Accused Technique for Implementing Standardized Error Correction Does Not Infringe
May 02, 2001
Last Month at the Federal Circuit - June 2001
Judges: Clevenger (author), Newman, and Bryson
In Oak Technologies, Inc. v. International Trade Commission, No. 00-1078 (Fed. Cir. May 2, 2001), the Federal Circuit affirmed the ITC’s finding of no infringement on the part of a collection of companies known as “MediaTek” of Oak Technologies, Inc.’s (“Oak”) U.S. Patent No. 5,581,715 (“the ‘715 patent”).
The ‘715 patent claims a CD-ROM controlling device including “data error detection and correction means for correcting said assembled data, said detection and correction means including error correction circuitry . . . and a cyclic redundancy checker.” In general terms, the claimed device functions as an error filter between the disk containing the data and the host computer to which the data are being transferred. This function is accomplished, as interpreted by the ITC, by first performing an error check on a sector of data, then performing a correction of any errors occurring in that sector, and lastly rechecking the corrected sector of data.
The Federal Circuit agreed with the ITC that “said assembled data” referred to an entire sector of data being transferred to the host computer and not to elements of data less than a sector. Specifically, the Court focused on the intrinsic evidence wherein Oak had acknowledged that in the context of CD-ROM technology, error-correction functions operate on a sector-by-sector basis. Oak argued, to no avail, that such an interpretation was misguided and that “assembled data” merely refers to CD-ROM data sent in serial form from the CD drive to the host computer. The Court cited the Yellow Book, the international manual that standardized the manner in which data are stored on CDs, for confirmation that both error detection and error correction are accomplished by a sector-bysector scanning of the disk. And, as the Court noted, Oak’s patent contemplates Yellow Book compliance.
The Federal Circuit then turned to the issue of the sequence of events in the claimed errorcorrection circuitry of the ‘715 patent. The Court agreed with the ITC that the term “after” indicates that the claimed sequence first requires error detection, followed by a Reed-Solomon error correction, and then a cyclic-redundancy check of the corrected
sector. The specification explains that errorcorrection circuitry would first perform Reed- Solomon error correction on each sector of data. Then, a cyclic-redundancy check of the corrected data would follow. Logically, the Court reasoned, the first error detection and the subsequent error correction would have to be completed before the initiation of the cyclic-redundancy checker. Moreover, nowhere in the written intrinsic record was there a discussion of error detection and correction where those two steps did not occur in that particular sequence.
Finally, the Court considered the term “cyclic redundancy checker” (“CRC”). Oak argued that such language is not specific and, in fact, refers to any circuitry that performs a cyclic-redundancy check. However, the Federal Circuit found that, by interpreting this term in light of the other terms, specifically “assembled data” and “after,” the only logical interpretation was that the CRC processed only sectors of data that already had been error corrected. While the Court acknowledged that other variations of CRC existed at the time of invention that would have been known in the art, it found no evidence in the intrinsic evidence that any of these alternative CRC operations were ever implemented in the invention. Accordingly, the Court agreed with the ITC that the term CRC means the errordetection process that follows error correction.
Turning to the issue of infringement, the Federal Circuit agreed with the ITC’s finding that the MediaTek circuit does not meet the claim limitation requiring a CRC to be performed on a sector of data that had already undergone error correction. Specifically, the Court noted that the MediaTek circuit performs its CRC on a sector of data before error correction. The Court, therefore, agreed with the ITC’s finding of no literal infringement.
The Federal Circuit then analyzed whether the MediaTek circuit infringed the ‘715 patent under the DOE. The Court agreed with the ITC that differences between the claimed error-correction circuit and the accused circuit were substantial and, thus, there was no infringement under the DOE. First, the ‘715 patent uses a generator polynomial to perform a long-division operation on the entire error-detection codeword. The MediaTek circuit, however, uses an entirely different method, whereby the error location and pattern data obtained by the error detector are divided by the generator polynomial and the resultant is added to the initial error-detection remainder. Second, the claimed circuit requires the Reed-Solomon error correction to occur before the CRC performs its error detection. While the MediaTek circuit includes these two steps, the CRC always precedes the Reed-Solomon error correction. Third, the ‘715 patent circuit corrects errors in its data in complete sectors after those sectors have been error detected. The MediaTek circuit, however, performs simultaneous checks and updates to a thirty-two-bit error-detection code (“EDC”) remainder. Fourth, the patented circuit performs its error correction as different operations in sequential form, whereas the MediaTek circuit performs its CRC before error correction and then continuously updates the EDC remainder while error correction takes place.