KR20100130141A - Apparatus and method of measuring channel status in multiple carrier system - Google Patents

Abstract

PURPOSE: A method and an apparatus for measuring a channel state in a multiple carrier system are provided to flexibly perform a scheduling by efficiently measuring the channel state of a carrier. CONSTITUTION: A terminal obtains information about a cell_Cset, a terminal_Cset and/or measurement_Cset from a base station(S1010). The terminal communicates with the base station using the terminal_Cset(S1020). The terminal determines whether the channel information about the measurement_Cset is transmitted to the base station in a communication with the base station(S1030). The terminal transmits the channel information about the sub set or measurement_Cset to the base station(S1040). The terminal communicates with the base station using the changed terminal_Cset(S1050,S1060).

Description

Apparatus and method for measuring channel status in multi-carrier systems {APPARATUS AND METHOD OF MEASURING CHANNEL STATUS IN MULTIPLE CARRIER SYSTEM}

The present invention relates to a multi-carrier system. Specifically, the present invention relates to an apparatus and method for measuring channel conditions in a multi-carrier system.

Wireless communication systems are widely deployed to provide various kinds of communication services such as voice and data. In general, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA) systems, frequency division multiple access (FDMA) systems, time division multiple access (TDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single carrier frequency (SC-FDMA). division multiple access (MCD) systems and multi-carrier frequency division multiple access (MC-FDMA) systems.

The present invention provides a method and apparatus for measuring channel conditions in a wireless communication system. It is also an object of the present invention to provide an apparatus and method for measuring channel conditions in a multi-carrier system.

Technical problems to be achieved in the present invention are not limited to the above technical problems, and other technical problems which are not mentioned may be clearly understood by those skilled in the art from the following description. will be.

In one aspect of the present invention, a method and apparatus for transmitting channel information to a base station by a terminal in a wireless communication system supporting carrier aggregation, the method comprising: identifying a plurality of component carriers used in the base station; Identifying a first set of component carriers and a second set of component carriers from the plurality of component carriers; Communicating with the base station using the first set of component carriers; And transmitting channel information on the second set of component carriers to the base station when a predetermined condition is satisfied.

In another aspect of the present invention, there is provided a radio frequency (RF) unit configured to transmit and receive a radio signal with a base station; A memory for storing information transmitted and received with the base station and parameters necessary for the operation of the terminal; And a processor coupled to the RF unit and the memory, the processor configured to control the RF unit and the memory, the processor identifying a plurality of component carriers used in the base station; Identifying a first set of component carriers and a second set of component carriers from the plurality of component carriers; Communicating with the base station using the first set of component carriers; And if the predetermined condition is satisfied, the terminal configured to perform the channel information transmission method comprising transmitting channel information on the second component carrier set to the base station.

Information for identifying the first component carrier set and the second component carrier set may be signaled through a Radio Resource Control (RRC) message. In addition, information for identifying the first component carrier set and the second component carrier set may be transmitted through a downlink control channel.

The predetermined condition may be satisfied when channel information for the second component carrier set is requested from the base station. In addition, the predetermined condition may be satisfied when communication using the first component carrier set does not meet a predetermined criterion. The criteria may be predetermined or signaled (eg, system information, RRC message).

The channel information on the second component carrier set includes Channel Quality Indicator (CQI), Precoding Matrix Index (PMI), Rank Information (RI), Sounding Reference Signal (SRS), Receive Signal Strength Indicator (RSSI), and Reference Signal (RSRP). It may be transmitted through Received Power (RSC), Reference Signal Received Quality (RSRQ), or the like.

According to an aspect of the present invention, after transmitting channel information, the method may further include receiving change information about at least a portion of the first component carrier set and the second component carrier set from the base station.

According to embodiments of the present invention, it is possible to efficiently measure channel conditions in a wireless communication system. In detail, by efficiently measuring a channel state of a carrier in a multi-carrier system, scheduling can be performed flexibly and battery consumption can be reduced.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may 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 as part of the detailed description in order to provide a thorough understanding of the present invention, provide an embodiment of the present invention and together with the description, illustrate the technical idea of the present invention.
1 illustrates a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS).
2 illustrates a structure of a radio interface protocol between a UE and an E-UTRAN based on the 3GPP radio access network standard.
3 illustrates a structure of a radio frame used in LTE.
4 illustrates a structure of a downlink subframe in LTE.
5 illustrates a structure of an uplink subframe used in LTE.
6 and 7 illustrate periodic reporting of channel information.
8 shows an example of performing communication in a multi-component carrier situation.
9 illustrates a physical channel and signal transmission using the same.
10 and 11 illustrate an example in which a terminal and a base station communicate in a wireless communication system supporting frequency aggregation according to an embodiment of the present invention.
12 illustrates a relationship between a cell_Cset, a terminal_Cset, and a measurement_Cset according to an embodiment of the present invention.
13 shows an example of receiving information about measurement_Cset according to an embodiment of the present invention.
14 illustrates a base station and a terminal that can be applied to an embodiment in the present invention.

The configuration, operation, and other features of the present invention can be easily understood by the embodiments of the present invention described with reference to the accompanying drawings. Embodiments of the present invention may be used in various radio access technologies such as CDMA, FDMA, TDMA, OFDMA, SC-FDMA, MC-FDMA. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA (E-UTRA), and the like. UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of Evolved UMTS (E-UMTS) using E-UTRA. LTE-A (Advanced) is an evolution of 3GPP LTE.

The following embodiments are mainly described in the case where the technical features of the present invention is applied to the 3GPP system, but this is by way of example and the present invention is not limited thereto.

1 shows a network structure of an E-UMTS. E-UMTS is also called LTE system. For details of technical specifications of UMTS and E-UMTS, refer to Release 7 and Release 8 of the "3rd Generation Partnership Project; Technical Specification Group Radio Access Network", respectively.

Referring to FIG. 1, an E-UMTS is located at an end of a user equipment (UE) 120, a base station (eNode B; eNB) 110a and 110b, and a network (E-UTRAN) to be connected to an external network. Access Gateway (AG). The base station may transmit multiple data streams simultaneously for broadcast service, multicast service and / or unicast service. One or more cells exist in one base station. The cell may be set to various frequency bandwidths (eg, 1.25, 2.5, 5, 10, 15, 20 MHz). Different cells can provide different bandwidths. The base station controls data transmission and reception for a plurality of terminals. For downlink (DL) data, the base station transmits downlink scheduling information to inform the corresponding UE of time / frequency domain, encoding, data size, and HARQ (Hybrid Automatic Repeat and reQuest) related information. In addition, the base station transmits uplink scheduling information for uplink (UL) data and informs the time / frequency domain, encoding, data size, HARQ related information, etc. which can be used by the corresponding terminal. An interface for transmitting user traffic or control traffic may be used between base stations. The core network (CN) may be composed of an AG and a network node for user registration of the terminal. The AG manages the mobility of the UE in units of a tracking area (TA) composed of a plurality of cells.

2 shows an air interface protocol structure based on the 3GPP radio access network standard. The control plane refers to a path through which control messages are transmitted. The user plane refers to a path through which data (eg, voice and Internet packets) are transmitted.

The physical layer (PHY), which is the first layer, provides a service to a higher medium access control (MAC) layer through a transport channel. The PHY layer of the transmitting side and the receiving side provides a service through a physical channel. Physical channels utilize time, frequency, code, and space as radio resources. Physical channels can be modulated in various ways for multiple access. In case of LTE, the physical channel is modulated by the OFDMA scheme in the downlink and modulated by the SC-FDMA scheme in the uplink.

The second layer includes a MAC layer, a Radio Link Control (RLC) layer, and a Packet Data Convergence Protocol (PDCP) layer. The MAC layer provides a service to an upper RLC layer through a logical channel. The RLC layer supports reliable data transmission. The PDCP layer performs a header compression function to reduce unnecessary control information for efficiently transmitting IP packets such as IPv4 and IPv6 in a narrow bandwidth air interface.

The Radio Resource Control (RRC) layer located at the bottom of the third layer is defined only in the control plane. The RRC layer is responsible for control of logical channels, transport channels, and physical channels in connection with configuration, reconfiguration, and release of radio bearers (RBs). RB means a service provided by the second layer for data transmission between the terminal and the network. To this end, the RRC layers of the UE and the network exchange RRC messages with each other. If there is an RRC connected (RRC Connected) between the UE and the RRC layer of the network, the UE is in an RRC connected mode, otherwise it is in an RRC idle mode. The non-access stratum (NAS) layer above the RRC layer performs functions such as session management and mobility management.

3 illustrates a structure of a radio frame used in LTE.

Referring to FIG. 3, a radio frame has a length of 10 ms (327200 · T _s ) and includes 10 equally sized subframes. The subframe has a length of 1 ms and includes two slots. T _s represents the sampling time and is expressed as T _s = 1 / (15 kHz × 2048) = 3.2552 × 10 ⁻⁸ (about 33 ns). The slot includes a plurality of OFDMA (or SC-FDMA) symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. In the LTE system, one resource block includes 12 subcarriers x 7 (6) OFDMA (or SC-FDMA) symbols. The structure of the above-described radio frame is only an example, and the number / length of subframes, slots, or OFDMA (or SC-FDMA) symbols may be variously changed.

4 shows a structure of a downlink physical channel.

Referring to FIG. 4, a subframe includes a control region for transmitting scheduling information and other control information, and a data region for transmitting downlink data. The control region begins with the first OFDMA symbol of the subframe and includes one or more OFDMA symbols. The size of the control region may be set independently for each subframe. Various control channels including physical downlink control channels (PDCCHs) are mapped to the control region. The PDCCH is a physical downlink control channel and is allocated to the first n OFDMA symbols of a subframe. The PDCCH includes one or more Control Channel Elements (CCEs). The CCE includes nine neighboring Resource Element Groups (REGs). The REG includes four neighboring REs except for the reference signal.

The PDCCH informs the UE of information related to resource allocation of a paging channel (PCH) and a downlink-shared channel (DL-SCH), an uplink scheduling grant, and an HARQ information. The information transmitted through the PDCCH is collectively referred to as downlink control information (DCI). PDCCH has various formats according to the information. The PDCCH format is also called DCI format (DCI format). For example, DCI format 0 related to uplink scheduling is shown in Table 1.

 Field Bits  Comnent  Format  One  Uplink grant or downlink assignment  Hopping flag  One  Frequency hopping on / off  RB assignment  7 -  MCS  5 -  DMRS 3  Cyclic shift of demodulation reference signal : : :  RNTI / CRC 16  16 bit RNTI implicitly encoded in CRC  Total 38 -

* MCS: Modulation and Coding Scheme

* RNTI: Radio Network Temporary Identifer

CRC: Cyclic Redundancy Check

Which UE the PDCCH is transmitted is identified using the RNTI. For example, the PDCCH is CRC masked with an RNTI of "A", uplink radio resource allocation information (eg, frequency position) of "B", and transmission type information of "C" (eg, a transport block size, Modulation scheme, coding information, etc.). In this case, the UE in the cell monitors the PDCCH using its own RNTI, and the UE having the "A" RNTI performs uplink transmission according to the information of "B" and "C" obtained from the PDCCH.

The PDCCH is designed in which a channel ID and a terminal ID are associated with each other. That is, the position where one UE should search in one radio frame is determined according to the determined size of the PDCCH (eg, 0 to 3 OFDM symbols). The set of PDCCH candidates to be searched is defined as a search space. A search space S _k ^(L) having an aggregation level ^L level {1, 2, 4, 8} is defined as a set of PDCCH candidates. CCEs corresponding to PDCCH candidate m in the search space S _k ^(L) are defined as follows.

Where Y _k is defined later and i = 0,... , L-1 and m = 0,... , M ^(L) -1. M ^(L) is the number of PDCCH candidates that should be monitored within a given search space.

The terminal should monitor one common search space at aggregation levels 4 and 8 and the terminal-specific search space at aggregation levels 1, 2, 4 and 8. The common search space and the terminal-specific search space may overlap.

Table 2 shows an example of a search space that the UE should monitor in LTE.

For a common search space, Y _k is set to zero for aggregation levels L = 4 and L = 8. For the terminal-specific search space S _k ^(L) at the aggregation level L, Y _k is as follows.

Here, Y ₋₁ = n _RNTI ≠ 0, A = 39827, and D = 65537.

5 illustrates a structure of an uplink subframe used in LTE.

Referring to FIG. 5, an uplink subframe includes a plurality of slots (eg, two). The slot may include different numbers of SC-FDMA symbols according to the CP length. For example, in case of a normal CP, a slot may include 7 SC-FDMA symbols. The uplink subframe is divided into a data region and a control region. The data area includes a physical uplink shared channel (PUSCH) and is used to transmit data signals such as voice and video. The control region includes an uplink control channel (PUCCH) and is used to transmit control information. The PUCCH includes RB pairs located at both ends of the data region on the frequency axis and hops to a slot boundary. The control information includes HARQ ACK / NACK and downlink channel information (ie, downlink channel information). The downlink channel information includes Channel Quality Indicator (CQI), Precoding Matrix Index (PMI), Rank Information (RI), Receive Signal Strength Indicator (RSSI), Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and the like. Include. Meanwhile, the terminal transmits a sounding reference signal (SRS) to inform the base station of uplink channel information (ie, uplink channel information). The SRS is located in the last SC-FDMA symbol of the subframe and is transmitted over all or some bands of the data area. For convenience, downlink and uplink channel information are collectively referred to as channel information.

6 to 7 illustrate an example of transmitting CQI, which is downlink channel information.

Referring to FIG. 6, four CQI reporting modes exist for LTE. Specifically, the CQI reporting mode is divided into a wideband (WB) CQI and a subband (SB) CQI according to the CQI feedback type, and no PMI and a single PMI depending on whether PMI is transmitted. Divided by. The UE receives information consisting of a combination of a period and an offset to periodically report the CQI through RRC signaling.

FIG. 7A illustrates an example of transmitting channel information when the terminal receives information indicating {period '5', offset '1'}. Referring to FIG. 7A, when the period is '5' and the information indicating the offset '1' is received, the UE performs an offset of one subframe in the incremental direction of the subframe index from the 0th subframe in units of five subframes. Send channel information. The channel information is basically transmitted through the PUCCH, but if there is a PUSCH for data transmission at the same time, the channel information is transmitted together with the data through the PUSCH. The subframe index is a combination of a system frame number n _f and a slot index n _s , 0 to 19, and may be defined as 10 * n _f + floor (n _s / 2). floor () represents a rounding function. There is a type for transmitting only WB CQI and a type for transmitting both WB CQI and SB CQI. The type of transmitting only WB CQI transmits CQI information for the entire band in a subframe corresponding to every CQI transmission period. For the type of transmitting both WB CQI and SB CQI, WB CQI and SB CQI are transmitted alternately. If PMI should also be transmitted, the PMI information is transmitted along with the CQI information.

7B illustrates a system in which the system band is composed of 16 resource blocks (RBs). It is assumed that the system band is composed of two bandwidth parts (BP) and BP1, each BP is composed of two subbands (SB0, SB1), and each SB is composed of four RBs. . The above assumption is an example for explanation, and the number of BPs and the size of each SB may vary according to the size of the system band. In addition, the number of SBs constituting each BP may vary according to the number of RBs, the number of BPs, and the size of the SBs.

In the case of transmitting both WB CQI and SB CQI, the WB CQI is transmitted in the first CQI transmission subframe, and the CQI for the SB having a good channel state among SB0 and SB1 belonging to BP0 and the corresponding SB in the next CQI transmission subframe. Send the index of. Thereafter, in the next CQI transmission subframe, the CQI for the SB having a good channel state among the SB0s and SB1s belonging to the BP1 and the index of the corresponding SB are transmitted. As such, after transmitting the WB CQI, the CQI information for each BP is sequentially transmitted. CQI information for each BP may be sequentially transmitted 1 to 4 times between two WB CQIs. For example, when the CQI information for each BP is sequentially transmitted between two WB CQIs, they may be transmitted in the order of WB CQI ⇒ BP0 CQI ⇒ BP1 CQI ⇒ BP0 CQI ⇒ BP1 CQI ⇒ WB CQI. How many times each BP CQI is sequentially transmitted is signaled at a higher layer (eg, RRC layer).

The RI is signaled from a higher layer (eg, RRC layer) in a combination of how many times the WB CQI transmission period is transmitted and the offset in that transmission period. The offset of the RI is signaled as a value relative to the offset of the CQI. For example, if the offset of the CQI is '1' and the offset of the RI is '0', the RI has the same offset as the CQI. The offset of RI is defined as 0 and a negative value. If the offset of the RI is '0', the WB CQI and the transmission subframes of the RI overlap. In this case, the WB CQI is dropped and the RI is transmitted.

8 shows an example of performing communication under a multi-component carrier situation. 8 may correspond to an example of communication of the LTE-A system. The LTE-A system uses a carrier aggregation or bandwidth aggregation technique that collects a plurality of uplink / downlink frequency blocks and uses a larger uplink / downlink bandwidth to use a wider frequency band. Each frequency block is transmitted using a component carrier (CC). CC may mean a frequency block or a center carrier of a frequency block for carrier aggregation depending on the context, and they are mixed with each other.

Referring to FIG. 8, five 20 MHz CCs may be collected on the uplink and the downlink to support 100 MHz bandwidth. CCs may be contiguous or non-contiguous in the frequency domain. FIG. 8 illustrates a case where both the bandwidth of the UL CC and the bandwidth of the DL CC are the same and symmetrical. However, the bandwidth of each CC can be determined independently. For example, the bandwidth of the UL CC may be configured as 5 MHz (UL CC0) + 20 MHz (UL CC1) + 20 MHz (UL CC2) + 20 MHz (UL CC3) + 5 MHz (UL CC4). In addition, asymmetrical carrier aggregation in which the number of UL CCs and the number of DL CCs are different is possible. Asymmetric carrier aggregation may occur due to the limitation of available frequency bands or may be artificially established by network configuration. In addition, although the uplink signal and the downlink signal are illustrated as being transmitted through a one-to-one mapped CC, the CC in which the signal is actually transmitted may vary depending on the network configuration or the type of the signal. For example, the CC to which the scheduling command is transmitted may be different from the CC to which data is transmitted according to the scheduling command. In addition, the uplink / downlink control information may be transmitted through a specific UL / DL CC regardless of mapping between CCs.

On the other hand, even if the entire system band is composed of N CCs, a frequency band that can be used by a specific terminal may be limited to M (<N) CCs. Various parameters for carrier aggregation may be set in a cell-specific, UE group-specific, or UE-specific manner. Accordingly, when N CCs exist in a cell, the UE may receive PDSCH through all N CCs, but the base station may select a CC in which the UE may receive the PDSCH in a semi-static manner. It may be limited to <N) pieces. Hereinafter, embodiments of the present invention will be described mainly for the case where it is applied to N CCs, but it is obvious that the embodiments of the present invention are applied to M CCs. In addition, after dividing N (or M) CCs allocated to the UE into L CC groups, the embodiment of the present invention may be applied to each CC group.

9 illustrates a physical channel and signal transmission using the same. This embodiment will be described mainly for the initial access procedure of the multi-component carrier system, but is also applied to a single component carrier system except for the parts related to the multi-component carrier.

Referring to FIG. 9, when the UE is powered on or newly enters a cell, the UE performs an initial cell search operation such as synchronizing with the base station (S901). In this process, the UE attempts to detect a Synchronization Channel (SCH) signal in units of frequency rasters. The SCH includes a Primary SCH (P-SCH) and a Secondary SCH (S-SCH). When SCH signal detection is successful in one of the aggregated DL CCs, the UE may synchronize with the base station and acquire information such as a physical cell identifier (PCI). The UE may set the DL CC from which the SCH signal is detected as a reference DL CC for initial access or not set as a separate reference DL CC. For convenience, the DL CC from which the SCH signal is detected is referred to as a reference DL CC.

Thereafter, the terminal may receive a physical broadcast channel from the base station to obtain broadcast information in a cell. After completing the initial cell search, the UE may acquire more specific system information by receiving the PDSCH according to the information on the PDCCH (S902). The system information includes, for example, a DL transmission bandwidth (BW), a PHICH setting, a single frequency network (SFN), a number of transmission antennas of a base station, and the like. Specifically, the terminal receives system information (ie, SI-x) transmitted to the reference DL CC in order to obtain information required for initial access. In SI-x, UL BW, UL E-UTRA Absolute Radio Frequency Channel Number (EARFCN), higher layer signaling related to uplink / downlink channel configuration, and the like are transmitted. When the EARFCN and the BW of the UL CC are known through the system information, information on the DL-UL pair band is obtained from the FDD. In the case of a single component carrier system, DL and UL are mapped 1-to-1, whereas in a multi-component carrier system, DL and UL are 1-to-1, 1-to-many, or many-to-1. Can be mapped. The UL CC mapped with the reference DL CC may be set as the reference UL CC or may not be set as a separate reference UL CC. For convenience, the UL CC linked with the DL CC from which the SCH signal is detected is referred to as a reference UL CC.

The base station transmits cell-specific information about the multi-component carrier configuration through the reference DL CC, so that the terminal can know the component carrier configuration of the cell. In this process, the same PCI may be transmitted in multiple DL CCs aggregated in one cell, and the PCIs transmitted through the SCH may be different for each DL CC. If the terminal knows the component carrier configuration information of the cell, it is possible to move the component carrier through a simple handover process. Information on the component carrier configuration in the cell can be delivered to the terminal using a variety of methods (eg, extended SI-x, reserved area of the PBCH) is not particularly limited herein.

If there is no radio resource for the first access to the base station or signal transmission, the terminal may perform a random access (RA) process for the base station (S903 to S906). To this end, the UE obtains a Physical Random Access Channel (PRACH) parameter from the reference DL CC and transmits a specific sequence to the preamble through the PRACH on the reference UL CC (S903 and S905). When the base station receives the RACH preamble, the base station transmits a RACH response on the PDCCH / PDSCH on the DL CC (S904 and S906). If there are multiple DL CCs assigned, the RACH response may be sent on all / specific DC CCs. After receiving the RACH response, the UE transmits an RACH message 3 (message3; MSG3). The RACH MSG3 may include UE capability information and may use this information to negotiate UE capability between the BS and the UE through UE or UE-group specific RRC signaling immediately after the RACH process or the RACH process. The base station may allocate carrier aggregation information in a terminal-specific or terminal group-specific manner based on the negotiation information on the terminal capability.

The UE is allocated carrier aggregation information in a UE-specific or UE group-specific manner by RRC signaling after the initial access method or random access procedure described above, and receives a PDCCH / PDSCH as a general uplink / downlink signal transmission procedure (S907). And PUSCH / PUCCH transmission (S908). As an extension to the above-described method, after setting the initial transmission channel based on a single component broadcast wave, it may be extended to multi-component broadcast wave transmission through an additional process.

Arbitrary component carriers among a large number of component carriers used for various purposes such as obtaining diversity between multiple component carriers or performing component carrier failure or rate adaptation while transmitting / receiving DL / UL information based on a multi-component carrier You may need to change the set. Accordingly, channel information and measurement for this are needed to efficiently utilize and manage a plurality of component carriers.

However, any channel information transmission and measurement for all component carriers used in a cell or a base station may burden the terminal in terms of complexity, cost, and rationalization. In particular, channel information and / or measurement required for all component carriers without a specific trigger condition may result in serious battery consumption of the terminal. Therefore, it is additional overhead to inform the terminal of the channel information and / or component carrier requiring measurement according to a specific condition, and channel information and / or time information (eg, start time, offset, etc.) requiring measurement. Is present but may be efficient compared to the transmission and / or measurement of channel information for all component carriers. The channel information and / or measurement may be for a component carrier which is not currently used for data transmission among component carriers which are UE-specific or UE group-specifically allocated. In addition, the channel information and / or measurement may be for a component carrier which is included in a cell-specifically defined component carrier configuration and is not currently used for data transmission.

10 and 11 illustrate an example in which a terminal and a base station communicate in a wireless communication system supporting frequency aggregation according to an embodiment of the present invention. 10 is illustrated from the perspective of the terminal, and FIG. 11 is illustrated from the perspective of the base station.

Referring to FIG. 10, the terminal may obtain information regarding the cell_Cset, the terminal_Cset and / or the measurement_Cset from the base station (S1010 and S1110). Cell_Cset means a set of all component carriers constituting a cell or a base station. UE_Cset means a set of component carriers for transmitting and receiving data channels and / or control channels. The data channel includes PDSCH, PUSCH and the like and the control channel includes PDCCH, PUCCH and the like. Measurement_Cset means a set of component carriers requiring channel information and / or measurement. For convenience, Cset is not divided into uplink and downlink, but may be subdivided into uplink and downlink according to a context or an implementation method. For example, the cell_Cset may be divided into a cell_Cset_DL and a cell_Cset_UL, and the same applies to the terminal_Cset and the measurement_Cset.

12 illustrates the relationship between the cell_Cset, the terminal_Cset, and the measurement_Cset. Referring to FIG. 12, UE_Cset and measurement_Cset are the same as cell_Cset (FIG. 12A) or a subset of cell_Cset (FIGS. 12B-D). The measurement_Cset and the terminal_Cset may overlap each other (FIG. 12B) or may be mutually exclusive (FIG. 12C). UE_Cset may be a subset of measurement_Cset (FIG. 12 (d)). In addition, measurement_Cset may be a subset of UE_Cset (not shown). In general, the channel information on the UE_Cset can be measured by a Demodulation Reference Signal (DMRS) or a Cell-specific (or common) Reference Signal (DMRS) of the data being transmitted or the control channel. Can be defined as not overlapping with Cset. 11 separately defines measurement_Cset, but may also be defined as a component carrier except cell_Cset in cell_Cset. To this end, measurement_Cset is indicated by a dotted line in FIG. 11.

Information for setting the cell_Cset, the UE_Cset and / or the measurement_Cset is transmitted to the UE through system information (SI), RRC message, L1 / L2 control signaling (eg PDCCH) or MAC / RLC / PDCP PDU. It can be electrolyte. The information for setting the cell_Cset, the terminal_Cset and / or the measurement_Cset may be signaled simultaneously or independently (non) cyclically or in an event manner. In addition, the cell_Cset, the terminal_Cset and the measurement_Cset may be set using individually signaled information or may be set using information on another Cset. As an example, when the information on the UE_Cset is signaled, the measurement_Cset may be identified as a component carrier except for the UE_Cset in the cell_Cset. In addition, the information for setting the terminal_Cset and the measurement_Cset may include only the changed items as compared with the previous setting information. Although not limited thereto, the information for setting each Cset may include a component carrier (group) identifier.

If at least the cell_Cset and the terminal_Cset are set, the terminal may communicate with the base station using the terminal_Cset (S1020 and S1120). That is, data and control information may be received from the base station using the terminal_Cset_DL, and data and control information may be transmitted to the base station using the terminal_Cset_UL. The terminal determines whether it is necessary to transmit the channel information on the measurement_Cset to the base station in the process of communicating with the base station (S1030). The necessity of transmitting channel information for the measurement_Cset may be determined according to whether there is a need to change the UE_Cset or the cell_Cset. As an example, the necessity of transmitting channel information for measurement_Cset may be determined based on whether a predetermined criterion is satisfied. The predetermined criteria may be predetermined or signaled (eg, system information, RRC message). Whether the terminal satisfies a predetermined criterion may be determined by the terminal or the base station.

The case where the UE initiates transmission and / or measurement of channel information for measurement_Cset is not limited thereto, but is as follows. The data quality of a specific component carrier received by a terminal in terminal_Cset is poor. When the currently allocated UE_Cset does not reach the desired transmission rate by the UE and additional component carrier allocation is required (ie, when UE_Cset needs to be increased). When the UE needs to perform a handover (H / O) to the neighbor base station (ie, to measure the component carrier (set) of the neighbor cell.) Meanwhile, the base station transmits and / or transmits channel information about measurement_Cset Requests for measurements include, but are not limited to, the following: When a load is distributed to a particular component carrier and needs to be distributed A failure occurs for a particular component carrier A particular component carrier at a neighboring base station When you make a change request for (set).

If a predetermined criterion is satisfied at the base station, the base station transmits information requesting channel information to the terminal (S1130 and S1140). The base station requesting the terminal for channel information on measurement_Cset may be performed in various ways. Although not limited thereto, the channel information request for measurement_Cset may be delivered to the UE through an RRC message. For example, the base station determines the measurement ID (Measurement ID), type (type), command (setup, modify, release), measurement objects, measurement quantity (measurement quantity), reporting quantities to the terminal ) Or an RRC connection reestablishment message including one or more of reporting criteria (eg, cycle / event-trigger).

In addition, the channel information request for measurement_Cset may include channel information and / or information about a component carrier requiring measurement. The base station may inform the terminal of various types of information for channel information and / or measurement. How to interpret the information should be predetermined between the terminal and the base station. For example, the base station may directly transmit information about a component carrier requiring channel information to the terminal. In this case, the base station may directly transmit information on the measurement_Cset or a subset thereof to a specific terminal. As another example, the base station may transmit information about the component carrier that does not need channel information to the terminal. In this case, the base station may transmit information on (cell_Cset-measurement_Cset) or (part of cell_Cset-measurement_Cset) to a specific terminal. As another example, when the measurement_Cset and the terminal_Cset have an inclusion relationship, the base station may inform the terminal only about a subset in which the measurement_Cset and the terminal_Cset overlap.

If the terminal does not need to transmit the channel information, the communication is continued using the set terminal_Cset. Otherwise, the terminal transmits channel information about the measurement_Cset or a subset thereof to the base station (S1040 and S1150). Channel information on the uplink component carrier may be delivered to the base station using a sounding reference signal. Channel information on the downlink component carrier may be delivered to the base station using CQI, PMI, RI, and the like. The base station determines whether it is necessary to change the terminal_Cset and / or the measurement_Cset using the channel information for the measurement_Cset (S1160). If there is no need to change the base station continues the communication using the terminal and the previous terminal _Cset, otherwise the base station transmits the information about the changed terminal _Cset and / or measurement_Cset to the terminal (S1170). When the terminal receives the information on the changed terminal _Cset and / or measurement_Cset from the base station to communicate with the base station using the changed terminal _Cset (S1050, S1060 and S1180)

13A illustrates an example of receiving information on measurement_Cset according to an embodiment of the present invention. Referring to FIG. 13A, the terminal receives information on measurement_Cset from the base station (S1310). Thereafter, when necessary, the terminal transmits channel information on the measurement_Cset or a subset thereof to the base station (S1330). Information about the measurement_Cset may be transmitted to the UE through system information (SI), RRC message, L1 / L2 control signaling (eg, PDCCH) or MAC / RLC / PDCP PDU, but is not limited thereto. Information about the measurement_Cset may be signaled UE-specifically or UE group-specifically. The transmission of the information about the measurement_Cset may be transmitted through all CCs of the UE_Cset or only to the allocated primary CC or the reference DL CC in the UE_Cset.

In detail, the information about the measurement_Cset may be signaled semi-statically in a UE-specific manner using an RRC message. Although not limited thereto, the RRC message may relate to RRC disconnection, RRC connection request, RRC connection establishment, radio bearer establishment, radio bearer reset, RRC connection reset, and RRC connection reestablishment.

In addition, the information about the measurement_Cset may be delivered to the terminal through the L1 / L2 control signaling more dynamic than the RRC. Although not limited thereto, the following methods can be considered. The base station may transmit information on the measurement_Cset to the terminal using a dedicated channel. That is, information about measurement_Cset may be transmitted using a separate channel different from the PCFICH, PHICH or PDCCH of LTE. To this end, information about measurement_Cset may be transmitted to the control region (eg, behind the LTE PDCCH region) using the form of nCCE or nREG. When using a dedicated channel, it is possible to read only information about its own measurement_Cset for each terminal using CRC-protection (eg, CRC masking using RNTI).

Meanwhile, information about measurement_Cset may be transmitted through the existing PDCCH region without creating a separate dedicated channel. For example, information about measurement_Cset may be added to the DCI format. If the information on measurement_Cset is included only in the DCI format for the LTE-A terminal, there is no problem in backward compatibility because the DCI format of the LTE terminal is not affected. In addition, the information on the measurement_Cset may maintain the form of nCCE, but may limit the transmission location to be included in the common search space. Meanwhile, since the common search space is limited, the location may be limited to be transmitted only in the terminal-specific search space. In this case, the information about the measurement_Cset may be limited to be transmitted in a specific area (eg, the first or last part) of the terminal-specific search space. In this case, transmission of information about measurement_Cset may be a problem in the backward support of the LTE terminal, so that it may be transmitted only in the component carrier for LTE-A. However, when the search space of the existing PDCCH is expanded, information about measurement_Cset may be transmitted even by a component carrier supporting backward LTE.

FIG. 13B illustrates an example of transmitting channel information when duplicated information on measurement_Cset is received according to an embodiment of the present invention. If information on measurement_Cset is received in duplicate, the information on measurement_Cset may be the same or different. When the terminal receives duplicate information on the measurement_Cset, the terminal may apply the terminal-specific information in preference to the terminal-group common or cell-common information. In addition, the terminal may apply the information received by a specific method in preference to the information received by another method. Referring to FIG. 13B, the UE semi-statically receives information about measurement_Cset_1 through an RRC message (S1310) and sets its measurement_Cset to measurement_Cset_1 (S1312). Thereafter, the UE dynamically receives information about measurement_Cset_2 through L1 / L2 control signaling (eg, DCI format of PDCCH, separate dedicated physical control channel) (S1320), and then measures its measurement_Cset. Reset to _Cset_2 (S1322). That is, when the semi-static information and the dynamic information are repeatedly received, the semi-static information may be overridden with the dynamic information. Thereafter, the terminal transmits channel information on the measurement_Cset_2 or a subset thereof to the base station when necessary (S1330).

14 illustrates a base station and a terminal that can be applied to an embodiment in the present invention.

Referring to FIG. 14, a wireless communication system includes a base station (BS) 110 and a terminal (UE) 120. In downlink, the transmitter is part of the base station 110 and the receiver is part of the terminal 120. In uplink, the transmitter is part of the terminal 120 and the receiver is part of the base station 110. Base station 110 includes a processor 112, a memory 114, and a radio frequency (RF) unit 116. The processor 112 may be configured to implement the procedures and / or methods proposed in the present invention. The memory 114 is connected to the processor 112 and stores various information related to the operation of the processor 112. The RF unit 116 is connected with the processor 112 and transmits and / or receives a radio signal. The terminal 120 includes a processor 122, a memory 124, and an RF unit 126. The processor 122 may be configured to implement the procedures and / or methods proposed by the present invention. The memory 124 is connected with the processor 122 and stores various information related to the operation of the processor 122. The RF unit 126 is connected with the processor 122 and transmits and / or receives a radio signal. The base station 110 and / or the terminal 120 may have a single antenna or multiple antennas.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. 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 obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

In this document, the embodiments of the present invention have been mainly described with reference to the data transmission / reception relationship between the terminal and the base station. The specific operation described herein as being performed by the base station may be performed by its upper node, in some cases. That is, it is apparent that various operations performed for communication with a terminal in a network including a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A base station may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. In addition, the terminal may be replaced with terms such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), and the like.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

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 of the invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

The present invention can be applied to a multi-carrier system. Specifically, the present invention can be applied to an apparatus and method for measuring channel conditions in a multi-carrier system.

Claims (14)

In a wireless communication system supporting carrier aggregation, a method for a terminal to transmit channel information to a base station,
Identifying a plurality of component carriers used in the base station;
Identifying a first set of component carriers and a second set of component carriers from the plurality of component carriers;
Communicating with the base station using the first set of component carriers; And
And transmitting channel information on the second set of component carriers to the base station when a predetermined condition is satisfied. The method of claim 1,
The information for identifying the first component carrier set and the second component carrier set is signaled through a Radio Resource Control (RRC) message. The method of claim 1,
The information for identifying the first component carrier set and the second component carrier set is transmitted through a downlink control channel. The method of claim 1,
The predetermined condition is satisfied when the channel information for the second set of component carriers is requested from the base station. The method of claim 1,
And the predetermined condition is satisfied when communication using the first component carrier set does not satisfy a criterion. The method of claim 1,
The channel information on the second component carrier set includes Channel Quality Indicator (CQI), Precoding Matrix Index (PMI), Rank Information (RI), Sounding Reference Signal (SRS), Receive Signal Strength Indicator (RSSI), and Reference Signal (RSRP). Channel information transmission method characterized in that the transmission through Received Power (RS) or Reference Signal Received Quality (RSRQ). The method of claim 1,
And after receiving the channel information, receiving change information on at least a portion of the first component carrier set and the second component carrier set from the base station. A radio frequency (RF) unit configured to transmit and receive a radio signal with a base station;
A memory for storing information transmitted and received with the base station and parameters necessary for the operation of the terminal; And
A processor coupled to the RF unit and the memory, the processor configured to control the RF unit and the memory, wherein the processor includes:
Identifying a plurality of component carriers used in the base station;
Identifying a first set of component carriers and a second set of component carriers from the plurality of component carriers;
Communicating with the base station using the first set of component carriers; And
And transmitting a channel information on the second set of component carriers to the base station when a predetermined condition is satisfied. The method of claim 8,
And information for identifying the first component carrier set and the second component carrier set is signaled through a Radio Resource Control (RRC) message. The method of claim 8,
And the information for identifying the first component carrier set and the second component carrier set is transmitted through a downlink control channel. The method of claim 8,
The predetermined condition is satisfied when the channel information for the second component carrier set is requested from the base station. The method of claim 8,
Wherein the predetermined condition is satisfied when communication using the first component carrier set does not satisfy a criterion. The method of claim 8,
The channel information on the second component carrier set includes Channel Quality Indicator (CQI), Precoding Matrix Index (PMI), Rank Information (RI), Sounding Reference Signal (SRS), Receive Signal Strength Indicator (RSSI), and Reference Signal (RSRP). Terminal, characterized in that transmitted through Received Power (RS) or Reference Signal Received Quality (RSRQ). The method of claim 8,
And after receiving the channel information, receiving change information on at least a portion of the first component carrier set and the second component carrier set from the base station.

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