Constant subblock composition codes for simultaneous energy and information transfer

Motivated by code design for real-time simultaneous information and energy transfer, we characterize achievable rates and error exponents for discrete memoryless channels using constant subblock composition codes (CSCCs). All subblocks within every codeword in a CSCC have the same fixed composition. For a given channel, this composition may be chosen to balance the tradeoff of receiving high information rate and sufficient energy with every subblock duration. We provide a lower bound on the achievable rate by deriving a loss term relative to unconstrained random codes. We show that the error exponent for CSCCs is related to the error exponent for constant composition codes through the same loss term. We also compare achievable rates using CSCC with joint subblock decoding to the case where received subblocks are decoded independently for relatively faster information access.