BACKGROUND

1. Field

The present disclosure of the following description relates to a method and apparatus for acquiring angle information of a reference signal received at a user equipment (UE), and more particularly, to a method and apparatus for determining a scanning direction of a beam transmitted to a UE based on angle information of a reference signal.

2. Related Art

A communication system may include a core network, for example, a mobility management entity (MME), a serving gateway (SGW), a packet data network (PDN) gateway (PGW), a base station (e.g., a macro base station, a small base station, and a relay), a user equipment (UE), and the like. Communication between the base station and the UE may be performed using a variety of radio access technology (RAT), for example, 4-th generation (4G) communication technology, 5-th generation (5G) communication technology, wireless broadband (WiBro) technology, wireless local area network (WLAN) technology, and wireless personal area network (WPAN) technology.

As a frequency band used for wireless communication becomes higher in a gradual manner, pathloss of radio wave increases, which may lead to reducing cell coverage. To solve the aforementioned issue, a 5G mobile communication standard divides the cell coverage into a plurality of sections corresponding to an analog beam width, sequentially transmits a beam corresponding to each section, and covers the cell coverage.

A base station employs a beam sweeping method to select an optimal beam to be transmitted to a UE. However, if a position of the UE varies, a beam sweeping procedure needs to be performed again to determining direction of a beam for the UE. Therefore, wireless resources may be redundantly used.

SUMMARY

At least one example embodiment provides a method and apparatus for acquiring angle information of a signal received at a user equipment (UE) from a base station.

At least one example embodiment also provides a method and apparatus for determining a scanning direction of a beam for a UE based on angle information of a signal received at the UE from a base station.

According to an aspect, there is provided a method of acquiring angle information of a reference signal performed by a UE, the method including receiving a reference signal from a base station including a plurality of patch antennas; acquiring phase information depending on a carrier frequency of the reference signal based on received data of the reference signal measured at a plurality of sample times; and calculating an angle of departure (AoD) of the reference signal based on the phase information depending on the carrier frequency.

The plurality of patch antennas may include a first patch antenna configured to transmit a first subcarrier and a second patch antenna configured to transmit a second subcarrier different from the first subcarrier.

The phase information may depend on a sum of the carrier frequency and a difference between the first subcarrier and the second subcarrier.

A waveform of the reference signal may be configured to be continuous in a time interval greater than a size of an orthogonal frequency division multiplexing (OFDM) symbol.

The plurality of patch antennas may be configured to transmit subcarriers included in a predetermined subcarrier group and the subcarriers may be provided at equal intervals in a frequency domain.

The acquiring of the phase information may include acquiring a sample vector based on the received data of the reference signal; calculating a phase vector by performing an inner product on a discrete Fourier transform (DFT) coefficient vector for a DFT operation with respect to the sample vector; extracting a first sub-phase vector and a second sub-phase vector from the phase vector; and extracting the phase information from a conjugate product from the first sub-phase vector and the second sub-phase vector.

The conjugate product of the first sub-phase vector and the second sub-phase vector may include a conjugate product between a first component of the phase vector and a second component having an angular frequency index different from an angular frequency of the first component.

The conjugate product of the first sub-phase vector and the second sub-phase vector may be independent from a local clock error between the UE and the base station.

According to another aspect, there is provided a UE including a communicator; and a processor. The processor is configured to perform a process of receiving a reference signal from a base station including a plurality of patch antennas, a process of acquiring phase information depending on a carrier frequency of the reference signal based on received data of the reference signal measured at a plurality of sample times, and a process of calculating an AoD of the reference signal based on the phase information depending on the carrier frequency.

According to still another aspect, there is provided a beam selection method performed by a base station, the beam selection method including setting a subcarrier group allocated to a plurality of patch antennas; determining a reference signal sequence; transmitting a reference signal based on the subcarrier group and the reference signal sequence; acquiring information about an AoD of the reference signal from a UE; and determining a beam to be transmitted to the UE based on information about the AoD of the reference signal.

The plurality of patch antennas may include a first patch antenna configured to transmit a first subcarrier and a second patch antenna configured to transmit a second subcarrier different from the first subcarrier.

The reference signal sequence may be configured such that a waveform of the reference signal is configured to be continuous in a time interval greater than a size of an OFDM symbol.

Subcarriers included in the subcarrier group may be provided at equal intervals in a frequency domain.

According to at least one example embodiment, a UE may easily calculate a difference in travel distance or a difference in propagation delay time between signals received from different patch antennas.

According to at least one example embodiment, a UE may easily calculate an AoD of a reference signal from phase information corresponding to a difference in travel distance or a difference in propagation delay time between signals received from different patch antenna.

According to at least one example embodiment, a base station may omit a beam sweeping procedure based on information about an AoD of a reference signal, thereby preventing the redundant use of wireless resources.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

