WO2017043801A1 - Downlink signal reception method and user equipment, and downlink signal transmission method and base station - Google Patents

Abstract

Provided are a method and a device for transmitting and/or receiving a signal in a narrowband Internet of things (NB-IoT). A downlink data and a reference signal for the NB-IoT may be transmitted on one resource block in a subframe. The reference signal may be transmitted in a reference signal pattern, in which the reference signal is defined to have an identical interval between reference signals in remaining subcarrier except for a subcarrier used for a DC tone among subcarriers of the one resource block in the subframe.

Description

Downlink signal reception method and user equipment, Downlink signal transmission method and base station

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for downlink signal transmission or reception.

Various devices and technologies, such as smartphone-to-machine communication (M2M) and smart phones and tablet PCs, which require high data transmission rates, are emerging and spread. As a result, the amount of data required to be processed in a cellular network is growing very quickly. In order to meet this rapidly increasing data processing demand, carrier aggregation technology, cognitive radio technology, etc. to efficiently use more frequency bands, and increase the data capacity transmitted within a limited frequency Multi-antenna technology, multi-base station cooperation technology, and the like are developing.

A typical wireless communication system performs data transmission / reception over one downlink (DL) band and one uplink (UL) band corresponding thereto (frequency division duplex (FDD) mode). Or a predetermined radio frame divided into an uplink time unit and a downlink time unit in a time domain, and perform data transmission / reception through uplink / downlink time units (time division duplex). (for time division duplex, TDD) mode). A base station (BS) and a user equipment (UE) transmit and receive data and / or control information scheduled in a predetermined time unit, for example, a subframe (SF). Data is transmitted and received through the data area set in the uplink / downlink subframe, and control information is transmitted and received through the control area set in the uplink / downlink subframe. To this end, various physical channels carrying radio signals are configured in uplink / downlink subframes. In contrast, the carrier aggregation technique can collect a plurality of uplink / downlink frequency blocks to use a wider frequency band and use a larger uplink / downlink bandwidth, so that a greater amount of signals can be processed simultaneously than when a single carrier is used. .

Meanwhile, the communication environment is evolving in a direction in which the density of nodes that the UE can access in the vicinity is increased. A node is a fixed point capable of transmitting / receiving a radio signal with a UE having one or more antennas. A communication system having a high density of nodes can provide higher performance communication services to the UE by cooperation between nodes.

With the introduction of a new wireless communication technology, not only the number of UEs that a base station needs to provide service in a predetermined resource area increases, but also the amount of data and control information transmitted / received by UEs that provide service It is increasing. Since the amount of radio resources available for the base station to communicate with the UE (s) is finite, the base station uses finite radio resources to transmit uplink / downlink data and / or uplink / downlink control information to / from the UE (s). There is a need for a new scheme for efficient reception / transmission.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are apparent to those skilled in the art from the following detailed description. Can be understood.

Provided are a method and apparatus for transmitting and / or receiving a signal in a narrowband internet of things (NB-IoT). Downlink data and the NB-IoT reference signal may be transmitted on one resource block in a subframe. The reference signal may be transmitted in a reference signal pattern defined so that the interval of the reference signal is the same in the remaining subcarriers other than the subcarriers used for the DC tone among the subcarriers in the one resource block in the subframe.

When the user equipment receives a downlink signal through narrowband internet of things (NB-IoT),

Receiving downlink data and the reference signal for the NB-IoT on one resource block in a subframe; And

Demodulating the downlink data based on the reference signal;

The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

The reference signal is received in the reference signal pattern of the following table on the one resource block in the subframe:

TABLE 1

Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

Downlink signal receiving method.

In transmitting a downlink signal to a narrowband internet of things (NB-IoT) by the base station,

Transmitting the downlink data and the NB-IoT reference signal for supporting the downlink data on one resource block in a subframe,

The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

The reference signal is transmitted in the reference signal pattern of the following table on the one resource block in the subframe:

TABLE 1

Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

Downlink signal transmission method.

When the user equipment receives a downlink signal through narrowband internet of things (NB-IoT),

A radio frequency (RF) unit, and

A processor configured to control the RF unit, the processor comprising:

Controlling the RF unit to receive downlink data and the reference signal for the NB-IoT on one resource block in a subframe; And

And demodulate the downlink data based on the reference signal,

The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

The reference signal is received in the reference signal pattern of the following table on the one resource block in the subframe:

TABLE 1

Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

User device.

In transmitting a downlink signal to a narrowband internet of things (NB-IoT) by the base station,

A radio frequency (RF) unit, and

A processor configured to control the RF unit, the processor comprising:

And control the RF unit to transmit downlink data and the NB-IoT reference signal for supporting the downlink data on one resource block in a subframe,

The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

The reference signal is transmitted in the reference signal pattern of the following table on the one resource block in the subframe:

TABLE 1

Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

Base station.

In each aspect of the present invention, the reference signal pattern of Table 1 is a reference having a frequency shift value corresponding to an identifier of a cell in which one resource block is located among a plurality of reference signal patterns having different frequency shift values from each other. Signal pattern,

Downlink signal receiving method.

In each aspect of the present invention, the reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and The reference signal R2 is received in the pattern of the following table:

TABLE 2

,

Downlink signal receiving method.

In each aspect of the present invention, the reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and The reference signal R2 is received in the pattern of the following table:

TABLE 3

,

Downlink signal receiving method.

In each aspect of the present invention, the DC subcarrier is a subcarrier of k = 5 or k = 6 among the twelve subcarriers k∈ {0,1, ..., 11} in the one resource block,

Downlink signal receiving method.

The problem solving methods are only a part of embodiments of the present invention, and various embodiments reflecting the technical features of the present invention are based on the detailed description of the present invention described below by those skilled in the art. Can be derived and understood.

According to an embodiment of the present invention, the wireless communication signal can be efficiently transmitted / received. Accordingly, the overall throughput of the wireless communication system can be high.

According to one embodiment of the present invention, a low / low cost user equipment can communicate with a base station while maintaining compatibility with an existing system.

According to an embodiment of the present invention, a user device may be implemented at low / low cost.

According to one embodiment of the present invention, coverage may be enhanced.

According to an embodiment of the present invention, the user equipment and the base station can communicate in a narrow band.

The effects according to the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the detailed description of the present invention. There will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included as part of the detailed description in order to provide a thorough understanding of the present invention, provide an embodiment of the present invention and together with the description, illustrate the technical idea of the present invention.

1 illustrates an example of a radio frame structure used in a wireless communication system.

2 illustrates an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system.

3 illustrates a radio frame structure for transmission of a synchronization signal (SS).

4 illustrates a downlink (DL) subframe structure used in a wireless communication system.

5 shows an example of an uplink (UL) subframe structure used in a wireless communication system.

FIG. 6 illustrates a cell specific reference signal (CRS) and a user specific reference signal (UE-RS).

7 shows an example of a signal band for an MTC.

8 and 9 illustrate RS structures according to an embodiment of the present invention.

10 through 12 illustrate RS structures according to another embodiment of the present invention.

13 and 14 illustrate RS structures according to another embodiment of the present invention.

15 to 17 illustrate RS structures according to another embodiment of the present invention.

FIG. 18 is a diagram for describing a concept of space frequency block coding (SFBC).

19 illustrates methods of applying precoding to a new reference signal according to the present invention.

20 illustrates a cell-specific RS pattern of NB-IoT for two antenna ports.

22 to 24 illustrate the signal transmission / reception example on the IoT cell according to another embodiment of the present invention.

25 is a block diagram showing the components of the transmitter 10 and the receiver 20 for carrying out the present invention.

Hereinafter, exemplary 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 intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

The techniques, devices, and systems described below can be applied to various wireless multiple access systems. 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 (MCD) systems and multi-carrier frequency division multiple access (MC-FDMA) systems. CDMA may be implemented in a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented in radio technologies such as Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE) (i.e., GERAN), and the like. OFDMA may be implemented in wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (WiFi), IEEE 802.16 (WiMAX), IEEE802-20, evolved-UTRA (E-UTRA), and the like. UTRA is part of Universal Mobile Telecommunication System (UMTS), and 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of E-UMTS using E-UTRA. 3GPP LTE adopts OFDMA in downlink (DL) and SC-FDMA in uplink (UL). LTE-advanced (LTE-A) is an evolution of 3GPP LTE. For convenience of explanation, hereinafter, it will be described on the assumption that the present invention is applied to 3GPP LTE / LTE-A. However, the technical features of the present invention are not limited thereto. For example, even if the following detailed description is described based on the mobile communication system corresponding to the 3GPP LTE / LTE-A system, any other mobile communication except for the matters specific to 3GPP LTE / LTE-A is described. Applicable to the system as well.

For example, in the present invention, as in the 3GPP LTE / LTE-A system, an eNB allocates a downlink / uplink time / frequency resource to a UE, and the UE receives a downlink signal according to the allocation of the eNB and transmits an uplink signal. In addition to non-contention based communication, it can be applied to contention-based communication such as WiFi. In the non-competition based communication scheme, an access point (AP) or a control node controlling the access point allocates resources for communication between a UE and the AP, whereas a competition-based communication technique connects to an AP. Communication resources are occupied through contention among multiple UEs that are willing to. A brief description of the contention-based communication technique is a type of contention-based communication technique called carrier sense multiple access (CSMA), which is a shared transmission medium in which a node or a communication device is a frequency band. probabilistic media access control (MAC) protocol that ensures that there is no other traffic on the same shared transmission medium before transmitting traffic on a shared transmission medium (also called a shared channel). protocol). In CSMA, the transmitting device determines if another transmission is in progress before attempting to send traffic to the receiving device. In other words, the transmitting device attempts to detect the presence of a carrier from another transmitting device before attempting to transmit. When the carrier is detected, the transmission device waits for transmission to be completed by another transmission device in progress before initiating its transmission. After all, CSMA is a communication technique based on the principle of "sense before transmit" or "listen before talk". Carrier Sense Multiple Access with Collision Detection (CSMA / CD) and / or Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) are used as a technique for avoiding collision between transmission devices in a contention-based communication system using CSMA. . CSMA / CD is a collision detection technique in a wired LAN environment. First, a PC or a server that wants to communicate in an Ethernet environment checks if a communication occurs on the network, and then another device If you are sending on the network, wait and send data. That is, when two or more users (eg, PCs, UEs, etc.) simultaneously carry data, collisions occur between the simultaneous transmissions. CSMA / CD monitors the collisions to allow flexible data transmission. Technique. A transmission device using CSMA / CD detects data transmission by another transmission device and adjusts its data transmission using a specific rule. CSMA / CA is a media access control protocol specified in the IEEE 802.11 standard. WLAN systems according to the IEEE 802.11 standard use a CA, that is, a collision avoidance method, without using the CSMA / CD used in the IEEE 802.3 standard. The transmitting devices always detect the carrier of the network, and when the network is empty, wait for a certain amount of time according to their location on the list and send the data. Various methods are used to prioritize and reconfigure transmission devices within a list. In a system according to some versions of the IEEE 802.11 standard, a collision may occur, in which a collision detection procedure is performed. Transmission devices using CSMA / CA use specific rules to avoid collisions between data transmissions by other transmission devices and their data transmissions.

In the present invention, the UE may be fixed or mobile, and various devices which communicate with a base station (BS) to transmit and receive user data and / or various control information belong to the same. UE (Terminal Equipment), MS (Mobile Station), MT (Mobile Terminal), UT (User Terminal), SS (Subscribe Station), wireless device, PDA (Personal Digital Assistant), wireless modem ), A handheld device, or the like. In addition, in the present invention, a BS generally refers to a fixed station communicating with the UE and / or another BS, and communicates with the UE and another BS to exchange various data and control information. The BS may be referred to in other terms such as ABS (Advanced Base Station), Node-B (NB), evolved-NodeB (NB), Base Transceiver System (BTS), Access Point, and Processing Server (PS). In the following description of the present invention, BS is collectively referred to as eNB.

In the present invention, a node refers to a fixed point capable of transmitting / receiving a radio signal by communicating with a UE. Various forms of eNBs may be used as nodes regardless of their name. For example, a node may be a BS, an NB, an eNB, a pico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, or the like. Also, the node may not be an eNB. For example, it may be a radio remote head (RRH), a radio remote unit (RRU). RRH, RRU, etc. generally have a power level lower than the power level of the eNB. Since the RRH or RRU or less, RRH / RRU) is generally connected to the eNB by a dedicated line such as an optical cable, the RRH / RRU and the eNB are generally compared to cooperative communication by eNBs connected by a wireless line. By cooperative communication can be performed smoothly. At least one antenna is installed at one node. The antenna may mean a physical antenna or may mean an antenna port, a virtual antenna, or an antenna group. Nodes are also called points.

In the present invention, a cell refers to a certain geographic area in which one or more nodes provide communication services. Therefore, in the present invention, communication with a specific cell may mean communication with an eNB or a node that provides a communication service to the specific cell. In addition, the downlink / uplink signal of a specific cell means a downlink / uplink signal from / to an eNB or a node that provides a communication service to the specific cell. The cell providing uplink / downlink communication service to the UE is particularly called a serving cell. In addition, the channel state / quality of a specific cell means a channel state / quality of a channel or communication link formed between an eNB or a node providing a communication service to the specific cell and a UE. In an LTE / LTE-A based system, the UE transmits a downlink channel state from a specific node to a CRS in which antenna port (s) of the specific node are transmitted on a Cell-specific Reference Signal (CRS) resource allocated to the specific node. It may be measured using the CSI-RS (s) transmitted on the (s) and / or Channel State Information Reference Signal (CSI-RS) resources. For detailed CSI-RS configuration, reference may be made to 3GPP TS 36.211 and 3GPP TS 36.331 documents.

Meanwhile, the 3GPP LTE / LTE-A system uses the concept of a cell to manage radio resources. Cells associated with radio resources are distinguished from cells in a geographic area.

A "cell" in a geographic area may be understood as coverage in which a node can provide services using a carrier, and a "cell" of radio resources is a bandwidth (frequency) that is a frequency range configured by the carrier. bandwidth, BW). Downlink coverage, which is a range in which a node can transmit valid signals, and uplink coverage, which is a range in which a valid signal can be received from a UE, depends on a carrier carrying the signal, so that the coverage of the node is determined by the radio resources used by the node. It is also associated with the coverage of the "cell". Thus, the term "cell" can sometimes be used to mean coverage of a service by a node, sometimes a radio resource, and sometimes a range within which a signal using the radio resource can reach a valid strength. The "cell" of radio resources is described in more detail later.

The 3GPP LTE / LTE-A standard corresponds to downlink physical channels corresponding to resource elements carrying information originating from an upper layer and resource elements used by the physical layer but not carrying information originating from an upper layer. Downlink physical signals are defined. For example, a physical downlink shared channel (PDSCH), a physical broadcast channel (PBCH), a physical multicast channel (PMCH), a physical control format indicator channel (physical control) format indicator channel (PCFICH), physical downlink control channel (PDCCH) and physical hybrid ARQ indicator channel (PHICH) are defined as downlink physical channels, reference signal and synchronization signal Is defined as downlink physical signals. A reference signal (RS), also referred to as a pilot, refers to a signal of a predetermined special waveform known to the eNB and the UE. For example, a cell specific RS, UE- UE-specific RS, positioning RS (PRS), and channel state information RS (CSI-RS) are defined as downlink reference signals. The 3GPP LTE / LTE-A standard corresponds to uplink physical channels corresponding to resource elements carrying information originating from a higher layer and resource elements used by the physical layer but not carrying information originating from an upper layer. Uplink physical signals are defined. For example, a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH) are the uplink physical channels. A demodulation reference signal (DMRS) for uplink control / data signals and a sounding reference signal (SRS) used for uplink channel measurement are defined.

In the present invention, Physical Downlink Control CHannel (PDCCH) / Physical Control Format Indicator CHannel (PCFICH) / PHICH (Physical Hybrid automatic retransmit request Indicator CHannel) / PDSCH (Physical Downlink Shared CHannel) are respectively DCI (Downlink Control Information) / CFI ( Means a set of time-frequency resources or a set of resource elements that carry downlink format ACK / ACK / NACK (ACKnowlegement / Negative ACK) / downlink data, and also a Physical Uplink Control CHannel (PUCCH) / Physical (PUSCH) Uplink Shared CHannel / PACH (Physical Random Access CHannel) means a set of time-frequency resources or a set of resource elements that carry uplink control information (UCI) / uplink data / random access signals, respectively. PDCCH / PCFICH / PHICH / PDSCH / PUCCH / PUSCH / PRACH RE or the time-frequency resource or resource element (RE) assigned to or belonging to PDCCH / PCFICH / PHICH / PDSCH / PUCCH / PUSCH / PRACH, respectively. The PDCCH / PCFICH / PHICH / PDSCH / PUCCH / PUSCH / PRACH resource is referred to below .. In the following description, the user equipment transmits the PUCCH / PUSCH / PRACH, respectively. It is used in the same sense as transmitting a data / random access signal, and the expression that the eNB transmits PDCCH / PCFICH / PHICH / PDSCH is used for downlink data / control information on or through PDCCH / PCFICH / PHICH / PDSCH, respectively. It is used in the same sense as sending it.

In the following, CRS / DMRS / CSI-RS / SRS / UE-RS is assigned or configured OFDM symbol / subcarrier / RE to CRS / DMRS / CSI-RS / SRS / UE-RS symbol / carrier / subcarrier / RE It is called. For example, an OFDM symbol assigned or configured with a tracking RS (TRS) is called a TRS symbol, a subcarrier assigned or configured with a TRS is called a TRS subcarrier, and an RE assigned or configured with a TRS is called a TRS RE. . In addition, a subframe configured for TRS transmission is called a TRS subframe. Also, a subframe in which a broadcast signal is transmitted is called a broadcast subframe or a PBCH subframe, and a subframe in which a sync signal (for example, PSS and / or SSS) is transmitted is a sync signal subframe or a PSS / SSS subframe. It is called. OFDM symbols / subcarriers / RE to which PSS / SSS is assigned or configured are referred to as PSS / SSS symbols / subcarriers / RE, respectively.

In the present invention, the CRS port, the UE-RS port, the CSI-RS port, and the TRS port are an antenna port configured to transmit CRS, an antenna port configured to transmit UE-RS, and an antenna configured to transmit CSI-RS, respectively. Port, an antenna port configured to transmit TRS. Antenna ports configured to transmit CRSs may be distinguished from each other by the location of REs occupied by the CRS according to the CRS ports, and antenna ports configured to transmit UE-RSs may be UE-RS according to the UE-RS ports. The RSs may be distinguished from each other by locations of REs occupied, and antenna ports configured to transmit CSI-RSs may be distinguished from each other by locations of REs occupied by the CSI-RSs according to the CSI-RS ports. Therefore, the term CRS / UE-RS / CSI-RS / TRS port may be used as a term for a pattern of REs occupied by CRS / UE-RS / CSI-RS / TRS in a certain resource region.

1 illustrates an example of a radio frame structure used in a wireless communication system.

In particular, Figure 1 (a) shows a frame structure for frequency division duplex (FDD) used in the 3GPP LTE / LTE-A system, Figure 1 (b) is used in the 3GPP LTE / LTE-A system The frame structure for time division duplex (TDD) is shown.

Referring to FIG. 1, a radio frame used in a 3GPP LTE / LTE-A system has a length of 10 ms (307200 T _s ) and consists of 10 equally sized subframes (subframes). Numbers may be assigned to 10 subframes in one radio frame. Here, T _s represents the sampling time and is expressed as T _s = 1 / (2048 * 15 kHz). Each subframe has a length of 1 ms and consists of two slots. 20 slots in one radio frame may be sequentially numbered from 0 to 19. Each slot is 0.5ms long. The time for transmitting one subframe is defined as a transmission time interval (TTI). The time resource may be classified by a radio frame number (also called a radio frame index), a subframe number (also called a subframe number), a slot number (or slot index), and the like.

The radio frame may be configured differently according to the duplex mode. For example, in the FDD mode, since downlink transmission and uplink transmission are divided by frequency, a radio frame includes only one of a downlink subframe or an uplink subframe for a specific frequency band. In the TDD mode, since downlink transmission and uplink transmission are separated by time, a radio frame includes both a downlink subframe and an uplink subframe for a specific frequency band.

Table 1 illustrates a DL-UL configuration of subframes in a radio frame in the TDD mode.

DL-UL configuration

Downlink-to-Uplink Switch-point periodicity

Subframe number

0

One

2

3

4

5

6

7

8

9

0

5 ms

D

S

U

U

U

D

S

U

U

U

One

5 ms

D

S

U

U

D

D

S

U

U

D

2

5 ms

D

S

U

D

D

D

S

U

D

D

3

10 ms

D

S

U

U

U

D

D

D

D

D

4

10 ms

D

S

U

U

D

D

D

D

D

D

5

10 ms

D

S

U

D

D

D

D

D

D

D

6

5 ms

D

S

U

U

U

D

S

U

U

D

In Table 1, D represents a downlink subframe, U represents an uplink subframe, and S represents a special (special) subframe. The special subframe includes three fields of Downlink Pilot TimeSlot (DwPTS), Guard Period (GP), and Uplink Pilot TimeSlot (UpPTS). DwPTS is a time interval reserved for downlink transmission, and UpPTS is a time interval reserved for uplink transmission. Table 2 illustrates the configuration of a special subframe.

Special subframe configuration	Normal cyclic prefix in downlink			Extended cyclic prefix in downlink
	DwPTS	UpPTS		DwPTS	UpPTS
		Normal cyclic prefix in uplink	Extended cyclic prefix in uplink		Normal cyclic prefix in uplink	Extended cyclic prefix in uplink
0	6592T s	2192T s	2560T s	7680T s	2192T s	2560T s
One	19760T s			20480T s
2	21952T s			23040T s
3	24144T s			25600T s
4	26336T s			7680T s	4384T s	5120T s
5	6592T s	4384T s	5120T s	20480T s
6	19760T s			23040T s
7	21952T s			12800 · T s
8	24144T s			-	-	-
9	13168 · T s			-	-	-

2 illustrates an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system.

Referring to FIG. 2, a slot includes a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in a time domain and a plurality of resource blocks (RBs) in a frequency domain. An OFDM symbol may mean a symbol period. Referring to FIG. 2, a signal transmitted in each slot may be represented by a resource grid including N ^{DL / UL} _RB × N ^RB _sc subcarriers and N ^{DL / UL} _symb OFDM symbols. . Here, N ^DL _RB represents the number of resource blocks (RBs) in the downlink slot, and N ^UL _RB represents the number of _RBs in the UL slot. N ^DL _RB and N ^UL _RB depend on DL transmission bandwidth and UL transmission bandwidth, respectively. N ^DL _symb represents the number of OFDM symbols in the downlink slot, and N ^UL _symb represents the number of OFDM symbols in the UL slot. N ^RB _sc represents the number of subcarriers constituting one RB.

The OFDM symbol may be called an OFDM symbol, a Single Carrier Frequency Division Multiplexing (SC-FDM) symbol, or the like according to a multiple access scheme. The number of OFDM symbols included in one slot may vary depending on the channel bandwidth and the length of the cyclic prefix (CP). For example, in case of a normal CP, one slot includes 7 OFDM symbols, whereas in case of an extended CP, one slot includes 6 OFDM symbols. Although FIG. 2 illustrates a subframe in which one slot is composed of seven OFDM symbols for convenience of description, embodiments of the present invention can be applied to subframes having different numbers of OFDM symbols in the same manner. Referring to FIG. 2, each OFDM symbol includes N ^{DL / UL} _RB × N ^RB _sc subcarriers in the frequency domain. The type of subcarriers may be divided into data subcarriers for data transmission, reference signal subcarriers for transmission of reference signals, null subcarriers for guard band or direct current (DC) components. . The DC component is mapped to a carrier frequency f ₀ during an OFDM signal generation process or a frequency upconversion process. The carrier frequency is also called a center frequency ( f _c ).

One RB is defined as N ^{DL / UL} _symb contiguous OFDM symbols (e.g. 7) in the time domain and N ^RB _sc (e.g. 12) contiguous in the frequency domain It is defined by subcarriers. For reference, a resource composed of one OFDM symbol and one subcarrier is called a resource element (RE) or tone. Therefore, one RB is composed of N ^{DL / UL} _symb × N ^RB _sc resource elements. Each resource element in the resource grid may be uniquely defined by an index pair ( k , 1 ) in one slot. k is an index given from 0 to N ^{DL / UL} _RB × N ^RB _sc -1 in the frequency domain, and l is an index given from 0 to N ^{DL / UL} _symb -1 in the time domain.

On the other hand, one RB is mapped to one physical resource block (PRB) and one virtual resource block (VRB), respectively. The PRB is defined as N ^{DL / UL} _symb (eg 7) consecutive OFDM symbols or SC-FDM symbols in the time domain, and N ^RB _sc (eg 12) consecutive in the frequency domain Defined by subcarriers. Therefore, one PRB is composed of N ^{DL / UL} _symb × N ^RB _sc resource elements. Two ^RBs , each occupying N ^RB _sc consecutive subcarriers in one subframe and one in each of two slots of the subframe, are referred to as a PRB pair. Two RBs constituting a PRB pair have the same PRB number (or also referred to as a PRB index).

3 illustrates a radio frame structure for transmission of a synchronization signal (SS). In particular, FIG. 3 illustrates a radio frame structure for transmission of a synchronization signal and a PBCH in a frequency division duplex (FDD), and FIG. 3 (a) is configured as a normal cyclic prefix (CP). FIG. 3B illustrates a transmission position of an SS and a PBCH in a radio frame, and FIG. 3B illustrates a transmission position of an SS and a PBCH in a radio frame configured as an extended CP.

When the UE is powered on or wants to access a new cell, the UE acquires time and frequency synchronization with the cell and detects a ^cell's physical layer cell identity N ^cell _ID . Perform an initial cell search procedure. To this end, the UE receives a synchronization signal from the eNB, for example, a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), synchronizes with the eNB, and synchronizes with the eNB. , ID) and the like can be obtained.

Referring to FIG. 3, the SS will be described in more detail as follows. SS is divided into PSS and SSS. PSS is used to obtain time domain synchronization and / or frequency domain synchronization such as OFDM symbol synchronization, slot synchronization, etc., and SSS is used for frame synchronization, cell group ID and / or cell CP configuration (i.e., general CP or extension). It is used to get usage information of CP). Referring to FIG. 3, PSS and SSS are transmitted in two OFDM symbols of every radio frame, respectively. Specifically, in order to facilitate inter-RAT measurement, the SS may be configured in the first slot of subframe 0 and the first slot of subframe 5 in consideration of 4.6 ms, which is a Global System for Mobile Communication (GSM) frame length. Each is transmitted. In particular, the PSS is transmitted in the last OFDM symbol of the first slot of subframe 0 and the last OFDM symbol of the first slot of subframe 5, respectively, and the SSS is the second to second OFDM symbols and subframe of the first slot of subframe 0, respectively. Are transmitted in the second to second OFDM symbols, respectively, at the end of the first slot of five. The boundary of the radio frame can be detected through the SSS. The PSS is transmitted in the last OFDM symbol of the slot and the SSS is transmitted in the OFDM symbol immediately before the PSS. The transmission diversity scheme of the SS uses only a single antenna port and is not defined in the standard.

Since the PSS is transmitted every 5 ms, the UE detects the PSS to know that the corresponding subframe is one of the subframe 0 and the subframe 5, but the subframe may not know what the subframe 0 and the subframe 5 specifically. . Therefore, the UE does not recognize the boundary of the radio frame only by the PSS. That is, frame synchronization cannot be obtained only by PSS. The UE detects the boundary of the radio frame by detecting the SSS transmitted twice in one radio frame but transmitted as different sequences.

The UE that performs a cell discovery process using PSS / SSS and determines a time and frequency parameter required to perform demodulation of DL signals and transmission of UL signals at an accurate time point is further determined from the eNB. In order to communicate with the eNB, system information required for system configuration of the system must be obtained.

System information is configured by a Master Information Block (MIB) and System Information Blocks (SIBs). Each system information block includes a collection of functionally related parameters, and includes a master information block (MIB), a system information block type 1 (SIB1), and a system information block type according to the included parameters. 2 (System Information Block Type 2, SIB2), SIB3 ~ SIB17 can be classified.

The MIB contains the most frequently transmitted parameters that are necessary for the UE to have initial access to the eNB's network. The UE may receive the MIB via a broadcast channel (eg, PBCH). The MIB includes a downlink system bandwidth (dl-Bandwidth, DL BW), a PHICH configuration, and a system frame number (SFN). Therefore, the UE can know the information on the DL BW, SFN, PHICH configuration explicitly by receiving the PBCH. On the other hand, the information that the UE implicitly (implicit) through the reception of the PBCH includes the number of transmit antenna ports of the eNB. Information about the number of transmit antennas of the eNB is implicitly signaled by masking (eg, XOR operation) a sequence corresponding to the number of transmit antennas to a 16-bit cyclic redundancy check (CRC) used for error detection of the PBCH.

SIB1 includes not only information on time domain scheduling of other SIBs, but also parameters necessary for determining whether a specific cell is a cell suitable for cell selection. SIB1 is received by the UE through broadcast signaling or dedicated signaling.

The DL carrier frequency and the corresponding system bandwidth can be obtained by the MIB carried by the PBCH. The UL carrier frequency and corresponding system bandwidth can be obtained through system information that is a DL signal. If the UE that receives the MIB does not have valid system information stored for the cell, the UE receives the value of the DL bandwidth (BW) in the MIB until the system information block type 2 (SystemInformationBlockType2, SIB2) is received. Applies to). For example, the UE may acquire a system information block type 2 (SystemInformationBlockType2, SIB2) to determine the entire UL system band that can be used for UL transmission through UL-carrier frequency and UL-bandwidth information in the SIB2. .

In the frequency domain, PSS / SSS and PBCH are transmitted only within a total of six RBs, that is, a total of 72 subcarriers, three on the left and right around a DC subcarrier within a corresponding OFDM symbol, regardless of the actual system bandwidth. Therefore, the UE is configured to detect or decode the SS and the PBCH regardless of the downlink transmission bandwidth configured for the UE.

After the initial cell discovery, the UE may perform a random access procedure to complete the access to the eNB. To this end, the UE may transmit a preamble through a physical random access channel (PRACH) and receive a response message for the preamble through a PDCCH and a PDSCH. In case of contention based random access, additional PRACH transmission and contention resolution procedure such as PDCCH and PDSCH corresponding to the PDCCH may be performed.

After performing the above-described procedure, the UE may perform PDCCH / PDSCH reception and PUSCH / PUCCH transmission as a general uplink / downlink signal transmission procedure.

4 illustrates a downlink (DL) subframe structure used in a wireless communication system.

Referring to FIG. 4, the DL subframe is divided into a control region and a data region in the time domain. Referring to FIG. 4, up to three (or four) OFDM symbols located at the front of the first slot of a subframe correspond to a control region to which a control channel is allocated. Hereinafter, a resource region available for PDCCH transmission in a DL subframe is called a PDCCH region. The remaining OFDM symbols other than the OFDM symbol (s) used as the control region correspond to a data region to which a Physical Downlink Shared CHannel (PDSCH) is allocated. Hereinafter, a resource region available for PDSCH transmission in a DL subframe is called a PDSCH region.

Examples of DL control channels used in 3GPP LTE include a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical hybrid ARQ indicator channel (PHICH), and the like.

The PCFICH is transmitted in the first OFDM symbol of a subframe and carries information about the number of OFDM symbols used for transmission of a control channel within the subframe. The PCFICH informs the UE of the number of OFDM symbols used in the corresponding subframe every subframe. PCFICH is located in the first OFDM symbol. The PCFICH is composed of four resource element groups (REGs), and each REG is distributed in the control region based on the cell ID. One REG consists of four REs.

The set of OFDM symbols available for PDCCH in a subframe is given by the following table.

Subframe	Number of OFDM symbols for PDCCH when N DL RB > 10	Number of OFDM symbols for PDCCH when N DL RB ≤10
Subframe 1 and 6 for frame structure type 2	1, 2	2
MBSFN subframes on a carrier supporting PDSCH, configured with 1 or 2 cell- specfic antenna ports	1, 2	2
MBSFN subframes on a carrier supporting PDSCH, configured with 4 cell-specific antenna ports	2	2
Subframes on a carrier not supporting PDSCH	0	0
Non-MBSFN subframes (except subframe 6 for frame structure type 2) configured with positioning reference signals	1, 2, 3	2, 3
All other cases	1, 2, 3	2, 3, 4

A subset of downlink subframes in a radio frame on a carrier that supports PDSCH transmission may be set to MBSFN subframe (s) by a higher layer. Each MBSFN subframe is divided into a non-MBSFN region and an MBSFN region, where the non-MBSFN region spans one or two OFDM symbols, where the length of the non-MBSFN region is given by Table 3. Transmission in the non-MBSFN region of the MBSFN subframe uses the same CP as the cyclic prefix (CP) used for subframe zero. The MBSFN region in the MBSFN subframe is defined as OFDM symbols not used in the non-MBSFN region.

The PCFICH carries a control format indicator (CFI) and the CFI indicates one of 1 to 3 values. For downlink system bandwidth N ^DL _RB > 10, the number of OFDM symbols 1, 2 or 3, which is the span of DCI carried by the PDCCH, is given by the CFI, and the PDCCH for downlink system bandwidth N ^DL _RB ≤ 10 The number 2, 3 or 4 of OFDM symbols that are spans of the DCI carried by is given by CFI + 1.

The PHICH carries a Hybrid Automatic Repeat Request (HARQ) ACK / NACK (acknowledgment / negative-acknowledgment) signal as a response to the UL transmission. The PHICH consists of three REGs and is cell-specific scrambled. ACK / NACK is indicated by 1 bit, and the 1-bit ACK / NACK is repeated three times, and each repeated ACK / NACK bit is spread with a spreading factor (SF) 4 or 2 and mapped to the control region.

Control information transmitted through the PDCCH is referred to as downlink control information (DCI). DCI includes resource allocation information and other control information for the UE or UE group. The transmission format and resource allocation information of a downlink shared channel (DL-SCH) may also be called DL scheduling information or a DL grant, and may be referred to as an uplink shared channel (UL-SCH). The transmission format and resource allocation information is also called UL scheduling information or UL grant. The DCI carried by one PDCCH has a different size and use depending on the DCI format, and its size may vary depending on a coding rate. In the current 3GPP LTE system, various formats such as formats 0 and 4 for uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3, and 3A are defined for uplink. Hopping flag, RB allocation, modulation coding scheme (MCS), redundancy version (RV), new data indicator (NDI), transmit power control (TPC), and cyclic shift DMRS Control information such as shift demodulation reference signal (UL), UL index, CQI request, DL assignment index, HARQ process number, transmitted precoding matrix indicator (TPMI), and precoding matrix indicator (PMI) information The selected combination is transmitted to the UE as downlink control information. The following table illustrates the DCI formats.

DCI format		Description
0	Resource grants for the PUSCH transmissions (uplink)
One	Resource assignments for single codeword PDSCH transmissions
1A	Compact signaling of resource assignments for single codeword PDSCH
1B	Compact signaling of resource assignments for single codeword PDSCH
1C	Very compact resource assignments for PDSCH (e.g. paging / broadcast system information)
1D	Compact resource assignments for PDSCH using multi-user MIMO
2	Resource assignments for PDSCH for closed-loop MIMO operation
2A	Resource assignments for PDSCH for open-loop MIMO operation
2B	Resource assignments for PDSCH using up to 2 antenna ports with UE-specific reference signals
2C	Resource assignment for PDSCH using up to 8 antenna ports with UE-specific reference signals
3 / 3A	Power control commands for PUCCH and PUSCH with 2-bit / 1-bit power adjustments
4	Scheduling of PUSCH in one UL Component Carrier with multi-antenna port transmission mode

In addition to the DCI formats defined in Table 4, other DCI formats may be defined.

A plurality of PDCCHs may be transmitted in the control region. The UE may monitor the plurality of PDCCHs. The eNB determines the DCI format according to the DCI to be transmitted to the UE, and adds a cyclic redundancy check (CRC) to the DCI. The CRC is masked (or scrambled) with an identifier (eg, a radio network temporary identifier (RNTI)) depending on the owner or purpose of use of the PDCCH. For example, when the PDCCH is for a specific UE, an identifier (eg, cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. If the PDCCH is for a paging message, a paging identifier (eg, paging-RNTI (P-RNTI)) may be masked to the CRC. When the PDCCH is for system information (more specifically, a system information block (SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC. If the PDCCH is for a random access response, a random access-RNTI (RA-RNTI) may be masked to the CRC. CRC masking (or scramble) includes, for example, XORing the CRC and RNTI at the bit level.

In general, the DCI format that can be transmitted to the UE depends on a transmission mode (TM) configured in the UE. In other words, not all DCI formats may be used for a UE set to a specific transmission mode, but only certain DCI format (s) corresponding to the specific transmission mode may be used.

For example, the transmission mode is semi-statically configured by the upper layer so that the UE can receive a PDSCH transmitted according to one of a plurality of predefined transmission modes. . The UE attempts to decode the PDCCH only in DCI formats corresponding to its transmission mode. In other words, not all DCI formats are simultaneously searched by the UE in order to keep the computational load of the UE due to the blind decoding attempt below a certain level. Table 5 illustrates a transmission mode for configuring a multi-antenna technique and a DCI format in which the UE performs blind decoding in the transmission mode. In particular, Table 5 shows the relationship between the PDCCH and the PDSCH configured by C-RNTI (Cell Radio Network Temporary Identifier).

Transmission mode	DCI format	Search space	Transmission scheme of PDSCH corresponding to PDCCH
Mode 1	DCI format 1A	Common andUE specific by C-RNTI	Single-antenna port, port 0
	DCI format 1	UE specific by C-RNTI	Single-antenna port, port 0
Mode 2	DCI format 1A	Common andUE specific by C-RNTI	Transmit diversity
	DCI format 1	UE specific by C-RNTI	Transmit diversity
Mode 3	DCI format 1A	Common andUE specific by C-RNTI	Transmit diversity
	DCI format 2A	UE specific by C-RNTI	Large delay CDD or Transmit diversity
Mode 4	DCI format 1A	Common andUE specific by C-RNTI	Transmit diversity
	DCI format 2	UE specific by C-RNTI	Closed-loop spatial multiplexing or Transmit diversity
Mode 5	DCI format 1A	Common andUE specific by C-RNTI	Transmit diversity
	DCI format 1D	UE specific by C-RNTI	Multi-user MIMO
Mode 6	DCI format 1A	Common andUE specific by C-RNTI	Transmit diversity
	DCI format 1B	UE specific by C-RNTI	Closed-loop spatial multiplexing using a single transmission layer
Mode 7	DCI format 1A	Common andUE specific by C-RNTI	If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used, otherwise Transmit diversity
	DCI format 1	UE specific by C-RNTI	Single-antenna port, port 5
Mode 8	DCI format 1A	Common andUE specific by C-RNTI	If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used, otherwise Transmit diversity
	DCI format 2B	UE specific by C-RNTI	Dual layer transmission, port 7 and 8 or single-antenna port, port 7 or 8
Mode 9	DCI format 1A	Common andUE specific by C-RNTI	Non-MBSFN subframe: If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used, otherwise Transmit diversity.
	DCI format 2C	UE specific by C-RNTI	Up to 8 layer transmission, ports 7-14 or single-antenna port, port 7 or 8
Mode 10	DCI format 1A	Common andUE specific by C-RNTI	Non-MBSFN subframe: If the number of PBCH antenna ports is one, Single-antenna port, port 0 is used, otherwise Transmit diversity.
	DCI format 2D	UE specific by C-RNTI	Up to 8 layer transmission, ports 7-14 or single antenna port, port 7 or 8

Table 5 lists the transmission modes 1 to 10, but other transmission modes may be defined in addition to the transmission modes defined in Table 5.

Referring to Table 5, for example, a UE set to transmission mode 9 decodes PDCCH candidates of a UE-specific search space (USS) into DCI format 1A and uses a common search space. space, CSS) and USS PDCCH candidates are decoded in DCI format 2C. The UE may decode the PDSCH according to the DCI according to the DCI format that has been successfully decoded. If one succeeds in decoding the DCI in DCI format 1A in one of a plurality of PDCCH candidates, the UE decodes or transmits the PDSCH on the assumption that it is transmitted to the UE through the PDSCH from antenna ports 7-14 to eight layers. Alternatively, the PDSCH may be decoded on the assumption that a single layer from 8 is transmitted to the UE through the PDSCH.

For example, the transmission mode is semi-statically configured by the upper layer so that the UE can receive a PDSCH transmitted according to one of a plurality of predefined transmission modes. . The UE attempts to decode the PDCCH only in DCI formats corresponding to its transmission mode. In other words, not all DCI formats are simultaneously searched by the UE in order to keep the computational load of the UE due to the blind decoding attempt below a certain level.

The PDCCH is allocated to the first m OFDM symbol (s) in the subframe. Here, m is indicated by PCFICH as an integer of 1 or more.

The PDCCH is transmitted on an aggregation of one or a plurality of consecutive control channel elements (CCEs). CCE is a logical allocation unit used to provide a PDCCH with a coding rate based on radio channel conditions. The CCE corresponds to a plurality of resource element groups (REGs). For example, one CCE corresponds to nine REGs and one REG corresponds to four REs. Four QPSK symbols are mapped to each REG. The resource element RE occupied by the reference signal RS is not included in the REG. Thus, the number of REGs within a given OFDM symbol depends on the presence of RS. The REG concept is also used for other downlink control channels (ie, PCFICH and PHICH).

The CCEs available for PDCCH transmission in the system can be numbered from 0 to N _CCE -1, where N _CCE = floor ( N _REG / 9), where N _REG is the number of REGs not assigned to PCFICH or PHICH. Indicates.

The DCI format and the number of DCI bits are determined according to the number of CCEs. CCEs are numbered and used consecutively, and to simplify the decoding process, a PDCCH having a format consisting of n CCEs can be started only in a CCE having a number corresponding to a multiple of n. The number of CCEs used for transmission of a specific PDCCH is determined by the network or eNB according to the channel state. For example, in case of PDCCH for a UE having a good downlink channel (eg, adjacent to an eNB), one CCE may be sufficient. However, in case of PDCCH for a UE having a poor channel (eg, near the cell boundary), eight CCEs may be required to obtain sufficient robustness. In addition, the power level of the PDCCH may be adjusted according to the channel state.

In the 3GPP LTE / LTE-A system, a set of CCEs in which a PDCCH can be located for each UE is defined. The collection of CCEs in which a UE can discover its PDCCH is referred to as a PDCCH search space, simply a search space (SS). An individual resource to which a PDCCH can be transmitted in a search space is called a PDCCH candidate. The collection of PDCCH candidates that the UE will monitor is defined as a search space. The search space may have a different size, and a dedicated search space and a common search space are defined. The dedicated search space is a UE-specific search space (USS) and is configured for each individual UE. A common search space (CSS) is set for a plurality of UEs.

The following table illustrates the aggregation levels that define the search spaces.

Search space S (L) k			Number of PDCCH candidates M (L)
Type	Aggregation level L	Size [in CCEs]
UE-specific		One	6	6
	2	12	6
	4	8	2
	8	16	2
Common	4	16	4
	8	16	2

For each serving cell PDCCH monitored, the CCEs corresponding to the PDCCH candidate m in the search space S ^(L) _k are determined by " L * { Y _k + m ') mod floor ( N _{CCE, k} / L } + i ". Where = 0, ..., L- 1. m '= m for the common search space PDCCH For the UE-specific search space, for the serving cell where the PDCCH is monitored, the monitoring UE indicates the carrier indicator field. When the lyric as ^{m '= m + m (L} ) * n CI ( wherein n _CI wherein n _CI is the carrier indicator field (CIF) value), and if the monitoring UE is not set as a carrier indicator field m' = m (where m = 0, 1, ..., M ^(L) -1) M ^(L) is the number of PDCCH candidates to monitor at the aggregation level L within a given search space The carrier aggregation field value is the serving cell index ( ServCellIndex). ) and it may be the same. Y _k is set to zero for the two aggregation level L = 4 and L = 8 for the common search space. UE- in aggregation level L-specific search space For S ^(L) _{k, k} a variable Y is defined by the _{"Y k = (A · Y} k -1) mod D", where _{Y -1 = n RNTI ≠ 0,} A = 39827, D = 65537 and k = floor ( n _s / 2) and n _s is the slot number in the radio frame.

The eNB sends the actual PDCCH (DCI) on any PDCCH candidate in the search space, and the UE monitors the search space to find the PDCCH (DCI). Here, monitoring means attempting decoding of each PDCCH in a corresponding search space according to all monitored DCI formats. The UE may detect its own PDCCH by monitoring the plurality of PDCCHs. Basically, since the UE does not know where its PDCCH is transmitted, every Pframe attempts to decode the PDCCH until every PDCCH of the corresponding DCI format has detected a PDCCH having its own identifier. It is called blind detection (blind decoding).

For example, a specific PDCCH is masked with a cyclic redundancy check (CRC) with a Radio Network Temporary Identity (RNTI) of "A", a radio resource (eg, frequency location) of "B" and a transmission of "C". Assume that information about data to be transmitted using format information (eg, transport block size, modulation scheme, coding information, etc.) is transmitted through a specific DL subframe. The UE monitors the PDCCH using its own RNTI information, and the UE having the RNTI "A" detects the PDCCH, and the PDSCH indicated by "B" and "C" through the received PDCCH information. Receive

5 shows an example of an uplink (UL) subframe structure used in a wireless communication system.

Referring to FIG. 5, a UL subframe may be divided into a control region and a data region in the frequency domain. One or several physical uplink control channels (PUCCHs) may be allocated to the control region to carry uplink control information (UCI). One or several physical uplink shared channels (PUSCHs) may be allocated to a data region of a UL subframe to carry user data.

In the UL subframe, subcarriers having a long distance based on a direct current (DC) subcarrier are used as a control region. In other words, subcarriers located at both ends of the UL transmission bandwidth are allocated for transmission of uplink control information. The DC subcarrier is a component that is not used for signal transmission and is mapped to a carrier frequency f ₀ during frequency upconversion. The PUCCH for one UE is allocated to an RB pair belonging to resources operating at one carrier frequency in one subframe, and the RBs belonging to the RB pair occupy different subcarriers in two slots. The PUCCH allocated in this way is expressed as that the RB pair allocated to the PUCCH is frequency hopped at the slot boundary. However, if frequency hopping is not applied, RB pairs occupy the same subcarrier.

PUCCH may be used to transmit the following control information.

SR (Scheduling Request): Information used for requesting an uplink UL-SCH resource. It is transmitted using OOK (On-Off Keying) method.

HARQ-ACK: A response to a PDCCH and / or a response to a downlink data packet (eg, codeword) on a PDSCH. This indicates whether the PDCCH or PDSCH is successfully received. HARQ-ACK 1 bit is transmitted in response to a single downlink codeword, HARQ-ACK 2 bits are transmitted in response to two downlink codewords. HARQ-ACK response includes a positive ACK (simple, ACK), negative ACK (hereinafter, NACK), DTX (Discontinuous Transmission) or NACK / DTX. Here, the term HARQ-ACK is mixed with HARQ ACK / NACK, ACK / NACK.

Channel State Information (CSI): Feedback information for the downlink channel. CSI consists of channel quality information (CQI), precoding matrix indicator (PMI), precoding type indicator (PTI), and / or rank indication (RI) Can be. Of these, Multiple Input Multiple Output (MIMO) -related feedback information includes RI and PMI. RI means the number of streams or the number of layers that a UE can receive through the same time-frequency resource. PMI is a value reflecting a space characteristic of a channel and indicates an index of a precoding matrix that a UE prefers for downlink signal transmission based on a metric such as SINR. The CQI is a value indicating the strength of the channel and typically indicates the received SINR that the UE can obtain when the eNB uses PMI.

A typical wireless communication system performs data transmission or reception (in frequency division duplex (FDD) mode) through one DL band and one UL band corresponding thereto, or transmits a predetermined radio frame. The time domain is divided into an uplink time unit and a downlink time unit, and data transmission or reception is performed through an uplink / downlink time unit (in a time division duplex (TDD) mode). Recently, however, the introduction of a carrier aggregation or bandwidth aggregation technique using a larger UL / DL bandwidth by collecting a plurality of UL and / or DL frequency blocks in order to use a wider frequency band has been discussed. . Carrier aggregation (CA) performs DL or UL communication by using a plurality of carrier frequencies, and performs DL or UL communication by putting a fundamental frequency band divided into a plurality of orthogonal subcarriers on one carrier frequency. It is distinguished from an orthogonal frequency division multiplexing (OFDM) system. Hereinafter, each carrier aggregated by carrier aggregation is called a component carrier (CC).

For example, three 20 MHz CCs may be gathered in the UL and the DL to support a 60 MHz bandwidth. Each of the CCs may be adjacent or non-adjacent to each other in the frequency domain. For convenience, a case where both the bandwidth of the UL CC and the bandwidth of the DL CC are the same and symmetric has been described. However, the bandwidth of each CC may be determined independently. In addition, asymmetrical carrier aggregation in which the number of UL CCs and the number of DL CCs are different is possible. A DL / UL CC limited to a specific UE may be called a configured serving UL / DL CC at a specific UE.

Meanwhile, the 3GPP LTE-A standard uses the concept of a cell to manage radio resources. A "cell" associated with a radio resource is defined as a combination of DL resources and UL resources, that is, a combination of a DL CC and a UL CC. The cell may be configured with DL resources alone or with a combination of DL resources and UL resources. If carrier aggregation is supported, the linkage between the carrier frequency of the DL resource (or DL CC) and the carrier frequency of the UL resource (or UL CC) is indicated by system information. Can be. For example, a combination of DL and UL resources may be indicated by a System Information Block Type 2 (SIB2) linkage. Here, the carrier frequency means a center frequency of each cell or CC. Hereinafter, a cell operating on a primary frequency is referred to as a primary cell (Pcell) or a PCC, and a cell operating on a secondary frequency (or SCC) is referred to as a secondary cell. cell, Scell) or SCC. The carrier corresponding to the Pcell in downlink is called a DL primary CC (DL PCC), and the carrier corresponding to the Pcell in the uplink is called a UL primary CC (DL PCC). Scell refers to a cell that can be configured after RRC (Radio Resource Control) connection establishment is made and can be used for providing additional radio resources. Depending on the capabilities of the UE, the Scell may form a set of serving cells for the UE with the Pcell. The carrier corresponding to the Scell in downlink is called a DL secondary CC (DL SCC), and the carrier corresponding to the Scell in the uplink is called a UL secondary CC (UL SCC). In case of the UE that is in the RRC_CONNECTED state but the carrier aggregation is not configured or does not support the carrier aggregation, there is only one serving cell configured only for the Pcell.

The eNB may be used for communication with the UE by activating some or all of the serving cells configured in the UE or by deactivating some. The eNB may change a cell that is activated / deactivated and may change the number of cells that are activated / deactivated. Once the eNB assigns a cell-specific or UE-specifically available cell to a UE, once the cell assignment for the UE is fully reconfigured or the UE does not handover, At least one of the cells is not deactivated. A cell that is not deactivated may be referred to as a Pcell unless a global reset of cell allocation for the UE is performed. A cell that an eNB can freely activate / deactivate may be referred to as an Scell. Pcell and Scell may be classified based on control information. For example, specific control information may be set to be transmitted / received only through a specific cell. This specific cell may be referred to as a Pcell, and the remaining cell (s) may be referred to as an Scell.

A configured cell is a cell in which carrier aggregation is performed for a UE based on measurement reports from other eNBs or UEs among eNB cells, and is configured for each UE. The cell configured for the UE may be referred to as a serving cell from the viewpoint of the UE. In the cell configured in the UE, that is, the serving cell, resources for ACK / NACK transmission for PDSCH transmission are reserved in advance. The activated cell is a cell configured to be actually used for PDSCH / PUSCH transmission among cells configured in the UE, and is performed on a cell in which CSI reporting and SRS transmission are activated for PDSCH / PUSCH transmission. The deactivated cell is a cell configured not to be used for PDSCH / PUSCH transmission by the operation of a eNB or a timer. When the cell is deactivated, CSI reporting and SRS transmission are also stopped in the cell.

For reference, a carrier indicator (CI) means a serving cell index ( servCellIndex ), and CI = 0 is applied for the Pcell . The serving cell index is a short identity used to identify the serving cell, for example, one of an integer from 0 to 'the maximum number of carrier frequencies that can be set to the UE at one time-1'. May be assigned to one serving cell as the serving cell index. That is, the serving cell index may be referred to as a logical index used to identify a specific serving cell only among cells allocated to the UE, rather than a physical index used to identify a specific carrier frequency among all carrier frequencies.

As mentioned above, the term cell used in carrier aggregation is distinguished from the term cell which refers to a certain geographic area where communication service is provided by one eNB or one antenna group.

Unless otherwise specified, a cell referred to in the present invention refers to a cell of carrier aggregation which is a combination of a UL CC and a DL CC.

In the case of communication using a single carrier, since only one serving cell exists, the PDCCH carrying the UL / DL grant and the corresponding PUSCH / PDSCH are transmitted in the same cell. In other words, in the case of FDD under a single carrier situation, the PDCCH for the DL grant for the PDSCH to be transmitted in a specific DL CC is transmitted in the specific CC, and the PDSCH for the UL grant for the PUSCH to be transmitted in the specific UL CC is determined by the specific CC. It is transmitted on the DL CC linked with the UL CC. In the case of TDD under a single carrier situation, the PDCCH for the DL grant for the PDSCH to be transmitted in a specific CC is transmitted in the specific CC, and the PDSCH for the UL grant for the PUSCH to be transmitted in the specific CC is transmitted in the specific CC.

In contrast, in a multi-carrier system, since a plurality of serving cells can be configured, UL / DL grant can be allowed to be transmitted in a serving cell having a good channel condition. As such, when a cell carrying UL / DL grant, which is scheduling information, and a cell in which UL / DL transmission corresponding to a UL / DL grant is performed, this is called cross-carrier scheduling.

In the following description, a case where a cell is scheduled from a corresponding cell itself, that is, itself and a case where a cell is scheduled from another cell, is called self-CC scheduling and cross-CC scheduling, respectively.

3GPP LTE / LTE-A may support a merge of multiple CCs and a cross carrier-scheduling operation based on the same for improving data rate and stable control signaling.

When cross-carrier scheduling (or cross-CC scheduling) is applied, downlink allocation for DL CC B or DL CC C, that is, PDCCH carrying DL grant is transmitted to DL CC A, and the corresponding PDSCH is DL CC B or DL CC C may be transmitted. For cross-CC scheduling, a carrier indicator field (CIF) may be introduced. The presence or absence of the CIF in the PDCCH may be set in a semi-static and UE-specific (or UE group-specific) manner by higher layer signaling (eg, RRC signaling).

In the existing system premised to communicate with one node, UE-RS, CSI-RS, CRS, etc. are transmitted in the same location, so the UE delay delay of UE-RS port, CSI-RS port, CRS port Doppler spread, frequency shift, average received power, reception timing, etc. may not be considered. However, in a communication system to which CoMP (Coordinated Multi-Point) communication technology is applied, in which more than one node can simultaneously participate in communication with a UE, a PDCCH port, a PDSCH port, a UE-RS port, a CSI-RS port, and / or The characteristics of the CRS port may be different. For this reason, the concept of a quasi co-located antenna port is introduced for a mode in which multiple nodes are likely to participate in communication (hereinafter, CoMP mode).

The terms "quasi co-located" (QCL) or "quasi co-location" (QCL) may be defined in terms of antenna ports as follows: two antenna ports If they are pseudo co-located, the UE assumes that large-scale properties of the signal received from one of the two antenna ports can be inferred from the signal received from the other antenna port. can do. The large scale attributes consist of delay spread, Doppler spread, frequency shift, average received power and / or reception timing.

QCL may be defined in terms of channels as follows: If two antenna ports are pseudo co-located, the UE receives the large attributes of the channel that conveys a symbol on one of the two antenna ports. It can be assumed that the large properties of a given signal can be inferred from the large properties of a channel carrying a symbol on another antenna port. The large scale attributes consist of delay spreading, Doppler spreading, Doppler transitions, average gain and / or average delay.

In embodiments of the invention the QCL may follow one of the above definitions. Alternatively, the definition of QCL may be modified in such a way that antenna ports for which the QCL hypothesis holds in a similar fashion may be assumed to be in the same-position. For example, for antenna ports for which QCL is established, the QCL concept may be defined in such a manner that the UE assumes antenna ports of the same transmission point.

The UE cannot assume the same large attributes between the antenna ports for non-quasi co-located (NQC) antenna ports. In this case, a typical UE must perform independent processing for each set NQC antenna for timing acquisition and tracking, frequency offset estimation and compensation, delay estimation, and Doppler correction. do.

On the other hand, for antenna ports that can assume QCL, the UE has the advantage that it can perform the following operations:

For Doppler spreading, the UE filters the power-delay-profile, delay spreading and Doppler spectrum, and Doppler spread estimation results for one port for channel estimation (e.g., The same applies to Wiener filters, etc .;

For frequency transition and reception timing, the UE may apply time and frequency synchronization for one port and then apply the same synchronization to demodulation of another port;

For average received power, the UE may average reference signal received power (RSRP) measurements across two or more antenna ports.

For example, when the UE receives a specific DMRS-based downlink-related DCI format (eg, DCI format 2C) through PDCCH / EPDCCH, the UE performs channel estimation for the corresponding PDSCH through the configured DMRS sequence, and then the data. Demodulation is performed. If the DMRS port configuration received by the UE through this DL scheduling grant can assume a specific RS (e.g., a specific CSI-RS or a specific CRS or its own DL serving cell CRS, etc.) DMRS-based receiver processing performance can be improved by applying the estimate (s) of the large-scale attributes estimated from the specific RS port as it is during channel estimation.

FIG. 6 illustrates a cell specific reference signal (CRS) and a user specific reference signal (UE-RS). In particular, FIG. 6 shows the REs occupied by CRS (s) and UE-RS (s) in an RB pair of subframes having normal CP.

In the existing 3GPP LTE system, since CRS is used for both demodulation and measurement purposes, the CRS is transmitted over the entire downlink bandwidth in all downlink subframes in a cell supporting PDSCH transmission and configured in the eNB. It is transmitted from all antenna ports.

Referring to FIG. 6, CRSs are transmitted through antenna ports p = 0, p = 0,1, p = 0,1,2,3 according to the number of antenna ports of a transmitting node. The CRS 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 CRS is allocated in the control region, and the data channel is also allocated to a resource to which CRS is not allocated in the data region.

The UE may measure CSI using CRS, and may demodulate a signal received through PDSCH in a subframe including the CRS using CRS. That is, the eNB transmits a CRS at a predetermined position in each RB in all RBs, and the UE detects a PDSCH after performing channel estimation based on the CRS. For example, the UE measures a signal received at a CRS RE, and uses a ratio of the measured signal and the received energy of each RE to which the PDSCH of the received energy of the CRS RE is mapped to the PDSCH signal from the RE to which the PDSCH is mapped. Can be detected. However, when the PDSCH is transmitted based on the CRS, an unnecessary RS overhead occurs because the eNB needs to transmit the CRS for all RBs. In order to solve this problem, in the 3GPP LTE-A system, UE-specific RS (hereinafter, UE-RS) and CSI-RS are further defined in addition to the CRS. The UE-RS is used for demodulation and the CSI-RS is used to derive channel state information. UE-RS can be regarded as a kind of DRS. Since UE-RS and CRS are used for demodulation, they can be referred to as demodulation RS in terms of use. Since CSI-RS and CRS are used for channel measurement or channel estimation, they can be referred to as measurement RS in terms of use.

Referring to FIG. 6, UE-RS is supported for transmission of PDSCH and antenna port (s) p = 5, p = 7, p = 8 or p = 7,8, ..., υ + 6 (where, υ is transmitted through the number of layers used for transmission of the PDSCH. The UE-RS is present if PDSCH transmission is associated with the corresponding antenna port and is a valid reference only for demodulation of the PDSCH. The UE-RS is transmitted only on the RBs to which the corresponding PDSCH is mapped. That is, the UE-RS is configured 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 in every subframe regardless of the presence or absence of the PDSCH. In addition, unlike the CRS transmitted through all antenna port (s) regardless of the number of layers of the PDSCH, the UE-RS is transmitted only through the antenna port (s) respectively corresponding to the layer (s) of the PDSCH. Therefore, overhead of RS can be reduced compared to CRS.

In 3GPP LTE-A system, UE-RS is defined in a PRB pair. Referring to FIG. 6, for p = 7, p = 8 or p = 7,8, ..., υ + 6, in a PRB with frequency-domain index n _PRB assigned for corresponding PDSCH transmission A portion of the UE-RS sequence r ( m ) is mapped to complex modulation symbols a ^(p) _{k, l} in a subframe according to the following equation.

Where w _p ( i ), l ', m ' are given by

Here, n _s is a slot number in one radio frame and is one of integers from 0 to 19. Sequence for Normal CP

Is given according to the following table.

Antenna port p
7	[+1 +1 +1 +1]
8	[+1 -1 +1 -1]
9	[+1 +1 +1 +1]
10	[+1 -1 +1 -1]
11	[+1 +1 -1 -1]
12	[-1 -1 +1 +1]
13	[+1 -1 -1 +1]
14	[-1 +1 +1 -1]

For the antenna port p {7,8, ..., υ + 6}, the UE-RS sequence r ( m ) is defined as follows.

Here, N ^{max, DL} _RB is the largest downlink bandwidth setting and is expressed as a multiple of N ^RB _sc . c ( i ) is a pseudo-random sequence, defined by a length-31 Gold sequence. The output sequence c ( n ) of length M _PN , where n = 0, 1, ..., M _PN -1, is defined by the following equation.

Where N _C = 1600 and the first m-sequence is initialized to x ₁ (0) = 1, x ₁ (n) = 0, n = 1,2, ..., 30 and the second m-sequence is the sequence With values according to the application of

Denoted by

In Equation 3, a pseudo-random sequence generator for generating c ( i ) is initialized to c _init according to the following equation at the beginning of each subframe.

In Equation 5, the quantities corresponding to n ^(nSCID) _ID n ⁽ⁱ⁾ _ID (where i = 0,1) is a scrambling identifier n ^{DMRS, i} provided by a higher layer for UE-RS generation. _If the value for _ID is not provided by the upper layer or if DCI format 1A, 2B or 2C is used for the DCI associated with PDSCH transmission, then the physical layer cell identifier N ^cell _ID , otherwise n ^{DMRS, i} _ID .

In Equation 5, the value of n _SCID is 0 unless otherwise specified, and for SCSCH transmission on antenna ports 7 or 8, n _SCID is given by DCI format 2B or 2C associated with PDSCH transmission. DCI format 2B is a DCI format for resource assignment for PDSCH using up to two antenna ports with UE-RS, and DCI format 2C is a PDSCH using up to 8 antenna ports with UE-RS. DCI format for resource assignment for.

The reference-signal sequence r _{l, ns} ( m ) for the CRS is defined as follows.

Here, N ^{max, DL} _RB is the largest downlink bandwidth setting and is expressed as a multiple of N ^RB _sc . n _s is a slot number in a radio frame and l is an OFDM symbol number in a slot. The pseudo-random sequence c ( i ) is defined by equation (4). The pseudo-random sequence generator is initialized according to the following equation at the start of each OFDM symbol.

Here, N ^cell _ID means a physical layer cell identifier, and N _CP = 1 for a normal CP and N _CP = 0 for an extended CP.

In 3GPP LTE systems, CRS is defined in a PRB pair. Referring to FIG. 6, the reference-signal sequence r _{l, ns} ( m ) for CRS is complex modulation symbols a ^(p) _k used as reference symbols for antenna port p in slot n _s according to the following equation: mapped to _{, l} .

Where k , l , m 'are defined as

The variables v and v _shift define the position in the frequency domain for the other RSs, and v is given by the following equation.

The cell-specific frequency shift is given by v _shift = N ^cell _ID mod 6, where N ^cell _ID is a physical layer cell identifier, that is, a physical cell identifier.

On the other hand, if the RRH technology, cross-carrier scheduling technology, etc. are introduced, the amount of PDCCH to be transmitted by the eNB gradually increases. However, since the size of the control region in which the PDCCH can be transmitted is the same as before, the PDCCH transmission serves as a bottleneck of system performance. Channel quality can be improved by introducing the above-described multi-node system, applying various communication techniques, etc. However, in order to apply existing communication techniques and carrier aggregation techniques to a multi-node environment, introduction of a new control channel is required. For this reason, establishing a new control channel in the data region (hereinafter referred to as PDSCH region) rather than the existing control region (hereinafter referred to as PDCCH region) has been discussed. This new control channel is hereinafter referred to as the enhanced PDCCH (hereinafter referred to as EPDCCH).

The EPDCCH may be set in the latter OFDM symbols starting from the configured OFDM symbol, not the first OFDM symbols of the subframe. The EPDCCH may be configured using continuous frequency resources or may be configured using discontinuous frequency resources for frequency diversity. By using such an EPDCCH, it becomes possible to transmit control information for each node to the UE, and it is also possible to solve a problem that the existing PDCCH region may be insufficient. For reference, the PDCCH is transmitted through the same antenna port (s) as the antenna port (s) configured for transmission of the CRS, and the UE configured to decode the PDCCH demodulates or decodes the PDCCH using the CRS. can do. Unlike the PDCCH transmitted based on the CRS, the EPDCCH may be transmitted based on a demodulated RS (hereinafter, referred to as DMRS). Accordingly, the UE can decode / demodulate the PDCCH based on the CRS and the EPDCCH can decode / decode the DMRS based on the DMRS. The DMRS associated with the EPDCCH is transmitted on the same antenna port p ∈ {107,108,109,110} as the EPDCCH physical resource, and is present for demodulation of the EPDCCH only if the EPDCCH is associated with that antenna port, and on the PRB (s) to which the EDCCH is mapped. Only sent. For example, REs occupied by UE-RS (s) at antenna ports 7 or 8 may be occupied by DMRS (s) at antenna ports 107 or 108 on the PRB to which EPDCCH is mapped, and antenna ports 9 or 10 REs occupied by UE-RS (s) of may be occupied by DMRS (s) of antenna port 109 or 110 on a PRB to which EPDCCH is mapped. After all, like the UE-RS for demodulation of the PDSCH, the DMRS for demodulation of the EPDCCH, if the type of EPDCCH and the number of layers are the same, a certain number of REs for each RB pair are used for DMRS transmission regardless of the UE or cell. do.

For each serving cell, the higher layer signal may configure the UE as one or two EPDCCH-PRB-sets for EPDCCH monitoring. PRB-pairs corresponding to one EPDCCH-PRB-set are indicated by higher layers. Each EPDCCH-PRB set consists of a set of ECCEs numbered from 0 to N _{ECCE, p, k} −1. Here, N _{ECCE, p, k} is the number of ECCEs in the EPDCCH-PRB-set p of subframe k . Each EPDCCH-PRB-set may be configured for localized EPDCCH transmission or distributed EPDCCH transmission.

The UE monitors a set of EPDCCH candidates on one or more activated cells, as set by the higher layer signal for control information.

The collection of EPDCCH candidates to monitor is defined as EPDCCH UE specific search spaces. For each serving cell, the subframes for which the UE will monitor EPDCCH UE specific search spaces are set by the higher layer.

At aggregation level L ∈ {1,2,4,8,16,32}, EPDCCH UE-specific search space ES ^(L) _k is defined as a collection of EPDCCH candidates.

For EPDDCH-PRB-set p , the ECCEs corresponding to EPDCCH candidate m in search space ES ^(L) _k are given by the following equation.

Where i = 0, ..., L -1 and b = n _CI if the UE is set as a carrier indicator field for the serving cell whose EPDCCH is to be monitored, otherwise b = 0. n _CI is a carrier indicator field (CIF) value, and the carrier indicator field value is the same as a serving cell index ( servCellIndex ). m = 0, 1, ..., M ^(L) _p -1, and M ^(L) _p is the number of EPDCCH candidates to monitor at the aggregation level L in the EPDDCH-PRB-set p . The variable Y _{p, k} is defined by Y _{p, k} = ( A _p · Y _{p, k - 1} ) mod D , where Y _{p , -1} = n _RNTI ≠ 0, A ₀ = 39827, A ₀ = 39829, D = 65537 and k = floor ( n _s / 2). n _s is a slot number in a radio frame.

If the ECCE corresponding to the candidate in the EPDCCH is mapped to a PRB pair that overlaps in frequency with the transmission of the PBCH or PSS / SSS in the same subframe, the UE does not monitor the EPDCCH candidate.

The EPDCCH is transmitted using an aggregation of one or several consecutive advanced control channel elements (ECCEs). Each ECCE consists of a plurality of enhanced resource element groups (ERREGs). EREG is used to define the mapping of advanced control channels to REs. There are 16 REGs per PRB pair, which consist of a PRB in a first slot and a PRB in a second slot of one subframe, and the 16 REGs are numbered from 0 to 15. Among the REs in a PRB pair, the remaining REs except for the REs carrying the DMRS for demodulation of the EPDCCH (hereinafter, referred to as EPDCCH DMRS) are first cycled from 0 to 15 in increasing order of frequency, and then in increasing order of time. given when the PRB all RE pair except for the RE to carry of the inner RE EPDCCH DMRS are and have any one of the number of 15, an integer from 0, to any RE having the number i to configure the EREG the number i do. As such, it can be seen that the EREGs are distributed on the frequency and time axis within the PRB pair, and the EPDCCH transmitted using the aggregation of one or more ECCEs each consisting of a plurality of EREGs is also distributed on the frequency and time axis within the PRB pair. To be located.

The number of ECCEs used for one EPDCCH depends on the EPDCCH formats as given by Table 8, and the number of EREGs per ECCE is given by Table 9. Table 8 illustrates the supported EPDCCH formats, and Table 9 illustrates the number of ^REGs N ^EREG _ECCE per _ECCE . Both localized and distributed transports are supported.

EPDCCH format	Number of ECCEs for one EPDCCH, N ECCE EPDCCH
	Case a		Case b
	Localized transmission	Distributed transmission	Localized transmission	Distributed transmission
0	2	2	One	One
One	4	4	2	2
2	8	8	4	4
3	16	16	8	8
4	-	32	-	16

Normal cyclic prefix			Extended cyclic prefix
Normal subframe	Special subframe, configuration 3, 4, 8	Special subframe, configuration1, 2, 6, 7, 9	Normal subframe	Special subframe, configuration1, 2, 3, 5, 6
4		8

The EPDCCH may use localized transmission or distributed transmission, depending on the mapping of ECCEs to EREGs and PRB pairs. One or two sets of PRB pairs for which the UE monitors EPDCCH transmission may be set. All EPDCCH candidates in the EPDCCH set S _p (ie, EPDCCH-PRB-set) use only localized transmissions or only distributed transmissions, as set by the higher layer. ECCEs available for transmission of EPDCCHs in the EPDCCH set S _p in subframe k are numbered from 0 to N _{ECCE, p, k} −1. ECCE number n corresponds to the following EREG (s):

EREGs numbered ( n mod N ^ECCE _RB ) + jN ^ECCE _RB in the PRB index floor ( n / N ^ECCE _RB ) for localization mapping, and

PRB indices for variance mapping ( n + j max (1, N ^Sp _RB / N ^EREG _ECCE )) EREGs numbered floor ( n / N ^Sm _RB ) + jN ^ECCE _RB in mod N ^Sp _RB .

Here, j = 0, 1, ..., N ^EREG _ECCE -1, N ^EREG _ECCE is the number of EREGs per ^ECCE , N ^ECCE _RB = 16 / N ^EREG _ECCE is the number of ^ECCEs per resource block pair. The PRB pairs that make up the EPDCCH set S _p are assumed to be numbered in ascending order from 0 to N ^Sp _RB −1.

Case A in Table 8 is:

When DCI formats 2, 2A, 2B, 2C or 2D are used and N ^DL _RB ≧ 25, or

_{Special subframe in} any DCI format when n _EPDCCH <104, with normal cyclic prefix (CP) being normal subframes or special subframe configuration 3, 4, 8 When used in the field, it applies.

Otherwise, case B is used. The quantity n _EPDCCH for a particular UE is a downlink resource element ( k ,) that satisfies all of the following criteria, in a pair of physical resource blocks configured for possible EPDCCH transmission of the EPDCCH set S ₀ . is defined as the number of l )

A part of any one of 16 EREGs in the physical resource block pair,

Assume that it is not used for CRSs or CSI-RSs by the UE,

- the index satisfying a ≥ I l l _EPDCCHStart subframe l.

Here, l _EPDCCHStart is determined based on a CFI value carried by higher layer signaling epdcch - StartSymbol -r11 , higher layer signaling pdsch-Start-r11 , or PCFICH.

The resource elements ( k , l ) satisfying the criterion are mapped to antenna port p in order of first increasing index k , and then increasing index l , starting from the first slot in the subframe. Ends in the first slot.

For localized transmission, the single antenna port p to be used is given by n '= n _{ECCE, low} mod N ^ECCE _RB + n _RNTI mod min ( N ^ECCE _EPDCCH , N ^ECCE _RB ) and Table 10. Where n _{ECCE, low} is the lowest ECCE index used by this EPDCCH transmission in the EPDCCH set, n _RNTI corresponds to the RNTI associated with the EPDCCH malleability, and N ^ECCE _EPDCCH is the number of ECCEs used for the EPDCCH .

n '	Normal cyclic prefix		Extended cyclic prefix
	Normal subframes, Special subframes, configurations3, 4, 8	Special subframes, configurations 1, 2, 6, 7, 9	Any subframe
0	107	107	107
One	108	109	108
2	109	-	-
3	110	-	-

In the case of distributed transmission, each resource element in the EREG is associated with one of the two antenna ports in an alternating manner. Here, in the case of a normal CP, the two antenna ports p ∈ {107,109}, and in the case of an extended CP, the two antenna ports are p ∈ {107,108}.

Recently, machine type communication (MTC) has emerged as one of the important communication standardization issues. MTC mainly refers to information exchange performed between a machine and an eNB without human intervention or with minimal human intervention. For example, MTC can be used for data communication such as meter reading, level measurement, surveillance camera utilization, measurement / detection / reporting such as inventory reporting of vending machines, etc. It may be used for updating an application or firmware. In the case of MTC, the amount of transmitted data is small, and uplink / downlink data transmission or reception (hereinafter, transmission / reception) sometimes occurs. Due to the characteristics of the MTC, for the UE for MTC (hereinafter referred to as MTC UE), it is efficient to lower the UE manufacturing cost and reduce battery consumption at a low data rate. In addition, such MTC UEs are less mobile, and thus, the channel environment is hardly changed. When the MTC UE is used for eggs, meter reading, monitoring, etc., the MTC UE is likely to be located at a location that is not covered by a normal eNB, for example, a basement, a warehouse, a mountain, and the like. Considering the use of such an MTC UE, the signal for the MTC UE is better to have a wider coverage than the signal for a legacy UE (hereinafter, a legacy UE).

Considering the use of the MTC UE, the MTC UE is likely to require a signal with a wider coverage than the legacy UE. Therefore, when the PDCCH, PDSCH, etc. are transmitted to the MTC UE in the same manner as the eNB transmits to the legacy UE, the MTC UE has difficulty in receiving them. Therefore, in order to enable the MTC UE to effectively receive a signal transmitted by the eNB, the eNB may select a subframe repetition (subframe having a signal) when transmitting a signal to the MTC UE having a coverage issue. It is proposed to apply a technique for coverage enhancement such as repetition), subframe bundling, and the like. For example, a PDCCH and / or PDSCH may be transmitted through a plurality of subframes (eg, about 100) to an MTC UE having a coverage problem.

The data channel (e.g. PDSCH, PUSCH) and / or control channel (e.g. M-PDCCH, PUCCH, PHICH) may be repeated or repeated through multiple subframes for coverage enhancement (CE) of the UE. Can be sent using the technique of TTI bundling. For CE, control / data channels may be transmitted using techniques such as cross-subframe channel estimation, frequency (narrowband) hopping, and the like. Here, cross-subframe channel estimation means a channel estimation method that uses not only reference signals in subframes having corresponding channels but also reference signals in neighboring subframe (s).

The MTC UE may, for example, require a CE of up to 15 dB. However, not all MTC UEs exist in an environment requiring CE. In addition, the requirements for QoS of all MTC UEs are not the same. For example, devices such as sensors and meters may require high CE because they are less likely to be located in shadowed areas with less mobility and less data transmission and reception. However, wearable devices, such as smart watches, may have mobility and are likely to be located in places other than shaded areas with a relatively high amount of data transmission and reception. Therefore, not all MTC UEs require a high level of CE, and the capabilities required may vary depending on the type of MTC UE.

7 shows an example of a signal band for an MTC.

One way to lower the cost of the MTC UE, regardless of the operating system bandwidth of the cell, for example, in the reduced UE downlink and uplink bandwidth of 1.4 MHz of the MTC UE Operation can be made. At this time, the sub-band (= narrowarrow) in which the MTC UE operates may always be located at the center of the cell (eg, six center PRBs) as shown in FIG. In order to multiplex MTC UEs in a subframe, as shown in FIG. 7B, multiple subbands for MTC are placed in one subframe, so that the UEs use different subbands, or the UEs use the same subband. It is also possible to use a band but use a subband other than the subband consisting of six center PRBs.

In this case, the MTC UE cannot properly receive the legacy PDCCH transmitted through the entire system band, and the PDCCH for the MTC UE is transmitted in the OFDM symbol region in which the legacy PDCCH is transmitted due to a multiplexing issue with the PDCCH transmitted to other UEs. It may not be desirable. One way to solve this problem is to introduce a control channel transmitted in a subband in which the MTC operates for the MTC UE. As a downlink control channel for such a low-complexity MTC UE, the existing EPDCCH may be used as it is. Alternatively, the M-PDCCH for the MTC UE, which is a control channel in which the existing PDCCH / EPDCCH is modified, may be introduced. Hereinafter, in the present invention, the conventional EPDCCH or M-PDCCH for such a low-complexity MTC or normal complexity MTC UE is referred to as a physical downlink control channel as M-PDCCH. In addition, MTC-EPDCCH is used hereinafter as M-PDCCH.

In order to further reduce the cost of the MTC UE, an environment in which the MTC UE operates through a narrow bandwidth of about 200 KHz may be considered. Such an MTC UE, that is, an MTC UE capable of operating only within a narrow bandwidth, may operate backward compatible in a legacy cell having a bandwidth wider than 200 KHz. A clean frequency band without legacy cells may be deployed for this MTC UE only. In the present invention, a system that operates through a narrowband as small as one PRB in a legacy cell having a bandwidth wider than 200 KHz is referred to as an in-band narrowband (NB) Internet of Things (IoT), and legacy In a clean frequency band in which no cell exists, a system that operates through a narrow bandwidth, such as one PRB, for an MTC UE only is called a stand-alone NB IoT.

Hereinafter, a radio resource of one RB size operating with NB-IoT is referred to as an NB-IoT cell, an LTE radio resource in which communication occurs according to an LTE system, is called an LTE cell, and a GSM radio resource in which communication occurs according to a GSM system. It is called a GSM cell. The in-band NB IoT cell can operate in a 200 kHz bandwidth (without guard-band consideration) or 180 kHz bandwidth (without guard-band consideration) within the system band of the LTE cell.

To specify a wireless connection for the cellular IoT, based on an incompatible variant of E-UTRA, the following characteristics can be addressed:

* Improved indoor coverage,

* A massive number of low throughput devices,

Low delay sensitivity, ultra low instrument cost, and

* Low device power consumption and (optimized) network structure.

NB-IoT can support the operation of three different modes:

* 'Stand-alone operation', for example, which utilizes the spectrum currently being used by GERAN systems as a replacement for one or more GSM carriers,

'Guard band operation' utilizing unused resource blocks in the guard-band of the LTE subcarrier, and

'In-band operation' utilizing resource blocks in a normal LTE carrier.

In particular, the following may be supported:

180 kHz UE RF bandwidth for both downlink and uplink, and

OFDMA on downlink.

Two pneumatic options are considered: 15 kHz subcarrier spacing (with normal or extended CP) and 3.75 kHz subcarrier spacing,

For uplink, two options are considered: FDMA with Gaussian minimum shift keying (GMSK) modulation, and SC-FDMA including single-tone transmission as a special case of SC-FDMA.

In the following embodiments of the present invention, the expression "assuming" may mean that the subject transmitting the channel transmits the channel so as to correspond to the "assuming". The subject receiving the channel may mean that the channel is received or decoded in a form conforming to the "home", provided that the channel is transmitted to conform to the "home".

The present invention proposes a PBCH transmission scheme for an IoT UE in an NB-LTE environment in which an MTC UE operates in a narrow band of about 200 KHz.

Since a UE operating in an NB-LTE system (i.e., an IoT UE or an NB-LTE UE) can receive / transmit only within a small PRB area of one PRB, six PRBs are transmitted for transmission of a PBCH in an NB-LTE system. It may not be used as it is, and the NB-LTE UE may not receive the legacy PBCH. Therefore, there is a need for a new PBCH transmitted within narrow-bandwidth for NB-LTE UEs. The present invention proposes a PBCH transmission scheme for an MTC UE in an in-band NB LTE environment and a stand-alone NB LTE environment.

The present invention describes the transmission of the PBCH, but the present invention can be applied to the transmission of channels other than the PBCH (eg, PDCCH / EPDCCH / M-PDCCH, PDSCH). Hereinafter, for convenience, embodiments of the present invention are described assuming an environment in which an IoT UE operates in a system deployed for the IoT UE, but it is obvious that the present invention can be applied to other UEs and systems.

<A. NB- LTE PBCH  Reference signal for transmission>

-CRS based transmission

The transmission of the PBCH in the NB-LTE may be a CRS based transmission. In this case, the PBCH is transmitted through the antenna port through which the CRS is transmitted. In this case, the CRS may be an RS using an antenna port, an RE location, and / or a reference signal (RS) sequence of the legacy CRS.

In case of in-band NB LTE, the UE may perform reception of the PBCH using legacy CRS. In the case of the standalone PBCH, the CRS may be transmitted in a resource region (eg, a subframe region) in which the PBCH is transmitted. Alternatively, the CRS may be transmitted through all downlink subframe regions, that is, every subframe.

In order for the UE to use the legacy CRS, the number of PRB resources is located in the NB-LTE resource within the system bandwidth of the legacy cell where the legacy CRS and the NB-LTE share resources (or the number of times from the center frequency of the legacy cell). Location) and the cell ID of the legacy cell. To this end, the following method may be considered.

* If the legacy cell ID is equal to the cell ID of the NB-LTE cell, or assumes that the legacy cell ID can be inferred when the UE can detect the ID of the NB-LTE cell by a constant function,

Fixed PRB location for NB-LTE PBCH transmission: For example, one may assume that the NB-LTE PBCH is always transmitted centered at a distance of 36 + 6 subcarriers from the center; or

> Blind detection of PRB for NB-LTE (hereinafter referred to as NB-LTE PRB) using CRS detection for PRB

* Assuming legacy cell ID and NB-LTE cell ID are used independently,

> It may be assumed that the legacy cell ID is transmitted by the synchronization signal of the NB-LTE, or that the legacy cell ID is known to the UE by an additional signal, or may be assumed to be a fixed value.

New (new) cell-specific RS based transmission

PBCH transmission in NB-LTE may be transmitted on a new RS. In an in-band NB LTE environment, the UE may not know the cell ID of the legacy cell in which it operates and / or the PRB location in which the NB-LTE operates in the legacy cell, in which case the UE may receive the legacy CRS. Because there may not be. This new RS may be a structure such as an existing DMRS, that is, a UE-RS, or may be an RS having a new structure. The new RS may be made by moving several subcarriers or several OFDM symbols on the frequency axis and / or time axis to position the REs of the existing RS, or may be configured as a combination of existing RSs. For example, the pattern of DMRS used in the extended CP may be used as a new RS pattern in the regular CP. This includes the RE resource configuration, and RS operations such as scrambling, sequence generation, antenna mapping, etc. are newly defined or one of the RS operations such as scrambling, sequence generation, antenna mapping, etc. Can be used for In other words, from the implementation point of view of the UE, the new RS may be similar to the existing RS but different from the existing RS pattern and the new RS pattern. Since the PBCH is a channel that a UE in a cell should receive in common, this new RS may be a cell-specific RS.

In the case of in-band NB LTE, since the legacy CRS should be transmitted on the NB IoT band, a new RS must be transmitted in addition to the legacy CRS. On the other hand, in the case of standalone NB LTE, only a new RS can be transmitted without transmitting a legacy CRS on the corresponding NB IoT band. For example, assuming that the data mapping schemes are the same in legacy LTE systems and NB IoT systems, the new RS becomes the default RS and the legacy CRS assumes only rate-matching purposes, such as conventional zero-power CSI. Can be In other words, if data demodulation and measurement are performed with the new RS (s) and legacy CRS is to be transmitted, the value for the legacy CRS setting (cell ID% 6, where% is the modulo operator) is transmitted via the MIB or SIB. If the UE receives the legacy CRS configuration, the UE may assume that the CRS configuration is a zero-power CRS as if the neighbor cell is transmitting the CRS. Such zero-power CRS may also be used for CRS or PRS. In other words, this concept of zero-power RS, used for rate-matching in legacy RS REs, can be applied to PRS as well as CRS. For zero-power PRS, legacy PRS REs can be used for rate-matching. The zero-power CRS or zero-power PRS may vary for each subframe. The eNB may signal configuration for subframes with zero-power CRS or zero-power PRS through MIB / SIB or the like. Since the NB LTE UE will not use legacy CRS, if there is a zero-power CRS configuration, the NB LTE UE does not receive the CRS in the CRS REs and only uses it for rate-matching of data. In the MBSFN subframe, since the legacy CRS is not transmitted except for the legacy control region, the CRS REs need not be rate-matched. Thus, in subframes that cannot be configured as MBSFN subframes, data is rate-matched in the corresponding CRS REs by applying a zero-power CRS. If there is a zero-power CRS configuration, the UE may apply the zero-power CRS only in non-MBSFN capable subframes, eg, subframes # 0, # 1, # 4, and # 9 and other subframes. Zero-power CRS is not assumed when this NB LTE UE is set to a valid subframe that can be used. In other words, the UE assumes that a zero-power CRS exists only in non-MBSFN capable subframes (ie, subframes that cannot be set for MBSFN), and MBSFN capable subframes (ie, subframes that can be set for MBSFN). Can assume that there is no zero-power CRS. In this case, even in the MBSFN capable subframe, the legacy CRS is transmitted in the subframe not actually configured for the MBSFN. In a subframe that is MBSFN capable but not configured for MBSFN, since the UE assumes that zero-power CRS does not exist, the UE assumes that data is transmitted to itself without rate-matching data in legacy CRS REs. do. In this case, since the eNB needs to transmit legacy CRS for legacy UEs, the eNB punctures data transmitted from the legacy CRS REs to the NB LTE UE and transmits legacy CRS. Thus, the UE assumes that a zero-power CRS exists only in non-MBSFN capable subframes (ie, subframes that cannot be set for MBSFN) and in MBSFN capable subframes (ie, subframes that can be set for MBSFN). Assuming no zero-power CRS may mean that the network punctures the NB-LTE transmission when it has to transmit the legacy CRS. In the case of the PRS, it may be considered to set the PRS transmission subframe as invalid or to set a zero-power PRS for the PRS.

The new RS proposed in the present invention can be used not only for transmission of PBCH but also for transmission of other NB-LTE channels.

This new RS may have the following structure. The RS patterns proposed below for the new RS below include RS pattern (s) in which the RS patterns illustrated in the following figures have shifted (ie, v-shifted) in the frequency direction.

8 and 9 illustrate RS structures according to an embodiment of the present invention.

* The number of transmission (TX) antenna ports is 1

If the transmission of the PBCH for NB LTE is transmitted using one antenna port, the new RS uses the RE location of DMRS antenna ports 7 or 9 for new RS transmission as shown in FIG. 8 (a). Can be used.

Alternatively, when the transmission of the PBCH for NB LTE is transmitted using only one antenna port, in order to minimize the resource collision between the new RS and other channels / signals by reducing the number of OFDM symbols transmitted by the new RS, FIG. 8 (b) As shown in Fig. 6), both the RE positions from which the existing DMRS antenna port 7 and the antenna port 9 were transmitted are used for transmission of a new RS of a single (single0 antenna port), corresponding to half of the existing DMRS OFDM symbols. For example, a new RS may be transmitted through two OFDM symbols in a subframe, and a new RS may be transmitted through a total of six RE positions where DMRS was previously transmitted in one OFDM symbol. Can be sent.

Alternatively, when the transmission of the PBCH for NB LTE is transmitted using only one antenna port, for example, as shown in FIG. 8 (c) or FIG. 8 (d), the RE positions of the DMRS antenna ports 7 or 9 are used as they are. However, in order to reduce the RE density, RS may be transmitted only in DMRS OFDM symbols corresponding to half of existing DMRS OFDM symbols.

The antenna port through which the PBCH and the new RS are transmitted becomes antenna port 0, and may have the same antenna port as the legacy CRS. Alternatively, the antenna port through which the PBCH and the new RS are transmitted may be antenna ports 7 or 9. Alternatively, the antenna port through which the PBCH and the new RS are transmitted may be a new antenna port that was not used previously.

* If the number of TX antenna ports is 2

When the transmission of the PBCH for NB LTE is transmitted using two antenna ports, assuming that the antenna ports X and Y are transmitted with the new RS, the RE position where the new RS is transmitted is shown in FIG. 9 (a). As described above, antenna ports X and Y may transmit a new RS through the RE positions where DMRS antenna ports 7, 9 are transmitted, respectively.

Alternatively, when transmission of a PBCH for NB LTE is transmitted using two antenna ports, the RE position where a new RS is transmitted for each antenna port may be as shown in FIG. 9 (b).

Alternatively, when the transmission of the PBCH for NB LTE is transmitted using two antenna ports, as shown in the example of FIG. 9 (c) or 9 (d), the RE position of the DMRS antenna port 7 or 9 transmits a new RS. This is used for the purpose of RS, but RS can be transmitted only through the RE position of half of the existing RS RE position to reduce the RS RE density.

Alternatively, when transmission of a PBCH for NB LTE is transmitted using two antenna ports, in order to reduce the number of OFDM symbols transmitted by a new RS and to minimize resource collision between the new RS and another channel / signal, FIG. 9 (e) Or as shown in FIG. 9 (f), a new RS may be transmitted through two OFDM symbols in a subframe, and a new RS may be transmitted at a total of six RE positions per antenna port in one OFDM symbol. .

10 through 12 illustrate RS structures according to another embodiment of the present invention.

The new RS may be configured as follows in consideration of space frequency block coding (SFBC) transmission and direct current (dc) tone, where 'tone' may correspond to 'subcarrier'. A UE receiving data over one RB region (i.e., 180 kHz bandwidth) may need to use one of the subcarriers in one PRB as a dc tone, in this case, 5 located in the middle of one PRB. Subcarriers No. 6 or 6 can be used as dc tones, due to the physical characteristics of dc tones, the receiver does not detect signals on dc tones and affects them as noise. Therefore, the noise value is reduced, which helps to improve the performance, so it is desirable that no new RS is transmitted on the subcarriers used for these dc tones. In consideration of the characteristics of SFBC to be described, it is preferable that two REs to which one SFBC pair for transmitting data or PBCH (hereinafter, referred to as data / PBCH) are mapped are configured as the most continuous subcarriers. In view of the points, the present invention proposes that a new RS is located at the following RE position.

* When the number of TX antenna ports is 1

If the transmission of the PBCH for NB LTE is transmitted using only one antenna port, d.c. Depending on the location of the subcarrier used as the tone, a new RS may be transmitted at the RE location as shown in FIG. 10 (a) or 10 (b).

* If the number of TX antenna ports is 2

If the transmission of the PBCH for NB LTE is transmitted using only one antenna port, d.c. Depending on the location of the subcarrier used as the tone, a new RS may be transmitted at the RE location as shown in FIG. 11 or 12.

In the case of the RS RE location illustrated in FIG. 11, the RE location where one SFBC pair is transmitted may be configured as a continuous subcarrier, and thus it is easy to transmit data / PBCH using the SFBC scheme.

In the RS patterns of FIGS. 11A and 11D, RSs of two antenna ports may be code division multiplexed and transmitted through the same RE location.

In the case of the RS pattern of FIG. 12, an RS density is increased, thereby improving channel estimation performance.

Considering only the 11 subcarriers except for the 5 or 6 subcarriers located in the center of one PRB, the RE positions according to the RS patterns shown in FIGS. 10 and 11 may be expressed as shown in Table 11 below. The RE position according to the RS patterns illustrated in FIG. 12 may be represented as shown in Table 12.

	0	One	2	3	4	5	6	7	8	9	10	11	12	13
10					R	R							R		R
9
8
7
6
5					R	R							R		R
4
3
2
One
0					R	R							R	R

	0	One	2	3	4	5	6	7	8	9	10	11	12	13
10					R	R							R	R
9					R	R							R		R
8
7
6
5					R	R							R	R
4					R	R							R		R
3
2
One					R	R							R	R
0					R	R							R	R

In Table 11 and Table 12, "R" represents a new RS and a new RS may be mapped to an RE indicated by "R". In Tables 11 and 12, rows represent remaining subcarriers other than subcarriers used as dc tones, and row indexes 0 through 10 represent subcarrier indexes k 'sequentially assigned to the remaining subcarriers. Subcarrier index k 'is given except subcarriers used as dc tones, so subcarrier index k ' ∈ in Tables 11 and 12 {0,1,2,3,4,5,6,7,8,9,10} May be different from the subcarrier index k ∈ {0,1,2,3,4,5,6,7,8,9,10,11} assigned to 12 subcarriers in one PRB. In Tables 11 and 12, columns represent OFDM symbols in a subframe, and column indexes 0 to 13 represent OFDM symbol indexes l ∈ {0,1,2,3,4,5,6,7, 8,9,10,11,12,13}.

13 and 14 illustrate RS structures according to another embodiment of the present invention.

The new RS may be configured as follows in consideration of SFBC transmission. In particular, in order to improve the channel estimation performance, increasing the RS density of the new RS compared to the existing CRS or DMRS can be considered together. In addition, it is preferable that two REs in which one pair of SFBCs are transmitted in order to transmit data / PBCH through SFBC are configured with the most continuous subcarriers. Considering these points, it is suggested that a new RS be located at the following RE position. The proposed contents of the present invention include an RS pattern in which the proposed RS pattern is v-shifted.

* When the number of TX antenna ports is 1

If the transmission of the PBCH for NB LTE is transmitted using only one antenna port, d.c. Depending on the position of the subcarrier used as the tone, the RE position as shown in FIG. 13 (a), 13 (b), 13 (c) or 13 (d) may be used for new RS transmission.

* If the number of TX antenna ports is 2

If the transmission of the PBCH for NB LTE is transmitted using only one antenna port, d.c. Depending on the position of the subcarrier used as the tone, the RE position as shown in FIG. 14 (a), 14 (b), 14 (c) or 14 (d) may be used for new RS transmission.

In the case of the RS RE location illustrated in FIG. 14, the RE location where one SFBC pair is transmitted may be configured as a continuous subcarrier, and thus it is easy to transmit data / PBCH using the SFBC scheme. In addition, according to the RS pattern illustrated in FIG. 14, RSs of two antenna ports may be CDMed and transmitted through the same RE location. In addition, according to the RS pattern illustrated in FIG. 14, an RS density per antenna port is increased, thereby improving channel estimation performance.

Different values of the v-shift may be applied to the new RS according to the physical cell ID or the virtual cell ID. This v-shift value may be equal to the value of the v-shift (ie, v _shift ) applied to the legacy CRS. The v-shift value applied to the new RS may be equal to ' n ^cell _ID mod 6'. Here n ^cell _ID means (physical or virtual) cell ID. Alternatively, the value of the v-shift applied to the new RS may be different from the value of the v-shift applied to the legacy CRS. For example, the v-shift value applied to the new RS may be equal to ' n ^cell _ID mod 3'. Alternatively, the v-shift value applied to the new RS to transmit a new RS to a subcarrier position different from the legacy CRS may be equal to ' n ^cell _ID mode 3 + α'. Alternatively, the v-shift value applied to the new RS may be equal to the v-shift value applied to the legacy CRS plus a value of α. That is, the v-shift value applied to the new RS may be equal to ' n ^cell _ID mod 6 + α'.

15 to 17 illustrate RS structures according to another embodiment of the present invention.

In order to increase RS density and improve channel estimation performance in a frequency selective channel environment, a dense RS may be located for two or four OFDM symbols per antenna port as shown in FIG. 15 or 16. . For example, as shown in FIG. 15 (a) or FIG. 15 (b), the entire REs for two OFDM symbols may be used for transmission of an RS for one antenna port. In case there are two antenna ports, RS may be located as shown in FIG. Since RS overhead can be unnecessarily high, REs located in two OFDM symbols, such as in FIG. 15 (c) or FIG. 15 (d), are used for the transmission of RS for one antenna port, but even or odd The RS pattern, which cuts the RS density in half by placing the RS only at the RE position, can be used for transmission of a new RS. In this case, when there are two antenna ports, a new RS may be located in the PB pair in the same pattern as in FIG. 16 (b), 16 (c), or 16 (d).

One subcarrier of one subcarrier in one PRB is d.c. In consideration of the case of being used as a tone, the RS pattern as shown in FIG. 15 or FIG. 16 may be modified to the RS pattern as shown in FIG. 17. An RS pattern as shown in FIG. 15 or 16 is used for the new RS, with one subcarrier (eg, subcarrier # 5 or # 6) as shown in FIG. 17 (a) being d.c. Used as a tone and may be excluded from the RS transmit RE. Alternatively, an RS pattern as shown in FIG. 15 or FIG. 16 is used for the new RS, and as shown in FIG. 17 (b), two middle subcarriers may be excluded from the RS transmission RE. Alternatively, an RS pattern as shown in FIG. 15 or 16 may be used for the new RS, but subcarriers # 5 and # 11 may be excluded from the RS transmission RE as shown in FIG. 17 (c).

The contents of the present invention include a pattern transmitted through another OFDM symbol position in addition to the proposed OFDM symbol position.

A conventional sequence of DMRS or CRS is generated based on N ^{max, DL} _RB which is the maximum number of PRBs that an LTE system can have, as shown in Equations 3 and 6 below. Therefore, the same RS sequence is generated for the PRB region spaced by the same offset from the center frequency regardless of the cell bandwidth.

The following method may be considered in the sequence generation method of a new RS used in NB-LTE. Different sequence generation methods may be used between the standalone NB-LTE and the in-band NB-LTE. In addition, different sequence generation schemes may be used according to channels through which UE performs decoding based on a new RS. In addition, a different sequence generation scheme may be used for each subframe position where the UE receives a new RS.

Method A. In the case of in-band NB-LTE, a sequence configuration of a new RS may vary according to a position of a PRB region in which an NB-LTE UE operates in a cell in which an NB-LTE region exists. In particular, the sequence configuration of the new RS may vary according to the offset of the PRB region in which the NB-LTE region exists in the cell from the center frequency region of the cell in which the NB-LTE region exists.

Method B. A sequence generation of a new RS may be generated based on one PRB, which is a bandwidth of NB-LTE operation. That is, in generating a new sequence of RS of NB-LTE, N ^{max, DL} _RB may be equal to one. For example, if the RE position of the existing DMRS is applied to the new RS as it is, the RS sequence may be defined as follows.

Where M is the total number of REs of the new RS in the subframe, and c ( i ) is a pseudo-random sequence.

At this time, in order to prevent the randomization with the RS of the neighboring cell because the sequence of the new RS is the same for each PRB region where the NB-LTE operates, the new RS is assigned to the cell ID of the LB-LTE cell. Can be generated to depend on. For example, the random- pseudo sequence c ( i ) may be generated differently according to the cell ID. In the case of in-band NB-LTE, a plurality of NB-LTE regions may exist in the same cell. Although each NB-LTE region exists on the same cell, the plurality of NB-LTE regions may have separate cell IDs that are independent of each other. In this case, the cell ID used to generate the pseudo-random sequence c ( i ) is the cell ID assigned to each NB-LTE region, not the cell ID of the (LTE) cell in which the in-band NB-LTE region exists. Can be.

In the case of in-band NB-LTE, a new RS sequence may be generated using method A, and in the case of standalone NB-LTE, a new RS sequence may be generated. Alternatively, a new RS sequence using the method B may be transmitted in the subframe region in which the PBCH is transmitted, and a new RS sequence using the method A may be transmitted in the subframe region in which the remaining channels are transmitted. Alternatively, a new RS sequence using the method B may be transmitted in the subframe region in which the PBCH and the SIB are transmitted, and a new RS sequence using the method A may be transmitted in the subframe region in which the remaining control / data channels are transmitted.

<B. PBCH  Transmission subframe>

In the case of PBCH, it is preferable to transmit all possible resources, and it is preferable to transmit continuously in at least two subframes. Since it is preferable that the resources available for two subframes match, it is preferable that PBCH is transmitted in subframes # 9 and # 0. For in-band NB IoT, it may be considered that several narrowbands support NB-LTE UEs. In this case, by varying the timing of the PBCH transmitted to each NB, it is possible to change the number of repetitions of the PBCH that can be read by each UE for each coverage enhancement level at a predetermined time. For example, the PBCH is transmitted in a 40 ms period with an offset = 0 ms on the narrowband NB1 and the PBCH is transmitted in a 40 ms period with an offset = 10 ms on the narrow band NB2, so that the UE can read PBCH contents for each coverage enhancement level. ) Can be different. However, according to this method, since the UE does not know the starting point of PBCH detection if the UE does not know the PBCH timing, the complexity of blind decoding may be increased. However, according to this method, PBCH can be shared while maintaining independent NB-LTE cells for each NB. In other words, only one PBCH is transmitted on a cell, and UEs operating on different NBs of the cell, for example, independent NB-LTE cells, may receive the same PBCH. Although several NBs share the cell ID and transmit the same content through MIB / SIB, etc., the multiple NBs may be independently supported by multiple MIBs / SIBs to allow multiple UEs to be supported. On the contrary, common data may be transmitted to one or several NBs.

<C. PBCH  RE Mapping >

If there is an RS for decoding the PBCH in the resource in which the PBCH in the NB-LTE is transmitted, the PBCH may be rate-matched in the RE resource in which the RS is transmitted. The RS may be present according to any of the RS structures proposed in section A.

Meanwhile, as shown in FIGS. 8A, 8C, and 8D, the amount of RE resources to which a new RS is transmitted per OFDM symbol may be smaller than that of the existing DMRS. In this case, the neighboring RE resources (eg, the previous RE resources or the next RE resources in the same OFDM) of the RE resources to which the new RS is transmitted may be left as zero-power REs without being used for transmission of the PBCH. Instead, the new RS can be boosted twice as much power using that power. In this case, the PBCH may be rate-matched in the corresponding zero-power RE resource and transmitted.

When a new RS is transmitted on the NB-LTE, the new RS can transmit up to two (or four, eight) antenna ports, but in reality the new RS uses fewer antenna ports than the maximum number of antenna ports. Can be sent. Depending on the number of TX antenna ports of the eNB or the determination of the eNB, the number of antenna ports through which a new RS is transmitted may vary, and the total number of REs through which a new RS is transmitted and the RE location may vary.

RE mapping of the PBCH may be performed assuming the maximum number of antenna ports for a new RS. That is, assuming that all supported antenna ports for the new RS are used, the PBCH may be rate-matched without being transmitted in the RE location where the new RS exists. In this case, the UE can decode the PBCH without blind detection without knowing the number of antenna ports of the new RS.

Alternatively, RE mapping of the PBCH may be performed assuming the number of actual antenna ports through which a new RS is transmitted. That is, the PBCH may be rate-matched at the RE position where the new RS used in the cell is transmitted. In this case, when the UE does not know the number of antenna ports of the new RS, the UE may need to decode the PBCH through blind detection that attempts to decode the PBCH for each number of antenna ports. However, according to this method, since the PBCH is rate-matched only in the RE (s) to which the RS is actually transmitted, the PBCH can be transmitted without wasting resources.

<D. PBCH  Transmission scheme>

The legacy legacy PBCH was transmitted using a CRS-based transmit diversity scheme. If the number of TX antenna ports is 2, it was transmitted using SFBC.

If the number of TX antenna ports for transmitting PBCH is two, or if the number of TX antenna ports for transmitting PBCH is one but the number of TX antennas (ie, physical antennas) is two or more, the PBCH is based on a new RS. When transmitted, the present invention proposes to transmit / receive the PBCH through the following scheme. The following transmission scheme may be applied to transmission and reception of (E) PDCCH (hereinafter referred to as NB-PDCCH) and PDSCH (hereinafter referred to as NB-PDSCH) of NB-IoT as well as PBCH.

-SFBC

If the number of TX antenna ports is 2, the PBCH may be transmitted using the SFBC technique. In this case, the RE mapping of the PBCH may vary according to the number of REs to which a new RS is transmitted and the RE location.

FIG. 18 is a diagram for describing a concept of space frequency block coding (SFBC).

Applying SFBC using two antenna ports, for example, symbols S (i) and S (i + 1) are transmitted in the same OFDM symbol as shown in FIG. S (i) is transmitted through antenna port y and antenna port y + b at subcarrier x and subcarrier x + a, respectively, and S (i + 1) is the antenna port y + b at subcarrier x and subcarrier x + a, respectively. It may be transmitted through antenna port y. S (i) and S (i + 1) are referred to as one SFBC pair. In this case, when the NB-PDCCH is rate-matched at the RE position where the CSI-RS is transmitted, and when the NB-PDCCH is transmitted, a subcarrier (eg, subcarrier x and subcarrier x + a) in which one SFBC pair is transmitted is a. Can be greater than 2. If the interval between subcarriers in which one SFBC pair is transmitted is greater than 2, a channel change between the subcarrier x and the subcarrier x + a may increase, thereby reducing the performance of the SFBC.

For example, when there is a new RS as shown in FIG. 9 (a), 9 (b), 9 (e), or 9 (f), transmission of a new RS is performed within a specific OFDM symbol in which a PBCH is transmitted. Therefore, the interval between two REs in which one SFBC pair is transmitted becomes 3 REs. In this case, the present invention proposes that the PBCH transmission operates as follows.

Alt 1. Transmission of the PBCH on subcarrier x is rate-matched. NB-PDCCH is not transmitted in the rate-matched RE position. In this case, the SFBC pair may start transmission on the first subcarrier among subcarriers capable of transmitting NB-PDCCH after subcarrier x + a or subcarrier x + a.

Alt 2. Rate-match transmission of N-EPDCCH on both subcarriers x and x + a. At this time, NB-PDCCH is not transmitted in the rate-matched RE position. In this case, the SFBC may start transmission through the first subcarrier among the subcarriers capable of transmitting the NB-PDCCH after the subcarrier x + a + 1 or after the subcarrier x + a + 1.

Alt 3. NB-PDCCH is transmitted on subcarrier x, and transmission of the corresponding SFBC pair is dropped on subcarrier x + a. In this case, transmission of the next SFBC pair may be started on the subcarrier x + a.

On the other hand, when there is a new RS as shown in Fig. 9 (c) or 9 (d), the number of REs that can transmit the PBCH due to the transmission of the new RS in the specific OFDM symbol to which the PBCH is transmitted is an odd number As a result, one SFBC pair may not be transmitted completely within the same OFDM symbol. In this case, when the subcarrier position where one SFBC pair is transmitted is called subcarrier x and subcarrier x + a, the present invention proposes that PBCH transmission operates as follows.

Alt 1. Transmission of the PBCH on subcarrier x is rate-matched. In this case, the corresponding SFBC pair may be transmitted through the next OFDM symbol if the next OFDM symbol exists.

Alt 2. PBCH is transmitted on subcarrier x, and the remaining transmissions of the SFBC pair are dropped. At this time, if the next OFDM symbol is present, transmission of the next SFBC pair may be started in the next OFDM symbol.

Alt 3. Transmission of the PBCH over the corresponding OFDM symbol is rate-matched.

Alt 4. Within an OFDM symbol in which the number of REs for which the PBCH can be transmitted is odd, the transmission of the PBCH in the first RE of the RE resource where the PBCH is transmitted is rate-matched. In this case, the PBCH may be transmitted from the second available RE resource in the corresponding OFDM symbol.

Random precoding (or patterned precoding)

When a PBCH for NB-LTE is transmitted based on a new RS, an arbitrary precoding matrix may be applied to the PBCH and transmitted. The same precoding matrix may be applied to the PBCH in the same PRB region of the same subframe. In this case, in the same PRB region, a new RS may also be transmitted by applying the same precoding matrix as that of the PBCH.

Or when a PBCH for NB-LTE is transmitted based on a new RS, the PBCH may be previously known to the UE or other parameters (eg, subframe index, radio frame index, cell ID, and / or in-band NB LTE). In this case, a precoding matrix that can be inferred by the PRB position for NB-IoT in a cell may be applied. In this case, the new RS may be transmitted without 1) applying the precoding matrix, or 2) applying the same precoding matrix as that of the PBCH.

The same precoding matrix may be applied within the same PRB region of multiple subframes (eg, M subframes) for cross-subframe channel estimation.

In the case of PBCH, NB-PDCCH, and / or NB-PDSCH, the precoding matrix applied to a specific subframe may be determined through all or part of the following elements as follows.

* Time Index: A precoding matrix applied in a specific subframe may be determined according to a subframe index, a slot index, a system frame number (SFN), a subframe bundle index, and the like. Herein, the subframe bundle index is an index for identifying a bundle of the M subframes when the precoding matrix applied to transmission of the PBCH, NB-PDCCH, and / or NB-PDSCH is changed every M subframes. Means.

* Cell ID: The precoding matrix may be determined by the physical cell ID or the virtual cell ID set by the eNB. When the precoding matrix is determined by the virtual cell ID, the virtual cell ID may be set through the SIB or the RRC by the eNB. If the setting of the virtual cell ID is not transmitted, the default value for the virtual cell ID may be the same as the physical cell ID.

Frequency location: The precoding matrix may be determined by a narrowband index on which PBCH, NB-PDCCH, and / or NB-PDSCH are transmitted, a PRB location within a system bandwidth, and the like.

UE ID: In the case of NB-PDCCH and NB-PDSCH transmission, the precoding matrix may be determined by the UE ID.

Antenna diversity (antenna switching)

If the number of TX antenna ports is two, using the two antenna ports of the new RS and the PBCH, arbitrary precoding may be performed in the same manner as the transmission of the distributed EPDCCH. When the two antenna ports are referred to as the antenna ports X and Y, the antenna ports used among the antenna ports X and Y may be determined according to the RE position where the PBCH is transmitted as in the transmission of the distributed EPDCCH. For example, PBCHs transmitted on odd-numbered REs in an OFDM symbol may be transmitted using antenna port X, and PBCHs transmitted on even-numbered REs may be transmitted using antenna port Y. For each antenna port, a PBCH may be transmitted by applying an arbitrary precoding matrix or a patterned precoding matrix, and the same precoding matrix may be applied in the same PRB region of the same subframe. In this case, in the same PRB region, a new RS may also be transmitted by applying the same precoding matrix as that of the PBCH.

The same precoding matrix may be applied in the same PRB region of multiple subframes (eg, M subframes) for cross-subframe channel estimation.

Radio resource management (RRM) may be performed for the NB LTE cell. RRM provides the UE with a mobility experience, allowing UEs and networks to seamlessly manage mobility without significant user intervention, ensuring efficient use of available radio resources, and allowing eNBs to define predefined radios. It is an object of the present invention to provide mechanisms for satisfying radio resource related requirements. Providing Support for Seamless Mobility The main processes performed by the UE include cell search, measurements, handover and cell reselection. The eNB may provide a measurement configuration applicable to the UE for RRM. For example, an eNB may include a measurement configuration in which a UE includes a measurement object, a reporting configuration, a measurement identity, a quantity configuration, and a measurement gap for RRM. May be sent to the UE to trigger a measurement by the UE. The measurement target is an object to which the UE should perform measurement, for example, a single E-UTRA carrier frequency, inter-RAT (Radio Access Technology) UTRA measurement for intra-frequency and inter-frequency measurement. For a single UTRA frequency, a collection of GERAN carrier frequencies for inter-RAT GERAN measurements, a collection of cell (s) on a single carrier frequency for inter-RAT CDMA2000 measurements. Intra-frequency measurement means measurement at the downlink carrier frequency (s) of the serving cell (s), and inter-frequency measurement means any downlink carrier frequency of the downlink carrier frequency (s) of the serving cell (s). Means measurement at different frequency (s). The reporting setup is a list of reporting setups, each reporting setup indicating a reporting criterion indicating a criterion that triggers the UE to send a measurement report and the quantities that the UE should measure in the measurement report and It is set to a reporting format indicating related information. The measurement identifier is a list of measurement identifiers, and each measurement identifier links one measurement object and one report setting. By setting a plurality of measurement identifiers, it is possible not only to link one or more reporting settings to the same measurement object, but also to link one or more measurement objects to the same report setting. The measurement identifier is used as a reference number in the measurement report. The quantity setting defines the measurement quantities and associated filtering, which are used for all event evaluations and related reporting of that measurement type. One filter can be set for each measurement amount. The measurement gap indicates the period in which no UL / DL transmissions are scheduled so that the UE can use to perform the measurement. Upon receiving the measurement setup, the UE performs a reference signal received power (RSRP) measurement and a reference signal received quality (RSRQ) measurement using a CRS on a carrier frequency indicated as a measurement target. . RSRP measurements provide a cell-specific signal strength metric. RSRP measurements are primarily used to rank candidate cells (or candidate CCs) according to signal strength, or as input for handover and cell reselection determination. RSRP is defined for a particular cell (or a particular CC) as a linear average of the power contribution of the REs carrying the CRS within the considered frequency bandwidth. RSRQ is intended to provide a cell-specific signal quality metric, and is used mainly for ranking candidate cells (or candidate CCs) according to signal quality, similar to RSRP. RSRQ can be used as an input for handover and cell reselection, for example, when RSRP measurements do not provide enough information to make reliable mobility decisions. RSRQ is defined as " N * RSRP / RSSI", where N is the number of RBs of the RSSI measurement bandwidth. The received signal strength indicator (RSSI) is the total received wideband power, adjacent channel observed by the UE from all sources, including co-channel serving and non-serving cells, within the measurement bandwidth. It is defined as all kinds of power including interference channel interference, thermal noise and the like. Therefore, it can be said that RSRQ represents a ratio of pure RS power to total power received by the UE.

When performing radio resource management (RRM) measurement in an NB LTE cell, the UE may perform RRM measurement using a new RS. Due to the application of arbitrary precoding or patterned coding, the RS transmitted as a new RS may vary depending on the subframe. In the case of performing RRM measurement using a new RS transmitted periodically in a plurality of subframes, if the precoding matrices applied to the new RS used for the RRM measurement are different from each other, there may be a problem in that the UE performs the measurement properly. . In particular, when performing neighbor-cell measurement, this may be a problem because the UE does not know the precoding matrix applied to each subframe. Therefore, the present invention proposes that it can be assumed that the same precoding matrix is applied to a new RS for the region where the UE performs RRM measurement. For this purpose, the subframe period in which the same precoding matrix is applied to the new RS is 1) the same as the minimum period that the measurement gap can have, or 2) the number of periods that the measurement gap has or the minimum that the measurement gap can have. It can have a divisor of the period.

When the UE receives a set of restricted measurement subframe set from the eNB to perform RRM measurement, the UE may assume that the same precoding matrix has been applied in the subframe. Alternatively, if the UE receives a restricted measurement subframe set from the eNB, the UE may assume that a cell-specific RS is transmitted in the corresponding subframe. And it can be assumed that the UE-specific RS is transmitted in the remaining subframes. In addition, within the constrained measurement subframe set, it may be assumed that a specific / known precoding matrix has been applied to the RS or no precoding has been applied to the RS. In addition, in the remaining subframes, it may be assumed that the UE-specific precoding matrix may be applied with RS.

The transmission of PBCH, NB-PDCCH, and / or NB-PDSCH of NB-IoT operating in in-band environment is transmitted using SFBC technique, and PBCH of NB-IoT operating in stand-alone and / or guard-band environment. The transmission of the NB-PDCCH, and / or NB-PDSCH may be transmitted using any precoding or patterned precoding technique.

The antenna port through which the new RS and PBCH, NB-PDCCH, and / or NB-PDSCH are transmitted may be fixed to a specific value. Alternatively, in case of transmission of NB-PDCCH and NB-PDSCH, a new RS and an antenna port through which NB-PDCCH or NB-PDSCH is transmitted may be determined by UE ID. To use the legacy CRS together for channel estimation, the antenna port through which the new RS and the PBCH, NB-PDCCH, and / or NB-PDSCH are transmitted may be antenna port 0. Alternatively, the antenna port through which the new RS and the PBCH, NB-PDCCH, and / or NB-PDSCH are transmitted may be in a quasi co-located (QCL) relationship with antenna port 0.

The new RS is cell-specific so that the UE can assume that the new RS is always transmitted (at the promised location) in the narrow band in which it operates.

Or a new RS may be UE-specific, so that the UE may assume that it is transmitted (at the promised location) only during the time domain in which it receives the PBCH, NB-PDCCH, and / or NB-PDSCH.

<E. Cell-specific Precoding >

19 illustrates methods of applying precoding to a new reference signal according to the present invention.

The new RS may be an RS commonly used for reception of all channels as well as the PBCH. The precoding matrix applied to the new RS and data / control channels may be as follows.

As shown in FIG. 19A, the precoding matrix applied to the NB-LTE cell may be changed according to a random or predefined pattern in a specific subframe period. Alternatively, the precoding matrix used in each subframe may be inferred by a subframe index, a radio frame index, a cell ID, and / or a PRB position in a cell in the case of in-band NB-IoT LTE. The period and offset at which the precoding matrix is changed can be predefined or set to the UE via MIB, SIB, RRC, or the like.

As shown in FIG. 19B, the precoding matrix is changed in a specific subframe period, and there may be a subframe duration in which the same precoding matrix is applied to each period. In this case, a precoding matrix determined for each precoding matrix period is applied for the corresponding subframe duration. Information on a period and an offset in which the precoding matrix is changed and a subframe duration to which the precoding matrix determined for each period is applied may be predefined or set to the UE through MIB, SIB, RRC, or the like.

In one subframe region, the same precoding matrix determined in the same manner may be applied to the same antenna port. One subframe region may consist of one or a plurality of subframes according to a method of applying a precoding matrix.

Regardless of the type of the channel transmitted in the specific subframe region, the precoding matrix determined according to any one of the aforementioned methods may be applied.

Or the precoding matrix determined according to any one of the methods described above is used for cell-specific channel transmission (e.g., PBCH, broadcast data (SIB, paging and / or random access response), (E) PDCCH in common search space). ) Can only be applied.

Alternatively, the precoding matrix determined according to any one of the above methods may be applied only for transmission of UE-specific channel (eg, unicast data, (E) PDCCH in UE-specific search space).

Alternatively, the precoding matrix applied to the transmission of the cell-specific channel and the precoding matrix applied to the transmission of the UE-specific channel may be separately determined. In this case, the period and offset at which the precoding matrix is changed for the subframe region in which the cell-specific channel is transmitted and the subframe region in which the UE-specific channel is transmitted, and / or such precoding matrix is applied at each period. Each subframe duration may be set.

<F. NB- PBCH  Transfer>

Hereinafter, for convenience of description, the PBCH through which the NB-IoT is transmitted for the NB-IoT is referred to as NB-PBCH. Currently, the legacy PBCH is transmitted once within 10 ms, and the transmission period of the PBCH is 40 ms. In the case of NB-PBCH, the NB-PBCH is transmitted once within 10ms with a period of 640ms, so that in all scenarios (eg in-band NB-IoT, guard-band NB-IoT, standalone NB-IoT) ) Can be satisfied. If an in-band scenario that assumes only non-MBSFN capable subframes is available for NB-IoT operation, the total overhead of NB-PBCH transmission is about 25% of the total available resources in downlink. . To reduce the total overhead of the NB-PBCH, the size of the payload is reduced (so that the number of repetitions can be reduced) or the detection latency or target minimum coupling loss is minimal. Relaxation in terms of coupling loss (MCL) may be considered. In order to reduce the total overhead of the NB-PBCH, multiple NB-IoT carriers or multiple subframes available for NB-IoT operation may be considered. If the delay can be mitigated, the NB-PBCH can be sent somewhat intermittent to reduce the total overhead. Reducing the payload size of the NB-PBCH may increase the payload in SIB1, so reducing the payload size of the NB-PBCH may not solve the overall overhead problem. In this regard, in terms of delay, mitigation of requirements or intermittent NB-PBCH transmission may be further considered.

<G. NB- PBCH Mapping >

A common NB-PBCH mapping / structure may be used for all scenarios, and other NB-PBCH mapping / structure may be used depending on the scenarios. Whether the same structure is used or needs a different structure may depend on the following aspects:

The content of the NB-PDCH in each mode of operation (eg, standalone mode, both in-band mode and guard-band mode),

RS pattern used for NB-PBCH decoding in each mode of operation, and / or

Feasibility of operation mode indication by synchronization signals.

(1) NB-PBCH Content

For all scenarios, at least SFN or frame number index and scheduling information of SIB1 (if SIB1 is not scheduled by the control channel) is needed.

In addition, for the in-band scenario, the following information may be considered. The following information may be transmitted to SIB1 instead of NB-PBCH.

* PRB index or frequency information of the NB-IoT carrier within the legacy system bandwidth. An NB-IoT carrier that transmits SIB1 or other system information (SI) may be indicated in at least NB-PBCH, so that legacy CRS may also be used for SIB1 demodulation.

Valid subframe information for transmission of SIB1 or other SIs. Unlike the standalone or guard-band scenario, the in-band scenario needs to address MBSFN subframes.

(2) RS used for NB-PBCH decoding

In the in-band scenario for data demodulation, a legacy CRS pattern may be employed with an additional RS based on CDM-celled specific RS. Only the CDM cell-specific RS pattern can be considered for the standalone scenario. Since in-band legacy CRS may not be available for NB-PBCH decoding, at least in an in-band scenario another RS pattern may be needed for NB-PBCH decoding. CDM cell-specific RS patterns can be used to provide sufficient RS density for new RS patterns, and the CDM cell-specific RS patterns can be common between in-band NB-PBCH and standalone NB-PBCH. have. For example, the RS pattern of FIG. 11 (a), FIG. 11 (d), or FIG. 14 may be used as the CDM-cell-specific RS pattern.

As another example, the RS pattern of FIG. 20 may be used as the CDM-cell-specific RS pattern. 20 illustrates a cell-specific RS pattern of NB-IoT for two antenna ports. For inter-cell randomization, a v-shift value (eg, v _shift = cell ID% 3) may be used. Where% is the modulo operator.

(3) feasibility of operation mode signaling

Based on some design proposals and performance, approximately 4096 hypotheses that are distinguished from secondary synchronization signals (SSS) seem feasible. In this case, for 504 cell IDs, approximately eight additional values must be carried by the SSS. If the operation mode types are three or four, two values are needed that are left for other purposes, such as the frame index of the SSS transmission. However, the frame index of the SSS transmission can increase the UE blind detection for the SSS and reduce the detection performance. Therefore, if an operation mode is considered, it is more natural to distinguish between in-band scenarios and other scenarios because in-band scenarios and other scenarios may have different NB-PBCH mappings and contents.

<H. Antenna ports and Legacy  CRS Handling>

As a network may have a single or multiple antenna ports, similar to legacy PBCH, the UE may need to blindly search for the number of antenna ports. In consideration of RS overhead versus performance gain by additional antenna ports, the number of antenna ports may be limited to one or two when blindly searching for antenna ports.

In legacy PBCH, the network is assumed to support up to four antenna ports. In terms of NB-IoT mapping, the transmission scheme and the number of supported antenna ports need to be clarified. For legacy CRS, if the UE can assume that the cell ID of the NB-IoT and the cell ID of the legacy carrier are the same, the location of the legacy CRS can be identified even though the UE cannot decode the CRS. However, if rate-matching is considered, then rate-matching assuming four antenna ports needs to be considered, which may have a high overhead compared to puncturing. Also rate-matching is not feasible in in-band scenarios unless the mode of operation is known before NB-PBCH decoding. In this regard, the present invention proposes to use a puncturing mechanism for legacy CRS instead of rate-matching.

21 illustrates a legacy CRS cancellation according to the present invention.

Brute-force puncturing can affect performance. In this case, applying a Walsh code between two PBCH transmissions may be considered. For example, if the NB-PBCH is transmitted in subframes of the same index every 10 ms, the legacy CRS pattern is expected to be the same in each NB-PBCH transmission. Then, for example, the Walsh code [1 1] is applied to the NB-PBCH and the NB-IoT RS in the even-numbered radio frame (hereinafter, NB-RS), and the NB-PBCH and NB- in the odd-numbered radio frame. Walsh code [1-1] may be applied to the RS for IoT (hereinafter, NB-RS). When the UE receives the NB-PBCH, it may cancel out the legacy CRS between two consecutive NB-PBCHs shown in FIG. 21.

On the other hand, when the NB-IoT has a subcarrier spacing of 15 kHz, the adjacent channel leakage ratio (ACCL) is larger than the case where the NB-IoT has a subcarrier spacing of 3.75 kHz. Greater interference to GSM cells). For example, when the NB-IoT system of the 15 kHz subcarrier based on LTE is located in the neighboring frequency region of the GSM system, the NB-IoT system has a greater interference to the GSM system than when the NB-IoT system has a subcarrier spacing of 3.75 kHz. . In the present invention, when the NB-IoT has a 15 kHz subcarrier interval as in the conventional LTE, a method for reducing interference to a cell (eg, GSM cell) located in an adjacent frequency domain is proposed.

The present invention proposes a technique for reducing interference effects on a GSM system located in an adjacent frequency domain, but the present invention relates to a cell in which an NB-IoT cell uses another system other than GSM in an adjacent frequency region (eg, LTE). Cell, NB-IoT cell) may be applied to reduce the interference effect of the NB-IoT cell on the cells of the other system.

22 to 24 illustrate the signal transmission / reception example on the IoT cell according to another embodiment of the present invention.

<I. How to reduce interference to cells (eg GSM cells) located in adjacent frequency domains>

In order to reduce the interference effect on the GSM cell located in the adjacent frequency region, it is proposed that the NB-IoT cell or the LTE cell use the following method. The present invention proposes a transmission scheme in an NB-IoT cell for convenience of description, but the contents of the present invention can be applied to an LTE cell.

Method 1. As shown in FIG. 22 (a), one subcarrier or multiple subcarriers may not be used for NB-IoT transmission for each edge of the NB-IoT cell. Accordingly, the subcarrier (s) belonging to the corresponding subcarrier region may be a null subcarrier, that is, a zero-power subcarrier, which is not used for transmitting any signal / channel. Whether to use the corresponding subcarrier region may be set by the SIB or RRC signal.

Method 2. One subcarrier or multiple subcarriers may not be used for NB-IoT transmission for one edge portion of the NB-IoT cell as shown in FIG. 22 (b). The subcarrier (s) belonging to the subcarrier region may be a null subcarrier, that is, a zero-power subcarrier, which is not used for transmission of any signal / channel. Whether one edge subcarrier region is used and / or location information of an unused subcarrier may be set by an SIB or RRC signal.

Method 3. As shown in Fig. 22 (c), it can be assumed that the transmit power of a signal drops by α dB for one subcarrier or multiple subcarriers, respectively, for both edge portions of an NB-IoT cell. It can be assumed that the transmission power in one subcarrier or multiple subcarriers, respectively, for both edge portions of the NB-IoT cell is dropped by α dB compared to the following power.

Option 1. Average transmit power in other RE / subcarrier domains (of the same OFDM symbol)

Option 2. Average transmit power in the data transmission RE / subcarrier domain (of the same OFDM symbol)

* Option 3. (Average) transmit power in RS transmit RE / subcarrier domain of (same OFDM symbol)

In this case, whether or not power reduction in the corresponding subcarrier region and / or the amount of power reduction (eg, a value of α) may be set by the SIB or RRC signal.

Method 4. As shown in FIG. 22 (d), it may be assumed that a transmission power of a signal drops by α dB in one subcarrier or a plurality of subcarriers for one edge portion of an NB-IoT cell. In this case, it may be assumed that transmission power in one subcarrier (or multiple subcarriers) region of each edge portion of the NB-IoT cell is dropped by α dB compared to the following power.

Option 1. Average transmit power in other RE / subcarrier domains (of the same OFDM symbol)

Option 2. Average transmit power in the data transmission RE / subcarrier domain (of the same OFDM symbol)

* Option 3. (Average) transmit power in RS transmit RE / subcarrier domain of (same OFDM symbol)

In this case, whether or not the power reduction in the corresponding subcarrier region and / or the power reduction (eg, a value of α) may be set by the SIB or RRC signal.

<J. Cell-edge Subcarriers  When not using RS  Pattern>

In NB-IoT, DMRS as shown in FIG. 23 may be used for reception of PBCH, PDSCH, PDCCH, etc. instead of CRS. In this case, if the subcarrier (s) at one or both edges are not used for IoT communication to reduce the impact of interference on the GSM cell, as suggested in section I, some DMRS RE regions may not be used for the transmission of DMRS. do. Therefore, the present invention proposes a DMRS pattern that can be used in such a case.

When the RE positions of DMRS antenna ports 7, 8 are used for DMRS transmission of the NB-IoT, the UE may assume the following modified DMRS pattern.

Method 1. If the first subcarrier is not used, the UE may assume that the DMRS pattern shown in FIG. 24 (a) is applied. In addition, when the last subcarrier is not used, the UE may assume that the DMRS pattern as shown in FIG. 24 (b) is applied. Alternatively, if the subcarriers at both edges are not used, the UE may assume that the same DMRS pattern is applied to FIG. 4 (c). In this case, when all subcarrier regions are used for signal transmission, the RE position of the legacy DMRS may be used as it is.

Method 2. Given DMRS configuration by SIB or RRC signal, the UE may assume that the modified DMRS pattern is applied. The modified DMRS pattern may be the same as in FIG. 24A, 24B, or 24C. If the DMRS configuration is not given by the SIB or RRC signal, the UE may assume that the RE position of the legacy DMRS is used as it is.

Method 3. The DMRS pattern used through the SIB or RRC signal may be set. An example of a DMRS pattern that may be used may be the pattern in FIG. 24 (a), FIG. 24 (b), or FIG. 24 (c). If the DMRS configuration is not given by the SIB or RRC signal, the UE may assume that the RE position of the legacy DMRS is used as it is.

Method 4. Considering the possibility that one or both edge subcarriers are not used, the DMRS pattern as shown in FIG. 24 (c) can always be applied to NB-IoT transmission. That is, the DMRS pattern as shown in FIG. 24C may be used in the NB-IoT cell.

Method 5. The UE may determine the DMRS pattern applied to the cell through reception of the PSS / SSS. For example, the UE may determine a DMRS pattern applied to a corresponding cell through a PSS / SSS sequence and / or an OFDM symbol position.

When the RE positions of the DMRS antenna ports 7, 8, 9, and 10 are used for DMRS transmission of the NB-IoT, the UE may assume the following modified DMRS pattern.

Method 1. If the first subcarrier is not used, the UE may assume that the DMRS pattern shown in FIG. 24 (d) is applied. In addition, when the last subcarrier is not used, the UE may assume that the DMRS pattern as shown in FIG. 24 (e) is applied. Alternatively, if the subcarriers at both edges are not used, the UE may assume that the same DMRS pattern is applied to FIG. 24 (f). If all subcarrier regions are used for signal transmission, the RE position of the legacy DMRS may be used as it is.

Method 2. Given DMRS configuration by SIB or RRC signal, the UE may assume that the modified DMRS pattern is applied. The modified DMRS pattern may be the same as in FIG. 24 (d), FIG. 24 (e), or FIG. 24 (f). If the DMRS configuration is not given by the SIB or RRC signal, the UE may assume that the RE position of the legacy DMRS is used as it is.

Method 3. The DMRS pattern used may be set via an SIB or RRC signal. At this time, an example of the DMRS pattern that can be used may be the pattern of FIG. 24 (d), FIG. 24 (e) or FIG. 24 (f). If the DMRS configuration is not given by the SIB or RRC signal, the UE may assume that the RE position of the legacy DMRS is used as it is.

Method 4. Considering the possibility that one or both edge subcarriers are not used, the DMRS pattern as shown in FIG. 24 (f) can always be applied. That is, the DMRS pattern as shown in FIG. 24 (f) may be used in the NB-IoT cell.

Method 5. The UE may determine the DMRS pattern applied to the cell through reception of the PSS / SSS. For example, the UE may determine a DMRS pattern applied to a corresponding cell through a PSS / SSS sequence and / or an OFDM symbol position.

<K. How to determine the size of a transport block (TB)>

As suggested in Section I, if one side or both edge subcarriers are not used to reduce interference effects on GSM cells, the amount of RE resources available for actual data transmission is reduced. In this case, if the existing TB size determination method is used as it is, the determined TB size may become larger than the amount of resources that can actually transmit data, and thus data may not be properly transmitted.

Therefore, the present invention proposes methods for preventing the effective code rate of data transmission from increasing too much.

When subcarriers of one or both edges are not used for transmission of signals, the following method can be used to solve the problem of increasing an effective code rate.

Method 1. When the TB size determined as in the conventional method is called TBS, the final TB size, TBS ', may be determined as floor (TBS * alpha) or ceil (TBS * alpha). In this case, 'alpha' may be a value smaller than 1.

Method 2. When the maximum TB size that can be transmitted in the NB-IoT system exists, the smaller of the TB size determined as in the conventional method and the maximum TB size that can be transmitted in the NB-IoT system can be determined as the final TB size. Can be. If the maximum TB size that can be transmitted in the NB-IoT system is called max_TBS, and the TB size determined as in the conventional method is TBS, the final TB size TBS 'may be equal to min (max_TBS, TBS).

Method 3. After TB size is determined based on one TTI (e.g., one subframe), the TB maps to resources of multiple TTIs (e.g., two subframes) in order to increase the effective code rate. Can be sent.

The proposed method (s) for solving the problem of increasing the effective code rate may be applied by the following viewpoints / methods.

Option 1. In NB-IoT, a method for solving the problem of increasing the effective code rate can always be applied.

Option 2. In NB-IoT, if one or both cell-edge subcarriers are not used for the transmission of the signal, a method for solving the problem of increasing the effective code rate may be applied.

Option 3. If the setting regarding prevention of effective code rate increase is given by the SIB or RRC signal, a method for solving the problem of increasing the effective code rate may be applied.

25 is a block diagram showing the components of the transmitter 10 and the receiver 20 for carrying out the present invention.

The transmitter 10 and the receiver 20 are radio frequency (RF) units 13 and 23 capable of transmitting or receiving radio signals carrying information and / or data, signals, messages, and the like, and in a wireless communication system. The device is operatively connected to components such as the memory 12 and 22, the RF unit 13 and 23, and the memory 12 and 22, which store various types of information related to communication, and controls the components. And a processor (11, 21) configured to control the memory (12, 22) and / or the RF unit (13, 23), respectively, to perform at least one of the embodiments of the invention described above.

The memories 12 and 22 may store a program for processing and controlling the processors 11 and 21, and may temporarily store input / output information. The memories 12 and 22 may be utilized as buffers.

The processors 11 and 21 typically control the overall operation of the various modules in the transmitter or receiver. In particular, the processors 11 and 21 may perform various control functions for carrying out the present invention. The processors 11 and 21 may also be called controllers, microcontrollers, microprocessors, microcomputers, or the like. The processors 11 and 21 may be implemented by hardware or firmware, software, or a combination thereof. When implementing the present invention using hardware, application specific integrated circuits (ASICs) or digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays) may be provided in the processors 400a and 400b. Meanwhile, when implementing the present invention using firmware or software, the firmware or software may be configured to include a module, a procedure, or a function for performing the functions or operations of the present invention, and configured to perform the present invention. The firmware or software may be provided in the processors 11 and 21 or stored in the memory 12 and 22 to be driven by the processors 11 and 21.

The processor 11 of the transmission apparatus 10 is predetermined from the processor 11 or a scheduler connected to the processor 11 and has a predetermined encoding and modulation on a signal and / or data to be transmitted to the outside. After performing the transmission to the RF unit 13. For example, the processor 11 converts the data sequence to be transmitted into K layers through demultiplexing, channel encoding, scrambling, and modulation. The coded data string is also called a codeword and is equivalent to a transport block, which is a data block provided by the MAC layer. One transport block (TB) is encoded into one codeword, and each codeword is transmitted to a receiving device in the form of one or more layers. The RF unit 13 may include an oscillator for frequency upconversion. RF unit 13 is N _t ( N _t May include a positive integer greater than or equal to 1).

The signal processing of the receiver 20 is the reverse of the signal processing of the transmitter 10. Under the control of the processor 21, the RF unit 23 of the receiving device 20 receives a radio signal transmitted by the transmitting device 10. The RF unit 23 may include N _r receive antennas, and the RF unit 23 frequency down-converts each of the signals received through the receive antennas to restore the baseband signal. . The RF unit 23 may include an oscillator for frequency downconversion. The processor 21 may decode and demodulate a radio signal received through a reception antenna to restore data originally transmitted by the transmission apparatus 10.

The RF units 13, 23 have one or more antennas. The antenna transmits a signal processed by the RF units 13 and 23 to the outside under the control of the processors 11 and 21, or receives a radio signal from the outside to receive the RF unit 13. , 23). Antennas are also called antenna ports. Each antenna may correspond to one physical antenna or may be configured by a combination of more than one physical antenna elements. The signal transmitted from each antenna can no longer be decomposed by the receiver 20. A reference signal (RS) transmitted in correspondence with the corresponding antenna defines the antenna as viewed from the perspective of the receiver 20, and whether the channel is a single radio channel from one physical antenna or includes the antenna. Regardless of whether it is a composite channel from a plurality of physical antenna elements, the receiver 20 enables channel estimation for the antenna. That is, the antenna is defined such that a channel carrying a symbol on the antenna can be derived from the channel through which another symbol on the same antenna is delivered. In the case of an RF unit supporting a multi-input multi-output (MIMO) function for transmitting and receiving data using a plurality of antennas, two or more antennas may be connected.

In the embodiments of the present invention, the UE operates as the transmitter 10 in the uplink and the receiver 20 in the downlink. In the embodiments of the present invention, the eNB operates as the receiving device 20 in the uplink, and operates as the transmitting device 10 in the downlink. Hereinafter, the processor, the RF unit and the memory provided in the UE will be referred to as a UE processor, the UE RF unit and the UE memory, respectively, and the processor, the RF unit and the memory provided in the eNB will be referred to as an eNB processor, the eNB RF unit and the eNB memory, respectively.

The eNB processor of the present invention may configure NB-IoT according to any one of the above-described proposed methods of the present invention. For example, the eNB processor may be configured to allocate channel (s) for NB-IoT and / or RS for NB-IoT according to any one of the proposed methods of the present invention. The eNB processor may control the eNB RF unit to transmit channel (s) for NB-IoT and / or RS for NB-IoT on an NB-IoT cell according to any one of the proposed methods of the present invention.

It may be assumed that the UE processor of the present invention configures the NB-IoT according to any one of the above-described proposed methods of the present invention. For example, the UE processor may be configured to demodulate or decode a received signal assuming that channel (s) for NB-IoT and / or RS for NB-IoT are allocated according to any one of the proposed methods of the present invention. have. The UE processor may control the UE RF unit to receive channel (s) for NB-IoT and / or RS for NB-IoT on an NB-IoT cell according to any one of the proposed methods of the present invention.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable those skilled in the art to implement and practice the invention. Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Embodiments of the present invention may be used in a base station or user equipment or other equipment in a wireless communication system.

Claims (20)

1. When the user equipment receives a downlink signal through narrowband internet of things (NB-IoT),

   Receiving downlink data and the reference signal for the NB-IoT on one resource block in a subframe; And

   Demodulating the downlink data based on the reference signal;

   The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

   The reference signal is received in the reference signal pattern of the following table on the one resource block in the subframe:

   TABLE 1

   

   Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

   Downlink signal receiving method.
2. The method of claim 1,

   The reference signal pattern of Table 1 is a reference signal pattern having a frequency shift value corresponding to an identifier of a cell in which one resource block is located among a plurality of reference signal patterns having different frequency shift values.

   Downlink signal receiving method.
3. The method of claim 1,

   The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Received as:

   TABLE 2

   

   ,

   Downlink signal receiving method.
4. The method of claim 1,

   The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Received as:

   TABLE 3

   

   ,

   Downlink signal receiving method.
5. The method according to any one of claims 1 to 4,

   The DC subcarrier is a subcarrier of k = 5 or k = 6 among the twelve subcarriers k0 {0,1, ..., 11} in the one resource block,

   Downlink signal receiving method.
6. In transmitting a downlink signal to a narrowband internet of things (NB-IoT) by the base station,

   Transmitting the downlink data and the NB-IoT reference signal for supporting the downlink data on one resource block in a subframe,

   The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

   The reference signal is transmitted in the reference signal pattern of the following table on the one resource block in the subframe:

   TABLE 1

   

   Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

   Downlink signal transmission method.
7. The method of claim 6,

   The reference signal pattern of Table 1 is a reference signal pattern having a frequency shift value corresponding to an identifier of a cell in which one resource block is located among a plurality of reference signal patterns having different frequency shift values.

   Downlink signal transmission method.
8. The method of claim 6,

   The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Sent to:

   TABLE 2

   

   ,

   Downlink signal transmission method.
9. The method of claim 6,

   The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Sent to:

   TABLE 3

   

   ,

   Downlink signal transmission method.
10. The method according to any one of claims 6 to 9,

    The DC subcarrier is a subcarrier of k = 5 or k = 6 among the twelve subcarriers k0 {0,1, ..., 11} in the one resource block,

    Downlink signal transmission method.
11. When the user equipment receives a downlink signal through narrowband internet of things (NB-IoT),

    A radio frequency (RF) unit, and

    A processor configured to control the RF unit, the processor comprising:

    Controlling the RF unit to receive downlink data and the reference signal for the NB-IoT on one resource block in a subframe; And

    And demodulate the downlink data based on the reference signal,

    The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

    The reference signal is received in the reference signal pattern of the following table on the one resource block in the subframe:

    TABLE 1

    

    Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

    User device.
12. The method of claim 11,

    The reference signal pattern of Table 1 is a reference signal pattern having a frequency shift value corresponding to an identifier of a cell in which one resource block is located among a plurality of reference signal patterns having different frequency shift values.

    User device.
13. The method of claim 11,

    The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Received as:

    TABLE 2

    

    ,

    User device.
14. The method of claim 11,

    The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Received as:

    TABLE 3

    

    ,

    User device.
15. The method according to any one of claims 11 to 14,

    The DC subcarrier is a subcarrier of k = 5 or k = 6 among the twelve subcarriers k0 {0,1, ..., 11} in the one resource block,

    User device.
16. In transmitting a downlink signal to a narrowband internet of things (NB-IoT) by the base station,

    A radio frequency (RF) unit, and

    A processor configured to control the RF unit, the processor comprising:

    And control the RF unit to transmit downlink data and the NB-IoT reference signal for supporting the downlink data on one resource block in a subframe,

    The NB-IoT uses a limited channel bandwidth for the one resource block including 12 subcarriers in the frequency domain,

    The reference signal is transmitted in the reference signal pattern of the following table on the one resource block in the subframe:

    TABLE 1

    

    Where a row is the remaining subcarriers k'∈ {0, except for the DC subcarriers used as DC tones among the twelve subcarriers k∈ {0,1, ..., 11} of the one resource block. 1, ..., 10}, and a column represents orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and R represents the reference signal.

    Base station.
17. The method of claim 16,

    The reference signal pattern of Table 1 is a reference signal pattern having a frequency shift value corresponding to an identifier of a cell in which one resource block is located among a plurality of reference signal patterns having different frequency shift values.

    Base station.
18. The method of claim 16,

    The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Sent to:

    TABLE 2

    

    ,

    Base station.
19. The method of claim 16,

    The reference signal includes a reference signal R1 of a first antenna port for the NB-IoT and a reference signal R2 of a second antenna port for the NB-IoT, wherein the reference signal R1 and the reference signal R2 are patterns of the following table. Sent to:

    TABLE 3

    

    Base station.
20. The method according to any one of claims 16 to 19,

    The DC subcarrier is a subcarrier of k = 5 or k = 6 among the twelve subcarriers k0 {0,1, ..., 11} in the one resource block,

    Base station.

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