Optimization of Power Allocation in Multimedia Wireless Sensor Networks

2.1. Predictive Video Coding

In WMSN, usage of video encoders such as predictive encoders such as H.26x, MPEG-x, necessitates higher processing and memory capacities. The key idea of predictive coding is to utilize motion estimation and motion compression to reduce temporal redundancy, use Discrete Cosine Transformation (DCT) to remove spatial redundancy, and then use Huffman/Arithmetic Coding to reduce coding redundancy. The state-of-the-art predictive video encoders have very good rate distortion characteristics by following the classical complex encoder and simple decoder balance. The computational complexity of the encoder is much higher than that of the decoder.

Predictive coding can reach high compression ratios and dramatically reduce the bit rate of the source video. However, predictive coding schemes has the following disadvantages when being applied to WMSN: (1) high memory requirements due to the need to store reference frames (used for motion estimation); (2) processing delay caused by motion search; (3) high power consumption due to the complexity of motion estimation/compensation algorithms; (4) sensitivity to packet loss and errors in wireless transmission (Figure 1).

Figure 1.

Sensitivity to packet loss/damage in predictive coding