# US 2010/0166126 A1 · Ofdm reception device, ofdm reception integrated circuit, ofdm reception method, and ofdm reception program

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- Number: US 2010/0166126 A1
- Document ID: US20100166126A1
- Status: Published application
- Kind: A1
- Application number: 12/438,051
- Filed: 2008-01-08
- Published: 2010-07-01
- Earliest claimed: 2007-01-12
- Assignees: Panasonic Corporation
- Inventors: Yoshinobu Matsumura; Tomohiro Kimura
- Web page: https://patentgrep.com/patent/US20100166126A1

## CPC

- H04W 52/282: {taking into account the speed of the mobile}
- H04L 25/022: {of frequency response}
- H04L 25/0232: {by interpolation between sounding signals}
- H04L 25/03159: {operating in the frequency domain (H04L25/03165, H04L25/03178 take precedence)}
- H04L 25/03821: {Inter-carrier interference cancellation [ICI]}
- H04L 27/2647: {Arrangements specific to the receiver only (equalisation H04L27/01)}
- H04W 52/24: using SIR [Signal to Interference Ratio] or other wireless path parameters
- H04B 7/12: Frequency diversity
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04B: TRANSMISSION

## Abstract

An OFDM reception apparatus is provided that effectively suppresses a reduction in reception performance during high-speed mobile reception, thereby making it possible to achieve stable and high-speed mobile reception. To achieve this, the OFDM reception apparatus includes a transmission channel characteristic estimating unit for calculating a transmission channel characteristic value indicating phase and amplitude distortions in an OFDM signal for each sub-carrier, the phase and amplitude distortions occurring during propagation through a transmission channel, and calculating an n-th differentiation of the transmission channel characteristic value, and an interference component removing unit for using the transmission channel characteristic value and the n-th differentiation calculated for each of the sub-carriers by the transmission channel characteristic estimating unit, to remove an interference component between the sub-carriers from the OFDM signal. The transmission channel characteristic estimating unit performs a filtering process in a symbol direction with respect to the transmission channel characteristic value calculated for each of the sub-carriers to perform oversampling at intervals each smaller than a one-symbol interval, and uses transmission channel characteristic values existing in intervals each smaller than a two-symbol interval of the transmission channel characteristic values obtained by the oversampling to calculate the n-th differentiations.

## Claims

### Claim 1

An OFDM reception apparatus for receiving an OFDM signal including a plurality of sub-carriers arranged in a symbol direction and a carrier direction, via a transmission channel, the device comprising:
an orthogonal transform unit for performing orthogonal transform with respect to the received OFDM signal from a time domain into a frequency domain, to generate an OFDM signal in the frequency domain;
a first transmission channel characteristic estimating unit for calculating a transmission channel characteristic value indicating phase and amplitude distortions in the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers, the phase and amplitude distortions occurring during propagation through the transmission channel, and calculating an n-th (n is a natural number) differentiation of the transmission channel characteristic value for each of the sub-carriers; and
an interference component removing unit for using the transmission channel characteristic value and the n-th differentiation calculated for each of the sub-carriers by the first transmission channel characteristic estimating unit, to remove an interference component between the sub-carriers adjacent to each other in the symbol direction or the carrier direction, from the OFDM signal generated by the orthogonal transform unit,
wherein the first transmission channel characteristic estimating unit performs a filtering process in the symbol direction with respect to the transmission channel characteristic value calculated for each of the sub-carriers to perform oversampling at intervals each smaller than a one-symbol interval, and uses transmission channel characteristic values existing in intervals each smaller than two-symbol interval of the transmission channel characteristic values obtained by the oversampling to calculate the n-th differentiations.

### Claim 2 (depends on 1)

The OFDM reception apparatus according to claim 1, wherein
the interference component removing unit removes an ICI component that is an interference component between the sub-carriers adjacent to each other in the carrier direction.

### Claim 3 (depends on 2)

The OFDM reception apparatus according to claim 2, wherein
the first transmission channel characteristic estimating unit calculates a first differentiation of the transmission channel characteristic value calculated for each of the sub-carriers.

### Claim 4 (depends on 3)

The OFDM reception apparatus according to claim 3, wherein
the first differentiation of the transmission channel characteristic value calculated for each of the sub-carriers by the first transmission channel characteristic estimating unit, is calculated by a difference operation using two of the transmission channel characteristic values obtained by the oversampling.

### Claim 5 (depends on 2)

The OFDM reception apparatus according to claim 2, wherein
the interference component removing unit includes:
a first equalization unit for dividing the OFDM signal generated by the orthogonal transform unit by the transmission channel characteristic value calculated for each of the sub-carriers by the first transmission channel characteristic estimating unit, to remove a portion of the phase and amplitude distortions, thereby calculating a temporarily equalized OFDM signal;
an ICI component generating unit for using the temporarily equalized OFDM signal and the n-th differentiations calculated by the first transmission channel characteristic estimating unit, to generate the ICI component; and
a first subtraction unit for subtracting the ICI component from the OFDM signal generated by the orthogonal transform unit, to calculate an OFDM signal excluding the ICI component.

### Claim 6 (depends on 5)

The OFDM reception apparatus according to claim 5, wherein
the interference component removing unit further includes:
a second transmission channel characteristic estimating unit for calculating a transmission channel characteristic value of the OFDM signal excluding the ICI component for each of the sub-carriers; and
a second equalization unit for dividing the OFDM signal excluding the ICI component by the transmission channel characteristic values calculated by the second transmission channel characteristic estimating unit, to remove phase and amplitude distortions of the OFDM signal excluding the ICI component.

### Claim 7 (depends on 5)

The OFDM reception apparatus according to claim 5, wherein
the interference component removing unit further includes a second equalization unit for dividing the OFDM signal excluding the ICI component by the transmission channel characteristic value calculated for each of the sub-carriers by the first transmission channel characteristic estimating unit, to remove phase and amplitude distortions of the OFDM signal excluding the ICI component.

### Claim 8 (depends on 2)

The OFDM reception apparatus according to claim 2, wherein
the interference component removing unit includes:
an ICI component generating unit it for generating the ICI component;
a subtraction unit for subtracting and removing the ICI component generated by the ICI component generating unit from the OFDM signal generated by the orthogonal transform unit; and
an equalization unit for dividing an output signal of the subtraction unit by the transmission channel characteristic value calculated for each of the sub-carriers by the first transmission channel characteristic estimating unit, to remove phase and amplitude distortions of the output signal of the subtraction unit,
wherein the ICI component generating unit uses an output signal of the equalization unit and the n-th differentiations calculated by the first transmission channel characteristic estimating unit, to generate the ICI component having improved accuracy.

### Claim 9 (depends on 2)

The OFDM reception apparatus according to claim 2, wherein
the interference component removing unit includes:
an inverse matrix operating unit for calculating an inverse matrix of a matrix composed of a fixed coefficient matrix Ξ, the transmission channel characteristic value calculated for each of the sub-carriers by the first transmission channel characteristic estimating unit, and the n-th differentiations of the transmission channel characteristic values; and
an equalization unit for using the inverse matrix calculated by the inverse matrix operating unit, to remove the ICI component and the phase and amplitude distortions from the OFDM signal generated by the orthogonal transform unit.

### Claim 10 (depends on 2)

The OFDM reception apparatus according to claim 2, wherein
the first transmission channel characteristic estimating unit includes:
an SP extracting unit for extracting SP signals included in the plurality of sub-carriers from the OFDM signal generated by the orthogonal transform unit;
an SP generating unit for generating SP signals;
a division unit for dividing the SP signals extracted by the SP extracting unit by the SP signals generated by the SP generating unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each SP signal;
an interpolation unit for performing an interpolation process using the transmission channel characteristic value calculated for each SP signal by the division unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers;
an intra-symbol oversampling unit for performing a filtering process in the symbol direction with respect to the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to perform oversampling at intervals each smaller than a one-symbol interval; and
a subtraction unit for performing a subtraction process using transmission channel characteristic values obtained by the oversampling, to calculate the n-th differentiation of the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit.

### Claim 11 (depends on 2)

The OFDM reception apparatus according to claim 2, wherein
the first transmission channel characteristic estimating unit includes:
an SP extracting unit for extracting SP signals included in the plurality of subcarriers from the OFDM signal generated by the orthogonal transform unit;
an SP generating unit for generating SP signals;
a division unit for dividing the SP signals extracted by the SP extracting unit by the SP signals generated by the SP generating unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each SP signal;
an interpolation unit for performing an interpolation using the transmission channel characteristic value calculated for each SP signal by the division unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers;
an intra-symbol oversampling unit for performing a filtering process in the symbol direction with respect to the transmission channel characteristic value calculated for each of the sub-carriers by the division unit, to perform oversampling at intervals each smaller than a one-symbol interval; and
a subtraction unit for performing a subtraction process using transmission channel characteristic values obtained by the oversampling, to calculate n-th differentiations of transmission channel characteristic values of sub-carriers included in sub-carrier sequences arranged in the symbol, direction including SP signals; and
a carrier interpolation unit for performing an interpolation process in the carrier direction using the n-th differentiations of the transmission channel characteristic values calculated by the subtraction unit, to calculate the n-th differentiation of the transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers.

### Claim 12 (depends on 2)

The OFDM reception apparatus according to claim 2, wherein
the first transmission channel characteristic estimating unit includes:
an SP extracting unit for extracting SP signals included in the plurality of sub-carriers from the OFDM signal generated by the orthogonal transform unit;
an SP generating unit for generating SP signals;
a division unit for dividing the SP signals extracted by the SP extracting unit by the SP signals generated by the SP generating unit, to calculate transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each SP signal;
an intra-symbol oversampling unit for performing a filtering process in the symbol direction with respect to the transmission channel characteristic value calculated for each SP signal by the division unit, to perform oversampling at intervals each smaller than a one-symbol interval;
a subtraction unit for performing a subtraction process using transmission channel characteristic values obtained by the oversampling, to calculate n-th differentiations of transmission channel characteristic values of sub-carriers included in sub-carrier sequences arranged in the symbol direction including SP signals;
a carrier interpolation unit for performing an interpolation process in the carrier direction using the n-th differentiations of the transmission channel characteristic values calculated by the subtraction unit, to calculate the n-th differentiation of the transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers; and
interpolation unit for performing an interpolation process in the carrier direction using the transmission channel characteristic values obtained by the oversampling, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the subcarriers.

### Claim 13 (depends on 10)

The OFDM reception apparatus according to claim 10, wherein
the first transmission channel characteristic estimating unit further includes:
an H′ calculating unit for performing a difference operation process using the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to calculate on n-th differentiation of the transmission channel, characteristic value for each of the sub-carriers;
a comparison/determination unit for comparing speed information indicating moving speed of the OFDM reception apparatus with a predetermined threshold, to determine the moving speed; and
a selector for selecting and outputting one of the n-th differentiations calculated by the H′ calculating unit and the n-th differentiations calculated by the subtraction unit, based on a result of the determination by the comparison/determination unit.

### Claim 14 (depends on 11)

The OFDM reception apparatus according to claim 11, wherein
the first transmission channel characteristic estimating unit further includes:
an H′ calculating unit for performing a difference operation process using the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to calculate an n-th differentiation of the transmission channel characteristic value for each of the sub-carriers;
a comparison/determination unit for comparing speed information indicating moving speed of the OFDM reception apparatus with a predetermined threshold, to determine the moving speed; and
a selector for selecting and outputting one of the n-th differentiations calculated by the H′ calculating unit and the n-th differentiations calculated by the carrier interpolation unit, based on a result of the determination by the comparison/determination unit.

### Claim 15 (depends on 12)

The OFDM reception apparatus according to claim 12, wherein
the first transmission channel characteristic estimating unit further includes:
a H′ calculating unit for performing a difference operation process using the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to calculate an n-th differentiation of the transmission channel characteristic value for each of the sub-carriers;
a comparison/determination unit for comparing speed information indicating moving speed of the OFDM reception apparatus with a predetermined threshold, to determine the moving speed; and
a selector for selecting and outputting one of the n-th differentiations calculated by the H′ calculating unit and the n-th differentiations calculated by the carrier interpolation unit, based on a result of the determination by the comparison/determination unit.

### Claim 16 (depends on 7)

The OFDM reception apparatus according to claim 7, wherein
the first transmission channel characteristic estimating unit includes:
a first SP extracting unit for extracting SP signals included in the plurality of sub-carriers from the OFDM signal generated by the orthogonal transform unit;
a first SP generating unit for generating SP signals;
a first division unit for dividing the SP signals extracted by the first SP extracting unit by the SP signals generated by the first SP generating unit, to calculate a transmission channel characteristic value of OFDM signal generated by the orthogonal transform unit for each SP signal;
a second OP extracting unit for extracting SP signals from the OFDM signal excluding the ICI component;
a second SP generating unit for generating SP signals;
a second division unit for dividing the SP signals extracted by the second SP extracting unit by the SP signals generated by the second SP generating unit, to calculate a transmission channel characteristic value of the OFDM signal excluding the ICI component for each SP signal;
an interpolation unit for performing an interpolation process using a portion of the transmission channel characteristic values calculated for the SP signals by the first division unit, and the transmission channel characteristic values for the SP signals calculated by the second division unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers;
an intra-symbol oversampling unit for performing a filtering process in the symbol direction with respect to the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to perform oversampling at intervals each smaller than a one-symbol interval; and
second subtraction unit for performing a subtraction process using transmission channel characteristic values obtained by the oversampling, to calculate the n-th differentiation of the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit.

### Claim 17 (depends on 7)

The OFDM reception apparatus according to claim 7, wherein
the first transmission channel characteristic estimating unit includes:
a first SP extracting unit for extracting SP signals included in the plurality of sub-carriers from the OFDM signal generated by the orthogonal transform unit;
a first SP generating unit for generating SP signals;
a first division unit for dividing the SP signals extracted by the first SP extracting unit by the SP signals generated by the first SP generating unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each SP signal;
a second SP extracting unit for extracting SP signals from the OFDM signal excluding the ICI component;
a second SP generating unit for generating SP signals;
a second division unit for dividing the SP signals extracted by the second SP extracting unit by the SP signals generated by the second SP generating unit, to calculate a transmission channel characteristic value of the OFDM signal excluding the ICI component for each SP signal;
an interpolation unit for performing an interpolation process using a portion of the transmission channel characteristic values calculated for the SP signals by the first division unit, and the transmission channel characteristic values for the SP signals calculated by the second division unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers;
an intra-symbol oversampling unit for replacing portion of the transmission channel characteristic values calculated for the SP signals by the first division unit, with the transmission channel characteristic values for the SP signals calculated by the second division unit, and performing a filtering process in the symbol direction, to perform oversampling at intervals each smaller than a one-symbol interval;
a second subtraction unit for performing a subtraction process using transmission channel characteristic values obtained by the oversampling, to calculate n-th differentiations of transmission channel characteristic values of sub-carriers included in sub-carrier sequences arranged in the symbol direction including SP signals; and
a carrier interpolation unit for performing an interpolation process in the carrier direction using the n-th differentiations of the transmission channel characteristic values calculated by the second subtraction unit, to calculate the n-th differentiation of the transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers.

### Claim 18 (depends on 7)

The OFDM reception apparatus according to claim 7, wherein
the first transmission channel characteristic estimating unit includes:
a first SP extracting unit for extracting SP signals included in the plurality of sub-carriers from the OFDM signal generated by the orthogonal transform unit;
a first SP generating unit for generating SP signals;
a first division unit for dividing the SP signals extracted by the first SP extracting unit by the SP signals generated by the first SP generating unit, to calculate a transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each SP signal;
a second SP extracting unit for extracting SP signals from the OFDM signal excluding the ICI component;
a second SP generating unit for generating SP signals;
a second division unit for dividing the SP signals extracted by the second SP extracting unit by the SP signals generated by the second SP generating unit, to calculate a transmission channel characteristic value of the OFDM signal excluding the ICI component for each SP signal;
an intra-symbol oversampling unit for replacing a portion of the transmission channel characteristic values calculated for the SP signals by the division unit, with the transmission channel characteristic values for the SP signals calculated by the second division unit, and performing a filtering process in the symbol direction, to perform oversampling at intervals each smaller than of one-symbol interval;
second subtraction unit for performing a subtraction process using transmission channel characteristic values obtained by the over sampling, to calculate n-th differentiations of transmission channel characteristic values of sub-carriers included in sub-carrier sequences arranged in the symbol direction including SP signals;
a carrier interpolation unit for performing an interpolation process in the carrier direction using the n-th differentiations of the transmission channel characteristic values calculated by the second subtraction unit, to calculate the n-th differentiation of the transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers; and
an interpolation unit for performing an interpolation process in the carrier direction using the transmission channel characteristic values obtained by the oversampling, to calculate the transmission channel characteristic value of the OFDM signal generated by the orthogonal transform unit for each of the subcarriers.

### Claim 19 (depends on 16)

The OFDM reception apparatus according cc claim 16, wherein
the first transmission channel characteristic estimating unit further includes:
an H′ calculating unit for performing a difference operation process using the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to calculate an n-th differentiation of the transmission channel characteristic value for each of the sub-carriers;
a comparison/determination unit for comparing speed information indicating moving speed of the OFDM reception apparatus with a predetermined threshold, to determine the moving speed; and
a selector for selecting and outputting one of the n-th differentiations calculated by the H′ calculating unit and the n-th differentiations calculated by the subtraction unit, based on a result of the determination by the comparison/determination unit.

### Claim 20 (depends on 17)

The OFDM reception apparatus according to claim 17, wherein
the first transmission channel characteristic estimating unit further includes:
an H′ calculating unit for performing a difference operation process using the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to calculate an n-th differentiation of the transmission channel characteristic value for each of the sub-carriers;
a comparison/determination unit for comparing speed information indicating moving speed of the OFDM reception apparatus with a predetermined threshold, to determine the moving speed; and
a selector for selecting and outputting one of the n-th differentiations calculated by the H′ calculating unit and the n-th differentiations calculated by the carrier interpolation unit, based on a result of the determination by the comparison/determination unit.

### Claim 21 (depends on 18)

The OFDM reception apparatus according to claim 18, wherein
the first transmission channel characteristic estimating unit further includes:
an H′ calculating unit for performing a difference operation process using the transmission channel characteristic value calculated for each of the sub-carriers by the interpolation unit, to calculate an n-th differentiation of the transmission channel characteristic value for each of the sub-carriers;
comparison/determination unit for comparing speed information indicating moving speed of the OFDM reception apparatus with a predetermined threshold, to determine the moving speed; and
selector for selecting and outputting one of the n-th differentiations calculated by the H′ calculating unit and the n-th differentiations calculated by the carrier interpolation unit, based on a result of the determination by the comparison/determination unit.

### Claim 22

An integrated circuit for use in an OFDM reception apparatus for receiving an OFDM signal including a plurality of sub-carriers arranged in a symbol direction and a carrier direction, via a transmission channel, the circuit comprising:
an orthogonal transform unit for performing orthogonal transform with respect to the received OFDM signal from a time domain into a frequency domain, to generate an OFDM signal in the frequency domain;
a first transmission channel characteristic estimating unit for calculating a transmission channel characteristic value indicating phase and amplitude distortions in the OFDM signal generated by the orthogonal transform unit for each of the sub-carriers, the phase and amplitude distortions occurring during propagation through the transmission channel, and calculating an n-th (n is a natural number) differentiation of the transmission channel characteristic value for each of the sub-carriers; and
an interference component removing unit for using the transmission channel characteristic value and the n-th differentiation calculated for each of the sub-carriers by the first transmission channel characteristic estimating unit, to remove an interference component be the sub-carriers adjacent to each other in the symbol direction or the carrier direction, from the OFDM signal generated by the orthogonal transform unit,
wherein the first transmission channel characteristic estimating unit performs a filtering process in the symbol direction with respect to the transmission channel characteristic value calculated for each of the sub-carriers to perform oversampling at intervals each smaller than a one-symbol interval, and uses transmission channel characteristic values existing in intervals each smaller than a two-symbol interval of the transmission channel characteristic values obtained by the oversampling to calculate the n-th differentiations.

### Claim 23

An OFDM reception method for receiving an OFDM signal including a plurality of sub-carriers arranged in a symbol direction and a carrier direction, via a transmission channel, the method comprising the steps of:
performing orthogonal transform with respect to the received OFDM signal from a time domain into a frequency domain, to generate an OFDM signal in the frequency domain;
calculating a transmission channel characteristic vale indicating phase and amplitude distortions in the OFDM signal in the frequency domain for each of the sub-carriers, the phase and amplitude distortions occurring during propagation through the transmission channel, and calculating an n-th (n is a natural number) differentiation of the transmission channel characteristic value for each of the sub-carriers; and
using the calculated transmission channel characteristic value and n-th differentiation for each of the sub-carriers, to remove an interference component between the sub-carriers adjacent to each other in the symbol direction or the carrier direction, from the OFDM signal in the frequency domain,
wherein in the calculating the transmission channel characteristic value and the n-th differentiation, a filtering process is performed in the symbol direction with respect to the transmission channel characteristic values of the sub-carriers to perform oversampling at intervals each smaller than a one-symbol interval, and transmission channel characteristic values existing in intervals each smaller than a two-symbol interval of the transmission channel characteristic values obtained by the oversampling are used to calculate the n-th differentiations.

### Claim 24

A program executable by a computer that receives an OFDM signal including a plurality of sub-carriers arranged in a symbol direction and a carrier direction, via a transmission channel, the program causing the computer to execute the steps of:
performing orthogonal transform with respect to the received OFDM signal from a time domain into a frequency domain, to generate an OFDM signal in the frequency domain;
calculating a transmission channel characteristic value indicating phase and amplitude distortions in the OFDM signal in the frequency domain for each of the sub-carriers, the phase and amplitude distortions occurring during propagation through the transmission channel, and calculating an n-th (n is a natural number) differentiation of the transmission channel characteristic value for each of the sub-carriers; and
using the calculated transmission channel characteristic value and n-th differentiation for each of the sub-carriers, to remove an interference component between the sub-carriers adjacent to each other in the symbol direction or the carrier direction, from the OFDM signal in the frequency domain,
wherein in the calculating the transmission channel characteristic value and the n-th differentiation, a filtering process is performed in the symbol direction with respect to the transmission channel characteristic values of the sub-carriers to perform oversampling at intervals each smaller than a one-symbol interval, and transmission channel characteristic values existing in intervals each smaller than a two-symbol interval of the transmission channel characteristic values obtained by the oversampling are used to calculate the n-th differentiations.