3. (a) A researcher has designed a new modulation scheme. The constellation diagram is shown below. The carrier frequency of the system is set to fe, and the symbol duration is set to T. (0.1) bit-0 bit-1 (1.57,0) I (i) Plot the modulated signal representing 0011. In your plot, you should show two cycles for each symbol and specify its amplitude. (ii) Calculate the average energy per symbol for this modulation scheme. (iii) The researcher claims that the new design is better than the commonly used design in many aspects. Do you agree? If you agree, identify one aspect to support the claim. If you disagree, identify one aspect to challenge the claim. (b) Consider a protocol stack following the OSI reference model design. The protocol stack has three layers. The PCI sizes of layer 1, 2 and 3 are 20 bytes, 50 bytes and 10 bytes, respectively. While there is no size limit for the PDU of layer 1 and layer 3, the maximum PDU size of layer 2 is 500 bytes. A message with a size of 1024 bytes is generated by the user. The message is sent to layer 3 for encapsulation, then layer 2 and finally layer 1. Determine the number of PDUs generated by layer 1 to carry the message, and specify the size of each PDU (in bytes). (c) Two sites separated by 100 km require a communication link to perform data communication. The link uses B8ZS line coding and implements a Stop-and-Wait ARQ. The signal propagation speed on the link is 2 x 10 m/s. Assume that the frame processing time and acknowledgement transmission time are very short and can be ignored. (i) A binary stream of 0011000000010000000001 is transmitted on the link, where the leftmost bit is transmitted first. Determine the signal waveforms. You may either draw the pulses or use 0, + and - to indicates zero, positive and negative pulses, respectively. (ii) The link can operate at 50 Mbps or 100 Mbps. A test on the link has revealed that the frame error rate is 0.01 and 0.05 when the link operates at 50 Mbps and 100 Mbps respectively. The frame size is set to 1000 bits for the test. Determine which data rate setting for the link can lead to a higher link throughput when using Stop-and-Wait ARQ, and calculate the link throughput. (d) An Internet Service Provider (ISP) is given a class B IP address. The ISP has 6000 subscribers. For better management, the ISP has assigned each subscriber a subnet with a range of static IP addresses. Assume that the ISP assigns all its available IP addresses to all subscribers, determine the adequate subnet mask setting for the assignment. How many more new subscribers can the ISP support using this setting? Show your working