volume | PIER Journals

Abstract

Chirp sequence has been adopted in automotive applications for its simple generation and flexible integration within radar-centric systems. Besides, recent studies have shown its ability to carry data between communicating vehicles in the surroundings. Since the parameters adopted from current automotive radar sensors can differ at the transmitter side dependent on the automotive supplier, the carrier alignment of the communication receiver of one of the communicated nodes might not concur with the one in the transmitter. This paper presents a novel two-stage synchronization method for communication-assisted chirp sequence (CaCS) signals. The proposed synchronization method applies a sequence of up- and down-chirp as a preamble to estimate frequency and time offsets during the transmission. The suggested synchronization scheme supports partial chirp modulation systems and can be adapted for similar radar-centric systems that employ chirp modulation. The former stage performs a coarse synchronization, reallocates the receive carrier frequency, and corrects eventual time offsets between the communication receiver from one CaCS-node and the transmitter of another node. The carrier allocation at the communication receiver side is based on a combination of spectrum sensing via short-time Fourier transforms and image processing to estimate the transmitting signal pattern (slope, frequency offset, and delay). The latter stage, in its turn, relies on range-Doppler estimation to perform a fine correction of time and frequency offsets and compensates residual offsets of the coarse synchronization stage. Furthermore, the paper analyzes the case of a multi-user scenario with mutual interference between the signals that affects the synchronization and communication data detection. Besides, measurements are provided based on two completely unsynchronized software-defined radios to validate the proposed method. The study also illustrates the influence of the signal-to-noise ratio on the proposed method and verifies it with simulations in MATLAB. As a result, the offsets at the investigated CaCS-node are returned to recover the transmitted data correctly.

1. Roos, F., J. Bechter, C. Knill, B. Schweizer, and C. Waldschmidt, "Radar sensors for autonomous driving: Modulation schemes and interference mitigation," IEEE Microw. Mag., Vol. 20, No. 9, 58-72, 2019.
doi:10.1109/MMM.2019.2922120 Google Scholar

2. Hakobyan, G. and B. Yang, "High-performance automotive radar: A review of signal processing algorithms and modulation schemes," IEEE Signal Process. Mag., Vol. 36, No. 5, 32-44, 2019.
doi:10.1109/MSP.2019.2911722 Google Scholar

3. Waldschmidt, C., J. Hasch, and W. Menzel, "Automotive radar --- From first efforts to future systems," IEEE J. Microw., Vol. 1, No. 1, 135-148, 2021.
doi:10.1109/JMW.2020.3033616 Google Scholar

4. Bechter, J., F. Roos, M. Rahman, and C. Waldschmidt, "Automotive radar interference mitigation using a sparse sampling approach," Proc. Eur. Radar Conf. (EURAD), 90-93, 2017. Google Scholar

5. Aydogdu, C., M. F. Keskin, N. Garcia, H. Wymeersch, and D. W. Bliss, "Radchat: Spectrum sharing for automotive radar interference mitigation," IEEE Trans. Intell. Transp. Sys., Vol. 22, No. 1, 416-429, 2021.
doi:10.1109/TITS.2019.2959881 Google Scholar

6. Aydogdu, C., M. F. Keskin, G. K. Carvajal, O. Eriksson, H. Hellsten, H. Herbertsson, E. Nilsson, M. Rydstrom, K. Vanas, and H. Wymeersch, "Radar interference mitigation for automated driving: Exploring proactive strategies," IEEE Signal Process. Mag., Vol. 37, No. 4, 72-84, 2020.
doi:10.1109/MSP.2020.2969319 Google Scholar

7. Al-Hourani, A., R. J. Evans, S. Kandeepan, B. Moran, and H. Eltom, "Stochastic geometry methods for modeling automotive radar interference," IEEE Transactions on Intelligent Transportation Systems, Vol. 19, No. 2, 333-344, 2018.
doi:10.1109/TITS.2016.2632309 Google Scholar

8. IEEE Veh. Tech. Mag., Special Issue on V2V Communications 2(4), Dec. 2007.

9. Karagiannis, G., O. Altintas, E. Ekici, G. Heijenk, B. Jarupan, K. Lin, and T. Weil, "Vehicular networking: A survey and tutorial on requirements, architectures, challenges, standards and solutions," IEEE Communications Surveys Tutorials, Vol. 13, No. 4, 584-616, 2011.
doi:10.1109/SURV.2011.061411.00019 Google Scholar

10. 3GPP, Service requirements for enhanced V2X scenarios (3GPP TS 22.186 version 15.3.0 Release 15), 2020.

11. IEEE "IEEE Standard for Information technology --- Local and metropolitan area networks --- Specific requirements --- Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 6: Wireless Access in Vehicular Environments,", IEEE Std 802.11p-2010 (Amendment to IEEE Std 802.11-2007), 1-51, 2010. Google Scholar

12. Manolakis, K. and W. Xu, "Time synchronization for multi-link D2D/V2X communication," Proc. IEEE 89th Veh. Technol. Conf. (VTC-Fall), 1-6, 2016. Google Scholar

13. ETSI "Intelligent Transport Systems (ITS); Performance Evaluation of Self-Organizing TDMA as Medium Access Control Method Applied to ITS,", Access Layer Part, 2011-2012. Google Scholar

14. Sturm, C. and W. Wiesbeck, "Waveform design and signal processing aspects for fusion of wireless communications and radar sensing," Proc. IEEE, Vol. 99, No. 7, 1236-1259, 2011.
doi:10.1109/JPROC.2011.2131110 Google Scholar

15. De Oliveira, L. G., B. Nuss, M. B. Alabd, A. Diewald, M. Pauli, and T. Zwick, "Joint radar-communication systems: Modulation schemes and system design," IEEE Trans. Microw. Theory Techn., Mar. 2022. Google Scholar

16. Hassanien, A., M. G. Amin, E. Aboutanios, and B. Himed, "Dual-function radar communication systems: A solution to the spectrum congestion problem," IEEE Signal Process. Mag., Vol. 36, No. 5, 115-126, 2019.
doi:10.1109/MSP.2019.2900571 Google Scholar

17. Sit, Y. L., C. Sturm, T. Zwick, L. Reichardt, and W. Wiesbeck, "The OFDM joint radar-communication system: An overview," The 3rd Int. Conf. on Adv. in Satell. and Space Commun., SPACOMM 2011, 69-74, Budapest, Hungary, Apr. 17-22, 2011. Google Scholar

18. Braun, K. M. OFDM radar algorithms in mobile communication networks, Ph.D. dissertation, Karlsruher Institut fur Technologie (KIT), 2014.

19. De Oliveira, L. G., M. B. Alabd, B. Nuss, and T. Zwick, "An OCDM radar-communication system," 2020 14th Eur. Conf. Antennas Propag., 1-5, 2020. Google Scholar

20. De Oliveira, L. G., B. Nuss, M. B. Alabd, Y. Li, L. Yu, and T. Zwick, "MIMO-OCDM-based joint radar sensing and communication," 2021 15th Eur. Conf. Antennas Propag., 1-5, 2021. Google Scholar

21. Schmidl, T. and D. Cox, "Robust frequency and timing synchronization for OFDM," IEEE Trans. Commun., Vol. 45, No. 12, 1613-1621, 1997.
doi:10.1109/26.650240 Google Scholar

22. Ouyang, X. Digital signal processing for fiber-optic communication systems, Ph.D. dissertation, University College Cork, Ireland, 2017.

23., TI, AWR2243 Single-Chip 76- to 81-GHz FMCW Transceiver, 2020. Google Scholar

24. Barrenechea, P., F. Elferink, and J. Janssen, "FMCW radar with broadband communication capability," Proc. Eur. Radar Conf. (EURAD), 130-133, 2007. Google Scholar

25. Scheiblhofer, W., R. Feger, A. Haderer, and A. Stelzer, "Method to embed a data-link on FMCW chirps for communication between cooperative 77-GHz radar stations," Proc. Eur. Radar Conf. (EURAD), 181-184, 2015. Google Scholar

26. Lampel, F., R. F. Tigrek, A. Alvarado, and F. M. Willems, "A performance enhancement technique for a joint FMCW RadCom system," Proc. Eur. Radar Conf. (EURAD), 169-172, 2019. Google Scholar

27. Dwivedi, S., A. N. Barreto, P. Sen, and G. Fettweis, "Target detection in joint frequency modulated continuous wave (FMCW) radar-communication system," Proc. 16th Int. Symp. on Wireless Commun. Syst. (ISWCS), 277-282, 2019. Google Scholar

28. Dwivedi, S., M. Zoli, A. N. Barreto, P. Sen, and G. Fettweis, "Secure joint communications and sensing using chirp modulation," 2nd 6G Wireless Summit (6G SUMMIT), 1-5, 2020. Google Scholar

29. Alabd, M. B., B. Nuss, C. Winkler, and T. Zwick, "Partial chirp modulation technique for chirp sequence based radar communications," Proc. Eur. Radar Conf. (EURAD), 173-176, 2019. Google Scholar

30. Lampel, F., F. Uysal, F. Tigrek, S. Orru, A. Alvarado, F. Willems, and A. Yarovoy, "System level synchronization of phase-coded FMCW automotive radars for RadCom," 2020 14th Eur. Conf. Antennas Propag., 1-5, 2020. Google Scholar

31. Bernier, C., F. Dehmas, and N. Deparis, "Low complexity lora frame synchronization for ultra-low power software-defined radios," IEEE Trans. Commun., Vol. 68, No. 5, 3140-3152, 2020.
doi:10.1109/TCOMM.2020.2974464 Google Scholar

32. Martinez, A. B., A. Kumar, M. Chafii, and G. Fettweis, "A chirp-based frequency synchronization approach for flat fading channels," 2020 2nd 6G Wireless Summit (6G SUMMIT), 1-5, 2020. Google Scholar

33. Aydogdu, C., M. F. Keskin, and H. Wymeersch, "Automotive radar interference mitigation via multi-hop cooperative radar communications," 2020 17th European Radar Conference (EuRAD), 270-273, 2021.
doi:10.1109/EuRAD48048.2021.00076 Google Scholar

34. Winkler, V., "Novel waveform generation principle for short-range FMCW-radars," Proc. German Microw. Conf., 1-4, 2009. Google Scholar

35. Kronauge, M. and H. Rohling, "New chirp sequence radar waveform," IEEE Trans. Aerosp. Electron. Syst., Vol. 50, No. 4, 2870-2877, 2014.
doi:10.1109/TAES.2014.120813 Google Scholar

36., TI, LMX2491 6.4-GHz Low Noise RF PLL With Ramp/ChirpGeneration, 2017.
doi:10.1109/TAES.2014.120813 Google Scholar

37. Winkler, V., "Range doppler detection for automotive FMCW radars," Proc. Eur. Radar Conf. (EURAD), 166-169, 2007. Google Scholar

38. Alabd, M. B., L. G. de Oliveira, B. Nuss, W. Wiesbeck, and T. Zwick, "Time-frequency shift modulation for chirp sequence based radar communications," Proc. IEEE MTT-S Int. Conf. on Microw. for Intell. Mobility (ICMIM), 1-4, 2020. Google Scholar

39. Alabd, M. B., B. Nuss, L. G. de Oliveira, A. Diewald, Y. Li, and T. Zwick, "Modified pulse position modulation for joint radar communication based on chirp sequence," IEEE Microwave and Wireless Components Letters, 1-4, 2022. Google Scholar

40. Krawczyk, M. and T. Gerkmann, "STFT phase reconstruction in voiced speech for an improved single-channel speech enhancement," IEEE/ACM Trans. on Audio, Speech, and Language Process., Vol. 22, No. 12, 1931-1940, 2014.
doi:10.1109/TASLP.2014.2354236 Google Scholar

41. Muller, M., Fundamentals of Music Process, Springer International Publishing, 2015.
doi:10.1007/978-3-319-21945-5

42. Ester, M., H.-P. Kriegel, J. Sander, and X. Xu, "A density-based algorithm for discovering clusters in large spatial databases with noise," Proc. of the 2nd Int. Conf. on Knowledge Discovery and Data Mining, ser. KDD'96, 226-231, AAAI Press, 1996. Google Scholar

43. Baglivo, J. A., , Mathematica Laboratories for Mathematical Statistics, Society for Industrial and Applied Mathematics, 2005. Google Scholar

44. Vishwanath, T. G., M. Parr, Z.-L. Shi, and S. Erlich, "Synchronization in mobile satellite systems using dual-chirp waveform,", Patent, U.S. Patent 6,418,158 B1, Jul. 9, 2002. Google Scholar

45. Torres, L. L. T., F. Roos, and C. Waldschmidt, "Simulator design for interference analysis in complex automotive multi-user traffic scenarios," IEEE Radar Conf. (RadarConf20), 1-6, 2020. Google Scholar

46., Ettus Research. USRP. X300 and X310X Series. Google Scholar

Mr. Mohamad Basim Alabd

Dr. Benjamin Nuss

Dr. Lucas Giroto de Oliveira

Dr. Yueheng Li

Dr. Axel Diewald

Dr. Thomas Zwick