OFDM Signal Navigation NAV 2008 2 OFDM Signal Navigation NAV 2008 - - PowerPoint PPT Presentation

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Jan 27, 2023 679 likes •916 views

OFDM Signal Navigation NAV 2008 2 OFDM Signal Navigation NAV 2008 3 OFDM Signal Navigation NAV 2008 4 OFDM symbol c n,Kmin x Serial-parallel converter Symbol mapping Transported c n,Kmin+1 data x + c n,Kmax K min sequential

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NAV 2008 OFDM Signal Navigation 2

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NAV 2008 OFDM Signal Navigation 3

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NAV 2008 OFDM Signal Navigation 4

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NAV 2008 OFDM Signal Navigation 5

Transported data

cn,Kmin cn,Kmin+1 cn,Kmax x x x +

OFDM symbol

Kmin – sequential number of first carrier Kmax – sequential number of last carrier

Serial-parallel converter Symbol mapping

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NAV 2008 OFDM Signal Navigation 6

Transmitted data carriers Scattered pilot carriers Continual pilot carriers TPS carriers

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NAV 2008 OFDM Signal Navigation 7

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NAV 2008 OFDM Signal Navigation 8

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NAV 2008 OFDM Signal Navigation 9

Transmitted data carriers Scattered pilot carriers Continual pilot carriers TPS carriers

Signal snapshot processing

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NAV 2008 OFDM Signal Navigation 10

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NAV 2008 OFDM Signal Navigation 11

Mode 2K 8K No Power No Power scattered pilot carriers 143 13.7% boosted (16/9) 569 13.7% boosted (16/9) continual pilot carriers 45 4.3% boosted (16/9) 177 4.3% boosted (16/9) TPS carriers 17 0.9% normal (1) 68 0.9% normal (1) data carriers 1500 81.1% normal (1) 6003 81.1% normal (1) Total 1705 100 % 6817 100%

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NAV 2008 OFDM Signal Navigation 12

SNR [dB] Continual pilot carriers σr [m] Scatter & Continual pilot carriers σr [m] Complete signal σr [m] 5 0.487 0.425 0.180 10 0.274 0.239 0.101 15 0.144 0.126 0.053 20 0.086 0.075 0.032 25 0.048 0.042 0.018 30 0.028 0.025 0.010

4.3% of signal power 18% of signal power 100% of signal power

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NAV 2008 OFDM Signal Navigation 13

Data demodulation Ranging

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NAV 2008 OFDM Signal Navigation 14

Range measurement error of DLL

(derived from linearized model)

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DVB-T tuner OFDM

demod. &

FEC decod. Snapshot acquisition Demultiplex. Snapshot processing Nav. computer

Navigation message Pseudorange

DVB-T tuner OFDM

demod. &

FEC decod. Snapshot acquisition Demultiplex. Snapshot processing Nav. computer

Navigation message Pseudorange

Snapshot duration

2 ms

Acquisition period

100 ms

Frequency tuning

500 ms

USB

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NAV 2008 OFDM Signal Navigation 17

DVB-T signal gen.

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NAV 2008 OFDM Signal Navigation 18

DVB-T tuner OFDM

demod. &

FEC decod. Snapshot acquisition Demultiplex. Snapshot processing Nav. computer

Navigation message Pseudorange

Snapshot duration

2 ms

Acquisition period

100 ms

Frequency tuning

500 ms => Continual measurement <20 ms – fractional space synthesizer Higher performance hardware Low performance

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NAV 2008 OFDM Signal Navigation 19

DVB-T tuner OFDM

demod. &

FEC decod. Snapshot acquisition Demultiplex. Snapshot processing Nav. computer

Navigation message Pseudorange

Data demodulation Range estimation

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NAV 2008 OFDM Signal Navigation 20

Base band conversion Interpolation

FFT

Equalization & Demodulation

FEC decoding

Symbol timing & Carrier sync.

Data

Replica spectrum estimation

IFFT Averaging

Time of Arrival estimation

Range

Whole signal energy for range measurement
Typ. BER 10-3
Typ. BER 10-9

Long latency Continual pilot carrier replica

Simple replica generation
Suboptimal

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