First we have to take min[ W(C),W(R) ] where W(C)= capacity of network and W(R)= receiver window size.
Then Threshold will be 1/2(min of these two).
Now let sender window size=16 and Threshold turn out to be 8.
1,2,4,8,9,10,11,12,13,14,15,16,16,16,16,16.....