Optimized Cross-Layered Unequal Error Protection for SPIHT Coded Wireless Video Transmission

Transmission of coded video over erroneous channels (e.g., Internet and wireless networks) is always a challenging task. Error control strategies, to combat the channel errors, are generally applied at individual network layers leading to inefficient utilization of resources. The cross-layer design has emerged as alternative for efficient utilization of the available resources, such as bandwidth, delay, and transmission power to provide best quality of the reconstructed video. Furthermore, to efficiently utilize the resources, cross-layer error control parameters need to be optimized. Since, the optimal error control parameters change with channel conditions, new optimal values need to be calculated every time the channel condition changes. However, optimization of the parameters at the time of video transmission requires very high computational processing power otherwise it may induce a large transmission delay which is intolerable in video communication. In this paper, we propose an optimized cross-layered unequal error protection (UEP) scheme targeted for hand-held devices which have low processing power, uses pre-computed look-up table (LUT) that stores the optimal cross-layer error control parameters for a range of channel conditions. LUT is constructed using offline optimization of the parameters. For real time video communication, given a channel condition, the corresponding error control parameters are read from a LUT and are passed to the corresponding network layers. Thus, the proposed transmission system is simple and delivers best end-to-end quality of the video. Simulation results show that the proposed cross-layered UEP system can achieve up to 14-17 dB and 2-4 dB improvement in video quality over individual application layer optimized UEPs in additive white Gaussian noise and fading channel respectively at very poor channel conditions. Furthermore, the proposed system outperforms other contemporary methods.

I. Introduction

Compressed video is highly sensitive to transmission errors, due to which its transmission over the lossy channels such as wireless and Internet is a very challenging task. Over the years several error control strategies have been proposed to counter the effect of transmission errors [1], [2]. In most of the existing works, error control scheme is applied at individual layers of the network protocol such as application, transport, media access control (MAC) and physical layers. Popular error control strategies include forward error correction (FEC), adaptive modulation, automatic repeat request (ARQ), robust source coding, multiple-description coding, data partitioning, error concealment, scalable coding with transport prioritization and hierarchical modulation, etc. [1], [2].