Earch On QoS Of Multimedia Transmission In Wireless Environments

With the rapid development of wireless communication technologies and smart mobile terminals, multimedia technologies have won unprecedented applications and multimedia applications have increasingly become the subject of wireless network services. However, the high multimedia traffic burst, the delay-sensitivity of packet transmission and time varying channels reliability of wireless networks bring researchers a lot of challenges to ensure the quality of multimedia services. Firstly, the convergence of multimedia traffics shows high burst and the burst exists in all time scales. This means that the traditional traffic model based on Poisson process cannot capture the high burst and the analysis results may underestimate the demand for network resources. Secondly, packet size of multimedia services varies greatly and the effect of packet size on quality of multimedia services should be taken into consideration. However, this is often ignored and leads to inaccurate results. Thirdly, as an important part of multimedia services, real-time video is delay-sensitive. Real-time video packet must arrive at the receiver before its deadline, otherwise the packet is discarded and may affect the video quality or even result in playback interruption. Initial delay before playback startup at the receiver side can reduce the playback interruption probability. However, initial delay is also an important parameter affecting the quality of experience. The minimum initial delay to guarantee the requested playback interruption probability can acquire the optimal quality of experience.This paper focuses on the characteristics of multimedia and researches on the transmission quality of multimedia services in wireless environments. Aimed to provide a reference for resource allocation, scheduling and management and thereby improve the quality of multimedia service, we propose the reasonable analysis of the quality of service parameters using the queue theory.Firstly, the effect of the self-similarity of multimedia traffics convergence on the quality of multimedia services is studied. We focus on the burst of multimedia traffics and use the self-similar traffic model to describe it. Also, the variable packet size is taken into consideration and is assumed to follow the heavy tailed distribution. The tail distributions for quality of service metrics such as the distribution of delay and loss are derived from queueing theory perspective. The results show that the degree of self-similarity and the difference of packet size will reduce the quality of service and then will increase the demand for network resources.Secondly, real-time video services are the major of multimedia services and have the highest quality request. The parameter such as delay probability cannot reflect the real quality of transmission services. It should be ensured the requested playback interruption probability at the same time to get the minimum initial delay. We focus on the packet delay-sensitivity and proposed a novel model to describe the packet deadline. Based on the proposed model, the probability of packet loss due to expiration is derived from queueing theory perspective. The relationship between the playback interruption probability and initial delay is formulated with the parameters of playback rate, channel bit-error rate and so on. Finally, the theoretical analysis and simulations are performed to evaluate the impact of system parameters on the relationship between playback interruption probability and initial delay. This can provide a reference for setting smallest initial delay to guarantee the required playback interruption, and thus improve the video quality of users.