Abstract: The optimal tracking performance problem of single-input-single-output (SISO) networked control system with communication constraints is studied. The white noise in the forward channel and the feedback channel is considered simultaneously, and some new results are obtained: the optimal tracking performance depends on the unstable poles of the given plant, as well as the channel coding methods and white noise. They also show how the control system's tracking capability is constrained by the channel coding method and white noise in the communication channel. The optimal tracking performance reduces to the existing tracking performance of the control system without communication constraints. Simulation results illustrate the correctness of the results.