Green Heterogeneous Cloud Radio Access Networks: Potential Techniques, Performance Trade-offs, and Challenges

As a flexible and scalable architecture, heterogeneous cloud radio access networks (H-CRANs) inject strong vigor into the green evolution of current wireless networks. But the brutal truth is that EE improves at the cost of other indices such as SE, fairness, and delay. It is thus important to investigate performance trade-offs for striking flexible balances between energy-efficient transmission and excellent QoS guarantees under this new architecture. In this article, we first propose some potential techniques to energy-efficiently operate H-CRANs by exploiting their features. We then elaborate the initial ideas of modeling three fundamental trade-offs, namely EE-SE, EE-fairness, and EE-delay trade-offs, when applying these green techniques, and present open issues and challenges for future investigation. These related results are expected to shed light on green operation of H-CRANs from adaptive resource allocation, intelligent network control, and scalable network planning.