Multiple bitstream image transmission over wireless sensor networks
In this paper, we proposed a novel scheme for error robust and energy efficient image transmission over wireless sensor networks. The innovations of proposed scheme are two folds: multiple bitstream image encoding to achieve error robust transmission and small fragment burst transmission to achieve efficient transmission. In the case of image encoding, a multiple bitstream image encoding is developed based on the decomposition of images in the wavelet domain. We first group wavelet coefficients into multiple trees according to parent-child relationship and then code them separately by SPIHT algorithm to form multiple bitstreams. We show that such decomposition is able to reduce error propagation in transmission. To further enhance the error robustness, unequal error protection strategy with RCPC/CRC is implemented. The coding rate is designed based on the bit error sensitivity of different bit planes. In the stage of image transmission, we divide the multiple bit streams into small fragments and transmit them in burst. We demonstrate that such transmission strategy matches well with the media access control layer protocol as well as the link layer protocol currently employed in wireless sensor networks. We achieve energy efficient transmission by saving energy consumed on control overhead and device switching from sleep to active. Experimental results show that the proposed scheme has not only high energy efficiency in transmission but also graceful degradation in PSNR performance over high BERs channels in terms of image reconstruction quality at the base station.