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Raptor Code for Downlink Cooperative Wireless Cellular Networks

In the existing literatures on cooperative relay system, the coding scheme adopts the conventional fixed-rate code (traditional code). This paper first studies the rateless code, Raptor code, to cooperative wireless cellular system. In particular, we study the efficiency, reliability, and robustness of cooperative communication in a wireless cellular downlink environment by employing a new scheme based on combining a Raptor code with distributed space-time block code (DSTBC), when channel state information is not available at the transmitter. Considering the flexible code rate characteristic, we find a new measurement, total time slice, to evaluate the performance. Therefore, the number of total time slices at transmitting exactly and the average bit error rate (BER) of cooperation are presented by applying various encoding schemes. The time division multiple access scheme is proposed with half duplex mode. Based on theoretical analyses and simulation results, we show that without channel state information at the transmitter, the cooperative wireless cellular system using Raptor code and DSTBC yields significant performance gain, i.e., reducing the total transmission time and energy consumption, even in a low signal-to-noise ratio (SNR) environment.