Problem 10
Consider the following idealized LTE scenario. The downstream channel (see Figure \(6.20\) ) is slotted in time, across F frequencies. There are four nodes, \(\mathrm{A}, \mathrm{B}, \mathrm{C}\), and \(\mathrm{D}\), reachable from the base station at rates of \(10 \mathrm{Mbps}\), \(5 \mathrm{Mbps}, 2.5 \mathrm{Mbps}\), and \(1 \mathrm{Mbps}\), respectively, on the downstream channel. These rates assume that the base station utilizes all time slots available on all F frequencies to send to just one station. The base station has an infinite amount of data to send to each of the nodes, and can send to any one of these four nodes using any of the F frequencies during any time slot in the downstream sub-frame. a. What is the maximum rate at which the base station can send to the nodes, assuming it can send to any node it chooses during each time slot? Is your solution fair? Explain and define what you mean by "fair." b. If there is a fairness requirement that each node must receive an equal amount of data during each one second interval, what is the average transmission rate by the base station (to all nodes) during the downstream sub-frame? Explain how you arrived at your answer. c. Suppose that the fairness criterion is that any node can receive at most twice as much data as any other node during the sub-frame. What is the average transmission rate by the base station (to all nodes) during the subframe? Explain how you arrived at your answer.
Problem 12
What are the differences between a master device in a Bluetooth network and a base station in an \(802.11\) network?
Problem 13
In mobile IP, what effect will mobility have on end-to-end delays of datagrams between the source and destination?
Problem 14
What is the role of the "core network" in the \(3 \mathrm{G}\) cellular data architecture?
Problem 15
What is the role of the RNC in the \(3 \mathrm{G}\) cellular data network architecture? What role does the RNC play in the cellular voice network?
Problem 15
Consider two mobile nodes in a foreign network having a foreign agent. Is it possible for the two mobile nodes to use the same care-of address in mobile IP? Explain your answer.
Problem 16
If a node has a wireless connection to the Internet, does that node have to be mobile? Explain. Suppose that a user with a laptop walks around her house with her laptop, and always accesses the Internet through the same access point. Is this user mobile from a network standpoint? Explain.
Problem 16
In our discussion of how the VLR updated the HLR with information about the mobile's current location, what are the advantages and disadvantages of providing the MSRN as opposed to the address of the VLR to the HLR?
Problem 17
What is the difference between a permanent address and a care-of address? Who assigns a care-of address?
Problem 19
What are the purposes of the HLR and VLR in GSM networks? What elements of mobile IP are similar to the HLR and VLR?
