OFDM-Subcarrier Power Modulation With Two Dimensional Signal Constellations

An original modulation technique has been recently proposed for wireless communication systems known as OFDM- SPM (OFDM with Subcarrier Power Modulation). This technique utilizes a characteristic of the subcarriers of the OFDM block to carry extra data, this is the power of the subcarriers. Where the power level of each subcarrier conveys additional data bits. Presented here, the concept of OFDM-SPM is extended to the case of using two-dimensional signal constellations that consist of both in-phase and quadrature components such as QPSK Symbol modulation. Its performance is investigated over an AWGN (additive white Gaussian noise) channel. The adoption of this proposed scheme in future modulation techniques is studied by presenting OFDM-SPM with QPSK as a case of OFDM-SPM with higher order modulation schemes. The performance of the scheme in terms of the metrics of throughput and bit error rate (BER) of the system are discussed and analyzed. The results show that OFDM-SPM with QPSK vastly improves spectral efficiency especially when comparing with other techniques such as OFDM-SEM and OFDM-SNM which add a third data carrying dimension.. The results show that OFDM-SPM, unlike many other proposed schemes, can be used with higher order modulation schemes to provide the perceived gains consistently regardless of the modulation scheme order. Specifically, it is found out that the spectral efficiency can be doubled compared to conventional benchmark schemes available in the literature at the expense of a slight degradation in the BER.