KR20160090418A - Apparatus and method of downlink control information transmission and reception for MTC UEs - Google Patents

Abstract

The present invention proposes a method for monitoring a search space for transmitting and receiving downlink control information (DCI) for a user equipment (UE) supporting a low complexity UE category/type or a coverage enhancement operation for a machine type communication (MTC) operation in a 3GPP LTE/LTE-A system. In particular, the present invention provides a method for receiving a downlink control channel by a MTC UE, the method including the steps of: monitoring a search space in order to receive a downlink control channel by the MTC UE; and receiving the downlink control channel transmitted through the search space, wherein in the step of the monitoring, when a USS defined for the MTC UE and an CSS defined for all MTC UEs within a cell are defined in the same downlink sub-frame, the corresponding MTC UE preferentially monitors the CSS.

Description

[0001] The present invention relates to a method and apparatus for transmitting and receiving downlink control information for an MTC terminal,

The present invention relates to a method and apparatus for transmitting and receiving downlink control information (DCI) for a terminal supporting a low complexity UE category / type or coverage enhancement operation for a MTC (Machine Type Communication) operation in a 3GPP LTE / LTE- We propose a search space monitoring method.

The present invention provides a method for a MTC terminal to receive a downlink control channel, the method comprising: monitoring a search space for receiving a downlink control channel; And receiving a downlink control channel transmitted through the search space, wherein the step of monitoring includes the steps of: detecting a USS defined for the MTC terminal and a CSS defined for all MTC terminals in the same cell in the same downlink subframe If defined, the MTC terminal provides a method and apparatus for preferentially monitoring the CSS.

1 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.
2 is a block diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals whenever possible, even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Herein, the MTC terminal may mean a terminal supporting low cost (or low complexity) or a terminal supporting coverage enhancement. In this specification, the MTC terminal may mean a terminal supporting low cost (or low complexity) and coverage enhancement. Alternatively, the MTC terminal may refer to a terminal defined in a specific category for supporting low cost (or low complexity) and / or coverage enhancement.

In other words, the MTC terminal in this specification may mean a newly defined 3GPP Release-13 low cost (or low complexity) UE category / type for performing LTE-based MTC-related operations. Alternatively, the MTC terminal may support enhanced coverage over the existing LTE coverage or a UE category / type defined in the existing 3GPP Release-12 or lower that supports low power consumption, or a newly defined Release-13 low cost low complexity UE category / type.

The wireless communication system in the present invention is widely deployed to provide various communication services such as voice, packet data and the like. A wireless communication system includes a user equipment (UE) and a base station (BS, or eNB). The user terminal in this specification is a comprehensive concept of a terminal in wireless communication. It is a comprehensive concept which means a mobile station (MS), a user terminal (UT), an SS (User Equipment) (Subscriber Station), a wireless device, and the like.

A base station or a cell generally refers to a station that communicates with a user terminal and includes a Node-B, an evolved Node-B (eNB), a sector, a Site, a BTS A base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell.

That is, the base station or the cell in this specification is interpreted as a comprehensive meaning indicating a partial region or function covered by BSC (Base Station Controller) in CDMA, NodeB in WCDMA, eNB in LTE or sector (site) And covers various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU, and small cell communication range.

Since the various cells listed above exist in the base station controlling each cell, the base station can be interpreted into two meanings. i) the device itself providing a megacell, macrocell, microcell, picocell, femtocell, small cell in relation to the wireless region, or ii) indicating the wireless region itself. i indicate to the base station all devices that are controlled by the same entity or that interact to configure the wireless region as a collaboration. An eNB, an RRH, an antenna, an RU, an LPN, a point, a transmission / reception point, a transmission point, a reception point, and the like are exemplary embodiments of a base station according to a configuration method of a radio area. ii) may indicate to the base station the wireless region itself that is to receive or transmit signals from the perspective of the user terminal or from a neighboring base station.

Therefore, a base station is collectively referred to as a base station, collectively referred to as a megacell, macrocell, microcell, picocell, femtocell, small cell, RRH, antenna, RU, low power node do.

Herein, the user terminal and the base station are used in a broad sense as the two transmitting and receiving subjects used to implement the technical or technical idea described in this specification, and are not limited by a specific term or word. The user terminal and the base station are used in a broad sense as two (uplink or downlink) transmitting and receiving subjects used to implement the technology or technical idea described in the present invention, and are not limited by a specific term or word. Here, an uplink (UL, or uplink) means a method of transmitting / receiving data to / from a base station by a user terminal, and a downlink (DL or downlink) .

There are no restrictions on multiple access schemes applied to wireless communication systems. Various multiple access schemes such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, OFDM- Can be used. An embodiment of the present invention can be applied to asynchronous wireless communication that evolves into LTE and LTE-advanced via GSM, WCDMA, and HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000, and UMB. The present invention should not be construed as limited to or limited to a specific wireless communication field and should be construed as including all technical fields to which the idea of the present invention can be applied.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

In a system such as LTE and LTE-A, the uplink and downlink are configured based on one carrier or carrier pair to form a standard. The uplink and the downlink are divided into a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel, a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control Channel (EPDCCH) Transmits control information through the same control channel, and is configured with data channels such as PDSCH (Physical Downlink Shared CHannel) and PUSCH (Physical Uplink Shared CHannel), and transmits data.

On the other hand, control information can also be transmitted using EPDCCH (enhanced PDCCH or extended PDCCH).

In this specification, a cell refers to a component carrier having a coverage of a signal transmitted from a transmission point or a transmission point or transmission / reception point of a signal transmitted from a transmission / reception point, and a transmission / reception point itself .

The wireless communication system to which the embodiments are applied may be a coordinated multi-point transmission / reception system (CoMP system) or a coordinated multi-point transmission / reception system in which two or more transmission / reception points cooperatively transmit signals. antenna transmission system, or a cooperative multi-cell communication system. A CoMP system may include at least two multipoint transmit and receive points and terminals.

The multi-point transmission / reception point includes a base station or a macro cell (hereinafter referred to as 'eNB'), and at least one mobile station having a high transmission power or a low transmission power in a macro cell area, Lt; / RTI >

Hereinafter, a downlink refers to a communication or communication path from a multiplex transmission / reception point to a terminal, and an uplink refers to a communication or communication path from a terminal to a multiplex transmission / reception point. In the downlink, a transmitter may be a part of a multipoint transmission / reception point, and a receiver may be a part of a terminal. In the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of multiple transmission / reception points.

Hereinafter, a situation in which a signal is transmitted / received through a channel such as PUCCH, PUSCH, PDCCH, EPDCCH, and PDSCH is expressed as 'PUCCH, PUSCH, PDCCH, EPDCCH and PDSCH are transmitted and received'.

In the following description, an indication that a PDCCH is transmitted or received or a signal is transmitted or received via a PDCCH may be used to mean transmitting or receiving an EPDCCH or transmitting or receiving a signal through an EPDCCH.

That is, the physical downlink control channel described below may mean a PDCCH, an EPDCCH, or a PDCCH and an EPDCCH.

Also, for convenience of description, EPDCCH, which is an embodiment of the present invention, may be applied to the portion described with PDCCH, and EPDCCH may be applied to the portion described with EPDCCH according to an embodiment of the present invention.

Meanwhile, the High Layer Signaling described below includes RRC signaling for transmitting RRC information including RRC parameters.

The eNB performs downlink transmission to the UEs. The eNB includes a physical downlink shared channel (PDSCH) as a main physical channel for unicast transmission, downlink control information such as scheduling required for reception of a PDSCH, A physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission in a Physical Uplink Shared Channel (PUSCH). Hereinafter, the transmission / reception of a signal through each channel will be described in a form in which the corresponding channel is transmitted / received.

PDCCH and EPDCCH are defined as downlink physical control channels for transmitting downlink control information (DCI) for a UE in the conventional 3GPP LTE / LTE-A system. A certain LTE / LTE-A terminal monitors the UE-specific Search Space (USS) defined in the PDCCH or the EPDCCH and the CSS defined in the PDCCH, thereby generating UE-specific downlink control information scrambled with the C- And cell specific downlink control information scrambled with SI-RNTI, P-RNTI, and RA-RNTI. Specifically, in case of a UE-specific DCI including scheduling information for a UE-specific uplink / downlink data channel, CRC scrambling is performed on the C-RNTI of the corresponding UE, and USS and cell- and transmitted through the CSS of PDCCH which is a specific search space. Accordingly, the UE receives the UE-specific DCI for the UE and the UE-specific PDSCH transmitted from the BS through the monitoring of the CSS and the USS. In the case of a cell-specific DCI including scheduling information for system information (SIBs) and paging messages and Random Access Response (RAR) messages transmitted through the PDSCH for terminals in the corresponding cell , CRC scrambled with SI-RNTI, P-RNTI, and RA-RNTI, respectively, and transmitted through CSS, a cell-specific search space. Accordingly, the UEs in the corresponding cell acquire the scheduling information on the corresponding SIBs, the paging message, and the RAR by monitoring the CSS, and receive the PDSCH on which the corresponding SIBs, the paging message, and the RAR are transmitted.

Specifically, for the PDCCH / EPDCCH monitoring operation of the terminal defined in the existing LTE / LTE-A system, the contents of the standard specification document TS36.213 should be extracted and appended to appendix [1] below.

[ Low complexity UE category / type for MTC operation ]

As the LTE network spreads, mobile operators want to minimize the number of Radio Access Terminals (RATs) to reduce network maintenance costs. However, conventional MTC products based on a GSM / GPRS network are increasing, and MTC using a low data rate can be provided at low cost. Therefore, there is a problem in that two RATs must be operated respectively, since LTE network is used for general data transmission and GSM / GPRS network is used for MTC. Therefore, Of the total revenue.

To solve this problem, it is necessary to replace a cheap MTC terminal using a GSM / EGPRS network with an MTC terminal using an LTE network. To achieve this, a low complexity UE category that reflects various requirements for lowering the price of an LTE MTC terminal There is a need for the definition of / type and the need for standard techniques to support it.

In addition, about 20% of MTC terminals supporting MTC services such as smart metering are installed in a 'Deep indoor' environment such as a basement. Therefore, for successful MTC data transmission, the coverage of LTE MTC terminals is compared with the coverage of conventional LTE terminals It should be improved by about 15 dB. Also, if the performance degradation due to introduction of the low complexity UE category / type for the MTC operation is additionally considered, the coverage of the LTE MTC terminal should be improved by more than 15dB.

Various methods for robust transmission such as PSD boosting or low coding rate and time domain repetition are considered for each physical channel in order to improve the coverage while lowering the price of the LTE MTC terminal.

Specifically, the requirements of low complexity UE category / type for MTC operation are as follows.

  Reduced UE bandwidth of 1.4 MHz in downlink and uplink.

   ◆ Bandwidth reduced UEs should be able to operate within any system bandwidth.

   ◆ Frequency multiplexing of bandwidth reduced UEs and non-MTC UEs should be supported.

   ◆ The UE only needs to support 1.4 MHz RF bandwidth in downlink and uplink.

  ■ Reduced maximum transmit power.

  Reduced support for downlink transmission modes.

   ● further UE processing relaxations

     ◆ Reduced maximum transport block size for unicast and / or broadcast signaling.

     ◆ Reduced support for simultaneous reception of multiple transmissions.

     ◆ Relaxed transmit and / or receive EVM requirements including restricted modulation scheme. Reduced physical control channel processing (e.g., reduced number of blind decoding attempts).

    Reduced physical data channel processing (e.g., relaxed downlink HARQ time line or reduced number of HARQ processes).

   ◆ Reduced support for CQI / CSI reporting modes.

  ● Target a relative LTE coverage improvement - corresponding to 15 dB for FDD - for the UE category / type defined above and other UEs operating delay tolerant MTC applications with respect to their respective nominal coverage.

  ● Provide power consumption reduction for the UE category / type defined above, both in normal coverage and enhanced coverage, to target ultra-long battery life:

In the present invention, for convenience of description, the existing LTE terminal is referred to as a normal LTE terminal, and a new low complexity UE category / type satisfying the above conditions for the MTC operation will be simply referred to as an MTC terminal. Also, the normal LTE terminal or the MTC terminal supporting the coverage enhancement function or mode is referred to as a CE (coverage enhanced) terminal.

According to the conventional downlink data channel transmission / reception method, in the case of an LTE / LTE-A terminal connected to an arbitrary base station / cell, reception performance for a 20 MHz frequency bandwidth is guaranteed regardless of the operating frequency bandwidth, There was no limit to the monitoring of CSS and USS within the frame. However, as described above, when the CSS and the USS set through a single downlink subframe are not set within the range of 6 PRBs in the frequency domain due to the restriction of the reception bandwidth in the MTC terminal, Can not be performed.

In the present invention, when CSS and USS for the MTC terminal coexist via one downlink subframe, a search space monitoring method of the MTC terminal is proposed.

As described above, in case of the low-priced MTC terminal, since the reception bandwidth is limited to 1.4 MHz (6 PRBs), when connecting to an arbitrary LTE / LTE-A cell having a frequency band with a system bandwidth larger than 1.4 MHz, it is impossible to receive the PDCCH that is designed to be distributed over the entire bandwidth. Therefore, a new downlink control channel transmitted through six consecutive PRBs of a PDSCH for supporting a low-priced MTC terminal is required. Accordingly, the EPDCCH designed in the PDSCH region may be used as a downlink control channel for the corresponding MTC terminal, or a new type of PDCCH-like MTC dedicated downlink control channel may be designed.

If the downlink control channel for the MTC terminal is defined through the PDSCH region and the CSS and the USS for the MTC terminal are defined through the corresponding downlink control channel region, the method for monitoring the CSS and USS of the MTC terminal .

However, the present invention is not limited to the specific form of the downlink control channel for the MTC terminal defined in the PDSCH region, but may be applied to the CSS and USS of the MTC terminal defined in the downlink control channel region for the corresponding MTC terminal . That is, the present invention can be applied equally regardless of whether the EPDCCH is used as a downlink control channel for a corresponding MTC terminal or a downlink control channel for a new type of MTC terminal is designed.

Also, the configuration of the corresponding CSS or USS may be configured through a single downlink subframe or a plurality of downlink subframes according to a coverage level to which an MTC terminal or a normal LTE terminal belongs for CEs . (Here, the coverage level is a value defined by quantizing based on the degree of coverage enhancement required according to the radio channel condition, and the repetition frequency or power boosting value of the wireless channel transmitted according to the coverage level may vary.) However, The invention relates to a CSS and USS monitoring method of a MTC terminal and can be applied irrespective of the specific configuration method of the CSS and USS.

CSS Wow USS  liver monitoring  Priority-based monitoring  Way

When a USS defined for a corresponding MTC terminal and a CSS defined for all MTC terminals in a cell are defined in the same downlink subframe as a method of monitoring a downlink control channel of an arbitrary MTC terminal connected to an arbitrary cell / The MTC terminal can define to preferentially monitor the CSS.

As an example of this, an MTC sub-band consisting of consecutive 6 PRBs for low-cost MTC terminals can be defined regardless of the system bandwidth defined in any LTE cell. The MTC sub-band may be defined as two types of cell-specific MTC sub-band defined for all MTC terminals in the cell to receive in common and UE-specific MTC sub-band defined for each MTC terminal. In this case, the CSS for the MTC terminals is configured through the cell-specific MTC sub-band, and the USS for any MTC terminal can be defined to be configured through the UE-specific MTC sub-band for the corresponding MTC terminal have. If the cell-specific MTC sub-band and the UE-specific MTC sub-band are defined and the CSS and USS for the MTC terminal are configured based on the cell-specific MTC sub-band, band and UE-specific MTC sub-band are configured at the same time, and CSS and USS are configured through respective MTC sub-bands, the corresponding MTC terminal receives the cell-specific MTC sub-band preferentially, It can be defined to monitor preferentially. When the cell-specific MTC sub-band and the UE-specific MTC sub-band partially overlap or completely overlap in the frequency domain of the corresponding downlink sub-frame, the frequency bands of the corresponding cell-specific sub- ), The MTC terminal can additionally monitor only the USS included in the MTC terminal. Conversely, regardless of whether the cell-specific MTC sub-band overlaps with the UE-specific MTC sub-band in the frequency domain and whether the USS can be monitored through the cell-specific MTC sub-band, If CSS and USS are configured in the frame at the same time, the MTC terminal can define only monitoring for CSS and not for USS.

As another example of this, as described above, the cell-specific MTC sub-band for all MTC terminals in the cell and the UE-specific MTC sub-band set for each MTC terminal regardless of the coverage level, (Coverage Level) -specific MTC sub-band can be defined according to the following equation. Accordingly, in addition to the cell-specific CSS for all MTC terminals in the cell through the cell-specific MTC sub-band, CL-specific CSS for only MTC terminals belonging to the coverage level is additionally configured through the CL-specific MTC sub-band Can be defined. In this case, the reception priority can be defined in the order of cell-specific MTC sub-band, CL-specific MTC sub-band, and UE-specific MTC sub-band. Accordingly, when a MTC terminal is configured with a cell-specific MTC sub-band, a CL-specific MTC sub-band, and a UE-specific MTC sub-band simultaneously on the same downlink subframe, And thus it can be defined to preferentially monitor the cell-specific CSS compared to the CL-specific CSS and USS. Similarly, if the CL-specific MTC sub-band and the UE-specific MTC sub-band are simultaneously configured through the same downlink subframe, the CL-specific MTC sub-band is preferentially received according to the priority, Specific CSS can be defined to monitor preferentially. However, as in the first embodiment, when the MTC sub-band having a low priority and the search space are partially overlapped or fully overlapped within the MTC sub-band having the highest priority, the corresponding low-priority search space (e.g., CL- CSS or USS) can be additionally monitored. Alternatively, when a plurality of search spaces are set in one downlink subframe, it can be defined to monitor only the search space with the highest priority.

In addition, cell-specific MTC sub-band, CL-specific MTC sub-band, and UE-specific MTC sub-band are defined as in the second embodiment, , The sub-band reception priority is defined in the order of CL-specific MTC sub-band, cell-specific MTC sub-band, and UE-specific MTC sub-band, CL-specific CSS, cell-specific CSS, and USS.

However, although the embodiments described above are based on the case where the CSS and the USS are configured through one downlink sub-frame, when the corresponding CSS and the USS are configured through a plurality of downlink sub-frames for CE, Lt; / RTI > That is, in the range of the plurality of downlink subframes, the MTC sub-band with the highest priority and the search space with the highest priority according to the MTC sub-band are defined to be monitored according to the priority defined above. It is also possible to define additional monitoring of the search space of the car priority configured in the part.

1 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.

Referring to FIG. 1, a base station 1000 according to another embodiment includes a control unit 1010, a transmission unit 1020, and a reception unit 1030.

The control unit 1010 controls the overall operation of the base station according to the search space monitoring method of the MTC terminal when the CSS and the USS for the MTC terminal coexist through one downlink subframe required for carrying out the present invention .

The transmitting unit 1020 and the receiving unit 1030 are used to transmit and receive signals, messages, and data necessary for carrying out the present invention to and from the terminal.

2 is a block diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

2, a user terminal 1100 according to another embodiment includes a receiving unit 1110, a control unit 1120, and a transmitting unit 1130.

The receiving unit 1110 receives downlink control information, data, and messages from the base station through the corresponding channel.

If the CSS and the USS for the MTC terminal coexist via the one downlink subframe required for performing the above-described present invention, the controller 1120 controls the overall operation of the terminal according to the search space monitoring method of the MTC terminal do.

The transmitter 1130 transmits uplink control information, data, and a message to the base station through the corresponding channel.

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and portions of the standard documents are added to or contained in the scope of the present invention.

In addition, the contents of reference materials submitted together with this specification are also a part of this specification. Therefore, it is to be understood that all or part of the contents of the reference materials are added to or included in the scope of the present invention as falling within the scope of the present invention.

Reference 1: UE procedure for receiving the physical downlink shared channel

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (1)

A method for receiving a downlink control channel in an MTC terminal,
Monitoring the search space for reception of the downlink control channel by the MTC terminal; And
Receiving a downlink control channel transmitted through the search space,
Wherein the monitoring step is such that when the USS defined for the MTC terminal and the CSS defined for all the MTC terminals in the cell are defined in the same downlink subframe, the corresponding MTC terminal monitors the CSS preferentially.

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