WO2016089143A1

WO2016089143A1 - Method for performing uplink transmission on subframe to which reduced cp is applied and user device

Info

Publication number: WO2016089143A1
Application number: PCT/KR2015/013169
Authority: WO
Inventors: 정만영; 양윤오; 이상욱; 임수환; 황진엽
Original assignee: 엘지전자 주식회사
Priority date: 2014-12-05
Filing date: 2015-12-03
Publication date: 2016-06-09

Abstract

One embodiment of the present specification provides a method by which a user device performs an uplink transmission on a subframe to which a reduced cyclic prefix (CP) is applied. The method can comprise the steps of: receiving, from a serving cell, a signal about whether a CP having a more reduced length than that of a normal CP is applied; receiving, from the serving cell, an uplink resource allocation; and performing an uplink transmission by applying the reduced CP on a corresponding uplink subframe, wherein the reduced CP is applied such that a time-domain windowing technique is applied to an idle section occurring between symbols, thereby suppressing a spurious emission.

Description

Method and user equipment for performing uplink transmission on subframe to which reduced CP is applied

The present invention relates to mobile communications.

The 3rd Generation Partnership Project (3GPP) long term evolution (LTE), an improvement of the Universal Mobile Telecommunications System (UMTS), is introduced as a 3GPP release 8. 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink and single carrier-frequency division multiple access (SC-FDMA) in uplink.

Recently, 3GPP LTE-Advanced (LTE-A), an evolution of 3GPP LTE, has been commercialized.

Meanwhile, in LTE / LTE-A, radio resources on a time axis are divided into radio frame units. The radio frame includes 10 subframes, and one subframe includes two slots. One slot may include a plurality of orthogonal frequency division multiplexing (OFDM) symbols. How many OFDM symbols are included in one slot may vary depending on a cyclic prefix (CP).

In LTE / LTE-A, a normal CP and an extended CP are used.

Meanwhile, in order to accommodate the increasing traffic, it is expected that a small cell having a small cell coverage radius will be introduced in the next generation mobile communication system.

Since the small cell to be introduced in the next system is located in the vicinity of the terminal, it is expected to secure a line of sight (LoS) of near and propagation. In this case, since the propagation delay may be relatively small compared to the existing, the existing CP length may be unnecessarily long.

Therefore, the present disclosure aims to solve the above-mentioned problem.

In order to achieve the above object, one disclosure of the present specification provides a method for a user equipment to perform uplink transmission on a subframe to which a reduced cyclic prefix (CP) is applied. The method includes receiving a signal on whether to apply a CP of a length shorter than a normal CP from a serving cell; Receiving an uplink resource allocation from the serving cell; The method may include performing uplink transmission by applying a reduced CP on the uplink subframe. In this case, unnecessary radiation can be suppressed by applying a filter or a time-domain windowing technique to an idle section generated between symbols by applying the reduced CP.

The method may further include delivering capability information including information indicating whether the user equipment supports the reduced CP to the serving cell.

The method may further comprise performing a measurement on the serving cell and transmitting a measurement report including information on the maximum transmission delay. Whether to apply the reduced length CP may be determined by the serving cell based on the maximum transmission delay.

The method comprises the steps of: receiving a network signal comprising an Additional Maximum Power Reduction (A-MPR) value from the serving cell; The method may further include determining a transmission power on an uplink subframe to which the reduced CP is applied based on the A-MPR value.

The A-MPR value when the reduced CP is applied may be smaller than the A-MPR value when the general CP is applied.

In order to achieve the above object, one disclosure of the present specification provides a method for scheduling uplink based on a reduced CP in a base station. The method includes receiving capability information from the user device, the capability information comprising information indicating whether to support the reduced CP; Determining whether to apply a reduced CP to the UE based on the capability information; If it is determined to apply the reduced CP to the UE, determining an uplink subframe to which the reduced CP is to be applied; Transmitting an uplink grant including resource allocation on the uplink subframe.

The method may further comprise receiving a measurement report comprising information about the maximum transmission delay from the user device. Whether to apply the reduced CP to the UE may be determined based on the maximum transmission delay.

The method includes determining an Additional Maximum Power Reduction (A-MPR) value for the user device to which the reduced CP is to be applied; The method may further include transmitting a network signal including the determined A-MPR value to the user device.

In order to achieve the above object, one disclosure of the present disclosure also provides a user device for performing uplink transmission on a subframe to which a reduced cyclic prefix (CP) is applied. The user device includes: a transceiver; And it may include a processor for controlling the transceiver. The processor may include: receiving a signal on whether to apply a CP having a length shorter than a normal CP from a serving cell; Receiving an uplink resource allocation from the serving cell; A process of performing uplink transmission may be performed by applying a reduced CP on the corresponding uplink subframe. Here, the transmitter / receiver may suppress unwanted radiation by applying a filter or a time-domain windowing technique to an idle section generated between symbols by applying the reduced CP.

Applying a reduced CP according to the disclosure herein, suppresses unwanted radiation to adjacent bands. In addition, since the value of A-MPR (Additional Maximum Power Reduction), which has been conventionally used to suppress unwanted radiation, can be reduced due to the reduced CP, it is possible to prevent a decrease in cell coverage to some extent.

1 is an exemplary view showing a wireless communication system.

2 shows a structure of a radio frame according to FDD in 3GPP LTE.

3 is an exemplary diagram illustrating a resource grid for one uplink or downlink slot in 3GPP LTE.

4 shows a structure of a downlink subframe.

5 shows a structure of an uplink subframe in 3GPP LTE.

6 is a diagram illustrating an environment of a mixed heterogeneous network of macro cells and small cells, which may be a next generation wireless communication system.

7 shows an example of using a licensed band and an unlicensed band as carrier aggregation (CA).

8 illustrates an example of a reduced CP length in accordance with the disclosure herein.

9A illustrates an example in which a transmitter determines a CP length according to a maximum transmission delay of a channel measured by a receiver.

9B illustrates an example of determining a CP length according to a maximum transmission delay of a channel arbitrarily estimated by a transmitter.

10 illustrates a concept of a correlator for time synchronization at a receiving end.

11 is an exemplary diagram illustrating subframes to which different CP lengths are applied according to the disclosure of the present specification.

FIG. 12A is an exemplary diagram illustrating two OFDM symbols, FIG. 12B is an exemplary diagram illustrating unnecessary radiation when the time-domain windowing technique is not applied, and FIG. 12C is a conceptual diagram illustrating the concept of a time-domain windowing technique. And FIG. 12D shows an example in which unwanted radiation is removed by the application of the time-domain windowing technique.

13 shows an example of applying a reduced CP in the TDD-eIMTA technology.

14A and 14B are exemplary views illustrating a method of limiting transmission power of a terminal.

15 is a signal flow diagram summarizing the disclosure of the present specification.

16 is a block diagram illustrating a wireless communication system in which the present disclosure is implemented.

Hereinafter, the present invention will be applied based on 3rd Generation Partnership Project (3GPP) 3GPP long term evolution (LTE) or 3GPP LTE-A (LTE-Avanced). This is merely an example, and the present invention can be applied to various wireless communication systems. Hereinafter, LTE includes LTE and / or LTE-A.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments, and are not intended to limit the present invention. In addition, the technical terms used in the present specification should be interpreted as meanings generally understood by those skilled in the art unless they are specifically defined in this specification, and are overly inclusive. It should not be interpreted in the sense of or in the sense of being excessively reduced. In addition, when the technical terms used herein are incorrect technical terms that do not accurately represent the spirit of the present invention, it should be replaced with technical terms that can be understood correctly by those skilled in the art. In addition, the general terms used in the present invention should be interpreted as defined in the dictionary or according to the context before and after, and should not be interpreted in an excessively reduced sense.

Also, the singular forms used herein include the plural forms unless the context clearly indicates otherwise. In the present application, terms such as “consisting of” or “having” should not be construed as necessarily including all of the various components, or various steps described in the specification, and some of the components or some of the steps are included. It should be construed that it may not be, or may further include additional components or steps.

In addition, terms including ordinal numbers, such as first and second, as used herein may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but other components may be present in between. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. In addition, in describing the present invention, when it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, it should be noted that the accompanying drawings are only for easily understanding the spirit of the present invention and should not be construed as limiting the spirit of the present invention by the accompanying drawings. The spirit of the present invention should be construed to extend to all changes, equivalents, and substitutes in addition to the accompanying drawings.

The term base station, which is used hereinafter, generally refers to a fixed station for communicating with a wireless device, and includes an evolved-nodeb (eNodeB), an evolved-nodeb (eNB), a base transceiver system (BTS), and an access point (e.g., a fixed station). Access Point) may be called.

Further, hereinafter, the term UE (User Equipment), which is used, may be fixed or mobile, and may include a device, a wireless device, a terminal, a mobile station (MS), and a user terminal (UT). Other terms may be referred to as a subscriber station (SS) and a mobile terminal (MT).

1 is an exemplary view showing a wireless communication system.

As can be seen with reference to FIG. 1, a wireless communication system includes at least one base station (BS) 20. Each base station 20 provides a communication service for a particular geographic area (generally called a cell) 20a, 20b, 20c.

The UE typically belongs to one cell, and the cell to which the UE belongs is called a serving cell. A base station that provides a communication service for a serving cell is called a serving BS. Since the wireless communication system is a cellular system, there are other cells adjacent to the serving cell. Another cell adjacent to the serving cell is called a neighbor cell. A base station that provides communication service for a neighbor cell is called a neighbor BS. The serving cell and the neighbor cell are determined relatively based on the UE.

Hereinafter, downlink means communication from the base station 20 to the UE 10, and uplink means communication from the UE 10 to the base station 20. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the UE 10. In uplink, the transmitter may be part of the UE 10 and the receiver may be part of the base station 20.

Hereinafter, the LTE system will be described in more detail.

2 shows a structure of a radio frame according to FDD in 3GPP LTE.

The radio frame illustrated in FIG. 2 may refer to section 5 of 3GPP TS 36.211 V10.4.0 (2011-12) "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 10)".

Referring to FIG. 2, a radio frame includes 10 subframes, and one subframe includes two slots. Slots in a radio frame are numbered from 0 to 19 slots. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). TTI may be referred to as a scheduling unit for data transmission. For example, one radio frame may have a length of 10 ms, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.

The structure of the radio frame is merely an example, and the number of subframes included in the radio frame or the number of slots included in the subframe may be variously changed.

Meanwhile, one slot may include a plurality of orthogonal frequency division multiplexing (OFDM) symbols. How many OFDM symbols are included in one slot may vary depending on a cyclic prefix (CP).

Referring to FIG. 3, an uplink slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain and NRB resource blocks (RBs) in a frequency domain. For example, in the LTE system, the number of resource blocks (Resource Block RB), that is, the NRB may be any one of 6 to 110. The RB is also called a physical resource block (PRB).

A resource block (RB) is a resource allocation unit and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain and the resource block includes 12 subcarriers in the frequency domain, one resource block includes 7 × 12 resource elements (REs). It may include.

On the other hand, the number of subcarriers in one OFDM symbol can be used to select one of 128, 256, 512, 1024, 1536 and 2048.

In 3GPP LTE of FIG. 4, a resource grid for one uplink slot may be applied to a resource grid for a downlink slot.

4 shows a structure of a downlink subframe.

In FIG. 4, it is illustrated that 7 OFDM symbols are included in one slot by assuming a normal CP.

The DL (downlink) subframe is divided into a control region and a data region in the time domain. The control region includes up to three OFDM symbols preceding the first slot in the subframe, but the number of OFDM symbols included in the control region may be changed. A physical downlink control channel (PDCCH) and another control channel are allocated to the control region, and a PDSCH is allocated to the data region.

In 3GPP LTE, physical channels include a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), a physical downlink control channel (PDCCH), a physical control format indicator channel (PCFICH), and a physical hybrid (PHICH). ARQ Indicator Channel) and PUCCH (Physical Uplink Control Channel).

The PCFICH transmitted in the first OFDM symbol of a subframe carries a control format indicator (CFI) regarding the number of OFDM symbols (that is, the size of the control region) used for transmission of control channels in the subframe. The wireless device first receives the CFI on the PCFICH and then monitors the PDCCH.

Unlike the PDCCH, the PCFICH does not use blind decoding and is transmitted on a fixed PCFICH resource of a subframe. The PHICH carries a positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for a UL hybrid automatic repeat request (HARQ). The ACK / NACK signal for uplink (UL) data on the PUSCH transmitted by the wireless device is transmitted on the PHICH.

The Physical Broadcast Channel (PBCH) is transmitted in the preceding four OFDM symbols of the second slot of the first subframe of the radio frame. The PBCH carries system information necessary for the wireless device to communicate with the base station, and the system information transmitted through the PBCH is called a master information block (MIB). In comparison, system information transmitted on the PDSCH indicated by the PDCCH is called a system information block (SIB).

The PDCCH includes resource allocation and transmission format of downlink-shared channel (DL-SCH), resource allocation information of uplink shared channel (UL-SCH), paging information on PCH, system information on DL-SCH, and random access transmitted on PDSCH. Resource allocation of higher layer control messages such as responses, sets of transmit power control commands for individual UEs in any UE group, activation of voice over internet protocol (VoIP), and the like. A plurality of PDCCHs may be transmitted in the control region, and the UE may monitor the plurality of PDCCHs. The PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to a state of a radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

Control information transmitted through the PDCCH is called downlink control information (DCI). DCI is a resource allocation of PDSCH (also called DL grant), a PUSCH resource allocation (also called UL grant), a set of transmit power control commands for individual UEs in any UE group. And / or activation of Voice over Internet Protocol (VoIP).

The base station determines the PDCCH format according to the DCI to be sent to the UE, and attaches a cyclic redundancy check (CRC) to the control information. The CRC masks a unique radio network temporary identifier (RNTI) according to the owner or purpose of the PDCCH. If the PDCCH is for a specific UE, a unique identifier of the UE, for example, a cell-RNTI (C-RNTI) may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier, for example, p-RNTI (P-RNTI), may be masked to the CRC. If the PDCCH is for a system information block (SIB), a system information identifier and a system information-RNTI (SI-RNTI) may be masked to the CRC. A random access-RNTI (RA-RNTI) may be masked in the CRC to indicate a random access response that is a response to the transmission of the random access preamble of the UE.

In 3GPP LTE, blind decoding is used to detect the PDCCH. Blind decoding is a method of demasking a desired identifier in a cyclic redundancy check (CRC) of a received PDCCH (referred to as a candidate PDCCH) and checking a CRC error to determine whether the corresponding PDCCH is its control channel. . The base station determines the PDCCH format according to the DCI to be sent to the wireless device, attaches the CRC to the DCI, and masks a unique identifier (RNTI) to the CRC according to the owner or purpose of the PDCCH.

The uplink channel includes a PUSCH, a PUCCH, a sounding reference signal (SRS), and a physical random access channel (PRACH).

5 shows a structure of an uplink subframe in 3GPP LTE.

Referring to FIG. 5, an uplink subframe may be divided into a control region and a data region in the frequency domain. A physical uplink control channel (PUCCH) for transmitting uplink control information is allocated to the control region. The data area is allocated a PUSCH (Physical Uplink Shared Channel) for transmitting data (in some cases, control information may also be transmitted).

PUCCH for one UE is allocated to an RB pair in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers in each of a first slot and a second slot. The frequency occupied by RBs belonging to the RB pair allocated to the PUCCH is changed based on a slot boundary. This is called that the RB pair allocated to the PUCCH is frequency-hopped at the slot boundary.

The UE may obtain frequency diversity gain by transmitting uplink control information through different subcarriers over time. m is a location index indicating a logical frequency domain location of a resource block pair allocated to a PUCCH in a subframe.

The uplink control information transmitted on the PUCCH includes a hybrid automatic repeat request (HARQ) acknowledgment (ACK) / non-acknowledgement (NACK), a channel quality indicator (CQI) indicating a downlink channel state, and an uplink radio resource allocation request. (scheduling request).

The PUSCH is mapped to the UL-SCH, which is a transport channel. The uplink data transmitted on the PUSCH may be a transport block which is a data block for the UL-SCH transmitted during the TTI. The transport block may be user information. Alternatively, the uplink data may be multiplexed data. The multiplexed data may be a multiplexed transport block and control information for the UL-SCH. For example, control information multiplexed with data may include a CQI, a precoding matrix indicator (PMI), a HARQ, a rank indicator (RI), and the like. Alternatively, the uplink data may consist of control information only.

Carrier Aggregation (CA)

The carrier aggregation system will now be described.

The carrier aggregation system refers to aggregating a plurality of component carriers (CC). By the carrier aggregation, the meaning of the existing cell has been changed. According to carrier aggregation, a cell may mean a combination of a downlink component carrier and an uplink component carrier or a single downlink component carrier.

In the carrier aggregation, a cell may be divided into a primary cell, a secondary cell, and a serving cell. A primary cell means a cell operating at a primary frequency, and is a cell in which a UE performs an initial connection establishment procedure or a connection reestablishment procedure with a base station, or is indicated as a primary cell in a handover process. It means a cell. The secondary cell refers to a cell operating at the secondary frequency, and is established and used to provide additional radio resources once the RRC connection is established.

The carrier aggregation system may be divided into a contiguous carrier aggregation system in which aggregated carriers are continuous and a non-contiguous carrier aggregation system in which aggregated carriers are separated from each other. Hereinafter, simply referred to as a carrier aggregation system, it should be understood to include both the case where the component carrier is continuous and the case where it is discontinuous. The number of component carriers aggregated between the downlink and the uplink may be set differently. The case where the number of downlink CCs and the number of uplink CCs are the same is called symmetric aggregation, and when the number is different, it is called asymmetric aggregation.

When aggregation of one or more component carriers, the target carrier may use the bandwidth used by the existing system as it is for backward compatibility with the existing system. For example, the 3GPP LTE system supports bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz, and the 3GPP LTE-A system may configure a bandwidth of 20 MHz or more using only the bandwidth of the 3GPP LTE system. Alternatively, broadband can be configured by defining new bandwidth without using the bandwidth of the existing system.

Meanwhile, in order to transmit and receive packet data through a specific secondary cell in carrier aggregation, a UE must first complete configuration for a specific secondary cell. In this case, the configuration refers to a state in which reception of system information necessary for data transmission and reception for a corresponding cell is completed. For example, the configuration may include a general process of receiving common physical layer parameters required for data transmission and reception, media access control (MAC) layer parameters, or parameters required for a specific operation in the RRC layer. . When the set cell receives only the information that the packet data can be transmitted, the cell can be immediately transmitted and received.

The cell in the configuration complete state may exist in an activation or deactivation state. Here, activation means that data is transmitted or received or is in a ready state. The UE may monitor or receive the control channel (PDCCH) and the data channel (PDSCH) of the activated cell in order to identify resources allocated to the UE (which may be frequency, time, etc.).

Deactivation means that transmission or reception of traffic data is impossible, and measurement or transmission of minimum information is possible. The UE may receive system information (SI) necessary for packet reception from the deactivated cell. On the other hand, the UE does not monitor or receive the control channel (PDCCH) and the data channel (PDSCH) of the deactivated cell in order to check resources allocated to it (may be frequency, time, etc.).

Meanwhile, in the next generation mobile communication system, a small cell having a small cell coverage radius is expected to be added within the coverage of an existing cell, and the small cell is expected to handle more traffic. Since the existing cell has greater coverage than the small cell, it may be referred to as a macro cell. Hereinafter, a description will be given with reference to FIG. 7.

Referring to FIG. 6, a macro cell by an existing base station 200 is a heterogeneous network environment in which a macro cell overlaps with a small cell by one or more

small base stations

300a, 300b, 300c, and 300d. Since the existing base station provides greater coverage than the small base station, it is also called a macro base station (Macro eNodeB, MeNB). In this specification, the terms macro cell and macro base station are used interchangeably. The UE connected to the macro cell 200 may be referred to as a macro UE. The macro UE receives a downlink signal from the macro base station and transmits an uplink signal to the macro base station.

In such a heterogeneous network, the macro cell is set as the primary cell and the small cell is set as the secondary cell, thereby filling the coverage gap of the macro cell. In addition, by setting the small cell as the primary cell (Pcell) and the macro cell as the secondary cell (Scell), it is possible to improve the overall performance (boosting).

On the other hand, the illustrated

small cells

300b and 300c may expand or reduce their coverage in order to reduce interference effects on other adjacent

small cells

300a and 300d or the macro cell 200 according to a situation. Such expansion and contraction of coverage is called cell breathing. Alternatively, the

small cells

300b and 300c may be turned on or off depending on the situation.

<LTE-U (Unlicensed Spectrum) for Next Generation Mobile Communication System>

In recent years, as more communication devices require larger communication capacities, efficient use of limited frequency bands in future wireless communication systems has become increasingly important. Cellular communication systems such as LTE systems are also considering ways to utilize unlicensed bands such as 2.4 GHz band or unlicensed bands such as 5 GHz band for traffic bypass. This is called LTE-U.

In order to transmit and receive a signal through an unlicensed band carrier that does not guarantee exclusive use of a particular system, as shown in FIG. 7, a licensed band LTE-A band and an unlicensed band Using a carrier aggregation (CA) of unlicensed band, the small cell base station 300 may transmit a signal to the UE 100 or the UE may transmit a signal to the small cell base station. Here, for example, the carrier of the licensed band may be interpreted as a primary CC (can be referred to as PCC or PCell), and the carrier of the unlicensed band may be interpreted as a secondary CC (can be referred to as SCC or SCell). .

As such, since the unlicensed band operates under the support of a licensed band (i.e., LTE-A band), LTE-U is also referred to as licensed-assisted access (LTE-LAA).

As described above, LTE / LTE-A, a current mobile communication system, uses a scheme based on OFDMA in downlink and SC-FDMA in uplink. Further, even in the next generation mobile communication system in which small cells and technologies such as LTE-U or LTE-LAA are expected to be introduced, OFDMA / SC-FDMA is expected to be used as the current communication method.

However, in the OFDMA / SC-FDMA-based communication, the length of a cyclic prefix (CP) is designed in consideration of the maximum delay of a channel in order to prevent inter-symbol interference (ISI) in a large cell radius.

However, since the small cell to be introduced in the next system is located in the vicinity of the UE, it is expected to secure line of sight (LoS) of near and propagation. In this case, since the propagation delay may be relatively small compared to the macro cell environment, the cyclic prefix (CP) length presented in the existing 3GPP LTE Release-10 system may be unnecessarily long.

Disclosure of the Invention

Accordingly, the present specification proposes a shortened CP that occupies a number of samples shorter or smaller than the CP (cyclic prefix) length proposed in the existing 3GPP LTE Release-10 system. The reduced CP means shorter than the normal CP length.

In particular, in a heterogeneous network environment in which the existing macro cell and the small cell are mixed, the coverage of the cells is different from each other, so that the maximum path delay is different. Accordingly, the present specification proposes a method of applying different CP lengths to each maximum path delay in order to minimize resources wasteful by unnecessary long CP lengths.

As can be seen with reference to FIG. 8, the first reduced CP may be shorter in length than the normal CP. The second reduced CP may have a shorter length than the first reduced CP.

In consideration of the maximum path delay with each UE, each cell may independently apply CP lengths to the respective UEs to prevent ISI, resulting in waste of resources and lower transmission power.

In this case, a method for knowing the maximum transmission delay of each cell will be described.

I. Method for Cell to Know Maximum Transmission Delay

As a method for knowing the maximum transmission delay of each cell, there may be a method in which the transmitter reports the maximum transmission delay of the channel measured by the receiver, and a method in which each transmitter arbitrarily estimates the channel.

I-1. The scheme that the transmitter reports the maximum transmission delay of the channel measured by the receiver

The maximum transmission delay of the channel is basically possible through channel estimation at the receiving end. Therefore, when the receiving end reports the statistics of the maximum delay obtained through its channel estimator to the transmitting end, the transmitting end may apply only the CP of the minimum length accordingly.

Accordingly, this section informs the transmitting end of the transmission delay value of the channel measured by the receiving end, so that the transmitting end can apply a variable length CP.

Referring to FIG. 9A, a receiver measures a channel based on a signal received from a transmitter. The maximum transmission delay of the channel is also estimated during the channel measurement. The receiving end transmits the maximum transmission delay of the channel to the transmitting end while performing the measurement report. In the case of current LTE / LTE-A, the UE transmits the measurement report for the downlink channel to the cell, and the transmission delay for the uplink channel is informed to the UE through a timing adjustment procedure. Thus, through the measurement report and timing adjustment procedure, the method proposed in this section can be implemented.

Then, the transmitter can determine the CP length to be applied to the subframe to be transmitted based on the maximum transmission delay value of the channel informed by the receiver.

I-2. Method to utilize maximum transmission delay of channel arbitrarily estimated by transmitter

The maximum transmission delay of the channel is usually measured at the receiver. However, in the case of the TDD system, the transmission channel and the reception channel use the same frequency, and thus, the maximum transmission delay of the channel estimated in the previously received subframe may be the same as the delay of the channel delayed during transmission. In addition, even in the case of FDD, when the frequency difference between the downlink and the uplink is not large, the difference in the maximum transmission delay of the channel between each downlink / uplink may not be large. Accordingly, the base station or the UE may determine the CP length to be applied to the transmission subframe based on the maximum transmission delay of the channel estimated from the reception subframe.

Referring to FIG. 9B, a transmitter measures a channel based on a signal received from a receiver. The maximum transmission delay of the channel is also estimated during the channel measurement.

II. Signaling on CP Length

As described above, when the CP length varies with time, there is a problem in time synchronization for OFDM symbols. In an OFDM system, synchronization is typically performed by applying a correlation between a section corresponding to a CP of an OFDM symbol and a data section. Basically, a correlator that obtains a correlation performs time synchronization by calculating a correlation between a received signal and a signal delayed by a predetermined FFT size while moving a predetermined window size.

The performance of the correlator as shown in FIG. 10 is basically proportional to the window size. Thus, if the CP length varies over time, the performance of the correlator is basically limited by the reduced CP length. However, the environment in which variable length CP is used is expected to have a small maximum transmission delay as a near channel. Thus, since the SNR obtainable in the near channel will be relatively large, the reduced performance of the correlator may be compensated for due to the reduced CP length.

On the other hand, even if the reduced CP length is used, if the sliding buffer shown in FIG. 10 operates based on the normal CP length, additional performance degradation may occur.

Therefore, this section proposes that the sliding buffer in the correlator of the receiver can be dynamically changed by the reduced CP length. However, whether or not the sliding buffer can also be dynamically changed corresponds to one capability, so the receiving end needs to inform the transmitting end of the capability. Accordingly, the transmitter needs to distinguish among receivers to which the reduced CP length can be applied among several receivers.

To this end, the receiving end, for example, the UE may transmit information to the cell by including information on whether the reduced CP length can be applied in information on its capability (ie, UE Capability Information).

Similarly, the transmitting end, for example, the serving cell, may inform the UE whether the reduced CP length can be applied.

As an example, this section proposes the following signaling.

SupportVariableCP: Signaling whether the UE supports a reduced CP length in downlink or whether the CP length can be changed over time to the serving cell

EnableVariableCP: signaling indicating whether the serving cell supports a reduced CP length in uplink or whether the CP length can be changed in time

III. Serving Cell Scheduling

Unlike the OFDM-TDM system in which one UE is allocated to one OFDM symbol, the OFDMA scheme applied in LTE / LTE-A allows a plurality of UEs to be allocated to different frequency resources on the same OFDM symbol. Although a plurality of UEs are allocated to different frequency resources on the frequency axis, when operating on one OFDM symbol on the time axis, the same CP length should be applied to the plurality of UEs. Therefore, it is effective to schedule the UE according to the UE indicating the maximum transmission delay of similar length. An example of such group scheduling is shown in FIG. 11.

As can be seen with reference to FIG. 11, for example, a normal CP may be applied to any subframe (eg, subframe 0). In addition, a first reduced CP may be applied to another subframe (eg, subframe 3), and a second reduced CP may be applied to another subframe (eg, subframe 7).

The serving cell may resource schedule a plurality of UEs having a similar maximum transmission delay on subframe 0 to which the normal CP is applied. In addition, the serving cell may resource schedule a plurality of UEs having a similar maximum transmission delay on subframe 3 to which the first reduced CP is applied.

When using such a group scheduling scheme in the downlink, the serving cell only needs to group a plurality of UEs having similar maximum transmission delays, and the UE does not need any improvement.

On the other hand, when the UE uses a reduced CP, by using the idle interval caused by the reduced CP as a transition period between the previous OFDM symbol and the current OFDM symbol, variably filter or time-domain windowing (Time By applying the -domain windowing technique, it is possible to reduce the discontinuity of the time domain signal, thereby reducing unnecessary radiation emitted in and out of band.

The time-domain windowing technique is a technique that can reduce unnecessary radiation by applying a window defined in the time domain between adjacent symbols in an OFDM system to smooth the transition between adjacent symbols.

Referring to FIG. 12A, symbol n is cosine, but symbol n + 1 is sine, and two symbols are discontinuous as indicated by ellipses. If these two discontinuous symbols are transmitted without the time-domain windowing technique applied, undesired radiation will appear, as indicated by ellipses in FIG. 12B.

To limit this unwanted radiation, a transition between the two symbols can be smoothed as can be seen with reference to FIG. 12C. This is the time domain windowing technique. That is, the time domain windowing technique is to smoothly connect the end of the first symbol and the start of the second symbol in the time domain to smooth the transition between the two symbols. As such, when applying the time domain windowing technique, as shown in FIG. 12D, unnecessary radiation may be reduced and EVM may be increased.

On the other hand, when the reduced CP according to the disclosure of the present disclosure, it is possible to apply a time-domain windowing technique that is as large as the reduced CP length, thereby limiting the in-band and out-of-band radiation more efficiently. Will be.

IV. Example of reduced CP

The effect of applying the reduced CP may be increased in the A-MPR scheme according to the TDD-eIMTA technique and the network signaling (NS) signal.

TDD-eIMTA technology is a technology that can increase the transmission rate of the entire system by dynamically converting a subframe allocated as a basic uplink (UL) to a downlink (DL) in a TDD system. have. In downlink DL switched from uplink UL according to the eIMTA, interference is affected by an uplink signal of another cell. For example, when a neighbor cell converts an uplink subframe into a downlink subframe, but the serving cell schedules an uplink transmission to the UE in the uplink subframe, the serving cell is reduced to the UE. Can be set to use CP. As such, when the UE uses the reduced CP and applies a time-domain windowing technique, the uplink transmission of the UE is unnecessary to the frequency domain on the downlink subframe switched in the uplink subframe by the neighboring cell. The radiation is limited.

13 shows an example of applying a reduced CP in the TDD-eIMTA technology.

As can be seen with reference to FIG. 13, the serving cell uses TDD UL / DL configuration 0. On the other hand, the neighbor cell to which the eIMTA is applied is changed from TDD UL / DL configuration 0 to TDD UL / DL configuration 2.

Subframes

3, 4, 8, and 9 are converted to downlink instead of uplink by the neighboring cell to which the eIMTA is applied. Since the serving cell operates as it is with the existing UL / DL configuration 0, large interference caused by uplink transmission of the UE is introduced into the frequency resource on the downlink subframe switched from the uplink subframe by the neighboring cell. System performance is reduced.

In this case, UEs to apply a CP in which the serving cell is reduced on an uplink subframe of the serving cell existing at the same time position as the downlink subframe switched by the neighboring cell in the uplink subframe. When scheduling, the interference can be mitigated. That is, when the UE uses the reduced CP on the corresponding subframe and applies a time-domain windowing technique, the uplink transmission of the UE is performed on the downlink subframe switched in the uplink subframe by the neighbor cell. Undesired radiation in the frequency domain is limited.

In general, performing transmission in an allocated channel band causes unwanted emission to adjacent channels. In this case, the interference due to the radiation caused by the base station transmission can reduce the amount of interference introduced into the adjacent band by the high cost and the design of a large size RF filter due to the characteristics of the base station to less than the allowed criteria. On the other hand, in the case of UE, it is difficult to completely prevent the entry into the adjacent band due to the size limitation and the price limit for the power amplifier or pre-duplex filter RF device.

Therefore, it is necessary to limit the transmit power of the UE.

As can be seen with reference to FIG. 14A, the UE 100 performs transmission by limiting transmission power.

To limit the transmission strategy, the maximum power reduction (MPR) value decreases the linearity of the power amplifier (PA) when the peak-to-average power ratio (PAPR) is large. Depending on the modulation method, a maximum MPR value of 2dB can be applied.

On the other hand, as can be seen with reference to Figure 14b, the base station transmits a network signal (NS) to the UE (100) may apply A-MPR (Additional Maximum Power Reduction). Unlike the above-mentioned MPR, the A-MPR transmits a network signal (NS) to the UE 100 operating in a specific operating band, so that the base station transmits a network signal (NS) to the UE 100 to operate in a specific operating band. In addition, to reduce power. That is, when the UE applying the MPR receives the network signal NS, the transmission power is additionally determined by applying the A-MPR.

As such, the operation of the UE in the situation where it is necessary to limit the unnecessary radiation by the network signal NS can be improved as follows according to the application of the present invention.

1. If the maximum transmission delay of the channel is large: In this case, as in the past, the maximum available CP is used and A-MPR is applied to limit out-of-band emission.

2. When the maximum transmission delay of the channel is small: The CP length is reduced to match the maximum transmission delay of the channel, and thus the remaining interval is applied by applying the time-domain windowing technique to the previous OFDM symbol and the current OFDM symbol interval. Restrict. In this case, the time-domain windowing technique and A-MPR can be mixed properly. In general, the cell coverage radius is reduced when A-MPR is applied. However, by reducing the A-MPR value by the time-domain windowing technique, the cell coverage radius can be somewhat mitigated.

By introducing the reduced CP as described above, the UE can obtain the effect of reducing the transmission power, and can also obtain an additional interference limiting effect due to the reduction of the CP length. In particular, when the synchronization between the neighboring base station and the serving base station is inconsistent, the CP section used in each base station is located in the data section of the other base station. The interference limiting effect can be obtained by arranging UEs that require.

First, the serving cell 200a exchanges information with a neighbor cell 200b through an X2 interface. In this case, when the serving cell 200a and the neighbor cell 200b are TDD systems, the neighbor cell 200b may inform the serving cell 200a whether it applies the eIMTA.

On the other hand, the serving cell 200a requests the UE capability inquiry to the UE 100 as needed or instructed by a higher layer.

Then, the UE 100 transmits UE capability information to the serving cell 200a according to the request. In this case, the UE capability information may include the aforementioned supportVariableCP.

Based on the supportVariableCP, the serving cell 200a determines whether the UE 100 can apply the reduced CP.

Meanwhile, the UE 100 performs measurement and transmits a measurement report to the serving cell. The serving cell 200a determines whether to apply a reduced CP length based on the maximum transmission delay.

Subsequently, the serving cell 200a transmits an RRC signal including EnableVariableCP indicating whether to apply the reduced CP length to the UE 100.

Meanwhile, the serving cell 200a determines an A-MPR value based on the reduced CP. At this time, according to the use of the reduced CP, the value of the A-MPR may be reduced. For example, the required A-MPR value is 3 dB, but if the reduced CP is used, the A-MPR value may be reduced to 1 dB. Subsequently, a network signal including the determined A-MPR value, for example, an RRC signal, is transmitted to the UE 100.

On the other hand, the serving cell 200a determines a subframe to which the reduced CP is applied. The serving cell 200a determines a plurality of UEs to allocate resources in a subframe determined to apply the reduced CP.

The serving cell 200a transmits an uplink grant including uplink resource allocation to the UE 100. The uplink grant may be transmitted on the PDCCH.

The UE 100 determines transmission power based on the A-MPR.

The UE 100 performs uplink transmission with the determined transmission power on an uplink subframe to which the reduced CP is applied. In this case, the UE 100 may limit the unnecessary radiation to the adjacent band by applying the time-domain windowing technique to the effective period generated due to the reduced CP.

Embodiments of the present invention described so far may be implemented through various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof. Specifically, it will be described with reference to the drawings.

The base station 200 includes a processor 201, a memory 202, and an RF unit (RF (radio frequency) unit) 203. The memory 202 is connected to the processor 201 and stores various information for driving the processor 201. The RF unit 203 is connected to the processor 201 to transmit and / or receive a radio signal. The processor 201 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the base station may be implemented by the processor 201.

The UE 100 includes a processor 101, a memory 102, and an RF unit 103. The memory 102 is connected to the processor 101 and stores various information for driving the processor 101. The RF unit 103 is connected to the processor 101 and transmits and / or receives a radio signal. The processor 101 implements the proposed functions, processes and / or methods.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

Claims

A method for performing uplink transmission on a subframe to which a user equipment is applied with reduced cyclic prefix (CP),

Receiving a signal on whether to apply a CP having a length shorter than a normal CP from a serving cell;

Receiving an uplink resource allocation from the serving cell;

Performing uplink transmission by applying a reduced CP on the uplink subframe,

The reduced CP-based uplink transmission method of claim 4, wherein unnecessary radiation is suppressed by applying a time-domain windowing technique to an idle section generated between symbols by applying the reduced CP.
The method of claim 1,

And transmitting capability information including information indicating whether the user equipment supports the reduced CP to the serving cell.
The method of claim 1,

Performing measurements on the serving cell, and transmitting a measurement report including information about the maximum transmission delay,

The reduced CP-based uplink transmission method of claim 1, wherein whether to apply the reduced length CP is determined based on the maximum transmission delay by the serving cell.
The method of claim 1,

Receiving a network signal including an Additional Maximum Power Reduction (A-MPR) value from the serving cell;

And determining a transmission power on an uplink subframe to which the reduced CP is applied based on the A-MPR value.
The method of claim 4, wherein

The reduced CP-based uplink transmission method according to claim 1, wherein the A-MPR value when the reduced CP is applied is smaller than the A-MPR value when the general CP is applied.
A method for scheduling uplink based on a reduced CP in a base station,

Receiving capability information including information indicating whether to support a reduced CP from a user device;

Determining whether to apply a reduced CP to the UE based on the capability information;

If it is determined to apply the reduced CP to the UE, determining an uplink subframe to which the reduced CP is to be applied;

And transmitting an uplink grant including resource allocation on the uplink subframe.
The method of claim 6,

Receiving from the user device a measurement report comprising information about a maximum transmission delay,

Whether to apply the reduced CP to the UE is determined based on the maximum transmission delay.
The method of claim 6,

Determining an Additional Maximum Power Reduction (A-MPR) value for the user device to which the reduced CP is to be applied;

And transmitting the network signal including the determined A-MPR value to the user device.
The method of claim 8,

The reduced CP-based uplink transmission method according to claim 1, wherein the A-MPR value when the reduced CP is applied is smaller than the A-MPR value when the general CP is applied.
A user device for performing uplink transmission on a subframe to which a reduced cyclic prefix (CP) is applied,

A transceiver;

A processor for controlling the transceiver;

Receiving a signal on whether to apply a CP having a length shorter than a normal CP from a serving cell;

Receiving an uplink resource allocation from the serving cell;

Performing a process of performing uplink transmission by applying a reduced CP on the corresponding uplink subframe,

Wherein the transceiver is configured to suppress unnecessary radiation by applying a time-domain windowing technique to an idle section generated between symbols by applying the reduced CP.
The method of claim 10, wherein the transceiver unit

And transmitting the capability information including information indicating whether the user apparatus supports the reduced CP to the serving cell.
The method of claim 10,

The transceiver performs measurement on the serving cell, transmits a measurement report including information on the maximum transmission delay,

The user equipment, characterized in that whether to apply the CP of the reduced length is determined based on the maximum transmission delay by the serving cell.
The method of claim 10,

When the transceiver receives a network signal including an A-MPR (Additional Maximum Power Reduction) value from the serving cell, the processor performs an uplink subframe on which the reduced CP is applied based on the A-MPR value. And determine the transmit power.
The method of claim 13,

The A-MPR value when the reduced CP is applied to the user device, characterized in that less than the A-MPR value when the general CP is applied.