SoftMoW: Recursive and Reconfigurable Cellular WAN Architecture

The current LTE network architecture is organized into very large regions, each having a core network and a radio access network. The core network contains an Internet edge com-prised of packet data network gateways (PGWs). The radio network consists of only base stations. There are minimal in-teractions among regions other than interference management at the edge. The current architecture has several problems. First, mobile application performance is seriously impacted by the lack of Internet egress points per region. Second, the continued exponential growth of mobile traffic puts tremen-dous pressure on the scalability of PGWs. Third, the fast growth of signaling traffic known as the signaling storm prob-lem poses a major challenge to the scalability of the control plane. To address these problems, we present SoftMoW, a recursive and reconfigurable cellular WAN architecture that supports seamlessly inter-connected core networks, reconfig-urable control plane, and global optimization. To scale the control plane nation-wide, SoftMoW recur-sively builds up the hierarchical control plane with novel abstractions of both control plane and data plane entities. To enable scalable end-to-end path setup, SoftMoW presents a novel label swapping mechanism such that each controller only operates on its logical topology and each switch along the path only sees at most one label. SoftMoW supports new network-wide optimization functions such as optimal routing and inter-region handover minimization. We demonstrate that SoftMoW improves the performance, flexibility and scalability of cellular WAN using real LTE network traces with thousands of base stations and millions of subscribers. Our evaluation shows that path inflation and inter-region handovers can be reduced by up to 60 % and 44 % respectively