64 GFC Symbol Distribution and Bit Multiplexing Issue

64 GFC Symbol Distribution and Bit Multiplexing Issue T 11 -2017 -00094 -v 1. ppt Andy Joy Raul Oteyza

Background • Issue with 64 G Symbol Distribution and Bit Multiplexing • Burst error could corrupt up to 2 x more FEC symbols • Decreases Coding Gain • 64 GFC FEC is Reed-Solomon(544, 514) • 15 -error correcting code over GF(2^10) • Correct up to 15 10 -bit symbols • Corrects burst errors and single bit errors • Fibre Channel margin is significantly less than Ethernet • 57. 8 Gbps Fibre Channel • 53. 125 Gbps Ethernet v 1. 0 3/24/2017

Background - Continued v 1. 0 3/24/2017

Example – With Symbol Distribution & Bit Multiplexing RS-FEC Codeword 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 T X After 10 -bit Symbol Distribution 0 1 2 3 4 5 6 7 8 9 20 21 22 23 24 25 26 27 28 29 40 41 42 43 10 11 12 13 14 15 16 17 18 19 30 31 32 33 34 35 36 37 38 39 After Bit Multiplexing 0 10 1 11 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 30 21 31 22 32 23 33 24 34 25 35 26 36 27 37 28 38 29 39 40 50 41 51 42 52 Corrupt bit stream – burst error 0 10 1 11 2 12 3 13 4 14 5 15 6 16 7 17 8 18 9 19 20 30 21 31 22 32 23 33 24 34 25 35 26 36 27 37 28 38 29 39 40 50 41 51 42 52 After Bit De-multiplexing R X 0 1 2 3 4 5 6 7 8 9 20 21 22 23 24 25 26 27 28 29 40 41 42 43 10 11 12 13 14 15 16 17 18 19 30 31 32 33 34 35 36 37 38 39 RS-FEC Codeword 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 6 -bit burst error resulted in 4 10 -bit symbols corrupted 4 v 1. 0 3/24/2017

Example – Without Symbol Distribution & Bit Multiplexing RS-FEC Codeword 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 T X 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Corrupt bit stream – burst error 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 R X RS-FEC Codeword 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 6 -bit burst error resulted in 2 10 -bit symbols corrupted v 1. 0 3/24/2017

Analyzed Data Pattern • Fibre Channel Idles (BC 95 B 5 B 5) • • 8 B Format -> 66 B Format -> Scrambled -> 257 B Transcoded -> RS (544, 514) encoded With/Without Symbol Distribution and Bit Multiplexing Gray Mapping Alignment Marker (AM) • Inserted every 1, 024 FEC blocks • Four AMs total in analyzed pattern 6 v 1. 0 3/24/2017

Alignment Marker • 257 -bit Alignment Marker • From 802. 3 bj-2014. pdf, Clause 91. 5. 2. 6 • References Table 82 -2 in 802. 3 -2015_Section 6. pdf • Used FEC lane 0, amp_tx_4, amp_tx_8, amp_tx_12 + Pad bit value of 0 7 v 1. 0 3/24/2017

Alignment Marker - continued • • 8 Arrows point to the Alignment marker encoding that was used for analysis 802. 3 -2015_Section 6. pdf, Table 82 -2 Lane 0 sent first, Lane 12 sent last. • Example starting bit pattern is 1000_0011 0001_0110 … BIP 3 octet = 0 x. AA, BIP 7 octet = 0 x 55 v 1. 0 3/24/2017

Clock Content - definitions • All Transitions • All possible PAM 4 transitions that contain clocking information (12/16 or 75%) • • -1 to -1/3, -1 to +1 -1/3 to -1, -1/3 to +1/3, -1/3 to 1 +1/3 to -1, +1/3 to -1/3, +1/3 to 1 1 to +1/3, 1 to -1 • These aren’t transitions • 1 to 1, 1/3 to 1/3, -1/3 to -1/3, -1 to -1 • Symmetrical • Only symmetric PAM 4 transitions (4/16 or 25%) • • 9 -1 to +1 -1/3 to +1/3 to -1/3 +1 to -1 v 1. 0 3/24/2017

Clock Content vs Time With Symbol Distribution and Bit Mux Maximum run length of no clock content(symmetrical) = 54 Maximum run length of no clock content(all transitions) = 12 Without Symbol Distribution and Bit Mux Maximum run length of no clock content(symmetrical) = 52 Maximum run length of no clock content(all transitions) = 12 10 v 1. 0 3/24/2017

Probability Density Function Clock Content Without Symbol Distribution and Bit Mux 11 With Symbol Distribution and Bit Mux v 1. 0 3/24/2017

Probability Density Function 12 v 1. 0 3/24/2017

Baseline Wander Without Symbol Distribution and Bit Mux 13 With Symbol Distribution and Bit Mux v 1. 0 3/24/2017

Probability Density Function of Baseline Wander/DC Offset 14 v 1. 0 3/24/2017

Results of the Filtered Responses Without Code Distrib/Bit Mux With Code Distrib/Bit Mux Standard deviation of DC offset 0. 3681% 0. 3716% Mean for DC offset -0. 0187% -0. 0046% DC Offset (max) 1. 63% 1. 58% DC Offset (min) -1. 41% -1. 52% Clock content standard deviation(all transitions) 0. 0107 0. 0106 Clock content mean(all transitions) 0. 7499 0. 7493 Clock content standard deviation(symmetrical) 0. 0107 0. 0106 Clock content mean(symmetrical) 0. 2503 0. 2500 15 v 1. 0 3/24/2017

Baseline Wander/DC Offset of PAM-4 AM Only 16 v 1. 0 3/24/2017

Filtered Clock Content of PAM-4 AM only 17 v 1. 0 3/24/2017

Filtered Clock Content of PAM-4 AM Only Symmetrical Transitions 18 v 1. 0 3/24/2017

Proposal • Remove Symbol Distribution and Bit Multiplexing • No difference in Clock Content and Baseline Wander with and without Symbol Distribution and Bit Multiplexing • Gain back 0. 5 d. B or so of Coding Gain • Critical for 64 GFC given the higher line rate and lower corrected BER requirement • Ethernet = 1 e-13 • Fibre Channel = 1 e-15 19 v 1. 0 3/24/2017

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