RU2502191C1 - Method and apparatus for transmitting/receiving reference signal in wireless communication system - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: in a base station apparatus for transmitting a reference signal in a wireless communication system, a processor generates the same scrambling sequence for resource elements (RE) allocated to each layer for reference signal transmission, and spreads or covers Walsh codes such that scrambling sequences generated for the resource elements can be orthogonal to each other on a time axis, in order to generate a reference signal sequence. Here, the Walsh code spreading or covering by the processor is applied on a frequency axis based on a plurality of resource blocks (RB) or based on a pair of resource blocks, such that mutually different sequences having mutually different sequence values can be mapped between resource blocks or between pairs of resource blocks. A transmission module transmits the reference signal, to which the thus-generated reference signal sequence is applied, to user equipment via each layer.

EFFECT: generating a reference sequence for transmitting a reference signal on each layer.

15 cl, 71 dwg

Description

FIELD OF TECHNOLOGY

[0001] The present invention relates to a wireless communication system and, in particular, to a method and apparatus for transmitting / receiving a reference signal using the generated reference signal sequence.

BACKGROUND

[0002] We describe the LTE 3GPP system (Long-Term Development Project (hereinafter referred to as “LTE”) of the Third Generation Partnership Project) as an illustrative mobile communication system to which the present invention can be applied.

[0003] FIG. 1 shows an E-UMTS (Enhanced Universal Mobile Telecommunication System) network as an illustrative mobile communication system. E-UMTS is a system developed from UMTS (Universal Mobile Telecommunications System) and the fundamental standardization for E-UMTS is currently implemented by 3GPP. E-UMTS can be considered as an LTE system. Details of the technical descriptions of UMTS and E-UMTS can be found, respectively, in Release 7 and Release 8 of the “3 ^rd Generation Partnership Project; Technical specification Group Radio Access Network. ”

[0004] Referring to FIG. 1, the E-UMTS includes an access gateway (AG), which is located at the user equipment (UE), eNode B, and network (E-UTRAN) terminals and is connected to an external network. The eNode B can simultaneously transmit multiple data streams for a broadcast service, a multicast service, and / or a single address service.

[0005] One or more cells belong to one eNode B. A cell is tuned to one of the 1.25, 2.5, 5, 10, 15, and 20 MHz bands and provides a plurality of UEs with a downlink or uplink transmission service. Different cells can be configured to provide different bands. The eNode B controls the transmission / reception of data to / from a plurality of UEs. The eNode B signals the time / frequency areas in which downlink data, a coding scheme, a data size, hybrid automatic retransmission request (HARQ) related information, etc. will be transmitted. to the corresponding UE by transmitting downlink scheduling information regarding the downlink data to the UE.

[0006] The eNode B signals the time / frequency domains that the UE may use, a coding scheme, data size, HARQ related information, etc. to the UE by transmitting uplink scheduling information regarding the uplink data to the UE. You can use the interface to transfer user traffic or control traffic between the eNode B. The core network (CN) may consist of an AG and a network node for registering a UE user. AG manages the mobility of the UE based on a tracking area (TA) configured for multiple cells.

[0007] Although wireless technologies have been developed to provide LTE based on Broadband Code Division Multiple Access (WCDMA), the needs and expectations of users and carriers are constantly increasing. In addition, wireless access technologies are constantly evolving, and thus technological progress is needed to increase competitiveness. Technological advances include reducing the cost of transmitting one bit, increasing service availability, flexible use of the frequency band, simple structure and open interface, proper power consumption of the UE, etc.

[0008] Recently, 3GPP has standardized technology following LTE. This technology is referred to as “LTE-Advanced” or “LTE-A”. One of the main differences between LTE and LTE-A is the system bandwidth. LTE-A is designed to support a wide frequency band up to 100 MHz. For this purpose, carrier aggregation or band aggregation is used to implement broadband communications using multiple frequency blocks. Carrier aggregation uses multiple frequency blocks as one logical frequency band to obtain a wider frequency band. The frequency band of each frequency block can be set based on the frequency band of the system block used in LTE. Each frequency block is transmitted using a component carrier.

[0009] However, in LTE-A, a method for generating a reference sequence for transmitting a reference signal at each level when transferring the reference signals at eight levels is not considered.

DETAILED DESCRIPTION OF THE INVENTION

Technical problems

[0010] An object of the present invention is to provide a method for transmitting / receiving a reference signal in a wireless communication system.

[0011] Another object of the present invention is to provide an apparatus for transmitting / receiving a reference signal in a wireless communication system.

[0012] Technical problems to be solved by the present invention are not limited to the aforementioned technical problem, and one skilled in the art, based on the following description, can clearly understand other technical problems not mentioned above.

Technical solutions

[0013] According to an aspect of the present invention, a method for transmitting a reference signal to an eNode B in a wireless communication system includes the steps of: generating a pseudo-random sequence for each level using a first m-sequence and a second m-sequence; generating a reference signal sequence using the generated pseudo-random sequence and the Walsh code; and transmitting the reference signal to which the reference signal sequence generated for each level is applied to the user equipment (UE) for each level, the pseudo-random sequence being generated using the sequence initialization value, the sequence initialization value being generated using the slot number in the radio frame, the values The cell ID of the physical layer, and a value indicating the group of level indexes, differentiated by frequency.

[0014] According to another aspect of the present invention, a method for transmitting a reference signal to an eNode B in a wireless communication system includes the steps of: generating the same scrambling sequence for resource elements (REs) allocated to each layer for transmitting a reference signal; generating a reference signal sequence by spreading or covering with Walsh codes so that the scrambling sequences generated for RE are orthogonal to each other on the time axis; and transmitting the reference signal to which the generated reference signal sequence is applied to the UE through each level, wherein spreading or Walsh code coverage is applied on the frequency axis, based on a plurality of resource blocks (RB) or based on a pair of resource blocks, so that different sequences having mutually different sequence values are displayed between resource blocks or between pairs of resource blocks.

[0015] When expanding over a spectrum or covering with a Walsh code, in a first resource block of a plurality of pairs of resource blocks, Walsh code elements can be applied to the first code division multiplexing (CDM) group so that the Walsh code elements are one-to-one displayed in RE of the first the subcarrier allocated to the first resource block, in the direction of the time axis, are one-to-one displayed in the RE of the second subcarrier in the opposite direction of the time axis, and are one-to-one displayed in the RE of the third sub-carrier in the temporarily direction axis, and in the second resource block of the plurality of pairs of resource blocks, the Walsh code elements can be applied to the first CDM group, so that the Walsh code elements are one-to-one displayed in the RE of the first subcarrier allocated to the second resource block in the opposite direction of the time axis, mutually were uniquely mapped to the RE of the second subcarrier in the direction of the time axis, and one to one were mapped to RE of the third subcarrier in the opposite direction of the time axis.

[0016] In the first and second pairs of resource blocks, the Walsh code elements can be applied to the second CDM group in an order different from the order in which the Walsh code elements are applied to the first CDM group.

[0017] When generating a reference signal sequence, different sequences having different sequence values can be repeated based on two pairs of resource blocks on the frequency axis.

[0018] The Walsh code elements from the CDM groups can be applied to level 1 as (1, 1, 1, 1), applied to level 2 as (1, -1, 1, -1), applied to level 3 as (1, 1, -1, -1) and apply to level 4 as (1, -1, -1, 1).

[0019] According to another aspect of the present invention, an eNode B device for transmitting a reference signal in a wireless communication system includes: a processor generating a pseudorandom sequence for each level using a first m-sequence and a second m-sequence, and generating a reference signal sequence with using the generated pseudo-random sequence and Walsh code; and a transmission module transmitting a reference signal to which the reference signal sequence generated for each level is applied to the UE for each level, the processor generating a pseudo-random sequence using the sequence initialization value, the sequence initialization value being generated using the slot number in the radio frame, the values The cell ID of the physical layer, and a value indicating the group of level indexes, differentiated by frequency.

[0020] According to another aspect of the present invention, an eNode B for transmitting a reference signal in a wireless communication system includes a processor generating the same scrambling sequence for resource elements (REs) allocated to each layer for transmitting a reference signal and generating a sequence the reference signal by spreading over the spectrum or covering with Walsh codes so that the scrambling sequences generated for RE are orthogonal to each other on the time axis; and a transmission module transmitting the reference signal to which the generated sequence of the reference signal is applied to the UE through each level, wherein the spreading or Walsh code coverage by the processor is applied on the frequency axis, based on a plurality of resource blocks (RB) or based pairs of resource blocks, so that mutually different sequences having mutually different sequence values are displayed between resource blocks or between pairs of resource blocks.

Advantages of the Invention

[0021] The method for generating and transmitting a reference signal sequence according to the present invention can significantly improve the communication characteristics of the eNode B and UE in the LTE-A3GPP system.

[0022] It is obvious that the foregoing general description and the following detailed description of the present invention are illustrative and explanatory and are intended to provide an additional explanation of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, included to provide a further understanding of the invention, and included in and constitute part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principle of the invention. In the drawings:

[0024] FIG. 1 shows an E-UMTS network as an illustrative mobile communication system;

[0025] FIG. 2 shows the structure of a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP wireless access network;

[0026] FIG. 3 is a diagram describing physical channels used in a 3GPP system and a general method for transmitting signals using them;

[0027] FIG. 4 shows an illustrative radio frame structure used in the 3GPP LTE system, which is one of the mobile communication systems;

[0028] FIG. 5 shows the structure of the downlink and uplink subframes of a 3GPP LTE system;

[0029] FIG. 6 shows a structure of a time-frequency resource grid for a downlink in an 3GPP LTE system;

[0030] FIG. 7 shows a simulation of a multi-input multi-output communication system (MIMO);

[0031] FIG. 8 shows channels between N _T transmit antennas and receive antenna i;

[0032] FIG. 9 shows the overall system structure for SC-FDMA and OFDMA;

[0033] FIG. 10 shows an illustrative uplink structure of an SC-FDMA system for a 3GPP LTE system;

[0034] FIG. 11 shows an exemplary SC-FDMA uplink transmission frame structure for a 3GPP LTE system;

[0035] FIG. 12 shows an example of a data signal mapping relationship for an SC-FDMA-based MIMO system;

[0036] FIG. 13 shows illustrative reference signal patterns for a 3GPP LTE system;

[0037] FIG. 14 shows an example RE pattern multiplexed with code division for DRS levels 1 and 2 in RB;

[0038] FIG. 15 shows an illustrative method for generating a DRS sequence;

[0039] FIG. 16 shows an illustrative method for generating a DRS sequence;

[0040] FIG. 17 shows an illustrative method for generating a DRS sequence;

[0041] FIG. 18 shows illustrative methods for generating a sequence in RB;

[0042] FIG. 19 shows an illustrative method for generating a DRS sequence;

[0043] FIG. 20 shows illustrative methods for generating a sequence in RB;

[0044] FIG. 21 shows an illustrative method for generating a DRS sequence in an RB;

[0045] FIG. 22 shows an illustrative method for transmitting DRS using a DRS sequence in the case of two cells;

[0046] FIG. 23 shows an illustrative method for generating a sequence in RB;

[0047] FIG. 24 shows an illustrative method for transmitting DRS using a DRS sequence in the case of two cells;

[0048] FIG. 25 shows an illustrative method for applying precoding to two DRS layers, mapping DRS levels to four transmit antennas and transmitting DRS levels, and a power difference between OFDM symbols in DRS transmission using the method;

[0049] FIG. 26 shows illustrative methods for generating a DRS sequence;

[0050] FIG. 27 shows an illustrative method for transmitting DRS using a DRS sequence generated according to the method shown in FIG. 26;

[0051] FIG. 28 (a) and 28 (b) show illustrative methods for generating a DRS sequence;

[0052] FIG. 29 (a) and 29 (b) show illustrative methods for generating a DRS sequence;

[0053] FIG. 30 shows an example of transmitting a DRS signal using a DRS sequence in the case of two cells;

[0054] FIG. 31 shows an alternative to the DRS sequence generating method shown in FIG. 26;

[0055] FIG. 32 (a) and 32 (b) show illustrative methods for generating a DRS sequence for each OFDM symbol;

[0056] FIG. 33 shows a sequence display method associated with the methods shown in FIG. 32 (a) and 32 (b);

[0057] FIG. 34 (a) shows an example orthogonal code coverage code template used for a particular DRS layer;

[0058] FIG. 34 (b) and 34 (c) show examples of using the Walsh code in RB;

[0059] FIG. 35 shows an illustrative method for displaying a Walsh code in a frequency set of CDM REs;

[0060] FIG. 36 (a) and 36 (b) show examples of code switching for two levels;

[0061] FIG. 37 shows an example of code switching for two levels;

[0062] FIG. 38 (a) and 38 (b) show examples of Walsh code switching for four levels;

[0063] FIG. 39 shows an illustrative method for generating two sequences;

[0064] FIG. 40 shows an example of DRS transmission using a DRS sequence in the case of two cells;

[0065] FIG. 41 shows an example of DRS transmission using a DRS sequence in the case of two cells;

[0066] FIG. 42 shows an example of DRS transmission using a DRS sequence in the case of two cells;

[0067] FIG. 43 (a) shows an example of DRS transmission using the generated DRS sequence;

[0068] FIG. 43 (b) shows the transmitted power according to the transmission scheme shown in FIG. 43 (a);

[0069] FIG. 44 shows an example of a DRS transmission using a generated DRS sequence;

[0070] FIG. 45 shows an illustrative method for allocating CDM code to each layer;

[0071] FIG. 46 (a) shows an example of transmitting an RS DM sequence;

[0072] FIG. 46 (b) shows the transmitted power according to the transmission scheme shown in FIG. 46 (a);

[0073] FIG. 47 shows an illustrative method for displaying a DRS sequence;

[0074] FIG. 48 shows an example of DRS transmission using a generated DRS sequence;

[0075] FIG. 49 shows an illustrative method for applying a Walsh code to RS DM;

[0076] FIG. 50 and 51 show illustrative methods for applying a Walsh code to four RS DMs;

[0077] FIG. 52 shows an illustrative method for displaying an RS DM sequence; and

[0078] FIG. 53 shows a block diagram of an apparatus 50 according to an embodiment of the present invention.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0079] Consider preferred embodiments of the present invention with reference to the accompanying drawings. The detailed description below with reference to the accompanying drawings is intended to illustrate illustrative embodiments of the present invention, and not to show only embodiments that can be implemented according to the invention. For example, although the following detailed description includes specific details to provide a thorough understanding of the present invention, it will be apparent to those skilled in the art that the present invention can be practiced without such specific details. For example, the following detailed description is based on the fact that a mobile communication system is used according to the “Third Generation Partnership Project for Long-Term Development Project” (LTE 3GPP). However, the description is applicable to any other mobile communication system, with the exception of the specific features inherent in the 3GPP LTE system.

[0080] In some cases, well-known structures and devices are omitted or shown in a block diagram, with emphasis on the essential features of structures and devices, so as not to complicate the understanding of the essence of the present invention. The same reference numbers will be used throughout this specification to refer to the same or similar parts.

[0081] In the following description, it is assumed that the term "user equipment" (UE) refers to a mobile or stationary user terminal device, for example, such as a mobile station (MS), advanced mobile station (AMS), etc., and is intended that the term "base station" (BS) refers to any network edge node, for example, Node B, advanced Node B (eNB or eNode B), access point (AP), etc., communicating with the UE.

[0082] In a mobile communication system, the UE may receive information from the eNode B in the downlink and transmit information to the eNode B in the uplink. The information that the MS transmits or receives includes data and various types of control information. There are many physical channels according to the types and uses of the information that the MS transmits or receives.

[0083] The methods, devices and systems described herein can be used in various wireless access technologies, for example, code division multiple access (CDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), multiple access single-carrier frequency division (SC-FDMA), etc. CDMA can be implemented using radio technology, such as Universal Terrestrial Radio Access System (UTRA) or CDMA 2000. TDMA can be implemented using radio technology, such as Global System for Mobile Communications (GSM) / Generalized Packet Radio Service (GPRS) / “Development of GSM with increased data rate” (EDGE). OFDMA can be implemented using radio technology, for example, standards (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved-UTRA (E-UTRA), etc. Institute of Electrical and Electronics Engineers. UTRA is part of the universal mobile communications system (UMTS). The third-generation partnership project (LTE 3GPP) long-term development project is part of Advanced-UMTS (E-UMTS) using E-UTRA. LTE 3GPP uses OFDMA on the downlink and uses SC-FDMA on the uplink. LTE-Advanced (LTE-A) is the next step in the development of LTE 3GPP.

[0084] For clarity, the present invention focuses on LTE 3GPP / LTE-A. However, the technical features of the present invention are not limited to this.

[0085] FIG. 2 shows the structure of a control plane and a user plane of a radio interface protocol between a UE and an E-UTRAN based on a 3GPP wireless access network.

[0086] Referring to FIG. 2, the control plane is the path along which control messages used for the UE 120 and the network for call administration are transmitted. The user plane is the path along which data generated at the application level is transmitted, i.e. audio data, internet packet data, etc.

[0087] The physical layer, the first layer, provides a service for transferring information to a higher layer using a physical channel. The physical layer is associated with a medium access control (MAC) layer corresponding to a higher layer through a transport channel. Data is transferred between the MAC layer and the physical layer through the transport channel. Data is transmitted through a physical channel between the physical levels of the transmitter and receiver. The physical layer uses time and frequency as radio resources. In particular, the physical layer is modulated on the downlink through orthogonal frequency division multiple access (OFDMA) and is modulated on the uplink using single carrier frequency division multiple access (SC-FDMA).

[0088] The MAC layer corresponding to the second layer provides service for a radio link control (RLC) layer corresponding to a higher layer through a logical channel. The RLC layer supports reliable data transfer. The function of the RLC level can be implemented as a function block at the MAC level. The Layer 2 Packet Data Convergence Protocol (PDCP) layer provides a header compression function to reduce the amount of control information that is not required to efficiently transmit an IP packet, such as IPv4 or IPv6, in a narrow band air interface.

[0089] The radio resource control (RRC) level corresponding to the lowest level of the third level is set only in the control plane. The RRC layer controls the logical channel, transport channel, and physical channels, as well as the configuration, reconfiguration, and release of unidirectional radio channels. Unidirectional radio channels are intended for services provided by the second layer for transmitting data between the UE and the network. For this, the RRC levels of the UE and the network exchange RRC messages. The UE is in RRC connection mode when the RRC layers of the UE and the network are RRC connected, and in idle mode when they are not RRC connected. A non-access layer (NAS) layer level corresponding to a higher level than the RRC layer performs session management and mobility management.

[0090] One cell constituting the eNode B 110 is tuned to one of the frequency bands 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplink transmission service for the UE. Different cells can be configured to provide different frequency bands.

[0091] Downlink transport channels for transmitting data from a network to a UE include a broadcast channel (BCH) carrying system information, a paging channel (PCH) carrying a paging message, a downlink shared channel (SCH) transmitting user traffic or management messages, etc. A traffic message or a downlink multicast or broadcast service control message can be transmitted on a downlink SCH or on a separate downlink multicast (MCH) channel. The uplink transport channels for transmitting data from the UE to the network includes a random access channel (RACH) transmitting an initial control message and an uplink shared channel (SCH) carrying user traffic or control messages. The logical channel located above the transport channel and displayed in the transport channel includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), a multicast traffic channel (MTCH) etc.

[0092] FIG. 3 shows the physical channels used in the 3GPP system and a general method for transmitting signals using physical channels.

[0093] Referring to FIG. 3, when the UE is turned on or when it enters a new cell, the UE performs an initial cell search to achieve synchronization with eNode B (S310). For an initial cell search, the UE receives a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from eNode B and obtains synchronization with eNode B and information, for example, cell identification (ID) from P-SCH and S- SCH. Then, the UE may receive a physical broadcast channel (PBCH) from the eNode B and receive broadcast information in a cell from the PBCH. The UE may check the state of the downlink channel by receiving a downlink reference signal (DL RS) in an initial cell search step.

[0094] Upon completion of the initial cell search, the UE may obtain more specific system information by receiving a physical downlink control channel (PDCCH) and receiving a physical downlink shared channel (PDSCH) according to information carried on a PDCCH (S320).

[0095] Then, the UE may perform a random access procedure (S330-S360) to terminate access to the BS. As part of the random access procedure, the UE may transmit the preamble on the physical random access channel (PRACH) (S330 and S350) and receive a response message to the preamble on the PDCCH and its corresponding PDSCH (S340 and S360). If the random access procedure is based on competition, the UE may further implement a competition resolution procedure.

[0096] After the above random access procedure, the UE may receive the PDCCH / PDSCH (S370) and transmit the physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) (S380) in the general uplink signal transmission procedure communication / downlink. The control information that the UE transmits to the eNode B includes an acknowledgment / negative acknowledgment signal (ACK / NACK) of a downlink / uplink, a channel quality indicator (CQI), a precoding matrix index (PMI), and a rank indicator (RI ) In the case of LTE 3GPP systems, the UE may transmit control information, for example CQI / PMI / RI, through the PUSCH and / or PUCCH.

[0097] FIG. 4 illustrates an exemplary radio frame structure used in the 3GPP LTE system, which is one of the mobile communication systems.

[0098] Referring to FIG. 4, the radio frame has a duration of 10 ms (327200 · T _s ) and includes 10 subframes. Each subframe has a duration of 1 ms and includes two slots. Each slot has a duration of 0.5 ms (15360 · T _s ). Here, T _s denotes the sampling time and is expressed as T _s = 1 / (15 kHz × 2048) = 3.2552 × 10 ^-8 (approximately 33 ns). One slot includes multiple OFDM symbols or SC-FDMA symbols and multiple resource blocks in the frequency domain.

[0099] In LTE, one resource block includes 12 subcarriers × 7 (6) OFDM symbols or SC-FDMA symbols. A transmission time interval (TTI), an elementary time interval for data transmission, may be configured by one or more subframes. The structure of the radio frame is shown for illustration purposes only. Thus, the number of subframes included in the radio frame, or the number of slots included in the subframe, or the number of OFDM symbols or SC-FDMA symbols included in the slot, can be changed in various ways.

[00100] FIG. 5 shows the downlink and uplink subframe structures for the 3GPP LTE system, which is one of the mobile communication systems.

[00101] Referring to FIG. 5 (a), the downlink subframe includes two slots in the time domain. A maximum of three OFDM symbols located at the front of the first slot in the downlink subframe correspond to a control area assigned with a control channel. The remaining OFDM symbols correspond to the data area assigned to the physical downlink shared channel (PDSCH).

[00102] Examples of downlink control channels used in 3GPP LTE include a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical HARQ indicator channel, etc. PCFICH is transmitted in the first OFDM symbol of the subframe and carries information regarding the number of OFDM symbols (i.e., the size of the control area) used to transmit control channels in the subframe. The control information transmitted on the PDCCH is referred to as downlink control information (DCI). DCI includes uplink resource allocation information, downlink resource allocation information, transmit (Tx) uplink power control command for an arbitrary UE group, etc. The PHICH carries an acknowledgment (ACK) / negative acknowledgment (NACK) signal for the hybrid uplink hybrid automatic retransmission request (HARQ). Thus, an ACK / NACK signal is transmitted via PHICH in response to the uplink data transmitted from the UE.

[00103] Next, a PDCCH will be described.

[00104] The PDCCH may carry resource allocation and transport format (DL provisioning) for PDSCH, resource allocation information (UL provisioning) for PUSCH, a set of transmit power control commands on separate UEs in an arbitrary UE group, activation of a voice over Internet protocol (VoIP ) etc. In the control area, multiple PDCCHs can be transmitted. The UE may track multiple PDCCHs. The PDCCH is configured as a combination of one or more consecutive control channel elements (CCEs) and may be transmitted through a control area after it has undergone block-wise interleaving. CCE is a logical allocation unit used to code the PDCCH based on the state of the radio channel. CCE corresponds to many resource element groups. The PDCCH format and the number of bits of the available PDCCH are determined according to the correlation between the number of CCEs and the code rate provided by the CCE.

[00105] The control information transmitted on the PDCCH is referred to as DCI. Table 1 presents DCI according to DCI formats.

Table 1 DCI format Description DCI format 0 Used for planning PUSCH DCI format 1 Used to schedule one codeword PDSCH DCI 1A format Used for compact scheduling of one PDSCH codeword and random access procedure initiated by the PDCCH command DCI 1B format Used for compact scheduling of one PDSCH codeword with precoding information DCI 1C format Used for very compact planning of one PDSCH codeword DCI 1D format Used for compact scheduling of one PDSCH codeword with precoding and power offset information DCI 2 format Used for scheduling PDSCHs in a UE configured for closed loop spatial multiplexing mode DCI 2A format Used for scheduling PDSCHs in a UE configured for open loop spatial multiplexing mode DCI 3 format Used to transmit TPC commands for PUCCH and PUSCH with 2-bit power controls DCI 3A format Used to transmit TPC commands for PUCCH and PUSCH with single-bit power controls

[00107] DCI format 0 corresponds to uplink resource allocation information, DCI 1 and DCI 2 format correspond to downlink resource allocation information, and DCI 3 format and DCI 3A format correspond to uplink transmit power control command in arbitrary UE groups.

[00108] Referring to FIG. 5 (b), the uplink subframe may be divided in the frequency domain into a control area and a data area. A control area is allocated with a physical uplink control channel (PUCCH) for transferring uplink control information. A data area is allocated with a physical uplink shared channel (PUSCH) for carrying user data. To maintain the properties of a single carrier, one UE does not transmit both PUCCH and PUSCH. A PUCCH for one UE is allocated to an RB pair in a subframe. RBs belonging to the RB pair occupy different subcarriers in the respective two slots. The RB pair allocated by PUCCH undergoes frequency switching at the slot boundary.

[00109] FIG. 6 shows the structure of a time-frequency resource grid for a downlink in an LTE 3GPP system, which is one of the mobile communication systems.

поднесущих и

символов OFDM. Здесь,

представляет количество RB в слоте DL, и

представляет количество поднесущих, составляющих один RB.

представляет количество символов OFDM в слоте нисходящей линии связи

зависит от полосы передачи нисходящей линии связи соты и должно удовлетворять условию

. Здесь,

обозначает минимальную полосу нисходящей линии связи, поддерживаемую системой беспроводной связи, и

обозначает максимальную полосу нисходящей линии связи, поддерживаемую системой беспроводной связи. Хотя

и

, они не ограничиваются этими значениями. Количество символов OFDM, входящих в один слот, может зависеть от длины циклического префикса [Cyclic Prefix] (CP) и интервала поднесущих. В случае многоантенной передачи, можно задать по одной сетке ресурсов на антенный порт.[00110] Referring to FIG. 6, a downlink signal transmitted in each slot may be described by a resource grid including

subcarriers and

OFDM characters. Here,

represents the number of RBs in the DL slot, and

represents the number of subcarriers making up one RB.

represents the number of OFDM symbols in the downlink slot

depends on the downlink transmission band of the cell and must satisfy the condition

. Here,

denotes the minimum downlink bandwidth supported by the wireless communication system, and

denotes the maximum downlink bandwidth supported by the wireless communication system. Though

and

, they are not limited to these values. The number of OFDM symbols included in one slot may depend on the length of the cyclic prefix [Cyclic Prefix] (CP) and the subcarrier interval. In the case of multi-antenna transmission, you can specify one grid of resources per antenna port.

, и l- индекс во временной области, имеющий одной из значений

.[00111] Each resource element (RE) in the resource grid for each antenna port can be uniquely identified by a pair of indices (k, l) in the slot. Here, k is the index in the frequency domain having one of the values

, and l is an index in the time domain having one of the values

.

[00112] The RB shown in FIG. 6 is used to describe a mapping relationship between a particular physical channel and RE. RB can be divided into a physical resource block (PRB) and a virtual resource block (VRB).

последовательных символов OFDM во временной области и

последовательных поднесущих в частотной области.

и

могут иметь заранее определенные значения. Например,

и

могут быть заданы согласно таблице 2. Соответственно, один PRB включает в себя

RE. Один PRB может соответствовать одному слоту во временной области и соответствовать 180 кГц, но PRB этим не ограничивается.[00113] PRB is set as

consecutive OFDM symbols in the time domain and

serial subcarriers in the frequency domain.

and

may have predefined values. For example,

and

can be set according to table 2. Accordingly, one PRB includes

RE. One PRB may correspond to one slot in the time domain and correspond to 180 kHz, but the PRB is not limited to this.

table 2 Configuration

Normal cyclic prefix Δf = 15 kHz 12 7 Extended cyclic prefix Δf = 15 kHz 6 Δf = 7.5 kHz 24 3

в частотной области. Соотношение между номером

PRB и RE

в одном слоте в частотной области удовлетворяет условию

.[00115] PRB takes a value in the range from 0 to

in the frequency domain. The relationship between the number

PRB and RE

in one slot in the frequency domain satisfies the condition

.

VRB выделяется паре VRB в двух слотах в одном подкадре. Другими словами,

VRB принадлежащие первому слоту из двух слотов, составляющих один подкадр, выделяются с одним из индексов от 0 до

, и

VRB, принадлежащие второму слоту из двух слотов, также выделяются с одним из индексов

.[00116] VRB and PRB are the same size. VRB can be divided into localized VRB (LVRB) and distributed VRB (DVRB). For each type VRB, one number

VRB is allocated to a VRB pair in two slots in one subframe. In other words,

VRBs belonging to the first slot of two slots making up one subframe are allocated with one of the indices from 0 to

, and

VRBs belonging to the second slot of two slots are also allocated with one of the indices

.

[00117] We describe the MIMO technology. MIMO technology is an abbreviation of the technology of many inputs and many outputs. MIMO technology uses multiple transmit (Tx) antennas and multiple receive (Rx) antennas to improve data transmission / reception efficiency, whereas previously the traditional technique generally used a single transmit antenna and a single receive antenna. In other words, MIMO technology allows the transmitting side or the receiving side of a wireless communication system to use multiple antennas, which, in turn, can improve throughput or performance. For convenience of description, the term “MIMO” can be understood as “multi-antenna technology”.

[00118] In particular, MIMO technology is independent of a single antenna path for receiving a single complete message, collects many pieces of data received through several antennas, and generates complete data. As a result, MIMO technology allows you to increase the speed of data transfer in a specific range or allows you to increase the range of the system at a specific data transfer speed.

[00119] The new generation mobile communication technology requires a higher data transfer rate than traditional mobile communication technology, so it is expected that an effective MIMO technology is suitable for the new generation mobile communication technology. Based on this assumption, MIMO communication technology is a new generation mobile communication technology applicable to mobile communication terminals or transponders and is able to expand the data transmission area so that it can overcome the data transfer limitation of other mobile communication systems due to various limited situations .

[00120] Meanwhile, MIMO technology, among various technologies capable of increasing data transfer efficiency, can significantly increase transmission and reception throughput without allocating additional frequencies and without further increasing power. Due to these technical advantages, most companies and developers pay particular attention to this MIMO technology.

[00121] In FIG. 7 shows a general MIMO communication system.

[00122] Referring to FIG. 7, if the number of transmit antennas increases to N _T , and at the same time, the number of receive antennas increases to N _R , the theoretical channel capacity of the MIMO communication system increases in proportion to the number of antennas, in contrast to the above case, when only the transmitter or receiver uses several antennas, which can significantly increase the transfer speed and frequency efficiency. In this case, the transfer rate achieved by increasing the channel capacity is equal to the product of the maximum transfer rate (R _o ) achieved using a single antenna and the speed increment (R _i ), and can theoretically increase. The increment of speed (R _i ) can be represented by the following equation 1:

[00123] [Equation 1]

[00124]

[00125] We proceed to a detailed description of the mathematical modeling of the communication method for use in the aforementioned MIMO system.

[00126] First of all, as follows from FIG. 7, it is assumed that there are N _T transmit antennas and N _R receive antennas.

[00127] In the case of a transmission signal, the maximum number of pieces of transmission information is N _T , provided that N _T transmit antennas are used, so that the transmission signal can be represented by the specific vector shown in the following equation 2:

[00128] [Equation 2]

[00129]

[00130] Meanwhile, the individual pieces of transmission information s ₁ , s ₂ , ..., s _NT may have different transmission powers. In this case, if we designate the individual transmit powers as P ₁ , P ₂ , ..., P _NT , the transmission information having the adjusted transmit power can be represented by the specific vector shown in the following equation 3.

[00131] [Equation 3]

[00132]

представляет собой диагональную матрицу мощности передачи, которую можно представить следующим уравнением 4.[00133] In equation 3,

represents the diagonal matrix of transmit power, which can be represented by the following equation 4.

[00134] [Equation 4]

[00135]

[00136] An information vector having an adjusted transmit power is multiplied by a weight matrix W, which allows the configuration of N _{T of} actually transmitted transmission signals (Tx) x ₁ , x ₂ , ..., x _NT . In this case, the weight matrix is adapted to appropriately distribute the transmission information to the individual antennas according to the channel conditions of transmission. The aforementioned transmission signals x ₁ , x ₂ , ..., x _NT can be represented by the following equation 5 using the vector x.

[00137] [Equation 5]

[00138]

[00139] In equation 5, w _ij is the weight coefficient between the i-th transmit antenna and the j-th piece of transmission information, and W is the matrix of weights. The matrix W is called the weight matrix or precoding matrix.

[00140] Moreover, the aforementioned transmission signal (x) can be considered differently in two cases, that is, in the first case, when spatial diversity is used, and in the second case, when spatial multiplexing is used.

[00141] In the case of spatial multiplexing, different signals are multiplexed and the multiplexed signals are transmitted to the destination, which is why the elements of the information vector s have different values. Otherwise, if spatial diversity is used, the same signal is retransmitted along several channel paths, which is why the elements of the information vector s have the same value.

[00142] Obviously, a combination of the spatial multiplexing scheme and the spatial diversity scheme can also be considered. In other words, the same signal is transmitted through three transmitting antennas according to the spatial diversity scheme, and the remaining signals are spatially multiplexed and then transmitted to the destination. Then, if N _R receive antennas are used, the receive signals y ₁ , y ₂ , ..., y _{NR of the} individual antennas can be represented by the specific vector y shown in the following equation 6.

[00143] [Equation 6]

[00144]

[00145] When modeling channels in a MIMO wireless communication system, they can be distinguished according to the indices of the transmitting and receiving antennas. The channel between the jth transmitting antenna and the ith receiving antenna is denoted by h _ij . Note that the index of the receiving antenna precedes the index of the transmitting antenna in h _ij . Channels can be co-represented as a vector or matrix. We describe an example of a vector representation.

[00146] In FIG. 8 shows a channel from N _T transmit antennas to the ith receive antenna.

[00147] Referring to FIG. 8, channels from the N _T transmit antennas to the ith receive antenna can be represented by the following equation 7.

[00148] [Equation 7]

[00149]

[00150] Thus, all channels from N _T transmit antennas to N _R receive antennas can be represented by the following equation 8.

[00151] [Equation 8]

[00152]

в сумме с N_R приемными антеннами задается следующим вектором.[00153] The actual channels are processed by the indicated channel matrix H and then added to the additive white Gaussian noise (AWGN). Awgn

in total with N _R receiving antennas is given by the following vector.

[00154] [Equation 9]

[00155]

[00156] Based on the above mathematical modeling, the received vector signal is set as

[00157] [Equation 10]

[00158]

[00159] The number of rows and columns of the channel matrix H, representing the state of the channels, are determined according to the number of receiving and transmitting antennas. In particular, the number of rows in the channel matrix H is equal to the number N_R receiving antennas and the number of columns in the channel matrix H is equal to the number N_T transmitting antennas. Thus, the channel matrix H has size N_R× N_T.

[00160] The matrix rank is defined as a smaller number from the number of independent rows and the number of independent columns in the matrix. Accordingly, the rank of the matrix does not exceed the number of rows or columns of the matrix. The rank of the channel matrix H, rank (H) satisfies the following limiting condition.

[00161] [Equation 11]

[00162]

[00163] On the other hand, the properties of the precoding matrix can be observed. The channel matrix H without taking into account the precoding matrix can be represented by the following equation 12.

[00164] [Equation 12]

[00165]

для k-го принятого сигнала задается уравнением 13, при условии, что приемник работает по принципу минимальной среднеквадратической ошибки (MMSE).[00166] In general, the signal to noise ratio + interference (SINR)

for the k-th received signal is given by equation 13, provided that the receiver operates on the principle of minimum mean square error (MMSE).

[00167] [Equation 13]

[00168]

, выражаемый матрицей предварительного кодирования, можно представить с использованием

, показанной в уравнении 14.[00169] However, an effective channel

expressed by a precoding matrix can be represented using

shown in equation 14.

[00170] [Equation 14]

[00171]

[00172]

задается следующим уравнением 15, исходя из того, что используется приемник MMSE.[00173] Thus, the kth effective receive SINR

is given by the following equation 15, based on the fact that the MMSE receiver is used.

[00174] [Equation 15]

[00175]

[00176]

и j-м вектором-столбцом

, матрицу

предварительного кодирования, подвергнутую перестановке, можно представить следующим уравнением 16.[00177] Here, it is possible to observe some efficiency at the receiving SINR depending on changes in the precoding matrix based on theoretical justification. First, you can start by checking the efficiency of column permutation in a single precoding matrix. In other words, in the case of a permutation between the ith column vector

and jth column vector

matrix

precoding subjected to permutation can be represented by the following equation 16.

[00178] [Equation 16]

[00179]

с матрицей

предварительного кодирования и эффективный канал

, подвергнутый перестановке, с матрицей

предварительного кодирования можно представить, соответственно, уравнением 17.[00180] Accordingly, the effective channel

with matrix

pre-coding and efficient channel

rearranged with matrix

precoding can be represented, respectively, by equation 17.

[00181] [Equation 17]

[00182]

[00183]

[00184]

[00185]

[00186] From equation 17 it follows that even if the two column vectors are swapped, the value of the receiving SINR does not change except for the order, so that the channel capacity / total throughput can remain constant. Thus, by analogy with equations 14 and 15, it is possible to obtain the rearranged effective channel and the kth receiving SINR.

[00187] [Equation 18]

[00188]

[00189]

[00190] [Equation 19]

[00191]

[00192] In Equation 19, attention should be paid to the fact that the interfering and noise members are equal to each other, as indicated in Equation 20.

[00193] [Equation 20]

[00194]

можно представить следующим уравнением 21.[00195] Re-receiving SINR

can be represented by the following equation 21.

[00196] [Equation 21]

[00197]

[00198]

с конкретным вектором-столбцом в одной матрице предварительного кодирования. Просто, в некоторых примерах,

могут быть возможными значениями.[00199] Secondly, you can start by checking the multiplexing efficiency

with a specific column vector in a single precoding matrix. Just, in some examples,

may be possible values.

, где

мультиплексирован с k-м столбцом, можно представить следующим уравнением 22.[00200]

where

multiplexed with the kth column, can be represented by the following equation 22.

[00201] [Equation 22]

[00202]

можно представить следующим уравнением 23.[00203] Here, the receiving SINR

can be represented by the following equation 23.

[00204] [Equation 23]

[00205]

[00206]

с конкретным вектором-столбцом в матрице предварительного кодирования не приводит ни к какому изменению в приемном SINR и канальной емкости/суммарной пропускной способности.[00207] According to equation 23, it can be observed that simple multiplexing

with a particular column vector in the precoding matrix does not lead to any change in the receiving SINR and channel capacity / total throughput.

[00208] In FIG. 9 shows the overall system structure for OFDMA and SC-FDMA.

[00209] In a common OFDM or SC-FDMA based MIMO antenna system, the data signal is complexly mapped to a transmission symbol. First, the transmitted data is divided into code words. For most applications, the codeword is equivalent to the transport block specified by the medium access control (MAC) layer. Each codeword is separately encoded using a channel encoder, for example, based on a turbo code or convolutional code of the tail bits. After encoding, the code word is negotiated according to the frequency of the signals to the appropriate sizes, and then displayed in levels. For SC-FDMA transmission, discrete Fourier transform (DFT) precoding is performed at each level, and DFT is not applied for OFDM transmission, as shown in FIG. 9.

[00210] Then, the signal subjected to DFT conversion at each level is multiplied by a vector / precoding matrix and mapped to the ports of the transmit antenna. Note that the ports of the transmitting antenna can again be mapped to the actual physical antennas through antenna virtualization.

[00211] The total cubic metric (CM) of a single carrier signal (for example, SC-FDMA transmission signals) is much smaller than that of many carriers. This general principle also applies to peak power to average power (PAPR) ratios. CM and PAPR are associated with the dynamic range that the transmitter power amplifier (PA) must support. With the same PA, any transmission signal whose CM or PAPR is smaller than any other waveform can be transmitted with higher transmit power. On the contrary, if the maximum power PA is fixed and the transmitter needs to transmit a signal with high CM or PAPR, it should reduce the transmitted power a little more than for a signal with low CM. The reason that a single carrier signal has a lower CM than multi-carrier signals is because a large number of signals overlap in many carrier signals, which sometimes leads to common-mode summation of the signals. This feature can lead to an increase in signal amplitude. This is why the OFDM system has large PAPR or CM values.

[00212] If the resulting signal y consists only of an information symbol x ₁ , then this signal can be considered as a single carrier signal, for example, y = x ₁ . If the resulting signal y consists of multiple information symbols x ₁ , x ₂ , x ₃ , ..., x _N , then the signal can be considered as a signal of many carriers, for example, y = x ₁ + x ₂ + x ₃ + x _N. PAPR or CM is proportional to the number of information symbols coherently summed with each other with the formation of the resulting waveform of the signal, but the values reach saturation after a certain number of information symbols. Therefore, if the resulting waveform of the signal is created by summing a small number of signals on one carrier, then CM or PAPR will be much less than that of many carriers, slightly more than that of a pure signal of one carrier.

[00213] In FIG. 10 shows an illustrative uplink structure of an SC-FDMA system for a 3GPP LTE system, and FIG. 11 illustrates an exemplary SC-FDMA uplink transmission frame structure for a 3GPP LTE system.

[00214] In the LTE Rel-8 system, a system structure and a transmission frame for uplink SC-FDMA according to FIG. 10 and FIG. 11. The basic transmission unit is one subframe. Two slots form one subframe, and depending on the configuration of the cyclic prefix (for example, normal CP or extended CP), the number of SC-FDMA symbols in the slot is 7 or 6. At least one SC-FDMA reference symbol exists in each slot signal that is not used for data transmission. Multiple subcarriers exist in a single SC-FDMA symbol. A Resource Element (RE) is a complex information symbol mapped to a unit subcarrier. In the case of using precoding with DFT transform, RE is a single information symbol mapped to the DFT transform index, since the DFT transform size and the number of subcarriers used in transmission are the same for SC-FDMA.

[00215] The LTE-A system provides spatial multiplexing of up to four layers for uplink transmission. In single-user uplink spatial multiplexing, up to two transport blocks can be transmitted from the scheduled terminal in a subframe for each uplink component carrier. Depending on the number of transmission layers, the modulation symbols associated with each of the transport blocks are mapped to one or two layers according to the same principle as for downlink spatial multiplexing in LTE Rel-8. In addition, DFT-precoded OFDM is adopted as a multiple access scheme for transmitting uplink data, both in the absence and in the presence of spatial multiplexing. In the case of multiple component carriers, there is one DFT per component carrier. In LTE-A, in particular, on each component carrier, both frequency-continuous and frequency-discrete resource allocation are supported.

[00216] In FIG. 12 shows an example of a data signal mapping relationship for an SC-FDMA-based MIMO system.

[00217] If the number of codewords is N _C and the number of levels is N _L , then the number N _{C of} information symbols or a multiple of N _C information symbols will be displayed in the number N _L or the number multiple of N _L symbols. DFT transform precoding for SC-FDMA does not change the size of the layer. When performing precoding into levels, the number of information symbols will change from N _L to N _T , due to multiplication by a matrix of size N _T × N _L. In general, the 'rank' of transmission of spatially multiplexed data is equal to the number of layers carrying data in a given transmission instance (N _L in the example shown in FIG. 12).

[00218] In order for future communication systems to support extremely high data rates, for example, 1 Gbit / s, they must support higher rank data transmissions, for example, rank 8 data transmissions. In order for information spatially multiplexed by levels to be correctly transmitted and received, a well-defined reference signal sequence is required for demodulation and channel estimation. Given the placement of the control signal and other reference signals necessary for inverse IE measurements, constructing a reference signal sequence for data information spatially multiplexed by levels is a complex and difficult task. The present invention provides a method for inserting a specialized reference signal sequence into RBs containing data information.

[00219] In certain communication systems, such as LTE, reference signals (RS) for demodulating data and channel estimation for multiple spatial layers can be inserted into the RE in the subframe of FIG. 13.

[00220] Let us describe the RS transmitted and received between the transmitter and the receiver in a mobile communication system.

[00221] In a wireless communication system, when transmitting a packet (or signal) from a transmitter to a receiver, the packet may be distorted during transmission due to the nature of the radio channel. To successfully receive the signal, the receiver must compensate for the distortion of the received signal using channel information. So that the receiver can receive channel information, the transmitter transmits a signal known to the transmitter and receiver, and the receiver obtains knowledge of the channel information based on the distortion of the signal received over the air. This signal is called a reference signal or a pilot signal.

[00222] In order to transmit a packet from a transmitter to a receiver, in general, one transmit antenna and one receive antenna are used. However, in most modern mobile communication systems, the efficiency of data transmission and reception is enhanced by the use of multiple transmit antennas and multiple receive antennas. In the case of transmitting and receiving data through multiple antennas in order to increase throughput and improve communication characteristics at the transmitter or receiver of the mobile communication system, there is a reference signal for each transmit antenna. A receiver can successfully receive a signal transmitted from each transmit antenna using a reference signal for each transmit antenna.

[00223] In mobile communication systems, reference signals are generally divided into two categories according to their use. The reference signals include a reference signal for acquiring channel information and a reference signal for demodulating data. Since the first is used by the UE to obtain channel information regarding the downlink, it must be transmitted in a wide band, and even a UE not receiving downlink data in a particular subframe must receive and measure it. In addition, this reference signal for channel measurement can be used in the measurement of handover (handover). The latter is transmitted to the eNode B with the corresponding resources when the eNode B transmits a downlink signal. The UE may perform channel estimation and data demodulation by receiving this reference signal. The reference signal for demodulating data must be transmitted in the area in which data is transmitted.

[00224] For the LTE Release-8 system, one of the mobile communication systems, two types of downlink reference signals for a unicast service are defined, namely a common RS (CRS) for receiving channel status information and measuring a handover and a specialized RS ( DRS) (corresponding to a UE-dependent reference signal) used to demodulate data. In the LTE Release-8 system, RS, depending on the UE RS, is used only for data demodulation, and CRS is used both for receiving channel information and for data demodulation. CRS is a cell-specific reference signal, and eNode B transmits CRS for each subframe in a wide band. CRS is transmitted for a maximum of four antenna ports according to the number of transmit antennas in eNode B. For example, CRS for antenna ports # 0 and # 1 is transmitted when the number of transmit antennas in eNode B is 2, while CRS for antenna ports # 0 and # 3 is transmitted when the number of transmit antennas in eNode B is 4.

[00225] In FIG. 13 (a), 13 (b), and 13 (c) illustrate exemplary RS patterns for the 3GPP LTE system.

[00226] In FIG. 13 (a), 13 (b) and 13 (c) show the placement of RS in one RB. In RB, there may be multiple RSs transmitted for different purposes. The common reference signal (CRS) shown in FIG. 13 is a common reference signal of a cell that is transmitted in the full band of the system. CRS can be used to demodulate data transmissions, channel estimation, channel tracking, cell detection, and other purposes. A dedicated reference signal (DRS) is a reference signal that can be used to demodulate data, and it is only transmitted to RBs in which the UE receives data transmissions. DRS is transmitted as a signal depending on the UE, so the UE, in general, cannot know about DRS transmissions of other UEs. To support up to N spatial layer data transmissions, up to N DRS are required.

[00227] In the examples below, it is assumed that the system supports up to 8 spatial layer data transmissions. In order for a system to support good multi-user MIMO (MU-MIMO) transmissions, the DRS transmitted for each UE must be eight orthogonal or have very good correlation properties. Additionally, a system supporting up to 8 layers will be able to transmit DRS for each layer, where different combinations of UEs can exclusively use one or more layers for their data transmission. In the LTE-A DRS system, RS data demodulation (RS DM) may be called.

[00228] DRS for each layer can be multiplexed in several ways. These methods may be a combination of code division multiplexing (CDM), frequency division multiplexing (FDM), and time division multiplexing (TDM). In FIG. 13 (a), 13 (b) and 13 (c) show examples of CDM and FDM-based DRS multiplexing. Given 12 REs for level 1 and level 2 (similar DRS sequence display methods apply to DRS levels 3 and 4, and even levels 5, 6, 7, and 8), according to FIG. 14 in one RB is 12 RE.

[00229] In FIG. 14 illustrates an example RE pattern occupied by code-multiplexed DRS layers 1 and 2 in one RB.

[00230] Referring to FIG. 14, a code can be applied to RE 1410 and 1420, for example, the Walsh-Hadamard code (i.e., multiply RE 1410 by +1 and multiply RE 1420 by +1 or multiply RE 1410 by +1 and multiply RE 1420 by -1, in as a result, two consecutive in the time dimension of RE are multiplied by the Walsh code). We describe how to apply the actual DRS sequence to each DRS RE. In general, RBs allocated to a specific UE may be a subset of the total RB available for use in the system.

[00231] In FIG. 15 shows an illustrative method for generating a DRS sequence.

[00232] Referring to FIG. 15, in a full system band, some RBs may be allocated to a specific UE, for example, for scheduling. According to FIG. 15, the eNode B may generate DRS sequences equal to the RB size corresponding to the full system bandwidth. The eNode B may schedule for a specific UE using a DRS sequence corresponding to RBs allocated to the UE from all generated DRS sequences.

[00233] In FIG. 16 shows another illustrative method for generating a DRS sequence.

[00234] Referring to FIG. 16, in contrast to the DRS sequence generation method shown in FIG. 15, the eNode B may generate a DRS sequence equal to the size of the RB data allocated to a particular UE. In this case, the eNode B may schedule a plurality of UEs to which various RBs have been allocated by spatial multiplexing, for example MU-MIMO. When different RBs are allocated to the spatially multiplexed UEs, a DRS sequence used for each UE is generated so that the sequences used in the spatially multiplexed RBs are different from each other.

[00235] Referring to FIG. 16 (a), oblique areas are RBs allocated for transmitting DRS to a particular UE. The eNode B may generate a DRS sequence using an RS sequence equal to the size of the RB data allocated to a particular UE.

[00236] In FIG. 16 (b) shows a case where the eNode B generates different DRS sequences for each of the UEs UE1 and UE2. In this case, the DRS for each IE will not be orthogonal and will lead to poor channel estimation and, ultimately, to loss of performance. To use the orthogonal DRS for each transmission layer for multiple UEs, the DRS for code-multiplexed layers must have the same sequence. In the case of DRS, frequency-multiplexed layers do not need to have the same sequence.

[00237] In FIG. 17 shows an illustrative method for generating a DRS sequence.

[00238] There is a method of generating a DRS sequence for each of the allocated RBs. The sequence used for DRS can be generated for each allocated RB. To randomize the sequence template used in each RB, a separate DRS sequence is generated for each RB. One way to generate different sequences for different RBs is to set the RB index as part of the initialization value of the sequence generation function.

[00239] We describe three methods for adding (or inserting) a sequence for a plurality of REs used for CDM in one RB, with reference to FIG. eighteen.

[00240] In FIG. 18 (a), 18 (b) and 18 (c) illustrate illustrative methods for generating a sequence in one RB.

[00241] The sequence generating methods shown in FIG. 18 (a), 18 (b), and 18 (c) provide sequence generation for a plurality of REs used for CDM in one RB.

[00242] The first sequence generation method according to FIG. 18a (a) provides for generating a single DRS sequence for code-multiplexed DRS RE levels. According to this first sequence generation method, a long sequence is generated and displayed at the DRS RE position common to all DRM CDM levels. A separate Walsh code (Walsh code coverage) is applied for each DRS level to ensure orthogonality between different DRS levels. The advantage of having a long sequence and the possibility of different sequence elements between the REs multiplied by the Walsh code is the effective randomization of the DRS RE, which leads to an increase in the randomization of interference with respect to other cells.

[00243] The second sequence generation method shown in FIG. 18 (b), provides for the generation of one or more DRS sequences for code-multiplexed DRS RE levels. According to a second sequence generation method, a long sequence is generated and displayed at the RE DRS position, where the same sequence is repeated on the resources in which the Walsh code (spectrum expansion by the Walsh code) is to be applied. Sequences for different levels may be different. For each DRS level, a separate Walsh code is applied to ensure orthogonality between different DRS levels. According to this method, since the same sequence is repeated for all REs in which the Walsh code is applied, different levels may have different DRS sequences, however, orthogonality between different DRS levels is maintained. This enables orthogonal transmission of DRS even between different cells, where the DRS sequences are different. According to a second sequence mapping method, the level index may be an input value for a DRS sequence generation initialization value.

[00244] A third method for generating the sequence of FIG. 18 (c) is a mixed method between the first and second sequence generation methods shown in FIG. 18 (a) and 18 (b). It is possible that different DRS sequences are mapped to DRS REs for each element of the RE sets multiplied by the Walsh code. In the example shown in FIG. 18 (c), two different DRS sequences are mapped to the DRS RE position, and therefore, the Walsh code is applied to different DRS sequences. According to this method, the DRS sequences can be configured so that the second DRS sequence actually matches the first DRS sequence. In the case where different DRS sequences are configured the same way, the third sequence generation method may look like the second sequence generation method. In the case where the DRS sequences are different from each other, the third sequence generation method may be similar to the first sequence generation method. This method can be configured to randomize DRS interference between other cells and maintain orthogonality of DRS transmissions between cells.

[00245] According to a third sequence generation method, a level index and possibly the same or different DRS sequences between indicators of a plurality of REs multiplied by a Walsh code can be input values for a DRS sequence generation initialization value.

[00246] In FIG. 19 shows an illustrative method for generating a DRS sequence.

[00247] According to the second method, the sequence used for DRS is generated for the full system bandwidth, and each allocated RB uses a portion of the long DRS sequence. Three methods for inserting a sequence for a plurality of REs used for CDM are described.

[00248] In FIG. 20 (a), 20 (b) and 20 (c) illustrate illustrative methods for generating a sequence in one RB.

[00249] In FIG. 20 (a), 20 (b), and 20 (c) show how to insert a sequence for a plurality of REs used for a CDM scheme in one RB.

[00250] A first sequence generation method is shown in FIG. 20 (a). A long DRS sequence is generated, and part of the long DRS sequence is used for DRS for a particular RB. A long DRS sequence may be mapped from a subcarrier located at the lowest frequency to a subcarrier located at the highest frequency. Depending on which RB is used for data transmission, the DRS sequence for a particular RB will use the portion of the long DRS sequence already mapped to the full band of the system. According to a first method for generating a sequence, the same DRS sequence is used for different OFDM symbols by which a single plurality of Walsh codes are multiplied (spectrum expansion with a Walsh code). This allows for the possibility of different DRS sequences between layers and yet provides orthogonality between DRS layers, and additionally provides orthogonality of DRS between different cells.

[00251] According to the second sequence generating method shown in FIG. 20 (b), a long DRS sequence is generated, and part of a long DRS sequence is used for DRS for a particular RB. A long DRS sequence may be mapped from a subcarrier located at the lowest frequency to a subcarrier located at the highest frequency. Depending on which RB is used for data transmission, the DRS sequence for a particular RB will use the portion of the long DRS sequence already mapped to the full band of the system. According to a second sequence generation method, possibly different DRS sequences are used for different OFDM symbols by which a single plurality of Walsh codes are multiplied. In this case, the basic DRS sequence for each of the layers that are code division multiplexed is the same, and different DRS levels use different Walsh codes on top of the given basic DRS sequence.

[00252] DRSs for different layers that are frequency division multiplexed can have basic DRS sequences. The second sequence generation method can be applied by having a separate DRS sequence for each OFDM symbol. The level index, the OFDM symbol index, and possibly the slot number (or subframe number) may be input values for the DRS sequence generation initialization value.

[00253] Additionally, for the second sequence generation method, the system can configure the DRS sequences for different OFDM symbols the same, so that the same DRS sequence is used for REs multiplied by a plurality of Walsh codes, as in the first sequence generation method shown in FIG. 20 (a). In the example of FIG. 20 (b), the DRS sequences b _i and d _i may coincide with the DRS sequences a _i and c _i , respectively. This allows you to configure the first sequence generation method shown in FIG. 20 (a), just like the second sequence generation method shown in FIG. 20 (b). In this case, the same or different DRS sequence for indicating the configuration of different OFDM symbols may be an input value for the DRS sequence generation initialization value.

[00254] The third sequence generation method shown in FIG. 20 (c) is essentially a bitwise multiplication according to the first and second methods of generating the sequence. The DRS sequence generated according to the method shown on the left side of FIG. 20 (c) corresponds to one RB, and the DRS sequence generated according to the method shown in the right part of FIG. 20 (c) also corresponds to one RB. Elements generated in RB can be multiplied to re-generate the DRS sequence. In this case, the generation of the DRS sequence for two RBs may be repeated. If the LTE 3GPP system has a system bandwidth corresponding to 12 RBs, DRS sequence generation for two RBs may be repeated six times.

[00255] According to this method, an RS sequence extended over a spectrum by Walsh codes can be further scrambled with different RS sequences that have different sequence values in all REs. According to this method, the loss of the effect of randomization of interference due to an RS sequence spread over the spectrum by Walsh codes (the same sequence for different OFDM DRS symbols) is reduced by secondary scrambling of the RS sequence. The third method of generating the sequence can also be implemented by having two input fields in the value of the sequence generation, which controls the different properties of the sequence, and a single sequence RS. The third method of generating the sequence is especially useful if the groups of cells cooperate so that the cells in the group share different Walsh codes, and at the same time, the cells in another group require randomization.

[00256] Describe the sequence initialization value necessary to generate a DRS sequence.

[00257] To support effective MU-MIMO, a DRS sequence cannot be triggered by a UE ID, but can only be initialized by a combination of cell ID, subframe number (or slot number), OFDM symbol index (in subframe or slot), level index, normal or extended CP etc. (i.e., the same or different DRS sequences to indicate the configuration of different OFDM symbols). Additional sequence initialization parameters may be a level index (numbered in DRS CDM levels) and a frequency shift index (numbered between FDM DRS levels, to distinguish between DRS that are mapped to completely different sets of time-frequency RE positions).

[00258] Additionally, the DRS sequence can be mapped to the DRS RE layer so that either the Walsh code extends the DRS sequence in time or the Walsh code covers (multiplies by) the DRS sequence. Since the sequence extended over the spectrum by Walsh codes improves the orthogonality property, while the sequence covered by Walsh codes improves the cross-correlation property. How the system can be configured in the Walsh code method is shown in the DRS mapping process.

длиной

, где

, определяется следующим уравнением 24. [00259] Here, it is assumed that all DRS sequences are generated using a pseudo random binary sequence generator. Pseudorandom sequences are specified by a Gold sequence of length 31. The output sequence

long

where

is defined by the following equation 24.

[00260] [Equation 24]

[00261]

и первая m-последовательность инициализируется согласно

.[00262] where

and the first m-sequence is initialized according to

.

с помощью значения, зависящего от применения последовательности. Здесь,

обозначает первую m-последовательность генератора последовательностей Голда, и

обозначает вторую m-последовательность генератора последовательностей Голда. Если не указано обратное, значение инициализации последовательности Голда выражает значение инициализации второй m-последовательности.[00263] The initialization of the second m-sequence is expressed as

using a value depending on the application of the sequence. Here,

denotes the first m-sequence of the Gold sequence generator, and

denotes the second m-sequence of the Gold sequence generator. Unless otherwise indicated, the Gold sequence initialization value expresses the initialization value of the second m-sequence.

[00264] For all methods of generating a DRS sequence, the present invention proposes to use a level index value that indicates which set of the set of CDM REs among all the sets of CDS / DRM REs is used as part of the sequence generation initialization value. Here, not all level index pointer values should be different for all DRS levels. Some DRS layers may have the same level index indicator. The level index indicator can be represented as a frequency shift indicator.

[00265] According to the first and second sequence generating methods of FIG. 18 (a) and 18 (b), the available DRS sequence generation function and its initialization value can be represented by the following equations 25 and 26.

[00266] [Equation 25]

[00267]

обозначает индекс блока ресурсов соответствующей передачи PDSCH, и

обозначает код Уолша, умножаемый на последовательность DRS. Пример значения инициализации последовательности, где

обозначает функцию округления до ближайшего меньшего целого числа,

является значением, меньшим или равным

, задается следующим уравнением 26.[00268] Here

denotes the resource block index of the corresponding PDSCH transmission, and

denotes a Walsh code multiplied by a DRS sequence. Example sequence initialization value, where

denotes the function of rounding to the nearest smaller integer,

is a value less than or equal to

is given by the following equation 26.

[00269] [Equation 26]

[00270]

является функцией индекса уровня DRS и используется как значение, которое указывает группу уровней, дифференцированных по частоте.[00271] According to a third sequence display method illustrated in FIG. 18 (c), the available DRS sequence generation function and its initialization value can be represented by the following equations 27 and 28. Here,

is a function of the DRS level index and is used as a value that indicates a group of levels differentiated by frequency.

[00272] [Equation 27]

[00273]

обозначает индекс блока ресурсов соответствующей передачи PDSCH,

обозначает код Уолша, умножаемый на последовательность DRS,

- индекс уровня для базовой последовательности DRS, и

- индекс последовательности DRS, который является функцией индекса символа OFDM. Это позволяет использовать два одинаковых индекса последовательности DRS в RB. Разные уровни DRS могут иметь одну и ту же базовую последовательность для применения кода Уолша и обеспечения ортогональности между ними. Иллюстративное значение инициализации последовательности задается следующим уравнением 28.[00274] Here

denotes the resource block index of the corresponding PDSCH transmission,

denotes a Walsh code multiplied by a DRS sequence,

- level index for the basic sequence of DRS, and

- DRS sequence index, which is a function of the OFDM symbol index. This allows the use of two identical DRS sequence indexes in RB. Different DRS levels may have the same basic sequence for applying the Walsh code and ensuring orthogonality between them. An exemplary sequence initialization value is given by the following equation 28.

[00275] [Equation 28]

[00276]

- номер слота в радиокадре,

обозначает ID соты физического уровня, и

является функцией индекса уровня DRS и обозначает значение, позволяющее отличать разные группы индексов уровня друг от друга по частотам.[00277] Here

- slot number in the radio frame,

denotes the cell ID of the physical layer, and

is a function of the DRS level index and denotes a value that allows you to distinguish different groups of level indices from each other in frequency.

[00278] According to the first sequence generating method of FIG. 20 (a), the available DRS sequence generation function and its initialization value can be represented by the following equations 29 and 30. Equation 29 represents an example of generating a DRS sequence, and equation 30 represents an initial value for generating a DRS sequence.

[00279] [Equation 29]

это номер символа OFDM в слоте,

- номер слота в одном радиокадре, и

- код Уолша, умноженный на скремблирующую кодовую последовательность, применяемую к символу OFDM с индексом

, имеющему слот номер

.[00280] Here

this is the OFDM symbol number in the slot,

- slot number in one radio frame, and

- Walsh code multiplied by the scrambling code sequence applied to the OFDM symbol with index

having a slot number

.

[00281] [Equation 30]

[00282]

- индекс последовательности DRS, который является функцией индекса символа OFDM, и

- индекс уровня для базовой последовательности DRS. Разные уровни DRS могут иметь одну и ту же базовую последовательность для применения кода Уолша и обеспечения ортогональности между ними. Индекс последовательности DRS может быть индексом, который нумерует символы OFDM, содержащие RE DRS в подкадре. В случае, когда определенная последовательность DRS в разных символах OFDM имеет одну и ту же последовательность DRS, можно выбирать одно и то же значение

, что приводит к генерации одной и той же последовательности. Если для уровня DRS в RB используются две разные последовательности DRS, то

может иметь, например, значение 2. Определенные уровни имеют разную информацию уровня базовой последовательности, дополнительно вставленную в значение инициализации, что представлено следующими уравнениями 31 и 32.[00283] Here

a DRS sequence index, which is a function of the OFDM symbol index, and

- level index for the basic DRS sequence. Different DRS levels may have the same basic sequence for applying the Walsh code and ensuring orthogonality between them. The DRS sequence index may be an index that numbers OFDM symbols containing DRS REs in a subframe. In the case where a particular DRS sequence in different OFDM symbols has the same DRS sequence, the same value can be selected

, which leads to the generation of the same sequence. If two different DRS sequences are used for the DRS level in RB, then

may have, for example, a value of 2. Certain levels have different information of the level of the basic sequence, additionally inserted in the initialization value, which is represented by the following equations 31 and 32.

[00284] [Equation 31]

это номер слота в радиокадре,

-ID соты физического уровня, и

- код Уолша, умноженный на последовательность, применяемую к символу OFDM с индексом

, имеющему слот номер

.

это номер символа OFDM в слоте.[00285] Here

this is the slot number in the radio frame,

-ID cells of the physical layer, and

- Walsh code multiplied by the sequence applied to the OFDM symbol with index

having a slot number

.

this is the OFDM symbol number in the slot.

[00286] Since DRS is a specialized reference signal, it may not be necessary to differentiate the sequence between the normal CP and the extended CP, whereby, the CP information is not input into the initialization value. An exemplary sequence initialization value may be defined by the following equation 32.

[00287] [Equation 32]

[00288]

- номер слота в радиокадре,

-ID соты физического уровня, и

- значение для указания группы индексов уровня, которое является функцией индекса уровня DRS. Группы индексов уровня могут различаться частотами. Таким образом,

является индикатором сдвига частоты (0 или 1), который является функцией индекса уровня DRS. Для систем с уровнями DRS, не более двух значений

может быть задано равными 0. Примеры значения

приведены в нижеследующих таблицах 3, 4 и 5.[00289] Here

- slot number in the radio frame,

-ID cells of the physical layer, and

- a value to indicate a group of level indices, which is a function of the DRS level index. Groups of level indices can vary in frequency. In this way,

is an indicator of the frequency shift (0 or 1), which is a function of the DRS level index. For systems with DRS levels, no more than two values

can be set to 0. Examples of value

are given in the following tables 3, 4 and 5.

Table 3 Level Index (numbered from 1) NFO value 1, 2, 5 or 7 0 3, 4, 6, or 8 one

Table 4 Level Index (numbered from 1) NFO value 1, 2, 5 or 6 0 3, 4, 7 or 8 one

Table 5 Level Index (numbered from 1) NFO value 1, 2, 3 or 4 0 5, 6, 7 or 8 one

[00293] According to the second sequence generating method illustrated in FIG. 20 (b), the available DRS sequence generation function and its initialization value can be represented by the following equations 33 and 34.

[00294] [Equation 33]

- индекс последовательности DRS, который является функцией индекса символа OFDM, и

обозначает код Уолша, умноженный на индекс последовательности DRS

со слотом номер

.[00295] Here

a DRS sequence index, which is a function of the OFDM symbol index, and

denotes a Walsh code times the DRS sequence index

with slot number

.

[00296] [Equation 34]

[00297]

- индекс последовательности DRS, который является функцией индекса символа OFDM. Индекс последовательности DRS может быть индексом, который нумерует символы OFDM, содержащие RE DRS в подкадре. В случае, когда определенная последовательность DRS в разных символах OFDM имеет ту же последовательность DRS, можно выбирать одно и то же значение

, что приводит к генерации одной и той же последовательности. Определенные уровни имеют разную информацию уровня базовой последовательности, дополнительно вставленную в значение инициализации. Это можно представить следующим уравнением 35.[00298] Here

- DRS sequence index, which is a function of the OFDM symbol index. The DRS sequence index may be an index that numbers OFDM symbols containing DRS REs in a subframe. In the case where a specific DRS sequence in different OFDM symbols has the same DRS sequence, the same value can be selected

, which leads to the generation of the same sequence. Certain levels have different basic sequence level information, further inserted into the initialization value. This can be represented by the following equation 35.

[00299] [Equation 35]

[00300]

[00301] The second sequence display method shown in FIG. 20 (c) can be implemented in three ways.

[00302] The first implementation of the method involves the presence of two sequences of Gold codes, initialized with different initialization values. An example of generating a DRS sequence is expressed by the following equation 36.

[00303] [Equation 36]

и

это последовательности DRS, генерируемые с использованием последовательностей Голда, инициализируемых разными значениями инициализации, соответственно.[00304] Here

and

these are DRS sequences generated using Gold sequences initialized with different initialization values, respectively.

.[00305] A possible property of initializing a Gold code for the first sequence is described below.

.

[00306] 1. Different sequences for each code division multiplexed layer

[00307] 2. Different sequences for each level, frequency division multiplexed

[00308] 3. The same sequence for REs multiplied by the Walsh code

[00309] 4. Different sequences for different cells

можно представить одним из следующих уравнений 37, 38 и 39.[00310] The initialization value for the first sequence

can be represented by one of the following equations 37, 38 and 39.

[00311] [Equation 37]

[00312]

[00313] [Equation 38]

[00314]

[00315] [Equation 39]

[00316]

.[00317] A possible property of initializing a Gold code for a second sequence is described below.

.

[00318] 1. The same sequence for all layers multiplexed with code division

[00319] 2. The same or different sequences for different levels, frequency division multiplexed

[00320] 3. Different sequences for RE multiplied by Walsh code

[00321] 4. Different sequences for different cells

можно представить одним из следующих уравнений 40, 41, 42 и 43.[00322] Initialization value for the second sequence

can be represented by one of the following equations 40, 41, 42 and 43.

[00323] [Equation 40]

[00324]

[00325] [Equation 41]

[00326]

[00327] [Equation 42]

[00328]

[00329] [Equation 43]

[00330]

. Это позволяет генерировать разные последовательности между первой и второй последовательностями для создания разных последовательностей в случае создания аналогичных значений инициализации.[00331] In the example, the initialization value for the second sequence, expressed in equations 40-43, can be reordered and displayed. For example, as follows:

. This allows you to generate different sequences between the first and second sequences to create different sequences in the case of creating similar initialization values.

[00332] According to the sequence generating method illustrated in FIG. 20 (c), one of the RS sequences is initialized by a combination of a cell ID, an OFDM symbol index (or an OFDM DRS counter / symbol index), a level index, and a frequency shift index. Another RS sequence is initialized by a combination of N _I , OFDM symbol index (or OFDM DRS counter / symbol index). The first RS sequence will have the same RS sequence for different REs multiplied by the Walsh code, and the second RS sequence will not have the same RS sequence for different REs multiplied with Walsh codes.

[00333] The value of N _I may be the identification number of a cell operating in coordinated multipoint mode (CoMP), or a value shared by multiple cells. The value of N _I must be signaled to the UE so that the UE correctly receives the RS sequence. This means that the essential property of the first initialization value remains unchanged for all OFDM symbols included in the DRS, while the second initialization value is different for the different OFDM symbols included in the DRS.

[00334] In FIG. 21 shows an illustrative method for generating a DRS sequence in one RB.

[00335] In FIG. 21 shows the case where different sequences are generated for the levels, and the spreading using the Walsh code is used. According to FIG. 21, different sequences are used for different DRS levels of CDM, and different Walsh codes are used to maintain orthogonality between the DRS levels. Each sequence used for each DRS CDM layer is spread across a Walsh code spectrum. This means that for the unit set RE, spread over the spectrum by the Walsh code, the same sequence value is used, different from the product value of the Walsh code elements.

[00336] In FIG. 22 shows an illustrative method for transmitting DRS using a DRS sequence for which two cells are generated.

[00337] The equation of the signal received by the receiver shown in the right part of FIG. 22 and the channel estimated for the signal received at the receiving antenna port can be represented by the following equations 44 and 45.

[00338] [Equation 44]

[00339]

[00340] Here, h ₀ , h ₁ , h ₂ and h ₃ denote the effective channel coefficients, a _i , and b _i denote the scrambling code sequences, and n ₀ and n ₁ denote noise.

[00341] [Equation 45]

[00342]

[00343] From equations 44 and 45, it follows that the estimated effective channel has only one interference factor Z ₁ . Thus, the interference factor affects the effective channel coefficient estimated at the receiver.

[00344] In FIG. 23 shows an illustrative method for generating a sequence in one RB.

[00345] In FIG. 23 shows a case where an eNode B generates the same sequence for layers and uses a Walsh code spread. According to FIG. 23, different sequences are used for different DRS levels of CDM, and different Walsh codes are used to maintain orthogonality between the DRS levels. The illustrative sequence used according to the method shown in FIG. 23 provides maximum randomization of inter-cell interference between cells.

[00346] In FIG. 24 illustrates an example method for transmitting DRS using a DRS sequence for which two cells are generated.

[00347] The equation of the received signal and the estimated channel in terms of the port of the receiving antenna

[00348] The equation of the signal received by the receiver shown on the right side of FIG. 24, and the channel estimated for the signal received at the receiving antenna port can be represented by the following equations 46 and 47.

[00349] [Equation 46]

[00350]

[00351] Here, h ₀ , h ₁ , h ₂ and h ₃ denote the coefficients of the effective channel, a _i , and b _i denote the scrambling code sequences, and n ₀ and n ₁ denote noise.

[00352] [Equation 47]

[00353]

[00354] From equation 45 it follows that the estimated effective channel coefficient has four different coefficients Z _1, Z ₂ , Z ₃ and Z ₄ , and the randomized coefficients can cancel each other, thus providing a more accurate channel estimate with respect to h ₀ . From the equations it can be seen that the sequence display method shown in FIG. 23 has a four times greater randomization effect than the sequence display method illustrated in FIG. 21.

[00355] To maximize randomization of interference from the DRS sequence from other cells, ideally, the DRS sequence should have random values in all REs, but at the same time, to maintain orthogonality between DRS levels, the same DRS should be used DRS sequence. The difficulty in providing the same DRS sequence at all levels is that, under certain precoding conditions, the Walsh code leads to a significant difference in power between OFDM symbols.

[00356] In FIG. 25 (a) and 25 (B) show an illustrative method of applying precoding to two DRS levels and mapping DRS levels to four transmit antennas, and power differences between adjacent OFDM symbols in transmitting DRS according to the method.

[00357] Referring to FIG. 25 (a), a transmitter may apply precoding to two DRS layers and transmit DRS layers through four transmit antennas. In the case of applying the precoding shown in FIG. 25, signals transmitted through respective transmit antennas for each symbol are shown on the right side of FIG. 25 (a). In the case where the transmitter transmits signals, thus, power differences between adjacent OFDM symbols can reach approximately 2.25 dB, according to FIG. 25 (b).

[00358] In FIG. 26 shows an illustrative method for generating a DRS sequence.

[00359] According to the method shown in FIG. 26, for each level, a separate sequence undergoes a Walsh code extension, after which a Walsh code extended sequence is scrambled.

[00360] The first sequence denoted by 'a' in FIG. 26 is used to differentiate sequences between levels of CDM. The second sequence, denoted by 's', is used to differentiate the sequences between the symbols indicated at a higher level. The designation indicated at a higher level may be, for example, a cell ID, a CoMP cell group ID, or another designation defined to distinguish a DRS sequence from corresponding designations. It is desirable that the first sequence denoted by 'a' does not change the value on the set of REs multiplied by Walsh codes (for example, two consecutive REs of the OFDM symbol). The Walsh code can be multiplied over the first sequence. Essentially, this can be achieved by spreading (multiplying the Walsh code by a sequence to form a longer sequence) in the time dimension of the first sequence in which REs are placed for DRS using the Walsh-Hadamard code. The second sequence, denoted by 's', arbitrarily changes the values on all REs. The second sequence is level-invariant and, therefore, the same general sequence is used at all levels.

[00361] In FIG. 27 illustrates an exemplary method for transmitting DRS using the DRS sequence generated according to the method shown in FIG. 26.

[00362] The equation of the signal received by the receiver shown in the right part of FIG. 27 and the channel estimated for the signal received at the receiving antenna port can be represented by the following equations 48 and 49.

[00363] [Equation 48]

[00364]

[00365] [Equation 49]

[00366] From equations 48 and 49 it follows that the estimated effective channel coefficients have four different coefficients Z _1, Z ₂ , Z ₃ and Z ₄ , and the randomized coefficients can cancel each other, thus providing a more accurate channel estimate with respect to h ₀ . From the equations it follows that the sequence mapping method shown in FIG. 27 has the same level of interference randomization effect as the sequence display method shown in FIG. 23, and four times stronger randomization effect than the sequence display method described with reference to FIG. 21.

[00367] In FIG. 28 (a) and 28 (b) illustrate illustrative methods for generating a DRS sequence.

.[00368] A first level sequence can be generated using a Gold code sequence, which is described below. Alternatively, the first sequence may be a fixed sequence in which the sequences for the second, third and fourth levels are defined as complex values on a unit circle with some fixed phase shift relative to the first level sequence. For example, as shown in FIG. 28 (a) if the sequence of the first level is given as {{+1, +1, +1}, {+1, +1, +1}}, where the elements in the illustrative values of the representation of the sequence are in RB (before spreading over the spectrum Walsh code), the sequence for the second level can be set as

.

,

,

}, {

,

,

}}, где k- индекс уровня (пронумерованный от 1), n- индекс RB, и f1-f6 обозначают индекс временно-частотного RE в RB. Примером значения на единичной окружности, используемого для уровней, отличных от первого уровня, является последовательность Задова-Чу, например,

или

.[00369] In the general case, based on the fact that the first sequence for the first level is all '1' ({{+1, +1, +1}, {+1, +1, +1}}), the first the sequence for other levels can be set as {{

,

,

}, {

,

,

}}, where k is the level index (numbered from 1), n is the RB index, and f1-f6 denote the time-frequency RE index in RB. An example of a value on a unit circle used for levels other than the first level is the Zadov-Chu sequence, for example,

or

.

[00370] Additionally, a first sequence for each level can be generated using a combination of a sequence of complex values on a unit circle with a fixed phase shift and a sequence of random complex values generated from sequences such as the Gold code. A similar example is shown in FIG. 29 (a) and 29 (b). In FIG. 29 (a) and 29 (b) show an illustrative method for generating a DRS sequence.

[00371] The sequence generating methods illustrated in FIG. 21, 23 and 26 can be redefined in another way. The sequence display method illustrated in FIG. 26 provides for the use of different sequences for different levels, while the sequence does not change in time (in contrast to the Walsh code multiplier). Alternatively, the sequence display method illustrated in FIG. 24 provides for the use of the same sequence for different levels, while the sequence changes over time. The sequence display method illustrated in FIG. 21 has potential problems with randomizing interference from other cells, while the sequence mapping method illustrated in FIG. 23 has potential problems with constructing a PA on an eNode B. The sequence mapping method illustrated in FIG. 26 covers the sequence display methods of FIG. 21 and 23, involving the use of different sequences for different levels and different sequences in time. To maintain orthogonality, the sequence display method shown in FIG. 26 provides for the generation of two types of sequences. One of the sequences is designed to create different sequences between levels, and other sequences change the sequence in time. Additionally, the values of the sequences of both types can vary in frequency.

[00372] the sequence display method illustrated in FIG. 26, can be implemented in different ways. The first implementation of the method consists in generating different sequences for the corresponding levels, expanding over the spectrum of sequences using the Walsh code, and then multiplying by the second sequence common to all levels. A second implementation of the method is to generate a common sequence for the levels, cover the sequence using a Walsh code, and then multiply by a second sequence that differs for each level. Other alternative implementations of the method include reorganizing the sequence display for the first and second sequences and multiplying by Walsh codes.

[00373] Alternatively, different sequences can be generated for the respective levels, and Alamouti coding can be applied to the sequences.

[00374] In FIG. 30 shows an example of transmitting a DRS signal using a DRS sequence generated in two cells.

[00375] According to this method, different sequences are generated for the respective layers, and Alamouti coding is applied to each pair of sequences to ensure orthogonality between the layers. This method provides good randomization of interference from different cells and, at the same time, effectively provides different sequences for the respective levels.

[00376] In FIG. 31 shows an alternative example of a DRS sequence display method shown in FIG. 26.

[00377] The sequence display method illustrated in FIG. 26 provides for the multiplication of part of the sequences to form the final DRS sequence. In other words, the method generates the complete DRS sequence (referred to in the LTE-A systems as the RS DM sequence), by expanding the spectrum of the sequence depending on the level and multiplying certain portions of the sequence extended by the spectrum with Walsh codes depending on the level by a scrambling sequence, level independent. In particular, the second sequence can be multiplied by pairs of the first sequence, which is efficiently spread over the spectrum by the Walsh code. This can be achieved by '1' in the part of the second sequence, which scrambles only part of the sequence spread over the spectrum by Walsh codes (first sequence), as shown in the example in FIG. 31.

[00378] In FIG. 32 (a) and 32 (b) illustrate illustrative methods for generating a DRS sequence for each OFDM symbol.

[00379] As shown in FIG. 32 (a) according to this DRS mapping method, a sequence for a first sequence and / or a second sequence used in DRS for each layer is generated according to a maximum band in each OFDM symbol containing DRS.

можно задать согласно следующему уравнению 50. Окончательная последовательность будет функцией номера подкадра (или слота) в радиокадре и номера символа OFDM в подкадре.[00380] The sequence for the RB allocated to each UE uses a portion of the long sequence generated for the full band. Final sequence

can be specified according to the following equation 50. The final sequence will be a function of the number of the subframe (or slot) in the radio frame and the number of the OFDM symbol in the subframe.

[00381] [Equation 50]

и

представляют собой последовательности DRS, генерируемые с использованием последовательностей Голда, инициализируемых разными значениями инициализации.[00382] Here

and

are DRS sequences generated using Gold sequences initialized with different initialization values.

можно задать согласно следующему уравнению 51. Окончательная последовательность будет функцией номера подкадра (или слота) в радиокадре и номера символа OFDM в подкадре.[00383] Referring to FIG. 32 (b), a DRS sequence may be generated for each subframe. According to this sequence mapping method, a sequence for a first sequence and / or a second sequence used in DRS for each layer is generated according to the maximum band in each subframe. Additionally, the generated long sequence will be mapped to all REs in the RB until the sequence is mapped to the next RB. The sequence for RB uses the portion of the long sequence generated for the full band. Final sequence

can be specified according to the following equation 51. The final sequence will be a function of the subframe (or slot) number in the radio frame and the OFDM symbol number in the subframe.

[00384] [Equation 51]

[00385] According to the sequence display method shown in FIG. 32 (b), the length of the sequence for the first sequence and the second sequence are different from each other for the reason that the first sequence is spectrally spread by the Walsh-Hadamard code. An expanded spectrum of the first sequence will ultimately have the same sequence length as the second sequence.

[00386] In FIG. 33 shows in more detail a sequence display method associated with the methods shown in FIG. 32 (a) and 32 (B).

[00387] In general, a sequence is initially mapped to a frequency measurement in RB and then mapped to OFDM symbols containing DRS REs. The scrambling sequence is displayed in such a way that all CDM DRS levels are mapped to the frequency dimension and then mapped to OFDM symbol RE sets including DRS REs. Using this method, the UE can begin to estimate the channel when the UE generates a DRS sequence when the UE only partially received the downlink subframe.

[00388] We will describe randomization with a Walsh code.

[00389] In order to permit high power transmission, for certain ports of the transmitting antenna based on certain precoding matrices, consideration may be given to using Walsh codes with cyclic shift in the frequency dimension. This means that from the point of view of the unit level, DRS, RE multiplied by the Walsh code will change in frequency. In particular, Walsh codes multiplied by RE sets will be Walsh codes with cyclic shift. We assume that the Walsh code length is 2, and two orthogonal codes for this Walsh code are specified as W _0.1 and W _1.1 . Additionally, orthogonal cyclic shift codes can be designated as W _0.2 and W _1.2 .

[00390] W _0.1 = {+ 1, + 1}

[00391] W _1.1 = {+ 1, -1}

[00392]

[00393] W _0.2 = {+ 1, + 1}

[00394] W _1,2 = {- 1, + 1}

[00395] We assume that the length of the Walsh code is 4, and four orthogonal codes for this Walsh code are defined as W _0.1 and W _1.1 . Additionally, orthogonal cyclic shift codes are defined as W _{0, k} , W _{1, k} , W _{2, k} and W _{3, k} , where k is the value of the cyclic shift.

[00396] W _0.1 = {+ 1, + 1, + 1, + 1}

[00397] W _1.1 = {+ 1, -1, + 1, -1}

[00398] W _2.1 = {+ 1, + 1, -1, -1}

[00399] W _3.1 = {+ 1, -1, -1, + 1}

[00400]

[00401] W _0.2 = {+ 1, + 1, + 1, + 1}

[00402] W _1,2 = {- 1, + 1, -1, + 1}

[00403] W _2.2 = {+ 1, -1, -1, + 1}

[00404] W _3,2 = {- 1, -1, + 1, + 1}

[00405]

[00406] W _0.3 = {+ 1, + 1, + 1, + 1}

[00407] W _1.3 = {+ 1, -1, + 1, -1}

[00408] W _2,3 = {- 1, -1, + 1, + 1}

[00409] W _3.3 = {- 1, + 1, + 1, -1}

[00410]

[00411] W _0.4 = {+ 1, + 1, + 1, + 1}

[00412] W _1.4 = {- 1, + 1, -1, + 1}

[00413] W _2.4 = {- 1, + 1, + 1, -1}

[00414] W _3.4 = {+ 1, + 1, -1, -1}

[00415] Each DRS layer uses a Walsh code W _{n, m} to multiply DRS sequences, where n is the DRS level index and m is a function of the subcarrier index. One example is m = k mod 2 or m = k mod 4, where k is the subcarrier index counting only the subcarriers carrying DRS. This means that the exact orthogonal code coverage code pattern used for a specific DRS level in an RB can vary between RBs.

[00416] In FIG. 34 (a) shows an example orthogonal code coverage code template used for a particular DRS layer, and FIG. 34 (b) and 34 (c) show examples of using the Walsh code in RB.

[00417] Multiplying by a Walsh code with a different cyclic shift for each subcarrier (so that the cyclic Walsh code pattern is repeated every 2 or 4 RB) allows to reduce the power difference between OFDM symbols from the point of view of a single transmit antenna.

[00418] The fact is that symbols combined in power (symbols 2 * S _i after precoding) according to FIG. 25 (b), which causes a difference in power between OFDM symbols, is mainly interleaved between multiple OFDM symbols. This reduces the concentration of power in a single OFDM symbol by randomizing power-combined symbols over time.

[00419] In FIG. 35 illustrates an example method for displaying Walsh codes in a frequency set of CDM REs.

[00420] A randomization method will be described using the method shown in FIG. 35. Walsh codes can be mapped in different ways to frequency sets RE CDM or time-frequency sets RE CDM. One example is the mapping of Walsh code elements into sets of CDM REs forward in time for a particular first RB pair (or 1 RB) and mapping of Walsh code elements into different sets of CDM REs backward in time for a second RB pair adjacent to the first RB pair.

[00421] Elements of the Walsh code applied to the first pair RB and the second pair RB adjacent to the first pair RB correspond to elements of a plurality of Walsh codes. For one or more RB pairs, multiple CDM groups may exist. For example, for each RB pair, there may be a CDM 1 group and a CDM 2 group. It is assumed that the set of Walsh codes that will be applied to each RB pair is expressed as {a, b, c, d}. When the Walsh code is applied to a specific CDM group (for example, CDM group 1) in the first RB pair, the Walsh code elements a, b, c and d in the set of Walsh codes {a, b, c, d} can be displayed in RE in this way so that the Walsh code elements a, b, c, and d are one-to-one displayed (applied) in RE in the direction of the time axis, one-to-one displayed in RE in the direction opposite to the direction of the time axis, and then one-to-one displayed in RE in the direction time axis.

[00422] When a Walsh code is applied to a specific CDM group (eg, CDM group 1) in a second RB pair adjacent to the first RB pair, the Walsh code elements a, b, c and d in the set of Walsh codes {a, b, c , d} can be displayed in RE so that the elements of the Walsh code a, b, c and d are first one-to-one displayed in RE in the direction opposite to the direction of the time axis, one-to-one displayed in RE in the direction of the time axis, and then mutually -uniquely displayed in RE in the opposite direction to the time axis.

[00423] In the first and second pairs of RBs, the Walsh code is applied to CDM group 1 and CDM group 2 in switching mode. For example, when the Walsh code elements a, b, c, and d are one-to-one displayed in RE in the direction of the time axis in the CDM group 1 of the first pair RB, the Walsh code elements c, d, a and b can be displayed one-to-one in RE in the direction the time axis in CDM group 2 in the form of a switched CDM group 1 (i.e., the orders of the Walsh code elements applied to CDM group 1 and CDM group 2 are different from each other). This switch can also be applied to the second RB pair. As described above, Walsh code elements in switched form can be applied to each CDM group in each RB. To randomize code interference between layers, you can use code switching for each layer in the time-frequency sets of CDM REs. According to this method, each layer uses a Walsh code in a specific time-frequency set of CDM REs (RE set to which CDM applies).

[00424] In FIG. 36 (a) and 36 (b) show an example of code switching for two levels.

[00425] In the example shown in FIG. 36 (a) and 36 (b), the length of the Walsh code is 2, W _0.0 is the Walsh code {+1, +1}, and W _1.0 is the Walsh code {+1, -1}. If we denote the Walsh code used in a certain time-frequency set RE CDM, as W _k (where k denotes the code index), then the value of k may be a function of frequency or time-frequency. One example is k = (I _RB + I _freq + n _s ) mod 2, where I _RB is the RB index, n _s is the slot index, and I _freq is the frequency index of the RE CDM set in RB, which can take values 0, 1 and 2. Another example is k = (I _RB mod 3 + I _freq ).

[00426] In FIG. 37 shows an example of code switching for two levels.

[00427] In the example shown in FIG. 37, a Walsh code length of 4 is used. The Walsh code is denoted by W _k , k is the code index. An example of the Walsh code W _k can be represented as follows.

[00428] W ₀ = {+ 1, + 1, + 1, + 1}

[00429] W ₁ = {+ 1, -1, + 1, -1}

[00430] W ₂ = {+ 1, + 1, -1, -1}

[00431] W ₃ = {+ 1, -1, -1, + 1}

[00432] or

[00433] W ₀ = {+ 1, + 1, + 1, + 1}

[00434] W ₁ = {+ 1, -1, + 1, -1}

[00435] W ₂ = {+ 1, -1, -1, + 1}

[00436] W ₃ = {+ 1, + 1, -1, -1}

[00437] Additionally, it is possible to combine code switching in the frequency or time-frequency set of CDM REs and the Walsh code mapping that are mentioned above.

[00438] When the randomization of the Walsh code mapping shown in FIG. 35, and a Walsh code length of 4 is used; sequences between layers are not randomized.

[00439] In FIG. 38 (a) and 38 (b) show an example of switching Walsh codes for four levels.

[00440] From FIG. 38 (a) it follows that no randomization of values between level 1 and level 4 is performed. In this particular case, you might consider using DFT-based code to randomize characters between all levels. In the case of using the orthogonal code based on the DFT of FIG. 38 (b), it is possible to achieve effective randomization of values for any combination of levels. Here, it is possible to use the converted DFT code sequence instead of the values of the DFT sequence (column vectors of the DFT matrix) indicated below.

[00441]

, и U- унитарная матрица). Заметим, что при переключении кодов также можно использовать код на основе DFT, а также другие признаки, упомянутые в этом описании изобретения.[00442] Instead of using column vectors of the DFT matrix as a code to provide orthogonality between levels, column vectors M '(where

, and U is a unitary matrix). Note that when switching codes, it is also possible to use DFT-based code, as well as other features mentioned in this description of the invention.

[00443] Referring to FIG. 38 (a) when the randomization of the Walsh code mapping shown in FIG. 35 is applied to the Walsh code mapping shown in FIG. 38 (a) and a Walsh code length of 4 is used, as described above, sequences between layers are not randomized. The Walsh code elements described with reference to FIG. 35 can be represented by the 4 * 4 matrix below, which can be applied to the Walsh code mapping shown in FIG. 38.

[00444]

[00445] In this 4 * 4 matrix, the Walsh code elements (a, b, c, d) may vary in levels. For example, the Walsh code elements (a, b, c, d) are (1, 1, 1, 1), which corresponds to the first column of the 4 * 4 matrix at level 1, (1, -1, 1, -1), which corresponds to the second column of the 4 * 4 matrix at level 2, (1, 1, -1, -1), which corresponds to the third column of the 4 * 4 matrix at level 3, and (1, -1, -1, 1), which corresponds to the fourth column of the 4 * 4 matrix at level 4.

[00446] Walsh code elements (a, b, c, d) can be mapped to a plurality of RB pairs (for example, first and second RB pairs) for each level using the same method as the method shown in FIG. 35.

[00447] Referring to FIG. 38 (a), (a, b, c, d) = (1, 1, 1, 1) are displayed in RE in the direction of the time axis, (1, 1, 1, 1) are displayed in RE in the opposite direction of the time axis, and then (1, 1, 1, 1) are displayed in RE in the direction of the time axis at level 2. Although in FIG. 38 (a) only REs are shown for two subcarriers at level 1, Walsh code elements are applied to three subcarriers for one CDM group in one RB pair, as mentioned above. At level 3, (a, b, c, d) = (1, 1, -1, -1) are first displayed in RE in the direction of the time axis, (1, 1, -1, -1) are displayed in RE in the direction opposite the direction of the time axis, and then (1, 1, -1, -1) are displayed in RE in the direction of the time axis.

[00448] As described above, the Walsh code sequence used according to FIG. 38 (a) can be displayed so that it repeats for multiple frequency elements (for example, two RBs).

[00449] We describe the value of the sequence initialization.

длиной

, где

, можно задать следующим уравнением 52.[00450] It is contemplated that all DRS sequences are generated using a pseudo random binary sequence generator. Pseudorandom sequences are specified by a Gold sequence of length 31. The output sequence

long

where

can be defined by the following equation 52.

[00451] [Equation 52]

[00452]

, и первая m-последовательность инициализируется согласно

.[00453] Here,

, and the first m-sequence is initialized according to

.

с помощью значения, зависящего от применения последовательности. Здесь,

обозначает первую m-последовательность генератора последовательностей Голда, и

обозначает вторую m-последовательность генератора последовательностей Голда. Если не указано обратное, значение инициализации последовательности Голда выражает значение инициализации второй m-последовательности. С этой точки зрения, значение инициализации для последовательности

обозначается

.[00454] The initialization of the second m-sequence is expressed as

using a value depending on the application of the sequence. Here,

denotes the first m-sequence of the Gold sequence generator, and

denotes the second m-sequence of the Gold sequence generator. Unless otherwise indicated, the Gold sequence initialization value expresses the initialization value of the second m-sequence. From this point of view, the initialization value for the sequence

is indicated

.

[00455] In FIG. 39 shows an illustrative method for generating two sequences.

[00456] The initialization parameters loaded into the shift registers of the initialization values for the first and second sequences use the shift register fields for each parameter. In addition, the initialization parameter loaded in the first sequence should not coincide in relation to the position of the shift register with the initialization parameter loaded in the second sequence. This ensures that the two sequences do not generate the same sequence values. Equation 53 represents an example of sequence generation.

[00457] [Equation 53]

[00458]

[00459]

[00460]

и

обозначают последовательности DRS, генерируемые с использованием последовательностей Голда, инициализируемых разными значениями инициализации,

- индекс последовательности DRS, который является функцией индекса символа OFDM, и

обозначает код Уолша, умножаемый на индекс последовательности DRS

слота номер

.[00461] Here

and

denote DRS sequences generated using Gold sequences initialized with different initialization values,

a DRS sequence index, which is a function of the OFDM symbol index, and

denotes a Walsh code multiplied by a DRS sequence index

slot number

.

[00462] The first sequence responsible for scrambling the values between different DRS levels may need the following combination of parameters in the initialization value. N _layer is the level index, N _cellid is the cell ID, n _s is the slot index in the radio frame, l is the OFDM symbol index in the subframe, and k is the OFDM DRS symbol index in the subframe.

[00463] The second sequence, responsible for scrambling the values between different indicated higher-level IDs, may need the following combination of parameters in the initialization value. N _LH-ID is the specified ID of a higher level (for example, cell ID, CoMP group ID, etc.), N _cellid is the cell ID, n _s is the slot index in the radio frame, l is the OFDM symbol index in the subframe, and k - index of the OFDM symbol in the subframe.

[00464] Illustrative initialization values can be represented by the following equations 54 and 55.

[00465] [Equation 54]

[00466]

[00467]

[00468] [Equation 55]

[00469]

[00470]

[00471] In equations 54 and 55, the initialization value i ₁ , i ₂ , i ₃ and i ₄ should be selected so that information loaded into the shift register of the initialization value is loaded at different positions of the shift register (for example, i ₁ = 7, i ₂ = 16, i ₃ = 0, and i ₄ = 3, assuming that the N _layer is 3 bits, N _HL-ID is 9 bits, l can take values from 0 to 13, k can take values from 0 to 3 , and n _s can take values from 0 to 20).

[00472] We describe another illustrative method for displaying a sequence. The following equation 56 represents an example of sequence generation.

[00473] [Equation 56]

[00474]

[00475]

[00476]

- индекс последовательности DRS, который является функцией индекса символа OFDM, и

обозначает код Уолша, умножаемый на индекс последовательности DRS

слота номер

.[00477] Here

a DRS sequence index, which is a function of the OFDM symbol index, and

denotes a Walsh code multiplied by a DRS sequence index

slot number

.

[00478] The first sequence responsible for scrambling the values between different DRS levels may need the following combination of parameters in the initialization value. N _layer is the level index, and N _cellid is the cell ID.

[00479] The second sequence, responsible for scrambling the values between different indicated higher-level IDs, may need the following combination of parameters in the initialization value. N _LH-ID is the specified higher-level ID (for example, cell ID, CoMP group ID, etc.), and N _cellid is the cell ID, n _s is the slot index in the radio frame.

[00480] Illustrative initialization values can be represented by the following equation 57.

[00481] [Equation 57]

[00482]

[00483]

[00484] In this example, the initialization value i ₁ , i ₂ , and i ₃ should be selected so that information loaded into the shift register of the initialization value is loaded at different positions of the shift register (for example, i ₁ = 3, i ₂ = 12, and i ₃ = 0, assuming that the N _layer is 3 bits, N _HL-ID is 9 bits of information).

[00485]

[00486] AN ALTERNATIVE METHOD FOR GENERATION AND DISPLAYING A SEQUENCE

[00487] You can also generate and display the first sequence (referred to as a level-dependent sequence, spread over the spectrum by Walsh codes) by generating a sequence of length equal to the length of the extracted RBs. At the same time, it is also possible to generate and display a second sequence (referred to as a level-independent sequence) by generating a sequence of length equal to the strip of the system (or even possibly equal to the maximum RB size provided by the specifications). In this case, the sequence initialization value can be represented by the following equation 58.

[00488] [Equation 58]

[00489] The first sequence (referred to as a level-dependent sequence, spread over a Walsh code spectrum) responsible for scrambling values between different DRS levels and providing orthogonality between DRS levels may need the following combination of parameters in the initialization value, which include N _layer denoting a level index, N _cellid denoting a cell ID, N _rnti representing a UE ID, and n _s representing a slot index in a radio frame.

[00490] A second sequence (referred to as a level-independent sequence) responsible for scrambling values between different indicated higher-level IDs may need the following combination of parameters in the initialization value. Options include N_LH-IDdenoting said higher level ID (e.g., cell ID, CoMP group ID, etc.), N_cellidrepresenting the cell ID, and n_s, denotes the slot index in the radio frame.

[00491] Illustrative initialization values can be represented by the following equation 59.

[00492] [Equation 59]

[00493]

[00494]

[00495]

[00496] According to the above examples, the initialization values may take the values i ₁ = 0, i ₂ = 9, i ₃ = 30, i ₄ = 16 and i ₅ = 0, and N _HL-ID is 9 bits of information.

[00497] It is also possible to load the level index into one of the m-sequences for the first sequence (referred to as a level-dependent sequence extended over the spectrum by Walsh codes) and load the values consisting of the cell ID, UE ID, and index into another m-sequence subframe.

, и значение инициализации второй m-последовательности первого кода Голда можно обозначить как

.[00498] Here, the initialization value of the first m-sequence of the first Gold code can be denoted as

, and the initialization value of the second m-sequence of the first Gold code can be denoted as

.

, и

.[00499] Here

, and

.

[00500] In this example, i ₁ = 0, i ₂ = 9, i ₃ = 1, i ₄ = 16, i ₅ = 0, and N _HL-ID is 9 bits of information.

[00501] Let us describe the reasons for the randomization of inter-cell interference, and methods of randomization.

[00502] In FIG. 40 shows an example of DRS transmission using a DRS sequence for which two cells are generated.

[00503] The equation of the received signal and the estimated channel in terms of the port of the receiving antenna, shown on the right side of FIG. 40 are formulated as equations 60 and 61.

[00504] [Equation 60]

[00505]

[00506] Here, h ₀ , h ₁ , h ₂ and h ₃ denote the effective channel coefficients, a _i and c _i denote scrambling code sequences, and n ₀ and n ₁ denote noise.

[00507] [Equation 61]

[00508]

[00509]

[00510] In FIG. 41 shows an example of DRS transmission using a DRS sequence for which two cells are generated.

[00511] The equation of the received signal and the estimated channel in terms of the port of the receiving antenna, according to FIG. 41 are formulated as equations 62 and 63.

[00512] [Equation 62]

[00513]

[00514] Here, h ₀ , h ₁ , h ₂ and h ₃ denote the effective channel coefficients, s _i and x _i denote scrambling code sequences, and n ₀ and n ₁ denote noise.

[00515] [Equation 63]

[00516]

[00517]

[00518] In the case of equations 62 and 63 related to FIG. 41, the inter-level interference from other cells is spread across the spectrum at all levels due to a larger number of interference randomization factors, compared with equations 60 and 61 associated with FIG. 40. This method allows for the complete randomization of interference.

[00519] In FIG. 42 shows an example of DRS transmission using a DRS sequence for which two cells are generated.

[00520] The method shown in FIG. 42 allows the same randomization effect of interference to be achieved as Walsh code coverage according to the mixed method.

[00521] The equation of the received signal and the estimated channel in terms of the port of the receiving antenna, according to FIG. 42 are formulated as equations 64 and 65.

[00522] [Equation 64]

[00523]

[00524] Here, h ₀ , h ₁ , h ₂ and h ₃ denote the effective channel coefficients, s _i and x _i denote scrambling code sequences, and n ₀ and n ₁ denote noise.

[00525] [Equation 65]

[00526] In FIG. 43 (a) shows an example of DRS transmission using the generated DRS sequence, and FIG. 43 (b) shows the transmitted power according to the transmission scheme shown in FIG. 43 (a).

[00527] Having the same DRS sequence for two layers (possibly even four levels) code division multiplexed may be associated with a lack of differences in transmit power between adjacent OFDM symbols under certain precoding conditions, as shown in FIG. 43 (b).

[00528] Referring to FIG. 43 (a), it is assumed that only a sequence that is independent of level is used. This means that the same sequence is used at each level. In addition, the precoding matrix [+1, -1, +1, -1; +1, + j, -1, +1] is used for wideband precoding for the UE, which occupies most of the band. The maximum difference in transmit power due to the combination of the precoded Walsh codes can be up to a difference in power of +1 dB ~ -1.25 dB compared to the other OFDM symbols of FIG. 43 (b). In a possible case for LTE-A, where four levels can be code-multiplexed, the possible maximum difference in transmitted power is further increased to +2.4 dB ~ -1.24 dB.

[00529] In FIG. 44 shows an example of DRS transmission using the generated DRS sequence.

[00530] Referring to FIG. 44, if the sequences used in the levels may have different sequence values, then the effect of power concentration and power zeroing can be randomized. This power concentration occurs when a particular symbol has 2 * S _i (fully amplifying summation) after precoding according to FIG. 43, and power zeroing occurs on a subcarrier of a particular frequency and at OFDM symbol positions when the particular symbol of the precoding matrix is 0 (totally weakening summation).

[00531] Since the value of the sequence varies with frequency and time, the fully reinforcing and attenuating summation is effectively randomized, thereby avoiding the worst case scenario (when there is reinforcing or attenuating summation in the full band). Thus, in order to avoid this power concentration of specific antenna ports, the sequences for different levels must be different so that the power concentration can be distributed between different REs and effectively suppressed.

[00532] We describe a method for solving the problem of changing the Walsh code and the peak / average power ratio.

[00533] In FIG. 45 illustrates an example method for allocating CDM code to each layer.

[00534] When the same sequence is applied to all layers, RS DM for each layer maintains orthogonality between RS DMs using different CDM codes. The simplest way to assign a CDM code for each RS DM level is to assign the code {+1, +1} to the first level and {+1, -1} to the second level for all CDM RE sets in the allocated RBs, according to FIG. 45.

[00535] In FIG. 46 (a) shows an example of RS DM sequence transmission and in FIG. 46 (b) shows the transmitted power according to the transmission scheme shown in FIG. 46 (a).

[00536] RS DM sequences for the respective layers are multiplied by a precoding element and multiplexed with each other. This means that for a particular row vector of the precoding matrix, for example [+1, +1] or [+1, -1], the RS DM sequence values are combined and transmitted to the physical antenna port, according to FIG. 46 (a). Due to the combination of CDM codes on the physical antenna port, a certain precoded RE can have zero power, and certain precoded REs can have double power.

[00537] In FIG. 46 (a) shows RS DM sequences at each transmit antenna before precoding and after precoding. According to FIG. 45 (b), when wideband precoding and two-layer transmission are assumed, all RE RS DMs on a physical antenna port in a specific OFDM symbol may have double power or zero power. In addition, if it is assumed that four layers are multiplexed in CDM mode and transmitted, a particular RS DM RE in a particular OFDM symbol may have four times the power, and other RS RS DMs may have zero power. In FIG. 46 (b) shows the worst case scenario for a particular physical antenna port when the average transmit power for each OFDM symbol changes.

[00538] In FIG. 47 shows an illustrative method for displaying a DRS sequence.

[00539] Large peak-to-average power ratios (PAs) for specific REs are a significant problem on eNode B. Some PAs must be designed to allow higher output power to be transmitted in certain OFDM symbols. From this point of view, it is advantageous to randomize CDM codes so that the values of the precoded RS DM vary in frequency. According to one method for randomizing CDM codes, Walsh codes are displayed differently on each subcarrier frequency transmitting RS DM, according to FIG. 46.

[00540] In FIG. 48 shows an example of DRS transmission using the generated DRS sequence.

[00541] The average power from the transmit antenna 1 can be obtained by summing the RE on the subcarrier k and k + 4. Although the Walsh code can slightly reduce peak power, this does not completely fix the problem. Thus, a more general approach to solving the peak power problem needs to be considered.

[00542] In FIG. 49 shows an illustrative method for applying a Walsh code to RS DM.

[00543] An approach to solving the peak power problem is to randomize the Walsh code for the second level. The Walsh code can be multiplied by different values on each subcarrier carrying RS DM, as shown in FIG. 48. If it is possible to sufficiently randomize each level of RS DM, then the problem of peak power even for four levels of CDM can be eliminated. This means that multiplying each Walsh code by a specific value in the frequency domain or time domain allows you to randomize the precoded RE RS DMs for each physical antenna port.

[00544] In FIG. 50 and 51 illustrate illustrative methods for applying a Walsh code to four RS DMs.

[00545] Referring to FIG. 50 and 51, different fixed sequences are multiplied by the Walsh code of each RS DM level in the frequency domain (or even the time domain, based on the fact that a Walsh code of length 2 is used). This allows you to orthogonalize all RS DMs, as well as randomize peak power.

[00546] In FIG. 52 shows an illustrative method for displaying an RS DM sequence.

[00547] In order to implement an effective channel estimation on the side of the UE, the scrambling code used for RS DM must be displayed in the direction in which the UE generates a scrambling code and performs channel estimation. Since the CDM RS DM code is applied in the time domain, it would be advantageous for a particular UE implementation to map the RS DM sequence to all CDM pairs and then go to the next subcarrier frequency. The proposed display method is shown in FIG. fifty.

[00548] The problem of peak power due to the use of the same Walsh code for different RE CDM sets may be significant for the PA eNode B construct. To solve this problem, the Walsh code used at each level can be multiplied by a certain (or even random ) value, which allows you to randomize precoded RE RS DM. This will be a scalable solution, especially if you decide to have four levels of CDM RS DM for LTE Rel-10. An example of this method for two levels of CDM is shown in FIG. 50. It is possible to implement an effective channel estimation of a UE by displaying a scrambling RS DM code according to FIG. fifty.

[00549] The term "1 RB" described in the present invention includes 1 RB pair. Thus, 1 RB includes 12 subcarriers in the frequency domain and 7 OFDM symbols in the time domain, while 1 RB pair includes 14 OFDM symbols in the time domain. In the present invention, “1 RB” is used in such a way that it includes resources corresponding to 1 pair of RB.

[00550] In FIG. 53 is a block diagram of an apparatus 50 according to an embodiment of the present invention.

[00551] Referring to FIG. 53, the device 50 may be a UE or eNode B. The device 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit 55.

[00552] The layers of the radio interface protocol are implemented in the processor 51. The processor 51 provides a control plane and a user plane. The function of each level can be implemented in the processor 51. The memory 52 is connected to the processor 51 and is designed to store operating systems, applications and shared files.

[00553] The display unit 54 displays various information and can use known elements, for example, a liquid crystal display (LCD), an organic LED display (OLED), etc.

[00554] The user interface unit 55 may be configured by a combination of known user interfaces, such as a keypad, touch screen, etc.

[00555] An RF unit 53 is connected to the processor 51 and transmits / receives RF signals. The RF unit 53 can be divided into a processor transmission module (not shown) and a reception module (not shown).

[00556] The layers of the air interface protocol between the UE and eNode B can be divided into a first layer (L1), a second layer (L2) and a third layer (L3) based on the three lower layers of the Open Systems Interconnection (OSI) model, well known in communication systems.

[00557] The physical layer belongs to the first level and provides a service for transmitting information on a physical channel. The radio resource management layer (RRC) belongs to the third layer and provides radio resource management between the UE and the network. The UE and the network exchange RRC messages through the RRC layer.

[00558] The embodiments of the present invention described below are combinations of elements and features of the present invention. Elements or features may be considered selectively unless otherwise indicated. Each element or feature can be practiced without combining with other elements or features. In addition, an embodiment of the present invention can be formulated by combining parts of elements and / or features. The operating procedures described in accordance with embodiments of the present invention may be reorganized. Some constructions of any one embodiment may be included in another embodiment and may be replaced with corresponding constructions of another embodiment. It will be apparent to those skilled in the art that items that do not explicitly refer to each other in the appended claims may be presented together as an embodiment of the present invention or may be included as a new item by subsequent modification upon application.

[00559] Embodiments of the present invention can be provided by various means, for example, hardware, software, hardware, software, or combined. In a hardware configuration, methods according to embodiments of the present invention can be provided by one or more of a specialized integrated circuit (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), gate arrays, programmable by the user (FPGA), processors, controllers, microcontrollers, microprocessors, etc.

[00560] In a firmware or software configuration, embodiments of the present invention may be implemented in the form of a module, procedure, function, etc. For example, program code may be stored in a memory unit and executed by a processor. The memory unit is located inside or outside the processor and can transmit data to the processor and receive it from it through various known means.

[00561] It will be apparent to those skilled in the art that the present invention can be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present invention. Therefore, the above-described embodiments should be considered in all aspects by way of illustration, but not limitation. The scope of the invention should be determined by the attached claims and their legal equivalents, and not the above description, and all changes that do not violate the meaning and scope of equivalence of the attached claims are to be considered here.

INDUSTRIAL APPLICABILITY

[00562] An apparatus and method for transmitting / receiving a reference signal in a wireless communication system according to the present invention can be applied to wireless communication systems, for example, LTE 3GPP, LTE-A, IEEE 802.16 systems, etc.

Claims (15)

1. A method for transmitting a reference signal depending on a user equipment (UE) by an eNode B in a wireless communication system, comprising the steps of:
generating a scrambling sequence for resource elements (REs) allocated to each layer for transmitting a reference signal depending on the UE,
generating a sequence of a reference signal depending on the UE by using Walsh code coverage so that the scrambling sequences generated for RE are orthogonal to each other, and
transmitting a reference signal depending on the UE to which the generated sequence of the reference signal depending on the UE is applied to the user equipment (UE) for each level,
moreover, the coverage of Walsh codes is applied so that different sequence values are placed between the first pair of resource blocks (RB) and the second pair of RB, and
wherein the second RB pair is adjacent to the first RB pair in the frequency domain. 2. The method according to claim 1, in which the scrambling sequence is a sequence corresponding to at least one RB pair isolated for the UE from sequences generated over the entire passband. 3. The method according to claim 1, in which the coverage of Walsh codes is applied so that different sequence values are placed between the third pair of RB and the fourth pair of RB,
wherein the third RB pair is adjacent to the second RB pair and the fourth RB pair in the frequency domain, and
wherein the first identical sequence values are mapped to the first RB pair and the third RB pair, and the second identical sequence values are mapped to the second RB pair and the fourth RB pair. 4. The method according to claim 1, in which the Walsh code coverage in the first RB pair is applied so that the first elements of the Walsh code are applied to the first group of levels, and the second elements of the Walsh code are applied to the second group of levels,
moreover, a different element of the Walsh code is applied to each level of the first group of levels, and
moreover, a different Walsh code element is applied to each level of the second group of levels. 5. The method according to claim 4, in which the first elements of the Walsh code are [1111] for the first level, [1-11-1] for the second level, [11-1-1] for the third level and [1-1-11 ] for the fourth level. 6. The method according to claim 4, in which the first elements of the Walsh code are applied to the first group of levels so that the first element of the Walsh code is sequentially one-to-one displayed in the RE of the first subscriber allocated to the first pair RB, in the direction of the time domain, sequentially one one-to-one is displayed in the RE of the second subscriber allocated to the first pair of RBs in the opposite direction of the time domain, and sequentially one-to-one is displayed in the RE of the third subscriber allocated to the first pair of RBs in the direction of the time domain. 7. The method according to claim 6, in which the first elements of the Walsh code are applied to the first group of levels so that the first elements of the Walsh code are sequentially one-to-one displayed in the RE of the first subscriber allocated to the second pair RB in the opposite direction of the time domain, sequentially one-to-one is displayed in the RE of the second subscriber allocated to the second pair RB in the direction of the time domain, and sequentially one-to-one is displayed in the RE of the third subscriber in the opposite direction of the time domain allocated to the first pair of RE. 8. The method according to claim 6, in which the second elements of the Walsh code are applied to the second group of levels so that the second elements of the Walsh code are sequentially one-to-one displayed in the RE of the fourth subscriber allocated to the first pair RB, in the direction of the time domain, sequentially one one-to-one is displayed in the RE of the fifth subscriber allocated to the first pair of RBs in the opposite direction of the time domain, and sequentially one-to-one is displayed in the RE of the sixth subscriber allocated to the first pair of RBs in the direction of the time domain. 9. The method of claim 8, in which the second elements of the Walsh code are applied to the second group of levels so that the second elements of the Walsh code are sequentially one-to-one displayed in the RE of the fourth subscriber allocated to the second pair RB in the opposite direction of the time domain, sequentially one-to-one is displayed in the RE of the fifth subscriber allocated to the second pair of RBs in the direction of the time domain, and sequentially one-to-one is displayed in the RE of the sixth subscriber allocated to the second pair of RBs in the opposite direction of the time domain. 10. A method for receiving a reference signal depending on a user equipment (UE) by a UE in a wireless communication system, comprising the steps of:
receiving a reference signal depending on the UE, to which the generated sequence of the reference signal depending on the UE is applied, from the eNode B for each level,
moreover, the sequence of the reference signal depending on the UE is generated by using a scrambling sequence for resource elements (RE) allocated to each level for transmitting the reference signal depending on the UE, and by covering with Walsh codes so that the scrambling sequences generated for RE are orthogonal each other,
moreover, the coverage of Walsh codes is applied so that different sequence values are displayed between the first pair of RB and the second pair of RB, and
wherein the second RB pair is adjacent to the first RB pair in the frequency domain. 11. The method of claim 10, wherein the scrambling sequence is a sequence corresponding to at least one RB pair allocated to the UE from sequences generated over the entire passband. 12. The method of claim 10, wherein the Walsh code coverage is applied such that different sequence values are mapped between a third RB pair and a fourth RB pair,
wherein the third RB pair is adjacent to the second RB pair and the fourth RB pair in the frequency domain, and
wherein the first identical sequence values are mapped to the first RB pair and the third RB pair, and the second identical sequence values are mapped to the second RB pair and the fourth RB pair. 13. The method according to claim 10, in which the coverage of Walsh codes in the first pair of RB is applied so that the first elements of the Walsh code are applied to the first group of levels, and the second elements of the Walsh code are applied to the second group of levels,
moreover, a different element of the Walsh code is applied to each level of the first group of levels,
moreover, a different element of the Walsh code is applied to each level of the second group of levels, and
the first elements of the Walsh code are [1111] for the first level, [1-11-1] for the second level, [11-1-1] for the third level and [1-1-11] for the fourth level. 14. An eNode B for transmitting a user equipment (UE) dependent signal in a wireless communication system, said eNode B comprising:
a processor configured to generate a scrambling sequence for resource elements (REs) allocated to each level for transmitting a UE-dependent reference signal and generating a sequence of a UE-dependent reference signal by covering with Walsh codes such that scrambling sequences generated for RE are orthogonal to each other, and
a radio frequency unit configured to transmit a UE-dependent reference signal to which a generated sequence of a UE-dependent reference signal is applied to a user equipment (UE) through each level,
moreover, the coverage of Walsh codes is applied so that different sequence values are mapped between the first pair of RB and the second pair of RB, and
wherein the second RB pair is adjacent to the first RB pair in the frequency domain. 15. A user equipment (UE) for receiving a reference signal depending on the UE in a wireless communication system, said UE comprising:
a processor configured to control the reception of a reference signal depending on the UE, to which the generated sequence of the reference signal depending on the UE, from the eNode B through each level, is applied,
moreover, the sequence of the reference signal, depending on the UE, is generated by using a scrambling sequence for resource elements (RE) allocated to each level for transmitting the reference signal, depending on the UE, and by covering with Walsh codes so that the scrambling sequences generated for RE are orthogonal to each other friend
moreover, the coverage of Walsh codes is applied so that different sequence values are mapped between the first pair of RB and the second pair of RB, and
wherein the second RB pair is adjacent to the first RB pair in the frequency domain.

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