A new concept of multi-band carrier-less amplitude and phase modulation for bandlimited visible light communications

In this paper, we propose a novel method of multi-band carrier-less amplitude and phase (m-CAP) modulation for optical wireless communication (OWC) systems. In conventional m-CAP systems, the total signal bandwidth is divided into m equally distributed subcarriers. In this work, for the first time, we set the subcarrier bandwidths such that the first subcarrier is the same as the LED bandwidth, and subsequently distribute the remaining bandwidth equally between m - 1 subcarriers. We show that using m = 4, 6, 8 and 10 subcarriers and 16-QAM, the first subcarrier is able to achieve a bit error rate (BER) target of 10-4 (i.e., which is below the 7% forward error correction (FEC) BER limits of 3.8 × 10-3)at Eb/N0 = 15.5 dB. This is a power penalty of -1.5 dB to achieve the same average performance as the first five, four and three subcarriers of the conventional 10, 8 and 6-CAP and a power penalty of ~1 dB for new 4-CAP to achieve the average performance of the first two subcarriers of the conventional 4-CAP. Consequently, using the proposed m-CAP concept we show a reduction in the complexity by reducing the number of finite impulse response (FIR) filters by 80%, 75%, -67% and 50% in contrast to the conventional 10, 8, 6, and 4-CAP, respectively.