N·A_{t} < A_{t}+2·A_{p}+A_{t_{ACK}}) :′′′< br >< math > U = N·A_{t}·(\frac{P_{F}}{A_{t} + 2 · A_{p} + A_{t_{ACK}}} +\frac{1 − P_{F}}{T_{o} + A_{t} + 2 · A_{p} + A_{t_{ACK}}})