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1 ITEC851 Mobile Data Networks Assignment 1 Due: Tuesday (Week 8) – 1st of October, 2019, 6 pm (Via Turnitin). Total Marks: 70 Weighting (Value): 10% This assignment has been designed to test the following areas: Medium Access Control Wireless LAN Mobile IP 1. (18 marks) A CDMA system includes two stations X and Y. The Walsh codes for stations X and Y are (-1 1 -11 -1 1 -11) and (-1 -111 -1 -111) respectively. a. Show the output at the receiver, if X transmits a data bit 1 and Y does not transmit (2 marks) b. Show the output at the receiver, if X transmits a data bit 0 and Y does not transmit (2 marks) c. Show the output at the receiver, if X transmits a data bit 1 and Y transmits a data bit 1. Assume the received power from both X and Y is the same (2 marks) d. Show the output at the receiver, if X transmits a data bit 0 and Y transmits a data bit 1. Assume the received power from both X and Y is the same (2 marks) e. Show the output at the receiver, if X transmits a data bit 1 and Y transmits a data bit O. Assume the received power from both X and Y is the same (2 marks) f. Show the output at the receiver, if X transmits a data bit 0 and Y transmits a data bit O. Assume the received power from both X and Y is the same (2 marks) g. Show the output at the receiver, if X transmits a data bit 1 and Y transmits a data bit 1. Assume the received power from Y is twice the received power from X; this can be represented by showing the received signal component from X as consisting of elements of magnitude 1(+1, -1) and the received signal component from Y as consisting of elements of magnitude 2 (+2, - 2) (3 marks) h. Show the output at the receiver, if X transmits a data bit 0 and B transmits a data bit 1. Assume the received power from Y is twice the received power from X (3 marks) 2. [6 marks] The dual busy tone multiple access (DBTMA) scheme splits the single common channel into two sub-channels: a data channel and a control channel. 2 Data packets are transmitted on the data channel. Control packets (RTS/CTS) are transmitted on the control channel. Explain the rationale behind this design principle. Identify and explain two key limitations of this scheme. (300 words) 3. [12 marks] a. [4 marks] Identify and explain two main causes of collision in 802.11 mobile ad hoc networks. (200 words) b. [8 marks] It is argued that using the fragmentation scheme of CSMA/CA for data transmission results in performance improvement. Explain why? Highlight and briefly explain a few deficiencies of this approach to data transmission. (300 words) 4. [14 marks] a. [8 marks] Assume there is a bidirectional transmission (e.g. DATA/ACK or RTS/CTS/DATA/ACK) using the 802.11 protocol between a pair of nodes. In this scenario, is it possible for a node that is currently an exposed node to any one node in this transmitter-receiver pair, to be a hidden node when the roles of the transmitting and receiving nodes are switched? If yes, then explain how with the aid of an example. If no, then explain why. (400 words) b. [6 marks] Highlight and explain the key limitations of the binary exponential back-off (BEB) algorithm that is used in CSMA/CA. Explain how the multiplicative increase and linear decrease (MILD) algorithm used in the MACAW protocol can address these deficiencies. Explain why the MILD algorithm may also suffer from performance degradation. (400 words) 5. [8 marks] Consider a novel Mobile IP scheme in which a mobile station announces its permanent (home) IP address to agents in foreign networks. These agents, in turn, announce this information to other routers using their regular routing protocol update messages. What are some benefits and drawbacks of this scheme when compared to the IETF Mobile IP scheme? (300 Words) 6. [12 marks] (Refer to figure 1) An organization has deployed a campus network using cellular IP. The cellular IP network extends the wired infrastructure of the campus as shown in figure 1 below. The gateways in cellular IP connect their respective wireless segments to the wired segment. Each Base Station in the wireless segment provides layer 3 functionality (in other words, they act as IP forwarding engines). The campus network supports multicast routing. All the components in the wireless part strictly adhere to cellular IP standard. Assume that this campus network deploys a Source Based Multicast Routing scheme – a protocol that builds source based multicast distribution trees (Refer to the appendix for a brief explanation on Source Based Multicast Routing). 3 Figure 1 A visiting mobile node MN enters the wireless network and initially gets registered to its home network via BS1-G1 and acquires a Care of Address (CoA - an address from the campus network address space). The CoA assigned to the MN remains unchanged irrespective of MN’s movements within the campus network. In other words, MN does not need to acquire a new CoA upon moving to a wireless segment under the same or under a different gateway. While initially at BS1, the MN joins a multicast group G whose scope is local to this campus network (all sources, and members reside in the campus network). Assume that hosts H1, H3, H5, and H7 are members of this group with H1 and H7 also acting as Multicast sources. Furthermore, assume that MN itself is a source for multicast traffic. In this scenario, explain what problems can arise in multicast communication due to MN’s mobility. (300 Words) 4 Submission You must make an online submission on ilearn via Turnitin. Assignments will normally be marked and returned online. There are no hardcopy submissions for written assignments. Ensure you submit the correct file. The submission process shows you a complete preview of your entire assignment after you have uploaded it, but before you have submitted it. Carefully check through every single page to ensure everything is there and the correct version has been uploaded, and only then press CONFIRM. Multiple submissions may be possible via Turnitin prior to the final due date and time of an assessment task. Teaching staff will use the originality report to judge whether plagiarism has occurred and whether penalties should apply for breaches of the Academic Honesty Policy. Any similar text identified by Turnitin will be considered carefully to see if it is indeed a breach of the Academic Honesty Policy. Note Answers must be within the specified word limit which is an absolute word limit and no excess will be allowed. Assumptions (if any) must be stated clearly in your answers. Remember, there may not be one right answer for some of the questions. Rather, your explanations do need to present your case clearly. The explanations you provide do not have to be long - a concise answer is preferred to a rambling one. Assessment For all questions in this assignment not only the contents but also the presentation will affect your mark. You will lose marks (and not necessarily only a small portion) if there are problems with the presentation, particularly with clarity. This means that your answers to each question should be a coherent statement and that the spelling and grammar of your submission will be taken into account in assessing its presentation. For full marks, your answers should all be clear, coherent and correct, and also strictly within the word limits. The questions will be marked individually, the marks totalled, and a final grade assigned that is no more than indicated by the total marks, and no more than allowed by the standards specified above and in the unit outline. Plagiarism You should be well aware of the University's plagiarism policy. In this assignment, you must be particularly careful to avoid plagiarising your articles or any other sources of information. It is important that you do not attempt to write your answers by pasting together pieces of text that you find on the Internet. You need to write your own words and phrases that express your own ideas. 5 Appendix Source Based Multicast Routing Consider a single sender. In source based multicast Routing, the routing process builds shortest path trees rooted at the sender. The router delivers packets to each receiver along the shortest path. In a nutshell, it builds a shortest path spanning tree routed at the source to all intended destinations. Source Based Multicast Routing (SBMR) (Refer to Figure 2) The SBMR techniques implement the Reverse Path Multicast (RPM) algorithm. The RPM constructs an implicit spanning tree for each source. It accepts a packet from a source S, on link L, if L is the shortest path toward S (Reverse Path Check) Uses a unicast routing table which contains shortest paths to each node in the network In this technique, the first packet flooded across the internetwork. The packet scope is restricted by a TTL value. Due to flooding, all routers in the network get a copy of the packet. Routers not having any downstream router in a multicast tree are called leaf routers. If a leaf router has no group members on its sub-networks, a Prune message is sent upstream to parent router (one hop up). The prune state is maintained in every router. This process is repeated every hop upwards. These cascaded prune messages create/truncate the original RPM tree. Prune information only held for a certain lifetime (soft state). A Graft message is sent to quickly recover back a previous pruned branch. It cancels out the previously received prune message. Graft cascades reliably hop by