Patent Application
20070280097
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the disclosure. In the drawings:
The present invention can be described by the embodiments presented herein. It is understood, however, that the embodiments described are not necessarily limitations to the invention, but only exemplary implementations.
Having summarized various aspects of the present invention, reference will now be made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawings, there is no intent to limit the invention to the embodiment or embodiments disclosed therein. On the contrary the intent is to cover all alternatives, modifications and equivalents included within the scope of the invention as defined by the appended claims.
It is noted that the drawings presents herein have been provided to illustrate certain features and aspects of the embodiments according to the invention. A variety of alternative embodiments and implementations may be realized consistent with the scope and spirit of the present invention.
It is also noted that the drawings presents herein are not all in scale. Some components are out of scale in order to provide a more detailed and comprehensive descriptions.
Please refer to
Moreover, after receiving the equalized received signal Rk(eq), a de-mapping and pilot insertion step 230 could convert the preliminary signal estimation of transmitted base-band symbol Ŝk by: 1) suppressing sub-carriers to zero, 2) replacing pilot sub-carriers by known values, and 3) de-mapping data transmission sub-carriers to nearest positions in constellation plot. In other words, a preliminary signal Ŝk could be generated in this step 230. Thereafter, applying equation 3, an estimation of the total noise {circumflex over (D)}k could be calculated by a noise estimation/calculation step 240.
However, because impulsive noise appears occasionally, the present invention takes into account the signal to the total noise ratio. In cases where the total noise can be ignored because it is too small, steps 260 to 290 could be omitted. Since the signal Ŝk and the noise {circumflex over (D)}k could be determined from the de-mapping and pilot insertion step 230 and the noise estimation step 240, a SNR (Signal to Noise Ratio) value
could be calculated and compared to a threshold value in a SNR comparison step 250. If the SNR value is greater than the threshold value, the flow would go directly to a Viterbi decoding step 299 for further processing of Rk(eq). On the other hand, if the SNR value is less than the desired threshold value, the next step is step 260.
As mentioned in the prior art, the total noise vector {circumflex over (D)}k is transformed into time domain {circumflex over (d)}k by an Inverse FFT step 260. Next, the time domain representation of impulsive noise ûk could be re-constructed by equations 4 and 5 in a peak detection step 270. In a next FFT step 280, the frequency domain representation of impulsive noise Ûk could be transformed from the time domain representation of impulsive noise ûk. Subsequently, according to equation 6, the equalized received signal Rk(comp) could be calculated by a noise suppression step 290 and sent to the Viterbi decoding step 299 for further processing.
Please refer to
As mentioned earlier, a SNR comparison block 350 is configured to calculate the SNR, where
from the signal output Ŝk of the processing block 330 and the total noise output {circumflex over (D)}k of the processing block 340. And the SNR value is compared to a given threshold value. In the case where the SNR value is greater than the threshold value, the equalized received signal Rk(eq) is sent to a Viterbi decoder 399. Otherwise, the total noise {circumflex over (D)}k would be forwarded to an inverse FFT block 360 to determine the impulsive noise.
Receiving the total noise {circumflex over (D)}k, the inverse FFT block 360 would transform {circumflex over (D)}k into the time domain representation of total noise {circumflex over (d)}k. Next, a peak detection block 370 could reconstruct the time domain representation of impulsive noise ûk according to equations 4 and 5. Taking time domain representation ûk as input, another FFT block 380 would transform it into the frequency domain representation of impulsive noise Ûk. Subsequently, according to equation 6, the equalized received signal Rk(comp) could be calculated by a noise suppression block 390 according to the received impulsive noise Ûk, the equalized received signal Rk(eq), and an inversion of the ideal channel estimation Hk via an inverter 370. The equalized received signal Rk(comp) is then sent to the Viterbi decoder 399 for further processing.
Now please refer to
Where the SNR is greater than the desired threshold value, the proposed method would be benefited by omitting the impulsive noise detection step 430. As mentioned, the impulsive noise detection step 430 involves IFFT, peak detection, FFT, and suppression calculations. Omitting these computation-intense steps can improve system performance and reduce computing power consumption.
It is understood that several modifications, changes, and substitutions are intended in the foregoing disclosure, and in some instances, some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.
