1. Positioning in Chinese Digital Television
Network Using TDS-OFDM Signals
Linglong Dai, Zhaocheng Wang, Changyong Pan, and Sheng Chen
Tsinghua University, Beijing, China
University of Southampton, Southampton SO17 1BJ, U.K.

2. 基于TDS-OFDM信号的时频二维定位算法提纲 1
研究背景 2
基于TDS-OFDM信号的时频二维定位算法 3
仿真结果 4 结论

3. DTV-Based Positioning
Global Positioning System (GPS) [Kaplan05]
Worldwide (Oceans, desert)
Hard to use in indoors, dense urban areas
National security Compass
Digital Television (DTV)-Based Positioning
Advantages [Spilker05]
Much higher received power : 40 dB (10000 times)
Wider signal bandwidth
Lower Doppler effect
DTV-Based Positioning: a promising complementary to GPS

4. Positioning Using OFDM
Positioning Using OFDM Signals
Correlation-based timing synchronization algorithms [Shalom09] [Mensing07] [Martin09]
Low complexity
Low Accuracy
Super-resolution algorithms (e.g., MUSIC) [Khanzada08] [Li04]
High accuracy
High complexity
Current DTV-Based Positioning Solutions
ATSC: Correlation based on the SYNC signal [Spilker05]
ATSC/ASTC-M/H: orthogonal Kasami sequences ssuperimposed on the normal TV signals [Wang06]
DVB-T: Correlation based on the frequency-domain pilots [Kovar08]
DVB-H: Artificial delays in single frequency network (SFN) [Thevenon09]
Positioning based on
Chinese DTV standard
(TDS-OFDM signal)
Very few ! 4

5. Positioning Using TDS-OFDM Signal
Contents 1
Background 2
Positioning Using TDS-OFDM Signal 3
Simulation Results 4
Conclusion 5 5

6. TDOA-Based Positioning Model in SFN
Single Frequency Network (SFN)
Most DTV systems are deployed in SFN mode
6 SFN transmitters in Hongkong
Better coverage and higher spectral efficiency
Synchronicity among different transmitters in SFN
Time Difference of Arrival (TDOA)
Remove the common TOA estimation error
Receiver location: intersection of hyperbolic curves
Two fundamental issues
Accurate TOA estimation
Transmitter identification 6

7. Positioning Using TDS-OFDM Signals (1)
Regarding TPS as Frequency-Domain Pilots
Transmission parameter signaling (TPS)
Inform the coding rate, modulation schemes, etc.
36 TPS out of the 3780 subcarriers [DTMB06]
Invariant property of TPS regarded as known pilots
Training information: time-domain onlytime-frequency domains 7

8. Positioning Using TDS-OFDM Signals (2)
TDM of TPS as Orthogonal Frequency-Domain Pilots
Time-division multiplexing (TDM) of TPS for transmitter identification
Provide the orthogonality in the time domain
No impact on normal TV program 8

9. Positioning Using TDS-OFDM Signals (3)
Impact of the transmission delay on the received OFDM signal
Integral delay: time shift by samples in the time domain
Fractional delay: phase rotation of in the frequency domain
Transmission delay:
Integral delay
Fractional delay
Received signal: 9

10. Positioning Using TDS-OFDM Signals (3)
Time-Frequency Positioning Algorithm
Integral TOA estimation using time-domain PN sequence
Time-domain correlation to find the correlation peaks
Timing accuracy:
Several meters 10

11. Positioning Using TDS-OFDM Signals (3)
Fractional TOA estimation using frequency-domain TPS
Firstly: facilitate correlation peaks identification
Secondly: fractional delay estimation 11

12. Performance Analysis Ranging Accuracy Average ranging time
Computational Complexity
High accuracy
Fast
Method
Complexity
Correlation-based
Super-resolution-based
Proposed time-frequency method
acceptable 12

13. Positioning Using TDS-OFDM Signal
Contents 1
Background 2
Positioning Using TDS-OFDM Signal 3
Simulation Results 4
Conclusion 13 13

14. Simulation Results (1) Main parameters 1. Higher accuracy
Central carrier：UHF (770 MHz)
Signal bandwidth： 7.56 MHz
Channel：ITU Indoor A
SARFT 8
M = 4
Modulation：QPSK/16QAM
Sampling rate：7.56 MHz*4
N=3780, K=420
1. Higher accuracy
2. Coincides with the theoretical bound 14 14

15. Simulation Results (2) Accuracy in multi-path channels is also high 15

16. Simulation Results (3)
No impact on normal TV program reception 16 16

17. Positioning Using TDS-OFDM Signal
Contents 1
Background 2
Positioning Using TDS-OFDM Signal 3
Simulation Results 4
Conclusion 17 17

18. Brief Conclusions
The positioning solution using TDS-OFDM signals for Chinese DTV standard in SFN is proposed in this paper;
The TPS embedded in the TDS-OFDM signal is time-division multiplexed as orthogonal frequency-domain pilots;
The proposed time-frequency positioning scheme jointly utilizes the time-domain PN sequence and frequency-domain TPS (pilots) for accurate TOA estimation of each transmitter;
Results obtained have shown that the proposed positioning scheme achieves a higher positioning accuracy compared with the state-of-the-art methods, while imposing a low complexity.

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20. ありがとう
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