In this paper, we consider the decode-and-forward (DF) relay network system over Rician fading channels. We derive an analytical expression for the outage probability of the highest achievable information rate of the system, which can be evaluated by employing standard numerical techniques. We also obtain some simple but tight lower and upper bounds on the derived outage probability by using the geometrical representation of the distribution of the Hermitian quadratic form. Furthermore, we investigate the impact of the correlation coefficient between the transmitted signals from the source and relay. We disclose that when the Rice factors are relatively large, the optimal correlation coefficient that minimizes the outage probability is not necessarily zero, and instead it generally depends on the signal-to-noise ratios (SNRs), Rice factors, as well as the rate threshold.