Data compression techniques in Wireless Sensor Networks

The advancement in the wireless technologies and digital integrated circuits led to the development of Wireless Sensor Networks (WSN). WSN consists of various sensor nodes and relays capable of computing, sensing, and communicating wirelessly. Nodes in WSNs have very limited resources such as memory, energy and processing capabilities. Many image compression techniques have been proposed to address these limitations; however, most of them are not applicable on sensor nodes due to memory limitation, energy consumption and processing speed. To overcome this problem, we have selected Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) image compression techniques as they can be implemented on sensor nodes. Both DCT and DWT allow an efficient trade-off between compression ratio and energy consumption. In this paper, both DCT and DWT are analyzed and implemented using TinyOS on TelosB hardware platform. The metrics used for performance evaluation are peak signal-to-noise ratio (PSNR), compression ratio (CR), throughput, end-to-end (ETE) delay and battery lifetime. Moreover, we also evaluated DCT and DWT in a single-hop and in multi-hop networks. Experimental results show that DWT outperforms DCT in terms of PSNR, throughput, ETE delay and battery lifetime. However, DCT provides better compression ratio than DWT. The average media access control layer (MAC) delay for both DCT and DWT is also calculated and experimentally demonstrated. A comprehensive literature review for data compression techniques in WSN is presented.DCT and DWT compression techniques are analyzed and implemented using TinyOS on a hardware platform TelosB.DWT has a higher PSNR and a faster compression technique than DCT.The experimental results show that the overall performance of DWT is better than DCT.As the number of intermediate nodes is increased, the performance of both techniques degrades.