Cross-Layer Techniques for Adaptive Video Streaming over Wireless Networks
- PDF / 710,190 Bytes
- 9 Pages / 600 x 792 pts Page_size
- 88 Downloads / 219 Views
Cross-Layer Techniques for Adaptive Video Streaming over Wireless Networks Yufeng Shan Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA Email: [email protected] Received 16 July 2003; Revised 9 June 2004 Real-time streaming media over wireless networks is a challenging proposition due to the characteristics of video data and wireless channels. In this paper, we propose a set of cross-layer techniques for adaptive real-time video streaming over wireless networks. The adaptation is done with respect to both channel and data. The proposed novel packetization scheme constructs the application layer packet in such a way that it is decomposed exactly into an integer number of equal-sized radio link protocol (RLP) packets. FEC codes are applied within an application packet at the RLP packet level rather than across different application packets and thus reduce delay at the receiver. A priority-based ARQ, together with a scheduling algorithm, is applied at the application layer to retransmit only the corrupted RLP packets within an application layer packet. Our approach combines the flexibility and programmability of application layer adaptations, with low delay and bandwidth efficiency of link layer techniques. Socket-level simulations are presented to verify the effectiveness of our approach. Keywords and phrases: video streaming, wireless, cross layer, multimedia.
1.
INTRODUCTION
Real-time streaming media over wireless networks, such as live video streaming of a football match to a wireless terminal, is becoming an increasingly important application. In order to be real time, the end-to-end delay of the delivery system should be minimized, given a certain quality requirement. Traditional streaming systems (http://www.microsoft.com/windows/windowsmedia, http://www.real.com) use a large receiver buffer to absorb channel variation and to facilitate the utility of errorrecovery schemes. The receiver prebuffering time usually varies from several seconds to tens of seconds, which is not suitable for real-time streaming. In this paper, we propose a set of building blocks for channel and application adaptive real-time wireless streaming applications. Our approach combines the flexibility and programmability of application layer adaptations, with low delay and bandwidth efficiency of link layer techniques. We propose a novel packetization scheme so that forward error correction (FEC) codes can be applied within an application packet at radio link protocol (RLP) packet level rather than across different application packets and thus reduce delay at the receiver. Furthermore, a priority-based automatic repeat request (ARQ), together with a scheduling algorithm, is applied at the application layer to retransmit only the corrupted RLP packets to improve the wireless bandwidth efficiency.
Unlike wired packet switched networks that suffer from congestion-related loss and delay, the wireless networks have to deal with a time-varying, error-prone, physical channel that in many ins
Data Loading...
