THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. 2018 Apr.; 29(4), 299 307. http://dx.doi.org/10.5515/kjkiees.2018.29.4.299 ISSN 1226-3133 (Print) ISSN 2288-226X (Online) Design and Analysis of 4D-8PSK-TCM System Considering the Nonlinear HPA Environment 안창영 유상범 이상규 유흥균 Changyoung An Sang-Burm Ryu* Sang-Gyu Lee* Heung-Gyoon Ryu 요약 X 4D-8PSK-TCM(Four Dimensional 8-ary Phase Shift Keying Trellis Coded Modulation) HPA(High Power Amplifier),, BER(Bit Error Rate). HPA. 2, 2.25 bits/channel-symbol 4D-8PSK-TCM., PAPR(Peak to Average Power Ratio), SRRC(Square Root Raised Cosine) Roll-off 0.35, HPA 15 20 db OBO(Output Back-Off), 1 db OBO. Abstract Considering a nonlinear high power amplifier(hpa) and a predistorter, we have designed a four-dimensional 8-ary phase shift keying trellis-coded modulation(4d-8psk-tcm) system, which is recommended for X-band satellite communications. Subsequently, we have evaluated and analyzed the spectrum, constellation characteristics, and BER performance of the system. In satellite communications, owing to the limited power, nonlinear characteristics that determine the operating point of the HPA must be analyzed because the HPA consumes high power. We herein report the design of the 4D-8PSK-TCM system, with efficiencies of 2 and 2.25 bits/channel-symbol. The simulation results confirmed that a 0.35 roll-off value is effective, considering the low peak-to-average power ratio(papr) characteristic and the narrow occupation bandwidth of the spectrum. It also confirmed that approximately 15 20 db of output backoff(obo) value is required at the HPA when the predistorter is not used, and approximately 1 db of the OBO value is required when the predistorter is used. Key words: Satellite Communication, 4D-8PSK-TCM, Nonlinear HPA, Predistortion, Viterbi Algorithm. 서론 CCSDS(Consultative Committee on Space Data Systems) X 2017. 2016 ( ) (No. 2016R1D1A1B01008046). (Department of Electronics Engineering, Chungbuk National University) * (Payload Electronics Team, Korea Aerospace Research Institute) Manuscript received October 13, 2017 ; Revised November 16, 2017 ; Accepted March 8, 2018. (ID No. 20171013-107) Corresponding Author: Heung-Gyoon Ryu (e-mail: ecomm@cbu.ac.kr) c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved. 299
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 29, no. 4, Apr. 2018. 8PSK(Phase Shift Keying)-TCM(Trellis Coded Modulation) 4D(Four Dimension) 4D-8PSK- TCM [1],[2]. 4D-8PSK-TCM TCM [3]. [4],[5]. HPA(High Power Amplifier). HPA. HPA. HPA [6],[7]., OOB(Out-Of- Band), (mask). OBO(Output Back-Off). OBO, HPA, OBO. OOB,.,.. HPA HPA., OBO. HPA. 4D-8PSK-TCM HPA. 4D-8PSK-TCM (shaping) SRRC(Square Root Raised Cosine), PAPR(Peak to Average Power Ratio), OBO.,,, HPA., CCSDS 4D-8PSK- TCM.,. SRRC, HPA, OBO, BER(Bit Error Rate).. 4D-8PSK-TCM 시스템 4D-8PSK-TCM 4. 8, 9, 10, 11. 2, 2.25 bits/channal-symbol 4D-8PSK-TCM. 2-1 Transmitter 4D-8PSK-TCM (differential encoder), (convolutional coder), (constellation mapper), 8PSK (modulator) [2],[3]. 3. 2,,, 2.25,,. 3 3-8 (modulo-8 adder). (code rate) 3/4, 3, 1. 그림 1. 4D-8PSK-TCM Fig. 1. Block diagram of 4D-8PSK-TCM transmitter. 300
6 (memory register), (constraint length) 7. 64. 4D-8PSK-TCM.,. -8 4 8-PSK 12. 8-PSK 3 8-PSK 4 8-PSK,. 1 4D-8PSK-TCM. 8, 9.. (1) (2) 4D- 8PSK-TCM. Mod. 2 bits/channel-symbol 4D-8PSK- TCM (1) [3]. mod mod mod mod (1) 2.25 bits/channel-symbol 4D-8PSK- TCM (2) [3]. 4D-8PSK-TCM 8-PSK 4 (Subset). 4D-8PSK-TCM. 2 8-PSK 1, 0 4, 1 5, 2 6, 3 7.., 2 bits/channel-symbol 4,,, [0, 0, 0, 0], [,,, ] [,,, ]. (auxiliary trellis).,,,, 4. 2-2 Receiver 4D-8PSK-TCM 4. (general trellis) Viterbi [3] [5].,,,, 4. 2 4D-8PSK-TCM. 4D-8PSK-TCM TMU (Transition Metric Unit), VD(Viterbi Decoder), SDU(Symbol Detection Unit), DMU(De-Mapper Unit), DFD(Differential Decoder). mod mod mod mod (2) 그림 2. 4D-8PSK-TCM Fig. 2. Block diagram of 4D-8PSK-TCM receiver. 301
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 29, no. 4, Apr. 2018. TMU 4. TMU (reference symbol) Euclidean. 4. 2, 2., 4. VD TMU C0, C1, C2, C3 Viterbi. VD BM(Branch Metric) PM(Path Metric), PM (trace back). 1 2 bits/channel-symbol 4D-8PSK- TCM. 1 x0, x1, x2, x3,,,. 0 표 1. 2 4D-8PSK-TCM Table 1. Auxiliary trellis information for 4D-8PSK-TCM with 2 bits/channel-symbol. State of auxiliary trellis Parallel branches State x3,x2,x1,x0 Combinations for BM 0 0000 C0+C0+C0+C0, C2+C2+C2+C2 1 0001 C0+C0+C0+C2, C2+C2+C2+C0 2 0010 C1+C1+C1+C1, C3+C3+C3+C3 3 0011 C1+C1+C1+C3, C3+C3+C3+C1 4 0100 C0+C0+C2+C2, C2+C2+C0+C0 5 0101 C0+C0+C2+C0, C2+C2+C0+C2 6 0110 C1+C1+C3+C3, C3+C3+C1+C1 7 0111 C1+C1+C3+C1, C3+C3+C1+C3 8 1000 C0+C2+C0+C2, C2+C0+C2+C0 9 1001 C0+C2+C0+C0, C2+C0+C2+C2 10 1010 C1+C3+C1+C3, C3+C1+C3+C1 11 1011 C1+C3+C1+C1, C3+C1+C3+C3 12 1100 C0+C2+C2+C0, C2+C0+C0+C2 13 1101 C0+C2+C2+C2, C2+C0+C0+C0 14 1110 C1+C3+C3+C1, C3+C1+C1+C3 15 1111 C1+C3+C3+C3, C3+C1+C1+C1 x0 0. x0 0 0, 2, 4, 6, 8, 10, 12, 14 8. 8. BM 2. 0 BM. PM PM BM. VD 4 BM PM. VD BM PM (traceback depth). 3. VD, PM. x0 x1, x2, x3. PM PM BM. VD. SDU. SDU VD 4. SDU VD 4,.. 2 bits/channel-symbol 4D-8PSK- 그림 3. Fig. 3. Trace-back process in trellis diagram of general trellis. 302
TCM 2, 2.25, 2.5, 2.75 bits/channelsymbol 4, 8, 16. DMD VD SDU (Constellation Demapping)., DFD 3 (Differential Decoding). TMU, VD, SDU, DMD, DFD. 2 2.25.. 비선형 HPA 와전치왜곡기 X 4D-8PSK-TCM HPA. 4. 3-1 Nonlinear HPA HPA. HPA,. HPA Saleh. Saleh AM/AM AM/PM. (3) (4) Saleh [6]. a r t AM AM A r ta r t r t AM P M A r t r t (3),.. (3) (4) 표 2. 2.25 4D-8PSK- TCM Table 2. Auxiliary trellis information for 4D-8PSK-TCM with 2.25 bits/channel-symbol. State of auxiliary trellis Parallel branches State x3,x2,x1,x0 Combinations for BM 0 0000 1 0001 2 0010 3 0011 4 0100 5 0101 6 0110 7 0111 8 1000 9 1001 10 1010 11 1011 12 1100 13 1101 14 1110 15 1111 3-2 Predistortor C0+C0+C0+C0, C2+C2+C2+C2, C0+C2+C0+C2, C2+C0+C2+C0 C2+C1+C2+C1, C2+C3+C2+C3, C0+C3+C0+C3, C0+C1+C0+C1 C0+C0+C0+C2, C0+C2+C0+C0, C2+C2+C2+C0, C2+C0+C2+C2 C0+C1+C0+C3, C0+C3+C0+C1, C2+C1+C2+C3, C2+C3+C2+C1 C3+C3+C3+C3, C1+C3+C1+C3, C3+C1+C3+C1, C1+C1+C1+C1 C3+C0+C3+C0, C3+C2+C3+C2, C1+C0+C1+C0, C1+C2+C1+C2 C1+C1+C1+C3, C3+C1+C3+C3, C3+C3+C3+C1, C1+C3+C1+C1 C1+C0+C1+C2, C3+C0+C3+C2, C1+C2+C1+C0, C3+C2+C3+C0 C0+C0+C2+C2, C2+C2+C0+C0, C0+C2+C2+C0, C2+C0+C0+C2 C0+C3+C2+C1, C2+C3+C0+C1, C2+C1+C0+C3, C0+C1+C2+C3 C2+C2+C0+C2, C0+C0+C2+C0, C2+C0+C0+C0, C0+C2+C2+C2 C2+C3+C0+C3, C0+C3+C2+C3, C0+C1+C2+C1, C2+C1+C0+C1 C1+C1+C3+C3, C1+C3+C3+C1, C3+C1+C1+C3, C3+C3+C1+C1 C3+C2+C1+C0, C1+C0+C3+C2, C1+C2+C3+C0, C3+C0+C1+C2 C3+C1+C1+C1, C3+C3+C1+C3, C1+C1+C3+C1, C1+C3+C3+C3 C3+C2+C1+C2, C3+C0+C1+C0, C1+C0+C3+C0, C1+C2+C3+C2 HPA HPA, 303
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 29, no. 4, Apr. 2018. 표 3. Table 3. Simulation parameters. 그림 4. SRRC, HPA, 4D-8PSK-TCM Fig. 4. Block diagram of 4D-8PSK-TCM considering SRRC filter, nonlinear HPA, and predistorter., (soft limiter). (5) (6) Saleh [7]. (5) (6) Parameters Modulation Convolutional coder General trellis Auxiliary trellis Transmission mode Values 4D-8PSK-TCM Code rate=3/4 # of memory register=6 64 states with 8 paths 16 states # of output bits=4 2, 2.25 bits/channel symbol Roll-off factor( ) of SRRC filter 0, 0.35, 0.5, 1 Nonlinear HPA model Output back-off Saleh model AM-AM=[2.1587 1.1517] AM-PM=[4.0033 9.1040] 0, 1, 3, 5, 7, 10, 15, 20 db. 0.35, 0.5, 1 3.5 db PAPR.. 0 (5), (6)..,,, Saleh.. 결과및분석 SRRC, HPA, 4D-8PSK-TCM,,, BER. 3. CCSDS [3], HPA. 5 4D-8PSK-TCM PAPR. 0, PAPR 그림 5. Roll-off 4D-8PSK-TCM PAPR (2 bits/channel-symbol) Fig. 5. PAPR characteristic of 4D-8PSK-TCM transmit signal (2 bits/channel-symbol). 304
. 4D-8PSK-TCM, 0.35. 0.5 PAPR 3.1 db 0.4 db., PAPR, 4D-8PSK-TCM SRRC, 0.35,, PAPR. 6 HPA Saleh AM/AM AM/PM.,. 6(a) 0 db (saturation point), OBO. Saleh AM/AM, 2.1587, 1.1517, AM/PM, 4.0033, 9.1040, 0 db 6.68 db, OBO. 7 OBO 2bits/channel-symbol 4D-8PSK-TCM. 7(a), 7(b), 7(c), 7(d) (a) AM/AM (b) AM/PM 그림 6. Saleh AM/AM AM/PM Fig. 6. AM/AM and AM/PM characteristics of Saleh model. (a) OBO=0 db, w/o PD (c) OBO=0 db, w/ PD (b) OBO=20 db, w/o PD (d) OBO=1 db, w/ PD 그림 7. OBO 4D-8PSK-TCM (2 bits/channel-symbol, Roll-off factor=0.35) Fig. 7. Spectrum characteristic of 4D-8PSK-TCM transmit signal according to OBO and PD (2 bits/channel-symbol, Roll-off factor=0.35).., HPA 6 MHz NTIA (spectrum mask)., 20 db OBO, 1 db OBO.,, HPA. 8 9 4D-8PSK-TCM HPA, BER. OBO HPA, OBO 15 20 db HPA 4D-8PSK-TCM BER. 305
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 29, no. 4, Apr. 2018. 그림 8. HPA 4D-8PSK-TCM OBO BER (2 bits/channel-symbol, =0.35) Fig. 8. BER performance of 4D-8PSK-TCM system considering nonlinear HPA according to OBO(2 bits/ channel-symbol, =0.35). 그림 10. HPA 4D-8PSK- TCM OBO BER (2 bits/ channel-symbol, =0.35) Fig. 10. BER performance of 4D-8PSK-TCM system considering nonlinear HPA and PD according to OBO (2 bits/channel-symbol, =0.35). 그림 9. HPA 4D-8PSK-TCM OBO BER (2.25 bits/channel-symbol, =0.35) Fig. 9. BER performance of 4D-8PSK-TCM system considering nonlinear HPA according to OBO(2.25 bits/ channel-symbol, =0.35)., HPA OBO, OBO. OBO. 10 11, HPA 4D- 8PSK-TCM BER., HPA BER OBO 1 db 그림 11. HPA 4D-8PSK- TCM OBO BER (2.25 bits/channel-symbol, =0.35) Fig. 11. BER performance of 4D-8PSK-TCM system considering nonlinear HPA and PD according to OBO (2.25 bits/channel-symbol, =0.35).., OBO. HPA.. 결론 X CCSDS 4D-8PSK-TCM, 306
SRRC, HPA, BER. 4D- 8PSK-TCM HPA, HPA 4D-8PSK-TCM, 15 20 db OBO, 1 db OBO., HPA, HPA. References [1] S. B. Ryu, E. S. Kang, S. G. Lee, D. K. Lee, J. T. Lee, and H. C. Lee, et al., "A study on the high speed data rate downlink systems of 4D-8PSK-TCM in low earth orbit," in Proceedings of Symposium of the Korean Institute of Communications and Information Sciences, Jun. 2016, pp. 5-6. [2] Radio Frequency and Modulation Systems - Part 1: Earth Stations and Spacecraft, CCSDS 401.0-B: Blue Book, Issue 2000-06, Apr. 2009. [3] Band-Efficient Modulation, CCSDS 401(3.3.6) Green Book, Apr. 2003. [4] A. Guérin, G. Lesthievent, and J. L. Issler, "Telemetry architectures for furture earth observation missions: over 1 Gbit/s in X-band," ITC2010, San Diego, Oct. 2010. [5] J. He, Z. Wang, and H. Liu, "An efficient 4-D 8PSK TCM decoder architecture," IEEE Transactions on Very Large Scale Integration(VLSI) Systems, vol. 18, no. 5, pp. 808-817, May 2010. [6] P. Drotar, J. Gazda, D. Kocur, and P. Galajda, "MC- CDMA performance analysis for different spreading codes at HPA Saleh model," in 2008 18th International Conference Radioelektronika, Prague, 2008, pp. 1-4. [7] M. M. Shammasi, S. M. Safavi, "Performance of a predistorter based on Saleh model for OFDM systems in HPA nonlinearity," in 2012 14th International Conference on Advanced Communication Technology(ICACT), Pyeongchang, 2012, pp. 148-152. 2013 2 : ( ) 2015 2 : ( ) 2015 3 : [ 주관심분야 ],, B5G 1993 : ( ) 1995 : ( ) 2011 : ( ) 1995 :, [ 주관심분야 ],, EESS, 1996 ( ) 2001 ( ) 2010 ( ) 2011 : [ 주관심분야 ],,, 1988 : 2002 3 2004 2 : [ 주관심분야 ],, B5G/6G, 307