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Accurate Position Location in TDS-OFDM Based DTV Broadcasting Networks

This paper proposes a novel positioning scheme for Chinese DTV systems using PN-MC training sequence in the guard interval of TDS-OFDM signal frame, achieving high accuracy in distance estimation. The proposed scheme has low complexity and achieves positioning accuracy of less than 0.1m when SNR is greater than 15dB.

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Accurate Position Location in TDS-OFDM Based DTV Broadcasting Networks

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  1. Accurate Position Location in TDS-OFDM Based Digital Television (DTV) Broadcasting Networks Linglong Dai, Zhaocheng Wang, Jun Wang, Jintao Wang, and Yu Zhang Tsinghua University, Beijing, China

  2. Contents 1 Background 2 Time-Frequency Positioning Algorithm 3 Simulation Results 4 Conclusion

  3. DTV Based Positioning • Advantage over GPS[1] • Low Doppler effect due to fixed transmitter location • DTV signal has a power advantage of more than 40 dB • Reception in the presence of blockage and indoor environments • OFDM: robust to multi-path effect • Current Solutions • American DTV standard ATSC[2] • Correlation based scheme using the synchronization signals • The positioning accuracy was about several meters • European DTV standard DVB-T[3] • Correlation based scheme using frequency-domain pilots • The positioning accuracy is in the order of decimeters • Chinese DTV standard TDS-OFDM[4] • No solution !

  4. State-of-The-Art Positioning with OFDM Signals • Correlation Based Timing Synchronization Algorithms[5-8] • Traditional or improved timing synchronization • Locate the boundaries of OFDM blocks • Complexity is low • The accuracy limited by sampling rateseveral meters • Super Resolution Algorithms Based [9-10] • Adopt Super resolution algorithms on estimated channel frequency response • multiple signal classification (MUSIC) [9] • maximum likelihood (ML) [10] • matrix pencil (MP) [11] • Positioning accuracy is higher • Complexity is unacceptablyhigh for commercial receivers

  5. Contents 1 Background 2 Time-Frequency Positioning Algorithm 3 Simulation Results 4 Conclusion

  6. PN-MC training sequence • TDS-OFDM signal frame structure • Multi-Carrier PN (PN-MC) Sequence • Good Channel Estimation Performance [13] • Ideal Autocorrelation for Synchronization

  7. Time-Frequency Positioning Algorithm • Received PN-MC over the kth subcarrier Transmission delay normalized by sampling period Ts integral fractional is the channel frequency response (CFR) • Impact of the transmission delay • Time shift by samples in the time domain • Phase rotation by in the frequency domain

  8. Time-Frequency Positioning Algorithm • Integral Delay Estimation Using Time-Domain Correlation • Equivalent to timing synchronization in TDS-OFDM receiver • Timing Accuracy within • Insufficient for accurate positioning • Sampling rate of 7.56 MHz • Over-sampled by four (30.24 MHz) Ranging error of 20 m Ranging error of 5 m • Fractional Delay Estimation in Frequency-Domain • The received PN-MC can be simplified to be [16]

  9. Time-Frequency Positioning Algorithm • Step 1: Remove index k by G-lag autocorrelation • Step 2: Avoid phase ambiguity problem [17] by differential correlation • Step 3: Fractional delay byaveraging • Ranging Result for Positioning

  10. Performance Analysis • Positioning Accuracy • Cramer-Rao lower bound (CRLB) of the fractional delay estimator [18] • Thus, the positioning accuracy is is SNR • Computational Complexity

  11. Contents 1 Background 2 Joint Code Acquisition and DFS Estimation 3 Simulation Results 4 Conclusion

  12. Positioning Accuracy over AWGN Parameters: • PN-MC length 255 • cyclic extension length 165 • Sampling rate 30.24 MHz • Channel AWGN • The proposed scheme has the best positioning accuracy • When SNR is 15 dB, Estimation error is about 5 m for Mensing’s method [6] • 0.35 m for MP scheme [11] • 0.06 m for the proposed method • Simulated RMSE approaches the CRLB when SNR>10 dB

  13. Positioning Accuracy over Multi-path Channel Parameters: • PN-MC length 255 • cyclic extension length 165 • Sampling rate 30.24 MHz • Channel Brazil A & Brazil B • Positioning accuracy deteriorates a little • 0.06 m over AWGN channel • 0.096 m over Brazil A channel • 0.10 m over Brazil B channel

  14. Contents 1 Background 2 Joint Code Acquisition and DFS Estimation 3 Simulation Results 4 Conclusion

  15. Conclusions • This paper proposes a novel positioning scheme for Chinese DTV systems by using PN-MC training sequence in the guard interval of the time domain synchronous OFDM (TDS-OFDM) signal frame • The joint time-frequency positioning algorithm utilizes the properties of the received PN-MC sequence both in the time and frequency domain with respect to transmission delay • Distance estimation with high accuracy can be achieved • The positioning accuracy of less than 0.1 m when SNR is greater than 15 dB is achieved over both AWGN and the simulated multi-path channels • The complexity of the proposed scheme is low

  16. References (1) [1] E. D. Kaplan and C. Hegarty, Understanding GPS: Principles and Applications, 2nd ed. Boston, USA: Artech House Publishers, 2005. [2] M. Rabinowitz and J. Spilker, “A new positioning system using television synchronization signals,” IEEE Trans. Broadcast., vol. 51, no. 1, pp. 51–61, Mar. 2005. [3] P. Kovar and F. Vejrazka, “Multi system navigation receiver,” in Proc. IEEE/ION Position Location and Navigation Symposium (PLANS’08), May 2008, pp. 860–864. [4] Framing Structure, Channel Coding and Modulation for Digital Television Terrestrial Broadcasting System. Chinese National Standard, GB 20600-2006, Aug. 2006. [5] O. Bar-Shalom and A. J. Weiss, “Efficient direct position determination of orthogonal frequency division multiplexing signals,” IET Radar Sonar and Navigation, vol. 3, no. 2, pp. 101–111, Jun. 2009. [6] C. Mensing, S. Plass, and A. Dammann, “Synchronization algorithms for positioning with OFDM communications signals,” in Proc. 4th Workshop on Positioning, Navigation and Communication (WPNC’07), Mar. 2007, pp. 205–210. [7] R. K. Martin, J. S. Velotta, and J. F. Raquet, “Bandwidth efficient cooperative TDOA computation for multicarrier signals of opportunity,” IEEE Trans. Signal Processing, vol. 57, no. 6, pp. 2311–2322, Jun. 2009. [8] R. K. Martin, C. Yan, and H. H. Fan, “Bounds on distributed TDOAbased localization of OFDM sources,” in Proc. IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP’09), Apr. 2009, pp. 2289–2292. [9] X. Li and K. Pahlavan, “Super-resolution TOA estimation with diversity for indoor geolocation,” IEEE Trans. Wireless Commun., vol. 3, no. 1, pp. 224–234, Jan. 2004.

  17. References (2) [10] P. J. Voltz and D. Hernandez, “Maximum likelihood time of arrival estimation for real-time physical location tracking of 802.11a/g mobile stations in indoor environments,” in Proc. IEEE/ION Position Location and Navigation Symposium (PLANS’04), Apr. 2004, pp. 585–591. [11] T. J. S. Khanzada, A. R. Ali, and A. S. Omar, “Time difference of arrival estimation using super resolution algorithms to minimize distance measurement error for indoor positioning systems,” in Proc. IEEE International Conference on Multitopic Conference (INMIC’08), Dec. 2008, pp. 443–447. [12] H. Meyr, M. Moeneclaey, and S. Fechtel, Digital Communication Receivers: Synchronization, Channel Estimation and Signal Processing. New York, USA: John Wiley Sons, 1997. [13] Y. Zeng and T. S. Ng, “Pilot cyclic prefixed single carrier communication: channel estimation and equalization,” IEEE Signal Processing Lett., vol. 12, no. 1, pp. 56–59, Jan. 2005. [14] J. Wang, Z. Yang, C. Pan, M. Han, and L. Yang, “A combined code acquisition and symbol timing recovery method for TDS-OFDM,” IEEE Trans. Broadcast., vol. 49, no. 3, pp. 304–308, Sep. 2003. [15] M. Morelli, C. C. J. Kuo, and M. O. Pun, “Synchronization techniques for orthogonal frequency division multiple access (OFDMA): A tutorial review,” Proc. IEEE, vol. 95, no. 7, pp. 1394–1427, Jul. 2007. [16] D. K. Kim, S. H. Do, H. B. Cho, H. J. Chol, and K. B. Kim, “A new joint algorithm of symbol timing recovery and sampling clock adjustment for OFDM systems,” IEEE Trans. Consumer Electron., vol. 44, no. 3, pp. 1142–1149, Aug. 1998. [17] M. Speth, S. Fechtel, G. Fock, and H. Meyr, “Optimum receiver design for OFDM-based broadband transmission-part II: A case study,” IEEE Trans. Commun., vol. 49, no. 4, pp. 571–578, Apr. 2001. [18] S. M. Kay, Fundamentals of Statistical Signal Processing: Estimation Theory, 1st ed. New Jersey, USA: Prentice-Hall, 1993. [19] Digital Television Systems-Brazilian Tests-Final Report. SET/ABERT ANATEL SP, May 2000.

  18. Thank you for your suggestions !

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