WO2013119053A1

WO2013119053A1 - Method for allocating reference signal antenna port for transmission diversity technique in wireless communication system, and apparatus for same

Info

Publication number: WO2013119053A1
Application number: PCT/KR2013/000991
Authority: WO
Inventors: 서한별
Original assignee: 엘지전자 주식회사
Priority date: 2012-02-09
Filing date: 2013-02-07
Publication date: 2013-08-15

Abstract

In the present invention, disclosed is a method for a base station transmitting a downlink control channel to a user equipment in a wireless communication system. More particularly, the method comprises the steps of: establishing resource element subsets comprising a plurality of resource elements; allocating a transmission resource for the downlink control channel in units of the resource element subsets; alternately allocating to the plurality of resource elements two antenna ports for demodulation-reference signals (DM-RS); and transmitting the downlink control channel to the user equipment through the transmission resource that is allocated by using the DM-RSs of the antenna ports that are allocated.

Description

【Specification】

[Name of invention]

Reference Signal Antenna Port Allocation Method for Transmit Diversity in Wireless Communication System and Apparatus Therefor

Technical Field

[1] The present invention relates to a wireless communication system. More specifically, the present invention relates to a reference signal antenna port allocation method and apparatus for the transmission diversity scheme in a wireless communication system.

Background Art

[2] As an example of a wireless communication system to which the present invention can be applied, a 3GPP LTE (3rd Generation Partnership Project Long Term Evolution (LTE) 5) communication system will be described in brief.

1 is a diagram schematically illustrating an E-UMTS network structure as an example of a wireless communication system. The E-UMTSC Evolved Universal Mobile Telecommunications System (E-UMTSC) system is an evolution from the existing Universal Mobile Telecommunications System (UMTS) and is currently undergoing basic standardization in 3GPP. In general, the E-UMTS may be referred to as a Long Term Evolution (LTE) system. For details of the technical specifications of UMTS and E JMTS, refer to Release 7 and Release 8 of the "3rd Generation Partnership Project; Technical Specification Group Radio Access Network".

[4] Referring to FIG. 1, an E-UMTS is located at an end of a user equipment (UE), a base station (eNode B; eNB), and a network (E-UT AN) and connected to an external network (Access gateway). Gateway; AG). The base station may transmit multiple data streams simultaneously for broadcast service, multicast service and / or unicast service.

[5] One or more cells exist in one base station. The cell is set to one of bandwidths such as 1.44, 3, 5, 10, 15, and 20Mhz to provide downlink or uplink transmission services to multiple terminals. Different cells may be set to provide different bandwidths. The base station controls data transmission and reception for a plurality of terminals. For downlink (DL) data, the base station transmits downlink scheduling information to inform the corresponding terminal of time / frequency domain, encoding, data size, and HARQ Hybrid Automatic Repeat and reQuest (related information) related data. In addition, the uplink (UL) data _. On the other hand, the base station transmits uplink scheduling information to the corresponding terminal and informs the time / frequency domain, encoding, data size, HARQ related information, etc. which can be used by the corresponding terminal. An interface for transmitting user traffic or control traffic may be used between base stations. The core network (CN) may consist of an AG and a network node for user registration of the terminal. The AG manages the mobility of the UE in units of a tracking area (TA) composed of a plurality of cells.

[6] Wireless communication technology has been developed up to LTE based on WCDMA, but the demands and expectations of users and operators are continuously increasing. In addition, as other radio access technologies continue to be developed, new technological evolution is required to be competitive in the future. Reduced cost per bit, increased service availability, flexible use of frequency bands, simple structure and open interface, and adequate power consumption of the terminal are required. [Detailed Description of the Invention]

[Technical problem]

Based on the above discussion, a method and apparatus for allocating a reference signal antenna port for a transmission diversity scheme in a wireless communication system will now be proposed.

Technical Solution

In a wireless communication system according to an embodiment of the present invention, a method for transmitting a downlink control channel to a terminal by a base station includes: setting resource element subsets comprising a plurality of resource elements; Allocating transmission resources for the downlink control channel in units of the resource element subset; Alternating allocation of two antenna ports for DM-RS (Demodulat ion-Reference Signal) to the plurality of resource elements; And transmitting the downlink control channel to the terminal through the allocated transmission resource by using the DM-RSs of the allocated antenna ports. Characterized in that it comprises a step.

Meanwhile, in another embodiment of the present invention, in a wireless communication system, a base station apparatus sets resource element subsets composed of a plurality of resource elements and allocates transmission resources for a downlink control channel in units of the resource element subsets. And a processor for alternately allocating two antenna ports for a demodul at ion-reference signal (DM-RS) to the plurality of resource elements; And wireless communication modules for transmitting the downlink control channel to the terminal through the allocated transmission resource by using the DM-RSs of the allocated antenna ports.

In the embodiments of the present invention, the indexes of the antenna ports of the two DM-RSs are based on the number of available resource elements or the length of the cyclic prefix of the subframe in which the downlink control channel is transmitted. It is characterized in that determined based on.

[11] Preferably, when the downlink control channel is transmitted in a subframe to which a general cyclic prefix is applied, the antenna ports of the two DM-RSs are antenna ports of the DM-RS that are not multiplexed on the same resource element. It features. In addition, when the downlink control channel is transmitted in a subframe to which extended cyclic prefix is applied, the antenna ports of the two DM-RSs are antenna ports of the DM-RS multiplexed on the same resource element.

[12] More preferably, when the downlink control channel is transmitted in a subframe to which a general cyclic prefix is applied, the indexes of the antenna ports of the two DM-RSs are 7 and 9, respectively. In addition, when the downlink control channel is transmitted in a subframe to which the extended cyclic prefix is applied, the indexes of the antenna ports of the two DM-RSs are 7 and 8.

Advantageous Effects

According to an embodiment of the present invention, in order to apply the transmit diversity scheme, it is possible to efficiently allocate a reference signal for a downlink control channel, particularly an antenna port of a DM-RS.

[14] Effects obtained in the present invention are not limited to the above-mentioned effects. And other effects not mentioned will be clearly understood by those skilled in the art from the following description.

[Brief Description of Drawings]

1 is a diagram schematically illustrating an E-UMTS network structure as an example of a wireless communication system.

FIG. 2 is a diagram illustrating a control plane and a user plane structure of a radio interface protocol between a UE and an E-UTRAN based on the 3GPP radio access network standard.

FIG. 3 is a diagram for explaining physical channels used in a 3GPP system and a general signal transmission method using the same.

4 is a configuration diagram of a multi-antenna communication system.

5 is a diagram illustrating a structure of a downlink radio frame used in an LTE system.

FIG. 6 is a diagram illustrating a resource unit used to configure a downlink control channel in an LTE system.

FIG. 7 is a diagram illustrating a structure of an uplink subframe used in an LTE system.

8 is a diagram illustrating a multiple node system in a next generation communication system.

[23] FIG. 9 is a diagram illustrating a PDSCH scheduled by an E-PDCCH and an E-PDCCH.

10 shows an example of a PDCCH region and an E-PDCCH region in one subframe.

11 and 12 illustrate the structure of a reference signal in an LTE system supporting downlink transmission using four antennas.

13 and 14 illustrate examples of DM-RS allocation in a subframe to which a general CP defined in the 3GPP standard document is currently applied.

[27] FIG. 15 shows an example of DM-RS allocation in a subframe to which an extended CP defined in the current 3GPP standard document is applied.

16 illustrates resource elements for E-PDCCH transmission according to an embodiment of the present invention. An example of assigning an antenna port is shown.

17 illustrates a block diagram of a communication device according to an embodiment of the present invention.

[Form for implementation of invention]

[30] The embodiments of the present invention described with reference to the accompanying drawings below.

The construction, operation and other features of the invention will be readily understood. Below

The described embodiments are examples in which the technical features of the present invention are applied to a 3GPP system.

The present specification uses an LTE system and an LTE-A system to describe an embodiment of the present invention.

Although described, this is by way of example an embodiment of the present invention which communication corresponding to the above definition

It can also be applied to the system. In addition, the present specification is based on the FDD scheme of the present invention

An embodiment is described, but this is by way of example only and the embodiment of the present invention is H-FDD scheme or

It can be easily modified and applied to the TDD scheme.

2 is a diagram illustrating a radio between a UE and an E-UTRAN based on a 3GPP radio access network standard.

Control Plane of the Radio Interface Protocol and

A diagram illustrating a user plane structure. Control plane is terminal (User

Equipment; Control messages used by the UE and the network to manage calls

It means the transmission path. The user plane is the data generated by the application tradeoff,

For example, this means a path through which voice data or Internet packet data is transmitted.

[33] The physical layer, which is the first layer, is overlaid using a physical channel.

It provides information transfer service to the layer.

The physical layer is different from the upper medium access control layer.

It is connected via the transport channel (Trans antenna port Channel). Through the transmission channel

Data moves between the medium access control layer and the physical layer. Sender and receiver

Data moves between physical layers through physical channels. The physical channel is time and

Use frequency as a radio resource. Specifically, the physical channel is in the downlink

0FDMA (modulated by Orthogonal Frequency Division Multiple Access) scheme,

In uplink, it is modulated by Single Carrier Frequency Division Multiple Access (SC-FDMA).

[34] The Medium Access Control (MAC) layer of the second layer It provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The RLC layer of the second layer supports reliable data transmission. The functions of the RIX layer may be implemented as functional blocks inside the MAC. Almost 12 layers of Packet Data Convergence Protocol (PDCP) negotiations perform header compression, which reduces unnecessary control information for efficient transmission of IP packets such as IPv4 or IPv6 over narrow bandwidth interfaces.

The radio resource control (RRC) layer located at the bottom of the third layer is defined only in the control plane. The RRC layer is responsible for the control of logical channels, transport channels, and physical channels in connection with configuration, re-conf igurat ion, and release of radio bearers (RBs). RB means a service provided by the second layer for data transmission between the terminal and the network. To this end, the RRC layers of the UE and the network exchange RC messages with each other. When there is an RRC connected (RRC Connected) between the UE and the RRC layer of the network, the UE is in an RRC connected mode, otherwise it is in an RRC idle mode. The non-access stratum (NAS) layer above the RRC layer performs functions such as session management and mobility management.

One cell constituting the base station ( _e NB) is set to one of bandwidths such as 1.4, 3, 5, 10, 15, and 20Mhz to provide downlink or uplink transmission services to various terminals. Different cells may be configured to provide different bandwidths.

A downlink transport channel for transmitting data from a network to a terminal includes a broadcast channel (BCH) for transmitting system information, a paging channel (PCH) for transmitting a paging message, and a downlink shared channel (SCH) for transmitting user traffic or a control message. ). Traffic or control messages of a downlink multicast or broadcast service may be transmitted through a downlink SCH or may be transmitted through a separate downlink multicast channel (MCH). Meanwhile, the uplink transmission channel for transmitting data from the terminal to the network includes a random access channel (RAC) for transmitting an initial control message and an uplink shared channel (SCH) for transmitting user traffic or a control message. Above the transmission channel, Logical channels mapped to a transport channel include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), an MCCHC multicast control channel (MTCH), a multicast traffic channel (MTCH), and the like.

FIG. 3 is a diagram for describing physical channels used in a 3GPP system and a general signal transmission method using the same.

If the terminal is powered on or newly enters the cell, the terminal performs an initial cell search operation such as synchronizing with the base station (S301). To this end, the UE receives a Primary Synchronization Channel (P-SCH) and a Secondary Synchronization Channel (S—SCH) from the base station, synchronizes with the base station, and obtains information such as a Sal ID. have. Thereafter, the terminal may receive a physical broadcast channel from the base station to obtain broadcast information in the cell. On the other hand, the terminal may receive a downlink reference signal (DL RS) in the initial cell search step to confirm the downlink channel state.

[40] The UE which has completed the initial cell search receives a physical downlink control channel (PDCCH) and a physical downlink control channel (PDSCH) according to the information carried on the PDCCH for a more specific system. Information can be obtained (S302).

On the other hand, when the first access to the base station or there is no radio resource for signal transmission, the terminal may perform a random access procedure (RACH) for the base station (steps S303 to S306). To this end, the UE may transmit a specific sequence to the preamble through a physical random access channel (PRACH) (S303 and S305), and may receive a voice response message for the preamble through the PDCCH and the Daesung PDSCH ( S304 and S306). In case of contention-based RACH, a contention resolution procedure may be additionally performed.

After performing the above procedure, the UE performs a PDCCH / PDSCH reception (S307) and a physical uplink shared channel (PUSCH) / physical uplink control channel as a general uplink / downlink signal transmission procedure. Physical Uplink Control Channel; PUCCH) may be performed (S308). In particular, the terminal receives downlink control information (DCI) through the PDCCH. In this case, the DCI includes control information such as resource allocation information for the terminal, and the format is different depending on the purpose of use.

On the other hand, the control information transmitted by the terminal to the base station through the uplink or received by the terminal from the base station is a downlink / uplink ACK / NACK signal, CQK Channel Quality Indicator (CQK), ΡΜΙ (Precoding Matrix Index), RI ( Rank Indicator). In the 3GPP LTE system, the terminal may transmit the above-described control information such as CQI / PMI / RI through the PUSCH and / or PUCCH.

[44] or less MIM0. The system will be described. MIMO (Multiple-Input Multiple-Output) is a method of using a plurality of transmission antennas and a plurality of reception antennas, and this method can improve the transmission and reception efficiency of data. That is, the transmitting end of the wireless communication system can increase capacity and improve performance by using a plurality of antennas at the receiving end. In the following description, MIM0 may be referred to as a “multi-antenna”.

In the multi-antenna technique, it does not rely on a single antenna path to receive one entire message. Instead, in multi-antenna technology, data fragments received from multiple antennas are gathered and merged to complete the data. Using multi-antenna technology, it is possible to improve the data transmission rate within a cell area of a specified size or to increase system coverage while guaranteeing a specific data transmission rate. In addition, this technique can be widely used in mobile communication terminals and repeaters. According to the multiple antenna technology, it is possible to overcome the transmission limit in the mobile communication according to the prior art, which used a single antenna.

4 is a configuration diagram of a multiple antenna (MIM0) communication system according to the present invention. Transmitter had a transmitting antenna is installed dog Ν _τ, the receiving end has a receiving antenna installed dog N _R. Thus, when a plurality of antennas are used at both the transmitting end and the receiving end, the theoretical channel transmission capacity is increased than when the plurality of antennas are used at either the transmitting end or the receiving end. Channel transmission The increase in capacity is proportional to the number of antennas. Therefore, the transmission rate is improved and the frequency efficiency is improved. If the maximum transmission rate when using one antenna is R。, the transmission rate when using multiple antennas is theoretically the maximum transmission as shown in Equation 1 below. The rate R。 may be increased by multiplying the rate increase rate Ri. Where Ri is the lesser of N and Ν _τ _R.

[47] [Equation 1]

_[48 ] ^ = rnin (N _r , NJ

For example, in a MIM0 communication system using four transmit antennas and four receive antennas, it is theoretically possible to obtain a transmission rate four times higher than that of a single antenna system. Since the theoretical capacity increase of such a multi-antenna system was proved in the mid 90s, various techniques for substantially improving the data rate have been actively studied to date, and some of these techniques have already been developed for 3G mobile communication and next generation WLAN. It is reflected in various wireless communication standards.

[50] The current trends of multi-antenna researches include the study of information theory aspects related to the calculation of multi-antenna communication capacity in various channel and multi-access environments, the measurement of radio channels and model derivation of multi-antenna systems, and the improvement of transmission reliability. Active research is being conducted from various viewpoints, such as research on space-time signal processing technology for improving data rate.

In order to describe the communication method in the multi-antenna system in a more specific manner, mathematical modeling may be expressed as follows. As shown in FIG. 7, it is assumed that there are N _τ transmit antennas and N _R receive antennas. First, referring to the transmission signal, when there are Ν _τ transmit antennas, the maximum transmittable information is Ν _τ, and thus the transmission information may be represented by a vector shown in Equation 2 below.

[52] [Equation 2]

[53] ^{s =} Lw-，-

[54] Meanwhile, each transmission information

To do different transmit power In this case, if each transmission power is ^ '^'^'"'^" ^, the transmission information of which transmission power is adjusted is represented by a vector as in Equation 3 below.

[55] [Equation 3] ^

In addition, when ^S is represented using the diagonal matrix P of the transmission power, Equation 4 below.

[58] [Equation 4]

On the other hand, consider a case in which a weight matrix ^W is applied to the information vector ⁸ whose transmission power is adjusted, ^and thus constitutes Ν _τ transmitted signals ^ '^'^""'^ r ₇ }. Here, the weight matrix plays a role of properly distributing transmission information to each antenna according to a transmission channel situation. Such a transmission signal

， X ·, χ

^Ντ can be expressed as Equation 5 below using a vector. here

It means the weight between the first transmission antenna and the first information. ^W is called a weight matrix or a precoding matrix.

[61] [Equation 5]

[62]

[63] In general, the physical meaning of the rank of a channel matrix is _: It is the maximum number of other information that can be sent. Therefore, the rank of a channel matrix is defined as the minimum of the number of independent rows or columns, so the rank of the matrix can be greater than the number of rows or columns. There will be no. For example, the tank (rank (H)) of the channel matrix H is limited as shown in Equation 6 below.

[64] [Equation 6]

[ ₆ 5] r nk Ji) <min (iV _r , N _R )

In addition, each of the different information transmitted using the multi-antenna technique will be defined as a 'stream' or simply 'stream'. Such a 'stream' may be referred to as a 'layer ^' . The number of transport streams can then, of course, be no greater than the rank of the channel, which is the maximum number that can send different information. Therefore, the channel matrix H can be expressed as Equation 7 below.

[67] [Equation 7]

^[ ₆₈ ^] # of streams <rank (H) ≤ min (iV _r , N _R )

[69] where "# of streams" represents the number of streams. Meanwhile, it should be noted that one stream may be transmitted through more than one antenna.

[70] There may be various ways of treating one or more streams to several antennas. This method can be described as follows according to the type of multiple antenna technology. When one stream is transmitted through multiple antennas, it can be seen as a spatial diversity scheme, and when multiple streams are transmitted through multiple antennas, it can be regarded as a spatial multiplexing scheme. Of course, a hybrid form of spatial diversity and spatial multiplexing is also possible.

FIG. 5 is a diagram illustrating a control channel included in a control region of one subframe in a downlink radio frame. The number of OFDM symbols included in one subframe may vary depending on the length of the cyclic prefix (CP) or whether it is a normal CP or an extended CP and the spacing of subcarriers. And subcarrier spacing is 15 kHz.

Referring to FIG. 5, a subframe consists of 14 0FDM symbols. According to the subframe configuration, the first 1 to 3 OFDM symbols are used as the control region and the remaining 13-11 OFDM symbols are used as the data region.

In FIG. 5, R1 to R4 represent reference signals (RSs) or pilot signals for antennas 0 to 3. The RS is fixed in a constant pattern in a subframe regardless of the control region and the data region. The control channel is allocated to a resource to which no RS is allocated in the control region, and the traffic channel is also allocated to a resource to which no RS is allocated in the data region. Control channels allocated to the control region include a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid-ARQ Indicator CHannel (PHICH), and a Physical Downlink Control CHannel (PDCCH).

The PCFICH is a physical control format indicator channel and informs the UE of the number of OFDM symbols used for the PDCCH in every subframe. The PCFICH is located in the first OFDM symbol and is set in preference to the PHICH and PDCCH. The PCFICH is composed of four Resource Element Groups (REGs), and each REG is distributed in the control region based on the cell ID Cell IDentity. One REG is composed of four resource elements (REs). RE represents a minimum physical resource defined by one subcarrier and one OFDM symbol. The PCFICH value indicates a value of 1 to 3 or 2 to 4 depending on the bandwidth and is modulated by Quadrature Phase Shift Keying (QPSK).

The PHICH is a physical hybrid automatic repeat and request (HARQ) indicator channel and is used to carry HARQ ACK / NACK for uplink transmission. That is, PHICH represents a channel through which DL ACK / NACK information for UL HARQ is transmitted. PHICH is 1

It is composed of REGs and is cell-specifically scrambled.

ACK / NACK is indicated by 1 bit and modulated by binary phase shift keying (BPSK). The modulated ACK / NACK is spread with Spreading Factor (SF) = 2 or 4. A plurality of PHICHs mapped to the same resource constitutes a PHICH group. The number of PHICH to the PHICH groups to be multiplexed ^is, it is determined according to the number of spreading codes. The PHICH (group) is repeated three times to obtain diversity gain in the frequency domain and / or the time domain.

[76] The PDCCH is a physical downlink control channel for the first n OFDM symbols of a subframe. Is assigned. Here, n is indicated by the PCFICH as an integer of 1 or more. The PDCCH consists of one or more CCEs. The PDCCH informs each UE or UE group of information related to resource allocation of a transmission channel (PCH) and a DL ink-shared channel (DL-SCH), an uplink scheduling grant, and HARQ information. . Paging channel (PCH) and Down 1 ink-shared channel (DL-SCH) are transmitted through PDSCH. Accordingly, the base station and the terminal generally transmit and receive data through the PDSCH except for specific control information or specific service data.

Data of PDSCH is transmitted to which UE (one or a plurality of UEs), and information on how the UEs should receive and decode PDSCH data is included in the PDCCH and transmitted. For example, a particular PDCCH is masked with a cyclic redundancy check (CRC) with a Radio Network Temporary Identity (RTI) of "A", and a radio resource (eg, frequency location) of "B" and "C". It is assumed that information about data transmitted using the transmission format information (e.g., transport block size, modulation scheme, coding information, etc.) is transmitted through a specific subframe. ^. In this case, the terminal in the sal ^' monitors the PDCCH using the R TI information it has, and if there is at least one terminal having an "A" RNTI, the terminals receive the PDCCH, and the information of the received PDCCH Receive the PDSCH indicated by " B "

6 shows a resource unit used to configure a downlink control channel in an LTE system. In particular, FIG. 6 shows a case where the number of transmit antennas of the base station is 1 or 2, and FIG. 6 (b) shows a case where the number of transmit antennas of the base station is four. Only the RS (Reference Signal) pattern is different according to the number of transmitting antennas, and the method of setting a resource unit associated with the control channel is the same.

Referring to FIG. 6, the basic resource unit of the downlink control channel is a resource element group (REG). The REG consists of four neighboring resource elements (REs) with the exception of the RS. REG is shown in bold in the figures. PCFICH and PHICH include 4 REGs and 3 REGs, respectively. The PDCCH is composed of CCE (Control Channel Elements) units, and one CCE includes nine REGs. In order to confirm whether a PDCCH composed of L CCEs is transmitted to the UE, the UE is configured to check M ^{(L) (} ≥L) CCEs arranged in consecutive or specific rules. There may be a plurality of L values to be considered by the UE for PDCCH reception. The CCE sets that the UE needs to check for PDCCH reception are called a search space. For example, the LTE system defines a search area as shown in Table 1.

[81] [Table 1]

Here, CCE aggregation level L represents the number of CCEs constituting the PDCCH, ¾ ⁽¹⁾ represents the search region of the CCE aggregation level L, ¾1 ⁽⁾ is a candidate to be monitored in the search region of the aggregation level L Number of PDCCHs.

The search area may be divided into a UE-specific search space that is accessible only to a specific terminal and a _co- _on search space that allows access to all terminals in a cell. Can be. The terminal monitors a common search region with CCE aggregation levels of 4 and 8, and monitors a terminal-specific search region with CCE aggregation levels of 1, 2, 4, and 8. The common search area and the terminal specific search area may overlap _. have/

In addition, the position of the first (with the smallest index) CCE in the PDCCH search region given to any UE for each CCE aggregation level value is changed every subframe according to the UE. This is called hashing of the PDCCH search region.

The CCE may be distributed in a system band. More specifically, a plurality of logically continuous CCEs may be input to an interleaver, and the interleaver performs a function of mixing the input CCEs in REG units. Thus, one CCE Frequency / time resources are physically transmitted in the entire frequency / time domain in the control region of the subframe. As a result, the control channel is configured in units of CCE, but interleaving is performed in units of REGs, thereby maximizing frequency diversity and interference randomization gain.

Referring to FIG. 7, an uplink subframe may be divided into a region to which a Physical Uplink Control CHannel (PUCCH) carrying control information is allocated and a region to which a Physical Uplink Shared CHannel (PUSCH) carrying user data is allocated. The middle part of the subframe is allocated to the PUSCH, and both parts of the data area are allocated to the PUCCH in the frequency domain. Control information transmitted on the PUCCH includes an ACK / NAC used for HARQ, a CQKChannel Quality Indicator indicating a downlink channel state, a RKRank Indicator for MIM0), and a SR (Scheduling Request), which is an uplink resource allocation request. The PUCCH for one UE uses one resource block occupying a different frequency in each slot in a subframe. That is, two resource blocks allocated to the PUCCH are frequency hopping at the slot boundary. In particular, FIG. 7 illustrates that PUCCH having m = 0, PUCCH having m = l, PUCCH having m = 2, and PUCCH having m = 3 are allocated to a subframe.

On the other hand, the current wireless communication environment is rapidly increasing the data demand for the cellular network due to the emergence and spread of various devices that require M2M (Machine ᅳ to Machine) communication and high data transmission. To meet high data demands, communication technologies are evolving into multi-antenna technology, multi-base station cooperation technology, etc. to increase data capacity within a limited frequency, such as carrier aggregation technology to efficiently use more frequency bands. ， Communication environment evolves toward increasing density of nodes that can be accessed around users. Systems with such high density nodes can exhibit higher system performance by cooperation between furnaces. This approach allows each node to be an independent base station (Base Station (BS), Advanced BS (ABS), Node-B (NB), eNode-B (eNB), Access Point (AP), etc.). It has much better performance than when it does not cooperate with each other.

8 is a diagram illustrating a multi-node system in a next generation communication system. .

[90] Referring to FIG. 8, if all nodes are managed to transmit and receive by one controller and each node acts as a subset of antennas of one sal, the system is a distributed multi-node forming one cell. It can be seen as a distributed multi-node system (D 丽 S). In this case, individual nodes may be given a separate Node ID, or may operate like some antennas in a cell without a separate Node ID. However, if the nodes have different cell identifiers (IDs), this can be viewed as a multi-cell system. If the multiple cells are configured in an overlapped form according to coverage, this is called a multi-tier network.

On the other hand, Node—B, eNode-B, PeNB), HeNB, Remote Radio Head (RRH), relay, and distributed antenna may be nodes, and at least one antenna is installed in one node. Nodes are also called transmission points. A node generally refers to an antenna group separated by a predetermined interval or more, but in the present invention, the node may be applied even if the node is defined as an arbitrary antenna group regardless of the interval.

Due to the introduction of the multi-node system and the relay node described above, it is possible to apply various communication techniques to improve channel quality, but to apply the aforementioned MIM0 technique and inter-cell cooperative communication technique to a multi-node environment. To this end, the introduction of a new control channel is required. Due to this necessity, the newly introduced control channel is E-PDCCH (Enhanced-PDCCH), and it is decided that the control channel is allocated to a data region (hereinafter, referred to as a PDSCH region) instead of an existing control region (hereinafter, referred to as a PDSCH region). . In conclusion, it is possible to transmit the control information for the node for each terminal through the E-PDCCH can also solve the problem that the existing PDCCH region may be insufficient. For reference, the E-PDCCH is not provided to the legacy legacy terminal, and can be received only by the LTE-A terminal. In addition, the E-PDCCH is transmitted and received based on the DM-RS, which is a UE-specific reference signal, rather than the CRS, which is an existing cell specific reference signal.

9 illustrates a structure of a radio frame in an LTE TDD system. LTE TDD In the system, a radio frame consists of two half frames, each half frame comprising four general subframes including two slots, a downlink pilot time slot (DwPTS), a guard period (GP) and It consists of a special subframe including an UpPTSOJplink Pilot Time Slot.

In the special subframe, the DwPTS is used for initial cell search, synchronization, or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. That is, DwPTS is used for downlink transmission and UpPTS is used for uplink transmission. In particular, UpPTS is used for PRACH preamble or SRS transmission. In addition, the guard interval is a period for removing interference caused in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

[95] With respect to the special subframe, the current 3GPP standard document defines a configuration as shown in Table 2 below. ^ = 1 / (15000x2048) in Table 2

UpPTS is indicated and the remaining area is set as a protection interval.

[96] [Table 2]

FIG. 10 is a diagram illustrating a PDSCH scheduled by an E-PDCCH and an E-PDCCH.

Referring to FIG. 10, an E-PDCCH generally indicates a PDSCH region for transmitting data. The UE may perform a blind decoding process on the search region for the E-PDCCH in order to detect the presence or absence of its own E-PDCCH.

[99] The E-PDCCH performs the same scheduling operation as that of the existing PDCCH (ie, PDSCH and PUSCH control), but when the number of UEs connected to a node such as an RRH increases, more E-PDCCHs are added in the PDSCH region. There may be a drawback that the complexity may increase due to an increase in the number of blind decodings allocated and performed by the UE.

In general, since a single PRB-pair control channel signal includes a large amount of resource elements, the available resource elements included in the single PRB pair are divided into one or more resource element subsets, and the resource element subsets. It is desirable to transmit the E-PDCCH by using appropriately.

Meanwhile, the resource element subset may be referred to as an E-CCE which is a transmission unit of the E-PDCCH, and one E-PDCCH may combine and transmit one or a plurality of E-CCEs according to an aggregation level.

Alternatively, the resource element subset may be referred to as another unit constituting the E-CCE, E-REG. In this case, the E—CCE may be defined as a set of E-REGs located in a plurality of PRB-pairs. Likewise, one E-PDCCH may combine and transmit one or a plurality of E-CCEs according to an aggregation level. have

Hereinafter, the reference signal will be described in more detail.

In general, a reference signal that is known to both the transmitting side and the receiving side together with data is transmitted from the transmitting side to the receiving side for channel measurement. Such a reference signal informs the modulation technique as well as the channel measurement to play a demodulation process. A reference signal is divided into a dedicated RS (DRS) for a base station and a specific UE, that is, a UE-specific reference signal and a common reference signal (co'on RS), which is a cell-specific reference signal for all UEs in a cell. . In addition, the cell-specific reference signal includes a reference signal for measuring the CQI / PMI / RI in the terminal to report to the base station, this is referred to as Channel State Informat ion-RS (CSI-RS).

11 and 12 illustrate LTE supporting downlink transmission using four antennas. It is a figure which shows the structure of the reference signal in a system. In particular, FIG. 11 illustrates a case of normal cyclic prefix, and FIG. 12 illustrates a case of extended cyclic prefix.

Referring to FIGS. 11 and 12, 0 to 3 described in the grid are CRS (Co (on Reference Signal) which is a cell-specific reference signal transmitted for channel measurement and data demodulation for each of antenna ports 0 to 3. The CRS, which is the cell specific reference signal, may be transmitted to the terminal not only in the data information region but also in the entire control information region.

In addition, 'D' described in the grid refers to a downlink DM-RS (DM-RS) which is a UE-specific RS, and the DM-RS supports single antenna port transmission through a data region, that is, a PDSCH. The terminal is signaled through the upper layer whether the DM-RS which is the terminal specific RS is present. 11 and 12 illustrate DM-RSs for antenna port 5, and 3GPP standard document 36.211 also defines DM-RSs for antenna ports 7 to 14, that is, 8 antenna ports in total.

13 and 14 illustrate examples of DM-RS allocation in a subframe to which a general CP defined in the 3GPP standard document is currently applied. In particular, FIG. 13 shows the case of antenna port 7 and antenna port 8, and FIG. 14 shows the case of antenna port 9 and antenna port 10. FIG.

13 and 14, in the DM-RS group 1, a DM-RS corresponding to an antenna port {7, 8} is mapped to the same resource element by a code division multiplexing scheme using an antenna port sequence. In DM-RS group 2, DM-RSs corresponding to antenna ports {9, 10} are similarly mapped to the same resource elements by code division multiplexing using antenna-specific sequences.

[110] FIG. 15 shows an example of DM-RS allocation in a subframe to which an extended CP defined in the current 3GPP standard document is applied.

Referring to FIG. 15, it can be seen that only antenna ports 7 and 8 are allocated in a subframe to which an extended CP is applied, and two antenna ports are included in the same DM-RS group. Therefore, they are mapped to the same resource element by a code division multiplexing technique. The present invention proposes a method of determining an antenna port of a DM-RS for an E-PDCCH.

[113] Comparing FIG. 13 and FIG. 14, which is a case of a general CP, with FIG. 15, which is a case of an extended CP, a large number of resource elements can be used for downlink transmission in a general downlink subframe. Even when used as RS, the DM-RS overhead can be kept relatively low, while the number of resource elements that can be used for downlink transmission, such as in a short length DwPTS, is similar to that of a typical downlink subframe. In order to maintain the DM-RS overhead, less resources should be used as DM-RS.

As described above, according to the structure of the DM-RS of the current LTE system, the antenna port 7 and the antenna port 8 are separated and transmitted by mutually orthogonal codes in the same resource element, and the antenna port 9 and the antenna port 10 The code is divided into two orthogonal codes and transmitted in separate resources. DM-RSs transmitted by being separated by codes in the same resource element may be referred to as one code division multiplex (CDM) group.

Accordingly, in the resource element transmitting the DM-RS, the transmission powers of the DM-RSs transmitted to the antenna port 7 and the antenna port 8 are summed up, respectively, and the transmission of the DM-RS transmitted to the antenna port 9 and the antenna port 10 is performed. The power is transmitted in the form of summing. That is, when there is a limit on the power available in the individual resource element, the DM-RS of the antenna port transmitted in the same resource element is divided and divided into the power, and as a result, the transmission power of the individual antenna port is reduced.

On the other hand, if only one antenna port is transmitted in one CDM group, DM-RS transmission power amplification may be easier because all transmission powers of the corresponding resource element may be used by the DM-RS of the corresponding antenna port. However, since the DM-RS needs to be transmitted using more resource elements, the DM-RS overhead may increase.

The present invention proposes a method of properly selecting a set of DM-RSs to be used for transmission in consideration of the relationship between the DM-RS transmission power amplification effect and the DM-RS overhead. Hereinafter, for convenience of description, two of the antenna port 7 to the antenna port 10 An example of a method of transmitting DM-RS using an antenna port will be described. In particular, when two antenna ports are selected to transmit DM-RS, a transmission diversity scheme may be applied to a signal (ie, E ᅳ PDCCH or PDSCH) that is modulated and demodulated using the DM-RS. Examples of the city method include a space frequency block coding (SFBC) or a beam cycling method for converting a precoder applied to each resource element according to a predefined method. In this case, a specific example of the beam cycling method may include that different antenna ports are applied to each resource element. In particular, this transmission diversity scheme is suitable for transmission of control signals that require more stable transmission.

According to the principles of the present invention, when a relatively large number of resource elements can be used for E-PDCCH transmission, DM-RSs belonging to different CDM groups are used to utilize transmit power amplification. That is, DM-RS to be used for channel demodulation is transmitted using antenna port 7 and antenna port 9 (or antenna port 8 and antenna port 10). More specifically, in order to apply the beam cycling method, the antenna port 7 and the antenna port 9 (or the antenna port 8 and the antenna port 10) belonging to different CDM groups for each resource element are cyclically applied. will be.

On the other hand, when a relatively small number of resource elements are used for channel transmission, as described above, one CDM group is selected to transmit DM-RS in order to reduce DM-RS overhead. In the example above, antenna port 7 and antenna port 8 (or antenna port 9 and antenna port 10) are used. More specifically, to apply the beam cycling method, antenna port 7 and antenna port 8 or antenna port 9 and antenna port 10 belonging to the same CDM group for each resource element are applied cyclically.

For the relative magnitude comparison of resource elements, a proper threshold may be defined and appropriate actions may be taken depending on whether the number of resource elements available for E-PDCCH transmission or the number of OFDM symbols is above or below the above threshold.

Or, it may be classified according to the type of the subframe. For example, in a typical downlink subframe, antenna port 7 and antenna belonging to different CDM groups Port 9 is used, but in special subframe, antenna port 7 and antenna port 8 belonging to the same CDM group are used.

Alternatively, appropriate operation may be taken according to the CP length. For example, use antenna port 7 and antenna port 9 in a normal CP with a relatively large number of resource elements, but use antenna port 7 and antenna in an extended CP with fewer resource elements. Is to use port 8.

Alternatively, the base station may inform the set of antenna ports to be used for each subframe through a higher layer signal in advance.

In another embodiment of applying the principles of the present invention, in order to apply transmit power amplification, a DM-RS always located in a different CDM group is used, and the number of resource elements available for E-PDCCH transmission is small. In some cases, instead of transmitting DM-RS in some DM-RS resource elements, the remaining DM-RS resource elements may be used as available resource elements for the E-PDCCH.

For example, if antenna port 7 and antenna port 9 are used, and the number of available OFDM symbols decreases below a certain number, 4 OFDM symbols are always shown as in the DM-RS allocation example of FIGS. 13 and 14. Rather than transmitting the DM-RS using all, the DM-RS may be transmitted using only two OFDM symbols, which are the first or the subsequent OFDM symbols among the four OFDM symbols.

Or, since only one DM-RS of one antenna port is transmitted in one CDM group, it is not necessary to spread the DM-RS signal for two adjacent resource elements. Accordingly, when the number of resource elements available for E-PDCCH transmission is small, only DM ᅳ RS signals corresponding to the first symbol and the third symbol (black is the second symbol and the fourth symbol) may be transmitted.

16 shows an example of allocating an antenna port to resource elements for E-PDCCH transmission according to an embodiment of the present invention. In particular, FIG. 16 illustrates an example of allocating antenna ports in units of available resource elements constituting E ᅳ REG. FIG. 16A illustrates a subframe of a general CP, and FIG. 16B illustrates a subframe of an extended CP. In the case where E-PDCCH transmission is performed in FIG. Also, in FIG. 16, the number in the grid indicates the corresponding resource. Indicates the DM-RS antenna port index assigned to the element.

Referring to FIG. 16 (a), in a normal CP in which a relatively large number of resource elements exist, antenna port 7 and antenna port 9 are E for the beam cycling method. It can be seen that the resources are cyclically allocated for the available resource elements constituting the -REG.

On the other hand, referring to FIG. 16 (b), in the extended CP in which fewer resource elements exist, for the beam cycling method, the antenna port 7 and the antenna port 8 It can be seen that is recursively allocated for the available resource elements constituting the E-REG.

Referring to FIG. 17, the communication device 1700 includes a processor 1710, a memory 1720, an RF module 1730, a display module 1740, and a user interface modules 1750.

The communication device 1700 is illustrated for convenience of description and some modules may be omitted. In addition, the communication device 1700 may further include necessary modules. In addition, some of the hairs in the communication device 1700 can be divided into more granular hairs. The processor 1710 is configured to perform an operation according to an embodiment of the present invention illustrated with reference to the drawings. In detail, the detailed operation of the processor 1710 may refer to the contents described with reference to FIGS. 1 to 16.

The memory 1720 is connected to the processor 1710 and stores an operating system, an application, a program code, and a data set. The RF modules 1730 are connected to the processor 1710 and perform a function of converting a baseband signal into a radio signal or converting a radio signal into a baseband signal. To this end, the RF modules 1730 perform analog conversion, amplification, filtering and frequency up-conversion or their reverse processes. Display modules 1740 are connected to the processor 1710 and display various information. The display modules 1740 may use well-known elements such as, but not limited to, a liquid crystal display (LCD), a light emitting diode (LED), and a zero light emitting diode (0LED). The user interface modal 1750 is connected with the processor 1710 and is well connected such as a keypad, touch screen, etc. It can consist of any combination of known user interfaces.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component ^' or feature is to be considered optional unless stated otherwise. Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some components and / or features to constitute an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of one embodiment may be included in another embodiment, or may be replaced with other configurations or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

An embodiment according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more appli cation specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), Field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of modules, procedures, functions, etc. that perform the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention. Industrial Applicability

The reference signal antenna port allocation method and apparatus for the transmission diversity scheme in the wireless communication system as described above have been described with reference to the example applied to the 3GPP LTE system, but in addition to the 3GPP LTE system, It is possible to apply.

Claims

[Range of request]

[Claim 1]

A method for transmitting a downlink control channel to a terminal by a base station in a wireless communication system,

Setting resource element subsets consisting of a plurality of resource elements;

Allocating transmission resources for the downlink control channel in units of the resource element subset;

Alternately allocating two antenna ports for a demodul at ion-reference signal (DM-RS) to the plurality of resource elements; And

And transmitting the downlink control channel to the terminal through the allocated transmission resource by using the DM-RSs of the allocated antenna ports.

Downlink control channel transmission method.

[Claim 2]

The method of claim 1,

The index of the antenna ports of the two DM-RS is,

And determining based on the number of available resource elements or the length of a cyclic prefix of the subframe in which the downlink control channel is transmitted.

[Claim 3]

The method of claim 1,

When the downlink control channel is transmitted in a subframe to which a general cyclic prefix is applied, the antenna ports of the two DM-RSs are

Characterized in that the antenna ports of the DM-RS that are not multiplexed on the same resource element,

Downlink control channel transmission method.

[Claim 4]

The method of claim 1, When the downlink control channel is transmitted in a subframe to which a general cyclic prefix is applied, the indexes of the antenna ports of the two DM-RSs are 7 and 9,

Downlink control channel transmission method.

[Claim 5]

The method of claim 1,

When the downlink control channel is transmitted in a subframe to which extended cyclic prefix is applied, the antenna ports of the two DM-RSs are

Characterized in that the antenna ports of the DM-RS multiplexed on the same resource element,

Downlink Control Channel Transmission Method.

6. The ^'

The method of claim 1,

When the downlink control channel is transmitted in a subframe to which extended cyclic prefix is applied, the indexes of the antenna ports of the two DM-RSs are 7 and 8,

Downlink control channel transmission method.

[Claim 7]

As a base station apparatus in a wireless communication system,

Setting a resource element subset consisting of a plurality of resource elements, allocating a transmission resource for a downlink control channel in units of the resource element subset, and demodul at ion-reference to the plurality of resource elements A processor that alternately allocates two antenna ports for Signal; And

And a wireless communication module for transmitting the downlink control channel to the terminal through the allocated transmission resources using DM-RSs of the allocated antenna ports.

Base station equipment.

[Claim 8] The method of claim 7,

The processor is,

Indexes of the antenna ports of the two DM-RSs;

And determine based on the number of available resource elements or the length of a cyclic prefix in the subframe in which the downlink control channel is transmitted.

[Claim 9]

The method of claim 7,

The processor is,

When the downlink control channel is transmitted in a subframe to which a general cyclic prefix is applied, the antenna ports of the two DM-RSs are determined as antenna ports of the DM-RS that are not multiplexed on the same resource element.

Base station device.

[Claim 10]

The method of claim 7, wherein

The processor is,

When the downlink control channel is transmitted in a subframe to which a general cyclic prefix is applied, the indexes of the antenna ports of the two DM-RSs are determined to be 7 and 9,

Base station device.

[Claim 11]

The method of claim 7,

The processor is,

When the downlink control channel is transmitted in a subframe to which extended cyclic prefix is applied, the antenna ports of the two DM-RSs are determined as antenna ports of the DM-RS multiplexed on the same resource element.

Base station device.

[Claim 12] The method of claim 7,

The processor is,

When the downlink control transmission is performed in a subframe to which extended cyclic prefix is applied, an index of the antenna ports of the two DM-RSs is set to 7

Characterized by determining,

Base station equipment.