BOMA and OFDM/OQAM modulation for a radio-over-fiber system with enhanced spectral efficiency.

A novel radio-over-fiber system with enhanced spectral efficiency is proposed by using a building-block-sparse-constellation-based orthogonal multiple access (BOMA) technique, and orthogonal frequency-division multiplexing with offset quadrature amplitude modulation (OFDM/OQAM) technique. With the help of BOMA, a user with good signal-to-noise ratio (SNR) can use the frequency band of a user with poor SNR to transmit extra information by sharing the same well-designed constellation. Moreover, the cycle prefix in OFDM is no longer required due to the properly designed prototype filters in OFDM/OQAM, contributing to maximum spectral efficiency (SE). To optimize transmission performance, four types of sparse constellations with different Euclidean distances between constellation points are designed. In our experiment, BOMA-OFDM/OQAM signals with a total net rate of 1.84 Gb/s and average SE of 4.6 bit/s/Hz are successfully transmitted over 25.2 km standard single-mode fiber for two users with wireless distances of 0.8 m and 0.3 m, respectively. Experimental results show that SE is increased by 37.7% compared with the traditional orthogonal frequency-division multiple access technique.