A general way to generate a random binary signal would be to use the “Random Number” block that has been elaborated here, followed by using 2 “Constant” blocks, elaborated here for binary 1 and 0. Finally, feed the output of “Random Number” block to the condition input of the “Switch” Block elaborated here. A condition that can be used is if the input value is greater than mean, output 1 from the “Constant” block. Else, the other constant block output is passed through the switch.
Assuming you have the Communications Toolbox installed, to generate a pseudorandom bit sequence in Simulink, you can use the “Bernoulli Binary Generator” Block that has been elaborated here.