Research Of Dynamic Spectrum Access In Cognitive Radio Network

Wireless technology is proliferating rapidly, and the vision of wireless communications offers the promise of many individual benefits, so the number of wireless devices is much broader, and this explosion of wireless applications creates an ever-increasing demand for more radio spectrum. However, most easily usable spectrum bands have been allocated, although many studies have shown that these bands are significantly underutilized. These considerations have motivated the thought of cognitive radio technology; which can sense the operating environment and dynamically use the white spectrum to achieve the best performance. So it provides an effective solution to solve the spectrum shortage and low frequency resource utilization situation.At first, we represent the background of cognitive radio, and then introduce the development situation of cognitive radio and its standardization process. Second we introduce some key technology of cognitive radio, and then analysis the dynamic spectrum access in three aspects. We focus on the secondary user how to schedule the sensing and transmission actions to make the highest spectrum usage in opportunistic spectrum access.Based on the existing research results, we consider the energy consumption of sensing and transmission action and propose a dynamic spectrum access strategy that can achieve minimum energy consumption with sacrificing only neglectable throughput. We assume the PU channel states transit in a non-time-slotted manner; the SU dynamically schedules its actions, i.e., sensing, transmission or sleeping, according to a defined utility function. The difference between our work and previous ones is that we consider the rewarding and penalty of appropriate and inappropriate sleep actions in optimizing the utility function:those sleep actions obeying the rule will be rewarded and those opposite actions will be penalized. The SU schedules its action of sensing and sleeping so as to reach a tradeoff between minimum energy consumption and protection of the PU. By maximizing the mean benefit, the proposed strategy exhibits a simple threshold-based structure. Simulation results show that the proposed scheme can greatly reduce energy cost and achieve similar PU collision rate as previous work, with only neglectable throughput reduction.We find that some bands were occupied the almost same time by the primary users periodically. For the special type of spectrum use mode, we improve the dynamic spectrum access strategy which is proposed in the last section. We use the setting of linear retreats way in rest time length when the channel is busy. Simulation results show that the proposed scheme can reduce energy cost and achieve similar PU collision rate as previous work, with only neglectable throughput reduction.