Causal ordering group communication for cognitive radio ad hoc networks

In this paper, we discuss the causal ordering group communication for cognitive radio (CR) networks. The issue of causal ordering has been studied extensively by previous works. However, these works considered the problem at the application layer and the methods in the works incurred high communication overhead and the long latency for message delivery. In this paper, we discuss the causal ordering at the network layer.The problem of our concern is: given a group communication request in a CR network, how to set up the connection so that the causal ordering of the group communication can be preserved, and the bandwidth consumption of the communication is minimized. We propose a two-phase method to solve it. In the method, we first construct a multicast tree for the communication, and then assign slots for all tree links. It is proved that the method can preserve the causal ordering of messages without extra communication overhead nor the latency for delivering messages. Simulations are conducted to show the performance of our proposed method.