KR102586204B1 - Method and apparatus for transmitting signal using unlicensed band in celluar system - Google Patents

Abstract

A method of transmitting resources, comprising performing CCA for an unlicensed band, occupying a channel in the unlicensed band according to the CCA, and determining whether to transmit the resource based on the location of the TTI in the COT for the channel. And a device and a HARQ retransmission method using an unlicensed band are provided.

Description

Method and device for transmitting signals in a cellular system using an unlicensed band {METHOD AND APPARATUS FOR TRANSMITTING SIGNAL USING UNLICENSED BAND IN CELLUAR SYSTEM}

This disclosure relates to a method and device for transmitting signals in a cellular system using an unlicensed band.

As the number of mobile Internet users through mobile communication systems increases, ways to increase the capacity of mobile communication systems are being sought. One way is to increase the bandwidth for mobile communication systems, and this can be achieved through securing additional licensed spectrum. However, the costs required to license and use the licensed band frequencies are high, and the licensed band frequencies allocated for mobile communication systems are limited. Accordingly, plans to provide mobile communication services through unlicensed frequency bands or TV White Space, which have relatively many available frequency bands and are also inexpensive, are being considered. Additionally, a method of sharing frequencies in licensed/unlicensed bands between mobile communication system operators is also being considered.

Communication systems that use frequencies in a shared frequency band (hereinafter referred to as “unlicensed band”) have the following limitations.

First, the transmission power is limited to minimize the impact on other systems sharing unlicensed band frequencies. Therefore, if a licensed band system and an unlicensed band system are installed in the same location, a coverage hole may occur.

Additionally, to ensure fair coexistence with adjacent unlicensed band systems, unlicensed band frequencies must be used discontinuously or opportunistically. Accordingly, transmission reliability of control channels and common channels of the mobile communication system may be lowered.

Additionally, unlicensed band frequency regulations must be observed. A system using unlicensed frequency bands must perform a clear channel assessment (CCA) for data transmission and determine whether to use the channel based on the CCA results. According to the CCA results, the device (or system) that occupies the channel may have channel occupancy time restricted according to frequency regulations, cannot occupy the channel for a time exceeding the maximum channel occupancy time, and must use CCA to reoccupy the channel. There is a need to perform additionally.

Due to these limitations of the unlicensed band system, a scenario in which the system is installed/operated in a complementary manner with the licensed band system rather than a system that independently uses the unlicensed band (Standalone System) is being considered. In this scenario, control functions that require reliability, such as terminal control and mobility management, are performed by a system operating in a licensed band frequency, and traffic functions such as increasing wireless transmission speed and distributing wireless traffic load are complemented by an unlicensed band system. It works. That is, the carrier in the licensed band performs control and traffic functions, and the carrier in the unlicensed band performs traffic functions. The above operation can be implemented through carrier aggregation technology, and as an example of CA, a licensed band LTE carrier, an unlicensed band FDD carrier, or an unlicensed band TDD carrier operating uplink and downlink simultaneously can be aggregated, respectively. there is.

Cellular systems can guarantee service quality when providing mobile communication services by utilizing advanced interference control technology and low-cost and abundant frequency resources in unlicensed bands. At this time, new coexistence technology and interference control technology are needed to secure the above advantages in various regulations of the unlicensed band and coexistence with other unlicensed band systems. In particular, carrier aggregation technology and corresponding operation that take into account the characteristics of licensed and unlicensed bands are needed. In addition, services equivalent to existing cellular systems must be provided by providing reliability of wireless transmission and reflecting limitations (characteristics) for device operation in unlicensed bands.

One embodiment provides a method and device for transmitting resources using an unlicensed band.

Another embodiment provides a HARQ retransmission method using an unlicensed band.

According to one embodiment, a method for receiving resources capable of measuring a channel in an unlicensed band is provided. The resource reception method includes receiving resources in an occupied channel through clear channel assessment (CCA) for an unlicensed band, and determining whether to perform measurement based on the resources.

In the resource reception method, whether to transmit the resource may be determined based on the location of the TTI in the COT for the channel.

The determining step in the resource reception method may include measuring the state of the channel when the resource is a CSI-RS resource.

The determining step in the resource reception method may include measuring interference from another system when the resource is a ZP CSI-RS resource among CSI-RS resources.

The determining step in the resource reception method may include measuring the state of the channel when the resource is an NZP CSI-RS resource among CSI-RS resources.

The determining step in the resource reception method may include measuring interference on the channel when the resource is a CSI-IM resource.

According to another embodiment, it includes at least one processor, a memory, and a wireless communication unit, wherein the at least one processor executes at least one program stored in the memory to perform a clear channel assessment (CCA) for an unlicensed band. performing a step, and occupying a channel in the unlicensed band according to the CCA, and measuring the channel based on the location of the transmission time interval (TTI) within the channel occupancy time (COT) for the channel. A base station is provided that performs the step of determining whether to transmit available resources.

When the base station performs the step of determining, the at least one processor may include transmitting resources if the TTI is a partial subframe and the length of the partial subframe is longer than a predetermined length. .

When performing the step of determining at least one processor, the base station may perform a step of not transmitting resources if the TTI is a partial starting subframe.

When performing the step of determining, the base station, at least one processor, may perform the step of not transmitting resources if the TTI is a partial ending subframe.

When the base station performs the step of determining, the at least one processor will perform the step of not transmitting resources in the first TTI or the last TTI among at least one TTI included in the COT, or the first TTI and the last TTI. You can.

When the base station performs the step of determining that the TTI is a partial starting subframe, the base station uses orthogonal frequency division multiplexing (OFDM) to transmit resources to the TTI. If a symbol is included, the step of transmitting resources in the OFDM symbol can be performed.

When the base station performs the step of determining that the TTI is a partial ending subframe, the base station uses orthogonal frequency division multiplexing (OFDM) to transmit resources to the TTI. If a symbol is included, the step of transmitting resources in the OFDM symbol can be performed.

When performing the determining step, the base station may perform the step of determining whether to transmit resources according to the number of orthogonal frequency division multiplexing (OFDM) symbols included in the TTI. there is.

According to another embodiment, a Hybrid Automatic Retransmission Request (HARQ) retransmission method using an unlicensed band is provided. The HARQ retransmission method includes transmitting data through an uplink unlicensed band to a base station, and when a retransmission request for data is received from the base station, retransmitting data through an uplink licensed band.

In the HARQ retransmission method, receiving a retransmission request may mean receiving a NACK from the base station through the downlink licensed band.

Receiving a retransmission request in the HARQ retransmission method may mean receiving resource allocation containing information requesting retransmission of data from the base station through the downlink licensed band.

Receiving a retransmission request in the HARQ retransmission method may mean receiving resource allocation including parameters for retransmission from the base station through the downlink licensed band.

The HARQ retransmission method may further include receiving ACK and/or NACK for data from the base station through the downlink licensed band when cross-carrier scheduling is performed for the terminal. .

The HARQ retransmission method may further include receiving an ACK and/or NACK for data from the base station through a downlink unlicensed band when self scheduling is performed for the terminal.

When allocating resources for a mobile wireless access system, a reliable service can be provided by efficiently operating unlicensed bands, which are less reliable than licensed bands, together with licensed bands.

1 is a conceptual diagram showing a data transmission process of a base station and a terminal according to an embodiment.
2A and 2B are conceptual diagrams showing a HARQ retransmission process according to an embodiment.
FIG. 3A is a diagram showing a downlink protocol stack of a wireless communication system according to an embodiment, and FIG. 3B is a diagram showing a downlink protocol stack of a master base station and an auxiliary base station according to an embodiment.
Figure 4 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 1 according to an embodiment.
Figure 5 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 1 according to another embodiment.
Figure 6 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 1 according to another embodiment.
Figures 7A to 7C are conceptual diagrams showing an uplink HARQ retransmission process in an unlicensed band in Method 1 according to an embodiment.
Figure 8 is a flowchart showing a downlink HARQ retransmission process of Method 1 according to an embodiment.
Figure 9 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 2 according to an embodiment.
Figures 10A to 10C are conceptual diagrams showing an uplink HARQ retransmission process in an unlicensed band in Method 2 according to an embodiment.
Figure 11 is a flowchart showing a downlink HARQ retransmission process of Method 2 according to an embodiment.
Figure 12 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 3 according to an embodiment.
Figures 13A to 13C are conceptual diagrams showing an uplink HARQ retransmission process in an unlicensed band in Method 3 according to an embodiment.
Figure 14 is a flowchart showing the downlink HARQ retransmission process of Method 2 according to an embodiment.
Figure 15 is a conceptual diagram showing channel measurement method 1 according to another embodiment.
Figure 16 is a conceptual diagram showing channel measurement method 2 according to another embodiment.
Figure 17 is a conceptual diagram showing channel measurement method 3 according to another embodiment.
Figure 18 is a conceptual diagram showing a CSI-RS setting method according to an embodiment.
Figure 19 is a conceptual diagram showing a CSI-RS setting method according to another embodiment.
Figure 20 is a conceptual diagram showing a CSI-RS setting method according to another embodiment.
Figure 21 is a conceptual diagram showing a method for measuring the channel state of a terminal according to an embodiment.
Figure 22 is a conceptual diagram showing a method of measuring the channel state of a terminal according to another embodiment.
Figure 23 is a conceptual diagram showing a channel status reporting method according to an embodiment.
Figure 24 is a block diagram showing a wireless communication system according to one embodiment.

Below, with reference to the attached drawings, embodiments of the present disclosure will be described in detail so that those skilled in the art can easily implement the present invention. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein. In order to clearly explain the description in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, terminal refers to a mobile station (MS), a mobile terminal (MT), an advanced mobile station (AMS), and a high reliability mobile station (HR-MS). ), subscriber station (SS), portable subscriber station (PSS), access terminal (AT), user equipment (UE), machine type communication device, MTC device), etc., and may include all or part of the functions of MT, MS, AMS, HR-MS, SS, PSS, AT, UE, etc.

In addition, the base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), access point (AP), radio access station (RAS), base transceiver station (BTS), mobile multihop relay (MMR)-BS, relay that acts as a base station station (RS), a relay node (RN) that acts as a base station, an advanced relay station (ARS) that acts as a base station, and a high reliability relay station (HR) that acts as a base station. -RS), small base station [femto BS, home node B (HNB), home eNodeB (HeNB), pico BS, macro BS, micro BS ), etc.], etc., and may include all or part of the functions of ABS, NodeB, eNodeB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR-RS, small base station, etc. there is.

FIG. 1 is a conceptual diagram illustrating a data transmission process of a base station and a terminal according to an embodiment, and FIGS. 2A and 2B are conceptual diagrams illustrating a HARQ retransmission process according to an embodiment.

Referring to Figure 1, the base station performs CCA in the unlicensed band and transmits data to the terminal. At this time, the base station may occupy the channel and transmit data (transmitted via Unlicensed Component Carrier (UCC)) during the channel occupancy time (COT) as a result of CCA. However, if a NACK (transmitted through a Licensed Component Carrier (LCC)) occurs for data transmitted during the channel occupancy time, the data corresponding to the NACK cannot be retransmitted if the maximum channel occupancy time has passed. may occur. This is because the base station must perform CCA again.

FIG. 2A is a conceptual diagram showing a case where cross-carrier scheduling is performed on the uplink, and FIG. 2B is a conceptual diagram showing a case where self-scheduling is performed on the uplink.

In Figure 2a, after the terminal performs CCA and notifies the base station of scheduling information through the uplink UCC, if a NACK occurs for data transmitted from the base station to the terminal through the downlink LCC, the COT allocated to the terminal is exceeded, so the data There is a problem where retransmission is not possible.

In Figure 2b, when the terminal and the base station each occupy the UCC through the CCA to transmit uplink resource allocation (UL grant) and uplink data, and when NACK occurs for the UL grant or uplink data, the base station and the terminal use COT There is a problem where retransmission is not possible afterward.

Meanwhile, to improve small cells in cellular networks considered by 3GPP, three scenarios related to small cell deployment, spectrum, traffic, and compatibility with previous standards were defined, and technical issues and solutions for the defined scenarios were discussed. It has been done. Scenario 1 is a scenario in which macro cells and small cells use the same frequency in an overlapping structure. Scenario 2 is a scenario in which macro cells and small cells use different frequencies in an overlapping structure. Scenario 3 is a scenario in which only small cells deployed in a structure where macro cells and small cells do not overlap are used.

In this description, in order to solve the HARQ retransmission problem in the unlicensed band, a HARQ retransmission processing method (Method 1) through the carrier on which previous data transmission was performed, and a HARQ retransmission processing method through LCC when previous data transmission was performed through UCC (Method 1) Method 2), a method of processing HARQ retransmission through an available carrier of LCC or UCC when the previous data transmission was performed through UCC (Method 3), and a method of processing HARQ retransmission according to carrier change (Method 4) are described. To solve the HARQ retransmission problem in the unlicensed band, two or more of the methods listed above may be combined, or one method may be applied and then another method may be applied after a certain time, or another method may be additionally set. Or, information indicating at least one of the above methods is transmitted to a higher layer (e.g., LTE's radio resource control (RRC) layer level signaling or media access control (MAC) layer control element ( It can be transmitted through a control element (CE), etc.). Alternatively, at least one of the above methods, predefined between the base station and the terminal, may be performed.

Figure 4 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 1 according to an embodiment.

Referring to FIG. 4, HARQ retransmission can be performed through the carrier used for initial data transmission (shown based on FDD, but can be applied equally or similarly to TDD). When performing this method, the timing for HARQ retransmission, currently defined as LTE HARQ RTT (round trip time), needs to be changed as shown in Equation 1 below. At this time, LTE HARQ RTT is 8 subframes based on FDD and k+4 subframes based on TDD, where k is the time delay or interval between downlink transmission and uplink feedback due to downlink transmission, and FDD is 4, and TDD may vary depending on UL/DL configuration (refer to 3GPP TS36.213).

In Equation 1, Ki is an index calculated from the last subframe included in the maximum COT, and T _inter-tx is data transmission performed through the occupied channel after CCA, and the occupied channel as a result of the next CCA. Indicates the time (subframe unit) until data transmission.

According to method 1, for HARQ retransmission, an additional CCA is required, which may cause transmission delay. If the transmission delay exceeds the maximum allowable RTT (max_RTT), the data transmission fails and a new data transmission is attempted.

Referring to FIG. 4, since whether or not a channel is occupied is determined according to the CCA result, when HARQ retransmission is performed on data transmitted before the first subframe of the occupied channel after the second CCA, many retransmissions are performed in the first subframe. This can happen.

Figure 5 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 1 according to another embodiment.

Referring to FIG. 5, if the channel is not occupied at the time of retransmission, HARQ retransmission may be performed after sequentially extending the subframes corresponding to the retransmission. At this time, as the retransmission point, k in the unlicensed band, defined as a value defined in the cellular system (for example, k = 4 in the case of 3GPP FDD) or a value defined in existing FDD/TDD, can be used. And at this time, subframe k is sequentially extended and then set to subframe k' as shown in Equation 2 below, so that HARQ retransmission can be performed.

In Equation 2, T _inter-tx is the time (subframe unit) from when data is transmitted through a channel occupied by a CCA to when data is transmitted through a channel occupied as a result of the next CCA. And, the timing for HARQ retransmission is determined according to Equation 3 below.

Figure 6 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 1 according to another embodiment.

Referring to FIG. 6, if the channel is not occupied at the time when HARQ retransmission is to be performed, after retransmission is performed similarly to FIG. 5, if the channel is occupied at the time of data retransmission, at the time of HARQ retransmission It can be retransmitted to the corresponding subframe.

In FIGS. 4 to 6, the HARQ retransmission method is described based on downlink data, but the method described with reference to FIGS. 4 to 6 can be applied equally or similarly to HARQ retransmission for uplink data transmission. In the case of uplink data transmission, the feedback interval (e.g., 3GPP physical HARQ indicator channel, PHICH) transmitted from the base station to the terminal may be kPHICH.

Figures 7A to 7C are conceptual diagrams showing an uplink HARQ retransmission process in an unlicensed band in Method 1 according to an embodiment.

Figure 7a shows a case where resources are allocated to the uplink through cross-carrier scheduling, and Figures 7b and 7c show a case where resources are allocated to the uplink through self-scheduling. In Figure 7b, the terminal performs CCA to transmit uplink data, accesses the channel, and then occupies the channel (access/occupancy (holding or reservation) to the channel), and in Figure 7c, the base station performs CCA to transmit uplink data of the terminal. This CCA is performed to access/occupy the channel. The uplink HARQ retransmission process in the unlicensed band may be the same or similar to when retransmission is performed on the same carrier as the previous carrier.

Figure 8 is a flowchart showing a downlink HARQ retransmission process of Method 1 according to an embodiment.

Referring to FIG. 8, first, the base station transmits downlink data to the terminal along with a new data indicator (NDI) through UCC (NDI is toggled) (S901). At this time, the redundancy version (RV) is 0 (RV=0). Afterwards, the terminal that has received the downlink data transmits HARQ ACK/NACK to the base station through the LCC (S902). Then, the base station notifies the UCC cell of the terminal's ACK/NACK (S903), and if there is no NACK, the UCC cell transmits new data in the downlink (S904). However, when the terminal transmits NACK, the base station increases the repetition version (RV++) and retransmits data corresponding to the NACK through UCC without NDI toggled (NDI is not toggled) (S905). Afterwards, the terminal transmits HARQ ACK/NACK to the base station through the LCC (S906), and the base station notifies the terminal's ACK/NACK through the UCC cell (S907). That is, according to one embodiment, HARQ ACK/NACK indicating success or failure of data transmitted through an unlicensed band may be transmitted to the base station through a licensed band, and at this time, HARQ retransmission is performed through the carrier used for previous data transmission. It can be done.

Below, based on FIGS. 9 to 11, a method (method 2) for processing HARQ retransmission through LCC when previous data transmission was performed through UCC will be described in detail.

Figure 9 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 2 according to an embodiment.

Referring to FIG. 9, initial transmission of data is performed in an unlicensed band, and HARQ retransmission is performed in a licensed band. In Figure 9, the HARQ retransmission process is shown based on the FDD system, but the same or similar application is possible to TDD. According to method 2, no additional CCA is required for HARQ retransmission, and the HARQ RTT time is not reset. That is, after receiving data, feedback on the data is performed on the given resource, and retransmission is performed when the feedback is NACK. However, at this time, since retransmission of data is performed through a licensed band carrier, the terminal receives the control channel of the licensed band and performs preliminary operations for data reception (data transmission in the case of uplink data transmission). In addition, when data initially transmitted/retransmitted in the licensed band (first data) and licensed band retransmitted data (second data) corresponding to data transmitted in the unlicensed band are simultaneously transmitted in the same subframe, the first data and the first data 2 Data must be distinguished from each other.

To distinguish between first data and second data, a method of extending the HARQ process may be used.

In this case, depending on the operating characteristics of the HARQ process that operates independently for each carrier, a separate HARQ process ID may be defined/assigned, which is different from the HARQ process ID (Identification) assigned (granted) to the primary cell (PCell). Each case is not distinguished through the HARQ process ID (or index) for each carrier.

Alternatively, each case can be distinguished by adding a bit for an unlicensed band carrier to the existing HARQ process ID. For example, in an FDD system, a 3-bit HARQ process ID may be changed to 3+N bits, and in a TDD system, a 4-bit HARQ process ID may be changed to 4+N bits. At this time, N is the number of unlicensed band carriers. For example, if there is one unlicensed carrier in the FDD system, 4 bits can be used as the HARQ process ID, 0b0000 to 0b0111 can be used as the HARQ process ID of the licensed band carrier, and 0b1000 to 0b1111 can be used as the HARQ process ID of the unlicensed band carrier. Alternatively, when there are two unlicensed carriers in FDD, 5 bits are used as the HARQ process ID, 0b00000~0b00111 as the HARQ process ID of the licensed band carrier, 0b01000~0b01111 as the HARQ process ID of the first unlicensed band carrier, and 0b10000 ~0b10111 can be used as the HARQ process ID of the second unlicensed band carrier. This method can be applied to the TDD system in the same way as the FDD system, except that 4 bits are used as the HARQ process ID of the licensed band carrier.

When the HARQ process is expanded, HARQ-related information included in the control channel for data transmission/retransmission (e.g., (enhanced, E) physical downlink control channel (PDCCH) of 3GPP) information) needs to be changed and expanded.

Alternatively, a method of distinguishing HARQ processes may be used to distinguish first data and second data. This method uses a predetermined bit among the bits of the HARQ process ID as a carrier index. That is, according to this method, the identifier of the unlicensed band carrier (e.g., carrier indicator) is used as a carrier index, or the unlicensed band carrier identifier is sorted from small to large value, HARQ-specific Identifiers can be newly defined. At this time, the carrier identifier or redefined carrier identifier can also be used to distinguish the HARQ process, and is an identifier for cellular operation in the unlicensed band (e.g., carrier indication for resource allocation, carrier addition/assignment/activation/deactivation It can be used as an identifier for creation/removal, carrier indication of successful CCA, target channel (or carrier) indication for channel (or carrier) change, etc. Additionally, the carrier identifier according to this method can be mapped using a carrier indicator among the fields included in DCI used for resource allocation in carrier aggregation of 3GPP. Additionally, the carrier identifier may be added when a carrier indicator is added to the conditions included in cross-carrier scheduling and when data allocation information/retransmission information corresponding to data transmitted in an unlicensed band is indicated.

Alternatively, in order to distinguish between first data and second data, the method of instructing data transmission (resource allocation instruction) may be changed. According to this, when data is transmitted/allocated in a cellular system, it is included in the carrier identifier to inform the receiving device of the fact of transmission/allocation of data, and the retransmitted data identifies the carrier used in the previous transmission, thereby enabling the HARQ process. It can be done.

Based on the method of classifying the HARQ process described above, the HARQ process can operate by identifying the carrier used in the previous transmission when resource allocation/instruction is performed through the carrier (license) on which retransmission is performed.

Figures 10A to 10C are conceptual diagrams showing an uplink HARQ retransmission process in an unlicensed band in Method 2 according to an embodiment.

Referring to FIGS. 10A to 10C, the HARQ process classification method described above can also be applied to uplink data services.

Figure 10a shows a case where resources are allocated through cross-carrier scheduling, and Figures 10b and 10c show a case where resources are allocated through self-scheduling. In Figure 10b, the terminal accesses/occupies the channel through the CCA for uplink data transmission, and in Figure 10c, the base station accesses/occupies the channel through the CCA for the terminal's uplink data transmission. Additionally, in the case of self-scheduling as shown in FIGS. 10b and 10c, when data transmission is performed on the same carrier as the carrier used to indicate resource allocation information for initial data transmission, HARQ ACK/NACK (e.g., HARQ ACK/NACK) corresponding to the data , 3GPP's PHICH) can be transmitted through a carrier used to indicate resource allocation information. In order to transmit HARQ ACK/NACK from the base station to the unlicensed band, the base station must access/occupy the channel through CCA. In general, HARQ ACK/NACK feedback can be transmitted after a predetermined time has elapsed (e.g., after 4ms for FDD, 4~7ms for TDD, see 3GPP TS36.213) after data transmission. However, if CCA is performed before the channel must be occupied and data must be transmitted, or if the channel is determined to be already in use (busy or occupied) as a result of the CCA, the base station cannot transmit HARQ ACK/NACK. For this purpose, one or a combination of two or more of the methods below can be used.

The base station can transmit HARQ ACK/NACK through the licensed band where retransmission is performed.

Alternatively, the base station may omit HARQ ACK/NACK feedback if transmission is successful.

Alternatively, when the base station does not transmit HARQ ACK/NACK and allocates resources to the terminal through a licensed band in which retransmission is performed, it can indicate that it is a retransmission of previous data so that the terminal can know whether the data has been retransmitted. Information (i.e., information requesting retransmission of data) may be included in resource allocation, or parameters for HARQ retransmission may be set when allocating resources for HARQ retransmission.

Figure 11 is a flowchart showing a downlink HARQ retransmission process of Method 2 according to an embodiment.

Referring to FIG. 11, first, the base station transmits downlink data to the terminal along with a (toggled) New Data Indicator (NDI) through UCC (NDI is toggled) (S1201). At this time, the redundancy version (RV) is 0 (RV=0). Afterwards, the terminal receiving the downlink data transmits HARQ ACK/NACK to the base station through the LCC (S1202). Then, the base station informs the LCC cell of the ACK/NACK of the terminal (S1203) and determines whether the terminal transmitted NACK in the LCC cell (S1204).

If the terminal transmits ACK (i.e., not NACK), new data is transmitted again in the downlink through UCC (S1205). However, when the terminal transmits a NACK, buffering and sharing are performed between the downlink LCC and the downlink UCC (s1206), and the base station increases the repetition version (RV++), this time through the LCC. Data corresponding to NACK is retransmitted without NDI toggled (NDI is not toggled) (S1207). Afterwards, the terminal transmits HARQ ACK/NACK to the base station through the LCC (S1208), and the HARQ ACK/NACK of the terminal is known as an LCC cell (S1209). That is, according to one embodiment, HARQ ACK/NACK, which indicates whether data transmitted through an unlicensed band is successful, can be transmitted to the base station through a licensed band, and at this time, HARQ retransmission can also be performed through a licensed band.

Figure 12 is a conceptual diagram showing a downlink HARQ retransmission process in an unlicensed band in Method 3 according to an embodiment.

Referring to FIG. 12, the first data is transmitted through an unlicensed band, and then HARQ retransmission is performed through an available carrier at the time of HARQ retransmission (the carrier used for previous data transmission in the licensed band/unlicensed band or another unlicensed band carrier). (Figure 12 is shown based on an FDD system, but can be applied equally or similarly to a TDD system). In method 3, an additional CCA for retransmission (method 1) may be performed, retransmission using a licensed band (method 2) may be performed, and another CCA (third CCA) performed for data transmission. Data retransmission may be performed on the occupied channel.

For this purpose, in Method 3, the HARQ process needs to be distinguished, and the method defined in Method 2 can be applied. At this time, after receiving the data, feedback on the data is performed at given time and frequency resources, retransmission is performed when the feedback is NACK, and the terminal uses the same carrier as the previous carrier or a different carrier (licensed or third unlicensed). In order for data to be retransmitted, actions can be taken to receive licensed band control channels and data (data transmission in the case of uplink data transmission) and actions to receive unlicensed band control channels and data. If data retransmission is performed through the same carrier as the carrier used for previous data transmission, method 1 may be followed.

Figures 13A to 13C are conceptual diagrams showing an uplink HARQ retransmission process in an unlicensed band in Method 3 according to an embodiment.

The HARQ retransmission process in the unlicensed band according to Method 3 can be applied to the uplink as well as the downlink. In this case, the uplink data service also includes cases where data retransmission continues through the carrier used for previous data transmission, and the application of method 3 to the uplink HARQ process is similar to the downlink case, so detailed description is omitted. do.

Figure 13a shows a case where resources are allocated through cross-carrier scheduling, and Figures 13b and 13c show a case where resources are allocated through self-scheduling.

At this time, in Figure 13b, the terminal performs access to/occupies the channel by performing CCA for uplink data transmission, and in Figure 13c, the base station performs access/occupation of the channel through CCA for uplink data transmission of the terminal. do. In the case of self-scheduling of FIGS. 13B and 14C, when data transmission is performed through the first carrier used to indicate resource allocation information for data transmission, HARQ ACK/NACK (e.g., 3GPP (PHICH) may pass through the carrier used to indicate resource allocation information. However, in order for a base station to transmit HARQ ACK/NACK using an unlicensed band, it must perform CCA to access/occupy the channel. Generally, HARQ ACK/NACK feedback is performed at a certain time after data transmission (for example, after 4ms for FDD systems, 4~7ms for TDD systems). CCA is generally performed before it is necessary to occupy the channel and transmit data, but if the CCA result determines that the channel is already in use (busy or occupied), the base station can transmit HARQ ACK/NACK using the unlicensed band. I can't. As a result of CCA, one or a combination of two or more of the four methods below can be used to enable the base station to transmit HARQ ACK/NACK even when the channel in the unlicensed band is in use.

1. HARQ ACK/NACK is transmitted to the carrier selected among the licensed/unlicensed bands where retransmission takes place.

2. Regardless of the carrier on which retransmission occurs, HARQ ACK/NACK is transmitted on a licensed band carrier.

3. If data is successfully transmitted, HARQ ACK/NACK feedback is omitted (this method is also applicable to method 1)

4. Instead of transmitting HARQ ACK/NACK, if resources are allocated through a carrier on which data retransmission is performed, the fact that the resource is for retransmission of previous data may be included in the resource allocation, or when allocating resources for HARQ retransmission, HARQ The terminal can determine whether to retransmit HARQ using the parameters set for retransmission (this method is also applicable when method 1 is performed)

Figure 14 is a flowchart showing the downlink HARQ retransmission process of Method 2 according to an embodiment.

Referring to FIG. 14, first, the base station transmits downlink data (NDI is toggled) to the terminal through LCC or UCC (S1501). At this time, repeat version (redundancy version, RV) is 0 (RV = 0). Afterwards, the terminal that has received downlink data transmits HARQ ACK/NACK to the base station through the LCC (S1502). And the base station transmits to the LCC cell or UCC cell. The terminal's ACK/NACK is announced (S1503), and the LCC cell or UCC cell determines whether the terminal transmitted NACK (S1504).

If the terminal transmits ACK (i.e., not NACK), new data is transmitted again in the downlink through LCC or UCC (S1505). However, when the terminal transmits NACK, the base station increases the repetition version (RV++) and retransmits data corresponding to the NACK without NDI (NDI is not toggled) through LCC or UCC (S1506). Afterwards, the terminal transmits HARQ ACK/NACK to the base station through the LCC (S1507), and the HARQ ACK/NACK of the terminal is known as an LCC cell or UCC cell (S1508). That is, according to one embodiment, HARQ ACK/NACK, which indicates whether data transmitted through an unlicensed band is successful, can be transmitted to the base station through a licensed band, and at this time, HARQ retransmission can also be performed through a licensed band.

Another embodiment provides a data transmission and retransmission method according to carrier management when carrier management is required, such as changing/deleting/adding/activating/deactivating a carrier. In other words, in order for the mobile wireless access system to operate properly in carrier aggregation between unlicensed bands and licensed bands, carrier aggregation between unlicensed bands, or carrier aggregation between licensed bands, carrier aggregation, such as changing/deleting/adding/activating/deactivating carriers, etc. Because it requires management.

When carrier aggregation is performed for two or more bands, one carrier is operated as a primary carrier and the other carrier is operated as a secondary carrier. The auxiliary carrier may be changed according to the unlicensed band frequency regulations if the auxiliary carrier is in an unlicensed band, or in accordance with carrier operation regulations if the auxiliary carrier does not comply with the unlicensed band frequency regulations, or according to the user's policy or base station settings, etc. /Select/Delete/Add/Activate/Deactivate etc. can be performed. Due to the nature of carrier aggregation, data can be transmitted and retransmitted through a carrier that is currently capable of data transmission, and according to carrier management, data exchange can be performed with a carrier that is capable of data transmission at the time of data transmission. According to the carrier aggregation method of 3GPP LTE, data retransmission (HARQ) can be performed only on the carrier on which the initial data transmission was performed.

When a carrier is deactivated (deleted/cancelled), one of the following methods or a combination of two or more methods may be used.

First, there is a method to hold (postpone) carrier deactivation (delete/cancellation) until data transmission is successfully completed or until the maximum allowable time (number of times, time, etc.) of HARQ operation.

Or, based on the time of carrier deactivation command (request) (subframe n) to the time of deactivation (subframe n+k1), the time of deactivation request (subframe n) and the time of deactivation (subframe n+k1). Alternatively, there is a method that allows data transmission/retransmission only before/after a predetermined time (subframe n±k2) before and after the deactivation request point. If HARQ retransmission is required due to failure in transmission/retransmission of previous data after the above point,

Data transmission may be deemed to have failed and the data may be transmitted anew (retransmission not permitted), or data retransmission may be performed through a carrier that is newly available for service, or the deactivated carrier may be activated again within a certain period of time and data may be transmitted. If it can be used, data may be retransmitted through the carrier, and a downlink control channel, etc. may be operated according to resource allocation for retransmission.

According to another embodiment, when resource allocation is performed instead of HARQ ACK/NACK being omitted, transmission of a control channel including HARQ ACK/NACK information such as PHICH may be omitted. At this time, if the PHICH channel is omitted, retransmission can be distinguished through resource allocation, but PHICH-related information (PHICH duration, etc.) including an indication of the length of the PDCCH (length in OFDM symbol units) needs to be defined. That is, according to the 3GPP LTE standard, the terminal can determine the area of the PDCCH (length of OFDM symbol unit) based on the PHICH duration set by the base station, but accurate operation may be required. The terminal can determine the area of the PDCCH (eg, control format indicator (CFI)) through one or a combination of two or more of the methods below.

1. When the PHICH duration is set to an extended PHICH duration, a method of including information about the area of the PDCCH in the extended PHICH duration. At this time, the information about the area of the PDCCH may be as long as the PHICH duration extended from the first OFDM symbol in the subframe or TTI.

2. A method of including information about the area of the PDCCH in the physical control format indicator channel (PCFICH) instead of the extended PHICH duration. At this time, the information about the area of the PDCCH is the length expressed as PCFICH from the first OFDM symbol in the subframe or TTI (e.g., CFI if N _RB ^DL >10 or CFI+1 if N _RB ^DL ≤10), Alternatively, it may be the length expressed as PCFICH from the time the PCFICH is transmitted (e.g., CFI if N _RB ^DL >10 or CFI+1 if N _RB ^DL ≤10).

3. A method of determining OFDM symbols up to the start of a physical downlink shared channel (PDSCH) or EPDCCH in one subframe or one TTI as a PDCCH area.

4. Third method (e.g., RRC signaling, a method of including information about the area of the PDCCH in an initial signal or reservation signal that may be included when occupying/using a channel after CCA, etc.) A method of setting or expressing information about the area of the PDCCH with a predefined value.

5. A method of indicating information about the PDCCH area in the licensed band or having a PDCCH area of the same length as the licensed band.

In another embodiment, a method of operating a channel for data transmission when a cellular system is operated in an unlicensed band is described.

According to the unlicensed band frequency operation regulations for operating a cellular system in an unlicensed band, each device in the cellular system determines whether the channel can be occupied according to the CCA result (i.e., if the channel is idle) and occupies the channel. If possible, data can be transmitted by occupying the channel. Interference during data transmission can be reduced by channel occupancy and use according to the CCA results. However, an interference measurement method is needed to solve the hidden node problem in the unlicensed band. This is because it is difficult to accurately measure interference in the case of interference by a terminal or a significant amount of time is required to measure the channel. Additionally, in order to provide optimal service to the terminal, channel measurement is necessary when selecting an appropriate channel with good quality among several channels.

In another embodiment, the channel can be measured using the method below. In another embodiment, a zero power (ZP) channel state information-reference signal (CSI-RS) and a non-zero power (NZP) CSI-RS are used as data (e.g. For example, a base station that transmits simultaneously with a PDSCH transmission is called an on-state UCC cell, and a base station that transmits only ZP CSI-RS or NZP CSI-RS is called an off-state UCC cell. That is, regardless of the CCA result (on/off state), the UCC cell can transmit at least one of ZP CSI-RS and NZP CSI-RS.

First, the terminal uses the zero power (ZP) channel state information-reference signal (CSI-RS) of the on-state UCC cell and the non-zero power (non-zero power) of the off-state UCC cell. , NZP) The channel can be measured through CSI-RS (on state UCC + off state UCC).

Figure 15 is a conceptual diagram showing channel measurement method 1 according to another embodiment.

On state UCC cells (i.e., providing data services by performing channel access/occupation through CCA) can perform data transmission within the unlicensed band, but off state UCC cells that cannot occupy the channel as a result of CCA can Data cannot be transmitted. However, referring to FIG. 15, the terminal can measure the channel of the off-state UCC while receiving data through the on-state UCC. For this purpose, the on-state UCC cell (or carrier) does not transmit data in the area where CSI-RS is transmitted (i.e., ZP CSI-RS), and the off-state UCC cell transmits NZP CSI in the ZP CSI-RS area of the on-state UCC cell. -Send RS. Therefore, the terminal can perform channel measurement for the off-state UCC. And ZP CSI-RS and NZP CSI-RS are the same as subframe 0 including the primary synchronization signal (PSS)/secondary synchronization signal (SSS), the OFDM symbol on which PSS/SSS is transmitted It is set to an OFDM symbol other than this.

If there are two or more off-state UCC cells, each off-state UCC cell can transmit NZP CSI-RS simultaneously, or only a predetermined off-state UCC can transmit NZP CSI-RS at a predetermined moment. For example, it may be preset to transmit CSI-RS in one off-state UCC cell predetermined for each subframe. When two or more off-state UCC cells transmit NZP CSI-RS simultaneously, the UE can use the NZP CSI-RS for interference control by measuring the interference between NZP CSI-RSs. When only one off state UCC cell transmits NZP CSI-RS at a time, the terminal uses NZP CSI-RS for carrier selection (carrier selection among a plurality of carriers that is serviceable or can provide optimal service). It can be used to detect priority devices (e.g. priority users or radar) in unlicensed bands. When there is only one off-state UCC cell, the terminal can measure both interference and channel quality through NZP CSI-RS, and can also be used for interference control or carrier selection. Alternatively, the terminal can use the ZP CSI-RS of the on-state UCC cell to measure the channel of another cell in the area corresponding to the ZP CSI-RS (or CSI-IM).

Figure 16 is a conceptual diagram showing channel measurement method 2 according to another embodiment.

Referring to FIG. 16, on-state UCC cells (cells that provide data services by accessing/occupying channels through CCA) perform data transmission within the unlicensed band, but only on-state UCC cells perform CSI- ZP CSI-RS is transmitted in the transmission area of RS. The terminal can measure the degree of channel interference based on data transmitted from unlicensed band devices such as neighboring UCC cells or WiFi in the CSI-RS transmission area. Additionally, the terminal may detect devices that should be prioritized (e.g., priority user, radar) in the unlicensed band.

Alternatively, the terminal can perform channel measurement using DRS (or DS) defined in Rel-12 small cell.

Figure 17 is a conceptual diagram showing channel measurement method 3 according to another embodiment.

In Figure 17, the small cell that occupies the CCA result channel transmits DRS, and the small cell that does not occupy the CCA result channel fails to transmit DRS. Referring to FIG. 17, among UCC cells, a cell transmitting DRS (i.e., UCC1) transmits a DRS signal and transmits ZP CSI-RS in the CSI-RS transmission area. And, a cell that does not transmit DRS (i.e., UCC2) transmits NZP CSI-RS in the CSI-RS transmission area of UCC1. And even when the UCC cell is in the on state, DRS can be transmitted to support the channel measurement method. The terminal receiving the DRS transmitted from the base station, instead of measuring the channel of UCC1 in the CSI-RS transmission area, interferes with interference from other cells (e.g., UCC2) (e.g., UCC cells that do not cooperate with UCC1 or WiFi signals, etc.) can be measured. Alternatively, by transmitting a signal by which each cell can be distinguished for each cooperating cell, the terminal can select a carrier or detect a device that should be prioritized in the unlicensed band. For example, a specific UCC cell may transmit a signal only in a specific subframe, or the signal may be designed so that each cell can be distinguished even if the signal is transmitted in the same section. Meanwhile, in the case of a subframe in which PSS/SSS is included in DRS when transmitting DRS, the CSI-RS transmission area can be set to be located by avoiding the OFDM symbol in which PSS/SSS is transmitted.

Another embodiment describes a method of configuring resources for channel measurement/reporting.

In 3GPP LTE, channel state measurement is controlled by the base station. Channel status measurement involves measuring/reporting the entire system band (wideband). Includes measurement/reporting for some of the system bands (subbands). Additionally, depending on the reporting cycle, it can be divided into periodic report/aperidic report. Resources for channel state measurement include CSI-RS and Channel State Information-interference Measurement (CSI-IM).

Cellular systems (License Assisted Access, LAA) in unlicensed bands can access, occupy, and use channels through competition with other cellular systems operating in Wi-Fi or other unlicensed bands. Because the channel must be used through competition, while the serving base station is transmitting data, Wi-Fi or another LAA cannot transmit data, or the serving base station cannot transmit data and Wi-Fi or another LAA transmits data. . Therefore, an efficient interference measurement method for unlicensed bands is needed.

Channel status measurement is performed in the service band with the base station, and because data can be continuously transmitted due to the nature of the licensed band, the terminal can perform channel status measurement through CSI-RS/CSI-IM in a preset section. . However, since channel access/use is performed through competition in the unlicensed band, transmission of CSI-RS/CSI-IM cannot be guaranteed, and while the base station is transmitting data to the terminal, other devices (Wi-Fi or other LAA) interference may be measured inaccurately. According to another embodiment, channel state measurement in the unlicensed band may be performed through one or a combination of two or more of the methods below.

1. Measurement of channel status through cell specific RS (CRS)

This is a method that can be generally used even in unlicensed bands, when CSI-RS is not set, in the case of TM (transmission mode) 1 to TM8 supported by 3GPP LTE, and in the case of precoding matrix indicator-rank indicator-report (precoding matrix indicator) It can be used in the case of TM9 where -rank indicator-report, PMI-RI-Report) is not set.

2. (NZP) Channel status measurement through CSI-RS

It can be used in the case of TM9, TM10, etc., where CSI-RS resource configuration is set and PMI-RI-Report is set.

3. Channel status measurement through ZP CSI-RS

The terminal measures interference in the area where ZP CSI-RS is configured (e.g., ZP CSI-RS resource configuration, configured through csi-SubframePatternConfig).

4. Channel status measurement through CSI-IM

This is an area for measuring interference supported by 3GPP LTE TM10, etc., and can be set through CSI-IM resource configuration, and the terminal measures interference in the set area.

5. Measure channel status through interfering resources (e.g. resources for RSSI measurement, etc.)

The terminal can define resources for measuring interference (RSSI) to other devices in the unlicensed band and perform channel state measurement by setting/using resources for RSSI measurement.

In one embodiment, CSI-RS may be set as follows.

CSI-RS is set by CSI-RS resource configuration and may include information defined in 7.2.5 of TS36.213. Meanwhile, according to unlicensed band frequency regulations, in order for a cellular system to operate in an unlicensed band, CCA must be performed for channel access/occupancy/use, and the occupied channel must not exceed the maximum channel occupancy time (COT). Additionally, because channel occupancy/use is difficult to guarantee the LTE subframe boundary, there may be a transmission time interval (TTI) that is less than 1 ms or greater than 1 ms. Additionally, continuity of channel occupancy/use is not guaranteed. Therefore, the following contents may be included in the CSI-RS resource configuration for cellular operation in the unlicensed band. The information below can be applied equally/similarly to how to set up CSI-IM.

- Adjustment of CSI-RS configuration is as follows.

For each FDD/TDD frame type, configurations range from 0 to 19 for FDD and 0 to 31 for TDD. However, in the unlicensed band, a new frame type can be defined regardless of FDD/TDD, so the CSI-RS configuration can be set in the four ways below.

CSI-RS configuration setting method 1: Assume the same frame type as the PCell frame type and set the CSI-RS configuration.

CSI-RS configuration setting method 2: The frame type of the unlicensed band is set, and the CSI-RS configuration is set according to the set frame type.

Method 3 for setting up the CSI-RS configuration: Setting up the CSI-RS configuration without setting the unlicensed band frame type.

CSI-RS configuration setting method 4: Set the CSI-RS configuration by adding a new CSI-RS configuration, as shown in Table 1 below.

CSI-RS
composition Number of CSI-RS configurations
(Number of CSI-RS configured) 1 or 2 4 8 (k',l') _ns mod 2 (k',l') _ns mod 2 (k',l') _ns mod 2 k (9,2) 0 (9,2) 0 (9,2) 0 k+1 (8,2) 0 (8,2) 0 k+2 (3,2) 0 k+3 (2,2) 0

- Adjustment of CSI-RS subframe configuration (I _{CSI - RS} ) is as follows.

If Equation 4 is satisfied according to I _{CSI - RS} , CSI-RS is included in the corresponding subframe.

In Equation 4, n _f is the system frame number, n _s is the slot number within a radio frame, and Δ _{CSI - RS} is the CSI-RS subframe offset. (subframe unit), and T _{CSI - RS} is the CSI-RS period (subframe unit, i.e., 5, 10, 20, 40, or 80ms).

In order for the terminal to measure the channel state through CSI-RS, CSI-RS must be transmitted while the channel is occupied/used. However, if the maximum channel occupancy time (COT) is less than the minimum transmission period of CSI-RS (i.e., 5 ms), a subframe containing the CSI-RS may not exist within the channel occupancy time. In one embodiment, the settings of the CSI-RS are adjusted to ensure that a subframe containing the CSI-RS exists within the channel occupancy time. In one embodiment, CSI-RS is set according to the conditions below, and CSI-RS can be set by combining two or more conditions.

Condition 1: T' _{CSI - RS} ≤ min(T _{CSI - RS} , max COT)

Condition 2: T' _{CSI - RS} = max COT

Condition 3: Include CSI-RS in every kth subframe within COT (k=1,2,...,maxCOT).

Condition 3-1: Set the COT length (number of subframes) within the COT in the form of a bitmap and include the CSI-RS in the subframe for which the bitmap is set, or configure the bitmap to the number of slots within the COT. Set for.

Condition 4: Reuse the existing I _{CSI - RS} /T _{CSI - RS} , and include CSI-RS only when the time of inclusion of CSI-RS and the time of channel occupancy/use overlap.

Condition 5: Whether or not to transmit CSI-RS is indicated in every subframe, or the inclusion of CSI-RS is indicated only in subframes that include CSI-RS, and CSI-RS resource configuration (particularly, CSI-RS configuration) is specified. Set it so that the terminal recognizes Resource Element (RE) information that includes CSI-RS in the subframe.

- The limits of the subframe in which CSI-RS is transmitted are as follows.

Due to the characteristics of CCA, data transmission may not occur in accordance with the start/end time of the subframe. In particular, the first and last TTI within the COT may start/end in the middle of the subframe. At this time, settings for CSI-RS may be required in the data transmission section within the COT. In one embodiment, it is possible to set (include, exclude, etc.) whether CSI-RS is included (included or not included) in the data transmission section within the COT using the method below.

CSI-RS transmission method 1: Restrict CSI-RS from being transmitted in the first/last TTI within the COT.

CSI-RS transmission method 2: The first/last TTI is a partial subframe (in this case, the first TTI may be a partial starting subframe and the last TTI may be a partial ending subframe) In this case, transmission of CSI-RS is restricted. That is, even if an OFDM symbol that can include CSI-RS is included according to the CSI-RS configuration, the partial subframe is limited to not include CSI-RS, and the terminal does not perform an operation for channel measurement.

CSI-RS transmission method 3: Even if the first/last TTI is a partial start subframe or a partial end subframe, CSI-RS is transmitted if an OFDM symbol on which CSI-RS can be transmitted is included.

CSI-RS transmission method 4: If the first/last TTI is a partial start subframe or a partial end subframe, if it is less than a certain length (i.e., the number of OFDM symbols included in the TTI), CSI-RS is transmitted according to CSI-RS settings. Even if set to include, transmission of CSI-RS is restricted. However, if the length is longer than a certain length and CSI-RS is set to be included, CSI-RS is transmitted (included).

If CSI-RS is set to be included in an OFDM symbol that overlaps CRS, it can be restricted as follows.

Method 1: Limit to not include CRS and set to include CSI-RS.

Method 2: Restrict to not include CSI-RS (do not set), and set to include (transmit) CRS.

OFDM symbols that overlap with PSS/SSS can be restricted as follows.

Method 1: Limit to not include PSS/SSS and set to include CSI-RS.

Method 2: Restrict to not include CSI-RS (do not set), and set to include (transmit) PSS/SSS.

Method 3: When the OFDM symbol including PSS/SSS is set to include CSI-RS, set to include CSI-RS only in the remaining resources (subcarriers) excluding resources for PSS/SSS transmission.

In one embodiment, ZP CSI-RS may be set as follows.

In order to operate LAA in the unlicensed band according to the unlicensed band frequency regulations, CCA for access/occupancy/use of the channel is performed, and channel occupancy through CCA must not exceed the maximum channel occupancy time (COT). At this time, because it is difficult to occupy/use the channel depending on the LTE subframe boundary, a TTI that is less than 1ms or greater than the existing 1ms may exist. Additionally, continuity of channel occupancy/use cannot be guaranteed. Therefore, for cellular operation in the unlicensed band, zeroTxPowerResourceConfigList can be included in the ZP CSI-RS resource configuration.

zeroTxPowerCSI-RSConfigList consists of a 16-bit bitmap and is generally applied when there are 4 antenna ports. However, like NZP CSI-RS settings, it is set as follows to provide various types of ZP CSI-RS. It can be.

Method 1: Assuming that the frame in the unlicensed band is the same frame type as that of the PCell, how to set zeroTxPowerResourceConfigList.

In this case, i) the existing zeroTxPowerResourceConfigList may be reused, or ii) the number of antenna ports (# of antenna port) may be included in the zeroTxPowerResourceConfigList.

Method 2: How to set the frame type of the unlicensed band and set zeroTxPowerResourceConfigList accordingly.

In this case, i) the existing zeroTxPowerResourceConfigList may be reused as is, or ii) the number of antenna ports may be included in the zeroTxPowerResourceConfigList.

Method 3: How to set zeroTxPowerResourceConfigList without setting the frame type of the unlicensed band.

In this case, i) the existing zeroTxPowerResourceConfigList may be reused as is, or ii) the number of antenna ports may be included in the zeroTxPowerResourceConfigList.

Method 4: How to enable ZP CSI-RS settings by adding a new zeroTxPowerResourceConfigList as shown in Table 2 below.

CSI reference
signal
configuration Number of CSI reference signals configured 1 or 2 4 8 (k',l') _ns mod 2 (k',l') _ns mod 2 (k',l') _ns mod 2 k (9,2) 0 (9,2) 0 (9,2) 0 k+1 (8,2) 0 (8,2) 0 k+2 (3,2) 0 k+3 (2,2) 0

zeroTxPowerSubframeConfig(I _{CSI - RS} ) is as follows.

If Equation 5 is satisfied according to I _{CSI - RS} , ZP CSI-RS may be included in the corresponding subframe.

In Equation 5, n _f is the system frame number, n _s is the slot number within a radio frame, and Δ _{CSI - RS} is the CSI-RS subframe offset. (subframe unit), and T _{CSI - RS} is the CSI-RS period (subframe unit, i.e., 5, 10, 20, 40, or 80ms).

Meanwhile, in order for the terminal to measure the channel state through CSI-RS, CSI-RS must be transmitted while the channel is occupied/used. However, if the maximum channel occupancy time (COT) is less than the minimum transmission period of the ZP CSI-RS (i.e., 5 ms), there may not be a subframe containing the ZP CSI-RS within the channel occupancy time. In one embodiment, the settings of the ZP CSI-RS are adjusted to ensure that a subframe containing the ZP CSI-RS exists within the channel occupancy time. In one embodiment, ZP CSI-RS is set according to the conditions below, and ZP CSI-RS can be set by combining two or more methods.

Method 1: T' _{CSI - RS} ≤ min(T _{CSI - RS} , max COT)

Method 2: T' _{CSI - RS} = max COT

Figure 18 is a conceptual diagram showing a CSI-RS setting method according to an embodiment.

Referring to FIG. 18, in the case of Method 1 and Method 2, by adjusting T _{CSI - RS} to a value less than or equal to COT, the UE can measure CSI-RS transmitted in COT and report the measurement result.

Figure 19 is a conceptual diagram showing a CSI-RS setting method according to another embodiment.

Method 3: Method of transmitting CSI-RS in every kth subframe (k=1,2, ..., maxCOT) in COT. In this case, the terminal can measure CSI-RS and report the measurement results.

Method 3-1: A method of setting the COT length (number of subframes) in bitmap form and transmitting CSI-RS in the subframe indicated as a bitmap.

Method 4: Instructing the terminal whether to transmit CSI-RS in every subframe, or instructing the terminal whether to transmit CSI-RS only in subframes containing CSI-RS. In this case, the UE can recognize Resource Element (RE) information including CSI-RS within a subframe through CSI-RS resource configuration (particularly CSI-RS configuration).

Meanwhile, the bitmap may indicate the number of slots in the COT. Referring to FIG. 19, it may indicate that CSI-RS is transmitted in the 3rd subframe, such as 0010.

Figure 20 is a conceptual diagram showing a CSI-RS setting method according to another embodiment.

Method 4: How to reuse existing I _{CSI - RS} and T _{CSI - RS} . That is, referring to FIG. 20, the UE assumes that COT and T _{CSI - RS} partially overlap, measures the channel only through CSI-RS transmitted during COT, and reports the measurement result.

Method 5: How to reuse the existing I _{CSI - RS} /T _{CSI - RS} . In this case, the terminal performs channel measurement assuming that the ZP CSI-RS is included at the time the ZP CSI-RS is located, regardless of channel occupancy/use.

Method 6: How to reuse the existing I _{CSI - RS} /T _{CSI - RS} . In this case, if the UE does not occupy/use the channel at the time the ZP CSI-RS is located, channel measurement is performed.

Method 7: How ZP CSI-RS configuration is performed as RRC, etc. (e.g., one or a combination of two or more of sequence, DCI in PDCCH, PCFICH, PHICH). In this case, the UE may be instructed whether or not a ZP CSI-RS is included in each subframe.

Method 8: How to include ZP CSI-RS configuration over DCI without setting it up with ZP CSI-RS.

Meanwhile, CSI-RS transmission subframes may be limited. Due to the nature of CCA, data may not be transmitted in accordance with the subframe start/end time. In particular, if the first TTI and last TTI within the COT start/end in the middle of a subframe, configuration for ZP CSI-RS may be required in the data transmission section within the COT. In one embodiment, it is possible to set whether the ZP CSI-RS is included (included or not included) in the data transmission section within the COT using the method below. At this time, one of the methods below may be selectively applied, or two or more methods may be combined.

Method 1: Restrict ZP CSI-RS from being transmitted (included) in the first/last TTI.

Method 2: If the first/last TTI is a partial subframe, limit (i.e. do not include) transmission of ZP CSI-RS. That is, the ZP CSI-RS is restricted from being included in OFDM symbols that may include the ZP CSI-RS according to the CSI-RS configuration, and the UE does not perform operations for channel measurement.

Method 3: Even if the first/last TTI is a partial subframe, if it contains an OFDM symbol that can include CSI-RS according to the CSI-RS setting, ZP CSI-RS is included.

Meanwhile, when CSI-RS is set to include in an OFDM symbol that overlaps CRS, it may be limited as follows.

Method 1: Restrict the OFDM symbol that overlaps the CRS from including the CRS and include (transmit) the CSI-RS.

Method 2: Restrict the ZP CSI-RS from being included in OFDM symbols overlapping with the CRS and include (transmit) the CRS.

Additionally, if CSI-RS is set to be included in an OFDM symbol that overlaps PSS/SSS, it may be limited as follows.

Method 1: Limit OFDM symbols overlapping with PSS/SSS to not include PSS/SSS and include (transmit) CSI-RS.

Method 2: Limit CSI-RS to not be included in OFDM symbols overlapping with PSS/SSS and include (transmit) PSS/SSS.

Method 3: If CSI-RS is set to be included in an OFDM symbol including PSS/SSS, CSI-RS is limited to being included only in the remaining resources (subcarriers) excluding resources for PSS/SSS transmission.

Next, the channel measurement method through RSSI will be described in detail. In one embodiment, RSSI can be used in a method of measuring the channel state of a serving base station using CRS. In particular, RSSI can be used to measure interference, and can be set/measured through the method below. At this time, one of the methods below may be selectively applied, or two or more methods may be combined.

Method 1: How to measure RSSI using NZP CSI-RS. The terminal measures the channel status in the transmission area configured to include NZP CSI-RS.

Method 2: How to measure RSSI using ZP CSI-RS (or CSI-IM). The terminal measures the channel status in the transmission area configured to include ZP CSI-RS.

Method 3: Method of measuring channel status in an area/section that does not occupy the channel (non-COT).

Method 4: A method of measuring the channel state in OFDM symbols that do not contain a CRS within the COT that occupies the channel.

Method 5: A method of measuring the channel state in OFDM symbols that do not include CSI-RS/CRS within the COT occupying the channel.

Meanwhile, the terminal can measure interference by performing RSSI measurement on all subcarriers of the system band instead of measuring RSSI using CSI-RS/CRS. In this case, one of the methods below may be selectively applied, or two or more methods may be combined.

- When measuring the channel status within COT or in an unoccupied area (non-COT), if the section (time) set for RSSI measurement overlaps with the section where the channel is occupied due to non-continuous channel occupancy, , the terminal may be configured not to perform channel measurement. That is, the terminal can be set to perform channel measurement only in a section where the set section and the occupied channel do not overlap. The terminal can measure the channel state from the corresponding subframe to a specific period (subframe, slot, or OFDM symbol) according to Equation 6 below.

In Equation 6, n _f is the system frame number, n _s is the slot number within a radio frame, Δ _RSSI is the subframe offset (subframe unit), and T _RSSI is the period of RSSI (subframe unit).

- The terminal may be set to measure the channel state during a specific period (subframe, slot, or OFDM symbol) indicated (or preset) in the kth subframe (or slot) before/after COT.

- The terminal can be set to measure RSSI in the corresponding subframe if the base station does not occupy the CCA result channel based on information about the section in which CCA is performed, received from the base station.

- If the channel is already occupied/used by the base station in the section where RSSI must be measured, the base station terminates (ends use of) the occupied channel a predetermined time (≥0) before the measurement section of the terminal, and the terminal The RSSI of the channel whose occupation has been released can be measured. Alternatively, if the terminal recognizes that the channel is occupied/used by the base station (recognition based on the base station's instructions or the terminal's data reception), the terminal measures RSSI until it recognizes the channel termination (end of use) by the serving base station. You can postpone or postpone the measurement until the next RSSI measurement period, and then measure RSSI again when RSSI measurement is possible. Alternatively, if the serving base station is occupying/using the channel during the RSSI measurement period, the base station can set the terminal to not measure the RSSI of the channel.

- If the base station does not occupy the channel when data transmission is expected after a certain period from DRS transmission or uplink resource allocation, the terminal can be configured to measure RSSI.

FIG. 21 is a conceptual diagram showing a method for measuring the channel state of a terminal according to one embodiment, and FIG. 22 is a conceptual diagram showing a method for measuring the channel state of a terminal according to another embodiment. Referring to FIG. 21, if DRS is not transmitted because the base station cannot occupy the channel, the terminal can measure RSSI in the section in which DRS is not transmitted. Referring to FIG. 22, the terminal may not receive data transmitted from the base station due to channel occupation failure, or if the terminal fails to transmit uplink data to be transmitted to the base station due to channel occupation failure (e.g., n+k point in time), RSSI can be measured. At this time, the base station can inform the terminal of the fact that it is attempting to occupy a channel or that it has failed to occupy the channel through the licensed band. In the case of uplink data transmission, the terminal already knows the time point (n+k) at which data transmission is expected from the time point (n) at which uplink resources are allocated, so RSSI can be measured if the channel is not occupied at time n+k.

Next, the channel measurement and reporting method within COT is explained in detail. As described above, when only partial subframes (some OFDM symbols of the entire TTI) are used due to channel occupancy time restrictions, the terminal can measure the channel status through the method below. At this time, one of the methods below may be selectively applied, or two or more methods may be combined.

Method 1: A method in which the terminal performs measurement only when the COT is used as a downlink frame.

Method 2: A method in which the terminal performs measurement only when the partial subframe is longer than or equal to a predetermined length. In this case, if the partial subframe is less than a predetermined length, it may be assumed (limited) that CSI-RS, PSS/SSS, etc. for channel measurement are not included.

Method 3: A method in which the UE performs measurement only when the partial subframe includes RS for channel measurement, such as CRS and CSI-RS.

And, at this time, the terminal can report the measured channel status to the base station through the method below. At this time, one of the methods below may be selectively applied, or two or more methods may be combined.

Method 1: Reporting method using the uplink control channel (e.g., PUCCH) of the licensed band.

Method 2: Reporting method using an uplink control channel (e.g., PUCCH) in an unlicensed band.

Method 3: A method of reporting by including it in the data when transmitting uplink data in the licensed band (e.g., PUSCH).

Method 4: A method of reporting by including it in the data when transmitting uplink data in an unlicensed band (e.g., PUSCH).

And, the reporting time of the measured channel state can be set in the following method. At this time, one of the methods below may be selectively applied, or two or more methods may be combined.

Method 1: Periodic reporting

In this case, reporting of the measured channel state may be performed through an uplink control channel (e.g., PUCCH), and reporting may be performed at time n+k (the first uplink subframe with k≥4). . Figure 23 is a conceptual diagram showing a channel status reporting method according to an embodiment. Referring to FIG. 23, since the channel state can be measured when the channel is occupied, the measurement result can be reported in the n+kth subframe based on the channel's occupancy point (n), taking into account discontinuous channel occupancy. there is. Measurement results of the channel state may be reported over a certain period of time or a certain number of times. In addition, measurement results of the same content or measurement results after a predetermined time excluding measurement results before a predetermined time based on the time of measurement reporting may be reported.

Method 2: Aperiodic reporting

In this case, reporting of measurement results may be performed through an uplink control channel (e.g., PUCCH) at the base station's request (e.g., through PUSCH) or by predetermined settings. Reporting may be performed at the n+kth uplink subframe based on the time (n) at which the base station's request is received. In addition, based on the measurement reporting time, measurement results previous to a predetermined time can be set not to be included in the n+k subframe time, and if necessary, the measurement results can be recalculated and then reported. The base station allocates upstream resources for reporting (at time n), but the channel is not occupied between n and n+k subframes, or the channel is occupied but resources for channel measurement (e.g., CSI-RS/CSI -IM, etc.) are not transmitted during the corresponding section, or if the terminal fails to load measurement results in the uplink subframe at the time of n+k subframe (i.e., transmitting only general data), the terminal may be notified to the base station, or data may not be transmitted. At this time, the fact that the terminal reports to the base station may include previously measured channel status (relatively old channel measurement value for the occupied channel). When the terminal transmits an uplink subframe at n+k subframe time, if data to report the measurement result of the channel state is additionally allocated, the terminal transmits only general data or adds the above information (e.g. For example, it cannot be measured) can be included. This fact may include previously measured channel conditions (relatively older measurements of occupied channels). Since the channel is occupied discontinuously, and the channel state can be measured only when the channel is occupied, n+k subframes (e.g., the first uplink subframe with k≥4) subframes based on the occupation point (n) Measurement results can be reported through frames.

Method 1 and Method 2 for reporting measurement results of channel status are combined, or when combined with reporting results of measurements on other channels (e.g., main carrier channel measurement reports, other subcarrier channel measurement reports), other channel measurements are performed. Priority is given and measurement results for that channel may be omitted from reporting. In particular, if a channel measurement is not performed and a measurement report for another channel must be made simultaneously, the measurement result for that channel may be omitted by giving priority to measurement of the other channel.

Figure 24 is a block diagram showing a wireless communication system according to one embodiment.

Referring to FIG. 24, a wireless communication system according to an embodiment includes a base station 2410 and a terminal 2420.

The base station 2410 includes a processor 2411, a memory 2412, and a radio frequency unit (RF unit) 2413. The memory 2412 is connected to the processor 2411 and may store various information for driving the processor 2411 or at least one program executed by the processor 2411. The wireless communication unit 2413 is connected to the processor 2411 and can transmit and receive wireless signals. The processor 2411 may implement functions, processes, or methods proposed in embodiments of the present disclosure. At this time, in the wireless communication system according to an embodiment of the present disclosure, the wireless interface protocol layer may be implemented by the processor 2411. The operation of the base station 2410 according to one embodiment may be implemented by the processor 2411.

The terminal 2420 includes a processor 2421, a memory 2422, and a wireless communication unit 2423. The memory 2422 is connected to the processor 2421 and can store various information for driving the processor 2421 or at least one program executed by the processor 2421. The wireless communication unit 2423 is connected to the processor 2421 and can transmit and receive wireless signals. The processor 2421 may implement functions, steps, or methods proposed in embodiments of the present disclosure. At this time, in the wireless communication system according to an embodiment of the present disclosure, the wireless interface protocol layer may be implemented by the processor 2421. The operation of the terminal 2420 according to one embodiment may be implemented by the processor 2421.

In embodiments of the present disclosure, the memory may be located inside or outside the processor, and the memory may be connected to the processor through various known means. Memory is various forms of volatile or non-volatile storage media, for example, memory may include read-only memory (ROM) or random access memory (RAM).

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also possible. It falls within the scope of rights.

Claims (20)

A terminal that measures a channel in an unlicensed band of a wireless communication system,
comprising a processor, a memory, and a wireless communication unit, wherein the processor executes a program stored in the memory,
Receiving configuration information for a channel state information-reference signal (CSI-RS), and
Receiving the CSI-RS based on the configuration information
Including,
The configuration information indicates a CSI-RS subframe in which the CSI-RS is transmitted,
The terminal assumes that the CSI-RS is not transmitted within the partial start subframe or the partial end subframe even if the partial start subframe and the partial end subframe belong to the CSI-RS subframe. In paragraph 1:
The processor executes the program,
Measuring the state of the channel based on the CSI-RS
A terminal that performs. In paragraph 2,
When performing the step of measuring the state of the channel based on the CSI-RS, the processor:
Measuring interference from other systems when the resource for the CSI-RS is a zero-power (ZP) CSI-RS resource
A terminal that performs. In paragraph 2,
The resource for the CSI-RS is a non-zero-power (NZP) CSI-RS resource. In paragraph 2,
When performing the step of measuring the state of the channel based on the CSI-RS, the processor:
Measuring interference for the channel when the resource for the CSI-RS is a channel state information-interference measurement (CSI-IM) resource.
A terminal that performs. A terminal that measures a channel in an unlicensed band of a wireless communication system,
comprising a processor, a memory, and a wireless communication unit, wherein the processor executes a program stored in the memory,
Receiving configuration information for a channel state information-reference signal (CSI-RS), and
Receiving the CSI-RS based on the configuration information
Including,
The configuration information indicates a CSI-RS subframe in which the CSI-RS is transmitted,
The terminal assumes that the CSI-RS is not transmitted within the synchronization subframe even if the synchronization subframe belongs to the CSI-RS subframe. In paragraph 6:
The processor executes the program,
Measuring the state of the channel based on the CSI-RS
Terminal to perform further. In paragraph 7:
When performing the step of measuring the state of the channel based on the CSI-RS, the processor:
Measuring interference from other systems when the resource for the CSI-RS is a zero-power (ZP) CSI-RS resource
A terminal that performs. In paragraph 7:
The resource for the CSI-RS is a non-zero-power (NZP) CSI-RS resource. In paragraph 7:
When performing the step of measuring the state of the channel based on the CSI-RS, the processor:
Measuring interference for the channel when the resource for the CSI-RS is a channel state information-interference measurement (CSI-IM) resource.
A terminal that performs. A method of measuring a channel in an unlicensed band of a wireless communication system, comprising:
A terminal receiving configuration information for a channel state information-reference signal (CSI-RS), and
The terminal receiving the CSI-RS based on the configuration information
Including,
The configuration information indicates a CSI-RS subframe in which the CSI-RS is transmitted,
The UE assumes that the CSI-RS is not transmitted within the synchronization subframe even if the synchronization subframe belongs to the CSI-RS subframe. delete delete delete delete delete delete delete delete delete

Images