Lower Bound on Delay in a Random Multiple Access System

We consider a multistation packet transmission network with a Poisson input of intensity $\lambda$. The stations send packets through a shared channel with ternary feedback (success, conflict, empty). A function of $\lambda$ is found such that the mean packet delay is not less than this function for any random multiple access algorithm. The lower-bound function equals 0 for $\lambda=0$ and $\infty$ for $\lambda=0{.}587$.