Assessment item 3— Assignment 3 Due date: Monday Week 14 ASSESSMENT Weighting: 35% 3 Design Problem (80 marks) A two story industrial building includes a factory floor in the ground floor and offices in the first floor. Both levels have a floor area of 100mx100m and the ceiling height for ground floor and first floor are 10 m and 3 m respectively. This factory contains 200 machines that need to be monitored and controlled from a control system (control algorithm running from a computer) located in the control room upstairs. Furthermore the workers in offices need to communicate and exchange information with each other as well as supervisors in the factory floor below. This office also needs to communicate with the company head office situated off site. Your task is to design a communication network to satisfy the different communication requirements of this scenario. Following are the data rate requirements of the system: 1. Each machine has sensors that generate data at a rate of 0.5 Mbps and the amount of data coming from the control system back to the machines at 10 kbps. 2. There are 500 computers in the office and each needs a 500 kbps download speed and 100kbos upload speed. Assume half the communication is with the outside world. 3. 20 supervisors in the factory floor need to have 20 Mbps downlink (to monitor some machines) and 100 kbps uplink speeds. Prepare a report of maximum 10 pages including any graphics and references addressing the design problem. The report should include, as a minimum, the following information: • What is the general capacity of the equipment required? You are not required to find the exact data requirements. The goal is to get a general feel for the dimension of the network. For example is 10Mbps capacity enough for the network? There is no single correct answer to this question. Think about factors you would consider in designing a network and justify your answer based on these factors. • Technologies/standards/protocols to be used and justify your decision. For example would you use one technology to cover all the requirements or would you have different technologies to cover different requirements. Why did you select a particular strategy? • Decisions behind the selection of such technologies. Think about factors you need to consider in designing a network. You have come across a lot of the technical factors such as capacity, error performance etc., but think of what are the other factors that influence such a design, such as costs. Again you do not need to go into details. Youneed to demonstrate that you are aware of these factors. Use these factors to justify your decision. • Comment of hardware and software implementations of the system. What are the hardware required, what sort of software is required to implement. You do not need to identify specific software or hardware components. It is enough to say N router with M interfaces and x Gbps capacity etc., What type of cables do you need to use? Would you use wireless or wired? Why? • Layout/topology/architecture of the network. Provide a diagram of how the different equipment is connected together again justify your decisions. • Limitations of the selected technologies. As the requirements are only loosely defined, you may add your own sensible system requirements to make the problem more specific. This would allow you to think of how you would specify a network design problem. If you add your own specifications, clearly state them at the beginning of the document. Your task is to look at different solutions and identify the best according to your criteria. Always discuss alternatives, rather than saying I pick this particular technology. It should something along the lines of both A and B can work here, but I pick A due to reason 1 and reason 2. You are strongly encouraged to use web resources for this assessment. All the resources you use should be properly referenced in the report. As mentioned above the objective of this exercise is to demonstrate that you can utilise the knowledge gained from the course material to solve a design problem. I do not expect a complete design that can be directly applied to the solution. Watch out for the page limitations and do your best to cover all the above mentioned issues in under the 10 page limit. There is no one correct answer for this problem. However there can be wrong answers. For example a system that cannot support the data rates required is not correct. You are highly encouraged to discuss this problem with other students on the forum, but the report must be individual work. Other Problems 1. The figure below illustrates an example timing diagram for the Distributed Coordination Function (Basic Access mode) in IEEE 802.11 wireless LANs. It shows the procedure for Station A sending a DATA frame (with payload = 500 bytes) to Station B, which is subsequently acknowledged. Make the following assumptions: • All Stations can hear each others’ transmissions • Backoff interval = Slottime x Random(0,31) • Next random number (from Random(0,31) function) of station C = 7 • Next random number (from Random(0,31) function) of station D = 11 • Station C has a DATA frame ready to transmit to B at the point marked x • Station D has a DATA frame ready to transmit to A at the point marked x Complete the timing diagram for the transmissions of Stations C and D. That is, draw a diagram as in figure below, and show where necessary the DIFS, SIFS, ACK, DATA,Backoff and Deference for ALL stations. Your diagram does not have to be to scale, but the ordering of events must be clear (e.g. in the current diagram it is clear that the SIFS at station B starts at the same time the DATA from station A is completed). [10 marks] 2. Consider a 802.11 node that has large number of packets to send. In CSMA/CA protocol a station that successfully transmits a packet does not immediately go back to sensing the channel for a DIFS interval and then transmit the packet if the channel is ideal for that DIFS interval. It initiates a random backoff procedure before sending the next packet. Explain why the protocol was designed that way. [10 marks]