Question

(a) Distinguish between simplex, half-duplex, and duplex links in a computer network. (b) Distinguish between three multiple access mechanisms used in present day wireless networks (1 (1 Marks) Marks) 3. (c) Two users like to communicate their 4-bit messages 1011 and 1110 to the cell tower by spreading their messages using the orthogonal Walsh codes 1111 and 1010, respectively. Verify the mutual orthogonality of these Walsh codes using the property that their exclusive OR sum contains number of 1s and Os. Show that the original user messages can be obtained by using their respective spreading sequences from the analog mixture of the spread messages. equal (3 Marks) Note: Convert the analog mixture into a binary stream by considering the values above signal average as 1s and those below as zeros. For example, the stream [0,2,1,0] with signal average of 0.75 may be converted into binary stream [0, 1, 1, 0]. (d) What is hand-off (handover) and why is it necessary in mobile wireless communications? Differentiate between the three types of handoff mechanisms. 4 Marks)

Answer 1

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