In CDMA/CD when one sender sends others just listen and wait for their chance to send even receiver could not send. The receiver sends acknowledgment after receiving full frame.
Tpropagation = 2km / 2 *108 =10 MicroSec
Transmission = 512 bits / 10Mbps = 51.2 MicroSec
Transmission = 32bit Ack / 10Mbps = 3,2 MicroSec
1.Transmission delay for sender =51.2 MicroSec
2. Propagation delay from sender to receiver * 2 =20 MicroSec
3. Wait till the time channel has been free =1 propagation Delay =10MicroSec
4. Ack Tramsmission Delay =3,2 MicroSec
5. Propagation delay from receiver to sender * 2 =20MicroSec
6.Wait till the time channel has been free Because of Ack =10 MicroSec
Sum of all these = 114.4MicroSec
10Mb can be send in 1 sec So 114.4 MicroSec= 1144bits
Efficiency = Actual amount of data can be sent / Capacity of Channel for given period.
= (512-32) / 1144 = 0.4195
Effective Bandwidth = 0.4195 * 10Mbps =4.195Mbps