Research On Image Processing Algorithms And Communication Security For Video-Guided Missile System

Video-guided missile is a kind of precision-guided weapons. It is a bomb with a video camera in the nose that can get the real-time target image, then transmit the image to control center through wireless up channel. Then the manipulators can select the target in which they interest in the image and send the commands to guide the bomb to attack it. For the limited wireless bandwidth, image which contains much data has to be compressed by high compression ratio; therefore, it is difficult for manipulators to confirm attacking targets. Because this system was applied in the military confrontation,the problem should deserve attention and consideration in video-guided missile system that how to display suspected target quickly and keep the communication security.In order to solve this problem, in this paper some method are proposed based on the region of interest coding, the error-resilience modes and the structure of code-stream in JPEG2000 standard after analyzing the characteristics of video-guided missile system.Firstly, an EBCOT-based ROI coding algorism was presented. The unit of EBCOT coding in JPEG2000 standard is block, some blocks only overlap with ROI mask in a small part, but all the coefficients in this block were assigned the same high priority. That will lead to the image of ROI decreasing sharply which is transmitted in limited wireless channel of video-guided missile system. The coefficients of background and ROI were distinguished in one block with ROI mask, and then adjusted their priority with a factor based on EBCOT. The adjustment was graded for practical applications. Manipulator can adjust the weight factor to improve the compression efficiency by yielding a good ROI and degrading the priority of background coefficient in the ROI code block. The proposed method show higher compression efficiency, lower complexity and good reconstructed ROI image quality in lower channel capacity.Secondly, aiming at infrared imaging guidance missile system, an automatic ROI extraction algorithm was proposed based on image gray. In the infrared image the gray value of object regions is always higher and the background which has uniform distribution. According to this feature IR image were segmented to many blocks in spatial information, calculated the mean of gray value to each block, find the block in which the maximal gray value is by sorting and then got the ROI through extending the block with maximal gray value. In this algorithm a rectangle ROI mask is got which only two points, the top left point and the bottom right point, can express, so just only the two points is transmitted. Therefore the proposed approach can fix on ROI rapidly and achieve good target searching performance.Thirdly, a joint source-channel decoding (JSCD) method was designed in video-guided missile system. JPEG2000 is used to perform source decoding with certain error-resilience modes; and a regular low-density parity-check (LDPC) code is selected as the channel error correcting code. For Sum-Product iterative channel decoder, each iterative results are send to source decoder; JPEG2000 decoder with error-resilience modes detects the first error bit in each block and feedbacks the information to channel decoder which update the log-likelihood ratio(LLR) of partial codeword bits. A novel feedback coefficient is applied in this system. Simulation results show that the JSCD scheme can accelerate the iterative procedure, and improve the channel SNR of communication.Finally, a novel scheme was proposed to protect the communication data from interception and falsification, the scheme was based on the Elliptic Curve Cryptosystem (ECC). Now the security of military radio communication were depends mainly on spread spectrum technology; but with the development of electronic product and computing capacity, it's difficult to ensure the safety of information very well. In order to solve this problem, Elliptic Curve Public Cryptosystem is introduced into video-guided system. The system send the command data to the missile which is encrypted with the public key of missile and then the missile receives decrypts this command data with the private key of missile. For image information, combining with the structure of JPEG2000 code-stream, only some important parameters and partial extraction data were protected, the process of encrypting and decrypting were inverse to command data processing. The proposed method not only enhances the communication security but also confirm the identity information.