LANGUAGE English SOURCE IEEE Communications Magazine, vol. 55, no. 11, pp. 54-60, Nov. 2017. Published Date:2017-11 ABSTRACT Renewable EH technology is expected to be pervasively utilized in 5G mobile networks to support sustainable network developments and operations. However, the renewable energy supply is inherently random and intermittent, which could lead to energy outage, energy overflow, QoS degradation, and so on. Accordingly, how to enhance renewable energy sustainability is a critical issue for green networking. To this end, an energy-sustainable traffic steering framework is proposed in this article, where the traffic load is dynamically adjusted to match energy distributions in both the spatial and temporal domains by means of interand intra-tier steering, caching, and pushing. Case studies are carried out, which demonstrate that the proposed framework can reduce on-grid energy demand while satisfying QoS requirements. Research topics and challenges of energy-sustainable traffic steering are also discussed.