Joint sensing interval and channel access optimization in energy harvesting hybrid active/passive symbiotic networks

Abstract

The radio frequency spectrum became crowded because of the huge number of wireless devices, hence cognitive radio networks (CRNs) should increase the efficiency of spectrum utilization. Moreover, energy-saving techniques are becoming essential to prolong the devices’ life. Consequently, this work considers a hybrid active/passive (interweave/backscatter) symbiotic network while adopting the energy harvesting technology and applying the sensing interval concept. The sensing interval concept helps the secondary users (SUs) to transmit their data for consecutive time slots depending on the sensing result of the first time slot. This concept helps the SUs to reduce the consumed energy in sensing the channel each time slot. The hybrid transmission mode improves the spectrum utilization. The energy harvesting technology, the sensing interval concept, and the backscatter mode improve the energy efficiency. These spectrum utilization and energy efficient techniques are combined, for the first time, in one model. To deal with the mixed system state (the energy of the SUs which is fully observable state and the primary users activity which is partially observable state due to the imperfect sensing) and take the future rewards into consideration, a mixed observable Markov decision process is proposed. Moreover, we derive a closed form expression for the data outage probability of the backscatter transmission with/without spectrum sensing. The numerical results show that the proposed model prevails over the other models in the literature in terms of throughput and energy efficiency. Moreover, the interference on the primary user receiver due to applying the sensing interval concept is reduced by introducing a new penalty parameter.