Rateless802.11: Extending WiFi applicability in extremely poor channels

Abstract Due to its limited error correction capability, 802.11 can hardly work in scenarios where the channel fading or interference is very severe, such as industrial internet of things. In this paper, we propose Rateless802.11, a cross-layer scheme which can work as a middleware over common commodity 802.11 devices, that extends the applicability of 802.11 in extremely poor channels. Rateless802.11 concatenates LT codes with 802.11 convolutional codes in the transmitter side to introduce proper redundancies in an incremental manner, so that the uncorrupted bits of MAC protocol data units (MPDU) can be adequately exploited, enhancing the error correction capability significantly. In order to ensure its compatibility with commodity devices, Rateless802.11 adopts a well-designed process flow of received packets at the receiver side, within which some novel decoding procedures are employed to achieve a better decoding performance. Specifically, since the random seed used in the scrambling process could be polluted during the descrambling process in commodity 802.11 device due to the poor channel condition, we propose a method to protect and recover the seed based on the linearity of scrambling sequences. Moreover, we propose a belief-propagation based integrated decoder, which decodes convolutional codes and LT codes together in a joint manner, leading to much less information-loss and decoding delay than serial decoding. Both numerical and real-trace driven simulations show that Rateless802.11 improves the throughput of 802.11 in extremely poor channels by several to dozens of times compared with state-of-the-art solutions.