QUESTION 4

a. FOUR (4) channels are multiplexed using Time Division Multiplexing (TDM). If each channel sends at a rate of 4Kbps and multiplexes 1 byte per channel, determine:

1. The size of a frame (in bits).

2. The frame rate (in frame per second)

3. A frame duration (in second)

4. Bit rate of the link (in bps)

b. Automatic Repeat Request (ARQ) is an error-control mechanism for data transmission which uses acknowledgements and timeouts to achieve reliable data transmission over an unreliable communication link. Sketch an appropriate figure that express the following scenario.

1. The first frame is transmitted by a sender and acknowledged by a receiver.
2. The second frame is transmitted by the sender but lost.
3. After time out, the second frame is re-transmitted by the sender and acknowledged by the receiver.
4. The third frame is transmitted by the sender and acknowledged by the receiver, but the acknowledgement frame is lost.
5. After the time out, the frame is re-transmitted by the sender.

(note that, the data frame is numbered with 0,1,0,1,; while the acknowledgement frame is numbered with 1,0,1,0,)

c. For a Phase Shift Key (PSK) signal, the minimum bandwidth required to transmit such a signal is equal to its baud rate. Determine the bandwidth for a 4-PSK signal transmitted at 4Kbps in half-duplex mode.