2. Briefly describe three multiple access methods used in cellular network. Also give an example (an analogy of conference meeting) for each access method. 3. What is the purpose of interleaving used in CDMA? If the input sequence is 1011 0110 1100 1001, what is the output sequence after the bit stream goes through a 4x4 interleaving matrix? (Show both the matrix and the output sequence) 4. What are the differences between IMS call and SIP call? (Show three differences)