WO2016182238A1

WO2016182238A1 - Method and device for transmitting adaptive partial subframe in unlicensed frequency band, method and device for dividing frame structure, and method and device for transmitting signal

Info

Publication number: WO2016182238A1
Application number: PCT/KR2016/004568
Authority: WO
Inventors: 윤찬호; 고영조; 백승권; 김은경
Original assignee: 한국전자통신연구원
Priority date: 2015-05-12
Filing date: 2016-04-29
Publication date: 2016-11-17

Abstract

Provided is a method for a transmitter transmitting a signal through an unlicensed band channel. If an unlicensed band channel is in an idle state, a transmitter transmits, through the unlicensed band channel, an initial signal for preempting the unlicensed band channel. According to the time point of transmission of the initial signal, the transmitter includes in a frame burst a first partial subframe to be transmitted after the initial signal. Further, the transmitter transmits the frame burst through the unlicensed band channel.

Description

Method and apparatus for transmitting adaptive partial subframe in unlicensed frequency band, method and apparatus for classifying frame structure, and method and apparatus for transmitting signal

The present invention relates to a method and apparatus for transmitting an adaptive partial subframe in a wireless communication cellular system in an unlicensed frequency band, a method and apparatus for classifying a frame structure, and a method and apparatus for transmitting a signal.

Conventional long term evolution (LTE) cellular networks have been operated only in licensed bands. Despite the development of technology to continuously increase capacity, as the demand for high capacity and high speed data services increases, the LTE standard is not limited to the existing licensed band but accommodates an unlicensed band rich in frequency bandwidth. To increase capacity. This capacity increase plan is currently in the 3rd generation partnership project (3GPP) standardization stage.

However, for the unlicensed band, unlike licensed bands that are not disturbed by other operators or other devices and have a high degree of freedom, coexistence with devices operating in other unlicensed bands should be solved. In other words, there is a need for a channel access and occupancy type in which a device can use the channel for a limited time when the opportunity is given without significantly reducing the performance of other devices on the same unlicensed channel.

In order to solve this coexistence problem, a method known as a 'carrier after transmission method' (eg, clear channel assessment (CCA) or listen before talk (LBT)) is widely used. The channel approach is first made by channel monitoring. That is, the device detects activity of an unlicensed band channel that is shared with other devices, and if the energy of the channel is measured, suspends transmission of the radio signal, and conversely, if the energy of the channel is not detected (that is, channel idle state) ), Use the channel (wireless signal transmission or output).

When the device detects an idle state of a channel and transmits a signal, other devices sense energy on the channel and determine that the channel is busy and suspend transmission of the signal. That is, the channel access method of the unlicensed band may be one type of time-division multiple access scheme in which time is divided so that a plurality of devices access a wireless channel.

In addition, the LTE frame of the unlicensed band should be time synchronized with the LTE frame operating in the licensed band. There is a need for a technique for improving signal transmission efficiency in the presence of such constraints.

An object of the present invention is to provide a method and apparatus for improving signal transmission efficiency in an unlicensed band.

According to an embodiment of the present invention, a method is provided by a transmitter for transmitting a signal over a channel in an unlicensed band. The transmitting method of the transmitter may include transmitting an initial signal for preempting the unlicensed band channel through the unlicensed band channel when the unlicensed band channel is in an idle state; Including a first partial subframe to be transmitted after the initial signal in a frame burst according to a transmission time of the initial signal; And transmitting the frame burst over the unlicensed band channel.

The transmitting of the initial signal may include transmitting the initial signal immediately without waiting for a start time of a time domain symbol when the unlicensed band channel is in an idle state.

Including the first partial subframe in the frame burst may include including a second partial subframe at an end of the frame burst according to a transmission time of the initial signal.

The first partial subframe may have one of a time length corresponding to one slot and a time length corresponding to a time shifted downlink pilot time slot (DwPTS).

The second partial subframe may have a time length corresponding to DwPTS.

The initial signal may include a reservation signal having a variable length.

Generating the time domain sequence includes converting the physical cell ID of the transmitter to binary; And generating the frequency domain sequence including, as an element, a value corresponding to each digit of the binary number among (1 + j) and (-1-j).

The time taken to transmit the 128 time domain sequences for the reservation signal may be equal to the transmission time of one orthogonal frequency division multiplexing (OFDM) symbol except for a cyclic prefix (CP).

The initial signal may include a reservation signal and a synchronization reference signal transmitted after the reservation signal.

The transmitting of the initial signal may include generating the sync reference signal having a time length corresponding to one orthogonal frequency division multiplexing (OFDM) symbol.

The step of including the first partial subframe in the frame burst, the transmission time of the initial signal is 1st, 2nd, 3rd, 4th, 5th, or 14 out of 14 orthogonal frequency division multiplexing (OFDM) symbols In the case of the sixth OFDM symbol, the method may include generating the first partial subframe having a time length corresponding to one slot.

Including the second partial subframe at the end of the frame burst, the transmission time of the initial signal except for the first, second, and third OFDM symbols out of 14 orthogonal frequency division multiplexing (OFDM) symbols In the case of, the method may include generating the second partial subframe.

The step of including the first partial subframe in the frame burst corresponds to 12 OFDM symbols when the transmission time of the initial signal corresponds to the first OFDM symbol among 14 orthogonal frequency division multiplexing (OFDM) symbols. Generating the first partial subframe having a length of time; And generating the first partial subframe having a time length corresponding to seven OFDM symbols when the transmission time of the initial signal corresponds to the sixth OFDM symbol among the 14 OFDM symbols.

The including the first partial subframe in the frame burst may include configuration information for a first subframe in which a first indicator is transmitted and for a second subframe following the first subframe. Generating the first indicator indicating setting information; And including the first indicator in the frame burst.

The first subframe may be one of a partial subframe and a full subframe.

The first indicator may indicate at least one of the number of orthogonal frequency division multiplexing (OFDM) symbols occupied in the first subframe and the number of OFDM symbols occupied in the second subframe.

The first indicator may indicate whether the second subframe corresponds to a downlink subframe, a special subframe, or an uplink subframe.

According to another embodiment of the present invention, a method is provided by a transmitter for transmitting a signal through a channel of an unlicensed band. The transmitting method of the transmitter may include transmitting first grant information for transmission of a first receiver through the unlicensed band channel; And transmitting first information indicating a time point at which the first grant information is transmitted through the unlicensed band channel.

The transmitting of the first information may include: a first subframe corresponding to the subframe through which the first grant information is transmitted and having a predetermined value, from among a predetermined number of subframes in the past, based on a time point at which the first information is transmitted; And generating the first information including one bit.

In the transmitting method of the transmitter, when a signal corresponding to the first grant information is not received from the first receiver, second information indicating a time point at which the first grant information is transmitted is transmitted through the unlicensed band channel. It may further comprise the step.

The second information may include a first bit corresponding to a subframe in which the first grant information is transmitted among a predetermined number of subframes in the past based on a time point when the second information is transmitted. can do.

In addition, according to another embodiment of the present invention, a method for transmitting a signal through a channel of the unlicensed band is provided. The transmission method of the terminal may include receiving, from a base station, first grant information for uplink transmission of the terminal through the unlicensed band channel at a first time point; Receiving, from the base station, first information indicating a transmission time point of the first grant information through the unlicensed band channel; And when the transmission time point of the first grant information determined based on the first information coincides with the first time point, transmitting the first uplink signal corresponding to the first grant information through the unlicensed band channel. Transmitting to the base station.

The transmitting of the first uplink signal to the base station may include: generating a first bit corresponding to a subframe in which the first grant information is transmitted and a subframe in which the second grant information is transmitted; Determining a bit order between the first bit and the second bit when including two bits; And determining the transmission order between the second uplink signal corresponding to the second grant information and the first uplink signal based on the bit order.

The transmitting of the first uplink signal to the base station may include: checking a state of the unlicensed band channel for a predetermined time; And when the unlicensed band channel is in an idle state, transmitting the first uplink signal to the base station through the unlicensed band channel.

The predetermined time may be shorter than the time for the base station to check the state of the unlicensed band channel.

According to the exemplary embodiment of the present invention, when the terminal occupies the channel of the unlicensed band, the terminal only needs to confirm the presence or absence of transmission at a predetermined time point, thereby accurately knowing the point of channel occupation. In addition, through this accuracy, the UE can efficiently receive and process the partial subframes transmitted by the base station.

In addition, according to an embodiment of the present invention, in the unlicensed band in which discontinuous transmission is performed according to regulatory requirements (eg, LBT, time limit of maximum continuous transmission), the efficiency of data transmission can be increased.

In addition, according to an embodiment of the present invention, even when uplink and downlink are present together, transmission efficiency of each data link can be improved.

In addition, according to an embodiment of the present invention, a scheduling-based cellular network may preserve a mechanism capable of performing uplink transmission by an indication of a base station in an unlicensed band.

1 is a diagram showing the structure of a radio frame used in a licensed mobile communication system according to an embodiment of the present invention.

2 is a diagram illustrating a method of using an unlicensed band in an LTE system according to an embodiment of the present invention.

3 is a diagram illustrating a structure of a preamble according to an embodiment of the present invention.

4 is a diagram illustrating an example of the signal [w (n)] shown in FIG. 3.

5 is a diagram illustrating a transmission position of an FSTF signal according to an embodiment of the present invention.

6 is a flowchart illustrating a method of generating an FSTF signal according to an embodiment of the present invention.

7 is a diagram illustrating an example of a signal [y (n)] when the available bandwidth is 20 MHz according to an embodiment of the present invention.

FIG. 8 is a diagram showing the frequency spectral density of the signal [y (n)] shown in FIG.

9 illustrates a correlation value of an FSTF signal according to an embodiment of the present invention.

10 illustrates a communication device using an unlicensed band according to an embodiment of the present invention.

11 is a diagram illustrating uplink and downlink multiplexed transmission based on time applied to LTE frame structure-type 2;

12 is a diagram illustrating a timing relationship between UL grant of a licensed band and physical hybrid automatic repeat request indicator channel (PHICH) transmission.

FIG. 13 is a diagram illustrating a problem that may occur when an uplink signal and a downlink signal are transmitted at a preset timing in an unlicensed band.

FIG. 14 is a diagram illustrating a case in which uplink transmission fails or a collision occurs due to a long guard interval in an LTE uplink and downlink frame structure for an unlicensed band.

FIG. 15 is a diagram illustrating a method for reducing a length of a guard interval by transmitting a reservation signal of a variable length after downlink pilot time slot (DwPTS) transmission according to an embodiment of the present invention.

16 is a diagram illustrating a method of adjusting a length of a guard interval by copying a baseband signal of a licensed band according to an embodiment of the present invention.

17 illustrates a TDD-LTE frame format configuration for a LAA when the maximum continuous transmission length is 4 ms according to an embodiment of the present invention.

18 illustrates a structure of a frame format indicator-type 2 according to various bandwidths according to an embodiment of the present invention.

FIG. 19 is a diagram illustrating a cell-specific reference signal (CRS) mapping method on a frequency axis and a modulation method for each symbol when the number of PRBs corresponding to the entire bandwidth is 25 according to an embodiment of the present invention.

20 illustrates a CRS mapping flow after encoding of a frame format indicator according to an embodiment of the present invention.

21 is a diagram illustrating a TDD-LTE frame format configuration for a LAA when the maximum continuous transmission length is 10 ms according to an embodiment of the present invention.

22 is a diagram illustrating a relationship between aggregated uplink transmission time indicator signal (AUTTIS) information and uplink transmission according to an embodiment of the present invention.

FIG. 23 is a diagram illustrating a relationship between an AUTTIS binary bit structure and an UL grant according to an embodiment of the present invention.

24 illustrates a short LBT performed immediately before uplink transmission according to an embodiment of the present invention.

FIG. 25 illustrates a time point at which LBT is performed in an unlicensed band, a time point at which an initial signal is transmitted, a time point at which a partial subframe is transmitted, and a structure thereof according to an embodiment of the present invention.

FIG. 26 illustrates a structure of an initial signal and a relationship between an initial signal and a partial subframe according to an embodiment of the present invention. FIG.

FIG. 27 is a diagram illustrating a structure of a variable length reservation signal utilized for an initial signal according to an embodiment of the present invention.

FIG. 28 illustrates a case in which a compact synchronization reference signal (CSRS) is transmitted in time synchronization with OFDM symbol 7 of a licensed band in an unlicensed band according to an embodiment of the present invention.

29 is a diagram illustrating a transmission time of a CSRS classified according to a transmission time of a reservation signal according to an embodiment of the present invention.

30 illustrates a frequency domain symbol configuration of a CSRS according to an embodiment of the present invention.

31 illustrates a frequency structure of CSRS type-2 according to an embodiment of the present invention.

32 is a diagram illustrating a frame form in which a reservation signal is transmitted immediately before a data subframe.

FIG. 33 is a diagram illustrating a frequency division duplexing (FDD) based subframe structure.

34 is a diagram illustrating a method of increasing transmission efficiency using a partial subframe according to an embodiment of the present invention.

FIG. 35 is a diagram illustrating a relationship between a transmission time of a starting partial subframe and a transmission time of a reservation signal and a synchronization signal according to an embodiment of the present invention.

36 illustrates a transmission time of one 'CP + OFDM symbol' including a plurality of VLRSs according to an embodiment of the present invention.

37 illustrates a frequency domain structure of a CSRS according to an embodiment of the present invention.

38 is a diagram illustrating a case where a CSRS transmission is canceled by the determination of a base station according to an embodiment of the present invention.

39, 40, 41, and 42 illustrate an initial partial subframe and a ending partial subframe based on a transmission time of a VLRS when the maximum transmission length is 4 ms according to an embodiment of the present invention. It is a figure which shows a structure.

43 is a diagram illustrating a relationship in which a downlink control information channel and a downlink data channel of a partial subframe are mapped to a frequency domain according to an embodiment of the present invention.

FIG. 44 is a diagram showing a configuration of CCSI information of a first subframe (or a first SPS) when the maximum continuous transmission length limit is 4 ms according to an embodiment of the present invention.

45 is a diagram illustrating a CCSI information configuration of a second subframe (or second SPS) when the maximum continuous transmission length limit is 4 ms according to an embodiment of the present invention.

46 illustrates downlink and uplink frame configurations using VLRS, CSRS, partial subframe (TS-DwPTS), downlink full subframe, UpPTS, and uplink subframe according to an embodiment of the present invention. to be.

FIG. 47 is a view illustrating downlink and uplink frame configuration using VLRS, partial subframe (TS-DwPTS), downlink full subframe, UpPTS, and uplink subframe according to an embodiment of the present invention.

FIG. 48 is a diagram illustrating downlink and uplink frame configuration using VLRS, CSRS, partial subframe (TS-DwPTS), downlink full subframe, and uplink subframe according to an embodiment of the present invention.

FIG. 49 illustrates downlink and uplink frame configurations using VLRS, partial subframe (TS-DwPTS), downlink full subframe, and uplink subframe according to an embodiment of the present invention.

50 is a diagram illustrating a relationship between UL grant and AUTTIS information and uplink transmission according to an embodiment of the present invention.

FIG. 51 is a diagram illustrating a relationship between an AUTTIS binary bit structure and an UL grant according to an embodiment of the present invention. FIG.

52 is a view showing short LBT performed immediately before uplink transmission according to an embodiment of the present invention.

53 illustrates a transmitter according to an embodiment of the present invention.

54 illustrates a receiver according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is 'connected' to another part, it includes not only 'directly connected' but also 'electrically connected' with another element in between. .

Throughout the specification and claims, when a portion is said to include a certain component, it means that it can further include other components, except to exclude other components unless specifically stated otherwise.

Throughout the specification, a terminal may be a mobile terminal, a mobile station, an advanced mobile station, a high reliability mobile station, a subscriber station, a portable device. It may also refer to a portable subscriber station, an access terminal, user equipment, and the like, and may include a terminal, a mobile terminal, a mobile station, an advanced mobile station, a high reliability mobile station, a subscriber station, a mobile subscriber station, It may also include all or part of the functionality of an access terminal, user equipment, and the like.

In addition, the base station (BS) may be an advanced base station, a high reliability base station, a node B, an evolved node B, an eNodeB, an access point. (access point), radio access station, base transceiver station, mobile multihop relay (MSR) -BS, relay station serving as base station, high reliability relay serving as base station (high reliability relay station), repeater, macro base station, small base station and the like, may be referred to as a base station, advanced base station, HR-BS, Node B, eNodeB, access point, wireless access station, transmission and reception base station, MMR-BS, It may also include all or part of the functionality of a repeater, high reliability repeater, repeater, macro base station, small base station, and the like.

Meanwhile, in the present specification, 'A or B' may include 'A', 'B', or 'both A and B'.

1. One. 비면허Unlicensed 주파수 대역의 무선 통신 셀룰러 시스템에서 자동 시간 동기를 획득하는 방법 A method for obtaining automatic time synchronization in a wireless communication cellular system in frequency band

In order to use the unlicensed band in the LTE cellular network, it is a principle that the time frame must be synchronized with the LTE frame operated in the licensed band. Therefore, LTE cellular network must occupy channel in unlicensed band and solve time synchronization problem with licensed band.

Licensed and unlicensed bands have different channel characteristics, such as delay spread. Therefore, when the terminal performs time synchronization of the received frame, the optimal symbol timing is different in the licensed band and the unlicensed band. The existing licensed band has a structure capable of time synchronization correction and tracking of the terminal through transmission of a primary synchronization signal (PSS) every 5 ms. However, the base station cannot transmit the PSS for time synchronization every 5ms in the unlicensed band. This is because factors such as the LBT regulation mentioned above, the maximum continuous transmission time limit, and channel occupancy of other devices are affected. Therefore, due to the discontinuity of the unlicensed band and the unpredictable channel occupancy probability, it is difficult to obtain periodic time synchronization.

Hereinafter, a description will be given of a communication method capable of keeping time synchronization of a received signal and maintaining frame synchronization with a licensed band when a licensed band mobile communication system intends to use an unlicensed band. The following describes a communication method using an unlicensed band in a licensed mobile communication system.

1 is a diagram showing the structure of a radio frame used in a mobile communication system of a licensed band according to an embodiment of the present invention.

Referring to FIG. 1, in a Long Term Evolution (LTE) system, which is a typical mobile communication system operating a licensed band, one frame has a length of 10 ms and 10 subframes (# 0 to # 9) in the time domain. ). Each subframe # 0 to # 9 has a length of 1ms and consists of two slots S1 and S2. Each slot S1, S2 has a length of 0.5 ms. Slots S1 and S2 include a plurality of transmission symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. The resource block includes a plurality of subcarriers in the frequency domain. The transmission symbol may be referred to as an orthogonal frequency division multiplex (OFDM) symbol, an OFDMA symbol, an SC-FDMA symbol, etc. according to a multiple access scheme. The number of transmission symbols included in one slot may vary depending on the channel bandwidth or the length of the cyclic prefix (CP). For example, in an LTE system, one slot includes seven transmission symbols in the case of a normal CP, but one slot includes six transmission symbols in the case of an extended CP. The number of subframes included in the radio frame, the number of slots included in the subframe, and the number of transmission symbols included in the slot may be variously changed.

Referring to FIG. 2, the LTE system supports a License Assisted Access (LAA) that integrates a licensed frequency band and an unlicensed frequency band to meet data requirements. In other words, the LTE system does not limit the frequency used to the licensed band, but provides additional capacity and faster data rates by securing insufficient frequencies through the 5GHz unlicensed band.

The unlicensed band is a frequency band that is free for anyone to use, and no exclusive license to the frequency is guaranteed. Unlicensed bands are used by Wireless Local Area Network (WLAN) devices, commonly called WiFi. Therefore, in order to use an unlicensed band in an LTE system, it is necessary to effectively avoid a problem of interference with WLAN devices providing services in the same band.

In order to describe a method for using an unlicensed band in an LTE system, in FIG. 2, an LTE device that intends to use the same unlicensed band as two

WLAN devices

110 and 120 and WLAN devices 110 and 120 (hereinafter, referred to as 'LTE LAA'). Device 200) and an LTE device 300 using a licensed band. Herein, the device may mean a base station or a terminal.

First, a basic access mechanism of medium access control (MAC) in a WLAN system is a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism. The CSMA / CA mechanism basically adopts a listen before talk (LBT) connection mechanism. Accordingly, the

WLAN devices

110 and 120 may perform a clear channel assessment (CCA) for sensing a wireless channel before starting transmission. If the

WLAN device

110 or 120 determines that the wireless channel is in an idle state for a predetermined period (for example, a DCF inter-frame space (DIFS) period), a delay for channel access to avoid collision Set a time (eg, WLAN random backoff period) to wait longer before starting WLAN frame transmission. On the other hand, when the

WLAN device

110, 120 detects that the wireless channel is in a busy state as a result of CCA sensing, the

WLAN device

110, 120 does not start transmission until the wireless channel is idle. Wait

As such, by applying the WLAN random backoff period, since the

WLAN devices

110 and 120 attempt frame transmission after waiting for different times, collisions may be minimized.

The LTE LAA device 200 uses a listen before talk (LBT) mechanism as an access mechanism to use an unlicensed band. The LBT mechanism is a method of periodically checking the occupied state (used) of a channel before a signal is talked. Like the WLAN system, when the LTE LAA device 200 determines that the radio channel is in an idle state as a result of the LBT, the LTE LAA device 200 waits by setting a delay period (for example, an LTE random backoff period) for channel access, and then waiting for the corresponding radio. Start subframe transmission over the channel. On the other hand, if it is detected that the radio channel is occupied, the LTE LAA device 200 does not start transmission and waits until the radio channel becomes idle.

Since the LTE device 300 uses a licensed licensed band, when data to be transmitted is generated, the LTE device 300 may directly transmit an LTE frame having the structure shown in FIG. 1.

Next, a description will be given in detail of a method in which the LTE LAA device 200 uses an unlicensed band wireless channel in an environment in which the

WLAN devices

110 and 120, the LTE LAA device 200, and the LTE device 300 coexist.

First, as shown in FIG. 2, it is assumed that the WLAN device 110 transmits a WLAN frame, and the LTE device 300 continuously transmits an LTE subframe because interference with an unlicensed band signal does not occur. .

When the WLAN device 110 is transmitting a WLAN frame, the WLAN device 120 and the LTE LAA device 200 determine that the channel of the unlicensed band is occupied and withhold transmission. After transmission of the WLAN frame by the WLAN device 110, the WLAN device 120 and the LTE LAA device 200 detects that the channel is in the idle state through the CCA.

If the WLAN device 120 detects that the channel is idle during the DIFS time, the WLAN device 120 may wait for a further WLAN random backoff period before transmitting. Similarly, if the LTE LAA device 200 detects that the channel is idle by performing LBT, the LTE LAA device 200 may transmit after waiting for the LTE random backoff period.

As such, the WLAN device 120 and the LTE LAA device 200 may compete to use an unlicensed band. In order to transmit data by winning the competition, the WLAN device 120 and the LTE LAA device 200 first pass a q section corresponding to an arbitrary delay time. One device can transmit. Here, q may be a counter in units of 1us as a temporal concept. In the case of the WLAN device 120, q is the sum of the DIFS time and the WLAN random backoff period, and in the case of the LTE LAA device 200, q is the sum of the delay time by the LBT function and the LTE random backoff period. In general, the DIFS time is set to 34us, and the WLAN random backoff interval is set to a multiple of 9us including 0. The sum of the delay time and the LTE random backoff period by the LBT function is set to N * 20us, and N is basically set arbitrarily.

As shown in FIG. 2, when the LTE LAA device 200 first passes a q section, the LTE LAA device 200 transmits a preamble and then transmits an LTE subframe including data to be transmitted. . The preamble may be transmitted until the start point or a designated time point of the next subframe. The preamble is first transmitted to recognize the channel of the unlicensed band as occupied immediately from the perspective of another device, and also to serve as an assistant for synchronizing with the LTE subframe of the licensed band. In this case, the

WLAN devices

110 and 120 having data to be transmitted detect that the channel is occupied due to the preamble transmitted by the LTE LAA device 200 and suspend transmission.

Subsequently, after the LTE LAA device 200 completes transmission of one LTE subframe according to the size of data to be transmitted, the

WLAN devices

110 and 120 detect that the channel is idle and compete to occupy the channel. To start.

When the WLAN device 110 first passes the q section, the WLAN device 110 transmits the WLAN frame.

After the transmission of the WLAN device 110 is finished, the WLAN device 120 and the LTE LAA device 200 detects that the channel is idle and starts a race to occupy the channel. As shown in FIG. 2, when the LTE LAA device 200 passes the q section first, the LTE LAA device 200 transmits an LTE subframe including data to be transmitted after transmitting the preamble. In this case, one or more LTE subframes may be continuously transmitted according to the size of data to be transmitted.

In this way, the

WLAN devices

110 and 120 and the LTE LAA devices 200 having data to be transmitted start a race to occupy the channel, and the device occupying the channel transmits the data through the competition.

In particular, the LTE LAA device 200 starts a race to occupy a channel regardless of the boundary of the LTE subframe and occupies the channel, and when the channel is occupied, the LTE LAA device 200 transmits a preamble to the LTE subframe. Can transmit The preamble has a variable length and may be equal to or shorter than the length of the subframe.

As such, the LTE LAA device 200 may transmit the unlicensed band by using the LBT function and the preamble without changing (modification) the LTE subframe of the physical layer used in the existing licensed band. In addition, the LTE LAA device 200 may coexist with other types of devices such as WLAN and may be used for a predetermined period of time by occupying a channel without causing or receiving interference.

Currently, LBT is defined in ETSI, and the LTE LAA device 200 according to an embodiment of the present invention transmits data in an unlicensed band by utilizing a preamble in an unlicensed band.

The preamble according to an embodiment of the present invention may be transmitted to the boundary of the subframe such as the start point or the end point of the subframe section of the LTE license band for time synchronization with the LTE license band. In addition, the preamble may be transmitted not to the boundary of the subframe but to the boundary of the slot in the subframe or the boundary of a specific symbol in the subframe. If the subframes of the unlicensed band and the licensed band are temporally synchronized, there is an advantage in terms of implementation or scheduling, and the basic premise is that such synchronization should be performed at the current standardization stage.

3 is a diagram illustrating a structure of a preamble according to an embodiment of the present invention, and FIG. 4 is a diagram illustrating an example of a signal [w (n)] illustrated in FIG. 3.

Referring to FIG. 3, the length of the preamble is flexible. The preamble includes a signal [w (n)] and a fine time symbol training field (FSTF) signal [v (n)].

The signal w (n) may consist of at least one basic unit sequence and has a variable length.

The FSTF signal v (n) is located after the signal w (n) and has a length of one transmission symbol. The FSTF signal [v (n)] may be used at the receiving end to time-synchronize the received signal and keep synchronized with the LTE subframe of the licensed band.

In FIG. 3, the preamble is transmitted to a specific section within the subframe instead of the boundary of the subframe, and the specific section may be a slot or a transmission symbol.

Referring to FIG. 4, the basic unit sequence of the signal [w (n)] has a length of about 0.521us and has a waveform having a real value and an imaginary value.

The digital sample rate of LTE is 30.72 MHz. It takes 0.326us [1 / (30.72e6)] to transmit one sample, and 0.521us [to send 16 samples. = 16 / (30.72e6)]. That is, the basic unit sequence of the preamble corresponds to 16 sample lengths.

For reference, the transmission time of the LTE OFDM symbol is 66.67us [= 2048 / (30.72e6)], the transmission time / length of the CP is 4.69us [= 144 / (30.72e6)]. The length of one LTE subframe is 1 ms [= 30720 / (30.72e6)]. Therefore, when the basic unit sequence of the preamble is transmitted in 1920 consecutively, it becomes 1ms.

In the time domain having 16 sample lengths, the basic unit sequence s (n) is generated by Equation 1.

In Equation 1, p is a constant for normalizing the signal, and the sequence z (k) and the index k in the frequency domain are defined as in Equation 2.

Equation 2 is

Means.

In Equation 2, a _-5 to a ₅ are complex numbers and are defined as Equation 3 by binary bits.

Binary bits b- ₅ to b ₅ are the physical cell IDs of the base stations defined in the LTE specification, as shown in Equation 4.

and

Is determined by the mapping.

Where B (.) Is a binary operator function that converts to binary. E.g,

= 2

Assuming that = 97, binary b _-5 b _-4 b _-3 b _-2 b _-1 b ₁ b ₂ b ₃ b ₄ b ₅ is determined to be 110000110. Thus z (k) becomes [0 0 0 -1-j -1-j 1 + j 1 + j 1 + j 0 1 + j 1 + j -1-j -1-j 1 + j 0 0]. .

When p is 4, when z (k) is converted into the time domain using Equation 1, the basic unit sequence s (n) is represented by Equation 5.

The signal w (n) may be generated by repeating this basic unit sequence s (n).

3, the LTE LAA device 200 occupies a channel, transmits at least one basic unit sequence to a specified time point, and then transmits an FSTF signal [v (n)] for OFDM symbol timing. Can be.

The FSTF signal [v (n)] for OFDM symbol timing is fixed to 2192 or 2208 sample lengths based on a sampling of 30.72 MHz. The 2192 or 2208 sample length is expressed as the sum of the 2048 sample length and the CP length. That is, the FSTF signal [v (n)] has a length of 2192 or 2208 samples according to the length of the CP, and the length is determined according to the symbol position of the LTE subframe of the licensed band.

In general, in an LTE subframe of a licensed band, in case of a normal CP, one slot includes 7 transmission symbols, and the CP of the first symbol in the first slot and the second slot has a length of 160 samples. The CP of the second to seventh symbols in the second slot has a length of 144 samples. Therefore, if the FSTF signal [v (n)] is transmitted in the first symbol position of the LTE subframe of the licensed band, the FSTF signal [v (n)] has a length of 2208 samples, and the FSTF signal [v (n)] is licensed. If transmitted in the symbol position of any one of the second to seventh symbols of the LTE subframe of the band has a length of 2192 samples.

As shown in FIG. 3, if the FSTF signal v (n) is transmitted at the fifth symbol position, the FSTF signal v (n) may be generated with a length of 2192 samples.

Referring to FIG. 5, the transmission positions of the FSTF signals [v (n)] are determined as 3, 6, 9, and 12th symbols of odd subframes, and 1, 4, 7, 10, and 13 of even subframes. It is assumed that the first symbol is set. In this case, if the channel is occupied by the LBT before the start point of the third symbol of the odd subframe, the signal [w (n)] is transmitted until the end of the second symbol, and then the FSTF signal [v ( n)] is transmitted from the start of the third symbol to the end of the third symbol. If the channel is occupied by the LBT before the start point of the sixth symbol from the start of the third symbol of the odd subframe, the signal [w (n)] is transmitted until the end of the fifth symbol, and then the FSTF signal. [v (n)] is transmitted from the beginning of the sixth symbol to the end of the sixth symbol. If the channel is occupied by the LBT before the start point of the ninth symbol from the start point of the sixth symbol of the odd subframe, the signal [w (n)] is transmitted until the end of the eighth symbol, and then the FSTF signal. [v (n)] is transmitted from the beginning of the ninth symbol to the end of the ninth symbol. If the channel is occupied by the LBT before the start point of the twelfth symbol from the start point of the ninth subframe, the signal [w (n)] is transmitted until the end of the eleventh symbol, and then the FSTF signal. [v (n)] is transmitted from the start of the 12th symbol to the end of the 12th symbol.

In this way, the FSTF signal [v (n)] is transmitted during one symbol period.

Referring to FIG. 6, the FSTF signal [v (n)] is composed of a signal [y (n)] having a length of 2048 samples in order to obtain efficient synchronization with an LTE subframe of a licensed band and has a time of 66.67us. Has a transmission time.

The LTE LAA device 200 generates a signal y (n) using a Golay sequence having a sample length of 1024. The golay sequence may be generated using Equation 6.

In Equation 6, D _k = [1 8 2 32 4 16 64 128 256 512], where k = 1, 2, ..., 10. D _k is a Dirac delta function that has a value of 1 when n = 0 and a value of 0 for other n. In addition, A _k (n) and B _k (n) have a value of 0 in an interval of n <0 and n≥2 ^k .

The element b _k that determines the vector of W _k is a physical cell identifier (eg,

Wow

Is defined by concatenated bipolar symbols. As shown in equation (7) from b ₁ to b ₂

From the remaining b ₃ to b ₁₀

Indicates. therefore

Wow

When concatenated with, a 10-bit variable is expressed as in Equation 8.

E.g

Is 2

Is 97, the concatenated binary sequence is 0110000110. When BPSK modulation is performed on concatenated binary sequences, W _k becomes [1 -1 -1 1 1 1 1 -1 1].

As an example, when D _k is [1 4 2] and W _k is = [1 −1 1], Z ₈ (n) = A ₃ (7-n) may be generated as shown in Equation 9. have. Where k = 1, 2, 3.

The LTE LAA device 200 uses equation 6 and W _k = [b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ b ₉ b ₁₀ ] (k = 1, 2,…, 10). An initial sequence is generated (S610). The LTE LAA device 200 applies Z ₁₀₂₄ (n) = A ₁₀ 1023-n to generate an initial sequence.

In order to apply spectrum shaping of the initial sequence Z ₁₀₂₄ (n), the LTE LAA device 200 converts the initial sequence Z ₁₀₂₄ (n) into a frequency domain sequence as shown in Equation 10 (S620).

here,

to be.

The LTE LAA device 200 maps the sequence transformed into the frequency domain into the frequency extended sequence Y (k) as shown in Equation 11 (S630).

Next, the LTE LAA device 200 applies the transmission bandwidth extension to the sequence Y (k). That is, the LTE LAA device 200 generates a sequence Y '(k) having an extended transmission bandwidth as shown in Equation 12 (S640). In this case, the expansion of the transmission bandwidth is in accordance with the European ETSI transmission regulations.

That is, 32 subcarriers are added to both band edge portions, and thus 64 subcarriers are added to the total sequence compared to the sequence Y (k) shown in Equation (11).

Finally, the LTE LAA device 200 converts the sequence Y '(k) in which the transmission bandwidth is extended into a sequence in the time domain as shown in Equation 13 (S650).

Here, N _CP represents the length of the CP, p is a scaling factor for normalizing the power of the transmission signal.

FIG. 7 is a diagram illustrating an example of a signal y (n) when the available bandwidth is 20 MHz, and FIG. 8 is a frequency spectral density of the signal y (n) shown in FIG. 7. The figure which shows.

When the vector component of D _k is set to [1 8 2 32 4 16 64 128 256 512], and the vector component of W _k is set to [1 -1 -1 -1 -1 -1 1 -1 1], By the method described with reference to FIG. 5, a signal y (n) in the time domain as shown in FIG. 6 may be generated.

The frequency spectral density of the signal y (n) generated as described above is shown in FIG. 8. That is, it can be seen that the signal [y (n)] occupies 16.32 MHz, which is more than 80% of the bandwidth 20 MHz. The results of this spectrum meet the European ETSI regulations.

When the LTE LAA device (for example, the terminal) receiving the FSTF signal knows the signal [y (n)], the correlation value [v (n)] of the FSTF signal may appear as shown in FIG. Assuming that the correlation value does not match as 0, the maximum value of the correlation value has an average correlation value of 30dB or more in case that time synchronization does not match.

Accordingly, the UE in the unlicensed band obtains reference timing information for correcting time synchronization (ie, FFT window timing) based on the correlation result of the FSTF signal.

As such, a correlator is required to receive the FSTF signal and estimate the time synchronization at the terminal. Since the FSTF signal is generated based on the Golay sequence, an efficient Golay correlator is used to reduce the complexity of the correlator. Can be significantly lowered. An efficient Golay correlator does not have to perform addition or subtraction 1023 times to have a correlation value of a Golay sequence of 1024 lengths used previously, but only 10 [= log (1024)] additions or subtractions. Using a ray correlator can dramatically reduce the number of additions or subtractions.

The generation process of the FSTF signal described above has been described based on a frequency bandwidth of 20 MHz (30.72 MHz sample rate).

If the transmission bandwidth is 10MHz, it is possible to generate a signal y (n) for a frequency bandwidth of 10MHz using a Golay sequence of length 512. In this case, Z ₅₁₂ (n) = A ₉ (511-n) is converted into a sequence in the frequency domain by applying Equation (14).

In Equation 14, Z ₅₁₂ (n) = A ₉ (511-n) is represented by D _k = [1 8 2 32 4 16 64 128 256] (k = 1, 2,…, 9) and W _k = [b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ b ₉ ] (k = 1, 2, ..., 9) can be generated by substituting the equation (6).

As such, the sequence transformed into the frequency domain may be mapped to a frequency extended sequence in a manner similar to Equation 11, and the frequency extended sequence may be mapped to a sequence Y '(k) having an extended transmission bandwidth as shown in Equation 15. have.

That is, a total of 32 subcarriers are added to the frequency-extended sequence by adding 16 subcarriers to each band edge.

Finally, Y '(k) having an extended transmission bandwidth is converted into a signal in the time domain as shown in Equation 16.

Here, in case of a transmission bandwidth of 10 MHz, N _CP is 72 or 80.

On the other hand, when the transmission bandwidth is 5MHz, Z ₂₅₆ (n) = A ₈ (255-n) is converted into a sequence of the frequency domain as shown in equation (17).

In Equation 17, Z ₂₅₆ (n) = A ₈ (255-n) is represented by D _k = [1 8 2 32 4 16 64 128] (k = 1, 2,…, 8) and W _k = [b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ ] (k = 1, 2, ..., 8) can be generated by substituting the equation (6).

As such, the sequence transformed into the frequency domain may be mapped to a frequency extended sequence in a manner similar to Equation 11, and the frequency extended sequence may be mapped to a sequence Y '(k) having an extended transmission bandwidth as shown in Equation 18. have.

That is, eight subcarriers are added to each band edge portion, resulting in a total of 16 subcarriers added to the frequency-extended sequence.

Finally, the sequence Y '(k) in which the transmission bandwidth is extended is converted into a call in the time domain as shown in Equation 19.

Here, in case of a transmission bandwidth of 5MHz, N _CP is 36 or 40.

Meanwhile, W _k = [b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ b ₈ b ₉ b ₁₀ ] (k = 1, 2,…, 10) described above is replaced with 10 instead of the physical cell identifier of the base station. It may also be used for transmitting system broadcast information capable of informing a message of bits.

Referring to FIG. 10, a communication device 1100 using an unlicensed band includes a processor 1110, a transceiver 1120, and a memory 1130. The communication device 1100 using the unlicensed band may be implemented in the LTE LAA device 200. As described above, the LTE LAA device 200 may be a base station or a terminal.

Processor 1110 competes with WLAN devices to occupy an unlicensed band before transmitting data. The processor 1110 checks the occupied state of the channel by performing LBT, and if it is determined that the channel is in an idle state, waits for an LTE random backoff period and then occupies the corresponding channel, the other device occupies the corresponding channel. In order to be recognized as and to synchronize with the subframe of the licensed band to generate a preamble and transmits the preamble through the transceiver 1120. The processor 1110 may generate the preamble by the method described with reference to FIGS. 3 to 5. In particular, the processor 1110 may generate the FSTF signal in the manner described with reference to FIG. 5. Next, the processor 1110 generates an LTE subframe for data transmission, and transmits the LTE subframe through the transceiver 1120.

The transceiver 1120 transmits a preamble and an LTE subframe.

The memory 1130 stores instructions for execution in the processor 1110 or temporarily loads instructions from a storage device (not shown), and the processor 1110 is stored in the memory 1130 or Run the loaded command.

The processor 1110 and the memory 1130 may be connected to each other through a bus (not shown), and an input / output interface (not shown) may also be connected to the bus. In this case, the transceiver 1120 may be connected to the input / output interface, and peripheral devices such as an input device, a display, a speaker, and a storage device may be connected.

According to the embodiment of the present invention, the LTE system can be operated by applying the specifications of the LTE physical layer in the unlicensed band, while maintaining frame synchronization with the licensed band without greatly changing the standard of the existing LTE physical layer.

In addition, according to an embodiment of the present invention, the receiver easily estimates the time synchronization of the received signal by using a sequence generated in a pattern based on a physical cell ID known to the base station and the terminal for time synchronization estimation. And dramatically lower complexity correlators can be used to reduce battery consumption.

In addition, according to an embodiment of the present invention, the function of transmitting the promised digital information through the preamble can be extended, so that various functions can be performed at once.

In addition, according to an embodiment of the present invention, a good element technology of the standardization technology for LTE operation in the unlicensed band can be provided.

2. 2. 비면허Unlicensed 주파수 대역의 무선 통신 셀룰러 시스템에서 시간 상향 프레임 및 시간 하향 프레임 구조를 획득하는 방법 A method of acquiring a time up frame and a time down frame structure in a wireless communication cellular system in a frequency band

Hereinafter, a method of acquiring a time up frame and a time down frame structure in a wireless communication cellular system in an unlicensed frequency band and an efficient uplink transmission and retransmission mechanism for an unlicensed band will be described.

In addition, hereinafter, a method of configuring a guard period for an unlicensed band LTE system supporting uplink and downlink in a time division duplexing (TDD) format will be described.

In addition, hereinafter, a method of configuring a guard interval that minimizes interference will be described.

In addition, hereinafter, a method of configuring a license assisted access (LTE-LAA) TDD frame structure and a frame format indicator suitable for an unlicensed band will be described.

In addition, hereinafter, a method of determining an uplink signal transmission timing that is suitable for an unlicensed band and is opportunistic and adaptive by using an aggregated uplink grant signal will be described.

Method and apparatus according to an embodiment of the present invention may belong to the physical layer of the LTE wireless mobile communication system. Specifically, the method and apparatus according to an embodiment of the present invention, in the unlicensed band in which signals are transmitted continuously, consider to operate the uplink (UL) and downlink (DL) signal of the LTE system. Frame structure, transmission, and control techniques.

LTE frame of the unlicensed band can be basically divided into downlink and uplink, like the LTE frame of the licensed band. Accordingly, the existing frame structure (FS) type 2 of the licensed band may preferentially be applied to the unlicensed band.

FIG. 11 is a diagram showing uplink and downlink multiplexed transmission based on time applied to LTE TS-Type 2. FIG.

One radio frame illustrated in FIG. 11 may have a length of T _f . Here, T _f may be 10 ms (= 307200 * T _s ). T _s can be defined as 1 / 30.72 MHz = 32.552ns. One radio frame may include ten subframes (numbered 0 to 9). One subframe may have a length of 1ms (= 30720 * T _s ). One time slot may have a length of T _slot . Here, the T _slot may be 15360 * T _s .

The special subframe may include a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS).

As illustrated in FIG. 11, the FS-type 2 of the licensed band may be divided into a transmission interval for a base station and a transmission interval for a terminal.

The section Txp1 illustrated in FIG. 11 is a section in which the terminal transmits a signal. The section Txp2 illustrated in FIG. 11 is a section in which the base station transmits signals as remaining sections except for the section Txp1 and the GP among the entire sections. Therefore, DwPTS is a transmission interval for the base station, and UpPTS is a transmission interval for the terminal.

The GP section is a section between DwPTS and UpPTS and may have a length of at least 47.396us (= 1456 * T _s ). Specifically, the GP is a period in which the base station and the terminal do not transmit a signal, and a time in which a switching time of a radio frequency (RF) and a switching time of a radio frequency (RF) according to a difference in distance between a transmitting end and a receiving end are considered. Can have. The minimum time for a GP is 1456 / 30.72MHz = 47.39us according to the current LTE specification. This idle time is sufficient time for an unlicensed band device (eg, a Wi-Fi device) to perform CCA and occupy a channel.

In addition, the existing GP length may not be appropriate for the characteristic of the unlicensed band having less coverage than the small cell due to the relatively low output. The small cell coverage of the unlicensed band is determined to be up to 140ms, and the round trip time of transmission and reception takes only about 0.5us when calculated using the speed of light. Even if the switching time of the RF is added to the round trip delay time, it may be less than 15us in total.

Therefore, it is necessary to determine the appropriate GP length for the small cell. If the length of the GP is determined to be shorter or similar to the interframe space (IFS) time, such as the distributed coordinate function interframe space (DIFS) of Wi-Fi, then the unlicensed band LTE transmission bursts of uplink and downlink, After determining the CCA of the device, it is possible to block the source of interference caused by the transmission signal output.

However, to define a GP length shorter than the existing minimum GP length, it is necessary to transmit any continuous signal after DwPTS (or UpPTS). However, 71us, an orthogonal frequency division multiplexing (OFDM) symbol unit of the current standard, is too long to fill a portion of an existing GP to make a short GP length (more than 47.39us, the GP minimum length according to the current standard). Kim). Thus, to create a GP that is shorter than 47.39us and has a length similar to Wi-Fi's IFS (eg 34us for DIFS), the preamble signal itself and the ability to fill a continuous signal, such as a preamble, between the DwPTS and the GP itself. Need a definition.

The LTE subframe of the unlicensed band is based on the application of the principle of supporting CA (carrier aggregation) function that the time synchronization with the LTE subframe operated in the licensed band should not be allowed to be shifted by a predetermined value or more. When the device occupies a channel through the LBT, it rarely starts channel occupancy at the boundary point of the subframe, and generally occupies the channel after the LBT in the middle part of the subframe. In this case, data transmission should be performed in the form of partial subframes. In the current LTE standard, partial subframe transmission is supported only in the form of DwPTS and UpPTS.

However, when the device starts to occupy the channel after the LBT is unpredictable, and the length of the DwPTS and UpPTS is limited, there is a problem of data transmission efficiency. In order to increase the transmission efficiency of the unlicensed band, a new partial subframe needs to be defined.

Particularly in regions such as Europe and Japan, new partial subframes are needed because of the limitations on the length of signals that can be transmitted continuously by radio and communication regulations.

Specifically, in the case of Japan, continuous signal transmission of 4 ms or more is impossible. Therefore, continuous signal transmission in Japan cannot follow the time division duplexing (TDD) -LTE frame format-type 2 criterion of a licensed band designed based on a 10 ms length. In particular, when continuous signal transmission is limited to 10 ms or less, the fewer special subframes (including DwPTS, GP, and UpPTS) illustrated in FIG. 11, the higher the transmission efficiency.

Therefore, since the TDD-LTE standard of the current licensed band is defined so that two special subframes exist in 10ms units, a problem that is not currently supported in the LTE standard is solved so that one special subframe exists in 10ms units. Should be. Therefore, a new TDD-LTE specification suitable for unlicensed band LTE operation needs to be defined.

As described above, like the LTE frame of the unlicensed band, the LTE frame of the unlicensed band may be basically divided into downlink and uplink in the TDD form. Uplink data transmission may be performed after grant of the base station.

In the case of an existing licensed band, a terminal granted a grant from a base station transmits an uplink signal at a predetermined time point.

In detail, FIG. 12 illustrates a case in which a downlink signal and an uplink signal are transmitted in an LTE frequency division duplexing (FDD) system in a licensed band.

As illustrated in (a1) of FIG. 12, when the terminal receives downlink control information (including UL grant) transmitted through downlink control information (DCI) at the time points Ts1a and Ts2a, the time point Ts1a Signal is transmitted from Ts2b to Ts1b and Ts2b. The base station transmits PHICH (ACK) information indicating that there is no problem in demodulation of the signal of the terminal.

As illustrated in (a1) of FIG. 12, since signal transmission and reception are processed for each subframe unit, when the base station transmits a UL grant at different time points Ts1a and Ts2a in time, each time point Ts1a, When 8ms have elapsed from Ts2a), a response PHICH is transmitted to the UE. In summary, an uplink signal is transmitted at a time point Ts1b or Ts2b 4ms have elapsed from the time points Ts1a and Ts2a at which the UL grant is transmitted, and a base station is transmitted when 4ms have elapsed from the time points Ts1b and Ts2b. The UE informs the UE of an acknowledgment signal (eg, an ACK signal or a negative acknowledgment signal).

As illustrated in (a2) of FIG. 12, when a demodulation error occurs in the uplink transmission signal received from the terminal or the uplink signal is not received, the base station downlinks the NACK signal to the terminal using the PHICH channel. By transmitting as a link signal, the terminal requests retransmission of an uplink signal.

The time difference between the transmission and the response made by the base station and the terminal is fixed at 4 ms, and a retransmission mechanism (eg, hybrid acknowledgment) is performed synchronously at 4 ms intervals. Accordingly, in the licensed band, synchronous timing may be maintained in which the transmission and reception response time interval is kept constant without a separate signal indicator related to transmission timing.

However, in the unlicensed band, the mechanism and response to the synchronous transmission are not guaranteed. In the case of uplink transmission, if the result of the LBT performed after the time difference between the predetermined transmission and the response (for example, 4 ms) is that the corresponding channel is busy, the UE cannot transmit the uplink signal. The terminal attempts to retransmit the uplink signal. As a result, the uplink transmission efficiency is lowered, and in the worst case, the terminal may continue to attempt retransmission only.

In detail, FIG. 13 illustrates a Wi-Fi device WFD1 operating in an unlicensed band, a base station LLa1, a plurality of terminals UE1 and UE2, and a base station LLa2 operating in a licensed band.

As illustrated in FIG. 13, when a shared channel is occupied by another device (eg, WFD1) and the corresponding channel is busy at a time point Ts3b, the UE UE2 may perform a DCI by the base station LLa1. In principle, it is necessary to give up the signal transmission from the time Ts3a (including the UL grant) to the time Ts3b after a preset time (for example, 4 ms) has elapsed.

For example, when the UE UE2 fails to transmit an uplink signal due to the channel occupancy of the Wi-Fi device WFD1 at the time point Ts3b, a NACK signal and a new UL grant are received from the base station LLa1 at the time point Ts3c. Receive The UE UE2 attempts to retransmit an uplink signal at a time point Ts3d after 4ms has elapsed from the time point Ts3c, but fails to retransmit due to channel occupancy of the Wi-Fi device WFD1.

For another example, the UE UE1 transmits an uplink signal at a time Ts4b 4ms elapsed from the time Ts4a at which the UL grant of the base station LLa1 is transmitted. The base station LLa1 cannot transmit a response signal due to the channel occupancy of the Wi-Fi device WFD1 at a time point Ts4c after 4 ms has elapsed from the time point Ts4b. The terminal UE1 which has not received the response signal retransmits the uplink signal at a time point Ts4d after 4ms has elapsed from the time point Ts4c.

As illustrated in FIG. 13, when a channel is busy at a transmission timing designated for uplink or a transmission timing designated for downlink, a retransmission process is performed. In this case, if the mechanism of the licensed band is applied to the unlicensed band as it is and the uplink transmission proceeds, the transmission efficiency may be very low.

Therefore, there is a need for an efficient uplink transmission and retransmission mechanism for the unlicensed band. Specifically, flexibility in uplink transmission time is required. In addition, when uplink transmission time for first transmission of new data and timing for retransmission must be considered at the same time, a channel resource and timing allocation method and a channel access method for this are needed.

FIG. 14 is a diagram illustrating a case in which uplink transmission fails or a collision occurs due to a long guard interval in an LTE uplink and downlink frame structure for an unlicensed band. Specifically, FIG. 14 illustrates WLAN devices STA1 and STA2 and LTE base station LLa1 operating in an unlicensed band, and a base station LLa2 operating in a licensed band.

A method of designing a GP or extended DwPTS preamble that prevents or minimizes interference will be described with reference to FIG. 14. The GP or DwPTS preamble may be applied to a frame supporting uplink and downlink.

The periods PSF1a and PSF1b, DwPTS, and UpPTS of the subframe illustrated in FIG. 14 correspond to partial subframes.

Specifically, in FIG. 14, the LTE base station LLa1 operating in the unlicensed band has the same unlicensed band (eg, 5 GHz frequency band) as two IEEE 802.11a / n / ac wireless local area network (WLAN) devices STA1 and STA2. ) Is illustrated. In this case, we describe how to ensure coexistence and synchronization between unlicensed and licensed bands. The LTE base station LLa1 may be an LTE license assisted access (LAA) device. Meanwhile, the LTE base station LLa1 may be operated in both an unlicensed band and a licensed band, and in this case, the signal of the unlicensed band and the licensed band can be simultaneously transmitted.

CCA is a method of determining whether a wireless channel is in use using an energy level. Similarly, LBT performs the same function as CCA. Successful CCA or LBT for a channel means that the device that performed the CCA or LBT occupies the channel. The busy state of a channel indicates that the channel is occupied, and the idle state of the channel indicates that no device is using the channel.

As illustrated in FIG. 14, when the WLAN device STA1 first transmits a signal by occupying a channel of an unlicensed band in time, each of the WLAN device STA2 and the LTE base station LLa1 is busy. It determines that it is busy and suspends signal transmission.

After transmission of the WLAN device STA1, the WLAN device STA2 and the LTE base station LLa1 detect that the corresponding channel is in an idle state.

When the WLAN device STA2 detects an idle state of a corresponding channel by using the CCA check function, the WLAN device STA2 prepares a signal transmission, but according to the specification, a time delay period such as DIFS and random back-off is used. Transmission must be performed after coarse (e.g. distributed coordinate function (DCF), which is a function of channel access scheme for WLAN).

Similarly, when the LTE base station LLA1 performs an LBT function including channel activity detection and an arbitrary delay function to detect an idle state of a channel, the LTE base station LLa1 prepares a signal transmission after a random delay. (E.g., LBT capabilities of the European telecommunications standards institute (ETSI) standard).

At this time, the WLAN device STA2 and the LTE base station LLa1 compete to use the unlicensed band, and the device that has passed the random delay time q as described above wins the competition and transmits a signal. have. Here q is a temporal concept and can be a counter in us units.

Therefore, each of the WLAN device STA2 and the LTE base station LLa1 may transmit a signal after a certain total delay time q of a certain delay and a random backoff has passed. In the case of WLAN device STA2, q is DIFS time (e.g. 34us) and random backoff (e.g. multiple of 9us (including 0), i.e. 0 to N * 9us time, provided N is IEEE 802.11 In accordance with the specification). In the case of the LTE base station LLa1, q by the LBT function is equal to xIFS value similar to the DIFS of WLAN and random backoff (e.g., N * 20us, where N is basically random and ETSI regulates the maximum value of N). May be 24).

For example, in the first idle period, when the LTE base station LLa1 undergoes a random backoff period (xIFS + CCA check), the WLAN device STA2 first passes through the 'DIFS + random backoff period'. And start transmitting the WLAN frame at time Ts5a.

For another example, in the second idle period, the LTE base station LLa1 wins a competition with the WLAN device STA1 and the WLAN device STA2 and starts transmitting a signal at a time point Ts5b. At this time, the LTE frame transmitted by the LTE base station (LLa1) may be of the FS-type 2 form consisting of uplink and downlink. Therefore, uplink transmission is performed after downlink transmission, and the GP may be located between the downlink transmission and the uplink transmission. However, the WLAN device STA1 detects the corresponding channel as an idle state in the GP section, passes the 'CCA + random backoff' time, and starts transmitting the WLAN frame at the time Ts5c.

In this case, the UE ignores the signal transmission of the WLAN device STA1 for the LTE uplink transmission of the unlicensed band and performs signal transmission (electronic), or if it detects that the corresponding channel is busy, The link signal transmission may not be performed (the latter). In the former case, both the LTE signal and the Wi-Fi signal are adversely affected by the reception performance due to signal collisions. In the latter case, since the terminal does not allow uplink transmission, throughput degradation of the LTE-LAA system occurs. In order to prevent this from happening, it is necessary to reduce the length of the GP, but according to the current LTE specification, it is not possible to reduce the GP to meet the time corresponding to the Wi-Fi DIFS period.

Therefore, hereinafter, a method of reducing GP by transmitting a reservation signal having a variable length after transmitting DwPTS will be described.

FIG. 15 is a diagram illustrating a method of reducing a length of a guard interval by transmitting a reservation signal of a variable length after DwPTS transmission according to an embodiment of the present invention.

As illustrated in FIG. 15, after the DwPTS transmission, a reservation signal (or preamble) of variable length may be transmitted following the DwPTS.

Specifically, FIG. 15 illustrates a structure of a preamble (reservation signal) according to an embodiment of the present invention. The s (n) region of the reservation signal having a variable length may include a minimum signal unit transmission interval having a length of about 0.521us. If the digital sample rate of LTE is 30.72 MHz, the time T _s to transmit one sample takes 1 / (30.72e6) = 0.326us.

Thus, according to an embodiment of the present invention, the transmission time of the sequence having length 16 is approximately 0.521us (= 16 / (30.72e6)). For reference, the transmission time of an LTE OFDM symbol is 2048 / (30.72e6) = 66.67us. The transmission time (or length) of the cyclic prefix is 144 / (30.72e6) = 4.69us or 160 / (30.72e6) = 5.2083us. The length (or transmission time) of one LTE t subframe is 30720 / (30.72e6) = 1 ms. That is, when 1920 sequences of the basic unit of the preamble (reservation signal) are transmitted in succession, 1 ms (ie, one LTE subframe may be divided into 1920 intervals).

A sequence s (n) of the time domain having a length of 16 may be generated by Equation 20 below.

Where p is a constant to normalize the signal,

Indicates.

The sequence z (k) and the index k of the frequency domain may be defined as in Equation 21 below.

In Equation 21, a _- ₅ to a ₅ are complex numbers, and can be defined by Equation 22 below by binary bits.

Binary bit b _- b from ₅ to _5, is a physical cell (physical cell) ID of the base station defined in the LTE standard

and

It may be determined by, and mapped to Equation 23 below.

Where B (.) Is a binary operator function that converts to binary. E.g,

= 2

Assuming = 97, the number of binaries

Is determined by 0110000110. So z (k) is

Becomes

When p is 4, if z (k) is converted to the time domain based on Equation 20, the following s (n) sequence can be generated.

Since the variable length preamble (reservation signal) according to the embodiment of the present invention has a granularity of about 0.521 us, it may have a high degree of freedom with respect to extended DwPTS length adjustment. As a result, the length of the GP can be freely designed. For example, when the special subframe configuration of TDD-LTE assuming a normal cyclic prefix is set to '3', the lengths of DwPTS and UpPTS are 24144 * T _s and 2192 * T _{s, respectively.} Becomes The length of the GP eventually becomes 4384 * T _s . 4384 * T _s corresponds to a length of 4384 / 30.72MHz = 142.7us. To reduce this length, the reservation signal should be 108.7us (= 142.7us-34us) so that the GP's length is close to the Wi-Fi DIFS value of 34us. Therefore, when 209 sequences s (n) are generated, the reserved signal has a length of 108.85us (= 209 * 16 / 30.72MHz), and the GP has a length of 33.85us close to 34us.

FIG. 16 illustrates a method of adjusting a length of a guard interval GP by copying a baseband signal of a licensed band according to an embodiment of the present invention.

As illustrated in FIG. 16, without the above-described reservation signal, a baseband signal (OFDM modulated signal) transmitted in a licensed band may be copied as is and transmitted in an unlicensed band. Specifically, after the DwPTS transmission in the unlicensed band, the baseband signal of the licensed band may be copied and then transmitted after the DwPTS.

In the method illustrated in FIG. 16, the signal of the licensed band may be copied in multiple T _s sample units.

On the other hand, another method of adjusting the length of the GP is to generate an arbitrary signal having energy and transmit it in place of the above-described reservation signal.

Accordingly, the GP length adjusting method according to an embodiment of the present invention transmits energy in any form through an unlicensed band channel, thereby preventing the channel from being idle after detecting the CCA, and the GP length of the WiFi It is a method to correspond to the IFS section.

Hereinafter, a method of configuring a TDD LTE-LAA frame structure and a frame format indicator (FFI) suitable for an unlicensed band will be described.

When a special subframe is limited to one in the TDD LTE frame structure and the frame type has an uplink and a downlink burst form, as illustrated in FIG. 17, a TDD-LTE frame format for an unlicensed band may be generalized. have.

In detail, the TDD-LTE frame format for the unlicensed band illustrated in FIG. 17 may be applied to a downlink-only frame.

In the TDD-LTE frame format illustrated in FIG. 17, the positions of the special subframes and the total length of the transmission burst of the TDD-LTE frame format are expressed using 6 bits of the n bits allocated to the FFI. Can be. For example, in the LAA frame format 4, the position of the special subframe and the total length of the transmission burst of the TDD-LTE frame format may be represented by 000100. For another example, in LAA frame format 3, the position of the special subframe and the total length of the transmission burst of the TDD-LTE frame format may be represented by 000011. For another example, in LAA frame format 2, the position of the special subframe and the total length of the transmission burst of the TDD-LTE frame format may be represented by 000010.

As illustrated in FIG. 17, a structure of a TDD based frame format (eg, LAA frame formats 4, 3, 2, ..., x) suitable for an unlicensed band includes a reserved signal, an FFI, a downlink partial subframe, and a downlink. It may include a link subframe, a DwPTS, a GP, an UpPTS, an uplink subframe, an uplink partial subframe, and the like.

The reservation signal and the FFI may be included in an initial signal. The FFI may include at least two OFDM symbols.

Transmission of the UpPTS may be canceled so that a reservation signal located before the GP may be transmitted longer.

Hereinafter, a method of configuring the FFI will be described.

FFI may be represented in the frequency domain, as illustrated in FIG. 18 or 19.

18 illustrates a structure of a frame format indicator (FFI) -type 2 according to various bandwidths according to an embodiment of the present invention.

The FFI may include a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS) on the frequency axis.

First, the PSS will be described.

PSS has the same signal configuration and mapping form of the frequency axis as the licensed band LTE system. As illustrated in FIG. 18, the PSS region may occupy six PRBs belonging to an intermediate point among physical resource blocks (PRBs) (eg, 24 to 100) corresponding to the total frequency bandwidth determined by the system. Here, one PRB corresponds to 12 subcarriers.

The process of generating the frequency domain sequence d _u (n) for the PSS and mapping the frequency domain may be defined as in Equation 24 below.

In Equation 24, u may be defined as shown in Table 1 below.

Root indices for the PSS

N_ID^(2)N_ID ^ (2)	Root index u Root index u
00	2525
1One	2929
22	3434

In Table 1, N_ID ^ (2) is

Indicates.

The frequency subcarrier index k of the PSS mapped to the frequency domain is

(Where n = 0,1,2, ..., 61).

here,

Represents the number of PRBs corresponding to the total bandwidth of the system,

Is 12. Considered in the unlicensed band

May be 25, 50, 75, or 100.

The frequency subcarrier index k of the PSS mapped to the void area is

(Where n = -5, -4, ...,-1,62,63, ... 66).

The SSS will be described.

SSS can be divided in half. Specifically, as illustrated in FIG. 18, a region corresponding to each half of the SSS (three PRBs) is mapped to a lower or higher frequency region than the PSS region. The method of generating the SSS region may be defined as in Equation 25 below.

In Equation 25, ₀ ≦ n ≦ 30, and the indexes m ₀ and m ₁ are physical layer cell identity groups as shown in Equation below.

Can be determined by.

here,

May be one of the values of Table 2 below. In other words,

May be one of 0 to 167.

Mapping between physical-layer cell-identity group and the indices m ₀ and m ₁

N_ID^(1) N_ID ^ (1)	m₀ m ₀	m₁ m ₁	N_ID^(1)N_ID ^ (1)	m₀ m ₀	m₁ m ₁	N_ID^(1)N_ID ^ (1)	m₀ m ₀	m₁ m ₁	N_ID^(1)N_ID ^ (1)	m₀ m ₀	m₁ m ₁	N_ID^(1)N_ID ^ (1)	m₀ m ₀	m₁ m ₁
00	00	1One	3434	44	66	6868	99	1212	102102	1515	1919	136136	2222	2727
1One	1One	22	3535	55	77	6969	1010	1313	103103	1616	2020	137137	2323	2828
22	22	33	3636	66	88	7070	1111	1414	104104	1717	2121	138138	2424	2929
33	33	44	3737	77	99	7171	1212	1515	105105	1818	2222	139139	2525	3030
44	44	55	3838	88	1010	7272	1313	1616	106106	1919	2323	140140	00	66
55	55	66	3939	99	1111	7373	1414	1717	107107	2020	2424	141141	1One	77
66	66	77	4040	1010	1212	7474	1515	1818	108108	2121	2525	142142	22	88
77	77	88	4141	1111	1313	7575	1616	1919	109109	2222	2626	143143	33	99
88	88	99	4242	1212	1414	7676	1717	2020	110110	2323	2727	144144	44	1010
99	99	1010	4343	1313	1515	7777	1818	2121	111111	2424	2828	145145	55	1111
1010	1010	1111	4444	1414	1616	7878	1919	2222	112112	2525	2929	146146	66	1212
1111	1111	1212	4545	1515	1717	7979	2020	2323	113113	2626	3030	147147	77	1313
1212	1212	1313	4646	1616	1818	8080	2121	2424	114114	00	55	148148	88	1414
1313	1313	1414	4747	1717	1919	8181	2222	2525	115115	1One	66	149149	99	1515
1414	1414	1515	4848	1818	2020	8282	2323	2626	116116	22	77	150150	1010	1616
1515	1515	1616	4949	1919	2121	8383	2424	2727	117117	33	88	151151	1111	1717
1616	1616	1717	5050	2020	2222	8484	2525	2828	118118	44	99	152152	1212	1818
1717	1717	1818	5151	2121	2323	8585	2626	2929	119119	55	1010	153153	1313	1919
1818	1818	1919	5252	2222	2424	8686	2727	3030	120120	66	1111	154154	1414	2020
1919	1919	2020	5353	2323	2525	8787	00	44	121121	77	1212	155155	1515	2121
2020	2020	2121	5454	2424	2626	8888	1One	55	122122	88	1313	156156	1616	2222
2121	2121	2222	5555	2525	2727	8989	22	66	123123	99	1414	157157	1717	2323
2222	2222	2323	5656	2626	2828	9090	33	77	124124	1010	1515	158158	1818	2424
2323	2323	2424	5757	2727	2929	9191	44	88	125125	1111	1616	159159	1919	2525
2424	2424	2525	5858	2828	3030	9292	55	99	126126	1212	1717	160160	2020	2626
2525	2525	2626	5959	00	33	9393	66	1010	127127	1313	1818	161161	2121	2727
2626	2626	2727	6060	1One	44	9494	77	1111	128128	1414	1919	162162	2222	2828
2727	2727	2828	6161	22	55	9595	88	1212	129129	1515	2020	163163	2323	2929
2828	2828	2929	6262	33	66	9696	99	1313	130130	1616	2121	164164	2424	3030
2929	2929	3030	6363	44	77	9797	1010	1414	131131	1717	2222	165165	00	77
3030	00	22	6464	55	88	9898	1111	1515	132132	1818	2323	166166	1One	88
3131	1One	33	6565	66	99	9999	1212	1616	133133	1919	2424	167167	22	99
3232	22	44	6666	77	1010	100100	1313	1717	134134	2020	2525	--	--	--
3333	33	55	6767	88	1111	101101	1414	1818	135135	2121	2626	--	--	--

In Table 2, N_ID ^ (1) is

Indicates.

2 sequences

Wow

The m ₀ and m ₁ values (values defined in Table 2) that apply to

It is an element for shifting the m-sequence of. And the process can be defined as the following equation.

here,

Is

(Where 0 ≦ i ≦ 30), where x (i) is

It can be defined as The initial state is equal to x (0) = 0, x (1) = 0, x (2) = 0, x (3) = 0 and x (4) = 1.

c ₀ (n) and c ₁ (n) are two scrambling sequences, determined by the PSS identity (identity), consisting of the two m-sequences below:

Can be determined by.

here,

Represents a PSS identity group.

Is

(Where 0 ≦ i ≦ 30), and x (i) is

(Where 0≤

≤ 25). The initial state is equal to x (0) = 0, x (1) = 0, x (2) = 0, x (3) = 0 and x (4) = 1.

Scrambling sequence

Wow

Consists of the following m-sequences

It may consist of a sequence of.

Where m ₀ and m ₁ depend on the values in Table 2

Is

(Where 0 ≦ i ≦ 30). And x (i) is

(Where 0≤

On the other hand, the frequency subcarrier index k of the SSS mapped to the frequency domain,

(Where n = 0,1,2, ..., 30) and

(N = 31,32, ..., 61).

Considered in the unlicensed band

May be 25, 50, 75, or 100.

The frequency subcarrier index k of the SSS mapped to the void region is

(N = -36, -35, ...,-32,93,94, ..., 97)

One subcarrier has a bandwidth of 15 KHz. Thus, six PRBs occupy a bandwidth of 1.08 MHz.

Finally, the CRS including frame information and uplink scheduling information will be described. As illustrated in FIG. 18, the CRS region before or after the synchronization signal PSS and SSS regions may occupy 6 to 41 PRBs. The structure of the CRS will be described in detail with reference to FIG. 19.

S ₀ , S ₁ ,..., S ₁₂ illustrated in FIG. 19 represent modulation symbols constituting the CRS.

The CRS region (region to which the CRS is mapped) has a CRS structure (using two antenna ports (eg, antenna ports 0 and 1)) mapped to the existing LTE OFDM symbol 0, and is represented by Equation 26 below. Can be defined.

In Equation 26, a denotes a signal input to an inverse fast Fourier transform (IFFT) block as a complex symbol. In Equation 26, p represents an antenna port number and corresponds to index k of the frequency axis and index l of the OFDM symbol.

In Equation 26, k, l, m may be defined as follows.

Where v is

Where v _shift is

It can be defined as.

Represents a physical cell ID.

Specifically, FIG. 19

Is 25 (ie, the total bandwidth of the system is 5 MHz), CRS mapping of the frequency axis is illustrated.

In Equation 26, r _l (m) is composed of differential quadrature phase shift keying (D-QPSK) symbols and may be mapped as in Equation 27 below.

s _init is the QPSK symbol (x = I + jQ) and the in-phase and quadrature-phase

to be. here

Is a coded bit to which channel coding is applied and may have a length of 46 (eg,

).

Therefore, the length of the transmitted information b _i is a variable length n less than 32, and is input as the input bit length n of the second order RM (Reed Muller) code (32, n). C ₀ , c ₁ , ..., c _{13, which} are the most significant bit 14 bits of the coded bits c ₀ , c ₁ , ..., c ₃₁ , are the original 32 bits. Concatenated with the outputs c ₀ , c ₁ , ..., c ₃₁ , resulting in 46 bits (e.g.,

).

20 is a diagram illustrating a CRS mapping flow after encoding of a frame format indicator (FFI) according to an embodiment of the present invention.

The transmission information n bits (e.g., b ₀ , b ₁ , ..., b _n-1 ) to which encoding is applied are 6 bits indicating the length of the transmission frame burst and the position of the special subframe, and the aggregated upstream. It may include (n-6) bits for an aggregated uplink transmission time indicator signal (AUTTIS). The transmission information n bits (e.g., b ₀ , b ₁ , ..., b _n-1 ) is encoded through RM code encoding, so that the bit stream

Becomes And bit stream

After bit extension is applied, D-QPSK modulation is applied. For r _l (i) generated through D-QPSK modulation, subcarrier mapping is applied.

In addition, the FFI may be used for frequency offset and channel estimation of the LAA TDD-LTE frame. As illustrated in FIG. 17 or FIG. 18, two OFDM symbols included in the FFI are repeatedly transmitted. By using the characteristics of the FFI, the UE may estimate an accurate carrier frequency offset (CFO) in the time domain. .

FFI can also be used for channel estimation function purposes. When channel coding demodulation is made, bit decoding is performed on the bits transmitted by the base station. When the terminal configures a transmission D-QPSK symbol by performing estimation using the decoded bit sequence, the terminal may determine a reference symbol originally intended to be transmitted by the base station. Then, since the UE can estimate the phase difference with respect to the actually received CRS, it can use the FFI as a channel estimation purpose for the received data. Of course, the terminal can also decode the synchronization signals PSS and SSS. In detail, the terminal may perform channel estimation on 12 PRBs corresponding to the synchronization signals PSS and SSS by restoring a reference symbol and comparing the received symbol with an actual received signal.

A partial subframe is used for the case where only a part of the subframe is transmitted, such as DwPTS or UpPTS, rather than taking the form of an intact subframe, as illustrated in FIG. 17. In the current TDD-LTE specification, only DwPTS consisting of 3, 6, 9, 10, 11, or 12 OFDM symbols is defined, but according to an embodiment of the present invention, one DwPTS or UpPTS is defined. It may consist of two, four, five, seven, or eight OFDM symbols.

In detail, FIG. 21 illustrates an LTE-LAA TDD frame format that may be added through the extension structure of FIG. 17 when the maximum continuous transmission limit is 10ms.

In FIG. 21, it is illustrated that 6 bits of the n bits allocated to the FFI can be expressed except for the AUTTIS information. The FFI may include AUTTIS information, the location of the special subframe, and the total length of the transmission burst in the TDD-LTE frame format. The structure (or principle) of the LAA frame format illustrated in FIG. 21 is the same as or similar to the structure (or principle) of the LAA frame format illustrated in FIG. 17.

For example, in the LAA frame format 6 illustrated in FIG. 21, the location of the special subframe and the total transmission burst length of the TDD-LTE frame format may be represented by 010110. For another example, in LAA frame format 7, the location of the special subframe and the total transmission burst length of the TDD-LTE frame format may be represented by 010111. For another example, in LAA frame format 8, the location of the special subframe and the total length of the transmission burst of the TDD-LTE frame format may be represented by 011000. For another example, in the LAA frame format 15, the location of the special subframe and the total length of the transmission burst of the TDD-LTE frame format may be represented by 011111.

As illustrated in FIG. 21, a LAA frame format (eg, LAA frame formats 15, ..., 8-6, ..., x) may include a reserved signal, an FFI, a downlink partial subframe, and a downlink subframe. , DwPTS, GP, UpPTS, uplink subframe, and uplink partial subframe.

Hereinafter, a method of determining an opportunistic and adaptive uplink signal transmission timing suitable for an unlicensed band by using an aggregated uplink grant transmission time grant signal (AUTTIS) will be described.

The transmission time point of the uplink signal may be efficiently configured for the unlicensed band based on the frame structure illustrated in FIGS. 17 and 21.

22 is a diagram illustrating a relationship between aggregated uplink transmission time indicator signal (AUTTIS) information and uplink transmission according to an embodiment of the present invention. In detail, FIG. 22 illustrates a Wi-Fi device WFD1, a base station LLa1, and terminals UE1 and UE2 operating in an unlicensed band and a base station LLa2 operating in a licensed band.

As illustrated in FIG. 22, the AUTTIS included in the FFI includes information on an uplink frame response transmission indication for a subframe time in which a grant is granted (transmitted) within a length of a window for the AUTTIS. Imply, Here, the window for the AUTTIS corresponds to the past N subframes (eg, 12) based on a time point when the AUTTIS signal is transmitted.

That is, when the UEs that are granted the demodulation demodulate the AUTTIS, the sub-grants are granted (transmitted) among N (eg, 12) subframes in the past based on the subframe time point when the AUTTIS is transmitted. A transmission grant signal matching the timing of the frame can be checked.

In FIG. 22, a UL grant is granted (transmitted) at

subframe numbers

373, 375, and 379. That is, the UL grant (UL grant # 1) for the UE (UE2) is issued (transmitted) in SFN 373, the UL grant (UL grant # 2, UL for the UE UE1 in SFN 375 and 379). grant # 3) is issued (transmitted).

For example, the base station LLa1 approaches an unlicensed band channel at the timing of SFN 378, confirms that the channel is idle, and sends an initial signal after a certain back-off. send. Initial signals include reservation signals and FFI (including AUTOTIS). When the UE UE1 demodulates the AUTTIS included in the initial signal, the UE UE1 may check whether the grant (UL grant # 3) has been received in the past subframe from the time of performing the demodulation. That is, from another viewpoint, UEs UE1 and UE2 can obtain information on when uplink transmission can be performed through demodulation of AUTTIS.

FIG. 23 is a diagram illustrating a relationship between an AUTTIS binary bit structure and an UL grant according to an embodiment of the present invention. In detail, FIG. 23 illustrates a Wi-Fi device WFD1, a base station LLa1, and terminals UE1 and UE2 operating in an unlicensed band, and a base station LLa2 operating in a licensed band.

As illustrated in FIG. 23, the AUTTIS may represent, in subframe units, subframes in which grant information is transmitted among N (eg, 12) subframes in the past based on a subframe time point in which the AUTTIS is transmitted. Can be. For example, in the case of N = 12, AUTTIS may consist of 12 bits.

Since the transmission order of the terminal is determined from the bit closest to the MSB of the AUTTIS, the transmission order of the terminal may be automatically determined. If a plurality of terminals receive a grant at the same subframe time and transmit a signal, the plurality of terminals simultaneously transmit signals through frequency division multiplexing, as in the operation of a conventional licensed band. Can be.

In FIG. 23, the base station LLa1 gives (transmits) a UL grant (UL grant # 1) for the UE UE1 to the SFN 373, and a UL grant for the UE UE2 to the SFN 375 and SFN 379. A case of lowering (transmitting) (UL grant # 2, UL grant # 3) is illustrated.

As illustrated in FIG. 23, when each of bits for SFN 373 and SFN 375 is set to 1 out of 12 bits of AUTTIS belonging to FFI transmitted to SFN 378, the UEs UE1 and UE2 may correspond to the corresponding bits. AUTTIS is received at SFN 378 and subsequently demodulated. The UE UE1 related to the grant, which is issued (transmitted) to SFN 373, performs uplink transmission at the timing of SFN 380. In addition, the UE UE2 related to a grant issued (transmitted) at SFN 375 performs uplink transmission at the timing of SFN 381.

Therefore, AUTTIS transmitted to SFN 378 is 000000010100 (N = 12 case), and AUTTIS transmitted to SFN 384 is 000100010000 (N = 12 case). That is, among the bits of AUTTIS transmitted to SFN 378, two bits having a value of 1 are the bits closest to the MSB among the two bits having the value of 1 by the base station LLa1 at SFN 373. The bit corresponding to the transmitted UL grant (UL grant # 1) and the next closest bit to the MSB correspond to the UL grant (UL grant # 2) transmitted by the base station LLa1 at SFN 375.

Therefore, since there is no grant transmitted from SFN 374, UE UE1 and UE2 may perform uplink transmission sequentially from SFN 380 and SFN 381, and also the base station LLa1. It can be seen that the UEs UE1 and UE2 sequentially transmit an uplink signal without a gap. That is, the terminal UE1 corresponding to the bit closest to the MSB among the bits having a value of 1 belonging to AUTTIS may transmit an uplink signal before the other terminal UE2.

As a result, when the initial signal transmission by the base station LLa1 in the unlicensed band becomes possible, the base station LLa1 utilizes AUTTIS, which is asynchronous, adaptive, and aggregated in uplink. The transmission timing can be efficiently informed to the terminal. In addition, the method of utilizing AUTTIS has an advantage that uplink transmission does not have to be performed when 4ms have elapsed from a UL grant time.

AUTTIS according to an embodiment of the present invention may have a function for separately notifying a retransmission request. In the method according to the embodiment of the present invention, asynchronous retransmission scheduling is performed differently from the synchronous type hybrid automatic repeat request (HARQ) uplink transmission timing base for the existing licensed band.

As illustrated in FIG. 23, the base station LLa1 performs retransmission for an uplink subframe transmitted in SFN 381 by the UE UE2 through AUTTIS belonging to the FFI transmitted in SFN 384. Ask. The UE UE2 retransmits the uplink subframe in SFN 385.

Since the AUTTIS transmitted to the SFN 384 indicates the UL grant (UL grant # 2) transmitted to the SFN 375, retransmission of the uplink signal received by the base station LLa at the SFN 381 is not performed. Is done.

The AUTTIS transmitted to SFN 384 is 000100010000 (N = 12), where the bit closest to the MSB of the two bits with a value of 1 is the UL grant transmitted by the base station LLa at SFN 375. Grant # 2), and the next closest bit to the MSB corresponds to the UL grant (UL grant # 3) transmitted by the base station (LLa1) in SFN 379. That is, since the bit closest to the MSB among the two bits having the value of 1 corresponds to retransmission, the UE UE2 retransmits in SFN 385 and receives an UL grant transmitted in SFN 379. An uplink subframe corresponding to # 3) is transmitted in SFN 386.

24 illustrates a short LBT performed immediately before uplink transmission according to an embodiment of the present invention. In detail, FIG. 24 illustrates a Wi-Fi device WFD1, a base station LLa1, and a terminal UE2 operating in an unlicensed band and a base station LLa2 operating in a licensed band.

In detail, FIG. 24 illustrates a case in which the UE UE1 transmits an uplink signal after performing a short LBT operation before performing uplink transmission. The case where the short LBT does not apply is the default.

The method illustrated in FIG. 24 may be a method of additionally applying short LBT to the method illustrated in FIG. 23. For example, the UE UE2 may perform a short LBT before performing uplink transmission in SFN 381. For another example, the UE UE2 performs short LBT before performing retransmission for the uplink signal transmitted to SFN 381 at SFN 385 and performs short LBT before performing uplink transmission at SFN 386. Can be done. Meanwhile, the length of the subframe after the short LBT (eg, 13 OFDM symbol lengths) may be different from the length of the LTE subframe (eg, 14 OFDM symbol lengths).

If the shared channel is busy during the short LBT interval, the UE UE1 cancels uplink transmission.

However, when short LBT is applied (e.g., FIG. 24) and short LBT is not applied (e.g., FIG. 23), the overall uplink transmission timing and mechanism in terms of subframes indicated by the AUTTIS are considered. There is no difference in

Meanwhile, the length of the short LBT may be (16 + 9 * k) us. Where k is a parameter determined by the system.

According to an embodiment of the present invention, an interference causing problem that may be generated due to the use of a time division duplexing-based LTE frame format in which uplink and downlink exist in an unlicensed band can be solved.

In addition, according to an embodiment of the present invention, by adding a function not previously supported, by changing the structure of the special subframe of the TDD-LTE frame format, the interference problem caused in the guard period and the uplink transmission time Can be solved. Through this, it is possible to increase the transmission efficiency and to prevent signal collision on the wireless channel, thereby increasing the overall network throughput.

In addition, according to an embodiment of the present invention, the frame format related to the ratio and timing between the uplink subframe and the downlink subframe may be changed according to the scheduling change of the base station, and information about the frame format may be efficiently transmitted.

In addition, according to an embodiment of the present invention, the frame format indicator signal, not only for providing information about the frame format, but also for estimating frequency synchronization, such as a carrier frequency offset, And it can be used as channel estimation for demodulation of the data signal. Through this, it is possible to increase the transmission efficiency in the LTE operation of the unlicensed band.

In addition, according to an embodiment of the present invention, by efficiently applying uplink transmission in consideration of the licence-exempt characteristic to the scheduling-based LTE uplink system, not only the efficiency of the LTE-LAA network but also the network efficiency of all systems that share and use the unlicensed band. Can be increased.

3. 3. 비면허Unlicensed 주파수 대역의 무선 통신 셀룰러 시스템에서 초기 신호를 전송하는 방법 Method of transmitting initial signal in wireless communication cellular system in frequency band

In addition, the channel specification is not defined in the current LTE specification, and a procedure of detecting a channel in small units in a synchronized existing frame structure and transmitting a radio signal to quickly occupy the channel is not defined.

Currently, the frame structure of LTE is suitable for the licensed band, it is difficult to apply to the unlicensed band as it is. In fact, the unlicensed band is an environment in which multiple devices coexist and LTE signals are forced to be discontinuously transmitted by LBT. In the unlicensed band, the maximum channel occupancy time (max-COT) that the device can continuously transmit signals is limited (eg, Japan: 4 ms, Europe: 10 ms). Because of this limitation, the reception signal synchronization technology of some terminals, which could be applied to the existing licensed band receiver based on the discontinuous signal, is also difficult to apply to the unlicensed band.

In addition, there may be a case where the base station does not transmit a signal by the maximum continuous transmission length limit. For example, in Europe, even if the maximum continuous transmission length is 10 ms, a case where the base station continuously transmits a signal may be 7 ms. In this case, the procedure itself that the base station delivers information about whether the current continuous transmission length is maximum or not, and information about what length the current continuous transmission length is specifically (e.g., n units per subframe). However, it is not defined in the current LTE specification.

In addition, when a discovery reference signal (DRS) periodically transmitted by a small cell LTE base station for an existing licensed band is detected as busy by an LBT operation in an unlicensed band, It can't be sent. That is, there is a problem that the DRS applied to the current LTE licensed band cannot be transmitted periodically in the unlicensed band. The reason is that, due to regulations such as the LBT (including the contents of the CCA), in the unlicensed band, it is not guaranteed that the signal transmission succeeds at the correct timing periodically. For example, a wireless channel may be occupied by DRS of another device (eg, Wi-Fi, radar, and the like) or another base station. In such a situation, it is difficult for the device to quickly confirm an indication on whether the DRS transmission is successful, and in the current licensed band, a signal indicating whether the base station attempts to transmit the DRS transmission is not defined. .

Accordingly, a useful initial signal needs to be defined that solves all of the above problems and that is feasible for LTE wireless network operation in an unlicensed band.

Hereinafter, a method of transmitting an initial signal in a wireless communication cellular system in an unlicensed frequency band will be described.

In addition, hereinafter, a method of operating an unlicensed band LTE system characterized by discontinuous downlink burst frame transmission will be described.

In addition, hereinafter, a method for generating an initial signal for matching time synchronization and frequency synchronization of a received signal and for maintaining fine frame synchronization between an unlicensed band and a licensed band will be described.

In addition, a channel estimation method through an initial signal, which can improve the performance of a coherent signal demodulation method, will be described below.

In addition, hereinafter, a method of indicating the uplink and downlink aggregation frame length and the uplink transmission time using an initial signal will be described.

In addition, hereinafter, a method of quickly indicating whether the DRS transmission is successful using an initial signal will be described.

The method and apparatus according to the embodiment of the present invention may belong to the physical layer of the LTE wireless mobile communication system. In more detail, the method and apparatus according to an embodiment of the present invention may relate to the design of a signal transmitted from a base station to a terminal in an LTE system operating in an unlicensed band. In addition, the method and apparatus according to the embodiment of the present invention may relate to an initial signal transmission technique in which the characteristics of a signal transmission scheme of an unlicensed band rather than a licensed band are reflected. In addition, the method and apparatus according to an embodiment of the present invention, by using the initial signal, a plurality of pieces of information (eg, uplink and downlink data frame configuration information, DRS configuration information, time synchronization and frequency synchronization, channel estimation information) It may be related to the technology to provide.

Specifically, in FIG. 25, an LTE base station LLb1 to be operated in an unlicensed band has the same unlicensed band (eg, 5 GHz frequency) as the IEEE 802.11a / n / ac wireless local area network (WLAN) or Wi-Fi devices STA1b and STA2b. Band) is illustrated. In this case, we describe how to coexist and to ensure synchronization between the unlicensed and licensed bands. The LTE base station LLb1 may be an LTE license assisted access (LAA) device. Meanwhile, the LTE base station LLb1 may be operated in both an unlicensed band and a licensed band, and in this case, the signal of the unlicensed band and the licensed band can be simultaneously transmitted.

As illustrated in FIG. 25, when the Wi-Fi device STA1b is first transmitting a signal (Wi-Fi frame) by occupying a channel of an unlicensed band in time, each of the Wi-Fi device STA2b and the LTE base station LLb1 may be associated with each other. It determines that the channel is busy and suspends signal transmission.

After the signal transmission of the Wi-Fi device STA1b is finished, the Wi-Fi device STA2b and the LTE base station LLb1 detect that the corresponding channel is in an idle state.

When the Wi-Fi device STA2b detects the idle state of the channel using the CCA check function, it prepares for signal transmission, but according to the IEEE 802.11 standard, DIFS (distributed coordinate function interframe space) and random backoff (random) The signal transmission must be performed after a time delay period called back-off (eg, a distributed coordinate function (DCF), which is a function of a channel access method for Wi-Fi).

Similarly, when the LTE base station LLb1 detects an idle state of a corresponding channel by performing LBT including CCA and an arbitrary delay function, the LTE base station LLb1 prepares a signal transmission after passing a random random delay. (E.g., LBT capabilities of the European telecommunications standards institute (ETSI) standard).

At this time, the Wi-Fi device STA2b and the LTE base station LLb1 compete to use an unlicensed band, and the device that has passed the random delay time q first wins the competition and receives a signal. Can transmit Here, q is a temporal concept and may be a counter in units of 1 to 9 us.

Accordingly, each of the Wi-Fi device STA2b and the LTE base station LLb1 may transmit a signal after a certain total delay time q of a certain delay and a random backoff has passed. In the case of the Wi-Fi device STA2b, as described above, q is a DIFS time 34us and a random backoff (e.g., a multiple of 9us (including 0), i.e. a time of 0 to N * 9us, provided that N is May conform to the IEEE 802.11 standard). In the case of the LTE base station LLb1, q by the LBT function is similar to the IFFS value of the WLAN and xIFS value, and random backoff (e.g., N * 20us, where N is basically random and ETSI regulates the maximum value of N). May be 24).

For example, when the Wi-Fi device STA2b is undergoing a random backoff period (DIFS + CCA check), the LTE base station LLb1 first passes an arbitrary q period (extended CCA check) and at a time point Tb1a. An initial signal is transmitted and a partial subframe having a payload and an LTE subframe are transmitted. Due to the initial signal transmitted by the LTE base station LLb1, the Wi-Fi devices STA1b and STA2b detect that the channel is occupied and do not perform signal transmission.

LTE base station (LLb2) operating in the licensed band does not cause signal interference with the unlicensed band, but transmits a continuous signal and transmits the signal based on a format of a constant subframe, thereby allowing time for the unlicensed band. Provide a reference. The length of the LTE subframe is defined in the standard as 1ms (1000us).

In this case, the LBT may include a function of avoiding collision with not only the Wi-Fi devices STA1b and STA2b but also other LTE base stations LLb1. Until the time point when the LTE base station LLb1 starts signal transmission (e.g., Tb1a), the channel in the unlicensed band remains idle. Therefore, after it is determined that the unlicensed channel is idle, the LTE base station LLb1 completes transmission of 'one partial subframe + one full subframe' after transmitting the initial signal at the time point Tb1a. Thereafter, the Wi-Fi device STA1b and the Wi-Fi device STA2b detect that the channel is in an idle state and start a competition to occupy the channel. The Wi-Fi device STA1b first passes a random delay time q and starts signal transmission at the time point Tb1b.

After the signal transmission of the Wi-Fi device STA1b is completed, the LTE base station LLb1 wins the competition again, occupies the channel and transmits an initial signal at the time point Tb1c, and '2 partial subframes + 2 full subframes'. Send '. In the remaining sections, each of the Wi-Fi device STA1b and the Wi-Fi device STA2b wins the competition and occupies the channel.

The LBT, initial signal, and partial subframes can be transmitted in the unlicensed band by using the physical layer subframes used in the existing licensed band without modification, and also suitable for the unlicensed band. Allow burst frame formats to be provided. In accordance with an embodiment of the present invention, the initial signal is transmitted at the beginning of a signal burst that is transmitted discontinuously.

Subframes following the initial signal (including payload data (eg, physical downlink shared channel (PDSCH))) may be partial or fractional subframes or full subframes. FIG. 26 illustrates a case in which a partial subframe is located after the initial signal. The partial subframe may include a time-shifted downlink pilot time slot (DwPTS). The full subframe may have a length of 30720 * T _s . Where T _s = 1 / (30.72e6) second.

The initial signal may include a reservation signal and a compact synchronization reference signal (CSRS). The reservation signal may have a variable length. The CSRS may have a fixed length (eg, 1 OFDM symbol + CP (cyclic prefix)). For example, the CSRS may have a length of 2192 * T _s or 2208 * T _s .

The reserved signal field having a variable length may include sequences consisting of 4, 8, or 16 samples. 27 illustrates a case where the reserved signal field includes sequences of 16 samples.

When one reserved signal sequence is referred to as s (n), the s (n) region may include a minimum signal unit transmission interval having a length of about 0.521us. If the baseband digital sampling rate of LTE is 30.72 MHz, the time T _s to transmit one sample is 0.0326us (= 1 / (30.72e6)). If the digital sampling rate of the baseband is 15.36 MHz, T _s is 0.0651us (= 1 / (15.36e6)), and if the digital sampling rate of the baseband is 7.68 MHz, T _s is 0.1302us (= 1 /(7.68e6))

Thus, according to an embodiment of the present invention, the transmission time of a sequence having a length of 16 * T _s is approximately 0.521us (= 16 / (30.72e6)). Even when the sampling rate is 15.36 MHz, the transmission time of the sequence is 0.521us (= 8 / 15.36e6), and even when the sampling rate is 7.68MHz, the transmission time of the sequence is 0.521us (= 4 / 7.68e6). For reference, the transmission time of the LTE OFDM symbol is 66.67 us (= 2048 / (30.72e6)). The transmission time or length of the CP (cyclic prefix) is 4.69us (= 144 / (30.72e6)) or 5.2083us (= 160 / (30.72e6)). The length or transmission time of one LTE subframe is 1 ms (= 30720 / (30.72e6)). That is, when 1920 sequences, which are the basic units of the preamble (reservation signal), are transmitted continuously, 1 ms (1 LTE subframe may be divided into 1920 intervals).

The sequence s (n) of the time domain, having a length of 32, can be generated by Equation 28 below.

In equation (28), p is a constant for normalizing the signal,

to be.

The sequence z (k) and the index k of the frequency domain may be defined as in Equation 29 below.

In Equation 29, a _- ₅ to a ₅ are complex numbers, and can be defined as in Equation 30 below by binary bits.

and

It may be determined by, and mapped to Equation 31 below.

Where B (.) Is a binary operator function that converts to binary. E.g,

= 2

Assuming = 97, binary number

Is determined by 0110000110. So z (k) is

Becomes

If z (k) is transformed into the time domain based on equation (28), the sequence s (n) is generated. s (n) has 32 samples in the time domain. In a system with a 30.72 MHz sampling bandwidth (e.g. 100 PRB (physical resource block)), if 16 of the 32 samples of s (n) are transmitted sequentially, the 16 samples sequentially transmitted are approximately 0.5us. It is a sequence with temporal granularity. The PRB is a basic unit that occupies resources in the frequency domain corresponding to 12 subcarriers in one OFDM symbol. Likewise, in a system with a 15.36 MHz sampling bandwidth (e.g., 50 PRBs), eight samples are sequentially transmitted out of 32 samples of s (n), and in a system with a 7.68 MHz sampling bandwidth (e.g., 25 PRBs), s ( Four samples are sequentially transmitted among the 32 samples possessed by n).

In a system occupying a bandwidth of 20 MHz, a fast fourier transform (FFT) 2048 is applied for the conversion to the frequency domain, and 100 PRBs can transmit valid data. Likewise, in a system occupying a bandwidth of 10 MHz, the FFT 1024 is applied for the conversion to the frequency domain, and the number of PRBs capable of transmitting valid data is 50. Likewise, in a system occupying a bandwidth of 5 MHz, the FFT 512 is applied to convert to the frequency domain, and the number of PRBs capable of transmitting valid data is 25. One subcarrier occupies a bandwidth of 15KHz.

The temporal length of the sequence s (n) is short and may have a length of the greatest common divisor corresponding to the OFDM symbol and the CP length according to the bandwidth (eg, 100, 50, or 25 PRBs). Because of this, the sequence s (n) has a high degree of freedom, and even when the device is not occupying the channel of the unlicensed band immediately at the timing when the LBT is terminated and the signal transmission starts, the delay until the time when the actual s (n) is transmitted ( Since the delay is sufficiently short, it is possible to co-exist with other devices and to synchronize the time synchronization between the unlicensed and licensed bands.

In addition, since the reservation signal is transmitted in a constant pattern, the AGC (automatic gain control) process at the receiving end can be effectively completed in a short time. In particular, in the situation where the device does not receive the unlicensed band frame for a while due to the discontinuity of the transmission frame, even if the response characteristic of the radio channel changes and the power of the input frame changes rapidly, the reservation signal can be used to effectively respond to the AGC process. The reservation signal for channel reservation may not be transmitted depending on the situation, and may be generated and transmitted through a method other than the above-described method (eg, a method of copying a license band signal as it is).

FIG. 28 illustrates a case in which a compact synchronization reference signal (CSRS) is transmitted in time synchronization with OFDM symbol 7 of a licensed band in an unlicensed band according to an embodiment of the present invention. FIG. 28 illustrates an LTE base station LLb1 in an unlicensed band and an LTE base station LLb2 in a licensed band.

As illustrated in FIG. 28, the CSRS transmitted by the LTE base station LLb1 after the reservation signal may include one OFDM symbol. Specifically, the CSRS is located between the reservation signal and the partial subframe (or full subframe).

The location of the CSRS is related to the number (or location) of a specific OFDM symbol of the subframe corresponding to the licensed band. For example, FIG. 28 illustrates a case in which a CSRS is transmitted in OFDM symbol 7 of OFDM symbols 0 to 13 of a licensed band. The start and end of the reservation signal are determined by the transmission time of the fine symbol time field (FSTF), and likewise, the frame format indicator (FFI) can be automatically mapped to specific OFDM symbol numbers of the licensed band.

The length of the CSRS can be fixed at 2192 * T _s or 2208 * T _s based on 30.72MHz sampling.

Since the timing of signal transmission after the LBT success for the channel of the unlicensed band may occur in all cases within the subframe, a method of transmitting the synchronization reference signal CSRS according to one of the 14 OFDM symbols in the subframe may be easily considered. Can be. However, if the CSRS is not transmitted at all possible OFDM symbol positions and the CSRS is transmitted only in a limited set of OFDM symbol numbers, the terminal receiving the initial signal may limit the candidate time of the OFDM symbol number at which the CSRS is received. This can benefit from low implementation complexity.

Specifically, FIG. 29 exemplifies a case in which the transmission time of the CSRS is limited to the sixth and thirteenth OFDM symbols.

If all 14 OFDM symbols (numbered 0 to 13) are considered, the probability of success of position estimation of the CSRS becomes 1/14. However, if there is a limit at the time of transmission of the CSRS as illustrated in FIG. 29, the position of the CSRS Estimation success probability is increased to 1/2, and also the effect of limiting the type of partial subframes can be obtained.

On the other hand, the time point that can be immediately transmitted after the LBT is one of the 14 OFDM symbol number transmission timing of the subframe. Thus, in order for the CSRS to be transmitted only at a specific OFDM symbol location, the actual signal transmission time of the base station can be variably adjusted using the reservation signal, as illustrated in FIG. 29. Here, the transmission of the reservation signal does not start at the boundary of the OFDM symbol, and as illustrated in FIG. 29, the transmission of the reservation signal may be immediately started at the time when it is determined that signal transmission is possible after the LBT operation is completed. That is, the reserved signal may have a length of 1 OFDM symbol or more, or may have a length of a fractional OFDM symbol transmission.

Therefore, the terminal does not demodulate the variable length reservation signal, and instead detects the CSRS using a correlator (eg, a cross correlator). In addition, the terminal compares the detected timing of the CSRS with the timing of the licensed band to imply what kind of case the temporal transmission positions of the LTE partial subframe and the full subframe of the unlicensed band transmitted by the base station correspond to. It can be known implicitly. FIG. 29 illustrates a case where each of partial and full subframes of an unlicensed band transmitted by a base station corresponds to 7 OFDM symbols and 14 OFDM symbols.

The default length of the CSRS sequence f ₁₀₂₄ (n) is 2048 * T _s based on the 30.72MHz sampling rate and occupies 66.67us of transmission time. The length of the CPS added to the CSRS sequence f ₁₀₂₄ (n) is 2192 * T _s or 2208 * T _s , and occupies a transmission time of 71.35us or 71.875us.

CSRS Type 1 will be described with reference to FIG. 30.

In detail, FIG. 30 illustrates a frequency structure of CSRS type 1 that occupies one OFDM symbol when the bandwidth is 5 MHz. CSRS type 1 includes a primary synchronization signal (PSS) and an encoded secondary synchronization signal (eSSS).

First, the PSS of CSRS type-1 will be described.

PSS has the same configuration and mapping of the frequency axis as the licensed band LTE system. The PSS may occupy six PRBs belonging to an intermediate point among PRBs corresponding to the entire frequency bandwidth determined by the system. Here, one PRB corresponds to 12 subcarriers.

A process of generating a frequency domain sequence d _u (n) for the PSS and mapping the frequency domain may be defined as in Equation 32 below.

In Equation 32, u may be defined as shown in Table 3 below.

Root indices for the PSS

N_ID^(2)N_ID ^ (2)	Root index u Root index u
00	2525
1One	2929
22	3434

In Table 3, N_ID ^ (2) is

Indicates.

The frequency subcarrier index k of the PSS mapped to the frequency domain may be defined as in Equation 33 below.

In equation (33), n = 0,1,2, ..., 61,

Is 12. Considered in the unlicensed band

May be 25, 50, 75, or 100.

The frequency subcarrier index k of the PSS mapped to the void area is

(Where n = -5, -4, ...,-1,62,63, ..., 66).

The following describes the eSSS of CSRS type-1.

SSS applied to the existing licensed band has a role of distinguishing 168 sub cell IDs. Therefore, when three IDs of the PSS and the SSS are combined, a total of 504 physical cell identities (PCIs) may be generated. Therefore, the subcell ID of the SSS can be sufficiently represented by 8 bit (2 ⁸ = 256) information. The existing SSS, like PSS, occupies six PRBs based on the center frequency of the entire system bandwidth and is mapped in the frequency domain. However, PSS and SSS are mapped to different OFDM symbols. Therefore, if the existing design is inherited as it is and the initial signal is configured, CSRS occupies at least two OFDM symbols, a large overhead factor. Hereinafter, a method of including the PSS and the SSS in one OFDM symbol and lowering the probability of demodulation failure that may occur in the existing SSS demodulation will be described.

As described above, the SSS is a physical layer cell identity group

There are 168 IDs. Therefore, 168 IDs may be represented by 8 bits.

The eight bits may be further divided into two SSS subcell IDs (four bits).

The SSS subcell ID corresponding to the four bits may be encoded through the Reed Muller channel encoder RMs 32 and 4. Specifically, the encoding application method may be defined as in Equations 34 and 35 below.

In Equation 34, M _{i, 0} to M _{i, 3} represent a basic sequence for encoding using four Reed-Muller channel coding, _{i in} M _{i, 0} to M _{i, 3} is the index of the sequence, 0 to 3 represent a sequence number.

In Equation 35, a _n represents an input bit. For example, a 4 bit input can be converted to a 32 bit output.

A sequence generated based on Equations 34 and 35 is modulated through binary phase shift keying (BPSK), and a modulation process may be defined as in Equation 36 below.

The modulated signal based on Equation 36, through a differential (differential) modulation process and a _x d (.), _X d (.) May be encoded as shown in Equation 37 below.

Finally, the number of symbols for representing the eSSS is 66. In other words, the SSS subcell ID requires 33 symbols.

The 33 differentially modulated SSS subcell ID symbols are generated n times. Here, the number of repetition generations n is determined according to the system bandwidth. Specifically, the value of n may be defined as shown in Table 4 below according to the system bandwidth.

Number of repeatable frequencies of repeating SSS subcell ID symbols

PRB

nn
100100	1515
7575	1111
5050	77
2525	33

The number of symbols of the total BPSK that can be transmitted per port illustrated in Table 4 depends on the system bandwidth, and the mapping method for the case where the system bandwidth is 25 PRBs (n = 3) is illustrated in FIG. 30. In detail, when the total system bandwidth is 5 MHz, the eSSS subcell ID is mapped to resource element regions corresponding to 18 PRBs except for the PSS.

Meanwhile, 'eSSS + additional frame information (AFI)' may be transmitted after being encoded and modulated. Specifically, the SSS may be expressed in 8 bits, but when the device intends to transmit AFI through CSRS, the SSS may be concatenated with the 8 bit SSS and transmitted. In addition, the minimum unit of a transmitted bit may be a 4 bit unit. When the device generates and transmits an eSSS by encoding only 8 bit SSS, n = 3 repetitive transmission may be applied on the frequency, but when there is a bit for additional information, repetition of 'eSSS + AFI' The number of transmissions may be limited.

AFI may be used as a signal indicating the length of the burst frame and the transmission interval of the downlink and uplink signals. Also, the AFI may include information for identifying whether the last subframe of the downlink burst is a partial subframe as illustrated in FIG. 29.

Next, CSRS Type 2 will be described with reference to FIG. 31.

In detail, FIG. 31 illustrates a frequency structure of CSRS type 2 that occupies one OFDM symbol. As illustrated in FIG. 31, CSRS type-2 includes a cell-specific reference signal (CRS).

The CRS region (region where CRS is mapped) may have a CRS structure (using two antenna ports (eg, 0 and 1)) mapped to the existing LTE OFDM symbol 0. Can be defined.

In Equation 38, a represents a signal input to an inverse fast Fourier transform (IFFT) block as a complex symbol. In Equation 38, p represents an antenna port number and corresponds to index k of the frequency axis and index l of the OFDM symbol.

May be defined as in Equation 39 below.

In Equation 39, l represents an OFDM symbol number of a licensed band, n _s represents a slot number of a licensed band,

Represents the total bandwidth of the downlink. In Equation 39, c (i) may be defined as Equation 40 below.

In Equation 40, N _c = 1600 and the first m-sequence x ₁ (.) Is x ₁ (0) = 1, x ₁ (n) = 0 (where n = 1,2, ..., 30) Is initialized to).

The second m-sequence x ₂ (.)

Is initialized to

Where initial seed c _init is

Is defined as

Represents one of the 504 PCIs.

In Equation 39, k related to the frequency domain mapping may be defined as in Equation 41 below.

In equation (41), v is It can be defined as

In Equation 41, α is

It can be defined as

In equation (41), v _shift is

It can be defined as

On the other hand, for one burst, one OFDM symbol for the above CSRS may be transmitted, or the CSRS may be transmitted two or more times.

According to an embodiment of the present invention, the terminal may adjust AGC (automatic gain control) and time synchronization even in an unlicensed band (having a discontinuous downlink frame feature) by using an initial signal, and may perform OFDM between the unlicensed band and the licensed band. (orthogonal frequency division multiplexing) Symbol time and frame synchronization retention can be fined every burst.

In addition, according to an embodiment of the present invention, the terminal can quickly and efficiently determine whether the downlink burst signal corresponds to the signal.

In addition, according to an embodiment of the present invention, the device may obtain additional channel estimates for signals that are transmitted discontinuously.

In addition, according to an embodiment of the present invention, the terminal may know the form and arrangement of a partial subframe of the burst frame input to the terminal on the basis of the time point at which the initial signal is detected.

Also in accordance with an embodiment of the present invention, the device may convey additional information about the burst signal.

In addition, according to an embodiment of the present invention, the initial signal may be a key element technology of license assisted access (LTE-LAA), which is a standardization technology for LTE operation in an unlicensed band.

4. 비면허4. Unlicensed 주파수 대역의 무선 통신 셀룰러 시스템에서 In a wireless communication cellular system in the frequency band 적응적Adaptive 부분 서브프레임을 전송하는 방법 및 장치 Method and apparatus for transmitting partial subframe

The method according to the embodiment of the present invention belongs to the physical layer of the LTE wireless mobile communication system. Specifically, the method according to the embodiment of the present invention may be related to a partial subframe transmission method for operating the LTE system uplink and downlink signals in the unlicensed band in which signals are transmitted discontinuously. In addition, the method according to an embodiment of the present invention may relate to a technique for classifying a frame structure and a frame structure for a partial subframe.

32 is a diagram illustrating a frame form in which a reservation signal is transmitted immediately before a data subframe. In detail, FIG. 32 illustrates a case in which a reservation signal is transmitted immediately before a data subframe in order to align an unlicensed band LTE signal with a licensed band LTE signal at a subframe boundary. have.

FIG. 32 illustrates WLAN devices STA1c and STA2c and LTE base station LLc1 operating in an unlicensed band, and LTE base station LLc2 operating in a licensed band. The LTE base station LLc1 may be an LTE license assisted access (LAA) device. Meanwhile, the LTE base station LLc1 may be operated in both an unlicensed band and a licensed band. In this case, the signal of the unlicensed band and the licensed band may be simultaneously transmitted. That is, the LTE base station LLc1 and the LTE base station LLc2 may be included in one base station. The WLAN devices STA1c and STA2c may be Wi-Fi devices.

The LTE frame in the unlicensed band should be time synchronized with the LTE frame operating in the licensed band. The device has to solve this, with occupying the channel. Here, as shown in FIG. 32, the time synchronization must be correct, while the device coexists with devices (eg, STA1c and STA2c) operating in the unlicensed band, and the unlicensed band signal of the corresponding device is subframe boundary of the licensed band ( subframe boundary).

As illustrated in FIG. 32, the LTE base station LLc1 in the unlicensed band has prerequisites for supporting carrier aggregation (CA) function. That is, the LTE base station LLc1 needs to synchronize the temporal subframe boundary synchronization with respect to the LTE subframe of the licensed band in order to transmit the signal of the unlicensed band. Therefore, it is extremely unlikely that a time point at which signal transmission occurs after carrier detection (eg, performing CCA) occurs at a subframe boundary. That is, transmission after CCA is mainly performed at a point not at the boundary of the subframe. In this case, as illustrated in FIG. 32, the LTE base station LLc1 utilizes a preamble (or a reserved signal having a variable length). Any energy can be transmitted from the channel occupancy until the data transmission. For example, when the LTE base station LLc1 occupies a channel of the unlicensed band, the LTE base station LLc1 may transmit a reservation signal during the interval INTR1. Through this, the LTE base station LLc1 may prevent other devices STA1c and STA2c of the unlicensed band from occupying the corresponding channel. This method can fit subframe boundaries but has low data transmission efficiency. If the preamble (or reservation signal) is long enough, there is enough room for the LTE base station LLc1 to perform data transmission. However, in the current standard, since data may be transmitted only in units of subframes, data transmission is impossible in the interval INTR1 in which a preamble (or a reservation signal) is transmitted.

In particular, in regions such as Europe and Japan, there is a restriction on the length of a signal that can be transmitted continuously at maximum continuous due to radio wave and communication regulations, so that when the signal is transmitted as in the method illustrated in FIG. 32, the transmission efficiency is lower.

Hereinafter, types of partial subframes and transmission time points of partial subframes for improving transmission efficiency in the unlicensed band will be described. In addition, hereinafter, a structure and format of a frame burst including a partial subframe and a method of indicating the same will be described.

The method according to the embodiment of the present invention may be based on the LTE FDD scheme.

In the case of FDD, as illustrated in FIG. 33, one radio frame includes 10 subframes. One subframe occupies 1 ms and includes two slots. That is, one slot occupies 0.5 ms.

Each slot includes seven orthogonal frequency division multiplexing (OFDM) symbols, and the length of the cyclic prefix (CP) for the first OFDM symbol (0, 7) in each slot is 160 * T _s , and the remaining 6 OFDM CP for symbols (Nos. 1-6, 8-13) is 144 * T _s to be. As illustrated in FIG. 33, the length of each OFDM symbol is 2048 * T _s . Therefore, the transmission time of one slot is 15360 * T _s . Where T _s is 0.0326us (= 1 / (30.72e6)) based on the 20 MHz bandwidth.

4.1. Unlicensed Types of Partial Subframes and Transmission Times of Partial Subframes for Enhanced Transmission Efficiency in a Band

As described above, in FIG. 32, the LTE base station LLc1 operating in the unlicensed band is the same unlicensed band (eg, 5 GHz) as two IEEE 802.11a / n / ac wireless local area network (WLAN) devices STA1c and STA2c. Frequency band), a method of ensuring coexistence and synchronization with a licensed band is illustrated.

As illustrated in FIG. 32, when the WLAN device STA1c transmits a signal (WLAN frame) by occupying a channel of an unlicensed band first, each of the WLAN device STA2c and the LTE base station LLc1 may be associated with each other. It determines that the unlicensed band channel is busy and suspends signal transmission.

After signal transmission of the WLAN device STA1c is finished, the WLAN device STA2c and the LTE base station LLc1 detect that the corresponding channel is in an idle state.

When the WLAN device STA2c detects an idle state of a corresponding channel using the CCA check function, the WLAN device (STA2c) prepares a signal transmission, but, according to the specification, distributed coordinate function interframe space (DIFS) and random back-off Signal transmission must be performed after passing a time delay period (eg, a distributed coordinate function (DCF) which is a function of a channel access scheme for a WLAN).

Similarly, the LTE base station LLc1 performs an LBT function including channel activity detection and a random delay function, and transmits a signal after passing a random random delay when detecting an idle state of a corresponding channel. (E.g., LBT function of European telecommunications standards institute).

At this time, each of the WLAN device STA2c and the LTE base station LLc1 contends to use an unlicensed band, and a device that first passes a random delay time q wins the competition and receives a signal. Can transmit Here, q is a temporal concept and may be a counter in us units.

Therefore, the WLAN device STA2c and the LTE base station LLc1 may transmit signals only after a certain total delay time of a certain delay and a random backoff passes. In the case of the WLAN device STA2c, as described above, q is the DIFS time (e.g. 34us) and the Landon backoff (e.g., multiples of 9us (including 0), i.e. time of 0 to N * 9us, , N may be in accordance with the IEEE 802.11 standard). In the case of the LTE base station LLc1, q by the LBT function is similar to the IFFS value of the WLAN and xIFS value and random backoff (e.g., N * 20us, where N is basically random and the maximum value is 24 according to the regulation of ETSI). May be).

For example, in the first idle period of FIG. 32, when the LTE base station LLc1 undergoes a random backoff period (DIFS + CCA check), the WLAN device STA2c first passes a 'DIFS + random backoff period'. The WLAN frame is transmitted at the time point Tc1a.

For another example, in the second idle period of FIG. 32, the LTE base station LLc1 wins a competition with the WLAN devices STA1c and STA2c and starts signal transmission from the midpoint Tc1b of the subframe. The LTE frame burst of the unlicensed band transmitted by the LTE base station LLc1 may include a variable-length reservation signal (VLRS), a partial subframe, and a full subframe. The maximum transmission length limit can be satisfied.

However, in the current LTE standard, since data can be transmitted only in subframe units, as illustrated in FIG. 32, preamble transmission of an excessively long time is performed. This inefficient transmission structure can occur sufficiently in the unlicensed band. Under the principle of CA, transmission efficiency can be improved if the reservation signal contains a data signal which is actually valid. How a partial subframe may be used in the example of FIG. 32 will be described with reference to FIG. 34.

34 is a diagram illustrating a method of increasing transmission efficiency using a partial subframe according to an embodiment of the present invention. In detail, FIG. 34 illustrates a method of improving transmission efficiency in an unlicensed band while satisfying time synchronization and maximum transmission length regulation between an unlicensed band LTE signal and a licensed band LTE signal.

As illustrated in FIG. 34, the long VLRS illustrated in FIG. 32 may be replaced with a short VLRS, a compact synchronization reference signal (CSRS), and a starting partial subframe (SPS). In addition, an ending partial subframe (EPS) may be added to the end of the transmission. That is, in the example of FIG. 34, the transmission efficiency corresponding to the SPS and the EPS may be improved as compared to the example of FIG. 32. 34 illustrates an example in which the LTE base station LLc1 continuously transmits one SPS, three full subframes, and one EPS after VLRS and CSRS transmission.

For unlicensed band LTE, the SPS can utilize slots or downlink pilot time slots (DwPTSs) defined in existing time division duplexing (TDD) LTE-based specifications, and EPS can utilize DwPTS.

The DwPTS interval is one of the types of partial subframes for the downlink, and has a variable length according to a configuration, for example, three, six, nine, ten, eleven, and twelve OFDM symbols. It may have a length of one of the dogs. According to the length of each DwPTS section, a transmit block size (TBS) is defined. A partial subframe (eg, SPS, EPS) according to an embodiment of the present invention may be inserted into a slot having a length corresponding to seven OFDM symbols or one of 3, 6, 9, 10, 11, and 12 OFDM symbols. Leverage the DwPTS partial subframe with the corresponding length.

On the other hand, prior to the transmission of the SPS consisting of slots or DwPTS, it is necessary to adjust the transmission time to the unlicensed band. In addition, there is a need for a definition of CSRS transmitted between the VLRS and the SPS.

As illustrated in FIG. 34, a synchronization signal CSRS is transmitted after the preamble (or VLRS). In addition, the SPS may be transmitted immediately after the synchronization signal CSRS is transmitted. This structure will be described in detail with reference to FIG. 35.

FIG. 35 is a diagram illustrating a relationship between a transmission time of a starting partial subframe and a transmission time of a reservation signal and a synchronization signal according to an embodiment of the present invention. Specifically, FIG. 35 illustrates a relationship between the transmission time of the SPS and the transmission time of the VLRS, and the relationship between the transmission time of the SPS and the transmission time of the CSRS. Here, the SPS may utilize a slot or time-shifted DwPTS (hereinafter, referred to as 'TS-DwPTS').

As illustrated in FIG. 35, the SPS is transmitted after the VLRS and the CSRS are transmitted, and the SPS may include a common control subframe indicator (CCSI). Full subframes transmitted after the SPS may also include CCSI, and EPS may also include CCSI. The full subframe may be transmitted instead of the EPS.

The VLRS and CSRS illustrated in FIG. 35 will be described, and the slot or TS-DwPTS including data will be described.

4.1.1. VLRS

The region of the sequence v (n) for the preamble (or VLRS) having a variable length may include a minimum signal unit transmission interval having a length of about 0.521us. When the digital sample rate of LTE is 30.72 MHz, the time T _s taken to transmit one sample is 0.326us (= 1 / (30.72e6)). Thus, when the digital sampling rate is 30.72 MHz, the transmission time of a sequence having length 16 (16 samples) is 16 / (30.72e6) = 0.521us. For reference, the transmission time of an LTE OFDM symbol is 2048 / (30.72e6) = 66.67us. The transmission time (or length) of the CP is 144 / (30.72e6) = 4.69us or 160 / (30.72e6) = 5.2083us. The length (or transmission time) of one LTE subframe is 30720 / (30.72e6) = 1 ms. That is, if the sequence, which is the basic unit of the preamble (or VLRS), is transmitted in 1920 consecutively, it becomes 1 ms (one LTE subframe may be divided into 1920 intervals). Hereinafter, the sequence for the VLRS is called a VLRS sequence.

The VLRS sequence v (n) of the time domain having a length of 16 may be generated by Equation 42 below.

In equation (42), p is a constant for normalizing the signal,

(Where f _s is sampling rate and N is number of elements of v (n)). In Equation 42, the VLRS sequence v (n) includes 16 elements.

The VLRS sequence z (k) and the index k in the frequency domain may be defined as in Equation 43 below.

In Equation 43, the index k may have a value of -N / 2 to N / 2-1 (eg, -8 to 7).

In Equation 43, a _- ₄ to a ₄ are complex numbers, and can be defined by Equation 44 below by binary bits.

In Equation 44, binary bits b _- ₄ to b _{4 are parts} of a physical cell ID of a base station defined in the LTE standard.

May be mapped to Equation 45 below.

Where B (.) Is a binary operator function that converts to binary. E.g,

Assume that = 97, binary number

Is determined by 01100001. Therefore, z (k) is

Becomes

When p is 4, if z (k) is transformed into the time domain based on Equation 42, the following VLRS sequence v (n) having a length of 16 can be generated.

Since the variable length preamble (or VLRS) has a granularity of about 0.5us, it can have a high degree of freedom, and the device occupies the coexistence channel at any point in the subframe and licenses under any circumstances. It is possible to match the OFDM symbol time synchronization with the band.

As illustrated in FIG. 36, when the digital sampling rate of LTE is 30.72 MHz, the time taken to continuously transmit a plurality of VLRS sequences (having a length of 16) is determined by transmission of one 'CP + OFDM symbol'. Exactly the time taken. One VLRS sequence v (n) may have a length (number of samples) of 16, 12, 8, or 4.

Specifically, the time taken to continuously transmit 128 VLRS sequences v (n) is exactly the same as the transmission time of one OFDM symbol. The length (or transmission time) of the CP for each of

OFDM symbols

0 or 7 of the subframe is equal to the time taken to continuously transmit 10 VLRS sequences. The length (or transmission time) of the CP for each of OFDM symbols 1 to 6 or 8 to 13 of a subframe is equal to the time taken to continuously transmit nine VLRS sequences.

On the other hand, when the digital sampling rate of the LTE is 15.36MHz, the time it takes to transmit one of the sample T _s is 1 / a (15.36e6) = 0.651us. Therefore, when the digital sampling rate is 15.36 MHz, the transmission time of the VLRS sequence having a length of 8 is 8 / (15.36e6) = 0.521us.

The VLRS sequence v (n) of the time domain having a length of 8 may be generated by Equation 46 below.

In equation (46), p is a constant for normalizing the signal,

to be.

The VLRS sequence z (k) and the index k in the frequency domain may be defined as in Equation 47 below.

In Equation 47, a _- ₂ to a ₂ are complex numbers, and can be defined by Equation 48 below by binary bits.

The binary bits, b _- ₂ through b ₂ , are part of the physical cell ID of the base station defined in the LTE specification.

It may be determined by the even bit of, and may be mapped to Equation 49 below.

In Equation 49, B _EVEN (.) Is a function of converting an input value into a binary number and extracting an even bit among the converted bits. And

The maximum size of is 255. E.g,

Assume that = 97 is an even-bit collection

Is determined to be 0100. So z (k) is

Becomes

When p is 4, if z (k) is converted to the time domain based on Equation 46, the next VLRS sequence v (n) having a length 8 may be generated.

4.1.2. CSRS

37 illustrates a frequency domain structure of a CSRS according to an embodiment of the present invention. Specifically, FIG. 37 illustrates a frequency structure of CSRS (having a length of time corresponding to one OFDM symbol) that occupies one OFDM symbol. In Figure 37,

Denotes the number of physical resource blocks (PRBs) corresponding to the total downlink bandwidth of the system, and one PRB includes 12 subcarriers.

The frequency domain to which the CSRS is mapped may have a CSRS structure (using antenna port 0) mapped to OFDM symbol 0 of the existing LTE subframe, and may be generated by Equation 50 below.

In Equation 50, a denotes a signal input to an inverse fast Fourier transform (IFFT) block as a complex symbol. In Equation 50, p represents an antenna port number and corresponds to index k of the frequency axis and index l of the OFDM symbol. May be defined as in Equation 51 below.

In Equation 51, l denotes an OFDM symbol number of a licensed band and n _s denotes a slot number of a licensed band.

Denotes the largest PRB number corresponding to the entire downlink bandwidth. c (i) may be defined as in Equation 52 below.

In Equation 52, N _c = 1600 and the first m-sequence x ₁ (.) Is x ₁ (0) = 1, x ₁ (n) = 0 (where n = 1,2, ..., 30) Is initialized to).

The second m-sequence x ₂ (.)

Is initialized to

Here, the initial seed c _init is

Is defined as

Represents a physical cell identity (PCI) of the base station and represents one of 504 PCIs.

In Equation 50, an index k related to frequency domain mapping may be defined as in Equation 53 below.

In Equation 53, v may be defined as v = 0.

In Equation 53, α is

It can be defined as

In equation 53, v _shift is

It can be defined as

As illustrated in FIG. 38, the transmission of the CSRS may be canceled by the determination of the LTE base station LLc1. Specifically, the SPS may be transmitted without the CSRS after the VLRS is transmitted.

4.1.3. SPS , FS ( full subframe ), And EPS

As described above, the SPS may be configured as a slot or TS-DwPTS. The SPS may be transmitted in time after the VLRS and CSRS transmissions.

As illustrated in FIG. 35 or 38, the EPS corresponds to the end of the continuous transmission and may be transmitted in the form of DwPTS.

Hereinafter, a partial subframe defined using a slot or a DwPTS will be described, and an overall frame burst format that can be configured corresponding to a case that can occur in an unlicensed band will be described.

TS-DwPTS and DwPTS may be defined as shown in Table 5 below.

Definition and Length of DwPTS and TS-DwPTS

Partial subframe lengthPartial subframe length	DwPTSDwPTS	TS-DwPTSTS-DwPTS
3 OFDM symbols3 OFDM symbols	6592T_s 6592 T _s	6576T_s 6576 T _s
6 OFDM symbols6 OFDM symbols	13168T_s 13168 T _s	13152T_s 13152 T _s
9 OFDM symbols9 OFDM symbols	19760T_s 19760 T _s	19744T_s 19744 T _s
10 OFDM symbols10 OFDM symbols	21952T_s 21952 T _s	21936T_s 21936 T _s
11 OFDM symbols11 OFDM symbols	24144T_s 24144 T _s	24128T_s 24128 T _s
12 OFDM symbols12 OFDM symbols	26336T_s 26336 T _s	26320T_s 26320 T _s

However, the SPS is not configured by the result of the LBT, and a full subframe may be transmitted without the SPS.

If the transmission time of the VLRS is determined to be the time corresponding to one of the 14 OFDM symbols in the subframe according to the LBT result, the SPS is configured and the full subframe immediately without the SPS and the case transmitted after the 'VLRS + CSRS'. This case is configured and transmitted after 'VLRS + CSRS' will be described with reference to FIGS. 39 to 42.

FIG. 39 is a diagram illustrating an initial partial subframe and a ending partial subframe configuration based on a transmission time of a VLRS when the maximum transmission length is 4 ms according to an embodiment of the present invention.

Specifically, FIG. 39 illustrates a case where the SPS is configured as a slot. That is, FIG. 39 exemplifies a case in which the SPS has a length of seven OFDM symbols.

39 illustrates a case where the transmission time of the CSRS is limited to the 6 and 13 OFDM symbols.

As illustrated in FIG. 39, a time point at which transmission can be performed immediately after LBT is one of 14 OFDM symbol number transmission timings of a subframe. Therefore, in order for the CSRS to be transmitted only at specific OFDM symbol positions (No. 6 and No. 13), the actual signal transmission time of the LTE base station LLc1 may be variably adjusted using the VLRS. Here, the transmission of the VLRS does not start at the boundary of the OFDM symbol, and as illustrated in FIG. 39, the transmission of the VLRS may be immediately started at the time when it is determined that signal transmission is possible after the LBT operation is completed. That is, the LTE base station LLc1 may immediately transmit the VLRS at a signal transmission possible time without waiting for the start time of the OFDM symbol. The VLRS may have a length of at least one OFDM symbol, or may have a length of a fractional OFDM symbol (eg, a length smaller than the length of one OFDM symbol).

In FIG. 39, the case in which the EPS has three, six, nine, ten, eleven, or twelve OFDM symbols is illustrated.

As illustrated in FIG. 39, the SPS or the EPS may or may not be configured according to the transmission time of the VLRS.

40 is a diagram illustrating an initial partial subframe and a final partial subframe configuration based on a transmission time of a VLRS when the maximum transmission length is 4 ms according to another embodiment of the present invention. Specifically, FIG. 40 illustrates a case where the SPS is configured as a slot and the CSRS is excluded.

40 differs from the embodiment of FIG. 39 in that CSRS transmission is canceled.

FIG. 41 is a diagram illustrating an initial partial subframe and a last partial subframe configuration based on a transmission time of a VLRS when the maximum transmission length is 4 ms according to another embodiment of the present invention. FIG. In detail, FIG. 41 illustrates a case where the SPS is configured based on the TS-DwPTS.

In FIG. 41, the case where the SPS has a length of 12, 11, 10, 9, 7, 6, or 3 OFDM symbols is illustrated.

FIG. 41 exemplifies a case where the transmission time of the CSRS is OFDM symbols 1 to 4, 6, 7, 10, or 13.

As illustrated in FIG. 41, the transmission of the VLRS is not started at the boundary of the OFDM symbol, and the transmission of the VLRS may be immediately started at the time when it is determined that signal transmission is possible after the LBT operation is completed.

In FIG. 41, the case where EPS has three, six, nine, ten, eleven, or twelve OFDM symbols is illustrated.

As illustrated in FIG. 41, the SPS or the EPS may or may not be configured according to the transmission time of the VLRS.

FIG. 42 is a diagram illustrating an initial partial subframe and a final partial subframe configuration based on a transmission time of a VLRS when the maximum transmission length is 4 ms according to another embodiment of the present invention. In detail, FIG. 42 exemplifies a case in which the SPS is configured based on the TS-DwPTS and the CSRS is excluded.

The embodiment of FIG. 42 differs from the embodiment of FIG. 41 in that CSRS transmission is canceled.

The number of types of DwPTS which is a concept of partial subframes (eg, SPS and EPS) according to an embodiment of the present invention is limited. As long as the positions of the partial subframes are shuffled, frame burst formats in all cases can be created. In addition, since independent scheduling is possible for each partial subframe, even when retransmission is performed, the terminal may necessarily receive a signal in one of the frame types of FIGS. 39 to 42.

4.1.4. CCSI

In the LTE frame structure for the LAA, as illustrated in FIG. 39, an initial portion of valid data transmission is limited to a partial subframe (actually a slot) or a full subframe, depending on a transmission time of the VLRS. In addition, the form of the frame transmitted following the initial portion of the data transmission may be a partial subframe or a full subframe again. In addition, the last part of the data transmission may be a partial subframe or a full subframe.

Accordingly, the terminal (receiver) receives information on whether the current or next subframe received is a partial subframe, a full subframe, or a special subframe, and a control channel (eg, a physical downlink control channel (PDCCH)). It can be recognized through the CCSI information included in). CCSI information may be defined as shown in Tables 6 and 7 below, and the base station may transmit CCSI information through a PDCCH which is a control channel.

Definition and length of least significant bit (LSB) 4 bits included in CCSI

CCSI signalCCSI signal	Current or Next subframe configurationCurrent or Next subframe configuration
00	Next subframe is 3 OFDM symbolsNext subframe is 3 OFDM symbols
1One	Next subframe is 6 OFDM symbolsNext subframe is 6 OFDM symbols
22	Next subframe is 9 OFDM symbolsNext subframe is 9 OFDM symbols
33	Next subframe is 10 OFDM symbolsNext subframe is 10 OFDM symbols
44	Next subframe is 11 OFDM symbolsNext subframe is 11 OFDM symbols
55	Next subframe is 12 OFDM symbolsNext subframe is 12 OFDM symbols
66	Next subframe is full (14 OFDM symbols)Next subframe is full (14 OFDM symbols)
77	Current subframe is 3 OFDM symbolsCurrent subframe is 3 OFDM symbols
88	Current subframe is 6 OFDM symbolsCurrent subframe is 6 OFDM symbols
99	Current subframe is 9 OFDM symbolsCurrent subframe is 9 OFDM symbols
1010	Current subframe is 10 OFDM symbolsCurrent subframe is 10 OFDM symbols
1111	Current subframe is 11 OFDM symbolsCurrent subframe is 11 OFDM symbols
1212	Current subframe is 12 OFDM symbolsCurrent subframe is 12 OFDM symbols
1313	Current subframe is full and end of transmissionCurrent subframe is full and end of transmission
1414	ReservedReserved
1515	ReservedReserved

Definition of the most significant bit (MSB) 3 bits included in CCSI

CCSI signalCCSI signal	Current or Next subframe configurationCurrent or Next subframe configuration
00	Next subframe is a downlink subframeNext subframe is a downlink subframe
1One	Next subframe is a special subframe and end of downlink subframeNext subframe is a special subframe and end of downlink subframe
22	Next 1 subframe is an uplink subframe Next 1 subframe is an uplink subframe
33	Next 2 subframes are uplink subframes Next 2 subframes are uplink subframes
44	Next 3 subframes are uplink subframes Next 3 subframes are uplink subframes
55	Next 4 subframes are uplink subframes Next 4 subframes are uplink subframes
66	Next 5 subframes are uplink subframes Next 5 subframes are uplink subframes
77	Next 6 subframes are uplink subframes Next 6 subframes are uplink subframes

As illustrated in FIG. 35 or 38, the CCSI may be included in a control channel of a partial subframe (eg, SPS, EPS) or a full subframe, and the CCSI may have a total of 7 bit information. CCSI may indicate configuration information on the current subframe or the next subframe. Specifically, the LSB 4 bits of the CCSI represents the number of OFDM symbols occupied in the current or next subframe and may be defined as shown in Table 6. The MSB 3 bits of the CCSI indicate whether the next subframe is a downlink subframe, a special subframe or an uplink subframe, and may be defined as shown in Table 7.

43 is a diagram illustrating a relationship in which a downlink control information channel and a downlink data channel of a partial subframe are mapped to a frequency domain according to an embodiment of the present invention. Specifically, FIG. 43 exemplifies a PDCCH, an enhanced PDCCH (EPDCCH), and a physical downlink shared channel (PDSCH) for downlink, an uplink pilot time slot (UpPTS) and a physical uplink shared channel (PUSCH) for uplink. have.

As illustrated in FIG. 43, a DwPTS (or TS-DwPTS) or a slot may be composed of a PDCCH (or EPDCCH) region and a PDSCH region. The PDCCH (or EPDCCH) includes downlink control information (DCI). PDSCH transmits data.

Since the ePDCCH may have fewer resources than the PDCCH, the ePDCCH may be allocated to the PDSCH region alone without the PDCCH. The PDCCH includes CCSI information.

4.2. Unlicensed To support uplink in the band CCSI Signaling And the transmission time of the special subframe, the full subframe, and the partial subframe.

Hereinafter, a method of transmitting an uplink signal using an SPS, a full subframe, a special subframe, an EPS, and a CCSI (in a control channel) will be described.

In detail, FIG. 44 illustrates an LTE-LAA TDD frame format in which uplink and downlink exist together. The LTE-LAA TDD frame format of FIG. 44 may be classified through the application of FIG. 35 or 38.

In Case 1 illustrated in FIG. 44, the LTE-LAA TDD frame format includes a VLRS, a CSRS, a downlink SPS (including CCSI), a special subframe (DwPTS, VLRS, GP, UpPTS), and two uplink full sub subs. It may include a frame.

In Case 2 illustrated in FIG. 44, the LTE-LAA TDD frame format includes VLRS, CSRS, downlink SPS (including CCSI), downlink full subframe, special subframe (DwPTS, VLRS, GP, UpPTS), and It may include an uplink full subframe.

In Case 3 illustrated in FIG. 44, the LTE-LAA TDD frame format includes a VLRS, a CSRS, a downlink SPS (including CCSI), two downlink full subframes, and a special subframe (DwPTS, VLRS, GP, UpPTS). ) May be included.

In Case 4 illustrated in FIG. 44, the LTE-LAA TDD frame format may include a VLRS, a CSRS, a downlink SPS (including CCSI), and three downlink full subframes.

The LTE-LAA TDD frame format of FIG. 44 may be represented through 7 bit CCSI included in the PDCCH.

As illustrated in FIG. 44, 7 bit CCSI information included in the SPS includes a contiguous downlink subframe (or downlink partial subframe), a special subframe, and an uplink subframe (or uplink partial subframe). It can be determined by the configuration and transmission time.

In Case 1 illustrated in FIG. 44, CCSI information included in the SPS is 0010010. Specifically, to inform that the subframe transmitted after the SPS is a special subframe, the MSB 3 bit of the CCSI (7 bits) becomes 001, and the downlink transmission portion (DwPTS) of the special subframe includes 9 OFDM symbols. In order to indicate the information that occupies, the LSB 4 bit of the CCSI (7 bits) is 0010.

In Case 2, Case 3, and Case 4 illustrated in FIG. 44, the CCSI information included in the SPS is 0000110. Specifically, to inform that the subframe transmitted after the SPS is a downlink subframe, the MSB 3 bits of the CCSI are 000, and the subframe transmitted after the SPS is called a full subframe (which occupies 14 OFDM symbols). To inform the information, the LSB 4 bit of CCSI is 0110.

As illustrated in FIG. 45, CCSI information included in a subframe (special subframe or downlink subframe) transmitted after the SPS is different from CCSI information (FIG. 44) included in the SPS.

In the continuous transmission burst of Case 1 illustrated in FIG. 45, the CCSI information included in the special subframe after the SPS is 0111010. Specifically, to inform that the subframe transmitted at the next subframe timing is an uplink subframe and two uplink subframes are configured, the MSB 3 bit of the CCSI (7 bits) becomes 011. And to inform that the downlink transmission part (DwPTS) of the current special subframe occupies 10 OFDM symbols, the LSB 4 bit of the CCSI (7 bits) is 1010.

In Case 2 illustrated in FIG. 45, the CCSI information included in the subframe after the SPS is 0010011. Specifically, to inform that the subframe transmitted after the current subframe is a special subframe and the end of the downlink subframe, the MSB 3 bit of the CCSI (7 bits) is 001. In order to indicate that the downlink transmission portion (DwPTS) of the special subframe after the current subframe occupies 10 OFDM symbols, the LSB 4 bit of the CCSI (7 bits) becomes 0011.

In

Cases

3 and 4 illustrated in FIG. 45, the CCSI information included in the special subframe after the SPS is 0000110. Specifically, to inform that the subframe after the current subframe is a downlink subframe, the MSB 3 bit of the CCSI (7 bits) becomes 000. In order to indicate that the downlink subframe after the current subframe is a full subframe (which occupies 14 OFDM symbols), the LSB 4 bit of the CCSI (7 bits) becomes 0110.

Meanwhile, as illustrated in FIG. 44 or FIG. 45, the uplink includes an UpPTS and a legacy LTE uplink subframe. Between the downlink transmission period and the uplink transmission period, there is a VLRS and a void guard period (GP) in which no signal is transmitted.

FIG. 47 is a diagram illustrating downlink and uplink frame configuration using VLRS, partial subframe (TS-DwPTS), downlink full subframe, UpPTS, and uplink subframe according to an embodiment of the present invention. .

46 and 47 illustrate a case in which a downlink SPS has a length of 7 OFDM symbols and a DwPTS of a special subframe has a length of 12 OFDM symbols.

The embodiment of FIG. 47 differs from the embodiment of FIG. 46 in that CSRS is not transmitted.

If a special subframe is transmitted, the position at which the special subframe can be transmitted is relative depending on when the initial VLRS is transmitted. 46 and 47, the reason why a special subframe is not transmitted from the initial transmission signal is because a UE (receiver) is configured for processing time for performing uplink transmission after demodulating CCSI. This may be due to a lack of margin. That is, in order for the terminal to sufficiently provide the time margin necessary for demodulating the information of the CCSI included in the downlink transmission and preparing for the uplink transmission, all initial transmissions are performed in the downlink transmission. As a result, the difference between the time point at which CCSI of the initial downlink data transmission signal (eg, SPS or starting full subframe) is transmitted and the time point at which the first uplink transmission is made becomes 1.5 subframe or more.

Thus, as illustrated in FIG. 46 or 47, the downlink subframe (or partial subframe) is transmitted at least once before the special subframe.

48 and 49 illustrate a case in which a downlink SPS has a length of 7 OFDM symbols and a DwPTS of a special subframe has a length of 12 OFDM symbols.

48 and 49 differ from the embodiment of FIGS. 46 and 47 in that an uplink signal is transmitted without an UpPTS.

The embodiment of FIG. 49 differs from the embodiment of FIG. 48 in that CSRS is not transmitted.

4.3. Aggregated uplink transmission time grant signal ( AUTTIS : aggregated uplink transmission time indicator signal ), Unlicensed Suitable for bands Opportunity Adaptive adaptive A method of determining uplink signal transmission timing

Based on the frame structure illustrated in FIG. 44 or 45, a transmission time of an uplink signal may be efficiently determined according to an unlicensed band.

50 is a diagram illustrating a relationship between UL grant and AUTTIS information and uplink transmission according to an embodiment of the present invention. 50 illustrates an example of a Wi-Fi device STA3c and terminals UE1 and UE2 that operate in an unlicensed band, and an LTE base station LLc1 that operates in both an unlicensed band and a licensed band.

In detail, in FIG. 50, when the LTE unlicensed band system and the Wi-Fi system coexist, it is illustrated when the terminal that is granted the grant of the base station should perform uplink transmission.

As illustrated in FIG. 50, UL grants are issued (transmitted) at

subframe numbers

373, 375, and 379. That is, UL grant # 1 for CCSI and UE2 is transmitted at the timing of SFN 373 and UL grant # 1 for CCSI and UE1 at the timing of

SFN

375 and 379 at the timing of SFN 373. 2, UL grant # 3) is transmitted. In the present specification, transmitting or receiving a signal at SFN A includes transmitting or receiving a signal at the timing of SFN A.

When the UL grant is transmitted, the UEs UE1 and UE2 that have received the UL grant prepare to perform uplink transmission. However, the time point at which the UEs UE1 and UE2 actually transmit the uplink signal is immediately after the time point at which the AUTTIS is received.

As illustrated in FIG. 50, when UL grants (UL grant # 1, # 2, # 3) are transmitted at

SFNs

373, 375, and 379, the LTE base station LLc1 is assigned to

SFNs

378 and 384. Verify that the unlicensed band channel is idle at the timing of the burn. The LTE base station LLc1 succeeds in accessing the corresponding channel, and transmits the VLRS and the CSRS after a certain back-off. CSRS may be omitted and replaced with VLRS.

The LTE base station LLc1 transmits a control channel (eg, PDCCH) including AUTTIS and CCSI at

timings SFN

379 and 385.

Subsequently, at

timings SFN

379 and 385, UEs UE1 and UE2 demodulate the AUTTIS included in the control channel.

When the UEs UE1 and UE2 successfully demodulate the AUTTIS, the UE transmits time information in the past N (eg, 8) subframe times from the demodulation time point. Here, the terminal transmission time information means transmission time information of the transmittable terminal determined by the LTE base station LLc1. That is, since UEs UE1 and UE2 know the time point of receiving the UL grant through the previous control channel reception, the UL grant time indicated by AUTTIS and the UL grant actually received by the UEs UE1 and UE2. If the time points of) coincide with each other, the UEs UE1 and UE2 may perform uplink transmission.

As described above, the AUTTIS included in the control channel (eg, PDCCH) includes information on an uplink frame response transmission indication with respect to a subframe time in which a UL grant is transmitted within a length of a window for the AUTTIS. Imply, Here, the window for AUTTIS corresponds to N subframes (eg, eight) in the past based on the AUTTIS transmission time point.

That is, if the UEs UE1 and UE2 that have received UL grants demodulate the AUTTIS, the past N (eg, 8) are based on the subframe time point (eg, SFN 379 or 385) where the AUTTIS is transmitted. In the subframes, it is possible to check a grant signal that matches the timing of the subframe in which the UL grant is transmitted.

Meanwhile, in FIG. 50, UEs UE1 and UE2 do not check whether an unlicensed band channel is in an idle state. That is, when UEs UE1 and UE2 receive AUTTIS, if a predetermined time (for example, 4 ms) has elapsed from the time point of receiving the UL grant, the UE UE1 and UE2 are upgraded according to the order indicated by AUTTIS without checking the channel state. Link transmission can be performed. To this end, the LTE base station LLc1 performs scheduling (eg, continues transmitting VLRS) for the unlicensed band channel.

Transmission and retransmission of the UEs UE1 and UE2 will be described in detail with reference to FIG. 51.

FIG. 51 is a diagram illustrating a relationship between an AUTTIS binary bit structure and an UL grant according to an embodiment of the present invention. FIG. FIG. 51 illustrates a Wi-Fi device STA3c and terminals UE1 and UE2 that operate in an unlicensed band and an LTE base station LLc1 that operates in both an unlicensed band and a licensed band. Specifically, the embodiment of FIG. 51 is based on the embodiment of FIG. 50.

As illustrated in FIG. 51, AUTTIS may represent, in subframe units, subframes in which UL grant information is transmitted among N (eg, 8) subframes in the past, based on when AUTTIS is transmitted. have. For example, in the case of N = 8, AUTTIS may consist of 8 bits.

Since the transmission order of the terminal is determined from the bit closest to the MSB of the AUTTIS, the transmission order for the plurality of terminals may be automatically determined.

For example, UL grant # 1 for UE2 is transmitted at SFN 373 and UL grant # 2 and # 3 for UE1 at

SFN

375 and 379 are transmitted. Assuming transmission, the transmission timing of UEs UE1 and UE2 will be described in detail.

As illustrated in FIG. 51, AUTTIS received by UEs UE1 and UE2 at the timing of SFN 379 may provide information about SFNs for which UL grant is granted among SFN 369 to SFN 376. Inform).

When each of bits for SFN 373 and SFN 375 is set to 1 among 8 bits of AUTTIS transmitted from SFN 379 (when bits for the remaining SFN are set to 0), UEs UE1 and UE2 are SFN 379. After receiving and demodulating the corresponding AUTTIS at the UE, UE2 related to the UL grant (UL grant # 1) transmitted at SFN 373 performs uplink transmission at the timing of SFN 380 and is transmitted at SFN 375. The UE UE1 related to the UL grant # 2 performs uplink transmission at the timing of SFN 381. That is, the UE UE2 confirms that among the 8 bits of AUTTIS transmitted in SFN 379, four bits before the bit for SFN 373 have a value of 0, and the SFN following SFN 379 in which AUTTIS is transmitted. Uplink transmission is performed at 380. The UE UE1 confirms that there is one bit (bit for SFN 373) having a value of 1 before the bit for SFN 375 among the 8 bits of AUTTIS transmitted from SFN 379, and AUTTIS Waits one subframe time from the transmitted SFN 379 and then performs uplink transmission in SFN 381.

That is, 2 bits (bits for SFN 373 and SFN 375) are set to 1 out of 8 bits of AUTTIS transmitted from SFN 379. The UL grant (UL grant # 1) corresponding to the bit closest to the MSB among the two bits having the value of 1 has priority to transmit a signal. Accordingly, the UE UE2 transmits an uplink signal before the UE UE1 in SFN 380, and then the UEUE1 performs an uplink signal transmission in SFN381.

The AUTTIS transmitted in SFN 379 is 00001010 (if N = 8), and the AUTTIS transmitted in SFN 385 is 10001000 (if N = 8). That is, among the bits of the AUTTIS transmitted in SFN 379, two bits have a value of 1, and among the two bits having the value of 1, the bit closest to the MSB is the LTE base station (LLc1) in SFN 373. Corresponds to the UL grant (UL grant # 1) transmitted by the MSB, and the next bit closest to the MSB corresponds to the UL grant (UL grant # 2) transmitted by the LTE base station LLc1 at SFN 375.

Therefore, since there is no UL grant transmitted from SFN 374, UE UE2 and UE1 can perform uplink transmission sequentially from SFN 380 and SFN 381, and the LTE base station LLc1. It can also be seen that the UEs UE2 and UE1 sequentially transmit an uplink signal without a gap.

As a result, when AUTTIS transmission is possible by the LTE base station LLc1 in the unlicensed band, the LTE base station LLc1 is asynchronous, adaptive, and aggregated to efficiently uplink transmission timing. It can inform the UE (UE1, UE2). In addition, the method using AUTTIS has the advantage that uplink transmission does not need to be performed when a predetermined time (for example, 4 ms) has elapsed from the UL grant time, that is, transmission time flexibility.

If a plurality of terminals receive a UL grant at the same subframe time and transmit a signal, the plurality of terminals simultaneously transmit signals through frequency division multiplexing, as in the operation of a conventional licensed band. Can transmit

On the other hand, AUTTIS may have a function for notifying the retransmission request separately. In the method according to the embodiment of the present invention, asynchronous retransmission scheduling may be performed, unlike a hybrid automatic repeat request (HARQ) uplink transmission timing based scheme of a synchronous type, which is a scheme for an existing licensed band. .

As illustrated in FIG. 51, the LTE base station LLc1 requests the UE UE1 to retransmit an uplink subframe transmitted by the UE UE at SFN 381 through a licensed band at SFN 383. . That is, when the base station LLc1 does not receive the uplink subframe transmitted by the terminal UE1 in SFN 381, the LTE base station LLc1 may request the terminal UE1 to retransmit the corresponding uplink subframe. The UE UE1 retransmits the uplink subframe in SFN 386.

Since the AUTTIS transmitted from SFN 385 indicates the UL grant (UL grant # 2) transmitted from SFN 375 (MSB 1 bit of AUTOTTIS has a value of 1), the AUTTIS is transmitted to the LTE base station LLc1. Retransmission is performed for the uplink signal received at SFN 381. In FIG. 51, a window for AUTTIS transmitted from SFN 385 corresponds to SFN 375 to SFN 382.

The AUTTIS transmitted on SFN 385 is 10001000 (if N = 8), where the bit closest to the MSB of the two bits with a value of 1 is the UL grant transmitted by the LTE base station (LLc1) on SFN 375. (UL grant # 2), and the next closest bit to the MSB corresponds to the UL grant (UL grant # 3) transmitted by the LTE base station LLc1 in SFN 379. That is, since the bit closest to the MSB among the two bits having the value of 1 corresponds to retransmission, the UE UE1 retransmits in SFN 386 and receives an UL grant transmitted in SFN 379. An uplink subframe corresponding to # 3) is transmitted in SFN 387.

52 is a view showing short LBT performed immediately before uplink transmission according to an embodiment of the present invention. FIG. 52 illustrates a Wi-Fi device STA3c and a terminal UE1 operating in an unlicensed band and an LTE base station LLc1 operating in both an unlicensed band and a licensed band.

FIG. 52 illustrates a case where the LTE base station LLc1 transmits a control channel including AUTTIS and CCSI at the timing of SFN 386.

As illustrated in FIG. 52, the UE UE1 may transmit an uplink signal after performing a short LBT operation before performing uplink transmission. The case where the short LBT is not applied (eg, the embodiment of FIG. 51) corresponds to a default.

As illustrated in FIG. 52, the time of the short LBT performed by the UE UE1 is shorter than the time of the LBT described above (eg, the time of the LBT performed by the LTE base station LLc1).

If the shared channel is busy during the short LBT period, the UE UE1 cancels the uplink transmission. If the shared channel is idle, the UE UE1 performs the uplink transmission.

However, when the short LBT is applied (e.g., the embodiment of FIG. 52) and when the short LBT is not applied (e.g., the embodiment of FIG. 51), the overall uplink transmission timing indicated in subframe units by the AUTTIS and There is no difference in mechanism. That is, although the embodiment of FIG. 52 is different from the embodiment of FIG. 51 in that a short LBT is applied, the remaining operating principle of the embodiment of FIG. 52 is similar to that of FIG. 51.

On the other hand, as illustrated in FIG. 52, when the UE UE1 performs a short LBT, an uplink subframe having a length smaller than the full subframe (eg, not the full subframe (14 OFDM symbols)) (eg, 13 or 12 OFDM symbols) may be transmitted after a short LBT.

On the other hand, the length of the short LBT may be (16 + 9 * k) us. Where k is a parameter determined by the system.

The transmitter Tx100 includes a processor Tx110, a memory Tx120, and a radio frequency (RF) converter Tx130.

The processor Tx110 may be configured to implement the procedures, functions, and methods described herein in connection with transmission of a base station or transmission of a terminal. In addition, the processor Tx110 may control each component of the transmitter Tx100.

The memory Tx120 is connected to the processor Tx110 and stores various information related to the operation of the processor Tx110.

The RF converter Tx130 is connected to the processor Tx110 and transmits or receives a radio signal. The transmitter Tx100 may have a single antenna or multiple antennas.

The transmitter Tx100 may be a base station or a terminal.

54 illustrates a receiver according to an embodiment of the present invention.

The receiver Rx200 includes a processor Rx210, a memory Rx220, and an RF converter Rx230.

The processor Rx210 may be configured to implement the procedures, functions, and methods described herein with respect to reception of a base station or reception of a terminal. In addition, the processor Rx210 may control each component of the receiver Rx200.

The memory Rx220 is connected to the processor Rx210 and stores various information related to the operation of the processor Rx210.

The RF converter Rx230 is connected to the processor Rx210 and transmits or receives a radio signal. The receiver Rx200 may have a single antenna or multiple antennas.

The receiver Rx200 may be a terminal or a base station.

Meanwhile, the embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but may be implemented through a program or a recording medium on which the program is recorded to realize a function corresponding to the configuration of the embodiment of the present invention. Such implementations can be readily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims

A method in which a transmitter transmits a signal through a channel in an unlicensed band,

When the unlicensed band channel is in an idle state, transmitting an initial signal through the unlicensed band channel to preempt the unlicensed band channel;

Including a first partial subframe to be transmitted after the initial signal in a frame burst according to a transmission time of the initial signal; And

Transmitting the frame burst over the unlicensed band channel

Transmission method of the transmitter comprising a.
The method of claim 1,

Transmitting the initial signal,

If the unlicensed band channel is in an idle state, transmitting the initial signal immediately without waiting for the start of a time domain symbol,

Including the first partial subframe in the frame burst,

Including a second partial subframe at the end of the frame burst according to a transmission time of the initial signal.

Method of transmission of the transmitter.
The method of claim 2,

The first partial subframe has one of a time length corresponding to one slot and a time length corresponding to a time shifted downlink pilot time slot (DwPTS),

The second partial subframe has a time length corresponding to DwPTS.

Method of transmission of the transmitter.
The method of claim 1,

The initial signal comprises a reservation signal having a variable length,

Transmitting the initial signal,

Generating a time domain sequence for the reservation signal using Equation 1 below;

Method of transmission of the transmitter.

[Equation 1]

(v (n): the time domain sequence containing N elements, p: normalization constant,
, f s : sampling rate, z (k): frequency domain sequence including an element having a value based on the physical cell ID of the transmitter)
The method of claim 4, wherein

Generating the time domain sequence,

Converting the physical cell ID of the transmitter to binary; And

Generating the frequency domain sequence comprising as an element a value corresponding to each digit of the binary number among (1 + j) and (-1-j);

Method of transmission of the transmitter.
The method of claim 1,

The initial signal comprises a reservation signal having a variable length,

The time taken to transmit the 128 time domain sequences for the reservation signal is equal to the transmission time of one orthogonal frequency division multiplexing (OFDM) symbol except for a cyclic prefix (CP).

Method of transmission of the transmitter.
The method of claim 1,

The initial signal includes a reservation signal and a synchronization reference signal transmitted after the reservation signal,

Transmitting the initial signal,

Generating the sync reference signal having a time length corresponding to one orthogonal frequency division multiplexing (OFDM) symbol

Method of transmission of the transmitter.
The method of claim 7, wherein

Generating the synchronization reference signal,

Determining a frequency region to which the synchronization reference signal is mapped based on the index k obtained by Equation 1 below.

Method of transmission of the transmitter.

[Equation 1]

(
, z = 0 or α, v = 0,
,
,
= Number of physical resource blocks (PRBs) corresponding to the total bandwidth,
Is the largest PRB number corresponding to the full bandwidth,
: Physical cell ID of the transmitter)
The method of claim 1,

Including the first partial subframe in the frame burst,

When the transmission time of the initial signal corresponds to the first, second, third, fourth, fifth, or sixth OFDM symbols among 14 orthogonal frequency division multiplexing (OFDM) symbols, one slot corresponds to one slot Generating the first partial subframe having a time length

Method of transmission of the transmitter.
The method of claim 2,

Including the second partial subframe at the end of the frame burst,

Generating the second partial subframe when the transmission time of the initial signal corresponds to the rest of the 14 orthogonal frequency division multiplexing (OFDM) symbols except for the 1st, 2nd, and 3rd OFDM symbols. doing

Method of transmission of the transmitter.
The method of claim 1,

Including the first partial subframe in the frame burst,

Generating the first partial subframe having a time length corresponding to twelve OFDM symbols when a transmission time of the initial signal corresponds to a first OFDM symbol among fourteen orthogonal frequency division multiplexing (OFDM) symbols; And

Generating the first partial subframe having a time length corresponding to seven OFDM symbols when a transmission time of the initial signal corresponds to a sixth OFDM symbol among fourteen OFDM symbols;

Method of transmission of the transmitter.
The method of claim 1,

Including the first partial subframe in the frame burst,

Generating the first indicator indicating configuration information on a first subframe in which a first indicator is transmitted and configuration information on a second subframe following the first subframe; And

Including the first indicator in the frame burst,

The first subframe is one of a partial subframe and a full subframe.

Method of transmission of the transmitter.
The method of claim 12,

The first indicator,

Represents at least one of the number of orthogonal frequency division multiplexing (OFDM) symbols occupied in the first subframe and the number of OFDM symbols occupied in the second subframe

Method of transmission of the transmitter.
The method of claim 13,

The first indicator,

Indicates whether the second subframe corresponds to a downlink subframe, a special subframe, and an uplink subframe.

Method of transmission of the transmitter.
A method in which a transmitter transmits a signal through a channel in an unlicensed band,

Transmitting first grant information for transmission of a first receiver on the unlicensed band channel; And

Transmitting first information indicating a time point at which the first grant information is transmitted through the unlicensed band channel.

Transmission method of the transmitter comprising a.
The method of claim 15,

The step of transmitting the first information,

From among a predetermined number of subframes in the past, based on the time point at which the first information is transmitted, the first information corresponding to the subframe through which the first grant information is transmitted and including a first bit having a predetermined value Generating steps

Method of transmission of the transmitter.
The method of claim 15,

If the signal corresponding to the first grant information is not received from the first receiver, transmitting second information indicating a time point at which the first grant information is transmitted through the unlicensed band channel,

The second information may include a first bit corresponding to a subframe in which the first grant information is transmitted among a predetermined number of subframes in the past based on a time point when the second information is transmitted. doing

Method of transmission of the transmitter.
A method for a terminal to transmit a signal through a channel of an unlicensed band,

Receiving, from a base station, first grant information for uplink transmission of the terminal through the unlicensed band channel at a first time point;

Receiving, from the base station, first information indicating a transmission time point of the first grant information through the unlicensed band channel; And

When the transmission time point of the first grant information determined based on the first information coincides with the first time point, the base station transmits a first uplink signal corresponding to the first grant information through the unlicensed band channel. Steps to transfer to

Transmission method of the terminal comprising a.
The method of claim 18,

Transmitting the first uplink signal to the base station,

The first bit and the first bit when the first information includes a first bit corresponding to a subframe in which the first grant information is transmitted and a second bit corresponding to a subframe in which the second grant information is transmitted. Determining a bit order between two bits; And

Determining a transmission order between a second uplink signal corresponding to the second grant information and the first uplink signal based on the bit order.

Transmission method of the terminal.
The method of claim 18,

Transmitting the first uplink signal to the base station,

Checking the state of the unlicensed band channel for a predetermined time; And

When the unlicensed band channel is in an idle state, transmitting the first uplink signal to the base station through the unlicensed band channel;

The predetermined time is shorter than the time for the base station to check the state of the unlicensed band channel.

Transmission method of the terminal.