RU2518405C2 - Method and apparatus for transmitting downlink reference signal in wireless communication system supporting multiple antennae - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method and apparatus for transmitting a downlink reference signal in a wireless communication system supporting multiple antennae are disclosed. The method of transmitting Channel State Information-Reference Signals (CSI-RSs) for eight or less antenna ports includes steps of selecting one of a plurality of CSI-RS Resource Element (RE) groups defined in a data region of a downlink subframe and mapping CSI-RS for the eight or less antenna ports to the selected CSI-RS RE group, and transmitting the downlink subframe in which the CSI-RS for the eight or less antenna ports are mapped. The plurality of CSI-RS RE groups are defined such that a transmission diversity RE pair for data transmitted in the downlink subframe is not broken.

EFFECT: high transmission channel throughput.

12 cl, 36 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a wireless communication system, in particular to a method and apparatus for transmitting a downlink reference signal in a wireless communication system supporting multiple antennas.

State of the art

A Multiple Input / Multiple Output (MIMO) system refers to a system for improving data transmission / reception efficiency using multiple transmit antennas and multiple receive antennas. MIMO technology includes a spatial diversity scheme and a spatial multiplexing scheme. The spatial diversity scheme is acceptable for transmitting user equipment (UE) data that travels at high speed, because by the diversity gain, the reception reliability is increased or the radius of the cell is increased. The spatial multiplexing scheme can increase the data transfer rate without increasing the system bandwidth by transmitting different data simultaneously.

In a MIMO system, each transmit antenna has an independent data channel. The transmit antenna may be a virtual antenna or a physical antenna. The receiver estimates the channel for each transmit antenna and receives data transmitted from each transmit antenna. Channel estimation refers to the process of compensating for signal distortion due to attenuation in order to recover a received signal. Attenuation refers to a phenomenon in which signal intensity changes rapidly due to delay in multipath propagation and time delay in a wireless communication system environment. To estimate the channel, a reference signal is required, known to both the transmitter and the receiver. The reference signal (RS) may be referred to as a pilot signal in accordance with the standard.

The downlink reference signal is a pilot signal for coherent demodulation, such as Physical Downlink Shared Channel (PDSCH), Physical Control Format Indicator Channel (PCFICH), Hybrid Physical Indicator Channel (PHICH) and Physical Downlink Control Channel Communications (PDCCH). The downlink reference signal includes a Common Reference Signal (CRS) shared by all UEs in a cell and a Dedicated Reference Signal (DRS) for a specific UE. CRS may be referred to as a cell reference. DRS may be referred to as a reference signal set for the UE or a Demodulation Reference Signal (DMRS).

In a system with an antenna configuration (for example, in a system in accordance with the LTE-A standard that supports eight transmit antennas), designed as an extension of an existing communication system (for example, a system based on LTE Version 8 or 9 standards) that supports four transmit antennas , to improve the transmission scheme and ensure effective control of the reference signal, DMRS-based data demodulation was considered. That is, in order to provide data transmission through additional antennas, DMRS for two or more layers can be determined. Since DMRSs are precoded using the same precoding encoder as for data, it is possible to easily evaluate channel information to demodulate data at the receiving side without extracting precoding information.

The downlink receiving side may obtain precoded channel information for the extended antenna configuration through DMRS. However, separate reference signals are required in addition to DMRS to obtain pre-encoded channel information. In a system based on the LTE-A standard, reference signals may be determined to obtain Channel Status Information (CSI) at the receiving end, i.e. CSI-RS.

Disclosure of invention

Technical challenge

An object of the present invention is to provide a method and apparatus for transmitting Channel State Information Reference Signals (CSI-RS) on Downlink Resource Elements (RE) in order to efficiently perform channel estimation on a downlink receiving side during transmission Multiple Input / Multiple Output (MIMO) design.

Technical solution

An object of the present invention can be achieved by providing a method for transmitting Channel State Information Reference Signals (CSI-RS) for eight or less antenna ports, the method including the steps of selecting one of a plurality of CSI- Resource Elements (RE) groups. RSs defined in the data area of the downlink subframe, and map the CSI-RS for eight or less antenna ports to the selected CSI-RS RE group; and transmitting the downlink subframe to which CSI-RSs are mapped for eight or less antenna ports, wherein the plurality of CSI-RS RE groups are determined such that the transmit diversity RE pair for data transmitted in the downlink subframe is not disturbed.

The downlink subframe may be configured with a normal Cyclic Prefix (CP), and the number of CSI-RS RE groups displaying CSI-RS for eight antenna ports may be five within one Resource Block (RB), and one the CSI-RS RE group can be defined at two adjacent subcarrier positions of two adjacent Orthogonal Frequency Division Multiplexing (OFDM) symbols and other two different adjacent adjacent subcarriers, separated from said two adjacent subcarrier positions by four subcarriers, per resource elements that do not have Common Reference Signals (CRS) and Reference Demodulation Signals (DMRS).

A plurality of CSI-RS RE groups into which CSI-RSs are mapped for two antenna ports, or a plurality of CSI-RS RE groups into which CSI-RS mappings for four antenna ports can be defined as a subset of a plurality of CSI-RS REs into which CSI-RSs are displayed for eight antennas.

Five CSI-RS RE groups to which CSI-RSs are mapped for eight antenna ports within one RB may include a first CSI-RS RE group of third, fourth, ninth, and tenth subcarriers in the sixth and seventh OFDM symbols; a second RE CSI-RS group of first, second, seventh and eighth subcarriers in the tenth and eleventh OFDM symbols; a third CSI-RS RE group of third, fourth, ninth, and tenth subcarriers in the tenth and eleventh OFDM symbols; a fourth REI CSI-RS group of fifth, sixth, eleventh, and twelfth subcarriers in the tenth and eleventh OFDM symbols; and a fifth CSI-RS RE group of third, fourth, ninth, and tenth subcarriers in the thirteenth and fourteenth OFDM symbols.

A plurality of CSI-RS RE groups are defined as RE positions of one CSI-RS RE group shifted in time and frequency domains with respect to another CSI-RS RE group.

CSI-RS for two antenna ports from CSI-RS for eight or less antenna ports can be multiplexed using a Code Division Multiplexing (CDM) scheme using orthogonal codes 2 in length over two adjacent OFDM symbols on the same subcarrier.

In a different downlink subframe different from said downlink subframe, CSI-RSs for eight or less antenna ports are mapped to another CSI-RS RE group, excluding one CSI-RS RE group selected from a plurality of CSI-RS RE groups for said downlink subframe.

In another aspect of the present invention, there is provided a method for measuring channel information on Channel Status Information Reference Signals (CSI-RSs) for eight or less antenna ports, the method including the steps of receiving a downlink subframe in which CSI -RS for eight or less antenna ports are mapped to one CSI-RS RE group selected from a plurality of CSI-RS RE groups defined in the data area of the downlink subframe; and measuring channel information for each antenna port using a CSI-RS for eight or less antenna ports, wherein the plurality of CSI-RS RE groups are determined such that the transmit diversity RE pair for data transmitted in the downlink subframe is not destroyed.

The downlink subframe may be configured with a normal Cyclic Prefix (CP), with the number of CSI-RS RE groups to which CSI-RS is mapped for eight antenna ports may be five within one Resource Block (RB), and one the CSI-RS RE group can be defined at two adjacent subcarrier positions of two adjacent Orthogonal Frequency Division Multiplexing (OFDM) symbols and other two different adjacent adjacent subcarriers, separated from said two adjacent subcarrier positions by four subcarriers, per resource elements that do not have Common Reference Signals (CRS) and Reference Demodulation Signals (DMRS).

A plurality of CSI-RS RE groups into which CSI-RSs are mapped for two antenna ports, or a plurality of CSI-RS RE groups into which CSI-RS mappings for four antenna ports can be defined as a subset of a plurality of CSI-RS REs into which CSI-RSs are displayed for eight antennas.

Five CSI-RS RE groups to which CSI-RSs are mapped for eight antenna ports within one RB may include a first CSI-RS RE group of third, fourth, ninth, and tenth subcarriers in the sixth and seventh OFDM symbols; a second RE CSI-RS group of first, second, seventh and eighth subcarriers in the tenth and eleventh OFDM symbols; a third CSI-RS RE group of third, fourth, ninth, and tenth subcarriers in the tenth and eleventh OFDM symbols; a fourth REI CSI-RS group of fifth, sixth, eleventh, and twelfth subcarriers in the tenth and eleventh OFDM symbols; and a fifth CSI-RS RE group of third, fourth, ninth, and tenth subcarriers in the thirteenth and fourteenth OFDM symbols.

A plurality of CSI-RS RE groups are defined as RE positions of one CSI-RS RE group shifted in time and frequency domains with respect to another CSI-RS RE group.

CSI-RS for two antenna ports from CSI-RS for eight or less antenna ports can be multiplexed using a Code Division Multiplexing (CDM) scheme using orthogonal codes of two equal lengths to two adjacent OFDM symbols in the same subcarrier.

In a different downlink subframe different from said downlink subframe, CSI-RSs for eight or less antenna ports are mapped to another CSI-RS RE group, excluding one CSI-RS RE group selected from a plurality of CSI-RS RE groups for downlink subframe.

In another aspect of the present invention, there is provided a base station for transmitting Channel State Information Reference Signals (CSI-RS) for eight or less antenna ports, the base station including a receiving module configured to receive an uplink signal from user equipment; a transmission module, configured to transmit a downlink signal to user equipment; and a processor configured to control a base station including a transmission module and a reception module, wherein the processor is further configured to select one of a plurality of CSI-RS RE groups defined in the data area of the downlink subframe and display a CSI-RS for eight or less antenna ports to a selected CSI-RS RE group, and transmitting a downlink subframe into which CSI-RS is mapped for eight or less antenna ports by a transmission module, and wherein many CSI-RS RE groups are defined the same so that the transmission diversity RE pair for data transmitted in the downlink subframe is not destroyed.

In another aspect of the present invention, there is provided user equipment for measuring channel information on Channel Status Information Reference Signals (CSI-RS) for eight or less antenna ports, wherein the user equipment includes a receiving module configured to receive a downlink signal from the base station; a transmission module, configured to transmit an uplink signal to a base station; and a processor configured to control user equipment including a reception module and a transmission module, wherein the processor is further configured to receive a downlink subframe in which CSI-RSs for eight or less antenna ports are mapped to a single CSI-RE group An RS selected from a plurality of CSI-RS RE groups defined in a data area of a downlink subframe by a receiving module and measuring channel information of each of the antenna ports using CSI-RS for eight or less antenna over comrade, and wherein the plurality of groups of RE CSI-RS defined in a way that is not destroyed by steam RE transmit diversity for the data transmitted in the downlink subframe.

The above general description of the present invention and the following detailed description of the present invention are merely exemplary and provide further description of the appended claims of the present invention.

Preferred Results

In accordance with embodiments of the present invention, it is possible to provide a method and apparatus for multiplexing CSI-RS in downlink physical resources and transmitting multiplexed CSI-RSs so that the receiving side of the downlink can efficiently perform channel estimation. In addition, it is possible to provide a method and apparatus for reducing inter-cell interference caused by CSI-RS transmission while maintaining data transmission efficiency by providing as many CSI-RS RE group patterns as possible without destroying transmission diversity RE pairs.

Additional advantages of the present invention will be partially discussed in the following description, and partially will become apparent to a person skilled in the relevant field when studying the following description, or can be obtained by putting the present application into practice.

Brief Description of the Drawings

The accompanying drawings, which are included to provide a more complete understanding of the invention, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. The drawings show the following:

FIG. 1 is a diagram showing a structure of a downlink radio frame.

FIG. 2 is an example of a resource grid in one downlink slot.

FIG. 3 is a diagram showing a structure of a downlink subframe.

FIG. 4 is a diagram illustrating an uplink frame structure.

FIG. 5 is a diagram showing a configuration of a multi-antenna wireless communication system.

FIG. 6 is a diagram of the general structure of an SC-FDMA and OFDMA system.

FIG. 7 is a diagram showing the structure of an uplink SC-FDMA system of a Version-8 LTE system.

FIG. 8 is a diagram showing a transmission frame structure of an uplink SC-FDMA system of an Version-8 LTE system.

FIG. 9 is a diagram showing a data signal mapping relationship in a MIMO system based on SC-FDMA transmission.

FIG. 10 illustrates CRS and DRS patterns mapped to a Downlink Resource Block (RB) defined in an existing 3GPP LTE system (e.g., Version-8).

FIG. 11 is an example of a DRMS template supporting maximum Rank-8 transmission.

FIG. 12-16 are diagrams illustrating various examples of the CSI-RE RE group.

FIG. 17-19 are diagrams illustrating the placement of a CSI-RS RE group taking into account a transmission diversity RE pair.

FIG. 20 is a diagram illustrating an abrupt change in a CSI-RS RE group.

FIG. 21 is a diagram illustrating a function for mapping virtual indexes of CSI-RS groups to physical indexes of CSI-RS groups.

FIG. 22 and 23 are examples of the RE CSI-RS group in the case of eight transmit antennas.

FIG. 24 is a diagram illustrating a CSI-RS mapping method in the case of eight transmit antennas.

FIG. 25 and 26 are examples of the RE CSI-RS group in the case of four transmit antennas.

FIG. 27 is a diagram illustrating a CSI-RS mapping method in the case of four transmit antennas.

FIG. 28 and 29 are other examples of the CSI-RS RE group in the case of four transmit antennas.

FIG. 30 is a diagram illustrating a CSI-RS mapping method in the case of four transmit antennas.

FIG. 31 is another example of a CSI-RS RE group in the case of four transmit antennas.

FIG. 32 and 33 are examples of the RE CSI-RS group in the case of two transmit antennas.

FIG. 34 is another example of a CSI-RS RE group in the case of two transmit antennas.

FIG. 35 is a flowchart illustrating a CSI-RS transmission method and a channel information acquiring method.

FIG. 36 is a configuration of a wireless communication system including a base station and user equipment, in accordance with an exemplary embodiment of the present invention.

The implementation of the invention

The following embodiments are proposed by combining the constituent components and characteristics of the present invention in accordance with a predetermined format. The individual constituent components or characteristics should be considered as optional factors, provided that there are no additional comments. If necessary, the individual constituent components or characteristics may not be combined with other components or characteristics. Some constituent components and / or characteristics may be combined to implement embodiments of the present invention. The sequence of operations disclosed in the embodiments of the present invention may be changed to another. If necessary, some components or characteristics of any embodiment may also be included in other embodiments or may be replaced by those present in other embodiments.

Embodiments of the present invention are disclosed based on a data communication interaction between a base station and a terminal. In this case, the base station is used as the end node of the network through which the base station can directly communicate with the terminal. The specific operations performed by the base station in the present invention can also be performed, if necessary, by a higher level node with respect to the base station.

In other words, it will be apparent to those skilled in the art that various operations allowing the base station to communicate with a terminal in a network of several network nodes, including the base station, will be performed by a base station or other network node other than the base station. The term “Base Station (BS)” can be replaced by a fixed station, Node-B, eNode-B (eNB) or access point, if necessary. The term “relay” can be replaced by a Relay Node (RN) or Relay Station (RS). The term “terminal” can also be replaced by User Equipment (UE), Mobile Station (MS), Mobile Subscriber Station (MSS) or Subscriber Station (SS), if necessary.

It should be noted that the specific terms disclosed in the present invention are provided for convenience of description and a better understanding of the present invention, and the use of these specific terms can be replaced with another format within the technical scope or essence of the present invention.

In some cases, well-known structures and devices are omitted so as not to obscure the concept of the present invention, and important functions of structures and devices are shown in block diagram form. Identical conventions will be used throughout the drawings to refer to the same or like parts.

Exemplary embodiments of the invention are supported by standards documents, disclosed with respect to at least one of wireless access systems, including the system of the Institute of Electrical and Electronics Engineers (IEEE) 802, Project Partnership 3 ^it Generations system design system Long Term Evolution (LTE) 3GPP and 3GPP2 system. In particular, steps or parts that are not described here to more clearly show the technical idea of the present invention, in embodiments of the present invention can be supported by the above documents. All terminology used here may be supported by at least one of the above documents.

The following embodiments of the present invention can be applied to a variety of wireless access technologies, for example CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access) ), SC-FDMA (Frequency Division Multiple Access and Single Carrier) and the like. CDMA can be implemented using wireless (or radio) technology such as UTRA (Universal Terrestrial Radio Access) or CDMA2000. TDMA can be implemented using wireless (or radio) technology such as GSM (Global System for Moving Object Communication) / GPRS (General Packet Radio Service) / EDGE (Increased Data Transfer Rates for GSM Development). OFDMA can be implemented using wireless (or radio) technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20 and E-UTRA (Developed by UTRA). UTRA is part of UMTS (Universal Mobile Communications System). The 3GPP standard (Partnership Project 3 of ^its Generation), referred to as LTE (Long-Term Development), is part of the E-UMTS (Developed by UMTS) that uses E-UTRA. 3GPP LTE uses OFDMA in the downlink and uses SC-FDMA in the uplink. Advanced LTE Standard (LTE-A) is a developed version of 3GPP LTE. WiMAX can be explained by the IEEE 802.16e standard (WirelessMAN-OFDMA reference system) and the advanced IEEE 802.16m standard (Advanced WirelessMAN-OFDMA system). For clarity, the following description focuses on 3GPP LTE and LTE-A. However, the technical features of the present invention are not limited to this.

The structure of the downlink radio frame will be described with reference to FIG. one.

In an Orthogonal Frequency Division Multiplexing (OFDMA) cellular packet radio communication system, uplink / downlink data packets are transmitted in units of subframes. One subframe is defined as a predetermined time interval including a plurality of OFDM symbols. The 3GPP LTE standard supports a Type 1 radio frame structure applicable to Frequency Division Duplex Communication (FDD) and a Type 2 radio frame structure applicable to Time Division Duplex Communication (TDD).

FIG. 1 is a diagram showing a structure of a type 1 radio frame. A downlink radio frame includes 10 subframes, and one subframe includes two slots in a time domain. The time required to transmit one subframe is specified in the Transmission Time Interval (TTI). For example, one subframe may be 1 ms long, and one slot may be 0.5 ms long. One slot may include multiple OFDM symbols in the time domain and include multiple Resource Blocks (RB) in the frequency domain. Since the 3GPP LTE system uses OFDMA in the downlink, the OFDM symbol indicates one symbol duration. An OFDM symbol may be referred to as an SC-FDMA symbol or a symbol duration. RB is a resource allocation unit and includes multiple adjacent subcarriers in one slot.

The number of OFDM symbols included in one slot may vary according to the configuration of the Cyclic Prefix (CP). CP includes advanced CP and normal CP. For example, if OFDM symbols are configured by normal CP, then the number of OFDM symbols included in one slot may be seven. If the OFDM symbols are configured by the extended CP, then the length of one OFDM symbol is increased, and the number of OFDM symbols included in one slot is less than that fits in the case of normal CP. For example, in the case of an extended CP, the number of OFDM symbols included in one slot may be six. If the channel state is unstable, for example, if the User Equipment (UE) is moving at high speed, then an advanced CP can be used to further reduce interference between characters.

In the case of using normal CP, since one slot includes seven OFDM symbols, then one subframe includes 14 OFDM symbols. In this case, the first two of the three OFDM symbols of each subframe may be allocated to the Physical Downlink Control Channel (PDCCH), and the remaining OFDM symbols may be allocated to the Physical Downlink Shared Channel (PDSCH).

The structure of the radio frame is only an example. Accordingly, the number of subframes included in the radio frame, the number of slots included in the subframe, or the number of symbols included in the slot, can vary in various ways.

FIG. 2 is a diagram showing an example of a resource grid in one downlink slot. OFDM symbols are configured by normal CP. According to FIG. 2, a downlink slot includes a plurality of OFDM symbols in a time domain and includes a plurality of RBs in a frequency domain. Although, as an example, FIG. 2 shows that one downlink slot includes seven OFDM symbols, and one RB includes 12 subcarriers, the present invention is not limited to this. Each resource grid element is referred to as a Resource Element (RE). For example, RE a (k, l) is located on the kth subcarrier and in the lth OFDM symbol. In the case of normal CP, one RB includes 12 × 7 RE (in the case of extended CP, one RB includes 12 × 6 RE). Since the distance between the subcarriers is 15 kHz, one RB includes about 180 kHz in the frequency domain. N ^DL denotes the number of RBs included in the downlink slot. N ^{DL is} determined based on the downlink transmission bandwidth established by scheduling from the base station.

FIG. 3 is a diagram showing a structure of a downlink subframe. A maximum of three OFDM symbols of the front of the first slot within one subframe correspond to a control area for which a control channel is allocated. The remaining OFDM symbols correspond to the data region for which the Physical Downlink Shared Channel (PDSCH) is allocated. The basic transmission unit is one subframe. Those. PDCCH and PDSCH are allocated over two slots. Examples of downlink control channels used in the 3GPP LTE system include, for example, Physical Control Format Indicator Channel (PCFICH), Physical Downlink Control Channel (PDCCH), Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH), and etc. The PCFICH is transmitted in the first OFDM symbol of the subframe and includes information on the number of OFDM symbols used to transmit the control channel in the subframe. The PHICH includes an HARQ ACK / NACK signal in response to an uplink transmission. The control information transmitted by the PDCCH relates to Downlink Control Information (DCI). The DCI includes uplink or downlink scheduling information or an uplink transmit power control command for a specific group of UEs. The PDCCH may include Resource Allocation and Transmission Format of the Downlink Shared Channel (DL-SCH), Resource Information about the Allocation of the Uplink Shared Channel (UL-SCH), Paging Channel Search Information (PCH), system information in DL-SCH, resource allocation for a higher-level control message, such as a Random Access Response (RAR) transmitted over PDSCH, a set of transmit power control commands for individual UEs in a specific UE group, control information transmit power, Voice over IP (VoIP) activation, etc. Within the control area, multiple PDCCHs may be transmitted. The UE may track multiple PDCCHs. PDCCHs are transmitted by aggregation from one or more adjacent (continuous) control channel elements (CCEs). CCE is a logical allocation unit used to provide PDCCH with a coding rate based on the state of the radio channel. CCE corresponds to many resource element groups. The PDCCH format and the number of available bits are determined based on the relationship between the number of CCEs and the coding rate provided by the CCE. The base station determines the PDCCH format in accordance with the DCI to be transmitted to the UE, and attaches the Cyclic Redundancy Check (CRC) Control to the control information. The CRC is masked using a Temporary Radio Access Network Identifier (RNTI) according to the owner or use of the PDCCH. If the PDCCH is for a specific UE, then the RNTI of the cell (C-RNTI) of the UE may be masked in the CRC. Alternatively, if the PDCCH is for paging message, then the paging indicator identifier (P-RNTI) may be masked in the CRC. If the PDCCH is for system information (in particular, a system information block (SIB)), then the identifier of system information and the system information RNTI (SI-RNTI) can be masked in the CRC. In order to indicate a random access response, which is a response to the transmission of the random access preamble by the UE, a random access RNTI (RA-RNTI) may be masked in the CRC.

FIG. 4 is a diagram showing an uplink frame structure. The uplink subframe may be divided into a control area and a data area in the frequency domain. In the control area, the Uplink Physical Control Channel (PUCCH) including uplink control information is allocated. A Physical Uplink Shared Channel (PUSC) is highlighted in the data area, including user data. In order to provide a single carrier property, the UE does not simultaneously transmit PUCCH and PUSCH. A PUCCH for one UE is allocated in an RB pair in a subframe. RBs belonging to the RB pair occupy different subcarriers with respect to two slots. Thus, an allocated PUCCH RB pair is defined as “frequency hopping” at the slot boundary.

Multiple Input / Multiple Output Modeling System (MIMO)

The MIMO system improves data transmission / reception efficiency using multiple transmit antennas and multiple receive antennas. In MIMO technology, the path of one antenna is not used to receive the entire message, i.e. entire data can be received by combining multiple pieces of data received through multiple antennas.

FIG. 5 is a diagram showing a configuration of a multi-antenna wireless communication system. As shown in FIG. 5 (a) if the number of transmitting antennas is increased to N _T and the number of receiving antennas is increased to N _R , then the theoretical transmission capacity of the communication channel increases in proportion to the number of antennas, as opposed to the case where many antennas are used only in the transmitter or receiver. Accordingly, there is the possibility of increasing the transfer rate and significantly increasing the frequency utilization efficiency. As the transmission capacity of the communication channel increases, the transfer rate can theoretically be increased by multiplying the maximum transfer rate R ₀ when using one antenna by the rate increase coefficient R _i .

Equation 1

$$R_i=\min (N_T,N_R)$$

For example, in a MIMO system using four transmit antennas and four receive antennas, it is theoretically possible to obtain a transfer rate that is four times faster than a system with a single antenna. After an increase in the theoretical throughput of the MIMO system was proved in the mid-1990s, various technologies have been actively developed to significantly increase the speed of data transfer. In addition, several technologies are already being applied in various radio standards, such as third-generation mobile communications and next-generation wireless local area networks (LANs).

In accordance with the studies carried out so far in the field of MIMO antennas, various studies are actively carried out, such as studies in the field of information theory related to calculating the communication bandwidth of the MIMO antenna in different channel environments and multiple access environments; research into the model and measurement of radio channels of the MIMO system; and research into spatio-temporal signal processing technologies to improve transmission reliability and transmission rate.

The communication method of the MIMO system will be described in more detail using mathematical modeling. In the above system, it is assumed that there are N _T transmit antennas and N _R receive antennas.

In the transmitted signals, if N _T transmit antennas are present, then the number of parts of the maximum information possible for transmission is N _T. The transmitted information can be expressed as follows.

Equation 2

$$S={\lfloor S_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">S</figure-callout>}}_2,...,S_{N_T}\rfloor }^T$$

может иметь разные мощности передачи. Если соответствующими мощностями передачи являются $$P_1,P_2,\dots ,P_{N_T}$$

, то передаваемая информация с настроенными мощностями может быть выражена следующим образом:Information Transmitted $$S_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">S</figure-callout>}}_2,...,S_{N_T}$$

may have different transmission powers. If the corresponding transmission powers are $$P_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">P</figure-callout>}}_2,...,P_{N_T}$$

, then the transmitted information with the configured capacities can be expressed as follows:

Equation 3

$$\stackrel{\wedge }{S}={\left[{\stackrel{\wedge }{S}}_{\mathrm{one}},{\stackrel{\wedge }{S}}_2,...,{\stackrel{\wedge }{S}}_{N_T}\right]}^T={\left[P_{\mathrm{one}}{S}_{\mathrm{one}},P_2{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">S</figure-callout>}}_2,...,P_{N_T}{S}_{N_T}\right]}^T$$

может быть выражена с использованием диагональной матрицы P мощностей передачи следующим образом.In addition, $$\stackrel{\wedge }{S}$$

can be expressed using the diagonal matrix P of transmission powers as follows.

Equation 4

$$\stackrel{\wedge }{S}=\left[\begin{array}{cccc}{P}_{\mathrm{one}}& & & 0\\ & {\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">P</figure-callout>}}_2& & \\ & & \ddots & \\ 0& & & P_{N_T}\end{array}\right]\left[\begin{array}{c}{S}_{\mathrm{one}}\\ {\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\\ ⋮\\ S_{N_T}\end{array}\right]=Ps$$

сконфигурированы посредством применения весовой матрицы W к информационному вектору $$\stackrel{\wedge }{S}$$

с настроенными мощностями передачи. Весовая матрица W служит для соответствующего распределения передаваемой информации между каждой антенной в соответствии с состоянием канала транспортировки и т.д. Тогда $$x_1,x_2,\dots ,x_{N_T}$$

могут быть выражены с использованием вектора X следующим образом.Assume that N _T actually transmitted signal $$x_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">x</figure-callout>}}_2,...,x_{N_T}$$

configured by applying the weight matrix W to the information vector $$\stackrel{\wedge }{S}$$

with tuned transmission powers. The weight matrix W serves for the appropriate distribution of the transmitted information between each antenna in accordance with the state of the transport channel, etc. Then $$x_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">x</figure-callout>}}_2,...,x_{N_T}$$

can be expressed using the vector X as follows.

Equation 5

$$X=\left[\begin{array}{c}\begin{array}{c}{x}_{\mathrm{one}}\\ x_2\\ ⋮\end{array}\\ \begin{array}{c}{x}_i\\ ⋮\\ x_{N_T}\end{array}\end{array}\right]=\left[\begin{array}{c}\begin{array}{ccc}{w}_{\mathrm{eleven}}& {\mathrm{<figure-callout\; id="12"\; label="w"\; filenames="00000080.png,00000083.png"\; state="\{\{state\}\}">w</figure-callout>}}_{12}& \cdots \\ w_{21}& {\mathrm{<figure-callout\; id="22"\; label="w"\; filenames="00000071.png,00000076.png"\; state="\{\{state\}\}">w</figure-callout>}}_{22}& \cdots \\ ⋮& & \ddots \end{array}\\ \begin{array}{ccc}{w}_{i\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="w\; i"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">w\; </figure-callout>}}_i& \cdots \\ ⋮& & \ddots \\ w_{N_T\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="w\; N\; T"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">w\; </figure-callout>}}_{N_T}& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{w}_{\mathrm{one}{N}_T}\\ w_{\mathrm{one}{N}_T}\\ \end{array}\\ \begin{array}{c}{w}_{i{N}_T}\\ \\ w_{N_T{N}_T}\end{array}\end{array}\right]\left[\begin{array}{c}\begin{array}{c}\stackrel{\wedge }{S_{\mathrm{one}}}\\ \stackrel{\wedge }{S_{\mathrm{one}}}\\ \end{array}\\ \begin{array}{c}\stackrel{\wedge }{S_j}\\ \\ \stackrel{\wedge }{S_{N_T}}\end{array}\end{array}\right]=W\stackrel{\wedge }{S}=WPs$$

where W _ij denotes the weight coefficient for the i-th transmitting antenna and j-th information. W is also referred to as a precoding matrix.

The transmitted signal x may be processed differently using two schemes (e.g., a spatial diversity scheme and a spatial multiplexing scheme). In the case of the spatial multiplexing scheme, various signals are multiplexed, and the multiplexed signal is transmitted to the receiver in such a way that the elements of the information (s) vector (s) have different values. In the case of a spatial diversity scheme, the same signal is repeatedly transmitted through a plurality of channel paths, so that the elements of the information (s) vector (s) have the same value. A combination of a spatial multiplexing scheme and a spatial diversity scheme may be considered. Those. the same signal can, for example, be transmitted through three transmit antennas in accordance with a spatial diversity scheme, and the remaining signals can be transmitted to the receiver using the spatial multiplexing scheme.

антенн выражаются следующим образом:If there are N _R receiving antennas, then the corresponding received signals $$y_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">y</figure-callout>}}_2,...,y_{N_R}$$

antennas are expressed as follows:

Equation 6

$$y={\left[y_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">y</figure-callout>}}_2,...,y_{N_R}\right]}^T$$

If the channels are modeled in a MIMO radio communication system, then the channels may differ in transmit / receive antenna indices. The channel from the transmitting antenna j to the receiving antenna i is denoted by h _ij . At h _{ij, the} indices of the receiving antennas precede the indices of the transmitting antennas, taking into account the order of the indices.

FIG. 5 (b) is a diagram showing channels from N _T transmit antennas to receive antenna i. Channels can be combined and expressed as a vector and matrix. In FIG. 5 (b) channels from N _T transmit antennas to receive antenna i can be expressed as follows:

Equation 7

$$h_i^T=\left[h_{i\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="h\; i"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_i,...,h_{i{N}_T}\right]$$

Accordingly, all channels from N _T transmit antennas to N _R receive antennas can be expressed as follows:

Equation 8

$$H=\left[\begin{array}{c}\begin{array}{c}{h}_{\mathrm{one}}^T\\ h_2^T\\ \end{array}\\ \begin{array}{c}{h}_i^T\\ \\ h_{N_R}^T\end{array}\end{array}\right]=\left[\begin{array}{c}\begin{array}{ccc}{h}_{\mathrm{eleven}}& {\mathrm{<figure-callout\; id="12"\; label="h"\; filenames="00000080.png,00000083.png"\; state="\{\{state\}\}">h</figure-callout>}}_{12}& \cdots \\ h_{21}& {\mathrm{<figure-callout\; id="22"\; label="h"\; filenames="00000071.png,00000076.png"\; state="\{\{state\}\}">h</figure-callout>}}_{22}& \cdots \\ ⋮& & \ddots \end{array}\\ \begin{array}{ccc}{h}_{i\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h\; i"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_i& \cdots \\ ⋮& & \ddots \\ h_{N_R\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h\; N\; R"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_{N_R}& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{h}_{\mathrm{one}{N}_T}\\ h_{2N_T}\\ \end{array}\\ \begin{array}{c}{h}_{i{N}_T}\\ \\ h_{N_R{N}_T}\end{array}\end{array}\right]$$

, добавляемый к N_T передающим антеннам, может быть выражен следующим образом:Additive White Gaussian Noise (AWGN) to the actual channels after the channel matrix H. Awgn $$n_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">n</figure-callout>}}_2,...,n_{N_R}$$

added to the N _T transmit antennas can be expressed as follows:

Equation 9

$$n={\left[n_{\mathrm{one}},{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">n</figure-callout>}}_2,...,n_{N_R}\right]}^T$$

Through the above mathematical modeling, the received signals can be expressed as follows:

Equation 10

$$y=\left[\begin{array}{c}\begin{array}{c}{y}_{\mathrm{one}}\\ {\mathrm{<figure-callout\; id="21"\; label="y"\; filenames="00000089.png"\; state="\{\{state\}\}">y</figure-callout>}}_{21}\\ ⋮\end{array}\\ \begin{array}{c}{y}_i\\ ⋮\\ y_{N_R}\end{array}\end{array}\right]=\left[\begin{array}{c}\begin{array}{ccc}{h}_{\mathrm{eleven}}& {\mathrm{<figure-callout\; id="12"\; label="h"\; filenames="00000080.png,00000083.png"\; state="\{\{state\}\}">h</figure-callout>}}_{12}& \cdots \\ h_{21}& {\mathrm{<figure-callout\; id="22"\; label="h"\; filenames="00000071.png,00000076.png"\; state="\{\{state\}\}">h</figure-callout>}}_{22}& \cdots \\ ⋮& & \ddots \end{array}\\ \begin{array}{ccc}{h}_{i\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h\; i"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_i& \cdots \\ ⋮& & \ddots \\ h_{N_R\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h\; N\; R"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_{N_R}& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{h}_{\mathrm{one}{N}_T}\\ h_{2N_T}\\ \end{array}\\ \begin{array}{c}{h}_{i{N}_T}\\ \\ h_{N_R{N}_T}\end{array}\end{array}\right]\left[\begin{array}{c}\begin{array}{c}{x}_{\mathrm{one}}\\ x_2\\ ⋮\end{array}\\ \begin{array}{c}{x}_i\\ ⋮\\ x_{N_T}\end{array}\end{array}\right]+\left[\begin{array}{c}\begin{array}{c}{n}_{\mathrm{one}}\\ {\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\\ ⋮\end{array}\\ \begin{array}{c}{n}_i\\ ⋮\\ n_{N_R}\end{array}\end{array}\right]=Hx+n$$

The above description focuses on the case where a single user uses the MIMO system. However, it is possible to apply the MIMO system to multiple users to obtain multi-user diversity. Now this option will be briefly described.

The attenuation channel reduces the efficiency of the wireless communication system. The channel gain varies according to time, frequency and space. As channel gain decreases, performance degradation increases. The diversity scheme uses the fact that the probability that all of several independent channels have a low gain is small to solve the attenuation problem. Various diversity schemes are possible, including a multi-user diversity scheme.

When several users are present inside the cell, since the gain of the user channels is stochastically independent, the probability that all users have low gain is very small. According to the information theory, if the transmit power of the base station is sufficient, then all channels are allocated to the user with the highest channel gain among several users present in the cell in order to maximize the total bandwidth of the communication channels. The multi-user diversity scheme can be divided into three schemes.

The timing scheme of multi-user diversity is to allocate the channel to the user with the highest gain, regardless of whether the channel changes over time. A multi-user diversity diversity scheme consists of allocating subcarriers to a user with a maximum gain in each frequency band in a multi-carrier frequency system such as OFDM.

If the channel changes slowly in a system that does not use multiple carriers, then the user with the highest channel gain takes the channel for a long time. Accordingly, other users cannot communicate. In this case, you need to trigger a channel change in order to use the multi-user diversity scheme.

Further, the spatial scheme of multi-user diversity exploits the fact that the gain of user channels differ depending on space. The implementation example presented here includes Arbitrary Patterning (RBF), etc. The RBF is also referred to as “unplanned beamforming” and causes a channel change, allowing the transmitter to perform beamforming with a specific weight using multiple antennas.

A multi-user MIMO scheme (MU-MIMO) that uses the multi-user diversity scheme described above in a MIMO scheme will be described.

In the MU-MIMO scheme, the number of users and the number of antennas of each user in the transmitter / receiver can be combined in different ways. The MU-MIMO scheme may be described for the downlink (forward link) and uplink (reverse link). The downlink refers to the case where the base station transmits signals to multiple UEs. The uplink refers to the case where several UEs transmit signals to a base station.

In the downlink, in the extreme case, for example, one user can receive a signal through a total of N _R antennas and a total of N _R users can receive a signal using a single antenna. In addition, a combination of the limiting cases described above is possible. Those. a specific user may use one receiving antenna, and a specific user may use three receiving antennas. In any case, it is noted that the total number of receiving antennas is defined as N _R. This case mainly relates to MIMO Broadcast Channel (BC) or Spatial Division Multiple Access (SDMA).

In the uplink, in the extreme case, one user can transmit a signal using a total of N _T antennas, and a total of N _T users can transmit a signal using a single antenna. In addition, a combination of the limiting cases described above is possible. Those. a specific user may use one transmit antenna, and a specific user may use three transmit antennas. In any case, it is noted that the total number of transmitting antennas is defined as N _T. This case is usually referred to as a MIMO Multiple Access Channel (MAC). Since the uplink and downlink are mutually symmetrical, the circuitry used in any one of the uplink or downlink can be used in the other.

N_T.The number of rows and columns of the channel matrix H indicating the channel state is determined by the number of transmitting and receiving antennas. The number of rows of the channel matrix H is equal to the number N _{R of} receiving antennas, and the number of its columns is equal to the number N _{T of} transmitting antennas. Those. the channel matrix H is the matrix N _R $$\times$$

N _T.

The rank of the matrix is determined by the smallest of the number of rows or columns that are independent of each other. Accordingly, the rank of the matrix is not greater than the number of rows or columns. The rank rank (H) of the channel matrix H is limited as follows:

Equation 11

$$\text{rank (H)}\le {\text{min (N}}_{\text{T}},N_R)$$

When a matrix is decomposed in terms of eigenvalues, then the rank can be determined by the number of eigenvalues, excluding 0. Similarly, when a matrix is decomposed in terms of singular numbers of the matrix, then the rank can be determined by the number of singular numbers, excluding 0. Accordingly, the physical value of the rank in the channel the matrix can be the maximum number of different transmitted information in a given channel.

In MIMO transmission, the concept of “rank” refers to the number of routes for independently transmitted signals, and the concept of “number of levels” refers to the number of signal streams transmitted on each route. In general, since the transmitter transmits levels quantitatively corresponding to the number of ranks used to transmit the signal, the rank has the same meaning as the number of levels, unless otherwise stated.

The following describes the characteristics of the precoding matrix. For example, the channel matrix H, excluding the precoding matrix, can be expressed as follows:

Equation 12

$$H=\left[\begin{array}{c}\begin{array}{ccc}{h}_{\mathrm{eleven}}& {\mathrm{<figure-callout\; id="12"\; label="h"\; filenames="00000080.png,00000083.png"\; state="\{\{state\}\}">h</figure-callout>}}_{12}& \cdots \\ h_{21}& {\mathrm{<figure-callout\; id="22"\; label="h"\; filenames="00000071.png,00000076.png"\; state="\{\{state\}\}">h</figure-callout>}}_{22}& \cdots \\ ⋮& & \ddots \end{array}\\ \begin{array}{ccc}{h}_{i\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h\; i"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_i& \cdots \\ ⋮& & \ddots \\ h_{N_R\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h\; N\; R"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_{N_R}& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{h}_{\mathrm{one}{N}_T}\\ h_{2N_T}\\ \end{array}\\ \begin{array}{c}{h}_{i{N}_T}\\ \\ h_{N_R{N}_T}\end{array}\end{array}\right]=\left[\begin{array}{cc}\begin{array}{ccc}{h}_{\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">h</figure-callout>}}_2& \cdots \end{array}& h_{N_T}\end{array}\right]$$

In general, if it is given that the receiver has a Minimum Mean Square Error (MMSE), then ρ _k (Ratio of the kth received Signal to Noise and Noise (SINR)) is defined as follows:

Equation 13

$${\rho }_k=SIN{R}_k=h_k^H{\left(N_0{I}_{N_R}+{\displaystyle \sum _{\begin{array}{l}i=\mathrm{one}\\ i\ne k\end{array}}^{N_R}{h}_i{h}_i^H}\right)}^{-\mathrm{one}}{h}_k$$

в приложении к матрице предварительного кодирования может быть выражен, используя матрицу W предварительного кодирования, следующим образом:Effective channel $$\tilde{H}$$

as applied to the precoding matrix, can be expressed using the precoding matrix W as follows:

Equation 14

$$\tilde{H}=HW=\left[\begin{array}{c}{\overrightarrow{h}}_{\mathrm{one}}^T\\ {\overrightarrow{h}}_2^T\\ ⋮\\ {\overrightarrow{h}}_{N_R}^T\end{array}\right]\left[\begin{array}{cccc}{w}_{\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">w</figure-callout>}}_2& \cdots & w_{N_R}\end{array}\right]=\left[\begin{array}{c}\begin{array}{ccc}{\overrightarrow{h}}_{\mathrm{one}}^T{w}_{\mathrm{one}}& {\overrightarrow{h}}_{\mathrm{one}}^{\mathrm{<figure-callout\; id="2"\; label="T\; w"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">T\; </figure-callout>}}{w}_{}{}_2& \cdots \\ {\overrightarrow{h}}_2^T{w}_{\mathrm{one}}& {\overrightarrow{h}}_2^{\mathrm{<figure-callout\; id="2"\; label="T\; w"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">T\; </figure-callout>}}{w}_{}{}_2& \cdots \\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{\overrightarrow{h}}_{N_R}^T{w}_{\mathrm{one}}& {\overrightarrow{h}}_{N_{\mathrm{<figure-callout\; id="2"\; label="R\; T\; w"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">R\; </figure-callout>}}}^T{w}_{}{}_2& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{\overrightarrow{h}}_{\mathrm{one}}^T{w}_{N_R}\\ {\overrightarrow{h}}_2^T{w}_{N_R}\\ ⋮\end{array}\\ {\overrightarrow{h}}_{N_R}^T{w}_{N_R}\end{array}\right]=\left[\begin{array}{cccc}{\tilde{h}}_{\mathrm{one}}& {\tilde{h}}_2& \cdots & {\tilde{h}}_{N_T}\end{array}\right]$$

Accordingly, if it is assumed that a receiver with MMSE is being used, then ρ _k is determined as follows:

Equation 15

$${\tilde{\rho }}_k=SIN{R}_k={\tilde{h}}_k^H{\left(N_0{I}_{N_R}+{\displaystyle \sum _{\begin{array}{l}i=\mathrm{one}\\ i\ne k\end{array}}^{N_R}{\tilde{h}}_i{\tilde{h}}_i^H}\right)}^{-\mathrm{one}}{\tilde{h}}_k=\left[\begin{array}{cccc}{w}_k^H{\overrightarrow{h}}_{\mathrm{one}}^{*}& w_k^H{\overrightarrow{h}}_2^{*}& \cdots & w_k^H{\overrightarrow{h}}_{N_R}^{*}\end{array}\right]{\left(N_0{I}_{N_R}+{\displaystyle \sum _{\begin{array}{l}i=\mathrm{one}\\ i\ne k\end{array}}^{N_R}{\tilde{h}}_i{\tilde{h}}_i^H}\right)}^{-\mathrm{one}}\left[\begin{array}{c}{\overrightarrow{h}}_{\mathrm{one}}^T{w}_k\\ {\overrightarrow{h}}_2^T{w}_k\\ ⋮\\ {\overrightarrow{h}}_{N_R}^T{w}_k\end{array}\right]$$

предварительного кодирования после перестановки может быть выражена следующим образом:The effect on SINR, based on changes in the precoding matrix, can be confirmed theoretically. First, the efficiency of column permutation in a single precoding matrix can be confirmed. Those. in the case of permutation between the vector W _{i of the} i-th column and the vector W _{j of the} j-th column, the matrix $$\stackrel{\wedge }{W}$$

precoding after permutation can be expressed as follows:

Equation 16

$$\begin{array}{l}W=\left[\begin{array}{cc}\begin{array}{cccc}{W}_{\mathrm{one}}& \cdots & W_i& \cdots \end{array}& \begin{array}{ccc}{W}_j& \cdots & W_{N_R}\end{array}\end{array}\right]\\ \stackrel{\wedge }{W}=\left[\begin{array}{cc}\begin{array}{cccc}{W}_{\mathrm{one}}& \cdots & W_j& \cdots \end{array}& \begin{array}{ccc}{W}_i& \cdots & W_{N_R}\end{array}\end{array}\right]\end{array}$$

в соответствии с матрицей W предварительного кодирования и эффективный канал $$\stackrel{\wedge }{H}$$

в соответствии с матрицей $$\stackrel{\wedge }{W}$$

предварительного кодирования могут быть выражены следующим образом:Accordingly, the effective channel $$\tilde{H}$$

according to the precoding matrix W and the effective channel $$\stackrel{\wedge }{H}$$

according to the matrix $$\stackrel{\wedge }{W}$$

precoding can be expressed as follows:

Equation 17

$$\begin{array}{l}\tilde{H}=HW=\left[\begin{array}{c}{\overrightarrow{h}}_{\mathrm{one}}^T\\ {\overrightarrow{h}}_2^T\\ ⋮\\ {\overrightarrow{h}}_{N_R}^T\end{array}\right]\left[\begin{array}{cccc}{w}_{\mathrm{one}}& \cdots & w_i& \cdots \begin{array}{cc}{w}_j& \begin{array}{cc}\cdots & w_{N_R}\end{array}\end{array}\end{array}\right]=\left[\begin{array}{c}\begin{array}{ccc}{\overrightarrow{h}}_{\mathrm{one}}^T{w}_{\mathrm{one}}& \cdots & {\overrightarrow{h}}_{\mathrm{one}}^T{w}_i\\ {\overrightarrow{h}}_2^T{w}_{\mathrm{one}}& \cdots & {\overrightarrow{h}}_2^T{w}_i\\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{\overrightarrow{h}}_{N_R}^T{w}_{\mathrm{one}}& \cdots & {\overrightarrow{h}}_{N_R}^T{w}_i\end{array}\end{array}\begin{array}{c}\begin{array}{c}\cdots \\ \cdots \\ ⋮\end{array}\\ \cdots \end{array}\begin{array}{c}\begin{array}{ccc}{\overrightarrow{h}}_{\mathrm{one}}^T{w}_j& \cdots & {\overrightarrow{h}}_{\mathrm{one}}^T{w}_{N_T}\\ {\overrightarrow{h}}_2^T{w}_j& \cdots & {\overrightarrow{h}}_2^T{w}_{N_T}\\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{\overrightarrow{h}}_{N_R}^T{w}_j& \cdots & {\overrightarrow{h}}_{N_R}^T{w}_{N_T}\end{array}\end{array}\right]\\ =\left[\begin{array}{cccc}{\tilde{h}}_{\mathrm{one}}& \cdots & {\tilde{h}}_i& \cdots \begin{array}{ccc}{\tilde{h}}_j& \cdots & {\tilde{h}}_{N_T}\end{array}\end{array}\right]\end{array}$$

Equation 18

$$\begin{array}{l}\stackrel{\wedge }{H}=H\stackrel{\wedge }{W}=\left[\begin{array}{c}{\overrightarrow{h}}_{\mathrm{one}}^T\\ {\overrightarrow{h}}_2^T\\ ⋮\\ {\overrightarrow{h}}_{N_R}^T\end{array}\right]\left[\begin{array}{cccc}{w}_{\mathrm{one}}& \cdots & w_j& \cdots \begin{array}{cc}{w}_i& \begin{array}{cc}\cdots & w_{N_R}\end{array}\end{array}\end{array}\right]=\left[\begin{array}{c}\begin{array}{ccc}{\overrightarrow{h}}_{\mathrm{one}}^T{w}_{\mathrm{one}}& \cdots & {\overrightarrow{h}}_{\mathrm{one}}^T{w}_j\\ {\overrightarrow{h}}_2^T{w}_{\mathrm{one}}& \cdots & {\overrightarrow{h}}_2^T{w}_j\\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{\overrightarrow{h}}_{N_R}^T{w}_{\mathrm{one}}& \cdots & {\overrightarrow{h}}_{N_R}^T{w}_j\end{array}\end{array}\begin{array}{c}\begin{array}{c}\cdots \\ \cdots \\ ⋮\end{array}\\ \cdots \end{array}\begin{array}{c}\begin{array}{ccc}{\overrightarrow{h}}_{\mathrm{one}}^T{w}_i& \cdots & {\overrightarrow{h}}_{\mathrm{one}}^T{w}_{N_T}\\ {\overrightarrow{h}}_2^T{w}_i& \cdots & {\overrightarrow{h}}_2^T{w}_{N_T}\\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{\overrightarrow{h}}_{N_R}^T{w}_i& \cdots & {\overrightarrow{h}}_{N_R}^T{w}_{N_T}\end{array}\end{array}\right]\\ =\left[\begin{array}{cccc}{\tilde{h}}_{\mathrm{one}}& \cdots & {\tilde{h}}_j& \cdots \begin{array}{ccc}{\tilde{h}}_i& \cdots & {\tilde{h}}_{N_T}\end{array}\end{array}\right]\end{array}$$

In equations 17 and 18, even when two column vectors are rearranged, the received SINR does not change, except for its order, and the total transmission channel throughput can be fixed by the sum. Even in Equations 14 and 15, the effective channel after permutation and ρ _k can be obtained as follows:

Equation 19

$$\stackrel{\wedge }{H}=H\stackrel{\wedge }{W}=\left[\begin{array}{c}{\overrightarrow{h}}_{\mathrm{one}}^T\\ {\overrightarrow{h}}_2^T\\ ⋮\\ {\overrightarrow{h}}_{N_R}^T\end{array}\right]\left[\begin{array}{cccc}{\stackrel{\wedge }{w}}_{\mathrm{one}}& {\stackrel{\wedge }{w}}_2& \cdots & {\stackrel{\wedge }{w}}_{N_R}\end{array}\right]=\left[\begin{array}{c}\begin{array}{ccc}{\overrightarrow{h}}_{\mathrm{one}}^T{\stackrel{\wedge }{w}}_{\mathrm{one}}& {\overrightarrow{h}}_{\mathrm{one}}^T{\stackrel{\wedge }{w}}_2& \cdots \\ {\overrightarrow{h}}_2^T{\stackrel{\wedge }{w}}_{\mathrm{one}}& {\overrightarrow{h}}_2^T{\stackrel{\wedge }{w}}_2& \cdots \\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{\overrightarrow{h}}_{N_R}^T{\stackrel{\wedge }{w}}_{\mathrm{one}}& {\overrightarrow{h}}_{N_R}^T{\stackrel{\wedge }{w}}_2& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{\overrightarrow{h}}_{\mathrm{one}}^T{\stackrel{\wedge }{w}}_{N_R}\\ {\overrightarrow{h}}_2^T{\stackrel{\wedge }{w}}_{N_R}\\ ⋮\end{array}\\ {\overrightarrow{h}}_{N_R}^T{\stackrel{\wedge }{w}}_{N_R}\end{array}\right]=\left[\begin{array}{cccc}{\stackrel{\wedge }{h}}_{\mathrm{one}}& {\stackrel{\wedge }{h}}_2& \cdots & {\stackrel{\wedge }{h}}_{N_T}\end{array}\right]$$

Equation 20

$${\stackrel{\wedge }{\rho }}_k=SIN{R}_k={\stackrel{\wedge }{h}}_k^H{\left(N_0{I}_{N_R}+{\displaystyle \sum _{\begin{array}{l}i=\mathrm{one}\\ i\ne k\end{array}}^{N_R}{\stackrel{\wedge }{h}}_i{\stackrel{\wedge }{h}}_i^H}\right)}^{-\mathrm{one}}{\stackrel{\wedge }{h}}_k$$

In Equation 20, the part relating to interference and noise can be expressed as follows:

Equation 21

$${\left(N_0{I}_{N_R}+{\displaystyle \sum _{\begin{array}{l}i=\mathrm{one}\\ i\ne k\end{array}}^{N_R}{\stackrel{\wedge }{h}}_i{\stackrel{\wedge }{h}}_i^H}\right)}^{-\mathrm{one}}=\left[\begin{array}{c}\begin{array}{ccc}{a}_{\mathrm{eleven}}^k& a_{12}^k& \cdots \\ a_{21}^k& a_{22}^k& \cdots \\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{a}_{N_R\mathrm{one}}^k& a_{N_{R}2}^k& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{a}_{\mathrm{one}{N}_R}^k\\ a_{2N_R}^k\\ ⋮\end{array}\\ a_{N_R{N}_R}^k\end{array}\right]$$

может быть выражено следующим образом:Newly Accepted SINR $${\stackrel{\wedge }{\rho }}_k$$

can be expressed as follows:

Equation 22

$$\begin{array}{l}{\stackrel{\wedge }{\rho }}_k=SIN{R}_k={\stackrel{\wedge }{h}}_k^H{\left(N_0{I}_{N_R}+{\displaystyle \sum _{\begin{array}{l}i=\mathrm{one}\\ i\ne k\end{array}}^{N_R}{\stackrel{\wedge }{h}}_i{\stackrel{\wedge }{h}}_i^H}\right)}^{-\mathrm{one}}{\stackrel{\wedge }{h}}_k={\stackrel{\wedge }{h}}_k^H\left[\begin{array}{c}\begin{array}{ccc}{a}_{\mathrm{eleven}}^k& a_{12}^k& \cdots \\ a_{21}^k& a_{22}^k& \cdots \\ ⋮& ⋮& ⋮\end{array}\\ \begin{array}{ccc}{a}_{N_R\mathrm{one}}^k& a_{N_{R}2}^k& \cdots \end{array}\end{array}\begin{array}{c}\begin{array}{c}{a}_{\mathrm{one}{N}_R}^k\\ a_{2N_R}^k\\ ⋮\end{array}\\ a_{N_R{N}_R}^k\end{array}\right]{\stackrel{\wedge }{h}}_k\\ ={\displaystyle \sum _{i=\mathrm{one}}^{N_R}{\displaystyle \sum _{j=\mathrm{one}}^{N_R}\stackrel{\wedge }{w}}}{}_k\overrightarrow{h}{}_i^{*}\times a_{ij}\times {\overrightarrow{h}}_j^T{\stackrel{\wedge }{w}}_k\end{array}$$

. Например, $$e^{-j\theta }$$

может быть ±1 или ±j. $${\tilde{W}}_k$$

, полученная посредством умножения k-го столбца на $$e^{-j\theta }$$

, может быть выражена следующим образом:Further, in one precoding matrix, the efficiency for multiplying a particular column vector by $$e^{-j\theta }(0\le \theta \le \pi )$$

. For example, $$e^{-j\theta }$$

may be ± 1 or ± j. $${\tilde{W}}_k$$

obtained by multiplying the kth column by $$e^{-j\theta }$$

can be expressed as follows:

Equation 23

$${\tilde{W}}_k=e^{-j\theta }{\stackrel{\wedge }{W}}_k$$

может быть выражено следующим образом:Accepted SINR $${\tilde{\rho }}_k$$

can be expressed as follows:

Equation 24

$$\begin{array}{l}{\tilde{\rho }}_k={\displaystyle \sum _{i=\mathrm{one}}^{N_R}{\displaystyle \sum _{j=\mathrm{one}}^{N_R}\tilde{w}}}{}_k\overrightarrow{h}{}_i^{*}\times a_{ij}\times {\overrightarrow{h}}_j^T{\tilde{w}}_k={\displaystyle \sum _{i=\mathrm{one}}^{N_R}{\displaystyle \sum _{j=\mathrm{one}}^{N_R}{e}^{+j\theta }\stackrel{\wedge }{w}}}{}_k\overrightarrow{h}{}_i^{*}\times a_{ij}\times {\overrightarrow{h}}_j^T{e}^{-j\theta }{\stackrel{\wedge }{w}}_k\\ ={\displaystyle \sum _{i=\mathrm{one}}^{N_R}{\displaystyle \sum _{j=\mathrm{one}}^{N_R}\stackrel{\wedge }{w}}}{}_k\overrightarrow{h}{}_i^{*}\times a_{ij}\times {\overrightarrow{h}}_j^T{\stackrel{\wedge }{w}}_k={\stackrel{\wedge }{\rho }}_k\end{array}$$

не оказывает влияния на принимаемое SINR и отношение пропускной способности канала связи к сумме.From the result of Equation 24, it can be seen that the multiplication of a particular column vector of the precoding matrix by $$e^{-j\theta }$$

does not affect the received SINR and the ratio of the bandwidth of the communication channel to the sum.

In the MIMO system, various MIMO transmission schemes (transmission modes) may be used. The MIMO transmission / reception scheme used for the operation of the MIMO system may include a Frequency Switching Transmit Diversity (FSTD) scheme, a Spatial Frequency Block Coding (SFBC) scheme, a Spatial-Temporal Block Coding (STBC) scheme, a Cyclic Delay Diversity scheme (CDD), Time Switching Transmit Diversity Scheme (TSTD), etc. At rank 2 or higher, a Spatial Multiplexing (SM) scheme, a Generalized Cyclic Delay (GCDD) diversity scheme, a Selective Virtual Antenna Switcher (S-VAP), etc. may be used.

The FSTD scheme consists in allocating subcarriers with different frequencies to signals transmitted via several antennas in order to obtain diversity gain. The SFBC scheme consists in effectively applying the selectivity of the spatial domain and the frequency domain in order to obtain diversity gain and gain in multi-user scheduling. The STBC scheme consists in applying spatial domain and time domain selectivity. A CDD scheme is to obtain diversity gain using a propagation delay between transmit antennas. The TSTD scheme consists in the time separation of signals transmitted through several antennas. The spatial multiplexing scheme consists of transmitting different data through antennas in order to increase the data transfer rate. The GCDD scheme consists in applying the selectivity of the time domain and the frequency domain. The S-VAP scheme uses a single precoding matrix and includes an S-VAP with Multiple Codewords (MCW) to mix multiple codewords between antennas for spatial diversity or spatial multiplexing and an S-VAP with One Codeword (SCW) using one the codeword.

In accordance with the various MIMO transmission schemes described above (MIMO transmission modes), various scheduling signaling formats (DCI PDCCH formats) can be used. Those. scheduling signaling formats may vary in accordance with various MIMO transmission modes, and user equipment may determine a MIMO transmission mode in accordance with the scheduling signaling format.

In an MIMO system, an open system (or a circuit independent of channel status) without using feedback information from a receiver, and a closed circuit (or circuit depending on channel status) that uses feedback from a receiver can be used. With a closed circuit, the receiver transmits feedback information to the transmitter regarding the channel status, and the transmitter checks the channel status, thereby increasing the efficiency of the wireless communication system. The closed-loop MIMO system uses a precoding scheme to minimize channel effects by allowing the transmitter to perform a predetermined process regarding the transmitted data using feedback information regarding channel conditions transmitted from the receiver. The precoding scheme includes a codebook-based precoding scheme and a precoding scheme for quantizing channel information and returning quantized channel information.

MIMO system in accordance with OFDM and SC-FDMA Scheme

In general, in a MIMO system in accordance with the OFDM scheme and the SC-FDMA scheme, the data signal undergoes complex mapping within transmitted symbols. First, the data is divided into code words. Typically, the code words correspond to the transfer units specified by the MAC layer. Code words are encoded individually using a channel encoder, for example, with a turbo code or convolutional code to form an end bit combination. The coded codewords are matched in speed to the appropriate size and displayed in levels. In the SC-FDMA transmission with respect to the layers, precoding is performed using the Discrete Fourier Transform (DFT), and the DFT is not applied to the OFDM transmission. At each level, DFT signals are multiplied by a vector / precoding matrix and mapped to the transmit antenna port. Transmit antenna ports can be mapped to physical antennas using the antenna virtualization method.

FIG. 6 is a diagram showing the general structure of an SC-FDMA and OFDMA system. In FIG. 6 N is less than M. S-to-P means that the serial signal is converted to a parallel signal, and P-to-S means that the parallel signal is converted to a serial signal. As shown in FIG. 6, in the SC-FDMA system transmitter, the input information symbols pass through the serial-parallel conversion module 611, the N-point DFT module 612, the subcarrier display module 613 and the M-point Inverse DFT (IDFT) module 614, the parallel-serial conversion module 615, a CP adding module 616 and a digital-to-analog conversion module 617 so that the signal is transmitted through the channel. In the receiver of the SC-FDMA system, the signal received through the channel passes through the analog-to-digital conversion module 621, CP removal module 622, serial-parallel conversion module 623, M-point DFT module 624, subcarrier compensation / inverse module 625, N- module 626 a point IDFT, a parallel-serial conversion module 627, and a detection module 628 to recover information symbols. In the OFDMA system, the N-point DFT module 612 and the SC-FDMA system parallel-to-serial conversion module 615 may be omitted, and the parallel-serial conversion may be performed by the CP add module 616. In addition, the serial-parallel conversion module 623 and the N-point IDFT receiver module 626 of the SC-FDMA system may be omitted.

In general, a Third Degree Metric (CM) or Peak Power to Average Power Ratio (PAPR) of a single carrier signal, such as an SC-FDMA transmission signal, is significantly lower than a multi-carrier signal. The CM and PAPR values are related to the dynamic range provided by the Transmitter Power Amplifier (PA). In the case of using the same PA, a transmitted signal with a lower CM or PAPR value than another signal can be transmitted with a higher transmit power. In other words, if the maximum power PA is fixed, then the transmit power is set lower than that of a signal with a low CM or PAPR, in order to allow the transmitter to transmit a signal with a high CM or PAPR. The reason that a single-carrier signal has a lower CM or PAPR value than a multi-carrier signal is that in the case of a multi-carrier signal, many signals overlap each other in order to apply phase matching to the signal. In this case, the signal amplitude may be increased, and the OFDM system may have a high PAPR or CM value.

If the transmitted signal y includes only one information symbol x ₁ , then this signal may be a signal with one carrier in the form y = x ₁ . And if the transmitted signal y includes many information symbols x ₁ , x ₂ , x ₃ , ..., x _N , then this signal can be a signal with several carriers in the form y = x ₁ + x ₂ + x ₃ + ... + x _N. The PAPR or CM value is proportional to the number of information symbols that are logically sequentially summed into a transmission waveform but overflow when the number of information symbols reaches a predetermined value. Accordingly, if the waveform is formed by summing a small number of signals with one carrier, then the CM or PAPR value is significantly lower than that of a signal with several carriers, but have a value slightly larger than that of a signal with one carrier.

FIG. 7 is a diagram showing the structure of an uplink SC-FDMA system of a Version-8 LTE system. The structure of the LTE Version-8 LTE system uplink SC-FDMA system includes a scrambling module 710, a modulation mapping module 720, a transform precoding encoder 730, a resource element mapping module 740, and an SC-FDMA signal generating module 750, as shown in FIG. . 7. As shown in FIG. 7, the transform precoding encoder 730 corresponds to the N-point DFT module 612 in FIG. 6, the resource element mapping module 740 corresponds to the subcarrier mapping module 613 of FIG. 6, and the SC-FDMA signal conditioning module 750 corresponds to the M-point IDFT module 614, the parallel-serial conversion module 615, and the CP adding module 616 in FIG. 6.

FIG. 8 is a diagram showing a frame structure of an uplink SC-FDMA system of an LTE Version-8 LTE system. The basic transmission unit is one subframe. One subframe includes two slots, and the number of SC-FDMA symbols included in one slot is 7 or 6 according to the configuration of the CP (e.g., normal CP or advanced CP). In FIG. 8 shows a normal CP in which one slot includes seven SC-FDMA symbols. At least one SC-FDMA Reference Signal (RS) symbol is included in each slot and is not used for data transmission. Multiple subcarriers are included in one SC-FDMA symbol. Resource Element (RE) is a complex information symbol mapped to a single subcarrier. If DFT precoding is performed, then since the DFT size and the number of subcarriers used for transmission are identical in SC-FDMA, then the RE corresponds to one information symbol mapped to one DFT index.

In the LTE-A system, up to four layers of spatial multiplexing is provided for uplink transmission. In the case of single-user uplink spatial multiplexing, a maximum of two transfer units may be transmitted from the planned UE in one subframe for each component carrier. A component carrier refers to a carrier from an aggregation unit in a carrier aggregation technology for physically aggregating a plurality of component carriers to obtain the same effect as with the logical use of a large band. Modulation symbols associated with each transfer unit may be displayed in one or two levels based on the number of transfer levels. Depending on the mapping between blocks and transport layers, the same principle may be used as the mapping between blocks and transport layers in LTE Version-8 downlink spatial multiplexing. In both cases, when spatial multiplexing is used and not used, the DFT precoding OFDM scheme can be used as an uplink data transmission scheme with multiple access. In the case of multiple component carriers, a single DFT may be applied based on the component carrier. In particular, in the LTE-A system, continuous (contiguous) in frequency and discontinuous (non-contiguous) frequency of resources can be supported for each component of the carrier.

N_L. В целом, ранг передачи пространственно мультиплексированных данных равен количеству (например, N_L) уровней для переноса данных в заданный момент передачи. Как показано на Фиг. 9, модули DFT для передачи сигналов восходящей линии связи, используя схему SC-FDMA, размещены перед кодером предварительного кодирования и после модулей отображения уровней. Таким образом, расширенные DFT сигналы, предварительно закодированные из расчета на уровень, подвергаются сужению IFFT и передаются, тем самым сохраняя характеристики PAPR или CM из-за того, что расширение DFT и сужение IFFT являются смещением по отношению к предварительному кодированию.FIG. 9 is a diagram showing data signal mapping dependencies in a MIMO system based on SC-FDMA transmission. The SC-FDMA system may include level display modules for displaying the signals to be transmitted into levels corresponding to the number of a particular rank, a predetermined number of DFT modules for performing DFT expansion with respect to each of a predetermined number of level signals, and an encoder precoding for selecting a precoding matrix from a codebook stored in the memory and performing precoding with respect to the transmitted signals. In FIG. 9, if the number of codewords is N _C and the number of levels is N _L , then N _C information symbols and information symbols in an amount equal to an integer multiple of N _C can be displayed in N _L levels or in levels in an amount equal to the whole a multiple of N _L. DFT precoding for SC-FDMA does not change the size of the layer. If precoding is performed with respect to the level, then the number of information symbols is changed from N _L to N _T by multiplying the matrix N _T $$\times$$

N _L. In general, the rank of transmitting spatially multiplexed data is equal to the number (for example, N _L ) of levels for transferring data at a given moment of transmission. As shown in FIG. 9, DFT modules for transmitting uplink signals using the SC-FDMA scheme are placed before the precoding encoder and after the layer mapping units. Thus, the extended DFT signals, pre-encoded per level, are IFFT narrowed and transmitted, thereby preserving the PAPR or CM characteristics due to the fact that the DFT extension and IFFT narrowing are biased with respect to precoding.

Reference Signal (RS)

In a radio communication system, since packets are transmitted through radio channels, the signal may be distorted during transmission. In order to allow the receiving side to correctly receive the distorted signal, the distortion of the received signal must be corrected using channel information. In order to detect channel information, a signal transmission method that both the transmitting side and the receiving side is aware of, and a channel information detection method using the degree of distortion when the signal is received through the channel, are mainly used. The signal mentioned above is referred to as a pilot signal or reference signal (RS).

When transmitting and receiving data using multiple antennas, in order to correctly receive the signal, the state of the channel between the transmitting antennas and the receiving antennas must be detected. Accordingly, each transmit antenna has a separate RS.

The downlink RS includes a Common RS (CRS) shared by all UEs in a cell, and a dedicated RS (DRS) for a specific UE only. Using such RSs, information can be provided for channel estimation and demodulation.

The receiving side (UE) evaluates the channel status by CRS and returns an indicator related to channel quality, such as Channel Quality Indicator (CQI), Pre-Coding Matrix Index (PMI) and / or Rank Indicator (RI), transmitting side (eNodeB). CRS may also be referred to as RS for a particular cell.

DRS can be transmitted via RE if data demodulation on PDSCH is required. The UE may accept the presence / absence of DRS from a higher layer and receive information indicating that the DRS is valid only when the PDSCH is displayed. DRS may also be called predefined for UE RS or RS Demodulation (DMRS).

частоту по оси времени. Т.е. по оси времени один RB имеет длину в 14 символов OFDM в случае нормального CP.FIG. 10 is a diagram showing a pattern of CRS and DRS mapped to a downlink RB defined in an existing 3GPP LTE system (e.g., Version-8). Downlink RB as an RS mapping unit may be expressed in units of 12 subcarriers in one subframe $$\times$$

frequency along the time axis. Those. along the time axis, one RB has a length of 14 OFDM symbols in the case of normal CP.

FIG. 10 shows RS positions in RBs in a system in which an eNodeB supports four transmit antennas. In FIG. 10 Resource Elements (RE), designated as “0”, “1”, “2” and “3”, indicate the positions of the CRS indices of 0, 1, 2 and 3 antenna ports. In FIG. 10 RE, designated as "D", indicates the position of the DRS defined in LTE Version-8 (or Version-9). The following describes in detail CRS.

CRS is used to estimate the channel of the physical antenna port and is distributed throughout the band as RS, which, as a rule, can be received by all located in the cell UE. CRS can be used to obtain CSI and demodulate data.

CRS is defined in various formats according to the configuration of the transmitting side antenna (eNodeB). The 3GPP LTE system (e.g., Version-8) supports various antenna configurations, and the downlink side (eNodeB) has three antenna configurations: one antenna, two transmit antennas and four transmit antennas. If the eNodeB transmits with a single antenna, then RSs are organized for one antenna port. If the eNodeB transmits with two antennas, then RSs are organized for the two antenna ports using the Time Division Multiplexing (TDM) and / or Frequency Division Multiplexing (FDM) scheme. Those. RSs for two antenna ports are organized in different time resources and / or different frequency resources so that they can be distinguished from each other. In addition, if the eNodeB is transmitting with four antennas, then RSs for the four antenna ports are organized using the TDM / FDM scheme. Channel information estimated by the CRS side (UE) receiving the downlink signal can be used to demodulate data transmitted using a transmission scheme such as single antenna transmission, transmission diversity, closed spatial multiplexing, open spatial multiplexing or Multi-user MIMO (MU-MIMO).

If multiple antennas are supported, then when RSs are transmitted from a specific antenna port, RSs are transmitted in RE positions indicated in accordance with the RS pattern, and no signal is transmitted in REs specified for another antenna port.

The rule for mapping CRS to RB is defined by Equation 25.

Equation 25

$$\begin{array}{l}k=6m+(v+v_{shift})\mathrm{mod}6\\ l=\{\begin{array}{c}\begin{array}{ccc}0N_{symb}^{DL}-3& e\mathrm{from}l\mathrm{and}& p\in \left\{0.1\right\}\end{array}\\ \begin{array}{ccc}\mathrm{one}& e\mathrm{from}l\mathrm{and}& p\in \left\{\mathrm{2,3}\right\}\end{array}\end{array}\\ m=\mathrm{0,1,\; ...,\; 2}\cdot N_{RB}^{DL}-\mathrm{one}\\ m^{\prime }=m+N_{RB}^{\max ,DL}-N_{RB}^{DL}\\ v=\{\begin{array}{c}\begin{array}{ccc}0& e\mathrm{from}l\mathrm{and}& \begin{array}{ccc}p=0& \mathrm{and}& l=0\end{array}\\ 3& e\mathrm{from}l\mathrm{and}& \begin{array}{ccc}p=0& \mathrm{and}& l\ne 0\end{array}\\ 3& e\mathrm{from}l\mathrm{and}& \begin{array}{ccc}p=\mathrm{one}& \mathrm{and}& l=0\end{array}\end{array}\\ \begin{array}{ccc}0& e\mathrm{from}l\mathrm{and}& \begin{array}{ccc}p=\mathrm{one}& \mathrm{and}& l\ne 0\end{array}\\ 3(n_s\mathrm{mod}2)& e\mathrm{from}l\mathrm{and}& p=2\\ 3+3(n_s\mathrm{mod}2)& e\mathrm{from}l\mathrm{and}& p=3\end{array}\end{array}\\ v_{shift}=N_{ID}^{cell}\mathrm{<figure-callout\; id="6"\; label="mod"\; filenames="00000082.png,00000085.png"\; state="\{\{state\}\}">mod</figure-callout>}6\end{array}$$

обозначает количество символов OFDM одного слота нисходящей линии связи, $$N_{RB}^{DL}$$

обозначает количество RB, выделенных нисходящей линии связи, n_S обозначает индекс слота, а $$N_{ID}^{cell}$$

обозначает ID соты. mod обозначает операцию по модулю. Позиция RS в частотной области зависит от значения V_shift. Поскольку значение V_shift зависит от ID соты, то позиция RS имеет значение частотного сдвига, который меняется в соответствии с сотой.In Equation 25, k is the subcarrier index, l is the symbol index, and p is the antenna port index. $$N_{symb}^{DL}$$

denotes the number of OFDM symbols of one downlink slot, $$N_{RB}^{DL}$$

denotes the number of RBs allocated downlink, n _S denotes the slot index, and $$N_{ID}^{cell}$$

denotes a cell ID. mod stands for modulo operation. The position of RS in the frequency domain depends on the value of V _shift . Since the V _shift value depends on the cell ID, the RS position has a frequency shift value that changes in accordance with the cell.

To increase the efficiency of channel estimation by CRS, CRS positions in the frequency domain can be shifted to vary in accordance with cells. For example, if RSs are located in the interval of three subcarriers, then RSs will be located in 3k subcarriers in one cell and placed in (3k + 1) subcarriers in another cell. Given one antenna port, RSs are arranged in an interval of 6 REs (i.e., an interval of 6 subcarriers) in the frequency domain and are separated from the REs that host the RSs allocated for the other antenna port by 3 REs in the frequency domain.

In addition, power enhancement is applied to CRS. A power increase indicates that RSs are transmitted using higher power by attracting RE powers, excluding the REs allocated to RS among the REs of one OFDM symbol.

In the time domain, RSs are placed from the index (l = 0) of the symbol of each slot, as a starting point, at a constant interval. The time interval is determined differently according to the length of the CP. RSs are located at 0 and 4 character indices of the slot in the case of normal CP and are placed at 0 and 3 character indices of the slot in the case of extended CP. Only one maximum of two antenna ports are defined in one OFDM symbol. Accordingly, in relation to transmission with four transmitting antennas, RS for antenna ports 0 and 1 are located at 0 and 4 character indexes (0 and 3 character indices in case of extended CP) slots, and RS for antenna ports 2 and 3 are located at 1 character index slots. The RS frequency positions for antenna ports 2 and 3 in the frequency domain change with respect to each other in the second slot.

In order to provide spectrum efficiency at a higher level than the existing 3GPP LTE system (e.g., Version-8), a system (e.g., LTE-A system) with an expanded antenna configuration can be created. An expanded antenna configuration may have, for example, eight transmit antennas. In an advanced antenna configuration system, support is required for UEs that operate in an existing antenna configuration, i.e., backward compatibility is required. Accordingly, it is necessary to maintain the RS pattern in accordance with the existing antenna configuration and create a new RS pattern for the additional configuration of the antenna. If the CRS for new antenna ports is added to the system with the existing antenna configuration, then RS losses quickly increase and thus the data transfer speed drops. Given these issues, the creation of a new RS (CSI-RS) is required to measure CSI for new antenna ports. Details regarding them will be described after the description of DRS. The following is described in detail DRS.

DRS (or RS for a specific UE) is used to demodulate data. The precoding weight used for a particular UE when transmitting with multiple antennas is also used unchanged in the RS to evaluate the equivalent channel in which the forwarding channel and the precoding weight transmitted from each transmit antenna are combined when the UE receives the RS.

The existing 3GPP LTE system (for example, Version-8) supports transmission with a maximum of four transmitting antennas and is defined by DRS to generate a rank 1 radiation pattern. DRS to generate a rank 1 radiation pattern is also indicated by RS for the antenna port index 5. The DRS rule mapped to RB is defined by Equations 26 and 27. Equation 26 is for normal CP, and Equation 27 is for advanced CP.

Equation 26

$$\begin{array}{l}k=(k^{\prime })\mathrm{mod}{N}_{sc}^{RB}+N_{sc}^{RB}\cdot n_{PRB}\\ k^{\prime }=\{\begin{array}{c}\begin{array}{ccc}\mathrm{four}{m}^{\prime }+v_{shift}& e\mathrm{from}l\mathrm{and}& l\in \left\{\mathrm{2,3}\right\}\end{array}\\ \begin{array}{ccc}\mathrm{four}{m}^{\prime }+(2+v_{shift})\mathrm{mod}\mathrm{four}& e\mathrm{from}l\mathrm{and}& l\in \left\{\mathrm{5,6}\right\}\end{array}\end{array}\\ l=\{\begin{array}{c}\begin{array}{cc}3& l^{\prime }=0\\ 6& l^{\prime }=\mathrm{one}\end{array}\\ \begin{array}{cc}2& l^{\prime }=2\\ 5& l^{\prime }=3\end{array}\end{array}\\ l^{\prime }=\{\begin{array}{c}\begin{array}{ccc}0.1& e\mathrm{from}l\mathrm{and}& n_s\mathrm{<figure-callout\; id="2"\; label="mod"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">mod</figure-callout>}2=0\end{array}\\ \begin{array}{ccc}\mathrm{2,3}& e\mathrm{from}l\mathrm{and}& n_s\mathrm{<figure-callout\; id="2"\; label="mod"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">mod</figure-callout>}2=\mathrm{one}\end{array}\end{array}\\ m^{\prime }=\mathrm{0,1,\; ...,\; 3}{N}_{RB}^{PDSCH}-\mathrm{one}\end{array}$$

Equation 27

$$\begin{array}{l}k=(k^{\prime })\mathrm{mod}{N}_{sc}^{RB}+N_{sc}^{RB}\cdot n_{PRB}\\ k^{\prime }=\{\begin{array}{c}\begin{array}{ccc}3m^{\prime }+v_{shift}& e\mathrm{from}l\mathrm{and}& l=\mathrm{four}\end{array}\\ \begin{array}{ccc}3m^{\prime }+(2+v_{shift})\mathrm{mod}3& e\mathrm{from}l\mathrm{and}& l=\mathrm{one}\end{array}\end{array}\\ l=\{\begin{array}{cc}\mathrm{four}& l^{\prime }\in \left\{0.2\right\}\\ \mathrm{one}& l^{\prime }=\mathrm{one}\end{array}\\ l^{\prime }=\{\begin{array}{c}\begin{array}{ccc}0& e\mathrm{from}l\mathrm{and}& n_s\mathrm{<figure-callout\; id="2"\; label="mod"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">mod</figure-callout>}2=0\end{array}\\ \begin{array}{ccc}\mathrm{1,2}& e\mathrm{from}l\mathrm{and}& n_s\mathrm{<figure-callout\; id="2"\; label="mod"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">mod</figure-callout>}2=\mathrm{one}\end{array}\end{array}\\ m^{\prime }=\mathrm{0,1,\; ...,\; 4}{N}_{RB}^{PDSCH}-\mathrm{one}\\ v_{shift}=N_{ID}^{cell}\mathrm{<figure-callout\; id="3"\; label="mod"\; filenames="00000077.png,00000082.png"\; state="\{\{state\}\}">mod</figure-callout>}3\end{array}$$

обозначает размер ресурсного блока в частотной области и выражается количеством поднесущих. $$n_{PRB}$$

обозначает номер физического ресурсного блока. $$N_{RB}^{PDSCH}$$

обозначает ширину полосы RB передачи PDSCH. n_s обозначает индекс слота, а $$N_{ID}^{cell}$$

обозначает ID соты. mod обозначает операцию по модулю. Позиция RS в частотной области зависит от значения V_shift. Поскольку значение V_shift зависит от ID соты, то позиция RS имеет значение частотного сдвига, которое меняется в соответствии с сотой.In Equations 26 and 27, k denotes the subcarrier index, l denotes the symbol index, and p denotes the index of the antenna port. $$N_{SC}^{RB}$$

denotes the size of the resource block in the frequency domain and is expressed by the number of subcarriers. $$n_{PRB}$$

denotes the number of the physical resource block. $$N_{RB}^{PDSCH}$$

denotes the bandwidth of the RB transmit PDSCH. n _s denotes the slot index, and $$N_{ID}^{cell}$$

denotes a cell ID. mod stands for modulo operation. The position of RS in the frequency domain depends on the value of V _shift . Since the V _shift value depends on the cell ID, the RS position has a frequency shift value that changes in accordance with the cell.

In the LTE-A system, which is a developed version of the 3GPP LTE system, higher-order MIMOs, multi-cell transmission, an advanced MU-MIMO scheme, or the like are considered. In order to provide effective RS control and developed transmission schemes, data demodulation based on DMRS is considered. Those. in order to support data transmission through the added antennas separately from the DMRS (index 5 of the antenna ports) to form the radiation pattern of Rank 1 defined in the existing 3GPP LTE system (for example, Version-8), DMRS for two or more levels can be determined. Since DMRS is precoded with the same precoding encoder as the data, the receiving side can easily evaluate channel information for demodulating the data without separating the precoding information.

By organizing DMRSs supporting radio transmission with a maximum Rank of 8, DMRSs for layers can be multiplexed and organized. Time Division Multiplexing (TDM) indicates that DMRSs for two or more layers are located at different time resources (eg, OFDM symbols). Frequency Division Multiplexing (FDM) indicates that DMRSs for two or more layers are located on different frequency resources (e.g., subcarriers). Code Division Multiplexing (CDM) indicates that DMRSs for two or more layers located on the same radio resources are multiplexed using an orthogonal sequence (or orthogonal overlap).

FIG. 11 is a diagram showing an example of a DMRS template supporting transmission with a maximum Rank-8. In FIG. 11, a control area (first through third symbols of one subframe) indicates REs over which PDCCHs may be transmitted. The CRSs for the 4 transmit antennas indicate the REs in which the CRSs for those described with reference to FIG. 10 ports “0”, “1”, “2” and “3” antennas. In this case, the value of V _shift is 0.

In general, in the case of SU-MIMO transmission, the number of DMPS antenna ports (or virtual antenna ports) used for data transmission is equal to the transmission rank for data transmission. In this case, DMRS antenna ports (or virtual antenna ports) can be numbered 1 through 8, and the smallest “N” DMRS antenna port can be used to transmit SU-MIMO rank “N”.

If the DMRS antenna ports are numbered as shown in FIG. 11, the total number of REs for which data is not transmitted due to the organization of the DMRS within one transmission layer is determined in accordance with the transmission rank. At a low rank (for example, Rank 1 or 2), the number of REs used to transmit the DMRS may be 12 in one RB. At a high rank (for example, a Rank of 3 to 8), the number of REs used to transmit the DMRS may be 24 in one RB. That is, as shown in FIG. 11, in the case of Rank 2, DMRS for levels 1 and 2 can be transmitted in 12 REs (RE shown by the DMRS positions for levels 1, 2, 5, and 7 in Fig. 11), and in the case of Rank 3, DMRS for levels 1 and 2 are transmitted in 12 REs, and DMRSs for layer 3 can be transmitted in 12 additional REs (REs shown by the DMRSs for layers 3, 4, 6 and 8 in FIG. 11). The RE positions in which DMRSs are located for each level are exemplary, and the present invention is not limited to this.

CSI-RS Template

The present invention proposes a new method of organizing (multiplexing) CSI-RS radio resources, taking into account the above positions CRS and DMRS. CSI-RSs may be transmitted by the base station and may be used by the UE to evaluate CSI. CSI measured by CSI-RS may include precoding information (eg, Pre-Coding Matrix Index (PMI)); the number of preferred transmission levels (e.g., Rank Indicator (RI)); and a preferred Modulation and Coding Scheme (MCS) (e.g., Channel Quality Indicator (CQI)).

CRS are necessary for the correct functioning of the UE (existing UE), which operates in accordance with the existing LTE system, and DMRS are necessary for easy demodulation of data with an expanded antenna configuration. Accordingly, in order to ensure efficient reception of channel information by the downlink receiving side via CSI-RS, it is necessary to determine the CSI-RS pattern (positions in resource blocks) so that the maximum number of CSI-RSs is transmitted taking into account CRS and DMRS organization radio resources. This is done so that the UE can correctly evaluate the channel between the serving cell and the UE when resolving the conflict between the CSI-RS from the neighboring cell and the CSI-RS from the serving cell. Accordingly, with the increase in the number of distinguishable CSI-RS patterns that can be used by the serving cell, it is possible to guarantee an increase in channel estimation efficiency through CSI-RS.

In the present invention, REs used by the CSI-RS group of antenna ports are grouped, and the CSI-RS RE group includes adjacent REs that are available in the frequency domain. The configuration of the CSI-RS group using adjacent REs in the frequency domain serves to prevent the destruction of the base transmission block for transmission diversity schemes such as Spatial Frequency Block Coding (SFBC) and SFBC-FSTD Transmission Frequency Diversity (SFBC-FSTD), which may occur due to the organization of CSI-RS. In more detail, since in REs in which CSI-RSs are transmitted, data cannot be transmitted, if the data is transmitted in the base transmission unit for transmit diversity, and CSI-RSs are located only in part of the transmission base unit, transmission diversity RE pairs for data transmission can be destroyed.

один RB (12 поднесущих) в частотной области). Т.е. доступные RE, в которых могут быть размещены CSI-RS, соответствуют невыделенным RE на Фиг. 11.Available REs relate to REs that do not include CRS and DMRS in the data area, excluding control areas (first to third OFDM symbols of the downlink subframe) in the RB downlink (one subframe (12 or 14 OFDM symbols) in the time areas of $$\times$$

one RB (12 subcarriers) in the frequency domain). Those. the available REs in which CSI-RSs can be located correspond to the unallocated REs in FIG. eleven.

Examples of the CSI-RS RE group are shown in FIG. 12-16.

In FIG. 12 shows an example of arranging CSI-RS RE groups on two adjacent subcarriers. In FIG. 12 it can be seen that the CSI-RS RE groups are defined in RE, excluding REs in which CRS and DMRS are located.

In FIG. 13 shows an example of arranging CSI-RS RE groups on four adjacent subcarriers. In FIG. 13, it may seem that a particular CSI-RS RE group is located on five subcarriers. However, since CSI-RSs are not transmitted to the REs hosting the CRS from among the CSI-RS REs, it can be seen that the CSI-RS REs are placed in four REs.

In FIG. 14 shows an example of arranging CSI-RS RE groups on two adjacent subcarriers. In FIG. 14 you can see that the CSI-RS RE groups are not defined in the OFDM symbols in which the CRSs are located.

In FIG. 15 shows an example of arranging CSI-RS RE groups on four adjacent subcarriers. In FIG. 15, it can be seen that CSI-RS RE groups are not defined in OFDM symbols in which CRS and DMRS are located.

In FIG. 16 shows an example of arranging CSI-RS RE groups on four adjacent subcarriers. In FIG. 16, it is noted that CSI-RSs are not transmitted at RE CRS positions. In FIG. 16, it can be seen that CSI-RS RE groups are not defined in OFDM symbols in which DMRSs are located.

Shown in FIG. 12-16 CSI-RS RE groups are used to transmit the CSI-RS set by the antenna ports of one cell. For example, if one cell is transmitting using two CSI-RS antenna ports and the CSI-RS RE group size is 2, then the CSI-RS RE for two CSI-RS antenna ports can be mapped to one CSI-RS RE group. If one cell transmits using four CSI-RS antenna ports and the CSI-RS RE group size is 4 RE, then the CSI-RS RE for four CSI-RS antenna ports can be mapped to one CSI-RS RE group. If one cell transmits using eight CSI-RS antenna ports and the CSI-RS RE group size is 4 RE, then the CSI-RS RE for eight CSI-RS antenna ports can be mapped to two CSI-RS RE groups. It is not required that two CSI-RS RE groups be placed continuously (i.e., adjacent) and they can be placed in specific CSI-RS RE groups in RB.

In a simple embodiment of channel estimation, the CSI-RS RE pattern can be equally configured across the entire bandwidth (in a subframe that does not include at least a primary broadcast channel, a primary synchronization channel, and a secondary synchronization channel). Mapping CSI-RS antenna ports to fewer CSI-RS groups is important in the case where the cell supports transmit diversity for a particular base station. If CSI-RS REs are distributed among a plurality of CSI-RS groups, then a plurality of RE pairs encoded in the SFBC spatio-temporal coding scheme can be destroyed with respect to the transmission diversity scheme. This is because the SFBC and SFBC-FSTD transmission diversity schemes use a RE base unit to which spatial frequency coding and / or antenna-selective / frequency-selective diversity is applied. CSI-RS transmission in certain REs can destroy base diversity blocks and decrease transmission diversity scheme efficiency.

Among the embodiments of the CSI-RS RE group of the present invention, embodiments of the CSI-RS RE groups shown in FIG. 12, 14 and 16 are more preferred with respect to other embodiments, since none of the CSI-RS REs mapped to one CSI-RS RE group destroys any one or more SFBC RE pairs. However, in the present invention, CSI-RS RE groups defined in FIG. 13 and 15.

According to FIG. 17 in OFDM symbols that do not include CRS or DMRS, one CSI-RS RE group (each includes four REs) in one RB can be defined by four adjacent REs. CSI-RS RE groups do not intersect with each other. CSI-RS RE groups are equal to the base RE group (s) to which transmission diversity is applied. If each CSI-RS RE group has only two REs, then the CSI-RS RE group can be defined by two adjacent REs.

As shown in FIG. 18, if the CSI-RS RE group includes four REs, then the CSI-RS RE group located in the same OFDM symbols as the DMRS RE may not include four adjacent available REs belonging to the same transmission diversity RE group . In this case, the CSI-RS RE group located in the same OFDM symbols as the DMRS RE can be defined as two sets, each of which includes two REs, and each set may include two adjacent REs belonging to different transmission diversity RE groups. In FIG. 18, a single rectangle surrounded by a solid bold line indicates a set including two REs, and a group of two rectangles surrounded by a solid bold line configures one group of CSI-RS REs. With this definition of the CSI-RS RE group, the CSI-RS RE group including four REs defines two RE sets, and Alamouti coding (SFBC) and antenna / frequency selective diversity can be used across two RE sets. This is because of the four adjacent REs (four adjacent REs, including one rectangle surrounded by a bold dashed line, and one rectangle surrounded by a bold solid line, and, accordingly, two base transmit diversity blocks, each of which includes four adjacent REs shown in Fig. 18) the first two REs (for example, a rectangle surrounded by a bold dashed line) are mapped to common antenna ports 0 and 2 encoded using SFBC, and the next two REs (for example, a rectangle circled in bold solid line) are mapped to common antenna ports 1 and 3, encoded using SFBC. Those. in a transmit diversity base unit including four adjacent REs, if CSI-RS REs are mapped to the first two REs, then the first two REs cannot be used for common antenna ports 0 and 2. Similarly, in a transmit diversity base unit including four adjacent REs, if the CSI-RS REs are mapped to the last two REs, then the last two REs cannot be used for common antenna ports 1 and 3. Accordingly, if the last two REs of the same transmit diversity base unit (first four adjacent REs) are taken and first two REs of another base unit ra transmit (the next four adjacent REs), it is possible to configure a virtual transmit diversity base unit using four REs. The determination of the RE CSI-RS group from OFDM symbols including DRMS is important in that it is possible to effectively maintain the puncture balance of all common antenna ports 0, 1, 2, and 3 when the CSI-RS REs are mapped to certain types of CSI-RE groups RS. The puncture indicates that if CSI-RSs are transmitted over specific REs, then REs cannot be used for common antenna ports.

As shown in FIG. 19, if the CSI-RS RE group includes four REs, then the CSI-RS RE group located in the same OFDM symbols as the CRS RE may not include four adjacent available REs belonging to the same transmission diversity RE group . Conceptually, CSI-RS RE groups can be configured in OFDM symbols including CRS, as shown in FIG. 19. Through this configuration of the RE CSI-RS group, the puncture balance of common antenna ports can be effectively maintained.

As shown in FIG. 20, the CSI-RS RE of the antenna port mapped to the CSI-RS RE group can change (shift or shuffle) within each CSI-RS transmission subframe. In FIG. 20 “1”, “2”, “3” and “4” denote the REs used for CSI-RS antenna ports 0, 1, 2 and 3.

Hopping can be done in many ways.

N субкадрах, N≥2). N может быть, например, 4, а четыре радиокадра соответствуют периоду, в котором передается первичный широковещательный канал.For example, in each transmission subframe, the time and frequency offset of the CSI-RS RE group is determined. The CSI-RS RE group hopping pattern may be repeated once in one radio frame (10 subframes) or N radio frames (10 $$\times$$

N subframes, N≥2). N may be, for example, 4, and four radio frames correspond to the period in which the primary broadcast channel is transmitted.

As another example, a virtual index of a CSI-RS group is defined, and a mapping function of a step change (shuffle or permutation) is defined to map a virtual index of a CSI-RS group to a physical index of a CSI-RS group (see Fig. 21). In such a display function, a virtual index cyclic shift method, a subunit interleaver or a Quadratic Permutation Polynomial (QPP) interleaver may be used.

In the virtual index cyclic shift method, the CSI-RS group is mapped to the virtual index. In connection with the cyclic shift of the virtual index, a case may be considered where the UE operates in accordance with the Cooperative Multipoint (CoMP) transmission scheme. The CoMP transmission scheme is an advanced MIMO transmission scheme applied to a multi-cell environment, which can increase the throughput of a UE located at a cell boundary and improve system efficiency. A collaborative processing scheme for cooperative beamforming may be used. In a CoMP transmission scheme, a UE that receives data through the cooperation of several cells can transmit information over channels from several cells to the UE to each cell belonging to several cells (CoMP transmission cluster). Virtual indices can be set so as not to overlap with each other between cells belonging to the same CoMP transmission cluster. Cells belonging to different CoMP clusters can use the same virtual indexes, but each CoMP cluster can cyclically shift indexes when virtual indexes are mapped to physical indexes. As a result of this, orthogonal mapping of the CSI-RS RE group within one CoMP cluster is possible. A non-orthogonal mapping of the RE CSI-RS group between different CoMP clusters and a different mapping of the RE CSI-RS group between different CoMP clusters by cyclic shift of virtual indices are possible.

Further, a block interleaver may be used to mix the display of the CSI-RS RE group between cells. The indexes of the RE CSI-RS groups can be defined as v _k (k = 1, 2, ..., L), and L can denote the input size of the interleaver. The block interleaver is configured by a matrix, and input information can be written to the interleaver in rows, and output information can be read from the interleaver in columns. Those. when the information is written to the interleaver, the information is written in one line, increasing the column number, and the information is written in the next line if one line is filled. When information is read from an interleaver, information is read from one column, increasing the row number, and information is read from the next column when all information is read from the first column. The columns of the matrix configuring the block interleaver can be rearranged. Alternatively, a block interleaver may be configured such that information is recorded in columns and information is read in rows.

If the block interleaver described above is used, then the indices of the CSI-RS group can be mixed efficiently. The following equation shows an example of a block interleaver matrix into which CSI-RS indices are entered row by row.

Equation 28

$$D=\left[\begin{array}{cccc}{v}_{\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="00000058.png,00000077.png"\; state="\{\{state\}\}">v</figure-callout>}}_2& \cdots & v_N\\ v_{N+\mathrm{one}}& v_{N+2}& \cdots & v_{2N}\\ ⋮& ⋮& \ddots & ⋮\\ v_{(M-\mathrm{one})N+\mathrm{one}}& v_{(M-\mathrm{one})N+2}& \cdots & v_{MN}\end{array}\right]$$

In Equation 28, M is the largest integer satisfying L≤MN. In the case of MN> L, N _D = MN-L and v _{L + j} = [Empty] (j = 1, 2, ..., N _D ) can be determined. Those. if the number L of indexes of CSI-RS groups does not correspond exactly to the size of the matrix of the block interleaver, then an empty value can be inserted into the elements in the number N _D obtained by subtracting the number L of indices of CSI-RS groups from the size MN of the interleaver. An empty value is discarded when output from the block interleaver. Those. CSI-RS group indices are read from the interleaver, excluding null values. The permutation of the block interleaver columns can be defined as follows:

Equation 29

$$\pi =\left\{\pi (i)=j\right\}i,j,=\mathrm{1,2,\; ...,}N$$

The matrix subjected to column swap operations in accordance with Equation 29 may be expressed as follows:

Equation 30

$$F=\left[\begin{array}{cccc}{v}_{\pi (\mathrm{one})}& v_{\pi (2)}& \cdots & v_{\pi (N)}\\ v_{\pi (\mathrm{one})+N}& v_{\pi (2)+N}& \cdots & v_{\pi (N)+N}\\ ⋮& ⋮& \ddots & ⋮\\ v_{\pi (\mathrm{one})+(M-\mathrm{one})N}& v_{\pi (2)+(M-\mathrm{one})N}& \cdots & v_{\pi (N)+MN}\end{array}\right]$$

The output of the block interleaver can be read in columns. In Equation 30, data output begins with v _{Π (1) of the} first column and the sequence of output of indices can be {v _{Π (1) + N} , ..., v _{Π (1) + (M-1) N} , v _{Π (2)} , ..., v _{Π (N) + MN} }. If an empty value is present, then the empty value, as described above, may be ignored when reading.

Different CoMP clusters may use different column permutations or different cyclic shift values may be applied before the CSI-RS group indexes are displayed in the interleaver matrix. Thus, different mixing of CSI-RS group indices can be applied in different CoMP clusters.

FIG. 22 shows an example of a CSI-RS RE group in the case of eight transmit antennas. In the case of eight transmit antennas, eight CSI-RSs are required to be transmitted to the UE. In the present embodiment, when a normal CP subframe is configured in the cell, a CSI-RS RE group with four SFBC encoded RE pairs is proposed. One CSI-RS RE group includes two RE sets, and one RE set includes two RE pairs (i.e., four REs). Those. within one RE set, four REs are adjacent in the time and frequency domains (a square surrounded by a bold solid line in FIG. 22 corresponds to one RE set), and two RE sets can be separated by four subcarriers in the frequency domain. Thus, from the point of view of the transmitter, the same CSI-RS RE group pattern can be used in OFDM symbols with DMRS and OFDM symbols without CRS or DMRS. The RE positions circled in FIG. 22 with a bold dashed line, serve to effectively maintain the puncture balance of the common antenna ports in the base transmission diversity unit, similar to the description in FIG. eighteen.

In the present embodiment, CSI-RS RE groups are shifted in the time and / or frequency domain in each cell. Those. the CSI-RS RE group template can be used in one cell, and the time-shifted and / or frequency-shifted template of this CSI-RS RE group template can be used in another cell.

12 поднесущих в частотной области), позиция группы RE CSI-RS, обозначенная как 1, соответствует третьей, четвертой, девятой и десятой позициям поднесущей в шестом и седьмом символах OFDM, позиция группы RE CSI-RS, обозначенная как 2, соответствует первой, второй, седьмой и восьмой позициям поднесущей в десятом и одиннадцатом символах OFDM, позиция группы RE CSI-RS, обозначенная как 3, соответствует третьей, четвертой, девятой и десятой позициям поднесущей в десятом и одиннадцатом символах OFDM, позиция группы RE CSI-RS, обозначенная как 4, соответствует пятой, шестой, одиннадцатой и двенадцатой позициям поднесущей в десятом и одиннадцатом символах OFDM, и позиция группы RE CSI-RS, обозначенная как 5, соответствует третьей, четвертой, девятой и десятой позициям поднесущей в тринадцатом и четырнадцатом символах OFDM. Соответственно, разные шаблоны групп RE CSI-RS могут одновременно использовать пять сот.Each cell may skip between the possible options for the position of the CSI-RS RE group at each transmission moment in relation to the CSI-RS transmission. Examples of possible position options of the CSI-RS RE group are shown in FIG. 23. I.e. two squares surrounded by a bold solid line, indicated by 1 in FIG. 23, represent one possible variation of the position of the RE CSI-RS group and, likewise, two squares surrounded by a bold solid line, indicated by 2, 3, 4 or 5, represent possible variations of the position of the RE CSI-RS group. For example, in one RB (14 OFDM symbols in the time domain $$\times$$

12 subcarriers in the frequency domain), the position of the CSI-RS RE group, designated as 1, corresponds to the third, fourth, ninth and tenth subcarrier positions in the sixth and seventh OFDM symbols, the position of the CSI-RS RE group, indicated as 2, corresponds to the first, second , seventh and eighth subcarrier positions in the tenth and eleventh OFDM symbols, the position of the CSI-RS RE group, denoted by 3, corresponds to the third, fourth, ninth and tenth subcarrier positions in the tenth and eleventh OFDM symbols, the position of the CSI-RS RE group, denoted as 4, corresponds to the fifth, sixth, the eleventh and twelfth subcarrier positions in the tenth and eleventh OFDM symbols, and the CSI-RS RE group position, denoted as 5, corresponds to the third, fourth, ninth and tenth subcarrier positions in the thirteenth and fourteenth OFDM symbols. Accordingly, different CSI-RS RE group templates can simultaneously use five cells.

From the point of view of the transmitting antenna, the transmit power can be redistributed in the frequency domain, but cannot be redistributed in the time domain. In other words, if the total transmit power is limited, then certain REs of one OFDM symbol can borrow power from other REs within the OFDM symbol in order to realize a power increase. If the CSI-RSs for different antenna ports are multiplexed and orthogonalized, then the orthogonality cannot be maintained when a different power increase is applied to each CSI-RS. In order to maintain orthogonality, it is required to transmit all CSI-RSs in the same OFDM symbol, so that the CSI-RSs borrow the same power from other REs in order to realize a power increase. If the CSI-RS RE group is defined as shown in FIG. 23, two methods may be considered for displaying CSI-RS antenna ports. Examples of two methods are shown in FIG. 24 (a) and 24 (b).

In FIG. 24 (a) two squares surrounded by a bold solid line inside one RB show one RE CSI-RS group. For clarity, other REs are not shown. According to the first display method shown in FIG. 24 (a), the CSI-RS mapping can be switched between RBs and all CSI-RS antenna ports can be effectively mapped to the same OFDM symbol. More specifically, within a CSI-RS RE group with an odd RB index, CSI-RSs for four antenna ports are mapped to the first OFDM symbol (e.g., 1.2 / 3.4), and CSI-RSs for the remaining four antenna ports are mapped to the second OFDM symbol (e.g., 5.6 / 7.8). A CSI-RS mapping with an even RB index is performed back to that with an odd RB index in the time domain, and CSI-RS insertion patterns are changed between OFDM symbols. Those. within a CSI-RS RE group with an even RB RBI, CSI-RSs for four antenna ports are mapped to the first OFDM symbol (e.g., 5.6 / 7.8), and CSI-RSs for the remaining antenna ports are mapped to a second OFDM symbol (e.g. 1.2 / 3.4). Thus, CSI-RSs for all eight transmit antenna ports can be mapped to a single OFDM symbol (two RBs each).

In FIG. 24 (b) the horizontal axis denotes the frequency domain, and the vertical axis denotes the code resource region. Although in FIG. 24 (b) to describe a case in which CSI-RS RE groups use different code resources, two CSI-RS RE groups are shown (one CSI-RS RE group includes two squares surrounded by a bold solid line), it is noted that CSI-RS RE groups are represented at the same time / frequency position. According to the second display method shown in FIG. 24 (b), four CSI-RSs (1,2 / 3,4) can be multiplied by the first orthogonal code {+1, +1} and placed in one OFDM symbol using the FDM scheme, and the remaining four CSI-RSs ( 5.6 / 7.8), can be multiplied by the second orthogonal code {+1, -1} and placed in the same OFDM symbol and subcarrier. Thus, all CSI-RSs for eight antenna ports can be transmitted in the same OFDM symbol within the same RB. Since the number of REs available for CSI-RS transmission in one OFDM symbol is 4, two CSI-RS sets can undergo CDM using orthogonal time extension codes. Time domain orthogonal code multiplexing may be referred to as CDM-T multiplexing. As orthogonal codes, for example, Walsh-Hadamard codes can be used. Four RE groups multiplexed by the CDM scheme can be formed, and in each of the four CSI-RS RE groups for antenna ports can be multiplexed by the FDM scheme.

FIG. 25-27 show examples of CSI-RS multiplexing when four CSI-RSs are transmitted in one cell. Multiplexing four CSI-RSs may be a shorthand multiplexing option for eight CSI-RSs. Those. for multiplexing eight CSI-RSs as described in FIG. 23, eight REs (two squares surrounded by a bold solid line) may be used, and a subset (four REs) may be used to multiplex four CSI-RSs. For example, four CSI-RSs may be displayed in four RE units (one square circled in bold by the solid line in FIGS. 25-27) adjacent in the time and frequency domain. A CSI-RS group in which four CSI-RSs are multiplexed can be defined so that two SFBC RE pairs (where one SFBC RE pair is two REs adjacent in the frequency domain) are adjacent in the time domain. Those. four RE groups (one square surrounded by a bold solid line) adjacent in the time / frequency domain can be defined as one CSI-RS RE group. As shown in FIG. 26, 10 CSI-RS RE group patterns can be defined and one of 10 CSI-RS RE group patterns can be used to transmit four CSI-RSs. As shown in FIG. 27 (a), the CSI-RS mapping may be performed such that CSI-RSs alternate between odd RBs and even RBs in the time domain. Thus, all CSI-RSs for four antenna ports can be transmitted in the same OFDM symbols over two RBs, and power redistribution can be fully utilized. As shown in FIG. 27 (b), when CSI-RS is mapped, two CSI-RSs can be multiplexed in one CSI-RS RE group (a square surrounded by a bold solid line) using the FDM scheme and can be multiplied by orthogonal code resources {+1, +1} and {+1, -1} of length 2 in the time domain so that two CSI-RSs are multiplexed by the CDM-T scheme, thereby multiplexing 4 CSI-RSs in one CSI-RS RE group. Details regarding the placement of a CSI-RS RE group and multiplexing of a plurality of CSI-RSs in a CSI-RS RE group can be described by the same principles as those used in the above embodiments, and a re-description will be omitted for clarity.

In the present embodiment, the CSI-RS RE group is shifted in the time and / or frequency domain in each cell. Those. the CSI-RS RE group template can be used in one cell, and the time-and / or frequency-shifted template of this CSI-RS RE group template can be used in another cell. Each cell may skip between the possible options for the position of the CSI-RS RE group at each transmission moment in relation to the CSI-RS transmission. Examples of possible position options of the CSI-RS RE group are shown in FIG. 26, and 10 possible options for the position of the CSI-RS RE group may be presented. Accordingly, different CSI-RS RE group templates can simultaneously use 10 cells.

FIG. 28-30 show other examples of CSI-RS multiplexing when four CSI-RSs are transmitted in one cell. Multiplexing four CSI-RSs may be a shorthand multiplexing option for eight CSI-RSs. Those. for multiplexing eight CSI-RSs as described in FIG. 23, eight REs (two squares surrounded by a bold solid line) may be used, and a subset (four REs) may be used to multiplex four CSI-RSs. For example, as shown in FIG. 28, four CSI-RSs may be mapped to four CSI-RS REs represented in the same OFDM symbol. Four CSI-RS REs may be defined such that two REs (SFBC RE pair) adjacent in the frequency domain that are used as SFBC pair are separated by four subcarriers in the same OFDM symbol. Four CSI-RS REs can configure one CSI-RS RE group. Thus, as shown in FIG. 29, 13 CSI-RS RE group patterns can be defined, and one CSI-RS RE group of 13 CSI-RS RE group patterns can be used for 4 CSI-RS transmission. As shown in FIG. 30, for CSI-RS transmission for four antenna ports within a single RE group, CSI-RSs can be multiplexed using an FDM scheme. Details regarding the placement of a CSI-RS RE group and multiplexing of a plurality of CSI-RSs in a CSI-RS RE group can be described by the same principles as in the embodiments described above, and a repeated description will be omitted for clarity.

In the present embodiment, the CSI-RS RE group is shifted in the time and / or frequency domain in each cell. Those. the CSI-RS RE group template can be used in one cell, and the time-and / or frequency-shifted template of this CSI-RS RE group template can be used in another cell. Each cell may skip between the possible options for the position of the CSI-RS RE group at each transmission moment in relation to the CSI-RS transmission. Examples of possible position options of the CSI-RS RE group are shown in FIG. 29, and 13 possible options for a CSI-RS RE group position may be presented. Accordingly, different patterns of RE CSI-RS groups can simultaneously use 13 cells.

As described above, the CSI-RS RE group for four CSI-RS antenna ports can be defined as a predefined abbreviated version of the CSI-RS RE group template (for example, the CSI-RS RE template in Fig. 23) for eight CSI- antenna transmission ports RS and the abbreviated version can be defined as a set of different RE positions. For example, as shown in FIG. 31, a CSI-RS RE group for four CSI-RS antenna ports can be defined as two REs on two adjacent OFDM symbols at a predetermined position of a subcarrier of a CSI-RS RE group template (for example, the CSI-RS RE template in FIG. 23) for eight CSI-RS antenna ports and two REs on two adjacent OFDM symbols at a different subcarrier position (for example, a subcarrier position separated from a predetermined subcarrier position by five subcarriers). One CSI-RS RE group includes four REs and CSI-RSs for four CSI-RS antenna ports can be transmitted one after another in each RE. In this case, four CSI-RSs can be multiplexed using a TDM / FDM scheme. Alternatively, in a single CSI-RS RE group, CSI-RSs for two CSI-RS antenna ports can be multiplexed using a CDM-T scheme using orthogonal codes of length 2, over two REs represented in the same subcarrier, and The CSI-RSs for the remaining two CSI-RS antenna ports can be multiplexed using the CDM-T scheme using orthogonal codes of length 2 at two REs presented in another subcarrier. In the CSI-RS RE group for the four CSI-RS antenna ports shown in FIG. 31, within one RB, 10 possible variants of the CSI-RS RE group may be presented. One cell can choose one of 10 possible options for the position of the CSI-RS RE group, and another cell can choose another possible option, so that each cell transmits CSI-RS for four CSI-RS antenna ports without crossing.

FIG. 32 and 33 show examples of CSI-RS multiplexing when two CSI-RSs are transmitted from one cell. Multiplexing two CSI-RSs may be a shorthand multiplexing option for eight CSI-RSs. Those. for multiplexing eight CSI-RSs as described in FIG. 23, eight REs (two squares surrounded by a bold solid line) may be used, and a subset (two REs) may be used to multiplex two CSI-RSs. For example, as shown in FIG. 32, two CSI-RSs may be defined as two REs (SFBC RE pair) adjacent in the frequency domain, which are used as SFBC pair. Two CSI-RS REs can configure one CSI-RS RE group. Thus, as shown in FIG. 32, 26 patterns of the CSI-RS RE group can be defined, and one CSI-RS RE group of 26 CSI-RS RE groups can be used for CSI-RS transmission 2. For CSI-RS transmission for two antenna ports within the same RE group, CSI-RSs can be multiplexed using the FDM scheme. Details regarding the placement of a CSI-RS RE group and multiplexing of a plurality of CSI-RSs in a CSI-RS RE group can be described by the same principles as in the embodiments described above, and a repeated description will be omitted for clarity.

In the present embodiment, the CSI-RS RE group is shifted in the time and / or frequency domain in each cell. Those. the CSI-RS RE group template can be used in one cell, and the time-and / or frequency-shifted template of this CSI-RS RE group template can be used in another cell. Each cell may skip between the possible options for the position of the CSI-RS RE group at each transmission moment in relation to the CSI-RS transmission. Examples of possible position options of the CSI-RS RE group are shown in FIG. 33, and 26 possible options for a CSI-RS RE group position may be presented. Accordingly, different CSI-RS RE group templates can simultaneously use 26 cells.

As described above, the CSI-RS RE group for two CSI-RS antenna ports can be defined as a predefined abbreviated version of the CSI-RS RE group template (for example, the CSI-RS RE template in Fig. 23) for eight CSI- antenna transmission ports RS and the abbreviated version can be defined as a set of different RE positions. For example, as shown in FIG. 34, a CSI-RS RE group for two CSI-RS antenna ports can be defined as two REs on two adjacent OFDM symbols at a predetermined position of a subcarrier of a CSI-RS RE group template (for example, the CSI-RS RE template in FIG. 23) for eight CSI-RS antenna ports. One CSI-RS RE group includes two REs and CSI-RSs for two CSI-RS antenna ports can be transmitted one after another in each RE. In this case, two CSI-RSs can be multiplexed using a TDM / FDM scheme. Alternatively, in a single CSI-RS RE group, CSI-RSs for two CSI-RS antenna ports can be multiplexed using a CDM-T scheme using orthogonal codes of 2 lengths over two REs represented in the same subcarrier. In the CSI-RS RE group for the two CSI-RS antenna ports shown in FIG. 34, within one RB, 20 possible variants of the CSI-RS RE group can be represented. One cell can choose one of 20 possible options for the position of the CSI-RS RE group, and the other cell can choose another possible option, so that each cell transmits CSI-RS for two CSI-RS antenna ports without intersection.

FIG. 35 is a diagram illustrating a CSI-RS transmission method and a channel information acquiring method.

In step S3510, the base station may select one of a plurality of CSI-RS RE groups defined in the data area of the downlink subframe to transmit CSI-RS for 8 or less antenna ports.

A plurality of CSI-RS RE groups may be defined such that transmission diversity RE pair (e.g., SFBC pair) for data transmitted in a downlink subframe is not destroyed. For example, if the downlink subframe has a normal CP configuration, then for eight transmit antennas within a single RB, the number of CSI-RS RE groups may be five, as shown in FIG. 23. I.e. each of the plurality of CSI-RS RE groups can be defined at two adjacent carrier positions of two adjacent OFDM symbols and two other adjacent carrier positions separated from the above two adjacent carrier positions by four subcarriers in REs that do not have CRS and DMRS. A plurality of CSI-RS RE groups can be defined as RE positions, where one CSI-RS RE group is shifted in time and frequency domain with respect to another CSI-RS RE group.

A plurality of CSI-RS RE groups to which CSI-RSs are mapped for four antenna ports can be defined as a subset of a plurality of CSI-RS REs to which CSI-RS mappings for eight antenna ports are mapped. For example, in the case of four transmit antennas, the plurality of CSI-RS RE groups may be 10 CSI-RS RE groups in FIG. 26 or 10 CSI-RS RE groups in FIG. 31. As an alternative to four transmit antennas, 13 CSI-RS RE groups in FIG. 29.

A plurality of CSI-RS RE groups into which CSI-RSs are mapped for two antenna ports can be defined as a subset of a plurality of CSI-RS REs into which CSI-RS mappings for eight antenna ports are mapped. For example, in the case of two transmit antennas, the plurality of CSI-RS RE groups may be 20 CSI-RS RE groups in FIG. 34. As an alternative to the two transmit antennas, 26 CSI-RS RE groups in FIG. 33.

In step S3520, the base station can map the CSI-RS for eight or less antenna ports to one CSI-RS RE group selected from a plurality of CSI-RS RE groups. At this stage, the CSI-RS for two of the CSI-RS antenna ports for eight or less antenna ports can be multiplexed using a CDM-T scheme using orthogonal codes of length 2 for two adjacent OFDM symbols in the same subcarrier.

In step S3530, the base station may transmit a downlink subframe to which CSI-RSs for eight or less antenna ports are mapped.

If in one CSI-RS subframe for eight or less antenna ports are transmitted in a state when they are mapped to one selected CSI-RS RE group, then in another CSI-RS subframe for eight or less antenna ports can be mapped to CSI-RS RE group different from the selected CSI-RS RE group.

In step S3540, the UE may receive a downlink subframe from the base station in which CSI-RSs for eight or less antenna ports are mapped to one CSI-RS RE group selected from a plurality of CSI-RS RE groups defined in the data area of the downlink subframe communication.

In step S3550, the UE can measure channel information for each antenna port using CSI-RS for eight or less antenna ports. In addition, the UE may return measured channel information (CSI) to the base station.

Although for clarity, a method is described in accordance with one embodiment of the present invention performed by a base station and a UE, the various embodiments of the present invention described above may be applied.

FIG. 36 is a diagram showing a configuration of a wireless communication system including a base station and a UE in accordance with an exemplary embodiment of the present invention.

Base station 3610 (eNB) may include a reception module 3611, a transmission module 3612, a processor 3613, a memory 3614, and an antenna 3615. The reception module 3611 may receive various signals, data, and information from the UE. Transmission module 3612 may transmit a variety of signals, data, and UE information. The processor 3613 may be configured to control the overall operation of the base station 3610, including the reception module 3611, the transmission module 3612, the memory 3614, and the antenna 3615. The antenna 3615 may include multiple antennas.

Base station 3610, in accordance with one embodiment of the present invention, can transmit CSI-RS for eight or less antenna ports. The base station processor 3613 may select one of a plurality of CSI-RS RE groups defined in the data area of the downlink subframe and display the CSI-RS for eight or less antenna ports. Processor 3613 may transmit a downlink subframe to which CSI-RSs for eight or less antenna ports are mapped via transmission module 3612. The plurality of CSI-RS RE groups may be determined such that the transmit diversity RE pair is not destroyed for data transmitted in the downlink subframe.

A processor 3613 performs a function for processing information received from the UE and information to be transmitted, and memory 3614 can store the processed information for a predetermined time and can be replaced by another component, such as a buffer (not shown).

UE 3620 may include a reception module 3621, a transmission module 3622, a processor 3623, a memory 3624, and an antenna 3625. A reception module 3621 may receive various signals, data and information from a base station. Transmission module 3622 may transmit a variety of signals, data, and information to a base station. A processor 3623 may be configured to control the overall functioning of the UE 3620, including a reception module 3621, a transmission module 3622, a memory 3624, and an antenna 3625. The antenna 3625 may include multiple antennas.

UE 3620, in accordance with one embodiment of the present invention, can measure channel information on CSI-RS for eight or less antenna ports. The UE processor 3623 may be configured to receive a downlink subframe in which CSI-RSs for eight or less antenna ports are mapped to a single CSI-RS RE group selected from a plurality of CSI-RS RE groups defined in the data area of the downlink subframe communication through the module 3621 reception. The processor 3623 may be configured to measure channel information for the antenna ports using CSI-RS for eight or less antenna ports. The plurality of CSI-RS RE groups may be determined such that the transmit diversity RE pair is not destroyed for data transmitted in the downlink subframe.

The processor 3623 performs the function of processing the information received by the UE and the information to be transmitted, and the memory 3624 can store the processed information for a predetermined time and can be replaced by another component, such as a buffer (not shown).

Embodiments in accordance with the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof.

If an embodiment in accordance with the present invention is implemented through hardware, an embodiment of the present invention can be implemented through one or more specialized integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

If an embodiment in accordance with the present invention is implemented using firmware or software, an embodiment of the present invention may be implemented by a type of module, procedure, or function that performs the functions or operations described above. The software code can be stored in a memory module and then can be powered by a processor. A memory module may be located inside or outside the processor in order to transmit and receive data to / from the processor through various means that are well known.

Various embodiments have been described in a preferred embodiment of the invention.

A detailed description of exemplary embodiments of the present invention has been given in order to enable one skilled in the art to practice and practice the invention. Although the invention has been described with reference to exemplary embodiments, one skilled in the art will appreciate that various modifications and variations can be made with respect to the present invention without departing from the spirit and scope of the invention described in the appended claims. For example, one of skill in the art can use each construct described in the above embodiments in combination with each other. Accordingly, the invention should not be limited to the specific embodiments described herein, but should correspond to the broadest possible scope, not inconsistent with the principles and new features disclosed herein.

It will be apparent to those skilled in the art that various modifications and variations can be made with respect to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Industrial Applicability

Although the description of the above embodiments of the present invention focuses mainly on the 3GPP LTE group system, the present invention should not be limited only by the exemplary assumptions made in the description of the present invention. Moreover, embodiments of the present invention can be used in various types of mobile communication systems using the MIMO method by using the same method.

Claims (12)

1. A method for transmitting Reference Signals — Channel Status Information (CSI-RS) for eight or less antenna ports, the method comprising the steps of:
transmit the CSI-RS in the downlink subframe,
wherein the CSI-RSs are mapped to one set of Resource Elements (RE) from the plurality of variants of the RE set, the RE set including a plurality of RE
the number of RE set options in the set for eight antenna ports is five,
however, five RE set options for eight antenna ports within a resource area defined by fourteen Orthogonal Frequency Division Multiplexing (OFDM) symbols and twelve subcarriers in a downlink subframe include:
a first RE set option defined in the third, fourth, ninth, and tenth subcarriers in the sixth and seventh OFDM symbols;
a second RE set option defined in the first, second, seventh and eighth subcarriers in the tenth and eleventh OFDM symbols;
a third RE set option defined in the third, fourth, ninth, and tenth subcarriers in the tenth and eleventh OFDM symbols;
a fourth embodiment of the RE set defined in the fifth, sixth, eleventh and twelfth subcarrier positions in the tenth and eleventh OFDM symbols; and
the fifth embodiment of the RE set, defined in the third, fourth, ninth and tenth subcarriers in the thirteenth and fourteenth OFDM symbols. 2. The method according to claim 1, in which:
the downlink subframe is configured using a normal Cyclic Prefix (CP),
each of the plurality of RE set options is defined in two adjacent OFDM symbols, two adjacent subcarrier positions, and two other adjacent subcarriers, separated from the two adjacent subcarrier positions by four subcarriers, on resource elements not used for Common Reference Signals (CRS) and Demodulation Reference Signals (DMRS). 3. The method of claim 2, wherein the plurality of RE kit options for two antenna ports and the plurality of RE kit options for four antenna ports are defined as a subset of the plurality of RE kit options for eight antennas. 4. The method according to claim 1, in which one variant of the RE set is shifted relative to another variant of the RE set in at least one of the time domain or frequency domain. 5. The method of claim 1, wherein the CSI-RS for two antenna ports of CSI-RS for eight or less antenna ports are multiplexed using a Code Division Multiplexing (CDM) scheme using two orthogonal codes of two characters OFDM in the same subcarrier. 6. A method for measuring channel information by Reference Signals — Channel Status Information (CSI-RS) for eight or less antenna ports, the method comprising the steps of:
receiving a CSI-RS in a downlink subframe; and
measure channel information based on CSI-RS for eight or less antenna ports,
wherein the CSI-RSs are mapped to one set of Resource Elements (RE) from the plurality of variants of the RE set, the RE set including a plurality of RE
the number of RE set options in the set for eight antenna ports is five,
however, five RE set options for eight antenna ports within a resource area defined by fourteen Orthogonal Frequency Division Multiplexing (OFDM) symbols and twelve subcarriers in a downlink subframe include:
a first RE set option defined in the third, fourth, ninth, and tenth subcarriers in the sixth and seventh OFDM symbols;
a second RE set option defined in the first, second, seventh and eighth subcarriers in the tenth and eleventh OFDM symbols;
a third RE set option defined in the third, fourth, ninth, and tenth subcarriers in the tenth and eleventh OFDM symbols;
a fourth embodiment of the RE set defined in the fifth, sixth, eleventh and twelfth subcarrier positions in the tenth and eleventh OFDM symbols; and
the fifth embodiment of the RE set, defined in the third, fourth, ninth and tenth subcarriers in the thirteenth and fourteenth OFDM symbols. 7. The method according to claim 6, in which:
the downlink subframe is configured using a normal Cyclic Prefix (CP),
each of the plurality of RE set options is defined in two adjacent OFDM symbols, two adjacent subcarrier positions, and two other adjacent subcarriers, separated from the two adjacent subcarrier positions by four subcarriers, on resource elements not used for Common Reference Signals (CRS) and Demodulation Reference Signals (DMRS). 8. The method of claim 7, wherein the plurality of RE kit options for two antenna ports and the plurality of RE kit options for four antenna ports are defined as a subset of the plurality of RE kit options for eight antennas. 9. The method according to claim 6, in which one variant of the RE set is shifted relative to another variant of the RE set in at least one of the time domain or frequency domain. 10. The method of claim 6, wherein the CSI-RS for two antenna ports of CSI-RS for eight or less antenna ports are multiplexed using a Code Division Multiplexing (CDM) scheme using two orthogonal codes of two characters OFDM in the same subcarrier. 11. Base station for transmitting Reference Signals - Channel Status Information (CSI-RS) for eight or less antenna ports, wherein the base station contains:
a receiving module, configured to receive an uplink signal from user equipment;
a transmission module, configured to transmit a downlink signal to user equipment; and
a processor configured to control a base station including a reception module and a transmission module,
wherein the processor is configured to transmit CSI-RS in the downlink subframe using the transmission module, and
wherein the CSI-RSs are mapped to one set of Resource Elements (RE) from the plurality of variants of the RE set, the RE set including a plurality of RE
the number of RE set options in the set for eight antenna ports is five,
however, five RE set options for eight antenna ports within a resource area defined by fourteen Orthogonal Frequency Division Multiplexing (OFDM) symbols and twelve subcarriers in a downlink subframe include:
a first RE set option defined in the third, fourth, ninth, and tenth subcarriers in the sixth and seventh OFDM symbols;
a second RE set option defined in the first, second, seventh and eighth subcarriers in the tenth and eleventh OFDM symbols;
a third RE set option defined in the third, fourth, ninth, and tenth subcarriers in the tenth and eleventh OFDM symbols;
a fourth embodiment of the RE set defined in the fifth, sixth, eleventh and twelfth subcarrier positions in the tenth and eleventh OFDM symbols; and
the fifth embodiment of the RE set, defined in the third, fourth, ninth and tenth subcarriers in the thirteenth and fourteenth OFDM symbols. 12. User equipment for measuring channel information by Reference Signals - Channel Status Information (CSI-RS) for eight or less antenna ports, while user equipment contains:
a receiving module, configured to receive a downlink signal from a base station;
a transmission module, configured to transmit an uplink signal to a base station; and
a processor configured to control user equipment including a reception module and a transmission module,
wherein the processor is configured to receive CSI-RS in the downlink subframe by the CSI-RS-based channel information reception and measurement module for eight or less antenna ports, and
wherein the CSI-RSs are mapped to one set of Resource Elements (RE) from the plurality of variants of the RE set, the RE set including a plurality of RE
the number of RE set options in the set for eight antenna ports is five,
however, five RE set options for eight antenna ports within a resource area defined by fourteen Orthogonal Frequency Division Multiplexing (OFDM) symbols and twelve subcarriers in a downlink subframe include:
a first RE set option defined in the third, fourth, ninth, and tenth subcarriers in the sixth and seventh OFDM symbols;
a second RE set option defined in the first, second, seventh and eighth subcarriers in the tenth and eleventh OFDM symbols;
a third RE set option defined in the third, fourth, ninth, and tenth subcarriers in the tenth and eleventh OFDM symbols;
a fourth embodiment of the RE set defined in the fifth, sixth, eleventh and twelfth subcarrier positions in the tenth and eleventh OFDM symbols; and
the fifth embodiment of the RE set, defined in the third, fourth, ninth and tenth subcarriers in the thirteenth and fourteenth OFDM symbols.

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