Modified Robust Soliton Distribution (MRSD) with Improved Ripple Size for LT Codes

In this letter, we propose a scheme to modify robust Soliton distribution (RSD) with respect to the expected ripple size. We only adjust the proportion of degree 1, degree 2 and the maximum degree to derive the modified RSD (MRSD). Thus the proposed scheme contains only two variables and its complexity does not increase with the code length. Our objective is to increase the mean of the expected ripple size while decreasing its variance at the same time. Furthermore, sequential quadratic programming is introduced to maximize the objective function under certain constraints. Simulation results show that, with different code lengths, MRSD saves 2% to 5.8% overhead to decode entire input symbols, compared to RSD.