Rate-sensitive CoMP beamforming plus sensible snooze for energy-QoE tradeoff in cognitive small cell networks

Small cells, specific femtocells aim to improve throughput and customer experience indoors, which prospectively develop into an indispensable part to complement macrocells. Since network operators progressively consider ecological and economical sustainable development, energy-saving and interference-free have grown to be crucial challenges for “green” femtocells, especially under ultra-dense deployment. To this end, we introduce coordinated multi-point (CoMP) femto-base stations (FBSs) to exploit intra-femto interference and multiple-input single-output beamforming in cognitive underlay to mitigate cross-tier interference, integrated with another key effort to best conserve overall FBSs power. It is formulated as a quasi mixed-integer convex optimization problem, decomposed and carried out separately via innovative transformations. A novel FBSs CoMP-selecting scheme, sensitive to femto-user traffic rate, is proposed to rapidly obtain the effective solution to fundamental CoMP beamforming issue. Furthermore, a policy of diminishing the CoMP set by deactivating feasible no-load FBSs to snooze, is proposed to actually minimize entire power consumption, wherein FBSs static, dynamic and backhauling power is jointly evaluated by accordingly proposed two hierarchical iterative algorithms. Network-level simulations under practical configurations, in contrast to prior work, demonstrate the proposals can achieve a proper tradeoff between retaining significant energy-efficient FBSs operation and assuring preferable quality of consumers experience.