One hundred stations on a pure ALOHA network share a lMbps c

One hundred stations on a pure ALOHA network share a l-Mbps channel. If frames are 1000 bits long, find the throughput if each station is sending 2 frames per second. (Repeat the Exercise for slotted ALOHA)

Solution

Solution

We want to find the throughput for PURE ALOHA & SLOTTED ALOHA.

The throughput for PURE ALOHA (S) is G*e-^2G ------- (i)

Here G = average number of frames generated by the system during one frame transmission time or load.

G= Frame Transmission time (Tfr)*number of stations (ns)*number of frame per second (nfs).

Frame Transmission time (Tfr) =Frame_Size/Channel_Speed=

                                                          1000 bits/ 1 Mbps=10³/10⁶ = 10^-3= 1 millisecond=1ms.

G = 100 _* 10^-3_* 2 = 0.2

Now put the value of G into eq (i)

S = .2_*e^-2*.2 = .2_*e^-.4 = 13.40 %

This means that each station can successfully send only 0 .2681 frames per second.

The throughput for SLOTTED ALOHA (S) is G*e-^G ------- (ii)

Here G = average number of frames generated by the system during one frame transmission time or load.

G= Frame Transmission time (Tfr)*number of stations (ns)*number of frame per second (nfs).

Frame Transmission time (Tfr) =Frame_Size/Channel_Speed=

                                                          1000 bits/ 1 Mbps=10³/10⁶ = 10^-3= 1 millisecond=1ms.

G = 100 _* 10^-3_* 2 = 0.2

Now put the value of G into eq (ii)

S=.2 _* e^.2 = 0.1637 = 16.37%

This means that each station can successfully send only 0.3274 frames per second.