  This paper investigates a three-node multiple-input multiple-output relay
system suffering from co-channel interference (CCI) at the multi-antenna relay.
Contrary to the conventional relay networks, we consider the scenario that the
relay is an energy harvesting (EH) node and has no embedded energy supply. But
it is equipped with a rechargeable battery such that it can harvest and
accumulate the harvested energy from RF signals sent by the source and
co-channel interferers to support its operation. Leveraging the inherent
feature of the considered system, we develop a novel accumulate-then-forward
(ATF) protocol to eliminate the harmful effect of CCI. In the proposed ATF
scheme, at the beginning of each transmission block, the relay can choose
either EH operation to harvest energy from source and CCI or information
decoding (ID) operation to decode and forward source's information while
suffering from CCI. Specifically, ID operation is activated only when the
accumulated energy at the relay can support an outage-free transmission in the
second hop. Otherwise, EH operation is invoked at the relay to harvest and
accumulate energy. By modeling the finite-capacity battery of relay as a
finite-state Markov Chain (MC), we derive a closed-form expression for the
system throughput of the proposed ATF scheme over mixed Nakagami-m and Rayleigh
fading channels. Numerical results validate our theoretical analysis, and show
that the proposed ATF scheme with energy accumulation significantly outperforms
the existing one without energy accumulation.
