Subject : Satellite Communication and Networks

Topic : Space Segment Access and Utilization

Marks : 5M

The multiple access methods which employ fixed assignment scheme are not suitable when the user data is in the burst.

In fixed access method,the channel capacity is wasted.A user does not have any data to send because time slot is preassigned in fixed access schemes.

A multiple access method in which assignment of channel allowed only when the user transmits data,is more efficient in terms of channel utilization.

Such technique is known as demand assignment multiple access technique.The random access technique is a fixed demand assignment technique with no access control.

ALOHA is a random access system developed by university Hawall in 1971 for computer communication where data is in the form of packets.