Joint sensing period optimization and transmission time allocation for cognitive radio networks

To maximize the channel utilization, an opportunistic spectrum access (OSA) strategy for a slotted secondary user (SU) overlaying an unslotted primary network under interference constraint (IC) and energy consumption constraint (ECC) is proposed. The IC is modeled by the average temporal overlap between SU and PU. On the other hand, since SU is periodic, thus the sensing period will affect the energy consumption and the identified result of the state of channel, which will affect the spectrum utilization. For example, smaller period will cause more energy consumption for sensing and better identified results, and vice versa. Thus, suitable period should be chosen for better spectrum utilization. Then, the ECC, defined as a function of the sensing period, is proposed. The allocation of sensing period and transmission time are optimized based on the channel modeling of an ON/OFF continuous time Markov chain and the closed-form solutions are derived. The closed-form solutions show that the proposed OSA strategy has low computational cost. Numerical results show that the optimal transmission time and inverse of sensing period are near linear equation of the maximum tolerable energy consumption per unit time when both IC and ECC take effect.