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L1 detection performances on LMS-ITS channel

L1 detection performances on LMS-ITS channel. Benjamin Ros , Christelle BOUSTIE Benjamin.ros@cnes.fr , christelle.boustie@cnes.fr. Introduction. In the standardization process, simulations on L1 detection have shown that

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L1 detection performances on LMS-ITS channel

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  1. L1 detection performances on LMS-ITS channel Benjamin Ros , Christelle BOUSTIE Benjamin.ros@cnes.fr, christelle.boustie@cnes.fr

  2. Introduction • In the standardization process, simulations on L1 detection have shown that • Native DVB-T2 L1 encoding was not robust enough against terrestrial mobile Channel • Samsung has proposed Additional Parity (AP) concept mixed with time diversity to increase L1 detection probability • Results seamed that AP put in previous frame would bring enough robustness even in TU6 channel (Cf Samsung NGH 751) contribution, providing well suited parameters • Recent results have been brought in LMS-SU channel • CNES has developped a “L1 post” simulation chain, in which AP and spreading algorithms (close to Samsung approach) are implemented based on a DVB-T2 waveform • Simulations are run over LMS-ITS channel • Effect of PLP number, spreading granularity, interleaving length are studied

  3. Simulator Cross Validation Validation of native DVB-T2 encoding in QPSK 4/9 is done regarding results of NGH105 (SAMSUNG/NOKIA) contribution Channel = TU6 QPSK 1/2 Doppler = 80 Hz BW = 8 MHz GI = ¼ Mode = 8k Frame = 0.25 s Nb PLP = 32 / 45 No additional parity 45 45 3

  4. L1 data (for DVB-T2 and NGH) • DVB-T2 case • L1 signaling field is located on P2 symbols • L1 pre number of bits : 168 + 32 (CRC) = 200 bits • L1 post : 213 + 137 x Num_PLP bits • L1 post config : 102 + 89xNum_PLP bits • L1 post dynamic : 79 + 48xNumPLP bits • 32 CRC bits • NGH phase 1 case (based on Samsung NGH 755 contribution) • Adding some fields to L1 config • (L1_AP_Start + L1_NUM_AP_blocks) + (L1_AP_lenght+ L1_AP_Frame_pointer+ L1_AP_RSV)*NumPLP • 20 + 12 * NumPLP • Total L1 post size is becoming 233 + 149 x Num_PLP bits • if 1 PLP, “NGH” L1 post is 382 bits size, 2 PLPs 531 bits, 10 PLP 1723 bits, 16 PLP 2617 bits, 32 PLP 5001 bits

  5. Remember L1 post encoding : • BCHblock code is zero padded in complement to L1 post to fulfil BCH input • Zero padded data + BCH parity are encoded with LDPC • LDPC parity is punctured according to the size of L1 post • In DVB-T2, only L1 post, BCH_FEC and remaining LDPC parity bits are sent • Additional Parity building principle : • Total LDPC parity is sorted in a circular buffer starting with punctured bits • Additional Parity vector is built by parsing circular buffer • Total Additonal parity vector size depends on system parameters (see next slide) Additional Parity Building (near from Samsung first Proposition) Nldpc Kldpc BCH input (Kbch) BCHFEC Total LDPC parity Puncturing Npunc Remaining Punctured Circular buffer Punctured Remaining … Total additional Parity vector AP_BlockSize * Nb_blocks

  6. Additional Parity Building • Independently from PLP number , it has been decided to set Additional Parity size to the total LDPC parity size • “Effective Coding Rate” CR is depending on PLP number • Total parity is split in AP_Nb_Blocks • Blocks are spread on other frames with a given interval (see next slide) overall additional parity size = LDPC parity size (before puncturing) LDPC total parity size Removed Remaining AP block size ~ (Nldpc-Kldpc)/ Nb blocks ( Here : Nb blocks = 4 ) AP_BlockSize * Nb blocks

  7. L1post k+10 AP1k+13 AP2k+16 • 1st Step : L1 post native encoding is buffered • 2nd Step : Additional Parity blocks are computed and buffered • 3rd Step : AP blocks are transmitted in advance, every AP_interval frames • Lastly, native L1 post is transmitted • Note that Additional Parity blocks corresponding to different frames are transmitted in the same P2 field Additional Parity : Shifting AP1k+12 L1post k+9 AP2k+15 AP_Nb_Blocks = 2, AP_Interval = 3 L1post k+8 AP1k+11 AP2k+14 L1post k+7 AP1k+10 AP2k+13 AP_Nb_Blocks L1post k+6 AP1k+9 AP2k+12 ….. L1post k+5 AP1k+8 AP2k+11 time AP1k+7 L1post k+10 AP1k+10 AP2k+10 L1post k+4 AP2k+10 L1post k+3 AP1k+6 L1post k+9 AP1k+9 AP2k+9 AP2k+9 AP1k+5 L1post k+8 AP1k+8 AP2k+8 L1post k+2 AP2k+8 AP_Interval L1post k+7 AP1k+7 AP2k+7 L1post k+1 AP1k+4 AP2k+7 AP1k+3 L1post k+6 AP1k+6 AP2k+6 L1post k AP2k+6 L1post k+5 AP1k+5 AP2k+5 L1post k-1 AP1k+2 AP2k+5 AP_Interval L1post k+4 AP1k+4 AP2k+4 L1post k-2 AP1k+1 AP2k+4 L1post k+3 AP1k+3 AP2k+3 L1post k-3 AP1k AP2k+3 L1post k-4 AP1k-1 L1post k+2 AP1k+2 AP2k+2 AP2k+2 L1post k+1 AP1k+1 AP2k+1 L1post k-5 AP1k-2 AP2k+1 L1post k-6 AP1k-3 L1post k AP1k AP2k AP2k P2 field 1st Step 2nd Step 3rd Step

  8. Only NGH frame (sat case) • Physical layer setting • LMS ITS Channel with 40° elevation, 60 Km/h • QPSK ½, LDPC 4K • BW = 5 MHz, FFT 2k, Guard Interval 1/8 • NGH Frame period : 250 ms • Max AP dispersion : 5 - 10 s • L1 Additionnal parity settings Simulation Parameters NGH-2 NGH-1 NGH0 NGH+1 L1-2 + AP+3 L10 + AP+5 L1-1 + AP+4

  9. Results : LMS-ITS with additional parity (FER, BER) Legend : number of PLP;AP_1block_cell_size /AP_Nb_Blocks/AP_interval Convergence of BER 10-5 @ 10 -12 dB. L1 error rate 10-4 expected @ at least 11 dB

  10. Results : LMS-ITS with additional parity (ESR5) Legend : number of PLP;AP_1block_cell_size /AP_Nb_Blocks/AP_interval  ESR5 90% reached @ 7 - 9 dB

  11. Analysis of recent SAMSUNG results (NGH 1319) 600 ms Results on LMS-SU channel 400 ms NGH-1 DVB-T2 NGH0 L1-1 + AP0 L1 + AP+1 • L1 encoded with LDPC 4k code very low coding rate • L1 modulated in BPSK • Spreading of L1 Additional parity in the last NGH frame, meaning 600ms before current frame • LMS-SU channel  ESR5 90% reached @ 3 - 4 dB

  12. Conclusions • Additional Parity, powerful mean of robustness, has been introduced by SAMSUNG in NGH standardisation • This technology is getting more efficient when associated with spreading • Other configurations are also acceptable : reduced spreading can be introduced providing a little more favourable environment (LMS-SU) associated with more robust Modulation/Coding scheme (BPSK + LDPC 4K) • Nevertheless, 600ms interleaving can not be reached with reduced spreading scheme because there is no transport of DVB-T2 frames on satellite link 12

  13. Backing Slides

  14. L1 disposition in P2 cells time L1 pre cells L1 post cells Additional parity cells Data cells CP2 frequency NP2 T2 Frame

  15. DVB-T2 - L1 Chain : HUB Nbch = Klpdc Ksig Kbch Nldpc Ksig L1post generator Scrambling BCH Padding BCH coder LDPC coder Nldpc-Npunc -(Kbch-Ksig) NP2 x NbUsefulCarrierrs Nldpc-Npunc LDPC Shortenning BCH unpadding AP Merge Data Merge Mapper Framing OFDM Modulation Guard Interval Insertion AP_NbBlocs x AP_BlockSize Random Bits Data 15

  16. DVB-T2 - L1 Chain : UE Channel Estimation OFDM Filter Deframing H(f) Propa Guard Interval Removal Demodulation Channel Equalization Deframing Demapper SH NP2 x NbUsefulCarrierrs Nldpc-Npunc -(Kbch-Ksig) Nbch = Klpdc Nldpc-Npunc Nldpc Kbch Ksig AP Split BCH Repadding LDPC Unshortenning LDPC Decoder Data Remove BCH Decoder BCH Unpadding UnScrambling AP_NbBlocs x AP_BlockSize 16

  17. DVB-T2 - L1 Chain : PROPAGATION A way to avoid data computation : Temporal Convolution AWGN channel Channel Response L1 Filter 0 TL1 3TL1 5TL1 time 2TL1 4TL1 channel T : Frame duration TL1 : L1post duration time 0 T 2T 3T 4T 5T TL1 17

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