Horstein, Burnashev, Shayevitz and Feder, Naghshvar et al. and others have studied sequential transmission of a K-bit message over the binary symmetric channel (BSC) with full, noiseless feedback using posterior matching. Yang et al. provide an improved lower bound on the achievable rate using martingale analysis that relies on the small-enough difference (SED) partitioning introduced by Naghshvar et al. SED requires a relatively complex encoder and decoder. To reduce complexity, this paper replaces SED with relaxed constraints that admit the small enough absolute difference (SEAD) partitioning rule. The main analytical results show that achievable-rate bounds higher than those found by Yang et al. are possible even under the new constraints, which are less restrictive than SED. The new analysis does not use martingale theory for the confirmation phase and applies a surrogate channel technique to tighten the results. An initial systematic transmission further increases the achievable rate bound. The simplified encoder associated with SEAD has a complexity below order O(K^2) and allows simulations for message sizes of at least 1000 bits. For example, simulations achieve 99% of of the channel's 0.50-bit capacity with an average block size of 200 bits for a target codeword error rate of 10^(-3).

翻译：Horstein、Burnashev、Shayevitz与Feder、Naghshvar等人以及其它研究者先后研究了在具有完整无噪声反馈的二元对称信道（BSC）上，利用后验匹配对K比特消息进行序贯传输。Yang等人通过引入马氏链分析，基于Naghshvar等人提出的"足够小差异"（SED）划分规则，改进了可达速率的下界。然而SED要求编码器和解码器具有相对高的复杂度。为降低复杂度，本文采用更宽松的约束条件替代SED，提出了"足够小绝对差"（SEAD）划分规则。主要分析结果表明：即使在比SED限制更少的新约束条件下，仍可能获得比Yang等人研究更高界的可达速率。新分析未采用确认阶段的鞅理论，而是应用代理信道技术收紧结论。引入初始系统传输进一步提升了可达速率界。与SEAD对应的简化编码器复杂度低于O(K²)量级，支持对至少1000比特消息长度的仿真验证。例如，在目标码字错误率为10^{-3}时，采用200比特平均块长即可实现信道0.50比特容量99%的传输效率。