Impact of DFE Error Propagation on FEC-Based High-Speed I/O Links

Low-Latency Burst Error Detection and Correction in Decision-Feedback Equalization

“…The state transitions probabilities are easily calculated using the standard error function. For example, the probability of going from state 8 to state 6 is much less than the probability of going from state 8 to state 9 as depicted in the pdfs, P 8,6 = 1 2 Q( −h(0)−2h (1) σ ) << P 8,9 = 1 2 Q( −h(0)+2h (1) σ ) for this given channel. Similarly, all other state transition probabilities were also calculated.…”

“…As expected, due to the wrong decisions, the noise margin severely degrades. Especially, if the tap magnitudes are higher, the probability of error burst increases exponentially [1]. In practice, direct feedback structure creates timing constrain -the decision and subtraction must happen within 1 UI and that is hard to meet at 10+ Gb/s.…”

Statistical BER Analysis of Wireline Links With Non-Binary Linear Block Codes Subject to DFE Error Propagation

“…The statistical model proposed in [16] will be introduced in this section to estimate the pre-FEC BER in the presence of DFE error propagation. We first explain how DFE error propagation is modeled using Markov chain theory, and then apply trellis-based dynamic programming to efficiently collect probabilities of all error patterns that are needed for post-FEC BER calculation in Section IV.…”

“…Past work on post-FEC BER estimation has focused on systems with BCH codes which operate in GF(2) using 2-PAM signaling [16]. A Markov chain model from [17] was adopted in [16] to account for DFE error propagation, and possible burst-error patterns are systematically grouped through trellis-based dynamic programming. However, 4-PAM signaling is becoming increasingly critical for 50 Gb/s+ wireline links [18]- [20], often with DFEs [21], [22].…”

“…Our proposed BER estimation method for wireline links is an extension of [16], and provides a set of tools to assist in making architectural choices for wireline transceivers, such as co-design of the equalization and FEC in the presence of DFE error propagation and various noise sources. An extension from 2-PAM to Gray-Coded 4-PAM signaling is included in our model to calculate the bit-error probability for a multi-bit PAM symbol accurately.…”