The requirements for 5G technology create a need to focus on the fronthaul link. Therefore, it is important to test and evaluate different infrastructures and techniques in order to select the optimal fronthauling solution that maximizes both capacity and cost savings. 5G fronthaul links connect the radio unit (RU) and the distributed unite (DU), whereas in 4G architecture (LTE/LTE-A), the connection is between the remote radio head (RRH) and the baseband unit (BBU) pool. Hence, the optical infrastructure adopted for the 5G fronthaul link can also be feasible for the 4G, since these two architectures are supposed to co-exist in the same network.

The use of optical fiber for the transmission of radio frequency (RF) signals over the fronthaul link offers a larger bandwidth than the radio link and the coaxial cable. Therefore, the signal is transported with low loss since there is no interference with other RF signals. One of the prominent research topics is the application of the 5G waveforms on optical architecture for fronthaul, backhaul, and last meter networks.

The aim of this Special Issue is to collate both original research and review articles that focus on enhancing 4G system performance in order to fulfill the requirements for 5G, by simultaneously acting on the transmitter (TX), the transmission channel, and the receiver (RX).

Potential topics include but are not limited to the following:

• 5G wireless trends and technologies
• Cloud radio access networks (C-RAN)
• Massive multiple-input and multiple-output (MIMO) networks
• Coordinated multipoint (CoMP) architecture
• 5G radio over fiber (RoF) architecture
• Intensity modulation-direct detection (IM-DD) architecture
• 5G optical coding
• VLC communications/FSO communications
• Low-latency metro and access networks
• Industry standard development for 5G-oriented optical networking