Optimization of Block-Wise MLSE Algorithm for BICM-ID Systems over ISI Channels

Tóm tắt

The maximum likelihood sequence estimation (MLSE) equalizer achieves optimal performance over channels affected by inter-symbol interference (ISI); however, its complexity grows exponentially with the channel impulse response length. To address this, a block-wise MLSE approach combined with bit-interleaved coded modulation with iterative decoding (BICM-ID) is proposed, leveraging mutually independent signal blocks to enable parallel implementation, which significantly reduces computational complexity and processing latency for real-time applications. This paper analyzes and optimizes the precoding block length n₂ in the block-wise MLSE algorithm over ISI channel models with different impulse response lengths L. Simulation results show that the bit error rate (BER) performance of the system depends strongly on n₂, and that a saturation threshold exists. When n₂ > 2L, inter-block interference is effectively suppressed, allowing the BER performance to asymptotically approach that of the full-sequence MLSE. Conversely, when n₂ < 2L, residual inter-block interference leads to significant performance degradation or the appearance of an error floor. This quantitative design rule optimizes the precoding block length, effectively balancing performance and complexity for block-wise MLSE deployments in BICM-ID systems.