In this paper the Markov data-based LQG control problem is considered. The
Markov data-based quadratic cost function over some finite interval [0, N].
To solve this problem, we show LQG control problem is to find the optimal
control sequence which minimizes that a complete input-output description o
f the system is not necessary. Obviously a complete state space model is no
t necessary! for this problem either. The main contributions of this paper
include: (i) develop a new data-based LQG controller in a recursive form an
d a batch-form, (ii) derive a closed form expression for the system's optim
al performance in terms of the Markov parameters, (iii) develop an algorith
m for choosing the output weighting matrix, and (iv) demonstrate that the a
mount of information about the system required by the data-based controller
design is less than the amount required to construct the full state space
model. A numerical example is given to show the effectiveness of the darn-b
ased design method.