KR20150131901A - Method and apparatus for processing a transmit signal in communication system - Google Patents

Abstract

Various embodiments of the present invention are directed to an apparatus and method for processing a transmit signal using a window function that changes the spectral characteristics of a symbol, the apparatus comprising: a symbol generator for generating a plurality of consecutive symbols; And a symbol windowing processor coupled to the symbol generator, wherein the symbol windowing processor applies a third window function using a difference between the first window function and the second window function, Change the spectral characteristics of each of a plurality of consecutive symbols, and process neighboring symbols of the plurality of consecutive symbols for which spectral characteristics have changed, such that some of the neighboring symbols overlap each other. Also, various embodiments are possible.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a transmission signal processing apparatus,

Various embodiments of the present invention are directed to an apparatus and method for processing a transmit signal using a window function that alters the spectral characteristics of a symbol such as a spectrum emission mask or a side-lobe attenuation in a spectrum will be.

Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) divides a data stream having a high data rate into a plurality of data streams having a low data rate, and parallelly divides the data streams into a plurality of parallel data streams using a plurality of subcarriers. . Such OFDM / OFDMA has a high data rate and frequency efficiency, and is robust to a frequency fading channel.

On the other hand, in LTE (Long Term Evolution), which is standardized in 3GPP, a single carrier-frequency division multiple access (SC-FDMA) scheme is used for uplink data transmission.

SC-FDMA can be seen as a modified version of OFDMA. In SC-FDMA, as in OFDMA, the transmitter transmits information symbols using different orthogonal frequencies (subcarriers). However, the transmitter of the SC-FDMA scheme sequentially transmits the sub-carriers, not the simultaneous sub-carriers.

In order to prevent the orthogonality of the subcarriers from being lost due to the channel in the OFDM / OFDMA / SC-FDMA scheme, a guard interval (guard) longer than the delay spread of the channel between the OFDM / OFDMA / SC- interval can be added to eliminate Inter-Symbol Interference (ISI). A CP (Cyclic Prefix) is inserted into the guard interval to ensure continuity of the entire symbol interval including the guard interval. That is, if a part of a symbol is copied and inserted as a CP in the guard interval and placed at the beginning of the symbol, the symbols are cyclically extended to avoid Inter-Carrier Interference (ICI).

In addition, the OFDM / OFDMA / SC-FDMA scheme can implement parallel transmission of subcarriers using Inverse Fast Fourier Transform (IFFT) on the transmitting side and Fast Fourier Transform (FFT) on the receiving side. Accordingly, each of the subcarriers of the OFDM / OFDMA / SC-FDMA signal has a sinc function, and they are overlapped while maintaining the orthogonality between them. Due to the characteristics of the sinc function, the OFDM / OFDMA / SC-FDMA signal is not a band limited signal and has a characteristic of causing interference in the adjacent band.

In order to reduce the adjacent band interference, instead of transmitting data to all the subcarriers in the IFFT frequency band, a method of not transmitting signals to some subcarriers at both ends of the corresponding band is used. However, since the side lobe of the sinc function itself is relatively large, if the adjacent band interference is to be eliminated by only this method, the number of subcarriers that do not transmit data must be increased a lot, and the frequency efficiency becomes significantly worse.

Accordingly, time windowing is mainly used as a method of reducing adjacent band interference while maintaining frequency efficiency. Using time windowing, side-lobes can be effectively reduced. Among these windows used in the windowing technique, a raised cosine window is most commonly used. For example, by reducing the size of the out-of-band spectrum using a window such as the up cosine, interference between adjacent channels can be reduced.

As another example, a technique for attenuating the side-lobe spectrum of a signal may employ a lowpass / bandpass filtering scheme.

However, the coefficient value of the upside cosine window is limited in that the sidelobe attenuation rate is determined in the output spectrum and the degree of attenuation is adjusted only by the roll off factor due to the change of the window length. Therefore, even if this windowing technique is used, a spectrum emission mask may not be satisfied. In this case, an additional low-pass filter (LPF) may be required.

As described above, a technique for attenuating the side lobe spectrum of an output signal in an OFDM / OFDMA / SC-FDMA system is generally a windowing scheme. The windowing method smoothly increases or decreases the rectangular shape of a symbol by applying a cyclic prefix (CP) or a windowing to ascend or descend the data at the end of the symbol. By performing such processing, the sidelobe portion can be attenuated in the sinc-shaped spectrum. The side lobe attenuation is essentially used to meet the spectral emission mask or adjacent channel leakage ratio (ACLR) specified in each communication standard, which minimizes interference to adjacent channels . This spectral attenuation can be achieved with an analog baseband pass filter in the RFIC, but especially where the part very close to the main lobe is difficult to attenuate with an analog filter, it must be handled in the digital domain. Also, the side lobe of the output signal can be increased again due to the non-linear property of the RFIC or the power amplifier (PA) even if the standard specification is satisfied in the output portion of the digital domain. Therefore, it is desirable to determine the margin for the spectral radiant mask or the ALCR in consideration of the non-linear property of the RFIC or the power amplifier.

Various embodiments of the present invention propose a window function to obtain a larger spectral radiant mask or margin value for ALCR than a raised cosine window.

Various embodiments of the present invention can provide a transmitting apparatus and method using a side-lobe position adjustable window (SPAW).

Various embodiments of the present invention may provide an apparatus and method for reducing inter-channel interference using a window function without using a lowpass / bandpass filtering scheme.

According to various embodiments of the present invention, there is provided a transmitting apparatus comprising: a symbol generator for generating a plurality of consecutive symbols; And a symbol windowing processor coupled to the symbol generator, wherein the symbol windowing processor applies a third window function using a difference between the first window function and the first window function and the second window function, Modifies the spectral characteristics of each of the consecutive symbols,

The neighboring symbols among the plurality of consecutive symbols whose spectral characteristics are changed can be processed so that a part thereof overlaps each other.

According to various embodiments of the present invention, there is provided a transmission method comprising: generating a plurality of consecutive symbols; Changing a spectral characteristic of each of the plurality of consecutive symbols by applying a first window function and a third window function using a difference between the first window function and a second window function; And processing the neighboring symbols among the plurality of consecutive symbols for which the spectral characteristic is changed such that a part of the neighboring symbols overlap each other.

According to various embodiments of the present invention, there is provided a transmitter, comprising: a communication modem, the communication modem generating a plurality of consecutive symbols and generating a first window function and a second window function, A third window function using a difference may be applied to change the spectral characteristics of each of the plurality of consecutive symbols and to process the neighboring symbols of the plurality of consecutive symbols whose spectral characteristics have been changed have.

As described above, by changing the degree of side-lobe attenuation in the spectrum of a signal by using a side-lobe position adjustable window (SPAW), it is possible to reduce the side-lobe attenuation in a spectrum larger than a raised cosine window without requiring additional LPF A margin for the spectral radiation mask can be ensured.

값에 따른 윈도윙 형태를 도시하고 있다.
도 8은 본 발명의 다양한 실시 예에 따른 SPAW에서

값에 따른 스펙트럼 변화를 도시하고 있다.
도 9는 본 발명의 다양한 실시 예에 따른 SC-FDMA 방식의 송신기의 동작 흐름도를 도시하고 있다.
도 10은 본 발명의 다양한 실시 예에 따른 OFDM 방식의 송신기의 동작 흐름도를 도시하고 있다.
도 11은 본 발명의 다양한 실시 예에 따른 SPAW를 이용한 심볼 처리 방법을 도시하고 있다.FIG. 1 illustrates an example of using a sinc function for a channel (Inter-symbol Interference (ISI) free channel) without intersymbol interference according to various embodiments of the present invention.
Figure 2 illustrates the frequency response of the channel shown in Figure 1 in accordance with various embodiments of the present invention.
FIG. 3 (a) is a functional block diagram of a transmitter of the SC-FDMA scheme according to various embodiments of the present invention.
FIG. 3 (b) is a functional block diagram of an OFDM transmitter according to various embodiments of the present invention.
FIG. 4 (a) shows a symbol to which a window function according to various embodiments of the present invention is applied.
FIG. 4B shows an example in which a part of two symbols to which a window function according to various embodiments of the present invention is applied is superimposed.
FIG. 5 illustrates a raised cosine window characteristic according to various roll off factors according to various embodiments of the present invention.
FIG. 6 illustrates a spectral change according to a roll-off coefficient of a raised cosine window according to various embodiments of the present invention.
Figure 7 illustrates a side-lobe Position Adjustable Window (SPAW) according to various embodiments of the present invention.

And a windowing type according to a value.
Figure 8 is a block diagram of a SPAW in accordance with various embodiments of the present invention.

Lt; RTI ID = 0.0 > value. ≪ / RTI >
9 is a flowchart illustrating an operation of a transmitter of an SC-FDMA scheme according to various embodiments of the present invention.
10 is a flowchart illustrating an operation of an OFDM transmitter according to various embodiments of the present invention.
FIG. 11 illustrates a symbol processing method using SPAW according to various embodiments of the present invention.

Various embodiments of the invention will now be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and these may be changed according to the intention of the user, the operator, or the like. Therefore, the definition should be based on the contents throughout this specification.

Hereinafter, various embodiments of the present invention will be described with respect to an apparatus and a method for processing a transmission signal by applying a window function. The application of the window function may be defined as a sample unit product of a window function and a time domain sample sequence.

In the following description, the application of the window function can be used with the same meaning as the windowing term.

In the windowing process, the increased symbol length due to the windowing does not change before and after the windowing process by overlapping with the windowed before and after symbols. This is because it uses a rounded cosine window function satisfying the nyquist criterion.

Generally, a Nyquist criterion for a zero ISI condition can be used to create an inter-symbol interference (ISI) free channel as shown in FIG. Assuming that the channel impulse function is h (t), the channel satisfies Equation (1) in the case of a channel without inter-symbol interference.

Here, n is an integer value, and TS is a symbol period. The frequency domain is transformed as shown in Equation (2).

Where H (f) is the Fourier transform function of h (t). In the Nyquist test, the signal sampled in the time domain is given in the form of a Dirac delta function with respect to the sampling time. Or as shown in FIG. 2, the condition that the intersymbol interference becomes zero when the sum of the folded spectrum of the signal in the frequency domain is a constant. In the case of windowing, the duality of the time / frequency domain of the Nyquist test is satisfied. That is, the windowing processes the signal to be constant in the time domain instead of being a constant in the frequency domain. It is used to apply the pulse to the window function of the time domain. That is, if the two symbols to which the window function satisfying the Nyquist criterion are applied overlap each other, the final result is a constant, and therefore, there is no difference in the power before and after the windowing process. If the power difference between the CP interval and the symbol interval is not satisfied, it may affect the power control performance such as time domain automatic gain control (TD-AGC).

The degree of spectral attenuation can be changed by adjusting the windowing length or adjusting the windowing shape as proposed in the present invention. However, in the method of adjusting the windowing length, since the windowing is directly applied to the CP (Cyclic Prefix) part and the end data part of the symbol, the longer the length, the shorter the CP length. There is an effect of degrading the performance of the signal error vector magnitude (EVM). Therefore, there is always a limit to how the window wing length is increased.

The Long Term Evolution (LTE) standard supports variable system bandwidth, especially in the 3 MHz bandwidth, since the spectrum emission mask starts from a very close distance, which is only 150 kHz away from the main signal, it is difficult to meet the specifications of the spectrum emission mask. Table 1 below shows the margins at the beginning of the spectral radiant mask using the up-angle cosine window with the 1RB PUSCH signal being located at the rightmost or leftmost position in the 3 MHz bandwidth and transmitting at the maximum power of 23 dBm. That is, the margin for power measured at 1.5M-30 / 2kHz to 1.5M + 30 / 2kHz is shown. As a result of the conventional method, a margin of 4 dB is obtained even when 32 samples of the window size are used. In this case, since the CP length is 40 samples (only the first symbol in the LTE slot when IFFT 512 is used) or 36 samples (the remaining symbols when IFFT 512 is used), a large part of the CP occupies a windowing region. The signal can be distorted. Here, the margin may be measured based on the spectrum measured at the digital final stage.

Windowing size at 3MHz 4 8 12 16 20 24 32 Sepctrum emission mask margin (dB) -3.1911 -3.0868 -2.5832 -1.7849 -0.7191 1.4036 3.9689

If the original signal is distorted by multiplying the signal with the long windowing coefficient by the CP section signal, it will adversely affect frequency or time synchronization and tracking systems such as time domain automatic frequency control (TD-AFC) using a correlation method The performance of the entire communication system can be degraded. Therefore, it is desirable to minimize the distortion of the CP section signal while satisfying the spectrum. Therefore, rather than adjusting the spectrum by increasing the windowing length, a method of adjusting the windowing function as proposed in the present invention may be preferable.

If you want to get enough spectrum margins while reducing the windowing size conventionally, you can use additional LPF as well as windowing. Since the LPF requires a finite-impulse-response (FIR) structure having many taps in order to attenuate directly from the 150 kHz portion of the main signal while maintaining a very small passband ripple, not only is the overall hardware size increased, Filter can cause a lot of power consumption in the terminal.

FIG. 3 (a) is a functional block diagram of a transmitter of the SC-FDMA scheme according to various embodiments of the present invention.

Referring to FIG. 3A, the SC-FDMA transmitter includes an N-point DFT 301, a subcarrier mapper 303, an M-point IFFT 305, a CP inserter 307, a symbol windowing processor 309, and an interpolation filter unit 311.

At the input of the transmitter, the baseband modulator (not shown) converts the binary inputs into various types of signals, including binary phase shift keying (BPSK), quaternary PSK, 16-level quadrature amplitude modulation (16-QAM) Into a sequence of complex numbers in one of the possible modulation formats. The transmitter adopts a modulation format that conforms to the current channel state, and thereby can adopt a transmission bit rate.

The transmitter groups the modulation symbols into blocks each containing N symbols. The first step of SC-FDMA subcarrier modulation is to perform an N-point discrete Fourier transform with an N-point DFT (Discrete Fourier Transform) 301 to generate symbols in the frequency domain in time domain symbols. Although not shown, a serial / parallel conversion unit may be added to convert the serial symbols to parallel symbols before performing the DFT.

Then, the subcarrier mapper 303 may map each of the N DFT outputs to one of M transmittable (M> N) orthogonal subcarriers. The typical value of M is 1024 or 2048 subcarriers and N = M / Q is an integer that is a divisor of M. Q is the bandwidth extension factor of the symbol sequence. If all terminals transmit N symbols per block, the system can potentially handle Q simultaneous transmissions without co-channel interference. The result of the subcarrier mapping is a complex subcarrier amplitude set (l = 0, 1, 2, ..., M-1), where N of amplitude is not zero.

For example, the IFFT is essentially a summation of M orthogonally modulated subcarriers at various offset frequencies (from the carrier frequency), and the IFFT is a summation of M orthogonally modulated subcarriers at various offset frequencies Inverse fast Fourier transform is performed to generate a symbol sequence in the time domain. Although not shown, a parallel / serial transform unit for converting a time domain parallel signal to an IFFT is serially added.

In various embodiments, inverse discrete Fourier transform (IDFT) may be performed instead of IFFT.

CP inserter 307 adds a symbol set called a cyclic prefix (CP) to the complex time-domain symbol sequence to provide a guard time to prevent inter-block interference (IBI) due to multipath propagation.

The symbol windowing processor 309 applies the window function of the time domain to the time-domain sample sequence of the symbol to match the specified spectral emission mask and adds the portions of adjacent symbols close to the edges of the time- Can be overlapped. In various embodiments, the symbol windowing processor 309 may include a Hanning window function, or a Triangular window function, or a SideWing (window) function, which is a linear combination of the Hanning window function and the triangular window function. lobe Position Adjustable Window) to process the edge of the symbol.

The interpolation filter unit 311 performs interpolation twice or four times with respect to the windowed processed time domain signal.

FIG. 3 (b) is a functional block diagram of an OFDM transmitter according to various embodiments of the present invention.

Referring to FIG. 3B, the S / P converter 300, the subcarrier mapper 302, the IFFT 304, the P / S converter 306, the CP inserter 308, the symbol windowing A processor 310, and an interpolation filter unit 312.

The serial / parallel converter 300 converts the serial symbols into parallel symbols, the subcarrier mapper 302 maps the parallel symbols to one of the orthogonal subcarriers, and the IFFT 304 performs inverse fast Fourier transform ), And the parallel / serial converter 306 converts the time-domain parallel signals into serial signals.

CP inserter 307 adds a symbol set called a cyclic prefix (CP) to the complex time-domain symbol sequence to provide a guard time to prevent inter-block interference (IBI) due to multipath propagation.

The symbol windowing processor 310 applies a window function of the time domain to the time-domain sample sequence of the symbol to match the specified spectral emission mask and applies the window function of the time domain to the portions of the adjacent symbols that are close to the edges of the time- Can be overlapped. In various embodiments, the symbol windowing processor 309 may include a Hanning window function, or a Triangular window function, or a SideWing (window) function, which is a linear combination of the Hanning window function and the triangular window function. lobe Position Adjustable Window) to process the edge of the symbol.

The interpolation filter unit 312 performs interpolation twice or four times on the windowed time-domain signal.

FIG. 4 (a) shows a symbol to which a window function according to various embodiments of the present invention is applied.

Referring to FIG. 4A, Ts represents one symbol period as a symbol period, Tg represents a guard interval, and Tb represents an effective symbol interval. As shown in FIG. 4 (a), one symbol consists of a guard interval Tg followed by an effective symbol interval Tb. As described above, the guard interval Tg is copied and inserted as a CP (Cyclic Prefix) after the guard interval Tg during the valid symbol interval Tb. In various embodiments, the guard interval may be zero padded.

In various embodiments, for a signal of one symbol period Ts, the interval from the start of the symbol period Ts to the head window size m is multiplied by Equation (6) or Equation (7) -m is multiplied by 1, and a period from Ns-m to the end of the symbol is multiplied by Equation (6) or Equation (7) to find that one-symbol interval windowing is performed. Here, since the interval from the beginning window size m to Ns-m is multiplied by 1, it is the same as the original signal, and the section of the leading window size m and the window size m of the trailing window are mapped to the original signal This is the windowing interval that gives distortion. Ns is the number of time samples for the symbol period Ts.

FIG. 4B shows an example in which a part of two symbols to which a window function according to various embodiments of the present invention is applied is superimposed.

Referring to FIG. 4B, Ts represents one symbol period as a symbol period, Tg represents a guard interval, and Tb represents an effective symbol interval. The 3-symbol interval windowing scheme is a window scheme in which a signal of a previous symbol and a signal of a next symbol are superimposed on a prefix portion Tprefix and a postfix portion Tpostfix of the current symbol, respectively, as shown in FIG. 4 (b) Technique.

A Hann window or a Hanning window of a plurality of windows can be defined as Equation (3).

It can be confirmed that the handwind function is a special case of the generalized Hamming window defined in Equation (4) below.

The Raised cosine window can be defined as Equation (5), and when the transition period is compared with the hand window, since the values a and b are the same (when the sign is ignored) (constant factor), it can be understood that they are the same window function.

Here, 0??? 1.

FIG. 5 shows the characteristic of the upward cosine window function due to the change of the roll-off coefficient beta.

Referring to FIG. 5, in Equation (5), β denotes a roll-off factor that is a ratio of the window length to the total symbol length.

FIG. 6 shows a spectrum of a 64 subcarrier OFDM / SC_FDMA system to which the raised cosine window function is applied according to the change of the roll-off coefficient.

Fig. 6 shows the spectral change according to the roll-off factor (change in? In Fig. 5).

Among the many kinds of window functions discussed in the academic world, Hann (Hanning), Hamming, Triangular, Rectangular (flat-top), Parzen, Welch, Blackman, Nuttall, Gaussian, Tukey, Slepian, Kaiser There is a window function of. Among these, the window function satisfying the Nyquist criterion is limited to Hann, Triangular, and Rectangular window. Therefore, using other window functions other than these window functions can not be used in the system because the power becomes larger or smaller when windows are overlapped with each other.

In the present invention, a SPAW (Side-lobe Position Adjustable Window) capable of spectral control is proposed. SPAW is a linear combination of the Hanning window function and the triangular window function satisfying the Nyquist criterion, and can be defined as Equation (6).

Equation (6) can be expressed as Equation (7) below.

Here, L _length means a window length that ascending or descending. Equation (6) or Equation (7) can be derived as a linear combination of a Hanning window and a triangular window satisfying the Nyquist detection method.

)이며, 두 번째 항은 해닝 윈도우

와 삼각 윈도우의 차로 나타낼 수 있다.The first term in Equation (6) is a triangular window portion

), The second term is the Hanning window

And the triangular window.

The windowing coefficient value proposed by the value of alpha in Equation (6) or Equation (7) is different, and when? Is 0, the triangular window is equal to 1, and when it is 1, it is equal to the Hanning window coefficient. FIG. 7 is a graph illustrating window coefficient values when an interval in the range of -1.9 < = alpha &lt; = 1.0 is changed to 0.1 interval in Equation (6) or Equation (7). Since the triangular window and the Hanning window basically satisfy the Nyquist test method, even if? Changes, the Nyquist test method can be satisfied (the amplitude value is 0.5 in the x-axis 16th sample in FIG. 7, ). Also, in general, a value of greater than 0 and less than 1 is applied, but in various embodiments of the present invention the value is not limited and may have a negative value and a value greater than one.

값에 따른 스펙트럼 변화를 도시하고 있다.Figure 8 is a block diagram of a SPAW in accordance with various embodiments of the present invention.

Lt; RTI ID = 0.0 &gt; value. &Lt; / RTI &gt;

) 그 다음 삼각 윈도우(triangular window) 함수(α=0)일 때가 크고(

) 올림형 코사인 윈도우(raised cosine window) 함수(α=1)가 가장 적다. 예컨대, 올림형 코사인 윈도우 함수의 경우 스펙트럼 방사 마스크에 대한 마진이 거의 없다.Referring to FIG. 8, the margin for the spectrum emission mask is the largest when SPAW (α = -1.1) at the beginning of the spectrum emission mask is one example

) Then the triangular window function (α = 0) is large (

) The least raised cosine window function (α = 1) is the least. For example, in the case of the upside cosine window function, there is little margin for spectrum emission mask.

FIG. 8 shows a result of a spectrum change due to a change in value when a PUSCH signal having an RB size of 1 RB and an RB offset of 14 is transmitted at a maximum power of 23 dBm in an LTE 3 MHz bandwidth. In FIG. 8, lines 810 and 820 show General E-UTRA spectrum emission masks specified in 3GPP TS36.101 shown in Table 2 below. In Table 3 below, the margin values for the spectrum emission mask for various values of alpha were measured for several intervals. The result of the conventional method, raised cosine windowing, shows about 1dB margin, but it shows that the margin increases to 8.6dB when α value is -1.5. However, in this case, since the margin decreases in the other area, the value of α is set to -1.1 when it is determined from the whole viewpoint. These margins can be changed by the analog LPF on the back of the DAC. Even if the margin is low, the part where the analog filtering is sufficient can be compensated by the analog filtering, so that the influence is not great. However, since analog filtering is very difficult at the beginning of the spectrum emission mask measurement, the proposed windowing method can be very useful because the signal must be output to the DAC with sufficient margin in digital.

Spectrum emission limit (dBm) / Channel bandwidth ? F _OOB (MHz) 1.4MHz 3.0MHz 5MHz 10MHz 15MHz 20MHz Measurement bandwidth ± 0-1 -10 -13 -15 -18 -20 -21 30 kHz ± 1-2.5 -10 -10 -10 -10 -10 -10 1 MHz ± 2.5-2.8 -25 -10 -10 -10 -10 -10 1 MHz ± 2.8-5 -10 -10 -10 -10 -10 1 MHz ± 5-6 -25 -13 -13 -13 -13 1 MHz ± 6-10 -25 -13 -13 -13 1 MHz ± 10-15 -25 -13 -13 1 MHz ± 15-20 -25 -13 1 MHz ± 20-25 -25 1 MHz

Window size 24 Spectrum emission mask margin (dB) alpha value 1.5MHz Centered 30kHz Margin measured at BW Margins measured at 1.65MHz center 30k BW Margins measured at 2.5 MHz center 30k BW EVM (dB) -1.9 8.3064 5.4995 30.4888 -35.08 -1.5 8.6324 7.1813 31.2689 -35.34 -1.4 8.5631 7.6711 31.5599 -36.11 -1.3 8.4581 8.1719 31.8749 -36.38 -1.2 8.2845 8.7021 32.0838 -36.67 -1.1 8.0805 9.267 32.2395 -37.27 -One 7.8304 9.853 32.4459 -37.58 -0.9 7.8304 10.5083 32.6038 -37.9 -0.8 7.2398 11.2034 32.9725 -38.25 -0.7 6.9304 11.9485 33.1399 -38.59 -0.6 6.5911 12.7685 33.3046 -38.97 -0.5 6.2409 13.6326 33.637 -39.35 0 4.4999 19.498 34.5859 -41.51 0.5 2.8666 21.5285 35.0452 -44.29 One 1.4091 15.1636 35.4043 -47.96

9 is a flowchart illustrating an operation of a transmitter of an SC-FDMA scheme according to various embodiments of the present invention.

Referring to FIG. 9, the SC-FDMA transmitter performs DFT processing on a data symbol in operation 900, allocates a data symbol to a desired frequency domain position in operation 902, performs IFFT processing in operation 904, And the windowing is performed using the SPAW function in operation 908, and the interpolation is performed in operation 910.

For example, in the windowing operation, the end of data necessary for SPAW processing of the next symbol is stored in the buffer. Therefore, the SPAW scheme can be applied simultaneously to the end portion of the stored previous symbol and the portion before the current symbol CP. SPAW ascending in the CP of the current symbol and SPAW descending in the previous symbol data are simultaneously processed so that these two signals are superimposed and output. The descending SPAW has ascending SPAW has a symmetric structure with respect to the intermediate point.

10 is a flowchart illustrating an operation of an OFDM transmitter according to various embodiments of the present invention.

Referring to FIG. 10, the OFDM transmitter converts a serial data symbol to a parallel data symbol in operation 1000, allocates a data symbol to a desired frequency domain position in operation 1002, performs IFFT processing in operation 1004, The parallel signal of the area is converted to serial, the CP is attached to the front part of the symbol in operation 1008, the windowing is performed using the SPAW function in operation 1008, and the interpolation is performed in operation 1010.

For example, the OFDM transmitter constitutes the same transmission path as the SC-FDMA transmitter, but the DFT processing in the OFDM transmitter is omitted. In addition, in the case of using the conventional upside cosine window method, a margin for the additional spectrum emission mask is obtained only by using a high order low pass filter (LPF) after the windowing process. If the main-lobe and side-lobes in the spectrum are very close (eg LTE uplink 1.4M, 3M case), a high-order low-pass filter can only be used to achieve greater attenuation of the sidelobes . However, even if the value of the parameter? Is changed in the SPAW function proposed in the present invention, a margin for a sufficient spectral radiation mask is obtained, so that a high-order low-pass filter becomes unnecessary.

FIG. 11 illustrates a symbol processing method using SPAW according to various embodiments of the present invention.

Referring to FIG. 11, the symbol windowing processors 309 and 310 perform a windowing operation using the SPAW function (see FIG. 4A) at the end of the first symbol in operation 1100, (For example, CP) of the second symbol is subjected to windowing using the SPAW function (see FIG. 4A), and the two windows windowed by the SPAW method are superimposed and output 4 (b)). And perform oversampling and interpolation on the superimposed symbols in 1106 operation.

Although a linear combination of the triangular window and the Hanning window is exemplified, it is composed of several linear combinations of Hann, Hanning, Raised cosine, and Triangular window functions satisfying the specifications of the spectrum emission mask or ACLR and satisfying the Nyquist criterion .

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

301: DFT unit, 303: subcarrier mapper
305: M-point IFFT, 307: CP inserter,
309: Symbol windowing processor, 311: Interpolation filter unit,
300: serial / parallel conversion unit, 302: subcarrier mapper,
304: IFFT, 306: parallel / serial conversion unit,
308: CP inserter, 310: Symbol windowing processor,
312: interpolation filter section.

Claims (20)

In the transmitting apparatus,
A symbol generator for generating a plurality of consecutive symbols; And
A symbol windowing processor coupled to the symbol generator,
Wherein the symbol windowing processor comprises:
A third window function using a difference between the first window function and the first window function and the second window function is applied to change spectral characteristics of each of the plurality of consecutive symbols,
And processes the neighboring symbols among the plurality of consecutive symbols whose spectral characteristics have been changed so that a part thereof overlaps each other.
The method according to claim 1,
Wherein the first window function is a triangular window function, the second window function is a Hanning window function,
Wherein the first window function is a Hanning window function and the second window function is a triangular window function.
The method according to claim 1,
Wherein the third window function is defined by the following equation.

here,

,

Is a parameter that determines the degree of side-lobe spectral attenuation of the output signal.
The method according to claim 1,
The spectral characteristics of the symbol
A transmitter that is a spectrum emission mask or Adjacent Channel Leakage Ratio (ACLR).
The method according to claim 1,
If the symbol is an SC-FDMA (Single Carrier Frequency Division Multiple Access) symbol,
For N modulated data symbol groups,
A DFT unit for performing an N-point discrete Fourier transform (DFT) on the N modulated data symbols to generate a set of N frequency-domain components of the N modulated data symbols;
A subcarrier mapper for mapping the N frequency domain components of the N modulated data symbols to N subcarriers of subband M subcarrier widths (M > N) to generate a set of M complex subcarrier amplitudes;
Performing an M-point Inverse Fast Fourier Transform on the set of M complex subcarrier amplitudes to generate a reference sequence of M discrete time domain values to generate a complex time domain signal; And
And a CP insertion unit for adding a cyclic prefix (CP) to the complex time-domain signal.
The method according to claim 1,
If the symbol is an orthogonal frequency division multiplexing (OFDM) symbol,
A serial / parallel converter for converting serial bit data into parallel bit data;
A symbol mapping unit for mapping a bit data packet from the serial / parallel conversion unit into a predetermined symbol packet according to a data size of a predetermined unit bit;
An IFFT unit for performing inverse fast Fourier transform (IFFT) on a symbol packet from the symbol mapping unit and converting a symbol packet in a frequency domain into a symbol packet in a time domain;
A parallel / serial converter for converting a parallel symbol packet from the IFFT unit into a serial symbol packet; And
And a CP inserter forming a symbol transmission packet by adding a cyclic prefix (CP) to the symbol packet from the parallel / serial converter (14).
The method according to claim 1,
Wherein a region where a part of the two consecutive symbols overlap is a cyclic prefix (CP) of a symbol.
In the transmission method,
Generating a plurality of consecutive symbols;
Changing a spectral characteristic of each of the plurality of consecutive symbols by applying a first window function and a third window function using a difference between the first window function and a second window function; And
And processing the neighboring symbols of the plurality of consecutive symbols for which spectral characteristics have been changed so that a part thereof overlaps each other.
9. The method of claim 8,
Wherein the first window function is a triangular window function, the second window function is a Hanning window function,
Wherein the first window function is a Hanning window function and the second window function is a triangular window function.
9. The method of claim 8,
Wherein the third window function is defined by the following equation.

here,

,

Is a parameter that determines the degree of side-lobe spectral attenuation of the output signal.
9. The method of claim 8,
The spectral characteristics of the symbol
A spectral emission mask or an Adjacent Channel Leakage Ratio (ACLR).
9. The method of claim 8,
If the symbol is an SC-FDMA (Single Carrier Frequency Division Multiple Access) symbol,
The process of generating the symbol includes:
For N modulated data symbol groups,
Performing an N-point discrete Fourier transform (DFT) on the N modulated data symbols to generate a set of N frequency domain components of the N modulated data symbols;
Mapping the N frequency-domain components of the N modulated data symbols to N subcarriers of sub-M subcarrier widths (M > N) to generate a set of M complex-carrier amplitudes;
Performing an M-point Inverse Fast Fourier Transform on the set of M complex subcarrier amplitudes to generate a reference sequence of M discrete time domain values to generate a complex time domain signal; And
And adding a cyclic prefix (CP) to the complex time-domain signal.
9. The method of claim 8,
If the symbol is an OFDM (Orthogonal Frequency Division Multiplexing) symbol,
Converting serial bit data into parallel bit data;
Mapping a bit data packet from the serial / parallel conversion unit into a predetermined symbol packet according to a data size of a predetermined unit bit;
Converting a symbol packet in a frequency domain into a symbol packet in a time domain by performing inverse fast Fourier transform (IFFT) on the symbol packet from the symbol mapping unit;
Converting a parallel symbol packet from the IFFT unit into a serial symbol packet;
And forming a symbol transmission packet by adding a cyclic prefix (CP) to the symbol packet from the parallel / serial converter (14).
9. The method of claim 8,
Wherein a region where a part of the two consecutive symbols overlap is a cyclic prefix (CP) of a symbol.
In the transmitter,
A communication modem, comprising:
Generating a plurality of consecutive symbols and
A third window function using a difference between the first window function and the first window function and the second window function is applied to change spectral characteristics of each of the plurality of consecutive symbols,
And processing the neighboring symbols among the plurality of consecutive symbols whose spectral characteristics have been changed such that a part of the neighboring symbols overlap each other.
16. The method of claim 15,
Wherein the first window function is a triangular window function, the second window function is a Hanning window function,
Wherein the first window function is a Hanning window function and the second window function is a triangular window function.
16. The method of claim 15,
Wherein the third window function is defined by: &lt; EMI ID = 17.0 &gt;

here,

,

Is a parameter that determines the degree of side-lobe spectral attenuation of the output signal.
16. The method of claim 15,
The spectral characteristics of the symbol
A transmitter that is a spectrum emission mask or Adjacent Channel Leakage Ratio (ACLR).
16. The method of claim 15,
If the symbol is a Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol,
For N modulated data symbol groups,
Performing an N-point discrete Fourier transform (DFT) on the N modulated data symbols to generate a set of N frequency domain components of the N modulated data symbols,
Mapping the N frequency-domain components of the N modulated data symbols to N subcarriers of subband M subcarrier widths (M > N) to generate a set of M complex-carrier amplitudes,
Performing an M-point Inverse Fast Fourier Transform on the set of M complex subcarrier amplitudes to generate a reference sequence of M discrete time domain values to generate a complex time domain signal,
And adding a cyclic prefix (CP) to the complex time-domain signal.
16. The method of claim 15,
If the symbol is an OFDM (Orthogonal Frequency Division Multiplexing) symbol,
Converts serial bit data into parallel bit data,
A bit-data packet from the serial-to-parallel conversion unit is mapped to a predetermined symbol packet according to a data size of a predetermined unit bit,
(IFFT) the symbol packet from the symbol mapping unit to convert the symbol packet in the frequency domain into a symbol packet in the time domain,
Converts the parallel symbol packet from the IFFT unit into a serial symbol packet,
And forms a symbol transmission packet by adding a cyclic prefix (CP) to the symbol packet from the parallel / serial converter (14).

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