Study Of Image Coding Algorithm For Wireless Multimedia Sensor Networks

There are a large number of video data have to be processed and transmitted in resource-constrained wireless multimedia sensor networks (WMSN). One possible way to achieve the maximum utilization of those resources is to apply an adaptive video coding scheme, which must consider the trade-off among energy consumption, compression ratio and image quality. The state-of-the-art in video coding techniques, the major research challenges and the objectives of video coding for WMSN are discussed. Existing solutions and theoretical explorations of video coding for WMSN are investigated and classified, including single source coding and distributed source coding. Finally, fundamental issues of single source coding are discussed, and future research trends in this area are outlined.The image communication behavior of a wireless video sensor and its performance under resource constrained wireless multimedia sensor networks is studied. Energy consumption and rate distortion model of DCT and DWT based image compression and transmission is developed. Based on energy consumption and rate distortion model proposed, resource allocation is optimized with limited energy and bandwidth. Encoding coefficients are adapted according to the activity of monitoring scene, and then the energy consumption will be minimized. Simulations results are conducted to show the performance of our work. The proposed scheme dramatically reduces image compression and transmission energy consumption under expected image distortion and transmission rate.With resource-constrained wireless multimedia sensor networks, image coding and transmission must respect the trade-off among energy consumption, compression ratio and image quality. The problem of compression of video-surveillance image sequences collected by a wireless multimedia sensor network is studied. To reduce the computation complexity, a low-complexity image compression scheme based on change detection and adapted JPEG is proposed. Change detection is used to locate the region of interest and cut down the data for transmission, fast DCT is used to reduce the computation complexity. Such an image compression scheme provides a graceful trade-off between the reconstructed images quality and the sensor nodes'lifetime. Computation complexity analysis and simulations on the parking lot images are conducted to show the performance of our work.For sufficient utilization of constraint resource on generating high-resolution images with wide field of view, an algorithm takes fully account the redundant visual information among multiple video sensors is proposed. Image block searching algorithm is applied for image registration to decrease the energy consumption, sum of absolute difference algorithm is adapted to improve the accuracy of image registration, and weighted mean algorithm is applied for image stitching. Data volumes of transmission are decreased after image mosaicking, which can efficiently reduce the network loading. Simulation results demonstrate that the computation complexity of proposed algorithm is lower than other image mosaicking algorithm, under certain image registration accuracy and image quality.An energy efficient JPEG2000image compression scheme is adapted for wireless multimedia sensor networks. The algorithm determines the parameter of quantization and the wavelet image compression transform level to meet the image quality requirement and channel condition. Semi-reliable transmission enables packet forward or discarding by intermediate nodes according to residual energy and data priority. Simulation results show that proposed image compression scheme provides a graceful trade-off between the reconstructed images quality and the total energy consumption of sensor nodes.