Flexible Multilevel Coding with Concatenated Polar-Staircase Codes for M-QAM

Abstract

In this work, a multilevel coding (MLC) based coded modulation scheme with two degrees of freedom in rate flexibility is proposed and compared with a bit-interleaved coded modulation (BICM) scheme from a performance versus complexity perspective. The proposed MLC scheme is based on a rate flexible inner soft-decision polar code and utilizes an outer hard-decision staircase code structure as in the 400ZR concatenated forward error-correcting code. The performance of the MLC scheme is investigated for a range of inner code lengths, inner decoder list sizes, and signaling with 16 and 64 quadrature amplitude modulation, respectively. The MLC is designed such that a portion of the staircase encoded bits can bypass the inner code. The number of required inner soft-decision decoders can thus be reduced, thereby saving computational complexity. The proposed MLC scheme simultaneously offers up to a 53.7% reduction in the number of inner decoders and up to 0.55 dB of performance improvement when compared with the similar BICM approach.

Experimental Demonstration of Rate-Adaptive Concatenated Codes for Flexible Optical Networks

“…2. Similar to [7], the MLC has a slight performance advantage over BICM at the higher SNR channels, while also reducing the complexity.…”

“…The performance-optimized and rate adaptive inner (N pc , K pc ) polar code is obtained by choosing a single frozen set at which the system performance over the range of data rates is relatively constant. The frozen set is designed according to the desired BER threshold p of the outer code, as specified in [7]. After fixing the CFEC parameters, rateadaptivity can be achieved by tuning the number of inner code information bits, K pc .…”

“…In the encoding process, the information bits are encoded and the generated parity bits are arranged into a staircase block. The resultant outer encoded bits are first interleaved by the interleaver π 1 and then de-multiplexed into T M LC = (J × D 2 )/(K pc + L 0 ) sub-blocks [7], where J, D 2 , and L 0 are the total number of staircase blocks transmitted, size of each staircase block, and the number of bits that bypass the inner SD code, respectively. Each sub-block is of size K pc + L 0 and the number of L 0 and/or K pc bits can be tuned at the de-multiplexer (DEMUX) to (i) achieve rate adaptivity with two degrees of freedom, (ii) control the amount of inner SD decoding operations and (iii) simultaneously switch between BICM (L 0 = 0) and MLC (L 0 = 0).…”

“…Concatenated FEC (CFEC) is an efficient technique for optical communications, where high reliability as well as high data rate is required. In particular, a serial concatenation of outer hard-decision (HD) and inner soft-decision (SD) codes is gaining traction due to complexity reduced FEC decoders [2]- [7]. For a CFEC scheme, the design of inner SD codes plays an important role, since an SD decoder generally dissipates more power relative to their HD counterparts [8].…”

“…To offer rate-adaptivity with fine granularity, a bitinterleaved coded modulation (BICM) based CFEC solution was proposed in [5], where a performance optimized and rate-adaptive inner polar code is employed. More recently, we proposed a concatenated multilevel coding scheme [7] having rate-adaptivity with two degrees of freedom with fine granularity which offers better complexity and performance compared to the BICM scheme of [5].…”