  This paper investigates the energy efficient resource allocation for
orthogonal frequency division multiple access (OFDMA) relay systems, where the
system is supplied by the conventional utility grid and a renewable energy
generator equipped with a storage device. The optimal usage of radio resource
depends on the characteristics of the renewable energy generation and the
mobile traffic, which exhibit both temporal and spatial diversities. Lyapunov
optimization method is used to decompose the problem into the joint flow
control, radio resource allocation and energy management without knowing a
priori knowledge of system statistics. It is proven that the proposed algorithm
can result in close-to-optimal performance with capacity limited data buffer
and storage device. Simulation results show that the flexible tradeoff between
the system utility and the conventional energy consumption can be achieved.
Compared with other schemes, the proposed algorithm demonstrates better
performance.
