KR102923322B1 - Apparatus for dynamic power back off in mobile communication system - Google Patents

Abstract

A device for dynamic power backoff according to an embodiment of the present invention includes a storage unit that stores power backoff information indicating the number of MCS levels and layers to which power backoff is applied and the power backoff value to be applied, a backoff search unit that confirms the number of MCS levels and layers assigned to a user device and detects a power backoff value corresponding to the confirmed number of MCS levels and layers from the power backoff information, and a backoff processing unit that applies the detected power backoff value when transmitting a downlink signal to the user device.

Description

Apparatus for dynamic power back-off in mobile communication system

The present invention relates to a transmission power control technology, and more specifically, to a device for dynamic power backoff in a mobile communication system.

Error Vector Magnitude (EVM) is a measure of the modulation quality of a modulated signal within a given spectrum band in wireless digital communication. EVM represents the difference between the actual transmitted signal and an ideal reference signal as a percentage. If the signal is perfectly aligned with the ideal, EVM is 0%. As EVM increases, the signal-to-noise ratio (SINR) quality of the user equipment may deteriorate.

Korean Patent Publication No. 2011-0063758, published on June 14, 2011 (Title: Coordinated Power Boost and Power Backoff)

The purpose of the present invention is to provide a device for dynamic power backoff that takes into account not only MCS but also the number of layers in a mobile communication system.

In order to achieve the above-described purpose, a device for dynamic power back-off in a mobile communication system according to a preferred embodiment of the present invention includes a storage unit for storing power back-off information indicating the number of MCS levels and layers to which power back-off is applied and a power back-off value to be applied, a back-off search unit for checking the number of MCS levels and layers assigned to a user device and detecting a power back-off value corresponding to the checked number of MCS levels and layers from the power back-off information, and a back-off processing unit for applying the detected power back-off value when transmitting a downlink signal to the user device.

The above backoff search unit is characterized in that it detects an MCS allocation index and an antenna port index in the DCI of the PDCCH to check the level of the MCS allocated to the user device and the number of layers allocated to the user device.

The above power backoff information includes a lowest MCS level defining the lowest MCS level to which power backoff is applied for each number of layers, a highest MCS level defining the highest MCS level to which power backoff is applied for each number of layers, and a backoff value defining the power backoff value to be applied for each number of layers.

The above backoff search unit checks the number of layers and the MCS level assigned to the user device, and then searches for the lowest MCS level and the highest MCS level of the layers corresponding to the number of layers assigned to the user device in the power backoff information, and checks whether the MCS level assigned to the user device falls within the range of the searched lowest MCS level and the highest MCS level, thereby checking whether the number of layers assigned to the user device and the MCS level fall within the range of the lowest MCS level and the highest applicable MCS level per layer.

The above backoff search unit is characterized in that, if the result of the above verification falls within the above range, it detects a power backoff value corresponding to the number of layers allocated to the user device and the MCS level from the backoff value of the power backoff information.

According to the present invention, power backoff can be applied selectively only for transmissions requiring Error Vector Magnitude (EVM) compensation by considering not only the MCS level assigned to a user device but also the number of layers. This allows for maximizing downlink transmission speed.

FIG. 1 is a drawing for explaining a mobile communication system according to an embodiment of the present invention.
FIG. 2 is a drawing for explaining the configuration of a device for dynamic power backoff in a mobile communication system according to an embodiment of the present invention.
FIG. 3 is a flowchart illustrating a method for dynamic power backoff in a mobile communication system according to an embodiment of the present invention.

Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. However, when describing the operating principles of preferred embodiments of the present invention in detail, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. This is to convey the gist of the present invention more clearly without obscuring it by omitting unnecessary explanation. In addition, the present invention can be modified in various ways and can have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this does not intend to limit the present invention to specific embodiments, and it should be understood that the present invention includes all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Additionally, when a component is referred to as being "connected" or "connected" to another component, this means that the component can be connected or connected logically or physically. In other words, while a component may be directly connected or connected to another component, it should be understood that other components may exist in between, and that the component may be connected or connected indirectly.

In addition, the terminology used in this specification is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In addition, it should be understood that the terms "comprises" or "has" described in this specification are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, a device supporting dynamic power back-off according to an embodiment of the present invention will be described in detail with reference to the drawings. Throughout the drawings, parts with similar functions and actions will be designated by the same reference numerals, and any redundant description thereof will be omitted. Furthermore, to avoid ambiguity in the concepts of the present invention, well-known structures and devices may be omitted or illustrated in block diagram form focusing on the core functions of each structure and device.

First, the network environment to which the embodiment of the present invention applies will be described. Figure 1 is a diagram illustrating a mobile communication system according to an embodiment of the present invention. Referring to Figure 1, the communication system according to the embodiment of the present invention includes a core network (CN), a base station (10), and multiple user devices (20).

The core network (CN) includes more entities, including a Mobility Management Entity (MME), a Serving Gateway (SGW), a Packet Data Network Gateway (PGW), a Home Subscriber Server (HSS), a Policy and Charging Rules Function (PCRF), and a Packet Data Network (PDN), but a detailed description thereof is omitted as it is not the gist of the present invention.

A base station (10) is a device that provides wireless access services to a user device (20) in a wireless section. The base station (10) may be exemplified by a gNB, a wireless access network device that provides wireless access services to a user device (20) according to 5G technology based on 5G NR (New Radio) of 3GPP Rel. 15. However, the base station (10) of the present invention is not limited to gNB, and can be applied to all wireless access network devices that provide wireless access services to a user device (20).

EVM (Error Vector Magnitude) is a measure of the modulation quality of a modulated signal within a certain spectrum band in a wireless digital communication method. EVM expresses the difference between an actual transmitted signal and an ideal reference signal as a ratio. When the signal is completely identical to the ideal signal, EVM is 0%, and as EVM increases, the reception SINR (Signal-to-Noise Ratio) quality of the user equipment (20) may deteriorate. As a condition for satisfying EVM, the condition of "EVM < 2%" is required for all modulation methods (QPSK, 16QAM, 64QAM, 256QAM, etc.). In order to satisfy EVM, the base station (10) must increase PAPR (Peak-to-Average Power Ratio), but it is physically difficult to increase PAPR for high-order modulation methods, so the output power is lowered to satisfy EVM. That is, in order to satisfy EVM, the base station (10) performs power backoff, which reduces the output power compared to the maximum output and transmits it.

According to the conventional technology, the base station (10) performs power backoff only based on the MCS level, and thus performs power backoff even when the EVM is improved due to the number of layers. However, when performing power backoff in a state where the EVM is improved, there is no significant change in the EVM, but the downlink SINR (Signal to Interference plus Noise Ratio) is reduced. This is because the reception power of the user device (20) is reduced due to the reduction in the transmission power of the base station (10).

However, according to an embodiment of the present invention, the base station (10) adaptively performs power backoff by considering not only the MCS level assigned to the user device (20) but also the number of layers. Accordingly, power backoff can be performed only when necessary, without performing power backoff when EVM is improved due to the number of layers.

Next, the configuration of a device for dynamic power back-off in a mobile communication system according to an embodiment of the present invention will be described. FIG. 2 is a diagram illustrating the configuration of a device for dynamic power back-off in a mobile communication system according to an embodiment of the present invention. Referring to FIG. 2, a base station (10) includes a communication unit (110), a storage unit (120), and a control unit (130).

The communication unit (110) is for communicating with the user device (20) in a wireless section. The communication unit (110) can receive an uplink (UL: Up Link) signal from the user device (20) or transmit a downlink (DL: Down Link) signal to the user device (20) under the control of the control unit (130). The communication unit (110) may include an RF (Radio Frequency) transmitter (Tx) that up-converts and amplifies the frequency of a transmitted signal and an RF receiver (Rx) that low-noise amplifies and frequency-converts a received signal. In addition, the communication unit (110) may include a modem that modulates a transmitted signal and demodulates a received signal.

The storage unit (120) serves to store data required for the operation of the base station (10). In particular, the storage unit (120) stores power backoff information according to an embodiment of the present invention. This power backoff information includes the number of MCS levels and layers to which power backoff is applied, and a power backoff value according to the number of MCS levels and layers.

The power backoff information is expressed through three parameters for each of the multiple layers. That is, the power backoff information includes the lowest MCS level (startMcsForLayerX), the highest MCS level (endMcsForLayerX), and the backoff value (backoffValueForLayerX) for each of the multiple layers. Here, X represents the number of layers. These parameters (startMcsForLayerX, endMcsForLayerX, backoffValueForLayerX) can be set by the operator.

The lowest MCS level (startMcsForLayerX) defines the lowest MCS level to which the power backoff will be applied, based on the number of layers. When the number of layers (X) is 1 to 8, there are a total of 8 parameters, including startMcsForLayer1, startMcsForLayer2, ??, and startMcsForLayer8, and each of the 8 parameters defines the lowest MCS level to which the power backoff will be applied, for each case where the number of assigned layers is 1, 2, ??, and 8.

The highest MCS level (endMcsForLayerX) defines the highest MCS level to which power backoff will be applied, based on the number of layers. When the number of layers (X) is 1 to 8, there are a total of 8 parameters, including endMcsForLayer1, endMcsForLayer2, ??, endMcsForLayer8, and each of the 8 parameters defines the highest MCS level to which power backoff will be applied, for each case where the number of assigned layers is 1, 2, ??, 8.

The backoff value (backoffValueForLayerX) defines the power backoff value to be applied according to the number of layers. When the number of layers (X) is 1 to 8, there are a total of 8 parameters including backoffValueForLayer1, backoffValueForLayer2, ??, backoffValueForLayer8, and each of the 8 parameters defines the power backoff value to be applied when the number of allocated layers is 1, 2, ??, 8. These power backoff values may be fixed regardless of the number of layers, or may be applied differentially depending on the number of layers.

Meanwhile, each type of data stored in the storage unit (120) can be registered, deleted, changed, or added according to the administrator's operation.

The control unit (130) controls the overall operation of the base station (10) and the signal flow between internal blocks of the base station (10), and can perform a data processing function for processing data. The control unit (130) may be a central processing unit, a digital signal processor, etc. The control unit (130) includes a control channel processing unit (131), a shared channel processing unit (133), a backoff search unit (200), and a backoff processing unit (300).

The backoff search unit (200) checks the number of MCS (Modulation and Coding Scheme) levels and layers assigned to the user device (20), and detects a power backoff value corresponding to the number of MCS levels and layers checked in the power backoff information of the storage unit (120).

The control channel processing unit (131) transmits a downlink control channel (PDCCH: Physical Downlink Control Channel) signal to inform the user device (20) of transmission resources allocated for downlink (DL) signal transmission according to scheduling. In particular, the control channel processing unit (131) transmits a downlink grant (DL grant: downlink resource allocation signal) through the PDCCH in each slot. The DCI (Downlink Control Information) message included in the downlink grant includes an MCS allocation index and an antenna port index. The MCS allocation index indicates the MCS allocated to the user device (20), and the antenna port index indicates the number of layers allocated to the user device (20).

Accordingly, the backoff search unit (200) can check the MCS level and number of layers of the user device (20) from the DCI of the PDCCH. That is, the backoff search unit (200) can check the MCS allocated to the user device (20) through the MCS allocation index in the DCI, and can check the number of layers allocated to the user device (20) through the antenna port index.

The backoff search unit (200) checks the number of layers and MCS levels assigned to the user device (20), and then searches for the lowest MCS level (startMcsForLayerX) and highest MCS level (endMcsForLayerX) of the layers corresponding to the number of layers assigned to the user device (20) in the power backoff information stored in the storage unit (120). Then, the backoff search unit (200) checks whether the MCS level assigned to the user device (20) falls within the range of the lowest MCS level (startMcsForLayerX) and highest MCS level (endMcsForLayerX).

If, as a result of the verification, the MCS level assigned to the user device (20) falls within the range of the lowest MCS level (startMcsForLayerX) to the highest MCS level (endMcsForLayerX) found, the transmission power for the user device (20) becomes a target of power backoff. Accordingly, if the MCS level assigned to the user device (20) falls within the range of the lowest MCS level (startMcsForLayerX) to the highest MCS level (endMcsForLayerX) found, the backoff search unit (200) detects the power backoff value corresponding to the number of layers and the MCS level assigned to the user device (20) from the backoff value (backoffValueForLayerX) of the power backoff information stored in the storage unit (120).

Then, the backoff processing unit (300) controls the communication unit (110) to apply the power backoff value detected by the backoff search unit (200) when the shared channel processing unit (133) transmits a downlink signal to the corresponding user device (20). The following Table 1 is intended to explain the operation when it is assumed that only a maximum of four layers can be assigned to one user device (20), for example.

Number of layers Power backoff information
(parameter) MCS level 27 26 … 21 20 19 … 1 startMcsForLayer1 = 27
endMcsForLayer1 = 0
backoffValueForLayer1 = 0 0 0 … 0 0 0 0 2 startMcsForLayer2 = 27endMcsForLayer2 = 0
backoffValueForLayer2 = 0 0 0 … 0 0 0 0 3 startMcsForLayer3 = 27
endMcsForLayer3 = 23
backoffValueForLayer3 = 1 1 1 … 0 0 0 0 4 startMcsForLayer1 = 27
endMcsForLayer1 = 20
backoffValueForLayer1 = 1.5 1.5 1.5 … 1.5 1.5 0 0

According to Table 1, the backoff processing unit (300) processes power backoff as follows. The shared channel processing unit (133) basically transmits data to the user device (20) through a PDSCH signal. At this time, the shared channel processing unit (133) transmits a PDSCH signal including data through transmission resources allocated to the corresponding user device (20) according to the downlink grant of the PDCCH transmitted by the control channel processing unit (131).

The backoff processing unit (300) basically does not apply power backoff to MCSs in sections that are not set to the lowest MCS level (startMcsForLayerX) and highest MCS level (endMcsForLayerX). That is, the backoff value for the unset MCS section is 0 dB.

When one layer is allocated, the backoff processing unit (300) applies a power backoff of 0 dB to a downlink signal (e.g., PDSCH) transmitted to the user device (20), regardless of the MCS level allocated to the user device (20). That is, the power backoff is not applied.

In the case where two layers are allocated, the backoff processing unit (300) applies a power backoff of 0 dB to the downlink signal (e.g., PDSCH) transmitted to the user device (20), regardless of the MCS level allocated to the user device (20). That is, the power backoff is not applied.

In the case where three layers are allocated, the backoff processing unit (300) applies a power backoff of 1 dB to the downlink signal (e.g., PDSCH) transmitted to the user device (20) if the MCS level allocated to the user device (20) is 23 to 27.

In the case where four layers are allocated, the backoff processing unit (300) applies a power backoff of 1.5 dB to the downlink signal (e.g., PDSCH) transmitted to the user device (20) if the MCS level allocated to the user device (20) is 20 to 27.

In the example of Table 1, the backoff value (backoffValueForLayerX) is described as a fixed value for each number of identical layers. However, the present invention is not limited to this, and even when the number of identical layers is the same, different backoff values (backoffValueForLayerX) may be applied if the MCS levels are different.

Next, a method for dynamic power backoff in a mobile communication system according to an embodiment of the present invention will be described. Fig. 3 is a flowchart illustrating a method for dynamic power backoff in a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 3, the storage unit (120) of the base station (10) stores power backoff information indicating the MCS level and the number of layers to which power backoff is applied and the power backoff value to be applied in step S110. The power backoff information is expressed through three parameters for each of the plurality of layers. That is, the power backoff information includes the lowest MCS level (startMcsForLayerX), the highest MCS level (endMcsForLayerX), and the backoff value (backoffValueForLayerX) for each of the plurality of layers. Here, X represents the number of layers. These parameters (startMcsForLayerX, endMcsForLayerX, backoffValueForLayerX) can be set by the operator.

The backoff search unit (200) checks the MCS level and the number of layers allocated to the user device (20) from the DCI of the PDCCH at step S120. That is, the backoff search unit (200) can detect the MCS allocation index and antenna port index from the DCI of the PDCCH to check the level of the MCS allocated to the user device and the number of layers allocated to the user device.

Next, the backoff search unit (200) searches for the lowest MCS level and the highest MCS level of the layer corresponding to the number of layers allocated to the user device (20) in the power backoff information of the storage unit (120) at step S130.

Then, the backoff search unit (200) checks whether the MCS level assigned to the user device (20) falls within the range of the lowest MCS level and the highest MCS level searched in step S140.

As a result of the verification in step S140, if it falls within the above range, the backoff search unit (200) detects a power backoff value corresponding to the number of layers and the MCS level allocated to the user device (20) from the backoff value of the power backoff information in step S150. Then, the backoff processing unit (300) applies the power backoff value detected by the backoff search unit (200) when the shared channel processing unit (133) transmits a downlink signal, such as a PDSCH signal, to the user device (20) in step S160.

On the other hand, if the result of the verification at step S140 falls within the above range, the backoff processing unit (300) proceeds to step S170, and the shared channel processing unit (133) does not apply power backoff when transmitting a downlink signal, such as a PDSCH signal, to the user device (20).

Meanwhile, the method according to an embodiment of the present invention may be provided in the form of a computer-readable medium suitable for storing computer program commands and data. Such a computer-readable recording medium may include program commands, data files, data structures, etc., alone or in combination, and includes all types of recording devices that store data that can be read by a computer system. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical media such as CD-ROMs (Compact Disk Read Only Memory) and DVDs (Digital Video Disks); magneto-optical media such as floptical disks; and hardware devices specifically configured to store and execute program commands such as ROMs (Read Only Memory), RAMs (Random Access Memory), and flash memory. In addition, the computer-readable recording medium may be distributed across network-connected computer systems, so that computer-readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the technical field to which the present invention belongs.

While the preferred embodiments of the present invention have been described and illustrated to illustrate the technical concept of the present invention, it will be readily apparent to those skilled in the art that the present invention is not limited to the configuration and operation described herein, and that numerous modifications and variations are possible without departing from the scope of the technical concept. Accordingly, all such appropriate modifications and variations, as well as their equivalents, should be considered within the scope of the present invention.

In a mobile communication system according to the present invention, a device for dynamic power backoff applies power backoff considering not only the MCS level assigned to a user device but also the number of layers, thereby selectively applying power backoff only to transmissions requiring Error Vector Magnitude (EVM) compensation. Accordingly, downlink transmission speeds can be maximized. The present invention has sufficient potential for commercialization or sales and is thus clearly and realistically feasible, and therefore possesses industrial applicability.

10: Base station 20: User device
110: Communications 120: Storage
130: Control unit 131: Control channel processing unit
133: Shared channel processing unit 135: Backoff search unit
137: Backoff Search Unit

Claims (5)

A storage unit that stores power backoff information indicating the number of MCS levels and layers to which power backoff is applied and the power backoff value to be applied; and
A backoff search unit that checks the number of MCS levels and layers assigned to a user device and detects a power backoff value corresponding to the confirmed MCS levels and number of layers from the power backoff information; and
A backoff processing unit that applies the detected power backoff value when transmitting a downlink signal to the user device, except in cases where the signal quality is improved due to the number of layers;
characterized by including
A device for applying dynamic power backoff. In the first paragraph,
The above backoff search unit
It is characterized in that the level of MCS allocated to the user device and the number of layers allocated to the user device are checked by detecting the MCS allocation index and antenna port index in the DCI of the PDCCH.
A device for applying dynamic power backoff. In the first paragraph,
The above power backoff information is
The lowest MCS level, which defines the lowest MCS level to which power backoff will be applied based on the number of layers,
The highest MCS level, which defines the highest MCS level to which power backoff will be applied based on the number of layers,
characterized by including a backoff value defining a power backoff value to be applied according to the number of layers.
A device for applying dynamic power backoff. In the third paragraph,
The above backoff search unit
After checking the number of layers and MCS level assigned to the above user device,
Search for the lowest MCS level and highest MCS level of the layer corresponding to the number of layers allocated to the user device in the above power backoff information.
It is characterized by checking whether the MCS level assigned to the user device falls within the range of the lowest MCS level and the highest MCS level searched.
A device for applying dynamic power backoff. In paragraph 4,
The above backoff search unit
As a result of the above verification, if it falls within the above range,
It is characterized in that the power backoff value corresponding to the number of layers allocated to the user device and the MCS level is detected from the backoff value of the power backoff information.
A device for applying dynamic power backoff.