The fifth generation (5G) cellular networks set ambitious goals that require technological advances in both wireless and transport network infrastructures, especially regarding cost and carbon footprint. In this context, a promising architecture for 5G aggregation networks is the recently proposed Claud-Radio Access Network (C-RAN). However, it will face the serious challenges related to (1) efficient use of network resources, (2) low-latency requirements, and (3) scalability. Seems that optical aggregation networks based on wavelength division multiplexing are the outstanding candidates to meet high-capacity and low-latency requirements. However, to reduce cost and power consumption, there has been a recent push towards the consolidation of the network by merging the access and metro transport where flexible-grid transmission is also considered. This becomes questionable in the context of the traditional C-RAN. Therefore, alternatives are being analysed including different function splits between cell-site and baseband equipment, and millimetre-wave carriers instead of optical carriers for interconnecting cell-site equipment and access central office. Hence, 5G-DRIVE project aims to explore the impact of transport cost and wireless channel (de-) aggregation technique on resource efficiency (cost, spectrum, power consumption) and service availability in aggregation network that uses optical or millimetre-wave carriers for interconnecting cell-site and baseband equipment.