Question

R1. What is the difference in how wireless hosts are connected and what services must be provided between “Infrastructure mode” and “ad hoc” mode?

R3. Define and explain how each are different:

path loss,

multipath propagation,

interference from other sources

R5. Why are beacon frames used in 802.11 ?

R8. How are Ethernet and 802.11 frame structures different?

R14. What frame structure mode of operation types are supported by Wi-max? What does Wi-max architecture resemble?

R19. What are the purposes of the HLR and VLR in GSM networks? What elements of mobile IP are similar to the HLR and VLR?

R21. What are the three approaches that can be taken to avoid having a single wireless link degrade the performance of an end- end transport-layer TCP connection?

Chapter 6 Problems

P6. Looking at CSMA/CA: In step 4 of the CSMA/ CA protocol, a station that successfully transmits a frame begins the CSMA/ CA protocol for a second frame at step 2!, rather than at step 1. Why not transmit the second frame immediately (if the channel is sensed idle)?

P7. Suppose an 802.11b station is configured to always reserve the channel with the RTS/ CTS sequence. Suppose this station suddenly wants to transmit 10,000 bytes of data, and all other stations are idle at this time. As a function of SIFS and DIFS (this means the equation contains SIFS and DIFS as the only unknown variables), and ignoring propagation delay and assuming no bit errors, calculate the time in seconds required to transmit the frame and receive the acknowledgment. Assume transmission rate of 11Mbps. Suggestion: list the frames that must be sent, compute size and time of each and yes you do know the size of the control frames, then add it up. Show your work.

P9. Looking at the 802.15.1 Bluetooth frame- How many address bits support active connections in a Bluetooth frame header? How many active slaves can be supported? How many total connections?

P11. In Section 6.5, one proposed solution that allowed mobile users to maintain their IP addresses as they moved among foreign networks was to have a foreign network advertise a highly specific route to the mobile user and use the existing routing infrastructure to propagate this information throughout the network. We identified scalability as one concern. Suppose that when a mobile user moves from one network to another, the new foreign network advertises a specific route to the mobile user, and the old foreign network withdraws its route. Consider how routing information propagates in a distance-vector algorithm (particularly for the case of inter-domain routing among networks that span the globe).

Will other routers be able to route datagrams immediately to the new foreign network as soon as the foreign network begins advertising its route?   Why or Why not?

Is it possible for different routers to believe that different foreign networks contain the mobile user? Why or Why not?

Answer 1

Ans:

R₁:

Difference between "Infrastructure mode" and "Ad-hoc mode" In terms of wireless hosts connection as follows:

Sr. No.	Infrastructure Mode	Ad-Hoc Mode
1	Wireless hosts are associated with base station in infrastructure mode	Wireless hosts have no infrstructure to get connected in ad-hoc mode
2	Connected networks provide only traditional services	Network services must be provided by hosts themselves

R3:

Whenver any electromagnetic signal is travelled through a matter, it will be attenuated which causes Path Loss.

When the paths are of different lengths between a sender and a receiver,the portions of electromagnetic wave reflects off objects and ground, then signal which is being received at receiver gets blurred which is known as Multipath propagation.

If a signal is transmitted at a particular frequency and if any other signal is also transmitted nearby at a similar frequency or closer then this phenomenon is called Interference from other sources to the desired source