WO2017034227A1

WO2017034227A1 - Channel direction information acquisition method and device

Info

Publication number: WO2017034227A1
Application number: PCT/KR2016/009159
Authority: WO
Inventors: Pengfei Sun; Bin Yu
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2015-08-21
Filing date: 2016-08-19
Publication date: 2017-03-02

Abstract

The present invention provides a channel direction information acquisition method. In a terminal, the terminal transmits, to another terminal, a first signal for a first resource, based on beamforming regarding a first angle, transmits, to another terminal, a second signal for a second resource based on beamforming regarding a second angle, wherein a first beam for the first signal and a second beam for the second signal are overlapped, and receives, from the another terminal, information for a channel direction. The present invention further provides a channel direction information acquisition method applying to a receiving terminal, a corresponding transmitting terminal device and a corresponding receiving terminal device. According to the technical solution provided by the present invention, reliable channel direction information can be provided.

Description

CHANNEL DIRECTION INFORMATION ACQUISITION METHOD AND DEVICE

The present invention relates to wireless communication technology fields, and more particularly, to a channel direction information acquisition method and device.

To meet the demand for wireless data traffic having increased since deployment of 4th generation (4G) communication systems, efforts have been made to develop an improved 5th generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a 'Beyond 4G Network' or a 'Post Long Term Evolution (LTE) System'.

The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.

In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.

Multiple-Input-Multiple-Output (MIMO) technology can improve spectrum efficiency of a wireless communication system by using space resources of channels, and has become an important cellular communication technology. In order to obtain corresponding spectrum gain, a transmitter has to obtain Channel Direction Information (CDI) to perform pre-coding calculation and other MIMO signal processing. Channel State Information (CSI) includes the CDI and Channel Quality Information (CQI). A prerequisite to perform closed-loop MIMO transmission in a MIMO system is to obtain accurate CDI, which is also a key to impact system performance.

In Long Term Evolution (LTE) system corresponding to Evolved Universal Terrestrial Radio Access (E-UTRA) specifications drafted by 3rd Generation Partnership Project (3GPP), there are different CDI acquisition methods according to different duplex modes. The LTE duplex modes include Time Division Dulplexing (TDD) and Frequency Division Dulplexing (FDD).

In a TDD system, an uplink channel and a downlink channel use same spectrum resources, thus, have Channel Reciprocity. Thus, a TDD base station can obtain equivalent CDI of the downlink channel through estimating the corresponding uplink channel. A terminal can transmit Sounding Reference Signals (SRS) to assist channel estimation. The SRSs transmitted by terminals are generated through using a dedicated sequence to support channel estimation and reference signal multiplexing, e.g., Zadoff-Chu (ZC) sequence, Pseudo-Noise sequence, and the SRSs are known by both terminals and base stations. When the CDI is obtained through SRS transmission and channel estimation, a shortcoming is pilot contamination. In particular, in the LTE system, the SRSs allocated to different terminals in a same cell are orthogonal with each other. Thus, the base station may perform interference free channel estimation to obtain the CDI of the uplink channel. However, in the LTE system, SRS sequences allocated to terminals in different cells are non-orthogonal. When the base station estimates uplink channel CDI of terminals in the cell, the terminals are interfered by the uplink SRSs from terminals in another cell. That is, the CDI of the channel in the cell estimated by the base station overlaps CDI of channels from terminals in another cell to the base station, which is called as the pilot contamination. The pilot contamination causes serious impact for downlink and uplink data transmission in the system.

1) when the base station transmits data to an expected terminal by using directional pre-coding, it is equivalent to transmit directional data to terminals on overlapped channels in neighbor cells, thus, the directional data becomes serious inter-cell interference.

2) when the base station receives data from an expected terminal on the uplink channel by using directional processing, it is equivalent to perform enhancement processing for data of terminals on overlapped channels in neighbor cells, thus, interference on the overlapped channels is amplified.

Thus, the pilot contamination restricts system capacity, especially when the number of antennas is increased, system performance improvement is seriously restricted.

Large-scale MIMO (or referred to as Massive MIMO) is considered as an important enabling technology used to greatly improve spectrum efficiency in the further 5th Generation (5G) cellular communication system. In a system using the Large-scale MIMO, rich signal processing freedom is used, interference among terminals and interference among cells are reduced, calculation complexity is reduced, and communication link quality is efficiently improved. In addition, the Large-scale MIMO can efficiently reduce power consumption of a single antenna unit, and can improve power efficiency of the entire system. With development of adopted spectrums from low frequencies to high frequencies (gradually decreasing form factors of antennas), in further, base stations and mobile devices can use antennas several times more than antennas used by existing base stations and existing mobile devices. At present, feasibility and industrial utilization of more than 64 antennas have already been verified in a prototype verification system. A method for implementing Large-scale MIMO in millimeter wave bands includes procedures as follows. A base station configured with Large-scale MIMO generates extremely narrow transmission beams to serve multiple terminals by using a phase difference among antennas when a distance between antennas is small (a half-carrier-wavelength level). A terminal is also configured with multiple antennas to form different gains for different directions of arrival. The terminal selects a received beam with a large gain to perform data reception. When each transmission beam of the base station serves a terminal, interference among terminals is greatly reduced. When neighbor base stations use different transmission beams with different directions to serve respective terminals, interference among cells is greatly reduced. It can be seen through theoretical analysis that in a Large-scale MIMO system, when a transmitter can accurately obtain CDI of a channel, as the number of antennas is increased, a signal-to-noise ratio (SNR) between an uplink channel and a downlink channel can be improved, and the corresponding system capacity can be significantly improved for tens or even hundreds of transmission antennas. However, when the pilot contamination occurs, actual system capacity of the Large-scale MIMO system is seriously reduced. Even when transmission power of the base station becomes low, the entire system is still interference limited. The impact of the pilot contamination is fatal for the Large-scale MIMO system. Thus, a new CDI acquisition method has to be provided to solve the pilot contamination in the Large-scale MIMO system, which is meaningful to improve system capacity.

In a FDD system, an uplink channel and a downlink channel are respectively in different frequency bands, thus, do not have Channel Reciprocity. In this condition, a terminal has to occupy uplink channel resources to feed downlink channel CDI back to the base station. A method is explicit feedback. In particular, the terminal quantizes the downlink channel CDI by using a fixed codebook, and reports a quantization result to the base station through the uplink channel. Another method is implicit feedback. In particular, the base station selects an expected precoding code from several fixed codes, and reports the selected result to the base station through the uplink channel. In order to make the base station obtain sufficiently accurate downlink channel CDI, uplink feedback overhead of the terminal is increased as the number of antennas of the base station is increased regardless which method is used. It means that a method for obtaining CDI based on feedback in the existing FDD system is not suitable for the Large-scale MIMO system. That is because when the number of antennas becomes huge, the uplink CDI feedback overhead will become a serious burden of the system.

It can be seen from above that when 5G communication system is designed, the CDI acquisition problem in the Large-scale MIMO system has to be solved. If a method for quickly and efficiently obtaining CDI can be provided, signal overhead of the system is efficiently reduced, the pilot contamination is relieved, spectrum efficiency brought by the Large-scale MIMO is ensured, and system capacity in a cell is improved.

The present invention provides channel direction information acquisition methods and devices, so as to provide reliable channel direction information.

The present invention provides a channel direction information acquisition method, applying to a transmitting terminal. The method includes:

transmitting a first probing signal on a first resource by using beamforming a central angle of which is a first angle;

transmitting a second probing signal on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space; and

receiving channel direction information from a receiving terminal.

Preferably, a beamforming weight of the first probing signal is:

a beamforming weight of the second probing signal is:

wherein θ+Φ is the central angle of the beamforming of the first probing signal;

θ-Φ is the central angle of the beamforming of the second probing signal;

Φ is an overlapping angle of the two beams;

d is a distance between antennas;

λ is a wavelength;

N is the number of antennas.

Preferably, 2Φ < ω,

wherein ω is a 3dB beam width of a single beam, or

Φ is equal to an angle from a central direction of a beam to a first cross zero angle of the beam.

Preferably, the first resource and the second resource are wireless communication resources in different times and different frequencies; or

the first resource and the second resource are wireless communication resources within a coherence bandwidth.

Preferably, the first probing signal is a common reference signal of a UE, and the second probing signal is a UE specific reference signal.

Preferably, the transmitting terminal transmits only the first probing signal or the second signal to a designated terminal, and/or the transmitting terminal simultaneously transmits the first probing signal and the second signal to the designated terminal.

The present invention further provides a transmitting terminal device. The transmission terminal device includes a first transmitting module, a second transmitting module, and a receiving module, wherein

the first transmitting module is configured to transmit a first probing signal on a first resource by using beamforming a central angle of which is a first angle;

the second transmitting module is configured to transmit a second probing signal on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space; and

the receiving module is configured to receive channel direction information from a receiving terminal.

The present invention further provides a channel direction information acquisition method applying to a receiving terminal. The method includes:

receiving a first probing signal on a first resource by using beamforming a central angle of which is a first angle;

receiving a second probing signal on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space;

determining channel direction difference according to a power of the first probing signal and a power of the second probing signal;

feeding the channel direction difference as channel direction information back to a transmitting terminal.

Preferably, determining channel direction difference according to the power of the first probing signal and the power of the second probing signal comprises:

calculating a power average of the first probing signal P₁, calculating a power average of the second probing signal P₂;

calculating a ratio r,

determining the channel direction difference according to a relation between the r and the channel direction difference.

The present invention further provides a receiving terminal device. The receiving terminal device includes a first receiving module, a second receiving module, a difference determining module and a feedback module, wherein

the first receiving module is configured to receive a first probing signal on a first resource by using beamforming a central angle of which is a first angle;

the second receiving module is configured to receive a second probing signal on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space;

the difference determining module is configured to determine channel direction difference according to a power of the first probing signal and a power of the second probing signal;

the feedback module is configured to feed the channel direction difference as channel direction information back to a transmitting terminal.

The present invention further provides a method for operating a terminal. The method comprises transmitting, to another terminal, a first signal for a first resource, based on beamforming regarding a first angle, transmitting, to the another terminal, a second signal for a second resource, based on beamforming regarding a second angle, wherein a first beam for the first signal and a second beam for the second signal are at least overlapped, and receiving, from the another terminal, information for a channel direction.

The present invention further provides a terminal. The terminal comprises a transceiver is configured to transmit, to another terminal, a first signal for a first resource, based on beamforming regarding a first angle, transmit, to the another terminal, a second signal for a second resource, based on beamforming regarding a second angle, wherein a first beam for the first signal and a second beam for the second signal are overlapped, and receive, from the another terminal, information for a channel direction.

The present invention further provides a method for operating a terminal. The method comprises receiving, from another terminal, a first signal for a first resource based on beamforming regarding a first angle, receiving, from the another terminal, a second signal for a second resource based on beamforming regarding a second angle, wherein a first beam for the first signal and a beam for the second signal are overlapped, generating information for a channel direction based on a first power of the first signal and a second power of the second signal, and transmitting, to the another terminal, the information.

The present invention further provides a terminal. The terminal comprises a transceiver configured to receive, from another terminal, a first signal for a first resource, based on beamforming regarding a first angle and receive, from the another terminal, a second signal for a second resource based on beamforming regarding a second angle, wherein a first beam for the first signal and a second beam for the second signal are overlapped, and a controller configured to generate information for a channel direction based on a first power of the first signal and a second power of the second signal. The transceiver is further configured to transmit, to the another terminal, the information.

It can be seen from the above technical solution that, in the channel direction information acquisition method provided by the present invention, a transmitting terminal transmits a first probing signal on a first resource by using beamforming a central angle of which is a first angle, transmits a second probing signal on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space, and receives channel direction information from a receiving terminal. Thus, the transmission terminal can obtain reliable channel direction information.

According to the present invention, a method and an apparatus to acquire channel direction information are provided so that a transmission terminal can obtain reliable channel direction by using overlapped beams.

FIG. 1 illustrates a flowchart for a transmitting terminal according to an embodiment of the present invention;

FIG. 2 illustrates a schematic diagram illustrating overlapped beams according to an embodiment of the present invention;

FIG. 3 illustrates a schematic diagram illustrating a relation between channel direction difference and a power ratio according to an embodiment of the present invention;

FIG. 4 illustrates a schematic diagram illustrating configuration of different probing signals for multiple UEs according to an embodiment of the present invention;

FIG. 5 illustrates a schematic diagram illustrating transmission of two groups of probing signals through different slots according to an embodiment of the present invention;

FIG. 6 illustrates a schematic diagram illustrating transmission of two groups of probing signals through a common reference signal and a UE specific reference signal according to an embodiment of the present invention;

FIG. 7 illustrates a schematic diagram illustrating transmission of two groups of probing signals through a demodulating signal and a new reference signal according to an embodiment of the present invention;

FIG. 8 illustrates a schematic diagram illustrating a structure of a transmitting terminal device according to an embodiment of the present invention;

FIG. 9 illustrates a schematic diagram illustrating a structure of a receiving terminal device according to an embodiment of the present invention;

FIG. 10 illustrates a flowchart for a terminal according to an embodiment of the present invention; and

FIG. 11 illustrates a flowchart for another terminal according to an embodiment of the present invention.

The present invention will be described in further detail hereinafter with reference to accompanying drawings and embodiments to make the objective, technical solution and merits therein clearer.

The present invention provides a technical solution for quickly obtaining channel direction information. In this technical solution, channel direction information is estimated through two groups of overlapped beams. According to preferable embodiments as follows, the technical solution provided by the present invention is described in details.

First Embodiment

In the embodiment, a basic method for estimating channel direction information by using overlapped beams is provided. FIG. 1 illustrates a flowchart for a transmitting terminal according to a first embodiment of the present invention. As shown in FIG. 1, the method includes procedures as follow.

At step 105, a first probing signal is transmitted on a first resource by using beamforming a central angle of which is a first angle.

At step 110, a second probing signal is transmitted on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space.

At step 115, channel direction information is received from a receiving terminal.

The transmitting terminal respectively transmits the first probing signal and the second signal probing by using beamformings with two different central directions. Preferably, central angles are respectively θ+Φ and θ-Φ. Since a difference between the two central angles are only 2Φ, the two beams are overlapped in space. FIG. 2 illustrates a schematic diagram illustrating two groups of overlapped beams in space according to an embodiment of the present invention. As shown in FIG. 2, beams in a first group (an elliptic region with black spots on a white background) are not overlapped with each other, beams in a second group (an elliptic region with a white background) are not overlapped with each other, but the beams in the first group and the beams in the second group have a large overlapped part. In an example, the transmitting terminal may perform phase shift for the beams in the first group to obtain the beams in the second group. Different reference signals are respectively used for the beams in the first group and the beams in the second group so that the receiving terminal can distinguish the beams in the two groups. An overlapping angle of the two groups of the beams may satisfy 2Φ < ω, wherein ω is a 3dB beam width of a single beam, or Φ is equal to an angle from a central direction of a beam to a first cross zero angle of the beam. In particular, the transmitting terminal may use the following weights on multiple antennas to implement the multiple overlapped beams above.

A weight of the first probing signal is:

A weight of the second probing signal is:

wherein d is a distance between antennas, λ is a wavelength, and N is the number of antennas. Based on the method above, the receiving terminal may detect the channel direction through detecting strength of different reference signals. In particular, two groups of reference signals are detected, the averaged power P₁,P₂ of the two groups of the reference signals are obtained, and then r is calculated through the following equation:

A channel direction difference θ₀-θ corresponding to the calculated ratio r is determined according to a relation between the ratio r and the θ₀-θ as shown in FIG. 3, wherein θ₀ is a channel direction of the receiving terminal. It can be seen that the receiving terminal may deduce the channel direction of the receiving terminal according to the one-to-one relation. Since the channel direction detection provided by the method above has a high accuracy, the method above is referred to as high-accuracy detection. Since resolution provided by conventional methods cannot exceed width of each beam, the conventional methods are referred to as coarse detection.

Second Embodiment

In the embodiment, an explanatory example that a method in the present invention applies to a communication system is provided. In the communication system, since each group of probing signals may work alone and different groups of probing signals use different reference signal resources from each other, a base station may dynamically allocate two groups of overlapped probing signals. The base station may only configure a group of probing signals for a user equipment (UE) having a low probing accuracy requirement, e.g., a UE having a good channel condition and a low moving speed. Thus, the number of probing signals in the system is reduced, and resource overhead of the probing signals is reduced. The base station may configure two groups of probing signals for a UE having a high probing accuracy requirement to perform high accuracy channel direction information detection. FIG. 4 illustrates a schematic diagram illustrating configuration for multiple UEs according to an embodiment of the present invention. UEs in a first set are configured with the first probing signal, UEs in a second set are configured with the second probing signal, and UEs in a third set are configured with the first probing signal and the second probing signal. It can be seen that the UEs in the first set and the UEs in the second set may use a conventional method to obtain coarse channel direction information, and the UEs in the third set may use the method in the first embodiment to obtain accurate channel direction information.

In another example, as shown in FIG. 5, the two groups of probing signals are respectively transmitted in different slots, wherein a time interval between the two slots is short to maintain a coherence bandwidth. In each slot, each UE may independently use a probing signal to perform coarse channel direction information detection. Probing signals respectively in two neighbor slots may be used together to perform high accuracy channel information detection as described in the first embodiment for the UE requiring the high accuracy channel information detection. Advantages of this method are in that there is no additional reference signal resource overhead, the base station does not need to perform special configuration for the UE, and the UE can determine whether the high-accuracy detection is performed.

Third Embodiment

Implementing methods for allocating a resource for a probing signal are provided in the embodiment. It can be seen from above that the probing signal is generated by performing beamforming for a reference signal in a data block. Thus, data block design may consider how a time and frequency resource is allocated for each probing signal. An implementing method includes transmitting two groups of probing signals by using common reference signals. Thus, all UEs may receive the two groups of the probing signals so as to perform high accuracy channel direction detection. Another implementing method includes only transmitting a first probing signal by using a common reference signal (i.e., the first probing signal is the common reference signal for all terminals in a cell region) and transmitting a second probing signal by using a UE Specific Reference Signal for a UE requiring the high-accuracy detection (i.e., the second probing signal is the UE specific reference signal for a single terminal). Since the UE specific reference signal is transparent for other UEs, the system may flexibly implement the coarse detection and the high-accuracy detection. FIG. 6 illustrates a schematic diagram illustrating transmission of a first probing signal and a second probing signal based on a common reference signal and a UE specific reference signal in LTE system according to an embodiment of the present invention. In a receiving terminal, if the UE specific reference signal is not configured, only the common reference signal is used for the channel direction detection, and a UE specific reference signal resource may still be used for data transmission. Alternatively, the UE may use the two kinds of reference signals to perform high-accuracy detection.

After initially obtaining the channel direction information, the terminal usually continuously tracks changes of the channel direction information, so as to feed latest channel direction information back to the transmitting terminal in time. A reasonable method includes transmitting the probing signal by using a demodulation reference signal. Since a same beamforming method is used for the demodulation reference signal and a data signal, the demodulation reference signal may be set as the first probing signal. A new reference signal resource is allocated to transmit the second probing signal, and the second probing signal may occupy a time and frequency resource of the data signal. The transmitting terminal notifies the receiving terminal when transmitting the second probing signal. The receiving terminal extracts the demodulation reference signal and the second probing signal in pre-defined resources, so as to implement high accuracy channel direction information detection. Thus, the existing demodulation reference signal is reasonably used in this method, probing signal resource overhead is reduced, and the receiving terminal is assisted to perform the high accuracy channel direction information detection. FIG. 7 illustrates a schematic diagram illustrating transmission of two groups of probing signals through a LTE demodulation signal and a new reference signal for performing high accuracy channel direction detection according to an embodiment of the present invention.

The present invention provides a transmitting terminal device corresponding to a method above. FIG. 8 illustrates a schematic diagram illustrating a structure of a transmitting terminal device according to an embodiment of the present invention. As shown in FIG. 8, the transmitting terminal device includes a first transmitting module, a second transmitting module, and a receiving module.

The first transmitting module is configured to transmit a first probing signal on a first resource by using beamforming a central angle of which is a first angle.

The second transmitting module is configured to transmit a second probing signal on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space.

The present invention further provides a receiving terminal device corresponding to a method above. FIG. 9 illustrates a schematic diagram illustrating a structure of a receiving terminal device according to an embodiment of the present invention. As shown in FIG. 9, the receiving terminal device includes a first receiving module, a second receiving module, a difference determining module and a feedback module.

The first receiving module is configured to receive a first probing signal on a first resource by using beamforming a central angle of which is a first angle.

The second receiving module is configured to receive a second probing signal on a second resource by using beamforming a central angle of which is a second angle, wherein a beam used for the first probing signal and a beam used for the second probing signal are overlapped in space.

The difference determining module is configured to determine channel direction difference according to a power of the first probing signal and a power of the second probing signal.

FIG. 10 illustrates a flowchart for a terminal according to an embodiment of the present invention. In FIG. 10, the terminal may be a transmitting terminal and another terminal may be a receiving terminal.

At step 1005, the terminal transmits a first signal for a first resource. In here, the terminal transmits, to the another terminal, the first signal for the first resource based on beamforming regarding a first angle.

At step 1010, the terminal transmits a second signal for a second resource. In here, the terminal transmits, to the another terminal, the second signal for the second resource based on beamforming regarding a second angle. A beam for the first signal and a beam for the second signal may be at least overlapped in space.

At step 1015, the terminal receives information for a channel direction from the another terminal. The information for the channel direction may be generated at the another terminal.

FIG. 11 illustrates a flowchart for a terminal according to an embodiment of the present invention. In FIG. 11, the terminal may be a receiving terminal and another terminal may be a transmitting terminal.

At step 1105, the terminal receives a first signal for a first resource. In here, the terminal receives, from the another terminal, the first signal for the first resource based on beamforming regarding a first angle.

At step 1110, the terminal receives a second signal for a second resource. In here, the terminal receives, from the another terminal, the second signal for the second resource based on beamforming regarding a second angle. A beam for the first signal and a beam for the second signal may be at least overlapped in space.

At step 1115, the terminal generates information for a channel direction. In here, the terminal generates the information for the channel direction based on a power of the first signal and a power of the second signal.

At step 1120, the terminal transmits the information for a channel direction to the another terminal. The another terminal obtains a reliable channel direction based on the information.

The foregoing is only preferred examples of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent substitution and improvement without departing from the spirit and principle of the present invention are within the protection scope of the present invention.

Claims

A method for operating a terminal, the method comprising:

transmitting, to another terminal, a first signal for a first resource, based on beamforming regarding a first angle;

transmitting, to the another terminal, a second signal for a second resource, based on beamforming regarding a second angle, wherein a first beam for the first signal and a second beam for the second signal are at least overlapped; and

receiving, from the another terminal, information for a channel direction.
The method of claim 1, wherein

a beamforming weight of the first signal is:

, and

a beamforming weight of the second signal is:

wherein θ+Φ is a central angle of the beamforming regarding the first signal;

θ-Φ is a central angle of the beamforming regarding the second signal;

Φ is an overlapping angle of each of the first beam and the second beam;

d is a distance between antennas;

λ is a wavelength; and

N is the number of antennas.
The method of claim 2, wherein the overlapping angle is smaller than a half of ω, and

wherein the ω is a 3dB beam width of a single beam.
The method of claim 2, wherein the overlapping angle is smaller than a half of ω, and

wherein the Φ is equal to an angle from a central direction of a beam to a first cross zero angle of each of the first beam and the second beam.
The method of claim 1, wherein the first resource and the second resource are wireless communication resources in different times and different frequencies.
The method of claim 1, wherein the first resource and the second resource are wireless communication resources within a coherence bandwidth.
The method of claim 1, wherein the first signal comprises a common reference signal of a UE, and the second signal comprises a UE specific reference signal.
The method of claim 1, wherein the terminal transmits at least one the first signal and the second signal to a designated terminal.
A terminal comprising:

a transceiver is configured to:

transmit, to another terminal, a first signal for a first resource, based on beamforming regarding a first angle;

transmit, to the another terminal, a second signal for a second resource, based on beamforming regarding a second angle, wherein a first beam for the first signal and a second beam for the second signal are overlapped; and

receive, from the another terminal, information for a channel direction.
A method for operating a terminal, the terminal, comprising:

receiving, from another terminal, a first signal for a first resource based on beamforming regarding a first angle;

receiving, from the another terminal, a second signal for a second resource based on beamforming regarding a second angle, wherein a first beam for the first signal and a beam for the second signal are overlapped;

generating information for a channel direction based on a first power of the first signal and a second power of the second signal; and

transmitting, to the another terminal, the information.
The method of claim 10, wherein the generating the information for a channel direction comprises:

determining a first power average for the first signal;

determining a second power average for the second signal;

determining a ratio based on the first power average and the second power average; and,

generating the information for the channel direction based on a relation between the ratio and a channel direction difference.
The method of claim 11, wherein the ratio is:

,

wherein the r is the ratio, the P₁ is the first power average, and the P₂ is the second power average.
A terminal comprising:

a transceiver configured to:

receive, from another terminal, a first signal for a first resource, based on beamforming regarding a first angle; and

receive, from the another terminal, a second signal for a second resource based on beamforming regarding a second angle, wherein a first beam for the first signal and a second beam for the second signal are overlapped; and

a controller configured to generate information for a channel direction based on a first power of the first signal and a second power of the second signal,

wherein the transceiver is further configured to transmit, to the another terminal, the information.