A Study of Opportunistic Multicast Scheduling (OMS) over Wireless Networks
|關鍵字:||機會主義群播排程;群播;全球互通微波存取;分層視訊群播;opportunistic multicast scheduling;multicast;WiMAX;layered video multicasting|
The ever-increasing demand for richer multimedia contents anytime, anywhere, on any devices, has driven the development of highly efficient content distribution technologies over wireless networks. In particular, opportunistic multicast scheduling (OMS) has recently emerged as one of the most promising techniques for content delivery, which effectively increases throughput with reduced delay by exploiting multiuser diversity inherent in wireless networks. In this dissertation, we consider the problem of multicasting a common set of data to all subscribers on the downlink of a wireless network. Two issues of wireless multicasting are studied and investigated: i) reducing feedback load of OMS, and ii) transmitting real-time multimedia over heterogeneous wireless terminal devices. For reducing feedback load of OMS, a Weakly Consistent OMS scheme for channel condition feedback reduction is presented. Channel condition feedbacks, although it allows the scheduler to exploit the multiuser diversity, it results in overhead which may interfere the uplink traffic in the system. Our proposed scheme is able to reduce the feedback load while maintaining the multicast throughput performance comparable with the case of full feedback. For our proposed OMS, we further propose an equation for system operators to determine the best size of feedback interval for the subscribers to update their channel conditions. Our analysis shows that the size of feedback interval determined through our equation can significantly reduce the feedback load in the system while providing comparable throughput performance to the subscribers. For real-time multimedia transmission over heterogeneous terminal devices, an effective layered video multicasting (LVM) algorithm is presented, and a prototyping system called WiMAX-LVM is developed. The WiMAX-LVM system is a working realization for LVM over mobile WiMAX, which can serve as a basis for future researches in creating video-related multicasting services over orthogonal frequency-division multiple access (OFDMA)-based fourth generation (4G) wireless networks. The research results presented in this dissertation provide some useful mechanisms and guidelines for broadband wireless operators to achieve high system performance in their networks.
|Appears in Collections:||Thesis|