KR101868621B1 - Method for transmitting aperiodic SRS and controlling for uplink transmit power of aperiodic SRS based on aperiodic SRS triggering - Google Patents

Abstract

A method of transmitting an SRS based on an aperiodic sounding reference signal (SRS) triggering in a wireless communication system and a method of controlling uplink transmission power for transmitting an aperiodic SRS are disclosed . A method for transmitting an SRS based on an aperiodic Sounding Reference Signal (SRS) triggering method according to the present invention includes: receiving a plurality of aperiodic SRS configuration information from a base station; Receiving an indicator for triggering an aperiodic SRS transmission from the base station; A subframe index for receiving the aperiodic SRS transmission triggering indicator, a subframe index for receiving the aperiodic SRS transmission triggering indicator, a time interval between the non-periodic SRS transmission subframe corresponding to the received subframe of the aperiodic SRS transmission triggering indicator, Selecting specific aperiodic SRS configuration information from the plurality of aperiodic SRS configuration information based on at least one of a relationship and an uplink channel condition; And transmitting an aperiodic SRS for the aperiodic SRS transmission triggering indicator based on the selected aperiodic SRS configuration information, wherein the plurality of aperiodic SRS configuration information corresponds to the aperiodic SRS transmission triggering indicator And may include information about resources that transmit aperiodic SRS.
Also, in accordance with the present invention, a terminal may receive a power offset value for aperiodic SRS transmissions from a base station and may use it to determine a transmit power value for aperiodic SRS transmissions.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SRS transmission method based on aperiodic sounding reference signal triggering of a UE and a control method of an uplink transmission power for transmitting aperiodic SRS,

[0001] The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting an aperiodic sounding reference signal (SRS) triggering-based SRS transmission method and an uplink transmission power for transmitting aperiodic SRS And a control method.

Wireless communication technologies have been developed up to LTE based on Wideband Code Division Multiple Access (WCDMA), but the demands and expectations of users and operators are continuously increasing. In addition, since other wireless access technologies are continuously being developed, new technology evolution is required to be competitive in the future. Cost reduction per bit, increased service availability, use of flexible frequency band, simple structure and open interface, and proper power consumption of terminal.

Recently, 3GPP has been working on standardization of follow-up technology for LTE. In this specification, this technique is referred to as 'LTE-A'. One of the main differences between LTE systems and LTE-A systems is the difference in system bandwidth and the introduction of repeaters. The LTE-A system is aimed at supporting broadband up to 100 MHz and uses carrier-aggregation or bandwidth aggregation techniques to achieve broadband using multiple frequency blocks. . Carrier aggregation allows a plurality of frequency blocks to be used as one large logical frequency band to use a wider frequency band. The bandwidth of each frequency block may be defined based on the bandwidth of the system block used in the LTE system. Each frequency block is transmitted using a component carrier.

The 3GPP LTE-A system supports aperiodic SRS transmission in addition to the existing periodic SRS transmission in order to guarantee the accuracy of the uplink channel estimation. In order to support the aperiodic SRS transmission, non-periodic SRS configuration information and uplink transmission power control for aperiodic SRS transmission are required. However, specific acyclic SRS configuration information for supporting aperiodic SRS transmission and a method for controlling uplink transmission power for aperiodic SRS transmission have not been specifically proposed yet.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an SRS transmission method based on aperiodic sounding reference signal (SRS) triggering.

Another aspect of the present invention is to provide a method for controlling uplink transmission power for a UE to transmit aperiodic SRS.

Another object of the present invention is to provide a terminal apparatus for transmitting aperiodic SRS based on aperiodic sounding reference signal (SRS) triggering.

According to another aspect of the present invention, there is provided a terminal apparatus for controlling an uplink transmission power for transmitting aperiodic SRS.

The technical problems to be solved by the present invention are not limited to the technical problems and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method for transmitting an SRS based on an aperiodic sounding reference signal (SRS) triggering method, the method comprising: receiving a plurality of aperiodic SRS comprising the steps of: receiving configuration information; Receiving an indicator for triggering an aperiodic SRS transmission from the base station; Based on at least one of a subframe index on which the aperiodic SRS transmission triggering indicator is received, a time relationship between the reception subframe of the aperiodic SRS transmission triggering indicator and an aperiodic SRS transmission subframe corresponding to the aperiodic SRS transmission triggering indicator, Selecting non-periodic SRS configuration information from the non-periodic SRS configuration information of the non-periodic SRS configuration information; And transmitting an aperiodic SRS for the aperiodic SRS transmission triggering indicator based on the selected aperiodic SRS configuration information, wherein the plurality of aperiodic SRS configuration information corresponds to the aperiodic SRS transmission triggering indicator And may include information about resources that transmit aperiodic SRS. Herein, the transmission of the aperiodic SRS is performed such that, when the subframe receiving the aperiodic SRS transmission triggering indicator is the subframe n, the first non-periodic SRS transmission subframe, which is the fastest subframe among the preliminarily configured periodic SRS transmission subframes subsequent to the subframe n, SRS transmission sub-frame or the non-periodic SRS transmission triggering sub-frame is a sub-frame n, the second non-periodic SRS which is the fastest sub-frame of the periodic SRS transmission sub- Transmission sub-frame.

If the subframe index n that received the aperiodic SRS transmission triggering indicator is an even number, the step of transmitting the aperiodic SRS may include transmitting a partial band on the frequency axis of the first aperiodic SRS subframe or the second aperiodic SRS subframe and may transmit the aperiodic SRS through a partial-band. Wherein if the transmission power is insufficient to transmit the aperiodic SRS corresponding to the aperiodic SRS transmission triggering indicator, then transmitting the aperiodic SRS through a predefined fallback aperiodic SRS resource in the sub-band .

Or if the subframe index n that received the aperiodic SRS transmission triggering indicator is an odd number, the step of transmitting the aperiodic SRS may include, on the frequency axis of the first aperiodic SRS subframe or the second aperiodic SRS subframe, And may transmit the aperiodic SRS over the full-band. Wherein if the transmission power is insufficient to transmit the aperiodic SRS corresponding to the aperiodic SRS transmission triggering indicator, then transmitting the aperiodic SRS via a predefined fallback aperiodic SRS resource in the full-band .

Alternatively, if the time relationship between the subframe n, which is the subframe that received the aperiodic SRS transmission triggering indicator, and one or more periodic SRS transmission subframes allocated to the UE, is a time difference corresponding to four subframes, Select a first aperiodic SRS configuration during a periodic SRS configuration, and transmit the aperiodic SRS according to the first aperiodic SRS configuration through the first aperiodic SRS subframe. Wherein the aperiodic SRS can be transmitted over the full-band on the frequency axis of the first aperiodic SRS subframe.

Alternatively, if the time relationship between the subframe n, which is the subframe receiving the aperiodic SRS transmission triggering indicator, and one or more periodic SRS transmission subframes allocated to the UE is not a time difference corresponding to four subframes, Select a second non-periodic SRS configuration during an aperiodic SRS configuration, and transmit the aperiodic SRS according to the second aperiodic SRS configuration through the second aperiodic SRS subframe. Wherein the aperiodic SRS may be transmitted on the sub-band on the frequency axis of the second aperiodic SRS subframe.

Or selects a second non-periodic SRS configuration of the plurality of non-periodic SRS configurations when the uplink channel condition is worse than a predefined channel condition level, And may transmit the aperiodic SRS through a partial-band on the frequency axis of the periodic SRS subframe or the second aperiodic SRS subframe.

Or selects a first non-periodic SRS configuration of the plurality of non-periodic SRS configurations if the uplink channel condition is better than a pre-defined channel condition level, Periodic SRS over the full-band on the frequency axis of the first aperiodic SRS subframe or the second aperiodic SRS subframe.

According to another aspect of the present invention, there is provided a method of controlling uplink transmission power for transmitting an aperiodic sounding reference signal (SRS) according to an embodiment of the present invention, Receiving a power offset value for the aperiodic SRS transmission; Determining the aperiodic SRS transmission power value using a power offset value for the aperiodic SRS transmission; And transmitting the aperiodic SRS to the determined aperiodic SRS transmit power value. The power offset value for the aperiodic SRS transmission is a value received through the upper layer signaling and may be a specific value for each UE. The method may further include receiving an indicator for triggering the aperiodic SRS transmission from the base station, and the aperiodic SRS transmission may be performed according to the aperiodic SRS transmission triggering indicator. In addition, the determination of the aperiodic SRS transmission power value may be determined in units of subframes.

According to another aspect of the present invention, there is provided a method for controlling an uplink transmission power for transmitting an aperiodic sounding reference signal (SRS) in a wireless communication system according to another embodiment of the present invention. The method comprising: receiving a power offset value for a periodic SRS transmission and a power offset value for an aperiodic SRS transmission from a base station; Receiving an indicator for triggering aperiodic SRS transmission from the base station; And determining a transmission power value for the aperiodic SRS transmission using the power offset value for the aperiodic SRS transmission according to the aperiodic SRS transmission triggering indicator.

According to another aspect of the present invention, a terminal apparatus for transmitting an SRS based on an aperiodic sounding reference signal (SRS) triggering includes a plurality of aperiodic SRS configurations from a base station, A receiver for receiving an indicator for triggering information and aperiodic SRS transmission; Based on at least one of a subframe index on which the aperiodic SRS transmission triggering indicator is received, a time relationship between the reception subframe of the aperiodic SRS transmission triggering indicator and an aperiodic SRS transmission subframe corresponding to the aperiodic SRS transmission triggering indicator, A processor for selecting specific aperiodic SRS configuration information from the aperiodic SRS configuration information of the non-periodic SRS configuration information; And a transmitter for transmitting an aperiodic SRS for the aperiodic SRS transmission triggering indicator based on the selected aperiodic SRS configuration information, wherein the plurality of aperiodic SRS configuration information corresponds to the aperiodic SRS transmission triggering indicator And may include information about resources that transmit aperiodic SRS.

According to another aspect of the present invention, there is provided a terminal apparatus for controlling an uplink transmission power for transmitting an aperiodic sounding reference signal (SRS) according to the present invention, Receiving a power offset value for SRS transmission; A processor for determining the aperiodic SRS transmit power value using a power offset value for the aperiodic SRS transmission; And a transmitter for transmitting the aperiodic SRS with the determined aperiodic SRS transmit power value.

The UE transmits the aperiodic SRS according to the aperiodic SRS structure according to the present invention, thereby helping to more accurately estimate the uplink channel status. In addition, the UE may determine whether a non-periodic SRS transmission triggering indicator is received based on a subframe index received from the non-periodic SRS transmission triggering indicator, a time relationship between the non-periodic SRS transmission triggering subframe and the corresponding non-periodic SRS transmission subframe, It is possible to improve communication performance by selecting aperiodic SRS configuration information from among aperiodic SRS configuration information and transmitting aperiodic SRS.

In addition to helping to more accurately estimate the uplink channel condition, adaptive non-periodic SRS configuration switching also allows for SRS coverage problems and uplink signal interference in co-channel HetNet scenarios Problems can be solved efficiently.

Also, it is possible to transmit aperiodic SRS by determining the aperiodic SRS transmission power using the uplink power control formula for the aperiodic SRS transmission proposed in the present invention.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a block diagram showing the configuration of a base station 205 and a terminal 210 in a wireless communication system 200 according to the present invention.
2 is a diagram illustrating a structure of a radio frame used in a 3GPP LTE system, which is an example of a mobile communication system,
FIGS. 3A and 3B are diagrams illustrating the structure of DL and UL subframes in a 3GPP LTE system, which is an example of a mobile communication system;
4 is a diagram illustrating a downlink time-frequency resource grid structure used in the present invention.
5 is a block diagram of a general multi-antenna (MIMO) communication system,
6 shows a channel from NT transmit antennas to receive antenna i,
7A and 7B are diagrams showing reference signal patterns in a 3GPP LTE system, which is an example of a mobile communication system. FIG. 7A shows a reference signal pattern when a normal CP (Cyclic Prefix) FIG. 7B is a diagram showing a reference signal pattern when an extended CP is applied, FIG.
8 is a diagram illustrating an example of a configuration of an uplink subframe including an SRS symbol,
9A and 9B are diagrams illustrating an example of a sub-frame for cell-specific periodic SRS transmission and an example of a sub-frame for UE-specific periodic SRS transmission, respectively;
10A, 10B, and 10C illustrate an example of an operation of dynamically selecting a plurality of SRS configurations using a time relationship between a subframe receiving an aperiodic SRS triggering grant and a corresponding aperiodic SRS transmission subframe, respectively In the drawings,
11 is a diagram for explaining an aperiodic SRS operation when a subframe index classification of an aperiodic SRS triggering grant arrival point is applied as another criterion;
12A and 12B are diagrams illustrating an example of an aperiodic SRS subframe in an SRS configuration,
FIG. 13 is a diagram for explaining the aperiodic SRS configuration of FIGS. 12A and 12B and the switching of the aperiodic SRS configuration operation according to the point of time when the UE receives the aperiodic SRS triggering grant;
14A and 14B are diagrams for explaining a fallback aperiodic SRS transmission,
15A to 15C are diagrams for explaining a method of reusing cell-specific SRS resources for efficient aperiodic SRS transmission when a cell-specific SRS resource (sub-frame) is allocated with a period of 2 ms
Figure 16 is an illustration of a UE-specific periodic SRS subframe,
FIGS. 17A to 17C are diagrams for explaining an operation of dynamically selecting a plurality of SRS configurations using a time relationship between an aperiodic SRS triggering grant reception sub-frame and a corresponding aperiodic SRS transmission sub-frame, respectively; FIGS.
18 is a diagram for explaining an aperiodic SRS transmission corresponding to a case where a subframe index classification at an aperiodic SRS triggering grant reception time point of the UE is applied as another criterion;
19A and 19B are diagrams each showing an example of an aperiodic SRS sub-frame of SRS configuration
FIG. 20 is a diagram for explaining the aperiodic SRS configuration of FIGS. 19A and 19B and the switching of an aperiodic SRS configuration operation according to a point of time when a terminal receives an aperiodic SRS triggering grant,
FIGS. 21A and 21B are diagrams for explaining a new type of aperiodic SRS transmission using a part of aperiodic SRS transmission resources divided into fallback aperiodic SRS transmission resources. FIG.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. For example, the following detailed description assumes that a mobile communication system is a 3GPP LTE and an LTE-A system. However, other than specific aspects of 3GPP LTE and LTE-A, Applicable.

In some instances, well-known structures and devices may be omitted or may be shown in block diagram form, centering on the core functionality of each structure and device, to avoid obscuring the concepts of the present invention. In the following description, the same components are denoted by the same reference numerals throughout the specification.

In the following description, it is assumed that the UE collectively refers to a mobile stationary or stationary user equipment such as a UE (User Equipment), an MS (Mobile Station), and an AMS (Advanced Mobile Station). It is also assumed that the base station collectively refers to any node at a network end that communicates with a terminal such as a Node B, an eNode B, a BS (Base Station), and an AP (Access Point).

In a mobile communication system, a user equipment can receive information from a base station through a downlink / backhaul downlink, and the terminal can also transmit information through an uplink. The information transmitted or received by the terminal and the base station includes data and various control information, and various physical channels exist depending on the type of information transmitted or received by the terminal and the base station.

1 is a block diagram showing the configuration of a base station 105 and a terminal 110 in a wireless communication system 100. As shown in FIG.

Although one base station 105 and one terminal 110 are shown to simplify the wireless communication system 100, the wireless communication system 100 may include one or more base stations and / or one or more terminals .

2, a base station 105 includes a transmit (Tx) data processor 115, a symbol modulator 120, a transmitter 125, a transmit and receive antenna 130, a processor 180, a memory 185, a receiver 190, a symbol demodulator 195, and a receive data processor 197. The terminal 110 includes a transmission (Tx) data processor 165, a symbol modulator 170, a transmitter 175, a transmission / reception antenna 135, a processor 155, a memory 160, a receiver 140, A demodulator 155, and a receive data processor 150. Although the antennas 130 and 135 are shown as one in the base station 105 and the terminal 110 respectively, the base station 105 and the terminal 110 have a plurality of antennas. Therefore, the base station 105 and the terminal 110 according to the present invention support a Multiple Input Multiple Output (MIMO) system. In addition, the base station 105 according to the present invention can support both a Single User-MIMO (SU-MIMO) and a Multi User-MIMO (MIMO) scheme.

On the downlink, the transmit data processor 115 receives traffic data, formats, codes, and interleaves and modulates (or symbol maps) the coded traffic data to generate modulation symbols Symbols "). A symbol modulator 120 receives and processes the data symbols and pilot symbols to provide a stream of symbols.

The symbol modulator 120 multiplexes the data and pilot symbols and transmits it to the transmitter 125. At this time, each transmission symbol may be a data symbol, a pilot symbol, or a signal value of zero. In each symbol period, the pilot symbols may be transmitted continuously. The pilot symbols may be frequency division multiplexed (FDM), orthogonal frequency division multiplexed (OFDM), time division multiplexed (TDM), or code division multiplexed (CDM) symbols.

Transmitter 125 receives the stream of symbols and converts it to one or more analog signals and further modulates (e.g., amplifies, filters, and frequency upconverts) The antenna 130 transmits the generated downlink signal to the mobile station.

In the configuration of the terminal 110, the antenna 135 receives the downlink signal from the base station and provides the received signal to the receiver 140. The receiver 140 adjusts (e.g., filters, amplifies, and downconverts) the received signal and digitizes the conditioned signal to obtain samples. The symbol demodulator 145 demodulates the received pilot symbols and provides it to the processor 155 for channel estimation.

Symbol demodulator 145 also receives a frequency response estimate for the downlink from processor 155 and performs data demodulation on the received data symbols to obtain a data symbol estimate (which is estimates of the transmitted data symbols) And provides data symbol estimates to a receive (Rx) data processor 150. [ The receive data processor 150 demodulates (i.e., symbol demaps), deinterleaves, and decodes the data symbol estimates to recover the transmitted traffic data.

 The processing by symbol demodulator 145 and received data processor 150 is complementary to processing by symbol modulator 120 and transmit data processor 115 at base station 205, respectively.

On the uplink, the terminal 110 processes the traffic data and provides data symbols. The symbol modulator 170 may receive and multiplex data symbols, perform modulation, and provide a stream of symbols to the transmitter 175. A transmitter 175 receives and processes the stream of symbols to generate an uplink signal. The antenna 135 transmits the generated uplink signal to the base station 105.

In the base station 105, an uplink signal is received from the terminal 110 via the antenna 130, and the receiver 190 processes the received uplink signal to acquire samples. The symbol demodulator 195 then processes these samples to provide received pilot symbols and data symbol estimates for the uplink. The receive data processor 197 processes the data symbol estimates to recover the traffic data transmitted from the terminal 110.

The processors 155 and 180 of the terminal 110 and the base station 105 respectively instruct (for example, control, adjust, manage, etc.) the operation in the terminal 110 and the base station 105. Each of the processors 155, 180 may be coupled to a memory 160, 185 that stores program codes and data. The memories 160 and 185 are connected to the processor 180 to store operating systems, applications, and general files.

The processors 155 and 180 may also be referred to as a controller, a microcontroller, a microprocessor, a microcomputer, or the like. Meanwhile, the processors 155 and 180 may be implemented by hardware or firmware, software, or a combination thereof. (DSP), digital signal processing devices (DSPDs), programmable logic devices (PLDs), and the like may be used to implement embodiments of the present invention using hardware, , FPGAs (field programmable gate arrays), and the like may be provided in the processors 155 and 180.

Meanwhile, when implementing embodiments of the present invention using firmware or software, firmware or software may be configured to include modules, procedures, or functions that perform the functions or operations of the present invention. Firmware or software configured to be stored in the memory 155 may be contained within the processor 155 or 180 or may be stored in the memory 160 or 185 and be driven by the processor 155 or 180. [

Layers of a wireless interface protocol between a terminal and a base station and a wireless communication system (network) are divided into a first layer (L1), a second layer (L2) based on the lower three layers of an open system interconnection ), And a third layer (L3). The physical layer belongs to the first layer and provides an information transmission service through a physical channel. An RRC (Radio Resource Control) layer belongs to the third layer and provides control radio resources between the UE and the network. The UE and the base station can exchange RRC messages through the RRC layer with the wireless communication network.

2 is a diagram illustrating a structure of a radio frame used in a 3GPP LTE system, which is an example of a mobile communication system.

Referring to FIG. 2, one radio frame has a length of 10 ms (327200 Ts) and is composed of 10 equal sized subframes (subframes). Each subframe has a length of 1 ms and is composed of two slots. Each slot has a length of 0.5 ms (15360 Ts). Here, Ts represents the sampling time, and is represented by Ts = 1 / (15 kHz x 2048) = 3.2552 x 10-8 (about 33 ns). A slot includes a plurality of OFDM symbols or SC-FDMA symbols in a time domain, and a plurality of resource blocks in a frequency domain.

In the LTE system, one resource block includes 12 subcarriers x 7 (6) OFDM symbols or SC-FDMA (Single Carrier-Frequency Division Multiple Access) symbols. A TTI (Transmission Time Interval), which is a unit time at which data is transmitted, may be defined in units of one or more subframes. The number of subframes included in a radio frame or the number of slots included in a subframe and the number of OFDM symbols or SC-FDMA symbols included in a slot can be variously changed have.

3A and 3B are diagrams illustrating the structure of downlink and uplink subframes in a 3GPP LTE system, which is an example of a mobile communication system.

Referring to FIG. 3A, one downlink subframe includes two slots in the time domain. A maximum of 3 OFDM symbols preceding the first slot in the DL subframe are control regions to which control channels are allocated, and the remaining OFDM symbols are data regions allocated PDSCH (Physical Downlink Shared Channel).

The downlink control channels used in the 3GPP LTE are a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), and a Physical Hybrid-ARQ Indicator Channel (PHICH). The PCFICH transmitted in the first OFDM symbol of the subframe carries information on the number of OFDM symbols (i.e., the size of the control region) used for transmission of the control channels in the subframe. The control information transmitted through the PDCCH is referred to as downlink control information (DCI). DCI indicates uplink resource allocation information, downlink resource allocation information, and uplink transmission power control commands for arbitrary terminal groups. The PHICH carries an ACK (Acknowledgment) / NACK (Not-Acknowledgment) signal for an uplink HARQ (Hybrid Automatic Repeat Request). That is, the ACK / NACK signal for the uplink data transmitted by the UE is transmitted on the PHICH.

Now, the downlink physical channel PDCCH will be described.

The base station transmits a resource allocation and transmission format (also referred to as a DL grant) of the PDSCH, resource allocation information of the PUSCH (also referred to as UL grant), a set of transmission power control commands for individual terminals in an arbitrary terminal group, Activation of Voice over Internet Protocol (VoIP), and the like. A plurality of PDCCHs can be transmitted in the control domain, and the UE can monitor a plurality of PDCCHs. The PDCCH consists of one or several consecutive aggregations of Control Channel Elements (CCEs). A PDCCH composed of a set of one or several consecutive CCEs can be transmitted through the control domain after subblock interleaving. The CCE is a logical allocation unit used to provide the PDCCH with the coding rate according to the state of the radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of bits of the possible PDCCH are determined according to the relationship between the number of CCEs and the coding rate provided by the CCEs.

The control information transmitted through the PDCCH is referred to as downlink control information (DCI). Table 1 below shows the DCI according to the DCI format.

DCI format 0 indicates uplink resource allocation information, DCI formats 1 and 2 indicate downlink resource allocation information, and DCI formats 3 and 3A indicate uplink TPC (transmit power control) commands for arbitrary terminal groups .

In the LTE system, a brief description will be given of how a base station maps resources for transmission of a PDCCH.

In general, a base station can transmit scheduling assignment information and other control information on a PDCCH. The physical control channel may be transmitted in one aggregation or in a plurality of continuous control channel elements (CCEs). One CCE includes nine Resource Element Groups (REGs). The number of REGs not assigned to the Physical Control Format Indicator CHannel (PHCCH) or the Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH) is NREG. The CCE available in the system is from 0 to NCCE-1

to be). PDCCH supports multiple formats as shown in Table 3 below. One PDCCH composed of n consecutive CCEs starts with a CCE performing i mod n = 0 (where i is a CCE number). Multiple PDCCHs may be transmitted in one subframe.

Referring to Table 2, the base station can determine the PDCCH format according to how many areas the control information and the like are to be sent. The UE can reduce the overhead by reading the control information in the CCE unit. Likewise, the repeater can also read the control information in R-CCE units. In the LTE-A system, a Resource Element (RE) can be mapped in units of R-CCE (Relay-Control Channel Element) to transmit R-PDCCH for an arbitrary repeater.

Referring to FIG. 3B, the UL subframe may be divided into a control region and a data region in a frequency domain. The control region is allocated to a PUCCH (Physical Uplink Control CHannel) carrying uplink control information. The data area is allocated to a PUSCH (Physical Uplink Shared CHannel) for carrying user data. To maintain single carrier characteristics, one terminal does not transmit PUCCH and PUSCH at the same time. The PUCCH for one UE is allocated to an RB pair in one subframe. RBs belonging to the RB pair occupy different subcarriers in each of the two slots. The RB pair assigned to the PUCCH is frequency hopped at the slot boundary.

4 is a diagram illustrating a downlink time-frequency resource grid structure used in the present invention.

The downlink signals transmitted in each slot are

×

Subcarriers < RTI ID = 0.0 >

(Orthogonal Frequency Division Multiplexing) symbols of OFDM symbols. here,

Represents the number of resource blocks (RBs) in the downlink,

Represents the number of sub-carriers constituting one RB,

Represents the number of OFDM symbols in one downlink slot.

Depends on the downlink transmission bandwidth configured in the cell

≤

≤

. here,

Is the smallest downlink bandwidth supported by the wireless communication system

Is the largest downlink bandwidth supported by the wireless communication system.

= 6

= 110, but is not limited thereto. The number of OFDM symbols included in one slot may be different depending on the length of a cyclic prefix (CP) and the interval between subcarriers. In the case of multiple antenna transmissions, one resource grid per antenna port may be defined.

Each element in the resource grid for each antenna port is called a resource element (RE) and is uniquely identified by the index pair (k, l) in the slot. Where k is the index in the frequency domain, l is the index in the time domain, k is 0, ...,

-1, l is 0, ...,

-1. ≪ / RTI >

The resource block shown in FIG. 4 is used to describe a mapping relationship between certain physical channels and resource elements. The RB can be divided into a physical resource block (PRB) and a virtual resource block (VRB). The one PRB is a time-

Lt; RTI ID = 0.0 > OFDM < / RTI &

Lt; / RTI > subcarriers. here

and

May be a predetermined value. E.g

and

Can be given as shown in Table 1 below. Therefore, one PRB

×

Resource elements. One PRB corresponds to one slot in the time domain and corresponds to 180 kHz in the frequency domain, but is not limited thereto.

In the frequency domain,

-1. ≪ / RTI > The relationship between the PRB number n _PRB in the frequency domain and the resource element (k, l) in one slot is

.

The size of the VRB is equal to the size of the PRB. The VRB can be defined by dividing into a localized VRB (Localized VRB) and a distributed VRB (Distributed VRB). For each type of VRB, a pair of VRBs in two slots in one subframe are assigned together with a single VRB number n _VRB .

The VRB may have the same size as the PRB. Two types of VRBs are defined. The first type is Localized VRB (LVRB), and the second type is Distributed VRB (DVRB). For each type of VRB, a pair of VRBs is assigned over two slots in one subframe with a single VRB index (which may be referred to as a VRB number hereinafter). In other words, the subframe belonging to the first one of the two slots constituting one subframe

The number of VRBs is 0

-1 ", and " 1 " in the second slot among the above two slots The number of VRBs is also 0

-1. ≪ / RTI >

Hereinafter, a general multi-antenna (MIMO) technique will be briefly described. MIMO is a reduction method of "Multi-Input Multi-Output", and it is possible to improve transmission / reception data efficiency by adopting multiple transmit antennas and multiple receive antennas by avoiding the use of one transmit antenna and one receive antenna . That is, a technique for increasing the capacity or improving the performance by using multiple antennas at the transmitting end or the receiving end of the wireless communication system. Hereinafter, " MIMO " will be referred to as " multiple antennas ".

The multi-antenna technique is a technique for collecting a piece of fragmentary data received from multiple antennas, without relying on a single antenna path, to receive a whole message. This can improve the speed of data transmission in a particular range or increase the system range for a particular data rate.

Next generation mobile communication requires much higher data rate than existing mobile communication, so efficient multi-antenna technology is expected to be necessary. In such a situation, MIMO communication technology is a next generation mobile communication technology that can be widely used for mobile communication terminals and repeaters, and is attracting attention as a technology capable of overcoming transmission limitations of other mobile communication due to limitations due to expansion of data communication have.

Meanwhile, a multi-antenna (MIMO) technique using a plurality of antennas at both the transmitting and receiving ends of various transmission efficiency enhancement technologies currently being studied is a method for drastically improving communication capacity and transmission / reception performance without additional frequency allocation or power increase It is receiving the greatest attention now.

5 is a block diagram of a general multi-antenna (MIMO) communication system.

As shown in FIG. 5, if the number of transmission antennas is increased to NT and the number of reception antennas is increased to NR, the number of transmission antennas is increased, As the capacity increases, the transmission rate can be improved and the frequency efficiency can be improved remarkably. The transmission rate in accordance with the increase of the channel transmission capacity may theoretically increase by multiplying the maximum transmission rate Ro when using one antenna by the following rate of rate increase Ri. The rate increase rate Ri can be expressed by the following equation (1).

In order to describe the communication method in the above-described multi-antenna system more specifically, it can be expressed as follows when it is mathematically modeled.

First, it is assumed that NT transmit antennas and NR receive antennas exist as shown in FIG.

First of all, regarding the transmission signal, if there are NT transmit antennas, the maximum transmittable information is NT, which can be expressed by the following equation (2).

On the other hand, each transmission information S1, S2, ...,

In this case, the respective transmission powers are P1, P2, ...,

, The transmission information whose transmission power is adjusted can be represented by a vector as shown in the following Equation 3. " (3) "

Also,

Can be expressed by the following equation (4) as a diagonal matrix P of transmission power.

On the other hand, the information vector whose transmission power is adjusted is then multiplied by the weighting matrix W to obtain NT transmitted signals x1, x2, ...,

. Here, the weight matrix plays a role of appropriately distributing the transmission information to each antenna according to the transmission channel condition and the like. The transmission signals x1, x2, ...,

Can be expressed by the following equation (5) using the vector x.

In Equation (5), w _ij denotes a weight between the i-th transmission antenna and j-th transmission information, and W denotes a matrix thereof. Such a matrix W is called a weight matrix or a precoding matrix.

Meanwhile, the transmission signal x may be divided into a case of using spatial diversity and a case of using spatial multiplexing.

When spatial multiplexing is used, different signals are multiplexed and transmitted, so that the elements of the information vector s have different values. On the other hand, when the spatial diversity is used, the same signal is transmitted through various channel paths, The elements of vector s all have the same value.

Of course, a method of mixing spatial multiplexing and spatial diversity can be considered. That is, for example, the same signal may be transmitted using three transmit antennas using spatial diversity, and the remaining signals may be multiplexed with each other. Next, when there are N _R reception antennas, the reception signals y ₁ , y ₂ , ...,

Is expressed as a vector y as shown in the following Equation (6).

Meanwhile, when a channel is modeled in a multi-antenna communication system, a channel can be classified according to a transmission / reception antenna index, and a channel passing from a transmission antenna j to a reception antenna i is denoted by h _ij . Here, note that the order of indexes of h _ij is the index of the receiving antenna and the index of the transmitting antenna. These channels can be grouped together and displayed in vector and matrix form. An example of a vector representation is as follows.

6 is a diagram showing channels from N _T transmit antennas to receive antenna i

As shown in FIG. 6, a channel arriving from a total of N _T transmit antennas to receive antenna i can be expressed as Equation (7).

Also, if all the channels passing through the NR receive antennas from the NT transmit antennas are represented by the matrix expression as expressed by Equation (7), the following Equation (8) can be obtained.

On the other hand, since the actual channel is added with additive white Gaussian noise (AWGN) after passing through the channel matrix H as described above, the white noise n1, n2, ...,

Is expressed by the following equation (9).

Through modeling of the transmission signal, the received signal, the channel, and the white noise as described above, each in the multi-antenna communication system can be represented by the following relationship (10).

On the other hand, the number of rows and columns of the channel matrix H indicating the state of the channel is determined by the number of transmitting and receiving antennas. As described above, the number of rows is equal to the number of reception antennas NR, and the number of columns is equal to the number of transmission antennas NT. That is, the channel matrix H becomes an NR x NT matrix.

In general, the rank of a matrix is defined as the minimum number of independent rows or columns. Thus, the rank of the matrix can not be greater than the number of rows or columns. For example, the rank (rank (H)) of the channel matrix H is limited as shown in Equation (11).

In a mobile communication system, when a transmitting terminal transmits a packet (or a signal) to a receiving terminal, a packet transmitted by the transmitting terminal is transmitted through a wireless channel, so that a signal may be distorted during transmission. In order to correctly receive the distorted signal at the receiving end, the receiving end can receive the correct signal by determining the channel information and correcting the distortion of the transmission signal by the channel information in the received signal. In order to obtain information of the channel, it is necessary to transmit a signal known to both the transmitting end and the receiving end. That is, when a signal known to the receiving end is received through a channel, a method of finding information of the channel with a degree of distortion of the signal is mainly used. At this time, a signal known to both the transmitting end and the receiving end is referred to as a reference signal It is called a pilot signal.

In the past, when a transmitting terminal transmits a packet to a receiving terminal, one transmitting antenna and one receiving antenna have been used so far. However, in most recent mobile communication systems, a method of improving transmit / receive data efficiency by employing multiple transmit antennas and multiple receive antennas is used. In the case of transmitting and receiving data using multiple antennas in order to improve the capacity and communication performance at the transmitting end or the receiving end of the mobile communication system, there is a separate reference signal for each transmission antenna. The receiving end can receive the signals transmitted from the respective transmitting antennas by using the known reference signals for the respective transmitting antennas.

In a mobile communication system, reference signals can be roughly classified into two types according to their purposes. The reference signal is used for the purpose of obtaining channel information and for data demodulation. Since the former can acquire channel information on the downlink, the former needs to be transmitted in a wide band, and even a terminal that does not receive downlink data in a specific subframe can receive and measure the reference signal. . The reference signal for channel measurement can also be used for measurement of handover and the like. The latter is a reference signal transmitted together with a corresponding resource when the base station transmits the downlink signal. The terminal can perform channel estimation by receiving the reference signal, and thus can demodulate the data. These demodulation reference signals must be transmitted in the area where data is transmitted.

7A and 7B are diagrams showing reference signal patterns in a 3GPP LTE system, which is an example of a mobile communication system. FIG. 7A shows a reference signal pattern when a normal CP (Cyclic Prefix) And FIG. 7B is a diagram showing a reference signal pattern when an extended CP is applied.

In the 3GPP LTE release-8 system, which is an example of a mobile communication system, two kinds of downlink reference signals are defined for a unicast service. A common reference signal (CRS) and a dedicated reference signal (DRS) (corresponding to a UE-specific reference signal) used for data demodulation, There are two reference signals called < RTI ID = 0.0 > In the LTE Release-8 system, UE-specific reference signals are used only for data demodulation and CRS is used for both channel information acquisition and data demodulation. The CRS is a cell-specific reference signal, and the base station transmits a CRS every sub-frame over a wideband. In a cell-specific CRS, reference signals for up to four antenna ports are transmitted according to the number of transmission antennas of a base station.

As shown in FIGS. 7A and 7B, CRS (1, 2, 3, 4) for four antenna ports represent reference signals R0, R1, R2, and R3, respectively, ) Are allocated so that time-frequency resources do not overlap in 1RB. In a LTE system, when a CRS is mapped to a time-frequency resource, a reference signal for one antenna port on the frequency axis is mapped to one RE per 6 REs (Resource Element). Since one RB is composed of 12 REs on the frequency axis, RE for one antenna port uses 2 REs per RB.

As shown in Figures 7 (a) and 7 (b), DRS (shown as "D") is supported for single-antenna port transmission of the PDSCH. The UE can receive information on whether there is a UE-specific RS from the upper layer or the like. If data demodulation is required, the UE-specific RS is transmitted to the terminal via the resource element. On the other hand, the RS mapping rule to the resource block RS can be expressed by the following equations (12) to (14). Equation (12) is an expression for expressing the CRS mapping rule. Equation (13) is for expressing the mapping rule of the DRS to which the normal CP is applied, and Equation (14) is for expressing the mapping rule of the DRS to which the extended CP is applied.

In Equations (12) to (14), k and p denote subcarrier indices and antenna ports, respectively.

, n _s ,

Represents the number of RBs allocated to the downlink, the number of slot indexes, and the number of cell IDs, respectively. The location of the RS depends on the V _shift value in terms of frequency domain.

In 3GPP LTE-A system, which is a standard of next generation mobile communication system, it is expected to support Coordinated Multi Point (CoMP) method and Multi User-MIMO (MU-MIMO) method which is not supported in the existing system to improve data transmission rate. Here, the CoMP system refers to a system in which two or more base stations or cells cooperate with each other to improve communication performance between a terminal and a base station (cell or sector) in a shadow area.

The CoMP scheme can be classified into cooperative MIMO joint processing (CoMP-Joint Processing, CoMP-JP) and CoMP-Coordinated Scheduling / Beamforming (CoMP-CS / CB).

In the joint processing (CoMP-JP) scheme in the case of downlink, the UE can instantaneously simultaneously receive data from each base station that performs CoMP and can combine received signals from each base station to improve reception performance . Alternatively, in the cooperative scheduling / beamforming scheme (CoMP-CS), the UE can receive data via beamforming through one base station instantaneously.

In the joint processing (CoMP-JP) scheme in the uplink, each base station can simultaneously receive the PUSCH signal from the terminal. Alternatively, in the cooperative scheduling / beamforming scheme (CoMP-CS), only one of the base stations receives the PUSCH, and the decision to use the cooperative scheduling / beamforming scheme is determined by the cooperating cell (or base stations) .

In the MU-MIMO technique, a base station allocates each antenna resource to another UE, and selects and schedules a UE capable of a high data rate for each antenna. This MU-MIMO scheme is a technique for improving system throughput.

8 is a diagram illustrating an example of a configuration of an uplink subframe including an SRS symbol.

Referring to FIG. 8, a sounding reference signal (SRS) is not related to uplink data and / or control information transmission, and is mainly used to evaluate channel quality so that frequency-selective scheduling is possible on the uplink . However, the SRS may be used for other purposes such as providing various functions or improving power control for recently unscheduled terminals. SRS is a reference signal used for uplink channel measurement, and is a pilot signal transmitted from each terminal to a base station, and is used by a base station to estimate a channel state from each terminal to a base station. The channel for transmitting the SRS may have a different transmission bandwidth and transmission period for each terminal according to the state of each terminal. Based on the channel estimation result, the base station can determine which UE's data channel to schedule in each subframe.

Under the assumption that the radio channel is reciprocal between the uplink and the downlink, the SRS can be used to estimate the downlink channel quality. This assumption is valid in a time division duplex (TDD) system in which the uplink and downlink share the same frequency domain and are separated in the time domain. The subframe in which the SRS is transmitted by the UE in the cell may be indicated by cell-specific broadcast signaling. A 4-bit cell-specific 'srssubframeConfiguration' parameter indicates the 15 possible sets of subframes within which each SRS can be transmitted. This configuration provides flexibility in adjusting the SRS overhead. As shown in FIG. 9, the UE can transmit the SRS through the last SC-FDMA symbol in the configured subframe.

Therefore, the SRS and the demodulation-reference signal (DM-RS) for data demodulation are located in different SC-FDMA symbols in the subframe. The sounding reference signals of the UEs transmitted in the last SC-FDMA of the same subframe can be classified according to frequency positions. Since the PUSCH data of the UE is not transmitted through the SC-FDMA symbol designed for SRS, in the worst case, 7% of the sounding overhead is generated by having the SRS symbol in every subframe.

SRS is generated by a Constant Amplitude Zero Auto Correlation (CAZAC) sequence or the like, and sounding reference signals transmitted from a plurality of terminals are generated by a CAZAC sequence having different cyclic shift values? (

)to be. here

Is the SRS sequence.

here

Is a value set to each terminal by an upper layer and has an integer value between 0 and 7. CAZAC sequences generated from one CAZAC sequence through a cyclic shift have characteristics of zero correlation with sequences having different cyclic shift values from each other. Using these characteristics, the SRSs in the same frequency domain can be classified according to the CAZAC sequence cyclic shift value. The SRS of each terminal is allocated on the frequency according to the parameters set by the base station. The UE performs frequency hopping of the sounding reference signal so as to transmit the SRS to the entire uplink data transmission bandwidth.

As described above, in the 3GPP LTE Release 8/9 system, the SRS transmission of the UE only supports periodic SRS transmission, so that the BS can estimate the uplink channel quality of each UE. At this time, the channel estimated by the base station is used for functions such as frequency dependent scheduling, link level adaptation, timing estimation, and UL power control . The base station transmits an SRS uplink configuration to each terminal through UE-specific or cell-specific higher layer signaling (e.g., RRC signaling) through SRS parameters You can send it. The BS can inform the UE of the SRS uplink configuration information as an SRS uplink configuration information element message type as shown in Table 4 below.

Table 5 below shows SRS configuration parameters included in the Sounding RS-UL-Config information element message type in Table 4 above.

Referring to Table 4 and Table 5, SRS configuration information informed to the UE by the BS includes SRS configuration parameters such as srsBandwidthConfiguration parameter, srsSubframeConfiguration parameter, srsBandwidth parameter, frequencyDomainPosition parameter, SrsHoppingBandwidth parameter, duration parameter, srsConfigurationIndex parameter, transmissionComb Parameter. The srsBandwidthConfiguration parameter indicates the maximum SRS bandwidth information in the cell, and the srsSubframeConfiguration parameter indicates the subframe set information to which the UE transmits the SRS in the cell. The base station may inform the terminal of the srsSubframeConfiguration parameter by cell-specific signaling. As shown in Table 4, the base station transmits the srsSubframeConfiguration parameter to the terminal with a size of 4 bits (sc0, sc1, sc2, sc3, sc4, sc5, sc6, sc7 sc8 sc9 sc10 sc11 sc12 sc13 sc14 sc15) You can signal it. The srsBandwidth parameter indicates the SRS transmission bandwidth of the UE, the frequencyDomainPosition parameter indicates the location of the frequency domain, the SrsHoppingBandwidth parameter indicates the SRS frequency hopping size, and the duration parameter indicates whether the SRS transmission is one SRS transmission or the periodic SRS transmission. A periodicity and a subframe offset (for example, a time unit from the first subframe of a frame to a subframe through which the first SRS is transmitted), and the transmissionComb parameter indicates a transmission comb offset.

The base station can inform the terminal of the srsBandwidthConfiguration parameter and the srsSubframeConfiguration parameter by the cell-specific signaling. Alternatively, the base station can transmit the SRSBandwidth parameter, the frequencyDomainPosition parameter, the SrsHoppingBandwidth parameter, the duration parameter, the srsConfigurationIndex parameter, -specific) signaling.

The 3GPP LTE Release 10 system supports aperiodic SRS transmissions for more adaptive uplink channel quality estimation and efficient SRS resource utilization than existing systems. A method of triggering an aperiodic SRS transmission is still under discussion, for example, the base station can trigger by a DL / UL grant in the PDCCH. That is, the BS may transmit the DL grant or the UL grant including the aperiodic SRS transmission triggering indicator for triggering the aperiodic SRS transmission of the UE, or may define a new message format and transmit the DL grant or UL grant. In the present invention, a message triggering an aperiodic SRS transmission of a terminal is referred to as an aperiodic SRS triggering grant (or an aperiodic SRS triggering indicator, etc.) and will be described below.

In the present invention, the base station can give information about multiple aperiodic SRS configurations to the UE through higher layer signaling. The plurality of aperiodic SRS configuration information transmitted by the base station includes information on the subframe index information on which the aperiodic SRS ranging ring grant is received, the time relationship between the receiving subframe of the aperiodic SRS triggering grant and the corresponding aperiodic SRS transmission subframe , Information on resources for aperiodic SRS transmissions, and the like. The present invention proposes a scheme in which a UE selectively applies a plurality of aperiodic SRS configurations. In particular, the UE uses the non-periodic SRS ranging ring grant to determine the non-periodic SRS configuration using the received subframe index information or the time relationship between the received subframe of the aperiodic SRS triggering grant and the corresponding aperiodic SRS transmission subframe ) Can be adaptively switched.

Here, the number of aperiodic SRS configurations depends on the subframe index classification of the aperiodic SRS triggering grant arrival point or the time relationship definition between the reception subframe of the aperiodic SRS triggering grant and the corresponding aperiodic SRS transmission subframe . The scheme proposed in the present invention is advantageous in that it does not require additional signaling overhead for switching aperiodic SRS configuration. Also, adaptive non-periodic SRS configuration switching provides an SRS coverage problem and a co-channel It is possible to effectively solve the uplink signal interference problem of HetNet (heterogeneous network).

Specific SRS resources defined in the 3GPP LTE Release 8/9 system and cell-specific SRS resources defined in the 3GPP LTE Release 8/9 system and the UE-specific non-periodic SRS resources, May consider reusing UE-specific periodic SRS resources. Therefore, this scheme has less overhead required for signaling SRS resource location information and enables efficient SRS resource usage compared to schemes that define new additional aperiodic SRS resources.

The aperiodic SRS configurations that the base station transmits via higher layer signaling can be defined variously, with parameters such as SRS bandwidth, comb, hopping bandwidth, starting physical resource block (PRB) allocation, etc. having different values.

The proposed scheme does not merely determine whether an aperiodic SRS is transmitted or not through an aperiodic SRS triggering grant but rather adaptively switches a plurality of aperiodic SRS configurations so that the uplink channel status change There is an advantage that it can cope efficiently. Especially in situations such as HetNet, the proper non-periodic SRS configuration may vary depending on the location of the terminal. To cover this, the base station informs the terminal about the resources of a plurality of aperiodic SRS configurations in addition to a plurality of aperiodic SRS configuration and aperiodic SRS configuration, and the terminal's processor 255 appropriately selects one of them It needs to work. For example, the UE may be grouped in a subframe in which the corresponding PDCCH descends according to the timing at which the PDCCH including the UL grant (e.g., UL grant triggering aperiodic SRS transmission triggering or UL grant triggering PUSCH transmission) tied) non-periodic SRS configuration.

Hereinafter, the non-periodic SRS transmission timing of the UE will be described. Assuming that the UE receives an aperiodic SRS triggering grant in a subframe n of a particular frame (i.e., a subframe with a subframe index n), the UE's aperiodic SRS transmission time may be, for example, Specific SRS sub-frame after cell-specific SRS sub-frame or sub-frame n + 3. In addition to these cell-specific periodic SRS resources, the UE can also perform aperiodic SRS transmission through UE-specific aperiodic SRS resources and UE-specific periodic SRS resources. However, the present invention is not limited thereto.

In addition, when the aperiodic SRS transmission time points of different UEs overlap and the available aperiodic SRS resources are insufficient, the non-periodic SRS transmission is performed considering the aperiodic SRS bandwidth of each UE and the transmission period of the periodic SRS. It can be given priority.

9A and 9B are diagrams illustrating an example of a sub-frame for cell-specific periodic SRS transmission and an example of a sub-frame for UE-specific periodic SRS transmission, respectively.

Referring to FIG. 9A, the base station may configure periodic SRS subframes (subframes 1, 3, 5, 7, 9) (a hatched subframe region in FIG. 9A) at a 2 ms period as a cell-specific periodic SRS configuration.

Referring to FIG. 9B, a UE-specific periodic SRS configuration is shown. The base station may allocate some sets in a subframe set composed of cell-specific periodic SRS subframes to UE-specific periodic SRS subframes for a particular UE. In FIG. 9B, as an example, the BS allocates periodic SRS subframes (subframes 1, 5, and 9) to a specific UE at a period of 4 ms as a UE-specific periodic SRS configuration. In this case, a specific terminal that has been allocated a terminal-specific periodic SRS subframe from the base station transmits a periodic terminal-specific SRS in subframes 1, 5 and 9 (subframe regions hatched in FIG. 9B) .

10A, 10B, and 10C illustrate an example of an operation of dynamically selecting a plurality of SRS configurations using a time relationship between a subframe receiving an aperiodic SRS triggering grant and a corresponding aperiodic SRS transmission subframe, respectively .

10A, 10B, and 10C, the base station configured subframes 1, 3, 5, 7, and 9 as cell-specific periodic SRS subframes, and subframes 1, 5, SRS sub-frame.

The base station may set up a plurality of aperiodic SRS configurations and notify the terminal thereof. These aperiodic SRS configurations are denoted by a first aperiodic SRS configuration and a second aperiodic SRS configuration, respectively. The information on the plurality of aperiodic SRS configurations is informed to the UE by upper layer signaling or the like. The information on the aperiodic SRS configuration may include information on when the UE transmits the aperiodic SRS and information on the resources for the aperiodic SRS transmission. In particular, the UE may transmit the aperiodic SRS after the UE receives the aperiodic SRS triggering grant from the closest (or fastest) cell-specific periodic SRS subframe or subframe n + 3 in the subframe (n) May be in a cell-specific periodic SRS subframe cell coming soon. In addition, aperiodic SRS may be transmitted through UE-specific SRS resources and UE-specific periodic SRS resources, as well as cell-specific periodic SRS resources. In the present invention, as an example, the aperiodic SRS configuration assumes that the UE sets the time of transmitting the aperiodic SRS to the closest cell-specific periodic SRS subframe in the subframe (subframe n) receiving the aperiodic SRS triggering grant . It is also assumed that the cell-specific periodic SRS transmission subframe is set to a period of 2 ms as an example, as shown in FIG. 9A.

The second aperiodic SRS configuration is for the UE to transmit aperiodic SRS in the subframe n + 2 for the aperiodic SRS triggering grant received in subframe n (n = 1,2, ...). The first aperiodic SRS configuration is for the UE to transmit the aperiodic SRS in subframe n + 2 for the aperiodic SRS triggering grant received in subframe n + 1. As such, the processor 255 of the terminal may select a particular SRS configuration among a plurality of SRS configurations based on the time relationship between the subframe receiving the aperiodic SRS triggering grant and the corresponding aperiodic SRS transmission subframe, You can perform the selected SRS configuration operation. As an example, in the 3GPP LTE and LTE-A systems, one frame normally includes 10 subframes, and it is assumed that indexes 1 through 10 of each subframe included in one frame are given.

Referring to FIG. 10A, as a second non-periodic SRS configuration, a time relationship between a sub-frame receiving an aperiodic SRS triggering grant and a corresponding non-periodic SRS transmission sub-frame (i.e., Frame is 2, the UE transmits an aperiodic SRS to the non-periodic SRS triggering grant received from the sub-frame n (n = 1, 2, ...) n + 2 (in this case, the time difference between the reception timing of the aperiodic SRS triggering grant and the transmission timing of the aperiodic SRS is 2). In this case, the partial band (for example, Band). ≪ / RTI > That is, if the UE is configured to receive an aperiodic SRS transmission triggering grant in subframe 1 and to transmit aperiodic SRS in subframe 3, the UE may transmit an aperiodic SRS through sub-band 1010 of subframe 3 have. Similarly, if the terminal is configured to receive an aperiodic SRS transmission triggering grant in subframe 5 and to transmit aperiodic SRS in subframe 7, the terminal may transmit an aperiodic SRS through sub-band 1020 of subframe 7 have.

10B, as a first non-periodic SRS configuration, a time relationship between a subframe receiving an aperiodic SRS triggering grant and a corresponding non-periodic SRS transmission subframe (i.e., an aperiodic SRS triggering grant (N = 1, 2, ...) received in the subframe n + 1 (n = 1, 2, ...) when the index difference between the received subframe and the corresponding aperiodic SRS transmission subframe is 1, (E.g., the entire band on the frequency axis of sub-frame n + 2) 1030, 1040, in the sub-frame n + 2, where the periodic SRS is transmitted

Here, the partial-band SRS transmission operation refers to a case where a mobile station transmits SRS using only a part of a sub-frame band allocated for SRS transmission, and the full-band SRS transmission operation refers to a case where a mobile station transmits an SRS transmission It can be said that the SRS is transmitted using the entire band in the band of the allocated subframe.

Full-band aperiodic SRS transmission can be selected mainly when the uplink channel state between the BS and the MS is good, for example, using the same transmission band as the MS adjacent to the BS or the macro BS (MeNB) A macro terminal (MUE) remote from the home base station (HeNB) can perform a full-band aperiodic SRS transmission operation. On the other hand, the partial-band aperiodic SRS transmission operation can be selected when the uplink channel state between the BS and the MS is not good. For example, A macro terminal that is located in or near the area of the home base station using the uplink signal may perform a partial-band aperiodic SRS transmission operation.

The processor 255 of the UE adaptively switches the proposed first non-periodic SRS configuration and the second non-periodic SRS configuration flexibly based on the current network status, communication environment, aperiodic SRS triggering grant reception time, It is possible to efficiently cope with the coverage problem and the uplink signal interference problem of the co-channel HetNet.

In particular, the second aperiodic SRS configuration shown in FIG. 10A is a partial-band aperiodic SRS transmission scheme, which is a transmission scheme through frequency hopping partial-bands 1010 and 1020 , The terminal can effectively solve the SRS coverage problem by concentrating its transmission power on a part of the entire SRS resource area.

According to the first aperiodic SRS configuration shown in FIG. 10B, if the UE is configured to receive an aperiodic SRS transmission triggering grant in subframe 2 and to transmit aperiodic SRS in subframe 3, It is possible to transmit the aperiodic SRS through the band 1030. Similarly, if the terminal is configured to receive an aperiodic SRS transmission triggering grant in subframe 6 and to transmit aperiodic SRS in subframe 7, the terminal may transmit an aperiodic SRS through the full-band 1040 of subframe 7 have.

The non-periodic SRS configuration shown in FIG. 10C is set to a partial-band aperiodic SRS transmission scheme like the second aperiodic SRS configuration, but the uplink signal of the co-channel HetNet It can be set in a frequency-hopping manner in order to solve the interference problem. Here, the uplink signal transmission bands of the macro terminal and the home terminal are designated as fixed partial-bands 1050 and 1060 orthogonal to each other.

Also, the first aperiodic SRS configuration and the second aperiodic SRS configuration may be defined by any one of the combinations of Figs. 10A and 10B, or 10B and 10C, respectively, and the base station may define defined combination information and / or And can transmit the selected combination information to the terminal through higher layer signaling.

11 is a diagram for explaining an aperiodic SRS operation when a subframe index classification of an aperiodic SRS triggering grant arrival point is applied as another criterion.

Referring to FIG. 11, the BS allocates subframes 1, 3, 5, 7 and 9 in a cell-specific periodic SRS subframe and subframes 1, 5 and 9 in a UE- . According to the aperiodic SRS configuration shown in FIG. 11, the processor 255 of the UE determines if among the plurality of SRS configurations, the index of the subframe in which the aperiodic SRS triggering grant is arrived is odd (n = 1, 3, 5,? 9), the first aperiodic SRS configuration may be selected (in this case, the subframe index is indexed to 1 in the first subframe) and the index of the subframe in which the aperiodic SRS triggering grant is received The second aperiodic SRS configuration can be selected.

For example, if the UE receives an aperiodic SRS transmission triggering grant in subframe 1, which is an odd index subframe, the UE transmits the full-band 1110 in subframe 3, which is the closest cell-specific periodic SRS subframe in subframe 1 Lt; RTI ID = 0.0 > SRS. ≪ / RTI > In addition, when the UE receives an aperiodic SRS transmission triggering grant in subframe 6, which is an even index subframe, the UE transmits a non-periodic SRS transmission triggering grant through sub-band 1120 in subframe 7, which is the closest cell- Can be transmitted.

11, when a base station assigns a UE-specific periodic SRS subframe index n (for example, n = 1, 5, 9) allocated to a specific UE in a specific frame , And the non-periodic SRS triggering grant divides the received subframe into subframes at time n-4 or n-4. Here, the definition of the n-4 time point can be variously specified by different values. In FIG. 11, when the UE receives the aperiodic SRS triggering grant in a subframe with a subframe index of 1 (i.e., the first subframe (subframe 1)), Frame in the subframe 3 which is the nearest (or fastest) cell-specific periodic SRS subframe subsequent to the subframe 1, ) ≪ / RTI > 1110. < RTI ID = 0.0 > When the UE receives an aperiodic SRS triggering grant in a subframe (i.e., subframe 6) having a subframe index of 6, the subframe 6 is allocated to n-4 of the subframe index 9 (i.e., subframe 9) The UE can perform the SRS transmission operation through the sub-band 1120 in the subframe 7 which is the closest cell-specific periodic SRS subframe in the subframe 6.

In this manner, when the UE receives the aperiodic SRS triggering grant in the subframe at the n-4 time point, it can operate with the full-band aperiodic sounding, that is, with the third aperiodic SRS configuration, And operate with partial-band aperiodic sounding, i.e., operate in the fourth aperiodic SRS configuration. Here, the contents common to the first and second aperiodic SRS configurations are such that the UE transmits the aperiodic SRS through the closest cell-specific periodic SRS subframe in the subframe in which the aperiodic SRS triggering grant is received It is. The third and fourth aperiodic SRS configurations can be established by the base station and the base station can inform the terminal through upper layer signaling.

12A and 12B are views showing an example of a subframe in an aperiodic SRS configuration, respectively.

Referring to FIG. 12A, the base station may configure the fifth aperiodic SRS configuration so that the terminal transmits aperiodic SRS through sub-bands of subframes with subframe indices 1, 5, 9. As shown in FIG. 12A, in the fifth non-periodic SRS configuration, the UE can transmit SRS through sub-bands in sub-frames 1, 5 and 9 since the SRS transmission period and the sub-frame offset are 4ms and 0ms, respectively.

Also, referring to FIG. 12B, the base station may configure the UE to transmit aperiodic SRS through the full-band of subframes 3 and 7 as a sixth aperiodic SRS configuration. As shown in FIG. 12B, in the sixth non-periodic SRS configuration, the SRS transmission period and the subframe offset are 4ms and 2ms, respectively, so that the UE can transmit SRS through the entire band in the subframes 3 and 7. At this time, in the fifth and sixth aperiodic SRS configurations, the resources for the aperiodic SRS transmission subframe reuse resources for the cell-specific periodic SRS transmission, so that the period of the subframe in which the aperiodic SRS is transmitted is the cell- May be specified as a multiple of the periodic SRS subframe period or the same value. The fifth and sixth aperiodic SRS configuration information (including information on the SRS transmission subframe according to the SRS configuration) can be informed by the base station through the upper layer signaling.

13 is a diagram for explaining the aperiodic SRS configuration of FIGS. 12A and 12B and the switching of the aperiodic SRS configuration operation according to the point of time when the UE receives the aperiodic SRS triggering grant.

When the UE performs the transmission of the aperiodic SRS through the closest cell-specific periodic SRS subframe in the subframe that received the aperiodic SRS triggering grant, the SRS of the closest cell- Depending on the configuration, aperiodic SRS transmissions can be different.

For example, as shown in FIG. 13, the base station allocates subframes 1, 3, 5, 7, and 9 as periodic SRS transmission subframes as a cell-specific periodic SRS configuration. In addition, the base station may allocate subframes 1, 5, and 9 in a UE-specific periodic SRS transmission subframe. If the UE receives an aperiodic SRS triggering grant in subframe 1, the UE can transmit aperiodic SRS through subframe 3, which is the closest cell-specific periodic SRS subframe to subframe 1. At this time, since the closest cell-specific SRS subframe 3 at the time of receiving the aperiodic SRS triggering grant corresponds to the subframe configured with the sixth aperiodic SRS configuration in FIG. 12B, And may transmit aperiodic SRS over a full-band 1310. [ As another embodiment, similar to the third aperiodic SRS configuration, subframe 1, in which the UE receives the aperiodic SRS triggering grant, corresponds to subframe 5, which is a cell-specific periodic SRS subframe, at n-4 time point Frame, the UE can transmit aperiodic SRS through the full-band 1310 of subframe 3.

In addition, when the UE receives an aperiodic SRS triggering grant in subframe 8, the UE can transmit aperiodic SRS through subframe 9 which is the closest cell-specific periodic SRS subframe in subframe 8. At this time, since the nearest cell-specific SRS subframe 9 at the time of receiving the aperiodic SRS triggering grant is the subframe set in the fifth aperiodic SRS configuration shown in FIG. 12A, And may transmit aperiodic SRS through band 1320. As another embodiment, similar to the fourth SRS configuration, since the subframe 8 receiving the aperiodic SRS triggering grant does not correspond to the subframe at the n-4 time point with respect to the subframe 3, - it is possible to transmit aperiodic SRS through band 1320. In addition, subframe 9 is allocated to a UE-specific periodic SRS subframe to perform periodic SRS transmission basically, but exceptionally, when it overlaps with an aperiodic SRS transmission time point, the UE cancels the periodic SRS and transmits an aperiodic SRS do.

14A and 14B are diagrams for explaining a fallback aperiodic SRS transmission, respectively.

The seventh non-periodic SRS configuration and the eighth non-periodic SRS configuration shown in FIG. 14A and FIG. 14B, respectively, are the same as the seventh non-periodic SRS configuration shown in FIG. The UE is configured to transmit aperiodic SRS over the full-band or the partial-band using a time difference.

The base station may allocate SRS subframes as shown in FIG. 14A as the seventh aperiodic SRS configuration. The seventh non-periodic SRS configuration is a configuration for transmitting aperiodic SRS over the entire band similar to the aperiodic SRS triggering scheme (i.e., the first SRS aperiodic configuration scheme) shown in FIG. 10B. However, in the seventh aperiodic SRS configuration, the existing full-band non-periodic SRS resource is referred to as a 'reconfigured full-band non-periodic SRS resource 1410 and a' fallback non-periodic SRS resource ' 1415).

As shown in FIG. 14A, the fallback aperiodic SRS resource 1415 may use a portion of the reduced resource block (RB) region 1415 of the allocated all-band aperiodic SRS resource 1410. Alternatively, the fallback aperiodic SRS resource 1415 may be predefined as a disjoint resource region with the full-band aperiodic SRS resource.

The method represented by the fallback aperiodic SRS resource in FIGS. 14A and 14B is based on the two fallback aperiodic SRS resource allocation schemes ('reconfigured full-band aperiodic SRS resource' and 'fallback non- SRS resource '), but not both. In addition, the fallback aperiodic SRS resource 1415 occupies a relatively small area of resources than the reconstructed full-band aperiodic SRS resource 1410, and the fallback aperiodic SRS resources 1415 and 1425 occupy a relatively small area of the SRS transmission subframe Frequency hopping pattern.

The switching between the reconfigured full-band aperiodic SRS resources and the fallback aperiodic SRS resources is performed such that the processor 255 of the terminal has the power required to successfully transmit the aperiodic SRSs in the self-reconfigured full-band aperiodic SRS resource 1410 The SRS is transmitted through the reconstructed full-band aperiodic SRS resource 1410 if it is sufficient, and if it is insufficient, the SRS is fallback to the fallback non-periodic SRS resource 1415, . At this time, since the switching to the fallback aperiodic SRS resource 1415 is performed by the determination and determination of the processor 255 of the UE, the base station needs to find the resource region in which the aperiodic SRS is transmitted through blind decoding The UE 255 of the UE determines whether the transmission power is sufficient. If the UE determines that the transmission power is sufficient, the UE transmits the reconstructed full-band aperiodic SRS resource 1410 in the subframe 3, Lt; RTI ID = 0.0 > SRS. ≪ / RTI > Also, if the UE receives the aperiodic SRS triggering grant in subframe 6 and the processor 255 of the UE determines that the transmission power is insufficient, the UE switches from the subframe 7 to the fallback aperiodic SRS transmission scheme, And may transmit aperiodic SRS through SRS resource 1415. [ This operation can also be applied to a partial-band aperiodic sounding scheme.

The base station may configure the SRS subframe as shown in FIG. 14B as the eighth non-periodic SRS configuration. 14B, the eighth non-periodic SRS configuration operates by dividing a partial-band aperiodic SRS resource into a 'reconfigured partial-band aperiodic SRS resource' 1430 and a 'fallback non-periodic SRS resource' 1440 Indicates an aperiodic SRS transmission scheme. Here, the aperiodic SRS triggering method follows the same scheme as the scheme used in FIG. 10A (i.e., the second aperiodic SRS configuration) described above, and the fallback aperiodic SRS resource 1440 is part- May be predefined as a disjoint resource region from the SRS resource 1430. [ Alternatively, some reduced RB regions of the partial-band aperiodic SRS resources allocated to fallback aperiodic SRS resources 1440 may be used.

In FIG. 14B, if the UE receives an aperiodic SRS triggering grant in subframe 1, and the processor 255 of the UE determines that the transmission power is sufficient, then the UE can perform partial-band aperiodic SRS The SRS transmission can be successfully performed through the resource 1430. In addition, if the UE receives the aperiodic SRS triggering grant in subframe 5 and the processor 255 of the UE determines that the transmission power is insufficient, the UE switches to the fallback aperiodic SRS scheme, And may transmit aperiodic SRS via resource 1450. [ At this time, the UE can perform the aperiodic SRS transmission through the fallback aperiodic SRS resource 1450. Therefore, the UE can effectively solve the SRS coverage problem by self-adaptively dropping the aperiodic SRS resources. Then, if the UE transmits an aperiodic SRS through a fallback aperiodic SRS resource, the base station needs to find the resource region through which the aperiodic SRS is transmitted through blind decoding.

Here, it is described that the processor 255 of the UE determines whether or not power is enough to switch in the fallback aperiodic SRS scheme. However, it is also described that the serving cell is determined to have a strong When the UE is notified of neighbor cell interference information such as information indicating that interference will occur, the specific band can be operated in the fallback aperiodic SRS scheme. For example, if a terminal A located at an edge of an adjacent cell A transmits an SRS in a specific band of the subframe 1 and this SRS uplink transmission acts as strong interference to the cell B, the cell B transmits an uplink (E.g., 1 bit), such as instructing an intra-cell UE to transmit an aperiodic SRS via a fallback aperiodic SRS resource in consideration of interference. Then, the UE in the cell B can transmit the SRS through the fallback aperiodic SRS resource in the subframe 1 based on the signaling. The cell A and the cell B can exchange information related to the uplink interference through the backhaul and allocate the SRS resources of the UEs in the cell in consideration of uplink interference due to the SRS transmission of the adjacent cell.

15A is a diagram showing a configuration of a cell-specific SRS subframe configuration and a cell-specific SRS resource, FIG. 15B is a diagram showing an SRS configuration in which cell-specific periodic SRS resources and cell-specific aperiodic SRS resources are multiplexed, 15C is a diagram showing an example of an aperiodic SRS subframe structure.

Referring to FIG. 15A, a BS configures a cell-specific SRS subframe into subframes 1, 3, 5, 7, and 9 in a 2 ms cycle according to a rule preset for a cell-specific SRS subframe, SRS resources can be allocated. The UE may transmit aperiodic SRS through a subframe or an aperiodic SRS subframe in which cell-specific periodic SRS resources and cell-specific aperiodic SRS resources are multiplexed. .

Referring to FIGS. 15B and 15C, a base station may multiplex a cell-specific periodic SRS resource and an aperiodic SRS resource such as subframes 1, 5, and 9 among the cell-specific SRS subframes configured in FIG. Frame ', and' aperiodic SRS subframe 'such as subframes 3 and 7. Here, the subframe in which the cell-specific periodic SRS resource and the aperiodic SRS resource are multiplexed is a scheme in which the cell-specific SRS resource is divided into 'periodic SRS resource' 1510 and 'aperiodic SRS resource' 1520.

The division scheme of the cell-specific SRS resource is divided into two regions (for example, two subbands) orthogonal to each other in the frequency domain, or a whole set of pairs of usable comb and cyclic shifts Divided into two disjoint subsets and then assigned to periodic SRS resources and non-periodic SRS resources, respectively. As an example of the latter scheme, we divide the two usable combs into full-band sounding and partial-band sounding purposes, then divide the eight cyclic shifts that can be combined with each comb into half, And can be assigned to aperiodic SRS resources.

For example, terminal A may send an aperiodic SRS through an aperiodic SRS resource 1520 in subframe 1, while terminal B may transmit a periodic SRS through a periodic SRS resource 1510 in subframe 1 have. That is, the aperiodic SRS of the terminal A and the periodic SRS of the terminal B can be multiplexed in the subframe 1 and transmitted. In addition, one terminal may multiplex the aperiodic SRS and the periodic SRS in the subframe 1 and transmit the same with different combs to the periodic SRS and the aperiodic SRS, thereby making the channel estimation of the specific bandwidth more efficient can do.

Referring to FIG. 15C, the base station can allocate resources for the aperiodic SRS transmission in the sub-frames 3 and 7 in the cell-specific SRS subframe configured in FIG. 15A as the full-band 1530.

As shown in FIGS. 15B and 15C, the base station can allocate the cell-specific periodic and aperiodic SRS resources multiplexed with each other to the non-periodic SRS sub-frame alternately with the assigned cell-specific SRS sub- have. For example, the base station may be configured to multiplex cell-specific periodic and aperiodic SRS resources in a cell-specific SRS subframe 1, followed by a cell-specific SRS subframe 3 to constitute an aperiodic SRS subframe, The next cell-specific SRS sub-frame 5 may again be configured to multiplex cell-specific periodic and aperiodic SRS resources (ninth aperiodic SRS configuration). The rules used here can be variously defined in various ways. In addition, the distinction between the periodic SRS resources and the aperiodic SRS resources shown in FIG. 15B is not limited to the result of using only one of the two cell-specific SRS resource segmentation schemes described above. And the result of using it.

In addition, when an aperiodic SRS transmission is required in a subframe in which cell-specific periodic SRS resources and aperiodic SRS resources are multiplexed, the UE can transmit SRSs over designated aperiodic SRS resources. Since the UE does not know when an aperiodic SRS triggering indicator (e.g., grant) will arrive, the base station can pre-allocate resources for transmitting aperiodic SRS of the UEs in advance. In a subframe in which cell-specific cyclic and aperiodic SRS resources are multiplexed, periodic SRS transmission is set as a basic scheme. However, when the SRS transmission time overlaps with an aperiodic SRS transmission time, the UE cancels periodic SRS transmission, May be preferentially performed.

16 is a diagram illustrating a UE-specific periodic SRS subframe configuration.

The base station can allocate the SRS transmission subframe to the specific terminal as shown in FIG. 16 as the tenth SRS configuration. The tenth SRS configuration allocates a UE-specific periodic SRS subframe in a specific frame at a period of 2 ms. For example, in a particular frame, subframes 1, 3, 5, 7, and 9 are assigned to UE-specific periodic SRS subframes. Among these UE-specific periodic SRS subframes, some subframes can be configured as cell-specific periodic SRS and non-periodic SRS multiplexed subframes, which are indicated by dashed lines in FIG. In the subframe indicated by the dashed line in FIG. 16, the cell-specific periodic SRS and aperiodic SRS resources are illustrated in a frequency division multiplexing manner, but the present invention is not limited thereto. In subframes 1, 5, and 9, the cell-specific periodic SRS and the aperiodic SRS may be multiplexed and transmitted. For example, in subframes 1, 5, and 9, terminal A may transmit periodic SRS and terminal B may transmit aperiodic SRS. Alternatively, in the subframes 1, 5, and 9, the terminal A can multiplex the cyclic SRS and the aperiodic SRS in one subframe and simultaneously transmit them. The period of the periodic SRS subframe that is specifically allocated to each UE may be a multiple of the subframe period in which the cell-specific periodic and aperiodic SRS resources are multiplexed, or may be specified to the same value.

FIGS. 17A to 17C are diagrams for explaining an operation of dynamically selecting a plurality of SRS configurations using a time relationship between an aperiodic SRS triggering grant reception sub-frame and a corresponding aperiodic SRS transmission sub-frame, respectively.

Here, the UE has two non-periodic SRS configurations, which are represented by the 11th SRS configuration and the 12th SRS configuration, respectively. It is assumed that an aperiodic SRS transmission time point of the UE is designated as a nearest (or fastest) cell-specific SRS subframe subsequent to a subframe in which an aperiodic SRS triggering grant is received, and the period of the cell- 2 ms.

The base station can allocate the SRS subframe as shown in FIG. 17A as the eleventh SRS configuration. If the terminal receives an aperiodic SRS triggering grant in a subframe n (e.g., n = 5, 9), the processor 255 of the terminal may select the eleventh SRS configuration, and in accordance with the eleventh SRS configuration The UE may transmit the aperiodic SRS in subframe n + 2 (i.e., n + 2 = 7, 1) through subbands 1710 and 1720, respectively. Particularly, in the 11th SRS configuration, the partial bands 1710 and 1720 to which the UE transmits aperiodic SRS are configured in a frequency hopped form.

The base station can allocate SRS subframes as shown in FIG. 17B as a twelfth SRS configuration. If the UE receives an aperiodic SRS triggering grant in a subframe n (n = 2, 8), the processor 255 of the UE may select a twelfth SRS configuration, and in accordance with the twelfth SRS configuration, May be transmitted over the entire band in subframe n + 1 (i.e., n + 1 = 3, 9).

As an example, in the 3GPP LTE and LTE-A systems, one frame normally includes 10 subframes, and it is assumed that indexes 1 through 10 of each subframe included in one frame are given. When the time difference between the subframe receiving the aperiodic SRS triggering grant and the subframe index receiving the aperiodic SRS triggering grant and the index difference between the subframe index transmitting the aperiodic SRS are 2, For example, as shown in FIG. 17A, when the UE receives an aperiodic SRS triggering grant in subframe 5, the processor 255 of the UE selects the 11th SRS configuration, and according to the 11th SRS configuration, Periodic SRS transmission operation through the sub-band 1710 in FIG. Meanwhile, if the time difference between the reception sub-frame of the aperiodic SRS triggering grant and the sub-frame to which the aperiodic SRS is to be transmitted is smaller than the index difference between the sub-frame index in which the aperiodic SRS triggering grant is received and the sub- 17B, the processor 255 of the terminal selects the twelfth SRS configuration, and when the non-periodic SRS triggering grant is selected in the sub-frame 8 as shown in FIG. And performs an aperiodic SRS transmission operation. In the subframe 9 of FIG. 17B, the resource through which the aperiodic SRS is transmitted is indicated by a dotted line 1740, but is actually transmitted over the entire band. That is, the aperiodic SRS can be divided into cyclic SRS transmission, comb, and cyclic shift, and can be transmitted through the entire band.

And, when full-band or partial-band aperiodic SRS transmission is required in a subframe multiplexed with cell-specific cyclic and aperiodic SRS, the terminal transmits a signal according to the first aperiodic SRS configuration SRS transmission according to the second non-periodic SRS configuration or SRS transmission according to the second non-periodic SRS configuration.

As shown in FIG. 17A, the SRS coverage problem can be effectively solved by allocating the partial-band aperiodic SRS resources with a frequency hopping pattern (i. E. Allocating as 1710, 1720) by diversity gain or the like.

The base station can allocate the SRS subframe as shown in FIG. 17C as the thirteenth SRS configuration. The 13th aperiodic SRS configuration shown in FIG. 17C is an example of a partial-bandwidth aperiodic SRS configuration that is different from the SRS configuration of FIG. 17A, and is a partial-bandwidth aperiodic SRS scheme that does not use a frequency hopped scheme. In the thirteenth aperiodic SRS configuration, a partial-band aperiodic SRS transmission without using a frequency hopping scheme is configured. If the UE receives an aperiodic SRS triggering grant in subframe 5, it can transmit aperiodic SRS through subbands 1750 of subframe 7, which is the fastest subframe following subframe 5. In addition, if the UE receives an aperiodic SRS triggering grant in subframe 9, it can transmit aperiodic SRS through subbands 1760 of subframe 1 of the next frame following subframe 9. The partial-band aperiodic SRS transmission scheme without using the frequency hopping scheme is very effective in mitigating the uplink signal interference problem caused by using the co-channel between the heterogeneous networks.

FIG. 18 is a view for explaining aperiodic SRS transmission corresponding to a case where a subframe index classification at an aperiodic SRS triggering grant reception time point of the UE is applied as another criterion; FIG.

18, when the index of the subframe in which the UE receives the aperiodic SRS triggering grant is an odd number (for example, in subframe 1 as shown in FIG. 18) Lt; RTI ID = 0.0 > SRS < / RTI > On the other hand, when the index of the receiving subframe of the aperiodic SRS triggering grant is even (for example, subframe 6 as shown in FIG. 18), the terminal performs partial-band aperiodic SRS transmission operation Can be performed.

18, when a UE-specific periodic SRS subframe index assigned to a specific UE is n, a UE receives a non-periodic SRS triggering grant from a subframe And the sub-frame at the index n-4 and the sub-frames other than the index n-4. Here, the definition of the time point of the subframe n-4, which is the index n-4, can be variously specified by different values.

If the UE receives the aperiodic SRS triggering grant at subframe n-4, it can transmit the aperiodic SRS through the full-band of the closest periodic SRS subframe in subframe n. Alternatively, if the UE receives the aperiodic SRS triggering grant in another subframe of the subframe n-4, the UE transmits the aperiodic SRS through the sub-band of the closest periodic SRS subframe in the subframe n . Both SRS configurations use a scheme in which the UE transmits an aperiodic SRS transmission over the nearest periodic SRS subframe in the subframe that received the aperiodic SRS triggering grant.

As shown in FIG. 18, for example, when the UE receives an aperiodic SRS triggering grant in subframe 1, since subframe 1 is a subframe at n-4 time point of subframe 5 (n = 5) May perform operations to transmit aperiodic SRS through full-band 1810. [ In addition, when the UE receives an aperiodic SRS triggering grant in subframe 6, since subframe 6 does not correspond to a subframe at n-4 time point of subframe 9 (n = 9) 1820). ≪ / RTI >

Figs. 19A and 19B are diagrams illustrating an example of an aperiodic SRS sub-frame of SRS configuration, respectively.

In Figs. 19A and 19B, frames subsequent to the second frame exist, but the second frame has been described and described for convenience of explanation. As shown in FIG. 19A, the SRS transmission period and the subframe offset may be 4ms and 2ms, respectively, in order to transmit the SRS through the partial-band. The base station may configure sub-frames 3 and 7 of the first frame and sub-frames 1 and 5 of the second frame as SRS sub-frames through the partial-band. That is, the terminal may transmit SRSs through sub-bands in subframes 3, 7 in the first frame and subframes 1, 5 in the second frame following the first frame. As shown in FIG. 19B, the SRS transmission period and the sub-frame offset may be set to 4 ms and 0 ms, respectively, in the SRS configuration for transmitting the SRS through the full-band. The base station may configure sub-frames 1, 5, 9 of the first frame, sub-frame 3 of the second frame, etc. as SRS sub-frames over the full-band. The UE can transmit the SRS through the entire band in subframes 1, 5, and 9 of the first frame and in subframe 3 in the second frame following the first frame.

Since the resources for the SRS transmission subframe in each SRS configuration reuse the resources for the cell-specific periodic SRS transmission, the period of the subframe in which the aperiodic SRS is transmitted is a multiple of the cell-specific periodic SRS subframe period Shape or the same value. As described above, the information about the subframe for transmitting the SRS through the partial-band and the subframe for transmitting the SRS through the full-band may be established beforehand between the base station and the terminal, but the base station may transmit the upper layer signaling You can also send it through.

FIG. 20 is a diagram for explaining the aperiodic SRS configuration of FIGS. 19A and 19B and the switching of an aperiodic SRS configuration operation according to a point of time when a terminal receives an aperiodic SRS triggering grant. FIG.

The base station may allocate SRS resources in full-band in subframes 1, 5 and 9, but may also be composed of subframes multiplexed with cell-specific periodic SRS resources and cell-specific aperiodic SRS resources. The base station divides the SRS resources in this multiplexed subframe into two orthogonal regions (e.g., two subbands), or separates the entire set of available comb and cyclic shift pairs Divided into two disjoint subsets and then assigned to periodic SRS resources and non-periodic SRS resources, respectively.

In FIG. 20, it is assumed that the UE sets the transmission time point of the aperiodic SRS as the closest cell-specific SRS subframe in the subframe in which the aperiodic SRS triggering grant is received. As shown in FIG. 20, when the UE receives an aperiodic SRS triggering grant in subframe 2, the UE receives a non-periodic SRS triggering grant through subframe 3, which is the cell- Periodic SRS can be transmitted. At this time, since the subframe 3 is set as the SRS transmission subframe through the partial-band in FIG. 19A, the UE transmits the aperiodic SRS through the sub-band 2010 in the subframe 3. In addition, when the UE receives an aperiodic SRS triggering grant in subframe 8, it transmits an aperiodic SRS through the closest cell-specific SRS subframe 9. At this time, since the subframe 9 in which the SRS is transmitted is set as a subframe transmitting the SRS in the full-band in FIG. 19B, the UE transmits the aperiodic SRS in the sub-frame 20 through the full-band 2020 21A and 21B are diagrams for explaining a new type of aperiodic SRS transmission using a part of aperiodic SRS transmission resources divided into fallback aperiodic SRS transmission resources.

Here, the fallback aperiodic SRS resource 2115 may use a reduced resource block (RB) region of the allocated aperiodic SRS transmission resource 2110. Alternatively, the fallback aperiodic SRS resource may be divided into a disjoint SRS transmission resource and a disjoint resource region, a complete set of pairs of usable combs and cyclic shifts, , And then divided into an aperiodic SRS resource and a fallback non-periodic SRS resource, respectively. The allocated fallback aperiodic SRS transmission resources shown in FIGS. 21A and 21B do not refer to only one of the above-mentioned two fallback aperiodic SRS transmission resource allocation schemes, but include both of them.

The partial-band aperiodic SRS transmission scheme shown in FIG. 21A is a scheme for transmitting full-band aperiodic SRS in an aperiodic SRS triggering scheme similar to FIG. If the UE receives an aperiodic SRS triggering grant in subframe 2, the UE shall transmit an aperiodic SRS through sub-band 2110 of subframe 3, which is the closest cell-specific periodic SRS subframe in subframe 2 . If the UE receives an aperiodic SRS triggering grant in subframe 6, the UE can transmit an aperiodic SRS in subframe 7 which is the closest cell-specific periodic SRS subframe in subframe 6. At this time, the processor 255 of the UE may switch to transmit the SRS through the fallback aperiodic SRS transmission resource 2120 on the basis of insufficient transmission power or the like in the subframe 7.

Also, the full-band aperiodic SRS transmission shown in FIG. 21B is an all-band aperiodic SRS transmission scheme with an aperiodic SRS transmission triggering scheme similar to FIG. When the UE receives an aperiodic SRS triggering grant in subframe 3 according to the all-band aperiodic SRS transmission scheme shown in FIG. 21B, the UE transmits a sub-frame corresponding to the sub- SRS can be transmitted in Frame 5. At this time, the UE may transmit the aperiodic SRS through the fallback aperiodic SRS resource 2130 in the subframe 5. In addition, when the UE receives the aperiodic SRS triggering grant in subframe 8, the UE transmits the SRS through the entire band 2140 in subframe 9 corresponding to the cell-specific periodic SRS transmission subframe closest to subframe 8 .

The SRS configuration information of FIG. 21A and FIG. 21B can be informed to the mobile station by the upper layer signaling or the like.

So far, 3GPP LTE Release 10 or later systems have described the manner in which a UE transmits aperiodic SRS. The purpose of introducing aperiodic SRS in the 3GPP LTE Release 10 system is to improve the quality of the channel estimation of the base station while reducing the overhead of periodic SRS transmission and to perform channel estimation more accurately and adaptively.

As another embodiment of the present invention, when performing aperiodic SRS transmission by various aperiodic SRS triggering schemes, non-periodic SRS transmission is performed in order to improve the accuracy and efficiency of the channel estimation result obtained through aperiodic SRS transmission of the UE. SRS transmission power control using periodic SRS transmission power control and other methods. The method proposed by the present invention can be applied to various aperiodic SRS duration environments.

 The existing SRS transmission power formula can be expressed by the following Equation (16).

Here, i denotes a subframe index, and P _SRS (i) denotes SRS power transmitted in subframe i (i.e., subframe of index i). In Equation (16), the BS determines parameters semi-staticly determined by upper layer signaling through the upper layer signaling and parameters that dynamically determine and inform via the TPC (Transmit Power Control) command of the PDCCH Consists of.

,

,

,

,

The base station notifies the terminal through the upper layer signal,

The base station dynamically informs the UE through the TPC command of the PDCCH.

Is a value signaled by the base station to the UE as a value semi-statically configured at an upper layer as a terminal-specific parameter (e.g., 4 bits) that is a power offset value for SRS transmission.

Is a value indicating the current PUSCH power control adjustment state and can be expressed by a current absolute value or an accumulated value. 0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1}, where j = 0 or 1, as a cell-specific parameter for the base station to transmit, for example, (J) = 1 when j = 2. (j) is a value that the base station informs the terminal.

P _CMAX represents the transmit power of the configured terminal, M _SRS denotes the bandwidth of the SRS transmitted in the subframe i expressed as a number of resource blocks, P _{O _ PUSCH} (j) is the cell given from the upper layer-specific nominal component ( nominal component P _{O _ NOMINAL _ PUSCH} (j) and the sum of the terminal-specific components P _{O _ UE _ PUSCH} (j) provided by the upper layer.

PL is the downlink path loss (or signal loss) estimate that the UE calculated in dB, expressed as PL = referenceSignalPower- higher layer filteredRSRP.

The formula for different transmission power control of the periodic SRS and aperiodic SRS can be defined by redefining the configuration parameters of Equation 16 or by adding new parameters.

The power control formula for SRS transmission proposed by the present invention can be expressed as Equation (17).

Here, V denotes a power offset applied only to the aperiodic SRS transmission, and the base station can signal the terminal with one or more values through an upper layer signal. If V is set to one value, the same aperiodic SRS power offset can always be applied regardless of DCI format (0/3 / 3A) and the type of UE-specific parameter Accumulation - enabled . On the other hand, if V is set to more than one value, the aperiodic power offset can be applied differently depending on the combination of DCI format (0/3 / 3A) and Accumulation - enabled value. For example, the power offset applied after receiving the TPC command of the PDCCH may be set differently depending on the type of the SRS transmitted in the subframe i by the UE. At this time, the periodic SRS and the aperiodic SRS

,

,

,

, PL,

Are common, and only the V value is applied differently.

Other power control formulas for SRS transmission proposed in the present invention can be expressed as Equation (18). This power control formula allows the transmission power offset of periodic SRS and aperiodic SRS to be calculated and operated completely independently. That is, in Equation 17,

Can be redefined as shown in Equation (18) below. In such an operating mode,

,

,

,

, The PL values are shared between the periodic SRS and the aperiodic SRS,

Only the values are applied differently.

here,

The existing

, But the δ _PUSCH value selected according to the combination of the DCI format (0/3 / 3A) and the Accumulation - enabled value can be set differently. Also,

To

And a completely different calculation method and δ _PUSCH value.

Additionally, as shown in Equation (18) above, in the power control equation

Values are independent and not common among power control schemes for periodic SRS transmissions and power control schemes for aperiodic SRS transmissions. like this,

Is applied independently for periodic SRS transmission and aperiodic SRS transmission, a method using TPC information of the DCI format transmitted for aperiodic SRS triggering is proposed. The DCI format used by the base station for aperiodic SRS triggering may use the existing DCI format including aperiodic SRS triggering bits or the newly defined DCI format only for aperiodic SRS triggering. It is also assumed that the DCI format for aperiodic SRS triggering always has 2 bits of TPC information. Under this condition, the proposed scheme directly informs the UE of the power offset value through the 2-bit TPC information dynamically. The power offset may be an absolute value or an accumulated value, and this power offset only affects the transmission power control of the aperiodic SRS.

Another power control formula for SRS transmission proposed by the present invention can be expressed as Equation (19).

In this scheme, a base station transmits UE-specific signals through an upper layer signal,

Signals are sent in two instead of one, so that different power offsets are applied depending on the type of SRS. The base station distinguishes between periodic SRS transmission and non-periodic SRS transmission,

Value to the terminal. For example, with a trigger type 0, the base station can inform the UE of the power offset value for periodic SRS transmission by upper layer signaling. In addition, the base station can notify the UE of the power offset value for the aperiodic SRS transmission by the upper layer signaling based on the trigger type 1 (trigger type 1). Here, the base station can transmit the power offset value for the aperiodic SRS transmission to the UE through the DCI format 0/4 / 1A in the FDD and TDD systems, or in the DCI format 2B / 2C format in the TDD system, . ≪ / RTI > When trigger type 0 and trigger type 1 are triggered (or generated) in the same subframe, the terminal can only perform trigger type 1 SRS transmission (i.e., aperiodic SRS transmission).

in this case,

Are common to the power control equation for transmitting periodic SRS and the power control equation for transmitting aperiodic SRS. Also,

instead

May be used to perform the same operation. Accordingly, the processor 255 of the MS applies the SRS offset value according to the corresponding mode, based on the power offset value for the periodic SRS transmission and the power offset value for the aperiodic SRS transmission received through the upper layer signaling from the base station The uplink transmission power value and the aperiodic SRS transmission power value for periodic SRS transmission can be calculated.

Another power control formula for SRS transmission proposed by the present invention can be expressed by the following Equation (20).

This scheme is a hybrid scheme in which the UE combines the power for periodic SRS transmission and the power for non-periodic SRS transmission as a combination of the first scheme described in Equation (17) and the third scheme described in Equation (19) You can set it differently. For example, after setting the power offset for the aperiodic SRS transmission power using Equation (19), the power offset of Equation (17) may be additionally applied to widen the range of the offset value selection. In yet another embodiment, the transmission power offset of the aperiodic SRS set through Equation 19 may be a coarse value, and the power offset applied through Equation 17 may be a relatively fine value It is possible to perform more detailed power control than the conventional method. The same effects and results can also be obtained by a combination of the method using Equation (18) and the method using Equation (19).

The embodiments described above are those in which the elements and features of the present invention are combined in a predetermined form. Each component or feature shall be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to construct embodiments of the present invention by combining some of the elements and / or features. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims (20)

A method for transmitting an aperiodic sounding reference signal (SRS) in a wireless communication system,
A first power offset value set for periodic SRS transmissions from a base station, a second power offset value set for aperiodic SRS transmissions, and a plurality of SRSs set UE-specific for the aperiodic SRS transmissions, Receiving information about parameter sets through higher layer signaling;
Receiving a downlink control information (DCI) format including an indicator for triggering the aperiodic SRS transmission from the base station; And
When the periodic SRS transmission and the aperiodic SRS transmission overlap in a particular subframe, the periodic SRS transmission is dropped and the ratio of the first SRS parameter set to the non- Transmitting the periodic SRS,
Wherein the SRS parameter set set for the previous aperiodic SRS transmission of the terminal is a second SRS parameter set of the plurality of SRS parameter sets and the first SRS parameter set and the second SRS parameter set are different SRS parameter sets ,
Wherein the aperiodic SRS is transmitted with the determined uplink transmission power based on the second power offset value,
Wherein the first power offset value and the second power offset value are independently defined values. The method according to claim 1,
Wherein the uplink transmission power determined for the aperiodic SRS transmission is determined in units of subframes. The method according to claim 1,
Wherein the first power offset value and the second power offset value are semi-statically configured values. delete An apparatus for transmitting an aperiodic sounding reference signal (SRS) in a wireless communication system,
receiving set;
transmitter; And
≪ / RTI >
The receiver is configured to receive a first power offset value set for periodic SRS transmissions from a base station, a second power offset value set for aperiodic SRS transmissions, and a UE-specific Receiving information on a plurality of SRS parameter sets via higher layer signaling,
Receiving a downlink control information (DCI) format including an indicator for triggering the aperiodic SRS transmission from the base station,
Wherein the processor is configured to: when the periodic SRS transmission and the aperiodic SRS transmission overlap in a particular subframe, the transmitter drops the periodic SRS transmission and the first SRS of the plurality of SRS parameter sets And to transmit the aperiodic SRS based on the parameter set,
Wherein the SRS parameter set set for the previous aperiodic SRS transmission of the terminal is a second SRS parameter set of the plurality of SRS parameter sets and the first SRS parameter set and the second SRS parameter set are different SRS parameter sets ,
Wherein the aperiodic SRS is transmitted with the determined uplink transmission power based on the second power offset value,
Wherein the first power offset value and the second power offset value are independently defined values. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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