On the Design of Routing Protocols for MIMO Ad Hoc Networks under Uniform and Correlated Traffic

In this paper we investigate the effects of different routing choices in a MIMO ad hoc network. The MIMO physical layer provides a number of degrees of freedom that a correct protocol design could exploit to the network's advantage. To illustrate this point, we compare two approaches. The first is fixed shortest path forwarding, with routes computed a priori. The second involves a dynamic relay choice based on a specific metric. This metric has been designed to yield an overall assessment of the relay's ability to forward packets. A key point of our design lies in its cross- layer nature, that allows to harvest the advantages coming from the interaction of the physical layer and the upper layers. To this end, we propose here a technique to track the receive capabilities of eligible forwarders so as to avoid that they become overloaded and unable to demultiplex superimposed waveforms. We carry out a detailed performance evaluation to assess the improvements provided by our solution with respect to the baseline shortest path routing protocol, and conclude that a standard design paradigm, that splits routing and lower-level protocols, severely limits performance.