  The explosive growth of global mobile traffic has lead to a rapid growth in
the energy consumption in communication networks. In this paper, we focus on
the energy-aware design of the network selection, subchannel, and power
allocation in cellular and Wi-Fi networks, while taking into account the
traffic delay of mobile users. The problem is particularly challenging due to
the two-timescale operations for the network selection (large timescale) and
subchannel and power allocation (small timescale). Based on the two-timescale
Lyapunov optimization technique, we first design an online Energy-Aware Network
Selection and Resource Allocation (ENSRA) algorithm. The ENSRA algorithm yields
a power consumption within O(1/V) bound of the optimal value, and guarantees an
O(V) traffic delay for any positive control parameter V. Motivated by the
recent advancement in the accurate estimation and prediction of user mobility,
channel conditions, and traffic demands, we further develop a novel predictive
Lyapunov optimization technique to utilize the predictive information, and
propose a Predictive Energy-Aware Network Selection and Resource Allocation
(P-ENSRA) algorithm. We characterize the performance bounds of P-ENSRA in terms
of the power-delay tradeoff theoretically. To reduce the computational
complexity, we finally propose a Greedy Predictive Energy-Aware Network
Selection and Resource Allocation (GP-ENSRA) algorithm, where the operator
solves the problem in P-ENSRA approximately and iteratively. Numerical results
show that GP-ENSRA significantly improves the power-delay performance over
ENSRA in the large delay regime. For a wide range of system parameters,
GP-ENSRA reduces the traffic delay over ENSRA by 20~30% under the same power
consumption.
