Multi-channel data broadcast attracts increasingly focus in recent years. For the complex and large multimedia data like images, audios, and videos etc, multi-channel data broadcast is a promising approach to mitigate various limitations of data dissemination in mobile environment, such as narrow bandwidth, unreliable connections, and battery limitation. However, existing data broadcast schemes are inefficient for employing multiple channels. In this paper, we present five novel multimedia data broadcast schemes (SDAA, ISDAA, LDAA, AEA, and COA) specifically designed for wireless multichannel communications. The key idea behind those schemes is to utilize SVC (Scalable Video Coding) to generate data segments with different qualities and implement indexing and channel assignment to minimize the expected waiting time for clients. In terms of waiting time minimization, we prove theoretically that SDAA is a 4/3-approximation algorithm and ISDAA is a 6/5-approximation algorithm for global allocation, and AEA can achieve locally optimal solution. We show that integrating SDAA and AEA form a best schedule for practical applications. We provide numerical experiments by using a SVC dataset and a YouTube dataset to evaluate the system performance and prove the efficiency of our schemes. We also propose a multiple video broadcast framework and analyze its performance.

With the development of wireless communication and social network, wireless network service demands have increased rapidly in recent years. To amplify the wireless signals and expand the coverage of wireless networks, wireless relay nodes are introduced. This paper addresses the problem of finding an optimal deployment of access points and wireless relay nodes in an arbitrary environment to provide all the potential users with higher quality wireless network services. Our ambition is to maximize the coverage rate and to minimize the energy consumption of the relay nodes. Correspondingly, we design a scheme named OR-Play: an optimal relay placement scheme to provide high-quality wireless services, which consists of three phases. First, OR-Play provides an area coverage for an arbitrary area. We use the virtual force model to determine the positions of wireless devices, including access points and relay nodes, and thus extend the network lifetime. In the second phase, OR-Play selects access points by a 2-approximation algorithm for the metric k-center problem. In the third phase, we define a new problem: k-minimum energy broadcasting trees. We design a distributed greedy strategy to determine the broadcasting trees, based on which the power of relay nodes are precisely assigned. Finally, the simulation results validate the effectiveness and efficiency of OR-Play.