  We investigate joint information and energy cooperative schemes in a
slotted-time cognitive radio network with a primary transmitter-receiver pair
and a set of secondary transmitter-receiver pairs. The primary transmitter is
assumed to be an energy-harvesting node. We propose a three-stage cooperative
transmission protocol. During the first stage, the primary user releases a
portion of its time slot to the secondary nodes to send their data and to power
the energy-harvesting primary transmitter from the secondary radio-frequency
signals. During the second stage, the primary transmitter sends its data to its
destination and to the secondary nodes. During the third stage, the secondary
nodes amplify and forward the primary data. We propose five different schemes
for secondary access and powering the primary transmitter. We derive
closed-form expressions for the primary and secondary rates for all the
proposed schemes. Two of the proposed schemes use distributed beamforming to
power the primary transmitter. We design a sparsity-aware relay-selection
scheme based on the compressive sensing principles. Our numerical results
demonstrate the gains of our proposed schemes for both the primary and
secondary systems.
