streams and the CQI at that time.

  Thereafter, the transmitter transmits the reference CQI to all receivers in the cell (step S104). This reference CQI can be measured or determined by a transmitter or receiver for smooth signal transmission and reception between the transceivers, or can be flexibly set for high system performance. This reference CQI value may be applied commonly to all receivers or may be applied separately to each receiver or each receiver group. The technique for determining the value of the reference CQI will be described below. When the reference CQI is received in step S104, the receiver compares the received reference CQI with the CQI of the communication channel using the stream received for each antenna included in the receiver (step S106). The CQI of each antenna communication channel can be measured based on a pilot signal periodically transmitted by the transmitter, or can be measured based on a stream received from the transmitter. Thus, after measuring the CQI of the communication channel for each antenna, the receiver can periodically measure the channel quality for each antenna included in the receiver.

  After comparing the received reference CQI with the CQI of the channel corresponding to the stream received for each antenna in step S106, the receiver sets the channel state based on the comparison result (step S108). Here, “setting the channel state” means setting the activation / inactivation of the transmission / reception channel based on the comparison result. The process of setting the channel state to active means a process of performing communication by connecting the channel of the transmitter and the corresponding antenna. Also, the process of setting the channel state to inactive means a process of releasing (or disconnecting) the channel of the transmitter and the corresponding antenna to disable communication, or setting the reference CQI to the CQI of the corresponding stream. .

  The activity indicates that the corresponding stream can be used as the preset CQI value because the CQI value of the corresponding stream is equal to or greater than the preset CQI value. Deactivation indicates that the CQI value of the corresponding stream cannot be used as the preset CQI value because the CQI value of the corresponding stream is smaller than the preset CQI value, or the CQI value participates in stream scheduling. Indicates that it cannot be done. For example, if the CQI value of a given stream is a natural number greater than the reference CQI (i.e., the real value is the same as the reference CQI, but only the decimal value is greater than the reference CQI), the natural number with the decimal value removed (i.e. The same integer as the reference CQI) is set as the CQI of the corresponding stream.

  Thus, when the CQI of the communication channel is greater than or equal to the reference CQI, the receiver sets the channel state to active. However, if the communication channel CQI is less than the reference CQI, the receiver sets the channel state to inactive.

  After performing step S108, the receiver transmits an active / inactive signal indicating the set channel state to the transmitter (step S110). The number of active / inactive signals may be one depending on the receiver, or may be the same as the number of antennas depending on the channel state of the antenna included in the receiver. Such an active / inactive signal is 1 bit in size.

  When active / inactive signals are received from a plurality of receivers, the transmitter transmits a stream to one or more receivers using a channel corresponding to the received active / inactive signals. The multi-user MIMO service is performed according to the activation / deactivation signal received from (step S112).

  FIG. 3 is a block diagram illustrating an example of active / inactive switching feedback technology in a multi-user MIMO system according to an embodiment of the present invention.

  Referring to FIG. 3, the receiver receives a plurality of streams from the transmitter and detects a stream having the maximum CQI among the received streams. As shown in the figure, the CQI of the first stream is 1.5, the CQI of the second stream is 4, the CQI of the third stream is 2.5, and the CQI of the fourth stream is 2. Assume. The receiver transmits the highest CQI = 4 among the received CQI values to the base station. Thereafter, when the reference CQI detected by the plurality of techniques is received from the transmitter, the receiver compares the CQI of the plurality of streams with the received reference CQI, and activates / deactivates based on the comparison result. Transmit the signal to the transmitter. That is, as illustrated, the receiver transmits an inactive signal to the transmitter when the first stream has CQI = 1.5 and is active when the third stream has CQI = 2.5. The signal is transmitted to the transmitter, and if it is the fourth stream with CQI = 2, the active signal is transmitted to the transmitter. As described above, an active / inactive switching feedback technique for reducing the amount of feedback information in a multi-user MIMO system will be described, and a transceiver applied to this system will be described later.

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

  Referring to FIG. 4, the transmitter transmits a channel state detection unit 110 for detecting a channel state for each receiver based on CQIs received from a plurality of receivers and a plurality of antennas according to the detected channel state. Control unit 120 for controlling precoding and multiplex output of streams, encoding and modulating unit 130 for encoding and modulating a plurality of streams, and a plurality of antennas for the encoded and modulated streams And a multiple output unit 140 that performs multiple output.

  The transmitter also includes a memory (not shown) for storing reference CQIs to be applied to a plurality of receivers and for storing channel state information received from the plurality of receivers. Then, the control unit 120 includes a module for determining a reference CQI using methods A and B described later and transmitting the reference CQI to the receiver.

  First, the transmitter sets the reference CQI value using one of the following two methods (A, B).

  The method for determining the reference CQI by the transmitter can be divided into two methods A and B in the case where the transmitter knows the statistical distribution of CQI and the case where the transmitter does not know the statistical distribution of CQI.

A. If you know the statistical distribution of CQI

  If the statistical distribution of CQI is known, the transmitter can determine the reference CQI using the following <Equation 1>.

In <Equation 1>, the CQI _reference indicates the reference CQI, and α indicates the probability (CQI acceptance rate) that the transmitter determines that the given CQI is active, and is preset by the transmitter. That is, the transmitter can set a given CQI to active by adjusting the probability α. For example, in <Equation 1>, α = 0.7 means that the ratio of CQIs equal to or higher than the _reference CQI (that is, CQI _reference ) to all CQIs is set to 70%. Thus, the transmitter can determine the reference CQI by adjusting the probability α.

  This probability α can be influenced by the number of users or the number of antennas at each receiver. That is, when the number of users is small, the transmitter sets the probability α high to set the reference CQI value low, and when the number of users is large, the transmitter sets the establishment α to set the reference CQI value high. Setting it low improves system performance. Thus, the probability α can be adjusted. By setting the reference CQI low, the transmitter can communicate with multiple users or multiple antennas.

B. If you do not know the statistical distribution of CQI

  If the transmitter does not know the statistical distribution of CQI, the reference CQI can be adjusted using activity rates received from multiple users or multiple antennas. For example, when the activity rate received from the user is high, the transmitter increases the reference CQI value. In contrast, when the activity rate is low, the transmitter lowers the reference CQI value to improve system performance.

  <Equation 2> can be used to adjust the reference CQI value over time when the transmitter does not know the statistical distribution of CQI.

  Using <Equation 2>, the transmitter can calculate the reference CQI used at the specific time (t + 1). In <Equation 2>

Is the reference CQI used at time t + 1, α _target is the activity rate targeted by the system, and α ^(t) is the activity rate actually reported by one or more receivers at time t. . Further, w represents a constant used for determining the change width of the reference CQI according to time.

  By using <Equation 2> in this way, the target activation rate of the system can be achieved at a specific time even if the transmitter does not know the statistical distribution of CQI.

  After determining the reference CQI by the above method, the control unit 120 transmits the reference CQI to the receiver.

  Thereafter, the transmitter transmits the stream to the receiver, and the receiver transmits the CQI of each stream to the transmitter based on the received stream. The channel state detection unit 110 included in the transmitter receives the CQI for each stream from the receiver. The CQI is received from a plurality of receivers, and includes information on a channel set by each receiver based on the received stream. That is, the CQI includes ON information indicating that the channel is set to active and OFF information indicating that the channel is set to inactive.

  When information indicating whether the channel state is active or inactive is received, the transmitter detects the channel state of a plurality of antennas included in the receiver, and provides the detected result to the control unit 120. The control unit 120 controls transmission of a plurality of streams. That is, in order to transmit a plurality of input streams to a plurality of receivers, the controller 120 pre-codes the plurality of input streams and performs channel processing according to active and / or inactive signals received from the receiver. Generate a matrix. In addition, the controller 120 forms an antenna beam included in the transmitter to transmit the precoded stream through the multiple output unit 140 to a plurality of receivers. Thereafter, the control unit 120 transmits the stream to the plurality of receivers through the beamforming antenna.

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

  Referring to FIG. 5, the transmitter assumes that a threshold and a reference CQI are preset for application to the receiver. As described above, the reference CQI can be set using at least one of the methods A and B described above, or can be set by the user of each receiver.

  As shown in the figure, the transmitter transmits the stream to the receiver in step S200. The streams to be transmitted can be transmitted one by one through one antenna of the transmitter or simultaneously through multiple antennas of the transmitter. In this way, the stream transmitted from the transmitter is transmitted to one or more receivers. Upon receiving this stream, the receiver measures the channel quality for each antenna or channel through the received stream. The receiver then detects the highest quality value of the measured quality, i.e. the CQI value of the stream with the highest channel gain in the received stream and transmits the detected quality value to the transmitter To do. Upon receiving the CQI of the stream having the highest channel gain from the receiver, the transmitter transmits the reference CQI to the receiver (Steps S202 and S204).

  The reference CQI is set in each transmitter for each receiver, or can be determined using at least one of the methods A and B described above. The reference CQI can be adjusted according to the channel transmission state, system state, and receiver priority.

  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, when the reference CQI is received, the receiver compares the CQI of the remaining stream with the received reference CQI, and transmits the comparison result to the transmitter. This remaining stream can be received by the receiver through one antenna, or can be received through multiple antennas by stream.

  For example, if the reference CQI value is smaller than the CQI of each stream as a result of comparing the reference CQI value with the CQI of each of the remaining streams, the receiver transmits an active 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 inactive signal to the transmitter.

  When an active / inactive signal, that is, channel state information is received 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 meaning that the transmitter uses an antenna having a higher channel quality or data rate among a plurality of antennas included in the transmitter.

  After the antenna beamforming is formed in step S208, the transmitter transmits the stream to the receiver through the beamforming antenna in step S210.

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

  Referring to FIG. 6, the receiver 200 includes a channel quality measurement unit 210 for measuring quality for each channel through a stream received from the transmitter, and a measured channel-specific quality value, that is, a measured CQI for each channel. The control unit 220 that compares the reference CQI with the reference CQI, the memory 230 that stores the comparison result value from the reference CQI and the control unit 220, the multiplex reception unit 240 that multiplex-receives the stream received from the transmitter, A decoding and demodulating unit 250 for decoding and demodulating the stream. The receiver also includes a transmission unit (not shown) for transmitting the comparison result to the transmitter.

  In the following, the following operation is described based on one receiver, but the described operation is for all receivers that have received a reference CQI from the transmitter or for all receivers in the service area of the transmitter. However, it is obvious that the same can be applied. Also, feedback information is generated by all the proposals in the present invention, and the generated feedback information is transmitted to the transmitter.

  Referring to FIG. 6, the transmitter provides a MIMO service to the receiver. Thus, in order to provide multi-antenna services, the transmitter and receiver can be equipped with multiple antennas. That is, the receiver receives each stream through a plurality of antennas.

  The channel quality measurement unit 210 measures the quality (ie, CQI) of the downlink channel through the stream received for each antenna. Alternatively, the channel quality measurement unit 210 can measure the CQI through a stream having the highest channel quality among all received streams. Then, the channel quality measurement unit 210 transmits the CQI measured for each stream to the control unit 220. When receiving the CQI measured for each stream, the control unit 220 compares the measured CQI with the reference CQI value. The reference CQI received from the transmitter is a threshold value for determining whether or not the antenna included in the receiver can be set to be active or inactive.

  After comparing the CQI of each stream and the reference CQI value in this way, if the reference CQI is equal to or higher than the CQI of the stream, the control unit 220 sets the channel in which the stream is received to be inactive (that is, OFF mode). To do. The controller 220 stores an inactive signal according to the set result in the memory 230. However, if the reference CQI is smaller than the CQI of the stream, the control unit 220 sets the channel in which the stream is received to be active (that is, ON mode). Similarly, the control unit 220 stores an activation signal according to the set result in the memory 230.

  The control unit 220 can compare the activation or deactivation signals for each stream one by one and store them in the memory, or when the comparison results of all the streams are completed, the activation or deactivation signals of all the streams are stored in the memory. Can be stored.

  Thereafter, when the comparison of each stream or all the streams is completed, the control unit 220 transmits the active and / or inactive signals stored in the memory 230 to the transmitter.

  Hereinafter, a method for transmitting an active / inactive signal in a receiver according to an embodiment of the present invention includes a method C for transmitting active / inactive signals generated for each stream one by one, and active / inactive of all streams. It is divided into the method D which transmits a signal simultaneously.

C. When transmitting active / inactive signals generated for each stream

  Hereinafter, a feedback information transmission / reception method of a receiver in a multi-user MIMO system according to an embodiment of the present invention will be described in detail with reference to FIG. 7A.

  When the reference CQI is received from the transmitter, the receiver compares the received reference CQI with the CQI of each stream received from the transmitter (steps S300 and S302). Each stream can be received through one antenna of the receiver or can be received through multiple antennas provided in the receiver. This reference CQI is commonly applied to each stream.

  If the received reference CQI is equal to or higher than the CQI of the stream received from the transmitter, the receiver sets the channel on which the stream is received to be inactive (steps S304 and S306). Setting the channel to inactive means that the receiver does not receive any more streams from the transmitter through the corresponding channel. Thus, in order to avoid additional reception of the stream, the receiver generates an inactive signal (that is, an OFF signal) according to the result set in step S306.

  However, when the reference CQI value received in step S304 is smaller than the CQI of each stream received from the transmitter, the receiver sets the channel in which the stream is received to be active (steps S304 and S310). After the channel is set active in step S310, the receiver generates an active signal (that is, an ON signal) according to the setting result in step S312.

  The receiver transmits the active or inactive signal generated in steps S308 and S312 to the transmitter (step S314). When step S314 is completed, the receiver checks whether steps S304 to S314 have been performed for all streams (step S316). That is, the receiver compares the reference CQI with the CQI of each stream for all received streams. If the comparison between the reference CQI and the CQI of each stream is not completed in step S316, the receiver returns to step S304.

D. When transmitting active / inactive signals of all streams simultaneously

  Hereinafter, a feedback information transmission / reception method of a receiver in a multi-user MIMO system according to an embodiment of the present invention will be described in detail with reference to FIG. 7B.

  Referring to FIG. 7B, the proposed method for transmitting active / inactive signals of all streams of the receiver according to the present invention is similar to the method of FIG. 7A shown in steps S300 to S306 and step S310. .

  In FIG. 7B, after comparing the received reference CQI with the CQI of the corresponding stream, if the received reference CQI is equal to or higher than the CQI of the stream in step S400, the receiver determines the channel on which the stream is received. Is set to inactive (steps S402 to S406). In step S406, after setting the channel in which the stream is received to be inactive, the receiver stores the inactive signal generated for each stream according to the set result in the memory (step S408). However, if the received reference CQI is smaller than the CQI of the stream, the receiver sets the channel in which the stream is received to be active (step S410). In step S410, after setting the channel in which the stream is received to be active, the receiver stores the active signal generated for each stream according to the set result in the memory (step S412).

  After performing steps S404 to S412 for all the streams, the receiver transmits the active / inactive signal stored in the memory to the transmitter (step S414).

  Although the present invention has been described above with reference to specific embodiments, it is understood that various changes in form and details may be made without departing from the scope of the claims. It is clear to those who have knowledge. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined based on the description of the claims and equivalents thereof.

It is a figure which shows the structure of the multiuser MIMO system by embodiment of this invention. 3 is a flowchart illustrating a feedback method of a multi-user MIMO system according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating an example of active / inactive switching feedback technology in a multi-user MIMO system according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a feedback information receiver of a transmitter in a multi-user MIMO system according to an embodiment of the present invention. 4 is a flowchart illustrating a method for transmitting and receiving feedback information of a transmitter in a multi-user MIMO system according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a feedback information transmitting / receiving apparatus of a receiver in a multi-user MIMO system according to an embodiment of the present invention. 5 is a flowchart illustrating a feedback information transmission / reception method of a receiver in a multi-user MIMO system according to an embodiment of the present invention. 5 is a flowchart illustrating a feedback information transmission / reception method of a receiver in a multi-user MIMO system according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 Channel state detection part 120 Control part 130 Encoding and modulation part 140 Multiple output part 150 User selection part 160 Single beam forming part 200 Receiver 210 Channel quality measurement part 220 Control part 230 Memory 240 Multiple reception part 250 Decoding and demodulation 300 receiver

Claims (25)

A transmitter for receiving feedback information in a multiple input multiple output (MIMO) system,
A channel state detector for receiving channel setting information from the receiver after transmitting a reference CQI (Channel Quality Information) to the receiver, and detecting a channel state of the receiver based on the received channel setting information;
A control unit for controlling beam forming of a plurality of antennas using the detected channel state;
Only including,
The reference CQI is a threshold value for setting whether to activate a channel of a stream between the transmitter and the receiver;
The transmitter according to claim 1, wherein the channel setting information is information indicating whether or not a CQI of the stream is equal to or higher than the reference CQI . The reference CQI is
To be determined differently for the first case where the transmitter knows the statistical distribution of CQIs received from multiple receivers and the second case where it does not know the statistical distribution of the CQIs The transmitter according to claim 1. In the first case, the reference CQI is
The transmitter according to claim 2, wherein a probability less than a CQI corresponding to the statistical distribution is actually determined to be equal to a preset channel activity rate. In the second case, at a predetermined time (t + 1), the reference CQI is
The channel activity rate targeted by the transmitter is subtracted from the actual activity rate received from the receiver received at a predetermined time t, and the subtracted value is multiplied by a value that determines the change width of the reference CQI according to the time. 3. The transmitter according to claim 2, wherein the transmitter is determined by adding a reference CQI used at the predetermined time t to the multiplied value. The channel setting information is
The transmitter according to claim 1, further comprising information indicating an active and / or inactive state according to a channel state of the receiver. A method for receiving feedback information of a transmitter in a MIMO system, comprising:
Determining a reference CQI to be applied to multiple channels of the receiver;
Transmitting the determined reference CQI to the receiver;
Receiving configuration information of the channel from the receiver;
I have a,
The reference CQI is a threshold value for setting whether to activate a channel of a stream between the transmitter and the receiver;
The method for receiving feedback information of a transmitter, wherein the channel setting information is information indicating whether a CQI of the stream is equal to or higher than the reference CQI .   The method may further include detecting a channel state for each antenna of the receiver when the setting information is received, and forming an antenna beam for the transmitter using the detected channel state for each antenna. Item 7. A method for receiving feedback information of a transmitter according to Item 6. The reference CQI is
The transmitter is determined to be different depending on a first case where the statistical distribution of CQI received from a plurality of receivers is known and a second case where the transmitter does not know the statistical distribution of CQI. The feedback information receiving method of a transmitter according to claim 6. In the first case, the reference CQI is
9. The method of claim 8, wherein a probability less than a CQI corresponding to the statistical distribution is actually determined to be equal to a preset channel activation rate. In the second case, at a predetermined time (t + 1), the reference CQI is
Subtracting the channel activity rate targeted by the transmitter from the actual activity rate received from the receiver received at a predetermined time t, and multiplying the subtracted value and a value that determines a change width of the reference CQI according to the time; 9. The method according to claim 8, wherein the value is determined by adding the reference CQI used at the predetermined time t to the multiplied value. The setting information includes
The method according to claim 6, further comprising information indicating an active and / or inactive state according to a channel state of the receiver. The method of claim 8, wherein, in the first case, the reference CQI is calculated using the following equation.

Here, the CQI _reference indicates a reference CQI, and α indicates a prestored probability that the transmitter will determine a given CQI as active. The method of claim 8, wherein, in the second case, the reference CQI is calculated using the following equation.

here,

Is the reference CQI used at time t + 1, α _target is the activity rate targeted by the system, α ^(t) is the activity rate reported by one or more receivers at time t, and w is the reference by time. Constants that determine the change width of CQI are shown respectively. A receiver for transmitting feedback information in a MIMO system,
A channel quality measurement unit that measures the CQI of each stream received from the transmitter;
A controller that compares the CQI of the stream with a reference CQI received from the transmitter, and sets a corresponding channel according to the comparison result;
A transmitter for transmitting the comparison result to a transmitter;
Including
The controller is
When CQI of the stream is in the reference CQI above, receiver unit you and sets the channel of the stream to the active state. A receiver for transmitting feedback information in a MIMO system,
A channel quality measurement unit that measures the CQI of each stream received from the transmitter;
A controller that compares the CQI of the stream with a reference CQI received from the transmitter, and sets a corresponding channel according to the comparison result;
A transmitter for transmitting the comparison result to a transmitter;
Including
The controller is
If CQI of the stream is less than the reference CQI, received instrument you and sets the channel of the stream to the inactive state. The controller is
Channel state information is generated according to the comparison result and transmitted to the transmitter .
The receiver according to any one of claims 14 and 15, wherein the channel state information is information indicating whether or not a CQI of the stream is equal to or higher than the reference CQI . The receiver of claim 16, wherein the channel state information is 1 bit. A method for transmitting feedback information of a receiver in a MIMO system, comprising:
Receiving a reference 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 it to the transmitter;
Have
By comparison with the CQI of the received reference CQI with the stream, further receiver device in the feedback information transmission method further comprising a step of setting at least one the of the corresponding channel activity or non-activity. A method for transmitting feedback information of a receiver in a MIMO system, comprising:
Receiving a reference 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 it to the transmitter;
Have
The channel state information is
Wherein the reference CQI is greater than or equal to CQI of the stream, receiver unit of the feedback information transmission method it and sets the channel to the stream was received, to Inactivation. A method for transmitting feedback information of a receiver in a MIMO system, comprising:
Receiving a reference 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 it to the transmitter;
Have
The channel state information is
If the reference CQI is less than the CQI of the stream, the feedback information transmission method of the receiver device it and sets the channel to the stream was received, to activity. A MIMO system for transmission and reception CQI,
A transmitter for transmitting a plurality of streams and a reference CQI to a receiver, and when channel state information is received from the receiver, a transmitter that forms an antenna beam according to the received channel state information;
A receiver that compares the reference CQI with the CQI of the stream, sets the corresponding channel to at least one of active and / or inactive according to the comparison result, generates channel state information, and transmits the channel state information to the transmitter When,
Only including,
The reference CQI is a threshold value for setting whether to activate a channel of a stream between the transmitter and the receiver;
The MIMO system according to claim 1, wherein the channel state information is information indicating whether a CQI of the stream is equal to or higher than the reference CQI . The transmitter is
Actual activity received from one or more receivers at a predetermined time t at a predetermined time (t + 1) when the probability that the reference CQI is less than the CQI corresponding to the statistical distribution is equal to the preset channel activation rate Subtracting the channel activity rate targeted by the transmitter by a rate, multiplying the subtracted value and a value used to determine a change width of a reference CQI according to time, and multiplying the multiplied value by the predetermined time t. The MIMO system according to claim 21, wherein the reference CQI is determined by adding a reference CQI to be used. The transmitter is
It is characterized in that at least one receiver having a poor CQI or a good CQI located in a cell boundary region or a shaded region is grouped, and a common reference CQI is transmitted to the grouped receivers. The MIMO system according to claim 21 . A CQI transmission / reception method for a MIMO system,
Determining a reference CQI using the CQI received from the receiver and transmitting to the receiver;
Receiving the reference CQI, comparing the reference CQI with a CQI of a stream received from the transmitter;
Setting the channel through which the stream is received to at least one of active and inactive according to the comparison result, and transmitting the set channel information to the transmitter;
A CQI transmission / reception method comprising: The reference CQI is
When the probability less than the CQI corresponding to the statistical distribution is the same as the preset channel activation rate, the actual activation rate received from one or more receivers at a predetermined time t at a predetermined time (t + 1). The transmitter subtracts the target channel activity rate, multiplies the subtracted value and the value used to determine the change width of the reference CQI by the time, and uses the multiplied value at the predetermined time t. 25. The CQI transmission / reception method according to claim 24, which is determined by adding a reference CQI.

Images