Expanding‐Window‐Based Unequal Error Protection ROFC‐LF Mechanism for Underwater Acoustic Networks

Underwater acoustic networks (UANs) play a crucial role in the Smart Ocean. UANs are also a key technology to realize the digitization, ecology and safety of the ocean. Therefore, the study of UANs has received widespread attention. The highly dynamic changing topology of UANs results in a limited time for data transmission. In addition, different classes of data have different impacts on the quality of reconstructed underwater images and videos. Thus, encoding mechanisms with unequal error protection (UEP) are required to provide unequal protection to the data. The recursive online fountain code with limited feedback (ROFC‐LF) is suitable for UANs because of its low overhead and simple codec process. An expanding‐window‐based UEP ROFC‐LF mechanism is proposed to address the problems of the ROFC‐LF. These problems include the presence of loops, the inability to provide UEP functionality, and the inability to precisely control feedback. The expanding‐window‐based UEP ROFC‐LF mechanism employs an expanding‐window strategy and a priority strategy in the build‐up phase and the completion phase, respectively. These two strategies make this mechanism realize UEP function. The encoding overhead is reduced through a circle‐avoidance algorithm and feeding back the minimum IDs of the undecoded components. Additionally, a feedback strategy based on pre‐generated sequences is proposed for accurate control of the feedback process. Finally, this encoding mechanism is theoretically analysed based on random graph theory, and the theoretical analysis is the same as the simulation experiment results. The results show that the encoding mechanism not only accelerates the recovery of the MID but also achieves precise control of the feedback. Therefore, the mechanism proposed in this paper is well‐suited for UANs.