TECHNICAL FIELD

The present invention relates to a wireless communication system. Specifically, the present invention relates to a channel access method and a device using the same in a wireless communication system operating in an unlicensed band.

BACKGROUND ART

After commercialization of 4th generation (4G) communication system, in order to meet the increasing demand for wireless data traffic, efforts are being made to develop new 5th generation (5G) communication systems. The 5G communication system is called as a beyond 4G network communication system, a post LTE system, or a new radio (NR) system. In order to achieve a high data transfer rate, 5G communication systems include systems operated using the millimeter wave (mmWave) band of 6 GHz or more, and include a communication system operated using a frequency band of 6 GHz or less in terms of ensuring coverage so that implementations in base stations and terminals are under consideration.

A 3rd generation partnership project (3GPP) NR system enhances spectral efficiency of a network and enables a communication provider to provide more data and voice services over a given bandwidth. Accordingly, the 3GPP NR system is designed to meet the demands for high-speed data and media transmission in addition to supports for large volumes of voice. The advantages of the NR system are to have a higher throughput and a lower latency in an identical platform, support for frequency division duplex (FDD) and time division duplex (TDD), and a low operation cost with an enhanced end-user environment and a simple architecture.

For more efficient data processing, dynamic TDD of the NR system may use a method for varying the number of orthogonal frequency division multiplexing (OFDM) symbols that may be used in an uplink and downlink according to data traffic directions of cell users. For example, when the downlink traffic of the cell is larger than the uplink traffic, the base station may allocate a plurality of downlink OFDM symbols to a slot (or subframe). Information about the slot configuration should be transmitted to the terminals.

In order to alleviate the path loss of radio waves and increase the transmission distance of radio waves in the mmWave band, in 5G communication systems, beamforming, massive multiple input/output (massive MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beam-forming, hybrid beamforming that combines analog beamforming and digital beamforming, and large scale antenna technologies are discussed. In addition, for network improvement of the system, in the 5G communication system, technology developments related to evolved small cells, advanced small cells, cloud radio access network (cloud RAN), ultra-dense network, device to device communication (D2D), vehicle to everything communication (V2X), wireless backhaul, non-terrestrial network communication (NTN), moving network, cooperative communication, coordinated multi-points (CoMP), interference cancellation, and the like are being made. In addition, in the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC), which are advanced coding modulation (ACM) schemes, and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA), which are advanced connectivity technologies, are being developed.

Meanwhile, in a human-centric connection network where humans generate and consume information, the Internet has evolved into the Internet of Things (IoT) network, which exchanges information among distributed components such as objects. Internet of Everything (IoE) technology, which combines IoT technology with big data processing technology through connection with cloud servers, is also emerging. In order to implement IoT, technology elements such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology are required, so that in recent years, technologies such as sensor network, machine to machine (M2M), and machine type communication (MTC) have been studied for connection between objects. In the IoT environment, an intelligent internet technology (IT) service that collects and analyzes data generated from connected objects to create new value in human life can be provided. Through the fusion and mixture of existing information technology (IT) and various industries, IoT can be applied to fields such as smart home, smart building, smart city, smart car or connected car, smart grid, healthcare, smart home appliance, and advanced medical service.

Accordingly, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as a sensor network, a machine to machine (M2M), and a machine type communication (MTC) are implemented by techniques such as beamforming, MIMO, and array antennas. The application of the cloud RAN as the big data processing technology described above is an example of the fusion of 5G technology and IoT technology. Generally, a mobile communication system has been developed to provide voice service while ensuring the user's activity.

However, the mobile communication system is gradually expanding not only the voice but also the data service, and now it has developed to the extent of providing high-speed data service. However, in a mobile communication system in which services are currently being provided, a more advanced mobile communication system is required due to a shortage phenomenon of resources and a high-speed service demand of users.

In recent years, with the explosion of mobile traffic due to the spread of smart devices, it is becoming difficult to cope with the increasing data usage for providing cellular communication services using only the existing licensed frequency spectrums or licensed frequency bands.

In such a situation, a method of using an unlicensed frequency spectrum or an unlicensed frequency band (e.g., 2.4 GHz band, 5 GHz band, 6 GHz band, 52.6 GHz or higher band, or the like) for providing cellular communication services is being discussed as a solution to the problem of lack of spectrum.

Unlike in licensed bands in which telecommunications carriers secure exclusive use rights through procedures such as auctions, in unlicensed bands, multiple communication devices may be used simultaneously without restrictions on the condition that only a certain level of adjacent band protection regulations are observed. For this reason, when an unlicensed band is used for cellular communication service, it is difficult to guarantee the communication quality to the level provided in the licensed band, and it is likely that interference with existing wireless communication devices (e.g., wireless LAN devices) using the unlicensed band occurs.

In order to use LTE and NR technologies in unlicensed bands, research on coexistence with existing devices for unlicensed bands and efficient sharing of wireless channels with other wireless communication devices is to be conducted in advance. That is, it is required to develop a robust coexistence mechanism (RCM) such that devices using LTE and NR technologies in the unlicensed band do not affect the existing devices for unlicensed bands.

DISCLOSURE

Technical Problem

An object of an embodiment of the present invention is to provide a channel access method and a device using the same for performing transmission in a wireless communication system operating in an unlicensed band.

Technical Solution

According to an embodiment of the present invention, a user equipment (UE) wirelessly communicating with a base station in an unlicensed band includes a communication module and a processor controlling the communication module. The processor may be configured to receive a grant for scheduling a plurality of uplink transmissions from the base station, and when the UE attempts a first fixed duration-based channel access for a first transmission which is one of the plurality of uplink transmissions and fails in the first fixed duration-based channel access, may be configured to attempt a second fixed duration-based channel access for a second transmission which is a transmission following the first transmission. The first fixed duration-based channel access is a channel access in which, when a channel is sensed to be idle within a first fixed duration, the UE performing the first fixed duration-based channel access is allowed to perform a transmission immediately after the first fixed duration. The second fixed duration-based channel access is a channel access in which, when the channel is sensed to be idle within a second fixed duration, the UE performing the second fixed duration-based channel access is allowed to perform a transmission immediately after the second fixed duration.

The first fixed duration may be shorter than the second fixed duration.

The first fixed duration may be 16 μs, and the second fixed duration may be 25 μs. The grant may indicate a fixed duration-based channel access as a channel access type, and indicate a channel access priority used to access a channel in which the plurality of uplink transmissions are performed.

The grant may indicate the first fixed duration-based channel access as the channel access type.

The grant may include one or more grants for scheduling the plurality of uplink transmissions, and the plurality of uplink transmissions may be contiguous without a gap in time.

According to an embodiment of the present invention, a base station wirelessly communicating with a UE in an unlicensed band includes a communication module and a processor controlling the communication module. The processor may be configured to perform a transmission to the UE immediately after a gap between a transmission of the UE and the transmission to the UE without sensing within a maximum channel occupancy time in a channel in which the transmission of the UE is performed, when a duration of the transmission of the UE is less than the maximum channel occupancy time and the gap is not greater than a first fixed duration. In this case, the first fixed duration is 16 μs.

The processor may be configured to perform the transmission to the UE immediately after the gap between the transmission of the UE and the transmission to the UE without sensing within a predetermined duration when the gap is not greater than the first fixed duration, and the predetermined duration may be a constraint applied to the transmission of the base station separately from the maximum channel occupancy time.

The processor may be configured to attempt a first fixed duration-based channel access in a channel in which the transmission of the UE is performed when the gap between the transmission of the UE and the transmission to the UE is equal to the first fixed duration. The first fixed duration-based channel access may be a channel access in which, when the channel is sensed to be idle within a first fixed duration, the base station performing the first fixed duration-based channel access is allowed to perform an transmission immediately after the first fixed duration.

The processor may be configured to attempt the second fixed duration-based channel access in a channel in which the transmission of the UE is performed when the gap between the transmission of the UE and the transmission to the UE is not greater than the second fixed duration. The second fixed duration-based channel access may be a channel access in which, when the channel is sensed to be idle during a second fixed duration, the base station performing the second fixed duration-based channel access is allowed to perform a transmission immediately after the second fixed duration. In this case, the second fixed duration is 25 μs.

Channel occupancy including the transmission of the UE and the transmission of the base station to the UE may be initiated by the base station.

Channel occupancy including the transmission of the UE and the transmission of the base station to the UE may be initiated by the UE.

According to an embodiment of the present invention, a method for operating a UE wirelessly communicating with a base station in the unlicensed band may include: receiving a grant for scheduling a plurality of uplink transmissions from the base station; and when the UE attempts a first fixed duration-based channel access for a first transmission which is one of the plurality of uplink transmissions and fails in the first fixed duration-based channel access, attempting a second fixed duration-based channel access for a second transmission which is a transmission following the first transmission. In this case, the first fixed duration-based channel access may be a channel access in which, when the channel is sensed to be idle within a first fixed duration, the UE performing the first fixed duration-based channel access is allowed to perform a transmission immediately after the first fixed duration, and the second fixed duration-based channel access may be a channel access in which, when the channel is sensed to be idle during a second fixed duration, the UE performing the second fixed duration-based channel access is allowed to perform a transmission immediately after the second fixed duration.

The first fixed duration may be shorter than the second fixed duration.

The first fixed duration may be 16 μs, and the second fixed duration may be 25 μs.

The grant may indicate a fixed duration-based channel access as a channel access type, and may indicate a channel access priority used to access a channel in which the plurality of uplink transmissions are performed.

The grant may indicate the first fixed duration-based channel access as the channel access type.

The grant may include one or more grants for scheduling the plurality of uplink transmissions, and the plurality of uplink transmissions may continue without a gap in time.

According to an embodiment of the present invention, a method for operating a base station wirelessly communicating with a UE in an unlicensed band includes performing a transmission to the UE immediately after a gap between a transmission of the UE and the transmission to the UE without sensing within a maximum channel occupancy time in a channel in which transmission of the UE is performed, when a duration of the transmission of the UE is less than the maximum channel occupancy time and the gap is not greater than a first fixed duration. In this case, the first fixed duration is 16 μs.

The method may further include performing the transmission to the UE immediately after the gap between the transmission of the UE and the transmission to the UE without sensing within a predetermined duration when the gap is not greater than the first fixed duration. In this case, the predetermined duration may be a constraint applied to the transmission of the base station separately from the maximum channel occupancy time.

The method may further include attempting the first fixed duration-based channel access in a channel in which the transmission of the UE is performed when the gap between the transmission of the UE and the transmission to the UE is equal to the first fixed duration. In this case, the first fixed duration-based channel access may be a channel access in which, when the channel is sensed to be idle within a first fixed duration, the base station performing the first fixed duration-based channel access is allowed to perform a transmission immediately after the first fixed duration.

The method may further include attempting the second fixed duration-based channel access in a channel in which the transmission of the UE is performed when the gap between the transmission of the UE and the transmission to the UE is not greater than the second fixed duration. In this case, the second fixed duration-based channel access may be a channel access in which, when the channel is sensed to be idle during a second fixed duration, the base station performing the second fixed duration-based channel access is allowed to perform a transmission immediately after the second fixed duration. Furthermore, the second fixed duration may be 25 μs.

Channel occupancy including the transmission of the UE and the transmission of the base station to the UE may be initiated by the base station.

Channel occupancy including the transmission of the UE and the transmission of the base station to the UE may be initiated by the UE.

Advantageous Effects

An embodiment of the present invention provides a channel access method and a device using the same for performing transmission in a wireless communication system operating in an unlicensed band.

The effect to be achieved by the present invention is not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those of ordinary skill in the art from the following description.

