ATSC a), a) A Carrier Frequency Synchronization Scheme for modified ATSC Systems Young Gon Jeon a) and Joon Tae Kim a) 3D HDTV (3-Dimensional High Definition Television). 3D HDTV HDTV ATSC (Advanced Television Systems Committee) 8-VSB (8-Vestigial Side Band). PN (Pseudo-Noise) VSB. ATSC. ATSC ( %). ATSC, ATSC PN. ATSC. Fitz PN. QAM (Quadrature Amplitude Modulation) VSB. VSB QAM,. PN. Abstract Recently, studies of 3D HDTV broadcasting technology have been processed actively. Korea is making efforts to modify Advanced Television Systems Committee (ATSC) 8-Vestigial Side Band (8-VSB) systems for terrestrial 3D HDTV broadcasting services. We intend to adopt a new frame structure to use PN (Pseudo-Noise) sequence as frame header, and VSB modulation. PN sequence is used to recover carrier freqeuncy offset, carrier phase error. In this paper, we will describe this system as the modified ATSC systems. The receiver of the modified ATSC system should be able to estimate and recover carrier frequency offset exactly. A existing ATSC systems inserts pilot to recover carrier frequency offset, on the other hand the modified ATSC systems use PN sequence to recovery carrier frequency offset without the use of pilot. In this paper, we introduce carrier frequency recovery (CFR) scheme for the modified ATSC systems. The proposed CFR scheme is composed of coarse CFR scheme using Fitz algorithm and fine CFR scheme using a simple PN sequence correlation algorithm. And, the symbol information of QAM modulated signal is contained in both In-phase (I)channel and Quadrature-phase (Q)channel. However the symbol information of VSB modulated signal is contained in I channel, and Q channel is just Hilbert transform of I channel. For the reason, VSB modulated symbols can not have fixed phase like QAM modulated symbols, and VSB modulated symbols is more sensitive to carrier frequency offset. Therefore we perform phase correction of received PN sequence to improve performance. Keyword : Carrier Frequency Recovery, Carrier Frequency Synchronization, 3D HDTV, ATSC
., 3D HDTV. 3D HDTV,, 2 (TTA) [] 3D HDTV,,, /. (RAPA) 3DTV [2] 3DTV, 3DTV, DB(, / ), 3DTV. ATSC (Advanced Television Systems Committee) 8-VSB (8-Vestigial Side Band) [3][4]. ATSC 8-VSB 6MHz TV 9.2Mbps, HD 92 8( ) 2(TV) 3() 24(RGB).()= 29.8Mbps 3D HDTV. 3D HDTV. ATSC 8-VSB, [5]. [6] [5], ISI (Inter Symbol Interference) a) Department of Electronics Engineering, Konkuk University : (jtkim@konkuk.ac.kr), ( ). [KI356 8, 3D HDTV ] (2 26 ),(2 2 2 ), (2 2 2 ) PN (Pseudo-Noise). ATSC.. ATSC Fig.. A frame structure of modified ATSC systems ATSC (Frame header) (Frame body) PN,. PN,,,. ATSC ATSC 8-VSB. ATSC. ASTC VSB (DC.25V),, ATSC PN. ATSC. Fitz [7], PN [8]. [7]-[3]. QAM
(In-phase), (Quadrature-phase) [9]. VSB, [9]. VSB QAM,. PN. PN PN. QAM PSK, VSB.. QAM VSB. QAM (Quadrature Amplitude Modulation) QAM APK (Amplitude Phase shift Keying). QAM,. 256QAM. 6QAM, 32QAM, 64QAM ADSL. 2. VSB (Vestigial Side Band) (VSB),. VSB 3 4 8-VSB 6-VSB, 8 6.. 3. QAM VSB 2 (a) (b) VSB QAM. QAM 3.5 2 -.5 -.5-2 - -3-2 -.5 - -.5.5.5 2 (a) 8-VSB -.5 -.5 - -.5.5.5 (b) 64-QAM 2. 8-VSB 64-QAM Fig. 2. A difference between 8-VSB constellation and 64-QAM constellation
2 (b), VSB 2 (a)... VSB 3 QAM PN VSB PN. QAM VSB, VSB. 3 (b), VSB PN QAM PN. 3 (c) (d) PN. 3 (c) QAM, VSB 3 (d).5 3 2.5 -.5 - - -2 -.5 -.5 - -.5.5.5 (a) QAM -3 -.5 - -.5.5.5 (b) VSB.5 3 2.5 -.5 - - -2 -.5 -.5 - -.5.5.5 (c) % QAM 3. QAM VSB Fig. 3. A difference between QAM constellation and VSB constellation with frequency offset -3-3 -2-2 3 (d) % VSB
. VSB. VSB PN,,, () 7. arg 단 PN, PN, PN, N PN, k. PN (k-)/2+ ~ N-(k-)/2- PN, N-(k-). 42 PN 65, 32 ((65-)/2) 32 ((65-)/2) 356 PN. VSB 4 (b) QAM,. 2. ATSC.,. 5. 2. %, 3.5 2 -.5 -.5-2 - -3-3 -2-2 3 (a) % VSB () 4. % VSB Fig. 4. A constellation of VSB modulated signal with % frequency offset -.5 -.5 - -.5.5.5 (b) % VSB ()
5. Fig. 5. Carrier Frequency Recovery Scheme. % Data-aided Kay [], L&W [], L&R [2], M&M [3], Fitz. Fitz..., z(k) PN, w(k) w(m),, N. PN (z(k)) VSB PN.. Table. The frequency offset estimator algorithm Kay L&W
L&R Fitz M&M 6 (a), 6 (b) %. L&R, Fitz, M&M N 4., L&W, M&M, Kay, L&R, Fitz. Kay L&W Eb/No, L&R, Fitz, M&M.
Estimated Carrier Frequency Offset.5.4.3.2. -. -.2 -.3 -.4 Kay L&W L&R Fitz M&M -.5 -.5 -.4 -.3 -.2 -...2.3.4.5 Normalized Carrier Frequency Offset (a) Normalized estimation variance -2-4 -6-8 - Kay L&W L&R Fitz M&M -2 2 4 6 8 2 4 6 8 2 Eb/No (b) 6. Fig. 6. A comparison of a carrier frequency offset estimator performance Fitz. 2,. 2. Kay L&W, L&W L&R. L&W, Kay L&R, Fitz, M&M.,, Kay L&W. L&R, Fitz, M&M, % Fitz. 2. Table 2. A comparison of hardware complexity of a carrier frequency offset estimator Estimator Multiplications Arc-Tangent Operations Kay 7 355 L&W 7 L&R(N=4) 49 Fitz(N=4) 48 4 M&M(N-4) 426 4 2.2. 7 PN. PN PN PN,, (2). 7. PN Fig. 7. A simple PN symbols block correlation algorithm
PN, PN, PN. PN PN.. 8 (a) PN, (b). 8 PN, PN. 3.. 9. (3).5 x -4-5.895 x -5 Estimated Carrier Frequency Offset.5 -.5 - Normalized residual carrier frequency -5.9-5.95-5.9-5.95 -.5-2 - 2 3 Normalized Carrier Frequency Offset x -4 (a) PN -5.92 5 5 2 Eb/No (b) 8. Fig. 8. Fine frequency offset estimating range and Normalized residual carrier frequency after coarse CFO recovery 9. Fig. 9. A phase error recovery algorithm
PN,. PN. QAM PN π,. VSB PN,. π PN, (3).,. (4) VSB PN, (3). arg arg PN, PN, PN, BPSK PN, VSB - -2 BER(Bit Error Rate) -3-4 -5-6 -7 Ideal (Un-coded 64-QAM) Ideal (Un-coded 8-VSB) Proposed CFR without Phase Correction (64-QAM) Proposed CFR without Phase Correction (8-VSB) Proposed CFR with Phase Correction (8-VSB) -8 2 4 6 8 2 4 6 8 2 Eb/No. BER Fig.. BER performance
4.5 5 x -7 4 Proposed CFR without Phase Correction Proposed CFR with Phase Correction 3.5 3 MSE 2.5 2.5.5 2 4 6 8 2 4 6 8 2 Eb/No. Fig.. The mean square estimation error PN. QAM,., VSB,..., AWGN. ATSC (PN ). 455 PN455 496, 8-VSB 64-QAM. Fitz N 4.. 8-VSB 64-QAM BER... 3D HDTV ATSC. Fitz, PN. VSB,
.,. [], http://www.tta.or.kr [2] 3DTV, http://www.3dtvkorea.or.kr [3] ATSC A/53, ATSC digital television standard, Sep. 995. [4] ATSC A/54, Guide to the use of the ATSC digital television standard, Sep. 995. [5],, 3D HDTV ATSC,, 5 5, pp.68-696, 2 9. [6],, 3D HDTV ATSC,, 5 6, pp. 83-83, 2. [7] M. P. Fitz, "Further Results in the Fast Estimation of a Single Frequency," in IEEE Trans. Communications, vol. 42. No. 2/3/4/, pp. 862-864, Feb./Mar./Apr. 994. [8] Alan Barieri and Giulio Colavolpe, "On Pilot-Symbol-Assisted Carrier Synchronization for DVB-S2 Systems," IEEE Trans. Broadcasting, vol. 53, No. 3, September 27. [9] K. J. Kerpez, "A Comparison of QAM and VSB for Hybrid Fiber/Coax Digital Transmission," in IEEE Trans. Broadcasting., vol. 4, No., pp. 9-6, Mar. 995. [] S. Kay, "A Fast and Accurate Single Frequency Estimator," IEEE Trans. Acoust., Speech, Signal Processing, ASSP-37, 987-99, Dec. 989 [] B. C. Lovell and R. C. Williamson, "The statistical performance of some instantaneous frequency estimators." IEEE Trans. Acoust., Speech, Signal Processing, vol. 4, pp. 78-723, July 992. [2] M. Luise and R. Reggiannini, "Carrier frequency recovery in all-digital modems for burst-mode transmissions, " IEEE Trans. Communications., vol. 43. No. 2/3/4, pp. 69-78, Feb./Mar./ Apr. 995. [3] M. Morelli and U. Mengali, "Feedforward frequency estimation for PSK: a tutorial review," European Trans. Telecomm., vol. 9, pp.3-6, Mar./Apr. 998. - 2 : - 2 ~ : - :, - 99 : - 993 : - 998 : - 998 ~ 23 : LG DTV - 23 ~ : - :,,