lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll US005512957A United States Patent [19] [11] Patent Number: 5,512,957 Hulyalkar [45] Date of Patent: Apr. 30, 1996 METHOD AND APPARATUS FOR No. 1, Jan. 1993, pp. 111-118. COMBATING CO-CHANNEL NTSC Ungerboeck, “Channel Coding with Multilevel/Phase Sig INTERFERENCE FOR DIGITAL TV nals”, IEEE Trans. on Info. Theory, vol. IT-28, No. 1, Jan. TRANSMISSION , ' 1982, pp. 55—67. Wei, “Precoding Technique for Partial-Response Channels Inventor: Samir N. Hulyalkar, White Plains, with Applicaiotns to HDTV Transmission”, IEEE Journal on NY. Selected Areas in Comm, vol. 11, No. 1, Jan. 1993, pp. 127-135. Assignee: Philips Electronics North America Eyuboglu, “Detection of Coded Modulation Signals on Corp., New York, N.Y. Linear, Severly Distorted Channels Using Decision-Feed back Noise Prediction with Interleaving”, IEEE Trans. on Comm, vol. 36, No. 4, Apr. 1988, pp. 401-409. [21] Appl. No.: 230,360 Tomlinson, “New Automatic Equaliser Employing Modulo [22] Filed: Apr. 20, 1994 Arithmetic”, Electronics Letters, Mar. 25, 1971, vol. 7, Nos. 5/6, pp. 138-139. Related U.S. Application Data Harashima et al., “Matched-Transmission Technique for Channels With Inter-symbol Interference”, IEEE Trans. on [63] Continuation-impart of Ser. No. 197,773, Feb. 10, 1994. Comm, vol. COM-20, No. 4, Aug. 1972, pp. 774-779. “Advanced Digital Television: System Description”, Jan. [51] Int. Cl.6 ................................................... .. H04N 5/455 20, 1992, Philips Laboratories. [52] U.S. Cl. .......................... .. 348/607; 348/21; 375/350; “VSB Transmission System Zenith Electronics Corpora , 455/296 tion”, Dec. 17, 1993, Technical Details. [58] Field of Search ................................... .. 348/607, 726, “Technical Details—Digital Spectrum Compatible”, Zenith, 348/608, 21, 611, 409, 618; 455/296, 308, Sep. 23, 1991. 63; 375/99, 102, 103; H04N 5/38, 5/455 “Summary Description of Terrestrial and Cable Bakeolf Systems”, General Instruments, Jan. 17, 1994. [56] References Cited “Digicipher HDTV System Description”, General Instru ment Corporation, Aug. 22, 1991. U.S. PATENT DOCUMENTS “Channel Compatible Digicipher HDTV System”, Massa 3,652,992 3/1972 K011 ................................... .. 340/1463 chusetts Institute of Technology, Apr. 3, 1992. 4,833,693 5/1989 Eyuboglu ..... .. 375/99 4,965,789 10/1990 Bottau et al. 348/411 Primary Examiner—]ames J. Groody 5,086,340 2/1992 Citta et a1. .. 358/141 Assistant Examiner-Je?rey S. Murrell 5,087,975 2/1992 Citta et al. .. 358/183 Attorney, Agent, or Firm-Michael E. Marion 5,121,203 6/1992 Citta . .. 358/141 5,181,112 l/1993 Citta et a1. 348/608 [57] ABSTRACT 5,325,188 6/1994 Scarpa .............. .. 375/103 5,349,589 9/1994 Chennakeshu et a1. ...... .. .. 371/43 An ATV receiver having a decoder which is designed to process a subset limited trellis pre-coded television signal. OTHER PUBLICATIONS The decoder processes co-channel interference so as to Eyuboglu et al., “Trellis Precoding: Combined Coding, produce at the ?lter output of a rejection ?lter, a residual Precoding and Shaping for Intersymbol Interference Chan interference spectrum which is as ?at as possible. The ?lter nels”, IEEE Trans. on Info. Theory, vol. 38, No. 3, Mar. exploits the fact that only the picture and the sound carriers 1992, pp. 301-314. need to be su?iciently attenuated and cancels NTSC co Forney, “Trellis Shaping”, IEEE Trans. on Info. Theory, vol. channel interference with only a small degradation in per 38, No. 2, Mar. 1992, pp. 281-300. formance when AWGN is also present. Heegard et al., “Practical Coding for QAM Transmission of HDTV”, IEEE Journal on Selected Areas in Comm, vol. 11, 9 Claims, 13 Drawing Sheets 65 1 SAMPLING AT 80 as " 6° ( SYMBDLRATE 2 ‘High —> CONQQTEH >51 REJECTIONNTSC ;—>: ANDPHASEEGUALIZER : FILTER - TRACKER 70/ "“ll"" 11 V ‘ SYNCAND 92, BI-HATE TIMING CONTROL 90 r i r ____ “1-5! _______ 110 :sorr-nrmsmu THELLIS gDElNIERLEAVER, SYMBOL Peel» 1 ‘::::::::::::::%R:8::::: XL BYTE -> DECQJSDEH -> T0 MPEG AwlsoFr DECISION mans i DE'NTERLEAVER DECODER ( l —>i:DEINTERLEAVER SIMBOL /DEC0DERFOR4VSB ;,» 100 105 "1,7 """"""" " US. Patent Apr. 30, 1996 Sheet 3 of 13 5,512,957 I SEGA>55 Q k5-- I I I I : \:\_ i 5558$558892 _mmw _.Qmzi?mam?i.. mnQE mmo AJ?“2,520?56$:55 @5922x:Va+ m: 205D2 US. Patent Apr. 30, 1996 Sheet 4 of 13 5,512,957 C) o é N l-E a:“2%525?;a2. mn.205223202$5.2 fu@25855E5" Ail?E525A“.. muv m5 m“5%All?A m.|l....+ u........--" AA|55m22 AIIIIITwzzéwA.." n25n"4| 5 “AAl,5%Z_ “m5iA._$23 Emmim"AAll mmnu58%555_ m(\o?n55; meow"“m._.<mAlN:A0 I n__ ‘IAQ un025f k 2% v5:Em E35; US. Patent Apr. 30, 1996 Sheet 5 0f 13 5,512,957 0 81-0 B A C ‘EL-A C D 81-0 B FIG. 5 US. Patent Apr. 30, 1996 Sheet 6 of 13 5,512,957 QQQEQQEzeEca< M58 MEEm> mEoo mm? v#6SEE 555; US. Patent Apr. 30, 1996 Sheet 7 of 13 5,512,957 a 6 180 D B —— D B _/ A c 2 A c l I I I 18 Is‘ 2‘ '2 '6 a D B _2—- D B A C 5“ A C -a FIG. 7 US. Patent Apr. 30, 1996 Sheet 8 of 13 5,512,957 SEGMENT V88 DATA FRAME SYNC 4 . I~+—————832 SYMBOLS———-+| FIELD SYNC #1 3‘ 3 SEGMENTS DATA + FEC FIELD SYNC #2 48.6 ms 3T 3 SEGMENTS DATA + FEC ‘++——1 SEGMENT = 77.7ps———>l US. Patent Apr. 30, 1996 Sheet 10 of 13 5,512,957 25# 5&5A EHE E>§EEE E5522AT" m<4Em EN”E;5:m Nm2%m v‘1+. o~m\0mm\wcmmm.ll 5imN55\552%A1.Ar, 2E: am{aI?réé?zgwm. géz??mémm4m. mmH EaA. 532585Mq\ m4m. gézgmmaomv ééézg(EEa, AM.Am.4m.mm?géz?mmacEEEEEQaEaA...A5% OWN sac\4”.Am.4m.m gag555%4i2% 221%\am \5sf /mw ca/n‘J. 552% US. Patent Apr. 30, 1996 Sheet 12 0f 13 5,512,957 4e+03 - 3e+03 _ HISTOGRAM - BlNf =0 2e+03~ ' #ams =1oo - BIN CENTER =-10.9 - BIN coum =0 1e+03— UNDERFLOW = o — OVERFLOW =0 0 I | l i | 5,512,957 1 2 lVIETHOD AND APPARATUS FOR which causes noise enhancement because the noise also COMBATING CO-CHANNEL NTSC passes through the NTSC rejection ?lter. INTERFERENCE FOR DIGITAL TV A method for using a generalized pre-coder and a corre TRANSMISSION sponding decoder for the case when uncoded QAM/VSB 5 modulation is used, is described in “New Automatic Equal~ This application is a continuation in part of US. patent izer Employing Modulo Arithmetic”, Electronic Letters, pp. application Ser. No. 08/197,773 ?led on Feb. 10, 1994, 138-139, March 1971, by M. Tomlinson and in “Matched (PHA 21-869), which is incorporated by reference herein. Transmission Technique for Channels With Intersymbol Interference”, IEEE Transactions on Communications, vol. BACKGROUND OF THE INVENTION 10 COM-20, no. 4, pp. 774-780, August 1972, by H. Harashima and H. Miyakawa, which are incorporated by The Federal Communications Commission and cable tele reference herein. vision testing organizations such as CableLabs have been The implementation of a pre-coder along with a trellis evaluating digital television delivery systems in order to encoder and the corresponding decoder is described in choose a new television “standar ” which someday will “Trellis Precoding: Combined Coding, Precoding and Shap replace NTSC in the United States. These systems all ing for Intersymbol Interference Channels”, IEEE Transac involve digital coding and data compression techniques, for tions on Information Theory, vol. 38, no. 2, pp. 301-314, example those utilizing the MPEG digital coding algorithms March 1992, by M. V. Eyuboglu and G. D. Fomey, which is or variations thereof. incorporated by reference herein. In this paper, it is shown The FCC plans to test and approve an advanced television that the asymptotic coding gain of the trellis code is (ATV) standard in 1994 comprising for example, high unchanged when a pre-coder is used with the corresponding de?nition television (HDTV) and standard de?nition decoder for this case. The performance of a concatenated (SDTV) digital signals for terrestrial broadcasting. Although coding approach of using an outer RS (Reed~Solomon) the speci?cs of the standard are yet to be fully tested and encoder and an inner trellis encoder is dependent however, agreed upon, the FCC has indicated that the system will 25 on the performance at larger error probabilities and not on initially take the form of a so called “simulcast” approach. asymptotic performance, as shown for example in “Practical The new ATV signals will have to ?t into currently unused Coding for QAM Transmission of HDTV” IEEE Journal on television channels (so-called “taboo” channels) and ini Selected Areas in Communications, vol 11, no. 1, pp. tially coexist with conventional analog television signals 111-118, January 1993, by C. Heegard, S. Lery and W. Paik, without co-channel interference. which is incorporated by reference herein. NTSC will be used hereinafter to represent one example Because the input to the Grand Alliance HDTV transmis of conventional television broadcasting. Other examples sion system is an MPEG packet of 188 bytes, an RS code would be SECAM and PAL. Although NTSC is exempli?ed with parameters (208,188,10), which is a 10 byte error herein, it is not meant to be construed as a limitation and will correcting code, was chosen to be used with the Zenith be used herein synonymously with “conventional” to rep 35 approach. This choice is reasonable given the ease of resent conventional television in general. implementation of implementing a RS decoder for byte— In 1994 the FCC will test the so-called “Grand Alliance” correction capability of up to 10-12 bytes.