Radio unit for transmitting uplink signal from which noise is removed

Abstract

A radio unit (O-RU) of the present invention amplifies an analog uplink signal received from a user terminal via an antenna by using a low-noise amplifier (LNA), converts the amplified analog uplink signal into a digital uplink signal by using an analog-to-digital converter (ADC), performs a signal processing operation including digital filtering and modulation to improve signal quality, then performs fast Fourier transform (FFT) on the digital uplink signal for orthogonal frequency division multiplexing (OFDM), detects noise in the frequency domain, removes the detected noise, then converts the signal into an eCPRI packet, and transmits same to a fronthaul multiplexer device.

Description

Radio unit transmitting a noise-removed uplink signal

[0001] The present invention relates to a radio unit (O-RU) of an open wireless access network (O-RAN), and more specifically, to a radio unit that removes noise from an uplink signal and transmits it in an environment constituting a shared cell.

[0002] The Open Radio Access Network (O-RAN) standardizes the fronthaul interface connecting the Radio Units (O-RUs) and Distribution Units (O-DUs) required for base station equipment implementation as an open interface. Additionally, the method for providing Shared Cell services based on this open interface has also been standardized. Shared Cell services involve one or more Radio Units (O-RUs) forming the same cell to provide the same service; to achieve this, packet copy and packet combine functions are defined to transmit the same data to multiple Radio Units constituting the same cell.

[0003] More specifically, to provide shared cell services, a fronthall multiplexer (FHM) is introduced, and a network structure is defined in which multiple radio units are connected to the fronthall multiplexer (FHM). In the case of downstream data transmission, when a single data signal is transmitted from the distribution unit (O-DU), the fronthall multiplexer (FHM) copies and delivers the received data from the distribution unit to multiple radio units (O-RUs) that constitute the same pre-configured cell. In the case of upstream data transmission, each radio unit (O-RU) constituting the same cell transmits data; the fronthall multiplexer (FHM) receives these data signals, combines them into a single signal, and delivers it to the distribution unit (O-DU). This process is called the combine operation.

[0004] When a fronthall multiplexer (FHM) merges uplink signals, it merges uplink signals received from all connected radio units (O-RUs). However, due to the characteristics of 4G-LTE or 5G-NR, resource blocks used by a specific radio unit (O-RU) are not used by other radio units (O-RUs). Consequently, resource blocks of the same frequency and time used by radio units (O-RUs), excluding the specific radio unit (O-RU), contain only noise components. Since the fronthall multiplexer (FHM) merges resource blocks of the same frequency and time from radio units (O-RUs) regardless of whether the resource blocks contain only noise components, the power of the noise components is added, resulting in a problem where the signal-to-noise ratio (SNR) of the output signal decreases.

[0005] The present invention aims to provide a radio unit that improves the system noise figure of a merged output signal by ensuring that the power of noise components is not added even when a fronthall multiplexer merging up-up signals in a fronthall network merges up-up signals.

[0006] A radio unit (O-RU) according to the first embodiment of the present invention is a device that constitutes a shared cell in an open wireless access network (O-RAN) and includes an RF front-end unit, a digital front-end unit, and a physical lower separation layer unit.

[0007] The RF front-end amplifies the analog uplink signal received from the user terminal via the antenna through a low-noise amplifier.

[0008] The digital front-end converts the analog up-up signal amplified through an analog-to-digital converter (ADC) into a digital up-up signal and performs signal processing operations, including digital filtering and modulation, to improve signal quality.

[0009] The physical sub-separation layer performs a Fast Fourier Transform on the digital up-up signal for orthogonal frequency division multiplexing, detects noise in the frequency domain, and removes the detected noise.

[0010] The O-RAN interface unit converts the noise-removed digital uplink signal into an eCPRI packet and transmits it to the fronthall multiplexer device.

[0011] The physical sub-separation layer determines the region where the signal power magnitude is smaller than the peak noise power magnitude as a noise region, and removes noise by making the signal power magnitude of the region determined as a noise region zero.

[0012] Since the radio unit of the present invention removes noise from the uplink signal and transmits it, even if the fronthall multiplexer merges the uplink signals transmitted by the radio units constituting the shared cell, the power of the noise component is not added, thereby improving the system noise figure of the merged output signal.

[0013] Figure 1 illustrates, as an example, the concept of merging uplink signals in a shared cell environment.

[0014] Figure 2 illustrates, in an exemplary manner, the concept of increased noise when merging uplink signals received from multiple radio units (O-RU).

[0015] FIG. 3 is a block diagram illustrating the configuration of the radio unit of the present invention.

[0016] Figure 4 is an example conceptually illustrating the difference between a signal in the time domain and a signal in the frequency domain.

[0017] Figure 5 illustrates the concept of the radio unit of the present invention removing noise from an uplink signal.

[0018] The foregoing and additional aspects are embodied in the embodiments described with reference to the attached drawings. It is understood that the components of each embodiment may be combined in various ways within the embodiment unless otherwise stated or contradictory. Each block in the block diagram may represent a physical part in some cases, but in others, it may be a logical representation of a part of the function of a single physical part or a function spanning multiple physical parts. Sometimes, the entity of a block or part thereof may be a set of program instructions. These blocks may be implemented in whole or in part by hardware, software, or a combination thereof.

[0019]

[0020] FIG. 1 illustrates an exemplary concept of merging uplink signals in a shared cell environment. A fronthaul multiplexer (20) is located between a distributed unit (O-DU, 30) and a radio unit (O-RU, 10-1 to 10-N, hereinafter 10) in an open wireless access network (O-RAN) to merge uplink signals (eCPRI messages) received from a plurality of radio units (O-RU, 10) constituting a shared cell and transmit them to the distributed unit (O-DU, 30).

[0021] FIG. 2 illustrates, by way of example, the concept of increased noise when merging uplink signals received from multiple radio units (O-RUs). As previously explained, the fronthall multiplexer device (20) performs the function of merging uplink signals transmitted from multiple radio units (O-RUs, 10) constituting a shared cell. When merging signals, the power of the noise component is added due to the characteristics of noise. In the case of mobile communication signals, not only are they divided by frequency or time, but the superposition principle is also applied so that the signal power before and after merging does not change. FIG. 2 illustrates that the uplink signal from RU#1 includes both signal power and noise power, while the uplink signals from other RUs include only noise power. Since the power of the noise component is added but the signal power is not changed, the signal-to-noise ratio (SNR) decreases after merging. When the fronthall multiplexer device (20) receives and merges uplink signals from 16 radio units (O-RUs), the signal-to-noise ratio of the signal after merging decreases by 12 dB compared to before merging.

[0022] FIG. 3 is a block diagram illustrating the configuration of a radio unit of the present invention. A radio unit (O-RU, 10) according to the first embodiment of the present invention is a device that forms a shared cell in an open wireless access network (O-RAN) and includes an RF front-end unit (100), a digital front-end unit (110), a physical sub-separation layer unit (120), and an O-RAN interface unit (130).

[0023] The radio unit (O-RU, 10) is a device that transmits and receives data signals to and from the distribution unit (O-DU, 30) using Front Haul, and converts analog / digital signals to provide data to the user terminal (UE). The radio unit (O-RU, 10) receives data from the distribution unit (O-DU, 30) or transmits converted data to the user terminal (UE).

[0024] This specification describes only the configuration related to the function of removing noise from the uplink signal. The description of the configuration related to the downlink signal processing function and other functions is omitted.

[0025] The radio unit (O-RU, 10) provides a communication cell to the user terminal (UE) and provides an Open Radio Access Network (O-RAN) interface function and a Low-PHY function, which is a lower part of the physical layer (PHY).

[0026] The RF front-end unit (100) amplifies the analog uplink signal received from the user terminal via the antenna (ANT, 101) through the low-noise amplifier (LNA, 102). The RF front-end unit (100) receives and transmits radio frequency signals. The RF front-end unit (100) is a collective term for all components located between the antenna (101) and the RF transceiver. The main components of the RF front-end unit (100) include a power amplifier (PA) that increases the strength of the transmitted signal and transmits it to the antenna, a low-noise amplifier (LNA, 102) that amplifies the weak signal of the received signal to improve the signal-to-noise ratio, a filter that reduces interference and improves signal quality by passing or blocking only signals of a specific frequency band, and a switch that is responsible for switching the transmission and reception paths or switching between multiple frequency bands. The power amplifier (PA) is used for the downlink, the low-noise amplifier (LNA, 102) is used for the uplink, and each filter and switch is used in both directions.

[0027] The digital front end (110) converts an analog up-up signal amplified through an analog-to-digital converter (ADC, 111) into a digital up-up signal and performs signal processing operations including digital filtering and modulation (112) to improve signal quality. The digital front end (110) can provide a signal conversion function that converts an analog signal into a digital signal and a digital signal into an analog signal through an analog-to-digital converter (ADC, 111) and a digital-to-analog converter (DAC), a digital signal processing function that improves signal quality and minimizes errors by performing various signal processing operations such as digital filtering (Filter, 112), modulation (Modulation, 112), demodulation, and equalization, and a bandwidth management function that efficiently manages the wide frequency bandwidth of 5G and supports signal processing in various frequency bands.

[0028] The physical lower separation layer (Low-PHY, 120) performs a fast Fourier transform on the digital up-up signal for orthogonal frequency division multiplexing, detects noise in the frequency domain, and removes the detected noise. The physical sub-separation layer (120) may provide a CP removal function (121) for removing a cyclic prefix (CP) before the fast Fourier transform, an FFT / IFFT processing function (122) for supporting signal processing in the frequency domain by performing a fast Fourier transform (FFT) and an inverse transform (IFFT) for orthogonal frequency division multiplexing (OFDM), a channel coding and decoding function for ensuring data integrity by applying channel coding (e.g., LDPC, Polar coding) for error detection and correction and decoding the received signal, a multi-antenna processing function for performing signal processing between multiple antennas using MIMO (Multiple Input Multiple Output) technology and increasing data transmission efficiency through spatial multiplexing, a synchronization and frequency offset correction function for improving signal quality by maintaining time and frequency synchronization between transmission and reception and correcting frequency offsets, a function for detecting noise in the frequency domain (Noise Detector, 123), and a function for removing detected noise (Noise Remover, 124).

[0029] FIG. 4 is an example conceptually illustrating the difference between a signal in the time domain and a signal in the frequency domain. FIG. 4 (a) and (b) illustrate the same uplink signal as a signal in the frequency domain and a signal in the time domain. As illustrated in FIG. 4, noise included in the signal in the time domain is practically impossible to distinguish from the signal data, but in the frequency domain, the signal data and the noise are clearly distinguishable. By finding and removing this noise segment from the signal in the frequency domain, the physical sub-separation layer (120) can ensure that even when uplink signals are merged in a fronthall multiplexer device (20) that merges uplink signals from multiple radio units (O-RU, 10) in a shared cell environment, the noise is not superimposed and merged.

[0030] The O-RAN interface unit (130) converts the noise-removed digital uplink signal into an eCPRI packet (131) and transmits it to the fronthall multiplexer device (20). The O-RAN interface unit (130) converts the uplink signal into an eCPRI packet used in an open fronthall network so that it can be transmitted via Ethernet (132) and transmits it to the fronthall multiplexer device (20).

[0031] FIG. 5 illustrates the concept of noise removal from an uplink signal by the radio unit of the present invention. According to the first embodiment of the present invention, the physical sub-separation layer (120) determines a signal in a region where the power magnitude of the signal is smaller than the peak noise power magnitude as a noise region, and removes noise by making the power magnitude of the signal in the region determined as a noise region zero.

[0032] The physical sub-separation layer (120) calculates power for each sub-carrier of the signal in the frequency domain of the digital up-up signal and determines that the corresponding sub-carrier frequency domain is a noise domain if the calculated power magnitude is smaller than the set peak noise power. As another example, the physical sub-separation layer (120) may determine that the corresponding sub-carrier frequency domain is a noise domain if the root mean square value of the power magnitude of the sub-carrier frequency in the frequency domain of the digital up-up signal is smaller than the set peak noise power.

[0033] For the signal shown in FIG. 5 (b), the physical sub-separation layer (20) removes noise by setting the power of the area determined to be noise of the digital up-signal to 0, as shown in FIG. 5 (a).

[0034] FIG. 5(b) can be seen as representing a signal in the frequency domain of an uplink signal transmitted by a radio unit of the prior art, and FIG. 5(a) can be seen as representing a signal in the frequency domain in which the radio unit of the present invention removes noise from the uplink signal in the frequency domain.

[0035]

[0036] Although the present invention has been described above with reference to embodiments with reference to the accompanying drawings, it is not limited thereto and should be interpreted to encompass various modifications that can be obviously derived from them by those skilled in the art. The claims are intended to encompass such modifications.

Claims

1. In a radio unit (O-RU) constituting a shared cell in an open wireless access network (O-RAN), An RF front-end section that amplifies an analog uplink signal received from a user terminal via an antenna through a low-noise amplifier; A digital front-end unit that converts an analog up-up signal amplified through an analog-to-digital converter (ADC) into a digital up-up signal and performs signal processing operations including digital filtering and modulation to improve signal quality; A physical sub-separation layer that performs a fast Fourier transform on a digital up-up signal for orthogonal frequency division multiplexing, detects noise in the frequency domain, and removes the detected noise; O-RAN interface unit that converts a noise-removed digital uplink signal into an eCPRI packet and transmits it to a fronthall multiplexer device; A radio unit that transmits a noise-removed uplink signal, including 2. In Paragraph 1, The physical sub-separation layer determines the signal in the region where the signal power magnitude is smaller than the peak noise power magnitude as the noise region, A radio unit that transmits a noise-removed uplink signal.

3. In Paragraph 2, The physical lower separation layer removes noise by making the power magnitude of the signal in the region determined to be noise zero, A radio unit that transmits a noise-removed uplink signal.

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