The development of wireless technologies makes telemedicine more and more popular. However, due to the broadcast and openness nature of radio propagation, it makes the image transmitted over wireless channel much easier to be eavesdropped. Moreover, delay requirements is another concern in most application scenarios. To deal with the security issue, a secure scheme for wireless image transmissions based on fountain coding and adaptive resource allocation is proposed in this paper. For fountain-coded transmissions, the transmitter must firstly encode the source image packets into fountain packets using fountain codes before sending these fountain packets over the channels. At the receiving end, receiver can recover the original image if and only if a sufficient number of fountain packets have been correctly received and then a feedback signal will be sent to transmitter to end transmission. Therefore, the transmission secrecy will be achieved if the legitimate receiver can get enough fountain packets precede eavesdropper. To achieve this, adaptive resource allocation relative to the legitimate channel is used to ensure a higher packet reception rate at the legitimate receiver for the independent channel fading characteristic of legitimate receiver and eavesdropper. A medical image usually consists of region of interest (ROI) and background (BG). With respect to BG, ROI tends to contain important diagnostic information and need a higher reliability requirement. Source image packets can be divided into ROI source packets and BG source packets accordingly. In this condition, superposition coding, which can make transmitter deliver two packets simultaneously, is employed to reduce the transmission time delay. The simulation results show that the proposed scheme can achieve considerable gains in terms of image transmission security and the delay requirement.
['Caihong Han', 'Li Sun', 'Qinghe Du']
Securing Image Transmissions via Fountain Coding and Adaptive Resource Allocation