Abstract
LetN(t) be a birth-death process onN= {0,1,2,· ··} governed by the transition rates λn> 0 (n≧ 0) andμη> 0 (n≧ 1). LetmTmbe the conditional first-passage time from r to n, given no visit tomwherem The downward conditional first-passage timenTmis defined similarly. It will be shown that, foranyλn> 0 andμη> 0. The limiting behavior ofis considerably different from that of the ordinary first-passage timewhere, under certain conditions, exponentiality sets in asn→∞. We will prove that, when λn→ λ > 0 andμημ> 0 asn→ ∞withρ= λ/μ <1, one hasasr→ ∞whereTBP(λ,μ)is the server busy period of anM/M/1 queueing system with arrival rate λand service rateμ.