Cooperative Multicast For Multimedia Transmission Over Cognitive Radio Networks

With the rapid development of wireless communication and high-data rate applications, Multimedia service has become an indispensable part in people's life. The rapid growth of multimedia service makes it more hash for the demand for bandwidth and latency. Since it is possible to dynamic access authorization spectrum without affecting the communication of primary users, cognitive radio can make full use of spectrum resources, so as to flexibility adapt to the multimedia transmission.Multimedia service tends to be subscribed by more than one user at the same time. Cooperative wireless multicast not only can make the same wireless network resources serve more users to improve spectrum efficiency to a great extent, but also can act as relays to help users with bad channel condition to effectively enhance the transmission efficiency of multimedia transmission.The transmission rate of multicast system is limited by the user with the worst channel condition. By decomposing the multimedia contents into two layers for transmitting, the scalable video coding can provide different users with different service quality, so as to effectively improve the system throughput.According to the problem of efficient multimedia multicast transmission in cognitive radio networks, this paper put forward a cognitive multimedia cooperative multicast communication scheme. The proposed scheme considers the cooperation between the cognitive system and the primary system, the secondary user act as the cooperative relay to improve the performance of primary system. In return, the cognitive user can gain more opportunity to access the wireless channel and transmit more data of secondary system. Through joint time and power distribution, the scheme can maximize the total throughput of the primary system and the utility of secondary system at the same time, which can achieve a win-win situation. The proposed scheme ensures all of the multicast users can receive basic layer of the information. However, due to some users may get a severely bad channel condition, in order to maximize the overall throughput of the primary system, we need to exclude some bad users and provide the enhancement layer multicast service to a limited set of users with a relative good channel conditions. Simulation results show that compared to traditional multimedia transmission over cognitive radio, our proposed scheme can improve the multimedia service quality efficiently, when the number of multicast users increased and the demand data rate of basic layer increased.