Coded modulation with a constraint on the minimum channel symbol duration

A coded modulation scheme is described which improves the error performance of constant envelope data transmission without requiring more bandwidth. This is achieved by controlling the minimum channel symbol duration by run-length limited (RLL) encoding. It is shown that the same amount of information can be transmitted within the same minimum channel symbol duration with a coding gain of 4 dB compared with the uncoded modulation. The bandwidth is analyzed using the power spectra of channel signals. As a practical application, we consider bandwidth limited transmission with a restriction on the maximum transmitted power. Following a discussion of a coded modulation principle, constructed RLL codes and the evaluation of their code performances are provided, and the simulation results for BPSK and 2-FSK modulations are presented. Comparisons are strictly made on the basis of equal information rate and the same minimum channel symbol duration.