  This paper investigates the design of spatially coupled low-density
parity-check (SC-LDPC) codes constructed from connected-chain ensembles for
bit-interleaved coded modulation (BICM) schemes. For short coupling lengths,
connecting multiple SC-LDPC chains can improve decoding performance over
single-chains and impose structured unequal error protection (UEP). A joint
design of connected-chain ensembles and bit mapping to further exploit the UEP
from codes and high-order modulations is proposed. Numerical results
demonstrate the superiority of the proposed design over existing
connected-chain ensembles and over single-chain ensembles with existing bit
mapping design.
