Video Communications Over Wireless Ad-Hoc Networks Using Source Coding Diversity and Multiple Paths

Abstract

Providing reliable video communications over wireless ad-hoc networks is becoming increasingly important as these networks become widely employed in military, homeland defense security, and disaster recovery applications. However, wireless ad-hoc networks have a dynamically changing topology that can cause failures of links and nodes, thus resulting in path loss. Additionally, video communications over wireless ad-hoc networks can suffer from noise and fading effects in the channel. Therefore, it is important to provide error resilience for reliable video communications over such an error-prone network. A number of solutions have been proposed for this problem, including source coding diversity and multipath routing. Source coding diversity methods such as multiple description coding (MDC) have proven to be effective for robust video communications, especially when combined with network path diversity (Gogate et al., 2002; Mao et al., 2003; Apostolopoulos & Trott, 2004). We investigate new MDC methods combined with path diversity to enhance the error resilience of video communications over wireless ad hoc networks. The basic idea of MDC is to encode the video sequence into several descriptions for transmission over multiple paths. Each description can be independently decoded and combined with the other descriptions to provide an acceptable video quality. When more descriptions are received for reconstruction, higher video quality can be achieved. As long as all descriptions are not lost simultaneously, somewhat acceptable quality can be maintained. In order to reduce the likelihood of simultaneous loss of descriptions, different descriptions are transmitted through different paths. This is referred as MDC with path diversity, which reduces the possibility of simultaneous loss of different descriptions and enables load balancing in networks. Many MDC algorithms have been proposed (Goyal, 2001) and they can be divided into three categories: subsampling algorithms in the temporal (Apostolopoulos, 2001), spatial (Franchi et al., 2005) or frequency domain (Reibman et al., 2001), multiple description quantization algorithms (Vaishampayan, 1993; Dumitrescu & Wu, 2009), and multiple description transform coding (Wang et al., 2001). Wang, Reibman & Lin (2005) provides a good review for MDC algorithms. Since subsampling methods are easy to implement and compatible with different video standards, they have been the most commonly investigated MDC algorithms. These methods generally work in the spatial, temporal, or frequency domain to generate multiple 3