5G wireless backhaul networks: Challenges and research advances

5G networks are expected to achieve gigabit-level throughput in future cellular networks. However, it is a great challenge to treat 5G wireless backhaul traffic in an effective way. In this article, we analyze the wireless backhaul traffic in two typical network architectures adopting small cell and millimeter wave communication technologies. Furthermore, the energy efficiency of wireless backhaul networks is compared for different network architectures and frequency bands. Numerical comparison results provide some guidelines for deploying future 5G wireless backhaul networks in economical and highly energy-efficient ways.International Science and Technology Cooperation Program of China (Grant No. 2014DFA11640 and 0903), the National Natural Science Foundation of China (NSFC) (Grant No. 61271224, 61301128 and 61471180), NFSC Major International Joint Research Project (Grant No. 61210002), the Hubei Provincial Science and Technology Department (Grant No. 2013BHE005), the Fundamental Research Funds for the Central Universities (Grant No. 2013ZZGH009 and 2014QN155), and EU FP7-PEOPLE-IRSES (Contract/Grant No. 247083, 318992 and 610524).Scopu