Figure 2.20: State transition diagram of FSM based SNG after mapping transition probability into state of 3 − tuples
Since three independent random sources are applied in this design, the FSM makes a transition by
observing the following 3 − tuples: (1, −, −) represents a transition probability 1/2, similarly, (0, 1, −) and (0, 0, 1) corespond to 1/4 and 1/8, respectively (’-’ denotes a donrt care). This mapping of state
transition based upon these 3 − tuples is shown in Fig.2.20.
In order to analyse the quality of this approach, the output probability using bit stream of length 1024 is messured. This experiment is repeated a number of 10000 times, then the statistic attributes are investigated to evaluate this method. Fig.2.21 shows that the generated probabilities are close to the expected one, i.e, the quality of this method is acceptable.
Besides the low-cost in using input source, the correlation between the output of the state machine doesn’t affect the primary statistic of the output [4], in contrast to that of combinational logic. This method consequently promises a reasonalbe choice in design of SNG.