Cooperative communication system with systematic Raptor codes

Implementing rateless codes in cooperative scheme has attracted a lot of interest recently. It is an efficient and flexible solution for many practical communication areas, such as Digital Video Broadcasting (DVB). In this paper, we propose a relay scheme using systematic Raptor code which is standardized in 3GPP. The advantage of systematic over non-systematic Raptor code is that when there is no packet lost in the transmission, there is no need for decoding. To improve the performance, Reed-Solomon (RS) code is concatenated as an inner code. Every two Raptor symbols to which a 32-bit cyclic redundancy check (CRC) are appended will be encoded into one RS codeword. Additionally, we develop ways of optimizing the system with channel state information (CSI) at the transmitter, including adaptive RS coding rates and adaptive cooperation of relay. It is shown from the simulation results that besides the inherent advantage of systematic coding, this scheme has a noticeable efficiency gain over the system without relay.