Reseach On Cognitive Wireless Network Distributed Proactive Spectrum Handoff Technology

In the spectrum utilization, it has a fixed allocation for limited available spectrum and better performance spectrum, while it need more demand for spectrum in fact. The other hand, the existing spectrum utilization ratio is not very high. So in cognitive wireless network, when the authorized user does not use the spectrum, that is when the channel is idle, cognitive user uses idle spectrum to communicate without affecting authorized users performance, in order to increase the utilization ratio of the spectrum. This paper mainly studies the spectrum handoff in cognitive wireless networks.Based on inaccurate sensing information distributed proactive spectrum handoff algorithms, cognitive users does not require clock synchronization and interaction of the spectrum handoff information. We use the three channel states to define the state of channel. Using false alarm probability, missing detection probability, wrong detection probability, cognitive users amend the channel state transition probability, correcting the situations of inaccurate sensing information, effectively improving the accuracy of forecasting channel occupancy in the future. Through this algorithm, cognitive users choose the best channel to communicate, reducing cognitive users the times of reactive spectrum handoff and the times of conflict during the spectrum handoff. Compared with centralized proactive spectrum handoff, this algorithm also reduces the computational complexity of additional overhead.Based on spectrum aggregation technology distributed proactive spectrum handoff algorithm, by sensing the entire spectrum channel states, in addition to channel state transition probability matrix, cognitive users forecast the probability of each channel state of the next time slot. Choosing the best aggregate region, and the best channels of meeting the spectrum requirements in the aggregate region, reduce the times of reactive aggregate region handoff. At the same time, the times of proactive aggregate region handoff, the times of the total of aggregate region handoff, the times of conflict in the channel access and communication, etc, have better improved.The main innovative point of this article: in the condition of distributed proactive spectrum handoff, cognitive users don’t need clock synchronization and spectrum information, by changing channel state from the previous two to three, joining the sense of other cognitive users. We take into account not only the conflict between cognitive user and the authorized user, but also takes into account the conflict between cognitive users. While we take advantage of the error probability of sensing channel state to amend the channel state transition probability, correcting the inaccurate sensing information. On the basis of this model, we propose two algorithms: based on inaccurate sensing information distributed proactive spectrum handoff algorithms, based on spectrum aggregation technology distributed proactive spectrum handoff algorithm.