The Cognitive Relay Cooperative Multimedia Sensor Networks And Power Control Study

The available spectrum of wireless multimedia sensor networks is limited and interfered precious during communication, so it is an important challenge to guarantee the quality of service in multimedia data transmission. In this paper, a cognitive radio based wireless multimedia sensor network is introduced to provide data transmissions with quality of service requirements. To meet the real-time transport and bandwidth requirements, relays cooperation and transmission power control are studied in this paper.Firstly, a Q-learning based relays cooperation mechanism is proposed to support real-time traffic. The multimedia sensor nodes can switch to available channels that detected by cognitive nodes. According to the spectrum sensing results of the cognitive nodes, a service aware criterion is designed to decide whether the multimedia sensor node needs cooperative relays. The reward value of Q function is designed as the ratio of the residual energy and communication energy consumption. A satisfaction function based on transmission distance and signal to noise ratio is proposed. Considering the reward value and the satisfaction, relays are selected to reduce data transmission delay.Secondly, a power control algorithm of optimizing the channel capacity under interference constraint is proposed. It aims at ensuring the quality of service requirements of multimedia data and reducing the interference generated by the multimedia sensor nodes. According to the channel information that sensed by the cognitive nodes, the range of transmit power is get through the inequality constraint of primary user's transmission performance. On this basis, the transmit power value of source node and relays can be calculated via convex optimization under the goal of maximizing the channel capacity.Finally, performance evaluations of the proposed cooperation transmission mechanism and the power control scheme are taken under OPNET simulation. The data transfer delay and interference grade are analyzed, and the results show the reasonability of the cooperation transmission mechanism and the power control scheme.