WO2019004735A1 - Method and apparatus for transceiving wireless signal in wireless communication system - Google Patents

Abstract

The present invention relates to a wireless communication system, and particularly, to a method and an apparatus for same, the method comprising: a step for repeatedly receiving a downlink synchronization signal; a step for detecting the downlink synchronization signal; and a step of detecting a duplex mode in a time domain on the basis of the repetition interval of the downlink synchronization signal, wherein the repetition interval is N1 when the duplex mode is FDD, the repetition interval is N2 when the duplex mode is TDD, and wherein N1 is smaller than N2.

Description

Method and apparatus for transmitting and receiving wireless signals in a wireless communication system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system, and more particularly, to a wireless signal transmission and reception method and apparatus. The wireless communication system includes a Narrowband Internet of Things (NB-IoT) -based wireless communication system.

Background of the Invention [0002] Wireless communication systems are widely deployed to provide various types of communication services such as voice and data. Generally, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access) systems.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for efficiently performing a wireless signal transmission and reception process.

The technical problems to be solved by the present invention are not limited to the technical problems and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method of detecting a duplex mode in a wireless communication system, the method comprising: repeatedly receiving a downlink synchronization signal; Detecting the downlink synchronization signal; And detecting the duplex mode based on a repetition interval of the downlink synchronization signal in a time domain, wherein when the duplex mode is FDD (Frequency Division Duplex), the repetition interval is N1, and the duplex mode is TDD (Time Division Duplex), the repetition interval is N2, and N1 is smaller than N2.

According to another aspect of the present invention, there is provided a terminal used in a wireless communication system, the terminal comprising: a Radio Frequency (RF) module; And a processor configured to repeatedly receive the downlink synchronization signal, detect the downlink synchronization signal, and detect a duplex mode based on a repetition interval of the downlink synchronization signal in the time domain, If the duplex mode is Frequency Division Duplex (FDD), the repetition interval is N1, and if the duplex mode is TDD (Time Division Duplex), the repetition interval is N2 and N1 is less than N2.

Preferably, the downlink synchronization signal includes a Narrowband Primary Synchronization Signal (NPSS). In the FDD mode, N1 corresponds to one radio frame, and in the TDD mode, N2 corresponds to a plurality of radio frames.

Preferably, the NPSS is a Zadoff-chu sequence of length 11 defined by a root index, the root index is n in FDD mode, the root index is 11-n in TDD mode, n May be an integer.

Preferably, the NSSS is received via 11 consecutive OFDM symbols to which a cover code is applied, and in the FDD mode, the cover code is [1 1 1 -1 -1 -1 1 1 -1 -1] The cover code may be [1 1 -1 1 -1 -1 -1 -1 -1 -1 1].

Preferably, the downlink synchronization signal includes NSSS (Narrowband Secondary Synchronization Signal). In the FDD mode, N1 corresponds to two radio frames. In the TDD mode, N2 corresponds to 2 * m radio frames, m may be an integer of 1 or more.

Preferably, the method further comprises repeatedly receiving a Narrowband Reference Signal (NRS), wherein the initialization value of the sequence used to generate the NRS is P for FDD mode, P + a for TDD mode, ID (Narrowband Cell Identity), and a may represent a non-zero integer.

Preferably, the wireless communication system may include a wireless communication system supporting Narrowband Internet of Things (NB-IoT).

According to the present invention, wireless signal transmission and reception can be efficiently performed in a wireless communication system.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 illustrates physical channels used in a 3GPP LTE (-A) system, which is an example of a wireless communication system, and a general signal transmission method using them.

Fig. 2 illustrates the structure of a radio frame.

3 illustrates a resource grid of a downlink slot.

4 shows a structure of a downlink sub-frame.

5 illustrates a structure of an uplink subframe used in LTE (-A).

Figure 6 illustrates the structure of a self-contained subframe.

Figure 7 illustrates the frame structure defined in 3GPP NR.

Figure 8 illustrates the placement of an in-band anchor carrier at an LTE bandwidth of 10 MHz.

FIG. 9 illustrates a location where an NB-IoT downlink physical channel / signal is transmitted in an FDD LTE system.

FIG. 10 illustrates resource allocation of an NB-IoT signal and an LTE signal in an in-band mode.

11-14 illustrate an existing and NSSS resource mapping according to the present invention.

Figures 15 to 19 illustrate the cross-correlation properties of the conventional and the NSSS according to the present invention.

20 illustrates a duplex mode detection process according to the present invention.

FIG. 21 illustrates a base station and a terminal that can be applied to the present invention.

The following description is to be understood as illustrative and non-limiting, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access And can be used in various wireless access systems. CDMA may be implemented in radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. The TDMA may be implemented in a wireless technology such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long term evolution (LTE) is part of E-UMTS (Evolved UMTS) using E-UTRA and LTE-A (Advanced) is an evolved version of 3GPP LTE. For clarity of description, 3GPP LTE / LTE-A is mainly described, but the technical idea of the present invention is not limited thereto.

In a wireless communication system, a terminal receives information from a base station through a downlink (DL), and the terminal transmits information through an uplink (UL) to a base station. The information transmitted and received by the base station and the terminal includes data and various control information, and various physical channels exist depending on the type / use of the information transmitted / received.

1 is a view for explaining a physical channel used in a 3GPP LTE (-A) system and a general signal transmission method using the same.

The terminal that is powered on again or the cell that has entered a new cell performs an initial cell search operation such as synchronizing with the base station in step S101. To this end, a mobile station receives a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from a base station and synchronizes with the base station and stores information such as a cell identity . Then, the terminal can receive the physical broadcast channel (PBCH) from the base station and obtain the in-cell broadcast information. Meanwhile, the UE can receive the downlink reference signal (DL RS) in the initial cell search step to check the downlink channel state.

Upon completion of the initial cell search, the UE receives a Physical Downlink Control Channel (PDCCH) and a physical downlink control channel (PDSCH) according to physical downlink control channel information in step S102, System information can be obtained.

Then, the terminal may perform a random access procedure such as steps S103 to S106 to complete the connection to the base station. To this end, the UE transmits a preamble through a Physical Random Access Channel (PRACH) (S103), and transmits a response message for a preamble through the physical downlink control channel and the corresponding physical downlink shared channel (S104). In the case of contention based random access, the transmission of the additional physical random access channel (S105) and the physical downlink control channel and corresponding physical downlink shared channel reception (S106) ). ≪ / RTI >

The UE having performed the procedure described above transmits a physical downlink control channel / physical downlink shared channel reception step S107 and a physical uplink shared channel (PUSCH) / physical downlink shared channel A Physical Uplink Control Channel (PUCCH) transmission (S108) may be performed. The control information transmitted from the UE to the Node B is collectively referred to as Uplink Control Information (UCI). The UCI includes HARQ ACK / NACK (Hybrid Automatic Repeat and Request Acknowledgment / Negative ACK), SR (Scheduling Request), CSI (Channel State Information) The CSI includes a Channel Quality Indicator (CQI), a Precoding Matrix Indicator (PMI), a Rank Indication (RI), and the like. The UCI is generally transmitted through the PUCCH, but may be transmitted via the PUSCH when the control information and the traffic data are to be simultaneously transmitted. In addition, UCI can be transmitted non-periodically through the PUSCH according to the request / instruction of the network.

Fig. 2 illustrates the structure of a radio frame. The uplink / downlink data packet transmission is performed in units of subframes, and a subframe is defined as a time interval including a plurality of symbols. The 3GPP LTE standard supports a Type 1 radio frame structure applicable to Frequency Division Duplex (FDD) and a Type 2 radio frame structure applicable to TDD (Time Division Duplex).

2 (a) illustrates the structure of a Type 1 radio frame. The downlink radio frame is composed of 10 subframes, and one subframe is composed of two slots in a time domain. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). For example, the length of one subframe may be 1 ms and the length of one slot may be 0.5 ms. One slot includes a plurality of OFDM symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. In the 3GPP LTE system, since OFDM is used in the downlink, an OFDM symbol represents one symbol period. An OFDM symbol may also be referred to as an SC-FDMA symbol or a symbol interval. A resource block (RB) as a resource allocation unit may include a plurality of consecutive subcarriers in one slot.

The number of OFDM symbols included in the slot may vary according to the configuration of the CP (Cyclic Prefix). CP has an extended CP and a normal CP. For example, when an OFDM symbol is configured by a normal CP, the number of OFDM symbols included in one slot may be seven. When the OFDM symbol is configured by the extended CP, since the length of one OFDM symbol is increased, the number of OFDM symbols included in one slot is smaller than that of the normal CP. For example, in the case of the extended CP, the number of OFDM symbols included in one slot may be six. If the channel state is unstable, such as when the UE moves at a high speed, an extended CP may be used to further reduce inter-symbol interference.

When a normal CP is used, the slot includes 7 OFDM symbols, so that the subframe includes 14 OFDM symbols. The first three OFDM symbols at the beginning of a subframe may be allocated to a physical downlink control channel (PDCCH), and the remaining OFDM symbols may be allocated to a physical downlink shared channel (PDSCH).

2 (b) illustrates the structure of a Type 2 radio frame. The Type 2 radio frame is composed of two half frames. The half frame includes 4 (5) normal sub-frames and 1 (0) special sub-frames. The normal subframe is used for uplink or downlink according to the UL-DL configuration (Uplink-Downlink Configuration). The subframe consists of two slots.

Table 1 illustrates a subframe configuration in a radio frame according to the UL-DL configuration.

Uplink-downlink configuration

Downlink-to-Uplink Switch point periodicity

Subframe number

0

One

2

3

4

5

6

7

8

9

0

5ms

D

S

U

U

U

D

S

U

U

U

One

5ms

D

S

U

U

D

D

S

U

U

D

2

5ms

D

S

U

D

D

D

S

U

D

D

3

10ms

D

S

U

U

U

D

D

D

D

D

4

10ms

D

S

U

U

D

D

D

D

D

D

5

10ms

D

S

U

D

D

D

D

D

D

D

6

5ms

D

S

U

U

U

D

S

U

U

D

In the table, D denotes a downlink subframe, U denotes an uplink subframe, and S denotes a special subframe. The special subframe includes a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). The DwPTS is used for initial cell search, synchronization, or channel estimation in the UE. UpPTS is used to synchronize the channel estimation at the base station and the uplink transmission synchronization of the UE. The guard interval is a period for eliminating the interference caused in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink. The structure of the radio frame is merely an example, and the number of subframes in the radio frame, The number of symbols, and the number of symbols may be variously changed.

3 illustrates a resource grid of a downlink slot.

Referring to FIG. 3, the downlink slot includes a plurality of OFDM symbols in the time domain. Here, one downlink slot includes seven OFDM symbols, and one resource block (RB) is illustrated as including 12 subcarriers in the frequency domain. However, the present invention is not limited thereto. Each element on the resource grid is referred to as a Resource Element (RE). One RB includes 12 x 7 REs. The number NDL of RBs included in the downlink slot depends on the downlink transmission band. The structure of the uplink slot may be the same as the structure of the downlink slot.

4 illustrates a structure of a downlink subframe.

Referring to FIG. 4, a maximum of 3 (4) OFDM symbols located in front of a first slot in a subframe corresponds to a control region to which a control channel is allocated. The remaining OFDM symbol corresponds to a data area to which a physical downlink shared chanel (PDSCH) is allocated, and the basic resource unit of the data area is RB. Examples of downlink control channels used in LTE include physical control format indicator channel (PCFICH), physical downlink control channel (PDCCH), physical hybrid ARQ indicator channel (PHICH), and the like. The PCFICH is transmitted in the first OFDM symbol of the subframe and carries information about the number of OFDM symbols used for transmission of the control channel in the subframe. The PHICH is a response to an uplink transmission and carries an HARQ ACK / NACK (acknowledgment / negative-acknowledgment) signal. The control information transmitted via the PDCCH is referred to as DCI (downlink control information). The DCI includes uplink or downlink scheduling information or an uplink transmission power control command for an arbitrary terminal group.

The control information transmitted through the PDCCH is called DCI (Downlink Control Information). The DCI format defines the formats 0, 3, 3A and 4 for the uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for the downlink. Depending on the DCI format, the type of the information field, the number of information fields, and the number of bits of each information field are different. For example, the DCI format may include a hopping flag, an RB assignment, a modulation coding scheme (MCS), a redundancy version (RV), a new data indicator (NDI), a transmit power control (TPC) A HARQ process number, a precoding matrix indicator (PMI) confirmation, and the like. Therefore, the size (size) of the control information matched to the DCI format differs according to the DCI format. On the other hand, an arbitrary DCI format can be used for transmission of two or more types of control information. For example, DCI format 0 / 1A is used to carry either DCI format 0 or DCI format 1, which are separated by a flag field.

The PDCCH includes a transmission format and a resource allocation of a downlink shared channel (DL-SCH), resource allocation information on an uplink shared channel (UL-SCH), paging information on a paging channel (PCH), system information , Resource allocation information of a higher-layer control message such as a random access response transmitted on the PDSCH, transmission power control command for an individual terminal in an arbitrary terminal group, activation of VoIP (voice over IP), and the like . A plurality of PDCCHs may be transmitted within the control domain. The UE can monitor a plurality of PDCCHs. The PDCCH is transmitted on one or a plurality of consecutive control channel element (CCE) aggregations. The CCE is a logical allocation unit used to provide a PDCCH of a predetermined coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups (REGs). The format of the PDCCH and the number of bits of the available PDCCH are determined according to the correlation between the number of CCEs and the code rate provided by the CCE. The base station determines the PDCCH format according to the DCI to be transmitted to the UE, and adds a CRC (cyclic redundancy check) to the control information. The CRC is masked with a unique identifier (called a radio network temporary identifier (RNTI)) according to the owner of the PDCCH or usage purpose. If the PDCCH is for a particular terminal, the unique identifier of the terminal (e.g., C-RNTI (cell-RNTI)) is masked in the CRC. In another example, if the PDCCH is for a paging message, a paging indication identifier (e.g., P-RNTI (p-RNTI)) is masked to the CRC. If the PDCCH is related to system information (more specifically, a system information block (SIB) described later), a system information identifier (e.g. SI-RNTI) is masked in the CRC. A random access-RNTI (RA-RNTI) is masked in the CRC to indicate a random access response, which is a response to the transmission of the terminal's random access preamble.

The PDCCH carries a message known as Downlink Control Information (DCI), and the DCI includes resource allocation and other control information for one terminal or terminal group. In general, a plurality of PDCCHs may be transmitted in one subframe. Each PDCCH is transmitted using one or more CCEs (Control Channel Elements), and each CCE corresponds to nine sets of four resource elements. The four resource elements are referred to as Resource Element Groups (REGs). Four QPSK symbols are mapped to one REG. The resource element assigned to the reference signal is not included in the REG, and thus the total number of REGs within a given OFDM symbol depends on the presence of a cell-specific reference signal. The REG concept (i.e., group-by-group mapping, each group including four resource elements) is also used for other downlink control channels (PCFICH and PHICH). That is, REG is used as a basic resource unit of the control area. Four PDCCH formats are supported as listed in Table 2.

PDCCH format	Number of CCEs (n)	Number of REGs	Number of PDCCH bits
0	One	9	72
One	2	8	144
2	4	36	288
3	5	72	576

CCEs are used consecutively numbered, and in order to simplify the decoding process, a PDCCH with a format composed of n CCEs can only be started with a CCE having the same number as a multiple of n. The number of CCEs used for transmission of a specific PDCCH is determined by the base station according to the channel condition. For example, if the PDCCH is for a terminal with a good downlink channel (e.g., close to the base station), a single CCE may be sufficient. However, for a terminal with a bad channel (e. G., Near cell boundaries), eight CCEs may be used to obtain sufficient robustness. In addition, the power level of the PDCCH can be adjusted to the channel conditions. The approach introduced in the LTE is to define a limited set of CCE locations where the PDCCH can be located for each terminal. A limited set of CCE locations where a terminal can locate its PDCCH may be referred to as a Search Space (SS). In LTE, the search space has a different size according to each PDCCH format. In addition, UE-specific and common search spaces are separately defined. The UE-Specific Search Space (USS) is set individually for each UE, and the range of the Common Search Space (CSS) is known to all UEs. The UE-specific and common search space may overlap for a given UE. In case of having a fairly small search space, since there is no remaining CCE when some CCE locations are allocated in a search space for a specific UE, the base station in the given subframe may not be able to find CCE resources to transmit PDCCH to all available UEs. In order to minimize the possibility of such blocking leading to the next sub-frame, a UE-specific hopping sequence is applied to the starting position of the UE-specific search space.

Table 3 shows the sizes of common and UE-specific search spaces.

PDCCH format	Number of CCEs (n)	Number of candidates in common search space	Number of candidates in dedicated search space
0	One	-	6
One	2	-	6
2	4	4	2
3	8	2	2

In order to keep the computational load under the total number of blind decodings (BDs) under control, the terminal is not required to search all defined DCI formats simultaneously. Generally, within a UE-specific search space, the terminal always searches formats 0 and 1A. Formats 0 and 1A have the same size and are separated by flags in the message. In addition, the terminal may be required to receive an additional format (e.g., 1, 1B or 2 depending on the PDSCH transmission mode set by the base station). In the common search space, the terminal searches Formats 1A and 1C. Further, the terminal can be set to search Format 3 or 3A. Formats 3 and 3A have the same size as formats 0 and 1A and can be distinguished by scrambling the CRC with different (common) identifiers, rather than with a terminal-specific identifier. PDSCH transmission scheme according to transmission mode, and information contents of DCI formats are listed below. Transmission Mode (TM)

● Transmission mode 1: Transmission from single base station antenna port

● Transmission mode 2: Transmit diversity

● Transmission mode 3: Open-loop space multiplexing

● Transmission mode 4: closed-loop spatial multiplexing

● Transmission mode 5: Multi-user MIMO

● Transmission mode 6: closed-loop rank-1 precoding

● Transmission mode 7: Single-antenna port (port 5) transmission

● Transmission Mode 8: Transmission of dual-layer transmission (ports 7 and 8) or single-antenna port (ports 7 or 8)

● Transmission mode 9: Transmission of up to 8 layers (ports 7 to 14) or single-antenna port (ports 7 or 8)

DCI format

● Format 0: Resource Grant for PUSCH transmission (uplink)

● Format 1: Resource allocation for single codeword PDSCH transmission ( transmission modes 1, 2 and 7)

● Format 1A: Compact signaling of resource allocation for single codeword PDSCH (all modes)

Format 1B: Compact resource allocation for PDSCH (mode 6) using rank-1 closed-loop precoding

● Format 1C: Very compact resource allocation for PDSCH (eg, paging / broadcast system information)

● Format 1D: Compact resource allocation for PDSCH (mode 5) using multi-user MIMO

Format 2: Closed - Resource allocation for PDSCH (mode 4) of root MIMO operation

Format 2A: resource allocation for PDSCH (mode 3) of open-loop MIMO operation

● Format 3 / 3A: Power control command with 2-bit / 1-bit power adjustment value for PUCCH and PUSCH

5 illustrates a structure of an uplink subframe used in LTE (-A).

Referring to FIG. 5, the subframe 500 is composed of two 0.5 ms slots 501. Assuming a length of a normal cyclic prefix (CP), each slot is composed of 7 symbols 502, and one symbol corresponds to one SC-FDMA symbol. A resource block (RB) 503 is a resource allocation unit corresponding to 12 subcarriers in the frequency domain and one slot in the time domain. The structure of the uplink sub-frame of the LTE (-A) is roughly divided into a data area 504 and a control area 505. The data region refers to a communication resource used for transmitting data such as voice and packet transmitted to each terminal and includes a physical uplink shared channel (PUSCH). The control region means a communication resource used for transmitting an uplink control signal, for example, a downlink channel quality report from each terminal, a reception ACK / NACK for a downlink signal, an uplink scheduling request, etc., and a PUCCH Control Channel). A sounding reference signal (SRS) is transmitted through a SC-FDMA symbol located last in the time axis in one subframe. The SRSs of the UEs transmitted in the last SC-FDMA of the same subframe can be classified according to the frequency location / sequence. The SRS is used to transmit the uplink channel state to the base station, and is periodically transmitted according to the subframe period / offset set by the upper layer (e.g., RRC layer) or aperiodically transmitted according to the request of the base station.

In the next generation RAT (Radio Access Technology), self-contained subframes are considered to minimize data transfer latency. Figure 6 illustrates the structure of a self-contained subframe. In FIG. 6, the hatched area indicates the DL control area and the black part indicates the UL control area. The unmarked area may be used for DL data transmission or for UL data transmission. Since DL transmission and UL transmission are sequentially performed in one subframe, DL data can be transmitted in a subframe and UL ACK / NACK can be received. As a result, when a data transmission error occurs, the time required to retransmit the data is reduced, and the transfer latency of the final data can be minimized.

As an example of configurable / configurable self-contained subframe types, at least the following four subframe types may be considered. Each section was listed in chronological order.

- DL control interval + DL data interval + GP (Guard Period) + UL control interval

- DL control interval + DL data interval

- DL control interval + GP + UL data interval + UL control interval

- DL control interval + GP + UL data interval

In the DL control period, PDFICH, PHICH, and PDCCH can be transmitted, and in the DL data interval, PDSCH can be transmitted. In the UL control period, the PUCCH can be transmitted, and in the UL data interval, the PUSCH can be transmitted. The GP provides a time gap in the process of switching from the transmission mode to the reception mode or from the reception mode to the transmission mode. Some OFDM symbols at the time of switching from DL to UL within a subframe can be set to GP.

In the 3GPP NR system environment, OFDM parameters such as subcarrier spacing (SCS) and duration of an OFDM symbol (OS) based thereon may be set differently between a plurality of cells merged into one UE. Accordingly, the (absolute time) interval of a time resource (e.g., SF, slot or TTI) (for convenience, TU (Time Unit)) composed of the same number of symbols can be set differently between merged cells. Here, the symbol may include an OFDM symbol and an SC-FDMA symbol.

Figure 7 illustrates the frame structure defined in 3GPP NR. Like the radio frame structure of LTE / LTE-A (see FIG. 2), one radio frame in 3GPP NR is composed of 10 subframes, and each subframe has a length of 1 ms. One subframe includes one or more slots and the slot length depends on the SCS. 3GPP NR supports SCS at 15KHz, 30KHz, 60KHz, 120KHz and 240KHz. Here, the slot corresponds to the TTI in Fig.

Table 4 illustrates that the number of symbols per slot, the number of slots per frame, and the number of slots per subframe are different according to SCS.

SCS (15 * 2 ^ u)	Number of symbols in the slot	Number of slots in the frame	Number of slots in subframe
15KHz (u = 0)	14	10	One
30 kHz (u = 1)	14	20	2
60 kHz (u = 2)	14	40	4
120KHz (u = 3)	14	80	8
240 kHz (u = 4)	14	160	16

Hereinafter, the NB-IoT (Narrow Band - Internet of Things) will be described. For convenience, NB-IoT based on the 3GPP LTE standard is mainly described, but the following description can be equally applied to the 3GPP NR standard. To this end, some technical configurations can be modified (eg, LTE band -> NR band, subframe -> slot) .NB-IoT has three modes of operation: in-band, guard- The same requirements apply to each mode.

(1) In-band mode: Some of the resources in the LTE band are allocated to the NB-IoT.

(2) Guard-band mode: Utilizing the protection frequency band of LTE, the NB-IoT carrier is placed as close as possible to the edge subcarrier of LTE.

(3) Stand-alone mode: All carriers in the GSM band are allocated to the NB-IoT.

The NB-IoT terminal searches for an anchor carrier in units of 100 kHz for initial synchronization, and the center frequency of an anchor carrier in in-band and guard-band should be within ± 7.5 kHz from a channel raster of 100 kHz . In addition, the middle six PRBs of LTE PRBs are not allocated to NB-IoT. Anchor carriers can therefore only be located in a specific PRB.

Figure 8 illustrates the placement of an in-band anchor carrier at an LTE bandwidth of 10 MHz.

Referring to FIG. 8, a DC (Direct Current) subcarrier is located in the channel raster. PRB indices 4, 9, 14, 19, 30, 35, 40, and 45 are located at a center frequency of ± 2.5 kH from the channel raster because the center frequency interval between adjacent PRBs is 180 kHz. Similarly, the center frequency of a PRB suitable for an anchor carrier at an LTE bandwidth of 20MHz is located at ± 2.5kHz from the channel raster, and the center frequency of a PRB suitable for an anchor carrier at LTE bandwidths of 3MHz, 5MHz and 15MHz is ± 7.5kHz from the channel raster Located.

In guard-band mode, the PRB immediately adjacent to the edge PRB of LTE at a bandwidth of 10 MHz and 20 MHz has a center frequency of ± 2.5 kHz from the channel raster. In the case of bandwidths of 3 MHz, 5 MHz, and 15 MHz, the center frequency of the anchor carrier can be positioned at ± 7.5 kHz from the channel raster by using the guard frequency band corresponding to three subcarriers from the edge PRB.

Stand-alone mode anchor carriers are arranged in 100kHz channel raster, and all GSM carriers including DC carriers can be used as NB-IoT anchor carriers.

The NB-IoT supports multi-carrier and can be a combination of in-band + in-band, in-band + guard-band, guard-band + guard-band and stand-alone + stand-alone.

The NB-IoT downlink uses an OFDMA scheme with a 15 kHz subcarrier spacing. This provides orthogonality between subcarriers to facilitate coexistence with LTE systems.

The NB-IoT downlink is provided with physical channels such as Narrowband Physical Broadcast Channel (NPBCH), Narrowband Physical Downlink Shared Channel (NPDSCH), and Narrowband Physical Downlink Control Channel (NPDCCH). Narrowband Primary Synchronization Signal (NPSS) Primary Synchronization Signal), and NRS (Narrowband Reference Signal).

The NPBCH transmits the MIB-NB (Master Information Block-Narrowband), which is the minimum system information required for the NB-IoT terminal to access the system, to the UE. The NPBCH signal has a total of eight Repeat transmission is possible. The TBS (Transport Block Size) of the MIB-NB is 34 bits, and is updated every 640 ms TTI cycle. The MIB-NB includes information such as an operation mode, a system frame number (SFN), a number of Hyper-SFN, a cell-specific reference signal (CRS) port number, and a channel raster offset.

The NPSS consists of a ZC (Zadoff-Chu) sequence with a sequence length of 11 and a root index of 5. NPSS can be generated according to the following equation.

Here, S (1) for the OFDM symbol index 1 can be defined as shown in Table 5. [

Cyclic prefix length	S (3), ..., S (13)
Normal	One	One	One	One	-One	-One	One	One	One	-One	One

NSSS consists of a combination of a ZC sequence with a sequence length of 131 and a binary scrambling sequence such as a Hadamard sequence. The NSSS indicates the PCID through the combination of the above sequences to the NB-IoT terminals in the cell. The NSSS can be generated according to the following equation.

Here, the variables applied to Equation (2) can be defined as follows.

Here, the binary sequence b _q (m) is defined as shown in Table 6, and b ₀ (m) to b ₃ (m) correspond to 1, 32, 64 and 128 columns of the 128th order Hadamard matrix, respectively. Cyclic shift of the frame number n _f (cyclic shift) θ _f may be defined as shown in Equation (4).

q	b q (0), ... b q (127)
0	[1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
One	[1 -1 -1 1 -1 1 -1 -1 1 1 -1 -1 -1 -1 1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 1 -1 -1 -1 -1 1 -1 -1 1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1]
2	[1 -1 -1 -1 -1 1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 -1 - 1 1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 -1 -1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 -1 1 1 - 1 1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 1 1 -1 -1 -1 -1 1]
3	[1 -1 -1 -1 -1 1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1 -1 - 1 1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 -1 1 -1 -1 -1 -1 1 -1 -1 -1 -1 -1 1 -1]

Here, nf denotes a radio frame number. mod represents a modulo function.

The NRS is provided as a reference signal for channel estimation necessary for downlink physical channel demodulation and is generated in the same manner as LTE. However, NB-PCID (Narrowband-Physical Cell ID) (or NCell ID, NB-IoT base station ID) is used as an initial value for initialization. The NRS is transmitted over one or two antenna ports (p = 2000, 2001).

NPDCCH has the same transmit antenna configuration as NPBCH and carries DCI. Three types of DCI formats are supported. The DCI format N0 includes NPUSCH (Narrowband Physical Uplink Shared Channel) scheduling information, and the DCI formats N1 and N2 include NPDSCH scheduling information. NPDCCH can transmit up to 2048 repetitions to improve coverage.

NPDSCH is used to transmit data (e.g., TB) on a transport channel such as a downlink-shared channel (DL-SCH) or a paging channel (PCH). The maximum TBS is 680 bits and it is possible to transmit up to 2048 times to improve coverage.

FIG. 9 illustrates a location where an NB-IoT downlink physical channel / signal is transmitted in an FDD LTE system.

Referring to FIG. 9, the NPBCH is transmitted in the first subframe of each frame, the NPSS is transmitted in the sixth subframe of each frame, and the NSSS is transmitted in the last (e.g., tenth) subframe of every even frame. The NB-IoT terminal acquires frequency, symbols, and frame synchronization using the synchronization signals NPSS and NSSS and searches for 504 PCIDs (i.e., base station IDs). The LTE synchronization signal is transmitted over six PRBs, and the NB-IoT synchronization signal is transmitted over one PRB.

In the NB-IoT, the uplink physical channel is composed of NPRACH (Narrowband Physical Random Access Channel) and NPUSCH, and supports single-tone transmission and multi-tone transmission. Single-tone transmission is supported for subcarrier spacing of 3.5 kHz and 15 kHz, and multi-tone transmission is only supported for 15 kHz subcarrier spacing. The 15 Hz subcarrier spacing in the uplink can maintain the orthogonality with the LTE to provide optimal performance, but the 3.75 kHz subcarrier spacing can degrade the orthogonality, resulting in performance degradation due to interference.

The NPRACH preamble consists of four symbol groups, each symbol group consisting of a CP and five (SC-FDMA) symbols. NPRACH only supports single-tone transmission of 3.75kHz subcarrier spacing and provides a CP of 66.7μs and 266.67μs to support different cell radiuses. Each group of symbols performs frequency hopping and the hopping pattern is as follows. The subcarriers transmitting the first symbol group are determined in a pseudo-random manner. The second symbol group has one subcarrier hop, the third symbol group has six subcarrier hopping, and the fourth symbol group has one subcarrier hop. In the case of repeated transmission, the frequency hopping procedure is repeatedly applied. In order to improve the coverage, the NPRACH preamble can be repeatedly transmitted up to 128 times.

NPUSCH supports two formats. NPUSCH format 1 is used for UL-SCH transmission and the maximum TBS is 1000 bits. NPUSCH Format 2 is used for uplink control information transmission such as HARQ ACK signaling. NPUSCH format 1 supports single- / multi-tone transmission, and NPUSCH format 2 supports only single-tone transmission. For single-tone transmission, use pi / 2-BPSK and quadrature phase shift keying (pi / 4-QPSK) to reduce the Peat-to-Average Power Ratio (PAPR).

In stand-alone mode and guard-band mode, all resources included in 1 PRB can be allocated to NB-IoT. However, in the case of the in-band mode, resource mapping is limited in order to coexist with the existing LTE signal. For example, in the in-band mode, resources (0 to 2 OFDM symbols in each subframe) classified as the LTE control channel allocation region can not be allocated to the NPSS / NSSS, and the NPSS / NSSS symbols mapped to the LTE CRS RE Is punctured.

FIG. 10 illustrates resource allocation of an NB-IoT signal and an LTE signal in an in-band mode. Referring to FIG. 10, the NPSS and the NSSS are not transmitted in the OFDM symbols corresponding to the control region of the LTE system (for example, the first three OFDM symbols in the subframe) regardless of the operation mode for ease of implementation. In addition, the LTE CRS RE and the NPSS / NSS RE colliding on the physical resource are mapped so as not to affect the LTE system.

After the cell search, the NB-IoT terminal demodulates the NPBCH in the absence of system information other than the PCID. Therefore, the NPBCH symbol can not be mapped to the LTE control channel assignment region. In the absence of system information, the NB-IoT terminal assumes four LTE antenna ports (eg p = 0, 1, 2 and 3) and two NB-IoT antenna ports (eg p = 2000, 2001) Therefore, the NPBCH can not be allocated to the CRS RE and the NRS RE. Thus, the NPBCH is rate-matched to the given available resources.

After the NPBCH demodulation, the NB-IoT terminal obtains information on the number of CRS antenna ports, but still can not know the information on the LTE control channel allocation region. Therefore, the NPDSCH that transmits SIB1 (System Information Block type 1) data is not mapped to the resource classified as the LTE control channel allocation region.

However, unlike the NPBCH, an RE that is not actually allocated to the LTE CRS can be allocated to the NPDSCH. Since the NB-IoT UE has acquired all the information related to the resource mapping after receiving the SIB1, the Node B maps the NPDSCH (excluding SIB1) and the NPDCCH to the available resources based on the LTE control channel information and the CRS antenna port number can do.

Example: Duplex Mode Classification and Detection

NB-IoT supports only FDD to 3GPP Rel-14, but 3GPP Rel-15 will introduce TDD support. Therefore, it is necessary to design a TDD NB-IoT system so that a terminal designed to support only FDD does not mistake the TDD system as an FDD system. In addition, it is necessary to design a TDD NB-IoT system so that a terminal supporting both TDD and FDD can effectively detect the duplex mode. Especially, unnecessary operation due to duplex mode error may be fatal to a terminal in which a requirement for low-power operation is important, such as an NB-IoT system.

First, a method of distinguishing the duplex mode in the existing LTE system will be described. The LTE frame structure type is divided into three, and the frame structure types 1 and 2 are used for FDD and TDD systems, respectively. Frame structure type 3 is used for LAA (Licensed Assisted Access) service and is defined based on frame structure type 2 so that it is suitable for coexistence with other technologies in a license-exempt carrier. Here, since frame structure type 3 is used only in a license-exempt carrier, it need not be distinguished from other frame structure types and initial operations (e.g., downlink synchronization process). On the other hand, frame structure types 1 and 2 operating in the license carrier need to be designed such that the terminal does not perform as much unnecessary additional operations due to duplex mode misconception in the initial operation process.

In LTE, the duplex mode is determined in the course of SSS detection, and specifically, the duplex mode detection depends on the relative (OFDM) symbol distance difference between the PSS and SSS. When the duplex mode is detected as TDD, information such as a UL / DL configuration and a special subframe format is transmitted to the UE via SIB1. On the other hand, if the duplex mode detection is wrong, a problem may occur in the terminal operation in the following procedure.

(1) When FDD is detected as TDD

In the process of measuring the RSRP based on the cell ID detected by the PSS / SSS, some DL subframes may be mistaken as UL subframes. As a result, some DL sub-frames are not included in the RSRP measurement, and the RSRP measurement accuracy can be degraded. However, if the SNR is not very low, the UE can determine the cell ID detected by the PSS / SSS as the actually detected cell and attempt to detect the PBCH based on the RSRP measured based on the insufficient CRS. At this time, in the case of an Enhanced Machine-Type Communication (eMTC) terminal, a newly added PBCH OFDM symbol for eMTC may be erroneously selected, and PBCH detection may fail. However, if the eMTC terminal does not use the newly added PBCH OFDM symbol or if the SNR environment is sufficiently good, there is still a probability of detecting the PBCH. A legacy LTE terminal that does not use the newly added PBCH OFDM symbol for eMTC service can naturally succeed in PBCH detection. Thereafter, the SIB1 detection and message analyzing process can not analyze the SIB1 differently designed according to the duplex mode, or can operate based on the SIB1 that is misinterpreted. In this process, the UE can recognize that the cell search is wrong. That is, when FDD is detected as TDD, there may be a problem that the erroneous operation is performed for a while even after the initial synchronization process.

(2) When detecting TDD as FDD

In the process of measuring the RSRP based on the cell ID detected by the PSS and the SSS, the RSRP measurement may be quite inaccurate as some UL subframes are mistaken for DL subframes. As a result, it can be seen that the initial cell search is erroneously performed. However, there is still a probability that the duplex mode is not correctly detected in the initial cell search process, and that subsequent subsequent operations can continue to be performed. In this case, it is possible to perform the unnecessary subsequent process described in " FDD is detected as TDD misidentified. &Quot;

An unnecessary additional operation of the terminal due to the duplex mode error detection has a disadvantage of increasing initial access latency and power consumption. In addition, NB-IoT has a narrower system bandwidth and a smaller channel raster spacing than LTE systems. Therefore, when it is determined late that the duplex mode error detection of (1) and (2) is late, the LTE terminal can skip the entire system band and resume cell search in the next channel raster. However, NB-IoT skips only the 1RB band based on LTE and resumes cell search in the next channel raster. Therefore, if duplex mode is incorrectly detected in the initial synchronization process, the effect of initial access latency and power consumption may be much more severe in the NB-IoT system.

Hereinafter, the present invention proposes a method for distinguishing / detecting a duplex mode in an NB-IoT system. More specifically, the present invention proposes a method and apparatus that are effective in terms of power consumption and minimize the probability of false detection in distinguishing / detecting a duplex mode. Also, the present invention proposes a method and apparatus for minimizing the duplex mode detection error probability in the initial synchronization process and preventing the duplex mode error detection in the physical layer at various stages. The proposed methods of the present invention can randomize different duplex modes to minimize unnecessary power consumption and initial access latency of the terminal. Further, the proposed methods of the present invention may be applied to each other, or only a specific step may be selectively applied to the system. In addition, the proposed methods of the present invention are not limited to the NB-IoT system, and may be applied to any system that allows many repetitive transmissions for a low-power low-cost terminal such as eMTC. Also, the present invention can be used as a duplex mode classification method of a newly designed communication system. For example, the present invention can be used as a method for distinguishing a duplex mode in 3GPP NR. In this case, some technology configurations may be modified to accommodate 3GPP NR (eg, LTE band -> NR band, subframe -> slot).

Although the present invention mainly focuses on the classification / detection of the duplex mode, the present invention can be used for other purposes (e.g., classification / detection of other communication modes). For example, the present invention can be used to signal whether a wake-up signal / indication (e.g., wake-up on / off) is transmitted.

Method # 1: How to distinguish between primary synchronization signal (PSS)

Unlike the existing legacy LTE PSS, the NB-IoT system does not include cell ID information in the NPSS. That is, the NPSS based on the Frank-Zadoff-Chu sequence (hereinafter referred to as Chu sequence and Zadoff-sequence) defined by the sequence length and the root index uses only the root index (u) = 5 and 504 NCell IDs (NB- IoT Cell ID) is included in NSSS. The NPSS of length 11 is transmitted in the fifth subframe of every radio frame and transmitted over the remaining 11 OFDM symbol periods except for the first three OFDM symbol intervals, which are potential control areas in the subframe. The Chu sequence transmitted over 11 OFDM symbols is modulated with a cover code of length 11 over 11 OFDM symbols, and the same cover code is used for each radio frame. Therefore, the UE can acquire only the approximate timing and frequency synchronization through the NPSS. As already well known, the Chu sequence of length L is characterized in that the complexity of the complex multiplication does not increase when calculating the mutual-correlation of the root indexes u1 and u2 (= L-u1). However, since cross-correlation between different root indices is not perfect,

Correlation may exist. This is not a small value when considering the length of NPSS with L = 11, but it is not limited to 1, which is randomized into a cover code over 11 OFDM symbols (e.g., [1 1 1 -1 -1 -1 1 1 -1 -1]). In view of taking the average over the one sub-frame, compared to the perfect self-correlation value between u1 and u1, u2 and u2,

, Which is twice as low as the PSS using three different root indices. Therefore, the duplex mode information can be added to the NPSS in the following manner. The following methods can be selectively applied or combined. The following method can be applied to reduce ambiguity with 10-ms period FDD NPSS and ambiguity with 20-ms FDD NSSS even if the transmission periods of NPSS and NSSS differ from the existing 10 ms and 20 ms, respectively (eg, longer transmission period) have.

(1-1) Method of allocating new duplex mode information to the root index (L-u1)

Root index 6 can be used to specify the TDD mode. In this case, the existing root index 5 can be used to specify the FDD mode. Of course, it is also possible to use a root index other than the 5th and 6th times, and in such a case, the calculation complexity of the terminal can be increased to some extent.

(1-2) Assigning duplex mode information to a new cover code

A new cover code [1 1 -1 1 -1 -1 -1 -1 -1 -1 1] can be used to specify the TDD mode. In this case, the existing cover code [1 1 1 1 -1 -1 1 1 1 -1 -1] can be used to specify the FDD mode (see Table 5). An arbitrary cover code may be used instead of the existing cover code, or a cover code having a frequency of '1' and '-1' may be used. However, since [1 1 -1 -1 -1 -1 1 -1 -1 -1 1] has considerably low mutual correlation with the cover code defined in the current NPSS, it is possible to effectively reduce the duplex mode error detection of the UE.

The method # 1 can minimize the NPSS detection probability of the terminal supporting only the existing FDD. Also, according to the method # 1, a terminal supporting both a newly defined TDD NB-IoT terminal and FDD / TDD can minimize the detection of a duplex mode error from the initial synchronization initial stage. In particular, the method (1-1) provides an additional advantage of reducing the number of complex multiplications for NPSS detection.

Method # 2: How to distinguish by SSS (Secondary synchronization signal)

In general, an LTE terminal detects a plurality of candidate PSS timings and cell IDs through a PSS detection process, and attempts to detect an SSS by calculating an SSS position from a corresponding PSS position. That is, the UE attempts to detect the SSS at a plurality of SSS candidate positions, and the SSS has a specific relationship with the detected PSS. This is a characteristic that can be effectively used for duplex mode detection when PSS and SSS are defined to have different time differences according to the duplex mode. Accordingly, the LTE UE can confirm the PSS detection result again in the SSS detection process, and prevent erroneous detection of the cell ID and the duplex mode through the PSS and the SSS based on the PSS detection result. On the other hand, in the NB-IoT system, since all the base stations transmit the same NPSS, it is difficult to confirm the result of the NPSS detection in the NSSS detection process. For example, when the subframe offset of NSSS and NPSS is differently defined according to the duplex mode, there may be more than one NPSS having a detected NSSS position and a relative subframe offset in the UE. In this case, an error may occur in the duplex mode detection of the terminal. In particular, since NPSS information and NSSS sequence have no relationship other than the subframe offset, it is difficult to confirm NPSS and NSSS detection. Therefore, in the present invention, the following method is proposed to identify / identify the duplex mode. The following methods can be selectively applied or combined. The following method can be applied to reduce the ambiguity with the FDD NPSS of 10ms period and the ambiguity with the FDD NSSS of 20ms period even when the transmission period of the NPSS and the NSSS changes from the existing 10ms and 20ms (for example, the transmission period becomes longer).

(2-1) How to set the sub-frame offset of NPSS and NSSS differently according to the duplex mode

In the existing FDD NB-IoT, NPSS is transmitted in subframe 5 of every radio frame, and NSSS is transmitted in subframe 9 in every even-numbered radio frame. Here, ignoring the radio frame number, NPSS and NSSS are defined to have 4 subframe offsets. Therefore, in the TDD NB-IoT, the subframe offset interval between NPSS and NSSS can be defined to have a value other than 4. When applied at the same time as method # 1, when detecting NPSS for the TDD mode in the NPSS detection step, the NB-IoT terminal attempts to detect the NSSS at a position different from the NSSS subframe position defined in the FDD NB-IoT .

(2-2) How to set the resource mapping order / scheme of NSSS differently according to the duplex mode

In the case of the method (2-1), the position of the TDD NSSS subframe to be detected and the position of the NPSS subframe having the specific subframe offset are determined not only in the subframe offset defined in the TDD but also in the subframe offset already defined in the FDD All of which may overlap. This is a problem that can occur because the UE selects multiple NPSS candidate sets in the NPSS detection process. To solve this problem, it is necessary to establish a specific relationship with the NPSS in the NSSS. In one of these ways, the resource mapping order of the NSSS can be different depending on the duplex mode. This can be quite different from resource mapping of NSSS in the subframe defined in the existing FDD. FIG. 11 shows an existing NSSS resource mapping, and FIGS. 12 to 14 illustrate an NSSS resource mapping according to the present invention. FIG. 12 shows a method of shifting the position of the resource mapping start OFDM symbol by the characteristic value in the scheme of FIG. 11 (Alt 1-1). 13 is a method for performing the resource mapping procedure in reverse in the method of FIG. 11 (Alt 2-1), FIG. 14 is a method for applying time-priority mapping, having the same start position and ending position as the method of FIG. 11 Alt 2-2).

15 shows the cross-correlation characteristics of the existing NSSS. Referring to FIG. 15, the existing NSSS has a mutual-correlation value corresponding to a sequence length when u and u 'are the same, and otherwise has a relatively low mutual correlation value. The cross-correlation properties of the proposed resource mapping scheme can be seen in Figures 16-18, respectively. According to Alt 1-1, it can be seen that the inter-correlation characteristic with the existing NSSS Zadoff-Chech sequence corresponds to about 50% in some u and u 'combinations. Also, according to Alt 2-1, most u and u 'combinations show a low mutual-correlation value with the existing NSSS Zadoff-Chek sequence, but have a mutual-correlation value of about 70% or more in a specific u and u' combination Can be confirmed. On the other hand, according to Alt 2-2, it can be confirmed that all combinations of u and u 'have a relatively low mutual-correlation value with the existing Zadoff-Chu sequence.

(2-3) How to configure the sequence configuration of NSSS differently according to the duplex mode

For the purpose similar to the method (2-2), information on the duplex mode can be added to the sequence of the NSSS. When applied at the same time as Method # 1, the effect is the same as adding NPSS to NSSS. The sequence of NPSS defined in Section 10.2.7.2 of 3GPP TS 36.211 is as shown in Equation 5.

At this time,? _F applied to Equation (5) is defined by the following equation.

Here, n _f denotes a radio frame number. The N ^Ncell _ID is determined from q and u in Equation (5). Unlike the NPSS, the NSSS does not repeatedly transmit one OFDM symbol for 11 OFDM symbol intervals with different cover codes. In the case of NSSS, the NSSS sequence defined by Equation (5) is mapped to 132 REs in a frequency-preferred mapping scheme for 11 OFDM symbol intervals and transmitted.

If the aSSSS is defined by modifying u and &thgr; _f among the information constituting the SS sequence, it may affect the NSSS detection of the legacy NB-IoT terminal. Therefore, the present invention proposes a method of adding b _q (m) of NSSS (see Table 6) defined in Table 10.2.7.2.1-1 of 3GPP TS 36.211. However, θ _f is because it can suppress the effect on the performance when adding a new value according to the implementation of the NB-UE large IoT, we propose a method of adding the value of θ _f also.

(2-3-1) How to add θ _f

As can be seen from Equation (6), in the NSSS for FDD, 0 _f , 0, 33/132, 66/132, 99/132 cycles every 20 msec. On the other hand, the NSSS for TDD can rotate θ _f every 33 ms, 99/264, 165/264, 231/264 every 20 msec, circulate to a subset of 4 values, or fix it to a specific value. FIG. 19 shows a cross-correlation value (Legacy NB-IoT w / NSSS) in the case of using the existing NSSS (i.e., NSSS for FDD) and? _{F in the case of} using 33/264, 99/264, 165/264 and 231/264 cross with θ _f values applied to TDD NSSS when receiving the selected TDD NSSS - correlation value (legacy NB-IoT w / aNSSS ) and cross with θ _f of the existing NSSS - correlation value (Proposed NB-IoT w / aNSSS ). Cross-as it can be seen from the distribution of the correlation values, used in the conventional _{FDD NSSS θ f = {0,} 33/132, 66/132, 99/132} and other θ _f = {33/264, 99/264, 165/264, 231/264} values of the TDD NSSS do not interfere with each other. Observation of the inter-correlation values allows the θ _f of the TDD NSSS to be selected as a set of values other than {0, 33/132, 66/132, 99/132}, but θ _f = {33/264, 99 / 264, 165/264, 231/264}, more memory may be needed for sequence generation at the NB-IoT terminal.

(2-3-2) How to add b _q (m)

TDD NSSS can be configured by changing / adding only b _q (m) in (FDD) NSSS defined in Table 10.2.7.2.1-1 of TS.36.211 without changing the ZDP sequence of NSSS. In this case, the legacy NB-IoT terminal does not attempt to detect the changed or added b _q (m), and the NB-IoT terminal attempting to detect the TDD NSSS can reuse the result of the complex multiplication used for NSSS detection . Therefore, b _q to be used for a TDD NSSS (m) is one of 128 primary Hadamard matrix used in b _q (m) of the existing NSSS, 32, 64, 128 columns instead, 16, 48, 80, using the 112 columns .

Equation (7) shows a method of generating a Hadamard matrix. The 128th Hadamard matrix corresponds to k = 7.

Method # 3 How to distinguish by NRS

For reasons similar to those described in method # 2, the LTE terminal still manages a plurality of candidate cell IDs after detecting the PSS / SSS. Then, RSRP is measured based on the CRS for each detected candidate cell ID, and the candidate cell ID is again calculated based on the measured RSRP. This is because the cell ID detected through the PSS / SSS may be inaccurate, so that the cell search result is measured by measuring the RSRP based on the CRS including the cell ID information, and the self- This is because the mutual-correlation value is unsuitable for representing signal intensity or quality information of the corresponding cell. For the same reason, information obtained from NPSS / NSSS also needs to be included in NRS in NB-IoT. That is, although the NRS already includes the NCell ID, it is necessary to reflect the additional duplex mode obtained in the NPSS / NSSS detection process. This can be seen as a process of confirming the NCell ID and duplex mode information of the initial synchronization process using NPSS and NSSS. Specifically, the present invention proposes the following method as a technique for distinguishing and confirming a duplex mode. The following methods can be selectively applied or combined. In the following method, even when the transmission periods of NPSS, NSSS and NPBCH are different from those of the conventional 10 ms, 20 ms and 10 ms (for example, the transmission period becomes longer), the ambiguity with 10 ms cycle FDD NPSS, ambiguity with 20 ms FDD NSSS, FDD can be applied together to reduce ambiguity with NPBC.

(3-1) Setting a default sub-frame for transmitting NRS differently according to the duplex mode

In the FDD NB-IoT system up to 3GPP Rel-14, the NRS transmission subframe that can be assumed by the UE before acquiring the MIB-NB information includes 0/4 subframes and 9 subframes to be. In the TDD NB-IoT system, the 5th subframe in which the NRS can not be transmitted in the FDD NB-IoT system can be defined as an NRS transmission subframe that can be assumed by the UE before the MIB-NB detection. That is, in the FDD NB-IoT, since the NPSS is transmitted in the 5th subframe, the NRS can not be transmitted, whereas in the TDD NB-IoT, the 5th subframe can always be reserved as the DL subframe, It can be designated as an NRS subframe. Accordingly, in the FDD mode, the NRS is transmitted in the 0th / 4th / 9th subframe, and in the TDD mode, the NRS can be transmitted in the 0th / 5th / 9th subframe. However, such a method can restrict the subframe positions in which the NPSS and the NSSS can be transmitted in the TDD NB-IoT system. Also, considering that the subframes usable as downlink subframes in the TDD system are always 0/9 subframes, it is difficult to perfectly set the default NRS subframe between the FDD and the TDD system.

(3-2) How to set the resource mapping order / scheme of NRS differently according to the duplex mode

The location of an RE (Resource Element) (hereinafter referred to as an NRS RE) to which an NRS is transmitted may be changed according to the NCell ID, like the CRS. That is, in the FDD NB-IoT, the position of the NRS RE in the frequency domain is changed in the same manner as the CRS, and the OFDM symbol to which the NRS can be transmitted is selected so that the RE position does not overlap with the other reference signals of the legacy LTE system. Therefore, the method of changing the RE position of the NRS according to the duplex mode is significantly restricted. With this in mind, the simplest way to differentiate the NRS resource mappings within the limited available RE location according to the duplex mode is to use v and v _shift in TS 36.211 clause 10.2.6.2 differently depending on the duplex mode (eg FDD, TDD) It is defined.

Specifically, in order to confirm the TDD mode, the NRS resource mapping method can be changed as shown in Equation (8). In addition, there are various ways to define the NRS resource mapping method differently. Equation 9 represents the existing NRS resource mapping scheme in TS36.211 10.2.6.2 and can be used to verify the FDD mode. Therefore, a terminal that has detected a duplex mode erroneously can confirm the results of the previous cell search in the RSRP measurement process based on the NRS.

Here, v and v _shift define positions for different reference signals in the frequency domain. p denotes the antenna port, and N ^DL _symb denotes the number of OFDM symbols in the slot (e.g., 7). The N ^NCell _ID indicates the NCell ID, and is the same as the N ^cell _ID (= PCID) if not indicated otherwise in the upper layer.

The NRS sequence rl _{, ns} (m) is mapped as a multi-valued modulation symbol a ^(p) _{k, l} as follows: a ^(p) _{k, l} is the reference signal symbol for antenna port p in slot n _s Is used.

Here, k denotes a subcarrier index, and 1 denotes an OFDM symbol index in a slot n _s . N ^{max, and DL} _RB represents the maximum number of _RBs in the downlink band.

(3-2) How to configure the sequence configuration of NRS differently according to the duplex mode

The method of generating the NRS sequence according to the duplex mode can be different. The NRS sequence can be modified in a considerable number of ways, and a method of expanding the method illustrated in the present invention or modifying some contents may be considered. The proposed NRS sequence configuration can be used not only for the RSRP measurement based on the NRS, but also for the demodulation process for confirming the duplex mode with the upper layer signal proposed in method # 4.

(3-2-1) How to initialize PN sequence differently from existing FDD NRS

The existing FDD NRS sequence is defined using Equation (14) below. Referring to Equation (14), NRS is defined by a pseudo random (PN) sequence c (n). The pseudo-random sequence c (n) is composed of two m-sequences as shown in the following equation.

Where n = 0, 1, ..., M _PN -1 and M _PN indicates the sequence length. Nc = 1600 and the first m-sequence is initialized to x ₁ (0) = 1, x ₁ (n) = 0, n = 0,1, ..., The second m-sequence

.

The initialization value c _init is given by the following equation at the beginning of each OFDM symbol.

Here, n _s is a slot within a radio frame denotes an index (0 ~ 19), l represents an OFDM symbol index within the slot ^{(0 ~ 6), N Ncell} ID represents the ID NCell. N ^Ncell _ID is the same as N ^cell _ID (= PCID) unless it is given separately by the upper layer.

To separate the duplex mode, ^Ncell _ID N + N (eg, N = 1) instead of N ^Ncell _ID as an initial value of a PN sequence for the NRS TDD may be used in the equation (12). Meanwhile, the initial value of the PN sequence for the FDD NRS may be N ^Ncell _ID as shown in Equation (12).

(3-2-2) Scrambling the entire generated PN sequence

The entire PN sequence generated according to the duplex mode can be toggled at the bit-level or scrambled in a specific sequence.

(3-2-3) How to map PN sequence I / Q differently from existing FDD NRS

Equation (13) shows an example of changing a sequence based on an existing NRS sequence, and Equation (14) shows an existing NRS sequence (refer to Equations (11) to (12)). The NRS sequence of Equation (13) is used for TDD mode identification, and the NRS sequence of Equation (14) can be used for FDD mode identification. That is, the I / Q mapping of the NRS sequence may be defined differently depending on the duplex mode. In the I / Q mapping, I represents a real part and Q represents an imaginary part.

Method # 4: How to distinguish duplex mode with system information

In methods # 1 to # 3, cell search and duplex mode detection results are acknowledged over various stages of the physical layer, and finally duplex mode can be confirmed using an upper layer (e.g., RRC) signal. For this purpose, the duplex mode can be explicitly informed on a message basis via MIB-NB, SIB1-NB, another SIB-NB or a third SIB1-NB. At this time, the modified NRS of the method # 3 can be used together in the demodulation process. The message may directly include information indicating a reserved field or bit information on the duplex mode (e.g., TDD). In addition, information about the duplex mode (e.g., TDD) can be indirectly reported using an undefined state of some fields in the message. In addition, the duplex mode can be distinguished by differently scrambling the message according to the duplex mode (FDD / TDD) or by varying the CRC masking according to the duplex mode (FDD / TDD). Here, the CRC may include the CRC of the message itself, or the CRC of the PDCCH that schedules the message. Also, by making the payload size of the message different according to the duplex mode (FDD / TDD), the UE can confirm the duplex mode through blind decoding. In the following method, even when the transmission periods of NPSS, NSSS and NPBCH are different from those of the conventional 10 ms, 20 ms and 10 ms (for example, the transmission period becomes longer), the ambiguity with 10 ms cycle FDD NPSS, ambiguity with 20 ms FDD NSSS, FDD can be applied together to reduce ambiguity with NPBC.

Method # 5: How to set some signal and channel period which is essential in TDD NB-IoT different from FDD NB-IoT

The FDD NB-IoT system supports up to 164 dB of MCL (Maximum Coupling Loss). The high MCL in the FDD NB-IoT reflects the NB-IoT service features that can be located deep within the building for metering, while reducing the burden of additional base station installations for the NB-IoT service in a very large area Respectively. In order to satisfy such a high MCL, the 3GPP standard allows many repetitive transmissions to downlink / uplink signals and channels, and largely satisfies the MCL requirement using the following gain.

(1) Average and diversity gain by repeated transmission

(2) cross-subframe channel estimation during repeated transmission

In the TDD NB-IoT system, since the number of consecutive downlink / uplink subframes is limited, it is difficult to obtain the gain of (1) (2). However, in general, the TDD system is suitable for narrow coverage as compared to the FDD system, so the required MCL can be lowered in the TDD NB-IoT system. Accordingly, the periodicity of some signals (eg, NPSS, NSSS) and channels (eg, NPBCH and SIB1-NB) required in the TDD NB-IoT system can be designed to be equal to or larger than that of the FDD NB-IoT. Therefore, the period of the signal / channel to which the methods # 1 to # 4 are applied can also be changed considering the MCL reduction. That is, the proposed method of the present invention can be applied to a case in which the period of some signal / channels, which are indispensably required in the TDD NB-IoT, is different from that of the FDD NB-IoT. A concrete example is as follows.

(1) When the TDD NPSS period is 10 ms x N

  A. N is an integer of 1 or more. Method # 1 can be applied when the duplex mode is TDD regardless of N. [

(2) When the TDD NSSS period is 20 ms x M

  A. M is an integer greater than or equal to one not less than N. Method # 2 can be applied when the duplex mode is TDD irrespective of M. M can be determined according to N.

B. Regardless of M, the entire sequence repeat transmission unit of NSSS may be four. That is, in the FDD NB-IoT, the NSSS is transmitted every 20 ms for 80 ms, and the period of 80 ms can be obtained through the NSSS detection. On the other hand, when the NSSS of 20 ms × M period is transmitted in the TDD NB-IoT, a period of 80 ms × M can be obtained through the TDD NSSS. Accordingly, in the FDD NB-IoT, NSSS is transmitted in the last subframe of the radio frame satisfying the mod (n _f , 2) = 0, while in the TDD NB-IoT, mod (n _f , 2M) = 0 is satisfied NSSS may be transmitted in a specific subframe of the radio frame. n _f represents a radio frame number / index.

(3) When the TDD MIB-NB TTI (NPBCH repeat transmission unit) is 640 ms x K

  A. K is an integer equal to or greater than 1 that is not less than M. Methods # 3 to # 4 can be applied when the duplex mode is TDD irrespective of K. Further, K may be determined according to N and / or M.

B. If K is greater than 1, MIB-NB may be transmitted every 10 ms x K. At this time, the same MIB-NB information can be transmitted for 640 ms x K, and the radio frame number to which the MIB-NB is transmitted can be limited to a case where mod (n _f , K) = 0 is satisfied. Alternatively, a mod (n _f + mod (Ncell ID, K), K) = 0 may be defined to include Ncell ID information in the wireless frame number. The radio frame offset method can be defined by various methods. If K is greater than 1, the method of preventing the transmission of the TDD NPBCH to every radio frame or the method of changing the radio frame offset in which the TDD NPBCH is transmitted according to the Ncell ID is different And is included in the method proposed by the present invention. On the other hand, in the FDD mode, the MIB-NB can be transmitted every 10ms, and the same MIB-NB information can be transmitted for 640ms.

  C. If K is greater than 1, the "4-bit SystemFrameNumber-MSB" (hereinafter referred to as SFN) and the "2-bit hyperSFN-LSB" (hereinafter referred to as HSFN) of the MIB-NB may be different. For example, the SFN may be reduced in size by a "4-K + 1" bit (field), or the interpretation of a value of 1 unit may be different by 10 ms × K. In addition, the HSFN may be maintained as two bits as before, or the HSFN may be increased to " 2 + K-1 " bits to represent a larger range of HSFNs with " K-1 " bits omitted from the SFN. Also, the " K-1 " bits omitted from the SFN can be used for other purposes. On the other hand, in the FDD mode, SFN and HSFN of the MIB-NB can be maintained at 4 bits and 2 bits, respectively.

(4) When the TDD SIB1-NB TTI (SIB1-NB modification boundary) is 40.96s x L

  A. L is an integer of 1 or more. Methods # 3 to # 4 can be applied when the duplex mode is TDD irrespective of L. Further, L may be determined according to N, M and / or K. If the SIB1-NB modification boundary does not differ according to the duplex mode, L can be fixed to 1 regardless of other parameters.

  B. When L is greater than 1: Unlike 3GPP Rel-14, the change boundary of SIB1-NB can be changed to an SFN that satisfies (H-SFN * 1024 + SFN) mod (4096 x L) = 0.

  C. When L is 1: Like 3GPP Rel-14, the change boundary of SIB1-NB can be defined as SFN satisfying (H-SFN * 1024 + SFN) mod 4096 = 0.

Regardless of L, SIB1-NB can be repeatedly transmitted every 20ms x W for 160ms x W. Here, W is an integer of 1 or more. The radio frame offset and number at which the SIB1-NB is transmitted can be changed in consideration of the NCell ID, the number of SIB1-NB repetition times, and W. [ Where W may have a particular relationship with K and / or M.

20 illustrates a duplex mode detection process according to the present invention.

Referring to FIG. 20, a terminal repeatedly receives one or more downlink signals from a base station (S2002). Herein, one or more downlink signals include NPSS, NSSS, NPBCK, MIB-NB, and SIB-NB. In this regard, reference is made to Fig. 9 and the description thereof. Thereafter, the terminal can detect one or more downlink signals (S2004). The one or more repeatedly received downlink signals may be combined in the detection process. The terminal may then detect / determine the duplex mode to use for subsequent communications based on the characteristics of the one or more detected downlink signals. For this, the methods # 1 to # 5 proposed above can be used alone or in combination. Here, the duplex mode means the FDD mode and the TDD mode, but can be generalized to the first communication mode and the second communication mode. For example, the terminal may detect / determine a wake-up signal / indication (e.g., wake-up on / off) based on the characteristics of one or more detected downlink signals.

FIG. 21 illustrates a base station and a terminal that can be applied to the present invention.

Referring to FIG. 21, a wireless communication system includes a base station (BS) 110 and a terminal (UE) 120. If the wireless communication system includes a relay, the base station or the terminal may be replaced by a relay.

The base station 110 includes a processor 112, a memory 114, and a radio frequency (RF) unit 116. The processor 112 may be configured to implement the procedures and / or methods suggested by the present invention. The memory 114 is coupled to the processor 112 and stores various information related to the operation of the processor 112. [ The RF unit 116 is coupled to the processor 112 and transmits and / or receives wireless signals. The terminal 120 includes a processor 122, a memory 124 and a radio frequency unit 126. The processor 122 may be configured to implement the procedures and / or methods suggested by the present invention. The memory 124 is coupled to the processor 122 and stores various information related to the operation of the processor 122. [ The RF unit 126 is coupled to the processor 122 and transmits and / or receives radio signals.

The embodiments described above are those in which the elements and features of the present invention are combined in a predetermined form. Each component or feature shall be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to construct embodiments of the present invention by combining some of the elements and / or features. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

In the present document, the embodiments of the present invention have been mainly described with reference to a signal transmission / reception relationship between a terminal and a base station. This transmission / reception relationship is equally or similarly extended to the signal transmission / reception between the terminal and the relay or between the base station and the relay. The specific operation described herein as being performed by the base station may be performed by its upper node, in some cases. That is, it is apparent that various operations performed for communication with a terminal in a network including a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A base station may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. In addition, the terminal may be replaced by terms such as a UE (User Equipment), a Mobile Station (MS), and a Mobile Subscriber Station (MSS).

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

In the case of an implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, a procedure, a function, or the like for performing the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit of the invention. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

The present invention can be used in a terminal, a base station, or other equipment of a wireless mobile communication system.

Claims (14)

1. A method for a terminal to detect a duplex mode in a wireless communication system,

   Repeatedly receiving a downlink synchronization signal;

   Detecting the downlink synchronization signal; And

   Detecting the duplex mode based on a repetition interval of the downlink synchronization signal in a time domain,

   Wherein the repeating interval is N1 when the duplex mode is FDD (Frequency Division Duplex), and the repeating interval is N2 when the duplex mode is TDD (Time Division Duplex), and N1 is smaller than N2.
2. The method according to claim 1,

   Wherein the downlink synchronization signal includes a Narrowband Primary Synchronization Signal (NPSS), wherein N1 corresponds to one radio frame in the FDD mode, and N2 corresponds to a plurality of radio frames in the TDD mode.
3. The method according to claim 1,

   Wherein the NPSS is a Zadoff-chu sequence of length 11 defined by a root index, the root index is n in FDD mode, the root index is 11-n in TDD mode, and n is an integer .
4. The method according to claim 1,

   The NSSS is received through 11 consecutive OFDM symbols to which a cover code is applied. In the FDD mode, the cover code is [1 1 1 -1 -1 -1 1 1 -1 -1] The code is [1 1 -1 1 -1 -1 1 -1 -1 -1 1].
5. The method according to claim 1,

   In the FDD mode, N1 corresponds to two radio frames. In the TDD mode, N2 corresponds to 2 * m radio frames, and m corresponds to 1 (N) / RTI >
6. The method according to claim 1,

   Wherein the initialization value of the sequence used to generate the NRS is P in the FDD mode, P + a in the TDD mode, and P is the NCell ID (Narrowband Cell Identity), and a represents a non-zero integer.
7. The method according to claim 1,

   Wherein the wireless communication system includes a wireless communication system supporting Narrowband Internet of Things (NB-IoT).
8. A terminal used in a wireless communication system,

   An RF (Radio Frequency) module; And

   The processor comprising:

   And repeatedly receives the downlink synchronization signal,

   Detects the downlink synchronization signal,

   And to detect a duplex mode based on a repetition interval of the downlink synchronization signal in the time domain,

   Wherein the repeating interval is N1 when the duplex mode is FDD (Frequency Division Duplex), the repeating interval is N2 when the duplex mode is TDD (Time Division Duplex), and N1 is less than N2.
9. 9. The method of claim 8,

   The downlink synchronization signal includes a Narrowband Primary Synchronization Signal (NPSS). In the FDD mode, N1 corresponds to one radio frame. In the TDD mode, N2 corresponds to a plurality of radio frames.
10. 9. The method of claim 8,

    The NPSS is a Zadoff-chu sequence of length 11 defined by a root index. In the case of FDD mode, the root index is n. In case of TDD mode, the root index is 11-n, .
11. 9. The method of claim 8,

    The NSSS is received through 11 consecutive OFDM symbols to which a cover code is applied. In the FDD mode, the cover code is [1 1 1 -1 -1 -1 1 1 -1 -1] The code is [1 1 -1 1 -1 -1 -1 -1 -1 -1 1].
12. 9. The method of claim 8,

    In the FDD mode, N1 corresponds to two radio frames. In the TDD mode, N2 corresponds to 2 * m radio frames, and m corresponds to 1 (N) Or more.
13. 9. The method of claim 8,

    The processor is also configured to repeatedly receive an NRS (Narrowband Reference Signal), wherein the initialization value of the sequence used to generate the NRS is P for FDD mode, P + a for TDD mode, and P is an NCell ID Narrowband Cell Identity), and a represents a non-zero integer.
14. 9. The method of claim 8,

    Wherein the wireless communication system includes a wireless communication system supporting a Narrowband Internet of Things (NB-IoT).

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