KR102449736B1 - Method and apparatus for transmitting and receiving discovery reference signal through channel of unlicensed frequency band - Google Patents

Abstract

A method for a base station to transmit a discovery reference signal (DRS) through a channel of an unlicensed band is provided. The base station attempts first access to the unlicensed band channel in order to transmit the first DRS within a first DRS measurement timing configuration (DMTC) period. And when the first access fails, the base station attempts a second access to the unlicensed band channel at a predetermined period shorter than the first DMTC period in order to transmit a second DRS within the first DMTC period. do.

Description

Method and apparatus for transmitting and receiving a discovery reference signal through a channel of an unlicensed frequency band

The present invention relates to a method and apparatus for transmitting and receiving a discovery reference signal in a wireless communication cellular system based on an unlicensed frequency band.

A conventional long term evolution (LTE) cellular network has been operated only in a licensed band. Despite the fact that technology has been developed for continuous capacity increase, as the demand for high-capacity and high-speed data services increases, the LTE standard increases capacity by accommodating unlicensed bands, not limited to the existing licensed bands. method was adopted. Currently, the standardization process for this is being actively carried out.

However, for the unlicensed band, the problem of coexistence with devices operating in other unlicensed bands needs to be solved, unlike the licensed band having a high degree of freedom without being disturbed by other operators or other devices. That is, there is a need for a channel access and occupation method that can be used temporarily when an opportunity is given without significantly lowering the performance of other devices on the same unlicensed channel.

In order to solve this coexistence problem, a method known as a 'carrier detection after transmission method' (eg, a clear channel assessment (CCA) method or a listen before talk (LBT) method) is widely used. The channel access method is first achieved by channel monitoring. That is, the device detects the activity of the unlicensed channel shared with other devices, and if the energy of the channel is measured, it suspends the wireless signal transmission, and conversely, when the energy of the channel is not detected, the corresponding channel is used. (wireless signal transmission or output). When a device detects an idle state of a channel and transmits a signal, other devices detect energy on the corresponding channel, determine that the corresponding channel is busy, and suspend signal transmission. That is, the channel access method of the unlicensed band may be a type of time-division multiple access method in which a plurality of devices access a wireless channel by dividing time. The operation of the cellular system in the unlicensed band is mainly performed in small cells. Therefore, a discovery reference signal (DRS) applied to a small cell may also be equally applied (or utilized) to an unlicensed band.

An existing small cell LTE base station (hereinafter, 'small base station') based on a licensed band is turned off when there is no access terminal in order to minimize interference to an adjacent base station. However, when the small base station is completely turned off, since a terminal approaching within coverage cannot check the existence of the corresponding base station, when the small base station is in an off state, a discovery reference signal (DRS) periodically ) and broadcasts the presence or absence of a small base station in the off state. The DRS always includes a reference signal such as a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS), and is transmitted periodically (eg, 40, 80, 160 ms, or 320 ms period). . The UE may use the DRS to analyze the ID of the cell to which it currently belongs, the base station signal strength, and the channel quality information. In addition, the terminal may receive the DRS of the adjacent cell, and report RRM (radio resource management) information to the base station.

Therefore, the terminal approaching within the coverage of the small base station in the off state receives the DRS, and always reports a report for providing the RRM of the small base station to the macro cell base station (macro cell) in the on state ( Hereinafter, it is reported to the 'macro base station'). Then, the macro base station turns the small base station in the off state into the on state, and the small base station can provide a service to the terminal within the coverage. Once the small base station is turned on, it continuously transmits CRS. The UE may continuously acquire, estimate, and track time synchronization and frequency synchronization for a received signal through a continuous CRS.

As such, DRS is used for the purpose of minimizing interference from adjacent small (or macro) cells as well as a means for efficiently using power in the existing small base station licensed band and a reliable means for RRM reporting of the UE. This DRS may be used for the purpose of switching a small base station using an unlicensed band from an off state to an on state like the licensed band. However, even when a macro cell turns on a small base station operating in an unlicensed band, due to the restrictions on the usage period of the unlicensed band channel due to the characteristics of the time division access type of the unlicensed band (eg, Japan does not allow continuous transmission in time of 4 ms or more), It is not possible to perform continuous CRS transmission after turning on a small cell like a licensed band. Therefore, in the unlicensed band, the method of maintaining the time and frequency synchronization by the terminal receiving the continuous CRS like the operation applied to the licensed band is not applied. In the end, the UE needs to receive time-frequency synchronization with the small base station in terms of maintaining the DRS occasion (discovery reference signal transmission) by using the occasional occurrence. That is, only when the DRS occasion occurs in the unlicensed band, the basic operation of the terminal related to DRS reception is assumed, which is also used for the purpose of receiving the time synchronization and frequency synchronization provided by the CRS included in the DRS. do. However, assuming such a basic operation, it may be difficult to maintain synchronization with the base station when DRS is not received more than a certain frequency.

In addition, it is difficult to achieve time-frequency synchronization through the initial single DRS reception. Because the PSS and SSS synchronization signals of the existing DRS have narrowband characteristics, the terminal performs precise OFDM (orthogonal frequency division multiplexing) symbol timing for signals of unlicensed bands using relatively widebands through single DRS reception. It is difficult to obtain exactly. Therefore, in the case of initial synchronization (when the terminal first receives the DRS of the small base station) only with the PSS and the SSS, the terminal must receive the DRS corresponding to the serving cell several times to obtain relatively precise OFDM symbol timing.

In addition, the DRS of the unlicensed band should be able to be used in parallel for the original purpose of not only maintaining the time-frequency synchronization of the terminal, but also reporting the RRM to the base station. However, if even DRS is not received, it may not be able to report RRM to the PCell. As such, the DRS signal in the unlicensed band is an important signal that must be frequently received from the standpoint of the terminal, but the reception rate in the unlicensed band is statistically low. In particular, there is a reason that the reception rate of the DRS is lower than the reception rate of the general data signal. In principle, DRS transmission is transmitted at a fixed period. Therefore, the transmission period is limited to a fixed period, and if the channel is busy during this period, the transmission opportunity is transferred to the next period. This is because, in the unlicensed band, periodic transmission of DRS is not guaranteed due to regulations such as LBT (including the contents of CCA). That is, this is because a case in which a radio channel is occupied in the DRS occasion period by another device (eg, Wi-Fi, radar, and the like) may occur. In addition, in particular, LTE frames in unlicensed bands have a principle that time synchronization with LTE frames operated in licensed bands must match, because it is based on the concept of carrier aggregation of the LTE standard. Therefore, the unlicensed band has a limited transmission condition in which the channel is occupied in a time division format and the frame synchronization with the licensed band must coincide. Due to the additional requirements related to such frame alignment, the probability that the DRS is not periodically transmitted in the unlicensed band may be additionally increased.

Another additional problem is related to the DRS false alarm. Even if the base station succeeds in transmitting a discovery reference signal (DRS) signal through LBT in the unlicensed band, the basic operation of the terminal in the unlicensed band is to check the validity of whether the received signal is DRS or not. That is, to distinguish whether a signal received in a discovery reference signal (DRS) period is a DRS or an invalid signal (eg, a Wi-Fi signal, etc.), a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a CRS Determination must be performed through decoding of (cell-specific reference signal). In addition, the determination process includes determining whether the DRS separately received by the terminal is the DRS of the adjacent base station. As a result, there is a constraint problem in that the UE must periodically detect the DRS in the unlicensed band and receive the DRS at a certain frequency or more. Therefore, a false alarm problem may occur. Since there is no physical discrimination method for error checking such as cyclic redundancy check (CRC), there is always a probability of a false alarm that the terminal determines that the DRS signal and Wi-Fi signal of another base station are the DRS signals of a valid serving cell. .

Accordingly, there is a need for a method for solving the above-mentioned problems.

An object of the present invention is to solve the above-mentioned problems, and to provide a method and an apparatus for transmitting DRS in an unlicensed frequency band.

According to an embodiment of the present invention, a method for a base station to transmit a discovery reference signal (DRS) through a channel of an unlicensed band is provided. The DRS transmission method of the base station may include: attempting first access to the unlicensed band channel to transmit a first DRS within a first DMTC (DRS measurement timing configuration) period; and attempting a second access to the unlicensed band channel at a predetermined period shorter than the first DMTC period in order to transmit a second DRS within the first DMTC period when the first access fails do.

The predetermined period may be a period in which a synchronization signal is transmitted in a licensed band.

The attempting the second access may include attempting the second access in the predetermined period until the second DRS transmission is successful within the first DMTC period.

The synchronization signal may include at least one of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS).

The predetermined period may be 5 ms.

The DRS transmission method of the base station may further include multiplexing and transmitting the second DRS and a physical downlink shared channel (PDSCH) when the second access is successful.

The DRS transmission method of the base station further includes, when the second access is successful, transmitting the synchronization signal included in the second DRS in the same resource element as the resource element in which the synchronization signal is transmitted in a licensed band. can do.

The step of attempting the second access may include: detecting the unlicensed band channel; and when it is detected that the unlicensed band channel is idle, transmitting a reservation signal having a variable length to reserve the unlicensed band channel.

In the DRS transmission method of the base station, when the second access is successful, a first fine symbol time field (FSTF) signal for notifying the terminal of transmission of the second DRS is provided after the time when transmission of the reservation signal is terminated. The method may further include transmitting the second DRS before the transmission time.

The second DRS may include a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS).

Time points at which the transmission of the second DRS starts and ends may coincide with a boundary of a subframe for a licensed band.

The predetermined period may correspond to the length of a subframe for a licensed band.

The step of attempting the second access may include attempting the second access at the predetermined period until the transmission of the second DRS is successful within a DMTC window set within the first DMTC period. can

Also, according to another embodiment of the present invention, there is provided a method in which a base station transmits a discovery reference signal (DRS) through a channel of an unlicensed band. The DRS transmission method of the base station includes: generating a first DRS having a predetermined time length; and mapping the first signal to the remaining time domain symbols other than the time domain symbols to which the signal is mapped among the time domain symbols belonging to the first DRS.

The first signal may include at least one of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

In the mapping of the first signal, the first signal transmitted through a channel of a licensed band in the same time domain symbol as the remaining time domain symbol of the first DRS is combined with the remaining time domain symbol of the first DRS. It may include the step of mapping to .

The generating of the first DRS may include generating a cell-specific reference signal (CRS).

The mapping of the first signal may include mapping to at least one of the remaining time domain symbols of the first DRS by using a CRS included in the first DRS as the first signal.

The mapping of the first signal may include generating a cell-specific broadcast signal (CBS) using one antenna port as the first signal.

Also, according to another embodiment of the present invention, a method for a terminal to receive a discovery reference signal (DRS) through a channel of an unlicensed band is provided. The DRS reception method of the terminal includes: determining whether a first fine symbol time field (FSTF) signal for a first DRS is detected within a DRS measurement timing configuration (DMTC) period; and attempting to detect a second FSTF signal for a second DRS at a predetermined period when the detection of the first FSTF signal fails.

The DRS reception method of the terminal may further include receiving the second DRS together with a physical downlink shared channel (PDSCH) when the detection of the second FSTF signal is successful.

The predetermined period may be a period in which a synchronization signal is transmitted in a licensed band.

According to an embodiment of the present invention, even if a DRS transmission failure occurs because the LBT function is applied to the unlicensed band, the base station and the terminal can effectively cope with it autonomously.

On the other hand, there is a probability that the DRS cannot be transmitted at every predetermined timing due to the characteristics of the unlicensed band, and it is difficult to provide precise OFDM symbol timing through only one DRS reception for PSS and SSS, which are the existing narrowband synchronization signals. For this reason, when transmission failure occurs, it takes time for the terminal to acquire time synchronization corresponding to that amount. However, according to an embodiment of the present invention, the UE acquires accurate OFDM symbol timing through a synchronization signal (eg, a fine symbol time field (FSTF) type-A signal, or an FSTF type-B signal) only by receiving the DRS once. and, through this, it is possible to shorten the synchronization acquisition time of the terminal.

In addition, according to an embodiment of the present invention, since only a preamble and an OFDM symbol synchronization signal FSTF for occupying and reserving a channel are added to a DRS burst before DRS (or extended DRS) transmission, the existing LTE physical layer The standard is not significantly changed and synchronization between the licensed band and the unlicensed band may be maintained, and the method according to an embodiment of the present invention may be applied to the unlicensed band for operation of the LTE system.

Also, according to an embodiment of the present invention, a good element technology that can be applied to LTE-LAA (license assisted access) of LTE operation standardization technology for unlicensed band may be provided.

In addition, according to an embodiment of the present invention, since the existing DRS structure is used as it is, it is possible to multiplex and transmit the DRS as in the case of transmitting data such as a physical downlink shared channel (PDSCH).

In addition, according to the embodiment of the present invention, since the length of the DRS occasion is not fixed, when the length of the DRS occasion is shorter than the length of one subframe (eg, a unit less than the length of 14 OFDM symbols) It can be configured on the system, and it is possible to systematically configure the DRS occasion to have a relatively long length (eg, 1 to 5 ms).

1 is a diagram illustrating a predictable DRS transmission result that may be generated in an unlicensed band.
2 is a diagram illustrating a time point at which an eDRS is transmitted in an unlicensed band according to an embodiment of the present invention.
3 is a diagram illustrating a detailed timing of a time point at which DRS is transmitted in an unlicensed band and a time point at which a preamble is transmitted after LBT according to an embodiment of the present invention.
4 is a diagram illustrating a detailed timing of when eDRS is transmitted in an unlicensed band and a time when a preamble is transmitted after LBT according to an embodiment of the present invention.
5 is a diagram illustrating a case in which PDSCH and DRS are multiplexed and transmitted according to an embodiment of the present invention.
6 is a diagram illustrating a detailed timing of when an eDRS is transmitted in an unlicensed band and a time when a preamble is transmitted after the LBT according to another embodiment of the present invention.
7 is a diagram illustrating a structure of a variable length preamble applied to DRS or eDRS of an unlicensed band according to an embodiment of the present invention.
8 is a diagram illustrating a preamble having a short length according to another embodiment of the present invention.
9 is a diagram illustrating a preamble having a long length according to another embodiment of the present invention.
10 is a diagram illustrating a default DRS according to an embodiment of the present invention.
11 is a diagram illustrating a method of filling a portion of a DRS with a physical downlink control channel (PDCCH) and a PDSCH signal of a licensed band according to an embodiment of the present invention.
12 is a diagram illustrating a method of filling a void section of a DRS with an existing reference signal according to an embodiment of the present invention.
13 is a diagram illustrating a method of filling a void section of a DRS with a cell-specific broadcast signal (CBS) according to an embodiment of the present invention.
14 is a diagram illustrating a CBS mapping method on a frequency axis and a modulation method for each symbol according to an embodiment of the present invention.
15 is a diagram illustrating a base station according to an embodiment of the present invention.
16 is a diagram illustrating a terminal according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily implement them. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, a terminal is a mobile terminal, a mobile station, an advanced mobile station, a high reliability mobile station, a subscriber station, a portable It may refer to a portable subscriber station, an access terminal, user equipment, etc., and may refer to a terminal, a mobile terminal, a mobile station, an advanced mobile station, a high reliability mobile station, a subscriber station, a portable subscriber station, It may include all or some functions of an access terminal, user equipment, and the like.

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

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

An existing small cell LTE base station (hereinafter, 'small base station') based on a licensed band is turned off when there is no access terminal in order to minimize interference to an adjacent base station. However, when the small base station is completely turned off, since a terminal approaching within coverage cannot check the existence of the corresponding base station, when the small base station is in an off state, a discovery reference signal (DRS) periodically ) and broadcasts the presence or absence of a small base station in the off state. The DRS always includes a reference signal such as a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS), and is transmitted periodically (eg, 40, 80, 160 ms, or 320 ms period). . The UE may use the DRS to analyze the ID of the cell to which it currently belongs, the base station signal strength, and the channel quality information. In addition, the terminal may receive the DRS of the adjacent cell, and report RRM (radio resource management) information to the base station.

Therefore, the terminal approaching within the coverage of the small base station in the off state receives the DRS, and always reports a report for providing the RRM of the small base station to the macro cell base station (macro cell) in the on state ( Hereinafter, it is reported to the 'macro base station'). Then, the macro base station turns the small base station in the off state into the on state, and the small base station can provide a service to the terminal within the coverage. Once the small base station is turned on, it continuously transmits CRS. The UE may continuously acquire, estimate, and track time synchronization and frequency synchronization for a received signal through a continuous CRS.

As such, DRS is used for the purpose of efficiently using power in the existing small base station licensed band and being a reliable means for RRM reporting of the UE, as well as minimizing interference from adjacent small (or macro) cells. This DRS may be used for the purpose of switching a small base station using an unlicensed band from an off state to an on state like the licensed band. However, even if the macro cell turns on the small base station operating in the unlicensed band, due to the regulation of the period of use of the unlicensed channel due to the nature of the time division connection type of the unlicensed band (eg. After that, continuous CRS transmission is not possible. Therefore, in the unlicensed band, the method of maintaining the time and frequency synchronization by the terminal receiving the continuous CRS like the operation applied to the licensed band is not applied. In the end, the UE needs to receive time-frequency synchronization with the small base station in terms of maintaining the DRS occasion (discovery reference signal transmission) by using the occasional occurrence. That is, only when the DRS occasion occurs in the unlicensed band, the basic operation of the terminal related to DRS reception is assumed, which is also used for the purpose of receiving the time synchronization and frequency synchronization provided by the CRS included in the DRS. do. However, assuming such a basic operation, it may be difficult to maintain synchronization with the base station when DRS is not received more than a certain frequency.

In addition, it is difficult to achieve time-frequency synchronization with the initial single DRS reception. Because the PSS and SSS synchronization signals of the existing DRS have narrowband characteristics, precise OFDM (orthogonal frequency division multiplexing) symbol timing for signals in unlicensed bands using relatively widebands is accurately obtained through single DRS reception. It is difficult to do. Therefore, in the case of initial synchronization (when the UE first receives the DRS of the small base station) with only the PSS and the SSS, the UE must receive the DRS corresponding to the serving cell several times to obtain relatively precise OFDM symbol timing. can

The method according to an embodiment of the present invention may belong to the physical layer of the LTE wireless mobile communication system. Specifically, when the LTE system is operated in an unlicensed band, RRM (radio resource management) may be operated based on the content reported by the terminal to the base station. DRS may be an effective reference signal for such RRM. A method according to an embodiment of the present invention relates to a method for transmitting such a DRS. DRS is periodically transmitted by the base station, and DRS transmission may be suspended or canceled due to the characteristics of the unlicensed band.

Hereinafter, a method of operating an LTE system in an unlicensed band, which is characterized by discontinuous signal transmission due to regulation, and conditions and procedures for DRS transmission in the unlicensed band (which may be useful for small cells) will be described. do.

Also, hereinafter, a procedure for a case in which a channel is busy in a predetermined DMTC (DRS measurement timing configuration) period will be described.

Also, a method of designing a DRS synchronization reference signal serving as a reference for time synchronization and frequency synchronization in order to synchronize or maintain synchronization with a data reception signal of a terminal will be described below.

On the other hand, a resolution suitable for a signal of an unlicensed band using a wideband is required. Hereinafter, a method of providing accurate fast Fourier transform (FFT) timing of an OFDM symbol using a DRS synchronization reference signal defined in a part of a DRS burst will be described. Also, below, a method of designing a DRS synchronization reference signal for matching frame synchronization between an unlicensed band and a licensed band for more accurate RRM reporting will be described.

Also, below, a modified DRS structure will be described so that the DRS has a signal continuous characteristic according to the unlicensed band.

1 is a diagram illustrating a predictable DRS transmission result that may be generated in an unlicensed band.

Specifically, in FIG. 1, the LTE base station (LL2) to be operated in the unlicensed band is the same unlicensed band (eg, 5 GHz frequency band) as one IEEE 802.11a/n/ac wireless local area network (WLAN) device (LL1). The LTE base station LL2 may be an LTE license assisted access (LAA) device. Meanwhile, the LTE base station LL2 may be operated in both the unlicensed band and the licensed band, in this case In, it is possible to simultaneously transmit the signal of the unlicensed band and the signal of the licensed band.

More specifically, in FIG. 1, the LTE base station LL2 coexists with the Wi-Fi device LL1 and the LTE base station LL3 of the licensed band while maintaining synchronization with the licensed band, and transmitting DRS in the designated DRS transmission section. , the foreseeable situations that may arise are illustrated. LTE base station (LL3) is operated in a licensed band.

The clear channel assessment (CCA) illustrated in FIG. 1 is a determination method in which the Wi-Fi device LL1 determines whether a wireless channel is being used by another device through an energy level. When the CCA for the wireless channel succeeds, the Wi-Fi device LL1 transmits a signal of the Wi-Fi frame through the corresponding channel. Here, the success of CCA for a channel means that a device that has performed CCA occupies the corresponding channel.

Similarly, LBT (listen before talk) illustrated in FIG. 1 is a method of performing the same function as CCA. The busy state indicates that the channel is occupied, and the idle state indicates that no device is using the corresponding channel. The DMTC period indicates a period during which the DRS is transmitted, and FIG. 1 exemplifies a case where the DMTC period is 40 ms (= length of 4 LTE frames). 1 illustrates a case where the start and end of the DMTC period coincide with the boundary of the LTE frame. DRS duration (duration) or DRS occasion (occasion) indicates a time during which the DRS is continuously transmitted.

1 illustrates a case in which the LTE base station LL2 is periodically transmitting the DRS in time, but a situation in which the third DRS cannot be transmitted occurs. Immediately before transmitting the third DRS, the LTE base station LL2 determines that the channel of the unlicensed band is busy (the Wi-Fi device LL1 occupies the channel of the unlicensed band at the time), and cancels the DRS transmission. Similarly, the LTE base station LL2 fails to transmit the 5th and 6th DRS (at that time, the Wi-Fi device LL1 occupies the corresponding unlicensed band channel), and the DRS transmission failure illustrated in FIG. 1 is actually sufficient in the unlicensed band. can occur

As such, in the unlicensed band, the periodicity of DRS is not guaranteed because several devices share and use channels irregularly. Therefore, there is a need for a technique capable of supplementing DRS transmission in response to such an environment. As a method for this, an auxiliary extended DRS transmission function will be described with reference to FIG. 2 .

2 is a diagram illustrating a time point at which an eDRS is transmitted in an unlicensed band according to an embodiment of the present invention. Specifically, FIG. 2 illustrates a method of attempting DRS retransmission every predetermined period (eg, 5 ms). Here, the predetermined period for DRS retransmission may be a period in which synchronization signals (PSS, SSS) are transmitted in a licensed band, for example, 5 ms.

The basic DRS of the unlicensed band is transmitted when the LBT succeeds at the transmission time of the PSS (primary synchronization signal) and the SSS (secondary synchronization signal) of the licensed band, and at the same timing as the timing set in the DMTC. Here, the success of LBT for a channel means that a device that has performed LBT occupies the corresponding channel.

Extended DRS (hereinafter 'eDRS') is, when LBT is performed every 5 ms (ie, when PSS or SSS is transmitted in a licensed band) and LBT succeeds, to make up for failed DRS transmission within the DMTC period, is sent For example, when the LTE base station LL2 fails to transmit periodic DRS (eg, 3rd, 5th, 6th DRS transmission), LBT may be performed every 5ms after DRS transmission failure, and LBT is successful eDRS can be transmitted to (Ts1a, Ts1b, Ts1c).

The detailed timing in which the PSS and SSS are transmitted in the licensed band and the LBT operation are linked will be described with reference to FIG. 3 .

3 is a diagram illustrating a detailed timing of a time point at which DRS is transmitted in an unlicensed band and a time point at which a preamble is transmitted after LBT according to an embodiment of the present invention.

As illustrated in FIG. 3 , the DRS may include PSS, SSS, cell-specific reference signal (CRS), and channel state information (CSI)-reference signal (RS). In order for the timing at which the synchronization signals (PSS, SSS) included in the DRS are transmitted coincide with the timing at which the synchronization signals (PSS, SSS) are transmitted in the licensed band (eg, the synchronization signal transmitted by the LTE base station LL2) If the transmission time of the PSS and SSS coincides with the transmission time of the synchronization signal (PSS, SSS) transmitted by the LTE base station LL3), the DMTC window may be set to 5 ms. That is, when the LTE frame is 10 ms, the DMTC window may be 5 ms. Also, the length of DMTC may be 0.85729166 ms having a length of at least 12 OFDM symbols. In FIG. 3, one LTE frame includes 10 LTE subframes, the DRS duration is the same as the length (eg, 1 ms) of one LTE subframe, and the LTE base station LL3 synchronizes the synchronization signal ( PSS, SSS) is exemplified.

When DRS transmission is successful at the configured DRS transmission time, the DRS burst (Bdrs1) is a reservation signal having a variable length, a fine symbol time field (FSTF) informing the OFDM symbol synchronization standard. A type-A signal (or preamble signal (s(n))), and DRS. Specifically, the LTE base station LL2 may transmit a reservation signal to reserve the corresponding channel when the LBT for the channel of the unlicensed band is successful, and transmit the FSTF type-A signal for time synchronization through the corresponding channel. Alternatively, the reservation signal may be continuously transmitted instead of the time synchronization signal without transmitting the time synchronization signal), and the DRS may be transmitted through the corresponding channel at the set DRS transmission time point.

4 is a diagram illustrating a detailed timing of when eDRS is transmitted in an unlicensed band and a time when a preamble is transmitted after LBT according to an embodiment of the present invention.

Specifically, in FIG. 4 , if the LTE base station LL2 fails to transmit the DRS in the set DMTC period, eDRS transmission may be attempted at a time point (Ts2b) that has elapsed 5 ms from the time point (Ts2a) at which the DRS transmission fails. Specifically, the LTE base station LL2 may perform LBT before 5 ms has elapsed from the time point Ts2a at which the DRS transmission fails.

The eDRS burst Bdrs2 may be configured almost the same as the DRS burst Bsrs1. However, the eDRS burst Bdrs2 includes FSTF type-B instead of FSTF type-A.

If the LTE base station LL2 does not succeed in eDRS transmission even at the time point Ts2b, it re-attempts the eDRS transmission at a time point Ts2c that has elapsed 5 ms from the time point Ts2b. If the LTE base station LL2 does not succeed in eDRS transmission even at the time point Ts2c, it re-attempts the eDRS transmission at a time point 5 ms elapsed from the time point Ts2c. That is, when the LTE base station LL2 fails to transmit DRS at the DRS transmission time (Ts2a) set within the DMTC period, the eDRS transmission is continuously attempted at a predetermined period (eg, 5 ms) until the next DMTC period is reached. can do. For example, when the DMTC period is set to 40 ms, the LTE base station LL2 may make a total of 7 additional eDRS transmission attempts.

Meanwhile, even if the LTE base station LL2 succeeds in DRS or eDRS transmission, additional retransmission may be performed a predetermined number of times (eg, N times) as needed.

Meanwhile, DRS or eDRS may be transmitted simultaneously with a physical downlink shared channel (PDSCH), that is, downlink data.

5 is a diagram illustrating a case in which PDSCH and DRS are multiplexed and transmitted according to an embodiment of the present invention.

A method of attempting DRS (or eDRS) retransmission every predetermined period (eg, 5 ms), as illustrated in FIG. 5, multiplexes the DRS (or eDRS) and the downlink data signal and transmits it have an advantage For example, as illustrated in FIG. 5 , the LTE base station LL2 transmits a reservation signal through the corresponding channel to reserve the corresponding channel when the LBT for the channel of the unlicensed band is successful, and for time synchronization The FSTF type-A signal may be transmitted through the corresponding channel, and the PDSCH and DRS may be multiplexed and transmitted through the corresponding channel. Here, the FSTF type-A may be omitted and replaced with a reservation signal.

On the other hand, as illustrated in FIG. 5, synchronization signals (PSS, SSS) transmitted every predetermined period (eg, 5 ms) in the licensed band are transmitted at the same time point and resource element as the licensed band in the unlicensed band. Since this is maintained, ambiguity does not occur when the UE demodulates the PDSCH.

In any case (eg, when the start time and end time of the downlink burst of the unlicensed band are variable), the UE is a synchronization signal (PSS, SSS) and CSI-RS resource in any PRB (physical resource block) and OFDM symbol position. You know exactly if an element should be skipped. For this reason, among the components of the signal received by the terminal, the component (position of PSS, SSS, CSI-RS) included in the DRS (or eDRS) and the time / frequency side signal mapping performed for the PDSCH (mapping) There is no problem of ambiguity (ie, rate-matching of the receiving end).

On the other hand, since the basic configuration of DRS (or eDRS) includes PSS, SSS, and CRS (CSI-RS is an optional component), DRS (or eDRS) does not collide with PDSCH in terms of resource elements. That is, since the resource mapping in the unlicensed band is the same as the existing resource mapping in the licensed band, the signal itself in which the DRS (or eDRS) and the PDSCH are multiplexed does not have a particularly new signal structure. As a result, the signal in which the DRS (or eDRS) and the PDSCH are multiplexed has the same signal structure as the signal of the licensed band.

6 is a diagram illustrating a detailed timing of when an eDRS is transmitted in an unlicensed band and a time when a preamble is transmitted after the LBT according to another embodiment of the present invention.

Specifically, FIG. 6 exemplifies a method of attempting eDRS transmission at a predetermined period (eg, 1 ms unit) within the set DMTC window period. Here, a predetermined period for eDRS retransmission may correspond to a length (eg, 1 ms) of a subframe for a licensed band.

In this method, the transmission of the eDRS burst (Bdrs2) may be attempted as many times as the number of times one is insufficient in the number of times the length of the DMTC window is divided by 1 ms. For example, as illustrated in FIG. 6 , when the DMTC window is set to 5 ms, if the LTE base station LL2 fails to transmit the DRS at the DRS transmission time (Ts3a), eDRS retransmission within the DMTC window is 4 can try once. The LTE base station LL2 cannot attempt eDRS transmission other than the DMTC window period.

According to the method illustrated in FIG. 6, due to mis-alignment between the positions of the synchronization signals (PSS, SSS) of the licensed band and the positions of the synchronization signals (PSS, SSS) included in the eDRS, rate-matching ) may cause ambiguity. For this reason, in the method illustrated in FIG. 6, the case of transmitting the eDRS together with the PDSCH is excluded. That is, as illustrated in FIG. 6 , the LTE base station LL2 transmits the eDRS without multiplexing it with the PDSCH.

On the other hand, the DRS (or eDRS) burst of the unlicensed band according to the embodiment of the present invention may have the following four characteristics.

- Preamble (reservation signal) for channel reservation

- FSTF signal (eg, FSTF type-A signal, or FSTF type-B signal) for Fine OFDM symbol timing

- DRS waveform in continuous burst form

- How to set the length of DRS

The preamble (reservation signal) and FSTF signal, which are components other than the DRS (or eDRS) among the components of the DRS (or eDRS) burst, may not be transmitted in order to increase the DRS signal transmission probability depending on circumstances. In addition, the FSTF signal may be replaced with a preamble (reservation signal) depending on circumstances.

Hereinafter, the above four characteristics will be described in detail.

First, a preamble (reservation signal) for channel reservation will be described in detail with reference to FIGS. 7 to 9 .

7 is a diagram illustrating a structure of a variable length preamble applied to DRS or eDRS of an unlicensed band according to an embodiment of the present invention. 8 is a diagram illustrating a preamble having a short length according to another embodiment of the present invention. 9 is a diagram illustrating a preamble having a long length according to another embodiment of the present invention.

The preamble (reservation signal) for channel reservation has a variable length and may have a maximum length of 1 ms.

Specifically, the preamble (reservation signal) for channel reservation may have a variable length, and, as illustrated in FIGS. They may have the same or shorter length. In FIGS. 8 and 9 , the WLAN device LL4 transmitting the WLAN frame signal may be the Wi-Fi device LL1 . 8 exemplifies a case in which the LTE base station LL2 transmits a preamble (reservation signal) having a relatively short length, and in FIG. 9 , the LTE base station LL2 transmits a preamble (reservation signal) having a relatively long length. A case of transmission is exemplified.

By utilizing the preamble (reservation signal), the LTE device (eg, LL2) of the unlicensed band coexists with devices (eg, LL1, LL4) of other models (eg, WLAN) without giving or receiving interference, the channel of the unlicensed band It can be occupied and used for a certain period of time. This preamble (reservation signal) may be transmitted up to the starting point (or ending time) of the subframe period of the LTE licensed band. Therefore, time synchronization between the signal transmission section of the licensed band and the signal transmission section of the unlicensed band can be realized. When temporal synchronization is provided between the subframes of the unlicensed band and the licensed band, there is an advantage in terms of performance, implementation, or scheduling of a carrier aggregation (CA) function. Therefore, the current standardization is based on the basic premise that such a motive should be achieved.

Specifically, FIG. 7 illustrates a structure of a preamble applied to a DRS (or eDRS) burst (eg, Bdrs1, Bdrs2). The preamble signal s(n) exists before the boundary of the subframe, and the preamble signal s(n) may be first generated based on 30.72 MHz sampling.

The region of the preamble (reservation signal) characterized by the variable length may include a minimum signal unit transmission period having a length of about 0.521 us, as illustrated in FIG. 7 . When the digital sample rate of LTE is 30.72 MHz, the time taken to transmit one sample (T _s ) is 1/(30.72e6) = 0.326us. Accordingly, according to an embodiment of the present invention, the transmission time of a sequence having a length of 16 is 16/(30.72e6) = 0.521us. For reference, the transmission time of the 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. And the length (or transmission time) of one LTE subframe is 30720/(30.72e6)=1ms. That is, if 1920 sequences that are the basic unit of the preamble (reservation signal) are transmitted continuously, it becomes 1 ms (ie, one LTE subframe can be divided into 1920 sections).

A sequence s(n) in the time domain having a length of 16 may be generated by Equation 1 below.

을 나타낸다.where p is a constant for normalizing the signal,

indicates

A sequence z(k) and an index k in the frequency domain may be defined as in Equation 2 below.

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

과

에 의해 결정되어, 아래의 수학식 4에 매핑될 수 있다.Binary bits b _{- 5} to _b5 are the physical cell IDs of the base station defined in the LTE standard.

class

, and may be mapped to Equation 4 below.

=2 이고

=97 라고 가정하면, 바이너리 수

는 0110000110로 결정된다. 따라서 z(k)는 [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] 가 된다.Here, B(.) is a binary operator function that converts to binary. for example,

=2 and

Assuming =97, the number of binary

is determined to be 0110000110. So 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 transformed into the time domain based on Equation 1, the following s(n) sequence can be generated.

Since the variable length preamble (reservation signal) according to an embodiment of the present invention has a granularity of about 0.5us, a device (eg, LL2) operated in an unlicensed band has a high degree of freedom and coexists in any situation It is possible to occupy a channel and synchronize time with a licensed band (ie, subframe time).

8 illustrates a case in which the LTE base station LL2 occupies the channel of the unlicensed band near the end of the LTE subframe of the licensed band. In this case, the LTE base station LL2 may transmit a preamble (reservation signal) having a short length.

9 exemplifies a case in which the LTE base station LL2 occupies the channel of the unlicensed band near the beginning of the subframe after passing the boundary of the LTE subframe of the licensed band. In this case, the LTE base station LL2 may transmit a preamble (reservation signal) having a long length.

On the other hand, in order to increase the probability for transmitting the DRS or eDRS according to the result of the LBT, the transmission of the preamble signal s(n) may be canceled. Similarly, the transmission of the FSTF signal may be canceled.

An FSTF signal (eg, FSTF type-A signal or FSTF type-B signal) for fine OFDM symbol timing will be described in detail.

An FSTF region configured to acquire time synchronization may consist of one OFDM symbol. The FSTF signal sequence may be positioned after the preamble (reserved) signal s(n) and between the data region (eg, DRS region, or eDRS region). The length of the FSTF signal sequence may be fixed to 2192 or 2208 based on 30.72 MHz sampling.

A basic FSTF sequence, s ₁₀₂₄ (n), consists of a length of 2048 time samples, and may occupy a transmission time of 66.67 us in time. The method of constructing s ₁₀₂₄ (n) starts with generating a Golay sequence having a length of 1024 first. Equation 5 below may be used as a method of generating the Golay sequence.

는 Dirac Delta 함수(인덱스 n이 0일 때 1의 출력 값을 가지고, 그 외에는 0의 출력 값을 가짐)를 의미한다. In Equation 5,

stands for the Dirac Delta function (with an output value of 1 when the index n is 0, and an output value of 0 otherwise).

로 정의된다.In Equation 5,

is defined as

Also, A _k (n) and B _k (n) have a value of 0 in the interval n<0 and 2 ^k ≤ n.

,

)를 바탕으로 구성되는, 연접된(concatenated) 바이폴라 비트들(bi-polar bits)을 나타낸다. y _k is the physical cell ID (eg,

,

), which represents concatenated bipolar bits.

에 기초해 구해질 수 있고, 나머지 8개의 비트들은

에 기초해 구해질 수 있다.As in Equation 6 below, bipolar bits y ₁ to y ₂ are

can be obtained based on , and the remaining 8 bits are

can be obtained based on

In Equation 6, B (.) represents a bipolar sign operator. In addition, the binary bit is expressed as a vector, which can be expressed as in Equation 7 below.

=2 이고

=97 이라 가정하면, 연접된 바이너리 시퀀스(concatenated binary sequence)

는 0110000110가 된다.

는 기지국의 물리적 셀 ID에 기초해 구해지는 시퀀스의 원소 중 k번째 원소를 나타낸다.for example,

=2 and

Assuming =97, the concatenated binary sequence is

becomes 0110000110.

denotes the k-th element among the elements of the sequence obtained based on the physical cell ID of the base station.

간의 바이너리 가산(binary addition)(또는 scrambling)은, 아래의 수학식 8과 같이 정의될 수 있다.Here, 10 bits of LSB (least significant bit) (or most significant bit (MSB)) of 28 bits of public land mobile network (PLMN) ID (identification) of the base station and

Binary addition (or scrambling) between the two can be defined as in Equation 8 below.

는 PLMN ID의 바이너리 비트 k번째를 나타낸다(

는 기지국의 PLMN ID에 기초해 구해지는 시퀀스의 원소 중 k번째 원소). 수학식 8에서 W_k는 기지국의 물리적 셀 ID와 PLMN ID 간의 스크램블에 기초해 바이너리 가산 후 구해지는 시퀀스의 원소 중 k번째 원소를 나타낸다. 따라서 만약

의 LSB가

로 구성되어 있고,

가

로 구성되어 있다면, W_k 는

in Equation 8

represents the kth binary bit of the PLMN ID (

is the k-th element among the elements of the sequence obtained based on the PLMN ID of the base station). In Equation 8, W _k represents the k-th element among the elements of the sequence obtained after binary addition based on the scramble between the physical cell ID of the base station and the PLMN ID. So if

LSB of

is composed of

go

If it consists of , then W _k is

가 적용될 수 있다. eDRS에 적용되는 FSTF 타입-B 신호에는 골레이 이니셜 시퀀스

가 적용될 수 있다.Using Equations 5 and 8, a Golay initial sequence may be generated. Here, in the FSTF type-A signal applied to the DRS, the Golay initial sequence

can be applied. FSTF type-B signals applied to eDRS contain a Golay initial sequence

can be applied.

Meanwhile, in order to generate an FSTF signal (eg, an FSTF type-A signal or an FSTF type-B signal), z ₁₀₂₄ (n) may be converted into a frequency domain as shown in Equation 9 below.

(또는 vector)로 매핑될 수 있다.The sequence converted to the frequency domain is an extended sequence as shown in Equation 10 below.

(or vector).

Here, bandwidth extension of the transmission signal may be used. The extension of the bandwidth (or transmission width) may be defined as in Equation 11 below.

That is, by adding 32 subcarriers to both band edges, a result of adding a total of 64 subcarriers can be obtained.

가 시간 도메인으로 다시 변환되면, 아래의 수학식 12와 같이 정의되는 시퀀스 s₁₀₂₄(n)가 생성될 수 있다.Finally

When is converted back to the time domain, a sequence s ₁₀₂₄ (n) defined as in Equation 12 below may be generated.

In Equation 12, N _CP represents the length of the cyclic prefix. In Equation 12, p is a scaling factor for normalizing the power of the transmission signal. In Equation 12, T _s represents a time taken to transmit one sample.

As a result, the base station may notify whether DRS transmission is successful in the unlicensed band through FSTF signal (eg, FSTF type-A signal, or FSTF type-B signal) transmission. Since the FSTF type-A signal is transmitted between the reservation signal and the DRS, the UE may periodically detect the FSTF type-A signal during the DMTC period. If the FSTF type-A signal is not detected within the DMTC period period, the UE may perform an operation of detecting the FSTF type-B signal in the non-DMTC period period at a predetermined period (eg, 5 ms interval). If the FSTF signal (eg, FSTF type-A signal, FSTF type-B signal) is detected, the UE may recognize that the DRS will be transmitted soon.

On the other hand, since the FSTF signal (eg, FSTF type-A signal, FSTF type-B signal) is generated as binary information in which the physical cell ID and the PLMN ID are scrambled, the FSTF signal (eg, FSTF type-A signal, The possibility that the FSTF type-B signal) collides with the DRS of the adjacent small base station is low, and the probability of being uniquely identified is high.

However, depending on circumstances, the FSTF signal (eg, FSTF type-A signal, FSTF type-B signal) is replaced with a preamble s(n) having a length of 2192 or 2208, or an FSTF signal (eg, FSTF type-A signal, FSTF) Type-B signal) may be canceled.

A continuous burst-type DRS waveform will be described in detail with reference to FIGS. 10 to 14 .

10 is a diagram illustrating a default DRS according to an embodiment of the present invention. In FIG. 10, p denotes an antenna port number.

In the unlicensed band, the DRS is transmitted periodically, but the DRS itself may have a discontinuous characteristic. That is, when there is no data to be transmitted, as illustrated in FIG. 10 , the DRS is a specific OFDM symbol (eg, OFDM symbols 1-3, 5, 6, 8-10, 12, 13) It may have a form in which no signal is transmitted.

Specifically, FIG. 10 exemplifies a case in which the DRS includes synchronization signals (PSS, SSS) and the length of the DRS is 1 ms.

As illustrated in FIG. 10 , even if synchronization signals (PSS, SSS) are included in the DRS, no signals are transmitted at times corresponding to timings of OFDM symbol numbers 1-3, 8, 12, and 13. The time it takes for one OFDM symbol to be transmitted is approximately 71us. If the channel is maintained in an idle state for about 71us (or more), a device such as Wi-Fi (eg, LL1) recognizes that the corresponding channel is in an idle state. to try to transmit a signal. In such a situation, signal collision may occur between other devices or between the LAA network and the unlicensed band, which may adversely affect overall network performance.

Therefore, in order to prevent the collision situation as described above, a method of artificially making a channel idle among sections constituting the DRS to be busy may be considered. The three methods (method M110, method M120, and method M130) according to an embodiment of the present invention are a DRS void period (a period in which a signal is not transmitted, eg, OFDM symbols 1-3, 5, 6, 8) Configures an alternative transmission signal for sections -10, 12, and 13). However, sections 12 and 13 of the OFDM symbol may be left as void sections.

11 is a diagram illustrating a method of filling a part of DRS with PDCCH and PDSCH signals of a licensed band according to an embodiment of the present invention. In FIG. 11, p denotes an antenna port number.

As illustrated in FIG. 11 , the method M110 of filling the void section with an artificial signal is a PDSCH signal corresponding to a void section among PDSCH signals transmitted in a licensed band in units of OFDM symbols. How to copy in a section.

Specifically, in FIG. 11, a PCell (primary cell) operating in a licensed band transmits a PDCCH in OFDM symbol 0-3 interval, transmits a PDSCH in OFDM symbol 4-13 interval, and OFDM symbols 0, 4, 7, A case of transmitting the CRS in section 11 is exemplified.

A secondary cell (SCell) operating in an unlicensed band may equally transmit the PDCCH and the PDSCH transmitted by the PCell in the corresponding OFDM symbol period in the void period of the DRS (eg, OFDM symbol periods 1-3). . In addition, the SCell is PDSCH, SSS, PSS, CSI- transmitted by the PCell in another void interval of the DRS (eg, OFDM symbol 5, 6, 8-10, 12, 13 interval) in the corresponding OFDM symbol interval. RS and a demodulation-reference signal (DM-RS) may be transmitted equally.

12 is a diagram illustrating a method of filling a void section of a DRS with an existing reference signal according to an embodiment of the present invention. In FIG. 12, p denotes an antenna port number.

Method M120 is a method of filling several void OFDM sections by expanding or adding a reference signal (eg, CRS), as illustrated in FIG. 12 .

Method M120 extends the CRS (antenna ports 0 and 1) mapped to OFDM symbols 0, 4, and 7, and the void interval of the DRS illustrated in FIG. 10 (eg, OFDM symbol 1- 3 and fill in sections 8-10). In addition, the method M120 may fill in the CSI-RS and synchronization signals (PSS, SSS) in an area that may not be filled (eg, OFDM symbols 5, 6, and 9-10 sections).

13 is a diagram illustrating a method of filling a void section of a DRS with a cell-specific broadcast signal (CBS) according to an embodiment of the present invention. In FIG. 13, p denotes an antenna port number.

Method M130 is a method of inserting a CBS signal into a void section of the DRS. Here, the CBS is a signal having the same resource element mapping as the existing CRS, but having a different symbol configuration from the CRS.

Specifically, the CBS region (the region to which the CBS is mapped) may have a structure of a CRS (using one antenna port (eg, antenna port 0)) mapped to the existing LTE OFDM symbol 0 or 7, as shown below. It can be defined by Equation 13 of For example, in FIG. 13 , CBS is mapped to resource elements corresponding to subcarriers 0 and 6 among resource elements corresponding to OFDM symbols 1-3, and subcarriers 3 among resource elements corresponding to OFDM symbol 8 A case in which CBS is mapped to resource elements corresponding to and 9 is exemplified.

In Equation 13, a represents a signal input to an inverse fast Fourier transform (IFFT) block as a complex symbol. And in Equation 13, p represents an antenna port, and corresponds to index k of the frequency axis and index l of the OFDM symbol.

In Equation 13, k, l, and m may be defined as in Equation 14 below.

는 전체 시스템 하향링크 대역폭에 대응하는 PRB 개수를 의미하고,

는 전체 시스템 하향링크 대역폭에 대응하는 가장 큰 PRB 번호를 나타낸다. In Equation 14,

means the number of PRBs corresponding to the entire system downlink bandwidth,

denotes the largest PRB number corresponding to the entire system downlink bandwidth.

로 정의될 수 있고, v_shitf는

로 정의될 수 있다.

는 물리적 셀 ID를 나타낸다.v is

can be defined as , v _shitf is

can be defined as

represents a physical cell ID.

14 is a diagram illustrating a CBS mapping method on a frequency axis and a modulation method for each symbol according to an embodiment of the present invention.

S ₀ , S ₁ , ..., S ₄₈ illustrated in FIG. 14 represent modulation symbols constituting CBS.

가 25(5MHz bandwidth)라 가정하면, 총 49개의 CBS 심볼(S₀~S₄₈, 단, 첫번째 변조 심볼(S₀)은 dummy)이 전 대역

에 매핑될 수 있고, 총 CBS 심볼은 98 비트에 매핑될 수 있다.

Assuming that is 25 (5 MHz bandwidth), a total of 49 CBS symbols (S ₀ ~S ₄₈ , however, the first modulation symbol (S ₀ ) is a dummy) for the entire bandwidth

may be mapped to , and the total CBS symbols may be mapped to 98 bits.

D-QPSK(differential quadrature phase shift keying) 심볼로 구성되며, 아래의 수학식 15와 같이 정의될 수 있다.In Equation 13,

It is composed of a differential quadrature phase shift keying (D-QPSK) symbol and can be defined as in Equation 15 below.

이다. 수학식 15에서,

는 채널 코딩이 적용된, 코드화된 비트(coded bit)를 나타낸다. 수학식 15에서 C는 전체 코드워드(codeword)의 길이를 나타내며,

는 25인 경우에, C는 49이다. 도 14에는 대역폭이 C+1개의 PRB를 포함하는 경우가 예시되어 있다.In Equation 15, s _init is a QPSK symbol (x=I+jQ), and in-phase and quadrature-phase are

to be. In Equation 15,

denotes a coded bit to which channel coding is applied. In Equation 15, C represents the length of the entire codeword,

is 25, then C is 49. 14 exemplifies a case in which the bandwidth includes C+1 PRBs.

After the void period of the DRS is filled through at least one of the above-described method M110, method M120, and method M130, a DRS (or eDRS) burst may be transmitted.

A method of adjusting the length of the DRS will be described.

Specifically, the device (eg, LL2) transmits the DRS when it is determined that the channel is idle through the LBT in the unlicensed band. At this time, the length of the DRS itself can be adjusted.

The method of adjusting the length of the DRS may be applied when the downlink PDSCH data is not included in the DRS. The length of the DRS may be determined by the number of OFDM symbols. Therefore, the number of possible OFDM symbol transmissions of DRS N _DRS may be determined by Equation 16 below.

In Equation 16, T _DRS is a unit of time previously designated by RRC (radio resource control), and has a unit of second. In Equation 16, T _s is 1/30.72e6 = 0.000000032552 second.

In summary, since the length of the DRS occasion is not set to a single value, the DRS occasion has a length shorter than the length of one subframe (eg, to have a length less than the length of 14 OFDM symbols), It can be configured on the system. Alternatively, the DRS occasion may be configured on the system to have a relatively long length (eg, 1 to 5 ms).

15 is a diagram illustrating a base station according to an embodiment of the present invention.

The base station 100 includes a processor 110 , a memory 120 , and a radio frequency (RF) converter 130 .

The processor 110 may be configured to implement the procedures, functions, and methods described herein with respect to a base station (eg, LL2). In addition, the processor 110 may control each configuration of the base station 100 .

The memory 120 is connected to the processor 110 and stores various information related to the operation of the processor 110 .

The RF converter 130 is connected to the processor 110 and transmits or receives a wireless signal. And the base station 100 may have a single antenna or multiple antennas.

16 is a diagram illustrating a terminal according to an embodiment of the present invention.

The terminal 200 includes a processor 210 , a memory 220 , and an RF converter 230 .

The processor 210 may be configured to implement the procedures, functions, and methods described herein with respect to the terminal. In addition, the processor 210 may control each configuration of the terminal 200 .

The memory 220 is connected to the processor 210 and stores various information related to the operation of the processor 210 .

The RF converter 230 is connected to the processor 210 and transmits or receives a wireless signal. And the terminal 200 may have a single antenna or multiple antennas.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. is within the scope of the right.

Claims (20)

A method for a base station to transmit a discovery reference signal (DRS) through a channel of an unlicensed band, comprising:
attempting a first access to the unlicensed band channel to transmit the DRS within a DRS measurement timing configuration (DMTC) period;
if the first access fails, attempting a second access to the unlicensed band channel in order to transmit the DRS within the DMTC period; and
If the second access is successful in front of a subframe other than the synchronization subframe, the DRS is multiplexed with a physical downlink shared channel (PDSCH) or a physical downlink control channel (PDCCH). transmitting in the subframe without
including,
The synchronization subframe is a subframe corresponding to a subframe in which a synchronization signal is transmitted in a licensed band, the DRS transmission method of the base station. According to claim 1,
The step of attempting the second access comprises:
Including the step of attempting the second access until the DRS transmission is successful within the DMTC period
DRS transmission method of the base station. According to claim 1,
The synchronization signal includes at least one of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS),
DRS transmission method of the base station. According to claim 1,
If the first access or the second access is successful before the synchronization subframe, multiplexing the DRS with the PDSCH and transmitting the DRS in the synchronization subframe
DRS transmission method of the base station further comprising a. 3. The method of claim 2,
Transmitting the DRS in the subframe without multiplexing it with the PDSCH or PDCCH comprises:
Transmitting the synchronization signal included in the DRS in the same resource element as the resource element in which the synchronization signal of the licensed band is transmitted
Containing, DRS transmission method of the base station. According to claim 1,
The step of attempting the second access comprises:
detecting the unlicensed band channel; and
When it is detected that the unlicensed band channel is idle, transmitting a reservation signal having a variable length to reserve the unlicensed band channel
DRS transmission method of the base station. 7. The method of claim 6,
Transmitting the reservation signal comprises:
generating a time domain sequence for the reservation signal based on a frequency domain sequence including an element having a value based on the physical cell ID of the base station
DRS transmission method of the base station. 7. The method of claim 6,
When the second access is successful, a first fine symbol time field (FSTF) signal for notifying the terminal of the transmission of the DRS is transmitted from the time when the transmission of the reservation signal is finished to before the transmission time of the DRS. step
DRS transmission method of the base station further comprising a. 9. The method of claim 8,
Transmitting the first FSTF signal comprises:
obtaining a first sequence based on a sequence obtained based on a public land mobile network (PLMN) ID of the base station; and
based on the first sequence, generating a Golay sequence for the first FSTF signal
DRS transmission method of the base station. 10. The method of claim 9,
The step of generating the Golay sequence comprises:
generating the Golay sequence using a Dirac Delta function having a value of 1 when input n=0 and a value of 0 otherwise
DRS transmission method of the base station. According to claim 1,
The DRS includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a cell-specific reference signal (CRS),
The time points at which the transmission of the DRS starts and ends coincides with the boundary of the subframe for the licensed band.
DRS transmission method of the base station. According to claim 1,
The step of attempting the second access comprises:
Including the step of attempting the second access in a predetermined period until the transmission of the DRS is successful within the DMTC period,
The predetermined period corresponds to the length of the subframe for the licensed band,
DRS transmission method of the base station. 13. The method of claim 12,
The step of attempting the second access comprises:
Including the step of attempting the second access in the predetermined period until the transmission of the DRS is successful within a DMTC window set within the DMTC period
DRS transmission method of the base station. A method for a base station to transmit a discovery reference signal (DRS) through a channel of an unlicensed band, comprising:
If access to the unlicensed band channel that attempts to transmit the DRS within a DMTC (DRS measurement timing configuration) period succeeds in front of a subframe other than a synchronization subframe, a physical downlink control channel (physical downlink control) channel, PDCCH) or a physical downlink shared channel (PDSCH) not mapping in the subframe together with the DRS; and
If the access is successful before the synchronization subframe, mapping the PDCCH or the PDSCH to the DRS in the synchronization subframe
A DRS transmission method of a base station comprising a. delete delete delete delete A method for a terminal to receive a discovery reference signal (DRS) through a channel of an unlicensed band, comprising:
determining whether a reservation signal for the DRS is detected within a DRS measurement timing configuration (DMTC) period;
if the detection of the reservation signal fails, attempting to detect the reservation signal for the DRS at a predetermined period;
When the reservation signal is detected, when the first subframe following the reservation signal is not a subframe corresponding to the synchronization subframe in which the synchronization signal is transmitted in the licensed band, the DRS is received in the first subframe and the physical Determining that a downlink shared channel (physical downlink shared channel, PDSCH) or a physical downlink control channel (PDCCH) is not received in the first subframe
A DRS reception method of a terminal comprising a. 20. The method of claim 19,
When the reservation signal is detected, when the first subframe following the reservation signal is a subframe corresponding to the synchronization subframe, the DRS is connected to the PDSCH and a physical downlink control channel (PDCCH) Determining that it is received in the first subframe together
DRS reception method of the terminal.

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