Joint Wireless Fronthaul and OFDMA Resource Allocation in Ultra-Dense CRAN.

Ultra-dense (UD) wireless networks and cloud radio access networks (CRAN) are two promising network architectures for the emerging 5G wireless communication systems. By jointly employing UD network with CRAN, a new appealing network solution is proposed, termed UD-CRAN, which can achieve ultra-high-throughput wireless connectivity. In UD-CRAN, a wireless fronthaul is practically favorable to connect a central processor (CP) with distributed remote radio heads (RRHs), due to its lower cost and higher flexibility to deploy. As the wireless fronthaul capacity is limited, it motivates considering the downlink transmission in a UD-CRAN where the wireless fronthaul is shared among the RRHs via time division multiple access~(TDMA), while the RRHs jointly transmit to the users via orthogonal frequency division multiple access (OFDMA). The joint resource allocation over the TDMA-based wireless fronthaul and OFDMA-based wireless transmission is investigated to maximize the weighted sum rate of all users. Although the problem is combinatorial and non-convex, we propose a Lagrange duality based solution, which can be efficiently computed with good accuracy. To further reduce the complexity, we also propose a greedy search based heuristic, which achieves close to optimal performance under practical setups. Finally, we compare the performance of proposed solutions with other benchmark schemes by simulations, which show significant throughput gains of the proposed joint resource allocation approach.