Fountain-Code Aided File Transfer in 802.11 WLANs

Abstract —Fountain codes constitute novel erasure codes, whichhave been standardized for Forward Error Correction (FEC)in broadcast network protocols and by the Third-GenerationPartnersonhip Project (3GPP). The basic operational units ofFountain codes are source packets, which have a particular fixedlength. These codes are invoked here in an 802.11 Wireless LocalArea Network (WLAN) scenario for protecting file transfers.More specifically, the optimal packet length is selected by con-sidering the 802.11 Media Access Control (MAC) retransmissionrate and the properties of the physical layer’s modulation scheme.Naturally, owing to the limited memory of the encoders/decoders,large source files must be decomposed into shorter transportblocks. Therefore, methods for partitioning the file and acknowl-edging the successful transmission of each block are also proposedhere. Compared to the file transfer regime operating without FECover the classic TCP protocol, the proposed regime requires alower threshold SNR for accomplishing a successful file transferand hence enhances the transmission efficiency by about 50%.

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