PRAC: Exploiting partial packets without cross-layer or feedback information

This paper proposes a partial packet recovery scheme, called Packetized Rateless Algebraic Consistency (PRAC). PRAC exploits intra and inter-packet consistency to identify and recover erroneous packet segments, without recourse to cross-layer or detailed feedback information. In the absence of cross-layer coordination or detailed feedback, the prevailing methods proposed in the literature have discarded packets with errors. PRAC uses a rateless linear packet code for data encoding and an iterative decoding process consisting of a search algorithm and an algebraic consistency rule (ACR) check. It allows, but not relies upon, the use of any PHY FEC code, requires no feedback other than a notification of completion and, in the absence of partial packets, incurs no overhead. Our implementation and experimental results in a 7-node indoor testbed using wireless boards equipped with CC2500 radio transceivers reveal that PRAC offers an average throughput gain of 35% compared to a baseline ARQ scheme discarding partial packets and 13% compared to an ideal genie-aided HARQ (iHARQ) scheme. Specifically for links with high PERs, PRAC significantly enhances their robustness and its maximum throughput gain is 148% and 34% compared against the baseline and iHARQ schemes, respectively.