KR20180105529A - Method for processing transmission signal and apparatus for the same - Google Patents

Abstract

Disclosed is a method for processing a signal performed in a communication node for optimizing the quality of a DAC output transmission signal. The method comprises the steps of: generating a data stream based on the number of sub carriers for each channel; performing normalization and normalization reduction for the data stream based on the maximum number of sub carriers, an IFFT port size included in the communication node, and a DAC port size included in the communication node among the number of sub carriers for each channel; and transmitting the reduced data stream. Accordingly, a quantization error can be minimized, and an effect due to a noise to a final output of a transmission signal can be minimized.

Description

TECHNICAL FIELD [0001] The present invention relates to a transmission signal processing method and apparatus,

The present invention relates to a method and apparatus for processing a transmission signal, and more particularly to a method and apparatus for processing a transmission signal in an orthogonal frequency division multiplexing network.

BACKGROUND OF THE INVENTION In cellular communication networks, a user equipment is capable of transmitting and receiving data units through a base station. For example, if there is a data unit to be transmitted to the second terminal, the first terminal can generate a message including the data unit to be transmitted to the second terminal, and transmit the generated message to the first base station Lt; / RTI > The first base station can receive the message from the first terminal and confirm that the destination of the received message is the second terminal. The first base station can transmit the message to the second base station to which the second terminal, which is the confirmed destination, belongs. The second base station can receive the message from the first base station and confirm that the destination of the received message is the second terminal. The second base station may transmit the message to the second terminal, which is the identified destination. The second terminal can receive the message from the second base station and obtain the data unit contained in the received message.

Among the transmission and reception procedures of the data unit described above, Orthogonal Frequency Division Multiplexing (OFDM) based communication may be as follows.

To perform signal transmission, signals occupying various bandwidths (e.g., signals occupying various numbers of subcarriers) may be input to the transmitter.

A signal occupied by various bandwidth input to the transmitter can be IFFT (Inverse Fast Fourier Transform) -transformed.

The resulting value of the IFFT transform, that is, the time domain signal input to the digital-to-analog converter (DAC), which occurs when IFFT conversion of signals occupying various bandwidths is performed, may have various sizes. The size of the time domain signal input to the DAC can be expressed in bits.

If the size of the signal input to the DAC is equal to the size (or number) of the DAC input port, the signal to noise ratio (SNR) of the analog signal output from the DAC can be maximized.

Also, when the magnitude of the signal input to the DAC corresponds to the magnitude of the DAC input port, the quantization error of the analog signal output from the DAC can be reduced.

However, when the size of the signal input to the DAC is smaller than or greater than the size of the DAC input port, the quantization error of the analog signal output from the DAC may become large. If the quantization error of the analog signal output from the DAC increases, the quality of the signal may be degraded.

It is an object of the present invention to provide a method for optimizing the quality of a DAC output transmission signal by including a normalization process between a signal output from the IFFT and a signal input to the DAC.

According to an aspect of the present invention, there is provided a signal processing method performed in a communication node, the method including generating a data stream based on a number of subcarriers per channel; Based on a maximum number of subcarriers among the number of subcarriers per channel, an IFFT (Inverse Fast Fourier Transform) port size included in the communication node, and a DAC (digital analog convert) port size included in the communication node, Performing a normalization on the output data stream such that a size of a data stream output from the DAC corresponds to a size of the DAC port; Performing a reduction on the data stream output from the DAC port based on the maximum number of subcarriers and the IFFT port size; And transmitting the reduced data stream.

According to the present invention, there is an effect that quality of a transmission signal is improved in a transmitter of an orthogonal frequency division multiplexing network. Specifically, when the number of DAC input ports (or the number of input bits) is relatively small (5 bits or less) and the number of subcarriers of the IFFT input is relatively small, the transmission signal quality is greatly improved.

Therefore, according to the present invention, when a DAC having a relatively small number of input ports of a DAC is used, the quantization error can be minimized and the quality of a transmission signal can be improved.

1 is a conceptual diagram showing an embodiment of a communication network.
2 is a block diagram showing an embodiment of a communication node constituting a communication network.
3 is a block diagram showing a first embodiment of a configuration of a transmission / reception apparatus of a communication node.
4 is a block diagram showing a second embodiment of a configuration of a transmission / reception apparatus of a communication node.
5 is a flow diagram illustrating one embodiment of a communication method in a communication network.
6 is a conceptual diagram specifically showing an embodiment of a communication method in a communication network.
7 is a block diagram illustrating one embodiment of a system for performing simulations of embodiments of a communication method.
8 is a graph illustrating a bit error rate when the number of subcarriers is 12 according to a conventional method.
9 is a graph illustrating a bit error rate when the number of subcarriers is 12 according to the proposed method.
10 is a graph illustrating a bit error rate when the number of subcarriers is 120 according to a conventional method.
11 is a graph illustrating a bit error rate when the number of subcarriers is 120 according to the proposed method.
12 is a graph illustrating a bit error rate when the number of subcarriers is 600 according to a conventional method.
13 is a graph illustrating a bit error rate when the number of subcarriers is 600 according to the proposed method.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

In the following, a wireless communication network to which embodiments according to the present invention are applied will be described. The wireless communication network to which the embodiments according to the present invention are applied is not limited to the following description, and the embodiments according to the present invention can be applied to various wireless communication networks.

1 is a conceptual diagram showing an embodiment of a communication network.

1, a communication network 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes may be a wireless communication device based on a communication protocol based on a code division multiple access (CDMA) communication protocol, a communication protocol based on a wideband CDMA (WCDMA), a communication protocol based on a time division multiple access (TDMA) based communication protocol, an orthogonal frequency division multiplexing (OFDM) based communication protocol, an OFDMA (orthogonal frequency division multiple access) based communication protocol, a single carrier-FDMA based communication protocol, a non-orthogonal multiple access-based communication protocol, and a space division multiple access (SDMA) -based communication protocol. Each of the plurality of communication nodes may have the following structure.

2 is a block diagram showing an embodiment of a communication node constituting a communication network.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to the network to perform communication. The communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each component included in the communication node 200 may be connected by a bus 270 and communicate with each other.

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods in accordance with embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be constituted of at least one of a volatile storage medium and a nonvolatile storage medium. For example, the memory 220 may comprise at least one of read-only memory (ROM) and random access memory (RAM).

3 is a block diagram showing a first embodiment of a configuration of a transmission / reception apparatus of a communication node.

3, the communication node may include a transmission control unit 300, a transmission unit 310, a radio frequency (RF) unit 320, and the like. The transmission unit 310 may include a channel generation unit 311, a resource mapping unit 312, an IFFT (Inverse Fast Fourier Transform) unit 313, and a DAC (Digital to Analog Converter) 314.

The transmission control unit 300 may be the processor 210 of FIG. The transmitter 310 and the RF unit 320 may be the transmitter / receiver 230 of FIG.

The channel generation unit 311 of the transmission unit 310 can receive the number of subcarriers per channel from the transmission control unit 300. [

The channel generator 311 can generate a data stream based on the number of subcarriers per channel received from the transmission control unit 300 for each TTI (Transmission Time Interval).

The channel generation unit 311 may transmit the data stream to the resource mapping unit 312. The resource mapping unit 312 can receive the data stream from the channel generation unit 311. [

The resource mapping unit 312 may map the received data stream to a resource on an OFDM symbol basis. The OFDM symbol unit may typically be 3.2 microseconds. The resource mapping unit 312 may transmit the data stream mapped to the resource to the IFFT unit 313.

The IFFT unit 313 can receive the data stream mapped to the resource from the resource mapping unit 312. The IFFT unit 313 can convert a data stream mapped to a resource for each TTI from a frequency domain to a time domain (hereinafter referred to as 'IFFT transform').

으로 표현될 수 있다.The size of the IFFT-transformed data stream can be expressed in units of bits. For example, if the size of the IFFT-transformed data stream is n bits, then the size of the IFFT-

. ≪ / RTI >

The IFFT unit 313 can transmit the IFFT-converted data stream to the DAC 314. The DAC 314 can receive the IFFT-converted data stream from the IFFT unit 313. [

The DAC 314 may perform a digital-to-analog conversion on the IFFT-transformed data stream. That is, the DAC 314 may generate an analog signal based on the IFFT-transformed data stream. The DAC 314 can transmit an analog signal to the RF unit 320. [ The RF unit 320 may transmit the analog signal received from the DAC 314.

If the size of the data stream input to the DAC 114 and the size (or number) of the input ports of the DAC 114 are not the same, the quantization error may increase in the DAC 314 and the DAC 314 The signal-to-noise ratio (SNR) of the analog signal output from the antenna may be low.

Therefore, when the size of the data stream input to the DAC 114 does not correspond to the size of the input port of the DAC 114, the quality of the transmission signal may be degraded. Hereinafter, a transmission signal processing method in a communication network for solving the above problems can be described.

4 is a block diagram showing a second embodiment of a configuration of a transmission / reception apparatus of a communication node.

4, the communication node may include a transmission control unit 400, a transmission unit 410, an RF unit 420, and the like. The transmission unit 410 includes a channel generation unit 411, a resource mapping unit 412, an IFFT unit 413, a normalization unit 414, a DAC 415, a normalization reductive unit 416, and a bandwidth calculation unit 417 .

The transmission control unit 400 may be the processor 210 of FIG. The transmitting unit 410 and the RF unit 420 may be the transmitting and receiving unit 230 of FIG.

In FIG. 4, the normalization unit 414, the normalization / reduction unit 416, and the bandwidth calculation unit 417 may be additionally included in the configuration of FIG. The functions of the normalization unit 414, the normalization / reduction unit 416, and the bandwidth calculation unit 417 may be described in detail with reference to FIG.

5 is a flow diagram illustrating one embodiment of a communication method in a communication network.

Referring to FIG. 5, the transmission control unit 400 may transmit the subcarrier number information for each channel to the channel generation unit 411 of the transmission unit 410. FIG. The number of subcarrier information per channel may indicate information about occupied bandwidth per channel.

The channel generator 411 of the transmitter 410 may receive the number of subcarriers per channel from the transmission controller 400 (S500).

The bandwidth calculation unit 417 can receive the number of subcarriers per channel from the transmission control unit 400. [ The bandwidth calculator 417 may store 'maximum number of subcarriers' information having the maximum number of subcarriers per channel based on the received number of subcarriers per channel.

The bandwidth calculation unit 417 can transmit the maximum number of subcarrier numbers to the normalization unit 414 and the normalization reduction unit 416. [ The maximum number of subcarrier information may be used in the normalization process in the normalization unit 414. [ The maximum number of subcarriers may be used in the normalization and reduction process in the normalization and reduction unit 416.

The channel generation unit 411 of the transmission unit 410 can receive the number of subcarriers per channel from the transmission control unit 400. [

The channel generation unit 411 may generate a data stream based on the channel-by-channel subcarrier number information received from the transmission control unit 400 for each TTI (S510).

The channel generation unit 411 may transmit the data stream to the resource mapping unit 412. The resource mapping unit 412 can receive the data stream from the channel generation unit 411. [

The resource mapping unit 412 may map the received data stream to a resource in OFDM symbol units (S520). The resource mapping unit 412 can transmit the data stream mapped to the resource to the IFFT unit 413.

The IFFT unit 413 can receive the data stream mapped to the resource from the resource mapping unit 312. The IFFT unit 413 can IFFT-convert the data stream mapped to the resource for each TTI (S530).

Specifically, the IFFT transform may be as follows.

6 is a conceptual diagram specifically showing an embodiment of a communication method in a communication network.

Referring to FIG. 6, the number of subcarriers input to the IFFT unit 413 may be 1/4, 1/2, and 3/4 times the input port size included in the IFFT unit 413.

The IFFT unit 413 can perform IFFT conversion for converting the data stream mapped to the resource from the frequency domain to the time domain. The size of the IFFT-transformed data stream can be obtained by the following equation.

Here, ifft (x) may be a function related to an IFFT transformation for transforming a data stream mapped to a resource from a frequency domain to a time domain. The IFFT-transformed data stream may be configured on an OFDM symbol basis.

을 포함하고 있을 수 있다. 따라서

을 곱해줌으로써 IFFT 변환된 데이터 스트림의 크기를 조정할 수 있다. IFFT_SIZE는 IFFT부(413)에 포함된 입출력 포트 크기를 지시할 수 있다.ifft (x)

. ≪ / RTI > therefore

The size of the IFFT-converted data stream can be adjusted. The IFFT_SIZE may indicate the size of the input / output port included in the IFFT unit 413. [

으로 표현될 수 있다.The size of the IFFT-transformed data stream can be expressed in units of bits. For example, if the size of the IFFT-transformed data stream is n bits, then the size of the IFFT-

. ≪ / RTI >

Referring again to FIG. 5, the IFFT unit 413 may transmit the IFFT-converted data stream to the normalizing unit 414. [ The normalization unit 414 can receive the IFFT-transformed data stream from the IFFT unit 413.

The normalization unit 414 uses the maximum number of subcarriers received from the bandwidth calculation unit 417 for each TTI and the size of the IFFT-converted data stream received from the IFFT unit 413, The size of the DAC input port and the size of the DAC input port may be matched (S540).

Specifically, the normalization process may be as follows.

Referring again to FIG. 6, the normalization process of the IFFT-transformed data stream can be expressed by the following equation.

으로 표현될 수 있다.y may be the size of the IFFT transformed data stream. y can be expressed in units of bits. For example, if the size of the IFFT-transformed data stream is n bits, then the size of the IFFT-

. ≪ / RTI >

The normalizing unit 414 can adjust the size of the data stream so that the size of the IFFT-converted data stream matches the size of the IFFT input / output port.

The normalization unit 414 may perform rounding to adjust the size of the data stream input to the DAC 415 to match the DAC input port size. How to scale and round the data stream to fit the IFFT input and output port sizes can be included in the normalization process.

The rounding can be performed by the following equation.

Where z can indicate the size of the rounded data stream to fit the DAC input port size. The normalization unit 414 can obtain a normalized data stream having a size of the data stream z.

Here, the number of IFFT output bits may indicate that the size of the output port included in the IFFT 413 is expressed in a bit unit. The number of DAC input bits may indicate that the input port size of the DAC 415 is represented in bit units.

일 수 있다. For example, if the number of input / output bits is n bits, then the input / output port size is n squared of 2

Lt; / RTI >

Referring again to FIG. 5, DAC 415 may receive a normalized data stream to match the DAC input port size.

The DAC 415 may perform DAC conversion of the normalized data stream received from the normalization unit 414 for each TTI (S550). The DAC 415 may obtain the DAC-converted analog signal through the DAC conversion of the normalized data stream.

The DAC 415 may transmit the DAC-converted analog signal to the normalization / reduction unit 416. The normalization reverting unit 416 can receive the DAC-converted analog signal.

The normalization re- duction unit 416 can receive maximum subcarrier number information from the bandwidth calculation unit 417. [ The normalization reverting unit 416 may perform normalization reverting to reduce the magnitude of the signal that was adjusted in the DAC-converted analog signal normalization process (S560).

Specifically, the normalization reduction process may be as follows.

Referring again to FIG. 6, the normalization reverting unit 416 may perform normalization and reduction of the DAC-converted data stream. The normalization and reduction can be performed by the following equation.

The normalization re- duction unit 416 can use the maximum subcarrier number information received from the bandwidth calculation unit 417 for each TTI for normalization and reduction.

을 DAC 변환된 아날로그 신호에 곱할 수 있다.The normalization and reduction unit 416 normalizes Reciprocal of

Can be multiplied by the DAC-converted analog signal.

The normalization / reduction unit 416 may obtain a reduced analog signal through a normalization / reduction process.

Referring again to FIG. 5, the normalization / reduction unit 416 may transmit the reduced analog signal to the RF unit 420. The RF unit 420 can transmit the analog signal received from the reducing unit 416. [

7 is a block diagram illustrating one embodiment of a system for performing simulations of embodiments of a communication method.

Referring to FIG. 7, the normalization / reduction unit 416 may transmit the reduced analog signal to the FFT unit 710.

The reduced data stream may include an additive white Gaussian noise (AWGN) The AWGN may be a noise having a normal distribution. The normalization and reduction unit 416 may transmit the reduced analog signal including the noise to the FFT unit 710.

The channel generator 411 may transmit the data stream to an uncoded bit error rate (uncoded BER) calculator 750.

The FFT unit 710 may transmit the reduced analog signal including the noise to the equalizer 720 and the channel estimator 730. The channel estimator 730 may receive the reduced analog signal containing noise and perform channel estimation.

The channel estimation unit 730 may transmit the channel estimated analog signal to the equalizer 720. [ The equalizer 720 may indicate an apparatus that adjusts the received signal by adjusting the relative intensity of each signal including the various frequency bands.

The equalizer 720 may emphasize or reduce a particular frequency band. The equalizer 720 may transmit the intensity adjusted analog signal to a hard decision 740.

The hard decision 740 can distinguish between 0 and 1 in the intensity adjusted data stream. The hard decision 740 may indicate a device having the ability to distinguish between 0 and 1 from the intensity adjusted data stream. The hard decision unit 740 can transmit an analog signal, which is divided into 0s and 1s, to the bit error calculator 750.

The bit error rate calculator 750 can calculate the bit error rate based on the channel number information received from the channel generator 411 and the data stream divided by 0 and 1 received from the hard decision unit 740 .

The bit error rate measurement simulation of the present invention for confirming the transmission signal quality may include a normalization unit 414 and a normalization reduction unit 416. [ The simulation of the present invention can be performed by measuring a bit error rate when noise is included in a transmission signal, that is, an analog signal.

The conventional bit error rate measurement simulation for confirming the transmission signal quality may not include the normalization unit 414 and the normalization reduction unit 416 in the configuration of FIG. That is, the conventional simulation can be performed by measuring the bit error rate without normalization and normalization reduction.

8 to 13 may be a value obtained by fixing the input / output port size of the IFFT unit 413 to 1024 and measuring the bit error rate.

8 is a graph illustrating a bit error rate when the number of subcarriers is 12 according to a conventional method.

9 is a graph illustrating a bit error rate when the number of subcarriers is 12 according to the proposed method.

Referring to Figures 8 and 9, the vertical axis of the graph may indicate the bit error rate. The abscissa of the graph indicates the signal-to-noise ratio in digital communication as Eb / No (energy per bit to noise power spectral density ratio).

The graph of FIG. 8 may be a result of an experiment using a conventional method that does not include the normalization unit 414 and the normalization reduction unit 416 in the configuration of FIG. The graph of FIG. 9 may be a result of an experiment using the proposed method including the normalizing unit 414 and the normalizing and reducing unit 416 in the configuration of FIG.

If the number of DAC input bits is 4 bits, the DAC input port size can be 16, which is 4 of 2. If the number of DAC input bits is 5 bits, the DAC input port size can be 32, which is 5 of 2 squared.

If the number of DAC input bits is 6 bits, the DAC input port size can be 64, which is 6 of 2. If the number of DAC input bits is 7 bits, the DAC input port size can be 128, which is 7 of 2.

If the number of DAC input bits is 8 bits, the DAC input port size can be 256, which is the power of 2, the power of 8.

In this graph, the number of subcarriers is set to 12, and the number of DAC input bits is increased from 4 to 8, which can be an experimental result. When the number of DAC input bits is 5 bits or less, it can be confirmed that the bit error rate is lower than that of the graph of FIG. 8 in the graph of FIG. 9 in which the experiment is performed by the proposed method.

10 is a graph illustrating a bit error rate when the number of subcarriers is 120 according to a conventional method.

11 is a graph illustrating a bit error rate when the number of subcarriers is 120 according to the proposed method.

Referring to Figures 10 and 11, the vertical axis of the graph may indicate the bit error rate. The abscissa of the graph indicates the signal-to-noise ratio in digital communication as Eb / No.

The graph of FIG. 10 may be a result of a conventional method in which the normalizing unit 414 and the normalizing and reducing unit 416 are not included in the configuration of FIG. The graph of FIG. 11 may be a result of an experiment using the proposed method including the normalizing unit 414 and the normalizing and reducing unit 416 in the configuration of FIG.

In this graph, the number of subcarriers is 120, and the number of DAC input bits is increased from 4 to 8, which can be an experimental result. When the number of DAC input bits is 4 bits or less, it can be confirmed that the bit error rate is lower than the graph of FIG. 10 in the graph of FIG. 11 in which the experiment is performed by the proposed method.

12 is a graph illustrating a bit error rate when the number of subcarriers is 600 according to a conventional method.

13 is a graph illustrating a bit error rate when the number of subcarriers is 600 according to the proposed method.

Referring to Figures 12 and 13, the vertical axis of the graph can indicate the bit error rate. The abscissa of the graph indicates the signal-to-noise ratio in digital communication as Eb / No.

The graph of FIG. 12 may be a result of an experiment using a conventional method that does not include the normalizing unit 414 and the normalizing and reducing unit 416 in the configuration of FIG. 13 may be a result of an experiment using the proposed method including the normalizing unit 414 and the normalizing reducing unit 416 in the configuration of FIG.

In this graph, the number of subcarriers is set to 12, and the number of DAC input bits is increased from 4 to 8, which can be an experimental result. When the number of DAC input bits is 4 bits or less, it can be confirmed that the bit error rate is lower than the graph of FIG. 12 in the graph of FIG. 13 where the experiment is performed by the proposed method.

The methods according to the present invention can be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the computer readable medium may be those specially designed and constructed for the present invention or may be available to those skilled in the computer software.

Examples of computer readable media include hardware devices that are specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by the compiler 1, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims (1)

A signal processing method performed at a communication node,
Generating a data stream based on the number of subcarriers per channel;
Based on a maximum number of subcarriers among the number of subcarriers per channel, an IFFT (Inverse Fast Fourier Transform) port size included in the communication node, and a DAC (digital analog convert) port size included in the communication node, Performing a normalization on the output data stream such that a size of a data stream output from the DAC corresponds to a size of the DAC port;
Performing a reduction on the data stream output from the DAC port based on the maximum number of subcarriers and the IFFT port size; And
And transmitting the reduced data stream.

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