Method for generating reference signal sequence in multi-antenna wireless communication system and apparatus for same

Abstract

The present application discloses a method in which a base station transmits a reference signal sequence in a wireless communication system. In detail, the method comprises the steps of: generating a pseudo-random sequence using a first m-sequence and a second m-sequence; generating the reference signal sequence using the pseudo-random sequence; and transmitting the reference signal to a mobile station via antenna ports different from one another. The second m-sequence has an initial value containing parameters for discriminating reference signal sequences among users.

Claims

1. A method of transmitting a user equipment (UE) specific reference signal sequence by a base station (BS) in a wireless communication system, the method comprising: generating the UE specific reference signal sequence based on a pseudo-random sequence defined by a first m-sequence and a second m-sequence; transmitting the UE specific reference signal sequence to a UE, wherein an initial value of the first m-sequence is a fixed value, wherein an initial value of the second m-sequence is determined using a cell identity, wherein the cell identity is configured based on a transmission mode of the BS, wherein the pseudo-random sequence is represented as c(n) and is defined by following equation A:
c(n)=(x.sub.1n+N.sub.C)+x.sub.2(n+N.sub.C))mod 2
x.sub.1(n+31)=(x.sub.1(n+3)+x.sub.1(n))mod 2
x.sub.2(n+31)=(x.sub.2(n+3)+x.sub.2(n+2)+x.sub.2(n+1)+x.sub.2(n))mod 2,[Equation A] where N.sub.C=1600, wherein the first m-sequence is represented as x.sub.1(n) and is initialized with x.sub.1(0)=1, x.sub.1(n)=0, n=1, 2, . . . , 30, and wherein the second m-sequence is represented as x.sub.2(n), and wherein an initial value of the second m-sequence is represented by
(n.sub.s/2+1).Math.(2n.sub.ID+1).Math.2.sup.16+k, wherein k is an indicator indicated by a physical downlink control channel (PDCCH), where n.sub.s is a slot number within a radio frame and n.sub.ID is the cell identity.

2. The method of claim 1, wherein the UE specific reference signal sequence is represented as r(m) and is defined by following equation B: $\begin{array}{cc}r\left(m\right)=\frac{1}{\sqrt{2}}\left(1-2.Math.c\left(2m\right)\right)+j\frac{1}{\sqrt{2}}\left(1-2.Math.c\left(2m+1\right)\right),m=0,1,\mathrm{.Math.},12N_{\mathrm{RB}}^{\mathrm{PDSCH}}-1,& .Math.\mathrm{equation}B.Math.\end{array}$ where N.sub.RB.sup.PDSCH is a number of resource blocks allocated to a Physical downlink shared channel (PDSCH).

3. A base station (BS) in a wireless communication system, the BS comprising: a processor for generating a user equipment (UE) specific reference signal sequence based on a pseudo-random sequence defined by a first m-sequence and a second m-sequence; and a Radio Frequency (RF) module for transmitting the UE specific reference signal sequence to a UE, wherein an initial value of the first m-sequence is a fixed value, wherein an initial value of the second m-sequence is determined using a cell identity, wherein the cell identity is configured based on a transmission mode of the BS, wherein the pseudo-random sequence is represented as c(n) and is defined by following equation A:
c(n)=(x.sub.1n+N.sub.C)+x.sub.2(n+N.sub.C))mod 2
x.sub.1(n+31)=(x.sub.1(n+3)+x.sub.1(n))mod 2
x.sub.2(n+31)=(x.sub.2(n+3)+x.sub.2(n+2)+x.sub.2(n+1)+x.sub.2(n))mod 2,[Equation A] where N.sub.C=1600, wherein the first m-sequence is represented as x.sub.1(n) and is initialized with x.sub.1(0)=1, x.sub.1(n)=0, n=1, 2, . . . , 30, and wherein the second m-sequence is represented as x.sub.2(n), and wherein an initial value of the second m-sequence is represented by
(n.sub.s/2+1).Math.(2n.sub.ID+1).Math.2.sup.16+k, wherein k is an indicator indicated by a physical downlink control channel (PDCCH), where n.sub.s is a slot number within a radio frame and n.sub.ID is the cell identity.

4. A method for receiving a user equipment (UE) specific reference signal sequence at a UE in a wireless communication system, the method comprising: receiving the UE specific reference signal sequence from a base station (BS); and demodulating a Physical downlink shared channel (PDSCH) based on the UE specific reference signal sequence, wherein the UE specific reference signal sequence is generated based on a pseudo-random sequence defined by a first m-sequence and a second m-sequence, wherein an initial value of the first m-sequence is a fixed value, wherein an initial value of the second m-sequence is determined using a cell identity, wherein the cell identity is configured based on a transmission mode of the BS, wherein the pseudo-random sequence is represented as c(n) and is defined by following equation A:
c(n)=(x.sub.1n+N.sub.C)+x.sub.2(n+N.sub.C))mod 2
x.sub.1(n+31)=(x.sub.1(n+3)+x.sub.1(n))mod 2
x.sub.2(n+31)=(x.sub.2(n+3)+x.sub.2(n+2)+x.sub.2(n+1)+x.sub.2(n))mod 2,[Equation A] where N.sub.C=1600, wherein the first m-sequence is represented as x.sub.1(n) and is initialized with x.sub.1(0)=1, x.sub.1(n)=0, n=1, 2, . . . , 30, and wherein the second m-sequence is represented as x.sub.2(n), and wherein an initial value of the second m-sequence is represented by
(n.sub.s/2+1).Math.(2n.sub.ID+1).Math.2.sup.16+k, wherein k is an indicator indicated by a physical downlink control channel (PDCCH), where n.sub.s is a slot number within a radio frame and n.sub.ID is the cell identity.

5. The method according to claim 4, wherein the UE specific reference signal sequence is represented as r(m) and is defined by following equation B: $\begin{array}{cc}r\left(m\right)=\frac{1}{\sqrt{2}}\left(1-2.Math.c\left(2m\right)\right)+j\frac{1}{\sqrt{2}}\left(1-2.Math.c\left(2m+1\right)\right),m=0,1,\mathrm{.Math.},12N_{\mathrm{RB}}^{\mathrm{PDSCH}}-1,& .Math.\mathrm{equation}B.Math.\end{array}$ where N.sub.RB.sup.PDSCH is a number of resource blocks allocated to a Physical downlink shared channel (PDSCH).

6. A user equipment (UE) in a wireless communication system, the UE comprising: a Radio Frequency (RF) module for receiving a UE specific reference signal sequence from a base station (BS); and a processor for demodulating a Physical downlink shared channel (PDSCH) based on the UE specific reference signal sequence, wherein the UE specific reference signal sequence is generated based on a pseudo-random sequence defined by a first m-sequence and a second m-sequence, wherein an initial value of the first m-sequence is a fixed value, wherein an initial value of the second m-sequence is determined using a cell identity, wherein the cell identity is configured based on a transmission mode of the BS, wherein the pseudo-random sequence is represented as c(n) and is defined by following equation A:
c(n)=(x.sub.1n+N.sub.C)+x.sub.2(n+N.sub.C))mod 2
x.sub.1(n+31)=(x.sub.1(n+3)+x.sub.1(n))mod 2
x.sub.2(n+31)=(x.sub.2(n+3)+x.sub.2(n+2)+x.sub.2(n+1)+x.sub.2(n))mod 2,[Equation A] where N.sub.C=1600, wherein the first m-sequence is represented as x.sub.1(n) and is initialized with x.sub.1(0)=1, x.sub.1(n)=0, n=1, 2, . . . , 30, and wherein the second m-sequence is represented as x.sub.2(n), and wherein an initial value of the second m-sequence is represented by
(n.sub.s/2+1).Math.(2n.sub.ID+1).Math.2.sup.16+k, wherein k is an indicator indicated by a physical downlink control channel (PDCCH), where n.sub.s is a slot number within a radio frame and n.sub.ID is the cell identity.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram for a configuration of a general multi-antenna (MIMO) communication system.

(2) FIG. 2 is a diagram of structures of control and user planes of a radio interface protocol between a user equipment and E-UTRAN based on 3GPP radio access network specification.

(3) FIG. 3 is a diagram for explaining physical channels used for 3GPP system and a general method of transmitting a signal using the same.

(4) FIG. 4 is a diagram for an example of a structure of a radio frame used for LTE system.

(5) FIG. 5 is a diagram for an example of a structure of a downlink (DL) radio frame used for LTE system.

(6) FIG. 6 is a diagram for an example of a control channel included in a control region of one subframe in a DL radio frame.

(7) FIG. 7 is a conceptional diagram for CoMP (coordinated multi-point) scheme of an intra base station (intra eNB) and an inter base station (inter eNB) according to a related art.

(8) FIG. 8 is a diagram for a structure of a reference signal in LTE system supportive of DL transmission using 4 antennas.

(9) FIG. 9 is an exemplary block diagram of a user equipment according to one embodiment of the present invention.

BEST MODE FOR INVENTION

(10) Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described in the following description may include the examples showing that the technical features of the present invention are applied to 3GPP system.

(11) Although an embodiment of the present invention is exemplarily described in the present specification using the LTE system and the LTE-A system, the embodiment of the present invention may be also applicable to any kinds of communication systems corresponding to the above definitions. Although an embodiment of the present invention is exemplarily described with reference to FDD scheme in the present specification, the embodiment of the present invention is easily modifiable and applicable to H-FDD or TDD scheme.

(12) FIG. 2 is a diagram of structures of control and user planes of a radio interface protocol between a user equipment and E-UTRAN based on 3GPP radio access network specification. Especially, FIG. 2(a) is a diagram of structures of control plane of the radio interface protocol, and FIG. 2(b) is a diagram of structures of user plane of the radio interface protocol. First of all, a control plane may mean a passage for transmitting control messages used by a user equipment and a network to mange a call. And, a user plane may mean a passage for transmitting such data generated from an application layer as voice data, internet packet data and the like.

(13) A physical layer, i.e., a first layer, provides an information transfer service to an upper layer using a physical channel. The physical layer is connected to a medium access control layer located above via a transport channel. Data are transferred between the medium access control layer and the physical layer via the transport channel. Data are transferred between a physical layer of a transmitting side and a physical layer of a receiving side via a physical channel. The physical channel uses time and frequency as radio resources. In particular, a physical layer is modulated in downlink by OFDMA (orthogonal frequency division multiple access) scheme and is modulated in uplink by SC-FDMA (single carrier frequency division multiple access) scheme.

(14) A medium access control (hereinafter abbreviated MAC) layer of a second layer provides a service to a radio link control (hereinafter abbreviated RLC) layer of an upper layer via a logical channel. The RLC layer o the second layer supports reliable data transfer. A function of the RLC layer can be implemented using a function block within the MAC. A packet data convergence protocol (hereinafter abbreviated PDCP) layer of the second layer performs a header compression function for reducing unnecessary control information to transmit such an IP packet as IPv4 and IPv6 in a radio interface having a narrow bandwidth.

(15) A radio resource control (hereinafter abbreviated RRC) layer located on a lowest level of a third layer is defined in a control plane only. The RRC layer is responsible for controlling logical channel, transport channel and physical channels in association with configuration, reconfiguration and release of radio bearers (RBs). In this case, the RB means a service provided by the second layer for a data transfer between a user equipment and a network. For this, the RRC layer of the user equipment exchanges RRC messages with the RRC layer of the network. If there is an RRC connection established between RRC layers of the user equipment and the network, the user equipment may be in a connected mode. Otherwise, the user equipment may be in an RRC idle mode. NAS (non-access stratum) layer above the RRC layer may perform such a function as session management, mobility management and the like.

(16) One cell, which constructs a base station (eNB), is set to one of bandwidths including 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz and the like and may then provide an uplink or downlink transmission service to a plurality of user equipments. Different cells can be set to provide different bandwidths, respectively.

(17) A downlink transport channel for transporting data to a user equipment from a network may include one of a broadcast channel (BCH) for transporting system information, a paging channel (PCH) for transmitting a paging message, a downlink shared channel (SCH) for transmitting a user traffic or a control message and the like. A traffic or control message of a downlink multicast or broadcast service can be transmitted via a downlink SCH or a separate downlink multicast channel (MCH). Meanwhile, an uplink transport channel for transmitting data from a user equipment to a network may include one of a random access channel (RACH) for transmitting an initial control message, an uplink shared channel (SCH) for transmitting a user traffic or a control message or the like. A logical channel located above a transport channel to be mapped by a transport channel may include one of BCCH (Broadcast Control Channel), PCCH (Paging Control Channel), CCCH (Common Control Channel), MCCH (Multicast Control Channel), MTCH (Multicast Traffic Channel) and the like.

(18) FIG. 3 is a diagram for explaining physical channels used for 3GPP system and a general method of transmitting a signal using the same.

(19) If a power of a user equipment is turned on or the user equipment enters a new cell, the user equipment may perform an initial cell search for matching synchronization with a base station and the like [S301]. For this, the user equipment receives a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from the base station, matches synchronization with the base station and then obtains information such as a cell ID and the like. Subsequently, the user equipment receives a physical broadcast channel from the base station and is then able to obtain intra-cell broadcast information. Meanwhile, the user equipment may receive a downlink reference signal (DL RS) in the initial cell searching step and may be then able to check a downlink channel status.

(20) Having completed the initial cell search, the user equipment may receive a physical downlink control channel (PDCCH) and a physical downlink shared control channel (PDSCH) according to information carried on the physical downlink control channel (PDCCH) and may be then able to obtain system information in further detail [S302].

(21) Meanwhile, if the user equipment initially accesses the base station or fails to have a radio resource for signal transmission, the user equipment may be able to perform a random access procedure (RACH) on the base station [S303 to S306]. For this, the user equipment may transmit a specific sequence as a preamble via a physical random access channel (PRACH) [S303, S305] and may be then able to receive a response message via PDCCH and a corresponding PDSCH in response to the preamble [S304, S306]. In case of contention based RACH, it may be able to perform a contention resolution procedure in addition.

(22) Having performed the above mentioned procedures, the user equipment may be able to perform PDCCH/PDSCH reception [S307] and PUSCH/PUCCH (physical uplink shared channel/physical uplink control channel) transmission [S308] as a general uplink/downlink signal transmission procedure. Meanwhile, control information transmitted/received in uplink/downlink to/from the base station by the user equipment may include DL/UL ACK/NACK signal, CQI (channel quality indicator), PMI (precoding matrix index), RI (rank indicator) and the like. In case of the 3GPP LTE system, the user equipment may be able to transmit the above-mentioned control information such as CQI, PMI, RI and the like via PUSCH and/or PUCCH.

(23) FIG. 4 is a diagram for an example of a structure of a radio frame used for LTE system.

(24) Referring to FIG. 4, a radio frame has a length of 10 ms (327200.Math.T.sub.s) and is constructed with 10 subframes in equal size. Each of the subframes has a length of 1 ms and is constructed with two slots. Each of the slots has a length of 0.5 ms (15360 T.sub.s). In this case, T.sub.s indicates a sampling time and is expressed as T.sub.s=1/(15 kHz2048)=3.255210.sup.8 (about 33 ns). The slot includes a plurality of OFDM symbols in a time domain and includes a plurality of resource blocks (RB) in a frequency domain. In the LTE system, one resource block includes 12 subcarriers7 or 6 OFDM symbols. A transmission time interval (TTI), which is a unit time for transmitting data, can be determined by at least one subframe unit. The above described structure of the radio frame is just exemplary. And, the number of subframes included in a radio frame, the number of slots included in a subframe and/or the number of OFDM symbols included in a slot may be modified in various ways.

(25) FIG. 5 is a diagram for an example of a structure of a downlink (DL) radio frame used for LTE system.

(26) Referring to FIG. 5, a DL radio frame may include 10 subframes equal to each other in size. A subframe in 3GPP LTE system may be defined by a basic time unit of packet scheduling for all DL link frequency. Each subframe may be divided into a time interval (i.e., control region) for transmission of scheduling information and other control informations and a time interval (i.e., data region) for DL data transmission. The control region starts with a 1.sup.st OFDM symbol and may include at least one or more OFDM symbols. A size of the control region may be set independent per subframe. The control region may be used to transmit L1/L2 (layer 1/layer 2) control signal. And, the data region may be used to transmit DL traffic.

(27) FIG. 6 is a diagram for an example of a control channel included in a control region of one subframe in a DL radio frame.

(28) Referring to FIG. 6, a subframe may include 14 OFDM symbols. First 1 to 3 OFDM symbols may be used as a control region and the rest of 13 to 11 OFDM symbols may be used as a data region, in accordance with subframe settings. In the drawing, R1 to R4 indicate reference signals (RS) or pilot signals for antennas 0 to 3, respectively. The RS may be fixed to a predetermined pattern in a subframe irrespective of the control region or the data region. The control region may be assigned to a resource, to which the RS is not assigned, in the control region. And, a traffic channel may be assigned to a resource, to which the RS is not assigned, in the data region. Control channels assigned to the control region may include PCFICH (Physical Control Format Indicator CHannel), PHICH (Physical Hybrid-ARQ Indicator CHannel), PDCCH (Physical Downlink Control CHannel) and the like.

(29) FIG. 7 is a conceptional diagram for CoMP (coordinated multi-point) scheme of an intra eNB and an inter eNB according to a related art.

(30) Referring to FIG. 7, intra base stations 710 and 720 and an inter base station 730 exist in a multi-cell environment. In LTE (long term evolution) system, an intra base station is constructed with several cells (or sectors). Cells belonging to a base station having a specific user equipment belong thereto have relation as the intra base stations 710 and 720 with the specific user equipment. In particular, cells belonging to the same base station of the cell having a user equipment belong thereto are the cells corresponding to the intra base stations 710 and 720. And, cells belonging to other base stations become the cells corresponding to the inter base station 730.

(31) Thus, cells based on the same base station of a specific user equipment are physically co-located, they may share information (e.g., data, channel state information (CSI), etc.) with each other. Yet, cells based on another base station may be able to exchange inter-cell information via a backhaul 740 and the like. Referring to FIG. 7, a single cell MIMO user 750 within a single cell may communicate with one serving base station in one cell (or sector). A multi-cell MIMO user 760 located on a cell boundary may be able to communicate with a plurality of serving base stations in a multi-cell (or multi-sector).

(32) Coordinated multi-point (CoMP) scheme (hereinafter abbreviated CoMP scheme) may include the system to improve throughput of a user located on a cell boundary by applying enhanced MIMO transmission in a multi-cell environment. If the CoMP scheme is applied, it may be able to reduce inter-cell interference in the multi-cell environment. If the CoMP scheme is used, a mobile station may be provided with a support from multi-cell base stations jointly. Moreover, each base station may be able to enhance system performance by supporting at least one or more mobile stations MS1, MS2, . . . MSK simultaneously using the same radio frequency resource. Moreover, the base station may be able to perform space division multiple access (SDMA) method based on state information of a channel between the base station and the mobile station. Operating modes of the CoMP scheme can be categorized into a joint processing mode of a coordinated MIMO type through data sharing and a CS/CB (coordinated scheduling/coordinated beamforming) mode.

(33) In a wireless communication system having the CoMP scheme applied thereto, a serving base station and at least one or more coordinated base stations may be connected to a scheduler via a backbone network. The scheduler may be able to operate by receiving feedback of channel information on a channel state between each of the mobile stations (MS1, MS2, . . . MSK) and the coordinated base station. For instance, the scheduler may schedule information for a coordinated MIMO operation for the serving base station and the at least one coordinated base station. In particular, the scheduler may directly instruct each base station of the coordinated MIMO operation.

(34) In the following description, the reference signal may be explained in detail. Generally, for the channel measurement, a reference signal already known to both a transmitting side and a receiving side is transmitted to the receiving side by the transmitting side. This reference signal indicates a modulation scheme as well as the channel measurement to play a role in activating a demodulating process. And, reference signals may be classified into a dedicated RS (DRS) for a base station and a specific mobile station and a common RS (CRS) for all mobile stations.

(35) FIG. 8 is a diagram for a structure of a reference signal in LTE system supportive of DL transmission using 4 antennas. Particularly, FIG. 8 (a) shows a case of a normal cyclic prefix and FIG. 8 (b) shows a case of an extended cyclic prefix.

(36) Referring to FIGS. 8, 0 to 3 written in lattices may mean cell-specific CRS transmitted for channel measurement and data demodulation in a manner of corresponding to ports 0 to 3, respectively. D written in a lattice may mean a UE-specific RS which is a dedicated RS and may support a single antenna port transmission via a data region, i.e., PDSCH. A user equipment receives signaling for a presence or non-presence of the UE-specific RS via an upper layer.

(37) In a related art LTE system, for the scrambling of a reference signal and a physical channel, the reference signal us generated using a pseudo-random sequence c(n). The pseudo-random sequence c(n) may be defined as Formula 8 using a gold sequence having a length 31.
c(n)=(x.sub.1n+N.sub.C)+x.sub.2(n+N))mod 2
x.sub.1(n+31)=(x.sub.1(n+3)+x.sub.1(n))mod 2
x.sub.2(n+31)=(x.sub.2(n+3)+x.sub.2(n+2)+x.sub.2(n+1)+x.sub.2(n))mod 2[Formula 8]

(38) In Formula 8, N.sub.C is 1600 and a 1.sup.st m-sequence has an initial value of x.sub.1(0) set to 1 and x.sub.1(n) set to 0 (yet, n is 130). An initial value of a 2.sup.nd m-sequence is defined as c.sub.init=.sub.i=0.sup.30x.sub.2(i).Math.2.sup.i and its value may be determined in accordance with a usage of the corresponding sequence.

(39) In a cell-specific reference signal, the emit may be defined as Formula 9 and may be initialized for each OFDM symbol.
c.sub.init=2.sup.10.Math.(7.Math.(n.sub.s+1)+l+1).Math.(2.Math.N.sub.ID.sup.cell+1)+2.Math.N.sub.ID.sup.cell+N.sub.CP[Formula 9]

(40) In Formula 9, the n.sub.s indicates a slot number in a radio frame and the N.sub.ID.sup.cell indicates a cell ID. The N.sub.CP has a value of 1 for a normal CP and has a value of 0 for an extended CP.

(41) In MBSFN reference signal, the c.sub.init may be defined as Formula 1. And, In the MBSFN reference signal, the c.sub.init may be initialized for each OFDM symbol.
c.sub.init=2.sup.9.Math.(7.Math.(n.sub.s+1)+l+1).Math.(2.Math.N.sub.ID.sup.MBSFN+1)=N.sub.ID.sup.MBSFN[Formula 10]

(42) In Formula 10, the N.sub.ID.sup.MBSFN may be signaled to a user equipment via an upper layer.

(43) Finally, in a UE-specific reference signal, the c.sub.init may be defined as Formula 11 and may be initialized at a start point of a subframe.
c.sub.init=(n.sub.s/2+1).Math.(2N.sub.ID.sup.cell+1).Math.2.sup.16+n.sub.RNTI[Formula 11]

(44) In Formula 11, the n.sub.RNTI may specifically have a different value according to an application. In particular, SPS-RNTI is used for a semi-persistent transmission) or C-RNTI may be used for a non-semi-persistent transmission.

(45) Meanwhile, DM-RS may be a reference signal used to decode data received by a user equipment from a base station. The base station transmits the DM-RS by applying the same matrix applied to data. Therefore, the DM-RS is a UE-specific reference signal and may be generated using a pseudo-random sequence c(n) as show in Formula 12.

(46) $\begin{array}{cc}{r}_{n_s}\left(m\right)=\frac{1}{\sqrt{2}}\left(1-2.Math.c\left(2m\right)\right)+j\frac{1}{\sqrt{2}}\left(1-2.Math.c\left(2m+1\right)\right),m=0,1,\mathrm{.Math.},12N_{\mathrm{RB}}^{\mathrm{PDSCH}}-1& \left[\mathrm{Formula}12\right]\end{array}$

(47) A reference signal sequence shown in Formula 12 may be applicable to a single-cell single-user MIMO transmission, a single-cell multi-user MIMO transmission, a multi-cell single-user MIMO transmission and a multi-cell multi-user MIMO transmission all.

(48) The present invention may propose that the initial value c.sub.init of the 2.sup.nd m-sequence used for the pseudo-random sequence generation in Formula 12 is separately defined to be applicable to MIMO transmission modes. In particular, as shown in Formula 11, the c.sub.init proposed by the present invention may be characterized in having factors set to N.sub.ID.sup.cell and n.sub.RNTI and further including a scramble discriminating parameter N.sub.DRS as a factor.

(49) In this case, if a cell-specific reference signal and a DM-RS co-exist in the same OFDM symbol, the N.sub.DRS may be set to a value of 1. Otherwise, the N.sub.DRS may be set to a value of 0. And, the N.sub.DRS may be separately signaled from a base station via DCI format 2B received on PDCCH. Moreover, the N.sub.ID.sup.cell may mean a cell ID or a group ID of a user group in a multi-cell multi-user MIMO mode.

(50) Finally, regarding n.sub.RNTI, SPS-RNTI may be used for semi-persistent transmission or C-RNTI may be usable for a non-semi-persistent transmission. Yet, the n.sub.RNTI may be set to 0 in accordance with a multiplexing scheme of DM-RS.

(51) In LTE system, when there are 2 antenna ports for DM-RS transmission, if a multiplexing scheme is frequency division multiplexing, c.sub.init may be defined as Formula 13.
c.sub.init=N.sub.DRS2.sup.30=(n.sub.s/2+1).Math.(2N.sub.ID.sup.cell+1).Math.2.sup.16n.sub.RNTI[Formula 13]

(52) Moreover, regarding the c.sub.init for supporting a single-cell multi-user MIMO mode transmission, if a multiplexing scheme for an antenna port is frequency division multiplexing, the n.sub.RNTI may be set to 0 to define the c.sub.init.
c.sub.init=N.sub.DRS2.sup.30+(n.sub.s/2+1).Math.(2N.sub.ID.sup.cell=1).Math.2.sup.16[Formula 14]
c.sub.init=N.sub.DRS2.sup.14+(n.sub.s/2+1).Math.(2N.sub.ID.sup.cell+1).[Formula 15]
c.sub.init=N.sub.DRS+(n.sub.s/2+1).Math.(2N.sub.ID.sup.cell+1).Math.2.sup.16[Formula 16]

(53) In the CoMP scheme, it may be preferable that the N.sub.ID.sup.cell is set to indicate a serving cell ID for CoMP transmission. Hence, Formula 12 may be modified into Formula 17.
c.sub.init=N.sub.DRS2.sup.30+(n.sub.s/2+1).Math.(2N.sub.ID.sup.serving cell+1).Math.2.sup.16+n.sub.RNTI[Formula 17]

(54) Likewise, if a multiplexing scheme for an antenna port is frequency division multiplexing, the n.sub.RNTI may be set to 0 to define the c.sub.init as Formulas 18 to 20.
c.sub.init=N.sub.DRS2.sup.30+(n.sub.s/2+1).Math.(2N.sub.ID.sup.serving cell+1).Math.2.sup.16[Formula 18]
c.sub.init=N.sub.DRS2.sup.14+(n.sub.s/2+1).Math.(2N.sub.ID.sup.serving cell+1)[Formula 19]
c.sub.init=N.sub.DRS+(n.sub.s/2+1).Math.(2N.sub.ID.sup.serving cell+1).Math.2.sup.16[Formula 20]

(55) For a multi-cell multi-user MIMO transmission in the CoMP scheme, the N.sub.ID.sup.cell is set to N.sub.ID.sup.MU indicating a serving cell ID of CoMP transmission or an ID of a UE group to define the emit as Formula 21 to 23.
c.sub.init=N.sub.DRS2.sup.30+(n.sub.s/2+1).Math.(2N.sub.ID.sup.MU+1).Math.2.sup.16[Formula 21]
c.sub.init=N.sub.DRS2.sup.14+(n.sub.s/2+1).Math.(2N.sub.ID.sup.MU+1)[Formula 22]
c.sub.init=N.sub.DRS+(n.sub.s/2+1).Math.(2N.sub.ID.sup.MU+1).Math.2.sup.16[Formula 23]

(56) Particularly, in Formulas 21 to 23, if the N.sub.ID.sup.MU is an ID of a serving cell, a reference signal may be set as a cell-specific reference signal. If the N.sub.ID.sup.MU is an ID of a UE group, a reference signal may be set as a UE-specific reference signal.

(57) FIG. 9 is an exemplary block diagram of a user equipment according to one embodiment of the present invention.

(58) Referring to FIG. 9, a user equipment 900 may include a processor 910, a memory 920, an RF module 930, a display module 940 and a user interface module 950.

(59) The user equipment 900 is illustrated for clarity and convenience of the description and some modules thereof may be omitted. Moreover, the user equipment 900 may be able to further include at least one necessary module. And, some modules of the user equipment 900 may be further divided into sub-modules. The processor 910 may be configured to perform operations according to the embodiment of the present invention exemplarily described with reference to the accompanying drawings.

(60) In particular, the processor 190 may perform operations required for multiplexing a control signal and a data signal. And, the detailed operations of the processor 910 may refer to the contents described with reference to FIGS. 1 to 8.

(61) The memory 920 may be connected to the processor 910 and may store operating systems, applications, program codes, data and the like. The RF module 930 may be connected to the processor 910 and may perform a function of converting a baseband signal to a radio signal or a function of converting a radio signal to a baseband signal. For this, the RF module 930 may perform analog conversion, amplification, filtering and frequency uplink transform or inverse processes thereof. The display module 940 may be connected to the processor 910 and may display various kinds of informations. The display module 940 may include such a well-known component as LCD (Liquid Crystal Display), LED (Light Emitting Diode), OLED (Organic Light Emitting Diode) and the like, by which the present invention may be non-limited. The user interface module 950 may be connected to the processor 910 and may include a combination of well-known interfaces including a keypad, a touchscreen and the like.

(62) The above described embodiments correspond to combination of elements and features of the present invention in prescribed forms. And, it is able to consider that the respective elements or features are selective unless they are explicitly mentioned. Each of the elements or features can be implemented in a form failing to be combined with other elements or features. Moreover, it is able to implement an embodiment of the present invention by combining elements and/or features together in part. A sequence of operations explained for each embodiment of the present invention can be modified. Some configurations or features of one embodiment can be included in another embodiment or can be substituted for corresponding configurations or features of another embodiment. It is apparent that an embodiment can be configured by combining claims, which are not explicitly cited in-between, together without departing from the spirit and scope of what is claimed is or that those claims can be included as new claims by revision after filing an application.

(63) In the present disclosure, embodiments of the present invention may be described centering on the data transmission/reception relations between a relay node and a base station. In this disclosure, a specific operation explained as performed by a base station may be performed by an upper node of the base station in some cases. In particular, in a network constructed with a plurality of network nodes including a base station, it is apparent that various operations performed for communication with a terminal can be performed by a base station or other network nodes except the base station. In this case, base station may be replaced by such a terminology as a fixed station, a Node B, an eNode B (eNB), an access point and the like. And, a terminal may be replaced by such a terminology as UE (User Equipment), MS (Mobile Station), MSS (Mobile Subscriber Station) and the like.

(64) Embodiments of the present invention may be implemented using various means. For instance, embodiments of the present invention can be implemented using hardware, firmware, software and/or any combinations thereof. In case of the implementation by hardware, one embodiment of the present invention may be implemented by at least one selected from the group consisting of ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), processor, controller, microcontroller, microprocessor and the like.

(65) In case of the implementation by firmware or software, one embodiment of the present invention may be implemented by modules, procedures, and/or functions for performing the above-explained functions or operations. Software code may be stored in a memory unit and may be then drivable by a processor. The memory unit may be provided within or outside the processor to exchange data with the processor through the various means known to the public.

(66) While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.

INDUSTRIAL APPLICABILITY

(67) As mentioned in the foregoing description, although a method of generating a reference signal sequence in a multi-antenna wireless communication system and apparatus therefor are described mainly with reference to examples applied to 3GPP LTE system, the present invention may be applicable to various kinds of multi-antenna wireless communication systems as well as the 3GPP LTE system.