WO2012105766A2 - 무선 통신 시스템에서 셀간 간섭 조정 방법 및 장치 - Google Patents
무선 통신 시스템에서 셀간 간섭 조정 방법 및 장치 Download PDFInfo
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- WO2012105766A2 WO2012105766A2 PCT/KR2012/000641 KR2012000641W WO2012105766A2 WO 2012105766 A2 WO2012105766 A2 WO 2012105766A2 KR 2012000641 W KR2012000641 W KR 2012000641W WO 2012105766 A2 WO2012105766 A2 WO 2012105766A2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
- H04W16/04—Traffic adaptive resource partitioning
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0023—Interference mitigation or co-ordination
- H04J11/005—Interference mitigation or co-ordination of intercell interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
- H04L5/0035—Resource allocation in a cooperative multipoint environment
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0058—Allocation criteria
- H04L5/0073—Allocation arrangements that take into account other cell interferences
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0091—Signaling for the administration of the divided path
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W24/00—Supervisory, monitoring or testing arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/12—Wireless traffic scheduling
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/27—Control channels or signalling for resource management between access points
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
- H04W72/541—Allocation or scheduling criteria for wireless resources based on quality criteria using the level of interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0078—Timing of allocation
- H04L5/0085—Timing of allocation when channel conditions change
Definitions
- the following description relates to a wireless communication system, and more particularly, to a method and apparatus for performing inter-cell interference coordination in a wireless communication system.
- heterogeneous network refers to a network in which the macro base station 110 and the micro base stations 121 and 122 coexist even with the same radio access technology (RAT).
- RAT radio access technology
- the macro base station 110 has a wide coverage and high transmit power, and means a general base station of a wireless communication system.
- the macro base station 110 may be referred to as a macro cell.
- the micro base stations 121 and 122 may be referred to as, for example, a micro cell, a pico cell, a femto cell, a home eNB (HeNB), a relay, or the like. It may be.
- the micro base stations 121 and 122 are small versions of the macro base station 110 and may operate independently while performing most of the functions of the macro base station, and may be installed in an area covered by the macro base station or not covered by the macro base station. A base station of the non-overlay type.
- the micro base stations 121 and 122 may accommodate fewer terminals with narrower coverage and lower transmit power than the macro base station 110.
- the terminal 131 may be directly served by the macro base station 110 (hereinafter referred to as a macro-terminal), and the terminal 132 may be served by the micro base station 122 (hereinafter referred to as a micro-terminal). In some cases, the terminal 132 existing within the coverage of the micro base station 122 may be served from the macro base station 110.
- the micro base station may be classified into two types according to the access restriction of the terminal.
- the first type is a closed subscriber group (CSG) micro base station
- the second type is an open access (OA) or open subscriber group (OSC) micro base station.
- CSG micro base station may serve only authorized specific terminals
- OSG micro base station may serve all terminals without a separate access restriction.
- interference may occur in the downlink signal from the macro base station received by the macro terminal due to the strong downlink signal from the micro base station.
- the terminal served by the micro base station may receive strong interference due to the downlink signal of the macro base station.
- inter-cell interference coordination Inter- Cell Interference Coordination (ICIC) may be performed.
- ICIC may be performed on time resources or frequency resources. For example, one cell may inform the neighbor cell (s) of the magnitude of its downlink / uplink interference (or transmit power) in a particular frequency domain. Alternatively, one cell may inform the neighbor cell (s) of a time domain in which it does not perform downlink / uplink scheduling.
- ICIC on frequency resources is defined to be applied without any time resource (ie, all time resources), and ICIC on time resources without any frequency resource (ie, all frequencies). On a resource). Therefore, when the ICIC on the time resource and the ICIC on the frequency resource are applied at the same time, a problem may occur in which the time and frequency resource to which the ICIC is applied cannot be specified.
- the method for performing inter-cell interference coordination (ICIC) in a wireless communication system receives a second cell from the first cell; The second cell asserting validity of the frequency domain ICIC information of the first cell based on the time domain ICIC information of the first cell; And performing, by the second cell, uplink or downlink scheduling based on the result of the assumption.
- ICIC inter-cell interference coordination
- a method for performing inter-cell interference coordination (ICIC) in a wireless communication system wherein a first cell is time-domain ICIC information of the first cell and the first cell Transmitting the frequency domain ICIC information of the second cell; Predicting a result of the hypothesis of the second cell about the validity of the frequency domain ICIC information of the first cell based on the time domain ICIC information of the first cell; And performing, by the first cell, uplink or downlink scheduling based on the prediction result.
- ICIC inter-cell interference coordination
- a base station of a second cell for performing inter-cell interference coordination (ICIC) in a wireless communication system includes a transmission / reception module for transmitting and receiving a signal with a first cell; And a processor controlling the base station including the transmission and reception module; The processor is configured to receive time domain ICIC information of the first cell and frequency domain ICIC information of the first cell from the first cell through the transmit / receive module; Associating validity of the frequency domain ICIC information of the first cell based on the time domain ICIC information of the first cell; The uplink or downlink scheduling of the second cell may be performed based on the result of the assumption.
- ICIC inter-cell interference coordination
- a base station of a first cell for performing inter-cell interference coordination (ICIC) in a wireless communication system includes a transmission / reception module for transmitting and receiving a signal with a second cell; And a processor controlling the base station including the transmission and reception module; The processor is configured to transmit time domain ICIC information of the first cell and frequency domain ICIC information of the first cell to the second cell through the transmission / reception module; Predict a result of the hypothesis of the second cell about the validity of the frequency domain ICIC information of the first cell based on the time domain ICIC information of the first cell; The uplink or downlink scheduling of the first cell may be performed based on the prediction result.
- ICIC inter-cell interference coordination
- the time domain ICIC information of the first cell may include silent subframe configuration information of the first cell.
- the hypothesizing may include assuming that the frequency domain ICIC information of the first cell is invalid in downlink subframe n in which the first cell is configured as a silent subframe.
- the frequency domain ICIC information that is assumed to be invalid may be Relative Narrowband Transmission Power (RNTP) of the first cell.
- RNTP Relative Narrowband Transmission Power
- the hypothesizing step assumes that the frequency domain ICIC information of the first cell is invalid in an uplink subframe n + k corresponding to a downlink subframe n set by the first cell as a silent subframe. It may include the step.
- the frequency domain ICIC information which is assumed to be invalid, may include one or more of an uplink interference overhead indication (IOI) or an uplink high interference indication (HII) of the first cell.
- IOI uplink interference overhead indication
- HAI uplink high interference indication
- Scheduling information for uplink transmission in the uplink subframe n + k may be transmitted in the downlink subframe n.
- the hypothesizing may include assuming that the frequency domain ICIC information of the first cell is valid in a subframe in which the first cell is not set as a silent subframe.
- the method may further include determining a time resource and a frequency resource used for interference measurement in the second cell based on the result of the hypothesizing.
- a resource region in which the frequency domain ICIC information of the first cell is valid may be determined on a time resource and a frequency resource.
- the silent subframe may be a subframe in which the first cell is set to Almost Blank Subframe (ABS).
- ABS Almost Blank Subframe
- the present invention it is possible to determine whether to apply frequency resource ICIC information based on time resource ICIC information so that the ICIC operation can be performed correctly and efficiently by clearly specifying the time resource and frequency resource location to which ICIC is applied. Can be provided.
- FIG. 1 is a diagram illustrating a heterogeneous network wireless communication system 100 including a macro base station and a micro base station.
- FIG. 2 is a diagram illustrating a structure of a downlink radio frame.
- 3 is a diagram illustrating a resource grid in a downlink slot.
- FIG. 4 is a diagram illustrating a structure of a downlink subframe.
- 5 is a diagram illustrating a structure of an uplink subframe.
- FIG. 6 is a configuration diagram of a wireless communication system having multiple antennas.
- FIG. 7 is a diagram illustrating an example of the present invention for ICIC operation when ICIC information on time and frequency resources of one cell is transferred to another cell.
- FIG. 8 is a diagram illustrating an example of the present invention for the ICIC operation when the ICIC information for the time resource of one cell and the ICIC information for the frequency resource of another cell are exchanged with each other.
- FIG. 9 is a diagram illustrating a configuration of a base station apparatus according to the present invention.
- each component or feature may be considered to be optional unless otherwise stated.
- Each component or feature may be embodied in a form that is not combined with other components or features.
- some components and / or features may be combined to form an embodiment of the present invention.
- the order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.
- the base station has a meaning as a terminal node of the network that directly communicates with the terminal.
- the specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases.
- a 'base station (BS)' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point (AP), and the like.
- the repeater may be replaced by terms such as relay node (RN) and relay station (RS).
- the term “terminal” may be replaced with terms such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), a subscriber station (SS), and the like.
- Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802 system, 3GPP system, 3GPP LTE and LTE-Advanced (LTE-A) system and 3GPP2 system. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.
- CDMA code division multiple access
- FDMA frequency division multiple access
- TDMA time division multiple access
- OFDMA orthogonal frequency division multiple access
- SC-FDMA single carrier frequency division multiple access
- 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).
- GSM Global System for Mobile communications
- GPRS General Packet Radio Service
- EDGE Enhanced Data Rates for GSM Evolution
- 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).
- UTRA is part of the Universal Mobile Telecommunications System (UMTS).
- 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink.
- LTE-A Advanced
- WiMAX can be described by the IEEE 802.16e standard (WirelessMAN-OFDMA Reference System) and the advanced IEEE 802.16m standard (WirelessMAN-OFDMA Advanced system). For clarity, the following description focuses on 3GPP LTE and 3GPP LTE-A systems, but the technical spirit of the present invention is not limited thereto.
- a structure of a downlink radio frame will be described with reference to FIG. 2.
- uplink / downlink data packet transmission is performed in units of subframes, and one subframe is defined as a predetermined time interval including a plurality of OFDM symbols.
- the 3GPP LTE standard supports a type 1 radio frame structure applicable to frequency division duplex (FDD) and a type 2 radio frame structure applicable to time division duplex (TDD).
- the downlink radio frame consists of 10 subframes, and one subframe consists of two slots in the time domain.
- the time it takes for one subframe to be transmitted is called a transmission time interval (TTI).
- TTI transmission time interval
- one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.
- One slot includes a plurality of OFDM symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain.
- RBs resource blocks
- a resource block (RB) is a resource allocation unit and may include a plurality of consecutive subcarriers in one slot.
- the number of OFDM symbols included in one slot may vary depending on the configuration of a cyclic prefix (CP).
- CP has an extended CP (normal CP) and a normal CP (normal CP).
- normal CP normal CP
- the number of OFDM symbols included in one slot may be seven.
- the OFDM symbol is configured by an extended CP, since the length of one OFDM symbol is increased, the number of OFDM symbols included in one slot is smaller than that of the normal CP.
- the number of OFDM symbols included in one slot may be six. If the channel state is unstable, such as when the terminal moves at a high speed, an extended CP may be used to further reduce intersymbol interference.
- one subframe includes 14 OFDM symbols.
- the first two or three OFDM symbols of each subframe may be allocated to a physical downlink control channel (PDCCH), and the remaining OFDM symbols may be allocated to a physical downlink shared channel (PDSCH).
- PDCCH physical downlink control channel
- PDSCH physical downlink shared channel
- Type 2B is a diagram illustrating the structure of a type 2 radio frame.
- Type 2 radio frames consist of two half frames, each of which has five subframes, a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS).
- DwPTS downlink pilot time slot
- GP guard period
- UpPTS uplink pilot time slot
- One subframe consists of two slots.
- DwPTS is used for initial cell search, synchronization or channel estimation at the terminal.
- UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal.
- the guard period is a period for removing interference generated in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.
- one subframe consists of two slots regardless of the radio frame type.
- the structure of the radio frame is only an example, and the number of subframes included in the radio frame or the number of slots included in the subframe and the number of symbols included in the slot may be variously changed.
- One downlink slot includes seven OFDM symbols in the time domain and one resource block (RB) is shown to include 12 subcarriers in the frequency domain, but the present invention is not limited thereto.
- one slot includes 7 OFDM symbols in the case of a general cyclic prefix (CP), but one slot may include 6 OFDM symbols in the case of an extended-CP (CP).
- CP general cyclic prefix
- Each element on the resource grid is called a resource element.
- One resource block includes 12 ⁇ 7 resource elements.
- the number of N DLs of resource blocks included in the downlink slot depends on the downlink transmission bandwidth.
- the structure of the uplink slot may be the same as the structure of the downlink slot.
- FIG. 4 is a diagram illustrating a structure of a downlink subframe.
- Up to three OFDM symbols at the front of the first slot in one subframe correspond to a control region to which a control channel is allocated.
- the remaining OFDM symbols correspond to data regions to which a physical downlink shared channel (PDSCH) is allocated.
- Downlink control channels used in the 3GPP LTE system include, for example, a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), and a Physical HARQ Indicator Channel.
- PCFICH Physical Hybrid automatic repeat request Indicator Channel
- the PCFICH is transmitted in the first OFDM symbol of a subframe and includes information on the number of OFDM symbols used for control channel transmission in the subframe.
- the PHICH includes a HARQ ACK / NACK signal as a response of uplink transmission.
- Control information transmitted through the PDCCH is referred to as downlink control information (DCI).
- DCI includes uplink or downlink scheduling information or an uplink transmit power control command for a certain terminal group.
- the PDCCH is a resource allocation and transmission format of the downlink shared channel (DL-SCH), resource allocation information of the uplink shared channel (UL-SCH), paging information of the paging channel (PCH), system information on the DL-SCH, on the PDSCH Resource allocation of upper layer control messages such as random access responses transmitted to the network, a set of transmit power control commands for individual terminals in an arbitrary terminal group, transmission power control information, and activation of voice over IP (VoIP) And the like.
- a plurality of PDCCHs may be transmitted in the control region.
- the UE may monitor the plurality of PDCCHs.
- the PDCCH is transmitted in an aggregation of one or more consecutive Control Channel Elements (CCEs).
- CCEs Control Channel Elements
- the CCE is a logical allocation unit used to provide a PDCCH at a coding rate based on the state of a radio channel.
- the CCE corresponds to a plurality of resource element groups.
- the format of the PDCCH and the number of available bits are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.
- the base station determines the PDCCH format according to the DCI transmitted to the terminal, and adds a cyclic redundancy check (CRC) to the control information.
- the CRC is masked with an identifier called a Radio Network Temporary Identifier (RNTI) according to the owner or purpose of the PDCCH.
- RNTI Radio Network Temporary Identifier
- the cell-RNTI (C-RNTI) identifier of the terminal may be masked to the CRC.
- a paging indicator identifier P-RNTI
- the PDCCH is for system information (more specifically, system information block (SIB))
- SI-RNTI system information RNTI
- RA-RNTI Random Access-RNTI
- RA-RNTI may be masked to the CRC to indicate a random access response that is a response to the transmission of the random access preamble of the terminal.
- the uplink subframe may be divided into a control region and a data region in the frequency domain.
- a physical uplink control channel (PUCCH) including uplink control information is allocated to the control region.
- a physical uplink shared channel (PUSCH) including user data is allocated.
- PUCCH physical uplink control channel
- PUSCH physical uplink shared channel
- one UE does not simultaneously transmit a PUCCH and a PUSCH.
- PUCCH for one UE is allocated to an RB pair in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers for two slots. This is called a resource block pair allocated to the PUCCH is frequency-hopped at the slot boundary.
- FIG. 6 is a configuration diagram of a wireless communication system having multiple antennas.
- the theoretical ratio is proportional to the number of antennas, unlike when a plurality of antennas are used only in a transmitter or a receiver.
- Channel transmission capacity is increased. Therefore, the transmission rate can be improved and the frequency efficiency can be significantly improved.
- the transmission rate can theoretically increase as the rate of increase rate R i multiplied by the maximum transmission rate R o when using a single antenna.
- a transmission rate four times higher than a single antenna system may be theoretically obtained. Since the theoretical capacity increase of multi-antenna systems was proved in the mid 90's, various techniques to actively lead to the actual data rate improvement have been actively studied. In addition, some technologies are already being reflected in various wireless communication standards such as 3G mobile communication and next generation WLAN.
- the research trends related to multi-antennas to date include the study of information theory aspects related to the calculation of multi-antenna communication capacity in various channel environments and multi-access environments, the study of wireless channel measurement and model derivation of multi-antenna systems, improvement of transmission reliability, and improvement of transmission rate. Research is being actively conducted from various viewpoints, such as research on space-time signal processing technology.
- the transmission signal when there are N T transmit antennas, the maximum information that can be transmitted is N T.
- the transmission information may be expressed as follows.
- Each transmission information The transmit power may be different.
- Each transmit power In this case, the transmission information whose transmission power is adjusted may be expressed as follows.
- Weighting matrix N T transmitted signals actually applied by applying Consider the case where is configured.
- Weighting matrix Plays a role in properly distributing transmission information to each antenna according to a transmission channel situation.
- Vector It can be expressed as follows.
- Received signal is received signal of each antenna when there are N R receiving antennas Can be expressed as a vector as
- channels may be divided according to transmit / receive antenna indexes. From the transmit antenna j to the channel through the receive antenna i It is indicated by. Note that in the order of the index, the receiving antenna index is first, and the index of the transmitting antenna is later.
- FIG. 6 (b) is a diagram illustrating a channel from the N T transmit antennas to the receive antenna i .
- the channels may be bundled and displayed in vector and matrix form.
- a channel arriving from a total of N T transmit antennas to a receive antenna i may be represented as follows.
- AWGN Additive White Gaussian Noise
- the received signal may be expressed as follows through the above-described mathematical modeling.
- the channel matrix indicating the channel state The number of rows and columns of is determined by the number of transmit and receive antennas.
- Channel matrix The number of rows is equal to the number of receive antennas N R
- the number of columns is equal to the number of transmit antennas N T. That is, the channel matrix The matrix is N R ⁇ N T.
- the rank of a matrix is defined as the minimum number of rows or columns that are independent of each other. Thus, the rank of the matrix cannot be greater than the number of rows or columns.
- Channel matrix Rank of ( ) Is limited to
- rank may be defined as the number of nonzero eigenvalues when the matrix is eigenvalue decomposition.
- another definition of rank may be defined as the number of nonzero singular values when singular value decomposition is performed. Therefore, the physical meaning of rank in the channel matrix is the maximum number that can send different information in a given channel.
- CoMP transmission and reception techniques also referred to as co-MIMO, collaborative MIMO, network MIMO, etc.
- CoMP technology can increase the performance of the terminal located in the cell-edge (cell-edge) and increase the average sector throughput (throughput).
- inter-cell interference may reduce performance and average sector yield of a terminal located in a cell boundary.
- ICI inter-cell interference
- existing LTE system is located in a cell-boundary in an environment that is limited by interference by using a simple passive technique such as fractional frequency reuse (FFR) through UE-specific power control.
- FFR fractional frequency reuse
- the method for the terminal to have a proper yield performance has been applied.
- CoMP transmission scheme may be applied.
- CoMP schemes applicable to downlink can be classified into joint processing (JP) techniques and coordinated scheduling / beamforming (CS / CB) techniques.
- JP joint processing
- CS / CB coordinated scheduling / beamforming
- the JP technique may use data at each point (base station) of the CoMP cooperative unit.
- CoMP cooperative unit means a set of base stations used in a cooperative transmission scheme.
- the JP technique can be classified into a joint transmission technique and a dynamic cell selection technique.
- the joint transmission technique refers to a technique in which a PDSCH is transmitted from a plurality of points (part or all of CoMP cooperative units) at a time. That is, data transmitted to a single terminal may be simultaneously transmitted from a plurality of transmission points. According to the joint transmission technique, the quality of a received signal may be improved coherently or non-coherently, and may also actively cancel interference with other terminals.
- Dynamic cell selection scheme refers to a scheme in which PDSCH is transmitted from one point (of CoMP cooperative units) at a time. That is, data transmitted to a single terminal at a specific time point is transmitted from one point, and other points in the cooperative unit do not transmit data to the corresponding terminal at that time point, and a point for transmitting data to the corresponding terminal is dynamically selected. Can be.
- CoMP cooperative units may cooperatively perform beamforming of data transmission for a single terminal.
- data is transmitted only in the serving cell, but user scheduling / beamforming may be determined by coordination of cells of a corresponding CoMP cooperative unit.
- coordinated multi-point reception means receiving a signal transmitted by coordination of a plurality of geographically separated points.
- CoMP schemes applicable to uplink may be classified into joint reception (JR) and coordinated scheduling / beamforming (CS / CB).
- the JR scheme means that a signal transmitted through a PUSCH is received at a plurality of reception points.
- a PUSCH is received only at one point, but user scheduling / beamforming is determined by coordination of cells of a CoMP cooperative unit. It means to be.
- the terminal can be jointly supported data from a multi-cell base station.
- each base station can improve the performance of the system by simultaneously supporting one or more terminals using the same radio frequency resource (Same Radio Frequency Resource).
- the base station may perform a space division multiple access (SDMA) method based on channel state information between the base station and the terminal.
- SDMA space division multiple access
- a serving base station and one or more cooperating base stations are connected to a scheduler through a backbone network.
- the scheduler may operate by receiving feedback of channel information about channel states between respective terminals and the cooperative base stations measured by each base station through the backbone network.
- the scheduler may schedule information for collaborative MIMO operation for the serving base station and one or more cooperating base stations. That is, the scheduler may directly give an indication of the cooperative MIMO operation to each base station.
- the CoMP system may be referred to as operating as a virtual MIMO system by combining a plurality of cells into one group, and basically, a communication technique of a MIMO system using multiple antennas may be applied.
- the MIMO scheme may be divided into an open-loop scheme and a closed-loop scheme.
- the open-loop MIMO scheme means that the transmitter performs MIMO transmission without feedback of the channel state information from the MIMO receiver.
- the closed-loop MIMO scheme means that the transmitter performs MIMO transmission by receiving the channel state information from the MIMO receiver.
- each of the transmitter and the receiver may perform beamforming based on channel state information in order to obtain a multiplexing gain of the MIMO transmit antenna.
- the transmitting end eg, the base station
- the channel state information (CSI) fed back may include a rank indicator (RI), a precoding matrix index (PMI), and a channel quality indicator (CQI).
- RI rank indicator
- PMI precoding matrix index
- CQI channel quality indicator
- RI is information about channel rank.
- the rank of the channel means the maximum number of layers (or streams) that can transmit different information through the same time-frequency resource. Since the rank value is determined primarily by the long term fading of the channel, it can be fed back over a generally longer period (ie less frequently) compared to PMI and CQI.
- PMI is information about a precoding matrix used for transmission from a transmitter and is a value reflecting spatial characteristics of a channel.
- Precoding means mapping a transmission layer to a transmission antenna, and a layer-antenna mapping relationship may be determined by a precoding matrix.
- the PMI corresponds to a precoding matrix index of a base station preferred by the terminal based on a metric such as a signal-to-interference plus noise ratio (SINR).
- SINR signal-to-interference plus noise ratio
- CQI is information indicating channel quality or channel strength.
- CQI may be expressed as a predetermined Modulation and Coding Scheme (MCS) combination. That is, the fed back CQI index indicates a corresponding modulation scheme and code rate.
- MCS Modulation and Coding Scheme
- the CQI is a value that reflects the received SINR that can be obtained when the base station configures the spatial channel using the PMI.
- MU-MIMO multiuser-MIMO
- LTE-A systems systems that support extended antenna configurations (eg, LTE-A systems) are considering acquiring additional multiuser diversity using a multiuser-MIMO (MU-MIMO) scheme.
- MU-MIMO multiuser-MIMO
- the precoding information fed back by the receiver may be indicated by a combination of two PMIs.
- One of the two PMIs (first PMI) has the property of long term and / or wideband and may be referred to as W1.
- the other one of the two PMIs (second PMI) has a short term and / or subband attribute and may be referred to as W2.
- W1 reflects the frequency and / or time average characteristics of the channel.
- W1 reflects the characteristics of a long term channel in time, reflects the characteristics of a wideband channel in frequency, or reflects the characteristics of a wideband channel in frequency while being long term in time. It can be defined as.
- W1 is referred to as channel state information (or long term-wideband PMI) of long term-wideband attribute.
- W2 reflects a relatively instantaneous channel characteristic compared to W1.
- W2 is a channel that reflects the characteristics of a short term channel in time, reflects the characteristics of a subband channel in frequency, or reflects the characteristics of a subband channel in frequency while being short term in time. It can be defined as status information.
- W1 is referred to as channel state information (or short-term subband PMI) of short-term-subband attribute.
- the precoding matrices representing the channel information of each attribute are There is a need to construct separate codebooks that are constructed (ie, the first codebook for W1 and the second codebook for W2).
- the form of the codebook configured as described above may be referred to as a hierarchical codebook.
- determining a codebook to be finally used using the hierarchical codebook may be referred to as hierarchical codebook transformation.
- a codebook may be converted using a long term covariance matrix of a channel as shown in Equation 12 below.
- W1 long-term wide-band PMI
- a codebook eg, a first codebook
- W2 short-term subband PMI
- W1 corresponds to a precoding matrix included in the first codebook that reflects channel information of the long-term-band attribute.
- W2 short-term subband PMI
- W2 represents a codeword constituting a codebook (for example, a second codebook) made to reflect channel information of short-term-subband attributes. That is, W2 corresponds to a precoding matrix included in the second codebook reflecting channel information of short-term subband attributes.
- W represents the codeword of the converted final codebook.
- norm (A) means a matrix in which norm is normalized to 1 for each column of the matrix A.
- W1 and W2 may have a structure as shown in Equation 13 below.
- W1 may be defined as a block diagonal matrix, and each block is the same matrix X i .
- One block X i may be defined as a matrix of size (Nt / 2) ⁇ M. Where Nt is the number of transmit antennas.
- the M value can be determined so that the feedback overhead does not increase too much while maintaining proper feedback accuracy.
- W2 Represents a predetermined phase value, respectively.
- 1 ⁇ k, l, m ⁇ M and k, l, m are integers, respectively.
- the codebook structure shown in Equation 13 above uses a cross-polarized (X-pol) antenna configuration, where the spacing between antennas is dense (typically, the distance between adjacent antennas is less than half the signal wavelength). It is a structure designed to reflect the correlation characteristics of the channel occurring in the case).
- the cross-polar antenna configuration can be shown in Table 1 below.
- the 8Tx cross-polar antenna configuration may be expressed as being composed of two antenna groups having polarities perpendicular to each other.
- Antennas of antenna group 1 (antennas 1, 2, 3, 4) have the same polarity (eg vertical polarization) and antennas of antenna group 2 (antennas 5, 6, 7, 8) have the same polarity ( For example, it may have horizontal polarization.
- the two antenna groups are co-located.
- antennas 1 and 5 may be installed at the same position
- antennas 2 and 6 may be installed at the same position
- antennas 3 and 7 may be installed at the same position
- antennas 2 and 8 may be installed at the same position.
- the antennas in one antenna group have the same polarity as a uniform linear array (ULA), and the correlation between antennas in one antenna group has a linear phase increment characteristic.
- the correlation between antenna groups has a phase rotated characteristic.
- Equation 14 shows an example in which the final codeword W is determined by multiplying the W1 codeword by the rank 1 and the W2 codeword.
- Equation 14 the final codeword is represented by a vector of Nt ⁇ 1, and a higher vector ( ) And subvector ( Structured as two vectors of).
- Parent vector ) Represents the correlation characteristics of the horizontal polarity antenna group of the cross polarity antenna
- the lower vector ( ) Represents the correlation characteristics of the vertical polar antenna group.
- single-cell MU-MIMO can be enabled by using high accuracy channel feedback, and similarly, high accuracy channel feedback is required in CoMP operation.
- CoMP JT operation since several base stations cooperatively transmit the same data to a specific UE, it may theoretically be regarded as a MIMO system in which a plurality of antennas are geographically dispersed. That is, even in the case of MU-MIMO operation in CoMP JT, as in single-cell MU-MIMO, high level of channel information accuracy is required to avoid co-scheduling between UEs.
- CoMP CB operation sophisticated channel information is required to avoid interference caused by the neighboring cell to the serving cell.
- Inter-cell interference coordination (ICIC)
- inter-cell interference coordination may be applied.
- Existing ICIC can be applied for frequency resources or for time resources.
- ICIC Interference Overhead Indication
- IOI UL Interference Overhead Indication
- UL HII UL HII
- the RNTP is information indicating downlink transmission power used by a cell transmitting an ICIC message in a specific frequency subregion.
- setting the RNTP field for a specific frequency subregion to a first value may mean that downlink transmission power of the corresponding cell does not exceed a predetermined threshold in the corresponding frequency subregion. Can be.
- setting the RNTP field for a specific frequency subregion to a second value may mean that the cell cannot promise downlink transmission power in the frequency subregion. .
- the value of the RNTP field is 0, the downlink transmission power of the cell in the corresponding frequency sub-region may be considered low.
- the value of the RNTP field is 1, the corresponding cell in the corresponding frequency sub-domain may be considered.
- the downlink transmission power cannot be regarded as low.
- the UL IOI is information indicating the amount of uplink interference experienced (or received) by a cell transmitting an ICIC message in a specific frequency subdomain. For example, setting the IOI field for a specific frequency subregion to a value corresponding to a high interference amount may mean that the cell is experiencing strong uplink interference in the frequency subregion.
- the cell receiving the ICIC message may schedule a terminal using a low uplink transmission power among terminals served by the cell in a frequency sub region corresponding to an IOI indicating strong uplink interference.
- the UEs since the UEs perform uplink transmission with low transmission power in the frequency sub-region corresponding to the IOI indicating strong uplink interference, the uplink interference experienced by the neighbor cell (that is, the cell transmitting the ICIC message) can be alleviated. Can be.
- the UL HII is information indicating the degree of interference (or uplink interference sensitivity) that an uplink transmission in a cell transmitting an ICIC message can cause for a corresponding frequency subregion. For example, when the HII field is set to a first value (eg, 1) for a specific frequency subregion, a cell transmitting an ICIC message may schedule a terminal of a strong uplink transmission power for that frequency subregion. It can mean that there is a possibility. On the other hand, when the HII field is set to a second value (for example, 0) for a specific frequency subregion, it is likely that a cell transmitting an ICIC message schedules a terminal of weak uplink transmission power for the corresponding frequency subregion. It can mean that there is.
- a first value eg, 1
- a cell transmitting an ICIC message may schedule a terminal of a strong uplink transmission power for that frequency subregion. It can mean that there is a possibility.
- a second value for example, 0
- the cell receiving the ICIC message preferentially schedules the UE in the frequency sub region in which the HII is set to the second value (for example, 0) and the frequency sub in which the HII is set to the first value (for example, 1). In the region, by scheduling terminals that can operate well even with strong interference, interference from a cell that transmits an ICIC message can be avoided.
- a given entire time domain is divided into one or more sub-domains (eg, subframe units) on frequency, and each A method of exchanging between cells whether or not silencing the time sub-region is defined.
- the cell transmitting the ICIC message may transmit information indicating that silencing is performed in a specific subframe to neighboring cells, and do not schedule PDSCH or PUSCH in the subframe.
- the cell receiving the ICIC message may schedule uplink and / or downlink transmission for the terminal on a subframe in which silencing is performed in the cell which transmitted the ICIC message.
- Silence may refer to an operation in which a specific cell does not perform most signal transmission on uplink and downlink (or 0 or weak power transmission is performed) in a specific subframe.
- a specific cell may configure a specific subframe as a multicast broadcast single frequency network (MBSFN) subframe.
- MBSFN multicast broadcast single frequency network
- a signal is transmitted only in the control region and no signal is transmitted in the data region.
- an interfering cell may set a specific subframe to an Almost Blank Subframe (ABS) or ABS-with-MBSFN.
- ABS Almost Blank Subframe
- ABS refers to a subframe in which only the CRS is transmitted in the control region and the data region of the downlink subframe, and other control information and data are not transmitted (or only weak power transmission is performed). However, even in ABS, downlink channels and downlink signals such as PBCH, PSS, and SSS may be transmitted. ABS-with-MBSFN means that the CRS of the data area is not transmitted in the above-described ABS. As described above, silencing may be performed in units of a specific subframe, and information indicating whether silencing is performed may be referred to as a silent subframe pattern.
- the silent subframe described in the embodiments of the present invention may be understood as a subframe in which no signal is transmitted or a subframe in which a signal of weak power is transmitted.
- the silent subframe is exemplarily described as a subframe in which no signal is transmitted.
- the principles described in the present invention may be equally applied. It is revealed.
- ICIC information (eg, RNTP, IOI, HII) for a frequency resource is applied to a specific frequency subregion in all subframes without an indication of which subframe is applied.
- ICIC information (e.g., a silent subframe pattern) for a time resource is defined to be applied to all frequency domains without an indication of which frequency domain to apply to. Therefore, when one cell transmits both the ICIC message for the frequency resource and the ICIC message for the time resource to neighboring cells, the time and frequency resource to which the ICIC operation is applied cannot be clearly specified.
- the present invention can specify a location on a time resource of another cell from a location on a time resource at which an ICIC operation of one cell is performed in consideration of a difference in subframe timing even when the subframe boundaries between cells are not identical.
- a location on a time resource of another cell from a location on a time resource at which an ICIC operation of one cell is performed in consideration of a difference in subframe timing even when the subframe boundaries between cells are not identical.
- a cell that determines and transmits a silent subframe pattern corresponds to an interfering cell (or an aggressor cell), and a cell that receives a silent subframe pattern of a neighboring cell is an interfering cell (or victim). cell).
- This embodiment relates to the ICIC operation of each cell when the silent subframe pattern and the RNTP information of one cell are applied together.
- a cell transmitting ICIC information (eg, RNTP, IOI, HII, and a silent subframe pattern) is called a first cell, and a cell receiving ICIC information is called a second cell.
- the first cell informs the second cell of information on its RNTP, IOI, HII, etc. while the first cell informs the second cell of the subframe pattern in which silencing is performed.
- the present invention is not limited thereto, and even when ICIC information of one cell is received in one or more neighboring cells, the principles described in the present invention may be applied in the same manner.
- FIG. 7 is a diagram illustrating an example of the present invention for ICIC operation when ICIC information on time and frequency resources of one cell is delivered to another cell.
- the first cell determines frequency resource ICIC information (eg, RNTP) and time resource ICIC information (eg, a silent subframe pattern), and removes the frequency resource and time resource ICIC information determined in step S720. Can transmit to 2 cells.
- frequency resource ICIC information eg, RNTP
- time resource ICIC information eg, a silent subframe pattern
- the second cell may assume validity of the frequency resource ICIC information based on the time resource ICIC information received from the first cell. For example, when the first cell indicates DL subframe n as a silent subframe, this means that there is no PDSCH transmission of the first cell in subframe n, and more specifically, in all frequency domains of subframe n. This means that there is no PDSCH transmission of the first cell. Therefore, in the subframe n, the downlink transmission power of the first cell is set very low in the entire frequency domain (that is, only the power according to the minimum signal transmission), so the downlink transmission of the first cell is determined based on a predetermined threshold. It is preferable to assume that the RNTP information indicating the relative strength of power has no meaning.
- the second cell may assume that there is no application of the RNTP indication of the first cell (or do not interpret the RNTP indication) in the DL subframe indicated by the first cell as the silent subframe.
- the second cell ignores the value of the RNTP field transmitted by the first cell for the silent subframe of the first cell and sets the RNTP value of the first cell to 0 for all frequency subregions (ie, Downlink transmission power may be lower than a predetermined threshold).
- the second cell may be regarded as validating the RNTP indication of the first cell only in subframe (s) in which the first cell is not set as a silent subframe.
- the second cell can freely perform downlink scheduling without considering intercell interference. (Step S730). Accordingly, the efficiency of resource utilization can be improved.
- the RNTP transmitted to the second cell is valid. It can be predicted not to perform (step S750). That is, the first cell anticipates that the second cell receiving the RNTP may cause high interference in downlink for all frequency resources regardless of the RNTP in the silent subframe of the first cell. Link scheduling may be performed (step S760).
- This embodiment relates to the ICIC operation of each cell when the silent subframe pattern and IOI / HII information of one cell are applied together. Since the present embodiment relates to uplink transmission, a timing relationship between uplink transmission and transmission of scheduling information therefor will be described first.
- PUSCH transmission in UL subframe n + k may be performed according to scheduling information (ie, UL grant information) received in DL subframe n.
- scheduling information ie, UL grant information
- the k value may be fixed to 4 in the case of the FDD system, and may be determined according to Tables 2 and 3 below in the TDD system.
- Table 2 shows configuration for an uplink subframe and a downlink subframe in a 3GPP LTE TDD system.
- D denotes a DL subframe
- U denotes a UL subframe
- S denotes a special subframe.
- the special subframe is a subframe including DwPTS, GP, and UpPTS described in FIG. 2.
- Table 3 shows a difference (ie, k) value of a PDCCH and a PUSCH transmission time point in a 3GPP LTE TDD system.
- the first cell determines frequency resource ICIC information (eg, IOI and / or HII) and time resource ICIC information (eg, a silent subframe pattern), and the frequency resource and time resource determined in step S720.
- ICIC information may be transmitted to the second cell.
- the second cell may assume validity of the frequency resource ICIC information based on the time resource ICIC information received from the first cell. First, from the time resource ICIC information, the second cell may assume as follows.
- DL subframe n is configured as a silent subframe
- there is no transmission of the PDCCH in subframe n and thus no PUSCH transmission in subframe n + k is performed.
- the second cell transmits the PUSCH in the UL subframe n + k without additional information. You will notice that it will not be performed.
- the second cell may assume the validity of the frequency resource ICIC information (IOI or HII) received together with the time resource ICIC information as follows.
- IOI and HII provided by the first cell to the second cell have no meaning at least for the UL subframe n + k. That is, the IOI of the first cell indicates the degree of uplink interference experienced by the first cell in a specific frequency subregion, and the HII of the first cell indicates the strong interference caused by the first cell in a specific frequency subdomain. Since the first cell does not perform uplink transmission in subframe n + k, the IOI or HII of the first cell becomes information that the second cell does not need to consider at all in subframe n + k.
- step S730 the case of IOI is demonstrated concretely.
- the second cell receives information that the first cell configures DL subframe n as a silent subframe, it may be assumed that the UL IOI of the first cell is not applied in the UL subframe n + k.
- the second cell ignores the IOI value transmitted by the first cell for subframe n + k and sets the IOI value of the first cell to 0 for all frequency sub-areas (that is, experienced by the first cell). Low uplink interference).
- the second cell may also consider the UL IOI information of the first cell to be valid only for the subframe n + k in which the subframe n is not set to the silent subframe.
- the request to reduce the inter-cell interference is a frequency sub-region (or the first cell is subjected to high uplink interference received through the UL IOI of the first cell). Also in the frequency subregion indicating that the first cell has set the subframe n as the silent subframe, the second cell may freely perform uplink scheduling without considering the intercell interference in the subframe n + k ( Step S740). Accordingly, the efficiency of resource utilization can be improved.
- the first cell is the second cell in the UL subframe n + k. It is possible to predict that the IOI sent to the user is invalid (step S750). That is, the first cell anticipates that the second cell receiving the UL IOI may cause high interference in uplink for all frequency resources regardless of the IOI of the first cell in the UL subframe n + k. Own uplink scheduling can be performed (step S760).
- the first cell can transmit to the second cell HII information indicating that it will cause high uplink interference in a specific frequency sub-domain along with information indicating that subframe n is set as a silent subframe. have.
- the second cell will not have the PUSCH transmission of the first cell in subframe n + k when subframe n is indicated as a silent subframe, so that the UL HII of the first cell is applied to subframe n + k. Can be assumed not to be.
- the second cell ignores the HII value transmitted by the first cell for subframe n + k and sets the HII value of the first cell to 0 for all frequency sub-areas (ie, caused by the first cell). May be overridden).
- the second cell may also consider the UL HII information of the first cell to be valid only for the subframe n + k in which the subframe n is not set to the silent subframe.
- the second cell may freely perform uplink scheduling without considering intercell interference in subframe n + k (step S740). Accordingly, the efficiency of resource utilization can be improved.
- the first cell even if the first cell indicates the degree of uplink interference caused by the UE for a specific frequency sub-region, if it configures the DL subframe n as a silent subframe, the first cell has its own in the UL subframe n + k. It can be predicted that the HII transmitted to this second cell is invalid (step S750). That is, the first cell anticipates that the second cell receiving the UL HII may cause high interference in uplink for all frequency resources regardless of the HII of the first cell in the UL subframe n + k. Own uplink scheduling can be performed (step S760).
- the present embodiment relates to resource determination for interference measurement when time resource ICIC information and frequency resource ICIC information of one cell are applied together.
- the interfering cell may change the transmit power in the time domain (eg, set up a silent subframe pattern), or change the transmit power in the frequency domain (eg, set up an RNTP).
- variable transmit power in the time / frequency domain of the interfering cell if the interfering cell performs interference measurements by averaging the interference over all resource regions, the result is interference for the entire frequency / time resource.
- Characteristic may be representative, but may not be used as an interference characteristic for a particular frequency / time resource. As such, if the sophisticated interference characteristics for a particular time / frequency resource cannot be determined, it is difficult to select an appropriate MCS for that particular time / frequency resource. For example, in order for a terminal to correctly calculate a CSI for a specific time / frequency resource region, interference measurement for the corresponding time / frequency resource region should be correctly performed.
- interference cells may be limited to a specific time / frequency resource region where the same (or similar) interference level is expected to perform interference measurement.
- the terminal may perform the interference measurement by taking the average of the interference only in a specific time / frequency resource region.
- the base station may inform the user equipment through upper layer signaling (for example, RRC signaling) for determining time and / or frequency resource regions that are limited for the interference measurement of the user equipment.
- ICIC information eg, silent subframe pattern
- ICIC information eg, RNTP, IOI, HII
- the interfering cell performs silencing on a specific time / frequency resource or performs a high intensity downlink transmission. It may be unclear.
- the base station when the base station informs the user equipment of the interference measurement, the RNTP of the cell is meaningless in the silent subframe of the interfering cell (that is, low interference is expected in all bands on the frequency of the silent subframe). ) Can be considered.
- the UE when the UE performs interference measurement limited to a specific frequency resource, if the specific frequency resource targets an interference resource having a low frequency, and the interference cell performs silencing in a specific subframe, the UE may interfere with the interference cell. In the silent subframe of, unlimited interference measurements can be performed in the entire frequency domain.
- the base station can inform the terminal of information about a set of subframes (that is, subframes that allow interference measurement over the entire band), which is an exception of the interference measurement for the limited frequency resource, through the higher layer signal.
- the frequency resource ICIC is based on whether or not the interfering cell is silenced in a specific subframe from the point of view of the interfering cell.
- This embodiment relates to the ICIC operation of each cell when the time resource ICIC information of one cell and the frequency resource ICIC information of another cell are exchanged with each other.
- FIG. 8 is a diagram illustrating an example of the present invention for the ICIC operation when the ICIC information for the time resource of one cell and the ICIC information for the frequency resource of another cell are exchanged with each other.
- a first cell is a cell for determining ICIC information (for example, a silent subframe pattern) for its own time resource (step S810) and transmitting (step S830).
- the second cell may receive it.
- the second cell corresponds to a cell for determining (step S820) and transmitting (step S840) ICIC information (for example, RNTP, IOI, and HII) on a frequency resource, and the first cell may receive the same. .
- This embodiment relates to the ICIC operation of each cell when the RNTP of the second cell is applied in the silent subframe of the first cell.
- the first cell sets DL subframe n as a silent subframe (S810) and informs the second cell of this (S830).
- the second cell may set a specific frequency subregion as a low downlink transmission power region (S820), and inform the first cell of this via RNTP (S840).
- the DL subframe n is a resource in which the first cell performs a silencing operation over the entire band
- the DL cell subframes a low downlink transmission power on a specific frequency subregion configured as RNTP. If the same applies to the frame n, the corresponding frequency resource of the subframe n is not sufficiently used by the first cell and also not sufficiently used by the second cell. To solve this inefficiency, the validity of the time resource ICIC information of the first cell and the RNTP information of the second cell in each of the first and second cells may be assumed as follows.
- the first cell ignores the RNTP transmitted by the second cell and may assume that the second cell uses high downlink transmission power in the entire frequency band. (S850).
- the second cell may use high downlink transmit power even for a specific frequency subband set to a low downlink transmit power region according to RNTP determined by the first cell for DL subframe n configured as a silent subframe. (S860).
- each cell may be defined as follows.
- the first cell may inform the UE belonging to the fact that a high interference can be received over the entire frequency band in a specific subframe through the higher layer signal (S870). Accordingly, when the UEs of the first cell perform measurements such as CSI or RSRQ (Reference Signal Received Quality) for a specific frequency subband, when the specific frequency subband is a low interference region, it is indicated through a higher layer signal. Measurement may be performed except for a specific subframe. Alternatively, in performing measurement of terminals of the first cell, when the specific frequency subband is a high interference region, the measurement over the entire frequency band is performed in the specific frequency subband in a specific subframe indicated by a higher layer signal. It is assumed that the measurement has the same properties, and the measurement may be performed through an operation such as interpolation.
- the second cell may transmit information indicating to the neighboring cells except the first cell to use high transmit power over the entire frequency band without following the RNTP transmitted by the specific subframe (S880). Neighbors receiving this may utilize information received from the second cell for downlink scheduling.
- This embodiment relates to the ICIC operation of each cell when the HII of the second cell is applied in the silent subframe of the first cell.
- the first cell may set DL subframe n as a silent subframe (S810) and inform the second cell of the DL subframe (S830).
- the second cell may set a specific frequency sub-region to a low uplink transmit power region or a high uplink transmit power region (S820), and may inform the first cell through HII (S840).
- the UL grant for uplink transmission in the UL subframe n + k is set to a timing relationship transmitted in the DL subframe n
- the DL subframe n is set to a silent subframe in the first cell
- the UL sub It can be seen that the uplink transmission of the first cell is substantially absent in the frame n + k.
- the UL subframe n + k it is advantageous in terms of resource utilization efficiency to use high uplink transmission power in the entire frequency band regardless of the HII transmitted by the second cell. Accordingly, the validity of the time resource ICIC information of the first cell and the HII information of the second cell in each of the first and second cells may be assumed as follows.
- the first cell sets DL subframe n as a silent subframe, the first cell ignores HII transmitted by the second cell for UL subframe n + k, and the second cell has high uplink transmission power in the entire frequency band. Can be assumed to use (S850).
- the second cell When the first cell sets DL subframe n as a silent subframe, the second cell also has a high frequency even in a specific frequency subband set to a low uplink transmission power region according to HII determined by the UE for the UL subframe n + k. Uplink transmission power may be used (S860).
- both the first and second cells may assume that the HII of the second cell is invalid.
- the operation of each cell can be defined as follows.
- the first cell considers that the HII of the second cell is not valid in a specific UL subframe (UL subframe n + k in which DL subframe n is set as a silent subframe), and thus, UL for terminals served by the first cell.
- Scheduling may be performed (S870).
- multiple subframe scheduling may be used when UL grant information for scheduling PUSCH transmission in UL subframe n + k cannot be transmitted in DL subframe n, which is a silent subframe.
- the UL grant information for scheduling the PUSCH transmission in the UL subframe n + k is a DL subframe other than the DL subframe n (eg, DL subframe n-1). Can be sent from.
- the UL grant information transmitted in the DL subframe n-1 may include a signaling field indicating that the PUSCH transmission scheduled by the corresponding UL grant is performed in the UL subframe n + k.
- the second cell may inform other neighboring cells except the first cell that it will use high transmit power over the entire band without following the HII transmitted by the subcell in a specific subframe. Adjacent cells that receive it may utilize this information for uplink scheduling.
- the second cell may transmit information to other neighboring cells except for the first cell, indicating that high transmission power is to be used for the entire frequency band without following the HII transmitted in a specific subframe (S880). Neighbors receiving this may utilize information received from the second cell for uplink scheduling.
- This embodiment relates to the ICIC operation of each cell when the IOI of the second cell is applied in the silent subframe of the first cell.
- the first cell may set DL subframe n as a silent subframe (S810) and inform the second cell of the DL subframe (S830).
- the second cell may determine a specific frequency subregion in which it is experiencing a high level of interference (S820), and inform the first cell of this via the IOI (S840). That is, the second cell may transmit the IOI to request the first cell to lower the interference level of the first cell in a specific frequency sub-domain.
- DL subframe n is configured as a silent subframe in the first cell
- UL transmission of the first cell is substantially absent in the UL subframe n + k (multiple subs described in Embodiment 4-2 herein). It is assumed that there is no application of frame scheduling). Accordingly, since the interference from the first cell is lowered in the entire frequency band in the subframe n + k from the perspective of the second cell, the IOI (or the interference reduction request) of the second cell is automatically generated in the subframe n + k. It may be assumed to be accepted (S860 and S880).
- uplink transmission is performed in the entire frequency band including a specific frequency subregion in which the second cell is indicated to undergo high uplink interference in the IOI of the second cell. Therefore, even if the ICIC operation according to the IOI reception of the second cell is not performed separately, the same result as that of automatically performing the operation according to the interference reduction request of the second cell is obtained (S850 and S870). In other words, it is assumed that frequency sub-areas for which the second cell requests interference reduction through the IOI are limited to the content of the subframe in which uplink scheduling is performed in a subframe that is not configured as a silent subframe in the first cell. Can be.
- This embodiment relates to a method of using an additional signal indicating the validity of frequency resource ICIC information.
- the first cell and the second cell may exchange additional signals indicating whether frequency resource ICIC information (eg, RNTP, HII, IOI) is valid in a specific subframe.
- the first cell and the second cell may transmit a pattern indicating in which subframe the frequency resource ICIC information is valid (or not valid) in the form of a bitmap.
- a subframe in which the frequency resource ICIC information is not valid may correspond to a silent subframe.
- the first cell and the second cell may transmit signaling indicating which frequency domain and in which subframe the frequency resource ICIC information is valid (or invalid). That is, in addition to simply indicating the validity of the frequency domain ICIC information for each subframe, it may indicate whether the frequency resource ICIC information is valid in a specific subframe and a specific frequency domain. Specifically, in the first cell and the second cell, the frequency resource ICIC information is valid in all subframes regardless of the silent subframe setting in a specific frequency domain, and is not valid in some subframe (s) in other specific frequency domains. It can exchange signaling indicating.
- a frequency domain in which frequency resource ICIC information is valid in all subframes may be a signal that can be transmitted uplink even if it is not based on uplink dynamic scheduling information received through the PDCCH (eg, periodic CSI reporting, SRS transmission, SPS).
- uplink dynamic scheduling information received through the PDCCH eg, periodic CSI reporting, SRS transmission, SPS.
- SPS Service-Persistent Scheduling
- the first cell and the second cell may exchange scheduling information (such as frequency domain allocation information for transmitting the corresponding signal) of a signal that can be transmitted without dynamic scheduling.
- a frequency domain in which frequency resource ICIC information is not valid in a specific subframe may be a frequency domain used for uplink transmission by uplink dynamic scheduling information received through a PDCCH.
- the second cell may freely schedule uplink transmission in the frequency domain.
- the subframe in which the UL grant for a subframe of the first cell is received is a silent subframe
- the second cell in the corresponding subframe that is, subframe n + k when subframe n is a silent subframe
- Uplink transmission can be freely performed in the frequency domain.
- a DL subframe is configured as a silent subframe
- a UL grant scheduling UL transmission in a UL subframe has a timing relationship received in the DL subframe
- the corresponding UL subframe may also be used. It has been explained on the assumption that it implicitly corresponds to a silent subframe. That is, in the above-described embodiments, if a DL subframe n is a silent subframe, a paring relationship is assumed that the UL subframe n + k is also a silent subframe. However, in order to more flexibly apply the silent subframe configuration, the configuration for the DL silent subframe and the configuration for the UL silent subframe may be separated. To this end, a bitmap message indicating the UL silent subframe pattern may be explicitly exchanged between the cells via a backhaul link.
- the assumption about the validity of the frequency resource ICIC information in the specific subframe and the operation in each cell may be defined as follows.
- This DL-UL subframe relationship is uplinked in a UL subframe n + k according to a scheme such as multiple subframe scheduling as described above in the first cell (eg, a UL grant received in DL subframe n-1). How the link transmission is performed) may be defined.
- the second cell when the first cell transmits frequency resource ICIC information (eg, RNTP, IOI, and HII) to the second cell, the second cell includes a DL subframe in which the RNTP of the first cell is a silent subframe.
- ICIC information eg, RNTP, IOI, and HII
- the second cell includes a DL subframe in which the RNTP of the first cell is a silent subframe.
- n + k is not a silent subframe, it is assumed that IOI and HII of the first cell are valid, and thus the second cell may perform PUSCH scheduling.
- the first and second cells ignore the RNTP of the second cell in DL subframe n, which is a silent subframe, and the second cell. It may be assumed that the cell performs downlink transmission with high transmission power in DL subframe n. Meanwhile, since the UL subframe n + k is not a silent subframe, it may be assumed that the IOI and HII of the second cell are valid.
- the first cell may be regarded as not scheduling PUSCH transmission in UL subframe n + k in DL subframe n.
- the first cell transmits frequency resource ICIC information (eg, RNTP, IOI, and HII) to the second cell
- ICIC information eg, RNTP, IOI, and HII
- the DL subframe n is not a silent subframe, so the second cell is the first cell. It can be assumed that the RNTP of the cell is valid. Meanwhile, since the UL subframe n + k is a silent subframe, the second cell may assume that IOI and HII of the first cell are invalid.
- the second cell may perform PUSCH transmission in the UL subframe n + k.
- the second cell may perform PUSCH transmission in the UL subframe n + k.
- information for scheduling PUSCH transmission in UL subframe n + k of the second cell is transmitted in DL subframe n, and DL subframe n. Since the first cell is a subframe that is not set as a silent subframe, interference from the first cell may exist.
- the uplink in the UL subframe n + k in a DL subframe other than the DL subframe n Scheduling link transmission or uplink transmission in UL subframe n + k in DL subframe n should be able to avoid interference of the first cell.
- a multiple subframe scheduling scheme eg, a scheme in which PUSCH transmission of UL subframe n + k is performed according to a UL grant transmitted in DL subframe n-1) may be applied.
- a new control channel (eg, e-PDCCH (e-PDCCH)) transmitted using a specific resource region (eg, a frequency region with low interference in the time domain in which the PDSCH of the first cell is transmitted) in DL subframe n (PDCCH or enhanced-PDCCH)) may be used to schedule PUSCH transmission in UL subframe n + k.
- a specific resource region eg, a frequency region with low interference in the time domain in which the PDSCH of the first cell is transmitted
- DL subframe n e.g, a specific resource region (eg, a frequency region with low interference in the time domain in which the PDSCH of the first cell is transmitted) in DL subframe n (PDCCH or enhanced-PDCCH)
- a specific resource region eg, a frequency region with low interference in the time domain in which the PDSCH of the first cell is transmitted
- DL subframe n e.g, a frequency region with low interference in the time domain in
- the first and second cells are downlinked in consideration of the RNTP of the second cell in DL subframe n instead of the silent subframe. Link transmission can be scheduled. Meanwhile, since the UL subframe n + k is a silent subframe, the first and second cells may operate under the assumption that the IOI and HII of the second cell of the second cell are invalid.
- FIG. 9 is a diagram illustrating a configuration of a base station apparatus according to the present invention.
- the base station apparatus 910 may include a transmission / reception module 911, a processor 912, a memory 913, and a plurality of antennas 914.
- the plurality of antennas 914 means a base station apparatus that supports MIMO transmission and reception.
- the transmission / reception module 911 may transmit and / or receive various signals, data, and information from other cells and / or terminals.
- the processor 912 may control the overall operation of the base station apparatus 900.
- the base station apparatus 900 may be configured to perform inter-cell interference coordination (ICIC) in a wireless communication system.
- the base station apparatus 900 shown in FIG. 9 may be a base station apparatus of a first cell or may be a base station apparatus of a second cell. That is, the first and second cells may correspond to sectors of the same base station, or the base station apparatus of the first cell and the base station apparatus of the second cell may correspond to different base station apparatuses.
- the processor 912 of the base station apparatus of the first cell may include time domain ICIC information (eg, silent subframe setting information) of the first cell and frequency domain ICIC information (eg, RNTP, UL IOI) of the first cell.
- UL HII may be configured to be transmitted to the second cell through the transmission / reception module 911.
- the processor 912 of the base station apparatus of the first cell also assumes the validity of the frequency domain ICIC information of the first cell based on the time domain ICIC information of the first cell and operates accordingly.
- the second cell may be configured to predict a result of an assumption performed by the second cell on the validity of the frequency domain ICIC information of the first cell.
- the processor 912 of the base station apparatus of the first cell may be configured such that the first cell performs uplink or downlink scheduling based on the prediction result.
- the processor 912 of the base station apparatus of the second cell may be configured to receive time domain ICIC information of the first cell and frequency domain ICIC information of the first cell from the first cell through the transmission / reception module 911. . Further, the processor 912 of the base station apparatus of the second cell may be configured to assume the validity of the frequency domain ICIC information of the first cell based on the time domain ICIC information of the first cell. The processor 912 of the base station apparatus of the second cell may be configured to perform uplink or downlink scheduling of the second cell based on the result of the hypothesis.
- the processor 912 of the base station apparatus 900 performs a function of processing the information received by the base station apparatus 900, information to be transmitted to the outside, and the like.
- the memory 913 stores the calculated information and the like for a predetermined time. And may be replaced by a component such as a buffer (not shown).
- the description of the base station apparatus 900 may be similarly applied to a relay apparatus as a downlink transmitting entity or an uplink receiving entity.
- Embodiments of the present invention described above may be implemented through various means.
- embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.
- a method according to embodiments of the present invention may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), and Programmable Logic Devices (PLDs). It may be implemented by field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.
- ASICs Application Specific Integrated Circuits
- DSPs Digital Signal Processors
- DSPDs Digital Signal Processing Devices
- PLDs Programmable Logic Devices
- FPGAs field programmable gate arrays
- processors controllers, microcontrollers, microprocessors, and the like.
- the method according to the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function 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.
- Embodiments of the present invention as described above may be applied to various mobile communication systems.
Abstract
Description
Claims (15)
- 무선 통신 시스템에서 셀간 간섭 조정(ICIC)을 수행하는 방법으로서,제 1 셀의 시간 영역 ICIC 정보 및 상기 제 1 셀의 주파수 영역 ICIC 정보를 상기 제 1 셀로부터 제 2 셀이 수신하는 단계;상기 제 2 셀이 상기 제 1 셀의 상기 시간 영역 ICIC 정보에 기초하여 상기 제 1 셀의 상기 주파수 영역 ICIC 정보의 유효성을 가정(assume)하는 단계; 및상기 가정하는 단계의 결과에 기초하여 상기 제 2 셀이 상향링크 또는 하향링크 스케줄링을 수행하는 단계를 포함하는, ICIC 수행 방법.
- 제 1 항에 있어서,상기 제 1 셀의 시간 영역 ICIC 정보는 상기 제 1 셀의 사일런트 서브프레임 설정 정보를 포함하는, ICIC 수행 방법.
- 제 2 항에 있어서,상기 가정하는 단계는,상기 제 1 셀이 사일런트 서브프레임으로 설정한 하향링크 서브프레임 n에서, 상기 제 1 셀의 상기 주파수 영역 ICIC 정보가 유효하지 않은 것으로 가정하는 단계를 포함하는, ICIC 수행 방법.
- 제 3 항에 있어서,상기 유효하지 않은 것으로 가정되는 상기 주파수 영역 ICIC 정보는, 상기 제 1 셀의 RNTP(Relative Narrowband Transmission Power)인, ICIC 수행 방법.
- 제 2 항에 있어서,상기 가정하는 단계는,상기 제 1 셀이 사일런트 서브프레임으로 설정한 하향링크 서브프레임 n에 대응하는 상향링크 서브프레임 n+k에서, 상기 제 1 셀의 상기 주파수 영역 ICIC 정보가 유효하지 않은 것으로 가정하는 단계를 포함하는, ICIC 수행 방법.
- 제 5 항에 있어서,상기 유효하지 않은 것으로 가정되는 상기 주파수 영역 ICIC 정보는, 상기 제 1 셀의 상향링크 IOI(Interference Overhead Indication) 또는 상향링크 HII(High Interference Indication) 중 하나 이상을 포함하는, ICIC 수행 방법.
- 제 5 항에 있어서,상기 상향링크 서브프레임 n+k에서의 상향링크 전송에 대한 스케줄링 정보는 상기 하향링크 서브프레임 n에서 전송되는, ICIC 수행 방법.
- 제 2 항에 있어서,상기 가정하는 단계는,상기 제 1 셀이 사일런트 서브프레임으로 설정하지 않은 서브프레임에서 상기 제 1 셀의 상기 주파수 영역 ICIC 정보가 유효한 것으로 가정하는 단계를 포함하는, ICIC 수행 방법.
- 제 1 항에 있어서,상기 가정하는 단계의 결과에 기초하여 상기 제 2 셀에서의 간섭 측정에 이용되는 시간 자원 및 주파수 자원을 결정하는 단계를 더 포함하는, ICIC 수행 방법.
- 제 1 항에 있어서,상기 제 1 셀로부터 상기 제 1 셀의 상기 주파수 영역 ICIC 정보가 유효한 자원 영역을 지시하는 정보를 수신하는 단계를 더 포함하고,상기 가정하는 단계는 상기 제 1 셀의 상기 주파수 영역 ICIC 정보가 유효한 자원 영역을 지시하는 정보에 기초하여 수행되는, ICIC 수행 방법.
- 제 10 항에 있어서,상기 제 1 셀의 상기 주파수 영역 ICIC 정보가 유효한 자원 영역은, 시간 자원 및 주파수 자원 상에서 결정되는, ICIC 수행 방법.
- 제 2 항에 있어서,상기 사일런트 서브프레임은 상기 제 1 셀이 ABS(Almost Blank Subframe)로 설정한 서브프레임인, ICIC 수행 방법.
- 무선 통신 시스템에서 셀간 간섭 조정(ICIC)을 수행하는 방법으로서,제 1 셀이 상기 제 1 셀의 시간 영역 ICIC 정보 및 상기 제 1 셀의 주파수 영역 ICIC 정보를 제 2 셀에게 전송하는 단계;상기 제 1 셀의 상기 시간 영역 ICIC 정보에 기초한 상기 제 1 셀의 상기 주파수 영역 ICIC 정보의 유효성에 대한 상기 제 2 셀의 가정의 결과를 예측하는 단계; 및상기 예측 결과에 기초하여 상기 제 1 셀이 상향링크 또는 하향링크 스케줄링을 수행하는 단계를 포함하는, ICIC 수행 방법.
- 무선 통신 시스템에서 셀간 간섭 조정(ICIC)을 수행하는 제 2 셀의 기지국으로서,제 1 셀과 신호를 송수신하는 송수신 모듈; 및상기 송수신 모듈을 포함하는 상기 기지국을 제어하는 프로세서를 포함하고;상기 프로세서는,상기 제 1 셀의 시간 영역 ICIC 정보 및 상기 제 1 셀의 주파수 영역 ICIC 정보를 상기 제 1 셀로부터 상기 송수신 모듈을 통하여 수신하고;상기 제 1 셀의 상기 시간 영역 ICIC 정보에 기초하여 상기 제 1 셀의 상기 주파수 영역 ICIC 정보의 유효성을 가정(assume)하고;상기 가정의 결과에 기초하여 상기 제 2 셀의 상향링크 또는 하향링크 스케줄링을 수행하도록 구성되는, ICIC 수행 기지국.
- 무선 통신 시스템에서 셀간 간섭 조정(ICIC)을 수행하는 제 1 셀의 기지국으로서,제 2 셀과 신호를 송수신하는 송수신 모듈; 및상기 송수신 모듈을 포함하는 상기 기지국을 제어하는 프로세서를 포함하고;상기 프로세서는,상기 제 1 셀의 시간 영역 ICIC 정보 및 상기 제 1 셀의 주파수 영역 ICIC 정보를 상기 송수신 모듈을 통하여 상기 제 2 셀에게 전송하고;상기 제 1 셀의 상기 시간 영역 ICIC 정보에 기초한 상기 제 1 셀의 상기 주파수 영역 ICIC 정보의 유효성에 대한 상기 제 2 셀의 가정의 결과를 예측하고;상기 예측 결과에 기초하여 상기 제 1 셀의 상향링크 또는 하향링크 스케줄링을 수행하도록 구성되는, ICIC 수행 기지국.
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EP20187440.1A EP3745636A1 (en) | 2011-02-06 | 2012-02-03 | Method and apparatus for inter-cell interference coordination in a wireless communication system |
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US14/754,338 US9439210B2 (en) | 2011-02-06 | 2015-06-29 | Method and apparatus for inter-cell interference coordination in a wireless communication system |
US15/238,494 US9948437B2 (en) | 2011-02-06 | 2016-08-16 | Method and apparatus for inter-cell interference coordination in a wireless communication system |
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EP2672746A4 (en) | 2018-02-28 |
KR101809958B1 (ko) | 2017-12-18 |
US9439210B2 (en) | 2016-09-06 |
EP2672746A2 (en) | 2013-12-11 |
US9088394B2 (en) | 2015-07-21 |
US20130295949A1 (en) | 2013-11-07 |
US9948437B2 (en) | 2018-04-17 |
EP3745636A1 (en) | 2020-12-02 |
US20160359597A1 (en) | 2016-12-08 |
KR20140036136A (ko) | 2014-03-25 |
WO2012105766A3 (ko) | 2012-12-13 |
US20150305060A1 (en) | 2015-10-22 |
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