The 5G STEPFWD projects proposed a new network architecture at both the edge and fronthaul/midhaul domains that utilized the Ultra Dense Wavelength Division Multiplexing (UDWDM) technique in order to support a high number of small cells at the access domain; this was realised through the application of an UDWDM Passive Optical Network (PON). Thus, the small-cells were connected to the PONs through fiber links between two Optical Line Terminals (OLTs), and/or by point-to-point fiber links, and/or small-scale fiber protection rings among locally adjacent Optical Network Units (ONUs).
The 5G STEPFWD project defined a set of objectives that referred to the optical, wireless, and optical-wireless domains of the network, which were presented as follows:
At the wireless domain, 5G STEP-FWD aimed to:
1. assess fundamental trade-offs between spectrum and infrastructure sharing, in multi-network operator environment;
2. develop a disruptive device- or user-centric cellular concept, which allowed smart overlaid peer-to-peer communications;
3. introduce novel base station switching off schemes for mmWave-based HetNets with renewable energy capabilities;
4. re-think the concept of antenna design for mmWave hyper dense network, by configuring it in a flexible and adaptive manner.
At the optimal domain, 5G STEP-FWD aimed to:
1. develop efficient optical transceivers that were compatible with the UDWDM technology;
2. investigate PON configurations that were UDWDM-compatible, targeting to minimize the cost, maximizing the ONU population and satisfying QoS;
3. develop innovative wavelength/bandwidth allocation techniques applicable to ring-based architectures that interconnect multiple PONs.
At the optical-wireless domain, 5G STEP-FWD aimed to:
1. propose a novel converged mmWave-UDWDM PON network design that interconnected multiple PONs;
2. propose novel modulation techniques for enabling the transmission of mmWave signals over UDWDM-PONs;
3. design an SDN-based architecture for the efficient utilization of the multi-PON wireless and optical resources.
