Cooperation above the physical layer: The case of a simple network

In this paper, we investigate the effects of ldquonetwork-levelrdquo cooperation in a wireless three-node network with packet erasure links. Cooperation is achieved through the relaying of packets from the node farthest away from the destination by the intermediate node. We consider both scheduled access and random access, and compare the performance metrics of ldquostability regionrdquo and ldquothroughput regionrdquo. We observe that the throughput region depends on the priority choices at the relay node, and may or may not be equal to the stability region, which is shown to be independent of the priority choices. By contrast, in the non-cooperative random access system, the stability region and the throughput region are proved to be identical. Furthermore, if we apply network coding at the relay node, there is no improvement either in the stability region or in the throughput region over plain store-and-forward routing.