Implementation trade-offs of fountain codes in LTE and LTE-A

The fountain codes are attractive for efficient multicast delivery of large data or multimedia files over unreliable wireless channels. These codes are standardized and intended to operate at the application layer. In this paper, the fountain codes are incorporated into the LTE protocol stack at the medium access (MAC) layer. It is shown that the MAC layer implementation of the fountain codes requires that not only the LTE parameters are optimized, but also, that the adaptive modulation and coding (AMC) scheme mechanism is modified. Provided that such optimization and modifications are adopted, for instance, in the LTE-Advanced, the MAC layer fountain codes can significantly outperform the application layer fountain codes in terms of the energy consumption-transmission delay trade-off.