Method and device for controlling transmission of sounding reference signal in radio connection system supporting machine type communication

The present invention relates to a wireless connection system that supports Machine Type Communication (MTC), in particular, a method in which an MTC terminal transmits a Sounding Reference Signal (SRS), and transmission of SRS when transmitting uplink data. It relates to a method of controlling the above and a device supporting it.

Wireless connection systems are widely deployed to provide various communication services such as voice and data. In general, a wireless connection system is a multiple access system that can share available system resources (bandwidth, transmit power, etc.) to support communication with multiple users. Examples of multiple access systems include CDMA (code division multiple access) systems, FDMA (frequency division multiple access) systems, TDMA (time division multiple access) systems, OFDMA (orthogonal frequency division multiple access) systems, and SC-FDMA (single). There is a carrier frequency division multiple access) system.

<p> The present invention relates to a method of transmitting a Sounding Reference Signal (SRS) in a wireless communication environment that supports MTC, and a device that supports the method.</p><p> An object of the present invention is to provide an SRS configuration method and an SRS transmission method for repeatedly transmitting SRS in an MTC environment.</p><p> Another object of the present invention is to provide a method of transmitting SRS and uplink data for frequency retuning when the SRS transmission subband and the subband for transmitting uplink data do not match in an MTC environment. It is in.</p><p> Still another object of the present invention is to provide a method of transmitting SRS and uplink data when the SRS transmission subframe and the subframe for transmitting uplink data are different in the MTC environment.</p><p> Yet another object of the present invention is to provide a device that supports such a method.</p><p> The technical objectives to be achieved in the present invention are not limited to the matters mentioned above, and other technical problems not mentioned are described below from the examples of the present invention to the technical objects to which the present invention belongs. It may be considered for those with normal knowledge in the field.</p>

<p> The present invention provides a method of controlling transmission of SRS in a wireless connection system that supports machine-type communication and a device that supports these methods.</p><p> As an aspect of the present invention, in a wireless connection system that supports machine-type communication (MTC), a method in which an MTC terminal controls sounding reference signal (SRS) transmission receives an upper layer signal including information about SRS that is repeatedly transmitted. It can include a step of configuring the SRS based on information about the SRS, and a step of transmitting the SRS in a subband to which a frequency-hopped physical uplink shared channel (PUSCH) is assigned. At this time, the subband is composed of six physical resource blocks (PRBs), and the SRS may be sequentially transmitted to the frequency-hopped subband.</p><p> In another aspect of the invention, an MTC terminal that controls sounding reference signal (SRS) transmission in a wireless connection system that supports machine-type communication (MTC) is a transmitter, receiver, and processor for controlling SRS transmission. Can be provided. At this time, the processor controls and receives the upper layer signal including the information about the SRS to be repeatedly transmitted, configures the SRS based on the information about the SRS, controls the transmitter, and sets the frequency of the SRS. The physical uplink shared channel (PUSCH) to be hopped may be configured to transmit in the assigned subband. At this time, the subband is composed of six physical resource blocks (PRBs), and the SRS may be sequentially transmitted to the frequency-hopped subband.</p><p> The upper layer signal can further include subband information indicating the subband to which the SRS is transmitted.</p><p> SRS may be transmitted sequentially in one PRB unit.</p><p> The SRS may be repeatedly transmitted a predetermined number of times in a subband.</p><p> The SRS may be an SRS transmitted periodically or at the request of the base station.</p><p> The mode of the invention described above is only a part of the preferred embodiments of the present invention, and various examples reflecting the technical features of the present invention are for those who have ordinary knowledge in the art. , Will be derived and understood based on the detailed description of the invention described in detail below.</p>

<p> According to the examples of the present invention, the following effects can be obtained.</p><p> First, the base station can more reliably estimate the uplink channel for the MTC terminal located in a poor environment by receiving the repeatedly transmitted SRS.</p><p> Secondly, the MTC terminal JP by utilizing SRS generation method and SRS transmission method for SRS repeat transmissions Yu, uplink channel can be efficiently utilized for the MTC terminal.</p><p> Third, the amount of data transmission processing is lost by dropping the SRS transmission and transmitting only the PUSCH due to frequency retuning that may occur when the MTC terminal does not match the SRS transmission subband and the PUSCH transmission subband. Can be reduced.</p><p> The effects obtained from the examples of the present invention are not limited to the effects mentioned above, and other effects not mentioned above are usually described in the field of technology to which the present invention belongs from the following description of the examples of the present invention. It will be clearly derived and understood by those who have the knowledge of. That is, an effect unintended in carrying out the present invention can also be derived from the examples of the present invention by a person having ordinary knowledge in the field of the present invention.</p>

The accompanying drawings included as part of a detailed description to aid an understanding of the invention provide various embodiments of the invention. In addition, the accompanying drawings are used to explain embodiments of the present invention along with detailed description.<figref num="1">It is a figure for demonstrating the physical channel and the signal transmission method using these.</figref><figref num="2">It is a figure which shows an example of the structure of a wireless frame.</figref><figref num="3">It is a figure which illustrates the resource grid (resource grid) for a downlink slot.</figref><figref num="4">It is a figure which shows an example of the structure of the uplink subframe.</figref><figref num="5">It is a figure which shows an example of the structure of a downlink subframe.</figref><figref num="6">It is a figure which shows an example of the carrier merging used in the component carrier (CC) and LTE-A system.</figref><figref num="7">It is a figure which shows the structure of the subframe of the LTE-A system by cross-carrier scheduling.</figref><figref num="8">It is a figure which shows an example of the serving cell composition by cross carrier scheduling.</figref><figref num="9">It is a figure which shows one of the SRS transmission methods used in the Example of this invention.</figref><figref num="10">FIG. 10 (a) is a diagram showing the concept of periodic SRS transmission, and FIG. 10 (b) is a diagram showing the concept of aperiodic SRS transmission.</figref><figref num="11">It is a figure which shows one of the methods which the MTC terminal repeats SRS transmission when the trigger type is 0 among the SRS transmission methods.</figref><figref num="12">It is a figure which shows one of the methods which the MTC terminal repeats SRS transmission in the case of the trigger type 1 among the SRS transmission methods.</figref><figref num="13">It is a figure for demonstrating one of the methods of performing SRS transmission at the time of frequency hop.</figref><figref num="14">It is a figure for demonstrating the method of controlling SRS transmission when the subband for uplink transmission and the subband for SRS transmission do not match.</figref><figref num="15">It is a figure explaining the apparatus which can embody the method described with respect to FIG. 1 to FIG.</figref>

The embodiments of the present invention described in detail below relate to a method of transmitting SRS in a wireless connection system that supports machine-type communication and a device that supports the method.

The following examples combine the components and features of the present invention in a predetermined form. Each component or feature can be considered as selective unless otherwise explicitly mentioned. Each component or feature can be implemented in a form that does not combine with other components or features. It is also possible to combine some components and / or features to form an embodiment of the present invention. The order of operations described in the examples of the present invention may be changed. Some configurations or features of one embodiment may be included in other embodiments or may be replaced by corresponding configurations or features of other embodiments.

In the description of the drawings, the procedure or step that may obscure the gist of the present invention is omitted, and the procedure or step that can be understood at the level of those skilled in the art is also omitted.

Throughout the specification, when a component is referred to as "contains" a component, this does not mean to exclude the other component, and may further include the other component, unless otherwise specified. Means. In addition, terms such as "... part", "... machine", and "module" described in the specification mean a unit for processing at least one function or operation, which is hardware. It can be embodied by software, or a combination of hardware and software. Also, "a or an", "one", "the" and similar related terms are used in the context of describing the invention (particularly in the context of the following claims). It may be used in both singular and plural senses unless specifically indicated in the specification or explicitly refuted by the context.

In the present specification, the embodiment of the present invention has been described focusing on the data transmission / reception relationship between the base station and the mobile station. Here, the base station has a meaning as a terminal node of a network that directly communicates with a mobile station. In some cases, the specific operation performed by the base station in this document may be performed by the upper node of the base station.

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

Further, the "terminal" referred to in the embodiment of the present invention is a user device (UE: User Equipment), a mobile station (MS: Mobile Station), a subscriber terminal (SS: Subscriber Station), and a mobile subscriber terminal (SS: Subscriber Station). It may be replaced with terms such as MSS: Mobile Subscriber Station), mobile terminal (Mobile Terminal), or advanced mobile terminal (AMS).

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

The embodiments of the present invention can be supported by standard documents disclosed in at least one of the wireless connection systems IEEE 802.xx system, 3GPP (3rd Generation Partnership Project) system, 3GPP LTE system and 3GPP2 system. In particular, the examples of the present invention can be supported by the documents of 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS 36.213, 3GPP TS 36.321 and 3GPP TS 36.331. That is, obvious steps or parts not described in the examples of the present invention can be described with reference to the above document. In addition, all the terms disclosed in this document can be explained by the above standard documents.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. The detailed description disclosed below, along with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention, not to indicate the only embodiment in which the invention can be practiced.

In addition, the specific terms used in the examples of the present invention are provided to assist the understanding of the present invention, and the use of such specific terms is not deviated from the technical idea of the present invention. It may be changed to a form.

In the following, a 3GPP LTE / LTE-A system will be described as an example of a wireless connection system to which the embodiment of the present invention can be applied.

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

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

UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP LTE (Long Term Evolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA, and adopts OFDMA on the downlink and SC-FDMA on the uplink. The LTE-A (Advanced) system is an improved system of the 3GPP LTE system. In order to clarify the description of the technical features of the present invention, examples of the present invention will be described focusing on the 3GPP LTE / LTE-A system, but may be applied to an IEEE 802.16e / m system or the like.

1.3GPP LTE / LTE_A system

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

1.1 System in general

FIG. 1 is a diagram for explaining a physical channel that can be used in an embodiment of the present invention and a signal transmission method using these.

A terminal that is turned on again with the power turned off or that has entered a new cell performs initial cell search work such as synchronizing with the base station at the S11 stage. Therefore, the terminal receives the primary synchronization channel (P-SCH: Primary Synchronization Channel) and the secondary synchronization channel (S-SCH: Secondary Synchronization Channel) from the base station and synchronizes with the base station, and the cell ID, etc. Get information.

After that, the terminal can receive the physical broadcast channel (PBCH) signal from the base station and acquire the in-cell broadcast information.

On the other hand, the terminal can confirm the downlink channel status by receiving the downlink reference signal (DL RS) at the initial cell search stage.

The terminal that has completed the initial cell search uses the Physical Downlink Control Channel (PDCCH) and the Physical Downlink Shared Channel (PDSCH) based on the physical downlink control channel information at the S12 stage. It can be received and more specific system information can be obtained.

The terminal can then perform a random access procedure (Random Access Procedure) such as steps S13 to S16 to complete the connection to the base station. To this end, the terminal transmits a preamble via a physical random access channel (PRACH) (S13), via a physical downlink control channel and its corresponding physical downlink sharing channel. A response message to the preamble can be received (S14). In competition-based random access, the terminal resolves conflicts such as sending additional physical random access channel signals (S15) and receiving physical downlink control channel signals and their corresponding physical downlink shared channel signals (S16). You can perform the procedure (Contention Resolution Procedure).

After that, the terminal that has performed the above procedure receives the physical downlink control channel signal and / or the physical downlink shared channel signal (S17), and the physical uplink as a general uplink / downlink signal transmission procedure. It is possible to transmit (S18) a link shared channel (PUSCH) signal and / or a physical uplink control channel (PUCCH) signal.

The control information transmitted by the terminal to the base station is collectively called uplink control information (UCI). UCI includes HARQ-ACK / NACK (Hybrid Automatic Repeat and reQuest Acknowledgment / Negative-ACK), SR (Scheduling Request), CQI (Channel Quality Indication), PMI (Precoding Matrix Indication), RI (Rank Indication) information, etc. ..

In LTE systems, UCIs are generally transmitted cyclically via PUCCH, but may be transmitted via PUSCH if control information and traffic data should be transmitted simultaneously. UCI may also be transmitted aperiodically via PUSCH in response to network requests / instructions.

FIG. 2 shows the structure of the wireless frame used in the embodiment of the present invention.

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

1 Radio frame is T_f= 307200 . T_s= 10ms long, T_slot= 15360 . T_sIt consists of 20 slots with an even length of 0.5ms and an index from 0 to 19. One subframe is defined as two consecutive slots, and the i-th subframe is composed of slots corresponding to 2i and 2i + 1. That is, a radio frame is composed of 10 subframes. The time it takes to transmit one subframe is called TTI (transmission time interval). Here, Ts represents the sampling time and is displayed as Ts = 1 / (15kHz × 2048) = 3.2552 × 10-8 (about 33ns). A slot contains a plurality of OFDM symbols or SC-FDMA symbols in the time domain and a plurality of resource blocks in the frequency domain.

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

In a full-duplex FDD system, 10 subframes can be used simultaneously for downlink transmission and uplink transmission in each 10ms section. At this time, the uplink transmission and the downlink transmission are distinguished by the frequency domain. On the other hand, in a half-duplex FDD system, the terminal cannot transmit and receive at the same time.

The structure of the radio frame described above is merely an example, and the number of subframes contained in the radio frame, the number of slots contained in the subframe, or the number of OFDM symbols contained in the slots may be changed in various ways. ..

Figure 2 (b) shows a frame structure type 2. Type 2 frame structure applies to TDD systems. 1 wireless frame is T_f= 307200 . T_s= 10ms long, 153600 . T_sIt consists of two half-frames with a length of = 5ms. Each half frame is 30720 . T_sIt consists of 5 subframes with a length of 1ms. The i-th subframe is each T corresponding to 2i and 2i + 1._slot= 15360 . T_s= Consists of two slots with a length of 0.5ms. Here, Ts represents the sampling time and is displayed as Ts = 1 / (15kHz × 2048) = 3.2552 × 10-8 (about 33ns).

Type 2 frames include special subframes consisting of three fields: DwPTS (Downlink Pilot Time Slot), Guard Period (GP), and UpPTS (Uplink Pilot Time Slot). Here, DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used to synchronize channel estimation at a base station and upstream transmission at a terminal. The protection section is a section for removing the interference caused by the uplink due to the multiple path delay of the downlink signal between the uplink and the downlink.

Table 1 below shows the special frame configuration (DwPTS / GP / UpPTS length).

<tables num="1"><img file="JP2019205193A_D0001.tif" /></tables>

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

Referring to FIG. 3, one downlink slot contains multiple OFDM symbols in the time domain. Here, it is assumed that one downlink slot contains 7 OFDM symbols and one resource block contains 12 subcarriers in the frequency domain, but the present invention is not limited to this.

Each element is a resource element on the resource grid, and one resource block contains 12 × 7 resource elements. The number of resource blocks contained in a downlink slot NDL depends on the downlink transmit bandwidth. The structure of the uplink slot may be the same as the structure of the downlink slot.

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

With reference to FIG. 4, uplink subframes are divided into a control domain and a data domain in the frequency domain. A PUCCH that carries uplink control information is assigned to the control area. A PUSCH that carries user data is assigned to the data area. To maintain single carrier characteristics, one terminal does not transmit PUCCH and PUSCH at the same time. RB pairs are assigned to PUCCH for one terminal in the subframe. The RBs that belong to the RB pair occupy different subcarriers in each of the two slots. This is called frequency hopping of the RB pair assigned to PUCCH at the slot boundary.

FIG. 5 shows the structure of the downlink subframe that can be used in the examples of the present invention.

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

PCFICH carries information about the number of OFDM symbols (ie, the size of the control area) transmitted in the first OFDM symbol in the subframe and used for transmission of the control channel within the subframe. PHICH is a response channel for uplinks and carries ACK (Acknowledgement) / NACK (Negative-Acknowledgement) signals for HARQ (Hybrid Automatic Repeat Request). The control information transmitted via PDCCH is called downlink control information (DCI). The downlink control information includes uplink resource allocation information, downlink resource allocation information, or uplink transmit (Tx) power control instructions for any terminal group.

1.2 PDCCH (Physical Downlink Control Channel)

1.2.1 PDCCH General

PDCCH is a DL-SCH (Downlink Shared Channel) resource allocation and transmission format (that is, downlink grant (DL-Grant)) and UL-SCH (Uplink Shared Channel) resource allocation information (that is, uplink grant (UL)). -Grant)), for paging information in PCH (Paging Channel), system information in DL-SCH, and upper-layer control messages such as random access response sent in PDSCH. It can carry resource allocation, a set of transmission power control instructions for individual terminals in any terminal group, and information on whether or not VoIP (Voice over IP) is activated.

Multiple PDCCHs may be transmitted within the control area and the terminal can monitor multiple PDCCHs. A PDCCH is composed of an aggregation of one or more consecutive CCEs (control channel elements). A PDCCH composed of one or more contiguous sets of CCEs can be transmitted through the control region after undergoing subblock interleaving. The CCE is a logical allocation unit used to provide the PDCCH with the code rate according to the state of the radio channel. CCE corresponds to multiple resource element groups (REGs). The relationship between the number of CCEs and the code rate provided by the CCEs determines the format of the PDCCH and the number of possible bits of the PDCCH.

1.2.2 PDCCH structure

Multiple multiplexed PDCCHs for multiple terminals may be transmitted within the control area. PDCCH consists of one or more contiguous CCE aggregations. CCE refers to the unit corresponding to 9 sets of REG composed of 4 resource elements. Four QPSK (Quadrature Phase Shift Keying) symbols are mapped to each REG. Resource elements occupied by the reference signal (RS) are not included in the REG. That is, the total number of REGs in the OFDM symbol may differ depending on whether or not a cell-specific reference signal exists. The concept of REG, which maps four resource elements to one group, can also be applied to other downlink control channels (eg PCFICH or PHICH). N REGs that cannot be assigned to PCFICH or PHICH_REGIf so, the number of CCEs available in the system is<maths num="1"><img file="JP2019205193A_D0002.tif" /></maths>And each CCE is 0 to N_CCEIt has an index up to -1.

To simplify the terminal decoating process, the PDCCH format containing n CCEs may start with a CCE that has the same index as a multiple of n. That is, if the CCE index is i<maths num="2"><img file="JP2019205193A_D0003.tif" /></maths>It may start with a CCE that meets.

The base station can use {1,2,4,8} CCEs to form one PDCCH signal, where {1,2,4,8} is the CCE aggregation level. ). The number of CCEs used to transmit a particular PDCCH is determined by the base station depending on the channel state. For example, a PDCCH for a terminal with good downlink channel status (when in close proximity to a base station) may be sufficient with only one CCE. On the other hand, for terminals with poor channel conditions (when at cell boundaries), 8 CCEs may be required for robustness. Moreover, the power level of the PDCCH may also be adjusted to match the channel state.

Table 2 below shows the PDCCH format. The CCE set level supports four PDCCH formats, as shown in Table 2.

<tables num="2"><img file="JP2019205193A_D0004.tif" /></tables>

The reason why the CCE set level is different for each terminal is that the format of the control information carried on the PDCCH or the MCS (Modulation and Coding Scheme) level is different. MCS level means the code rate and modulation order used for data coding. Adaptive MCS levels are used for link adaptation. Generally, about 3 to 4 MCS levels can be considered in the control channel that transmits control information.

Explaining the format of control information, the control information transmitted via PDCCH is called downlink control information (DCI). The composition of the information carried on the PDCCH payload may differ depending on the DCI format. The PDCCH payload means an information bit. Table 3 below shows DCI in DCI format.

<tables num="3"><img file="JP2019205193A_D0005.tif" /></tables>

Refer to Table 3, the DCI formats include format 0 for PUSCH scheduling, format 1 for scheduling one PDSCH code word, format 1A for simple (compact) scheduling of one PDSCH code word, Format 1C for very simple scheduling of DL-SCH, Format 2 for PDSCH scheduling in Closed-loop spatial multiplexing mode, Open-loop spatial multiplexing mode There are formats 2A for PDSCH scheduling in, and formats 3 and 3A for transmitting TPC (Transmission Power Control) instructions for uplink channels. DCI format 1A can be used for PDSCH scheduling regardless of which transmission mode is set on the terminal.

The PDCCH payload length may vary depending on the DCI format. In addition, the type of PDCCH payload and its length may differ depending on whether or not it is simple (compact) scheduling, or the transmission mode set in the terminal.

The transmission mode can be configured so that the terminal receives downlink data via PDSCH. For example, downlink data via PDSCH includes scheduled data on the terminal, paging, random access response, or broadcast information via BCCH. Downlink data via PDSCH is related to the DCI format signaled via PDCCH. The transmission mode can be semi-statically set in the terminal by upper layer signaling (for example, RRC (Radio Resource Control) signaling). The transmission mode can be distinguished into single antenna transmission and multi-antenna transmission.

The transmission mode of the terminal is set semi-statically by upper layer signaling. For example, for multi-antenna transmission, transmit diversity, open-loop or closed-loop spatial multiplexing, MU-MIMO (Multi-user-Multiple Input Multiple Output). , And beam forming. Transmission diversity is a technology that enhances transmission reliability by transmitting the same data with multiple transmission antennas. Spatial multiplexing is a technology that enables multiplex transmission antennas to simultaneously transmit different data and transmit high-speed data without increasing the bandwidth of the system. Beam formation is a technique for increasing the SINR (Signal to Interference plus Noise Ratio) of a signal by giving a weighted value according to the channel state with a multiple antenna.

The DCI format depends on the transmission mode set in the terminal. There is a Reference DCI format that the terminal monitors according to the transmission mode set to itself. As follows, the transmission mode set in the terminal can have 10 transmission modes.

(1) Transmission mode 1: Single antenna port; Port 0

(2) Transmission mode 2: Transmit Diversity

(3) Transmission mode 3: Open-loop Spatial Multiplexing

(4) Transmission mode 4: Closed-loop Spatial Multiplexing

(5) Transmission mode 5: Multiple user MIMO

(6) Transmission mode 6: Closed loop rank = 1 precoding

(7) Transmission mode 7: Precoding to support single-layer transmission, not based on codebook

(8) Send mode 8: Precoding to support up to 2 layers, not based on codebook

(9) Send mode 9: Precoding to support up to 8 layers, not based on codebook

(10) Transmission mode 10: Precoding to support up to 8 layers, not based on codebook, used for CoMP

1.2.3 PDCCH transmission

The base station determines the PDCCH format by the DCI to be transmitted to the terminal, and adds CRC (Cyclic Redundancy Check) to the control information. The CRC masks a unique identifier (for example, RNTI (Radio Network Temporary Identifier)) depending on the owner and usage of the PDCCH. If it is a PDCCH for a specific terminal, a terminal-specific identifier (for example, C-RNTI (Cell-RNTI)) can be masked to CRC. Alternatively, if it is a PDCCH for a paging message, the paging instruction identifier (for example, P-RNTI (Paging-RNTI)) can be masked to CRC. If it is a PDCCH for system information, more specifically a system information block (SIB), then a system information identifier (eg SI-RNTI (system information)). RNTI)) can be masked to CRC. RA-RNTI (random access-RNTI) can be masked to CRC to indicate the random access response, which is the response to the transmission of the terminal's random access preamble.

Subsequently, the base station performs channel coding on the control information to which the CRC is added to generate coded data. At this time, channel coding can be performed at the code rate according to the MCS level. The base station performs rate matching according to the CCE set level assigned to the PDCCH format and modulates the encoded data to generate a modulated symbol. At this time, a modulation sequence based on the MCS level can be used. The modulation symbols that make up one PDCCH may have a CCE set level of 1, 2, 4, or 8. The base station then maps the modulation symbols to physical resource elements (CCE to RE mapping).

1.2.4 Blind Decoding (BS)

Multiple PDCCHs may be transmitted within one subframe. That is, the control area of one subframe has indexes 0 to N._{CCE, k}Consists of multiple CCEs with -1. Where N_{CCE, k}Means the total number of CCEs in the control area of the kth subframe. The terminal monitors multiple PDCCHs for each subframe. Here, monitoring means that the terminal attempts to decode each of the PDCCHs in the monitored PDCCH format.

The base station does not provide information about where the PDCCH is located in the control area allocated to the terminal within the subframe. The terminal cannot know where and in which CCE set level or DCI format its PDCCH is transmitted in order to receive the control channel transmitted from the base station, and the terminal candidate within the subframe. ) To monitor its own PDCCH. This is called blind decoding (BD). Blind decoding means that after the terminal de-masking its own terminal identifier (UE ID) in the CRC part, the CRC error is examined and it is confirmed whether or not the PDCCH is its own control channel. Refer to the method.

In active mode, the terminal monitors the PDCCH per subframe to receive the data sent to it. In DRX mode, the terminal wakes up in the monitoring section for each DRX cycle and monitors the PDCCH in the subframe corresponding to the monitoring section. The subframe in which PDCCH is monitored is called a non-DRX subframe.

In order to receive the PDCCH transmitted to itself, the terminal must perform blind decoding for all CCEs existing in the control area of the non-DRX subframe. Since the terminal cannot know which PDCCH format will be transmitted, it must decode all PDCCH at the possible CCE population level until it succeeds in blind decoding the PDCCH within each non-DRX subframe. .. The terminal cannot figure out how many CCEs the PDCCH for itself uses and must attempt detection at all possible CCE population levels until successful blind decoding of the PDCCH.

The LTE system defines the search space (SS) concept for blind decoding of terminals. The search space means a set of PDCCH candidates for the terminal to monitor and can have different sizes for each PDCCH format. The search space can include a shared search space (CSS: Common Search Space) and a terminal specific search space (USS: UE-specific / Dedicated Search Space).

In the case of the shared search space, all terminals can recognize the size of the shared search space, but the terminal specific search space can be set individually for each terminal. Therefore, the terminal must monitor all terminal-specific search spaces and shared search spaces in order to decode the PDCCH, thus performing up to 44 blind decodings (BDs) in one subframe. .. This does not include blind decoding with different CRC values (eg C-RNTI, P-RNTI, SI-RNTI, RA-RNTI).

Due to search space constraints, it is possible that the base station may not have enough CCE resources to transmit PDCCH to all terminals that attempt to transmit PDCCH within a given subframe. This is because the resources remaining after being assigned the CCE position may not be included in the search space of a specific terminal. To minimize such barriers that can continue in the next subframe, a terminal-specific hopping sequence can be applied to the starting point of the terminal-specific search space.

Table 4 shows the sizes of the shared search space and the terminal specific search space.

<tables num="4"><img file="JP2019205193A_D0006.tif" /></tables>

To reduce the load on the terminal due to the number of blind decoding attempts, the terminal does not search in all defined DCI formats at the same time. Specifically, the terminal always searches for DCI formats 0 and 1A in the terminal specific search space. At this time, DCI formats 0 and 1A have the same size, but the terminal uses the flag for format 0 / format 1A differentiation used to distinguish DCI formats 0 and 1A contained in the PDCCH. The format can be distinguished. In addition to DCI format 0 and DCI format 1A, other DCI formats may be required for the terminal, and DCI formats 1, 1B, and 2 are examples.

In the shared search space, the terminal can search DCI formats 1A and 1C. Also, the terminal may be set to search for DCI format 3 or 3A, where DCI formats 3 and 3A have the same size as DCI formats 0 and 1A, but the terminal is scrambled by an identifier other than the terminal specific identifier. The DCI format can be distinguished by using the CRC.

Search space<maths num="3"><img file="JP2019205193A_D0007.tif" /></maths>Is the set level<maths num="4"><img file="JP2019205193A_D0008.tif" /></maths>Means the PDCCH candidate set by. The CCE by the PDCCH candidate set m of the search space can be determined by the following equation 1.

[Equation 1]<maths num="5"><img file="JP2019205193A_D0009.tif" /></maths>

Where M^(L)Represents the number of PDCCH candidates by CCE set level L for monitoring in the search space, m = 0, ..., M^(L)It is -1. i is an index that specifies an individual CCE for each PDCCH candidate in PDCCH, and i = 0, ···, L-1.<maths num="6"><img file="JP2019205193A_D0010.tif" /></maths>And n_sRepresents the slot index within the radio frame.

As mentioned above, the terminal monitors both the terminal specific search space and the shared search space to decode the PDCCH. Here, the shared search space (CSS) supports the PDCCH with the set level of {4,8}, and the terminal specific search space (USS) supports the PDCCH with the set level of {1,2,4,8}. To support. Table 5 shows the PDCCH candidates monitored by the terminal.

<tables num="5"><img file="JP2019205193A_D0011.tif" /></tables>

Referencing Equation 1, for a shared search space, Y for two set levels, L = 4 and L = 8._kIs set to 0. On the other hand, in the case of the terminal specific search space, Y for the set level L_kIs defined as in Equation 2.

[Equation 2]<maths num="7"><img file="JP2019205193A_D0012.tif" /></maths>

here,<maths num="8"><img file="JP2019205193A_D0013.tif" /></maths>And n_RNTIRepresents the RNTI value. Also, A = 39827 and D = 65537.

2. Carrier Aggregation (CA) environment

2.1 CA General

3GPP LTE (3rd Generation Partnership Project Long Term Evolution; Rel-8 or Rel-9) system (hereinafter referred to as LTE system) is a multiple carrier wave that divides a single component carrier (CC: Component Carrier) into multiple bands and uses it. A modulation (MCM: Multi-Carrier Modulation) method is used. However, in 3GPP LTE-Advanced systems (LTE-A systems), carrier merging (CA:) uses one or more component carriers in combination to support a wider system bandwidth than LTE systems. A method such as Carrier Aggregation) can be used. Carrier merging can also be referred to as carrier aggregation, carrier matching, multi-component carrier environment (Multi-CC), or multi-carrier environment.

In the present invention, multicarrier means carrier merging (or carrier merging), in which case carrier merging is not only merging between adjacent carriers, but also between non-contiguous carriers. It also means annexation. Further, the number of component carriers collected in the downlink and the uplink may be set differently. When the number of downlink component carriers (hereinafter referred to as "DL CC") and the number of uplink component carriers (hereinafter referred to as "UL CC") match, it is called symmetric merging. When the numbers are different, it is called asymmetric merging. Such carrier merging may be paraphrased into terms such as carrier aggregation, bandwidth aggregation, spectrum aggregation, and the like.

Carrier merging, which consists of combining two or more component carriers, aims to support up to 100MHz bandwidth in LTE-A systems. When combining one or more carriers with a bandwidth smaller than the target bandwidth, the bandwidth of the combined carriers is used in the existing system to maintain backward compatibility with the existing IMT system. It can be limited to bandwidth.

For example, existing 3GPP LTE systems support {1.4,3,5,10,15,20} MHz bandwidth, and 3GPP LTE-advanced systems (ie LTE-A) are compatible with existing systems. Therefore, only those bandwidths can be used to support bandwidths greater than 20 MHz. The carrier merging system used in the present invention can also define a new bandwidth to support carrier merging, regardless of the bandwidth used in the existing system.

Moreover, such carrier merging can be distinguished into an intra-band CA and an inter-band CA. Intra-band carrier merging means that multiple DL CCs and / or UL CCs are located adjacent or close to each other on frequency. In other words, it can mean that the carrier frequencies of DL CC and / or UL CC are located in the same band. On the other hand, an environment far away in the frequency domain can be called an inter-Band CA. In other words, it can mean that the carrier frequencies of multiple DL CCs and / or UL CCs are located in different bands from each other. In this case, the terminal can use a plurality of RF (radio frequency) ends for communication in the carrier merged environment.

LTE-A systems use the concept of cells to manage radio resources. The carrier merging environment described above can be referred to as a multiple cells environment. A cell is defined as a combination of downlink resource (DL CC) and uplink resource (UL CC), or uplink resource is not a required element. Therefore, the cell can be composed of the downlink resource alone or both the downlink resource and the uplink resource.

For example, if a particular terminal has one configured serving cell, it can have one DL CC and one UL CC. However, when a specific terminal has two or more set serving cells, it may have as many DL CCs as there are cells, and the number of UL CCs may be the same or smaller. Alternatively, DL CC and UL CC may be configured in reverse. That is, when a specific terminal has a plurality of set serving cells, a carrier merge environment in which UL CC is larger than the number of DL CC may be supported.

Carrier generation and recombination (CA) may also be understood as the merging of two or more cells with different carrier frequencies (cell center frequencies). The term "cell" in carrier generation is described in terms of frequency and must be distinguished from the commonly used "cell" as a geographical area covered by a base station. Hereinafter, the above-mentioned intra-band carrier merging is referred to as an intra-band multiplex cell, and the inter-band carrier merging is referred to as an inter-band multiplex cell.

The cells used in the LTE-A system include a primary cell (PCell: Primary Cell) and a secondary cell (S Cell: Secondary Cell). The P cell and S cell can be used as a serving cell. In the case of a terminal that is in the RRC_CONNECTED state but carrier merge is not set or does not support carrier merge, there is only one serving cell consisting of only P cells. On the other hand, in the case of a terminal in the RRC_CONNECTED state and in which carrier merging is set, one or more serving cells may exist, and the entire serving cell includes a P cell and one or more S cells.

Serving cells (P cell and S cell) can be set using RRC parameters. PhysCellId is the physical layer identifier of the cell and has an integer value from 0 to 503. SCellIndex is a short identifier used to identify an S cell and has an integer value from 1 to 7. The ServCellIndex is a short identifier used to identify a serving cell (P cell or S cell) and has an integer value from 0 to 7. A value of 0 is applied to the P cell and the SCellIndex is given in advance to apply to the S cell. That is, the cell having the smallest cell ID (or cell index) in the ServCellIndex is the P cell.

Cell P means a cell operating on the primary frequency (or primary CC). The terminal may be used to perform the initial connection establishment process, the connection resetting process, or the cell specified in the handover process. Further, the P cell means a cell that is the center of control-related communication among the serving cells set in the carrier merge environment. That is, the terminal can receive and transmit the PUCCH allocation only in its own P cell, and can use only the P cell when acquiring system information or changing the monitoring procedure. E-UTRAN (Evolved Universal Terrestrial Radio Access) is a handover procedure that uses RRC Connection Reconfigutaion messages in the upper layer, including mobility control info, for terminals that support the carrier merge environment. Therefore, it is possible to change only the P cell.

The S cell can mean a cell operating on a secondary frequency (or Secondary CC). Only one P cell may be assigned to a specific terminal, and one or more S cells may be assigned. The S cell can be configured after the RRC connection has been set up and can be used to provide additional radio resources. In the serving cell set in the carrier merge environment, PUCCH does not exist in the cells other than the P cell, that is, the S cell.

When adding an S cell to a terminal that supports a carrier merge environment, E-UTRAN can provide all system information about the behavior of related cells in the RRC_CONNECTED state using a dedicated signal. Changes in system information can be controlled by releasing and adding related S cells, at which time the upper layer RRC Connection Reconfigutaion message can be used. Rather than broadcasting in the associated S cell, E-UTRAN may perform specific signaling having different parameters for each terminal.

After the initial security activation process has begun, E-UTRAN can configure a network containing one or more S cells in addition to the P cells initially configured in the connection setup process. In a carrier merge environment, cells P and S can operate as their respective component carriers. In the following examples, the primary component carrier (PCC) may be used interchangeably with the P cell and the secondary component carrier (SCC) may be used interchangeably with the S cell.

FIG. 6 is a diagram showing an example of the component carrier (CC) used in the embodiment of the present invention and the carrier merging used in the LTE_A system.

Figure 6 (a) shows the single carrier structure used in LTE systems. Component carriers include DL CC and UL CC. One component carrier can have a frequency range of 20MHz.

Figure 6 (b) shows the carrier merge structure used in the LTE_A system. Figure 6 (b) shows the case where three component carriers with a frequency size of 20 MHz are combined. There are 3 DL CCs and 3 UL CCs each, but there is no limit to the number of DL CCs and UL CCs. In the case of carrier merging, the terminal can monitor three CCs at the same time, can receive downlink signals / data, and can transmit uplink signals / data.

If N DL CCs are managed in a specific cell, the network can assign M (M N) DL CCs to the terminals. At this time, the terminal can monitor only M limited DL CCs and receive the DL signal. The network can also prioritize L (L M N) DL CCs and assign the main DL CCs to terminals, in which case the UE must monitor L DL CCs. It doesn't become. This method may be applied equally to uplink transmission.

The linkage between the carrier frequency (or DL CC) of the downlink resource and the carrier frequency (or UL CC) of the uplink resource can be indicated by an upper layer message such as an RRC message or system information. For example, the combination of DL resource and UL resource can be configured by the linkage defined by SIB2 (System Information Block Type 2). Specifically, linkage can mean a mapping relationship between the DL CC to which the PDCCH carrying the UL grant is transmitted and the UL CC using the UL grant, and the DL CC (or DL CC) to which the data for HARQ is transmitted. It can also mean the mapping relationship between UL CC) and UL CC (or DL CC) to which the HARQ ACK / NACK signal is transmitted.

2.2 Cross Carrier Scheduling

The carrier merging system includes a self-scheduling method and a cross carrier scheduling method from the viewpoint of scheduling for a carrier (or carrier wave) or a serving cell. Cross-carrier scheduling can also be referred to as cross-component carrier scheduling (Cross Component Carrier Scheduling) or cross-cell scheduling (Cross Cell Scheduling).

In self-scheduling, PDCCH (DL grant) and PDSCH are transmitted in the same DL CC, or PUSCH transmitted by PDCCH (UL grant) transmitted in DL CC is linked with DL CC that received UL grant. It means that it is sent by UL CC.

Cross-carrier scheduling is when the PDCCH (DL grant) and PDSCH are sent in different DL CCs, or the PUSCH sent by the PDCCH (UL grant) sent in the DL CC is linked to the DL CC that received the UL grant. It means that it is sent by UL CC other than UL CC.

Cross-carrier scheduling can be activated or deactivated in a UE-specific manner and informs each terminal semi-statically using higher layer signaling (eg, RRC signaling). be able to.

When cross-carrier scheduling is activated, the PDCCH needs a carrier indicator field (CIF) that tells which DL / UL CC the PDSCH / PUSCH indicated by the PDCCH is transmitted. For example, PDCCH can allocate PDSCH or PUSCH resources to one of multiple component carriers using CIF. That is, the CIF is set when the PDSCH or PUSCH resource is assigned to one of the DL / UL CCs in which PDCCHs on the DL CC are multiplexed. In this case, the LTE Release-8 DCI format may be extended by CIF. At this time, the set CIF may be fixed to the 3-bit field, and the set CIF position may be fixed regardless of the DCI format size. You may also reuse the LTE Release-8 PDCCH structure (same coding and same CCE-based resource mapping).

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

If cross-carrier scheduling is possible, the terminal needs to monitor PDCCH for multiple DCIs in the control area of the monitoring CC by CC-specific transmission mode and / or bandwidth. Therefore, it is necessary to configure a search space and PDCCH monitoring that can support this.

In a carrier merge system, a terminal DL CC set refers to a set of DL CCs scheduled for a terminal to receive a PDSCH, and a terminal UL CC set is a set of UL CCs scheduled for a terminal to send a PUSCH. Point to. In addition, the PDCCH monitoring set means a set of at least one DL CC that performs PDCCH monitoring. The PDCCH monitoring set may be the same as the terminal DL CC set or may be a subset of the terminal DL CC set. The PDCCH monitoring set can include at least one of the DL CCs in the terminal DL CC set. Alternatively, the PDCCH monitoring set may be defined separately from the terminal DL CC set. DL CCs contained in the PDCCH monitoring set can be configured to always allow self-scheduling for linked UL CCs. Such a terminal DL CC set, terminal UL The CC set and PDCCH monitoring set can be set to terminal specific (UE-specific), terminal group specific (UE group-specific), or cell specific (Cell-specific).

When cross-carrier scheduling is deactivated, it means that the PDCCH monitoring set is always identical to the terminal DL CC set, in which case another signaling-like instruction to the PDCCH monitoring set is given. Not necessary. However, when cross-carrier scheduling is activated, it is preferred that the PDCCH monitoring set be defined within the terminal DL CC set. That is, in order to schedule PDSCH or PUSCH to the terminal, the base station transmits PDCCH only through the PDCCH monitoring set.

FIG. 7 is a diagram showing a subframe structure of the LTE-A system by cross-carrier scheduling used in the embodiment of the present invention.

As shown in Figure 7, the DL subframe for LTE-A terminals has three downlink component carriers (DL CCs) combined and DL CC "A" is configured as the PDCCH monitoring DL CC. Is shown. If CIF is not used, each DL CC can send a PDCCH to schedule its PDSCH without CIF. On the other hand, if the CIF is used by higher layer signaling, only one DL CC "A" can use the CIF to send a PDCCH that schedules its own PDSCH or PDSCH of another CC. At this time, DL CCs "B" and "C" that are not set as PDCCH monitoring DL CC do not transmit PDCCH.

FIG. 8 is a diagram showing an example of a serving cell configuration by cross-carrier scheduling used in the embodiment of the present invention.

In a wireless connection system that supports carrier generation and recombination (CA), a base station and / or a terminal can be composed of one or more serving cells. In FIG. 8, the base station can support a total of four serving cells, cell A, cell B, cell C and cell D, terminal A is composed of cells A, B and C, and terminal B is It is assumed that the terminal C is composed of B cell, C cell and D cell, and the terminal C is composed of B cell. Here, at least one of the cells configured in each terminal can be set as a P cell. At this time, the P cell is always in the activated state, and the S cell may be activated or deactivated by the base station and / or the terminal.

In FIG. 8, the configured cells are cells of the base station that can be added to the CA based on the measurement report message from the terminal, and can be set for each terminal. The configured cell reserves a resource for sending an ACK / NACK message for sending a PDSCH signal in advance. An activated cell is a cell that is configured to actually transmit a PDSCH signal and / or a PUSCH signal among the configured cells, and transmits a CSI report and an SRS (Sounding Reference Signal) transmission. Do. A de-activated cell is a cell that is configured not to send or receive PDSCH / PUSCH signals by a base station command or timer operation, and CSI reporting and SRS transmission are also interrupted. ..

3. Sounding reference signal (SRS)

3.1 LTE / LTE-A system SRS

FIG. 9 is a diagram showing one of the SRS transmission methods used in the examples of the present invention.

SRS is used to estimate channel quality to allow frequency-selective scheduling on the uplink. At this time, the SRS transmission is performed regardless of the uplink data transmission and / or the uplink control information transmission. However, SRS can be used to improve power control or to provide a variety of new features for upcoming unscheduled terminals. For example, various new functions include initial MCS (Modulation and Coding Scheme) selection, initial power control for data transmission, time priority (TA) and so-called frequency semi-selective scheduling. At this time, frequency semi-selective scheduling means that frequency resources are selectively allocated to the first slot of the subframe and pseudo-randomly hopped to other frequencies in the second slot.

SRS can also be used to estimate downlink channel quality under the assumption that the uplink and downlink of the radio channel are reciprocal. Such an assumption is particularly useful for time division multiplexing (TDD) systems where the uplink and downlink share the same frequency spectrum and are separated in the time domain.

The subframe in which the SRS transmitted by any terminal in each cell is transmitted is indicated by cell-specific broadcast signaling. The cell-specific "srsSubframeConfiguration" parameter indicates a set of 15 possible subframes in which SRS can be transmitted within each radio frame. Such a configuration can provide flexibility in adjusting the SRS overhead for deployment scenarios. The 16th configuration in the cell is mainly the approach to the high speed terminal, and it is changed to turn off SRS completely in the cell.

SRS transmission consists of the SC-FDMA symbol at the end of the subframe. Therefore, SRS and DM-RS are located on separate SC-FDMA symbols. Also, PUSCH data transmission is not allowed on the SC-FDMA symbol assigned to SRS, and in the worst case, SRS overhead can occur about 7% per subframe.

Each SRS symbol is generated by a basic sequence in a given time interval and bandwidth, and all terminals in the cell use the same basic sequence. At this time, SRS transmissions from a large number of terminals in the cell can be orthogonally classified by separate circular transitions of the basic sequence. SRS sequences from other cells can be partitioned by assigning a separate basic sequence between each cell. However, orthogonality is not guaranteed between the basic sequences.

3.2 Terminal sounding signal transmission method

The method of transmitting the sounding reference signal by the terminal will be described below.

The terminal can send SRS on the SRS resource for each serving cell based on two trigger types. Trigger type 0 means a periodic SRS transmission method dictated by upper layer signaling, and trigger type 1 is transmitted via PDCCH to FDD and TDD schemes. It means the aperiodic SRS transmission method required through DCI format 2B / 2C / 2D transmitted via PDCCH for DCI format 0/4 / 1A or TDD scheme.

When SRS transmission by trigger types 0 and 1 occurs in the same subframe in the same serving cell, the terminal only performs SRS transmission by trigger type 1. The terminal can be configured with SRS parameters for trigger type 0 and / or trigger type 1 for each serving cell. In the following, the SRS parameters that are configured to specify or semi-statically serve the serving cell by the upper layer signal for the trigger type 0 and / or the trigger type 1 will be described.

Transmission comb as defined in section 5.5.3.2 of the 3GPP TS 36.211 standard document.<maths num="9"><img file="JP2019205193A_D0014.tif" /></maths>(Transmission comb) is configured for trigger type 0 and each trigger type 1.

3GPP TS 36.211 Starting physical resource block assignment as defined in Section 5.5.3.2 of the standard document n_RRCThe parameters are configured for trigger type 0 and each trigger type 1.

For trigger type 0, the duration parameter may be configured in a single subframe or indefinitely until it is released.

SRS transmission cycle T for trigger type 0_SRSAnd SRS subframe offset T_offsetThe srs-ConfigIndex ISRS parameters that indicate are defined in Tables 7 and 8 described below, and for trigger type 1, the SRS transmission cycle T._{SRS, 1}And the srs-ConfigIndex ISRS parameters indicating the SRS subframe offset Toffset, 1 are defined in Tables 10 and 11 described below.

SRS Bandwidth B as defined in Section 5.5.3.2 of the 3GPP TS 36.211 Standards Document_SRSThe parameters are configured for trigger type 0 and each trigger type 1.

Frequency hopping bandwidth as defined in Section 5.5.3.2 of the 3GPP TS 36.211 standard document b_hopThe parameters are configured for trigger type 0.

Circular transition n as defined in Section 5.5.3.1 of the 3GPP TS 36.211 standard document^cs_SRSThe parameters are configured for trigger type 0 and each trigger type 1.

Antenna port number N_pThe parameters are configured for trigger type 0 and each trigger type 1.

Three SRS parameter sets (eg, srs-ConfigApDCI-Format4) are composed of upper layer signals for trigger type 1 and DCI format 4. The 2-bit SRS request field contained in DCI format 4 indicates the SRS parameter set given in Table 6 below.

<tables num="6"><img file="JP2019205193A_D0015.tif" /></tables>

For trigger type 1 and DCI format 0, one SRS parameter set srs-ConfigApCDI-Format0 is configured by upper layer signaling. For trigger type 1 and DCI format 1A / 2B / 2C / 2D, one common SRS parameter set srs-ConfigApCDI-Format1a2b2c is configured by upper layer signaling.

Trigger type 1 can be triggered when the 1-bit SRS request field contained in DCI format 0 / 1A / 2B / 2C / 2D is set to "1" (ie, a positive SRS request). If the terminal is configured with SRS parameters for DCI format 0 / 1A / 2B / 2C / 2D by higher layer signaling, then there is a 1-bit SRS request field in DCI format 0 / 1A for frame structure type 1. It contains a 1-bit SRS request field in DCI format 0 / 1A / 2B / 2C / 2D for frame structure type 2.

Serving cell specific SRS transmission band C_SRSAnd the serving cell specific SRS transmission subframe is composed of upper layer signaling (eg, MAC, RRC message, etc.).

When the antenna selection is activated for the serving cell given to the terminal that assists the transmit antenna selection, the index of the terminal antenna that transmits the SRS transmitted to the time nSRS is in Equation 3 or Equation 4 below. Given as.

[Equation 3]<maths num="10"><img file="JP2019205193A_D0016.tif" /></maths>

Equation 3 shows when frequency hopping is deactivated for part or all of the sounding band (ie,<maths num="11"><img file="JP2019205193A_D0017.tif" /></maths>) Indicates the terminal antenna index.

[Equation 4]<maths num="12"><img file="JP2019205193A_D0018.tif" /></maths>

Equation 4 shows that frequency hopping is activated (ie, b)._hop&lt;B_SRS) Indicates the terminal antenna index. In Equations 3 and 4, the parameter values BSRS, bhop, Nb, and nSRS can refer to section 5.5.3.2 of the 3GPP TS 36.211 standard document. Also, unless single SRS transmission is configured on the terminal<maths num="13"><img file="JP2019205193A_D0019.tif" /></maths>Is set to. At this time, N_{b b}Regardless of the value<maths num="14"><img file="JP2019205193A_D0020.tif" /></maths>Is assumed to be. If the terminal consists of one or more serving cells, we do not expect the terminal to transmit SRS simultaneously through separate antenna ports.

The terminal is a serving cell and N_pIt can be configured to transmit SRS on multiple antenna ports. N_pThe value can be notified to the terminal by an upper layer signal. For PUSCH transmission mode 1<maths num="15"><img file="JP2019205193A_D0021.tif" /></maths>And for PUSCH transmission mode 2 for PUSCH composed of two antenna ports<maths num="16"><img file="JP2019205193A_D0022.tif" /></maths>And for the 4 antenna ports configured for PUSCH<maths num="17"><img file="JP2019205193A_D0023.tif" /></maths>Is.

A terminal configured to transmit SRS on the multiple antenna ports of the serving cell transmits SRS to all of the transmitting antenna ports configured within one SC-FDAM symbol in the same subframe of the serving cell. There must be. The SRS transmit bandwidth and start physical resource block allocation parameters are set to be the same for all the configured antenna ports of the corresponding serving cell.

Terminals that are not configured in the Timing Advanced Group (TAG) do not transmit SRS each time SRS and PUSCH transmissions are duplicated with the same symbol. TAG means a group of serving cells with the same TA for uplink synchronization with a base station in a carrier generation and recombination (CA) environment.

For TDD, if there is one SC-FDMA symbol in the UpPTS of a given serving cell, the SC-FDMA symbol can be used for SRS transmission. If there are two SC-FDMA symbols in the UpPTS of a given serving cell, the two SC-FDAM symbols can be assigned to the same terminal, and both can be used for SRS transmission.

A terminal that is not configured with multiple TAGs does not perform trigger type 0 SRS transmission if the trigger type 0 SRS transmission and PUCCH format 2 / 2a / 2b transmission collide within the same subframe. If a terminal that is not configured with multiple TAGs collides with trigger type 1 SRS transmission and PUCCH format 2a / 2b transmission or PUCCH format 2 transmission for HARQ information transmission within the same subframe, trigger type 1 SRS transmission is performed. Not performed. If a terminal that is not configured with multiple TAGs collides with PUCCH format 2 transmission excluding HARQ information transmission and trigger type 1 SRS transmission within the same subframe, PUCCH format 2 transmission excluding HARQ information transmission will not be performed. ..

When the ackNackSRS-SimultaneousTransmission parameter is set to "FALSE", terminals not configured with multiple TAGs will have PUCCH transmission and / or positive SR for SRS transmission and HARQ-ACK information transmission within the same subframe. If there is a collision, SRS transmission is not performed. When the ackNackSRS-SimultaneousTransmission parameter is set to "TRUE", terminals not configured with multiple TAGs will have PUCCH transmission and / or reduced format for SRS transmission and HARQ-ACK information transmission within the same subframe. When it collides with a positive SR that uses, SRS transmission is performed.

A terminal that is not configured with multiple TAGs does not perform SRS transmission if SRS transmission collides with PUCCH transmission for HARQ information transmission and / or a positive SR that uses the general PUCCH format within the same subframe.

In UpPTS, if the SRS transmission section overlaps with the PRACH area for preamble format 4 or exceeds the range of the uplink system bandwidth configured in the serving cell, the terminal does not perform SRS transmission.

The ackNackSRS-SimultaneousTransmission parameter provided by the upper layer determines whether the terminal simultaneously transmits PUCCH and SRS containing HARQ-ACK information within the same subframe. When the terminal is configured to transmit HARQ-ACK and SRS over PUCCH in the same subframe, in the cell-specific SRS subframe of the primary cell, the terminal uses the reduced PUCCH format to perform HARQ-ACK. And send SR. At this time, the HARQ-ACK or SR symbol corresponding to the SRS position is punctured. Even if the terminal does not perform SRS transmission within the cell-specific SRS subframe of the primary cell, the reduced PUCCH format is used within that subframe. Otherwise, the terminal uses general PUCCH format 1 / 1a / 1b or general PUCCH format 3 for HARQ-ACK and SR transmission.

SRS cycle T_SRSParameters and SRS subframe offset T_offsetTrigger type 0 SRS configurations for parameters are defined for FDD and TDD in Tables 7 and 8, respectively.

<tables num="7"><img file="JP2019205193A_D0024.tif" /></tables>

<tables num="8"><img file="JP2019205193A_D0025.tif" /></tables>

SRS transmission cycle parameter T_SRSIs identified as a serving cell and is selected from a set or subframe of {2,5,10,20,40,80,160,320} ms. 2ms T in TDD_SRSFor periodic parameters, the two SRS resources are configured in a given serving cell in a halfframe containing UL subframes.

T_SRSFor TDD or FDD of&gt; 2, SRS transmit instances (instances) of trigger type 0 in a given serving cell<maths num="18"><img file="JP2019205193A_D0026.tif" /></maths>Is determined by the subframe that satisfies. At this time, for FDD<maths num="19"><img file="JP2019205193A_D0027.tif" /></maths>Means the subframe index within the frame, for TDD, k_SRSIs defined in Table 9 below. Also, T_SRSFor TDD with = 2, the SRS send instance is<maths num="20"><img file="JP2019205193A_D0028.tif" /></maths>It is a subframe that satisfies.

<tables num="9"><img file="JP2019205193A_D0029.tif" /></tables>

SRS transmission cycle T for SRS transmission with trigger type 1 in the serving cell_{SRS, 1}And SRS subframe offset T_{offset, 1}Is defined for FDD and TDD in Tables 10 and 11, respectively.

<tables num="10"><img file="JP2019205193A_D0030.tif" /></tables>

<tables num="11"><img file="JP2019205193A_D0031.tif" /></tables>

Periodic parameter T for SRS transmission_{SRS, 1}Is a serving cell specific value and is selected from subframes or {2,5,10} ms sets. For a 2ms SRS transmission cycle in TDD, two SRS resources are configured in a given serving cell in a halfframe containing UL subframes.

In serving cell c, a terminal configured with type 1 SRS transmission and not configured by a carrier indicator field is in serving cell c if it detects a positive SRS request in PDCCH / EPDCCH scheduling PUSCH / PDSCH on serving cell c. Send SRS.

In the serving cell c, a terminal configured with a type 1 SRS transmission and configured with a carrier indicator field will have a serving cell c that corresponds to the carrier indicator field when it detects a positive SRS request in the PDCCH / EPDCCH that schedules PUSCH / PDSCH. Send SRS above.

In serving cell c, when a terminal configured with type 1 SRS transmission detects a positive SRS request in subframe n of serving cell c, FDD and T_{SRS, 1}For TDD&gt; 2,<maths num="21"><img file="JP2019205193A_D0032.tif" /></maths>as well as<maths num="22"><img file="JP2019205193A_D0033.tif" /></maths>Start SRS transmission within the first subframe that satisfies. Or, the terminal is T_{SRS, 1}For TDD with = 2<maths num="23"><img file="JP2019205193A_D0034.tif" /></maths>Start SRS transmission in the first subframe that satisfies. At this time, for FDD, frame n_fIn<maths num="24"><img file="JP2019205193A_D0035.tif" /></maths>Indicates the subframe index.

A terminal configured with a trigger type 1 SRS transmit has a type 1 SRS triggering event associated with a trigger type 1 SRS transmit parameter configured with other values by higher layer signaling for the same serving cell and the same subframe. Do not expect to receive.

The terminal does not transmit the SRS when the SRS collides with the PUSCH transmission corresponding to the retransmission of the same transmission block or the random access response as part of the competition based on the random access process within the same subframe.

3.3 Periodic SRS transmission and aperiodic SRS transmission

FIG. 10 (a) is a diagram showing the concept of periodic SRS transmission, and FIG. 10 (b) is a diagram showing the concept of aperiodic SRS transmission. At this time, periodic SRS transmission means SRS transmission of trigger type 0, and aperiodic SRS transmission means SRS transmission of trigger type 1.

First, the periodic SRS transmission will be described. Referring to FIG. 10 (a), the SRS transmission parameters for SRS transmission are transmitted from the base station to the terminal via a higher layer signal (eg, RRC signal) (S1010).

The SRS transmission parameters are the SRS transmission bandwidth parameter that indicates the bandwidth occupied by one SRS transmission, the hopping bandwidth parameter that indicates the frequency region in which the SRS transmission hops on the frequency, and the position where the SRS transmission starts on the frequency region. Frequency position parameters to indicate, transmission comb parameters to indicate SRS transmission positions or patterns, cyclic shift parameters to distinguish between SRSs, periodic parameters to indicate SRS transmission cycles, and It can include a subframe offset parameter that indicates the subframe to which the SRS is transmitted. At this time, the subframe offset parameter can specify a cell-specific SRS subframe, a terminal-specific SRS subframe, or the like.

The terminal can periodically perform SRS transmission at a fixed time interval of 2 ms to 160 ms based on the SRS transmission parameter (S1030).

At this time, since the SRS symbol must not be used for PUSCH transmission, all terminals in the cell may know in advance in which subframe in the cell the SRS transmission occurs.

Next, the aperiodic SRS transmission will be described. Aperiodic SRS transmissions are triggered by signaling on the PDCCH as part of scheduling approval. The frequency domain structure of aperiodic SRS transmission is the same as that of periodic SRS. However, when the aperiodic SRS is transmitted is set for each terminal through upper layer signaling.

Referring to FIG. 10 (b), the SRS transmission parameters for SRS transmission are transmitted from the base station to the terminal via a higher layer signal (eg, RRC signal) (S1020).

At this time, the SRS transmission parameters used in the aperiodic SRS transmission are basically the same as the SRS transmission parameters used in the periodic SRS transmission.

When requesting aperiodic SRS transmission, the base station transmits a PDCCH signal or an E-PDCCH signal in which the SRS request field is set to the terminal. At this time, the E-PDCCH signal means the control information transmitted via the PDSCH region. For a description of the PDCCH signal, see Section 1 above (S1040).

A terminal that explicitly receives a request for aperiodic SRS transmission at the S1040 stage can perform aperiodic SRS transmission in the corresponding subframe (S1060).

4. SRS transmission method of MTC terminal

4.1 MTC terminal

The LTE-A system will configure low-priced / low-specification terminals mainly for data communication such as meter reading of measuring instruments, water level measurement, utilization of surveillance cameras, and inventory reporting of vending machines in the next wireless communication system. I am considering it. In the embodiment of the invention seen, such a terminal will be referred to as an MTC (Machine Type Communication) terminal for convenience.

In the case of MTC terminals, the amount of transmitted data is small and upper link / downlink data transmission / reception occurs frequently, so it is efficient to reduce the unit price of the terminal and reduce battery consumption in accordance with such a low data transmission rate. Is the target. Such an MTC terminal is characterized by low mobility, and therefore has a characteristic that the channel environment is almost unchanged. Currently, LTE-A is considering ensuring that such MTC terminals have wider coverage than existing ones, which is why various coverage enhancement techniques for MTC terminals are available. It is being discussed.

The MTC terminal can be installed in an area (eg, basement, etc.) where the transmission environment is not as good as that of a legacy UE (that is, a general terminal). When a repeater or the like is installed for such an MTC terminal, a large amount of cost can be consumed for capital investment. Therefore, for MTC terminals operating in areas where the radio wave environment is poor, it may be efficient to provide stable communication by repeatedly transmitting downlink or uplink channels.

In the following, the SRS transmission method of the MTC terminal will be described in detail. At this time, the SRS transmission method can operate based on the methods described in Sections 1 to 3.

4.2 SRS transmission method-1

The SRS is then used to schedule the PUSCH by being transmitted on the uplink channel to assist in uplink channel measurements at the base station. At this time, the radio wave environment may be poor in the channel environment in which the MTC terminal is located. Therefore, the MTC terminal can be configured to repeatedly transmit SRS so that the base station can effectively estimate the uplink channel.

4.2.1 How to configure SRS for MTC terminals

The SRS transmitted by the MTC terminal can be configured to be repeatedly transmitted. The transmission of the SRS sequence is determined by the cell specific parameter and the UE specific parameter. At this time, it is preferable that the repeated transmission of SRS is performed in the time domain. Therefore, the sequence characteristics and transmission band of SRS can be set to be the same during the iterative transmission period of SRS.

The SRS transmission bandwidth is determined by the SRS bandwidth and SRS hopping related parameters, and for SRS iterative transmission, the SRS bandwidth and SRS hopping parameters maintain the same values during the SRS iterative transmission interval. Can be set as.

The SRS sequence is defined in the 3GPP TS 36.211 standard document as follows: (1) sequence group number u (sequence group number u) and (2) base sequence number v (2) determined by the transmission band and the presence or absence of sequence hopping. It can be determined by the base sequence number v), (3) the circular transition parameter which is the SRS transmission parameter, and (4) the SRS transmission antenna port.

The reason why the SRS is repeatedly transmitted in the time domain is to combine the SRS repeatedly received by the base station and improve the uplink channel estimation performance. Therefore, it is preferable that the SRS sequence does not change during the iterative transmission section. That is, the same SRS sequence can be repeatedly transmitted.

For this reason, the parameter values u and v used to determine the SRS sequence are preferably fixed during the iteration interval. In addition, sequence group hopping for SRS can be deactivated, and u and v can be set to constant values during repeated transmission intervals.

The method for setting the sequence group number u will be described below. The parameter value u for repeated SRS transmission can be defined as in Equation 5 below.

[Equation 5]<maths num="25"><img file="JP2019205193A_D0036.tif" /></maths>

In Equation 5, f_ghIs a function that indicates the group hopping pattern, f_ssMeans the SRS sequence transition pattern. At this time,<maths num="26"><img file="JP2019205193A_D0037.tif" /></maths>Determined to a value that satisfies, N^cell_IDMeans the cell identifier and np indicates the SRS transmission cycle. That is, in this case, the same SRS sequence is set to be used in all SRS iterative transmission intervals. At this time, if sequence group hopping is deactivated, f_gh(n_p) = 0 can be set.

Alternatively, if sequence group hopping is kept constant during the first SRS iteration interval and then set to use another SRS sequence in the next SRS iteration interval, f._gh(n_p) To SRS transmission cycle (n)_p) The function can be set to an arbitrary value. That is, the terminal can transmit SRS using a separate SRS sequence for each SRS iterative transmission cycle. Also at this time, the same SRS sequence is repeatedly transmitted within one SRS repeated transmission cycle.

The method for setting the basis sequence number v will be described below. The v value can be set to "0" as in existing LTE / LTE-A systems when the SRS transmission band is 6RB or less. When the SRS transmission band is 6RB or more, sequence hopping can be deactivated and the v value can be configured to be set to "0". This is because in existing LTE / LTE-A systems, the v value will have a separate value when activating sequence hopping, but the v value will be the same for each other when the MTC terminal repeatedly transmits SRS. This is to set to.

Alternatively, SRS sequence hopping is set to have the same v value between one iterative transmission interval and different v values between the next iterative transmission intervals by a method such as sequence group hopping. can do. At this time, the v value is the SRS transmission cycle (n)._p) The function can be set to any value.

As described above, the terminal can generate and transmit SRS according to the parameter values set by the base station. At this time, the terminal can generate the same SRS sequence in all SRS transmission cycles and repeatedly transmit it, or generate a separate SRS sequence for each SRS transmission cycle and repeatedly transmit it.

4.2.2 SRS transmission method

In the MTC environment, the transmission bandwidth of the MTC terminal can be limited to a specific bandwidth (eg, 6PRB). In this case, the transmission bandwidth of the SRS transmitted by the terminal can also be limited. However, the system bandwidth can be larger than the transmit bandwidth supported by the MTC terminal, so in order for the MTC terminal to be scheduled in the subband of the system bandwidth, the SRS should also be transmitted in the subband. Can be set to. For example, the system bandwidth can be divided into a large number of subbands corresponding to the bandwidth of the MTC terminal, and SRS can be set to be transmitted in one or more of the corresponding subbands.

At this time, the order in which the SRS is transmitted in the sub-band can be set to the sub-band index order (eg, sub-band index order having a low frequency) or a predetermined order. Therefore, the terminal can transmit the SRS via the subband in such an order. When there are one or more subbands to which SRS is transmitted, it is preferable that SRS repeated transmission is started in the next serve band after all SRS repeated transmissions are completed in one subband.

In order to repeatedly transmit SRS in the time domain, the terminal needs to be set with a large number of SRS configurations. For example, it is preferable that the base station is set so that the terminal repeatedly performs SRS transmission in the SRS subframe commonly set in the serving cell. For example, the SRS subframe commonly set for the serving cell can be (1) set to the cell-specific SRS subframe for SRS transmission assigned to the general terminal of the existing LTE / LTE-A system, or (2). ) Can be set to a cell-specific SRS subframe newly defined for MTC terminals. That is, it is possible to define a cell-specific MTC SRS subframe for the MTC terminal to repeatedly transmit SRS.

The following methods can be considered for SRS iterative transmission.

(1) Method 1: The base station can explicitly inform the terminal of the cell-specific SRS subframe to be used for SRS repetitive transmission. In this case, SRS repetitive transmission occurs only in the subframe specified by the base station, and general SRS transmission can be performed in the remaining subframes. That is, SRS repetitive transmission may not occur continuously in each SRS transmission cycle.

(2) Method 2: The base station can specify the number of subframes required for repeated transmission from the terminal-specific SRS subframe offset in the cell-specific SRS subframe. In the embodiment of the present invention, the terminal-specific SRS subframe can be defined as a concept included in the cell-specific SRS subframe.

In the case of method 2, SRS repetitive transmission can be continuously performed only in the terminal-specific SRS subframe instructed by the base station among the cell-specific SRS subframes. For example, SRS transmission may be performed only in the subframe specified by the base station, and SRS repetitive transmission may not occur in the remaining SRS transmission cycle.

(3) Method 3: The base station explicitly specifies the first subframe number (that is, subframe offset) and the last SRS subframe of the terminal-specific SRS subframe that performs SRS iterative transmission among the cell-specific SRS subframes. Can be instructed.

In the case of the method 3, the terminal can repeatedly transmit SRS to the cell-specific SRS subframe from the first subframe corresponding to the SRS subframe offset to the SRS subframe last specified by the base station. In the case of method 3, SRS repetitive transmission may not be performed in continuous SRS subframes depending on the setting of cell-specific SRS subframes. For example, if cell-specific SRS subframes are not set continuously, SRS iterations are performed only on cell-specific SRS subframes included within the SRS iteration cycle, and on the remaining subframes. It may not be.

FIG. 11 is a diagram showing one of the methods in which the MTC terminal repeatedly transmits SRS when the trigger type is 0 among the SRS transmission methods. In particular, FIG. 11 (a) shows a method in which a general terminal periodically transmits an SRS, and FIG. 11 (b) shows a method in which an MTC terminal periodically transmits an SRS.

FIG. 12 is a diagram showing one of the methods in which the MTC terminal repeatedly transmits SRS when the trigger type 1 is used among the SRS transmission methods. In particular, FIG. 12 (a) shows a method in which a general terminal transmits SRS aperiodically, and FIG. 12 (b) shows a method in which an MTC terminal transmits SRS aperiodically.

For the SRS transmission method of FIGS. 11 (a) and 12 (a), the SRS transmission method described in Section 3 can be referred to. As the method in which the MTC terminals in FIGS. 11 (b) and 12 (b) repeatedly transmit SRS, the methods 1 to 3 described in Section 4.2.2 can be applied. In FIGS. 11 (b) and 12 (b), the MTC terminal uses the SRS generated by the SRS configuration method described in Section 4.2.1 for each SRS transmission cycle or a predetermined number of times in a subframe that receives a request for SRS transmission. It can be sent repeatedly.

At this time, the SRS iterative transmission is repeated only in the SRS subframe specified by the base station among the cell-specific SRS subframes (method 1), or the base station among the terminal-specific SRS subframes in the cell-specific SRS subframe It can be repeated only in the indicated SRS subframe (Method 2 or 3).

At this time, if the cell-specific SRS subframes are not continuously configured, the MTC terminal (1) repeatedly transmits SRS only in the cell-specific SRS subframe within a predetermined number of subframes for SRS repeated transmission. Or (2) Specifying the cell of the first SRS iterative transmission section If SRS is repeatedly transmitted only in the SRS subframe and SRS cannot be repeatedly transmitted as many times as the number of repetitions, the cell of the next SRS iterative transmission section is specified. The remaining SRS can be sent repeatedly in SRS subframes.

Alternatively, the base station can set the number of SRS repeat transmissions and the interval. For example, in an MTC environment, assume that the MTC terminal requires n repeated SRS transmissions. At this time, when setting the SRS iterative transmission section, the base station sets the SRS iterative transmission section in consideration of the number of repeated transmissions n, the number x of cell-specific SRS subframes, and the number y of terminal-specific SRS subframes. Can be done. If y&gt; x&gt; = n, the base station can instruct the terminal to transmit SRS repeatedly only n times. If y&gt; n&gt; x or x&gt; n&gt; y, the base station can be configured to increase the iterative transmission cycle by nx or ny iterative transmissions to the terminal.

4.3 SRS transmission method-2

Different SRS transmission combs can be used to facilitate multiplexing with SRS of other terminals while the terminal repeatedly transmits SRS.

That is, there are two SRS transmission combs in one RB, but the MTC terminal uses the first SRS transmission comb within the iterative transmission section for SRS iterative transmission, and the SRS transmission is transmitted in other subframes. Can be configured to use a second SRS transmit comb. For this purpose, the base station can notify the setting of the SRS transmission comb through upper layer signaling / MAC signaling / L1 signaling and the like.

4.4 SRS transmission limit

Hereinafter, the SRS transmission restriction method applicable to the above-mentioned SRS transmission method will be described.

4.4.1 SRS transmission restriction by trigger type

SRS transmission can be divided into trigger type 0 (that is, periodic SRS transmission) transmitted by the setting of the upper layer and trigger type 1 (that is, aperiodic SRS transmission) instructed to start transmission by PDCCH. it can. At this time, since the MTC terminal is placed in a poor MTC radio wave environment, it can be set to support only one of the trigger types 0 and 1.

For example, an MTC terminal can be configured to support only trigger type 1. In this case, the MTC terminal can perform SRS iterative transmission only when requested by the base station. Of course, the MTC terminal can be configured to support only trigger type 0. If only trigger type 0 is supported, the MTC terminal can assume that there are no aperiodic SRS requests from the base station. At this time, the DCI format SRS request field that makes an aperiodic SRS request may not be transmitted or may be used for other purposes.

4.4.2 Behavior when simultaneously transmitting SRS and other uplink channels

When the MTC terminal repeatedly transmits SRS, a subframe in which uplink control information (for example, HARQ-ACK, SR (Scheduling Request) transmission, periodic CSI transmission and / or aperiodic CSI transmission, etc.) is transmitted. There may be situations where SRS repetitive transmissions are performed together. In this case, the base station can be set in advance by using an upper layer signal (for example, RRC, MAC signal, etc.) so as not to perform SRS transmission in the same subframe. That is, when the SRS iterative transmission section and the subframe in which the uplink control information is transmitted overlap, it can be set so that the SRS iterative transmission is not performed in the overlapping subframe.

In this case, the base station and / or the terminal can calculate the number of repeated transmissions by assuming that the SRS transmission has actually been performed even when the SRS is not actually transmitted. This is complicated because if SRS drops occur frequently due to simultaneous SRS transmission with other uplink channels, the SRS iterative transmission cycle will be different for each terminal and multiplexing will occur. It can complement the disadvantage of being able to increase the degree. That is, even if the MTC terminal cannot transmit all the SRS that are repeatedly transmitted until the next iterative transmission time by SRS drop after setting the SRS iterative transmission start time, the MTC terminal and / or the base station can transmit the SRS configuration information or the SRS. New SRS iterative transmissions can be initiated based on the configuration parameters. Such a method has the advantage of facilitating the management of the base station and reducing the complexity of the system.

As another embodiment, the MTC terminal can complete the SRS iterative transmission by calculating only the number of actual repeated SRS transmissions. This increases the complexity of SRS multiplexing, but can relatively improve channel estimation performance using SRS.

4.4.3 Transmission format restriction method

In a subframe in which SRS iterative transmission and HARQ-ACK / SR iterative transmission are performed at the same time, the MTC terminal uses a shortened format for HARQ-ACK / SR transmission in a cell-specific SRS subframe. It can be configured to do using format). For example, the ackNackSRS-SimultaneousTransmission parameter for general terminals of LTE / LTE-A systems and the MTCackNackSRS-SimultaneousTransmission parameter for MTC terminals can be assumed. For example, if the ackNackSRS-SimultaneousTransmission parameter is set to "TRUE" and the MTCackNackSRS-SimultaneousTransmission parameter is set to "FALSE", then by setting two parameters, SRS in the legacy cell specific SRS subframe and the MTC cell specific SRS subframe. You can determine the transmission format of. As another example, other parameters defined in the LTE / LTE-A system can be used instead of the two parameters described above. In this case, the SRS transmission format is always set to the reduced format.

However, the MTC terminal can be configured to use the general format for HARQ-ACK / SR transmission in subframes that are not cell-specific SRS subframes in the SRS iterative transmission section. In this case, at the base station (receiver) that receives HARQ-ACK / SR, HARQ-ACK / SR transmitted in the cell-specific SRS subframe and HARQ-ACK / SR transmitted in a subframe that is not the cell-specific SRS subframe. After combining the SRs separately, the final decoding can be performed.

4.5 How to use DM-RS

In the embodiment of the present invention described above, DM-RSs in different subframes can be set to be used in order to improve the channel estimation performance for UL data transmitted via PUSCH.

For this reason, it is preferable that DM RSs of different subframes are configured to have the same frequency band and the same sequence by a method such as parameter setting for repeated transmission of SRS. That is, it is preferable that the base station transmits an upper layer parameter indicating the presence or absence of channel estimation using DM-RS of different subframes to the terminal.

For example, a base station can inform an MTC terminal that one of the subframes of DM-RS can be used with repeated SRS transmissions to estimate uplink channels.

The method for setting the u value of the DM-RS sequence is described below.

The base station can deactivate group hopping, which determines the u of PUSCH DM-RS used for uplink channel estimation, along with repeated SRS transmissions. This is to ensure that the PUSCH DM-RS has the same DM-RS sequence during repeated transmissions. Alternatively, the base station should be set to keep the u value of PUSCH DM-RS at the same value in the first subframe set and to have a separate u value in the second subframe set. Can be done. The u value of DM-RS can be expressed by the following equation 6.

[Equation 6]<maths num="27"><img file="JP2019205193A_D0038.tif" /></maths>

In Equation 6, n_p^DMRSIs a parameter that indicates the number of subframes for estimating UL channels using DM-RS together.<maths num="28"><img file="JP2019205193A_D0039.tif" /></maths>Is. At this time, when using DM RS of continuous p subframes, n_p^DMRSMeans a parameter that is assigned an arbitrary new value for every p subframes.

The following describes how to set the v value of the DM-RS sequence. When the DM RS transmission band is 6RB or less, the v value is preferably set to "0" as in the existing case for transmission. When the DM RS transmission band is 6 RB or more, it is preferable to deactivate sequence hopping and set the v value to "0" for transmission.

Alternatively, sequence hopping is set so that subframe sets that perform channel estimation using DM-RS by a method such as sequence group hopping have the same v value, and separate v values are set between the next transmission intervals. Can be set to have. At this time, the v value is a parameter indicating the number of subframes for which channel estimation is performed using DM RS._p^DMRSIt can be set to any value with the function of. That is, it can be set to have a separate v value for each subframe set for channel estimation using DM-RS.

5. How to send PUSCH and SRS on MTC terminal

5.1 SRS transmission method during frequency hop

When transmitting uplink data with PUSCH, the MTC terminal may be configured to perform frequency hopping or switch the subband for transmitting PUSCH. In this case, the diversity gain is increased, so that the MTC terminal in Coverage Enhancement (CE) mode can reduce the number of repeated PUSCH transmissions, and the MTC terminal in Low Cost (LC) mode. Can get performance gain.

FIG. 13 is a diagram for explaining one of the methods of performing SRS transmission at the time of frequency hop.

For base stations, it is preferred that the MTC terminal transmit the SRS in a subband with PUSCH frequency hops or a subband with frequency switching in order to determine the MCS for PUSCH.

The base station transmits the subband information indicating the frequency hop or the subband to be switched in this way to the MTC terminal in a semi-static manner using an upper layer signal such as RRC signaling. Can be set (S1310).

Based on the subband information, the MTC terminal knows which subband the PUSCH is hopped from or which subband is switched. Therefore, the MTC terminal can transmit PUSCH and SRS in the corresponding subband. At this time, the contents described in FIGS. 9 to 12 can be referred to for the method of transmitting the SRS (S1320).

The transmission bandwidth at which the SRS is transmitted can be set in various ways. Currently, according to the 3GPP LTE standard document, the minimum unit for transmitting SRS is 4PRB. However, in CE mode MTC terminals, transmitting SRS with one PRB has a power boosting effect compared to transmitting SRS with four PRBs, thus improving channel estimation performance. be able to. Therefore, the MTC terminal can be set to transmit SRS in units of 1 PRB.

The MTC terminal in LC mode can sequentially transmit SRS in the subband set in the upper layer at the time of SRS transmission. In particular, if the CE mode MTC terminal is configured to transmit SRS in the same subband at the time of X SRS transmission and then transmit X SRS again in the next subband, the channel estimation performance by repeated SRS transmission is performed. Can be improved.

In an MTC terminal in FDD LC mode, when the number of subbands is M (M&gt; 2) and the UE specific SRS transmission cycle is set to be larger than 2 ms, the subband srs to which SRS is transmitted is transmitted._{b b}(n) (subband index n (0,1, ..., n)) can be expressed by the following equation 7.

[Equation 7]<maths num="29"><img file="JP2019205193A_D0040.tif" /></maths>

In equation 7, n_fIs the system frame number, n_sIs the slot number, T_SRSRepresents the UE-specific SRS transmission cycle.

When an MTC terminal in CE mode transmits X times of SRS in the same subband and then switches the subband, the subband srs in which the SRS is transmitted_{b b}(n) (subband index n (0,1, ..., n)) can be expressed as in Equation 8 below.

[Equation 8]<maths num="30"><img file="JP2019205193A_D0041.tif" /></maths>

In the SRS transmission method such as Equations 7 and 8, SRS may be transmitted at the same time as other uplink channels, so that it may be dropped and not transmitted. In this case, the MTC terminal does not transmit the SRS in the corresponding subband at the corresponding time point, and can transmit the SRS again in the subband determined by the formula 7 or the formula 8 at the next transmission time point.

5.2 How the MTC terminal controls SRS transmission

In the MTC mode that supports frequency hop, the transmission cycle of SRS that transmits SRS can be set to 2 ms or more. Therefore, MTC terminals can be configured not to expect an SRS transmission cycle of 1 ms, which means that SRS transmissions are not repeated in consecutive subframes.

This is because terminals that support MTC can only send and receive radio channels with a limited bandwidth (eg, 6PRB), so frequency retuning (frequency) to match the frequency if the transmitting or receiving subband changes. retuning) Time is required. Therefore, when the MTC terminal is set to transmit SRS in continuous subframes, throughput loss occurs due to the time gap due to the frequency retuning time. There is.

For example, when an MTC terminal repeatedly transmits PUSCH and / or PUCCH in continuous subframes n and n + 1, and then transmits SRS in subframes n and n + 1, it transmits PUSCH and / or PUCCH. The subband that sends and the subband that sends SRS may not match, and frequency retuning is required. Therefore, the MTC terminal can be configured to drop the SRS transmitted in subframe n or n + 1 and transmit only PUSCH and / or PUCCH.

FIG. 14 is a diagram for explaining a method of controlling SRS transmission when the subband for uplink transmission and the subband for SRS transmission do not match.

If the PUSCH is transmitted at the time of transmitting the SRS in the MTC that supports the frequency hop, it is preferable not to transmit the SRS unless the PUSCH transmission subband and the SRS transmission subband match. This is because the time for SRS transmission may be insufficient if the frequency tuning time is secured. This will be described in detail with reference to FIG.

The base station can transmit an upper layer signal including SRS transmission parameters for SRS transmission to the MTC terminal (S1410).

If frequency hop or subband switching is applied to the MTC terminal at the S1410 stage, further subband information indicating the subband to transmit the SRS may be transmitted.

If there is a PUSCH to transmit at the time when the MTC terminal supporting frequency hop transmits SRS (including both periodic and triggering methods), the MTC terminal has a subband to transmit SRS and a subband to transmit PUSCH. It is possible to check whether or not matches (S1420).

If the subband that transmits PUSCH and the subband that transmits SRS do not match, the MTC terminal is configured not to drop the SRS and transmit it. This is because the time for SRS transmission may be insufficient to secure the frequency retuning time to eliminate the subband mismatch. Therefore, MTC terminals can drop SRS transmissions and only perform PUSCH transmissions. In addition, PUSCH data can be transmitted with the SC-FDMA symbol to which SRS is transmitted (S1430a).

At the S1420 stage, if the subband that transmits PUSCH and the subband that transmits SRS match, the MTC terminal can transmit PUSCH and SRS in the relevant subband of the relevant subframe (S1430b).

As another aspect of this embodiment, it is preferred that SRS is not transmitted in consecutive subframes when PUSCH is transmitted in consecutive subframes. However, if the size of the subband of the subframe (nth SF) to which SRS is transmitted does not match the size of the subband of the subframe (n + 1th SF) to which PUSCH is transmitted, SRS transmission Is preferably dropped. This is because the frequency retuning time is secured for the limited bandwidth and the loss of data processing amount is prevented.

In the above-described embodiment of the present invention, the sub-band can be referred to as a narrow band. Further, the channel for the MTC terminal to transmit and receive data or the channel for performing SRS transmission can be configured in a narrow band.

6. Embodying device

The device described in FIG. 15 is a means capable of embodying the methods described in FIGS. 1 to 14.

A terminal (UE: User Equipment) can act as a transmitter on the uplink and as a receiver on the downlink. In addition, the base station (eNB: e-Node B) can operate as a receiver on the uplink and as a transmitter on the downlink.

That is, terminals and base stations may include transmit modules (Tx modules) 1540 and 1550, and receive modules (Rx modules) 1560 and 1570, respectively, to control the transmission and reception of information, data and / or messages. , Antennas 1500, 1510, etc. for transmitting and receiving information, data and / or messages.

Further, the terminal and the base station are provided with processors 1520 and 1530 for carrying out the above-described embodiment of the present invention, and memories 1580 and 1590 capable of temporarily or continuously storing the processing process of the processor, respectively. Can be done.

The terminal described with reference to FIG. 15 may be an MTC terminal, and the base station is a base station that supports MTC. Examples of the present invention can be carried out by using the components and functions of the terminal and the base station apparatus described above. For example, the processor of an MTC terminal can drop or transmit SRS based on whether the subband that transmits PUSCH and the subband that transmits MTC SRS match. The base station processor uses upper layer signaling to transmit SRS configuration information and / or subband information to the MTC terminal, and in the subband indicated by the subband information, transmits the SRS generated based on the SRS configuration information. Can be. For details, refer to Sections 1 to 5.

The transmit and receive modules included in the terminal and base station include packet modulation / demodulation function for data transmission, high-speed packet channel coding function, Orthogonal Frequency Division Multiple Access (OFDMA) packet scheduling, and time division duplex. (TDD: Time Division Duplex) Can perform packet scheduling and / or channel multiplexing functions. Further, the terminal and the base station of FIG. 15 can further include a low power RF (Radio Frequency) / IF (Intermediate Frequency) module.

On the other hand, as terminals in the present invention, personal digital assistants (PDAs), cellular phones, personal communication service (PCS) phones, GSM (Global System for Mobile) phones, WCDMA (Wideband CDMA) phones , MBS (Mobile Broadband System) phones, Hand-Held PCs, laptops, Smart phones, or Multi Mode-Multi Band (MM-MB) terminals can be used. it can.

Here, the smartphone is a terminal that combines the advantages of a mobile communication terminal and a personal mobile terminal, and the mobile communication terminal is used for schedule management, fax transmission / reception, Internet connection, etc., which are the functions of the personal mobile terminal. It can mean a terminal with integrated data communication functions. In addition, the multi-mode multi-band terminal has a built-in multi-modem chip and works with both mobile Internet systems and other mobile communication systems (for example, CDMA (Code Division Multiple Access) 2000 system, WCDMA (Wideband CDMA) system, etc.). Refers to a terminal that can be used.

Examples of the present invention can be embodied by various means. For example, the embodiments of the present invention can be embodied by hardware, firmware, software, or a combination thereof.

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

In the case of realization by firmware or software, the method according to the embodiment of the present invention can also be embodied in the form of a module, procedure or function that executes the function or operation described above. For example, the software code may be stored in memory units 1580, 1590 and driven by processors 1520, 1530. The memory unit is provided inside or outside the processor, and data can be exchanged with the processor by various known means.

The present invention may be embodied as another particular form without departing from the spirit and essential features of the present invention. Therefore, the above detailed description should not be construed in a restrictive manner in any aspect and should be considered as exemplary. The scope of the invention must be determined by the reasonable interpretation of the appended claims, and any modification within the equivalent scope of the invention is within the scope of the invention. In addition, the examples may be constructed by combining claims that are not explicitly cited within the scope of claims, or may be included as new claims by amendment after filing.

The embodiments of the present invention are applicable to various wireless connection systems. Examples of various wireless connection systems include 3GPP (3rd Generation Partnership Project), 3GPP2 and / or IEEE 802.xx (Institute of Electrical and Electronic Engineers 802) systems. The embodiments of the present invention can be applied not only to the various wireless connection systems described above, but also to any technical field to which these various wireless connection systems are applied.