KR20120087773A - Method and device for generating reference signal in cellular mobile communication system - Google Patents

Abstract

The cellular mobile communication system attempts initial access to obtain C-port information from a base station, transmits an SRS, selects a distributed antenna for D-port information, and communicates with the base station through the selected distributed antenna and a central antenna. And C-port information disposed in the center of the cell when initial access of the terminal is attempted, and after the SRS transmission is instructed to the terminal, the SRS is distributed in a central antenna and a cell, thereby partially transmitting the cell. Receives through distributed antennas transmitting and receiving with the terminal in the area, analyzes the SRS, selects at least one distributed antenna and informs the terminal of the selected D-port information of the selected distributed antennas, and then selects the selected distributed antenna and the central antenna The base station is configured to communicate with the terminal through.
A distributed antenna system (DAS) of a cellular mobile communication system can provide improved mobile communication service compared to CAS by distributing antennas evenly in a service area of a cell. According to the present invention, in a cellular mobile communication system in which a plurality of base stations exist, many types of DM-RS sequences are used in a distributed antenna system (DAS) in which antennas operated by each base station are distributed and arranged in a service area of a corresponding base station. It is provided to facilitate the DM-RS separation of multiple terminals operating in the same RB. Through this, we will maximize the utilization of RS resources in the DAS. Accordingly, the cellular mobile communication system according to the embodiment of the present invention efficiently generates and transmits a DM-RS through antennas disposed in the center and the periphery of the cell, thereby providing high data to each terminal regardless of the position of the terminals located in the cell. There is an advantage that can be transmitted and received at the transmission rate.

Description

METHOD AND DEVICE FOR GENERATING REFERENCE SIGNAL IN CELLULAR MOBILE COMMUNICATION SYSTEM}

The present invention relates to a method and apparatus for generating a reference signal in a cellular mobile communication system in which a plurality of base stations exist. In particular, a distributed antenna system in which antennas operated by each base station are distributed and arranged in a service area of a corresponding base station. A method and apparatus for efficiently generating a reference signal in a system (DAS).

The mobile communication system is evolving into a high speed, high quality wireless packet data communication system for providing data service and multimedia service, instead of providing a voice-oriented service in the early days. Recent 3GPP high speed downlink packet access (HSDPA), high speed uplink packet access (HSUPA), long term evolution (LTE), long term evolution advanced (LTE-A), high rate packet data (HRPD) of 3GPP2, and IEEE Various mobile communication standards such as 802.16 were developed to support high speed, high quality wireless packet data transmission services. In particular, the LTE system was developed to efficiently support high-speed wireless packet data transmission, and maximizes wireless system capacity by utilizing various wireless access technologies. The LTE-A system is an advanced wireless system of the LTE system and has improved data transmission capability compared to LTE.

Existing third generation wireless packet data communication systems such as HSDPA, HSUPA, and HRPD use techniques such as adaptive modulation and coding (AMC) and channel sensitive scheduling to improve transmission efficiency. By utilizing the AMC method, the transmitter can adjust the amount of data to be transmitted according to the channel state. That is, if the channel condition is poor, the transmitter reduces the amount of data to be transmitted to meet the desired level. If the channel condition is good, the transmitter increases the amount of data to be transmitted. Can be. When the channel sensitive scheduling resource management method is used, the system capacity is increased compared to allocating and serving a channel to one user because the transmitter selectively services a user having a good channel condition among several users. This increase in capacity is called the multi-user diversity gain. In short, the AMC method and the channel sensitive scheduling method are methods of applying appropriate modulation and coding schemes at a time when it is determined to be the most efficient by receiving partial channel state information from the receiver.

The AMC method may also include a function of determining the number or rank of spatial layers of a signal to be transmitted when used with a multiple input multiple output (MIMO) transmission scheme. In this case, the AMC method considers not only the code rate and modulation scheme but also how many layers are transmitted using MIMO to determine the optimal data rate.

Recently, studies are being actively conducted to convert CDMA (code division multiple access), which is used in second and third generation mobile communication systems, to orthogonal frequency division multiple access (OFDMA) in a next generation system. 3GPP and 3GPP2 have begun standardizing on evolutionary systems using OFDMA. It is known that the capacity can be increased in the OFDMA method as compared to the CDMA method. One of various causes of capacity increase in the OFDMA scheme is that frequency domain scheduling can be performed. Just as the channel gains capacity gains through channel-sensitive scheduling as the channel changes over time, more capacity gains can be achieved if the channel utilizes different characteristics depending on frequency.

In the prior art, a cellular system composed of a plurality of cells is constructed as shown in FIG. 1 to provide a mobile communication service utilizing the aforementioned various methods.

1 is a diagram illustrating a transmitting and receiving antenna disposed at the center of each cell in a cellular mobile communication system composed of three cells.

Referring to FIG. 1, three cells of a cell 100, a cell 110, and a cell 120 are configured, and the reference numeral 160 illustrates a cell structure of the cell 100. In this case, the cell 100 includes an antenna 130, a user equipment (UE) 140, and a terminal 150 located at the center, such as 160. The antenna 130 provides a mobile communication service to two terminals located at 100. The terminal 140 provided with the mobile communication service using the antenna 130 has a relatively low data transmission rate because the distance to the antenna 130 is relatively far compared to the terminal 150.

As shown in FIG. 1 above. Each cell antenna of each cell 100-120 has a form of a central antenna system (CAS) disposed in the center of the cell. In the case of a CAS, even if a plurality of antennas are arranged in each cell, these antennas are arranged in the center of the cell and operate to communicate with the service area of the cell. When the antennas for each cell are arranged and operated in the form of CAS in the cellular mobile communication system as shown in FIG. 1, a reference signal is used to measure downlink channel state for each cell or to demodulate the downlink signal. signal). In the LTE-A system of 3GPP, the UE estimates channel information necessary for demodulation of a downlink signal by using a demodulation reference signal (DM-RS) transmitted by a base station, and channel status of CSI-RS (CSI-RS). The terminal measures a channel state between the base station and itself by using an information reference signal.

FIG. 2 is a diagram illustrating positions of a DM-RS and a CSI-RS transmitted from a base station to a terminal in an LTE-A system.

Referring to FIG. 2, signals for four DM-RS ports may be transmitted at positions corresponding to reference numerals 220 and 221, respectively. That is, signals for DM-RS ports 7, 8, 11, and 13 are transmitted to a position corresponding to 220, and signals for DM-RS ports 9, 10, 12, and 14 are transmitted to a position corresponding to 221. In addition, different DM-RS ports corresponding to the same location are distinguished through a code division multiplexing (CDM) method. Codes assigned to each DM-RS port are defined as shown in Table 1 below.

The DM-RS sequence transmitted at the positions of the DM-RS ports is defined as in Equation 1 below.

는 하향 링크에서 사용 가능한 주파수 자원 단위(resource block; RB)의 개수를 나타내고, m은 수열의 인덱스를 나타내며, DM-RS 포트 별로 RB당 12개의 DM-RS 자원에 대한 수열 인덱스의 매핑 방법은 주파수 우선 매핑 방법으로서 도 3에 나타내었다.

는 pseudo-random 수열로서, 이 수열의 발생기에 대한 초기값은 다음의 <수학식 2>와 같이 정의된다.In <Equation 1>

Denotes the number of frequency resource blocks (RBs) available in the downlink, m denotes a sequence index, and a mapping method of sequence indexes for 12 DM-RS resources per RB per DM-RS port is frequency. First, as a mapping method, it is shown in FIG.

Is a pseudo-random sequence, and the initial value of the generator of the sequence is defined as in Equation 2 below.

는 셀 ID를 나타내고, n_SCID는 스크램블링 구분 정보를 나타내며 PDCCH를 통해 전달되는 DCI format 2B 또는 2C 내의 스크램블링 구분 필드(scrambling identity field)에 의해 0 또는 1로 결정된다. 즉, 같은 셀 내에서 안테나 포트들은 동일한 셀 ID를 갖기 때문에, 안테나 포트별 DM-RS 수열은 n_SCID에 의해 구분되는 두 가지만 존재한다.here

_{Denotes a} cell ID, n _SCID denotes scrambling classification information, and is determined to be 0 or 1 by a scrambling identity field in DCI format 2B or 2C transmitted through PDCCH. That is, since antenna ports have the same cell ID in the same cell, there are only two DM-RS sequences distinguished by n _SCIDs .

Referring to FIG. 2, signals for two CSI-RS antenna ports may be transmitted for each location at locations 200 through 219. That is, the base station transmits signals for two CSI-RS antenna ports for downlink measurement at one location such as location 200 to the UE. As shown in FIG. 2, in the cellular system composed of a plurality of cells, a CSI-RS can be transmitted by allocating a separate location for each cell. For example, the cell 100 of FIG. 1 transmits the CSI-RS at position 200, the cell 110 transmits the CSI-RS at position 205, and the cell 120 transmits the CSI-RS at position 210. As described above, the allocation of time and frequency resources for CSI-RS transmission at different locations for each cell is to prevent CSI-RSs of different cells from generating mutual interference with each other.

The CSI-RS sequence transmitted at the location of the CSI-RS ports is defined as in Equation 3 below.

In Equation 3, c (i) is a pseudo-random sequence, and the initial value of the generator of the sequence is defined as in Equation 4 below.

In Equation 4, l denotes an OFDM symbol order in one slot, and N _CP is determined to be 0 or 1 depending on the length of a cyclic prefix (CP) used in a cell.

In the case of using the CAS method as shown in FIG. 1, since the transmitting and receiving antennas of each base station are concentrated in the center of the cell, there is a limit in supporting a high data rate to the terminal away from the center of the cell. That is, in the CAS, providing a high data rate to all terminals existing in a cell is greatly influenced by where the terminal is located in the cell. Therefore, the conventional cellular mobile communication system can transmit and receive at a high data rate in the case of a terminal located relatively close to the antennas disposed in the center of the cell, but there is a problem that can not be the case of a terminal located in a relatively distant place.

An object of the present invention is to propose a method and related apparatus for generating a DM-RS suitable for a DAS in order to construct a Distributed Antenna System (DAS) based on an LTE-A system and to effectively operate distributed antennas.

In the cellular mobile communication system according to the present invention for solving the above problems, the reference signal generation method, at least two scrambling parameters for each user terminal is determined corresponding to a plurality of antennas distributed in the service area of the base station And generating a demodulation reference signal sequence for each of the antennas by combining the scrambling variables, and transmitting the demodulation reference signal sequence through each of the antennas. . The reference signal generation method in the cellular mobile communication system according to the present invention for solving the above problem, the process of determining a scrambling variable for each user terminal corresponding to a plurality of antennas distributed in the service area of the base station And generating a demodulation reference signal sequence for the user terminal according to the scrambling variable, and transmitting the demodulation reference signal sequence through each of the antennas. At this time, in the method of generating a reference signal according to the present invention, some of the antennas use resources orthogonal to the rest, and the generation process includes any one of the antennas for the user terminal in the antennas. And transmitting control information for changing a spreading factor used to receive the demodulation reference signal sequence to the user terminal.

On the other hand, in the cellular mobile communication system according to the present invention for solving the above problems, the reference signal generating apparatus, at least two scrambling parameters for each user terminal corresponding to a plurality of antennas distributed in the service area of the base station And a control unit for determining demodulation, a scrambler for generating a demodulation reference signal sequence for each of the antennas by combining the scrambling variables, and a transmitter for transmitting the demodulation reference signal sequence through each of the antennas. Characterized in that.

In addition, the reference signal generation device in the cellular mobile communication system according to the present invention for solving the above problems, for determining a scrambling variable for each user terminal corresponding to a plurality of antennas distributed in the service area of the base station And a control unit, a scrambler for generating a demodulation reference signal sequence for the user terminal according to the scrambling variable, and a transmitter for transmitting the demodulation reference signal sequence through each of the antennas. At this time, in the reference signal generation apparatus according to the present invention, some of the antennas use resources orthogonal to the rest, and the control unit, when any one of the antennas for the user terminal in the antennas use the orthogonal resources And transmitting control information for changing a spreading factor used to receive the demodulation reference signal sequence.

A distributed antenna system (DAS) of a cellular mobile communication system can provide improved mobile communication service compared to CAS by distributing antennas evenly in a service area of a cell. According to the present invention, an efficient DM-RS is generated in a distributed antenna system (DAS) in which antennas operated by each base station are distributed in a service area of a corresponding base station in a cellular mobile communication system having a plurality of base stations. We want to maximize the use of RS resources in the DAS. Accordingly, the cellular mobile communication system according to the embodiment of the present invention efficiently generates and transmits a DM-RS through antennas disposed in the center and the periphery of the cell, thereby providing high data to each terminal regardless of the position of the terminals located in the cell. There is an advantage that can be transmitted and received at the transmission rate.

1 is a diagram illustrating a transmitting and receiving antenna disposed in a center of each cell in a cellular mobile communication system consisting of three cells;
2 is a diagram illustrating the positions of a DM-RS and a CSI-RS transmitted by a base station to a terminal in an LTE-A system;
3 is a diagram illustrating a mapping method for DM-RS resources of a DM-RS sequence;
4 is a diagram illustrating a configuration of a distributed antenna system for distributing and transmitting antennas for each cell in a cellular mobile communication system according to an embodiment of the present invention;
5 is a view for explaining a situation to be solved and an DM-RS signal generation method according to the embodiment of the present invention,
6 is a diagram illustrating a DM-RS sequence generation procedure of a base station according to the first embodiment of the present invention;
7 is a diagram illustrating a DM-RS sequence generation procedure of a base station according to a second embodiment of the present invention;
8 is a view showing a DM-RS sequence generation procedure of a base station according to a third embodiment of the present invention;
9 is a view showing an apparatus for generating a DM-RS sequence of a base station according to embodiments of the present invention; and
FIG. 10 is a diagram illustrating a procedure of generating a DM-RS by a base station in consideration of switching of a new scrambling and an application of an existing scrambling according to the first embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with the accompanying drawings. In addition, in describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

Further, in describing the embodiments of the present invention in detail, an OFDM-based wireless communication system, in particular the 3GPP EUTRA standard will be the main target, but the main subject of the present invention is another communication system having a similar technical background and channel form. In addition, it is possible to apply with a slight modification in the range without departing greatly from the scope of the present invention, which will be possible in the judgment of those skilled in the art.

In general, a cellular wireless mobile communication system is achieved by building a plurality of cells in a limited area. In each cell, base station equipment dedicated to mobile communication in the cell is located in the center of the cell area. The base station equipment is composed of an antenna for transmitting a radio signal and a signal processing portion, and provides a mobile communication service to the terminals in the cell at the center of the cell. The system in which the antenna is installed in the center of the cell is called a centralized antenna system (CAS), and a general mobile communication system is this type.

A contrasting system is a Distributed Antenna System (hereinafter referred to as DAS). The DAS can provide an improved mobile communication service compared to CAS by distributing the antennas evenly over the service area of the base station. The present invention relates to a distributed antenna system (DAS) distributed in a service area of each base station. The present invention seeks to maximize the use of RS resources in a DAS by generating an efficient DM-RS in the DAS. That is, in the cellular mobile communication system in which a plurality of base stations exist, antennas distributed in a distributed antenna system (DAS) in which antennas operated by each base station are distributed and arranged in a service area of a corresponding base station This paper proposes a method and a related apparatus for generating a DM-RS suitable for a DAS in order to effectively manage them.

As described above, providing a high data rate to all terminals existing in a cell in the CAS is greatly influenced by where the terminal is located in the cell. Due to the antennas located in the center of the cell, a relatively close terminal can transmit and receive at a high data rate, but a relatively far terminal is difficult to provide a high data rate. The present invention to solve the above problems by building a cellular mobile communication system in the form of a DAS.

4 is a diagram illustrating a structure of a mobile communication system according to an embodiment of the present invention. In this case, it is assumed that the mobile communication system of the present embodiment is composed of three cells. Here, a base station is located in the center of each service area, and the antennas of the base station are distributed and disposed in the entire service area of each base station.

Referring to FIG. 4, the mobile communication system according to the present embodiment includes a plurality of cells 300, 310, and 320, and a central antenna 330 and a cell (centered at each cell 300, 310, and 320). There are a plurality of distributed antennas 360, 370, 380, and 390, a first terminal 340, and a second terminal 350 that are distributed in all service areas in 300, 310, and 320. Here, each of the cells 300, 310, and 320 may be formed of small cells of the central antenna 330 and the distributed antennas 360, 370, 380, and 390. At this time, each cell 300, 310, 320 is operated with one cell ID. That is, in each cell 300, 310, 320, the central antenna 330 and the distributed antennas 360, 370, 380, and 390 have the same cell ID. The first terminal 340 and the second terminal 350 is a communication antenna corresponding to at least one selected from the central antenna 330 and the distributed antennas 360, 370, 380, 390 for uplink or downlink transmission Through the mobile communication service is provided from the base station.

For example, the first terminal 340 is provided with a mobile communication service from the base station through the distributed antennas 380 and 390 in a nearby location, and the second terminal 350 is a mobile communication service from the base station through the central antenna 330. Can be provided. If the mobile communication system supports CAS, since the first terminal 340 is far from the central antenna 330, the data transmission rate is relatively low. However, if the mobile communication system supports the DAS, the first terminal 340 can be provided with a relatively high speed data transmission through the close distributed antennas (380, 390).

FIG. 5 is a diagram illustrating a situation to be solved through an embodiment of the present invention and a method of generating a DM-RS signal according to the present invention.

Referring to FIG. 5, the central antenna 401 of the base station is disposed in the center of the cell 400 using the DAS, and the distributed antennas 410, 411, 412, 413, 414 and 415 of the base station are located in the entire service area. Are distributed. In this case, it is assumed that the UE UE1 420 receives downlink information through the distributed antenna 410 and the UE2 421 receives downlink information through the distributed antenna 411 in the cell 400. Further, suppose that the base station decides to transmit downlink information about two UEs through each distributed antenna in the same RB at the same time. In this case, when the DM-RS sequence is used as in Equation 1, as in LTE-A, two UEs receiving downlink information through the same RB for the same n _SCID value are perfectly matched as shown in FIG. 3. The use of -RS resources and sequences causes each DM-RS to interfere with each other. Therefore, if LTE-A downlink DM-RS transmission method designed in consideration of CAS in LTE-A system is introduced into DAS as it is, resource cannot be used efficiently, and it is the same for UEs using different distributed antennas in consideration of DAS. There is a need for a new method of creating and transmitting downlink DM-RSs to enable RB allocation.

A first, second, and third method for generating a downlink DM-RS for a DAS, which enables a base station to simultaneously transmit information on a plurality of UEs in the same RB through a plurality of antennas among a central antenna or distributed antennas. , And the fourth embodiment will be described in detail.

In this case, the DM-RS generation method according to the first, second and third embodiments of the present invention distinguishes the DM-RS by adding a DM-RS sequence using at least two scrambling variables. That is, the base station determines at least two scrambling variables for each UE in correspondence with the antennas distributed and distributed in the corresponding service area. The base station then combines the scrambling variables to generate a DM-RS sequence for each of the antennas. The base station also transmits a DM-RS sequence through each of the antennas.

Example 1

The DM-RS generation method according to the first embodiment of the present invention uses scrambling using n _RNTI value which is a unique number of a UE additionally allocated by a base station in addition to scrambling of a DM-RS sequence by n _SCID in Equation 1. Introduce more. This allows DAS to use a wider variety of DM-RS sequences than CAS. That is, the DM-RS sequence according to the first embodiment is generated as shown in Equation 5 below.

In Equation 5, c (i) is a pseudo-random sequence, and an initial value of the generator of the sequence is defined as in Equation 6 below.

개의 서로 다른 값을 출력하는 함수이다. <수학식 6>에서 대한 예시로

를 고려할 수 있다. 이는 n_SCID가 0 또는 1의 값만 가진다는 점을 고려하고 가능한 G 값을 충분히 보장할 수 있도록 하는 방법이다. 이 방법을 일반화하여

와 같이 설정할 수도 있으며 여기서 n은 16보다 작은 값이다. 그리고 <수학식 6>에서 수열의 초기값에 mod G 를 도입하는 이유는 같은 RB 내에 다른 UE를 위한 DM-RS의 개수에 한정을 두어 간섭 측정(interference measurement)이 용이하도록 하기 위함이며 G가 커질수록 동시에 사용 능한 DM-RS의 개수는 늘어나지만 간섭 측정이 복잡하고 불확실해지게 된다. G 값은 사전에 결정되어 있는 값일 수도 있고 중앙의 기지국이 방송(broadcasting) 채널을 통해 셀 내의 단말들로 알려줄 수도 있다.Where G is the number of sequences to be added using n _RNTI and f (a, b) is a with 0 or 1 and b with 0 to G-1 as input.

Outputs two different values. As an example in <Equation 6>

May be considered. This method takes into account that n _SCID has only a value of 0 or 1, and ensures a sufficient G value. Generalize this method

It can be set as follows, where n is a value less than 16. In addition, the reason for introducing mod G in the initial value of the sequence in Equation 6 is to limit the number of DM-RSs for other UEs in the same RB to facilitate interference measurement. As the number of DM-RSs available at the same time increases, the interferometry becomes complicated and uncertain. The G value may be a predetermined value or the central base station may inform the terminals in the cell through a broadcasting channel.

If a new scrambling initial value such as Equation 6 is newly used, the previously developed LTE Release 9 or 10 terminals do not recognize the new scrambling. Therefore, even if the terminal to which the new scrambling and the existing terminals are allocated to port 7 and port 8 using orthogonal sequences, as shown in Table 1, orthogonality cannot be guaranteed due to different scrambling. Therefore, there is a need to devise a method for supporting efficient multi-user MIMO (MU-MIMO) operation by guaranteeing orthogonality of port 7 and port 8 for the existing terminals and the new terminals. As a method for this, it may be considered that the terminal applying the new scrambling enables the existing scrambling to be applied in the situation of operating the MU-MIMO with the existing terminals and otherwise enables the dynamic switching to apply the new scrambling. . That is, a bit indicating whether to use existing scrambling or new scrambling may be added to downlink control information transmitted through the downlink control channel so that the terminal may apply .scrambling accordingly. Here, the new scrambling has an initial value according to Equation 6, and the existing scrambling has an initial value according to Equation 2. Information on whether to apply the new scrambling may be included in control information for downlink scheduling for determining resource allocation and MCS.

6 is a diagram illustrating a new DM-RS sequence generation procedure of a base station according to the first embodiment of the present invention.

Referring to FIG. 6, the embodiment starts from step 500 where the base station confirms scheduling for a UE operating in a DAS situation. That is, the base station identifies the UE for scheduling corresponding to each of the antennas. In step 510, the base station checks the n _RNTI value of the UE to be scheduled and [n _RNTI]. Calculate mod G]. That is, the base station uses the n _RNTI value and mod G of the UE to determine [n _RNTI]. mod G] is determined by the scrambling variable. Thereafter, the base station sets n _SCID in step 520 and generates a DM-RS sequence for the UE by using Equation 6. At this time, n _SCID is configured to prevent collision in consideration of n _RNTI values of other UEs scheduled in the same RB. That is, the base station determines n _SCID as a scrambling variable. And the base station is n _SCID and [n _RNTI mod G] to generate a DM-RS sequence for the UE. Finally, the DM-RS sequence generated in step 530 is transmitted to the corresponding RB through the corresponding antenna port, and the DM-RS generation and transmission process is completed. In contrast, the terminal is [n _RNTI In consideration of the new scrambling using mod G], the channel is estimated through the DM-RS and downlink data is received. Herein, a procedure for generating a DM-RS in consideration of switching of a new scrambling and an existing scrambling application will be described later with reference to FIG. 10.

Second Embodiment

The DM-RS generation method according to the second embodiment of the present invention further introduces scrambling of the DM-RS sequence through additional dynamic control information in addition to scrambling of the DM-RS sequence by n _SCID in LTE-A. In the above-described embodiment, the n- _RNTI value, which is semi-static information, is used, whereas the DM-RS transmission method according to the present embodiment can simultaneously perform DM-RS scrambling and DM-RS antenna port designation through dynamic control information. It is possible to generate various DM-RS sequences for DAS. Introducing scrambling of the DM-RS sequence through dynamic control information may be useful to prevent collisions where the same DM-RS sequence is used simultaneously in different distributed antennas, rather than using semi-static information.

As described above, LTE-A supports two DM-RS sequences using n _SCID having a value of 0 or 1. For this purpose, three bits of the downlink control information are defined as shown in Table 2 below.

If not specified in Table 2, the n _SCID value is always set to zero.

The DM-RS generation method according to the second embodiment of the present invention can sufficiently utilize n _SCID and additionally introduce a new parameter n _SCID2 to support DM-RS transmitted simultaneously through more distributed antennas. do. In addition, by limiting the number of layers that can be used for information transmitted through the distributed antenna to ensure more types of DM-RS sequence. If the number of layers that can be used through the distributed antenna is limited to 4, DM-RS can be generated using the following <Table 3>.

value One CW Two CW 0 1 layer, port 7, n _SCID = 0 n _SCID2 = 0 2 layer, port 7-8, n _SCID = 0 n _SCID2 = 0 One 1 layer, port 7, n _SCID = 1 2 layer, port 7-8, n _SCID = 1 2 1 layer, port 8, n _SCID = 0 3 layer, port 7-9, n _SCID = 0 3 1 layer, port 8, n _SCID = 1 3 layer, port 7-9, n _SCID = 1 4 2 layer, port 7-8, n _SCID = 0 4 layer, port 7-10, n _SCID = 0 5 2 layer, port 7-8, n _SCID = 1 4 layer, port 7-10, n _SCID1 = 1 6 3 layer, port 7-9, n _SCID = 0 5 layer, port 7-11, n _SCID = 0 7 4 layer, port 7-10, n _SCID = 0 6 layer, port 7-12, n _SCID = 0 8 1 layer, port 7, n _SCID = 0 n _SCID2 = 1 7 layer, port 7-13, n _SCID = 0 9 1 layer, port 7, n _SCID = 1 8 layer, port 7-14, n _SCID = 0 10 1 layer, port 8, n _SCID = 1 2 layer, port 7-8, n _SCID = 0 n _SCID2 = 0 11 1 layer, port 8, n _SCID = 0 2 layer, port 7-8, n _SCID = 1 12 2 layer, port 7-8, n _SCID = 0 3 layer, port 7-9, n _SCID = 0 13 2 layer, port 7-8, n _SCID = 1 3 layer, port 7-9, n _SCID = 1 14 3 layer, port 7-9, n _SCID = 0 4 layer, port 7-10, n _SCID = 0 15 4 layer, port 7-10, n _SCID = 0 4 layer, port 7-10, n _SCID = 1

In Table 2, which is the case of LTE-A, n _SCID is used only as 0 when one codeword is transmitted in two layers and two codewords are transmitted in three or four layers. This is because it is designed considering only the characteristics of the multi-user MIMO (MU-MIMO) of the LTE-A system. However, in case of DAS, n _SCID is used as 1 in <Table 3> because n _SCID value must be fully utilized within the limited number of distributed antenna layers. In addition, n _SCID2 was introduced to secure the number of various DM-RS sequences.

In the case of <Table 3>, the number of layers transmitted to the distributed antenna is limited to 4, but distributed antennas may support only a smaller number of layers because equipment cost must be reduced. If the number of layers through the distributed antenna is 2, DM-RS can be generated using the following <Table 4>.

In the case of Table 4, by limiting the number of layers through the distributed antenna to 2, when the two codewords are transmitted, only one bit can be added to increase the number of n _SCID2 possible to five. Also, considering that one codeword is transmitted only to multiple layers in an LTE or LTE-A system, only one codeword is transmitted, and n _SCID2 is extended only for one layer when only one codeword is transmitted. Three kinds of n _SCID2 can be obtained. That is, an additional n _SCID2 can be used by excluding an initial transmission from a central antenna and retransmission of the distributed antenna.

In the case of generating the DM-RS using Table 3 or Table 4, the DM-RS sequence is generated by using Equation 7 below.

In Equation 7, c (i) is a pseudo-random sequence, and the initial value of the generator of the sequence is defined as in Equation 8 below.

In Equation 8, f (n _SCID , n _SCID2 ) is a function that generates a possible value by combining n _SCID and n _SCID2 .

7 is a diagram illustrating a DM-RS sequence generation procedure of a base station according to the second embodiment of the present invention.

Referring to FIG. 7, the embodiment starts from step 600 with a base station confirming scheduling for a UE operating in a DAS situation. That is, the base station identifies the UE for scheduling corresponding to each of the antennas. In step 610, the base station determines scrambling variables corresponding to the UE in consideration of collision of UEs using an RB such as a UE to be scheduled. That is, the base station sets n _SCID and n _SCID2 values as scrambling variables. Thereafter, in step 620, the base station checks the number of layers and antenna ports of the UE to be scheduled and determines control information using Table 3 or Table 4. That is, the base station determines the control information using the scrambling variables, the number of layers, and the antenna port.

Next, the base station transmits the control information determined in step 630 to the UE via the control channel. Thereafter, the base station generates a DM-RS sequence for the UE by using Equation 7 in step 640, transmits the DM-RS through the antenna port to the corresponding RB, and finishes the DM-RS generation and transmission process. That is, the base station generates and transmits a DM-RS sequence for the corresponding UE by combining n _SCID and n _SCID2 values.

Third Embodiment

The DM-RS generation method according to the third embodiment of the present invention uses an additional nDI (new data indicator) bit for an inactivated codeword that is not used in LTE-A when transmitting one codeword. _The difference from the second embodiment described above is that the _SCID2 value is secured.

In the method of generating a DM-RS according to the third embodiment of the present invention, if the number of layers that can be used through the distributed antenna is limited to 4, the DM-RS may be generated using the following Table 5. .

In the case of <Table 5>, when one codeword is transmitted, five n _SCID2 values can be obtained by using NDI bits for an inactive codeword that is not used in LTE-A. In addition, considering that one codeword is transmitted only to multiple layers in an LTE or LTE-A system, only one codeword is transmitted when only one codeword is transmitted. _SCID2 was extended. That is, an additional n _SCID2 can be used by excluding an initial transmission from a central antenna and retransmission of the distributed antenna.

In the case of <Table 5>, the number of layers transmitted to the distributed antenna is limited to 4. However, if the number of layers through the distributed antenna is suggested as 2, the DM-RS can be generated using the following <Table 6>. have.

value One CW Two CW 0 1 layer, port 7, n _SCID = 0 n _SCID2 = 0 2 layer, port 7-8, n _SCID = 0 n _SCID2 = 0 One 1 layer, port 7, n _SCID = 1 2 layer, port 7-8, n _SCID = 1 2 1 layer, port 8, n _SCID = 0 3 layer, port 7-9, n _SCID = 0 3 1 layer, port 8, n _SCID = 1 4 layer, port 7-10, n _SCID = 0 4 2 layer, port 7-8, n _SCID = 0 5 layer, port 7-11, n _SCID = 0 5 2 layer, port 7-8, n _SCID = 1 6 layer, port 7-12, n _SCID = 0 6 3 layer, port 7-9, n _SCID = 0 7 layer, port 7-13, n _SCID = 0 7 4 layer, port 7-10, n _SCID = 0 8 layer, port 7-14, n _SCID = 0 8 1 layer, port 7, n _SCID = 0 n _SCID2 = 1 2 layer, port 7-8, n _SCID = 0 n _SCID2 = 1 9 1 layer, port 7, n _SCID = 1 2 layer, port 7-8, n _SCID = 1 10 1 layer, port 8, n _SCID = 1 2 layer, port 7-8, n _SCID = 0 n _SCID2 = 2 11 1 layer, port 8, n _SCID = 0 2 layer, port 7-8, n _SCID = 1 12 1 layer, port 7, n _SCID = 0 n _SCID2 = 2 2 layer, port 7-8, n _SCID = 0 n _SCID2 = 3 13 1 layer, port 7, n _SCID = 1 2 layer, port 7-8, n _SCID = 1 14 1 layer, port 8, n _SCID = 1 2 layer, port 7-8, n _SCID = 0 n _SCID2 = 4 15 1 layer, port 8, n _SCID = 0 2 layer, port 7-8, n _SCID = 1 16 1 layer, port 7, n _SCID = 0 n _SCID2 = 3 N / A 17 1 layer, port 7, n _SCID = 1 18 1 layer, port 8, n _SCID = 1 19 1 layer, port 8, n _SCID = 0 20 1 layer, port 7, n _SCID = 0 n _SCID2 = 4 21 1 layer, port 7, n _SCID = 1 22 1 layer, port 8, n _SCID = 1 23 1 layer, port 8, n _SCID = 0 24 1 layer, port 7, n _SCID = 0 n _SCID2 = 5 25 1 layer, port 7, n _SCID = 1 26 1 layer, port 8, n _SCID = 1 27 1 layer, port 8, n _SCID = 0 28 1 layer, port 7, n _SCID = 0 n _SCID2 = 6 29 1 layer, port 7, n _SCID = 1 30 1 layer, port 8, n _SCID = 1 31 1 layer, port 8, n _SCID = 0

값 확보하였고, 중앙 안테나에서 초기 전송이 발생하고 분산 안테나에서 이에 대한 재전송이 발생하는 경우는 배제하여 추가 n_SCID2를 사용할 수 있도록 하였다.In the case of <Table 6>, as in the case of <Table 5>, when one codeword is transmitted, an additional NDI bit is used for the deactivated codeword which was not used in LTE-A.

A new n _SCID2 can be used by excluding the initial transmission at the central antenna and retransmission at the distributed antenna.

If the number of layers through the distributed antenna is 1, DM-RS can be generated using the following <Table 7>.

In the case of <Table 7>, as in the case of <Table 6>, an additional n _SCID2 value is secured by using NDI bits for the deactivated codewords not used in LTE-A. In addition, in Table 7, three n _SCID2s can be used with only 3 bits, so that an additional DM-RS sequence considering DAS can be additionally used without using additional bits for LTE-A.

8 is a diagram illustrating a DM-RS sequence generation procedure of a base station according to a third embodiment of the present invention.

Referring to FIG. 8, the present embodiment starts from step 700 where the base station confirms scheduling for a UE operating in a DAS situation. That is, the base station identifies the UE for scheduling corresponding to each of the antennas. In step 710, the base station determines the number of codewords to transmit to the UE to be scheduled. In this case, the base station may determine scrambling variables corresponding to the UE in consideration of collision of UEs using an RB such as a UE to be scheduled. That is, the base station may set n _SCID and n _SCID2 values as scrambling variables. If it is confirmed in step 710 that the number of codewords is one, the base station considers collisions of UEs that use the same RB as the UE to be scheduled, including the NDI bits for the codeword deactivated in step 720. Set the control information corresponding to>, <Table 6>, or <Table 7>. At this time, the base station can check the number of layers and antenna ports of the UE to be scheduled. The base station may determine the control information using the scrambling parameters, the number of layers, and the antenna port. If the number of codewords is confirmed as two in step 710, the base station considers collisions of UEs that use the same RB without including the NDI bit in step 721, and then uses Table 5, Table 6, or Table 7. Set the control information corresponding to>.

Next, the base station transmits the control information determined in step 730 to the UE via the control channel. Thereafter, the base station generates a DM-RS sequence for the UE using Equation 7 in step 740, and transmits the DM-RS through the corresponding antenna port to the corresponding RB, and finishes the DM-RS generation and transmission process. That is, the base station generates and transmits a DM-RS sequence for the corresponding UE by combining n _SCID and n _SCID2 values. At this time, after receiving the control information, the UE checks whether the number of codewords to be used is one or two, and sets the NDI bit for each case or not so as to set <Table 5>, <Table 6>, or < Check the control information corresponding to Table 7>.

On the other hand, in the above-described embodiments, the base station transmits [n _RNTI to n _SCID] . An example of generating a DM-RS sequence for a UE by combining mod G] or n _SCID2 is _disclosed , but is not limited thereto. In other words, the base station is [n _RNTI to n _SCID mod G] and n _SCID2 may be combined to generate a DM-RS sequence for the UE. In other words, the base station is _assigned to n _SCID [n _RNTI By combining at least one of mod G] or n _SCID2 to generate a DM-RS sequence for the UE, implementation of the present invention is possible.

Fourth embodiment

The DM-RS generation method according to the fourth embodiment of the present invention does not add a new DM-RS sequence to distinguish DM-RSs from various distributed antennas, but uses orthogonal resources not used in LTE-A in DAS. There is a difference from the above-described embodiments in that the DM-RS is used to distinguish the DM-RS.

In LTE-A, when a codeword is transmitted to 1, 2, 3, or 4 layers, the spreading factor (SF) of an orthogonal sequence is set to 2, and 7 to 10 of 13 on the DM-RS port 7 Use only until. If the UE detects the DM-RS by setting SF in the orthogonal sequence to 4, the DM-RS ports 11 to 13 are orthogonal to the DM-RS ports 7 to 10. Therefore, in the DAS situation, if SF is set to 4 and additionally uses orthogonal resources not used in LTE-A in a specific layer situation, more distributed antennas can be supported. That is, in the fourth embodiment of the present invention, after limiting the number of layers that can be used through the distributed antenna to 4, a DM-RS is generated according to <Table 8>.

The base station sets the DM-RS port and the n _SCID value in consideration of UEs scheduled simultaneously according to <Table 8>, and then transmits 4 bits of control information to the terminal and transmits the DM-RS on the corresponding port. When the UE operates in the DAS situation, the SF is set to 4 and the DM-RS is received.

9 is a diagram illustrating an apparatus for generating a DM-RS sequence of a base station according to embodiments of the present invention.

Referring to FIG. 9, the base station includes channel encoders 800 and 810, modulators 820 and 830, a scrambler 840, a controller 850, and a multiplexer 860. And a transmitter 870.

The channel encoders 800 and 810 perform channel coding on control information or data, respectively. The modulators 820 and 830 modulate the channel coded signal using modulation schemes such as QPSK, 16QAM, and 64QAM. The scrambler 840 scrambles the modulated signal, CRS, DM-RS, and CSI-RS. At this time, the scrambler 840 scrambles each signal in a scrambling sequence corresponding thereto in a subframe. Here, the scrambling sequence is determined by the initial value of each signal. The controller 850 determines an initial value of the scrambling sequence for each signal. The controller 850 transmits the initial value of the scrambling sequence for each signal to the scrambler 840. The multiplexer 860 multiplexes the signals on a frequency and time axis, and transmits the signals on a subframe in an OFDMA manner at the transmitter 870. Meanwhile, in the present embodiment, the case where the multiplexer 860 is positioned at the distal end of the scrambler 850 is disclosed, but is not limited thereto. That is, even if the multiplexer 860 is located at the front end of the scrambler 850, implementation of the present invention is possible.

At this time, the controller 850 determines at least two scrambling variables for each UE in correspondence with a plurality of antennas distributed and distributed in the service area of the base station. At this time, the controller 850 identifies the UE for scheduling corresponding to each of the antennas. In addition, the controller 850 uses the n _RNTI value and the mod G of the UE according to the first embodiment of the present invention to [n _RNTI]. mod G] may be determined as a scrambling variable, and n _SCID may be determined as a scrambling variable. Alternatively, the controller 850 may determine scrambling variables corresponding to the UE in consideration of another UE using the same RB as the UE according to the second and third embodiments of the present invention. Alternatively, the controller 850 may determine the number of codewords to transmit to the UE according to the third embodiment of the present invention. In addition, if the number is one, the controller 850 may determine the scrambling variables using the NDI bit of the codeword to be deactivated.

The scrambler 840 combines the scrambling variables to generate a DM-RS sequence for each of the antennas. In this case, the scrambler 840 may check the number of layers and antenna ports of the UE and determine control information using the scrambling parameters, the number of layers, and the antenna port according to the second and third embodiments of the present invention.

The transmitter 870 transmits a DM-RS sequence through each of the antennas. At this time, if the control information is determined by the sequence generator, the transmitter 870 may transmit the control information to the UE.

On the other hand, some of the antennas may use resources that are orthogonal to the rest. At this time, when the antenna for a specific UE uses orthogonal resources, the control unit 850 controls control information for changing the SF set from 2 to 4 to receive the DM-RS sequence in the UE according to the fourth embodiment of the present invention. May be transmitted to the UE. That is, if the DM-RS port of the antenna for the UE corresponds to 11 to 13, the control unit 850 may generate and transmit control information to set the SF to 4 to the UE.

FIG. 10 is a diagram illustrating a procedure of generating a DM-RS by a base station in consideration of switching of a new scrambling and an application of an existing scrambling according to the first embodiment of the present invention.

Referring to FIG. 10, the embodiment starts from step 900 with the base station confirming whether a UE to be scheduled uses a new scrambling or an existing scrambling. If, in step 910, the base station determines that the UE to be scheduled to apply a new scrambling, the base station then turns on the bit for applying a new scrambling in the downlink control information to inform the terminal that the new scrambling is applied in step 920 It is set to and transmits this information through the downlink control channel.

Thereafter, in step 930, the DM-RS to which the new scrambling is applied using Equation 6 is transmitted to the UE through the corresponding antenna port in the corresponding RB along with downlink data. If the base station determines that the UE to be scheduled to apply the existing scrambling in step 910, then the base station is a bit for applying a new scrambling in the downlink control information to inform the terminal that the existing scrambling is applied in step 921 Is set to OFF and this information is transmitted through the downlink control channel. Thereafter, in step 931, the DM-RS to which the conventional scrambling using Equation 1 is applied is transmitted to the UE through the corresponding antenna port in the corresponding RB along with downlink data.

On the other hand, the UE checks a bit for applying a new scrambling in the downlink control information. If this bit is set to ON, the UE receives a DM-RS using Equation 6, estimates a channel, recovers data, and then turns OFF. If set, the receiver recovers data after estimating the channel by receiving the DM-RS using Equation 1.

Embodiments of the present invention disclosed in the specification and drawings are only specific examples to easily explain the technical contents of the present invention and aid the understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

Claims (13)

A method for generating a reference signal in a cellular mobile communication system,
Determining at least two scrambling variables for each user terminal in correspondence with a plurality of antennas distributed in a service area of the base station;
Generating a demodulation reference signal sequence for each of the antennas by combining the scrambling variables;
And transmitting the demodulation reference signal sequence through each of the antennas. The method of claim 1, wherein the determining process,
Identifying a user terminal for scheduling corresponding to each of the antennas;
And determining the scrambling variable as a function of the number of sequences to add to the demodulation reference signal sequence using the unique number of the user terminal and the unique number. The method of claim 1, wherein the determining process,
Identifying a user terminal for scheduling corresponding to each of the antennas;
And determining the scrambling variables corresponding to the user terminal in consideration of another user terminal using the same resource block as the user terminal. The method of claim 3, wherein the determining process,
Determining the number of codewords to transmit to the user terminal;
And if the number is one, determining the scrambling variables using NDI bits of codewords that are deactivated. The method of claim 3, wherein the generating process,
Identifying a number of layers of the user terminal and any one port for the user terminal among the antennas;
Determining control information using the scrambling variables, the number of layers, and a port and transmitting the control information to the user terminal;
And generating a demodulation reference signal sequence for the user terminal by combining the scrambling variables. A method for generating a reference signal in a cellular mobile communication system,
Determining a scrambling variable for each user terminal in correspondence with a plurality of antennas distributed in a service area of a base station;
Generating a demodulation reference signal sequence for the user terminal according to the scrambling variable;
Transmitting the demodulation reference signal sequence through each of the antennas;
Some of the antennas use resources that are orthogonal to the rest,
The generation process,
Transmitting control information to the user terminal to change a spreading factor used to receive the demodulation reference signal sequence when one of the antennas for the user terminal uses the orthogonal resource in the antennas. Characterized by a reference signal generation method. An apparatus for generating a reference signal in a cellular mobile communication system,
A control unit for determining at least two scrambling variables for each user terminal corresponding to a plurality of antennas distributed in a service area of the base station;
A scrambler for combining the scrambling parameters to generate a demodulation reference signal sequence for each of the antennas;
And a transmitter for transmitting the demodulation reference signal sequence through each of the antennas. The method of claim 7, wherein the control unit,
Identifying a user terminal for scheduling corresponding to each of the antennas,
And the scrambling variable is determined as a function of the number of sequences to add to the demodulation reference signal sequence using the unique number of the user terminal and the unique number. The method of claim 7, wherein the control unit,
Identifying a user terminal for scheduling corresponding to each of the antennas,
And the scrambling variables corresponding to the user terminal in consideration of another user terminal using the same resource block as the user terminal. 10. The apparatus according to claim 9,
Determine the number of codewords to transmit to the user terminal,
And if the number is one, determining the scrambling variables using NDI bits of a codeword which is inactivated. The method of claim 9, wherein the scrambler,
Check the number of layers of the user terminal and any one port for the user terminal among the antennas,
Determine the control information using the scrambling variables, the number of layers and the port,
And a combination of the scrambling variables to generate a demodulation reference signal sequence for the user terminal. The method of claim 11, wherein the transmitter,
And when the control information is determined, transmitting the control information to the user terminal. An apparatus for generating a reference signal in a cellular mobile communication system,
A control unit for determining a scrambling variable for each user terminal in correspondence with a plurality of antennas distributed in a service area of the base station;
A scrambler for generating a demodulation reference signal sequence for the user terminal according to the scrambling variable;
A transmitter for transmitting the demodulation reference signal sequence through each of the antennas,
Some of the antennas use resources that are orthogonal to the rest,
The control unit,
When the one of the antennas for the user terminal using the orthogonal resources in the antennas, the reference signal generation, characterized in that for controlling to transmit the control information for changing the spreading factor used to receive the demodulation reference signal sequence Device.

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