A Network-Coded Diversity Protocol for Collision Recovery in Slotted ALOHA Networks

We propose a collision recovery scheme for symbol-synchronous slotted ALOHA (SA) based on physical layer network coding over extended Galois Fields. Information is extracted from colliding bursts allowing to achieve higher maximum throughput with respect to previously proposed collision recovery schemes. An energy analysis is also performed, and it is shown that, by adjusting the transmission probability, high energy efficiency can be achieved. The paper also addresses several practical aspects, namely frequency, phase, and amplitude estimation, as well as partial symbol asynchronism. A performance evaluation is carried out using the proposed algorithms, revealing remarkable performance in terms of normalized throughput.