Q1 Find the bit length of a LAN if the data rate is 1 Gbps a

Q1: Find the bit length of a LAN if the data rate is 1 Gbps and the medium length in meters for a communication between two stations is 200 m. Assume the propagation speed in the medium is 2 *10^8 m/s.?

Q2: 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

Q1.

Propagation speed = 2*10^8 m/s

Data rate = 1gbps = 1*10^9 bits/s

Bit length = (length / propagation speed) . rate

Bit length = (200/2*10^8)*10^9

Therefore, bit length = 1000

Q2.

Assume Frame Transmission time = Tfr, G = load, ns = number of stations and nfs = number of frame per second.

We can first calculate Tfr and G, and then the throughput.

Tfr = (1000 bits) / 1 Mbps = 1 ms

G = ns × nfs × Tfr = 100 × 2 × 1 ms = 0.2

For pure ALOHA Throughput S = G × e^2G 13.40 percent.

This means that each station can successfully send only 0.268 frames per second.

For slotted ALOHA,

We can first calculate Tfr and G, and then the throughput.

Tfr = (1000 bits) / 1 Mbps = 1 ms

G = ns × nfs × Tfr = 100 × 2 × 1 ms = 0.2

For slotted ALOHA Throughput S = G × e^G 5.164499756×10¹¹ > 1

This means that each station can successfully send full 2 frames per second.