Chapter 7: Wireless and mobile networks

Question 1

What does it mean for a wireless network to be operating in “infrastructure mode”?

Answer 1

That the wireless hosts connect to the nearest base station to send and receive data. The base-station infrastructure provides services such as:
-routing
-address assignment (DHCP work)
-DNS-like name translation

Question 2

If the wireless network is not in infrastructure mode, what mode of operation is it in, and what is the difference between that mode of operation and infrastructure mode?

Answer 2

The network is in ad-hoc mode. The hosts operating on this network communicate directly between each other, instead of through access points like in infrastructure mode.
The hosts themselves must provide for services such as routing, address assignment, DNS-like name translation, and more.
ad-hoc mode networks often have a short range and can be “fucked” by a mountain between hosts. But it is more practical at places not suited for mounting big connection towers.

Question 3

What are the differences between the following types of wireless channel impairments(svekkelser): path loss, multipath propagation, interference from other sources?

Answer 3

The key difference is the way the impairments are caused.
- path loss: is caused by the environment the signal travels through, such as long distances, obstacles, and absorption by the environment.
- multiparty propagation: is caused by elements reflection the signal on its way. Causing multiple versions of the same signal to arrive at the reciever.
- interference from other sources: is caused by other sources transmitting in the same frequency band

Question 4

As a mobile node gets farther and farther away from a base station, what are two actions that a base station could take to ensure that the loss probability of a transmitted frame does not increase?

Answer 4

• Increase the transmission power(overføringskraft)
• Decrease the data rate

Question 5

how/why does the base station methods “increase transmission power” & “Decrease the data rate” to ensure that the loss probability of a transmitted frame does not increase while a mobile node gets farther away work?

Answer 5

• Increase the transmission power(overføringskraft)
  As the distance between the mobile node and base station increases, the signal strength decreases.
• Decrease the data rate
  The signal-to-noise ratio can be increased, making the signal easier to detect and reducing the probability of errors.