Optimization of Delayed Bit-interleaved Coded Modulation in the High-SNR Regime

In this letter, we investigate the capacity of delay schemes in delayed bit-interleaved coded modulation (DBICM) at high signal-to-noise ratios (SNR) using alternative methods to numerical integration. A closed-form formula is derived to approximate the DBICM capacity at high SNR. For Gray codes, DBICM capacity is proven as asymptotically optimal irrespective of the delay scheme and we further characterize the minute variations in finite SNR values. Compared to BICM using the binary reflected Gray Code, an improvement of 0.1 dB in the BER performance is achieved using a non-Gray bit-labeling combined with its optimized DBICM delay scheme.