  To facilitate wireless transmission of multimedia content to mobile users, we
propose a content caching and distribution framework for smart grid enabled
OFDM networks, where each popular multimedia file is coded and distributively
stored in multiple energy harvesting enabled serving nodes (SNs), and the green
energy distributively harvested by SNs can be shared with each other through
the smart grid. The distributive caching, green energy sharing and the on-grid
energy backup have improved the reliability and performance of the wireless
multimedia downloading process. To minimize the total on-grid power consumption
of the whole network, while guaranteeing that each user can retrieve the whole
content, the user association scheme is jointly designed with consideration of
resource allocation, including subchannel assignment, power allocation and
power flow among nodes, where the user association scheme decides which SN
serves which user. First, the optimal power allocated to each subchannel and
the power flows among nodes are derived analytically. Then, the user
association problem is decoupled from the subchannel assignment problem, and
the proposed user association scheme has leveraged the multicasting nature of
the content download process. To decide which subchannel is assigned to which
node, the number of subchannels assigned to each node is first determined,
according to the green energy generating rate and the associated traffic
offload, and then the corresponding subchannels are selected from the total
assigned system spectrum. Simulation results demonstrate that bringing content,
green energy and serving node closer to the end user can notably reduce the
on-grid energy consumption.
