  In this paper, we propose an opportunistic network coding (ONC) scheme in
cellular relay networks, which operates depending on whether the relay decodes
source messages successfully or not. A fully distributed method is presented to
implement the proposed opportunistic network coding scheme without the need of
any feedback between two network nodes. We consider the use of proposed ONC for
cellular downlink transmissions and derive its closed-form outage probability
expression considering cochannel interference in a Rayleigh fading environment.
Numerical results show that the proposed ONC scheme outperforms the traditional
non-cooperation in terms of outage probability. We also develop the
diversity-multiplexing tradeoff (DMT) of proposed ONC and show that the ONC
scheme obtains the full diversity and an increased multiplexing gain as
compared with the conventional cooperation protocols.
