CN107667565B

CN107667565B - Method for allocating resources in a cellular network using unlicensed frequency bands and apparatus therefor

Info

Publication number: CN107667565B
Application number: CN201680032285.4A
Authority: CN
Inventors: 朴承勋; 文廷民; 柳善姬; 郑柄薰; 郑丁寿
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2015-04-09
Filing date: 2016-04-05
Publication date: 2022-01-28
Anticipated expiration: 2036-04-05
Also published as: WO2016163709A1; CN107667565A

Abstract

A 5G or quasi-5G communication system is disclosed which is provided to support a higher data transmission rate than that of a 4G communication system such as LTE. A method and apparatus for transmitting information in a communication system is disclosed. A method for allocating resources in a cellular network using unlicensed frequency bands, comprising the steps of: generating at least one resource allocation signal containing information indicating a plurality of consecutive uplink subframes capable of communicating over the unlicensed frequency band; transmitting a resource allocation signal to a User Equipment (UE) through an unlicensed frequency band for a duration of at least one downlink subframe; and receiving uplink data from the UE for the duration of the consecutive uplink subframes.

Description

Method for allocating resources in a cellular network using unlicensed frequency bands and apparatus therefor

Technical Field

The present disclosure relates to a method and apparatus for allocating resources for an unlicensed band (unlicensed band) in a system that shares resources for device-to-device communication.

Background

In order to meet the increasing demand for wireless data services since the commercialization of 4 th generation (4G) communication systems, efforts have been made to develop improved 5 th generation (5G) communication systems or quasi-5G (pre-5G) communication systems. Therefore, the 5G communication system or the quasi-5G communication system is also referred to as a super 4G network communication system or a Long Term Evolution (LTE) system.

In order to achieve high data rates, it is being considered to implement a 5G communication system in an ultra high frequency (mm wave) band (e.g., 60GHz band). In the 5G communication system, beamforming, massive Multiple Input Multiple Output (MIMO), full-dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and massive antenna techniques have been discussed to mitigate propagation path loss and increase propagation distance in the ultra-high frequency band.

For system network improvements, in 5G communication systems, techniques such as evolved small cells, advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, coordinated multipoint (CoMP), and interference cancellation have been developed.

In 5G systems, Advanced Coding Modulation (ACM) schemes including hybrid Frequency Shift Keying (FSK) and Quadrature Amplitude Modulation (QAM) modulation (FQAM) and Sliding Window Superposition Coding (SWSC), and advanced access schemes including filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and Sparse Code Multiple Access (SCMA) have been developed.

In order to increase the speed and capacity of LTE networks along with the development of LTE, improved technologies such as LTE (LTE-U) in unlicensed spectrum (unlicensed spectrum) using a shared frequency band have been studied. LTE-U or Licensed-Assisted Access (LAA) refers to a technology for supporting quality of service (QoS) and smooth mobility by integrating a Licensed spectrum (Licensed spectrum) or a Licensed band (Licensed band) and an unlicensed spectrum (unlicensed band) or an unlicensed band and a Licensed band for existing LTE communication using Carrier Aggregation (CA), and processing all control signals and signaling using a stable Licensed band as an anchor (anchor). Furthermore, LTE-U or LAA ensures a wide data pipe based on the extension of unlicensed bands, providing users with an improved mobile broadband experience.

Since unlicensed frequency bands are shared frequency bands available to any technology or device, most countries have enacted regulations regarding the use of unlicensed frequency bands. To reduce interference between devices in the unlicensed band, the transmission power of devices using the unlicensed band may be limited to a level lower than that of the licensed band.

Transmission rules for a shared frequency band like an unlicensed band or an unlicensed band provide various types of schemes to mitigate signal interference between devices, such as a scheme to limit transmission power to prevent reception power within a certain distance from being greater than or equal to a certain value, a scheme to skip a position on time or frequency resources or to allow only some of the total resources to be used, a scheme to listen for a signal from another device and to allow transmission when the reception power of the signal is less than a certain value, and the like.

Existing cellular communications such as LTE require a resource allocation procedure based on channel measurements and link adaptation that adaptively determines the transmission capacity of the transmission/reception link. However, in a shared frequency band such as an unlicensed frequency band for which coexistence rules of different communication systems are established, several problems may occur in application of the existing resource allocation scheme. As a result, a need has arisen for new resource allocation schemes for communications using unlicensed frequency bands.

Disclosure of Invention

The present disclosure provides a method and apparatus for transmitting and receiving a signal in a communication system.

The present disclosure also provides a method and apparatus for controlling physical channel parameters of a communication link in a system sharing communication resources.

The present disclosure also provides a method and apparatus for allocating resources for a cellular network sharing resources in an unlicensed frequency band.

The present disclosure also provides a method and apparatus for allocating resources to solve the problems of increased delay and increased signaling load due to listen-before-talk (LBT) failure in an unlicensed band.

The present disclosure also provides a method and apparatus for minimizing loss and efficiently using a frequency band for cellular communication in a shared frequency band.

A method for allocating resources in a cellular network using an unlicensed frequency band according to an embodiment of the present disclosure includes: the apparatus generally includes means for generating at least one resource assignment signal comprising information indicating a plurality of consecutive Uplink (UL) sub-frames communicable over an unlicensed frequency band, means for transmitting the resource assignment signal to a User Equipment (UE) over the unlicensed frequency band during at least one Downlink (DL) sub-frame, and means for receiving UL data from the UE during the consecutive UL sub-frames.

A method for receiving resource allocation in a cellular network using an unlicensed frequency band according to an embodiment of the present disclosure includes: the method includes receiving at least one resource assignment signal from an evolved node b (eNB) during at least one DL subframe, the at least one resource assignment signal including information indicating a plurality of consecutive UL subframes communicable over an unlicensed frequency band, identifying the plurality of consecutive UL subframes based on the resource assignment signal and other control signals, and transmitting UL data to the eNB during the consecutive UL subframes.

An eNB for allocating resources in a cellular network using an unlicensed frequency band according to an embodiment of the present disclosure includes: a controller configured to generate at least one resource assignment signal comprising information indicative of a plurality of consecutive UL sub-frames communicable over an unlicensed frequency band; and a transceiver configured to transmit a resource assignment signal to the UE during at least one DL sub-frame and to receive UL data from the UE during a plurality of consecutive UL sub-frames.

A UE for receiving resource allocation in a cellular network using an unlicensed frequency band according to an embodiment of the present disclosure includes: a transceiver configured to receive at least one resource assignment signal from the eNB during at least one DL sub-frame, the at least one resource assignment signal including information indicating a plurality of consecutive UL sub-frames communicable over the unlicensed frequency band, and to transmit UL data to the eNB during the consecutive UL sub-frames, and a controller configured to identify the plurality of consecutive UL sub-frames based on the resource assignment signal and other control signals, and to notify the transceiver of the identified consecutive UL sub-frames.

Drawings

The above and other aspects, features and advantages of certain exemplary embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings.

Fig. 1A and 1B illustrate a communication procedure using an unlicensed frequency band;

fig. 2 shows a process for determining the transmission capacity of a transmit/receive link in existing cellular communications such as LTE;

fig. 3A illustrates an example of a Downlink (DL) scheduling procedure suitable for embodiments of the present disclosure;

fig. 3B illustrates an example of an Uplink (UL) scheduling procedure suitable for embodiments of the present disclosure;

fig. 4A illustrates a frame structure of an unlicensed band suitable for use with embodiments of the present disclosure;

fig. 4B illustrates a radio frame structure suitable for use with embodiments of the present disclosure;

FIG. 5 illustrates single subframe resource allocation according to an embodiment of the disclosure;

fig. 6 illustrates multi-subframe resource allocation according to an embodiment of the present disclosure;

fig. 7 illustrates a hybrid subframe resource allocation in accordance with an embodiment of the present disclosure;

fig. 8 illustrates a multi-frame resource allocation in accordance with an embodiment of the present disclosure;

fig. 9 illustrates a transmission procedure for UL grant and UL data in the existing LTE system;

fig. 10 illustrates a transmission process of UL grant and UL data using a timing offset according to an embodiment of the present disclosure;

fig. 11 and 12 illustrate a transmission procedure of UL grant and UL data indicating the start and end of consecutive UL subframes according to an embodiment of the present disclosure;

fig. 13-16 illustrate transmission procedures of UL grant and UL data for semi-statically indicating the start and end (length) of consecutive UL subframes according to an embodiment of the present disclosure;

fig. 17 to 21 illustrate hybrid automatic repeat request (HARQ) process Identifiers (IDs) set for a plurality of subframes according to an embodiment of the present disclosure;

fig. 22 is a flowchart illustrating an operation of an evolved node b (enb) for performing multi-frame resource allocation in accordance with an embodiment of the present disclosure;

fig. 23 is a flowchart illustrating an operation of a User Equipment (UE) for receiving a multi-frame resource allocation according to an embodiment of the present disclosure.

Fig. 24 is a flowchart illustrating a process for transmitting multiple UL (M-UL) grants and data according to an embodiment of the present disclosure;

fig. 25 is a flowchart illustrating an operation of an eNB for transmitting block Acknowledgement (ACK)/negative ACK (nack) according to an embodiment of the present disclosure;

fig. 26 is a flowchart illustrating an operation of a UE for receiving block ACK/NACK according to an embodiment of the present disclosure;

FIG. 27 is a diagram used to describe the hidden node problem of a wireless fidelity (Wi-Fi) network in accordance with an embodiment of the present disclosure;

fig. 28 is a block diagram of a UE according to an embodiment of the present disclosure; and

fig. 29 is a block diagram of an eNB according to an embodiment of the present disclosure.

Throughout the drawings, like reference numerals will be understood to refer to the same or similar elements, features and structures.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

When describing the embodiments of the present disclosure, technical problems that are known in the technical field of the present disclosure and are not directly related to the present disclosure will not be described. The subject matter of the present disclosure will be described more clearly without being obscured by the omission of unnecessary description.

For the same reason, some elements in the drawings will be exaggerated, omitted, or simplified. The dimensions of each element do not fully reflect the actual dimensions of the element. In each figure, the same or corresponding elements will be referred to by the same reference numerals.

Advantages and features of the present disclosure and methods of accomplishing the same will become apparent with reference to the following embodiments as described in conjunction with the accompanying drawings. However, the present disclosure is not limited to the disclosed embodiments, but may be implemented in various ways, and embodiments are provided to complete the disclosure of the present disclosure and allow those of ordinary skill in the art to understand the scope of the present disclosure. The present disclosure is defined by the category of claims. Like reference numerals will refer to like elements throughout the specification.

It will be understood that each block of the flowchart illustrations, and combinations of flowchart illustrations, can be implemented by computer program instructions. These computer program instructions may also be stored in a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block(s). These computer program instructions may also be stored in a computer-usable or computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-usable or computer-readable memory produce an article of manufacture including instructions that implement the function specified in the flowchart block(s). The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block(s).

In addition, each block represents a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in other implementations, the functions noted in the block(s) may occur out of the order. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

In exemplary embodiments of the present invention, the term "as used herein"

A unit "means a software or hardware component, such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), that performs certain tasks. However, the "

The meaning of unit is not limited to software or hardware. A "unit" may advantageously be configured to reside on the addressable storage medium and configured to reproduce the one or more processors. Thus, the "

A unit "may include, for example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Component a and "

The functions provided in the unit "may be combined into fewer components and"

Unit ", or furtherDivided into further components and "

A cell ". Further, the components and unit(s) may be implemented to execute one or more CPUs in a device or secure multimedia card.

While embodiments of the present disclosure will be described in detail with a focus on wireless communication systems having a particular channel structure, it will be apparent to those of ordinary skill in the art that the main subject matter that will be claimed in this specification is also applicable to other communication systems and services having similar technical background without significantly departing from the scope of the present disclosure.

Before describing embodiments of the present disclosure in detail, examples of interpretable meanings of several terms used herein will be provided. It should be noted, however, that the meaning of the terms is not limited to the examples provided below.

A Base Station (BS) is an entity that communicates with User Equipment (UE) and may also be referred to as a BS, a Base Transceiver Station (BTS), a node b (nb), an evolved node b (enb), an Access Point (AP), etc. In particular, at least one of the embodiments of the present disclosure described below may be implemented in a heterogeneous network (HetNet) including a primary eNB and a secondary eNB, and the primary eNB may be referred to as a macro BS, a primary cell (PCell), etc., and the secondary eNB may be referred to as a small BS, a secondary cell (SCell), etc.

A UE is an entity that communicates with an eNB and may also be referred to as a UE, device, Mobile Station (MS), Mobile Equipment (ME), terminal, etc.

In the heterogeneous network, the UE transmits and receives primary system information and control signals, exchanges mobile-sensitive traffic such as voice with the PCell, and exchanges traffic important for an instantaneous transmission amount such as data with the SCell. Here, the PCell may be set to a licensed band (licensed band), and the SCell may be set to a shared band, i.e., an unlicensed band. Examples of this type of cellular communication system may include an LTE Licensed Assisted Access (LAA) system. UEs that additionally use the shared band may be referred to as LAA UEs, while UEs that only use the existing licensed band may be referred to as LTE UEs.

The UE in the eNB area is in a Radio Resource Control (RRC) idle state or an RRC connected state.

RRC IDLE (RRC IDLE): the UE selects an eNB (or cell), monitors a paging channel, and acquires System Information (SI), but does not exchange data with the eNB.

RRC connection (RRC CONNECTED): the UE monitors the control channel and exchanges data with the eNB through the data channel. The UE reports various measurements of the eNB and neighboring enbs to assist in the scheduling of the eNB.

Devices using the unlicensed band are classified into frame-based devices (FBEs) and load-based devices (LBEs). A communication procedure on a per device basis will now be described.

Fig. 1A illustrates a communication procedure using an unlicensed frequency band for FBEs.

Referring to fig. 1A, a transmitter performs a Clear Channel Assessment (CCA)102 for at least 20 μ s (microseconds) before performing a transmission 104 over an unlicensed frequency band. CCA 102 is an operation in which the transmitter measures the magnitude of interference to determine whether another device is currently using an unlicensed frequency band. The transmitter does not perform transmission if the interference magnitude measured as a result of the CCA is greater than or equal to a certain value, and performs transmission 104 if the measured interference magnitude is less than a certain value. The transmission 104 has a fixed frame period 110 and starts at the start timing of a frame continuing from the CCA period immediately. The transmitter occupies an unlicensed band (106) from a shortest 1ms to a longest 10ms by performing CCA once and must be idle without performing transmission during a minimum 5% of a Channel Occupancy Time (COT) 106. This is referred to as an idle period 108. If it is determined as a result of the CCA 102 that another device is currently using the unlicensed band, the transmitter performs CCA again after the fixed frame period 110.

Fig. 1B illustrates a communication procedure using an unlicensed frequency band for LBE.

Referring to fig. 1B, as in FBE, the transmitter performs CCA 112 for at least 20 μ s before performing transmission 116 over the unlicensed band. The transmitter performs transmission if it is determined that no device is using the unlicensed band as a result of the CCA 112. However, if it is determined that another device is currently using the unlicensed band, the transmitter performs an additional CCA 114, unlike the case of the FBE. This is referred to as extended cca (ecca) 114. ECCA 114 includes N CCA times, where N indicates a backoff counter value randomly selected in [1, q ], and q indicates a Contention Window Size (CWS). The CWS may be given by the eNB or determined by the UE. If it is determined as a result of the ECCA 114 that no device is currently using the unlicensed band, the transmitter performs transmission 116. The transmitter may occupy the unlicensed band for a time, i.e., a maximum value of (13/32) × q ms of the COT118, after which the transmitter performs ECCA again, and during the time when the transmitter performs ECCA, the transmitter has an idle period 120.

FBE and LBE have advantages and disadvantages, respectively. LBEs may exhibit better performance than FBEs, taking into account the probability of occupying unlicensed bands. This is because upon a CCA failure, the FBE may not be able to perform CCA again in a fixed frame period, and the LBE may perform ECCA, i.e., N additional CCAs, after the CCA failure in order to occupy the unlicensed band. Next, FBE is simpler than LBE in view of scheduling, i.e., transmission of control channels. The FBE may use the unlicensed band based on a subframe boundary, i.e., control channel transmission timing. However, LBE is arbitrarily selected as N of the number of CCAs in ECCA, so that the timing of starting to use an unlicensed band may not coincide with a subframe boundary. Accordingly, the LBE reserves a portion of the first subframe and performs transmission of the control channel and the data channel starting from the second subframe. FBEs are less damaging than LBEs to nearby Wi-Fi devices sharing unlicensed frequency bands. Generally, LBEs have a higher probability of occupying unlicensed bands than FBEs, which means that Wi-Fi devices occupy more opportunities to occupy unlicensed bands.

Meanwhile, even when using an unlicensed band, the UE needs to maintain a connection with the licensed band in order to provide a reliable cellular communication service in a mobile environment. Accordingly, delay-sensitive services such as voice and the like are transmitted in the licensed band, and data services are transmitted using the licensed band and the unlicensed band is transmitted in due course, thereby increasing a possible data transfer rate.

Fig. 2 shows a procedure for determining the transmission capacity of a transmit/receive link in existing cellular communications, such as LTE.

Referring to fig. 2, in DL, a UE measures a Reference Signal (RS)202 of an eNB and reports the signal quality of the RS 202 to the eNB through a Channel Quality Indicator (CQI) 204. The RS 202 of the eNB may include a common/cell-specific reference signal (CRS) or a channel state information reference signal (CSI-RS) commonly assigned to all UEs in the service area of the eNB, or a UE-specific RS assigned to a specific UE. The UE may be controlled by the eNB to report channel quality to the eNB periodically or aperiodically through CQI 204. The UE uses the UL control channel for periodic reporting and the UL data channel for aperiodic reporting.

The eNB performs scheduling based on the UE reported CQI 204 to determine the UE to be allocated physical resource blocks and provides the scheduled UE with UE-specific allocation information based on the scheduling results in

operations

206 and 208. A resource assignment (or allocation) signal (or UL/DL grant) indicating the location of allocated DL resources and resource assignment information, i.e., physical parameters such as a Modulation and Coding Scheme (MCS) index and hybrid automatic repeat request (HARQ) related information, are scrambled by an identity of the UE, e.g., a cell radio network temporary identity (C-RNTI) or a mobile broadcast service (MBMS) RNTI (M-RNTI), and transmitted through a Physical Downlink Control Channel (PDCCH), and the UE having received the resource assignment signal receives DL data on a Physical Downlink Shared Channel (PDSCH) through a physical resource block indicated by the resource assignment signal.

For UL, the eNB measures the RS from the UE to discern UL signal quality. The RS of a UE may be a Sounding RS (SRS) that the eNB periodically (2-320ms) allocates to a particular UE. Unlike current standards, demodulation rs (dmrs) transmitted by a UE together with UL data for operation in a shared band may be used for UL measurement in an unlicensed band. Based on the CQI obtained through measurement of the RS transmitted from the UE, the eNB performs UL scheduling for determining the UE to which the physical resource block is to be allocated, and provides the scheduled UE with UE-specific allocation information based on the scheduling result. A resource assignment signal indicating the allocated UL resource is scrambled by identification information of the UE and transmitted through the PDCCH, and the UE having received the resource assignment signal transmits UL data on a Physical Uplink Shared Channel (PUSCH) through a physical resource block indicated by the resource assignment signal.

Until the eNB completes link adaptation and channel measurement for the UE, a delay time longer than a predetermined time is required due to necessary signal transmission/reception and processing. For example, referring to the DL operation shown in fig. 2, the UE consumes two subframes to measure RS 202 (e.g., CRS) transmitted from the eNB per DL subframe and report CQI 204 through a Physical Uplink Control Channel (PUCCH) allocated to each UL subframe. The eNB needs one subframe to perform

channel estimation

206 and 1 to k subframes to perform scheduling 208 for resource allocation and for determining MCS index depending on the implementation. Therefore, the minimum CQI feedback delay 212 possible is 4 ms.

Since the minimum period of SRS is 2 subframes in the UL, one more subframe delay is generated than in the UL, so that the CQI feedback delay 212 is a minimum of 5 ms. As the period of SRS increases, the total CQI feedback delay also increases.

As such, existing LTE systems may provide minimal CQI feedback delay when measuring periodic RSs. However, in a shared frequency band, such as an unlicensed frequency band, in which coexistence rules of different communication systems are established, three problems as described below may occur in application of the existing resource allocation scheme.

1) Measurement inaccuracy of periodic RS

2) Discontinuous use of radio resources

3) CQI reporting timing delay

Regarding the first problem, the eNB cannot be guaranteed to transmit the periodic RS due to LBT specification, or there may be a serious amount of variation in the measurement of the periodic RS although there is no specification problem. The UE performs measurement in the location of the periodically allocated RS, and may perform measurement in a resource location where the RS is not actually transmitted if the LBT attempt by the eNB fails. In certain regions such as europe, even with LBT provisions, Short Control Signals (SCS) may be transmitted without using LBT. The SCS must be designed such that the transmitter transmits the SCS by only occupying 5% of the resources within 50 ms. Even if periodic RS transmission is possible in this manner, the UE may experience discontinuous interference from neighboring Wi-Fi APs/UEs or asynchronous cell eNBs or LTE UEs belonging to asynchronous cell eNBs. The cause of non-continuous interference may be CCA or hidden nodes. For example, if a CCA threshold is set to a UE, a UE that has received a signal from a non-serving eNB having higher power than the CCA threshold does not transmit its signal. In this case, the transmission probability of the devices adjacent to the eNB may be different from when LBT of the eNB succeeds to when LBT of the eNB fails, resulting in a significant difference in the amount of interference. The amount of interference causes inaccuracies in the RS measurements. The first problem also occurs in the same manner when the SRS of the UE is transmitted in the UL.

The second problem corresponds to the case when aperiodic RSs are measured. That is, even if the eNB transmits the periodic RS, the UE performs measurement of the aperiodic RS as a result depending on whether LBT succeeds or fails, which causes a measurement error problem. Whether LBT succeeds or fails is arbitrary, so that a channel measured when LBT last succeeded and a channel measured when LBT currently succeeded are highly likely to be different from each other. When one UE is allocated a plurality of consecutive subframes, the eNB may perform scheduling based on channel quality measured in a previous subframe, but as described above, a delay of at least 4ms may be generated between channel measurement and resource allocation. That is, resource allocation based on the CQI measured in the nth subframe may be made in the (n +4) th subframe. Therefore, if there is a large difference between the timing when LBT was last successful and the timing when LBT was currently successful, it may be inevitable to perform transmission in the current first four subframes based on inaccurate channel measurements.

A third problem is the generation of additional delay time for reporting CQI, which makes accurate channel measurement difficult. This problem may occur when data transmission is performed in DL. That is, when a UE measuring an RS of the eNB performs reporting using UL resources allocated by the eNB, if the CCA of the FBE fails by the eNB, a delay of four subframes or more is generated for the UE to receive a new grant; an additional delay of four subframes or more may be generated if the CCA used by the UE to report measurements fails. In the same case, for LBE, various UEs in the eNB may contend to send measurement reports on the UL.

In the embodiments described below, a resource allocation scheme capable of minimizing loss will be proposed in consideration of the three problems derived above.

Due to difficulties in periodic channel measurement, the UE performs CQI reporting and occupies a channel based on channel measurement values obtained after LBT of the eNB succeeds. To this end, the eNB allocates resources of temporally adjacent subframes to the UE.

Although aperiodic channel measurements are employed, a minimum delay of 4ms in the DL and a minimum delay of 5ms in the UL can be generated. Thus, for example, in DL, the CQI measured in the first subframe may be reflected in the scheduling only after the COT is longer than at least 4 ms. As a result, based on accurate CQI during 4ms, the eNB may not be able to perform MCS determination for four frames, selecting a conservative MCS index for the subframe.

If the LBT of the UE fails, i.e., a busy channel is detected, the UE needs to receive resource allocation again from the eNB and may generate a 7ms delay for the resource allocation, including a Scheduling Request (SR), a 3ms interval, a UL grant, a 4ms interval, and an order of data transmission. Accordingly, if it is determined that the LBT failure rate is high, the eNB may allocate resources for consecutive subframes through a single grant.

Fig. 3A shows an example of a DL scheduling procedure suitable for embodiments of the present disclosure.

Referring to fig. 3A, an eNB transmits DL resource information indicating physical channel parameters (e.g., MCS index, etc.) and resources allocated by scheduling to a UE through a PDCCH in operation 302. In operation 304, the eNB transmits user data through the PDSCH on the physical resource block indicated by the DL resource information. In operation 306, the UE transmits ACK/NACK as a HARQ response with respect to user data. A delay of 4ms may be generated between the user data of the DL and the ACK/NACK. If the HARQ response is a NACK, the eNB retransmits the user data in operation 308.

Fig. 3B illustrates an example of a UL scheduling procedure suitable for embodiments of the present disclosure.

Referring to fig. 3B, in operation 312, a UE having user data or control information to be transmitted in UL transmits an SR to an eNB through a PUCCH. In operation 314, the eNB performs scheduling in response to the SR and transmits a UL grant, i.e., UL resource information, corresponding to the scheduling through the PDCCH. Scheduling may consume, for example, 3 ms. In operation 316, the UE transmits user data, a Buffer Status Report (BSR), or a Power Headroom Report (PHR) through a PUSCH on a physical resource block indicated by UL resource information. To prepare for UL transmission over PUSCH, 4ms may be required. In operation 318, the eNB transmits ACK/NACK for UL reception through the PUSCH through a Physical HARQ Indication Channel (PHICH).

Fig. 4A illustrates an FBE frame structure for unlicensed bands suitable for use with embodiments of the present disclosure.

Referring to fig. 4A, in an FBE frame structure, one frame duration 402 may include 10 subframes, i.e., 10ms, in consideration of an LTE structure. For COT 406 and idle period 408, resource allocation must be performed to make the eNB comply with regulatory requirements. For example, if the COT 406 is 9ms, the idle period 408 needs to be longer than 5% (9 × 0.05 ═ 0.45) of the COT 406. The idle period 408 in one frame duration 402 of 10ms may be 1ms, according to regulatory requirements.

Fig. 4B illustrates a radio frame structure suitable for use with embodiments of the present disclosure.

Referring to fig. 4B, one radio frame 412 includes 10 subframes, each of which may operate as a DL subframe 414, a special subframe 416, or a UL subframe 418 depending on UL/DL subframe configuration. In one radio frame 412, the role, number and location of the subframes are configured by the eNB through higher layer signaling. The special subframe 416 exists between the DL subframe 414 and the UL subframe 418 and includes a downlink pilot time slot (DwPTS), a gap time period (GP), and an uplink pilot time slot (UpPTS). In the illustrated example, in the UL/DL subframe structure used in the unlicensed band, DL subframes are continuously allocated and then UL subframes are continuously allocated.

The eNB performs LBT in the CCA period 404 for signal transmission and performs resource allocation if the channel is determined to be empty (i.e., LBT is successful). Various embodiments of resource allocation performed by an eNB will be described below.

Fig. 5 illustrates single subframe resource allocation according to an embodiment of the disclosure.

Referring to fig. 5, in each subframe contained in the COT 504 in the frame duration 502, the eNB informs the UE of the resource location and resource allocation information (e.g., including MCS index and/or HARQ-related information) through a control channel (PDCCH or ePDCCH)506a or 506 b. The UE performs data communication in each

subframe

508a or 508b according to the control channel 506a or 506b of each subframe. From subframe #0 to subframe #3, the eNB has no previous CQI report, and thus determines resource allocation information according to a transport format (MCS index, etc.) determined by the eNB without reflecting the CQI report. Therefore, the control channel from subframe #0 to subframe #3 is likely to indicate the same transmission format.

Fig. 6 illustrates multi-subframe resource allocation according to an embodiment of the present disclosure.

Referring to fig. 6, the eNB informs resource location and resource allocation information (e.g., MCS index and/or HARQ-related information) of UEs of other subframes in the COT 604 through a control channel (PDCCH or ePDCCH)606 of the first subframe in a frame duration 602 after LBT success. The UE performs data communication in subframes 608a and 608b of the control channel 606 corresponding to the first subframe. By performing resource allocation for a plurality of subframes using the control channel 606 of one subframe, the load of the control channel may be reduced, but the eNB may not be able to allocate an appropriate transmission format (MCS index, etc.) from subframe #4 based on the CQI reported from subframe # 0.

Fig. 7 illustrates a hybrid subframe resource allocation according to an embodiment of the disclosure.

Referring to fig. 7, the multi-subframe control channel 706 for subframes #0 to #3 and the single-subframe control channels 710a and 710b for subframes #4 to #8 are separated. That is, the eNB informs the resource location and resource allocation information of UEs of a predetermined number (e.g., four) of

subframes

708a and 708b in the COT 704 through a control channel (PDCCH or ePDCCH)706 of the first subframe in the frame duration 702 after the LBT success. The UE performs data communication in four

subframes

708a and 708b of the control channel 706 corresponding to the first subframe. The eNB may adaptively allocate a transmission format starting from subframe #4 based on the CQI reported from subframe # 0. Accordingly, the control channels 710a and 710b for the sub-frame following the sub-frame #4 in the COT 704 include resource location and resource allocation information determined based on the CQI, and the UE performs data communication in the

respective sub-frames

712a and 712b corresponding to the control channels 710a and 710b of the sub-frames #4 to # 8.

Fig. 8 illustrates a multi-frame resource allocation according to an embodiment of the present disclosure.

Referring to fig. 8, the eNB informs the resource location and resource allocation information of the UE of the first frame duration 802 and at least one frame duration 804 continuing therefrom through a control channel 806 of the first subframe in the first frame duration 802 after the LBT success. The UE performs data communication in a plurality of corresponding sub-frames 808a and 808b in a plurality of

frame durations

802 and 804 using a control channel 806 of the first frame.

In order to perform resource allocation for a plurality of sub-frames (or sub-frames, hereinafter collectively referred to as a plurality of sub-frames) in advance, the control channel needs to include a resource assignment signal containing information on additionally allocated resources. The eNB may include a resource assignment or allocation signal for multi-subframe resource allocation, an identifier for distinguishing the resource assignment signal for multi-subframe resource allocation from an existing resource assignment signal for single subframe resource allocation. In embodiments, the identifier may comprise an absolute value of a subframe number or System Frame Number (SFN) indicating the location of the resource to be allocated in the future, or an offset of a subframe (frame or subframe unit) through which the current resource assignment signal is transmitted. The eNB may also include information in the multi-subframe resource assignment signal indicating additional allocations that will include N subframes (or N frames).

Upon receiving the control channel, the UE determines whether the control channel includes an existing resource assignment signal (i.e., a single subframe resource allocation) or a new resource assignment signal for a multi-subframe resource allocation. For multi-subframe resource allocation, the UE identifies the location of the allocated resources (across multiple subframes or multiple frames) based on the currently received resource assignment signal. The UE performs data communication at the identified resource location.

If the CCA is configured for LBT before the allocated resource location, the UE determines whether an RS or a channel securing notification signal (channel securing notification signal) is received to check whether the serving eNB has secured the channel. Upon receiving the RS or the channel securing notification signal from the serving eNB, the UE performs data communication according to the transport format indicated by the serving eNB in the resource location allocated in advance by the multi-subframe resource assignment signal received in advance. For the case where the UE receives a grant through the PCell or other SCell, the eNB indicates to the UE whether to check the RS or channel assurance notification signal of the eNB.

For UL, the eNB performs LBT before the previously allocated resources through a multi-subframe resource assignment signal. If the LBT is successful, the UE performs transmission at a location of a resource previously allocated through the resource assignment signal according to a transmission format indicated in advance by the eNB. If the LBT of the UE fails, the UE waits until the previously allocated next CCA period to perform the same LBT operation. In an embodiment, for multiple resources allocated by a single resource allocation and CCAs performed before the location of the resources, the UE may selectively perform LBT for only some CCAs, rather than performing LBT for all CCAs. The resource(s) for which such selective LBT is to be performed may be set by the eNB or may be selected by the UE randomly or under certain conditions.

In an embodiment, the UE may send success/failure information for LBT to the eNB. The success/failure information of LBT may be transmitted together with UL data or feedback signals, and may include a bitmap, a subframe index, a success/failure subframe number, etc., corresponding to a plurality of CCA periods. In an embodiment, the UE may report LBT success/failure information in an immediately previous subframe or a scheduling ID (e.g., C-RNTI or M-RNTI) of the UE in a previous subframe or a current subframe to the eNB. From the report from the UE, the eNB may determine that the transmission of the UE allocated to the previous subframe was delayed by one subframe due to LBT failure. Depending on the system, the scheduling ID may be replaced by the HARQ process ID.

[ configuration of multiple UL (M-UL) grants ]

In the existing LTE system, the eNB indicates UL resources and transmission parameters (MCS index, etc.) of one UL subframe by using one UL grant (i.e., one resource assignment signal). In general, a minimum interval of 4ms is required between the timing of transmitting the UL grant and the location of the UL resource (e.g., the UL subframe to which the PUSCH is allocated). The interval is determined based on a time required for the UE to configure a UL transport block containing transmission data after receiving the UL grant. In the existing LTE standard, to simplify operations, the UL grant and the allocated PUSCH are designed to operate with a fixed interval of 4ms therebetween. The following < table 1> shows an Information Element (IE) field included in the UL grant in the existing LTE system.

[ Table 1]

The UL grant may include at least one of: a flag indicating a format of DL Control Information (DCI) included in the UL grant (i.e., a flag for format 0/format 1A distinction), a frequency hopping flag indicating whether frequency hopping is applied in allocated resources, N _ ULhop indicating a frequency hopping interval, Resource Block Assignment (RBA) indicating a location of allocated resources, MCS, Redundancy Version (RV), New Data Indicator (NDI), Cyclic Shift (CS) information for DMRS sequence, UL subframe index for Time Division Duplex (TDD) mode, DL Assignment Index (DAI) for TDD mode, CQI request, resource assignment type, and Transmit Power Control (TPC).

The location of the allocated UL resource is indicated by the RBA field, and since the number of Resource Blocks (RBs) with respect to the Bandwidth (BW) is given as Max _ RB, the number of allocated RBs is N _ RB ═ floor (RBA/Max _ RB) +1, and the start location of the allocated RBs is RB _ offset ═ RBA mod Max _ RB. Here, RB _ offset is indicated by UL grant in initial transmission and by PHICH in retransmission. The eNB may indicate changes of CS and RB _ offset of DMRS for retransmission of a packet through PHICH.

In an embodiment, to allocate multiple UL resources (subframes or frames), multiple grants are used, and each UL grant may indicate one UL resource. Each UL grant indicates at least one UL resource block provided on a time/frequency domain in one UL subframe. Accordingly, the eNB may variously specify an interval from the UL grant to the corresponding PUSCH to instruct the UE to use the UL resource block in a plurality of UL subframes.

In another embodiment, the eNB may allocate UL RBs for consecutive UL subframes by using one grant. According to the characteristics of LBT, discontinuous resource access attempts cause frequent contention and increase the possibility that another device secures a channel, so that if resource securing is successful once, it is effective to continuously use resources.

If PUSCH transmission for N consecutive UL subframes is indicated by one grant, the eNB may indicate a UL subframe in which LBT may be performed and a UL subframe in which PUSCH transmission may be performed. In another embodiment, the eNB may indicate a UL subframe in which both LBT and PUSCH transmissions may be performed and a UL frame in which only PUSCH transmissions may be performed. In embodiments, the eNB may also indicate UL subframes in which both LBT and SRS transmission may be performed, or UL subframes in which both LBT and Physical Random Access Channel (PRACH) transmission may be performed. The UL subframe may be indicated using a UE-specific control signal or a common control signal. For example, a common control signal may be used to indicate UL subframes in which LBT can be performed.

Various embodiments of a method of indicating UL subframes for LBT and PUSCH transmission opportunities (occasions) by an eNB will be described below.

a) The LBT UL subframe and the PUSCH transmission opportunity operate on a one-to-one basis (N is a positive integer) according to the indications of the N LBT UL subframes and the N PUSCH transmission opportunities. In case of at least one LBT failure, the number of PUSCH transmission opportunities actually performed is equal to or less than N. The eNB may use the same control signal to indicate the LBT opportunity and the PUSCH opportunity.

b) According to the indication of N LBT UL subframes and N PUSCH transmission opportunities, if LBT succeeds in an LBT UL subframe, N consecutive PUSCH transmissions begin. If LBT succeeds once in LBT UL subframe, the number of PUSCH transmission opportunities is equal to N despite LBT failure. The eNB may use the same control signal to indicate the LBT opportunity and the PUSCH opportunity.

c) The LBT UL subframe and PUSCH transmission opportunity operate on a one-to-one basis according to indications of N LBT UL subframes and M PUSCH transmission opportunities (N, M is a positive integer). The number of PUSCH transmission opportunities is equal to or less than M in case of at least one LBT failure. The eNB may separately indicate the LBT opportunity and the PUSCH opportunity using different messages.

d) According to the indication of N LBT UL subframes and M PUSCH transmission opportunities, if LBT succeeds in an LBT UL subframe, M consecutive PUSCH transmissions start. If LBT succeeds once in LBT UL subframe, the number of PUSCH transmission opportunities is equal to M despite LBT failure. The eNB may separately indicate the LBT opportunity and the PUSCH opportunity using different messages.

e) According to the indication of N LBT and PUSCH transmission UL subframes and M PUSCH transmission opportunities, if LBT succeeds in an LBT UL subframe (i.e., nth subframe), M consecutive PUSCH transmissions start from an (N +1) th UL subframe.

The N LBT UL subframes (i.e., LBT opportunities) are indicated by grant or by a separate control signal such as common DCI, common UL Control Information (UCI), RRC signaling, DL/UL subframe configuration (start/length) information, etc. The N or M PUSCH transmission opportunities are indicated by grant or by a separate control signal such as dedicated UCI, RRC signaling, or the like. The same signal (or grant or RRC signaling) may indicate the number of LBT UL subframes and the number of PUSCH transmission opportunities at a time if the number of LBT UL subframes and the number of PUSCH transmission opportunities are equal to each other.

In an embodiment, LBT UL subframes may be indicated as being discontinuously arranged with an interval K therebetween. If K is 2, it means that the UL subframe is set to [0, 3, 6. ], if K is 1, it means that the UL subframe is set to [0, 2, 4, 6. ], and if K is 0, it means that the UL subframe is set to [0, 1, 2, 3, 4,5, 6. ]. K may be indicated by grant, common/dedicated UCI, or RRC signaling. In this case, the number M of PUSCH transmission opportunities is set equal to N or N × K.

In an embodiment, the eNB may transmit an index indicating one of the groups of LBT UL subframes. For example, if the index is 0, a set of UL subframes [0, 1, 2, 6,7, 8] is indicated, and if the index is 1, a set of UL subframes [1, 4, 7, 9] is indicated. In an embodiment, each group of UL subframes may be indicated by a bitmap, which may be transmitted by the eNB. For example, a set of UL subframes [1, 4, 7, 9] may be indicated by a bitmap {0, 1, 0, 0, 1, 0, 0, 1 }.

Upon receiving a grant (or RRC signaling) of the eNB indicating an LBT UL subframe, the UE determines a UL subframe or PUSCH in which transmission is to be performed according to a predetermined rule. Various embodiments of the grant by the eNB and the interpretation thereof by the UE will be described below. In the following embodiments, performing LBT in a specific subframe may be part of an LBT procedure for the UE. That is, the UE starts the LBT procedure before the specific subframe and performs the remaining portion of the LBT procedure in the CCA or ECCA period of the specific subframe.

In an embodiment, the UE treats the subframe x subframes after the subframe in which the UE received the grant as the beginning of an LBT UL subframe. The UE performs LBT in the indicated subframe and, if LBT succeeds, transmits UL data in the subsequent PUSCH transmission resource. For example, if a grant is received in the nth subframe and the (n + x) th subframe includes [ CCA ] [ PUSCH ] (here, [ CCA ] denotes a CCA period and [ PUSCH ] denotes a PUSCH period), the UE performs LBT in the CCA period of the (n + x) th subframe, and if LBT succeeds, the UE performs PUSCH transmission in the PUSCH period of the (n + x) th subframe. In another example, if the (n + x) th and (n + x +1) th subframes include [ PUSCH ] [ CCA ], the UE performs LBT in the CCA period of the (n + x) th subframe and performs PUSCH transmission in the PUSCH period of the (n + x +1) th subframe.

In an embodiment, the UE treats the subframe indicated by the grant as a PUSCH transmission opportunity, i.e. the beginning of a UL PUSCH transmission subframe. The UE performs LBT before the indicated subframe and transmits UL data in the PUSCH transmission resource of the indicated subframe. For example, if the grant indication includes an (n + x) th subframe of [ CCA ] [ PUSCH ], the UE performs LBT in a CCA period of the (n + x) th subframe and performs PUSCH transmission in a PUSCH period of the (n + x) th subframe if LBT is successful. In another example, if the grant indicates an (n + x) th subframe and the (n + x-1) th and (n + x) th subframes include [ PUSCH ] [ CCA ], the UE performs LBT in a CCA period of the (n + x-1) th subframe and performs PUSCH transmission in a PUSCH period of the (n + x) th subframe.

The UL subframe index (ULSI) in the UL grant indicating the allocated UL subframe resources may be expressed by one of various schemes provided below according to a time standard.

1) The ULSI is expressed based on a subframe index of the PCell.

2) The ULSI is expressed based on the subframe index of the scheduling cell carrying the control channel.

3) The ULSI is expressed based on the subframe index of the scheduling cell carrying the data.

4) The ULSI is expressed based on a start subframe (DL subframe) of a DL burst (burst).

5) The ULSI is expressed based on the starting subframe (UL subframe) of the UL burst.

When determining a UL subframe to communicate using the unlicensed frequency band, the UE determines the CWS and performs Contention Window (CW) countdown (countdown) starting from the CWS.

CW is typically an exponential back-off algorithm required to access resources in the unlicensed band. The transmitter attempts LBT for an initial CCA period, e.g., up to 20 μ β, and compares the energy level measured in the initial CCA period to a CCA threshold to determine whether LBT succeeded or failed. If the measured energy level (in dBm) is greater than the CCA threshold, the transmitter determines that the channel is occupied (busy); otherwise, the transmitter determines that the channel is empty (idle). If the channel is idle, the transmission may be performed immediately after the initial CCA period. If the channel is busy, the transmitter switches to the ECCA procedure. ECCA includes N CCAs, where N is an arbitrarily selected value of [1, q ], and q is a CWS value. In this case, the parameter q may be adjusted depending on the situation. The range of q may be controlled between a minimum value of q (min _ q) and a maximum value of q (max _ q). Min _ q is used when ECCA is initially performed. The value of the parameter q may be incremented from min _ q, e.g. based on two times depending on certain conditions. For example, in a wireless Local Area Network (LAN) system, if the receiver does not transmit an ACK, the transmitter interprets that no ACK is received as a NACK and sets the value of q to be used in the next ECCA to min _ qx 2. Upon receiving the ACK from the receiver, the transmitter sets the value of q to be used in the next ECCA to an initial value min _ q. Various types of back-off algorithms may be used depending on the system. For cellular mobile communication, for example, if 80% of HARQ ACK feedback with respect to the first DL subframe of a DL burst (consecutive DL subframes) transmitted by the eNB is NACK, the value of q may be increased by two times.

The UE determines the CWS and performs a CW countdown from either of the following cases.

1) When UL traffic is generated in the UE, and thus a UL transmission request arrives at the physical layer from a higher layer,

2) when an SR is transmitted to an eNB in response to generation of a UL transmission request in a UE,

3) when the UE transmits an SR to the eNB and receives an UL grant from the eNB,

4) when the UE transmits a BSR for an UL grant from the eNB,

5) when the UE receives ACK for the BSR through PHICH.

The multi-grant, i.e., the grant with respect to a plurality of subframes (multi-subframe), and the operations of the UE and the eNB will be described in detail below. More specifically, various embodiments will be described below to determine 1) when to perform PUSCH transmission, 2) when to perform LBT, 3) which HARQ process ID to send, and 4) the procedure in case of LBT failure when the UE receives a grant.

< table 2> shows IE fields included in the multi-grant according to an embodiment of the present disclosure.

[ Table 2]

In the above table, the numbers in [ ] are tables mapped to bit strings to express discontinuous values. For example, in [1, 2, 4, 8], 1 may be expressed as 00, 2 may be expressed as 01, 4 may be expressed as 10, 8 may be expressed as 11.

In < table 2>, the UL grant may include at least one of a multi-subframe assignment (MSA) length field and an MSA end field. The UE may be informed of the non-included fields implicitly by another control signal or explicitly by a higher layer message such as RRC signaling or SIB. The MSA length field may indicate one subframe, but may also indicate the number of unit groups if a plurality of subframes are consecutively allocated without using LBT in the middle. For example, if a basic scheduling unit of a plurality of subframes is set to 2 subframes (e.g., set by RRC signaling or SIB message) for the UE, when 4 th, 5 th, 6 th, and 7 th subframes after the nth subframe from which the UL grant is received are assigned to the UE, two subframes such as the subframe [4,5] and the subframe [6,7] are allocated as one unit group. To express these characteristics, the MSA start field is set to 0 and 1, and the MSA length field is set to 2. That is, the MSA start field is also expressed in an offset based on the set of cells. According to an embodiment, the group of cells is not explicitly set, and one burst cell (DL and UL subframes or UL subframe) may be implicitly determined. In the following embodiment, a case where the basic unit allocated to a subframe is 1 subframe is described.

The HARQ process field may indicate a HARQ process ID or HARQ process IDs designated for the allocated UL subframe. To specify a plurality of HARQ process IDs for the allocated UL subframe, in an embodiment, the eNB includes one HARQ process ID in the HARQ process field, and the UE identifies the HARQ process ID indicated by the HARQ process field and a predetermined number of at least one HARQ process ID following the indicated HARQ process ID, and determines to use the HARQ process ID for the allocated UL subframe. The number of HARQ process IDs after the indicated HARQ process ID may be determined based on the MSA length field.

For example, the eNB sets the HARQ process field to HARQ process ID # 3. If the MSA length field is 3 and the predetermined basic unit is 1, the UE determines to allocate HARQ process IDs #3, #4, and #5 based on the HARQ process field and the MSA length field. In another example, the eNB sets the HARQ process field to HARQ process ID # 3. If the MSA length field is 3 and the predetermined basic unit is 2, the UE determines to allocate HARQ process IDs #3, #4, #5, #6, #7, and #8 based on the HARQ process field and the MSA length field.

In an embodiment, the eNB allocates a continuous HARQ process ID in addition to the previously used HARQ process ID(s), and the UE identifies the newly allocated HARQ process ID(s) in addition to the previously used HARQ process ID(s). For example, if the HARQ process field is set to HARQ process ID #3, the MSA length field is 3, and the basic unit is 1, if HARQ process ID #4 has been used for UL communication between the eNB and the UE, the UE determines to allocate HARQ process IDs #3, #5, and # 6.

[ when PUSCH Transmission is performed ]

The UE receives a UL grant from the eNB through a PDCCH (or ePDCCH) and transmits UL data through a PUSCH of a UL subframe determined in advance or according to timing information indicated by the UL grant. The UE determines the location of resources to be used for transmission of UL data and physical channel parameters (i.e., transmission parameters) based on the UL grant.

Fig. 9 illustrates a transmission procedure for UL grant and UL data in the existing LTE system.

Referring to fig. 9, a COT 902 existing after ECCA includes five DL subframes and three UL subframes. The timing offset between the timing of receiving a specific UL grant and the timing of transmitting UL data is fixed to 4 ms. Therefore, in order to continuously allocate

PUSCHs

906a, 906b, and 906c to UL subframes #5, #6, and #7, the eNB transmits

UL grants

904a, 904b, and 904c in DL subframes #1, #2, and # 3. For example, after receiving the UL grant 904a in subframe #1, the UE transmits UL data during subframe #5 through the PUSCH 906a at the resource location indicated by the UL grant.

Fig. 10 illustrates a transmission procedure of UL grant and UL data using a timing offset according to an embodiment of the present disclosure.

Referring to fig. 10, the COT 1002 includes five DL subframes and three UL subframes. No fixed timing offset is used between the UL grant and the UL data. The eNB sets an offset to the UE through the UL grant between a timing of receiving the UL grant and a timing of transmitting UL data. In the illustrated example, the UL grant includes a plurality of offsets, e.g., [4,5, 6] Transmission Time Intervals (TTIs) or [0, 1, 2] TTIs, and the UE specifies the UL subframe to which PUSCH is allocated with the application of the offsets based on the timing of receiving the UL grant. The TTI may be set to, for example, 1ms, which is a length of 1 subframe. Here, it is shown that one UL grant includes a plurality of offsets for a plurality of PUSCH transmission opportunities, but in a modified embodiment, N UL grants including offsets for N PUSCH transmission opportunities may be respectively transmitted in one DL subframe. In other embodiments described below, to indicate multiple PUSCH transmission opportunities, one UL grant or multiple UL grants may be sent.

In an embodiment, if the start timing of the allocated UL subframe is fixed (e.g., after 4ms from the timing at which the UL grant is received), information on the start timing may be omitted from the transmission. In an embodiment, an eNB may include multiple MSA length fields and as many MSA start fields as MSA length fields in an UL grant for a UE.

Fig. 11 illustrates a transmission procedure of UL grant and UL data for indicating the start and end of consecutive UL subframes according to an embodiment of the present disclosure.

Referring to fig. 11, the COT 1102 includes five DL subframes and three UL subframes. The eNB indicates the start and end or the start and length of consecutive UL subframes (i.e., subframes #5, #6, and #7)1106a, 1106b, and 1106c to which the PUSCH is allocated by using one UL grant 1104.

In another embodiment, UL grant 1104 may include at least one of the following combinations of IEs.

a) UE specific start information & UE specific end (length) information,

b) UE specific start information & common end (length) information,

c) common start information & UE specific end (length) information, an

d) Common start information & common end (length) information.

Here, UE specific information is applied to a specific UE, and common information is applied to any UE that receives UL grant 1104, common DCI, or higher layer messages. In another embodiment, start and end (length) information of consecutive UL sub-frames may be assigned to a group of UEs.

Fig. 12 illustrates a transmission procedure of UL grant and UL data indicating the start and end of consecutive UL subframes according to an embodiment of the present disclosure.

Referring to fig. 12, in subframe #0 in the COT 1202, the eNB transmits a UL grant 1204a including end (or start) information indicating an end subframe (i.e., subframe #7)1206c in consecutive UL subframes to which a PUSCH is allocated, and in a subsequent subframe #1, transmits a UL grant 1204b including start (or end or length) information indicating a first subframe (i.e., subframe # 5). The UE prepares for UL data transmission by receiving UL grant 1204a and specifies

UL subframes

1206a, 1206b, and 1206c for transmitting UL data by receiving UL grant 1204 b. In another embodiment, the UE determines the location of the ending UL subframe based on UL grant 1204a and specifies

UL subframes

1206a, 1206b, and 1206c for transmitting UL data while preparing UL data transmission based on UL grant 1204 b.

In various embodiments, start information and end (length) information indicating consecutive UL subframes for transmitting UL data using the unlicensed band may be signaled using i) one grant, ii) two grants separately, or iii) one grant and one physical layer (layer 1, L1) (e.g., common/dedicated DCI for PDCCH). In various embodiments, the end (length) information may be i) determined based on a start timing of the start information, ii) determined based on a start of a DL burst (consecutive DL subframes), iii) determined based on a start of a UL burst (consecutive UL subframes), iv) determined based on a subframe where DL-UL handover occurs (i.e., a special subframe), v) determined based on a timing of transmitting the start or end (length) information, vi) a subframe index of a PCell, or vii) a subframe index of an SCell. The start and end (length) information may be expressed by combining at least one of the above embodiments.

Fig. 13 and 16 illustrate transmission procedures of UL grant and UL data for semi-statically indicating the start and end (length) of consecutive UL subframes according to an embodiment of the present disclosure.

Referring to fig. 13, in subframe #1 of COT 1302, the eNB dynamically notifies the UE of start information on

consecutive UL subframes

1308a, 1308b, 1308c to which the PUSCH is allocated through UL grant 1304. The end (length) 1308 of

consecutive UL subframes

1308a, 1308b, and 1308c may be semi-statically configured for each UE, e.g., by RRC signaling. The UE specifies

UL subframes

1308a, 1308b, and 1308c for transmission of UL data over PUSCH in the unlicensed band based on RRC signaling and UL grant 1304.

In an embodiment, UL grant 1304 or common control signal/message may include one of the following combinations of IEs.

a) UE specific start information & UE specific end (length) information,

b) UE specific start information & common end (length) information,

c) common start information & UE specific end (length) information, an

d) Common start information & common end (length) information.

Here, the UE-specific information is applied to a specific UE (i.e., a scheduled UE) that has received the UL grant, and the common information is applied to any UE that has received the UL grant 1304 or the common control signal/message. In another embodiment, start and end (length) information of consecutive UL subframes may be allocated to a group of UEs.

In various embodiments, start information of consecutive UL subframes in which UL data is to be transmitted using an unlicensed band may be notified using i) a grant, ii) an L1 signal (e.g., a common/dedicated DCI for a PDCCH), or iii) a Medium Access Control (MAC) Control Element (CE). In various embodiments, the end information of the consecutive UL subframes may be notified using i) MAC CE, ii) RRC signaling, iii) a higher layer control signal of a data region, or iv) a SIB of a Broadcast Channel (BCH).

In various embodiments, the start information may be determined based on i) a timing of transmitting the grant, ii) a timing of the PCell, or iii) a start of a DL burst (consecutive DL subframe) of the SCell.

In various embodiments, the end (length) information may be i) determined based on the start timing indicated by the start information, ii) determined based on the start of a DL burst (consecutive DL subframes), iii) determined based on the start of a UL burst (consecutive UL subframes), iv) determined based on subframes where DL-UL handover occurs, or v) determined based on the timing of transmitting the start information. The start and end (length) information may be expressed by combining at least one of the above embodiments.

Referring to the example of fig. 14, the UL grant 1404 transmitted in subframe #1 of the COT 1402 includes start information on

consecutive UL subframes

1410a, 1410b, and 1410c to which the PUSCH is allocated. The start (length) 1408 of

consecutive UL subframes

1410a, 1410b and 1410c is set jointly for the UE by a common L1 signal 1406 (e.g., common DCI or SIB for PDCCH). The UE receives the common L1 signal 1406 and the UL grant 1404 and specifies

UL subframes

1410a, 1410b and 1410c for transmitting UL data over PUSCH in the unlicensed band.

Referring to the example of fig. 15, common DCI, e.g., indicating an ending DL subframe in COT 1502, indicates start information on consecutive UL subframes 1510a, 1510b, 1510c to which PUSCH is allocated through a UE common L1 signal 1506, and the length 1508 of the consecutive subframes 1510a, 1510b, and 1510c is set for each UE through RRC signaling. The UE receives the common L1 signal 1506 and RRC signaling and specifies UL subframes 1510a, 1510b, and 1510c for transmission of UL data over PUSCH in the unlicensed band.

In this case, the UL grant 1504 transmitted in subframe #1 in the COT 1502 includes transmission parameters (e.g., MCS index, HARQ process ID, etc.) for UL data of the consecutive UL subframes 1510a, 1510b, and 1510 c. The UE specifies UL subframes 1510a, 1510b, and 1510c by applying UE-specific length information given through RRC signaling based on a first UL subframe (i.e., subframe #5) after an ending DL subframe (i.e., subframe #4) indicated by the common DCI, and configures UL data transmitted through the UL subframes 1510a, 1510b, and 1510c based on the UL grant 1504.

Referring to the example of fig. 16, start information on

consecutive UL subframes

1610a, 1610b, 1610c to which PUSCH is allocated is indicated by an L1 signal 1606 common to UEs (e.g., common DCI indicating an end DL subframe in the COT 1602), and the length 1608 of the

consecutive subframes

1610a, 1610b, 1610c is set in common by an L1 signal or SIB.

Similar to the example of fig. 15, the UL grant 1604 sent in subframe #1 includes transmission parameters (e.g., MCS index, HARQ process ID, etc.) for UL data of

consecutive UL subframes

1610a, 1610b, and 1610 c. The UE specifies

UL subframes

1610a, 1610b, and 1610c by applying common length information given through an L1 signal or SIB based on a first UL subframe (i.e., subframe #5) after an ending DL subframe (i.e., subframe #4) indicated by the common DCI, and configures UL data transmitted through the UL subframes 1610a, 1610b, and 1610c based on a UL grant 1604.

In an embodiment, the common length information is given by an L1 signal or SIB, but may be determined based on a COT 1602 indicating the number of DL and UL subframes (i.e., the total length of DL and UL bursts) or the number of UL subframes (i.e., the length of UL bursts). For example, if the length of the UL burst is given as 3, the UE may determine three subframes, i.e., subframes #5, #6, and #7, starting from the first UL subframe as transmission resources in which UL data is transmitted in the unlicensed frequency band.

In an embodiment, the eNB semi-statically informs the UE of start and end (length) information of consecutive UL subframes that will use the unlicensed band. The UE transmits UL data through the unlicensed band during the notified UL subframe.

In various embodiments, the start and end (length) information may be configured as follows:

a) UE specific start information & UE specific end (length) information,

b) UE specific start information & common end (length) information,

c) common start information & UE-specific end (length) information, or

d) Common start information & common end (length) information.

Here, UE specific information is applied to a specific UE, and common information is applied to any UE that receives start and end (length) information. In another embodiment, the UE group may be assigned start and end (length) information.

In various embodiments, the start information or the end (length) information may be notified using i) MAC CE, ii) RRC signaling, iii) a higher layer control signal of a data region, or iv) a SIB of BCH.

In various embodiments, the start information may be determined based on i) a timing of transmitting a control signal indicating the start information, ii) a timing of a PCell, or iii) a start of a DL burst (continuous DL subframe) of the SCell.

[ when LBT is performed ]

Before the eNB sends UL data over PUSCH in multiple UL subframes indicated by the UL grant, the UE must perform LBT and succeed. Various embodiments for determining the timing for performing LBT (hereinafter referred to as LBT timing) will be described below. Depending on the structure of the CCA, the CCA period may be in a beginning portion of a first subframe in which UL data may be transmitted (i.e., the beginning of the PUSCH period) or may be in an end portion of a subframe immediately preceding a subframe in which UL data may be transmitted.

In an embodiment, the UE performs LBT before each allocated UL subframe. For example, the UE receives a UL grant in the nth subframe and receives an instruction for PUSCH transmission from the (n + m) th subframe to the (n + m +3) th subframe through the UL grant. Then, the UE performs LBT in a CCA period immediately before each PUSCH transmission subframe. For example, the UE may perform LBT in a CCA period located in a portion of the (n + m-1) th subframe to determine a transmission in the (n + m) th subframe. If the LBT of the UE is successful, UL data transmission is allowed in one UL subframe. Next, the UE recovers LBT for transmission in the next UL subframe.

In an embodiment, if LBT succeeds once, the UE may perform LBT-free transmission during N consecutive UL subframes. That is, LBT is performed once every N subframes in the allocated UL subframe. The value N is indicated semi-statically by the eNB to the UE through MAC CE, RRC signaling, or higher layer messages. The UE determines LBT timing with period N based on at least one of the following criteria:

a) the timing of the receipt of the UL grant is,

b) the timing of the start of the UL burst,

c) the start timing of the DL burst, an

d) Start timing of a frame of the PCell.

In an embodiment, the eNB may transmit a dynamic control signal indicating UL subframes in which LBT must be performed. The dynamic control signal may be, for example, at least one of UL grant and common/dedicated L1 signaling. Indication information of UL subframes in which LBT must be performed may be determined based on predetermined reference timing. The reference timing may be, for example, a timing when an UL grant including indication information is received, a timing when L1 signaling including indication information is received, a start timing of an UL burst, a start timing of a DL burst, and a start timing of a PCell frame. The UE determines the LBT timing based on the reference timing or a first LBT timing estimated from the reference timing by using the following indication information contained in the dynamic control signal.

In various embodiments, the indication information may be configured as follows:

a) the number of UL subframes in which UL data can be continuously transmitted without performing LBT,

b) the time period in which LBT is to be performed (which may be expressed as a number of subframes),

c) information indicating subframe(s) in which LBT must be performed and information indicating subframe(s) in which LBT is not performed (which may be a subframe index or bitmap, for example), and

d) the location of the next subframe in which LBT must be performed (e.g., which may be a subframe index or offset).

[ which HARQ process ID to send ]

The at least one UL grant related to the plurality of UL subframes that can be used for transmitting UL data in the unlicensed band is a transmission parameter regarding the plurality of UL subframes and includes frequency resource allocation information, MCS index, and HARQ-related information. Here, the HARQ-related information may include an HARQ process ID and RV allocated for each UL subframe. At least one of the transmission-related information other than the information indicating the allocated subframe in the existing UL grant may be notified through an M-UL grant or a higher layer message (e.g., RRC signaling). When using higher layer messages, the UE may be allowed to reuse the same resource allocation and HARQ information a certain number of times within a predetermined time or in a periodic location. However, when transmission using one HARQ process ID is completed, the next HARQ process ID must be used in a predetermined order. According to an embodiment, when using an M-UL grant, the eNB may indicate the subframe(s) used for PUSCH transmission by using the earliest incoming DL burst or earliest ending DL subframe as a reference. According to another embodiment, if the location of the UL subframe in which the HARQ process ID is specified through the M-UL grant is different from the location indicated through the M-UL grant, the previous time information needs to be rewritten.

Fig. 17 to 21 illustrate HARQ process IDs set for a plurality of subframes according to an embodiment of the present disclosure.

Referring to fig. 17, the eNB allocates the same HARQ process ID (#3 of the illustrated example) for multiple UL subframes 1702 by using UL grant(s) (1704), the HARQ process ID being fixed during the multiple UL subframes 1702. The UE interprets the resource location to which the HARQ process ID is applied as fixed and, in case of LBT failure, there is no opportunity to reattempt LBT. In the illustrated example, if the LBT of the UE succeeds during a CCA period immediately before the first UL subframe (i.e., subframe #5) (1706), the UE transmits UL data during subframe #5 by using HARQ process ID # 3. If the UE fails LBT for all allocated UL subframes (i.e., subframes #5, #6, and #7) (1708), the UE has no transmission opportunity for UL data. If the UE fails LBT for the first two UL subframes (i.e., subframes #5 and #6) and succeeds LBT for the end UL subframe (i.e., subframe #7) (1710), the UE transmits UL data in subframe # 7. In an embodiment, after LBT success with respect to subframe #5, the UE transmits the same data through the additionally allocated resources without completing transmission, thereby applying HARQ TTI bundling that improves the reception performance of the eNB.

Referring to fig. 18, the eNB allocates the same HARQ process ID (#3 in the illustrated example) for multiple UL subframes 1802 by using UL grant(s) (1806), but the HARQ process ID is not fixed only for multiple UL subframes 1802. In the event of LBT failure, the UE may reattempt LBT for resources of the subsequent subframe.

If the UE succeeds even only once in the multiple allocated UL subframes 1802 (1808), the UE does not perform additional transmissions in the multiple allocated UL subframes 1802. If the UE is unsuccessful in all LBTs for multiple allocated UL subframes 1802 (1810) and the eNB previously informs the UE of extended UL subframes 1804, the UE may reattempt LBTs for at least one of the extended UL subframes 1804. For example, if the maximum allowed length of DL and UL bursts is 8ms and the allocated DL and UL bursts is 6ms, an additional 2ms is allowed as the extended UL subframe 1804. To this end, the eNB informs the UE of the maximum allowable length of the COT used in the current burst or a specific time period by using an L1 signal or RRC signaling.

In an embodiment, the UE may use the extended UL subframe as a separate UL burst after the maximum allowed length of DL and UL bursts of 8 ms. To access resources for a separate UL burst, the UE may use LBT in LTE class 4 instead of class 2 of LTE.

If the UE fails all LBTs in the allocated UL subframe 1802 (1810), the UE determines whether there is at least one extended UL subframe 1804 based on the maximum allowed length. If there is at least one extended UL subframe 1804, the UE reattempts LBT for the extended UL subframe 1804.

If the UE fails LBT for the first two allocated UL subframes (i.e., subframes #5, #6) and succeeds LBT for the ending UL subframe (i.e., subframe #7) (1812), the UE transmits UL data in subframe #7 and does not use extended UL subframe 1804.

Referring to fig. 19, the eNB assigns a plurality of different HARQ process IDs (#3, #4, and #5) to a plurality of UL sub-frames 1902 (1904). The UE interprets the resource location to which the HARQ process ID is applied as fixed and has no chance of reattempting in case of LBT failure. In the illustrated example, if the LBT of the UE during the CCA period immediately before the first UL subframe (i.e., subframe #5) succeeds (1906), the UE transmits UL data during subframe #5 by using HARQ process ID #3, but LBT fails in subsequent subframes #6 and #7, and thus cannot transmit other HARQ process IDs #4 and # 5. If the UE fails LBT for all allocated UL subframes (i.e., subframes #5, #6, and #7) (1908), the UE has no transmission opportunity for UL data of HARQ process IDs #3, #4, and # 5. If the UE fails LBT for the first two UL subframes (i.e., subframes #5, #6) and succeeds LBT for the ending UL subframe (i.e., subframe #7) (1910), the UE transmits UL data for HARQ process ID #5 in subframe #7 and transmission of UL data for HARQ process IDs #3 and #4 is aborted.

Referring to fig. 20, the eNB allocates a plurality of different HARQ process IDs (#3, #4, #5 in the illustrated example) for a plurality of UL subframes 2002 by using UL grant(s) (2006), but the HARQ process IDs are not fixed only for the plurality of UL subframes 2002. In the event of LBT failure, the UE may reattempt LBT for resources of the subsequent subframe. In case of reattempting LBT, the UE uses UL grant, i.e., HARQ process ID, for UL data failed LBT with respect to the previous UL subframe. If the LBT is successful, the UE transmits UL data by using an UL grant, i.e., HARQ process ID, for the next subsequent UL data. The above-described operations are performed in multiple allocated UL subframes 2002 or may be performed during extended UL subframe(s) 2004 additionally allocated by the eNB.

Once LBT succeeds (2008) in the first UL subframe allocated (i.e., subframe #5), the UE transmits UL data for HARQ process ID #3 in subframe # 5. If the LBT attempt for the next UL subframe (i.e., subframe #6) fails, the UE reattempts LBT to transmit UL data of HARQ process ID #4 in the next UL subframe (i.e., subframe # 7). If all LBTs fail for UL subframes (i.e., subframes #6, #7), the UE retries LBT for the subsequent first extended UL subframe 2004, and if LBT succeeds, the UE transmits UL data by using HARQ process ID # 4. Similarly, the UE LBT succeeds in the second extended UL subframe 2004 and transmits UL data by using HARQ process ID # 5.

If all LBTs fail (2010) for the allocated UL subframe (i.e., subframes #5, #6, #7), the UE retries LBT for the subsequent first extended UL subframe (i.e., subframe #5)2004 and, if LBT succeeds, the UE transmits UL data for HARQ process ID # 3. Next, the UE succeeds in LBT for the second extended UL subframe (i.e., subframe #6)2004 and transmits UL data by using HARQ process ID #4 of subframe # 6. There are no more extended UL subframes, so the UE has no transmission opportunity for HARQ process ID # 5.

Since all LBTs failed 2012 for the allocated first and second UL subframes (i.e., subframes #5, #6), and LBTs succeeded for the allocated end UL subframe (i.e., subframe #7), the UE may transmit UL data for HARQ process ID # 3. Since there is an unused HARQ process ID, the UE attempts LBT for the subsequent first extended UL subframe 2004, and if LBT succeeds, the UE transmits UL data by using HARQ process ID # 4. Next, the UE succeeds in LBT for the second extended UL subframe 2004 and transmits UL data by using HARQ process ID # 5.

As shown in fig. 20, if the UE transmits UL data by using a HARQ process ID different from a HARQ process ID indicated by the eNB in a specific subframe, i.e., a HARQ process ID that cannot be transmitted in a previous subframe due to LBT failure, the eNB needs to identify the HARQ process ID changed in the corresponding subframe. For example, the UE changes a cyclic shift of the DMRS sequence according to the determined rule and transmits UL data by using the changed cyclic shift. The eNB detects a cyclic shift changed according to the determined rule while receiving UL data, and may know how many times the UE fails in LBT or how many HARQ process IDs among HARQ process IDs allocated in the UL grant are discarded from the detected cyclic shift. If the UE acquires UL resources and transmits UL data, the eNB may receive the UL data by using HARQ process IDs having the same order as allocated in the UL grant.

Referring to fig. 21, the eNB allocates a plurality of different HARQ process IDs (#3, #4, #5 as illustrated) for a plurality of UL subframes 2102 by using UL grant(s) (2106), but the HARQ process IDs are fixed for the plurality of UL subframes 2102. In the event of LBT failure, the UE may reattempt LBT for resources of the subsequent subframe. In case of LBT failure, the UE will not re-attempt to transmit UL data of the same HARQ process ID in subsequent resources. If the LBT is successful, the UE transmits UL data according to the UL grant for the next HARQ process ID. The above operations are performed in multiple allocated subframes 2102 or may be performed during extended UL subframe(s) 2104 otherwise allocated by the eNB. The UE may reattempt to transmit UL data in the first HARQ process ID of LBT failure in extended UL subframe 2104. Here, the foremost HARQ process ID means a minimum value when HARQ process IDs are arranged in the order of subframe indexes allocated to the HARQ process IDs in the UL grant or a minimum value in the order of the HARQ process IDs.

Once LBT succeeds (2108) in the first UL subframe (i.e., subframe #5) for allocation, the UE transmits UL data for HARQ process ID #3 in subframe # 5. If the LBT attempt fails for the next UL subframe (i.e., subframe #6), transmission of UL data for HARQ process ID #4 is aborted and the UE reattempts LBT to transmit UL data for HARQ process ID #5 in the next UL subframe (i.e., subframe # 7). If all LBTs of the UL subframes (i.e., subframes #6 and #7) fail, the UE retries LBTs for the subsequent first extended UL subframe 2104, and if LBTs succeed, the UE transmits UL data in the first extended UL subframe 2104 by using the foremost HARQ process ID (i.e., #4) for which transmission failed. Similarly, the UE LBT succeeds in the second extended UL subframe 2104 and transmits UL data by using HARQ process ID # 5.

If all LBTs fail (2110) for the allocated UL subframes (i.e., subframes #5, #6, and #7), the UE re-attempts LBTs for the subsequent first extended UL subframe 2104, and if LBTs succeed, the UE transmits UL data for the first HARQ process ID (i.e., #3) for which transmission failed in the first extended UL subframe 2104. Next, the UE succeeds in LBT in the second extended UL subframe 2104 and fails in transmission, and then transmits UL data of the next HARQ process ID (i.e., #4) in the second extended UL subframe 2104. Since there are no more extended UL subframes, the UE has no transmission opportunity for HARQ process ID # 5.

Since all LBTs in the allocated first and second UL subframes (i.e., subframes #5 and #6) (2112) failed and LBTs succeeded in the allocated end UL subframe (i.e., subframe #7), the UE may transmit UL data for HARQ process ID # 5. Since there is an unused HARQ process ID, the UE attempts LBT for the following first extended UL subframe 2104, and if LBT succeeds, the UE transmits UL data by using HARQ process ID # 3. Next, the UE succeeds in LBT for the second extended UL subframe 2104 and transmits UL data by using HARQ process ID # 4.

As shown in fig. 21, if the UE transmits UL data for a HARQ process ID different from the HARQ process ID indicated by the eNB in a specific extended UL subframe, i.e., a HARQ process ID that is not transmitted in the originally allocated UL subframe, the eNB needs to identify the changed HARQ process ID in the corresponding extended UL subframe. For example, the eNB receives a retransmission of UL data by using the first HARQ process ID of the HARQ process ID(s) that failed transmission in the non-extended UL subframe(s).

Fig. 22 is a flowchart illustrating an operation of an eNB for performing multi-frame resource allocation according to an embodiment of the present disclosure.

Referring to fig. 22, in operation 2205, an eNB determines whether to allocate resources of a plurality of subframes (or frames) to a UE to support UL transmission in an unlicensed frequency band. If it is determined that resources for the plurality of sub-frames are allocated, the eNB generates a resource assignment signal indicating resource allocation for the resources for the plurality of sub-frames in operation 2210. On the other hand, if it is determined that there is no need to allocate resources of a plurality of sub-frames, the eNB generates a resource assignment signal indicating resource allocation for resources of a single sub-frame in operation 2225. In operation 2215, the eNB sends a resource assignment signal to the UE through at least one UL grant or other control signal. The transmission of the resource assignment signal may be performed by at least one of the above embodiments. The eNB may also transmit additional information, e.g., start information and/or end (length) information and transmission parameters, required for the UE to transmit UL data using the unlicensed frequency band through a UL grant or other control signal. In operation 2220, the eNB receives UL data from the UE through the unlicensed frequency band during the sub-frame(s) allocated based on the transmitted information.

Fig. 23 is a flowchart illustrating an operation of a UE for receiving a multi-frame resource allocation according to an embodiment of the present disclosure.

Referring to fig. 23, in operation 2305, the UE receives a resource assignment signal from the eNB through a UL grant or other control signal. In operation 2310, the UE determines whether a plurality of subframes have been allocated based on the received signal. If a plurality of sub-frames have been allocated, the UE determines resource locations of the allocated plurality of sub-frames based on the resource assignment signal and other control signals in operation 2315. On the other hand, if multiple sub-frames have not been allocated, the UE identifies a resource location of the allocated single sub-frame based on the timing of receipt of the resource assignment signal or other control signals in operation 2325. The identification of the resource location may be performed by at least one of the above embodiments. In operation 2320, the UE transmits UL data to the eNB over the unlicensed frequency band during the subframe(s) allocated based on the received signal.

[ Block ACK ]

There may be various cases as shown in table 3 depending on which of the PCell and SCell to be used by the UE transmits a channel measurement report for the RS or transmits ACK/NACK feedback for data transmission.

[ Table 3]

	Channel measurement reporting	ACK/NACK feedback
			Case I-1	PCell	PCell
Case I-2	PCell	SCell
			Case II-1	SCell	PCell
Case II-2	SCell	SCell

If the LAA system is configured in the FDD mode, one frequency band may be set for one of DL and UL, so that one shared frequency band is basically set for DL in a general case. In the FDD mode, another shared frequency band to be set for the UL is required, and thus an operation of simultaneous radio resource access to at least two shared frequency bands is required. That is, the UE must operate in two or more shared frequency bands. According to the operation of CA or hybrid networks in the current LTE standard, LBT is not easily supported for multiple shared frequency bands. Therefore, in order to avoid such a complicated operation, the UE may perform radio resource access to the UL through the existing PCell.

If the LAA system is configured in TDD mode, both DL and UL can be set in one frequency band, and thus the UE can transmit a channel measurement report or ACK/NACK feedback for the DL subframe in the UL subframe. However, since less UL subframes than DL subframes are set, if the UE fails to obtain resources of UL, UL transmission is delayed to several subframes later. Accordingly, the UE may leave the UL subframe empty or transmit a reservation signal after LBT succeeds before a predetermined time from the next DL subframe. As such, when the UL subframe is not used, the UE may perform UL transmission in the PCell.

To support resource allocation for multiple subframes (or frames), one of the following two feedback procedures may be used.

1) A UE that has received a multi-frame resource assignment signal may send feedback regarding the reception of data for individual resources.

2) A UE that has received a multi-frame resource assignment signal may send block feedback, i.e., a block ACK, regarding the reception of data for multiple resources.

Considering a case where transmission and reception are discontinuously performed according to whether the eNB succeeds or fails in resource occupancy, the feedback must indicate not only success or failure in data reception but also include information on ACK/NACK in resources (subframes or HARQ processes) among a plurality of resources. The eNB stores information on LBT success or failure in a previous subframe and determines whether ACK/NACK reported by the UE corresponds to actual data transmission to appropriately control a retransmission operation with respect to the UE.

[ frequency reuse ]

In the case of FBE, a synchronized eNB may be able to signal using frequency reuse (i.e., reuse-1 specified in LTE). Reuse-1 of LTE means that all neighboring enbs maximize spectral efficiency by using the same frequency channel. The CCA period for performing LBT is configured at the same timing so that the UE can receive a signal from the serving eNB at a timing when the neighboring eNB does not transmit a signal. Therefore, if the frequency channel is empty due to LBT, the eNB simultaneously performs transmission in the frequency channel.

However, in case of LBE, eNB uses a backoff counter (back-off counter) set randomly, thereby performing LBT at different timings. Thus, if a neighboring eNB is already transmitting signals in a particular frequency channel, the eNB may not perform transmission and may be able to perform ECCA after the frequency channel becomes empty. Even if enbs belonging to mobile network operators with the same Public Land Mobile Network (PLMN) are synchronized with each other, it may not be possible to use reuse-1 if the above problem is not solved.

To this end, the signals of the enbs may be configured such that the UE may distinguish the signals of enbs belonging to the same mobile network operator. In an embodiment, an eNB with successful LBT may include a cell ID and a PLMN ID in the transmission signal. In order to include the cell ID and the PLMN ID in the transmission signal, the transmission signal from the eNB needs to include at least 67 μ s (microseconds) of Orthogonal Frequency Division Multiplexing (OFDM) or single carrier frequency division multiple access (SC-FDMA) symbols. Therefore, even if the shortest possible signal is configured, the eNB's signal is longer than the shortest 20 μ s CCA period.

To solve this problem, a transmitter (eNB or UE) stores a channel strength value or a reception power value received in a CCA period in a memory while attempting to receive a signal from a neighboring eNB. If a signal from at least one neighbor eNB is received, the transmitter calculates a power value of the received signal and removes a sum of power values received from the at least one neighbor eNB from previously stored reception power values calculated with channel strength values received during the CCA period or previously stored reception power values. In this way, the transmitter readjusts the backoff counter according to the reception power value calculated as a result of LBT during a plurality of CCA periods. The sum of the received power values from the neighboring enbs may be averaged over a predetermined time period. The average sum of the reception power values is used to adjust the reception power value calculated in the subsequent CCA period. Once the backoff counter becomes 0 by repeating such an operation, the transmitter may transmit a signal.

To achieve reuse-1 without separating signals received from neighboring enbs, network-based control may be performed as described below.

A Mobility Management Entity (MME) or a control server in an operator network sets a plurality of enbs into a group. The eNB exchanges information with other enbs in the same group through an MME or control server or X2 interface.

An embodiment for supporting frequency reuse in communications using unlicensed frequency bands will be described below.

1) The MME or control server randomly determines the value N of the backoff counter for a specific eNB group in the range of [0, N ]. The value n of the backoff counter may also be determined by a representative eNB in the eNB group or a representative eNB in multiple eNB groups. The multiple enbs or groups of enbs may be co-located or located in different locations.

2) The MME or the control server informs the other (k-1) eNBs in the same group of the value n of the backoff counter. Such other enbs determine to use the backoff counter value n for LBT. The value n of the backoff counter may also be set to the other (k-1) enbs by the eNB group or a representative eNB in the eNB group.

3) Each eNB performs LBT in an ECCA period based on a backoff counter, which is decreased if the channel is empty (idle).

4) The eNB that recognizes that the channel is occupied (busy) during the ECCA period stores the current backoff counter and freezes the LBT operation, and then reports the freezing of LBT to the MME, the control server, or a representative eNB in the eNB group(s). The report of the LBT freeze may include a stored value of a backoff counter.

5-1) among k eNBs forming the eNB group, it is determined that all eNBs having the LBT result free perform DL transmission again until the backoff counter becomes 0 and return to 1). The eNB having performed DL transmission reports to the MME, the control server, or a representative eNB in the eNB group that the eNB has performed DL transmission.

5-2) if all k enbs report an LBT freeze in the ECCA period, the MME, control server, or representative eNB in the eNB group indicates the minimum backoff counter value among backoff count values reported from enbs belonging to the eNB group to the k enbs to readjust backoff counter values of other enbs to the minimum backoff counter value. Each eNB instructed to readjust the backoff counter value does 3) to recover LBT.

[ multiple UL grants and data Transmission procedure ]

Fig. 24 is a flowchart illustrating a process for transmitting multiple UL (M-UL) grants and data according to an embodiment of the present disclosure.

Referring to fig. 24, in operation 2405, an eNB transmits an M-UL grant for allocating a plurality of UL subframes #1, #2, #3, and #4 communicable through an unlicensed band to a UE. Immediately before UL subframe #1, the UE performs LBT for CCA or ECCA and succeeds 2410, and transmits UL data #1 and #2 during UL subframes #1 and # 2. If the basic unit of multi-subframe scheduling is set to 2 subframes, the UE performs LBT2415 for CCA or ECCA again immediately before UL subframe #3, and if LBT succeeds, UL data #3 and #4 are transmitted during UL subframes #3 and # 4. In operation 2420, the eNB transmits block ACK/NACK for the received UL data #1, #2, #3, and # 4. The block ACK/NACK indicates reception success/failure with respect to UL data #1, #2, #3, and # 4.

In operation 2425, the eNB transmits an M-UL grant for allocating a plurality of UL subframes #1, #2, #3, and #4 communicable through the unlicensed frequency band to the UE. Immediately before UL subframe #1, the UE attempts LBT 2435 for CCA or ECCA, but LBT fails. Then, the UE waits during UL subframes #1 and #2 without performing transmission. If LBT for CCA or ECCA is attempted immediately before UL subframe #3 and LBT succeeds 2435, the UE transmits UL data #3 and #4 during UL subframes #3 and #4 and receives block ACK/NACK 2440 from the eNB. Meanwhile, if ACK/NACK is transmitted to the PCell instead of the SCell, the existing ACK/NACK feedback procedure is used.

Fig. 25 is a flowchart illustrating an operation of an eNB for transmitting block ACK/NACK according to an embodiment of the present disclosure.

Referring to fig. 25, an eNB generates an M-UL grant for a UE in operation 2505 and transmits the M-UL grant in operation 2510. In operation 2515, the eNB receives UL data in the resource location allocated through the M-UL grant, and determines whether the eNB successfully receives the UL data in operation 2520. If the UL data has been successfully received, the eNB stores the presence or absence of an error of the UL data in operation 2525 and proceeds to operation 2530. In operation 2530, the eNB transmits block ACK/NACK indicating the presence or absence of an error to the UE on a subframe basis.

Meanwhile, if UL data is not received in operation 2520 or after information on the presence or absence of an error is stored in operation 2525, the eNB determines whether there is still allocated UL subframe(s) in operation 2535. If there are more allocated UL subframe(s), the eNB moves to the next allocated location in operation 2540 and proceeds to operation 2515.

Fig. 26 is a flowchart illustrating an operation of a UE for transmitting block ACK/NACK according to an embodiment of the present disclosure.

Referring to fig. 26, in operation 2605, the UE receives an M-UL grant and identifies an allocated UL subframe by using the M-UL grant and other control signals if necessary. The UE attempts LBT for CCA or ECCA immediately before the allocated UL subframe in operation 2610, and determines whether the LBT of the UE is successful in operation 2615. If the LBT is successful, the UE transmits UL data during at least one subsequent UL subframe in operation 2620 and proceeds to operation 2625. On the other hand, if the LBT fails, the UE directly proceeds to operation 2625.

The UE determines in operation 2625 whether a next CCA is set, and if the next CCA is not set, the UE proceeds to operation 2635 to receive a block ACK/NACK for the transmitted UL data. On the other hand, if the next CCA is set, the UE moves to a time period for the next CCA in operation 2630 and proceeds to operation 2610.

[ scheduling of hidden nodes ]

Fig. 27 is a view for describing a hidden node problem of a Wi-Fi network according to an embodiment of the present disclosure.

Referring to fig. 27, when the UE2704 receives a signal from the eNB 2702, the UE2704 may also receive a signal from the Wi-Fi AP 2706 at a location where the UE2704 may not be able to sense the signal from the eNB 2702, and the signal from the AP 2706 acts as interference to a desired signal (i.e., a signal from a serving eNB). Since the eNB 2702 can operate as a hidden node of the AP 2706 in this way, such a problem will be referred to as a hidden node problem.

To mitigate the hidden node problem in the channel measurement of the UE, the UE may consider whether the eNB occupies resources during the channel measurement.

Therefore, the UE can perform channel measurement for three cases provided below. The channel measurement result may include a Reference Signal Received Power (RSRP) with respect to a signal of the serving eNB, a signal-to-interference-and-noise ratio (SINR) including the signal and interference of the serving eNB, a Reference Signal Received Quality (RSRQ), or a Received Signal Strength Indicator (RSSI).

1) When the eNB occupies resources and the UE is allocated resources, the UE performs channel measurement and measures all of the CRS-based RSRP, the DRS-based RSRP, RSRQ, and RSSI.

2) When the eNB occupies resources but the UE does not allocate resources, the UE performs channel measurement and measures CRS-based RSRP and RSSI.

3) When the eNB does not occupy resources and the UE does not allocate resources, the UE performs channel measurement and measures RSSI.

If a hidden node is present, in case 1) and 2), the SINR is given by (signal power of serving eNB)/{ (interfering signal power of hidden node) + (noise power) }. For 3), there is no serving eNB signal, so that the UE can measure { (full signal power) + (noise power) }. The UE may distinguish RSSI _ accounted measured at a timing when the eNB occupies the resource from RSSI _ unoccupied measured at a timing when the eNB does not occupy the resource, calculate a difference RSSI _ gap between RSSI _ accounted and RSSI _ unoccupied, and correct the CQI value in consideration of the RSSI _ gap when measuring SINRs of cases 1) and 2).

Fig. 28 is a block diagram of a UE device according to an embodiment of the disclosure.

Referring to fig. 28, a UE 2800 may include a transceiver 2810 and a controller 2830 for controlling an operation of the UE 2800, the transceiver 2810 including a transmitter 2815 and a receiver 2820 for performing signal transmission and reception with another device (e.g., an eNB). In the present disclosure, embodiments of resource allocation for unlicensed bands may be construed as being performed by the controller 2830. However, the controller 2830 and the transceiver 2810 need not be implemented as separate modules, and may be implemented as one component in the form of a single chip, for example.

Referring to fig. 29, an eNB 2900 may include a transceiver 2910, and a controller 2930 for controlling operations of the UE 2900, the transceiver 2910 including a transmitter 2915 and a receiver 2920 for performing signal transmission and reception with another device (e.g., a UE or another eNB). In the present disclosure, the embodiment of resource allocation for unlicensed bands may be construed as being performed by the controller 2930. However, the controller 2930 and the transceiver 2910 need not be implemented as separate modules, and may be implemented as one component in the form of a single chip, for example.

It should be noted that the LAA control/data signaling scheme, the operation procedure of the LAA UE, the resource frame configuration, and the structures of the UE and eNB devices are not intended to limit the scope of the present disclosure. All the elements or operations described with reference to fig. 1 to 29 should not be construed as essential elements for implementing the present disclosure, and it may be implemented within a range not to destroy the gist of the present disclosure even including some elements.

The above-described operations of the BS or UE may be implemented by including a memory device storing corresponding program codes in elements of a transmitter, a receiver, the BS or the UE. That is, the controller of the BS or UE performs the above-described operations by reading and executing program codes stored in the memory device by means of a processor or a Central Processing Unit (CPU).

As described herein, various components or modules in an entity, eNB, or UE may operate using hardware circuitry, e.g., complementary metal oxide semiconductor-based logic circuitry, firmware, software, and/or using hardware circuitry, such as a combination of hardware, firmware, and/or software embedded in a machine-readable medium. For example, various electronic configurations and methods may be performed using electronic circuits such as transistors, logic gates, and Application Specific Integrated Circuits (ASICs).

While the embodiments of the present disclosure have been described, various changes may be made without departing from the scope of the present disclosure. Accordingly, the scope of the disclosure should be determined by the appended claims and their equivalents rather than by the described embodiments.

Claims

1. A method for allocating resources for an unlicensed frequency band in a cellular network, the method comprising:

transmitting downlink control information in a Downlink (DL) subframe, the downlink control information including second information indicating a number of a plurality of scheduled Uplink (UL) subframes in an unlicensed frequency band;

receiving uplink data in a scheduled uplink subframe of an unlicensed frequency band,

wherein the scheduled uplink subframe is determined based on the information indicating the number of the plurality of scheduled UL subframes.

2. The method of claim 1, wherein the scheduled UL subframe is indicated by at least one of the following combinations: UE-specific start information and UE-specific end or length information, UE-specific start information and common end or length information for consecutive UL subframes, common start information and UE-specific end or length information for consecutive UL subframes, and common start information and common end or length information for consecutive UL subframes.

3. The method of claim 1, wherein the scheduled uplink subframes are consecutive scheduled uplink subframes.

4. The method of claim 2, wherein the start information is transmitted through a UL grant, common or dedicated DL Control Information (DCI) of a physical layer, or a Medium Access Control (MAC) Control Element (CE), and

the end or length information is transmitted through a MAC CE, Radio Resource Control (RRC) signaling, a higher layer control signal of a data region, or a System Information Block (SIB) of a Broadcast Channel (BCH).

5. The method of claim 1, wherein the downlink control information further comprises a same hybrid automatic repeat request (HARQ) process Identifier (ID) or different HARQ process IDs allocated to a plurality of consecutive UL subframes, and

each of the plurality of HARQ process IDs is fixedly allocated for a respective UL subframe or is available in another UL subframe.

6. A method for receiving resource allocations for an unlicensed frequency band in a cellular network, the method comprising:

receiving downlink control information in a Downlink (DL) subframe from a base station, the downlink control information including second information indicating a number of a plurality of scheduled Uplink (UL) subframes in an unlicensed frequency band;

determining a scheduled UL subframe based on the information indicating the number of the plurality of scheduled UL subframes; and is

Transmitting UL data to the base station during the scheduled UL subframe.

7. The method of claim 6, wherein the scheduled UL subframe is indicated by at least one of the following combinations: UE-specific start information and UE-specific end or length information, UE-specific start information and common end or length information for consecutive UL subframes, common start information and UE-specific end or length information for consecutive UL subframes, and common start information and common end or length information for consecutive UL subframes.

8. The method of claim 7, wherein the scheduled uplink subframes are consecutive scheduled uplink subframes.

9. The method of claim 7, wherein the start information is transmitted through a UL grant, common or dedicated DL Control Information (DCI) of a physical layer, or a Medium Access Control (MAC) Control Element (CE), and

10. The method of claim 6, wherein the downlink control information further comprises a same hybrid automatic repeat request (HARQ) process Identifier (ID) or different HARQ process IDs allocated to a plurality of consecutive UL subframes, and

11. The method of claim 6, further comprising:

performing Listen Before Talk (LBT) for using a first subframe among consecutive UL subframes; and

determining that UL communication over the unlicensed frequency band is possible during the first subframe or a predetermined number of subframes including the first subframe and the first subframe if the LBT is successful,

wherein the timing of performing LBT is determined based on at least one of: a timing at which the resource assignment signal is received, a start timing of an occupiable UL subframe for communication over the unlicensed frequency band, a start timing of an occupiable DL subframe for communication over the unlicensed frequency band, and a frame start timing of the licensed frequency band.

12. A base station for allocating resources for an unlicensed frequency band in a cellular network, the base station comprising:

a controller; and

a transceiver configured to:

receiving UL data in a scheduled UL subframe of an unlicensed frequency band,

13. A User Equipment (UE) for receiving resource allocations for an unlicensed frequency band in a cellular network, the UE comprising:

a transceiver configured to receive downlink control information in a Downlink (DL) subframe from a base station, the downlink control information including second information indicating a number of a plurality of scheduled Uplink (UL) subframes in an unlicensed frequency band, and transmit UL data to the base station during the scheduled UL subframes; and

a controller configured to determine a scheduled UL subframe based on the information indicating the number of the plurality of scheduled UL subframes, and to notify the transceiver of the identified scheduled UL subframe.

14. The base station of claim 12, wherein the scheduled UL subframe is indicated by at least one of the following combinations: UE-specific start information and UE-specific end or length information, UE-specific start information and common end or length information for consecutive UL subframes, common start information and UE-specific end or length information for consecutive UL subframes, and common start information and common end or length information for consecutive UL subframes.

15. The base station of claim 12, wherein the scheduled uplink subframes are consecutive scheduled uplink subframes.

16. The base station of claim 14, wherein the start information is transmitted through a UL grant, common or dedicated DL Control Information (DCI) of a physical layer, or a Medium Access Control (MAC) Control Element (CE), and

17. The base station of claim 12, wherein the downlink control information further includes a same hybrid automatic repeat request (HARQ) process Identifier (ID) or different HARQ process IDs allocated to a plurality of consecutive UL subframes, and

18. The UE of claim 13, wherein the scheduled UL subframe is indicated by at least one of the following combinations: UE-specific start information and UE-specific end or length information, UE-specific start information and common end or length information for consecutive UL subframes, common start information and UE-specific end or length information for consecutive UL subframes, and common start information and common end or length information for consecutive UL subframes.

19. The UE of claim 13, wherein the scheduled uplink subframes are consecutive scheduled uplink subframes.

20. The UE of claim 18, wherein the start information is transmitted through an UL grant, common or dedicated DL Control Information (DCI) of a physical layer, or a Medium Access Control (MAC) Control Element (CE), and

21. The UE of claim 13, wherein the downlink control information further includes a same hybrid automatic repeat request (HARQ) process Identifier (ID) or a different HARQ process ID allocated to a plurality of consecutive UL subframes, and

22. The UE of claim 13, wherein the controller is further configured to: