  The field of the coded modulations witnessed its golden era as the simulated
achievable bit rates (ABRs) were getting close to the channel capacities of the
finite alphabet inputs. However, when working at a single channel, the previous
researches are mostly restricted in scope of single input and single output. In
contrast, for achieving higher spectral efficiency, the present authors propose
a method that builds upon the parallel transmission of two signals that are
separated at the receiver. The signal separation is enabled by, so called, the
double mapping modulation working through Hamming- to Euclidean space.
Consequently, the ABR summation of the two signals is found higher the channel
capacity of BPSK input. Both the theoretical- and simulation result confirm
this approach.
