Network Coded ALOHA for Wireless Multihop Networks

The purpose of this paper is to show the possibility of combining slotted ALOHA with network coding in wireless multihop networks. In particular, we focus on a star topology in which outer nodes exchange data with each other through a center node. The question is how much the throughput increases by adopting network coding at the center node. To answer this question, we analyze the performance of slotted ALOHA for a star topology. In our analysis, there are two versions of slotted ALOHA: conventional ALOHA, and so-called network coded ALOHA, where the center node makes a network coding with the XOR operation to encode bi-directional traffic of the outer nodes. By analyzing the star topology, we can understand how to control the congested node in a wireless multihop network, where a lot of traffic passes through the node. In our analysis, we make cross- layer optimization over physical and MAC layers. Our conclusion is that network coded ALOHA is a good alternative to support the congested node, compared to the other wireless MAC, e.g., CSMA/CA Index.