Exercise 3.4: Use the script in file ofdmfsk.R to plot the signal which would be received under the following circumstances. In all cases let us suppose the time unit is nanoseconds, and the signal to be transmitted is 0, 1, 0:
(a) the bit rate is 0.1, the delay offset between one path and another is 1, and the frequencies are 1.5 and 3;
(b) the bit rate is 0.1, the delay offset between one path and another is 1, and the frequencies are 1.5 and 1.6;
(c) the bit rate is 0.04, the delay offset between one path and another is 5, and the frequencies are 1.5 and 3;
After producing the plots, comment on them as follows:
(a) is it possible, in each case, to visually detect the message from the signal?
(b) for each situation, indicate if you believe the message will be receivable in this situation, and explain why.
(c) does the ability/inability to visually detect the signal mean that the signal can/cannot be detected electronically?
Exercise 3.9: It has become established practice to define network security by means of rules. These rules can take many deferent forms. Although security is often concerned with preventing access, good security requires consideration
of other aspects than merely preventing access. Rules may state what types of service or activity are not allowed, and also what should be allowed. Rules may take precedence over other rules. Complete set of rules for the following situations:
(a) A network of wireless access which is provided in a nationwide network of hotels;
(b) a university campus network (with three types of user academics, admin, and students);
(c) a home wireless network. In each case, include both positive and negative rules, and also rules which are not simply about access, and attempt to ensure that the resulting set of rules is unambiguous, complete, and consistent.
• Criteria
• A plot of two signals in each of the three cases has been prepared and included in the assignment. The relevant R code for each plot has also been included in the assignment.
• An answer to question (a): "is it possible, in each case, to visually detect the message from the signal?" has been provided, with adequate justification, for each of the three cases.
• An answer to question (b): " indicate if you believe the message will be receivable in this situation, and explain why." has been provided, with adequate justification, for each of the three cases.
• An answer to question (c): "does the ability/inability to visually detect the signal mean that the signal can/cannot be detected electronically?" has been provided, with adequate justification, for each of the three cases.
• In Exercise 3.9, a satisfactory set of rules has been provided for all three situations, including rules which describe what users can do, rules which describe what they can't do.
• In addition to classifying rules as positive and negative, rules are also classified as automatically enforced rules (by the software and hardware), on the one hand, and rules which apply to the clients, managers, and human parties to the system in general, on the other hand.
• The issue of how the identity of users should be managed has been addressed in the security rules.
• The issue of security rules for administration users has been addressed.
• The completeness and consistency of the rules has been satisfactorily discussed.