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

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 number of first carrier x K max – sequential number of last carrier OFDM Signal Navigation NAV 2008 5

Continual pilot carriers Transmitted data carriers TPS carriers Scattered pilot carriers OFDM Signal Navigation NAV 2008 6

OFDM Signal Navigation NAV 2008 7

OFDM Signal Navigation NAV 2008 8

Continual pilot carriers Transmitted data carriers TPS carriers Scattered pilot carriers Signal snapshot processing OFDM Signal Navigation NAV 2008 9

OFDM Signal Navigation NAV 2008 10

Mode 2K 8K No Power No Power scattered pilot 13.7% 13.7% 143 569 carriers boosted (16/9) boosted (16/9) continual pilot 4.3% 4.3% 45 177 carriers boosted (16/9) boosted (16/9) TPS carriers 0.9% 0.9% 17 68 normal (1) normal (1) data carriers 81.1% 81.1% 1500 6003 normal (1) normal (1) Total 1705 100 % 6817 100% OFDM Signal Navigation NAV 2008 11

100% of signal power 18% of signal power 4.3% of signal power SNR [dB] Continual pilot Scatter & carriers Continual pilot Complete signal carriers σ r [m] σ r [m] σ r [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 OFDM Signal Navigation NAV 2008 12

Data demodulation Ranging OFDM Signal Navigation NAV 2008 13

Range measurement error of DLL (derived from linearized model) OFDM Signal Navigation NAV 2008 14

OFDM Signal Navigation NAV 2008 15

Navigation Navigation OFDM OFDM message message demod. & Demultiplex. demod. & Demultiplex. FEC decod. FEC decod. DVB-T DVB-T Nav. Nav. tuner tuner computer computer Snapshot Snapshot Snapshot Snapshot acquisition acquisition processing processing Pseudorange Pseudorange USB • Snapshot duration 2 ms • Acquisition period 100 ms • Frequency tuning 500 ms OFDM Signal Navigation NAV 2008 16

DVB-T signal gen. OFDM Signal Navigation NAV 2008 17

Low performance Higher performance hardware Navigation OFDM message demod. & Demultiplex. FEC decod. DVB-T Nav. tuner computer Snapshot Snapshot acquisition processing Pseudorange • Snapshot duration 2 ms => Continual measurement • Acquisition period 100 ms <20 ms – fractional space • Frequency tuning 500 ms synthesizer OFDM Signal Navigation NAV 2008 18

Data demodulation Navigation OFDM message demod. & Demultiplex. FEC decod. DVB-T Nav. tuner computer Snapshot Snapshot acquisition processing Pseudorange Range estimation OFDM Signal Navigation NAV 2008 19

- Simple replica generation - Whole signal energy for range measurement - Suboptimal Symbol timing Typ. BER 10 -9 Typ. BER 10 -3 & Carrier sync. Long latency Equalization FEC Base band Data FFT Interpolation & decoding conversion Demodulation Replica Continual pilot spectrum carrier replica estimation Time of IFFT Averaging Arrival Range estimation OFDM Signal Navigation NAV 2008 20

OFDM Signal Navigation NAV 2008 21