阅读说明：本技术 无线通信系统中通过镜面反射的车辆微波成像方法和设备 (Method and apparatus for microwave imaging of vehicle by specular reflection in wireless communication system ) 是由 蔡赫秦 高承佑 黄凯宾 王锐 张泽中 于 2019-07-31 设计创作，主要内容包括：无线通信系统中通过镜面反射的车辆微波成像方法和设备。本发明的一个实施方式涉及一种在无线通信系统中由感测车辆SV执行车辆图像重构的方法,该方法包括以下步骤：从目标车辆TV接收多个步进频率连续波SFCW；在所述多个SFCW的不同频率范围中接收签名波形；基于签名波形使用到达相位差PDoA执行同步；重构TV的一个或更多个虚拟图像；以及从所确定的一个或更多个虚拟图像推导真实图像。(A method and apparatus for microwave imaging of a vehicle by specular reflection in a wireless communication system. One embodiment of the present invention relates to a method of performing vehicle image reconstruction by sensing a vehicle SV in a wireless communication system, the method comprising the steps of: receiving a plurality of stepped frequency continuous waves SFCW from a target vehicle TV; receiving a signature waveform in different frequency ranges of the plurality of SFCWs; performing synchronization using the arrival phase difference PDoA based on the signature waveform; reconstructing one or more virtual images of the TV; and deriving a real image from the determined one or more virtual images.)

1. A method of performing vehicle image reconstruction by a sensing vehicle SV in a wireless communication system, the method comprising:

receiving a plurality of stepped frequency continuous waves SFCW from a target vehicle TV;

receiving a signature waveform in different frequency ranges of the plurality of SFCWs;

performing synchronization using a phase difference of arrival (PDoA) based on the signature waveform;

reconstructing one or more virtual images of the TV;

a real image is derived from the determined one or more virtual images VI.

2. The method of claim 1, wherein the signature waveforms correspond to two pairs of signature waveforms, each pair of signature waveforms containing two signature waveforms, each pair of signature waveforms being transmitted via a different representative antenna at the TV.

3. The method of claim 2, wherein each pair of the signature waveforms is received at a different frequency outside of a bandwidth of the SFCW.

4. The method of claim 1, wherein synchronization is performed by deriving a synchronization gap between the TV and the SV, wherein a synchronization gap is derived based on a phase difference between SFCWs in one of two pairs of signature waveforms.

5. The method of claim 1, wherein the one or more VIs are reconstructed using a 3D fourier transform.

6. The method of claim 1, wherein the deriving of the real image is performed based on a symmetric position of the reflective side of the specular vehicle at the VI using the real image.

7. The method according to claim 6, wherein the two common points of the virtual image/, are

8. the method of claim 7, wherein the two common points correspond to two representative antennas of the TV.

9. The method of claim 7, wherein the two common points of the real image are x₁＝(x₁，y₁，z₁) And x₂＝(x₂，y₂，z₂)。

10. The method of claim 9, wherein (x)₁，x₂) Is expressed as

Wherein, theta^(l)Representing the axis from x to as two common points: (

11. The method of claim 10, wherein said x-axis corresponds to a direction of movement of said SV.

12. A sensing vehicle SV performing vehicle image reconstruction in a wireless communication system, a first terminal comprising:

a transmitting device and a receiving device; and

a processor for processing the received data, wherein the processor is used for processing the received data,

wherein the processor is configured to: receiving a plurality of stepped frequency continuous waves SFCW from a target vehicle TV; receiving a signature waveform in different frequency ranges of the plurality of SFCWs; performing synchronization using a phase difference of arrival (PDoA) based on the signature waveform; reconstructing one or more virtual images VI of the TV; and deriving a real image from the determined one or more virtual images.

Technical Field

The following description relates to a wireless communication system, and more particularly, to a method and apparatus for performing beam search or beam transmission based on position error information.

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 communication for a plurality of users by sharing available system resources (bandwidth, transmission power, etc.) among the plurality of 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 where a direct link is established between User Equipments (UEs) and the UEs exchange voice and data directly without the intervention of an evolved node b (enb). D2D communication may encompass UE-to-UE communication as well as peer-to-peer communication. In addition, 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 rapidly increasing data traffic. For example, since the devices exchange data directly with each other through D2D communication without eNB intervention, network overhead may be reduced compared to conventional wireless communication. In addition, it is expected that the introduction of D2D communication will reduce the procedures of the eNB, lower the power consumption of devices participating in D2D communication, increase the data transmission rate, increase the capacity of the network, spread the load, and extend the cell coverage.

Currently, vehicle-to-all (V2X) communications in conjunction with D2D communications are being considered. Conceptually, V2X communication encompasses vehicle-to-vehicle (V2V) communication, vehicle-to-pedestrian (V2P) communication for communication between vehicles and different types of terminals, and vehicle-to-infrastructure (V2I) communication for communication between vehicles and roadside units (RSUs).

With the advancement of object detection, recognition and mapping based on the fusion of different sensing technologies, autonomous driving has become a reality. 2D or 3D imaging is an important part of autonomous driving, as image information can assist the vehicle in object recognition and route planning [1 ]. In recent years, real-time detection systems based on light detection and ranging (LiDAR) and visual data have become very popular, with laser scanners and cameras being used for data collection. Ultrasonic sensors also play an important role in short-range detection [2 ]. However, all of the detection and identification techniques described above do not work well under non line of sight (NLoS) conditions. To cope with this problem, some techniques have been proposed by establishing vehicle-to-vehicle (V2V) communication, which enables vehicles to share information through collaboration. But V2V communication cannot be stabilized under dynamic road conditions. In the present specification, an imaging system using millimeter waves is proposed, which is capable of capturing a 3D image around a vehicle under LoS and NLoS conditions. Furthermore, in fog days, laser scanners and cameras may perform poorly, while millimeter wave (MMW) systems are more robust.

Multiple sensors are widely used for autonomous driving, where information collection from different sensors helps to ensure driving safety and to intelligently plan routes [3 ]. The alignment of information from different sensors improves the accuracy and reliability of sensing. The most widely used sensors include cameras, LiDAR, radar sensors, and the like. Among all types of sensors, the MMW system is mainly considered as a radar sensor in autonomous driving to ensure driving safety in fog, which can provide both high resolution and appropriate detection range. For MMW imaging techniques, conventional Synthetic Aperture Radar (SAR) 4 and inverse synthetic aperture radar ISAR 5 rely on the motion of sensors or targets, which are well established for use in aircraft or spacecraft. In the past few years, highly integrated circuits with modest cost have been available in MMW frequencies. Therefore, imaging technologies based on MMW antenna arrays are becoming increasingly popular due to their high resolution and fast electronic scanning capabilities [6 ]. Array-based imaging techniques can be divided into three categories: single station switch arrays, Multiple Input Multiple Output (MIMO) arrays, and phased arrays. However, all of these MMW imaging techniques are based on the requirement of an antenna scanning process, where the antennas transmit signals in turn, because if all transmit and receive antennas are turned on simultaneously, the round-trip distance cannot be determined. The scanning process is very time consuming, especially for 3D imaging. Some compressive sensing techniques [6], [7] have been proposed to reduce the scanning time, however some safety issues may result if applied to autonomous driving.

Disclosure of Invention

Technical problem

An object of the present disclosure is to provide a method of acquiring a shape of a target vehicle.

It will be appreciated by those skilled in the art that the objects that can be achieved with the present disclosure are not limited to those specifically described above, and that the above and other objects that can be achieved with the present disclosure will be more clearly understood from the following detailed description.

Technical scheme

In one aspect of the present invention, there is provided herein a method of performing vehicle image reconstruction by a Sensing Vehicle (SV) in a wireless communication system, the method comprising the steps of: receiving a plurality of Stepped Frequency Continuous Waves (SFCW) from a Target Vehicle (TV); receiving a signature waveform in different frequency ranges of a plurality of SFCWs; performing synchronization using a phase difference of arrival (PDoA) based on the signature waveform; reconstructing one or more virtual images of the TV; and deriving a real image from the determined one or more Virtual Images (VI).

The signature waveforms correspond to two pairs of signature waveforms, each pair containing two signature waveforms.

Each pair of signature waveforms is transmitted from two representative antennas at the TV.

Each pair of signature waveforms is received at a different frequency outside the bandwidth of the SFCW.

Synchronization is performed by deriving the synchronization gap between the TV and the SV.

The synchronization gap is derived based on a phase difference between the SFCWs in one of the two pairs of signature waveforms.

Reconstructing the one or more VIs using a 3D fourier transform.

The derivation of the real image is performed based on the symmetric position of the reflective side of the specular vehicle at VI using the real image.

Two common points of the virtual image l are

And

the two common points correspond to two representative antennas of the TV.

Two common points of the real image are x₁＝(x₁，y₁，z₁) And x₂＝(x₂，y₂，z₂)。

(x₁，x₂) Is expressed as

Wherein, theta^(l)Representing the axis from x to as two common points: (And x₁) Or (a)

And x₂) The directed angle of the virtual line in between,

φ^(l)is the directed angle of the line segment from the x-axis to vl, l₁And l₂Is VI₁And VI₂。

The x-axis corresponds to the direction of movement of the SV.

In another aspect of the present invention, provided herein is a Sensing Vehicle (SV) performing vehicle image reconstruction in a wireless communication system, the first terminal comprising: a transmitting device and a receiving device; and a processor, wherein the processor is configured to: receiving a plurality of Stepped Frequency Continuous Waves (SFCW) from a Target Vehicle (TV); receiving a signature waveform in different frequency ranges of a plurality of SFCWs; performing synchronization using a phase difference of arrival (PDoA) based on the signature waveform; reconstructing one or more VIs of the TV; and deriving a real image from the determined one or more VIs.

Advantageous effects

According to the embodiment of the present invention, the shape of the target vehicle invisible from the sensing vehicle is acquired.

Those skilled in the art will appreciate that the effects that can be achieved with the present disclosure are not limited to those specifically described above, and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.

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. In the drawings:

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 showing 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 relaying of a D2D signal.

FIG. 8 is a diagram illustrating an example D2D resource pool for D2D communication.

Fig. 9 is a diagram illustrating a Scheduling Assignment (SA) period.

Fig. 10 shows a frame structure available in a new Radio Access Technology (RAT).

Fig. 11 illustrates a synchronization method.

Fig. 12 shows the relationship between VI and TV.

Fig. 13 shows an initial setting of a scene.

Fig. 14 shows an imaging reconstruction of VI.

Fig. 15 shows an initial setting of a scene.

Fig. 16 shows the geometrical relationship between different VI and TV.

Fig. 17 is a diagram showing the configuration of a transmitting apparatus and a receiving apparatus.

Detailed Description

The embodiments of the present disclosure described below are combinations of elements and features of the present disclosure. 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 a combination of partial elements and/or features. The order of operations described in the embodiments of the present disclosure may be rearranged. Some configurations or features of any 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, description is made focusing on a data transmission and reception relationship between a Base Station (BS) and a User Equipment (UE). The BS is a terminal node of a network that directly communicates 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 configured by 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" may be replaced with the terms "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.

As used herein, the term "cell" may be applied to transmission and reception points such as base stations (enbs), sectors, Remote Radio Heads (RRHs), and relays, and may also be used by a particular transmission/reception point expansively to distinguish between component carriers.

Specific terms used for the embodiments of the present disclosure are provided to aid understanding of the present disclosure. These specific terms may be replaced with other terms within the scope and spirit of the present disclosure.

In some cases, in order to prevent the concept of the present disclosure from being ambiguous, structures and devices of known art will be omitted or will be shown in the form of block diagrams based on the main functions of the respective structures and devices. 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 may be supported by standard documents disclosed for at least one of wireless access systems, Institute of Electrical and Electronics Engineers (IEEE)802, 3 rd generation partnership project (3GPP), 3GPP long term evolution (3GPP LTE), LTE-advanced (LTE-a), and 3GPP 2. Steps or components that are not described in order to make the technical features of the present disclosure clear may be supported by those documents. In addition, all terms disclosed herein can be described by the standard documents.

The techniques described herein may be used in various radio access technologies 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 IEEE802.11(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) using E-UTRA. 3GPP LTE employs OFDMA for the downlink and SC-FDMA for the uplink. LTE-A is an evolution of 3GPP LTE. WiMAX may be described by the IEEE802.16e standard (wireless metropolitan area network (wireless MAN) -OFDMA reference system) and the IEEE802.16 m standard (wireless MAN-OFDMA advanced system). For clarity, the present application focuses on 3GPP LTE and 3GPP 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 and/or downlink data packets are transmitted in sub-frames. One subframe is defined as a predetermined time 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) shows a type 1 radio frame structure. The downlink radio frame is divided into 10 subframes. Each subframe is further divided into two slots in the time domain. A unit time for transmitting one subframe is defined as a Transmission Time Interval (TTI). For example, one subframe may have a duration of 1ms and one slot may have a duration of 0.5 ms. The slot includes a plurality of OFDM symbols in a time domain and includes a plurality of Resource Blocks (RBs) in a frequency domain. Since the 3GPP LTE system employs OFDMA for downlink, an OFDM symbol represents one symbol period. The OFDM symbols may be referred to as SC-FDMA symbols or symbol periods. An RB is a resource allocation unit including a plurality of contiguous subcarriers in a slot.

The number of OFDM symbols in one slot may vary according to a 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 the slot is less than that of the normal CP. Therefore, when the extended CP is used, for example, 6 OFDM symbols may be included in one slot. Extended CP may be used to further reduce inter-symbol interference (ISI) if the channel conditions are getting worse, e.g., during fast movement of the UE.

In case of a normal CP, since one slot includes 7 OFDM symbols, one subframe includes 14 OFDM symbols. The first two or three OFDM symbols of each subframe may be allocated to a Physical Downlink Control Channel (PDCCH), and the other OFDM symbols may be allocated to a Physical Downlink Shared Channel (PDSCH).

Fig. 1 (b) shows a type 2 radio frame structure. The type 2 radio frame includes two half frames, each having 5 subframes, a downlink pilot time slot (DwPTS), a Guard Period (GP), and an uplink pilot time slot (UpPTS). Each subframe is divided into two slots. The DwPTS is used for initial cell search, synchronization, or channel estimation in the UE. UpPTS is used for channel estimation at eNB and acquisition of uplink transmission synchronization with UE. The GP is a period between uplink and downlink, which cancels uplink interference due to multipath delay of a downlink signal. Regardless of the type of radio frame, one subframe includes two slots.

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 shows the structure of a downlink resource grid for the duration of one downlink slot. The downlink slot includes 7 OFDM symbols in the time domain and the 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, the downlink slot may include 7 OFDM symbols, and in case of an extended CP, the downlink slot may include 6 OFDM symbols. The individual elements of the resource grid are referred to as Resource Elements (REs). RB includes 12 × 7 REs. Number N of RBs in a downlink slot^DLDepending on the downlink transmission bandwidth. The uplink time slot may have the same structure as the downlink time slot.

Fig. 3 shows a structure of a downlink subframe. The first three OFDM symbols of the first slot in the downlink subframe are used for a control region to which a control channel is allocated, and the other OFDM symbols of the downlink subframe are used for a data region to which a 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 about the number of OFDM symbols used for transmission of 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 transmits uplink or downlink scheduling information, or uplink transmission power control commands for the UE group. The PDCCH transmits information on resource allocation and transport format of 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 of a higher layer control message (e.g., random access response) transmitted on the PDSCH, a set of transmission power control commands of individual UEs in a UE group, transmission power control information, voice over internet protocol (VoIP) activation information, and the like. Multiple PDCCHs 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. The CCE includes a plurality of RE groups. The format of the PDCCH and the number of available bits of 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 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 points 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, a CRC of the PDCCH may be masked by a paging indicator identifier (P-RNTI). If the PDCCH carries system information, in particular, a System Information Block (SIB), a CRC thereof may be masked by a System information ID and a System information RNTI (SI-RNTI). In order to indicate that the PDCCH carries a random access response in response to a random access preamble transmitted by the UE, its CRC may be masked by a random access RNTI (RA-RNTI).

Fig. 4 shows 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. To maintain the property of single carrier, the UE does not transmit PUCCH and PUSCH simultaneously. The PUCCH of the UE is allocated to an RB pair in the subframe. The RBs in the RB pair occupy different subcarriers in two slots. That is, 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. Due to 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 to enable a receiver to acquire channel information, a transmitter transmits a signal known to both the transmitter and the receiver, and the receiver acquires 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, it is necessary to know a channel state between a transmission (Tx) antenna and a reception (Rx) antenna in order to successfully receive a signal. Therefore, the RS should be transmitted through each Tx antenna.

The RS can be divided into a downlink RS and an uplink RS. In the current LTE system, the uplink RS includes:

i) demodulation reference signals (DMRSs) for channel estimation to facilitate coherent demodulation of information transmitted on PUSCH and PUCCH; and

ii) Sounding Reference Signals (SRS) for the eNB or network to measure the quality of the uplink channel at different frequencies.

The downlink RS is divided 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) DM-RS for coherent demodulation of PDSCH when PDSCH is transmitted;

iv) a channel state information-reference signal (CSI-RS) carrying CSI when transmitting downlink DM-RS;

v) MBSFNRS for coherent demodulation of signals transmitted in Multimedia Broadcast Single Frequency Network (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 use: RS for channel information acquisition and RS for data demodulation. Since its purpose is that the UE acquires downlink channel information, the former should be transmitted in a wide frequency band and received even by the UE that has not received downlink data in a specific subframe. This RS is also used for handover-like situations. The latter is an RS that the eNB transmits along with downlink data in a specific resource. The UE may demodulate data through a ranging channel using the RS. This RS should be transmitted in the data transmission region.

Modeling of MIMO systems

Fig. 5 is a diagram showing 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 N_TAnd the number of Rx antennas is increased to N_RThe theoretical channel transmission capacity increases in proportion to the number of antennas. Therefore, the transmission rate can be improved and the frequency efficiency can be significantly improved. As the channel transmission capacity increases, the transmission rate can theoretically increase the maximum transmission rate R with a single antenna_oTo rate increase ratio R_iAs many products as there are.

[ formula 1]

R_i＝min(N_T，N_R)

For example, in a MIMO communication system using four Tx antennas and four Rx antennas, a transmission rate four times higher than that of a single antenna system can be obtained. Since this theoretical capacity increase of MIMO systems has been demonstrated in the 90 s of the 20 th century, many attempts are being made to various technologies to significantly improve data transmission rates. In addition, these technologies have been partially adopted as standards for various wireless communications such as 3G mobile communications, next generation wireless LANs, and the like.

The trend of MIMO-related studies is illustrated as follows. First, many attempts are being made in various aspects to develop and study information theoretical studies related to various channel configurations and MIMO communication capacity calculation and the like in a multiple access environment, radio channel measurement and model derivation studies for MIMO systems, space-time signal processing technology studies for transmission reliability enhancement and transmission rate improvement, and the like.

To explain the communication method in the MIMO system in detail, mathematical modeling may be represented as follows. Suppose there is N_TA Tx antenna and N_RAnd an Rx antenna.

With respect to the transmitted signal, if N is present_TA plurality of Tx antennas, the maximum number of transmittable information is N_T. Therefore, the transmission information can be represented as shown in equation 2.

[ formula 2]

Furthermore, the information may be transmitted separately for each piece of informationThe transmission powers are set differently from each other. If the transmission power is set to be respectively

The transmission information having the adjusted transmission power may be represented as equation 3.

[ formula 3]

In addition, the first and second substrates are,

the diagonal matrix P of available transmission powers is represented as equation 4.

[ formula 4]

It is assumed that the transmission power is adjusted by applying a weight matrix W to an information vector with adjusted transmission power

To configure the actually transmitted N_TA transmission signal

The weight matrix W is used to appropriately allocate transmission information to each antenna according to the transmission channel state.

Can be represented by the following vector X.

[ formula 5]

In-situ type₅In, w_ijRepresents a weight between the ith Tx antenna and the jth information. W is also called a precoding matrix.

If N is present_RAn Rx antenna, each receiving signal of the antenna

Can be expressed as follows.

[ formula 6]

If channels are modeled in the MIMO wireless communication system, the channels may be distinguished according to Tx/Rx antenna indexes. Channel from Tx antenna j to Rx antenna i is defined by h_ijAnd (4) showing. At h_ijIn (1), it should be noted that the index of the Rx antenna precedes the index of the Tx antenna in consideration of the order of the indexes.

FIG. 5 (b) shows the slave N_TDiagram of channels of Tx-to-Rx-antennas i. The channels may be combined and represented in vector and matrix form. In FIG. 5 (b), from N_TThe channels of the Tx antennas to the Rx antenna i can be represented as follows.

[ formula 7]

Thus, from N_TFrom Tx antenna to N_RAll channels of the Rx antennas can be expressed as follows.

[ formula 8]

AWGN (additive white gaussian noise) is added to the actual channel after the channel matrix H. Respectively increase to N_RAWGN of an Rx antenna

Can be expressed as follows.

[ 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 antennas_RThe number of columns is equal to the number N of Tx antennas_T. I.e. the channel matrix H is N_R×N_TAnd (4) matrix.

The rank of the matrix is defined by the smaller of the number of rows and columns, which are 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 restricted as follows.

[ formula 11]

rank(H)≤min(N_T，N_R)

In addition, when eigenvalue decomposition is performed on the matrix, the rank of the matrix may also be defined as the number of non-zero eigenvalues. Similarly, when performing a singular value decomposition on a matrix, the rank of the matrix may 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 over which different information may be sent.

In the description of this document, "rank" of MIMO transmission indicates the number of paths capable of independently transmitting signals on a specific time and frequency resource, and "number of layers" indicates the number of signal streams transmitted through each path. In general, since a transmitting end transmits the number of layers corresponding to a rank number, one rank has the same meaning as the number of layers unless specifically mentioned.

Synchronization acquisition of D2D UE

Synchronization acquisition between UEs in D2D communication will now be described in the context of a legacy LTE/LTE-a system based on the above description. In an OFDM system, if time/frequency synchronization is not acquired, the resulting inter-cell interference (ICI) may make it impossible to multiplex different UEs in an OFDM signal. It is inefficient if each individual D2D UE acquires 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 that other UEs may utilize 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), and 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 as a similar/modified/repeated structure with 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 a Secondary Synchronization Signal (SSS). If the UE synchronizes its 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 that the UE should first obtain before D2D signal transmission and reception (e.g., D2DSS related information, Duplex Mode (DM), TDD UL/DL configuration, resource pool related information, type of application related to D2DSS, etc.). 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 a codeword generated through 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 case shown in fig. 7, the D2DSS may be relayed for communication with D2D of the out-of-coverage UE. The D2DSS may be relayed via multiple hops. The following description is given based on the following recognition: the relay of the SS covers D2DSS transmission in a separate format according to SS reception time and direct Amplify and Forward (AF) relay of the SS transmitted by the eNB. As the D2DSS is relayed, the in-coverage UE may communicate directly with the out-of-coverage UE.

D2D resource pool

Fig. 8 shows an example of a first UE (UE1), a second UE (UE2), and resource pools used by UE1 and UE2 to perform D2D communications. 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 the D2D communication scheme. The UE selects a resource element corresponding to a specific resource from a resource pool corresponding to the set of resources, and the UE transmits a D2D signal using the selected resource element. The UE2 corresponding to the receiving UE receives the configuration of a resource pool in which the UE1 can transmit signals and detects the 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 a predetermined resource. Typically, a resource pool comprises a plurality of resource units. The UE selects one or more resource units from among a plurality of resource units and can use the selected resource unitsFor D2D signaling. Fig. 8 (b) shows an example of configuring a resource unit. Referring to (b) of fig. 8, the entire frequency resource is divided into N_FA resource unit, and the whole time resource is divided into N_TAnd (4) a resource unit. Specifically, N can be defined in total_F*N_TAnd (4) a resource unit. In particular, the resource pool may be in terms of N_TThe period of one subframe is repeated. Specifically, as shown in fig. 8, one resource unit may periodically and repeatedly appear. Alternatively, the index of the physical resource unit to which the logical resource unit is mapped may be changed according to 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 intending to transmit D2D signals.

Resource pools can be classified into various types. First, the resource pools may be classified according to the contents of the D2D signals transmitted through the respective resource pools. For example, the content of the D2D signal may be classified into various signals, and a separate resource pool may be configured according to each content. The content of the D2D signal may include a scheduling assignment (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) required to modulate and demodulate 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 SA and D2D data are transmitted in a multiplexed manner in the same resource unit, the D2D data channels other than the SA information may be transmitted only in the resource pool for the D2D data channel. In other words, 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 (e.g., IDs of UEs, etc.) for enabling neighboring UEs to discover a transmitting UE transmitting information.

Although the contents of the D2D signals are identical to each other, different resource pools may be used according to the transmission/reception properties of the D2D signals. For example, in case of the same D2D data channel or the same discovery message, the D2D data channel or discovery signal may be classified into different resource pools according to a transmission timing determination scheme of the D2D signal (e.g., whether the D2D signal is transmitted at a time when the synchronization reference signal is received or with a timing added by a prescribed timing advance), a resource allocation scheme (e.g., whether a transmission resource of each signal is designated by the eNB or each transmitting UE selects each 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 a transmission power of the D2D UE, and the like. For clarity, a method in which the eNB directly specifies the transmission resources of the D2D transmission UE is referred to as mode 1 (mode 3 in case of V2X). If a transmission resource region is pre-configured or an eNB designates the transmission resource region and the UE directly selects a transmission resource from the transmission resource region, it is referred to as mode 2 (mode 4 in case of V2X). In case of performing D2D discovery, if the eNB directly indicates the resource, it is referred to as type 2. If the UE directly selects transmission resources from a predetermined resource region or a resource region indicated by the eNB, it is referred to as type 1.

SA transmission/reception

Mode 1 UEs may send 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. The mode 2 UE may select a time-frequency resource from the configured resources and transmit an SA in the selected time-frequency resource.

The SA period may be defined as shown in fig. 9. Referring to fig. 9, a first SA period may start in a subframe spaced apart from a specific system frame by a predetermined offset saoffsetiindicator indicated by higher layer signaling. Each SA cycle may include a pool of SA resources and a pool of subframes for D2D data transmission. The SA resource pool may include the last subframe indicated as carrying the SA in the first subframe to subframe bitmap saSubframeBitmap of the SA period. The resource pool for D2D data transmission may include subframes used for actual data transmission by applying a time-resource pattern (T-RPT) or a time-resource pattern (TRP) for transmission in mode 1. As shown, if the number of subframes included in the SA period other than the SA resource pool is greater than the T-RPT bit number, T-RPT may be repeatedly applied, and the last applied T-RPT may be truncated as long as the number of remaining subframes. The transmitting UE performs transmission at a position in the indicated T-RPT corresponding to 1 set in the T-RPT bitmap and transmits one medium access control layer protocol data unit (MAC PDU) four times.

In vehicle-to-vehicle communication, a periodic message type of Cooperative Awareness Message (CAM), an event triggered message type of Distributed Environment Notification Message (DENM), and the like may be transmitted. The CAM may contain basic vehicle information such as dynamic state information about the vehicle (including direction and speed), static vehicle data (e.g., size), exterior lighting conditions, and route history. The size of the CAM message may be 50 to 300 bytes. The CAM message will be broadcast and the delay will be shorter than 100 ms. DENM may be a message generated in an unexpected situation such as a vehicle failure or accident. DENM may be less than 3000 bytes in size and any vehicle within transmission range may receive the message. In this case, DENM may have a higher priority than CAM. Having a high priority may mean that transmission having a higher priority is preferentially performed when transmission is simultaneously triggered from the perspective of the UE, or that transmission of a message having a higher priority among a plurality of messages is preferentially attempted in terms of time. From the perspective of multiple UEs, messages with higher priority may be set to be less subject to interference than messages with lower priority to reduce the probability of reception errors. When security overhead is included, the CAM may have a larger message size than when security overhead is not included.

Similar to radar systems, conventional MMW imaging systems use coherent signals for detection, where a transmitter and a receiver are connected [8 ]. However, due to the long scanning process, the system may not work in real time. In our scenario, a Target Vehicle (TV) transmits a signal using an antenna located around the body, while a Sensing Vehicle (SV) recovers shape information from the received signal. In this scenario, the imaging algorithm allows the TV to transmit all the signals together. Thus eliminating the need for a scanning process. Further, the conventional imaging technology detects the shape of an object based on reflection processing, and in our work, shape information is contained in the position of a transmission antenna. Therefore, the entire process is more efficient compared to the conventional art. With the help of multiple specular vehicles (MVs), we have dealt with the more general problem that TVs may not be visible to sensing vehicles. In practice, the LoS situation is an easier problem, where the receiver can distinguish the signals in the LoS by their power levels and get the position information directly. On the other hand, a common point detection method has been proposed which calculates position information of a TV using signals reflected from a plurality of paths. The LoS condition is also indicated to be a special case and can be addressed in the same way in this specification.