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

R3. Define and explain how each aredifferent:

path loss,

multipath propagation,

interference from other sources

R5. Why are beacon frames used in 802.11 ?

R8. How are Ethernet and 802.11 framestructures different?

R14. What frame structure mode of operationtypes are supported by Wi-max? What does Wi-max architectureresemble?

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

R21. What are the threeapproaches that can be taken to avoid having a singlewireless link degrade the performance of an end- endtransport-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 beginsthe CSMA/ CA protocol for a second frame at step 2!, rather than atstep 1. Why not transmit the second frame immediately (if thechannel is sensed idle)?

P7. Suppose an 802.11b station is configured toalways reserve the channel with the RTS/ CTS sequence. Suppose thisstation suddenly wants to transmit 10,000 bytes of data, and allother stations are idle at this time. As a function of SIFS andDIFS (this means the equation contains SIFS and DIFS as the onlyunknown variables), and ignoring propagation delay and assuming nobit errors, calculate the time in seconds required to transmit theframe and receive the acknowledgment. Assume transmission rate of11Mbps. Suggestion: list the frames that must be sent, compute sizeand time of each and yes you do know the size of the controlframes, 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 Bluetoothframe header? How many active slaves can be supported? How manytotal connections?

P11. In Section 6.5, one proposed solution thatallowed mobile users to maintain their IP addresses as they movedamong foreign networks was to have a foreign network advertise ahighly specific route to the mobile user and use the existingrouting infrastructure to propagate this information throughout thenetwork. We identified scalability as one concern. Suppose thatwhen a mobile user moves from one network to another, the newforeign network advertises a specific route to the mobile user, andthe old foreign network withdraws its route. Consider how routinginformation propagates in a distance-vector algorithm (particularlyfor the case of inter-domain routing among networks that span theglobe).

Will other routers be able to route datagrams immediately to thenew foreign network as soon as the foreign network beginsadvertising its route?   Why or Why not?

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