Question 1 [30 pts] a. Explain the difference between circuit-switching and packet- switching operation. [15 pts] b. What is the principal application that has driven the design of circuit-switching networks? [5 pts] c. What are some of the limitations of using a circuit-switching network for data transmission? [10 pts] Question 2 [30 pts a. Assume we wish to transmit a 56-kbps data stream using spread spectrum Find the channel bandwidth required when SNR = 0.1, 0.01, and 0.001. (15pts) b. Spectrum of a channel between 15 MHz and 20 MHz; SNRdB = 20 What is the capacity of this channel and how many signalling levels are required? (15 pts) dBA some Question 3 [40 pts] Explain the OSI reference and TCP/IP models in details. List ways in which the OSI reference model and the TCP/IP reference model are the same and differ. (40 pts)