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This paper describes the development of a steering strategy that is intended to improve the frequency stability of UTC (KRIS). An experimental time scale is supposed to be generated by steering an active H-maser with carrier-phase (CP) GPS time transfer. One of the goals of this paper is to achieve an improved long-term frequency stability and, at the same time, not seriously perturb the short-term stability of the H-maser. Emphasis is placed on the fact that a real-time GPS CP time transfer is utilized to compute the time difference. The Kalman estimator is utilized for the GPS time transfer, and the optimal control technique is employed to steer the H-maser toward the reference clock, which is the GPS system time (GPST) in this case. The expected performance of the strategy is assessed based on the actual six-month data of the UTC (KRIS), and the relative performance assessment is conducted with respect to the frequency instability by comparing it against the currently operational time scale of the UTC(KRIS).