Method for performing communication by terminal using multiple antennas according to cyclic delay diversity (CCD) in wireless communication system and apparatus therefor
阅读说明：本技术 在无线通信系统中由终端使用多个天线根据循环延迟分集(ccd)执行通信的方法及其设备 (Method for performing communication by terminal using multiple antennas according to cyclic delay diversity (CCD) in wireless communication system and apparatus therefor ) 是由 蔡赫秦 于 2018-04-06 设计创作，主要内容包括：根据各种实施方式,提供了在无线通信系统中由终端使用多个天线根据循环延迟分集(CDD)执行通信的方法及其设备。公开了根据循环延迟分集(CDD)执行通信的方法及其设备,该方法包括以下步骤：基于终端的移动速度,确定所述CDD的延迟值的延迟范围；确定设定的延迟范围内的所述CDD的延迟值；以及将根据所确定的所述延迟值而周期性延迟的信号发送到目标终端,其中,基于所述终端的所述移动速度来确定预设的延迟范围。(According to various embodiments, a method of performing communication according to Cyclic Delay Diversity (CDD) by a terminal using a plurality of antennas in a wireless communication system and an apparatus thereof are provided. Disclosed are a method of performing communication according to Cyclic Delay Diversity (CDD) and an apparatus thereof, the method including the steps of: determining a delay range of the delay value of the CDD based on the moving speed of the terminal; determining a delay value of the CDD within a set delay range; and transmitting a signal, which is periodically delayed according to the determined delay value, to a target terminal, wherein a preset delay range is determined based on the moving speed of the terminal.)
1. A method of performing communication according to cyclic delay diversity, CDD, using multiple antennas by a user equipment, UE, in a wireless communication system, the method comprising:
determining a delay range of the delay value of the CDD based on the moving speed of the user equipment;
determining a delay value of the CDD within the delay range; and
transmitting a signal, which is periodically delayed according to the determined delay value, to the target UE.
2. The method of claim 1, wherein the delay value is determined based on a relative velocity with the target UE.
3. The method of claim 1, wherein the delay value is determined with a preset delay range based on a delay spread with the target UE.
4. The method of claim 2, wherein the relative velocity is determined by considering at least one of a Cooperative Awareness Message (CAM) and a Basic Security Message (BSM) received from the target UE.
5. The method of claim 2, wherein the delay value is determined based on a relative velocity between the UE and the target UE when the UE is a predetermined distance or more from the target UE.
6. The method of claim 2, wherein the delay value is determined based on a relative speed between the UE and the target UE if a Reference Signal Received Power (RSRP) of a signal received from the target UE is equal to or greater than a preset reference value.
7. The method of claim 1, wherein the delay value is randomly selected within a preset delay range in each of a media access control layer protocol data unit (MACPDU), a symbol, and a subframe of the signal.
8. The method of claim 1, wherein the UE increases the delay value within a preset delay range if a request to retransmit the signal is received.
9. The method of claim 1, wherein the UE decreases the delay value within a preset delay range if a request to retransmit the signal is received.
10. The method of claim 1, wherein the delay value is determined based on a bandwidth of a channel over which a signal is transmitted.
11. The method of claim 1, wherein the delay value is determined based on a distance from the target UE.
12. The method of claim 1, wherein the delay value is determined differently for each antenna in the multiple antennas.
13. The method of claim 12, wherein the delay values are determined in such a way that a difference in delay values between adjacent ones of the multiple antennas is greater than a difference between non-adjacent ones of the multiple antennas.
14. The method of claim 1, wherein the delay value is determined to be a different value depending on the presence or absence of a line of sight, LOS, of a channel over which the signal is transmitted.
15. A user equipment, UE, for performing communication according to cyclic delay diversity, CDD, using multiple antennas in a wireless communication system, the UE comprising:
a transceiver comprising a plurality of antennas; and
a processor configured to determine a delay range of delay values of the CDD based on a moving speed of the UE, determine delay values of the CDD within the delay range, and transmit a signal periodically delayed according to the determined delay values to a target UE,
wherein the preset delay range is determined based on a moving speed of the UE.
Technical Field
The present specification relates to a wireless communication system, and more particularly, to a method of performing communication according to cyclic delay diversity (CCD) using multiple antennas by a user equipment and an apparatus thereof.
Background
Wireless communication systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless communication system is a multiple access system that supports its communication by sharing available system resources (bandwidth, transmission power, etc.) among multiple users. For example, multiple-access systems include Code Division Multiple Access (CDMA) systems, Frequency Division Multiple Access (FDMA) systems, Time Division Multiple Access (TDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and multi-carrier frequency division multiple access (MC-FDMA) systems.
Device-to-device (D2D) communication is a communication scheme in which a direct link is established between User Equipments (UEs) and the UEs exchange voice and data directly without the involvement of an evolved node b (enb). D2D communication can cover UE-to-UE communication and peer-to-peer communication. In addition, the D2D communication may be applied to machine-to-machine (M2M) communication and Machine Type Communication (MTC).
D2D communication is being considered as a solution to the overhead of enbs due to the rapid growth of data traffic. For example, since the devices directly exchange data with each other through D2D communication without the participation of an eNB, network overhead can be reduced, compared to conventional wireless communication. In addition, the introduction of D2D communication is expected to reduce the procedures of the eNB, reduce the power consumption of devices participating in D2D communication, improve data transmission rates, increase the regulatory capacity of the network, distribute load and extend cell coverage.
Currently, D2D communication is being considered in conjunction with vehicle network (V2X) communication. Conceptually, V2X communication covers vehicle-to-vehicle (V2V) communication, vehicle-to-pedestrian (V2P) communication for communication between a vehicle and different types of terminals, and vehicle-to-infrastructure (V2I) communication for communication between a vehicle and a roadside unit (RSU).
Disclosure of Invention
Technical task
A technical task of the present invention is to enable a User Equipment (UE) to change a diversity gain according to CDD to correspond to a channel status change by determining a delay value of CDD based on at least one of speed and transmission parameters.
It will be appreciated by persons skilled in the art that the objects that can be achieved with the present disclosure are not limited to what has been particularly described hereinabove and that the above objects and other objects that can be achieved with the present disclosure will be more clearly understood from the detailed description that follows.
Technical scheme
In one technical aspect of the present specification, provided herein is a method of performing communication according to Cyclic Delay Diversity (CDD) using multiple antennas by a user equipment in a wireless communication system, the method including: determining a delay range of the delay value of the CDD based on the moving speed of the user equipment; determining a delay value of the CDD within the delay range; and transmitting a signal periodically delayed according to the determined delay value to a target user equipment.
According to an example, the delay value is determined based on a relative velocity with the target user equipment.
Determining the delay value based on the delay spread with the target user equipment with the preset delay range.
Determining the relative velocity by considering at least one of a Collaboration Awareness Message (CAM) and a Basic Security Message (BSM) received from the target user equipment.
Determining the delay value based on a relative velocity between the user device and the target user device when the user device is a predetermined distance or more from the target user device.
Determining the delay value based on a relative speed between the user equipment and the target user equipment if the RSRP of the signal received from the target user equipment is equal to or greater than a preset reference value.
Randomly selecting the delay value within a preset delay range in each of a symbol, a subframe, and a MAC PDU of the signal.
And if a retransmission request of the signal is received, the user equipment increases the delay value within the preset delay range.
And if a retransmission request of the signal is received, the user equipment reduces the delay value within the preset delay range.
The delay value is determined based on a bandwidth of a channel through which the signal is transmitted.
Determining the delay value based on a relative velocity with the target user equipment.
The delay value is determined differently for each antenna of the multiple antennas.
Determining the delay values in a manner that a difference in delay values between adjacent ones of the multiple antennas is greater than a difference between non-adjacent ones of the multiple antennas.
And, it is determined that the delay value is a different value according to the presence or absence of the line of sight LOS of the channel through which the signal is transmitted.
Advantageous effects
A method of performing communication according to Cyclic Delay Diversity (CDD) by a user equipment using multiple antennas and an apparatus thereof can suitably change a diversity gain of CDD to correspond to a channel state change by determining a delay value of CDD based on at least one of speed and transmission parameters.
The effects that can be obtained from the present invention are not limited by the above-mentioned effects. Also, other effects not mentioned may be clearly understood by those of ordinary skill in the art to which the present invention pertains from the following description.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.
Fig. 1 is a diagram illustrating a structure of a radio frame;
fig. 2 is a diagram illustrating a resource grid during the duration of one downlink slot;
fig. 3 is a diagram illustrating a structure of a downlink subframe;
fig. 4 is a diagram illustrating a structure of an uplink subframe;
fig. 5 is a diagram illustrating a configuration of a wireless communication system having a plurality of antennas;
fig. 6 is a diagram illustrating a subframe carrying a device-to-device (D2D) synchronization signal;
fig. 7 is a diagram illustrating a relay device of a D2D signal;
FIG. 8 is a diagram illustrating an exemplary D2D resource pool for D2D;
fig. 9 is a diagram illustrating a scheduling Assignment (AS) period;
fig. 10 illustrates an example of a connection scheme between a TXRU and an antenna element;
fig. 11 illustrates an example of a self-contained subframe structure.
Fig. 12 is a flowchart for describing a method of determining a delay value to apply CDD according to an embodiment of the present invention.
Fig. 13 is a diagram schematically illustrating a User Equipment (UE) performing D2D communication.
Detailed Description
The embodiments of the present disclosure described below are combinations of elements and features of the present disclosure. These elements or features may be considered optional unless otherwise mentioned. Each element or feature may be practiced without being combined with other elements or features. In addition, embodiments of the present disclosure may be constructed by combining parts of elements and/or features. The order of operations described in the embodiments of the present invention may be rearranged. Some configurations or features of any one embodiment may be included in another embodiment and may be replaced with corresponding configurations or features of another embodiment.
In the embodiments of the present disclosure, a description will be made centering on a data transmission and reception relationship between a Base Station (BS) and a User Equipment (UE). The BS is a terminal node in the network that communicates directly with the UE. In some cases, certain operations described as being performed by the BS may be performed by an upper node of the BS.
That is, it is apparent that, in a network composed of a plurality of network nodes including the BS, various operations performed for communication with the UE may be performed by the BS or network nodes other than the BS. The term "BS" may be replaced with the terms "fixed station", "node B", "evolved node B (eNode B or eNB)", "Access Point (AP)", and the like. The term "relay device" may be replaced with the term "Relay Node (RN)" or "Relay Station (RS)". The term "terminal" may be replaced with the terms "UE", "Mobile Station (MS)", "mobile subscriber station (MSs)", "Subscriber Station (SS)", etc.
The term "cell" used herein may be applied to a transmission point and a reception point such as a base station (eNB), a zone, a Remote Radio Head (RRH), and a relay device, and may also be widely used by a specific transmission/reception point to distinguish component carriers.
Specific terms used for the embodiments of the present disclosure are provided to aid understanding of the present disclosure. It is within the scope and spirit of the present disclosure that certain terms may be replaced with other terms.
In some cases, in order to prevent the concepts of the present disclosure from being blurred, the structures and devices of the known art will be omitted, or will be shown in the form of block diagrams based on the main function of each structure and device. Further, wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.
Embodiments of the present disclosure can be supported by standard documents published for at least one of the following: wireless access systems, Institute of Electrical and Electronics Engineers (IEEE)802, third generation partnership project (3GPP), 3GPP long term evolution (3GPP LTE), LTE advanced (LTE-a), and
The techniques described herein may be used in various wireless access systems such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and so on. CDMA may be implemented as a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA 2000. The TDMA may be implemented as a radio technology such as global system for mobile communications (GSM)/General Packet Radio Service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented as a radio technology such as IEEE 802.11(Wi-Fi), IEEE802.16(WiMAX), IEEE 802.20, evolved UTRA (E-UTRA), and so on. UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3GPP LTE is part of an evolved UMTS (E-UMTS) that uses E-UTRA. 3gpp lte employs OFDMA for the downlink and SC-FDMA for the uplink. LTE-A is an evolution of 3GPP LTE. WiMAX can be described by the IEEE802.16 e standard (wireless metropolitan area network (WirelessMAN) -OFDMA reference system) and the IEEE802.16m standard (WirelessMAN-OFDMA advanced system). For clarity, the present application focuses on 3gpp LTE and LTE-a systems. However, the technical features of the present disclosure are not limited thereto.
LTE/LTE-A resource structure/channel
Referring to fig. 1, the structure of a radio frame will be described below.
In a cellular Orthogonal Frequency Division Multiplexing (OFDM) wireless packet communication system, uplink data packets and/or downlink data packets are transmitted in sub-frames. One subframe is defined as a predetermined period including a plurality of OFDM symbols. The 3GPP LTE standard supports a type-1 radio frame structure applicable to Frequency Division Duplex (FDD) and a type-2 radio frame structure applicable to Time Division Duplex (TDD).
Fig. 1 (a) illustrates a
The number of OFDM symbols in one slot may vary depending on Cyclic Prefix (CP) configuration. There are two types of CP: extended CP and normal CP. In case of a normal CP, one slot includes 7 OFDM symbols. In case of the extended CP, the length of one OFDM symbol increases, and thus the number of OFDM symbols in one slot is less than that in case of the normal CP. Therefore, when the extended CP is used, for example, 6 OFDM symbols may be included in one slot. If the channel state deteriorates (e.g., during fast UE movement), extended CP may be used to further reduce inter-symbol interference (ISI).
In case of a normal CP, one subframe includes 14 OFDM symbols because one slot includes 7 OFDM symbols. The first two or three OFDM symbols of each subframe may be allocated to a Physical Downlink Control Channel (PDCCH), while the other OFDM symbols may be allocated to a Physical Downlink Shared Channel (PDSCH).
Fig. 1 (b) illustrates a
The above radio frame structure is only exemplary, and thus it is to be noted that the number of subframes in a radio frame, the number of slots in a subframe, or the number of symbols in a slot may vary.
Fig. 2 illustrates a structure of a downlink resource grid for the duration of one downlink slot. One downlink slot includes 7 OFDM symbols in the time domain and one RB includes 12 subcarriers in the frequency domain, which does not limit the scope and spirit of the present disclosure. For example, in case of a normal CP, one downlink slot may include 7 OFDM symbols, and in case of an extended CP, one downlink slot may include 6 OFDM symbols. The individual elements of the resource grid are referred to as Resource Elements (REs). One RB includes 12 × 7 REs. The number NDL of RBs in a downlink slot depends on the downlink transmission bandwidth. The uplink time slot may have the same structure as the downlink time slot.
Fig. 3 illustrates a structure of a downlink subframe. The first three OFDM symbols at the beginning of the first slot in the downlink subframe are used for the control region to which the control channel is allocated, and the other OFDM symbols of the downlink subframe are used for the data region to which the PDSCH is allocated. Downlink control channels used in the 3GPP LTE system include a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), and a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH). The PCFICH is located in the first OFDM symbol of the subframe, and carries information on the number of OFDM symbols used to transmit control channels in the subframe. The PHICH transmits a HARQ acknowledgement/negative acknowledgement (ACK/NACK) signal in response to uplink transmission. Control information carried on the PDCCH is referred to as Downlink Control Information (DCI). The DCI conveys uplink or downlink scheduling information, or uplink transmission power control commands for a UE group. The PDCCH transmits information on resource allocation and a transport format for a downlink shared channel (DL-SCH), resource allocation information on an uplink shared channel (UL-SCH), paging information of a Paging Channel (PCH), system information on the DL-SCH, information on resource allocation for a higher layer control message such as a random access response transmitted on the PDSCH, a set of transmission power control commands for individual UEs in a UE group, transmission power control information, voice over internet protocol (VoIP) activation information, and the like. Multiple PDSCCHs may be transmitted in the control region. The UE may monitor multiple PDCCHs. The PDCCH is formed by aggregating one or more consecutive Control Channel Elements (CCEs). The CCE is a logical allocation unit for providing the PDCCH at a coding rate based on a state of a radio channel. One CCE includes a plurality of RE groups. The format of the PDCCH and the number of available bits for the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs. The eNB determines a PDCCH format according to the DCI transmitted to the UE, and adds a Cyclic Redundancy Check (CRC) to the control information. The CRC is masked by an Identifier (ID) called a Radio Network Temporary Identifier (RNTI) according to an owner or usage of the PDCCH. If the PDCCH is directed to a specific UE, its CRC may be masked by a cell RNTI (C-RNTI) of the UE. If the PDCCH is used for a paging message, the CRC of the PDCCH may be masked by a paging indicator identifier (P-RNTI). If the PDCCH carries system information, specifically, a System Information Block (SIB), its CRC may be masked by a system information ID and a system information RNTI (SI-RNTI). To indicate that the PDCCH carries a random access response in response to the random access preamble transmitted by the UE, its CRC may be masked by a random access RNTI (RA-RNTI).
Fig. 4 illustrates a structure of an uplink subframe. The uplink subframe may be divided into a control region and a data region in the frequency domain. A Physical Uplink Control Channel (PUCCH) carrying uplink control information is allocated to the control region, and a Physical Uplink Shared Channel (PUSCH) carrying user data is allocated to the data region. In order to maintain the characteristics of a single carrier, the UE does not transmit PUSCH and PUCCH simultaneously. A PUCCH for a UE is allocated to an RB pair in a subframe. The RBs in the RB pair occupy different subcarriers in the two slots. Therefore, it can be said that the RB pair allocated to the PUCCH hops on a slot boundary.
Reference Signal (RS)
In a wireless communication system, packets are transmitted over a radio channel. Depending on the nature of the radio channel, packets may be distorted during transmission. In order to successfully receive a signal, a receiver should compensate for distortion of the received signal using channel information. In general, in order for a receiver to be able to acquire channel information, a transmitter transmits a signal known to both the transmitter and the receiver, and the receiver learns the channel information based on distortion of the signal received on a radio channel. This signal is called a pilot signal or RS.
In the case of data transmission and reception through a plurality of antennas, in order to successfully perform signal reception, it is necessary to know a channel state between a transmission (Tx) antenna and a reception (Rx) antenna. Therefore, the RS should be transmitted through each Tx antenna.
The RS may be divided into a downlink RS and an uplink RS. In the current LTE system, the uplink RS includes:
i) demodulation-reference signal (DM-RS) for channel estimation for coherent demodulation of information transmitted on PUSCH and PUCCH; and
ii) Sounding Reference Signals (SRS) for the eNB or the network to measure the quality of the uplink channel at different frequencies.
The downlink RS is classified into:
i) a cell-specific reference signal (CRS) shared among all UEs of a cell;
ii) a UE-specific RS dedicated to a specific UE;
iii) a DM-RS for coherent demodulation of PDSCH when PDSCH is transmitted;
iv) channel state information-reference signal (CSI-RS) carrying CSI when downlink DM-RS is transmitted;
v) a Multimedia Broadcast Single Frequency Network (MBSFN) RS for coherent demodulation of signals transmitted in MBSFN mode; and
vi) a positioning RS for estimating geographical location information about the UE.
RSs can also be divided into two types according to their purpose: RS for channel information acquisition and RS for data demodulation. Since it is intended for the UE to acquire downlink channel information, the former RS should be transmitted in a wide band and received even by the UE that does not receive downlink data in a specific subframe. The RS is also used in the same situation as the handover. The latter RS is an RS that the eNB transmits together with downlink data in a specific resource. The UE can demodulate data by using the RS measurement channel. The RS should be transmitted in the data transmission region.
Modeling of MIMO systems
Fig. 5 is a diagram illustrating a configuration of a wireless communication system having a plurality of antennas.
As shown in (a) of fig. 5, unlike the case where a plurality of antennas are used only in a transmitter or a receiver, if the number of Tx antennas is increased to NTAnd the number of Rx antennas is increased to NRThe theoretical channel transmission capacity increases in proportion to the number of antennas. Therefore, it is possible to improve the transmission rate and significantly improve the frequency efficiency. As the channel transmission capacity increases, the transmission rate can theoretically increase the product of the maximum transmission rate Ro and the rate increase ratio Ri when a single antenna is utilized.
[ formula 1]
Ri＝min(NT，NR)
For example, in a MIMO communication system using 4 Tx antennas and 4 Rx antennas, a
The trend of the MIMO-related studies is explained as follows. First, many continuous efforts are made in various aspects to develop and study information theory studies related to MIMO communication capacity calculation and the like in various channel configurations and multiple access environments, radio channel measurement and model derivation studies for MIMO systems, spatio-temporal signal processing technology studies for transmission reliability enhancement and transmission rate improvement and the like, and the like.
To explain the communication method in the MIMO system in detail, mathematical modeling can be represented as follows. Assuming the presence of NTRoot Tx antenna and NRA root Rx antenna.
With respect to the transmitted signal, if N is presentTThe maximum number of pieces of information that can be transmitted is N for the root Tx antennaT. Therefore, the transmission information can be represented as shown in
[ formula 2]
In addition, the transmission information s may be individually transmitted for each piece of transmission information s1，s2，…，
[ formula 3]
In addition, a diagonal matrix P of transmission power may be used as represented in
[ formula 4]
By providing the signal with an adjusted transmission powerInformation vectorApplying a weight matrix W to configure the actual transmitted NTA transmission signal x1，x2，…，
[ formula 5]
In
If N is presentRA root Rx antenna, the signal y received by the corresponding antenna can be expressed as follows1，y2，…，
[ formula 6]
If channels are modeled in the MIMO wireless communication system, the channels can be distinguished according to Tx/Rx antenna indexes. By using hijTo represent the channel from Tx antenna j to Rx antenna i. At hijNote that, in terms of the order of indexes, the index of the Rx antenna precedes the index of the Tx antenna.
FIG. 5 (b) is a view illustrating the slave NTGraph of the channels from the root Tx antenna to Rx antenna i. The channels may be combined and expressed in vector and matrix fashion. In thatIn fig. 5 (b), the following may be expressedTThe channel from the Tx antenna to Rx antenna i.
[ formula 7]
Thus, the slave N can be expressed as followsTRoot Tx antenna to NRAll channels of the root Rx antenna.
[ formula 8]
After the channel matrix H, AWGN (additive white gaussian noise) is added to the actual channel. Can be expressed as followsRRoot Rx antenna added AWGNn1，n2，…，
[ formula 9]
Through the above mathematical modeling, the received signal can be represented as follows.
[ formula 10]
In addition, the number of rows and columns of the channel matrix H indicating the channel state is determined by the number of Tx antennas and Rx antennas. The number of rows of the channel matrix H is equal to the number N of Rx antennasRAnd the number of columns of the channel matrix H is equal to the number N of Tx antennasT. That is, the channel matrix H is NR×NTAnd (4) matrix.
The rank of the matrix is defined by the lesser of the number of rows and the number of columns independent of each other. Thus, the rank of the matrix is not greater than the number of rows or columns. The rank (H) of the channel matrix H is constrained as follows.
[ formula 11]
rank(H)≤min(NT，NR)
In addition, when the matrix undergoes eigenvalue decomposition, the rank of the matrix may also be defined as the number of nonzero eigenvalues. Similarly, when the matrix undergoes singular value decomposition, the rank of the matrix may also be defined as the number of non-zero singular values. Thus, the physical meaning of the rank of the channel matrix may be the maximum number of channels that can be used to transmit different pieces of information.
In the description of this document, the "rank" of MIMO transmission indicates the number of paths capable of independently transmitting signals on a specific time and frequency resource, and the "number of layers" indicates the number of signal streams transmitted through the respective paths. In general, since a transmitting end transmits the number of layers corresponding to the number of ranks, one rank has the same meaning as the number of layers unless otherwise stated.
D2D Synchronization acquisition for a UE
Synchronization acquisition between UEs in D2D communication will now be described based on the above description in the context of a legacy LTE/LTE-a system. In an OFDM system, if time/frequency synchronization is not acquired, the resulting inter-cell interference (ICI) may make multiplexing of different UEs in the OFDM signal impossible. It would be inefficient if each individual D2D UE acquired synchronization by directly transmitting and receiving a synchronization signal. Thus, in a distributed node system such as a D2D communication system, a particular node may transmit a representative synchronization signal and other UEs may use the representative synchronization signal to acquire synchronization. In other words, some nodes, which may be enbs, UEs, and synchronization reference nodes (SRNs, also referred to as synchronization sources), may transmit D2D synchronization signals (D2DSS), while the remaining UEs may transmit and receive signals in synchronization with the D2 DSS.
The D2DSS may include a primary D2DSS (PD2DSS) or Primary Sidelink Synchronization Signal (PSSS) and a secondary D2DSS (SD2DSS) or Secondary Sidelink Synchronization Signal (SSSS). The PD2DSS may be configured to have a similar/modified/repeated structure to a Zadoff-Chu sequence of a predetermined length or a Primary Synchronization Signal (PSS). Unlike DL PSS, PD2DSS may use different Zadoff-chu root indices (e.g., 26, 37). Also, the SD2DSS may be configured to have a similar/modified/repeated structure of an M-sequence or Secondary Synchronization Signal (SSS). If the UEs synchronize their timing with the eNB, the eNB acts as SRN and the D2DSS is PSS/SSS. Unlike the PSS/SSS of DL, PD2DSS/SD2DSS follows UL subcarrier mapping scheme. Fig. 6 shows a subframe in which a D2D synchronization signal is transmitted. The physical D2D synchronization channel (PD2DSCH) may be a (broadcast) channel carrying basic (system) information (e.g., D2DSS related information, Duplex Mode (DM), TDD UL/DL configuration, resource pool related information, type of application related to D2DSS, etc.) that the UE should first obtain before D2D signal transmission and reception. The PD2DSCH may be transmitted in the same subframe as the D2DSS or in a subframe following the frame carrying the D2 DSS. DMRS may be used to demodulate PD2 DSCH.
The SRN may be a node that transmits the D2DSS and the PD2 DSCH. The D2DSS may be a specific sequence, and the PD2DSCH may be a sequence representing specific information or code words resulting from a predetermined channel coding. The SRN may be an eNB or a specific D2D UE. In the case of partial or out of network coverage, the SRN may be a UE.
In the scenario shown in fig. 7, the D2DSS may be relayed for D2D communication with out-of-coverage UEs. The D2DSS may be relayed by multiple hops. The following description is given with the following understanding: the relay device of the SS relays transmission of the D2DSS in a separate format according to the SS reception time and direct Amplification and Forwarding (AF) of the SS transmitted by the eNB. When the D2DSS is relayed, the in-coverage UEs may communicate directly with the out-of-coverage UEs.
D2D resource pool
Fig. 8 shows an example of resource pools used by a first UE (UE1), a second UE (UE2), and a UE1 and a UE2 when performing D2D communication. In (a) of fig. 8, the UE corresponds to a terminal or a network apparatus such as an eNB that transmits and receives signals according to a D2D communication scheme. The UE selects a resource element corresponding to a specific resource from a resource pool corresponding to a set of resources, and the UE transmits a D2D signal using the selected resource element. UE corresponding to receiving UE2 receive a configuration of a resource pool in which the UE1 can transmit signals, and detect a signal of the UE1 in the resource pool. In this case, if the UE1 is located within the coverage of the eNB, the eNB may inform the UE1 of the resource pool. The resource pool may be informed by a different UE if the UE1 is located outside the coverage of the eNB, or may be determined by predetermined resources. Typically, a resource pool comprises a plurality of resource units. The UE selects one or more resource elements from among the plurality of resource elements and may be capable of D2D signaling using the selected resource elements. Fig. 8 (b) shows an example of configuring a resource unit. Referring to (b) of fig. 8, the entire frequency resource is divided into NFA resource unit, and dividing the entire time resource into NTAnd (4) a resource unit. In particular, N can be defined in totalF×NTAnd (4) a resource unit. In particular, may be represented by NTEach subframe is a periodically repeated resource pool. Specifically, as shown in fig. 8, one resource unit may occur periodically and repeatedly. Alternatively, the index of the physical resource unit to which the logical resource unit is mapped may be changed in a predetermined pattern according to time to obtain a diversity gain in the time domain and/or the frequency domain. In this resource element structure, the resource pool may correspond to a set of resource elements that can be used by UEs intended to send D2D signals.
Resource pools can be classified into various types. First, the resource pools may be classified according to the contents of the D2D signal transmitted through each resource pool. For example, the content of the D2D signal may be divided into various signals, and separate resource pools may be configured according to each of the content. The content of the D2D signal may include scheduling assignments (SA or physical side link control channel (PSCCH)), a D2D data channel, and a discovery channel. The SA may correspond to a signal including information on a resource location of the D2D data channel, information on a Modulation and Coding Scheme (MCS) necessary for modulating and demodulating the data channel, information on a MIMO transmission scheme, information on a Timing Advance (TA), and the like. The SA signal may be transmitted on the same resource elements in a data multiplexed manner as D2D. In this case, the SA resource pool may correspond to a resource pool that transmits SA and D2D data in a multiplexed manner. The SA signal may also be referred to as a D2D control channel or a physical side link control channel (PSCCH). The D2D data channel (or physical side link shared channel (PSSCH)) corresponds to a pool of resources used by the transmitting UE to transmit user data. If the SA and D2D data are transmitted in a multiplexed manner in the same resource unit, only the D2D data channels other than the SA information are transmitted in the resource pool of the D2D data channel. In other words, the REs used to transmit SA information in a particular resource unit of the SA resource pool may also be used to transmit D2D data in the D2D data channel resource pool. The discovery channel may correspond to a resource pool of messages that enable a neighboring UE to discover a transmitting UE that transmits information such as the UE's ID.
Although the contents of the D2D signals are identical to each other, it may use different resource pools according to the transmission/reception properties of the D2D signals. For example, in the case of the same D2D data channel or the same discovery message, the D2D data channel or discovery signal may be divided into different resource pools according to a transmission timing determination scheme of the D2D signal (e.g., whether the D2D signal is transmitted at the time of receiving the synchronization reference signal or at the timing of adding a prescribed timing advance), a resource allocation scheme (e.g., whether the transmission resource of the individual signal is designated by the eNB or the individual transmitting UE selects the individual signal transmission resource from the pool), a signal format (e.g., the number of symbols occupied by the D2D signal in a subframe, the number of subframes for transmitting the D2D signal), a signal strength from the eNB, a strength of transmission power of the D2D UE, and the like. For clarity, a method in which the eNB directly specifies transmission resources of the D2D transmission UEs is referred to as mode 1 (
SA transmission/reception
Mode-1 UEs may transmit SAs (D2D control signals or Sidelink Control Information (SCI)) in resources configured by the eNB. For mode-2 UEs, the eNB configures resources for D2D transmissions. Mode-2 the UE may select a time-frequency resource from the configured resources and transmit the SA in the selected application-frequency resource.
The SA period may be defined as illustrated in fig. 9. Referring to fig. 9, the first SA period may start in a subframe spaced apart from a specific system frame by a predetermined offset SAOffsetIndicator indicated by higher layer signaling. Each SA period may include a pool of SA resources and a pool of subframes for D2D data transmission. The SA resource pool may include the first subframe to the last subframe indicated as carrying the SA in the subframe bitmap saSubframeBitmap of the SA period. The resource pool for D2D data transmission may include subframes for actually transmitting data by applying a time-resource pattern (T-RPT) or a time-resource pattern (TRP) for transmission in
In V2V communication, a Cooperation Awareness Message (CAM) of periodic message type, a Distributed Environment Notification Message (DENM) of event triggered message type, etc. may be sent. The CAM may transmit basic vehicle information, including dynamic state information about the vehicle, such as direction and speed, static data of the vehicle, such as dimensions, ambient lighting status, path details, and the like. The CAM may be 50 to 300 bytes in length. The CAM is broadcast and its delay should be shorter than 100 ms. DENM may be generated when an unexpected event occurs, such as a vehicle malfunction or accident. DENM may be shorter than 3000 bytes and may be received by all vehicles within transmission range. DENM may have a higher priority than CAM. When the messages are said to have a higher priority, this may mean that, from the perspective of one UE, in the case of messages sent simultaneously, the higher priority messages are sent most importantly or at an earlier time than any other of the plurality of messages. From the perspective of multiple UEs, messages with higher priority may be subject to less interference than messages with lower priority, thereby having a reduced probability of reception error. With respect to a CAM, when the CAM includes a security overhead, the CAM may have a larger message size than it would without the security overhead.
Fig. 10 illustrates an example of a connection scheme between a TXRU and an antenna element.
Fig. 10 (a) illustrates that TXRUs are connected to the sub-arrays. In this case, the antenna element is connected to only one TXRU. Unlike (a) of fig. 10, (b) of fig. 10 illustrates that the TXRU is connected to all antenna elements. In this case, the antenna element is connected to all TXRUs. In fig. 10, W indicates the phase vector multiplied by the analog phase shifter. That is, the direction of analog beamforming is determined by W. In this case, the mapping between CSI-RS antenna ports and TXRUs may be 1 to 1 or 1 to many.
As more and more communication devices require greater communication capacity, the demand for more advanced mobile broadband communication than the conventional RAT (radio access technology) has been issued. In addition, a large-scale MTC (machine type communication) technology that provides various services at any time and anywhere by connecting a plurality of devices and objects is also one of major issues to be considered in next-generation communication. Further, communication system designs have been discussed that consider services/UEs that are susceptible to reliability and delay. In view of this state, introduction of the next generation RAT has been discussed, and the next generation RAT will be referred to as a new RAT in the present invention.
The self-contained subframe structure shown in fig. 11 is considered in a fifth generation new RAT to minimize data transmission delay in a TDD system. FIG. 11 illustrates an example of a self-contained subframe structure.
In fig. 11, a diagonal region indicates a downlink control region, and a black region indicates an uplink control region. The unmarked area may be used for downlink data transmission or uplink data transmission. In this structure, downlink transmission and uplink transmission are performed in an appropriate order within one subframe, whereby downlink data can be transmitted and uplink ACK/NACK can be received within the subframe. As a result, when an error occurs at the time of data transmission, the time required for data retransmission can be reduced, whereby the delay of final data transfer can be minimized.
In this self-contained subframe structure, the eNB and the UE need a time gap to switch from a transmission mode to a reception mode or vice versa. For this, some OFDM Symbols (OS) at the time of switching to uplink in the self-contained subframe structure are set as a guard period.
An example of a self-contained subframe type that may be configured in a system operating based on a new RAT may consider the following four subframe types.
-downlink control period + downlink data period + GP + uplink control period
-downlink control period + downlink data period
-downlink control period + GP + uplink data period + uplink control period
-downlink control period + GP + uplink data period
In the 5G new RAT, the signaling scheme may differ according to service or requirements. For example, a transmission time unit of enhanced mobile broadband (eMBB) may be relatively long, while a transmission time unit of ultra-reliable low-delay communication (URLLC) may be relatively short.
Depending on the service type, particularly in the case of emergency services, the URLLC signal can be transmitted on the corresponding resource even during transmission of the eMBB. Therefore, URLLC transmission may consider preempting part of the transmission resources of the eMBB, either in terms of the network or the UE.
In this case, due to the preemption, a portion of the transmission resources of the eMBB having a relatively long transmission time unit may be punctured (puncuture), and the eMBB signal may be modified because it is superimposed on another signal, such as a URLLC signal.
When URLLC transmits a partial resource that preempts eMBB transmission, there is a high probability that the UE cannot decode a specific Code Block (CB) for transmitting eMBB. In particular, this situation may cause decoding failure of a specific CB even when the channel status is good. Thus, the 5G new RAT may consider performing retransmission in CB units rather than Transport Block (TB) units.
Beamforming with respect to millimeter waves
Further, in the millimeter wave (mmW), since the wavelength is short, a plurality of antennas can be mounted in the same region. That is, considering that the wavelength at the 30GHz band is 1cm, a total of 64(8 × 8) antenna elements may be mounted at intervals of 0.5 λ (wavelength) in the case of a two-dimensional array in a panel of 4 × 4 cm. Therefore, in a recent trend in the mmW field, an attempt is made to increase Beamforming (BF) gain using a plurality of antenna elements to improve coverage or throughput.
In this case, if each antenna element includes a transceiver unit (TXRU) to enable adjustment of the transmit power and phase of each antenna element, each antenna element may perform independent beamforming for each frequency resource. However, it is not very feasible to install TXRUs in all of the approximately 100 antenna elements in terms of cost. Therefore, a method of mapping a plurality of antenna elements to one TXRU using analog phase shifters and adjusting a beam direction has been considered. However, this method has the disadvantage that frequency selective beamforming is not possible, since only one beam direction is generated within the whole frequency band.
As an intermediate form of digital BF and analog BF, a hybrid BF having B TXRUs less than Q antenna elements may be considered. In the case of hybrid BF, the number of beam directions that can be transmitted simultaneously is limited to B or less, depending on how the B TXRUs and Q antenna elements are connected.
Channel dependent cyclic delay diversity
Cyclic delay diversity is a method of transmitting a symbol transmitted by each antenna by delaying the symbol by a predetermined time in a multi-antenna system (in addition, a delay value of each antenna may be different). The delay in the frequency domain is a linear phase rotation, thereby bringing about the effect of beam circulation per frequency resource.
For example, if a first antenna is configured to transmit without delay and a second antenna is configured to have a delay equal to a prescribed delay value (or θ), a phase rotation according to the following formula occurs on the ith subcarrier.
That is, as the beam direction is changed for each Resource Element (RE), the beam cycle for each RE may be considered to occur in the frequency domain. In this case, the diversity gain of the CDD may be changed according to how the delay value (or θ) of each antenna is set. A method of determining the delay value (or θ) according to the transmission parameter is described as follows.
According to one embodiment, the delay value (or θ) may be set to be different based on the bandwidth of data transmission. For example, since a channel in the frequency domain is likely to be flat when narrowband is transmitted, the channel can be changed more quickly using a large delay value (or θ). In contrast, since the channel is likely to have been selected at the time of wide bandwidth transmission, a small value is used for the delay value (or θ), so that the channel can be changed relatively slowly in the frequency domain. In this case, the performance of channel estimation can be improved.
Here, the difference in transmission bandwidths may include a difference in transmitted physical layer channels. For example, if the transmission bandwidth of the control channel and the transmission bandwidth of the data channel are 2RB and 10RB, respectively, the delay value (or θ) of the data channel may be set to a value different from that of the control channel.
Alternatively, the delay value (or θ) may be set in advance for a specific physical channel. For example, since the transmission bandwidth of the control channel is fixed and should be demodulated without other information in advance, in this case, the delay value (or θ) may be fixed. It can be said that the delay value (or θ) is fixed to a preset value for the control channel, and may have different values for the data channel according to the transmission bandwidth.
Alternatively, the delay value (or θ) of each antenna port and/or the number of antenna ports for data transmission may be signaled to a receiving user equipment (Rx UE) through physical or higher layer signaling of the UE. In case the Base Station (BS) signals the delay value (or θ) for each antenna port and/or the number of antenna ports in this way, the BS may signal this information to the UE by physical or higher layer signaling.
Alternatively, in the case where several physical channels need to be simultaneously transmitted within the same Transmission Time Interval (TTI), the delay value (or θ) may be determined using the maximum or minimum value among the delay values (or θ) or weighted averages of each channel. That is, if the delay value (or θ) is determined to be one of the maximum or minimum value of the delay value (or θ) and the weighted average value of each channel, the delay value of each channel may be different due to the application of the time delay in the time domain. In this case, according to the implantation of Inverse Fast Fourier Transform (IFFT) for each channel individually, it is possible to prevent the complexity of the UE from increasing.
According to one embodiment, the delay value (or θ) may be determined to be different according to the presence or absence OF Line-OF-Sight (LOS) and Non-Line-OF-Sight (NLOS) OF the channel. The transmitting user equipment (Tx UE) may determine the delay value (or θ) used when LOS or NLOS differently. The situation-dependent delay value (or θ) may include a predetermined value or a value indicated to the UE by the network through physical or higher layer signaling.
Furthermore, in the case of LOS, since a specific subcarrier falls into a severe attenuation, the application of CDD may degrade performance compared to the case where CDD is not applied. Thus, in the case of an LOS channel, CDD may not be used. For example, when the time domain response of the channel is h (t) 1, the frequency domain gain response may be expressed as the following equation.
|H(i)|2＝1+cos(2πθi/NFFT)
In this case, | h (i) | ventilated wind on a specific subcarrier2May become 0.
Thus, in LOS, using CDD may instead degrade performance. In view of this, the delay value (or theta) in LOS may be 0 (CDD not applied).
Further, the Tx UE may obtain the presence or absence of LOS/NLOS of the channel through channel reciprocity or in a manner that the Rx UE informs the Tx UE of the presence or absence of LOS/NLOS through physical or higher layer signaling.
According to one embodiment, the delay value (or θ) may be determined by correlating with the delay spread. Here, the delay spread may include a definition of a time delay or a combined effect between a first received radio wave and a next reflected received radio wave passing through different paths in a multi-path environment of the radio waves. For example, a Tx UE may measure the delay spread from other UEs or receive a transmission of information about the delay spread signaled from another UE. Alternatively, if a value of delay spread between UEs is signaled by the network (or BS), the delay value (or θ) may be determined based on the delay spread.
This scheme, limited to small delay CDD, can be applied. The large delay CDD is applicable regardless of the delay spread based selection since it will apply a delay over the CP length in OFDM. Accordingly, the delay value (or θ) used in the case where the delay spread is equal to or greater than the predetermined threshold value (e.g., the CP length) and the delay value (or θ) used in the case where the delay spread is less than the predetermined threshold value may be determined in different manners from each other. It can be said that if the delay spread is less than a predetermined threshold (e.g., CP length), the delay value can be determined based on the delay spread. If the delay spread is equal to or greater than a predetermined threshold (e.g., CP length), the delay value may not be determined from the delay spread.
Alternatively, the delay value (or θ) may be determined by linking according to the target range. Depending on the target range, the probability that the channel is LOS may be different from the probability that the channel is NLOS or the average delay spread may be different. Therefore, by considering this case, the presence or absence of application of CDD (or delay value) may vary according to the distance from the target UE, which targets a specific message.
According to one embodiment, a randomly selected delay value (or θ) may be transmitted for each OFDM symbol, group of OFDM symbols, subframe, or MAC Protocol Data Unit (PDU). In this case, the maximum value of the delay may be set according to the implementation of the UE or determined by the maximum, minimum or average delay spread measured by the UE. Alternatively, the maximum value of the delay may be determined within a range signaled by the network (or BS). According to this method, the optimal delay value may be different by a change of a channel or for each Rx UE. This is to prevent a specific UE from being unable to continuously decode at a specific timing during transmission by randomly selecting a delay value (or θ).
In this case, the order of change of the delay values (or θ) may be random or predetermined. For example, the UE performs transmission by setting the delay value (or θ) to a small value. In doing so, the UE may apply a large value to the delay value (or θ) whenever a retransmission occurs. Alternatively, the UE performs transmission by setting the delay value (or θ) to a low value. In doing so, the UE may change the delay value (or θ) to a smaller value whenever retransmission occurs.
Alternatively, different delay values (or θ) may be set for OFDM symbols/OFDM symbol groups. In this case, the minimum unit for the changed delay value (or θ) may be a range for applying channel estimation of the same RS symbol. For example, in the case where a single demodulation reference signal (DMRS) port is used in a single slot (e.g., 7 symbols) or subframe, the delay value (or θ) does not change during 7 symbols or subframes. That is, in order to correctly estimate a channel in a data symbol, the data symbol has the same delay value (or θ) as a symbol transmitted by a Reference Signal (RS).
Alternatively, in the case where the delay value (or θ) is determined within a range set by the network (or BS), the UE may change the usable range of the delay value (or θ) according to the moving speed of the UE. For example, a range of delay values used by a UE currently moving within a predetermined velocity region may be set to be different from a range of delay values used by a UE currently moving within another predetermined velocity region. For this purpose, the network (or BS) may set each speed range delay value (or θ) or delay value range through physical or higher layer signaling. This parameter may be predetermined by a UE that is out of the coverage of the network (or BS).
For example, as the UE moves fast, if the UE has obtained sufficient diversity according to the movement of the UE, the UE may use a small delay value (or θ) or
Further, although the delay value (or θ) may be determined according to the moving speed of the UE, the UE may measure the maximum/minimum/average relative speed between the UEs through the cooperation awareness message/basic security message (CAM/BSM) received by the UE, and then set the delay value (or θ) or the applicable delay value (or θ) range to be different according to the measurement result. In this case, since the change of the channel will change according to the relative speed of the UE, the UE can more accurately reflect the state of the channel. For this purpose, information such as a delay value (or θ), a range of the delay value (or θ), and the like according to the maximum/minimum/average relative speed of the UE may be signaled to the UE by the network (or BS) through physical layer or higher layer signaling.
In particular, the UE may determine the delay value (or θ) by considering a channel state with a specific counterpart UE. For example, the UE may determine the delay value (or θ) by considering a velocity with respect to the UE located in a predetermined distance or a longer distance. For this purpose, if Reference Signal Received Power (RSRP) of a signal received from a specific UE is less than (or equal to or greater than) a predetermined threshold, the UE may set a delay value (or θ) by considering a relative speed between UEs. This is to maximize diversity targeting UEs located in a certain distance or longer, because UEs located in a certain distance or longer may have a relatively poor packet reception rate. In this case, the UE may determine the delay value (or θ) by considering an average/maximum/minimum delay spread or a relative speed of a specific counterpart UE or UE group.
According to one embodiment, when there are a plurality of antennas, if the antennas are closer to each other (e.g., higher correlation), a larger delay value (or θ) difference may be set. For example, when the delay value applied for each antenna in the 4-antenna system is represented as [
Alternatively, each antenna group may employ a different CDD scheme. For example, when there are 4 antennas, a small delay CDD is used for
With respect to large delay CDD, Rx UEs can correctly receive signals only if a separate Reference Signal (RS) port is allocated. For example, when CDD is applied to 2 antennas, small delay CDD enables the RX UE to perform correct reception using a single demodulation reference signal (DMRS) port. In contrast, the large delay CDD enables the Rx UE to perform correct reception only when transmission is performed using two DMRS ports. However, in case that the Rx UE is performing blind search for a large delay, the Rx UE may perform channel estimation using only a single DMRS port although a separate port is not allocated. For example, in case of performing a delay up to a delay value (here, the delay value is equal to or greater than the CP length) at the second antenna, the Rx UE may perform blind search on θ. In this case, the Rx UE will find the maximum peak from
Accordingly, a method of configuring a DMRS port differently for CDD according to the operation of an Rx UE (or receiver) can be considered. Only when Rx UE (or receiver) uses θ outside the delay range of blind search, additional DMRS ports can be allocated. For example, the small delay CDD may be viewed as the Rx UE blindly searching for delays within the CP length. In this regard, where only small delay CDD is applied, only one DMRS port may be allocated. On the other hand, if θ is equal to or greater than the CP length and the Rx UE does not perform the delay search within the CP length, the Tx UE should allocate an additional DMRS port. Although in the case of large delay CDD, the Rx UE may perform as many delay searches as large delay values. In this case, the Rx UE may operate using a single DMRS port.
All or some of the proposed embodiments may be applied to at least one of the control signal and the data signal. Alternatively, a separate scheme may be applied to each of the control signal and the data signal. Furthermore, the content of the present invention is not limited to only UE-to-UE direct communication, but may be used for uplink or downlink. In this case, the BS, the relay node, and the like may use the proposed method. Since examples of the above-proposed schemes can be included as one of implementation methods of the present invention, they can be obviously considered as one of the proposed schemes. Further, while the schemes presented above may be implemented independently, they may be implemented in combinations (or mergers) of some of the proposed schemes. The information on whether the proposed method is applied or not (or the information on the rule of the proposed method) may be defined to be notified to the UE by the BS through predefined signaling (e.g., physical layer signaling or higher layer signaling).
Fig. 12 is a flowchart for describing a method of determining a delay value to apply CDD according to an embodiment of the present invention.
Referring to fig. 12, the UE may determine a preset delay range corresponding to a speed range to which the moving speed of the UE belongs. Here, the preset range is preset differently for each speed range. For example, if the moving speed is at
The UE determines that a prescribed value within the determined preset delay range is a delay value, and then may transmit a signal, which is periodically delayed by applying CDD according to the determined delay value, to the target UE. In this case, the UE may determine the delay value by considering a channel state or the like. Here, the channel status means a bandwidth of a channel through which a signal is transmitted, presence or absence of straightness (LOS/NLOS), delay spread, target range (e.g., distance from a target UE), moving speed, relative speed, doppler shift according to speed, doppler spread, etc. [ S303 ].
The UE may transmit a signal, which is periodically delayed by applying the delay value determined for each antenna, to the target UE. For example, when the plurality of antennas includes 4 antennas and the determined delay value is 90 °, a signal to which the delay value is applied (i.e., 0 °), a signal to which the delay value is applied (i.e., 90 °), a signal to which the delay value is applied (i.e., 180 °), and a signal to which the delay value is applied (i.e., 270 °) may be transmitted to the target UE through the first to fourth antennas, respectively S305.
According to one embodiment, the UE may determine a delay value within a preset delay range according to a bandwidth of a channel. Information on a delay value corresponding to each bandwidth of a channel may be preset by considering channel change information according to the channel bandwidth. For example, when the bandwidth of a channel is narrower than a specific reference width, if the channel is flat, the UE may set the delay value to a large value to change the channel (i.e., diversity of the channel increases). In contrast, if the bandwidth of the channel is wider than a specific reference width, the UE may set the delay value to be low to improve the performance of channel estimation since sufficient channel diversity has been ensured. That is, the delay value may be preset to different values according to the bandwidth of the channel by considering the selection possibility according to the bandwidth of the channel.
Alternatively, the UE may set different delay values according to the presence or absence of straightness of channel (LOS). If it is determined that the straightness of the channel (LOS) is ensured, the UE may not use CDD to prevent a particular sub-carrier from getting severely attenuated or determine that the delay value is a very small value. In contrast, if the straightness of the channel NLOS is not ensured, the UE may determine that the prescribed value in the preset delay range is a delay value. That is, the UE may determine the delay value differently according to whether the channel is NLOS or LOS.
Alternatively, the UE may determine the delay value based on the delay spread of the channel. For this purpose, the UE may directly measure the delay spread with the target UE or be provided with information about the delay spread measured by the target UE. The UE may ensure sufficient diversity by setting the delay values differently based on the measured delay spread. Further, the UE stores information on a corresponding delay value of each delay spread in advance, and may determine a delay value corresponding to a delay spread measured based on the stored information.
Alternatively, the UE may determine the delay value by considering the target range. Here, the target range may be determined based on a distance between the UE and the target UE. For example, the UE may determine the delay value differently according to whether the target range is less than a preset threshold. Further, information on a corresponding delay value of each target range may be preset. The delay value according to the target range may be preset in consideration of the fact that the probability that the channel is LOS varies according to the distance from the target UE and the fact that the average delay spread varies according to the distance. Based on the preset information, the UE may determine a delay value corresponding to the target range.
According to one embodiment, the UE may determine at least one of the delay value and the preset delay range based on a relative speed with the target UE. For this purpose, the UE may detect a relative velocity with the target UE based on the received CAM/BSM message of the target UE. For example, the CAM/BSM message may include moving speed information on the target UE, and the UE may detect the relative speed by finding a difference between the moving speed of the target UE and the moving speed of the UE included in the CAM/BSM message. In this case, the UE may determine the preset delay range based on the detected relative speed. Alternatively, the UE may determine the corresponding delay range with reference to the minimum value, the maximum value, and the average value of the detected relative velocities. Also, as described above, the UE may receive information on a preset delay range different for each relative speed range from the BS in advance and then store the received information.
Alternatively, the UE may accumulate information on the detected relative velocity for a predetermined time, and determine that the velocity of at least one of the minimum value, the maximum value, and the average value is the reference velocity based on the accumulated information of the relative velocity. The UE may determine a delay range based on the reference velocity, and determine that a value corresponding to the relative velocity (or the reference velocity) detected within the determined delay range is a delay value.
Further, information on a preset delay range and a delay value for each relative speed (or reference speed) may be signaled to the UE through physical or higher layer signaling in advance.
According to one embodiment, when transmitting a signal for a target UE located in a predetermined distance or more, the UE may determine a delay value for CDD application. In doing so, the UE may detect the relative velocity and determine a delay value for the CDD application based on the detected relative velocity. That is, the UE may maximize diversity by selectively applying CDD to signals to transmit to the target UE. In this case, it is possible to prevent a signal reception rate (or a packet reception rate) of the target UE within a predetermined distance or more from being relatively lowered.
Alternatively, if RSRP of a signal received from the target UE is less than a preset threshold, the UE may determine a delay value by considering a relative speed with the target UE and then transmit a signal to which CDD according to the delay value is applied to the target UE.
According to one embodiment, the UE may randomly select a delay value within a predetermined delay range. This is to prevent the target UE from being unable to continuously decode a signal at a specific timing due to a change in the optimum delay value due to a channel change. That is, the UE randomly selects a delay value within a predetermined delay range, thereby preventing successive decoding of the signal by the target UE from failing. In particular, the UE may randomly select a delay value within a preset delay range in each of a symbol unit, a subframe unit, and a MAC PDU unit of a signal.
Fig. 13 is a diagram schematically showing a User Equipment (UE) that performs D2D communication.
With continued reference to fig. 13, a
The
The
Specific configurations of the transmitting point device and the UE may be implemented such that the details described in the various embodiments of the present invention may be applied independently or such that two or more of the embodiments are applied simultaneously. Redundant description is omitted for clarity.
In the example of fig. 13, the description of the
Embodiments of the invention may be implemented by various means, such as hardware, firmware, software, or combinations thereof.
In a hardware configuration, embodiments of the present disclosure may be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, and the like.
In a firmware or software configuration, the method according to the embodiment of the present disclosure may be implemented in the form of a module, a procedure, a function, and the like. The software codes may be stored in memory units and executed by processors. The memory is located inside or outside the processor, and may transmit and receive data to and from the processor via various known means.
As previously mentioned, a detailed description of preferred embodiments of the present disclosure has been given to enable those skilled in the art to make and perform the present disclosure. While the foregoing has been with reference to the preferred embodiments of the present disclosure, those skilled in the art will appreciate that various modifications and alterations to the present disclosure can be made within the scope of the present disclosure. For example, a person skilled in the art may use the components described in the above embodiments in combination. The above embodiments are therefore to be understood as illustrative in all respects and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, rather than by the description above, and all changes that come within the meaning and range of equivalency of the appended claims are intended to be embraced therein.
Those skilled in the art will appreciate that the present disclosure may be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present disclosure. The above embodiments are therefore to be understood as illustrative in all respects and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, rather than by the description above, and all changes that come within the meaning and range of equivalency of the appended claims are intended to be embraced therein. It is obvious to those skilled in the art that claims that are not explicitly cited in each other in the appended claims may be presented in combination as an embodiment of the present disclosure or included as a new claim by subsequent modification after filing the application.
Industrial applicability
The above embodiments of the present disclosure are applicable to various mobile communication systems.
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