The error performance of various 8-VSB TCM decoders for reception of terrestrial digital television is analyzed. In previous work, 8-state TCM decoders were proposed and implemented for terrestrial broadcasting of digital television. In this paper, the performance of a 16-state TCM decoder is analyzed and simulated. It is shown that not only a 16-state TCM decoder outperforms one with 8-states, but it also has much smaller error coefficients

Morelos-Zaragoza, Robert H.

Rhee, Dojun

English

San Jose State University

On the Error Performance of 8-VSB TCM Decoder for ATSC Terrestrial Broadcasting of Digital Television

SJSU ScholarWorks

San Jose State UniversitySJSU ScholarWorksFaculty Publications Electrical Engineering2000On the Error Performance of 8-VSB TCMDecoder for ATSC Terrestrial Broadcasting ofDigital TelevisionDojun RheeLSI Logic CorporationRobert H. Morelos-ZaragozaSONY Computer Science Laboratories, Inc., robert.morelos-zaragoza@sjsu.eduFollow this and additional works at: https://scholarworks.sjsu.edu/ee_pubPart of the Electrical and Computer Engineering CommonsThis Article is brought to you for free and open access by the Electrical Engineering at SJSU ScholarWorks. It has been accepted for inclusion in FacultyPublications by an authorized administrator of SJSU ScholarWorks. For more information, please contact scholarworks@sjsu.edu.Recommended CitationDojun Rhee and Robert H. Morelos-Zaragoza. "On the Error Performance of 8-VSB TCM Decoder for ATSC Terrestrial Broadcastingof Digital Television" Faculty Publications (2000)-218.ISlT 2000, Sorrento, Italy, June 25-30,2000 On the Error Performance of 8-VSB TCM Decoder for ATSC Terrestrial Broadcasting of Digital Television Dojun Rhee LSI Logic Corporation e-mail: drheeols i l .  com Abstract - T h e  error performance of various 8-VSB TCM decoders for reception of terrestrial  digital  tele- vision is analyzed. I n  previous work, 8-state TCM de- coders were proposed a n d  implemented for terrestrial  broadcasting of digital  television. I n  this  paper, t h e  performance of a 16-state TCM decoder is analyzed a n d  simulated.  It is  shown t h a t  no t  only a 16-state TCM decoder outperforms one  with 8-states, b u t  i t  also has  much smaller error coefficients. I .  INTRODUCTION The Digital Television standard [1,2] describes a broadcast- ing system designed to transmit high quality video and audio as well aas data over a single 6 MHz channel. In order to maximize service area, the terrestrial broadcast mode incor- porate both an NTSC rejection filter (in the receiver) and trellis coding. When the NTSC rejection filter is activated in the receiver, a trellis decoder for the combination of a four- state trellis encoder and the filter is used. In the paper, the error performance of various TCM decoders is studied, with and without the NTSC rejection (1-D) filter. In the previous results [1,2], a combined 8-state trellis decoder is employed for the case with NTSC rejection filter. We propose a 16-state TCM decoder and analyze and simulate its error performance. The results show that the error performance improves, with respect to &state TCM decoders, a t  the cost of doubling the memory requirements. In return, a 16state TCM decoder has much smaller error coefficients and does not require precoding to operate. 11. ENCODER MODEL FOR ATSC TERRESTRIAL BROADCASTING OF DIGITAL TELEVISION In the ATSC terrestrial broadcasting system specification, the 8-VSB transmission subsystem employs a rate-2/3 4-state Ungerboeck trellis code, with the uncoded bit precoded. The 4state  feedback encoder and the bits-te8 PAM symbol m a p  per are shown in Fig. 1 (a). The NTSC interference rejection (comb) filter is a one tap linear-feed-forward (1-D) filter. Its purpose is to reduce the analog NTSC interference that is caused by a carrier tone. However, the received signals are also modified. The 8 signal levels are converted to 15 lev- els. While providing needed co-channel interference benefits, it is well-known that the (1-D) filter degrades white noise per- formance by 3 dB. This is because the filter output is the subtraction of two full gain paths and, as white noise is un- correlated from symbol to symbol, the noise power doubles. There is an additional 0.3 dB degradation due to error prop- agation introduced by precoding. 111. APPROXIMATED ERROR PERFORMANCE ANALYSIS 'This work was supported by LSI Logic Corp. Robert H. MorelosZaragoza SONY Computer Science Laboratories, Inc. e-mail: morelosQcs1. sony . Co. jp  In the approximations presented in this section, we inter- pret the trellis code with decoding depth k, as a terminated zero-tail (ZT) (3k, 2k - m) block code [3]. (For the four-state trellis decoder, m = 2, while for 8- and 16state trellis de- coders, m = 3 and m = 4, respectively.) When plotting the expressions with respect to the energy per bit-to-noise ratio (&/NO), a rate correction of RL (dB) is applied, to account for the rate loss due to trellis termination, where RL = (2k - m ) / 2 k .  With the NTSC interference rejection filter in the receiver, the number of states in the decoder in- creases, due to a signal constellation of increased dimension- ality. ~ In the guide to the ATSC system[2], a (1-D) filter is recommended that increases the number of signal levels from 8 of the original 8-PAM constellation to 15 at  the output of the filter. To analyze the performance of the eight-state trel- lis decoder, a truncated union bound is computed using the technique of [3] as follows. A polynomial state transition ma- triz II9X) for the &state trellis is used, with branch weights equal to X d ,  where d denotes the squared Euclidean distance (SED) with respect to the all-zero branch and X is an inde- terminant. For each set of three parallel branches between two states i , j ,  an element ni,,(X) in matrix II is a poly- nomial ni,,(X) = Xdl + X d a  + Xds, where d , , j  = 1,2,3, denotes the SED from the branch output to the all-zero se- quence output. Using symbolic mathematical software, the value of the k-th power n k ( X )  is computed and the coef- ficients of $:(X) yield the weight distribution of the ZT (3k, (2k - 3)) block code. For the 8-state trellis decoder, with. k = 54, n$)(X) = 5696XS6 + 1520X48 + 4O4X4O and for 16 state trellis decoder, nF:)(X) = 840XS6 + 248X48 + 101X40. As shown above, the error coefficients for the MSED for the 16-state trellis decoder is much smaller than that of &state trellis decoder. I V .  CONCLUSION The simulation and approximated error performance shows that a TCM decoder with 16states outperforms one with 8- state by approximately 0.33 dB at  a BER of lo-'. Finally, while the &state decoder must use a precoder for the uncoded bit to be able to decode properly, the proposed 16-state de- coder does not and has a better error performance. REFERENCES [l] ATSC Standard A/53, ATSC Digital Television Standard, 1995. [2] Guide to the Use of The ATSC Digital Television Standard A/54, ATSC Digital Television Standard, 1995. [3] J. K. Wolf and A. J. Viterbi, "On the Weight Distribution of Linear Block Codes Formed from Convolutional Codes", ZEEE Zh" Comm., vol. 44, no. 9, pp. 1049-1051, Sept. 1996. 21 8 0-7803-5857-0/00/$10.00 02000 IEEE. 

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On the Error Performance of 8-VSB TCM Decoder for ATSC Terrestrial Broadcasting of Digital Television

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