KR20150015386A

KR20150015386A - Method for providing information of interference in mobile communication systems

Info

Publication number: KR20150015386A
Application number: KR1020140095956A
Authority: KR
Inventors: 신준우
Original assignee: 한국전자통신연구원
Priority date: 2013-07-31
Filing date: 2014-07-28
Publication date: 2015-02-10

Abstract

Disclosed is a method for providing interference information of a mobile communications system. The method for providing interference information, which is carried out in a base station, includes the steps of: obtaining in-cell interference signal information which interferes in a signal of a damaged terminal; and transmitting the in-cell interference signal information to the damaged terminal. In the step of transmitting the in-cell interference signal information, reference signal generation related information of an in-cell interference signal is transmitted, or frequency resource allocation information and pre-coding matrix indicator (PMI) allocation information of the in-cell interference signal are transmitted. Therefore, the damaged terminal can realize an improved receiver based on the received interference information, thereby efficiently removing interference.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of providing interference information in a mobile communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an interference cancellation technique in a mobile communication system, and more particularly, to a method of providing interference information required for interference cancellation in a mobile communication system.

There are two major scenarios of the mobile communication system that can apply the interference cancellation and suppression technique based on network cooperation.

One is a scenario in which a base station removes or suppresses inter-user interference in a multi-user multiple-input multiple-output (MU-MIMO) environment supporting multiple antennas based on multiple users in the same cell. This is a scenario in which inter-cell interference experienced by a user terminal located in a cell boundary region is removed or suppressed.

The advanced receiver is a network cooperative interference cancellation and suppression technology currently under discussion in a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) -Advanced Standardization Conference. It is a receiver that can be used in a receiver of a mobile communication system Algorithm. An improved receiver means a receiving method capable of eliminating or suppressing intra-cell interference and inter-cell interference.

In order for the victim UE affected by the interference to remove the interference through the improved receiver, it is necessary to know exactly the interference signal, the channel information related to the interference signal, and the synchronization information.

However, up to now, no specific method has been proposed for correctly transmitting the interference information necessary for operating the improved receiver to the victim terminal.

That is, in the current LTE or LTE-Advanced system, each user terminal decodes only the PDCCH (Physical Downlink Control Channel) or the EPDCCH (Enhanced PDCCH) allocated to itself. Therefore, interference from other user terminals or other cells There is no way to know the information about.

Therefore, in order to eliminate the interference by operating the improved receiver by the affected terminal affected by the interference, there is a need for a method capable of providing not only control information on a desired signal but also control information on an interference signal.

An object of the present invention is to provide a method for transmitting interference information to a victim terminal so that a victim terminal affected by interference in a mobile communication system can eliminate intra-cell interference and inter-cell interference.

According to an aspect of the present invention, there is provided a method of providing interference information, the method comprising: obtaining intra-cell interference signal information for interfering with a signal of a victim terminal; And transmitting the intra-cell interference signal information to the victim terminal. In the step of transmitting the intra-cell interference signal information, information related to the reference signal generation of the intra-cell interference signal is transmitted, Frequency resource allocation information and PMI (Precoding Matrix Indicator) allocation information.

Herein, in the step of transmitting the intra-cell interference signal information to the victim terminal, the DM-RS generation related information is provided as the intra-cell interference signal information in case of DM-RS based transmission, An indication value corresponding to the DM-RS of the inter-cell interference signal among the indication values assigned to combinations of the port number and the scrambling ID.

Here, the combination of the antenna port number and the scrambling ID may include a combination of antenna port numbers 7 and 8 and a scrambling ID.

Here, in the step of transmitting the intra-cell interference signal information to the victim terminal, frequency resource allocation information and PMI allocation information of the intra-cell interference signal are transmitted to the intra-cell interference signal information in case of CRS (Cell Specific RS) , Frequency resource allocation information of all inter-cell interference signals and PMI allocation information to the victim terminal.

Herein, in the step of transmitting the intra-cell interference signal information to the victim terminal, frequency resource allocation information and PMI allocation information of the intra-cell interference signal are transmitted with the intra-cell interference signal information in case of CRS-based transmission, Only the frequency resource allocation information and the PMI allocation information for at least one interference signal selected according to a predetermined reference among the signals can be transmitted.

Here, the frequency resource allocation information and the PMI allocation information for the selected at least one interference signal may be separately transmitted to the victim terminal, or the interference including the frequency resource allocation information and the PMI allocation information for the selected at least one interference signal Can be transmitted to the victim terminal through an information map.

Here, the interference information map may be configured by allocating PMI information to subbands corresponding to frequency resources allocated to the selected at least one interference signal and components of each subband.

In the step of transmitting the intra-cell interference signal information to the victim terminal, control information related to a signal to be transmitted to the victim terminal and the intra-cell interference signal information are transmitted to a single DCI (Downlink Control Information) And DCI including the intra-cell interference signal information can be independently transmitted.

According to another aspect of the present invention, there is provided an interference information providing method performed by a base station, the method comprising: acquiring inter-cell interference signal information for interfering with a signal of a victim terminal; And transmitting the inter-cell interference signal information to the terminal. In the step of transmitting the inter-cell interference signal information, at least one of the reference signal generation information of the inter-cell interference signal, the resource allocation information of the reference signal, It conveys one information.

Here, in the step of acquiring the inter-cell interference signal information, the base station may receive the inter-cell interference signal from at least one other base station through a backhaul.

Here, the reference signal generation information includes at least one of an antenna port, a slot number, a scrambling ID, a virtual cell ID, and an RNTI (Radio Network Temporary Identifier) information as the generation information of a Demodulation Reference Signal (DM-RS) , Cell specific RS (CRS) generation information, at least one of a cell ID, a cyclic prefix length, and slot number information.

Here, the slot number information may constitute a parameter value corresponding to each slot number, and may transmit a parameter value corresponding to a slot number related to the inter-cell interference signal among the parameter values.

Here, the resource allocation information of the reference signal may include at least one of mapping pattern information and frequency displacement information as resource allocation information of the DM-RS, at least one of antenna port number and cell ID information And may include one piece of information.

Here, in the step of transmitting the inter-cell interference signal information to the victim terminal, the DM-RS generation information for signals acting as interference with respect to the frequency resource block allocated to the signal of the victim terminal among the plurality of inter- And DM-RS resource allocation information.

In the step of transmitting the intercell interference signal information to the victim terminal, when the antenna port 5 is applied to the DM-RS based inter-cell interference signal, only the cell ID and the cyclic prefix length of the inter-cell interference signal can be transmitted.

When at least one of the antenna ports 7 to 14 is applied to the DM-RS based inter-cell interference signal in the step of transmitting the inter-cell interference signal information to the victim terminal, the antenna port number, A scrambling ID, a cell ID, and slot number information.

Here, in the step of transmitting the inter-cell interference signal information to the victim terminal, the antenna port number and the scrambling ID information of the inter-cell interference signal are transmitted, and a combination of an antenna port number or a combination of an antenna port number and a scrambling identifier A unique indication value can be assigned, and an indication value corresponding to the DM-RS of the interference signal can be transmitted.

In the step of transmitting the inter-cell interference signal information to the victim terminal, a combination of the antenna port number and the scrambling identifier is classified into a specific number considering the DM-RS mapping pattern according to the antenna port number, After the eigenvalues are allocated, the eigenvalues allocated in the case of the DM-RS mapping pattern of the inter-cell interference signal can be transmitted.

When transmitting the intercell interference signal information to the victim terminal, the CRS generation information, the CRS resource allocation information, the Precoding Matrix Indicator (PMI) information of the inter-cell interference signal, Allocation information and resource allocation information of the inter-cell interference signal.

Here, in the step of transmitting the intercell interference signal information to the victim terminal, when the intercell interference signal is transmitted based on the CRS, the parameter value corresponding to the antenna port number may be transmitted to the victim terminal.

According to the interference information providing method of the mobile communication system as described above, it is possible to transmit the intra-cell interference signal and the covariance matrix information on the inter-cell interference signal to the lost terminal so that the lost terminal can remove the interference signal using the improved receiver .

Therefore, in a multi-cell environment, a terminal can efficiently remove intra-cell interference and inter-cell interference using an improved receiver.

1 is a conceptual diagram illustrating an example of intra-cell interference in an OFDMA system.
Figure 2 shows the DM-RS resource mapping for antenna ports 7 and 8.
3 shows a configuration example of a precoding matrix index map.
4 is a conceptual diagram illustrating an example of inter-cell interference in an OFDMA system.
Figures 5A and 5B show DM-RS resource mappings for antenna ports 7-14.
6 is a conceptual diagram for explaining a DM-RS mapping combination.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

A "terminal" used in the present application includes a user equipment (UE), a mobile station (MS), a mobile terminal (MT), a user terminal, a user terminal (UT) An access terminal (AT), a subscriber unit, a subscriber station (SS), a wireless device, a wireless communication device, a wireless transmit / receive unit (WTRU) Or < / RTI > other terms.

A 'base station' used in the present application generally refers to a fixed point for communicating with a terminal, and includes a base station, a Node-B, an eNode-B, a BTS (Base Transceiver System), an access point (Access Point), and the like.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate a thorough understanding of the present invention, the same or similar reference numerals are used for the same or similar components in the drawings and redundant explanations of the same components are omitted.

Hereinafter, an interference cancellation method according to an embodiment of the present invention will be described focusing on an IRC (Interference Rejection Combining) receiver that performs an interference suppression function among the improved receivers. However, the technical idea of the present invention is not limited to the IRC receiver, but can be applied to various receivers that perform the interference cancellation function.

First, an environment and a signal model of a mobile communication system to which an advanced receiver is applied will be described.

When an inter-cell interference signal and an inter-cell interference signal coexist in a signal received by a receiving apparatus, the received signal can be modeled as shown in Equation (1).

In Equation (1), y ^{[m, k]} denotes a signal received by the k-th user located in the m-th cell. m, n means the index of the cell, and k, j means the index of the terminal. H denotes a channel coefficient, P denotes a precoding matrix, s denotes a transmission signal, and n denotes noise.

In Equation 1, the first term on the right side means a desired signal, the second term means an intra-cell interference element, the third term means an inter-cell interference element, and the last term means a noise element.

The detection signal of the IRC receiver of the k-th UE located in the m-th cell can be defined as Equation (2).

In Equation (2), the last term in parentheses on the right side means estimated noise and noise power.

The receiving apparatus can estimate the transmission signal using Equations (1) and (2) as shown in Equation (3).

In Equation (3)

Denotes a transmission signal estimated by the k-th UE in the m-th cell.

The detection signal of the IRC receiver shown in Equation (2) can be implemented on the assumption that the reception apparatus knows not only the information on the desired signal but also the information on the interference signal. Here, the receiving apparatus transmits DM-RS (Demodulation Reference Signal) or CRS (Cell Specific RS) according to a method defined in the existing 3GPP LTE-A standard, And a Physical Downlink Control Channel (PDCCH). However, there is no definition of a method for acquiring information on an interference signal.

Accordingly, the present invention provides a method for transmitting interference signal information required for designing an IRC receiver for a k-th user of an m-th cell to a corresponding receiver.

Hereinafter, a method of transmitting an interference signal for implementing an IRC receiver will be described in detail.

The interference-related information for implementing the IRC receiver is covariance matrix information in which interference channel information and precoding matrix information used for transmitting an interference signal are combined. That is, the interference-related information corresponds to the second term and the third term among the terms included in the brackets on the right side in Equation (2).

The interfering signal is generated by inter-cell interference caused when a base station applies MU-MIMO to a user terminal in a cell using the same time and frequency resources, inter-cell interference due to signals transmitted from adjacent cells, cell interference. In particular, inter-cell interference can also be caused by MU-MIMO or single-user transmission.

Hereinafter, a method of transmitting information related to intra-cell interference and a method of transmitting information related to inter-cell interference will be described separately. In the case of a method of transmitting inter-cell interference, it is assumed that neighboring base stations exchange interference-related information through an ideal backhaul without delay.

■ How to communicate information related to intra-cell interference

Intra-cell interference refers to spatial interference occurring between user terminals in a cell when a base station operates a multi-user multiple-input multiple-output (MU-MIMO) using the same time and frequency resources.

Currently, MU-MIMO in LTE-A operates on DM-RS basis in Transmission Mode (TM) 7, 8 and 9, or on CRS basis in TM 5.

Hereinafter, a method of acquiring covariance information of an interference signal according to the transmission mode will be described.

Method of transmitting interference information in DM-RS based transmission environment

When performing channel estimation based on DM-RS in a receiving apparatus, effective channel information in which channel information and precoding information are combined can be obtained.

However, within the range of the existing LTE-A standard, victim user equipment (hereinafter abbreviated as 'victim terminal') affected by interference can not know the DM-RS generation related information about the intra-cell interference signal .

In order for the victim terminal to estimate the effective channel for intra-cell interference, it is necessary to know the DM-RS generation related information of the interfering signal.

The initialization parameter for DM-RS generation defined in the current LTE-A standard is shown in Equation (4).

In Equation (4), v denotes the number of layers. Further, the definitions of other parameters shown in Equation (4) are as defined in the LTE-A standard specification.

In order to avoid the terminal to create a DM-RS of the interference signal of the interference signal antenna port number (antenna port number), the slot number (slot number; n _s), the scrambling identity _{(scrambling ID; n SCID),} RNTI (Radio Network Temporary Identifier (n _RNTI ), virtual cell ID (n _ID ⁽ⁱ⁾ ), and the like. Here, the scrambling ID information is required in the case of the antenna ports 7 to 14, and the RNTI information is necessary in the case of the antenna port 5. In addition, the virtual cell ID information is required in the case of the antenna ports 7 to 14.

According to the current LTE-A standard, antenna port 5 is not applied in MU-MIMO. Therefore, there is no need to apply the DM-RS based antenna port 5 in the modeling of the inter-cell interference signal, so that information related to the antenna port 5 need not be considered.

On the other hand, in the case of antenna ports 7 to 6 + v, information on the antenna port number, scrambling ID (n _SCID ), and virtual cell _ID ^{(DMRS, i)} for the interference signal should be transmitted to the terminal. Here, a virtual cell ID _{^{(n ID (DMRS, i)}} ) if the cell is not working as a CoMP (coordinate multipoint transmission / reception) is therefore of the same value as a cell ID (N _ID ^cell), the intra-cell interference environment It is not necessary to inform the terminal separately of the virtual cell ID. However, when the cell operates in the CoMP mode, the 9-bit information corresponding to the virtual cell ID must be notified to the terminal.

Meanwhile, in order to apply an appropriate reception method for each resource element (RE), the receiving apparatus must know the frequency resource (block) allocation information of the interference signal.

If the desired signal and the co-scheduled interference signal use the same time and frequency resources, no separate information related to resource allocation may be needed.

1 is a conceptual diagram illustrating an example of intra-cell interference in an OFDMA (Orthogonal Frequency Division Multiple Access) system. 1 illustrates an inter-terminal interference relationship in a case where a resource 110 allocated to a victim terminal is scheduled in common with a resource 120 allocated to the interfering terminal 1 and a resource 130 allocated to the interfering terminal 2. FIG.

It may happen that the frequency bands of the interfering terminal 1 and the interfering terminal 2 are commonly scheduled so that the frequency bands of the interfering terminal 1 and the interfering terminal 2 overlap as shown in Fig.

1, interference occurs in the frequency resource area A (111) of the victim terminal by the signal transmitted from the interference terminal 1, and in the frequency resource area B (112), the interference terminal 2 The interference is generated by the signal transmitted from the antenna.

Therefore, the IRC receiver of the victim terminal should be applied differently for the frequency resource area A and the frequency resource area B, respectively.

In case of DM-RS based transmission, if the base station notifies only the DM-RS related information of the interference signal to be schedulously scheduled to the terminal, the affected terminal calculates DM-RS for the corresponding frequency band based on the DM- It is possible to estimate the effective channel of the interference signal. Then, the victim terminal can remove the interference by applying the estimated effective channel information to the interference parameter of the IRC receiver. Here, when the interference signal is not allocated, the channel estimation value of the interference signal is close to '0', and when the interference signal exists, the channel estimation value has a value corresponding to the interference signal. As described above, since the IRC receiver removes the interference by applying the estimated channel, if there is interference, the interference information is reflected to the IRC receiver through the channel estimation value. If there is no interference, the interference information is not reflected to the IRC receiver .

Meanwhile, in the method of acquiring information related to the inter-cell interference signal, in the case of DM-RS based transmission, it is not necessary to transmit frequency resource (block) allocation information to the UE.

Hereinafter, a method of informing the victim terminal by associating the DM-RS generation parameter (scrambling ID) of the interference signal with the resource mapping pattern (or the orthogonal Walsh code) of the DM-RS will be described.

In the current LTE-A standard, it is defined that only antenna port 7 or 8 operates in MU-MIMO situation.

Figure 2 shows the DM-RS resource mapping for antenna ports 7 and 8. In FIG. 2, 1 denotes an index of a time domain.

As illustrated in FIG. 2, the DM-RS may be mapped to have orthogonality using a Walsh code of length 2 (length 2) for a specific subcarrier of a subframe. Also, it is possible to distinguish four UEs that are commonly scheduled by allocating two DM-RSs with different scrambling IDs for each Walsh code.

Accordingly, the victim terminal can perform channel estimation by separating the DM-RS of the desired signal and the DM-RS of the interference signal based on the Walsh code and the scrambling ID.

The LTE-A standard defines a combination of an antenna port number, a layer number, and a scrambling ID, and describes a method of explicitly transmitting the information to a victim terminal using a defined combination value have.

In the present invention, the following two methods are provided for transmitting information related to inter-cell interference to a terminal in consideration of a combination defined in the LTE-A standard.

In the first method, a combination of an antenna port number and scrambling ID information for an interference signal is configured, and an indication value for a message of each combination is configured as shown in Table 1. Then, using Table 1, This is a method of explicitly delivering the indication value to the victim terminal. Here, the message according to the combination of the antenna port number and the scrambling ID and the indication value for each message as shown in Table 1 should be set in common between the UE and the BS, and should be known to each other in advance.

The victim terminal obtains the antenna port information and the scrambling ID information for the interference signal based on the indication value received from the base station, and estimates the desired channel and the interference channel by using the obtained information.

The reason for including the messages for indicating values 4 and 5 in Table 1 is to consider the case where the number of transmission layers of the desired signal and the number of transmission layers of the interference signal differ. For example, when a scrambling ID 0 (n _SCID = 0) is applied to the signal transmitted to the victim terminal (i.e., a desired signal) with the antenna port 7, the signal of the multiuser that is commonly scheduled with the victim terminal is transmitted to the antenna ports 7 and 8 And scrambling ID 1 (n _SCID = 1) may be applied. That is, when a single layer transmission is applied to an affected terminal, an interference signal to which a dual layer transmission is applied may be included in a received signal. According to the present invention, the information can be provided to the victim terminal using Table 1 also in the above case.

In the second method, the base station does not explicitly transmit the antenna port information and the scrambling ID information for the interference signal to the mobile station, but instead transmits the antenna port number set (i.e., {7,8}) and the scrambling ID set That is, a blind test is performed on {0, 1} to estimate the effective channel of the interference signal. At this time, the victim terminal can perform the blind test while changing the Walsh code for the antenna port number, and perform the blind test for the scrambling ID while changing the DM-RS generation. In addition, channel estimation performance may be applied as an estimation criterion of interference signal information through blind test, or reception performance using IRC may be applied.

Among the above two methods, the first method is efficient in terms of the computational complexity of the receiving apparatus, but has a drawback in that resource overhead for information transmission increases. On the other hand, the second method is advantageous in terms of resource overhead, but has a disadvantage in that the complexity of the receiving apparatus increases.

In addition, among the DM-RS-related parameters of the interference signal, parameters to be explicitly transmitted to the victim terminal include a new DCI (Downlink Control Information) including DCI (Downlink Control Information) information of a desired signal to be transmitted to the victim terminal, (I.e., transmission using a single DCI), and additionally transmitting a DCI including parameter information related to the interference signal to the terminal in addition to the DCI transmission for the desired signal (i.e., &Lt; / RTI >

Method of transmitting interference information in CRS-based transmission environment

Unlike the DM-RS based channel estimation method in which a receiving apparatus can estimate an effective channel (that is, actual channel information and precoding information), in a CRS-based channel estimation method, a receiving apparatus can estimate only channel information.

Therefore, the victim terminal should be able to know the CRS generation information, the CRS resource allocation information, the frequency resource allocation information of the interference signal, and the Precoding Matrix Indicator (PMI) allocation information for the IRC receiver. In the DM-RS-based channel estimation method, the frequency resource allocation information is not needed because the effective channel estimation is performed. However, in the CRS-based channel estimation process, the frequency resource allocation information and PMI allocation information for each interference signal must be given, The effective channel for the interference signal can be estimated.

In order to generate a CRS, initialization parameters of a reference signal, i.e., a cell ID and a cyclic prefix length information are required. However, since the information is cell-specific information, common signaling is not required for the UE located in the same cell. Also, the CRS allocation information does not require additional signaling for the same reason as described above.

Therefore, the base station may transmit only the frequency resource (block) allocation information of the interference signal and the PMI allocation information corresponding to the allocated frequency resource separately to the lost terminal.

The following two methods can be considered as a method for transmitting frequency resource (block) allocation information and PMI allocation information of an interference signal to an affected terminal.

The first method is to transmit frequency resource (block) allocation information and PMI allocation information of all intra-cell interference signals to the victim terminal. In this case, there is an advantage that the information about the interference signal is explicitly transmitted to the victim terminal. However, this method has a disadvantage in that the amount of information to be transmitted to the UE increases as the number of the interfering terminals and the PMI allocation information to be applied to the interference signal (i.e., the PMI is different for each subband) .

The second method is a method for compensating for the disadvantage of the first method. In the second method, frequency resource (block) allocation information and PMI allocation information for an interference signal dominantly affecting a victim terminal among a plurality of intra- Lt; / RTI > Here, the base station can select an interference signal that has a dominant influence on the victim terminal according to a predefined criterion. For example, the base station can select an interference signal to transmit information to the victim terminal by applying various criteria such as the degree of overlapping of the resources allocated to the signal of the victim terminal and the resources allocated to the interference signal, and the position between the terminals.

In the second method, the BS may transmit the frequency allocation information and the PMI allocation information of the dominant interference signals separately from each other as a method of transmitting the frequency allocation information and the PMI allocation information to the UE. Alternatively, as illustrated in FIG. 3, And transmits the PMI map to the victim terminal.

3 shows a configuration example of a precoding matrix index map.

As illustrated in FIG. 3, the BS constructs a subband-based map corresponding to the frequency resource allocated to each of the interference signals dominantly affecting the lost terminal, and assigns PMI information to each component of the map have. In this case, frequency allocation information is implicitly allocated to the PMI map.

As with the DM-RS-related parameter transmission method of the above-described interference signal, among the CRS-related parameters of the interference signal, parameters to be explicitly transmitted to the victim terminal include DCI information of a desired signal to be transmitted to the victim terminal (I.e., transmission using a single DCI), and a DCI including parameter information related to an interference signal in addition to the DCI transmission for a desired signal may be additionally transmitted to the terminal (I.e., transmission using multiple DCIs).

How to communicate information related to inter-cell interference

In the case of an intercell interference signal, most of the interference signals may not be a common scheduled signal so that the terminal uses the same time and frequency resources as the desired signal.

4 is a conceptual diagram illustrating an example of inter-cell interference in an OFDMA system. 4, an interference relation between a resource 410 allocated to a victim terminal located in an arbitrary cell and resources 420 and 430 allocated to interference signals transmitted from other cells adjacent to the victim terminal cell .

As illustrated in FIG. 4, some of the frequency resources (i.e., resource blocks) allocated to the victim terminal may overlap resources allocated to the interference signals from neighboring cells. Here, unlike the inter-cell interference signal, the inter-cell interference signal can be operated as SU (Single User) -MIMO or MU-MIMO.

The base stations operating each cell can exchange information related to the inter-cell interference signal through the backhaul link. Here, it is assumed that the backhaul link is an ideal backhaul with no delay or error.

Effective Channel Estimation Method for Different Cells in DM-RS based Transmission Environment

In order to estimate the effective channel of the inter-cell interference signal based on the DM-RS, the affected terminal must know the DM-RS generation related parameter of the interference signal, the DM-RS resource allocation information, and the frequency resource allocation information of the interference signal. Here, the DM-RS resource allocation information may include DM-RS pattern information and frequency shift information according to the cell ID, and the frequency displacement information is only required when the antenna port 5 is used.

The reason why the victim terminal needs to know the frequency resource allocation information of the interference signal is that if the frequency resource allocated to the victim terminal and the frequency resource allocated to the interference signal do not match as shown in Fig. 4, The IRC receiver must be implemented differently according to the interference signal.

According to the LTE-A standard, the frequency resource allocation information is transmitted to the UE through the DCI, and is allocated up to 12 bits.

Meanwhile, the frequency resource allocation information of the inter-cell interference signal is transmitted to the base station of a cell providing an interference signal (hereinafter, referred to as an 'interference cell') through a backhaul link (hereinafter referred to as a ' To the base station.

In a simple method, when a base station of an interference cell explicitly transmits frequency resource allocation information of an intercell interference signal to a base station of a lost cell and a base station of the lost cell delivers the information to the lost terminal, Considering the frequency resource allocation information of the signal, a method of operating the IRC receiver can be considered. However, when an inter-cell interference signal is generated from a plurality of cells or a plurality of inter-cell UEs, a resource overhead for transmitting frequency resource allocation information corresponding to a plurality of inter-cell interference signals increases.

In the present invention, when a base station of a victim cell receives and receives information on an interference signal allocated to a frequency resource used by a victim terminal through a backhaul link, the frequency resource allocation information of the interference signal is explicitly transmitted to the victim terminal RS generation related parameters and DM-RS resource allocation information for signals that act as interference to the frequency resource block (RB) allocated to the signal of the victim terminal. Since the DM-RS based channel estimation estimates the effective channel (i.e., channel information and PMI) of the interference signal, if the estimated value of the corresponding interference channel is large, the IRC receiver significantly reflects the influence of the interference signal, If the estimated value is small, it is considered that the influence is reflected to the IRC receiver little.

Based on the information on the inter-cell interference signal received from the base station, the terminal performs DM-RS-based channel estimation on the frequency resource, performs channel estimation on the desired signal and the interference signal, One effective channel information is reflected in the IRC receiver.

The above method has a disadvantage in that the amount of computation is increased because channel estimation has to be performed on the assumption that the lost terminal has interference even for frequency resources that may be free from interference. However, it is possible to reduce the resource to transmit frequency resource allocation information of the interference signal There is an advantage.

The DM-RS generation related parameters may include antenna ports 5 and 7 to 14, slot number n _s , scrambling ID n _SCID , virtual cell ID n _ID ^i, have. Here, the virtual cell ID is required only when the antenna ports 7 to 14 are applied, and the RNTI is only needed when the antenna port 5 is applied.

The DM-RS generation-related parameters are transmitted from the base station of the interference cell to the base station of the victim cell located on the victim terminal through the backhaul link, and then transmitted to the victim cell through the new It can be delivered to the victim terminal by DCI or delivered to the victim terminal through multiple DCIs.

The victim terminal can generate the DM-RS of the inter-cell interference signal based on the parameters received from the base station.

In the case of the slot number, the UE can recognize the frame through the frame sync acquired using the Primary Synchronization Signal (PSS) and the Secondary Synchronization Signal (SSS) in one cell.

Therefore, in order to transmit the slot number of the inter-cell interference signal to the mobile station, a separate signaling parameter (T _SLOT ) for each slot number is defined as shown in Table 2 below, and a parameter corresponding to the slot number A method of transmitting to the terminal can be applied.

In order for the victim terminal to estimate the channel for the inter-cell interference signal, DM-RS resource allocation information is required. In the case where the antenna port 5 is applied (since the MU-MIMO operation may not be applied since it is an inter-cell interference signal), unlike the remaining antenna ports, there is no orthogonalization according to the use of Walsh codes, (frequency shift). Here, the type of the frequency variation may vary depending on the length (CP length) of the cyclic prefix.

Therefore, in case of the antenna port 5, if the cell ID and the CP length (T _CP ) of the inter-cell interference signal are transmitted to the terminal, the terminal can perform channel estimation on the inter-cell interference signal based on the DM-RS. For CP length, it is generally assumed that the damaged cell and the interference cell are the same. If the CP length of the collided cell and the CP of the collided cell are different, it is difficult to apply the IRC receiver because the bandwidth of the RE is changed.

On the other hand, in the case of antenna ports 7 to 14, although there is no frequency variation based on the cell ID, an orthogonal Walsh code is assigned to each antenna port.

Figures 5A and 5B show DM-RS resource mappings for antenna ports 7-14. In FIGS. 5A and 5B, 1 denotes an index of a time domain.

As shown in FIGS. 5A and 5B, a DM-RS to which a DM-RS is mapped differs according to an antenna port number, and a DM-RS mapped to each sub-carrier is also a DM-RS pattern ) Is different.

That is, up to four orthogonal Walsh codes may be assigned to a particular subcarrier, and there are two such subcarrier sets. Thus, a maximum of eight antenna ports (i.e., antenna ports 7 through 14) may be configured to have orthogonality.

In addition, when generating the DM-RS, the virtual cell ID is reflected to discriminate the DM-RS by randomization or orthogonalization according to the inter-cell interference condition. For example, when the virtual cell IDs are the same, the orthogonalization and the virtual cell IDs are different, the randomization can be applied.

In DM-RS generation, the scrambling ID is also assigned to 0 or 1 per antenna port and is reflected in the DM-RS sequence generation to further improve the randomization effect.

In summary, the victim terminal can perform channel estimation by separating the DM-RS for each layer through an antenna port number, a virtual cell ID, and a scrambling ID.

Meanwhile, in the LTE-A standard, an antenna port number and a scrambling ID combination are configured to transmit antenna port number information and scrambling ID information to a terminal, and an indication value is assigned to each combination message, .

The present invention provides a method for transmitting inter-cell interference information in consideration of the above-described contents.

First, a case where a normal CP (normal CP) is applied (i.e., using antenna ports 7 to 14) will be described.

The first method is a method of explicitly transmitting an antenna port number and a scrambling ID of an intercell interference signal. According to the LTE-A standard, when the transmission layer is 3 to 8, that is, when antenna ports 7 to 9, 7 to 10, 7 to 11, 7 to 12, 7 to 13 or 7 to 14 are used at the same time, 0 so that the scrambling ID information is not transmitted separately. In the present invention, an indication value for a combination of an antenna port and a scrambling identifier as shown in Table 3 is constructed in consideration of the above-mentioned contents, and a method of transmitting an indication value corresponding to an intercell interference signal is used. At this time, the cell ID (or virtual cell ID) information and slot number information for DM-RS generation should be transmitted together.

In the case of the first method described above, since the antenna port number is explicitly transmitted to the terminal, the terminal can correctly recognize the DM-RS pattern (or Walsh code).

In the second method, the proportion of the information occupied by the indication values for the antenna ports 7 and / or 8 among the contents of Table 3 is large, and when the antenna ports 7 and 8 are used as shown in FIGS. 5A and 5B, Considering that the DM-RS mapped in the case of using port 9 or more are different from each other, the combination shown in Table 3 is simplified to two cases as shown in Table 4, It is a method to transmit indication value.

Table 4 shows an example in which the antenna port 7 and / or 8 is defined as Case A, the antenna ports 7 to 14 are defined as Case B, the indication value 0 is assigned to Case A, and the indication value 1 is assigned to Case B .

6 is a conceptual diagram for explaining a DM-RS mapping combination.

In the present invention, as shown in FIG. 6, the antenna ports 7 and / or 8 (Case A) are mapped to one specific subcarrier, and the antenna ports 7 to 14 (Case B) Carriers are mapped to any one of consecutive subcarriers. Table 4 is used to simplify and transmit the antenna port information and the scrambling ID information of the inter-cell interference signal to the terminal.

In the second method, the BS transmits only the indication value of the corresponding case of the antenna port of the interference signal among Case A and Case B to the UE. The victim terminal performs a blind test on the DM-RS pattern (or Walsh code) and the scrambling ID set belonging to the corresponding Case based on the Case information received from the base station to estimate the channel.

For example, if the affected terminal recognizes that there is a signal corresponding to the case A of the interference signals, it is assumed that the interference signal corresponds to any one of the antenna port 7, the antenna port 8, and the antenna ports 7 and 8, A blind test is performed on the scrambling ID set for the DM-RS pattern (or Walsh code) corresponding to each antenna port to separate the channels and estimate them. In the same way, if the affected terminal recognizes that there is a signal corresponding to Case B among the interference signals, the combination included in Case B has the values 6 to 11 (i.e., antenna ports 7 to 9 , 7 to 10, 7 to 11, 7 to 12, 7 to 13, and 7 to 14), a blind test is performed by applying the DM-RS pattern (or Walsh code) corresponding to each combination. In Case B, since the scrambling ID is fixed to 0, the victim terminal need not consider the blind test for the scrambling ID. In the second method, information such as the cell ID (or virtual cell ID) and the slot number for DM-RS generation must be explicitly transmitted to the victim terminal.

In the third method, as shown in Tables 3 and 4, information on the antenna port and the scrambling ID is not explicitly transmitted to the terminal, but all combinations (i.e., combination of antenna port and scrambling ID) A blind test is performed on the channel to distinguish channels and then estimate the channel. Here, the set in which the victim terminal performs the blind test is the same as Case A and Case B in Table 4. In the case of the third method, information such as a cell ID (or a virtual cell ID) and a slot number for DM-RS generation must be explicitly transmitted to the victim terminal.

Among the three methods for transmitting the intercell interference information, the implementation complexity increases in the order of method 1, method 2 and method 3, and the amount of information that the base station transmits to the terminal increases in the order of method 3, method 2, and method 1 .

In case of extended CP, only antenna ports 7 and 8 are applied. Therefore, the intra-cell interference information transmission method described above can be applied to the inter-cell interference information transmission method when the extended CP is applied.

In the above-described method of transmitting intercell interference information, the parameters to be transmitted to the victim terminal may be generated and transmitted by generating a new DCI including the DCI information of the desired signal to be transmitted to the victim terminal, (I.e., transmission using a single DCI), and DCI including parameter information related to the interference signal in addition to the DCI transmission for the desired signal may be additionally transmitted to the terminal (i.e., transmission using multiple DCIs).

Channel Estimation and PMI-related Information Delivery Method for Different Cells in CRS-based Transmission Environment

Unlike the intra-cell interference occurring in the MU-MIMO transmission environment, inter-cell interference is caused by transmission diversity (TM 3), spatial diversity (TM 4), MU-MIMO (TM 5) Or the like can be applied.

In order to perform CRS-based channel estimation on the inter-cell interference signal, the victim terminal must know the CRS generation-related parameter, the CRS resource mapping information, the PMI allocation, and the frequency resource allocation information of the related interference signal.

The CRS generation related parameter may include a cell ID (N _ID ^CELL ), a CP length (length), and a slot number (n _s ) information. The CRS resource allocation related parameter may include an antenna port and cell ID information. In the case of CP length, the CP length of the interference cell and that of the damaged cell are generally the same.

In case of CRS-based inter-cell interference, PMI allocation information should also be delivered to the victim terminal.

Since the UE can acquire information such as the cell ID, the slot number, and the antenna port in the process of receiving the PSS / SSS and the PBCH in one cell, the information can be transmitted without allocating additional resources. That is, the UE can acquire the cell ID and the slot number based on the received PSS / SSS, and can acquire the antenna port information based on the received PBCH. However, in the inter-cell interference environment, even when the information is transmitted from the base station of the interference cell to the base station of the lost cell through the backhaul, additional parameters such as T _SLOT and T _CP described above are required to transmit the information to the UE .

CRS antenna ports (0 to 3) are implicitly transmitted through the CRC masking information of the PBCH in the existing intra-cell environment. Therefore, in the inter-cell interference environment, a separate signaling parameter is required to transmit the CRS-based antenna port of the interference cell to the UE.

In the present invention, as shown in Table 5, a parameter value (T _AP ) is assigned to each CRS antenna port, and a parameter value corresponding to the corresponding antenna port is transmitted to the terminal.

Meanwhile, CRS resource mapping information is also required for the victim terminal to perform CRS-based channel estimation on an inter-cell interference signal. The CRS resource is mapped according to the antenna port number and the cell ID. Therefore, since the CRS resource mapping information is overlapped with the CRS generation related parameter, there is no additional signaling overhead associated with the CRS resource mapping information.

The transmission of the frequency allocation information of the inter-cell interference signal related to the PMI allocation can be performed in the same manner as in the intra-cell interference described above. That is, the victim terminal may explicitly transmit necessary parameters to all the interference signals, or may transmit only the parameters related to the interference signal that has a dominant influence.

The method of transmitting CRS-related information and PMI information of the above-described inter-cell interference signal to the UE through the PDCCH (i.e., single DCI or multiple DCI) as in the DM-RS based interference signal information transmission method described above .

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

110: Resource allocated to the victim terminal
120: Resource allocated to the interfering terminal 1
130: resource allocated to the interfering terminal 2
410: Resource allocated to the victim terminal
420: Resource allocated to the interfering terminal
430: Resource allocated to the interfering terminal

Claims

As an interference information providing method performed in a base station,
Acquiring intra-cell interference signal information for interfering with a signal of the victim terminal; And
And transmitting the intra-cell interference signal information to the victim terminal,
In the transmitting of the intra-cell interference signal information, reference signal generation related information of the intra-cell interference signal is transmitted, or frequency resource allocation information and Precoding Matrix Indicator (PMI) allocation information of the intra-cell interference signal are transmitted And the interference information is transmitted to the base station.

In claim 1,
In the case of transmitting the intra-cell interference signal information to the victim terminal, DM-RS generation related information is provided as the intra-cell interference signal information in case of DM-RS based transmission, And an indication value corresponding to a DM-RS of the inter-cell interference signal among the indication values allocated to the combinations of the scrambling ID and the scrambling ID.

In claim 2,
Wherein the combination of the antenna port number and the scrambling ID includes a combination of antenna port numbers 7 and 8 and a scrambling ID.

In claim 1,
In the step of transmitting the intra-cell interference signal information to the victim terminal, frequency resource allocation information and PMI allocation information of the intra-cell interference signal are transmitted with the intra-cell interference signal information in case of CRS (Cell Specific RS) And transmits the frequency resource allocation information and the PMI allocation information of the inter-cell interference signal to the victim terminal.

In claim 1,
In the step of transmitting the intra-cell interference signal information to the victim terminal, frequency resource allocation information and PMI allocation information of the intra-cell interference signal are transmitted with the intra-cell interference signal information in case of CRS-based transmission, And only the frequency resource allocation information and the PMI allocation information for at least one interference signal selected according to a preset reference are transmitted.

In claim 5,
The frequency resource allocation information and the PMI allocation information for the selected at least one interference signal may be separately transmitted to the victim terminal or an interference information map including frequency resource allocation information and PMI allocation information for the selected at least one interference signal, and transmitting the interference information to the victim terminal through the map.

In claim 6,
Wherein the interference information map is configured by assigning PMI information to subbands corresponding to frequency resources allocated to the selected at least one interference signal and components of each subband.

In claim 1,
In the step of transmitting the intra-cell interference signal information to the victim terminal,
A DCI including a signal to be transmitted to the victim terminal, and a DCI including the intra-cell interference signal information in a single DCI (Downlink Control Information) including control information related to a signal to be transmitted to the victim terminal and intra- And transmitting the interference information independently.

As an interference information providing method performed in a base station,
Acquiring inter-cell interference signal information for interfering with a signal of a victim terminal; And
And transmitting the inter-cell interference signal information to the victim terminal,
Wherein the step of transmitting the inter-cell interference signal information includes at least one of a reference signal generation information of the inter-cell interference signal, resource allocation information of the reference signal, and resource allocation information of the inter-cell interference signal, The method comprising:

In claim 9,
In the step of acquiring the inter-cell interference signal information,
Wherein the base station receives the inter-cell interference signal from at least one other base station through a backhaul.

In claim 9,
The reference signal generation information includes:
The generation information of DM-RS (Demodulation Reference Signal) includes at least one of an antenna port, a slot number, a scrambling ID, a virtual cell ID, and RNTI (Radio Network Temporary Identifier)
Wherein the cell information includes at least one of a cell ID, a cyclic prefix length, and slot number information as CRS (Cell Specific RS) generation information.

In claim 11,
Wherein the slot number information constitutes a parameter value corresponding to each slot number and transmits a parameter value corresponding to a slot number related to the inter-cell interference signal among the parameter values.

In claim 9,
The resource allocation information of the reference signal includes at least one of mapping pattern information and frequency displacement information as resource allocation information of the DM-RS, or at least one of an antenna port number and cell ID information Information on the interference information.

In claim 9,
In the step of transmitting the inter-cell interference signal information to the victim terminal,
And transmits only the DM-RS generation information and the DM-RS resource allocation information for the signals serving as interference to the frequency resource block allocated to the signal of the victim terminal among the plurality of inter-cell interference signals. Way.

In claim 9,
In the step of transmitting the inter-cell interference signal information to the victim terminal,
When the antenna port 5 is applied to the DM-RS based inter-cell interference signal, only the cell ID and the cyclic prefix length of the inter-cell interference signal are transmitted.

In claim 9,
In the step of transmitting the inter-cell interference signal information to the victim terminal,
And transmits the antenna port number, the scrambling ID, the cell ID, and the slot number information of the inter-cell interference signal when at least one of the antenna ports 7 to 14 is applied to the DM-RS based inter-cell interference signal. Information delivery method.

In claim 16,
In the step of transmitting the inter-cell interference signal information to the victim terminal,
An antenna port number and scrambling ID information of the inter-cell interference signal are transmitted, a unique indication value is assigned to each combination of an antenna port number and a combination of an antenna port number and a scrambling ID, and an indicator corresponding to a DM- Value of the interference information.

In claim 16,
In the step of transmitting the inter-cell interference signal information to the victim terminal,
A DM-RS mapping pattern of an inter-cell interference signal is divided into a specific number of cases, a DM-RS mapping pattern of an inter-cell interference signal, And transmits the eigenvalues allocated to the UEs when the UE is in the coverage area.

In claim 16,
In the step of transmitting the inter-cell interference signal information to the victim terminal,
And transmits CRS generation information, CRS resource allocation information, Precoding Matrix Indicator (PMI) allocation information, and resource allocation information of the inter-cell interference signal of the inter-cell interference signal when the inter-cell interference signal is transmitted based on the CRS. The method comprising:

In claim 16,
In the step of transmitting the inter-cell interference signal information to the victim terminal,
And when the intercell interference signal is transmitted based on the CRS, the parameter value corresponding to the antenna port number is transmitted to the victim terminal.