Algorithm And Simulation Implementation Of Multi-hop Cognitive Collaborative Communications

With the rapid development of wireless communication technologies and applications, the scale of wireless network is showing exponential growth and more and more spectrum is required, but spectrum resources are not unlimited. Today, the insufficiency of wireless spectrum resources has restricted the further development of wireless communication. Some studies have found that the inefficient spectrum management strategies and defective channel allocation mechanisms are the main reasons for the spectrum being exhausted. As a new, dynamic and intelligent technology, cognitive radio technology can manage, utilize and allocate spectrum and channels efficiently and has become the research focus of the wireless communication in this context.The fading characteristics of the wireless channel prevent the channel capacity and the QoS from increasing and improving. Multi-antenna technology can effectively overcome the above characteristics and improve performance of the network, the equipment, however, are not easy to achieve, which results in the collaborative communication technology. Collaborative communication is actually a technology that wireless devices use a single antenna to simulate multi-antenna (Virtual multi-antenna technology). It can improve the capacity of wireless communication systems as well as the QoS and the performance of the communication systems.It has become the research focuses of the future wireless communication to reduce the transmit power of the wireless communication equipments to achieve the goal of "Green Communication" under the guarantee of communication performance. Directional antenna technology can focus energy in the range of the main lobe so that it can reduce power loss and lower and then reduce transmit power. At the same time, since the energy within the scope of side lobe is much less that it can reduce the interference with other devices and then improve the efficiency of spectrum utilization.This thesis describes the cognitive radio technology, collaborative communication technology and the directional antenna technology in detail, and then analyses those technologies comprehensively. The second users use the licensed spectrum of the primary users to communicate in cognitive radio networks. This thesis presents a scheme of spectrum access of second users in the cases when primary users are using channels or not respectively. When there is a relatively long distance between senders and receivers of second users and multiple hop transmission is needed, this thesis applies the idea of collaborative communication to the construction of multi-hop path, combines the omnidirectional antenna technology with directional antenna technology to propose a multi-hop algorithm based on omnidirectional and directional.