Renxiang Huang

Methodologies on designing a hybrid shared-mesh-protected WDM network with sparse wavelength conversion and regeneration

In a wavelength-routed WDM optical network, having regeneration and wavelength conversion at every node is not cost-effective. However, in a nation-wide backbone network, regeneration is required for some lightpaths. With shared-mesh protection, wavelength-conversion is helpful in increasing the wavelength sharing among protection paths therefore can improve resource-utilization. In this work we study the problem of selecting wavelength-conversion and regeneration sites in such a network. We show that the wavelength converter placement problem can be formulated as an integer linear program and propose several heuristics for solving the sparse wavelength conversion and regeneration problem.

Cross-Layer Design for Wireless Video Streaming

We present a cross-layer approach to the design of a wireless video streaming system, which includes the development of an adaptive radio link buffer and congestion control algorithm and the adoption of the H.264/SVC scalable video format. The proposed system performs a group-of-pictures (GOP) based post-channel adaptation, which does not require the channel status information at the media server. Video packets are prioritized in a GOP-by-GOP manner based on the dependence relation within a GOP. We employ H.264/SVC for the video stream preparation to provide the flexibility and adaptability of compressed video data. The priority information is conveyed in the header extension of the network abstraction layer unit (NALU) of H.264/SVC, which is parsed by a media aware network element (MANE) to realize an efficient transmission and congestion control. The performance of the proposed algorithm is verified by the computer simulation.

Video Streaming over 3G Networks with GOP-Based Priority Scheduling

A bandwidth-efficient video streaming algorithm over the cdma2000 1x EV-DO network using GOP-based priority scheduling is proposed in this work. The proposed algorithm performs an application adaptation by considering the postchannel status to cope with the fluctuating wireless mobile radio channel. The peak-signal-to-noise-ratio (PSNR) value and the number of buffer underflows at the mobile terminal (MT) are used as performance metrics to indicate the spatial and temporal quality of received video, respectively. It is demonstrated by computer simulation that the proposed priority scheduling algorithm adapts source bit rates of pre-encoded video streams to the bandwidth fluctuation of wireless channels well and yields satisfactory spatial and temporal video quality.