A relay can increase degrees of freedom in bursty mimo interference networks

We explore the benefits of relays¹ in multi-user wireless networks with bursty user traffic, where intermittent data traffic restricts the users to bursty transmissions. Specifically, we investigate a two-user bursty MIMO Gaussian interference channel (IC) with a relay, where two Bernoulli random states govern the bursty user traffic. We show that an in-band relay can provide a degrees of freedom (DoF) gain in this bursty channel. This beneficial role is in contrast to the role in the non-bursty channel which is not as significant to provide a DoF gain. More importantly, we demonstrate that for certain antenna configurations, an in-band relay can help achieve an interference-free performance with increased DoF. Particularly, we find the benefits of a relay substantial with low user traffic, as the DoF gain can scale linearly with the number of antennas at the relay. To this end, we derive an outer bound from which we obtain a necessary condition for interference-free DoF performances. Then, we develop a novel scheme that exploits information of the bursty traffic states to achieve the performances.