Variable m-CAP for bandlimited Visible Light Communications

The multi-band carrier-less amplitude and phase (m-CAP) modulation technique has been demonstrated as a significant candidate for use in visible light communication (VLC) systems, as spectral efficiency becomes ever more important. When employing m-CAP modulation, the signal bandwidth is typically split into m equally distributed subcarriers regardless of the -3 dB bandwidth. Thus, in this paper we investigate the impact of splitting the signal bandwidth into unequally spaced subcarriers on the m-CAP VLC system performance. We demonstrate that by allocating different bandwidths for individual subcarriers, we can achieve up to 36% improvement in data rate for 6-CAP (i.e. 6 subcarriers). We show that the higher the order of the variable m-CAP, the more significant improvement in data rate becomes even for a highly bandlimited VLC system when compared to the conventional m-CAP scheme.