Necessary and sufficient conditions for recurrence and transience of Markov chains, in terms of inequalities

For an aperiodic, irreducible Markov chain with the non-negative integers as state space it is shown that the existence of a solution to in which yi → ∞is necessary and sufficient for recurrence, and the existence of a bounded solution to the same inequalities, with yk < y o, · · ·, yN –1 for some k ≧ N, is necessary and sufficient for transience.