KR20110127051A - Device and method for communicating csi-rs(channel state information reference signal) in wireless communication system - Google Patents

Abstract

PURPOSE: A device for processing a channel state measurement reference signal of a wireless communication system and a method thereof are provided to prevent transmission of an additional CRS when channel estimation and channel measurement of UE are supported, thereby efficiently using limited wireless resources. CONSTITUTION: A base station receives sub frame information and transmission state information of eNB about a DRS in a sub frame wherein the sub frame information transmits a CSI-RS. The transmission state of a DRS is checked in a sub frame which transmits the CSI-RS. A DRS transmission location is determined by V_shift. A CSI-RS pattern which does not collide with the DRS and a CSI-RS pattern for transmitting a CSI-RS are determined. A CSI-RS pattern for transmitting a CSI-RS is determined among all CSI-RS patterns.

Description

Apparatus and method for processing channel state measurement reference signal in wireless communication system {DEVICE AND METHOD FOR COMMUNICATING Channel State Information reference signal (CSI-RS) IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to an apparatus and method for processing a signal for measuring a radio channel state in a wireless communication system employing a multiple access scheme.

In the 3rd generation evolutionary wireless mobile communication system standard, a reference signal is a common reference signal (CRS) and a dedicated reference signal (DRS) as follows depending on whether a dedicated signal is used for a specific terminal. Divided. First, the common reference signal is referred to as a cell-specific RS or a common RS (CRS) in a 3GPP LTE system, and is a reference signal transmitted to all terminals of a cell to which a corresponding base station belongs. A reference signal pattern that can be distinguished for each antenna port is defined to enable channel estimation and measurement for transmission using multiple antennas. LTE systems support up to four antenna ports. Secondly, the dedicated reference signal is a reference signal additionally transmitted separately from the common reference signal and is transmitted only to a specific terminal designated by the base station. In 3GPP LTE (-A) system, it is also referred to as UE-specific RS and DRS, and is generally used to support a base station when performing data traffic channel transmission using non-codebook based precoding.

In the LTE-A system, which is an upgraded system of the LTE system, a demodulation reference signal (DM-RS) for channel estimation for up to eight layers is transmitted in addition to the above CRS and DRS. FIG. 1 is a diagram illustrating a structure in which a CRS and a DRS are transmitted in an LTE system, and illustrates a structure of a radio frame, a subframe, and a physical resource block (PRB).

Referring to FIG. 1, one radio frame includes 10 subframes, and one subframe is transmitted for 1 msec. That is, one radio frame is transmitted for 10 msec, and consists of 10 subframes as shown in FIG. In FIG. 1, reference numeral 110 denotes one of ten subframes forming a radio frame. During each subframe, the LTE eNB transmits to OFDMA in a system bandwidth period. One subframe consists of a plurality of resource blocks (RBs) in the frequency domain. One RB consists of 12 subcarriers in the frequency domain and 6 OFDM symbols in the time domain. In addition, subcarriers transmitted during one subframe are located at equal intervals in the frequency domain. In FIG. 1, reference numeral 120 denotes one pair of a plurality of RBs forming a system bandwidth. The number of RBs transmitted in the LTE signal structure as shown in FIG. 1 is determined according to the system bandwidth.

The PRB, such as 120, is a combination of time and frequency resources of the structure, such as 130. As shown in 130 of FIG. 1, each RB pair includes 12 subcarriers in a frequency domain and frequency and time resources corresponding to 12 OFDM symbol intervals in a time interval. In a PRB, if one subcarrier is called a resource element (RE) within one OFDM symbol period, one data symbol or reference signal symbol may be transmitted per RE.

The PRB 130 includes a total of 12 subcarriers and 12 OFDM symbol intervals. That is, in FIG. 1, the PRB 130 is composed of a total of 144 REs. An area corresponding to the first three OFDM symbol intervals in the PRB 130 is a control region, and a control channel for transmitting eNB control information necessary for receiving a traffic channel to a UE. Used. The control region is a region corresponding to the first three OFDM symbol intervals, but may be composed of 1 or 2 OFDM symbol intervals according to the eNB's decision.

In FIG. 1, reference numeral 140 denotes a data RE used to transmit a traffic channel. Reference numeral 150 is a CRS RE used to transmit a CRS that the UE uses for channel estimation and measurement. Since the location of the Data RE and the CRS RE is transmitted at a location common to both the eNB and the UE, when the UE receives the PRB, it may be determined at which location the CRS is transmitted and at which location the traffic channel is transmitted.

All indexing starts at zero. As an example, it can be seen that 12 OFDM symbols forming an RB pair in FIG. 1 are indexed 0 to 11 times.

FIG. 2 is a diagram illustrating an example in which a UE measures channel quality and informs an eNB in an LTE system.

Referring to FIG. 2, the UE measures channel quality for all RB pairs existing within a system bandwidth in subframe 230 including a plurality of RBs. The signal used by the UE to measure the channel quality of each RB pair is a CRS signal transmitted by a base station as shown by reference numeral 220. Since the CRS signals are transmitted with constant transmission power in all PRBs, the UE can determine which RB pair has a relatively good channel quality by comparing the reception strengths of the CRS signals received in each PRB. In addition, it is possible to determine which data rate can be supported in a specific RB pair based on the absolute reception strength of the received CRS signal. In this case, the determined channel quality related information is mapped in the form of channel feedback information defined in the LTE system and then notified to the eNB using an uplink control channel as shown by reference numeral 240 of FIG. 2. In FIG. 2, channel feedback information transmitted by the UE as 240 is received by the eNB and used to perform downlink transmission of subframes 251, 252, 253, 254, and 255. The eNB may obtain information on data rate, preferred precoding, and preferred RB pair that the UE can support based on channel feedback information transmitted by the UE, and perform downlink scheduling by using the information. Adaptive Modulation & Coding (AMC) is performed.

In FIG. 2, the eNB uses the channel feedback information received from the UE 240 until it receives new channel feedback information 260. In addition, in FIG. 2, only one UE transmits channel feedback information. However, in a real system, a plurality of UEs are designed to simultaneously transmit channel feedback information.

However, the conventional method as described above has the following problems. In the LTE system, UEs measure channel quality by receiving a CRS transmitted by an eNB. When measuring channel quality by measuring CRS as shown in FIG. 2, the number of layers that an eNB can transmit using MIMO technology is limited by the number of antenna ports of the CRS. In the LTE system, up to four antenna ports can be supported in the standard. Therefore, more than four CRS antenna ports cannot be supported, and as a result, the MIMO transmission of the eNB can be performed only with up to four layers.

Another problem when supporting channel estimation and channel measurement of UEs using CRS is that the eNB should always transmit CRS. Therefore, in order to support more than four antenna ports that LTE can support, additional CRSs for additional antenna ports need to be transmitted. Such additional CRS transmission is inefficient in that it concentrates limited radio resources only on channel estimation and channel measurement.

FIG. 3 illustrates a CRS, a DRS, a DM-RS, and a PDSCH which is a data channel signal transmitted by an eNB in an LTE-A system in one RB pair. The CRS is transmitted using four subcarriers in OFDM symbols 0, 1, 3, 6, 7, and 9, and the subcarrier positions may be different for each cell. In addition, DRS is transmitted using four subcarriers in OFDM symbols 4, 7, and 10, respectively, and the subcarrier position may be different for each cell.

In FIG. 3, since the eNB of the LTE-A system should be able to transmit signals to the LTE terminal and the LTE-A terminal, the eNB should also be able to transmit the reference signal for the LTE terminal in addition to the reference signal for the LTE-A terminal.

The present invention proposes a CSI-RS transmission scheme in which the UE effectively performs channel measurement in the LTE-A system and at the same time efficiently uses radio resources of the eNB. The CSI-RS transmission scheme considers efficient radio resource operation in one eNB viewpoint, separation of CSI-RS transmitted in cells constituting each eNB in a plurality of eNB viewpoints in time and frequency space. .

In a method of processing a CSI-RS by a base station in a wireless communication system according to an embodiment of the present invention, a process of determining a subframe in which to transmit a CSI-RS, and a DRS in the determined subframe should also be transmitted, V_shift and V_shift. Determining a DRS transmission location according to the DRS, determining a CSI_RS pattern that does not collide with the DRS and a CSI-RS pattern for transmitting the CSI-RS, and all CSI-RS patterns when the DRS is not transmitted in the determined subframe Characterized in that the process of determining the CSI-RS pattern to transmit the CSI-RS.

In addition, in a wireless communication system according to an embodiment of the present invention, a method for processing a CSI-RS by a terminal includes receiving subframe information through which the CSI-RS is transmitted to the base station and information on whether the eNB transmits the DRS in the corresponding subframe. And a process of checking whether the DRS is also transmitted in a subframe in which the CSI-RS is to be transmitted, and when the DRS should also be transmitted, determine a DRS transmission position according to V_shift and V_shift, and do not collide with the DRS. Determining a CSI-RS pattern for transmitting the CSI-RS, and determining a CSI-RS pattern for transmitting the CSI-RS among all the CSI-RS patterns when the DRS is not transmitted.

In the wireless communication system according to an embodiment of the present invention, when the DRS should also be transmitted in a subframe in which the CSI-RS is transmitted, the CSI_RS pattern and the CSI-RS do not collide with the DRS and determine a DRS transmission position according to V_shift and V_shift. A base station for determining a CSI-RS pattern for transmitting the CSI-RS pattern, and for determining a CSI-RS pattern for transmitting the CSI-RS among all the CSI-RS patterns when the DRS is not transmitted, and subframe information for transmitting the CSI-RS to the base station; And receiving information on whether the eNB transmits the DRS in the corresponding subframe, and when the DRS should also be transmitted in the subframe in which the CSI-RS is transmitted, determine a DRS transmission position according to V_shift and V_shift, and do not collide with the DRS. Determines the CSI_RS pattern and the CSI-RS pattern to transmit the CSI-RS, and if the DRS is not transmitted, consisting of a terminal for determining the CSI-RS pattern to transmit the CSI-RS out of all the CSI-RS patterns .

In a wireless communication system according to an embodiment of the present invention, when UEs receive a CRS transmitted by an eNB and measure channel quality, the number of layers that the eNB can transmit using MIMO technology is limited by the number of antenna ports of the CRS. Do not receive. In addition, even in case of supporting channel estimation and channel measurement of UEs using CRS, it is not necessary to transmit additional CRS, thereby efficiently using limited radio resources. In addition, the eNB of the LTE-A system may transmit a reference signal for the LTE terminal in addition to the reference signal for the LTE-A terminal.

1 is a diagram illustrating a structure for transmitting a CRS and a DRS in an LTE system
FIG. 2 illustrates an example in which a UE measures channel quality and notifies an eNB in an LTE system; FIG.
3 is a diagram illustrating a PDSCH, which is a CRS, DRS, DM-RS, and data channel signal transmitted by an eNB in an LTE-A system, in one RB pair;
4 is a diagram illustrating a structure of transmitting a CSI-RS of an eNB in an LTE-A system.
5 is a view for explaining the position in time and frequency space to be used when transmitting the CSI-RS in an embodiment of the present invention;
FIG. 6 illustrates CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an embodiment of the present invention.
7 is a diagram illustrating CSI-RS patterns used when performing transmission for four CSI-RS antenna ports in an embodiment of the present invention.
FIG. 8 illustrates another CSI-RS pattern used when transmitting four CSI-RS antenna ports in an embodiment of the present invention.
FIG. 9 illustrates CSI-RS patterns used when transmitting two CSI-RS antenna ports in an embodiment of the present invention.
FIG. 10 illustrates another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an embodiment of the present invention.
FIG. 11 illustrates a method of the present invention that can prevent inefficient transmission waste that may occur when using the CSI-RS pattern of FIG. 10. FIG.
FIG. 12 illustrates yet another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an embodiment of the present invention.
FIG. 13 illustrates another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an embodiment of the present invention.
14 illustrates a method of the present invention for optimizing control information when using the CSI-RS pattern of FIG. 13 in an embodiment of the present invention.
FIG. 15 illustrates yet another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an embodiment of the present invention.
FIG. 16 illustrates yet another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an embodiment of the present invention.
17 is a diagram illustrating a CSI-RS pattern according to an embodiment of the present invention when the DM-RS is present in DM-RS position 2;
FIG. 18 is a diagram illustrating a CSI-RS pattern according to an embodiment of the present invention when a DM-RS exists at a DM-RS location different from a DM-RS location 1 and a DM-RS location 2; FIG.
FIG. 19 illustrates still another CSI-RS patterns for CSI-RS transmission in an embodiment of the present invention. FIG.
20 illustrates still another CSI-RS patterns for CSI-RS transmission in an embodiment of the present invention.
FIG. 21 illustrates still another CSI-RS patterns for CSI-RS transmission in an embodiment of the present invention. FIG.
FIG. 22 is a diagram illustrating a PDSCH, which is a CRS, a DRS, a DM-RS, and a data channel signal transmitted by an eNB, when transmitting a subframe using a normal cyclic prefix in an LTE-A system, in one RB pair
FIG. 23 is a diagram for explaining a location in time and frequency space to be used when transmitting a CSI-RS in an LTE-A system transmitting using a normal cyclic prefix.
FIG. 24 illustrates CSI-RS patterns used for CSI-RS transmission for eight CSI-RS antenna ports in an LTE-A system using a normal cyclic prefix according to an embodiment of the present invention.
FIG. 25 illustrates a collision between DRSs having different V_shift values and six CSI-RS patterns of FIG. 24.
FIG. 26 illustrates a method for an eNB to determine one of a plurality of applicable CSI-RS patterns such that a CSI-RS and a DRS do not collide in an embodiment of the present invention. FIG.
FIG. 27 is a diagram illustrating a method for self-determining a CSI-RS determined by an eNB when an eNB determines a CSI-RS pattern in which an CSI-RS and a DRS do not collide with each other according to an embodiment of the present invention.
FIG. 28 uses the CSI-RS pattern of FIG. 24 according to an embodiment of the present invention, and transmits signals for each CSI-RS antenna port for efficiently using transmission power when transmitting CSI-RS using CDM and FDM. Drawing showing how to cycle change position
FIG. 29 illustrates another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to an embodiment of the present invention.
30 is a diagram illustrating still another CSI-RS patterns for 8 CSI-RS antenna ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to an embodiment of the present invention.
FIG. 31 illustrates another CSI-RS patterns for eight CSI-RS antennal ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to an embodiment of the present invention.
FIG. 32 is a diagram illustrating still another CSI-RS patterns for 8 CSI-RS antennal ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

The present invention relates to a general wireless mobile communication system, and more particularly, in a wireless mobile communication system using a multiple access scheme using a multi-carrier, such as orthogonal frequency division multiple access (OFDMA), The present invention relates to a transmission and reception method and an efficient operation of a channel state information reference signal (CSI-RS) transmitted by a base station to help measure channel quality (wireless channel state).

The current mobile communication system has evolved into a high-speed, high-quality wireless packet data communication system for providing data service and multimedia service, instead of providing an initial voice-oriented service. To this end, several standardization organizations, such as 3GPP, 3GPP2, and IEEE, are proceeding with the 3rd generation evolutionary mobile communication system standard using the multiple access method using multi-carriers. Recently, various mobile communication standards such as Long Term Evolution (LTE) of 3GPP, Ultra Mobile Broadband (UMB) of 3GPP2, and 802.16m of IEEE are based on the multiple access method using multi-carrier. Was developed to support it.

Existing 3rd generation evolutionary mobile communication systems such as LTE, UMB, 802.16m are based on multi-carrier multiple access method, and apply Multiple Input Multiple Output (MIMO, multiple antenna) and beam- to improve transmission efficiency. It features various techniques such as forming (beamforming), adaptive modulation and coding (AMC), and channel sensitive (channel sensitive) scheduling. Various techniques described above improve the transmission efficiency by concentrating or adjusting the amount of data transmitted from various antennas according to channel quality, and selectively transmitting data to users having good channel quality. Improve system capacity performance. Most of these techniques operate based on channel state information between an evolved Node B (eNB) and a Base Station (eNB) and a UE (User Equipment (MS)). It is necessary to measure the channel status between the two, which is used Channel Status Indication reference signal (CSI-RS). The aforementioned eNB refers to a downlink transmitting and uplink receiving apparatus located at a predetermined place, and one eNB performs transmission and reception for a plurality of cells. A plurality of eNBs are geographically distributed in one mobile communication system, and each eNB performs transmission and reception for a plurality of cells.

In mobile communication systems, time, frequency, and power resources are limited. Therefore, if more resources are allocated to the reference signal, the resources that can be allocated for the traffic channel transmission can be reduced, thereby reducing the absolute amount of data transmitted. In this case, the performance of channel measurement and estimation may be improved, but the total system capacity performance may be deteriorated because the absolute amount of transmitted data is reduced. Therefore, appropriate allocation is required between the resource for the reference signal and the resource for the traffic channel transmission to derive optimal performance in terms of overall system capacity.

A reference signal is a signal used for demodulation and decoding of a received data symbol by measuring a state of a channel between a base station and users such as channel strength, distortion, interference strength, and Gaussian noise in a wireless mobile communication system. Another use of the reference signal is to measure radio channel conditions. The receiver may determine the state of the radio channel between itself and the transmitter by measuring the reception strength of the reference signal transmitted by the transmitter at the promised transmission power over the radio channel. The state of the radio channel thus determined is used to determine what data rate the receiver requests from the transmitter.

In the recent 3rd generation evolution wireless mobile communication system standards such as 3GPP LTE (-A) or IEEE 802.16m, multiple access scheme is a multiple access scheme using multiple subcarriers such as orthogonal frequency division multiplexing (multiple access) (OFDM). Is mainly adopted. In the wireless mobile communication system using the multiple access scheme using the multiple subcarriers, a difference occurs in the channel estimation and measurement performance depending on how many time symbols and subcarriers the reference signal is located in time and frequency. In addition, channel estimation and measurement performance is also affected by how much power is allocated to the reference signal. Accordingly, when more radio resources such as time, frequency, and power are allocated to the reference signal, channel estimation and measurement performance is improved, thereby improving demodulation and decoding performance of the received data symbol and increasing accuracy of channel state measurement.

However, in the general mobile communication system, since radio resources such as time, frequency, and transmission power that can transmit a signal are limited, when a large number of radio resources are allocated to a reference signal, radio resources that can be allocated to a data signal are relatively reduced. . For this reason, the radio resource allocated to the reference signal should be appropriately determined in consideration of system throughput.

The present invention relates to a method of transmitting and receiving a reference signal transmitted to measure channel quality of a wireless channel and a method of efficiently operating the same in a plurality of cells. In the LTE-A system according to an embodiment of the present invention, a UE proposes a CSI-RS transmission scheme that efficiently performs channel measurement and efficiently uses radio resources of an eNB. To this end, in the embodiment of the present invention, a plurality of CSI-RS patterns are defined and allocated to each cell, and CSI-RSs are alternately used alternately for each PRB to alternately transmit transmit power of all antenna ports for transmission of CSI-RSs. Take advantage.

The CSI-RS transmission scheme proposed in the present invention avoids a section that cannot be utilized to transmit CSI-RS and can coexist in the same RB pair as the DRS.

4 is a diagram illustrating CSI-RS transmission of an eNB in an LTE-A system.

Referring to FIG. 4, the LTE-A system performs downlink transmission in units of 1 msec in a time interval and in units of 1 physical resource block (PRB) in a frequency interval. Here, the PRB consists of 12 subcarriers. In addition, a time interval of 1 msec consists of 12 OFDM symbols. One PRB is composed of 12 subcarriers and 12 OFDM symbols are transmitted for 1 msec. This is the case when an LTE or LTE-A system has a 15KHz interval between subcarriers and uses an extended cyclic prefix length. In addition to the LTE or LTE-A system, the interval between subcarriers may be 7.5KHz, it may use a length other than the extended cyclic prefix. In the case of a normal cyclic prefix, 14 OFDM symbols are transmitted during a time interval of 1 msec. When transmitting using the extended cyclic prefix as described above, 144 resource elements (REs) formed of 12 OFDM symbols and 12 subcarriers are called RB pairs. In the case of the extended cyclic prefix, the RB pair is composed of 144 REs, and in the case of the normal cyclic prefix, the RB pair is composed of 168 REs.

In FIG. 4, the eNB transmits subframe 440 to subframe 451. In subframe 440, CSI-RS is transmitted in subframe 440, subframe 445, and subframe 450 of subframe 451. That is, the temporal transmission period of the CSI-RS is 5 msec or 5 subframes. The transmission of the CSI-RS means that the CSI-RS is transmitted in one or a plurality of PRBs constituting the subframe 440. Reference numeral 435 of FIG. 4 specifically illustrates an RB pair for transmitting CSI-RSs among a plurality of RB pairs forming a subframe 340. In the PRB in which the CSI-RS is transmitted as shown in 435, the CSI-RS for the separate antenna port is transmitted as shown in 431, 432, 433, and 434. That is, 431 transmits CSI-RS for antenna ports 0 and 1, and 332 transmits CSI-RS for antenna ports 2 and 3.

In FIG. 4, the PRB to which the CSI-RS is not transmitted is transmitted in the form of 436, and it can be seen that the CSI-RS does not exist as compared with 435.

The LTE-A system is different from the LTE system in that LTE-A terminals perform channel measurement using the CSI-RS of 431, 432, 433, and 434 instead of the CRS of 420 of FIG. 4.

In order to design an efficient CSI-RS transmission method, it is necessary to properly determine the position in the time and frequency space in which the CSI-RS is transmitted. 5 is a view for explaining the position in time and frequency space to be used when transmitting the CSI-RS. FIG. 5 illustrates a region capable of transmitting CSI-RS in an LTE-A system within one RB pair. FIG. 5 corresponds to a case where the LTE-A system transmits a transmission signal using an extended cyclic prefix.

In FIG. 5, 36 REs corresponding to OFDM symbols 0, 1, and 2 may not be used to transmit CSI-RSs because they are required to transmit control signals for LTE and LTE-A terminals. In addition, since 48 REs corresponding to OFDM symbols 3, 6, 7, and 9 are used to transmit CRSs, they cannot be used to transmit CSI-RSs. In addition, a total of 32 REs located in a subcarrier in which DM-RSs are transmitted in OFDM symbols 4, 5, 10, and 11 may be used to transmit CSI-RSs because they are required to transmit DM-RSs for LTE-A terminals. none.

When the REs that cannot transmit the CSI-RS as shown in FIG. 5 are excluded, the number of REs that can be used to transmit the CSI-RS in one RB pair is 28. In FIG. 5, the DRS for the LTE terminal is not considered in determining a section in which the CSI-RS cannot be transmitted. This is because the DRS for the LTE terminal is not transmitted in all time and frequency domains but is a signal that can be determined whether or not transmission is selectively performed according to the eNB's decision. That is, the eNB does not transmit the DRS when the CSI-RS is to be transmitted using the same RE through which the DRS is transmitted in the section in which the CSI-RS is transmitted, as shown by reference numeral 440 of FIG. 4, and the CSI as shown by the reference number 441. -RS is transmitted to the LTE terminal by selecting a subframe in which the RS is not transmitted.

As described above, the transmission of the DRS for the LTE terminal may be performed only in a subframe in which the CSI-RS is not transmitted, according to the determination of the eNB, but this is a limitation in the radio resource management viewpoint of the eNB. It is advantageous in terms of performance improvement of the LTE terminal that the DRS can transmit the DRS even in a subframe in which the CSI-RS is transmitted without such a restriction.

In the CSI-RS transmission scheme proposed in the present invention, it is possible to coexist in the same RB pair as the DRS while avoiding a section that cannot be used to transmit the CSI-RS in FIG. In order for the CSI-RS to coexist with the DRS in the same RB pair, the CSI-RS should not be transmitted in OFDM symbols 4 and 10 in addition to the section in which the CSI-RS cannot be transmitted in FIG. 5. That is, the CSI-RS should be transmitted using 8 REs of OFDM symbols 5 and 11 and 12 REs of OFDM symbol 8 in FIG. 5.

6 shows CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission according to the present invention. 6 corresponds to a case where the LTE-A system transmits a transmission signal using an extened cyclic prefix.

6 is composed of two CSI-RS patterns each capable of transmitting signals for eight CSI-RS antenna ports. The first pattern consists of four REs located in OFDM symbol 5 and four REs located in OFDM symbol 8. The second pattern consists of four REs located in OFDM symbol 8 and four REs located in OFDM symbol 11. In FIG. 5, it can be seen that the CSI-RS is not transmitted in the time and frequency domain determined that the CSI-RS cannot be transmitted. In addition, the CSI-RS is not transmitted even in the OFDM symbols 4, 7, and 10 in which the DRS can be transmitted.

6 shows that one base (base) pattern is formed. That is, CSI-RS pattern 1 moves by three OFDM symbol intervals on the time axis and two subcarriers on the frequency axis to obtain CSI-RS Pattern2. As such, when a plurality of different CSI-RS patterns are obtained with one base (base) pattern, complexity in implementing a CSI-RS transceiver can be reduced.

In FIG. 6, two different CSI-RS patterns exist for eight CSI-RS antenna ports. As such, when there are a plurality of non-overlapping CSI-RS patterns, they may be allocated to two cells. That is, in FIG. 6, CSI-RSs for eight CSI-RS antenna ports in one RB pair have reuse factor 2. In general, the greater the reuse factor, the less the mutual interference between different cells in a mobile communication system having a plurality of cells exists.

In FIG. 6, one CSI-RS pattern consists of eight REs, and thus can transmit signals for up to eight CSI-RS antenna ports. Signals for the eight CSI-RS antenna ports may be transmitted using code division multiplexing (CDM) and frequency division multiplexing (FDM) or using time division multiplexing (TDM) and FDM.

The REs in which the signals of CSI-RS pattern 1 and CSI-RS pattern 2 are transmitted in FIG. 6 are shown in Table 1 below.

CSI-RS Pattern 1 CSI-RS Pattern 2 RE A: OFDM symbol 5, subcarrier 0 RE A: OFDM symbol 8, subcarrier 2 RE B: OFDM symbol 8, subcarrier 0 RE B: OFDM symbol 11, subcarrier 2 RE C: OFDM symbol 5, subcarrier 3 RE C: OFDM symbol 8, subcarrier 5 RE D: OFDM symbol 8, subcarrier 3 RE D: OFDM symbol 11, subcarrier 5 RE E: OFDM symbol 5, subcarrier 6 RE E: OFDM symbol 8, subcarrier 8 RE F: OFDM symbol 8, subcarrier 6 RE F: OFDM symbol 11, subcarrier 8 RE G: OFDM symbol 5, subcarrier 9 RE G: OFDM symbol 8, subcarrier 11 RE H: OFDM symbol 8, subcarrier 9 RE H: OFDM symbol 11, subcarrier 11

In FIG. 6, when the CDM and the FDM are used, signals for two CSI-RS antenna ports are transmitted to two REs located in the same subcarrier among the REs having the same CSI-RS pattern. For example, in FIG. 6, signals of CSI-RS antenna ports 0 and 1 are added to RE A and RE B of CSI-RS pattern 1 by being spread with different orthogonal codes of length 2 and then transmitted. In addition, the signals of CSI-RS antenna ports 2 and 3 are added to RE C and RE D of the CSI-RS pattern 1 by being spread with different orthogonal codes of length 2, respectively, and then transmitted. In addition, the signals of CSI-RS antenna ports 4 and 5 are added to RE E and RE F of the CSI-RS pattern 1 by being spread with different orthogonal codes of length 2, respectively, and then transmitted. In addition, the signals of CSI-RS antenna ports 6 and 7 are added to RE G and RE H of the CSI-RS pattern 1 by being spread with different orthogonal codes of length 2, respectively, and then transmitted.

In FIG. 6, when transmitting signals for eight CSI-RS antenna ports using CDM and FDM, each antenna port is transmitted using REs of each pattern as shown in Table 2.

CSI-RS antenna port 0 Spread with Walshcode (+1 +1) of length 2 and send to RE A, RE B CSI-RS antenna port 1 Spread with Walshcode (+1 -1) of length 2 and send to RE A, RE B CSI-RS antenna port 2 Spread with Walshcode (+1 +1) of length 2 and send to RE C, RE D CSI-RS antenna port 3 Spread to Walsh code (+1 -1) of length 2 and send to RE C, RE D CSI-RS antenna port 4 Spread with Walshcode (+1 +1) of length 2 and send to RE E, RE F CSI-RS antenna port 5 Spread to length 2 Walsh code (+1 -1) and send to RE E, RE F CSI-RS antenna port 6 Spread with Walshcode (+1 +1) of length 2 and send to RE G, RE H CSI-RS antenna port 7 Spread to Walsh code (+1 -1) of length 2 and send to RE G, RE H

Table 2 shows an example of transmitting signals for each CSI-RS antenna port by CDS when using the location of each CSI-RS pattern of FIG. 6. The present invention uses the location of each CSI-RS pattern of FIG. 6 and includes a case where signals for each CSI-RS antenna port are mapped to different REs.

In addition, in FIG. 6, when transmitting signals for eight CSI-RS antenna ports using TDM and FDM, each antenna port is transmitted as shown in Table 3.

CSI-RS antenna port 0 Send to RE A CSI-RS antenna port 1 Send to RE B CSI-RS antenna port 2 Send to RE C CSI-RS antenna port 3 Send to RE D CSI-RS antenna port 4 Send to RE E CSI-RS antenna port 5 Send to RE F CSI-RS antenna port 6 Send to RE G CSI-RS antenna port 7 Send to RE H

The method for transmitting signals for each CSI-RS antenna port shown in Table 2 and Table 3 is one of a plurality of specific methods that can be implemented within the CSI-RS pattern determined as shown in FIG. 6 according to the present invention. . The present invention also includes a combination of another CSI-RS antenna port and a transmission method that can be implemented in the CSI-RS pattern determined as shown in FIG. For example, in the case of using CDM and FDM, other combinations besides the combination of the signals for the CSI-RS antenna ports shown in Table 2, spreading codes, and two REs used for transmission are included in the present invention.

FIG. 6 illustrates CSI-RS patterns used when transmitting 8 CSI-RS antenna ports. FIG. 7 illustrates CSI-RS patterns used when transmitting 4 CSI-RS antenna ports according to the present invention. 7 corresponds to a case where the LTE-A system transmits a transmission signal using an extened cyclic prefix.

The CSI-RS patterns for the four CSI-RS antenna ports of FIG. 7 are designed to be included in one of the CSI-RS patterns for the eight CSI-RS antenna ports of FIG. In general, this is called a nested property. In the CSI-RS design, the nested property means that a pattern for a smaller number of CSI-RS antenna ports is included in a pattern for a larger number of CSI-RS antenna ports. When the nested property as described above, it is easy to implement a transceiver, and also has a CSI-RS pattern for an antenna port having less characteristics of the CSI-RS pattern for more antenna ports. That is, as the CSI-RS pattern for the eight CSI-RS antenna port of FIG. 6 does not collide with the DRS for the LTE terminal, the CSI-RS patterns for the CSI-RS antenna port of FIG. 7 are also LTE. It does not collide with the DRS for the terminal. In addition, as shown in FIG. 6, when one base pattern is provided, different CSI-RS patterns may be obtained by moving one CSI_RS pattern on a frequency axis and a time axis.

In FIG. 7, CSI-RS for four CSI-RS antenna ports in one RB pair has reuse factor 4.

The CSI-RS pattern for the four CSI-RS antenna ports of FIG. 7 also uses CDM and FDM or TDM and FDM as in the CSI-RS pattern for the eight CSI-RS antenna ports of FIG. Can be sent.

In FIG. 7, when transmitting signals for four CSI-RS antenna ports using CDM and FDM, each antenna port is transmitted using REs of each pattern as shown in Table 4.

CSI-RS antenna port 0 Spread with Walshcode (+1 +1) of length 2 and send to RE A, RE B CSI-RS antenna port 1 Spread with Walshcode (+1 -1) of length 2 and send to RE A, RE B CSI-RS antenna port 2 Spread with Walshcode (+1 +1) of length 2 and send to RE C, RE D CSI-RS antenna port 3 Spread to Walsh code (+1 -1) of length 2 and send to RE C, RE D

In addition, in FIG. 7, when transmitting signals for four CSI-RS antenna ports using TDM and FDM, each antenna port is transmitted as shown in Table 5.

CSI-RS antenna port 0 Send to RE A CSI-RS antenna port 1 Send to RE B CSI-RS antenna port 2 Send to RE C CSI-RS antenna port 3 Send to RE D

FIG. 6 illustrates CSI-RS patterns used when transmitting 8 CSI-RS antenna ports. 8 illustrates another CSI-RS pattern used when transmitting the four CSI-RS antenna ports according to the present invention. 8 corresponds to a case in which the LTE-A system transmits a transmission signal using an extended cyclic prefix. In FIG. 8, CSI-RS for four CSI-RS antenna ports in one RB pair has reuse factor 4.

FIG. 6 illustrates CSI-RS patterns used when transmitting 8 CSI-RS antenna ports. 9 illustrates CSI-RS patterns used when transmitting two CSI-RS antenna ports according to the present invention. 9 corresponds to a case in which the LTE-A system transmits a transmission signal using an extened cyclic prefix. In FIG. 9, the CSI-RS for two CSI-RS antenna ports in one RB pair has a reuse factor of 8.

The CSI-RS pattern for the two CSI-RS antenna ports of FIG. 9 also uses CDM and FDM or TDM and FDM as in the CSI-RS pattern for the eight CSI-RS antenna ports of FIG. Can be sent. In FIG. 9, when transmitting signals for two CSI-RS antenna ports using CDM and FDM, each antenna port is transmitted using REs of each pattern as shown in Table 6.

CSI-RS antenna port 0 Spread with Walshcode (+1 +1) of length 2 and send to RE A, RE B CSI-RS antenna port 1 Spread with Walshcode (+1 -1) of length 2 and send to RE A, RE B

In addition, in FIG. 9, when transmitting signals for two CSI-RS antenna ports using TDM and FDM, each antenna port is transmitted as shown in Table 7.

CSI-RS antenna port 0 Send to RE A CSI-RS antenna port 1 Send to RE B

FIG. 10 illustrates another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission according to the present invention. 10 corresponds to a case where the LTE-A system transmits a transmission signal using an extened cyclic prefix.

The CSI-RS patterns for the eight CSI-RS antenna ports of FIG. 10 also have one base pattern. That is, the CSI-RS pattern 2 can be obtained by moving the CSI-RS pattern 1 by six subcarriers along the frequency axis.

The CSI-RS pattern for the eight CSI-RS antenna ports of FIG. 10 may also be transmitted using CDM and FDM or TDM and FDM as in FIG. 6. In addition, CSI-RS patterns for four or two CSI-RS antenna ports having nested properties may be obtained in the CSI-RS pattern for the eight CSI-RS antenna ports of FIG. 10.

In the case of the CSI-RS pattern for the eight CSI-RS antenna ports of FIG. 10, in the case of OFDM symbols 5 and 11, signals of all the CSI-RS antenna ports are not transmitted, but only signals of some CSI-RS antenna ports are transmitted. For example, when transmitting using CDM and FDM, signals of CSI-RS antenna ports 0, 1, 2, and 3 among 8 CSI-RS antenna ports are transmitted in OFDM symbol 5, but the remaining CSI-RS antenna ports 4, 5, and 6 are transmitted. , 7 signals are not transmitted. As described above, only transmitting some antenna ports in one OFDM symbol is inefficient in terms of operating an eNB transmit power. When the eNB is configured with a plurality of CSI-RS antenna ports, if only one signal for some CSI-RS antenna ports is transmitted in one OFDM symbol as shown in FIG. 10, the eNB cannot use the transmit power for the remaining antenna ports.

For example, in the OFDM symbol 5, only signals of CSI-RS antenna ports 0, 1, 2, and 3 are transmitted in RE A and RE C. RE A and RE C do not perform transmission on CSI-RS antenna ports 4, 5, 6 and 7. The problem is that since there is no RE that transmits CSI-RS antenna ports 4, 5, 6, and 7 in the same OFDM symbol, the power that RE A and RE C do not use is not used efficiently and is wasted. In the case of FIG. 6, when the CDM and the FDM are used, all the CSI-RS antenna ports are transmitted in the OFDM symbol 5. There is no such problem.

FIG. 11 illustrates a method of the present invention capable of preventing inefficient waste of transmission power that may occur when the CSI-RS pattern of FIG. 10 is used.

FIG. 11 transmits the CSI-RS using the CSI-RS pattern of FIG. 10 as in 1100 in the RB pair of the half of the system bandwidth when using the CSI-RS pattern of FIG. The pair transmits the CSI-RS using the CSI-RS pattern modified from the CSI-RS pattern of FIG. 10 as shown in 1110. 1110 of FIG. 11 is a RE position in which CSI-RS antenna ports 0, 1, 2, and 3 are transmitted and a CSI-RS antenna ports 4, 5, 6, and 7 are transmitted by modifying the CSI-RS pattern of FIG. The locations are interchangeable.

When transmitting as shown in FIG. 11, signals of all CSI-RS antenna ports are transmitted in all OFDM symbols transmitting CSI-RS. As such, when signals of all CSI-RS antenna ports are transmitted in an OFDM symbol transmitting CSI-RS, waste of transmission power can be prevented by exchanging unused power for each CSI-RS antenna port in each RE. have.

FIG. 12 shows still another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission according to the present invention. 12 corresponds to a case in which the LTE-A system transmits a transmission signal using an extended cyclic prefix.

FIG. 12 has one difference compared with FIGS. 6 and 10 that similarly support eight CSI-RS antenna ports. In the case of FIG. 12, two CSI-RS patterns have different base patterns.

FIG. 13 shows another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission according to the present invention. FIG. 13 corresponds to a case where the LTE-A system transmits a transmission signal using an extended cyclic prefix.

13 is composed of three CSI-RS patterns capable of supporting eight CSI-RS antenna ports, each of which does not collide with the DRS. It can be seen that the CSI-RS patterns 1 and 2 of FIG. 13 are the same as the CSI-RS patterns 1 and 2 of FIG. 6. The difference between FIG. 13 and FIG. 6Dml is CSI-RS pattern 3. The CSI-RS pattern 3 of FIG. 23 has the same base pattern as the other two CSI-RS patterns. The characteristic of the CSI-RS pattern 3 is that the DM-RS is transmitted using the RE position where the RS can be transmitted. As mentioned in FIG. 5, subcarriers 1, 2, 4, 5, 7, 8, 10, 11 of OFDM symbols 4 and 5 and subcarriers 0, 1, 3, 4, 6, 7, of OFDM symbols 10 and 11 9 and 10 are used to transmit the DM-RS. In particular, subcarriers 2, 5, 8, 11 of OFDM symbols 4 and 5 and subcarriers 1, 4, 7, and 10 of OFDM symbols 10 and 11 perform MIMO transmissions in which the number of layers allocated per UE is greater than 2 in LTE-A. In this case, it is used to transmit DM-RS. That is, in case of the RB pair having the number of layers allocated per UE in LTE-A less than or equal to 2, subcarriers 2, 5, 8, 11 of OFDM symbols 4 and 5 and subcarriers 1, 4, 7, 10 of OFDM symbols 10 and 11 DM-RS is not transmitted to

The CSI-RS pattern 3 of FIG. 13 is transmitted using some of subcarriers 2, 5, 8, 11 of OFDM symbols 4 and 5 and subcarriers 1, 4, 7, and 10 of OFDM symbols 10 and 11. For this reason, in a subframe in which CSI-RS pattern 3 is transmitted, MIMO transmission in which the number of layers allocated per UE is larger than 2 cannot be performed. Although this is a limitation in performing MIMO transmission, it has the advantage of increasing the number of CSI-RS patterns and the CSI-RS system in the LTE-A system because the interval where the transmission rank restriction of MIMO transmission occurs is part of all subframes. Applicable if you need to increase the number of patterns.

When the CSI-RS pattern 3 of FIG. 13 is used, in the subframe in which the CSI-RS pattern 3 is not transmitted, even if the number of layers that can be allocated per UE of the MIMO may be greater than 2, in the subframe in which the CSI-RS is transmitted, The number of layers that can be allocated is limited to two or less. As such, the linkage between CSI-RS pattern 3 and MIMO transmission may be used to optimize control information for the corresponding MIMO transmission in LTE-A. 14 is a view for explaining the above-described optimization of control information according to the present invention.

In FIG. 14, it is assumed that an eNB transmits CSI-RS in subframe intervals of 1400, 1405, and 1410, and uses the CSI-RS antenna pattern 3 of FIG. 13. In case of such CSI-RS transmission, downlink MIMO transmission is limited to 2 for the number of layers that can be allocated per UE in subframes of 1400, 1405, and 1410. On the other hand, in the remaining subframes except for the subframes of 1400, 1405, and 1410 in FIG. 14, up to 8, which is the maximum number of layers per UE defined in the LTE-A system, may be performed. According to the present invention, when transmitting using the CSI-RS pattern 3 of FIG. 13, when transmitting as shown in FIG. 14, the number of assignable layers per UE of downlink MIMO in some subframes is limited to 2, so that the control signal transmitted in the corresponding subframe Can also be optimized accordingly. That is, since the control signals transmitted in the subframes of 1400, 1405, and 1410 need only transmit control information for up to two layers to the UE, the number of bits of the control signal to be transmitted may be small when compared with the control signals transmitted in the remaining subframes. have. That is, when the number of layers that can be allocated per UE for each subframe occurs as shown in FIG. 14, the number of bits of the control signal according to the present invention is changed accordingly to minimize the amount of information of the control signal.

FIG. 15 shows another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission according to the present invention. FIG. 15 corresponds to a case in which the LTE-A system transmits a transmission signal using an extended cyclic prefix.

FIG. 15 provides four CSI-RS patterns. CSI-RS patterns 1 and 2 are the same as those of FIG. 6, and CSI-RS patterns 3 and 4 are added as compared to FIG. 6. Since the CSI-RS patterns 3 and 4 of FIG. 15 are transmitted at the RE location where the DM-RS can be transmitted, the layer can be allocated per UE in the subframe in which the corresponding CSI-RS pattern is transmitted as in the case of FIG. The number of will be limited. In addition, since the CSI-RS patterns 3 and 4 of FIG. 15 are in a position where they may collide with the DRS, there is a disadvantage in that the DRS cannot be transmitted when the CSI-RS is transmitted using the CSI-RS patterns 3 and 4. On the other hand, it is advantageous to provide four CSI-RS patterns capable of supporting eight CSI-RS antenna ports.

16 shows another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission according to the present invention. 16 corresponds to a case in which the LTE-A system transmits a transmission signal using an extended cyclic prefix.

16 provides four CSI-RS patterns. CSI-RS patterns 1 and 2 are the same as those of FIG. 6, and CSI-RS patterns 3 and 4 are added as compared to FIG. 6. Since the CSI-RS patterns 3 and 4 of FIG. 16 are transmitted at the RE positions where the DM-RS can be transmitted, the layer can be allocated per UE in the subframe in which the corresponding CSI-RS pattern is transmitted as in the case of FIG. The number of will be limited. In addition, since the CSI-RS patterns 3 and 4 of FIG. 16 are in a position that may collide with the DRS, there is a disadvantage in that the DRS cannot be transmitted when the CSI-RS is transmitted using the CSI-RS patterns 3 and 4. On the other hand, it is advantageous to provide four CSI-RS patterns capable of supporting eight CSI-RS antenna ports.

An important feature of the CSI-RS patterns of FIGS. 13, 15, and 16 according to the present invention is that the CSI-RS patterns 1 and 2 specified in FIG. 6 are basically supported, and at the same time, DM-RS using additional CSI-RS patterns is provided. In other words, it is used in connection with the use of DRS.

In the CSI-RS pattern of FIGS. 6 to 13, 15, and 16, the DM-RS is present at the following <DM-RS location 1> and is transmitted using the <DM-RS location 1>. Applicable when

<DM-RS Position 1>

Subcarriers 1 and 2 of OFDM symbols 4 and 5

Subcarriers 4 and 5 of the OFDM symbols 4 and 5

Subcarrier 7, 8 of OFDM symbols 4, 5

Subcarriers 10 and 11 of OFDM symbols 4 and 5

Subcarrier 0, 1 of OFDM symbol 10, 11

Subcarriers 3 and 4 of the OFDM symbols 10 and 11

Subcarriers 6 and 7 of the OFDM symbols 10 and 11

Subcarriers 9 and 10 of the OFDM symbols 10 and 11

The DM-RS may exist at the following position <DM-RS position 2> instead of the position of the <DM-RS position 1>.

<DM-RS Position 2>

Subcarriers 1 and 2 of OFDM symbols 4 and 5

Subcarriers 4 and 5 of the OFDM symbols 4 and 5

Subcarrier 7, 8 of OFDM symbols 4, 5

Subcarriers 10 and 11 of OFDM symbols 4 and 5

Subcarriers 1 and 2 of the OFDM symbols 10 and 11

Subcarriers 4 and 5 of the OFDM symbols 10 and 11

Subcarrier 7, 8 of OFDM symbols 10, 11

Subcarriers 10 and 11 of the OFDM symbols 10 and 11

If there is a DM-RS in the <DM-RS position 2> as described above, the CSI-RS pattern should also be changed accordingly.

17 illustrates a CSI-RS pattern according to the present invention when the DM-RS is present in the <DM-RS position 2>. FIG. 17 corresponds to a case where the LTE-A system transmits a transmission signal using an extended cyclic prefix.

The first of two CSI-RS patterns for the eight CSI-RS antenna ports of FIG. 17 is the same as the case of FIGS. 6, 10, and 12. The CSI-RS antenna port patterns for the eight CSI-RS antennas are DRS and Can be transmitted without collision. On the other hand, since the second CSI-RS pattern of FIG. 17 transmits using the OFDM symbol 10, collision with the DRS may occur.

The CSI-RS pattern of the present patent may also be applied to DM-RS positions different from the DM-RS position 1 and the DM-RS position 2. 18 shows a CSI-RS pattern according to the present invention for another DM-RS location. An important feature of the CSI-RS patterns for the eight CSI-RS antenna ports of FIGS. 6, 17, and 18 is that one of the two CSI-RS antenna patterns is always transmitted in OFDM symbol 5 and OFDM symbol 8, and has a length. Spreads to orthogonal codes of two. As described above, the CSI-RS signal is skipped without being transmitted to the OFDM symbols 6 and 7 in order to transmit the fifth OFDM symbol and the eighth OFDM symbol. The reason for transmitting the CSI-RS using the CSI-RS pattern as described above is to prevent collision with the antenna port 5 signal, that is, the DRS. In addition, the CSI-RS signals are not transmitted in OFDM symbols 6 and 7 in order to transmit the OFDM symbols 5 and the OFDM symbols 8 and use an orthogonal code having a length of 2, regardless of the positions of the DM-RS signals. 17 and 18 show characteristics of the CSI-RS antenna patterns.

In a subframe having the extended CP, the DM-RS is always transmitted using OFDM symbols 4 and 5, and is transmitted using 8 REs in OFDM symbols 4 and 5, respectively. That is, since one RB is composed of 12 REs on the frequency side, four REs are REs to which a DM-RS is not transmitted. One of the CSI-RS patterns proposed in the present invention is characterized in that it is most important to transmit the REs in which the DM-RS is not transmitted in the OFDM symbol 5 and the REs located at the same position on the frequency of the OFDM symbol 8. .

One of the CSI-RS patterns for the eight CSI-RS antenna ports of FIGS. 6, 17, and 18 has positions as shown in Tables 8 and 9 below.

CSI-RS Pattern 1 RE A OFDM symbol 5, subcarrier K RE B OFDM symbol 8, subcarrier K RE C OFDM symbol 5, subcarrier L RE D OFDM symbol 8, subcarrier L RE E OFDM symbol 5, subcarrier M RE F OFDM symbol 8, subcarrier M RE G OFDM symbol 5, subcarrier N RE H OFDM symbol 8, subcarrier N

In Table 8, subcarriers K, L, M, and N correspond to subcarrier indexes of REs not used for DM-RS transmission in OFDM symbols 4 and 5 within one RB. For example, in the case of FIG. 18, since the DM-RS is transmitted to subcarriers 0, 1, 3, 4, 7, 8, 10, and 11, values of K, L, M, and N are 2, 5, 6, and 9, respectively. As described above, one of the CSI-RS patterns for the eight CSI-RS antenna ports proposed by the present invention is the transmission of the DM-RS among the subcarriers of the OFDM symbol 5 when the position of the DM-RS is determined in the OFDM symbols 4 and 5 It is transmitted using a subcarrier that is not used for the same subcarriers of OFDM symbol 8. For this reason, even if the position of the DM-RS is different from those of FIGS. 6, 12, and 18 in the frequency domain, the CSI-RS pattern may be determined as shown in Table 8 above.

Another CSI-RS pattern for the subframe having the extended CP can be determined using the same base pattern for the DM-RS transmission location as shown in FIG. On the other hand, if the transmission location of the DM-RS is different from FIG. 6, another base pattern may be additionally used as shown in FIGS. 17 and 18. According to the present invention, when another base pattern is additionally used as shown in FIGS. 17 and 18, another CSI-RS pattern has the following positions.

CSI-RS Pattern 2 RE A OFDM symbol 10, subcarrier S RE B OFDM symbol 11, subcarrier S RE C OFDM symbol 10, subcarrier T RE D OFDM symbol 11, subcarrier T RE E OFDM symbol 10, subcarrier U RE F OFDM symbol 11, subcarrier U RE G OFDM symbol 10, subcarrier V RE H OFDM symbol 11, subcarrier V

In Table 9, subcarriers S, T, U, and V correspond to subcarrier indexes of REs not used for DM-RS transmission in OFDM symbols 10 and 11 within one RB. For example, in the case of FIG. 18, since the DM-RS is transmitted to subcarriers 0, 1, 3, 4, 7, 8, 10, and 11, the values of S, T, U, and V are 2, 5, 6, and 9, respectively. In another example of FIG. 17, since the DM-RS is transmitted to subcarriers 0, 2, 3, 5, 6, 8, 9, and 11, the values of S, T, U, and V are 1, 4, 7, and 10. . As described above, one of the CSI-RS patterns for the eight CSI-RS antenna ports proposed by the present invention is DM- among the subcarriers of the OFDM symbols 10 and 11 when the position of the DM-RS is determined in the OFDM symbols 10 and 11. It is transmitted using a subcarrier that is not used for RS transmission. For this reason, even if the position of the DM-RS is different from those of FIGS. 6, 12, and 18 in the frequency domain, the CSI-RS pattern may be determined as shown in Table 9 above.

The reason for determining another CSI-RS pattern as shown in Table 9 is that the CSI-RS pattern does not collide with the DM-RS and can transmit the CSI-RS.

The CSI-RS pattern in the subframe transmitted by the extended CP proposed in the present invention consists of a CSI-RS pattern for at least two CSI-RS antenna ports that do not collide with each other, the first CSI-RS pattern is shown in Table 8 As shown in FIG. 6 or Table 9, the second CSI-RS pattern is transmitted using OFDM symbols 5 and 8. By using the CSI-RS pattern for the eight CSI-RS antenna ports as described above, the CSI-RS patterns for four or two CSI-RS antenna ports having nested properties may also be derived as described above. .

19 illustrates a CSI-RS pattern in a subframe transmitted by another extended CP proposed by the present invention.

A total of four CSI-RS transmission patterns of FIG. 19 can transmit CSI-RS for eight CSI-RS antenna ports. The CSI-RS patterns of FIG. 19 are all made based on one base pattern. That is, the CSI-RS patterns 1, 2, 3, and 4 have the same shape except that only subcarrier and OFDM symbol positions are different from each other.

Among the CSI-RS patterns of FIG. 19, CSI-RS pattern1 and CSI-RS pattern2 are the same as the CSI-RS pattern1 and CSI-RS pattern2 of FIG. 6. 19, CSI-RS pattern3 and CSI-RS pattern4 were added. The CSI-RS pattern 3 and the CSI-RS pattern 4 may be used only when a common reference signal (CRS) is transmitted to only two antenna ports as shown in FIG. 19. That is, when the CRS is transmitted only through the first and second antenna ports, the CSI-RS pattern3 and the CSI-RS pattern4 may be transmitted.

Another characteristic of the CSI-RS pattern 3 and the CSI-RS pattern 4 of FIG. 19 is that the antenna port 5 signal, that is, may collide with the DRS signal. Such characteristics are not applicable to the CSI-RS pattern1 and the CSI-RS pattern2. Although CSI-RS pattern3 and CSI-RS pattern4 can be used in a limited case when CRS is transmitted to two antenna ports and no antenna port 5 signal is transmitted, the reuse factor of CSI-RS can be increased in a multicell system. This is useful because it has an effect.

In addition, another advantage of the CSI-RS pattern of FIG. 19 is that four CSI-RS patterns are made using one base pattern. As such, when all CSI-RS patterns are made with one base pattern, it is easy to implement a CSI-RS receiver.

19 illustrates CSI-RS patterns for eight CSI-RS antenna ports. The CSI-RS patterns of FIG. 19 may be extended to CSI-RS patterns for four or two CSI-RS antenna ports as in FIGS. 7 and 8.

In FIG. 19, signals for two CSI-RS antenna ports transmitted to the same subcarrier in one CSI-RS pattern may be transmitted by CDM or TDM and FDM as described above. For example, when the CDM is transmitted, the signal for the first CSI-RS antenna port transmitted to subcarrier 2 of CSI-RS pattern 3 is spread to Walsh code 0 of length 2 and transmitted to the second CSI-RS antenna port transmitted to subcarrier 2. The signal for spread is spread with Walsh code 1 of length 2.

20 illustrates a CSI-RS pattern in a subframe transmitted by another extended CP proposed by the present invention.

20 may be applied when the number of CRS antenna ports is two and the number of DM-RS antenna ports is two or less. A total of six CSI-RS transmission patterns of FIG. 20 can transmit CSI-RS for eight CSI-RS antenna ports. The CSI-RS patterns of FIG. 20 are all made based on one base pattern. That is, the CSI-RS patterns 1, 2, 3, 4, 5, and 6 have the same shape except that only subcarrier and OFDM symbol positions are different from each other.

Among the CSI-RS patterns of FIG. 20, the CSI-RS patterns 1, 2, and 3 may not be overlapped with the antenna port 5 signal in a subframe transmitted to the extended CP shown in FIG. 3. This is because the CSI-RS patterns 1, 2, and 3 of FIG. 20 are not transmitted in the OFDM symbols 4, 7, and 10, as mentioned above. On the other hand, the CSI-RS patterns 4, 5, and 6 of FIG. 20 may overlap positions with the antenna port 5 signal. For this reason, in the case of the LTE-A system using the antenna port 5, it is possible to determine whether to use the CSI-RS 4, 5, 6 of the CSI-RS patterns of FIG. That is, in case of LTE-A system using antenna port 5, one of the CSI-RS patterns 1, 2, and 3 is transmitted by selecting CSI-RS.

The REs in which the signals of the CSI-RS pattern 1 and the CSI-RS pattern 2 of FIG. 20 are transmitted are shown in Table 10 below.

CSI-RS Pattern 1 CSI-RS Pattern 2 RE A: OFDM symbol 5, subcarrier 0 RE A: OFDM symbol 8, subcarrier 2 RE C: OFDM symbol 5, subcarrier 3 RE C: OFDM symbol 8, subcarrier 5 RE D: OFDM symbol 8, subcarrier 3 RE D: OFDM symbol 11, subcarrier 5 RE E: OFDM symbol 5, subcarrier 6 RE E: OFDM symbol 8, subcarrier 8 RE G: OFDM symbol 5, subcarrier 9 RE G: OFDM symbol 8, subcarrier 11 RE H: OFDM symbol 8, subcarrier 9 RE H: OFDM symbol 11, subcarrier 11

The REs in which the signals of CSI-RS pattern 3 and CSI-RS pattern 4 are transmitted in FIG. 20 are shown in Table 11 below.

CSI-RS Pattern 3 CSI-RS Pattern 4 RE A: OFDM symbol 8, subcarrier 1 RE A: OFDM symbol 7, subcarrier 1 RE C: OFDM symbol 8, subcarrier 4 RE C: OFDM symbol 7, subcarrier 4 RE D: OFDM symbol 11, subcarrier 4 RE D: OFDM symbol 10, subcarrier 4 RE E: OFDM symbol 8, subcarrier 7 RE E: OFDM symbol 7, subcarrier 7 RE G: OFDM symbol 8, subcarrier 10 RE G: OFDM symbol 7, subcarrier 10 RE H: OFDM symbol 11, subcarrier 10 RE H: OFDM symbol 10, subcarrier 10

The REs in which the signals of the CSI-RS pattern 5 and the CSI-RS pattern 6 of FIG. 20 are transmitted are shown in Table 12 below.

CSI-RS Pattern 5 CSI-RS Pattern 6 RE A: OFDM symbol 4, subcarrier 0 RE A: OFDM symbol 4, subcarrier 2 RE C: OFDM symbol 4, subcarrier 3 RE C: OFDM symbol 4, subcarrier 5 RE D: OFDM symbol 7, subcarrier 3 RE D: OFDM symbol 7, subcarrier 5 RE E: OFDM symbol 4, subcarrier 6 RE E: OFDM symbol 4, subcarrier 8 RE F: OFDM symbol 7, subcarrier 6 RE F: OFDM symbol 7, subcarrier 8 RE G: OFDM symbol 4, subcarrier 9 RE G: OFDM symbol 4, subcarrier 11 RE H: OFDM symbol 7, subcarrier 9 RE H: OFDM symbol 7, subcarrier 11

The CSI-RS pattern defined by FIG. 20, Table 10, Table 11, and Table 12 is a position in one RB pair. The system bandwidth of the LTE-A system is composed of a plurality of RB pairs, and the CSI-RS pattern defined by FIGS. 20, 10, 11, and 12 is repeated for every RB pair.

21 shows a CSI-RS pattern in a subframe transmitted by another extended CP proposed by the present invention.

20 may be applied when the number of CRS antenna ports is two and the number of DM-RS antenna ports is two or less. A total of six CSI-RS transmission patterns of FIG. 20 can transmit CSI-RS for eight CSI-RS antenna ports. The CSI-RS patterns of FIG. 20 are all made based on one base pattern. That is, the CSI-RS patterns 1, 2, 3, 4, 5, and 6 have the same shape except that only subcarrier and OFDM symbol positions are different from each other.

Among the CSI-RS patterns of FIG. 21, the CSI-RS patterns 1, 2, and 3 may not be overlapped with the antenna port 5 signal in a subframe transmitted to the extended CP shown in FIG. 3. This is because the CSI-RS patterns 1, 2, and 3 of FIG. 21 are not transmitted in the OFDM symbols 4, 7, and 10, as mentioned above. On the other hand, the CSI-RS patterns 4, 5, and 6 of FIG. 21 may overlap positions with the antenna port 5 signal. For this reason, in the case of the LTE-A system using the antenna port 5, it is possible to determine whether to use the CSI-RS 4, 5, 6 of the CSI-RS patterns of FIG. That is, in case of LTE-A system using antenna port 5, one of the CSI-RS patterns 1, 2, and 3 is transmitted by selecting CSI-RS.

The REs in which the signals of the CSI-RS pattern 1 and the CSI-RS pattern 2 of FIG. 21 are transmitted are shown in Table 13 below.

CSI-RS Pattern 1 CSI-RS Pattern 2 RE A: OFDM symbol 5, subcarrier 0 RE A: OFDM symbol 8, subcarrier 2 RE C: OFDM symbol 5, subcarrier 3 RE C: OFDM symbol 8, subcarrier 5 RE D: OFDM symbol 8, subcarrier 3 RE D: OFDM symbol 11, subcarrier 5 RE E: OFDM symbol 5, subcarrier 6 RE E: OFDM symbol 8, subcarrier 8 RE G: OFDM symbol 5, subcarrier 9 RE G: OFDM symbol 8, subcarrier 11 RE H: OFDM symbol 8, subcarrier 9 RE H: OFDM symbol 11, subcarrier 11

The REs in which the signals of the CSI-RS pattern 3 and the CSI-RS pattern 4 of FIG. 21 are transmitted are shown in Table 14 below.

CSI-RS Pattern 3 CSI-RS Pattern 4 RE A: OFDM symbol 8, subcarrier 1 RE A: OFDM symbol 7, subcarrier 1 RE C: OFDM symbol 8, subcarrier 4 RE C: OFDM symbol 7, subcarrier 4 RE D: OFDM symbol 11, subcarrier 4 RE D: OFDM symbol 10, subcarrier 4 RE E: OFDM symbol 8, subcarrier 7 RE E: OFDM symbol 7, subcarrier 7 RE G: OFDM symbol 8, subcarrier 10 RE G: OFDM symbol 7, subcarrier 10 RE H: OFDM symbol 11, subcarrier 10 RE H: OFDM symbol 10, subcarrier 10

The REs in which the signals of the CSI-RS pattern 5 and the CSI-RS pattern 6 of FIG. 21 are transmitted are shown in Table 15 below.

CSI-RS Pattern 5 CSI-RS Pattern 6 RE A: OFDM symbol 4, subcarrier 0 RE A: OFDM symbol 7, subcarrier 2 RE C: OFDM symbol 4, subcarrier 3 RE C: OFDM symbol 7, subcarrier 5 RE D: OFDM symbol 7, subcarrier 3 RE D: OFDM symbol 10, subcarrier 5 RE E: OFDM symbol 4, subcarrier 6 RE E: OFDM symbol 7, subcarrier 8 RE G: OFDM symbol 4, subcarrier 9 RE G: OFDM symbol 7, subcarrier 11 RE H: OFDM symbol 7, subcarrier 9 RE H: OFDM symbol 10, subcarrier 11

It can be seen that the CSI-RS patterns of FIGS. 20 and 21 consist of one base pattern. When the base pattern is formed as described above, there is an advantage of easily implementing the CSI-RS transceiver. In addition, FIG. 20 and FIG. 21 have three CSI-RS patterns that do not collide with the antenna port, respectively, and thus may be applicable to a base station using antenna port 5 in the LTE-A system.

The CSI-RS patterns of FIGS. 20 and 21 may transmit signals for a plurality of CSI-RS antenna ports using various multiplexing methods. For example, you can use CDM on the time base. In this case, two REs transmitted using the same subcarrier in one CSI-RS pattern can be CDM using length 2 orthogonal codes. You can also use CDM on the frequency axis. In this case, CDM may be performed using orthogonal codes in a plurality of REs transmitted using the same OFDM symbol in one CSI-RS pattern.

The CSI-RS patterns of FIGS. 6 to 21 correspond to a case of transmitting using a subframe having an extended cyclic prefix in LTE and LTE-A systems. In addition to the subframe using the extended cyclic prefix, the LTE and LTE-A systems can also transmit the subframe using the normal cyclic prefix.

FIG. 22 illustrates a CRS, a DRS, a DM-RS, and a data channel signal PDSCH transmitted by an eNB in one RB pair when a subframe is transmitted using a normal cyclic prefix in the LTE-A system. The CRS is transmitted using four subcarriers in OFDM symbols 0, 1, 4, 6, 7, 8, 11, and 12, respectively, and the subcarrier position may be different for each cell. In addition, DRS is transmitted using three subcarriers in OFDM symbols 3, 6, 9, and 12, respectively, and the subcarrier position may be different for each cell.

FIG. 23 is a diagram for describing a location in time and frequency space to be used when transmitting CSI-RS in an LTE-A system that transmits using a normal cyclic prefix. FIG. 23 illustrates a region capable of transmitting CSI-RS in an LTE-A system within one RB pair.

In FIG. 23, 36 REs corresponding to OFDM symbols 0, 1, and 2 may not be used to transmit CSI-RSs because they are required to transmit control signals for LTE and LTE-A terminals. In addition, since 48 REs corresponding to OFDM symbols 4, 7, 8, and 11 are used to transmit CRSs, they cannot be used to transmit CSI-RSs. In addition, a total of 32 REs located in a subcarrier in which DM-RSs are transmitted in OFDM symbols 5, 6, 12, and 13 can be used to transmit CSI-RSs because they are required to transmit DM-RSs for LTE-A terminals. none.

FIG. 24 illustrates CSI-RS patterns used for CSI-RS transmission for eight CSI-RS antenna ports in an LTE-A system using a normal cyclic prefix according to the present invention.

24 is composed of six CSI-RS patterns each capable of transmitting signals for eight CSI-RS antenna ports. All six patterns consist of two REs located in OFDM symbols 5 and 6, four REs located in OFDM symbols 9 and 10, and two REs located in OFDM symbols 12 and 13.

In FIG. 24, one CSI-RS pattern consists of eight REs, and thus, signals for up to eight CSI-RS antenna ports can be transmitted. Signals for the eight CSI-RS antenna ports may be transmitted using code division multiplexing (CDM) and frequency division multiplexing (FDM) or using time division multiplexing (TDM) and FDM.

The REs in which the signals of the CSI-RS pattern 1 and the CSI-RS pattern 2 of FIG. 24 are transmitted are shown in Table 16, Table 17, and Table 18 below.

CSI-RS Pattern 1 CSI-RS Pattern 2 RE A: OFDM symbol 5, subcarrier 2 RE A: OFDM symbol 5, subcarrier 7 RE B: OFDM symbol 6, subcarrier 2 RE B: OFDM symbol 6, subcarrier 7 RE C: OFDM symbol 9, subcarrier 0 RE C: OFDM symbol 9, subcarrier 6 RE D: OFDM symbol 10, subcarrier 0 RE D: OFDM symbol 10, subcarrier 6 RE E: OFDM symbol 9, subcarrier 3 RE E: OFDM symbol 9, subcarrier 9 RE F: OFDM symbol 10, subcarrier 3 RE F: OFDM symbol 10, subcarrier 9 RE G: OFDM symbol 12, subcarrier 2 RE G: OFDM symbol 12, subcarrier 7 RE H: OFDM symbol 13, subcarrier 2 RE H: OFDM symbol 13, subcarrier 7

CSI-RS Pattern 3 CSI-RS Pattern 4 RE A: OFDM symbol 5, subcarrier 3 RE A: OFDM symbol 5, subcarrier 8 RE B: OFDM symbol 6, subcarrier 3 RE B: OFDM symbol 6, subcarrier 8 RE C: OFDM symbol 9, subcarrier 1 RE C: OFDM symbol 9, subcarrier 7 RE D: OFDM symbol 10, subcarrier 1 RE D: OFDM symbol 10, subcarrier 7 RE E: OFDM symbol 9, subcarrier 4 RE E: OFDM symbol 9, subcarrier 10 RE F: OFDM symbol 10, subcarrier 4 RE F: OFDM symbol 10, subcarrier 10 RE G: OFDM symbol 12, subcarrier 3 RE G: OFDM symbol 12, subcarrier 8 RE H: OFDM symbol 13, subcarrier 3 RE H: OFDM symbol 13, subcarrier 8

CSI-RS Pattern 1 CSI-RS Pattern 2 RE A: OFDM symbol 5, subcarrier 4 RE A: OFDM symbol 5, subcarrier 9 RE B: OFDM symbol 6, subcarrier 4 RE B: OFDM symbol 6, subcarrier 9 RE C: OFDM symbol 9, subcarrier 2 RE C: OFDM symbol 9, subcarrier 8 RE D: OFDM symbol 10, subcarrier 2 RE D: OFDM symbol 10, subcarrier 8 RE E: OFDM symbol 9, subcarrier 5 RE E: OFDM symbol 9, subcarrier 11 RE F: OFDM symbol 10, subcarrier 5 RE F: OFDM symbol 10, subcarrier 11 RE G: OFDM symbol 12, subcarrier 4 RE G: OFDM symbol 12, subcarrier 9 RE H: OFDM symbol 13, subcarrier 4 RE H: OFDM symbol 13, subcarrier 9

Some of the six CSI-RS patterns of FIG. 24 collide with the DRS for the LTE terminal. The V_shift value of the collision between the six CSI-RS patterns and the DRS of FIG. 24 is determined. The V_shift serves to move the DRS in the subcarrier unit in the frequency domain with an offset value in the subcarrier unit in the frequency domain.

FIG. 25 illustrates that the DRS having different V_shift values collide with the six CSI-RS patterns of FIG. 24.

In FIG. 25, when the V_shift value is V_shift1, as in 2500, CSI-RS pattern 1, CSI-RS pattern 4, and CSI-RS pattern 6 collide with the DRS. In addition, when the V_shift value is V_Shift2, as in 2510, CSI-RS pattern 1, CSI-RS pattern 3, CSI-RS pattern 6 collides with the DRS. In addition, when the V_shift value is equal to 2520 on V_Shift3, CSI-RS pattern 2, CSI-RS pattern 3, and CSI-RS pattern 5 collide with the DRS. Even if the V_shift value is different as shown in FIG. 25, CSI-RS patterns for the eight CSI-RS antenna ports of FIG. 24 according to the present invention are guaranteed not to collide with at least three DRS. The V_shift value is determined according to a Cell_ID value for distinguishing each cell in LTE and LTE-A systems. The value of V_shitf and Cell_ID have a relationship of V_shift = Cell_ID mod 3.

The CSI-RS patterns of FIG. 24 guarantee three non-collision CSI-RS patterns regardless of the V_shift value of the DRS. Using the characteristics of the CSI-RS pattern of FIG. 24, the LTE-A system transmits 8 CSI-RS antenna ports by applying one of the CSI-RS patterns that do not collide in the corresponding subframe section when transmitting the DRS for the LTE terminal. May transmit the CSI-RS for. For example, in case of Vshift1 as shown in 2500 of FIG. 25, the eNB uses the CSI-RS pattern in one of the CSI-RS pattern 2, CSI-RS pattern 3, and CSI-RS pattern 5 in a subframe in which DRS should be transmitted. Send RS As such, having CSI-RS patterns that do not collide with a plurality of DRSs is an important feature of the present invention. If there are CSI-RS patterns that do not collide with the three DRSs, the reuse factor of the CSI-RS becomes 3 even in the subframe transmitting the DRS, which may have an advantage of reducing the effect of inter-cell interference.

FIG. 26 illustrates a method of determining one of a plurality of applicable CSI-RS patterns by an eNB so that the CSI-RS and the DRS do not collide according to the present invention.

In step 2600 of FIG. 26, the eNB determines a subframe to transmit the CSI-RS. In step 2610 of FIG. 26, the eNB determines whether to also transmit a DRS in a subframe determined to transmit the CSI-RS. If it is determined in step 2610 that the DRS should also be transmitted in the subframe in which the CSI-RS is to be transmitted, the eNB determines V_shift using the Cell_ID in step 2620. The transmission position of the DRS is determined in step 2630 by the V_shift value determined in step 2620. After the transmission location of the DRS is determined in step 2630, the eNB determines which CSI-RS pattern does not collide with the DRS in step 2640. As an example, when the V_shift value of the DRS is V_shift2 in FIG. 25, it is determined as CSI-RS pattern2, CSI-RS pattern3, and CSI-RS pattern 4.

In step 2640, the eNB that determines which CSI-RS antenna patterns are available without collision with the DRS determines in step 2650 which CSI-RS antenna pattern is used to transmit the CSI-RS. A method of determining which CSI-RS antenna pattern to use in step 2650 according to the present invention uses the following equation.

In Equation 1, N_A is the number of CSI-RS patterns that do not collide with the DRS determined in step 2640. The above equation generates an integer from 0 to N_A-1 when there are N_A applicable CSI-RS patterns while avoiding collision with the DRS. In Equation 1, one of the applicable CSI-RS patterns is determined using the result value obtained by the Cell_ID and the number of applicable CSI-RS patterns. In order to determine by using Equation 1, different integer values from 0 to N_A-1 are pre-assigned to the applicable CSI-RS patterns, and then the CSI-RS pattern is determined by using the resultant values. As an example, when the V_shift value is V_shift2 in FIG. 25, one of three CSI-RS patterns of CSI-RS pattern2, CSI-RS pattern3, and CSI-RS pattern4 should be used to avoid collision with the DRS. The eNB assigns CSI_ID values of 0, 1, and 2 to CSI-RS pattern2, CSI-RS pattern3, and CSI-RS pattern4, respectively, and then applies its Cell_ID to Equation 1 to determine the CSI_ID to be used. If the Cell_ID value is 10, since the N_A value is 3 in the above example, the CSI_ID value is 1 and the eNB uses the CSI-RS pattern3. In Equation 1, another value of N_A may be applied according to a V_shift value.

When the DRS is not transmitted in the subframe transmitting the CSI-RS in step 2610 of FIG. 26, the eNB determines a CSI-RS pattern to be used when transmitting the CSI-RS among all CSI-RS patterns applicable in the step 2660. A method of determining which CSI-RS antenna pattern is to be used in step 2660 uses Equation 2 below.

In Equation 2, N_B is the number of all applicable CSI-RS patterns. For example, in FIG. 24, the value of N_B is 6. In the embodiment of the present invention, the method of determining the CSI-RS pattern by Equation 1 and Equation 2 determines the CSI_ID by differently setting the N_A and N_B values according to the existence of the DRS, and accordingly the CSI-RS pattern This has an important characteristic that is determined. In Equation 2, since N_B is the number of all applicable CSI-RS patterns, it has a fixed value regardless of V_shift.

FIG. 27 illustrates a method for self-determining a CSI-RS determined by an eNB when an eNB determines and uses a CSI-RS pattern in which the CSI-RS and a DRS do not collide with each other according to the present invention. .

In step 2700 of FIG. 27, the UE determines the Cell_ID of the eNB. The method of determining the Cell_ID in step 2700 is performed by receiving a control channel transmitted by an eNB. In step 2710, the UE receives information on the subframe in which the CSI-RS is transmitted from the eNB. In step 2720, the UE is informed from the eNB about whether the eNB transmits the DRS in the corresponding subframe. In the present invention, the information is referred to as DRS_ONOFF as a signal transmitted to all terminals receiving a data signal from the eNB. Upon receiving the DRS_ONOFF information in step 2720, the UE determines whether the DRS is transmitted in a subframe in which the CSI-RS is transmitted, as follows.

■ DRS_ONOFF = 0: DRS is not transmitted in the subframe in which CSI-RS is transmitted.

■ DRS_ONOFF = 1: DRS is transmitted in the subframe in which CSI-RS is transmitted.

In step 2730 of FIG. 27, when the UE determines whether the DRS is transmitted according to the DRS_ONOFF value, when the DRS is transmitted in the subframe in which the CSI-RS is transmitted, the UE determines the V_shift value using the Cell_ID as in step 2740. A method of determining the V_shift value in step 2740 is shown in Equation 1 above. The UE, having determined the V_shif t value in step 2740, determines the DRS transmission location according to the V_shift value in step 2750. After the DRS transmission location determined in step 2750 is determined, the UE determines which CSI-RS does not collide with the DRS in step 2760, and determines one of them to receive CSI-RS in step 2770. Specific methods used in steps 2760 and 2770 are the same as those used in steps 2640 and 2650 of FIG. 26. This is because the UE and the eNB must determine the CSI-RS pattern in the same manner so that the UE can receive exactly what the eNB has transmitted.

If it is determined in step 2730 that the DRS is not transmitted in the subframe transmitting the CSI-RS, the UE determines a CSI-RS pattern to be used when transmitting the CSI-RS among all applicable CSI-RS patterns as shown in step 2780. The specific method used in step 2780 is the same as the specific method used in step 2660 of FIG. 26.

FIG. 27 is applicable to a case in which the UE determines itself which CSI-RS pattern to select by using the same method as the CSI-RS pattern determination method of the eNB. In addition to the method illustrated in FIG. 27, it is also possible to notify the UE directly about which CSI-RS pattern to use when the eNB does not provide information on the DRS.

The signal for each CSI-RS antenna port of FIG. 24 may be transmitted using CDM and FDM as shown in Table 2 or may be transmitted using TDM and FDM as shown in Table 3 above. When the CSI-RS pattern of FIG. 24 uses CDM and FDM or TDM and FDM, signals of all CSI-RS antenna ports are not transmitted in one OFDM symbol. It is the same as the case of FIG. Not all CSI-RS antenna port signals are transmitted in one OFDM symbol can be solved by cyclically changing the position in the RB pair through which the CSI-RS antenna port is transmitted as shown in FIG.

FIG. 28 is a CSI-RS pattern of FIG. 24 according to the present invention. When transmitting CSI-RS using CDM and FDM, the CSI-RS antenna port can transmit signals efficiently so that transmission power can be efficiently used. It shows how to change the circulation.

When FIG. 28 uses the CSI-RS pattern of FIG. 24, CSI-RS is transmitted using the CSI-RS pattern of FIG. 24 as shown in 2800 in 1/4 RB pairs constituting a system bandwidth. The other 1/4 RB pairs transmit the CSI-RS using the CSI-RS pattern modified from the CSI-RS pattern of FIG. 24 as shown in 2810. In another 1/4 RB pairs, the CSI-RS is transmitted using the CSI-RS pattern modified from the CSI-RS pattern of FIG. 24 as shown in 2820. In the other 1/4 RB pairs, 2830 and 2830 are transmitted. As described above, the CSI-RS is transmitted using the CSI-RS pattern modified from the CSI-RS pattern of FIG. 24.

As shown in FIG. 28, signals of all CSI-RS antenna ports are transmitted in all OFDM symbols transmitting CSI-RS. As such, when signals of all CSI-RS antenna ports are transmitted in OFDM symbols transmitting CSI-RS, waste of transmission power can be prevented by exchanging unused power for each CSI-RS antenna port in each RE.

The CSI-RS patterns of FIG. 24 are structures for eight CSI-RS antenna ports. As above, the CSI-RS pattern for the four CSI-RS antenna ports having the nested properties based on the CSI-RS patterns of FIG. 24 and the CSI-RS pattern for the two CSI-RS antenna ports are also described above. It can be obtained in the same way.

FIG. 29 illustrates another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to the present invention.

FIG. 30 illustrates another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to the present invention.

The CSI-RS patterns of FIGS. 29 and 30 also have a reuse factor of 6 as in FIG. 24. One important difference compared to the case of FIG. 24 is that the number of CSI-RS patterns that do not collide with the DRS is small when the DRS is present. On the other hand, since one CSI-RS is distributed in up to four OFDM symbols, when transmitting using CDM and FDM, four types of CSI-RS patterns are cyclically changed as shown in FIG. Likewise, if two types of CSI-RS patterns are cyclically changed, efficient transmission power can be used even when transmitting.

FIG. 31 illustrates another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to the present invention.

FIG. 31 illustrates a cyclic shift based on an intermediate section in the frequency domain of RB. That is, in FIG. 31, it can be seen that the positions of E and F of the CSI-RS antenna pattern 1 have moved one subcarrier section compared to RE A, RE B, or RE C, RE D of the same CSI-RS pattern. . In addition, it can be seen that the positions of E and F of the CSI-RS antenna pattern 2 have moved one subcarrier interval compared to RE A, RE B, or RE C, RE D of the same CSI-RS pattern. In addition, the positions of RE E and RE F of the CSI-RS antenna pattern 3 were shifted in two subcarrier sections in the opposite direction compared to the positions of RE A and RE B according to the cyclic shift.

32 shows another CSI-RS patterns for eight CSI-RS antenna ports for CSI-RS transmission in an LTE-A system transmitting using a normal cyclic prefix according to the present invention.

32 shows mirroring based on an intermediate section in the frequency domain of the RB. That is, in FIG. 31, the position of each CSI-RS pattern forms a reflection relationship with respect to the intermediate section in the frequency region of RB. In FIG. 31, the distance from the middle point of RB is the same as that of RE C and RE D of CSI-RS pattern having the same positions of RE E and RE F of CSI-RS antenna pattern 1. In addition, the distance from the middle point of RB is the same as that of RE A and RE B of the same CSI-RS pattern of RE G and RE H of the CSI-RS antenna pattern 1.

The CSI-RS pattern of FIGS. 31 and 32 is a method for maximizing the number of CSI-RS patterns that do not collide with the DRS. When using the CSI-RS pattern of FIGS. 31 and 32, a CSI-RS pattern that does not overlap at least two DRSs exists even if the V_shift of the DRS has any value.

On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. That is, it will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented.

Claims (3)

In the method for processing a CSI-RS in a base station in a wireless communication system,
Determining a subframe in which to transmit the CSI-RS;
When the DRS should also be transmitted in the determined subframe, determining a DRS transmission position according to V_shift and V_shift, and determining a CSI_RS pattern that does not collide with the DRS and a CSI-RS pattern for transmitting the CSI-RS;
When the DRS is not transmitted in the determined subframe, the CSI-RS processing method of the base station characterized in that the process of determining the CSI-RS pattern to transmit the CSI-RS out of all the CSI-RS patterns. In the method for the terminal to process the CSI-RS in a wireless communication system,
Receiving subframe information in which the CSI-RS is transmitted to the base station and information on whether the eNB transmits the DRS in the subframe;
Checking whether the DRS is also transmitted in the subframe in which the CSI-RS is to be transmitted;
When the DRS is also to be transmitted, determining a DRS transmission position according to V_shift and V_shift, determining a CSI_RS pattern that does not collide with the DRS and a CSI-RS pattern for transmitting the CSI-RS;
If the DRS is not transmitted, the CSI-RS processing method of the base station of the terminal characterized in that the process of determining the CSI-RS pattern to transmit the CSI-RS out of all the CSI-RS patterns. In a wireless communication system,
If DRS should also be transmitted in a subframe to transmit CSI-RS, determine the DRS transmission position according to V_shift and V_shift, determine the CSI_RS pattern that does not collide with the DRS and the CSI-RS pattern to transmit the CSI-RS, and determine the DRS A base station for determining a CSI-RS pattern to transmit CSI-RS among all CSI-RS patterns when not transmitting;
Receives subframe information to which the CSI-RS is transmitted to the base station and information on whether the eNB transmits the DRS in the corresponding subframe, and if the DRS should also be transmitted in the subframe to which the CSI-RS is transmitted, the DRS according to V_shift and V_shift Determine the transmission location, determine the CSI_RS pattern that does not collide with the DRS and the CSI-RS pattern to transmit the CSI-RS, and if the DRS is not transmitted, the CSI-RS pattern to transmit the CSI-RS among all the CSI-RS patterns Wireless communication system comprising a terminal for determining the.

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