A Tunable Wireless Multicarrier Communication Employing Multiple Vector Modulation With 4QAM-OFDM on a Single Optical Carrier

A wireless communication system with tunable multicarrier based on optical comb is investigated in this paper. This study is an initial attempt to modulate multiple vector microwave signals with different frequency on a single optical carrier, and then transmit these optical signals over a standard single-mode fiber with the length of 30 km, and finally demodulate them at the remote unit via a photoelectric direct detector without strict frequency-phase synchronization. Such a design can decrease the equipment cost and improve the frequency efficiency. In the transmitting terminal unit (TTU), a flat multi-wavelength optical comb with 13 channels and the channel space of 10 GHz can be obtained by the microwave photonics technology. In the radio-frequency remote unit (RRU), we can not only obtain the wireless carriers with the frequency of 5 GHz, 10 GHz, 35 GHz, 40 GHz, 65 GHz, 70 GHz, 95 GHz, and 100 GHz via a photoelectric direct detector that are used for wireless transmission between the mobile terminal and the radio-frequency remote unit, but also get three optical sources that can be utilized for the uplink. Meanwhile, the wireless access rate can reach up to 20 Gbps between RRU and MT. In this arrangement, compared with a conventional microwave photonics link, the optical spectrum utilization efficiency and transmission rate not only can be doubled, but also the maintenance cost of RRU can be reduced greatly.