Wireless Video Multicast With Beamforming Antenna

Wireless multicast is an efficient technique for delivering shared media and data such as mobile TV, sports telecast, video conference, location-based services, software update and network management. Due to the shared nature of wireless medium, one multicast transmission can potentially reach all desired clients, thereby saving precious wireless resources.To improve the performance of wireless video multicast service, some key techniques such as Scalable video coding (SVC) and adaptive modulation and coding (AMC) are involved. But wireless multicast based video delivery with traditional omni antenna is constrained by the client with the lowers channel quality within a multicast group. Beamforming antenna is a na?ve and effective physical-layer technology that can increase the SNR at the clients on particular directions by applying different weights on the array antenna elements to form beam patterns thereby increasing the minimum channel quality among the clients that form the multicast group. Thus it can be utilized to enhance the wireless multicast video transmission. However focusing the energy in one direction typically reduces the footprint of signals in other directions and thus restricts the wireless multicast advantage. Due to this inherent tradeoff between multicasting and beamforming, efficient schemes on beam scheduling are required for wireless multicast transmission. The dissertation focuses on the research of wireless video multicast mechanisms with beamforming antenna and consists of the following three aspects:(1) Validation of the beamforming model. There are two important models of beamforming antenna:overlapping beam model and non-overlapping beam model. We implement experiments in indoor environment and outdoor environment to validate the correctness of these two models. Measurements from clients under rotating beams prove that the overlapping beam model and non-overlapping beam model are reasonable and practical.(2) Optimizing video multicast with overlapping beamforming antenna. The models for optimizing problems, including optimizing delay and optimizing utility respectively, are built and then problems are proved to be NP-hard. For the problem of optimizing delay we propose a log(C)-approximation greedy algorithm where C is the number of clients in the multicast group. For the problem of optimizing utility, unified approximation algorithms with a parameter that controls both the algorithms'complexity and approximation factor are proposed for multi-resolution video stream and scalable video coding stream, respectively.(3) Optimizing video multicast with non-overlapping beamforming antenna. We also formulate the problem of optimizing video multicast delay/utility with non-overlapping composite beamforming antenna and prove that both problems are NP-hard. Approximation algorithms with low complexity are proposed for optimizing video multicast delay. As for the problem of optimizing system utility, we first propose an optimal algorithm which is used in systems with small number of beams, and then propose a sub-optimal algorithm for any system.