A Survey of Client-Controlled HetNets for 5G

With the rise and widespread deployment of a vast array of wireless radio access technologies (e.g., 3G, 4G/LTE, 802.11, Bluetooth, and Femto) and the growth of interest in potential 5G technologies such as millimeter-wave radio, coupled with the rapid increase in the number of network edge devices with multiple radio interfaces, the question of network control and client-to-base-station association becomes an important issue. Older, well-studied centralized control schemes where a single computational entity harvests channel information from individual clients in order to determine optimal resource allocations for each client is no longer tenable: Such methods require significant signaling overhead which does not scale well with the expected number of hundreds of thousands of smart client devices with multiple radio interfaces capable of leveraging many different radio access technologies (RATs). With the rise of these smart devices, which come with significant computational power, it is now possible to ask the question: Can the network allow the client control over RAT selection and association in order to meet some client-driven or network-driven objective, and to what degree does the network assist the client in making these choices? This question becomes particularly important given the increasing interest in standardization and deployment of client-controlled edge networking, or Fog networking. In this paper, we explore the spectrum of client-controlled HetNets for 5G networks: From the fully devolved distributed local control approach, where clients make local decisions without any assistance from the network, to the hybrid control approach where clients may make decisions given some global information provided by the network.