JP2014535188A - Signal transmitting / receiving apparatus and method in distributed antenna system - Google Patents

Abstract

An apparatus and method for transmitting and receiving signals in a distributed antenna system (DAS) is provided. A method for determining an initial state in a distributed antenna system includes a step of receiving a predetermined value through upper signaling and a step of determining an initial state based on the predetermined value, wherein the predetermined value is determined according to a transmission point. The initial state of a different scramble sequence is a set value.

Description

  The present invention relates to a wireless mobile communication system, and more particularly, to a signal transmitting / receiving apparatus and method in a distributed antenna system.

  In general, a cellular radio mobile communication system is established by establishing a plurality of cells in a limited area. A base station component responsible for mobile communication within each cell is located in the center of the cell. A base station (BS) component is an antenna or a signal processing part that transmits a radio signal, and provides mobile communication services to terminals (User Equipments, UEs) in the cell at the center of the cell. Thus, a system in which an antenna is installed at the center of a cell is called a centralized antenna system (CAS), and a general mobile communication system is an example of such a system.

  There is a distributed antenna system (DAS) different from CAS.

  However, the conventional DAS, when compared with the CAS, requires a system that can provide an improved mobile communication service by uniformly distributing the antennas in the cell service area.

  An object of the present invention is to address at least the above-mentioned problems and / or disadvantages and provide at least the following conveniences. That is, an object of the present invention is to provide a demodulation reference signal (DMRS) for efficient communication in a distributed antenna system (DAS) in which antennas are arranged in a manner distributed over the service area of each base station. It is to provide a method for determining an initial state for generating a scrambling sequence.

  In order to achieve the above object, according to one aspect of the present invention, a method for determining an initial state in a distributed antenna system (DAS) is provided. The method includes a step of receiving a predetermined value through upper signaling, and a step of determining an initial state based on the predetermined value, wherein the predetermined value indicates that an initial state of a scramble sequence that differs according to a transmission point is determined. The set value is indicated.

  According to another aspect of the present invention, an apparatus for determining an initial state in a distributed antenna system (DAS) is provided. The apparatus includes a receiving unit that receives a predetermined value using higher-level signaling, and a control unit that determines an initial state based on the predetermined value, and the predetermined value varies depending on a transmission point. The initial state has another set value.

  According to yet another aspect of the invention, a method for determining an initial state in a distributed antenna system (DAS) is provided. The method includes receiving a scrambling code identifier (SCID) and determining whether the initial state determined based on the received scrambling code identifier is a legacy initial state or a new initial state. And a step of performing.

  According to yet another aspect of the invention, an apparatus for determining an initial state in a distributed antenna system (DAS) is provided. The apparatus includes: a receiving unit that receives a scrambling code identifier (SCID); and whether the initial state determined based on the received scrambling code identifier is a legacy initial state or a new initial state. And a control unit for determining.

  According to the present invention, without separate notification from the eNB, the UE can identify the initial state based on the scrambling sequence generated and used for scrambling the E-PDCCH.

  Moreover, UE and eNB can acquire the interference randomization effect between DMRS transmitted by the transmission point which has the same cell ID using the method for determining a new initial state.

  Furthermore, a scrambling sequence can be obtained using a method for determining a new initial state.

  The foregoing and other aspects, features, and advantages of embodiments of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which:

It is a figure which shows the several cell in the conventional system. FIG. 2 is a diagram illustrating a downlink resource block (RB) of a long term evolution-advanced (LTE-A) system. It is a figure which shows the resource element (RE) in which 1 port channel state information reference signal (Channel Status Information Reference Signal, CSI-RS), 2 port CSI-RS, 4 port CSI-RS, and 8 port CSI-RS are transmitted. is there. It is a figure which shows the some transmission point in a distributed antenna system (DAS). FIG. 3 is a diagram illustrating downlink control information (DCI) transmitted through a physical downlink control channel (PDCCH) according to an embodiment of the present invention. 3 is a flowchart illustrating an operation of a base station (BS) according to an embodiment of the present invention. 5 is a flowchart illustrating an operation of a terminal (UE) according to an embodiment of the present invention. FIG. 3 is a diagram illustrating a relationship between an extended PDCCH (E-PDCCH) and a physical downlink shared channel (PDSCH).

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Further, in describing the present invention, when it is determined that a specific description of a related known function or configuration unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Further, the terms described later are defined in consideration of the function of the present invention, and can be changed depending on the intention of the user, the operator, or the custom. Therefore, the above terms must be defined based on the entire contents of this specification.

In the embodiments of the present invention, an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) wireless communication system based on, in particular, the Third Generation Partnership Project ^{(3 rd Generation Partnership Project, 3GPP} ) extended universal terrestrial Although specifically described on the basis of the enhanced universal terrestrial radio access (EUTRA) standard, the main gist of the present invention has a similar technical background and channel configuration as long as they do not significantly depart from the scope of the present invention. It will be apparent to those skilled in the art that other communication systems are applicable and that various changes and modifications of the embodiments described herein are possible.

  In a mobile communication system having a plurality of base stations, the present invention provides a downlink in a distributed antenna system (DAS) in which an antenna operated by each base station is distributed over a service area of a corresponding base station. A method for performing interference measurement at a terminal for efficient communication is disclosed.

  Since the early stage of providing voice-centric communication services, mobile communication systems have evolved into high-speed and high-quality wireless packet data communication systems to provide data services and multimedia services. Recently, 3GPP high-speed downlink packet access (High Speed Downlink Packet Access, HSDPA), high-speed uplink packet access (High Speed Uplink Packet Access, HSUPA), LTE (Long Term Evolution), LTE-A (Long Term Evolution Advanced) ) Various mobile communication standards such as 3GPP2 High Rate Packet Data (HRPD) and IEEE 802.16 have been developed to support high speed and high quality wireless packet data transmission services. In particular, LTE systems developed to efficiently support high-speed wireless packet data transmission utilize various wireless connection technologies to maximize wireless system capacity. The LTE-A system, which has advanced from the LTE system, has an improved data transmission capability when compared to the LTE system.

  LTE generally refers to a base station and a terminal component corresponding to Release 8 or 9 of the 3GPP standards organization, and LTE-A refers to a base station and a terminal component corresponding to Release 10 of the 3GPP standards organization. means. Even after standardizing the LTE-A system, the 3GPP standards body is developing standardization for subsequent releases with improved performance based on the standardized LTE-A system.

  Existing third generation and fourth generation wireless packet data communication systems such as HSDPA, HSUPA, HRPD, LTE / LTE-A are adaptive modulation and coding (AMC) to improve transmission efficiency. Scheme and channel-sensitive scheduling scheme are used. When using the AMC scheme, the transmitter can adjust the amount of data transmitted according to channel conditions. That is, when channel conditions are poor, the transmitter matches the reception error probability to the desired level by reducing the amount of data transmitted. When the channel condition is good, the transmitter matches the reception error probability to the desired level by increasing the amount of data transmitted and efficiently transmits a lot of information. When utilizing channel sensitive scheduling resource management scheme, the system capacity is allocated after the channel is assigned to the user in order for the transmitter to selectively serve users having excellent channel conditions among multiple users. Increased compared to providing services. Such an increase in capacity is usually referred to as multi-user diversity gain. AMC schemes and channel sensitive scheduling schemes receive partial channel state information fed back from a receiver and apply appropriate modulation and coding techniques at the most efficient time.

  When used with a multiple input multiple output (MIMO) transmission scheme, the AMC scheme can determine the number or rank of the spatial layers of the transmission signal. In addition, the AMC scheme determines an optimal data transmission rate and considers not only the coding rate and modulation scheme but also the number of layers for transmission using MIMO.

  Recently, research to replace CDMA (Code Division Multiple Access), which is a multiple access method used in second and third generation mobile communication systems, with OFDMA (Orthogonal Frequency Division Multiple Access) in next generation mobile communication systems. Is actively progressing. 3GPP and 3GPP2 have begun standardization work on evolved systems based on OFDMA. Since frequency domain scheduling can be performed on the frequency axis, the OFDMA scheme is expected to increase capacity compared to the CDMA scheme. The channel sensitive scheduling method can be used to obtain the capacity gain from the characteristic that the channel changes with time, and the capacity gain can be obtained using the characteristic that the channel changes depending on the frequency.

  Generally, in a mobile communication system, a mobile communication network composed of a plurality of cells is established in order to expand the system capacity. At this time, the size of each cell is determined according to the transmission power of the corresponding cell.

FIG. 1 is a diagram showing a plurality of cells arranged in a conventional system.
In FIG. 1, transmission points 100 transmitting with high transmission power form cells having a large area, and transmission points 110, 120, 130, and 140 transmitting relatively low transmission power are within 100 cell areas. A cell having a small area is formed. In FIG. 1, transmission points 100, 110, 120, 130, and 140 transmit a plurality of mobile communication services in each cell by transmitting and receiving radio signals using one antenna or a plurality of antennas at each position. To the terminal. Transmission points 150 that transmit with high transmission power form other cells with large areas, and transmission points 160, 170, 180, and 190 that transmit relatively low transmission power are small within 150 cell areas. A cell having a region is formed. The ten cells formed by the transmission points 100, 110, 120, 130, 140, 150, 160, 170, 180, and 190 each have a unique cell ID. The cell ID is a value assigned to each cell so that the terminal can identify each cell, and 500 or more cell IDs are supported in the LTE / LTE-A system.

  In FIG. 1, signals transmitted by each cell are transmitted differently using corresponding cell IDs. In particular, in the case of a downlink PDSCH demodulation reference signal (DMRS) used by a UE to perform channel estimation in an LTE-A system, scrambling applied for signal randomization. The sequence is applied differently according to the cell ID. The DMSCH for PDSCH is a reference signal transmitted from the eNB to the UE so as to enable channel estimation for performing channel restoration for the PDSCH.

  In the LTE-A system, a signal is transmitted using the OFDMA scheme. The bandwidth for signal transmission in the LTE-A system is divided into a plurality of resource blocks (RBs), and the UE receives a traffic signal through one or more RBs.

  FIG. 2 is a diagram illustrating a downlink RB of the LTE-A system. One RB is composed of 12 subcarriers in the frequency domain, and is composed of 14 OFDM symbols on the time axis. The minimum frequency and time resource that can carry data in one RB is called a resource element (RE), and RB is 168 (12 subcarriers × 14 OFDM symbols) REs. Composed.

  As shown in FIG. 2, not only a cell specific reference signal (CRS), a DMRS (Demodulation Reference Signal), a PDSCH (Physical Downlink Shared Channel), and a control channel, but also signals that perform different functions. Are transmitted in one RB. A channel status information reference signal (CSI-RS) is transmitted at positions 200 to 219 in FIG. The CSI-RS is transmitted in one or more of the positions 200 to 219, and the PDSCH is not transmitted in the position where the CSI-RS is transmitted, but in the position not configured for the CSI-RS in the positions 200 to 219. PDSCH is sent instead.

  FIG. 3 shows a resource element (RE) in which a 1-port channel status information reference signal (Channel Status Information Reference Signal, CSI-RS), 2-port CSI-RS, 4-port CSI-RS, and 8-port CSI-RS are transmitted. FIG. It can be seen from FIG. 3 that the transmission positions of 1-port CSI-RS and 2-port CSI-RS have sub-pattern characteristics included in the transmission positions of 4-port CSI-RS. Moreover, the transmission position of 4 port CSI-RS has the sub-pattern characteristic contained in the transmission position of 8 port CSI-RS. For example, the transmission location 320 where one 4-port CSI-RS can be transmitted is included in the transmission location 330 where one 8-port CSI-RS can be transmitted.

  As shown in FIG. 1, when there are a plurality of cells having different cell IDs, different scrambling is applied to the DMRS for PDSCH in FIG. 2 according to the cell ID. By applying different scrambling, interference generated between DMSCHs for PDSCH transmitted from different cells can be efficiently randomized, thereby improving channel estimation performance. Specifically, the scrambling sequence applied to each cell is generated using an initial state as shown in Equation (1).

  Generally, a scrambling sequence is generated according to a generator polynomial, and a scrambling sequence value generated according to an initial state changes when the scrambling sequence is generated. In Equation (1),

Indicates a cell ID value and has a variable value according to the cell ID. Therefore, cells having different cell IDs have different initial states, so that the PDSCH DMRS is scrambled with different scrambling sequences.

  In the LTE-A system as described above, the function of performing scrambling in different cells is a random interference system when a distributed antenna system (DAS), which is an advanced mobile communication system, is established. There is a limit to conversion. The reason is that, in the case of DAS, as in the conventional system, the transmitter and the receiver provide mobile communication services by being placed at distributed points, but each cell has a unique cell ID. This is because a plurality of transmission points (Transmission Points) share one cell ID.

  FIG. 4 is a diagram showing a plurality of transmission points in the distributed antenna system (DAS). In FIG. 4, a transmission point 400 that performs transmission with high transmission power and a transmission point 410, 420, 430, and 440 that perform transmission with low transmission power all share one cell ID. In this way, in the case of a DAS in which a plurality of transmission points share one cell ID, allocation of radio resources at a plurality of transmission points to one terminal is compared with the conventional mobile communication as shown in FIG. And can be executed efficiently.

  In the case of DAS as shown in FIG. 4, when a plurality of transmission points share one cell ID, when using the DMRS scrambling scheme for PDSCH defined in the current LTE-A system, The transmission point uses a scrambling sequence generated based on the same initial state, and as a result, efficient interference randomization cannot be performed. That is, in FIG. 4, the PDSCH DMRS transmitted from the transmission point where the cell ID is set to 0 is effectively interfered with the PDSCH DMRS transmitted from the transmission point where the cell ID is set to 1. A randomizing effect can be obtained, but the same effect cannot be obtained between transmission points having the same cell ID.

  Therefore, the present invention achieves efficient interference randomization by appropriately assigning an initial state necessary for generating a PDSCH DMRS scrambling sequence in a DAS having a plurality of transmission points sharing the same cell ID. Disclosed are methods that can be achieved.

  As described above, in the DAS, in the DMRS for PDSCH transmitted in the downlink, the initial state of the scrambling sequence is determined according to the cell ID, so that an interference randomization effect can be achieved between transmission points having the same cell ID. Can't get. In order to solve such a problem, it is necessary to set an initial state of a different scrambling sequence for each different transmission point in the same cell. In the present invention, several important conditions for applying the new initial state of the scrambling sequence are presented as follows.

  Condition 1: In DAS, each transmission point must be able to use a scrambling sequence based on a new initial state.

  Condition 2: In DAS, each transmission point must be able to use not only a new initial state but also a scrambling sequence based on a legacy initial state.

  Condition 3: It should be possible to dynamically change between the legacy initial state and the new initial state according to the network decision.

  Condition 1 is necessary to efficiently perform interference randomization when transmitting to UEs that support DAS. Condition 2 is necessary to perform multi-user MIMO (MU-MIMO) that performs transmission with the same time and frequency resources for UEs that do not support DAS and UEs that support DAS. A conventional terminal that does not support DAS cannot support a scrambling sequence based on a new initial state proposed in the present invention. In order to simultaneously perform MU-MIMO transmission to legacy UEs and UEs supporting new initial states with the same time and frequency resources using multiple antennas, DMRS for PDSCH does not achieve interference randomization well. However, it must be transmitted using a scrambling sequence based on the legacy initial state.

  Condition 3 may execute transmission to a terminal that supports DAS for each transmission point according to the determination of the scheduler, or perform transmission to a terminal that supports DAS and a terminal that supports only the conventional technology. It is important to be good. That is, in a specific time period, the DMRS scrambles the DMRS using the scrambling sequence based on the new initial state when transmitting to a terminal that supports the scrambling sequence based on the new initial state. However, in other time periods, the PDSCH DMRS is scrambled using a scrambling sequence based on the legacy initial state for legacy terminals that do not support DAS. As if each transmission point supports a scrambling sequence based on the legacy initial state and a scrambling sequence based on the new initial state, a UE that supports DAS must support all two scrambling sequences.

  In order to utilize the scrambling sequence based on the new initial state, the initial state must be determined by a method shared by the UE and the eNB. The present invention proposes a plurality of methods applicable to the LTE-A system as a method for determining a new initial state. In the following, methods 1 to 6 for determining a new initial state for DMRS for PDSCH are proposed.

Method 1: Method of determining an initial state according to the position of the CSI-RS port 15 and the number of CSI-RS ports CSI-RS is a reference signal used by the UE to measure a downlink channel in LTE-A. is there. In the LTE-A system, CSI-RS corresponds to ports 15 to 22. Table 1 shows the positions of CSI-RS ports 15 and the number of CSI-RS ports possible in the LTE-A system. That is, Table 1 shows the position of the CSI-RS port 15 with respect to the number of CSI-RS ports in the normal cyclic prefix subframe of the LTE-A system.

  In Table 1, if the CSI-RS has 1, 2, 4, and 8 port numbers, it can have 20, 10 and 5 possible port 15 positions, respectively. Recognize. In general, transmission points located at a short distance transmit CSI-RS at different positions in order to avoid interference. Thus, the initial state of the scrambling sequence for the DMSCH for PDSCH in the DAS is expressed by using the feature that CSI-RSs at different positions are set at transmission points located at a short distance. ) Can be determined.

  Here, the 1-port CSI-RS and the 2-port CSI-RS have the same number of CSI-RS ports. In such a case, the same initial state may be set instead of setting an individual initial state.

  Another method for determining a new initial state according to the position of the CSI-RS port 15 and the number of CSI-RS ports uses Equation (6) as follows.

  Here, i has a value as shown in Table 2 below according to the number of CSI-RS ports. Table 2 below shows i according to the number of CSI-RS ports in Equation (6).

  The method for setting the initial state of a new scrambling sequence for PDRS DMRS based on Equation (6) is to determine the initial state by comprehensively considering the number and position of possible CSI-RS ports. It is. Such a method has an advantage of changing only the number of bits having a relatively small initial state when compared with the equations (2) to (5). The method for determining the initial state of the DMSCH for PDSCH based on Equation (6) is the same as in Equations (2) to (5), and the individual initial states in the case of 1-port CSI-RS and 2-port CSI-RS. The same initial state may be set instead of setting.

Method 2: Method of Determining Initial State According to Location of CSI-RS Port 15 According to the location of CSI-RS port 15, the initial state of a new scrambling sequence for PDSCH DMRS can be determined as follows. .

  Here, as shown in Table 3, the i value can be determined according to the position of the CSI-RS port 15 possible in the LTE-A system.

Method 3: Method for Determining Initial State According to 8-Port CSI-RS Pattern Including Transmission CSI-RS Pattern In LTE-A system, 1-port CSI-RS, 2-port CSI-RS, and 4-port CSI-RS are all FIG. 3 shows an 8-port CSI-RS sub-pattern. That is, the transmission positions of 1-port CSI-RS, 2-port CSI-RS, and 4-port CSI-RS are included in the specific 8-port CSI-RS transmission positions. Using such characteristics, the initial state of a new scrambling sequence for PDSCH DMRS can be determined based on which 8-port CSI-RS sub-pattern. Table 4 below shows the i value according to which 8-port CSI-RS is included based on the following formula (8).

  When the initial state of the new scrambling sequence of the DMRS for PDSCH is determined according to Equation (8) and Table 4, all CSI-RSs included in the same 8-port CSI-RS have the same initial state. Have.

Method 4: Method for Determining Initial State According to Relative Position in 8-Port CSI-RS Pattern Including Transmit CSI-RS Pattern As shown in FIG. 3, the CSI-RS in the LTE-A system uses a specific rule. Designed to have. For example, the transmission position 300 in FIG. 3 where the 2-port CSI-RS is transmitted and the transmission position 304 in FIG. 3 where the other 2-port CSI-RS is transmitted are the 8-port CSI-RS including each 2-port CSI-RS. Have the same relative position. That is, the relative position of the transmission position 300 in FIG. 3 with respect to the transmission position 330 of the 8-port CSI-RS and the relative position of the transmission position 304 in FIG. 3 with respect to the transmission position 331 of the 8-port CSI-RS are the same. The initial state of the new scrambling sequence for the PDSCH DMRS can be determined using the relative position for the 8-port CSI-RS as shown in Table 5 below. Table 5 below shows the i value according to the relative transmission position in the port CSI-RS transmission position, and is based on the following formula (9).

  In the method described above, the i value is set in consideration of the number of CSI-RS ports. As shown in Table 6 below, the initial state of a new scrambling sequence for the PDSCH DMRS can be determined as shown in Table 6 below, considering only the relative position of the CSI-RS port 15. Table 6 below shows i values according to the relative transmission position of the port 15 in the port CSI-RS transmission position, and is based on the following formula (10).

Indicates a physical layer cell identifier, n _SCID indicates the number of scrambling code identifiers, i value sets the number of CSI-RS ports, and n _S indicates a slot number in the radio frame.

  When determining the initial state of the scrambling sequence for the DMSCH for PDSCH according to the CSI-RS configuration as in methods 1 to 4 described above, when setting a plurality of CSI-RSs, the initial state is determined according to the plurality of initial states. Can be done.

Method 5: Method for Determining the Initial State According to Upper Signaling In Method 1 to Method 4, the new initial state of the scrambling sequence for the PDSCH DMRS is set according to the CSI-RS setting. Such a method achieves its objective without additional signaling between the eNB and the UE, but is difficult to optimize according to the situation because it is performed according to predetermined rules. In order to overcome such disadvantages, the eNB notifies the UE of which initial state is specifically utilized through individual upper signaling. In this case, the eNB may notify the UE of all information corresponding to the initial state, or may notify the UE of some information. In general, since some of the initial state is predetermined, the previously determined value may be used without additional notification, and the eNB notifies the UE only of the remaining part. Also good. For example, a new initial state of the scrambling sequence for PDSCH DMRS is determined as shown in Equation (11) below.

here,

ビットで表現可能な情報である。 Is determined by an individual process. As a result, the eNB notifies the UE only of the i value in Expression (11) for the determination of the initial state using the upper signaling proposed in the present invention. As shown in Equation (11), when i is in the range of 0 to K−1, the initial state is

Information that can be expressed in bits.

  In addition to equation (11) of method 5, the initial state can be determined using equation (12).

  When comparing with equation (11), in equation (12):

は、Ｘに置き換えられることが分かる。

Is replaced by X.

  In Equation (12), X is a value that has an information amount of 9 bits and is notified to the terminal using upper signaling. In legacy LTE / LTE-A systems, the initial state for DMRS

は、個別の上位シグナリングなしにプライマリ同期信号（ＰＳＳ）及びセカンダリ同期信号（ＳＳＳ）の同期チャネルを受信するＵＥにより判定される値である。本発明で提案する数式（１２）は、ＰＳＳ及びＳＳＳを用いて判定した

Is a value determined by the UE that receives the synchronization channel of the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) without separate upper signaling. Formula (12) proposed in the present invention was determined using PSS and SSS.

の代わりにｅＮＢが上位シグナリングを通してＵＥに通知するＸ及びｉに基づいて初期状態を決定する。このような方法を使用する場合に、数式（１１）と比較してさらに多くの初期状態からの選択が可能である。

Instead, the initial state is determined based on X and i that the eNB notifies the UE through higher level signaling. When such a method is used, it is possible to select from a larger number of initial states as compared with Equation (11).

  In Equation (12), in addition to the method of determining the initial state based on X and i, a method of determining the initial state using only X is also possible. This is similar to the case where i is always fixed to '0'. Such a method can reduce implementation complexity by enabling reuse of the initial state of DMRS defined in legacy LTE / LTE-A. In this manner, when the initial state is determined using only X, the eNB notifies the UE which initial state to use through higher level signaling with the X value.

Method 6: Determining the initial state according to the UE's RNTI Method 5 determines a new initial state using individual upper signaling. When such method 5 is used, the additional overhead due to higher level signaling is inevitable. One method for avoiding the above overhead is to determine an initial state using a radio network temporary identifier (RNTI) provided for each UE. The RNTI is used to identify the UE and is transmitted over the network when connected to the LTE / LTE-A system regardless of whether the UE performs Coordinated Multipoint transmission (CoMP). . By using the RNTI provided in this way, no additional upper signaling as in method 5 is required. In order to determine a new initial state using RNTI, the following formula (13) or formula (14) is used.

  In Equation (14), G is an integer greater than 1.

  Methods 1 to 6 are methods for determining an initial state of a new scrambling sequence for the PDSCH DMRS. As previously mentioned, there are several conditions that must be satisfied when scrambling the PDSCH DMRS for each transmission point in the DAS. Methods 1 to 5 determine a new initial state that satisfies condition 1. In addition, the scrambling of the DMRS for PDSCH needs to appropriately use the scrambling sequence generated by the legacy initial state and the scrambling sequence generated by the new initial state determined by the methods 1 to 6. is there. That is, the legacy initial state and the new initial state must be changed by scheduling determination for each subframe.

  For such a function, the present invention proposes a method for notifying which DMRS is scrambled using which initial state through the PDCCH of the LTE system. For this purpose, the information 'CoMP scrambling index' is newly added to the PDCCH and transmitted for notification whenever the eNB allocates downlink radio resources to the UE. The information 'CoMP scrambling index' is transmitted through the PDCCH, but is notified by the same method using E-PDCCH (Enhanced PDCCH), which is an enhanced PDCCH channel.

  Table 7 below relates to the first embodiment in which which initial state is used to notify the DMSCH for PDSCH is scrambled through the PDCCH.

  Table 7 shows a number of new initial states. The presence of a plurality of new initial states in this way is because cooperative transmission using a plurality of transmission points is possible in DAS. When coordinated transmission is used, the UE may also receive downlink transmission at any one of multiple transmission points per subframe, as determined by the central controller, A downlink transmission can also be received at the transmission point.

  In Table 7, the legacy initial state and the new initial state can all have the same cell ID, but by having different cell IDs from each other, transmission of transmission points and adjacent cells having the same cell ID in DAS Enables coordinated transmission between points.

  In Table 7, the new initial state is determined prior to notification through the PDCCH using one of method 1 to method 6 proposed in the present invention. In the method 1 to the method 4, the initial state is determined according to the CSI-RS set in the UE, and in the method 5, the initial state is determined by individual upper signaling. Also in method 6, the initial state is determined by the UE's RNTI.

  Table 8 below relates to a second embodiment in which which initial state is used to notify the DMSCH for PDSCH is scrambled through the PDCCH.

  In Table 8, there are multiple legacy initial states and multiple new initial states. The plurality of new initial states exist in this way because cooperative transmission using a plurality of transmission points is possible in DAS. Also, the existence of a plurality of legacy initial states is to enable coordinated transmission between adjacent cells that are not established in a distributed antenna configuration. In Tables 7 and 8, the plurality of initial states includes at least one legacy initial state. The present invention allows a UE to use a new initial state and a legacy initial state simultaneously. It is also possible to use only the new initial state using the same method. In Tables 7 and 8, all legacy initial states are replaced or removed with new initial states.

  The notification of the initial state for the scrambling sequence of the DMRS for PDSCH through the PDCCH proposed in the present invention is performed using 2 bits as in the above-described embodiment. An additional initial state is reported using additional bits. In addition, it is possible to notify which one of one legacy initial state and one new initial state is used by using one bit. In the above description, the legacy initial state may be determined implicitly according to the cell ID of the serving cell to which the UE is connected without separate upper signaling, and in the above-described method, the initial state is determined individually. May be determined using higher-level signaling.

  Another method of notifying the UE which initial state to use uses a combination of a CoMP scrambling index and a scrambling code identification (SCID) defined in the legacy LTE-A system. Table 9 below relates to a third embodiment in which the initial state is used to notify the DMSCH for PDSCH is scrambled via the PDCCH.

  The SCID defined in legacy LTE-A determines only the least significant bit (LSB) in the initial state of scrambling for DMRS. However, when applying the method proposed in the present invention, the SCID can be combined with the CoMP scrambling index to determine not only the initial LSB of scrambling for DMRS but also other bits. That is, in Table 9, the CoMP scrambling index and the SCID do not determine only one LSB bit of the legacy SCID in the initial state, but one of the plurality of initial states determined by the methods 1 to 6. To decide. The plurality of initial states determined by the above-described method are different from each other by a plurality of bits. That is, when the CoMP scrambling index and the SCID in Table 9 are used together, the SCID does not determine a 1-bit LSB as in the prior art. Which initial state is specified by the information obtained by combining the CoMP scrambling index and the SCID is determined by the methods 1 to 6.

  Table 10 below relates to a fourth embodiment for notifying which PDRS DMRS is scrambled using the initial state through the PDCCH.

  In LTE-A, the SCID has a 1-bit information amount, but is transmitted after being combined with DMRS port allocation information. In this case, only when the number of allocated DMRS ports is 1 or 2, the SCID has a value of '0' or '1', and the number of allocated DMRS ports is 3 or more. The SCID is fixed to '0'. As shown in Table 9 and Table 10, when a combination of CoMP scrambling index and SCID is used, unlike the prior art, even if three or more DMRS ports are allocated, the scrambling sequence for DMRS The initial state can be assigned differently.

  As described above, even when three or more DMRS ports are assigned, by assigning different initial states, there is an advantage of enabling interference randomization between transmission points in DAS. That is, when using only the SCID, if three or more DMRS ports are allocated, the SCID always has a value of '0', thereby using a fixed initial state. However, when the CoMP scrambling index proposed in the present invention is used together with the SCID as shown in Tables 9 and 10, a different initial state can be assigned even if the SCID has a value of '0'. The methods proposed in Tables 7 and 8 have such advantages as well.

  FIG. 5 is a diagram illustrating downlink control information (DCI) transmitted through the PDCCH according to the present invention.

  In FIG. 5, the CoMP scrambling index 500 proposed in the present invention is transmitted along with the SCID 510 and other DCI related information 520 through the PDCCH. The UE can use the CoMP scrambling index 500 to determine which initial state based scrambling sequence is used, as described above. In FIG. 5, SCID 510 is 1-bit information and is defined in the legacy LTE / LTE-A system to enable MU-MIMO at one transmission point. Such values are included in the equations (1) to (10). In addition to the method of transmitting SCID 510 as 1-bit information, SCID 510 may be combined with DMRS port allocation information for transmission. That is, the UE can determine a new initial state using one of the methods 1 to 6 before receiving the CoMP scrambling index 500 and the SCID 510 of FIG. Thereafter, the UE receives the information of FIG. 5 from the eNB through the PDCCH and is therefore notified of which initial state the DMRS is scrambled by.

  FIG. 6 determines the initial state of a new scrambling sequence for a PDSCH DMRS according to the present invention, and the eNB scrambling which PDSCH DMRS for which scrambling sequence is generated and which scrambling sequence is transmitted It is a figure which shows the process of notifying UE of an initial state whether it is used for performing.

  In FIG. 6, the eNB determines in step 600 how to configure the CSI-RS configuration of the UE associated with the DAS. In step 610, the eNB notifies the UE of the CSI-RS configuration of the UE determined in step 600 through higher level signaling. After the UE's CSI-RS configuration is notified in this way, in step 620, the eNB performs scheduling for determining to which UE the downlink resource is allocated. In step 620, after the eNB determines which UE to transmit the PDSCH which is a traffic channel, in step 630, whether the corresponding UE is a UE that supports a new initial state for DMRS scrambling. The corresponding action is executed according to the above. If in step 630 it is determined that the UE does not support a new initial state for DMRS scrambling for PDSCH, the eNB may use the PDSCH scrambled in step 640 with a scrambling sequence based on the legacy initial state. Send DMRS. As in step 640, if the UE does not support the new initial state, the CoMP scrambling index proposed in the present invention is not transmitted.

  However, if in step 630 the UE supports a new initial state, the eNB determines in step 650 which initial state the corresponding UE uses to generate the scrambling sequence. In step 650, the initial state applied to the corresponding UE is one of the legacy initial state and the new initial state, as in Table 7 or Table 8. The initial state determined in step 650 is notified to the UE in step 660 through E-PDCCH, which is an extended channel of PDCCH or PDCCH. eNB transmits PDSCH and DMSCH for PDSCH to corresponding UE together with PDCCH.

  In FIG. 6, it is assumed that the new initial state is determined by the CSI-RS configuration. That is, assume that one of methods 1 to 4 is used. The present invention applies a similar sequence of steps when method 5 and method 6 are used, which allows the eNB to inform the UE which initial state is used.

  FIG. 7 is a diagram illustrating a process of determining an initial state of a new scrambling sequence for a PDSCH DMRS according to the present invention and determining which PDSCH DMRS to which the initial state is applied is transmitted from the eNB. It is.

  In step 700 of FIG. 7, the UE is notified of the CSI-RS configuration related to the DAS from the eNB. Using the CSI-RS configuration notified in step 700, the UE determines the initial state of a new scrambling sequence for the PDSCH DMRS. At this time, one of the methods 1 to 4 proposed in the present invention is used. One of the methods 1 to 6 is used to notify the UE of the initial state of the new scrambling sequence for the PDSCH DMRS. In this case, regardless of the CSI-RS configuration in step 700, the eNB can notify the UE directly through upper signaling which initial state to use.

  In step 700 and step 710 of FIG. 7, after the UE determines the initial state used for the new scrambling sequence for the DMRS for PDSCH, in step 720, the PDCCH or PDCCH improved channel E -DCI (520) as shown in FIG. 5 is received using PDCCH. In step 720, the UE that has received the DCI determines which initial scrambling sequence has been generated using the CoMP scrambling index 500. In step 720, if the CoMP scrambling index is '00', the UE scrambles through a scrambling sequence generated using the legacy initial state when the eNB transmits the downlink PDSCH DMRS in step 740. In step 760, PDSCH which is a traffic channel is received.

  However, if the CoMP scrambling index is not '00' in step 730, the UE determines that scrambling is performed using the scrambling sequence generated by the new initial state, and in step 750, corresponding In step 760, PDSCH which is a traffic channel is received using the scrambling sequence to be performed. In FIG. 7, one of methods 1 to 4 is used to determine a new initial state according to the CSI-RS configuration, and the CoMP scrambling index has 2-bit information and is defined as shown in Table 7. Assume that. Similarly, such a process is applicable to Method 5, Method 6, and Table 8.

  In FIG. 7, the initial state of scrambling for DMRS is determined using only the CoMP scrambling index. Further, as shown in Table 8, the method of using the SCID together with the CoMP scrambling index can be applied to the same process as in FIG. That is, in FIG. 7, the CoMP scrambling index is applied together with the SCID as shown in Table 8, and after the CoMP scrambling index and SCID are received in step 720 of FIG. 7, in step 730, the CoMP scrambling index and SCID are changed. Used to determine the initial state.

  In an LTE-A system that supports DAS, E-PDCCH can be supported for efficient control channel transmission. FIG. 8 is a diagram illustrating a relationship between E-PDCCH and PDSCH. In FIG. 8, the E-PDCCH is transmitted to a specific portion of radio resources, as indicated at 800. The E-PDCCH at portion 800 is used to notify the corresponding UE of the DCI necessary to receive the PDSCH of a particular UE, as indicated at 810. E-PDCCH is an extended channel of PDCCH used as a control channel in legacy LTE / LTE-A systems. E-PDCCH can be operated based on DMRS in the same way as PDSCH, but PDCCH is based on CRS. Therefore, it is very different from PDCCH in that it can always be operated.

  When the E-PDCCH is used based on DMRS, it is necessary to define which initial state is used for the scrambling sequence generated by the corresponding DMRS for PDCCH. In general, in the case of DMRS for PDSCH, the UE notifies the UE of which scrambling sequence generated based on which initial state is generated by the E-PDCCH or PDCCH that is the control channel.

  However, in the case of a control channel such as E-PDCCH, there is no other control channel that notifies this individually. In order to solve such a problem, in the case of E-PDCCH, one initial state among a plurality of initial states used to generate a scrambling sequence for the DMRS for PDSCH is set and used. . That is, in the case of DMRS for E-PDCCH, a scrambling sequence generated based on the corresponding initial state is always used. The DMRS for E-PDCCH uses one of the initial states of the DMRS for PDSCH. For example, as shown in Table 7, when there are four applicable initial states, the eNB sets one of these states as the initial state for the E-PDCCH.

  The E-PDCCH is transmitted together with the DMRS scrambled using a scrambling sequence generated based on a predetermined dedicated initial state. For this purpose, the UE is notified of the E-PDCCH notified in the initial setting without being notified or determining for each subframe which scrambling sequence based on which initial state the E-PDCCH has been scrambled. E-PDCCH is received using a scrambling sequence based on the initial state for PDCCH.

  As described above, the initial DMRS scrambling state for E-PDCCH is set to one of the initial DMRS scrambling states for PDSCH. In order to set the scrambling initial state of the DMRS for E-PDCCH, the eNB uses the RRC signaling to indicate to the UE which one of the scrambling initial states of the DMRS for PDSCH is used. Can be notified. The scrambling initial state of the DMRS for E-PDCCH can be determined by a method agreed in advance between the UE and the eNB. In order to do this, one of the methods determined by a method agreed in advance between the UE and the eNB is the highest reception strength among the transmission points where the CSI-RS configuration is set. A strong scrambling initial state can be used. In general, since the UE can periodically notify the eNB of the reception strength of the reference signal measured for each transmission point, when using the method described above, the UE is not notified individually. The UE can determine which initial state the E-PDCCH is scrambled with a generated scrambling sequence.

  Meanwhile, although not shown in the drawings, not only the methods 1 to 6 according to the embodiment of the present invention but also a processor (or control unit) capable of executing the operation proposed in the present invention may be provided in the terminal and the base station. Good.

  Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the scope and spirit of the invention. The scope of the present invention should not be limited to the above-described embodiments, but should be defined within the scope of the appended claims and their equivalents.

400 Transmission points for transmission with high transmission power 410, 420, 430, 440 Transmission points for transmission with low transmission power 500 CoMP scrambling index 510 SCID

Claims (14)

A method for determining an initial state in a distributed antenna system (DAS) comprising:
Receiving a predetermined value through upper signaling; and
Determining an initial state based on the predetermined value,
The method for determining an initial state in a distributed antenna system, wherein the predetermined value indicates a value in which an initial state of a different scramble sequence is set according to a transmission point.   The initial state in the distributed antenna system according to claim 1, wherein the initial state is determined based on at least one of an antenna port position, the number of antenna ports, and an antenna pattern. how to.   The method of claim 1, wherein the predetermined value is 9 bits.   The method of claim 1, wherein at least one of the initial states is a legacy initial state.   The initial state for the extended physical downlink control channel (E-PDCCH) is a value set in advance through upper signaling, and determines an initial state in the distributed antenna system according to claim 1. how to. An apparatus for determining an initial state in a distributed antenna system (DAS),
A receiving unit that receives a predetermined value using upper signaling; and
A control unit for determining an initial state based on the predetermined value,
The apparatus for determining an initial state in a distributed antenna system, wherein the predetermined value has another value in which an initial state of a different scramble sequence is set according to a transmission point.   The initial state in the distributed antenna system according to claim 6, wherein the initial state is determined based on at least one of a position of an antenna port, a number of antenna ports, and an antenna pattern. Device to do.   7. The apparatus for determining an initial state in a distributed antenna system according to claim 6, wherein the predetermined value is 9 bits.   7. The apparatus for determining an initial state in a distributed antenna system according to claim 6, wherein at least one of the initial states is a legacy initial state.   The initial state for an extended physical downlink control channel (E-PDCCH) is a value set in advance through upper signaling, and determines an initial state in the distributed antenna system according to claim 6. Device to do. A method for determining an initial state in a distributed antenna system (DAS), comprising:
Receiving a scrambling code identifier (SCID);
Determining whether the initial state determined based on the received scramble code identifier is a legacy initial state or a new initial state. How to judge.   The method of claim 11, further comprising determining whether the initial state determined based on the multi-point coordinated transmission (CoMP) scrambling index is a legacy initial state or a new initial state. Of determining an initial state in a distributed antenna system. An apparatus for determining an initial state in a distributed antenna system (DAS),
A receiver for receiving a scrambling code identifier (SCID);
An initial state in the distributed antenna system, comprising: a control unit that determines whether the initial state determined based on the received scramble code identifier is a legacy initial state or a new initial state A device that determines   The control unit according to claim 13, wherein the control unit determines whether the initial state determined based on a multipoint coordinated transmission (CoMP) scrambling index is a legacy initial state or a new initial state. An apparatus for determining an initial state in the described distributed antenna system.

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