KR20150128339A - Method and apparatus of search space control for d2d communication - Google Patents

Abstract

The present invention relates to a method for supporting device to device (D2D) communications, which comprises the following steps: configuring an extended search space for D2D communications; mapping a physical downlink control channel (PDCCH) carrying at least one from D2D scheduling assignment (SA) grant and D2D data grant with one or more control channel elements (CCE) in the extended search space; and transmitting the mapped PDCCH to a terminal. According to the present invention, the extended search space carrying related control information for the D2D communications, is defined, thereby effectively supporting the D2D communications.

Description

TECHNICAL FIELD [0001] The present invention relates to a search space control method for a D2D communication,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to a search space control method and apparatus for device to device (D2D) communication.

Device to Device communication (D2D) is a communication method that has been available since the days of analog radios and has a very long history. However, the inter-terminal communication in the wireless communication system is different from the existing inter-terminal communication.

The inter-terminal communication in the wireless communication system uses a transmission / reception technology (for example, a physical channel, etc.) of the wireless communication system in a frequency band of the wireless communication system or other bands but does not go through an infrastructure It means communication that exchanges user data directly between terminals. That is, the two terminals perform communication while being a source and a destination of data, respectively. This provides the advantage of enabling wireless communication in areas other than the limited wireless communication infrastructure and reducing the network load of the wireless communication system.

Direct communication between terminals may be performed using a communication method using a wireless LAN such as IEEE 802.11 or a license-exempt band such as Bluetooth, but it is difficult to provide a planned and controlled service using the communication method using the license-exempt band. In particular, performance can be drastically reduced by interference. On the other hand, the direct communication between the terminals operated or provided in the licensed band or inter-system interference controlled environment can support QoS (Quality of Service), increase frequency utilization efficiency through frequency reuse, The possible distance can be increased.

In the terminal-to-terminal communication in the licensed band, that is, in the inter-terminal communication based on the cellular communication, the base station can allocate resources for D2D communication and the cellular uplink channel or uplink subframes can be used as the allocated resources . In this case, it is necessary to distinguish whether the control information transmitted from the base station is for D2D communication, and a search space for communication between the terminals needs to be defined. However, there is no published yet specific structure or design of a search space for inter-terminal communication, and a transmission method and reception method of control information for inter-terminal communication.

SUMMARY OF THE INVENTION The present invention provides a signaling method and apparatus for D2D communication.

It is another object of the present invention to provide a method and apparatus for controlling a search space for D2D communication.

Another technical object of the present invention is to provide a search space for D2D communication.

Another object of the present invention is to provide a D2D PDCCH (Physical Downlink Control Channel) search space.

It is another object of the present invention to provide a search space function and a hashing function for defining a search space for D2D communication.

According to an aspect of the present invention, there is provided a method for supporting D2D (Device to Device) communication performed by a base station. The method comprises constructing an Extended Search Space for D2D communication, and transmitting a Physical Downlink Control Channel (PDCCH) carrying at least one of a D2D SA (Scheduling Assignment) grant and a D2D data grant to the extension Mapping to at least one control channel element (CCE) in a search space, and transmitting the mapped PDCCH to a terminal.

According to another aspect of the present invention, there is provided a base station supporting D2D communication. The base station configures an extended search space for D2D communication and transmits a PDCCH carrying at least one of the D2D SA grant and the D2D data grant to at least one control channel elements (CCE) in the extended search space A mapping processor, and an RF unit for transmitting the mapped PDCCH to the UE.

According to another aspect of the present invention, there is provided a method for supporting D2D (Device to Device) communication performed by a terminal. The method comprises the steps of detecting an Extended Search Space for D2D communication and transmitting a Physical Downlink (PDCCH) PDCCH (Physical Downlink (PDCCH)) for carrying at least one of a D2D SA (Scheduling Assignment) grant and a D2D data grant Control Channel), detecting the PDCCH based on the blind decoding, generating at least one of D2D SA and D2D data based on the detected PDCCH, and generating D2D SA, and D2D data to the receiving terminal.

According to another aspect of the present invention, there is provided a terminal supporting D2D (Device to Device) communication. The terminal detects an Extended Search Space for D2D communication and transmits a Physical Downlink Control (PDCCH) for carrying at least one of a D2D SA (Scheduling Assignment) grant and a D2D data grant on the extended search space A processor for performing blind decoding on the PDCCH, detecting the PDCCH, and generating at least one of D2D SA and D2D data based on the detected PDCCH, and a processor for generating at least one of the generated D2D SA and D2D data And an RF unit for transmitting the RF signal to the receiving terminal.

According to the present invention, since an extended search space for carrying related control information for D2D communication is defined, it is possible to efficiently support D2D communication.

1 shows a wireless communication system to which the present invention is applied.
2 and 3 schematically show the structure of a radio frame applied to the present invention.
4 is a diagram for explaining the concept of a cellular network-based D2D communication applied to the present invention.
5 shows a search space for D2D according to an example of the present invention.
6 and 7 show a search space for D2D according to another example of the present invention.
8 illustrates a D2D grant transmission method for D2D communication according to the present invention.
9 shows a D2D grant reception method for D2D communication according to the present invention.
10 is an example of a block diagram illustrating a wireless communication system supporting D2D communication according to the present invention.

Hereinafter, some embodiments 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 even though they are shown in different drawings. In the following description of the embodiments 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 disclosure rather unclear.

1 shows a wireless communication system to which the present invention is applied.

Referring to FIG. 1, a wireless communication system 10 is widely deployed to provide various communication services such as voice, packet data, and the like. The wireless communication system 10 includes at least one base station 11 (evolved-NodeB, eNB). Each base station 11 provides communication services to specific cells (15a, 15b, 15c). The cell may again be divided into multiple regions (referred to as sectors).

A user equipment (UE) 12 may be fixed or mobile and may be a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, (personal digital assistant), a wireless modem, a handheld device, and the like. The base station 11 may be referred to by other terms such as a base station (BS), a base transceiver system (BTS), an access point, a femto base station, a home node B, and a relay. Cells are meant to cover various coverage areas such as megacell, macrocell, microcell, picocell, and femtocell.

Hereinafter, downlink (DL) refers to communication from the base station 11 to the terminal 12, and uplink (UL) refers to communication from the terminal 12 to the base station 11. In the downlink, the transmitter may be part of the base station 11, and the receiver may be part of the terminal 12. In the uplink, the transmitter may be part of the terminal 12, and the receiver may be part of the base station 11. There are no restrictions on multiple access schemes applied to wireless communication systems. (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier-FDMA , OFDM-CDMA, and the like. 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.

The layers of the radio interface protocol between the terminal and the base station are divided into a first layer (L1), a second layer (L1), and a second layer (L2) based on the lower three layers of an Open System Interconnection A second layer (L2), and a third layer (L3). Among them, the physical layer belonging to the first layer provides an information transfer service using a physical channel.

The physical layer is connected to a MAC layer (Media Access Control) layer through a transport channel. The data is transmitted between the MAC layer and the physical layer through a transmission channel. The transport channel is classified according to how the data is transmitted over the air interface. Further, data is transmitted through physical channels between different physical layers (i.e., between the physical layer of the terminal and the base station). The physical channel can be modulated by an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and uses time, frequency, and space generated by a plurality of antennas as radio resources.

2 and 3 schematically show the structure of a radio frame applied to the present invention.

Referring to FIG. 2 and FIG. 3, one radio frame includes ten subframes, and one subframe includes two consecutive slots. A basic time (length) unit for transmission control in a radio frame is referred to as a transmission time interval (TTI). The TTI may be 1ms. The length of one subframe (1 subframe) is 1 ms, and the length of one slot may be 0.5 ms.

A slot may comprise a plurality of symbols in the time domain. For example, in a wireless system using OFDMA in a downlink (DL), the symbol may be an Orthogonal Frequency Division Multiplexing (OFDM) symbol, and in an uplink (UL) In the case of a wireless system using Single Carrier-Frequency Division Multiple Access (FDMA), the symbol may be a Single Carrier-Frequency Division Multiple Access (SC-FDMA) symbol. On the other hand, the representation of the symbol period in the time domain is not limited by the multiple access scheme or name.

The number of symbols included in one slot may vary according to the length of a CP (Cyclic Prefix). For example, in the case of a normal CP, one slot includes seven symbols, and in the case of an extended CP, one slot may include six symbols.

A resource element (RE) represents a smallest time-frequency unit to which a modulation symbol of a data channel or a modulation symbol of a control channel is mapped. A resource block (RB) is a resource allocation unit and includes time-frequency resources corresponding to 180 kHz on the frequency axis and 1 slot on the time axis. On the other hand, a resource block pair (PBR) means a resource unit including two consecutive slots on the time axis.

Several physical channels can be used in the physical layer, and the physical channels can be mapped to the radio frame and transmitted. As a downlink physical channel, a physical downlink control channel (PDCCH) / enhanced physical downlink control channel (EPDCCH) includes a resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH) Request information. The PDCCH / EPDCCH may carry an uplink grant informing the UE of the resource allocation of the uplink transmission. PDCCH and EPDCCH are different in the resource area to be mapped. A DL-SCH is mapped to a PDSCH (Physical Downlink Shared Channel). The Physical Control Format Indicator Channel (PCFICH) informs the UE of the number of OFDM symbols used in the PDCCH and is transmitted every subframe. The Physical Hybrid ARQ Indicator Channel (PHICH) is a downlink channel that carries an HARQ (Hybrid Automatic Repeat reQuest) ACK (Acknowledgment) / NACK (Non-acknowledgment) signal, which is a response of an uplink transmission. The HARQ ACK / NACK signal may be referred to as an HARQ-ACK signal.

A control channel through which a PDCCH is transmitted in a downlink physical channel is composed of a logical CCE sequence including a plurality of control channel elements (CCEs). Hereinafter, the CCE sequence is a set of all CCEs constituting a control region in one subframe. The CCE corresponds to a plurality of resource element groups. For example, a CCE may correspond to nine resource element groups. A resource element group is used to define the mapping of control channels to resource elements. For example, one resource element group may be composed of four resource elements.

A plurality of PDCCHs may be transmitted within the control domain. The PDCCH carries downlink control information (DCI) such as scheduling assignment. The PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). The format of the PDCCH and the number of possible PDCCH bits are determined according to the number of CCEs constituting the CCE aggregation level. The CCE aggregation level is a CCE unit for searching the PDCCH. The size of the CCE aggregation level is defined by the number of adjacent CCEs. For example, the CCE aggregation level may be an element of {1, 2, 4, 8}.

The following table shows examples of the format of the PDCCH according to the CCE aggregation level, and the number of bits of the possible PDCCH.

PDCCH format CCE integration level Number of resource element groups Number of PDCCH bits 0 One 9 72 One 2 18 144 2 4 36 288 3 8 72 576

On the other hand, as an uplink physical channel, a Physical Random Access Channel (PRACH) carries a random access preamble. The Physical Uplink Control Channel (PUCCH) includes HARQ-ACK, which is a response of downlink transmission, channel status information (CSI) indicating a downlink channel status, for example, a channel quality indicator (CQI) Uplink control information such as a precoding type indicator (PTI), a rank indicator (RI), and the like. The Physical Uplink Shared Channel (PUSCH) carries an Uplink Shared Channel (UL-SCH).

PUSCH, and the uplink data may be a transport block (TB), which is a data block for a UL-SCH transmitted during a TTI (Transmission Time Interval). The transport block may include user data. Alternatively, the uplink data may be multiplexed data. The multiplexed data may be a multiplexed transport block for UL-SCH and UL control information. That is, if there is user data to be transmitted in the uplink, the uplink control information may be multiplexed together with the user data and transmitted through the PUSCH.

Meanwhile, in recent years, in the frequency band of the wireless communication system or in other bands, D2D communication using direct transmission / reception technology of the wireless communication system but directly exchanging user data between terminals without going through an infrastructure (for example, a base station) A plan is being considered. D2D communication enables wireless communication in an area other than a limited wireless communication infrastructure and reduces the network load of the wireless communication system. In addition, D2D communication provides advantages such as disaster information and the like can be transmitted to terminals even when the base stations do not operate smoothly in a situation of war, disaster or the like.

A terminal transmitting a signal based on D2D communication is referred to as a transmission terminal (Tx UE), and a terminal receiving a signal based on communication between terminals is defined as a reception terminal (Rx UE). The transmitting terminal transmits a discovery signal, and the receiving terminal can receive the discovery signal. The roles of the transmitting terminal and the receiving terminal may be changed. On the other hand, the signal transmitted by the transmitting terminal may be received by two or more receiving terminals. Also, in the D2D communication according to the present invention, the first terminal transmits data and control signals in the uplink, and the second terminal receives the uplink data and the control signal transmitted from the first terminal. Thus, an SC-FDMA symbol may be used to construct a physical channel carrying data and control signals.

4 is a diagram for explaining the concept of a cellular network-based D2D communication applied to the present invention.

Referring to FIG. 4, a cellular communication network including a first base station 410, a second base station 420, and a first cluster 430 is configured. The first terminal 411 and the second terminal 412 belonging to the cell provided by the first base station 410 perform communication through a normal access link (cellular link) through the first base station 410. [ This is an In-coverage-single-cell inter-terminal communication scenario. Meanwhile, the first terminal 411 belonging to the first base station 410 can perform terminal-to-terminal communication with the fourth terminal 421 belonging to the second base station 420. This is an In-coverage-multi-cell inter-terminal communication scenario. The fifth terminal 431 other than the network coverage may create one cluster 430 together with the sixth terminal 432 and the seventh terminal 433 to perform communication with the terminals. This is an out-of-coverage inter-terminal communication scenario. Also, the third terminal 413 can perform terminal-to-terminal communication with the sixth terminal 432, which is a partial-coverage terminal-to-terminal communication scenario. In this way, the inter-terminal communication link can be performed between devices having the same cell as a serving cell, between devices having different cells as a serving cell, and can be performed between a device connected to a serving cell and a serving cell ), Or between devices not connected to a serving cell. In particular, D2D communication may be required between devices outside of network coverage for the purpose of public safety and the like.

In order to perform D2D data transmission / reception through D2D communication, relevant control information must be transmitted / received between the terminals. The relevant control information may be referred to as a Scheduling Assignment (SA). The Rx terminal may perform a configuration for receiving D2D data based on the SA. The SA includes, for example, a New Data indicator (NDI), a Transmit UE Identification (Tx) ID, a Redundancy Version indicator, an MCS indication, a Resource Allocation , And a power control indication.

Here, NDI indicates whether the current transmission is a repetition of data, i.e., retransmission or new. The receiver can combine the same data based on NDI. The Tx terminal ID indicates the ID of the transmitting terminal. The RV indicator indicates the redundancy version by specifying the different starting points in the circular buffer for the encoded buffer reading. Based on the RV indicator, the transmitting terminal may choose various redundancy versions for the repetition of the same packet. The MCS indication indicates the MCS level for D2D communication. The resource allocation instruction indicates to which time / frequency physical resource the corresponding D2D data is allocated to be transmitted. The power control instruction will be a command for the terminal that has received the information to control the size of power appropriate for the D2D transmission.

For a terminal supporting D2D communication, a radio resource for D2D communication may be an uplink channel of the (cellular) radio communication system. In this case, the SA and data for the D2D communication may be transmitted based on the structure of the PUSCH among the uplink physical channels of the wireless communication system. That is, for the physical channel for D2D communication, the PUSCH structure can be reused. For example, a 24-bit CRC (Cyclic Redundancy Check) can be inserted in the physical channel for D2D communication, and turbo coding can be used. Rate matching may also be used for bit size matching and generating multiple transmissions. Scrambling can be used for interference randomization. Also, PUSCH Demodulation Reference Signal (DMRS) can be used for channel estimation.

At the perspective of the Tx terminal, the Tx terminal may operate in two modes for resource allocation.

Mode 1 is the case where a base station or relay node (hereinafter referred to as a base station, which may include a relay node) schedules certain resource (s) for D2D communication. That is, in mode 1, the specific resource (s) used for transmitting the D2D data and the D2D control information (SA) of the Tx terminal is designated by the base station or the relay node. Mode 2 is a case where the UE directly selects a specific resource (s) in the resource pool. That is, in mode 2, the Tx terminal directly designates specific resource (s) for transmission of D2D data and D2D control information.

A D2D capable terminal supports at least mode 1 for in-coverage D2D communication. A D2D capable terminal supports mode 2 for at least out-of-coverage or edge-of-coverage D2D communication.

D2D communications may include unicast communications, groupcast communications, and broadcast communications. In this case, the Tx terminal performing the D2D broadcast communication may be called a broadcasting terminal. For D2D broadcast communication, an SA indicating the location of the resource (s) for reception of an associated physical channel carrying D2D data must be transmitted by the broadcasting terminal. The resource (s) may be implicitly and / or explicitly indicated based on the content of the SA resource or SA.

In Mode 1, the location of the resource (s) for transmission of the (by) SA by the broadcasting terminal and the location of the resource (s) for transmission of the D2D data is given by the base station. That is, the D2D SA grant and the D2D data grant are given from the base station to the terminal. Here, the D2D SA grant instructs the Tx terminal to transmit the D2D SA, and the D2D data grant instructs the Tx terminal to transmit the D2D data. The D2D data grant may be transmitted concurrently with or at the same time as the SA grant. The D2D SA grant and the D2D data grant may be transmitted via the PDCCH / EPDCCH.

In Mode 2, the resource pool for the SA may be pre-configured and / or semi-statically allocated. In this case, the Tx UE can select a resource for the SA in the resource pool for transmission of the SA.

If the Tx terminal is located outside of coverage, the resources for D2D broadcast data are selected in the resource pool. In this case, the resource pool may be pre-configured or semi-statically allocated.

If the Tx terminal supports mode 1, the base station may send a D2D SA grant and a D2D data grant for D2D communication to the Tx terminal. If the D2D SA grant and the D2D data grant are transmitted through an existing UE specific search space, the Tx UE transmits a PDCCH for carrying DCI information for WAN (Wireless Area Nework) communication (existing cellular communication) And the PDCCH carrying the D2D SA grant and / or the D2D data grant for D2D communication must be monitored on a UE specific search space (USSS). In this case, the PDCCH in the UE-specific search space on one subframe may be excessively allocated, thereby increasing the possibility of PDCCH blocking. Here, PDCCH blocking refers to a phenomenon in which some PDCCHs are not mapped in a corresponding subframe when PDCCHs are allocated more than the available resource space in one subframe.

In addition, the number of DCIs to be monitored by the Tx terminal on one subframe increases. For example, DCI format 0 / 1a, Transmission Mode (DC) specific DCI format (e.g., DCI format 2 / 2a / 2b / 2c / 2d), DCI format 4 (if the uplink MIMO (Multiple Input Multiple Output) is possible) as well as the DCI that points to the D2D SA grant and the D2D data grant. In this case, there is a problem that PDCCH for WAN DCI transmission and PDCCH for D2D SA / data grant transmission have to share a limited UE specific search space.

In this case, the UE-specific search space may have potential overlap with a common search space (CSS) for the corresponding Tx UE, a UE-specific search space for other UEs connected to the same serving cell, There is potential for overlapping. This may further increase the PDCCH blocking probability for the UE.

Meanwhile, the PUSCH can be transmitted on the uplink based on the DCI indicating the uplink grant among the DCIs for WAN communication, and the D2D transmission using the PUSCH structure on the uplink based on the D2D SA / data grant for D2D communication Can be performed. In this case, the timing of the PUSCH transmission for the WAN communication and the D2D transmission (for the Tx terminal to the Rx terminal) for the D2D communication may be different from each other. For example, the PUSCH transmission timing for the WAN communication is determined based on the related uplink grant reception time and the uplink scheduling / HARQ timing (in the case of FDD, 4 ms after the uplink grant is received, ms), the timing of D2D transmission for D2D communication is not yet defined strictly, and it is judged that FDD / TDD can be applied when both are equal to or greater than 4 ms after receiving D2D SA / data grant. Therefore, it may be necessary to monitor the above-mentioned various DCIs (e.g., WAN / D2D DCIs) in one subframe. In this situation, fortunately, terminals after Release 12 (Rel-12), which is supposed to fundamentally support Carrier Aggregation and uplink MIMO, can have improved computing power to solve the above problem It is expected to be a big help.

Therefore, it is required to design an extended search space for PDCCH that carries D2D SA / data grant to reduce PDCCH blocking probability with existing DCI grants (eg WANs).

1. A method based on a hashing function with a new Radio Network Temporary Identifier (RNTI)

A new RNTI for the D2D SA / Data Grant (D2D Grant) can be defined. Hereinafter, the new RNTI may be referred to as D2D-RNTI. Currently, C-RNTI, SPS C-RNTI, etc. are used as initial seed value of hashing function for DCI transmission for WAN communication. The D2D-RNTI value is used as the initial seed value of the hashing function for the D2D SA / data grant transmission for the D2D communication, and for the PDCCH for carrying the D2D SA / data grant based on the D2D-RNTI value, Space can be indicated. In this case, a bit of blind decoding attempt may be added in the Tx terminal, but as mentioned above, this increase in complexity does not have a great effect considering the computation power of the terminals after Release 12.

Specifically, it is as follows.

The Tx terminal uses blind decoding to detect the PDCCH transmitted from the base station. Blind decoding is a method for checking whether a PDCCH / EPDCCH is a control channel by checking a CRC error by demodulating a unique identifier (RNTI) in a CRC of a received PDCCH (referred to as a PDCCH candidate) . The extended search space for D2D communication according to the present invention is a space where the Tx terminal monitors (blind decodes) a set of PDCCH candidates for D2D communication. In order to find the location of the extended search space for the D2D communication, the Tx terminal may implement a hashing function. The hashing function can use the D2D-RNTI as an input.

First, the search space will be described as follows. The search space can be denoted S ^(L) _{k, n} . The CCEs corresponding to the PDCCH candidate m of the search space S ^(L) _{k, n} with respect to the (downlink) serving cell in which the PDCCH is monitored can be given by the following equation (1). That is, the position of the search space can be detected based on the following equation (1). Equation (1) can be called a search space function.

로서 0 부터 9까지의 서브프레임 인덱스이고, n_s는 0 내지 19의 슬롯(slot) 번호이다. 1, 2, 4, and 8 as an aggregation level of CCE, m is 0, ..., M-1, ^(L) -1, M ^(L) is the number of PDCCH candidates to be monitored in the given search space, N _{CCE , k} is the total number of CCEs in subframe #k, k =

, And n _s is a slot number from 0 to 19, where n is a number from 0 to 9,

M '= m for the common search space. (M ⁾ = m + M ^(L) · n ⁽ n ⁾ , when the monitoring terminal is configured with a cell indicator field (CIF), with respect to the terminal specific search space (including the extended search space for the D2D communication) _CI , where n _CI is the cell indicator field value. ii) If the monitoring indication of the monitoring terminal is that the field is not configured, then m'= m. In the present invention, it is assumed that the UE performing D2D communication is not configured with carrier aggregation and cross-carrier scheduling.

On the other hand, Y _k is determined by the following equation (2). Equation 2 represents a hashing function according to the present invention.

Referring to Equation (2), A = 39872, D = 65537, and Y _-1 = n _RNTI ? 0. n _RNTI represents the associated RNTI value. For example, in a common search space, a Paging-RNTI (P-RNTI), a System Information-RNTI (SI-RNTI), or a Random Access-RNTI (RA-RNTI) may be used according to each common control information. In addition, in the UE-specific search space, a unique identifier of the UE, for example, a C-RNTI (Cell-RNTI) may be used.

In this case, the number of PDCCH candidates to be monitored for each aggregation level can be expressed as follows.

Search space The number of PDCCH candidates
M ^(L) type Aggregation Level L Size [in CCEs] Terminal specific
(UE-specific) One 6 6 2 12 6 4 8 2 8 16 2 Common
4 16 4 8 16 2

Meanwhile, for the extended search space for the D2D communication, the D2D-RNTI value may be used in the n _RNTI of Equation (2). That is, Y _-1 = n _{D2D - RNTI} ? 0 may be applied.

Also, in this case, the number of PDCCH candidates monitored by the Tx terminal in the extended search space for D2D communication may be expressed as, for example, as follows.

Search space The number of PDCCH candidates
M ^(L) type Aggregation Level L Size [in CCEs] Terminal specific
(UE-specific) One 3 3 2 6 3 4 8 2 8 8 One

Referring to Table 3 above, the number of PDCCH candidates according to each aggregation level is shown in the search space for the D2D SA / Data Grant (i.e., D2D Grant). According to Table 3, the total number of blind decodings performed by the Tx terminal is increased by 9 times (3 + 3 + 2 + 1) compared with the conventional method.

5 shows a search space for D2D according to an example of the present invention.

Referring to FIG. 5, each block represents a CCE, and each search space assumes an aggregation level 1 (AL 1). The WAN-specific search space is allocated to six CCEs in a control region of a downlink physical channel, and an extended search for D2D communication is performed for three CCEs in a region that does not overlap with a UE- Space is disposed. The PDCCH carrying the D2D grant may be detected in one of the three CCEs in the extended search space. According to the present invention, an extended search space for D2D communication can be provided.

2. Continuous Extended Search Space based on C-RNTI (Cell-RNTI) based hashing function

It is possible to provide an extended search space for the D2D grant without using a new RNTI for the D2D SA / Data Grant (D2D Grant). For this purpose, a hashing function based on the existing C-RNTI is utilized, and an extended search space can be provided by changing some parameters as follows.

M = M + M ^(L) N for the extended search space for the D2D grant in Equation 1, which is the above-described search space function. In this case, N may be any number or greater than one. i) As an example, N = 1, ii) as another example, N may be an indication via higher layer signaling, and iii) as another example, N = f (C-RNTI). Here, f () is a random function.

First, for example, if N = 1, an extended search space for the D2D grant is provided (or defined) continuously in the search space defined for the WAN. That is, a fixed search space for the D2D grant is located immediately after the terminal specific search space defined for the WAN.

In another example, when N is indicated through upper layer signaling, the extended search space is defined (M ^{(L)) for} each AL from the M ^(L) N-th CCE based on the start point of the UE-specific search space defined for the WAN Or positioned). Where the N value may be transmitted as the base station signals the parameters for D2D communication to the Tx terminal.

As another example, the N value may be randomly generated based on the random function f (). In this case, the C-RNTI value and the slot index may be used as a seed value for the random function. In this case, the extended search space may be defined (or positioned) for each AL from the M ^(L) N CCEs based on the start point of the UE-specific search space defined for the WAN. For example, the random function may be expressed by the following equation (3).

이고, A 값은 미리 특정 값으로 정해지거나, 시그널링을 통하여 설정될 수 있다.In Equation (3), c _init =

, And the value of A may be set to a specific value in advance or may be set through signaling.

In the above examples, the number of PDCCH candidates monitored by the Tx terminal in the extended search space for D2D communication may be expressed as, for example, as follows.

Search space The number of PDCCH candidates
M ^(L) type Aggregation Level L Size [in CCEs] Terminal specific
(UE-specific) One 3 3 2 6 3 4 8 2 8 8 One

6 and 7 show a search space for D2D according to another example of the present invention. In FIGS. 6 and 7, each block is a CCE unit, and each search space assumes an aggregation level 1 (AL).

Referring to FIG. 6, a UE-specific search space for a WAN is allocated to specific CCEs within a control region of a downlink physical channel, and an extended search space for D2D communication is located immediately after the UE- Are continuously disposed. This is the case where the value of N is 1. 7, when a UE-specific search space for a WAN is allocated to specific CCEs within a control region of a downlink physical channel, an extended search space for D2D communication is allocated to a UE- Spaced apart. This is the case where the N value may not be 1 ^, and the extended search space may be arranged from M ^(L) N CCEs after the starting point of the UE-specific search space defined for the WAN.

According to the present invention as described above, an extended search space for carrying related control information for D2D communication can be provided. Accordingly, the PDCCH blocking probability in the UE-specific search space can be reduced and the D2D communication can be efficiently supported.

8 illustrates a D2D grant transmission method for D2D communication according to the present invention. Herein, it is described that the D2D grant may include the D2D SA grant and the D2D data grant.

Referring to FIG. 8, the base station configures an extended search space for D2D communication (S800). The extended search space is a space in which the Tx terminal performs blind decoding to detect a PDCCH carrying a D2D SA / data grant transmitted from a base station. The base station can construct the extended search space based on the search space function and the hashing function. The corresponding functions may be implemented based on Equations (2) and (3) described above. In this case, for example, the newly defined D2D-RNTI value for the D2D communication may be substituted into the variable n _RNTI of the hashing function to indicate the location of the extended search space on the logical CCE column. As another example, the variable m '= m + M ^(L) N of the search space function may be substituted to indicate the location of the extended search space on the logical CCE column for the physical channel. Where N = 1, N may be indicated via higher layer signaling, or N may be indicated via a random function.

The base station maps the PDCCH carrying the D2D SA / data grant to at least one CCE on the extended search space (S810). That is, the base station may map the PDCCH carrying the D2D SA grant to at least one CCE on the extended search space, or may map the PDCCH carrying the D2D data grant to at least one CCE on the extended search space . If the D2D SA grant and the D2D data grant are transmitted on the same PDCCH, the base station may map the PDCCH to at least one CCE on the extended search space.

The base station transmits the mapped PDCCH to the Tx terminal (S820). The mapped PDCCH may be detected by the Tx terminal based on blind decoding as described above.

9 shows a D2D grant reception method for D2D communication according to the present invention.

Referring to FIG. 9, the Tx terminal detects an extended search space for D2D communication (S900). Here, the extended search space may be detected based on the search space function and the hashing function used by the base station. The corresponding functions may be implemented based on Equations (2) and (3) described above.

The Tx UE blind-decodes the PDCCH carrying the D2D SA / data grant on the extended search space (S910). For example, the Tx UE may de-mask a specific RNTI on the CRC of candidate PDCCHs received on a specific search space (extended search space) and check whether the corresponding PDCCH is its own control channel by checking the CRC error. Based on the blind decoding, the Tx UE may detect a PDCCH carrying the D2D SA / Data Grant.

The Tx terminal transmits D2D SA / D2D data for D2D communication to the Rx terminal based on the detected PDCCH (S920).

10 is an example of a block diagram illustrating a wireless communication system supporting D2D communication according to the present invention.

10, a base station 1000 includes a processor 1005, a memory 1010, and an RF unit (radio frequency unit) 915. The memory 1010 is connected to the processor 1005 and stores various information for driving the processor 1005. [ The RF unit 1015 is connected to the processor 1005 to transmit and / or receive a radio signal. The processor 1005 implements the proposed functions, procedures and / or methods for performing the operations according to the present invention. In the above-described embodiments, the operation of the base station can be implemented by the processor 1005. [

Specifically, processor 1005 may configure an extended search space for published D2D communications herein.

The processor 1005 may also generate the D2D SA / data grant and transmit it to the Tx terminal 1030 through the RF unit 1015. [ The D2D SA grant and the D2D data grant may be included in the same or different PDCCH and transmitted to the Tx terminal 1030. [ In this case, the processor 1050 controls the PDCCH carrying the D2D SA grant and / or the D2D data grant to be mapped to at least one CCE on the extended search space, and transmits the PDCCH to the Tx terminal 1030 ).

The Tx terminal 1030 includes a processor 1035, a memory 1040, and an RF section 1045. The memory 1040 is coupled to the processor 1035 to store various information for driving the processor 1035. The RF unit 1045 is coupled to the processor 1035 to transmit and / or receive wireless signals. Processor 1045 implements suggested functions, procedures and / or methods for performing operations in accordance with the present invention. The operation of the Tx terminal 1030 in the above-described embodiment may be implemented by the processor 1035. [

RF section 1045 receives candidate PDCCHs including the PDCCH carrying the D2D SA / data grant.

Processor 1035 detects the extended search space for D2D communication and controls to blind decode the PDCCH carrying the D2D SA / data grant on the extended search space. Processor 1035 may detect the PDCCH carrying the D2D SA / Data Grant based on the blind decoding.

The processor 1035 transmits D2D SA and / or D2D data to the Rx terminal 1060 via the RF unit 1045 based on the D2D SA / data grant.

The Rx terminal 1060 includes a processor 1065, a memory 1070, and an RF section 1075. The memory 1070 is coupled to the processor 1065 and stores various information for driving the processor 1065. [ The RF unit 1075 is coupled to the processor 1065 to transmit and / or receive wireless signals. Processor 1065 implements a set of functions, procedures, and / or methods for performing D2D communications.

The RF unit 1045 receives the D2D SA and / or D2D data from the Tx terminal 1030.

The processor may comprise an application-specific integrated circuit (ASIC), other chipset, logic circuitry and / or a data processing device. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. The RF unit may include a baseband circuit for processing the radio signal. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module is stored in memory and can be executed by the processor. The memory may be internal or external to the processor and may be coupled to the processor by any of a variety of well known means.

In the exemplary system described above, although the methods are described on the basis of a flowchart or a flowchart as a series of steps or blocks, the present invention is not limited to the order of steps, and some steps may be performed in a different order than the steps described above Can occur at the same time. It will also be appreciated by those skilled in the art that the steps depicted in the flowcharts or flowcharts are not exclusive and that other steps may be included or that one or more steps in a flowchart or flowchart may be deleted without affecting the scope of the present invention.

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 (20)

A method for supporting D2D (Device to Device) communication performed by a base station,
Configuring an extended search space for D2D communication;
Mapping a physical downlink control channel (PDCCH) carrying at least one of a D2D Scheduling Assignment (SA) grant and a D2D data grant to at least one control channel elements (CCE) in the extended search space; And
And transmitting the mapped PDCCH to the UE. The method according to claim 1,
Wherein the extended search space is constructed based on a search space function and a hashing function. 3. The method of claim 2,
Wherein the extended search space is configured based on a D2D-RNTI (Radio Network Temporary Identifier) value. 3. The method of claim 2,
Wherein the search space function is represented by the following equation (1), and the hashing function is expressed by the following equation (2): D2D communication support method,

(One)
Where L is the aggregation level of the CCE, 1, 2, 4, or 8, and m is 0, ..., M ^(L) -1 , M ^(L) is the number of PDCCH candidates to be monitored in the extended search space, N _{CCE , k} is the total number of CCEs in subframe #k, k =

As a sub-frame index from 0 to 9, n _s is from 0 to 19 slots (slot) number, if the terminal is configured to monitor if a cell indicator field (cell indicator field, CIF), m'= m + M ^{( L)} n _CI where n _CI is the cell indicator field value, and if the monitoring indication is a cell indication that the field is not configured, m '= m, Y _k is the hashing function,

(2)
Here, A = 39872, D = 65537, Y _-1 = n _{D2D - RNTI} ≠ 0, and n _{D2D - RNTI} indicates a D2D-RNTI (Radio Network Temporary Identifier) value. 3. The method of claim 2,
Wherein the search space function is represented by the following equation (3), and the hashing function is expressed by the following equation (4)

(3)
Where L is the aggregation level of the CCE, 1, 2, 4, or 8, and m is 0, ..., M ^(L) -1 , M ^(L) is the number of PDCCH candidates to be monitored in the extended search space, N _{CCE , k} is the total number of CCEs in subframe #k, k =

As a sub-frame index from 0 to 9, n, and _s is from 0 to 19 slots (slot) ^{number, m'= m + M (L} ) · N and, N≥1, Y _k is the hashing function,

(4)
Here, A = 39872, D = 65537, Y _-1 = n _RNTI ? 0, and n _RNTI indicates a C-RNTI (Cell Radio Network Temporary Identifier) value. 6. The method of claim 5,
Wherein N = 1. 6. The method of claim 5,
Wherein the N is indicated via higher layer signaling. ≪ RTI ID = 0.0 > 11. < / RTI > 6. The method of claim 5,
Wherein the N is indicated based on a random function. 3. The method of claim 2,
Wherein the location of the extended search space on a logical CCE column is indicated based on the search space function and the hashing function. A base station supporting D2D communication,
A processor configured to configure an extended search space for D2D communication and to map a PDCCH carrying at least one of the D2D SA grant and the D2D data grant to at least one control channel elements (CCE) ; And
And an RF unit for transmitting the mapped PDCCH to a mobile station. A method of supporting D2D (Device to Device) communication performed by a terminal,
Detecting an Extended Search Space for D2D communication;
Blind decoding a Physical Downlink Control Channel (PDCCH) carrying at least one of a D2D SA (Scheduling Assignment) grant and a D2D data grant on the extended search space;
Detecting the PDCCH based on the blind decoding;
Generating at least one of D2D SA and D2D data based on the detected PDCCH; And
And transmitting at least one of the generated D2D SA and D2D data to a receiving terminal. 12. The method of claim 11,
Wherein the extended search space is detected based on a search space function and a hashing function. 13. The method of claim 12,
Wherein the extended search space is detected based on a D2D-RNTI (Radio Network Temporary Identifier) value. 13. The method of claim 12,
Wherein the search space function is expressed by the following equation (5), and the hashing function is expressed by the following equation (6): D2D communication support method

(5)
Where L is the aggregation level of the CCE, 1, 2, 4, or 8, and m is 0, ..., M ^(L) -1 , M ^(L) is the number of PDCCH candidates to be monitored in the extended search space, N _{CCE , k} is the total number of CCEs in subframe #k, k =

As a sub-frame index from 0 to 9, n _s is from 0 to 19 slots (slot) number, if the terminal is configured to monitor if a cell indicator field (cell indicator field, CIF), m'= m + M ^{( L)} n _CI where n _CI is the cell indicator field value, and if the monitoring indication is a cell indication that the field is not configured, m '= m, Y _k is the hashing function,

(6)
Here, A = 39872, D = 65537, Y _-1 = n _{D2D - RNTI} ≠ 0, and n _{D2D - RNTI} indicates a D2D-RNTI (Radio Network Temporary Identifier) value. 13. The method of claim 12,
Wherein the search space function is expressed by the following equation (7), and the hashing function is expressed by the following equation (8): < EMI ID =

(7)
Where L is the aggregation level of the CCE, 1, 2, 4, or 8, and m is 0, ..., M ^(L) -1 , M ^(L) is the number of PDCCH candidates to be monitored in the extended search space, N _{CCE , k} is the total number of CCEs in subframe #k, k =

As a sub-frame index from 0 to 9, n, and _s is from 0 to 19 slots (slot) ^{number, m'= m + M (L} ) · N and, N≥1, Y _k is the hashing function,

(8)
Here, A = 39872, D = 65537, Y _-1 = n _RNTI ? 0, and n _RNTI indicates a C-RNTI (Cell Radio Network Temporary Identifier) value. 16. The method of claim 15,
Wherein N = 1. 16. The method of claim 15,
Wherein the N is indicated via higher layer signaling. ≪ RTI ID = 0.0 > 11. < / RTI > 16. The method of claim 15,
Wherein the N is indicated based on a random function. 13. The method of claim 12,
Wherein the location of the extended search space on a logical CCE column is indicated based on the search space function and the hashing function. As a terminal supporting D2D (Device to Device) communication,
A Physical Downlink Control Channel (PDCCH) for detecting an Extended Search Space for D2D communication and carrying at least one of a D2D SA (Scheduling Assignment) Grant and a D2D Data Grant on the extended search space Blind decoding, detecting the PDCCH, and generating at least one of D2D SA and D2D data based on the detected PDCCH; And
And an RF unit for transmitting at least one of the generated D2D SA and D2D data to a receiving terminal.

Images