Question

1. What are the differences between the following types of wireless channel

impairments: path loss, multipath propagation, interference from other sources?

2. Suppose N people want to communicate with each of N-1 other people using

symmetric key encryption. All communication between any two people I and j, is

visible to all other people in this group of N, and no other person in this group

should be able to decode their communication. How many keys are required in

the system as a whole? Now suppose that public key encryption is used. How

many keys are required in this case?

Answer 1

Solution

2)

Path loss

Signal strength will be decreased because of path loss. The reason behind this it has to pass through things for example walls.
The person who will receive signals which will not be strong due to path loss

Multi path propagation

This will also happens due to signals
In this different signal lengths will be used for multiple path
When the electromagnetic waves reflecting from the ground, due to reflection from the ground it will take different path with different signal lengths

Interface from other sources

It will occur same kind of frequency signals transferred in the wireless network
For example
Wireless phone and Wireless LAN between these there are chances of interference

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