Mixed Signal Challenges, Opportunities and Wireline Signaling.

Dr Hossain Seminar
Wednesday, July 14, 2021
Zoom Meeting


The landscape of analog mixed-signal research is rapidly evolving and creating new scopes and opportunities. The first half of the talk will present different research themes currently pursued in Prof. Hossain’s group. He will briefly explain the motivation, recent progress, and significant milestones achieved in these research areas. The second half of the presentation will take a deeper dive into an example research work in the area of high-speed wireline signaling. To achieve the projected bandwidth increase in data centers (2x in 4 years), we either need to compensate for more loss or improve spectrum efficiency. Unfortunately, both approaches will create an SNR challenge in link design. For example, PAM-4 modulation improves spectrum efficiency by 2X compared to NRZ signaling, but eye height reduces by 3X, translating to a 9 dB SNR penalty. In reality, SNR penalty is much higher, which requires forward error correction (FEC) to improve the raw BER from 10-6 to 10-12 at the cost of significant latency, complexity, and overhead.  Therefore, it is critical to address the SNR and BER issue in multilevel signaling.  This work proposes a sequence-coded PAM-4 link that provides 4-dB SNR gain for a low loss channel and 6-dB SNR gain for a high loss channel with 12.5% bandwidth overhead. The implemented prototype link includes sequence-coded transmitter and a self-converging and reduced state trellis structure at the receiver reconfigurable to support pulse amplitude modulation (PAM)-4 or PAM-5. Exploiting the channel ISI, the transmitter creates a trellis structure by independently setting the tap weights and skew between the MSB and LSB digital-to-analog converters (DACs). The receiver, including the digital decoder, consumes only 52 mW. The implemented transceiver in 28-nm fully depleted silicon-on-insulator (FDSOI) operates up to 32 Gb/s with 2.6-pJ/bit efficiency compensating up to 30-dB loss. Sequence-coded PAM-5 reduces hardware complexity by 66% compared to one-tap loop-unrolled decision feedback equalization (DFE) for similar performance. Finally, based on these ideas 112 Gb/s and 224 Gb/s solutions will be presented. The talk will conclude with the future direction of high-speed link design.



Masum Hossain received the M.Sc. degree from Queen’s University, Kingston, ON, Canada, in 2005, and the Ph.D. degree from the University of Toronto, Toronto, ON, in 2010. From 2008 to 2010, he was with the Analog and Mixed-Signal Division, Gennum Corporation, Burlington, ON, where he was involved in developing the world’s highest capacity and most power-efficient cross point router solution. He was a Senior Member of Technical Staff with the Rambus Laboratory, Sunnyvale, CA, USA, where he was involved in advanced equalization and clock recovery techniques for  interfaces. He has spent several years in industrial research. In 2013, he joined the Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada, where he established his Mixed-Signal Research group.  Dr. Hossain was a recipient of the Best Student Paper Award at the 2008 IEEE Custom Integrated Circuits Conference and the Analog Device’s Outstanding Student Designer Award in 2010. In 2016, he received the Rambus’s distinguished inventor award for 20 unique patents.

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