PPT Slide
1. [10 pts] Derive the Stop-and-wait ARQ utilization formula:
U = (1-P)/(1+2a). Show your work used to get key intermediate results.
W/o ARQ: the only useful part is the transmission time
U=Tf/[(Tf+2Tp)] = 1/(1+2?)
W/ ARQ, U = 1/[Nr(1+2?)], …. Eqn (1)
Nr = expected number of cycles to complete transmission
Nr=? i Pi-1(1-P).
Now ? Pi =1/(1-P), and ? i Pi-1 = d/dp (? Pi) = 1/(1-P)2
So, Nr = (1-P)/(1-P)2 = 1/(1-P)
Substituting in Eqn (1), we get:
U=(1-P)/(1+2?)