Aerospace Instrument-Making Annotation << Back Method for Optimal Estimation for System with Packet-Delay in Input without Time Stamp Chen Hao In recent years, the progress of sensor systems and network transmission technology has made complex network systems widely used. However, with the expansion of system scale and the limitation of communication capacity, packet delay has become an important issue in the signal transmission process between agents. This paper studies the optimal estimation problem of agents with input delays without timestamps, and proposes two state space update methods: fi xed delay and random delay. For random input delay, a random input signal update method is proposed. Kalman filter based on block matrix method is used for optimal estimation. The observability of the new equivalent system is evaluated by the numerical observability criterion. Finally, the correctness of the proposed method is verified by simulation experiments. Keywords: Packet-delay system, optimal estimation, networked multiagent system, Kalman filter. DOI: 10.25791/aviakosmos.5.2026.1555 Pp. 16-23.