abstract = "Traditional single-tiered wireless communications
networks cannot scale to satisfy exponentially rising
demand. Operators are increasing capacity by densifying
their existing macro cell deployments with co-channel
small cells. However, cross-tier interference and load
balancing issues present new optimization challenges in
channel sharing heterogeneous networks (HetNets).
One-size-fits-all heuristics for allocating resources
are highly suboptimal, but designing ad hoc controllers
requires significant human expertise and manual
fine-tuning. In this paper, a unified, flexible, and
fully automated approach for end-to-end optimization in
multi-layer HetNets is presented. A hill climbing
algorithm is developed for reconfiguring cells in real
time in order to track dynamic traffic patterns.
Schedulers for allocating spectrum to user equipment
are automatically synthesized using grammar-based
genetic programming. The proposed methods for
configuring the HetNet and scheduling in the
time-frequency domain can address ad hoc objective
functions. Thus, the operator can flexibly tune the
tradeoff between peak rates and fairness. Far cell edge
downlink rates are increased by up to 250percent
compared with non-adaptive baselines. Alternatively,
peak rates are increased by up to 340percent. The
experiments illustrate the utility and future potential
of natural computing techniques in software-defined
wireless communications networks.",