Receiver and related signal processing method

Abstract

The present invention discloses a signal processing method, which comprises the following steps: using an FFT window to process the last symbol of a first subframe in a frame to generate a frequency domain signal, wherein the FFT window has a first FFT window starting point; performing an IFFT operation according to the frequency domain signal to generate a channel impulse response; performing channel estimation on the channel impulse response to generate a channel profile; determining a second FFT window starting point according to the channel profile of the last symbol of the first subframe, the attribute of the first symbol of the second subframe in the frame, and the first FFT window starting point; and using the FFT window having the second FFT window starting point to process the first symbol of the second subframe in the frame to generate another frequency domain signal.

Description

Technical Field

[0001] The present invention relates to a receiver disposed in a display. Background Art

[0002] In the Advanced Television Systems Committee (ATSC) version 3.0 specification, a frame architecture for use in an orthogonal frequency-division multiplexing (OFDM) system is disclosed, wherein each frame includes a plurality of subframes, and each subframe may have different parameters, for example, each frame may have a different Fast Fourier Transform (FFT) length, a different guard interval length, or a different scattered pilot pattern. Therefore, when switching to the next subframe with different parameters, inter-symbol interference (ISI) may occur in the channel estimation operation due to a poorly selected FFT window position, or a poorly configured position of a channel impulse response (CIR), resulting in a reduction in subsequent decoding performance or failure to perform decoding correctly. Summary of the invention

[0003] Therefore, one of the objectives of the present invention is to provide a receiver disposed in a display, which can perform a channel estimation operation on a current subframe according to a portion of parameters used in a previous subframe, so as to solve the problem in the subframe switching process in the prior art.

[0004] In one embodiment of the present invention, a signal processing method is disclosed, which includes the following steps: using an FFT window to process the last symbol of a first subframe in a frame to generate a first frequency domain signal, wherein the FFT window has a first FFT window starting point; performing an IFFT operation based on the first frequency domain signal to generate a first channel impulse response; performing channel estimation on the first channel impulse response to generate a first channel profile of the last symbol of the first subframe; determining a second FFT window starting point based on the first channel profile of the last symbol of the first subframe, the properties of the first symbol of the second subframe in the frame, and the first FFT window starting point; and using the FFT window having the second FFT window starting point to process the first symbol of the second subframe in the frame to generate a second frequency domain signal.

[0005] In one embodiment of the present invention, a receiver is disclosed, which includes an FFT circuit, an IFFT circuit, a channel estimation circuit, and an FFT window starting point calculation circuit. The FFT circuit uses an FFT window to process the last symbol of a first subframe in a frame to generate a first frequency domain signal, wherein the FFT window has a first FFT window starting point; the IFFT circuit performs an IFFT operation according to the first frequency domain signal to generate a first channel impulse response; the channel estimation circuit performs channel estimation on the first channel impulse response to generate a first channel profile of the last symbol of the first subframe; and the FFT window starting point calculation circuit determines a second FFT window starting point according to the first channel profile of the last symbol of the first subframe, the attribute of the first symbol of the second subframe in the frame, and the first FFT window starting point, wherein the FFT circuit uses the FFT window with the second FFT window starting point to process the first symbol of the second subframe in the frame to generate a second frequency domain signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 FIG. 1 is a schematic diagram of a receiver according to an embodiment of the present invention.

[0007] Figure 2 A schematic diagram of the architecture for receiving signals compliant with ATSC version 3.0.

[0008] Figure 3 Schematic diagram of an OFDM symbol and FFT window.

[0009] Figure 4 It is a schematic diagram of the frequency domain signal.

[0010] Figure 5 Schematic diagram of the channel impulse response.

[0011] Figure 6 Schematic diagram of shifting the channel impulse response by an offset.

[0012] Figure 7 The figure is a flowchart of a signal processing method applied in a receiver according to an embodiment of the present invention. DETAILED DESCRIPTION

[0013] Figure 1 FIG. 1 is a schematic diagram of a receiver 100 according to an embodiment of the present invention. Figure 1As shown, the receiver 100 includes an FFT circuit 110, a scattered pilot processing circuit 120, an Inverse Fast Fourier Transform (IFFT) circuit 130, a channel estimation circuit 140, and an FFT window start point calculation circuit 150. In this embodiment, the receiver 100 is disposed in a display, such as a television, and the operation of the receiver 100 supports the ATSC version 3.0 standard, however, the present invention is not limited thereto.

[0014] In the operation of the receiver 100, it is assumed that the received signal received by the receiver 100 is a received signal compliant with ATSC version 3.0, and the received signal has the following characteristics: Figure 2 The architecture shown. Figure 2 As shown, a frame of the received signal sequentially includes a bootstrap signal 210, a preamble signal 220 and a plurality of subframes ( Figure 2 n subframes SF0 to SFn are shown, wherein the preamble 210 is used for the receiver 100 to identify, and the preamble 220 includes the relevant attributes of the subframes SF0 to SFn, such as the FFT length and guard interval length of the OFDM symbol in each subframe SF0 to SFn, and the scattered pilot pattern, etc. When the receiver 100 receives a signal with Figure 2 In the frame shown, the FFT circuit 110 performs a fast Fourier transform on the received signal to generate a frequency domain signal. Figure 3 , an OFDM symbol includes a guard interval and data, wherein the content of the guard interval is copied from the latter content of the data, and the guard interval includes a non-inter-symbol interference region (ISI free region), that is, when the FFT circuit 110 performs a fast Fourier transform, the FFT window starting point FFT_start used needs to be located in the non-inter-symbol interference region to avoid subsequent inter-symbol interference. Ideally, the FFT window starting point FFT_start is located in the center of the non-inter-symbol interference region as much as possible. Figure 4A schematic diagram of a frequency domain signal 400 output by the FFT circuit 110 is shown, wherein the frequency domain signal 400 corresponds to a portion of the content of a subframe. The frequency domain signal 400 includes a plurality of scattered pilots and a plurality of data units, wherein the distribution method and number of the scattered pilots constitute a scattered pilot pattern, wherein the frequency domain signal 400 is described by taking the SP3.2 pattern in the ATSC version 3.0 specification as an example, and in this embodiment, the scattered pilot processing circuit 120 performs an interpolation operation on the scattered pilots in the frequency domain signal 400, so that the frequency domain signal 400 has a scattered pilot in every three units after processing. Since the scattered pilot pattern and the processing method of the scattered pilot processing circuit 120 are already well known to those having ordinary knowledge in the art, the relevant details are not repeated here.

[0015] Next, the IFFT circuit 130 performs an inverse fast Fourier transform on the processed frequency signal output by the scattered pilot processing circuit 120 to generate Figure 5 The channel impulse response shown in FIG. 1 includes a main region and multiple image regions, and the number of image regions is determined according to the scattered pilot mode. For example, if there is one scattered pilot in every N cells, the channel impulse response will have (N-1) image regions. Figure 5 The following is an example of a scattered pilot in every three cells. Figure 5 The width of the main region and each mirror region is the FFT window length divided by the above 'N'. For example, assuming that the FFT window length is '8192' and there is a scattered pilot in every three cells (ie, N=3), the width of the main region and each mirror region is '8192 / 3'.

[0016] Next, in the operation of the channel estimation circuit 140, first, referring to Figure 6 , the channel estimation circuit 140 will shift the channel impulse response by a channel offset CC_bias to generate an adjusted channel impulse response, wherein the channel offset CC_bias is used to make the channel impulse response be located in the center of the main area, so as to facilitate subsequent operations on the channel profile. Figure 6 After obtaining the adjusted channel impulse response, the channel estimation circuit 140 performs a filtering operation on the adjusted channel impulse response to filter out the image components therein, and then filters out the noise components in the main area to generate a processed channel impulse response; thereafter, the channel estimation circuit 140 performs a fast Fourier transform operation and an equalization operation on the processed channel impulse response to obtain a channel profile of each OFDM symbol for operation of the back-end circuit.

[0017] In the above operations of the FFT circuit 110, the scattered pilot processing circuit 120, the IFFT circuit 130, and the channel estimation circuit 140, the FFT window starting point FFT_start and the channel offset CC_bias are two important parameters that will affect the subsequent signal processing, and these two parameters can be adjusted to appropriate values ​​after the channel estimation circuit 140 determines the channel profile, so that the FFT window starting point FFT_start is located in the center of the non-inter-symbol interference area, and the adjusted channel impulse response can also be located in the center of the main area. After the FFT window starting point FFT_start and the channel offset CC_bias are adjusted to the optimal values, since the OFDM symbols of the same subframe have the same properties, such as the same FFT length and guard interval length, scattered pilot mode, etc., the subsequent OFDM symbols of the subframe can be processed using the same FFT window starting point FFT_start and channel offset CC_bias.

[0018] However, when the subframe is switched, for example, subframe SF0 switches to subframe SF1, since the properties of subframe SF1 are not completely the same as the properties of subframe SF0, the receiver 100 may use inappropriate FFT window starting point FFT_start and channel offset CC_bias when processing the first symbol of subframe SF1, which may cause difficulties in subsequent processing. Therefore, this embodiment proposes an FFT window starting point calculation circuit 150 to calculate the FFT window starting point FFT_start and channel offset CC_bias used to process the first symbol of subframe SF1 based on the channel configuration file calculated for the last OFDM symbol of subframe SF0 and the properties of subframe SF1; and then adjust the FFT window starting point FFT_start and channel offset CC_bias to the optimal value based on the channel configuration file corresponding to the first OFDM symbol of subframe SF1.

[0019] Specifically, since the channel profiles of two adjacent OFDM symbols are generally not very different, the FFT window starting point calculation circuit 150 directly regards the channel profile calculated for the last OFDM symbol of subframe SF0 as the channel profile of the first OFDM symbol of subframe SF1, and then calculates the FFT window starting point FFT_start and the channel offset CC_bias of the first symbol of subframe SF1 when the receiver 100 processes it according to the attribute difference between subframe SF1 and subframe SF0. ​​For example, the FFT window starting point FFT_start_1 of the first symbol of subframe SF1 can be calculated using the following formula:

[0020] FFT_start_1=FFT_start_0+FFT_size+GI_len_1+FFT_win_adj;

[0021] Wherein 'FFT_start_0' is the starting point of the FFT window used by the receiver 100 when processing the last symbol of the subframe SF0, 'FFT_size' is the FFT length used by the receiver 100 when processing the last symbol of the subframe SF0, 'GI_len_1' is the length of the guard interval of the subframe SF1, and 'FFT_win_adj' is an adjustment amount. 'FFT_win_adj' in the above formula can be obtained according to the difference in properties between the subframe SF1 and the subframe SF0, for example, when the length of the guard interval of the subframe SF1 is greater than the length of the guard interval of the subframe SF0, 'FFT_win_adj' is set to a negative value, and when the length of the guard interval of the subframe SF1 is less than the length of the guard interval of the subframe SF0, 'FFT_win_adj' is set to a positive value. It should be noted that the above calculation method is only used as an example. Since the correlation between the FFT window starting point FFT_start and the channel offset CC_bias and the attribute relationship of the subframe can be obtained from the calculation method of the relevant circuit, the FFT window starting point calculation circuit 150 can infer the FFT window starting point FFT_start and the channel offset CC_bias applicable to the subframe SF1 through the above correlation.

[0022] Figure 7 1 is a flow chart of a signal processing method applied to a receiver 100 according to an embodiment of the present invention. Referring to the contents described in the above embodiments, the flow of the signal processing method is as follows:

[0023] Step 700: The process starts.

[0024] Step 702: Use an FFT window to process the last symbol of a first subframe in a frame to generate a first frequency domain signal, wherein the FFT window has a first FFT window starting point.

[0025] Step 704: Perform an IFFT operation according to the first frequency domain signal to generate a first channel impulse response.

[0026] Step 706: Perform channel estimation on the first channel impulse response according to the first channel offset to generate a first channel profile of the last symbol of the first subframe.

[0027] Step 708: Determine a second FFT window starting point and a second channel offset according to the first channel profile of the last symbol of the first subframe, the attribute of the first symbol of the second subframe in the frame, the first FFT window starting point and the first channel offset.

[0028] Step 710: Use the FFT window having the second FFT window starting point to process the first symbol of the second subframe in the frame to generate a second frequency domain signal.

[0029] Step 712: Perform an IFFT operation according to the second frequency domain signal to generate a second channel impulse response.

[0030] Step 714: Perform channel estimation on the second channel impulse response according to the second channel offset to generate a second channel profile of the first symbol of the second subframe.

[0031] Step 716: Update the second FFT window starting point and the second channel offset according to the second channel profile of the first symbol of the second subframe for use in subsequent symbols of the second subframe.

[0032] To briefly summarize the present invention, in the receiver and related signal processing method of the present invention, the FFT window starting point and channel offset are calculated by using the channel configuration file of the last symbol of the current subframe and the first symbol attribute of the next subframe for use by the first symbol of the next subframe. This can effectively improve the problem of poor subsequent signal quality or reduced decoding performance caused by subframe switching in the prior art.

[0033] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

[0034] Description of Reference Numerals

[0035] 100: Receiver

[0036] 110:FFT circuit

[0037] 120: scattered pilot processing circuit

[0038] 130:IFFT circuit

[0039] 140: Channel estimation circuit

[0040] 150: FFT window starting point calculation circuit

[0041] 210: Preamble signal

[0042] 220: Preamble signal

[0043] 400: Frequency domain signal

[0044] 700~716: Steps

[0045] CC_bias: channel offset

[0046] FFT_start: FFT window starting point

[0047] SF0~SFn: subframe

Claims

1. A signal processing method, comprising: Using a fast Fourier transform (FFT) window to process the last symbol of a first subframe in a frame to generate a first frequency domain signal, wherein the FFT window has a first FFT window starting point; Performing an inverse fast Fourier transform (IFFT) operation according to the first frequency domain signal to generate a first channel impulse response; performing channel estimation on the first channel impulse response to generate a first channel profile of a last symbol of the first subframe; Determine a second FFT window starting point according to a first channel profile of a last symbol of the first subframe, an attribute of a first symbol of a second subframe in the frame, and the first FFT window starting point; as well as The first symbol of the second subframe in the frame is processed using the FFT window having the second FFT window starting point to generate a second frequency domain signal.

2. The signal processing method according to claim 1, further comprising: Performing an IFFT operation according to the second frequency domain signal to generate a second channel impulse response; performing channel estimation on the second channel impulse response to generate a second channel profile for a first symbol of the second subframe; and The second FFT window starting point is updated according to the second channel configuration file to generate an updated second FFT window starting point for use in subsequent symbols of the second subframe.

3. The signal processing method as claimed in claim 1, wherein the step of performing channel estimation on the first channel impulse response to generate a first channel profile of the last symbol of the first subframe comprises: shifting the first channel impulse response by a first channel offset to generate an adjusted first channel impulse response; filtering the adjusted first channel impulse response to generate a processed first channel offset; as well as Generating a first channel profile of a last symbol of the first subframe according to the processed first channel offset; as well as The signal processing method also includes: A second channel offset is determined according to a first channel profile of a last symbol of the first subframe, an attribute of a first symbol of a second subframe in the frame, and the first channel offset.

4. A receiver comprising: A fast Fourier transform (FFT) circuit, used to process the last symbol of the first subframe in the frame using an FFT window to generate a first frequency domain signal, wherein the FFT window has a first FFT window starting point; An inverse fast Fourier transform (IFFT) circuit, configured to perform an IFFT operation according to the first frequency domain signal to generate a first channel impulse response; a channel estimation circuit, configured to perform channel estimation on the first channel impulse response to generate a first channel profile of a last symbol of the first subframe; as well as An FFT window starting point calculation circuit is used to determine a second FFT window starting point according to a first channel configuration file of a last symbol of the first subframe, an attribute of a first symbol of a second subframe in the frame, and the first FFT window starting point; The FFT circuit uses the FFT window having the second FFT window starting point to process the first symbol of the second subframe in the frame to generate a second frequency domain signal.

5. The receiver of claim 4 , wherein the IFFT circuit performs an IFFT operation according to the second frequency domain signal to generate a second channel impulse response, the channel estimation circuit performs channel estimation on the second channel impulse response to generate a second channel profile for the first symbol of the second subframe, and the FFT window starting point calculation circuit updates the second FFT window starting point according to the second channel profile to generate an updated second FFT window starting point for use in subsequent symbols of the second subframe.

6. The receiver of claim 4 , wherein the channel estimation circuit shifts the first channel impulse response by a first channel offset to generate an adjusted first channel impulse response, filters the adjusted first channel impulse response to generate a processed first channel offset, and generates a first channel profile of a last symbol of the first subframe according to the processed first channel offset; and the channel estimation circuit determines a second channel offset according to the first channel profile of the last symbol of the first subframe, an attribute of a first symbol of a second subframe in the frame, and the first channel offset.

7. The receiver of claim 6, wherein the IFFT circuit performs an IFFT operation based on the second frequency domain signal to generate a second channel impulse response; the channel estimation circuit shifts the second channel impulse response by a second channel offset to generate an adjusted second channel impulse response, filters the adjusted second channel impulse response to generate a processed second channel offset, and generates a second channel profile for the first symbol of the second subframe based on the processed second channel offset. 8 . The receiver of claim 7 , wherein the channel estimation circuit updates the second channel offset according to the second channel configuration file to generate an updated second channel offset for use in subsequent symbols of the second subframe.

9. The receiver of claim 4, wherein the second subframe has different attributes from the first subframe.

10. The receiver of claim 9, wherein the FFT length, guard interval length, and scattered pilot pattern of each symbol in the second subframe are not completely the same as the FFT length, guard interval length, and scattered pilot pattern of each symbol in the first subframe.

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