4.5.1 Solving the Balance EquationsWe can now proceed to solve the balance equations expressing all steadystate probabilities P_{n}, n = 0, 1, 2, . . . in terms of one of them and then taking advantage of the fact that It is common practice in queueing theory to express P_{1}, P_{2}, P_{3}, . . . in terms of P_{0}, the steadystate probability of an empty system. Working with (4.22) and (4.23) or, equivalently (and preferably) with (4.24), we have
Going now back to (4.25), It follows that the system can reach steady state only if . For, otherwise, P_{0} = P_{1} = P_{2} = ... = 0 (i.e., the number of users in the system never "stabilizes"). Assuming that the system does reach steady state, the probabilities P_{n}, n = 0, 1, 2,. . . , are now given by the fundamental expressions (4.30) and (4.28), and other quantities of interest can be computed from these probabilities. For instance, and _{q}, , and _{q}, can then be obtained from (4.10), (4.11), and (4.13).
