WO2015147568A1

WO2015147568A1 - Method for transceiving discovery signal in wireless access system and apparatus for supporting same

Info

Publication number: WO2015147568A1
Application number: PCT/KR2015/002976
Authority: WO
Inventors: 김봉회; 이윤정
Original assignee: 엘지전자 주식회사
Priority date: 2014-03-26
Filing date: 2015-03-26
Publication date: 2015-10-01

Abstract

The present invention relates to a wireless access system and provides a method for transceiving a discovery signal and apparatuses for supporting the same. A method for transmitting a discovery signal by a base station in a wireless access system, according to one embodiment of the present invention, comprises the steps of: determining a resource region to which at least one from among a reference signal, a synchronous signal, and a control channel is transmitted in a subframe, as a first discovery region to which a discovery signal is to be transmitted; allocating a predetermined resource block, from the center of a system bandwidth supported by the wireless access system in the first discovery region, to a second discovery region; adjusting the second discovery region on the basis of a size of the system bandwidth and a size of the predetermined resource block; and transmitting a discovery signal through the adjusted second discovery region.

Description

[Specifications

[Name of invention]

Discovery signal transmission / reception method in wireless access system and apparatus supporting same [Technical field]

The present invention relates to a wireless access system, and to a method for transmitting and receiving a discovery signal and an apparatus supporting the same.

Background Art

[2] Wireless access systems are widely deployed to provide various kinds of communication services such as voice and data. In general, a wireless access system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency (SC-FDMA). division multiple access) system.

[Detailed Description of the Invention]

[Technical problem]

An object of the present invention is to provide a method for efficiently transmitting and receiving a discovery signal.

Another object of the present invention is to provide a method for a UE to transmit a discovery signal for efficiently searching for an ON / OFF operation of a serving cell with respect to a serving cell (or a small cell) performing ON / OFF. .

Another object of the present invention is to provide a method for transmitting a discovery signal for a sal search in a wireless access system supporting a new carrier type (NCT).

Another object of the present invention is to provide a method for allocating a discovery area to which a discovery signal is transmitted in a wireless access system supporting NCT and CA.

Another object of the present invention is to provide an apparatus supporting the aforementioned methods. [8] The technical objects to be achieved in the present invention are not limited to the above-mentioned matters, and other technical problems not mentioned above are common in the art to which the present invention belongs from the embodiments of the present invention described below. It can be considered by those who have knowledge.

Technical Solution

The present invention relates to a wireless access system, and to provide a method for transmitting and receiving a discovery signal and apparatuses supporting the same.

According to an aspect of the present invention, a method for transmitting a discovery signal by a base station in a wireless access system includes: a first region in which a discovery signal is transmitted in a resource region in which one or more of a reference signal, a synchronization signal, and a control channel are transmitted in a subframe; Determining a discovery area, allocating a predetermined resource block to a second discovery area at a center of a system bandwidth supported by a wireless access system among the first discovery areas, and based on a size of a system bandwidth and a size of a predetermined resource block And adjusting a second discovery region and transmitting a discovery signal through the adjusted second discovery region.

As another aspect of the present invention, a base station for transmitting a discovery signal in a wireless access system may include a transmitter, a receiver, and a processor configured to control the transmitter and the receiver to transmit the discovery signal. In this case, the processor determines a resource region in which one or more of a reference signal, a synchronization signal, and a control channel are transmitted in a subframe as a first discovery region to which a discovery signal is to be transmitted, and supports a system bandwidth supported by a wireless access system among the first discovery regions. Allocates a predetermined resource block to the second discovery region at the center of the second and adjusts the second discovery region based on the size of the system bandwidth and the size of the predetermined resource block, but controls the transmitter to adjust the adjusted second discovery region And may transmit the discovery signal via the control panel.

[12] In aspects of the present invention, the reference signal is a cell reference signal (CRS) or a channel quality indication reference signal (CSI-RS), and the synchronization signal is a primary synchronization signal (PSS) and / or a secondary synchronization signal (SSS). The control channel may be a physical downlink control channel (PDCCH).

In addition, the serving cell to which the discovery signal is transmitted may be a new carrier type (NCT) cell to which one or more of a reference signal, a synchronization signal, and a control channel are not transmitted. The method may further include performing an initialization process to exchange scrambling information and sequence information of the discovery signal with the terminal.

[15] The above-described aspects of the present invention are merely some of the preferred embodiments of the present invention, and various embodiments reflecting the technical features of the present invention will be described below by those skilled in the art. It can be derived and understood based on the detailed description of the invention.

Advantageous Effects

According to the embodiments of the present invention, the following effects can be obtained.

First, the discovery signal can be efficiently transmitted and received.

Second, the UE can efficiently perform cell search using the discovery signal in a radio access system that supports New Carrier Type (NCT).

Third, in a wireless access system supporting NCT and CA, by defining a discovery area to which a discovery signal is transmitted, a cell on-off operation can be effectively implemented in a small cell environment.

[20] The effects obtained in the embodiments of the present invention are not limited to the above-mentioned effects, and other effects not mentioned above are described in the following description of the embodiments of the present invention. It can be clearly derived and understood by those skilled in the art. That is, unintended effects of practicing the present invention may also be derived from those of ordinary skill in the art from the embodiments of the present invention.

[Brief Description of Drawings]

[21] It is included as part of the detailed description to help understand the present invention, and the accompanying drawings provide various embodiments of the present invention. In addition, the accompanying drawings are used to describe embodiments of the present invention with a detailed description.

1 is a diagram for explaining physical channels and a signal transmission method using the same.

2 shows the structure of a radio frame.

FIG. 3 is a diagram illustrating a resource grid for a downlink slot.

4 shows a structure of an uplink subframe. 5 shows the structure of a downlink subframe.

6 shows a subframe structure of an LTE-A system according to cross carrier scheduling.

FIG. 7 illustrates an example of a subframe to which a cell specific reference signal (CRS) is allocated.

8 is a diagram illustrating an example of subframes in which a channel state information reference signal (CSI-RS) is allocated according to the number of antenna ports.

FIG. 9 illustrates an example of a subframe to which a UE-specific reference signal (UE-RS) is allocated.

10 shows an example of a frame structure indicating a position at which a synchronization signal is transmitted.

FIG. 11 is a diagram illustrating one method of generating a floater signal. FIG.

12 is a diagram illustrating one method of transmitting and receiving a discovery signal.

FIG. 13 is a diagram for illustrating an example of a system band in which a discovery signal is transmitted.

FIG. 14 is a diagram illustrating one method of allocating and adjusting a discovery area. FIG.

The apparatus illustrated in FIG. 15 is a means in which the methods described with reference to FIGS. 1 to 14 may be implemented.

[Form for implementation of invention]

Embodiments of the present invention provide a method for transmitting and receiving a discovery signal and devices supporting the same.

The following embodiments combine the components and features of the present invention in a predetermined form. Each component or feature may 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. In addition, some components and / or features may be combined to form an embodiment of the present 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. In the description of the drawings, procedures or steps that may obscure the gist of the present invention are not described, and procedures or steps that can be understood by those skilled in the art are not described.

Embodiments of the present invention have been described with reference to data transmission / reception relations between a base station and a mobile station. Here, the base station is meant as a terminal node of a network that directly communicates with a mobile station. Certain operations described as being performed by the base station in this document may be performed by an upper node of the base station in some cases.

That is, various operations performed for communication with a mobile station in a network consisting of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. . In this case, the 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an advanced base station (ABS), or an access point.

Further, in embodiments of the present invention, a terminal may be a user equipment (UE), a mobile station (MS), a subscriber station (SS), or a mobile subscriber station (MSS). It may be replaced with terms such as Mobile Subscriber Station, Mobile Terminal, or Advanced Mobile Station (AMS).

In addition, the transmitting end refers to a fixed and / or mobile node that provides a data service or a voice service, and the receiving end refers to a fixed and / or mobile node that receives a data service or a voice service. Therefore, in uplink, a mobile station can be a transmitting end and a base station can be a receiving end. Similarly, in downlink, a mobile station may be a receiving end and a base station may be a transmitting end.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the IEEE 802.XX system, the 3rd Generation Partnership Project (3GPP) system, the 3GPP LTE system, and the 3GPP2 system, which are wireless access systems. The embodiments of the present invention may be supported by 3GPP TS 36.21 1, 3GPP TS 36.212, 3GPP TS 36.213, 3GPP TS 36.321 and / or 3GPP TS 36.331 documents. That is, obvious steps or portions not described among the embodiments of the present invention may be described with reference to the above documents. In addition, all terms disclosed in this document may be described by the above standard document.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is illustrative of the present invention. It is intended to describe exemplary embodiments and not to represent the only embodiments in which the invention may be practiced.

In addition, specific terms used in the embodiments of the present invention are provided to aid the understanding of the present invention, and the use of the specific terms may be in other forms without departing from the technical spirit of the present invention. can be changed.

The following techniques are code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access (SC-FDMA). It can be applied to various wireless access systems such as).

[48] CDMA may be implemented by radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented by a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA).

[49] UTRA is a part of Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. The LTE-A (Advanced) system is an improved system of the 3GPP LTE system. In order to clarify the description of the technical features of the present invention, embodiments of the present invention are described mainly for the 3GPP LTE / LTE-A system, but can be applied to the IEEE 802.16e / m system and the like.

[50] 1. 3GPP LTE / LTE-A System

In a wireless access system, a terminal receives information from a base station through downlink (DL) and transmits information to a base station through uplink (UL). The information transmitted and received between the base station and the terminal includes general data information and various control information, and various physical channels exist according to the type / use of the information transmitted and received. [52] 1.1 System General FIG. 1 is a diagram for explaining physical channels that can be used in embodiments of the present invention and a signal transmission method using the same.

In the state in which the power is turned off, the terminal is powered on again or enters a new cell, and performs an initial cell search operation such as synchronizing with the base station in step S1. 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 cell ID.

Thereafter, the terminal may receive a physical broadcast channel (PBCH) signal from the base station to acquire broadcast information in the cell. On the other hand, the UE may check the downlink channel state by receiving a downlink reference signal (DL RS) in the initial cell search step.

After completing the initial cell search, the UE receives a physical downlink control channel (PDCCH) according to physical downlink control channel (PDCCH) and physical downlink control channel information in step S12. To obtain more specific system information.

Subsequently, the terminal may perform a random access procedure such as step S13 to step S16 afterwards to complete the access to the base station. To this end, the UE transmits a preamble through a physical random access channel (PRACH) (S 13), and a preamble through a physical downlink control channel and a corresponding physical downlink shared channel. In response to the response message can be received (S14). In case of contention-based random access, the UE may perform additional layer resolution procedures such as transmitting additional physical random access channel signals (S15) and receiving physical downlink control channel signals and corresponding physical downlink shared channel signals (S16). Contention Resolution Procedure) can be performed.

After performing the above-described procedure, the UE subsequently receives a physical downlink control channel signal and / or a physical downlink shared channel signal (S17) and a physical uplink shared channel as a general uplink / downlink signal transmission procedure. A physical uplink shared channel (PUSCH) signal and / or a physical uplink control channel (PUCCH) signal may be transmitted (S18).

The control information transmitted from the terminal to the base station is collectively referred to as uplink control information (UCI). UCI is HARQ-ACK / NACK (Hybrid

Automatic Repeat and reQuest Acknowledgement / Negative-ACK, SR (Scheduling Request), Channel Quality Indication (CQI), Precoding Matrix Indication (PMI), and Rank Indication (RI) information.

In the LTE system, UCI is generally transmitted periodically through a PUCCH, but may be transmitted through a PUSCH when control information and traffic data are to be transmitted at the same time. In addition, the UCI can be aperiodically transmitted through the PUSCH by the network request / instruction.

2 illustrates a structure of a radio frame used in embodiments of the present invention.

2 (a) shows a frame structure type 1. Type 1 frame structure can be applied to both full duplex Frequency Division Duplex (FDD) systems and half duplex FDD systems.

[63] One radio frame has a length of 3G72G (T _S = 10 ms, an equal length of r _slot = 1536 (T _s = 5 m _S , and an index of ₀ to ₉ is assigned. _It consists of ₂₀ slots, one subframe is defined as two consecutive slots, and the i-th subframe is composed of slots corresponding to 2i and 2i + l, that is, a radio frame is 10 consists of a sub-frame (subframe). is referred to as the time it takes to transmit a single sub-frame (transmission time interval) TTI. here, Ts represents the sampling period, Ts = l / (15kHzx2048) = 3.2552xl coming ⁸ A slot includes a plurality of OFDM symbols or SC-FDMA symbols in the time domain and a plurality of resource blocks in the frequency domain.

One slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain. Since 3GPP LTE uses OFDMA in downlink, the OFDM symbol is for representing one symbol period. The OFDM symbol may be referred to as one SC-FDMA symbol or symbol period. A resource block is a resource allocation unit and includes a plurality of consecutive subcarriers in one slot.

In a full-duplex FDD system, 10 subframes may be used simultaneously for downlink transmission and uplink transmission during each 10 ms period. At this time, uplink and downlink transmission are separated in the frequency domain. On the other hand, in the case of a half-duplex FDD system, the terminal cannot transmit and receive at the same time. [66] The structure of the above-described radio frame, the number of OFDM symbols included in the only with ^U said, the number of slots included in the number or sub-frame of the capsule should subframe in a radio frame, a slot in one example of the various Can be changed.

2 (b) shows a frame structure type 2. Type 2 frame structure is applied to TDD system. One radio frame (radio frame) is composed of f eu = 307200 7 = 10 ms ₂ and two frame profiles (half-frame) has a has a length, 1536GG eu 7 = ⁵ ms in length. Each half frame consists of five subframes with a length of 30 ⁷² 0 ^' 7 = l ms. the i-th subframe is composed of each _slot r = l ⁵³ 6G _s = ₂ slots each having a length of a ⁵ ms which corresponds to 2i and 2i + l. Here, T _s represents the sampling time and is represented by T _s = l / (15kHzx2048) = 3.2552xl 0-8 (about 33ns).

The type 2 frame includes a special subframe consisting of three fields: a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). Here, DwPTS is used for initial cell search, synchronization, or channel estimation in the terminal. UpPTS is used for channel estimation at base station and synchronization of uplink transmission of UE. The guard period 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.

[69] The following table 1 shows the structure of a special frame (length of DwPTS / GP UpPTS).

[70] [Table 1]

FIG. 3 is a diagram illustrating a resource grid for a downlink slot that can be used in embodiments of the present invention.

Referring to FIG. 3, one downlink slot includes a plurality of OFDM symbols in the time domain. Here, one downlink slot includes seven OFDM symbols, One resource block is not limited to one described by way of example, it comprises a portion 12 ^'the carrier in the frequency domain.

[73] Each element on the resource grid is a resource element, and one resource block includes 12 X 7 resource elements. The number NDL of resource blocks included in the downlink slot depends on the downlink transmission bandwidth. The structure of the uplink slot may be the same as the structure of the downlink slot.

4 shows a structure of an uplink subframe that can be used in embodiments of the present invention.

Referring to FIG. 4, an uplink subframe may be divided into a control region and a data region in the frequency domain. The control region is allocated a PUCCH carrying uplink control information. The data area is allocated with a PUSCH carrying user data. In order to maintain a single carrier characteristic, one UE does not simultaneously transmit a PUCCH and a PUSCH. An RB pair is allocated to a PUCCH for one UE in a subframe. RBs belonging to the RB pair occupy different subcarriers in each of the two slots. This RB pair allocated to the PUCCH is said to be frequency hopping at the slot boundary (slot boundary).

5 shows a structure of a downlink subframe that can be used in embodiments of the present invention.

Referring to FIG. 5, up to three OFDM symbols from the OFDM symbol index 0 in the first slot of a subframe are control regions to which control channels are allocated, and the remaining OFDM symbols are data regions to which the PDSCH is allocated. data region). An example of a downlink control channel used in 3GPP LTE includes a Physical Control Format Indicator Channel (PCFICH), a PDCCH, and a Physical Hybrid-ARQ Indicator Channel (PHICH).

[78] The PCFICH carries information on the number of OFDM symbols (that is, the size of a control region) in which a first OF of a subframe is transmitted in a VI symbol and used for transmission of control channels in the subframe. PHICH is a male answer channel for the uplink, and carries an ACK (Acknowledgement) / NACK (Negative-Acknowledgement) signal for a hybrid automatic repeat request (HARQ). Control information transmitted through the PDCCH is called downlink control information (DCI). Downlink control information is uplink Resource allocation information, downlink resource allocation information, or an uplink transmission (Tx) power control command for a certain UE group.

[79] 1.2 Carrier Aggregation (CA) Environment

[80] 1.2.1 CA General

[81] 3GPP LTE (3rd Generation Partnership Project Long Term Evolution (Rel-8 or Rel-9) system (hereinafter referred to as LTE system) is a multi-carrier modulation using a single component carrier (CC) by dividing into multiple bands. (MCM: Multi-Carrier Modulation) is used. However, in a 3GPP LTE-Advanced system (eg, Rel-10 to Rel-12; hereinafter, LTE-A system), a carrier combination using a combination of one or more component carriers to support a wider system bandwidth than the LTE system ( You can use a method such as CA: Carrier Aggregation. Carrier coupling may be replaced by the terms carrier aggregation, carrier matching, multi-component carrier environment (Multi-CC) or multicarrier environment.

In the present invention, the multi-carrier means the aggregation of carriers (or carrier aggregation), wherein the aggregation of carriers means not only merging between contiguous carriers but also merging between non-contiguous carriers. . In addition, the number of component carriers aggregated between downlink and uplink may be set differently. When the number of downlink component carriers (hereinafter referred to as 'DL CC') and the number of uplink component carriers (hereinafter referred to as 'UL CC') are the same, it is called symmetric merging. Is called asymmetric merging.

Such carrier combining may be commonly used with terms such as carrier aggregation, bandwidth aggregation, spectrum aggregation, and the like. In the LTE-A system, a carrier combination consisting of two component carriers combined is aimed at supporting up to 100 MHz bandwidth. When combining one or more carriers having a bandwidth smaller than the target band, the bandwidth of the combining carrier may be limited to the bandwidth used by the existing system to maintain backward compatibility with the existing IMT system.

For example, the existing 3GPP LTE system supports {1.4, 3, 5, 10, 15, 20} MHz bandwidth, and the 3GPP LTE-advanced system (ie, LTE-A) is compatible with the existing system. In order to support bandwidths larger than 20 MHz, Can be. In addition, the carrier combining system used in the present invention may support carrier combining by defining a new bandwidth regardless of the bandwidth used in the existing system.

In addition, the carrier coupling may be classified into an intra-band CA and an inter-band CA. Intra-band carrier coupling means that a plurality of DL CCs and / or UL CCs are located adjacent to or adjacent in frequency. In other words, it may mean that the carrier frequencies of the DL CCs and / or UL CCs are located in the same band. On the other hand, an environment far from the frequency domain may be called an inter-band CA. In other words, it may mean that the carrier frequencies of the plurality of DL CCs and / or UL CCs are located in different bands. In this case, the terminal may use a plurality of radio frequency (RF) terminals to perform communication in a carrier coupling environment.

[86] The LTE-A system uses the concept of a cell to manage radio resources. The carrier binding environment described above may be referred to as a multiple cell environment. A cell is defined as a combination of a downlink resource (DL CC) and an uplink resource (UL CC), but the uplink resource is not required. Therefore, the cell may be configured with only downlink resources, or with downlink resources and uplink resources.

For example, when a specific UE has only one configured serving cell, it may have one DL CC and one UL CC, but when a specific UE has two or more configured serving cells Has as many DL CCs as the number of cells and the number of UL CCs may be equal to or less than that. Or, conversely, DL CC and UL CC may be configured. That is, when a specific UE has a plurality of configured serving cells, a carrier combining environment having more UL CCs than the number of DL CCs may be supported.

Carrier coupling (CA) may also be understood as the merging of two or more cells, each having a different carrier frequency (center frequency of the cell). Here, the term 'cell' should be distinguished from 'cell' as a geographic area covered by a commonly used base station. Hereinafter, the above-described intra-band carrier coupling is referred to as an intra-band multicell, and the inter-band carrier coupling is referred to as an inter-band multicell.

The cell used in the LTE-A system includes a primary cell (PCell) and a secondary cell (SCell). P cells and S cells may be used as a serving cell. In RRC_CONNECTED state, but carrier coupling is not established Or, for a terminal that does not support carrier aggregation, there is only one serving cell consisting of a PCell. On the other hand, in case of a UE in RRC_CONNECTED state and carrier aggregation is configured, one or more serving cells may exist, and the entire serving cell includes a P cell and one or more S cells.

[90] The serving cells (P cell and S cell) may be configured through an RRC parameter. PhysCellld is a Sal's physical layer identifier, which has an integer value from 0 to 503. ServCelllndex is a short identifier used to identify a serving cell (P cell or S cell) and has an integer value from 0 to 7. A value of 0 is applied to the P cell, and SCelllndex is given in advance to apply to the S cell. That is, a cell having the smallest cell ID (or cell index) in ServCelllndex becomes a Pcell.

A P cell refers to a cell operating on a primary frequency (or primary CC). The UE may be used to perform an initial connection establishment process or to perform a connection re-establishment process, and may also refer to a cell indicated in a handover process. In addition, the P cell refers to a cell which is the center of control-related communication among serving cells set in a carrier coupling environment. That is, the terminal may receive and transmit a PUCCH only in its own Pcell, and may use only the Pcell to acquire system information or change a monitoring procedure. E-UTRAN (Evolved Universal Terrestrial Radio Access) uses a higher layer RRCConnectionReconfigutaion message including mobility controllnfo to a terminal supporting a carrier combining environment for a handover procedure. You can only change it.

The S cell may refer to a cell operating on a secondary frequency (or secondary CC). Only one psal is allocated to a specific terminal, and one or more SCells may be allocated. The S cell is configurable after the RRC connection is established and can be used to provide additional radio resources. PUCCH does not exist in the remaining cells except the P cell, that is, the S cell, among the serving cells configured in the carrier combining environment.

When the E-UTRAN adds the S cell to the UE supporting the carrier coupling environment, the E-UTRAN may provide all system information related to the operation of the related cell in the RRC_CONNECTED state through a dedicated signal. The change of the system information may be controlled by the release and addition of the related S cell, and at this time, an RRC connection reconfigutaion message of a higher layer may be used. E-UTRAN related Rather than broadcasting in a given cell, dedicated signaling with different parameters for each terminal may be performed.

After the initial security activation process is started, the E-UTRAN may configure a network including one or more S cells in addition to the P cell initially configured in the connection establishment process. In the carrier bonding environment, the PCell and SSell may act as respective component carriers. In the following embodiments, the primary component carrier (PCC) may be used in the same sense as the P cell, and the secondary component carrier (SCC) may be used in the same meaning as the S cell. [95] 1.2.2 Cross Carrier Scheduling

In a carrier combining system, there are two types of a self-scheduling method and a cross carrier scheduling method in terms of scheduling for a carrier (or carrier) or a serving cell. Cross carrier scheduling may be referred to as Cross Component Carrier Scheduling or Cross Cell Scheduling.

[97] In self-scheduling, a UL is transmitted in which a DL Grant (PDCCH) and a PDSCH are transmitted in the same DL CC, or a PUSCH transmitted according to a PDCCH (UL Grant) transmitted in the DL CC is linked to a DL CC in which the UL Grant has been received. Means to be transmitted through the CC.

[98] In cross-carrier scheduling, a PDCCH (DL Grant) and a PDSCH are transmitted to different DL CCs, or a PUSCH transmitted according to a PDCCH (UL Grant) transmitted from a DL CC is linked to a DL CC having received an UL grant. This means that it is transmitted through a UL CC other than the UL CC.

[99] Whether or not cross-carrier scheduling may be activated or deactivated UE-specifically and may be known semi-statically for each UE through higher layer signaling (eg, RRC signaling). have.

When cross carrier scheduling is activated, a carrier indicator field (CIF: Carrier Indicator Field) indicating a PDSCH / PUSCH indicated by the corresponding PDCCH is transmitted to the PDCCH. For example, the PDCCH may allocate a PDSCH resource or a PUSCH resource to one of a plurality of component carriers using CIF. That is, when the PDCCH on the DL CC allocates PDSCH or PUSCH resources to one of the DL / UL CC multi-aggregated, the CIF is set. In this case, LTE The DCI format of Release-8 can be extended according to CIF. At this time, the set CIF can be fixed to 3bit field or the set CIF can be fixed regardless of DCI format size. In addition, the PDCCH structure (same coding and resource mapping based on the same CCE) of LTE Release-8 may be reused.

On the other hand, CIF is not configured when the PDCCH on the DL CC allocates PDSCH resources on the same DL CC or PUSCH resources on a single linked UL CC. In this case, the same PDCCH structure (same coding and resource mapping based on the same CCE) and DCI format as in LTE Release-8 may be used.

[1021 When cross-carrier scheduling is possible, the UE needs to monitor PDCCHs for a plurality of DCIs in the control region of the monitoring CC according to a transmission mode and / or bandwidth for each CC. Therefore, it is necessary to configure the search space and PDCCH monitoring to support this.

In the carrier combining system, the terminal DL CC set indicates a set of DL CCs scheduled for the terminal to receive a PDSCH, and the terminal UL CC set indicates a set of UL CCs scheduled for the UE to transmit a PUSCH. In addition, the PDCCH monitoring set represents a set of at least one DL CC that performs PDCCH monitoring. The PDCCH monitoring set may be the same as the UE DL CC set or may be a subset of the UE DL CC set. The PDCCH monitoring set may include at least one of DL CCs in the terminal DL CC set. Alternatively, the PDCCH monitoring set may be defined separately regardless of the UE DL CC set. The DL CC included in the PDCCH monitoring set may be configured to always enable self-scheduling for the linked UL CC. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring set may be configured UE-specifically, UE group-specifically, or cell-specifically.

When cross-carrier scheduling is deactivated, it means that the PDCCH monitoring set always matches the UE DL CC set. In this case, an indication such as separate signaling for the PDCCH monitoring set is not necessary. However, when cross carrier scheduling is activated, the PDCCH monitoring set is preferably defined in the terminal DL CC set. That is, in order to schedule PDSCH or PUSCH for the UE, the base station transmits the PDCCH through only the PDCCH monitoring set. FIG. 6 illustrates cross carrier scheduling used in embodiments of the present invention.

A subframe structure of the LTE-A system is shown.

Referring to FIG. 6, three DL component carriers (DL CCs) are combined in a DL subframe for an LTE-A terminal, and DL CC V represents a case in which a PDCCH monitoring DL CC is configured. If CIF is not used, each DL CC may transmit a PDCCH for scheduling its PDSCH without CIF. On the other hand, when CIF is used through higher layer signaling, only one DL CC 'A' may transmit a PDCCH for scheduling its PDSCH or PDSCH of another CC using the CIF. At this time, DL CCs' Β 'and' C that are not configured as PDCCH monitoring DL CCs do not transmit the PDCCH.

[107] 1.3 Physical Downlink Control Channel (PDCCH)

[108] 1.3.1 PDCCH General

PDCCH includes resource allocation and transmission format (ie, DL-Grant) of DL-SCH and resource allocation information of UL-SCH (ie, UL grant) (UL-Grant), upper-layer control such as paging information in paging channel (PCH), system information in DL-SCH, and random access response transmitted in PDSCH It may carry resource allocation for a message, a set of transmission power control commands for individual terminals in a certain terminal group, information on whether voice over IP (VoIP) is activated or the like.

A plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH consists of an aggregation of one or several consecutive CCEs (control channel elements). A PDCCH composed of one or several consecutive CCEs may be transmitted through a control region after subblock interleaving. CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups (REGs). The format of the PDCCH and the number of possible bits of the PDCCH are determined by the correlation between the number of CCEs and the coding rate provided by the CCEs. [111] 1.3.2 PDCCH Structure

A plurality of multiplexed PDCCHs for a plurality of UEs may be transmitted in a control region. The PDCCH is composed of one or more consecutive CCE aggregations (CCE aggregation). CCE refers to a unit that spans nine sets of REGs consisting of four resource elements. Each REG is mapped with four Quadrature Phase Shift Keying (QPSK) symbols. Resource elements occupied by a reference signal (RS) are not included in the REG. That is, the total number of REGs in the OFDM symbol may vary depending on whether a specific reference signal exists. The concept of REG that maps four resource elements to one group may be applied to another downlink control channel (eg, PCFICH or PHICH). If REG is not assigned to PCFICH or PHICH, the number of CCEs available in the system is ^N CCE-.

^ J, with each starting from 0

^ CCE-has an index up to ¹

In order to simplify the decoding process of the UE, a PDCCH format including n CCEs may start with a CCE having an index equal to a multiple of n. That is, when the CCE index is i, it may start from a CCE that satisfies / mod "= 0.

[114] The base station may use {1, 2, 4, 8} CCEs to configure one PDCCH signal, wherein {1, 2, 4, 8} is called a CCE aggregation level. It is. The number of CCEs used for transmission of a specific PDCCH is determined by the base station according to the channel state. For example, a PDCCH for a terminal having a good downlink channel state (close to a base station) may be divided into only one CCE. Van ^'side, in the case of having a channel that is poor (in the case at the cell edge), the terminal may be required for strength (robustness), the eight CCE are cheungbun. In addition, the power level of the PDCCH may also be adjusted to match the channel state.

The following Table 2 shows the PDCCH formats, and four PDCCH formats are supported as shown in Table 2 according to the CCE aggregation level.

[116] [Table 2]

PDCCH format Number of CCEs (n) Number of REGs Number of PDCCH bits

0 1 9 72

1 2 18 144

2 4 36 288

3 8 72 576 The reason why the CCE aggregation level is different for each UE is because the format of the control information carried on the PDCCH or the Modulation and Coding Scheme (MCS) level are different. MCS level refers to the code rate and modulation order used for data coding. Adaptive MCS levels are used for link adaptation. In general, three to four MCS levels may be considered in a control channel for transmitting control information.

Referring to the format of the control information, the control information transmitted through the PDCCH is referred to as downlink control information (DCI). The configuration of information carried in the PDCCH payload may vary depending on the DCI format. The PDCCH payload means an information bit. Table 3 below shows DCI according to DCI format.

[119] [Table 3]

Format 1 for scheduling of PDSCH codewords, Format 1A for compact scheduling of one PDSCH codeword, Format 1C for very simple scheduling of DL-SCH, closed-loop spatial multiplexing format 2 for PDSCH scheduling in multiplexing mode, format 2A for PDSCH scheduling in open-loop spatial multiplexing mode, format 2B for two-layer transmission using DM-RS, and DM-RS There are formats 2C for multi-layer transmission and formats 3 and 3A for transmission of a transmission power control (TPC) command for an uplink channel. In addition, DCI format 4 for PUSCH scheduling in a multi-antenna port transmission mode has been added. DCI format 1A may be used for PDSCH scheduling regardless of which transmission mode is configured for the UE. The PDCCH payload length may vary depending on the DCI format. In addition, the type and length thereof of the PDCCH payload may vary depending on whether it is simple scheduling or a transmission mode configured in the terminal.

The transmission mode may be configured for the UE to receive downlink data through the PDSCH. For example, the downlink data through the PDSCH may include scheduled data, paging, random access response, or broadcast information through BCCH. Downlink data through the PDSCH is related to the DCr format signaled through the PDCCH. The transmission mode may be set semi-statically to the terminal through higher layer signaling (eg, RRC (Radio Resource Control) signaling). The transmission mode may be classified into single antenna transmission or multi-antenna transmission.

The UE sets a transmission mode semi-statically through higher layer signaling. For example, multi-antenna transmissions include transmit diversity, open-loop or closed-loop spatial multiplexing, and multi-user-multiple input multiple outputs. ) Or beam forming. Transmit diversity is a technique of increasing transmission reliability by transmitting the same data in multiple transmit antennas. Spatial multiplexing is a technique that allows high-speed data transmission without increasing the bandwidth of the system by simultaneously transmitting different data from multiple transmit antennas. Beamforming is a technique of increasing the signal to interference plus noise ratio (SINR) of a signal by applying weights according to channel conditions in multiple antennas.

[124] The DCI format is dependent on a transmission mode configured in the terminal (depend on). The UE has a reference DCI format for monitoring according to a transmission mode configured for the UE. The transmission mode set in the terminal may have ten transmission modes as follows.

Transmission Mode 1: Single Antenna Transmission

* Transmission mode 2: Transmit diversity

Transmission mode 3: Open-Loop codebook based precoding if the layer is larger than one, and transmit diversity if the rank is 1

Transmission mode 4: closed-loop codebook based precoding

Transport Mode 5: Transport Mode 4 Version of Multi-User MIMO

Transmission mode 6: closed loop codebook based precoding in special cases limited to single layer transmission Transfer Mode 7: Precoding not based on codebooks that only support single layer transfer (release 8)

Transmission mode 8: Precoding not based on codebook supporting up to 2 layers (release 9)

Transfer Mode 9: Precoding not based on codebooks supporting up to 8 layers (release 10)

* Transmission mode 10: Precoding not based on codebook supporting up to 8 layers, COMP use (release 11) [125] 1.3.3 PDCCH transmission

The base station determines the PDCCH format according to the DCI to be transmitted to the terminal and attaches a CRC (Cyclic Redundancy Check) to the control information. The CRC is masked with a unique identifier (eg, Radio Network Temporary Identifier (RNTI)) according to the owner or purpose of the PDCCH. If the PDCCH for a specific terminal, a unique identifier (eg, C-RNTI (Cell-RNTI)) of the terminal may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier (eg, P-RNTI (Paging-RNTI)) may be masked to the CRC. If the system information, more specifically, the PDCCH for a system information block (SIB), a system information identifier (eg, a system information RNTI) may be masked to the CRC. A random access-RNTI (RA-RNTI) may be masked in the CRC to indicate a random access response that is a male answer to transmission of the random access preamble of the terminal.

Subsequently, the base station performs channel coding on the control information added with the CRC to generate coded data. In this case, channel coding may be performed at a code rate according to the MCS level. The base station performs rate matching on the CCE aggregation level allocated to the PDCCH format, and modulates the coded data to generate modulated symbols. At this time, a modulation sequence according to the MCS level may be used. The modulation symbols constituting one PDCCH may have one of 1, 2, 4, and 8 CCE aggregation levels. Thereafter, the base station maps the modulation symbols to physical resource elements (CCE to RE mapping). 1.4 Reference Signal (RS)

[129] Hereinafter, reference signals that can be used in embodiments of the present invention. Explain.

FIG. 7 is a diagram illustrating an example of a subframe to which a cell specific reference signal (CRS) is allocated, which can be used in embodiments of the present invention.

7 shows an allocation structure of a CRS when a system supports four antennas. In 3GPP LTE / LTE-A system, CRS is used for decoding and channel state measurement. Accordingly, the CRS is transmitted over the entire downlink bandwidth in all downlink subframes in a cell supporting PDSCH transmission, and is transmitted in all antenna ports configured in the eNB.

Specifically, the CRS sequence is mapped to complex-valued modulation symbols used as reference symbols for antenna port p in slot n _s .

The UE may measure the CSI using the CRS and may decode the downlink data signal received through the PDSCH in the subframe including the CRS. That is, the eNB transmits the CRS at a predetermined position in each RB in all RBs, and the UE detects the PDSCH after performing channel estimation based on the CRS. For example, the UE measures the signal received at the CRS RE. The UE may detect the PDSCH signal from the PD to which the PDSCH is mapped by using a ratio of the reception energy for each CRS RE and the reception energy for each RE to which the PDSCH is mapped.

As described above, when the PDSCH signal is transmitted based on the CRS, the eNB needs to transmit the CRS for all RBs, thereby causing unnecessary RS overhead. In order to solve this problem, the 3GPP LTE-A system further defines a UE-specific RS (hereinafter, UE-RS) and a channel state information reference signal (CSI-RS) in addition to the CRS. UE-RS is used for demodulation, and CSI-RS is used to derive channel state information.

The UE-RS and the CRS are used for demodulation, and thus, may be referred to as demodulation RS in terms of use. That is, the UE-RS may be regarded as a kind of DM-RS (DeModulation Reference Signal). In addition, since CSI-RS and CRS are used for channel measurement or channel estimation, they may be referred to as RS for channel state measurement in terms of use.

8 is a diagram illustrating an example of subframes in which CSI-RSs that can be used in embodiments of the present invention are allocated according to the number of antenna ports.

The CSI-RS is a downlink reference signal introduced in the 3GPP LTE-A system not for demodulation but for measuring the state of a wireless channel. 3GPP LTE-A system for CSI-RS transmission A plurality of CSI-RS settings are defined. In subframes in which CSI-RS transmission is configured, the CSI-RS sequence is mapped according to complex modulation symbols used as reference symbols on antenna port p.

FIG. 8 (a) shows 20 CSI-RS configurations 0 to 19 available for CSI-RS transmission by two CSI-RS ports among CSI-RS configurations, and FIG. 8 (b) Shows ten CSI-RS configurations 0-9 available by four CSI-RS ports of the CSI-RS configurations _: FIG. 8 (c) shows eight CSI-RS ports of the CSI-RS configurations. The five CSI-RS configurations 0-4 that can be used are shown.

In this case, the CSI-RS port means an antenna port configured for CSI-RS transmission. Since the CSI-RS configuration varies depending on the number of CSI-RS ports, even if the CSI-RS configuration numbers are the same, different CSI-RS configurations are achieved if the number of antenna ports configured for CSI-RS transmission is different.

On the other hand, unlike the CRS configured to be transmitted every subframe, the CSI-RS is set to be transmitted at a predetermined transmission period corresponding to a plurality of subframes. Accordingly, the CSI-RS configuration depends not only on the positions of REs occupied by the CSI-RS in a resource block pair but also on the subframe in which the CSI-RS is configured.

In addition, even if the CSI-RS configuration numbers are the same, if the subframes for CSI-RS transmission are different, the CSI-RS configuration may be regarded as different. For example, if the CSI-RS transmission period (r _CSI-RS ) is different or the start subframe (A _CSI-RS ) configured for CSI-RS transmission in one radio frame is different, the CSI-RS configuration may be different.

[142] Hereinafter, CSI varies according to (1) CSI-RS configuration to which CSI-RS configuration number is assigned and (2) CSI-RS configuration number, number of CSI-RS ports, and / or subframes to which CSI-RS is configured. In order to distinguish the -RS configuration, the latter configuration is referred to as a CSI-RS resource configuration. The setting of the former 1 is also referred to as CSI-RS configuration or CSI-RS pattern.

[143] The eNB informs the UE of CSI-RS resource configuration, the number of antenna ports, CSI-RS pattern, CSI-RS subframe configuration / CSI- used for transmission of CSI-RSs. UE, UE assumption on reference PDSCH transmitted power for CSI feedback, informs about P _c , zero power CSI-RS configuration list, zero power CSI-RS subframe configuration, etc. Can give

[144] CSI-RS subframe configuration index / _CS1-RS is for the presence (occurrence) of CSI-RSs Subframe Configuration Period r _CSI-RS and Subframe Offset A _CSI-RS . Table 4 below illustrates CSI-RS subframe configuration index / _CSI-RS according to r _csl - _RS and A _CSW 1.

[145] [Table 4]

In this case, subframes satisfying Equation 1 become subframes including the CSI-RS.

[147] [Equation 1]

(10 " _f + k / ² J ^{" A} CSI-RS) ^mod ^ CSI-RS = 0

After the 3GPP LTE-A system, a UE set to a defined transmission mode (for example, transmission mode 9 or another newly defined transmission mode) performs channel measurement using CSI-RS and performs UE-RS. PDSCH can be decoded.

9 is a diagram illustrating an example of a subframe to which a UE-specific reference signal (UE-RS) is allocated, which can be used in embodiments of the present invention.

Referring to FIG. 9, a corresponding subframe illustrates REs occupied by UE-RS among REs in a resource block pair of a regular downlink subframe having a normal CP.

[151] UE-RS is supported for transmission of PDSCH signal and antenna port (s) are ρ = 5, ρ = Ί .. /? = 8 or 7 = 7, 8, ... ^ + 6 (where 1) may be the number of layers used for transmission of the PDSCH. The UE-RS exists when a PDSCH transmission is associated with a corresponding antenna port, and is a valid reference signal only for demodulation of the PDSCH signal.

[152] The UE-RS is transmitted only on RBs to which a corresponding PDSCH signal is mapped. That is, the UE-RS is set to be transmitted only in the RB (s) to which the PDSCH is mapped in the subframe in which the PDSCH is scheduled, unlike the CRS configured to be transmitted every subframe regardless of the presence or absence of the PDSCH. In addition, unlike the CRS transmitted through all the antenna port (s) regardless of the number of layers of the PDSCH, the UE-RS uses the antenna port (s) corresponding to the layer (s) of the PDSCH respectively. Only sent through Therefore, using the UE-RS, the overhead of the RS can be reduced compared to the CRS.

In the 3GPP LTE-A system, UE-RS is defined in a PRB pair. Referring to FIG. 9, for p = 7, ^ = 8 or = 7,8., Υ + 6, in a PRB having a frequency-domain index n _PRB assigned for corresponding PDSCH transmission, UE- Part of the RS sequence is mapped to complex modulation symbols in a particular subframe.

[154] The UE-RS is transmitted through antenna port (s) respectively corresponding to the layer (s) of the PDSCH. That is, it can be seen that the number of UE-RS ports is proportional to the transmission tank of the PDSCH. On the other hand, if the number of layers is 1 or 2, 12 REs for each RB pair are used for UE-RS transmission. If the number of layers is greater than 2, 24 REs for each RB pair are used for UE-RS transmission. do. In addition, the positions of REs (ie, UE-RS REs) occupied by the UE-RS in the RB pair are the same for each UE-RS port regardless of the cell.

[155] As a result, the number of DM-RS REs is the same in RBs in which PDSCHs for specific UEs are mapped in specific subframes. However, in RBs allocated to different UEs in the same subframe, the number of DM-RS REs included in corresponding RBs may vary according to the number of layers transmitted.

[156] 1.5 Sync Signal

A synchronization signal (SS) is composed of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS). In addition, the synchronization signal is a signal used when performing synchronization acquisition and cell search between the terminal and the base station.

FIG. 10 is a diagram illustrating an example of a frame structure indicating a position at which a synchronization signal is transmitted. In particular, FIGS. 10 (a) and 10 (b) show a frame structure for transmission of an SS in a system using a basic cyclic prefix (CP) and an extended CP, respectively.

The synchronization signal is transmitted in the second slot of subframe 0 and subframe 5, respectively, taking into account the GSM frame length of 4.6 ms for ease of inter-RAT (Radio Access Technology) measurement. At this time, the boundary for the radio frame can be detected through the SSS.

10 (a) and 10 (b), the PSS is transmitted in the last OFDM symbol of slots 0 and 5, and the SSS is transmitted in the OFDM symbol immediately before the PSS. SS has three PSSs A total of 504 physical cell IDs can be transmitted through a combination of 168 SSSs. In addition, since the SS and the PBCH are transmitted within 6 RB of the system bandwidth, the UE can always detect and decode the SS and PBCH signals regardless of the size of the transmission bandwidth.

The transmit diversity scheme of the SS uses only a single antenna port. That is, a single antenna transmission or a transparent transmission scheme (eg, PVS, TSTD, CDD) can be used.

[162] 1.5.1 Host signal (PSS)

[163] A Zadoff-Chu (ZC) sequence of length 63 is defined in the frequency domain and used as the PSS sequence. The ZC sequence is defined by the following equation.

[164] [Equation 2] d _u (n) = e ^{J Nzc}

In Equation 2, Nzc represents a length 63 of the ZC sequence, and du (n) represents a PSS sequence according to the root index u. In this case, a sequence element n = 31 corresponding to a direct current (DC) subcarrier is punctured.

In order to facilitate filter design for synchronization, nine remaining subcarriers of 6RB (= 72 subcarriers) corresponding to the middle of the bandwidth are always transmitted with a value of zero. In order to define a total of three PSS, values of u = 25, 29, and 34 may be used. At this time, u 29 and 34 have a conjugate symmetry relationship, so that two correlations can be performed simultaneously. Here, conjugate symmetry means the relationship of the following equation (3). Using the conjugate symmetry feature, one-shot correlators for u = 29 and 34 can be implemented, which can reduce the overall computation by about 33.3%.

[167] [Equation 3] d _u («) = (-1)"(<^ N _ZC ( ^N )), when N _zc is even number.

d _u (n) = (d _{N? c} __ _u , when N _zc is odd number.

[168] 1.5.2 Float Signal (SSS)

[169] The SSS is generated by interleaving and joining two m-segments of length 31. In this case, the two sequences may be combined to identify a 168 cell group ID. As a sequence of SSS, the SSS is robust in frequency-selective environment and can reduce the computation amount by fast m-sequence transformation using fast fast adamant transform. In addition, configuring the SSS with two short codes has been proposed to enjoy the amount of computation of the terminal.

Referring to FIG. 11, it can be seen that two m-segments defined in the logical domain are interleaved and mapped in the physical domain. For example, when defining two m-segments used for SSS code generation as SI and S2, respectively, if the SSS of subframe index 0 transmits a cell group identifier in two combinations of (SI, S2), the sub The SSS of frame index 5 is swapped to (S2, S1) and transmitted, whereby a 10 ms frame boundary can be distinguished. In this case, the used SSS code uses the generated polynomial of c ⁵ +; c ² ₊ l, and a total of 31 codes can be generated through different cyclic shifts.

In order to improve reception performance, two different PSS-based sequences are defined and scrambled in SSS, but scrambled in different sequences in S1 and S2. Subsequently, SI scrambling may be performed by defining a Sl-based scrambling code. At this time, the sign of the SSS is exchanged in units of 5ms, but the PSS-based scrambling code is not exchanged. The PSS-based scrambling code is defined by six cyclic shifts according to the PSS index in the m-sequence generated from the generation polynomial of cW + l, and the S1-based scrambling code is ^ + ^ + + χ '+ ι We define eight cyclic shift versions according to the index of S1 in the m-sequence generated from the polynomial of.

[173] 2. New Carrier Type (NCT)

In legacy LTE release 8/9/10/1 1 systems, Cell Specific Reference Signal (CRS) and Primary Synchronization Signal (PSS) are transmitted through a downlink component carrier. Reference signals such as Signal, Secondary Synchronization Signal (SSS), PDCCH, PBCH, and control channel are transmitted.

However, in the next wireless access system, some or all of CRS, PSS / SSS, PDCCH, PBCH, etc. are not transmitted due to the improvement of the interference problem and the carrier scalability, or the existing LTE / LTE-A It is possible to introduce a downlink component carrier that is transmitted in a relatively very long period (for example, more than 10ms or several tens of ms to hundreds of ms) compared to the system. In embodiments of the present invention, such a carrier is extended for convenience. This is defined as an extension carrier or a new carrier type (NCT).

The NCT described in the present invention may be one of S cells when the base station supports CA, and when the CoMP is supported, the NCT is a carrier or serving cell provided for cooperative transmission of data from a neighboring base station. Can be. In addition, the NCT may be a sal that is synchronized to a reference sal (eg, Psal) as a small sal.

[177] 2.1 Radio Resource Measurement (RRM) Method in NCT

In case of supporting carrier aggregation (CA) in a wireless access system, PDSCH / PUSCHs may be scheduled through a PDCCH in a scheduling scheme in each carrier (ie, a serving cell). Alternatively, PDSCH / PUSCH of another serving cell may be scheduled through a PDCCH transmitted through one serving cell using a cross carrier scheduling method (see Section 1.2). In the embodiments of the present invention, the term carrier used in CA may be used in the same sense as a serving cell.

In this case, in order to add a serving cell to the CA as a secondary carrier or secondary serving cell to the CA, the terminal must perform a neighbor cell measurement process. In general, a neighbor cell measurement process is performed using a common reference signal (CRS), which may be called a radio resource measurement process.

[180] 3. Method of transmitting a discovery signal

[181] 3.1 Discovery Transmission / Reception Method

The discovery signal is transmitted for the purpose of identifying the sal. In particular, when a serving cell (or small cell) is turned on or off, the discovery signal is used to indicate whether the corresponding cell is on or off. For example, when the serving cell is turned off, the serving cell may support the UE to quickly access by transmitting a discovery signal.

For this purpose, the discovery signal is preferably designed in consideration of the interference between 쎌. For example, the discovery signal may be scrambled for interference randomization. In this case, the UE may distinguish the discovery signal transmitted from each cell only when the discovery information and the scrambling information of the discovery signal are known in advance.

Therefore, in the period in which the discovery signal is transmitted, the terminal communicates with each cell through initialization. The scrambling information and the sequence information can be configured. If the UE does not know the scrambling information and / or sequence information of the discovery signal, the complexity of the UE implementation increases in proportion to the uncertainty of the scrambling information, so that the UE performs one initialization with each cell. It is desirable to. For example, in a subframe in which the discovery signal is transmitted, the UE may acquire configuration information (eg, sequence information and scrambling information) about the discovery signal through initialization with the base station.

Alternatively, when the terminal performs sal detection using the discovery signal for several subframes, the terminal and / or serving cell initializes scrambling information on the discovery signal for each subframe or scrambling only at the beginning of each subframe. It is preferable to carry out.

In embodiments of the present invention, the terminal and / or the base station may initialize the scrambling information for the discovery signal as a function of a cell identifier (Cell ID). In addition, a cyclic prefix length or subframe number may also be considered when composing scrambling information.

Referring to FIG. 12, a base station or a wireless access system of a serving cell may allocate a resource region to which a discovery signal is to be transmitted (S1210).

In operation S1210, the location where the discovery signal is transmitted may be allocated to a fixed location on the system or may be semi-statically or dynamically allocated by the base station. For example, when a discovery signal is transmitted in an NCT cell, the discovery signal may be transmitted at a location where CRS, CSI-RS, PSS / SSS, PDCCH, and / or PBCH of an existing system are transmitted.

When the discovery signal is transmitted in a subframe in which the discovery signal is transmitted from the serving cell or in several subframes, the UE configures the discovery signal through initialization with the base station of the serving cell in the first subframe in which the discovery signal is transmitted. A beam may be received (S1220).

The configuration information about the discovery signal may include scrambling information and sequence information about the discovery signal, and the scrambling information and sequence information may be initialized as a function of a cell identifier.

If the resource region to which the discovery signal is transmitted is semi-statically or dynamically allocated in step S1210, the information about the discovery resource region may be transmitted through system information or PDCCH / EPDCCH or the initialization process of FIG. To terminal Can be sent together.

Thereafter, the base station of the serving cell may transmit the discovery signal through the allocated resource region (S1230).

In another aspect of the present invention, the base station of the serving cell may have information about a discovery signal for one or more neighboring base stations. In this case, in step S1230, the base station may transmit information on discovery signals for neighboring cells to the terminal.

The UE may receive and decode the discovery signal based on the discovery signal configuration information obtained in step S1220. In addition, the terminal may detect the serving cell based on the received discovery signal (S1240).

In FIG. 12, only one serving cell and one terminal are illustrated, but the methods described with reference to FIG. 12 may be equally applied to a network environment in which two or more serving cells and two or more terminals are arranged. [197] 3.2 Discovery Signal Transmission Area

In a small cell environment, a discovery signal may be transmitted through the entire system bandwidth or a portion of the system bandwidth (eg, X RB) in order to effectively implement an on-off operation of the small cell. . In the embodiments of the present invention, for convenience of description, a resource region to which a discovery signal is transmitted is defined as a discovery region. Hereinafter, methods of allocating a discovery area used in operation S1210 will be described.

3.2.1 System Bandwidth and Discovery Area Configuration

FIG. 13 is a diagram illustrating an example of a system band in which a discovery signal is transmitted.

13 (a) shows a case where a system band is composed of an even number of RBs (eg, 12 RBs), and FIG. 13 (b) shows a case where the system band consists of an odd number of RBs (eg, 15 It is a figure which shows RB). In this case, the discovery signal may be transmitted to an area corresponding to the center X RB of the system bandwidth. In FIG. 13, it is assumed that an area in which a discovery signal is transmitted is composed of an even number of RBs (eg, 6 RBs).

13 (b), when the system bandwidth consists of an odd number of RBs, both 5 RBs (ie, RB # 5 to RB # 9) and 5 RBs based on the center frequency Only the number of subcarriers corresponding to 1/2 RB of RB # 4 and RB # 10 corresponding to the end portion corresponds to the transmission region of the discovery signal. For example, if 1 RB consists of 12 subcarriers, then 1/2 RB consists of 6 consecutive subcarriers. Thus, as shown in FIG. 13 (b), the system bandwidth of an odd number of RBs in a small cell is shown. When the discovery signal is transmitted only at the center 6 RB of the discovery signal, the discovery signal is transmitted only to the frequency region corresponding to the center 72 subcarriers.

In this case, the discovery signal is transmitted only in the frequency domain corresponding to 6 subcarriers in RB # 4 and RB # 10 among the RBs corresponding to the discovery region. If a discovery signal can be set to be transmitted in a region where CRS is transmitted at the center x RB (x is an integer greater than or equal to 6), an opposite case occurs when X is odd. That is, discovery is only in the frequency domain corresponding to 1/2 RB of two RBs corresponding to both ends of the center (χ-1) RBs and (x-1) RBs in the system bandwidth composed of even RBs. The signal can be sent.

The discovery region described in FIG. 13 may be configured as the resource region described in operation S1210 of FIG. 12.

[205] 3.2.2 Discovery Area Setup Based on PRB

The discovery region may be defined as a time / frequency position of the PRB. For example, a discovery signal may be transmitted in a resource region such as a time / frequency location of a CSI-RS in an existing legacy system (eg, LTE / LTE-A system). In a legacy system, the CSI-RS may be transmitted in a resource region of various time / frequency units according to a setting position.

In this case, the discovery signal is transmitted according to whether the resource location of the time / frequency to which the CSI-RS is allocated in one PRB corresponds to the first 1/2 RB or the latter 1/2 RB. The PRB can be determined. As shown in FIG. 13B, a case where the system bandwidth is 15 RB and the discovery area is configured by the central 6 RB will be described as an example. If the CSI-RS resource area is allocated to the first 1/2 RB, the discovery area is set to RB # 5 to RB # 10. If the CSI-RS is allocated to the later 1/2 RB, the discovery area is RB. Can be set to # 4 ~ RB # 9.

For another example, assume a case where a CRS resource region of a legacy system is used as a discovery region. That is, since the CRS is not transmitted in the NCT cell or the small cell, the discovery signal may be transmitted in the CRS resource region. CRS is based on the v-shift value The position of the frequency may vary, which is present not only in the first 1/2 RB but also in the later 1/2 RB in the frequency domain within one PRB. At this time, a method of transmitting a discovery signal is as follows.

[209] (1) Method 1: Assigning the resource area of CRS corresponding to RB # (¾ ^ J-[~ RB # (^ j + [-l)) of the portion corresponding to the central X RB as the discovery area In the case of Fig. 13 (b), RB # 4 to RB # 9 are allocated to the discovery area.

(2) Method 2: A method of allocating a resource region of a CRS corresponding to RB # (^ J 一 + 1) to RB # ₍ ^ J +) among the portions corresponding to the central X RBs as a discovery region. In the case of FIG. 13B, RB # 5 to RB # 10 are allocated to the discovery area.

(3) Method 3: The base station in the frequency domain of the portion corresponding to the center X RB

A resource area corresponding to a later 1/2 RB of a PRB to which a CRS is transmitted may be allocated to a later 1/2 RB of [) as a discovery area. In addition, the base station

In the first 1/2 RB of + j), a resource region corresponding to a later 1/2 RB of the PRB to which the CRS is transmitted may be allocated as a discovery region. In the case of FIG. 13B, later 1/2 RBs of RB # 4 to first 1/2 RBs of RB # 10 may be allocated to the discovery region.

(4) Method ⁴ : The base station can allocate a central (X + 1) RB to the discovery area. In the case of FIG. 13B, RB # 4 to RB # 10 may be allocated to the discovery area.

These methods may be equally applicable to the case where one of the transmission areas such as CSI-RS, PSS / SSS, PBCH, etc. is used as the discovery area in addition to the CRS.

3.2.3 How to adjust the discovery area

Hereinafter, the method of adjusting the discovery area described above will be described again from the viewpoint of the base station.

14 is a diagram illustrating one method of allocating and adjusting a discovery area.

The base station or the radio access system may configure and allocate a discovery area in a small cell or NCT cell. In this case, the base station may determine which resource region among the CSI-RS, CRS, PSS / SSS, PDCCH, and / or PBCH resource regions is used as the first discovery region (S1410).

In step S1410, every subframe, a subframe in which a discovery signal is transmitted, or It can be performed periodically in a static or semi-static manner. Alternatively, when the NCT cell or the small cell is disposed, it may be determined to use one or more of the above-described resource regions as the first discovery resource region.

The base station allocates a predetermined resource block (eg, X RB) at the center of the system bandwidth of the first discovery area in every subframe, a subframe in which a discovery signal is transmitted, or subframes periodically set in a static or semi-static manner. Can be allocated to the second discovery area (S1420).

In this case, the base station may adjust the second discovery area in consideration of y RB which is the size of the system bandwidth. For example, the second discovery area of the central X RB allocated in step S1420 may be adjusted within a range of 1 RB using the methods described in FIGS. 13 and 3.2.1 or 3.2.2 (S1430).

The base station may transmit a discovery signal to the terminal through the adjusted second discovery area.

The method described in FIG. 14 may be performed in step S1210 of FIG. 12. That is, the base station of the serving cell or the like may adjust the discovery area using the method described with reference to FIG. 14 when allocating a resource area for transmitting the discovery signal.

As another aspect of the present invention, the terminal may be configured to detect only a discovery signal of a certain region. For example, when the center 6 RB of the system bandwidth is set as an area in which the discovery signal is transmitted, the terminal may be configured to receive the discovery signal by decoding only the center 6RB to detect the discovery signal.

[224] 5. Implementation device

The apparatus described in FIG. 15 is a means in which the methods described in FIGS. 1 to 14 may be implemented.

A UE (User Equipment) can operate as a transmitter in uplink and live-receive in downlink. In addition, the " 7- " station (eNB: e-Node B) can operate as a receiver in uplink and as a transmitter in downlink.

That is, the terminal and the base station may include a transmitter (Transmitter 1540, 1550) and a receiver (Reception Module (1550, 1570), respectively) to control the transmission and reception of information, data and / or messages, information , Antennas 1500 and 1510 for transmitting and receiving data and / or messages. In addition, the terminal and the base station each of the processor (Processor: 1520, 1530) for performing the above-described embodiments of the present invention and the memory (1580, 1590) that can temporarily or continuously store the processing of the processor Each may include.

Embodiments of the present invention can be performed using the components and functions of the above-described terminal and base station apparatus. For example, the processor of the base station may set the transmission position of the control information transmitted from the legacy system as the discovery area to which the discovery signal is to be transmitted. Subsequently, the processor of the base station may inform the terminal of the scrambling information and the sequence information of the discovery signal through initialization with the terminal through the transmitter. In addition, the processor may control the transmitter to transmit the discovery signal to the terminal through the discovery area. The processor of the terminal obtains scrambling information and sequence information of the discovery signal through initialization with the base station, and receives and decodes the discovery signal through the allocated discovery area by controlling the receiver.

A transmitter and a receiver included in a terminal and a base station include a packet modulation demodulation function, a high speed packet channel coding function, an orthogonal frequency division multiple access (OFDMA) packet scheduling, and a time division duplex (TDD). Time Division Duplex) may perform packet scheduling and / or channel multiplexing. In addition, the terminal and the base station of FIG. 15 may further include a low power radio frequency (RF) / intermediate frequency (IF) device.

Meanwhile, in the present invention, the terminal is a personal digital assistant (PDA), a cell phone phone, a personal communication service (PCS) phone, a GSM (Global System for Mobile) phone, a WCDMA (Wideband CDMA). ) Used in phones, mobile broadband system (MBS) 푠, hand-held PCs, notebook PCs, smart phones or multi-mode multi-band (MM-MB) terminals Can be.

Here, a smart phone is a terminal that combines the advantages of a mobile communication terminal and a personal portable terminal, and includes a terminal incorporating a data communication function such as schedule management, fax transmission and reception, etc., which are functions of a personal portable terminal. Can mean. In addition, multimode multiband terminals can be equipped with a multi-modem chip to operate in both portable Internet systems and other mobile communication systems (e.g., code division multiple access (CDMA) 2000 systems, wideband CDMA (WCDMA) systems, etc.). Speak the terminal. Embodiments of the present invention may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

In the case of implementation by hardware, the method according to embodiments of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), and PLDs (PLDs). programmable logic devices (FPGAs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the functions or operations described above. For example, software code may be stored in the memory units 1580 and 1590 and driven by the processors 1520 and 1530. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

The present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. The foregoing detailed description, therefore, is not to be taken in a limiting sense in all respects and should be considered as illustrative, the scope of the invention being determined by reasonable interpretation of the appended claims, and within the equivalent scope of the invention. All changes of are included in the scope of the present invention. In addition, the claims may be incorporated into claims that do not have an explicit citation relationship in the claims, or may be incorporated into new claims by amendment after filing.

Industrial Applicability

Embodiments of the present invention can be applied to various wireless access systems. Examples of various radio access systems include 3rd Generation Partnership Project (3GPP), 3GPP2 and / or IEEE 802.xx (Institute of Electrical and Electronic Engineers 802) systems. Embodiments of the present invention can be applied not only to the various radio access systems, but also to all technical fields to which the various radio access systems are applied.

Claims

【Scope of Claim】

[Claim 1]

A method for a base station to transmit a discovery signal in a wireless access system, comprising: determining a resource area where one or more of a reference signal, a synchronization signal, and a control channel are transmitted in a subframe as a first discovery area where the discovery signal is to be transmitted;

allocating a predetermined resource block at the center of a system bandwidth supported by the wireless access system among the first discovery areas to a second discovery area; adjusting the second discovery area based on the size of the system bandwidth and the size of the predetermined resource block; and

A discovery signal transmission method comprising transmitting the discovery signal through the adjusted second discovery area.

【Claim 2】

According to clause 1,

The reference signal may be a cell reference signal (CRS) or a channel quality indicator reference signal (CSI-

RS),

The synchronization signal is a primary synchronization signal (PSS) and/or a secondary synchronization signal (SSS), and the control channel is a physical downlink control channel (PDCCH).

【Claim 3】

In clause 1,

A serving cell where the discovery signal is transmitted does not transmit one or more of the reference signal, the synchronization signal, and the control channel.

【Claim 4】

According to clause 1,

A discovery signal transmission method further comprising performing an initialization process to exchange scrambling information and sequence information for the discovery signal with a terminal.

【Claim 5】

According to clause 1, A discovery signal transmission method further comprising transmitting resource region information indicating the adjusted second discovery region to the terminal.

【Claim 6】

The base station that transmits the discovery signal in the wireless access system is,

transmitter;

receiving set; and

A processor configured to control the transmitter and the receiver to transmit the discovery signal,

The processor:

determining a resource area in which one or more of a reference signal, a synchronization signal, and a control channel are transmitted in a subframe as a first discovery area in which the discovery signal is to be transmitted;

allocating a predetermined resource block at the center of a system bandwidth supported by the wireless access system among the first discovery areas to a second discovery area;

adjusting the second discovery area based on the size of the system bandwidth and the size of the predetermined resource block;

A base station configured to control the transmitter to transmit the discovery signal through the adjusted second discovery area.

【Claim 7】

In clause 6,

The reference signal is a cell reference signal (CRS) or a channel quality indication reference signal (CSI-RS),

【Claim 8】

According to clause 6,

A serving cell in which the discovery signal is transmitted is a base station in which one or more of the reference signal, the synchronization signal, and the control channel are not transmitted.

【Claim 9】

According to clause 6, The base station further comprising performing an initialization process to exchange scrambling information and sequence information for the discovery signal with the terminal.

【Claim 10】

According to clause 6,

The processor is configured to control the transmitter to transmit resource area information indicating the adjusted second discovery area to the terminal.