Physical-layer Network Coding on the Random-access Channel

We consider a physical-layer network coding strat- egy for the random-access channel, based on compute-and- forward. When packets collide, it is possible to reliably recover a linear combination of the packets at the receiver. Over many rounds of transmission, the receiver can thus obtain many linear combinations and eventually recover all original packets. This is by contrast to slotted ALOHA where packet collisions lead to complete erasures. In previous work we introduced a compute- and-forward strategy for the two-user random-access channel. In the current work we consider an arbitrary number of users. The strategy is shown to be significantly superior to the best known strategies, including multipacket reception.