100G Signaling Options over Backplane Classes IEEE P802.3bj January 2012 Newport Beach FutureWei Hiroshi Takatori Hiroshi.Takatori@huawei.com Contributors and Supporters Albert Vareljian Sanjay Kasturia, Inphi FutureWei TECHNOLOGIES CO., LTD. Page 1
Outline 1. Signaling Options (Line Code and Transmission Type) 2. SNR Margin Analysis (Salz) over 50 Channels (Old/New) 3. Representative Channels for Time-Domain Simulation 4. Simulation Result Analysis 5. Roadmap to the Next Generation 400G System 6. Summary FutureWei TECHNOLOGIES CO., LTD. Page 2
100G Signaling Options 1 Option 1: PAM-2, 25Gbaud*, 4-Lane Option 2: PAM-4, 12.5Gbaud, 4-Lane 2 Option 3: PAM-4C*, 6.25Gbaud, 8-Lane (Full Duplex by EC) 50 Industry Backplane CHs ( New Material, KR, and Pre-KR) are evaluated with three different options. *1) No coding overhead assumed at this stage *2) 4-D TCM Coded as per 802.3ab, 1000BASE-T FutureWei TECHNOLOGIES CO., LTD. Page 3
IL, Crosstalk (db) 802.3ab Channel Mapped to 802.3ba 10 0 Nyquist IL -10-20 -30 KR CAT5, 100m Freq. Scaled by x50 (12.5G/250M) -40-50 -60-70 Power Sum FEXT -80-90 10 7 10 8 10 9 10 10 Frequency (Hz) 802.3ab (1000BASE-T) Channel IL is much more relaxed vs. KR at Nyquist. Makes 8-lane Bi-Directional Signaling a Promising Candidate over KR-compliant and Pre-KR Channels FutureWei TECHNOLOGIES CO., LTD. Page 4
Noise Margin (db) (db) SNR Margin (Salz) (-146dBm/Hz BGN, w/o FEC) 25 20 15 10 5 Noise Margin = Salz SNR SNR_ref SNR_ref = 16.9dB (PAM-2) 23.9dB (PAM-4) BER = 1.E-12 6dB Margin 1. PAM-4 has advantage over PAM-2 for greater loss CHs. 2. However, PAM-2 and, to some extent, PAM-4 channel support not widest. 3. PAM-4C covers higher IL and boarder majority of the channels. 0-5 -10-90 -80-70 -60-50 -40-30 -20-10 Channel Loss at 12.5GHz (db) Insertion Loss @ 12.5GHz (db) RED: PAM-2 BLACK: PAM-4 GREEN: PAM-4C Further analysis is done by the time domain behavioral simulation that included key system impairments and IC implementation losses. FutureWei TECHNOLOGIES CO., LTD. Page 5
Channels for Time-Domain Analysis CH1 Improved Materials 1 Meter Backplane Channel, IBM http://www.ieee802.org/3/100gcu/public/channel.html Similar to above from TE, Merson, Q-Logic, and FCI CH2 KR Compliant Typical Backplane channel designed after KR CH3 KR Marginal http://www.ieee802.org/3/ap/public/sep04/dambrosia_01_0904.pdf etc CH1 IL: 29.2dB @ 12.5GHz ICR: 13.1dB KR-req. CH2 IL: 39dB @ 12.5GHz ICR: 8.7dB CH3 IL: 59.5dB @ 12.5GHz ICR: -27dB FutureWei TECHNOLOGIES CO., LTD. Page 6
SNR (db) Amplitude Time Domain Behavioral Simulation Reference PHY TX: 5dBm, 3~4 tap FIR filter with 1 st order LPF, 40dB THD RX: CTLE, High-pass filter, 16 tap DFE, 40dB THD Jitter: 0.35ps(rms), both transmit and receive clock Noise: NEXT, FEXT, and BGN (-152, 146, and -140dBm/Hz) 1 0.5 0-0.5 FEXT FEXT + -152-146 Adaptation NEXT dbm/hz dbm/hz -140 dbm/hz -1 0 1 2 3 4 5 6 7 Iteration Time (symbol) x 10 4 30 20 10 16.9dB Sampled EYE SNR = 21.1dB 15.0dB 9.9dB 6.0dB 0 0 1 2 3 4 5 6 7 Iteration Time (symbol) x 10 4 Impairments are added in time one by one after the adaptation. 1. FEXT 20000~ 2. FEXT + NEXT 30000~ 3. FEXT + NEXT + BGN 40000~ The noise margin is calculated by subtracting SNR_ref. from SNR. SNR_ref = 16.9dB (PAM-2) = 23.9dB (PAM-4) Result shown in this page uses - Option-1(PAM-2, 25Gbaud) - CH-2 (KR compliant). Noise margin in this case is +4.2dB (Crosstalk only) -1.9dB (BGN = -152dBm/Hz) -7dB (BGN = -146dBm/Hz) -10.9dB(BGN=-140dBm/Hz) Simulations are repeated for three options over different channels. FutureWei TECHNOLOGIES CO., LTD. Page 7
Noise Margin Result Time Domain Behavioral Simulation BGN (dbm / Hz) CH1 Improved Material CH2 KR Compliant CH3 KR Marginal Option1 PAM2, 25G baud Option2 PAM4, 12.5G baud Option3 PAM4C, 6.25G baud Full Duplex -152 4.4 db -1.9 db FAIL -146 2.5-7 FAIL -140-1.7-10.9 FAIL -152 5.8 db 3.4 db -6.2 db -146 4.4 0.8-7.2-140 1.0-3.6-9.9-152 9.0 db 9.5 db 2.7 db -146 8.2 7.9 2.1-140 6.4 4.5 0.3 No FEC coding gain is included Package + BGA crosstalk are not included FutureWei TECHNOLOGIES CO., LTD. Page 8
SNR (db) Feasibility of Next Gen 400G System Channel: CH1 (IBM 1m Backplane) Signaling: PAM-4C, 25Gbaud (OPTION-3, 4X speed) 35 30 25 20 15 10 Adaptation (EQL and EC) FEXT + NEXT + BGN -152dBm/Hz -146 dbm/hz -140 dbm/hz Assuming 5dB coding gain, greater than 3dB noise margin is possible. 400G system is feasible. Followings will be necessary for industry grade products. 5 Full duplex 0 0 1 2 3 4 5 6 7 8 9 x 10 4 Iteration Time (symbol) A. Minor material improvement over CH1 B. SerDes porting by 4X. FutureWei TECHNOLOGIES CO., LTD. Page 9
Summary 1. Three signaling options have been studied over key classes of channels --- Improved Low-loss material, KR, and Pre-KR 2. PAM-2 is marginal even with improved Low-loss material and requires extremely low noise environment. 3. PAM-4 would work over Low-loss channels, however, w/o FEC it would be marginal over KR spec backplanes. 4. PAM-4C will work well over KR backplanes with sufficient margin even w/o additional FEC. 5. PAM-4C is the best performing signaling so far on a roadmap to the next generation 400G system. FutureWei TECHNOLOGIES CO., LTD. Page 10