CN101964769B - Channel estimation method and device - Google Patents

Abstract

The invention discloses a channel estimation method, which comprises the following steps of: carrying out reverse fast Fourier transform operation of second numerical value sampling points on first numerical value initially estimated frequency domain channel responses to generate first time domain channel pulse responses, wherein the second numerical value is smaller than the first numerical value; carrying out time-domain windowing filtering processing on the first time domain channel pulse responses to generate second time domain channel pulse responses; carrying out smoothing operation on the second time domain channel pulse responses of a plurality of groups of different time domains to generate a smooth time domain channel pulse response; and carrying out fast Fourier transform operation on first numerical value sampling points of the smooth time domain channel pulse response to generate a frequency domain channel response.

Description

Channel estimation method and device

[ technical field ] A method for producing a semiconductor device

The present invention relates to channel estimation techniques, and more particularly, to a channel estimation method and apparatus for an Orthogonal Frequency Division Multiplexing (OFDM) communication system.

[ Prior Art ] A method for producing a semiconductor device

In a wireless communication system (wireless communication system), since a radio channel (radio channel) usually has a multipath fading (multipath fading) effect, there is a problem of intersymbol interference (ISI) in a received signal. To eliminate intersymbol interference, an equalizer (equalizer) is typically provided in the receiver, and the equalizer operation requires information on the Channel Impulse Response (CIR), so that the estimation of the CIR plays a critical role in mobile radio systems.

Also, OFDM has been an important communication technology in the field of wireless communication, mainly increasing data transmission rate. For example, IEEE 802.11a adopts OFDM technology, and the data transmission rate can reach 54 Mbps; while IEEE 802.11b does not use OFDM technology, its data transmission rate is only 11 Mbps. Therefore, it is an important issue to efficiently estimate the channel impulse response of the OFDM system to eliminate the inter-symbol interference and to take advantage of the high transmission rate of OFDM. In OFDM systems, channel estimates, i.e., channel impulse response estimates, are typically obtained by using pilot symbols (pilot symbols) known a priori by the transmitter and receiver.

Referring to fig. 1, a block diagram of a conventional OFDM channel estimation apparatus is shown. As shown in fig. 1, the conventional OFDM channel estimation apparatus includes a 4096-sampling-point IFFT operation unit 101, a mirror signal rejection operation unit 102, a 4096-sampling-point FFT operation unit 103, and a frequency-domain channel response smoothing unit 104.

The 4096 sampling point IFFT operation unit 101 is used for initially estimating the frequency domain channel response

4096 sample point Inverse Fast Fourier Transform (IFFT) operations are performed to generate a time domain channel impulse response

Referring to fig. 2, there are 4096 time domain channel impulse response calculated values in the frequency and time distribution of the carrier: □ □ □ the flow of the air in the air conditioner,

4096 subcarriers are total for the existing OFDM channel, wherein one of every 8 subcarriers is a pilot subcarrier for carrying a pilot symbol, and the remaining subcarriers are called data subcarriers for carrying data symbols; that is, of the 4096 subcarriers, 512 pilot subcarriers are used to carry pilot symbols and 3584 data subcarriers are used to carry data symbols. In the time-frequency plane of fig. 3, 17 × 4096 symbols transmitted by the conventional OFDM channel are shown. The initial estimated frequency domain channel response

Estimation of (2), in generalIs obtained by performing a least square error operation on the frequency domain transmission value and the frequency domain reception value of the pilot symbol at each pilot subcarrier. I.e. the initial estimated frequency domain channel responseThe algorithm is only applied at the frequency location k corresponding to the pilot subcarrier, and the frequency domain channel response values at the other frequency locations corresponding to the data subcarriers are made 0. The distribution pattern of the 512 pilot symbols in the 4096 sub-carriers is divided into two types, an even type and an odd type, the even type being: ● O ● O ● X ● X ● X ●

The odd number type is: o ● O ● O ● X ● X ● X ●

Wherein ● represents pilot symbols corresponding to pilot subcarrier frequency positions of 0, 8, 16, 24.. multidot.4088 in the even-numbered type and 4, 12, 20, 28.. multidot.multidot.4092 in the odd-numbered type; o represents a data symbol; x represents the arrangement on the left of the repeat. So the initial estimated frequency domain channel response

The distribution of 512 pilot symbols in 4096 sub-carriers is divided into two types, i.e., even-numbered frequency-domain channel response and odd-numbered frequency-domain channel response. The initial estimated frequency domain channel response

The even-numbered frequency domain channel responses and the odd-numbered frequency domain channel responses are transmitted to the 4096 sampling point IFFT operation unit 101 in an interlaced manner.

The image signal rejection operation unit 102 is used to reserve the 4096 time domain channel impulse responses

The front and back 256 time domain channel impulse response calculated values are respectively calculated, and the other 3584 time domain channel impulse response calculated values belonging to the image signal are filtered to generate a time domain channelImpulse response

That is, it is

<math> <mrow> <msub> <mover> <mi>h</mi> <mo>~</mo> </mover> <mi>w</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mover> <mi>h</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>,</mo> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mo>[</mo> <mn>0,255</mn> <mo>]</mo> <mo>&cup;</mo> <mo>[</mo> <mn>3840,4095</mn> <mo>]</mo> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> <mo>,</mo> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mo>[</mo> <mn>256,3839</mn> <mo>]</mo> </mtd> </mtr> </mtable> </mfenced> <mo>.</mo> </mrow> </math>

The 4096 sample point FFT operation unit 103 is configured to respond to the time domain channel impulse response

4096 sample point Fast Fourier Transform (FFT) operations are performed to generate a frequency domain channel response

k＝0~4095。

The smoothing unit 104 for frequency domain channel response is used to smooth the frequency domain channelResponse to

17 groups of data: □ □ □ the flow of the air in the air conditioner,

performing an arithmetic mean operation to generate a frequency domain channel response

Wherein

In the conventional OFDM channel estimation apparatus, the 4096 sampling point Inverse Fast Fourier Transform (IFFT) operation samples may have non-zero values only at 512 sampling points, and the rest are zero, so the 4096 IFFT calculation size is too large and lacks efficiency, and there is room for improvement. Therefore, the present invention researches a method for reducing the IFFT computation scale according to the system characteristics of the China Mobile Multimedia Broadcasting (CMMB) OFDM, in order to maintain the same channel estimation performance at a low computation scale, thereby providing a low-cost solution.

In view of the above, the present invention provides a novel algorithm to complete channel estimation, which can use a smaller-scale IFFT calculation to adaptively adjust the calculation formula according to the initial estimation frequency domain channel response sampling pattern, thereby greatly reducing the overall calculation scale.

[ summary of the invention ]

It is an object of the present invention to provide a low-cost and low-power channel estimation method for adaptively estimating the impulse response of a channel for a receiver to perform a compensation function.

Another objective of the present invention is to provide a low-cost and low-power channel estimation apparatus for adaptively estimating the impulse response of the channel for the receiver to perform the compensation function.

It is still another object of the present invention to provide a channel estimation scheme with low computational complexity, which can adaptively adjust the calculation formula according to the sampling pattern of the initial estimated frequency domain channel response to achieve the estimation of the channel impulse response with a smaller scale Inverse Fast Fourier Transform (IFFT) calculation.

To achieve the above objects of the present invention, a channel estimation method is proposed, which comprises performing an inverse fast fourier transform operation of second numerical sampling points on a first numerical initial estimation frequency domain channel response to generate a first time domain channel impulse response, wherein the second numerical value is smaller than the first numerical value; performing a time domain window filtering process on the first time domain channel impulse response to generate a second time domain channel impulse response; performing a smoothing operation on the second time domain channel impulse responses of a plurality of groups of different time domains to generate a smoothed time domain channel impulse response; and performing a fast fourier transform operation of the first numerical sample point on the smoothed time domain channel impulse response to generate a frequency domain channel response.

To achieve the above objects, the present invention further provides a channel estimation device, which comprises an inverse fast fourier transform operation unit for performing an inverse fast fourier transform operation of a second number of sampling points on an initially estimated frequency domain channel response of a first number of response values to generate a first time domain channel impulse response, wherein the second number is smaller than the first number; a window filter processing unit, for performing a time domain window filtering process on the first time domain channel impulse response to generate a second time domain channel impulse response; a smoothing unit, for performing a smoothing operation on the second time domain channel impulse responses of multiple groups of different time domains to generate a smoothed time domain channel impulse response; and a fast fourier transform operation unit for performing fast fourier transform operation of the first numerical sample point on the smoothed time domain channel impulse response to generate a frequency domain channel response.

To further clarify the structure, features and objects of the present invention, a better understanding of the present invention may be had by reference to the following drawings and detailed description of the preferred embodiments.

[ description of the drawings ]

Fig. 1 is a block diagram of a conventional OFDM channel estimation apparatus.

Fig. 2 is a diagram illustrating a time-domain channel impulse response of the IFFT operation result shown in fig. 1.

Fig. 3 is a diagram showing a pilot sampling distribution diagram of a CMMB OFDM initial estimation frequency domain channel response to a time-frequency plane according to the prior art.

Fig. 4 is a diagram illustrating a pilot sampling distribution diagram of the CMMB OFDM initial estimation frequency domain channel response to the time-frequency plane according to the present invention.

Fig. 5 is a diagram illustrating a flow chart of channel estimation according to an embodiment of the invention.

FIG. 6 is a diagram illustrating the temporal window filtering process according to the present invention.

FIG. 7 is a block diagram of a channel estimation device according to an embodiment of the present invention.

FIG. 8 is a block diagram of an embodiment of the 512-sampling-point IFFT unit of FIG. 7.

FIG. 9 is a block diagram of another embodiment of the 512-sampling-point IFFT unit of FIG. 7.

FIG. 10 is a block diagram of an embodiment of the smoothing unit of the time domain channel impulse response of FIG. 7.

[ description of main reference symbols ]

4096 sampling point IFFT arithmetic unit 101

Image signal rejection arithmetic unit 102

4096 sample point FFT arithmetic units 103, 704

Smoothing unit 104 for frequency domain channel response

512 sampling point IFFT operation unit 701

Window filtering processing unit 702

Smoothing unit 703 for time domain channel impulse response

192 sample point buffers 801, 802, 901

512 sample point IFFT calculators 803, 804, 902

Multipliers 805, 806, 903

Adders 807 and 906

Selection switch 904

Time domain channel impulse response buffer 905

Time domain channel impulse response storage unit 1001

Smoothing calculator 1002

[ detailed description ] embodiments

Referring to fig. 4, after studying the China Mobile Multimedia Broadcasting (CMMB) OFDM system, it is found that 4096 sub-carriers have guard bands (guard bands) and all sub-carriers within the guard bands are not used to avoid inter-signal interference,therefore, only 192 × 2 pilot subcarriers are actually used and distributed in two discontinuous sectors. In addition, the pilot symbol distribution of the CMMB OFDM system can be divided into two types, an even type and an odd type, which alternately appear on the time domain axis. Therefore, the frequency domain channel response can be estimated initially

The 4096 sampling point IFFT operation is simplified as follows: even type calculation formula:

<math> <mrow> <mover> <mi>h</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>4095</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nk</mi> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> </mrow> </math>

<math> <mrow> <mo>=</mo> <mrow> <munder> <munder> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>2</mn> </mrow> </munder> <mrow> <mi>m</mi> <mo>&Element;</mo> <mo>[</mo> <mn>0,191</mn> <mo>]</mo> </mrow> </munder> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nk</mi> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>+</mo> <munder> <munder> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>3</mn> </mrow> </munder> <mrow> <mi>m</mi> <mo>&Element;</mo> <mo>[</mo> <mn>0,191</mn> <mo>]</mo> </mrow> </munder> </mrow> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nk</mi> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> </mrow> </math>

<math> <mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>2</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>+</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>3</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> </mrow> </math>

<math> <mrow> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>2</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> <mo>+</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>3</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> </mrow> </math>

<math> <mrow> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>511</mn> </munderover> <mi>A</mi> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> <mo>+</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>511</mn> </munderover> <mi>B</mi> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> </mrow> </math>

wherein,

$A\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+2),m=0~191\\ 0,m=192~511\end{array}\right.,$ $B\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+1536+1020+3),m=0~191\\ 0,m=192~511\end{array}\right..$

since two groups of 192 pilot subcarriers are distributed in n e [0, 255 respectively]And n ∈ [3840,4095]So only n is in the range of 0, 255]And n ∈ [3840,4095]Computing

Odd-numbered calculation formula:

<math> <mrow> <mover> <mi>h</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>4095</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nk</mi> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> </mrow> </math>

<math> <mrow> <mo>=</mo> <mrow> <munder> <munder> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>6</mn> </mrow> </munder> <mrow> <mi>m</mi> <mo>&Element;</mo> <mo>[</mo> <mn>0,191</mn> <mo>]</mo> </mrow> </munder> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nk</mi> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>+</mo> <munder> <munder> <mi>&Sigma;</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>7</mn> </mrow> </munder> <mrow> <mi>m</mi> <mo>&Element;</mo> <mo>[</mo> <mn>0,191</mn> <mo>]</mo> </mrow> </munder> </mrow> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nk</mi> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> </mrow> </math>

<math> <mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>6</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>+</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>7</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> </mrow> </math>

<math> <mrow> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>6</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> <mo>+</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>191</mn> </munderover> <mover> <mi>H</mi> <mo>~</mo> </mover> <mrow> <mo>(</mo> <mn>8</mn> <mi>m</mi> <mo>+</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>7</mn> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> </mrow> </math>

<math> <mrow> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>511</mn> </munderover> <mi>A</mi> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> <mo>+</mo> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;n</mi> <mrow> <mo>(</mo> <mn>1536</mn> <mo>+</mo> <mn>1020</mn> <mo>+</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow> <mn>4096</mn> </mfrac> </mrow> </msup> <mo>[</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>m</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>511</mn> </munderover> <mi>B</mi> <mrow> <mo>(</mo> <mi>m</mi> <mo>)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mi>j</mi> <mfrac> <mrow> <mn>2</mn> <mi>&pi;nm</mi> </mrow> <mn>512</mn> </mfrac> </mrow> </msup> <mo>]</mo> </mrow> </math>

wherein,

$A\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+6),m=0~191\\ 0,m=192~511\end{array}\right.,$ $B\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+1536+1020+7),m=0~191\\ 0,m=192~511\end{array}\right..$

the IFFT operation of 512 sampling points of the invention is implemented only for 512 points such as n ∈ [0, 255] and n ∈ [3840,4095 ], and the other 3584 points do not need IFFT operation, because the impulse response of the time domain channel between non-n ∈ [0, 255] and non-n ∈ [3840,4095 ] is an image signal, and the image signal is filtered after IFFT operation.

Based on the above formula derivation, a channel estimation method is proposed, which can greatly reduce the calculation scale and circuit cost. Referring to fig. 5, a flow chart of an embodiment of channel estimation is shown. As shown in fig. 5, this embodiment comprises the following steps: initial estimation frequency domain channel response to first value response value

Performing IFFT operation of the second numerical sampling point to generate the first time domain channel impulse response

(step a); for the first time domain channel impulse responsePerforming a time-domain windowing (time-domain windowing) process to generate a second time-domain channel impulse response

(step b); for the second time domain channel impulse response of multiple groups of different time domains

Should perform a smoothing operation to generate a smoothed time domain channel impulse response

(step c); and smoothing the time domain channel impulse response

Performing FFT operation on the first value sampling point to generate a frequency domain channel response

(step d). The following is a detailed description of each step.

In step a, the initial frequency domain channel response of the response value with the first value is estimatedPerforming IFFT operation of the second numerical sampling point to generate the first time domain channel impulse response

From the above equations, the same effect can be achieved by using 512-sampling point IFFT as 4096-point IFFT, so when the first value is 4096, the second value can be 512. The IFFT operation of 512 sampling points includes the even-numbered calculation formula and the odd-numbered calculation formula, wherein the IFFT operation is even-numberedThe calculation formula is that k is 8m +2 and k is 8m +2559, wherein m is 384 sampling points such as 0-191 and the like have non-zero sampling values, and the sampling values at the other sampling points of k are set to be zero; the odd-numbered calculation formula of the IFFT operation has non-zero sampling values at 384 sampling points, such as 0-191, and k is 8m +2563, and the sampling values at the other sampling points of k are set to zero. Wherein the IFFT operation of the second digital sampling point comprises:

and

the 512 samples required are:

$A\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+2),m=0~191\\ 0,m=192~511\end{array}\right.$ (of the even-numbered type),

$B\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+1536+1020+3),m=0~191\\ 0,m=192~511\end{array}\right.$ (even type); or

$A\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+6),m=0~191\\ 0,m=192~511\end{array}\right.$ (odd number)Type(s),

$B\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+1536+1020+7),m=0~191\\ 0,m=192~511\end{array}\right.$ (odd type), i.e. samples only in

m is between 0 and 191 and has a non-zero value, and between 192 and 511 is zero. The IFFT operation of 512 sampling points only needs to aim at n belonging to [0, 255]]And n ∈ [3840,4095]When 512 points are implemented, the rest 3584 points do not need IFFT operation because the non-n is equal to [0, 255]]And n ∈ 3840,4095]The inter-time domain channel impulse response is an image signal, and the image signal is filtered after performing the IFFT operation. In step b, the first time domain channel impulse response is processed

Performing a time-domain windowing (time-domain windowing) process to generate a second time-domain channel impulse response

The time domain windowThe filtering process is used to filter out noise. Referring to FIG. 6, the window filtering process filters the first time domain channel impulse response according to a threshold value and a window lengthFiltering the time domain channel impulse response outside the window length and below the threshold value to generate the second time domain channel impulse response

Wherein the window length is a function of echo delay (echo delay) associated with multipath of the signal; the threshold value is a weighted average of the impulse responses of the time-domain channels within the window.

In step c, the second time domain channel impulse responses of a plurality of groups of different time domains

Performing a smoothing operation to generate a smoothed time domain channel impulse responseIn this embodiment, 17 sets of second time domain channel impulse responses with continuous time domain are used, which include a channel impulse response of a time to be estimated and 8 sets of channel impulse responses before and after the time axis thereof, and the smoothing operation may be an averaging operation or a weighting operation. I.e., step c is responsive to the second time domain channel impulseThe smoothing operation is performed on 17 sets of data to calculate n ∈ [0, 255] respectively]And n ∈ [3840,4095]Wait for the 512-point response value, and n ∈ [256, 3839 ]]The response value of 3584 points is filled with zero, thereby generating 4096-point smooth time domain channel impulse response

More specifically, when the present invention employs an averaging operation, the operation is as follows:

when n is equal to 0, 255]Or n ∈ [3840,4095]，

When n is equal to [256, 3839 ]]， ${\hat{h}}_s\left(n\right)=0.$

When the present invention employs weighting, the weighting is determined by considering the channel variation on the time axis. When the channel changes violently on the time axis, the invention will increase the weight of the channel impulse response at the time to be estimated, and decrease the weight of the channel impulse response before and after the time to be estimated, so that the weight of the channel impulse response farther away from the time to be estimated is decreased, and the weight is generated in n ∈ [0, 255] according to the weighted average]And n ∈ [3840,4095]Wait 512 points to have response value, and in n epsilon [256, 3839 ]]The smooth time domain channel impulse response with the response value of 3584 point being zero

In step d, the smoothed time domain channel impulse response is processed

Performing FFT operation on the first value sampling point to generate a frequency domain channel response

Wherein the first value is 4096, and the initial estimated frequency domain channel response

Having the same number of frequency domain channel responses, i.e., step d generates frequency domains at all subcarrier frequencies k 0-4095Channel response value

Compared with the prior art, the IFFT with 512 sampling points can achieve the same effect as the IFFT with 4096 points, and the IFFT can be proved by the even number type calculation formula and the odd number type calculation formula, so the calculation amount required by the IFFT operation, the time domain window filtering processing and the smoothing operation can be greatly reduced.

Referring to fig. 7, a block diagram of a channel estimation device according to an embodiment of the invention is shown. As shown in fig. 7, the embodiment includes a 512-sampling-point IFFT operation unit 701, a window filtering unit 702, a time domain channel impulse response smoothing unit 703 and a 4096-sampling-point FFT operation unit 704.

The 512-sampling-point IFFT operation unit 701 is used for initially estimating the frequency domain response of the first numerical response valuePerforming 512-sampling point IFFT operation according to the even-numbered equation or the odd-numbered equation to generate a first time domain channel impulse response

The first value is 4096, the even-numbered calculation formula of the IFFT has non-zero sampling values (where the pilot symbol is located) only at 384 sampling points k being 8m +2 and k being 8m +2559, m being 0-191, and the sampling values at the other sampling points k being zero; the odd-numbered calculation formula of the IFFT operation may have non-zero sampling values only at 384 sampling points, where k is 8m +6, k is 8m +2563, m is 0-191, and the sampling values at the other sampling points of k are zero. Wherein the IFFT operation with the second numerical sampling points comprises:

and

the 512 samples required are:

$A\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+2),m=0~191\\ 0,m=192~511\end{array}\right.$ (of the even-numbered type),

$B\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+1536+1020+3),m=0~191\\ 0,m=192~511\end{array}\right.$ (even type); or

$A\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+6),m=0~191\\ 0,m=192~511\end{array}\right.$ (of the odd-numbered type),

$B\left(m\right)=\left\{\begin{array}{c}\tilde{H}(8m+1536+1020+7),m=0~191\\ 0,m=192~511\end{array}\right.$ (odd type), i.e. samples only in

m is between 0 and 191 and has a non-zero value, and between 192 and 511 is zero. The IFFT operation of 512 sampling points of the invention is implemented only for 512 points such as n ∈ [0, 255] and n ∈ [3840,4095 ], and the other 3584 points do not need to perform IFFT operation, because the time domain channel impulse response between non-n ∈ [0, 255] and non-n ∈ [3840,4095 ] is an image signal, and the image signal is filtered after IFFT operation.

The window filter processing unit 702 is used to filter noise. The window filter processing unit 702 filters the first time domain channel impulse response according to a threshold value and a window length

Filtering the time domain channel impulse response outside the window length and below the threshold value to generate the second time domain channel impulse response

Wherein the window length is a function of echo delay (echo delay) and is related to multipath of the signal; and the threshold value is a weighted average of the impulse response values of the time-domain channels in the window.

The time domain channel impulse response smoothing unit 703 is used for smoothing the second time domain channel impulse responses of a plurality of groups of different time domainsPerforming a smoothing operation to generate a smoothed time domain channel impulse response

In this embodiment, 17 sets of second time domain channel impulse responses with consecutive time domains are used, which correspond to the channel impulse response of the time to be estimated and 8 sets of channel impulse responses before and after the time axis, and the smoothing operation can be an averaging operation or a weighting operation to apply n ∈ [0, 255]]And n ∈ [3840,4095]The 512 points are equal to generate smooth response values respectively, and the rest n is equal to the [256, 3839 ]]The response values of 3584 points are zero-filled, thereby generating 4096-point smooth time domain channel impulse response

In more detail, when the averaging operation is employed, the operation is as follows:

when n is equal to 0, 255]Or n ∈ [3840,4095]，

When n is equal to [256, 3839 ]]， ${\hat{h}}_s\left(n\right)=0.$

When a weighting operation is employed, the present invention considers the channel variation on the time axis to determine the weighting. When the channel changes violently on the time axis, the weight of the channel impulse response of the time to be estimated is increased, the weight of the channel impulse response of the time before and after the time to be estimated is decreased, and the weight of the channel impulse response of the time farther away from the time to be estimated is decreased, so as to be in n ∈ [0, 255] according to the weighted average]And n ∈ [3840,4095]Wait 512 points to produce a smooth response value, while the rest n ∈ [256, 3839 ]]Zero padding the 3584 point response values to generate smooth time domain channel pulsesImpulse response

The 4096 sample point FFT operation unit 704 is configured to respond to the smoothed time domain channel impulse responsePerforming 4096 sample point FFT operation to generate a frequency domain channel responseWherein the frequency domain channel response

There is a frequency domain channel response value at all subcarrier frequencies where k is 0-4095.

Referring to fig. 8, a block diagram of an embodiment of the 512-sampling-point IFFT operation unit 701 of fig. 7 is shown. As shown in fig. 8, the embodiment includes two 192 sample point buffers 801 and 802, two 512 sample point IFFT calculators 803 and 804, two multipliers 805 and 806, and an adder 807.

The 192 sample point buffers 801 and 802 are used to buffer the initial estimated frequency domain channel responseWhen the initial estimation frequency domain channel response

When the sampling point distribution is even, the 192 sampling point buffers 801 and 802 are used to buffer the samples respectively $A\left(m\right)=\tilde{H}(8m+2),m=0~191$ And $B\left(m\right)=\tilde{H}(8m+1536+1020+3),m=0~191$ the initial estimation frequency domain channel response of the two discontinuous areas; when the initial estimation frequency domain channel response

When the sampling point distribution is odd, the 192 sampling point buffers 801 and 802 are used to buffer respectively $A\left(m\right)=\tilde{H}(8m+6),m=0~191$ And $B\left(m\right)=\tilde{H}(8m+1536+1020+7),m=0~191$ initial estimation frequency domain channel response of two discontinuous areas.

The 512-sample IFFT calculator 803 is coupled to the 192-sample bufferA processor 801 for performing a first IFFT calculation with 512 sampling points to generate a first IFFT value

Where n ∈ [0, 255 ∈ [ ]]Or n ∈ [3840,4095]。

The 512-sampling-point IFFT calculator 804 is coupled to the 192-sampling-point buffer 802 for performing 512-sampling-point second IFFT calculation to generate a first IFFT calculation

Two IFFT values

Where n ∈ [0, 255 ∈ [ ]]Or n ∈ [3840,4095]。

The multiplier 805 is used for calculating a first phase variable e^{j2πn(2+4i)/4096}And the first IFFT value

To generate a first partial time domain channel impulse response. Wherein the first phase variable e^{j2πn(2+4i)/4096}Dividing into two cases of i being 0 and 1; i-0 represents the initial estimated frequency domain channel responseThe distribution of sampling points belongs to the even number type, i-1 represents the initial estimation frequency domain channel response

The distribution of the sampling points belongs to the odd number type.

The multiplier 806 is used to generate a second phase variable e^{j2πn(2559+4i)/4096}And the product of the second IFFT value

A second fractional time domain channel impulse response is generated. Wherein the second phase variable e^{j2πn(2559+4i)/4096}Dividing into two cases of i being 0 and 1; i-0 represents the initial estimated frequency domain channel response

The distribution of sampling points belongs to the even number type, i-1 represents the initial estimation frequency domain channel responseThe distribution of the sampling points belongs to the odd number type. The adder 807 is used to combine the first partial time domain channel impulse response and the second partial time domain channel impulse response to generate the first time domain channel impulse response

Referring to fig. 9, a block diagram of another embodiment of the 512-sampling-point IFFT operation unit 701 of fig. 7 is shown. As shown in fig. 9, the embodiment includes a 192-sampling-point buffer 901, a 512-sampling-point IFFT calculator 902, a multiplier 903, a selection switch 904, a time-domain channel impulse response buffer 905, and an adder 906.

The 192 sample point buffer 901 is used to buffer the initial estimated frequency domain channel responseWhen the initial estimation frequency domain channel responseThe 192 sample buffer 901 is used to buffer the samples in sequence when the sample distribution is even $A\left(m\right)=\tilde{H}(8m+2),m=0~191$ And $B\left(m\right)=\tilde{H}(8m+1536+1020+3),m=0~191;$ when the initial estimation frequency domain channel response

When the sampling point distribution is odd, the 192 sampling point buffer 901 is used to buffer sequentially $A\left(m\right)=\tilde{H}(8m+6),m=0~191$ And $B\left(m\right)=\tilde{H}(8m+1536+1020+7),m=0~191.$ in the present embodiment, the IFFT calculation is completed only before the next 192 initial estimated frequency domain channel response values are sent to the 192 sampling point buffer 901, so that the 192 sampling point buffer 901 can buffer each 192 initial estimated frequency domain channel response values.

The 512-sampling-point IFFT calculator 902 is coupled to the 192-sampling-point buffer 901 for performing 512-samplingIFFT calculation of sampling points to generate an IFFT value

Or

Where n ∈ [0, 255 ∈ [ ]]Or n ∈ [3840,4095]。

The multiplier 903 is used to depend on a phase variable e^{j2πn(2+4i)/4096}(or e)^{j2πn(2559+4i)/4096}) And the IFFT value

(or

) The product of (a) and (b),

a first partial time domain channel impulse response (or a second partial time domain channel impulse response) is generated.

The selection switch 904 is used to select one of a first phase variable and a second phase variable as the phase variable. Wherein the first phase variable is e^{j2πn(2+4i)/4096}I is 0, 1; i-0 represents the initial estimated frequency domain channel response

The distribution of sampling points belongs to the even number type, i-1 represents the initial estimation frequency domain channel response

The distribution of the sampling points belongs to the odd number type. Wherein the second phase variable is e^{j2πn(2559+4i)/4096}I is 0, 1; i-0 represents the initial estimated frequency domain channel response

The distribution of sampling points belongs to the even number type, i-1 represents the initial estimation frequency domain channel response

The distribution of the sampling points belongs to the odd number type.

The time domain channel impulse response buffer 905 is coupled to the multiplier 903 for buffering a first partial time domain channel impulse response and a second partial time domain channel impulse response.

The adder 906 is used for combining the first partial time domain channel impulse response and the second partial time domain channel impulse response to generate the first time domain channel impulse response

Referring to fig. 10, a block diagram of an embodiment of the smoothing unit 703 for time domain channel impulse response of fig. 7 is shown. As shown in fig. 10, the embodiment includes a time domain channel impulse response storage unit 1001 and a smoothing calculator 1002.

The time domain channel impulse response storage unit 1001 is used to store the second time domain channel impulse response

The 17 groups □ □ □ of (a) are,

since the present application uses only 512-point IFFT, the time domain channel impulse response storage unit 1001 only needs 17 × 512 storage spaces, which can greatly reduce the storage unit requirements.

The smoothing calculator1002 is coupled to the time domain channel impulse response storage unit 1001 for storing the second time domain channel impulse response

The 17 sets of data of (1) perform smoothing operations. The smoothing operation can be an averaging operation or a weighting operation for the second time domain channel impulse response

Is operated to generate n e [0, 255 respectively]And n ∈ [3840,4095]Wait for the 512-point response value, and the rest n ∈ [256, 3839 ]]The response value of 3584 points is filled with zero, thereby generating 4096-point smooth time domain channel impulse response

In more detail, when the averaging operation is employed, the following operations are performed:

when n is equal to 0, 255]Or n ∈ [3840,4095]，

When n is equal to [256, 3839 ]]， ${\hat{h}}_s\left(n\right)=0,$

To generate the smoothed time domain channel impulse response

When the weighting operation is adopted, the weighting is determined by considering the channel variation on the time axis. When the channel changes violently on the time axis, the weight of the channel impulse response of the time to be estimated is increased, the weight of the channel impulse response of the time before and after is reduced, and the weight of the channel impulse response of the time channel farther away from the time to be estimated is reduced so as to be within n ∈ [0, 255 []And n ∈ [3840,4095]Wait 512 points to generate smooth response value, and the rest n is equal to [256, 3839 ]]The response value of 3584 points is filled with zero, thereby generating a smooth time domain channel impulse response

Therefore, by implementing the preferred embodiment of the present invention, a channel estimation scheme with low computational complexity, low cost and low power consumption can be provided, thereby improving the shortcomings of the prior art.

The present disclosure is a preferred embodiment, and local changes or modifications are introduced from the technical idea of the present disclosure and are easily inferred by those skilled in the art, such as changes in arrangement of pilot subcarriers, changes in the number of sampling points, changes in buffer size, changes in the number of average groups, changes in smoothing processing method, and the like, without departing from the scope of patent rights of the present disclosure.

In conclusion, no matter what the purpose, means and efficacy are, the technical features are different from the prior art, the invention is practical at first, and the patent requirements conforming to the invention are also solicited by the examination and review board and issued to the patent for the morning to benefit the society and bring convenience to the reality.

Claims (14)

1. A channel estimation method for use in an ofdm communication system, the method comprising the steps of:

performing an inverse fast fourier transform operation of a second number of samples on the first number of initial estimated frequency domain channel responses to generate a first time domain channel impulse response, wherein the first number is greater than the second number;

performing a window filtering process on the first time domain channel impulse response to generate a second time domain channel impulse response;

performing a smoothing operation on the second time domain channel impulse responses of a plurality of groups of different time domains to generate a smoothed time domain channel impulse response; and

performing a fast fourier transform operation of the first numerical sample point on the smoothed time domain channel impulse response to generate a frequency domain channel response; wherein, when the method is used in China Mobile Multimedia Broadcasting (CMMB) system, the first value is 4096 and the second value is 512.

2. The method of claim 1 wherein the window filtering processes the first time domain channel impulse response according to a threshold value and a window length, filtering out values outside and below the threshold value, wherein the window length is a function of echo delay and the threshold value is a weighted average of values of the first time domain channel impulse response within the window.

3. The method of claim 1 wherein the smoothing operation is one of an averaging operation and a weighting operation.

4. A channel estimation apparatus for use in an ofdm communication system, the apparatus comprising:

an inverse fast fourier transform operation unit for performing an inverse fast fourier transform operation of a second number of sampling points on the initially estimated frequency domain channel response of the first number of response values to generate a first time domain channel impulse response, wherein the first number is greater than the second number;

a window filter processing unit, for performing a window filter process on the first time domain channel impulse response to generate a second time domain channel impulse response;

a smoothing unit, for performing a smoothing operation on the second time domain channel impulse responses of multiple groups of different time domains to generate a smoothed time domain channel impulse response; and

a fast fourier transform operation unit for performing fast fourier transform operation of the first numerical sampling point on the smoothed time domain channel impulse response to generate a frequency domain channel response; wherein, when the method is used in China Mobile Multimedia Broadcasting (CMMB) system, the first value is 4096 and the second value is 512.

5. The apparatus of claim 4 wherein the window filtering is performed to filter the first time domain channel impulse response according to a threshold value and a window length, wherein the window length is a function of echo delay, and the threshold value is a weighted average of values of the first time domain channel impulse response within the window.

6. The apparatus of claim 4 wherein the smoothing operation is one of an averaging operation and a weighting operation.

7. The apparatus of claim 4, wherein the inverse fast Fourier transform operation unit comprises:

a buffer having a first buffer portion and a second buffer portion for buffering the initial estimated frequency domain channel response;

a first inverse fast fourier transform calculator coupled to the first buffer for performing a first inverse fast fourier transform calculation with the second digital sample point to generate a first inverse fast fourier transform value;

a first multiplier for multiplying a first phase variable by the first inverse fast fourier transform value to generate a first partial time domain channel impulse response;

a second inverse fast fourier transform calculator, coupled to the second buffer, for performing a second inverse fast fourier transform calculation on the second value sample points to generate a second inverse fast fourier transform value;

a second multiplier for multiplying a second phase variable by the second inverse fast fourier transform value to generate a second fractional time domain channel impulse response; and

an adder for combining the first partial time domain channel impulse response and the second partial time domain channel impulse response to generate the first time domain channel impulse response.

8. The apparatus of claim 7 wherein the first buffer portion and the second buffer portion each buffer 192 sampled response values of the initial estimated frequency domain channel response when used in China Mobile Multimedia Broadcasting (CMMB) system.

9. The apparatus of claim 8 wherein the first phase variable is e^{j2πn(2+4i)/4096}，n∈[0,255]And n is [3840,4095 ]]I =0, 1; when i =0 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an even number type, and when i =1 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an odd number type.

10. The apparatus of claim 8 wherein the second phase variable is e^{j2πn(2559+4i)/4096},n∈[0,255]And n is [3840,4095 ]]I =0, 1; when i =0 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an even number type, and when i =1 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an odd number type.

11. The apparatus of claim 4, wherein the inverse fast Fourier transform operation unit comprises:

a buffer for buffering the initial estimated frequency domain channel response;

an inverse fast fourier transform calculator, coupled to the buffer, for performing an inverse fast fourier transform calculation on the second value sample point to generate an inverse fast fourier transform value;

a selection switch for selecting one of a first phase variable and a second phase variable as an output phase variable according to the position of the channel;

a multiplier for multiplying the output phase variable by the inverse fast Fourier transform value to generate a temporary time domain channel impulse response;

a time domain channel impulse response buffer coupled to the multiplier for buffering the temporary time domain channel impulse response, wherein the temporary time domain channel impulse response comprises a first part of time domain channel impulse response related to the first phase variable and a second part of time domain channel impulse response related to the second phase variable; and

an adder for combining the first partial time domain channel impulse response and the second partial time domain channel impulse response to generate the first time domain channel impulse response; when the buffer is used in the China Mobile multimedia broadcasting system, 192 sampling point response values of the initial estimation frequency domain channel response are buffered in the buffer.

12. The apparatus of claim 11 wherein the first phase variable is e^{j2πn(2+4i)/4096},n∈[0,255]And n is [3840,4095 ]]I =0, 1; when i =0 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an even number type, and when i =1 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an odd number type.

13. The apparatus of claim 11 wherein the second phase variable is e^{j2πn(2559+4i)/4096},n∈[0,255]And n is [3840,4095 ]]I =0, 1; when i =0 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an even number type, and when i =1 represents that the distribution of the sampling points of the initial frequency domain channel response belongs to an odd number type.

14. The apparatus of claim 4, wherein the smoothing unit comprises:

a time domain channel impulse response storage unit for storing the second time domain channel impulse responses of the plurality of groups of different time domains; and

a smoothing calculator, coupled to the time domain channel impulse response storage unit, for performing the smoothing operation on the plurality of groups of the second time domain channel impulse responses in different time domains to generate the smoothed time domain channel impulse response.

Images