Performance analysis and optimization of LT codes with unequal recovery time and intermediate feedback
Rana Abbas, Mahyar Shirvanimoghaddam, Yonghui Li, Branka S. Vucetic · 2016
In this paper, we analyze Luby Transform (LT) codes with unequal recovery time (URT-LT) and intermediate feedback. Different sets of information symbols within a message block are allocated different priorities, where the higher prioritized sets are to be recovered in a shorter time. We divide the encoding process into stages where in each stage different sets are allocated different selection probabilities. A stage ends when one of the sets' recovery times expires. We incorporate an intermediate feedback that notifies the transmitter of the recovered information symbols at the end of each stage. These recovered symbols are then excluded from future encoding. We use the AND-OR tree analysis to find the optimal selection probabilities that guarantee the sets are recovered within the required time, with a relatively small error probability. We compare the scheme to the case where the sets are encoded and transmitted separately.