Optimal stopping for energy efficiency with delay constraints in Cognitive Radio networks

In this paper the problem of delay tolerant message data transmission scheduling over Cognitive Radio (CR) enabled wireless networks is considered with special emphasis on high mobility users (vehicles). The proliferation of delay tolerant applications (social networking updates, emails, updates over the air to mention just a few) can drive efficient utilization of available spectrum by Secondary Users (SU) under a CR enabled cellular network. Under the inherent stochasticity of available of transmission opportunities, the challenge is to select an optimized time duration to launch the data transmission in order to minimize the overall energy cost while satisfying the information delay constraint (with focus on delay-tolerant messages). To this end, a novel relaying scheme to deal with the problem of energy-delay trade-off, based on optimal stopping programming (OSP), is presented, whilst exploring different candidate solutions for message transmission. Additionally, we also factor energy consumption of DRAM that is used to store the message at the terminal and show its pivotal role on the different store carry and forward data transmission schemes.